Schlieren Texture of a Nematic Film

Schlieren Texture of a Nematic Film

Schlieren texture of a nematic film with surface point defects (boojums). This picture was taken under a polarization microscope with polarizer and analyzer crossed. From every point defect emerge four dark brushes. For these directions the director is parallel either to the polarizer or to the analyzer. The colors are newton colors of thin films and depend on the thickness of the sample. Point defects can only exist in pairs. One can see two types of boojuns with "opposite sign of topological charge," one type with yellow and red brushes, the other less colorful. The difference in appearance is due to different core structures for these defects of different "charge."

Polarization Microscope Images of Liquid Crystals

IMAGE 1:

Pair of point defects--"Boojums" in a thin, hybrid aligned nematic film.

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Polarizing microscope texture of a thin, liquid crystalline film. Two centers with emerging dark brushes represent "boojum," point defects in the molecular orientation of the liquid crystal. The defects are formed at the surface of a thin film of a nematic fluid, the simplest form of a liquid crystal. The thin film (one- to two-micrometers thick) is spread over the surface of an isotropic fluid (glycerine). The upper surface of the film is free (in contact with air). In the nematic, the rod-like, elongated molecules are free to move around, but they tend to be parallel to each other. The average direction of orientation is called the director. Since the direction of alignment in the plane of the film is not fixed, the film exhibits distortions, with the director changing from point to point. The changing interference colors of the film result from different director tilt near the "cores" of the defects. The dark bands mark the regions where the orientation of liquid crystal molecules is parallel to either the polarizer or analyzer of the optical microscope. Since both defects have a radial director orientation near the core, each defect emanates four dark brushes. The term "boojum" entered the world of science from Lewis Carroll's "The Hunting of the Snark," thanks to Professor David Mermin, who was the first to introduce the word in his Physical Review Letters article in 1977. At the time, Mermin was studying topological defects similar to those presented here, in a superfluid helium 3 that, amazingly, is also a liquid crystal in many respects.


IMAGE 2:

Thin, nematic film on isotropic surface--one-dimensional periodicity.

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This periodic stripe structure, seen under a polarizing microscope, occurs in a nematic fluid--the simplest form of a liquid crystal--when a thin film of the material is spread over the surface of an isotropic fluid (glycerine). The upper surface of the nematic film is free (in contact with air). In the nematic, the rod-like elongated molecules are free to move around, but they tend to remain parallel to each other; the average direction of orientation is called the director. By placing the nematic film between glycerine and air, one creates director distortions in the vertical plane, as the nematic-air interface favor normal (perpendicular) orientation of the director and the glycerine-nematic interface favors tangential (parallel) orientation. When the film is very thin, less than one micrometer, these distortions use too much energy and the system relaxes through periodic, in-plane director variations. The effect is similar to buckling instability of an elastic rod stressed at two ends; at some critical stress, the rod bulges. The periodic pattern illustrates a fine balance of elastic and surface anchoring forces. The picture shows a one-dimensional periodic pattern; the period varies from 5 to 150 micrometers, depending on the thickness of the film; more complex two-dimensional patterns can also be observed.


IMAGE 3:

Hybrid aligned nematic film.

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Polarizing microscope texture of a thin, liquid crystalline film. This highly nonuniform structure reflects spatial distortions in molecular orientation that occur in a nematic fluid, the simplest form of a liquid crystal. The thin, nematic film is spread over the surface of an isotropic fluid (glycerine). The upper surface of the film is free (in contact with air). In the nematic, the rod-like, elongated molecules are free to move around, but tend to remain parallel to each other. The average direction of orientation is called the director. By placing the nematic film between glycerine and air, one creates director distortions in the vertical plane, as the nematic-air interface favors normal (perpendicular) orientation of the director and the glycerine-nematic interface favors tangential (parallel) orientation. Since the direction of alignment in the plane of the film is not fixed, the film exhibits numerous distortions, with the director changing from point to point. The interference colors of the film result from different director tilt and some variation in the thickness of the film.

IMAGE 4:

Polarizing microscope texture of a smectic A liquid crystal. 

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In smectic A, rod-like, elongated molecules are arranged parallel to each other, forming layers of monomolecular length. The layers are stacked on top of each other and are flexible. When the smectic layers bend, they tend to preserve their equidistance, as it is fixed by the molecular length. The restriction of constant layer thickness leads to a peculiar geometry of deformations, so-called focal conic domains, in which the smectic layers are wrapped around line defects in the form of ellipses (seen in the figure) and hyperbolae (most of them are oriented normally to the plane of fiew). The ellipses form a fractal-type of structure, with smaller ones filling the gaps between the larger ones. The smectic order was discovered and correctly identified from optical observations of textures similar to the one shown here, on the basis of geometrical properties of ellipses and hyperbolae, before X-ray techniques were invented.

IMAGE 5:

Mathematically created model of smectic layers in three neighboring focal, conic domains.

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In smectic A, rod-like, elongated molecules are arranged parallel to each other, forming layers of monomolecular length, shown as surfaces in the model. The layers are stacked on top of each other and are flexible. When the smectic layers bend, they tend to preserve their equidistance, as it is fixed by the molecular length. The restriction of constant layer thickness leads to a peculiar geometry of deformations, so-called focal conic domains, in which the smectic layers are wrapped around line defects in the form of ellipses and hyperbolae. The smectic order was discovered and correctly identified from an optical observation of textures similar to the one shown here, on the basis of geometrical properties of ellipses and hyperbolae, before X-ray techniques were invented.

IMAGE 6:

Hybrid aligned nematic film.

