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Thursday, January 19, 2012

Automobile emissions control

Automobile emissions control covers all the technologies that are employed to reduce the air pollution-causing emissions produced by automobiles..

Nitrogen oxide

NOx is a generic term for the various nitrogen oxides produced during combustion.

They are believed to aggravate asthmatic conditions, react with the oxygen in the air to produce ozone, which is also an irritant and eventually form nitric acid when dissolved in water.
When dissolved in atmospheric moisture the result can be acid rain which can damage both trees and entire forest ecosystems.
For more information about the topicNitrogen oxide, read the full article at Wikipedia.org, or see the following related articles

Pollution

Environmental pollution is the release of environmental contaminants, generally resulting from human activity.

Carbon monoxide, sulfur dioxide and nitrogen oxides produced by industry and motor vehicles are common air pollutants.
Arguably the principal source of air pollutants worldwide is motor vehicle emissions, although many other sources have been found to contribute to the ever growing problem.
Principal stationary pollution sources include chemical plants, coal-fired power plants, oil refineries, nuclear waste disposal activity, incinerators, large animal farms, PVC factories, metals production factories, plastics factories, and other heavy industry.
Pollutants can cause disease, including cancer, lupus, immune diseases, allergies, and asthma.
Adverse air quality can kill many organisms including humans.
Motor vehicle emissions are one of the leading causes of air pollution.
Principal stationary pollution sources include chemical plants, coal-fired power plants, oil refineries, petrochemical plants, nuclear waste disposal activity, incinerators, large livestock farms (dairy cows, pigs, poultry, etc.), PVC factories, metals production factories, plastics factories, and other heavy industry.
Some of the more common soil contaminants are chlorinated hydrocarbons (CFH), heavy metals (such as chromium, cadmium--found in rechargeable batteries, and lead -- found in lead paint, aviation fuel and still in some countries, gasoline), MTBE, zinc, arsenic and benzene.
Ordinary municipal landfills are the source of many chemical substances entering the soil environment (and often groundwater), emanating from the wide variety of refuse accepted, especially substances illegally discarded there, or from pre-1970 landfills that may have been subject to little control in the U.S.
or EU.
Pollution can also be the consequence of a natural disaster.
For example, hurricanes often involve water contamination from sewage, and petrochemical spills from ruptured boats or automobiles.
Larger scale and environmental damage is not uncommon when coastal oil rigs or refineries are involved.
Some sources of pollution, such as nuclear power plants or oil tankers, can produce widespread and potentially hazardous releases when accidents occur.
Adverse air quality can kill many organisms including humans.
Ozone pollution can cause respiratory disease, cardiovascular disease, throat inflammation, chest pain, and congestion.
Water pollution causes approximately 14,000 deaths per day, mostly due to contamination of drinking water by untreated sewage in developing countries.
Oil spills can cause skin irritations and rashes.
Noise pollution induces hearing loss, high blood pressure, stress, and sleep disturbance.

Neutron Scattering Provides Window Into Surface Interactions

To better understand the fundamental behavior of molecules at surfaces, researchers at the U.S. Department of Energy's Oak Ridge National Laboratory are combining the powers of neutron scattering with chemical analysis.



Scientists have a fundamental interest in how molecules behave at solid surfaces because surface interactions influence chemistry, such as in materials for catalysis, drug delivery and carbon sequestration. Understanding these interactions allows researchers to tailor materials for a specific desirable outcome.
Michelle Kidder and A.C. Buchanan, physical organic chemists, and Ken Herwig, neutron scattering scientist, used neutron scattering to study the physical motion of a chemically attached organic molecule inside a silica nanopore, MCM41.
"There is a connection between a molecule's dynamic behavior or motion to its surroundings." Herwig said. "In particular, restricting the ability of a molecule to freely move by confining it to a small volume dramatically affects both the range and character of its movement. We are trying to gain insight into the connection between the changes in molecular motion and the changes in chemistry that occur when molecules are attached to a solid surface."
Herwig used neutron scattering to gain a unique perspective into molecular motion because neutrons are sensitive to the hydrogen atoms, which are present in many molecules that researchers are interested in. Additionally, neutron scattering simultaneously tells researchers how rapid the motion is and what type of motion they are observing on the atomic and nanoscale.
If scientists understand how pore size affects surface interactions, they can modify pore size to change a chemical product outcome.
To study surface interactions, Kidder synthesized both the organic molecules and MCM41 of different pore sizes, then chemically attached the molecules to the silica pore surface, which forms an organic-inorganic hybrid material. This hybrid material is used in studies to understand chemical decomposition pathways, where surface interactions were presumed to play a role.
"We are interested in understanding the thermo decomposition of molecules similar to those found in biomass resources," Kidder said. "What we have seen is that there are many local environmental factors that influence chemical reactivity and products, and one of those large influences occurs when a molecule is confined to a pore wall, where even the pore size has a large impact on reactivity."
ORNL researchers studied the molecular surface dynamics of an interior pore surface and observed that molecules tend to reside near the surface, as illustrated here.

