bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinematic quantities of finite elastic and plastic deformation
Authors: Fülöp Tamás , Ván Péter
Published: June 2012

Kinematic quantities for finite elastic and plastic deformations are defined via an approach that does not rely on auxiliary elements, such as reference frame and reference configuration, and that gives account of the inertial–noninertial aspects explicitly. These features are achieved by working on Galilean spacetime directly. The quantity expressing elastic deformations is introduced according to its expected role: to measure how different the current metric is from the relaxed/stressless metric. Further, the plastic kinematic quantity is the change rate of the stressless metric. The properties of both are analyzed, and their relationship with frequently used elastic and plastic kinematic quantities is discussed. One important result is that no objective elastic or plastic quantities can be defined from the deformation gradient. Copyright © 2012 John Wiley & Sons, Ltd.
A new closed‐form solution for analysis of unlined pressure tunnels under seepage forces
Authors: Fahimifar Ahamad , Zareifard Mohammad Reza
Published: June 2012

In this study, a simplified analytical closed‐form solution, considering plane strain and axial symmetry conditions, for analysis of a circular pressure tunnel excavated underwater table, is developed. The method accounts for the seepage forces with the steady‐state flow and is based on the generalized effective stress law. To examine the effect of pore pressure variations and also the boundary conditions at the ground surface, the formulations are derived for different directions around the tunnel. The proposed method can be applied for analysis and design of pressure tunnels. Illustrative examples are given to demonstrate the performance of the proposed solution and also to examine the effect of seepage forces on the stability of tunnels. The simplified analytical solution derived in this study is compared with numerical analyses. It is concluded that the classic solutions (Lame's thick‐walled solution), considering the internal pressure as a mechanical load applied to the tunnel surface, are not applicable to pervious media and can result in an unsafe design. Copyright © 2012 John Wiley & Sons, Ltd.
Pushing the limits of high‐resolution functional MRI using a simple high‐density multi‐element coil design
Authors: Petridou N. , Italiaander M. , van de Bank B. L. , Siero J. C. W. , Luijten P. R. , Klomp D. W. J.
Published: June 2012

Recent studies have shown that functional MRI (fMRI) can be sensitive to the laminar and columnar organization of the cortex based on differences in the spatial and temporal characteristics of the blood oxygenation level‐dependent (BOLD) signal originating from the macrovasculature and the neuronal‐specific microvasculature. Human fMRI studies at this scale of the cortical architecture, however, are very rare because the high spatial/temporal resolution required to explore these properties of the BOLD signal are limited by the signal‐to‐noise ratio. Here, we show that it is possible to detect BOLD signal changes at an isotropic spatial resolution as high as 0.55 mm at 7 T using a high‐density multi‐element surface coil with minimal electronics, which allows close proximity to the head. The coil comprises of very small, 1 × 2‐cm2, elements arranged in four flexible modules of four elements each (16‐channel) that can be positioned within 1 mm from the head. As a result of this proximity, tissue losses were five‐fold greater than coil losses and sufficient to exclude preamplifier decoupling. When compared with a standard 16‐channel head coil, the BOLD sensitivity was approximately 2.2‐fold higher for a high spatial/temporal resolution (1 mm isotropic/0.4 s), multi‐slice, echo planar acquisition, and approximately three‐ and six‐fold higher for three‐dimensional echo planar images acquired with isotropic resolutions of 0.7 and 0.55 mm, respectively. Improvements in parallel imaging performance (geometry factor) were up to around 1.5‐fold with increasing acceleration factor, and improvements in fMRI detectability (temporal signal‐to‐noise ratio) were up to around four‐fold depending on the distance to the coil. Although deeper lying structures may not benefit from the design, most fMRI questions pertain to the neocortex which lies within approximately 4 cm from the surface. These results suggest that the resolution of fMRI (at 7 T) can approximate levels that are closer to the spatial/temporal scale of the fundamental functional organization of the human cortex using a simple high‐density coil design for high sensitivity. Copyright © 2012 John Wiley & Sons, Ltd.
On a multiscale strategy and its optimization for the simulation of combined delamination and buckling
Authors: Saavedra K. , Allix O. , Gosselet P.
Published: June 2012

This paper investigates a computational strategy for studying the interactions between multiple through‐the‐width delaminations and global or local buckling in composite laminates taking into account possible contact between the delaminated surfaces. To achieve an accurate prediction of the quasi‐static response, a very refined discretization of the structure is required, leading to the resolution of very large and highly nonlinear numerical problems. In this paper, a nonlinear finite element formulation along with a parallel iterative scheme based on a multiscale domain decomposition is used for the computation of three‐dimensional mesoscale models. Previous works by the authors already dealt with the simulation of multiscale delamination assuming small perturbations. This paper presents the formulation used to include geometric nonlinearities into this existing multiscale framework and discusses the adaptations that need to be made to the iterative process to ensure the rapid convergence and the scalability of the method in the presence of buckling and delamination. These various adaptations are illustrated by simulations involving large numbers of DOFs. Copyright © 2012 John Wiley & Sons, Ltd.
Galerkin reduced‐order modeling scheme for time‐dependent randomly parametrized linear partial differential equations
Authors: Audouze Christophe , Nair Prasanth B.
Published: June 2012

