bluuebunny/crossref_metadata_2025 huggingface dataset:
Cholesteatoma imaging using modified echo-planar diffusion-weighted magnetic resonance imaging
Authors: Flook E , Izzat S , Ismail A
Published: September 2010

Introduction:

Imaging of cholesteatomas can be useful especially in cases of recurrent disease. Computed tomography scans have been recommended before primary surgery, but cholesteatoma tissue looks similar to inflammatory tissue. Diffusion-weighted magnetic resonance imaging is both sensitive and specific in detecting cholesteatoma, which appears as a bright signal on a dark background. Non-echo-planar diffusion-weighted magnetic resonance imaging is superior to routine echo-planar diffusion-weighted magnetic resonance imaging as it minimises susceptibility artefacts; however, the addition of this facility involves expensive magnetic resonance scanner upgrading.

Method:

To avoid the cost of such upgrading, we modified our echo-planar diffusion-weighted magnetic resonance imaging parameters and then scanned 15 consecutive cases of suspected cholesteatoma or suspected recurrent cholesteatoma.

Results:

Imaging results correlated well with clinical and/or operative findings.

Conclusion:

These results indicate that software adjustments can enable echo-planar diffusion-weighted magnetic resonance imaging to detect cholesteatomas reliably, and as effectively as non-echo-planar diffusion-weighted magnetic resonance imaging. This discovery has the potential to facilitate reliable delayed post-operative screening of canal wall up mastoidectomies, avoiding the need for a ‘second look’ procedure.
A humanoid robot capable of carrying heavy objects
Authors: Choi Hyeung-Sik , Na Wonhyun , Kang Dongwan
Published: September 2010

A new type of 28-DOF (degree of freedom) full-size humanoid robot, driven by a closed-chain type of joint actuation system, is developed in this paper. Each leg of the robot is composed of six joints, where three are at the hip, one is at the knee, and two are at the ankle. The robot has six joints for each arm, one balancing joint, and three joints for the head, with two cameras. The weight of the robot is 75 kg, and its height is 168 cm.

The actuation systems of the pitching joint for the arms and legs of the robot are designed based on a closed-chain mechanism composed of four bar links driven by a ball screw, and each leg of the robot is designed to support 95 kg weight to include a 20 kg payload that can be carried by the robot arms having very light designs (with weight 8.5 kg), but each capable of carrying a 10 kg payload.

An analysis of the closed-chain joint actuation systems of a light arm capable of handling heavy objects is performed, and the light arm is designed via finite-element method analysis performed using ANSYS. In addition, the kinematic analysis and the detailed structure of the arm and leg of the robot are performed.

The main controller uses the ARM processor and a distributed controller for the leg joints is developed using the TMS320c2407 processor with the communications between the main and joint controllers being performed via the CAN system.

Good performances of the proposed robot is demonstrated by presenting several experimental results; these include (1) experimentally handling a 13 kg payload, (2) through walking experiments of the robot supporting a 85 kg load, and (3) measurements of the arm and leg joint motors while performing walking experiments.
Efficiency of an agrosystem designed for family farming in the pre-Amazon region
Authors: Aguiar Alana das Chagas Ferreira , de Freitas Idelfonso Colares , Carvalho Cristina Silva , Marques Monroe Paulo Henrique , de Moura Emanoel Gomes
Published: September 2010

In the humid tropics, the continuous use of the same area reduces nutrient availability and increases the incidence of weeds. To circumvent these obstacles, farmers practice itinerant agriculture associated with slashing and burning with negative effects on the local and global environment. In search for a suitable system for humid tropical agriculture, the objective of this study was to investigate the performance of no-till alley cropping in conjunction with the use of annual legume crops grown during the off-season. The experiment was implemented in a one-hectare alley cropping system in which the leguminous tree clitoria (Clitoria fairchildiana R.A. Howard) was used. The experimental design consisted of randomized blocks with four replications of the following treatments: Stylosanthis (Stylosanthis capitata), showey rattlebox (Crotalaria spectabilis), sunn hemp (Crotalaria juncea), jack bean (Canavalia ensiformis) and a control with clitoria alone, without an annual legume. In January 2007 and 2008, maize was planted in each alley. One hundred and twenty days after annual legumes were sown, the total biomass was recorded. Weed incidence was assessed 35 days after maize planting. Analyses of the C, N, P, K, Ca and Mg contents of the legumes were carried out. To assess soil organic matter (SOM), composite soil samples from the surface 0–5 cm were collected from experimental plots. Two adjacent areas were also sampled for comparison: a 10-year-old secondary forest and an area of conventional tillage. The SOM was fractionated using a densitometric and a granulometric method. Conventional systems reduce the silt and free light organic matter fractions more than no till. The use of annual legumes changes the composition of the weed community, replacing the more aggressive types with those less competitive. The use of showy rattlebox (C. spectabilis) may be an effective strategy for reducing weed density in the long-season crop. Furthermore, relative to the use of leguminous trees alone, higher yields of maize can be obtained with the use of showy rattlebox (C. spectabilis) and sunn hemp (C. juncea) without the application of additional N.
Soil‐atmosphere exchange potential of NO and N2O in different land use types of Inner Mongolia as affected by soil temperature, soil moisture, freeze‐thaw, and drying‐wetting events
Authors: Yao Zhisheng , Wu Xing , Wolf Benjamin , Dannenmann Michael , Butterbach‐Bahl Klaus , Brüggemann Nicolas , Chen Weiwei , Zheng Xunhua
Published: September 2010

