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A new target design is presented to model high-energy radiative accretion shocks in polars. In this paper, we present the experimental results obtained on the GEKKO XII laser facility for the POLAR project. The experimental results are compared with 2D FCI2 simulations to characterize the dynamics and the structure of plasma flow before and after the collision. The good agreement between simulations and experimental data confirms the formation of a reverse shock where cooling losses start modifying the post-shock region. With the multi-material structure of the target, a hydrodynamic collimation is exhibited and a radiative structure coupled with the reverse shock is highlighted in both experimental data and simulations. The flexibility of the laser energy produced on GEKKO XII allowed us to produce high-velocity flows and study new and interesting radiation hydrodynamic regimes between those obtained on the LULI2000 and Orion laser facilities.
Much can be learned from terrestrial planets that appear to have had the potential to be habitable, but failed to realize that potential. Mars shows evidence of a once hospitable surface environment. The reasons for its current state, and in particular its thin atmosphere and dry surface, are of great interest for what they can tell us about habitable zone planet outcomes. A main goal of the MAVEN mission is to observe Mars’ atmosphere responses to solar and space weather influences, and in particular atmosphere escape related to space weather ‘storms’ caused by interplanetary coronal mass ejections (ICMEs). Numerical experiments with a data-validated MHD model suggest how the effects of an observed moderately strong ICME compare to what happens during a more extreme event. The results suggest the kinds of solar and space weather conditions that can have evolutionary importance at a planet like Mars.
We have made a 12CO(J = 1−0) survey of the LMC with NANTEN. A sample of 55 giant molecular clouds has been identified and comparisons with stellar clusters, HII regions and SNRs are presented. The connection between the clouds and cluster formation is discussed.
In this paper the Very High Energy (VHE) gamma-ray astronomy program at the University of Adelaide is described. VHE gamma rays with energies above ~5 × 1011eV are observed using the atmospheric Cerenkov technique. Results from the first three years observations at Woomera and the current upgrading of the telecope are described. The CANGAROO project, a collaboration between the University of Adelaide and a number of Japanese institutions, is also introduced.
The CANGAROO project incorporates two Čerenkov imaging telescopes at Woomera to obtain stereo images of very high-energy gamma-ray (and cosmic-ray) showers. The first stereo observations, with one imaging system, were made in March 1992, and preliminary stereo imaging observations began in July 1992. This paper describes the stereo imaging technique, the sources under investigation, and the indications from the first data sets.
The Collaboration of Australia and Nippon for a GAmma Ray Observatory in the Outback operates two large telescopes at Woomera (South Australia), which detect the Čerenkov light images produced in the atmosphere by electronpositron cascades initiated by very high energy (~1 TeV or 1012 eV) gamma rays. These gamma rays arise from a different mechanism than at EGRET energies: inverse Compton (IC) emission from relativistic electrons.
The spoke-like images are recorded by a multi-pixel camera which facilitates the rejection of the large numbers of oblique and ragged cosmic ray images. A field of view ~3.5° is required. The Australian team operates a triple 4 m diameter mirror telescope, BIGRAT, with a 37 photomultiplier tube camera and energy threshold 600 GeV. The Japanese operate a single, highly accurate 3.8 m diameter f/1 telescope and high resolution 256 photomultipler tube camera. In 1998 a new 7 m telescope is planned for Woomera with a design threshold ~;200GeV.
A fully coherent free electron laser (FEL) seeded with a higher-order harmonic (HH) pulse from high-order harmonic generation (HHG) is successfully operated for a sufficiently prolonged time in pilot user experiments by using a timing drift feedback. For HHG-seeded FELs, the seeding laser pulses have to be synchronized with electron bunches. Despite seeded FELs being non-chaotic light sources in principle, external laser-seeded FELs are often unstable in practice because of a timing jitter and a drift between the seeding laser pulses and the accelerated electron bunches. Accordingly, we constructed a relative arrival-timing monitor based on non-invasive electro-optic sampling (EOS). The EOS monitor made uninterrupted shot-to-shot monitoring possible even during the seeded FEL operation. The EOS system was then used for arrival-timing feedback with an adjustability of 100 fs for continual operation of the HHG-seeded FEL. Using the EOS-based beam drift controlling system, the HHG-seeded FEL was operated over half a day with an effective hit rate of 20%–30%. The output pulse energy was
at the 61.2 nm wavelength. Towards seeded FELs in the water window region, we investigated our upgrade plan to seed high-power FELs with HH photon energy of 30–100 eV and lase at shorter wavelengths of up to 2 nm through high-gain harmonic generation (HGHG) at the energy-upgraded SPring-8 Compact SASE Source (SCSS) accelerator. We studied a benefit as well as the feasibility of the next HHG-seeded FEL machine with single-stage HGHG with tunability of a lasing wavelength.
