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A new approach is proposed to analyze Bremsstrahlung X-rays that are emitted from laser-produced plasmas (LPP) and are measured by a stack type spectrometer. This new method is based on a spectral tomographic reconstruction concept with the variational principle for optimization, without referring to the electron energy distribution of a plasma. This approach is applied to the analysis of some experimental data obtained at a few major laser facilities to demonstrate the applicability of the method. Slope temperatures of X-rays from LPP are determined with a two-temperature model, showing different spectral characteristics of X-rays depending on laser properties used in the experiments.
We describe preliminary results from our study of multi-scale structures in Centaurus A (NGC 5128) obtained using the Chandra X-ray Observatory HRC-I observations. The high-angular resolution Chandra images reveal X-ray multi-scale structures in this object with unprecedented detail and clarity. The region surrounding the Cen A nucleus, believed to be associated with a supermassive black hole, shows structures on arcsecond scales clearly resolved from the central source.
The Korean Disaster Relief Team (KDRT) medical team, mainly composed of graduates from first government certified international disaster support education course, deployed to Haiti after the earthquake in January 2010, and operated a medical relief mission. The present study was designed to evaluate the KDRT medical team mission in Haiti.
Data were collected via an anonymous questionnaire that was distributed one day after the completion of the mission in Haiti. Questionnaires were composed of four categories.
The response rate for this survey was 72% (18/25). The KDRT members were relatively young, with 72% of personnel.
SiB6 has proved to a potentially useful material because of its excellent thermoelectrical properties above 700°C, low specific gravity, high degree of hardness, and moderate melting point. SiB6, which has poor sinterability with a conventional sintering technique due to the covalent characteristic, has been successfully densified fully using a spark plasma sintering(SPS) method. The SPS-processed specimens consisted of SiB6, SiB4 and SixBy phases. Pure SiB6 powder were densified fully at the sintering temperature of 1600°C. In particular, it was found that the rare earth element was very effective in evolving the microstructure of SiB6 phase, resulting in reducing the sintering temperature and controlling grain growth. These effects were discussed in details in terms of microstructure evolution during the SPS process.
Diffusivity of a strained heterostructure was theoretically investigated, and general diffusion equations with strain potential were deduced. There was an additional diffusivity by the strain potential gradient as well as by the concentration gradient. The strain-induced diffusivity was a function of concentration, and its temperature dependence was formulated. The activation energy of the strain-induced diffusivity was measured by high-resolution transmission electron microscopy. This result can be generally applied for the investigation of the diffusion in strained heterostructures.
We have deposited thin films of silicon dioxide, SiO2, and amorphous silicon, a- Si, by remote Plasma-Enhanced Chemical-Vapor Deposition (Remote PECVD), and have extended this process to the deposition of silicon suboxides, SiOx, 0<x<2. Heterostructures, comprised of alternating layers of SiO 2, and SiOx, x∼1, have been deposited by electronically controlling the flow of charged particles from the plasmageneration region into the deposition chamber, without interrupting the flow of process gases. We discuss the electrical properties of these heterojunction structures.
Molecular dynamics simulations using a bond-order potential were carried out to investigate the behavior under load of several <001> and <011> symmetrical tilt grain boundaries in diamond. Cohesive energies, work for fracture, maximum stresses and strains as functions of the type of grain boundary were evaluated. It was found that special short-periodic GBs possess higher strength and resistance to a crack propagation than GBs in the nearby misorientation range. Crack behavior in polycrystalline diamond samples under an applied load was also simulated, and found to be predominantly transgranular.
An amphoteric surfactant, cocamidopropyl betaine, was used for the synthesis of mesoporous zirconia. The carboxylate functionality of the surfactant permitted strong bonding with soluble zirconium species, while the quaternary ammonium group ensured large headgroup area and high solubility under acidic conditions. An amphoteric co-template [betaine, or (carboxymethyl)trimethylammonium hydroxide] improved uniformity of the hexagonal mesophase. Transmission electron microscopy (TEM) of the as-synthesized zirconium sulfate mesophase indicated hexagonal mesostructure, and low-angle X-ray diffraction (XRD) showed a 41 Å primary d-spacing and two higher order reflections of a hexagonal lattice. High surface area zirconia was produced by controlled base treatment of the hexagonal mesophase with sodium hydroxide, followed by calcination. TEM and XRD indicated that the mesostructure was stable to 350°C.
The UO2 in spent nuclear fuel is unstable under moist oxidizing conditions and will be altered to uranyl oxide hydrate phases. The transuranics released during the corrosion of spent fuel may also be incorporated into the structures of secondary U6+ phases. The incorporation of radionuclides into alteration products will affect their mobility. A series of precipitation tests were conducted at either 150 or 90°C for seven days to determine the potential incorporation of Ce4+ and Nd3+ (surrogates for Pu4+ and Am3+, respectively) into uranium phases. lanthinite ([U24+(UO2)4O6(OH)4(H2O)4](H2O)5) was produced by dissolying uranium oxyacetate in a solution containing copper acetate monohydrate as a reductant. The leachant used in these tests were doped with either 2.1 ppm cerium or 399 ppm neodymium. Inductively coupled plasmamass spectrometer (ICP-MS) analysis of the solid phase reaction products which were dissolved in a HNO3 solution indicates that about 306 ppm Ce (Kd = 1020) was incorporated into ianthinite, while neodymium contents were much higher, being approximately 24,800 ppm (Kd 115). Solid phase examinations using an analytical transmission electron microscope/electron energy-loss spectrometer (AEM/EELS) indicate a uniform distribution of Nd, while Ce contents were below detection. Becquerelite (Ca[(UO2)6O4(OH)6]·8H2O) was produced by dissolving uranium oxyacetate in a solution containing calcium acetate. The leachant in these tests was doped with either 2.1 ppm cerium or 277 ppm neodymium. ICP-MS results indicate that about 33 ppm Ce (Kd = 17) was incorporated into becquerelite, while neodymium contents were higher, being approximately 1,300 ppm (Kd = 5). Homogeneous distribution of Nd in the solid phase was noted during AEM/EELS examination, and Ce contents were also below detection.
