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'''''[[Clostridium difficile]]''''' is a spore-forming, anaerobic, toxin-producing bacterium that is a "common inhabitant of the colon flora in human infants and sometimes in adults. It produces a toxin that causes pseudomembranous enterocolitis in patients receiving antibiotic therapy." ''C. difficile'' superinfection after oral antibiotic therapy, leading to potentially fatal pseudomembranous enterocolitis, has been an increasingly severe public health problem. Indeed, many primary physicians now consider it wise to warn outpatients on antibiotics to seek immediate consultation if they develop severe diarrhea.
{{Image|SR-71 over mtns.jpg|right|300px| SR-71B loaned from the U.S. Air Force for use in high-speed, high-altitude research at the NASA Dryden Flight Research Center, Edwards, California.}}


C. difficile is present at low levels in the gut flora of about 3% of adults. These people however show no symptoms and do not need to be treated. The infection occurs when a person is treated with antibiotics targeted against other bacteria. The disease is for the most part nosocomial. Patients who are hospitalized come in contact and are often inoculated with the bacteria. When the patient is treated with antibiotics, especially those with a broad range of activity, the normal gut flora is disrupted, and C. difficile, with its multi-drug resistance, experiences overgrowth. The bacteria releases large quantities of enterotoxins (toxin A) and cytotoxins (toxin B), causing pseudomembranous enterocolitis.
The '''[[Lockheed SR-71]]''' (known unofficially as the '''Blackbird''', and by its crews as the '''Habu''' or the '''sled''') was an advanced, long-range, Mach 3 strategic reconnaissance aircraft developed from the Lockheed YF-12A and A-12 aircraft by the Lockheed Skunk Works. The SR-71 line was in service from 1964 to 1998, and it was the world's fastest and highest-flying operational manned aircraft throughout that entire period, an unparalleled achievement in aviation history. The aircraft flew so fast and so high that if the crew detected a surface-to-air missile launch, the standard evasive action was simply to accelerate. Thirteen aircraft are known to have been lost, all from non-combat related reasons.
 
[[Image:img2.gif|thumb|left|250px|scanning electron micrograph of C. difficile]]
The SR-71 included many novel and advanced technologies in order to achieve that performance; in particular, due to extensive frictional heating from its high speed, almost everything in the aircraft had to be specially produced; the airframe was built almost entirely of titanium, as operating temperatures were too high for aluminum. It was also one of the first aircraft to be have been built with a reduced radar cross section; however, the aircraft was not completely stealthy, and still had a fairly large radar signature. The chief designer, Kelly Johnson, was the man behind many of its advanced concepts. After his retirement, Ben Rich ran the program.
====History====
====History====
In 1935, Hall and O’Toole first isolated the bacteria from the stools of newborns and described it. They named it ''Bacillus difficilis'' because it was hard to isolate and grew very slowly in culture.
While the U-2 Dragon Lady reconnaissance aircraft produced immense value when it began to overfly the Soviet Union in 1956, it was accepted that this subsonic, nonstealthy aircraft eventually would be vulnerable to the Soviet air defense network. Indeed, one was shot down in May 1960, ending manned reconnaissance overflights of the Russian landmass. Overhead reconnaissance of the Soviet Union was taken over by satellites, but the SR-71 was already in development.
 
=====Predecessor models=====
C. difficile is an important pathogen that is currently increasing in its prevalence world-wide. A complete genome sequence would enable geneticists to come up with a more direct and efficient treatment against the pathogen. The genetic material encodes for antimicrobial resistance, production of toxins (virulence), host interaction (adaptations for survival and growth within the gut environment), and the production of surface structures. The understanding of how these genes interact with their environment will be useful in developing therapies against C. difficile associated diseases.
The A-12 Oxcart, designed for the CIA by Kelly Johnson at the Lockheed Skunk Works, was the precursor of the SR-71. Lockheed used the name "Archangel" for this design, but many documents use Johnson's preferred name for the plane, "the Article." As the design evolved, the internal Lockheed designation went from A-1 to A-12 as configuration changes occurred, such as substantial design changes to reduce the radar cross-section. The first flight took place at Groom Lake, Nevada, on April 25, 1962.  It was 'Article 121,' an A-12, but it was equipped with less powerful Pratt & Whitney J75s due to protracted development of the intended Pratt & Whitney J58. The J58s were retrofitted as they became available. The J58s became the standard power plant for all subsequent aircraft in the series (A-12, YF-12, MD-21) as well as the follow-on SR-71 aircraft.  Eighteen A-12 aircraft were built in four variations, of which three were YF-12As, prototypes of the planned F-12B interceptor version, and two were the M-21 variant (see below).


====Genome Structure====
The Air Force reconnaissance version was originally called the R-12 (see the opening fly page in Paul Crickmore's book ''SR-71, Secret Missions Exposed'', which contains a copy of the original R-12 labeled plan view drawing of the vehicle). However, during the 1964 presidential campaign, Senator Barry Goldwater continually criticized President Lyndon B. Johnson and his administration for falling behind the Soviet Union in the research and development of new weapon systems. Johnson decided to counter this criticism with the public release of the highly classified A-12 program and later the existence of the reconnaissance version.
Sebaihia et al (2006) determined the complete genomic sequence of ''C. difficile'' strain 630, a highly virulent and multidrug-resistant strain. It was found that the genome consists of a circular chromosome of 4,290,252 bp and a plasmid, pCD630, of 7,881 bp. The chromosome encodes 3,776 predicted coding sequences (CDSs), with resistance, virulence, and host interaction genes, while the plasmid carries only 11 CDSs, none of which has any obvious function. ''C. difficile'' has a highly mobile genome, with 11% of the genome consisting of mobile genetic elements, mostly in the form of conjugative transposons. Conjugative transposons are mobile genetic elements that are capable of integrating into and excising from the host genome and transferring themselves, and are responsible for the evolutionary acquisition by C. difficile of genes involved in resistance, virulence, and host interactions. Some of the mobile elements are prophage sequences. Host interaction genes involve genes that code for metabolic capability adaptations for survival and growth within the gut environment.


