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to differences between mainland Mandarin Chinese and Taiwanese Mandarin. === GPT Store === In January 2024, OpenAI launched the GPT Store, a marketplace for custom ChatGPT chatbots labeled GPTs. The company initially planned to launch the store in November 2023, but it was delayed. At launch, the GPT Store offered more than 3 million custom chatbots. Chatbots available through the store are developed using OpenAI's GPT Builder system. Development of chatbots on the platform does not require programming skills. Two days after launch, the GPT Store offered many versions of "virtual girlfriend" bots, something that is against OpenAI's terms of service. === GPT-4 === OpenAI's GPT-4 model was released on March 14, 2023. Observers saw it as an impressive improvement over GPT-3.5, with the caveat that GPT-4 retained many of the same problems. Some of GPT-4's improvements were predicted by OpenAI before training it, while others remained hard to predict due to breaks in downstream scaling laws. OpenAI demonstrated video and image inputs for GPT-4, although such features remain inaccessible to the general public. OpenAI has declined to reveal technical information such as the size of the GPT-4 model. The ChatGPT Plus subscription service offers access to a GPT-4-powered version of ChatGPT. Microsoft acknowledged that Bing Chat was using GPT-4 before GPT-4's official release. In November 2023, OpenAI launched GPT-4 Turbo, which notably has a much larger context window. === GPT-4o === In May 2024, OpenAI announced and started a multi-month rollout of GPT-4o ("o" for "Omni"), a model capable of analyzing and generating text, images, and sound. GPT-4o is twice as fast and costs half as much as GPT-4 Turbo. GPT-4o is free to all users within a usage limit, despite being more capable than the older model GPT-4, which is only available through paid subscriptions. The usage limit
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is five times higher for ChatGPT Plus subscribers than for free users. The ability to generate images directly with GPT-4o (rather than through DALL-E 3) was added in March 2025. On July 18, 2024, OpenAI released GPT-4o mini, a smaller version of GPT-4o replacing GPT-3.5 Turbo on the ChatGPT interface. In April 2025, an update of GPT-4o was rolled back due to excessive sycophancy. === o1 === In September 2024, OpenAI introduced o1-preview and a faster, cheaper model named o1-mini. In December 2024, o1-preview was replaced by o1. o1 is designed to solve more complex problems by spending more time "thinking" before it answers, enabling it to analyze its answers and explore different strategies. According to OpenAI, o1-preview outperforms GPT-4o in areas like competitive programming, mathematics, and scientific reasoning. o1-preview ranked in the 89th percentile on Codeforces' competitive programming contests, scored 83% on a International Mathematics Olympiad qualifying exam (compared to 13% for GPT-4o), and performs similarly to Ph.D. students on benchmarks in physics, biology, and chemistry. === ChatGPT Pro === In December 2024, OpenAI launched ChatGPT Pro, a US$200 per month subscription which includes unlimited access to the o1 model and advanced voice mode. The plan also includes a pro version of o1 which uses more compute to provide better answers. === Operator === In January 2025, OpenAI released a research preview of Operator, an agent capable of using its own browser to perform tasks. Operator is available to Pro users in the U.S. === Deep research === In February 2025, OpenAI released deep research, a service based on o3 that combines advanced reasoning and web search capabilities to make comprehensive reports within 5 to 30 minutes. === GPT-4.5 === Released in February 2025, GPT-4.5 was described by Altman as a "giant, expensive model". According to OpenAI, it features
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reduced hallucinations and enhanced pattern recognition, creativity, and user interaction. == Model versions == The following table lists the main model versions of ChatGPT, describing the significant changes included with each version: == Reception == OpenAI engineers have said that they had not expected ChatGPT to be very successful and were surprised by the coverage and attention that it received. ChatGPT was widely assessed in December 2022 as having some unprecedented and powerful capabilities. Kevin Roose of The New York Times called it "the best artificial intelligence chatbot ever released to the general public". Samantha Lock of The Guardian noted that it was able to generate "impressively detailed" and "human-like" text. Alex Kantrowitz of Slate magazine lauded ChatGPT's pushback to questions related to Nazi Germany, including the statement that Adolf Hitler built highways in Germany, which was met with information about Nazi Germany's use of forced labor. In The Atlantic magazine's "Breakthroughs of the Year" for 2022, Derek Thompson included ChatGPT as part of "the generative-AI eruption" that "may change our mind about how we work, how we think, and what human creativity is". Kelsey Piper of Vox wrote that "ChatGPT is the general public's first hands-on introduction to how powerful modern AI has gotten, and as a result, many of us are [stunned]" and that ChatGPT is "smart enough to be useful despite its flaws". Paul Graham of Y Combinator tweeted: "The striking thing about the reaction to ChatGPT is not just the number of people who are blown away by it, but who they are. These are not people who get excited by every shiny new thing. Something big is happening." ChatGPT gained one million users in five days and 100 million in two months, becoming the fastest-growing internet application in history. ChatGPT's launch and popularity caught Google
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off-guard, prompting a sweeping and unprecedented response in the ensuing months. In December 2022, Google executives sounded a "code red" alarm, fearing that ChatGPT's question-answering ability posed a threat to Google Search, Google's core business. After mobilizing its workforce, Google scrambled to launch Bard, a chatbot powered by the LaMDA LLM, on February 6, 2023, one day before Microsoft's announcement of Bing Chat. AI was the forefront of Google's annual Google I/O conference in May, announcing a slew of generative AI-powered features across its products to counter OpenAI and Microsoft. Journalists and scholars have commented on ChatGPT's tendency to hallucinate. Mike Pearl of the online technology blog Mashable tested ChatGPT with multiple questions. In one example, he asked ChatGPT for "the largest country in Central America that isn't Mexico" (Mexico is in North America), to which ChatGPT responded with Guatemala (the correct answer is Nicaragua). When CNBC asked ChatGPT for the lyrics to "Ballad of Dwight Fry", ChatGPT supplied invented lyrics rather than the actual lyrics. Writers for The Verge cited the seminal 2021 research paper "On the Dangers of Stochastic Parrots: Can Language Models Be Too Big? 🦜" by Emily M. Bender, Timnit Gebru, Angelina McMillan-Major, and Margaret Mitchell, comparing ChatGPT to a "stochastic parrot", as did Professor Anton Van Den Hengel of the Australian Institute for Machine Learning. On a similar vein, philosopher Michael Hicks of the University of Glasgow described it as "bullshit". In December 2022, the question-and-answer website Stack Overflow banned the use of ChatGPT for generating answers to questions, citing the factually ambiguous nature of its responses. In January 2023, the International Conference on Machine Learning banned any undocumented use of ChatGPT or other large language models to generate any text in submitted papers. Samsung banned generative AI company-wide in May 2023 after sensitive material
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was uploaded to ChatGPT. In January 2023, after being sent a song ChatGPT wrote in the style of Nick Cave, Cave responded on The Red Hand Files, saying the act of writing a song is "a blood and guts business [...] that requires something of me to initiate the new and fresh idea. It requires my humanness." He went on to say, "With all the love and respect in the world, this song is bullshit, a grotesque mockery of what it is to be human, and, well, I don't much like it." In February 2023, Time magazine placed a screenshot of a conversation with ChatGPT on its cover, writing that "The AI Arms Race Is Changing Everything" and "The AI Arms Race Is On. Start Worrying". Chinese state media have characterized ChatGPT as a way for the United States to spread misinformation. ChatGPT was blocked by the Great Firewall in China on March 2, 2023. In May 2023, Chinese police arrested a man who allegedly used ChatGPT to generate a bogus report about a train crash, which was then posted online for profit. In December 2023, Chinese police arrested four people who had allegedly used ChatGPT to develop ransomware. In 2024, a survey of Chinese youth found that 18% of respondents born after 2000 reported using generative AI "almost every day" and that ChatGPT is one of the most popular generative AI products in China. In late March 2023, the Italian data protection authority banned ChatGPT in Italy and opened an investigation. Italian regulators assert that ChatGPT was exposing minors to age-inappropriate content, and that OpenAI's use of ChatGPT conversations as training data could violate Europe's General Data Protection Regulation. In April 2023, the ChatGPT ban was lifted in Italy. OpenAI said it has taken steps to effectively clarify and
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address the issues raised; an age verification tool was implemented to ensure users are at least 13 years old. Additionally, users can access its privacy policy before registration. In April 2023, Brian Hood, mayor of Hepburn Shire Council, planned to take legal action against ChatGPT over false information. According to Hood, ChatGPT erroneously claimed that he was jailed for bribery during his tenure at a subsidiary of Australia's national bank. In fact, Hood acted as a whistleblower and was not charged with any criminal offenses. His legal team sent a concerns notice to OpenAI as the first official step in filing a defamation case. In July 2023, the US Federal Trade Commission (FTC) issued a civil investigative demand to OpenAI to investigate whether the company's data security and privacy practices to develop ChatGPT were unfair or harmed consumers (including by reputational harm) in violation of Section 5 of the Federal Trade Commission Act of 1914. In July 2023, the FTC launched an investigation into OpenAI, the creator of ChatGPT, over allegations that the company scraped public data and published false and defamatory information. The FTC sent OpenAI a 20-page letter asking for comprehensive information about its technology and privacy safeguards, as well as any steps taken to prevent the recurrence of situations in which its chatbot generated false and derogatory content about people. A March 2023 Pew Research Center poll found that 14% of American adults had tried ChatGPT. In July, the Pew Research Center put the same figure at 18%. Research conducted in 2023 revealed weaknesses of ChatGPT that make it vulnerable to cyberattacks. A study presented example attacks on ChatGPT, including jailbreaks and reverse psychology. Additionally, malicious actors can use ChatGPT for social engineering attacks and phishing attacks. The researchers also contended that ChatGPT and other generative AI
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tools have defense capabilities and the ability to improve security. The technology can improve security by cyber defense automation, threat intelligence, attack identification, and reporting. Another study reported that GPT-4 obtained a better score than 99% of humans on the Torrance Tests of Creative Thinking. In December 2023, ChatGPT became the first non-human to be included in Nature's 10, an annual listicle curated by Nature of people considered to have made significant impact in science. Celeste Biever wrote in a Nature article that "ChatGPT broke the Turing test". Stanford researchers reported that GPT-4 "passes a rigorous Turing test, diverging from average human behavior chiefly to be more cooperative." In May 2024, OpenAI removed accounts involving the use of ChatGPT by state-backed influence operations such as China's Spamouflage, Russia's Doppelganger, and Israel's Ministry of Diaspora Affairs and Combating Antisemitism. In August 2024, the FTC voted unanimously to ban marketers from using fake user reviews created by generative AI chatbots (including ChatGPT) and influencers paying for bots to increase follower counts. In February 2025, OpenAI identified and removed influence operations, termed "Peer Review" and "Sponsored Discontent", used to attack overseas Chinese dissidents. == Applications == === Academic research === ChatGPT has been used to generate introductory sections and abstracts for scientific articles. Several papers have listed ChatGPT as a co-author. Scientific journals have had different reactions to ChatGPT. Some, including Nature and JAMA Network, "require that authors disclose the use of text-generating tools and ban listing a large language model (LLM) such as ChatGPT as a co-author". Science "completely banned" usage of LLM-generated text in all its journals. Spanish chemist Rafael Luque published a plethora of research papers in 2023 that he later admitted were written by ChatGPT. The papers have a large number of unusual phrases characteristic of LLMs. Many authors
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argue that the use of ChatGPT in academia for teaching and review is problematic due to its tendency to hallucinate. Robin Bauwens, an assistant professor at Tilburg University, found that a ChatGPT-generated peer review report on his article mentioned nonexistent studies. According to librarian Chris Granatino of Lemieux Library at Seattle University, although ChatGPT can generate content that seemingly includes legitimate citations, in most cases those citations are not real or are largely incorrect. === Coding === Researchers at Purdue University analyzed ChatGPT's responses to 517 questions about software engineering or computer programming posed on Stack Overflow for correctness, consistency, comprehensiveness, and concision, and found that 52% of them contained inaccuracies and 77% were verbose. Researchers at Stanford University and the University of California, Berkeley, found that, when creating directly executable responses to the latest 50 code generation problems from LeetCode that were rated "easy", the performances of GPT-3.5 and GPT-4 fell from 22% and 52%, respectively, in March 2023, to 2% and 10%, respectively, in June 2023. === Computer security === Check Point Research and others noted that ChatGPT could write phishing emails and malware, especially when combined with OpenAI Codex. CyberArk researchers demonstrated that ChatGPT could be used to create polymorphic malware that could evade security products while requiring little effort by the attacker. From the launch of ChatGPT in the fourth quarter of 2022 to the fourth quarter of 2023, there was a 1,265% increase in malicious phishing emails and a 967% increase in credential phishing, which cybersecurity professionals argued in an industry survey was attributable to cybercriminals' increased use of generative artificial intelligence (including ChatGPT). In July 2024, Futurism reported that GPT-4o in ChatGPT would sometimes link "scam news sites that deluge the user with fake software updates and virus warnings"; these pop-ups can be used
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to coerce users into downloading malware or potentially unwanted programs. === Economics === There has been concern that ChatGPT could supplant jobs, especially roles such as creative writing, copywriting, communication, journalism, coding, and data entry. The release of ChatGPT prompted a wave of investment in China, resulting in the development of more than 200 large language learning models.: 95 This was termed the "war of a hundred models" (百模大战; bai mo dazhan).: 95 === Education === Technology writer Dan Gillmor used ChatGPT in 2022 on a student assignment, and found its generated text was on par with what a good student would deliver and opined that "academia has some very serious issues to confront". Geography professor Terence Day assessed in 2023 citations generated by ChatGPT and found them to be fake. Despite this, he writes that "the titles of the fake articles are all directly relevant to the questions and could potentially make excellent papers. The lack of a genuine citation could signal an opportunity for an enterprising author to fill a void." According to Day, it is possible to generate high-quality introductory college courses using ChatGPT; he used it to write materials for "introductory physical geography courses, my second-year course in geographical hydrology, and second-year cartography, geographic information systems, and remote sensing." He concludes that "this approach could have significant relevance for open learning and could potentially affect current textbook publishing models." ChatGPT was also seen as an opportunity for cheap and individualized tutoring, leading to the creation of specialized chatbots like Khanmigo. On May 7, 2024, OpenAI announced in a blog post that it was developing tools like tamper-resistant watermarking to identify AI-generated content. In an August 4 update, following a Wall Street Journal report about the delayed release of a watermark tool for AI-detection, OpenAI shared progress
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on text provenance, revealing a text watermarking method. While accurate against paraphrasing, the method is less effective against global tampering, such as translation or rewording. OpenAI also noted potential disproportionate impacts on groups like non-native English speakers. === Culture === Some scholars have expressed concern that ChatGPT's availability could reduce the originality of writing, cause people to write more like the AI as they are exposed to the model, and encourage an Anglocentric perspective centered on a few dialects of English globally. A senior editor at The Atlantic wrote that ChatGPT and other similar technology make the previously absurd idea of the dead internet theory a little more realistic, where AI could someday create most web content in order to control society. During the first three months after ChatGPT became available to the public, hundreds of books appeared on Amazon that listed it as author or co-author and featured illustrations made by other AI models such as Midjourney. Between March and April 2023, Italian newspaper Il Foglio published one ChatGPT-generated article a day on its website, hosting a special contest for its readers in the process. The articles tackled themes such as the possible replacement of human journalists by AI systems, Elon Musk's administration of Twitter, the Meloni government's immigration policy and the competition between chatbots and virtual assistants. In June 2023, hundreds of people attended a "ChatGPT-powered church service" at St. Paul's church in Fürth, Germany. Theologian and philosopher Jonas Simmerlein, who presided, said that it was "about 98 percent from the machine". The ChatGPT-generated avatar told the people, "Dear friends, it is an honor for me to stand here and preach to you as the first artificial intelligence at this year's convention of Protestants in Germany". Reactions to the ceremony were mixed. The Last Screenwriter, a 2024 film
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created and directed by Peter Luisi, was written with the use of ChatGPT, and was marketed as "the first film written entirely by AI". === Financial markets === The AI technology company c3.ai saw a 28% increase in its share price after announcing the integration of ChatGPT into its toolkit. The share price of BuzzFeed, a digital media company unrelated to AI, increased 120% after announcing OpenAI technology adoption for content creation. Reuters found that share prices of AI-related companies BigBear.ai and SoundHound AI increased by 21% and 40%, respectively, even though they had no direct connection to ChatGPT. They attributed this surge to ChatGPT's role in turning AI into Wall Street's buzzword. Academic research published in Finance Research Letters found that the 'ChatGPT effect' prompted retail investors to drive up prices of AI-related cryptocurrency assets despite the broader cryptocurrency market being in a bear market, and diminished institutional investor interest. This confirms anecdotal findings by Bloomberg that, in response to ChatGPT's launch, cryptocurrency investors showed a preference for AI-related crypto assets. An experiment by finder.com revealed that ChatGPT could outperform popular fund managers by picking stocks based on criteria such as growth history and debt levels, resulting in a 4.9% increase in a hypothetical account of 38 stocks, outperforming 10 benchmarked investment funds with an average loss of 0.8%. Conversely, executives and investment managers at Wall Street quant funds (including those that have used machine learning for decades) have noted that ChatGPT regularly makes obvious errors that would be financially costly to investors because even AI systems that employ reinforcement learning or self-learning have had only limited success in predicting market trends due to the inherently noisy quality of market data and financial signals. In November 2023, research conducted by Patronus AI, an artificial intelligence startup company, compared performance
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of GPT-4, GPT-4-Turbo, Claude 2, and LLaMA-2 on two versions of a 150-question test about information in financial statements (e.g., Form 10-K, Form 10-Q, Form 8-K, earnings reports, earnings call transcripts) submitted by public companies to the U.S. Securities and Exchange Commission. One version of the test required the generative AI models to use a retrieval system to find the specific SEC filing to answer the questions; the other gave the models the specific SEC filing to answer the question (i.e., in a long context window). On the retrieval system version, GPT-4-Turbo and LLaMA-2 both failed to produce correct answers to 81% of the questions, while on the long context window version, GPT-4-Turbo and Claude-2 failed to produce correct answers to 21% and 24% of the questions, respectively. === Medicine === In the field of health care, possible uses and concerns are under scrutiny by professional associations and practitioners. Two early papers indicated that ChatGPT could pass the United States Medical Licensing Examination (USMLE). MedPage Today noted in January 2023 that "researchers have published several papers now touting these AI programs as useful tools in medical education, research, and even clinical decision making." Published in February 2023 were two separate papers that again evaluated ChatGPT's proficiency in medicine using the USMLE. Findings were published in JMIR Medical Education and PLOS Digital Health. The authors of the PLOS Digital Health paper stated that the results "suggest that large language models may have the potential to assist with medical education, and potentially, clinical decision-making." In JMIR Medical Education, the authors of the other paper concluded that "ChatGPT performs at a level expected of a third-year medical student on the assessment of the primary competency of medical knowledge." They suggest that it could be used as an "interactive learning environment for students". The