More about this Image
Polarizing microscope texture of a thin, liquid crystalline film. This highly nonuniform structure reflects spatial distortions in molecular orientation that occur in a nematic fluid, the simplest form of a liquid crystal. The thin, nematic film (one- to two-micrometers thick) is spread over the surface of an isotropic fluid (glycerine). The upper surface of the film is free (in contact with air). In the nematic, the rod-like, elongated molecules are free to move around, but tend to be parallel to each other. The average direction of orientation is called the director. By placing the nematic film between glycerine and air, one creates director distortions in the vertical plane, as the nematic-air interface favors normal (perpendicular) orientation of the director and the glycerine-nematic interface favors tangential (parallel) orientation. Since the direction of alignment in the plane of the film is not fixed, the film exhibits numerous distortions, with the director changing from point to point. The interference colors of the film result from different director tilt and some variation in the thickness of the film. Very often, the director distortions collapse into "strings" of practically constant width, seen in the texture as parallel dark extinction bands. The dark bands mark the regions where the orientation of liquid crystal molecules is parallel to either the polarizer or analyzer.

IMAGE 7:

Thin, nematic film (0.4 micrometer) placed onto an isotropic substrate.

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Polarizing microscope texture of a thin, liquid crystalline film. This periodic stripe structure with two different periodicities and different directions occurs in a nematic fluid, the simplest form of a liquid crystal. The nematic film is spread over the surface of an isotropic fluid (glycerine). The upper surface is free (in contact with air). In the nematic, the rod-like, elongated molecules are free to move around, but they try to remain parallel to each other. The average direction of orientation is called the director. The director is distorted in the vertical plane, as the nematic-air interface favors normal (perpendicular) orientation and the glycerine-nematic interface favors tangential (parallel) orientation. When the film is very thin--less than one micrometer--these distortions use too much energy and the system relaxes through the periodic pattern of in-plane director variations. The effect is similar to buckling instability of an elastic rod stressed at two ends; at some critical stress, the rod bulges.

IMAGE 8:

Hybrid aligned nematic film.

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Polarizing microscope texture of a thin, liquid crystalline film. This highly nonuniform structure reflects spatial distortions in molecular orientation that occur in a nematic fluid, the simplest form of a liquid crystal. The thin, nematic film (one- to two-micrometers thick) is spread over the surface of an isotropic fluid (glycerine). The upper surface of the film is free (in contact with air). In the nematic, the rod-like, elongated molecules are free to move around, but tend to be parallel to each other. The average direction of orientation is called the director. By placing the nematic film between glycerine and air, one creates director distortions in the vertical plane, as the nematic-air interface favors normal (perpendicular) orientation of the director and the glycerine-nematic interface favors tangential (parallel) orientation. Since the direction of alignment in the plane of the film is not fixed, the film exhibits numerous distortions, with the director changing from point to point. The interference colors of the film result from different director tilt and some variation in the thickness of the film. The dark bands mark the regions where the orientation of liquid crystal molecules is parallel to either the polarizer or analyzer of the optical microscope.

IMAGE 9:

Polarizing microscope texture of a thin, liquid crystalline film.

More about this Image
This highly nonuniform structure reflects spatial distortions in molecular orientation that occur in a nematic fluid, the simplest form of a liquid crystal. The thin, nematic film (one- to two-micrometers thick) is spread over the surface of an isotropic fluid (glycerine). The upper surface of the film is free (in contact with air). In the nematic, the rod-like elongated molecules are free to move around, but tend to be parallel to each other. The average direction of orientation is called the director. By placing the nematic film between glycerine and air, one creates director distortions in the vertical plane, as the nematic-air interface favors normal (perpendicular) orientation of the director and the glycerine-nematic interface favors tangential (parallel) orientation. Since the direction of alignment in the plane of the film is not fixed, the film exhibits numerous distortions, with the director changing from point to point. The interference colors of the film result from different director tilt and some variation in the thickness of the film. The dark bands mark the regions where the orientation of liquid crystal molecules is parallel to either the polarizer or analyzer of the optical microscope. The sharp point with four dark brushes emerging from it is a topological point defect called boojum. The term "boojum" entered the world of science from Lewis Carroll's "The Hunting of the Snark," thanks to Professor David Mermin, who was the first to introduce the word in his Physical Review Letters article in 1977. At the time, Mermin was studying topological defects similar to those presented here, in a superfluid helium 3 that, amazingly, is also a liquid crystal in many respects.

IMAGE 10:

Polarizing microscope texture of a thin, liquid crystalline film.

More about this Image
This highly nonuniform structure reflects spatial distortions in molecular orientation that occur in a nematic fluid, the simplest form of a liquid crystal. The thin, nematic film (one- to two-micrometers thick) is spread over the surface of an isotropic fluid (glycerine). The upper surface of the film is free (in contact with air). In the nematic, the rod-like, elongated molecules are free to move around, but tend to be parallel to each other. The average direction of orientation is called the director. By placing the nematic film between glycerine and air, one creates director distortions in the vertical plane, as the nematic-air interface favors normal (perpendicular) orientation of the director and the glycerine-nematic interface favors tangential (parallel) orientation. Since the direction of alignment in the plane of the film is not fixed, the film exhibits numerous distortions, with the director changing from point to point. The interference colors of the film result from different director tilt and some variation in the thickness of the film. The dark bands mark the regions where the orientation of liquid crystal molecules is parallel to either the polarizer or analyzer of the optical microscope.

IMAGE 11:

Periodic square lattice, as seen under a polarizing microscope.

