bluuebunny/crossref_metadata_2025 huggingface dataset:
New Scandium Platinum Silicides: ScPt2Si with ‘Inverse’ MgCuAl2 Structure and Sc5Pt9Si7, a Variant of the Zr2Fe12P7‐Type
Authors: Lorenz Peter , Jung Walter
Published: April 2009

Two new scandium platinum silicides, ScPt2Si (orthorhombic, Cmcm, a = 3.6653(6) Å, b = 9.831(1) Å, c = 6.967(1) Å, Z = 4) and Sc5Pt9Si7 (hexagonal, P, a = 9.9418(5) Å, c = 3.8832(2) Å, Z = 1) were prepared by reaction of the elements in an electric arc furnace and subsequent annealing. The crystal structures were solved and refined from single crystal diffraction data. ScPt2Si crystallizes with an ‘inverse’ MgCuAl2 structure whereas Sc5Pt9Si7 forms a variant of the Zr2Fe12P7 type.
Parathyroid Carcinoma: Etiology, Diagnosis, and Treatment
Authors: Okamoto Takahiro , Iihara Masatoshi , Obara Takao , Tsukada Toshihiko
Published: April 2009

Background

The goal of the present study was to make our medical practice evidence‐based for patients with parathyroid carcinoma.

Methods

We posed six clinical questions relevant to the management of parathyroid cancer. A comprehensive search and critical appraisal of the literature was then carried out.

Results

Most of the literature retrieved was retrospective in design and differed in the definition of carcinoma. The distinction between unequivocal and equivocal carcinoma (or atypical adenoma) was not always made for the study populations. None of the studies indicated reproducibility of outcome measures. Of the histopathological features described in the literature based on the description of Schantz and Castleman, capsular/vascular invasions and trabecular growth pattern were the most specific, and fibrous bands were the most sensitive. None of the patients with “atypical adenoma” developed recurrence, whereas 25% of those with “equivocal carcinoma” did. Mutations in HRPT2, the gene responsible for hereditary hyperparathyroidism with jaw‐tumor syndrome, were strongly associated with sporadic parathyroid carcinoma. Severe hypercalcemia and its related clinical symptoms, extremely high levels of parathyroid hormone, osteitis fibrosa cystica, a palpable neck mass, and a relatively large depth–width ratio on ultrasonography, are the important features of parathyroid carcinoma. Disease‐specific survival rates reported in the literature were varied, reflecting the differences in the definitions of carcinoma, study populations, and interventions.

Conclusions

To establish valid evidence for patient management in the future, a collaboration of endocrine specialists is essential to conduct well‐designed clinical studies for this rare disease.
Multilevel Perspectives on Community Intervention: An Example from an Indo‐US HIV Prevention Project in Mumbai, India
Authors: Schensul Stephen L. , Saggurti Niranjan , Singh Rajendra , Verma Ravi K. , Nastasi Bonnie K. , Mazumder Papiya Guha
Published: April 2009

This paper explores the meaning and applicability of multilevel interventions and the role of ethnography in identifying intervention opportunities and accounting for research design limitations. It utilizes as a case example the data and experiences from a 6‐year, NIMH‐funded, intervention to prevent HIV/STI among married men in urban poor communities in Mumbai, India. The experiences generated by this project illustrate the need for multilevel interventions to include: (1) ethnographically driven formative research to delineate appropriate levels, stakeholders and collaborators; (2) identification of ways to link interventions to the local culture and community context; (3) the development of a model of intervention that is sufficiently flexible to be consistently applied to different intervention levels using comparable culturally congruent concepts and approaches; (4) mechanisms to involve community residents, community based organizations and community‐based institutions; and (5) approaches to data collection that can evaluate the impact of the project on multiple intersecting levels.
Generalised twists, $\mathrm{\mathbf{SO}}(n)$, and the $p$-energy over a space of measure preserving maps
Authors: Shahrokhi-Dehkordi M.S. , Taheri A.
Published: April 2009

Let

\Omega \subset \mathbb{R}^{n}

be a bounded Lipschitz domain and consider the energy functional

\mathbb{F}_{p}[\mathbf{u},\Omega ]: = p^{−1}\int \limits_{\Omega }|\mathrm{∇}\mathbf{u}(\mathbf{x})|^{p}\:d\mathbf{x},

with

p\in ]1,\infty[

over the space of measure preserving maps

\mathcal{A}_{p}(\Omega ) = \left\{\mathbf{u}∊W^{1,p}\left(\Omega ,\mathbb{R}^{n}\right):\:\mathbf{u}|_{\partial \Omega } = \mathbf{x},\:\mathrm{\det }\mathrm{∇}\mathbf{u} = 1\text{a.e. in}\Omega \right\}.

In this paper we introduce a class of maps referred to as
generalised
twists and
examine
them in connection with the Euler–Lagrange equations associated with

\mathbb{F}_{p}

over

\mathcal{A}_{p}(\Omega )

. The main result is a surprising discrepancy between
even
and
odd
dimensions. Here we show that in even dimensions the latter system of equations admit
infinitely
many smooth solutions, modulo isometries, amongst such maps. In odd dimensions this number reduces to
one
. The result relies on a careful analysis of the
full
versus the
restricted
Euler–Lagrange equations where a key ingredient is a
necessary
and
sufficient
condition for an associated vector field to be a
gradient
.