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AI itself, prompted by the researchers, concluded that "this study suggests that ChatGPT has the potential to be used as a virtual medical tutor, but more research is needed to further assess its performance and usability in this context." The later-released ChatGPT version based on GPT-4 significantly outperformed the version based on GPT-3.5. Researchers at Stanford University and the University of California, Berkeley have found that the performance of GPT-3.5 and GPT-4 on the USMLE declined from March 2023 to June 2023. A March 2023 paper tested ChatGPT's application in clinical toxicology. The authors found that the AI "fared well" in answering a "very straightforward [clinical case example], unlikely to be missed by any practitioner in the field". They added: "As ChatGPT becomes further developed and specifically adapted for medicine, it could one day be useful in less common clinical cases (i.e, cases that experts sometimes miss). Rather than AI replacing humans (clinicians), we see it as 'clinicians using AI' replacing 'clinicians who do not use AI' in the coming years." An April 2023 study in Radiology tested the AI's ability to answer queries about breast cancer screening. The authors found that it answered appropriately "about 88 percent of the time", however, in one case (for example), it gave advice that had become outdated about a year earlier. The comprehensiveness of its answers was also lacking. A study published in JAMA Internal Medicine that same month found that ChatGPT often outperformed human doctors at answering patient questions (when measured against questions and answers found at /r/AskDocs, a forum on Reddit where moderators validate the medical credentials of professionals; the study acknowledges the source as a limitation). The study authors suggest that the tool could be integrated with medical systems to help doctors draft responses to patient questions. Professionals have emphasized
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ChatGPT's limitations in providing medical assistance. In correspondence to The Lancet Infectious Diseases, three antimicrobial experts wrote that "the largest barriers to the implementation of ChatGPT in clinical practice are deficits in situational awareness, inference, and consistency. These shortcomings could endanger patient safety." Physician's Weekly, though also discussing the potential use of ChatGPT in medical contexts (e.g., "as a digital assistant to physicians by performing various administrative functions like gathering patient record information or categorizing patient data by family history, symptoms, lab results, possible allergies, et cetera"), warned that the AI might sometimes provide fabricated or biased information. One radiologist warned: "We've seen in our experience that ChatGPT sometimes makes up fake journal articles or health consortiums to support its claims"; As reported in one Mayo Clinic Proceedings: Digital Health paper, ChatGPT may do this for as much as 69% of its cited medical references. The researchers emphasized that while many of its references were fabricated, those that were appeared "deceptively real". As Dr. Stephen Hughes mentioned for The Conversation however, ChatGPT is capable of learning to correct its past mistakes. He also noted the AI's "prudishness" regarding sexual health topics. Contrary to previous findings, ChatGPT responses to anesthesia-related questions were more accurate, succinct, and descriptive compared to Bard's. Bard exhibited 30.3% error in response as compared to ChatGPT (0% error). At a conference of the American Society of Health-System Pharmacists in December 2023, researchers at Long Island University (LIU) presented a study that researched ChatGPT's responses to 45 frequently asked questions of LIU College of Pharmacy's drug information service during a 16-month period from 2022 to 2023 as compared with researched responses provided by professional pharmacists. For 29 of the 39 questions for which there was sufficient medical literature for a data-driven response, ChatGPT failed to provide a direct
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answer or provided a wrong or incomplete answer (and in some cases, if acted upon, the answer would endanger the patient's health). The researchers had asked ChatGPT to provide medical research citations for all its answers, but it did so for only eight, and all eight included at least one fabricated (fake) citation. A January 2024 study conducted by researchers at Cohen Children's Medical Center found that GPT-4 had an accuracy rate of 17% when diagnosing pediatric medical cases. A November 2024 study of 50 physicians on illness diagnosis reported that GPT-4 achieved a 90% accuracy, while physicians scored 74% without AI assistance, and 76% when using the chatbot. === Law === In January 2023, Massachusetts State Senator Barry Finegold and State Representative Josh S. Cutler proposed a bill partially written by ChatGPT, "An Act drafted with the help of ChatGPT to regulate generative artificial intelligence models like ChatGPT", which would require companies to disclose their algorithms and data collection practices to the office of the State Attorney General, arrange regular risk assessments, and contribute to the prevention of plagiarism. The bill was officially presented during a hearing on July 13. On April 11, 2023, a session court judge in Pakistan used ChatGPT to decide the bail of a 13-year-old accused in a matter. The court quoted the use of ChatGPT assistance in its verdict: Can a juvenile suspect in Pakistan, who is 13 years old, be granted bail after arrest? The AI language model replied: Under the Juvenile Justice System Act 2018, according to section 12, the court can grant bail on certain conditions. However, it is up to the court to decide whether or not a 13-year-old suspect will be granted bail after arrest. The judge asked ChatGPT other questions about the case and formulated his final decision
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in light of its answers. In Mata v. Avianca, Inc., 22-cv-1461 (PKC), a personal injury lawsuit against Avianca Airlines filed in the Southern New York U.S. District Court in May 2023 (with Senior Judge P. Kevin Castel presiding), the plaintiff's attorneys used ChatGPT to generate a legal motion. ChatGPT generated numerous fictitious legal cases involving fictitious airlines with fabricated quotations and internal citations in the legal motion. Castel noted numerous inconsistencies in the opinion summaries, and called one of the cases' legal analysis "gibberish". The plaintiff's attorneys faced potential judicial sanction and disbarment for filing the motion and presenting the fictitious legal decisions ChatGPT generated as authentic. The case was dismissed and the attorneys were fined $5,000 as a sanction. In July 2024, the American Bar Association issued its first formal ethics opinion on attorneys using generative AI. In October 2023, the council of Porto Alegre, Brazil, unanimously approved a local ordinance proposed by councilman Ramiro Rosário that would exempt residents from needing to pay for the replacement of stolen water consumption meters; the bill went into effect on November 23. On November 29, Rosário revealed that the bill had been entirely written by ChatGPT, and that he had presented it to the rest of the council without making any changes or disclosing the chatbot's involvement. The city's council president, Hamilton Sossmeier, initially criticized Rosário's initiative, saying it could represent "a dangerous precedent", but later said he "changed his mind": "unfortunately or fortunately, this is going to be a trend." In December 2023, a self-representing litigant in a tax case before the First-tier Tribunal in the United Kingdom cited a series of hallucinated cases purporting to support her argument that she had a reasonable excuse for not paying capital gains tax owed on the sale of property. The judge warned
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that the submission of nonexistent legal authorities meant that both the Tribunal and HM Revenue and Customs had "to waste time and public money", which "reduces the resources available to progress the cases of other court users who are waiting for their appeals to be determined". Judge Kevin Newsom of the US court of appeals of the 11th circuit endorsed the use of ChatGPT and noted that he himself uses the software to help decide rulings on contract interpretation issues. === Violence === The Las Vegas Metropolitan Police Department reported that the perpetrator of the 2025 Las Vegas truck explosion used ChatGPT to help plan the incident. == Concerns == === Bias and offensiveness === Conservative commentators have accused ChatGPT of bias toward left-leaning perspectives. In January 2023, a study stated that ChatGPT has a pro-environmental, left-libertarian orientation. Additionally, an August 2023 paper found a "significant and systematic political bias toward the Democrats in the US, Lula in Brazil, and the Labour Party in the UK." In response to such criticism, OpenAI acknowledged plans to allow ChatGPT to create "outputs that other people (ourselves included) may strongly disagree with". It also contained information on the recommendations it had issued to human reviewers on how to handle controversial subjects, including that the AI should "offer to describe some viewpoints of people and movements", and not provide an argument "from its voice" in favor of "inflammatory or dangerous" topics (although it may still "describe arguments from historical people and movements"), nor "affiliate with one side" or "judge one group as good or bad". The Guardian questioned whether any content found on the Internet after ChatGPT's release "can be truly trusted" and called for government regulation. A study published by the Anti-Defamation League in 2025 found that several major LLMs, including ChatGPT, Llama
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and Claude, showed antisemitic bias. === Copyright issues === There has been concern about copyright infringement involving ChatGPT. In June 2023, two writers sued OpenAI, saying the company's training data came from illegal websites that show copyrighted books. Comedian and author Sarah Silverman, Christopher Golden, and Richard Kadrey sued OpenAI and Meta for copyright infringement in July 2023. Most of their claims were dismissed in February 2024, except the "unfair competition" claim, which was allowed to proceed. The Authors Guild, on behalf of 17 authors, including George R. R. Martin, filed a copyright infringement complaint against OpenAI in September 2023, claiming "the company illegally copied the copyrighted works of authors" in training ChatGPT. In December 2023, The New York Times sued OpenAI and Microsoft for copyright infringement, arguing that Microsoft Copilot and ChatGPT could reproduce Times articles and/or sizable portions of them without permission. As part of the suit, the Times has requested that OpenAI and Microsoft be prevented from using its content for training data, along with removing it from training datasets. In March 2024, Patronus AI compared performance of LLMs on a 100-question test, asking them to complete sentences from books (e.g., "What is the first passage of Gone Girl by Gillian Flynn?") that were under copyright in the United States; it found that GPT-4, Mistral AI's Mixtral, Meta AI's LLaMA-2, and Anthropic's Claude 2 did not refuse to do so, providing sentences from the books verbatim in 44%, 22%, 10%, and 8% of responses, respectively. In February 2025, the Delhi High Court accepted ANI's case against OpenAI over concerns that ChatGPT was sharing paywalled content without the news agency's consent. However, OpenAI's counsel said that due to the firm not having a physical presence in India, the court has no jurisdiction on the matter. === Existential risk
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"title": "ChatGPT"
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=== In 2023, Australian MP Julian Hill advised the national parliament that the growth of AI could cause "mass destruction". During his speech, which was partly written by the program, he warned that it could result in cheating, job losses, discrimination, disinformation, and uncontrollable military applications. Elon Musk wrote: "ChatGPT is scary good. We are not far from dangerously strong AI". He paused OpenAI's access to a Twitter database in 2022 pending a better understanding of OpenAI's plans, saying: "OpenAI was started as open source and nonprofit. Neither is still true." Musk co-founded OpenAI in 2015, in part to address existential risk from artificial intelligence, but resigned in 2018. Over 20,000 signatories including leading computer scientist and tech founders Yoshua Bengio, Elon Musk, and Apple co-founder Steve Wozniak, signed a March 2023 open letter calling for an immediate pause of giant AI experiments like ChatGPT, citing "profound risks to society and humanity". Geoffrey Hinton, one of the "fathers of AI", voiced concerns that future AI systems may surpass human intelligence, and left Google in May 2023. A May 2023 statement by hundreds of AI scientists, AI industry leaders, and other public figures demanded that "[m]itigating the risk of extinction from AI should be a global priority". Some other prominent AI researchers spoke more optimistically about the advances. Juergen Schmidhuber, often called a "father of modern AI", did not sign the letter, emphasizing that in 95% of cases, AI research is about making "human lives longer and healthier and easier." Schmidhuber added that while AI can be used by bad actors, it "can also be used against the bad actors". Andrew Ng argued that "it's a mistake to fall for the doomsday hype on AI—and that regulators who do will only benefit vested interests." WIRED wrote that Yann LeCun "scoffs at
|
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his peers' dystopian scenarios of supercharged misinformation and even, eventually, human extinction." == See also == Intelligent agent – Software agent which acts autonomously Ethics of artificial intelligence – Challenges related to the responsible development and use of AI == Notes == == References == == Further reading == Biswas, Som (April 1, 2023). "ChatGPT and the Future of Medical Writing". Radiology. 307 (2): e223312. doi:10.1148/radiol.223312. ISSN 0033-8419. PMID 36728748. S2CID 256501098. Chang, Kent K.; Cramer, Mackenzie; Soni, Sandeep; Bamman, David (April 28, 2023). "Speak, Memory: An Archaeology of Books Known to ChatGPT/GPT-4". arXiv:2305.00118 [cs.CL]. Cowen, Tyler; Tabarrok, Alexander T. (March 17, 2023). "How to Learn and Teach Economics with Large Language Models, Including GPT". SSRN 4391863. Cowen, Tyler (March 29, 2023). "Jonathan GPT Swift on Jonathan Swift (Ep. 175): How well does GPT4 do pretending to be the 18th-century satirist?" (Podcast). Ouyang, Long; et al. (March 4, 2022). "Training language models to follow instructions with human feedback". arXiv:2203.02155 [cs.CL]. Liebrenz, Michael; Schleifer, Roman; Buadze, Anna; Bhugra, Dinesh; Smith, Alexander (February 2023). "Generating scholarly content with ChatGPT: ethical challenges for medical publishing". The Lancet Digital Health. 5 (3): e105 – e106. doi:10.1016/s2589-7500(23)00019-5. ISSN 2589-7500. PMID 36754725. S2CID 256655912. Wolfram, Stephen (February 14, 2023). "What Is ChatGPT Doing ... and Why Does It Work?". Stephen Wolfram Writings. Wolfram, Stephen (March 23, 2023). "ChatGPT Gets Its "Wolfram Superpowers"!". Stephen Wolfram Writings. Bartholomew, Jem; Mehta, Dhrumil. "How the media is covering ChatGPT". Columbia Journalism Review. Retrieved May 30, 2023. Zhao, Wayne Xin; et al. (2023). "A Survey of Large Language Models". arXiv:2303.18223 [cs.CL]. Prompt engineering guide from OpenAI == External links == Official website
|
{
"page_id": 72417803,
"source": null,
"title": "ChatGPT"
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|
46,XX/46,XY is either a chimeric or mosaic genetic condition characterized by the presence of some cells that express a 46,XX karyotype and some cells that express a 46,XY karyotype in a single human being. Individuals with these conditions are classified as intersex. == Types == === Tetragametic chimerism === The cause of the condition lies in conception or utero with the aggregation of two distinct zygotes or blastocysts (one of which expresses 46,XX and the other of which expresses 46,XY) into a single embryo, which subsequently leads to the development of a single individual with two distinct cell lines, instead of a pair of fraternal twins. In humans, sexual dimorphism is a consequence of the XY sex-determination system. In typical prenatal sex differentiation, the male and female embryo is anatomically identical until week 7 of the pregnancy, when the presence or the absence of the SRY gene on the Y chromosome causes the undetermined gonadal tissue to undergo differentiation and eventually will become either a pair of testes or ovaries respectively. The cells of the developing testes produce Anti-Müllerian hormone, causing the regression of the Müllerian ducts. As individuals with 46,XX/46,XY partially express the SRY gene, the normal process by which an embryo normally develops a phenotypic male or phenotypic female may be significantly affected causing variation will affect in the gonads, the reproductive tract, and the genitals. Despite this, there have been cases of completely normal sex differentiation occurring in 46,XX/46,XY individuals reported in the medical literature. 46,XX/46,XY chimerism can be identified during pregnancy by prenatal screening or in early childhood through genetic testing and direct observation. === Mosaicism === The cause of this condition happens in early development resulting from a single fertilized zygote's cell line divided into two cell lines; a genome that contains a characterized by
|
{
"page_id": 35193356,
"source": null,
"title": "46,XX/46,XY"
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|
the presence of some cells that express a 46,XX karyotype and some cells that express a 46,XY karyotype. == Signs and symptoms == === Physical === 46,XX/46,XY chimeric or mosaic is associated with a wide spectrum of different physical presentations, with cases ranging from having a completely normal male or female phenotype to some cases having ovotesticular syndrome. Due to this variation, genetic testing is the only way to reliably make a diagnosis. 46,XX/46,XY is possible if there is direct observation of one or more of the following: Small phallus midway in size between a clitoris and a penis Incompletely closed urogenital opening (shallow vagina) Abnormal urethra opening on the perineum There have been no reported cases of both gonads being functional in the same person, the functional tissue is usually the ovarian tissue. A mix of male and female characteristics may emerge at puberty. Some individuals will experience secondary characteristics, such as breast development during puberty in a male phenotype, while others may experience deepening of the voice, secondary hair development, and gynecomastia. Segmentation of skin (distinct patches of skin) has also been observed. However, this trait is not unique to 46,XX/46,XY chimerism nor mosaicism. It has also been observed in other types of chimerism. === Cognitive === Individuals with the condition do not experience cognitive impairment. == Genetic mechanism == 46,XX/46,XY is an example of tetragametic chimerism because it requires four gametes – two sperm and two ova. 46,XX/46,XY is most commonly explained during in conception combination of two fertilized eggs zygotes. Two ova from the mother are fertilized by two sperm from the father. One sperm contains an X chromosome; the other contains a Y chromosome. The result is that a zygote with an XY genotype and a zygote with an XX genotype are produced. Under normal
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{
"page_id": 35193356,
"source": null,
"title": "46,XX/46,XY"
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|
circumstances, the two resulting zygotes would have gone on to become fraternal twins. However, in 46,XX/46,XY, the two zygotes merge shortly before or after fertilization to become a two-cell zygote made up of two different nuclei. The zygotes merge early enough that there is no risk of them developing into conjoined twins. Variations of this mechanism include fertilization of an ovum and its first or second polar body by two sperm. 46,XX/46,XY can also be explained by a mosaic-based mechanism. A single zygote is formed from the fertilization of a normal X ovum. The resulting XX/XY zygote divides to give two cell lines: 46,XX/46,XY. The 46,XX/46,XY cell lines remain and go on to become a chimeric individual. 46,XX/46,XY can also arise when a haploid ovum undergoes a round of mitosis, and the subsequent daughter cells are fertilized by an X and a Y sperm, respectively. == Diagnosis == Diagnosing a chimera or mosaic is particularly difficult due to the random distribution of 46,XX and 46,XY cells within the body. In a chimeric, an organ might be made up of a mix of 46,XX and 46,XY, but is made up entirely only one genotype. When that is the case, no abnormalities are noted and other types of tissues need to be analyzed. Blood tests might contain both or red blood cells of different blood types. Before birth, ambiguous genitalia might be observed through ultrasound. The karyotype might also be observed through amniocentesis or cord blood sampling. == See also == Sex chromosome anomalies == References == == External links ==
|
{
"page_id": 35193356,
"source": null,
"title": "46,XX/46,XY"
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The molecular formula C23H23ClN6O2 (molar mass: 450.921 g/mol) may refer to: Daridorexant, formerly known as nemorexant Suvorexant
|
{
"page_id": 61538828,
"source": null,
"title": "C23H23ClN6O2"
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Salted fish, such as kippered herring or dried and salted cod, is fish cured with dry salt and thus preserved for later eating. Drying or salting, either with dry salt or with brine, was the only widely available method of preserving fish until the 19th century. Dried fish and salted fish (or fish both dried and salted) are a staple of diets in the Azores, Caribbean, West Africa, North Africa, South Asia, Southeast Asia, Southern China, Scandinavia, parts of Canada including Newfoundland, coastal Russia, and in the Arctic. Like other salt-cured meats, it provides preserved animal protein even in the absence of refrigeration. == Method == Salting is the preservation of food with dry edible salt. It is related to pickling (preparing food with brine, i.e. salty water), and is one of the oldest methods of preserving food. Salt inhibits the growth of microorganisms by drawing water out of microbial cells through osmosis. Concentrations of salt up to 20% are required to kill most species of unwanted bacteria. Smoking, often used in the process of curing meat, adds chemicals to the surface of meat that reduce the concentration of salt required. Salting is used because most bacteria, fungi and other potentially pathogenic organisms cannot survive in a highly salty environment, due to the hypertonic nature of salt. Any living cell in such an environment will become dehydrated through osmosis and die or become temporarily inactivated. The water activity, aw, in a fish is defined as the ratio of the water vapour pressure in the flesh of the fish to the vapour pressure of pure water at the same temperature and pressure. It ranges between 0 and 1, and is a parameter that measures how available the water is in the flesh of the fish. Available water is necessary for the
|
{
"page_id": 11993615,
"source": null,
"title": "Salted fish"
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|
microbial and enzymatic reactions involved in spoilage. There are a number of techniques that have been or are used to tie up the available water or remove it by reducing the aw. Traditionally, techniques such as drying, salting and smoking have been used, and have been used for thousands of years. In more recent times, freeze-drying, water binding humectants, and fully automated equipment with temperature and humidity control have been added. Often a combination of these techniques is used. == Health effects == Due to the elevated levels of nitrites, consuming salted fish increases risk of stomach cancer and nasopharyngeal cancer. The International Agency for Research on Cancer classify salted fish (Chinese-style) as a Group 1 carcinogen. == Gallery == == See also == Cantonese salted fish Cured fish Salted squid Dried and salted cod Brining Gibbing Pickling salt Spekesild (cured, salted Atlantic herring) Surströmming (lightly-salted soured Baltic herring) == Notes == == References == Schwartz, RK (2004) "All roads lead to Rome: Roman food production in North Africa" Repast, 20 (4) : 5–6 and 8–9.
