bluuebunny/crossref_metadata_2025 huggingface dataset:
From Wiki to Wow! Student Voice and Agency in an American Literature Class
Authors: Mantegna Sarah Tumblin
Published: May 2012

In this article the author tells the story of her experiences with a high school U.S. literature class composed of English language learners (ELLs). The students were from a variety of nations and cultures, spoke several different languages, and had a wide range of English proficiency levels. During their time together, the author and students went beyond the mandated literature curriculum in several ways. They expanded their interaction beyond the classroom through the use of technology in the form of a wiki, or collaborative website, and digital video. They developed close and lasting friendships that offered support and encouragement. Further, they co‐constructed a classroom environment that allowed them to explore and expand individual identities and to speak out on behalf ofELLs. The students' own words are included to help tell the collective story and give the reader a better sense of the class's achievements.
Human DNA damage by the synergistic action of 4‐aminobiphenyl and nitric oxide: An immunochemical study
Authors: Moinuddin  , Dixit Kiran , Ahmad Saheem , Shahab Uzma , Habib Safia , Naim Mohammad , Alam Khursheed , Ali Asif
Published: May 2012

4‐Aminobiphenyl (4‐ABP), an aromatic amine is a major environmental carcinogen found mainly in cigarette smoke. It has been vastly implicated in mutagenesis and cancer development. In this study, commercially available human placental DNA was exposed to 4‐ABP (1.3 mM) in presence of sodium nitroprusside (SNP; 8 mM) at 37°C for 3 h. The 4‐ABP + SNP‐mediated structural changes in human DNA were studied by ultraviolet, circular dichroism and fluorescence spectroscopy, thermal melting profile, agarose gel electrophoresis, and nuclease S1 digestibility assay. Spectroscopical analysis and melting temperature studies suggest structural perturbations in the DNA as a result of modification. This might be due to generation of single‐stranded regions and destabilization of hydrogen bonds. Modification was also visualized in agarose gel electrophoresis. Furthermore, nuclease S1 digestibility confirmed the generation of single strand breaks. Rabbits challenged with 4‐ABP‐SNP‐modified human DNA‐induced high‐titer immunogen‐specific antibodies, which showed Cross‐reaction with modified/unmodified DNA bases and ss‐DNA in competitive inhibition assay. The immunogen specificity of induced antibodies against 4‐ABP‐SNP‐modified human DNA was further confirmed in gel retardation assay. It may be concluded that induction of anti‐modified DNA antibodies could be due to perturbation in the DNA structure and its subsequent recognition by immunoregulatory cells as a foreign molecule. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 568–576, 2014.
Treatment of Common Bile Duct Stones in Sweden 1989–2006: An Observational Nationwide Study of a Paradigm Shift
Authors: Sandzén Birger , Haapamäki Markku M. , Nilsson Erik , Stenlund Hans C. , Öman Mikael
Published: May 2012

Background

The preferred strategies for treatment of common bile duct stones have changed from choledochotomy with cholecystectomy to sphincterotomy with or without cholecystectomy. The aim of the present study was to compare the effectiveness of these treatment strategies on a nationwide level in Sweden.

Methods

All patients with hospital care for benign biliary diagnoses 1988–2006 were identified in Swedish registers. Patients with common bile duct stones and a first admission with choledochotomy and or endoscopic sphincterotomy from 1989 through 2006 comprised the study group. These patients were analyzed with respect to readmission for biliary diagnoses and acute pancreatitis.

Results

Incidence of open and laparoscopic choledochotomy decreased from 19.4 to 5.2, whereas endoscopic sphincterotomy increased from 5.1 to 26.1 per 100,000 inhabitants per year, respectively. Among patients treated for common bile duct stones (n = 26,815), 60.0 % underwent cholecystectomy during the first hospital admission in 1989–1994, compared to 30.1 % in 2001–2006. The treatment strategy that included endoscopic sphincterotomy was associated with more readmissions for biliary diagnoses and increased risk for acute pancreatitis than the treatment strategy with choledochotomy. However, patients treated with endoscopic sphincterotomy and concurrent cholecystectomy at the index admission had the lowest risk of readmission.

Conclusions

Cholecystectomy has been increasingly separated from treatment of bile duct stones, and endoscopic sphincterotomy has superseded choledochotomy as a first alternative for bile duct clearance in Sweden. In patients fit for surgery, clearance of the common bile duct can be combined with cholecystectomy, as it probably reduces the need for biliary related readmissions.
Nummulites solitarius – Nummulites burdigalensis Lineage in Kutch with Remarks on the Age of Naredi Formation
Authors: Saraswati Pratul Kumar , Sarkar Urbashi , Banerjee Santanu
Published: May 2012

Three successive subspecies of Nummulites burdigalensis evolved from N. solitarius. These include N. burdigalensis keupperi, N. burdigalensis burdigalensis and N. burdigalensis cantabricus. The evolving lineage is traced in a borehole drilled through the Naredi Formation of Kutch. The associated taxa include N. solitarius and N. fraasi in the lower part and Assilina laxispira and A. spinosa in the upper part of the formation. The better stratigraphic resolution achieved by subspecies identification and the lately redefined Ilerdien Stage in the background of Early Eocene carbon isotope excursion marker, lead to constrain the age of Naredi Formation as Early Eocene, ranging from shallow-benthic zones SBZ6 to SBZ11.
Field and Petrographic Aspects of the Iron Ore Mineralizations of Gandhamardan Hill, Keonjhor, Orissa and their Genetic Significance
Authors: Bhattacharya H. N. , Ghosh Kaushik K.
Published: May 2012

