bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Unsteady Flow Characteristics in a High Pressure Turbine Cascade Based on a High-Order Large Eddy Simulation Turbulence Model
Authors: Jimbo Tomohiko , Biswas Debasish , Niizeki Yoshiki
Published: May 2012

In the present paper, unsteady viscous flow analysis around turbine blade cascade using a high-order LES turbulence model is carried out to investigate the basic physical process involved in the pressure loss mechanism. This numerical analysis is assessed to the wind tunnel cascade test. Basically, all the physical phenomena occurring in nature are the effect of some cause, and the effect can somehow be measured. However, to understand the cause, detail information regarding the visualization of the phenomena, which are difficult to measure, are necessary. Therefore, in the present paper, firstly the computed results are compared with the measured data, which are the final outcome of the cause (of the phenomena under investigation), to verify whether our physics-based model could qualitatively predict the measured facts or not. It was found that the present model could well predict measured data. Therefore, the rest of the computed information, which were difficult to measure, were used to visualize the overall flow behavior for acquiring some knowledge of the physical process associated with the pressure loss mechanism. The present study led to an understanding that the interaction of the vortex generated on the suction and pressure surface of the blade and the secondary vortex generated on the end wall, downstream of the trailing edge, resulted in the formation of a large vortex structure in this region. This unsteady three-dimensional flow characteristic is expected to play an important role in the pressure loss mechanism.
Showerhead Film Cooling Performance of a Turbine Vane at High Freestream Turbulence in a Transonic Cascade
Authors: Nasir Shakeel , Bolchoz Trey , Ng Wing-Fai , Zhang Luzeng J. , Koo Moon Hee , Anthony Richard J.
Published: May 2012

This paper experimentally investigates the effect of blowing ratio and exit Reynolds number/Mach number on the film cooling performance of a showerhead film cooled first stage turbine vane. The vane midspan was instrumented with single-sided platinum thin film gauges to experimentally characterize the Nusselt number and film cooling effectiveness distributions over the surface. The vane was arranged in a two-dimensional, linear cascade in a heated, transonic, blow-down wind tunnel. Three different exit Mach numbers of Mex = 0.57, 0.76 and 1.0—corresponding to exit Reynolds numbers based on vane chord of 9.7 × 105, 1.1 × 106 and 1.5 × 106, respectively—were tested with an inlet free stream turbulence intensity (Tu) of 16% and an integral length scale normalized by vane pitch (Λx/P) of 0.23. A showerhead cooling scheme with five rows of cooling holes was tested at blowing ratios of BR = 0, 1.5, 2.0, and 2.5 and a density ratio of DR = 1.3. Nusselt number and adiabatic film cooling effectiveness distributions were presented on the vane surface over a range of s/C = −0.58 on the pressure side to s/C = 0.72 on the suction side of the vane. The primary effects of coolant injection were to augment the Nusselt number and reduce the adiabatic wall temperature downstream of the injection on the vane surface as compared to no film injection case (BR = 0) at all exit Mach number conditions. In general, an increase in blowing ratio (BR = 1.5 to 2.5) showed noticeable Nusselt number augmentation on pressure surface as compared to suction surface at exit Mach 0.57 and 0.75; however, the Nusselt number augmentation for these blowing ratios was found to be negligible on the vane surface for exit Mach 1.0 case. At exit Mach 1.0, an increase in blowing ratio (BR = 1.5 to 2.5) was observed to have an adverse effect on the adiabatic effectiveness on the pressure surface but had negligible effect on suction surface. The effectiveness trend on the suction surface was also found to be influenced by a favorable pressure gradient due to Mach number and boundary layer transition in the region s/C = 0.28 to s/C = 0.45 at all blowing ratio and exit Mach number conditions. An increase in Reynolds number from exit Mach 0.76 to 1.0 increased heat transfer levels on the vane surface at all blowing ratio conditions. A large increase in Reynolds number adversely affected adiabatic effectiveness on the pressure surface at all blowing ratio conditions. On the suction surface, a large increase in Reynolds number also affected adiabatic effectiveness in the favorable pressure gradient and boundary layer transition region.
Stretching Affects Intracellular Oxygen Levels: Three-Dimensional Multiphysics Studies
Authors: Leopold Efrat , Gefen Amit
Published: May 2012

Multiphysics modeling is an emerging approach in cellular bioengineering research, used for simulating complex biophysical interactions and their effects on cell viability and function. Our goal in the present study was to integrate cell-specific finite element modeling—which we have developed in previous research to simulate deformation of individual cells subjected to external loading—with oxygen transport in the deformed cells at normoxic and hypoxic environments. We specifically studied individual and combined effects of substrate stretch levels, O2 concentration in the culture media, and temperature of the culture media on intracellular O2 levels in cultured myoblasts, in models of two individual cells. We found that (i) O2 transport became faster with the increasing levels of substrate stretch (ranging from 0 to 24%), and (ii) the effect of a 3  °C temperature drop on slowing down the O2 transport was milder with respect to the effect that strains had. The changes in cell geometry due to externally applied deformations could, hence, theoretically affect cell respiration, which should be a consideration in cellular mechanics experiments.
A simplified approach to characterizing a kilovoltage source spectrum for accurate dose computation
Authors: Poirier Yannick , Kouznetsov Alexei , Tambasco Mauro
Published: May 2012

Purpose:

To investigate and validate the clinical feasibility of using half‐value layer (HVL) and peak tube potential (kVp) for characterizing a kilovoltage (kV) source spectrum for the purpose of computing kV x‐ray dose accrued from imaging procedures. To use this approach to characterize a Varian® On‐Board Imager® (OBI) source and perform experimental validation of a novel in‐house hybrid dose computation algorithm for kV x‐rays.

