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 JANUARY 5, 2009 [No. 774]

Low cost marker diagnosis with new microfluidic glass and plastic protein chip:   researchers at Caltech in Pasadena have made microfluidic chips that can detect and quantify levels of a dozen different proteins in blood plasma simultaneously. The test needs only a single drop of blood and takes less than 10 minutes. The group used advanced microfluidic biochip and DNA microarray-patterning techniques to carve a series of large and small channels in a thin polymer film. Then, they bonded the film to a glass slide microarrayed with 12 strips of antibodies to specific indicator-of-disease proteins. The device separates blood plasma from whole blood cells, then steers the plasma and the proteins it contains over the antibody arrays for analysis. Fluorescence analysis then reveals any proteins bound to the microarrays, creating a bar-code readout of which proteins are present from each blood sample. When different concentrations of the same antibodies are placed on different microarray strips, the chips can also determine the abundance of target proteins as well. This technique should help develop low cost commercial and simple devices for finding disease protein markers in plasma, decreasing present clinical lab diagnosis cost by three orders of magnitude to just pennies per test.

For more information: Materials Research Society Fall Meeting, December (2008); Science December 19 (2008) page 1784.

WEEK OF DECEMBER 29, 2008 [No. 773]

Nanolaser using a current-driven nanotube made:   researchers at the IBM Watson Research Center (NY) have shown how the integration of carbon nanotubes with high-confinement photonic structures might lead to different types of active nanoscale photonic devices such as emitters, detectors, and modulators. Although emission from direct-bandgap, semiconducting, current-injected carbon nanotubes is weak, spectrally broad, diffuse, and no directional in nature, the group has streamlined carbon-nanotube emission by integrating a carbon-nanotube emitter with a planar microcavity. The nano-emitter is a back-gated, light-emitting field-effect transistor (FET) based on a semiconducting single-walled carbon nanotube in a planar lambda/2 optical microcavity formed by two mirrors. The microcavity is fabricated with three dielectric layer stacks (250 nm PMMA, 22 nm Al2O3, 250 nm SiO) sandwiched between a top 20-nm thick Au mirror and a bottom 100-nm thick Ag mirror. A single nanotube is placed on top of the Al2O3 layer and is oriented parallel to the top and bottom mirror layers for optimum coupling of the nanotube to the modes of the microcavity. The Au mirror is partially reflecting to allow for outcoupling of the cavity mode. The result is a spectral narrowing of the free-space emission of the nanotube that matches the spectral position, line shape, and linewidth of the longitudinal mode of the microcavity, regardless of the nanotube dimensions.

For more information: Laser Focus World, December (2008) page 21; Nature Nanotechnology, August 24 (2008).

WEEK OF DECEMBER 22, 2008 [No. 772]

Quantum state engineering tooling established:   researchers at the University of Florence have shown that if one photon is removed from a beam of coherent laser light, the light remains in the same coherent state. And therefore, they have shown that a coherent state is an eigentstate of the annihilation operator. It was already known (shown theoretically in 1963) that the addition and subtraction of single photons from coherent light does not affect its coherence and that changing the number of photons only changes the amplitude of the beam. In the experiment, a relatively intense laser beam is first passed through a highly-reflective beam splitter, which deflects most of the light into a coherent reference beam. The rest of the light travels straight through the beam splitter and emerges as a relatively weak but still coherent beam. This beam is then sent through a second beam splitter, which is extremely inefficient and only occasionally diverts a photon away from the beam and into a very sensitive detector. Then they looked for any changes in the coherence of the beam by recombining it with the reference beam in an interferometer. The group has put together "creation and annihilation" operators that add and remove photons and have established the noncommutivity of these operators.

For more information: Physicsworld, December 17 (2008); New Journal of Physics.

WEEK OF DECEMBER 15, 2008 [No. 771]

Prostate stem cells identified:   researchers at Genentech in San Francisco have identified a new marker CD117 that is specific to normal prostate stem cells (PSC) from which cancer stems cells might be derived. They looked in a region in the prostate considered to be the stem cell niche. The CD117 is expected to be a marker in human PSCs as well so it should help in the identification of human-prostate-cancer stem cells. This marker completes a set of three other already known cell-surface proteins common to candidate PSCs that together were not specific enough to isolate only potential PSCs. Combined, the four markers form a sort of PSC barcode that can be used to sort out cells from prostate tissue. The identified normal adult stem cells were proven to give rise to all of the cell types within a prostate in mice. These individual cells were used to generate prostates. If cancer stem cells are normal stem cells that have accumulated mutations and are responsible from growth of tumors, a therapy that specifically targets these subpopulations of cells would be needed for a more effective cancer treatment. This is required because, like normal stem cells, these cancer stem cells are long-lived and slow growing, so they are not killed off by treatments that target rapidly dividing, non-stem cancer cells.

For more information: Nature, December 11 (2008) pages 804 and XIII.

WEEK OF DECEMBER 8, 2008 [No. 770]

Artificial control of paralyzed limbs using cortical cells:   researchers at the University of Washington have shown that Macaca nemestrina monkeys can directly control stimulation of muscles using the activity of neurons in the motor cortex, thereby restoring goal directed movements to a transiently paralyzed arm. Neurons could control functional stimulation equally well regardless of any previous association to movement. This is the first demonstration that direct external connections between cortical cells and muscles can compensate for interrupted physiological pathways and restore volitional control of movement to paralyzed extremities.

For more information: Nature, December 4 (2008) page 639.

Heat transport within Earth's mantle dominated by radiation:   German scientists have obtained the near-infrared and optical absorption spectra of silicate perovskite (the main constituent of the lower mantle) to 125 gigapascals (1.25 Matm). The compound remains quite transparent up to the pressures at the core-mantle boundary. Estimates of radiative thermal conductivity derived from these spectra approach 10 w/m/K at lowermost mantle conditions. This implies that heat transport is dominated by radiation. The increase in radiative conductivity with temperature is less pronounced than expected from a T³ dependency.