In this paper, we consider the problem of constructing reduced‐order models of a class of time‐dependent randomly parametrized linear partial differential equations. Our objective is to efficiently construct a reduced basis approximation of the solution as a function of the spatial coordinates, parameter space, and time. The proposed approach involves decomposing the solution in terms of undetermined spatial and parametrized temporal basis functions. The unknown basis functions in the decomposition are estimated using an alternating iterative Galerkin projection scheme. Numerical studies on the time‐dependent randomly parametrized diffusion equation are presented to demonstrate that the proposed approach provides good accuracy at significantly lower computational cost compared with polynomial chaos‐based Galerkin projection schemes. Comparison studies are also made against Nouy's generalized spectral decomposition scheme to demonstrate that the proposed approach provides a number of computational advantages. Copyright © 2012 John Wiley & Sons, Ltd.
Social capital and nonprofit governance effectiveness
Authors: Fredette Christopher , Bradshaw Patricia
Published: June 2012

This article examines the important role of social resources in enhancing the effectiveness of nonprofit boards of directors, paying particular attention to the positive implications of social capital. Using data collected from a survey of 234 organizations operating in the Canadian nonprofit sector, we model the relationship between a three‐factor model of social capital and a multidimensional measure of governance effectiveness. Our results demonstrate the positive contribution that social capital makes to the capacity to govern effectively. Findings of our study support the need for renewed attention to social and relational considerations inside the boardroom.
Bullying as a style of personal relating: Personality characteristics and interpersonal aspects of self‐reports of bullying behaviours among Italian adolescent high school students
Authors: Fossati Andrea , Borroni Serena , Maffei Cesare
Published: June 2012

Two independent studies that were based on two independent samples of non‐clinical adolescents were used to evaluate the association between bullying behaviour, personality traits, attachment style and risk behaviour (such as substance abuse). In particular, Study 1 (N = 1024) was designed to test the associations between bullying and the Big Five personality traits measures. Low scores for Agreeableness and, to a lesser extent, for Conscientiousness characterized adolescents who reported the bullying behaviours. Study 2 (N = 763) was designed to explore the relationships between the bullying behaviours and the adult attachment construct and to evaluate the associations between bully, victim and prosocial attitudes and relationships with peers and substance abuse. The results of Study 2 showed that self‐reports of bullying behaviours were selectively correlated with dismissing attachment style, preference for relationship with deviant groups and excessive use of alcohol and use of substances. Copyright © 2012 John Wiley & Sons, Ltd.
Chemical and photochemical reactivity of 6‐hydroxymethyl‐7,8‐dihydropterin in aqueous solutions
Authors: Thomas Andrés H. , Oliveros Esther , Braun André M. , Espinosa Mariela S. , Lorente Carolina , Dántola M. Laura
Published: June 2012

6‐Hydroxymethyl‐7,8‐dihydropterin (H2Hmp) is an intermediate in the biosynthesis of folate, a precursor of coenzymes involved in the metabolism of nucleotides and amino acids. In this work, we have investigated the reactions undergone by H2Hmp in aqueous solutions at physiological pH, in the absence and in the presence of UV‐A radiation (320–400 nm). In air‐equilibrated solutions, H2Hmp undergoes slow thermal oxidation (half‐life 37 h) to yield 7,8‐dihydroxanthopterin (H2Xap) as the main product. The reaction of H2Hmp with hydrogen peroxide also yields H2Xap as a main product. In contrast, UV‐A excitation of H2Hmp leads to the formation of a dimer identified by electrospray ionization mass spectrometry. The corresponding quantum yield of H2Hmp consumption (Φ−R) was independent of O2 and reactant concentration and has a value of 0.10 (±0.02), more than twice higher than that measured for other 6‐subtituted 7,8‐dihydropterins. Copyright © 2012 John Wiley & Sons, Ltd.
Prework and precompletion of worksheets for process hazard analysis
Authors: Baybutt Paul
Published: June 2012

Prework in preparation for process hazard analysis (PHA) is vital for an efficient study. Precompletion of PHA worksheets in an effort to reduce the time needed for a PHA study may detract from the quality of the study and also may not be acceptable to regulators. Appropriate prework is described, and proposals are made for when worksheets can be precompleted. © 2012 American Institute of Chemical Engineers Process Saf Prog, 2012
The mixing state of aerosols over the Indo‐Gangetic Plain and its impact on radiative forcing
Authors: Srivastava Rohit , Ramachandran S.
Published: June 2012

