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Aneurysms of the right atrium are rare in the paediatric population. We report a case of a foetal diagnosis of right atrial aneurysm with associated atrial tachycardia in foetal and postnatal life. Unique to our case are the findings of isolated pericardial effusion without hydrops fetalis and the development of aortic coarctation in postnatal life.
Metal organic precursor has a sufficiently high vapor pressure at low temperature, contributing high-speed low-temperature MOCVD-MoS2 film formation. We fabricated monolayer MoS2 by 1 step cold-wall MOCVD using di-isopropyl-diazadiene-molybdenum tricarbonyl [i-Pr2DADMo(CO)3] and di-tertiary-butyl disulfide [(t-C4H9)2S2]. These precursors are able to be vaporized using bubbling system and deposited at low temperature. From the XPS investigations, Mo-S bonding peaks were observed and S:Mo ratio was calculated as 2:1, suggesting formation of MoS2. Moreover, molybdenum carbides and nitrogen impurities were not observed which was confirmed by XPS and EDX. From the results of Raman spectroscopy, AFM height distribution, and spectroscopic ellipsometry, it was determined that the film thickness is 0.64 nm which is corresponding to monolayer MoS2, the lateral grain size is approximately 100 nm, and the bandgap energy is 1.8 eV.
We report the investigation on the properties of a novel Te precursor (i-C3H7)2Te and its effectiveness in fabricating MoTe2. The vapor pressure of the precursor was obtained by measuring the pressure as a function of its temperature in a sealed chamber. As a result it showed a high vapor pressure of 552.1 Pa at room temperature. The decomposition of the precursor was also investigated using DFT calculation. It was shown that the most likely reaction during the course of the decomposition of (i-C3H7)2Te is (i-C3H7)2Te → H2Te + 2 C3H7. The effectiveness of the precursor on the fabrication of MoTe2 was also investigated. Sputter-deposited MoO3 was tellurized in a quartz-tube furnace at the temperature up to 440°C. The resulting film showed that the 80% of the original MoO3 was tellurized to form MoTe2. It was also shown that further optimization of tellurization is required in order to prevent formation of metal Mo and elemental Te.
MoS2(1−x)Te2x thin films were fabricated by high-temperature co-sputtering deposition and post-deposition tellurization annealing using novel Te precursor (i-C3H7)2Te for the first time. As a result, high crystal quality MoS2(1−x)Te2x (6.5 nm) were successfully fabricated with the Te concentration x ranging from 0.48 to 0.61 and band gap value from 0.80 to 0.87 eV. From the obtained band gap values of MoS2(1−x)Te2x, the bowing parameter b was determined to be 1.06 eV. When exploited in device use, if the required band gap value is known, the required composition can be calculated with the bowing parameter. We have also shown the compatibility of co-sputtering to alloy fabrication since the composition ratio can be easily controlled just by adjusting the radio frequency (RF) sputter power on different targets. The fabrication method can be applied to different transition metal dichalcogenide materials as well.
We report the synthesis of MoS2(1-x)Te2x by co-sputtering deposition and effect of mixture on its bandgap. The deposition was carried out at room temperature, and the sputtering power on individual MoS2 and MoTe2 targets were varied to obtain films with different compositions. Investigation with X-ray photoelectron spectroscopy confirmed the formation of Mo-Te and Mo-S bonds after post-deposition annealing (PDA), and one of the samples exhibited composition ratio of Mo:S:Te = 1:1.2:0.8 and 1:1.9:0.1 achieving 1:2 ratio of metal to chalcogen. Bandgap of MoS1.2Te0.8 and MoS1.9Te0.1 was evaluated with Tauc plot analysis from the extinction coefficient obtained by spectroscopic ellipsometry measurements. The obtained bandgaps were 1.0 eV and 1.3 eV. The resulting bandgap was lower than that of bulk MoS2 and higher than that of bulk MoTe2 suggesting mixture of both materials was achieved by co-sputtering.