For more information: Science, December 5 (2008) page 1529.

WEEK OF DECEMBER 1, 2008 [No. 769]

Simple primary electronic-based thermometer standard demonstrated:   researchers at the Helsinki University of Technology and NEC in Japan have invented a type of electronic thermometer that relates temperature directly to the Boltzmann constant and that is simpler to manufacture than others previously proposed. They use the fact that the electrical conductance of an array of tunnel junctions (tiny bits of insulator sandwiched between two metals) changes with temperature. Their single-junction thermometry technique provides good accuracy of measurements at low temperatures (≤ 1 K) by arranging the tunnel junctions in a circuit such that the conductance depends on the properties of just one junction. The tunnel junctions are created by first allowing a very thin layer of aluminum oxide to grow on the surface of µ-wide aluminum electrodes. Another electrode is then deposited on the oxide, creating a metal-insulator-metal junction through which electrons can tunnel. By scanning an applied voltage and measuring the current through the junction, a dip is observed (a dramatic drop in conductance occurs at small voltages with minimum value at 0 volts and rising values around 0 volts for positive and negative voltages). The dip width is proportional to the Boltzmann constant multiplied by the temperature.

For more information: Physicsworld, December 2 (2008); Phys. Rev. Lett., November 14 (2008) page 206801.

WEEK OF NOVEMBER 24, 2008 [No. 768]

Photonic nanomechanical principle shown:   researchers at Yale University have shown a new optical force that can be detected and exploited to move an entire semiconductor device. When they passed concentrated light through an embedded nanomechanical waveguide resonator they induce bending. The optical force causing this displacement can be measured as a change in the coupling between the resonator and its dielectric substrate. The force can be as high as 8 pN /µ/mw, enough to move nanoscale machinery on a chip. This optical force acts perpendicular to the direction of the light beam, so some electrical-based complex nanocomponents like mirrors would not be required in all-optical CMOS compatible photonic nanomechanical systems.

For more information: Nature, November 27 (2008) pages 480 and 458; Physicsworld, November 26 (2008).

Law for iceberg calving discovered:   a group of scientists in Pennsylvania State University and elsewhere in the US, have come up with a simple law that explains much ice-shelf break-up, an important ingredient in predicting the future of the Greenland and Antarctic ice sheets under the global warming process. Ice calving is simply proportional to the along-flow rate of spreading times the width of the shelf times the thickness of the shelf. For narrow shelves between two ridges, the sides hold back the ice, slowing the overall movement and making it harder to break the ice. Thicker ice shelves tend to spread more quickly. The spreading rate can be calculated from ice thickness and other variables already solved in well-established numerical models.

For more information: Science, November 28 (2008) page 1344; Physicsworld, November 27 (2008).

WEEK OF NOVEMBER 17, 2008 [No. 767]

Molecular evolution tracked during a chemical reaction:   a group lead by Japanese researchers has recorded transient impulsive Raman spectra during ultrafast photoisomerization of cis-stilbene in solution (important in the photochemistry of vision). The results demonstrate a gradual frequency shift of a low-frequency vibration of previously considered excited but stationary molecular parts. They observe the evolution of a vibrational motion representing nuclear motions with periods of 160 fs. The technique allows for tracking of molecular vibrations during reactions and the characterization of global motions of the entire molecule.

For more information: Science, November 14 (2008) pages 1073 and 1056.

An excess of galactic cosmic-ray high-energy electrons detected:   an international group of researchers has detected an excess of a factor of ~3 in the flux of cosmic-ray electrons in the 300 - 800 GeV range using the ATIC calorimeter experiment in a balloon high above the Antarctic. The discovery comes right after a similar report of an excess of cosmic-ray positrons. The source of each excess is not known but both indicate either new astrophysical sources or new physical processes. There is controversial speculation that both could be signatures of WIMP (weakly interacting massive particles, a leading candidate for dark matter) annihilation.

For more information: Physicsworld, November 20 (2008); Nature, November 20 (2008) pages 362 and 329.

WEEK OF NOVEMBER 10, 2008 [No. 766]

Cyclic stretching micro-mechanical AC generator:   a group lead by researchers at the Georgia Institute of Technology have used a zinc-oxide wire to create an AC current ~8 pA and a voltage of ~50 mV (~15 times more than with other micro generators). The tiny device generates electric power as it is stretched and then released. They bonded a single wire (4µ thick and 200µ long) onto a flexible insulating polyimide film. The wire is stretched by simply bending the film. The resulting voltage is caused by the piezoelectric effect. No sliding contacts at the ends of the wire are involved. To make an AC generator they connected one end of the wire to a Schottky barrier that allows current flow in only one direction. When the wire is stretched a voltage builds up across the wire, and then, when the wire is allowed to relax, a similar but opposite voltage appears across the wire. An AC voltage of about 50 mV is generated when the wire is stretched by about 0.1% and then released at a rate of 22 cycles per minute by a motor-driven mechanical arm. The device converts mechanical energy to electrical energy with an efficiency ~6.8%. Many wires can be integrated together to boost both the power and voltage output. Increasing the rate at which a wire is strained boosts both the output voltage and current.

For more information: Physicsworld, November 12 (2008); Nature Nanotechnology, November 9 (2008).