Changes in precipitation and temperature in Asian continental steppelands may affect soil physical, chemical and biological processes that control the biosphere‐atmosphere exchange of N‐trace gases. The changes include regional desertification, global warming and strong El Niño events that impact the large steppe land area in China and Mongolia. The area is so large that feedbacks to the global greenhouse gas balance may occur. In this study we investigated how changes in soil moisture and temperature, and especially drying‐rewetting and freeze‐thaw events, affect nitric oxide (NO) and nitrous oxide (N2O) fluxes from large intact soil cores taken from representative land use/cover types in the region of the Xilin River catchment, Inner Mongolia. These soil cores were incubated under varying conditions with respect to temperature (ranging from −10 to 15°C) and simulated rainfall (25, 45 and 65 mm). Following drying‐rewetting and freeze‐thaw transitions, we observed pulses of NO and N2O emissions from the soils of typical steppe, mountain meadow, sand dune and marshland. A comparable trend in soil CO2 emissions and soil air N2O concentrations indicated that the high substrate availability and rapid recovery of microbial activity after soil wetting and thawing resulted in high gas fluxes. Across the whole temperature range, NO and N2O fluxes from all soils, except for N2O emissions from marshland soils, showed a positive exponential relationship with soil temperature. A combination of soil temperature and soil moisture explained most of the observed variations in NO (up to 74–90%) and N2O (up to 67–89%) fluxes for individual soils. Spatial differences in NO emissions between land use/cover types could be explained by differences in soil organic carbon and pH, whereas spatial variations of N2O fluxes were primarily correlated with differences in soil microbial biomass. On the basis of the incubation under controlled conditions, the average annual flux, weighted by the areal extent of the different investigated land use/cover types in the region, was estimated at ∼3.9 ± 1.1 kg N ha−1 yr−1 for NO and 0.53 ± 0.20 kg N ha−1 yr−1 for N2O, respectively. It is noteworthy that our measurements were conducted using soil cores without a vegetation cover, which probably resulted in an overestimation of N‐trace gas fluxes. However, our results indicate that the rarely determined NO formation appears to be a significant pathway in the N cycle of semiarid steppe, which is highly sensitive to the climatic change taking place in these regions, especially an increase in intensity and frequency of drying‐wetting and freeze‐thaw cycles.
Madden‐Julian Oscillation in the tropical stratosphere
Authors: Weare Bryan C.
Published: September 2010

Links are sought between Madden‐Julian Oscillation (MJO)‐related variations in the troposphere and stratospheric winds, temperature, and ozone. Tropospheric variations of equatorial MJO‐filtered 200 hPa zonal winds define indices of MJO activity for two equatorial regions in the Indian and Western Pacific oceans. These indices are used to calculate composite means of MJO filtered winds, temperature, and ozone mixing ratio for eight height levels from the upper troposphere well into the stratosphere. Strong evidence is presented for significant and coherent MJO departures throughout the lower stratosphere. At 100 hPa, these departures show easterlies in the equatorial regions of the compositing centers and nearly symmetric anticyclonic centers at 25° poleward of those centers, which are associated with significant negative departures in both temperature and ozone mixing ratio. Near 40°N MJO departures of meridional velocity, temperature, and ozone mixing ratio generally tilt westward with height. The most important aspects of these features propagate eastward at a rate of about 5 m/s in the Eastern Hemisphere and several times faster in the Western Hemisphere.
Comparing flux‐averaged and resident concentration in a fractured bedrock using ground penetrating radar
Authors: Becker Matthew W. , Tsoflias Georgios P.
Published: September 2010

Saline tracer transport experiments were performed to compare flux‐averaged and resident concentration in a single subhorizontal fracture in sandstone bedrock. Tracer migration over a 14 m distance was monitored at an extraction well and imaged within the rock as it passed below a ground penetrating radar (GPR) positioned at the surface. Reflected radar amplitude was calibrated to tracer concentration by circulating saline fluid of known concentration through the fracture. Saline breakthrough curves measured at the well and within the rock were comparable but showed differences in both magnitude and shape. Transport differences were explored using flux‐averaged and resident concentration first‐passage‐time models combined with streamline advective tracking. Application of the appropriate transport model to the two breakthrough curves produced identical estimates of dispersivity and similar estimates of effective fracture aperture. The tracer‐derived fracture aperture also agreed reasonably well with hydraulic aperture derived from cross‐hole pump tests. The availability of both flux and resident concentrations helped constrain the interpretation of the flow and transport behavior in the fracture. Flow appeared to be highly channelized with less than half the hydraulically swept area of the fracture contributing to efficient tracer transport.
Quiet time ionospheric variability over Arecibo during sudden stratospheric warming events
Authors: Chau J. L. , Aponte N. A. , Cabassa E. , Sulzer M. P. , Goncharenko L. P. , González S. A.
Published: September 2010

