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data/en.wikipedia.org/wiki/Metascience-0.md
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title: "Metascience"
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source: "https://en.wikipedia.org/wiki/Metascience"
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category: "reference"
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tags: "science, encyclopedia"
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Metascience (also known as meta-research) is the use of scientific methodology to study science itself. Metascience seeks to increase the quality of scientific research and enhance its efficiency. It is also known as "research on research" and "the science of science", as it uses research methods to study how research is done and find where improvements can be made. Metascience concerns itself with all fields of research and has been described as "a bird's eye view of science". In the words of John Ioannidis, "Science is the best thing that has happened to human beings ... but we can do it better."
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In 1966, an early meta-research paper examined the statistical methods of 295 papers published in ten high-profile medical journals. It found that "in almost 73% of the reports read ... conclusions were drawn when the justification for these conclusions was invalid." Meta-research in the following decades found many methodological flaws, inefficiencies, and poor practices in research across numerous scientific fields. Many scientific studies could not be reproduced, particularly in medicine and the soft sciences. The term "replication crisis" was coined in the early 2010s as part of a growing awareness of the problem.
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Measures have been implemented to address the issues revealed by metascience. These measures include the pre-registration of scientific studies and clinical trials, as well as the founding of organizations such as CONSORT and the EQUATOR Network that issue guidelines for methodology and reporting. There are ongoing efforts aimed at addressing misuse of statistics, eliminating perverse incentives within academic institutions, improving the peer review process, systematically collecting data about the scholarly publication system, combating bias in scientific literature, and enhancing the overall quality and efficiency of the scientific process. As such, metascience is a big part of methods underlying the open science movement.
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== History ==
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In 1966, an early meta-research paper examined the statistical methods of 295 papers published in ten high-profile medical journals. It found that "in almost 73% of the reports read ... conclusions were drawn when the justification for these conclusions was invalid." A paper in 1976 called for funding for meta-research: "Because the very nature of research on research, particularly if it is prospective, requires long periods of time, we recommend that independent, highly competent groups be established with ample, long term support to conduct and support retrospective and prospective research on the nature of scientific discovery". In 2005, John Ioannidis published a paper titled "Why Most Published Research Findings Are False", which argued that a majority of papers in the medical field produce conclusions that are wrong. The paper went on to become the most downloaded paper in the Public Library of Science and is considered foundational to the field of metascience. In a related study with Jeremy Howick and Despina Koletsi, Ioannidis showed that only a minority of medical interventions are supported by 'high quality' evidence according to The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Later meta-research identified widespread difficulty in replicating results in many scientific fields, including psychology and medicine. This problem was termed "the replication crisis". Metascience has grown as a reaction to the replication crisis and to concerns about waste in research.
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Major publishers have committed resources to meta-research and quality improvement initiatives. Top journals such as Science, The Lancet, and Nature, provide ongoing coverage of meta-research and problems with reproducibility. In 2012 PLOS ONE launched a Reproducibility Initiative. In 2015 BioMed Central introduced a minimum-standards-of-reporting checklist to four titles.
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The first international conference in the broad area of meta-research was the Research Waste/EQUATOR conference held in Edinburgh in 2015; the first international conference on peer review was the Peer Review Congress held in 1989. In 2016, Research Integrity and Peer Review was launched. The journal's opening editorial called for "research that will increase our understanding and suggest potential solutions to issues related to peer review, study reporting, and research and publication ethics".
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On 8 July 2025, an editorial published in Nature announced the birth of the Metascience Alliance, a coalition of more than 25 funders, academic groups, companies, and other institutions that pursue metascience: the use of scientific methods to understand and improve science itself. The initiative was attended in London by more than 830 participants from around 65 countries. The editorial calls upon metascientists not to limit themselves to studies within academia, but to address the broader social needs, to communicate scientific uncertainty effectively, and rebuild public trust in science.
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== Fields and topics of meta-research ==
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Metascience can be categorized into five major areas of interest: Methods, Reporting, Reproducibility, Evaluation, and Incentives. These correspond, respectively, with how to perform, communicate, verify, evaluate, and reward research.
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=== Methods ===
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Metascience seeks to identify poor research practices, including biases in research, poor study design, abuse of statistics, and to find methods to reduce these practices. Meta-research has identified numerous biases in scientific literature, particularly the misuse of p-values and overreliance on significance testing.
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==== Scientific data science ====
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Scientific data science is the use of data science to analyse research papers. It encompasses qualitative and quantitative methods. Research in scientific data science includes fraud detection. and citation network analysis.
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==== Journalology ====
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Journalology, also known as publication science, is the scholarly study of all aspects of the academic publishing process. The field seeks to improve the quality of scholarly research by implementing evidence-based practices in academic publishing. The term "journalology" was coined by Stephen Lock, the former editor-in-chief of The BMJ. The first Peer Review Congress, held in 1989 in Chicago, Illinois, is considered a pivotal moment in the founding of journalology as a distinct field. The field of journalology has been influential in pushing for study pre-registration in science, particularly in clinical trials. Clinical-trial registration is now expected in most countries.
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=== Reporting ===
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Meta-research has identified poor practices in reporting, explaining, disseminating and popularizing research, particularly within the social and health sciences. Poor reporting makes it difficult to accurately interpret the results of scientific studies, to replicate studies, and to identify biases and conflicts of interest in the authors. Solutions include the implementation of reporting standards, and greater transparency in scientific studies (including better requirements for disclosure of conflicts of interest). There is an attempt to standardize reporting of data and methodology through the creation of guidelines by reporting agencies such as CONSORT and the larger EQUATOR Network.
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=== Reproducibility ===
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The replication crisis is an ongoing methodological crisis in which it has been found that many scientific studies are difficult or impossible to replicate. While the crisis has its roots in the meta-research of the mid- to late 20th century, the phrase "replication crisis" was not coined until the early 2010s as part of a growing awareness of the problem. The replication crisis has been closely studied in psychology (especially social psychology) and medicine, including cancer research. Replication is an essential part of the scientific process, and the widespread failure of replication puts into question the reliability of affected fields.
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Moreover, replication of research (or failure to replicate) is considered less influential than original research, and is less likely to be published in many fields. This discourages the reporting of, and even attempts to replicate, studies.
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=== Evaluation and incentives ===
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Metascience seeks to create a scientific foundation for peer review. Meta-research evaluates peer review systems including pre-publication peer review, post-publication peer review, and open peer review. It also seeks to develop better research funding criteria.
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Metascience seeks to promote better research through better incentive systems. This includes studying the accuracy, effectiveness, costs, and benefits of different approaches to ranking and evaluating research and those who perform it. Critics argue that perverse incentives have created a publish-or-perish environment in academia which promotes the production of junk science, low quality research, and false positives. According to Brian Nosek, "The problem that we face is that the incentive system is focused almost entirely on getting research published, rather than on getting research right." Proponents of reform seek to structure the incentive system to favor higher-quality results. For example, by quality being judged on the basis of narrative expert evaluations ("rather than [only or mainly] indices"), institutional evaluation criteria, guaranteeing of transparency, and professional standards.
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==== Contributorship ====
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Studies proposed machine-readable standards and (a taxonomy of) badges for science publication management systems that hones in on contributorship – who has contributed what and how much of the research labor – rather than using the traditional concept of plain authorship – who was involved in any way in the creation of a publication. A study pointed out one of the problems associated with the ongoing neglect of contribution nuanciation – it found that "the number of publications has ceased to be a good metric as a result of longer author lists, shorter papers, and surging publication numbers".
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==== Assessment factors ====
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Factors other than a submission's merits can substantially influence peer reviewers' evaluations. Such factors may however also be important such as the use of track-records about the veracity of a researchers' prior publications and its alignment with public interests. Nevertheless, evaluation systems – include those of peer-review – may substantially lack mechanisms and criteria that are oriented or well-performingly oriented towards merit, real-world positive impact, progress and public usefulness rather than analytical indicators such as number of citations or altmetrics even when such can be used as partial indicators of such ends. Rethinking of the academic reward structure "to offer more formal recognition for intermediate products, such as data" could have positive impacts and reduce data withholding.
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==== Recognition of training ====
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A commentary noted that academic rankings don't consider where (country and institute) the respective researchers were trained.
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==== Scientometrics ====
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Scientometrics concerns itself with measuring bibliographic data in scientific publications. Major research issues include the measurement of the impact of research papers and academic journals, the understanding of scientific citations, and the use of such measurements in policy and management contexts. Studies suggest that "metrics used to measure academic success, such as the number of publications, citation number, and impact factor, have not changed for decades" and have to some degrees "ceased" to be good measures, leading to issues such as "overproduction, unnecessary fragmentations, overselling, predatory journals (pay and publish), clever plagiarism, and deliberate obfuscation of scientific results so as to sell and oversell".
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Novel tools in this area include systems to quantify how much the cited-node informs the citing-node. This can be used to convert unweighted citation networks to a weighted one and then for importance assessment, deriving "impact metrics for the various entities involved, like the publications, authors etc" as well as, among other tools, for search engine- and recommendation systems.
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==== Science governance ====
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Science funding and science governance can also be explored and informed by metascience.
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===== Incentives =====
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Various interventions such as prioritization can be important. For instance, the concept of differential technological development refers to deliberately developing technologies – e.g. control-, safety- and policy-technologies versus risky biotechnologies – at different precautionary paces to decrease risks, mainly global catastrophic risk, by influencing the sequence in which technologies are developed. Conventional legislative and incentive structures may be insufficient to ensure proper scientific governance because they often respond too slowly or inadequately to emerging challenges.
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Other incentives to govern science and related processes, including via metascience-based reforms, may include ensuring accountability to the public (in terms of e.g. accessibility of, especially publicly-funded, research or of it addressing various research topics of public interest in serious manners), increasing the qualified productive scientific workforce, improving the efficiency of science to improve problem-solving in general, and facilitating that unambiguous societal needs based on solid scientific evidence – such as about human physiology – are adequately prioritized and addressed. Such interventions, incentives and intervention-designs can be subjects of metascience.
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===== Science funding and awards =====
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Scientific awards are one category of science incentives. Metascience can explore existing and hypothetical systems of science awards. For instance, it found that work honored by Nobel Prizes clustered in only a few scientific fields with only 36/71 having received at least one Nobel Prize. Of the 114/849 domains science could be divided into their DC2 and DC3 classification systems, five were shown to comprise over half of the Nobel Prizes awarded between 1995 and 2017 (particle physics [14%], cell biology [12.1%], atomic physics [10.9%], neuroscience [10.1%], molecular chemistry [5.3%]).
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A study found that delegation of responsibility by policy-makers – a centralized authority-based top-down approach – for knowledge production and appropriate funding to science with science subsequently somehow delivering "reliable and useful knowledge to society" is too simple.
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Measurements show that allocation of bio-medical resources can be more strongly correlated to previous allocations and research than to burden of diseases.
