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Notes: Vibrational excitation of an Ar55 cluster in collisions with He (Ekin=25 meV) is investigated by using classical trajectories and a highly approximate quantum mechanical method (vibrationally sudden approximation). The energy transfer from the helium atom to the cluster (ΔE) is calculated as a function of the scattering angle θ. It is found (i) that predominantly the modes corresponding to the cluster atoms in the outer shell are excited and (ii) that the probability for multi-phonon (Δn≥2) excitations steadily increases with the scattering angle. The results of both sets of calculations are generally in good agreement with measured energy loss spectra over the entire range of scattering angles. In the region θ(approximate)15°–30°, which—because single-phonon transitions dominate—is most important for determining the frequency distribution of the cluster, the quantum mechanical calculations are superior to classical mechanics; the latter fails to conserve zero-point energy and therefore leads to unrealistic energy transfer below ΔE(approximately-less-than)2 meV. © 1997 American Institute of Physics.

Notes: Superconducting tunnel junctions (STJs) are promising as high energy resolution x-ray detectors. However, the theoretical limit of the energy resolution of STJs has not yet been reached for several reasons. In many cases quasiparticle losses limit the energy resolution. We have investigated STJs with different multilayer structures by means of low temperature scanning electron microscopy. By measuring the quasiparticle lifetime of Nb junctions with and without Ta passivation at the surface, we have identified quasiparticle losses at the surface of nonpassivated junctions as the dominant loss process. The temperature dependence of the quasiparticle lifetime gives information about the loss mechanism. The influence of quasiparticle traps on the effective quasiparticle lifetime is discussed. © 1999 American Institute of Physics.

Notes: We present here a low-temperature (Ts〈630 °C) process for the selective epitaxial growth of Si that employs atomic hydrogen. Modulation of both the substrate temperature and the flux of atomic hydrogen gives alternating growth and suppression/etching cycles, resulting in a significant increase in selectivity. Epitaxial thin-film quality is essentially unaffected, as verified by in situ analysis via low-energy electron diffraction, and ex situ analysis via scanning electron and atomic-force microscopy. © 2001 American Institute of Physics.

Notes: The nucleation of copper on TiN and SiO2 surfaces has been investigated using a collimated molecular beam of hexafluroacetylacetonate copper(I) trimethylvinylsilane in ultrahigh vacuum. The Cu thin film precursor was delivered using a bubbler with H2 as the carrier gas and the substrate temperature was varied from 150 to 260 °C. Ex situ analysis of thin film morphology and microstructure has been conducted using scanning electron microscopy. On SiO2 surfaces the Cu nuclei density reaches a maximum near 5×1010 cm−2, nearly independent of substrate temperature. In contrast, on TiN surfaces the maximum nuclei density is strongly dependent on temperature, varying nearly two orders of magnitude from 150 to 260 °C. On TiN the nucleation process is described well by established kinetic models where a maximum in nuclei density (Nmax) is predicted with respect to the time, and where this quantity exhibits an Arrhenius dependence on substrate temperature. © 2002 American Institute of Physics.

Notes: Infection or immunization with measles virus induces a protective immune reaction including neutralizing antibodies against the haemagglutinin and fusion protein. The reactivity of the polyclonal IgG response of sera obtained from late convalescent donors was studied, using overlapping 15mer peptides covering the complete sequence of the measles virus haemagglutinin. Most sera reacted with a similar set of peptides generating a characteristic binding pattern. The reactive peptides correspond to a region mediating cell hemolysis (aa310–325), to regions which serve as targets to neutralizing antibodies and to a putative transmembrane region (aa35–58). The latter region contains also a human T-cell epitope providing evidence of a non-random association of T- and B-cell epitopes. We also immunized different strains of mice and rabbits with measles virus. In contrast to the human sera, animal sera with strong neutralizing activities did not react with any of the H-protein peptides. The mostly weak reactivities with the linear sequences contrast with the strong neutralizing activities of the human or animal antibodies, suggesting that these primarily recognize the fusion protein or conformational epitopes of the haemagglutinin protein.

Notes: 1. A clonal culture of the peritrich Epistylis pygmaeum was used for all observations and experiments. Motile cells preferentially attached to the eggs of three species of Brachionus but also attached to the body of adult B. angularis. Zooids on the transitory egg substratum developed only short stalks, while those on the body often developed long stalks and branched colonies. Selection for the eggs positions the ciliate near the cloaca, and thus high concentrations of fine particulate material excreted by the host. Settlement on eggs occurred equally well in the light and dark, and on moving and stationary eggs.2. Motile Epistylis cells attached to a wide variety of rotifer and crustacean zooplankton, but exhibited some pronounced selectivity. They readily settled on the eggs of other rotifers (Epiphanes, Polyarthra), on the carapace of several cladocerans (Ceriodaphnia, Daphnia, Diaphanosoma), and on the egg sacs of a copepod (Tropocyclops). They settled less readily on the bodies of the rotifers Asplanchna and Synchaeta, and rarely or never settled on the rotifer Keratella, the cladocerans Bosmina and Scapholeberis, and the body of the copepod.3. Epistylis populations initiated with a single zooid on Brachionus increased exponentially and often contained several hundred attached zooids and motile cells after 3 days at 20 °C. Observations of a culture initiated from a single telotroch provided new information about peritrich life cycles: (1) motile cells reproduced themselves at a rapid rate (λ = 4.26 day−1); (2) telotrochs produced or transformed into swimming zooids and vice versa. Functions of the two types of motile cells remain to be clarified. Telotrochs likely are specialised for finding and attaching to hosts. Swimming zooids can feed and reproduce, producing both their own cell type and telotrochs. Together, they should enhance dispersal and population growth, especially when hosts are rare.4. Life-table experiments with two species of Brachionus showed that colonisation by Epistylis had no effect on adult survival but significantly decreased fecundity, by 29% in both cases. Zooids attached to eggs could be a weight burden, increase drag, and possibly inhibit egg development. Those on the body of B. angularis also could interfere with coronal cilia, inhibiting feeding and further slowing locomotion. The ability of E. pygmaeum to select and then interfere with its hosts indicates that this epibiont has the potential to influence the species structure of zooplankton communities.