We present observations of the F‐region ionosphere over Arecibo, Puerto Rico (18.34°N, 66.75°W), during the January–February 2008 and January–February 2009 sudden stratospheric warming (SSW) events. For the first period (2008), we have used incoherent scatter radar (ISR) electron density and temperature measurements from the Arecibo Observatory (AO), as well as relative total electron content (TEC) derived from a dual‐frequency GPS receiver. For the second event (2009), during which we observed the largest recorded stratospheric warming, we have used the relative GPS TEC. Our analysis indicates that the ionosphere over Arecibo exhibits perturbations after the SSW, the effects are most visible during the daytime. The strongest signatures are observed in the TEC measurements, represented by large enhancements (with respect to non SSW days), particularly during daytime hours. However, the local time dependence of these enhancements is not the same in the two events. In addition, the data show that our results are consistent with the larger than normal daytime vertical drift differences observed at the magnetic equator over Jicamarca. The electron temperature is also affected during the daytime due to changes in electron density, indicating that the electron temperatures is influenced, indirectly, by changes in planetary wave activity in the lower altitudes.
Techniques for Precision-Based Visual Analysis of Projected Data
Authors: Schreck Tobias , von Landesberger Tatiana , Bremm Sebastian
Published: September 2010

The analysis of high-dimensional data is an important, yet inherently difficult problem. Projection techniques such as Principal Component Analysis, Multi-dimensional Scaling and Self-Organizing Map can be used to map high-dimensional data to 2D display space. However, projections typically incur a loss in information. Often, uncertainty exists regarding the precision of the projection as compared with its original data characteristics. While the output quality of these projection techniques can be discussed in terms of aggregate numeric error values, visualization is often helpful for better understanding the projection results. We address the visual assessment of projection precision by an approach integrating an appropriately designed projection precision measure directly into the projection visualization. To this end, a flexible projection precision measure is defined that allows the user to balance the degree of locality at which the measure is evaluated. Several visual mappings are designed for integrating the precision measure into the projection visualization at various levels of abstraction. The techniques are implemented in an interactive system, including methods supporting the user in finding appropriate settings of relevant parameters. We demonstrate the usefulness of the approach for visual analysis of classified and unclassified high-dimensional data sets. We show how our interactive precision quality visualization system helps to examine the preservation of original data properties in projected space.
Disk Diagram: An Interactive Visualization Technique of Fuzzy Set Operations for the Analysis of Fuzzy Data
Authors: Park Yeseul , Park Jinah
Published: September 2010

Fuzzy set refers to the data set which does not have separate, distinct clusters, and they contain data elements whose membership degrees are between 0.0 and 1.0. Many fuzzy sets exist in the real world, and one of the important issues is to make a decision from the fuzzy sets using visual analytics tools by extracting information in the data set intuitively. To analyze the element data in fuzzy sets, the visualization of fuzzy sets needs to show an overview of the data with membership degree and the relationship among the sets. In this article, we suggest an interactive visualization technique of fuzzy set operations, called Disk Diagram, which offers distribution of fuzzy data and two scenarios to allow users to interpret inter-dependency among fuzzy sets. A Disk Diagram enables to depict complexity of fuzzy sets by showing the degree of resemblance between the sets with the layout of star coordinates. This article describes the use of a Disk Diagram with two different data sets such as fuzzy disease set and terror related words set. Lastly, we report the results of heuristic evaluation to show that our technique supports visual perception, usability, and knowledge discovery process in the areas of visual representation and interaction.
A Multi-Phase Network Situational Awareness Cognitive Task Analysis
Authors: Erbacher Robert F. , Frincke Deborah A. , Wong Pak Chung , Moody Sarah , Fink Glenn
Published: September 2010

The goal of our project is to create a set of next-generation cyber situational-awareness capabilities with applications to other domains in the long term. The objective is to improve the decision-making process to enable decision makers to choose better actions. To this end, we put extensive effort into making certain that we had feedback from network analysts and managers and understand what their genuine needs are. This article discusses the cognitive task-analysis methodology that we followed to acquire feedback from the analysts. This article also provides the details we acquired from the analysts on their processes, goals, concerns, the data and metadata that they analyze. Finally, we describe the generation of a novel task-flow diagram representing the activities of the target user base.
A new ab initio potential energy surface and microwave and infrared spectra for the Ne–CO2 complex
Authors: Chen Rong , Jiao Erqiang , Zhu Hua , Xie Daiqian
Published: September 2010

We report a new three-dimensional potential energy surface for Ne–CO2 including the Q3 normal mode for the υ3 antisymmetric stretching vibration of the CO2 molecule. The potential energies were calculated using the supermolecular method at the coupled-cluster singles and doubles level with noniterative inclusion of connected triples [CCSD(T)], using a large basis set supplemented with midpoint bond functions. Two vibrationally averaged potentials with CO2 at both the ground (υ=0) and the first (υ=1) vibrational υ3 excited states were generated from the integration of the three-dimensional potential over the Q3 coordinate. Each potential was found to have a T-shaped global minimum and two equivalent linear local minima. The radial DVR/angular FBR method and the Lanczos algorithm are applied to calculate the rovibrational energy levels. Comparison with the available observed values showed an overall excellent agreement for the microwave and infrared spectra. The calculated band origin shifts were found to be 0.1306 and 0.1419 cm−1 for Ne–CO2 and Ne–C18O2, respectively, which are very close to the experimental values of 0.1303 and 0.1432 cm−1.
Self-alignment of silicon chips on wafers: A capillary approach
Authors: Berthier J. , Brakke K. , Grossi F. , Sanchez L. , Di Cioccio L.
Published: September 2010

