September 17, 2006, 10:14 PM CT

Small, low-noise oscillator

A new design for a microwave oscillator that is smaller, simpler, and produces clearer signals at a single frequency than comparable devices has been invented at the National Institute of Standards and Technology (NIST). Applications could include homeland security (e.g., surveillance of radio traffic for anomalous signals, or high-resolution digital imaging radar on unmanned aircraft), telecommunications (e.g., maintaining separation between frequencies in high-bandwidth networks), and perhaps even consumer devices (e.g., satellite television downlinks or directv satellite tv).

A patent was issued recently* for the NIST oscillator, which is about the size of a roll of 35 mm camera film. NIST researchers have built five prototypes on test fixtures, which offer several-orders-of-magnitude reductions in various types of self-generated signal interference, or noise, compared to typical commercial oscillators, resulting in improved frequency stability, according to David Howe, one of the inventors. In addition, the simple design reduces costs and improves reliability, while consuming less power than other oscillators of comparable signal purity. The small size could be an advantage on some surveillance platforms.

Microwave oscillators are used as reference or clock signals in many high-precision technologies. Through control of temperature and other variables, the oscillators produce a desired signal at one narrowly defined frequency while suppressing random, electronically induced "noise" generated by components. In the best microwave oscillators, the signal typically is amplified inside a metal cavity containing a solid insulating material that internally sustains microwaves and radio waves with minimal loss, especially at cryogenic temperatures, an expensive and complex design. By contrast, the NIST oscillator uses an ultra-stiff ceramic manifold that supports a single frequency with either a vacuum or air as the insulating medium.........

Posted by: Beverly      Permalink         Source

September 15, 2006, 2:06 PM CT

Water-life Connection A Close Look

Researchers led by Ohio State University physicist Dongping Zhong revealed these interactions for the first time, and report the results in the current issue of the Proceedings of the National Academy of Sciences.

No one has ever seen exactly how water molecules interact with proteins - even though water is the essential element for life. that is, not until now.

Proteins are complex molecules that form the main support structure for plant and animal cells, and they also regulate biochemical reactions.

Zhong's project aims eventually to explain how water helps enable life-supporting biological functions such as protein folding or enzyme catalysis. But for now, this early result ends decades of controversy on what happens in the microscopic realm where water and proteins meet.

The controversy, Zhong explained, stemmed from the fact that researchers across different disciplines used different methods to study the problem. Because of that, they got different answers on the speed with which these essential biochemical reactions take place.

"A biologist will tell you that water and proteins must interact on a nanosecond [one billionth of a second] time scale, because that's how fast proteins move," he said. "And a physicist will tell you that the interaction would happen much faster -- on the picosecond [one trillionth of a second] time scale -- because that's how fast water molecules move. And someone who uses X-rays will give you a different answer than someone who uses nuclear magnetic resonance and so on".........

Posted by: Beverly      Permalink         Source

September 15, 2006, 1:47 PM CT

Watch Seeds In 3D

Embryonic photosynthesis leads to the production of seed-internal oxygen that is important for seed development and quality. In order to visualise seed-internal structures that could serve for oxygen storage conventional microscopic methods could not be used because they require the seed to be cut thus leading to air escape. By using holotomography at the ESRF, researchers could get the full picture of an arabidopsis seed without any structural modification.

Scientists have identified individual cells within the seed and rendered them to show their three-dimensional organisation. They have also distinguished an intercellular air network, which should represent an important circulation system for air and perhaps water during germination. However, researchers can't yet assure that this is the path the oxygen follows to "feed" the seed: "Solving this question needs a nano-method to determine the exact composition of air in the network during seed formation, but unfortunately this method is not available yet", explains Silva Lerbs-Mache, the corresponding author of the paper.

The researchers used hard X-ray-based quantitative phase tomography at ESRF beamline ID19 to obtain three-dimensional images of an arabidopsis seed. This seed is a model plant for biologists and the first one for which the genome was sequenced. "This approach is to our knowledge the only imaging technique with the penetration capacity and imaged field size suited for an investigation at sub-micrometre resolution of an optically opaque object the size of a seed" explains Peter Cloetens, first author of the paper and scientist at the ESRF. It is applied for the first time to an autonomous living system, observed without object destruction, without staining, in air, and at room temperature.........

