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  1. Rapid diagnostic test - Wikipedia

    A rapid diagnostic test (RDT) is a medical diagnostic test that is quick and easy to perform. RDTs are suitable for preliminary or emergency medical screening and for use in medical facilities with limited resources. They also allow ...

  2. COVID-19 - Wikipedia

    t. e. Coronavirus disease 2019 ( COVID-19) is a contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease has since spread ...

  3. Reverse transcription polymerase chain reaction - Wikipedia
    • Nomenclature
    • History
    • Principles
    • Application
    • Challenges
    • Publication Guidelines
    • External Links

    The combined RT-PCR and qPCR technique has been described as quantitative RT-PCR or real-time RT-PCR (sometimes even called quantitative real-time RT-PCR), has been variously abbreviated as qRT-PCR, RT-qPCR, RRT-PCR, and rRT-PCR.In order to avoid confusion, the following abbreviations will be used consistently throughout this article: Not all authors, especially earlier ones, use this convention and the reader should be cautious when following links. RT-PCR has been used to indicate both real-time PCR (qPCR) and reverse transcription PCR (RT-PCR).

    Since its introduction in 1977, Northern blot has been used extensively for RNA quantification despite its shortcomings: (a) time-consuming technique, (b) requires a large quantity of RNA for detection, and (c) quantitatively inaccurate in the low abundance of RNA content. However, since its invention by Kary Mullisin 1983 RT PCR has since displaced northern blot as the method of choice for RNA detection and quantification. RT-PCR has risen to become the benchmark technology for the detection and/or comparison of RNA levels for several reasons: (a) it does not require post PCR processing, (b) a wide range (>107-fold) of RNA abundance can be measured, and (c) it provides insight into both qualitative and quantitative data. Due to its simplicity, specificity and sensitivity, RT-PCR is used in a wide range of applications from experiments as simple as quantification of yeast cells in wine to more complex uses as diagnostic tools for detecting infectious agents such as the avian flu vir...

    In RT-PCR, the RNA template is first converted into a complementary DNA (cDNA) using a reverse transcriptase (RT). The cDNA is then used as a template for exponential amplification using PCR. QT-NASBA is currently the most sensitive method of RNA detection available.[irrelevant citation]The use of RT-PCR for the detection of RNA transcript has revolutionized the study of gene expression in the following important ways: 1. Made it theoretically possible to detect the transcripts of practically any gene 2. Enabled sample amplification and eliminated the need for abundant starting material required when using northern blot analysis 3. Provided tolerance for RNA degradation as long as the RNA spanning the primer is intact

    The exponential amplification via reverse transcription polymerase chain reaction provides for a highly sensitive technique in which a very low copy number of RNA molecules can be detected. RT-PCR is widely used in the diagnosis of genetic diseases and, semiquantitatively, in the determination of the abundance of specific different RNA molecules within a cell or tissue as a measure of gene expression.

    Despite its major advantages, RT-PCR is not without drawbacks. The exponential growth of the reverse transcribed complementary DNA (cDNA) during the multiple cycles of PCR produces inaccurate end point quantification due to the difficulty in maintaining linearity. In order to provide accurate detection and quantification of RNA content in a sample, qRT-PCR was developed using fluorescence-based modification to monitor the amplification products during each cycle of PCR. The extreme sensitivity of the technique can be a double edged sword since even the slightest DNA contamination can lead to undesirable results. A simple method for elimination of false positive results is to include anchors, or tags, to the 5' region of a gene specific primer. Additionally, planning and design of quantification studies can be technically challenging due to the existence of numerous sources of variation including template concentration and amplification efficiency.Spiking in a known quantity of RNA i...

