bluuebunny/crossref_metadata_2025 huggingface dataset:
Price game and chaos control among three oligarchs with different rationalities in property insurance market
Authors: Ma Junhai , Zhang Junling
Published: November 2012

Combining with the actual competition in Chinese property insurance market and assuming that the property insurance companies take the marginal utility maximization as the basis of decision-making when they play price games, we first established the price game model with three oligarchs who have different rationalities. Then, we discussed the existence and stability of equilibrium points. Third, we studied the theoretical value of Lyapunov exponent at Nash equilibrium point and its change process with the main parameters' changes though having numerical simulation for the system such as the bifurcation, chaos attractors, and so on. Finally, we analyzed the influences which the changes of different parameters have on the profits and utilities of oligarchs and their corresponding competition advantage. Based on this, we used the variable feedback control method to control the chaos of the system and stabilized the chaos state to Nash equilibrium point again. The results have significant theoretical and practical application value.
Direct measurement of radiative scattering of surface plasmon polariton resonance from metallic arrays by polarization-resolved reflectivity spectroscopy
Authors: Lo H. Y. , Chan C. Y. , Ong H. C.
Published: November 2012

We have measured the radiative scattering from two-dimensional metallic arrays by using polarization-resolved reflectivity spectroscopy. We find the reflectivity spectra follow the Fano-like model that can be derived from temporal coupled mode theory and Jones matrix calculus. By orthogonally orienting the incident polarizer and the detection analyzer, reflectivity dips flip into peaks and the radiative scattering efficiency can be determined accordingly. The dependence of total radiative scattering efficiency on wavelength and hole diameter is found to agree well with Rayleigh scattering by single hole.
Kernel functions and Bäcklund transformations for relativistic Calogero-Moser and Toda systems
Authors: Hallnäs Martin , Ruijsenaars Simon
Published: November 2012

We obtain kernel functions associated with the quantum relativistic Toda systems, both for the periodic version and for the nonperiodic version with its dual. This involves taking limits of previously known results concerning kernel functions for the elliptic and hyperbolic relativistic Calogero-Moser systems. We show that the special kernel functions at issue admit a limit that yields generating functions of Bäcklund transformations for the classical relativistic Calogero-Moser and Toda systems. We also obtain the nonrelativistic counterparts of our results, which tie in with previous results in the literature.
Extremely slow photocurrent response from hemoprotein films in planar diode geometry
Authors: Nam Sungho , Kim Hwajeong , Degenaar Patrick , Ha Chang-Sik , Kim Youngkyoo
Published: November 2012

The photocurrent response in solid-state films of two different hemoproteins, horseradish peroxidase and cytochrome c, was studied by employing a geometry of planar diode device. The highest occupied molecular orbital energy of the two solid-state hemoproteins was measured using photoelectron yield spectroscopy. Results showed that the photocurrent response of hemoprotein films under white light illumination was found extremely slow (ca. 160–480 s) owing to the charge blocking by insulating surrounding parts of which size resulted in largely different photocurrent time scale between the two hemoprotein films.
Rare-event sampling: Occupation-based performance measures for parallel tempering and infinite swapping Monte Carlo methods
Authors: Doll J. D. , Plattner Nuria , Freeman David L. , Liu Yufei , Dupuis Paul
Published: November 2012

In the present paper we identify a rigorous property of a number of tempering-based Monte Carlo sampling methods, including parallel tempering as well as partial and infinite swapping. Based on this property we develop a variety of performance measures for such rare-event sampling methods that are broadly applicable, informative, and straightforward to implement. We illustrate the use of these performance measures with a series of applications involving the equilibrium properties of simple Lennard-Jones clusters, applications for which the performance levels of partial and infinite swapping approaches are found to be higher than those of conventional parallel tempering.
Design of a deuterium and tritium-ablator shock ignition target for the National Ignition Facility
Authors: Terry Matthew R. , Perkins L. John , Sepke Scott M.
Published: November 2012

Shock ignition presents a viable path to ignition and high gain on the National Ignition Facility (NIF). In this paper, we describe the development of the 1D design of 0.5 MJ class, all-deuterium and tritium (fuel and ablator) shock ignition target that should be reasonably robust to Rayleigh-Taylor fluid instabilities, mistiming, and hot electron preheat. The target assumes “day one” NIF hardware and produces a yield of 31 MJ with reasonable allowances for laser backscatter, absorption efficiency, and polar drive power variation. The energetics of polar drive laser absorption require a beam configuration with half of the NIF quads dedicated to launching the ignitor shock, while the remaining quads drive the target compression. Hydrodynamic scaling of the target suggests that gains of 75 and yields 70 MJ may be possible.
Digital-to-analog converter using a superconducting quantum interference device
Authors: Nakanishi Masakazu
Published: November 2012