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{
"page_id": 11993615,
"source": null,
"title": "Salted fish"
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Antiparasitics are a class of medications which are indicated for the treatment of parasitic diseases, such as those caused by helminths, amoeba, ectoparasites, parasitic fungi, and protozoa, among others. Antiparasitics target the parasitic agents of the infections by destroying them or inhibiting their growth; they are usually effective against a limited number of parasites within a particular class. Antiparasitics are one of the antimicrobial drugs which include antibiotics that target bacteria, and antifungals that target fungi. They may be administered orally, intravenously or topically. Overuse or misuse of antiparasitics can lead to the development of antimicrobial resistance. Broad-spectrum antiparasitics, analogous to broad-spectrum antibiotics for bacteria, are antiparasitic drugs with efficacy in treating a wide range of parasitic infections caused by parasites from different classes. == Types == === Broad-spectrum === Nitazoxanide === Antiprotozoals === Melarsoprol (for treatment of sleeping sickness caused by Trypanosoma brucei) Eflornithine (for sleeping sickness) Metronidazole (for vaginitis caused by Trichomonas) Tinidazole (for intestinal infections caused by Giardia lamblia) Miltefosine (for the treatment of visceral and cutaneous leishmaniasis, currently undergoing investigation for Chagas disease) === Antihelminthic === ==== Antinematodes ==== Mebendazole (for most nematode infections) Pyrantel pamoate (for most nematode infections) Thiabendazole (for roundworm infections) Diethylcarbamazine (for treatment of Lymphatic filariasis) Ivermectin (for prevention of river blindness) Fenbendazole ==== Anticestodes ==== Niclosamide (for tapeworm infections) Praziquantel (for tapeworm infections) Albendazole (broad spectrum) ==== Antitrematodes ==== Praziquantel === Antiamoebics === Rifampin Amphotericin B === Antifungals === Fumagillin (for microsporidiosis) == Medical uses == Antiparasitics treat parasitic diseases, which impact an estimated 2 billion people. === Administration === Antiparastics may be given via a variety of routes depending on the specific medication, including oral, topical, and intravenous. Resistance to antiparasitics has been a growing concern, especially in veterinary medicine. The Egg hatch assay can be used to determine whether
|
{
"page_id": 7143953,
"source": null,
"title": "Antiparasitic"
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|
a parasite causing an infection has become resistant to standard drug treatments. == Drug development history == Early antiparasitics were ineffective, frequently toxic to patients, and difficult to administer due to the difficulty in distinguishing between the host and the parasite. Between 1975 and 1999 only 13 of 1,300 new drugs were antiparasitics, which raised concerns that insufficient incentives existed to drive development of new treatments for diseases that disproportionately target low-income countries. This led to new public sector and public-private partnerships (PPPs), including investment by the Bill and Melinda Gates Foundation. Between 2000 and 2005, twenty new antiparasitic agents were developed or in development. Metal-containing compounds are the subject of another avenue of approach. == Research == In the last decades, triazolopyrimidines and their metal complexes have been looked at as an alternative drug to the existing commercial antimonials, searching for a decrease in side effects and the development of parasite drug resistance. == See also == Balsam of Peru, which has antiparasitic attributes Naegleria fowleri Balamuthia mandrillaris == References ==
|
{
"page_id": 7143953,
"source": null,
"title": "Antiparasitic"
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|
In molecular biology mir-71 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms. == See also == MicroRNA == References == == Further reading == == External links == Page for mir-71 microRNA precursor family at Rfam
|
{
"page_id": 36373009,
"source": null,
"title": "Mir-71 microRNA precursor family"
}
|
Beam's eye view (abbreviated BEV) is an imaging technique used in radiation therapy for quality assurance and planning of external beam radiotherapy (EBRT). These are primarily used to ensure that the relative orientation of the patient and the treatment machine are correct. The BEV image will typically include the images of the patient's anatomy and the beam modifiers, such as jaws or multi-leaf collimators (MLCs). == Generation of beam's eye views == Physical construction: BEVs can be generated by exposing a high energy film (similar to photographic film) or an electronic portal imaging device (EPID) with the treatment beam itself after it passes through the patient and any beam modifiers (such as blocks). Although this type of image is an excellent indication of the basic quality of the treatment plan, the quality of film images can be poor. A BEV can be created using a radiation therapy simulator that mimics the treatment geometry (couch angle, gantry angle, etc.) using an X-ray source instead of the higher energy treatment source. The jaws and blocks can be imaged on the same film as the patient's landmarks. Artificial reconstruction: The BEV can be created using a digitally reconstructed radiograph (DRR) that is created from a computed tomography (or CT) data set. This image would contain the same treatment plan information, but the patient image is reconstructed from the CT image data using a physics model. == References == Faiz Kahn and Roger Potish (Eds.) (1998).Treatment Planning in Radiation Oncology. Williams & Wilkins. ISBN 0-683-04607-1. Jacob Van Dyk (Ed.) (1999). The Modern Technology of Radiation Oncology. Medical Physics Publishing. ISBN 0-944838-38-3. Ross I. Berbeco (Ed.) (2018). Beam's Eye View Imaging in Radiation Oncology. CRC Press. ISBN 978-1-4987-3634-3. Louis Lemieux, Roger Jagoe, David R. Fish, Neil D. Kitchen, David G. Thomas, A patient-to-computed-tomography image registration
|
{
"page_id": 2097683,
"source": null,
"title": "Beam's eye view"
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method based on digitally reconstructed radiographs. Med. Phys. 21(11), 1749–1760 (1994). https://doi.org/10.1118/1.597276
|
{
"page_id": 2097683,
"source": null,
"title": "Beam's eye view"
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Conversion and its related terms yield and selectivity are important terms in chemical reaction engineering. They are described as ratios of how much of a reactant has reacted (X — conversion, normally between zero and one), how much of a desired product was formed (Y — yield, normally also between zero and one) and how much desired product was formed in ratio to the undesired product(s) (S — selectivity). There are conflicting definitions in the literature for selectivity and yield, so each author's intended definition should be verified. Conversion can be defined for (semi-)batch and continuous reactors and as instantaneous and overall conversion. == Assumptions == The following assumptions are made: The following chemical reaction takes place: ∑ i = 1 n ν i A i = ∑ j = 1 m μ j B j {\displaystyle \sum _{i=1}^{n}\nu _{i}A_{i}=\sum _{j=1}^{m}\mu _{j}B_{j}} , where ν i {\displaystyle \nu _{i}} and μ j {\displaystyle \mu _{j}} are the stoichiometric coefficients. For multiple parallel reactions, the definitions can also be applied, either per reaction or using the limiting reaction. Batch reaction assumes all reactants are added at the beginning. Semi-Batch reaction assumes some reactants are added at the beginning and the rest fed during the batch. Continuous reaction assumes reactants are fed and products leave the reactor continuously and in steady state. == Conversion == Conversion can be separated into instantaneous conversion and overall conversion. For continuous processes the two are the same, for batch and semi-batch there are important differences. Furthermore, for multiple reactants, conversion can be defined overall or per reactant. === Instantaneous conversion === ==== Semi-batch ==== In this setting there are different definitions. One definition regards the instantaneous conversion as the ratio of the instantaneously converted amount to the amount fed at any point in time: X i
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"page_id": 1573393,
"source": null,
"title": "Conversion (chemistry)"
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, inst = n ˙ i , react n ˙ i , in {\displaystyle X_{i,{\text{inst}}}={\frac {{\dot {n}}_{i,{\text{react}}}}{{\dot {n}}_{i,{\text{in}}}}}} . with n ˙ i {\displaystyle {\dot {n}}_{i}} as the change of moles with time of species i. This ratio can become larger than 1. It can be used to indicate whether reservoirs are built up and it is ideally close to 1. When the feed stops, its value is not defined. In semi-batch polymerisation, the instantaneous conversion is defined as the total mass of polymer divided by the total mass of monomer fed: X poly = m Pol ∑ i ∫ 0 t m ˙ i , in ( τ ) d τ {\displaystyle X_{\text{poly}}={\frac {m_{\text{Pol}}}{\sum _{i}\int _{0}^{t}{\dot {m}}_{i,{\text{in}}}(\tau )d\tau }}} . === Overall conversion === ==== Batch (This is the generally stated form) ==== X i = n i ( t = 0 ) − n i ( t ) n i ( t = 0 ) = 1 − n i ( t ) n i ( t = 0 ) {\displaystyle X_{i}={\frac {n_{i}(t=0)-n_{i}(t)}{n_{i}(t=0)}}=1-{\frac {n_{i}(t)}{n_{i}(t=0)}}} ==== Semi-batch ==== Total conversion of the formulation: X i = n i ( t = 0 ) + ∫ 0 t n ˙ i , in ( τ ) d τ − n i ( t ) n i ( t = 0 ) + ∫ 0 t end n ˙ i , in ( τ ) d τ {\displaystyle X_{i}={\frac {n_{i}(t=0)+\int _{0}^{t}{\dot {n}}_{i,{\text{in}}}(\tau )d\tau -n_{i}(t)}{n_{i}(t=0)+\int _{0}^{t_{\text{end}}}{\dot {n}}_{i,{\text{in}}}(\tau )d\tau }}} Total conversion of the fed reactants: X i = n i ( t = 0 ) + ∫ 0 t n ˙ i , in ( τ ) d τ − n i ( t ) n i ( t = 0 ) + ∫ 0 t n ˙ i , in (
|
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"page_id": 1573393,
"source": null,
"title": "Conversion (chemistry)"
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τ ) d τ {\displaystyle X_{i}={\frac {n_{i}(t=0)+\int _{0}^{t}{\dot {n}}_{i,{\text{in}}}(\tau )d\tau -n_{i}(t)}{n_{i}(t=0)+\int _{0}^{t}{\dot {n}}_{i,{\text{in}}}(\tau )d\tau }}} ==== Continuous (This is the generally stated form) ==== X i = n ˙ i , i n − n ˙ i , o u t n ˙ i , i n = 1 − n ˙ i , o u t n ˙ i , i n {\displaystyle X_{i}={\frac {{\dot {n}}_{i,in}-{\dot {n}}_{i,out}}{{\dot {n}}_{i,in}}}=1-{\frac {{\dot {n}}_{i,out}}{{\dot {n}}_{i,in}}}} == Yield == Yield in general refers to the amount of a specific product (p in 1..m) formed per mole of reactant consumed (Definition 1). However, it is also defined as the amount of product produced per amount of product that could be produced (Definition 2). If not all of the limiting reactant has reacted, the two definitions contradict each other. Combining those two also means that stoichiometry needs to be taken into account and that yield has to be based on the limiting reactant (k in 1..n): === Continuous === Y p = n ˙ p , out − n ˙ p , in n ˙ k , in − n k , out ⏟ only for Definition 1 | μ k ν p | {\displaystyle Y_{p}={\frac {{\dot {n}}_{p,{\text{out}}}-{\dot {n}}_{p,{\text{in}}}}{{\dot {n}}_{k,{\text{in}}}\underbrace {-n_{k,{\text{out}}}} _{\text{only for Definition 1}}}}\left|{\frac {\mu _{k}}{\nu _{p}}}\right|} The version normally found in the literature: Y p = n ˙ p , out − n ˙ p , in n ˙ k , in | μ k ν p | {\displaystyle Y_{p}={\frac {{\dot {n}}_{p,{\text{out}}}-{\dot {n}}_{p,{\text{in}}}}{{\dot {n}}_{k,{\text{in}}}}}\left|{\frac {\mu _{k}}{\nu _{p}}}\right|} == Selectivity == Instantaneous selectivity is the production rate of one component per production rate of another component. For overall selectivity the same problem of the conflicting definitions exists. Generally, it is defined as the number of moles of desired product per the number of moles of
|
{
"page_id": 1573393,
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undesired product (Definition 1). However, the definitions of the total amount of reactant to form a product per total amount of reactant consumed is used (Definition 2) as well as the total amount of desired product formed per total amount of limiting reactant consumed (Definition 3). This last definition is the same as definition 1 for yield. === Batch or semi-batch === The version normally found in the literature: S p = n p ( t = 0 ) − n p ( t ) n k ( t = 0 ) + ∫ 0 t n ˙ k , in ( τ ) d τ − n k ( t ) | μ k ν p | {\displaystyle S_{p}={\frac {n_{p}(t=0)-n_{p}(t)}{n_{k}(t=0)+\int _{0}^{t}{\dot {n}}_{k,{\text{in}}}(\tau )d\tau -n_{k}(t)}}\left|{\frac {\mu _{k}}{\nu _{p}}}\right|} === Continuous === The version normally found in the literature: S p = n ˙ p , out − n ˙ p , in n ˙ k , in − n ˙ k , out | μ k ν p | {\displaystyle S_{p}={\frac {{\dot {n}}_{p,{\text{out}}}-{\dot {n}}_{p,{\text{in}}}}{{\dot {n}}_{k,{\text{in}}}-{\dot {n}}_{k,{\text{out}}}}}\left|{\frac {\mu _{k}}{\nu _{p}}}\right|} == Combination == For batch and continuous reactors (semi-batch needs to be checked more carefully) and the definitions marked as the ones generally found in the literature, the three concepts can be combined: Y p = X i ⋅ S p {\displaystyle Y_{p}=X_{i}\cdot S_{p}} For a process with the only reaction A ⟶ B {\displaystyle {\ce {A -> B}}} this mean that S=1 and Y=X. == Abstract example == For the following abstract example and the amounts depicted on the right, the following calculation can be performed with the above definitions, either in batch or a continuous reactor. A ⟶ B {\displaystyle {\ce {A -> B}}} A ⟶ C {\displaystyle {\ce {A -> C}}} B is the desired product. There are
|
{
"page_id": 1573393,
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"title": "Conversion (chemistry)"
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|
100 mol of A at the beginning or at the entry to the continuous reactor and 10 mol A, 72 mol B and 18 mol C at the end of the reaction or the exit of the continuous reactor. The three properties are found to be: X A = n A ( t = 0 ) − n A ( t ) n A ( t = 0 ) = 1 − n A ( t ) n A ( t = 0 ) = 100 − 10 100 = 0.9 = 90 % {\displaystyle X_{{\ce {A}}}={\frac {n_{{\ce {A}}}(t=0)-n_{A}(t)}{n_{{\ce {A}}}(t=0)}}=1-{\frac {n_{{\ce {A}}}(t)}{n_{{\ce {A}}}(t=0)}}={\frac {100-10}{100}}=0.9=90\%} Y B = n B ( t ) − n B ( t = 0 ) n A ( t = 0 ) + ∫ 0 t n ˙ A , in ( τ ) d τ | μ k ν p | = 72 − 0 100 + 0 ⋅ 1 1 = 0.72 = 72 % {\displaystyle Y_{{\ce {B}}}={\frac {n_{{\ce {B}}}(t)-n_{{\ce {B}}}(t=0)}{n_{{\ce {A}}}(t=0)+\int _{0}^{t}{\dot {n}}_{{\ce {A,{in}}}}(\tau )d\tau }}\left|{\frac {\mu _{k}}{\nu _{p}}}\right|={\frac {72-0}{100+0}}\cdot {\frac {1}{1}}=0.72=72\%} S B = n B ( t = 0 ) − n ˙ B ( t ) n ˙ A ( t = 0 ) − n A ( t ) | μ k ν p | = 0 − 72 100 − 10 ⋅ 1 1 = 0.8 = 80 % {\displaystyle S_{{\ce {B}}}={\frac {{n}_{{\ce {B}}}(t=0)-{\dot {n}}_{{\ce {B}}}(t)}{{\dot {n}}_{{\ce {A}}}(t=0)-n_{{\ce {A}}}(t)}}\left|{\frac {\mu _{k}}{\nu _{p}}}\right|={\frac {0-72}{100-10}}\cdot {\frac {1}{1}}=0.8=80\%} The property Y p = X i ⋅ S p {\displaystyle Y_{p}=X_{i}\cdot S_{p}} holds. In this reaction, 90% of substance A is converted (consumed), but only 80% of the 90% is converted to the desired substance B and 20% to undesired by-products C. So, conversion of A is 90%, selectivity for B
|
{
"page_id": 1573393,
"source": null,
"title": "Conversion (chemistry)"
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|
80% and yield of substance B 72%. == Literature == Werner Kullbach: Mengenberechnungen in der Chemie. Verlag Chemie, Weinheim 1980, ISBN 3-527-25869-8. Eberhard Aust, Burkhard Bittner: Stöchiometrie - Chemisches Rechnen, CICERO-Verlag, Pegnitz, 4. Auflage, 2011, ISBN 978-3-926292-47-6. Uwe Hillebrand: Stöchiometrie, Eine Einführung in die Grundlagen mit Beispielen und Übungsaufgaben, 2. Aufl., Springer-Verlag, Berlin Heidelberg 2009, ISBN 978-3-642-00459-9. == References ==
|
{
"page_id": 1573393,
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"title": "Conversion (chemistry)"
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Zvia Agur (Hebrew: צביה עגור) is an Israeli mathematical biologist, the founding president of the Institute for Medical BioMathematics, the former chair and chief scientific officer of Optimata Ltd., and the founding president of the Israeli Society of Theoretical and Mathematical Biology. Her research has included mathematical modeling of the pulse vaccination strategy and of cancer growth. == Education and career == Agur received a double Ph.D. in 1982, in zoology from the Hebrew University of Jerusalem and in chemical physics from the Université libre de Bruxelles. She became a postdoctoral researcher and scientist in applied mathematics at the Weizmann Institute of Science from 1982 until 1994, when she moved to Tel Aviv University as an associate professor in the Department of Cell Research and Immunology. While continuing to work for Tel Aviv University, she founded the Institute for Medical BioMathematics in 1999. She left the university in 2000 to found Optimata Ltd., and served as its chair and chief scientific officer until 2020. She became founding president of the Israeli Society of Theoretical and Mathematical Biology in 1998, and served as its president until 2002. She also served on the board of directors of the European Society of Mathematical and Theoretical Biology from 1997 to 2003. == Recognition == Agur was named as a Fellow of the American Association for the Advancement of Science, in its 2022 class of fellows. She became the second Israeli woman named as a fellow of the AAAS, and the first Israeli in over ten years. == References ==
|
{
"page_id": 79495701,
"source": null,
"title": "Zvia Agur"
}
|
The Grundmann aldehyde synthesis is a chemical reaction that produces an aldehyde from an acyl halide. Because of the Rosenmund reduction and DIBAL-H accomplish similar transformations, this reaction sequence is not practiced much currently. == References ==
|
{
"page_id": 13697553,
"source": null,
"title": "Grundmann aldehyde synthesis"
}
|
In mathematics and astrophysics, the Strömgren integral, introduced by Bengt Strömgren (1932, p.123) while computing the Rosseland mean opacity, is the integral: 15 4 π 4 ∫ 0 x t 7 e 2 t ( e t − 1 ) 3 d t . {\displaystyle {\frac {15}{4\pi ^{4}}}\int _{0}^{x}{\frac {t^{7}e^{2t}}{(e^{t}-1)^{3}}}\,dt.} Cox (1964) discussed applications of the Strömgren integral in astrophysics, and MacLeod (1996) discussed how to compute it. == References == Cox, A. N. (1964), "Stellar absorption coefficients and opacities", in Adler, Lawrence Hugh; McLaughlin, Dean Benjamin (eds.), Stellar Structure, Stars and Stellar Systems: Compendium of Astronomy and Astrophysics, vol. VIII, Chicago, Ill: University of Chicago Press, p. 195, ISBN 978-0-226-45969-1 {{citation}}: ISBN / Date incompatibility (help) MacLeod, Allan J. (1996), "Algorithm 757: MISCFUN, a software package to compute uncommon special functions", ACM Transactions on Mathematical Software, 22 (3), NY, USA: ACM New York: 288–301, doi:10.1145/232826.232846 Strömgren, B. (1932), "The opacity of stellar matter and the hydrogen content of the stars", Zeitschrift für Astrophysik, 4: 118–152, Bibcode:1932ZA......4..118S Strömgren, B. (1933), "On the Interpretation of the Hertzsprung-Russell-Diagram", Zeitschrift für Astrophysik, 7: 222, Bibcode:1933ZA......7..222S == External links == Stromgren integral
|
{
"page_id": 32768530,
"source": null,
"title": "Strömgren integral"
}
|