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This periodic square lattice, seen under a polarizing microscope, occurs in a nematic fluid--the simplest form of a liquid crystal--when a thin film of the material is spread over the surface of an isotropic fluid (glycerine). The upper surface of the nematic film is free (in contact with air). In the nematic, the rod-like, elongated molecules are free to move around, but tend to remain parallel to each other. The average direction of orientation is called the director. By placing the nematic film between glycerine and air, one creates director distortions in the vertical plane, as the nematic-air interface favors normal (perpendicular) orientation of the director and the glycerine-nematic interface favors tangential (parallel) orientation. When the film is very thin--less than one micrometer--these distortions use too much energy and the system relaxes through periodic, in-plane director variations. The effect is similar to buckling instability of an elastic rod stressed at two ends; at some critical stress, the rod bulges. The periodic pattern illustrates a fine balance of elastic and surface anchoring forces. In this particular, rarely observed case, the director distortions adopt the form of square lattice; more often, one observes a periodic, one-dimensional pattern of stripes.

IMAGE 12:

Hybrid aligned nematic film.

More about this Image
Polarizing microscope texture of a thin, liquid crystalline film. This highly nonuniform structure reflects spatial distortions in molecular orientation that occur in a nematic fluid, the simplest form of a liquid crystal. The thin nematic film (one- to two-micrometers thick) is spread over the surface of an isotropic fluid (glycerine). The upper surface of the film is free (in contact with air). In the nematic, the rod-like elongated molecules are free to move around, but they tend to be parallel to each other. The average direction of orientation is called the director. By placing the nematic film between glycerine and air, one creates director distortions in the vertical plane, as the nematic-air interface favors normal (perpendicular) orientation of the director and the glycerine-nematic interface favors tangential (parallel) orientation. Since the direction of alignment in the plane of the film is not fixed, the film exhibits numerous distortions, with the director changing from point to point. The interference colors of the film result from different director tilt and some variation in the thickness of the film. The dark bands mark the regions where the orientation of liquid-crystal molecules is parallel to either the polarizer or analyzer of the optical microscope.

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The Zebrafish's Neural Circuit Prevents It From Biting Off More Than It Can Chew

Inhibiting certain brain cells sharpens animal's response to small and quick visual stimuli

Comparison of neural circuit activated by small quick cue versus large one in zebrafish larvae.

Between alerting us to danger and allowing us to spot prey, vision keeps many animals, including humans, alive. But exactly how does this important sense work, and why is it easier for us to spot movement of small objects in our field of vision, than to notice other things? The complexity of the neural network that supports vision has long baffled scientists.
Now, with a new technology, Claire Wyart in Ehud Isacoff's lab at the University of California at Berkeley and Filo Del Bene at Herwig Baier's lab at the University of California at San Francisco have been able to follow entire populations of retinal and brain cells in their test animal: the zebrafish larva, and solve some of the mysteries of its neural circuit that underlies its vision.

Using a newly developed genetically encoded fluorescent reporter of neural activity developed by Loren Looger at the Howard Hughes Medical Institute's Janelia Farm Research Campus, Wyart and Del Bene have been able to follow how large and small visual cues translate into electrical activity in a region of the zebrafish's brain.
The brain region of the zebrafish that receives input from the retina, called the optic tectum, is separated into layers. The top layer receives direct connections from retinal cells, and has a population of both excitatory and inhibitory neurons. These neurons connect to output neurons that project to other brain regions that control how the zebrafish chases prey.
Isacoff, Baier, Wyart and Del Bene have revealed that a large visual stimulus covering the entire field of vision (such as large floating debris, or another zebrafish) results in low output neuron activity. However small (prey-sized) items moving across the zebrafish's field of vision at a prey-like speed activate the output neurons very well. The basis of this "filtering" of information is that large visual stimuli massively activate the inhibitory cell population and inhibit the output cells, while small moving objects activate only a small number the inhibitory tectal cells, enabling the excitation to drive the output cells efficiently.
This mechanism gives the zebrafish good hunting responses to appropriate visual cues, and thereby helps keep it from biting off more than it can chew.
Isacoff and Baier demonstrated that the inhibition of neural activity by large visual stimuli is essential for hunting prey--as evidenced by the fact that prey capture was disrupted when the inhibitory cells were removed or prevented from emitting neurotransmitters.

What Triggers Mass Extinctions? Study Shows How Invasive Species Stop New Life

Collapse of Earth's marine life 378 to 375 million years ago holds key

The ocean in Devonian times: is past prologue in biodiversity collapse?

An influx of invasive species can stop the dominant natural process of new species formation and trigger mass extinction events, according to research results published in the journal PLoS ONE on December 29,2010.
The study of the collapse of Earth's marine life 378 to 375 million years ago suggests that the planet's current ecosystems, which are struggling with biodiversity loss, could meet a similar fate.
Although Earth has experienced five major mass extinction events, the environmental crash during the Late Devonian was unlike any other in the planet's history.
The actual number of extinctions wasn't higher than the natural rate of species loss, but very few new species arose.
"We refer to the Late Devonian as a mass extinction, but it was actually a biodiversity crisis," said Alycia Stigall, a scientist at Ohio University and author of the PLoS ONE paper.
"This research significantly contributes to our understanding of species invasions from a deep-time perspective."

