bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of Multiple Deliveries in Portugal: Indications of an Iberian Peninsula Pattern
Authors: Fuster Vicente , Santos Carlota , Román-Busto Jorge , Magalhaes Manuel
Published: August 2013

Information on multiple deliveries with regard to Portugal is scarce. Based on data provided by the Portuguese Institute of Statistics (INE), the rates for double and triple deliveries were calculated since 1930. The results obtained show for twins a uniform temporal pattern up to the 1970s. At this time rates decreased, but later they gradually recovered, reaching their maximum level in 2010. For triplets, the highest rates occurred between 1999 and 2002. For the period 1988–2011, the rates of multiple deliveries were related to a set of variables recorded in the INE database on live births. Significant differences (p < .001) between simple and multiple deliveries were obtained for maternal age, parity and marital status. Considering the year when the delivery occurred, significant differences (p < .001) persisted for maternal age regardless of the year. For the type of mating, significance was consistently found since the year 2002 (either by using the marital or the cohabitation criteria), and for parity since 2003. With regard to territorial variation, throughout seven periods between 1930 and 2011, the rates among the 20 administrative Portuguese territories, including the two insular districts of Açores and Madeira, were mostly stable for twinning rates, with a minimum level in 1970–1989. Regarding triplets, the greatest inter-district variation was found after 1980. The results of the Portuguese study on multiple deliveries are interpreted in the context of the Iberian Peninsula based on findings reported for Spain.
Weber, Marx and Contemporary Thailand
Authors: Hewison Kevin
Published: August 2013

Thailand's on-going political crisis began with agitation against the Thaksin Shinawatra-led government, saw a military coup and a spate of street-based protest and violence. Drawing on Marx and Weber and using the categories of class, status and party, it is argued that Thailand has reached a political turning point. Subaltern challenges to the hierarchical institutions of military, monarchy and bureaucracy appear to have resulted in political patterns of the past being set on a new trajectory. The social forces that congregate around old ideas associated with status honour – hierarchy, social closure and inequality, ‘Thai-style democracy’ and privilege – are challenged by those championing equality, access, voting and populism. While the balance of forces would suggest that an historical turning point has been achieved, reaction and unexpected outcomes remain possible.
Late to the Party: The Development of Partisanship in Thailand
Authors: Hicken Allen
Published: August 2013

This article investigates the emergence of new partisan identities in Thailand. Using data from Thailand's last several elections I trace the emergence of partisanship over the last 15 years, particularly in the north and northeast. The change in the nature of partisanship has helped turn long-simmering tensions into an increasingly intractable political conflict. This mass partisan alignment has upset the equilibrium of Thai politics, transforming what was once an inefficient but modest-stakes game of political horse-trading into a zero sum game with extremely high stakes.
Islamic Politics in Southeast Asia: A Critical Reassessment
Authors: Hadiz Vedi R.
Published: August 2013

The article argues for the utility of infusing the literature on Islamic politics in Southeast Asia with insights that may be gained from the literature on Islamic politics in North Africa and the Middle East. It suggests that such infusion, particularly of more explicitly historical sociology and political economy concerns, could reinvigorate the study of Islamic politics in Southeast Asia, which has been mostly dominated by cultural politics approaches and a concern for issues of doctrinal interpretation. Though this sort of literature has a rich and established tradition, it has lately succumbed to a more superficial security-oriented approach that has grown in influence since the advent of the War on Terror, in which Southeast Asia supposedly acts as a second front. Ironically, security-oriented analysts draw much of the material for their observations about Islamic ‘moderation’ and ‘radicalism’ from cultural politics analyses of Southeast Asian Islamic politics. Analyses based on historical sociology and political economy may provide alternative ways of understanding the evolution of Islamic politics in Southeast Asia by integrating such matters as post-colonial state development, Cold War era conflicts and the transforming effects of capitalist development on its social bases.
Being Chinese and Being Political in Southeast Asia
Authors: Khoo Boo Teik
Published: August 2013

Recent studies of the Chinese in Southeast Asia have tended to deconstruct the hybrid, transnational, diasporic, and de-territorialized attributes of ‘Chinese-ness’, and theorize the politics thereof. In contrast, earlier scholarship on the politics of Southeast Asia's ethnic Chinese raised many questions over the positions, rights, and roles associated with being ‘overseas Chinese’. Hence, many analyses of Chinese politics, from suppressed quietude to militant contestation, tended to ask, ‘Why and how was that politics Chinese?’ This article asks, instead, ‘Why and how were the Chinese political?’ within the larger rubric of Southeast Asian politics. It argues that posing the first question helped officialdom, academia and media to determine who among the ‘overseas Chinese’ were friends or foes. Asking the second question, it is argued, involves a boundary-crossing shift that sees the immigrant Chinese engaged in a full spectrum of Southeast Asian politics under the impacts of colonialism and nationalism, and capitalism and anti-capitalism. After exploring the shift in perspective from ‘being Chinese’ to ‘being political’, the article suggests that politics beyond China-oriented positions, state-bound stances, or preoccupations of ethnic identity, particularly in Malaysia transformed Southeast Asia to the point of ‘creating’ a ‘largely Chinese’ state out of Singapore.
Southeast Asia's New Nationalism: Causes and Significance
Authors: Vu Tuong
Published: August 2013

