bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of anisotropic black branes in asymptotically anti-de Sitter
Authors: Iizuka Norihiro , Maeda Kengo
Published: July 2012

Abstract

We investigate the four dimensional gravitational theories which admit homogeneous but anisotropic black brane solutions in asymptotically AdS space-time. The gravitational theories we consider are 1) Einstein-Maxwell-dilaton theory, and 2) EinsteinMaxwell-dilaton-axion theory with SL(2, R) symmetry. We obtain the solutions both analytically and numerically. Analytical solutions are obtained by perturbation from the isotropic solutions. Our solutions approach singular behavior at the horizon in the extremal limit but in non-extremal case, they are smooth everywhere. We also discuss how the third law of thermodynamics holds in our set-up.
Leading‐edge populations do not show low genetic diversity or high differentiation in a wind‐pollinated tree
Authors: Shi Miao‐Miao , Chen Xiao‐Yong
Published: July 2012

Climate changes can shift species’ ranges. Knowledge on genetic variation of the leading‐edge populations provides critical information to understand responses and adaptation of plants to projected climate warming. To date, the research into genetic variation of leading‐edge populations has been limited, particularly in the role of wind‐mediated pollen flow in maintaining high genetic variation. Castanopsis sclerophylla (Fagaceae) is a wind‐pollinated and gravity‐dispersed tree. In the present study, we used seven polymorphic microsatellites to genotype 482 samples from five leading‐edge and 12 non‐edge populations. Significant effects of recent population bottleneck events were found in three of the five leading‐edge populations, indicating that the leading‐edge populations might have been recolonized after the Last Glacial Maximum. Genetic diversity was higher, though not significantly, in leading‐edge than in non‐edge populations. Relationship between genetic diversity and latitude indicated an increasing trend of genetic diversity towards leading‐edge populations. No significant difference in genetic differentiation was found between leading‐edge and non‐edge populations. The inconsistence with the general predictions by leading‐edge colonization model could be explained by high gene flow via pollen grains. Pollen‐mediated gene flow could maintain high genetic diversity within and low differentiation among leading‐edge populations. In response to climate warming, high genetic variation may provide leading‐edge populations raw materials for evolutionary adaptation to future environmental conditions.
Genetic Counseling, Activism and ‘Genotype‐First’ Diagnosis of Developmental Disorders
Authors: Navon Daniel
Published: July 2012

This paper presents a sociological examination of the role of genetic counselors as advocates, not only for patients and their families, but also for genetic conditions themselves. In becoming activists for new disorders, genetic counselors are helping to create new categories that will shape expectations and treatment regimens for both existing patients and those who are yet to be diagnosed. By virtue of their expertise and their position at the intersection of several key professions and constituencies, genetic counselors are likely to play a central role in the way the genetic testing technologies, and especially ‘genotype‐first’ diagnosis, impacts the way we understand and categorize developmental difference. I outline some of the promises and dangers that this kind of activism holds for people with developmental disabilities, and particularly the challenge presented by systemic ascertainment bias in the face of genotype‐phenotype uncertainty. I argue that new testing techniques like microarray analysis that do not need to be targeted on the basis of clinical presentation throw these challenges into sharp relief, and that the genetic counseling community should consider how to marry advocacy for new genetic conditions with an emphasis on the indeterminate developmental potential of every child.
Governance and Design of Urban Infostructures
Authors: Wolfram Marc , Vogel Rico
Published: July 2012

Information, communication and knowledge creation are at the core of urban stakeholder interactions enabling the identification of vulnerabilities and the design of adequate responses to them. Urban infostructures play a crucial role within these processes, interfacing between a city’s ecological, social, technical, economic and political networks. Against this backdrop, this paper discusses the governance and design of urban infostructures from a socio-technical systems perspective. It, therefore, reviews pertinent technology components, as well as institutional and discursive frameworks and their respective influence on the identification and assessment of vulnerabilities and resilience building in cities. It concludes that approaches to developing urban infostructures should be a major concern when addressing urban resilience. There is a need to fully account for the hybrid character of urban infostructures as socio-technical systems, while also seizing opportunities for targeted transformation.
Missed opportunities for prevention of mother‐to‐child transmission of HIV‐1 in the NISDI Perinatal and LILAC cohorts
Authors: Read Jennifer S. , Cohen Rachel A. , Hance Laura Freimanis , Machado Elizabeth S. , Mussi‐Pinhata Marisa M. , Ceriotto Mariana , Santos Breno , Succi Regina , Pilotto Jose H. , Alarcon Jorge O. , Kreitchmann Regis
Published: July 2012

Objective

To evaluate cases of mother‐to‐child transmission of HIV‐1 at multiple sites in Latin America and the Caribbean in terms of missed opportunities for prevention.

Methods

Pregnant women infected with HIV‐1 were eligible for inclusion if they were enrolled in either the NISDI Perinatal or LILAC protocols by October 20, 2009, and had delivered a live infant with known HIV‐1 infection status after March 1, 2006.

Results

Of 711 eligible mothers, 10 delivered infants infected with HIV‐1. The transmission rate was 1.4% (95% CI, 0.7–2.6). Timing of transmission was in utero or intrapartum (n = 5), intrapartum (n = 2), intrapartum or early postnatal (n = 1), and unknown (n = 2). Possible missed opportunities for prevention included poor control of maternal viral load during pregnancy; late initiation of antiretrovirals during pregnancy; lack of cesarean delivery before labor and before rupture of membranes; late diagnosis of HIV‐1 infection; lack of intrapartum antiretrovirals; and incomplete avoidance of breastfeeding.

