bluuebunny/crossref_metadata_2025 huggingface dataset:
Excess Pore Pressures Around Underground Structures Following Earthquake Induced Liquefaction
Authors: Chian Siau Chen , Madabhushi Santana Phani Gopal
Published: February 2014

Underground structures located in liquefiable soil deposits are susceptible to floatation following an earthquake event due to their lower unit weight relative to the surrounding saturated soil. This inherent buoyancy may cause lightweight structures to float when the soil liquefies. Centrifuge tests have been carried out to study the excess pore pressure generation and dissipation in liquefiable soils. In these tests, near full liquefaction conditions were attained within a few cycles of the earthquake loading. In the case of high hydraulic conductivity sands, significant dissipation could take place even during the earthquake loading which inhibits full liquefaction from occurring. In the case of excess pore pressure generation and dissipation around a floating structure, the cyclic response of the structure may lead to the reduction in excess pore pressure near the face of the structure as compared to the far field. This reduction in excess pore pressure is due to shear-induced dilation and suction pressures arising from extensile stresses at the soil-structure interface. Given the lower excess pore pressure around the structure; the soil around the structure retains a portion of this shear strength which in turn can discourage significant uplift of the underground structure.
The heat stress for workers employed in a dairy farm
Authors: Marucci Alvaro , Monarca Danilo , Cecchini Massimo , Colantoni Andrea , Di Giacinto Simone , Cappuccini Andrea
Published: February 2014

The Italian dairy production is characterized by high heterogeneity. The typology quantitatively more important (80% of national production) is represented by cow’s milk cheeses (Grana Padano cheese, string cheese, Parmesan cheese, etc.), while the cheese from buffalo’s milk (especially string cheese such as mozzarella) and cheese from sheep and goats represents respectively 4% and 8% of the national dairy production, and are linked to specific regional contexts. Some phases of the cycle of milk processing occur at certain temperatures that are not comfortable for the workers also in relation to possible problems due to thermal shock. The aim of this study was to evaluate the risk of heat stress on workers operating in a dairy for processing of buffalo milk. The research was conducted at a dairy farm located in the province of Viterbo, Italy, during the spring-summer period. To carry out the research were detected major climatic parameters (air temperature, relative humidity, mean radiant temperature, air velocity) and the main parameters of the individual operators (clothing thermal insulation and the energy expenditure required from the work done by employees). Subsequently, main indices of heat stress assessment provided by the main technical standards were calculated. In particular have been calculated predicted mean vote and predicted percentage of dissatisfied in moderate thermal environments (environments in which the objective, in the design and management phases, is to achieve the thermal comfort), provided by the UNI EN ISO 7730 and the wet bulb globe temperature in severe hot environments (environments in which you must protect the health of workers) required by UNI EN ISO 27243. The results show some phases of risk from heat stress especially during times of test in which the internal air temperature exceeds the threshold of 30°C and possible solutions to improve the safety of the operators.
Hydrological model parameter dimensionality is a weak measure of prediction uncertainty
Authors: Pande S. , Arkesteijn L. , Savenije H. H. G. , Bastidas L. A.
Published: March 2014

Abstract. This paper presents evidence that model prediction uncertainty does not necessarily rise with parameter dimensionality (the number of parameters). Here by prediction we mean future simulation of a variable of interest conditioned on certain future values of input variables. We utilize a relationship between prediction uncertainty, sample size and model complexity based on Vapnik–Chervonenkis (VC) generalization theory. It suggests that models with higher complexity tend to have higher prediction uncertainty for limited sample size. However, model complexity is not necessarily related to the number of parameters. Here by limited sample size we mean a sample size that is limited in representing the dynamics of the underlying processes. Based on VC theory, we demonstrate that model complexity crucially depends on the magnitude of model parameters. We do this by using two model structures, SAC-SMA and its simplification, SIXPAR, and 5 MOPEX basin data sets across the United States. We conclude that parsimonious model selection based on parameter dimensionality may lead to a less informed model choice.
Fetal Homicide Laws: the Utmost Protection of Reproductive Autonomy
Authors: Correa Eryn
Published: March 2014

None
LEGO-based Robotics in Higher Education: 15 Years of Student Creativity
Authors: Danahy Ethan , Wang Eric , Brockman Jay , Carberry Adam , Shapiro Ben , Rogers Chris B.
Published: February 2014

Our goal in this article is to reflect on the role LEGO robotics has played in college engineering education over the last 15 years, starting with the introduction of the RCX in 1998 and ending with the introduction of the EV3 in 2013. By combining a modular computer programming language with a modular building platform, LEGO Education has allowed students (of all ages) to become active leaders in their own education as they build everything from animals for a robotic zoo to robots that play children's games. Most importantly, it allows all students to develop different solutions to the same problem to provide a learning community. We look first at how the recent developments in the learning sciences can help in promoting student learning in robotics. We then share four case studies of successful college-level implementations that build on these developments.
Freedom of the Press as a Discrete Constitutional Guarantee
Authors: Oliphant Benjamin
Published: March 2014

While “freedom of the press” is explicitly guaranteed in section 2(b) of the Charter, Canadian courts have tended to treat the term as a superfluity to be protected, if at all, through the related but conceptually distinct notion of freedom of expression. This paper argues that the absence of a discrete analytical framework for press freedom fails to give full meaning to the text of the Charter and is inconsistent with the Supreme Court’s own acknowledgment of the vital and unique importance of press freedom within the context of section 2(b). I suggest that the reasons provided for rejecting constitutional protection are typically based on the presumed absence of any workable Charter framework, which the analysis proposed here attempts to supply. To that end, this paper advances a three-step framework for the protection of newsgathering activity and illustrates its operation by applying it to the vexed issue of confidential sources. It concludes by suggesting that adopting a purposive interpretation of press freedom—as a freedom intended to guarantee the public’s “right to know”—would ensure that the Court’s doctrine matches its rhetoric and that this fundamental freedom is no longer treated as a mere constitutional redundancy.
Applying the Principle of Proportionality in Employment and Labour Law Contexts
Authors: Alon-Shenker Pnina , Davidov Guy
Published: March 2014

