Econstudentlog

Wikipedia articles of interest

i. Metric expansion of space.

“The metric expansion of space is the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion whereby the scale of space itself is changed. That is, a metric expansion is defined by an increase in distance between parts of the universe even without those parts “moving” anywhere. […]

This kind of expansion is different from all kinds of expansions and explosions commonly seen in nature. What we see normally as “space” and “distance” are not absolutes, but are determined by a metric that can change. In the metric expansion of space, rather than objects in a fixed “space” moving apart into “emptiness”, it is space itself which is changing. It is as if without objects themselves moving, space is somehow growing or shrinking between them: if it were possible to place a tape measure between even stationary objects, one would observe the scale of the tape measure changing to show more distance between them.

Because this expansion is caused by changes in the distance-defining metric, and not by objects themselves moving in space, this expansion (and the resultant movement apart of objects) is not restricted by the speed of light upper bound of special relativity. So objects can be moving at sub-light speed yet appear to be moving apart faster than light. […]

“The expansion of space is sometimes described as a force which acts to push objects apart. Though this is an accurate description of the effect of the cosmological constant, it is not an accurate picture of the phenomenon of expansion in general. For much of the universe’s history the expansion has been due mainly to inertia. The matter in the very early universe was flying apart for unknown reasons (most likely as a result of cosmic inflation) and has simply continued to do so, though at an ever-decreasing rate due to the attractive effect of gravity.

In addition to slowing the overall expansion, gravity causes local clumping of matter into stars and galaxies. Once objects are formed and bound by gravity, they “drop out” of the expansion and do not subsequently expand under the influence of the cosmological metric, there being no force compelling them to do so.”

This is complicated (if also fascinating) stuff, as there’s a lot of math doing work ‘behind the scenes’ and reasonably few people around who actually understands all that math. As they put it in the introduction:

“Due to the non-intuitive nature of the subject and what has been described by some as “careless” choices of wording, certain descriptions of the metric expansion of space and the misconceptions to which such descriptions can lead are an ongoing subject of discussion in the realm of pedagogy and communication of scientific concepts.[2][3][4][5]

Despite the fact that the article deals with very complex stuff this is not a ‘mathy’ article; I’d say the article is not too technical for most people with an interest in these matters to read it and obtain a greater understanding of the universe in which he or she lives. Note that progress in the field of observational cosmology is continually being made, so it’s not like the final version of this article has been written at this point. For example the article states that the most distant quasar currently known is 28 billion light years away (comoving distance), however the most distant object we have observed (discovered earlier this month) is now 30 lightyears away – even if that’s technically a galaxy and not a quasar, it’s highly likely that another, more distant quasar, will be found in the future (if you don’t feel like clicking the link to the wiki article about that galaxy, here’s one sentence from the article that may change your mind: “The galaxy in its observable timeframe was producing stars at a phenomenal rate, equivalent in mass to about 300 suns per year.[1]“).

ii. Cell membrane. These things are very important, yet most people probably don’t know a great deal about them. This article will teach you more. Khan Academy has stuff on this topic as well (you can start here – I’ve been thinking about blogging these videos, and maybe I will later on).

iii. Axe Murder incident. Short version: Two US Army officers got killed by North Korean soldiers while trying to cut down a tree in the Joint Security Area between North and South Korea. Some people higher up got angry about that and decided that that tree had to go, and so Operation Paul Bunyan was launched. With the aid of 23 American and South Korean vehicles, some detonation charges, two 30-man security platoons, a 64-man South Korean special forces company (..and a total task force of 813 men), a U.S. infantry company in 20 utility helicopters and 7 Cobra attack helicopters, some B-52 Stratofortresses escorted by  F-4 Phantom II fighter-bombers and South Korean F-5 Freedom Fighters, as well as a nearby aircraft carrier and a dozen C-130s ready to provide support plus 12,000 additional troops which were ordered to Korea, two eight-man teams of military engineers managed to cut down the tree. Here’s what all the fuss was about:

800px-DMZ_incident_tree

(Do note that the reason why the tree was not cut down completely was not interference from NK soldiers: “The stump of the tree, almost 6 m (20 ft) tall, was deliberately left standing.”)

iv. Maggot therapy.