"The knowledge is critical to determining the cause and extent of mass extinctions through time, especially the five biggest biodiversity crises in the history of life on Earth. It provides an important perspective on our current biodiversity crises."
The research suggests that the typical method by which new species originate--vicariance--was absent during this ancient phase of Earth's history, and could be to blame for the mass extinction.
Vicariance occurs when a population becomes geographically divided by a natural, long-term event, such as the formation of a mountain range or a new river channel, and evolves into different species.
New species also can originate through dispersal, which occurs when a subset of a population moves to a new location.
In a departure from previous studies, Stigall used phylogenetic analysis, which draws on an understanding of the tree of evolutionary relationships to examine how individual speciation events occurred.
She focused on one bivalve, Leptodesma (Leiopteria), and two brachiopods, Floweria and Schizophoria (Schizophoria), as well as a predatory crustacean, Archaeostraca.
These small, shelled marine animals were some of the most common inhabitants of the Late Devonian oceans, which had the most extensive reef system in Earth's history.
The seas teemed with huge predatory fish such as Dunkleosteus, and smaller life forms such as trilobites and crinoids (sea lilies).
The first forests and terrestrial ecosystems appeared during this time; amphibians began to walk on land.
As sea levels rose and the continents closed in to form connected land masses, however, some species gained access to environments they hadn't inhabited before.
The hardiest of these invasive species that could thrive on a variety of food sources and in new climates became dominant, wiping out more locally adapted species.
The invasive species were so prolific at this time that it became difficult for many new species to arise.
"The main mode of speciation that occurs in the geological record is shut down during the Devonian," said Stigall. "It just stops in its tracks."
Of the species Stigall studied, most lost substantial diversity during the Late Devonian, and one, Floweria, became extinct.
The entire marine ecosystem suffered a major collapse. Reef-forming corals were decimated and reefs did not appear on Earth again for 100 million years.
The giant fishes, trilobites, sponges and brachiopods also declined dramatically, while organisms on land had much higher survival rates.
The study is relevant for the current biodiversity crisis, Stigall said, as human activity has introduced a high number of invasive species into new ecosystems.
In addition, the modern extinction rate exceeds the rate of ancient extinction events, including the event that wiped out the dinosaurs 65 million years ago.
"Even if you can stop habitat loss, the fact that we've moved all these invasive species around the planet will take a long time to recover from because the high level of invasions has suppressed the speciation rate substantially," Stigall said.
Maintaining Earth's ecosystems, she suggests, would be helped by focusing efforts and resources on protection of new species generation.
"The more we know about this process," Stigall said, "the more we will understand how to best preserve biodiversity."
The research was also funded by the American Chemical Society and Ohio University.

Adult Squid Species Euprymna scolopes

An adult Euprymna scolopes, a species of bioluminescent sepiolid squid.

All animals have beneficial associations with microbes, the association between Euprymna scolopes and Vibrio fischeri is the only experimental model available to biologists so far.

Molecular Dynamics Simulation

Snapshot of a self-assembled elongated micelle of non-ionic surfactant molecules (penta- (ethyleneglycol)--dodecylether,C₁₂E₅) in water from a coarse grain molecular dynamics simulation. These sorts of molecules are used in everything from detergents and shampoo to drug-delivery systems. Structures like micelles and vesicles form and can trap or protect other materials. Researchers at Temple University's Institute for Computational Molecular Science model these structures on the National Center for Supercomputing Applications' (NCSA) Abe and Lincoln supercomputers. This image was created using visual molecular dynamics from the University of Illinois' Theoretical and Computational Biophysics Group, and it was rendered with the embedded Tachyon renderer. Researchers are also exploring another class of surfactants as a way of controlling the delivery of drugs in the body and improving their impact.

Scorpion Species Typhochactas mitchelli

Scorpion species Typhochactas mitchelli is among the smallest known scorpions and is part of the Typhlochactidae family of cave scorpions, endemic to Mexico. Like all scorpions, it fluoresces in long-wave ultraviolet light as this image of its ventral side highlights.

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In the course of evolution, researchers have assumed that specialized adaptations were irreversible. But research by Lorenzo Prendini, associate curator in the division of invertebrate zoology at the American Museum of Natural History, shows that the evolution of troglobites, or animals adapted for life in caves, is reversible. A new phylogenetic analysis of the family Typhlochactidae found that scorpions currently living closer to the surface (under stones and in leaf litter) evolved independently on more than one occasion from ancestors adapted to life further below the surface (in caves).

The family Typhlochactidae, which includes nine species of scorpions endemic to the karstic regions of eastern Mexico, have adapted to the dark with features such as loss of eyes and reduced pigmentation. Included in the family are one of the world's smallest scorpions, Typhlochactas mitchelli, and the scorpion found at the greatest depth (nearly 1 kilometer below the surface), Alacran tartarus.

For the study, data for 195 morphological characteristics among the species of Typhlochactidae was gathered, and included a detailed mapping of the positions of all trichobothria (sensory setae) on the pedipalps (the second pair of appendages on the first (anterior) major body section). The resulting phylogenetic tree shows that adaptation to life in caves has reversed among this group of scorpions: Two of the less specialized, surface-living species, T. mitchelli and T. sylvestris, share a common ancestor with a much more cave-adapted species, and a similar pattern was found for the third less specialized, surface-living species, T. sissomi.

Prendini says, "This unique group of eyeless Mexican scorpions may have started re-colonizing niches closer to the surface from the deep caves of Mexico after their surface-living ancestors were wiped out by the nearby Chicxuluxb impact along with non-avian dinosaurs, ammonites, and other species."

Biodiversity Loss: Detrimental to Your Health

Infectious diseases on the rise as species disappear

Infectious disease transmission links disease vectors, disease hosts and human habitations.

Plant and animal extinctions are detrimental to your health.

Species loss in ecosystems such as forests and fields results in increases in pathogens, or disease-causing organisms, the researchers found.

Global change is accelerating, bringing with it a host of unintended consequences.A better understanding of the role of environmental change in disease emergence and transmission is key to enabling both prediction and control of many infectious diseases. The species most likely to disappear as biodiversity declines are often those that buffer infectious disease transmission.

Those that remain tend to be the ones that magnify the transmission of infectious diseases like West Nile virus, Lyme disease and hantavirus.

"We knew of specific cases like West Nile virus and hantavirus in which declines in biodiversity increase the incidence of disease," says Felicia Keesing, an ecologist at Bard College in Annandale, N.Y..