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A study suggests that "[i]f peer review is maintained as the primary mechanism of arbitration in the competitive selection of research reports and funding, then the scientific community needs to make sure it is not arbitrary".
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Studies indicate there to is a need to "reconsider how we measure success" (see #Factors of success and progress).
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Funding data
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Funding information from grant databases and funding acknowledgment sections can be sources of data for scientometrics studies, e.g. for investigating or recognition of the impact of funding entities on the development of science and technology.
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===== Research questions and coordination =====
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===== Risk governance =====
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=== Science communication and public use ===
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Science derives its value as a global public good from two attributes: researchers must make knowledge claims and supporting evidence openly available for scrutiny, and they must communicate results promptly and effectively. Metascientific research is exploring topics of science communication such as media coverage of science, science journalism and online communication of results by science educators and scientists. Research shows that academics view social media primarily for amplifying their work. However, institutions should cultivate a culture emphasizing genuine research engagement over mere visibility. Science communication may also involve the communication of societal needs, concerns and requests to scientists.
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==== Alternative metrics tools ====
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Alternative metrics tools can be used not only for help in assessment (performance and impact) and findability, but also aggregate many of the public discussions about a scientific paper in social media such as reddit, citations on Wikipedia, and reports about the study in the news media which can then in turn be analyzed in metascience or provided and used by related tools. In terms of assessment and findability, altmetrics rate publications' performance or impact by the interactions they receive through social media or other online platforms, which can for example be used for sorting recent studies by measured impact, including before other studies are citing them. The specific procedures of established altmetrics are not transparent and the used algorithms can not be customized or altered by the user as open source software can. A study has described various limitations of altmetrics and points "toward avenues for continued research and development". They are also limited in their use as a primary tool for researchers to find received constructive feedback. (see above)
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==== Societal implications and applications ====
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It has been suggested that it may benefit science if "intellectual exchange—particularly regarding the societal implications and applications of science and technology—are better appreciated and incentivized in the future".
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==== Knowledge integration ====
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Primary studies "without context, comparison or summary are ultimately of limited value" and various types of research syntheses and summaries integrate primary studies. Progress in key social-ecological challenges of the global environmental agenda is "hampered by a lack of integration and synthesis of existing scientific evidence", with a "fast-increasing volume of data", compartmentalized information and generally unmet evidence synthesis challenges. According to Khalil, researchers are facing the problem of too many papers – e.g. in March 2014 more than 8,000 papers were submitted to arXiv – and to "keep up with the huge amount of literature, researchers use reference manager software, they make summaries and notes, and they rely on review papers to provide an overview of a particular topic". He notes that review papers are usually (only)" for topics in which many papers were written already, and they can get outdated quickly" and suggests "wiki-review papers" that get continuously updated with new studies on a topic and summarize many studies' results and suggest future research. A study suggests that if a scientific publication is being cited in a Wikipedia article this could potentially be considered as an indicator of some form of impact for this publication, for example as this may, over time, indicate that the reference has contributed to a high-level of summary of the given topic.
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==== Science journalism ====
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Science journalists play an important role in the scientific ecosystem and in science communication to the public and need to "know how to use, relevant information when deciding whether to trust a research finding, and whether and how to report on it", vetting the findings that get transmitted to the public.
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=== Science education ===
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Some studies investigate science education, e.g. the teaching about selected scientific controversies and historical discovery process of major scientific conclusions, and common scientific misconceptions. Education can also be a topic more generally such as how to improve the quality of scientific outputs and reduce the time needed before scientific work or how to enlarge and retain various scientific workforces.
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==== Science misconceptions and anti-science attitudes ====
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Many students have misconceptions about what science is and how it works. Anti-science attitudes and beliefs are also a subject of research. Hotez suggests antiscience "has emerged as a dominant and highly lethal force, and one that threatens global security", and that there is a need for "new infrastructure" that mitigates it.
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=== Evolution of sciences ===
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==== Scientific practice ====
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Metascience can investigate how scientific processes evolve over time. A study found that teams are growing in size, "increasing by an average of 17% per decade". (see labor advantage below)
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It was found that prevalent forms of non-open access publication and prices charged for many conventional journals – even for publicly funded papers – are unwarranted, unnecessary – or suboptimal – and detrimental barriers to scientific progress. Open access can save considerable amounts of financial resources, which could be used otherwise, and level the playing field for researchers in developing countries. There are substantial expenses for subscriptions, gaining access to specific studies, and for article processing charges. Paywall: The Business of Scholarship is a documentary on such issues.
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Another topic are the established styles of scientific communication (e.g. long text-form studies and reviews) and the scientific publishing practices – there are concerns about a "glacial pace" of conventional publishing. The use of preprint-servers to publish study-drafts early is increasing and open peer review, new tools to screen studies, and improved matching of submitted manuscripts to reviewers are among the proposals to speed up publication.
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==== Science overall and intrafield developments ====
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Metadata from research publications can be extracted, enriched, and made widely accessible through digital tools. OpenAlex is a free online index of over 200 million scientific documents that integrates and provides metadata such as sources, citations, author information, scientific fields and research topics. Its API and open source website can be used for metascience, scientometrics and novel tools that query this semantic web of papers. Another project under development, Scholia, uses metadata of scientific publications for various visualizations and aggregation features such as providing a simple user interface summarizing literature about a specific feature of the SARS-CoV-2 virus using Wikidata's "main subject" property.
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===== Subject-level resolutions =====
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Beyond metadata explicitly assigned to studies by humans, natural language processing and AI can be used to assign research publications to topics – one study investigating the impact of science awards used such to associate a paper's text (not just keywords) with the linguistic content of Wikipedia's scientific topics pages ("pages are created and updated by scientists and users through crowdsourcing"), creating meaningful and plausible classifications of high-fidelity scientific topics for further analysis or navigability.
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===== Growth or stagnation of science overall =====
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Metascience research is investigating the growth of science overall, using e.g. data on the number of publications in bibliographic databases. A study found segments with different growth rates appear related to phases of "economic (e.g., industrialization)" – money is considered as necessary input to the science system – "and/or political developments (e.g., Second World War)". It also confirmed a recent exponential growth in the volume of scientific literature and calculated an average doubling period of 17.3 years.
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However, others have pointed out that is difficult to measure scientific progress in meaningful ways, partly because it's hard to accurately evaluate how important any given scientific discovery is. A variety of perspectives of the trajectories of science overall (impact, number of major discoveries, etc) have been described in books and articles, including that science is becoming harder (per dollar or hour spent), that if science "slowing today, it is because science has remained too focused on established fields", that papers and patents are increasingly less likely to be "disruptive" in terms of breaking with the past as measured by the "CD index", and that there is a great stagnation – possibly as part of a larger trend – whereby e.g. "things haven't changed nearly as much since the 1970s" when excluding the computer and the Internet.
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Understanding potential slowdowns in scientific productivity could present opportunities to accelerate research and address humanity's most pressing challenges. For example, emphasis on citations in the measurement of scientific productivity, information overloads, reliance on a narrower set of existing knowledge (which may include narrow specialization and related contemporary practices) based on three "use of previous knowledge"-indicators, and risk-avoidant funding structures may have "toward incremental science and away from exploratory projects that are more likely to fail". The study that introduced the "CD index" suggests the overall number of papers has risen while the total of "highly disruptive" papers as measured by the index hasn't (notably, the 1998 discovery of the accelerating expansion of the universe has a CD index of 0). Their results also suggest scientists and inventors "may be struggling to keep up with the pace of knowledge expansion".
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To address potential anti-novelty bias, researchers have proposed novelty metrics that measure whether a study makes novel combinations of cited journals while accounting for methodological difficulty. Approaches include textual analysis and comparative bibliographic methods." Other approaches include pro-actively funding risky projects. (see above)
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=== Topic mapping ===
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Science maps could show main interrelated topics within a certain scientific domain, their change over time, and their key actors (researchers, institutions, journals). They may help find factors determine the emergence of new scientific fields and the development of interdisciplinary areas and could be relevant for science policy purposes. (see above) Theories of scientific change could guide "the exploration and interpretation of visualized intellectual structures and dynamic patterns". The maps can show the intellectual, social or conceptual structure of a research field. Beyond visual maps, expert survey-based studies and similar approaches could identify understudied or neglected societally important areas, topic-level problems (such as stigma or dogma), or potential misprioritizations. Examples of such are studies about policy in relation to public health and the social science of climate change mitigation where it has been estimated that only 0.12% of all funding for climate-related research is spent on such despite the most urgent puzzle at the current juncture being working out how to mitigate climate change, whereas the natural science of climate change is already well established.
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There are also studies that map a scientific field or a topic such as the study of the use of research evidence in policy and practice, partly using surveys.
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=== Controversies, current debates and disagreement ===
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instance: "kb-cron"
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Some research is investigating scientific controversy or controversies, and may identify currently ongoing major debates (e.g. open questions), and disagreement between scientists or studies. One study suggests the level of disagreement was highest in the social sciences and humanities (0.61%), followed by biomedical and health sciences (0.41%), life and earth sciences (0.29%); physical sciences and engineering (0.15%), and mathematics and computer science (0.06%). Such research may also show, where the disagreements are, especially if they cluster, including visually such as with cluster diagrams.
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=== Challenges of interpretation of pooled results ===
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Studies about a specific research question or research topic are often reviewed in the form of higher-level overviews in which results from various studies are integrated, compared, critically analyzed and interpreted. Examples of such works are scientific reviews and meta-analyses. These and related practices face various challenges and are a subject of metascience.
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Various issues with available studies such as, for example, heterogeneity of methods used may lead to faulty conclusions of the meta-analysis.
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=== Knowledge integration and living documents ===
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Various problems require swift integration of new and existing science-based knowledge. Especially setting where there are a large number of loosely related projects and initiatives benefit from a common ground or "commons".
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Evidence synthesis can be applied to important and, notably, both relatively urgent and certain global challenges: "climate change, energy transitions, biodiversity loss, antimicrobial resistance, poverty eradication and so on". It was suggested that a better system would keep summaries of research evidence up to date via living systematic reviews – e.g. as living documents. While the number of scientific papers and data (or information and online knowledge) has risen substantially, the number of published academic systematic reviews has risen from "around 6,000 in 2011 to more than 45,000 in 2021". An evidence-based approach is important for progress in science, policy, medical and other practices. For example, meta-analyses can quantify what is known and identify what is not yet known and place "truly innovative and highly interdisciplinary ideas" into the context of established knowledge which may enhance their impact. (see above)
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=== Factors of success and progress ===
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It has been hypothesized that a deeper understanding of factors behind successful science could "enhance prospects of science as a whole to more effectively address societal problems".
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==== Novel ideas and disruptive scholarship ====
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Two metascientists reported that "structures fostering disruptive scholarship and focusing attention on novel ideas" could be important as in a growing scientific field citation flows disproportionately consolidate to already well-cited papers, possibly slowing and inhibiting canonical progress. A study concluded that to enhance impact of truly innovative and highly interdisciplinary novel ideas, they should be placed in the context of established knowledge.