Conclusion

Early knowledge of HIV‐1 infection status (ideally before or in early pregnancy) would aid timely initiation of antiretroviral treatment and strategies designed to prevent mother‐to‐child transmission. Use of antiretrovirals must be appropriately monitored in terms of adherence and drug resistance. If feasible, breastfeeding should be completely avoided. Presented in part at the XIX International AIDS Conference (Washington, DC; July 22–27, 2012); abstract WEPE163.
Ventricular asystole due to atrial oversensing by a VVI pacemaker: VVT mode as a simple solution
Authors: Tanaka Kazushi , Fujimura Osamu
Published: July 2012

We report a rare case of atrial oversensing by a VVI pacemaker that caused ventricular asystole. Changing the programming to VVT mode not only eliminated the problem but also provided atrioventricular synchrony and rate responsiveness.
Parachute mitral valve accompanied by bicuspid aortic valve on three‐dimensional transesophageal echocardiography
Authors: Feng Tian‐Ying , Li Zhi‐An , He Yi‐Hua , Han Jian‐Cheng , Luan Shu‐Rong , Wang Lin‐Lin
Published: July 2012

We report the findings of three‐dimensional (3D) transesophageal echocardiography (TEE) in a patient with a parachute mitral valve (MV) accompanied by aortic valve (AV) malformation. The results indicated an enhanced echo in MV anterior leaves, incrassate, and shortened subvalvular chordae tendineae, and posteromedial papillary muscle that had echo reinforcement, calcification, retroposition, and a significant decrease compared with anterolateral papillary muscle. In addition, the anterolateral papillary muscle was huge, with the bilateral papillary muscles fused partly, and the posterior subvalvular chordae tendineae incrassate, shortened, and attached parachute‐like to the anterolateral papillary muscle. The MV appeared dome‐shaped for the open limit in diastole with an MV area of 1.6 cm. Moreover, the left ventricle increased in size and the bicuspid AV was malformed. Continuous wave Doppler angiograph showed that the flow rate increased to 398 cm/seconds at the AV orifice area. A 3D form of the MV structure was observed from the left ventricle using 3D‐TEE inspection. The anterolateral papillary muscle was fused with its posteromedial homologue. The chordae tendineae was attached to the anterolateral papillary with the parachute‐like structure, indicating dome movement.
Modified basket plate for inferior patellar pole avulsion fractures—A report of three cases
Authors: Huang Hui‐Cheng , Su Jiing‐Yuan , Cheng Yuh‐Min
Published: July 2012

In patients who have sustained an avulsion fracture of the inferior patellar pole, the extensor mechanism is disrupted and should be repaired. The normal height of the patella can be maintained by preserving the patellar pole, but fractures of the inferior pole of the patella are not easy to reduce and fix firmly. In contrast with partial patellectomy, which requires postoperative immobilization, internal fixation with a basket plate allows for immediate mobilization and early weight‐bearing. Owing to the unavailability of the basket plate in Taiwan, we have modified the plate with the titanium mesh as a possible alternative. We present three cases of this modified basket plate, which took place between 2008 and 2010. This technique avoided long‐term immobilization of the knee with good clinical results.
Re-evaluating the origins of late Pleistocene fire areas on Santa Rosa Island, California, USA
Authors: Rick Torben C. , Wah John S. , Erlandson Jon M.
Published: July 2012

At the close of the Pleistocene, fire regimes in North America changed significantly in response to climate change, megafaunal extinctions, anthropogenic burning and possibly, even an extraterrestrial impact. On California's Channel Islands, researchers have long debated the nature of late Pleistocene “fire areas,” discrete red zones in sedimentary deposits, interpreted by some as prehistoric mammoth-roasting pits created by humans. Further research found no evidence that these red zones were cultural in origin, and two hypotheses were advanced to explain their origin: natural fires and groundwater processes. Radiocarbon dating, X-ray diffraction analysis, and identification of charcoal from six red zones on Santa Rosa Island suggest that the studied features date between ~ 27,500 and 11,400 cal yr BP and resulted from burning or heating, not from groundwater processes. Our results show that fire was a component of late Pleistocene Channel Island ecology prior to and after human colonization of the islands, with no clear evidence for increased fire frequency coincident with Paleoindian settlement, extinction of pygmy mammoths, or a proposed Younger Dryas impact event.
Stand der Forschung zum Zusammenhang von Gesundheit und Bildung
Authors: Dadaczynski Kevin
Published: July 2012