    Quantitative RT-PCR assay is considered to be the gold standard for measuring the number of copies of specific cDNA targets in a sample but it is poorly standardized. As a result, while there are numerous publications utilizing the technique, many provide inadequate experimental detail and use unsuitable data analysis to draw inappropriate conclusions. Due to the inherent variability in the quality of any quantitative PCR data, not only do reviewers have a difficult time evaluating these manuscripts, but the studies also become impossible to replicate. Recognizing the need for the standardization of the reporting of experimental conditions, the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE, pronounced mykee) guidelines have been published by an international consortium of academic scientists. The MIQE guidelines describe the minimum information necessary for evaluating quantitative PCRexperiments that should be required for publication for encou...

  4. Coronavirus - Wikipedia

    The earliest reports of a coronavirus infection in animals occurred in the late 1920s, when an acute respiratory infection of domesticated chickens emerged in North America. Arthur Schalk and M.C. Hawn in 1931 made the first detailed report ...

  5. Singapore - Wikipedia

    Singapore (/ ˈ s ɪ ŋ (ɡ) ə p ɔːr / (listen)), officially the Republic of Singapore, is a sovereign island city-state in maritime Southeast Asia.It lies about one degree of latitude (137 kilometres or 85 miles) north of the equator, off the ...

  6. Sieve of Eratosthenes - Wikipedia
    • Overview
    • Algorithm and Variants
    • Computational Analysis
    • Algorithmic Complexity
    • Euler's Sieve
    • See Also
    • External Links

    A prime number is a natural number that has exactly two distinct natural number divisors: the number 1and itself. To find all the prime numbers less than or equal to a given integer nby Eratosthenes' method: 1. Create a list of consecutive integers from 2 through n: (2, 3, 4, ..., n). 2. Initially, let pequal 2, the smallest prime number. 3. Enumerate the multiples of p by counting in increments of p from 2p to n, and mark them in the list (these will be 2p, 3p, 4p, ...; the pitself should not be marked). 4. Find the smallest number in the list greater than p that is not marked. If there was no such number, stop. Otherwise, let pnow equal this new number (which is the next prime), and repeat from step 3. 5. When the algorithm terminates, the numbers remaining not marked in the list are all the primes below n. The main idea here is that every value given to pwill be prime, because if it were composite it would be marked as a multiple of some other, smaller prime. Note that some of th...


    The sieve of Eratosthenes can be expressed in pseudocode, as follows: This algorithm produces all primes not greater than n. It includes a common optimization, which is to start enumerating the multiples of each prime i from i2. The time complexity of this algorithm is O(n log log n), provided the array update is an O(1)operation, as is usually the case.

    Segmented sieve

    As Sorenson notes, the problem with the sieve of Eratosthenes is not the number of operations it performs but rather its memory requirements. For large n, the range of primes may not fit in memory; worse, even for moderate n, its cache use is highly suboptimal. The algorithm walks through the entire array A, exhibiting almost no locality of reference. A solution to these problems is offered by segmented sieves, where only portions of the range are sieved at a time.These have been known since...

    Incremental sieve

    An incremental formulation of the sieve generates primes indefinitely (i.e., without an upper bound) by interleaving the generation of primes with the generation of their multiples (so that primes can be found in gaps between the multiples), where the multiples of each prime p are generated directly by counting up from the square of the prime in increments of p (or 2p for odd primes). The generation must be initiated only when the prime's square is reached, to avoid adverse effects on efficie...

    The work performed by this algorithm is almost entirely the operations to cull the composite number representations which for the basic non-optimized version is the sum of the range divided by each of the primes up to that range or 1. n ∑ p ≤ n 1 p , {\\displaystyle n\\sum _{p\\leq n}{\\frac {1}{p}},} where nis the sieving range in this and all further analysis. By rearranging Mertens' second theorem, this is equal to n ( log log n + M ) as n approaches infinity, where M is the Meissel–Mertens constant of about 0.26149... The optimization of starting at the square of each prime and only culling for primes less than the square root changes the "n" in the above expression to √n (or n1/2) and not culling until the square means that the sum of the base primes each minus two is subtracted from the operations. As the sum of the first x primes is 1/2x2 log x and the prime number theorem says that x is approximately x/log x, then the sum of primes to n is n2/2 log n, and therefore the sum of ba...