Methods:

We characterized the spectrum of an imaging kV x‐ray source using the HVL and the kVp as the sole beam quality identifiers using third‐party freeware Spektr to generate the spectra. We studied the sensitivity of our dose computation algorithm to uncertainties in the beam's HVL and kVp by systematically varying these spectral parameters. To validate our approach experimentally, we characterized the spectrum of a Varian® OBI system by measuring the HVL using a Farmer‐type Capintec ion chamber (0.06 cc) in air and compared dose calculations using our computationally validated in‐house kV dose calculation code to measured percent depth‐dose and transverse dose profiles for 80, 100, and 125 kVp open beams in a homogeneous phantom and a heterogeneous phantom comprising tissue, lung, and bone equivalent materials.

Results:

The sensitivity analysis of the beam quality parameters (i.e., HVL, kVp, and field size) on dose computation accuracy shows that typical measurement uncertainties in the HVL and kVp (±0.2 mm Al and ±2 kVp, respectively) source characterization parameters lead to dose computation errors of less than 2%. Furthermore, for an open beam with no added filtration, HVL variations affect dose computation accuracy by less than 1% for a 125 kVp beam when field size is varied from 5 × 5 cm2 to 40 × 40 cm2. The central axis depth dose calculations and experimental measurements for the 80, 100, and 125 kVp energies agreed within 2% for the homogeneous and heterogeneous block phantoms, and agreement for the transverse dose profiles was within 6%.

Conclusions:

The HVL and kVp are sufficient for characterizing a kV x‐ray source spectrum for accurate dose computation. As these parameters can be easily and accurately measured, they provide for a clinically feasible approach to characterizing a kV energy spectrum to be used for patient specific x‐ray dose computations. Furthermore, these results provide experimental validation of our novel hybrid dose computation algorithm.
On using 3D γ‐analysis for IMRT and VMAT pretreatment plan QA
Authors: Wu Chuan , Hosier Kelly E. , Beck Kristen E. , Radevic Marlyn B. , Lehmann Joerg , Zhang Hao H. , Kroner Aaron , Dutton Sharon C. , Rosenthal Seth A. , Bareng Jonathan K. , Logsdon Mark D. , Asche David R.
Published: May 2012

Purpose:

To investigate using 3D γ analysis for IMRT and VMAT QA.

Methods:

We explored and studied 3D γ‐analysis by comparing TPS computed and EPID back‐projection reconstructed doses in patient's CT images. Two 3D γ quantities, γPTV and γ10, were proposed and studied for evaluating the QA results, and compared to 2D γ (MapCheck composite: γMC).

Results:

It was found that when 3%(global)/3 mm criteria was used, all IMRT and 90% of VMAT plans passed QA with a γ pass rate ≥90%. A significant statistical correlation was observed between 3D and 2D γ‐analysis results for IMRT QA if γ10 and γMC are concerned, but no significant relation is found between γPTV and γMC.

Conclusions:

3D γ analysis based on EPID dose back‐projection may provide a feasible tool for IMRT and VMAT pretreatment plan QA.
Regulated Virulence Controls the Ability of a Pathogen to Compete with the Gut Microbiota
Authors: Kamada Nobuhiko , Kim Yun-Gi , Sham Ho Pan , Vallance Bruce A. , Puente José L. , Martens Eric C. , Núñez Gabriel
Published: May 2012

Establishing an Enteric Infection

Complex and highly regulated interactions are required to keep the peace between the bacteria that reside in our gut and the immune system. How do pathogenic bacteria, such as the strains of
Escherichia coli
that cause gastroenteritis, get a foothold to establish an infection, and what is the role of resident bacteria in this process?

Kamada
et al.

(p.
1325
, published online 10 May; see the Perspective by

Sperandio

) infected mice orally with
Citrobacter rodentium
and found that mice with normal commensal microflora, which were better able to contain the infection than mice that lacked the commensals, which were not able to clear the infection.
Evidence of Things Not Seen
Authors: Murray Norman W.
Published: May 2012

The Kepler space telescope can determine the mass and orbital period of unseen planets orbiting distant stars.
Draft Genome Sequence of a Sphingomonas sp., an Endosymbiotic Bacterium Isolated from an Arctic Lichen Umbilicaria sp
Authors: Lee Jungeun , Shin Seung Chul , Kim Su Jin , Kim Bum-Keun , Hong Soon Gyu , Kim Eun Hye , Park Hyun , Lee Hyoungseok
Published: May 2012

Sphingomonas
sp. strain PAMC 26617 has been isolated from an Arctic lichen
Umbilicaria
sp. on the Svalbard Islands. Here we present the draft genome sequence of this strain, which represents a valuable resource for understanding the symbiotic mechanisms between endosymbiotic bacteria and lichens surviving in extreme environments.
Genome Sequence of Klebsiella oxytoca 11492-1, a Nosocomial Isolate Possessing a FOX-5 AmpC β-Lactamase
Authors: Hazen Tracy H. , Robinson Gwen L. , Harris Anthony D. , Rasko David A. , Johnson J. Kristie
Published: May 2012