As the limits of Moore’s law are approached, three-dimensional integration appears as the key to advanced microelectronic systems. Die-to-wafer assembly appears to be an unavoidable step to reach full integration. While robotic methods experience difficulties to accommodate fabrication speed and alignment accuracy, self-assembly methods are promising due to their parallel aspect, which overcomes the main difficulties of current techniques. The aim of this work is the understanding of the mechanisms of self-alignment with an evaporating droplet technique. Stable and unstable modes are examined. Causes for misalignments of chips on wafers and their evolution are investigated with the help of the SURFACE EVOLVER numerical software. Precautions for suitable alignment are proposed.
Substrate-induced strain and its effect in CrO2 thin films
Authors: Pathak M. , Sato H. , Zhang X. , Chetry K. B. , Mazumdar D. , LeClair P. , Gupta A.
Published: September 2010

We report a study of substrate-induced strain and its effect in (100) and (110) CrO2 thin films deposited on TiO2 substrates of respective orientations. While the (110) CrO2 films grow essentially strain-free, the (100) CrO2 films were found to be strained in all lattice directions—out of plane direction was compressively strained while in-plane directions were under tensile strain. Crystal lattice parameters were determined in strained (100) and strain-free (110) CrO2 films together with the amount of strain in the three lattice directions. We found substrate-induced strain to significantly affect the magnetic moment in the (100) CrO2 films at room temperature—reducing the magnetic moment with increasing strain in the (100) films while strain-free (110) CrO2 thin films have higher moments for all thicknesses. Qualitative macroscopic conductance behavior in the strained (100) and strain-free (110) CrO2 films were found to be comparable for temperatures in the range of 5–400 K, showing similar behavior at low temperature as well as near Tc.
A nondamaging electron microscopy approach to map In distribution in InGaN light-emitting diodes
Authors: Özdöl V. B. , Koch C. T. , van Aken P. A.
Published: September 2010

Dark-field inline electron holography and, for comparison, high-resolution transmission electron microscopy are used to investigate the distribution of indium in GaN-based commercial high-efficiency green light-emitting diodes consisting of InGaN multiquantum wells (QWs). Owing to the low electron doses used in inline holography measurements; this technique allows to map the indium distribution without introducing any noticeable electron beam-induced damage which is hardly avoidable in other quantitative transmission electron microscopy methods. Combining the large field of view with a spatial resolution better than 1 nm, we show that the InGaN QWs exhibit random alloy nature without any evidence of nanometer scale gross indium clustering in the whole active region.
Soft breakdown characteristics of ultralow-k time-dependent dielectric breakdown for advanced complementary metal-oxide semiconductor technologies
Authors: Chen Fen , Shinosky Michael
Published: September 2010

During technology development, the study of ultralow-k (ULK) time-dependent dielectric breakdown (TDDB) is important for assuring robust reliability. As the technology advances, the increase in ULK leakage current noise level and reversible current change induced by soft breakdown (SBD) during stress has been observed. In this paper, the physical origin of SBD and reversible breakdown, and its correlation to conventional hard breakdowns (HBDs) were extensively studied. Based on constant voltage stress (CVS) and constant current stress (CCS) results, it was concluded that SBD in ULK is an intrinsic characteristic for ULK material, and all first breakdown events most likely are soft instead of hard. Therefore, a unified understanding of SBD and HBD for low-k TDDB was established. Furthermore, the post-SBD and HBD breakdown conduction characteristics were explored and their impacts on circuit operation were discussed. Based on current limited constant voltage stress studies, it was found that the power dissipation, not the stored energy, determined the severity of ULK dielectric breakdown, and the postbreakdown conduction properties. A percolation-threshold controlled, variable-range-hopping (VRH) model was proposed to explain all postbreakdown aspects of SBD and HBD of ULK material.
Theoretical predictions of trends in spectroscopic properties of gold containing dimers of the 6p and 7p elements and their adsorption on gold
Authors: Pershina V. , Borschevsky A. , Anton J. , Jacob T.
Published: September 2010

Fully relativistic, four-component density functional theory electronic structure calculations were performed for the MAu dimers of the 7p elements, 113 through 118, and their 6p homologs, Tl through Rn. It was shown that the M–Au bond strength should decrease from the 6p to 7p homologs in groups 13 and 14, while it should stay about the same in groups 15 through 17 and even increase in group 18. This is in contrast with the decreasing trend in the M–M bond strength in groups 15 through 17. The reason for these trends is increasingly important relativistic effects on the np AOs of these elements, particularly their large spin-orbit splitting. Trends in the adsorption energies of the heaviest elements and their homologs on gold are expected to be related to those in the binding energies of MAu, while sublimation enthalpies are closely connected to the binding energies of the MM dimers. Lack of a correlation between the MAu and MM binding energies means that no correlation can also be expected between adsorption enthalpies on gold and sublimation enthalpies in groups 15 through 17. No linear correlation between these quantities is established in the row of the 6p elements, as well as no one is expected in the row of the 7p elements.
Pearl-necklace structures of molecular brushes with rigid backbone under poor solvent conditions: A simulation study
Authors: Theodorakis P. E. , Paul W. , Binder K.
Published: September 2010

