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Transition metal dichalcogenides are 2D structures with remarkable electronic, chemical, optical and mechanical properties. Monolayer and crystal properties of these structures have been extensively investigated, but a detailed understanding of the properties of their few-layer structures are still missing. In this work we investigated the mechanical differences between monolayer and multilayer WSe2 and MoSe2, through fully atomistic molecular dynamics simulations (MD). It was observed that single layer WSe2/MoSe2 deposited on silicon substrates have larger friction coefficients than 2, 3 and 4 layered structures. For all considered cases it is always easier to peel off and/or to fracture MoSe2 structures. These results suggest that the interactions between first layer and substrate are stronger than interlayer interactions themselves. Similar findings have been reported for other nanomaterials and it has been speculated whether this is a universal-like behavior for 2D layered materials. We have also analyzed fracture patterns. Our results show that fracture is chirality dependent with crack propagation preferentially perpendicular to W(Mo)-Se bonds and faster for zig-zag-like defects.
We present the results of a high-resolution CO-line survey using the Nobeyama Millimeter-wave Array at high-angular (⋐ 2–3″) and high spectral resolutions for the 15 CO-richest Virgo spirals. We derived exact rotation curves using position-velocity diagrams by applying the iteration method. the obtained RCs rise steeply in the central 100 pc. Surface-mass-density distributions by direct deconvolution of the RCs show massive cores of ⋐ 109M⊙ within 100 pc, suggesting the existence of DM cusps in the centres. Five galaxies were found to nest single-peaked extremely high-density molecular cores, where star formation is currently suppressed by the high differential rotation. We show that the deeper is the gravitational potential, the higher is the central gas density.
We have made a CO(J=2-1) observations using the Nobeyama 45m telescope aimed at examining the physical properties of the molecular gas in this object. The upper limit obtained is 1.8 mK (3σ) at a velocity resolution of 100 km s−1, which leads to an upper limit on the molecular gas mass of 5.3 × 1011M⊙, if we assume a line width of 250 km s−1 obtained in the CO(J = 5 - 4) line (rest-frame) and the Galactic CO-to-H2 conversion factor of 4.5 (M⊙ K km s−1 pc2). The line ratio between the 2–1 line and the 5–4 line as well as those from the 7–6 and the 4–3 lines (Omont et al. 1996, Nature, 382, 428) imply that the mean gas density is as high as 103–5 cm−3, which is comparable to that in nearby star burst galaxies (e.g., Solomon et al. 1992, ApJ, 387, L55).
We have made a CO (J=2−1) observation using the Nobeyama 45m telescope aimed at examining physical properties of the molecular gas in the object. Upper limit obtained is 1.8 mK (3σ) at a velocity resolution of 100 km s−1, which leads to an upper limit on the molecular gas mass of 5.3 × 1011M⊙, if we assume a line width of 250 km s−1 obtained in J = 5–4 line and the Galactic CO-to-H2 conversion factor of 4.5 M⊙ K km s−1 pc2. The line ratio between 2–1 line and 5–4 line as well as those from 7–6 and 4–3 lines (Omont et al. 1996) imply that the mean gas density is as high as 103–5 cm−3, which is comparable to that in nearby star burst galaxies (e.g., Solomon et al. 1992).
Since the bulk of the energy density of the Cosmic X-ray Background (CXB) resides in the harder energy band than that of the ROSAT band (0.5-2 keV) and since the X-ray sources identified in the ROSAT band have X-ray spectra softer than that of the CXB, investigation of nature of the X-ray sources at the harder energy band is indispensable to solve the origin of the CXB. However, only 2-3% of the CXB in the hard band (2-10 keV) had been resolved into discrete sources (Piccinotti et al. 1982, ApJ 253, 485). We present our preliminary results of optical follow-up observations of the ASCA Lynx deep survey.
Δ14C values of leaves of deciduous trees provide a means to map the regional-scale fossil fuel ratio in the atmosphere. We collected a batch of ginkgo (Ginkgo biloba Linnaeus, a deciduous tree) leaf samples from across Korea in the month of July in both 2010 and 2011 to obtain the regional distribution of Δ14C. The Δ14C values of the samples were measured using accelerator mass spectrometry (AMS) at the Korea Institute of Geoscience and Mineral Resources (KIGAM). The average of the Δ14C values from clean air sites in Korea in 2011 measured slightly lower than the average of Δ14C values in 2010. Distribution maps of Δ14C of 2011 and 2010 in Korea were made based on a series of Δ14C values of ginkgo leaf samples from Korea using the Geostatistical and Spatial analyst tools in ESRI's ArcMap software. The distribution maps of Δ14C showed that Δ14C values in the western part of Korea are lower than those in the eastern part of Korea. This is because the western part of Korea is densely populated and contains many industrial complexes, and also because westerly winds from China, containing CO2 from fossil fuel use, blow into Korea. We compared the distribution maps of 2010 and 2011 and tried to find traces of the Fukushima power plant accident in Japan.
