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Notes: A high brightness krypton fluoride Raman laser (wavelength 0.268 μm) generating 0.3 TW, 12 ps pulses with 20 μrad beam divergence and a prepulse of less than 10−10 has been focused to produce a 10 μm wide line focus (irradiances ∼0.8–4×1015 W cm−2) on plastic targets with a diagnostic sodium fluoride (NaF) layer buried within the target. Axial and lateral transport of energy has been measured by analysis of x-ray images of the line focus and from x-ray spectra emitted by the layer of NaF with varying overlay thicknesses. It is shown that the ratio of the distance between the critical density surface and the ablation surface to the laser focal width controls lateral transport in a similar manner as for previous spot focus experiments. The measured axial energy transport is compared to medusa [J. P. Christiansen, D. E. T. F. Ashby, and K. V. Roberts, Comput. Phys. Commun. 7, 271 (1974)] one-dimensional hydrodynamic code simulations with an average atom post-processor for predicting spectral line intensities. An energy absorption of ∼10% in the code gives agreement with the experimental axial penetration. Various measured line ratios of hydrogen- and helium-like Na and F are investigated as temperature diagnostics in the NaF layer using the ration [R. W. Lee, B. L. Whitten, and R. E. Strout, J. Quant. Spectrosc. Radiat. Transfer 32, 91 (1984)] code.

Notes: Using a high Tc superconducting grain boundary Josephson junction, harmonic mixing experiments in the mm waveband were carried out, aiming at as large a harmonic number and as high a signal frequency as possible. The dependencies of intermediate frequency output on dc bias, harmonic number, frequency of local oscillator (LO), and other parameters were carefully studied. Until now, our best result was the mixing between the signal at 95 GHz and the 105th harmonic of LO at about 900 MHz. Preliminary experiments using a high Tc harmonic mixer and phase-locking loop were tried to stabilize the frequency of a mm wave source.

Notes: The band structure and magnetic properties are studied for RFe11TiNx (R=Y, Nd, Sm; x=0,1) rare-earth iron intermetallic compounds using the linear muffin tin orbital with the atomic sphere approximation (LMTO-ASA) method. In order to elucidate the role played by the rare-earth atoms in these compounds, a full electron calculation is performed using a semirelativistic spin-polarized LMTO-ASA method in the local spin density approximation (LSDA) regime. The 4f electrons of the rare-earth atoms are considered to be valence electrons in the self-consistent calculations. For NdFe11TiN, a calculation in which the 4f electrons are treated as core-frozen states is also performed, and is compared with the full electron calculation. The effects of N atoms in these compounds are also discussed.

Notes: High quality YBa2Cu3O7−δ (YBCO) films have been epitaxially grown on low dielectric constant, low loss tangent (001)MgF2 substrates using a double buffer layer scheme. The YBCO films are (001) oriented, exhibit Tc's of 88–89 K with transition widths ≤0.5 K and Jc's of 4×106 A/cm2 at 77 K in zero field. Dielectric resonator experiments indicate unloaded Q values in excess of 30 000 at 77 K and 24 GHz in the unpatterned films. Films patterned into meanderline resonators and operating at 10 GHz, 79 K, exhibit surface resistance (Rs)〈1 m Ω suggesting near-future realization of low loss superconducting components in the millimeter-wave region.

Notes: Reflection high-energy electron diffraction intensity oscillations during Ge heteroepitaxy on Si(100) have been observed using a gas source molecular beam epitaxy system. Intensity oscillations can be observed over 6 ML (monolayers) of growth in the temperature range 400–650 °C. The oscillation frequency, however, varies from the first to subsequent layers and this variation is interpreted primarily as a change in the limiting growth kinetics as the surface composition changes from Si to Ge. Growth temperature and GeH4 flux dependence data indicate that the surface Ge concentration increases gradually, not abruptly, over the first several layers of deposition. Surface roughening effects which are attributed to Stranski–Krastanov type growth, are also found to contribute to the nonuniform oscillation frequency. © 1994 American Institute of Physics.