Bottle-brush polymers, where flexible side chains containing N=20 to 50 effective monomers are grafted to a rigid backbone, are studied by molecular dynamics simulations, varying the grafting density σ and the solvent quality. Whereas for poor solvents and large enough σ the molecular brush is a cylindrical object, homogeneous in axial direction, for intermediate values of σ an axially inhomogeneous structure of ”pearl-necklace” type is formed. The “pearls,” however, have a strongly nonspherical ellipsoidal shape, due to the fact that several side chains cluster together in one pearl, qualitatively consistent with predictions of Sheiko et al. [Eur. Phys. J. E 13, 125 (2004)] We analyze the structure of these pearls and study both the transition to the axially uniform cylinder at high σ and to the trivial pearl-necklace structure at small σ, where each pearl contains a single collapsed chain only.
The distribution of chemical elements in Al- or La-capped high-κ metal gate stacks
Authors: Bosman M. , Zhang Y. , Cheng C. K. , Li X. , Wu X. , Pey K. L. , Lin C. T. , Chen Y. W. , Hsu S. H. , Hsu C. H.
Published: September 2010

The spatial distribution of chemical elements is studied in high-κ, metal-gated stacks applied in field effect transistors. Using the transmission electron microscope (TEM)-based analytical techniques electron energy-loss spectroscopy (EELS) and energy-dispersive x-ray spectroscopy, it is demonstrated that Al2O3 and La2O3 capping layers show distinctly different diffusion profiles. The importance of the EELS collection angle is discussed. Popular chemical distribution models that assume La-rich interface layers are rejected.
Communication: Near edge x-ray absorption fine structure spectroscopy of aqueous adenosine triphosphate at the carbon and nitrogen K-edges
Authors: Kelly Daniel N. , Schwartz Craig P. , Uejio Janel S. , Duffin Andrew M. , England Alice H. , Saykally Richard J.
Published: September 2010

Near edge x-ray absorption fine structure (NEXAFS) spectroscopy at the nitrogen and carbon K-edges was used to study the hydration of adenosine triphosphate in liquid microjets. The total electron yield spectra were recorded as a function of concentration, pH, and the presence of sodium, magnesium, and copper ions (Na+/Mg2+/Cu2+). Significant spectral changes were observed upon protonation of the adenine ring, but not under conditions that promote π-stacking, such as high concentration or presence of Mg2+, indicating that NEXAFS is insensitive to the phenomenon. Intramolecular inner-sphere association of Cu2+ did create observable broadening of the nitrogen spectrum, whereas outer-sphere association with Mg2+ did not.
Titanium nitride films for ultrasensitive microresonator detectors
Authors: Leduc Henry G. , Bumble Bruce , Day Peter K. , Eom Byeong Ho , Gao Jiansong , Golwala Sunil , Mazin Benjamin A. , McHugh Sean , Merrill Andrew , Moore David C. , Noroozian Omid , Turner Anthony D. , Zmuidzinas Jonas
Published: September 2010

Titanium nitride (TiNx) films are ideal for use in superconducting microresonator detectors for the following reasons: (a) the critical temperature varies with composition (0<Tc<5 K); (b) the normal-state resistivity is large, ρn∼100 μΩ cm, facilitating efficient photon absorption and providing a large kinetic inductance and detector responsivity; and (c) TiN films are very hard and mechanically robust. Resonators using reactively sputtered TiN films show remarkably low loss (Qi>107) and have noise properties similar to resonators made using other materials, while the quasiparticle lifetimes are reasonably long, 10–200 μs. TiN microresonators should therefore reach sensitivities well below 10−19 W Hz−1/2.
A search for defect related ferromagnetism in SrTiO3
Authors: Crandles D. A. , DesRoches B. , Razavi F. S.
Published: September 2010

Room temperature ferromagnetic hysteresis is observed in commercial SrTiO3 substrates purchased from a variety of suppliers. It is shown that the ferromagnetic signal comes from the unpolished surfaces. Surface impurity phases cannot be detected using either x-ray diffraction or energy dispersive x-ray spectra on the unpolished surfaces. However, a possible correlation between surface disorder (x-ray diffraction peak linewidth) and ferromagnetism is observed. Ar ion bombardment (10–90 keV) can be used to produce surface layer disorder but is not found to induce ferromagnetism. Annealing of the substrates at temperatures ranging from 600 to 1100 °C is found to alter the hysteresis curves differently depending on whether the annealing is performed in air or in vacuum. Identical annealing behavior is observed if the substrates are artificially spiked with iron. This suggests that the ferromagnetic hysteresis of as purchased SrTiO3 could be due to Fe contamination of the unpolished surfaces. In addition, it is shown that no ferromagnetism is observed in samples that contain 1019–1021 cm−3 of oxygen vacancies if all the faces are polished.
Communication: Explicit construction of functional derivatives in potential-driven density-functional theory
Authors: Gaiduk Alex P. , Staroverov Viktor N.
Published: September 2010