The principle of proportionality, which is designed to limit abuse of power and infringement of human rights by governments and legislatures, has become a fundamental and binding legal principle in the jurisprudence of many countries. Ever since the seminal R. v. Oakes decision, when the Supreme Court of Canada interpreted section 1 of the Canadian Charter of Rights and Freedoms as entailing a three-step proportionality test, proportionality has become an important pillar of Canadian law. This article argues that the principle of proportionality actually extends, and should extend, to the private sphere—imposing limitations on employers and trade unions when using their powers. It first argues, at a descriptive level, that proportionality already plays a significant role (although often not explicitly) in various Canadian labour and employment law contexts, a role not sufficiently acknowledged thus far. It then turns to the normative level and explores the justifications for extending the application of proportionality to the private sphere and more specifically to the employment relationship. The article advocates a more explicit use and a structured application of the three-stage proportionality test in various employment and labour law contexts.
La relativité aquilienne en droit de la responsabilité civile — analyse comparée des systèmes germanique, canadien et québécois
Authors: Lacroix Mariève
Published: March 2014

L’auteure explore la théorie de la relativité aquilienne en droit comparé afin d’entamer, voire de nourrir un dialogue avec le système civiliste québécois. Elle jauge les potentialités d’une importation de la doctrine de la relativité aquilienne en matière de responsabilité extracontractuelle personnelle au Québec.

Dans une première partie, l’auteure expose la doctrine de la relativité aquilienne dans une perspective historique et comparatiste.

Dans une deuxième partie, elle prend pour illustration le droit civil allemand et la common law canadienne, car ils emploient des mécanismes distincts, mais qui convergent à restreindre le champ d’application de la responsabilité civile. Si la théorie de la relativité aquilienne puise ses racines dans la formule du Code civil allemand, notamment à l’article 823 BGB, qui édicte diverses dispositions législatives en tant que « petites » clauses générales de responsabilité, elle s’exprime à travers le délit de négligence et l’idée d’interférence des droits dans la common law canadienne.

Dans une troisième partie, prenant parti qu’il n’y a pas d’obstacle dirimant à la relativité aquilienne en droit québécois, elle sonde la volonté de favoriser une conception relative de la responsabilité civile. Le cas échéant, il est permis de s’arrêter sur la technique, laquelle commande d’identifier les mécanismes qui peuvent contenir dans des bornes raisonnables le périmètre de la responsabilité civile au Québec, ainsi que de situer ces mécanismes.
La historia de una vida en situación de frontera: migración, superación y trabajo en el “circuito sacoleiro”
Authors: Cardin Eric Gustavo
Published: March 2014

The research undertaken, and now presented here, was aimed at constructing additional understandings of the phenomenon of migration and of the smuggling practices along the border between Brazil and Paraguay. By articulating local knowledge and historically established theories, and exploring the life histories and occupational trajectories in the narratives collected, the text denounces the difficulty of thinking about the world in terms of paradigms and explores the subtleties of everyday life and its potential in the construction of the reality of these lives.
Poor CD4 recovery and risk of subsequent progression to AIDS or death despite viral suppression in a South African cohort
Authors: Takuva Simbarashe , Maskew Mhairi , Brennan Alana T , Long Lawrence , Sanne Ian , Fox Matthew P
Published: March 2014

Introduction

The prognostic role of CD4 response in the first six months of treatment in patients achieving early viral suppression during HIV treatment is unclear.

Methods

This was a cohort study of HIV‐positive adults initiating antiretroviral therapy (ART) between April 2004 and August 2007 who achieved viral suppression (<400 copies/ml) by six months on treatment in South Africa. Immunological response at six months was defined as: (1) absolute CD4 reached (<200 vs. ≥200 cells/ml); (2) absolute CD4 reached (0–49, 50–200 and ≥200 cells/ml); and (3) CD4 increase from ART initiation (<0, 0–49, 50–199 and ≥200 cells/ml). We used Cox regression models to determine the relationship between each definition and both new AIDS‐defining condition and death.

Results

A total of 4129 patients were eligible for analysis; 212 (5.1%) of those patients experienced a new AIDS‐defining condition and 154 (3.7%) died. Smaller CD4 gains by six months were associated with higher hazards of progression to AIDS (CD4<50 vs. ≥200 cells/ml; adjusted hazard ratio (aHR): 2.6; 95% CI: 1.2–2.1) and death (aHR: 2.8; 95% CI: 1.4–5.7). A decrease in CD4 count since ART initiation through six months (aHR: 2.4; 95% CI: 1.2–4.9) and smaller CD4 count gains (0–49 cells/ml; aHR: 2.0; 95% CI: 1.2–3.4 and 50–199 cells/ml; aHR: 1.5; 95% CI: 0.9–2.2) were also associated with greater risk of progression to AIDS compared to an increase of ≥200 cells/ml. When we examined mortality differences by gender among this virally suppressed cohort, a higher proportion of males died compared to females, 4.7% versus 3.2%, p=0.01. However, in multivariable analysis, we did not observe any significant differences: aHR: 1.39; 95% CI: 0.98–1.95.

