bluuebunny/crossref_metadata_2025 huggingface dataset:
RELIGION IN POLITICS: WHAT'S THE PROBLEM?
Authors: Talisse Robert B.
Published: January 2013

A few years ago, I, an American, was giving a talk at a political philosophy conference in the United Kingdom. My topic was religion in democratic politics, and I delivered what I thought was a splendid line of argument supporting the idea that religion has at most a highly constrained role to play in democratic politics. The audience was appreciative enough, but during the question and answer session, there emerged the charge that my paper had addressed a uniquely ‘American’ problem, a problem that was not of general significance to political philosophers outside of the United States. I replied that although the political scene in the contemporary United States provides many high-profile examples of the problem I had been addressing, the general problem of religion in politics confronts democracy as such. I then provided some cases from outside America in which the problem shows itself: the public slaying of Theo Van Gough, the controversy surrounding the publication of cartoon representations of Muhammad in Denmark, the reemergence of religiously-affiliated and reactionary political parties throughout Europe, and so on. Yet for the most part my audience remained unmoved.
FINE-TUNING THE MULTIVERSE
Authors: Wilkinson Tim
Published: January 2013

Gottfried Wilhelm Leibniz (1646–1716) was quite a thinker. As a philosopher, he made major contributions to epistemology, logic, the philosophy of religion and metaphysics. He was also an accomplished scientist, historian, and linguist. In mathematics, he built the first (admittedly somewhat unreliable) calculating machine able to perform all four elementary arithmetical operations, and devised the first proper formulation of binary numbers. Although Chinese and Indian scholars had developed several types of rudimentary binary notation centuries earlier, the number system at the heart of every modern computer was put together by Leibniz. As if that were not enough to guarantee his immortality, he also developed calculus independently of Isaac Newton, and it is mostly Leibniz's version that survives in our textbooks, due to his superior notation.
NOTE ON INDUCTION
Authors: Parent Ted
Published: January 2013

Some logic textbooks say, as if it were the received wisdom, that inductive arguments are partly defined by the thinker's intentions. The claim is that an inductive argument is one where the premises are intended to make the conclusion likely. This contrasts with a deductive argument, where the premises are intended to entail the conclusion. However, since entailing is one way of making more likely, a further way to distinguish induction is needed. The addition offered is that the premises are not intended to entail the conclusion. Taken together, the result is:

(1) An argument is inductive if the premises are (a) intended to make the conclusion likely, but (b) not intended to entail the conclusion.
PSYCHOANALYSIS, EMOTIONS AND LIVING A GOOD LIFE
Authors: Lacewing Michael
Published: January 2013

The central question of ethics is ‘How should I live?’. It covers not only actions (‘what should I do?’), but more broadly, our reactions and our characters, questions of what we should feel and how we should be as people. This has been the central concern of theories of virtue. Aristotle claimed that a virtue is a character trait that enables us to ‘stand well’ in relation to our desires and emotions. To be virtuous with regard to a type of emotion – anger, sadness, joy, fear, etc. – is to feel that type of emotion ‘at the right times, with reference to the right objects, towards the right people, with the right motive, and in the right way’ (Nicomachean Ethics, Book 2, Ch. 6, 1106b).
Genetic diversity of two Indian common bean germplasm collections based on morphological and microsatellite markers
Authors: Sharma P. N. , Díaz L. M. , Blair M. W.
Published: January 2013

India is the second most populous nation in the world after China, and its plant genetic resources are an important basis for crop improvement to meet human population needs. An important legume in the diet of the Indian population is common bean (Phaseolus vulgarisL.). Common beans are one of the many important legumes grown in India, but unlike others, its centre of origin is not in Asia but in the Americas. The objective of this study was to evaluate two collections of Indian common beans: one for an internationally available collection of Food and Agriculture Organization (FAO)-protected accessions and one from the north-western Himalayan region. In total, 149 Indian landraces were evaluated with a total of 24 microsatellites across the two collections, and these represented all common bean-growing states of India. A population structure analysis was used to find groups in each collection, and this was compared across the collections. The genetic analysis of the two sets of Indian accessions with neighbour-joining trees and principal component analysis categorized the landraces into Andean and Mesoamerican gene pool groups. The Andean genotypes dominated the north-western Himalayan collection while the FAO-protected accessions were predominantly Mesoamerican. The Indian subcontinent can be considered as a region of high bean diversity; however, very little introgression was observed between the gene pools in both the germplasm sets. Gene pool identity was further substantiated by the comparison of seed traits, particularly seed size. The role of the landraces in plant breeding programmes is discussed.
Demand for God and Government: The Dynamics of Religion and Public Opinion
Authors: Habel Philip , Grant J. Tobin
Published: January 2013

