VALLEY RESEARCH

Research News is a digest of science and technology news items arising from research and development magazines, newspapers, trade magazines, newsletters, and other news sources that Valley Research processes daily for the benefit of its customers everywhere. It is provided freely to our customers who are free in turn to post or transmit it to other interested researchers provided only that credit to Valley Research is given. Research News is updated approximately once a week.

Rodolfo Carrera, Editor

WEEK OF MAY 5, 2008 [No. 739]

A memresistor fabricated:   researchers at the HP labs in Palo Alto have attached a layer of doped TiO₂ to a layer of undoped TiO₂ and found that it exhibits hyterisis in current-voltage loops in the way Leon Chua predicted in 1971 the missing memresistor would. This element now completes the fundamental quartet of two-terminal circuit elements (resistor, capacitor, inductor, and memresistor). While a resistor opposes charge flow, an inductor opposes charge flow change, and a capacitor stores charge, the memresistor remembers the flowed through charge and changes its resistance accordingly. The group has reported that memresistance arises naturally in nanoscale systems where solid-state electronics and ionic transport are coupled under an external bias voltage. The fabrication of this non-linear resistor with memory followed a previously developed analytical model by the same group consisting of a thin piece semiconductor containing two different regions, a highly doped region of low resistance and a zero-doped region of high resistance. When a voltage is applied across the semiconductor, it causes some of the dopants to drift so that the combined resistance changes, thereby producing the characteristic hysteresis effect of memresistance. Anomalous behaviors observed in nano-electronics over the last decade might be understood as a manifestation of memresistive dynamics. Memresistors may allow a significant increase in functional density over that achieved by transistors.

For more information: Nature, May 1 (2008) pages 80 and 42; Physicsworld, April 30 (2008).

WEEK OF APRIL 28, 2008 [No. 738]

A full human genome sequenced at 100 times lower cost:   a group lead by Baylor College of Medicine and 454 Life Sciences researchers have completed the sequence (6 gigabases) of the diploid genome of James D. Watson, to 7.4-fold redundancy in two months using massively parallel sequencing in picoL size reaction vessels at a percent of the cost of traditional capillary electrophoresis methods (total cost ~$1M).

For more information: Nature, April 17 (2008) pages 872, 819, and 788.

Giant piezoresistance observed:   European scientists in France, Switzerland and UK have recorded the largest ever change in a bulk material's electrical resistance brought about by stretching the material at room temperature. A metal / Silicon hybrid piezoresistance yielded a gage factor (change in resistance per unit of strain) of 900. Simple metal-foil piezomaterials gage is typically 2. Expensive Si-based piezoresistors now have a gage of 100.

For more information: Physics News Update, May 1 (2008); Phys. Rev. Lett., April 11 (2008).

Auroral lights are polarized:   European researchers from France, Netherlands and Norway have confirmed that auroral light is polarized as claimed some fifty years ago by Bob Duncan (and set aside by prevailing wisdom since). Duncan considered that electrons from the solar wind trapped in the Earth's magnetic field collide with atoms at 200 km height leaving them in an excited quantum state. When returning to the ground state they fluoresce with polarized light.

For more information: Physicsworld, May 1 (2008); Geophys. Res. Lett, to be published (2008).

WEEK OF APRIL 21, 2008 [No. 737]

Some marine organisms increase ocean calcification as CO₂ rises:   an international team lead by European researchers has obtained laboratory evidence that calcification for coccolithophores is significantly increased by high CO₂ partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass. The findings show that coccolithophores are already responding ( they produce about a third of CaCO₃ in today's oceans) and will probably continue to respond to rising atmospheric CO₂ partial pressures which has important implications for biogeochemical modeling and the future of oceans and climate.

For more information: Science, April 18 (2008) page 336; Chem. Eng. News, April 21 (2008) page 43.

The Poisson ratio of buckypaper can be simply tuned:   US and Brazilian researchers have found that the in-plane Poisson's ratio (lateral contraction over stretch) of carbon nanotube sheets can be varied from positive to negative (width increases when stretched) by mixing single-walled and multi-walled nanotubes. Density-normalized sheet toughness, strength, and modulus were substantially increased by this mixing. Theory predicts the sign and magnitude of the Poisson's ratio from the relative ease of nanofiber bending and stretch. Increasing the amount of MWNTs in the paper produces a sharp transition from 0.06 to -0.20 in Poisson's ratio.

