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Information about glacier volume and ice thickness distribution is essential for many glaciological applications, but direct measurements of ice thickness can be difficult and costly. We present a new method that calculates ice thickness via an estimate of ice flux. We solve the familiar continuity equation between adjacent flowlines, which decreases the computational time required compared to a solution on the whole grid. We test the method on Columbia Glacier, a large tidewater glacier in Alaska, USA, and compare calculated and measured ice thicknesses, with favorable results. This shows the potential of this method for estimating ice thickness distribution of glaciers for which only surface data are available. We find that both the mean thickness and volume of Columbia Glacier were approximately halved over the period 1957–2007, from 281 m to 143 m, and from 294 km3 to 134 km3, respectively. Using bedrock slope and considering how waves of thickness change propagate through the glacier, we conduct a brief analysis of the instability of Columbia Glacier, which leads us to conclude that the rapid portion of the retreat may be nearing an end.
Complex oxides and semiconductors exhibit distinct yet complementary properties
owing to their respective ionic and covalent natures. By electrically coupling
oxides to semiconductors within epitaxial heterostructures, enhanced or novel
functionalities beyond those of the constituent materials can potentially be
realized. Key to electrically coupling oxides to semiconductors is controlling
the physical and electronic structure of semiconductor – crystalline
oxide heterostructures. Here we discuss how composition of the oxide can be
manipulated to control physical and electronic structure in
Ba1-xSrxTiO3/ Ge and
SrZrxTi1-xO3/Ge heterostructures. In the
case of the former we discuss how strain can be engineered through composition
to enable the re-orientable ferroelectric polarization to be coupled to carriers
in the semiconductor. In the case of the latter we discuss how composition can
be exploited to control the band offset at the semiconductor - oxide interface.
The ability to control the band offset, i.e. band-gap engineering, provides a
pathway to electrically couple crystalline oxides to semiconductors to realize a
host of functionalities.
Trematode tyrosinases (TYRs) play a major role in the tanning process during eggshell formation. We investigated the molecular and biochemical features of Paragonimus westermani TYR (PwTYR). The PwTYR cDNA was composed of 1568-bp encompassing a 1422-bp-long open reading frame (474-amino acid polypeptide). A strong phylogenetic relationship with Platyhelminthes and Deuterostomian orthologues was evident. The recombinant PwTYR expressed in prokaryotic cells promptly oxidized diphenol substrates, with a preferential affinity toward ortho-positioned hydroxyl groups. It demonstrated fairly weak activity for monophenol compounds. Diphenol oxidase activity was augmented with an increase of pH from 5·0 to 8·0, while monophenol oxidase activity was highest at an acidic pH and gradually decreased as pH increased. Transcription profile of PwTYR was temporally upregulated along with worm development. PwTYR was specifically localized in vitellocytes and eggs. The results suggested that conversion of tyrosine to L-dihydroxyphenylalanine by PwTYR monophenol oxidase activity might be rate-limiting step during the sclerotization process of P. westermani eggs. The pH-dependent pattern of monophenol and diphenol oxidase activity further proposes that the initial hydroxylation might slowly but steadily progress in acidic secreted vesicles of vitellocytes and the second oxidation process might be rapidly accelerated by neural or weak alkaline pH environments within the ootype.
Depression is common after acute coronary syndrome (ACS) with adverse effects on prognosis. There is little evidence on whether depression treatment improves quality of life (QoL) in ACS patients. The aim of this study was to investigate the effects of co-morbid depression and its treatment on QoL in ACS.
In total, 1152 patients were recruited at baseline, 2–14 weeks after a confirmed ACS episode, and 828 were followed 1 year thereafter. Of 446 baseline participants with co-morbid depressive disorders, 300 were randomized to a 24-week double blind trial of escitalopram or placebo, while the remaining 146 received medical treatment only (MTO). QoL was measured by the World Health Organization Quality of Life –Abbreviated form (WHOQOL-BREF).
At baseline, QoL was significantly lower in patients with co-morbid depressive disorder than those without. QoL improvement was significantly greater in those receiving escitalopram than those receiving placebo over the 24-week treatment period. In the 1-year follow-up, the better outcomes associated with escitalopram remained evident against both placebo and MTO.
Depression was significantly associated with worse QoL even in patients with recently developed ACS. Depression treatment was associated with QoL improvement in ACS patients in the 24-week treatment period, the effects of which extended to 1 year.