This paper explains the post-Cold War surge of nationalism in Southeast Asia and discusses its significance for regional peace and cooperation. As argued, the growth of nationalism as a form of mass politics has different causes in each Southeast Asian context where it occurs, but at the regional level the phenomenon can be explained by three factors: the failure of earlier nationalist movements to fully deliver their promises; a shift in the international and regional order (the end of the Cold War and the rise of China); and a change in domestic order (political liberalisation and democratisation) that was also occurring across many countries in the region. While the main mission of the new nationalism is the defence of national territory, the movements have the unintended impact of bringing together national communities once divided by Cold War ideologies. The phenomenon also poses some serious risks to regional peace and cooperation.
In Defence of Southeast Asia: A Case for Methodological Regionalism
Authors: Thompson Eric C.
Published: August 2013

Open nearly any general text on Southeast Asia and you will find that some space is taken up in the introduction assessing the reality and validity of the regional framework on which that text rests. Likewise, with the Association for Southeast Asian Nations (ASEAN), many scholars question whether or not the regional entity amounts to anything of any substance. In this article, I mount a defence of Southeast Asia as a regional framework in scholarship and draw attention to ASEAN as an evolving regional entity. While the concept of Southeast Asia among researchers and the politics of ASEAN are distinct issues, I treat them together in this article to highlight their interrelationship and parallels. My primary objective is to outline the displaced politics – of both academic andrealpolitikvarieties – embedded in deconstructive and dismissive critiques of both Southeast Asia and ASEAN. Critiques of both are not without value, as they sharpen our attention to processes through which supra-national regionalism is produced. Nevertheless, I argue that regionalism remains a valuable method in both politics and scholarship, in no small part as a counterweight to the hegemony of methodological nationalism in contemporary thought and research.
A late spring in Europe and the adaptability of plants
Authors: Hunter Philip
Published: August 2013

Plants seem to cope with unexpected climate conditions and retain a memory of past climates by epigenetic reprogramming. A better understanding of these mechanisms could allow breeders to create new crop varieties adapted to harsher conditions.
End‐group Functionalization of RAFT‐prepared Polymers Using Thiol‐X Chemistries
Authors: Lowe Andrew B.
Published: August 2013

Reactions of RAFT‐prepared copolymers in a series of thiol‐X reactions is discussed. Such reaction are facilitated by the fact that (co)polymers prepared via RAFT can be considered as masked macromolecular thiols by virtue of the polymerization mechanism and the use of thiocarbonylthio reagents as the polymerization mediating species. Removal of the thiocarbonylthio functional groups, most commonly located at the ω termini, post‐polymerization gives the corresponding polymeric thiols that are available for further reaction. Herein, we highlight how such species can be employed in reactions such as thiol‐Michael, thiol‐ene, thiol‐isocyanate and thiol‐epooxide reactions.
Analytic and algorithmic aspects of generalized harmonic sums and polylogarithms
Authors: Ablinger Jakob , Blümlein Johannes , Schneider Carsten
Published: August 2013

In recent three-loop calculations of massive Feynman integrals within Quantum Chromodynamics (QCD) and, e.g., in recent combinatorial problems the so-called generalized harmonic sums (in short S-sums) arise. They are characterized by rational (or real) numerator weights also different from ±1. In this article we explore the algorithmic and analytic properties of these sums systematically. We work out the Mellin and inverse Mellin transform which connects the sums under consideration with the associated Poincaré iterated integrals, also called generalized harmonic polylogarithms. In this regard, we obtain explicit analytic continuations by means of asymptotic expansions of the S-sums which started to occur frequently in current QCD calculations. In addition, we derive algebraic and structural relations, like differentiation with respect to the external summation index and different multi-argument relations, for the compactification of S-sum expressions. Finally, we calculate algebraic relations for infinite S-sums, or equivalently for generalized harmonic polylogarithms evaluated at special values. The corresponding algorithms and relations are encoded in the computer algebra package HarmonicSums.
Quantum resistance standard accuracy close to the zero-dissipation state
Authors: Schopfer F. , Poirier W.
Published: August 2013

We report on a comparison of four GaAs/AlGaAs-based quantum resistance standards using an original technique adapted from the well-known Wheatstone bridge. This work shows that the quantized Hall resistance at Landau level filling factor ν=2 can be reproducible with a relative uncertainty of 32×10−12 in the dissipationless limit of the quantum Hall effect regime. In the presence of a very small dissipation characterized by a mean macroscopic longitudinal resistivity Rxx(B)¯ of a few μΩ, the discrepancy ΔRH(B) between quantum Hall resistors measured on the Hall plateau at magnetic induction B turns out to follow the so-called resistivity rule Rxx(B)¯=αB×d(ΔRH(B))/dB. While the dissipation increases with the measurement current value, the coefficient α stays constant in the range investigated (40−120 μA). This result enlightens the impact of the dissipation emergence in the two-dimensional electron gas on the Hall resistance quantization, which is of major interest for the resistance metrology. The quantum Hall effect is used to realize a universal resistance standard only linked to the electron charge e and the Planck constant h and it is known to play a central role in the upcoming revised Système International of units. There are therefore fundamental and practical benefits in testing the reproducibility property of the quantum Hall effect with better and better accuracy.
Experimental and numerical investigation of a variable density swirling-jet stability
Authors: Di Pierro Bastien , Abid Malek , Amielh Muriel
Published: August 2013