Seasonal variations in mixing states of aerosols over an urban (Kanpur) and a rural location (Gandhi College) in the Indo‐Gangetic Plain (IGP) are determined using the measured and modelled optical properties, and the impact of aerosol mixing state on radiative forcing is examined. Different fractions of black carbon (BC) and water‐soluble aerosols in core‐shell mixing emerged as the probable mixing state during winter, monsoon and post‐monsoon over Kanpur. The degree of mixing, i.e. the percentage mass fraction of aerosols involved in core‐shell mixing, is found to exhibit seasonal variations. Owing to the abundance of mineral dust (MD) during the pre‐monsoon, MD coated by BC emerges as the most probable mixing state. Top‐of‐atmosphere (TOA) forcing changes its sign from positive for external mixing to negative for different probable mixing states during the pre‐monsoon over both locations, as single scattering albedo is lower for external mixing. However, for other seasons, the TOA forcing is negative for external and different probable core‐shell mixing states of aerosols. Surface aerosol forcing for probable mixing state during the post‐monsoon is higher (−44 W m−2) over Kanpur, and is lower (−24 W m−2) over Gandhi College. A regression between instantaneous model‐derived aerosol forcing and AERONET‐measured forcing yielded r2 > 0.9, which confirms the robustness of the methodology adopted to retrieve aerosol optical properties and estimate forcing. Heating rates over Kanpur and Gandhi College during the pre‐monsoon and monsoon are ∼0.75 K d−1 and ∼0.5 K d−1 respectively. Differences exist between measured and model‐derived asymmetry parameter, g, owing to the non‐sphericity of aerosols. However, aerosol radiative forcing is found to be weakly sensitive to the variation in g due to high (> 0.2) surface albedo. The modelling study provides new insights into the state of aerosol mixing, and indicates that aerosol mixing can vary depending on the type and abundance of aerosol species. Copyright © 2012 Royal Meteorological Society
Analytic upscaling of a local microphysics scheme. Part II: Simulations
Authors: Griffin Brian M. , Larson Vincent E.
Published: June 2012

Part I of this two‐part series presents a method to account for the effects of subgrid variability on average microphysical process rates. The method involves upscaling a local microphysics scheme, that is, computing a grid‐box average by integrating over an assumed probability density function (PDF). In this paper (Part II), the method is tested. The test case is based on research flight two (RF02) of the second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS‐II) field experiment. The upscaled microphysics scheme is incorporated into a single‐column model (SCM). Then two SCM simulations of the RF02 test case are performed. They are identical except that one upscales the local microphysics scheme and one does not. Both SCM simulations are compared with a benchmark large‐eddy simulation (LES) of the same test case using the same local microphysics scheme.

Compared to the local microphysics, the representation of variability inherent in the upscaled microphysics increases autoconversion of cloud droplets to raindrops and accretion (i.e. collection) of cloud droplets onto raindrops. The combined effect is that upscaling the microphysics in the RF02 case leads to significantly more rainwater at the ocean surface, in closer agreement to the LES. Copyright © 2012 Royal Meteorological Society
How important is the isothermal expansion effect in elevating equivalent potential temperature in the hurricane inner core?
Authors: Smith Roger K. , Montgomery Michael T.
Published: June 2012

We examine aspects of the thermodynamic structure of mature Atlantic hurricane Earl (2010) based on airborne dropwindsondes released from the upper troposphere during the National Aeronautics and Space Administration (NASA), Genesis and Rapid Intensification Processes (GRIP) experiment. Vertical sounding profiles of the data raise questions concerning the relative roles of isothermal expansion and relative humidity increase in elevating the equivalent potential temperature of air parcels spiralling inwards to the eyewall convection region. The observational results obtained for two successive days of this category 4 hurricane show that the isothermal expansion effect leads to roughly one half of the increment in equivalent potential temperature for boundary‐layer air parcels moving between the region outside the eyewall and the eyewall and eye region. Copyright © 2012 Royal Meteorological Society
Radiation protection issues related to the use of nuclear power
Authors: Wikman‐Svahn Per
Published: June 2012

Nuclear power generation require protection against harmful effects of ionizing radiation. Radiation protection is based on the linear, no‐threshold model of health risks at low doses and three fundamental principles: justification, optimization, and limitation. The practical application of radiation protection is divided into three areas: planned, emergency, and existing exposure situations. Planned exposure situations include difficult social issues related to the exposure of large populations, exposure of future generations, protection against accidents, and protection of the environment. Emergency and existing exposure situations are both characterized by heterogeneous distributions of exposures and complex social and economic aspects, which make assessment and evaluation of protective strategies complicated and value laden. Four problem areas of social and ethical issues stand out as central for radiation protection: The first is uncertainty and the influence of value judgments in scientific risk assessments. The second is distributions of risks and benefits between different individuals, both in space and time. The third is the problem of setting limits when there is no known level of exposure that is associated with a zero risk. The fourth central problem area is related to stakeholder influence and risk communication.

This article is categorized under:

Nuclear Power > Science and Materials
Aspects of holography for theories with hyperscaling violation
Authors: Dong Xi , Harrison Sarah , Kachru Shamit , Torroba Gonzalo , Wang Huajia
Published: June 2012

Abstract

We analyze various aspects of the recently proposed holographic theories with general dynamical critical exponentzand hyperscaling violation exponentθ. We first find the basic constraints onz,θfrom the gravity side, and compute the stress-energy tensor expectation values and scalar two-point functions. Massive correlators exhibit a nontrivial exponential behavior at long distances, controlled byθ. At short distance, the two-point functions become power-law, with a universal form forθ > 0. Next, the calculation of the holographic entanglement entropy reveals the existence of novel phases which violate the area law. The entropy in these phases has a behavior that interpolates between that of a Fermi surface and that exhibited by systems with extensive entanglement entropy. Finally, we describe microscopic embeddings of someθ ≠ 0 metrics into full string theory models — these metrics characterize large regions of the parameter space of Dp-brane metrics forp ≠ 3. For instance, the theory ofND2-branes in IIA super gravity hasz = 1 andθ = −1/3 over a wide range of scales, at largegsN.
Parton shower evolution with subleading color
Authors: Nagy Zoltán , Soper Davison E.
Published: June 2012

