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It is well known that black hole candidates, Cyg X-1 and GX 339-4, have distinct high and low states, known as bimodal states. Detailed spectroscopic studies of these X-ray sources have revealed high and low states corresponding to optically thick and thin states of the surrounding accretion disks.
An antenna in geostationary orbit was used for VLBI observations at 2.3 GHz, in combination with ground antennas in Australia and Japan. 23 of the 25 observed sources were detected on orbiter-ground baselines, with baseline lengths as large as 2.15 earth diameters. Brightness temperatures between 1012 K and 4 × 1012 K were measured for 10 sources.
We report NH3 observations of the Sgr A complex region including Sgr A West and the 20 km/s and 50 km/s molecular clouds (M–0.13–0.08 and M–0.02–0.07) using the Nobeyama Millimeter Array and the 45m telescope. NH3(1,1) and (2,2) lines were simultaneously observed to estimate the kinetic temperature. Our results suggest strong interaction between the molecular clouds and the continuum sources in the Sgr A complex. The interaction with continuum sources might be an important factor in determining the physical conditions of molecular gas in the galactic center region.
Here we discuss requirements for high performance and solution processable organic semiconductors, by presenting a systematic investigation of 7-alkyl-2-phenylbenzothieno[3,2-b]benzothiophenes (Ph-BTBT-Cn’s). We found that the solubility and thermal properties of Ph-BTBT-Cn’s depend systematically on the substituted alkyl-chain length n. The observed features are well understood in terms of the change of molecular packing motif with n: The compounds with n ≤ 4 do not form independent alkyl chain layers, whereas those with n ≥ 5 form isolated alkyl chain layers. The latter compounds afford a series of isomorphous bilayer-type crystal structures that form two-dimensional carrier transport layers within the crystals. We also show that the Ph-BTBT-C10 afford high performance single-crystalline field-effect transistors the mobility of which reaches as high as 15.9 cm2/Vs. These results demonstrate a crucial role of the substituted alkyl chain length for obtaining high performance organic semiconductors and field-effect transistors.
Observations of the angular distribution of the water masers in the nucleus of NGC4258 reveal the presence of a thin molecular disk in nearly perfect Keplerian orbit (Miyoshi et al., 1995; Moran et al., 1995). About 300 galaxies have been searched for nuclear water masers to a limiting sensitivity of about 0.1 Jy (e.g., Braatz, 1996); and 16 masers have been detected. The maser imaged by Miyoshi et al. (1995) offers the best example of disk structure. VLA data of NGC1068 shows evidence of disk structure (Gallimore et al., 1996; Greenhill & Gwinn, 1996) and NGC2639 has drifting features, which may be due to centripetal acceleration (Wilson et al., 1995).
The VLBA map of the H2O maser IC 1396N, which was obtained during the VSOP pre-launch survey, shows an ordered position of maser spots. The maser spots are located along an almost straight line with the separation between extreme maser spots of 20 mas. The radial velocity varies along the line from by 3 km s−1. In total 9 maser features have been located on the line, all of them unresolved by the VLBA beam. This geometry is consistent with the disk model of masers. The mass of the disk is estimated between 10−7 and 10−4 M⊙, depending on the thickness and density. The disk must be supported by a central star with the mass of about 0.07 M⊙. The H2O maser in IC 1396N may be a proto-planetary disk around a low mass protostar in the process of accretion.
We report the observations of compact steep-spectrum radio sources (CSSs) by VLBI at 22 and 43 GHz and single dich at 22, 43, and 92 GHz. Our results show that CSS also has an active core as well as other AGNs.
Chikungunya virus (CHIKV) and Ross River virus (RRV) of the genus Alphavirus, family Togaviridae are mainly transmitted by Aedes mosquitoes and the symptoms they cause in patients are similar to dengue. A chikungunya (CHIK) outbreak re-emerged in several Asian countries during 2005–2006. This study aimed to clarify the prevalence of CHIKV infection in suspected dengue patients in six countries in South Asia and Southeast Asia. Seven hundred forty-eight serum samples were from dengue-suspected patients in South Asia and Southeast Asia, and 52 were from patients in Fiji. The samples were analysed by CHIKV IgM capture ELISA, CHIKV IgG indirect ELISA and focus reduction neutralization test against CHIKV or RRV. CHIK-confirmed cases in South Asia, particularly Myanmar and Sri Lanka, were 4·6%, and 6·1%, respectively; and in Southeast Asia, particularly Indonesia, the Philippines and Vietnam, were 27·4%, 26·8% and 25·0%, respectively. It suggests that CHIK was widely spread in these five countries in Asia. In Fiji, no CHIK cases were confirmed; however, RRV-confirmed cases represented 53·6% of suspected dengue cases. It suggests that RRV is being maintained or occasionally entering from neighbouring countries and should be considered when determining a causative agent for dengue-like illness in Fiji.