We developed a digital-to-analog converter (DAC) having a current output and incorporating a superconducting quantum interference device (SQUID). The linearity of the device is based on the periodic dependence of the SQUID response on the magnetic flux coupling to the SQUID ring. The period is a flux quantum (Φo = h/2e, where h is Planck's constant and e is the elementary charge). Because of the device's quantum accuracy, the output is essentially linear. The SQUID DAC was constructed using a commercially available rf-SQUID, the periodicity of which has been experimentally verified below 3420 Φo. An adjustable number of current amplitudes are dependent on maximum output (Imax). The output current is adjustable to ∼100 000 different values when Imax ≃1 mA and ∼1 000 000 when Imax ≃0.1 mA. The short-term fluctuation of ∼0.15 ppm was attributable to flux resolution of the SQUID. As a demonstration, measurements showing the voltage linearity of a digital multimeter were performed.
Polyester μ-assay chip for stem cell studies
Authors: Piraino Francesco , Selimović Šeila , Adamo Marco , Pero Alessandro , Manoucheri Sam , Bok Kim Sang , Demarchi Danilo , Khademhosseini Ali
Published: November 2012

The application of microfluidic technologies to stem cell research is of great interest to biologists and bioengineers. This is chiefly due to the intricate ability to control the cellular environment, the reduction of reagent volume, experimentation time and cost, and the high-throughput screening capabilities of microscale devices. Despite this importance, a simple-to-use microfluidic platform for studying the effects of growth factors on stem cell differentiation has not yet emerged. With this consideration, we have designed and characterized a microfluidic device that is easy to fabricate and operate, yet contains several functional elements. Our device is a simple polyester-based microfluidic chip capable of simultaneously screening multiple independent stem cell culture conditions. Generated by laser ablation and stacking of multiple layers of polyester film, this device integrates a 10 × 10 microwell array for cell culture with a continuous perfusion system and a non-linear concentration gradient generator. We performed numerical calculations to predict the gradient formation and calculate the shear stress acting on the cells inside the device. The device operation was validated by culturing murine embryonic stem cells inside the microwells for 5 days. Furthermore, we showed the ability to maintain the pluripotency of stem cell aggregates in response to concentrations of leukemia inhibitory factor ranging from 0 to ∼1000 U/ml. Given its simplicity, fast manufacturing method, scalability, and the cell-compatible nature of the device, it may be a useful platform for long-term stem cell culture and studies.
Formation of dendrite domain structures in stoichiometric lithium niobate at elevated temperatures
Authors: Ya. Shur V. , Chezganov D. S. , Nebogatikov M. S. , Baturin I. S. , Neradovskiy M. M.
Published: November 2012

Formation of the dendrite-type self-organized domain structures during polarization reversal at elevated temperatures (above 230 °C) has been revealed and studied in stoichiometric lithium niobate LiNbO3 single crystals. Optical, confocal Raman, scanning electron, and piezoelectric force microscopy have been used for domain visualization. It has been shown experimentally that formation of the dendrite-like structures has been attributed to correlated nucleation caused by a field distribution in the vicinity of the charged domain walls.
Deep level transient spectroscopy and minority carrier lifetime study on Ga-doped continuous Czochralski silicon
Authors: Yoon Yohan , Yan Yixin , Ostrom Nels P. , Kim Jinwoo , Rozgonyi George
Published: November 2012

Continuous-Czochralski (c-Cz) crystal growth has been suggested as a viable technique for the fabrication of photovoltaic Si wafers due to its low resistivity variation of any dopant, independent of segregation, compared to conventional Cz. In order to eliminate light induced degradation due to boron-oxygen traps in conventional p-type silicon wafers, gallium doped wafers have been grown by c-Cz method and investigated using four point probe, deep level transient spectroscopy (DLTS), and microwave-photoconductance decay. Iron-gallium related electrically active defects were identified using DLTS as the main lifetime killers responsible for reduced non-uniform lifetimes in radial and axial positions of the c-Cz silicon ingot. A direct correlation between minority carrier lifetime and the concentration of electrically active Fe-Ga pairs was established.
Multireference equation-of-motion coupled cluster theory
Authors: Datta Dipayan , Nooijen Marcel
Published: November 2012