For more information: Science, April 25 (2008) page 504; Physicsworld, April 24 (2008).

WEEK OF APRIL 14, 2008 [No. 736]

Warping of space - time by quasars shown:   an international team lead by Finnish researchers have provided an important test of general relativity at the very strong gravitational field limit by analyzing the OJ287 quasar. This distant galactic core emits two opposite bright optical bursts about every 12 yrs. The group suggested in 1988 that the emission is powered by a primary black hole with mass ~ 18Bsuns. A second black hole some 200 times lighter passes through matter in the accretion disk of the primary black hole twice per orbit releasing a burst of energy. Based in two decades of observations and modeling the group was able to predict the 2007 burst with a day precision. The results are consistent with the quasar being a binary black hole system with the suggested masses and a precession of the secondary black hole of 39 deg / period ( vs. a precession of 0.1 deg / century in the case of Mercury due to the Sun-induced local space - time warping). The analysis suggests that the binary system is losing orbital energy by emitting gravitational waves. When this emission is not included in the calculation, the quasar outburst is predicted to occur 20 days later, providing indirect support for gravitational waves. This quasar seems now to be the brightest known source of gravitational waves in the universe.

For more information: Nature, April 10 (2008) page 851; Physicsworld, April 16 (2008).

WEEK OF APRIL 7, 2008 [No. 735]

Post-perovskite responsible for Earth's rotation fluctuations:   researchers at the Tokyo Institute of Technology prepared samples of perovskite (common MgFe silicate mineral) and tested its electrical conductivity in a laser-heated diamond anvil cell. At the high temperature and pressure expected at the core-mantle boundary inside Earth, the scientists observed the mineral undergo a phase transition to form post-perovskite. This transition is accompanied by a shift in the electronic structure of metal atoms, causing the conductivity to jump two orders of magnitude. It is a post-perovskite layer, perhaps 300-km thick, just above the core-mantle boundary that could give rise to Earth's observed rotational fluctuation.

For more information: Chem. Eng. News, April 7 (2008) page 51; Science, April 4 (2008) page 89.

3 D mapping of magnetic fields inside solids with micron resolution:   scientists in the Berlin Institute of Technology and elsewhere in Germany have used a beam of polarized neutrons from a nuclear reactor beamline to irradiate samples. As the neutrons travel through a sample, their magnetic moments rotate around the magnetic fields they encounter and the direction of their spin changes. The researchers measure the different spin angles, which depend on the strength of the magnetic fields traversed by the neutrons. The measured values are converted into intensities by a polarization analyzer, located behind the sample. Next, a position-sensitive detector measures these intensities to make a map of the magnetic fields inside the sample.

For more information: Physicsworld, April 8 (2008); Nature Physics on line.

WEEK OF MARCH 31, 2008 [No. 734]

Groups of spines are the functional units of brain plasticity:   researchers at the Howard Hughes Medical Institute in Virginia have investigated the neural basis of plasticity at a fine scale activating individual dendritic branches (each receiving thousands of excitatory synapses most of them on dendritic spines).They mimicked precisely patterned synaptic activation using laser stimulation of dendritic spines. Caged neurotransmitter glutamate is released from the cage by the laser, allowing glutamate to act locally on the dendritic spine. The laser is moved rapidly from one spine to the next to precisely mimic patterned synaptic activation. They show that when clusters of synapses on a dendritic branch are stimulated simultaneously, under conditions thought to mirror brain states during learning, repeated activation leads to gradual changes in the response of the branch. They observe that the coupling between local dendritic spikes and the soma of rat hippocampal CA1 pyramidal neurons can be modified in a branch-specific manner through an NMDA receptor-dependent regulation of dendritic Kv4.2 potassium channels. This shows the existence of an effective form of local dendritic spike plasticity. Branch strength potentiation represents a new form of information storage and memory formation.

For more information: Nature, March 27 (2008) pages 436 and 420.