Zusammenfassung. Die Diskussion um den Zusammenhang von Gesundheit und Bildung konzentriert sich in Deutschland bislang vor allem auf die Frage, welchen Einfluss Bildung auf Gesundheit hat. Für die Gesundheitsförderung und Prävention, insbesondere in Bildungs- und Erziehungssettings, ist jedoch ebenfalls von Bedeutung, ob ein und welcher Einfluss von Gesundheit auf Bildung ausgeht. Ziel des vorliegenden Beitrages ist es daher, einen Überblick über die internationale Befundlage zum Einfluss von Gesundheit auf Bildung zu geben. Entsprechend des nationalen Gesundheitsziels „gesund aufwachsen” werden dabei die Themenbereiche Ernährung, Bewegung und psychische Gesundheit fokussiert. Über eine systematische Datenbankrecherche ließen sich insgesamt 39 Längsschnittstudien identifizieren. Die Befundlage weist darauf hin, dass Übergewicht, Adipositas, mangelnde körperliche Aktivität und psychische Probleme einen negativen Einfluss auf die Schulleistung (Schulnoten), die Schulanwesenheit, den Schulabschluss sowie auch die Aufnahme und den Abschluss eines Studiums haben können. Dabei ließen sich eine Reihe von bedeutsamen Drittvariablen identifizieren (z.B. Sozialstatus, Ausmaß an Stigmatisierung). Die Ergebnisse liefern Hinweise für eine empirische Bestätigung der Annahmen des Ansatzes der guten gesunden Schule und geben überdies Anregungen für die Implementation und Evaluation von Maßnahmen der schulischen Gesundheitsförderung.
How Strongly Do Designated Causes and Contributing Factors Explain Helicopter Accidents at Night?
Authors: van Doorn Robert R. A.
Published: July 2012

Explaining helicopter accidents during night flights via isolated individual factors could be statistically improved. Individual significance tests should be complemented by measures of strength. Furthermore, the focus should shift to the combined contribution of identified potential factors.
Derivation of free energy expressions for tube models from coarse-grained slip-link models
Authors: Steenbakkers Rudi J. A. , Schieber Jay D.
Published: July 2012

We present the free energy of a single-chain mean-field model for polymer melt dynamics, which uses a continuous (tube-like) approximation to the discrete entanglements with surrounding chains, but, in contrast to previous tube models, includes fluctuations in the number density of Kuhn steps along the primitive path and in the degree of entanglement. The free energy is obtained from that of the slip-link model with fluctuating entanglement positions [J. D. Schieber and K. Horio, J. Chem. Phys. 132, 074905 (2010)]10.1063/1.3314727 by taking the continuous limit of (functions of) the discrete Kuhn-step numbers and end-to-end vectors of the strands between entanglements. This coarse-graining from a more-detailed level of description has the advantage that no ad hoc arguments need to be introduced. Moreover, the thermodynamic consistency of the slip-link model [J. D. Schieber, J. Non-Equilib. Thermodyn. 28, 179 (2003)]10.1515/JNETDY.2003.010 can be preserved. Fluctuations in the positions of entanglements lead to a harmonic bending term in the free energy of the continuous chain, similar to that derived by Read et al. [Macromolecules 41, 6843 (2008)]10.1021/ma8009855 starting from a modified GLaMM model [R. S. Graham, A. E. Likhtman, T. C. B. McLeish, and S. T. Milner, J. Rheol. 47, 1171 (2003)]10.1122/1.1595099. If these fluctuations are set to zero, the free energy becomes purely Gaussian and corresponds to the continuous limit of the original slip-link model, with affinely moving entanglements [J. D. Schieber, J. Chem. Phys. 118, 5162 (2003)]10.1063/1.1553764. The free energy reduces to that of Read et al. under their assumptions of a homogeneous Kuhn-step number density and a constant degree of entanglement. Finally, we show how a transformation of the primitive-path coordinate can be applied to make the degree of entanglement an outcome of the model instead of a variable. In summary, this paper constitutes a first step towards a unified mathematical formulation of tube models. The next step will be to formulate the dynamics of the primitive-path conformation and the entanglement density along the primitive path. Now that the free energy is known, statistical mechanics can be employed for this purpose.
On inferring liquid-liquid phase boundaries and tie lines from ternary mixture light scattering
Authors: Wahle Chris W. , Ross David S. , Thurston George M.
Published: July 2012

We investigate the possibility of using light scattering data in the single-phase regions of a ternary liquid mixture phase diagram to infer ternary mixture coexistence curves, and to infer tie lines joining the compositions of isotropic liquid phases in thermodynamic equilibrium. Previous analyses of a nonlinear light scattering partial differential equation (LSPDE) show that it provides for reconstruction of ternary [D. Ross, G. Thurston, and C. Lutzer, J. Chem. Phys. 129, 064106 (2008)10.1063/1.2937902; C. Wahle, D. Ross, and G. Thurston, J. Chem. Phys. 137, 034201 (2012)10.1063/1.4731694] and quaternary [C. Wahle, D. Ross, and G. Thurston, J. Chem. Phys. 137, 034202 (2012)] mixing free energies from light scattering data, and that if the coexistence curves are already known, it can also yield ternary tie lines and triangles [D. Ross, G. Thurston, and C. Lutzer, J. Chem. Phys. 129, 064106 (2008)10.1063/1.2937902]. Here, we show that the LSPDE can be used more generally, to infer phase boundaries and tie lines from light scattering data in the single-phase region, without prior knowledge of the coexistence curve, if the single-phase region is connected. The method extends the fact that the reciprocal light scattering intensity approaches zero at the thermodynamic spinodal. Expressing the free energy as the sum of ideal and excess parts leads to a natural family of Padé approximants for the reciprocal Rayleigh ratio. To test the method, we evaluate the single-phase reciprocal Rayleigh ratio resulting from the mean-field, regular solution model on a fine grid. We then use a low-order approximant to extrapolate the reciprocal Rayleigh ratio into metastable and unstable regions. In the metastable zone, the extrapolation estimates light scattering prior to nucleation and growth of a new phase. In the unstable zone, the extrapolation produces a negative function that in the present context is a computational convenience. The original and extrapolated reciprocal light scattering are jointly used as input to solving the LSPDE to deduce the mixing free energy and its convex hull. When projected onto the composition triangle, the boundary of the convexified part of the free energy is the phase boundary, and lines on the convexified region along which the second directional derivative is zero are the tie lines. We find that the tie lines and phase boundaries so deduced agree well with their exact values. This work is a step toward developing methods for inferring phase boundaries from real light scattering intensities measured with noise, from mixtures having compositions on a coarser grid.
Locally homogeneous spaces, induced Killing vector fields and applications to Bianchi prototypes
Authors: Papadopoulos G. O. , Grammenos Th.
Published: July 2012