"But we've learned that the pattern is much more general: biodiversity loss tends to increase pathogen transmission and infectious disease."
The finding holds true for various types of pathogens--viruses, bacteria, fungi--and for many hosts, whether humans, other animals or plants.
"When a clinical trial of a drug shows that it works," says Keesing, "the trial is halted so the drug can be made available. In a similar way, the protective effect of biodiversity is clear enough that we need to begin implementing policies to preserve it now."
Global biodiversity has declined at an unprecedented pace since the 1950s. Current extinction rates are estimated at 100 to 1,000 times higher than in past epochs, and are projected to rise dramatically in the next 50 years.
Expanding human populations are already increasing contact with novel pathogens through activities such as land-clearing for agriculture, and hunting for wildlife.
For example, in the case of Lyme disease,strongly buffering species like the opossum are lost when forests are fragmented, but white-footed mice thrive.
"The mice increase numbers of both the blacklegged tick vector [transmission pathway] and the pathogen that causes Lyme disease."
Scientists don't yet know, why the most resilient species--"the last ones standing when biodiversity is lost"--are the ones that also amplify pathogens.

Preserving natural habitats, the authors argue, is the best way to prevent this effect.
Identifying the variables involved in infectious disease emergence is difficult but critical.
Biodiversity is an important factor, as are land-use change--converting forest to agricultural land--and human population growth and behavior, he says. "When biological diversity declines, and contact with humans increases, you have a perfect recipe for infectious disease."
There is a need for a call for careful monitoring of areas in which large numbers of domesticated animals are raised.
"That would reduce the likelihood of an infectious disease jumping from wildlife to livestock, then to humans," says Keesing.
For humans and other species to remain healthy, it will take more than a village. We need an entire planet, the scientists say, one with its biodiversity thriving.

Broken Glass Yields Clues to Climate Change

Ordinary drinking glasses and atmospheric dust particles break apart in similar patterns

The comparative sizes of dust particles in the atmosphere, from a dust storm satellite photo.

Clues to future climate may be found in the way an ordinary drinking glass shatters.

Results of a study found that microscopic particles of dust can break apart in patterns that are similar to the fragment patterns of broken glass and other brittle objects.

The research, by National Center for Atmospheric Research (NCAR) scientist Jasper Kok, suggests there are several times more dust particles pumped into the atmosphere than previously believed, since shattered dust appears to produce an unexpectedly high number of large fragments.
The finding has implications for understanding future climate change because dust plays a significant role in controlling the amount of solar energy in the atmosphere.
Depending on their size and other characteristics, some dust particles reflect solar energy and cool the planet, while others trap energy as heat.
"As small as they are, conglomerates of dust particles in soils behave the same way on impact as a glass dropped on a kitchen floor," Kok says. "Knowing this pattern can help us put together a clearer picture of what our future climate will look like."
The study may also improve the accuracy of weather forecasting, especially in dust-prone regions. Dust particles affect clouds and precipitation, as well as temperature.
"This research provides valuable new information on the nature and distribution of dust aerosols in the atmosphere."

"The results may lead to improvements in our ability to model and predict both weather and climate."
Kok's research focused on a type of airborne particle known as mineral dust.
These particles are usually emitted when grains of sand are blown into soil, shattering dirt and sending fragments into the air.
The fragments can be as large as about 50 microns in diameter, or about the thickness of a fine strand of human hair.
The smallest particles, which are classified as clay and are as tiny as 2 microns in diameter, remain in the atmosphere for about a week, circling much of the globe and exerting a cooling influence by reflecting heat from the Sun back into space.
Larger particles, classified as silt, fall out of the atmosphere after a few days. The larger the particle, the more it will tend to have a heating effect on the atmosphere.
Kok's research indicates that the ratio of silt particles to clay particles is two to eight times greater than represented in climate models.
Since climate scientists carefully calibrate the models to simulate the actual number of clay particles in the atmosphere, the paper suggests that models most likely err when it comes to silt particles.
Most of these larger particles swirl in the atmosphere within about 1,000 miles of desert regions, so adjusting their quantity in computer models should generate better projections of future climate in desert regions, such as the southwestern United States and northern Africa.
Additional research will be needed to determine whether future temperatures in those regions will increase as much or more than currently indicated by computer models.
The study results also suggest that marine ecosystems, which draw down carbon dioxide from the atmosphere, may receive substantially more iron from airborne particles than previously estimated.
The iron enhances biological activity, benefiting ocean food webs, including plants that take up carbon during photosynthesis.
In addition to influencing the amount of solar heat in the atmosphere, dust particles also are deposited on mountain snowpacks, where they absorb heat and accelerate snowmelt.
Physicists have long known that certain brittle objects, such as glass, rocks, or even atomic nuclei, fracture in predictable patterns. The resulting fragments follow a certain range of sizes, with a predictable distribution of small, medium, and large pieces.
Scientists refer to this type of pattern as scale invariance or self-similarity.
Physicists have devised mathematical formulas for the process by which cracks propagate in predictable ways as a brittle object breaks.
Kok theorized that it would be possible to use these formulas to estimate the range of dust particle sizes. By applying the formulas for fracture patterns of brittle objects to soil measurements, Kok determined the size distribution of emitted dust particles.
To his surprise, the formulas described measurements of dust particle sizes almost exactly.
"The idea that all these objects shatter in the same way is a beautiful thing, actually," Kok says. "It's nature's way of creating order in chaos."

Ocean Acidification Changes Nitrogen Cycling in World Seas

New results indicate potential to reduce certain greenhouse gas emissions from oceans to atmosphere.

Water samples in the Sargasso Sea being collected for studies of ocean acidification.

Increasing acidity in the sea's waters may fundamentally change how nitrogen is cycled in them, say marine scientists.