WEEK OF MARCH 24, 2008  [No. 733]

Nanocrystals do the trick for better thermoelectrical properties:   researchers at Boston College and MIT have made a significant breakthrough in thermoelectricity by increasing the capability of one of the main thermoelectric materials by 20% after more than fifty years of trials. Specifically the figure of merit ZT (gives how good electricity conductor and how poor heat conductor the material is) for the BiSbTe has been increased from 1.0 to 1.2 at room temperature. The procedure involved milling the material into a fine powder that contained nanoparticles measuring 20 nm across and hot-pressing the powder into nanocrystalline ingots. They found that ZT peaks at 1.4 at 100 C. Electrical transport measurements on the ingots, together with microstructure and computer simulations, showed that the ZT improves thanks to the low thermal conductivity caused by increased phonon scattering at grain boundaries and defects in the material. However, the electrical conductivity of the material is not affected significantly by grain boundaries and defects. The high ZT in the temperature range 25 - 250 C makes these materials promising for cooling and waste heat recovery applications.

For more information: Physicsworld, March 22 (2008); Science, on line.

Single photon logic gates on Silicon:   scientists at the University of Bristol have built the first logic gates on a Si chip that can process individual photons. The chip, which measures several millimeters across, reproduces an earlier version of the gate that occupied several square meters of space on an optical bench. Instead of mirrors and beam splitters, they used coupled waveguides- micrometer-wide channels of transparent silica that can be fabricated on Si wafers using standard microelectronics techniques.

For more information: Physicsworld, March 27 (2008); Science, on line.

WEEK OF MARCH 17, 2008  [No. 732]

New class of high temperature superconductor compounds discovered:   researchers at the Tokyo Institute of Technology have reported that a layered Fe-based compound LaOFeAs undergoes superconducting transition under doping with negative F ions at the double negative O site. The transition temperature (Tc) exhibits a trapezoidal shape dependence on the atomic fraction of the negative F ion, with the highest Tc ~26K at 0.04-0.11 atomic fraction (negative F ion content). The crystalline material comprises layers of La and O sandwiched between layers of Fe and As and is doped with F ions. The new superconductor proves that high Tc superconductivity is not limited to Cu oxides and a few other compounds based on U, Ce and Pu.

For more information: Physicsworld, March 20 (2008); J. Am. Chem. Soc., Feb. 23 (2008) page 3296.

Single photon satellite communication demonstrated:   a team of Italian and Austrian scientists has shown that it is possible to send single photons from a satellite to a receiving station on Earth. The work paves the way for global quantum cryptography and more rigorous tests of quantum mechanics. By bouncing the beam off the satellite orbiting at 1,500 km, it is calculated that they receive an average of 0.4 photons / pulse. By precisely calculating when each pulse is to return to the observatory (accounting for the changing position of the satellite), they were able to show that the detected photons are those transmitted by the telescope and not stray photons from background sources.

For more information: Physicsworld, March 20 (2008); to be published at The New Journal of Physics.

WEEK OF MARCH 10, 2008 [No. 731]

The cosmic neutrino blanket confirmed:   analysis of five year data from the NASA's WMAP (Wilkinson Microwave Anisotropy Probe) have shown the faint signal in the cosmic microwave background that is associated to the neutrino sea liberated a second after the Big Bang. They have also provided an independent estimate of the number of neutrino families in nature (4.4 ± 1.5) and have constrained the combined mass of all types of neutrino to be less than 0.61 eV. The new combined limits imposed by the data on spectral index (this parameter is related to the slope of the angular power spectrum once its oscillatory features have been removed and is set to < 1.0 as in simple inflation models) and on gravitational waves (these are produced by motion on the quantum scale and blown up during inflation and can contribute < 20% of the total temperature anisotropy) rule out a swathe of inflation models. The age of the Universe has been set to 13.73 ± 0.12 Gyr and 95% of the Universe content has been set as dark matter and energy. According to the analysis of the data, at the time of recombination when atoms were formed and photons decoupled from the previous plasma, neutrinos made up 10% of the Universe, photons 15%, atoms 12%, dark matter 63%, and dark energy was negligible. Today, < 1% of the Universe is made of neutrinos and photons, 4.6% is atoms, 23% dark matter and 72% dark energy.

For more information: Physicsworld, March 12 (2008); to be published in The Astrophysical Journal.

