SUMMARY / RELATED TOPICS

Vitamin E

Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, rare and due to an underlying problem with digesting dietary fat rather than from a diet low in vitamin E, can cause nerve problems. Vitamin E is a fat-soluble antioxidant protecting cell membranes from reactive oxygen species. Worldwide, government organizations recommend; as of 2016, consumption was below recommendations according to a worldwide summary of more than one hundred studies that reported a median dietary intake of 6.2 mg per day for alpha-tocopherol. Research with alpha-tocopherol as a dietary supplement, with daily amounts as high as 2000 mg per day, has had mixed results. Population studies suggested that people who consumed foods with more vitamin E, or who chose on their own to consume a vitamin E dietary supplement, had lower incidence of cardiovascular diseases, cancer and other diseases, but placebo-controlled clinical trials could not always replicate these findings, there were some indications that vitamin E supplementation was associated with a modest increase in all-cause mortality.

As of 2017, vitamin E continues to be a topic of active clinical research. There is no clinical evidence. Both natural and synthetic tocopherols are subject to oxidation, so in dietary supplements are esterified, creating tocopheryl acetate for stability purposes. Both the tocopherols and tocotrienols occur in α, β, γ and δ forms, as determined by the number and position of methyl groups on the chromanol ring. All eight of these vitamers feature a chromane double ring, with a hydroxyl group that can donate a hydrogen atom to reduce free radicals, a hydrophobic side chain which allows for penetration into biological membranes. Of the many different forms of vitamin E, gamma-tocopherol is the most common form found in the North American diet, but alpha-tocopherol is the most biologically active. Palm oil is a source of tocotrienols. Vitamin E was discovered in 1922, isolated in 1935 and first synthesized in 1938; because the vitamin activity was first identified as essential for fertilized eggs to result in live births, it was given the name "tocopherol" from Greek words meaning birth and to bear or carry.

Alpha-tocopherol, either extracted from plant oils or, most as the synthetic tocopheryl acetate, is sold as a popular dietary supplement, either by itself or incorporated into a multivitamin product, in oils or lotions for use on skin. Vitamin E may have various roles as a vitamin. Many biological functions have been postulated, including a role as a fat-soluble antioxidant. In this role, vitamin E acts as a radical scavenger. At 323 kJ/mol, the O-H bond in tocopherols is about 10% weaker than in most other phenols; this weak bond allows the vitamin to donate a hydrogen atom to the peroxyl radical and other free radicals, minimizing their damaging effect. The thus-generated tocopheryl radical is recycled to tocopherol by a redox reaction with a hydrogen donor, such as vitamin C; as it is fat-soluble, vitamin E is incorporated into cell membranes, which are therefore protected from oxidative damage. Vitamin E affects gene expression and is an enzyme activity regulator, such as for protein kinase C – which plays a role in smooth muscle growth – with vitamin E participating in deactivation of PKC to inhibit smooth muscle growth.

Vitamin E deficiency is rare in humans, occurring as a consequence of abnormalities in dietary fat absorption or metabolism rather than from a diet low in vitamin E. One example of a genetic abnormality in metabolism is mutations of genes coding for alpha-tocopherol transfer protein. Humans with this genetic defect exhibit a progressive neurodegenerative disorder known as ataxia with vitamin E deficiency despite consuming normal amounts of vitamin E. Large amounts of alpha-tocopherol as a dietary supplement are needed to compensate for the lack of α-TTP Vitamin E deficiency due to either malabsorption or metabolic anomaly can cause nerve problems due to poor conduction of electrical impulses along nerves due to changes in nerve membrane structure and function. In addition to ataxia, vitamin E deficiency can cause peripheral neuropathy, myopathies and impairment of immune responses. In the United States vitamin E supplement use by female health professionals was 16.1% in 1986, 46.2% in 1998, 44.3% in 2002, but decreased to 19.8% in 2006.

