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The results of a submillimetre wavelength spectral line survey between 455.1 – 507.4 GHz of the Orion-KL hot cloud core are reported. 254 lines were detected, and are associated with 30 different molecular species or their isotopomeric variants. Apart from the abundant diatomic rotors such as CO and CS, the spectrum is dominated by SO, SO2 and CH3OH and large organic molecules such as (CH3)2O, CH3CN, C2H3CN, C2H5CN and HCOOCH3 which make up ∼ 72% of the total number of lines; unidentified lines ∼ 13%; and other lines the remaining ∼ 15% of the total. Rotational temperatures and column densities derived using standard rotation diagram analysis techniques were found to range from 70 – 600 K, and 1014 – 1017cm2 respectively.
Delirium and dementia are highly interrelated. However, few comprehensive epidemiological studies have examined this altered state of consciousness superimposed on dementia. We investigated the frequency of delirium in patients with dementia, its prevalence in patients with each dementia type, and its association with cerebrovascular disease (CVD) in patients with neurodegenerative dementias.
We studied 261 consecutive outpatients in the memory clinic of a psychiatric hospital between April 2010 and September 2011. All patients underwent routine laboratory tests and computed tomography (CT), and their Mini-Mental State Examination, Neuropsychiatric Inventory (NPI), Physical Self-Maintenance Scale (PSMS), and Delirium Rating Scale – Revised 98 scores were recorded. The diagnosis of delirium was based on the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, text revision. CVD was detected by CT.
Among the 206 patients with dementia, delirium was present in 40 (19.4%). The proportion of patients who experienced episodes of delirium was 14.7% in the Alzheimer's disease, 34.4% in the vascular dementia, 31.8% in the dementia with Lewy bodies, and none in frontotemporal lobar degeneration. Delirium was frequently observed in patients with dementia and CVD. The NPI total and agitation subscale scores were significantly higher in dementia patients with delirium than in those without delirium. PSMS scores were significantly lower for patients with delirium than for patients without delirium.
The frequency of delirium varies with each dementia type. In addition, delirium decreases activities of daily living, exaggerates behavioral and psychological symptoms dementia, and is associated with CVD in patients with neurodegenerative dementias.
A discharge-emission spectrometer and a cavity ringdown spectrometer have been developed to aid in the solution to the diffuse interstellar band (DIB) problem. A hollow cathode was used to generate molecular ions in a discharge because it has been suggested that molecular ions are probable DIB candidates. The discharge was produced by a pulsed voltage of 1300–1500 V. A wide wavelength range of optical emission from the discharge was examined by a HORIBA Jobin Yvon iHR320 monochromator. The dispersed discharge emission was detected by a photomultiplier and was recorded via a lock-in amplifier. The 2B3u–X2B2g electronic transition of the butatriene cation H2CCCCH2+ was observed in the discharge emission of 2-butyne H3CCCCH3. The frequency of the electronic transition was measured to be 20381 cm−1, and a comparison study was made with known DIB spectra.
The resolution of the discharge-emission spectrometer is insufficient to make precise comparisons between laboratory frequencies and astronomically observed DIB spectra. We therefore developed the cavity ringdown spectrometer using the same hollow cathode. The high sensitivity of this spectrometer was confirmed by the observation of the forbidden band of O2.
GaZnO and GaZnON thin films were deposited on both Si (100) and c-axis oriented sapphire substratesby RF co-sputtering of ZnO target and Ga2O3tablets in Ar/O2 and Ar/N2, respectively, by changing the number of Ga2O3tablets (NGa2O3) placed on the ZnO target in the range of 0 to 16.They were subsequently annealed in N2 at 800 °C and then, some of the samples formed by Ar/O2-sputtering were subjected to NH3 treatment at 650 °C for nitridation. XRD measurements revealed that the c-axis lattice parameter calculated from the ZnO (002) peak for GaZnON film son Si (100) was remarkably larger than for GaZnO films on Si (100). Moreover, ZnO (002) was observed up to NGa2O3=16 for GaZnON films formed on sapphire, while no XRD peaks were observed above NGa2O3=8 for GaZnON films on Si(100). Optical band-gap ofGaZnO and GaZnON films became wider from 3.34to 3.67 eVand from 3.21to 3.40 eV, respectively, with increasing NGa2O3 from 0 to 16. Photoluminescence spectra of GaZnO films showed band-to-band emission at 380nm, while those of GaZnON films exhibited broad and weak peaks centered at 550 nm and 647nm.