We explore the relationship between religiosity and public support for greater government services. We theorize that increases in religiosity and public opinion both reflect demands from citizens in the face of insecurity. We argue that religiosity is comprised of two factors: responses to insecurity; and long-held preferences for religion, or secularity. We show that previous studies that have observed increased religiosity leading to decreased support for government spending have not distinguished among religiosity as driven by secularity versus insecurity. To test our theory, we first estimate a series of simulations, and we then turn to the dynamics of aggregate religiosity and public opinion in the United States over the past fifty years, an environment where long-held preferences for religious goods have remained relatively stable. Consistent with our theory, religiosity and public opinion respond to insecurity; the series are positively correlated, move together through time, and react in similar ways to changes in GDP per capita. Our findings indicate that during times when there is greater insecurity, both religiosity and demand from government increase.
Non-degradative ubiquitination of the Notch1 receptor by the E3 ligase MDM2 activates the Notch signalling pathway
Authors: Pettersson Susanne , Sczaniecka Matylda , McLaren Lorna , Russell Fiona , Gladstone Karen , Hupp Ted , Wallace Maura
Published: January 2013

The Notch receptor is necessary for modulating cell fate decisions throughout development, and aberrant activation of Notch signalling has been associated with many diseases, including tumorigenesis. The E3 ligase MDM2 (murine double minute 2) plays a role in regulating the Notch signalling pathway through its interaction with NUMB. In the present study we report that MDM2 can also exert its oncogenic effects on the Notch signalling pathway by directly interacting with the Notch 1 receptor through dual-site binding. This involves both the N-terminal and acidic domains of MDM2 and the RAM [RBP-Jκ (recombination signal-binding protein 1 for Jκ)-associated molecule] and ANK (ankyrin) domains of Notch 1. Although the interaction between Notch1 and MDM2 results in ubiquitination of Notch1, this does not result in degradation of Notch1, but instead leads to activation of the intracellular domain of Notch1. Furthermore, MDM2 can synergize with Notch1 to inhibit apoptosis and promote proliferation. This highlights yet another target for MDM2-mediated ubiquitination that results in activation of the protein rather than degradation and makes MDM2 an attractive target for drug discovery for both the p53 and Notch signalling pathways.
Exploring the sequence–structure relationship for amyloid peptides
Authors: Morris Kyle L. , Rodger Alison , Hicks Matthew R. , Debulpaep Maya , Schymkowitz Joost , Rousseau Frederic , Serpell Louise C.
Published: January 2013

Amyloid fibril formation is associated with misfolding diseases, as well as fulfilling a functional role. The cross-β molecular architecture has been reported in increasing numbers of amyloid-like fibrillar systems. The Waltz algorithm is able to predict ordered self-assembly of amyloidogenic peptides by taking into account the residue type and position. This algorithm has expanded the amyloid sequence space, and in the present study we characterize the structures of amyloid-like fibrils formed by three peptides identified by Waltz that form fibrils but not crystals. The structural challenge is met by combining electron microscopy, linear dichroism, CD and X-ray fibre diffraction. We propose structures that reveal a cross-β conformation with ‘steric-zipper’ features, giving insights into the role for side chains in peptide packing and stability within fibrils. The amenity of these peptides to structural characterization makes them compelling model systems to use for understanding the relationship between sequence, self-assembly, stability and structure of amyloid fibrils.
Are the dynamics of a glass embedded in its elastic properties?
Authors: Potuzak Marcel , Guo Xiaoju , Smedskjaer Morten M. , Mauro John C.
Published: January 2013

The low temperature dynamics of glass are critically important for many high-tech applications. According to the elastic theory of the glass transition, the dynamics of glass are controlled by the evolution of shear modulus. In particular, the elastic shoving model expresses dynamics in terms of an activation energy required to shove aside the surrounding atoms. Here, we present a thorough test of the shoving model for predicting the low temperature dynamics of an oxide glass system. We show that the nonequilibrium viscosity of glass is governed by additional factors beyond changes in shear modulus.
Tuning surface-enhanced Raman scattering from graphene substrates using the electric field effect and chemical doping
Authors: Hao Qingzhen , Morton Seth M. , Wang Bei , Zhao Yanhui , Jensen Lasse , Jun Huang Tony
Published: January 2013

Graphene recently has been demonstrated to support surface-enhanced Raman scattering. Here, we show that the enhancement of the Raman signal of methylene blue on graphene can be tuned by using either the electric field effect or chemical doping. Both doping experiments show that hole-doped graphene yields a larger enhancement than one which is electron-doped; however, chemical doping leads to a significantly larger modulation of the enhancements. The observed enhancement correlates with the changes in the Fermi level of graphene, indicating that the enhancement is chemical in nature, as electromagnetic enhancement is ruled out by hybrid electrodynamical and quantum mechanical simulations.
Higher-order correlation functions and nonlinear response functions in a Gaussian trap model
Authors: Diezemann Gregor
Published: January 2013

The four-time correlation function of a general dynamical variable obeying Gaussian statistics is calculated for the trap model with a Gaussian density of states. It is argued that for energy-independent variables this function is reminiscent of the four-time functions that have been discussed earlier in the interpretation of the results of four-dimensional NMR experiments on supercooled liquids. Using an approximative relation between the four-time correlation function and the cubic response function the nonlinear susceptibility is calculated and the results are compared with the corresponding ones resulting from an exact calculation. It is found that the results of the approximation change the qualitative behavior of the modulus of the susceptibility. Whereas in the exact calculation a peak is found in the modulus in most cases, depending on temperature and the additional model parameters no such peak occurs in the approximation. This difference has its origin mainly in an incorrect estimate of the static response. The results are discussed in relation to recent experimental findings.
Multiple length and time scales of dynamic heterogeneities in model glass-forming liquids: A systematic analysis of multi-point and multi-time correlations
Authors: Kim Kang , Saito Shinji
Published: January 2013

