XUV Opacity of Aluminum between the Cold-Solid to Warm-Plasma Transition

We present calculations of the free-free XUV opacity of warm, solid-density aluminum at photon energies between the plasma frequency at 15 eV and the L-edge at 73 eV, using both density functional theory combined with molecular dynamics and a semi-analytical model in the RPA framework with the inclusion of local field corrections. As the temperature is increased from room temperature to 10 eV, with the ion and electron temperatures equal, we calculate an increase in the opacity in the range over which the degree of ionization is constant. The effect is less pronounced if only the electron temperature is allowed to increase. The physical significance of these increases is discussed in terms of intense XUV-laser matter interactions on both femtosecond and picosecond time-scales.Comment: 4 pages, 3 figure

Yttria and Ceria Doped Zirconia Thin Films Grown by Pulsed Laser Deposition

The Yttria stabilized Zirconia (YSZ) is a standard electrolyte for solid oxide fuel cells (SOFCs), which are potential candidates for next generation portable and mobile power sources. YSZ electrolyte thin films having a cubic single phase allow reducing the SOFC operating temperature without diminishing the electrochemical power density. Films of 8 mol % Yttria stabilized Zirconia (8YSZ) and films with addition of 4 weight % Ceria (8YSZ + 4CeO2) were grown by pulsed laser deposition (PLD) technique using 8YSZ and 8YSZ + 4CeO2 targets and a Nd-YAG laser (355 nm). Films have been deposited on Soda-Calcia-Silica glass and Si(100) substrates at room temperature. The morphology and structural characteristics of the samples have been studied by means of X-ray diffraction and scanning electron microscopy. Films of a cubic-YSZ single phase with thickness in the range of 1-3 µm were grown on different substrates.Fil: Saporiti, F.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Grupo de Materiales Avanzados; Argentina;Fil: Juarez, R. E.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Grupo de Materiales Avanzados; Argentina;Fil: Audebert, Fernando Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina; Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Grupo de Materiales Avanzados; Argentina;Fil: Boudard, M.. Centre National de la Recherche Scientifique. Laboratoire des Matériaux et du Génie Physique; Francia

Fluorescent Liquid Tetrazines

Tetrazines with branched alkoxy substituents are liquids at ambient temperature that despite the high chromophore density retain the bright orange fluorescence that is characteristic of this exceptional fluorophore. Here, we study the photophysical properties of a series of alkoxy-tetrazines in solution and as neat liquids. We also correlate the size of the alkoxy substituents with the viscosity of the liquids. We show using time-resolved spectroscopy that intersystem crossing is an important decay pathway competing with fluorescence, and that its rate is higher for 3,6-dialkoxy derivatives than for 3-chloro-6-alkoxytetrazines, explaining the higher fluorescence quantum yields for the latter. Quantum chemical calculations suggest that the difference in rate is due to the activation energy required to distort the tetrazine core such that the [Formula: see text] [Formula: see text] and the higher-lying [Formula: see text] [Formula: see text] states cross, at which point the spin-orbit coupling exceeding 10 cm [Formula: see text] allows for efficient intersystem crossing to occur. Femtosecond time-resolved anisotropy studies in solution allow us to measure a positive relationship between the alkoxy chain lengths and their rotational correlation times, and studies in the neat liquids show a fast decay of the anisotropy consistent with fast exciton migration in the neat liquid films

Evaluation of Iron Toxicity on Lowland Irrigated Rice in West Africa

In tropical areas, lowland rice (Oryza sativa L.) cultivation (with or without irrigation) is often hampered by iron toxicity. This edaphic stress is common in West African savanna and forest lowlands. It is a nutrient disorder associated with high iron concentrations in the soil solution. The reducing conditions of waterlogged lowland soils boost iron toxicity through solubilization of almost all iron in its ferrous form (Fe2+). This iron toxicity promoting edaphic features of lowland soils depends on the soil and climatic conditions, thus explaining the high spatiotemporal variability. The high quantity of ferrous ions in the soil solution upsets the mineral element balance in the rice and affects its growth. Ferrous iron (Fe2+) is abundantly taken up by the plant and becomes concentrated in the leaves, causing limb discoloration, reduced tillering, stunted growth, while substantially reducing yields. A survey was conducted to quantify the effects of iron toxicity on rice in three countries (Guinea, Ivory Coast and Ghana) in the West African subregion. It was confirmed that iron toxicity is a major edaphic constraint in cultivated lowlands as it affects more than 50% of lowlands and about 60% of cultivated rice plots on average. About 10% of lowland crop fields were even abandoned due to high iron toxicity stress. Studies have also shown that more than 55% of rice-growing areas are affected by excess iron. There is also a significant impact on yield since affected plots were found to have a mean 54% lower yield as compared to healthy plots