C band backscatter parameters contain information about the upper snowpack/firn in the dry snow zone. The wide incidence angle diversity of the Advanced Scatterometer (ASCAT) gives unprecedented characterisation of backscatter anisotropy, revealing the backscatter response to climatic forcing. The A (isotropic component) and M2 (bi-sinusoidal azimuth anisotropy) parameters are investigated here, in conjunction with data from atmospheric and snowpack models, to identify the backscatter response to surface forcing parameters (wind speed and persistence, precipitation, surface temperature, density and grain size). The long-term mean A parameter is successfully recreated with a regression using these drivers, indicating strong links between the A parameter and precipitation on long timescales. While the ASCAT time series is too short to determine which factors drive observed trends, factors influencing the seasonal and short timescale variability are revealed. On these timescales, A strongly responds to the propagation of surface temperature cycles/anomalies downward through the firn, via direct modulation of the dielectric constant. The influence of precipitation on A is small at shorter timescales. The M2 parameter is controlled by wind speed and persistence, through modification of monodirectionally-aligned surface roughness. This variability indicates that throughout much of coastal Antarctica, a microwave ‘snapshot’ is generally not representative of longer-term conditions.
Surface morphology evolution of epitaxially grown CeO2(110) layers on Si(100) substrates is studied using atomic force microscopy (AFM) and reflection high energy electron diffraction (RHEED). The surface has a faceted structure; a stripe-appearance and triangular-shape in plan- and cross-sectional views, respectively. AFM measurements clarify that as the layer thickness increases, the cross-sectional shape changes from a gable roof shape toward trapezoidal, which is consistent with RHEED analyses. The width of the facet monotonically increases with the layer thickness, while its height saturates at ∼5 nm above 600 nm in thickness, which means that the surface approaches smooth morphology. Ion channeling analyses indicate that the thicker the layer, the better the crystalline quality at the surface.
The surface of Ti-based bulk metallic glass (BMG) was irradiated by the femto-second laser and microgrooves were formed on the surface. The titanate nanomesh layers were fabricated on the micro-grooved BMG surface by hydrothermal-electrochemical (H-E) treatment changing the conditions of the concentration of electrolyte solution (0 and 5 M) and applying current density (0-200 mA/cm2). The bone-inducing capacity of the samples with different H-E treatment was confirmed by soaking them in a simulated body fluid for 12 days. The H-E treatment in higher concentration 5 M NaOH aq. and applying higher current density above 0.5 mA/cm2 exhibited excellent bioactivity inducing large hydroxyapatite crystallites.
Influence of the linear energy-momentum relationship in graphene on conductance and magnetoresistance (MR) in ferromagnetic metal (FM)/graphene/FM lateral junctions is studied in a numerical simulation formulated using the Kubo formula and recursive Green’s function method in a tight-binding model. It is shown that the contribution of electron tunneling through graphene should be considered in the electronic transport in metal/graphene/metal junctions, and that the Dirac point (DP) is effectively shifted by the band mixing between graphene and metal electrodes. It is shown that MR appears due to spin-dependent shift of DP or spin-dependent change in the electronic states at DPs. It is shown that the MR ratio caused by the latter mechanism can be very high when certain transition metal alloys are used for electrodes. These results do not essentially depend on the shape of the junction structure. However, to obtain high MR ratios, the effects of roughness should be small.