Water adsorption by porous low-k silica films results in increased dielectric constants and is often due to silanol groups on the pore surfaces. Reacting the silanols with silylating agents (e.g., hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMCS)) in supercritical CO2 (SC-CO2) can increase film hydrophobicity and can remove adsorbed water. In porous methylsilsesquioxane (MSQ) films (average pore size ∼ 3-4nm), it has been determined that supercritical silylation reactions do not substantially penetrate beyond the film surface.1,2 In this work we have examined the supercritical penetration behavior of silylating agents in low-k films with larger pore sizes (5-10nm). The depth and extent of reactants was determined by in situ infrared spectroscopy (FTIR), and surface hydrophobicity was examined by contact angle experiments.
Decreasing the circuit dimensions is driving the need for low-k materials with a lower dielectric constant to reduce RC delay, crosstalk, and power consumption. In case of spin-on organosilicate low-k films, the incorporation of a porogen is regarded as the only foreseeable route to decrease dielectric constant of 2.2 or below by changing a packing density. In this study, MTMS-BTMSE copolymers that had superior mechanical properties than MSSQ were blended with decomposable polymers as pore generators. While adding up to 40 wt % porogen into MTMS:BTMSE=100:50 matrix, optical, electrical, and mechanical properties were measured and the pore structure was also characterized by PALS. The result confirmed that there existed a tradeoff in attaining the low dielectric constant and desirable mechanical strength, and no more pores than necessary to achieve the dielectric objective should be incorporated. When the dielectric constant was fixed to approximately 2.3 by controlling BTMSE and porogen contents simultaneously, the thermo-mechanical properties of the porous films were also investigated for the comparison purpose. Under the same dielectric constant, the increase in BTMSE and porogen contents led to improvement in modulus measured by the nanoindentation technique but deterioration of adhesion strength obtained by the modified edge lift-off test.
Porous low dielectric films containing nano pores (∼20Å) with low dielectric constant (<2.2), have been prepared by using various kinds of cyclodextrin derivatives as porogenic materials. The pore structure such as pore size and interconnectivity can be controlled by changing functional groups of the cyclodextrin derivatives. We found that mechanical properties of porous low-k thin film prepared with mCSSQ (modified cyclic silsesquioxane) precursor and cyclodextrin derivatives were correlated with the pore interconnection length. The longer the interconnection length of nanopores in the thin film, the worse the mechanical properties of the thin film (such as hardness and modulus) even though the pore diameter of the films were microporous (∼2nm).
The Taiwan-America Occultation Survey (TAOS) aims to determine the number of small icy bodies in the outer reach of the Solar System by means of stellar occultation. An array of 4 robotic small (D=0.5 m), wide-field (f/1.9) telescopes have been installed at Lulin Observatory in Taiwan to simultaneously monitor some thousand of stars for such rare occultation events. Because a typical occultation event by a TNO a few km across will last for only a fraction of a second, fast photometry is necessary. A special CCD readout scheme has been devised to allow for stellar photometry taken a few times per second. Effective analysis pipelines have been developed to process stellar light curves and to correlate any possible flux changes among all telescopes. A few billion photometric measurements have been collected since the routine survey began in early 2005. Our preliminary result of a very low detection rate suggests a deficit of small TNOs down to a few km size, consistent with the extrapolation of some recent studies of larger (30–100 km) TNOs.
Nanostructured titanium carbonitride (TiC0.5N0.5) powders were synthesized by a Mg-thermal reduction process. The evaporated liquid solution made from TiCl4 + ¼C2Cl4 reacted with liquid magnesium protected with nitrogen gas. The extremely fine titanium carbonitride particles of about 50 nm were successfully produced by the reaction of Ti and C atoms released from chloride reduction with liquid magnesium and nitrogen gas. After the reduction process, the residual phases of MgCl2 and the excess Mg were removed by mechanical vacuum conditions. To obtain the maximized stoichiometry of product, the process optimization with thermodynamic study was performed with various experimental parameters such as reaction temperatures and solution feeding rates.
Recent government initiatives in the UK have focused on streamlining oncology services by reducing waiting times between urgent referral, assessment and treatment of patients with possible cancer. The performance of the Quick Early Diagnosis Dysphonia Clinic of the Queen Elizabeth Hospital, Birmingham, between May 1997 and April 2001 was reviewed. Of 721 patients reviewed, 123 (17 per cent) had clinically suspicious laryngeal lesions. Thirteen cases of epithelial hyperplastic laryngeal lesions and 27 laryngeal malignancies were diagnosed. There was no statistical link between early cancer detection and assessment within two weeks of referral. However, rapid-access clinics for dysphonia serve an important role in the reassurance and multidisciplinary management of patients with persistent hoarseness. Greater financial commitments are necessary to achieve compliance with objectives for a maximum two-week wait for patients with suspected laryngeal malignancy.
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