bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural basis for pH gating of plant aquaporins
Authors: Frick Anna , Järvå Michael , Törnroth-Horsefield Susanna
Published: February 2013

Plants have evolved to cope with fluctuations in water supply by gating their water channels known as aquaporins. During flooding, a rapid drop of cytosolic pH due to anoxia leads to a simultaneous closure of the aquaporins in the plasma membrane. The closing mechanism has been suggested to involve a conserved histidine on cytosolic loop D. Here we report the crystal structure of a spinach aquaporin at low pH, revealing for the first time the structural basis for how this pH‐sensitive histidine helps to keep the aquaporin in a closed state.
Nonlinear vorticity-banding instability in granular plane Couette flow: higher-order Landau coefficients, bistability and the bifurcation scenario
Authors: Shukla Priyanka , Alam Meheboob
Published: February 2013

The rapid granular plane Couette flow is known to be unstable to pure spanwise perturbations (i.e. perturbations having variations only along the mean vorticity direction) below some critical density (volume fraction of particles), resulting in the banding of particles along the mean vorticity direction: this is dubbed ‘vorticity banding’ instability. The nonlinear state of this instability is analysed using quintic-order Landau equation that has been derived from the pertinent hydrodynamic equations of rapid granular fluid. We have found analytical solutions for related modal/harmonic equations of finite-size perturbations up to quintic order in perturbation amplitude, leading to an exact calculation of both first and second Landau coefficients. This helped to identify the bistable nature of nonlinear vorticity-banding instability for a range of densities spanning from moderately dense to dense flows. For perturbations with small spanwise wavenumbers, the bifurcation scenario for vorticity banding unfolds, with increasing density from the dilute limit, as supercritical pitchfork $\rightarrow $ subcritical pitchfork $\rightarrow $ subcritical Hopf bifurcations. The transition from supercritical to subcritical pitchfork bifurcations is found to occur via the appearance of a degenerate/bicritical point (at which both the linear growth rate and the first Landau coefficient are simultaneously zero) that divides the critical line into two parts: one representing the first-order and the other the second-order phase transitions. Both subcritical oscillatory and stationary solutions have also been uncovered for dilute and dense flows, respectively, when the spanwise wavenumber is large. In all cases, the nonlinear solutions correspond to inhomogeneous states of shear stress and pressure along the vorticity direction, and hence are analogues of vorticity banding in other complex fluids. The quartic-order mean-flow resonance is evidenced in the parameter space for which the second Landau coefficient undergoes a jump discontinuity of infinite order. The importance of retaining higher-order terms to calculate the second Landau coefficient and their possible effects on the nature of bifurcations are elucidated.
Libration-induced mean flow in a spherical shell
Authors: Sauret Alban , Le Dizès Stéphane
Published: February 2013

We investigate the flow in a spherical shell subject to a time harmonic oscillation of its rotation rate, also called longitudinal libration, when the oscillation frequency is larger than twice the mean rotation rate. In this frequency regime, no inertial waves are directly excited by harmonic forcing. We show, however, that, through nonlinear interactions in the Ekman layers, it can generate a strong mean zonal flow in the interior. An analytical theory is developed using a perturbative approach in the limit of small libration amplitude $\varepsilon $ and small Ekman number $E$. The mean flow is found to be at leading order an azimuthal flow that scales as the square of the libration amplitude and depends only on the cylindrical radius coordinate. The mean flow also exhibits a discontinuity across the cylinder tangent to the inner sphere. We show that this discontinuity can be smoothed through multi-scale Stewartson layers. The mean flow is also found to possess a weak axial flow that scales as $O({\varepsilon }^{2} {E}^{5/ 42} )$ in the Stewartson layers. The analytical solution is compared to axisymmetric numerical simulations, and a good agreement is demonstrated.
Lattice ellipsoidal statistical BGK model for thermal non-equilibrium flows
Authors: Meng Jianping , Zhang Yonghao , Hadjiconstantinou Nicolas G. , Radtke Gregg A. , Shan Xiaowen
Published: February 2013

A thermal lattice Boltzmann model is constructed on the basis of the ellipsoidal statistical Bhatnagar–Gross–Krook (ES-BGK) collision operator via the Hermite moment representation. The resulting lattice ES-BGK model uses a single distribution function and features an adjustable Prandtl number. Numerical simulations show that using a moderate discrete velocity set, this model can accurately recover steady and transient solutions of the ES-BGK equation in the slip-flow and early transition regimes in the small-Mach-number limit that is typical of microscale problems of practical interest. In the transition regime in particular, comparisons with numerical solutions of the ES-BGK model, direct and low-variance deviational Monte Carlo simulations show good accuracy for values of the Knudsen number up to approximately $0. 5$. On the other hand, highly non-equilibrium phenomena characterized by high Mach numbers, such as viscous heating and force-driven Poiseuille flow for large values of the driving force, are more difficult to capture quantitatively in the transition regime using discretizations chosen with computational efficiency in mind such as the one used here, although improved accuracy is observed as the number of discrete velocities is increased.
Stability of a Gaussian pancake vortex in a stratified fluid
Authors: Negretti M. Eletta , Billant Paul
Published: February 2013