A generalization of the equation-of-motion coupled cluster theory is proposed, which is built upon a multireference parent state. This method is suitable for a number of electronic states of a system that can be described by similar active spaces, i.e., different linear combinations of the same set of active space determinants. One of the suitable states is chosen as the parent state and the dominant dynamical correlation is optimized for this state using an internally contracted multireference coupled cluster ansatz. The remaining correlation and orbital relaxation effects are obtained via an uncontracted diagonalization of the transformed Hamiltonian, \documentclass[12pt]{minimal}\begin{document}\smash{$\hat{\overline{H}}=e^{-\hat{T}}\hat{H}e^{\hat{T}}$}\end{document}H¯̂=e−T̂ĤeT̂, in a compact multireference configuration interaction space, which involves configurations with at most single virtual orbital substitution. The latter effects are thus state-specific and this allows us to obtain multiple electronic states in the spirit of the equation-of-motion coupled cluster approach. A crucial aspect of this formulation is the use of the amplitudes of the generalized normal-ordered transformed Hamiltonian \documentclass[12pt]{minimal}\begin{document}\smash{$\hat{\overline{H}}$}\end{document}H¯̂ as the residual equations for determining the internally contracted cluster amplitudes without any projection onto the excited configurations. These residuals have been termed as the many-body residuals. These equations are formally non-singular and thus allow us to solve for all amplitudes without discarding any, in contrast to other internally contracted approaches. This is desirable to ensure transferability of dynamical correlation from the parent state to the target states. Preliminary results involving the low-lying electronic states of C2, O2, and the excitation spectra of three transition metal atoms, e.g., Fe, Cr, and Mn, including hundreds of excited states, illustrate the potential of our approach.
A determining form for the two-dimensional Navier-Stokes equations: The Fourier modes case
Authors: Foias Ciprian , Jolly Michael S. , Kravchenko Rostyslav , Titi Edriss S.
Published: November 2012

The determining modes for the two-dimensional incompressible Navier-Stokes equations (NSE) are shown to satisfy an ordinary differential equation (ODE) of the form dv/dt = F(v), in the Banach space, X, of all bounded continuous functions of the variable \documentclass[12pt]{minimal}\begin{document}$s\in \mathbb {R}$\end{document}s∈R with values in certain finite-dimensional linear space. This new evolution ODE, named determining form, induces an infinite-dimensional dynamical system in the space X which is noteworthy for two reasons. One is that F is globally Lipschitz from X into itself. The other is that the long-term dynamics of the determining form contains that of the NSE; the traveling wave solutions of the determining form, i.e., those of the form v(t, s) = v0(t + s), correspond exactly to initial data v0 that are projections of solutions of the global attractor of the NSE onto the determining modes. The determining form is also shown to be dissipative; an estimate for the radius of an absorbing ball is derived in terms of the number of determining modes and the Grashof number (a dimensionless physical parameter).
Moderately converging ion and electron flows in two-dimensional diodes
Authors: Cavenago M.
Published: November 2012

Flow of particles in diodes is solved selfconsistently assuming an approximated system of flow lines, that can be easily represented by an analytic transformation in a complex plane, with assumed uniformity in the third spatial direction. Beam current compression is tunable by an angle parameter α0; transformed coordinate lines are circular arcs, exactly matching to the curved cathode usually considered by rectilinear converging flows. The curvature of flow lines allows to partly balance the transverse effect of space charge. A self-contained discussion of the whole theory is reported, ranging from analytical solution for selfconsistent potential to electrode drawing to precise numerical simulation, which serves as a verification and as an illustration of typical electrode shapes. Motion and Poisson equation are written in a curved flow line system and their approximate consistency is shown to imply an ordinary differential equation for the beam edge potential. Transformations of this equation and their series solutions are given and discussed, showing that beam edge potential has a maximum, so supporting both diode (with α0 ≅ π/3) and triode design. Numerical simulations confirm the consistency of these solution. Geometrical details of diode design are discussed: the condition of a zero divergence beam, with the necessary anode lens effect included, is written and solved, as a function of beam compression; accurate relations for diode parameters and perveance are given. Weakly relativistic effects including self-magnetic field are finally discussed as a refinement.
Predicting chaos in memristive oscillator via harmonic balance method
Authors: Wang Xin , Li Chuandong , Huang Tingwen , Duan Shukai
Published: November 2012