Banded iron formations of the Iron Ore Group (Archean greenstone belts) of Jharkhand-Orissa region, India host a good number of large iron ore deposits (Fe wt %> 62). Iron ore mineralization of Gandhamardan hill is one of them where iron ores occur in two stratigraphic horizons. One is strictly confined within banded iron formation (stratabound mineralization) with irregular geometry, and show fracture filling and replacement vein-type mineralization along the fringes of hard massive ores of the core. This type of mineralization is exposed along the western slope of the hill. Hard massive and laminated ores dominate this mineralization. The other type occurs as low dipping sheet like body above banded iron formation and covered by laterites forming the top of the hill. Flaky ores dominate this mineralization with formation of hard goethitic crust near the top. Both the mineralizations contain mineralized banded iron formation core-stones surrounded by hard massive or flaky iron ores. Hard massive ores are entirely represented by martite-microplaty hematite mineralogy. Hard laminated ores contain microplaty hematite and few martite grains representing early magnetites of the banded iron formation. Flaky ores are high porosity ores produced by leaching of silica, martite and microplaty hematite. Hard goethitic ores are developed due to replacement of martite and microplaty hematite or precipitation of goethite in the pore spaces.

Formation of iron ores within banded iron formation horizon, hydrothermal brecciation and replacement of jaspery blocks by iron ores, presence of mineralized banded iron formation core-stones within the massive hard ores and martite-microplaty hematite rich mineralogy of the ores strongly advocate in favour of hydrothermal origin for the Gandhamardan iron ore mineralization. Iron bearing reducing and alkaline basinal or deeply circulated meteoric water may be held responsible for the hydrothermal mineralization. The ore fluid became oxidizing with cooling. Such hydrothermal ores recorded further leaching and goethitization under supergene environment.
GIS based Morphometric Analysis of Yamuna Drainage Network in parts of Fatehabad Area of Agra District, Uttar Pradesh
Authors: Ansari Ziaur Rehman , Rao L. A. K. , Yusuf Alia
Published: May 2012

Remote Sensing and GIS techniques have been proved to be efficient tools in the delineation, updating and morphometric analysis of drainage basin. The present study incorporates a morphometric analysis of three sub-basins of Fatehabad area of Agra district using remote sensing and GIS techniques. The morphometric parameters of the sub-basins are classified under linear, areal and relief aspects. The drainage pattern exhibited by the main river Yamuna and its tributaries shows a dendritic pattern indicating homogenously underlain material while the mean bifurcation ratio values suggest that the geological structures are not disturbing the drainage pattern. The form factor value of sub-basins suggests that the main basin is more or less elongated. Circularity ratio values of the three sub-basins fall within range of elongated basin and low discharge. The area has low density indicating that the region has high permeable sub-soil material and dense vegetation. The values of drainage texture, drainage density and infiltration number indicate that sub-basin-III has the highest infiltration rate and low runoff, hence contributing most to the underground water resources. This study also indicates porous and permeable sub-soil condition in sub-basin-III. The values of sub-basin-I indicate low permeable subsoil material owning to high infiltration number value, hence low infiltration and high runoff.
3D Visualizing of Volumetric Surface Movement at Karstic Limestone Area
Authors: Alkouri Omar , Omar Husaini , Shariah Mohammed Abu , Rodzi Ahmad , Mansor Shattri , Yusof Zainuddin Md.
Published: May 2012

Limestone bedrock topography has complex phenomena and highly relief subsurface topography due to the presence of karstic features. Geotechnical and environmental problems arise whenever foundations are established on the surface of the limestone bedrock or within the overburden soils. Geographical information system (GIS) and remote sensing are emerging as powerful techniques widely applicable in natural resources management to detect land use changes and devise strategies based on these changes. The study focuses on using aerial photography for the detection of changes and effects of mining on geomorphology, especially the use of sequential images that allows to detect changes taken place from time to time, by using. Volumetric Surface Movement Spatiotemporal Data Model (VSMSDM) application has been employed to create karst terrain surface movements and visualized 3D information in the Virtual Geographical Information Systems (VGIS). VSMSDM application was implemented by developing prototype of visualization system using with integrated time in the TIN structure. The data have been collected from aerial photography in 1981 and 2004, and the results displayed that the proposed data model is able to view the changing in karst topography to detect significant landscapes and landforms changes.
Electronic properties of embedded MnAs nano-clusters in a GaAs matrix and (Ga,Mn)As films: Evidence of distinct metallic character
Authors: Rache Salles B. , Girard J. C. , David C. , Offi F. , Borgatti F. , Eddrief M. , Etgens V. H. , Simonelli L. , Marangolo M. , Panaccione G.
Published: May 2012

We investigated the electronic properties of MnAs nano-clusters embedded in GaAs by bulk sensitive photoemission spectroscopy and cross-sectional scanning tunneling microscopy/spectroscopy. We report experimental evidences that the clusters are metallic MnAs, in close resemblance to MnAs thin films, and display a sharp interface with the surrounding GaAs. These results are supported by the comparison with GaMnAs and MnAs film in the same experimental condition. Furthermore, we observe a clear Coulomb blockade effect, as due to confinement and their nanometric size.
d carrier induced intrinsic room temperature ferromagnetism in Nb:TiO2 film
Authors: Yang J. Y. , Han Y. L. , He L. , Dou R. F. , Xiong C. M. , Nie J. C.
Published: May 2012