Klebsiella oxytoca
strain 11492-1 was isolated from a perianal swab culture from a patient at the University of Maryland Medical Center in 2005. The
K. oxytoca
11492-1 draft genome contains multiple antibiotic resistance genes, including a FOX-5 AmpC β-lactamase encoded on a large IncA/C plasmid.
Complete Genome Sequence of Melissococcus plutonius DAT561, a Strain That Shows an Unusual Growth Profile and Is Representative of an Endemic Cluster in Japan
Authors: Okumura Kayo , Arai Rie , Okura Masatoshi , Kirikae Teruo , Takamatsu Daisuke , Osaki Makoto , Miyoshi-Akiyama Tohru
Published: May 2012

We report the complete genome sequence of
Melissococcus plutonius
DAT561, which is a causative agent of European foulbrood.
M. plutonius
DAT561 is a representative of nonfastidious strains isolated in Japan. The addition of potassium phosphate was not required for normal growth, unlike for typical
M. plutonius
strain/isolates.
Validity of self-reported prevalent cases of stroke and acute myocardial infarction in the Spanish cohort of the EPIC study
Authors: Machón Monica , Arriola Larraitz , Larrañaga Nerea , Amiano Pilar , Moreno-Iribas Concepción , Agudo Antonio , Ardanaz Eva , Barricarte Aurelio , Buckland Genevieve , Chirlaque MªDolores , Gavrila Diana , Huerta José María , Martínez Carmen , Molina Esther , Navarro Carmen , Quiros José Ramón , Rodríguez Laudina , Sanchez María José , González Carlos Alberto , Dorronsoro Miren
Published: May 2012

Background

Information on the validity of self-reported cases of stroke and acute myocardial infarction (AMI) is varied. The aim of this study was to assess the validity and agreement of self-reported prevalent cases of stroke and AMI in the Spanish cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC).

Methods

At recruitment, 1992–1996, and in the follow-up (3 years after recruitment), each participant in the Spanish EPIC cohort (15 630 men and 25 808 women) was asked if a doctor had ever said that they had had a stroke or AMI, and the results were compared with information available in medical records. Validity of self-reported prevalent cases of stroke and AMI was examined by calculating sensitivity, specificity, positive predictive values and κ statistics.

Results

The sensitivity of self-reported prevalent cases of stroke was 81.3% and that for AMI was 97.7%. The positive predictive value was 22.2% and 60.7% for stroke and AMI, respectively, whereas specificity was very high (>99%) for both diseases. The agreement between self-report questionnaire results and medical records was substantial (κ=0.75) for AMI but not for stroke (κ=0.35).

Conclusion

Self-reported information on stroke and AMI included in the EPIC questionnaire is a valid instrument for the assessment of AMI disease but should be used with caution in stroke.
Using natural experiments to evaluate population health interventions: new Medical Research Council guidance
Authors: Craig Peter , Cooper Cyrus , Gunnell David , Haw Sally , Lawson Kenny , Macintyre Sally , Ogilvie David , Petticrew Mark , Reeves Barney , Sutton Matt , Thompson Simon
Published: May 2012

Natural experimental studies are often recommended as a way of understanding the health impact of policies and other large scale interventions. Although they have certain advantages over planned experiments, and may be the only option when it is impossible to manipulate exposure to the intervention, natural experimental studies are more susceptible to bias. This paper introduces new guidance from the Medical Research Council to help researchers and users, funders and publishers of research evidence make the best use of natural experimental approaches to evaluating population health interventions. The guidance emphasises that natural experiments can provide convincing evidence of impact even when effects are small or take time to appear. However, a good understanding is needed of the process determining exposure to the intervention, and careful choice and combination of methods, testing of assumptions and transparent reporting is vital. More could be learnt from natural experiments in future as experience of promising but lesser used methods accumulates.
Whole exome sequencing identifies a splicing mutation in NSUN2 as a cause of a Dubowitz-like syndrome
Authors: Martinez Fernando Jose , Lee Jeong Ho , Lee Ji Eun , Blanco Sandra , Nickerson Elizabeth , Gabriel Stacey , Frye Michaela , Al-Gazali Lihadh , Gleeson Joseph G
Published: May 2012

Background

Dubowitz syndrome (DS) is an autosomal recessive disorder characterized by the constellation of mild microcephaly, growth and mental retardation, eczema and peculiar facies. Over 140 cases have been reported, but the genetic basis is not understood.

Methods

We enrolled a multiplex consanguineous family from the United Arab Emirates with many of the key clinical features of DS as reported in previous series. The family was analyzed by whole exome sequencing. RNA splicing was evaluated with reverse-transcriptase PCR, immunostaining and western blotting was performed with specific antibodies, and site-specific cytosine-5-methylation was studied with bisulfite sequencing.

Results

We identified a homozygous splice mutation in the NSUN2 gene, encoding a conserved RNA methyltransferase. The mutation abolished the canonical splice acceptor site of exon 6, leading to use of a cryptic splice donor within an AluY and subsequent mRNA instability. Patient cells lacked NSUN2 protein and there was resultant loss of site-specific 5-cytosine methylation of the tRNA(Asp GTC) at C47 and C48, known NSUN2 targets.