WEEK OF NOVEMBER 3, 2008 [No. 765]

Basic circuit models single-cell learning:   scientists at the University of California San Diego have linked a resistor R, an inductor L, and a capacitor C in series and then placed a memresistor across the capacitor to make an electronic circuit that is an analogue of how a single-celled organism learns. The recently realized memresistor has a resistance that varies according to the charge that has flowed through it and then, provides the memory needed for learning. When the external voltage is stable or varying non-periodically, the memresistor exists in a low-resistance state (which dampens the oscillation in voltage across the memresistor set up by the LC). However, when the external voltage varies periodically with a frequency close to the LC resonant frequency, the memresistor switches to a high resistance state, and the oscillations are much less damped. This high-resistance state can persist for so long that a single voltage dip input in the future can also trigger low-damped oscillations. That is, after the circuit receives a series of dips at its input it then remembers that, given just a single dip in the future, it should continue to produce a periodic output. Since periodic signals trigger the memory mechanism, it is expected that the circuit can be used to recognize particular inputs and then, carry out pattern recognition.

For more information: Physicsworld, October 31 (2008).

WEEK OF OCTOBER 27, 2008 [No. 764]

Fast and low cost sequencer proposed:   a scientist at California State University Northridge has proposed a way of sequencing an entire DNA strand without the need for blasting and supercomputer processing used in the conventional shotgun method. The technique involves cutting a very narrow slit (nanogap) in a graphene sheet. A voltage is applied perpendicular to the graphene's surface, which causes the DNA strand to pass slowly through the slit one base at a time. A second voltage is applied across the slit and electrons are able to tunnel across the nanogap via the base that happens to be passing through the slit. There are four different types of bases in a DNA molecule and each should support a different tunneling current, allowing the base type to be identified. While the idea of sequencing DNA by sending it through a tiny gap is not new, previous schemes had relied on using separate materials for the membrane and electrodes, and aligning the two materials has proved difficult. This design gets around this problem by having the graphene function as both membrane and electrode. If run continuously, this sequencer could read the whole human genome in 2.5 hrs. The detector could be made from a graphene sheet sandwiched between glass plates that are held together by van der Waals forces.

For more information: Physicsworld, October 28 (2008).

WEEK OF OCTOBER 20, 2008 [No. 763]

A single molecule trapped at room temperature:   scientists at Harvard have used an Anti-Brownian Electrokinetic (ABEL) trap to pin down one molecule at a time in an aqueous environment at room temperature. The fluorescently labeled molecule is tracked in an optical microscope and its random motion slowed by carefully timed surrounding electrode pulses. The electrodes are at distance that ensures no pollution of the sample environment by chemical effects. The µw electric kicks are imparted to the molecule along micro-channels in an underlying chip.

For more information: Physics New Update, October 23 (2008).

Prebiotic chemistry even more efficient than thought:   American and Mexican researchers have used liquid chromatography and mass spectrometry techniques to discover that a particular variation of the spark-flask apparatus experiments used in the "primordial soup" experiments by Miller at the University of Chicago in the early 50's, produced a wider variety of amino acids than initially reported by Miller. The classical experiments produced an electric discharge into a flask with CH₄, NH₃, H₂, and H₂O. The non-classical apparatus had an additional hot water mist added to the classical spark flask, simulating a water vapor-rich volcanic eruption.

For more information: Science, October 17 (2008) page 404; Chem. Eng. News, October 20 (2008) page 12.

WEEK OF OCTOBER 13, 2008 [No. 762]

Spin Seebeck effect observed for the first time:   Japanese scientists have discovered that a current of spin-polarized electrons can be generated by creating a temperature gradient along a length of a magnetic metal. The group has reported the observation of the thermal generation of driving power (or voltage) for electron spin. Using a recently developed spin-detection technique that involves the spin Hall effect, they have measured the spin voltage generated from a temperature gradient in a metallic magnet. This thermally induced spin voltage persists even at distances far from the sample ends, and spin can be extracted from every position in the magnet simply by attaching a metal. The team first deposited a 20 nm thick layer of a permanent magnet alloy (Ni₈₁Fe₁₉) onto a Sa substrate to create a sheet 6 mm long and 4 mm wide. The sheet was magnetized in the long direction (same direction as the temperature gradient). That causes an excess of spin-up electrons to build up at the cold end of the sheet and an excess of spin down electrons at the warm end. The spin Seebeck effect allows the pass of a pure spin current (a flow of electron spins without electric currents) over a long distance (mm's). This discovery is directly applicable in the production of voltage generators for driving spintronic devices.

For more information: Nature, October 9 (2008), pages 778 and 741; Physicsworld, October 8 (2008).

WEEK OF OCTOBER 6, 2008 [No. 761]

Eliminating the quantum-mechanical stickiness of MEMS and NEMS:   scientists at the Los Alamos laboratory in New Mexico have proposed a quite promising way to manipulate the Casimir force to make micromachines and nanomachines run smoother and with diminished or no friction at all. The idea is basically to coat the surfaces with magnetic metamaterials engineered to support eddy currents that compensate for the Casimir attraction. The copensation would come about because the virtual photons would induce electromagnetic fields in the surfaces that would push them apart so strongly that they would overwhelm the pressure of virtual photons squeezing the plates together.

For more information: For more information: IEEE Spectrum, October (2008), page 18.

Easy scale of vertical solid surfaces with nanoengineered pads:   researchers at the Georgia Institute of Technology have made a structure that looks at least similar to a gecko lizard foot using chemical vapor deposition of an ethyne-hydrogen-argon gas over a silicon substrate. By introducing an iron catalyst on the substrate and controlling the temperature and duration of deposition, they ended up with an array of vertical nanotubes with curly entangled tops. The material exhibits an anisotropic adhesive force distribution of 100 Ncm^-2 (an order of magnitude greater than a gecko foot) due to the shear-induced alignments of nanotube tops. If stuck to a wall it will resist a strong downwards tug, but if it is pulled directly away, it will peel off easily.

For more information: Science, October 10 (2008), page 238; Physicsworld, October 9 (2008).

