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Natural Experiment
A natural experiment is an empirical study in which individuals (or clusters of individuals) are exposed to the experimental and control conditions that are determined by nature or by other factors outside the control of the investigators. The process governing the exposures arguably resembles random assignment. Thus, natural experiments are ''observational studies'' and are not controlled in the traditional sense of a randomized experiment (an ''intervention study''). Natural experiments are most useful when there has been a clearly defined exposure involving a well defined subpopulation (and the absence of exposure in a similar subpopulation) such that changes in outcomes may be plausibly attributed to the exposure. In this sense, the difference between a natural experiment and a non-experimental observational study is that the former includes a comparison of conditions that pave the way for causal inference, but the latter does not. Natural experiments are employed as study des ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random Assignment
Random assignment or random placement is an experimental technique for assigning human participants or animal subjects to different groups in an experiment (e.g., a treatment group versus a control group) using randomization, such as by a chance procedure (e.g., flipping a coin) or a random number generator. This ensures that each participant or subject has an equal chance of being placed in any group. Random assignment of participants helps to ensure that any differences between and within the groups are not systematic at the outset of the experiment. Thus, any differences between groups recorded at the end of the experiment can be more confidently attributed to the experimental procedures or treatment. Random assignment, blinding, and controlling are key aspects of the design of experiments because they help ensure that the results are not spurious or deceptive via confounding. This is why randomized controlled trials are vital in clinical research, especially ones tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cluster (epidemiology)
A disease cluster is an unusually large aggregation of a relatively uncommon medical condition or event within a particular geographical location or period. Recognition of a cluster depends on its size being seen as greater than would be expected by the play of chance. Identification of a suspected disease cluster may initially depend on anecdotal evidence. Epidemiologists and biostatisticians need to assess whether the suspected cluster corresponds to an actual increase of disease in the area. Typically, when clusters are recognized, they are reported to public health departments in the local area. If clusters are of sufficient size and importance, they may be re-evaluated as outbreaks. John Snow's pioneering investigation of the 1854 cholera outbreak in Soho, London, is seen as a classic example of the study of such a cluster. References External links Disease Clusters: An Overview introduction to a course held by the Agency for Toxic Substances and Disease Registry {{dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) due to different numbers of neutrons in their nuclei. While all isotopes of a given element have almost the same chemical properties, they have different atomic masses and physical properties. The term isotope is formed from the Greek roots isos ( ἴσος "equal") and topos ( τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table. It was coined by Scottish doctor and writer Margaret Todd in 1913 in a suggestion to the British chemist Frederick Soddy. The number of protons within the atom's nucleus is called its atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Weapons Testing
Nuclear weapons tests are experiments carried out to determine nuclear weapons' effectiveness, yield, and explosive capability. Testing nuclear weapons offers practical information about how the weapons function, how detonations are affected by different conditions, and how personnel, structures, and equipment are affected when subjected to nuclear explosions. However, nuclear testing has often been used as an indicator of scientific and military strength. Many tests have been overtly political in their intention; most nuclear weapons states publicly declared their nuclear status through a nuclear test. The first nuclear device was detonated as a test by the United States at the Trinity site in New Mexico on July 16, 1945, with a yield approximately equivalent to 20 kilotons of TNT. The first thermonuclear weapon technology test of an engineered device, codenamed "Ivy Mike", was tested at the Enewetak Atoll in the Marshall Islands on November 1, 1952 (local date), also by t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crossover Study
In medicine, a crossover study or crossover trial is a longitudinal study in which subjects receive a sequence of different treatments (or exposures). While crossover studies can be observational studies, many important crossover studies are controlled experiments, which are discussed in this article. Crossover designs are common for experiments in many scientific disciplines, for example psychology, pharmaceutical science, and medicine. Randomized, controlled crossover experiments are especially important in health care. In a randomized clinical trial, the subjects are randomly assigned to different arms of the study which receive different treatments. When the trial has a repeated measures design, the same measures are collected multiple times for each subject. A crossover trial has a repeated measures design in which each patient is assigned to a sequence of two or more treatments, of which one may be a standard treatment or a placebo. Nearly all crossover are designed to h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Medical Journal
''The BMJ'' is a weekly peer-reviewed medical trade journal, published by the trade union the British Medical Association (BMA). ''The BMJ'' has editorial freedom from the BMA. It is one of the world's oldest general medical journals. Originally called the ''British Medical Journal'', the title was officially shortened to ''BMJ'' in 1988, and then changed to ''The BMJ'' in 2014. The journal is published by BMJ Publishing Group Ltd, a subsidiary of the British Medical Association (BMA). The editor-in-chief of ''The BMJ'' is Kamran Abbasi, who was appointed in January 2022. History The journal began publishing on 3 October 1840 as the ''Provincial Medical and Surgical Journal'' and quickly attracted the attention of physicians around the world through its publication of high-impact original research articles and unique case reports. The ''BMJ''s first editors were P. Hennis Green, lecturer on the diseases of children at the Hunterian School of Medicine, who also was its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myocardial Infarction
