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We present recent observation results of Sgr A* at millimeter obtained with VLBI arrays in Korea and Japan.
7 mm monitoring of Sgr A* is part of our AGN large project. The results at 7 epochs during 2013-2014, including high resolution maps, flux density and two-dimensional size measurements are presented. The source shows no significant variation in flux and structure related to the G2 encounter in 2014. According to recent MHD simulations by kawashima et al., flux and magnetic field energy can be expected to increase several years after the encounter; We will keep our monitoring in order to test this prediction.
Astrometric observations of Sgr A* were performed in 2015 at 7 and 3.5 millimeter simultaneously. Source-frequency phase referencing was applied and a combined ”core-shift” of Sgr A* and a nearby calibrator was measured. Future observations and analysis are necessary to determine the core-shift in each source.
Polycrystalline Si (Poly-Si) films were successfully grown at temperature less than 500 °C by using a direct Si ion beam deposition technique. In this process, the ion beam energy of Si- is directly coupled to the formation of the films. High substrate temperature (>600 °C), normally required for conventional CVD techniques, has been a major barrier for the Poly-Si Thin Film Transistor Liquid Crystal Display (TFT LCD) which uses a glass substrate. Thus, the ability to produce Poly-Si film below the glass transition temperature and to control the grain size will make this direct Si- ion beam deposition process a potential alternative technique for future TFT LCD. The grain size dependence on the ion beam energy and substrate temperature was investigated using a Transmission Electron Microscope (TEM). The grain size could be controlled from 0.1 μm to 1 μm at ion beam energies from 10 to 50 eV with a substrate temperature less than 500 °C. The resistivity of the as-deposited film was of the order of 100 Ωcm due to in-situ doping effect.
We identified 2 novel genes encoding different 2-Cys peroxiredoxins (PRxs), designated CsPRx2 and CsPRx3, in Clonorchis sinensis, which invades the human hepatobiliary tracts. The CsPRx2 gene expression was temporally increased along with the parasite's development and its protein product was detected in almost all parts of adult worms including subtegument, as well as excretory-secretory products. Conversely, CsPRx3 expression was temporally maintained at a basal level and largely restricted within interior parts of various tissues/organs. The recombinant forms of CsPRx proteins exhibited reducing activity against various hydroperoxides in the presence of either thioredoxin or glutathione (GSH) as a reducing equivalent, although they preferred H2O2 and GSH as a catalytic substrate and electron donor, respectively. A steady-state kinetic study demonstrated that the CsPRx proteins followed a saturable, Michaelis-Menten-type equation with the catalytic efficiencies (kcat/Km) ranging from 103 to 104 M−1 s−1, somewhat lower than those for other PRxs studied (104–105 M−1 s−1). The expression patterns and histological distributions specific to CsPRx2 and CsPRx3 might suggest different physiological functions of the antioxidant enzymes in protecting the worms against oxidative damage.
Melt-spun Fe73-Si16-B7-Nb3-Cu1 (at%) amorphous strip was pulverized and then crystallized to obtain nano-grain structure at 540° for 1h under a nitrogen atmosphere. Carbon black of 0.1∼ 1wt% and its dispersant were mixed with the nano-grain structured Fe-based powder for 1h via ball milling for 1h. The mixture was tape-cast with a polymer-based organic binder, and dried at 100° to make a thin sheet. The microstructure and electromagnetic wave absorption properties of the sheet were investigated using a network analyzer. As a result, the properties of electromagnetic wave absorption were improved by the increase of dielectric loss, which was mainly caused by the increase of complex permittivity with the addition of carbon black.
