著者

Maczka M. Hanuza J. Baran J. Hushur A. Kojima S.

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.125, no.24, pp.244503, 2006-12

被引用文献数

8

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The authors report the results of temperature-dependent Brillouin scattering from both transverse and longitudinal acoustic waves, heat capacity studies as well as room temperature Raman scattering studies on M2O–MgO–WO3–P2O5 glasses (M=K,Rb). These results were used to obtain information about structure and various properties of the studied glasses such as fragility, elastic moduli, ratio of photoelastic constants, and elastic anharmonicity. They have found that both glasses have similar properties but replacement of K+ ions by Rb+ ions in the glass network leads to decrease of elastic parameters and P44 photoelastic constant due to increase of fragility. Based on Brillouin spectroscopy they show that a linear correlation between longitudinal and shear elastic moduli holds over a large temperature range. This result supports the literature data that the Cauchy-type relation represents a general rule for amorphous solids. An analysis of the Boson peak revealed that the form of the frequency distribution of the excess density of states is in agreement with the Euclidean random matrix theory. The reason of the observed shift of the maximum frequency of the Boson peak when K+ ions are substituted for Rb+ ions is also briefly discussed.

著者

Kondo Takahiro Kato Hiroyuki S. Bonn Mischa Kawai Maki

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.126, no.18, pp.181103, 2007-05

被引用文献数

29 17

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The isothermal crystallization process of thin amorphous solid water (ASW) films on Ru(0001) has been investigated in real time by simultaneously employing helium atom scattering, infrared reflection absorption spectroscopy, and isothermal temperature-programmed desorption. The measurements reveal that the crystallization mechanism consists of random nucleation events in the bulk of the ASW films, followed by homogeneous growth. Morphological changes of the solid water film during crystallization expose the water monolayer just above the substrate to the vacuum during the crystallization process.

著者

Shigeta Yasuteru

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.128, no.16, pp.161103, 2008-04

被引用文献数

14 11

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We have derived a quantum distribution function in terms of cumulants that are expectation values of a (anti)symmetric-ordered product of position and momentum fluctuation operators. A second-order approximation leads a Gaussian distribution function, which is positive definite and has proper marginals so that the Shannon entropy can be evaluated.

著者

Ikeda Atsushi Miyazaki Kunimasa

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.135, no.5, pp.054901, 2011

被引用文献数

27 8

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We numerically study crystal nucleation and glassy slow dynamics of the one-component Gaussian core model (GCM) at high densities. The nucleation rate at a fixed supercooling is found to decrease as the density increases. At very high densities, the nucleation is not observed at all in the time window accessed by long molecular dynamics (MD) simulation. Concomitantly, the system exhibits typical slow dynamics of the supercooled fluids near the glass transition point. We compare the simulation results of the supercooled GCM with the predictions of mode-coupling theory (MCT) and find that the agreement between them is better than any other model glassformers studied numerically in the past. Furthermore, we find that a violation of the Stokes-Einstein relation is weaker and the non-Gaussian parameter is smaller than canonical glassformers. Analysis of the probability distribution of the particle displacement clearly reveals that the hopping effect is strongly suppressed in the high density GCM. We conclude from these observations that the GCM is more amenable to the mean-field picture of the glass transition than other models. This is attributed to the long-ranged nature of the interaction potential of the GCM in the high density regime. Finally, the intermediate scattering function at small wavevectors is found to decay much faster than its self part, indicating that dynamics of the large-scale density fluctuations decouples with the shorter-ranged caging motion.