We report an extensive and systematic investigation of the multi-point and multi-time correlation functions to reveal the spatio-temporal structures of dynamic heterogeneities in glass-forming liquids. Molecular dynamics simulations are carried out for the supercooled states of various prototype models of glass-forming liquids such as binary Kob–Andersen, Wahnström, soft-sphere, and network-forming liquids. While the first three models act as fragile liquids exhibiting super-Arrhenius temperature dependence in their relaxation times, the last is a strong glass-former exhibiting Arrhenius behavior. First, we quantify the length scale of the dynamic heterogeneities utilizing the four-point correlation function. The growth of the dynamic length scale with decreasing temperature is characterized by various scaling relations that are analogous to the critical phenomena. We also examine how the growth of the length scale depends upon the model employed. Second, the four-point correlation function is extended to a three-time correlation function to characterize the temporal structures of the dynamic heterogeneities based on our previous studies [K. Kim and S. Saito, Phys. Rev. E 79, 060501–R (2009)10.1103/PhysRevE.79.060501; K. Kim and S. Saito, J. Chem. Phys. 133, 044511 (2010)10.1063/1.3464331]. We provide comprehensive numerical results obtained from the three-time correlation function for the above models. From these calculations, we examine the time scale of the dynamic heterogeneities and determine the associated lifetime in a consistent and systematic way. Our results indicate that the lifetime of the dynamical heterogeneities becomes much longer than the α-relaxation time determined from a two-point correlation function in fragile liquids. The decoupling between the two time scales is remarkable, particularly in supercooled states, and the time scales differ by more than an order of magnitude in a more fragile liquid. In contrast, the lifetime is shorter than the α-relaxation time in tetrahedral network-forming strong liquid, even at lower temperatures.
Interaction of a small permanent magnet with a liquid metal duct flow
Authors: Heinicke Christiane , Tympel Saskia , Pulugundla Gautam , Rahneberg Ilko , Boeck Thomas , Thess André
Published: January 2013

If a permanent magnet is located near a liquid metal flow, the magnet experiences a Lorentz force, which depends on the velocity of the flow. This effect is embodied in a noncontact flow measurement technique called Lorentz force velocimetry (LFV). Although LFV is already under way for global flow measurement in metallurgy, the possibility of using LFV for local velocity measurement has not yet been explored. The present work is devoted to a comprehensive investigation of the Lorentz force acting upon a permanent magnet near a liquid metal flow in a square duct when the size of the magnet is sufficiently small to be influenced by only parts of the fluid flow. We employ a combination of laboratory experiments in the turbulent regime, direct numerical simulations of laminar and turbulent flows using a custom-made code, and Reynolds-averaged Navier-Stokes (RANS) simulations using a commercial code. We address three particular flow regimes, namely the kinematic regime where the back-reaction of the Lorentz force on the flow is negligible, the low-Reynolds number dynamic regime and the high-Reynolds number dynamic regime both being characterized by a significant modification of the flow by the Lorentz force. In all three regimes, the Lorentz force is characterized by a nondimensional electromagnetic drag coefficient CD, which depends on the dimensionless distance between the magnet and the duct h, the dimensionless size of the magnet d, the Reynolds number Re, and the Hartmann number Ha. We demonstrate that in the kinematic regime, CD displays a universal dependence on the distance parameter, expressed by the scaling laws CD ∼ h−2 for h ≪ 1 and CD ∼ h−7 for h ≫ 1. In the dynamic regime at low Re, the magnet acts as a magnetic obstacle and expels streamlines from its immediate vicinity. In the dynamic regime at high Re, we present experimental data on CD(Re) for 500 ≤ Re ≤ 104 and on CD(h) for 0.4 ≤ h ≤ 1 and demonstrate that they are in good agreement with numerical results obtained from RANS simulations for the same range of parameters.
Osmosis in a minimal model system
Authors: Lion Thomas W. , Allen Rosalind J.
Published: January 2013

Osmosis is one of the most important physical phenomena in living and soft matter systems. While the thermodynamics of osmosis is well understood, the underlying microscopic dynamical mechanisms remain the subject of discussion. Unravelling these mechanisms is a prerequisite for understanding osmosis in non-equilibrium systems. Here, we investigate the microscopic basis of osmosis, in a system at equilibrium, using molecular dynamics simulations of a minimal model in which repulsive solute and solvent particles differ only in their interactions with an external potential. For this system, we can derive a simple virial-like relation for the osmotic pressure. Our simulations support an intuitive picture in which the solvent concentration gradient, at osmotic equilibrium, arises from the balance between an outward force, caused by the increased total density in the solution, and an inward diffusive flux caused by the decreased solvent density in the solution. While more complex effects may occur in other osmotic systems, our results suggest that they are not required for a minimal picture of the dynamic mechanisms underlying osmosis.
Density functional theory and experimental study of the electronic structure and transport properties of La, V, Nb, and Ta doped SrTiO3
Authors: Baniecki J. D. , Ishii M. , Aso H. , Kurihara K. , Ricinschi Dan
Published: January 2013

