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Using frequency-modulated continuous wave radar data from the 32nd Chinese Antarctic Research Expedition in 2015/16, subsurface profiles were obtained along an East Antarctic inland traverse from Zhongshan station to Dome A, and four distinct regions were selected to analyze the spatiotemporal variability in historical surface mass balance (SMB). Based on depth, density, and age data from ice cores along the traverse, the radar data were calibrated to yield average SMB data. The zone 49–195 km from the coast has the highest SMB (235 kg m−2 a−1). The 780–892 km zone was most affected by the Medieval Warm Period and the Little Ice Age, and the SMB during ad 1454–1836 (71 kg m−2 a−1) was only one-quarter of that in the 20th century. The SMB in the 1080–1157 km zone fluctuates the most, possibly due to erosion or irregular deposition of snow by katabatic winds in low SMB areas with surface elevation fluctuations. Dome A (1157–1236 km) has the lowest SMB (29 kg m−2 a−1) and did not decrease during Little Ice Age. Understanding the spatiotemporal variability of SMB in a larger space can help us understand the complex climate history of Antarctica.
Echinococcus granulosus sensu stricto (s.s.), Echinococcus multilocularis and Echinococcus canadensis are the common causes of human echinococcosis in China. An accurate species identification tool for human echinococcosis is needed as the treatments and prognosis are different among species. The present work demonstrates a method for the simultaneous detection of these three Echinococcus species based on multiplex polymerase chain reaction (mPCR). Specific primers of this mPCR were designed based on the mitochondrial genes and determined by extensive tests. The method can successfully detect either separated or mixed target species, and generate expected amplicons of distinct size for each species. Sensitivity of the method was tested by serially diluted DNA, showing a detection threshold as less as 0.32 pg for both E. granulosus s.s. and E. canadensis, and 1.6 pg for E. multilocularis. Specificity assessed against 18 other parasites was found to be 100% except weakly cross-react with E. shiquicus. The assay was additionally applied to 69 echinococcosis patients and 38 healthy persons, confirming the high reliability of the method. Thus, the mPCR described here has high application potential for clinical identification purposes, and can further provide a useful tool for evaluation of serology and imaging method.
We report new field observations, zircon U–Pb ages and geochemical data for the discrete members of the Zhaheba ophiolite complex in northeastern Junggar of the Central Asian Orogenic Belt (CAOB) with the aim to understand the accretion process of the eastern Junggar terrane. The zircon age data reveal that the cumulates of the Zhaheba ophiolite crystallized at ~485 Ma while the volcanic sequences erupted at ~400 Ma. Thus, the volcanic sequences are not members of the Zhaheba ophiolite. Chromian spinels from the serpentinite have comparable elemental compositions to those of spinels from MORB-type ophiolites. Similarly, the rift affinity of clinopyroxene and positive zircon εHf(t) (13–20) and mantle δ18O (+5.37‰) values of the cumulates imply that the cumulates crystallized from primitive magmas derived from a depleted mantle source. Elemental and Nd isotopic compositions indicate that the basalts in the Zhaheba area were derived from partial melting of a mantle wedge metasomatized by adakitic melts and/or subduction-related fluids. The data presented in this contribution, together with previous studies, indicate that the Zhaheba–Almantai and Kelameili ophiolites were MORB-type, which implies that there were at least two mid-ocean ridges during Ordovician to early Devonian times in the Junggar Ocean. In the earlier stage, intra-oceanic subduction led to the formation of the intra-oceanic arc, and then the Kelameili ophiolite accreted to an intra-oceanic accretionary wedge. In the later stage, the Zhaheba–Almantai ophiolite accreted to the accretionary wedge along the southern margin of the Iritish suture zone during the roll-back of the subduction zone from north to south.
Designing and testing flight control algorithms for quadrotor UAVs (unmanned aerial vehicles) is not an easy task due to the risk of possible danger and damage during the practical flight. In order to improve the safety and efficiency of the flight control implementation, a low-cost real-time HILS (hardware-in-the-loop simulation) testbed for quadrotor UAVs is developed in this paper. To realize the HILS testbed, a miniature quadrotor is used as the main body, equipped with a micro AHRS (attitude heading reference system) unit and a self-build DSP (digital signal processor) board. The HILS is implemented by using xPC target. A compact PC/104 computer is utilized as the target computer, and a laptop PC is employed as the host computer. A desktop PC is used as flight visualization computer which runs FlightGear and Google Earth to show visual data, such as orientation and flight path of the quadrotor UAV. This testbed can be utilized for simulating various flight control algorithms, without losing safeness and reliableness. To demonstrate the effectiveness of the proposed testbed, a new nonlinear adaptive sliding mode based stabilization control algorithm is developed and verified on the HILS testbed.