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==== Mentorship, partnerships and social factors ====
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Other researchers reported that the most successful – in terms of "likelihood of prizewinning, National Academy of Science (NAS) induction, or superstardom" – protégés studied under mentors who published research for which they were conferred a prize after the protégés' mentorship. Studying original topics rather than these mentors' research-topics was also positively associated with success. Highly productive partnerships are also a topic of research – e.g. "super-ties" of frequent co-authorship of two individuals who can complement skills, likely also the result of other factors such as mutual trust, conviction, commitment and fun.
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==== Study of successful scientists and processes, general skills and activities ====
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The emergence or origin of ideas by successful scientists is also a topic of research, for example reviewing existing ideas on how Mendel made his discoveries, – or more generally, the process of discovery by scientists. Scientific discovery is fundamentally collaborative, involving the appropriation, modification, and combination of existing ideas rather than isolated innovation. Few studies examine the cognitive processes, information practices, and digital workflows that characterize productive researchers.
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==== Labor advantage ====
|
||||
A study theorized that in many disciplines, larger scientific productivity or success by elite universities can be explained by their larger pool of available funded laborers. The study found that university prestige was only associated with higher productivity for faculty with group members, not for faculty publishing alone or the group members themselves. This is presented as evidence that the outsize productivity of elite researchers is not from a more rigorous selection of talent by top universities, but from labor advantages accrued through greater access to funding and the attraction of prestige to graduate and postdoctoral researchers.
|
||||
|
||||
==== Ultimate impacts ====
|
||||
Success in science (as indicated in tenure review processes) is often measured in terms of metrics like citations, not in terms of the eventual or potential impact on lives and society, which awards (see above) sometimes do. Problems with such metrics are roughly outlined elsewhere in this article and include that reviews replace citations to primary studies. There are also proposals for changes to the academic incentives systems that increase the recognition of societal impact in the research process.
|
||||
|
||||
==== Progress studies ====
|
||||
A proposed field of "Progress Studies" could investigate how scientists (or funders or evaluators of scientists) should be acting, "figuring out interventions" and study progress itself. The field was explicitly proposed in a 2019 essay and described as an applied science that prescribes action.
|
||||
48
data/en.wikipedia.org/wiki/Metascience-5.md
Normal file
48
data/en.wikipedia.org/wiki/Metascience-5.md
Normal file
@ -0,0 +1,48 @@
|
||||
---
|
||||
title: "Metascience"
|
||||
chunk: 6/7
|
||||
source: "https://en.wikipedia.org/wiki/Metascience"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:19.902160+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
==== As and for acceleration of progress ====
|
||||
A study suggests that improving the way science is done could accelerate the rate of scientific discovery and its applications which could be useful for finding urgent solutions to humanity's problems, improve humanity's conditions, and enhance understanding of nature. Metascientific studies can seek to identify aspects of science that need improvement, and develop ways to improve them. If science is accepted as the fundamental engine of economic growth and social progress, this could raise "the question of what we – as a society – can do to accelerate science, and to direct science toward solving society's most important problems." One author clarified that funding science requires diverse approaches rather than a single model. DARPA models, curiosity-driven research, peer-champion mechanisms, and other approaches each have merit and application in different contexts. Nevertheless, evaluation of them can help build knowledge of what works or works best.
|
||||
|
||||
== Reforms ==
|
||||
Meta-research identifying flaws in scientific practice has inspired reforms in science. These reforms seek to address and fix problems in scientific practice which lead to low-quality or inefficient research.
|
||||
A 2015 study lists "fragmented" efforts in meta-research.
|
||||
|
||||
=== Pre-registration ===
|
||||
|
||||
The practice of registering a scientific study before it is conducted is called pre-registration. It arose as a means to address the replication crisis. Pregistration requires the submission of a registered report, which is then accepted for publication or rejected by a journal based on theoretical justification, experimental design, and the proposed statistical analysis. Pre-registration of studies serves to prevent publication bias (e.g. not publishing negative results), reduce data dredging, and increase replicability.
|
||||
|
||||
=== Reporting standards ===
|
||||
|
||||
Studies showing poor consistency and quality of reporting have demonstrated the need for reporting standards and guidelines in science, which has led to the rise of organisations that produce such standards, such as CONSORT (Consolidated Standards of Reporting Trials) and the EQUATOR Network.
|
||||
The EQUATOR network (Enhancing the QUAlity and Transparency Of health Research) is an international initiative that develops and promotes reporting guidelines for health research to improve the quality and reliability of medical literature. The EQUATOR Network was established with the goals of raising awareness of the importance of good reporting of research, assisting in the development, dissemination and implementation of reporting guidelines for different types of study designs, monitoring the status of the quality of reporting of research studies in the health sciences literature, and conducting research relating to issues that impact the quality of reporting of health research studies. The Network acts as an "umbrella" organisation, bringing together developers of reporting guidelines, medical journal editors and peer reviewers, research funding bodies, and other key stakeholders with a mutual interest in improving the quality of research publications and research itself.
|
||||
|
||||
== Applications ==
|
||||
|
||||
=== Information and communications technologies ===
|
||||
|
||||
Metascience is used in the creation and improvement of technical systems (ICTs) and standards of science evaluation, incentivation, communication, commissioning, funding, regulation, production, management, use and publication. Such can be called "applied metascience" and may seek to explore ways to increase quantity, quality and positive impact of research. One example for such is the development of alternative metrics.
|
||||
|
||||
==== Study screening and feedback ====
|
||||
Various websites or tools also identify inappropriate studies and/or enable feedback such as PubPeer, Cochrane's Risk of Bias Tool and RetractionWatch. Medical and academic disputes are as ancient as antiquity and a study calls for research into "constructive and obsessive criticism" and into policies to "help strengthen social media into a vibrant forum for discussion, and not merely an arena for gladiator matches". Feedback to studies can be found via altmetrics which is often integrated at the website of the study – most often as an embedded Altmetrics badge – but may often be incomplete, such as only showing social media discussions that link to the study directly but not those that link to news reports about the study. (see above)
|
||||
|
||||
==== Tools used, modified, extended or investigated ====
|
||||
Tools may get developed with metaresearch or can be used or investigated by such. Notable examples may include:
|
||||
|
||||
Search engines like Google Scholar are used to find studies and the notification service Google Alerts enables notifications for new studies matching specified search terms. Scholarly communication infrastructure includes search databases.
|
||||
Shadow library Sci-hub is a topic of metascience
|
||||
Personal knowledge management systems for research-, knowledge- and task management, such as saving information in organized ways with multi-document text editors for future use Such systems could be described as part of, along with e.g. Web browser (tabs-addons etc) and search software, "mind-machine partnerships" that could be investigated by metascience for how they could improve science.
|
||||
Scholia – efforts to open scholarly publication metadata and use it via Wikidata. (see above)
|
||||
Various software enables common metascientific practices such as bibliometric analysis.
|
||||
|
||||
==== Development ====
|
||||
According to a study "a simple way to check how often studies have been repeated, and whether or not the original findings are confirmed" is needed due to reproducibility issues in science. A study suggests a tool for screening studies for early warning signs for research fraud.
|
||||
|
||||
=== Medicine ===
|
||||
52
data/en.wikipedia.org/wiki/Metascience-6.md
Normal file
52
data/en.wikipedia.org/wiki/Metascience-6.md
Normal file
@ -0,0 +1,52 @@
|
||||
---
|
||||
title: "Metascience"
|
||||
chunk: 7/7
|
||||
source: "https://en.wikipedia.org/wiki/Metascience"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:19.902160+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
Clinical research in medicine is often of low quality, and many studies cannot be replicated. An estimated 85% of research funding is wasted. Additionally, the presence of bias affects research quality. The pharmaceutical industry exerts substantial influence on the design and execution of medical research. Conflicts of interest are common among authors of medical literature and among editors of medical journals. While almost all medical journals require their authors to disclose conflicts of interest, editors are not required to do so. Financial conflicts of interest have been linked to higher rates of positive study results. In antidepressant trials, pharmaceutical sponsorship is the best predictor of trial outcome.
|
||||
Blinding is another focus of meta-research, as error caused by poor blinding is a source of experimental bias. Blinding is not well reported in medical literature, and widespread misunderstanding of the subject has resulted in poor implementation of blinding in clinical trials. Furthermore, failure of blinding is rarely measured or reported. Research showing the failure of blinding in antidepressant trials has led some scientists to argue that antidepressants are no better than placebo. In light of meta-research showing failures of blinding, CONSORT standards recommend that all clinical trials assess and report the quality of blinding.
|
||||
Studies have shown that systematic reviews of existing research evidence are sub-optimally used in planning a new research or summarizing the results. Cumulative meta-analyses of studies evaluating the effectiveness of medical interventions have shown that many clinical trials could have been avoided if a systematic review of existing evidence was done prior to conducting a new trial. For example, Lau et al. analyzed 33 clinical trials (involving 36974 patients) evaluating the effectiveness of intravenous streptokinase for acute myocardial infarction. Their cumulative meta-analysis demonstrated that 25 of 33 trials could have been avoided if a systematic review was conducted prior to conducting a new trial. In other words, randomizing 34542 patients was potentially unnecessary. One study analyzed 1523 clinical trials included in 227 meta-analyses and concluded that "less than one quarter of relevant prior studies" were cited. They also confirmed earlier findings that most clinical trial reports do not present systematic review to justify the research or summarize the results.
|
||||
Many treatments used in modern medicine have been proven to be ineffective, or even harmful. A 2007 study by John Ioannidis found that it took an average of ten years for the medical community to stop referencing popular practices after their efficacy was unequivocally disproven.
|
||||
|
||||
=== Psychology ===
|
||||
|
||||
Metascience has revealed significant problems in psychological research. The field suffers from high bias, low reproducibility, and widespread misuse of statistics. The replication crisis affects psychology more strongly than any other field; as many as two-thirds of highly publicized findings may be impossible to replicate. Meta-research finds that 80-95% of psychological studies support their initial hypotheses, which strongly implies the existence of publication bias.
|
||||
The replication crisis has led to renewed efforts to re-test important findings. In response to concerns about publication bias and p-hacking, more than 140 psychology journals have adopted result-blind peer review, in which studies are pre-registered and published without regard for their outcome. An analysis of these reforms estimated that 61 percent of result-blind studies produce null results, in contrast with 5 to 20 percent in earlier research. This analysis shows that result-blind peer review substantially reduces publication bias.
|
||||
Psychologists routinely confuse statistical significance with practical importance, enthusiastically reporting great certainty in unimportant facts. Some psychologists have responded with an increased use of effect size statistics, rather than sole reliance on the p values.
|
||||
|
||||
=== Physics ===
|
||||
Richard Feynman noted that estimates of physical constants were closer to published values than would be expected by chance. This was believed to be the result of confirmation bias: results that agreed with existing literature were more likely to be believed, and therefore published. Physicists now implement blinding to prevent this kind of bias.