Soit

\Omega \subset \mathbb{R}^{n}

un domaine de Lipschitz borné, on considère la fonctionnelle d'énergie

\mathbb{F}_{p}[\mathbf{u},\Omega ]: = p^{−1}\int \limits_{\Omega }|\mathrm{∇}\mathbf{u}(\mathbf{x})|^{p}\:d\mathbf{x},

p \in ]1,\infty[

sur l'espace de fonctions conservant la mesure

\mathcal{A}_{p}(\Omega ) = \left\{\mathbf{u}∊W^{1,p}\left(\Omega ,\mathbb{R}^{n}\right):\:\mathbf{u}|_{\partial \Omega } = \mathbf{x},\:\mathrm{\det }\mathrm{∇}\mathbf{u} = 1\text{a.a. dans}\Omega \right\}.

On introduit une classe de fonctions appellée des torsions généralisée qui est examinée dans le cadre des équations d'Euler–Lagrange associée à

\mathbb{F}_{p}

sur

\mathcal{A}_{p}(\Omega )

. Le résultat principal est une surprenante différence de proprieté selon le parité de le dimension

n

. On démontre que pour

n

pair, ces équations admettent une infinité de solutions régulières qui sont des isometries, alors qu'en dimension impaire la solution est unique. Le résultat repose sur une analyse minutieuse de la version complète des équations d'Euler–Lagrange où l'ingrédient clé est une condition nécessaire et suffisante pour qu'un champ vectoriel soit un gradient.
CDF it all: Consensus prediction of intrinsically disordered proteins based on various cumulative distribution functions
Authors: Xue Bin , Oldfield Christopher J. , Dunker A. Keith , Uversky Vladimir N.
Published: April 2009

Many biologically active proteins are intrinsically disordered. A reasonable understanding of the disorder status of these proteins may be beneficial for better understanding of their structures and functions. The disorder contents of disordered proteins vary dramatically, with two extremes being fully ordered and fully disordered proteins. Often, it is necessary to perform a binary classification and classify a whole protein as ordered or disordered. Here, an improved error estimation technique was applied to develop the cumulative distribution function (CDF) algorithms for several established disorder predictors. A consensus binary predictor, based on the artificial neural networks, NN‐CDF, was developed by using output of the individual CDFs. The consensus method outperforms the individual predictors by 4–5% in the averaged accuracy.
The Plasmodium HU homolog, which binds the plastid DNA sequence‐independent manner, is essential for the parasite's survival
Authors: Sasaki Narie , Hirai Makoto , Maeda Katsura , Yui Ryoko , Itoh Kie , Namiki Syoko , Morita Teppei , Hata Masayuki , Murakami-Murofushi Kimiko , Matsuoka Hiroyuki , Kita Kiyoshi , Sato Shigeharu
Published: April 2009

The nuclear genome of the human malaria parasite Plasmodium falciparum encodes a homolog of the bacterial HU protein (PfHU). In this study, we characterised PfHU's physiological function. PfHU, which is targeted exclusively to the parasite's plastid, bound its natural target – the plastid DNA – sequence‐independently and complemented lack of HU in Escherichia coli. The HU gene could not be knocked‐out from the genome of Plasmodium berghei, implying that HU is important for the parasite's survival. As the human cell lacks the HU homolog, PfHU is a potential target for drugs to control malaria.
Article Commentary: Dr Ross McIntire, otolaryngologist, and his care of President Franklin D. Roosevelt
Authors: Ruben Robert J.
Published: April 2009

The role that otolaryngologist Ross McIntire, MD, played in the care of Franklin Delano Roosevelt, 32nd President of the United States, was documented by reviewing primary source material pertaining to the relationship of McIntire and Roosevelt. This included material from various archives including the Franklin D. Roosevelt Presidential Library at Hyde Park, New York; United States National Archives; and numerous autobiographies and diaries. McIntire's belief in the value of confidentiality and to provide information only on a need‐to‐know basis is consistent with the strategy that he had devised earlier for protecting his patient's privacy. In the context of his time and his position, Dr McIntire served his patient and his country well by making appropriate medical and wise personal judgments. The career of Dr Ross T. McIntire, otolaryngologist and personal physician to the 32nd president of the United States, engenders a sense of honor to our profession.
Ionospheric zonal velocities at conjugate points over Brazil during the COPEX campaign: Experimental observations and theoretical validations
Authors: Sobral J. H. A. , Abdu M. A. , Pedersen T. R. , Castilho Vivian M. , Arruda Daniela C. S. , Muella M. T. A. H. , Batista I. S. , Mascarenhas M. , de Paula E. R. , Kintner P. M. , Kherani E. A. , Medeiros A. F. , Buriti R. A. , Takahashi H. , Schuch N. J. , Denardini C. M. , Zamlutti C. J. , Pimenta A. A. , de Souza J. R. , Bertoni F. C. P.
Published: April 2009