Maggot therapy is also known as maggot debridement therapy (MDT), larval therapy, larva therapy, larvae therapy, biodebridement or biosurgery. It is a type of biotherapy involving the introduction of live, disinfected maggots (fly larvae) into the non-healing skin and soft tissue wound(s) of a human or animal for the purpose of cleaning out the necrotic (dead) tissue within a wound (debridement) and disinfection. […]

While at Johns Hopkins University in 1929, Dr. Baer introduced maggots into 21 patients with intractable chronic osteomyelitis. He observed rapid debridement, reductions in the number of pathogenic organisms, reduced odor levels, alkalinization of wound beds, and ideal rates of healing. All 21 patients’ open lesions were completely healed and they were released from the hospital after two months of maggot therapy.

After the publication of Dr. Baer’s results in 1931,[6] maggot therapy for wound care became very common, particularly in the United States. The Lederle pharmaceutical company commercially produced “Surgical Maggots”, larvae of the green bottle fly, which primarily feed on the necrotic (dead) tissue of the living host without attacking living tissue. Between 1930 and 1940, more than 100 medical papers were published on maggot therapy. Medical literature of this time contains many references to the successful use of maggots in chronic or infected wounds including osteomyelitis, abscesses, burns, sub-acute mastoiditis,[7][8] and chronic empyema.[9]

More than 300 American hospitals employed maggot therapy during the 1940s. The extensive use of maggot therapy prior to World War II was curtailed when the discovery and growing use of penicillin caused it to be deemed outdated. […] While in the past it was believed that maggots do not damage healthy tissue, this is in doubt now.[24] […]

The wound must be of a type which can actually benefit from the application of maggot therapy. A moist, exudating wound with sufficient oxygen supply is a prerequisite. Not all wound-types are suitable: wounds which are dry, or open wounds of body cavities do not provide a good environment for maggots to feed. […] In about 1/3 of all patients pain is increased.[12]

v. Oil shale (featured article).

Oil shale, also known as kerogen shale, is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons called shale oil (not to be confused with tight oilcrude oil occurring naturally in shales) can be produced. Shale oil is a substitute for conventional crude oil; however, extracting shale oil from oil shale is more costly than the production of conventional crude oil both financially and in terms of its environmental impact.[1][2] […]

Heating oil shale to a sufficiently high temperature causes the chemical process of pyrolysis to yield a vapor. Upon cooling the vapor, the liquid shale oil—an unconventional oil—is separated from combustible oil-shale gas (the term shale gas can also refer to gas occurring naturally in shales). Oil shale can also be burned directly in furnaces as a low-grade fuel for power generation and district heating or used as a raw material in chemical and construction-materials processing.[2][6]

Oil shale gains attention as a potential abundant source of oil whenever the price of crude oil rises.[7][8] At the same time, oil-shale mining and processing raise a number of environmental concerns, such as land use, waste disposal, water use, waste-water management, greenhouse-gas emissions and air pollution.[9][10] Estonia and China have well-established oil shale industries, and Brazil, Germany, and Russia also utilize oil shale.[2] […]

Oil shale, an organic-rich sedimentary rock, belongs to the group of sapropel fuels.[11] It does not have a definite geological definition nor a specific chemical formula, and its seams do not always have discrete boundaries. Oil shales vary considerably in their mineral content, chemical composition, age, type of kerogen, and depositional history and not all oil shales would necessarily be classified as shales in the strict sense.[3][12] According to the petrologist Adrian C. Hutton of the University of Wollongong, oil shales are not “geological nor geochemically distinctive rock but rather ‘economic’ term.”[13] Their common feature is low solubility in low-boiling organic solvents and generation of liquid organic products on thermal decomposition.[14] […]

The largest deposits in the world occur in the United States in the Green River Formation, which covers portions of Colorado, Utah, and Wyoming; about 70% of this resource lies on land owned or managed by the United States federal government.[26] Deposits in the United States constitute 62% of world resources; together, the United States, Russia and Brazil account for 86% of the world’s resources in terms of shale-oil content.[23] These figures remain tentative, with exploration or analysis of several deposits still outstanding. […] As of 2009, 80% of oil shale used globally is extracted in Estonia […]

The shale oil derived from oil shale does not directly substitute for crude oil in all applications. It may contain higher concentrations of olefins, oxygen, and nitrogen than conventional crude oil.[4] Some shale oils may have higher sulfur or arsenic content. […] The higher concentrations of these materials means that the oil must undergo considerable upgrading (hydrotreating) before serving as oil-refinery feedstock. […] Shale oil serves best for producing middle-distillates such as kerosene, jet fuel, and diesel fuel.”

October 27, 2013 - Posted by | Geology, history, medicine, Physics, wikipedia

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