Conclusions

Patients on ART with poor CD4 recovery early in treatment are at greater risk of progression to new AIDS diagnosis or death despite viral suppression. Approaches to managing this sub‐group of patients need further investigation.
Effect of Heat Treatment on the High-Purity Silica Glass Prepared from Amorphous and Crystalline Powders by Small Angle X-Ray Scattering
Authors: Shinohara Armando H. , Sekiya Edson H. , Torikai Delson , Ogata Daniela Y. , Suzuki Carlos K. , Kellermann Guinter , Torriani Iris L.
Published: March 2014

High-purity silica glass prepared from high-purity amorphous and crystalline powders by flame fusion and sintering at high temperatures in vacuum, was heat-treated at 1250°C for several periods of time and its structure was studied using the small-angle X-ray scattering technique. As a result, the structure of silica glass was dependent on its thermal history. The structure of as-fused silica glass samples prepared by flame fusion appeared to be quite similar, even though raw materials with different degrees of homogeneity were used. However, the structure of silica glass behaved differently after heat treatment. This different response of the structure of silica glass to heat treatment was analyzed in terms of impurity content and viscosity.
Charge Ordering in La1-xSrxMnO3 (x∼0.12)
Authors: Inami Toshiya , Ikeda Naoshi , Murakami Youichi , Koyama Ichirou , Wakabayashi Yuusuke , Yamada Yasusada
Published: March 2014

Synchrotron x-ray measurements were done on the charge ordered state of La1-x
Sr
x
MnO3 (x∼0.12). In accordance with previous neutron diffraction study, super-lattice reflections which double the b-axis were observed. From the extinction rule of the super-lattice reflections, layer-type charge ordering pattern is plausible. Temperature dependence of the super-lattice peaks might indicate that a certain kind of competition exists in this system.
Zinc Oxide Films Prepared with Undulator Beam
Authors: Yoshida Akira , Wakahara Akihiro
Published: March 2014

We prepared ZnO (Zinc oxide) thin films from diethylzinc(DEZ) and oxygen gas at very low temperatures using undulator beam. The substrate temperature was changed from -100°C to 150°C, and the source gas ratio [O2]/[DEZ] was varied from 10 to 1000. The carbon content was greatly reduced with increasing the source gas ratio and the substrate temperature, and carbon-free films were obtained. The optical transmittance was over 90%. The deposition rate was decreased when the substrate temperature was increased, in correspondence with the decreased coverage of DEZ adsorbed molecules on the substrate surface.
Angle-Resolved UPS Studies of Organic Thin Films
Authors: Ueno Nobuo
Published: March 2014

This paper describes recent progress of angle-resolved photoelectron spectroscopy using synchrotron radiation (SR-ARUPS) on organic thin films. SR-ARUPS has been growing to a new surface analysis technique which can offer concrete information on the molecular orientation at the film surface as well as on the origin of the electronic structure, both of which are important in understanding functions of organic thin films. Some examples of the experimental determination of the molecular orientation by SR-ARUPS are shown for epitaxial ultrathin films of phthalocyanines and bis(1,2,5-thiadiazolo)-p-quinobis (1,3-dithiole) (BTQBT). The orientation of pendant naphthalene groups at the surface of thin film of poly(2-vinylnaphthalene) is also shown, where the comparison between the results obtained by SR-ARUPS and near edge X-ray absorption fine structure (NEXAFS) spectroscopy is made in order to understand an advantage of SR-ARUPS. Furthermore, it is pointed out by showing the result on C60 thin film that the multicentered photoemission dominates the photoelectron intensity of thin films of large organic molecules.
Application of XAFS to Catalytic Materials
Authors: Vlaic Gilberto , Fonda Emiliano , Psaro Rinaldo , Sordelli Laura
Published: March 2014

EXAFS spectroscopy is a powerful technique to determine local structure of a selected atomic species in a sample in any aggregation state and under any kind of atmosphere; for these reasons it is widely used in catalysis. A brief phenomenological explanation of the EXAFS signal and a short description of data collection and data analysis methods are presented. A recent example of its application to a heterogeneous catalytic system is illustrated.
Diffuse X-Ray Reflectivity Study of Interface Roughness in Mo/Si Multilayers
Authors: Lee D. R. , Park Y. J. , Jeong Y. H. , Lee K.-B. , Takenaka H.
Published: March 2014

Diffuse x-ray reflectivity intensities were measured to characterize interface morphologies of Mo/Si multilayers with and without interleaved carbon thin layers. Parameters related to the interface morphologies can be obtained by fitting the measured intensities within the distorted wave Born approximation in such a way that intermixing widths of graded interfaces, correlated interface roughness amplitudes and vertical correlation lengths are obtained. The interface parameters of Mo/Si and Mo/C/Si/C multilayers are compared for as-grown samples and annealed ones.
Temperature Dependence of Photoemission Spectra and X-Ray Diffraction of Ag Nanofilm
Authors: Tanaka Akinori , Takahashi Kazutoshi , Sasaki Hiroyuki , Gondo Wakako , Suzuki Shoji , Sato Shigeru , Tsuchiko Masashi , Takahashi Yasuhiko , Ohshima Ken'ichi
Published: March 2014