We propose a method for imposing an important exact constraint on model Kohn–Sham potentials, namely, the requirement that they be functional derivatives of functionals of the electron density ρ. In particular, we show that if a model potential v(r) involves no ingredients other than ρ, ∇ρ, and ∇2ρ, then the necessary and sufficient condition for v(r) to be a functional derivative is ∂v/∂∇ρ=∇(∂v/∂∇2ρ). Integrability conditions of this type can be used to construct functional derivatives without knowing their parent functionals. This opens up possibilities for developing model exchange-correlation potentials that do not lead to unphysical effects common to existing approximations. Application of the technique is illustrated with examples.
Musings on thermostats
Authors: Evans Denis J. , Searles Debra J. , Williams Stephen R.
Published: September 2010

In 2005, Bright et al. gave numerical evidence that among the family of time reversible deterministic thermostats known as μ-thermostats, the conventional μ=1 thermostat proposed by Hoover and Evans is the only thermostat that is capable of generating an equilibrium state. Using the recently discovered relaxation theorem, we give a mathematical proof that this is true.
Coherent operation of a gap-tunable flux qubit
Authors: Zhu Xiaobo , Kemp Alexander , Saito Shiro , Semba Kouichi
Published: September 2010

We replace the Josephson junction defining a three-junction flux qubit’s properties with a tunable direct current superconducting quantum interference devices (dc-SQUIDs) in order to tune the qubit gap during the experiment. We observe different gaps as a function of the external magnetic pre-biasing field and the local magnetic field through the dc-SQUID controlled by high-bandwidth on chip control lines. The persistent current and gap behavior correspond to numerical simulation results. We set the sensitivity of the gap on the control lines during the sample design stage. With a tuning range of several gigahertz on a qubit dynamics timescale, we observe coherent system dynamics at the degeneracy point.
Magnetic hedgehog-like nanostructures
Authors: Brombacher C. , Falke M. , Springer F. , Rohrmann H. , Goncharov A. , Schrefl T. , Bleloch A. , Albrecht M.
Published: September 2010

Granular CoCrPt–SiO2 films with perpendicular magnetic anisotropy were deposited onto arrays of SiO2 nanoparticles with diameters down to 10 nm. Columnar CoCrPt grains with their c-axis pointing perpendicular to the particle surface were formed, creating a unique hedgehog-like cap structure. This peculiar structure induced by the curvature of the particles substantially modifies the magnetic properties. Underneath the CoCrPt pillars a continuous Co-rich layer was observed, which gives rise to enhanced intergranular exchange coupling resulting in single domain states. The temperature dependence of the coercivity and the angular dependence of the switching field were extracted and correlated with the microstructure.
Strain effects on hydrogen storage capability of metal-decorated graphene: A first-principles study
Authors: Zhou Miao , Lu Yunhao , Zhang Chun , Feng Yuan Ping
Published: September 2010

We report an investigation on strain-engineered adsorption of metal atoms on graphene and hydrogen storage capabilities of metal-decorated graphene by using first-principles approach based on density functional theory. We show that an applied strain not only stabilizes the supported metal atoms and prevents them from clustering but further increases the hydrogen storage capacity. Specifically, a tensile strain of 10% in graphene increases the adsorption energy of Li (Ti) atom by around 75% (71%) and the gravimetric density of hydrogen storage up to 15.4 wt % (9.5 wt %), with a binding energy of ∼0.2 eV/H2.
Comparison of bond scission sequence of methanol on tungsten monocarbide and Pt-modified tungsten monocarbide
Authors: Stottlemyer Alan Lee , Liu Ping , Chen Jingguang G.
Published: September 2010

The ability to control the bond scission sequence of OH, CH, and CO bonds is of critical importance in the effective utilization of oxygenate molecules, such as in reforming reactions and in alcohol fuel cells. In the current study, we use methanol as a probe molecule to demonstrate the possibility to control the decomposition pathways by supporting monolayer coverage of Pt on a tungsten monocarbide (WC) surface. Density functional theory (DFT) results reveal that on the WC and Pt/WC surfaces CH3OH decomposes via OH bond scission to form the methoxy (C∗H3 O) intermediate. The subsequent decomposition of methoxy on the WC surface occurs through the CO bond scission to form C∗H3, which reacts with surface H∗ to produce CH4. In contrast, the decomposition of methoxy on the Pt/WC surface favors the CH bond scission to produce C∗H2 O, which prevents the formation of the C∗H3 species and leads to the formation of a C∗O intermediate through subsequent deprotonation steps. The DFT predictions are validated using temperature programmed desorption to quantify the gas-phase product yields and high resolution electron energy loss spectroscopy to determine the surface intermediates from methanol decomposition on Pt, WC, and Pt/WC surfaces.
Lead-free piezoelectric (K0.5Na0.5)NbO3 thin films derived from chemical solution modified with stabilizing agents
Authors: Goh Phoi Chin , Yao Kui , Chen Zhong
Published: September 2010