|
||||
|
||||
=== Computer Science ===
|
||||
Web measurement studies are essential for understanding the workings of the modern Web, particularly in the fields of security and privacy. However, these studies often require custom-built or modified crawling setups, leading to a plethora of analysis tools for similar tasks. In a paper by Nurullah Demir et al., the authors surveyed 117 recent research papers to derive best practices for Web-based measurement studies and establish criteria for reproducibility and replicability. They found that experimental setups and other critical information for reproducing and replicating results are often missing. In a large-scale Web measurement study on 4.5 million pages with 24 different measurement setups, the authors demonstrated the impact of slight differences in experimental setups on the overall results, emphasizing the need for accurate and comprehensive documentation.
|
||||
|
||||
== Organizations and institutes ==
|
||||
|
||||
There are several organizations and universities across the globe which work on meta-research – these include the Meta-Research Innovation Center at Berlin, the Meta-Research Innovation Center at Stanford, the Meta-Research Center at Tilburg University, the Meta-research & Evidence Synthesis Unit, The George Institute for Global Health at India and Center for Open Science. Organizations that develop tools for metascience include OurResearch, Center for Scientific Integrity and altmetrics companies. There is an annual Metascience Conference hosted by the Association for Interdisciplinary Meta-Research and Open Science (AIMOS) and biannual conference hosted by the Centre for Open Science.
|
||||
|
||||
== See also ==
|
||||
|
||||
== References ==
|
||||
|
||||
== Further reading ==
|
||||
Bonett, D.G. (2021). Design and analysis of replication studies. Organizational Research Methods, 24, 513-529. https://doi.org/10.1177/1094428120911088
|
||||
Lydia Denworth, "A Significant Problem: Standard scientific methods are under fire. Will anything change?", Scientific American, vol. 321, no. 4 (October 2019), pp. 62–67.
|
||||
"The use of p values for nearly a century [since 1925] to determine statistical significance of experimental results has contributed to an illusion of certainty and [to] reproducibility crises in many scientific fields. There is growing determination to reform statistical analysis... Some [researchers] suggest changing statistical methods, whereas others would do away with a threshold for defining "significant" results." (p. 63.)
|
||||
Harris, Richard (2017). Rigor Mortis: How Sloppy Science Creates Worthless Cures, Crushes Hopes, and Wastes Billions. Basic Books. ISBN 978-0-465-09791-3.
|
||||
Fortunato, Santo; Bergstrom, Carl T.; et al. (2 March 2018). "Science of science". Science. 359 (6379) eaao0185. Bibcode:2018Sci...359o0185F. doi:10.1126/science.aao0185. PMC 5949209. PMID 29496846.
|
||||
|
||||
== External links ==
|
||||
|
||||
=== Journals ===
|
||||
Minerva: A Journal of Science, Learning and Policy
|
||||
Research Integrity and Peer Review
|
||||
Research Policy
|
||||
Science and Public Policy
|
||||
|
||||
=== Conferences ===
|
||||
Annual Metascience Conference
|
||||
@ -0,0 +1,51 @@
|
||||
---
|
||||
title: "Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals"
|
||||
chunk: 1/1
|
||||
source: "https://en.wikipedia.org/wiki/Scanning_Habitable_Environments_with_Raman_and_Luminescence_for_Organics_and_Chemicals"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:09.222442+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is an ultraviolet Raman spectrometer that uses fine-scale imaging and an ultraviolet (UV) laser to determine fine-scale mineralogy, and detect organic compounds designed for the Perseverance rover as part of the Mars 2020 mission. It was constructed at the Jet Propulsion Laboratory with major subsystems being delivered from Malin Space Science Systems and Los Alamos National Laboratory.
|
||||
SHERLOC has a calibration target with possible Mars suit materials, and it will measure how they change over time in the Martian surface environment.
|
||||
|
||||
|
||||
== Goals ==
|
||||
According to a 2017 Universities Space Research Association (USRA) report:
|
||||
|
||||
The goals of the SHERLOC investigation are to:
|
||||
Assess the habitability potential of a sample and its aqueous history.
|
||||
Assess the availability of key elements and energy source for life (C, H, N, O, P, S etc.).
|
||||
Determine if there are potential biosignatures preserved in Martian rocks and outcrops.
|
||||
Provide organic and mineral analysis for selective sample caching.
|
||||
To do this SHERLOC does the following:
|
||||
|
||||
Detects and classifies organics and astrobiologically relevant minerals on the surface and near subsurface of Mars.
|
||||
Bulk organic sensitivity of 10-5 to 10-6 w/w over a 7 x 7 mm spot.
|
||||
Fine scale organic sensitivity of 10-2 to 10-4 w/w spatially resolved at < 100 μm.
|
||||
Astrobiologically Relevant Mineral (ARM) detection and classification to < 100 μm resolution.
|
||||
|
||||
|
||||
== Construction ==
|
||||
|
||||
There are three locations on the rover where SHERLOC components are located. The SHERLOC Turret Assembly (STA) is mounted at the end of the rover arm. The STA contains spectroscopy and imaging components. The SHERLOC Body Assembly (SBA) is located on the rover chassis and acts as the interface between the STA and the Mars 2020 rover. The SBA deals with command and data handling, along with power distribution. The SHERLOC Calibration Target (SCT) is located on the front of the rover chassis and hold spectral standards.
|
||||
SHERLOC consists of both imaging and spectroscopic elements. It has two imaging components consisting of heritage hardware from the MSL MAHLI instrument. The Wide Angle Topographic Sensor for Operations and eNgineering (WATSON) is a built to print re-flight that can generate color images over multiple scales. The other, Autofocus Context Imager (ACI), acts as the mechanism that allows the instrument to get a contextual image of a sample and to autofocus the laser spot for the spectroscopic part of the SHERLOC investigation.
|
||||
|
||||
For Spectroscopy, it utilizes a NeCu laser to generate UV photons (248.6 nm) which can generate characteristic Raman and fluorescence photons from a scientifically interesting sample. The deep UV laser is co-boresighted to a context imager and integrated into an autofocusing/scanning optical system that allows correlation of spectral signatures to surface textures, morphology and visible features. The context imager has a spatial resolution of 30 μm and currently is designed to operate in the 400-500 nm wavelength range.
|
||||
|
||||
|
||||
== Results from Mars ==
|
||||
|
||||
Over the course of three years, SHERLOC and WATSON have been successfully collecting spectra and images of minerals and organics on the surface of Mars. Utilizing WATSON and ACI images, there was confirmation that the Jezero Crater floor consists of aqueously altered mafic material with various igneous origins. In addition, WATSON has been used to collect selfies of the Perseverance rover and the Ingenuity helicopter. Recently, it successfully sealed and stored the first two rock samples from Mars. Because of it, we now know that these rocks derived from a volcanic environment, and that there was liquid water there in Mars's past, that formed salts that SHERLOC has seen.
|
||||
|
||||
|
||||
== See also ==
|
||||
|
||||
|
||||
== References ==
|
||||
|
||||
|
||||
== External links ==
|
||||
Mars 2020 Mission - Home Page - NASA/JPL
|
||||
25
data/en.wikipedia.org/wiki/Scintillating_bolometer-0.md
Normal file
25
data/en.wikipedia.org/wiki/Scintillating_bolometer-0.md
Normal file
@ -0,0 +1,25 @@
|
||||
---
|
||||
title: "Scintillating bolometer"
|
||||
chunk: 1/1
|
||||
source: "https://en.wikipedia.org/wiki/Scintillating_bolometer"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:10.405931+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
A scintillating bolometer (or luminescent bolometer) is a scientific instrument using particle physics in the search for events with low energy deposition. These events could include dark matter, low energy solar neutrinos, double beta decay or rare radioactive decay. It works by simultaneously measuring both the light pulse and heat pulse generated by a particle interaction within its internal scintillator crystal. The device was originally proposed by L. Gonzalez-Mestres and D. Perret-Gallix (LAPP, IN2P3/CNRS)
|
||||
In their rapporteur contribution to the Proceedings of the XXIV International Conference on High-Energy Physics, Munich, August 1988, Gonzalez-Mestres and Perret-Gallix wrote :
|
||||
Perhaps bolometry should in some cases be combined with other detection techniques (luminescence?) in order to produce a primary fast signal as timing strobe. If light is used as a complementary signature, particle identification can be achieved through the heat-light ratio, where nucleus recoil is expected to be less luminescent than ionizing particles. The success of such a development would open the way to unprecedented achievements in background rejection for rare event experiments.
|
||||
Further explanations, including a description of the detector and possible applications incorporating in particular BGO and tungstates, were given by these authors in other papers such as their contribution to the March 1989 Moriond Meeting (pages 16–18).
|
||||
The luminescent bolometer has since then been developed by scientists from several groups, including the CNRS Institut d'Astrophysique Spatiale and University of Zaragoza collaboration in view of the proposed ROSEBUD particle detector experiment in the Canfranc Underground Laboratory. Rosebud uses a bismuth germanate (Bi4Ge3O12, "BGO") detector crystal.
|
||||
The CRESST collaboration is currently using the same kind of device with CaWO4 crystals in an experiment to detect dark matter at Laboratori Nazionali del Gran Sasso.
|
||||
|
||||
|
||||
== References ==
|
||||
|
||||
|
||||
== External links ==
|
||||
"Detection of Low Energy Solar Neutrinos and Galactic Dark Matter with Crystal Scintillators". (August 1988), published in Nuclear Instruments and Methods in Physics Research (July 1999).
|
||||
"Prototype Developed To Detect Dark Matter". Science Daily. 2009-09-25.
|
||||
"BGO Scintillating Bolometer: Its application in dark matter experiments" (PDF).
|
||||
@ -0,0 +1,68 @@
|
||||
---
|
||||
title: "Sensitive high-resolution ion microprobe"
|
||||
chunk: 1/1
|
||||
source: "https://en.wikipedia.org/wiki/Sensitive_high-resolution_ion_microprobe"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:11.541397+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
The sensitive high-resolution ion microprobe (also sensitive high mass-resolution ion microprobe or SHRIMP) is a large-diameter, double-focusing secondary ion mass spectrometer (SIMS) sector instrument that was produced by Australian Scientific Instruments in Canberra, Australia and now has been taken over by Chinese company Dunyi Technology Development Co. (DTDC) in Beijing. Similar to the IMS 1270-1280-1300 large-geometry ion microprobes produced by CAMECA, Gennevilliers, France and like other SIMS instruments, the SHRIMP microprobe bombards a sample under vacuum with a beam of primary ions that sputters secondary ions that are focused, filtered, and measured according to their energy and mass.
|
||||
The SHRIMP is primarily used for geological and geochemical applications. It can measure the isotopic and elemental abundances in minerals at a 10 to 30 μm-diameter scale and with a depth resolution of 1–5 μm. Thus, SIMS method is well-suited for the analysis of complex minerals, as often found in metamorphic terrains, some igneous rocks, and for relatively rapid analysis of statistical valid sets of detrital minerals from sedimentary rocks. The most common application of the instrument is in uranium–thorium–lead geochronology, although the SHRIMP can be used to measure some other isotope ratio measurements (e.g., δ7Li or δ11B) and trace element abundances.