An answer to the question: Can, in general, the adoption of a given symmetry induce a further symmetry, which might be hidden at a first level? has been attempted in the context of differential geometry of locally homogeneous spaces. Based on Cartan's theory of moving frames, a methodology for finding all symmetries for any n-dimensional locally homogeneous space is provided. The analysis is applied to three-dimensional spaces, whereby the embedding of them into a four-dimensional Lorentzian manifold is examined and special solutions to Einstein's field equations are recovered. The analysis is mainly of local character, since the interest is focused on local structures based on differential equations (and their symmetries), rather than on the implications of, e.g., the analytic continuation of their solution(s) and their dynamics in the large.
Thermocapillary effects on steadily evaporating contact line: A perturbative local analysis
Authors: Benselama Adel M. , Harmand Souad , Sefiane Khellil
Published: July 2012

The evaporation process taking place close to the three-phase contact line is considered and studied theoretically using a linear stability analysis approach. A domain perturbation method, taking into consideration thermocapillary effects and surface forces, is used to develop the higher-order solution in terms of series expansion about lubrication condition. A closed-form solution is found for the film thickness, the pressure jump across the liquid-vapor interface and the evaporative flux in the vicinity of the contact line. The key novelty in this work is considering thermocapillary instability for very thin films (∼10 nm) accounting for surface forces. For (quasi-) flat-very-thin films, the analysis shows no instability, which is consistent with general knowledge in this field. However, for films extending from a meniscus, as encountered in wetting configurations, it is found that the competition between London–van der Waals, capillary, and thermocapillary forces leads to contact line instability and behavior revealed for the first time. According to the sign of the Marangoni number, the instability can enhance (if positive) or reduce (if negative) the evaporation rate by widening out or narrowing, respectively, the contact region and, in both cases, significantly modifies the vortical structure of the flow. If the Marangoni number is positive, the film interface close to the contact line can exhibit corrugations. The occurrence of these latter is discriminated, in addition to the Marangoni number, by the value of three operating parameters, namely the film aspect ratio, the ratio of the film diffusive thermal resistance to evaporative heat transfer resistance, and the ratio of capillary pressure to disjoining pressure. By modifying the physical and operating parameters, it is also shown that the system can be optimized in order to suppress these corrugations.
Highly selective adsorption of methanol in carbon nanotubes immersed in methanol-water solution
Authors: Zhao Wen-Hui , Shang Bo , Du Sheng-Ping , Yuan Lan-Feng , Yang Jinlong , Cheng Zeng Xiao
Published: July 2012

The systems of open-ended carbon nanotubes (CNTs) immersed in methanol-water solution are studied by molecular dynamics simulations. For the (6,6) CNT, nearly pure methanol is found to preferentially occupy interior space of the CNT. Even when the mass fraction (MF) of methanol in bulk solution is as low as 1%, the methanol MF within the CNT is still more than 90%. For CNTs with larger diameters, the methanol concentrations within CNTs are also much higher than those outside CNTs. The methanol selectivity decreases with increasing CNT diameter, but not monotonically. From microscopic structural analyses, we find that the primary reason for the high selectivity of methanol by CNTs lies on high preference of methanol in the first solvation shell near the inner wall of CNT, which stems from a synergy effect of the van der Waals interaction between CNT and the methyl groups of methanol, together with the hydrogen bonding interaction among the liquid molecules. This synergy effect may be of general significance and extended to other systems, such as ethanol aqueous solution and methanol/ethanol mixture. The selective adsorption of methanol over water in CNTs may find applications in separation of water and methanol, detection of methanol, and preservation of methanol purity in fuel cells.
Ultraviolet stimulated electron source for use with low energy plasma instrument calibration
Authors: Henderson Kevin , Harper Ron , Funsten Herb , MacDonald Elizabeth
Published: July 2012

We have developed and demonstrated a versatile, compact electron source that can produce a mono-energetic electron beam up to 50 mm in diameter from 0.1 to 30 keV with an energy spread of <10 eV. By illuminating a metal cathode plate with a single near ultraviolet light emitting diode, a spatially uniform electron beam with 15% variation over 1 cm2 can be generated. A uniform electric field in front of the cathode surface accelerates the electrons into a beam with an angular divergence of <1° at 1 keV. The beam intensity can be controlled from 10 to 109 electrons cm−2 s−1.
Method to obtain absolute impurity density profiles combining charge exchange and beam emission spectroscopy without absolute intensity calibration
Authors: Kappatou A. , Jaspers R. J. E. , Delabie E. , Marchuk O. , Biel W. , Jakobs M. A.
Published: July 2012