We analyze in detail the zonal velocities of large‐scale ionospheric plasma depletions over two conjugate stations inferred from OI 630 nm airglow all‐sky images obtained during the Conjugate Point Equatorial Experiment (COPEX) campaign carried out in Brazil between October and November 2002. The conjugate stations were Boa Vista (BV) (geogr. 2.8N, 60.7W, dip angle 22.0°N) and Campo Grande (CG) (geogr. 20.5S, 54.7W, dip angle 22.32°S). Over Campo Grande, the zonal velocities were measured also by a system of spaced GPS scintillation receivers. The airglow zonal velocities at the conjugate sites were seen to agree very closely, except for a slightly increased velocity over CG which we attribute to the presence of the geomagnetic anomaly. The results show a high degree of alignment of the bubbles along the geomagnetic field lines during the bubble development phase and as the bubbles travel eastward, thereby suggesting that the neutral zonal wind effect in the zonal plasma motion is an integrated effect along the flux tube. The zonal velocities obtained from the GPS technique were always larger than those calculated by the airglow technique, which permitted observation of zonal plasma velocity shear between the altitudes of the airglow emitting layer and of the GPS scintillation. Theoretical ambient plasma zonal velocities calculated using the formulations by Haerendel et al. (1992) and Eccles (1998) are compared with the experimental results. Our results also reveal some degree of dependence of the zonal velocities on the solar flux (F10.7) and magnetic (Kp) indices during the COPEX period.
Observations of northern latitude ground‐surface and surface‐air temperatures
Authors: Woodbury Allan D. , Bhuiyan A. K. M. H. , Hanesiak John , Akinremi O. O.
Published: April 2009

Note that the magnitude of temperature increases reconstructed from borehole records seems to contrast with some proxy based reconstructions of surface air temperature (SAT) that indicate lower amounts of warming over the same period. We present data suggesting that ground and snow cover may bias climate reconstructions based on BT in portions of the Canadian northwest. Eight sites west of the Canadian cordillera, were examined for long‐term SAT and GST changes. At seven of these sites precise borehole temperature profiles are used for the first time since the 1960s, thereby exploring the linkage between GST and SAT. New readings were made at four of these locations. All sites showed significant increasing SAT trends, in terms of annual mean minimum and maximum temperatures. Over a 54 year period, the minimum temperatures increased between 1.1°C and 1.5°C while the maximum increased between 0.8°C and 1.5°C, among those eight stations. Observations of GST at those sites, however, showed no obvious climate induced perturbations. Therefore, we believe that a trend in our area towards an increase in SAT temperatures only over the winter and spring is being masked by freeze thaw and latent energy effects. These results are important, particularly in northern locations where ground and snow cover may play an important role in creating a seasonal bias in GST reconstructions from borehole surveys.
The Modified Pharaoh Approach: Stingless bees mummify beetle parasites alive
Authors: Greco Mark , Hoffmann Dorothee , Dollin Anne , Duncan Michael , Spooner-Hart Robert , Neumann Peter
Published: April 2009

Social insect colonies usually live in nests, which are often invaded by parasitic species. Workers from these colonies use different defence strategies to combat invaders. Nevertheless, some parasitic species are able to bypass primary colony defences due to their morphology and behaviour. In particular, some beetle nest invaders cannot be killed or removed by workers of social bees, thus creating the need for alternative social defence strategies to ensure colony survival. Here we show, using Diagnostic Radioentomology, that stingless bee workers Trigona carbonaria, immediately mummify invading destructive nest parasites Aethina tumida alive, with a mixture of resin, wax and mud, thereby preventing severe damage to the colony. In sharp contrast to the responses of honeybee and bumblebee colonies, the rapid live mummification strategy of T. carbonaria effectively prevents beetle parasite advancements and removes their ability to reproduce. The convergent evolution of live mummification by stingless bees and social encapsulation by honeybees suggests that colonies of social bees generally rely on, secondary defence mechanisms when harmful nest intruders cannot be killed or ejected easily. This process is analogous to immune responses in animals.
Aging as a consequence of misrepair -- A novel theory of aging
Authors: Wang Jicun , Michelitsch Thomas , Wunderlin Arne , Mahadeva Ravi
Published: April 2009

It is now increasingly realized that the underlying mechanisms which govern aging is a complex interplay of genetic regulation and damage accumulation. Aging as a result of accumulation of ‘faults’ on cellular and molecular levels, has been proposed in the damage (fault)-accumulation theory by Kirkwood 2006. However, this theory fails to explain some aging phenotypes such as fibrosis and premature aging, since terms such as ‘damage’ and ‘fault’ are not specified. Therefore we introduce here a specification of the underlying mechanism of aging and arrive at a novel theory: aging of the body is a result of the accumulation of Misrepair of tissue. It emphasizes: a) it is Misrepair, not the original damage, that accumulates and leads to aging; and b) aging can occur at different levels, however aging of the body takes place at least on the tissue level, but not necessarily on cellular/molecular level. The novel concept of Misrepair introduced here unifies the understanding of the roles of environmental damage, repair, gene regulation, and multicellular structure in the aging process. The Misrepair-accumulation theory introduced in the present paper gives explanations for the aging phenotypes, premature aging, and the difference of longevity in different species, and is consistent with the point of view of physical theory of complex systems.
A condition of cooperation. Games on network
Authors: Konno Tomohiko
Published: April 2009