The electronic structure and transport properties of donor doped SrTiO3 are studied using density functional theory with spin-orbit coupling and conductivity, Hall, and Seebeck effect measurements over a wide temperature range (100 K to 600 K). Split-off energies ΔSO are tunable through the dopant SO interaction strength and concentration varying from 28.1 meV for pure STO to 70.93 meV for SrTi0.5Nb0.5O3. At lower carrier concentrations and temperatures, SO coupling has a marked effect on both the filling dependence of the density-of-states mass as well as the temperature dependence of the Seebeck coefficient, with quantitative theoretical predictions based on DFT calculations that include the SO interaction in closer agreement to the experimental data. Moreover, the results suggest that the predictive power of the current theory is not unlimited, with less accuracy for the calculated S predicting the magnitude of the experimental S data at lower dopant concentrations than for degenerately doped systems. A concentration dependent mass enhancement of ∼2–5, relative to the density-of-states mass in the local density approximation, possibly due to the influence of electronic screening of the electron-phonon interaction, would bring the theoretical S in accord with the experimental S data. This additional carrier-dependent enhancement mechanism for S may give an additional degree of freedom in terms of designing new higher efficiency thermoelectric energy materials.
Composition and orientation dependence of high electric-field-induced strain in Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals
Authors: He Chongjun , Chen Hongbing , Bai Fei , Fan Zhibin , Sun Liang , Xu Feng , Wang Jiming , Liu Youwen , Zhu Kongjun
Published: January 2013

Relaxor based xPb(In1/2Nb1/2)O3–(1-x-y)Pb(Mg1/3Nb2/3)O3–yPbTiO3 single crystals [PIMNTx/(1-x-y)/y] have broader temperature usage range and comparable piezoelectric properties to (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 crystals. In this work, electric-field-induced strain behavior of PIMNT crystals with different orientation and composition was investigated. High strain with low hysteresis was observed in rhombohedral PIMNT25/44/31 crystal oriented along 〈001〉, rather than 〈011〉 and 〈111〉. Ultrahigh strain level up to 0.75% with linear curve can be achieved under 5 kV/mm electric field. The electric field induces phase transformation of PIMNT crystals is much higher than that of PIMNT crystals. These properties make PIMNT crystals promising candidate for high performance solid-state actuators.
Room-temperature operation of a radiofrequency diamond magnetometer near the shot-noise limit
Authors: Shin Chang S. , Avalos Claudia E. , Butler Mark C. , Trease David R. , Seltzer Scott J. , Peter Mustonen J. , Kennedy Daniel J. , Acosta Victor M. , Budker Dmitry , Pines Alexander , Bajaj Vikram S.
Published: January 2013

We operate a nitrogen-vacancy (NV−) diamond magnetometer at ambient temperatures and study the dependence of its bandwidth on experimental parameters including optical and microwave excitation powers. A model based on the Bloch equations is used to analyze the NV center's response time, τ, during continuous optical and microwave irradiation, and τ−1 is shown to be a weighted average of T1−1 and T2−1, where T1 and T2 are the longitudinal and transverse relaxation times of the electron spin during optical irradiation. We measured a maximum detection bandwidth of ∼1.6 MHz with optical excitation intensity of ∼2.3 MW/cm2, limited by the available optical power. The sensitivity of the NV ensemble for continuous-wave magnetometry in the presence of photon shot noise is analyzed. Two detection schemes are compared, one involving modulation of the fluorescence by an oscillating magnetic field while the microwave frequency is held constant, and the other involving double modulation of the fluorescence when the microwave frequency is modulated during the detection. For the first of these methods, we measure a sensitivity of 4.6 ± 0.3 nT/√Hz, unprecedented in a detector with this active volume of ∼10 μm3 and close to the photon-shot-noise limit of our experiment. The measured bandwidth and sensitivity of our device should allow detection of micro-scale NMR signals with microfluidic devices.
Glass transition in ultrathin films of amorphous solid water
Authors: Sepúlveda A. , Leon-Gutierrez E. , Gonzalez-Silveira M. , Rodríguez-Tinoco C. , Clavaguera-Mora M. T. , Rodríguez-Viejo J.
Published: January 2013

Nanocalorimetry at ultrafast heating rates is used to investigate the glass transition of nanometer thick films of metastable amorphous solid water grown by vapor deposition in an ultrahigh vacuum environment. Apparent heat capacity curves exhibit characteristic features depending on the deposition temperature. While films grown at T ≥ 155 K are completely crystallized, those deposited at 90 K show a relaxation exotherm prior to crystallization. Films grown between 135 and 140 K and subsequently cooled down to 90 K reveal a clear endothermic feature before crystallization, which is compatible with a glass-to-liquid transition. The onset temperature is located at 174 K at a heating rate of 2.4 × 104 K/s and is independent of film thickness in the range of 16–150 nm. Comparison of our data with other calorimetric measurements at various heating rates suggests that water is a strong glass former in the deeply supercooled state.
On the photophysics and photochemistry of the water dimer
Authors: Segarra-Martí Javier , Roca-Sanjuán Daniel , Merchán Manuela , Lindh Roland
Published: January 2013