''[[Clostridium difficile|.... (read more)]]''
===== Name and designation =====
The USAF had planned to redesignate the A-12 aircraft as the B-71 as the successor to the B-70 Valkyrie, whichhad two test Valkyries flying at Edwards Air Force Base, California. The B-71 would have a nuclear capability of 3 first-generation SRAM's (Short-Range Attack Missiles). The next designation was RS-71 (Reconnaissance-Strike) when the strike capability became an option. However, then USAF Chief of Staff Curtis LeMay preferred the SR designation and wanted the RS-71 to be named SR-71. Before the Blackbird was to be announced by President Johnson on February 29, 1964, LeMay lobbied to modify Johnson's speech to read SR-71 instead of RS-71. The media transcript given to the press at the time still had the earlier RS-71 designation in places, creating the myth that the president had misread the plane's designation.
''[[Lockheed SR-71|.... (read more)]]''

Revision as of 18:19, 1 September 2011

(PD) Photo: United States Air Force
SR-71B loaned from the U.S. Air Force for use in high-speed, high-altitude research at the NASA Dryden Flight Research Center, Edwards, California.

The Lockheed SR-71 (known unofficially as the Blackbird, and by its crews as the Habu or the sled) was an advanced, long-range, Mach 3 strategic reconnaissance aircraft developed from the Lockheed YF-12A and A-12 aircraft by the Lockheed Skunk Works. The SR-71 line was in service from 1964 to 1998, and it was the world's fastest and highest-flying operational manned aircraft throughout that entire period, an unparalleled achievement in aviation history. The aircraft flew so fast and so high that if the crew detected a surface-to-air missile launch, the standard evasive action was simply to accelerate. Thirteen aircraft are known to have been lost, all from non-combat related reasons.

The SR-71 included many novel and advanced technologies in order to achieve that performance; in particular, due to extensive frictional heating from its high speed, almost everything in the aircraft had to be specially produced; the airframe was built almost entirely of titanium, as operating temperatures were too high for aluminum. It was also one of the first aircraft to be have been built with a reduced radar cross section; however, the aircraft was not completely stealthy, and still had a fairly large radar signature. The chief designer, Kelly Johnson, was the man behind many of its advanced concepts. After his retirement, Ben Rich ran the program.

History

While the U-2 Dragon Lady reconnaissance aircraft produced immense value when it began to overfly the Soviet Union in 1956, it was accepted that this subsonic, nonstealthy aircraft eventually would be vulnerable to the Soviet air defense network. Indeed, one was shot down in May 1960, ending manned reconnaissance overflights of the Russian landmass. Overhead reconnaissance of the Soviet Union was taken over by satellites, but the SR-71 was already in development.

Predecessor models

The A-12 Oxcart, designed for the CIA by Kelly Johnson at the Lockheed Skunk Works, was the precursor of the SR-71. Lockheed used the name "Archangel" for this design, but many documents use Johnson's preferred name for the plane, "the Article." As the design evolved, the internal Lockheed designation went from A-1 to A-12 as configuration changes occurred, such as substantial design changes to reduce the radar cross-section. The first flight took place at Groom Lake, Nevada, on April 25, 1962. It was 'Article 121,' an A-12, but it was equipped with less powerful Pratt & Whitney J75s due to protracted development of the intended Pratt & Whitney J58. The J58s were retrofitted as they became available. The J58s became the standard power plant for all subsequent aircraft in the series (A-12, YF-12, MD-21) as well as the follow-on SR-71 aircraft. Eighteen A-12 aircraft were built in four variations, of which three were YF-12As, prototypes of the planned F-12B interceptor version, and two were the M-21 variant (see below).

The Air Force reconnaissance version was originally called the R-12 (see the opening fly page in Paul Crickmore's book SR-71, Secret Missions Exposed, which contains a copy of the original R-12 labeled plan view drawing of the vehicle). However, during the 1964 presidential campaign, Senator Barry Goldwater continually criticized President Lyndon B. Johnson and his administration for falling behind the Soviet Union in the research and development of new weapon systems. Johnson decided to counter this criticism with the public release of the highly classified A-12 program and later the existence of the reconnaissance version.

Name and designation

The USAF had planned to redesignate the A-12 aircraft as the B-71 as the successor to the B-70 Valkyrie, whichhad two test Valkyries flying at Edwards Air Force Base, California. The B-71 would have a nuclear capability of 3 first-generation SRAM's (Short-Range Attack Missiles). The next designation was RS-71 (Reconnaissance-Strike) when the strike capability became an option. However, then USAF Chief of Staff Curtis LeMay preferred the SR designation and wanted the RS-71 to be named SR-71. Before the Blackbird was to be announced by President Johnson on February 29, 1964, LeMay lobbied to modify Johnson's speech to read SR-71 instead of RS-71. The media transcript given to the press at the time still had the earlier RS-71 designation in places, creating the myth that the president had misread the plane's designation. .... (read more)