WEEK OF SEPTEMBER 29, 2008 [No. 760]

Room temperature MRI with single-spin sensitivity and nano resolution:   scientists at both Harvard and Stuttgart Universities have developed a new approach that exploits a single spin associated with a special flaw in diamond (nitrogen vacancy impurity center) to detect magnetic fields on the nanoscale. The single spin can be placed on the tip of a SPM to pick up signals by the spin of an electron or an atomic nucleus placed nearby. The probe spin can feel the presence of any magnetic fields created by nearby electrons or nuclei, which cause a shift in its EPR frequency. Owing to the ultralong relaxation times of N-vacancy electron spins in diamond, single spin MRI is possible and operates under ambient conditions.

For more information: Nature, October 2 (2008), pages 644, 648 and 606; Physicsworld, October 2 (2008).

Protein motion observed in the nanosecond time scale:   an international team of researchers at the ESRF in Grenoble has developed a synchrotron-based structural analysis technique, TR-WAXS (time-resolved wide-angle X-ray scattering), to observe the kinetics of protein conformational changes down to the nanosecond range (the popular existing WAXS has been limited to millisecond time resolution) under nearly physiological conditions. They observed conformation changes in hemoglobin caused by photodissociation of CO. Existing spectroscopic techniques with equivalent or better time resolution help study protein conformational changes, but they do not provide the detailed structural data that TR-WAXS does.

For more information: Chem. Eng. News, September 29 (2008), page 11; Nature Methods, September 21 (2008), page 881.

WEEK OF SEPTEMBER 22, 2008 [No. 759]

Measuring the basic unit of muscle contraction:   scientists at Stanford University in California have created a minimally invasive microendoscopy system that images basic contractile units of striated muscle (sarcomers composed of myosin motors and acting filaments) at work. They adapted a laser-scanning microscope with the objective focusing ultrashort pulsed laser illumination from a wave-length-tunable Ti:Sa laser onto the face of a gradient refractive index microendoscope. The excitation and resulting emission traveled part of the way along the same path, with a dichroic mirror sending the emission off to a PMT for detection.

For more information: Biophotonics International, September (2008), page 20.

Geomagnetic field flips due to interaction between two core layers:   researchers at the California Polytechnic University and the University of Wisconsin-Madison have measured ancient field patterns frozen into volcanic rocks to discover that there is a non-axial dipole component of Earth's magnetic field. The axial dipole main component is caused by convective flow deep within the liquid Fe core and is prevalent on Earth's surface. The weaker newly identified component comes from the top of the outer core and it seems to be the cause of the flipping that has occurred at times on Earth's magnetic field.

For more information: Physicsworld, September 25 (2008); Science, September 26 (2008), pages 1800 and 1756.

WEEK OF SEPTEMBER 15, 2008 [No. 758]

Nanosecond TEM:   scientists at the Lawrence Livermore Lab in California have used a photoemitted electron pulse (laser pumped electron gun) to probe dynamic events with snapshot diffraction and imaging at 15-nanosecond resolution inside of a dynamic transmission electron microscope (TEM). The moving reaction front of reactive nanolaminates is observed in situ. Time-resolved images and diffraction show a transient cellular morphology in a dynamically mixing, self-propagating reaction front, revealing brief phase separation during cooling, and thus provide insights into the mechanisms driving the self-propagating high-temperature synthesis.

For more information: Science, September 12 (2008), pages 1472 and 1413.

Stable quantum gas of polar molecules created:  a group lead by researchers at NIST-Boulder has created the first stable ultracold (350 nK) dense (10¹² cm^-3) quantum gas of molecules with large electric dipole moments. Unlike other quantum gases, the molecules interact with each other over relatively large distances. The group starts with a very cold gas that is a mixture of K/Rb atoms confined by a laser beam and within a magnetic field. A two wavelength NIR laser is used to cause the molecules to give up their internal energy as photons of red light, which exit the gas without heating it. This leaves the majority of the molecules in their lowest vibrational and rotational energy states. The team measured the dipole moment by applying a small electric field to the gas and determining the resultant shift in the molecule's energy levels using laser spectroscopy. Qbits made from such molecules would be robust to interference from outside influences and could be manipulated by the simple application of an electric field.

For more information: Science Online and Physicsworld, September 18 (2008).

WEEK OF SPTEMBER 8, 2008 [No. 757]

MicroTesla brain MRI demonstrated:   scientists at the Los Alamos Lab in New Mexico have obtained images of a living human brain using pre-polarization at 30 mT and image collection at just 46 µT. Using such small fields means that the frequency of the signals produced by the oscillating nuclear spins are similarly reduced from the usual RF range to around an audible 2 kHz. The magnetic resonance signals were detected using superconducting quantum-interference devices (SQUIDs) capable of detecting both nuclear spins (MRI) and neuronal activity fields for simultaneous magnetoencephalography (MEG) recording.

For more information: Journal of Magnetic. Resonance, September (2008), page 115; Nature, September 4 (2008) page 43.

Laser frequency comb used in astronomical spectrum calibration:   a group of German and Australian researchers have demonstrated the use of a laser frequency comb for wavelength calibration of a telescope. They combine the fiber optic laser frequency comb (spectrum of a fs mode-locked laser that delivers pulses at rep rates of ~1 GHz with equally spaced wavelengths) with a solar observation to precisely measure and calibrate the wavelengths of the spectrogram. They obtain absolute calibration with an equivalent Doppler precision of 9 m/s at ~1.5 µ. This technique promises wavelengths to be measured with a stable precision of 0.1 ppb and Doppler accuracies of 1 cm/s per year as required for real time measurement of the Universe acceleration.

For more information: Science, September 5 (2008), pages 1335, 1301, and 1268.