Polar Growth at the Bacterial Scale Reveals Potential New Targets for Antibiotic Therapy

 An international team of microbiologists led by Indiana University researchers has identified a new bacterial growth process -- one that occurs at a single end or pole of the cell instead of uniform, dispersed growth along the long axis of the cell -- that could have implications in the development of new antibacterial strategies.




Outer membrane proteins of an Agrobacterium tumefaciens cell were labeled in red, with images taken every 50 minutes as the cell grew. In panels three and four it is clear that the cell on the left (red) has kept all the labeled proteins, whereas the other cell has all new surface proteins.



Outer membrane proteins of an Agrobacterium tumefaciens cell were labeled in red, with images taken every 50 minutes as the cell grew. In panels three and four it is clear that the cell on the left (red) has kept all the labeled proteins, whereas the other cell has all new surface proteins.
Based on past detailed studies of rod-shaped bacteria such asEscherichia coli and Bacillus subtilis, it has been assumed that most bacteria grow by binary fission, a dispersed mode of growth involving insertion of new cell wall material uniformly along the long axis of the cell. Growth requires breaking the cell wall at numerous places along the cylinder to allow insertion of new cell wall material, enabling uniform elongation of the cell, with the process culminated by cleavage at the mid-point of the cell to create two symmetric new cells.

Science News (Jan 2012)


Most Distant Dwarf Galaxy Detected

Scientists have long struggled to detect the dim dwarf galaxies that orbit our own galaxy. So it came as a surprise on Jan. 18 when a team of astronomers using Keck II telescope's adaptive optics has announced the discovery of a dwarf galaxy halfway across the universe.


