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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.
Solid phase amorphization has been found to occur in all refractory metal and a number of rare—earth and platinum group metal thin film on silicon systems. For Ti/Si, Zr/Si, Hf/Si, V/Si, Nb/Si and Ta/Si systems, the growth of amorphous interlayer (a—interlayer) was found to follow a linear law in the initial stage. Si atom was found to be the dominant diffusing species in the solid phase amorphization in Ti/Si, Zr/Si and Hf/Si systems. For the Y/Si system, the stability of amorphous interlayer depends critically on the composition of the amorphous films.
Auto–correlation function analysis was utilized to determine the structure of the amorphous interlayers. HRTEM in conjunction with the fast Fourier transform were applied to determine the first nucleated crystalline phase. Simultaneous presence of multiphases was observed to occur in a number of refractory metal/Si systems. Interesting electrical properties of amorphous interlayers were found for Ti/Si, Zr/Si and Hf/Si systems.
Bulk metallic glasses foams are under consideration as highly functional material, such as energy absorbers or ultra-lightweight parts, due to their porous structure combined with desirable strengths at relatively low densities. Also, the characteristics of high surface area of foams synthesized from metallic glasses make them viable candidates as emerging materials such as high-sensitivity sensors, catalysts or hydrogen storage media. In current study, bulk metallic glass foams were fabricated by extruding powder mixtures comprised of metallic glasses blended with various kinds of fugitive phases followed by dissolution of the fugitive phases in an aqueous chemical solution, for example HNO3, to yield the final porous structure. As a result of dissolution process, porous metallic glass having uniformly distributed micro-scale porosity was fabricated using a sequential synthesis technique beginning with composite particles comprised of composites of MG and a fugitive phase followed by consolidation of the composite powders via warm extrusion.
While multiple DNase activities occur in the excretory/secretory products (ESPs) of the adult Haemonchus contortus, the DNase activities in ESPs of the infective larvae (L3) have not been studied. Thus, the DNase activities in ESPs of H. contortus L3 were investigated and compared to those of adults for developmental stage-specific analysis. The DNase activities had relative molecular masses (Mrs) of 34 and 36 kDa upon zymographic analysis at pH 5.0 and 7.0 when the larvae were incubated for over 48 h. The 34 and 36 kDa DNases of L3 ESPs were also detected in adult ESPs with similar characteristics. However, the 37 and 38.5 kDa DNases of the adult ESPs were not detected in the L3 ESPs. Since the 37 and 38.5 kDa DNase activities were mainly detected in adult ESPs, these activities appear to be specific to the adult stage whereas the other ESP DNase activities appear to be expressed during multiple stages of the parasite's life cycle. While the difference in DNase activities of L3 and adults remains obscure, the role of DNase in larval development should be further clarified and the identification of stage-specific developmental markers will lead to the discovery of specific factors that stimulate larval development.
In0.18 Ga0.82As/GaAs quantum well sample is prepared by molecular beam epitaxy. The integrated photoluminescence dependence on the excitation power intensity is studied. The critical exciton temperature is found to be around 210 K. The high critical exciton temperature is due to the increased in-plane confinement potential. To understand the photoluminescence behavior in this sample an assumption of the existence of trapping centers that has quantum dot-like effect is introduced. These trapping centers are due to In-atom segregation during growth, a multi-peak Gaussian fitting showed additional broad peak in the high energy side of the photoluminescence spectrum which is attributed to the segregated In-atoms. The segregated In-atoms cause additional confinement to be added to the system, and hence excitons survive longer with temperature. The results show that electron hole pairs in the studied quantum well sample are weakly correlated in the near room temperature region.
We have investigated the structural, compositional, interfacial, surface morphological and dielectric properties of Ba0.6Sr0.4TiO3 solid solution thin films La doped from 0 to 10 mol%. The doped thin films were prepared by the metalorganic solution deposition technique using carboxylate-alkoxide precursors. After post-deposition annealing in oxygen ambient at 750 °C the films were characterized via x-ray diffraction, Auger electron microscopy, field emission scanning electron microscopy, and atomic force microscopy. The electrical measurements were achieved in the metal-insulator-metal (MIM) configuration with Pt as the top and bottom electrode. Our results demonstrated that La doping had a strong effect on the films microstructural, dielectric and insulating properties. Specifically, 1 mol% La doped BST films exhibited a lower dielectric constant, 283 and higher resistivity 31.4×1013 W-cm with respect to that of undoped BST. The loss tangent and tunability (at 100 kHz) of the 1 mol% La doped BST films were 0.019 and 21% (at E=300kV/cm) respectively.