Temperature-dependent angle-resolved photoemission study for Ag nanofilm has been done in order to investigate in detail the quantized electronic structures. The angle-resolved photoemission spectra of Ag nanofilms exhibit the features derived from the quantized state of Ag s
p valence electron as well as Shockley-type surface state. The linewidth of the quantized state broaden and its intensity decreases with increasing a temperature. The linear temperature dependence of linewidth is explained as the phonon contribution to the photohole lifetime width. From an analysis of temperature-dependent intensity based on the standard Debye theory, it is found that the “effective” Debye temperature of Ag nanofilm is much smaller than bulk values. This suggests that the standard Debye-Waller factor does not quantitatively explain the present temperature dependence. Connected with these results, we have carried out a temperature-dependent x-ray diffraction study in order to investigate the thermal lattice properties. From these results, we discuss the electron-phonon interaction in Ag nanofilm.
Direct Observation of Charge and Orbital Ordering by Resonant X-ray Scattering
Authors: Murakami Y. , Hill J. P. , Gibbs D. , Blume M. , Kawada H. , Koyama I. , Tanaka M. , Kawata H. , Arima T. , Moritomo Y. , Tokura Y. , Hirota K. , Endoh Y.
Published: March 2014

Charge and orbital ordering states of manganites have been observed directly by using synchrotron x-ray diffraction techniques. The alternating pattern of Mn3+ and Mn4+ in charge ordering state was elucidated by the anomalous dispersion method. The orbital ordering at Mn3+ sites is presented based on resonant x-ray scattering near Mn K-absorption edge. The scattering mechanism has been developed by considering the splitting of the Mn 4p levels due to the orbital ordering. The coupling among the charge, spin and orbital degrees of freedom is discussed.
In-Plane Structural Analysis of CoCr Thin-Film Magnetic Media by Grazing Incidence X-Ray Diffraction
Authors: Ohsawa Michio , Hirose Takayuki , Teranish Hideaki , Ishiwata Osamu , Ataka Toyoji , Takahashi Nobuyuki , Komiya Satoshi , Iida Atsuo
Published: March 2014

CoCr thin-film magnetic media used in HDD (hard disk drive) usually show in-plane magnetic anisotropy. We have studied in-plane crystallographic structure of CoCr magnetic films on circumferentially textured and non-textured substrates by grazing incidence X-ray diffraction (GIXD) using synchrotron radiation. Textured substrate induces in-plane c-axis preferential alignment of hep-Co alloy crystallites to circumferential texture direction under the effect of texture roughness and sputtering deposition condition. Non-textured substrate produce in-plane isotropic structure. Sputtering process induce compressive strain in CoCr magnetic films on both textured and non-textured substrates. High energy ions in sputtering process are supposed to induce compressive strain through increasing non-strained interplanar spacings of hep-Co alloy crystallites.
Site-Selective Chemical State Analysis for Magnetite Structure Using Powder Spectro-Diffractometry
Authors: Xiao Yanan , Hayakawa Shinjiro , Gohshi Yohichi , Oshima Masaharu , Okudera Hiroki , Toraya Hideo , Ohsumi Kazumasa
Published: March 2014

In order to distinguish chemical states of two crystallographic sites in magnetite structure based on spectro-diffractometry, in-advance simulation and resonant X-ray powder diffraction experiments were performed for Co3O4 and Fe3O4 with incident X-ray energies near the absorption edges of Cobalt and Iron respectively. In this study, the chemical states of the two different crystallographic sites in the magnetite structure was clearly distinguished. The absorption edge of Cobalt atoms at A sites (8a) is lower than that at B sites (16d) while the absorption edge of Iron at A sites is higher than that at B sites. Those results are consistent with the result obtained from other methods.
First-Principles Electronic Structure Calculations of MnAs/GaAs(001) Magnetic Multilayers
Authors: Shirai Masafumi
Published: March 2014

First-principles electronic band-structure calculations are carried out for magnetic multilayers MnAs/GaAs(001) having the zinc-blende strucutre by using the full-potential linearized augmented-plane-wave (FLAPW) method in order to obtain an insight into their electronic and magnetic properties. In the ferromagnetic state so-called half-metallic behavior is found and the magnetic polarization antiparallel to the Mn moment is induced at the neighboring As sites. By comparing the calculated band-structure with the photoemission spectra observed for the III-V based diluted magnetic semiconductor (Ga,Mn)As, it is found that the many-body effect due to the electron-electron interaction between Mn 3d electrons is important in this system.
Short Range Order of Spin Moments in NdCo2 Studied by Magnetic EXAFS
Authors: Nakamura Tetsuya , Watanabe Yasuhiro , Mizumaki Masaichiro , Nanao Susumu
Published: March 2014

Magnetic Extended X-ray Absorption Fine Structure (MEXAFS) is a dichroic contribution to an x-ray absorption. The MEXAFS has been measured at Co K-edge in NdCo2 and at Fe K-edge in iron thin film. The Fourier analysis was carried out to obtain information about local magnetic structures in these systems. The positions and the sign of peaks in the imaginary part of Fourier transformed MEXAFS show a good agreement with those of conventional EXAFS for the iron thin film. In the case of NdCo2, the peak position for the nearest Nd shell was 2.89 Å in the imaginary part of Fourier transformed MEXAFS, which is the same sign with corresponding peak in EXAFS. The fact that the sign of the peak was positive for the spin moments of Nd, which was not the absorption element, can be explained that the spin polarization of photoelectrons outgoing from the absorbing atoms is antiparallel to that of an absorbing Co atom in NdCo2.
Deconvolution Analysis of Cu L-edge XANES for Quantification of Copper (II) Coordinations in Copper-aluminate Catalysts
Authors: Shimizu Ken-ichi , Maeshima Hajime , Yoshida Hisao , Satsuma Atsushi , Hattori Tadashi
Published: March 2014

