| 272471. |
- Sato, K., et al.
(författare)
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First-principles material design and perspective on semiconductor spintronics materials
- 2009
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 404:23-24, s. 5237-5243
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the electronic structure and magnetic properties of III–V compound semiconductor based dilute magnetic semiconductors (DMS) from first-principles. The electronic structure of DMS is calculated by using the Korringa–Kohn–Rostoker coherent potential approximation (KKR-CPA) method in connection with the local density approximation (LDA). Describing the magnetic properties by a classical Heisenberg model, effective exchange interactions are calculated by applying magnetic force theorem for two impurities embedded in the CPA medium. With the calculated exchange interactions, TC is estimated by using the mean field approximation, the random phase approximation and the Monte Carlo simulation. In the above compounds, the magnetic interactions are well described from double exchange picture. Due to the short-range interactions, high-TC is difficult to achieve in the presently investigated materials. Based on the present results, two strategies towards high-TC are proposed to realize useful DMS materials. One uses spinodal decomposition to realize high blocking temperature in super-paramagnetic blocking phenomena and the other uses co-doping method to realize high concentration doping of magnetic impurities for high-TC.
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| 272472. |
- Sato, K., et al.
(författare)
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First-principles theory of dilute magnetic semiconductors
- 2010
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Ingår i: Reviews of Modern Physics. - : APS. - 0034-6861 .- 1539-0756. ; 82:2, s. 1633-1690
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Tidskriftsartikel (refereegranskat)abstract
- This review summarizes recent first-principles investigations of the electronic structure and magnetism of dilute magnetic semiconductors (DMSs), which are interesting for applications in spintronics. Details of the electronic structure of transition-metal-doped III-V and II-VI semiconductors are described, especially how the electronic structure couples to the magnetic properties of an impurity. In addition, the underlying mechanism of the ferromagnetism in DMSs is investigated from the electronic structure point of view in order to establish a unified picture that explains the chemical trend of the magnetism in DMSs. Recent efforts to fabricate high-TC DMSs require accurate materials design and reliable TC predictions for the DMSs. In this connection, a hybrid method (ab initio calculations of effective exchange interactions coupled to Monte Carlo simulations for the thermal properties) is discussed as a practical method for calculating the Curie temperature of DMSs. The calculated ordering temperatures for various DMS systems are discussed, and the usefulness of the method is demonstrated. Moreover, in order to include all the complexity in the fabrication process of DMSs into advanced materials design, spinodal decomposition in DMSs is simulated and we try to assess the effect of inhomogeneity in them. Finally, recent works on first-principles theory of transport properties of DMSs are reviewed. The discussion is mainly based on electronic structure theory within the local-density approximation to density-functional theory.
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| 272473. |
- Sato, Kae, et al.
(författare)
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Microbead-based rolling circle amplification in a microchip for sensitive DNA detection
- 2010
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 10:10, s. 1262-1266
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Tidskriftsartikel (refereegranskat)abstract
- The sensitive detection and quantification of DNA targets in the food industry and in environmental and clinical settings are issues of utmost importance in ensuring contamination-free food, monitoring the environment, and battling disease. Selective probes coupled with powerful amplification techniques are therefore of major interest. In this study, we set out to create an integrated microchemical chip that benefits from microfluidic chip technology in terms of sensitivity and a strong detection methodology provided jointly by padlock probes and rolling circle amplification (RCA). Here, we have integrated padlock probes and RCA into a microchip. The chip uses solid phase capture in a microchannel to enable washing cycles and decrease analytical area, and employs on-bead RCA for single-molecule amplification and detection. We investigated the effects of reagent concentration and amount of padlock probes, and demonstrated the feasibility of detecting Salmonella.
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| 272474. |
- Sato, Masaaki, et al.