Mouse strain differences in immobility and in sensitivity to antidepressants have been observed in the forced swimming test (FST) and the tail suspension test (TST). However, the neurotransmitter systems and neural substrates that contribute to these differences remain unknown. To investigate the role of the hippocampal serotonin transporter (5-HTT), we measured baseline immobility and the immobility responses to fluoxetine (FLX) in the FST and the TST in male CD-1, C57BL/6, DBA and BALB/c mice. We observed strain differences in baseline immobility time, with CD-1 mice showing the longest and DBA mice showing the shortest. In contrast, DBA and BALB/c mice showed the highest sensitivity to FLX, whereas CD-1 and C57BL/6 mice showed the lowest sensitivity. Also we found strain differences in both the total 5-HTT protein level and the membrane-bound 5-HTT level (estimated by Vmax) as follows: DBA > BALB/c > CD-1 = C57BL/6. The uptake efficiency of the membrane-bound 5-HTT (estimated by 1/Km) was highest in DBA and BALB/c mice and lowest in CD-1 and C57BL/6 mice. A correlation analysis of subregions within the hippocampus revealed that immobility time was negatively correlated with Vmax and positively correlated with Km in the hippocampus. Therefore a higher uptake capacity of the membrane-bound 5-HTT in the hippocampus was associated with lower baseline immobility and greater sensitivity to FLX. These results suggest that alterations in hippocampal 5-HTT activity may contribute to mouse strain differences in the FST and the TST.
In 2008 January the 24th Chinese expedition team successfully deployed the Chinese Small Telescope ARray (CSTAR) to Dome A, the highest point on the Antarctic plateau. CSTAR consists of four 14.5cm optical telescopes, each with a different filter (g, r, i and open) and has a 4.5°×4.5° field of view (FOV). Based on the CSTAR data, initial statistics of astronomical observational site quality and light curves of variable objects were obtained. To reach higher photometric quality, we are continuing to work to overcome the effects of uneven cirrus cloud cirrus, optical “ghosts” and intra-pixel sensitivity. The snow surface stability is also tested for further astronomical observational instrument and for glaciology studies.
This article reports on microstructure and dielectric properties of Ba0.5Sr0.5Ti1−3y/2WyO3 ceramics. Dielectric peaks of the Ba0.5Sr0.5Ti1−3y/2WyO3 ceramics were markedly suppressed, broadened, and shifted to low temperature with increasing content of W. The limit of W incorporating into the barium strontium titanate (BST) lattice was y = 0.02. Two second phases (BaWO4 and Ba2Ti5O12) were formed above the solid solution limit of W in BST. The doping mechanism represents a new approach to develop microwave tunable materials. Dielectric properties of the Ba0.5Sr0.5Ti1−3y/2WyO3 ceramics could be optimized by the content of W. The sample with y = 0.05 had ε′ of 431, quality factor of 365 (at 2.111 GHz), and tunability of 11.5%, which makes a potential candidate for tunable microwave device applications in the wireless communication.
In this study, novel Si2Sb2Te6 phase change material is investigated in detail for the phase change memory application using transmission electron microscopy and X-ray photoelectron spectroscopy. The phenomenon that Te diffuses to the film surface during phase switching and successively evaporates out has been confirmed. The phase change memory cells employing Si2Sb2Te6 and Si3Sb2Te3 materials are fabricated and programmed. For the Si2Sb2Te6-based cell a data endurance of 5×105 cycles is achieved with a failure mode resembling reset stuck, which can be attributed to the migration of Tellurium during the operation cycles. It means that a thermally stable material system of SixSb2Te3 is preferred for the PCM applications.