Cu L3-edge XANES spectra of Cu-aluminate catalysts were recorded to clarify the local structure of Cu2+ cation in alumina matrix. XANES spectra of Cu-aluminate exhibited two different peaks, which were assigned, by comparison with those of reference compounds, to Cu2+ in tetrahedral and octahedral sites. To estimate the fraction of these Cu2+ species, a deconvolution analysis of XANES spectra was carried out. For CuAl2O4 (stoichiometric spinel), the ratio of the peak areas of the deconvoluted spectrum was in good agreement with the ratio of tetrahedral/octahedral previously determined by X-ray diffraction method. Thus, it is concluded that the fraction of Cu2+ ions on tetrahedral and octahedral sites can be estimated quantitatively from Cu L3-edge absorption spectra. This method was applied to a series of copper-aluminate catalysts, and it was shown that the fraction of Cu2+ on tetrahedral sites increased as Cu content increased.
XANES Studies of Mechanical Alloying Y2Co
Authors: Nakai Ikuo , Tokuyoshi Tetsuo
Published: March 2014

We report x-ray absorption near edge structure (XANES) and x-ray diffraction (XD) measurements for mechanically alloyed Y2Co. Mechanical alloying for 90 h produces a homogeneous amorphous Y2Co from mixture of crystalline Co and Y powders. During the milling till 90 h, the intensity of a pre-peak in the Co K edge XANES spectra shows a remarkable grow and its energy position shifts to the lower energy side. On the other hand, they are hardly changed after 90 h till 165 h. We discuss these behavior from the viewpoint of the Co-Co bonding.
Fermi Momentum of Conduction Electrons in Li Metal under High Pressure
Authors: Oomi Gendo , Honda Fuminori , Kagayama Tomoko , Itoh Fumitake , Sakurai Hiroshi , Kawata Hiroshi , Shimomura Osamu
Published: March 2014

Energy spectra of Compton-scattered X-ray from Li metal have been measured at high pressure using synchrotron radiation. Compton profile J(q) was obtained from the observed energy spectra. It was found that J(q) was affected by the application of pressure and the Fermi momentum q
F deduced from J(q) increased almost linearly with increasing pressure below 2 GPa. The pressure coefficient of q
F, q
F
-1∂q
F/∂P, was estimated to be 3.8×10-2 GPa-1, which is in good agreement with that obtained from the free electron model, 3.3×10-2 GPa-1.
Photoemission Spectra of LiNiO2 Catalyst for Oxidative Coupling of Methane
Authors: Miyazaki Takafumi , Aoki Masaru , Takayasu Osamu
Published: March 2014

Surface-lattice oxygen species of LiNiO2 with a layered structure were investigated for an oxidative reaction of methane. LiNiO2 resulted in formation of C2-hydrocarbons without by-products of carbon dioxide at an initial stage reaction which was an oxidative coupling process by surface lattice oxygen. For understanding of the origin of the catalytic activities, photoemission spectra of LixNi2-xO2 (0<x≦1) were measured. From comparison of the valence band structures, it was suggested that an anisotropic charge distribution and the layered structure contributed to the formation of active lattice oxygen and the catalytic performance of LiNiO2, respectively.
Soft X-ray Absorption Study of III-V Nitrides
Authors: Fukui Kazutoshi , Hirai Ryousuke , Yamamoto Akio , Naoe Syun-ichi , Tanaka Satoru
Published: March 2014

The soft X-ray absorption measurement around nitrogen K and aluminum K edge of the wurtzite AlN, GaN and their ternary compounds AlGaN have been performed. The incidence light angle dependence of the absorption spectra were clearly observed in all samples. A numerical component analysis is presented to separate the experimental K-absorption spectra into three partial spectra which correspond to in-plane, out-of-plane and angular independent components of the unoccupied p partial density of states.
Thermal Stability of Atom Configurations around Er Atoms Doped in InP by OMVPE
Authors: Ofuchi Hironori , Ito Takashi , Kawamoto Takeshi , Tabuchi Masao , Fujiwara Yasufumi , Takeda Yoshikazu
Published: March 2014

It has been found that there is a threshold growth temperature between 550°C and 580°C for the change of local structure around Er atoms in InP doped Er atoms grown by organometallic vapor phase epitaxy (OMVPE). To understand whether the structure change is induced at the growing surface or during the growth as an in situ annealing, the thermal stability of the local structures around the Er atoms doped in InP by the OMVPE at 530°C has been investigated by the extended X-ray absorption fine structure (EXAFS). The EXAFS analysis revealed that the local structure around the Er atoms, which existed substitutionally on In sites in the InP lattice, was stable against the post-growth annealing even for 1 h at 650°C. Therefore, it is concluded that the local structures are formed on the growth front, and not in the volume of InP by thermal annealing during or after the growth.
Growth Characteristics of Homoepitaxilal ZnTe Films Deposited by Synchrotron Radiation Using Metalorganic Sources
Authors: Nishio Mitsuhiro , Enoki Takeshi , Guo Qixin , Ogawa Hiroshi
Published: March 2014

ZnTe growth has been investigated, using (100) oriented ZnTe substrates, by the synchrotron-radiation-excited epitaxy at a very low pressure of ∼10-5 Torr. Diethylzinc (DEZn) and diethyltelluride (DETe) were used as source materials. The transport rate ratio of DETe to DEZn is an important factor for improving the crystallinity of the film. The epitaxial growth is attainable even at room temperature. The growth rate characteristics of epitaxial film as functions of substrate temperature and DETe transport rate suggest that the adsorption of source materials followed by the decomposition due to the surface excitation is important in the ZnTe growth.
Partial Structural Functions of Molten RbBr Estimated from the Anomalous X-ray Scattering Data
Authors: Saito Masatoshi , Kang Shinchul , Waseda Yoshio
Published: March 2014