著者

Ikeda Atsushi Miyazaki Kunimasa

出版者

American Institute of Physics

雑誌

The journal of chemical physics (ISSN:00219606)

巻号頁・発行日

vol.135, no.2, pp.024901, 2011-07

被引用文献数

15 16

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We numerically study thermodynamic and structural properties of the one-component Gaussian core model at very high densities. The solid-fluid phase boundary is carefully determined. We find that the density dependence of both the freezing and melting temperatures obey the asymptotic relation, log Tf, log Tm∝ − ρ2/3, where ρ is the number density, which is consistent with Stillinger's conjecture. Thermodynamic quantities such as the energy and pressure and the structural functions such as the static structure factor are also investigated in the fluid phase for a wide range of temperature above the phase boundary. We compare the numerical results with the prediction of the liquid theory with the random phase approximation (RPA). At high temperatures, the results are in almost perfect agreement with RPA for a wide range of density, as it has already been shown in the previous studies. In the low temperature regime close to the phase boundary line, although RPA fails to describe the structure factors and the radial distribution functions at the length scales of the interparticle distance, it successfully predicts their behaviors at longer length scales. RPA also predicts thermodynamic quantities such as the energy, pressure, and the temperature at which the thermal expansion coefficient becomes negative, almost perfectly. Striking ability of RPA to predict thermodynamic quantities even at high densities and low temperatures is understood in terms of the decoupling of the length scales which dictate thermodynamic quantities from the interparticle distance which dominates the peak structures of the static structure factor due to the softness of the Gaussian core potential.

著者

Islam M. M. Yamada A. Sakurai T. Kubota M. Ishizuka S. Matsubara K. Niki S. Akimoto K.

出版者

American Institute of Physics

雑誌

Journal of applied physics (ISSN:00218979)

巻号頁・発行日

vol.110, no.1, pp.014903, 2011

被引用文献数

8 6

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The Cu-dependent phase transition in polycrystalline CuGaSe2 thin films has been studied by an electron probe micro-analyzer (EPMA) and the synchrotron x-ray diffraction method. A Cu-deficiency parameter, Z, defined as (1 − Cu/Ga) was used to study the phase transition. Upon increasing the Z-value, the composition of the films on the Cu2Se-Ga2Se3 pseudo binary tie line was found to shift from the stoichiometric CuGaSe2 (1:1:2) (Z = 0) to the Ga-rich composition through the formation of several ordered defect compounds.The structural modification in the Cu-poor CuGaSe2 film has been investigated by the synchrotron x-ray diffraction method. The existence of the Cu-poor surface phase over the near-stoichiometric bulk CuGaSe2 film was confirmed by the fitting of the accelerated voltage dependent EPMA data.

著者

Yanagihara H. Uwabo K. Minagawa M. Kita Eiji Hirota Noriyuki

出版者

American Institute of Physics

雑誌

Journal of applied physics (ISSN:00218979)

巻号頁・発行日

vol.109, no.7, pp.07C122, 2011-04

被引用文献数

57 16

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We report on the magnetic properties of epitaxial cobalt-ferrite films with orientations parallel to [001] and [111] grown by a reactive molecular beam epitaxy method using pure ozone gas as an oxidation agent. Both Mössbauer spectroscopy and magnetization measurement of the CoFe2O4(001) film grown on MgO(001) indicate that the film has perpendicular magnetic anisotropy (PMA) with high coercivity, whereas the film of CoFe2O4(111) grown on α-Al2O3(0001) appears to be paramagnetic. The maximum uniaxial anisotropy energy for CoFe2O4(001) estimated from the magnetization and coercivity at room temperature is ≈ 3×106 erg/cm3.

著者

Tong XM Toshima N

出版者

IOP Publishing

雑誌

Journal of Physics: Conference Series (ISSN:17426588)

巻号頁・発行日

vol.288, no.01, pp.012018, 2011-04

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We proposed recently a theoretical method to study the infrared (IR) laser assisted photoabsorption cross sections over a broad energy range by a single calculation. We apply this method to study the IR laser assisted photoabsorption of Ne atoms near the first ionization threshold. The simulation results show that the IR field modifies the photoabsorption cross sections and the energy structures. This photoabsorption cross section is an important quantity to analyze the IR-laser assisted dynamical processes by an attosecond pulse, a pulse train or a free electron laser.