Linear stability of a variable density, and incompressible, swirling jet is studied at moderate Reynolds numbers, both experimentally and numerically. Mean flow characteristics are obtained experimentally. They show a correlation between axial velocity and density profiles. For low density ratios, s, the presence of self-sustained oscillations of the flow (global modes) is highlighted. Using direct numerical simulations (at low azimuthal wavenumbers m = 0, −1, −2) to study the local convective/absolute transition at the jet exit-nozzle, it is shown that frequencies of the local absolute-instability are in good agreement with those of the experimentally obtained global modes. Furthermore, it is found that increasing the swirl number q enhances the absolute instability for helical modes m = −1 and −2. Finally, it is also shown that the unstable selected mode, experimentally obtained, has the spatio-temporal properties of the absolutely unstable one obtained numerically.
Height probabilities in the Abelian sandpile model on the generalized finite Bethe lattice
Authors: Chen Haiyan , Zhang Fuji
Published: August 2013

In this paper, we study the sandpile model on the generalized finite Bethe lattice with a particular boundary condition. Using a combinatorial method, we give the exact expressions for all single-site probabilities and some two-site joint probabilities. As a by-product, we prove that the height probabilities of bulk vertices are all the same for the Bethe lattice with certain given boundary condition, which was found from numerical evidence by Grassberger and Manna [“Some more sandpiles,” J. Phys. (France) 51, 1077–1098 (1990)]10.1051/jphys:0199000510110107700 but without a proof.
On the state of water in 2.4 nm cylindrical pores of MCM from dynamic and normal specific heat studies
Authors: Tombari Elpidio , Johari G. P.
Published: August 2013

Relaxation phenomenon, thermodynamics, and phase transformation of water in nanopores has been studied by differential scanning calorimetry, usually on heating a precooled sample. Interpretation of such results is ambiguous, because the data do not indicate whether or not there is a thermal hysteresis between the heating and cooling paths. We argue that measurements on both the cooling and heating paths are needed, particularly for complex systems, and also measurements of the complex quantity are needed to ascertain that the Kramers-Kronig relations for a relaxation process are obeyed. We report a study of the real and imaginary components of the complex specific heat, Cp′ and Cp″, and the time-dependent Cp,app of water confined to 2.4 nm diameter cylindrical pores on both the cooling and heating paths, and use different thermal histories. Cp,app of nanoconfined water shows two exothermic peaks during cooling below 255 K at 12 K/h and only one endothermic peak on heating, and the enthalpy change determined from the exotherm is more than that determined from the endotherm. Cp,app and Cp′ of the partially crystallized water is higher at 240 K than at 275 K on the cooling path, and Cp,app and Cp′ of the partially crystalline water are lower at 240 K than at 275 K on the heating path, thus showing a thermal hysteresis in this range. Studies by using 60 K/h cooling and heating rates and the effect of heat treatment at selected temperatures confirm that the features observed are due to slow crystallization and slow melting. The endotherm observed on the heating path with onset at 220 K and peak at 227 K is due to gradual melting of the ice in nanopores, and not due to glass-softening transition, a liquid-liquid transition, or an approach toward the conjectured critical point of the supercooled water in the 2.4 nm pores.
Computational design of chemically propelled catalytic nanorotors
Authors: Chen Yanping , Shi Yunfeng
Published: August 2013

We designed catalytic nanorotors and investigated the rotational motion and energy conversion efficiency using reactive molecular dynamics in two dimensions. First, a two-arm nanorotor was constructed by decorating a slender beam with catalysts asymmetrically on its two long edges, while fixing the beam center as the rotational axis. Autonomous rotation was observed for the two-arm nanorotor immersing in a fuel environment. Here fuel molecules undergo exothermic combination reaction facilitated by the catalysts. It was found that the angular velocity increases with the catalyst coverage parabolically, while the rotary nanomotor efficiency stays roughly constant. These observations are consistent with a single-collision-momentum–transfer-based propulsion model. Furthermore, multi-arm nanorotors (up to eight arms) were constructed by carving radially distributed arms followed by decorating catalysts. For multi-arm nanorotors, both the angular velocity and the efficiency decrease as the number of arms increases. These behaviors contradict the aforementioned model, which are likely due to the deceleration from secondary collisions between products and the nanorotor arms. Our simulation results show that the optimal design for a nanorotor that maximizes its angular velocity and the motor efficiency is a two-arm nanorotor with nearly full coverage of catalysts.
A volume-of-fluid formulation for the study of co-flowing fluids governed by the Hele-Shaw equations
Authors: Afkhami Shahriar , Renardy Yuriko
Published: August 2013