The anomalous x-ray scattering (AXS) measurements for molten RbBr have been made using the energies close to the Rb K (15.202 keV) and Br K (13.470 keV) absorption edges for estimating three partial structural functions of Rb-Rb, Br-Br and Rb-Br pairs. The data processing for obtaining three partials includes the intensity data obtained at the energy of 17.0 keV, which is far from both edges and the help of the reverse Monte Carlo (RMC) simulation technique. The resultant partial structural functions of molten RbBr suggest that the configuration in the first Rb-Br coordination shell is found to be octahedral, as it is in the crystal.
Diffuse Scattering due to Anisotropic Phonon Softening in Ferroelastic Compounds NdNbO4 and LaNbO4
Authors: Kuroiwa Yoshihiro , Aoyagi Shinobu , Shobu Takahisa , Nozawa Koji , Tsunekawa Shin , Noda Yukio
Published: March 2014

X-ray diffraction studies have been performed in a ferroelastic compound NdNbO4 by synchrotron radiation at BL02B1 in SPring-8. Anisotropic diffuse scattering around Bragg reflections is observed prior to the phase transition. The diffuse streaks extend to the directions deviated from the crystal axes by 20° on the tetragonal basal plane of the high temperature phase. Diffuse streaks in LaNbO4 have been also observed by usual X-ray source, and the deviation angle of 23° is obtained. The origin of the diffuse scattering is considered for the most part the anisotropic phonon softening of the transverse acoustic mode at the Brillouin zone center. The deviation from the axes is caused by the low symmetry of the tetragonal phase with 4/m point group. The propagating directions of the soft phonon coincide with the orientations of the domain boundaries in the low temperature, monoclinic phase.
Study on Efficiency of Multi-Wire Tungsten Moderator for Slow Positron Source on SPring-8 Hard Synchrotron Radiation
Authors: Plokhoi Vladimir , Kandiev Yadgar , Samarin Sergey , Malyshkin Gennady , Baidin Grigory , Litvinenko Igor , Nikitin Valery
Published: March 2014

The paper provides results of numeric simulations of in-target positron production process, processes of moderation, thermalization, diffusion, and reemission of positrons in high efficiency multi-wire moderator made of tungsten monocrystalline wire with regular wire spacing. The paper looks into dynamics of slow positrons in the moderator's vacuum gaps taking into account of external fields. The possibility for using multi-wire moderator with non-regular structure - multi-layer “wire felt” moderator is discussed. According to maximal estimate the multi-wire moderators can reach very high efficiency of fast-slow positron transformation ∼10-2. Using such moderator the intensity of slow positron source on hard synchrotron radiation of SPring-8 can reach the level of ∼1011 e+/s.
SAXS/WAXS Investigations into the Self-Assembly of Zeolites
Authors: Komanschek Bernd U. , Moor Peter-Paul E. A. de , Beelen Theo P. M. , Santen Rutger A. van
Published: March 2014

Zeolites are materials with monodisperse pores and well-defined active sites, and are therefore especially suitable for tailor-made applications such as selective catalysts or adsorbents for specific systems. Knowledge of the fundamental processes during the preparation of zeolites is still extremely scarce. This is mainly due to experimental difficulties, which we have solved by performing simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) during the in-situ preparation of zeolites in a dedicated, rotating heating cell at Station 8.2 of the SRS at Daresbury Laboratory. Using in-situ SAXS/WAXS, for the first time the nanometer-scale precursors during a zeolite synthesis have been identified, and their formation and consumption have been monitored during the complete course of the crystallization process, covering extended length scales. Based on a broad range of zeolite crystallizations, an assembly mechanism has been proposed which is probably general for organic-mediated zeolite synthesis.
The Possibility of Phase-Contrast X-Ray Microtomography
Authors: Momose Atsushi , Hirano Keiichi
Published: March 2014

The spatial resolution attainable by phase-contrast X-ray computed tomography (CT) using an X-ray interferometer is discussed. Currently the spatial resolution is around 30 µm for the observation of biological soft tissues. The limiting factor of the spatial resolution is the thickness of a crystal wafer used in the X-ray interferometer as an X-ray half mirror. Based on this fact, a new design for an X-ray interferometer is proposed to improve the spatial resolution below 10 µm.
Photoelectron Microscopy and Its Applications to Semiconductor Science
Authors: Margaritondo Giorgio
Published: March 2014

Photoelectron spectromicroscopy, the combination of conventional photoelectron spectroscopy and high lateral resolution, is a novel technique that exploits the high brightness of the most recent synchrotron sources. We briefly review its main implementation modes and present some examples of applications, with particular emphasis on semiconductor interface research.
Photoluminescence Studies of Low Energy Hydrogen-Implanted AgGaTe2 Single Crystals
Authors: Bodnar Ivan V , Gremenok Valeri F , Martin Robert W , Yakushev Michael V , Pilkington Richard D , Hill Arthur E , Faunce Chester A , Berg Jaap A. Van den , Obraztsova Olga N , Tomlinson Robert D
Published: March 2014

Single crystals of AgGaTe2 (AGT) were implanted with 1015cm-2 of l00eV H+ at room temperature. The crystals were characterized, before and after implantation, using photoluminescence (PL) at temperatures from 8 to 300K. The PL spectra, taken at 8K before and after implantation, had two emission bands: a broad, high intensity band (A) centered at 0.85eV and a weaker band (E) at 1.35eV. Excitation intensity and temperature dependence analysis suggested an exciton-related recombination mechanism for band E. Band E was found to consist of two peaks at 1.338 (El) and 1.352eV (E2). Peak E2 was attributed to the ground state free exciton whilst peak El quenched rapidly with increasing temperature, suggesting it to originate from excitons bound to donors or acceptors. The band gap of AGT crystals was estimated to be 1.358eV at 8K, assuming an excitonic binding energy of 6 meV. The intensity of both A and E bands was found to increase considerably, following hydrogen implantation, without significant change in the shape of the PL spectra. The observed increase in the peak intensity following implantation is ascribed to passivation of non-radiative traps by hydrogen.
Thermal and crystallographic analysis of Cd(InxGa1-x)2S4 compounds
Authors: Asaka K. , Komatsu-Hidaka C. , Takizawa T. , Matsushita H.
Published: March 2014