This paper studies the possible chaotic behaviors in a memristive oscillator with cubic nonlinearities via harmonic balance method which is also called the method of describing function. This method was proposed to detect chaos in classical Chua's circuit. We first transform the considered memristive oscillator system into Lur'e model and present the prediction of the existence of chaotic behaviors. To ensure the prediction result is correct, the distortion index is also measured. Numerical simulations are presented to show the effectiveness of theoretical results.
Interplay between collective behavior and spreading dynamics on complex networks
Authors: Li Kezan , Ma Zhongjun , Jia Zhen , Small Michael , Fu Xinchu
Published: November 2012

There are certain correlations between collective behavior and spreading dynamics on some real complex networks. Based on the dynamical characteristics and traditional physical models, we construct several new bidirectional network models of spreading phenomena. By theoretical and numerical analysis of these models, we find that the collective behavior can inhibit spreading behavior, but, conversely, this spreading behavior can accelerate collective behavior. The spread threshold of spreading network is obtained by using the Lyapunov function method. The results show that an effective spreading control method is to enhance the individual awareness to collective behavior. Many real-world complex networks can be thought of in terms of both collective behavior and spreading dynamics and therefore to better understand and control such complex networks systems, our work may provide a basic framework.
Effective Fokker-Planck equation for birhythmic modified van der Pol oscillator
Authors: Yamapi R. , Filatrella G. , Aziz-Alaoui M. A. , Cerdeira Hilda A.
Published: November 2012

We present an explicit solution based on the phase-amplitude approximation of the Fokker-Planck equation associated with the Langevin equation of the birhythmic modified van der Pol system. The solution enables us to derive probability distributions analytically as well as the activation energies associated with switching between the coexisting different attractors that characterize the birhythmic system. Comparing analytical and numerical results we find good agreement when the frequencies of both attractors are equal, while the predictions of the analytic estimates deteriorate when the two frequencies depart. Under the effect of noise, the two states that characterize the birhythmic system can merge, inasmuch as the parameter plane of the birhythmic solutions is found to shrink when the noise intensity increases. The solution of the Fokker-Planck equation shows that in the birhythmic region, the two attractors are characterized by very different probabilities of finding the system in such a state. The probability becomes comparable only for a narrow range of the control parameters, thus the two limit cycles have properties in close analogy with the thermodynamic phases.
Faster than expected escape for a class of fully chaotic maps
Authors: Georgiou Orestis , Dettmann Carl P. , Altmann Eduardo G.
Published: November 2012

We investigate the dependence of the escape rate on the position of a hole placed in uniformly hyperbolic systems admitting a finite Markov partition. We derive an exact periodic orbit formula for finite size Markov holes which differs from other periodic expansions in the literature and can account for additional distortion to maps with piecewise constant expansion rate. Using asymptotic expansions in powers of hole size we show that for systems conjugate to the binary shift, the average escape rate is always larger than the expectation based on the hole size. Moreover, we show that in the small hole limit the difference between the two decays like a known constant times the square of the hole size. Finally, we relate this problem to the random choice of hole positions and we discuss possible extensions of our results to non-Markov holes as well as applications to leaky dynamical networks.
On well-posedness for a free boundary fluid-structure model
Authors: Ignatova Mihaela , Kukavica Igor , Lasiecka Irena , Tuffaha Amjad
Published: November 2012

We address a fluid-structure interaction model describing the motion of an elastic body immersed in an incompressible fluid. We establish a prioriestimates for the local existence of solutions for a class of initial data which also guarantees uniqueness.
Self-focusing of circularly polarized laser pulse in the hot magnetized plasma in the quasi-neutral limit
Authors: Sepehri Javan N. , Nasirzadeh Zh.
Published: November 2012

In this paper the problem of self-focusing of an intense laser beam in the hot magnetized plasma is studied. Using a relativistic two-fluid model, the propagation of intense circularly polarized laser beam along the external magnetic field is considered. The nonlinear equation describing the interaction of laser beam with magnetized hot plasma in the quasi-neutral approximation is derived. Expanding the nonlinear terms of current density and saving only the parabolic nonlinear terms, we investigated the self-focusing phenomenon for right- and left-hand circularly polarized laser beam. The evolution of laser beam spot size with Gaussian profile for both polarizations is considered and the effect of the temperature and external magnetic field on the self-focusing quality is studied. It is shown that for the right-hand polarization, the effect of temperature and external magnetic field on the self-focusing property is more considerable.
Effect of plasma resonances on dynamic characteristics of double graphene-layer optical modulator
Authors: Ryzhii V. , Otsuji T. , Ryzhii M. , Leiman V. G. , Yurchenko S. O. , Mitin V. , Shur M. S.
Published: November 2012