We have conducted 1.1 mm ALMA observations of a contiguous 105” × 50” or 1.5 arcmin2 window in the SXDF-UDS-CANDELS. We achieved a 5σ sensitivity of 0.28 mJy, giving a flat sensus of dusty star-forming galaxies with LIR ~6×1011L⊙ (if Tdust=40K) up to z ~ 10 thanks to the negative K-correction at this wavelength. We detected 5 brightest sources (S/N>6) and 18 low-significant sources (5>S/N>4; they may contain spurious detections, though). One of the 5 brightest ALMA sources (S1.1mm = 0.84 ± 0.09 mJy) is extremely faint in the WFC3 and VLT/HAWK-I images, demonstrating that a contiguous ALMA imaging survey uncovers a faint dust-obscured population invisible in the deep optical/near-infrared surveys. We find a possible [CII]-line emitter at z=5.955 or a low-z CO emitting galaxy within the field, allowing us to constrain the [CII] and/or CO luminosity functions across the history of the universe.
Cicatricial pemphigoid can affect all mucosa of the upper aerodigestive tract; however, hypopharyngeal involvement is less frequent.
This paper presents a 69-year-old male diagnosed as having cicatricial pemphigoid who was experiencing difficulty swallowing. Videofluorography with barium swallow demonstrated narrow flow through the medial hypopharynx, but not through the lateral hypopharynx. Direct laryngoscopy revealed that the postcricoid hypopharyngeal lumen had become narrow due to circumferential scar formation. Interestingly, detached thin membranous webs were observed beyond the circumferential scar.
This report describes important videofluorographic and direct laryngoscopic findings showing rare hypopharyngeal involvement in a case of cicatricial pemphigoid.
Vacancy-type defects in 60-keV Be+-implanted GaAs and InP were studied by a monoenergetic positron beam. The depth distributions of vacancy-type defects were obtained from measurements of Doppler broadening profiles of the positron annihilation as a function of incident positron energy. Vacancy-type defects introduced by ion implantation were observed in n-type GaAs. For p-type GaAs, however, this was not the case. This can be attributed to the recombination of vacancy-type defects and pre-existed interstitial-type defects in p-type GaAs. The defects induced by ion implantation in InP were also studied.
Optical properties of fully-strained wurtzite and zincblende InxGa1-xN/GaN multiple quantum well (MQW) structures were compared to discuss the origin of exciton localization. In contrast to the hexagonal InGaN MQWs, the photoluminescence (PL) peak energy of cubic InGaN MQWs showed a moderate blueshift with decreasing well thickness, L, and low-temperature PL decay time of the cubic MQWs did not depend strongly on L. The results imply that the wavefunction overlap in cubic InGaN MQWs was not reduced compared to the hexagonal ones, since they do not suffer from the electric field normal to the QW plane due either to spontaneous or piezoelectric polarization. Both MQWs exhibited a large and composition-dependent bandgap bowing, and time-resolved PL (TR-PL) signals showed a stretched-exponential decay even at room temperature. The exciton localization is considered to be an intrinsic property of InGaN.
A series of novel ionic chromophores consisting of a carbazole moiety and pyridinium rings connected by a double bond have been designed and synthesized as nonlinear optical materials. Their linear and nonlinear optical properties were investigated by semiempirical calculation and experiment. The absorption maximum wavelengths (lmax) of these ionic chromophores showed shifting to longer wavelength region than their corresponding electrically neutral compounds. These ionic chromophores possess large first hyperpolarizabilities (b).
In the fabrication of a-Si photoreceptor for electrophotography (Fig.1), it is important to understand physical and chemical reactions in glow-discharge plasma  in order to improve film quality and to achieve high deposition rate  and uniformity of the film, because of its thickness of about 30 μm and large area.
It has been found that photosensitivity of amorphous silicon (a-Si) photoreceptor fabricated by g1ow-discharge decomposition of SiH4 – B2H6 – Ar has specific relation to peak-to-peak value of Rf (13.5 MHz) voltage (Vp - p) and DC bias voltage (Vdc) on the Rf powered-electrode. The lower the Vp - p value is depressed, the higher the photosensitivity is improved. Dependences of the Vp - p value on deposition parameters such as gas pressure, distance between Rf powered-e1ectrode and aluminum substrate, Rf electric power and dilution ratio of SiH4 to Ar seem to indicate correlation of Vp - p with electron energy and electron density in the plasma.