Vortices in stably stratified fluids generally have a pancake shape with a small vertical thickness compared with their horizontal size. In order to understand what mechanism determines their minimum thickness, the linear stability of an axisymmetric pancake vortex is investigated as a function of its aspect ratio $\alpha $, the horizontal Froude number ${F}_{h} $, the Reynolds number $\mathit{Re}$ and the Schmidt number $\mathit{Sc}$. The vertical vorticity profile of the base state is chosen to be Gaussian in both radial and vertical directions. The vortex is unstable when the aspect ratio is below a critical value, which scales with the Froude number: ${\alpha }_{c} \sim 1. 1{F}_{h} $ for sufficiently large Reynolds numbers. The most unstable perturbation has an azimuthal wavenumber either $m= 0$, $\vert m\vert = 1$ or $\vert m\vert = 2$ depending on the control parameters. We show that the threshold corresponds to the appearance of gravitationally unstable regions in the vortex core due to the thermal wind balance. The Richardson criterion for shear instability based on the vertical shear is never satisfied alone. The dominance of the gravitational instability over the shear instability is shown to hold for a general class of pancake vortices with angular velocity of the form $\tilde {\Omega } (r, z)= \Omega (r)f(z)$ provided that $r\partial \Omega / \partial r\lt 3\Omega $ everywhere. Finally, the growth rate and azimuthal wavenumber selection of the gravitational instability are accounted well by considering an unstably stratified viscous and diffusive layer in solid body rotation with a parabolic density gradient.
Dispersive shock waves in viscously deformable media
Authors: Lowman Nicholas K. , Hoefer M. A.
Published: February 2013

The viscously dominated, low-Reynolds-number dynamics of multi-phase, compacting media can lead to nonlinear, dissipationless/dispersive behaviour when viewed appropriately. In these systems, nonlinear self-steepening competes with wave dispersion, giving rise to dispersive shock waves (DSWs). Example systems considered here include magma migration through the mantle as well as the buoyant ascent of a low-density fluid through a viscously deformable conduit. These flows are modelled by a third-order, degenerate, dispersive, nonlinear wave equation for the porosity (magma volume fraction) or cross-sectional area, respectively. Whitham averaging theory for step initial conditions is used to compute analytical, closed-form predictions for the DSW speeds and the leading edge amplitude in terms of the constitutive parameters and initial jump height. Novel physical behaviours are identified including backflow and DSW implosion for initial jumps sufficient to cause gradient catastrophe in the Whitham modulation equations. Theoretical predictions are shown to be in excellent agreement with long-time numerical simulations for the case of small- to moderate-amplitude DSWs. Verifiable criteria identifying the breakdown of this modulation theory in the large jump regime, applicable to a wide class of DSW problems, are presented.
Influence of membrane viscosity on capsule dynamics in shear flow
Authors: Yazdani Alireza , Bagchi Prosenjit
Published: February 2013

Most previous numerical studies on capsule dynamics in shear flow have ignored the role of membrane viscosity. Here we present a numerical method for large deformation of capsules using a Kelvin–Voigt viscoelastic model for the membrane. After introducing the model and the related numerical implementation, we present a comprehensive analysis of the influence of the membrane viscosity on buckling, deformation and dynamics. We observe that the membrane viscosity leads to buckling in the range of shear rate in which no buckling is observed for capsules with purely elastic membrane. For moderate to large shear rates, the wrinkles on the capsule surface appear in the same range of the membrane viscosity that was reported earlier for artificial capsules and red blood cells based on experimental measurements. In order to obtain stable shapes, it is necessary to introduce the bending stiffness. It is observed that the range of the bending stiffness required is also in the same range as that reported for the red blood cells, but considerably higher than that estimated for artificial capsules. Using the stable shapes obtained in the presence of bending stiffness, we analyse the influence of membrane viscosity on deformation, inclination and tank-treading frequency of initially spherical capsules. Membrane viscosity is observed to reduce the capsule deformation, and introduce a damped oscillation in time-dependent deformation and inclination. The time-averaged inclination angle shows a non-monotonic trend with an initial decrease reaching a minimum and a subsequent increase with increasing membrane viscosity. A similar non-monotonic trend is also observed in the tank-treading frequency. We then consider the influence of the membrane viscosity on the unsteady dynamics of an initially oblate capsule. The dynamics is observed to change from a swinging motion to a tumbling motion with increasing membrane viscosity. Further, a transient dynamics is also observed in which a capsule starts with one type of dynamics, but settles with a different dynamics over a long time.
The internal gravity wave field emitted by a stably stratified turbulent wake
Authors: Abdilghanie Ammar M. , Diamessis Peter J.
Published: February 2013

