We have used synchrotron radiation photoemission to probe the valence and core level electronic structure of compound-semiconductor monodisperse clusters (nanocrystals). These clusters exhibited a 10% or less variation relative to the mean diameter and were attached to the metal substrates via alkane chains. Direct evidence of gap broadening due to size variation in CdS clusters was observed. The novel utilization of alkane chain attachment is the key to eliminating the otherwise debilitating problem of sample charging, as occurs with powders. The quality of sample preparation was confirmed by other methods such as transmission electron microscopy, Raman scattering and x-ray diffraction. This work provides a direct link between photoemission studies of expitaxial ultra-thin films of compound semiconductors, the photon-spectroscopy measurements of cluster powders and the existing theories of quantum confinement in reduced dimensionality structures. 5 refs., 2 figs.

Fluorescence in situ hybridization (FISH) with chromosome-specific probes enables several new areas of cytogenetic investigation by allowing visual determination of the presence and normality of specific genetic sequences in single metaphase or interphase cells. in this approach, termed molecular cytogenetics, the genetic loci to be analyzed are made microscopically visible in single cells using in situ hybridization with nucleic acid probes specific to these loci. To accomplish this, the DNA in the target cells is made single stranded by thermal denaturation and incubated with single-stranded, chemically modified probe under conditions where the probe will anneal only with DNA sequences to which it has high DNA sequence homology. The bound probe is then made visible by treatment with a fluorescent reagent such as fluorescein that binds to the chemical modification carried by the probe. The DNA to which the probe does not bind is made visible by staining with a dye such as propidium iodide that fluoresces at a wavelength different from that of the reagent used for probe visualization. We show in this report that probes are now available that make this technique useful for biological dosimetry, prenatal diagnosis and cancer biology. 31 refs., 3 figs.

At the Nova Laser, the activation of a rubidium tracer incorporated in the shell of ICF targets has become a standard diagnostic technique for measuring the compressed shell areal density {l angle}{rho}{Delta}R{r angle}. The isotope {sup 85}Rb is activated by 14 MeV implosion neutrons to produce the isomer {sup 84m}Rb(t{sub {1/2}} = 20.5 min) which is used to determine the shell {l angle}{rho}{Delta}R{r angle} while the radioactive isotope {sup 86}Rb(t{sub 1/2} = 18.8 d) is used to determine the fraction of target debris collected as well as to assay the amount of rubidium in the target. The {sup 85}Rb(n,2n){sup 84m}Rb cross-section at 14.1 MeV was measured ({sigma} = 0.514 {plus minus} 0.080 b). Details of the detector system and experimental technique are given. 12 refs., 2 tabs.

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The laser beams irradiating a target at the Nova laser facility comprise a set of ten simultaneous events. Two streak cameras, whose resolutions are 40 ps, record the power history for each beam, five beams to a camera; their time bases are cross-timed with a fiducial pulse. Analysis of data recorded for target experiments conducted over a six month period show the precision for cross-timing signals between two streak cameras to be {plus minus}9 ps and for characterizing a single temporal feature of a pulse to be {plus minus}5 ps. Beam synchronization at the end of six months was within 20 ps of the synchronization at the beginning of the experiments. A beam timing shift greater than 25 ps can be detected on a single laser shot; shifts of 10 to 20 ps require several shots to detect. 2 refs., 6 figs.