This study compared the molecular characteristics of vancomycin-resistant Enterococcus faecium (VREF) isolates recovered from 20 non-tertiary-care hospitals (36 isolates) and three tertiary-care hospitals (26 isolates) in diverse geographical areas of Korea from October 2010 to April 2011. All isolates carried the vanA gene only, but 42% and 73% of non-tertiary and tertiary-care isolates expressed the VanB phenotype (teicoplanin minimum inhibitory concentration ⩽16 μg/ml). All isolates harboured insertion sequences, IS1542 and IS1216V, within Tn1546. The isolates from tertiary-care hospitals tended to have reduced Tn1546 lengths by deletion of sequences adjacent to IS elements. Multilocus sequence typing revealed eight sequence types within clonal complex 17 (CC17), but DNA fingerprinting by rep-PCR did not show clonal relatedness between the intra- and inter-hospital isolates. These results suggest that vanA, which has prevailed in tertiary-care hospitals of Korea since the 1990s, had been transferred horizontally to non-tertiary-care hospitals while the genetic rearrangement driven by evolutionary adaptation to adverse environments may have occurred in tertiary-care hospitals.
The Slewing Mirror Telescope (SMT) is the UV/optical telescope of UFFO-pathfinder. The
SMT optical system is a Ritchey-Chrétien (RC) telescope of 100 mm diameter pointed by
means of a gimbal-mounted flat mirror in front of the telescope. The RC telescope has a
17 × 17arcmin2 in Field of View and 4.3 arcsec resolution (full width half
maximum of the point spread function) The beam-steering mirror enables the SMT to access a
35 × 35degree region and point and settle within 1 sec. All mirrors were fabricated to
about 0.02 wavelengths RMS in wave front error (WFE) and 84.7% average reflectivity over
200 nm ~ 650 nm. The RC telescope was aligned to 0.05 wavelengths RMS in WFE (test
wavelength 632.8 nm). In this paper, the technical details of the RC telescope and slewing
mirror system assembly, integration, and testing are given shortly, and performance tests
of the full SMT optical system are reported.
The Ultra-Fast Flash Observatory (UFFO) is a space observatory for optical follow-ups of
gamma ray bursts (GRBs), aiming to explore the first 60 seconds of GRBs optical emission.
UFFO is utilized to catch early optical emissions from GRBs within few sec after trigger
using a Gimbal mirror which redirects the optical path rather than slewing entire
spacecraft. We have developed a 15 cm two-axis Gimbal mirror stage for the UFFO-Pathfinder
which is going to be on board the Lomonosov satellite which is to be launched in 2013. The
stage is designed for fast and accurate motion with given budgets of 3 kg of mass and 3
Watt of power. By employing stepping motors, the slewing mirror can rotate faster than 15
deg/sec so that objects in the UFFO coverage (60 deg × 60 deg) can be targeted in
~1 sec. The obtained targeting resolution is better 2 arcmin using a close-loop
control with high precision rotary encoder. In this presentation, we will discuss details
of design, manufacturing, space qualification tests, as well as performance tests.
Polycrystalline Si (Poly-Si) films were successfully grown at temperature less than 500 °C by using a direct Si ion beam deposition technique. In this process, the ion beam energy of Si- is directly coupled to the formation of the films. High substrate temperature (>600 °C), normally required for conventional CVD techniques, has been a major barrier for the Poly-Si Thin Film Transistor Liquid Crystal Display (TFT LCD) which uses a glass substrate. Thus, the ability to produce Poly-Si film below the glass transition temperature and to control the grain size will make this direct Si- ion beam deposition process a potential alternative technique for future TFT LCD. The grain size dependence on the ion beam energy and substrate temperature was investigated using a Transmission Electron Microscope (TEM). The grain size could be controlled from 0.1 μm to 1 μm at ion beam energies from 10 to 50 eV with a substrate temperature less than 500 °C. The resistivity of the as-deposited film was of the order of 100 Ωcm due to in-situ doping effect.
Hypermucoviscous (HV) isolates of Klebsiella pneumoniae have been linked to virulence potential in experimental infections. We examined 33 isolates of K. pneumoniae from patients with bacteraemia for the HV phenotype on agar culture, and determined their virulence potential by screening for capsular (K) serotype by polymerase chain reaction and the presence of seven virulence factor genes. Fourteen (42·4%) isolates expressed the HV phenotype and 11 of these were serotype K1 or K2; these serotypes were not identified in HV-negative isolates. The genes rmpA, rmpA2, aerobactin, wabG and allS were significantly more frequent in HV than non-HV isolates. Multilocus sequence typing identified 21 sequence types (ST), eight of which were found in HV-positive isolates and the clonal relatedness of isolates of the most frequent types (ST23 and ST11) from different hospitals was confirmed by pulsed-field gel electrophoresis. The HV phenotype was more associated with community-acquired infection with a lower frequency of fatal underlying illness, but with significantly more focal infections, notably liver abscesses. Clinicians should be aware of such clinical impacts of the HV phenotype.