Notes: We report the measurements of the electron-hole recombination rate in aqueous CdS colloids on the femtosecond time scale. A fast 2-ps decay and a slower 45-ps decay have been observed, and the decay dynamics are found to be very sensitive to the excitation laser intensity. Geminate electron-hole recombination, responsible for the 45-ps decay, dominates the decay process at low excitation intensities, while nongeminate recombination, accounting for the 2-ps decay, becomes more important at high excitation intensities.

Notes: We report the direct femtosecond measurements of the electron transfer process from CdS to TiO2 particles in a coupled colloidal system. The electrons initially created in the conduction band and quickly trapped at the liquid–solid interface in aqueous CdS colloids are found to be transferred to the colloidal TiO2 particles with a time constant of 2 ps, resulting in significantly slower electron–hole recombination. These coupled semiconductor colloids provide a potentially useful system for achieving efficient charge separation, which is important for many chemical reactions involving heterogeneous electron transfer.

Notes: The effects of bentazone application on fruit spike length, fruit coat thickness, seed maturation, total number of seeds per plant, seed mass and seed mass distribution in seven populations of Xanthium strumarium from two contrasting habitats were examined. The results showed that variations in fruit traits depended significantly on population and on bentazone treatment but not on habitat. Plants sprayed with bentazone produced significantly fewer fruits that contained at least one developed seed. Bentazone application also reduced mean seed mass in some populations by pushing the seed mass distribution to the small seed side. Spike length and fruit coat thickness are two important traits influencing the probability of seed predation. Bentazone application resulted in shorter spike length in some populations but longer spike length in some others. Fruit coat thickness showed substantial increase after bentazone treatment, suggesting that application of the herbicide may reduce the chance of seed predation. L'effet de traitements herbicides sur les caractères des fruits dans les populations de Xanthium strumarium L.Les effets de traitements par la bentazone sur la longueur des épis, sur 1'épaisseur des téguments. sur la maturation des graines, sur le nombre total de graines par plante, sur la masse des graines ainsi que sa distribution, ont étéétudiés dans sept populations de Xanthium strumarium provenant de deux habitats très différents. Les caractères des fruits dépendaient significativement de la population et du traitement à la bentazone mais pas de 1'habitat. Les plantes trailées à la bentazone produisaient significativement moins de fruits, qui contenaient au moins une graine développée. Le traitement par la bentazone réduisait aussi la masse moyenne des graines dans quelques populations en déplnçant la distribution des masses vers les faibles valeurs. La longueur de 1'épi et 1'épaisseur des téguments sont deux caractéres importants qui influencent la probabilité de prédation de la graine. Le traitement par la bentazone se traduisait par un raccourcissement des épis dans certaines populations et par un allongement dans d'autres. L'épaisseur des téguments augmentait après un traitement par la bentazone, suggérant que le traitement herbicide pourrait réduire la probabilité de prédation. Einfluß von Herbizidanwendungen auf die Fruchtbildung von Xanthium strumarium L.An 7 Xanthium-strumarium-Populalionen von 2 unterschiedlichen Standorten wurde der Einfluß von Bentazon auf die Rispenlänge, die Frucht-schalenstärke, die Samenreifung, die Gesamt-samenzahl pro Pflanze, die Samenmasse und die Samenmassenverteilung untersucht. Die Frucht-merkmale hingen signifikant von der Population und der Bentazon-Behandlung ab. aber nicht vom Standort. Die behandelten Pflanzen brachten signifikant weniger Früchte mil min-destens 1 entwickelten Samen hervor. Die Be-handlung reduzierte in einigen Populationen auch die mittlere Samenmasse, indem die Samenmassenverteilung zugunsten kleiner Samen verschoben war. Die Rispenlänge und die Fruchtschalenstärke sind hinsichtlich möglicher Samenschädigungen wichtige Merkmale. In einigen Populationen verringerte sich nach der Behandlung die Rispenlänge, in anderen war sie verlängert. Die Fruchtschalenstärke nahm nach der Behandlung erheblich zu, was vermutlich die Möglichkeit von Samenschädigungen herabsetzt.