Investigation of impurity transport properties in tokamak plasmas is essential and a diagnostic that can provide information on the impurity content is required. Combining charge exchange recombination spectroscopy (CXRS) and beam emission spectroscopy (BES), absolute radial profiles of impurity densities can be obtained from the CXRS and BES intensities, electron density and CXRS and BES emission rates, without requiring any absolute calibration of the spectra. The technique is demonstrated here with absolute impurity density radial profiles obtained in TEXTOR plasmas, using a high efficiency charge exchange spectrometer with high etendue, that measures the CXRS and BES spectra along the same lines-of-sight, offering an additional advantage for the determination of absolute impurity densities.
Reactions of Nb2 and Nb3 with CO, D2, N2, and O2: Reconciling experimental kinetics with density functional theory-calculated reaction profiles
Authors: Addicoat Matthew A. , Lim Kieran F. , Metha Gregory F.
Published: July 2012

Calculated energy profiles for the reactions of neutral Nb2 and Nb3 metal clusters with CO, D2, N2, and O2 are presented. In each reaction path, both a physisorption energy minimum, where the reactant remains intact, and a chemisorption energy minimum, where the reactant has dissociated, are calculated and linked by saddle points. We calculate branching ratios for the forward (dissociative) and reverse reactions which we compare with the experimental kinetic data. It is found that a combination of average thermal energies and barrier heights leads to wide variation in branching ratios which compares favourably to previously determined experimental reaction rates.
Top illuminated inverted organic ultraviolet photosensors with single layer graphene electrodes
Authors: Burkhardt Martin , Liu Wei , Shuttle Christopher G. , Banerjee Kaustav , Chabinyc Michael L.
Published: July 2012

Inverted, top-illuminated organic photodiodes are demonstrated using transparent electrodes including single layer graphene (SLG) and thin gold or silver with poly(3-hexylthiophene) and 1 -(3-methoxycarboyl)-propyl-1-phenyl-(6,6)C61 as active layer. The devices are free of both indium-tin-oxide and poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate). The maximum solar power conversion efficiencies were 0.3% for SLG due to its series resistance and ∼2% for gold and silver. The organic photodiodes with SLG electrodes had good external quantum efficiency at incident illumination less than 10 mW/cm2 and better performance than gold and silver at wavelengths below 300 nm making them attractive for ultraviolet photosensors.
Decoherence induced by conical intersections: Complexity constrained quantum dynamics of photoexcited pyrazine
Authors: Westermann Till , Manthe Uwe
Published: July 2012

Decoherence effects induced by conical intersecting potential energy surfaces are studied employing the correlation-based von Neumann (CvN) entropy which provides a measure of the complexity of the underlying wavefunction. As a prototypical example, the S0 → S2 excitation in pyrazine is investigated. The 24-dimensional wavepacket dynamics calculations presented utilize the multi-layer extension of the multi-configurational time-dependent Hartree (MCTDH) approach. An efficient numerical scheme is introduced which facilitates CvN entropy constrained wavepacket propagation within the multi-layer MCTDH approach. In unconstrained multi-layer MCTDH calculations, the CvN-entropy is found to provide a valuable analytical tool for studying the decoherence phenomena present. Investigating the CvN entropy after the S0 → S2 excitation as a function of time, a clear separation of time scales is obtained. It can be related to the different dynamical phenomena present: the initial transfer from the upper (S2) to the lower (S1) adiabatic electronic states rapidly generates vast amounts of CvN-entropy, while the subsequent motion on the anharmonic lower adiabatic potential energy surface only yields a slow increase of the CvN-entropy. Employing CvN-entropy constrained calculations, the sensitivity of the autocorrelation function, the absorption spectrum, and the diabatic electronic population dynamics to complexity constraints is analyzed in detail.
Symmetry preserving parameterization schemes
Authors: Popovych Roman O. , Bihlo Alexander
Published: July 2012

Methods for the design of physical parameterization schemes that possess certain invariance properties are discussed. These methods are based on different techniques of group classification and provide means to determine expressions for unclosed terms arising in the course of averaging of nonlinear differential equations. The demand that the averaged equation is invariant with respect to a subalgebra of the maximal Lie invariance algebra of the unaveraged equation leads to a problem of inverse group classification which is solved by the description of differential invariants of the selected subalgebra. Given no prescribed symmetry group, the direct group classification problem is relevant. Within this framework, the algebraic method or direct integration of determining equations for Lie symmetries can be applied. For cumbersome parameterizations, a preliminary group classification can be carried out. The methods presented are exemplified by parameterizing the eddy vorticity flux in the averaged vorticity equation. In particular, differential invariants of (infinite-dimensional) subalgebras of the maximal Lie invariance algebra of the unaveraged vorticity equation are computed. A hierarchy of normalized subclasses of generalized vorticity equations is constructed. Invariant parameterizations possessing minimal symmetry extensions are described and a restricted class of invariant parameterization is exhaustively classified. The physical importance of the parameterizations designed is discussed.
First principles study of cobalt hydride, CoH, and its ions CoH+ and CoH−
Authors: Sakellaris Constantine N. , Mavridis Aristides
Published: July 2012