High crystalline anatase TiO2 and Nb:TiO2 thin films were fabricated on LaAlO3 (100) substrates by pulsed laser deposition. Room temperature ferromagnetism was obtained in Nb:TiO2 but absent in pure TiO2. The Kondo effect and anomalous Hall effect observed in metallic Nb:TiO2 strongly confirmed the existence of exchange interaction between intrinsic local magnetic moments and carriers. High energy resolution x-ray photoelectron spectroscopy studies of the Nb:TiO2 thin film revealed clear signals of Ti3+ and Nb4+ ions, which had one unpaired d electron responsible for the local magnetic moments. This result consisted quite well with the spin polarized first principle calculation.
The evolution of solid density within a thermal explosion II. Dynamic proton radiography of cracking and solid consumption by burning
Authors: Smilowitz L. , Henson B. F. , Romero J. J. , Asay B. W. , Saunders A. , Merrill F. E. , Morris C. L. , Kwiatkowski K. , Grim G. , Mariam F. , Schwartz C. L. , Hogan G. , Nedrow P. , Murray M. M. , Thompson T. N. , Espinoza C. , Lewis D. , Bainbridge J. , McNeil W. , Rightley P. , Marr-Lyon M.
Published: May 2012

We report proton transmission images obtained subsequent to the laser assisted thermal ignition of a sample of PBX 9501 (a plastic bonded formulation of the explosive nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)). We describe the laser assisted thermal ignition technique as a means to synchronize a non-linear thermal ignition event while preserving the subsequent post-ignition behavior. We have obtained dynamic proton transmission images at two spatial magnifications and viewed both the radial and transverse axis of a solid cylindrical sample encased in aluminum. Images have been obtained with 3 to 15 μs temporal resolution and approximately 100 μm spatial resolution at the higher magnification. We observe case expansion from very early in the experiment, until case fragmentation. We observe spatially anisotropic features in the transmission which we attribute to cracking in the solid explosive, in agreement with previous measurements conducted on two dimensional samples with optical viewing. Digital analysis of the images also reveals spatially isotropic features which we attribute to the evolution of the loss of density by burning subsequent to thermal ignition.
Conservation laws and symmetries of quasilinear radial wave equations in multi-dimensions
Authors: Anco Stephen C. , MacNaughton Steven A. , Wolf Thomas
Published: May 2012

Symmetries and conservation laws are studied for two classes of physically and analytically interesting radial wave equations with power nonlinearities in multi-dimensions. The results consist of two main classifications: all symmetries of point type and all conservation laws of a general energy-momentum type are explicitly determined, including those such as dilations, inversions, similarity energies, and conformal energies that exist only for special powers or dimensions. In particular, all variational cases (when a Lagrangian formulation exists) and non-variational cases (when no Lagrangian exists) for these wave equations are considered. As main results, the classification yields generalized energies and radial momenta in certain non-variational cases, which are shown to arise from a new type of Morawetz dilation identity that produces conservation laws for each of the two classes of wave equations in a different way than Noether's theorem.
Construction of high-dimensional neural network potentials using environment-dependent atom pairs
Authors: Jose K. V. Jovan , Artrith Nongnuch , Behler Jörg
Published: May 2012

An accurate determination of the potential energy is the crucial step in computer simulations of chemical processes, but using electronic structure methods on-the-fly in molecular dynamics (MD) is computationally too demanding for many systems. Constructing more efficient interatomic potentials becomes intricate with increasing dimensionality of the potential-energy surface (PES), and for numerous systems the accuracy that can be achieved is still not satisfying and far from the reliability of first-principles calculations. Feed-forward neural networks (NNs) have a very flexible functional form, and in recent years they have been shown to be an accurate tool to construct efficient PESs. High-dimensional NN potentials based on environment-dependent atomic energy contributions have been presented for a number of materials. Still, these potentials may be improved by a more detailed structural description, e.g., in form of atom pairs, which directly reflect the atomic interactions and take the chemical environment into account. We present an implementation of an NN method based on atom pairs, and its accuracy and performance are compared to the atom-based NN approach using two very different systems, the methanol molecule and metallic copper. We find that both types of NN potentials provide an excellent description of both PESs, with the pair-based method yielding a slightly higher accuracy making it a competitive alternative for addressing complex systems in MD simulations.
Combinatorial growth of oxide nanoscaffolds and its influence in osteoblast cell adhesion
Authors: Acevedo-Morantes Claudia Y. , Irizarry-Ortiz Roberto A. , Caceres-Valencia Pablo G. , Singh Surinder P. , Ramirez-Vick Jaime E.
Published: May 2012