The growth behaviour of carbon nanotubes on the Fe-deposited Si (001) substrates by thermal chemical vapor deposition (CVD) has been investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The Fe films are deposited for 20 s–20 min by pulse-laser deposition. SEM results show that the growth characteristics of carbon nanotubes strongly depend on the Fe film deposition time. TEM and SEM results show that the pretreatment annealing at 800 °C causes the continuous Fe films to be broken up into nanoparticles 8–50 nm across and discontinuous islands 100 nm– 1.1 μm in size. It is shown that the Fe nanoparticles are essentially required for the formation of aligned carbon nanotubes. SEM results show that the growth behaviors of carbon nanotubes are strongly dependent on the pretreatment atmospheres. In addition, for the Ar gas-pretreated sample, a carbonaceous layer is formed near the surface region. TEM results show direct evidence that a base growth mode is responsible for the growth of carbon nanotubes in the present work. Based on the microscopy results, the pretreatment condition dependence of the growth behaviors of carbon nanotubes is discussed.
The good field-emission properties of carbon nanotubes coupled with their high mechanical strength, chemical stability, and high aspect ratio, make them ideal candidates for the construction of efficient and inexpensive field-emission electronic devices. The fabrication process reported here has considerable potential for use in the development of integrated radio frequency amplifiers or field emission-controllable cold electron guns for field emission displays. This fabrication process is compatible with currently used semiconductor processing technologies. Micropatterned vertically aligned carbon nanotubes were grown on planar Si surface or inside the trenches, using chemical vapor deposition, photolithography, pulsed-laser deposition, reactive ion etching, and the lift-off method. To control the field-emission current by a 3rd electrode, the gate electrode, we grew carbon nanotubes inside the trenches. This triode-type structure is the best to realize the gray-scale carbon nanotube field emission. This carbon nanotube fabrication process can be widely applied for the development of electronic devices using carbon nanotube field emitters as cold cathodes and could revolutionize the area of field-emitting electronic devices such as RF amplifiers and field emission displays.
Al was deposited on the both sides of p-type Si by the sputtering, and the pulsed KrF excimer laser was irradiated on the one side and both sides of Al dot contacts. Due to the thin-high doping recrystallized layer, the transitions from the Schottky diodes to the ohmic contacts via backward diodes were observed in I-V measurement. Good N-shape negative resistances and notches were observed in the diodes, and ohmic contacts. Possible interpretations of the orgin of these phenomena are discussed. And, the simple model of the effective barrier height reduction under the thermionic field emission was developed using WKB approximation, and tunneling theory. By the depth Auger analysis, Al, and Si profiles near Al-Si interface after the laser irradiation were observed.
The major problems of the GaAs/Si heteroepitaxy are the high density of threading dislocations and the high residual strain in the GaAs epilayers. The residual strain in the epilayer is attributed to the difference in contraction during cooling down from the growth temperature. It was reported previously that the residual stress in GaAs epilayer could be reduced by reducing the growth area using substrate patterning. In this paper, we report a new approach to grow strain- free GaAs layer on Si substrates. The residual strain in GaAs/Si is tensile in nature, therefore we attempted to compensate this thermally induced strain by compressive lattice mismatched strain. The thermally induced strain in the GaAs layer was successfully compensated by the lattice- mismatch induced strain using In0.032Ga0.968As. By that method, we could grow thin strain- free GaAs layers on Si without patterning. The strain relieving effect was confirmed by photoluminescence experiment.
A novel rectilinear negative carbon ion beam source for large-area coatings has been developed, based on SKION's Solid State Ion Beam Technology. The negative carbon ion beam is effectively produced by a primary cesium ion bombardment and the secondary negative carbon ion yield has been observed to be about 0.5. The ion source produces a negative carbon ion current density of 0.25 mA/cm2 at the extraction voltage of 4 kV. The ion beam energy can be independently controlled from 0 eV to 300 eV. Due to the rectilinear geometry for the production of ion beams, the scale-up of the ion beam in length direction can be easily obtained with no limit. Furthermore, the ion source uses no gas discharge to generate ion beams and does not use any hydrogen gas. The ion source can be operated in a high vacuum (<10-7 Torr), and the cesium vapors are filtered and recirculated. The ion source produces ultra-hard (50 GPa), atomically smooth (< 1 nm Ra), and hydrogen-free amorphous diamond-like-carbon (DLC) films over large areas.