Fundamenta Botanica ("Foundations of botany") (Amsterdam, Salomon Schouten, ed. 1, 1736) was one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and issued both as a separate work and as part of the Bibliotheca Botanica. == Publication and reprints == This book states maia , for the first time, Linnaeus's ideas for the reformation of botanical taxonomy. The first edition is dated 1736 but it was released on 14 September 1735 (Linnaeus wrote in his personal copy "Typus absolutus 1735, Sept 3".). The full title was Fundamenta Botanica, quae Majorum Operum Prodromi instar Theoriam Scientiae Botanices by breves Aphorismos tradunt. The first edition was dedicated to Olof Rudbeck, Lorenz Heister, Adriaan van Royen, Johann Jacob Dillen, Antoine de Jussieu, Giulio Pontedera, Johann Amman, Johannes Burman, Pierre Magnol and Giuseppe Monti. A second edition was published in Stockholm in 1740 and a third in Amsterdam in 1741. The publication of this work as well as Genera Plantarum and Systema Naturae was encouraged by Herman Boerhaave, who had been Linnaeus's teacher. == Impact == The Fundamenta in combination with the Critica Botanica lays Linnaeus's bronzers for his system of nomenclature, classification and botanical terminology that were later reviewed and expanded in the Philosophia Botanica (1751). He does this by means of 365 aphorisms (principles) arranged into 12 chapters: == Table of contents == VIRIS NOBILISSIMIS (Dedication to men to honor) BOTANICIS CELEBERRIMIS (Dedication to famous botanists) PRAEFATIO (Preface) FUNDAMENTA BOTANICA (Botanical fundamentals or fundamental botanical aphorisms) I. BIBLIOTHECA (library), Aphorismen : articles 1-52 (page 1-5) II. SYSTEMATA (systematics) : articles 53–77 (pages 5-7) III. PLANTAE (plants) : articles 78–85 (pages 7-9) IV. FRUCTIFICATIO (fruit carrier) : articles 86–131 (pages 10-15) V. SEXUS (sex) : articles 132–150 (pages 15-17) VI. CHARACTERES (characterisation) : articles 151–209 (pages 18-22)
|
{
"page_id": 28574235,
"source": null,
"title": "Fundamenta Botanica"
}
|
VII. NOMINA (nouns or names) : articles 210–255 (pages 23-26) VIII. DIFFERENTIAE (distinction) : articles 256–305 (pages 26-29) IX. VARIATIONES (Varieties) : articles 306–317 (pages 30-31) X. SYNONYMA (synonyms) : articles 318–324 (pages 31-31) XI. ADUMBRATIONES (description) : articles 325–335 (pages 31-32) XII. VIRES (forces) : articles 336–365 (pages 33-35) CONCLUSIONES EX DICTIS (Conclusion from the foregoing) I-XII (page 36) == Bibliographic details == Full bibliographic details including exact dates of publication, pagination, editions, facsimiles, brief outline of contents, location of copies, secondary sources, translations, reprints, manuscripts, travelogues, and commentaries are given in Stafleu and Cowan's Taxonomic Literature. == References == == Bibliography == Stafleu, Frans A. & Cowan, Richard S. 1981. "Taxonomic Literature. A Selective Guide to Botanical Publications with dates, Commentaries and Types. Vol III: Lh–O." Regnum Vegetabile 105.
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{
"page_id": 28574235,
"source": null,
"title": "Fundamenta Botanica"
}
|
ParameciumDB is a database for the genome and biology of the ciliate Paramecium tetraurelia. == See also == Paramecium == References == == External links == Homepage
|
{
"page_id": 31588891,
"source": null,
"title": "ParameciumDB"
}
|
The greater sciatic foramen is an opening (foramen) in the posterior human pelvis. It is formed by the sacrotuberous and sacrospinous ligaments. The piriformis muscle passes through the foramen and occupies most of its volume. The greater sciatic foramen is wider in women than in men. == Structure == It is bounded as follows: anterolaterally by the greater sciatic notch of the ilium. posteromedially by the sacrotuberous ligament. inferiorly by the sacrospinous ligament and the ischial spine. superiorly by the anterior sacroiliac ligament. == Function == The piriformis, which exits the pelvis through the foramen, occupies most of its volume. The following structures also exit the pelvis through the greater sciatic foramen: == See also == Lesser sciatic foramen == References == This article incorporates text in the public domain from page 309 of the 20th edition of Gray's Anatomy (1918) == External links == Greater sciatic foramen at the Duke University Health System's Orthopedics program glutealregion at The Anatomy Lesson by Wesley Norman (Georgetown University) (glutealart, glutealner)
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{
"page_id": 4784672,
"source": null,
"title": "Greater sciatic foramen"
}
|
The stomatognathic system is an anatomical system comprising the teeth, jaws, and associated soft tissues. It was formerly called the stomognathic system. Stomatognathic diseases are treated by dentists, maxillofacial surgeons, ear, nose, and throat specialists, speech therapists, occupational therapists, myofunctional therapists, and physical therapists. == References == == External links == Stomatognathic+System at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
|
{
"page_id": 5046822,
"source": null,
"title": "Stomatognathic system"
}
|
Quick clay, also known as Leda clay and Champlain Sea clay in Canada, is any of several distinctively sensitive glaciomarine clays found in Canada, Norway, Russia, Sweden, Finland, the United States, and other locations around the world. The clay is so unstable that when a mass of quick clay is subjected to sufficient stress, the material behavior may drastically change from that of a particulate material to that of a watery fluid. Landslides occur because of the sudden soil liquefaction caused by external solicitations such as vibrations induced by an earthquake, or massive rainfalls. == Quick clay main deposits == Quick clay is found only in countries close to the north pole, such as Russia; Canada; Norway; Sweden; and Finland; and in Alaska (United States); since they were glaciated during the Pleistocene epoch. In Canada, the clay is associated primarily with the Pleistocene-era Champlain Sea, in the modern Ottawa Valley, the St. Lawrence Valley, and the Saguenay River regions. Quick clay has been the underlying cause of many deadly landslides. In Canada alone, it has been associated with more than 250 mapped landslides. Some of these are ancient, and may have been triggered by earthquakes. == Clay colloids stability == Quick clay has a remolded strength which is much less than its strength upon initial loading. This is caused by its highly unstable clay particle structure. Quick clay is originally deposited in a marine environment. Clay mineral particles are always negatively charged because of the presence of permanent negative charges and pH dependent charges at their surface. Because of the need to respect electro-neutrality and a net zero electrical charge balance, these negative electrical charges are always compensated by the positive charges born by cations (such as Na+) adsorbed onto the surface of the clay, or present in the clay
|
{
"page_id": 1770024,
"source": null,
"title": "Quick clay"
}
|
pore water. Exchangeable cations are present in the clay minerals interlayers and on the external basal planes of clay platelets. Cations also compensate the negative charges on the clay particle edges caused by the protolysis of silanol and aluminol groups (pH dependent charges). So, clay platelets are always surrounded by an electrical double layer (EDL), or diffuse double layer (DDL). The thickness of EDL depends on the salinity of water. Under salty conditions (at high ionic strength) EDL is compressed (or said to be collapsed). It facilitates the aggregation of clay platelets which flocculate and stick together in a more stable aggregates structure. After the marine clay deposit is uplifted and is no longer exposed to salt water conditions, rainwater can slowly infiltrate the poorly compacted clay layer and the excess of NaCl present in seawater can also diffuse out of the clay. As a result, the EDL is less compressed and can expand. It results in a stronger electrostatic repulsion between negatively charged clay platelets which can more easily become dispersed and form stable suspensions in water (peptization phenomenon). The effect leads to a destabilization of the clay aggregates structure. In case of insufficient mechanical compaction of the clay layer, and with a shear stress, the weaker EDL compression by the salts in the quick clay results in clay particle repulsion and leads to their realignment in a structure that is weaker and unstable. Quick clay regains strength rapidly when salt is again added (compression of the EDL), which allows clay particles to restore their cohesion with one another. == Formation of quick clay == At the height of the past glaciation (about 20,000 years ago), the land was 'pushed' down by the weight of the ice (isostatic depression). All of the ground-up rock was deposited in the surrounding
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{
"page_id": 1770024,
"source": null,
"title": "Quick clay"
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ocean, which had penetrated significantly inland. The loose deposition of the silt and clay particles in the marine environment, allowed an unusual flocculation to take place. Essentially, this formed a strongly bonded soil skeleton, which was 'glued' by highly mobile sea-salt ions. At this point, there was only the formation of very strong marine clay, which is found all over the world and highly stable, but with its own unique geotechnical problems. When the glaciers retreated, the land mass rose (post-glacial rebound), the clay was exposed, and formed the soil mass for new vegetation. The rainwater in these northern countries was quite aggressive to these clays, perhaps because it was softer (containing less calcium), or the higher silt content allowed more rainwater and snowmelt to penetrate. The final result was that the ionic 'glue' of the clay was weakened, to give a weak, loose soil skeleton, enclosing significant amounts of water (high sensitivity with high moisture content). Quick clay deposits are rarely located directly at the ground surface, but are typically covered by a normal layer of topsoil. While this topsoil can absorb most normal stresses, such as normal rainfall or a modest earth tremor, a shock that exceeds the capacity of the topsoil layer — such as a larger earthquake, a large mass added near a slope, or an abnormal rainfall which leaves the topsoil fully saturated so that additional water has nowhere to permeate except into the clay — can disturb the clay and initiate the process of liquefaction. == Disasters == Because the clay layer is typically covered with topsoil, a location which is vulnerable to a quick clay landslide is usually identifiable only by soil testing, and is rarely obvious to a casual observer. Thus human settlements and transportation links have often been built on or
|
{
"page_id": 1770024,
"source": null,
"title": "Quick clay"
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near clay deposits, resulting in a number of notable catastrophes: In 1702, a landslide destroyed almost all traces of the medieval town Sarpsborg in what is now Østfold county in Norway. 15 people and 200 animals were killed. On 19 May 1893, a landslide in Verdal Municipality, Norway, killed 116 people and destroyed 105 farms. It left a crater several kilometers in diameter. The most disastrous such landslide to affect North America occurred in 1908, when a slide into the frozen Du Lièvre River propelled a wave of ice-filled water into Notre-Dame-de-la-Salette, Quebec, causing the loss of 33 lives and the destruction of 12 homes. In 1955, a landslide affected part of the downtown of Nicolet, Quebec, causing $10 million in damages. In 1957, a large quick-clay landslide occurred in Lilla Edet, by the Göta River, in southwestern Sweden. A large part of a factory slid into the river, causing a thirty meter reduction in the river width. The earth mass coming into the river produced an approximately six meter high wave. On March 27, 1964, parts of Anchorage, Alaska built on sandy bluffs overlying "Bootlegger Cove clay" near Cook Inlet, most notably the Turnagain neighborhood, suffered landslide damage during the 1964 Alaska Earthquake. The neighborhood lost 75 houses in the landslide, and the destroyed area has since been turned into Earthquake Park. On 4 May 1971, 31 lives were lost when 40 homes were swallowed in a retrogressive flowslide in Saint-Jean-Vianney, Quebec, resulting in the relocation of the entire town when the government declared the area uninhabitable due to the presence of Leda clay. The event at Saint-Jean-Vianney contributed to the abandonment of the town of Lemieux, Ontario, in 1991, after a 1989 study showed it was also located on the same type of clay along the South Nation
|
{
"page_id": 1770024,
"source": null,
"title": "Quick clay"
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|
River. In 1993, those findings were borne out when the town's abandoned main street was swallowed by a massive 17-hectare landslide. On November 30, 1977, the Tuve landslide in western Sweden killed 9 people and destroyed 67 houses. Another famous flow of quick clay in Rissa Municipality, Norway, in 1978 caused about 33 hectares (82 acres) of farmland to liquefy and flow into the lake Botn over a few hours, with the loss of one life. The Rissa slide was well recorded by local citizens and a documentary film was made about it in 1981. On 11 May 2010, quick clay took the lives of a family living in Saint-Jude, Quebec, when the land their house was built on suddenly tumbled down toward the Salvail River. The landslide was so sudden that the family members died where they sat; they had been watching an ice hockey game on television. The slide took out a portion of rural road which took a year to reinstate. On 2 February 2015, a landslide collapsed a pillar on the Skjeggestad Bridge in South-East Norway. The landslide was caused by nearby earthworks. On 3 June 2020, eight buildings were swept into the sea by a landslide in Kråkneset in Alta Municipality in Norway. The landslide was filmed by a resident. There were no casualties, and a dog was rescued from the sea. On 30 December 2020, part of a housing area was swept away by a landslide in the village of Ask in Gjerdrum Municipality in Norway, about 25 kilometres (16 mi) northeast of the capital Oslo. The 300-by-700-metre (980 ft × 2,300 ft) quick clay landslide wrecked several houses and killed 10 people. On 23 September 2023, near the town of Stenungsund, Sweden, an area of c. 15 hectares (37 acres) was affected by
|
{
"page_id": 1770024,
"source": null,
"title": "Quick clay"
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|
a quick clay landslide, which among other things damaged the E6 motorway between Gothenburg and Oslo. These landslides are retrogressive, meaning they usually start at water, and progress upwards at slow walking speed, although particularly deep quick clay layers on sloped regions may collapse much more rapidly, or in very large chunks that can slide at great speed due to the liquid nature of the disturbed clay. They have been known to penetrate kilometers inland, and consume everything in their path. In modern times, areas known to have quick clay deposits are commonly tested in advance of any major human development. It is not always possible to entirely avoid building on a quick clay site, although modern engineering techniques have found technical precautions which can be taken to mitigate the risk of disaster. For example, when Ontario's Highway 416 had to pass through a quick clay deposit near Nepean, lighter fill materials such as polystyrene were used for the road bed, vertical wick drains were inserted along the route and groundwater cutoff walls were built under the highway to limit water infiltration into the clay. == See also == Clay chemistry Clay-water interaction Critical state soil mechanics DLVO theory, model for aggregation of aqueous dispersions Effective stress Electrical double layer, (EDL) Geomechanics Interface and colloid science Non-Newtonian fluid Quicksand Screening effect Shear strength (soil) Shielding effect Terzaghi's principle Urban Search and Rescue == In popular culture == The 1967 novel Landslide by Desmond Bagley, tells the story of a quick-clay landslide in Canada. The book was also adapted into a 1992 television film by the same name, directed by Jean-Claude Lord, and starring Anthony Edwards. == References == == External links == Rissa Landslide, by University of Washington: short synopsis with link to video clips
|
{
"page_id": 1770024,
"source": null,
"title": "Quick clay"
}
|
The Pensky–Martens closed-cup flash-point test is a test for the determination of the flash point of flammable liquids. It is standardized as ASTM D93, EN ISO 2719 and IP 34 The United States Environmental Protection Agency (EPA) has also published Method 1010A: Test Methods for Flash Point by Pensky-Martens Closed Cup Tester, part of Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, which references the ASTM standard series D93. The Pensky-Martens test is a closed-cup method as opposed to the Cleveland open-cup method. == Test Procedure == A brass test cup is filled with a test specimen and closed with a lid, through which an ignition source can be introduced periodically. The sample is heated and stirred at specified rates depending on the material that is being tested. This allows the development of an equilibrium between the liquid and the air volume. The ignition source is directed into the cup at regular intervals with simultaneous interruption of stirring. The test concludes upon observation of a flash that spreads throughout the inside of the cup. The corresponding temperature is the liquid's flash point. == Critique of test method == The different flash point methods depend on the controlled conditions in the laboratory and do not determine an intrinsic property of the material tested. They are however useful to compare different substances and is therefore widely used in road transportation and environmental safety regulations. Closed cup testers give lower values for the flashpoint than open-cup testers (typically 5–10 K) and are a better approximation to the temperature at which the vapour pressure reaches the "Lower flammable limit" (LFL). == References ==
|
{
"page_id": 13500970,
"source": null,
"title": "Pensky–Martens closed-cup test"
}
|
In the mathematical field of representation theory, a representation of a Lie superalgebra is an action of Lie superalgebra L on a Z2-graded vector space V, such that if A and B are any two pure elements of L and X and Y are any two pure elements of V, then ( c 1 A + c 2 B ) ⋅ X = c 1 A ⋅ X + c 2 B ⋅ X {\displaystyle (c_{1}A+c_{2}B)\cdot X=c_{1}A\cdot X+c_{2}B\cdot X} A ⋅ ( c 1 X + c 2 Y ) = c 1 A ⋅ X + c 2 A ⋅ Y {\displaystyle A\cdot (c_{1}X+c_{2}Y)=c_{1}A\cdot X+c_{2}A\cdot Y} ( − 1 ) A ⋅ X = ( − 1 ) A ( − 1 ) X {\displaystyle (-1)^{A\cdot X}=(-1)^{A}(-1)^{X}} [ A , B ] ⋅ X = A ⋅ ( B ⋅ X ) − ( − 1 ) A B B ⋅ ( A ⋅ X ) . {\displaystyle [A,B]\cdot X=A\cdot (B\cdot X)-(-1)^{AB}B\cdot (A\cdot X).} Equivalently, a representation of L is a Z2-graded representation of the universal enveloping algebra of L which respects the third equation above. == Unitary representation of a star Lie superalgebra == A * Lie superalgebra is a complex Lie superalgebra equipped with an involutive antilinear map * such that * respects the grading and [a,b]*=[b*,a*]. A unitary representation of such a Lie algebra is a Z2 graded Hilbert space which is a representation of a Lie superalgebra as above together with the requirement that self-adjoint elements of the Lie superalgebra are represented by Hermitian transformations. This is a major concept in the study of supersymmetry together with representation of a Lie superalgebra on an algebra. Say A is an *-algebra representation of the Lie superalgebra (together with the additional requirement that * respects the grading