WEEK OF MARCH 3, 2008 [No. 730]

Coherent soft XR laser:   scientists at Colorado Sate University in Fort Collins have demonstrated an almost fully coherent soft X-ray laser. The laser operates at wavelengths of 18.9 nm and 13.9 nm. The latter is fine enough for EUV lithography which will be needed to manufacture the generation of chips that are to become available around 2011 with features that are just 22 nm, half as much as the most advanced today. The group generated low-energy seed pulses of EUV light by firing a Ti:Sa laser through a Ne gas cell. The generated harmonics were fed to an amplifier (plasma made by irradiating polished Mo or Ag slabs with pulses from another laser) that boosted the power only of the desired wavelengths (Mo amplified the 18.9 nm line and Ag boosted the 13.9 nm line).

For more information: Spectrum, March (2008) page 14.

Marine predators use Levy walks for foraging decisions:   an international team lead by English researchers from the Marine Biological Association at Plymouth, have analyzed over a million movement displacements recorded from animal-attached electronic tags to show that diverse marine predators (sharks, bony fishes, sea turtles and penguins) exhibit Levy-walk-like behavior close to a theoretical optimum. Prey density distributions also display Levy-like fractal patterns, suggesting response movements by predators to prey distributions. Simulations show that predators have higher encounter rates when adopting Levy-type foraging in natural-like prey fields compared with purely random landscapes.

For more information: Nature, February 28 (2008) page 1098.

WEEK OF FEBRUARY 25, 2008  [No. 729]

Ia supernovae produced by accretion in binary stars:   German and Dutch scientists have discovered a luminous source of low-energy X-rays in pre-supernova archival X-ray images at the position of the recent type Ia supernova (2007on) in the elliptical galaxy NGC 1404. Deep optical images (also archival from NASA's Chandra X-ray-observatory satellite) show no sign of this object. The researchers conclude that the X-ray source is the progenitor of the supernova, which favors the accretion model for this supernova. Type Ia supernovae are exploding stars that are used to measure the accelerated expansion of the Universe and are responsible for most of the Fe ever produced. It is generally agreed that the exploding star is a white dwarf (degenerate star) in a binary system; however it is not clear how the explosion is induced. The discovery here favors the idea that an exhausted white dwarf accretes material from its normal H-burning star companion until it exceeds the Chandrasekhar mass (1.39 x mass of Sun), collapses and explodes. The other option where two white dwarfs merge causing catastrophic collapse and explosion seems now less probable. The host galaxy is older (6-9 Gyr) than the age at which the explosions are expected with accretion in single degenerate binary systems.

For more information: Nature, February 14 (2008) pages 802 and 775.

WEEK OF FEBRUARY 18, 2008 [No. 728]

Solar systems similar to our own might be common:   an international team lead by Ohio State University scientists have detected a multiple-planet system using a gravitational microlensing technique. The star has half mass of the Sun and is 5000 light years away. The inner planet has a mass ~0.71 that of Jupiter and orbits at 2.3 AU from the star (vs. 5.2 for Jupiter). The outer planet is ~0.90 as massive as Saturn and lies at 4.6 AU from the star (vs. 9.5 AU for Saturn). The ratios of the planet's masses and of their distances from the star are similar to those of Jupiter and Saturn. Even the warmth that the dimmer star sheds on the planets is similar to what the Sun sheds on Jupiter and Saturn. The discovery could not have been possible with other techniques.

For more information: Science, February 15 (2008) pages 927 and 885; Physicsworld, February 14 (2008).

Ball lightning produced by ejected burning Si nanoparticles:   sraeli and French researchers have used a beam line at the ESRF, European Synchrotron Radiation Facility, to make fireballs in a microwave cavity and probe them with 12.5 keV X-rays at atmospheric pressure. They created a hotspot by concentrating microwaves with a Cu electrode, then touching the electrode to a borosilicate glass substrate. Upon retracting the electrode, a molten drop detached and vaporized into a buoyant fireball. Small-angle X-ray scattering revealed that the particles contained in the fireball are approximately 50 nm in diameter and form a radiative dusty plasma with n~10⁹ particles/cm³ and T ~1000 K.

For more information: Physics Today, February (2008) page 18; Phys. Rev. Lett., upcoming article.