Abstract

Parton shower Monte Carlo event generators in which the shower evolves from hard splittings to soft splittings generally use the leading color approximation, which is the leading term in an expansion in powers of
${{1} \left/ {{N_c^2}} \right.}$
, where N
c = 3 is the number of colors. We introduce a more general approximation, the LC + approximation, that includes some of the color suppressed contributions. There is a cost: each generated event comes with a weight. There is a benefit: at each splitting the leading soft × collinear singularity and the leading collinear singularity are treated exactly with respect to color. In addition, an LC + shower can start from a state of the color density matrix in which the bra state color and the ket state color do not match.
Eisenstein series for infinite-dimensional U-duality groups
Authors: Fleig Philipp , Kleinschmidt Axel
Published: June 2012

Abstract

We consider Eisenstein series appearing as coefficients of curvature corrections in the low-energy expansion of type II string theory four-graviton scattering amplitudes. We define these Eisenstein series over all groups in the E

n
series of string duality groups, and in particular for the infinite-dimensional Kac-Moody groups E
9, E
10 and E
11. We show that, remarkably, the so-called constant term of Kac-Moody-Eisenstein series contains only a finite number of terms for particular choices of a parameter appearing in the definition of the series. This resonates with the idea that the constant term of the Eisenstein series encodes perturbative string corrections in BPS-protected sectors allowing only a finite number of corrections. We underpin our findings with an extensive discussion of physical degeneration limits in D < 3 space-time dimensions.
The Credibility of Open Market Share Repurchase Signaling
Authors: Babenko Ilona , Tserlukevich Yuri , Vedrashko Alexander
Published: June 2012

Open market share repurchase announcements are commonly associated with equity undervaluation, but their signal about firm value can often be misleading. We conjecture that executives who buy shares of their firm before an announcement add credibility to the undervaluation signal. Consistent with this hypothesis, we find that announcement returns are positively related to past insider purchases, especially for firms that are priced less efficiently. Firms whose insiders bought more shares are also more likely to complete their repurchase plans. Finally, we find that insider purchases predict post-announcement stock returns.
In Memoriam: Professor Miomir Vukobratović (1931–2012)
Authors: Borovac Branislav
Published: June 2012

Professor Miomir Vukobratović passed away on March 11, 2012 at the age of 81. However, his achievements in robotics will remain with us always.

Miomir Vukobratović was born in 1931. He graduated in 1957 from the Faculty of Mechanical Engineering, University of Belgrade, where he also obtained his first PhD in 1964. In January 1958 he joined the Aeronautical Institute in Belgrade. At the beginning of 1965 he moved to the Mihajlo Pupin Institute in Belgrade, where he became director of the Robotics Laboratory. In 1980, he became professor at the Production Engineering Department of the Faculty of Mechanical Engineering, University of Belgrade.
Cup-products for the polyhedral product functor
Authors: BAHRI A. , BENDERSKY M. , COHEN F. R. , GITLER S.
Published: June 2012

Davis–Januszkiewicz introduced manifolds which are now known as moment-angle manifolds over a polytope [6]. Buchstaber–Panov introduced and extensively studied moment-angle complexes defined for any abstract simplicial complex K [4]. They completely described the rational cohomology ring structure in terms of the Tor-algebra of the Stanley-Reisner algebra [4].

Subsequent developments were given in work of Denham–Suciu [7] and Franz [9] which were followed by [1, 2]. Namely, given a family of based CW-pairs X, A) = {(Xi, Ai)}mi=1 together with an abstract simplicial complex K with m vertices, there is a direct extension of the Buchstaber–Panov moment-angle complex. That extension denoted Z(K;(X,A)) is known as the polyhedral product functor, terminology due to Bill Browder, and agrees with the Buchstaber–Panov moment-angle complex in the special case (X,A) = (D2, S1) [1, 2]. A decomposition theorem was proven which splits the suspension of Z(K; (X, A)) into a bouquet of spaces determined by the full sub-complexes of K.

This paper is a study of the cup-product structure for the cohomology ring of Z(K; (X, A)). The new result in the current paper is that the structure of the cohomology ring is given in terms of this geometric decomposition arising from the “stable” decomposition of Z(K; (X, A)) [1, 2]. The methods here give a determination of the cohomology ring structure for many new values of the polyhedral product functor as well as retrieve many known results.

Explicit computations are made for families of suspension pairs and for the cases where Xi is the cone on Ai. These results complement and extend those of Davis–Januszkiewicz [6], Buchstaber–Panov [3, 4], Panov [13], Baskakov–Buchstaber–Panov, [3], Franz, [8, 9], as well as Hochster [12]. Furthermore, under the conditions stated below (essentially the strong form of the Künneth theorem), these theorems also apply to any cohomology theory.
On complex oscillation, function-theoretic quantization of non-homogeneous periodic ordinary differential equations and special functions
Authors: Chiang Yik-Man , yu Kit-Wing
Published: June 2012