The photochemistry of the water dimer irradiated by UV light is studied by means of the complete active space perturbation theory//complete active space self-consistent field (CASPT2//CASSCF) method and accurate computational approaches like as minimum energy paths. Both electronic structure computations and ab initio molecular dynamics simulations are carried out. The results obtained show small shifts relative to a single water molecule on the vertical excitation energies of the dimer due to the hydrogen bond placed between the water donor (WD) and the water acceptor (WA). A red-shift and a blue-shift are predicted for the WD and WA, respectively, supporting previous theoretical and experimental results. The photoinduced chemistry of the water dimer is described as a process occurring between two single water molecules in which the effect of the hydrogen bond plays a minor role. Thus, the photoinduced decay routes correspond to two photodissociation processes, one for each water molecule. The proposed mechanism for the decay channels of the lowest-lying excited states of the system is established as the photochemical production of a hydrogen-bonded H2O…HO species plus a hydrogen H atom.
Orbital and asymptotic stability for standing waves of a nonlinear Schrödinger equation with concentrated nonlinearity in dimension three
Authors: Adami Riccardo , Noja Diego , Ortoleva Cecilia
Published: January 2013

We begin to study in this paper orbital and asymptotic stability of standing waves for a model of Schrödinger equation with concentrated nonlinearity in dimension three. The nonlinearity is obtained considering a point (or contact) interaction with strength α, which consists of a singular perturbation of the Laplacian described by a self-adjoint operator Hα, and letting the strength α depend on the wavefunction: \documentclass[12pt]{minimal}\begin{document}$i\dot{u}= H_\alpha u$\end{document}iu̇=Hαu, α = α(u). It is well-known that the elements of the domain of such operator can be written as the sum of a regular function and a function that exhibits a singularity proportional to |x − x0|−1, where x0 is the location of the point interaction. If q is the so-called charge of the domain element u, i.e., the coefficient of its singular part, then, in order to introduce a nonlinearity, we let the strength α depend on u according to the law α = −ν|q|σ, with ν > 0. This characterizes the model as a focusing NLS (nonlinear Schrödinger) with concentrated nonlinearity of power type. For such a model we prove the existence of standing waves of the form u(t) = eiωtΦω, which are orbitally stable in the range σ ∈ (0, 1), and orbitally unstable when σ ⩾ 1. Moreover, we show that for \documentclass[12pt]{minimal}\begin{document}$\sigma \in (0,\frac{1}{\sqrt{2}})$\end{document}σ∈(0,12) every standing wave is asymptotically stable in the following sense. Choosing initial data close to the stationary state in the energy norm, and belonging to a natural weighted Lp space which allows dispersive estimates, the following resolution holds: \documentclass[12pt]{minimal}\begin{document}$u(t) = e^{i\omega _{\infty } t} \Phi _{\omega _{\infty }} +U_t*\psi _{\infty } +r_{\infty }$\end{document}u(t)=eiω∞tΦω∞+Ut*ψ∞+r∞, where U is the free Schrödinger propagator, ω∞ > 0 and ψ∞, \documentclass[12pt]{minimal}\begin{document}$r_{\infty } \in L^2(\mathbb {R}^3)$\end{document}r∞∈L2(R3) with \documentclass[12pt]{minimal}\begin{document}$\Vert r_{\infty } \Vert _{L^2}\break = O(t^{-5/4}) \quad \textrm {as} \;\; t \rightarrow +\infty$\end{document}‖r∞‖L2=O(t−5/4) as t→+∞. Notice that in the present model the admitted nonlinearity for which asymptotic stability of solitons is proved is subcritical, in the sense that it does not give rise to blow up, regardless of the chosen initial data.
Comment on “On the consistency of solutions of the space fractional Schrödinger equation” [J. Math. Phys. 53, 042105 (2012)]
Authors: Hawkins E. , Schwarz J. M.
Published: January 2013

In Bayın's paper [J. Math. Phys. 53, 042105 (2012)]10.1063/1.4705268, he claims to prove the consistency of the purported piece-wise solutions to the fractional Schrödinger equation for an infinite square well. However, his calculation uses standard contour integral techniques despite the absence of an analytic integrand. The correct calculation is presented and supports our earlier work proving that the purported piece-wise solutions do not solve the fractional Schrödinger equation for an infinite square well [M. Jeng, S.-L.-Y. Xu, E. Hawkins, and J. M. Schwarz, J. Math. Phys. 51, 062102 (2010)]10.1063/1.3430552.
Electronic properties of two-dimensional covalent organic frameworks
Authors: Zhu P. , Meunier V.
Published: January 2013

The electronic properties of a number of two-dimensional covalent organic frameworks are studied using a combination of density functional theory and quasiparticle theory calculations. The effect of composition and system size on the electronic band gap is systematically considered for a series of systems, using van der Waals corrected density functional theory calculations to determine the effect of a graphene substrate on deposited covalent frameworks. We predict that covalent organic frameworks’ (COFs’) electronic properties, such as their band gap can be fine tuned by appropriate modifications of their structures, specifically by increasing organic chain-links in the framework. The effect of strain on the electronic properties is also studied. The graphene substrate is shown to not significantly alter the properties of COFs, thereby indicating the robustness of COFs’ intrinsic properties for practical applications.
Photo-induced exciton generation in polyvinylpyrrolidone encapsulated Ag2S core-shells: Electrochemical deposition, regular shape and high order of particle size distribution
Authors: Mukherjee Nillohit , Jana Sumanta , Gopal Khan Gobinda , Mondal Anup
Published: January 2013