Conclusion

Our findings establish NSUN2 as the first causal gene with relationship to the DS spectrum phenotype. NSUN2 has been implicated in Myc-induced cell proliferation and mitotic spindle stability, which might help explain the varied clinical presentation in DS that can include chromosomal instability and immunological defects.
Simulated diagnostic cerebral angiography in neurosurgical training: a pilot program
Authors: Spiotta Alejandro M , Rasmussen Peter A , Masaryk Thomas J , Benzel Edward C , Schlenk Richard
Published: May 2012

Introduction

Surgical simulation provides a zero-risk setting in which technical skills can be obtained through repetition. The feasibility and utility of simulated diagnostic cerebral angiography among neurosurgical residents and fellows was studied using an endovascular biplane angiography simulator.

Methods

Ten neurosurgical residents and four endovascular neurosurgery fellows were recruited into a standardized training protocol consisting of a didactic, demonstration and hands-on learning environment using the Simbionix simulator. Participants were instructed to catheterize the right internal carotid artery, left internal carotid artery and left vertebral artery. The task was repeated five times.

Results

All participants demonstrated improvement over the five trials. Residents performed actions that were perceived as potentially dangerous (n=8) while fellows performed the procedure with superior technique. Residents performed the task with an initial total procedure and fluoroscopy time of 6.6±4.3 min and 4.9±3.7 min, respectively, and improved on the fifth trial to 3.4±1.3 min (p=0.03) and 2.3±0.78 min (p=0.004), respectively. Residents approximated the efficiency of fellows for the third and fourth trial.

Conclusions

Incorporating an endovascular simulator is feasible for training purposes in a neurosurgical residency program. This study provides objective documentation of the facilitation of technical angiography skill acquisition by the use of simulation technology.
ON MODAL μ-CALCULUS OVER FINITE GRAPHS WITH SMALL COMPONENTS OR SMALL TREE WIDTH
Authors: D'AGOSTINO GIOVANNA , LENZI GIACOMO
Published: May 2012

This paper is a continuation and correction of a paper presented by the same authors at the conference GANDALF 2010. We consider the Modal μ-calculus and some fragments of it. For every positive integer k we consider the class SCCk of all finite graphs whose strongly connected components have size at most k, and the class TWk of all finite graphs of tree width at most k. As upper bounds, we show that for every k, the temporal logic CTL* collapses to alternation free μ-calculus in SCCk; and in TW1, the winning condition for parity games of any index n belongs to the level Δ2 of Modal μ-calculus. As lower bounds, we show that Büchi automata are not closed under complement in TW2 and coBüchi nondeterministic and alternating automata differ in TW1.
PLAYING MULLER GAMES IN A HURRY
Authors: FEARNLEY JOHN , ZIMMERMANN MARTIN
Published: May 2012

This work considers a finite-duration variant of Muller games, and their connection to infinite-duration Muller games. In particular, it studies the question of how long a finite-duration Muller game must be played before the winner of the finite-duration game is guaranteed to be able to win the corresponding infinite-duration game. Previous work by McNaughton has shown that this must occur after [Formula: see text] moves, and the reduction from Muller games to parity games gives a bound of n · n! + 1 moves. We improve upon both of these results, by giving a bound of 3nmoves.
TWO LOCAL STRATEGY ITERATION SCHEMES FOR PARITY GAME SOLVING
Authors: FRIEDMANN OLIVER , LANGE MARTIN
Published: May 2012

The problem of solving a parity game is at the core of many problems in model checking, satisfiability checking and program synthesis. Some of the best algorithms for solving parity game are strategy iteration algorithms. These are global in nature since they require the entire parity game to be present at the beginning. This is a distinct disadvantage because in many applications one only needs to know which winning region a particular node belongs to, and a witnessing winning strategy may cover only a fractional part of the entire game graph.

We present two local strategy iteration algorithms which explore the game graph on-the-fly whilst performing the improvement steps. We also compare them empirically with existing global strategy iteration algorithms and the currently only other local algorithm for solving parity games. It turns out that local strategy iteration can outperform these others significantly.
IMPROVED RELATED-KEY RECTANGLE ATTACK ON THE FULL HAS-160 ENCRYPTION MODE
Authors: WEI YUECHUAN , LI CHAO , CAO DAN
Published: May 2012

HAS-160, a Korean hash standard, has been widely used in the Korean industry. This paper aims to re-evaluate the security of HAS-160 in the encryption mode, a block cipher with the 512-bit key size and the 160-bit plaintext block size. A previous attack is based on a 71-round related-key distinguisher with probability 2-304. Using some delicate properties of HAS-160 and employing a bit-fixing technique, we present a 72-round related-key rectangle distinguisher with probability 2-290in this paper. Based on this new distinguisher, two key recovery attacks on the encryption mode of the full 80-round HAS-160 are performed, which improve the earlier results. The attacks presented in this paper are the best known results on HAS-160 in the encryption mode in terms of the number of attack rounds and the efficiency of attacks.
COHERENT STATE FUNCTIONAL INTEGRAL IN LOOP QUANTUM COSMOLOGY: ALTERNATIVE DYNAMICS
Authors: QIN LI , MA YONGGE
Published: May 2012