We report a novel method for high-throughput investigations on cell-material interactions based on metal oxide nanoscaffolds. These scaffolds possess a continuous gradient of various titanium alloys allowing the compositional and morphological variation that could substantially improve the formation of an osseointegrative interface with bone. The model nanoscaffold has been fabricated on commercially pure titanium (cp-Ti) substrate with a compositional gradients of tin (Sn), chromium (Cr), and niobium (Nb) deposited using a combinatorial approach followed by annealing to create native oxide surface. As an invitro test system, the human fetal osteoblastic cell line (hFOB 1.19) has been used. Cell-adhesion of hFOB 1.19 cells and the suitability of these alloys have been evaluated for cell-morphology, cell-number, and protein adsorption. Although, cell-morphology was not affected by surface composition, cell-proliferation rates varied significantly with surface metal oxide composition; with the Sn- and Nb-rich regions showing the highest proliferation rate and the Cr-rich regions presenting the lowest. The results suggest that Sn and Nb rich regions on surface seems to promote hFOB 1.19 cell proliferation and may therefore be considered as implant material candidates that deserve further analysis.
Thermal spin pumping and magnon-phonon-mediated spin-Seebeck effect
Authors: Uchida K. , Ota T. , Adachi H. , Xiao J. , Nonaka T. , Kajiwara Y. , Bauer G. E. W. , Maekawa S. , Saitoh E.
Published: May 2012

The spin-Seebeck effect (SSE) in ferromagnetic metals and insulators has been investigated systematically by means of the inverse spin-Hall effect (ISHE) in paramagnetic metals. The SSE generates a spin voltage as a result of a temperature gradient in a ferromagnet, which injects a spin current into an attached paramagnetic metal. In the paramagnet, this spin current is converted into an electric field due to the ISHE, enabling the electric detection of the SSE. The observation of the SSE is performed in longitudinal and transverse configurations consisting of a ferromagnet/paramagnet hybrid structure, where thermally generated spin currents flowing parallel and perpendicular to the temperature gradient are detected, respectively. Our results explain the SSE in terms of a two-step process: (1) the temperature gradient creates a non-equilibrium state in the ferromagnet governed by both magnon and phonon propagations and (2) the non-equilibrium between magnons in the ferromagnet and electrons in the paramagnet at the contact interface leads to “thermal spin pumping” and the ISHE signal. The non-equilibrium state of metallic magnets (e.g., Ni81Fe19) under a temperature gradient is governed mainly by the phonons in the sample and the substrate, while in insulating magnets (e.g., Y3Fe5O12), both magnon and phonon propagations appear to be important. The phonon-mediated non-equilibrium that drives the thermal spin pumping is confirmed also by temperature-dependent measurements, giving rise to a giant enhancement of the SSE signals at low temperatures.
Influence of anion on the quadratic nonlinearity and depolarization ratios of scattered second harmonic light from cation-π complexes
Authors: Pandey Ravindra , Mukhopadhyay S. , Ramasesha S. , Das Puspendu K. , Zyss Joseph
Published: May 2012

We have investigated quadratic nonlinearity (βHRS) and linear and circular depolarization ratios (D and D′, respectively) of a series of 1:1 complexes of tropyliumtetrafluoroborate as a cation and methyl-substituted benzenes as π-donors by making polarization resolved hyper-Rayleigh scattering measurements in solution. The measured D and D′ values are much lower than the values expected from a typical sandwich or a T-shaped geometry of a complex. In the cation-π complexes studied here, the D value varies from 1.36 to 1.46 and D′ from 1.62 to 1.72 depending on the number of methyl substitutions on the benzene ring. In order to probe it further, β, D and D′ were computed using the Zerner intermediate neglect of differential overlap-correction vector self-consistent reaction field technique including single and double configuration interactions in the absence and presence of BF4− anion. In the absence of the anion, the calculated value of D varies from 4.20 to 4.60 and that of D′ from 2.45 to 2.72 which disagree with experimental values. However, by arranging three cation-π BF4− complexes in a trigonal symmetry, the computed values are brought to agreement with experiments. When such an arrangement was not considered, the calculated β values were lower than the experimental values by more than a factor of two. This unprecedented influence of the otherwise “unimportant” anion in solution on the β value and depolarization ratios of these cation-π complexes is highlighted and emphasized in this paper.
Effect of anti-ferromagnet surface moment density on the hysteresis properties of exchange coupled antiferromagnet-ferromagnet systems: The case of bismuth-ferrite
Authors: Ashraf Khalid , Salahuddin Sayeef
Published: May 2012

We propose a generic formalism to estimate the anisotropies, exchange energies, and the surface antiferromagnet (AFM) moment of AFM-ferromagnet (FM) heterostructure systems that show spin glass like behavior. This scheme provides quantitative agreement with multiple experiments on epitaxial bismuth ferrite (BFO)-FM system that have been reported recently. We find that a single value of the interface coupling energy can reproduce both the exchange bias and the coercivity enhancement observed in experiments. We also find a surprisingly high surface AFM moment density that agrees well with measured values. This high moment on the BFO surface is indicative of a significant modulation of magnetic properties at the BFO-FM interface.
Electrical properties of (110) epitaxial lead-free ferroelectric Na0.5Bi0.5TiO3 thin films grown by pulsed laser deposition: Macroscopic and nanoscale data
Authors: Bousquet M. , Duclère J.-R. , Gautier B. , Boulle A. , Wu A. , Députier S. , Fasquelle D. , Rémondière F. , Albertini D. , Champeaux C. , Marchet P. , Guilloux-Viry M. , Vilarinho P.
Published: May 2012