Nanoquasicrystalline Al-Fe-Cr-Ti alloy matrix/γ-Al2O3 nanocomposite powders: The effect of the ball milling process

Quasicrystalline aluminium alloys and aluminium based nanocomposites with the advantage of high strength over commercial aluminium alloys have been studied for many years. In this work a nanoquasicrystalline Al-Fe-Cr-Ti alloy powder and a nanocomposite consisting of a mixture of a nanoquasicrystalline alloy and nanosize γ-Al2O3 powders were produced through mechanical milling with different milling speeds. It has been observed that a higher milling time or milling speed can improve the homogeneity of the γ-Al2O3 distribution. The α-Al crystallite size decreases and the hardness increases with the milling time. The smallest crystallite size (14 nm) and the highest hardness value (638 HV10g) were obtained for the nanocomposite after 30 h of milling at 250 rpm. As the α-Al crystallite size is the main change in the microstructure during the ball milling process, the change in the hardness of the milled powders was found to follow a Hall-Petch type relation with an exponent of 0.25

The use of the 1 mm laparoscope to assist in port insertion in pelvic oncological surgery

BACKGROUND: A 1 mm minilaparoscope (Lifeline Biotechnoligies, Florida, USA) was assessed for aiding port site insertions. METHODS: Ten consecutive patients having laparoscopic procedures in a gynaecological oncology unit were included. Minilaparoscopy was feasible in all cases and was used to insert the umbilical port under direct vision in all patients. In one case, a thick band of abdominal adhesions was identified and a further lateral port site was inserted to aid their dissection. RESULTS: The minilaparoscope correctly identified all 10 patients with peritoneal disease and identified all patients who were suitable for debulking procedures. CONCLUSION: Minilaparoscopy with the 1 mm endoscope appears to be safe and accurate and we feel that it has a place in helping the surgeon identify adhesions and peritoneal disease as well as assisting further port site insertion safely and with minimal complications

Modeling target bulk heating resulting from ultra-intense short pulse laser irradiation of solid density targets

Isochoric heating of solid-density matter up to a few tens of eV is of interest for investigating astrophysical or inertial fusion scenarios. Such ultra-fast heating can be achieved via the energy deposition of short-pulse laser generated electrons. Here, we report on experimental measurements of this process by means of time-and space-resolved optical interferometry. Our results are found in reasonable agreement with a simple numerical model of fast electron-induced heating. (C) 2013 AIP Publishing LLC.</p

Electrical, photoelectrical and morphological properties of ZnO nanowire networks grown on SiO2 and on Si

ZnO nanofibre networks (NFNs) were grown by vapour transport method on Si-based substrates. One type of substrate was SiO2 thermally grown on Si and another consisted of a Si wafer onto which Si nanowires (NWs) had been grown having Au nanoparticles catalysts. The ZnO-NFN morphology was observed by scanning electron microscopy on samples grown at 600 °C and 720 °C substrate temperature, while an focused ion beam was used to study the ZnO NFN/Si NWs/Si and ZnO NFN/SiO2 interfaces. Photoluminescence, electrical conductance and photoconductance of ZnO-NFN was studied for the sample grown on SiO2. The photoluminescence spectra show strong peaks due to exciton recombination and lattice defects. The ZnO-NFN presents quasi-persistent photoconductivity effects and ohmic I-V characteristics which become nonlinear and hysteretic as the applied voltage is increased. The electrical conductance as a function of temperature can be described by a modified three dimensional variable hopping model with nanometer-ranged typical hopping distances