WEEK OF SEPTEMBER 1, 2008 [No. 756]

Room temperature catalyst for disposal of inert fluorocarbons:   scientists from the Brandeis University in Boston have used a class of carborane-supported, highly electrophilic silylium compounds, to show that silylium-carborane catalysts are long-lived catalysts for hydrofluorination (conversion of very unreactive C-F bonds to C-H bonds) of trifluoromethyl and nonafluorobutyl groups by widely accessible silanes under mild conditions. The reactions are completely selective for aliphatic carbon-fluorine bonds in preference to aromatic carbon-fluorine bonds.

For more information: Chem. Eng. News, September 1 (2008), page 13; Science August 29 (2008) pages 1188 and 1168.

Geodynamo simulation gets worse as conditions are made more realistic:   researchers at Yokohama have used the 4,096 processor Earth Simulator supercomputer to do simulations of the geodynamo with conditions closer to reality than ever before. They find that both the convection flow and the magnetic field structures are qualitatively different from those found before. The convection takes the form of sheet plumes rather than the columnar cell structures usually found. A laminated flow pattern still acts as an efficient dynamo but the magnetic field produced is not predominantly dipolar.

For more information: Nature, August 28 (2008), pages 1106, 1058, and VII.

WEEK OF AUGUST 25, 2008  [No. 755]

Galactic emission filaments supported by magnetic fields:   scientists from Cambridge and elsewhere in UK and the US have used imaging from the Hubble Space Telescope to resolve long thin strands (thread-like structures) within the nebulosity of the emission-line filaments in the giant elliptical galaxy NGC 1275 at the center of the Perseus Constellation galaxy cluster. The bright filaments of ionized gas are dragged out from the center of the galaxy (where a black hole emits jets of gases) by radio-emitting bubbles rising buoyantly in the hot intracluster gas. When the bubbles become buoyant they drag some of the cooler gas from the center of the galaxy outwards (the observed filaments are simply this gas being dragged outwards). The filaments look as static markers of the feedback process by which energy is transferred from the central massive black hole to the surrounding gas. These filaments remain stable (they are thought to be at least 100 Myr old) despite the disruptive effects of extreme pressure by tidal shear forces and extreme heat by very hot (40 MK) surrounding gases. The team concludes that galactic magnetic fields (~10^-4 Gauss) within the threads maintain the filament's structure by holding the pressure balance with the surrounding gas. The stabilization of the filaments allows for the accumulation of a large mass of cold gas that delays star formation.

For more information: Nature, August 21 (2008), pages 968, IX and XI.

WEEK OF AUGUST 18, 2008 [No. 754]

Nanopillar magnetic moment flipped in one nanosecond:   scientists from the PTB in Germany have shown that by adequately controlling the temporal shape and length of a pulse of spin-polarized electrons and by applying small constant magnetic field, they can reduce the present flipping time of magnetic nanopillars by an order of magnitude. This could lead to magnetic access random memories that are as fast and as dense as conventional memory chips but less energy consuming and persistent after switching off the electric supply. Commercial GHz MRAMS might be a couple of years away now.

For more information: Physicsworld, August 21 (2008); Phys. Rev. Lett., to be published.

Solar cells with over 40% efficiency :   researchers at the Department of Energy NREL lab in Colorado, have produced a record solar-cell efficiency with a thin and light photovoltaic device that converts to electricity 40.8% of the concentrated sunlight it receives in tests. The group uses a high-sunlight conversion metamorphic triple-junction (with mismatched semiconductor lattices) solar cell made from a composite of GaInP and GaInAs materials, to split the solar spectrum into three equal parts to be absorbed by each of the cells three junctions.

For more information: Chem. Eng. News, August 18 (2008), page 26.

WEEK OF AUGUST 11, 2008 [No. 753]

Not instant quantum entanglement:   scientists from the University of Geneva have placed a lower boundary on the speed of any possible entanglement signal between entangled photons. They performed a test over more than 24 hrs between two villages separated by 18 km and approximately east-west oriented, with the source of entangled photons located precisely in the middle of the optical path. They calculated that if a privileged reference frame exists (with Earth's speed on it < 0.001 c), the entanglement signal speed would have to be > 10,000 c.

For more information: Nature, August 14 (2008), page 861; Physicsworld, August 13 (2008).

Working visual memory capacity explained:   researchers at the University College London have shown that visual memory capacity is not fixed by the number of objects (currently understood as four), but rather is a limited resource that is shared out dynamically between all items in the visual scene. This resource can be shifted flexibly between objects. The proportion of resources allocated to each item determines the precision with which it is remembered.

For more information: Science, August 8 (2008), page 851.

Dark energy identified by direct observation:   scientists from the University of Hawaii have analyzed the glow of the cosmic microwave background and have focused on a single sample of the biggest superclusters and supervoids. They have clearly shown how the superclusters are being stretched apart (rather than stay the same as predicted by general relativity). This is after a decade of the repulsive dark energy idea, the first time that its effect is neatly and reliably seen on a direct measurement (amounting to a millionth of a Kelvin photon energy variation).

For more information: Physicsworld, August 8 (2008)

WEEK OF AUGUST 4, 2008 [No. 752]

Ballistic molecular junctions fabricated:   an international team lead by researchers from the University of Leiden have fabricated the first highly conductive molecular junctions by forming a direct metal-carbon bond between a single organic molecule (benzene) and a metal (Pt) electrode. They verified that electrons are conducted easily between the two and measured the conductance of these devices to be the maximum value possible for a single electron channel.

For more information: Physicsworld, August 2 (2008); Phys. Rev. Lett., to be published.

Electrolysis simplified:   scientists at MIT have devised a novel cobalt phosphate catalyst for water splitting that forms in situ on the surface of an indium tin oxide electrode. This is a vast departure from expensive pt-based systems that require strongly basic or acidic conditions, operate at high temperature, and may never be economically viable on an industrial scale. The catalyst is made from inexpensive Co salts and K₃PO₄ buffer at neutral pH.