Posted by: Ethen      Permalink         Source

September 14, 2006, 8:48 PM CT

Ferns Provide Model For Tiny Motors

Scientists looked to ferns to create a novel energy scavenging device that uses the power of evaporation to move itself -- materials that could provide a method for powering micro and nano devices with just water or heat.

"We've shown that this idea works," said Michel Maharbiz, assistant professor of electrical engineering and computer science and principal investigator in the group that built the device. "If you build these things they will move. The key is to show that you can generate electricity from this".

As often happens, the research started while doctoral student Ruba Borno was exploring another idea entirely. Borno was interested in mimicking biological devices, specifically microchannels that plants use to transport water, so Maharbiz gave her a book on plants.

But something else in the book caught her attention - the section on how ferns spread their spores.

"It's essentially a microactuator," said Maharbiz, meaning that the fern sporangium transforms one form of energy, in this case heat via the evaporation of water, into motion. When the cells in the outer wall of the sporangium were water logged, the sporangium remained closed like a fist, storing the spores safely inside. But when the water in the outer wall evaporated, it caused the sporangium to unfurl and eject the spores into the environment.........

Posted by: Beverly      Permalink         Source

September 14, 2006, 8:37 PM CT

Paleontologists Find 67 Dinosaurs In One Week

One recent week in the Gobi Desert produced 67 dinosaur skeletons for a team of paleontologists from Montana and Mongolia who want to flesh out the developmental biology of dinosaurs.

Montana State University paleontologist Jack Horner said Wednesday that the same area yielded 30 skeletons last year, so scientists at MSU and Mongolia's Science and Technology University now have about 100 Psittacosaurus skeletons. The skeletons ranged in length from one to five feet and stood about two feet tall.

"That's what I was there for -- getting as a number of of those as we could possibly get," Horner said as he waited for the rest of the MSU team to return to Bozeman.

He was specifically looking for Psittacosaurus fossils because it was a very common dinosaur and would give him lots of specimens, Horner said. It would also keep away poachers and commercial fossil hunters who work in the area, but prefer rare fossils. Horner wants a large number of fossils so he can compare variations between skeletons and changes during growth.

The Psittacosaurus dinosaur, also known as a "parrot lizard," was a plant-eater that lived about 120 million years ago in the Early Cretaceous Period, Horner said. It was an ancestor of horned dinosaurs like the triceratops.........

Posted by: Beverly      Permalink         Source

September 14, 2006, 8:22 PM CT

Double Quantum Dots Control Kondo Effect

Two quantum dots connected by wires could help scientists better control the Kondo effect in experiments, according to a study by Ohio University and University of Florida physicists published in a recent issue of Physical Review Letters.

The Kondo effect occurs when electrons become trapped around the magnetic impurities in semiconductor materials, which prompts the electrons to change their spin. This phenomenon has intrigued scientists, as electronic correlations can create interesting and complex behavior in materials.

In the new work, scientists demonstrate how the two quantum dot system can behave in two different and interesting ways: As a simile for a Kondo-effect system where one quantum dot is used to "filter" the effect of the current leads, and as a way to study "pseudo-gapped" systems and correlations in them, which can help scientists understand structures such as superconductors.

"This last part is of great current interest to theorists and experimentalists who are exploring what are called quantum phase transitions, which are changes in systems that alter their behavior dramatically as a function of some parameter while remaining at zero (or very low) temperature," said Sergio Ulloa, a professor of physics and astronomy at Ohio University.........

Posted by: Beverly      Permalink         Source

September 14, 2006, 7:41 PM CT

Rodent's Bizarre Traits Deepen Mystery Of Genetics

A shadowy rodent has potential to shed light on human genetics and the mysteries of evolution.

Purdue University research has shown that the vole, a mouselike rodent, is not only the fastest evolving mammal, but also harbors a number of puzzling genetic traits that challenge current scientific understanding.

"Nobody has posters of voles on their wall," said J. Andrew DeWoody, associate professor of genetics in the Department of Forestry and Natural Resources, whose study appears this month in the journal Genetica. "But when it comes down to it, voles deserve more attention".