|
||||
|
||||
|
||||
== History and scientific impact ==
|
||||
The SHRIMP originated in 1973 with a proposal by Prof. Bill Compston, trying to build an ion microprobe at the Research School of Earth Sciences of the Australian National University that exceeded the sensitivity and resolution of ion probes available at the time in order to analyse individual mineral grains. Optic designer Steve Clement based the prototype instrument (now referred to as 'SHRIMP-I') on a design by Matsuda which minimised aberrations in transmitting ions through the various sectors. The instrument was built from 1975 and 1977 with testing and redesigning from 1978. The first successful geological applications occurred in 1980.
|
||||
The first major scientific impact was the discovery of Hadean (>4000 million year old) zircon grains at Mt. Narryer in Western Australia and then later at the nearby Jack Hills. These results and the SHRIMP analytical method itself were initially questioned but subsequent conventional analysis were partially confirmed. SHRIMP-I also pioneered ion microprobe studies of titanium, hafnium and sulfur isotopic systems.
|
||||
Growing interest from commercial companies and other academic research groups, notably Prof. John de Laeter of Curtin University (Perth, Western Australia), led to the project in 1989 to build a commercial version of the instrument, the SHRIMP-II, in association with ANUTECH, the Australian National University's commercial arm. Refined ion optic designs in the mid-1990s prompted development and construction of the SHRIMP-RG (Reverse Geometry) with improved mass resolution. Further advances in design have also led to multiple ion collection systems (already introduced in the market by a French company years before), negative-ion stable isotope measurements and on-going work in developing a dedicated instrument for light stable isotopes.
|
||||
Fifteen SHRIMP instruments have now been installed around the world and SHRIMP results have been reported in more than 2000 peer reviewed scientific papers. SHRIMP is an important tool for understanding early Earth history having analysed some of the oldest terrestrial material including the Acasta Gneiss and further extending the age of zircons from the Jack Hills and the oldest impact crater on the planet. Other significant milestones include the first U/Pb ages for lunar zircon and Martian apatite dating. More recent uses include the determination of Ordovician sea surface temperature, the timing of snowball Earth events and development of stable isotope techniques.
|
||||
|
||||
|
||||
== Design and operation ==
|
||||
|
||||
|
||||
=== Primary column ===
|
||||
In a typical U–Pb geochronology analytical mode, a beam of (O2)1− primary ions are produced from a high-purity oxygen gas discharge in the hollow Ni cathode of a duoplasmatron. The ions are extracted from the plasma and accelerated at 10 kV. The primary column uses Köhler illumination to produce a uniform ion density across the target spot. The spot diameter can vary from ~5 μm to over 30 μm as required. Typical ion beam density on the sample is ~10 pA/μm2 and an analysis of 15–20 minutes creates an ablation pit of less than 1 μm.
|
||||
|
||||
|
||||
=== Sample chamber ===
|
||||
The primary beam is 45° incident to the plane of the sample surface with secondary ions extracted at 90° and accelerated at 10 kV. Three quadrupole lenses focus the secondary ions onto a source slit and the design aims to maximise transmission of ions rather than preserving an ion image unlike other ion probe designs. A Schwarzschild objective lens provides reflected-light direct microscopic viewing of the sample during analysis.
|
||||
|
||||
|
||||
=== Electrostatic analyzer ===
|
||||
The secondary ions are filtered and focussed according to their kinetic energy by a 1272 mm radius 90° electrostatic sector. A mechanically-operated slit provides fine-tuning of the energy spectrum transmitted into the magnetic sector and an electrostatic quadrupole lens is used to reduce aberrations in transmitting the ions to the magnetic sector.
|
||||
|
||||
|
||||
=== Magnetic sector ===
|
||||
The electromagnet has a 1000 mm radius through 72.5° to focus the secondary ions according to their mass/charge ratio according to the principles of the Lorentz force. Essentially, the path of a less massive ion will have a greater curvature through the magnetic field than the path of a more massive ion. Thus, altering the current in the electromagnet focuses a particular mass species at the detector.
|
||||
|
||||
|
||||
=== Detectors ===
|
||||
The ions pass through a collector slit in the focal plane of the magnetic sector and the collector assembly can be moved along an axis to optimise the focus of a given isotopic species. In typical U-Pb zircon analysis, a single secondary electron multiplier is used for ion counting.
|
||||
|
||||
|
||||
=== Vacuum system ===
|
||||
Turbomolecular pumps evacuate the entire beam path of the SHRIMP to maximise transmission and reduce contamination. The sample chamber also employs a cryopump to trap contaminants, especially water. Typical pressures inside the SHRIMP are between ~7 × 10−9 mbar in the detector and ~1 × 10−6 mbar in the primary column (with oxygen duoplasmatron source).
|
||||
|
||||
|
||||
=== Mass resolution and sensitivity ===
|
||||
In normal operations, the SHRIMP achieves mass resolution of 5000 with sensitivity >20 counts/sec/ppm/nA for lead from zircon.
|
||||
|
||||
|
||||
== Applications ==
|
||||
|
||||
|
||||
=== Isotope dating ===
|
||||
For U-Th-Pb geochronology a beam of primary ions (O2)1− are accelerated and collimated towards the target where it sputters "secondary" ions from the sample. These secondary ions are accelerated along the instrument where the various isotopes of uranium, lead and thorium are measured successively, along with reference peaks for Zr2O+, ThO+ and UO+. Since the sputtering yield differs between ion species and relative sputtering yield increases or decreases with time depending on the ion species (due to increasing crater depth, charging effects and other factors), the measured relative isotopic abundances do not relate to the real relative isotopic abundances in the target. Corrections are determined by analysing unknowns and reference material (matrix-matched material of known isotopic composition), and determining an analytical-session specific calibration factor.
|
||||
|
||||
|
||||
== SHRIMP instruments around the world ==
|
||||
|
||||
|
||||
== References ==
|
||||
|
||||
|
||||
== External links ==
|
||||
Founding SHRIMP Lab at Australian National University
|
||||
Australian Scientific Instruments
|
||||
55
data/en.wikipedia.org/wiki/Sira_(notified_body)-0.md
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55
data/en.wikipedia.org/wiki/Sira_(notified_body)-0.md
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@ -0,0 +1,55 @@
|
||||
---
|
||||
title: "Sira (notified body)"
|
||||
chunk: 1/1
|
||||
source: "https://en.wikipedia.org/wiki/Sira_(notified_body)"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:12.660143+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
Sira is a UK-based notified body, specialising in ATEX, IECEX and North American product approvals.
|
||||
|
||||
|
||||
== Foundation ==
|
||||
Sira began life as the British Scientific Instrument Research Association (BSIRA). It was founded in 1918 by a Committee of the Privy Council for the promotion of scientific and industrial research and supported by the DSIR. The first members of the association were representatives of the optical industry, but these were joined in the same year by the electrical scientific instrument, electromedical, and X-ray industries. Its first director of research was Sir Herbert Jackson (1863–1936).
|
||||
BSIRA's London headquarters were destroyed in the Second World War and, in 1947, the association moved to a site in South Hill, Chislehurst, a Grade II Listed former private house called 'Sitka' By the 1960s, the association had become better-known as 'Sira'. It evolved into a group of British engineering companies, based in south London, that designed test equipment and provided calibration services.
|
||||
|
||||
|
||||
== Fate ==
|
||||
In 2006, Sira Test and Certification Ltd, Sira Defence and Security, and Sira Environmental were owned by Volveré plc. In July 2009, Volvere sold Sira Test and Certification Ltd, Sira Certification Service and Sira Environmental Ltd to CSA International.
|
||||
|
||||
|
||||
== Similar organizations ==
|
||||
Baseefa — a similar organization in the UK
|
||||
Canadian Standards Association a similar organization in Canada; also serves as a competitive alternative for USA products
|
||||
ETL SEMKO — a competing testing laboratory, part of Intertek; based in London, UK
|
||||
IAPMO R&T — certification body based in Ontario, California, USA
|
||||
MET Laboratories, Inc. — testing laboratory based in Baltimore, Maryland, USA
|
||||
NTA Inc — certification agency based in Nappanee, Indiana, USA
|
||||
NCC — a similar Brazilian approvals organisation
|
||||
TÜV — a similar German approvals organisation
|
||||
Underwriters Laboratories — testing organization, based in Northbrook, Illinois, USA
|
||||
TRaC Global — a test laboratory and certification body based in the UK
|
||||
|
||||
|
||||
== See also ==
|
||||
ANSI
|
||||
Consumers Union
|
||||
Good Housekeeping Seal
|
||||
NEMKO
|
||||
Product certification
|
||||
Quality control
|
||||
RoHS
|
||||
Safety engineering
|
||||
|
||||
|
||||
== References ==
|
||||
|
||||
|
||||
== External links ==
|
||||
Sira Certification
|
||||
Sira Consulting Ltd
|
||||
Sira Defence and Security
|
||||
Sira Defence and Security
|
||||
CSA International
|
||||
30
data/en.wikipedia.org/wiki/Spectronic_20-0.md
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30
data/en.wikipedia.org/wiki/Spectronic_20-0.md
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@ -0,0 +1,30 @@
|
||||
---
|
||||
title: "Spectronic 20"
|
||||
chunk: 1/2
|
||||
source: "https://en.wikipedia.org/wiki/Spectronic_20"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:13.785145+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
The Spectronic 20 is a brand of single-beam spectrophotometer, designed to operate in the visible spectrum across a wavelength range of 340 nm to 950 nm, with a spectral bandpass of 20 nm. It is designed for quantitative absorption measurement at single wavelengths. Because it measures the transmittance or absorption of visible light through a solution, it is sometimes referred to as a colorimeter. The name of the instrument is a trademark of the manufacturer.
|
||||
Developed by Bausch & Lomb and launched in 1953, the Spectronic 20 was the first low-cost spectrophotometer. It rapidly became an industry standard due to its low cost, durability and ease of use, and has been referred to as an "iconic lab spectrophotometer". Approximately 600,000 units were sold over its nearly 60 year production run. It has been the most widely used spectrophotometer worldwide. Production was discontinued in 2011 when it was replaced by the Spectronic 200, but the Spectronic 20 is still in common use. It is sometimes referred to as the "Spec 20".
|
||||
|
||||
== Design ==
|
||||
|
||||
The Bausch & Lomb Spectronic 20 colorimeter uses a diffraction grating monochromator combined with a system for the detection, amplification, and measurement of light wavelengths in the 340 nm to 950 nm range.
|
||||
|
||||
As shown in the schematic optical diagram (see left), polychromatic light from a source in the system passes through lenses which are reflected and dispersed by the diffraction grating to restrict the range of light wavelengths. This restricted range of wavelengths is then passed through the sample to be measured. The intensity of the transmitted light is determined by a phototube detector. Mechanical movement of the diffraction grating by means of the cam attached to the wavelength control enables the user to select for various wavelengths. This is the "λ knob", wherein λ refers to wavelength of light used for the measurement.