Coherent state functional integral for the minisuperspace model of loop quantum cosmology is studied. By the well-established canonical theory, the transition amplitude in the path integral representation of loop quantum cosmology with alternative dynamics can be formulated through group averaging. The effective action and Hamiltonian with higher-order quantum corrections are thus obtained. It turns out that for a nonsymmetric Hamiltonian constraint operator, the Moyal (star)-product emerges naturally in the effective Hamiltonian. For the corresponding symmetric Hamiltonian operator, the resulted effective theory implies a possible quantum cosmological effect in large scale limit in the alternative dynamical scenario, which coincides with the result in canonical approach. Moreover, the first-order modified Friedmann equation still contains the particular information of alternative dynamics and hence admits the possible phenomenological distinction between the different proposals of quantum dynamics.
NEUTRON ENRICHMENT OF THE NECK-ORIGINATED INTERMEDIATE MASS FRAGMENTS IN PREDICTIONS OF THE QMD MODEL
Authors: SKWIRA-CHALOT I. , CAP T. , SIWEK-WILCZYŃSKA K. , WILCZYŃSKI J.
Published: May 2012

The effect of neutron enrichment of the neck formed during reseparation of two colliding nuclei was studied with the aim to infer an information on the density dependence of the asymmetry energy term in the equation of state. By using a version of the QMD model of Łukasik it is shown that the neutrons-to-protons ratio of the intermediate mass fragments (IMF) emitted from the neck, 〈N/Z〉, is not a sufficiently sensitive observable to discriminate between different assumptions regarding the symmetry term of the equation of state. As an alternative, isotopic ratios of selected pairs of isotopes turned out to be useful observables more sensitive to the assumed form of the symmetry term of the equation of state. A comparison with experimental data on isotopic ratios for beryllium and boron IMFs from the 124 Sn + 64 Ni reaction at 35 MeV/nucleon tentatively suggests that the ASY-SOFT option of the symmetry energy term in EOS is preferred.
MACROECONOMICS AND SOVEREIGN RISK RATINGS
Authors: CANUTO OTAVIANO , DOS SANTOS PABLO F. PEREIRA , DE SÁ PORTO PAULO C.
Published: May 2012

The objective of this paper is to analyze the concept and determinants of "sovereign risk" and the role of the credit risk rating agencies which serve internationally as the main reference instruments employed by economic agents to assess this risk. The paper also tries to identify macroeconomic variables which could be associated with sovereign risk ratings awarded by rating agencies to each country. After examining the indicators on an individual basis, their potential as a group is tested econometrically as a determinant of the class of sovereign risk into which national economies fall. Our results constitute a set of indicators which emerging economies would be well advised to improve upon.
NUMERICAL INVESTIGATION OF FIVE-DIMENSIONAL GRAVITATIONAL COLLAPSES
Authors: SHINKAI HISA-AKI , YAMADA YUTA
Published: May 2012

We introduce our numerical studies of gravitational collapses in five-dimensional (5D) space-time, with a purpose of studying the cosmic censorship hypothesis and the hoop conjecture. The first model is the collapse of spindle matter which was performed by Shapiro and Teukolsky (1991) who announced an appearance of a naked singularity in 4D. Comparing with 4D cases, we found that 5D collapses proceed more rapidly, the final configurations tend to be spherical, and apparent horizon (AH) forms in wider parameter ranges. We also observed positive evidence for formation of a naked singularity in highly spindle cases as well. The second model is the formation of black-ring in 5D. Our code does not include angular momentum, but the model would be helpful for basic understandings. We constructed an initial data sequence with ring-shaped matter, and observed the topology of AHs, if formed. We found a critical ring radius for ring-shaped AH, and it suggests a dynamical transition of AH topology from ring-shaped to spherical. We demonstrate such an example in time evolution.
CAN TORSION BE TREATED AS JUST ANOTHER TENSOR FIELD?
Authors: NESTER JAMES M. , WANG CHIH-HUNG
Published: May 2012

Many alternative gravity theories use an independent connection which leads to torsion in addition to curvature. Some have argued that there is no physical need to use such connections, that one can always use the Levi-Civita connection and just treat torsion as another tensor field. We explore this issue here in the context of the Poincaré Gauge theory of gravity, which is usually formulated in terms of an affine connection for a Riemann-Cartan geometry (torsion and curvature). We compare the equations obtained by taking as the independent dynamical variables: (i) the orthonormal coframe and the connection and (ii) the orthonormal coframe and the torsion (contortion), and we also consider the coupling to a source. From this analysis we conclude that, at least for this class of theories, torsion should not be considered as just another tensor field.
FINITE TEMPERATURE CASIMIR EFFECT FOR PERFECTLY CONDUCTING PARALLEL PLATES IN (D + 1)-DIMENSIONAL SPACETIME
Authors: ZHAI XIANG-HUA , YANG YANG , LAI JIE
Published: May 2012

We study the finite temperature Casimir effect between perfectly conducting parallel plates in (D + 1)-dimensional spacetime by using zeta-function regularization technique. We get the analytical results for Casimir energy, Casimir free energy, Casimir entropy and Casimir pressure expressed by Riemann zeta function and Bessel function and give the asymptotic expressions for low and high temperature limits. In the case of D = 3, through mathematic transformation, we reproduce the standard results in the literature which is in most times obtained by using Green's function regularization technique.
MULTI-PUNCTURE INITIAL DATA IN NUMERICAL RELATIVITY
Authors: LIN CHUN-YU , CAO ZHOUJIAN , YO HWEI-JANG
Published: May 2012

We present a spectral multi-puncture initial data solver based on the LORENE library http://www.lorene.obspm.fr/ . The solver generates multi black holes initial data with arbitrary linear momentum and spin within a moderate computational resource. The local convergence test shows that the solution rapidly converged to a high precision.
THE ABSOLUTE POSITIVE PARTIAL TRANSPOSE PROPERTY FOR RANDOM INDUCED STATES
Authors: COLLINS BENOIT , NECHITA ION , YE DEPING
Published: May 2012

In this paper, we first obtain an algebraic formula for the moments of a centered Wishart matrix, and apply it to obtain new convergence results in the large dimension limit when both parameters of the distribution tend to infinity at different speeds.