We investigated the electrical characteristics of the MOSCAP structures with W/WNx/poly Si1−xGex gates stack using C-V and I-V. The low frequency C-V measurements demonstrated that the flat band voltage of the W/WNx /poly Si0.4Ge0.6 stack was lower than that of W/ WNx /poly Si0.2Ge0.8 stack by 0.3V, and showed less gate-poly-depletion-effect than that of W/ WNx /poly- Si0.2Ge0.8 gates due to the increase of dopant activation rate with the increase of Ge content in the poly Si1−xGex films. As Ge content in poly Si1−xGex increased, the leakage current level increased a little due to the increase of direct tunneling and QBD became higher due to the lower boron penetration.
High quality, transparent diamond films with relatively large deposition areas have been obtained from oxyacetylene combustion flames at the atmospheric pressure using nozzle tilted at an angle φ) with respect to the Mo substrates. These films are studied using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. Experimental results show that the surface morphology and microstructure depend strongly on the processing parameters such as the gas mixture ratio of acetylene to oxygen, substrate temperature, and the nozzle angle φ. The uniformity of diamond films have been improved using this tilted combustion flame technique and some problems related with this approach are discussed.
The effect of the crystallographic orientation of underlying poly-Si film on the thermal stability of the TiSi2 film was studied. Different preferred orientations of the poly-Si film were obtained by annealing poly-Si or amorphous Si films at various temperatures. The TiSi2 film was formed by the solid-state reaction of the Ti film sputtered on the poly-Si film. The thermal stability of the TiSi2 film was evaluated by changes in the sheet resistance and microstructural evolution during furnace anneals. The TiSi2 film on poly-Si with the <110> preferred orientation shows more stable conductivity during high temperature anneals than with the <111> orientation. The surface energy of underlying poly-Si is expected to influence the thermal stability of the TiSi2/poly-Si structure significantly. Better thermal stability of the TiSi2 film can be obtained by the higher surface energy of underlying poly-Si.
Raman scattering has been used to characterize ultrathin films of β-SiC, ranging in thickness from 38 nm to 240 nm. These films were prepared on the surface of a <100> Si substrate by a carbonization process at a temperature of 1300°C. In each case, the LO phonon near 970 cm−1 and the TO phonon near 795 cm−1 are observed, indicating the formation of β-SiC crystal. The Raman linewidths and peak positions indicate evidence of nonuniform stress and disorder. The Raman intensity of the TO phonon is nearly twice the intensity of the LO phonon measured both with and without the Si substrate, which indicates that the crystal growth was not entirely confined in the <100> direction.
Raman and photoluminescence (PL) spectra have been used to characterize A10.3Ga0.7As/GaAs multiple quantum well (MQW) structures that have been patterned by focused ion beam (FIB) implantation followed by rapid thermal annealing (RTA). Microprobe Raman scattering is used to identify the appropriate RTA and FIB implantation conditions that provide for removal of implantation-induced damage and for compositional intermixing. FIB patterned wire-like structures are characterized by spatially resolved PL spectra.
In this study, we investigate the gettering process of Fe in p-type Cz silicon after iron has been introduced at the solubility limit at 1000°C. Deep Level Transient Spectroscopy (DLTS) was used to measure [FeB], a fingerprint of [Fei], at the center of samples. The minority carrier diffusion length and lifetime were calculated from Electron Beam Induced Current (EBIC) measurements. The fact that [FeB] is proportional to the negative second power of the minority carrier diffusion length at the high [FeB] regime confirms that FeB donors are the dominant recombination centers limiting solar cell performance with high Fe contamination. By quenching after heat treatment, we can maintain and measure the kinetics and thermodynamics of gettering exclusively. The getter/silicon interface was studied by comparison of the gettering rates of molten Al at 620°C, 700°C, and 800°C, and iron silicide at 700°C. We model Fe gettering with respect to temperature, time, solubility and precipitate nuclei density. In the early stage of Fe gettering, the process is dominated by precipitate formation around oxygen precipitate nuclei. The precipitate density is estimated to be on the order of 5×108cm−3. In later stages, Fe outdiffusion contributes to the [Fei] reduction. The early stage precipitation limits [Fei] reduction after short time to the solubility at the gettering temperature.