We have investigated the phase transition and chemical reaction of Cd(InxGa1-x)2S4 (0 < x < 1) compounds by DTA along with powder X-ray diffraction, and constructed the phase diagram of the CdGa2S4 – CdIn2S4 pseudo binary system. The mixing of layer phase with either defect chalcopyrite or spinel is found to exist in a wide region between both ends of x. Layer single phase was found only in between x=0.58 and 0.68.
New Aspect of Dilute Magnetic Semiconductors
Authors: Takeyama Shojiro
Published: March 2014

Recent progress in physics of dilute magnetic semiconductors has been reviewed focusing rather on optical aspect of the spin related phenomena in II-VI dilute magnetic semiconductor low-dimensional structures. Various trials to develop new materials and low-dimensional structures in the field of dilute magnetic semiconductors are introduced.
Effect of Electron Irradiation on Properties of CuInSe2 Thin Films
Authors: Tanaka Tooru , Ohshima Takeshi , Itoh Hisayoshi , Okada Sohei , Wakahara Akihiro , Yoshida Akira
Published: March 2014

Effects of 2MeV electron irradiation on electrical properties of CuInSe2 thin films have been investigated, n-type CuInSe2 films in which carrier concentration were about 2×1017cm-3, were epitaxially grown on GaAs(001) substrate by RF diode sputtering. No significant change in the electrical properties was observed under the electron fluence less than 1016cm-2. As the electron fluence exceeded 1017cm-2, both carrier concentration and Hall mobility slightly decreased. The carrier removal rate was determined to be about 1cm-1, which is lower, compared to III-V compound materials.
X-Ray Diffraction and Photoreflectance Study of CuGaSe2 Epitaxial Layers
Authors: Tanaka Masahiro , Kodama Tomohiro , Nabetani Yoichi , Kato Takamasa , Matsumoto Takashi
Published: March 2014

The lattice constant a and c and transition energies E

A
, E

B
and E

C
of CuGaSe2 epitaxial layers of different thicknesses grown on GaAs(l00) substrates by iodide MBE are measured by X-ray diffraction and photoreflectance, respectively. E

A
increases, and E

B
and E

C
decrease as the c increases. The change in the transition energies are explained by the tetragonal distortion model using the parameters of the spin-orbit splitting energy Δ
s
o=0.232eV, the uniaxial deformation potential b=-1.551eV and the hydrostatic deformation potentials a

c
-a
ν=0.392eV.
MBE Growth and Characterization of Single Crystal and Bicrystal Permalloy (110) Thin Films
Authors: Yu Chin-Chung , Huang Jung-Chun-Andrew
Published: March 2014

Crystal structure and surface morphology of single crystal and bicrystal permalloy (110) thin films were investigated. The permalloy (110) single crystal can be stabilized on MgO (110) substrate. By using molybdenum as the seeding layer, the permalloy (110) bicrystal can be grown on MgO (001) substrate. The single crystal films show elongated grains along the [001] direction, while the bicrystal films possess isotropic grains.
Theoretical Predictions for Codoping Properties in Wide Band-gap Semiconductors
Authors: Katayama-Yoshida Hiroshi , Yamamoto Tetsuya
Published: March 2014

We review a new valence control method of codoping for the fabrication of low-resistivity p-type GaN, AlN, ZnSe, ZnO and CuInS2, which is proposed by ab initio electronic structure calculations. We propose the following codoping method (using both n- and p-type reactive dopants at the same time) to fabricate a low-resistivity p-type semiconductors; (1) GaN: [SiGa+2MgGa(or BeGa), H+2MgGa(or BeGa), and ON+2MgGa(or BeGa)], (2) AlN:[ON+2CN], (3) ZnO:[GaZn+2NO, AlZn+2NO and InZn+2NO, (4) ZnSe:[InZn+2NSe, ClSe+2NSe, 2LiZn+ClSe (or ISe), and TeSe+2NSe] and (5) CuInS2:[VCu+InCu+2P]. We compare our predictions of codoping with the recent sucessful codoping experiments for the fabrication of the low-resistivity p-type wide band-gap semiconductors.
Band Structure and Stability of Ternary Semiconductor Polytypes
Authors: Wei Su-Huai , Zhang Shengbai , Zunger Alex
Published: March 2014

We have developed a first-principles generalized one dimensional Ising model to study the band structures and stabilities of two types of ternary zinc-blende-based polytype series: type-a GaInP2 and type-b CuInSe2. We predict that the CuAu-like phase can coexist in nominally chalcopyrite CuInSe2. We also predict that type-II band alignment can exist between different ordered type-a GaInP2 polytypes.
Effect of Structural and Compositional Disorders on the Urbach's Energy in CuInSe2
Authors: Wasima Syed , Rincón Carlos , Hernández Elvis , Marín Giovanni , Bocaranda Pablo , Pérez Gerardo Sánchez
Published: March 2014