著者

Fukuda Junji Nakazawa Kohji

出版者

American Institute of Physics

雑誌

Biomicrofluidics (ISSN:19321058)

巻号頁・発行日

vol.5, no.2, pp.022205, 2011-06

被引用文献数

41

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Spheroid culture is a preferable cell culture approach for some cell types, including hepatocytes, as this type of culture often allows maintenance of organ-specific functions. In this study, we describe a spheroid microarray chip (SM chip) that allows stable immobilization of hepatocyte spheroids in microwells and that can be used to evaluate drug metabolism with high efficiency. The SM chip consists of 300-μm-diameter cylindrical wells with chemically modified bottom faces that form a 100-μm-diameter cell adhesion region surrounded by a nonadhesion region. Primary hepatocytes seeded onto this chip spontaneously formed spheroids of uniform diameter on the cell adhesion region in each microwell and these could be used for cytochrome P-450 fluorescence assays. A row of microwells could also be connected to a microchannel for simultaneous detection of different cytochrome P-450 enzyme activities on a single chip. The miniaturized features of this SM chip reduce the numbers of cells and the amounts of reagents required for assays. The detection of four cytochrome P-450 enzyme activities was demonstrated following induction by 3-methylcholantlene, with a sensitivity significantly higher than that in conventional monolayer culture. This microfabricated chip could therefore serve as a novel culture platform for various cell-based assays, including those used in drug screening, basic biological studies, and tissue engineering applications.

著者

Olivares-Tirado Pedro Tamiya Nanako Kashiwagi Masayo Kashiwagi Kimikazu

出版者

BioMed Central

雑誌

BMC health services research

巻号頁・発行日

vol.11, pp.103, 2011-05

被引用文献数

32 7

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Background: In Japan, as the number of elderly covered by the Long-term Care Insurance (LTCI) system hasincreased, demand for long-term care services has increased substantially and consequently growing expendituresare threatening the sustainability of the system. Understanding the predictive factors associated with long-termcare expenditures among the elderly would be useful in developing future strategies to ensure the sustainability ofthe system. We report a set of predictors of the highest long-term care expenditures in a cohort of elderly personswho received consecutive long-term care services during a year in a Japanese city.Methods: Data were obtained from databases of the LTC insurer of City A in Japan. Binary logistic regression wasused to examine the predictors of the highest long-term care expenditures. We used a simplified model thatfocused on the effects of disability status and type of services used, while controlling for several relevant factors.Goodness of fit, a multicollinearity test, and logistic regression diagnostics were carried out for the final model.Results: The study cohort consisted of 862 current users of LTCI system in city A. After controlling for gender andincome, age, increased utilization rate of benefits, decline in functional status, higher care needs level andinstitutional care were found to be associated with the highest LTCI expenditures. An increased utilization rate ofbenefits (OR = 24.2) was a strong main effect predictors of the high LTC expenditures. However, a significantinteraction between institutional care and high care need level was found, providing evidence of the combinedeffect of the two covariates.Conclusions: Beyond to confirm that disability status of elderly persons is the main factor driving the demand ofLTC services and consequently the expenditures, we showed that changes in utilization rate of benefits -a specificinsurance factor- and the use of institutional care conditional on the high care level, were strongest predictors ofthe highest LTC expenditures. These findings could become crucial for tracking policies aimed at ensuring financialsustainability of LTCI from a public insurer perspective in Japan.

著者

Huré J.-M. Hersant F. Surville C. Nakai N. Jacq T.

出版者

EDP Sciences

雑誌

Astronomy and astrophysics (ISSN:00046361)