Furthermore, the Vp - p and Vdc values have been measured in plasma of He, Ne (rare-gases with no Ramsauer effect), Ar, Kr, Xe (rare-gases with Ramsauer effect), and H2, N2, CH4, SiH4 (molecular-gases): Specific behaviors in Vp - p and Vdc seem to have correlation with collision cross - sections of electrons (with the energy of 2 ∼ 10 eV) in these gases.
The photocurrent behavior in polydiacetylene (PDA) single crystals of PTS (poly-(2, 4-hexadiyne-1, 6-diol bis(p-toluenesulfonate)) and MADF (poly-(1-(3-(methylamino)phenyl)-4-(3, 5-bis (trifluoromethyl)-phenyl) butadiyne)) have been investigated by using steady state photoconductivity measurements. These measurements were carried out as a function of sample temperature and incident light polarization. PTS and MADF show completely different behavior in these measurements. These differences between PTS and MADF suggest that the side groups of PDA strongly influence the photocurrent behavior in PDA.
Charge carrier generation and transport mechanisms in polydiacetylene thin film single crystals., poly-PTS (2,4-hexadiyne-1,6-diol bis(p-toluenesulfonate)) and poly- BTFP (bis-(4-n-butyl-2,3,5,6-tetra-fluorophenyl) butadiyne), are studied by using steady state and transient photoconductivity techniques. The electric field dependence of the steady state photocurrent is superlinear for both samples. Dependence of photocurrent on incident light polarization has been investigated. The polarization dependence of photocurrent has completely different behavior for the polydiacetylene PTS and BTFP. Single-gap transmission line experiment has been designed to directly measure the drift velocity of PTS single crystals. A drift velocity of the order of 106cm/s was measured.
SiO2 thin firms were fabricated in a remote electron cyclotron resonance (ECR) plasma by tctraethoxysilane (TEOS) as the silicon source. Oxygen was used as the plasma gas. A mesh was placed between the TEOS gas outlet and the substrate. In the present investigation a-SiO2 films were deposited with and without the mesh and film properties were studied comparatively. The deposition rate increased when the mesh was attached. The optimum deposition rate is observed when the mesh voltage was zero, that is the mesh was grounded. The deposition rates of both methods were also dependnt on the TEOS flow rate, applied microwave power and the substrate temperature. These three parameters have significant roles in controlling the film quality. Good quality SiO2 films can be obtained with a higher deposition rate when a mesh is attached.
Recent advances in understanding the ALE (atomic layer epitaxy) growth of ZnSe, ZnS and ZnTe are reviewed. The Ideal ALE growth is obtained in the substrate temperature range of 250–350°C for ZnSe. In the ALE growth of ZnSe and ZnTe, a unique self-limiting mechanism is observed, in which the deposition rate saturates at 0.5 monolayer per cycle. Furthermore, applications of ALE of II–VI compounds to the growth of strained layer superlattices are also reviewed.
A study of laser annealing of a-SiC:H films was carried out in order to obtain poly-SiC films. First, a-SiC:H films were fabricated at temperatures ranging from 30 to 400 °C. All these films show amorphous structure before the annealing process. After annealing by a single pulse of 248 nm laser, films show poly-SiC structure. The pulse energies used for these anneals varied from 30 to 300 mJ/pulse. After exposing to a laser pulse, the a-SiC:H films melt and recrystallize forming poly-SiC structure. In addition to this process, a fraction of the film is observed to be vaporized. This vaporized fraction depends on the original film composition, hardness and the laser pulse-energy. Electrical resistivity of the films before the annealing process lies in the region of 1015 Ωcm. This resistivity drops drastically after the annealing process.
detailed study was carried out in investigating the chemical reaction scheme involved with the deposition of a-SiC:H films by carbosilane sources in a remote hydrogen plasma. As the carbosilane sources, tetramethylsilane (TMS), hexamethyldisilane (HMDS) and tetrakis(trimethylsilyl)silane (TMSS) were used. Depositions were performed in the presence and absence of both UV radiation and H radicals. UV radiation activates only the TMS molecules out of the above three types of molecules in depositing a-SiC:H films. Other two monomers are seen to be activated by hydrogen radicals. It is proposed that the most susceptible bond to be broken at first by hydrogen radical is the Si-Si bond. A reaction model for the formation of a- SiC:H films was presented by considering the Me2Si=CH2 as the film forming precursor.