It is established that the phonon energy hνp involved in the formation of Urbach's tail in CuInSe2 depends linearly on the defect parameter related to its deviation from ideal stoichiometry. The empirical relation EU(T,N,P)=(KΘ/σo)[(l+P)/2+N{exp
(Θ/T)-l}-1] explains very well the temperature dependence of Urbach's energy EU. A linear correlation is found between hνp and both P and N. The extrapolated value of hνp at P = 0 agrees with the average energy of all the phonon modes and that at N = 0 with TF, the temperature at which structural transition from chalcopyrite to sphalerite phase occurs.
Optical Characterization of the Ordered Vacancy Compound CuGa3Se5
Authors: Rincón Carlos , Wasim Syed M. , Marín Giovanni , Hernández Elvis , Pérez Gerardo Sánchez , Galibert Jean
Published: March 2014

The lattice vibrational modes of the Ordered Vacancy Compound CuGa3Se5 have been obtained at 300 K by a combined analysis of infrared reflectivity and Raman spectra. Lines common to both spectra, observed at 48, 64, 105, 142, 187, 200, 218, 250, and 274 cm-1, were identified with E or B2 modes. The most intense peak at 166 cm-1 and those observed at 72 and 90 cm-1, which are only Raman active, are assigned to the AI and BI modes, respectively.
Interband Critical Points Near Absorption Edge of CaGa2S4
Authors: Mamedov Nazim , Iida Seishi , Toyota Hideyuki , Aoki-Matsumoto Tamao , Kato Ariyuki , Tagiev Bakhadur , Tagiev Oktai , Dzhabarov Rasim , Yamamoto Nobuyuki , Shishido Toetsu
Published: March 2014

The first spectroellipsometric investigation of the crystalline and amorphous CaGa2S4 was done in the photon energy region 1.5-5eV and temperature region 290–400K. Dielectric function spectra were obtained. It is shown that two interband critical points (CPs), E0 (4.40eV) and E1 (∼4.75eV), contribute into the direct interband optical transitions near the absorption edge of the polycrystalline CaGa2S4. In amorphous CaGa2S4 the “critical points” are rather smashed and lie at lower energies with as large a shift for E0-CP as 0.58 eV. The energy separation between E0 and E1 approaches ∼0.40eV. The temperature coefficient dE/dT for E0 was found to be -2.7×10-4eV/K. Preliminary study of a monocrystalline CaGa2S4 has confirmed that the E0-CP energy in polycrystalline CaGa2S4 is the gap energy (Eg) for direct transitions in this material, which are strongly polarized. The obtained data are discussed.
Temperature Dependence of the Optical Absorption of the Ternary Compound Ag2SnS3
Authors: Belandria Edgar , Fernández Braulio J.
Published: March 2014

We report in this work for the first time the temperature dependence of the optical absorption of the ternary compound Ag2SnS3. The optical absorption of this compound has been investigated in three samples from room temperature to 10K. We found that the fundamental absorption edge of Ag2SnS3 is consistent with a direct energy gap by allowed transitions of 1.43(2) eV at the lowest temperature measured and of 1.26(5) eV at room temperature. In two samples, the existence of a broad peak or band between 1.24 eV to 1.28 eV for temperatures below 190K is observed. The temperature dependencies of the energy gap show a behavior typical of that found for most semiconductors, that is, the energy gap decreases monotonically with temperature. The most important models are used to explain the energy gap shift and several parameters from these models are reported.
The Study of Fourier Transform Infrared Spectroscopy on 3-5 and 8-12 µm InAsSb/GaSb Superlattices
Authors: Juang Fuh-Shyang , Su Yan-Kuin , Yu Hsin Her , Liu Kou-Ju
Published: March 2014

The absorption energies for InAsSb/GaSb type II superlattices were characterized by Fourier Transform Infrared (FTIR) spectroscopy. The InAsSb/GaSb superlattice structures were sandwiched by n-InAs or p-GaSb inner and outer bulk layers. The effects of the thickness and doping concentration of inner and outer bulk layers on the interband and intersubband transitions have been studied in detail. If the modulated Fermi-level was located at an inappropriate position, the FTIR absorption peaks will shift and destroy. It was found that the intersubband transition hhl-lhl (first heavy hole to first light hole subband) disappeared when the inner bulk layer thickness was smaller than 0.6 µm or the outer bulk layer thinner than 0.15 µm. When the Fermi-level was modulated to lie between hhl and 1hl by changing the doping concentration of silane in bulk layers, the intensity of hhl-lh intersubband transition (λ=14 µm) increased to be much stronger than the Cl-hhl (first conduction subband to first heavy hole subband) transition (λ=3.8 µm). The superlattices sandwiched by p-type GaSb were also formed to study the Cl-hhl interband transitions. When the superlattices were sandwiched by p+-GaSb bulk layers, a stronger Cl-hhl absorption peak (λ=4 µm) was observed. But it disappeared when the superlattices were sandwiched by intrinsic GaSb bulk layers, because the Fermi-level of intrinsic GaSb rose above the Cl subband. So, 3-5 or 8-12 µm different wavelengths can be obtained by utilizing the different dopant-type and controlling the doping concentration of the bulk layers.
Piezoreflectance of Low Temperature Grown A10.3Ga0.7As/GaAs Multiple Quantum Wells
Authors: Lai C. Y. , Hsu T. M. , Wu Y. T.
Published: March 2014

In this study, we investigated intermixed multiple quantum wells by using the Piezoreflectance method. An energy blue shift due to interface disordering induced by vacancy enhanced Al-Ga interdiffusion was observed. A saturation in the energy shift was also observed in some specific samples. The behavior of this energy shift saturation can be well described by using a vacancy annihilation model. By comparing the calculated vacancy time constants, we predicted the onset of saturation and gave a quantitative explanation of the mechanism producing the energy shift saturation.