Visible light induced frequency switching behavior, exhibited by the electrochemically deposited thin films of polyvinylpyrrolidone (PVP) encapsulated Ag2S nanosphere (core-shell) is shown here. A low frequency (∼40 Hz) pulse was found to be generated upon illumination with 1 Sun due to excitonic transition, which also showed good switching behavior with the “on” and “off” state of the light. Capping of the semiconductor surface by a polymer like PVP reduces the surface states and thus lowers the built in barrier height and the width of depletion region. So, the number of photo generated but non recombining electron-hole pairs (excitons) increases, which put their signature in some unique physical properties like increase in photoluminescence (PL) intensity, light induced frequency switching behavior due to free exciton generation, etc. Here, the depositions were carried out on indium tin oxide coated glass substrates from an aqueous solution of AgNO3, thioacetamide, and PVP. The films were structurally characterized using high resolution X-ray diffraction, field emission scanning electron microscopy, and high resolution transmission electron microscopic techniques. The deposited particles were regular in shape with significantly high order of size distribution. Furrier transform infrared spectroscopy confirmed the presence of PVP as the encapsulating agent. Optical characterization, viz., UV – vis – NIR and NIR-PL revealed noteworthy amount of NIR emission from the deposited material.
Photonic microdisk resonators in aluminum nitride
Authors: Ghosh Siddhartha , Piazza Gianluca
Published: January 2013

We demonstrate integrated photonic microdisk resonators in sputtered c-axis oriented aluminum nitride (AlN) films. A 400 nm thick layer of AlN was patterned in a single lithography step with silicon dioxide used for the top and bottom cladding layers. AlN disks with a radius of 20 μm at various spacings to an 850 nm wide waveguide were tested. A loaded quality factor of 28 350 is shown in these microdisks, with an extracted peak shift over power ratio of 0.0495 pm/μW. The demonstration of photonic resonators in a piezoelectric material can lead to novel optomechanical functionalities.
Disorder effects on electronic bandgap and transport in graphene-nanomesh-based structures
Authors: Hung Nguyen V. , Chung Nguyen M. , Nguyen Huy-Viet , Dollfus P.
Published: January 2013

Using atomistic quantum simulation based on a tight binding model, we investigate the formation of electronic bandgap Eg of graphene nanomesh (GNM) lattices and the transport characteristics of GNM-based electronic devices (single potential barrier structure and p-n junction) including the atomic edge disorder of holes. We find that the sensitivity of Eg to the lattice symmetry (i.e., the lattice orientation and the hole shape) is significantly suppressed in the presence of disorder. In the case of strong disorder, the dependence of Eg on the neck width fits well with the scaling rule observed in experiments [Liang et al., Nano Lett. 10, 2454 (2010)]. Considering the transport characteristics of GNM-based structures, we demonstrate that the use of finite GNM sections in the devices can efficiently improve their electrical performance (i.e., high ON/OFF current ratio, good current saturation, and negative differential conductance behaviors). Additionally, if the length of GNM sections is suitably chosen, the detrimental effects of disorder on transport can be avoided to a large extent. Our study provides a good explanation of the available experimental data on GNM energy gap and should be helpful for further investigations of GNM-based devices.
Optical constants n and κ of various technical and optical glasses at λ = 10.59 μm
Authors: Gräf Stephan , Staupendahl Gisbert , Gerling Petra , Müller Frank A.
Published: January 2013

The optical constants n (refractive index) and κ (absorption index) of several technical and optical glasses were determined with high accuracy for the CO2 laser wavelength λ = 10.59 μm by angular- and polarization-dependent measurements of reflection at the surface of these glasses. The exact knowledge of n and κ is important for modeling the interaction between CO2 laser radiation and glasses. The investigations were made with low-intense CO2 laser radiation polarized perpendicular as well as parallel to the plane of incidence. The angle of incidence was varied in the range between 0° and 90°. The values of n and κ were determined by means of a fitting procedure between the measured values of the reflectivity and the theoretical curves from Fresnel's formulas. In the case of high absorbing index glasses, the accuracy of this method exceeds ±2% (n) and ±4% (κ), respectively. The measured values show significant differences between typical optical and technical glasses resulting in a linear absorption coefficient that is up to 12 times higher for optical glasses.
A correlation force spectrometer for single molecule measurements under tensile load
Authors: Radiom Milad , Honig Christopher D. F. , Walz John Y. , Paul Mark R. , Ducker William A.
Published: January 2013