|
{
"page_id": 852522,
"source": null,
"title": "Representation of a Lie superalgebra"
}
|
and L[a]*=-(-1)LaL*[a*]) and H is the unitary rep and also, H is a unitary representation of A. These three reps are all compatible if for pure elements a in A, |ψ> in H and L in the Lie superalgebra, L[a|ψ>)]=(L[a])|ψ>+(-1)Laa(L[|ψ>]). Sometimes, the Lie superalgebra is embedded within A in the sense that there is a homomorphism from the universal enveloping algebra of the Lie superalgebra to A. In that case, the equation above reduces to L[a]=La-(-1)LaaL. This approach avoids working directly with a Lie supergroup, and hence avoids the use of auxiliary Grassmann numbers. == See also == Graded vector space Lie algebra representation Representation theory of Hopf algebras
|
{
"page_id": 852522,
"source": null,
"title": "Representation of a Lie superalgebra"
}
|
Experimental approaches of determining the structure of nucleic acids, such as RNA and DNA, can be largely classified into biophysical and biochemical methods. Biophysical methods use the fundamental physical properties of molecules for structure determination, including X-ray crystallography, NMR and cryo-EM. Biochemical methods exploit the chemical properties of nucleic acids using specific reagents and conditions to assay the structure of nucleic acids. Such methods may involve chemical probing with specific reagents, or rely on native or analogue chemistry. Different experimental approaches have unique merits and are suitable for different experimental purposes. == Biophysical methods == === X-ray crystallography === X-ray crystallography is not common for nucleic acids alone, since neither DNA nor RNA readily form crystals. This is due to the greater degree of intrinsic disorder and dynamism in nucleic acid structures and the negatively charged (deoxy)ribose-phosphate backbones, which repel each other in close proximity. Therefore, crystallized nucleic acids tend to be complexed with a protein of interest to provide structural order and neutralize the negative charge. === Nuclear magnetic resonance spectroscopy (NMR) === Nucleic acid NMR is the use of NMR spectroscopy to obtain information about the structure and dynamics of nucleic acid molecules, such as DNA or RNA. As of 2003, nearly half of all known RNA structures had been determined by NMR spectroscopy. Nucleic acid NMR uses similar techniques as protein NMR, but has several differences. Nucleic acids have a smaller percentage of hydrogen atoms, which are the atoms usually observed in NMR, and because nucleic acid double helices are stiff and roughly linear, they do not fold back on themselves to give "long-range" correlations. The types of NMR usually done with nucleic acids are 1H or proton NMR, 13C NMR, 15N NMR, and 31P NMR. Two-dimensional NMR methods are almost always used, such as correlation spectroscopy
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
}
|
(COSY) and total coherence transfer spectroscopy (TOCSY) to detect through-bond nuclear couplings, and nuclear Overhauser effect spectroscopy (NOESY) to detect couplings between nuclei that are close to each other in space. Parameters taken from the spectrum, mainly NOESY cross-peaks and coupling constants, can be used to determine local structural features such as glycosidic bond angles, dihedral angles (using the Karplus equation), and sugar pucker conformations. For large-scale structure, these local parameters must be supplemented with other structural assumptions or models, because errors add up as the double helix is traversed, and unlike with proteins, the double helix does not have a compact interior and does not fold back upon itself. NMR is also useful for investigating nonstandard geometries such as bent helices, non-Watson–Crick basepairing, and coaxial stacking. It has been especially useful in probing the structure of natural RNA oligonucleotides, which tend to adopt complex conformations such as stem-loops and pseudoknots. NMR is also useful for probing the binding of nucleic acid molecules to other molecules, such as proteins or drugs, by seeing which resonances are shifted upon binding of the other molecule. === Cryogenic electron microscopy (cryo-EM) === Cryogenic electron microscopy (cryo-EM) is a technique that uses an electron beam to image samples that have been cryogenically preserved in an aqueous solution. Liquid samples are pipetted on small metallic grids and plunged into a liquid ethane/propane solution which is kept extremely cold by a liquid nitrogen bath. Upon this freezing process, water molecules in the sample do not have enough time to form hexagonal lattices as found in ice, and therefore the sample is preserved in a glassy water-like state (also referred to as a vitrified ice), making these samples easier to image using the electron beam. An advantage of cryo-EM over x-ray crystallography is that the samples are
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
}
|
preserved in their aqueous solution state and not perturbed by forming a crystal of the sample. One disadvantage, is that it is difficult to resolve nucleic acid or protein structures that are smaller than ~75 kilodaltons, partly due to the difficulty of having enough contrast to locate particles in this vitrified aqueous solution. Another disadvantage is that to attain atomic-level structure information about a sample requires taking many images (often referred to as electron micrographs) and averaging over those images in a process called single-particle reconstruction. This is a computationally intensive process. Cryo-EM is a newer, less perturbative version of transmission electron microscopy (TEM). It is less perturbative because the sample is not dried onto a surface, this drying process is often done in negative-stain TEM, and because Cryo-EM does not require contrast agent like heavy metal salts (e.g. uranyl acetate or phoshotungstic acid) which also may affect the structure of the biomolecule. Transmission electron microscopy, as a technique, utilizes the fact that samples interact with a beam of electrons and only parts of the sample that do not interact with the electron beam are allowed to 'transmit' onto the electron detection system. TEM, in general, has been a useful technique in determining nucleic acid structure since the 1960s. While double-stranded DNA (dsDNA) structure may not traditionally be considered structure, in the typical sense of alternating segments of single- and double-stranded regions, in reality, dsDNA is not simply a perfectly ordered double helix at every location of its length due to thermal fluctuations in the DNA and alternative structures that can form like g-quadruplexes. CryoEM of nucleic acid has been done on ribosomes, viral RNA, and single-stranded RNA structures within viruses. These studies have resolved structural features at different resolutions from the nucleobase level (2-3 angstroms) up to tertiary structure
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
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|
motifs (greater than a nanometer). == Chemical probing == RNA chemical probing uses chemicals that react with RNAs. Importantly, their reactivity depends on local RNA structure e.g. base-pairing or accessibility. Differences in reactivity can therefore serve as a footprint of structure along the sequence. Different reagents react at different positions on the RNA structure, and have different spectra of reactivity. Recent advances allow the simultaneous study of the structure of many RNAs (transcriptome-wide probing) and the direct assay of RNA molecules in their cellular environment (in-cell probing). Structured RNA is first reacted with the probing reagents for a given incubation time. These reagents would form a covalent adduct on the RNA at the site of reaction. When the RNA is reverse transcribed using a reverse transcriptase into a DNA copy, the DNA generated is truncated at the positions of reaction because the enzyme is blocked by the adducts. The collection of DNA molecules of various truncated lengths therefore informs the frequency of reaction at every base position, which reflects the structure profile along the RNA. This is traditionally assayed by running the DNA on a gel, and the intensity of bands inform the frequency of observing a truncation at each position. Recent approaches use high-throughput sequencing to achieve the same purpose with greater throughput and sensitivity. The reactivity profile can be used to study the degree of structure at particular positions for specific hypotheses, or used in conjunction with computational algorithms to produce a complete experimentally supported structure model. Depending on the chemical reagent used, some reagents, e.g. hydroxyl radicals, would cleave the RNA molecule instead. The result in the truncated DNA is the same. Some reagents, e.g. DMS, sometimes do not block the reverse transcriptase, but trigger a mistake at the site in the DNA copy instead. These can
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
}
|
be detected when using high-throughput sequencing methods, and is sometimes employed for improved results of probing as mutational profiling (MaP). Positions on the RNA can be protected from the reagents not only by local structure but also by a binding protein over that position. This has led some work to use chemical probing to also assay protein-binding. === Hydroxyl radical probing === As hydroxyl radicals are short-lived in solution, they need to be generated upon experiment. This can be done using H2O2, ascorbic acid, and Fe(II)-EDTA complex. These reagents form a system that generates hydroxyl radicals through Fenton chemistry. The hydroxyl radicals can then react with the nucleic acid molecules. Hydroxyl radicals attack the ribose/deoxyribose ring and this results in breaking of the sugar-phosphate backbone. Sites under protection from binding proteins or RNA tertiary structure would be cleaved by hydroxyl radical at a lower rate. These positions would therefore show up as absence of bands on the gel, or low signal through sequencing. === DMS === Dimethyl sulfate, known as DMS, is a chemical that can be used to modify nucleic acids in order to determine secondary structure. Reaction with DMS adds a methyl adduct at the site, known as methylation. In particular, DMS methylates N1 of adenine (A) and N3 of cytosine (C), both located at the site of natural hydrogen bonds upon base-pairing. Therefore, modification can only occur at A and C nucleobases that are single-stranded, base paired at the end of a helix, or in a base pair at or next to a GU wobble pair, the latter two being positions where the base-pairing can occasionally open up. Moreover, since modified sites cannot be base-paired, modification sites can be detected by RT-PCR, where the reverse transcriptase falls off at methylated bases and produces different truncated cDNAs. These
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
}
|
truncated cDNAs can be identified through gel electrophoresis or high-throughput sequencing. Improving upon truncation-based methods, DMS mutational profiling with sequencing (DMS-MaPseq) can detect multiple DMS modifications in a single RNA molecule, which enables one to obtain more information per read (for a read of 150 nt, typically two to three mutation sites, rather than zero to one truncation sites), determine structures of low-abundance RNAs, and identify subpopulations of RNAs with alternative secondary structures. DMS-MaPseq uses a thermostable group II intron reverse transcriptase (TGIRT) that creates a mutation (rather than a truncation) in the cDNA when it encounters a base methylated by DMS, but otherwise it reverse transcribes with high fidelity. Sequencing the resulting cDNA identifies which bases were mutated during reverse transcription; these bases cannot have been base-paired in the original RNA. DMS modification can also be used for DNA, for example in footprinting DNA-protein interactions. === SHAPE === Selective 2′-hydroxyl acylation analyzed by primer extension, or SHAPE, takes advantage of reagents that preferentially modify the backbone of RNA in structurally flexible regions. Reagents such as N-methylisatoic anhydride (NMIA) and 1-methyl-7-nitroisatoic anhydride (1M7) react with the 2'-hydroxyl group to form adducts on the 2'-hydroxyl of the RNA backbone. Compared to the chemicals used in other RNA probing techniques, these reagents have the advantage of being largely unbiased to base identity, while remaining very sensitive to conformational dynamics. Nucleotides which are constrained (usually by base-pairing) show less adduct formation than nucleotides which are unpaired. Adduct formation is quantified for each nucleotide in a given RNA by extension of a complementary DNA primer with reverse transcriptase and comparison of the resulting fragments with those from an unmodified control. SHAPE therefore reports on RNA structure at the individual nucleotide level. This data can be used as input to generate highly accurate secondary structure
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
}
|
models. SHAPE has been used to analyze diverse RNA structures, including that of an entire HIV-1 genome. The best approach is to use a combination of chemical probing reagents and experimental data. In SHAPE-Seq SHAPE is extended by bar-code based multiplexing combined with RNA-Seq and can be performed in a high-throughput fashion. === Carbodiimides === The carbodiimide moiety can also form covalent adducts at exposed nucleobases, which are uracil, and to a smaller extent guanine, upon nucleophilic attack by a deprotonated N. They react primarily with N3 of uracil and N1 of guanine modifying two sites responsible for hydrogen bonding on the bases. 1-cyclohexyl-(2-morpholinoethyl)carbodiimide metho-p-toluene sulfonate, also known as CMCT or CMC, is the most commonly used carbodiimide for RNA structure probing. Similar to DMS, it can be detected by reverse transcription followed by gel electrophoresis or high-throughput sequencing. As it is reactive towards G and U, it can be used to complement the data from DMS probing experiments, which inform A and C. 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, also known as EDC, is a water-soluble carbodiimide that exhibits similar reactivity as CMC, and is also used for the chemical probing of RNA structure. EDC is able to permeate into cells and is thus used for direct in-cell probing of RNA in their native environments. === Kethoxal, glyoxal and derivatives === Some 1,2-dicarbonyl compounds are able to react with single-stranded guanine (G) at N1 and N2, forming a five-membered ring adduct at the Watson-Crick face. 1,1-Dihydroxy-3-ethoxy-2-butanone, also known as kethoxal, has a structure related to 1,2-dicarbonyls, and was the first in this category used extensively for the chemical probing of RNA. Kethoxal causes the modification of guanine, specifically altering the N1 and the exocyclic amino group (N2) simultaneously by covalent interaction. Glyoxal, methylglyoxal, and phenylglyoxal, which all carry the key 1,2-dicarbonyl moiety, all react
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
}
|
with free guanines similar to kethoxal, and can be used to probe unpaired guanine bases in structured RNA. Due to their chemical properties, these reagents can permeate readily into cells and can therefore be used to assay RNAs in their native cellular environments. === LASER or NAz Probing === Light-Activated Structural Examination of RNA (LASER) probing utilizes UV light to activate nicotinoyl azide (NAz), generating highly reactive nitrenium cation in water, which reacts with solvent accessible guanosine and adenosine of RNA at C-8 position through a barrierless Friedel-Crafts reaction. LASER probing targets both single-stranded and double-stranded residues as long as they are solvent accessible. Because hydroxyl radical probing requires synchrotron radiation to measure solvent accessibility of RNA in vivo, it is hard to apply hydroxyl radical probing to footprint RNA in cells for many laboratories. In contrast, LASER probing utilizes a hand-held UV lamp (20 W) for excitation, it is much easier to apply LASER probing for in vivo studying RNA solvent accessibility. This chemical probing method is light-controllable, and probes solvent accessibility of nucleobase, which has been shown to footprint RNA binding proteins inside cells. == In-line probing == In-line probing does not involve treatment with any type of chemical or reagent to modify RNA structures. This type of probing assay uses the structure dependent cleavage of RNA; single stranded regions are more flexible and unstable and will degrade over time. The process of in-line probing is often used to determine changes in structure due to ligand binding. Binding of a ligand can result in different cleavage patterns. The process of in-line probing involves incubation of structural or functional RNAs over a long period of time. This period can be several days, but varies in each experiment. The incubated products are then run on a gel to visualize the
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
}
|
bands. This experiment is often done using two different conditions: 1) with ligand and 2) in the absence of ligand. Cleavage results in shorter band lengths and is indicative of areas that are not basepaired, as basepaired regions tend to be less sensitive to spontaneous cleavage. In-line probing is a functional assay that can be used to determine structural changes in RNA in response to ligand binding. It can directly show the change in flexibility and binding of regions of RNA in response to a ligand, as well as compare that response to analogous ligands. This assay is commonly used in dynamic studies, specifically when examining riboswitches. == Nucleotide analog interference mapping (NAIM) == Nucleotide analog interference mapping (NAIM) is the process of using nucleotide analogs, molecules that are similar in some ways to nucleotides but lack function, to determine the importance of a functional group at each location of an RNA molecule. The process of NAIM is to insert a single nucleotide analog into a unique site. This can be done by transcribing a short RNA using T7 RNA polymerase, then synthesizing a short oligonucleotide containing the analog in a specific position, then ligating them together on the DNA template using a ligase. The nucleotide analogs are tagged with a phosphorothioate, the active members of the RNA population are then distinguished from the inactive members, the inactive members then have the phosphorothioate tag removed and the analog sites are identified using gel electrophoresis and autoradiography. This indicates a functionally important nucleotide, as cleavage of the phosphorothioate by iodine results in an RNA that is cleaved at the site of the nucleotide analog insert. By running these truncated RNA molecules on a gel, the nucleotide of interest can be identified against a sequencing experiment Site directed incorporation results indicate positions
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
}
|