We present a computational framework to address the flow of two immiscible viscous liquids which co-flow into a shallow rectangular container at one side, and flow out into a holding container at the opposite side. Assumptions based on the shallow depth of the domain are used to reduce the governing equations to one of Hele-Shaw type. The distinctive feature of the numerical method is the accurate modeling of the capillary effects. A continuum approach coupled with a volume-of-fluid formulation for computing the interface motion and for modeling the interfacial tension in Hele-Shaw flows is formulated and implemented. The interface is reconstructed with a height-function algorithm. The combination of these algorithms is a novel development for the investigation of Hele-Shaw flows. The order of accuracy and convergence properties of the method are discussed with benchmark simulations. A microfluidic flow of a ribbon of fluid which co-flows with a second liquid is simulated. We show that for small capillary numbers of O(0.01), there is an abrupt change in interface curvature and focusing occurs close to the exit.
Non-axisymmetric annular curtain stability
Authors: Ahmed Zahir U. , Khayat Roger E. , Maissa Philippe , Mathis Christian
Published: August 2013

A stability analysis of non-axisymmetric annular curtain is carried out for an axially moving viscous jet subject in surrounding viscous gas media. The effect of inertia, surface tension, gas-to-liquid density ratio, inner-to-outer radius ratio, and gas-to-liquid viscosity ratio on the stability of the jet is studied. In general, the axisymmetric disturbance is found to be the dominant mode. However, for small wavenumber, the non-axisymmetric mode is the most unstable mode and the one likely observed in reality. Inertia and the viscosity ratio for non-axisymmetric disturbances show a similar stability influence as observed for axisymmetric disturbances. The maximum growth rate in non-axisymmetric flow, interestingly, appears at very small wavenumber for all inertia levels. The dominant wavenumber increases (decreases) with inertia for non-axisymmetric (axisymmetric) flow. Gas-to-liquid density ratio, curvature effect, and surface tension, however, exhibit an opposite influence on growth rate compared to axisymmetric disturbances. Surface tension tends to stabilize the flow with reductions of the unstable wavenumber range and the maximum growth rate as well as the dominant wavenumber. The dominant wavenumber remains independent of viscosity ratio indicating the viscosity ratio increases the breakup length of the sheet with very little influence on the size of the drops. The range of unstable wavenumbers is affected only by curvature in axisymmetric flow, whereas all the stability parameters control the range of unstable wavenumbers in non-axisymmetric flow. Inertia and gas density increase the unstable wavenumber range, whereas the radius ratio, surface tension, and the viscosity ratio decrease the unstable wavenumber range. Neutral curves are plotted to separate the stable and unstable domains. Critical radius ratio decreases linearly and nonlinearly with the wavenumber for axisymmetric and non-axisymmetric disturbances, respectively. At smaller Weber numbers, a wider unstable domain is predicted for non-axisymmetric modes. For both axisymmetric and non-axisymmetric modes, the disturbance frequency is found to be the same and equal to the negative of axial wavenumber. Finally, comparison between theory and existing experiment leads to good qualitative agreement. A more accurate comparison is not possible given the difference in flow conditions.
Coupled cluster calculations on TiO2 nanoclusters
Authors: Berardo Enrico , Hu Han-Shi , Kowalski Karol , Zwijnenburg Martijn A.
Published: August 2013

The excitation energies of the four lowest-lying singlet excited states of the TiO2, Ti2O4, and Ti3O6 clusters are calculated by a variety of different Equation-of-Motion Coupled Cluster (EOM-CC) approaches in order to obtain benchmark values for the optical excitations of titanium dioxide clusters. More specifically we investigate what the effect is of the inclusion of triple excitations “triples” in the (EOM-)CC scheme on the calculated excited states of the clusters. While for the monomer and dimer the inclusion of triples is found to only cause a rigid shift in the excitation energies, in the case of the trimer the crossing of the excited states is observed. Coupled cluster approaches where triples are treated perturbatively were found to offer no advantage over EOM-CCSD, whereas the active-space methods (EOM-CCSDt(II/I)) were demonstrated to yield results very close to full EOM-CCSDT, but at a much reduced computational cost.
Molecular dynamics study of network statistics in lithium disilicate: Qn distribution and the pressure-volume diagram
Authors: Habasaki J. , Ngai K. L.
Published: August 2013

Molecular dynamics simulations have been performed to study the structures along the pressure-volume diagram of network-glasses and melts exemplified by the lithium disilicate system. Experimentally, densification of the disilicate glass by elevated pressure is known and this feature is reasonably reproduced by the simulations. During the process of densification or decompression of the system, the statistics of Qn (i.e., SiO4 tetrahedron unit with n bridging oxygen linked to the silicon atom where n = 0, 1, 2, 3, or 4) change, and the percentage of the Q3 structures show the maximum value near atmospheric pressure at around Tg. Changes of Qn distribution are driven by the changes of volume (or pressure) and are explained by the different volumes of structural units. Furthermore, some pairs of network structures with equi-volume, but having different distributions of Qn (or different heterogeneity), are found. Therefore, for molecular dynamics simulations of the Qn distributions, it is important to take into account the complex phase behavior including poly-structures with different heterogeneities as well as the position of the system in the P-V-T diagram.
Sparsely corrupted stimulated scattering signals recovery by iterative reweighted continuous basis pursuit
Authors: Wang Kunpeng , Chai Yi , Su Chunxiao
Published: August 2013