Natural selection is often regarded as a result of severe competition. Defect seems beneficial for a single individual in many cases.However, cooperation is observed in many levels of biological systems ranging from single cells to animals, including human society. We have yet known that in unstructured populations, evolution favors defectors over cooperators. On the other hand, there have been much interest on evolutionary games^1,2^ on structured population and on graphs^3-16^. Structures of biological systems and societies of animals can be taken as networks. They discover that network structures determine results of the games. Together with the recent interest of complex networks^17,18^, many researchers investigate real network structures. Recently even economists study firms' transactions structure^19^. Seminal work^11^ derives the condition of favoring cooperation for evolutionary games on networks, that is, benefit divided by cost, b/c, exceeds average degree, (k). Although this condition has been believed so far^20^, we find the condition is b/c (k~nm~) instead. k~nm~ is the mean nearest neighbor degree. Our condition enables us to compare how network structure enhances cooperation across different kinds of networks. Regular network favors most, scale free network least. On ideal scale free networks, cooperation is unfeasible. We could say that (k) is the degree of itself, while k~nm~ is that of others. One of the most interesting points in network theory is that results depend not only on itself but also on others. In evolutionary games on network, we find the same characteristic.
Calculating the electric field in real human head by transcranial magnetic stimulation with shield plate
Authors: Lu Mai , Ueno Shoogo
Published: April 2009

In this paper, we present a transcranial magnetic stimulation (TMS) system by incorporating a conductive shield plate. The magnetic field, induced current density, and electric field in a real human head were calculated by impedance method and the results were compared with TMS without shielding. Our results show that the field localization can be improved by introducing a conductive shield plate; the stimulation magnitude (depth) in the brain is reduced comparing with the TMS without shielding. The strong magnetic field near the TMS coil is difficult to be efficiently shielded by a thinner conductive shield plate.
Modeling of the self-propagating reactions of nickel and aluminum multilayered foils
Authors: Gunduz Ibrahim Emre , Fadenberger Konrad , Kokonou Maria , Rebholz Claus , Doumanidis Charalabos C. , Ando Teiichi
Published: April 2009

In this study, we performed simulations of self-propagating reactions of nanoscale nickel-aluminum multilayers using numerical methods. The model employs two-dimensional heat transfer equations coupled with heat generation terms from, (1) 1D parabolic growth of intermetallic phases Ni2Al3 and NiAl in the thickness direction and (2) phase transformations such as melting and peritectic reactions. The model uses temperature dependent physical and chemical data, such as interdiffusion coefficients, specific heat capacities, and enthalpy of reactions obtained from previous independent work. The equations are discretized using a lagged Crank–Nicolson method. The results show that initially, the reaction front velocity is determined by the rapid growth of Ni2Al3 and the front temperature is limited by the peritectic reaction at ∼1406 K. After the front completely traverses the foil and the temperature reaches the peritectic point, the reaction slows down and the temperature rises by the growth of NiAl which is the only stable phase at these temperatures. The reaction is completed when the initial constituents are consumed and the temperature reaches the melting point of NiAl. Subsequently, the foil cools and solidifies to the final phase dictated by the overall composition. The computational results show excellent fit to experimental velocity and temperature measurements.
Efficient multiphase green phosphor based on strontium thiogallate
Authors: Nazarov Mihail , Noh Do Young , Byeon Clare Chisu , Kim Hyojung
Published: April 2009

Efficient multiphase green phosphors based on strontium thiogallate were synthesized by solid state reaction at 900–1000 °C with carbon as a reduction atmosphere. The detailed x-ray diffraction analysis, energy dispersive spectroscopy, Raman spectroscopy, and photoluminescence were carried out in order to enlarge the understanding of the radiative processes in multiphase green phosphors based on strontium thiogallate. The crystal field splitting, Stokes shift, redshift, and centroidal shift were estimated, and the results are in good agreement with mathematical calculations. Our study confirms that the proposed multiphase green phosphor based on strontium thiogallate is a good candidate for solid state lighting and display devices with higher intensity and better chromaticity coordinates in comparison with the known commercial phosphors.
Ionic size effect deformation on MnO6 octahedrons in colossal magnetoresistance strain film
Authors: Wu C. P. , Chou H. , Yuan F. P.
Published: April 2009

Strain effect on La0.67Ca0.33MnO3 and La0.8Ba0.2MnO3 films is investigated by x-ray diffraction and x-ray absorption spectrums. Findings show that due to the different ionic sizes of doped Ca or Ba ions, the strain effect acts differently in the way it deforms. The interfacial strain effect produces opposite influences on the lattice symmetry, the average Mn–O bond lengths, the average oxygen disorders, the coupling symmetries inside and in the vicinity of the MnO6 octahedrons, as well as producing an opposing trend in metal-insulator and magnetic transition temperatures of the strained La0.67Ca0.33MnO3 and La0.8Ba0.2MnO3 films.
Effect of hollow-core photonic crystal fiber microstructure on transverse optical trapping
Authors: Domachuk P. , Wolchover N. , Cronin-Golomb M. , Omenetto F. G.
Published: April 2009

We investigate numerically and experimentally all-optical control of particles inside water filled, silica, hollow-core photonic crystal fiber (HC-PCF). We use an optical trapping beam focused outside the fiber, through its microstructure, perpendicular to the HC-PCF and independent of the guided fiber core mode. Finite difference time domain simulations model trapping through HC-PCF microstructure: trapping along the length of the HC-PCF is well maintained despite the significant effects due to scattering of the HC-PCF core structure. Trapped silica microspheres inside a HC-PCF is demonstrated experimentally as a reversible, reliable technique to control particles in fiber independent of the guided fiber mode. We observe a broadband attenuation of the HC-PCF transmission upon loading a silica microsphere into the fiber core.
Nucleation period, surface roughness, and oscillations in mass gain per cycle during W atomic layer deposition on Al2O3
Authors: Wind R. W. , Fabreguette F. H. , Sechrist Z. A. , George S. M.
Published: April 2009

