Geomagnetic polarity change and faunal extinction in the southern ocean

Paleomnlagnietic polarity changes have been detected in nine deep-sea sedimentary cores (from the Pacific-Antarctic Basin) in which an extinction horizon of a radiolarian assemblage was previously independently determined. The depths of the polarity change 0.7 million years ago and the faunal boundary are closely correlated, confirming that the faunal extinction was locally virtually synchronous. Although the reason for the faunal extinction is unknown. the possibility of causal relationships between faunal extinction and factors directly involved with sedimentation rate, sedimentation rate variation, and sediment type appears to be excluded.     

Ecocoenotic aspects of goatsrue seed yield formation depending on density of phytocoenose

The dependence of goatsrue seed yield formation on the density of the phytocoenose, year of growth of the herbage stand, and provision of the growing seasons with moisture and temperature resources is determined The dynamics of density regulation of the process of self-regeneration of the agricultural population with a different initial density of the goatsrue plant stand is revealed.     

Inhibition of cholesterol crystal formation by apolipoproteins in supersaturated model bile

Apolipoproteins A-1 and A-2 were purified from human plasma. At concentrations present in human bile these proteins prolonged the nucleation time of cholesterol monohydrate crystals when added to model systems of supersaturated bile. In contrast, apolipoprotein C-3 and other serum proteins did not have this effect. Also, when human gallbladder bile was fractionated by gel filtration chromatography, apolipoproteins A-1 and A-2 were among the proteins present in a fraction of bile enriched in potent inhibitors of cholesterol crystal nucleation. These findings suggest that apolipoproteins A-1 and A-2 in supersaturated human gallbladder bile could inhibit the rate of formation of solid cholesterol crystals and thus help to prevent spontaneous cholesterol gallstone formation in humans.     

Molecular recognition by self-assembled monolayers of cavitand receptors

It is shown by angle-resolved x-ray photoelectron spectroscopy that cavitands derived from resorcin[4]arenes provided with four dialkylsulfide chains form stable monolayers on gold surfaces that are well organized by self-assembly. The cavitand headgroups at the surface of the resorcin[4]arene monolayer act as molecular recognition sites for small organic molecules with remarkable selectivity for perchloroethylene (C(2)Cl(4)). Comparative thermal desorption experiments indicate binding sites with high interaction energies of C(2)Cl(4) at the surface of the resorcin[4]arene monolayers. Fast and reversible "host-guest" interactions were found by the monitoring of extremely small mass changes (in the nanogram range) with a quartz microbalance oscillator provided with gold electrodes coated by resorcin[4]arene monolayers.     

Spin-dependent WIMP limits from a bubble chamber

Bubble chambers were the dominant technology used for particle detection in accelerator experiments for several decades, eventually falling into disuse with the advent of other techniques. We report here on a new application for these devices. We operated an ultraclean, room-temperature bubble chamber containing 1.5 kilograms of superheated CF3I, a target maximally sensitive to spin-dependent and -independent weakly interacting massive particle (WIMP) couplings. An extreme intrinsic insensitivity to the backgrounds that commonly limit direct searches for dark matter was measured in this device under operating conditions leading to the detection of low-energy nuclear recoils like those expected from WIMPs. Improved limits on the spin-dependent WIMP-proton scattering cross section were extracted during our experiments, excluding this type of coupling as a possible explanation for a recent claim of particle dark-matter detection.     

X-ray Photoelectron Spectroscopic Studies of Interactions in Multicomponent Metal and Metal Oxide Thin Films

Changes in chemical oxidation states in alloys and at solid-solid interfaces were monitored by using x-ray photoelectron spectroscopy. For an oxidized Nichrome surface, the chromium component was selectively converted to chromic oxide while nickel remained in the metallic state. When this surface was overlaid with a 20-angstrom-thick aluminum film, the chromic oxide was reduced to chromium and the aluminum was oxidized to aluminum oxide in a reaction zone consisting of no more than 10 angstroms of the interface. This scheme appeared general for solid-solid contacts and was predicted, to a first approximation, by bulk thermodynamic free energies.     

Heavy metal content in agroecosystems of the Orenburg oblast

Regularities of the distribution of heavy metals depending on the depth of the soil profile have been studied on benchmark plots in the orenburg oblast. Their content in soils and plant industry products has been established.