In this paper, we consider the problem of extracting the desired signals from noisy measurements. This is a classical problem of signal recovery which is of paramount importance in inertial confinement fusion. To accomplish this task, we develop a tractable algorithm based on continuous basis pursuit and reweighted ℓ1-minimization. By modeling the observed signals as superposition of scale time-shifted copies of theoretical waveform, structured noise, and unstructured noise on a finite time interval, a sparse optimization problem is obtained. We propose to solve this problem through an iterative procedure that alternates between convex optimization to estimate the amplitude, and local optimization to estimate the dictionary. The performance of the method was evaluated both numerically and experimentally. Numerically, we recovered theoretical signals embedded in increasing amounts of unstructured noise and compared the results with those obtained through popular denoising methods. We also applied the proposed method to a set of actual experimental data acquired from the Shenguang-II laser whose energy was below the detector noise-equivalent energy. Both simulation and experiments show that the proposed method improves the signal recovery performance and extends the dynamic detection range of detectors.
Transition and acoustic response of recirculation structures in an unconfined co-axial isothermal swirling flow
Authors: Santhosh R. , Miglani Ankur , Basu Saptarshi
Published: August 2013

This paper reports the first observations of transition from a pre-vortex breakdown (Pre-VB) flow reversal to a fully developed central toroidal recirculation zone in a non-reacting, double-concentric swirling jet configuration and its response to longitudinal acoustic excitation. This transition proceeds with the formation of two intermediate, critical flow regimes. First, a partially penetrated vortex breakdown bubble (VBB) is formed that indicates the first occurrence of an enclosed structure as the centre jet penetration is suppressed by the growing outer roll-up eddy; resulting in an opposed flow stagnation region. Second, a metastable transition structure is formed that marks the collapse of inner mixing vortices. In this study, the time-averaged topological changes in the coherent recirculation structures are discussed based on the non-dimensional modified Rossby number (Rom) which appears to describe the spreading of the zone of swirl influence in different flow regimes. Further, the time-mean global acoustic response of pre-VB and VBB is measured as a function of pulsing frequency using the relative aerodynamic blockage factor (i.e., maximum radial width of the inner recirculation zone). It is observed that all flow modes except VBB are structurally unstable as they exhibit severe transverse radial shrinkage (∼20%) at the burner Helmholtz resonant modes (100–110 Hz). In contrast, all flow regimes show positional instability as seen by the large-scale, asymmetric spatial shifting of the vortex core centres. Finally, the mixing transfer function M (f) and magnitude squared coherence λ2(f) analysis is presented to determine the natural coupling modes of the system dynamic parameters (u′, p′), i.e., local acoustic response. It is seen that the pre-VB flow mode exhibits a narrow-band, low pass filter behavior with a linear response window of 100–105 Hz. However, in the VBB structure, presence of critical regions such as the opposed flow stagnation region alters the linearity range with the structure showing a response even at higher pulsing frequencies (100–300 Hz).
Intrinsic features of flow around two side-by-side square cylinders
Authors: Alam Md. Mahbub , Zhou Y.
Published: August 2013

The wake of two side-by-side square cylinders is investigated in detail based on flow visualization at a Reynolds number (Re) of 300. The cylinder center-to-center spacing ratio T* (= T/W, W is the cylinder width) is varied from 1.0 to 5.0. The intrinsic features of the wake are explored, including the gap vortices, flow switch, stability, merging of two streets into one, etc. The qualitative information on these features is further complemented by the quantitative information extracted from hotwire data at Re = 4.7 × 104 using both spectral and cross-wavelet analyses. Four flow regimes are identified: (i) the single bluff body regime (T* < 1.2), (ii) the narrow and wide street regime (1.2 < T* < 2.1), (iii) the transition regime (2.1 < T* < 2.4), and (iv) the coupled-street regime (T* > 2.4). The gap flow is found to switch at two distinct time scales, referred to as macro and micro switches. Macro switch occurs at 1.2 < T* < 2.1, where the gap flow is slim in width and biased for a long duration ranging from several vortex shedding periods in the wide street to several hours. Micro switch is observed at 2.1 < T* < 2.4, where the gap flow is thick in width and switches at a frequency of twice the frequency of vortex shedding from the free-stream side of the cylinders. The two streets formed immediately behind the cylinders merge to a single street at a downstream location $x_c^*$xc* that depends on T*. A larger T* corresponds to a larger $x_c^*$xc*. Regime (iv) is characterized by two streets either inphased or antiphased. The antiphased streets persist longer than the inphased.
A novel flexure-based microgripper with double amplification mechanisms for micro/nano manipulation
Authors: Sun Xiantao , Chen Weihai , Tian Yanling , Fatikow Sergej , Zhou Rui , Zhang Jianbin , Mikczinski Manuel
Published: August 2013

This paper describes the design, modeling, and testing of a novel flexure-based microgripper for a large jaw displacement with high resolution. Such a microgripper is indispensable in micro/nano manipulation. In achieving a large jaw displacement, double amplification mechanisms, namely, Scott-Russell mechanism and leverage mechanism arranged in series, are utilized to overcome the limited output of microgrippers driven by piezoelectric actuators. The mechanical performance of the microgripper is analyzed using the pseudo rigid body model approach. Finite element analysis is conducted to evaluate the performance and validate the established models for further optimum design of the microgripper. The prototype of the developed microgripper is fabricated, with which experimental tests are carried out. The experimental results show that the developed microgripper is capable of handling various sized micro-objects with a maximum jaw displacement of 134 μm and a high amplification ratio of 15.5.
Theory and simulations of electron vortices generated by magnetic pushing
Authors: Richardson A. S. , Angus J. R. , Swanekamp S. B. , Ottinger P. F. , Schumer J. W.
Published: August 2013