Nucleation phenomena are critical for the fabrication of W/Al2O3 nanolaminates using atomic layer deposition (ALD) techniques. The nucleation and growth of W ALD on hydroxylated Al2O3 ALD surfaces and Al2O3 ALD on fluorinated W ALD surfaces was studied using in situ quartz crystal microbalance (QCM) and ex situ atomic force microscope (AFM) techniques. The QCM investigations revealed that Al2O3 ALD readily nucleated on the fluorinated W surface and displayed “substrate-enhanced growth.” In contrast, W ALD required 4–10 ALD cycles to nucleate on the hydroxylated Al2O3 surface and displayed “substrate-inhibited growth.” The W ALD nucleation period was shorter for higher Si2H6 and WF6 reactant exposures. The most rapid nucleation of W ALD on the Al2O3 surface occurred with much larger Si2H6 and WF6 exposures on the initial ALD cycle with the WF6 exposure prior to the Si2H6 exposure. By analyzing the individual Si2H6 and WF6 mass gain per cycle (MGPC), three main regions were identified in the W ALD nucleation and growth: initial deposition on Al2O3, W island growth and coalescence, and steady state growth. The root mean square (rms) roughness of the resulting W ALD film was dependent on the Si2H6 exposures and the number of ALD cycles required to nucleate the W ALD. A linear dependence was observed between the rms roughness and the number of ALD cycles required to reach one-half the maximum W MGPC. The W ALD also displayed very periodic oscillations in the W MGPC that were consistent with island nucleation and growth. Four local minima and three local maxima were observed in the W MGPC versus the number of ALD cycles. Comparing the results for W ALD on Al2O3 surfaces with recent simulations of ALD nucleation helps to establish the relationship between the nucleation period and surface roughness with island growth during nucleation.
Dose profile measurement using an imaging plate: Evaluation of filters using Monte Carlo simulation of 4 MV x-rays
Authors: Hashimoto Masatoshi , Tomita Tetsuya , Sawada Koichi , Fujibuchi Toshioh , Nishio Teiji , Nakagawa Keiichi
Published: April 2009

Computed radiography (CR) is gradually replacing film. The application of CR for two-dimensional profiles and off-axis ratio (OAR) measurement using an imaging plate (IP) in a CR system is currently under discussion. However, a well known problem for IPs in dosimetry is that they use high atomic number (Z) materials, such as Ba, which have an energy dependency in a photon interaction. Although there are some reports that it is possible to compensate for the energy dependency with metal filters, the appropriate thicknesses of these filters and where they should be located have not been investigated. The purpose of this study is to find the most suitable filter for use with an IP as a dosimetric tool. Monte Carlo simulation (Geant4 8.1) was used to determine the filter to minimize the measurement error in OAR measurements of 4 MV x-rays. In this simulation, the material and thickness of the filter and distance between the IP and the filter were varied to determine most suitable filter conditions that gave the best fit to the MC calculated OAR in water. With regard to changing the filter material, we found that using higher Z and higher density material increased the effectiveness of the filter. Also, increasing the distance between the filter and the IP reduced the effectiveness, whereas increasing the thickness of the filter increased the effectiveness. The result of this study showed that the most appropriate filter conditions consistent with the calculated OAR in water were the ones with the IP sandwiched between two 2 mm thick lead filters at a distance of 5 mm from the IP or the IP sandwiched directly between two 1 mm lead filters. Using these filters, we measured the OAR at 10 cm depth with 100 cm source-to-surface distance and surface 10×10 cm2 field size. The results of this measurement represented that it is possible to achieve measurements with less than within 2.0% and 2.0% in the field and with less than 1.1% and 0.6% out of the field by using 2 and 1 mm lead filters, respectively.
Implementation of a Morse potential to model hydroxyl behavior in phyllosilicates
Authors: Greathouse Jeffery A. , Durkin Justin S. , Larentzos James P. , Cygan Randall T.
Published: April 2009

The accurate molecular simulation of many hydrated chemical systems, including clay minerals and other phyllosilicates and their interfaces with aqueous solutions, requires improved classical force field potentials to better describe structure and vibrational behavior. Classical and ab initio molecular dynamics simulations of the bulk structure of pyrophyllite, talc, and Na-montmorillonite clay phases exhibit dissimilar behavior in the hydroxyl stretch region of power spectra derived from atomic trajectories. The classical simulations, using the CLAYFF force field, include either a standard harmonic potential or a new Morse potential parametrized for both dioctahedral and trioctahedral phases for the O–H bond stretch. Comparisons of classical results with experimental values and with ab initio molecular dynamics simulations indicate improvements in the simulation of hydroxyl orientation relative to the clay octahedral sheet and in the O–H bond stretch in the high frequency region of the power spectrum.
Oxygen and nitrogen impurities in microcrystalline silicon deposited under optimized conditions: Influence on material properties and solar cell performance
Authors: Kilper T. , Beyer W. , Bräuer G. , Bronger T. , Carius R. , van den Donker M. N. , Hrunski D. , Lambertz A. , Merdzhanova T. , Mück A. , Rech B. , Reetz W. , Schmitz R. , Zastrow U. , Gordijn A.
Published: April 2009