Nitrogen is one of the most important nutrients in the oceans. All organisms, from tiny microbes to blue whales, use nitrogen to make proteins and other important compounds.
Some microbes can also use different chemical forms of nitrogen as a source of energy.
One of these groups, the ammonia oxidizers, plays a pivotal role in determining which forms of nitrogen are present in the ocean. In turn, they affect the lives of many other marine organisms.
"Ocean acidification will have widespread effects on marine ecosystems, but most of those effects are still unknown."
"This report that ocean acidification decreases nitrification (the amount of nitrogen) is extremely important."
Very little is known about how ocean acidification may affect critical microbial groups like the ammonia oxidizers, "key players in the ocean's nitrogen cycle."

In six experiments spread across two oceans, the researchers looked at the response of ammonia oxidation rates to ocean acidification.
In every case where the researchers experimentally increased the amount of acidity in ocean waters, ammonia oxidation rates decreased.
These declines were remarkably similar in different regions of the ocean indicating that nitrification rates may decrease globally as the oceans acidify in coming decades.
Oceanic nitrification is a major natural component of production of the greenhouse gas nitrous oxide. From the seas, nitrous oxide then enters the atmosphere."All else being equal, decreases in nitrification rates therefore have the potential to reduce nitrous oxide emissions to the atmosphere."

Oceanic emissions of nitrous oxide are second only to soils as a global source of nitrous oxide.
With a pH decrease of 0.1 in ocean waters (making the waters more acidic), the scientists estimate a decrease in nitrous oxide emissions comparable to all current nitrous oxide emissions from fossil fuel combustion and industrial activity.
An important caveat, they say, is that nitrous oxide emissions from oceanic nitrification may be altered by other forms of global environmental change such as increased deposition of nitrogen to the ocean, or loss of oxygen in some key areas.
"That could offset any decrease due to ocean acidification, and needs to be studied in more detail," says Hutchins.
Another major implication of the findings is equally complex, the researchers say, but just as important.
As human-derived carbon dioxide permeates the sea, ammonia-oxidizing organisms will be at a significant disadvantage in competing for ammonia.
Over time, that would shift the available form of dissolved nitrogen in the surface oceans away from forms like nitrate that are produced by nitrification, and toward regenerated ammonium.
With a decrease in average ocean pH from 8.1 to 8.0 (greater acidity), the scientists estimate that up to 25 percent of the ocean's primary production could shift from nitrate- to ammonium-supported.
The consequences of such a shift are not easily predicted.

Gene tinkering makes grass grow swifter, higher, stronger

Tinkering with a single gene may give perennial grasses more robust roots and speed up the timeline for creating biofuels, according to researchers at the Duke Institute for Genome Sciences & Policy.



Researchers at Duke University have found a way to make certain plants grow faster and stronger by taking away a gene. Sounds counter-intuitive but according to the team, it works.
The plants they're working with are perennial grasses like switchgrass, a popular choice for creating biofuels. Though they can be harvested repeatedly, these grasses first need to fully establish their root system and that can take more than two years.
The team approached the challenge on a genetic level. They identified a gene that becomes active at the moment a cell stops dividing and begins to take on the characteristics of the mature cell it's destined to become. When the researchers disrupted the genes activity, the roots grew faster and the cells became larger. When they increased the genes activity, the roots grew slower. Taking away the gene was like giving the plant a way to live up to its full potential much faster.
For now the project is centered around biofuel plants, but this discovery could have much wider-ranging uses like creating bigger and stronger plants that pull more earth-warming carbon dioxide out of the atmosphere. Could there be other agricultural uses? Time will tell.

Undulatus Asperatus Clouds

Undulatus asperatus clouds over Ballston, Va., on the morning of April 13, 2010. Meteorologists are proposing that the asperatus clouds, which are rare, be designated as the first new cloud type to be named in over 50 years. Consideration is ongoing at this time.

Mexican Free-tailed Bats

Mexican free-tailed bats exiting a limestone cavern in southern Texas. The bats are mothers who have recently given birth. They are heading out to forage and will return by morning to nurse their babies. Approximately one-million mothers inhabit the cave at this time of year. (Date of Image: June 1988)

Frog Species Pristimantis adnus

New frog species Pristimantis adnus, discovered in 2010 in the Darien Province of Panama. The name of the new frog (one of two, newly identified species) is a Latinized version of the Spanish term for DNA, which is AND, and was chosen by researchers to underscore the usefulness of genetic techniques as they identify new frog species and determine the relationships between tropical frogs that may look very similar.

Frog Species Pristimantis educatoris

New frog species Pristimantis educatoris, discovered in 2010 in the Coclé Province of Panama. The new frog (one of two, newly identified species), from Omar Torrijos National Park, resembles a common frog, but larger. Round finger and toe pads proved it to be a different and unknown species.

Simulation of Frustrated Ising Spins

Four different frequencies in two separate laser beams interact with an ensemble of three ions to create a fully controllable system for creating any desired configuration of quantum spin states.

Friday Fact

Waters around Antarctica are so cold that they would kill tropical fish--but Antarctic fish produce natural antifreeze that keeps them alive.

Polar Bears: On Thin Ice? Extinction Can Be Averted, Scientists Say

Cutting greenhouse gases now is the key

A female polar bear walks along the shore of Canada's Hudson Bay, waiting for ice to form.

Polar bears were added to the threatened species list nearly three years ago when their icy habitat showed steady, precipitous decline because of a warming climate.
But it appears the Arctic icons aren't necessarily doomed after all, according to results of a study published in this week's issue of the journal Nature.
Scientists from several institutions, including the U.S. Geological Survey (USGS), the National Science Foundation (NSF) and the University of Washington, have found that if humans reduce greenhouse gas emissions significantly in the next decade or two, enough Arctic ice is likely to remain intact during late summer and early autumn for polar bears to survive.
"What we projected in 2007 was based solely on the business-as-usual greenhouse gas scenario," said Steven Amstrup, an emeritus researcher at the USGS and senior scientist at the Montana-based organization Polar Bears International. "That was a pretty dire outlook, but it didn't consider the possibility of greenhouse gas mitigation."