The internal gravity wave (IGW) field emitted by a stably stratified, initially turbulent, wake of a towed sphere in a linearly stratified fluid is studied using fully nonlinear numerical simulations. A wide range of Reynolds numbers,$\mathit{Re}= UD/ \nu \in [5\times 1{0}^{3} , 1{0}^{5} ] $and internal Froude numbers,$\mathit{Fr}= 2U/ (ND)\in [4, 16, 64] $($U$,$D$are characteristic body velocity and length scales, and$N$is the buoyancy frequency) is examined. At the higher$\mathit{Re}$examined, secondary Kelvin–Helmholtz instabilities and the resulting turbulent events, directly linked to a prolonged non-equilibrium (NEQ) regime in wake evolution, are responsible for IGW emission that persists up to$Nt\approx 100$. In contrast, IGW emission at the lower$\mathit{Re}$investigated does not continue beyond$Nt\approx 50$for the three$\mathit{Fr}$values considered. The horizontal wavelengths of the most energetic IGWs, obtained by continuous wavelet transforms, increase with$\mathit{Fr}$and appear to be smaller at the higher$\mathit{Re}$, especially at late times. The initial value of these wavelengths is set by the wake height at the beginning of the NEQ regime. At the lower$\mathit{Re}$, consistent with a recently proposed model, the waves propagate over a narrow range of angles that minimize viscous decay along their path. At the higher$\mathit{Re}$, wave motion is much less affected by viscosity, at least initially, and early-time wave propagation angles extend over a broader range of values which are linked to increased efficiency in momentum extraction from the turbulent wake source.
Stabilization of a swept-wing boundary layer by distributed roughness elements
Authors: Hosseini Seyed M. , Tempelmann David , Hanifi Ardeshir , Henningson Dan S.
Published: February 2013

The stabilization of a swept-wing boundary layer by distributed surface roughness elements is studied by performing direct numerical simulations. The configuration resembles experiments studied by Saric and coworkers at Arizona State University, who employed this control method in order to delay transition. An array of cylindrical roughness elements are placed near the leading edge to excite subcritical cross-flow modes. Subcritical refers to the modes that are not critical with respect to transition. Their amplification to nonlinear amplitudes modifies the base flow such that the most unstable cross-flow mode and secondary instabilities are damped, resulting in downstream shift of the transition location. The experiments by Saric and coworkers were performed at low levels of free stream turbulence, and the boundary layer was therefore dominated by stationary cross-flow disturbances. Here, we consider a more complex disturbance field, which comprises both steady and unsteady instabilities of similar amplitudes. It is demonstrated that the control is robust with respect to complex disturbance fields as transition is shifted from 45 to 65 % chord.
Viscous drop in compressional Stokes flow
Authors: Zabarankin Michael , Smagin Irina , Lavrenteva Olga M. , Nir Avinoam
Published: February 2013

The dynamics of the deformation of a drop in axisymmetric compressional viscous flow is addressed through analytical and numerical analyses for a variety of capillary numbers, $\mathit{Ca}$, and viscosity ratios, $\lambda $. For low $Ca$, the drop is approximated by an oblate spheroid, and an analytical solution is obtained in terms of spheroidal harmonics; whereas, for the case of equal viscosities ($\lambda = 1$), the velocity field within and outside a drop of a given shape admits an integral representation, and steady shapes are found in the form of Chebyshev series. For arbitrary $Ca$ and $\lambda $, exact steady shapes are evaluated numerically via an integral equation. The critical $\mathit{Ca}$, below which a steady drop shape exists, is established for various $\lambda $. Remarkably, in contrast to the extensional flow case, critical steady shapes, being flat discs with rounded rims, have similar degrees of deformation ($D\sim 0. 75$) for all $\lambda $ studied. It is also shown that for almost the entire range of $\mathit{Ca}$ and $\lambda $, the steady shapes have accurate two-parameter approximations. The validity and implications of spheroidal and two-parameter shape approximations are examined in comparison to the exact steady shapes.
Recurrent solutions of the Alber equation initialized by Joint North Sea Wave Project spectra
Authors: Ribal A. , Babanin A. V. , Young I. , Toffoli A. , Stiassnie M.
Published: February 2013

Linear instability of two-dimensional wave fields and its concurrent evolution in time is here investigated by means of the Alber equation for narrow-banded random surface waves in deep water subject to inhomogeneous disturbances. The probability of freak waves in the context of these simulations is also discussed. The instability is first studied for the symmetric Lorentz spectrum, and continued for the realistic asymmetric Joint North Sea Wave Project (JONSWAP) spectrum of ocean waves with variable directional spreading and steepness. It is found that instability depends on the directional spreading and parameters $\alpha $ and $\gamma $ of the JONSWAP spectrum, where $\alpha $ and $\gamma $ are the energy scale and the peak enhancement factor, respectively. Both influence the mean steepness of waves with such a spectrum, although in different ways. Specifically, if the instability stops as a result of the directional spreading, increase of the steepness by increasing $\alpha $ or $\gamma $ can reactivate it. A criterion for the instability is suggested as a dimensionless ‘width parameter’, $\Pi $. For the unstable conditions, long-time evolution is simulated by integrating the Alber equation numerically. Recurrent evolution is obtained, which is a stochastic counterpart of the Fermi–Pasta–Ulam recurrence obtained for the cubic Schrödinger equation. This recurrence enables us to study the probability of freak waves, and the results are compared to the values given by the Rayleigh distribution. Moreover, it is found that stability–instability transition, the most unstable mode, recurrence duration and freak wave probability depend solely on the dimensionless ‘width parameter’, $\Pi $.
Strong particle dispersion by weakly dissipative random internal waves
Authors: Bühler Oliver , Grisouard Nicolas , Holmes-Cerfon Miranda
Published: February 2013