We use this result to investigate APPT (absolute positive partial transpose) quantum states. We show that the threshold for a bipartite random induced state on Cd = Cd1 ⊗ Cd2, obtained by partial tracing a random pure state on Cd ⊗ Cs, being APPT occurs if the environmental dimension s is of order s0 = min (d1, d2)3 max (d1, d2). That is, when s ≥ Cs0, such a random induced state is APPT with large probability, while such a random states is not APPT with large probability when s ≤ cs0. Besides, we compute effectively C and c and show that it is possible to replace them by the same sharp transition constant when min (d1, d2)2 ≪ d.
Comparison of Two Types of Recessed-Gate Normally-Off AlGaN/GaN Heterostructure Field Effect Transistors
Authors: He Zhiyuan , Li Jialin , Wen Yuhua , Shen Zhen , Yao Yao , Yang Fan , Ni Yiqiang , Wu Zhisheng , Zhang Baijun , Liu Yang
Published: May 2012

In this report, two types of normally-off AlGaN/GaN heterostructure field effect transistors (HFETs) with recessed-gate structure have been fabricated by using common technique of induced coupled plasma (ICP) dry etching and a novel technique of selective area growth (SAG), respectively. The devices fabricated by SAG (SAG-HFET) showed better performance than that of ICP-HFETs with larger maximum drain current of 300 mA/mm, positive threshold voltage of 0.4 V, and lower pinch off channel leakage current (2.17×10-3 mA/mm). The analysis indicates that such obvious difference originated from the different AlGaN quality of the gate region under the Schottky contact, in which the damage to the gate region stemmed from dry etching can be avoided by the SAG technique so that the forming of higher quality Schottky contact can be guaranteed. These results indicate that SAG technique is a promising method for fabricating the normally-off GaN based HFETs.
Carboniferous appinitic intrusions from the northern North China craton: geochemistry, petrogenesis and tectonic implications
Authors: Zhang Xiaohui , Gao Yanlong , Wang Zhijun , Liu Hu , Ma Yuguang
Published: May 2012

Laser ablation inductively coupled plasma mass spectrometry zircon U–Pb dating and geochemical study document Carboniferous (
c
. 320–317 Ma) appinitic intrusions from the northern North China craton. The rock suite mainly consists of hornblende diorites and monzodiorites, with an SiO
2
range from 46.8 to 55.4%. These rocks exhibit high alkali contents, strong enrichment in large ion lithophile elements and light rare earth elements, and depletion in high field strength elements, with radiogenic
87
Sr/
86
Sr
i
ratios of 0.7058–0.7093, unradiogenic ϵ
Nd
(t) of −9.3 to −13.9 and zircon ϵ
Hf
(t) from −8.5 to −18.4. These geochemical features suggest that their generation may involve a distinctive two-stage process: (1) a precursory metasomatism stage of mantle peridotites by melts from subduction-related sediments; (2) a delayed partial melting stage probably initiated by post-subduction transcurrent movements along pre-existing lithospheric shear zones. These mafic to intermediate intrusions, plus other coeval mafic– ultramafic complexes and high Ba–Sr granites from neighbouring regions, not only witness a heterogeneously enriched subcontinental lithospheric mantle along the northern North China craton, but also attest to a reworking-dominated metacratonic process within a post-subduction transtensional regime.

Supplementary material:

Data on mineral composition, zircon dating and Hf isotopic composition are at
http://www.geolsoc.org.uk/SUP18513
.
An Early Mesozoic transcontinental palaeoriver in South China: evidence from detrital zircon U–Pb geochronology and Hf isotopes
Authors: She Zhenbing , Ma Changqian , Wan Yusheng , Zhang Jinyang , Li Min , Chen Ling , Xu Wenjing , Li Yanqing , Ye Longfei , Gao Jian
Published: May 2012

Detrital zircon geochronology reveals that Late Triassic–Early Jurassic fluvial sandstones from the major basins of the South China Craton have similar age patterns and define four populations at 2.6–2.4 Ga, 2.0–1.7 Ga, 850–700 Ma and 480–210 Ma. The late Palaeoproterozoic group is predominant in all of the five samples, and yielded remarkable age peaks at
c
. 1.85 Ga. These zircons have ϵ
Hf
(t) values between −22.5 and +3.6, suggesting derivation from reworked Archaean crust and minor juvenile crustal additions in the late Palaeoproterozoic. These characteristics differ from those of the Yangtze Block but correlate well with those of samples from the eastern Cathaysia Block. Palaeocurrent analysis of the Early Mesozoic sandstones shows predominant west- and NW-directed palaeoflows, supporting derivation of the sediments from the Cathaysia Block. The remarkable similarities in provenance signatures and spatial changes of lithofacies of the Triassic–Jurassic around the South China Craton delineate an east–west-trending sedimentary zone extending from Korea to West China. Accumulation of these sediments was probably related to the development of an active continental margin produced by westward subduction of the Palaeo-Pacific Plate. A
c
. 2000 km long westerly draining transcontinental palaeoriver probably had existed in the Early Mesozoic and fed the basins in Korea, South China and West China.