We have recently reported that multiple aster formation after in vitro fertilization (IVF) was one of the factors that negatively affected the developmental competence of vitrified-warmed bovine matured oocytes, and that short-term culture of the post-warm oocytes with an inhibitor of Rho-associated coiled-coil kinase (ROCK) suppressed the multiple aster formation and improved the blastocyst yield. The present study was conducted to investigate whether increased multiple aster formation following IVF was involved in impaired developmental competence of stored ovary-derived bovine oocytes. Oocytes retrieved from 1-day stored ovaries had lower developmental potential to day 8 blastocysts when compared with those from fresh ovaries (37 versus 63%). Immunostaining of α-tubulin 10 h post-IVF revealed that a higher incidence of multiple aster formation occurred in oocytes retrieved from stored ovaries than from fresh ovaries (31 versus 15%). Treatment of post-in vitro maturated (post-IVM) oocytes with ROCK inhibitor for 2 h significantly suppressed the incidence of multiple aster formation (10 versus 32% in the control group). However, the suppression effect of ROCK inhibitor on multiple aster formation in IVM/IVF oocytes did not improve blastocyst yield from stored ovary-derived oocytes (41 versus 37% in the control group). These results suggested that the higher incidence of multiple aster formation by bovine ovary storage was not responsible for the decreased developmental competence of IVF oocytes.
Although vitrification is a useful technique for preservation of bovine oocytes, the yield of blastocysts derived from the vitrified oocytes is still low. We have recently reported a new type of cryoinjury, multiple aster formation, by which pronuclear migration and development of vitrified–warmed and in vitro-fertilized bovine oocytes are impaired. The aim of the present study was to investigate the effect of glutathione (GSH) content of vitrified bovine oocytes on multiple aster formation and subsequent in vitro development. Treatment of bovine cumulus–oocyte complexes with β-mercaptoethanol (βME) and l-cysteine (Cys) during in vitro maturation resulted in 2.5-fold higher GSH content not only in fresh control but also in vitrified–warmed oocytes. The percentage of normally fertilized zygotes exhibiting sperm aster(s) was >95% in all four groups (with or without βME/Cys × fresh control or vitrified). The frequency of multiple aster formation in vitrified oocytes (three-fold higher than that in fresh control oocytes) was not affected by the increased level of intracellular GSH with βME/Cys. Consequently, the migration and development of pronuclei as well as the yield of blastocysts from vitrified–warmed oocytes (17 versus 41%) were not improved. In addition, there was no effect of increased GSH level on the yield of blastocysts in fresh control groups.
We present a new experimental approach to studying the mechanism of intrinsic gettering of Fe in Czochralski silicon crystals. We present our experimental method and results for as-grown and intrinsic gettered wafers with high and low-level Fe surface contamination. We found that when annealing at the Fe supersaturation temperature, Fe concentration decreases faster in intrinsic gettered wafers than in as-grown wafers. Concentration saturated with annealing time for each sample and the saturated Fe concentration followed a simple Arrhenius relationship. Re-emission of Fe from the bulk defect region occurred above the gettering temperature. We conclude that in intrinsic gettering, Fe precipitates preferentially in the bulk defect region when the Fe impurities supersaturate as temperature drops.
A solar eclipse is one of the most popular events in astronomy. Although it is the single astronomical event, it gives different images from place to place and changes in time. It is the most important message from astronomy to the public that an apparent face depends on the viewpoint and we should get the comprehensive view.
Electron beam excited plasma (EBEP) CVD is a novel fabrication route for poly Si. Deposition was carried out on Si and SiO2 layer from pure SiH4 without hydrogen dilution. Crystalline silicon (μc-Si:H) films were made with electron acceleration voltage, discharge current, source gas flow rate, chamber presser, substrate temperature varied systematically. Average grain size was about 10 nm. Crystalline ratio was up to 0.7 at the maximum. The films contain about 19 at% hydrogen in spite of no dilution. It is considered that EBEP supplies much about atomic hydrogen due to the high decomposability of the source gas.
