Physics & Mathematics

Surfactant curtails nanotube clumping in water, removing barrier to applications

Scientists have long touted carbon nanotubes as a futuristic means of delivering drugs, fortifying brittle materials and conducting current in miniaturized circuits. But attempts to introduce actual nanotubes into these roles have often been stopped in their tracks by the slender filaments’ stubborn and unhelpful tendency to clump together in solution. Now scientists at the University of Pennsylvania have found that a readily available chemical, a surfactant called sodium dodecylbenzene sulfonate (NaDDBS), disperses nanotubes in water with remarkable efficiency. The discovery, described in a paper published this month in the journal Nanoletters, represents an important step towards wider applications of nanotubes.

Telescope follows trail of neutrinos into deepest reaches of the universe

A unique telescope buried in Antarctic ice promises unparalleled insight into such extraordinary phenomena as colliding black holes, gamma-ray bursts, the violent cores of distant galaxies and the wreckage of exploded stars. An international team of physicists and astronomers report that the AMANDA telescope is capable of tracking high-energy neutrinos ? elusive subatomic particles ? to their sources, which are emitted by these signature events. Their findings will be published in the Feb. 1. 2003, issue of the Astrophysical Journal.

Astronomers Trace Microquasar’s Path Back in Time

Astronomers have traced the orbit through our Milky Way Galaxy of a voracious neutron star and a companion star it is cannibalizing, and conclude that the pair joined more than 30 million years ago and probably were catapulted out of a cluster of stars far from the Galaxy’s center. The pair of stars, called Scorpius X-1, form a “microquasar,” in which material sucked from the “normal” star forms a rapidly-rotating disk around the superdense neutron star. The disk becomes so hot it emits X-rays, and also spits out “jets” of subatomic particles at nearly the speed of light.

Researchers explore unusual properties of low-resistance ‘nanowire’ systems

Molecular wires are seen by scientists as one key to producing ever-smaller and faster electronic circuits and switches, like those used in computers and complex electronic devices. These “nanowires,” so called because they have dimensions on the order of a nanometer (a billionth of a meter), allow high rates of electron transfer and associated low resistance, or impedance to the flow of current. Now, research focused on finding good candidate materials for these wires is giving scientists a better understanding of how they work.

Vision researchers find that photon receptors pair up in neat rows

Using atomic-force microscopy, vision researchers have taken pictures of some of the eye’s photon receptors in their natural state, and have analyzed their packing arrangement. Their findings, published in the Jan. 9 issue of Nature, offer insight on how light signaling might be controlled in the retina’s outer edge. The retina receives light through rods and cones. Rods, which are most heavily concentrated on the retina’s outer edge, are sensitive to dim light and to movement, but not to color. Rods, like cones, face away from incoming light. Within rods, light causes a chemical reaction with rhodopsin. This begins a chain of stimulation along the visual pathway, which sends information to the brain for interpretation. The brain can detect one photon of light, the smallest unit of energy, when it is absorbed by a photoreceptor.

Deadly coral toxin exposes ion pump’s deepest secret

Right now, in your body, tiny pumps in the fatty membranes surrounding all your cells are hard at work pushing select charged ions, such as sodium, potassium or calcium, through those membranes. Like a water pump in a high-rise apartment building overcoming the force of gravity to move water up to a tank on its roof, these ion pumps work against “electrochemical gradients” to transport ions from one side of the membrane to the other. Now, researchers at The Rockefeller University report using palytoxin, a deadly coral-derived toxin, to pry open perhaps the ion pump’s deepest secret: that it is essentially a more elaborate version of an ion channel.

Research pushes quantum spin technology toward real-world applications

Researchers have provided “proof of concept that quantum spin information can be locally manipulated using high-speed electrical circuits,” according to an abstract of their paper being published on the “Science Express” website. The findings are significant because they demonstrate a solid-state quantum logic gate (i.e, control mechanism) that works with gating technologies in today’s electronics, today’s computers. This research also moves esoteric spin-based technologies of spintronics and quantum computing from the futuristic closer to within reach of present-day possibilities.