We systematically investigated the optimum growth condition of wide-bandgap quaternary InAlGaN for ultraviolet (UV) light-emitting diodes (LEDs) grown on SiC by metal organic vapor phase epitaxy (MOVPE). We obtained intense UV emission in the wavelength of 315-370 nm from quaternary InAlGaN, which was as high as blue emission from InGaN. We found that the optimized growth temperature of quaternary InAlGaN is shifted from 790 to 870 °C as the emission peak wavelength is changed from 370-315 nm. The strongest PL was obtained with the wavelength around 330 nm. The growth condition for intense PL is found to be decided by two factors, i.e., the carrier confinement in In segregation region and crystalline quality. We also found that the small In mole fraction of 2-5 % is enough to obtain maximally PL intensity for InAlGaN, which is much smaller value than that for InGaN, due to the large carrier confinement with small In fluctuation.
We report the results of comparison of radiation-induced defects (1 MeV electrons) in n+-p-p+ Si diodes doped with gallium or boron ranging in concentration from 8 × 1014 to 5 × 1016 cm-3, together with the impact of oxygen on radiation –induced defects. Present results provide evidence for new defects states in addition to those previously reported in gallium- and boron-doped Si. The combined boron and gallium data provide enough information to gain valuable insight into the role of the dopants on radiation-induced defects in Si. The interesting new future of our results is that the gallium appears to strongly suppress the radiation induced defect, especially hole level EV+0.36 eV, which is thought to act as a recombination center. Similarly the dominant electron level at EC-0.18 eV in B-doped Si (which act as a donor) has not been observed in Ga-doped CZ-grown Si.
We report the results of comparison of radiation-induced defects (1 MeV
electrons) in n+-p-p+ Si diodes doped with gallium or
boron ranging in concentration from 8 × 1014 to 5 ×
1016 cm−3, together with the impact of oxygen on
radiation –induced defects. Present results provide evidence for new defects
states in addition to those previously reported in gallium- and boron-doped
Si. The combined boron and gallium data provide enough information to gain
valuable insight into the role of the dopants on radiation-induced defects
in Si. The interesting new future of our results is that the gallium appears
to strongly suppress the radiation induced defect, especially hole level
EV+0.36 eV, which is thought to act as a recombination center.
Similarly the dominant electron level at EC-0.18 eV in B-doped Si
(which act as a donor) has not been observed in Ga-doped CZ-grown Si.
Some optoelectronic effects in porous Si (PS) have been investigated in relation to the visible luminescence mechanism. As regards photoluminescence (PL), particular emphasis is placed on the relationship between photoconduction (PC) and PL excitation (PLE) spectra, the interaction of external electric field and PL emission, and polarization properties of PL Main subjects of electroluminescence (EL) studies reported here are the dynamic behavior of EL operation and the formation of a large-area contact by a conducting polymer (polypyrrole: PP). The observed experimental results (almost complete coincidence of PC spectra with PLE ones, linear polarization memory of PL definite correlation between the polarization degree and the PL efficiency, and comparable response time of electrical PL quenching and EL to the PL decay time) are consistent with our hypothesis that the major process of PL takes place within Si nanocrystallites. The electrical characterization of light-emitting PS diodes with PP contacts ensures the usefulness of the contact formation by electropolymerization as a technique for uniform and efficient carrier injection into PS.
To verify the availability of a porous silicon (PS) technology for applications to photonic devices, fundamental chracteristics of PS waveguides are investigated. An edge-emitting device with an optical waveguide is fabricated by current modulation technique during anodization. The net internal loss for prepared samples is measured by varying the length of excitation beam. The experimental results show that the internal loss increases with decreasing the operation wavelength, possibly due to self-absorption and Rayleigh scattering. Besides the step-index PS waveguides, buried-type waveguides can be fabricated based on a doping modulation technique. A theoretical analysis about a bending loss is also carried out. The results of experimental and theoretical analyses suggest that a curveture radius capable of guiding lightwave can be significantly minimized, owing to a difinitely different refractive indedices between the core and cladding region.