Electrical properties of icosahedral phases (I-phase) that precipitated in Zr65Al7.5Cu7.5Ni10M10 (M=Ag, Pd), Zr65Al7.5Cu1.25Ni10M5 (M=Ag, Pd), Zr65Pd25Ni10 and Zr70Pd20Ni10 metallic glasses have been investigated. In-situ resistivity change with increasing temperature was measured at a heating rate of 0.67 K/s from room temperature. I-phase transformation was occurred in the supercooled liquid phase for Zr-Al-Cu-Ni-M glasses, followed by the crystallization to stable Zr2Ni- and Zr2Cu-type crystals. Ternary glasses exhibited the I-phase crystallization from the glass solid phase and subsequently the transformation of I-phase to crystal phases like Zr2Ni and Zr2Pd. The resistivity of I-phase decreased together with advancing I-phase precipitation, about 2 % compared to the resistivity of the supercooled liquid phase, for typical Zr65Al7.5Cu7.5Ni10Ag10 glass. On the other hand, Zr70Pd20Ni10 glass showed the resistivity increment of about 5 % just after completing I-phase crystallization. Low temperature conductivity of Zr65Al7.5Cu7.5Ni10Ag10 and Zr70Pd20Ni10 glasses and I-phases may be explained by the weak localization model of conduction electron in the range from about 20 K to room temperature.
Stereoscopic and electron tomographic observation methods using Transmission
Electron Microscope (TEM) were examined to characterize three-dimensionally
a shape and size of pores and spatial distribution in porous low dielectric
constant (low-k) films. In a case of TEM observation, nm size pores in an
amorphous film are difficult to be imaged since contrast from the amorphous
layer affect the pore imaging. An optimum image capture method at a modified
electron beam condition was studied in which the amorphous contrast from the
porous low-k film is weakened to enhance scattering contrast from the pores
and a matrix. As a result, a stereoscopic observation and 3-D reconstruction
images clarified that the shape of pores was not spherical but distorted and
almost pores were partially connected. For measuring pore size and spatial
distribution, connected pores were segmented into smaller pores by
separating at the narrowest part. From images after segmentation, it is
indicated that there existed more and larger pores at interfaces than a
center area. It was found that the pores did not homogeneously distribute in
the film but concentrated at the interfaces.
The vibrational spectra of N-pairs and nitrogen-vacancy-oxygen defects in nitrogen doped Czochralski silicon have been investigated using density functional theory calculations. We found that 771 cm−1 and 967 cm−1 lines measured by FTIR are fingerprints for N-pairs in interstitial position. These confirm that nitrogen atoms are paired and bonded to Si atoms. Calculated local vibration modes of N2On complexes provide the best matching with observed FTIR frequency of N-O complexes. Nonetheless, VmN2On (m,n =1,2) can develop during crystal cooling or wafer processing, as revealed by local vibrational modes falling around, 806 and 815 cm−1 FTIR frequencies.
The recent innovations in metallic glasses have led to new alloy classes that may be vitrified and a re-examination of the commonly used criteria for glass formation and stability. The new alloy classes are usually at least ternary systems and often higher order that can be grouped into two general categories. In one case large, bulk volumes may be slowly cooled to the glassy state which signifies a nucleation controlled synthesis. The other important class is represented by Al and Fe based glasses that can be synthesized only by rapid solidification processes such as melt spinning. These glasses are often called marginal glass formers that are synthesized under growth controlled kinetic conditions. With marginal glass forming alloys the termination of the amorphous state upon heating is often not characterized by a clear glass transition signal, Tg, but instead by the rapid onset of a primary crystallization reaction that represents the partial crystallization into a high number density of nanocrystals of the major component (i.e. Al or Fe) dispersed within a residual amorphous matrix. However, a closer examination by modulated or dynamic differential scanning calorimetry (DDSC) has identified a true reversible Tg signal that confirms the amorphous state and has revealed additional low temperature annealing behavior that impacts the overall thermal stability and microstructure evolution. At the same time alternate synthesis strategies involving deformation alloying by intense cold rolling reveals that the primary crystallization reaction can be bypassed. Alternatively other approaches have demonstrated that by suitable alloying it is possible to innoculate the primary crystallization reaction and increase the density of primary nanocrystals by about an order of magnitude. These developments represent a major level of microstructure control that have an impact on the structural performance and stability.
The magnetic properties of novel bulk glassy Nd60Fe30Al10 magnets around the transition to the paramagnetic state have been studied in order to understand the magnetic microstructure in these materials. Analyses of the critical behavior of the magnetic isotherms suggest a transition from a low field magnetic state to a ferromagnetic-like state upon the application of high enough magnetic fields. The ferromagnetic-like state is evidenced by a scaling of the magnetization curves with critical exponents λ=1.5(1), β=0.65(5), and TC=465 K. These results are consistent with the predictions for weak random magnetic anisotropy systems.