We analyze the dynamic operation of an optical modulator based on double graphene-layer (GL) structure utilizing the variation of the GL absorption due to the electrically controlled Pauli blocking effect. The developed device model yields the dependences of the modulation depth on the control voltage and the modulation frequency. The excitation of plasma oscillations in double-GL structure can result in the resonant increase of the modulation depth, when the modulation frequency approaches the plasma frequency, which corresponds to the terahertz frequency for the typical parameter values.
Bandwidth improvement of LiNbO3 ultrasonic transducers by half-concaved inversion layer approach
Authors: Chen J. , Dai J. Y. , Zhang C. , Zhang Z. T. , Feng G. P.
Published: November 2012

A novel type of half-concaved LiNbO3 plate with domain inversion layer has been proposed for fabricating high-frequency broadband ultrasonic transducers. Two opposite ferroelectric polarization layers with a curved boundary are presented after heat treatment in the half-concaved LiNbO3 plate with a total thickness of 110 μm. Characterization of the transducers illustrates that, without a matching layer, the self-focusing transducer with the half-concaved LiNbO3 plate has achieved 123% bandwidth at the center frequency of 60 MHz, which is a significant improvement over the planar inversion layer transducer.
The reflection of Rayleigh surface waves from single steps and grooves
Authors: Graczykowski B.
Published: November 2012

This paper presents the problem of Rayleigh surface waves which scatter over single surface inhomogeneities in the form of rectangular steps (downward or upward) or grooves. The reflection, transmission, and losses coefficients are calculated by means of the finite element method for waves propagating in isotopic silicon surface. The criterion of maximum value of reflection to losses (into the bulk) ratio is used to asses the optimal depth and width of the groove. The presented results are useful with regard to the Rayleigh surface waves reflectors in the optimization of periodic array of grooves.
Crystallography, magnetic, and magnetocaloric properties of Gd57.5Co20Al22.5 alloy
Authors: Fu H. , Wang M. X. , Zheng Q. , Luo D. B. , Teng B. H.
Published: November 2012

To understand the structure and magnetocaloric effect (MCE) of the crystallized Gd-Co-Al bulk metallic glasses, investigations were performed on the unknown phase of the crystallization product. As a result, the new ternary phases with composition of Gd57.5Co20Al22.5 have been found in the Gd-Co-Al alloy system. The as-cast alloy adopts the orthorhombic crystal system with the space group of Pbam. The alloy preserves the single phase structure during annealing but experiences structural phase transition to crystallize in a different structure. The as-cast alloy orders antiferromagnetically at 59 K and continuous field-induced metamagnetic transition can be observed. The annealed one orders ferromagnetically at 101 K. The magnetization measurements suggest that the antiferromagnetic and ferromagnetic interactions coexist in both the as-cast and the annealed samples and they have complex magnetic structure. MCE of the two samples are far lower than that of the Gd-Co-Al bulk metallic glasses.
Simultaneous measurement of the Seebeck coefficient and thermal conductivity in the cross-sectional direction of thermoelectric thick film
Authors: Jin Kim Sun , Hyung We Ju , Soo Kim Gyung , Jin Cho Byung
Published: November 2012

The measurement of the thermoelectric properties of thin film thermoelectric materials has been an issue due to the difficulty and inaccuracy. In this work, we present a new model to simultaneously extract the Seebeck coefficient and thermal conductivity in the cross-sectional direction of thin film thermoelectric material. The proposed method uses a sandwich structure composed of a metal electrode/TE film/metal electrode and measures the external Seebeck coefficient at two different intervals on the metal electrode. A theoretical model enables us to extract the Seebeck coefficient and thermal conductivity of the thermoelectric material from the two external Seebeck coefficient measurement values. The proposed method is applied to screen-printed ZnSb film with copper electrodes and the measurement results were found to lie in a reasonable range. Given that this method is simple to use, it will contribute to the development of thin film thermoelectric devices.
The relationship between two fast/slow analysis techniques for bursting oscillations
Authors: Teka Wondimu , Tabak Joël , Bertram Richard
Published: November 2012