( K 0.5 Na 0.5 ) NbO 3 (KNN)-based ferroelectric thin films were prepared by a chemical solution approach modified with both diethanolamine (DEA) and ethylenediaminetetraacetic acid (EDTA) as the stabilizing agents. The obtained KNN thin films exhibited a remarkably low leakage current and well-saturated polarization hysteresis loop. The effective piezoelectric strain coefficient d33 and voltage coefficient g33 under the clamping of the substrate were improved to 74.0 pm/V and 28.3 mm V/N, respectively. The reason for the superior properties was found that the addition of EDTA and DEA was effective in suppressing the volatilization of K and Na at moderate temperature before the crystallization.
Modeling the diode characteristics of boron nitride/silicon carbide heterojunctions
Authors: Brötzmann Marc , Gehrke Hans-Gregor , Vetter Ulrich , Hofsäss Hans
Published: September 2010

In this work, we investigate metal–amorphous semiconductor–semiconductor diodes made up of boron nitride/silicon carbide (BN/SiC) heterojunctions. We show that a general conduction model can be applied to this system to explain the measured current-voltage diode characteristics. The conduction model is based on a serial arrangement of a voltage dependent Frenkel–Poole resistance and an ideal Schottky diode. This model is refined to reflect the presence of an amorphous interface layer with thicknesses of about 7(2) nm between BN films and SiC substrates obtained from high resolution cross-section transmission electron microscopy measurements. We demonstrate that this results in an extended Frenkel–Poole and ideal diode model leading to an almost perfect agreement with the measured I-V characteristics of BN/SiC heterojunctions.
Ion wake effects on the Coulomb ion drag in complex dusty plasmas
Authors: Ki Dae-Han , Jung Young-Dae
Published: September 2010

The ion wake effects on the Coulomb drag force are investigated in complex dusty plasmas. It is shown that the ion wake effects significantly enhance the Coulomb ion drag force. It is also found that the ion wake effects on the Coulomb drag force increase with an increase in the Debye length. In addition, the ion wake effects on the momentum transfer cross section and Coulomb drag force are found to be increased with increasing thermal Mach number, i.e., decreasing plasma temperature. It is also found that the Coulomb ion drag force would be stronger for smaller dust grains.
Two-dimensional domain switching induced tensile fracture in a crack-free lead titanate zirconate ceramics under orthogonal electromechanical loading
Authors: Li Y. W. , Li F. X.
Published: September 2010

Domain switching in a soft lead titanate zirconate ceramics were investigated under orthogonal compression and electric loading. It is found when compression is higher than 200 MPa, both the polarization curve and strain curves indicate domain switching is nearly two-dimensional (2D) within planes perpendicular to the compressive direction. While as the compression reaches 350 MPa and the electric field reverses to negative coercive value, intergranular fracture occurs in the crack-free specimen along the midplane perpendicular to the electric field. This unusual fracture mode is attributed to the internal tensile stress caused by constrained 2D domain switching under orthogonal electromechanical loading.
Preconditioning immobilized imidazole arrays for optimal proton-transfer feasibility
Authors: Cavalcanti W. L. , Portaluppi D. F. , Joswig J.-O.
Published: September 2010

Classical molecular dynamics have been carried out in order to study the proton-transfer feasibility in immobilized imidazole arrays, taking into account their applications in new polymer electrolyte membrane fuel cells. The resulting trajectories have been analyzed with respect to the ability of forming hydrogen bonds, considering the angle distribution between the proton donor and acceptor groups. The dependence of the hydrogen-bond network is studied with respect to the variations of temperature, density of imidazole groups, and spacer lengths. According to the results, arrays of alkyl-imidazole molecules with three mobile CH2 groups are the most favorable to a proton-transfer reaction. Regarding the alkyl-imidazole density, no significant difference for the arrays with a spacing of 6 or 7 Å between the alkyl-imidazole molecules could be observed, whereas the 10 Å array presents a lower probability of a proton transfer. The optimal arrangement of the investigated systems is a spacing of 6 Å and a flexible chain length of three CH2 groups. These results confirm previous experimental and simulation analyses.
The Commensal Real-Time ASKAP Fast-Transients (CRAFT) Survey
Authors: Macquart Jean-Pierre , Bailes M. , Bhat N. D. R. , Bower G. C. , Bunton J. D. , Chatterjee S. , Colegate T. , Cordes J. M. , D'Addario L. , Deller A. , Dodson R. , Fender R. , Haines K. , Hall P. , Harris C. , Hotan A. , Johnston S. , Jones D. L. , Keith M. , Koay J. Y. , Lazio T. J. W. , Majid W. , Murphy T. , Navarro R. , Phillips C. , Quinn P. , Preston R. A. , Stansby B. , Stairs I. , Stappers B. , Staveley-Smith L. , Tingay S. , Thompson D. , van Straten W. , Wagstaff K. , Warren M. , Wayth R. , Wen L. ,   The CRAFT Collaboration
Published: September 2010

