Instability of diatomic deuterium in fcc palladium

To clarify some of the solid-state aspects of cold fusion in deuterated transition metal electrodes, we have carried out first-principles self-consistent total energy calculations for various configurations of atomic and diatomic deuterium inside fcc palladium. We find that the stability of the Pd+D system is controlled by the relative position of the deuterium-inducedantibonding level with respect to the Fermi energy. The equilibrium D-D distance in dense PdD up to =3 is found to be much larger than the free space value. The calculated Born-Oppenheimer energy surface of diatomic D₂ in crystalline palladiuim is shown to have but metastable local minima whose internuclear separation is at least 0.2 Ålarger than that of the isolated D₂ molecule. We conclude that D₂ incrystalline Pd will have a substantially lower tunneling probability than hitherto thought and that explanation for fusion mechanisms should be sought elsewhere.     

Comparison of Glass Vessels and Plastic Bags for Enclosing Living Plant Parts for Headspace Analysis

Plants release volatile chemicals into their surrounding air space that can affect the physiology of neighboring plants and influence the behavior of insects. In studying these interactions, it is desirable to collect volatiles from plants that have not been excised and are growing under as natural conditions as possible. We compared a vessel of borosilicate glass and Nylon-6 or polyester [poly(ethyleneterephthalate) or PET] cooking bags for enclosing plants during collection of volatiles. A push–pull airflow system was used, and volatiles were trapped on Tenax TA and analyzed by gas chromatography after thermal desorption. Low levels of impurities were found for the glass vessel and polyester bags. Nylon bags contained higher levels and more impurities. Recoveries of standards of 10 plant volatiles were measured in static and dynamic systems. In a static air system, there was good recovery only from the glass vessel. In a dynamic system, there was generally good recovery from both the glass vessel and polyester bags. Recoveries of α-pinene and (Z)-jasmone were poor throughout. The former was shown to have a very low breakthrough volume on the Tenax TA adsorbent, and the latter may be strongly adsorbed on glass. All three materials were essentially transparent in the IR and visible (photosynthetic) range but with significantly different absorptions in the UV range. In a simulated dynamic entrainment in full sunlight, internal vessel temperatures were higher than ambient by up to 9.5°C in the glass vessel and 7.5°C in the polyester bag. Lower increases in temperature relative to ambient (<1°C) were recorded when entrainments were conducted in the shade. In a field trial, the profiles of volatiles collected from an apple tree infested with rosy apple aphid using a glass vessel and a polyester bag were similar. Polyester bags are recommended as more convenient than glass vessels for the enclosure of plants during the collection of volatiles.     

Optimal neuronal tuning for finite stimulus spaces

The efficiency of neuronal encoding in sensory and motor systems has been proposed as a first principle governing response properties within the central nervous system. We present a continuation of a theoretical study presented by Zhang and Sejnowski, where the influence of neuronal tuning properties on encoding accuracy is analyzed using information theory. When a finite stimulus space is considered, we show that the encoding accuracy improves with narrow tuning for one- and two-dimensional stimuli. For three dimensions and higher, there is an optimal tuning width.     

Bead-assisted displacement immunoassay for staphylococcal enterotoxin B on a microchip

A microchip-based, displacement immunoassay for the sensitive laser-induced fluorescence detection of staphylococcal enterotoxin B is presented. The glass microchip device consists of a microchannel that contains a double weir structure for supporting antibody-functionalized microbeads. After a 30-min sample preparation step, the displacement assay was performed without user intervention and produced quantitative results in an additional 20 min. Linear detection responses were observed over 6 orders of magnitude and provided detection limits down to 1 fM (28.5 fg/mL). The surprisingly low detection limits are hypothesized to arise from field-based enrichment analogous to field-amplified stacking, chromatographic effects, and limited diffusion lengths in the microbead bed. The assay was challenged with bovine serum albumin, casein, and milk sample matrixes. This system has the potential to provide highly sensitive detection capabilities for target biomolecules.     

Cover Picture: Length‐Dependent Uptake of DNA‐Wrapped Single‐Walled Carbon Nanotubes (Adv. Mater. 7/2007)

Well‐defined length fractions of DNA‐wrapped single‐walled carbon nanotubes (SWNTs) of below 200 nm are taken up preferentially by IMR‐90 human lung fibroblasts, while longer DNA wrapped SWNTs are excluded from the cell interior (inset), report Matt Becker and coworkers on p. 939. The cover image construct includes overlaid images of the labeled cell membrane, the nuclei (blue), and the fluorescently labeled DNA wrapped SWNTs (red) that have gained access to the cell interior.     

Microgravity materials and life sciences research applications of digital holography

We investigate the utility of digital holographic interferometry for analyzing gravity-dependent mass transport phenomena as applicable to materials and life science research topics. Digital holography is useful for measurement of parameters that introduce phase changes in light traversing the material of interest, such as temperature or concentration variations in an aqueous environment. We have constructed, tested, and verified a compact, portable digital holographic monitor (DHM) suitable for characterization of transparent samples. It has proved useful for the study of systems such as protein crystal growth solutions and has been proposed for further application into studies involving microbial metabolism. The DHM is also sufficiently rugged for field operation in challenging environments a s may be encountered in a spacecraft or industrial setting. We discuss some system capabilities and limitations.     

Crystal Structure of Ni5P2

It is shown by x-ray diffraction, energy-dispersive x-ray spectrometry, and electron probe microanalysis that, at 800°C, the Ni–P system contains four phosphides in the composition range 25–33 at % P: Ni₃P, Ni₅P₂, Ni₁₂P₅, and Ni₂P. The structure of Ni₅P₂ is determined by single-crystal x-ray diffraction: sp. gr. P3¯c1, new structure type, a = 0.6613(3) nm, c = 1.2311(6) nm, 347 independent hklreflections with F _hkl > 4(F _hkl), R _F = 0.0346. The key structural features of Ni₅P₂ are discussed.     

Expected passes

Data Mining and Knowledge Discovery - Passes are by far football’s (soccer) most frequent event, yet surprisingly little meaningful research has been devoted to quantify them. With the...