Molybdenum disulfide (MoS2) thin films were fabricated by two-step chemical vapor deposition (CVD) using (t-C4H9)2S2 and the effects of temperature, gas flow rate, and atmosphere on the formation were investigated in order to achieve high-speed low-temperature MoS2 film formation. From the results of X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) investigations, it was confirmed that c-axis orientation of the pre-deposited Mo film has a significant involvement in the crystal orientation after the reaction low temperature sulfurization annealing and we successfully obtained 3 nm c-axis oriented MoS2 thin film. From the S/Mo ratios in the films, it was revealed that the sulfurization reaction proceeds faster with increase in the sulfurization temperature and the gas flow rate. Moreover, the sulfurization under the H2 atmosphere promotes decomposition reaction of (t-C4H9)2S2, which were confirmed by XPS and density functional theory (DFT) simulation.
In temperate zones, human respiratory syncytial virus (HRSV) outbreaks typically occur in cold weather, i.e. in late autumn and winter. However, recent outbreaks in Japan have tended to start during summer and autumn. This study examined associations of meteorological conditions with the numbers of HRSV cases reported in summer in Japan. Using data from the HRSV national surveillance system and national meteorological data for summer during the period 2007–2014, we utilized negative binomial logistic regression analysis to identify associations between meteorological conditions and reported cases of HRSV. HRSV cases increased when summer temperatures rose and when relative humidity increased. Consideration of the interaction term temperature × relative humidity enabled us to show synergistic effects of high temperature with HRSV occurrence. In particular, HRSV cases synergistically increased when relative humidity increased while the temperature was ⩾28·2 °C. Seasonal-trend decomposition analysis using the HRSV national surveillance data divided by 11 climate divisions showed that summer HRSV cases occurred in South Japan (Okinawa Island), Kyushu, and Nankai climate divisions, which are located in southwest Japan. Higher temperature and higher relative humidity were necessary conditions for HRSV occurrence in summer in Japan. Paediatricians in temperate zones should be mindful of possible HRSV cases in summer, when suitable conditions are present.
Molybdenum disulfide (MoS2), one of the transition-metal dichalcogenides, is a 2-dimensional semiconducting material that has a layered structure. Owing to excellent optical and electronic properties, the ultra-thin MoS2 film is expected to be used for various devices, such as transistors and flexible displays. In this study, we investigated the physical and chemical properties of sputtered-MoS2 film in the sub-10-nm region by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). As the results of Raman spectroscopy investigations, we observed two Raman modes, E12g and A1g, in the 2-dimensional MoS2 films. As the thickness of the MoS2 film decreased, the peak frequency difference between E12g and A1g modes increased. From the XPS investigations, we confirmed sulfur reductions from the 2-dimensional MoS2 films. Therefore, we considered that the sulfur vacancies in the MoS2 film affected the Raman peak positions. Moreover, we performed the additional sulfurization of sputtered-MoS2 films. From the XPS and Raman investigations, the quality of the sputtered-MoS2 films was improved by the additional sulfurization.
A thin film consisting of boron, carbon, and nitrogen (BCN) was grown on a polycrystalline Ni substrate by thermal chemical vapor deposition. The local elemental composition of the BCN film was analyzed by scanning Auger electron spectroscopy. The film is elementally highly inhomogeneous and consists of domains with a typical size of 1-10 μm and irregular shapes. The domain structure is strongly related to the structure of the grains of the polycrystalline Ni film beneath the domain. A thick domain is often formed on a small Ni grain. On a large and flat Ni grain, the film thickness is relatively small, and both the boron and nitrogen contents are often below the detection limit, indicating that it is a graphene domain. Boron and nitrogen contents are highly correlated, which is consistent with formation of hexagonal boron nitride. However, unbalanced boron and nitrogen contents are observed from thick domains.
