Bibliothek

Notizen: Flows with coherent structures allow see-free measurements of local velocity and velocity fluctuations. Continuous turbulent velocity histories in ionizing shock waves are obtained at a 10-MHz sampling rate. From this, correlation profiles and frequency spectra are determined which reveal the presence of prominent high-frequency components.

Notizen: Transmission electron microscopy (TEM) has been utilized to study the nickel-silicide growth in self-supported lateral-diffusion, thin-film couples by overlapping deposited layers of Ni and Si between two silicon oxide deposited films. Energy-dispersive x-ray spectroscopy, microdiffraction, and selected area diffraction were used to identify the Ni-silicide phases and their crystal structures. Long-grain growth of Ni2Si, as a result of phase-boundary migration induced by diffusion, was observed during in situ annealing between 500 and 750 °C in TEM. No preferred orientation or particular crystallographic relationship was found among the long grains.

Notizen: Binary diffusion coefficients at high dilution are measured for ethane and ethylene dissolved in cyclohexane at temperatures from 280.5 to 363.2 K and for benzene in cyclohexane and n-hexane up to their critical temperatures. With the effective hard-sphere diameters backed out from self-diffusion data from both solute and solvent molecules and fitted to Protopapas, Anderson, and Parlee's formula, the prediction with the Sung–Stell theory is found to agree to within ±7% of experimental data for wide ranges of solute-to-solvent mass and size ratios at temperatures up to the critical point.

Notizen: Novel gene which was microinjected into fertilized eggs of the goldfish replicated during the embryogenesis. A proportion of the novel gene has been integrated into the host DNS of the 50-day-old transgenic goldfish.

Notizen: Abstract A general model of multiprocessing and multiprocessor systems is given in terms of random fields and statistical mechanics. This model is called cellular processing which is a special application of cellular automata of von Neumann and Ulam. Cellular processing includes several well-known topics, such as image processing, VLSI optimization, and artificial intelligence.

Notizen: [Auszug] CHEN AND DILL REPLY-We agree with Cabane's point regarding the contrast variation technique, mentioned in the first paragraph on page 44 of our article1. But we must emphasize that the original paper by Bendedouch et al.2 did contain firm evidence that there is little penetration of water into the ...

Notizen: Summary Our previous investigations demonstrated an increase in the size of remaining synaptic sites as an intermediate or possible alternative to sprouting plasticity. The total amount of postsynaptic contact area remained relatively constant for each target neuron even though there was a marked decrease in the number of sites on these neurons. In addition, enlarged boutons containing numerous synaptic vesicles were positioned adjacent to enlarged postsynaptic sites. The question posed by this study was to determine whether dense projections, parts of the presynaptic grids of the remaining parallel fibres, spread to cover the enlarged postsynaptic sites, or if the number of these densities increased on each site to maintain the structural organization of the presynaptic grid. In addition, the number of synaptic vesicles per bouton was quantitated to determine whether they compensated by increasing their number in relationship to the increased area of the presynaptic grid. The number of parallel fibre synapses on Purkinje cells was reduced by transection of a narrow bundle of parallel fibres accompanied by a small lesion undercutting the molecular layer to destroy granule cells contributing to this bundle. The number of presynaptic dense projections was quantitated in control and lesioned preparations (using ethanolic phosphotungstic acid staining) in order to determine their correlation to the area of each site. In addition, the average number of synaptic vesicles in boutons was compared to the average size of boutons and the average contact area of the synaptic sites. At 3 to 7 days following partial deafferentation of Purkinje cells in adult rats, the density of dense projections of parallel fibre synapses on Purkinje cell spines remained uniform. This occurred throughout a range of reduction in the number of synapses in conjunction with a reciprocal increase in the size of sites. The finding of a uniform density of these projections and an increase in the size of sites implies that each granule cell axon must gain dense projections. In addition, the remaining presynaptic boutons had a uniform density of synaptic vesicles even though the volume of the boutons and the area of the synaptic contact doubled. Thus, the number of synaptic vesicles gained in proportion to the total enlargement of the contact site and the bouton size. These results strongly suggest that deficits or losses in synaptic connections of parallel fibre on Purkinje cell spines produces a compensation in the total number of synaptic vesicles and presynaptic dense projections of the remaining boutons. An enlargement of the presynaptic grid occurs in concert with redistribution of the constant total area of membrane occupied by macromolecules (or insertion of new ones) on remaining postsynaptic sites. These compensations could be facilitating efficacy of neuronal connections after lesions or neuronal attrition by re-establishing available transmitter and release sites in proportion to the constant amount of receptor area.

Notizen: Abstract Neutron activation analysis has been applied to the determination of ultra-trace amounts of arsenic based on the substoichiometric extraction of As(III) with thionalide. The arsenic content in high-purity trichlorosilane or silicon can be determined by the proposed method down to sub-ppb range with a very good reproducibility. Also, the data obtained were compared with results from atomic absorption spectrophotometry.