The new dwarf galaxy found by MIT's Dr. Simona Vegetti and colleagues is a satellite of an elliptical galaxy almost 10 billion light-years away from Earth. The team detected it by studying how the massive elliptical galaxy, called JVAS B1938 + 666, serves as a gravitational lens for light from an even more distant galaxy directly behind it. Their discovery was published in the Jan. 18 online edition of the journal Nature.
Like all supermassive elliptical galaxies, JVAS B1938 + 666's gravity can deflect light passing by it. Often the light from a background galaxy gets deformed into an arc around the lens galaxy, and sometimes what's called an Einstein ring. In this case, the ring is formed mainly by two lensed images of the background galaxy. The size, shape and brightness of the Einstein ring depends on the distribution of mass throughout the foreground lensing galaxy.
Vegetti and her team obtained extra sharp near-infrared image of JVAS B1938 + 666 by using the 10-meter Keck II telescope and its adaptive optics system, which corrects for the blurring effects of Earth's atmosphere, and provides stunningly sharp images. With these data, they neatly determined the mass distribution of JVAS B1938 + 666 as well as the shape and brightness of the background galaxy.
The researchers used a sophisticated numerical technique to derive a model of the lens galaxy's mass, as well as to map any excess lens mass that could not be accounted for by the galaxy. What they found was an excess mass near the Einstein ring that they attributed to the presence of a satellite, or "dwarf," galaxy. Vegetti's team also used a separate analytical model to test the detected excess mass. They found that a satellite galaxy is indeed required to explain the data.
"This satellite galaxy is exciting because it was detected in the excess-mass map despite its low mass," commented Robert Schmidt of the Center for Astronomy at Heidelberg University, in a related Nature article. "A natural question to ask is whether the satellite galaxy can be observed directly rather than by its gravitational effect on the shape of a background object. With current instrumentation, the answer is no. The object is simply too distant to be imaged directly. But the message here is that it is possible to spot these elusive objects around distant lens galaxies without knowing where to look for them."
Galaxies like our own are believed to form over billions of years through the merging of many smaller galaxies. So it's expected that there should be many smaller dwarf galaxies buzzing around the Milky Way. However, very few of these tiny relic galaxies have been observed which has led astronomers to conclude that many of them must have very few stars or possibly may be made almost exclusively of dark matter.
Scientists theorize the existence of dark matter to explain observations that suggest there is far more mass in the universe than can be seen. However, because the particles that make up dark matter do not absorb or emit light, they have so far proven impossible to detect and identify. Computer modeling suggests that the Milky Way should have about 10,000 satellite dwarf galaxies, but only 30 have been observed.
"It could be that many of the satellite galaxies are made of dark matter, making them elusive to detect, or there may be a problem with the way we think galaxies form," says Vegetti.
In the new study, Vegetti worked with Prof. Leon Koopmans of the University of Groningen, Netherlands; Dr. David Lagattuta and Prof. Christopher Fassnacht of the University of California at Davis; Dr. Matthew Auger of the University of California at Santa Barbara; and Dr. John McKean of the Netherlands Institute for Radio Astronomy.
"The existence of this low-mass dark galaxy is just within the bounds we expect if the Universe is composed of dark matter which has a low temperature. However, further dark satellites will need to be found to confirm this conclusion," says Vegetti.
The gravitational lens B1938+666 as seen in the infrared when observed with the 10-meter Keck II telescope with Adaptive Optics on Mauna Kea, Hawaii. In the center is a massive red galaxy 9.8 billion light-years from Earth that acts like a cosmic magnifying glass, distorting the light from an even more distant galaxy, 17.3 billion light-years away. The result is a spectacular Einstein ring image of the background galaxy. The team used distortions within the ring to find evidence for a low-mass dark galaxy, which is a satellite of the foreground lensing galaxy. Using this gravitational lensing effect the mass of the dark galaxy was found to be 200 million times the mass of the Sun, which is similar to the masses of the satellite galaxies found around our own Milky Way, but is 9.8 billion light-years further away.

Phobos-Grunt


Orbit Evolution

From launch, Phobos-Grunt was either venting gases or using its thrusters to attain a particular orientation. Either way, the thrust produced had an effect on the orbit. It can be seen in the plots of orbit parameters below.

Whatever the event(s), the thrusting ceased around Nov 20 and evolution of the orbit settled down, showing the usual signs of decay through air drag. The possible reasons and a discusssion of the changes can be found in the archive of the Seesat-L satellite oberver group. There is a link in the left-hand menu.

The Δv imparted by the episode was about 2m/s in total and, as evidenced by perigee rising but apogee falling very much as expected, the thrust was generally being applied near apogee when Phobos-Grunt was in sunlight. This fits nicely with the Russian statement that Phobos-Grunt was in "emergency mode" and systems were switched off upon entering the Earth's shadow.


Debris

On November 29, Spacetrack catalogued a piece of debris (2011-065G/30740) that had detached from Phobos-Grunt, it was listed as having re-entered the same day. The following day, a second debris object (2011-065H/30747) appeared also with a high rate of orbital decay. 2011-065H had no element sets after December 1 but it was another five days before Spacetrack issued a decay notice dated December 2.

They are plotted on the Orbital Period chart. 2011-65G is the very short line/dot near the top - there were two very similar element sets issued for precisely the same epoch. Several element sets were issued for 2011-065H. The density of both was low, hence the rapid decay of their orbits. Extrapolation indicates that 2011-65G separated November 29 around 03:00 UTC and 2011-065H departed amost exactly 24 hours later on November 30, also around 03:00 UTC.

The possibility exists that there may have been other debris that was more difficult to detect, or re-entered very quickly, and so failed to enter the public catalogue because NORAD was unable to get enough orbital data.


Debris Separation

Looking back at the way the two pieces departed, 2011-065G seems have been ejected somewhat more explosively than first thought. 2011-65H just seems to have drifted away.

