Tunneling spectroscopy of palladium-barium emitters

The surface of a palladium-barium cathode was studied using scanning probe microscopy techniques. Data from the tunneling spectroscopy showed the pattern of the electron work function distribution over a microscopic region on the emitter surface. This pattern is compared to the distribution of various phases in the palladium-barium alloy employed.     

General geotechnical concept of tunnel construction in Lefortovo (Moscow) and measures taken to protect historical buildings from deformation

A general concept is cited for the design of an underground transportation tunnel in the Lefortovo District. Attention is focused on problems of the tunnel's layout in plan and profile, the layout of sections, and selection of the driving technology. Results are presented for the numerical modeling of variations in the stress—strain state of the soil mass, which are associated with the tunnel's installation. A set of measures to protect existing architectural monuments is proposed. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 17–21, March–April, 1998.     

Structure and properties of porous silicon obtained by photoanodization

The results of an investigation of layers of porous silicon (PS), which was obtained by electrochemical etching of p-Si under different illumination conditions — natural light, incandescent light, and light from a mercury lamp with and without a filter — are reported. The structure of the layers was studied by double-crystal x-ray diffractometry, the composition was monitored by means of the IR absorption spectra, and the radiative properties were monitored according to the photoluminescence (PL) spectra. It was established that electrochemical etching under illumination produces PS with a higher porosity and more intense PL whose maximum is shifted into the short-wavelength region. These changes are accompanied by a large disordering of the structure and an increase in the oxygen content in the layer. It is concluded that illumination accelerates the chemical interaction of PS with the electrolyte due to oxidation. High-porosity porous silicon stored in air exhibits quenching of PL. Conversely, PL is excited in layers with a lower porosity. Aging of PS is characterized by an increase in the microdeformation of the layers, a decrease in the crystallite sizes with a partial loss of coherence between the crystallites and the substrate, and an increase in the fraction of the amorphous phase. Fiz. Tekh. Poluprovodn. 31, 1261–1268 (October 1997)     

Diurnal thermal cycling effects on microwave signatures of thin seaice

To investigate effects of diurnal thermal cycles on C-band polarimetric backscatter and millimeter-wave emission from sea ice, the authors carried out a winter experiment at the outdoor geophysical research facility (GRF) in the cold regions research and engineering laboratory (CRREL), the ice sheet grew from open sea water to a thickness of 10 cm in 2.5 days, during which they took polarimetric backscatter data with a C-band scatterometer, interlaced with brightness temperature measurements at 90 GHz in conjunction with meteorological and sea ice characterizations. The initial ice growth in the late morning was slow due to high insolation. As the air temperature dropped during the night, the growth rate increased significantly. Air temperature changed drastically from about -12 to -36°C between day and night, the diurnal thermal cycle repeated itself the next day and the growth rate varied in the same manner. Ice temperature profiles clearly show the diurnal response in the ice sheet with a lag of 2.5 h behind the time of the maximum short-wave incident solar radiation. The diurnal cycles are also evident in the millimeter-wave brightness temperature data, measured sea ice backscatter revealed substantial diurnal variations up to 6 dB with repeatable cycles in synchronization with the temperature cycles and the brightness temperature modulations, the diurnal cycles in backscatter indicate that the dominant scattering mechanism related to thermodynamic processes in sea ice is reversible, a diurnal backscatter model based on sea ice electrodynamics and thermodynamics explains the observed diurnal signature. This work shows that diurnal effects are important for inversion algorithms to retrieve sea ice geophysical parameters from remote sensing data acquired with a satellite synthetic aperture radar (SAR) or scatterometer on Sun-synchronous orbits     

Investigation of iron borate on the submillimeter waves

Antiferromagnetic resonance (AFMR) in iron borate at the frequency of 300 GHz at the room temperature in weak (down to 0.1T) external magnetic fieldH has been studied. The loss in AFMR line increased or decreased depending on the direction and magnitude ofH. Such properties ofFeBO ₃ monocrystals allows to design undirectional and modulation devices.     

Effect of spark discharge parameters on the ignition of gas mixtures

The influence of the duration and spatial extent of a heat-releasing spark discharge on the critical conditions of spark ignition of a reactive gas is considered. A region insensitive to the effect of these parameters and, thus, suitable for work with the instantaneous source model is defined. Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 5, pp. 3–7, September–October, 1993.     

Synchronization models for multimedia presentation with user participation

This paper addresses the key issue of providingflexible multimedia presentation with user participation and suggests synchronization models that can specify the user participation during the presentation. We study models like the Petrinet-based hypertext model and the object composition Petri nets (OCPN). We suggest adynamic timed Petri nets structure that can model pre-emptions and modifications to the temporal characteristics of the net. This structure can be adopted by the OCPN to facilitate modeling of multimedia synchronization characteristics with dynamic user participation. We show that the suggested enhancements for the dynamic timed Petri nets satisfy all the properties of the Petri net theory. We use the suggested enhancements to model typical scenarios in a multimedia presentation with user inputs.     

Morphology of amorphous layers ballistically deposited on a planar substrate

Identification of a specific biomolecular target appropriately sensitive to a wide array of anesthetics has been elusive. At concentrations close to their respective ED50's for anesthesia in man or other species, 18 compounds, differing in potencies up to 66,000 fold, inhibited cytochrome P450 mediated metabolism of aminopyrine, a synthetic substrate, and arachidonic acid (AA), an endogenous substrate, in isolated liver microsomes. There was a highly significant correlation for both substrates between the absolute concentrations required for anesthesia (EC50) and for inhibition of P450 activity (Ki or IC50). The mean Ki/EC50 ratio was 0.97 for inhibition of aminopyrine demethylase. The mean IC50/EC50 ratios were 0.42 and 0.64 for inhibition of two AA-derived products and 2.8 for a third; a mean ratio of 1.4 for inhibition of overall AA metabolism suggests interaction of general anesthetics with a composite of P450 isozymes. The universal cytochrome P450 monooxygenases, in conjunction with other lipid oxygenases (cyclooxygenases and lipoxygenases) participate in the second messenger AA cascade. In nerve cells the sensitivity of these enzymes to hydrophobic neurodepressant drugs may underlie the state of general anesthesia: reversible disruption of intracellular and intercellular signalling without impairment of enzymes vital to cell respiration.     

Evidence for a synergistic interaction between isoprenaline and timolol on intraocular pressure in conscious rabbits

1. Interaction between topical isoprenaline and timolol on intraocular pressure was studied in conscious rabbits through changes of the dose-response curves. 2. Both drugs caused a dose-dependent fall of intraocular pressure mainly by reducing the aqueous humour formation. 3. When combined, timolol increased the response to submaximal concentrations of isoprenaline as well as EC50 (from 2.06 x 10(-3) M to 3.63 x 10(-3) M) and slope (from 1.21 to 1.89), but peak response to isoprenaline remained unchanged. 4. Discordance between experimental and theoretical additive curves as well as an interaction index smaller than 1 show that the interaction between both drugs is synergistic.