We are developing a purely commensal survey experiment for fast (<5 s) transient radio sources. Short-timescale transients are associated with the most energetic and brightest single events in the Universe. Our objective is to cover the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view. Fast timescale transients open new vistas on the physics of high brightness temperature emission, extreme states of matter and the physics of strong gravitational fields. In addition, the detection of extragalactic objects affords us an entirely new and extremely sensitive probe on the huge reservoir of baryons present in the IGM. We outline here our approach to the considerable challenge involved in detecting fast transients, particularly the development of hardware fast enough to dedisperse and search the ASKAP data stream at or near real-time rates. Through CRAFT, ASKAP will provide the testbed of many of the key technologies and survey modes proposed for high time resolution science with the SKA.
Evaluation of protein adsorption and preferred binding regions in multimodal chromatography using NMR
Authors: Chung Wai Keen , Freed Alexander S. , Holstein Melissa A. , McCallum Scott A. , Cramer Steven M.
Published: September 2010

NMR titration experiments with labeled human ubiquitin were employed in concert with chromatographic data obtained with a library of ubiquitin mutants to study the nature of protein adsorption in multimodal (MM) chromatography. The elution order of the mutants on the MM resin was significantly different from that obtained by ion-exchange chromatography. Further, the chromatographic results with the protein library indicated that mutations in a defined region induced greater changes in protein affinity to the solid support. Chemical shift mapping and determination of dissociation constants from NMR titration experiments with the MM ligand and isotopically enriched ubiquitin were used to determine and rank the relative binding affinities of interaction sites on the protein surface. The results with NMR confirmed that the protein possessed a distinct preferred binding region for the MM ligand in agreement with the chromatographic results. Finally, coarse-grained ligand docking simulations were employed to study the modes of interaction between the MM ligand and ubiquitin. The use of NMR titration experiments in concert with chromatographic data obtained with protein libraries represents a previously undescribed approach for elucidating the structural basis of protein binding affinity in MM chromatographic systems.
Deletion of the Cel48S cellulase from
Clostridium thermocellum
Authors: Olson Daniel G. , Tripathi Shital A. , Giannone Richard J. , Lo Jonathan , Caiazza Nicky C. , Hogsett David A. , Hettich Robert L. , Guss Adam M. , Dubrovsky Genia , Lynd Lee R.
Published: September 2010

Clostridium thermocellum
is a thermophilic anaerobic bacterium that rapidly solubilizes cellulose with the aid of a multienzyme cellulosome complex. Creation of knockout mutants for Cel48S (also known as CelS, S
S
, and S8), the most abundant cellulosome subunit, was undertaken to gain insight into its role in enzymatic and microbial cellulose solubilization. Cultures of the Cel48S deletion mutant (S mutant) were able to completely solubilize 10 g/L crystalline cellulose. The cellulose hydrolysis rate of the S mutant strain was 60% lower than the parent strain, with the S mutant strain also exhibiting a 40% reduction in cell yield. The cellulosome produced by the S mutant strain was purified by affinity digestion, characterized enzymatically, and found to have a 35% lower specific activity on Avicel. The composition of the purified cellulosome was analyzed by tandem mass spectrometry with APEX quantification and no significant changes in abundance were observed in any of the major (>1% of cellulosomal protein) enzymatic subunits. Although most cellulolytic bacteria have one family 48 cellulase,
C. thermocellum
has two, Cel48S and Cel48Y. Cellulose solubilization by a Cel48S and Cel48Y double knockout was essentially the same as that of the Cel48S single knockout. Our results indicate that solubilization of crystalline cellulose by
C. thermocellum
can proceed to completion without expression of a family 48 cellulase.
MHC class I molecules are present both pre- and postsynaptically in the visual cortex during postnatal development and in adulthood
Authors: Needleman Leigh A. , Liu Xiao-Bo , El-Sabeawy Faten , Jones Edward G. , McAllister A. Kimberley
Published: September 2010

Immune molecules have been discovered recently to play critical roles in the development, function, and plasticity of the cerebral cortex. MHC class I (MHCI) molecules are expressed in the central nervous system and regulate activity-dependent refinement of visual projections during late postnatal development. They have also been implicated in neurodevelopmental diseases such as schizophrenia and autism. Despite the excitement generated by these unique roles for immune proteins in the brain, little is known about how these molecules regulate cortical connections. The first step toward elucidating the mechanism is to identify the spatial and temporal distribution of MHCI proteins throughout development. Using a pan-specific antibody that recognizes many MHCI variants for biochemistry and immunohistochemistry, we found that MHCI proteins are expressed in the rat visual cortex at all ages examined—during the peak of synaptogenesis, the critical period of synaptic refinement, and adulthood. Their abundance in the cortex peaked during early postnatal development, declining during periods of plasticity and adulthood. In contrast to current assumptions, pre- and postembedding immunogold electron microscopy (EM) revealed that MHCI proteins were present both pre- and postsynaptically at all ages examined. They were often found in the postsynaptic density and were closely associated with synaptic vesicles in the presynaptic terminal. These results suggest a previously undescribed model in which MHCI molecules function on both sides of the synapse to regulate connectivity in the mammalian visual cortex before, during, and after the establishment of connections.