Simple stochastic models and direct nonlinear numerical simulations of three-dimensional internal waves are combined in order to understand the strong horizontal particle dispersion at second-order in wave amplitude that arises when small-amplitude internal waves are exposed to weak dissipation. This is contrasted with the well-known results for perfectly inviscid internal waves, in which such dispersion arises only at fourth-order in wave amplitude.
Future lunar missions and investigation of dusty plasma processes on the Moon
Authors: POPEL SERGEY I. , ZELENYI LEV M.
Published: February 2013

From the Apollo era of exploration, it was discovered that sunlight was scattered at the terminators giving rise to “horizon glow” and “streamers” above the lunar surface. Subsequent investigations have shown that the sunlight was most likely scattered by electrostatically charged dust grains originating from the surface. A renaissance is being observed currently in investigations of the Moon. The Luna-Glob and Luna-Resource missions (the latter jointly with India) are being prepared in Russia. Some of these missions will include investigations of lunar dust. Here we discuss the future experimental investigations of lunar dust within the missions of Luna-Glob and Luna-Resource. We consider the dusty plasma system over the lunar surface and determine the maximum height of dust rise. We describe mechanisms of formation of the dusty plasma system over the Moon and its main properties, determine distributions of electrons and dust over the lunar surface, and show a possibility of rising dust particles over the surface of the illuminated part of the Moon in the entire range of lunar latitudes. Finally, we discuss the effect of condensation of micrometeoriod substance during the expansion of the impact plume and show that this effect is important from the viewpoint of explanation of dust particle rise to high altitudes in addition to the dusty plasma effects.
Arctic hierarchies? Norway, status and the high north
Authors: Wilson Rowe Elana
Published: February 2013

This article focuses on one potential motivation for a state's behaviour in international affairs, namely status-seeking, in order to shed light on Norway's Arctic politics and to discuss the role of hierarchies in Arctic politics more generally. The idea that a state's political elite seek national security and economic gain is well established in international relations (IR) literature. However, another key motivation of human behaviour – seeking status and respect – is frequently overlooked as a potential factor shaping states’ behaviour. The argument begins with a brief review of post-cold war Arctic politics followed by a discussion of the status-related literature in IR. Norway's position in the Arctic Council (AC) and in bilateral relations with Russia is then examined, with particular attention paid to the extent to which other Arctic states acknowledge and confirm Norway's status claims. Norway's status as an information provider, a convener and a bridge to Russia gives the country a degree of influence in Arctic multilateral settings. Given the Arctic region's relatively peaceful nature and the emphasis on circumpolar cooperation, space has been made for creative approaches to status. Size and military or economic greatness are not always decisive factors for taking a lead in today's Arctic politics.
Human security, the Arctic Council and climate change: competition or co-existence?
Authors: Nicol Heather N. , Heininen Lassi
Published: February 2013

We argue that the current understanding of the Arctic as a region fraught by increasing tension and competition under conditions of climate change is an incomplete story. It ignores many salient developments in furthering co-operation and human security agendas, and marginalises some of the more complex and interesting developments within the region. Such changes in ‘natural states’ do not, in and of themselves, create geopolitical and political instability. Rather, it is the way in which change is understood as a problem for institutional and international organs that creates conditions for co-operation or competition. In the Arctic today, the balance is tipped in favour of co-operation, but the situation is complex and many actors have vested interests.
The Formation of South African English
Authors: Bekker Ian
Published: February 2013

Of all the major colonial varieties of English, South African English (SAfE) is arguably the most under-studied. Its linguistic history is also one of the most complex, South Africa having been the site of a series of immigration events involving English-speakers from a vast array of regional and social backgrounds. On top of this the English spoken by native speakers of other languages also, conceivably, had a role to play in this dialect's formation. This paper provides a brief historical reconstruction of the formation of SAfE, drawing on recent work which seems to indicate that in many important respects SAfE is younger than many might suspect.
Involvement of PLA2, COX and LOX inRhinella arenarumoocyte maturation
Authors: Ortiz Maria Eugenia , Bühler Marta Inés , Zelarayán Liliana Isabel
Published: February 2013

InRhinella arenarum, progesterone is the physiological nuclear maturation inducer that interacts with the oocyte surface and starts a cascade of events that leads to germinal vesicle breakdown (GVBD). Polyunsaturated fatty acids and their metabolites produced through cyclooxygenase (COX) and lipoxygenase (LOX) pathways play an important role in reproductive processes. In amphibians, to date, the role of arachidonic acid (AA) metabolites in progesterone (P4)-induced oocyte maturation has not been clarified. In this work we studied the participation of three enzymes involved in AA metabolism – phospholipase A2(PLA2), COX and LOX inRhinella arenarumoocyte maturation. PLA2activation induced maturation inRhinella arenarumoocytes in a dose-dependent manner. Oocytes when treated with 0.08 μM melittin showed the highest response (78 ± 6% GVBD). In follicles, PLA2activation did not significantly induce maturation at the assayed doses (12 ± 3% GVBD). PLA2inhibition with quinacrine prevented melittin-induced GVBD in a dose-dependent manner, however PLA2inactivation did not affect P4-induced maturation. This finding suggests that PLA2is not the only phospholipase involved in P4-induced maturation in this species. P4-induced oocyte maturation was inhibited by the COX inhibitors indomethacin and rofecoxib (65 ± 3% and 63 ± 3% GVBD, respectively), although COX activity was never blocked by their addition. Follicles showed a similar response following the addition of these inhibitors. Participation of LOX metabolites in maturation seems to be correlated with seasonal variation in ovarian response to P4. During the February to June period (low P4response), LOX inhibition by nordihydroguaiaretic acid or lysine clonixinate increased maturation by up to 70%. In contrast, during the July to January period (high P4response), LOX inhibition had no effect on hormone-induced maturation.
Liquidity preference and interest-bearing money: the Ottoman Empire, 1840–1851
Authors: Burdekin Richard C. K. , Keskinel Meric
Published: February 2013