(författare)
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alpha(1A)-Adrenoceptors activate mTOR signalling and glucose uptake in cardiomyocytes
- 2018
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Ingår i: Biochemical Pharmacology. - : Elsevier BV. - 0006-2952 .- 1356-1839. ; 148, s. 27-40
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of G protein-coupled receptors to modulate mechanistic target of rapamycin (mTOR) activity is a newly emerging paradigm with the potential to link cell surface receptors with cell survival. Cardiomyocyte viability is linked to signalling pathways involving Akt and mTOR, as well as increased glucose uptake and utilization. Our aim was to determine whether the am-adrenoceptor (AR) couples to these protective pathways, and increased glucose uptake. We characterised alpha(1A)-AR signalling in CHO-K1 cells co-expressing the human alpha(1A)-AR and GLUT4 (CHO alpha(1A)GLUT4myc) and in neonatal rat ventricular cardiomyocytes (NRVM), and measured glucose uptake, intracellular Ga2* mobilization, and phosphorylation of mTOR, Akt, 5' adenosine monophosphate-activated kinase (AMPK) and S6 ribosomal protein (S6rp). In both systems, noradrenaline and the alpha(1A)-AR selective agonist A61603 stimulated glucose uptake by parallel pathways involving mTOR and AMPK, whereas another alpha(1A)-AR agonist oxymetazoline increased glucose uptake predominantly by mTOR. All agonists promoted phosphorylation of mTOR at Ser2448 and Ser2481, indicating activation of both mTORC1 and mTORC2, but did not increase Akt phosphorylation. In CHO alpha(1A)GLUT4myc cells, siRNA directed against rictor but not raptor suppressed alpha(1A)-AR mediated glucose uptake. We have thus identified mTORC2 as a key component in glucose uptake stimulated by alpha(1A)-AR agonists. Our findings identify a novel link between the alpha(1A)-AR, mTORC2 and glucose uptake, that have been implicated separately in cardiomyocyte survival. Our studies provide an improved framework for examining the utility of alpha(1A)-AR selective agonists as tools in the treatment of cardiac dysfunction.
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| 272475. |
- Sato, Mamiko, 1982, et al.
(författare)
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APEX and NOEMA observations of H 2 S in nearby luminous galaxies and the ULIRG Mrk 231: A possible relation between dense gas properties and molecular outflows
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 660
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Tidskriftsartikel (refereegranskat)abstract
- Context. In order to understand the evolution and feedback of active galactic nuclei (AGN) and star formation, it is important to use molecular lines as probes of physical conditions and chemistry. Aims. We use H2S to investigate the impact of starburst and AGN activity on the chemistry of the molecular interstellar medium in luminous infrared galaxies. Specifically, our aim is to search for evidence of shock enhancement of H2S related to galactic-scale mechanical feedback processes such as outflows. Methods. Using the APEX single-dish telescope, we have observed the 110 ~101 transition of ortho-H2S at 168 GHz towards the centres of 12 nearby luminous infrared galaxies. We have also observed the same line towards the ultra-luminous infrared galaxy Mrk 231 with the NOEMA interferometer. Results. We detected H2S towards NGC 253, NGC 1068, NGC 3256, NGC 4418, NGC 4826, NGC 4945, Circinus, M 83, and Mrk 231. Upper limits were obtained for NGC 1097, NGC 1377, and IC 860. We also detected line emission from HCN 2~1 in all galaxies in the APEX survey as well as HCO+, HNC, CH3CN, CH3OH, H2CS, HOC+, and SO in several of the sample galaxies. Mrk 231 has a rich 2 mm molecular spectrum and, in addition to H2S, we detect emission from HC3N, CH3OH, HC18O+, C2S, and CH3CCH. Four galaxies show elevated H2S emission relative to HCN: Circinus, NGC 3256, NGC 4826, and NGC 4418. We suggest that the high line ratios are caused by elevated H2S abundances in the dense gas. However, we do not find any clear connection between the H2S/HCN line intensity ratio and the presence (or speed) of molecular outflows in the sample galaxies. Therefore, H2S abundances do not seem to be globally affected by the large-scale outflows. In addition, the H2S/HCN line ratio is not enhanced in the line wings compared to the line core in Mrk 231. This suggests that H2S abundances do not increase in the dense gas in the outflow. However, we do find that the H2S and HCN luminosities (LH2S and LHCN) correlate well with the total molecular gas mass in the outflow, Moutflow(H2), in contrast to LCO and LHCO+. We also find that the line luminosity of H2S correlates with the total infrared luminosity in a similar way as that of H2O. Conclusions. We do not find any evidence of H2S abundance enhancements in the dense gas due to galactic-scale outflows in our sample galaxies, nor in the high-resolution study of Mrk 231. We discuss possible mechanisms behind the suggested H2S abundance enhancements in NGC 4418, Circinus, NGC 3256, and NGC 4826. These include radiative processes (for example X-rays or cosmic rays) or smaller-scale shocks. Further high-resolution and multi-transition studies are required to determine the cause behind the elevated H2S emission in these galaxies. We suggest that LH2S serves as a tracer of the dense gas content, similar to LHCN, and that the correlation between LH2S and Moutflow(H2) implies a relation between the dense gas reservoir and the properties and evolution of the molecular feedback. This potential link requires further study since it holds important keys to our understanding of how the properties of molecular outflows relate to those of their host galaxies. Finally, the similar infrared-correlation coefficients between H2S and H2O may indicate that they originate in the same regions in the galaxy: warm gas in shocks or irradiated by star formation or an AGN.