For male health professionals, rates for same years were 18.9%, 52.0%, 49.4% and 24.5%. The authors theorized that declining use in these populations may have been due to publications of studies that showed either no benefits or negative consequences from vitamin E supplements. Within the US military services, vitamin prescriptions written for active and retired military, their dependents, were tracked over years 2007–2011. Vitamin E prescriptions decreased by 53% while vitamin C remained constant and vitamin D increased by 454%. A report on vitamin E sales volume in the US documented a 50% decrease between 2000 and 2006, with a potential reason being a meta-analysis that concluded high-dosage vitamin E was associated with an increase in all-cause mortality; the U. S. Food and Nutrition Board set a Tolerable upper intake level at 1,000 mg per day derived from animal models that demonstrated bleeding at high doses; the European Food Safety Authority reviewed the same safety set a UL at 300 mg/day.

A meta-analysis of long-term clinical trials reported a non-significant 2%

Tok Airport

Tok Airport was a state-owned public-use airport located two nautical miles south of the central business district of Tok, in the Southeast Fairbanks Census Area of the U. S. state of Alaska. Tok Airport has one runway designated 13/31 with a 1,690 by turf surface. For the 12-month period ending December 31, 2005, the airport had 600 aircraft operations, an average of 50 per month: 83% general aviation and 17% air taxi. At that time there were 17 aircraft based at all single-engine. Tok Junction Airport is state-owned public-use located at 63°19′46″N 142°57′13″W, one nautical mile east of the central business district of Tok, it has one runway designated 7/25 with a 2,509 x 50 ft asphalt surface. Tok 2 Airport is a private-use airport located at 63°18′32″N 143°01′04″W, on the opposite side of Glenn Highway from the Tok Airport, it has one runway designated 10/28 with a 2,035 x 80 ft gravel surface. Aerial photo of Tok and Tok 2. Federal Aviation Administration, Alaska Region. Summer 1975. Airport diagram of Tok and Tok 2.

Federal Aviation Administration, Alaska Region. September 2004. Topographic map showing landing strip to the south. USGS The National Map via MSR Maps. July 1948. Accident history for TKJ at Aviation Safety Network

Kaj Aage Gunnar Strand

Kaj Aage Gunnar Strand was a Danish astronomer who worked in Denmark and the United States. He was Scientific Director of the U. S. Naval Observatory from 1963 to 1977, he specialized in astrometry work on double stars and stellar distances. Kaj Strand was born February 1907 in Hellerup, Denmark, on the outskirts of Copenhagen, he entered the University of Copenhagen in 1926, majored in astronomy, graduated in 1931 with Magister and Candidate Magister degrees. At the invitation of Ejnar Hertzsprung, during the 1930s he worked at Leiden on a program of photographing double stars. From 1938-42 Strand worked under Peter van de Kamp as a Research Associate at Swarthmore College, began the photographic double star program with the 24 in refractor telescope at the college's Sproul Observatory. During World War II he entered the U. S. Army, the U. S. Army Air Force, flew as a Captain and chief navigator on B-29 Superfortress tests; as head of the Navigation Department he was involved in operational training of special air crews, including the first atomic bomb crew.

After the war Strand returned to Swarthmore College, in 1946 began as an associate professor at Yerkes Observatory. In the same year he became chairman of the Astronomy Department at Northwestern University, was responsible for planning the University's new computer center. In 1958 Strand accepted a position as head of the Astrometry and Astrophysics Division at the U. S. Naval Observatory rising to the position of Scientific Director in 1963, he pioneered in the determination of stellar distances using reflecting telescopes, was responsible for the design and construction of the 61 in Strand Astrometric Telescope, dedicated in 1964 at the United States Naval Observatory Flagstaff Station in Arizona. Strand is known for his 1942 and 1957 claims of a planetary system around the nearby star 61 Cygni while working under the direction of Peter van de Kamp at the Sproul Observatory; these claims were refuted by Wulff Heintz of the Sproul Observatory. Strand was awarded the Guggenheim Fellowship in 1946.

The main-belt asteroid, 3236 Strand, is named for him. It was discovered on January 24, 1982 by E. Bowell at Lowell Observatory, Anderson Mesa Station in Flagstaff, Arizona, he died October 31, 2000 in Washington, D. C. at the age of 93. Peter van de Kamp Barnard's Star