巻号頁・発行日

vol.530, pp.A145, 2011-06

被引用文献数

16 6

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We exploit our formula for the gravitational potential of finite size, power-law disks to derive a general expression linking the mass of the black hole in active galactic nuclei (AGN), the mass of the surrounding disk, its surface density profile (through the power index s), and the differential rotation law. We find that the global rotation curve v(R) of the disk in centrifugal balance does not obey a power law of the cylindrical radius R (except in the confusing case s = −2 that mimics a Keplerian motion), and discuss the local velocity index. This formula can help to understand how, from position-velocity diagrams, mass is shared between the disk and the black hole. To this purpose, we checked the idea by generating a sample of synthetic data with different levels of Gaussian noise, added in radius. It turns out that, when observations are spread over a large radial domain and exhibit low dispersion (standard deviation σ ≲ 10% typically), the disk properties (mass and s-parameter) and black hole mass can be deduced from a non linear fit of kinematic data plotted on a (R,Rv2)-diagram. For σ ≳ 10%, masses are estimated fairly well from a linear regression (corresponding to the zeroth-order treatment of the formula), but the power index s is no longer accessible. We have applied the model to 7 AGN disks whose rotation has already been probed through water maser emission. For NGC 3393 and UGC 3789, the masses seem well constrained through the linear approach. For IC 1481, the power-law exponent s can even be deduced. Because the model is scale-free, it applies to any kind of star/disk system. Extension to disks around young stars showing deviation from Keplerian motion is thus straightforward.

著者

Cuong Nguyen Thanh Otani Minoru Iizumi Yoko Okazaki Toshiya Rotas Georgios Tagmatarchis Nikos Li Yongfeng Kaneko Toshiro Hatakeyama Rikizo Okada Susumu

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.99, no.5, pp.053105, 2011-08

被引用文献数

4 4

---

The transport properties of C59N encapsulated semiconducting single-walled carbon nanotubes (SWCNTs) (C59N-peapod) are investigated. Transport measurements of the peapods in field effect transistors (FETs) reveal that ∼14% of the C59N-peapod sample shows n-type behavior even though the electronic properties of the host SWCNTs are similar to those of C60-peapods that exhibit only p-type property. First-principles electronic-structure calculations reveal that the unique transport behavior originates from the monomer form of C59N encapsulated in SWCNTs. The singly occupied (SO) state of C59N lies in the energy gap of the SWCNT and the energy of this state increases substantially when electrons are injected. Because of this shift to higher energy, the SO state acts as a shallow donor state for the conduction band of the nanotube, which leads to n-type behavior in FET measurements.

著者

Sato Soshi Li Wei Kakushima Kuniyuki Ohmori Kenji Natori Kenji Yamada Keisaku Iwai Hiroshi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.98, no.23, pp.233506, 2011-06

被引用文献数

9

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Interfacial states of silicon nanowire field-effect transistors with rectangular-like cross-sections (wire height of 10 nm and widths of 9 and 18 nm) have been evaluated from the transfer characteristics in the subthreshold region measured at cryogenic temperatures, where kinks in the drain current becomes prominent. It is found that the kinks can be well-explained assuming local interfacial states near the conduction band (Ec). The main extracted local states have been shown to exist at 10 and 31 meV below Ec with the densities of 1.3×1013 cm−2/eV and 5.4×1012 cm−2/eV, respectively. By comparing two field-effect transistors with different wire widths, the former states can be assigned to the states located at the corner and the side surface of the wire, and the latter to the top and the bottom surfaces.

著者

Masumoto Yasuaki Hirata Yuuki Mohan Premila Motohisa Junichi Fukui Takashi

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.98, no.21, pp.211902, 2011-05

被引用文献数

9

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The photoluminescence from single InP/InAs/InP core-multishell nanowires (CMNs) was highly linearly polarized in perpendicular to the nanowire long axis. Taking account of dielectric confinement of light field, we found the internal optical dipole squared perpendicular to the nanotube long axis d0x2 is larger than that parallel to the axis d0z2 by two orders of magnitude. With the increase in the thickness of InAs nanotubes, the ratio β = d0x2/d0z2 increases. This strong anisotropy in β comes from nearly perfect wurtzite structure of InP/InAs/InP CMNs and small inclusion of pz-character into the Γ7(B)-hole state.