Bursting oscillations in excitable systems reflect multi-timescale dynamics. These oscillations have often been studied in mathematical models by splitting the equations into fast and slow subsystems. Typically, one treats the slow variables as parameters of the fast subsystem and studies the bifurcation structure of this subsystem. This has key features such as a z-curve (stationary branch) and a Hopf bifurcation that gives rise to a branch of periodic spiking solutions. In models of bursting in pituitary cells, we have recently used a different approach that focuses on the dynamics of the slow subsystem. Characteristic features of this approach are folded node singularities and a critical manifold. In this article, we investigate the relationships between the key structures of the two analysis techniques. We find that the z-curve and Hopf bifurcation of the two-fast/one-slow decomposition are closely related to the voltage nullcline and folded node singularity of the one-fast/two-slow decomposition, respectively. They become identical in the double singular limit in which voltage is infinitely fast and calcium is infinitely slow.
Linear trap with three orthogonal quadrupole fields for dust charging experiments
Authors: Beránek Martin , Čermák Ivo , Němeček Zdeněk , Šafránková Jana , Jeřáb Martin , Pavlů Jiří
Published: November 2012

Investigations of charging processes on a single dust grain under controlled conditions in laboratory experiments are the unique way to understand the behavior of dust grains in complex plasma (in space, in laboratory, or in technological applications). An electrodynamic trap is often utilized for both holding a single grain and continuously measuring its charge-to-mass ratio. We propose a modified design of the linear quadrupole trap with the electrodes split into two parts; each of them being supplied by a designated source. The paper presents basic calculations and the results of the trap prototype tests. These tests have confirmed our expectations and have shown that the suggested solution is fully applicable for the dust charging experiments. The uncertainty of determination of the dust grain charge does not exceed 10−3. The main advantages of the suggested design in comparison with other traps used for dust investigations can be summarized as: The trap (i) is more opened, thus it is suitable for a simultaneous application of the ion and electron beams and UV source; (ii) facilitates investigations of dust grains in a broader range of parameters; and (iii) allows the grain to move along the axis in a controlled way.
Time-synchronized continuous wave laser-induced fluorescence on an oscillatory xenon discharge
Authors: MacDonald N. A. , Cappelli M. A. , Hargus W. A.
Published: November 2012

A novel approach to time-synchronizing laser-induced fluorescence measurements to an oscillating current in a 60 Hz xenon discharge lamp using a continuous wave laser is presented. A sample-hold circuit is implemented to separate out signals at different phases along a current cycle, and is followed by a lock-in amplifier to pull out the resulting time-synchronized fluorescence trace from the large background signal. The time evolution of lower state population is derived from the changes in intensity of the fluorescence excitation line shape resulting from laser-induced fluorescence measurements of the \documentclass[12pt]{minimal}\begin{document}$6s^{\prime }[1/2]_{1}^{0} - 6p^{\prime }[3/2]_{2}$\end{document}6s′[1/2]10−6p′[3/2]2 xenon atomic transition at λ = 834.68 nm. Results show that the lower state population oscillates at twice the frequency of the discharge current, 120 Hz.
Ferrule-top nanoindenter: An optomechanical fiber sensor for nanoindentation
Authors: Chavan D. , van de Watering T. C. , Gruca G. , Rector J. H. , Heeck K. , Slaman M. , Iannuzzi D.
Published: November 2012

Ferrule-top probes are self-aligned all-optical devices obtained by fabricating a cantilever on the top of a ferruled optical fiber. This approach has been proven to provide a new platform for the realization of small footprint atomic force microscopes (AFMs) that adapt well to utilization outside specialized laboratories [D. Chavan et al., Rev. Sci. Instrum. 81, 123702 (2010)10.1063/1.3516044; D. Chavan et al., Rev. Sci. Instrum. 82, 046107 (2011)10.1063/1.3579496]. In this paper we now show that ferrule-top cantilevers can be also used to develop nanoindenters. Our instrument combines the sensitivity of commercial AFM-based indentation with the ease-of-use of more macroscopic instrumented indenters available today on the market. Furthermore, the all-optical design allows smooth operations also in liquids, where other devices are much more limited and often provide data that are difficult to interpret. This study may pave the way to the implementation of a new generation user-friendly nanoindenters for the measurement of the stiffness of samples in material sciences and medical research.
Recover soft x-ray spectrum using virtual flat response channels with filtered x-ray diode array
Authors: Tianming Song , Jiamin Yang , Rongqing Yi
Published: November 2012