We report the electrical properties, measured both at the macroscopic and nanometric scales, of epitaxial (110)-Na0.5Bi0.5TiO3 (NBT) thin films grown on (110)Pt/(110)SrTiO3 by pulsed laser deposition (PLD). The influence of the A-site composition (Na and/or Bi excess) on both the structural/microstructural characteristics and the electrical properties is discussed. Whatever the composition of the NBT target, the final layers are systematically epitaxially grown, with NBT crystallites mainly (110)-oriented, and as well (100)-oriented for some minor proportion. Atomic force microscopy (AFM) images reveal the coexistence of two kinds of grains presenting different shapes: namely flat and elongated grains, corresponding to (100)- and (110)-oriented NBT crystallites, respectively. The macroscopic ferroelectric properties were measured at room temperature. A rather well-defined shape of the hysteresis loops was obtained: the incorporation of a Bi excess in the target clearly improves the saturation of the loops. The ferroelectric performances are a remanent polarization (Pr) value, ranging from 7 to 14 μC/cm2, associated with a coercive field (Ec) in the range 68–85 kV/cm. In addition, at 105 Hz, the relative permittivity was about ɛr ∼ 255–410 and the dielectric losses (tan δ) were ∼6%–7%. Finally, the electrical properties at the local scale were investigated by coupling piezoresponse force microscopy (PFM) and tunneling AFM (TUNA) measurements. The collected data reveal that the two types of grains behave differently. The PFM amplitude signal of (110)-oriented grains is very contrasted and such grains are often divided in ferroelectric bi-domains of nanometric sizes, whereas the response of (100)-oriented grains is less contrasted and more homogeneous. The interpretation of the PFM signal is provided. The piezoloop recorded on a (110)NBT grain is strongly distorted and shifted along the vertical axis, in agreement with the vertical drift observed for macroscopic ferroelectric data. Finally, TUNA data clearly indicate that flat grains are leakier than elongated grains, highlighting the anisotropy of the electrical properties at the local scale.
Potential flux landscapes determine the global stability of a Lorenz chaotic attractor under intrinsic fluctuations
Authors: Li Chunhe , Wang Erkang , Wang Jin
Published: May 2012

We developed a potential flux landscape theory to investigate the dynamics and the global stability of a chemical Lorenz chaotic strange attractor under intrinsic fluctuations. Landscape was uncovered to have a butterfly shape. For chaotic systems, both landscape and probabilistic flux are crucial to the dynamics of chaotic oscillations. Landscape attracts the system down to the chaotic attractor, while flux drives the coherent motions along the chaotic attractors. Barrier heights from the landscape topography provide a quantitative measure for the robustness of chaotic attractor. We also found that the entropy production rate and phase coherence increase as the molecular numbers increase. Power spectrum analysis of autocorrelation function provides another way to quantify the global stability of chaotic attractor. We further found that limit cycle requires more flux and energy to sustain than the chaotic strange attractor. Finally, by detailed analysis we found that the curl probabilistic flux may provide the origin of the chaotic attractor.
Defect topologies in a nematic liquid crystal near a patchy colloid
Authors: Melle Michael , Schlotthauer Sergej , Mazza Marco G. , Klapp Sabine H. L. , Schoen Martin
Published: May 2012

Using isothermal-isobaric Monte Carlo simulations we investigate defect topologies due to a spherical colloidal particle immersed in a nematic liquid crystal. Defects arise because of the competition between the preferential orientation at the colloid's surface and the far-field director \documentclass[12pt]{minimal}\begin{document}$\widehat{\bm {n}}_{0}$\end{document}n̂0. Considering a chemically homogeneous colloid as a special case we observe the well-known surface and saturn ring defect topologies for weak and strong perpendicular anchoring, respectively; for homogeneous, strong parallel anchoring we find a boojum defect topology that has been seen experimentally [see P. Poulin and D. A. Weitz, Phys. Rev. E 57, 626 (1998)] but not in computer simulations. We also consider a heterogeneous, patchy colloid where the liquid-crystal molecules anchor either preferentially planar or perpendicular at the surface of the colloid. For a patchy colloid we observe a boojum ring defect topology in agreement with recent experimental studies [see M. Conradi, M. Ravnik, M. Bele, M. Zorko, S. Žumer, and I. Muševič, Soft Matter 5, 3905 (2009)]. We also observe two other novel defect topologies that have not been reported thus far neither experimentally nor theoretically.
Vertically integrated submicron amorphous-In2Ga2ZnO7 thin film transistor using a low temperature process
Authors: Ho Rha Sang , Jung Jisim , Soo Jung Yoon , Jang Chung Yoon , Ki Kim Un , Suk Hwang Eun , Keon Park Byoung , Joo Park Tae , Choi Jung-Hae , Seong Hwang Cheol
Published: May 2012

In this work, vertically integrated amorphous-In2Ga2ZnO7 (a-IGZO) thin film transistors (V-TFTs) with 310 nm channel length were fabricated using a low temperature process (<300  °C), and their device performance was evaluated. The fabricated V-TFTs show well behaved transfer characteristics with an Ion/Ioff current ratio greater than 104 and a threshold voltage of 1.7 V. The influence of the vertical structure on device performance was analyzed in detail. In addition, current polarity characteristics that arise from different metal/a-IGZO contacts were also examined. The non-optimum performance of the V-TFTs was attributed to the fringing-field effect, high defect density, and large source/drain contact resistance.
A molecular H2 potential for heterogeneous simulations including polarization and many-body van der Waals interactions
Authors: McLaughlin Keith , Cioce Christian R. , Belof Jonathan L. , Space Brian
Published: May 2012