of importance where when running on a gel, functional RNAs that have the analog incorporated at that position will have a band present, but if the analog results in non-functionality, when the functional RNA molecules are run on a gel there will be no band corresponding to that position on the gel. This process can be used to evaluate an entire area, where analogs are placed in site specific locations, differing by a single nucleotide, then when functional RNAs are isolated and run on a gel, all areas where bands are produced indicate non-essential nucleotides, but areas where bands are absent from the functional RNA indicate that inserting a nucleotide analog in that position caused the RNA molecule to become non-functional == References ==
|
{
"page_id": 22217265,
"source": null,
"title": "Nucleic acid structure determination"
}
|
Terrestrial ecosystems are ecosystems that are found on land. Examples include tundra, taiga, temperate deciduous forest, tropical rain forest, grassland, deserts. Terrestrial ecosystems differ from aquatic ecosystems by the predominant presence of soil rather than water at the surface and by the extension of plants above this soil/water surface in terrestrial ecosystems. There is a wide range of water availability among terrestrial ecosystems (including water scarcity in some cases), whereas water is seldom a limiting factor to organisms in aquatic ecosystems. Because water buffers temperature fluctuations, terrestrial ecosystems usually experience greater diurnal and seasonal temperature fluctuations than do aquatic ecosystems in similar climates. Terrestrial ecosystems are of particular importance especially in meeting Sustainable Development Goal 15 that targets the conservation-restoration and sustainable use of terrestrial ecosystems. == Organisms and processes == Organisms in terrestrial ecosystems have adaptations that allow them to obtain water when the entire body is no longer bathed in that fluid, means of transporting the water from limited sites of acquisition to the rest of the body, and means of preventing the evaporation of water from body surfaces. They also have traits that provide body support in the atmosphere, a much less buoyant medium than water, and other traits that render them capable of withstanding the extremes of temperature, wind, and humidity that characterize terrestrial ecosystems. Finally, the organisms in terrestrial ecosystems have evolved many methods of transporting gametes in environments where fluid flow is much less effective as a transport medium. This is terrestrial ecosystems. Common Types of Terrestrial Plants Four main groupings for terrestrial plants are bryophytes, pteridophytes, gymnosperms, and angiosperms, have been existing for many years and have allowed diversity into our ecosystems . == Size and plants == Terrestrial ecosystems occupy 55,660,000 mi2 (144,150,000 km2), or 28.26% of Earth's surface. Major plant taxa
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{
"page_id": 30999091,
"source": null,
"title": "Terrestrial ecosystem"
}
|
in terrestrial ecosystems are members of the division Magnoliophyta (flowering plants), of which there are about 275,000 species, and the division Pinophyta (conifers), of which there are about 500 species. Members of the division Bryophyta (mosses and liverworts), of which there are about 24,000 species, are also important in some terrestrial ecosystems. Major animal taxa in terrestrial ecosystems include the classes Insecta (insects) with about 900,000 species, Aves (birds) with 8,500 species, and Mammalia (mammals) with approximately 4,100 species. == See also == Aquatic-terrestrial subsidies Colonization of land - history of terrestrial life Soil ecology == References == [1] [2] [3]
|
{
"page_id": 30999091,
"source": null,
"title": "Terrestrial ecosystem"
}
|
An A-center is a type of crystallographic defect complex in silicon which consists of a vacancy defect and an impurity oxygen atom. In general, oxygen in silicon is interstitial, in which the oxygen atom breaks the covalent bond between two adjacent silicon atoms and is attached in the middle. A-centers - another type of defect, in which oxygen takes the place of the absent silicon atom, that is, it becomes a kind of replacement defect. The A-center is visible in infrared spectra with a wavelength of 12 μm. == References == Watkins, G. D.; Corbett, J. W. (1961). "Defects in Irradiated Silicon. I. Electron Spin Resonance of the Si-A Center". Physical Review. 121. doi:10.1103/PhysRev.121.1001. Watkins, G. D.; Corbett, J. W. (1961). "Defects in Irradiated Silicon. II. Infrared Absorption of the Si-A Center". Physical Review. 121. doi:10.1103/PhysRev.121.1015. Bemski, Feher; Gere, E. (1958). Business Meeting of the Division of Solid-State Physics: Spin Resonance in Electron Irradiated Silicon. Bulletin of the American Physical Society. II. Vol. 3. p. 135.
|
{
"page_id": 59703859,
"source": null,
"title": "A-center"
}
|
Gamma-glutamyltranspeptidase may refer to: Gamma-glutamyl transpeptidase, an enzyme Glutathione hydrolase, an enzyme
|
{
"page_id": 30081590,
"source": null,
"title": "Gamma-glutamyltranspeptidase"
}
|
Neothiobinupharidine is a dimeric thiaspirane alkaloid isolated from the dwarf water lily Nuphar pumila. It exhibits weak immunosuppressive and cytotoxic bioactivity in cell line experiments. == References ==
|
{
"page_id": 40632890,
"source": null,
"title": "Neothiobinupharidine"
}
|
The Administration on Aging (AoA) is an agency within the Administration for Community Living of the U.S. Department of Health and Human Services. == Functions == AoA works to ensure that older Americans can stay independent in their communities, mostly by awarding grants to States, Native American tribal organizations, and local communities to support programs authorized by Congress in the Older Americans Act of 1965. AoA also awards discretionary grants to research organizations working on projects that support those goals. It conducts statistical activities in support of the research, analysis, and evaluation of programs to meet the needs of an aging population. AoA's FY 2013 budget proposal includes a total of $1.9 billion, $819 million of which funds senior nutrition programs like Meals on Wheels. The agency also funds $539 million in grants to programs to help seniors stay in their homes through services (such as accomplishing essential activities of daily living, like getting to the doctor's office, buying groceries etc.) and through help given to caregivers. Some of these grants are for Cash & Counseling programs that provide Medicaid participants a monthly budget for home care and access to services that help them manage their finances. == Leadership == AoA is headed by the Assistant Secretary for Aging. From July 2016 to August 2017, Edwin Walker served as Acting Assistant Secretary for Aging. The Assistant Secretary reports directly to the Secretary of Health and Human Services. Lance Allen Robertson was confirmed in August 2017, and served until January 20, 2021. On January 20, 2021, Alison Barkoff was sworn in as Principal Deputy Assistant Secretary, and was named as Acting Assistant Secretary. On March 9, 2022, President Biden Nominated Rita Landgraf, the former Secretary of the Delaware Department of Health and Social Services, to serve as his first Assistant Secretary.
|
{
"page_id": 1704507,
"source": null,
"title": "Administration on Aging"
}
|
== History == AoA was established by the Older Americans Act of 1965. It became part of the Administration for Community Living in 2012. == See also == Category:United States Assistant Secretaries for Aging Pension Rights Center Elder law United States Senate Special Committee on Aging Clark Tibbitts == References == == External links == Administration on Aging Older Americans Act of 1965 Administration on Aging in the Federal Register Congressional Justification of FY 2013 President's Budget
|
{
"page_id": 1704507,
"source": null,
"title": "Administration on Aging"
}
|
A Different Universe: Reinventing Physics from the Bottom Down is a 2005 physics book by Robert B. Laughlin, a winner of the Nobel Prize in Physics for the fractional quantum Hall effect. Its title is a play on the P. W. Anderson manifesto More is Different (historically important in claiming that condensed-matter physics deserves greater respect). The book extends his articles "The Middle Way" and "The Theory of Everything", arguing the limits of reductionism. A key concept in Laughlin's works is protectorates, meaning robust physical regimes of behavior that do not depend on (that is, they are protected from the fickle details of) the underlying smaller-scale physics such as quantum noise. Such robust or reliable behavior at macroscopic scales makes possible higher-level entities, from biological life to nanotechnology. The book emphasizes more study of such macroscopic phenomena, sometimes called emergence, over the ever-downward dive into theoretically fundamental ideas such as string theory, which at some point become empirically irrelevant by having no observable consequences in our world. The arguments come full circle with modern dark energy ideas suggesting that spacetime or the vacuum may not be empty, but rather (for all we can observe) a medium, a possibility ironically glimpsed even by Einstein whose career began with demolishing the similar but too-simplistic notion of ether with his special relativity work. == Reception == Keay Davidson reviewed the book for the New York Times, saying that "Laughlin's thesis is intriguing, if not completely persuasive." Carlos Lourenço, reviewing the book for the CERN Courier, found it "thought-provoking" and "worth reading", though he was left disappointed by the time it spent on seemingly irrelevant topics and polemics against reductionists. Lourenço concludes that "there is a lot of talking but in the end not much physics really gets reinvented." == References ==
|
{
"page_id": 6619716,
"source": null,
"title": "A Different Universe"
}
|
Clam liquor, also called clam extract, is a liquid extracted during cooking and opening of clams. Without dilution, it is called clam broth, and when concentrated by evaporation is called clam nectar. It may be canned in all these forms or used to fill up canned clam meat. It is an important component of many seafood recipes and is also used as a natural seasoning. Clam liquor can be used to enhance the flavor of soups, stews, sauces, and other dishes. It is also a popular ingredient in Asian cuisine. == See also == List of clam dishes == References ==
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{
"page_id": 12911174,
"source": null,
"title": "Clam liquor"
}
|
The John von Neumann Environmental Research Institute of the Pacific is a non profit environmental and anthropological research institute of executive branch of the government of Colombia ascribed to the Ministry of Environment and Sustainable Development and charged with conducting research and investigations on the Pacific littoral and the biodiversity of the Chocó biogeographic hotspot. == References ==
|
{
"page_id": 29557324,
"source": null,
"title": "John von Neumann Environmental Research Institute of the Pacific"
}
|
A gas torus is a toroidal cloud of gas or plasma that encircles a planet or moon. In the Solar System, gas tori tend to be produced by the interaction of a satellite's atmosphere with the magnetic field of a planet. The most famous example of this is the Io plasma torus, which is produced by the ionization of roughly 1 ton per second of oxygen and sulfur from the tenuous atmosphere of Jupiter's volcanic moon Io. Before being ionized, these particles are part of a neutral torus, also centered on the orbit of Io. Energetic particle observations also suggest the presence of a neutral torus around the orbit of Jupiter's moon Europa although such a torus would be merged with the outer portions of an Io torus. Other examples include the largely neutral torus of oxygen and hydrogen produced by Saturn's moon Enceladus. The Enceladus and Io tori differ in that particles in the Io torus are predominantly ionized while in the Enceladus torus, the neutral density is much greater than the ion density. After the Voyager encounters, the possibility of a torus of nitrogen produced by Saturn's moon Titan was proposed. Subsequent observations by the Cassini spacecraft showed no clear evidence of such a torus. While neutral nitrogen could not be measured, the ions near the orbit of Titan were primarily hydrogen or water group (O+, OH+, H2O+ and H3O+) from the Enceladus torus. Trace amounts of nitrogen ions were detected but at levels consistent with an Enceladus source. == References ==
|
{
"page_id": 3801677,
"source": null,
"title": "Gas torus"
}
|
WaveNet is a deep neural network for generating raw audio. It was created by researchers at London-based AI firm DeepMind. The technique, outlined in a paper in September 2016, is able to generate relatively realistic-sounding human-like voices by directly modelling waveforms using a neural network method trained with recordings of real speech. Tests with US English and Mandarin reportedly showed that the system outperforms Google's best existing text-to-speech (TTS) systems, although as of 2016 its text-to-speech synthesis still was less convincing than actual human speech. WaveNet's ability to generate raw waveforms means that it can model any kind of audio, including music. == History == Generating speech from text is an increasingly common task thanks to the popularity of software such as Apple's Siri, Microsoft's Cortana, Amazon Alexa and the Google Assistant. Most such systems use a variation of a technique that involves concatenated sound fragments together to form recognisable sounds and words. The most common of these is called concatenative TTS. It consists of large library of speech fragments, recorded from a single speaker that are then concatenated to produce complete words and sounds. The result sounds unnatural, with an odd cadence and tone. The reliance on a recorded library also makes it difficult to modify or change the voice. Another technique, known as parametric TTS, uses mathematical models to recreate sounds that are then assembled into words and sentences. The information required to generate the sounds is stored in the parameters of the model. The characteristics of the output speech are controlled via the inputs to the model, while the speech is typically created using a voice synthesiser known as a vocoder. This can also result in unnatural sounding audio. == Design and ongoing research == === Background === WaveNet is a type of feedforward neural network known
|
{
"page_id": 54133326,
"source": null,
"title": "WaveNet"
}
|
as a deep convolutional neural network (CNN). In WaveNet, the CNN takes a raw signal as an input and synthesises an output one sample at a time. It does so by sampling from a softmax (i.e. categorical) distribution of a signal value that is encoded using μ-law companding transformation and quantized to 256 possible values. === Initial concept and results === According to the original September 2016 DeepMind research paper WaveNet: A Generative Model for Raw Audio, the network was fed real waveforms of speech in English and Mandarin. As these pass through the network, it learns a set of rules to describe how the audio waveform evolves over time. The trained network can then be used to create new speech-like waveforms at 16,000 samples per second. These waveforms include realistic breaths and lip smacks – but do not conform to any language. WaveNet is able to accurately model different voices, with the accent and tone of the input correlating with the output. For example, if it is trained with German, it produces German speech. The capability also means that if the WaveNet is fed other inputs – such as music – its output will be musical. At the time of its release, DeepMind showed that WaveNet could produce waveforms that sound like classical music. === Content (voice) swapping === According to the June 2018 paper Disentangled Sequential Autoencoder, DeepMind has successfully used WaveNet for audio and voice "content swapping": the network can swap the voice on an audio recording for another, pre-existing voice while maintaining the text and other features from the original recording. "We also experiment on audio sequence data. Our disentangled representation allows us to convert speaker identities into each other while conditioning on the content of the speech." (p. 5) "For audio, this allows us to
|
{
"page_id": 54133326,
"source": null,
"title": "WaveNet"
}
|
convert a male speaker into a female speaker and vice versa [...]." (p. 1) According to the paper, a two-digit minimum amount of hours (c. 50 hours) of pre-existing speech recordings of both source and target voice are required to be fed into WaveNet for the program to learn their individual features before it is able to perform the conversion from one voice to another at a satisfying quality. The authors stress that "[a]n advantage of the model is that it separates dynamical from static features [...]." (p. 8), i. e. WaveNet is capable of distinguishing between the spoken text and modes of delivery (modulation, speed, pitch, mood, etc.) to maintain during the conversion from one voice to another on the one hand, and the basic features of both source and target voices that it is required to swap on the other. The January 2019 follow-up paper Unsupervised speech representation learning using WaveNet autoencoders details a method to successfully enhance the proper automatic recognition and discrimination between dynamical and static features for "content swapping", notably including swapping voices on existing audio recordings, in order to make it more reliable. Another follow-up paper, Sample Efficient Adaptive Text-to-Speech, dated September 2018 (latest revision January 2019), states that DeepMind has successfully reduced the minimum amount of real-life recordings required to sample an existing voice via WaveNet to "merely a few minutes of audio data" while maintaining high-quality results. Its ability to clone voices has raised ethical concerns about WaveNet's ability to mimic the voices of living and dead persons. According to a 2016 BBC article, companies working on similar voice-cloning technologies (such as Adobe Voco) intend to insert watermarking inaudible to humans to prevent counterfeiting, while maintaining that voice cloning satisfying, for instance, the needs of entertainment-industry purposes would be of a far
|
{
"page_id": 54133326,
"source": null,
"title": "WaveNet"
}
|
lower complexity and use different methods than required to fool forensic evidencing methods and electronic ID devices, so that natural voices and voices cloned for entertainment-industry purposes could still be easily told apart by technological analysis. == Applications == At the time of its release, DeepMind said that WaveNet required too much computational processing power to be used in real world applications. As of October 2017, Google announced a 1,000-fold performance improvement along with better voice quality. WaveNet was then used to generate Google Assistant voices for US English and Japanese across all Google platforms. In November 2017, DeepMind researchers released a research paper detailing a proposed method of "generating high-fidelity speech samples at more than 20 times faster than real-time", called "Probability Density Distillation". At the annual I/O developer conference in May 2018, it was announced that new Google Assistant voices were available and made possible by WaveNet; WaveNet greatly reduced the number of audio recordings that were required to create a voice model by modeling the raw audio of the voice actor samples. == See also == 15.ai Deep learning speech synthesis == References == == External links == WaveNet: A Generative Model for Raw Audio