著者

Masumoto Yasuaki Yoshida Seitaro Ikezawa Michio Tomimoto Shinichi Sakuma Yoshiki

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.98, no.6, pp.061905, 2011-02

被引用文献数

5 4

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We observed that the biexciton binding energy in InAs quantum rhombic disks (QRDs) is enhanced by twice compared with that for InAs quantum dots (QDs) so far reported around 1.24 μm nearby the telecommunication wavelength. The heterodyne-detected four-wave-mixing detected the exciton-biexciton quantum beat superposed on photon echo decay, giving the biexciton binding energy of 3.4 meV to 3 monolayer (ML) InAs QRDs and 4.1 meV to 4 ML InAs QRDs, respectively. The largest biexciton binding energy of 4.1 meV in InAs QDs is ascribed to increased electron-hole overlap in confined geometry with a minimized strain distribution.

著者

Konabe Satoru Okada Susumu

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.98, no.7, pp.073109, 2011-02

被引用文献数

4

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We propose a method for optically probing the magnetic states of metallic atoms encapsulated in single-walled carbon nanotubes. The absorption spectrum is calculated by solving the Bethe–Salpeter equation, which includes the effects of magnetic atoms, under the tight-binding approximation. Due to the exchange interaction between excitons and polarized spins in ferromagnets, triplet excitons acquire a finite oscillator strength and can thus be excited by light. This mechanism is promising for detecting magnetic ordering of materials encapsulated in carbon nanotubes.

著者

Sawaki D. Kobayashi W. Moritomo Y. Terasaki I.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.98, no.8, pp.081915, 2011-02

被引用文献数

104 26

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We investigate thermal rectification in a bulk material with a pyramid shape to elucidate shape dependence of the thermal rectification, and find that rectifying coefficient R is 1.35 for this shape, which is smaller than R = 1.43 for a rectangular shape. This result is fully duplicated by our numerical calculation based on Fourier’s law. We also apply this calculation to a given shape, and show a possible way to increase R depending on the shape.

著者

Ohta Ryu Zushi Junta Ariizumi Takuma Kojima Seiji

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.98, no.9, pp.092909, 2011-02

被引用文献数

36

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The precursor dynamics of a cubic–tetragonal ferroelectric phase transition of potassium tantalate niobate (KTa1−xNbxO3 with x = 0.32) crystals is studied by Brillouin scattering. The appearance of the central peak (CP) and marked softening of the elastic constant c11 are clearly observed above the Curie temperature, TC–T, owing to the interaction between the LA mode and local polarization fluctuations of polar nanoregions (PNRs). The relaxation time determined by the CP width clearly shows a critical slowing down above TC–T, indicating an order–disorder feature of the ferroelectric phase transition. The size of a dynamic PNR is evaluated, and it increases toward TC–T.

著者

Hase Muneaki Tominaga Junji

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.99, no.3, pp.031902, 2011

被引用文献数

11 6

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We report on evaluation of lattice thermal conductivity of GeTe/Sb2Te3 superlattice (SL) by using femtosecond coherent phonon spectroscopy at various lattice temperatures. The time-resolved transient reflectivity obtained in amorphous and crystalline GeTe/Sb2Te3 SL films exhibits the coherent A1 optical modes at terahertz (THz) frequencies with picoseconds dephasing time. Based on the Debye theory, we calculate the lattice thermal conductivity, including scattering by grain boundary and point defect, umklapp process, and phonon resonant scattering. The results indicate that the thermal conductivity in amorphous SL is less temperature dependent, being attributed to dominant phonon-defect scattering.

著者

Umezawa Naoto Shiraishi Kenji

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.97, no.20, pp.202906, 2010-11

被引用文献数

11 12

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The solubility of silicon in high-permittivity (high-κ) oxides significantly affects the performance of field-effect transistors. Our comparative study of silicon impurities in La2O3 and HfO2 reveals that the stability of silicon at substitutional sites strongly depends on its coordination number. When substituted for lanthanum, a silicon atom fits comfortably in La2O3, thanks to the formation of a SiO4 tetrahedral structure. In addition, the substitutional silicon acts as a donor impurity in La2O3, increasing oxygen content in the oxide. This contributes to absorbing silicon and oxygen from the interface region, leading to the formation of lanthanum silicate at the La2O3/silicon interface.