A compact negative metal ion beam source for direct low energy metal ion beam depositions studies in ultra high vacuum (UHV) environment, has been developed. The ion source is based on SKION's Solid State Ion Beam Technology. The secondary negative metal ion beam is effectively produced by primary cesium positive ion bombardment (negative ion yield varies from 0.1-0.5 for carbon). The beam diameter is in the range of 0.2∼3.0 cm depending on the focusing and ion beam energy. The ion source produces negative ion currents of about 0.8 mA/cm2. The energy spread of the ion beam is less then ±5% of the ion beam energy. The energy of negative metal ion beam can be independently controlled in the range of 10-300 eV. Due to the complete solid state ion technology , the source can be operated while maintaining chamber pressures of less then 10-10 Torr.
The initial nucleation stages of sp3 bonded amorphous diamond on silicon substrates have been investigated. The energy of the incident carbon ions/atoms is understood as a key parameter for the vapor phase formation of amorphous diamond like carbon coatings. SKION's solid state carbon ion source is used for this study. The ion source is UHV compatible and capable of producing a controlled energy ion beam in the energy range of 5-300 eV. In the initial stage of the deposition, carbon is found to be deposited as a silicon carbide up to a thickness of about 180Á at room temperature. Silicon is diffused to the surface and forms SiC. As the energy of the ion beam increases, the formation of silicon carbide becomes apparent. Further carbon ion bombardment then leads to the formation of an sp3 bonded amorphous diamond film. Post-annealing above 900°C leads to the formation of crystalline silicon resulting in a Si-rich SiC surface due to silicon out-diffusion.
Intrinsic stress in a film-substrate system can have deleterious effects. To facilitate an understanding of stress generation and control film quality, measuring film stress is essential. In recent years research laboratories and industry have increasingly adopted indirect methods, which are usually based on the measurement of substrate deformation. The film stress is calculated by equations relating the stress to the deformation, such as the well-known Stoney's equation. However, when the two principal stresses at each point in the film plane are not equal and their distribution is nonuniform, the local application of Stoney's equation does not provide correct stress results. A numerical technique is presented, which overcomes these limitations and makes accurate stress determination possible.
Diamond films were grown over Si substrate at 1253K by the hot filament chemical vapor deposition method using CH4/H2 gas mixture, and intrinsic stresses in the film were deduced from the ex-situ curvature measurements. In order to account for the creep deformation of the Si substrate, an elastic/plastic stress and strain analysis were conducted. Results showed that intrinsic stresses were generally several times larger than the average film stresses and always positive increasing with the film thickness. For the film thickness larger than 10μm, stress relaxation by creep of the substrate became significant, and must be considered for the accurate assessment of the film stress in diamond. Later, an analysis based on the grain growth accounted for the development of intrinsic stresses reasonably well.
Diamond films were grown over Si substrate at 1253K by the hot filament chemical vapor deposition method using CH4/H2 gas mixture, and intrinsic stresses in the film were deduced from the ex-situ curvature measurements. In order to account for the creep deformation of the Si substrate, an elastic/plastic stress and strain analysis were conducted. Results showed that intrinsic stresses were generally several times larger than the average film stresses and always positive increasing with the film thickness. For the film thickness larger than 10μm, stress relaxation by creep of the substrate became significant, and must be considered for the accurate assessment of the film stress in diamond. Later, an analysis based on the grain growth accounted for the development of intrinsic stresses reasonably well
The characteristics of dopant activation by sequential lateral solidification in poly-Si films is investigated using sheet resistance measurement and Raman measurement. Sheet resistance of n+ and p+ doped poly-Si films decreases exponentially as the laser energy increases. The minimum sheet resistance of n+ doped poly-Si films is 150 Ω/□ which is near to that of rapid thermal annealing (RTA) while the minimum sheet resistance of p+ doped poly-Si films is 180 Ω/□ which is less than a half to that of RTA. The sheet resistance of n+ and p+ doped poly-Si increases as the laser energy increases when the laser energy is above 573 mJ/cm2 at which the nucleation occurs. Raman signal of n+ doped poly-Si films shows single peak at 515 cm-1 with all laser energy and has maximum intensity at 566 mJ/cm2 laser energy. Raman signal of p+ doped poly-Si films shows single peak below 413 mJ/cm2 laser energy and double peak above 444 mJ/cm2 laser energy where the fully melting of p+ doped poly-Si film occurs.