The influence of oxygen and nitrogen impurities on the performance of thin-film solar cells based on microcrystalline silicon (μc-Si:H) has been systematically investigated. Single μc-Si:H layers and complete μc-Si:H solar cells have been prepared with intentional contamination by admitting oxygen and/or nitrogen during the deposition process. The conversion efficiency of ∼1.2 μm thick μc-Si:H solar cells is deteriorated if the oxygen content in absorber layers exceeds the range from 1.2×1019 to 2×1019 cm−3; in the case of nitrogen contamination the critical impurity level is lower ([N]critical=6×1018–8×1018 cm−3). It was revealed that both oxygen and nitrogen impurities thereby modify structural and electrical properties of μc-Si:H films. It was observed that the both contaminant types act as donors. Efficiency losses due to oxygen or nitrogen impurities are attributed to fill factor decreases and to a reduced external quantum efficiency at wavelengths of >500 nm. In the case of an air leak during the μc-Si:H deposition process, the cell performance drops at an air leak fraction from 140 to 200 ppm compared to the total gas flow during i-layer deposition. It is demonstrated that oxygen and nitrogen impurities close to the p/i-interface have a stronger effect on the cell performance compared to impurities close to the n/i-interface. Moreover, thick μc-Si:H solar cells are found to be more impurity-sensitive than thinner cells.
Spin splitting of upper electron subbands in a SiO2/Si(100)/SiO2 quantum well with in-plane magnetic field
Authors: Niida Y. , Takashina K. , Fujiwara A. , Fujisawa T. , Hirayama Y.
Published: April 2009

We observe a lifting of the twofold spin degeneracy of conduction-band electrons in an upper-valley subband with in-plane magnetic field in a SiO2/Si(100)/SiO2 quantum well, which is manifest in a splitting of a feature in the conductivity accompanying the occupation of the upper-valley subband. The splitting increases in proportion to the in-plane magnetic field, allowing the product of the effective g-factor and effective mass g∗m∗ to be obtained. The value remains constant over wide ranges of valley splitting, total electron density, and potential bias.
Fast simulation of polymer chains
Authors: Hartmann Carsten , Schütte Christof , Kalibaeva Galina , Di Pierro Michele , Ciccotti Giovanni
Published: April 2009

We propose an algorithm for the fast and efficient simulation of polymers represented by chains of hard spheres. The particles are linked by holonomic bond constraints. While the motion of the polymers is free (i.e., no collisions occur) the equations of motion can be easily integrated using a collocation-based partitioned Gauss–Runge–Kutta method. The method is reversible, symplectic, and preserves energy. Moreover the numerical scheme allows the integration using much longer time steps than any explicit integrator such as the popular Verlet method. If polymers collide the point of impact can be determined to arbitrary precision by simple nested intervals. Once the collision point is known the impulsive contribution can be computed analytically. We illustrate our approach by means of a suitable numerical example.
Plasma pressure effect on the multiple low-shear toroidal Alfvén eigenmodes
Authors: Marchenko V. S.
Published: April 2009

It is shown that there is a critical thermal pressure gradient at which the polarizations of the multiple low-shear toroidal Alfvén eigenmodes (TAEs) are reversed. Below the critical value, the TAE spectrum consists of two bands of the even (odd) modes located in the upper (lower) part of the toroidal Alfvén gap, which is consistent with the zero-pressure limit [J. Candy, B. N. Breizman, J. W. Van Dam, and T. Ozeki, Phys. Lett. A 215, 299 (1996)]. Above the critical pressure, the odd (even) TAEs appear in the upper (lower) part of the gap.
Electrons and holes in a 40 nm thick silicon slab at cryogenic temperatures
Authors: Takashina K. , Nishiguchi K. , Ono Y. , Fujiwara A. , Fujisawa T. , Hirayama Y. , Muraki K.
Published: April 2009

We demonstrate low temperature operation of an electron-hole bilayer device based on a 40 nm thick layer of silicon in which electrons and holes can be simultaneously induced and contacted independently. The device allows the application of bias between the electrons and holes enhancing controllability over density and confining potential. We confirm that drag measurements are possible with the structure.
Optical and electronic properties of one-dimensional Ca3Co2O6 thin films: Influence of the oxygen pressure
Authors: Moubah R. , Colis S. , Schmerber G. , Petersen J. , Dinia A.
Published: April 2009

Thin films of Ca3Co2O6 were fabricated on c-cut sapphire substrates by pulsed laser deposition. The films are polycrystalline and can be grown in a large interval of oxygen pressure with significant influence on the film texture. X-ray photoelectron spectroscopy analyses indicated that only Co3+ ions are present in our samples for both octahedral and trigonal prismatic sites. The band gap measured by ultraviolet-visible light absorption experiments was found about 1.35 eV and slightly larger when the oxygen partial pressure during the deposition is increased from 10−3 to 7×10−2 mbar. Temperature dependent transport measurements showed a semiconducting behavior of the films and the associated band gap was found similar to the one evaluated by optical measurements and reported by theoretical studies.
Bacterial inactivation using atmospheric pressure single pin electrode microplasma jet with a ground ring
Authors: Kim Sun Ja , Chung T. H. , Bae S. H. , Leem S. H.
Published: April 2009

