Econstudentlog

Wikipedia articles of interest

i. Proportional hazards models. (work-related)

Proportional hazards models are a class of survival models in statistics. Survival models relate the time that passes before some event occurs to one or more covariates that may be associated with that quantity. In a proportional hazards model, the unique effect of a unit increase in a covariate is multiplicative with respect to the hazard rate. For example, taking a drug may halve one’s hazard rate for a stroke occurring, or, changing the material from which a manufactured component is constructed may double its hazard rate for failure. Other types of survival models such as accelerated failure time models do not exhibit proportional hazards. These models could describe a situation such as a drug that reduces a subject’s immediate risk of having a stroke, but where there is no reduction in the hazard rate after one year for subjects who do not have a stroke in the first year of analysis.”

ii. Radioisotope thermoelectric generator.

“A radioisotope thermoelectric generator (RTG, RITEG) is an electrical generator that obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect using an array of thermocouples.

RTGs have been used as power sources in satellites, space probes and unmanned remote facilities, such as a series of lighthouses built by the former Soviet Union inside the Arctic Circle. RTGs are usually the most desirable power source for robotic or unmaintained situations needing a few hundred watts (or less) of power for durations too long for fuel cells, batteries, or generators to provide economically, and in places where solar cells are not practical. Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit. […]

In addition to spacecraft, the Soviet Union constructed many unmanned lighthouses and navigation beacons powered by RTGs.[5] Powered by strontium-90 (90Sr), they are very reliable and provide a steady source of power. Critics[who?] argue that they could cause environmental and security problems as leakage or theft of the radioactive material could pass unnoticed for years, particularly as the locations of some of these lighthouses are no longer known due to poor record keeping. In one instance, the radioactive compartments were opened by a thief.[6] In another case, three woodsmen in Georgia came across two ceramic RTG heat sources that had been stripped of their shielding. Two of the three were later hospitalized with severe radiation burns after carrying the sources on their backs. The units were eventually recovered and isolated.[7]

There are approximately 1,000 such RTGs in Russia. All of them have long exhausted their 10-year engineered life spans. They are likely no longer functional, and may be in need of dismantling. Some of them have become the prey of metal hunters, who strip the RTGs’ metal casings, regardless of the risk of radioactive contamination.[8]

When I read this part, I couldn’t not think of this and this.

iii. List of unusual deaths. A lot of awesome stuff here. A few examples from the article:

iv. Limnic eruption.

“A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake water, suffocating wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe landslides, volcanic activity, or explosions can trigger such an eruption. Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes.”

v. HeLa. The woman died more than 60 years ago, but some of the descendants of the cancer cells that killed her survives to this day:

“A HeLa cell /ˈhlɑː/, also Hela or hela cell, is a cell type in an immortal cell line used in scientific research. It is the oldest and most commonly used human cell line.[1] The line was derived from cervical cancer cells taken on February 8, 1951[2] from Henrietta Lacks, a patient who eventually died of her cancer on October 4, 1951. The cell line was found to be remarkably durable and prolific as illustrated by its contamination of many other cell lines used in research.[3][4] […]

HeLa cells, like other cell lines, are termed “immortal” in that they can divide an unlimited number of times in a laboratory cell culture plate as long as fundamental cell survival conditions are met (i.e. being maintained and sustained in a suitable environment). There are many strains of HeLa cells as they continue to evolve in cell cultures, but all HeLa cells are descended from the same tumor cells removed from Mrs. Lacks. It has been estimated that the total number of HeLa cells that have been propagated in cell culture far exceeds the total number of cells that were in Henrietta Lacks’s body.[7] […]

HeLa cells were used by Jonas Salk to test the first polio vaccine in the 1950s. Since that time, HeLa cells have been used for “research into cancer, AIDS, the effects of radiation and toxic substances, gene mapping, and many other scientific pursuits”.[8] According to author Rebecca Skloot, by 2009, “more than 60,000 scientific articles had been published about research done on HeLa, and that number was increasing steadily at a rate of more than 300 papers each month.”[6]

v. Domesticated silver fox.

“The domesticated silver fox (marketed as the Siberian fox) is a domesticated form of the silver morph of the red fox. As a result of selective breeding, the new foxes became tamer and more dog-like.

The result of over 50 years of experiments in the Soviet Union and Russia, the breeding project was set up in 1959[1] by Soviet scientist Dmitri Belyaev. It continues today at The Institute of Cytology and Genetics at Novosibirsk, under the supervision of Lyudmila Trut. […]

Belyaev believed that the key factor selected for in the domestication of dogs was not size or reproduction, but behavior; specifically, amenability to domestication, or tameability. He selected for low flight distance, that is, the distance one can approach the animal before it runs away. Selecting this behavior mimics the natural selection that must have occurred in the ancestral past of dogs. More than any other quality, Belyaev believed, tameability must have determined how well an animal would adapt to life among humans. Since behavior is rooted in biology, selecting for tameness and against aggression means selecting for physiological changes in the systems that govern the body’s hormones and neurochemicals. Belyaev decided to test his theory by domesticating foxes; in particular, the silver fox, a dark color form of the red fox. He placed a population of them in the same process of domestication, and he decided to submit this population to strong selection pressure for inherent tameness.[3]

The result is that Russian scientists now have a number of domesticated foxes that are fundamentally different in temperament and behavior from their wild forebears. Some important changes in physiology and morphology are now visible, such as mottled or spotted colored fur. Many scientists believe that these changes related to selection for tameness are caused by lower adrenaline production in the new breed, causing physiological changes in very few generations and thus yielding genetic combinations not present in the original species. This indicates that selection for tameness (i.e. low flight distance) produces changes that are also influential on the emergence of other “dog-like” traits, such as raised tail and coming into heat every six months rather than annually.”

vi. Attalus I (featured).