The electronic structure of the diatomic species CoH, CoH+, and CoH− have been studied mainly by multireference configuration interaction (MRCI) methods and basis sets of quintuple quality. The restricted coupled-cluster with iterative singles + doubles + quasi-perturbative connected triples, RCCSD(T), approach was also employed, limited however to the ground states only. At the MRCI level we have constructed 27 (CoH), 24 (CoH+), and 12 (CoH−) potential energy curves correlating adiabatically to six, seven, and two energy channels, respectively. For the ground states scalar relativistic and core–subvalence effects have been taken into account. We report energetics, spectroscopic parameters, dipole moments, excitation energies, and spin–orbit coupling constants. Our CoH calculated results are in accord with experiment, but there is an interesting discrepancy between theory and experiment concerning the dipole moment, the former being significantly larger than the latter. Experimental results on CoH+ and CoH− are scarce. The ground state of CoH, CoH+, and CoH− are definitely of 3Φ, 4Φ, and 4Φ symmetries with calculated (experimental) dissociation energies $D_0^0 $D00 = 46.4 ± 0.5(45.0 ± 1.2), 49.6(47 ± 2), and 45.6(43.1 ± 1.2) kcal/mol, respectively. In all 24 calculated CoH states, a Co–to–H charge transfer of 0.2–0.3 e− is recorded; in CoH−, however, the negative charge resides almost exclusively on the Co atom.
A single-shot transmissive spectrometer for hard x-ray free electron lasers
Authors: Zhu Diling , Cammarata Marco , Feldkamp Jan M. , Fritz David M. , Hastings Jerome B. , Lee Sooheyong , Lemke Henrik T. , Robert Aymeric , Turner James L. , Feng Yiping
Published: July 2012

We report hard x-ray single-shot spectral measurements of the Linac Coherent Light Source. The spectrometer is based on a 10 μm thick cylindrically bent Si single crystal operating in the symmetric Bragg geometry to provide dispersion and high transmission simultaneously. It covers a spectral range >1% using the Si(111) reflection. Using the Si(333) reflection, it reaches a resolving power of better than 42 000 and transmits >83% of the incident flux at 8.3 keV. The high resolution enabled the observation of individual spectral spikes characteristic of a self-amplified spontaneous emission x-ray free electron laser source. Potential applications of the device are discussed.
Pullback attractors for a nonautonomous nonclassical diffusion equation with variable delay
Authors: Hu Zhiyuan , Wang Yejuan
Published: July 2012

We present the existence of pullback attractors in \documentclass[12pt]{minimal}\begin{document}$C_{H_0^1(\Omega )}$\end{document}CH01(Ω) and \documentclass[12pt]{minimal}\begin{document}$C_{H^2(\Omega ) \cap H_0^1(\Omega )}$\end{document}CH2(Ω)∩H01(Ω) for the processes associated with the nonautonomous nonclassical diffusion equations with delays. New methods for checking the asymptotical compactness of the solutions are used.
On the existence of Weibel instability in a magnetized plasma. II. Perpendicular wave propagation: The ordinary mode
Authors: Ibscher D. , Lazar M. , Schlickeiser R.
Published: July 2012

In a magnetized plasma with a temperature anisotropy T||>T⊥ (where || and ⊥ denote directions with respect to the uniform magnetic field B0), the nonresonant Weibel instability can develop and destabilize purely growing, ordinary plasma modes (k=k⊥). This paper presents a rigorous extended analysis of this instability on the basis of a new threshold b0(k), which enables to determine the instability conditions as well as the upper limits of the growth rates. Accurate analytical forms of the threshold conditions are provided here for the first time and for the full physical range of the temperature anisotropy and the parallel plasma beta. The marginal and threshold conditions for the plasma parameters, which directly lead to an instability of the ordinary mode, are explicitly derived numerically and analytically. The new analytical tools developed here provide premises for a comprehensive investigation of the interplay of this instability with the firehose instability, as they both can develop in the same conditions.
Photoacoustic tomography of tissue subwavelength microstructure with a narrowband and low frequency system
Authors: Yang Yiqun , Wang Shaohua , Tao Chao , Wang Xueding , Liu Xiaojun
Published: July 2012

Based on the analyzed relationship between the microstructure and the spectral parameters of photoacoustic signal, a tomography scheme with a narrowband and low frequency is designed to evaluate the subwavelength microstructure of tissues. Experiments show that this approach can differentiate the subwavelength microstructures of two melanomas-like samples, where their structure scales (49 and 199 μm) are much smaller than the working wavelength 0.3–1.5 mm of the imaging system. Since the microstructure is an effective indicator to tissue characteristics, the proposed imaging scheme could have the potential to classify different tissue types and achieve improved diagnosis in deep tissues.
Magnetoresistance effect in L1-MnGa/MgO/CoFeB perpendicular magnetic tunnel junctions with Co interlayer
Authors: Ma Q. L. , Kubota T. , Mizukami S. , Zhang X. M. , Naganuma H. , Oogane M. , Ando Y. , Miyazaki T.
Published: July 2012