Supplementary material:

Sensitive high-resolution ion microprobe and laser ablation–inductively coupled plasma mass spectrometry zircon U–Th–Pb and Hf isotope data are available at
www.geolsoc.org.uk/SUP18514
.
Large-scale, linked drainage systems in the NW European Triassic: insights from the Pb isotopic composition of detrital K-feldspar
Authors: Tyrrell Shane , Haughton Peter D. W. , Souders A. Kate , Daly J. Stephen , Shannon Patrick M.
Published: May 2012

Pb isotopic data from K-feldspars in Middle Triassic (Anisian) sandstones in the Wessex Basin, onshore SW UK, and the East Irish Sea Basin, some 350 km to the north, show that the same grain populations are present. This indicates that the drainage system (the ‘Budleighensis’ river) feeding these basins originated from the same source/s, most probably the remnant Variscan uplands to the south. Fluvial and aeolian sandstones have the same provenance, suggesting that if water- and wind-driven sands were originally derived from different sources, this has been obscured through reworking prior to final deposition. Significant recycling of feldspar from arkosic sandstones in earlier sedimentary basins can be ruled out. The provenance data agree with previous depositional models, indicating transport distances in excess of 400 km, with a drainage pattern that linked separate basins. This supports the idea that the regional fluvial system was driven by topography and episodic flooding events of sufficient magnitude to overcome evaporation and infiltration over hundreds of kilometres. Importantly, this drainage system appears to have been isolated and independent from those operating contemporaneously to the NW of the Irish and Scottish massifs, where the remnant Variscan uplands apparently exerted no influence on drainage or sand supply.
Virus Maturation
Authors: Veesler David , Johnson John E.
Published: May 2012

We examine virus maturation of selected nonenveloped and enveloped single-stranded RNA viruses, retroviruses, bacteriophages, and herpesviruses. Processes associated with maturation in the RNA viruses range from subtle (nodaviruses and picornaviruses) to dramatic (tetraviruses and togaviruses). The elaborate assembly and maturation pathway of HIV is discussed in contrast to the less sophisticated but highly efficient processes associated with togaviruses. Bacteriophage assembly and maturation are discussed in general terms, with specific examples chosen for emphasis. Finally the herpesviruses are compared with bacteriophages. The data support divergent evolution of nodaviruses, picornaviruses, and tetraviruses from a common ancestor and divergent evolution of alphaviruses and flaviviruses from a common ancestor. Likewise, bacteriophages and herpesviruses almost certainly share a common ancestor in their evolution. Comparing all the viruses, we conclude that maturation is a convergent process that is required to solve conflicting requirements in biological dynamics and function.
Allostery and the Monod-Wyman-Changeux Model After 50 Years
Authors: Changeux Jean-Pierre
Published: May 2012

The Monod-Wyman-Changeux (MWC) model was conceived in 1965 to account for the signal transduction and cooperative properties of bacterial regulatory enzymes and hemoglobin. It was soon extended to pharmacological receptors for neurotransmitters and other macromolecular entities involved in intracellular and intercellular communications. Five decades later, the two main hypotheses of the model are reexamined on the basis of a variety of regulatory proteins with known X-ray structures: (a) Regulatory proteins possess an oligomeric structure with symmetry properties, and (b) the allosteric interactions between topographically distinct sites are mediated by a conformational transition established between a few preestablished states with conservation of symmetry and ligand-directed conformational selection. Several well-documented examples are adequately represented by the MWC model, yet a few possible exceptions are noted. New questions are raised concerning the dynamics of the allosteric transitions and more complex supramolecular ensembles.
Filamins in Mechanosensing and Signaling
Authors: Razinia Ziba , Mäkelä Toni , Ylänne Jari , Calderwood David A.
Published: May 2012

Filamins are essential, evolutionarily conserved, modular, multidomain, actin-binding proteins that organize the actin cytoskeleton and maintain extracellular matrix connections by anchoring actin filaments to transmembrane receptors. By cross-linking and anchoring actin filaments, filamins stabilize the plasma membrane, provide cellular cortical rigidity, and contribute to the mechanical stability of the plasma membrane and the cell cortex. In addition to binding actin, filamins interact with more than 90 other binding partners including intracellular signaling molecules, receptors, ion channels, transcription factors, and cytoskeletal and adhesion proteins. Thus, filamins scaffold a wide range of signaling pathways and are implicated in the regulation of a diverse array of cellular functions including motility, maintenance of cell shape, and differentiation. Here, we review emerging structural and functional evidence that filamins are mechanosensors and/or mechanotransducers playing essential roles in helping cells detect and respond to physical forces in their local environment.
Protein Structure in Membrane Domains
Authors: Rath Arianna , Deber Charles M.
Published: May 2012