    The sieve of Eratosthenes is a popular way to benchmark computer performance. As can be seen from the above by removing all constant offsets and constant factors and ignoring terms that tend to zero as n approaches infinity, the time complexity of calculating all primes below n in the random access machine model is O(n log log n) operations, a direct consequence of the fact that the prime harmonic series asymptotically approaches log log n. It has an exponential time complexity with regard to input size, though, which makes it a pseudo-polynomial algorithm. The basic algorithm requires O(n)of memory. The bit complexity of the algorithm is O(n (log n) (log log n)) bit operations with a memory requirement of O(n). The normally implemented page segmented version has the same operational complexity of O(n log log n) as the non-segmented version but reduces the space requirements to the very minimal size of the segment page plus the memory required to store the base primes less than the...

    Euler's proof of the zeta product formula contains a version of the sieve of Eratosthenes in which each composite number is eliminated exactly once. The same sieve was rediscovered and observed to take linear time by Gries & Misra (1978). It, too, starts with a list of numbers from 2 to nin order. On each step the first element is identified as the next prime, is multiplied with each element of the list (thus starting with itself), and the results are marked in the list for subsequent deletion. The initial element and the marked elements are then removed from the working sequence, and the process is repeated: Here the example is shown starting from odds, after the first step of the algorithm. Thus, on the kth step all the remaining multiples of the kth prime are removed from the list, which will thereafter contain only numbers coprime with the first k primes (cf. wheel factorization), so that the list will start with the next prime, and all the numbers in it below the square of its...

    Eratosthenes, sieve ofat Encyclopaedia of Mathematics
    Sieve of Eratosthenes by George Beck, Wolfram Demonstrations Project.
  7. Chlamydia pneumoniae - Wikipedia
    • Life Cycle and Method of Infection
    • Diseases
    • Vaccine Research
    • External Links

    Chlamydia pneumoniae is a small gram negative bacterium (0.2 to 1 μm) that undergoes several transformations during its life cycle. It exists as an elementary body (EB) between hosts. The EB is not biologically active, but is resistant to environmental stresses and can survive outside a host for a limited time. The EB travels from an infected person to the lungs of an uninfected person in small droplets and is responsible for infection. Once in the lungs, the EB is taken up by cells in a pouch called an endosome by a process called phagocytosis. However, the EB is not destroyed by fusion with lysosomes, as is typical for phagocytosed material. Instead, it transforms into a reticulate body (RB) and begins to replicate within the endosome. The reticulate bodies must use some of the host's cellular metabolism to complete its replication. The reticulate bodies then convert back to elementary bodies and are released back into the lung, often after causing the death of the host cell. The...

    C. pneumoniae is a common cause of pneumonia around the world; it is typically acquired by otherwise-healthy people and is a form of community-acquired pneumonia. Its treatment and diagnosis are different from historically recognized causes, such as Streptococcus pneumoniae. Because it does not gram stain well, and because C. pneumoniae bacteria is very different from the many other bacteria causing pneumonia (in the earlier days, it was even thought to be a virus), the pneumonia caused by C. pneumoniae is categorized as an "atypical pneumonia".[citation needed] One meta-analysis of serological data comparing prior C. pneumoniaeinfection in patients with and without lung cancer found results suggesting prior infection was associated with an increased risk of developing lung cancer. In research into the association between C. pneumoniae infection and atherosclerosis and coronary artery disease, serological testing, direct pathologic analysis of plaques, and in vitro testing suggest i...

    There is currently no vaccine to protect against Chlamydia pneumoniae. Identification of immunogenic antigens is critical for the construction of an efficacious subunit vaccine against C. pneumoniae infections. Additionally, there is a general shortage worldwide of facilities which can identify/diagnose Chlamydia pneumoniae.