Bacterial inactivation experiment was performed using atmospheric pressure microplasma jets driven by radio-frequency wave of 13.56 MHz and by low frequency wave of several kilohertz. With addition of a ground ring electrode, the discharge current, the optical emission intensities from reactive radicals, and the sterilization efficiency were enhanced significantly. When oxygen gas was added to helium at the flow rate of 5 SCCM, the sterilization efficiency was enhanced. From the survival curve of Escherichia coli, the primary role in the inactivation was played by reactive species with minor aid from heat, UV photons, charged particles, and electric fields.
Leakage current by Frenkel–Poole emission in Ni/Au Schottky contacts on Al0.83In0.17N/AlN/GaN heterostructures
Authors: Arslan Engin , Bütün Serkan , Ozbay Ekmel
Published: April 2009

In order to determine the reverse-bias leakage current mechanisms in Schottky diodes on Al0.83In0.17N/AlN/GaN heterostructures, the temperature-dependent current-voltage measurements were performed in the temperature range of 250–375 K. In this temperature range, the leakage current was found to be in agreement with the predicted characteristics, which is based on the Frenkel–Poole emission model. The analysis of the reverse current-voltage characteristics dictates that the main process in leakage current flow is the emission of electrons from a trapped state near the metal-semiconductor interface into a continuum of states which associated with each conductive dislocation.
Distribution control of 1.55μm InAs quantum dots down to small numbers on truncated InP pyramids grown by selective area metal organic vapor phase epitaxy
Authors: Wang Hao , Yuan Jiayue , Rieger Torsten , van Veldhoven Peter J. , Nouwens Peter , Eijkemans Tom J. , de Vries Tjibbe , Smalbrugge Barry , Geluk Erik Jan , Nötzel Richard
Published: April 2009

Distribution control of InAs quantum dots (QDs) on truncated InP pyramids by selective area growth is reported. The top surface of the pyramids is composed of a (100) facet and high-index facets aside. The arrangement of the facets is governed by the shape of the pyramid base and top surface area. The QDs preferentially nucleate on the high-index facets determining position and distribution. The QD number is reduced with shrinking top surface size. Positioning of four, three, two, and single QDs is realized depending on the top surface’s shape and size. Emission from single QDs is observed at 1.55μm.
Light-extraction enhancement in GaN-based light-emitting diodes using grade-refractive-index amorphous titanium oxide films with porous structures
Authors: Liu Day-Shan , Lin Tan-Wei , Huang Bing-Wen , Juang Fuh-Shyang , Lei Po-Hsun , Hu Chen-Ze
Published: April 2009

Amorphous titanium oxide (a-TiOx:OH) films prepared by plasma-enhanced chemical-vapor deposition at 200 and 25 °C are in turn deposited onto the GaN-based light-emitting diode (LED) to enhance the associated light extraction efficiency. The refractive index, porosity, and photocatalytic effect of the deposited films are correlated strongly with the deposition temperatures. The efficiency is enhanced by a factor of ∼1.31 over that of the uncoated LEDs and exhibited an excellent photocatalytic property after an external UV light irradiation. The increase in the light extraction is related to the reduction in the Fresnel transmission loss and the enhancement of the light scattering into the escape cone by using the graded-refractive-index a-TiOx:OH film with porous structures.
Electronic and structural properties of molybdenum thin films as determined by real-time spectroscopic ellipsometry
Authors: Walker J. D. , Khatri H. , Ranjan V. , Li Jian , Collins R. W. , Marsillac S.
Published: April 2009

Real-time spectroscopic ellipsometry (RTSE) is shown to be an effective contactless probe of radio frequency magnetron sputtered molybdenum thin films used as the back electrode in chalcopyrite [Cu(In,Ga)Se2] solar cells. A series of Mo thin films was sputtered onto soda-lime glass substrates at Ar pressures ranging from 4 to 20 mTorr. RTSE measurements reveal how Ar pressure affects the nucleation and growth mechanisms that influence the films’ ultimate grain structure and properties. Determinations of the free electron relaxation times at optical frequencies reveal that higher pressures lead to a smaller average grain size and increased void volume fraction.
Intensive Movement in Wireless Digital Signal Processing: From Calculation to Envelopment
Authors: Mackenzie Adrian
Published: April 2009

The paper broadly concerns the set of algorithmic processes associated with wireless networks known as ‘digital signal processing’ (DSP). By virtue of its labyrinthine technical complexity, wireless DSP is a worst-case scenario for social science research into software and code. This specific type of real-time computation, however, is vital to the proliferation of wireless services, devices, and products, and hence to the recomposing–shape-shifting urban spaces they inhabit. The paper addresses the problem of accounting for the convoluted nature of the DSP associated with wireless communication. I argue that we can understand what is at stake in DSP only by changing focus away from abstract understandings of code, calculation, and software to specific design processes that fold new configurations of space and movement into wireless network signals. I argue that, at the moment, the ongoing dynamism of wireless networks could be just as important to understand as the altered modes of proximity, intimacy, colocation, and distance associated with wireless technologies such as mobile phones, wireless networks, game controllers, and remote controls. To this end, I frame wireless DSP in terms of intensive movement produced by a centre of envelopment. Centres of envelopment generate extensive changes, but they also change the nature of change itself.
Worlds of Affect: Virtual Geographies of Video Games
Authors: Shaw Ian Graham Ronald , Warf Barney
Published: April 2009