New necessary and sufficient conditions are given for the quantization of a class of periodic second-order non-homogeneous ordinary differential equations in the complex plane. The problem is studied from the viewpoint of complex oscillation theory first developed in works by Bank and Laine and Gundersen and Steinbart. We show that, when a solution is complex non-oscillatory (finite exponent of convergence of zeros), then the solution, which can be written as special functions, must degenerate. This gives a necessary and sufficient condition when the Lommel function has finitely many zeros in every branch, and this is a type of quantization for the non-homogeneous differential equation. The degenerate solutions are polynomial/rational-type functions, which are of independent interest. In particular, this shows that complex non-oscillatory solutions of this class of differential equations are equivalent to the subnormal solutions considered in a recent paper by Chiang and Yu. In addition to the asymptotics of special functions, the other main idea that we apply in our proof is a classical result by Wright that gives precise asymptotic locations of large zeros of a functional equation.
New global stability estimates for the Calderón problem in two dimensions
Authors: Santacesaria Matteo
Published: June 2012

We prove a new global stability estimate for the Gel’fand–Calderón inverse problem on a two-dimensional bounded domain. Specifically, the inverse boundary value problem for the equation ${- }\Delta \psi + v\hspace{0.167em} \psi = 0$ on $D$ is analysed, where $v$ is a smooth real-valued potential of conductivity type defined on a bounded planar domain $D$. The main feature of this estimate is that it shows that the smoother a potential is, the more stable its reconstruction is. Furthermore, the stability is proven to depend exponentially on the smoothness, in a sense to be made precise. The same techniques yield a similar estimate for the Calderón problem for electrical impedance tomography.
The East Anatolian Fault Zone: Seismotectonic setting and spatiotemporal characteristics of seismicity based on precise earthquake locations
Authors: Bulut Fatih , Bohnhoff Marco , Eken Tuna , Janssen Christoph , Kılıç Tuğbay , Dresen Georg
Published: June 2012

The East Anatolian Fault Zone (EAFZ) represents a plate boundary extending over ∼500 km between the Arabian and Anatolian plates. Relative plate motion occurs with slip rates ranging from 6 to 10 mm/yr and has resulted in destructive earthquakes in eastern Turkey as documented by historical records. In this study, we investigate the seismic activity along the EAFZ and fault kinematics based on recordings from a densified regional seismic network providing the best possible azimuthal coverage for the target region. We optimize a reference 1‐D velocity model using a grid‐search approach and re‐locate hypocenters using the Double‐Difference earthquake relocation technique. The refined hypocenter catalog provides insights into the kinematics and internal deformation of the fault zone down to a resolution ranging typically between 100 and 200 m. The distribution of hypocenters suggests that the EAFZ is characterized by NE‐SW and E‐W oriented sub‐segments that are sub‐parallel to the overall trend of the fault zone. Faulting mechanisms are predominantly left‐lateral strike‐slip and thus in good correlation with the deformation pattern derived from regional GPS data. However, we also observe local clusters of thrust and normal faulting events, respectively. While normal faulting events typically occur on NS‐trending subsidiary faults, thrust faulting is restricted to EW‐trending structures. This observation is in good accordance with kinematic models proposed for evolving shear zones. The observed spatiotemporal evolution of hypocenters indicates a systematic migration of micro‐ and moderate‐sized earthquakes from the main fault into adjacent fault segments within several days documenting progressive interaction between the major branch of the EAFZ and its secondary structures. Analyzing the pre versus post‐seismic phase for M > 5 events we find that aftershock activities are initially spread to the entire source region for several months but start to cluster at the central part of the main shock rupture thereafter.
Preceding, coseismic, and postseismic slips of the 2011 Tohoku earthquake, Japan
Authors: Ozawa Shinzaburo , Nishimura Takuya , Munekane Hiroshi , Suito Hisashi , Kobayashi Tomokazu , Tobita Mikio , Imakiire Tetsuro
Published: June 2012

We estimated the spatial and temporal evolution of the preceding aseismic slip from January 2003 to January 2011, the coseismic slip of the Tohoku earthquake, and the postseismic slip after the earthquake based on global positioning system (GPS) data. Time‐dependent analysis indicates aseismic slip offshore of Miyagi and Fukushima prefectures from 2004 associated with a series of subduction earthquakes that overlap the aseismic slip area. These preceding aseismic and coseismic slip areas are centered between the centers of the coseismic and afterslip areas of the Tohoku earthquake offshore of Miyagi prefecture, while they overlap the coseismic and afterslip areas of the Tohoku earthquake off Fukushima prefecture. The timing of moment magnitude nine (Mw9) ‐class earthquakes appears to be controlled by multiple preceding slip events, smaller earthquakes and their afterslip. The preceding aseismic and coseismic slip decreased the coupling rate off the Tohoku coast, suggesting the possibility that the preceding slip represented a precursive stage of the Tohoku earthquake. The afterslip of the Tohoku earthquake occurred in an area where the coseismic slip was not large, complementing the large coseismic slip zone. The afterslip along Iwate‐Miyagi extends up to 80 km in depth and is currently the sole mechanism of strain release in this depth range. The source region of the anticipated Miyagi‐Oki earthquake shows small postseismic slip after the Tohoku earthquake, reflecting the energy release at the time of the earthquake. Aftershock activity is roughly governed by an afterslip process.
Modeling waves and wind stress
Authors: Donelan M. A. , Curcic M. , Chen S. S. , Magnusson A. K.
Published: June 2012