Zr–N films were grown on glass and Si (100) substrate by radio-frequency magnetron sputtering using a mixture of high pure nitrogen and argon as sputtering gases. The structure and properties of Zr–N compounds in the films change with N2/(N2+Ar) flow ratio (RN2). At low RN2, a ZrN alloy with the rocksalt structure (denoted as γ-ZrNx) is formed. The N concentration x and lattice constant increases with increasing RN2, and x reaches 1 when the RN2 goes up to 20%. As the RN2 exceeds 20%, the film is composed of γ-ZrN and Zr3N4 phase with Th3P4 structure (denoted as c-Zr3N4). The relative content decreases for the γ-ZrN but increases for the c-Zr3N4 with increasing RN2, and a single phase of c-Zr3N4 was deposited on glass at RN2 of 100%. The c-Zr3N4 behaves with p-type conductivity with a band gap of 2.8 eV. The lattice constant of the c-Zr3N4 was measured to be ∼0.674 nm. The mechanism of the phase transition from γ-ZrN to c-Zr3N4 with increasing RN2 was suggested.
In Scanning Transmission Electron Microscopy (STEM) the High-Angle Annular Dark-Field (HAADF) signal increases with atomic number and sample thickness, while dynamic scattering effects and sample orientation have little influence on the contrast. The sensitivity of the HAADF detector for a FEI F30 transmission electron microscope has been calibrated. Additionally, a nearly linear relationship of the HAADF signal with the incident electron current is confirmed. Cross sections of multilayered samples for contrast calibration were obtained by focused ion-beam (FIB) preparation. These cross sections contained several layers with known composition. A database with several pure elements and compounds has been compiled, containing experimental data on the fraction of electrons scattered onto the HAADF detector for each nanometer of sample thickness. Contrast simulations are based on the multi-slice formalism and confirm the differences in HAADF-scattering contrast for the elements and compounds. TEM offers high lateral resolution, but contains little or no information on the thickness of samples. Thickness maps in energy-filtered transmission electron microscopy, convergent-beam electron diffraction and tilt series are so far the only methods to determine thicknesses of particles in a transmission electron microscope. We show that the calibrated HAADF contrast can be used to determine the thicknesses of individual nanoparticles deposited on carbon films. With this information the volumes of nanoparticles with known composition were determined.
Co-based brazing alloy CoFeNi(Si, B)CrTi was designed for SiC joining. The periodic banded reaction structure that existed at the interface between SiC and the traditional Ni-based or Co-based braze has been eliminated by the new brazing alloy. The maximum room-temperature four-point bend strength of 161 MPa was achieved for SiC/SiC joint under the optimum brazing condition of brazing filler thickness of 120 μm, brazing temperature of 1150 °C, and brazing time of 10 min. The corresponding reaction layer of the SiC/SiC joint is composed of multilayer silicides and TiC band, and many small TiC particles are scattered throughout the matrix of the central part of the joint. The joints thus exhibit stable high-temperature strength. It is believed that the formation of TiC in the joint contributes not only to the elimination of the periodic banded reaction structure, but also to the high joint strength and the high-temperature stability.
The conduction band offset of n-ZnO/n-6H-SiC heterostructures fabricated by rf-sputtered ZnO on commercial n-type 6H-SiC substrates has been measured. Temperature dependent current-voltage characteristics, photocapacitance, and deep level transient spectroscopy measurements showed the conduction band offsets to be 1.25 eV, 1.1 eV, and 1.22 eV, respectively.
Electrical properties of n-ZnO/n-GaN isotype heterostructures obtained by rf-sputtering of ZnO films on GaN layers grown by metal-organic vapour phase epitaxy are discussed. Current-voltage (I-V) characteristics of the n-ZnO/n-GaN diodes revealed highly rectifying behavior with forward and reverse currents ∼1.43×10-2 A/cm2 and ∼2.4×10-4 A/cm2, respectively, at ±5 V. From the Arrhenius plot built using temperature dependent current-voltage characteristics (I-V-T) an activation energy 0.125 eV was derived for the reverse bias leakage current path, and 0.62 eV for the band offset from forward bias measurements. From electron-beam induced current measurements the minority carrier diffusion length in ZnO was estimated in the range 0.125-0.175 mm, depending on excitation conditions. The temperature dependent EBIC measurements yielded an activation energy of 0.462 ± 0.073 V.