|
||||
|
||||
== Quantitative measurements ==
|
||||
|
||||
Many substances absorb light in the ultraviolet - visible light range. Absorption at any particular wavelength in the ultraviolet visible range is proportional to the concentration of the substances in the solution or other medium, in accord with the Beer–Lambert relationship. In a practical sense, the Beer–Lambert relationship can be stated as:
|
||||
|
||||
A = ε x l x c
|
||||
|
||||
in which A is the absorbance measured by the instrument, ε is the molar absorption coefficient of the sample, l is the pathlength of the light beam through the sample, and c is the concentration of the substance in the solution or medium. The Spectronic 20 is thereby commonly used for quantitative determination of the concentration of a substance of interest. The Spectronic 20 measures the absorbance of light at a pre-determined concentration, and the concentration is calculated from the Beer–Lambert relationship.
|
||||
The absorbance of the light is the base 10 logarithm of the ratio of the Transmittance of the pure solvent to the transmittance of the sample, and so the two absorbance and transmittance can be interconverted. Either transmittance or absorbance can therefore be plotted versus concentration using measurements from the Spectronic 20. Plotting a curve using percent transmittance of light yields an exponential curve. However, absorbance is linearly related to concentration, and so absorbance is often preferred for plotting a standard curve. This type of standard curve relates the concentration of the solution (on the x-axis) to measures of its absorbance (y-axis).
|
||||
To obtain such a curve, a series of dilutions of known concentration of a solution are prepared and readings are obtained for each of the dilutions (see plot at left). In this plot, the slope of the line is the product ε x l. By measuring a series of standards and creating the standard curve, it is possible to quantify the amount or concentration of a substance within a sample by determining the absorbance on the Spec 20 and finding the corresponding concentration on the calibration curve. Alternatively, the logarithm of percent transmittance can be plotted versus concentration to create a standard curve using the same procedure.
|
||||
The absorbance measured by the Spectronic 20 is the sum of the absorbance of each of the constituents of the solution. Therefore, the Spectronic 20 can be used to analyze more complex solutions. For example, if a sample solution has two light-absorbing compounds in it, then the user performs measurements at two different wavelengths and constructs standard curves for each compound. Then the concentration of each compound can be calculated algebraically.
|
||||
The Spectronic 20 can be used for turbidimetric measurements. In microbiological work, the turbidity of a liquid culture of bacterial cells relates to the cell count, and OD600 measurements can be conducted for this purpose using the Spectronic 20. Likewise the turbidity of water suspensions of clays and other particles of size suitable for light scattering can be quantitatively determined by means of a Spectronic 20. In the past, the Spectronic 20 was used for clinical diagnostic purposes.
|
||||
30
data/en.wikipedia.org/wiki/Spectronic_20-1.md
Normal file
30
data/en.wikipedia.org/wiki/Spectronic_20-1.md
Normal file
@ -0,0 +1,30 @@
|
||||
---
|
||||
title: "Spectronic 20"
|
||||
chunk: 2/2
|
||||
source: "https://en.wikipedia.org/wiki/Spectronic_20"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:13.785145+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
== Use ==
|
||||
Before testing a sample, the Spectronic 20 is calibrated using a blank solution, which is the pure solvent that is used in the experimental sample. It is typically water or an organic solvent. In this calibration, the transmittance is set at 100% using the calibration knob of the instrument (the amplifier control knob in the figure at right). The instrument can also optionally be calibrated with a stock solution of a sample at a concentration known to have an absorbance of 2 or else vendor supplied standards, using the light absorption knob in the diagram shown at right. After calibration, the user places a 1/2 inch test tube or cuvette containing the sample solution to be measured into the sample compartment. Calibration is repeated each time the wavelength is changed. It or a standard reference sample is generally used to periodically check for drift. To measure wavelengths above 650 nm, the bottom of the instrument is opened, and a red filter and a red-sensitive photocell is installed.
|
||||
The original design of the Spectronic 20 utilized an analog dial for readout of transmission from 100%T to 1%T (top scale), 0A - 2A (lower scale). Using the original instrument requires manual setting of the wavelength and making readings from a moving-needle analog display.
|
||||
|
||||
== Replacement ==
|
||||
The Spectronic 20D (launched in 1985) and later the 20D+ replaced the analog dial with a red digital LED readout, offering greater precision in the readout, if not greater accuracy in the actual reading. A side-by-side comparison of the features of the 20+ and 20D+ is available in the 2001 operating manual.
|
||||
The Spectronic 20 was replaced by the Spectronic 200 in the Thermo Scientific spectrophotometer product line in 2011. The Spectronic 200 utilizes an array detector and digital control of the measured wavelength, while retaining the characteristic λ knob of the Spec 20 for setting the wavelength. In addition to replicating the user modes of the Spec 20D+ (which it can emulate on a color LCD screen) the Spec 200 accommodates both test-tubes and square cuvettes without needing to install an adapter. Software modes described in the Spectronic 200's specifications include scanning, four wavelength simultaneous measurement, and quantitative analysis with up to four standards, in contrast to the SPEC 20D+ which offered only single point calibration.
|
||||
|
||||
== Product line history ==
|
||||
Originally introduced by Bausch & Lomb in 1953, the product line was sold to Milton Roy in 1985. Milton Roy sold its instrument group to Life Sciences International, renamed Spectronic Instruments, Inc. in 1995. Spectronics Instruments was purchased by Thermo Optek in 1997, renamed Spectronic-Unicam in 2001 and Thermo-Spectronic in 2002. In 2003 the product line was moved to Madison, WI and the brand renamed to Thermo Electron.
|
||||
With the merger of Thermo Electron and Fisher Scientific in 2006 the brand changed to Thermo Scientific, and remained such until the end of the production run. Spectronic 20 instruments found in labs today may bear any of the Bausch and Lomb, Milton Roy, Spectronic, Thermo Electron or Thermo Scientific brand names.
|
||||
|
||||
== Popular culture ==
|
||||
The Spectronic 20 is apparently one of the few lab instruments to remain intact after the destruction of the laboratory in the movie Back to the Future.
|
||||
|
||||
== References ==
|
||||
|
||||
== External links ==
|
||||
Spectronic 20, ChemLab Images and instructions (from Dartmouth College)
|
||||
Manufacturer's SPEC 200 webpage (from current manufacturer)
|
||||
@ -0,0 +1,37 @@
|
||||
---
|
||||
title: "Total Ozone Mapping Spectrometer"
|
||||
chunk: 1/1
|
||||
source: "https://en.wikipedia.org/wiki/Total_Ozone_Mapping_Spectrometer"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:14.947524+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
The Total Ozone Mapping Spectrometer (TOMS) was a NASA satellite instrument, specifically a spectrometer, for measuring the ozone layer. Of the five TOMS instruments which were built, four entered successful orbit. The satellites carrying TOMS instruments were:
|
||||
|
||||
Nimbus 7; launched October 24, 1978. Operated until 1 August 1994. Carried TOMS instrument number 1.
|
||||
Meteor-3-5; launched 15 August 1991. Operated until December 1994. Was the first and last Soviet satellite to carry a USA made instrument. Carried TOMS instrument number 2.
|
||||
ADEOS I; launched 17 August 1996. Operated until 30 June 1997. Mission was cut short by a spacecraft failure.
|
||||
TOMS-Earth Probe; launched on July 2, 1996. Operated until 2 December 2006. Carried TOMS instrument number 3.
|
||||
QuikTOMS; launched 21 September 2001. Suffered launch failure and did not enter orbit.
|
||||
Nimbus 7 and Meteor-3-5 provided global measurements of total column ozone on a daily basis and together provided a complete data set of daily ozone from November 1978 to December 1994. After an eighteen-month period when the program had no on-orbit capability, TOMS-Earth Probe launched on 2 July 1996, followed by ADEOS I. ADEOS I was launched on August 17, 1996, and the TOMS-instrument onboard provided data until the satellite which housed it lost power on June 30, 1997.
|
||||
TOMS-Earth Probe (Total Ozone Mapping Spectrometer - Earth Probe, TOMS-EP, originally just TOMS, COSPAR 1996-037A) was launched on July 2, 1996, from Vandenberg AFB by a Pegasus XL rocket. The satellite project was originally known as TOMS, back in 1989 when it was selected as a SMEX mission in the Explorer program. However, it found no funding as an Explorer mission and transferred to NASA's Earth Probe program, getting funding and becoming TOMS-EP. The small, 295 kg satellite was built for NASA by TRW; the single instrument was the TOMS 3 spectrometer. The satellite had a two-year planned life. TOMS-EP suffered a two-year delay to its launch due to launch failures of the first two Pegasus XL rockets. The launch delays led to alternations in the mission; the satellite was placed in a lower than originally planned orbit to achieve higher resolution and to enable more thorough study of UV-absorbing aerosols in the troposphere. The lower orbit was meant to complement measurements from ADEOS I enabling TOMS-EP to provide supplemental measurements. After ADEOS I failed in orbit, TOMS-EP was boosted to a higher orbit to replace ADEOS I. The transmitter for TOMS-Earth Probe failed on December 2, 2006.
|
||||
The only total failure in the series was QuikTOMS, which was launched on September 21, 2001, on a Taurus rocket from Vandenberg AFB, but did not achieve orbit.
|
||||
Since January 1, 2006, data from the Aura Ozone Monitoring Instrument (OMI) has replaced data from TOMS-Earth Probe. The Ozone Mapping and Profiler Suite on Suomi NPP and NOAA-20 have further continued the data record.
|
||||
|
||||
|
||||
== Gallery ==
|
||||
|
||||
|
||||
== References ==
|
||||
|
||||
|
||||
== External links ==
|
||||
|
||||
TOMS home page
|
||||
TOMS Volcanic Emissions Group
|
||||
|
||||
|
||||
== Further reading ==
|
||||
Bhartia, Pawan Kumar; McPeters, Richard D. (2018). "The discovery of the Antarctic Ozone Hole". Comptes Rendus Geoscience. 350 (7). Elsevier BV: 335–340. Bibcode:2018CRGeo.350..335B. doi:10.1016/j.crte.2018.04.006. hdl:2060/20190002263. ISSN 1631-0713.
|
||||
45
data/en.wikipedia.org/wiki/XyloTron-0.md
Normal file
45
data/en.wikipedia.org/wiki/XyloTron-0.md
Normal file
@ -0,0 +1,45 @@
|
||||
---
|
||||
title: "XyloTron"
|
||||
chunk: 1/1
|
||||
source: "https://en.wikipedia.org/wiki/XyloTron"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:16.064229+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
The XyloTron is an open-source, portable macroscopic wood identification system developed to support supply chain verification and the enforcement of laws against illegal logging. The device uses computer vision wood identification models to classify wood specimens based on their macroscopic anatomy and requires minimal operator training. Designed for use in laboratory and field settings, the system provides a non-destructive method to rapidly identify wood. The system's accuracy depends on the quality of the training data, the breadth and anatomical complexity of woods in the model, and the similarity of unknown samples to those included in the model. Use of the XyloTron is intended to help establish probable cause in cases of possible illegal logging, rather than for high-stakes legal enforcement or forensic confirmation. Microscopic analysis of wood specimens by a wood anatomist may still be required.