Vortex formation and propagation are observed in kinetic particle-in-cell (PIC) simulations of magnetic pushing in the plasma opening switch. These vortices are studied here within the electron-magnetohydrodynamic (EMHD) approximation using detailed analytical modeling. PIC simulations of these vortices have also been performed. Strong v×B forces in the vortices give rise to significant charge separation, which necessitates the use of the EMHD approximation in which ions are fixed and the electrons are treated as a fluid. A semi-analytic model of the vortex structure is derived, and then used as an initial condition for PIC simulations. Density-gradient-dependent vortex propagation is then examined using a series of PIC simulations. It is found that the vortex propagation speed is proportional to the Hall speed vHall≡cB0/4πneeLn. When ions are allowed to move, PIC simulations show that the electric field in the vortex can accelerate plasma ions, which leads to dissipation of the vortex. This electric field contributes to the separation of ion species that has been observed to occur in pulsed-power experiments with a plasma-opening switch.
Simulation of transport around the coexistence region of a binary fluid
Authors: Roy Sutapa , Das Subir K.
Published: August 2013

We use Monte Carlo and molecular dynamics simulations to study phase behavior and transport properties in a symmetric binary fluid where particles interact via Lennard-Jones potential. Our results for the critical behavior of collective transport properties, with particular emphasis on bulk viscosity, is understood via appropriate application of finite-size scaling technique. It appears that the critical enhancements in these quantities are visible far above the critical point. This result is consistent with an earlier report from computer simulations where, however, the authors do not quantify the critical singularity.
Poisson ratio and excess low-frequency vibrational states in glasses
Authors: Duval Eugène , Deschamps Thierry , Saviot Lucien
Published: August 2013

In glass, starting from a dependence of the Angell's fragility on the Poisson ratio [V. N. Novikov and A. P. Sokolov, Nature 431, 961 (2004)]10.1038/nature02947, and a dependence of the Poisson ratio on the atomic packing density [G. N. Greaves, A. L. Greer, R. S. Lakes, and T. Rouxel, Nature Mater. 10, 823 (2011)]10.1038/nmat3134, we propose that the heterogeneities are predominantly density fluctuations in strong glasses (lower Poisson ratio) and shear elasticity fluctuations in fragile glasses (higher Poisson ratio). Because the excess of low-frequency vibration modes in comparison with the Debye regime (boson peak) is strongly connected to these fluctuations, we propose that they are breathing-like (with change of volume) in strong glasses and shear-like (without change of volume) in fragile glasses. As a verification, it is confirmed that the excess modes in the strong silica glass are predominantly breathing-like. Moreover, it is shown that the excess breathing-like modes in a strong polymeric glass are replaced by shear-like modes under hydrostatic pressure as the glass becomes more compact.
Spontaneous electromagnetic fluctuations in unmagnetized plasmas. V. Relativistic form factors of weakly damped/amplified thermal modes
Authors: Felten T. , Schlickeiser R.
Published: August 2013

Closed analytical expressions for the spontaneously emitted fluctuation spectra of weakly damped/amplified fluctuations in unmagnetized plasmas are derived using fully relativistic dispersion functions and form factors for the important class of isotropic thermal plasmas. Especially, an electron-proton plasma is investigated in the limits of nonrelativistic and ultrarelativistic plasma temperatures. The results confirm the earlier nonrelativistic approach for positive values of the imaginary frequency γ and complete the nonrelativistic treatment for negative values of γ<0. The well known electrostatic, collective Langmuir mode also occurs within the relativistic theory of spontaneously emitted fluctuations and is analytically and graphically identified. For the first time, the ultrarelativistic temperature limit is analyzed for subluminal phase speeds, which leads to the identification of an additional, so far unknown, longitudinal subluminal collective mode.
Sub-structure of laser generated harmonics reveals plasma dynamics of a relativistically oscillating mirror
Authors: Braenzel J. , Andreev A. , Schnürer M. , Steinke S. , Platonov K. , Priebe G. , Sandner W.
Published: August 2013

Theoretical and experimental investigations of the dynamics of a relativistically oscillating plasma slab reveal spectral line splitting in laser driven harmonic spectra, leading to double harmonic series. Both series are well characterized with harmonics arising by two fundamental frequencies. While a relativistic oscillation of the critical density drives the harmonic emission, the splitting is a result of an additional acceleration during the laser pulse duration. In comparison with the oscillatory movement, this acceleration is rather weak and can be described by a plasma shock wave driven by the pressure of light. We introduce particle in cell simulations and an analytical model explaining the harmonic line splitting. The derived analytical formula gives direct access between the splitting in the harmonic spectrum and the acceleration of the plasma surface.
Precision control of charge coherence in parallel double dot systems through spin-orbit interaction
Authors: Jin Jinshuang , Tu Matisse Wei-Yuan , Wang Nien-En , Zhang Wei-Min
Published: August 2013