Zinc oxide (ZnO) thin films have emerged as one of the most promising oxide materials owing to their optical and electrical properties, together with their high chemical and mechanical stability. Chemical solution deposition (CSD) is attractive technique for obtaining ZnO thin films and has the advantages of easy control of the film composition and easy fabrication of a larger-area thin film at low cost. In this work, epitaxial ZnO thin films on SiC substrate were prepared by using a CSD method with a zinc naphthenate precursor. Precursor films were pyrolyzed at 500°C for 10 min in air and finally annealed at 600°C, 700°C, 800°C and 900°C for 30 min in air. Crystallinity and in-plane alignment of the films were investigated by X-ray diffraction theta-2 theta scan and pole-figure analysis. Scanning electron microscope, scanning probe microscope, and He-Cd laser (325 nm) are used to detect the surface morphology and photoluminescence of the films. The effects of annealing temperature on crystallinity and epitaxy of the films will be fully discussed on the basis of the results of X-ray diffraction analysis.
The yolk proteins of the silkworm, Bombyx mori, are important sources of nutrition and energy during embryo development. By analysing the yolk proteins from silkworm eggs, the composition and the metabolism of yolk proteins during embryo development stages can be studied at the proteome level. Yolk proteins were obtained from unfertilized eggs and eggs at different embryo development stages by dissection and then separated and analysed by two-dimensional electrophoresis and its corresponding image analysis system. It was discovered that over 200 proteins exist in mature silkworm eggs. Some specific spots of yolk proteins were found in different silkworm strains, while few differences in yolk proteins appeared during different development stages in the same silkworm strain. This result indicates that the silkworm embryo does not utilize yolk proteins selectively by absorbing one or some special proteins, but by absorbing the yolk protein grains one by one during development.
The new species, Termitomyces bulborhizus, is described from south-west China. The stipe of the basidiome is swollen into a prominent bulbous base at ground level, and this, together with the floccules on the stipe surface, distinguishes this species within the genus. T. bulborhizus is compared with closely related species, including three originally described from China, and a key to T. bulborhizus and related species is provided.
Solid phase crystallization (SPC) of a-Si: H at 600°C was investigated by transmission electron microscopy (TEM) and Raman spectroscopy in a cantilever structure, where the underlying SiO2 was removed prior to the crystallization. The absence of the underlying oxide leads to both a higher grain size and a lower intragranular defect density. The grain size increases from 0.6 μm in regions with the underlying oxide to 3.0 μm without the underlying oxide, and the intragranular defect density decreases one order of magnitude from ∼ 1011 cm-2 to ∼ 1010 cm-2. The improvements in material quality without the lower a-Si/SiO2 interface are thought to be due to a lower nucleation rate and a lower tensile stress with an easier silicon atomic rearrangement at the lower silicon interface.
An optically polished x-cut KTiOPO4 crystal of size 22×6×1.5mm3 was implanted with 2.8-MeV He ions to a dose of 1.5 × 1016 ions/cm2 at room temperature to form a waveguide. The prism coupling method was used to measure the modes and the fiber probe technique was used to measure the attenuation in the KTiOPO4 waveguide. The refractive index profile, nz, in the KTiOPO4 waveguide was given based on the procedure by Chandler and Lama [P.J. Chandler and F.L. Lama, Optica Acta 33, 123 (1986)]. The waveguide attenuation measured was 2.57 dB/cm for m = 1 mode. After annealing at 260 °C for 30 min, there was no obvious change in the KTiOPO4 waveguide attenuation.
X-cut potassium titanyl phosphate (KTiOPO4 or KTP) was implanted by multienergy MeV He+ implantation with a total dose of 2 × 1016 ions/cm2 at liquid nitrogen temperature. The energy and dose used are as follows: 3.3 MeV and 2 × 1015 ions/cm2, 3.2 MeV and 4 × 1015 ions/cm2, 3.1 MeV and 4 × 1015 ions/cm2, and 3.0 MeV and 1.0 × 1016 ions/cm2 to reduce tunneling effect. The 22 dark modes were measured by the isosceles prism coupling method. The 15 bright modes were observed after 250 °C, 60 min annealing. The result shows that the waveguide formation of KTiOPO4 implanted by MeV He+ is not strongly dependent on the cut direction, which is different from the waveguide formation of KTiOPO4 by ion exchange process.
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