A model for wave and wind stress prediction is constructed. The source functions that drive the space‐time evolution of the energy spectra are developed in form based on theory and laboratory and field experiments. The calibration factors (proportionality constants of the source functions) are determined from a comparison of modeled and observed significant height and mean period. The observations are for the month of January 2005 and are derived from an array of laser range finders mounted on a bridge between two platforms in the Ekofisk oil field in the North Sea. The model calculates the form stress on the waves and adds it vectorially to the sheltering‐modified skin stress. The resulting drag coefficient versus wind speed is shown to have the observed structure: low in light winds, increasing in moderate winds, and increasing more slowly in very strong winds. Modeled spectral shapes in the four quadrants of Hurricane Bonnie (1998) match the Scanning Radar Altimeter measurements. Modeled spectral properties in Hurricane Ike (2008) are compared against NDBC buoy estimates with good results. Drag coefficients in the mixed seas produced by hurricanes show dependence on wave age of the wind sea, swell propagation direction, and water depth. The need for wave and stress modeling for atmosphere‐ocean coupling is emphasized. The new wave model has all the necessary attributes to be the basis for such a coupler.
Coupled fluid flow and sediment deformation in margin‐scale salt‐tectonic systems: 1. Development and application of simple, single‐lithology models
Authors: Gradmann Sofie , Beaumont Christopher , Ings Steven J.
Published: June 2012

A methodology is presented to model coupled fluid flow and deformation in rifted continental margin composite salt and siliciclastic tectonic systems; and we investigate their compaction and overpressuring behavior associated with continental margin‐scale gravitational spreading. Compaction‐driven Darcy fluid flow in clastic sediments is coupled through the effective pressure to their frictional‐plastic yielding and mechanical deformation. Viscous flow of underlying salt is independent of fluid pressure. Numerical models are adapted to the Oligo‐Miocene phase of large‐scale gravitational failure in the northwestern Gulf of Mexico, and represent the first study of this system that includes dynamically evolving fluid pressure. Here we present the methodology and prototype models with single uniform sediment lithologies and simple parameterizations of their properties. The models serve to illustrate the interactions among compaction, generation of fluid overpressure, and gravitational failure and spreading. Mechanical and viscous compaction behavior of sandstone‐type and shale‐type sediments are investigated. Results demonstrate that mechanical compaction can generate moderate overpressure in thick shale‐type material, whereas high overpressure requires viscous compaction. In sandstone‐type material, only viscous compaction can generate significant overpressure, though this requires tens of millions of years. Changes in the stress regime during gravitational‐driven deformation enhance compaction and overpressure. Although illustrative of the methodology and basic processes, none of the prototype single‐lithology models satisfactorily reproduces Oligo‐Miocene fluid pressure and deformational regimes of the Gulf of Mexico. Numerical models of layered sediments together with an improved formulation of viscous compaction, presented in part 2 of this set of companion papers, are more successful.
Finite Rossby radius effects on vortex motion near a gap
Authors: Nilawar R. S. , Johnson E. R. , McDonald N. R.
Published: June 2012

This work investigates the effect of the Rossby radius of deformation on the motion of a vortex near a gap in an infinitely long barrier. A key parameter determining the behaviour of the vortex is a, the ratio of the Rossby radius of deformation to the width of the gap. Assuming quasi-geostrophic dynamics for a single-layer, reduced-gravity fluid, an integral equation is derived whose solution gives the velocity at any point in the fluid. The integral equation is solved numerically and the velocity field is integrated to give the trajectories of point vortices. Combined with the method of contour dynamics, the method can be used to compute the evolution of finite area patches of constant vorticity. The trajectories of point vortices and vortex patches are compared. The patches are initially circular and the centroids of those vortex patches that remain close to circular follow the trajectory and speed of their equivalent point vortices when appropriately normalised. The critical point vortex trajectory (the separatrix) which divides vortices that leap across the gap and those that pass through, is computed for various a. Decreasing the Rossby radius of deformation increases the tendency of vortices to pass through the gap. The effect of various background flows on both point vortex and vortex patch motion is also described.
Electron distribution and scattering in InAs films on low-k flexible substrates
Authors: Thanh Nguyen Cong , Shih Hong-An , Akabori Masashi , Suzuki Toshi-kazu
Published: June 2012

On low-k flexible substrates, we obtained InAs films with thickness ranging from several hundreds of nm to sub-10-nm, by epitaxial lift-off and van der Waals bonding. Using Hall measurements, we investigated the electron mobility and sheet concentration depending on the InAs film thickness L. In spite of the undoped InAs films, we do not observe electron depletion even for sub-10-nm thickness L, owing to the Fermi level pinning above the conduction band bottom. We observed three regimes of the behavior of the electron mobility μ with decrease in L: almost constant or slightly increasing μ with decrease in L for ≳150 nm, weakly decreasing μ for 150 nm≳L≳15 nm, and more rapidly decreasing μ proportional to Lγ with γ≃ 5–6 for L≲15 nm. By using Poisson-Schrödinger calculation, we examined the electron distribution in the film depending on L and the associated scattering mechanisms contributing to the behavior of μ, such as phonon, Coulomb, and thickness fluctuation scattering.
Velocity-map imaging at low extraction fields
Authors: Horke Daniel A. , Roberts Gareth M. , Lecointre Julien , Verlet Jan R. R.
Published: June 2012