High-density TiO2-CdS and ZnO-CdS core-shell nanocable arrays were synthesized on large-area Ti substrates. The CdS layers were deposited on the pre-grown vertically-aligned TiO2 (rutile) and ZnO nanowire arrays, with a controlled thickness (10~50 nm), using the vapor transport method. The ZnO-CdS nanocables consisted of single-crystalline wurtzite CdS shells whose  direction was aligned along the  wire axis of the wurtzite ZnO core, which is distinctive from the polycrystalline shell of the TiO2-CdS nanocables. We fabricated the photoelectrochemical cell using the ZnO-CdS photoelectrode exhibits much more efficient hydrogen generation than that using the TiO2-CdS one.
Measurement of material creep parameters by means of nanoindentation using continuous stiffness techniques avoids the problems associated with thermal drift that often plague creep measurements based on the time dependence of the indentation depth alone [1, 2]. Problems with thermal drift are negligible from a practical point of view during continuous stiffness measurements because the contact stiffness can be measured over a short time period, typically less than one second, during which time the displacements due to thermal drift are minimal. Determination of the time dependence of the indentation depth from the stiffness data relies on the well-known relation between contact stiffness and the square root of the contact area. For pyramidal indenters, the true indentation contact depth must be proportional to the contact stiffness, leading to the assumption that indentation depth is also proportional to the contact stiffness. In this study, we critically examine this assumption using data obtained from experiments on a relatively soft material, epoxy, and a relatively hard material, fused quartz. The results show that just after initial load application, the change in contact area may be different than that expected from the change in indentation depth. One possible explanation for the observed behavior is examined by finite element modeling.
This study was performed to assess the efficacy and safety profile of combination treatment with S-1 and cisplatin in patients with locally advanced squamous cell carcinoma of the head and neck.
Eligibility criteria comprised: histologically confirmed squamous cell carcinoma of the head and neck; stage three or four disease with no evidence of distant metastasis; evaluable lesions; adequate organ function; age 20–80 years; and a performance status of two or less. Cisplatin was infused over one hour on day one (75 mg/m2) and S-1 was administered orally for 14 consecutive days (days two to 15). The dosages of S-1 were calculated according to the patients' body surface area: 50 mg twice a day (body surface area <1.5 m2) or 60 mg twice a day (body surface area >1.5 m2). Each course was repeated every three weeks. After two courses, tumour response was evaluated by computed tomography and laryngoscopy. If a response was evident (either complete or partial), the patient received one more course of chemotherapy, before undergoing radical treatment such as radiotherapy or surgery.
All 30 patients were assessable for toxicity, and 29 patients for treatment response. The overall response was 89.7 per cent (complete response: nine; partial response: 17). The two-year estimated overall survival rate was 79.2 per cent. Adverse reactions occurred 128 times during 81 courses in the 30 cases. The most common grade three to four adverse event was neutropenia, which occurred in eight patients. Cases of non-haematological grade three or four toxicity included nausea and vomiting in four patients, stomatitis in two and diarrhoea in one.
S-1 plus cisplatin combination chemotherapy is effective against locally advanced squamous cell carcinoma of the head and neck, with only mild toxicity.