Video games are virtual worlds, each with its own, distinctive spatiality. This paper suggests that there are two interrelated conceptual dimensions to the study of video games. First, there are the representational issues concerning the worlds depicted in video games, such as those portraying hypersexualized women or Orientalist depictions of Arab enemies. We suggest, however, that these cultural, sexual, and political representations are not the only forces doing work on the player within the virtual world of a video game. This paper complements a purely representational approach by considering ‘affect’ as a precognitive force which disrupts and delights the player with reactions ranging from fear to joy. We argue that, as the spatiality of video games has evolved from simple two-dimensional to complex three-dimensional worlds; the importance of an affective experience to the player has become paramount. Exploiting and manipulating the player's sensory experience is now the central strategy for many game designers. The paper is divided in two interrelated sections: the first tackles representational issues from culture to violence, while the second section contributes to our understanding of video games as ‘worlds of affect’.
Using a bench-top rotor spinning system to measure variation between individual fleeces for predicting yarn and fabric characteristics
Authors: Schlink A. C. , Greeff J. C. , Ehni J. , Denning R.
Published: April 2009

There is limited information available on variation among individual fleeces in yarn and fabric performance. In this study, 45 mid-side fleece samples (~30 g clean wool) with a wide range in fibre diameter, fibre diameter variation, curvature and felt ball diameter were used to determine whether these fleece characteristics significantly affected yarn and fabric shrinkage, and fabric pilling. Mid-side wool samples ranged from 13.5 to 24.0 µm mean fibre diameter, 46–108°/mm curvature and 22.2–30.2 mm felt ball diameter. Yarn felt shrinkage was significantly (P < 0.001) correlated with fibre diameter (r = –0.52), and total yarn shrinkage (r = 0.99). Fabric felt shrinkage was significantly (P < 0.01) correlated with curvature (r = –0.62), standard deviation of curvature (r = –0.60), and felt ball diameter (r = –0.51). Fibre diameter and curvature accounted for 31% of the variation in yarn felt shrinkage. Standard deviation of curvature and felt ball diameter accounted for 33% of the variation in fabric shrinkage. Fabric pilling was significantly (P < 0.001) correlated with fibre diameter (r = 0.65), with fibre diameter and standard deviation of curvature accounting for 48% of the variation in fabric pilling. These results show that it is possible to predict yarn and fabric shrinkage and fabric pilling outcomes of individual fleeces using raw wool parameters. This study indicates that there is considerable phenotypic variation between individual Merino fleeces in the properties of yarn and fabric produced, suggesting that it is possible to quantitatively select individual sheep directly for yarn and fabric outcomes to improve the consumer performance of woollen fabrics.
Pendular proteins in gases and new avenues for characterization of macromolecules by ion mobility spectrometry
Authors: Shvartsburg Alexandre A. , Noskov Sergei Y. , Purves Randy W. , Smith Richard D.
Published: April 2009

Polar molecules align in electric fields when the dipole energy (proportional to field intensity
E
× dipole moment
p
) exceeds the thermal rotational energy. Small molecules have low
p
and align only at inordinately high
E
or upon extreme cooling. Many biomacromolecules and ions are strong permanent dipoles that align at
E
achievable in gases and room temperature. The collision cross-sections of aligned ions with gas molecules generally differ from orientationally averaged quantities, affecting ion mobilities measured in ion mobility spectrometry (IMS). Field asymmetric waveform IMS (FAIMS) separates ions by the difference between mobilities at high and low
E
and hence can resolve and identify macroion conformers based on the mobility difference between pendular and free rotor states. The exceptional sensitivity of that difference to ion geometry and charge distribution holds the potential for a powerful method for separation and characterization of macromolecular species. Theory predicts that the pendular alignment of ions in gases at any
E
requires a minimum
p
that depends on the ion mobility, gas pressure, and temperature. At ambient conditions used in current FAIMS systems,
p
for realistic ions must exceed ≈300–400 Debye. The dipole moments of proteins statistically increase with increasing mass, and such values are typical above ≈30 kDa. As expected for the dipole-aligned regime, FAIMS analyses of protein ions and complexes of ≈30–130 kDa show an order-of-magnitude expansion of separation space compared with smaller proteins and other ions.
Netrin-1 acts as a survival factor for aggressive neuroblastoma
Authors: Delloye-Bourgeois Céline , Fitamant Julien , Paradisi Andrea , Cappellen David , Douc-Rasy Setha , Raquin Marie-Anne , Stupack Dwayne , Nakagawara Akira , Rousseau Raphaël , Combaret Valérie , Puisieux Alain , Valteau-Couanet Dominique , Bénard Jean , Bernet Agnès , Mehlen Patrick
Published: April 2009

Neuroblastoma (NB), the most frequent solid tumor of early childhood, is diagnosed as a disseminated disease in >60% of cases, and several lines of evidence support the resistance to apoptosis as a prerequisite for NB progression. We show that autocrine production of netrin-1, a multifunctional laminin-related molecule, conveys a selective advantage in tumor growth and dissemination in aggressive NB, as it blocks the proapoptotic activity of the UNC5H netrin-1 dependence receptors. We show that such netrin-1 up-regulation is a potential marker for poor prognosis in stage 4S and, more generally, in NB stage 4 diagnosed infants. Moreover, we propose that interference with the netrin-1 autocrine loop in malignant neuroblasts could represent an alternative therapeutic strategy, as disruption of this loop triggers in vitro NB cell death and inhibits NB metastasis in avian and mouse models.
Character sheaves on disconnected groups, X
Authors: Lusztig G.
Published: April 2009

We classify the unipotent character sheaves on a fixed connected component of a reductive algebraic group under a mild condition on the characteristic of the ground field.