A highly accurate aniostropic intermolecular potential for diatomic hydrogen has been developed that is transferable for molecular modeling in heterogeneous systems. The potential surface is designed to be efficacious in modeling mixed sorbates in metal-organic materials that include sorption interactions with charged interfaces and open metal sites. The potential parameters are compatible for mixed simulations but still maintain high accuracy while deriving dispersion parameters from a proven polarizability model. The potential includes essential physical interactions including: short-range repulsions, dispersion, and permanent and induced electrostatics. Many-body polarization is introduced via a point-atomic polarizability model that is also extended to account for many-body van der Waals interactions in a consistent fashion. Permanent electrostatics are incorporated using point partial charges on atomic sites. However, contrary to expectation, the best potentials are obtained by permitting the charges to take on values that do not reproduce the first non-vanishing moment of the electrostatic potential surface, i.e., the quadrupole moment. Potential parameters are fit to match ab initio energies for a representative range of dimer geometries. The resulting potential is shown to be highly effective by comparing to electronic structure calculations for a thermal distribution of trimer geometries, and by reproducing experimental bulk pressure-density isotherms. The surface is shown to be superior to other similarly portable potential choices even in tests on homogeneous systems without strong polarizing fields. The present streamlined approach to developing such potentials allows for a simple adaptation to other molecules amenable to investigation by high-level electronic structure methods.
Energetic instability of polygonal micro- and nanowires
Authors: Wong Harris
Published: May 2012

Micro- and nanowires are commonly used in biological sciences, micro- and nanoelectronics, and optoelectronics, and their morphological stability needs to be understood and controlled. Previous linear-stability analyses of infinitely-long circular wires have shown that the critical wavelength for instability approaches infinity if the wire surface is facetted. Thus, Rayleigh’s instability is suppressed in finite facetted circular wires and possibly in finite facetted polygonal wires. This work studies the energetic stability of long facetted regular-polygonal and rectangular wires that are not in thermodynamic equilibrium. The long wire is assumed to break up into N identical equilibrium crystals with the same cross-sectional shape as the wire. The length of the wire is Nλ and that of the crystal is L. The surface energy of the system is found to decrease after breakup if λ/L>9/4-2/3N+… for N ≫ 1. This instability criterion holds for regular-polygonal wires of arbitrary sides and for rectangular wires of arbitrary aspect ratios. The criterion also applies to infinitely long equilibrium wires if N is set to infinity. Previous experimental studies of pore channels in sapphire have revealed that the facetted channels break up not by Rayleigh’s instability, but by tip shedding. The observed “crystal” separation to length ratio agrees with the above instability criterion.
Prediction of glass forming ability and glass forming range for electrodeposited binary Co-W alloys
Authors: Singh Ashish , Iyer Nikhilesh , Harimkar Sandip P.
Published: May 2012

This paper reports on the transition of crystalline to amorphous structure with increasing W content in electrodeposited binary Co-W alloys. The glass forming ability of the electrodeposited Co-based alloys, including Co-W alloy, is analyzed using deep eutectic criteria based on reduced liquidus temperature and relative composition ratio. MD simulations based on solid solution models indicated glass forming ability above 20 at. % W for Co-rich Co-W alloys, which is in good agreement with the experimental observations.
Observation of strong magnetoelectric effects in Ba0.7Sr0.3TiO3/La0.7Sr0.3MnO3 thin film heterostructures
Authors: Martínez R. , Kumar A. , Palai R. , Srinivasan G. , Katiyar R. S.
Published: May 2012

A robust magnetoelectric (ME) response is essential in multiferroic thin films for potential nonvolatile ME memory elements. We report strong ME effects in bilayers and superlattices of Ba0.7Sr0.3TiO3/La0.7Sr0.3MnO3 composite multiferroics. The low-frequency ME coefficient ranges from 35 to 300 mV/cm Oe, depending on thickness, superlattice periodicity, and bias magnetic field and ac magnetic field orientations. Data on ME coupling are fitted well with a modified free-body model to obtain information on magneto-mechanical coupling in the composites. The strong ME coupling in spite of anticipated substrate clamping is a step forward towards the realization of multistate memories and read-write elements.
Three-dimensional distribution of Al in high-k metal gate: Impact on transistor voltage threshold
Authors: Panciera F. , Baudot S. , Hoummada K. , Gregoire M. , Juhel M. , Mangelinck D.
Published: May 2012

The three-dimensional spatial distribution of Al in the high-k metal gates of metal-oxide-semiconductor field-effect-transistors is measured by atom probe tomography. Chemical distribution is correlated with the transistor voltage threshold (VTH) shift generated by the introduction of a metallic Al layer in the metal gate. After a 1050 °C annealing, it is shown that a 2-Å thick Al layer completely diffuses into oxide layers, while a positive VTH shift is measured. On the contrary, for thicker Al layers, Al precipitation in the metal gate stack is observed and the VTH shift becomes negative.
Measurements of the runaway electron energy during disruptions in the tokamak TEXTOR
Authors: Forster M. , Finken K. H. , Lehnen M. , Willi O. , Xu Y. ,   TEXTOR Team
Published: May 2012