GaP, GaAs, and InP nanowires were grown on graphitic layers by the vapor-liquid-solid method in a metalorganic vapor phase epitaxy chamber. On graphene/SiC(0001), Au particles as catalyst were formed at the steps by controlling the Au deposition rate and the annealing temperature in a low-energy electron microscopy system. GaP nanowires were grown on this substrate, and it was found that vertical nanowires were formed at the steps of the surface. We also performed GaP, GaAs, and InP nanowire growth on graphite substrates. Free-standing nanowires were obtained for all three materials, although they were vertically, diagonally, and laterally-oriented at the same time. The results suggested that the growth at the steps is the key to growing nanowires vertically on graphene surface.
We studied the electronic transport properties of monolayer and bilayer graphene in top-gated geometries. Monolayer and bilayer graphene were epitaxially grown by thermal decomposition of SiC. The half-integer quantum Hall effect under the gated environment was observed in monolayer graphene devices. The mobility of the monolayer and bilayer graphene devices showed distinct characteristics as a function of carrier density, which reflect their electronic structures. Strong temperature dependence at the charge neutrality point was observed in bilayer graphene devices, suggesting band gap opening.
To clarify the reaction process of Co and Fe with a oxide layer on Si substrates, the annealing processes were analyzed using spectroscopic photoemission and low-energy electron microscopy for a special surface where oxide areas and clean substrate areas (voids) coexist closely in a micrometer-order view. From analyses of XAS spectra and edge jump ratios obtained from the photoemission electron microscopy image, we clarified that Co atoms in the void area remain because of the formation of silicides, but that those on the oxide layer disappear because metallic Co atoms easily diffuse. In contrast, in the case of Fe, we found the formation of various silicides and their gradual diffusion into Si substrate even in the form of silicides.
We describe periodic arrangements of Ge islands grown on Si (111) using Ge deposition at room temperature and post-deposit annealing. A Mesh pattern of relaxed Ge islands is obtained under conditions of a Ge thickness of 10 Å and an annealing temperature of 400°C. The Mesh pattern is due to the preferential crystallization of α-Ge films at steps and at out-of-phase boundaries of 7×7 reconstructions. We also demonstrate that the Ge island pattern is modified when Ge is grown on a substrate changed by Si homoepitaxy or In adsorption.
We investigate step bunching during SiGe growth on vicinal Si(111) surfaces. Step bunching occurs irrespective of the misorientation angle and direction of the vicinal surface, the growth temperature, and the Ge concentration. At 550°C, the average number of the steps in the bunch increases with the Ge concentration. After growth of 10-nm-thick SiGe layers, twodimensional islands are formed on the terraces, which indicates that the terrace width has already been saturated. Therefore, the terrace width is mainly determined by the diffusion length of the adatom. The average number of steps in the bunch increases with the Ge concentration because the diffusion length increases with the Ge concentration. The diffusion length also increases with the temperature. So the higher the temperature is, the larger the step bunch becomes.
We describe three different aspects of the self-organization of steps and domain boundaries of a 7×7 reconstruction on SI(111) surfaces. The first is the formation of a triangular-tiled pattern of “1×1’ and 7×7 domains during the phase transition. ‘1÷1’ and 7×7 domains have different surface stresses. The triangular-tiled pattern is stabilized through stress relaxation. The second is the step arrangement inside a hole, which was fabricated by a standard lithographic technique. The step arrangement in the hole depends on the temperature. Below the ‘1×1’-to-7×7 phase transition, the hole has a three-fold symmetry consisting of step-bunched and non-bunched regions. This is because the step arrangement on the vicinal Si(111) surfaces depends on the direction of the steps. The third aspect is the formation of a pattern of steps and domain boundaries induced by Si growth. During the step-flow growth on Si(111), steps preferentially protrude along the domain boundaries on the lower terrace. The resulting changes in step shape induce a unique rearrangement of the domain boundaries, the number of which decreases during growth. However, when a periodic pattern is formed in the initial stages, it remains stable during growth.