New Ni-based bulk amorphous alloys in the alloy system Ni-Zr-Ti-X (X=Al, Si, P) and Ni-Zr- Ti-Si-Y (Y=Sn, Mo, Y) were developed through systematic alloy design based upon the empirical rules for high glass forming ability (GFA). Additions of a small amount of Si and/or Sn to a ternary Ni-Ti-Zr alloy are very effective to increase GFA as well as the undercooled liquid region (ΔTX). Changes in crystallization mode during continuous heating of amorphous phase and lowered liquidus temperature by quaternary and quinary additions are associated with the enhanced GFA and the enlarged ΔTx. Development of new Ni-based amorphous alloys with high GFA and large ΔTx expands structural application of amorphous alloys.
The influence on electrical properties of yttria-fully-stabilized zirconia with low contents of lanthana (up to 5 mol%) were studied. Phase transformation by XRD, lattice parameter, crystallite size, and chemical composition after 4h sintering at 1400°C were adopted for the characterization of the synthesized solid electrolyte. Electrical conductivity from 350°C to 800°C and frequency dependence by complex impedance method were measured to analyze the role of grain-bulk and grain boundary on the electrical conductivity respectively. Nicrostructures of the synthesized sample were observed by SEM(EDS) and TEM for the confirmation of segregation phenomena at grain boundary. Sinterability was improved in the limited amount of La2O3 addition up to 0.5 mol%. The electrical conductivity decreased with increasing the La2O3 addition overall, but slightly increased up to 1 mol% due to the substitution of La3+ for Zr4+. The overall electrical conductivity was much dependent on the contribution of grain-bulk. However, both the potential barrier in the lower La2O3 contents and segregation of second phases in the higher La2O3 contents influenced the electrical conductivity.
This Paper investigates the bending behavior of piezoelectric laminates under combined mechanical and electrical loading. The laminate has a PZT - 5H ceramic core sandwiched by graphite/epoxy plates. Three-point bending tests and in-situ acoustic emission measurements were conducted on the PZT-5H laminates preloaded by an applied electric field. The results show that the PZT-5H core fractures first and then delaminaton occurs along the tensile stressed interface between the PZT ceremic and the graphite/epoxy layer. Finite element analysis was performed to analyze stresses in the sandwich structure under combined mechanical and electrical loading. Consequently, the bending strength of the PZT core was evaluated from the experiment data. The electric field, either positive or negative, reduces the fracture strength of the pzt core.
Laser cleaning has emerged to effectively remove contaminants from solid surfaces. In this paper, recent progress on laser cleaning has been studied. First, a cleaning model is established for removal of particles from substrate surfaces. The model not only explains the influence of fluence on cleaning efficiency, but also predicts the cleaning thresholds. Following that, the optical resonance and near field effect are discussed for transparent particles with a size of α ∼ λ (radiation wavelength) which strongly influences the intensity distribution in the contacted area (substrate surface). The characterization of ejected particles during laser cleaning is finally investigated. It is found that the particle distribution curves closely fit to Gaussian curve.
Single-walled carbon nanotubes (SWNTs) were purified and cut into short length by the liquid phase oxidation using the typical oxidants such as HNO3, H2SO4 and their mixture. The SWNTacid solutions were refluxed at high temperature, filtered on poly tetra-fluoro ethylene (PTFE) filter paper. rinsed with distilled water, and then dried at room temperature. In order to find optimum purifying condition, acid solutions were made by mixing nitric / sulfuric acid by the different volume ratio. The reaction time was also varied from 1h to 6h. Through this method, purified SWNTs with the length of less than 2μm were successfully obtained, which was confirmed by scanning electron microscopy (SEM). From transmission electron microscopy (TEM) analysis, it was verified that SWNTs were purified with little damage on surface and metal catalysts were efficiently removed when sulfuric acid was mixed, which was also confirmed by energy disperse spectrum analysis (EDS). Moreover, size distribution of the purified SWNTs was characterized with Field Flow-Fractionation (FFF) method.