Legal restrictions theory suggests that interest-bearing money would dominate if there were no legal impediments precluding competition with non-interest-bearing currency. There are very few historical examples with meaningful issues of interest-bearing currency, however, and these tend to occur during extreme circumstances like civil war. The Ottoman Empire in the 1840s offers an unusual opportunity to observe large-scale issuance of interest-bearing notes under stable conditions over an extended period of time. This experience features government-issued interest-bearing money circulating in the absence of legal restrictions – with the data pointing to a liquidity preference favouring the smaller denominations most useful in daily transactions.
Protein-losing enteropathy following the Fontan procedure in a child with intestinal lactase deficiency treated with lactose-free diet
Authors: Kienast Wolfgang , Haeseler Klaus , Herterich Reinhard
Published: February 2013

A 12-year-old girl presented with a protein-losing enteropathy. Symptoms started 4 weeks after undergoing the Fontan procedure at the age of 1.5 years for mitral atresia, ventricular septal defect, and double-outlet right ventricle. Upon referral for 3 weeks of rehabilitation after multiple interventional measures and drug treatments, she appeared in a dystrophic state, with decreased plasma protein and electrolyte levels along with occasional tetanic convulsions. Blood glucose levels after a lactose tolerance test were markedly reduced. The introduction of a lactose-free diet was quickly effective, with plasma protein and electrolyte levels raised to normal levels, and the girl's body weight increased without ascites or oedema. Molecular genetic examination revealed a homozygous C/C13910 polymorphism in the LCT gene. Conclusion: Protein-losing enteropathy in the Fontan circulation may be provoked by lactase deficiency and should therefore be ruled out to exclude this rather common condition.
Emergence of anxiety-like behaviours in depressive-like Cpefat/fat mice
Authors: Rodriguiz Ramona M. , Wilkins John J. , Creson Thomas K. , Biswas Reeta , Berezniuk Iryna , Fricker Arun D. , Fricker Lloyd D. , Wetsel William C.
Published: February 2013

Cpefat/fat mice have a point mutation in carboxypeptidase E (Cpe), an exopeptidase that removes C-terminal basic amino acids from intermediates to produce bioactive peptides. The mutation renders the enzyme inactive and unstable. The absence of Cpe activity in these mutants leads to abnormal processing of many peptides, with elevated levels of intermediates and greatly reduced levels of the mature peptides. Cpefat/fat mice develop obesity, diabetes and infertility in adulthood. We examined whether anxiety- and/or depressive-like behaviours are also present. Anxiety-like responses are not evident in young Cpefat/fat mice (∼60 d), but appear in older animals (>90 d). These behaviours are reversed by acute treatment with diazepam or fluoxetine. In contrast, increased immobilities in forced swim and tail suspension are evident in all age groups examined. These behaviours are reversed by acute administration of reboxetine. In comparison acute treatments with fluoxetine or bupropion are ineffective; however, immobility times are normalized with 2 wk treatment. These data demonstrate that Cpefat/fat mice display depressive-like responses aged ∼60 d, whereas anxiety-like behaviours emerge ∼1 month later. In tail suspension, the reboxetine findings show that noradrenergic actions of antidepressants are intact in Cpefat/fat mice. The ability of acute fluoxetine treatment to rescue anxiety-like while leaving depressive-like responses unaffected suggests that serotonin mechanisms underlying these behaviours are different. Since depressive-like responses in the Cpefat/fat mice are rescued by 2 wk, but not acute, treatment with fluoxetine or bupropion, these mice may serve as a useful model that resembles human depression.
Religious Freedom and Majority Rule: Marsilius of Padua “on” Abdullahi Ahmed an-Na‘im and the “Secular” Islamic State
Authors: Koch Bettina
Published: February 2013

This article discusses Abdullahi Ahmed an-Na‘im's Islam and the Secular State from the perspective of Marsilius of Padua's political theory. Both authors share similar concepts of the relationship between religion, state policy, and the state, and allow for the integration of religious doctrines into state law. Nonetheless, the Marsilian conception provides stronger protection of unbelievers' and religious dissenters' civic rights. In the broader discourse on political theory of rights, Marsilius argues in favors of individual rights and a protection of minority rights, while an-Na‘im's theory of Shari‘a reform suggests a preference for a people's self-determination.
Metabolic Imaging of Bilateral Anterior Capsulotomy in Refractory Obsessive Compulsive Disorder: an FDG PET Study
Authors: Zuo ChuanTao , Ma Yilong , Sun BoMin , Peng Shichun , Zhang HuiWei , Eidelberg David , Guan YiHui
Published: February 2013