Optical properties of tensile strained AlxGa1-xN films of AlxGa1-xN/GaN heterostructures grown on sapphire were investigated by using polarization-resolved photoluminescence spectroscopy. Emissions from AlxGa1-xN with polarization of E//c and E⊥c were obtained at different peak energies. The energy separation of these emissions with polarization was increased linearly with the increase in Al mole fraction of the strained AlxGa1-xN, indicating that the energy separation was due to biaxial strain in the tensile strained AlxGa1-xN.
This paper describes studies on high-quality InN growth on sapphire by RF-MBE. Critical procedures to obtain high-quality InN films were investigated and (1) nitridation process of sapphire substrates prior to growth, (2) precise control of V/III ratio and (3) selection of optimum growth temperature were found to be essential. Detailed structural characterizations by XRD, TEM, Raman scattering and EXAFS indicate that InN films obtained in this study have ideal hexagonal wurtzite structure. FWHMs of ω-2Θ mode XRD and E2(high)-phonon-mode of Raman scattering are as small as 28.9 arcsec and 3.2 cm-1, respectively. True band gap energy of InN is also discussed based on optical characterization results obtained from well-characterized hexagonal InN grown in this study. PbS, instead of InGaAs, was used as a detector for PL study in order to solve the problem coming from the cut-off wavelength of InGaAs detector. Based on these systematic studies on structural and optical property characterizations using high-quality InN, true band-gap energy of InN is suggested to be less than 0.67 eV and approximately 0.65 eV at room temperature. Single-crystalline InN films are also successfully grown on Si substrates by a brief nitridation of the Si substrates. Significant improvement of InN crystal quality on Si substrates by the insertion of an AlN buffer layer is also demonstrated.
The microstructure of an InN buffer layer grown on (0001) sapphire at low temperature by radio-frequency molecular beam epitaxy (RF-MBE) is characterized by transmission electron microscopy. The low-temperature InN buffer layer is found to contain local inhomogeneous regions of island-like grains surrounded by misoriented InN grains and inclusions of cubic phase. The generation of such anti-phase InN nuclei near the island-like grains is expected to give rise to defects at the interface. It is considered that these anti-phase InN nuclei are formed by local fluctuations of stoichiometry due to inadequate surface migration during the growth of the InN buffer layer, indicating the important of controlling the surface stoichiometry during InN growth.
The effects of the nitridation process of (0001) sapphire on crystalline quality of InN were clearly demonstrated. The InN films were grown on NFM (nitrogen flux modulation) HT-InN or LT-InN buffer layers, which had been deposited on nitridated sapphire substrates. We found that low-temperature nitridation of sapphire is effective in improving the tilt distribution of InN films. Whereas the twist distribution remained narrow and almost constant, independent of nitridation conditions, when LT-InN buffer layers were used. The XRC-FWHM value of 54 arcsec for (0002) InN, the lowest reported to date, was achieved by using the LT-InN buffer layer and sapphire nitridation at 300°C for 3 hours.
A newly reported narrow bandgap for indium nitride means that the indium gallium nitride system of alloys can be a candidate for new high efficiency solar cells covering most of the solar spectrum. In this paper, n-InN films were grown on p-Si (100) substrates. We characterize, for the first time, photovoltaic properties using n-InN/p-Si hetero-junction grown by RF-MBE.
Cubic GaN is successfully grown on β-Ga2O3 by molecular beam epitaxy for the first time. Prior nitridation of the (100) β-Ga2O3 single-crystal substrate by exposure to electron cyclotron resonance nitrogen plasma causes the formation of a surficial (001) c-GaN layer, upon which homo-epitaxial growth of c-GaN can be achieved by radio-frequency molecular beam epitaxy. The epitaxial relationship is confirmed by electron microscopy to be (001) c-GaN // (100) β-Ga2O3,  c-GaN //  β-Ga2O3, and [1-10] c-GaN //  β-Ga2O3.