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| 272476. |
- Sato, Mamiko, 1982
(författare)
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H2S and dense gas in luminous infrared galaxies and their outflows
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Luminous infrared galaxies (LIRGs) are dusty galaxies that are going through an important and likely transient phase in their evolution. They experience rapid growth through bursts of star formation or an accreting supermassive black hole, an Active Galactic Nucleus (AGN). Radiative feedback from the AGN or starburst is absorbed by the dust and re-emitted in the infrared. Mechanical feedback in the form of outflows can effectively expel gas and dust from the central regions of the LIRGs. Thus, studying the physical processes and conditions of outflows is one of the key elements for a complete understanding of galaxy evolution. Especially molecular outflows are significant because cold and dense gas, that normally participates in star formation, can be highly affected by the presence of the central energy source. In some cases, the gas may even be accelerated to velocities over 1000 km s−1. Many fundamental questions about the formation or physical processes of these feedback mechanisms still remain to be answered. In this thesis, I put my attention to one molecule, hydrogen sulphide (H2S), as a new diagnostic tool to probe the physical conditions in the dense molecular gas in dusty galaxies and their outflows. One aim is to investigate if H2S can be used to study the outflow driving mechanisms. The observations with the Atacama Pathfinder Experiment (APEX) telescope and the IRAM Northern Extended Millimeter Array (NOEMA) are described in Paper I. In this paper, we present new detections of ground state H2S line emission in a sample of LIRGs, and compare intensities to other lines, such as HCN and HCO+ 2–1. At the observed resolution, we do not find any H2S abundance enhancements linked to the outflows. Instead, we find a possible relation between the dense gas reservoir and the properties and evolution of the molecular feedback. Another point we discuss is the similar infrared-correlation coefficient between H2S and H2O which may indicate a similar origin of their emission. For example from warm gas in shocks or in gas irradiated by star formation or an AGN. The next step is to look into the dense dusty galaxy nuclei with higher spatial resolution, and to proceed to radiative transfer modelling using multitransition lines of several molecular gas tracers, including H2S.
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| 272477. |
- Sato, Masaaki, et al.
(författare)
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Interaction with Caveolin-1 Modulates G Protein Coupling of Mouse beta(3)-Adrenoceptor
- 2012
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 287:24, s. 20674-20688
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Tidskriftsartikel (refereegranskat)abstract
- Caveolins act as scaffold proteins in multiprotein complexes and have been implicated in signaling by G protein-coupled receptors. Studies using knock-out mice suggest that beta(3)-adrenoceptor (beta(3)-AR) signaling is dependent on caveolin-1; however, it is not known whether caveolin-1 is associated with the beta(3)-AR or solely with downstream signaling proteins. We have addressed this question by examining the impact of membrane rafts and caveolin-1 on the differential signaling of mouse beta(3a)- and beta(3b)-AR isoforms that diverge at the distal C terminus. Only the beta(3b)-AR promotes pertussis toxin (PTX)-sensitive cAMP accumulation. When cells expressing the beta(3a)-AR were treated with filipin III to disrupt membrane rafts or transfected with caveolin-1 siRNA, the cyclic AMP response to the beta(3)-AR agonist CL316243 became PTX-sensitive, suggesting G alpha(i/o) coupling. The beta(3a)-AR C terminus, S (P-384) under bar PLNR (P-389) under bar DG (Y-392) under bar EGARP (P-398) under bar PT, resembles a caveolin interaction motif. Mutant beta(3a)-ARs (F389A/Y392A/F398A or P384S/F389A) promoted PTX-sensitive cAMP responses, and in situ proximity assays demonstrated an association between caveolin-1 and the wild type beta(3a)-AR but not the mutant receptors. In membrane preparations, the beta(3b)-AR activated G alpha(o) and mediated PTX-sensitive cAMP responses, whereas the beta(3a)-AR did not activate G alpha(i/o) proteins. The endogenous beta(3a)-AR displayed G alpha(i/o) coupling in brown adipocytes from caveolin-1 knock-out mice or in wild type adipocytes treated with filipin III. Our studies indicate that interaction of the beta(3a)-AR with caveolin inhibits coupling to G alpha(i/o) proteins and suggest that signaling is modulated by a raft-enriched complex containing the beta(3a)-AR, caveolin-1, G alpha(s), and adenylyl cyclase.