The 2007 study projected that only about one-third of the world's 22,000 polar bears might be left by mid-century if dramatic Arctic ice decline continued, and that eventually polar bears could disappear completely. The work led to the 2008 listing of polar bears as a threatened species.

"Our current research provides strong evidence that it's not too late to save polar bears from extinction," said DeWeaver, an atmospheric scientist. "We looked for Arctic sea ice tipping points in a climate model in which sea ice is known to be very sensitive to global warming, and we didn't find any."
The challenging issue, he said, is that even without tipping points, sea ice can undergo periods of rapid decline. "But these rapid declines occur due to a combination of natural volatility on a declining trend," says DeWeaver, "rather than a tipping point."
"Ultimately the outcome depends on how much greenhouse gas we add to the atmosphere in the future," he said, "not how much we've added until now."
"Our research offers a very promising, hopeful message, but it's also an incentive for mitigating greenhouse emissions," said Bitz.
Because the scientists specifically looked at whether there's a tipping point beyond which seasonal Arctic ice could not recover, they used a general circulation model in which the sea ice is particularly sensitive to rising temperatures.
Previous work by Bitz and others showed that unchecked temperature increases, along with natural environmental volatility, could result in the loss of vast areas of Arctic ice in less than a decade.
It also showed that with continued business-as-usual greenhouse gas emissions, the ice did not recover and largely disappeared altogether in following decades.
However, the new Nature paper indicates that if greenhouse gas emissions were reduced substantially in the near future, rapid ice losses would be followed by substantial retention of the remaining ice through this century--and partial recovery of the ice that disappeared during the rapid ice loss.
Polar bears depend on sea ice for access to ringed and bearded seals, their primary food source. During seasons when they can't reach ice, the bears mostly go without food and can lose about two pounds a day.
The periods when they don't have ice access have increased, and are expected to continue to do so with the current level of greenhouse gas emissions.
As part of this study, the potential sea-ice outlook generated by the general circulation model, as well as several features of polar bear life history, were placed into a larger network model.
The model can, for example, be used to examine the relationship between polar bears and their environment.
The results indicate that increased retention of sea-ice habitat because of greenhouse gas mitigation would allow polar bears to survive in greater numbers throughout this century, and in more areas of the Arctic, than would happen with no mitigation.
Amstrup divided the Arctic into four separate ecoregions according to the nature of ice typically found there.
The 2007 study showed a very high likelihood that polar bears would become extinct in two of those regions given current trends in greenhouse gas emissions.
"There's still a fairly high probability in both those regions that polar bears could disappear," Amstrup said.
"But with mitigation and aggressive management of hunting and other direct bear-human interactions, the probability of extinction would now be lower than the probability that polar bear numbers will simply be reduced.
"With mitigation, conditions for polar bears might even improve in the other two ecoregions. The benefit of mitigation to polar bears is substantial."

What "Pine" Cones Reveal About the Evolution of Flowers ???

Research genetically traces flowers to a single common ancestor

A non-flowering seed plant similar to this Zamia may have produced Earth's first flower.

From southern Africa's pineapple lily to Western Australia's swamp bottlebrush, flowering plants are everywhere.  Also called angiosperms, they make up 90 percent of all land-based, plant life.
New research published this week in the Proceedings of the National Academy of Sciences provides new insights into their genetic origin, an evolutionary innovation that quickly gave rise to many diverse flowering plants more than 130 million years ago. Moreover, a flower with genetic programming similar to a water lily may have started it all.
"Water lilies and avocado flowers are essentially 'genetic fossils' still carrying genetic instructions that would have allowed the transformation of gymnosperm cones into flowers," said biologist Doug Soltis, co-lead researcher at the University of Florida in Gainesville.
Gymnosperms are a group of seed-bearing plants that include conifers and cycads that produce "cones" as reproductive structures, one example being the well-known pine cone. "We show how the first flowering plants evolved from pre-existing genetic programs found in gymnosperm cones and then developed into the diversity of flowering plants we see today," he said. "A genetic program in the gymnosperm cone was modified to make the first flower."
But, herein is the riddle. How can flowers that contain both male and female parts develop from plants that produce cones when individual cones are either male or female? The solution, say researchers, is that a male gymnosperm cone has almost everything a flower has in terms of its genetic wiring.
Somehow a genetic change took place allowing a male cone to produce female organs as well--and, perhaps more importantly, allowed it to produce showy petal-like organs that enticed new interactions with pollination agents such as bees.
Analyzing genetic information encoded in a diverse array of evolutionarily distant flowers--water lily, avocado, California poppy and a small flowering plant frequently used by scientists as a model, Arabidopsis--researchers discovered support for the single cone theory.
A non-flowering seed plant, a cycad named Zamia, which makes pine cone-like structures instead of flowers, was also examined in the study.
"We extracted an essential genetic material, RNA, from the flowers' specific floral organs and in the case of Zamia, its cones, to see which genes were active," said co-lead investigator Pam Soltis, a curator at the Florida Museum of Natural History and an evolutionary geneticist at the University of Florida.
Researchers then compared the organs' profiles to a range of species representing ancient and more recent lineages of flowering plants. "This comparison allowed us to see aspects of the floral genetic program that are shared with gymnosperms, where they came from and also which aspects are shared among different groups of flowering plants and which differ," she explained.
The flowers of most angiosperms have four distinct organs: sepals, typically green; petals, typically colorful; stamens, male organs that produce pollen; and carpels, female organs that produce eggs. However, the flowers of more ancient lineages of angiosperms have organs that intergrade, or merge into one another through a gradual series of evolutionary reforms. For example, a stamen of a water lily produces pollen but it may also be petal-like and colorful and there is often no distinction between sepals and petals--instead, early flowers have organs called tepals.
The research team found a very significant degree of genetic overlap among intergrading floral organs in water lilies and avocado but less overlap in poppy and Arabidopsis. "In other words, the boundaries between the floral organs are not all that sharp in the early angiosperm groups-the organs are still being sorted out in a sense," said Doug Soltis.
The finding challenged researcher expectations that each floral organ in early angiosperms would have a unique set of genetic instructions as is the case in the evolutionarily derivedArabidopsis. Instead, the finding increased the likelihood that a single male cone was responsible for the world's first flowering plants owing to the elasticity of their genetic structure.
"In early flowers, a stamen is not much different genetically speaking than a tepal," said Doug Soltis. "The clearly distinct floral organs we all know and love today came later in flowering plant evolution--not immediately."
Researchers say better understanding of these genetic switches in early angiosperm flowers could one day help scientists in other disciplines such as medicine or agriculture.