For more information: Chem. Eng. News, August 4 (2008), page 7; Science, August 1 (2008), page 620.

Abrupt climate change in a year:   an international team lead by researchers from the University of Copenhagen have measured multiple climate proxies (like ¹⁸O for local temperature, D for ocean surface temperature, dust for Asian desert status, and Na for marine sea salt) in a single ice core from Greenland. Measuring several parameters in the same ice eliminates problems in trying to intercalibrate data from different sites. High-resolution measurements show yearly climate changes during two abrupt warmings within the last deglaciation.

For more information: Science, August 1 (2008), pages 680, 650 and 608.

WEEK OF JULY 28, 2008 [No. 751]

Plasma collimator for diode lasers:   researchers at Harvard University and Hamada's Photonics have used a patterned metallic film on the output facet of a semiconductor laser to absorb divergent light and reemit it in one direction. The film has a slit 2µ wide; adjacent to a series of parallel grooves 0.8µ wide, 1.5µ deep and separated by 8.9µ. The laser emits at 9.9µ. Some laser light is absorbed creating surface plasmons (collective electron excitations) on the surface of the film. The plasmons propagate across the film and are scattered by the grooves, which results in their conversion back into light with the same wavelength as the laser. The divergence of the plasmon-collimated laser was about 2.4 deg (vs. 63 deg for the bare laser).

For more information: Physicsworld, July 31 (2008); Nature Photonics, to be published.

Triggering of Earth's aurora sub-storms understood:   researchers working on NASA's Themis mission have uncovered a mechanism that drives the Northern and Southern Lights. Auroras form by the collisions of electrons and other charged particles in the magnetosphere. Occasional substorms create increases in size, brightness and coloring. Themis has spotted an isolated substorm shortly before a network of ground-based observatories detected an auroral brightening over the northern US. The data collected indicates that the solar wind induces magnetic field reconnection releasing magnetic energy and creating a substorm.

For more information: Physicsworld, July 25 (2008); Science, to be published.

WEEK OF JULY 21, 2008  [No. 750]

Liquid-based deformable mirror demonstrated:   researchers at Laval University in Quebec have built the first deformable liquid mirror from a magnetic liquid. They made their mirror from a ferrofluid containing tiny particles of magnetite (Fe₃O₄) each about 10 nm in diameter. When ferrofluids are exposed to a magnetic field, the bulk of the liquid becomes magnetized and its surface acquires a shape to minimize the energy of the system (this involves gravitational and magnetic forces as well as the surface tension of the liquid). The ferrofluid is contained in a dish that sits above a triangular array of 37 magnetic coils, each 5 mm in diameter. By controlling the current of each coil, the surface profile of the mirror can be manipulated at near MHz frequency.

For more information: Physicsworld, July 24 (2008).

Trick to increased catalytic efficiency identified:   scientists at the Dalian Institute of Chemical Physics have shown that confining metallic nanoparticles inside carbon nanotubes (CNT) alters the redox properties of the particles and can enhance their effectiveness as catalysts. They used a solution-phase method aided by ultrasonication to selectively deposit iron oxide nanoparticles inside CNTs. These particles are precursors for the catalyst used in FT synthesis, a C-coupling method for making synthetic fuels from mixtures of CO and H. They find that confined particles are more prone to chemical reduction than particles attached to the exterior of the nanotubes.

For more information: Chem. Eng. News, July 14 (2008) page 9; J. Am. Chem. Soc., to be published.

WEEK OF JULY 14, 2008 [No. 749]

Pumped atom laser demonstrated:   researchers at Australian National University have situated a lasing Bose-Einstein Condensate (BEC) some 8 µ beneath a second BEC, so that it can be drip fed with atoms from above. As the atoms from the upper BEC are falling they are slowed by an optical laser pointed upwards, which forces each atom to absorb a photon. Shortly after, the atoms emit their own photon downwards, thereby slowing their descent further. Then the atoms from the upper BEC join the lasing BEC without disturbing it, and without creating any noise.

For more information: Nature Physics, July 11 (2008); Physicsworld, July 17 (2008).

Graphene the strongest material ever:   researchers at Columbia University have shown grapheme to be the strongest material in the world due to the robustness of it covalent C-C bond. They indented graphene films, placed over holes on a Si wafer, using an AFM with a diamond tip with a radius of 20 nm (conventional Si tips would break before the grapheme breaks). If a sheet of cling film (with a typical thickness of 100 µ) were to have the same strength as pristine graphene, it would require a force of over 2 tons to puncture it with a pencil. The measured strength is > 200 times that of structural steel and > 20 times that of advanced C fibers.

For more information: Science, July 18 (2008) page 385; Physicsworld, July 17 (2008); Chem. Eng. News, July 21 (2008) page 46.

Single hydrogen atom seen:   scientists at the University of California, Berkeley have used a transmission electron microscope (TEM) to see a single H atom, the first time that a TEM has been used to image such a light atom. A graphene sheet was used as substrate because of its strength while being just an atom thick. Graphene has minimal influence when imaging the overlying material of interest (the carbon atoms within the graphene are invisible to the TEM).

For more information: Nature, July 17 (2008) page 319 and 283; Physicsworld, July 16 (2008); Chem. Eng. News, July 21 (2008) page 9.