Orbits heights of the two fragments are shown in the table above. Although 2011-065H is lower than Phobos-Grunt, it is consistent with having decayed through air drag in the twelve hours or so between separating and being catalogued. The orbit of 2011-065G is significantly different from Phobos-Grunt. It is a different shape and the inclination is different. Even without knowing precisely what happened, it is possible to estimate the minimum Δv involved.

In order to move between the two orbits there was an in-plane velocity change in the region of 14 metres per second. The 0°.12 change in inclination would have required at least 15 m/s of velocity at right angles to the orbit. Adding them together results in a minimum separation speed of 20 m/s. This is more of an explosive velocity.

In summary, it suggests an low-pressure explosive event (ruptured tank or battery?) but nothing violent enough to cause Phobos-Grunt to tumble in a way that could not be compensated by its attitude control system. As it departed, 2011-065G may have dislodged something else that became the second fragment when it eventually drifted away one day later.


Rotation

Observation to to the end showed that Phobos-Grunt was keeping itself steadily oriented, and up to the beginning of January was probably pointing towards the Sun as it would be expected to do if it were en-route to Mars. It certainly ws not "tumbling" as erroneously reported by the Planetary Society in a story on its Home web page.

Some observers reported a periodic variation and others that it had a steady appearance and there were occasional, but predictable, flares from flat surfaces - indicating stability. Phobos-Grunt was an elongated shape with solar panels so variation in brightness was to be expected as the viewing aspect changed. Russia was been trying to fire the engine to raise the orbit. This is not something that could have been contemplated if unpredictable tumbling was a fact.

Jan 4, Thierry Legault published a very distinctive image of Phobos-Grunt. Together with images obtained 24 hours earlier, it showed Phobos-Grunt stable, and moving in what Ted Molczan described as "shuttlecock mode". The major mass of the propellant tanks at one end of the craft was leading, with the solar panels acting like 'feathers' to keep it stable through aerodynamic drag.


Orbital Period

Phobos-Grunt Orbital Period


Perigee and Apogee

A point to note is that during the early-day period when Phobos-Grunt appeared to be operating its thrusters, the obvious change was the increasing height of perigee while apogee continued to decline as would be expected with orbital decay through atmospheric drag - see the notes on Orbit Evolution, above.

Perigee is traced in blue and apogee in red.

Phobos-Grunt Apsides


Rate of Decay

This is the value 'ndot2' from the Twoline Orbital Elements sets. The unsettled nature of the first few days' readings is down to thruster operation. The effect ceased around Nov 22.

After that, the occasional spike indicates an error or an uncertainty in the Spacetrack data. Ignore them, and the general trend is obvious, including a slow-down for several days from Dec 10. It possibly results from Phobos-Grunt orienting itself on the Sun and presenting a smaller cross section to the direction of travel..

Phobos-Grunt Decay Rate


Argument of Perigee

Towards the end, the Argument of Perigee started to drift from the smooth line that it had been following. The reason was that the apogee and perigee figures derived from the Twoline Orbital Element (TLE) sets relate to a standard model that assumes the orbit focus is the centre of a perfectly spherical globe. It is the reason that orbit data issued by Russia seem to differ from what is published elsewhere. Russia always quotes maximum and minimum heights above the Earth's true surface.

Because the Earth is pear-shaped, the actual location of the focus of the orbital ellipse is about 14 kilometres south of the equator, roughly on the Earth's north-south axis. At the 51° inclination of Phobos-Grunt's orbit, its true height above the Earth's surface (and, more-importantly, the upper atmosphere) while at its most northerly point is about 10km less than the TLE values would suggest, and the opposite is true in the southern hemisphere. As a result, once the difference in apogee and perigee height drops below 20 km, TLE-derived figures can start to lose their meaning.

In an extreme case, a TLE could indicate that the orbit is nearly circular with perigee at the most southerly point. The reality is that the satellite actually dips deeper into the atmosphere near northern apex of the orbit. As a result, changes in Eccentricity and Argument of Perigee can start to look random rather than following the smooth graph plot of an eccentric orbit.

This is the reason that comparisons should only be made between figures derived from the same sources or that are known to use the same orbital model.

Phobos-Grunt Argument of Perigee


Eccentricity

Phobos-Grunt Eccentricity


Charts on this page are produced using JpGraph.