|
||||
|
||||
|
||||
== Overview ==
|
||||
The XyloTron system was developed at the United States Department of Agriculture, Forest Service, Forest Products Laboratory in Madison, Wisconsin. Initial conceptual work began in late 2010. The XyloTron uses a laptop or desktop computer for computation and the XyloScope, which is specialized, custom-designed hardware that captures controlled imaging using a scientific-grade digital camera, lens, and lighting array.
|
||||
Unlike traditional wood identification techniques that rely on microscopic analysis by trained experts, the XyloTron uses image-based classification. It captures standardized images of a wood surface using the XyloScope then compares the image of the unknown specimen against a model trained on verified reference specimens. The system’s hardware and software are open source. Models used by the XyloTron are trained using labeled image datasets of known wood species, typically derived from scientific-quality reference collections. Because it is designed to work offline, the XyloTron can be deployed in remote field locations without internet access. Field trials in South America, Southeast Asia, and Africa have demonstrated the system’s utility in identifying timber suspected to be harvested illegally with minimal field agent training.
|
||||
|
||||
The initial design of the XyloScope was published in 2019 with engineering drawings and a bill of materials for the hardware, then was superseded by the 2020 publication of the XyloTron 2.0. The update added UV illumination and variable positioning of the lighting array, a mechanically superior design for focal stability, and freely available software for general imaging, reference imaging, and wood identification. Also included was a bill of materials, design files for the electronics, all 3D files, and an illustrated assembly manual. The XyloTron 2.0 supports imaging woods (or other materials) with UV fluorescence, as well as macroscopic imaging of charcoal for computer vision wood identification.
|
||||
Research using the XyloTron focused first on collaborative work developing wood identification models for specific regions. or groups of endangered or related species. Subsequently, scientists explored how much “noise” these models could tolerate and how to build highly accurate, larger models, for example, to cover North American commercial hardwoods. Current work is focused primarily on extracting wood anatomical data from XyloTron image datasets.
|
||||
|
||||
|
||||
== XyloPhone ==
|
||||
|
||||
The cost for a XyloTron unit is too high for many field deployment/inspection contexts. To address this cost concern, the Forest Products Laboratory developed a smartphone complement to the XyloTron, the XyloPhone. The XyloPhone unit is attached to a smartphone by a model-specific slide-on adapter that centers the XyloPhone unit over the phone’s built-in, high-resolution camera. By leveraging the comparative ubiquity of smartphones and by sourcing much lower-cost components (for example, the lens from a magnifying loupe rather than an expensive scientific lens) the price-point for a XyloPhone was less than one-twelfth that of a XyloTron. The XyloPhone design also incorporates white-light and UV illumination but lacks the ability to reposition the lighting array for charcoal identification.
|
||||
|
||||
|
||||
== Other uses ==
|
||||
|
||||
The XyloTron and XyloPhone were primarily intended to facilitate rapid macroscopic identification of wood, but both systems are suited to capture images of any objects that show interesting macroscopic variation, from fungi to feathers to fabrics to fuzzy leaves – or anything else one cares to examine.
|
||||
|
||||
|
||||
== See also ==
|
||||
Illegal logging
|
||||
Wood anatomy
|
||||
Forest governance
|
||||
Timber mafia
|
||||
|
||||
|
||||
== References ==
|
||||
|
||||
|
||||
== External links ==
|
||||
Video demonstration of the XyloTron
|
||||
Global Timber Tracking Network
|
||||
European Commission page on illegal logging, with links to FLEGT Regulation (adopted in 2005) and EU Timber Regulation (adopted in 2010)
|
||||
16
data/en.wikipedia.org/wiki/Z-tube-0.md
Normal file
16
data/en.wikipedia.org/wiki/Z-tube-0.md
Normal file
@ -0,0 +1,16 @@
|
||||
---
|
||||
title: "Z-tube"
|
||||
chunk: 1/1
|
||||
source: "https://en.wikipedia.org/wiki/Z-tube"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:17.202821+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
The Z-tube is an experimental apparatus for measuring the tensile strength of a liquid.
|
||||
It consists of a Z-shaped tube with open ends, filled with a liquid, and set on top of a spinning table. If the tube were straight, the liquid would immediately fly out one end or the other of the tube as it began to spin. By bending the ends of the tube back towards the center of rotation, a shift of the liquid away from center will result in the water level in one end of the tube rising and thus increasing the pressure in that end of the tube, and consequently returning the liquid to the center of the tube. By measuring the rotational speed and the distance from the center of rotation to the liquid level in the bent ends of the tube, the pressure reduction inside the tube can be calculated.
|
||||
Negative pressures, (i.e. less than zero absolute pressure, or in other words, tension) have been reported using water processed to remove dissolved gases. Tensile strengths up to 280 atmospheres have been reported for water in glass.
|
||||
|
||||
|
||||
== References ==
|
||||
433
data/en.wikipedia.org/wiki/Zeeman_slower-0.md
Normal file
433
data/en.wikipedia.org/wiki/Zeeman_slower-0.md
Normal file
@ -0,0 +1,433 @@
|
||||
---
|
||||
title: "Zeeman slower"
|
||||
chunk: 1/2
|
||||
source: "https://en.wikipedia.org/wiki/Zeeman_slower"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:18.309776+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
In atomic physics, a Zeeman slower is a scientific instrument that is commonly used in atomic physics to slow and cool a beam of hot atoms to speeds of several meters per second and temperatures below a kelvin. The gas-phase atoms used in atomic physics are often generated in an oven by heating a solid or liquid atomic sample to temperatures where the vapor pressure is high enough that a substantial number of atoms are in the gas phase. These atoms effuse out of a hole in the oven with average speeds on the order of hundreds of m/s and large velocity distributions (due to their high temperature). The Zeeman slower is attached close to where the hot atoms exit the oven and are used to slow them to less than 10 m/s (slowing) with a very small velocity spread (cooling).
|
||||
A Zeeman slower consists of a cylinder, through which an atomic beam travels, a pump laser that counterpropagates with respect to the beam's direction, and a magnetic field (commonly produced by a solenoid-like coil) that points along the cylinder's axis with a spatially varying magnitude. The pump laser, which is required to be near-resonant with atomic transition, Doppler-slows a certain velocity class within the velocity distribution of the beam. The spatially varying magnetic field is designed to Zeeman-shift the resonant frequency to match the decreasing Doppler shift as the atoms are slowed to lower velocities while they propagate through the Zeeman slower, allowing the pump laser to be continuously resonant and provide a slowing force.
|
||||
|
||||
== History ==
|
||||
The Zeeman slower was first developed by Harold J. Metcalf and William D. Phillips (who was awarded 1/3 of the 1997 Nobel Prize in Physics in part work for his work on the Zeeman slower). The achievement of these low temperatures led the way for the experimental realization of Bose–Einstein condensation, and a Zeeman slower can be part of such an apparatus.
|
||||
|
||||
== Principle ==
|
||||
According to the principles of Doppler cooling, an atom modelled as a two-level atom can be cooled using a laser. If it moves in a specific direction and encounters a counter-propagating laser beam resonant with its transition, it is very likely to absorb a photon. The absorption of this photon gives the atom a "kick" in the direction that is consistent with momentum conservation and brings the atom to its excited state. However, this state is unstable, and some time later the atom decays back to its ground state via spontaneous emission (after a time on the order of nanoseconds; for example, in rubidium-87, the excited state of the D2 transition has a lifetime of 26.2 ns). The photon will be reemitted (and the atom will again increase its speed), but its direction will be random. When averaging over a large number of these processes applied to one atom, one sees that the absorption process decreases the speed always in the same direction (as the absorbed photon comes from a monodirectional source), whereas the emission process does not lead to any change in the speed of the atom because the emission direction is random. Thus the atom is being effectively slowed down by the laser beam.
|
||||
There is nevertheless a problem in this basic scheme because of the Doppler effect. The resonance of the atom is rather narrow (on the order of a few megahertz), and after having decreased its momentum by a few recoil momenta, it is no longer in resonance with the pump beam because in its frame, the frequency of the laser has shifted. The Zeeman slower uses the fact that a magnetic field can change the resonance frequency of an atom using the Zeeman effect to tackle this problem.
|
||||
The average acceleration (due to many photon absorption events over time) of an atom with mass
|
||||
|
||||
|
||||
|
||||
M
|
||||
|
||||
|
||||
{\displaystyle M}
|
||||
|
||||
, a cycling transition with frequency
|
||||
|
||||
|
||||
|
||||
ω
|
||||
=
|
||||
c
|
||||
k
|
||||
+
|
||||
δ
|
||||
|
||||
|
||||
{\displaystyle \omega =ck+\delta }
|
||||
|
||||
, and linewidth
|
||||
|
||||
|
||||
|
||||
γ
|
||||
|
||||
|
||||
{\displaystyle \gamma }
|
||||
|
||||
, that is in the presence of a laser beam that has wavenumber
|
||||
|
||||
|
||||
|
||||
k
|
||||
|
||||
|
||||
{\displaystyle k}
|
||||
|
||||
, and intensity
|
||||
|
||||
|
||||
|
||||
I
|
||||
=
|
||||
|
||||
s
|
||||
|
||||
0
|
||||
|
||||
|
||||
|
||||
I
|
||||
|
||||
s
|
||||
|
||||
|
||||
|
||||
|
||||
{\displaystyle I=s_{0}I_{s}}
|
||||
|
||||
(where
|
||||
|
||||
|
||||
|
||||
|
||||
I
|
||||
|
||||
s
|
||||
|
||||
|
||||
=
|
||||
ℏ
|
||||
c
|
||||
γ
|
||||
|
||||
k
|
||||
|
||||
3
|
||||
|
||||
|
||||
|
||||
/
|
||||
|
||||
(
|
||||
12
|
||||
π
|
||||
)
|
||||
|
||||
|
||||
{\displaystyle I_{s}=\hbar c\gamma k^{3}/(12\pi )}
|
||||
|
||||
is the saturation intensity of the laser) is
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
a
|
||||
→
|
||||
|
||||
|
||||
|
||||
=
|
||||
|
||||
|
||||
|
||||
ℏ
|
||||
|
||||
|
||||
|
||||
k
|
||||
→
|
||||
|
||||
|
||||
|
||||
γ
|
||||
|
||||
|
||||
2
|
||||
M
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
s
|
||||
|
||||
0
|
||||
|
||||
|
||||
|
||||
1
|
||||
+
|
||||
|
||||
s
|
||||
|
||||
0
|
||||
|
||||
|
||||
+
|
||||
(
|
||||
2
|
||||
|
||||
δ
|
||||
′
|
||||
|
||||
|
||||
/
|
||||
|
||||
γ
|
||||
|
||||
)
|
||||
|
||||
2
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
.