“Attalus I (Greek: Ἄτταλος), surnamed Soter (Greek: Σωτὴρ, “Savior”; 269 BC – 197 BC)[1] ruled Pergamon, an Ionian Greek polis (what is now Bergama, Turkey), first as dynast, later as king, from 241 BC to 197 BC. He was the second cousin and the adoptive son of Eumenes I,[2] whom he succeeded, and was the first of the Attalid dynasty to assume the title of king in 238 BC.[3] He was the son of Attalus and his wife Antiochis.

Attalus won an important victory over the Galatians, newly arrived Celtic tribes from Thrace, who had been, for more than a generation, plundering and exacting tribute throughout most of Asia Minor without any serious check. This victory, celebrated by the triumphal monument at Pergamon (famous for its Dying Gaul) and the liberation from the Gallic “terror” which it represented, earned for Attalus the name of “Soter”, and the title of “king“. A courageous and capable general and loyal ally of Rome, he played a significant role in the first and second Macedonian Wars, waged against Philip V of Macedon. He conducted numerous naval operations, harassing Macedonian interests throughout the Aegean, winning honors, collecting spoils, and gaining for Pergamon possession of the Greek islands of Aegina during the first war, and Andros during the second, twice narrowly escaping capture at the hands of Philip.

Attalus was a protector of the Greek cities of Anatolia[4] and viewed himself as the champion of Greeks against barbarians.[5] During his reign he established Pergamon as a considerable power in the Greek East.[6] He died in 197 BC, shortly before the end of the second war, at the age of 72, having suffered an apparent stroke while addressing a Boeotian war council some months before.”

vii. East African Campaign (World War I)

“The East African Campaign was a series of battles and guerrilla actions which started in German East Africa and ultimately affected portions of Mozambique, Northern Rhodesia, British East Africa, Uganda, and the Belgian Congo. The campaign was effectively ended in November 1917.[10] However, the Germans entered Portuguese East Africa and continued the campaign living off Portuguese supplies.

The strategy of the German colonial forces, led by Lieutenant Colonel (later Generalmajor) Paul Emil von Lettow-Vorbeck, was to drain and divert forces from the Western Front to Africa. His strategy failed to achieve these results after 1916, as mainly Indian and South African forces, which were prevented by colonial policy from deploying to Europe, conducted the rest of the campaign.[11][12] […]

In this campaign, disease killed or incapacitated 30 men for every man killed in battle on the British side.[32]

viii. European bison (Wisent). I had never heard about those. Here’s what they look like:

“The European bison (Bison bonasus), also known as wisent (play /ˈvzənt/ or /ˈwzənt/) or the European wood bison, is a Eurasian species of bison. It is the heaviest surviving wild land animal in Europe; a typical European bison is about 2.1 to 3.5 m (7 to 10 ft) long, not counting a tail of 30 to 60 cm (12 to 24 in) long, and 1.6 to 2 m (5 to 7 ft) tall. Weight typically can range from 300 to 920 kg (660 to 2,000 lb), with an occasional big bull to 1,000 kg (2,200 lb) or more.[2][3][4] On average, it is slightly lighter in body mass and yet taller at the shoulder than the American bison (Bison bison). Compared to the American species, the Wisent has shorter hair on the neck, head and forequarters, but longer tail and horns.

European bison were hunted to extinction in the wild, with the last wild animals being shot in the Białowieża Forest in Eastern Poland in 1919 and in the Western Caucasus in 1927, but have since been reintroduced from captivity into several countries in Europe, all descendants of the Białowieża or lowland European bison. They are now forest-dwelling. They have few predators (besides humans), with only scattered reports from the 19th century of wolf and bear predation. […]

Historically, the lowland European bison’s range encompassed all lowlands of Europe, extending from the Massif Central to the Volga River and the Caucasus. It may have once lived in the Asiatic part of what is now the Russian Federation. Its range decreased as human populations expanded cutting down forests. The first population to be extirpated was that of Gaul in the 8th century AD. The European bison became extinct in southern Sweden in the 11th century, and southern England in the 12th. The species survived in the Ardennes and the Vosges until the 15th century.[7] In the early middle ages, the wisent apparently still occurred in the forest steppes east of the Ural, in the Altay Mountains and seems to have reached Lake Baikal in the east. The northern boundary in the Holocene was probably around 60°N in Finland.[8]

European bison survived in a few natural forests in Europe but its numbers dwindled. The last European bison in Transylvania died in 1790. In Poland, European bison in the Białowieża Forest were legally the property of the Polish kings until the Third partition of Poland. Wild European bison herds also existed in the forest until the mid-17th century. Polish kings took measures to protect the bison. King Sigismund II Augustus instituted the death penalty for poaching a European bison in Białowieża in the mid-16th century. In the early 19th century, Russian czars retained old Polish laws protecting the European bison herd in Białowieża. Despite these measures and others, the European bison population continued to decline over the following century, with only Białowieża and Northern Caucasus populations surviving into the 20th century.

During World War I, occupying German troops killed 600 of the European bison in the Białowieża Forest for sport, meat, hides, and horns. A German scientist informed army officers that the European bison were facing imminent extinction, but at the very end of the war, retreating German soldiers shot all but 9 animals.[9] The last wild European bison in Poland was killed in 1919, and the last wild European bison in the world was killed by poachers in 1927 in the western Caucasus. By that year fewer than 50 remained, all in zoos.”

October 19, 2012 - Posted by | biology, econometrics, history, Physics, statistics, wikipedia

No comments yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: