Pump-Probe Study of Carrier-Spin Injection in a Diluted Magnetic Double Quantum Well of CdMnTe/CdTe

A. Murayama,K. Nishibayashi,N. Kono,K. Saito,I. Souma,Y. Oka 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1

We study the dynamics of carrier-spin injection in a diluted magnetic semiconductor double quantum well (DMS-DQW) of CdMnTe/CdTe by means of pump-probe absorption spectroscopy. The time dependences of the absorption saturation intensity show the injection dynamics of spinpolarized electrons and heavy holes (hhs) from the DMS-CdMnTe into the non-magnetic CdTe wells, where separate tunneling of the electron and the hh is directly elucidated with time constants of 150 ps and 1 ns, respectively. The degree of circular polarization P of the absorption saturation increases from 0 to 70 ps after pumping in the non-magnetic CdTe well, which is caused by the injection of polarized electron spins in the DMS well. We observe a systematic dependence of the rise time of P on the magnetic eld. The faster polarization of the electron spin in the DMS well results in a faster electron-spin injection. The electron's spin polarization is accelerated in the DMS well by LO-phonon scattering at 6 T, where the electron spin splitting is close to the one-LO-phonon energy, which enables us to demonstrate a fast electron-spin injection with a time constant of 10 ps. We study the dynamics of carrier-spin injection in a diluted magnetic semiconductor double quantum well (DMS-DQW) of CdMnTe/CdTe by means of pump-probe absorption spectroscopy. The time dependences of the absorption saturation intensity show the injection dynamics of spinpolarized electrons and heavy holes (hhs) from the DMS-CdMnTe into the non-magnetic CdTe wells, where separate tunneling of the electron and the hh is directly elucidated with time constants of 150 ps and 1 ns, respectively. The degree of circular polarization P of the absorption saturation increases from 0 to 70 ps after pumping in the non-magnetic CdTe well, which is caused by the injection of polarized electron spins in the DMS well. We observe a systematic dependence of the rise time of P on the magnetic eld. The faster polarization of the electron spin in the DMS well results in a faster electron-spin injection. The electron's spin polarization is accelerated in the DMS well by LO-phonon scattering at 6 T, where the electron spin splitting is close to the one-LO-phonon energy, which enables us to demonstrate a fast electron-spin injection with a time constant of 10 ps.

Global and regional emission estimates for HCFC-22

Saikawa, E.,Rigby, M.,Prinn, R. G.,Montzka, S. A.,Miller, B. R.,Kuijpers, L. J. M.,Fraser, P. J. B.,Vollmer, M. K.,Saito, T.,Yokouchi, Y.,Harth, C. M.,Mü,hle, J.,Weiss, R. F.,Salameh, P. K.,Kim, J Copernicus GmbH 2012 Atmospheric chemistry and physics Vol.12 No.21

<P>Abstract. HCFC-22 (CHClF2, chlorodifluoromethane) is an ozone-depleting substance (ODS) as well as a significant greenhouse gas (GHG). HCFC-22 has been used widely as a refrigerant fluid in cooling and air-conditioning equipment since the 1960s, and it has also served as a traditional substitute for some chlorofluorocarbons (CFCs) controlled under the Montreal Protocol. A low frequency record on tropospheric HCFC-22 since the late 1970s is available from measurements of the Southern Hemisphere Cape Grim Air Archive (CGAA) and a few Northern Hemisphere air samples (mostly from Trinidad Head) using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. Since the 1990s high-frequency, high-precision, in situ HCFC-22 measurements have been collected at these AGAGE stations. Since 1992, the Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also collected flasks on a weekly basis from remote sites across the globe and analyzed them for a suite of halocarbons including HCFC-22. Additionally, since 2006 flasks have been collected approximately daily at a number of tower sites across the US and analyzed for halocarbons and other gases at NOAA. All results show an increase in the atmospheric mole fractions of HCFC-22, and recent data show a growth rate of approximately 4% per year, resulting in an increase in the background atmospheric mole fraction by a factor of 1.7 from 1995 to 2009. Using data on HCFC-22 consumption submitted to the United Nations Environment Programme (UNEP), as well as existing bottom-up emission estimates, we first create globally-gridded a priori HCFC-22 emissions over the 15 yr since 1995. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions. Our inversion indicates that the global HCFC-22 emissions have an increasing trend between 1995 and 2009. We further find a surge in HCFC-22 emissions between 2005 and 2009 from developing countries in Asia - the largest emitting region including China and India. Globally, substantial emissions continue despite production and consumption being phased out in developed countries currently. </P>

Measurement of theB¯→Xsγbranching fraction with a sum of exclusive decays

Saito, T.,Ishikawa, A.,Yamamoto, H.,Abdesselam, A.,Adachi, I.,Aihara, H.,Al Said, S.,Arinstein, K.,Asner, D. M.,Aushev, T.,Ayad, R.,Bakich, A. M.,Bansal, V.,Bhuyan, B.,Bobrov, A.,Bondar, A.,Bonvicini, American Physical Society 2015 PHYSICAL REVIEW D - Vol.91 No.5

Simulation of a Polarimeter for a Spin - Polarized Positron Beam

J. H. Kim,F. Saito,N. Suzuki,L. Wei,Y. Nagashima,T. Kurihara,A. Goto,Y. Itoh,Y. S. Lee,T. Hyodo 한국진공학회(ASCT) 2002 Journal of Korean Vacuum Science & Technology Vol.6 No.3

A performance of a new positron polarimeter is investigated by simulation using a charged-particle trajectory program. The results of the ray tracing are presented along with the details of the design parameters and projected system performance. A ray tracing analysis indicates that this design is capable of effectively transmitting positrons at beam energies varying from 0.1 to 30 keV within the beam diameter of 2-6 ㎜. However, the observed reflection of the positrons(1ower than 2 keV) at 12 kGauss indicated that further refinement of beam design is needed to produce a better positron polarimeter.

Hydrochlorofluorocarbon and hydrofluorocarbon emissions in East Asia determined by inverse modeling

Stohl, A.,Kim, J.,Li, S.,O&,apos,Doherty, S.,Mü,hle, J.,Salameh, P. K.,Saito, T.,Vollmer, M. K.,Wan, D.,Weiss, R. F.,Yao, B.,Yokouchi, Y.,Zhou, L. X. Copernicus GmbH 2010 Atmospheric Chemistry and Physics Vol.10 No.8

<P>Abstract. The emissions of three hydrochlorofluorocarbons, HCFC-22 (CHClF2), HCFC-141b (CH3CCl2F) and HCFC-142b (CH3CClF2) and three hydrofluorocarbons, HFC-23 (CHF3), HFC-134a (CH2FCF3) and HFC-152a (CH3CHF2) from four East Asian countries and the Taiwan region for the year 2008 are determined by inverse modeling. The inverse modeling is based on in-situ measurements of these halocarbons at the Japanese stations Cape Ochi-ishi and Hateruma, the Chinese station Shangdianzi and the South Korean station Gosan. For every station and every 3 h, 20-day backward calculations were made with the Lagrangian particle dispersion model FLEXPART. The model output, the measurement data, bottom-up emission information and corresponding uncertainties were fed into an inversion algorithm to determine the regional emission fluxes. The model captures the observed variation of halocarbon mixing ratios very well for the two Japanese stations but has difficulties explaining the large observed variability at Shangdianzi, which is partly caused by small-scale transport from Beijing that is not adequately captured by the model. Based on HFC-23 measurements, the inversion algorithm could successfully identify the locations of factories known to produce HCFC-22 and emit HFC-23 as an unintentional byproduct. This lends substantial credibility to the inversion method. We report national emissions for China, North Korea, South Korea and Japan, as well as emissions for the Taiwan region. Halocarbon emissions in China are much larger than the emissions in the other countries together and contribute a substantial fraction to the global emissions. Our estimates of Chinese emissions for the year 2008 are 65.3±6.6 kt/yr for HCFC-22 (17% of global emissions extrapolated from Montzka et al., 2009), 12.1±1.6 kt/yr for HCFC-141b (22%), 7.3±0.7 kt/yr for HCFC-142b (17%), 6.2±0.7 kt/yr for HFC-23 (>50%), 12.9±1.7 kt/yr for HFC-134a (9% of global emissions estimated from Velders et al., 2009) and 3.4±0.5 kt/yr for HFC-152a (7%). </P>

Hydrogen-rich gas production from waste plastics by pyrolysis and low-temperature steam reforming over a ruthenium catalyst

Namioka, T.,Saito, A.,Inoue, Y.,Park, Y.,Min, T.j.,Roh, S.a.,Yoshikawa, K. Applied Science Publishers 2011 APPLIED ENERGY Vol.88 No.6

Operating conditions for low-temperature pyrolysis and steam reforming of plastics over a ruthenium catalyst were investigated. In the range studied, the highest gas and lowest coke fractions for polystyrene (PS) with a 60gh<SUP>-1</SUP> scale, continuous-feed, two-stage gasifier were obtained with a pyrolyzer temperature of 673K, steam reforming temperature of 903K, and weight hourly space velocity (WHSV) of 0.10g-sample g-catalyst<SUP>-1</SUP>h<SUP>-1</SUP>. These operating conditions are consistent with optimum conditions reported previously for polypropylene. Our results indicate that at around 903K, the activity of the ruthenium catalyst was high enough to minimize the difference between the rates of the steam reforming reactions of the pyrolysates from polystyrene and polypropylene. The proposed system thus has the flexibility to compensate for differences in chemical structures of municipal waste plastics. In addition, the steam reforming temperature was about 200K lower than the temperature used in a conventional Ni-catalyzed process for the production of hydrogen. Low-temperature steam reforming allows for lower thermal input to the steam reformer, which results in an increase in thermal efficiency in the proposed process employing a Ru catalyst. Because low-temperature steam reforming can be also expected to reduce thermal degradation rates of the catalyst, the pyrolysis-steam reforming process with a Ru catalyst has the potential for use in small-scale production of hydrogen-rich gas from waste plastics that can be used for power generation.

Astrophysically Important 26Si States Studied with the 28Si(4He,6He)26Si Reaction

Y. K. Kwon,이춘식,J. Y. Moon,J. H. Lee,J. Y. Kim,M. K. Cheoun,S. Kubono,H. Yamaguchi,J. J. He,A. Saito,Y. Wakabayashi,H. Fujikawa,G. Amadio,N. Iwasa,K. Inafuku,L. H. Khiem,M. Tanaka,Y. Fuchi,A. A. Chen,S 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2

The emission of a 1.809-MeV γ-ray from the first excited state of 26Mg, followed by β-decay of 26Al in its ground state (denoted as 26Alg.s.), has been identied by several gamma-ray telescopes. To resolve the controversy over the possible sources of the observational 1.809-MeV γ-rays, one needs accurate knowledge of the production rate of 26Alg.s.. The 25Al(p,γ)26Si reaction is one of the most important astrophysical reactions to be investigated, but its rate is uncertain due to the lack of level information on 26Si above the proton threshold (Qpγ = 5.518 MeV). Illiadis et al. suggested that the 25Al(p,γ)26Si reaction should be dominated by a 3+ unnatural parity state at Ex = 5970 keV. Recent studies proposed several states as candidates for the 3+ states. However, the spin-parity assignments for these states are still uncertain. In the present work, we measured the 28Si(4He,6He)26Si reaction at 120 MeV to confirm the unnatural parity states just above the proton threshold. The measurement was performed with the high-resolution particle analyzer at the Center for Nuclear Study, University of Tokyo. We observed a total of 22 excited states in 26Si. The 7018-keV level, which was only observed by Bardayan et al. with the 28Si(p; t)26Si reaction, was confirmed in our measurement. Among the candidates of unnatural parity states at Ex = 5678, 5916, and 5945 keV, the 5918-keV state was only observed within the error of the excitation energy. A new state at Ex = 6101 keV was also identified.

Regulation of Major Histocompatibility (MHC) Class Ⅱ Human Leukocyte Antigen-DRα Gene Expression in Thyrocytes by Single Strand Binding Protein-1, a Transcription Factor That Also Regulates Thyrotropin Receptor and MHC Class I Gene Expression

BALDUCCI-SILANO, PINA L.,SUZUKI, KOICHI,OHTA, MASANORI,SAITO, JUN,OHMORI, MASAYUKI,MONTANI, VALERIA,NAPOLITANO, GIORGIO,SHONG, MINHO,TANIGUCHI, SHIN-ICHI,PIETRARELLI, MICHELE,LAVARONI, STEFANO,MORI, A 충남대학교 생물공학연구소 1999 생물공학연구지 Vol.7 No.-

The single strand binding protein (SSBP-1) is a positive regulator of TSH receptor gene expression and binds to an element with a GXXXXG motif. The S box of the mouse major histocompatibility classⅡ gene has multiple GXXXXG motifs and can also bind SSBP-1. The S box is one of four highly conserved elements on the 5'-flanking region of classⅡ genes that are necessary for interferon-γ (IFNγ) to overcome the normally suppressed state of the gene and induce aberrant classⅡ expression. In this report we show that SSBP-1, when overexpressed in FRTL-5 thyroid cells, is a positive regulator of human leukocyte antigen (HLA)-DRα classⅡ gene expression, as is IFNγ or the classⅡ trans-activator (CIITA). This is evidenced by increased exogenous promoter activity, increased endogenous RNA levels, and increased endogenous antigen expression after transfecting full-length SSBP-1 complementary DNA together with a HLA-DRα promoter-reporter gene chimera into TSH-treated FRTL-5 thyroid cells whose endogenous SSBP-1 levels are low. IFNγ reverses the ability of TSH to decrease endogenous SSBP-1 RNA levels. Also, whereas SSBP-1 transfection does not cause any increase in IFNγ-induced exogenous promoter activity, transfection of SSBP-1 and CIITA additively increases endogenous classⅡ RNA levels to levels measured in cells treated with IFNγ. Further, competition studies show that SSBP-1 binding is necessary for formation of the double strand protein/DNA complexes that are seen in electrophoretic mobility shift assays when the classⅡ 5'-flanking region is incubated with extracts from IFNγ-treated FRTL-5 cells and that have been previously associated with IFNγ-induced aberrant classⅡ expression. These data suggest that SSBP-1 is involved in the action of IFNγ to overcome the normally suppressed state of the classⅡ gene; it functions together with CIITA, whose expression is independently increased by IFNγ. The effect of SSBP-1 as a positive regulator of classⅡ promoter activity is lost in cells maintained without TSH, in which endogenous SSBP-1 RNA levels are already high in the absence of aberrant classⅡ gene expression. These data suggest that high levels of endogenous SSBP-1 are insufficient to cause aberrant classⅡ expression, but, rather, TSH or IFNγ treatment additionally modulates the cell, albeit differently, such that transfected or endogenous SSBP-1, respectively, can express its positive regulatory activity. The effect of TSH is consistent with reports indicating that TSH enhances the ability of IFNγ to increase classⅡ gene expression despite the fact IFNγ increases endogenous SSBP-1 to only the same levels as in cells untreated with TSH. Finally, the effect of SSBP-1 as a positive regulator is lost when GXXXXG motifs, which exist on both the coding and noncoding strands of the S box, are mutated. Consistent with this, mutation and oligonucleotide competition studies show that GXXXXG motifs are necessary for either strand of the S box to bind protein/DNA complexes containing SSBP-1 in FRTL-5 cell extracts or to bind to recombinant SSBP-1. They also suggest that the SSBP-1-binding sites on either strand of the HLA-DRα S box are functionally distinct. We conclude from these data that the positive regulatory action of SSBP-1 on classⅡ gene expression involves GXXXXG motifs on each strand of the highly conserved S box of the classⅡ 5'-flanking region. As SSBP-1 is modulated by IFNγ and is involved in classⅠ and TSH receptor as well as classⅡ gene expression in FRTL-5 cells, the sum of the data supports the hypotheses that common transcription factors regulate all three genes, and their altered activities may contribute to the development of autoimmunity. (Endocrinology 139: 2300-2313, 1998)

Analysis of Mortality from Asbestos-Related Diseases in Brazil Using Multiple Health Information Systems, 1996-2017

Algranti, Eduardo,Santana, Vilma S.,Campos, Felipe,Salvi, Leonardo,Saito, Cezar A.,Cavalcante, Franciana,Correa-Filho, Heleno R. Occupational Safety and Health Research Institute 2022 Safety and health at work Vol.13 No.3

Background: In Brazil, asbestos was intensively used from the 1960s until its ban in 2017. Mesothelioma, asbestosis, and pleural plaques are typical asbestos-related diseases (ARD-T). To create an ARD-T national database, death records from 1996-2017 were retrieved from several health information systems (HIS). Methods: All national HIS containing coded diagnoses (ICD-10) and death information were obtained. Linkage was performed to create a single database of ARD-T death records, either as underlying or contributory causes, in adults aged 30 years and older. Results: A total of 3,057 ARD-T death records were found, 2,405 (76.4%) of which being malignant mesotheliomas (MM). Pleural MM (n = 1,006; 41.8%) and unspecified MM (n = 792; 32.9%) prevailed. Male to female MM ratio (M:F) was 1.4:1, and higher ratios were found for non-malignant ARD-T: 3.5:1 for asbestosis and 2.4:1 for pleural plaques. Male crude annual mesothelioma mortality (CM_mm ×1,000,000) was 0.98 in 1996 and 2.26 in 2017, a 131.1% increment, while for females it was 1.04 and 1.25, a 20.2% increase, correspondingly. The small number of deaths with asbestosis and pleural plaques records precluded conclusive interpretations. Conclusions: Even with the linkage of several HIS, ARD-T in death records remained in low numbers. MM mortality in men was higher and showed a rapid increase and, along with non-malignant ARD-T, higher M:F ratios suggested a predominant pattern of work-related exposure. The monitoring of workplace and environmental asbestos exposure needs to be improved, as well as the workers surveillance, following the recent Brazilian ban.

INFLUENCE OF OPERATION PATTERNS OF LIGHT-DUTY FREIGHT VEHICLES ON NOx POLLUTION AT LOCAL ROADSIDES

A. SAITO,S. UEKI,Y. TAKADA 한국자동차공학회 2006 International journal of automotive technology Vol.7 No.3

Running tests on roads were conducted to clarify the influences of road infrastructure, traffic condition and vehicle’s emission level to the amount of emission at local roadsides, and to reveal the operation patterns which can reduce the emission peaks. NOx emission peaks of two light duty freight diesel vehicles which have different emission levels were evaluated by using an on-board measurement system. Tests were carried out with various payload conditions and road conditions. As a result many NOx emission peaks were observed when the vehicles were starting or accelerating at intersections. The test vehicle which has higher emission level caused higher frequency and level of NOx emission peaks. Shifting up at lower engine speed in combination with lower acceleration brought out not only reduction of NOx emission peaks level but also of CO₂ mass emission.