Of great interest to the academic and pharmaceutical research communities, helical transmembrane proteins are characterized by their ability to dissolve and fold in lipid bilayers—properties conferred by polypeptide spans termed transmembrane domains (TMDs). The apolar nature of TMDs necessitates the use of membrane-mimetic solvents for many structure and folding studies. This review examines the relationship between TMD structure and solvent environment, focusing on principles elucidated largely in membrane-mimetic environments with single-TMD protein and peptide models. Following a brief description of TMD sequence and conformational characteristics gleaned from the structural database, we present an overview of the conceptual models used to study folding in vitro. The impact of sequence and solvent context on the incorporation of TMDs into membranes, and its role in measurements of TMD self-assembly strengths, is then described. We conclude with a discussion of the nonspecific effects of membrane components on TMD stability.
Racemic Protein Crystallography
Authors: Yeates Todd O. , Kent Stephen B.H.
Published: May 2012

Although natural proteins are chiral and are all of one “handedness,” their mirror image forms can be prepared by chemical synthesis. This opens up new opportunities for protein crystallography. A racemic mixture of the enantiomeric forms of a protein molecule can crystallize in ways that natural proteins cannot. Recent experimental data support a theoretical prediction that this should make racemic protein mixtures highly amenable to crystallization. Crystals obtained from racemic mixtures also offer advantages in structure determination strategies. The relevance of these potential advantages is heightened by advances in synthetic methods, which are extending the size limit for proteins that can be prepared by chemical synthesis. Recent ideas and results in the area of racemic protein crystallography are reviewed.
Recent Advances in Magnetic Tweezers
Authors: De Vlaminck Iwijn , Dekker Cees
Published: May 2012

Since their first demonstration of manipulation and mechanical coiling of a single DNA molecule, magnetic tweezers have become a popular and widely used single-molecule manipulation technique. Magnetic tweezers have yielded a wealth of information on the elastic properties of (coiled) DNA and have provided critical insights into the dynamic activity of DNA-processing enzymes. Recent years have seen a wave of technological creativity, and a flurry of new methods and technological advances have been introduced to magnetic tweezers, which will enable more and previously inaccessible information to be extracted from biophysical systems. In this review, we survey the most important recent advances and reflect on more interesting twists to come.
Causes and Electoral Consequences of Party Policy Shifts in Multiparty Elections: Theoretical Results and Empirical Evidence
Authors: Adams James
Published: May 2012

The spatial model of elections identifies factors that motivate party elites to shift their policy positions, including changes in voters' policy preferences, rival parties' policy shifts, past election results, and changes in party elites' valence images with respect to dimensions of evaluation such as competence and integrity. I review empirical studies on multiparty elections, i.e., elections involving three or more major parties, that evaluate party elites' policy responses to these factors, along with empirical studies on the electoral consequences of parties' policy shifts. This review reveals a paradox: on the one hand, empirical studies conclude that parties systematically shift their policy positions in response to the factors that spatial modelers have identified. On the other hand, there is only weak and inconsistent empirical evidence that voters actually perceive parties' policy shifts, and/or that these shifts have significant electoral consequences. Thus the predictions of spatial theory are largely verified, whereas the assumptions that underpin spatial theory are called into question.
Electoral Accountability: Recent Theoretical and Empirical Work
Authors: Ashworth Scott
Published: May 2012

Competitive elections create a relationship of formal accountability between policy makers and citizens. Recent theoretical work suggests that there are limits on how well this formal accountability links policy decisions to citizen preferences. In particular, incumbents' incentives are driven not by the voters' evaluation of the normative desirability of outcomes but by the outcome's information about the incumbent's type (e.g., competence or ideology). This review surveys both this body of theory and the robust empirical literature it has spawned. It concludes with a short discussion of ongoing work that attempts to integrate this theoretical perspective with a richer view of policy-making institutions.
Geographic Information Systems and the Spatial Dimensions of American Politics
Authors: Cho Wendy K. Tam , Gimpel James G.
Published: May 2012

In research on American politics, the use of geographic information systems (GIS) is most often thought of in connection with redistricting and the study of election results. In the past ten years, political scientists have realized that GIS can help them address many research questions and data analysis tasks quite apart from these traditional applications. These include the analysis of point patterns and the detection of clustering; the study of diffusion of influence; and the measurement of spatial relationships involving key constructs such as proximity and distance, flow, and interaction. GIS tools also prove to be the exploratory complements to the suite of tools being used in spatial econometrics to test explicit hypotheses about the impact of geography and spatial arrangement on political outcomes.
International Regimes for Human Rights
Authors: Hafner-Burton Emilie M.
Published: May 2012

This article provides a roadmap for understanding the points of agreement and contention that characterize contemporary empirical scholarship on international human rights legal regimes. It explores what the statistical research teaches us about why states participate in these regimes; knowledge of how these regimes operate; and their relationship to actual human rights behavior. It also describes the central shortcomings of this research tradition and suggests a few areas especially promising for future research.
Why Comparative Politics Should Take Religion (More) Seriously
Authors: Grzymala-Busse Anna
Published: May 2012

The study of religion holds great promise for the study of identity, institutional origins, the state, and the strategies of institutional actors in comparative politics. Doctrinal differences translate into distinct patterns of state institutions, economic performance, and policy preferences. Religious attachments affect voting and popular mobilization. Churches can become powerful institutional players that lobby, influence policy, and form effective coalitions with both secular and denominational partners. Finally, natural religious monopolies and (conversely) resolutely secular countries show how churches have played a central role in the struggle of nations and states. The relationship is thus mutual: religion influences political attitudes and institutions, and politics affects religious practice and political activity.