    Type strain of Chlamydopila pneumoniae at BacDive- the Bacterial Diversity Metadatabase
  8. Emergency Use Authorization - Wikipedia
    • Use
    • History of Legal Authority For EUAs
    • Applicability and The Animal Efficacy Rule
    • Use During Pandemics
    • See Also

    A review article by Rizk et al provides a summary of the US experience in 2020 with pharmacological EUA approvals during the COVID-19 pandemic.It also provides a description of, and clinical rationale for, the EUA-approved drugs during the pandemic and concluding reflections on the EUA program and its potential future uses. After initial authorizations for serious diseases such as pandemic influenza and emerging diseases, EUAs were also authorized for medical countermeasures (MCMs) principally in response to public health emergencies such as bioterrorism, including chemical, biological, radiological and nuclear (CBRN) threats. Subsequent legislative authorities expanded the latitude of the class of drugs eligible for consideration, and the range of testing to which the drug or therapy has been subjected. The scope and applicability of EUAs is also affected by presidential executive orders (Title 3 of the Code of Federal Regulations), which may affect the definition of the situations...

    In the United States, EUAs are authorized by Section 564 of the Federal Food Drug and Cosmetic Act (FDCA) of 1938 (Public Law 75-717) as added and subsequently amended by the Project BioShield Act of 2004 (S. 15, Public Law 108-276) for funding of the development and procurement of medical countermeasures against CBRN threats, the Pandemic and All-Hazards Preparedness Reauthorization Act of 2013 (H.R. 307, Pub.L. 113–5 (text) (pdf)), the 21st Century Cures Act of 2016 (H.R. 34, Public Law 114-255) and Pub.L. 115–92 (text) (pdf)of 2017 (no short title).

    EUAs may be applied to drugs, devices or biological product. EUAs may either permit the emergency use of an unapproved drug, device or biologic product, or permit an unapproved use of an approved drug, device or biologic product. Furthermore, drugs, devices or biologic productsmay or may not have undergone human efficacy trials, due to risk, feasibility or ethical considerations. Drugs, devices or biologic products which have only been tested or approved under the animal efficacy rule are loosely known as animal products. Under certain conditions, an EUA may authorize the emergency use in humans, of drugs, devices or biologic products approved under the animal efficacy rule. EUAs may also only be implemented during the period of a public health emergency as defined by a declaration of the Secretary of Health and Human Services (HHS). Conditions determining the applicability of suchdeclarations may be specified by federal statute. Code of Federal Regulations or an presidential execut...

    In response to requests from the U.S. Centers for Disease Control and Prevention (CDC), on April 27, 2009, the FDA issued Emergency Use Authorizations to make available diagnostic and therapeutic tools to identify and respond to the 2009 swine flu pandemic under certain circumstances. The agency issued these EUAs for the use of certain powerful antiviral drugs, and for the quantitative PCR swine flu test. On February 4, 2020, the Secretary of HHS declared the public health emergency for the novel SARS-CoV-2 virus, which causes the disease COVID-19, for deployment of the FDA EUA for certain medical devices involved in the diagnosis of COVID-19. In February 2020, The FDA issued an EUA for COVID-19 testing CDC test kits for COVID-19. In 2020, the FDA issued EUAs for remdesivir, convalescent plasma, Fresenius Propoven 2% emulsion (propofol), hydroxychloroquine (revoked, although its license for established indications remains), and bamlanivimab – all in response to the COVID-19 pandemic...

  9. Dengue fever - Wikipedia

    Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. These may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic skin ...