In terms of the exact quantum master equation solution for open electronic systems, the coherent dynamics of two charge states described by two parallel quantum dots with one fully polarized electron on either dot is investigated in the presence of spin-orbit interaction. We demonstrate that the double dot system can stay in a dynamically decoherence free space. The coherence between two double dot charge states can be precisely manipulated through a spin-orbit coupling. The effects of the temperature, the finite bandwidth of lead, and the energy deviations during the coherence manipulation are also explored.
Refractive-index-based optofluidic particle manipulation
Authors: Soo Lee Kang , Heon Lee Kyung , Bok Kim Sang , Ho Jung Jin , Hang Ha Byung , Jin Sung Hyung , Soo Kim Sang
Published: August 2013

This letter describes optofluidic particle manipulation based on the refractive index contrast between the particle and the surrounding medium. A laser beam propagated along one sidewall of a microfluidic channel will introduce a force that pushes a high-refractive-index particle toward the Gaussian-shaped laser beam center axis. By contrast, a low-refractive-index particle will be pushed away from the beam center axis and toward the other sidewall of the channel because the direction of the gradient forces acting on such a particle is opposite the direction of the forces acting on a high-refractive-index particle. The gradient forces acting on a particle were calculated to predict and interpret the particle behavior. High-refractive-index and low-refractive-index particles, prepared from polystyrene latex (PSL) and hollow glass particles with refractive indices of 1.59 and 1.22, respectively, were employed. The PSL and hollow glass particles could be separated based on their refractive indices. Doubly attached identical particles behaved as a single particle.
Local stabilisation of polar order at charged antiphase boundaries in antiferroelectric (Bi0.85Nd0.15)(Ti0.1Fe0.9)O3
Authors: MacLaren Ian , Wang LiQiu , Morris Owen , Craven Alan J. , Stamps Robert L. , Schaffer Bernhard , Ramasse Quentin M. , Miao Shu , Kalantari Kambiz , Sterianou Iasmi , Reaney Ian M.
Published: August 2013

Observation of an unusual, negatively-charged antiphase boundary in (Bi0.85Nd0.15)(Ti0.1Fe0.9)O3 is reported. Aberration corrected scanning transmission electron microscopy is used to establish the full three dimensional structure of this boundary including O-ion positions to ∼±10 pm. The charged antiphase boundary stabilises tetragonally distorted regions with a strong polar ordering to either side of the boundary, with a characteristic length scale determined by the excess charge trapped at the boundary. Far away from the boundary the crystal relaxes into the well-known Nd-stabilised antiferroelectric phase.
Perspective: Hybrid solar cells: How to get the polymer to cooperate?
Authors: Weickert Jonas , Schmidt-Mende Lukas
Published: August 2013

Lately, a lot of attention has been paid to metal oxide-organic hybrid solar cells. In these devices, conjugated polymers replace the typically transparent hole transporter as usually used in solid-state dye-sensitized solar cells in order to maximize the photon absorption efficiency. However, to unleash the full potential of hybrid solar cells it is imperative to push the photocurrent contribution of the absorbing polymer.
Plasma wave instability in a quantum field effect transistor with magnetic field effect
Authors: Zhang Li-Ping , Xue Ju-Kui
Published: August 2013

The current-carrying state of a nanometer Field Effect Transistor (FET) may become unstable against the generation of high-frequency plasma waves and lead to generation of terahertz radiation. In this paper, the influences of magnetic field, quantum effects, electron exchange-correlation, and thermal motion of electrons on the instability of the plasma waves in a nanometer FET are reported. We find that, while the electron exchange-correlation suppresses the radiation power, the magnetic field, the quantum effects, and the thermal motion of electrons can enhance the radiation power. The radiation frequency increases with quantum effects and thermal motion of electrons, but decreases with electron exchange-correlation effect. Interestingly, we find that magnetic field can suppress the quantum effects and the thermal motion of electrons and the radiation frequency changes non-monotonely with the magnetic field. These properties could make the nanometer FET advantageous for realization of practical terahertz oscillations.
On the nucleation of PdSi and NiSi2 during the ternary Ni(Pd)/Si(100) reaction
Authors: Schrauwen A. , Demeulemeester J. , Kumar A. , Vandervorst W. , Comrie C. M. , Detavernier C. , Temst K. , Vantomme A.
Published: August 2013

During the solid phase reaction of a Ni(Pd) alloy with Si(100), phase separation of binary Ni- and Pd-silicides occurs. The PdSi monosilicide nucleates at temperatures significantly below the widely accepted nucleation temperature of the binary system. The decrease in nucleation temperature originates from the presence of the isomorphous NiSi, lowering the interface energy for PdSi nucleation. Despite the mutual solubility of NiSi and PdSi, the two binaries coexist in a temperature window of 100 °C. Only above 700 °C a Ni1–xPdxSi solid solution is formed, which in turn postpones the NiSi2 formation to a higher temperature due to entropy of mixing. Our findings highlight the overall importance of the interface energy for nucleation in ternary systems.
Evolution of threading screw dislocation conversion during solution growth of 4H-SiC
Authors: Harada S. , Yamamoto Y. , Seki K. , Horio A. , Mitsuhashi T. , Tagawa M. , Ujihara T.
Published: August 2013