The therapeutic benefits of bilateral capsulotomy for the treatment of refractory obsessive compulsive disorder (OCD) are probably attributed to interruption of the cortico-striato-thalamo-cortical circuitry. We evaluated resting brain metabolism and treatment response in OCD patients using positron emission tomography (PET) imaging. [18F]-fluoro-deoxy-glucose PET was performed in eight OCD patients precapsulotomy and postcapsulotomy. We determined metabolic differences between preoperative images in patients and those in eight age-matched healthy volunteers, and postoperative changes and clinical correlations in the patients. The OCD patients showed widespread metabolic increases in normalized glucose metabolism in the bilateral orbitofrontal cortex and inferior frontal gyrus, cingulate gyrus, and bilateral pons/cerebellum, and metabolic decreases bilaterally in the precentral and lingual gyri. Bilateral capsulotomy resulted in significant metabolic decreases bilaterally in the prefrontal cortical regions, especially in the dorsal anterior cingulate cortex (ACC) and in the medial dorsal thalamus and caudate nucleus. In contrast, metabolism increased bilaterally in the precentral and lingual gyri. Clinical improvement in patients correlated with metabolic changes in the bilateral dorsal ACC and in the right middle occipital gyrus after capsulotomy. This study underscores the importance of the internal capsule in modulating ventral prefrontal and dorsal anterior cingulate neuronal activity in the neurosurgical management of OCD patients.
What Went Wrong? the Flawed Concept of Cerebrospinal Venous Insufficiency
Authors: Valdueza José M , Doepp Florian , Schreiber Stephan J , van Oosten Bob W , Schmierer Klaus , Paul Friedemann , Wattjes Mike P
Published: February 2013

In 2006, Zamboni reintroduced the concept that chronic impaired venous outflow of the central nervous system is associated with multiple sclerosis (MS), coining the term of chronic cerebrospinal venous insufficiency (‘CCSVI’). The diagnosis of ‘CCSVI’ is based on sonographic criteria, which he found exclusively fulfilled in MS. The concept proposes that chronic venous outflow failure is associated with venous reflux and congestion and leads to iron deposition, thereby inducing neuroinflammation and degeneration. The revival of this concept has generated major interest in media and patient groups, mainly driven by the hope that endovascular treatment of ‘CCSVI’ could alleviate MS. Many investigators tried to replicate Zamboni's results with duplex sonography, magnetic resonance imaging, and catheter angiography. The data obtained here do generally not support the ‘CCSVI’ concept. Moreover, there are no methodologically adequate studies to prove or disprove beneficial effects of endovascular treatment in MS. This review not only gives a comprehensive overview of the methodological flaws and pathophysiologic implausibility of the ‘CCSVI’ concept, but also summarizes the multimodality diagnostic validation studies and open-label trials of endovascular treatment. In our view, there is currently no basis to diagnose or treat ‘CCSVI’ in the care of MS patients, outside of the setting of scientific research.
Modeling and Simulation to Optimize the Design and Analysis of Confirmatory Trials, Characterize Risk–Benefit, and Support Label Claims
Authors: Marshall SF , Hemmings R , Josephson F , Karlsson MO , Posch M , Steimer J‐L
Published: February 2013

The role of modeling and simulation (M&S) in the design and interpretation of phase III studies, from break out session 4 of the European Medicines Agency (EMA)/European Federation of Pharmaceutical Industries and Associations (EFPIA) M&S workshop, was divided into themes illustrated with case studies (Table 1): (1) M&S being conducted to support the design of confirmatory trials; (2) longitudinal model‐based test as primary inferential analysis (biosimilarity and disease progression trials); (3) assessment of benefit–risk ratio, approval and labeling of an unstudied dose or dosing regimen, and development of future regulatory guidance.

CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e27; doi:10.1038/psp.2013.4; advance online publication 27 February 2013
High throughput technology: approaches of research in homogeneous and heterogeneous catalysis
Authors: Schunk Stephan A. , Böhmer Natalia , Futter Cornelia , Kuschel Andreas , Prasetyo Eko , Roussière Thomas
Published: February 2013

High throughput experimentation (HTE) approaches and the choice of the design of experiment (DoE) tools are discussed with regard to their convenience and applicability in homogeneous and heterogeneous catalysis as a concerted workflow. Much attention is given to diverse methodologies and strategies, which are fundamental for the experimental planning. For two target reactions in two case studies presented in this chapter, HTE methods were applied to create and evaluate catalyst libraries. A homogeneous catalyst case study is illustrated first, which deals with parallel synthesis and screening of organometallic catalysts in the polymerisation of ethylene. The second case study (heterogeneous catalysis) focuses on coherent synthesis and testing of dopant effects on the performance of oxidation catalysts in a reaction of transformation of n-butane to maleic anhydride. Supporting examples from the literature described here show that careful planning of libraries and test conditions is vital in high throughput experimentation in order to deliver meaningful results leading to performance improvements or disruptive new findings.
Core-shell catalysts and bimodal catalysts for Fischer-Tropsch synthesis
Authors: Bao Jun , Tsubaki Noritatsu
Published: February 2013