Technical advance in astronomy improves diagnosis of eye diseases

A major technical advance in astronomy is making it possible for scientists to see individual living cells of the human retina clearly for the first time. This will greatly improve doctors’ ability to diagnose diseases of the retina such as glaucoma at an early stage, when intervention and treatment can prevent blindness.

NASA, universities to launch nanoelectronics institute

In an effort to help create spacecraft that can think, NASA and a group of six colleges led by Purdue University today are meeting in West Lafayette, Ind., to officially launch the NASA Institute for Nanoelectronics and Computing. Institute scientists and engineers will collaborate to work on methods to make electronics measured in nanometers — much smaller than today’s components. A nanometer is roughly 100,000 times smaller than the width of a human hair. Purdue scientists will work with researchers at Northwestern, Cornell and Yale universities, the University of Florida and the University of California at San Diego.

‘Moss in space’ project to test how plants grow ‘up’

An experiment scheduled for todays Space Shuttle Columbia mission may provide clues about just how plant growth is guided by gravity. The study, an extension of work from a previous shuttle mission in 1997, should test whether the absence of gravity changes how simple plants grow. The experiment will use common roof moss (Ceratodon purpureus), a plant that uses gravity to determine the direction that single cells grow.

Discovery of nearest known brown dwarf

A team of European astronomers has discovered a Brown Dwarf object (a ‘failed’ star) less than 12 light-years from the Sun. It is the nearest yet known. Now designated Epsilon Indi B, it is a companion to a well-known bright star in the southern sky, Epsilon Indi, previously thought to be single. The binary system is one of the twenty nearest stellar systems to the Sun. The brown dwarf was discovered from the comparatively rapid motion across the sky which it shares with its brighter companion : the pair move a full lunar diameter in less than 400 years. It was first identified using digitised archival photographic plates from the SuperCOSMOS Sky Surveys and confirmed using data from the Two Micron All Sky Survey. Follow-up observations with the near-infrared sensitive SOFI instrument on the ESO 3.5-m New Technology Telescope (NTT) at the La Silla Observatory confirmed its nature and has allowed measurements of its physical properties.

Is there a ‘Planet X’?

Forget about X-ray vision and gamma ray defence beams. Planet X isn’t a superhero home world but a hypothetical 10th planet in our solar system. “I think this question tends to be intriguing because of X – the unknown,” says astronomer John Percy. “But right now, we just don’t know if there is another planet lurking on the edges of the solar system.” Percy says there are thousands of small objects orbiting the Sun beyond Neptune and Pluto. Called Kuiper Belt Objects, astronomers do not consider these to be planets because of their relatively small size – the largest, Quaoar, is half the size of Pluto. They are icy and disintegrate if diverted by another cosmic body into an orbit closer to the Sun. If this occurs, he adds, they appear to us as comets.

Surprising Image Revises Understanding of Dwarf Galaxies

An intensive study of a neighboring dwarf galaxy has surprised astronomers by showing that most of its molecular gas — the raw material for new stars — is scattered among clumps in the galaxy’s outskirts, not near its center as they expected. “This tells us that the galaxies we call dwarf irregulars are even more irregular than we thought,” said Fabian Walter, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. “Our new work also shows that these galaxies probably are useful ‘laboratories’ for studying how stars were formed when the Universe was young,” Walter added.

Robotic telescope catches early afterglow of gamma-ray burst

A team of California astronomers announced today that its robotic telescope has captured one of the earliest images ever of the visible afterglow of a gamma-ray burst. The telescope started its exposures 108 seconds after the burst was detected by the HETE-2 satellite and continued for more than 2.5 hours, until brightening of the dawn sky halted the observations. The unprecedented record of the fading glow, captured Dec. 11, will help theorists as they puzzle out the physics of these bizarre cataclysmic events, which are heralded by a brief burst of energetic gamma rays and X-rays emitted billions of years ago and followed by a fading optical light.