WEEK OF FEBRUARY 11, 2008 [No. 727]

Alzheimer's plaques can grow rapidly:   scientists from the Harvard Medical School and Washington University have studied the kinetics of formation of extracellular protein deposits (amyloid plaques) using multiphoton laser confocal microscopy in a mouse model of Alzheimer's disease. They have observed remarkably different kinetics of plaque formation from that expected. New plaques formed in only 24 hours and their size and final characteristics stabilized within a week. The mature plaques originate from smaller amyloid deposits (microplaques) that support a fast but eventually stable growth of the plaques. In the early stages of the Alzheimer's, microplaques can damage neighboring axons and dendrites within days.

For more information: Nature, February 7 (2008) pages 720 and 638.

Spectroscopy of anti-hydrogen in electromagnetic confinement:   scientists at CERN have detected for the first time the presence of anti-hydrogen atoms in a combined Penning-Ioffe trap. Anti-protons are created in high energy collisions while positrons are produced in a radioactive source. The Penning trap holds the positrons and antiprotons to form anti-hydrogen atoms that are then confined in the Ioffe trap for analysis. Although there is not yet evidence of trapped anti-toms, the researchers have carried high-precision spectroscopy studies to prove that anti-atoms are produced and that the number of anti-atoms increases when the Ioffe trap is turned on.

For more information: Physics News Update, February 13 (2008); Phys. Rev. Lett., upcoming article.

WEEK OF FEBRUARY 4, 2008 [No. 726]

Abiogenic source of mantle-derived hydrocarbons:   cientists from the University of Washington and elsewhere in the US and Switzerland have demonstrated the existence of hydrocarbons (HCs) dissolved in hydrogen-rich fluids venting at the ultramafic-hosted Lost City hydrothermal vent field in the Atlantic Ocean. They have uncovered a distinct inverse trend in the stable carbon and hydrogen isotopic composition of C1 to C4 hydrocarbons compatible with FTT (Fischer-Tropsch) genesis which is the lengthening of carbon chains through a series of inorganic reactions. It has been difficult to demonstrate a purely mantle, abiogenic origin of previously identified HCs in the face of abundant biogenic HCs. Radiocarbon evidence rules out seawater bicarbonate as the C source for the FTT reactions, suggesting that a mantle-derived inorganic C source is leached from the host rocks. Mantle methane seems to be yielding HCs through these inorganic reactions. The group concludes that the abiotic synthesis of HCs in nature may occur in the presence of ultramafic rocks, water, and moderate amounts of heat. Because this system is likely representative of many similar systems in the oceans, an abundant source of mantle-derived HCs may be present on Earth now and in its early history.

For more information: Science, February 1 (2008) pages 604 and 545.

WEEK OF JANUARY 28, 2008 [No. 725]

The first radio made of nanotubes:   scientists from the University of Illinois have built radio frequency SWNT (single wall nanotubes) analog electronic devices, such as narrow band amplifiers operating in the VHF frequency band with power gains as high as 14 dB. They fabricated nanotube transistors, in which SWNT devices provide all the key functions, including resonant antennas, fixed RF amplifiers, RF mixers, and audio amplifiers. Unlike previous nanotube radios, which produced very weak signals that needed further amplification, the team was able to listen to a local broadcast on headphones connected directly to a nanotube transistor.

For more information: Proc. Natl. Acad. Sci. USA, January 28 (2008); Physicsworld, January 31 (2008).

Fine tuning of porosity:   scientists from the University of Tokyo have demonstrated control of pore nature in library synthesis of a class of porous crystalline materials. The bimolecular porous material has two molecular components, one of which can be easily replaced (like changing a cartridge in a pen). The flexibility allows the absorption properties of the crystalline metal-organic compound to be fine-tuned. They prepared a porous system in which an organic ligand donates electrons to ZnI forming coordination bonds. The resulting crystal structure traps aromatic molecules (triphenylenes) via non-covalent interactions to form two types of channels that recognize and bind small molecules. Which molecules are trapped depends on the chemical groups attached to the triphenylenes. The recognition properties of the channels can be fine-tuned by replacing the triphenylenes with others that have different chemical groups attached.

For more information: . Am. Chm. Soc., November 22 (2007); Nature, January 24 (2008) page 410.