The fully perpendicular magnetic tunnel junctions (p-MTJs) based on L10-MnGa and thin CoFeB electrodes with MgO barrier were reported in this letter. A thin Co layer was introduced between the MnGa layer and the MgO barrier layer to investigate interfacial effect on the device’s magnetic and transport properties. The magnetoresistance ratio improved significantly due to the Co insertion, and reached 40% at room temperature (80% at 5 K) when the Co thickness was 1.5 nm. Moreover, the junctions with Co interlayer exhibited four low-resistance states in one full cycle rather than two in normal MTJs. The physical origin was discussed by considering the coupling between MnGa and Co layers.
Bipolar conductivity in nanocrystallized TiO2
Authors: Islamov D. R. , Gritsenko V. A. , Cheng C. H. , Chin A.
Published: July 2012

This study calculated the contribution of electrons and holes to TiO2 conductivity in Si/TiO2/Ni structures by conducting experiments on the injection of minority carriers from n- and p-type silicon. Results show that electrons and holes contribute to the conductivity of TiO2, enabling two-band conductivity.
Physics of the intermediate layer between a plasma and a collisionless sheath and mathematical meaning of the Bohm criterion
Authors: Almeida N. A. , Benilov M. S.
Published: July 2012

A transformation of the ion momentum equation simplifies a mathematical description of the transition layer between a quasi-neutral plasma and a collisionless sheath and clearly reveals the physics involved. Balance of forces acting on the ion fluid is delicate in the vicinity of the sonic point and weak effects come into play. For this reason, the passage of the ion fluid through the sonic point, which occurs in the transition layer, is governed not only by inertia and electrostatic force but also by space charge and ion-atom collisions and/or ionization. Occurrence of different scenarios of asymptotic matching in the plasma-sheath transition is analyzed by means of simple mathematical examples, asymptotic estimates, and numerical calculations. In the case of a collisionless sheath, the ion speed distribution plotted on the logarithmic scale reveals a plateau in the intermediate region between the sheath and the presheath. The value corresponding to this plateau has the meaning of speed with which ions leave the presheath and enter the sheath; the Bohm speed. The plateau is pronounced reasonably well provided that the ratio of the Debye length to the ion mean free path is of the order of 10−3 or smaller. There is no such plateau if the sheath is collisional and hence no sense in talking of a speed with which ions enter the sheath.
Asymmetric error field interaction with rotating conducting walls
Authors: Paz-Soldan C. , Brookhart M. I. , Hegna C. C. , Forest C. B.
Published: July 2012

The interaction of error fields with a system of differentially rotating conducting walls is studied analytically and compared to experimental data. Wall rotation causes eddy currents to persist indefinitely, attenuating and rotating the original error field. Superposition of error fields from external coils and plasma currents are found to break the symmetry in wall rotation direction. The vacuum and plasma eigenmodes are modified by wall rotation, with the error field penetration time decreased and the kink instability stabilized, respectively. Wall rotation is also predicted to reduce error field amplification by the marginally stable plasma.
Role of ion mass in the generation of fluctuations and poloidal flows in a simple toroidal plasma
Authors: Goud T. S. , Ganesh R. , Saxena Y. C. , Raju D.
Published: July 2012

Generation of fluctuations and poloidal flow is investigated in a simple toroidal plasma, at a given magnetic field strength for varying ion masses. Under similar discharge conditions, the fluctuation induced poloidal flux is found to decrease with increasing ion mass. Consequently, the absolute net poloidal flow velocity is found to scale down systematically with increase in the ion mass. The net poloidal flow in units of ion acoustic velocity is, however, comparable for all masses on the low field side and shows minor variations on the high field side. The frequency of the first harmonic in the density and potential power spectra is found to decrease with decreasing absolute net flow. A transition occurs in the fluctuation behavior from highly coherent state to a turbulent state with increase in the ion mass, from argon to xenon.
Quantum effects in electron emission from and accretion on negatively charged spherical particles in a complex plasma
Authors: Mishra S. K. , Sodha M. S. , Misra Shikha
Published: July 2012

The authors have investigated the electron emissions (thermionic, electric field, photoelectric, and light induced field) from and electron accretion on a charged particle in a complex plasma, on the basis of a three region electrical potential model in and around a charged spherical particle in a complex plasma, characterized by Debye shielding. A continuous variation of the transmission coefficient across the surface of a particle (corresponding to emission and accretion) with the radial electron energy ɛr has been obtained. It is seen that the numerical values of the emission and accretion transmission coefficients [D(ɛr)] are almost the same. This is the necessary and sufficient condition for the validity of Saha’s equation for thermal equilibrium of a system of dust and electrons. This is in contrast to the earlier condition, which limited the range of validity of Saha’s equation to the range of the applicability of Born approximation. It is seen that D(ɛr) increases with increasing ɛr, increasing negative electric potential on the surface, decreasing radius, and deceasing Debye length. The electron currents, corresponding to thermionic, electric field, photoelectric and light induced field emission increase with increasing surface potential; this fact may have significant repercussions in complex plasma kinetics. Since numerically D(ɛr) is significantly different from unity in the range of ɛr of interest, it is necessary to take into account the D(ɛr)−ɛr dependence in complex plasma theory.
Transparent superhydrophobic/superhydrophilic coatings for self-cleaning and anti-fogging
Authors: Chen Yu , Zhang Yabin , Shi Lei , Li Jing , Xin Yan , Yang Tingting , Guo Zhiguang
Published: July 2012