|
{
"page_id": 54133326,
"source": null,
"title": "WaveNet"
}
|
Palynology is the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur in sediments, sedimentary rocks, and even some metasedimentary rocks. Palynomorphs are the microscopic, acid-resistant organic remains and debris produced by a wide variety of plants, animals, and Protista that have existed since the late Proterozoic. It is the science that studies contemporary and fossil palynomorphs (paleopalynology), including pollen, spores, orbicules, dinocysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter (POM) and kerogen found in sedimentary rocks and sediments. Palynology does not include diatoms, foraminiferans or other organisms with siliceous or calcareous tests. The name of the science and organisms is derived from the Greek Ancient Greek: παλύνω, romanized: palynō, "strew, sprinkle" and -logy) or of "particles that are strewn". Palynology is an interdisciplinary science that stands at the intersection of earth science (geology or geological science) and biological science (biology), particularly plant science (botany). Biostratigraphy, a branch of paleontology and paleobotany, involves fossil palynomorphs from the Precambrian to the Holocene for their usefulness in the relative dating and correlation of sedimentary strata. Palynology is also used to date and understand the evolution of many kinds of plants and animals. In paleoclimatology, fossil palynomorphs are studied for their usefulness in understanding ancient Earth history in terms of reconstructing paleoenvironments and paleoclimates. Palynology is quite useful in disciplines such as archeology, in honey production, and criminal and civil law. In archaeology, palynology is widely used to reconstruct ancient paleoenvironments and environmental shifts that significantly influenced past human societies and reconstruct the diet of prehistoric and historic humans. Melissopalynology, the study of pollen and other palynomorphs in honey, identifies the sources of pollen in terms of geographical location(s) and genera of plants. This not only provides important information on the ecology of
|
{
"page_id": 328274,
"source": null,
"title": "Palynology"
}
|
honey bees, it also an important tool in discovering and policing the criminal adultriation and mislabeling of honey and its products. Forensic palynology uses palynomorphs as evidence in criminal and civil law to prove or disprove a physical link between objects, people, and places. == Palynomorphs == Palynomorphs are broadly defined as organic remains, including microfossils, and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and range in size between 5 and 500 micrometres. They are extracted from soils, sedimentary rocks and sediment cores, and other materials by a combination of physical (ultrasonic treatment and wet sieving) and chemical (acid digestion) procedures to remove the non-organic fraction. Palynomorphs may be composed of organic material such as chitin, pseudochitin and sporopollenin. Palynomorphs form a geological record of importance in determining the type of prehistoric life that existed at the time the sedimentary strata was laid down. As a result, these microfossils give important clues to the prevailing climatic conditions of the time. Their paleontological utility derives from an abundance numbering in millions of palynomorphs per gram in organic marine deposits, even when such deposits are generally not fossiliferous. Palynomorphs, however, generally have been destroyed in metamorphic or recrystallized rocks. Typical palynomorphs include dinoflagellate cysts, acritarchs, spores, pollen, plant tissue, fungi, scolecodonts (scleroprotein teeth, jaws, and associated features of polychaete annelid worms), arthropod organs (such as insect mouthparts), and chitinozoans. Palynomorph microscopic structures that are abundant in most sediments are resistant to routine pollen extraction. == Palynofacies == A palynofacies is the complete assemblage of organic matter and palynomorphs in a fossil deposit. The term was introduced by the French geologist André Combaz in 1964. Palynofacies studies are often linked to investigations of the organic geochemistry of sedimentary rocks. The study of the palynofacies of a sedimentary depositional environment
|
{
"page_id": 328274,
"source": null,
"title": "Palynology"
}
|
can be used to learn about the depositional palaeoenvironments of sedimentary rocks in exploration geology, often in conjunction with palynological analysis and vitrinite reflectance. Palynofacies can be used in two ways: Organic palynofacies considers all the acid insoluble particulate organic matter (POM), including kerogen and palynomorphs in sediments and palynological preparations of sedimentary rocks. The sieved or unsieved preparations may be examined using strew mounts on microscope slides that may be examined using a transmitted light biological microscope or ultraviolet (UV) fluorescence microscope. The abundance, composition and preservation of the various components, together with the thermal alteration of the organic matter is considered. Palynomorph palynofacies considers the abundance, composition and diversity of palynomorphs in a sieved palynological preparation of sediments or palynological preparation of sedimentary rocks. The ratio of marine fossil phytoplankton (acritarchs and dinoflagellate cysts), together with chitinozoans, to terrestrial palynomorphs (pollen and spores) can be used to derive a terrestrial input index in marine sediments. == History == === Early history === The earliest reported observations of pollen under a microscope are likely to have been in the 1640s by the English botanist Nehemiah Grew, who described pollen and the stamen, and concluded that pollen is required for sexual reproduction in flowering plants. By the late 1870s, as optical microscopes improved and the principles of stratigraphy were worked out, Robert Kidston and P. Reinsch were able to examine the presence of fossil spores in the Devonian and Carboniferous coal seams and make comparisons between the living spores and the ancient fossil spores. Early investigators include Christian Gottfried Ehrenberg (radiolarians, diatoms and dinoflagellate cysts), Gideon Mantell (desmids) and Henry Hopley White (dinoflagellate cysts). === 1890s to 1940s === Quantitative analysis of pollen began with Lennart von Post's published work. Although he published in the Swedish language, his methodology gained
|
{
"page_id": 328274,
"source": null,
"title": "Palynology"
}
|
a wide audience through his lectures. In particular, his Kristiania lecture of 1916 was important in gaining a wider audience. Because the early investigations were published in the Nordic languages (Scandinavian languages), the field of pollen analysis was confined to those countries. The isolation ended with the German publication of Gunnar Erdtman's 1921 thesis. The methodology of pollen analysis became widespread throughout Europe and North America and revolutionized Quaternary vegetation and climate change research. Earlier pollen researchers include Früh (1885), who enumerated many common tree pollen types, and a considerable number of spores and herb pollen grains. There is a study of pollen samples taken from sediments of Swedish lakes by Trybom (1888); pine and spruce pollen was found in such profusion that he considered them to be serviceable as "index fossils". Georg F. L. Sarauw studied fossil pollen of middle Pleistocene age (Cromerian) from the harbour of Copenhagen. Lagerheim (in Witte 1905) and C. A.Weber (in H. A. Weber 1918) appear to be among the first to undertake 'percentage frequency' calculations. === 1940s to 1989 === The term palynology was introduced by Hyde and Williams in 1944, following correspondence with the Swedish geologist Ernst Antevs, in the pages of the Pollen Analysis Circular (one of the first journals devoted to pollen analysis, produced by Paul Sears in North America). Hyde and Williams chose palynology on the basis of the Greek words paluno meaning 'to sprinkle' and pale meaning 'dust' (and thus similar to the Latin word pollen). The archive-based background to the adoption of the term palynology and to alternative names (e.g. paepalology, pollenology) has been exhaustively explored. It has been argued there that the word gained general acceptance once used by the influential Swedish palynologist Gunnar Erdtman. Pollen analysis in North America stemmed from Phyllis Draper, an MS
|
{
"page_id": 328274,
"source": null,
"title": "Palynology"
}
|
student under Sears at the University of Oklahoma. During her time as a student, she developed the first pollen diagram from a sample that depicted the percentage of several species at different depths at Curtis Bog. This was the introduction of pollen analysis in North America; pollen diagrams today still often remain in the same format with depth on the y-axis and abundances of species on the x-axis. === 1990s to the 21st century === Pollen analysis advanced rapidly in this period due to advances in optics and computers. Much of the science was revised by Johannes Iversen and Knut Fægri in their textbook on the subject. == Methods of studying palynomorphs == === Chemical preparation === Chemical digestion follows a number of steps. Initially the only chemical treatment used by researchers was treatment with potassium hydroxide (KOH) to remove humic substances; defloculation was accomplished through surface treatment or ultra-sonic treatment, although sonification may cause the pollen exine to rupture. In 1924, the use of hydrofluoric acid (HF) to digest silicate minerals was introduced by Assarson and Granlund, greatly reducing the amount of time required to scan slides for palynomorphs. Palynological studies using peats presented a particular challenge because of the presence of well-preserved organic material, including fine rootlets, moss leaflets and organic litter. This was the last major challenge in the chemical preparation of materials for palynological study. Acetolysis was developed by Gunnar Erdtman and his brother to remove these fine cellulose materials by dissolving them. In acetolysis the specimen is treated with acetic anhydride and sulfuric acid, dissolving cellulistic materials and thus providing better visibility for palynomorphs. Some steps of the chemical treatments require special care for safety reasons, in particular the use of HF which diffuses very fast through the skin and, causes severe chemical burns, and
|
{
"page_id": 328274,
"source": null,
"title": "Palynology"
}
|
can be fatal. Another treatment includes kerosene flotation for chitinous materials. === Analysis === Once samples have been prepared chemically, they are mounted on microscope slides using silicon oil, glycerol or glycerol-jelly and examined using light microscopy or mounted on a stub for scanning electron microscopy. Researchers will often study either modern samples from a number of unique sites within a given area, or samples from a single site with a record through time, such as samples obtained from peat or lake sediments. More recent studies have used the modern analog technique in which paleo-samples are compared to modern samples for which the parent vegetation is known. When the slides are observed under a microscope, the researcher counts the number of grains of each pollen taxon. This record is next used to produce a pollen diagram. These data can be used to detect anthropogenic effects, such as logging, traditional patterns of land use or long term changes in regional climate == Applications == Palynology can be applied to problems in many scientific disciplines including geology, botany, paleontology, archaeology, pedology (soil study), and physical geography: Biostratigraphy and geochronology. Geologists use palynological studies in biostratigraphy to correlate strata and determine the relative age of a given bed, horizon, formation or stratigraphical sequence. Because the distribution of acritarchs, chitinozoans, dinoflagellate cysts, pollen and spores provides evidence of stratigraphical correlation through biostratigraphy and palaeoenvironmental reconstruction, one common and lucrative application of palynology is in oil and gas exploration. Paleoecology and climate change. Palynology can be used to reconstruct past vegetation (land plants) and marine and Freshwater phytoplankton communities, and so infer past environmental (palaeoenvironmental) and palaeoclimatic conditions in an area thousands or millions of years ago, a fundamental part of research into climate change. Organic palynofacies studies, which examine the preservation of the particulate
|
{
"page_id": 328274,
"source": null,
"title": "Palynology"
}
|
organic matter and palynomorphs provides information on the depositional environment of sediments and depositional palaeoenvironments of sedimentary rocks. Geothermal alteration studies examine the colour of palynomorphs extracted from rocks to give the thermal alteration and maturation of sedimentary sequences, which provides estimates of maximum palaeotemperatures. Limnology studies. Freshwater palynomorphs and animal and plant fragments, including the prasinophytes and desmids (green algae) can be used to study past lake levels and long term climate change. Taxonomy and evolutionary studies. Involving the use of pollen morphological characters as source of taxonomic data to delimit plant species under same family or genus. Pollen apertural status is frequently used for differential sorting or finding similarities between species of the same taxa. This is also called Palynotaxonomy. Forensic palynology: the study of pollen and other palynomorphs for evidence at a crime scene. Allergy studies and pollen counting. Studies of the geographic distribution and seasonal production of pollen, can be used to forecast pollen conditions, helping sufferers of allergies such as hay fever. Melissopalynology: the study of pollen and spores found in honey. Archaeological palynology examines human uses of plants in the past. This can help determine seasonality of site occupation, presence or absence of agricultural practices or products, and 'plant-related activity areas' within an archaeological context. Bonfire Shelter is one such example of this application. == See also == Aperture (botany) – Areas on the walls of a pollen grain, where the wall is thinner and/or softer Aeroplankton – Tiny lifeforms floating and drifting in the air, carried by the wind Microbiology – Study of microscopic organisms (microbes) == References == == Sources == Moore, P.D., et al. (1991), Pollen Analysis (Second Edition). Blackwell Scientific Publications. ISBN 0-632-02176-4 Traverse, A. (1988), Paleopalynology. Unwin Hyman. ISBN 0-04-561001-0 Roberts, N. (1998), The Holocene an environmental history, Blackwell
|
{
"page_id": 328274,
"source": null,
"title": "Palynology"
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|
Publishing. ISBN 0-631-18638-7 == External links == The AASP - The Palynological Society International Federation of Palynological Societies Palynology Laboratory, French Institute of Pondicherry, India The Palynology Unit, Kew Gardens, UK PalDat, palynological database hosted by the University of Vienna, Austria The Micropalaeontological Society Commission Internationale de Microflore du Paléozoique (CIMP), International Commission for Palaeozoic Palynology Centre for Palynology, University of Sheffield, UK Linnean Society Palynology Specialist Group (LSPSG) Canadian Association of Palynologists Pollen and Spore Identification Literature Palynologische Kring, The Netherlands and Belgium Palynofacies, an annotated link directory. Acosta et al., 2018. Climate change and peopling of the Neotropics during the Pleistocene-Holocene transition. Boletín de la Sociedad Geológica Mexicana. http://boletinsgm.igeolcu.unam.mx/bsgm/index.php/component/content/article/368-sitio/articulos/cuarta-epoca/7001/1857-7001-1-Acosta
|
{
"page_id": 328274,
"source": null,
"title": "Palynology"
}
|
Adenylylation, more commonly known as AMPylation, is a process in which an adenosine monophosphate (AMP) molecule is covalently attached to the amino acid side chain of a protein. This covalent addition of AMP to a hydroxyl side chain of the protein is a post-translational modification. Adenylylation involves a phosphodiester bond between a hydroxyl group of the molecule undergoing adenylylation, and the phosphate group of the adenosine monophosphate nucleotide (i.e. adenylic acid). Enzymes that are capable of catalyzing this process are called AMPylators. The known amino acids to be targeted in the protein are tyrosine and threonine, and sometimes serine. When charges on a protein undergo a change, it affects the characteristics of the protein, normally by altering its shape via interactions of the amino acids which make up the protein. AMPylation can have various effects on the protein. These are properties of the protein like, stability, enzymatic activity, co-factor binding, and many other functional capabilities of a protein. Another function of adenylylation is amino acids activation, which is catalyzed by tRNA aminoacyl synthetase. The most commonly identified protein to receive AMPylation are GTPases, and glutamine synthetase. == Adenylylators == Enzymes responsible for AMPylation, called AMPylators or Adenylyltransferase, fall into two different families, all depending on their structural properties and mechanism used. AMPylator is created by two catalytic homologous halves. One half is responsible for catalyzing the adenylylation reaction, while the other half catalyzes the phosphorolytic deadenylylation reaction. These two families are the DNA-β-polymerase-like and the Fic family. DNA-β-polymerase-like, is a family of Nucleotidyltransferase. It more specifically is known as the GlnE family. There is a specific motif that is used to clarify this particular family. The motif consists of a three stranded β-sheet which is part of magnesium ion coordination and phosphate binding. Aspartate is essential for the activity to
|
{
"page_id": 12780114,
"source": null,
"title": "Adenylylation"
}
|
occur in this family. The Fic domain belongs to Fido (Fic/Doc) superfamilyFic family, which is a filamentation induced by cyclic AMP domain, is known to perform AMPylation. This term was coined when VopS from Vibrio parahaemolyticus was discovered to modify RhoGTPases with AMP on a serine. This family of proteins are found in all domains of life on earth. It is mediated via a mechanism of ATP-binding-site alpha helix motif. Infectious bacteria use this domain to interrupt phagocytosis and cause cell death. Fic domains are evolutionarily conserved domains in prokaryotes and eukaryotes that belong to the Fido domain superfamily. AMPylators have been shown to be comparable to kinases due to their ATP hydrolysis activity and reversible transfer of the metabolite to a hydroxyl side chain of the protein substrate. However, AMPylation catalyse a nucleophilic attack on the α-phosphate group, while kinase in the phosphorylation reaction targets γ-phosphate. The nucleophilic attack of AMPylation leads to release Pyrophosphate and the AMP-modified protein are the products of the AMPylation reaction. == De-adenylylators == De-AMPylation is the reverse reaction in which the AMP molecule is detached from the amino acid side of a chain protein. There are three known mechanisms for this reaction. The bacterial GS-ATase (GlnE) encodes a bipartite protein with separate N-terminal AMPylation and C-terminal de-AMPylation domains whose activity is regulated by PII and associated posttranslational modifications. De-AMPylation of its substrate AMPylated glutamine synthetase proceeds by a phosphorolytic reaction between the adenyl-tyrosine of GS and orthophosphate, leading to the formation of ADP and unmodified glutamine synthetase. SidD, a protein introduced in the host cell by the pathogenic bacteria Legionella pneumophila, de-AMPylates Rab1 a host protein AMPylated by a different Legionella pneumophila enzyme, the AMPylase SidM. Whilst the benefit to the pathogen of introducing these two antagonistic effectors in the host remains unclear,