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| 272478. |
- Sato, Munehiko, et al.
(författare)
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Zensei : Embedded, Multi-electrode Bioimpedance Sensing for Implicit, Ubiquitous User Recognition
- 2017
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Ingår i: PROCEEDINGS OF THE 2017 ACM SIGCHI CONFERENCE ON HUMAN FACTORS IN COMPUTING SYSTEMS (CHI'17). - New York, NY, USA : ASSOC COMPUTING MACHINERY. ; , s. 3972-3985
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Konferensbidrag (refereegranskat)abstract
- Interactions and connectivity is increasingly expanding to shared objects and environments, such as furniture, vehicles, lighting, and entertainment systems. For transparent personalization in such contexts, we see an opportunity for embedded recognition, to complement traditional, explicit authentication. We introduce Zensei, an implicit sensing system that leverages bio-sensing, signal processing and machine learning to classify uninstrumented users by their body's electrical properties. Zensei could allow many objects to recognize users. E.g., phones that unlock when held, cars that automatically adjust mirrors and seats, or power tools that restore user settings. We introduce wide-spectrum bioimpedance hardware that measures both amplitude and phase. It extends previous approaches through multi-electrode sensing and high-speed wireless data collection for embedded devices. We implement the sensing in devices and furniture, where unique electrode configurations generate characteristic profiles based on user's unique electrical properties. Finally, we discuss results from a comprehensive, longitudinal 22-day data collection experiment with 46 subjects. Our analysis shows promising classification accuracy and low false acceptance rate.
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| 272479. |
- Sato, N., et al.
(författare)
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Domain Wall Based Spin-Hall Nano-Oscillators
- 2019
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 123
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Tidskriftsartikel (refereegranskat)abstract
- In the last decade, two revolutionary concepts in nanomagnetism emerged from research for storage technologies and advanced information processing. The first suggests the use of magnetic domain walls in ferromagnetic nanowires to permanently store information in domain-wall racetrack memories. The second proposes a hardware realization of neuromorphic computing in nanomagnets using nonlinear magnetic oscillations in the gigahertz range. Both ideas originate from the transfer of angular momentum from conduction electrons to localized spins in ferromagnets, either to push data encoded in domain walls along nanowires or to sustain magnetic oscillations in artificial neurones. Even though both concepts share a common ground, they live on very different timescales which rendered them incompatible so far. Here, we bridge both ideas by demonstrating the excitation of magnetic auto-oscillations inside nanoscale domain walls using pure spin currents. This Letter will shed light on the current characteristic and spatial distribution of the excited auto-oscillations.
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| 272480. |
- Sato Sakayachi, Fusako, 1979, et al.
(författare)
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Relationship Between Cervical, Thoracic, and Lumbar Spinal Alignments in Automotive Seated Posture
- 2019
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Ingår i: Journal of Biomechanical Engineering. - : ASME International. - 0148-0731 .- 1528-8951. ; 141:12
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the relationship between cervical, thoracic, and lumbar spinal alignments in one automotive occupant seated posture. An image data-set of the spinal column in the automotive seated posture, previously acquired by an upright open magnetic resonance imaging (MRI) system, was re-analyzed in this study. Spinal alignments were presented by the geometrical centers of the vertebral bodies extracted from the image data. Cervical, thoracic, and lumbar spinal alignments were analyzed separately with multidimensional scaling (MDS). Based on distribution maps of cervical, thoracic, and lumbar spinal alignments created by MDS, representative spinal alignment patterns of the cervical, thoracic, and lumbar spines and the relationship between cervical, thoracic, and lumbar spinal alignments were investigated. As a result, this study found a correlation between cervical and thoracic spinal alignments in an automotive occupant seated posture. According to representative spinal alignment patterns illustrated by the distribution map of spinal alignments, subjects who had kyphotic cervical spinal alignment tended to have less kyphotic thoracic spinal alignment, while subjects who had lordotic cervical spinal alignment tended to have more kyphotic thoracic spinal alignment. For lumbar spinal alignments, no prominent relationship was found between cervical and thoracic spinal alignment in the seated condition of this study.
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