We present a velocity-map imaging (VMI) setup for photoelectron imaging that utilizes low electric extraction fields. This avoids any complications that could arise from electrostatic interactions between the extraction field and the molecular properties that are probed and has a minimal effect on the trajectory of ions in ion beam experiments. By using an attractive potential supplied to the detector, and keeping the electrodes at ground (zero) potential, we show that fringe fields between the VMI arrangement and the vacuum chamber can be eliminated, which is important in experiments on ions.
Observation of columnar microstructure in lattice-matched InAlN/GaN grown by plasma assisted molecular beam epitaxy
Authors: Choi Soojeong , Wu Feng , Shivaraman Ravi , Young Erin C. , Speck James S.
Published: June 2012

Nominally lattice matched InAlN/GaN was grown by plasma-assisted molecular beam epitaxy, and the intrinsic microstructure was investigated via x-ray diffraction, transmission electron microscopy, and atom probe tomography. The InAlN showed a cellular structure, which was comprised of ∼10 nm wide Al-rich cores and ∼1 nm In-rich InAlN intercellular boundaries. Despite the strong laterally non-uniform In distribution, both vertical and lateral lattices are unperturbed by the cellular structure, as evidenced by strong thickness fringes in on-axis ω−2θ high resolution x-ray diffraction scans, coherence lengths derived from on-axis (0002) and off-axis (101¯2) ω−2θ high resolution x-ray diffraction scans, and a modified Williamson-Hall analysis for on-axis reflections.
Quantitative analysis and near-field observation of strong coupling between plasmonic nanogap and silicon waveguides
Authors: Salas-Montiel Rafael , Apuzzo Aniello , Delacour Cécile , Sedaghat Zohreh , Bruyant Aurélien , Grosse Philippe , Chelnokov Alexei , Lerondel Gilles , Blaize Sylvain
Published: June 2012

We present a near field optical study of a plasmonic gap waveguide vertically integrated on silicon. The experimental study is based on a near field scanning optical microscope configured in perturbation mode. This operation mode is described and modeled to give a physical insight into the measured signal. A high spatial resolution allows for the characteristics of the plasmonic gap modes, such as near field distributions, effective indices, direction of propagation, and coupling between perpendicularly polarized modes, to be imaged and analyzed with accuracy. This experimental work is supported by numerical simulations based on finite element optical mode solvers and by the application of the strongly coupled-mode theory to the device.
Electrowetting-driven variable-focus microlens on flexible surfaces
Authors: Li Chenhui , Jiang Hongrui
Published: June 2012

We demonstrate a flexible, electrowetting-driven, variable-focus liquid microlens. The microlens is fabricated using a soft polymer polydimethylsiloxane. The lens can be smoothly wrapped onto a curved surface. A low-temperature fabrication process was developed to reduce the stress on and to avoid any damage to the polymer. The focal length of the microlens varies between −15.0 mm to +28.0 mm, depending on the applied voltage. The resolving power of the microlens is 25.39 line pairs per mm using a 1951 United States Air Force resolution chart. The typical response time of the lens is around 50 ms.
Quenching of fluorescence of reduced graphene oxide by nitrogen-doping
Authors: Li Ming , Tang Nujiang , Ren Wencai , Cheng Huiming , Wu Wenbin , Zhong Wei , Du Youwei
Published: June 2012

N-doped graphene (NG) has been prepared by annealing reduced graphene oxide (RGO) in ammonia in atmosphere and in vacuum, respectively. The photoluminescence properties of RGO and NG have been examined systematically. The results showed that doping RGO with N can quench its fluorescence, and the fluorescence quenching of NG obtained in vacuum is more efficient than that prepared in atmosphere.
Enhanced oxidation of nanoscale In particles at the interface with a Si nanowire
Authors: Sutter E. , Sutter P.
Published: June 2012

We investigate the room-temperature oxidation of In nanoparticles at the tips of Si nanowires. This geometry allows a direct comparison of oxidation at the gas-indium interface and the interface to the Si nanowire. While the In2O3 at the free surface is polycrystalline with small limiting thickness, the oxidation at the nanoscale interface to Si gives rise to single crystalline In2O3 with a tenfold-enhanced thickness. Our results demonstrate interfacial modifications of oxidation at the nanoscale, which need to be considered in scaling electronic devices, and which can become a route for forming high-quality semiconductor-oxide interfaces in nanostructured materials, such as nanowires.
Influence of polarity on carrier transport in semipolar (2021¯) and (202¯1) multiple-quantum-well light-emitting diodes
Authors: Kawaguchi Yoshinobu , Huang Chia-Yen , Wu Yuh-Renn , Yan Qimin , Pan Chih-Chien , Zhao Yuji , Tanaka Shinichi , Fujito Kenji , Feezell Daniel , Van de Walle Chris G. , DenBaars Steven P. , Nakamura Shuji
Published: June 2012

We investigate the influence of polarity on carrier transport in single-quantum-well and multiple-quantum-well (MQW) light-emitting diodes (LEDs) grown on the semipolar (202¯1) and (2021¯) orientations of free-standing GaN. For semipolar MQW LEDs with the opposite polarity to conventional Ga-polar c-plane LEDs, the polarization-related electric field in the QWs results in an additional energy barrier for carriers to escape the QWs. We show that semipolar (2021¯) MQW LEDs with the same polarity to Ga-polar c-plane LEDs have a more uniform carrier distribution and lower forward voltage than (202¯1) MQW LEDs.
Mechanistic basis for low threshold mechanosensitivity in voltage-dependent K
+
channels
Authors: Schmidt Daniel , del Mármol Josefina , MacKinnon Roderick
Published: June 2012