|
||||
|
||||
|
||||
{\displaystyle {\vec {a}}={\frac {\hbar {\vec {k}}\gamma }{2M}}{\frac {s_{0}}{1+s_{0}+(2\delta '/\gamma )^{2}}}.}
|
||||
|
||||
|
||||
In the rest frame of the atoms with velocity
|
||||
|
||||
|
||||
|
||||
v
|
||||
|
||||
|
||||
{\displaystyle v}
|
||||
|
||||
in the atomic beam, the frequency of the laser beam is shifted by
|
||||
|
||||
|
||||
|
||||
|
||||
k
|
||||
|
||||
L
|
||||
|
||||
|
||||
v
|
||||
|
||||
|
||||
{\displaystyle k_{L}v}
|
||||
|
||||
. In the presence of a magnetic field
|
||||
|
||||
|
||||
|
||||
B
|
||||
|
||||
|
||||
{\displaystyle B}
|
||||
|
||||
, the atomic transition is Zeeman-shifted by an amount
|
||||
|
||||
|
||||
|
||||
|
||||
μ
|
||||
′
|
||||
|
||||
B
|
||||
|
||||
/
|
||||
|
||||
ℏ
|
||||
|
||||
|
||||
{\displaystyle \mu 'B/\hbar }
|
||||
|
||||
(where
|
||||
|
||||
|
||||
|
||||
|
||||
μ
|
||||
′
|
||||
|
||||
|
||||
|
||||
{\displaystyle \mu '}
|
||||
|
||||
is the magnetic moment of the transition). Thus, the effective detuning of the laser from the zero-field resonant frequency of the atoms is
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
δ
|
||||
′
|
||||
|
||||
=
|
||||
δ
|
||||
+
|
||||
k
|
||||
v
|
||||
−
|
||||
|
||||
|
||||
|
||||
|
||||
μ
|
||||
′
|
||||
|
||||
B
|
||||
|
||||
ℏ
|
||||
|
||||
|
||||
.
|
||||
|
||||
|
||||
{\displaystyle \delta '=\delta +kv-{\frac {\mu 'B}{\hbar }}.}
|
||||
|
||||
|
||||
The atoms for which
|
||||
|
||||
|
||||
|
||||
|
||||
δ
|
||||
′
|
||||
|
||||
=
|
||||
0
|
||||
|
||||
|
||||
{\displaystyle \delta '=0}
|
||||
|
||||
will experience the largest acceleration, namely
|
||||
|
||||
|
||||
|
||||
|
||||
a
|
||||
=
|
||||
η
|
||||
|
||||
a
|
||||
|
||||
max
|
||||
|
||||
|
||||
,
|
||||
|
||||
|
||||
{\displaystyle a=\eta a_{\text{max}},}
|
||||
|
||||
|
||||
where
|
||||
|
||||
|
||||
|
||||
η
|
||||
=
|
||||
|
||||
s
|
||||
|
||||
0
|
||||
|
||||
|
||||
|
||||
/
|
||||
|
||||
(
|
||||
1
|
||||
+
|
||||
|
||||
s
|
||||
|
||||
0
|
||||
|
||||
|
||||
)
|
||||
|
||||
|
||||
{\displaystyle \eta =s_{0}/(1+s_{0})}
|
||||
|
||||
, and
|
||||
|
||||
|
||||
|
||||
|
||||
a
|
||||
|
||||
max
|
||||
|
||||
|
||||
=
|
||||
ℏ
|
||||
k
|
||||
γ
|
||||
|
||||
/
|
||||
|
||||
(
|
||||
2
|
||||
M
|
||||
)
|
||||
|
||||
|
||||
{\displaystyle a_{\text{max}}=\hbar k\gamma /(2M)}
|
||||
|
||||
.
|
||||
The most common approach is to require that we have a magnetic field profile that varies in the
|
||||
|
||||
|
||||
|
||||
z
|
||||
|
||||
|
||||
{\displaystyle z}
|
||||
|
||||
direction such that the atoms experience a constant acceleration
|
||||
|
||||
|
||||
|
||||
a
|
||||
=
|
||||
η
|
||||
|
||||
a
|
||||
|
||||
max
|
||||
|
||||
|
||||
|
||||
|
||||
{\displaystyle a=\eta a_{\text{max}}}
|
||||
|
||||
as they fly along the axis of the slower. It has been recently shown, however, that a different approach yields better results.
|
||||
In the constant-deceleration approach we get
|
||||
|
||||
|
||||
|
||||
|
||||
v
|
||||
(
|
||||
z
|
||||
)
|
||||
=
|
||||
|
||||
|
||||
|
||||
v
|
||||
|
||||
i
|
||||
|
||||
|
||||
2
|
||||
|
||||
|
||||
−
|
||||
2
|
||||
a
|
||||
z
|
||||
|
||||
|
||||
,
|
||||
|
||||
|
||||
{\displaystyle v(z)={\sqrt {v_{i}^{2}-2az}},}
|
||||
|
||||
227
data/en.wikipedia.org/wiki/Zeeman_slower-1.md
Normal file
227
data/en.wikipedia.org/wiki/Zeeman_slower-1.md
Normal file
@ -0,0 +1,227 @@
|
||||
---
|
||||
title: "Zeeman slower"
|
||||
chunk: 2/2
|
||||
source: "https://en.wikipedia.org/wiki/Zeeman_slower"
|
||||
category: "reference"
|
||||
tags: "science, encyclopedia"
|
||||
date_saved: "2026-05-05T03:14:18.309776+00:00"
|
||||
instance: "kb-cron"
|
||||
---
|
||||
|
||||
|
||||
|
||||
|
||||
B
|
||||
(
|
||||
z
|
||||
)
|
||||
=
|
||||
|
||||
|
||||
|
||||
ℏ
|
||||
k
|
||||
|
||||
|
||||
μ
|
||||
′
|
||||
|
||||
|
||||
|
||||
v
|
||||
+
|
||||
|
||||
|
||||
|
||||
ℏ
|
||||
δ
|
||||
|
||||
|
||||
μ
|
||||
′
|
||||
|
||||
|
||||
|
||||
=
|
||||
|
||||
|
||||
|
||||
ℏ
|
||||
k
|
||||
|
||||
v
|
||||
|
||||
i
|
||||
|
||||
|
||||
|
||||
|
||||
μ
|
||||
′
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
1
|
||||
−
|
||||
|
||||
|
||||
|
||||
2
|
||||
a
|
||||
|
||||
|
||||
v
|
||||
|
||||
i
|
||||
|
||||
|
||||
2
|
||||
|
||||
|
||||
|
||||
|
||||
z
|
||||
|
||||
|
||||
+
|
||||
|
||||
|
||||
|
||||
ℏ
|
||||
δ
|
||||
|
||||
|
||||
μ
|
||||
′
|
||||
|
||||
|
||||
|
||||
,
|
||||
|
||||
|
||||
{\displaystyle B(z)={\frac {\hbar k}{\mu '}}v+{\frac {\hbar \delta }{\mu '}}={\frac {\hbar kv_{i}}{\mu '}}{\sqrt {1-{\frac {2a}{v_{i}^{2}}}z}}+{\frac {\hbar \delta }{\mu '}},}
|
||||
|
||||
|
||||
where
|
||||
|
||||
|
||||
|
||||
|
||||
v
|
||||
|
||||
i
|
||||
|
||||
|
||||
|
||||
|
||||
{\displaystyle v_{i}}
|
||||
|
||||
is the maximal velocity class that will be slowed; all the atoms in the velocity distribution that have velocities
|
||||
|
||||
|
||||
|
||||
v
|
||||
<
|
||||
|
||||
v
|
||||
|
||||
i
|
||||
|
||||
|
||||
|
||||
|
||||
{\displaystyle v<v_{i}}
|
||||
|
||||
will be slowed, and those with velocities
|
||||
|
||||
|
||||
|
||||
v
|
||||
>
|
||||
|
||||
v
|
||||
|
||||
i
|
||||
|
||||
|
||||
|
||||
|
||||
{\displaystyle v>v_{i}}
|
||||
|
||||
will not be slowed at all. The parameter
|
||||
|
||||
|
||||
|
||||
η
|
||||
|
||||
|
||||
{\displaystyle \eta }
|
||||
|
||||
(which determines the required laser intensity) is normally chosen to be around 0.5. If a Zeeman slower were to be operated with
|
||||
|
||||
|
||||
|
||||
η
|
||||
≈
|
||||
1
|
||||
|
||||
|
||||
{\displaystyle \eta \approx 1}
|
||||
|
||||
, then after absorbing a photon and moving to the excited state, the atom would preferentially re-emit a photon in the direction of the laser beam (due to stimulated emission), which would counteract the slowing process.
|
||||
|
||||
== Realization ==
|
||||
The required form of the spatially inhomogeneous magnetic field as we showed above has the form
|
||||
|
||||
|
||||
|
||||
|
||||
B
|
||||
(
|
||||
z
|
||||
)
|
||||
=
|
||||
|
||||
B
|
||||
|
||||
0
|
||||
|
||||
|
||||
+
|
||||
|
||||
B
|
||||
|
||||
a
|
||||
|
||||
|
||||
|
||||
|
||||
1
|
||||
−
|
||||
z
|
||||
|
||||
/
|
||||
|
||||
|
||||
z
|
||||
|
||||
0
|
||||
|
||||
|
||||
|
||||
|
||||
.
|
||||
|
||||
|
||||
{\displaystyle B(z)=B_{0}+B_{a}{\sqrt {1-z/z_{0}}}.}
|
||||
|
||||
|
||||
This field can be realized a few different ways. The most popular design requires wrapping a current-carrying wire with many layered windings where the field is strongest (around 20–50 windings) and few windings where the field is weak. Alternative designs include a single-layer coil that varies in the pitch of the winding and an array of permanent magnets in various configurations.
|
||||
|
||||
== Outgoing atoms ==
|
||||
The Zeeman slower is usually used as a preliminary step to cool the atoms in order to trap them in a magneto-optical trap. Thus it aims at a final velocity of about 10 m/s (depending on the atom used), starting with a beam of atoms with a velocity of a few hundred meters per second. The final speed to be reached is a compromise between the technical difficulty of having a long Zeeman slower and the maximal speed allowed for an efficient loading into the trap.
|
||||
A limitation of setup can be the transverse heating of the beam. It is linked to the fluctuations of the speed along the three axes around its mean values, since the final speed was said to be an average over a large number of processes. These fluctuations are linked to the atom having a Brownian motion due to the random reemission of the absorbed photon. They may cause difficulties when loading the atoms in the next trap.
|
||||
|
||||
== References ==
|
||||
Loading…
Reference in New Issue
Block a user