A method for the recovery of soft x-ray spectra in indirect-drive inertial confinement fusion experiments is presented. Virtual detection channels with bandpass responses are obtained using linear combinations of the channel response functions of a filtered x-ray diode array and a weighted correction is introduced to improve the recovery. These virtual channels can be used to calculate radiation fluxes in some specific photon energy bands and hence to recover the spectrum of the whole photon energy range from 80 eV to 4.5 keV. Examples are listed which demonstrate the capability of this method to unfold various spectra such as Planck spectra with different radiation temperatures and to obtain x-ray flux of certain narrow energy interval.
An asymptotically consistent approximant method with application to soft- and hard-sphere fluids
Authors: Barlow N. S. , Schultz A. J. , Weinstein S. J. , Kofke D. A.
Published: November 2012

A modified Padé approximant is used to construct an equation of state, which has the same large-density asymptotic behavior as the model fluid being described, while still retaining the low-density behavior of the virial equation of state (virial series). Within this framework, all sequences of rational functions that are analytic in the physical domain converge to the correct behavior at the same rate, eliminating the ambiguity of choosing the correct form of Padé approximant. The method is applied to fluids composed of “soft” spherical particles with separation distance r interacting through an inverse-power pair potential, ϕ = ε(σ/r)n, where ε and σ are model parameters and n is the “hardness” of the spheres. For n < 9, the approximants provide a significant improvement over the 8-term virial series, when compared against molecular simulation data. For n ⩾ 9, both the approximants and the 8-term virial series give an accurate description of the fluid behavior, when compared with simulation data. When taking the limit as n → ∞, an equation of state for hard spheres is obtained, which is closer to simulation data than the 10-term virial series for hard spheres, and is comparable in accuracy to other recently proposed equations of state. By applying a least square fit to the approximants, we obtain a general and accurate soft-sphere equation of state as a function of n, valid over the full range of density in the fluid phase.
In situ investigation of ion-induced dewetting of a thin iron-oxide film on silicon by high resolution scanning electron microscopy
Authors: Amirthapandian S. , Schuchart F. , Garmatter D. , Bolse W.
Published: November 2012

Using our new in situ high resolution scanning electron microscope, which is integrated into the UNILAC ion beamline at the Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt, Germany, we investigated the swift heavy ion induced dewetting of a thin iron oxide layer on Si. Besides heterogeneous hole nucleation at defects and spontaneous (homogeneous) hole nucleation, we could clearly identify a dewetting mechanism, which is similar to the spinodal dewetting observed for liquid films. Instead of being due to capillary waves, it is based on a stress induced surface instability. The latter results in the formation of a wavy surface with constant dominant wave-length and increasing amplitude during ion irradiation. Dewetting sets in as soon as the wave-troughs reach the film-substrate interface. Inspection of the hole radii and rim shapes indicates that removal of the material from the hole area occurs mainly by plastic deformation at the inner boundary and ion induced viscous flow in the peripheral zone due to surface tension.
Temperature dependence of large exchange-bias in TbFe-Co/Pt
Authors: Romer S. , Marioni M. A. , Thorwarth K. , Joshi N. R. , Corticelli C. E. , Hug H. J. , Oezer S. , Parlinska-Wojtan M. , Rohrmann H.
Published: November 2012

The exchange-bias effect provides unidirectional anisotropy to ferromagnetic thin-films in GMR and TMR sensors. It is weak because it relies on an inherently compensated coupling across a ferromagnet/antiferromagnet interface. We replace the antiferromagnet with a TbFe-based perpendicular-anisotropy amorphous ferrimagnet, coupling to an adjacent ferromagnet with 13-5 mJ/m2 for temperatures within 7.9–280 K. A large exchange-bias between 1.1 and 0.7 T in that temperature range ensues. The temperature dependence of the bias is step-like, and thus different from that of antiferromagnet-based exchange-bias systems. It suggests using this material in exchange-biased temperature assisted magnetic writing.
High intensity electron emission from ferroelectric cathode induced by a pyroelectric crystal
Authors: Hockley M. , Huang Z.
Published: November 2012

A high voltage pulse generated by changing the temperature of a pyroelectric crystal was used to trigger a strong ferroelectric electron emission from a ferroelectric cathode. Different configurations such as a positive or negative pulse being applied to the front or back of the ferroelectric cathode were investigated. Negative pulse applied to the front of the cathode was found to generate the largest emission current and total charges. These differences in emission properties are interpreted using the mechanism of surface plasma assisted electron emission.
Note: An asymmetric flexure mechanism for comb-drive actuators
Authors: Olfatnia M. , Sood S. , Awtar S.
Published: November 2012