Small rodents often confused for mice, except with shorter tails and beady eyes, voles live throughout the Northern Hemisphere and are often considered agricultural pests because they eat vegetation. Nevertheless, voles are an "evolutionary enigma" with many bizarre traits, DeWoody said. Understanding the basis for these traits could lead to better understanding of the same phenomena in human genetics and genetic disorders, and could have implications for gene therapy, he said.

The study focuses on 60 species within the vole genus Microtus, which has evolved in the last 500,000 to 2 million years. This means voles are evolving 60-100 times faster than the average vertebrate in terms of creating different species. Within the genus (the level of taxonomic classification above species), the number of chromosomes in voles ranges from 17-64. DeWoody said that this is an unusual finding, since species within a single genus often have the same chromosome number.........

Posted by: Beverly      Permalink         Source

September 14, 2006, 7:07 PM CT

Senecio Rowleyanus

The longest running plant sale at the garden occurs today and tomorrow: the 29th Annual Indoor Plant Sale. I had a grand time yesterday trying to photograph a few of the plants available, since I don't often get the opportunity to work with indoor plants.

A native of southwestern Africa, "string of beads" grows in arid habitats. The succulent beads are actually the leaves, modified for living through extended periods of drought. Dr. T. Ombrello of Union County College has written an intriguing article on the adaptations of this Senecio and the closely related Senecio herreianus, entitled Senecios, With Windows in Their Leaves. The narrow bands you can see on some of the beads consist of transparent tissue to allow light to penetrate the interior of the bead and increase photosynthesis without increasing water loss.

It might be worth revisiting my comments on diversity within the Asteraceae in the BPotD entry on Raoulia australis. There is simply an amazing amount of diversity of form and structure in this plant family.........

Posted by: Beverly      Permalink         Source

September 14, 2006, 6:23 PM CT

Mechanisms of Sudden Oak Death

By comparing the complete genome sequences of two plant-killing pathogens and related organisms, scientists from the U.S. Department of Energy Joint Genome Institute (DOE JGI), in collaboration with the Virginia Bioinformatics Institute (VBI) and others, have uncovered crucial aspects of the disease-causing mechanisms of "Sudden Oak Death" (SOD) and soybean root rot disease. The research, the result of a four-year, $4 million multi-agency project supported by DOE, U.S. Department of Agriculture (USDA), and the National Science Foundation (NSF), appears in the Sept. 1, 2006, edition of Science (vol. 313, No. 5791).

"This project best exemplifies how the capabilities that were established at the DOE JGI for sequencing the human genome are now proving to be essential for addressing important environmental challenges," said Eddy Rubin, DOE JGI Director. "We are now capable of rapidly responding to the urgent needs of the nation's largest industry, agriculture, where genome sequence information can be brought to bear on characterizing such economically important microorganisms as those that cause sudden oak death and soybean root rot. For these pathogens, the genome sequence is the wiring diagram of the cellular processes that can be targeted for novel detection systems and for safe and effective means of control".........

Posted by: Beverly      Permalink         Source

September 14, 2006, 6:11 PM CT

The First Tree Genome is Published

Wood from a common tree may one day factor prominently in meeting transportation fuel needs, according to scientists whose research on the fast-growing poplar tree is featured on the cover of tomorrow's edition of the journal Science.

The article, highlighting the analysis of the first complete DNA sequence of a tree, the black cottonwood or Populus trichocarpa, lays the groundwork that may lead to the development of trees as an ideal "feedstock" for a new generation of biofuels such as cellulosic ethanol. The research is the result of a four-year scientific and technical effort, led by the U.S. Department of Energy's Joint Genome Institute (DOE JGI) and Oak Ridge National Laboratory (ORNL), uniting the efforts of 34 institutions from around the world, including the University of British Columbia, and Genome Canada; Umeå Plant Science Centre, Sweden; and Ghent University, Belgium.

"Biofuels could provide a major answer to our energy needs by giving the United States a homegrown, environmentally friendlier alternative to imported oil," said DOE's Under Secretary for Science Dr. Raymond L. Orbach. "Fine-tuning plants for biofuels production is one of the keys to making biofuels economically viable and cost-effective. This research, employing the latest genomic technologies, is an important step on the road to developing practical, biologically-based substitutes for gasoline and other fossil fuels".........

Posted by: Beverly      Permalink         Source