We report a novel finding of slither propagation of shear bands on the fracture surface of a Cu47.5Zr47.5Al5 bulk metallic glass (BMG). The nanoscale heterogeneities in the as-cast state are aggregated along shear bands with irregular morphology. Such heterogeneities create a fluctuating stress field during shear band propagation leading to a slither propagation mode. The slither propagation of 10 to 15 nm wide shear bands is effective to improve both the plasticity and the “work-hardening-like” behavior of BMGs if the size, the morphology, and the elastic properties of the heterogeneities are intimately intercalated during solidification.
The aim of this study was to establish a basic manipulation protocol of preantral follicles for deriving developmentally competent oocytes. Primary, early and late secondary follicles retrieved from the ovaries of 14-day-old F1 (C57BL/6 × DBA2) female mice mechanically or enzymatically were cultured singly and in vitro growth of the follicles and maturation of intrafollicular oocytes were subsequently monitored. A mechanical method retrieved more (p < 0.0001) follicles (339 ± 48 vs. 202 ± 28) than an enzymatic method. However, the enzymatic method collected more singly isolated follicles that could be provided for subsequent culture (102 ± 26 vs. 202 ± 28). When an enzymatic method was employed, early and late secondary follicles required 9 and 6 days for reaching the maximal incidence of the pseudoantral stage. However, primary follicles were not possible to develop into the pseudoantral stage. The optimal duration of oocyte maturation from the onset of follicle culture was 7 days and 5–7 days for early and late secondary follicles, respectively. A general decrease in oocyte diameter (65.2–65.53 μm vs. 75 μm) and zona thickness (5.41–5.74 μm vs. 7.76 μm) was detected in in vitro-derived compared with in vivo-derived matured oocytes. Pronuclear formation was detected in 86–94% of mature oocytes after parthenogenetic activation and no significant difference was detected among groups. These results showed that preantral follicles retrieved by an enzymatic method underwent step-by-step growth in vitro, which could yield mature oocytes.
The utilisation of essential amino acids (EAA) by the mammary gland of lactating dairy cows fed fresh forages was studied to provide basic information useful in designing strategies to increase the production of milk protein from pasture-fed dairy cows. The relationship between the flux of EAA in the whole body and their uptake by the mammary gland was determined in four cows in early lactation (length of time in milk 44 (SD 14·5) d) producing 21 (SD 4·0) kg milk/d. The cows were maintained in metabolism stalls and fed fresh perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) pasture ad libitum or restricted to 75 % ad libitum intake. The whole-body fluxes of amino acids (AA) were measured using an arterio-venous infusion of universally 13C-labelled AA. Whole-body fluxes of fourteen AA were estimated. Isotope dilution indicated that mammary utilisation accounted for one-third of the whole-body flux of EAA, with individual AA ranging between 17 and 35 %. Isoleucine, leucine, valine and lysine were the EAA with the greatest partitioning towards the mammary gland (up to 36 % of the whole-body flux), which could reflect a potentially limiting effect on milk protein synthesis. In the case of AA with low partitioning to the mammary gland (for example, histidine), it is suggested that non-mammary tissues may have priority over the mammary gland and therefore the supply of this AA may also limit milk protein synthesis.
Automation of heavy construction machinery needs sensors that can detect each position under severe construction fields. Motivated by this need a hydraulic cylinder equipped with Hall sensors of Ga-As type has been developed. However, this sensor device has some problems associated with incorrect detection of positions owing to the existence of some magnetic slope and electric noises. To solve these problems, this paper proposes a digital stroke sensing cylinder enhanced by digital signal processing. An apparatus of two hydraulic systems coupled with each other is installed in an experimental setup to evaluate the performance of the developed digital stroke sensing cylinder. In order to control the position of a cylinder rod, a PWM method is used. Evaluation of the performance is carried out under artificial disturbances such as an impulse, addition of some magnetic slope, and additional noises.