The high transparent superhydrophobic surface covered with hollow spheres has been fabricated through a carbon template route. The as-prepared coating without treating with low surface energy materials showed superhdrophilic and anti-fogging properties while displayed superhydrophobic characteristics after surface modification. Furthermore, such superhydrophilic/superhydrophobic glasses both exhibited a relatively high transmittance, and it is also demonstrated that the thickness of coating affects the transmittance and wettability from a control experiment. For comparison, we studied the anti-fogging properties of the transparent superhydrophobic, superhydrophilic, and the ordinary glass, showing absolutely different fogging characteristics.
Cantilever driving low frequency piezoelectric energy harvester using single crystal material 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3
Authors: Xu Chundong , Ren Bo , Di Wenning , Liang Zhu , Jiao Jie , Li Lingying , Li Long , Zhao Xiangyong , Luo Haosu , Wang Dong
Published: July 2012

We present a high performance piezoelectric energy harvester CANtilever Driving Low frequency Energy harvester (CANDLE) consisting of cantilever beam and cymbal transducers based on piezoelectric single crystal 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3. Electrical properties of CANDLE under different proof masses, excitation frequencies, and load resistances are studied systematically. Under an acceleration of 3.2g (g = 9.8 m/s2), a peak voltage of 38 V, a maximum power of 3.7 mW were measured at 102 Hz with a proof mass of 4.2 g. Low resonance frequency and high power output performance demonstrate the promise of the device in energy harvesting for wireless sensors and low-power electronics.
Shot-to-shot reproducibility of a self-magnetically insulated ion diode
Authors: Pushkarev A. I. , Isakova Yu. I. , Khailov I. P.
Published: July 2012

In this paper we present the analysis of shot to shot reproducibility of the ion beam which is formed by a self-magnetically insulated ion diode with an explosive emission graphite cathode. The experiments were carried out with the TEMP-4M accelerator operating in double-pulse mode: the first pulse is of negative polarity (300–500 ns, 100–150 kV), and this is followed by a second pulse of positive polarity (150 ns, 250–300 kV). The ion current density was 10–70 A/cm2 depending on the diode geometry. The beam was composed from carbon ions (80%–85%) and protons. It was found that shot to shot variation in the ion current density was about 35%–40%, whilst the diode voltage and current were comparatively stable with the variation limited to no more than 10%. It was shown that focusing of the ion beam can improve the stability of the ion current generation and reduces the variation to 18%–20%. In order to find out the reason for the shot-to-shot variation in ion current density we examined the statistical correlation between the current density of the accelerated beam and other measured characteristics of the diode, such as the accelerating voltage, total current, and first pulse duration. The correlation between the ion current density measured simultaneously at different positions within the cross-section of the beam was also investigated. It was shown that the shot-to-shot variation in ion current density is mainly attributed to the variation in the density of electrons diffusing from the drift region into the A-K gap.
Computational study of nanosecond pulsed laser ablation and the application to momentum coupling
Authors: Yuan Hong , Tong Huifeng , Li Mu , Sun Chengwei
Published: July 2012

During the evaporation and ablation of a matter induced by intensive laser radiation, the vapor plasma is ejected from the surface of the target which induces the recoil pressure and impulse in the target. Impulse coupling of laser beams with matter has been extensively studied as the basis of laser propulsion and laser clearing space debris. A one-dimensional (1D) bulk absorption model to simulate the solid target ablated directly by the laser beam is presented; numerical calculation of impulse acting on the target in vacuum with different laser parameters is performed with fluid dynamics theory and 1D Lagrange difference scheme. The calculated results of the impulse coupling coefficients are in good agreement with the experimental results and Phipps’ empirical value. The simulated results show that the mechanical coupling coefficients decrease with the increment of laser intensity when the laser pulses generate plasma. The present model can be applied when the laser intensity is 108 – 1010 W/cm2, which will provide a guide to the study of momentum coupling of laser beams with matter.
Simultaneous enhancement of electronic and Li+ ion conductivity in LiFePO4
Authors: Lee Jaekwang , Pennycook Stephen J. , Pantelides Sokrates T.
Published: July 2012

Enhancing the electronic and ionic conductivity in Li compounds can significantly impact the design of batteries. Here, we explore the influence of biaxial strain on the electronic and Li+ ion conductivities of LiFePO4 by performing first-principles calculations. We find that 4% biaxial tensile strain (BTS) leads to 15 times increase in electronic conductivity and 50 times increase in Li+ ion conductivity at 300 K, respectively. Electronic conductivity is enhanced because BTS softens lattice distortions around a polaron, resulting in a reduction of the activation barrier. The extra volume introduced by tensile strain also reduces the barrier of Li+ ion migration.
Shear dependent nonlinear vibration in a high quality factor single crystal silicon micromechanical resonator
Authors: Zhu H. , Shan G. C. , Shek C. H. , Lee J. E.-Y.
Published: July 2012

The frequency response of a single crystal silicon resonator under nonlinear vibration is investigated and related to the shear property of the material. The shear stress-strain relation of bulk silicon is studied using a first-principles approach. By incorporating the calculated shear property into a device-level model, our simulation closely predicts the frequency response of the device obtained by experiments and further captures the nonlinear features. These results indicate that the observed nonlinearity stems from the material’s mechanical property. Given the high quality factor (Q) of the device reported here (∼2 × 106), this makes it highly susceptible to such mechanical nonlinear effects.