In the past decades, numerous efforts have been made to develop efficient catalyst systems for Fischer-Tropsch synthesis (FTS) reaction. This chapter reviews two successful examples of catalyst design and development for FTS reaction: the core-shell catalyst and bimodal catalyst. Their preparation methods, structures and catalytic performances are introduced. The core-shell catalysts are designed by coating a zeolite membrane on the surface of pre-shaped catalyst pellet. The catalysts show excellent performance for the direct synthesis of isoparaffins based on the FTS reaction. The formation of heavy hydrocarbons is suppressed completely and the middle isoparaffins become the main products. This core-shell structure provides a tailor-made confined reaction environment that result in spatially confined effects and shape selectivity. The bimodal catalysts are prepared using oxide or active components as building blocks to produce small pores inside large pores of homo- or hetero-atom support. The large pore size of the bimodal catalysts can be successfully controlled. Both the experiment investigations and mathematical simulation have demonstrated that the bimodal pore structure can increase the FTS activity through higher diffusion efficiency in large pores and higher dispersion of active metal particles via increased surface area. Besides the spatial effect, new chemical effects might appear with the formation of hetero-atom structure. The concepts and preparation methods of core-shell catalysts and bimodal catalysts provide insight and inspiration for other catalytic reactions.
Aggravated efficiency droop in vertical-structured gallium nitride light-emitting diodes induced by high temperature aging
Authors: Liu Lilin , Yang Jianfu , Ling Minjie , Zhong Jianwei , Teng Dongdong , Wang Gang
Published: February 2013

The present work demonstrates that aging at higher temperatures significantly aggravates “efficiency droop” in the n-side-up vertical-structured GaN-based light-emitting diodes (LEDs). The observed luminous efficiency droop is over 40% at the measuring current of 350 mA. This phenomenon closely relates with creeping of Au80Sn20 eutectic bonds. On one hand, the plastic deformation accumulated during creeping at higher aging temperatures will make the LED epilayers tensile strained at room temperature. The tensile strain induces a change of the internal quantum efficiency (IQE). The maximum variation of IQE related with strain states was around 20%. On the other hand, creeping under the thermal-mismatching induced tensile stress activates voids' nucleation and growth in the solder bonds. The distribution profile of voids in solder bonds will be mapped on the multiple quantum-well structure in vertical-structured LED chips. Local current densities can be much higher than the average current density used in the calculation of LED's efficiencies. Therefore, the efficiency roll-off value will shift toward the smaller bias direction and the total internal quantum efficiency will decrease as current increases.
Cu(In, Ga)Se2 microcells: High efficiency and low material consumption
Authors: Paire Myriam , Lombez Laurent , Donsanti Frédérique , Jubault Marie , Collin Stéphane , Pelouard Jean-Luc , Guillemoles Jean-François , Lincot Daniel
Published: February 2013

Using solar cells under concentrated illumination is known to improve the conversion efficiency while diminishing the active area and thus material consumption. Recent concentrator cell designs tend to go miniaturized devices, in the 0.5–1 mm range, enabling a better thermal evacuation due to higher surface to volume ratio. If the cell size is further reduced to the micrometric range, spreading resistance losses can be made vanishingly small. This is particularly interesting for the thin film technology which has been limited up to now to very low concentration systems, from ×1 to ×10, due to excessive resistive losses in the window layer and difficult thermal management of the cells, grown on glass substrates. A new solar cell architecture, based on polycrystalline Cu(In,Ga)Se2 (CIGS) absorber, is studied: microscale thin film solar cells. Due to the reduced lateral dimension of the microcells (5 to 500 μm in diameter), the resistive and thermal losses are drastically decreased, enabling the use of high concentration (>×100). This results in a breakthrough for concentration on this type of devices, which were previously limited to the low concentration range (about ×10). Due to light concentration, the open circuit voltage increases up to several thousand suns equivalent, to reach over 900 mV. The temperature increase is limited to less than 20 °C over the ambient at concentration around ×1000. A 5% absolute efficiency increase on microcells at ×475 is observed and a 21.3% ± 0.2% equivalent efficient microcell of 50 μm of diameter is measured.
Sensitization of ZnO nanowire arrays with CuInS2 for extremely thin absorber solar cells
Authors: Sanchez Sylvia , Aldakov Dmitry , Rouchon Denis , Rapenne Laëtitia , Delamoreanu Alexandru , Lévy-Clément Claude , Ivanova Valentina
Published: February 2013

We report on the photosensitization of electrodeposited ZnO nanowire arrays with CuInS2 (CIS) extremely thin layers prepared by two methods: successive ionic layer adsorption and reaction (SILAR) and electrochemical deposition (ECD). This is the first time that such core (ZnO)/shell (CIS) nanostructures are realized. Using SILAR method, 20 nm thick films composed of CIS nanoparticles are grown after 15 deposition cycles. The final layer thickness when prepared by SILAR technique depends on the number of deposition cycles and is used as a main parameter to control it. For the electrodeposited CIS films the passed charge density during deposition is used for monitoring the film thickness. These room-temperature solution based methods (SILAR and ECD) appear to be very suitable for preparing good quality, thin uniform (in nanometer scale) films of absorbing materials.
Effect of annealing on the loss kinetics of charge carriers in CdS films
Authors: Rabenok E. V. , Gapanovich M. V. , Bocharova S. I. , Meteleva-Fischer Y. , Bocharov K. V. , Novikov G. F.
Published: February 2013