The dynamical-mechanical properties of a small region of fluid can be measured using two closely spaced thermally stimulated micrometer-scale cantilevers. We call this technique correlation force spectroscopy (CFS). We describe an instrument that is designed for characterizing the extensional properties of polymer molecules that straddle the gap between the two cantilevers and use it to measure the stiffness and damping (molecular friction) of a dextran molecule. The device is based on a commercial atomic force microscope, into which we have incorporated a second antiparallel cantilever. The deflection of each cantilever is measured in the frequency range dc–1 MHz and is used to generate the cross-correlation at equilibrium. The main advantage of cross-correlation measurements is the reduction in thermal noise, which sets a fundamental noise limit to force resolution. We show that the thermal noise in our cross-correlation measurements is less than one third of the value for single-cantilever force microscopy. The dynamics of the cantilever pair is modeled using the deterministic motion of a harmonic oscillator initially displaced from equilibrium, which yields the equilibrium auto and cross-correlations in cantilever displacement via the fluctuation-dissipation theorem. Fitted parameters from the model (stiffness and damping) are used to characterize the fluid at equilibrium, including any straddling molecules.
In situ control of electronic phase separation in La1/8 Pr4/8Ca3/8MnO3/PNM-PT thin films using ferroelectric-poling-induced strain
Authors: Zhang T. , Wei Q. , Zheng R. K. , Wang X. P. , Fang Q. F.
Published: January 2013

The effects of ferroelectric-poling-induced strain on the transport and magnetic properties of the phase separated La1/8Pr4/8Ca3/8MnO3 (LPCMO) thin films epitaxially grown on the ferroelectric 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) single-crystal substrates were investigated. The ferroelectric poling reduces the in-plane tensile strain and enhances the out-of plane tensile strain of LPCMO film, which decreases the resistance and the charge ordering transition temperature but raises the low-field-magnetization of film. These results can be explained by the strain induced change in the volume fraction of coexisting phases, i.e., ferromagnetic, antiferromagnetic, and paramagnetic phases, demonstrating that the charge ordering phase transition of manganites film grown on the ferroelectric PMN-PT substrate can be controlled by modifying the poling state of single crystal substrate.
Internal relaxation in dye sensitized solar cells based on Zn2SnO4 nanostructures
Authors: Pimachev Artem , Kolesov Grigory , Chen Jiajun , Wang Wenyong , Dahnovsky Yuri
Published: January 2013

In this work we study the effect of internal relaxation in a (Bu4N)2Ru(dcbpyH)2(NCS)2 (N719) dye molecule in a dye sensitized solar cell. Experimentally measured light intensity dependencies of short circuit current and open circuit voltage for two different types of photoanodes, ZTO (Zn2SnO4) nanorods and nanoparticles, are explained in the framework of the proposed microscopic theory. This theory is based on a density matrix equation with a Markovian relaxation term. The computational results are in favor of the fast relaxation inside the unoccupied and occupied bands rather than slow interband electron-hole recombination. The difference in experimental dependencies for ZTO nanorods and nanoparticles is explained by the difference in the electron transfer matrix elements, and therefore, the electron transfer injection constants for the different morphologies of the photoanodes.
Formation and relaxation of RbHe exciplexes on He nanodroplets studied by femtosecond pump and picosecond probe spectroscopy
Authors: Giese C. , Mullins T. , Grüner B. , Weidemüller M. , Stienkemeier F. , Mudrich M.
Published: January 2013

Vibrationally resolved photoionization spectra of RbHe exciplexes forming on He nanodroplets are recorded using femtosecond pump-probe spectroscopy with amplitude-shaped probe pulses. The time-evolution of the spectra reveals an exciplex formation time ∼10 ps followed by vibrational relaxation extending up to ≳ 1 ns. This points to an indirect, time-delayed desorption process of RbHe off the He surface.
A cryogenic high pressure cell for inelastic neutron scattering measurements of quantum fluids and solids
Authors: Carmichael J. R. , Diallo S. O.
Published: January 2013

We present our new development of a high pressure cell for inelastic neutron scattering measurements of helium at ultra-low temperatures. The cell has a large sample volume of ∼140 cm3 and a working pressure of ∼7 MPa, with a relatively thin wall-thickness (1.1 mm)—thanks to the high yield strength aluminum used in the design. Two variants of this cell have been developed. The first cell is permanently joined components using electron-beam welding and explosion welding, methods that have little or no impact on the global heat treatment of the cell. The second cell discussed has modular and interchangeable components, which includes a capacitance pressure gauge, that can be sealed using the traditional indium wire technique. The performance of the cells have been tested in recent measurements on superfluid liquid helium near the solidification line.
Periodicity suppression in continuous-time dynamical systems by external forcing
Authors: Mathias Amanda C. , Rech Paulo C.
Published: January 2013

We investigate periodicity suppression by an external periodic forcing in different flows, each modeled by a set of three autonomous nonlinear first-order ordinary differential equations. By varying the amplitude of a sinusoidal forcing with a fixed angular frequency, we show through numerical simulations, including parameter planes plots, phase-space portraits, and the largest Lyapunov exponent, that windows of periodicity embedded in chaotic regions may be totally suppressed.
On the lock-on of vortex shedding to oscillatory actuation around a circular cylinder
Authors: Munday Phillip M. , Taira Kunihiko
Published: January 2013