For further improvements in AlGaN/GaN heterojunction field-effect transistor performance (HFET), it is necessary to reduce the leakage current of the GaN buffer layer. We found a correlation between the leakage current and the intensity of the yellow luminescence of GaN layers taken by UV lamp excitation. The GaN layers were grown by metal organic chemical vapor deposition on SiC substrates. When the samples were excited by a UV (365 nm) lamp, visible yellow luminescence was observed. The leakage current of the GaN buffer layer was measured after deposition of ohmic metal contact. We confirmed clear correlation between the leakage current and the luminescence intensity based from result that the samples with the larger leakage current showed the stronger luminescence intensity. This correlation gives us useful information to understand the drain-source leakage current of AlGaN/GaN HFET.
Current-voltage (IV) measurements and capacitance-voltage (CV) measurements have been carried out to investigate electrical properties of AlGaN/GaN-HEMT structures. By CV measurements of Schottky barrier diodes (SBDs) with large leak currents, we observed a distinct peak in CV profiling at low frequencies. The integral of this peak was found to have a correlation with a leak current. The behavior of this peak might be described by the Shockley-Read-Hall (SRH) model if we assume this peak is due to a phenomenon of an electron emission and capture by deep levels. Then Quasi-Fermi Level (Imref) at the bias point where this peak appears in CV profiling corresponds to energy depth of deep levels. That energy level can be approximated by Imref of two-dimensional (2D) electron gas. The result of our samples showed that the energy depth of deep levels from the conduction band is distributed from 320meV to 470meV for Al mole fraction from 0.19 to 0.30, respectively.
Cu2ZnSnS4 (CZTS) thin films were fabricated by using three RF co-sputtering continued with sulfurization method. The new type of thin film solar cells using CZTS as an absorber consists of buffer-layer and window-layer on CZTS films that were fabricated on a Mo-coated Soda Lime Glass (SLG) substrate. It was confirmed that CZTS solar cells with high conversion efficiency existed in a relatively narrow composition region. In this paper, the fabrication method of CZTS-based thin film solar cells in our laboratory was stated briefly and the influence of the composition ratio on the photovoltaic properties were presented. Furthermore, the properties of a genuine non-toxic solar cell using a Cd-free buffer-layer were introduced.
Production of biodiesel fuel (fatty acid methyl ester) by use of conventional method (alkaline catalyst method) requires deacidification process prior to the reaction and refining process to remove the catalyst after the reaction. These processes increase total cost required for production of biodiesel fuel. In order to solve the problem, authors recently proposed a method called superheated methanol vapor method. In a process with this method, superheated methanol vapor is continuously bubbled into the oil in the reactor vessel and reacted with triglycerides to form fatty acid methyl ester and glycerol. The fatty acid methyl ester and glycerol formed flows out of the reactor together with unreacted methanol vapor and is collected using a condenser. Reaction using the superheated methanol vapor method can be conducted at atmospheric pressure. Production of fatty acid methyl ester by use of the superheated methanol vapor method does not require refining process after the reaction because no catalyst is used in this method and fatty acid methyl ester can be separated from glycerol simply by sedimentation. The method does not require deacidification process prior to the reaction because not only triglyceride but also free fatty acid can be converted into fatty acid methyl ester by use of the method. Therefore, both initial and running costs required for biodiesel production are thought to be reduced by applying the method. In order to estimate the cost required by a process based on the superheated methanol vapor method, a demonstration plant (design productivity: 400 L/d) was constructed and its efficiency was evaluated. The plant could produce 425 L of fatty acid methyl ester in a day from used frying oil. Energy consumed in each unit of the demonstration plant was measured (electrical energy and thermal energy). Based on the energy consumption data obtained with the demonstration plant, production cost required with a practical scale plant (designed productivity: 6000 kL/y) was calculated. The cost required by the practical scale plant with the superheated methanol vapor method was estimated to be 40.2 yen/L (about 40 cent/L) while the cost required by a plant with the alkaline catalyst method was 62.5 yen/L (about 62 cent/L). The estimated cost includes depreciation cost, cost of repairing, labor cost, methanol cost and energy cost (heat and electricity). Most of the energy consumed by the plant was thermal energy and the plant could be automatically controlled. Therefore, required cost will be further decreased by installing the plant next to an incineration facility because thermal energy can be supplied from the facility and the labor cost can also be supported by the facility.