A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck or jaw. Often it occurs in the center or left side of the chest and lasts for more than a few minutes. The discomfort may occasionally feel like heartburn. Other symptoms may include shortness of breath, nausea, feeling faint, a cold sweat or feeling tired. About 30% of people have atypical symptoms. Women more often present without chest pain and instead have neck pain, arm pain or feel tired. Among those over 75 years old, about 5% have had an MI with little or no history of symptoms. An MI may cause heart failure, an irregular heartbeat, cardiogenic shock or cardiac arrest. Most MIs occur due to coronary artery disease. Risk factors include high blood pressure, smoking, diabetes, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smoking Ban
Smoking bans, or smoke-free laws, are public policies, including criminal laws and occupational safety and health regulations, that prohibit tobacco smoking in certain spaces. The spaces most commonly affected by smoking bans are indoor workplaces and buildings open to the public such as restaurants, bars, office buildings, schools, retail stores, hospitals, libraries, transport facilities, and government buildings, in addition to public transport vehicles such as aircraft, buses, watercraft, and trains. However, laws may also prohibit smoking in outdoor areas such as parks, beaches, pedestrian plazas, college and hospital campuses, and within a certain distance from the entrance to a building, and in some cases, private vehicles and multi-unit residences. The most common rationale cited for restrictions on smoking is the negative health effects associated with secondhand smoke (SHS), or the inhalation of tobacco smoke by persons who are not smoking. These include diseases s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helena, Montana
Helena (; ) is the capital city of Montana, United States, and the county seat of Lewis and Clark County. Helena was founded as a gold camp during the Montana gold rush, and established on October 30, 1864. Due to the gold rush, Helena would become a wealthy city, with approximately 50 millionaires inhabiting the area by 1888. The concentration of wealth contributed to the city's prominent, elaborate Victorian architecture. At the 2020 census Helena's population was 32,091, making it the fifth least populous state capital in the United States and the sixth most populous city in Montana. It is the principal city of the Helena Micropolitan Statistical Area, which includes all of Lewis and Clark and Jefferson counties; its population is 83,058 according to the 2020 Census. The local daily newspaper is the '' Independent Record''. The city is served by Helena Regional Airport (HLN). History The Helena area was long inhabited by various indigenous peoples. Evidence from the M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Economic Review
The ''American Economic Review'' is a monthly peer-reviewed academic journal published by the American Economic Association. First published in 1911, it is considered one of the most prestigious and highly distinguished journals in the field of economics. The current editor-in-chief is Esther Duflo, an economic professor at the Massachusetts Institute of Technology. The journal is based in Pittsburgh. In 2004, the ''American Economic Review'' began requiring "data and code sufficient to permit replication" of a paper's results, which is then posted on the journal's website. Exceptions are made for proprietary data. Until 2017, the May issue of the ''American Economic Review'', titled the ''Papers and Proceedings'' issue, featured the papers presented at the American Economic Association's annual meeting that January. After being selected for presentation, the papers in the ''Papers and Proceedings'' issue did not undergo a formal process of peer review. Starting in 2018, papers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David A
David (; , "beloved one") (traditional spelling), , ''Dāwūd''; grc-koi, Δαυΐδ, Dauíd; la, Davidus, David; gez , ዳዊት, ''Dawit''; xcl, Դաւիթ, ''Dawitʿ''; cu, Давíдъ, ''Davidŭ''; possibly meaning "beloved one". was, according to the Hebrew Bible, the third king of the United Kingdom of Israel. In the Books of Samuel, he is described as a young shepherd and harpist who gains fame by slaying Goliath, a champion of the Philistines, in southern Canaan. David becomes a favourite of Saul, the first king of Israel; he also forges a notably close friendship with Jonathan, a son of Saul. However, under the paranoia that David is seeking to usurp the throne, Saul attempts to kill David, forcing the latter to go into hiding and effectively operate as a fugitive for several years. After Saul and Jonathan are both killed in battle against the Philistines, a 30-year-old David is anointed king over all of Israel and Judah. Following his rise to power, David ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambeth Waterworks Company
The Lambeth Waterworks Company was a utility company supplying water to parts of south London in England. The company was established in 1785 with works in north Lambeth and became part of the publicly owned Metropolitan Water Board in 1904. Origins The Lambeth Waterworks Company, founded in 1785 to supply water to south and west London, established premises on the south bank of the River Thames close to the present site of Hungerford Bridge where the Royal Festival Hall now stands. The Company's first water-intake lay on the south side of the river, supplied directly from the river. After complaints that the water was foul, the intake was moved to the middle of the river. The Company expanded to supply Kennington in 1802 and about this time replaced its wooden pipes with iron ones. Infrastructure In 1832 the company built a reservoir at Streatham Hill, and in 1834 obtained an Act of Parliament to extend its area of supply. In the same year the company purchased of l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