Plasma particle simulations are performed using GRAPE-6, a special-purpose computer for calculating gravitational N-body systems. GRAPE-6 rapidly calculates the gravitational force between particles using specialized pipeline processors. The peak performance of a unit of GRAPE-6 reaches 985 GFLOPS. We investigated speeding up plasma simulations through the use of GRAPE-6 for the calculation of Coulomb interactions, which have the same form of central force as the gravitational force. As an example of plasma particle simulation using GRAPE-6, we simulated the Buneman instability. As another example of plasma particle simulation, we simulated a Coulomb crystal in a dusty plasma. The formation of a Coulomb crystal was observed under typical laboratory conditions. We found that GRAPE-6 can perform the entire operation of the simulation of a Coulomb crystal with 5 × 103 particles up to 210 times faster than a 1.6-GHz Pentium4 CPU.
Neosalanx reganius is a poorly studied salangid fish restricted
to the upper reaches of the Chikugo and the Midori River flowing into the Ariake Bay,
Kyushu, Japan. Samples of N. reganius were collected from brackish water areas
of the Chikugo River by eight cruises in 1998-2004 to characterize the distribution
pattern, feeding ecology in relation to ambient prey concentrations, fecundity and
condition of the fish. A total of 244 specimens were collected, 36 to 71 mm total
length, and 111 to 1301 mg body weight. The catch per unit of effort (CPUE; number of fish
collected by towing a larva net for 20 min) correlated positively with turbidity and
negatively with salinity. N. reganius is a planktivorous fish, fed on a single
calanoid copepod species Sinocalanus sinensis, which was the single most dominant
prey item in all stations during all cruises, contributing as high as 97.0% of the total
diet of the fish; the other prey items (other calanoids and cyclopoids, Daphnia
sp. and decapod mysid) together contributed only 3%. S. sinensis also dominated
in the environmental copepod composition. The CPUE showed significant correlation with copepod
dry biomass which increased upstream (r = 0.90; p < 0.05). Fecundity ranged 347-995
(mean 583 173) oocytes individual−1 and relative fecundities ranged 6.8-15.6
(mean 10.1 ± 2.4) oocytes mm−1 TL and 0.8-2.5 (mean 1.6 ± 0.5)
oocytes mg−1 of net body weight (weight taken after gonad extraction). Fecundity showed significant positive relationship with fish length and body weight. GSI ranged 29.4-58.8%
(mean 43.5 ± 7.9%) and had significant relationship with fish length and
body weight. Spawning individuals had higher allometry coefficient (b) and
condition factor (K) than the non-spawning individuals. The oligohaline upper
Chikugo estuary provides important feeding and spawning grounds for the fish
with sufficient prey abundance and turbidity maximum that seemed
advantageous for feeding and spawning of N. reganius in the Chikugo estuary. We suggest
that future research should emphasize on the spawning and early life ecology
of the fish in order to formulate effective conservation action.
Porous TiO2–P2O5 oxide was synthesized by the sol-gel method in the presence of tri-block copolymer (EO)20(PO)70(EO)20 (Pluronic123) in queous solution. The TiO2 nanocrystals with anatase structure precipitated in the as-synthesized TiO2–P2O5 materials at 80°C, considerably lower than that for traditional heat treatment in the solid state, which maintained a stable size of 3.6–4 nm upon calcinations below 500°C. It is believed that P2O5 glass phase prevents the coarsening of TiO2 nanocrystals below 500°C. The mixed oxide exhibited a specific surface area of 170–200 m2/g after calcining in the temperature range of 300–500°C.
This article reviews the fabrication technologies and optical characteristics of silica-based planar lightwave circuits (PLCs) on Si developed for photonic networks based on wavelength-division multiplexing (WDM). While there have been various planar optical waveguides made with different materials, silica-based PLCs are the most suitable for constructing practical devices because of their excellent design flexibility, stability, and reproducibility. These advantages mainly result from their material characteristics, that is, silica glass is chemically and physically stable. The article also describes the basic characteristics and recent development of arrayed waveguide grating (AWG) multiplexers/demultiplexers as a device application. Since AWGs offer the advantages of low-loss, high-output port counts and mass producibility, they have played a pivotal role in the construction of flexible, large-capacity WDM networks.