WEEK OF JULY 7, 2008 [No. 748]

Directed assembly of carbon nanotubes for network thin-film transistors:   esearchers at Stanford University and Samsung have devised a way to sort single-walled carbon nanotubes (SWNTs) according to their chirality by simply functionalizing the surface of Si. SWNTs are produced as a mix of both semiconducting and metallic nanotubes depending on their chirality. The group found that semiconducting nanotubes preferentially cling to substrates with a coating of primary amines, while metallic tubes hold fast to substrates functionalized with phenyl groups. So they added functional group coatings to the surface of Si substrates and then applied SWNTs via spin coating. From a typical SWNT blend, the team was able to make transistors enriched with 90-95% of the nanotubes of desired chirality. The technique allows for both efficiently separating the two types of nanotubes and to pattern them onto a substrate as thin films. In just one step they formed the heart of a transistor (i.e., the critical channel between electrodes made of aligned, densely packed semiconducting nanotubes) that turned off and on much more efficiently than previous transistors made with bunches of nanotubes (on / off ratio as high as 900,000) and comparably to Si. The new technique is amenable to large-scale fabrication.

For more information: Science, July 4 (2008) pages 101 and 12; Chem. Eng. News, July 7 (2008) page 8; Physicsworld, July 4 (2008).

WEEK OF JUNE 30, 2008 [No. 747]

Ordered mesoporous metals prepared:   researchers at Cornell University have developed a synthesis for ordered metallic materials that feature pores in the previous unattainable 10 nm size range. It has been difficult to achieve because metals have high surface energies that favor low surface areas that cause particles to cluster. The group used ionic-liquid ligands to render the 1.8 nm Pt particles soluble preventing their agglomeration. When combined with block copolymers, the metal particles self-assemble to form ordered metal-organic hybrid structures. Then they use various heat treatments and etching procedures to remove the organic components.

For more information: Chem. Eng. News, June 30 (2008) page 10; Science, June 27 (2008) page 1748.

Desalinization through nanomembranes shown:   scientists at the Lawrence Livermore Lab have created filtration membranes by embedding nanotubes in a SiN matrix and then uncapping the ends of the tubes by an etching process that also introduced carboxylate groups around tube entrances. The carboxylate groups form a ring of negative charges through which ions must pass to enter the tubes. In this way, the group has demonstrated that arrays of densely packed, vertically aligned carbon nanotubes can serve as membranes to filter ions out of water while allowing the water to flow significantly faster than through conventional filters. In these nanomembranes, ion exclusion stems primarily from electrostatic rather than spatial effects.

For more information: Chem. Eng. News, June 23 (2008) page 29; Proc. Natl. Acad. Sci. USA to be published.

WEEK OF JUNE 23, 2008 [No. 746]

Very high energy gamma rays emitted from 5 billion light years away detected:   an international team of scientists from the Max Planck Institute for Physics in Munich and elsewhere has detected a flare of VHEGRs created over 5 Byrs ago in the Radio Quasar 3C 279. This is the oldest such burst of gamma rays ever detected. These GRs, with energies between 80 and 500 GeV, traveled through the extragalactic background light (EBL), which is a strong absorber of such gamma rays. A conclusion of the measurements is that most current theories tend to over estimate the density of the EBL. Gamma-ray telescopes might be used to trace the evolution of the EBL much farther back in the history of the universe than expected before.

For more information: Science, June 27 (2008) page 1752; Physicsworld, June 26 (2008).

X-ray diffraction microscopy of a single virus:   scientists from UCLA have used X-rays to image single viruses by separating the diffraction pattern of the virus from that of their surroundings. The intensity of the resulting diffraction pattern is measured and the relative phases of the X-rays within the pattern are recovered by use of an algorithm. The new technique allows obtaining diffraction patterns of unstained viruses whose molecular masses are a thousandth of previous specimens. The group has generated high-contrast images of single viruses with a resolution of 22 nm. They used a coherent beam of X-rays in a synchrotron beam line but the technique could be used with small-scale lab X-rays sources as well.

For more information: Physicsworld, June 25 (2008).

WEEK OF JUNE 16, 2008J [No. 745]

Binding occurs when a protein spontaneously takes the right shape:   scientists from the Max Planck Institute for Biophysical Chemistry in Goettingen and Vanderbilt University in Nashville have used NMR to map out all possible shapes of free ubiquitin, a protein found in many living cells. The rather new NMR technique used here can follow the positions of atoms in a molecule on time scales for up to several microseconds (traditional NMR can only detect motion on nanosecond time scales). The team compared the structural ensemble of free protein shapes with the 46 shapes that ubiquitin is known to adopt when bound with larger structures (bound proteins have different shapes than their free counterparts). Free proteins are observed to fluctuate between many different shapes in the absence of a binding partner and the group discovered that every one of the bound shapes also occurred in the free protein. They concluded that no induced-fit motions are required for ubiquitin to adapt to its binding partners (this theory prevalent for over fifty years claims that a free protein is coaxed by its binding partner to undergo a gradual change in its shape during the binding process). Conformational selection has been hard to establish until now because standard techniques such as X-ray diffraction and conventional NMR cannot identify the large number of short-lived shapes that a free protein can adopt.

For more information: Science, June 13 (2008) pages 1471 and 1421; Physicsworld, June 17 (2008).

WEEK OF JUNE 9, 2008 [No. 744]

Artificial protein refolding shown:   scientists from the University of Massachusetts at Amherst have devised Au nanoparticles coated with 2-(10-mercaptodecyl) malonic acid and used them to refold thermally denatured proteins. Activity assays and circular dichroism spectroscopy have shown that the proteins refold into nearly native conformations. It needs to be shown if this technique can be used to refold proteins from chemically denatured states, as is often required for biotechnology applications. The nanoparticles prevent aggregation of unfolded proteins by binding to positively charged residues. Removing the nanoparticles by increasing the salt concentration of the solution frees the proteins to refold.

For more information: Chem. Eng. News, June 9 (2008) page38; Chem. Commun., to be published (2008).