To elucidate the epidemiology of widespread ciprofloxacin resistance in our Veterans Affairs medical center using whole cell DNA analysis.
In vitro study of ciprofloxacin resistant and susceptible Enterobacteriaceae isolated during the course of a clinical epidemiologic study of quinolone resistance.
Veterans Affairs Medical Center with acute care and long-term care divisions.
We examined 40 ciprofloxacin-resistant strains of Serratia marcescens, Proteus mirabilis, and Providencia stuartii using restriction endonuclease analysis of whole cell DNA and compared them with concomitantly isolated ciprofloxacin sensitive strains. We sought to determine whether resistant strains were identical to susceptible strains, indicating in vivo emergence of resistant strains from susceptible strains, and whether resistant strains were shared among patients. All 26 ciprofloxacin-resistant S marcestens isolates shared a single ecoRI restriction pattern. Multiple patterns were seen in the ciprofloxacin-susceptible S marcescens isolates; however, several isolates had a pattern matching that of the resistant isolates. Similar results were seen among the P mirabilis isolates. Three different ecoRI patterns were found among the ciprofloxacin-resistant P stuartii isolates; none matched those found among the susceptible isolates. The frequency of spontaneous emergence of ciprofloxacin resistance in susceptible S marcescens strains with restriction pattern matching that of the resistant strains was significantly higher than that of nonmatching strains.
Ciprofloxacin-resistant strains of Enterobacteriaceae became widespread within a short period of time. Resistant strains of S marcestens and P mirabilis arose from endemic susceptible strains. The resistant strain of S marcescens appeared to arise from a susceptible strain with a relatively high frequency of spontaneous ciprofloxacin resistance.
Iron aluminides based on Fe3Al are of interest as structural materials because of their excellent corrosion resistance in many environments. However, studies have shown that one of the major causes of low room temperature tensile ductility, which so far has limited the use of these alloys, is an environmental reaction involving aluminum in the presence of water vapor. During this reaction, atomic hydrogen is released, moves into the sample ahead of the crack tip during stressing, and causes failure before the true ultimate tensile strength of the material is reached. This reaction is reduced significantly by testing in oxygen or vacuum. In the present study, an Fe3Al-based alloy was tensile tested as a function of the level of water vapor in the test environment, from a vacuum of 10−4 Pa to a water vapor partial pressure of 1330 Pa. The results show that a water vapor level of as low as 133 Pa (1 torr) can result in significant embrittlement. The fracture mode remains transgranular cleavage, but the scale of the cleavage facets changes with the water vapor level.
An attempt to improve the ductility in Cr modified Ni3Al alloys is made by means of microstructural control. In order to select an alloy composition such that it locates in the γ ' single phase region at 1000 °C and in the γ + γ ' two-phase region at 1200 °C of the Ni-Al-Cr ternary phase diagram, we first calculated γ and γ ' phase boundaries, using the Cluster Variation Method. Single crystal specimens with desired composition of Ni-19.5Al-7.5Cr at% were grown and homogenized at the above two temperatures for 72 hours and the mechanical properties were tested at room temperature. It is found that the elongation of specimen homogenized at 1200 °C is almost twice as large as that of one homogenized at 1000 °C. The theoretically predicted microstructures and the γ precipitates are also confirmed by optical, SEM micrographs and EDS analysis. It is concluded that a small amount of disordered γ phase precipitates in the γ ' matrix can drastically enhance the tensile ductility of Ni3Al (Ll2)-base alloys
TiAl alloys with Cr, V, and Nb additions show promise as high temperature materials due to their high temperature strength and modulus. Dynamic recrystallization has been shown to be important for the processing and superplastic forming of these materials. Earlier studies have indicated that dynamic recrystallization may also occur during tensile straining at or near the proposed use temperature of these alloys. A systematic study has been conducted to determine the effects of various parameters - temperature, strain, strain rate, and microstructure, on the occurrence of dynamic recrystallization near expected use conditions. The conditions near the ductile to brittle transition temperature which bound the onset of dynamic recrystallization in tension and compression were investigated. The findings will be presented and affrelations will be drawn between the contributions of dynamic recrystallization and high temperature to the observed ductility.