Evolution of threading screw dislocation (TSD) conversion during the solution growth of 4H-SiC on a vicinal crystal of 4H-SiC(0001) was investigated by synchrotron X-ray topography. Selecting appropriate X-ray wavelength and g vector, we can change the penetration of X-ray, and the dislocation behaviors with the different depth were successfully observed. Evidently TSDs parallel to the c-axis having c-component Burgers vector were changed into defects on the (0001) basal planes with the same Burgers vector as the TSDs, propagating to the [11\documentclass[12pt]{minimal}\begin{document}$\bar{2}$\end{document}2¯0] step-flow direction by advancing macrosteps during the solution growth. The TSD conversions stochastically took place during the growth. The conversion rate was almost uniform and finally almost all TSDs were converted to the basal plane defects. The conversion rate was low at the very early stage of the growth, which implies that the macrosteps were not formed at the initial stage of the solution growth.
An investigation into the cumulative breakdown process of polymethylmethacrylate in quasi-uniform electric field under nanosecond pulses
Authors: Zhao Liang , Cang Su Jian , Bo Zhang Xi , Feng Pan Ya , Min Wang Li , Peng Fang Jin , Sun Xu , Lui Rui
Published: August 2013

A group of complete images on the discharge channel developed in PMMA in quasi-uniform electric field under nanosecond pulses are observed with an on-line transmission microscope. The characteristics of the cumulative breakdown process are also generalized, which include initiating from the vicinity of the cathode, developing to the anode with a branch-like shape, and taking on a wormhole appearance when final breakdown occurs. The concluded characteristics are explained by referring to the conceptions of “low density domain” and “free radical” and considering the initial discharge channel as a virtual needle. The characteristics are helpful for designers to enhance the lifetime of insulators employed on a nanosecond time scale.
Induced magneto-electric coupling in ferroelectric/ferromagnetic heterostructures
Authors: Carvell Jeffrey , Cheng Ruihua , Dowben P. A. , Yang Q.
Published: August 2013

Using an external magnetic field, we have demonstrated room temperature control of the electric polarization of a ferroelectric polymer, polyvinylidene fluoride (PVDF), in an artificial multiferroic structure. For ferroelectric PVDF polymer thin films in an iron-PVDF-iron heterostructure, both the ferroelectric coercivity and polarization display a hysteresis dependence on the external magnetic field. We also find that the thickness of the PVDF layer has an effect on the magnetoelectric coupling in our samples. We observe a giant magnetoelectric coupling with values as large as 3700 V/cm Oe to 41700 V/cm Oe.
Vacancies and defect levels in III–V semiconductors
Authors: Tahini H. A. , Chroneos A. , Murphy S. T. , Schwingenschlögl U. , Grimes R. W.
Published: August 2013

Using electronic structure calculations, we systematically investigate the formation of vacancies in III-V semiconductors (III = Al, Ga, and In and V = P, As, and Sb), for a range of charges (−3≤q≤3) as a function of the Fermi level and under different growth conditions. The formation energies were corrected using the scheme due to Freysoldt et al. [Phys. Rev. Lett. 102, 016402 (2009)] to account for finite size effects. Vacancy formation energies were found to decrease as the size of the group V atom increased. This trend was maintained for Al-V, Ga-V, and In-V compounds. The negative-U effect was only observed for the arsenic vacancy in GaAs, which makes a charge state transition from +1 to –1. It is also found that even under group III rich conditions, group III vacancies dominate in AlSb and GaSb. For InSb, group V vacancies are favoured even under group V rich conditions.
Lattice instability of Ni-Mn-Ga ferromagnetic shape memory alloys probed by hard X-ray photoelectron spectroscopy
Authors: Kimura A. , Ye M. , Taniguchi M. , Ikenaga E. , Barandiarán J. M. , Chernenko V. A.
Published: August 2013

Lattice instability of off-stoichiometric Ni-Mn-Ga based ferromagnetic shape memory alloys with different valence electron concentrations (e/a’s) has been studied by utilizing hard X-ray photoelectron spectroscopy. Comparison of two alloys with different e/a’s suggests that a rigid band model is not applicable to explain the different martensitic transition temperatures. It is revealed that the specimen with larger e/a shows larger density of the Ni 3d eg states near the Fermi energy compared to specimen with lower e/a. The results can be reasonably explained by the band Jahn-Teller effect.
Emission wavelength dependence of characteristic temperature of InGaN laser diodes
Authors: Bojarska Agata , Goss Jakub , Marona Łucja , Kafar Anna , Stańczyk Szymon , Makarowa Irina , Najda Stephen , Targowski Grzegorz , Suski Tadek , Perlin Piotr
Published: August 2013

We have determined thermal stability of various InGaN laser diodes emitting in the spectral range of 390-436 nm. Their characteristic temperature T0 increases steeply with the increasing emission wavelength, reaching the value of around 230 K. Our analysis of current-light characteristics and activation energy of electroluminescence proves that this behavior is predominantly related to the thermal escape of electrons from quantum wells, which depends critically on their depth.