WEEK OF JANUARY 21, 2008  [No. 724]

Protons identified as fast neurotransmitters:   researchers at the University of Utah have shown that protons can act as a direct transmitter from intestinal cells to stimulate muscle contraction. The group reached this conclusion while studying muscle contractions associated with defecation in Caernorhabditis elegans worms. They found that the contraction of intestinal muscles depends on two types of proteins: proton transporters (sodium/proton exchangers, ubiquitous in both worms and man) on the exterior of the intestine and proton receptors on the surface of muscles surrounding the intestine. Caged protons released by the transporters bind to the receptors, which open channels to admit Na ions into the muscle cells. The influx causes the muscles to contract.

For more information: Chem. Eng. News, January 14 (2008) page 10; Cell, January 11 (2008) page 149.

Synthetic organism within grasp:   scientists from the Venter Institute in Maryland have assembled a synthetic genome replicating Mycoplasma bacterium's genetic structure. The team strung together nucleotides to include all the genes of the naturally occurring bacterium but disrupted the genes that would enable it to infect other organisms. Previously last June the Institute inserted the DNA of one species of bacteria into cells of another bacteria species. That process booted up the genome of the donor bacteria, sparking it to life. They hope to use a similar trick to boot up the artificially created genome to synthesize a living organism later this year.

For more information: Wall Street Journal, January 25 (2008) page B3; Science, on line.

WEEK OF JANUARY 14, 2008 [No. 723]

Our galactic antimatter has been located at central binary stars:   an international team of researchers from the CNRS at Toulouse and from elsewhere have uncovered a distinct asymmetry in the 511-keV line emission coming from the inner Galactic disk (~10 - 50 deg. from the Galactic Center). This asymmetry resembles an asymmetry in the distribution of low mass X-ray binaries (pairs of either black holes or neutron stars) with strong emission at photon energies > 20 keV, indicating that they may be the dominant origin of the positrons. The distribution of the annihilation line radiation has been analyzed using more than four years of spectroscopy data from the INTEGRAL satellite. Although it had long been suspected that the electron-positron pair plasmas may exist in X-ray binaries, it was not evident that many of the positrons could escape to lose energy and ultimately annihilate with electrons in the interstellar medium and thus lead to the emission of a narrow 511-keV line. It is evaluated that up to a few times 10⁴¹ positrons escape per second from a typical hard low-mass X-ray binary. Positron production at this level in the Galactic bulge would reduce (and possibly eliminate) the need for more exotic explanations, such as those involving dark matter.

For more information: Nature, January 10 (2008) pages 159 and VI

WEEK OF JANUARY 7, 2008  [No. 722]

A new generation spectroscopy:   cientists at NIST-Boulder have done spectroscopy of a gas using optical frequency combs. The experiment examines the gas absorption on 155,000 lines spanning a wavelength range of 125 nm. The spectral line precision is 1 Hz (for spectral frequencies of 10¹⁴ Hz) and that compares with tens of MHz characterizing standard spectroscopy techniques. The spectroscopy work accomplished is equivalent to simultaneously sending 155,000 individual single frequency lasers through the sample and measuring the resulting amplitude and phase shift on each individual laser after absorption when any given line is resonant with any of the many quantum energy levels of the gas. Moreover, the spectrum is measured rapidly, using no moving mechanical parts. The group uses highly stabilized mode-locked lasers that emit femtosecond pulses at repetition frequencies of GHz. Special optical paths and techniques are used to make the comb teeth as fine and perfectly and evenly spaced as possible. The comb used for the spectroscopy is mixed with a second carefully-crafted frequency comb to produce a beat frequency pulse which is radiated into the gas. This then can be measured with conventional electronics to determine the specific absorption characteristics of the more than hundred thousand comb lines used in the new spectroscopy technique.

For more information: Physics News Update, January 11 (2008); Phys. Rev. Lett., January 11(2008).

NOTE: previous Research News (since WEEK OF MARCH 1, 1994 [No. 1], around the time when the Quantum Cascade Lasers were demonstrated at AT&T Bell Laboratories in Murray Hill, N.J., as promising MIR solid-state room temperature sources that would enable laser spectroscopy in the spectral region where fundamental rotational-vibrational transitions of most molecules take place) not posted.