Calorimetric measurements of the total runaway electron energy are carried out using a reciprocating probe during induced TEXTOR disruptions. A comparison with the energy inferred from runaway energy spectra, which are measured with a scintillator probe, is used as an independent check of the results. A typical runaway current of 100 kA at TEXTOR contains 30 to 35 kJ of runaway energy. The dependencies of the runaway energy on the runaway current, the radial probe position, the toroidal magnetic field and the predisruptive plasma current are studied. The conversion efficiency of the magnetic plasma energy into runaway energy is calculated to be up to 26%.
Compositional effect of WO3, MoO3, and P2O5 on Raman spectroscopy of tellurite glass for broadband and high gain Raman amplifier
Authors: Yuan J. , Yang Q. , Chen D. D. , Qian Q. , Shen S. X. , Zhang Q. Y. , Jiang Z. H.
Published: May 2012

In order to obtain broadband and high Raman gain coefficient in the tellurite glass, a detailed study of the effects of WO3, MoO3, and P2O5 in TeO2-ZnO-Na2O-Nb2O5 (TZNN) glass system on the thermal stabilities and Raman spectroscopic was performed. It was found that both WO3 and MoO3 improved the glass thermal stability and enhanced the bandwidth significantly. Higher Raman gain coefficients and broader bandwidth were realized in the MoO3 modified glasses than those of WO3 added glass. The tellurite glass containing 15 mol. % MoO3 exhibits the bandwidth 1.7 times larger than the silica glass and the Raman gain coefficient is as high as 38 times that of the silica glass. Moreover, with the addition of P2O5 in TeO2-ZnO-Na2O-Nb2O5-WO3 (TZNNW) and TeO2-ZnO-Na2O-Nb2O5-MoO3 (TZNNM) glass systems, the thermal stabilities can further be improved. On the other hand, the Raman bandwidth can further be broadened, especially in the TZNNMP glass system. The tellurite glass containing 15 mol. % MoO3 and 15 mol. % P2O5 shows the bandwidth 1.9 times larger than the silica glass and maintains high Raman gain coefficient which is as high as 37 times that of the silica glass, indicating this glass is a promising candidate as new gain media for broadband Raman fiber amplifier.
Microstructure analysis of novel ternary NiSi2−xAlx silicide layers on Si(001) formed by solid-state reaction
Authors: Mogilatenko A. , Beddies G. , Falke M. , Häusler I. , Neumann W.
Published: May 2012

Phase formation due to annealing of Al/Ni (z:1) films on Si was investigated on the nanometer scale as a function of Al content and annealing temperature. An addition of Al to the Ni-Si system followed by annealing at 500 °C results in the formation of different Ni-Al-Si compounds depending on the Al content. Furthermore, a reduction of disilicide formation temperature from 700 °C down to 500 °C was observed in the presence of Al. In particular, grains of ternary NiSi2−xAlx were observed at the NiSi/Si interface after the 500 °C annealing even for a small Al amount of z = 0.1. A 900 °C annealing leads to the formation of continuous NiSi2−xAlx layers. The interfacial roughness of the layers strongly depends on the Al content and reaches its minimum for an Al fraction (z) ranging from 0.2 to 0.4. Using results of transmission electron microscopy analysis, a model describing the formation of ternary NiSi2−xAlx is proposed.
A simple analysis of interband absorption in quantum well structure of III-V ternary and quaternary semiconductors
Authors: Dey Anup , Maiti Biswajit , Chanda (Sarkar) Debasree
Published: May 2012

A simple generalized theory is presented for the determination of interband optical absorption coefficient (IOAC) around band edges, in quantum well (QW) structure of non-parabolic semiconducting materials whose band structures obey the three band model of Kane. The dependence of absorption coefficient on wave-vector (k→) has also been investigated. IOAC has been calculated for a wide range of III–V compound semiconductors, such as InAs, InSb, Hg1−xCdxTe, and In1−xGaxAsyP1−y lattice matched to InP. It has been found that IOAC for QWs increases in steps with increasing photon energy and the positions of jumps of the coefficient are more closely spaced in the three band model of Kane than those with parabolic energy band approximations in all the cases. IOAC for QWs is largely dependent on the polarization direction of the incident light and on the well dimension as well. The expressions of IOAC presented in this article can easily be extended to incorporate the effects of different external conditions like strain, electric, and magnetic fields on IOAC. It has also been shown that under certain limiting conditions the expressions for IOAC reduces to the previously known results for wide band gap materials and this is the indication for it to be a generalized theory for IOAC.
Ionization energy of atoms obtained from GW self-energy or from random phase approximation total energies
Authors: Bruneval Fabien
Published: May 2012

A systematic evaluation of the ionization energy within the GW approximation is carried out for the first row atoms, from H to Ar. We describe a Gaussian basis implementation of the GW approximation, which does not resort to any further technical approximation, besides the choice of the basis set for the electronic wavefunctions. Different approaches to the GW approximation have been implemented and tested, for example, the standard perturbative approach based on a prior mean-field calculation (Hartree-Fock GW@HF or density-functional theory GW@DFT) or the recently developed quasiparticle self-consistent method (QSGW). The highest occupied molecular orbital energies of atoms obtained from both GW@HF and QSGW are in excellent agreement with the experimental ionization energy. The lowest unoccupied molecular orbital energies of the singly charged cation yield a noticeably worse estimate of the ionization energy. The best agreement with respect to experiment is obtained from the total energy differences within the random phase approximation functional, which is the total energy corresponding to the GW self-energy. We conclude with a discussion about the slight concave behavior upon number electron change of the GW approximation and its consequences upon the quality of the orbital energies.
Growth of metal and metal oxide nanowires driven by the stress-induced migration
Authors: Chen Mingji , Yue Yumei , Ju Yang
Published: May 2012