Coral Evolution in Action [IMAGES]

Natural fluorescence of Acropora millepora under dissecting microscope, a rare morph with cyan-colored tentacles.
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Acropora millepora on the reef at Magnetic Island, Australia.

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Light at night may affect weight gain

Researchers at The Ohio State University found that mice that were persistently exposed to light at night exhibited 50% more weight gain, even when holding their physical activity and eating habits constant, than counterparts who were not exposed to light at night.

Sea Slug Species Elysia Chlorotica

Sea slug species Elysia chlorotica feeding on Vaucheria litorea, a yellow-green algae.E. chlorotica sequesters chloroplasts from the algae into specialized cells lining the digestive diverticulum, and the chloroplasts are photosynthetically functional for 9 to 11 months. Nuclear-encoded, algal chloroplast genes necessary to the function of the sequestered chloroplasts have been horizontally transferred and integrated into the slug genome.

Scorpion Species Alacran tartarus

The scorpion species Alacran tartarus, from the family Typhlochactidae, has been found at the greatest depth of all scorpions--750 to 920 meters below the surface in the Sistema Huautla, Oaxaco, Mexico. 

More about this Pic

In the course of evolution, researchers have assumed that specialized adaptations were irreversible. But research by Lorenzo Prendini, associate curator in the division of invertebrate zoology at the American Museum of Natural History, shows that the evolution of troglobites, or animals adapted for life in caves, is reversible. A new phylogenetic analysis of the family Typhlochactidae found that scorpions currently living closer to the surface (under stones and in leaf litter) evolved independently on more than one occasion from ancestors adapted to life further below the surface (in caves).

The family Typhlochactidae, which includes nine species of scorpions endemic to the karstic regions of eastern Mexico, have adapted to the dark with features such as loss of eyes and reduced pigmentation. Included in the family are one of the world's smallest scorpions, Typhlochactas mitchelli, and the scorpion found at the greatest depth (nearly 1 kilometer below the surface), Alacran tartarus.

For the study, data for 195 morphological characteristics among the species of Typhlochactidae was gathered and included a detailed mapping of the positions of all trichobothria (sensory setae) on the pedipalps (the second pair of appendages on the first (anterior) major body section). The resulting phylogenetic tree shows that adaptation to life in caves has reversed among this group of scorpions: Two of the less specialized, surface-living species, T. mitchelli and T. sylvestris, share a common ancestor with a much more cave-adapted species, and a similar pattern was found for the third less specialized, surface-living species T. sissomi.

Prendini says, "This unique group of eyeless Mexican scorpions may have started re-colonizing niches closer to the surface from the deep caves of Mexico after their surface-living ancestors were wiped out by the nearby Chicxuluxb impact along with non-avian dinosaurs, ammonites, and other species." 

Sleep Deprived Kids !!!!!!!!!

Children suffer when they don't get enough sleep. From depression, irritability to obesity – getting enough shut eye matters – especially if that child is poor. 

Getting enough shut-eye really matters for children, and those who are poor need it the most

We all know kids, especially, need a good night's sleep in order to thrive. After studying thousands of children, psychologist Mona El-Sheikh, a professor of child development, says children who don't get enough shut-eye suffer serious consequences.

"They do not concentrate as well or perform well on tasks that are complex," she explains. "Even worse, they may be more likely to be depressed, sick or obese. Sleep is very important for brain development and also for emotional regulation."

As it turns out, what sleep gives, and what the lack of it takes away, may be magnified by poverty. "Poverty is a very, very major stressor for our children," says El-Sheikh.

 El-Sheikh and her team at Auburn University are studying sleep deprivation and how it impacts kids, including those who are otherwise deprived. One week before a child comes to the lab for tests, he or she is asked to wear an actigraph to bed for seven nights. The actigraph straps onto the wrist like a watch and monitors the child's movements during the night. It also reveals how many hours of sleep the child gets each night.

On average, El-Sheikh says the children studied get about seven and a half hours of sleep. Experts say children ages five to 10 need approximately 10 to 11 hours of sleep a night.

Once their sleep is assessed, children who have volunteered for the study go through a battery of tests at El-Sheikh's lab. Team members attach leads to the kids' bodies to monitor how they react to stress--whether it's a faster heart beat or sweaty palms. Then the researchers ratchet up the stress.

Children listen to two people having an argument. They are given a time deadline to perform a series of exercises. They're asked to figure out a Rubik's cube, and trace a star while looking in a mirror--a lot more difficult than it sounds. El-Sheikh says the findings are clear. Sleep matters more for kids, and those who are poor need it most.