New ranked strongest chemical base:   an international team lead by researchers from the University of Minnesota has discovered the world's strongest base, the gas-phase lithium monoxide anion, LiO^-. The compound wins out over the methyl anion, CH₃^-, the previous titleholder for three decades. CH₃^- until now had the highest measured affinity of any compound to regain a lost hydrogen ion, making it the strongest base. The team synthesized LiO^- by using Ar atoms to fragment LiC₂O₄^- in an electrospray ionization mass spectrometer. The process sequentially knocked out CO₂ and CO molecules to form LiO^-. Thermodynamic measurements on LiO^- confirmed its record basicity (LiOH is about 9 kcal/mol or 2% less acidic than CH₄).

For more information: Chem. Eng. News, June 9 (2008) page 10; Proc. Natl. Acad. Sci. USA, June 3 (2008) page 7647.

WEEK OF JUNE 2, 2008 [No. 743]

Solid state entanglement at room temperature:   an international team of scientists lead by scientists from Stuttgart University has demonstrated the creation of bipartite- and tripartite-entangled quantum states in a small quantum register consisting of individual ¹³C nuclei in a diamond lattice. Individual nuclear spins are controlled via their hyperfine coupling to a single electron at a nitrogen-vacancy defect center. They shine laser light placing some nuclei into a certain quantum state. By applying RF pulses they drive the spin of the nuclei to become entangled with one another. Quantum correlations are of high quality and persist on a millisecond time scale even at room temperature as required for quantum operations.

For more information: Science, June 6 (2008) page1326; Physicsworld, June 5 (2008).

Production of single crystals with a large percentage of reactive facets:   Australian and Chinese researchers have synthesized uniform anatase TiO₂ single crystals with a high percentage (47%) of {001} facets using HF acid as a morphology controlling agent. On the basis of theoretical predictions they have demonstrated that in fluorine-terminated surfaces the stability configuration, where the thermodynamically stable {101} facets dominate with a percentage of 94% over the more reactive {001} facets, can be reversed. The fluorated surface can be easily cleaned using heat treatment without altering the crystal structure and morphology.

For more information: Chem. Eng. News, June 2 (2008) page 12; Nature, May 29 (2008) page 638.

WEEK OF MAY 26, 2008 [No. 742]

Room temperature Terahertz laser:   researchers at Harvard and elsewhere in the US and Switzerland have made the first room-temperature coherent terahertz source based on commercially available semiconductor technology. Until now, the only compact semiconductor lasers to emit light at terahertz wavelengths were QCLs (quantum cascade lasers) and did so at below 200 K. The new QCL lasers are a few mm's in size, are electrically driven, and emit several nanowatts at room temperature, microwatts at 259 K (thermoelectric cooler temperature), and milliwatts (by optimizing the semiconductor nanostructure layers of the laser's active region and by improving the extraction efficiency of the terahertz radiation).

For more information: Physicsworld, May 28 (2008); Appl. Phys. Lett., May 28 (2008) 211104.

Nanotoxicology shown in cases:   scientists at the University of Edinburgh have injected 50 µg of rigid multiwalled carbon nanotubes (MWNTs) into the abdominal cavity of mice and observed their effect on the mesothelial layer of cells that line the cavity. They found that when MWNTs were straight and longer than 20 m, they caused the same type of inflammation and granuloma (scar formation) as asbestos. In contrast, shorter MWNTs, tangled nanotube aggregates, and nanoparticulate carbon black, did not cause any inflammation or granuloma formation. The indication is that toxicity is a function of size and shape, not chemistry.

For more information: Chem. Eng. News, May 26 (2008) page 9; Nat. Nanotechnol., to be published (2008).

WEEK OF MAY 19, 2008 [No. 741]

Practical polariton light emitting diode:   researchers at the University of Crete in Greece have fabricated a semiconductor polariton LED that works at near room temperature and is electrically driven (rather than operating at cryogenic temperatures and being powered by a laser like its predecessors). A polariton is a quasiparticle consisting of an exciton (electron-hole pair) and a photon (which is emitted when the electron and hole recombine). When a photon is emitted, it remains trapped in the material and creates another exciton so the cycle is repeated. Photons are trapped in a tiny microcavity that is created between two highly reflecting Bragg mirrors. Excitons are trapped in quantum wells placed at the two ends of the microcavity to enhance their coupling to the photons. Metal contacts are formed at the bottom and on the top of the device to inject electrons and holes respectively. The fabrication process used molecular beam epitaxy techniques. The group created an electron-hole pair in an InGaAs quantum well with distributed Bragg reflectors in both sides. Then, they constrained the polariton with highly reflective layers of GaAs and AlAs in both ends of the system. Finally they applied and electrical current to excite the system to emit light directly from polariton states creating a steady source of light at -38C (polariton electroluminescence had previously been achieved only at -196 C).

For more information: Nature, May 15 (2008) pages 372 and 297; Chem. Eng. News, May 19 (2008) page 9; Physicsworld, May 19 (2008).

WEEK OF MAY 12, 2008 [No. 740]

Biological eyes can see circularly polarized light:   German and Australian researchers have shown that mantis shrimp can detect any possible combination of linear and circular polarization. These creatures have two spherical compound eyes, each of which comprises hundreds of smaller eyes organized into three substructures, two hemispheres separated by a mid-band. The team shone light of different linear and circular polarizations on the three substructures of the small eye units and measured the electrical response of the photoreceptors within. They discovered that the photoreceptors in the hemisphere respond to light with different linear polarizations, while the mid-band was sensitive to circularly polarized light. They detect circular polarization in the mid-band region by first passing light through a biological cell that appears to act as a quarter wave plate converting circularly polarized light to linearly polarized light. This light is then detected by cells sensitive to linearly polarized light. This ability allows the shrimp to perceive very subtle changes in light polarization and improve their view of their environment. Some of their prey are transparent and hard to see in sea-water, except that they are packed with polarizing sugars which, consequently, can be detected. Since light reflecting from mantis shrimp is circularly polarized, polarization vision might also be involved in the mating process.

For more information: Physicsworld, May 14 (2008).

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.