[en] The authors have recently demonstrated in vitro proliferation of mouse Thy-1⁺ dendritic epidermal cells (EC) to Con A and IL-2. The purpose of the present study was to utilize limiting dilution analysis to determine the precursor frequency (PF) of Con A-responsive cells within EC enriched by Isolymph centrifugation for Thy-1⁺ cells (IEC). AKR IEC were cultured in 96 well U-plates (25-75 cells/well) with 2 μg/ml Con A and 2 x 10⁵ irradiated (1600 R) AKR spleen cells/well. Cultures were harvested after 7-21 days following ³H-thymidine pulsing. Results indicated a PF within IEC of 1.5-4.5%. Inclusion of 10 U/ml IL-2 enhanced significantly the proliferation in positive wells but did not alter this PF. In AKR mice, monoclonal antibody 20-10-5S has been shown to react with Thy-1⁺ EC, but not with peripheral T cells. FACS purification of IEC using 20-10-5S indicated that Con A responsiveness resides exclusively within the 20-10-5S⁺ population. The PF of Con A-responsive Thy-1⁺ EC was calculated by dividing the PF of IEC by the fraction of 20-10-5S⁺ cells (13-30%) in the IEC suspension. A significant proportion of Thy-1⁺ EC (∼12%) were found to possess Con A proliferative capacity. These studies will facilitate analysis at a clonal level of possible functional and phenotypic heterogeneity within the Thy-1⁺ EC population

[en] The neutral fractions were measured for 50-250 keV hydrogen emerging from a NiSi₂(111) surface at several grazing exit angles (the angle between the outgoing hydrogen and the surface). It was found first that the neutral fractions depend strongly on the exit angle, and the values become close to that for pure Si as the energy and the exit angle of the emitting hydrogen decrease. We compared the experimental results with the ones calculated by assuming that NiSi₂ consists of dense atomic layers of Si and Ni. The best fit is obtained with the structural model in which the topmost layer is composed of Si atoms and the second one is Ni atoms. (Author)

[en] Recently the authors reported that Con A stimulates in vitro proliferation of Thy-1+ dendritic epidermal cells (EC). They have not investigated the capacity of Con A-stimulated Thy-1+ EC to secrete IL-2-like activity (IL-2) 7-17EC is a 4 month-old line of Thy-1+ EC established from AKR/J EC by repeated stimulation with Con A and IL-2; these cells were 99% Thy-1+, but <1% L3T4+ and only 4-10% Lyt-2+. 7-17EC were harvested, washed, and plated in 96-well U-plates. Proliferation was assayed after 3H-thymidine pulsing; culture media was tested for IL-2 using the IL-2-dependent HT-2 cell line. With continuous Con A, marked IL-2 secretion (day 2 peak) was followed in parallel by proliferation (day 4 peak). In the absence of Con A, neither IL-2 nor proliferation was seen; however, both were recovered by addition of Con A to cells cultured first for 48 hr in media alone. 7-17EC proliferation was maximal at 0.5-2 μg Con A while maximal IL-2 secretion (100-200 U/ml) was seen at 4-8 μg/ml. That this amount of IL-2 was in excess of that required for their own optimal proliferation was supported by the failure of additional recombinant IL-2 (10 U/ml) to enhance Con A-stimulated proliferation of 7-17EC over a 4 day period. These findings further document the wide range of immunologic capabilities of Thy-1+ cells derived from epidermis

[en] Depth profiles and lattice strain at the interfaces were investigated in ultra thin (<5 nm) layers of HfSiON using high-resolution Rutherford backscattering spectrometry. The used samples were HfSiON films with three nominal nitrogen concentrations (5, 15 and 30 at.%) that were deposited by co-sputtering on Si(1 0 0) substrates using both Hf and Si targets. Accumulation of nitrogen near the interfaces was observed for all the samples, regardless of the nitrogen concentrations. The strain was evaluated by axial angular scan through the <1 1 1> direction. The results obtained from minimum yield dip shift showed that the highest concentration of nitrogen used in this study clearly induced relaxation of the interface strain. In addition, χ_min values at the interfaces, which are defined as the ratios of the minimum channelling yields to random yields, deteriorated with increasing of nitrogen concentration. These results suggest that the incorporation of nitrogen into the interface could cause defects in the interface because of the mismatch between the film and substrate atomic densities

[en] A strong angular dependence has been found first in the neutral fraction of medium-energy hydrogen emerging from NiSi₂(111). The angular dependence can be explained well in terms of the atomic arrangement and composition of the NiSi₂(111) surface and impact-parameter- (trajectory) dependent charge-exchange processes at a few atomic layers beneath the exit surface

[en] The target dependence of equilibrium charge-state distributions was studied for medium-energy (50--500-keV/u) hydrogen and boron emerging from solids. Using a backscattering method, charge fractions were measured for various elemental solid substances with atomically clean surfaces in a pressure range of 10^-8 Pa. The respective charge fractions of hydrogen and boron are found to oscillate with target atomic number Z_t, reflecting the periodic electron shell structures of the target atoms. Comparison between the Z_t oscillations of hydrogen and boron revealed that the oscillatory behavior depends on the final bound state of the captured electrons. This oscillatory behavior can reasonably be explained by the Oppenheimer-Brinkman-Kramers approximation

[en] Short communication. 10 refs

[en] We have examined the infrared (IR) spectra of electron-beam (EB) irradiated C₆₀ films, using in situ IR spectroscopy in the temperature range of 60-300 K. The irradiation-time evolution of the IR spectra shows that two highly intense new peaks finally appear around 565 and 1340 cm^-1 when the EB-induced C₆₀ polymerization was saturated. To determine the cross-linked structure of the polymer explicitly, we have compared the IR spectra with theoretical spectra obtained from the cross-linked structure of all C₁₂₀ stable isomers derived from the general Stone-Wales (GSW) rearrangement, using first-principles density-functional calculations. Since each C₁₂₀ isomer has the same cross-linked structure as that of its corresponding one-dimensional (1D) C₆₀ polymer, the IR modes obtained from the cross-linked structure of C₁₂₀ are close to those obtained from the corresponding 1D polymer. Comparison between the experimental and theoretical IR spectra suggests that the 1D peanut-shaped C₆₀ polymer has a cross-linked structure roughly similar to that of the P08 peanut-shaped C₁₂₀ isomer.

[en] A one-dimensional (1D) uneven peanut-shaped C₆₀ polymer formed from electron-beam (EB)-induced polymerization of C₆₀ molecules showed an anomalous increase in two characteristic infrared (IR) peak intensities, which are respectively due to the radial and tangential motion of the 1D polymer, when compared to the IR peaks of pristine C₆₀ films. This anomaly was analyzed on the basis of the vibrational van Hove singularity (VHS), using an extended thin-shell elastic model fully considering the effects of periodic radius modulation inherent to the 1D uneven peanut-shaped C₆₀ polymer. We succeeded in explaining the enhancement in the tangential peak intensity by VHS, whereas the origin to cause that in the radial peak intensity is still unclear. (paper)

No abstract available