Living cells respond to mechanical forces applied to their outer membrane through processes referred to as “mechanosensation”. Faced with hypotonic shock, to circumvent cell lysis, bacteria open large solute-passing channels to reduce the osmotic pressure gradient. In the vascular beds of vertebrate animals blood flow is regulated directly through mechanical distention-induced opening of stretch-activated channels in smooth muscle cells. Touch sensation is thought to originate in mechanically sensitive ion channels in nerve endings, and hearing in mechanically sensitive ion channels located in specialized cells of the ear. While the ubiquity of mechanosensation in living cells is evident, the ion channels underlying the transduction events in vertebrate animals have remained elusive. Here we demonstrate through electrophysiological recordings that voltage-dependent K
+
(Kv) channels exhibit exquisite sensitivity to small (physiologically relevant in magnitude) mechanical perturbations of the cell membrane. The demonstrated mechanosensitivity is quantitatively consistent with membrane tension acting on a late-opening transition through stabilization of a dilated pore. This effect causes a shift in the voltage range over which Kv channels open as well as an increase in the maximum open probability. This mechanically induced shift could allow Kv channels and perhaps other voltage-dependent ion channels to play a role in mechanosensation.
Myosin 1E coordinates actin assembly and cargo trafficking during clathrin-mediated endocytosis
Authors: Cheng Jackie , Grassart Alexandre , Drubin David G.
Published: June 2012

Myosin 1E (Myo1E) is recruited to sites of clathrin-mediated endocytosis coincident with a burst of actin assembly. The recruitment dynamics and lifetime of Myo1E are similar to those of tagged actin polymerization regulatory proteins. Like inhibition of actin assembly, depletion of Myo1E causes reduced transferrin endocytosis and a significant delay in transferrin trafficking to perinuclear compartments, demonstrating an integral role for Myo1E in these actin-mediated steps. Mistargeting of GFP-Myo1E or its src-homology 3 domain to mitochondria results in appearance of WIP, WIRE, N-WASP, and actin filaments at the mitochondria, providing evidence for Myo1E's role in actin assembly regulation. These results suggest for mammalian cells, similar to budding yeast, interdependence in the recruitment of type I myosins, WIP/WIRE, and N-WASP to endocytic sites for Arp2/3 complex activation to assemble F-actin as endocytic vesicles are being formed.
Analysis of population structure among Korean and Japanese Legionella pneumophila isolates using hsp60 sequences
Authors: Park Chan Geun , Kim Byoung Jun , Kim Hee‐Youn , Yun Yeo‐Jun , Ko Kwan Soo , Miyamoto Hiroshi , Kim Bum‐Joon , Kook Yoon‐Hoh
Published: June 2012

The population structure of Korean (150 strains) and Japanese (92 strains) Legionella pneumophila isolates along with 18 reference strains were investigated using hsp60 sequence (1647 bp) analysis. Twelve clonal subgroups (hsP‐I to hsP‐X and hsF‐I and hsF‐II) were designated on the hsp60 tree, inferred from representative sequences using the neighbor‐joining method. Some of the isolates showed unique subgroups depending on the source of isolates, including hsP‐I, hsF‐I, and hsF‐II from cooling tower water, and subgroups hsP‐VIII and hsP‐X from circulating hot water bath. These subgroups may be useful for epidemiological studies to chase or specify sources of infection in Korea and Japan.
Pharmacogenomics of warfarin in populations of African descent
Authors: Suarez‐Kurtz Guilherme , Botton Mariana R.
Published: June 2012

Warfarin is the most commonly prescribed oral anticoagulant worldwide despite its narrow therapeutic index and the notorious inter‐ and intra‐individual variability in dose required for the target clinical effect. Pharmacogenetic polymorphisms are major determinants of warfarin pharmacokinetic and dynamics and included in several warfarin dosing algorithms. This review focuses on warfarin pharmacogenomics in sub‐Saharan peoples, African Americans and admixed Brazilians. These ‘Black’ populations differ in several aspects, notably their extent of recent admixture with Europeans, a factor which impacts on the frequency distribution of pharmacogenomic polymorphisms relevant to warfarin dose requirement for the target clinical effect. Whereas a small number of polymorphisms in VKORC1 (3673G > A, rs9923231), CYP2C9 (alleles *2 and *3, rs1799853 and rs1057910, respectively) and arguably CYP4F2 (rs2108622), may capture most of the pharmacogenomic influence on warfarin dose variance in White populations, additional polymorphisms in these, and in other, genes (e.g. CALU rs339097) increase the predictive power of pharmacogenetic warfarin dosing algorithms in the Black populations examined. A personalized strategy for initiation of warfarin therapy, allowing for improved safety and cost‐effectiveness for populations of African descent must take into account their pharmacogenomic diversity, as well as socio‐economical, cultural and medical factors. Accounting for this heterogeneity in algorithms that are ‘friendly’ enough to be adopted by warfarin prescribers worldwide requires gathering information from trials at different population levels, but demands also a critical appraisal of racial/ethnic labels that are commonly used in the clinical pharmacology literature but do not accurately reflect genetic ancestry and population diversity.