The influence of the annealing treatment on the kinetics of the electron trapping processes in CdS thin films has been investigated using the contactless time-resolved microwave photoconductivity technique (TRMC) in 9 GHz band. The thin (<200 nm) CdS films were synthesized using two techniques: by the chemical deposition from the solution (CBD method) and by the pyrolysis of the aerosols of the aqueous solutions of the thiourea coordination compounds of cadmium (Cd(thio)2Cl2) on a heated substrate. Annealing in both the air and the nitrogen atmospheres resulted in an increase of the amplitude and characteristic decay time of the photoresponse. Two particular effects caused by the annealing treatments were observed: the structural improvement and the energy redistribution of the electron traps.
A new deposition process for Cu(In,Ga)(S,Se)2 solar cells by one-step electrodeposition of mixed oxide precursor films and thermochemical reduction
Authors: Duchatelet A. , Savidand G. , Vannier R. N. , Chassaing E. , Lincot D.
Published: February 2013

One step electrochemical deposition of Cu-In-Ga mixed oxide precursor film on Mo substrate is carried out by potentiostatic method in an acidic nitrate based electrolyte. Deposition parameters, such as ions concentration, deposition time and potential, enable to control accurately the layer composition and thickness. The oxide layer is subsequently transformed into metallic alloy by thermal reduction, and selenized into Cu(In,Ga)Se2 compound. First cell results show conversion efficiency up to 9.4%.
The study of influence of doping by iodine or gallium on the lifetime of photogenerated current carriers in CdTe
Authors: Gapanovich M. V. , Bocharov K. V. , Novikov G. F.
Published: February 2013

This study investigated how doping by iodine or gallium affects processes associated with current carriers by undertaking a kinetics investigation of electron loss processes in the CdTe samples prepared by direct ampoule method. Owing to these processes, the current carriers generated by light can be trapped or recombined after a thermalization process and fail to reach electrodes during their lifetime and adversely impact the photovoltaic performance of solar cells. The microwave photoconductivity method provides an effective means of obtaining direct data on the lifetime and energy distribution of traps for current carriers. The obtained lifetimes in doped materials were compared to those in initial polycrystalline CdTe and monocrystalline CdTe. The experimental results indicate that the free electron lifetimes become higher after the doping. We found that the lifetime in the doped polycrystalline samples was equal (for I-doped samples) or even higher (for Ga-doped samples) than in CdTe monocrystals. The model based on the self compensation effect was suggested for the explanation of the experimental results.
Effects of sulphur and air annealing on the properties of thermally evaporated SnS layers for application in thin film solar cell devices
Authors: Nwofe P. A. , Miles R. W. , Ramakrishna Reddy K. T.
Published: February 2013

Thin films of tin sulphide (SnS) have been deposited using the thermal evaporation method and the layers annealed in either air or an environment containing elemental sulphur to increase the grain size while minimising sulphur loss from the annealed layers. Scanning electron microscopy (SEM), X-ray diffractometer (XRD) and optical data are given for the as-deposited and annealed samples. Heterojunction devices were made with CdS as the n-type partner layer in the “superstrate configuration.” The spectral response of these devices exhibited the classic “heterojunction window effect.” Capacitance-voltage measurements indicated uniform doping of the SnS for low reverse biases (<0.5  V) with a carrier concentration 1014−1015cm−3 near to the junction and a built-in voltage of 0.85 V. Capacitance frequency measurements corresponded to an interface trap density of 3.06×1011FC−1cm−2.
A new kind of low-inductance transformer type magnetic switch (TTMS) with coaxial cylindrical conductors
Authors: Zhang Yu , Liu Jinliang
Published: February 2013

As important devices for voltage boosting and switching, respectively, pulse transformer and magnetic switch are widely used in pulsed power technology. In this paper, a new kind of transformer type magnetic switch (TTMS) with coaxial cylindrical conductors is put forward to combine the functions of voltage boosting and switching in one power device. As a compact combination device of discrete pulse transformer and magnetic switch, the compact TTMS decreases the required volume of magnetic cores in a large scale. The primary windings of the TTMS have a parallel combination structure so that the TTMS which only has 3 turns of secondary windings has a step-up ratio at 1:9. Before the magnetic core saturates, the TTMS has low unsaturated inductances of windings and good pulse response characteristics, so it can be used to substitute the Marx generator to charge the pulse forming line (PFL) at the ranges of several hundred kV and several hundred ns. After the core saturates, the cylindrical conductors can decrease the saturated inductance of the secondary windings of TTMS to a level less than 400 nH. As a result, the proposed TTMS can be used as the boosting transformer and main switch of helical Blumlein PFL to form the quasi-square voltage pulse on the 160 Ω load with a short pulse rise time only at 60 ns.