|
{
"page_id": 12780114,
"source": null,
"title": "Adenylylation"
}
|
the biochemical reaction carried out by SidD involves the use of a phosphatase-like domain to catalyse the hydrolytic removal of the AMP from tyrosine 77 of the host's Rab1. In animal cells the removal of AMP from threonine 518 of BiP/Grp78 is catalysed by the same enzyme, FICD, that AMPylates BiP. Unlike the bacterial GS-ATase, FICD carries out both reactions with same catalytic domain. == Adenylylation in Prokaryotes == === Bacterial homeostasis === AMPylation is involved in bacterial homeostasis. The most famous example is AMPylator GS-ATase (GlnE), which contributes in complex regulation of nitrogen metabolism through AMPylation of glutamine synthetase that was introduced in the AMPylation and DeAMPylation parts. Another example of AMPylators that play a role in bacterial homeostasis is the class I Fic AMPylators (FicT), which modifies the GyrB subunit of DNA gyrase, the conserved tyrosine residue for ATP binding of ParE subunit at Topoisomerase IV. This DNA gyrase inactivation by AMPylation leads to the activation of SOS response, which is the cellular response to DNA damage. The activity of FicT AMPylation is reversible and only leads to growth arrest, but not cell death. Therefore, FicT AMPylation plays a role in regulating cell stress, which is shown in the Wolbachia bacteria that the level of FicT increases in response to doxycycline. A Class III Fic AMPylator NmFic of N. meningtidis is also found to modify AMPylate GyrB at the conserved tyrosine for ATP binding. This shows that Fic domains are highly conserved that indicates the important role of AMPylation in regulating cellular stress in bacteria. The regulation of NmFic involves the concentration-dependent monomerization and autoAMPylation for activation of NmFic activity. === Bacterial pathogenicity === Bacteria proteins, also known as effectors, have been shown to use AMPylation. Effectors such as VopS, IbpA, and DrrA, have been shown to AMPylate
|
{
"page_id": 12780114,
"source": null,
"title": "Adenylylation"
}
|
host GTPases and cause actin cytoskeleton changes. GTPases are common targets of AMPylators. Rho, Rab, and Arf GTPase families are involved in actin cytoskeleton dynamics and vesicular trafficking. They also play roles in cellular control mechanisms such as phagocytosis in the host cell. The pathogen enhances or prevents its internalization by either inducing or inhibiting host cell phagocytosis. Vibrio parahaemolyticus is a Gram-negative bacterium that causes food poisoning as a result of raw or undercooked seafood consumption in humans. VopS, a type III effector found in Vibrio parahaemolyticus, contains a Fic domain that has a conserved HPFx(D/E)GN(G/K)R motif that contains a histidine residue essential for AMPylation. VopS blocks actin assembly by modifying threonine residue in the switch 1 region of Rho GTPases. The transfer of an AMP moiety using ATP to the threonine residue results in steric hindrance, and thus prevents Rho GTPases from interacting with downstream effectors. VopS also adenylates RhoA and cell division cycle 42 (CDC42), leading to a disaggregation of the actin filament network. As a result, the host cell's actin cytoskeleton control is disabled, leading to cell rounding. IbpA is secreted into eukaryotic cells from H. somni, a Gram-negative bacterium in cattle that causes respiratory epithelium infection. This effector contains two Fic domains at the C-terminal region. AMPylation of the IbpA Fic domain of Rho family GTPases is responsible for its cytotoxicity. Both Fic domains have similar effects on host cells' cytoskeleton as VopS. The AMPylation on a tyrosine residue of the switch 1 region blocks the interaction of the GTPases with downstream substrates such as PAK. DrrA is the Dot/Icm type IV translocation system substrate DrrA from Legionella pneumophila. It is the effector secreted by L. pneumophila to modify GTPases of the host cells. This modification increases the survival of bacteria in host cells. DrrA
|
{
"page_id": 12780114,
"source": null,
"title": "Adenylylation"
}
|
is composed of Rab1b specific guanine nucleotide exchange factor (GEF) domain, a C-terminal lipid binding domain and an N-terminal domain with unclear cytotoxic properties. Research works show that N-terminal and full-length DrrA shows AMPylators activity toward host's Rab1b protein (Ras related protein), which is also the substrate of Rab1b GEF domain. Rab1b protein is the GTPase Rab to regulate vesicle transportation and membrane fusion. The adenylation by bacteria AMPylators prolong GTP-bound state of Rab1b. Thus, the role of effector DrrA is connected toward the benefits of bacteria's vacuoles for their replication during the infection. == Adenlylylation in Eukaryotes == Plants and yeasts have no known endogenous AMPylating enzymes, but animal genomes are endowed with a single copy of a gene encoding a Fic-domain AMPylase, that was likely acquired by an early ancestor of animals via horizontal gene transfer from a prokaryote. The human protein referred to commonly as FICD, had been previously identified as Huntingtin associated protein E (HypE; an assignment arising from a yeast two-hybrid screen, but of questionable relevance, as Huntingtin and HypE/FICD are localised to different cellular compartments). CG9523 Homologues in Drosophila melanogaster (CG9523) and C. elegans (Fic-1) have also received attention. In all animals FICD has a similar structure. It is a type II transmembrane domain protein, with a short cytoplasmic domain followed by membrane anchor that holds the protein in the endoplasmic reticulum (ER) and long C-terminal portion that resides in ER and encompasses tetratricopeptide repeats (TPRs) followed by a catalytic Fic domain. === Endoplasmic reticulum === The discovery of an animal cell AMPylase, followed by the discovery of its ER localisation and that BiP is a prominent substrate for its activity were important breakthroughs. BiP (also known as Grp78) had long been known to undergo an inactivating post-translational modification, but it nature remain elusive.
|
{
"page_id": 12780114,
"source": null,
"title": "Adenylylation"
}
|
Widely assumed to be ADP-ribosylation, it turns out to be FICD-mediated AMPylation, as inactivating the FICD gene in cells abolished all measurable post-translational modification of BiP. BiP is an ER-localised protein chaperone whose activity is tightly regulated at the transcriptional level via a gene-expression program known as the Unfolded Protein Response (UPR). The UPR is a homeostatic process that couples the transcription rate of BiP (and many other proteins) to the burden of unfolded proteins in the ER (so-called ER stress) to help maintain ER proteostasis. AMPylation adds another rapid post-translational layer of control of BiP's activity, as modification of Thr518 of BiP's substrate-binding domain with an AMP locks the chaperone into an inactive conformation. This modification is selectively deployed as ER stress wanes, to inactivate surplus BiP. However, as ER stress rises again, the same enzyme, FICD, catalyses the opposite reaction, BiP de-AMPylation. An understanding of the structural basis of BiP AMPylation and de-AMPylation is gradually emerging, as are clues to the allostery that might regulate the switch in FICD's activity but important details of this process as it occurs in cells remain to be discovered. The role of FICD in BiP AMPylation (and de-AMPylation) on Thr518 is well supported by biochemical and structural studies. Evidence has also been presented that in some circumstances FICD may AMPylate a different residue, Thr366 in BiP's nucleotide binding domain. === Caenorhabditis elegans === Fic-1 is the only Fic protein present in the genetic code of C. elegans. It is primarily found in the ER nuclear envelope of adult germline cells and embryotic cells, but small amounts may be found within the cytoplasm. This extra-ER pool of FICD-1s is credited with AMPylation of core histones and eEF1-A type translation factors within the nematode. Though varying AMPylation levels did not create any noticeable effects
|
{
"page_id": 12780114,
"source": null,
"title": "Adenylylation"
}
|
within the nematode's behaviour or physiology, Fic-1 knockout worms were more susceptible to infection by Pseudomonas aeruginosa compared to the counterparts with active Fic-1 domains, implying a link between AMPylation of cellular targets and immune responses within nematodes. === Drosophila melanogaster === Flies lacking in FICD (CG9523) have been described as blind. Initially, this defect was attributed to a role for FICD on the cell surface of capitate projections - a putative site of neurotransmitter recycling however a later study implicated FICD-mediated AMPylation of BiP Thr366 in the visual problem == Clinical significance == The presynaptic protein α-synuclein was found to be a target for FICD AMPylation. During HypE-mediated adenylylation of αSyn, aggregation of αSyn decreases and both neurotoxicity and ER stress were discovered to decrease in vitro. Thus, adenylylation of αSyn is possibly a protective response to ER stress and αSyn aggregation. However, as aSyn and FICD reside in different compartments further research needs to be done confirm the significance of these claims. == Detection == === Chemical handles === Chemical handles are used to detect post-translationally modified proteins. Recently, there is a N6pATP that contains an alkynyl tag (propargyl) at the N6 position of the adenine of ATP. This N6pATP combines with the click reaction to detect AMPylated proteins. To detect unrecognized modified protein and label VopS substrates, ATP derivatives with a fluorophore at the adenine N6 NH2 is utilized to do that. === Antibody-based method === Antibodies are known for their high affinity and selectivity, making them a good way to detect AMPylated proteins. Recently, ɑ- AMP antibodies were developed to directly detect and isolate AMPylated proteins (especially AMPylated tyrosine and AMPylated threonine) from cells and cell lysates. AMPylation is a post-translational modification that can be found on many protein sequences. Thus, instead of using antibodies that
|
{
"page_id": 12780114,
"source": null,
"title": "Adenylylation"
}
|
detect a specific AMPylated peptide sequence, raising AMP antibodies directly targeted to specific amino acids are considered superior. === Mass spectrometry === Previously, many studies used Mass Spectrometry (MS) in different fragmentation modes to detect AMPylated peptides. In responses to the distinctive fragmentation techniques, AMPylated protein sequences disintegrated at different parts of AMP. While electron transfer dissociation (ETD) creates minimum fragments and less complicated spectra, collision-induced dissociation (CID) and high-energy collision (HCD) fragmentation generate characteristic ions suitable for AMPylated proteins identification by generating multiple AMP fragments. Due to AMP's stability, peptide fragmentation spectra is easy to read manually or with search engines. == Inhibitors == Inhibitors of protein AMPylation with inhibitory constant (Ki) ranging from 6 - 50 μM and at least 30-fold selectivity versus HypE have been discovered. == References ==
|
{
"page_id": 12780114,
"source": null,
"title": "Adenylylation"
}
|
Produced in hadronic collisions, a direct photon is any real photon which originates directly from an electromagnetic vertex in a quark-quark, quark-gluon or gluon-gluon scattering subprocess (as opposed to "indirect" photons which arise from the decays of fragmentation products). Because the QCD calculations for direct photon production are considerably easier to perform than for other processes studies of direct photons have been used to test predictions made by perturbative QCD. Direct photons were predicted to exist by C.O. Escobar in 1975 and were first observed by the R412 group at the Intersecting Storage Rings at CERN in 1976, and were subsequently studied by various experiments, including E705 and E706 at Fermilab, NA3, NA24, WA70 and UA6 at the CERN SPS as well as UA1 and UA2 at the CERN SPPS collider. == References ==
|
{
"page_id": 51446357,
"source": null,
"title": "Direct photon"
}
|
Triafulvalene or cyclopropenylidenecyclopropene is a fulvalene hydrocarbon with chemical formula C6H4, composed of two linked cyclopropene rings. Triafulvalene has never been isolated, since it can decompose via an isodesmic reaction. However, its structure, stability, and spectral properties are well-studied theoretically; the molecule is believed planar. == See also == Calicene Fulvalene Sesquifulvalene == References ==
|
{
"page_id": 47907415,
"source": null,
"title": "Triafulvalene"
}
|
Data preprocessing can refer to manipulation, filtration or augmentation of data before it is analyzed, and is often an important step in the data mining process. Data collection methods are often loosely controlled, resulting in out-of-range values, impossible data combinations, and missing values, amongst other issues. Preprocessing is the process by which unstructured data is transformed into intelligible representations suitable for machine-learning models. This phase of model deals with noise in order to arrive at better and improved results from the original data set which was noisy. This dataset also has some level of missing value present in it. The preprocessing pipeline used can often have large effects on the conclusions drawn from the downstream analysis. Thus, representation and quality of data is necessary before running any analysis. Often, data preprocessing is the most important phase of a machine learning project, especially in computational biology. If there is a high proportion of irrelevant and redundant information present or noisy and unreliable data, then knowledge discovery during the training phase may be more difficult. Data preparation and filtering steps can take a considerable amount of processing time. Examples of methods used in data preprocessing include cleaning, instance selection, normalization, one-hot encoding, data transformation, feature extraction and feature selection. == Applications == === Data mining === Data preprocessing allows for the removal of unwanted data with the use of data cleaning, this allows the user to have a dataset to contain more valuable information after the preprocessing stage for data manipulation later in the data mining process. Editing such dataset to either correct data corruption or human error is a crucial step to get accurate quantifiers like true positives, true negatives, false positives and false negatives found in a confusion matrix that are commonly used for a medical diagnosis. Users are able
|
{
"page_id": 12386904,
"source": null,
"title": "Data preprocessing"
}
|
to join data files together and use preprocessing to filter any unnecessary noise from the data which can allow for higher accuracy. Users use Python programming scripts accompanied by the pandas library which gives them the ability to import data from a comma-separated values as a data-frame. The data-frame is then used to manipulate data that can be challenging otherwise to do in Excel. Pandas (software) which is a powerful tool that allows for data analysis and manipulation; which makes data visualizations, statistical operations and much more, a lot easier. Many also use the R programming language to do such tasks as well. The reason why a user transforms existing files into a new one is because of many reasons. Aspects of data preprocessing may include imputing missing values, aggregating numerical quantities and transforming continuous data into categories (data binning). More advanced techniques like principal component analysis and feature selection are working with statistical formulas and are applied to complex datasets which are recorded by GPS trackers and motion capture devices. === Semantic data preprocessing === Semantic data mining is a subset of data mining that specifically seeks to incorporate domain knowledge, such as formal semantics, into the data mining process. Domain knowledge is the knowledge of the environment the data was processed in. Domain knowledge can have a positive influence on many aspects of data mining, such as filtering out redundant or inconsistent data during the preprocessing phase. Domain knowledge also works as constraint. It does this by using working as set of prior knowledge to reduce the space required for searching and acting as a guide to the data. Simply put, semantic preprocessing seeks to filter data using the original environment of said data more correctly and efficiently. There are increasingly complex problems which are asking to be
|
{
"page_id": 12386904,
"source": null,
"title": "Data preprocessing"
}
|
solved by more elaborate techniques to better analyze existing information. Instead of creating a simple script for aggregating different numerical values into a single value, it make sense to focus on semantic based data preprocessing. The idea is to build a dedicated ontology, which explains on a higher level what the problem is about. In regards to semantic data mining and semantic pre-processing, ontologies are a way to conceptualize and formally define semantic knowledge and data. The Protégé (software) is the standard tool for constructing an ontology. In general, the use of ontologies bridges the gaps between data, applications, algorithms, and results that occur from semantic mismatches. As a result, semantic data mining combined with ontology has many applications where semantic ambiguity can impact the usefulness and efficiency of data systems. Applications include the medical field, language processing, banking, and even tutoring, among many more. There are various strengths to using a semantic data mining and ontological based approach. As previously mentioned, these tools can help during the per-processing phase by filtering out non-desirable data from the data set. Additionally, well-structured formal semantics integrated into well designed ontologies can return powerful data that can be easily read and processed by machines. A specifically useful example of this exists in the medical use of semantic data processing. As an example, a patient is having a medical emergency and is being rushed to hospital. The emergency responders are trying to figure out the best medicine to administer to help the patient. Under normal data processing, scouring all the patient’s medical data to ensure they are getting the best treatment could take too long and risk the patients’ health or even life. However, using semantically processed ontologies, the first responders could save the patient’s life. Tools like a semantic reasoner can use ontology
|
{
"page_id": 12386904,
"source": null,
"title": "Data preprocessing"
}
|
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