  10. Hughes H-4 Hercules - Wikipedia
    • Design and Development
    • Operational History
    • Display
    • Specifications
    • See Also
    • References
    • External Links

    In 1942, the U.S. War Department needed to transport war materiel and personnel to Britain. Allied shipping in the Atlantic Ocean was suffering heavy losses to German U-boats, so a requirement was issued for an aircraft that could cross the Atlantic with a large payload. Wartime priorities meant the aircraft could not be made of strategic materials (e.g., aluminum). The aircraft was the brainchild of Henry J. Kaiser, a leading Liberty ship builder and manufacturer. Kaiser teamed with aircraft designer Howard Hughes to create what would become the largest aircraft yet built. It was designed to carry 150,000 pounds (68,000 kg), 750 fully equipped troops or two 30-ton M4 Sherman tanks.The original designation "HK-1" reflected the Hughes and Kaiser collaboration. The HK-1 aircraft contract was issued in 1942 as a development contract and called for three aircraft to be constructed in two years for the war effort. Seven configurations were considered, including twin-hull and single-hull...

    Hughes returned to California during a break in the Senate hearings to run taxi tests on the H-4.On November 2, 1947, the taxi tests began with Hughes at the controls. His crew included Dave Grant as copilot, two flight engineers, Don Smith and Joe Petrali, 16 mechanics, and two other flight crew. The H-4 also carried seven invited guests from the press corps and an additional seven industry representatives. In total, thirty-six people were on board. Four reporters left to file stories after the first two taxi runs while the remaining press stayed for the final test run of the day. After picking up speed on the channel facing Cabrillo Beach, the Hercules lifted off, remaining airborne for 26 seconds at 70 ft (21 m) off the water at a speed of 135 miles per hour (217 km/h) for about one mile (1.6 km). At this altitude, the aircraft still experienced ground effect.Nevertheless, the brief flight proved to detractors that Hughes' (now unneeded) masterpiece was flight-worthy—thus vindica...

    Ownership of the H-4 was disputed by the U.S. government, which had contracted for its construction. In the mid-1970s, an agreement was reached whereby the Smithsonian Institution's National Air and Space Museum would receive the Hughes H-1 Racer and section of the H-4's wing, the Summa Corporationwould pay $700,000 and receive ownership of the H-4, the U.S. government would cede any rights, and the aircraft would be protected "from commercial exploitation." In 1980, the H-4 was acquired by the Aero Club of Southern California, which later put the aircraft on display in a very large geodesic dome next to the Queen Mary ship exhibit in Long Beach, California. The large dome facility became known as the Spruce Goose Dome. The very large enclosed indoor dome area around the H-4 consisted of meeting and special event space, elaborate audio-visual displays about Howard Hughes and the aircraft itself, and dining areas for tourists. Many convention groups held large dinners, sales meetings...

    Performance specifications are projected. General characteristics 1. Crew:3 2. Length:218 ft 8 in (66.65 m) 3. Wingspan:320 ft 11 in (97.82 m) 4. Height:79 ft 4 in (24.18 m) 5. Fuselage height:30 ft (9.1 m) 6. Empty weight:250,000 lb (113,398 kg) 7. Powerplant: 8 × Pratt & Whitney R-4360 Wasp Major28-cylinder air-cooled radial piston engines, 3,000 hp (2,200 kW) each 8. Propellers: 4-bladed Hamilton Standard, 17 ft 2 in (5.23 m) diameter constant-speed propellers Performance 1. Cruise speed:250 mph (400 km/h, 220 kn) 2. Range:3,000 mi (4,800 km, 2,600 nmi) 3. Service ceiling:20,900 ft (6,400 m)


    1. Francillon, René J. McDonnell Douglas Aircraft since 1920: Volume II. Annapolis, Maryland: Naval Institute Press, 1990. ISBN 1-55750-550-0. 2. McDonald, John J. Howard Hughes and the Spruce Goose. Blue Ridge Summit, Pennsylvania: Tab Books Inc., 1981. ISBN 0-8306-2320-5. 3. Odekirk, Glenn E. Spruce Goose (Title inside cover: HK-1 Hercules: A Pictorial History of the Fantastic Hughes Flying Boat). Long Beach, California: Glenn E. Odekirk and Frank Alcantr, Inc., 1982. No ISBN. 4. Parker, Da...

    Evergreen Aviation & Space Museum, home of the Spruce Goose
    Vintage photos of Spruce Goose's construction