We have fabricated submonolayer-thick films of CdSe colloidal nanodots in order to investigate electronic properties of individual nanodots by conductive-tip atomic force microscopy (AFM). Topographic and current images of isolated single CdSe colloidal dots on single crystalline Au (111) surface which was covered with dodecanethiol self-assembled monolayer were obtained by AFM operating in contact mode with a conductive tip under appropriate bias voltages. In the current image, it is found that the dot regions have higher electric resistances due to tunneling resistance through the CdSe dots. We also found 10 nm-scale electric inhomogeneity around the dots, which may corresponds to the previously reported etch-pits of Au (111) surfaces formed during the deposition of the dodecanethiol molecules.
Lattice polarities and film qualities of GaN grown by rf-MBE were investigated concentrating on the use of different buffer layer processes at the initial stage. Direct clarifying by coaxial impact collision ion scattering spectra technique, together with RHEED and chemical wet etching, were applied to identify the lattice polarity of GaN films. XRD rocking curve and photoluminescence results showed that the qualities of GaN films with Ga-polarity were dramatic improved compared to those with N-polarity. Hall effect measurement results indicated that the mobility of the Ga-face film was increased to one order higher (568 cm2/Vs in maximum at room temperature) than that of N-face one.
We developed a heteroepitaxial growth technique for large-area β-SiC films on Si substrates without buffer layers at 850ºC and 1000ºC. The substrates were vicinal 4-inch (111) Si wafers. The β-SiC films had smooth surfaces and were crack-free. X-ray diffraction and electron diffraction analysis revealed that the films grown at 1000ºC were single crystals. Satisfactory characteristics were obtained in aMOSFET with a β-SiC/Si02/poly-Si substrate structure. Our evaluations indicate that the β-SiC films were high-quality crystals.
The technologies of laser crystallization and methods of SiO2 formation in remote plasma chemical vapor deposition or SiO evaporation with an oxygen ambient realize the fabrication of n-channel polycrystalline and amorphous silicon thin film transistors (poly-Si and a-Si TFTs) at a temperature lower than 300 °C. The defect density was achieved to be 2∼3×1011 cm−2eV−1 and threshold voltage was about IV for both TFTs. The maximum field effect mobility was 600 cm2/Vs for poly-Si TFTs and 2.6 cm2/Vs for a-Si TFTs. The mobility of poly-Si TFT decreased as the gate voltage increases. This is interpreted as that the electrons are confined in the narrow inversion layer and electron scattering with phonon is enhanced for higher normal electric field.
Transient conductance measurements were used to study rapid carrier generation during the laser doping of a silicon film. The movement of the liquid-solid interface was measured and the point of initiation of carrier generation frcn dopant atoms diffused to the molten silicon was determined. It was established that the dopant atais are activated at the nmorent the dopant diffused region solidified. Also, the laser doping technique was used to fabricate polycrystalline silicsn thin film transistors (Poly-Si TFT's) ata processing temperature of 250ºC.
This contribution summarizes some strategies that we followed for the optimization of supramolecular architectures aiming at controlling the binding and organization of biopolymers at solid/solution-interfaces in a membrane-mimetic approach. The examples given concern mostly self-assembly processes and the biorecognition between biotin and streptavidin.
Among various requirements for the a-Si TFT-LCD gate electrode, low resistivity is becoming more emphasized with the increase of display size and information content as well as process feasibility. We have developed a low resistivity Mo-W alloy as a material for gate buslines.
The Mo-W film was formed by DC magnetron sputtering using Ar or Kr as the working gas. The resistivity of the fabricated film was 16 μΩ-cm when deposited with Ar, and decreased to a value as low as 13 μΩ-cm with Kr, which was less than a half that of the conventional Mo-Ta film. Inverted staggered a-Si TFTs having Mo-W gate electrodes formed with Kr were fabricated, and good transfer performance with thermal- and electrical stability was obtained. The applicability of the new alloy to LCDs with large area and high resolution was shown.
We have investigated current-voltage characteristics of individual CdSe colloidal nanodots by conductive-tip atomic force microscopy (AFM). The colloidal nanodots were spun-coat and scattered on a self-assembled monolayer of thiophene molecules formed on Au (111) surfaces for single dot measurements. A thin SiO2 layer was deposited on the sample surface in order to prevent the dots being moved by the tip during measurement. We imaged the topography of isolated single dots by AFM operated in contact mode, and measured current-voltage characteristics with the conductive tip positioned on single dots; large conductivity changes which suggest resonant tunneling through a quantized energy level in the dot was observed even at room temperature.