We numerically investigate the influence of sinusoidal flow control on the von Kármán vortex shedding behind a circular cylinder in two-dimensional flow. Actuator location, direction, frequency, and amplitude are varied to examine their effects on the wake and the corresponding change in drag on the cylinder. We place focus on the conditions for which the cylinder wake locks onto the actuation frequency. The lock-on region is found to be consistent with stability horns observed in oscillator dynamics. Under certain conditions, the actuation reduces drag by elongating the wake structure to appear more streamlined than the wake without flow control. In other cases, the use of actuation led to less streamlined wakes, resulting in no significant drag reduction or for some instances in a drag increase. Purely steady and oscillatory actuation components are examined to highlight their individual influence on the lock-on and drag characteristics. We also note that low frequency oscillations are observed for cases in the neighborhood of the lock-on boundaries due to the competition between low and high-drag states.
Scaling investigation for the dynamics of charged particles in an electric field accelerator
Authors: Gouvêa Ladeira Denis , Leonel Edson D.
Published: January 2013

Some dynamical properties of an ensemble of trajectories of individual (non-interacting) classical particles of mass m and charge q interacting with a time-dependent electric field and suffering the action of a constant magnetic field are studied. Depending on both the amplitude of oscillation of the electric field and the intensity of the magnetic field, the phase space of the model can either exhibit: (i) regular behavior or (ii) a mixed structure, with periodic islands of regular motion, chaotic seas characterized by positive Lyapunov exponents, and invariant Kolmogorov–Arnold–Moser curves preventing the particle to reach unbounded energy. We define an escape window in the chaotic sea and study the transport properties for chaotic orbits along the phase space by the use of scaling formalism. Our results show that the escape distribution and the survival probability obey homogeneous functions characterized by critical exponents and present universal behavior under appropriate scaling transformations. We show the survival probability decays exponentially for small iterations changing to a slower power law decay for large time, therefore, characterizing clearly the effects of stickiness of the islands and invariant tori. For the range of parameters used, our results show that the crossover from fast to slow decay obeys a power law and the behavior of survival orbits is scaling invariant.
Suppression of bursting synchronization in clustered scale-free (rich-club) neuronal networks
Authors: Lameu E. L. , Batista C. A. S. , Batista A. M. , Iarosz K. , Viana R. L. , Lopes S. R. , Kurths J.
Published: January 2013

Functional brain networks are composed of cortical areas that are anatomically and functionally connected. One of the cortical networks for which more information is available in the literature is the cat cerebral cortex. Statistical analyses of the latter suggest that its structure can be described as a clustered network, in which each cluster is a scale-free network possessing highly connected hubs. Those hubs are, on their hand, connected together in a strong fashion (“rich-club” network). We have built a clustered scale-free network inspired in the cat cortex structure so as to study their dynamical properties. In this article, we focus on the synchronization of bursting activity of the cortical areas and how it can be suppressed by means of neuron deactivation through suitably applied light pulses. We show that it is possible to effectively suppress bursting synchronization by acting on a single, yet suitably chosen neuron, as long as it is highly connected, thanks to the “rich-club” structure of the network.
Equation of state of dense plasmas by ab initio simulations: Bridging the gap between quantum molecular dynamics and orbital-free molecular dynamics at high temperature
Authors: Danel J.-F. , Kazandjian L. , Zérah G.
Published: January 2013

The applicability of quantum molecular dynamics to the calculation of the equation of state of a dense plasma is limited at high temperature by computational cost. Orbital-free molecular dynamics, based on the Thomas-Fermi semiclassical approximation and possibly on a gradient correction, is the only simulation method currently available at high temperature. We show in the case of a dense boron plasma that the two approaches give pressures differing by a few percent even at temperatures as high as a few tens of electron-volts. We indicate how the pressures obtained by orbital-free molecular dynamics can be corrected in order to appear as a limit of the quantum molecular dynamics results as temperature increases. We thus obtain a method to calculate the equation of state of a dense plasma up to high temperatures where quantum molecular dynamics cannot be directly implemented.
Sub-Kelvin ac magnetic susceptometry
Authors: Schmidt M. A. , Silevitch D. M. , Woo N. , Rosenbaum T. F.
Published: January 2013

Designing an apparatus for experiments that operate deep into the milliKelvin regime requires a careful selection of materials and construction techniques, and often entails balancing mutually contradictory requirements. In the case of magnetic susceptibility measurements, this involves choosing materials that realize both high thermal conductivity for good heat sinking and low electrical conductivity for minimal eddy-current heating. A coil mounting system with a completely nonmetallic construction, achieved through the use of a sapphire skeleton and a machined carbon-fiber body, resolves this dilemma. This system permits the use of large ac magnetic field amplitudes at kHz frequencies and above, opening the door to studies of the nonlinear dynamics of a wide variety of magnetic systems that were previously inaccessible.
Impact of wavelength dependent thermo-elastic laser ablation mechanism on the generation of nanoparticles from thin gold films
Authors: Haustrup N. , O'Connor G. M.
Published: January 2013

This experimental study provides an insight into the wavelength dependence of femtosecond ablation mechanisms of thin gold films. A wavelength dependent, linear relationship was identified between the volume of the grain microstructure of 20 nm thick films and the volume of the nanoparticles generated during laser ablation. Laser ablation at 343 nm and 515 nm wavelengths resulted in the same linear relationship between the grain volume and the nanoparticle volume. However, no relationship at all was observed when ablated at 1030 nm. The wavelength dependence of these results was attributed to differing absorption mechanisms that ultimately lead to differing ablation mechanisms and nanoparticle formation.