High quality Al and CuO nanowries are fabricated by simply heating the Al and Cu samples in air. Although the experimental operations and the stress-induced migration processes are quite similar, the causes of the driving forces and the growth mechanism are completely different. For the growth of Al nanowires, the driving force is determined to be the compressive stresses caused by the thermal expansion mismatch between Al film and Si substrate, and the growth mechanism is proposed to be the extrusion of atoms from the bases of nanowires (EAFB). For the growth of CuO nanowires, the driving force is determined to be the compressive stresses caused by the formation of Cu oxide layers, and the growth mechanism is proposed to be the formation of oxide molecules on surfaces of the nanowires (FOOS). The direct experimental observations of both EAFB and FOOS are presented. It is also demonstrated that stress distribution on the macroscopic level, which is caused by thermal or mechanical manipulation, can also influence the growth of CuO nanowires, which makes it prospective to control the growth of metal oxide nanowires by designing the stress distribution within the sample from which the nanowires are generated.
Structure and fragility of supercooled Ga-In melts
Authors: Zhao Xiaolin , Bian Xiufang , Bai Yanwen , Li Xinxin
Published: May 2012

The melt structures and viscosities of Ga-In alloys were investigated by an x-ray diffractometer and a torsional oscillation viscometer. A difference in the temperature dependence of the viscosity between the supercooled and the superheated melt of Ga-In alloys was detected. Based on the concept of the melt fragility, we find that the fragility of the supercooled melt is larger than that of the superheated melt in this alloy system. Furthermore, the length of gallium covalent bond is larger in the supercooled melt. The cluster abruptly becomes much bigger, and the ordering degree increases obviously near the liquidus with decreasing temperature. This work provides a further understanding on the liquid–solid transition under the supercooled condition from the point of view of the melt dynamics.
Multielectron effects in high harmonic generation in N2 and benzene: Simulation using a non-adiabatic quantum molecular dynamics approach for laser-molecule interactions
Authors: Dundas Daniel
Published: May 2012

A mixed quantum-classical approach is introduced which allows the dynamical response of molecules driven far from equilibrium to be modeled. This method is applied to the interaction of molecules with intense, short-duration laser pulses. The electronic response of the molecule is described using time-dependent density functional theory (TDDFT) and the resulting Kohn-Sham equations are solved numerically using finite difference techniques in conjunction with local and global adaptations of an underlying grid in curvilinear coordinates. Using this approach, simulations can be carried out for a wide range of molecules and both all-electron and pseudopotential calculations are possible. The approach is applied to the study of high harmonic generation in N2 and benzene using linearly polarized laser pulses and, to the best of our knowledge, the results for benzene represent the first TDDFT calculations of high harmonic generation in benzene using linearly polarized laser pulses. For N2 an enhancement of the cut-off harmonics is observed whenever the laser polarization is aligned perpendicular to the molecular axis. This enhancement is attributed to the symmetry properties of the Kohn-Sham orbital that responds predominantly to the pulse. In benzene we predict that a suppression in the cut-off harmonics occurs whenever the laser polarization is aligned parallel to the molecular plane. We attribute this suppression to the symmetry-induced response of the highest-occupied molecular orbital.
Temperature dependence of carrier spin polarization determined from current-induced domain wall motion in a Co/Ni nanowire
Authors: Ueda K. , Koyama T. , Hiramatsu R. , Chiba D. , Fukami S. , Tanigawa H. , Suzuki T. , Ohshima N. , Ishiwata N. , Nakatani Y. , Kobayashi K. , Ono T.
Published: May 2012

We have investigated the temperature dependence of the current-induced magnetic domain wall (DW) motion in a perpendicularly magnetized Co/Ni nanowire at various temperatures and with various applied currents. The carrier spin polarization was estimated from the measured domain wall velocity. We found that it decreased more with increasing temperature from 100 K to 530 K than the saturation magnetization did.
GaMnAs: Position of Mn-d levels and majority spin band gap predicted from GGA-1/2 calculations
Authors: Pelá R. R. , Marques M. , Ferreira L. G. , Furthmüller J. , Teles L. K.
Published: May 2012

Among all magnetic semiconductors, GaMnAs seems to be the most important one. In this work, we present accurate first-principles calculations of GaMnAs within the GGA-1/2 approach: We concentrate our efforts in obtaining the position of the peak of Mn-d levels in the valence band and also the majority spin band gap. For the position of the Mn-d peak, we find a value of 3.3 eV below the Fermi level, in good agreement with the most recent experimental results of 3.5 and 3.7 eV. An analytical expression that fits the calculated Eg(x) for majority spin is derived in order to provide ready access to the band gap for the composition range from 0 to 0.25. We found a value of 3.9 eV for the gap bowing parameter. The results agree well with the most recent experimental data.
Absorption efficiency of gold nanorods determined by quantum dot fluorescence thermometry
Authors: Maestro L. M. , Haro-González P. , Coello J. G. , Jaque D.
Published: May 2012

In this work quantum dot fluorescence thermometry, in combination with double-beam confocal microscopy, has been applied to determine the thermal loading of gold nanorods when subjected to an optical excitation at the longitudinal surface plasmon resonance. The absorbing/heating efficiency of low (≈3) aspect ratio gold nanorods has been experimentally determined to be close to 100%, in excellent agreement with theoretical simulations of the extinction, absorption, and scattering spectra based on the discrete dipole approximation.