This Note presents a new asymmetric flexure design, the double parallelogram–tilted-beam double parallelogram (DP-TDP) flexure, that enables two times higher stroke in electrostatic comb-drive actuators, compared to the traditional symmetrically paired double parallelogram (DP-DP) flexure, while maintaining the same device footprint. Because of its unique kinematic configuration, the DP-TDP flexure provides an improved stiffness ratio between the bearing and actuation directions, thus delaying the on-set of sideways instability. Experimental testing of micro-fabricated comb-drive actuators with flexure beam length 1 mm and comb gap 5 μm demonstrates a stroke of 149 μm (at 86 V) for the proposed DP-TDP flexure, in comparison to 75 μm (at 45 V) for the traditional DP-DP flexure.
The N-leap method for stochastic simulation of coupled chemical reactions
Authors: Xu Yuting , Lan Yueheng
Published: November 2012

Numerical simulation of the time evolution of a spatially homogeneous chemical system is always of great interest. Gillespie first developed the exact stochastic simulation algorithm (SSA), which is accurate but time-consuming. Recently, many approximate schemes of the SSA are proposed to speed up simulation. Presented here is the N-leap method, which guarantees the validity of the leap condition and at the same time keeps the efficiency. In many cases, N-leap has better performance than the widely-used τ-leap method. The details of the N-leap method are described and several examples are presented to show its validity.
Well and ill-posedness for compressible Euler equations with vacuum
Authors: Jang Juhi , Masmoudi Nader
Published: November 2012

An interesting problem arising in gas and fluid dynamics is to understand the behavior of vacuum states, namely, the behavior of the system in the presence of vacuum. In this paper, we review and expand some local-in-time well-posedness results for one-dimensional compressible Euler equations for polytropic gases with a range of behaviors at the interface including the physical vacuum case. We also present some sort of ill-posedness results in some other cases. Finally, we present some conjectures about the change of behavior at the interface. This paper is a mixture of rigorous and formal calculations.
Tracking all-vapor instant gas-hydrate formation and guest molecule populations: A possible probe for molecules trapped in water nanodroplets
Authors: Uras-Aytemiz Nevin , Cwiklik Lukasz , Paul Devlin J.
Published: November 2012

Quantitative Fourier-transform infrared spectra for low-temperature (160–200 K) aerosols of clathrate-hydrate nanoparticles that contain large-cage catalysts and small-cage nonpolar guests have been extended to a broad range of vapor compositions and sampling conditions. The data better reveal the stages by which room-temperature vapor mixtures, when cooled below ∼220 K, instantly generate aerosols with particles composed exclusively of the corresponding clathrate hydrates. In particular the quantitative data help relate the nature of the hydrates that form to the composition of the aqueous nanodroplets of the first stages of the rapid transition from the all-vapor mixture. The overall transition from an all-vapor mixture to “gas”-hydrate nanocrystals is a multistage one that has been characterized as homogeneous nucleation and growth of solution nanodroplets (∼240 K) followed by nucleation and growth of the gas-hydrate particles (∼220 K); all occurring within a subsecond that follows pulsing of the warm vapor into a sampling cold chamber. This may serve well as a general description of the instantaneous generation of the gas-hydrate aerosols, but closer consideration of the nature of the sampling method, in context with recent computation-based insights to (a) gas-hydrate nucleation stages/rates and (b) the lifetimes of trapped small nonpolar molecules in cold aqueous nanodroplets, suggests a more complex multistage transition. The simulated lifetimes and extensive new quantitative infrared data significantly broaden the knowledge base in which the instantaneous transition from vapor to crystalline hydrate particles is viewed. The apparent need for a high occupancy of large-cage catalytic guest molecules currently limits the practical value of the all-vapor method. Only through greater clarity in the molecular-level description of the transition will the ultimate limits be defined.
Spinodal decomposition of a confined colloid-polymer system
Authors: Jamie E. A. G. , Dullens R. P. A. , Aarts D. G. A. L.
Published: November 2012

We study the demixing via spinodal decomposition of a fluid-fluid phase separating colloid-polymer mixture confined between parallel plates, where one of the phases completely wets both walls. Using confocal scanning laser microscopy, we are able to obtain real space images, both parallel and perpendicular to the cell walls. We observe three distinct morphologies: the formation of a bicontinuous network, which coarsens into cylindrical tubes bridging the plates, and finally develops into a network structure in two dimensions. Through image analysis of the system as a whole, and the tracking of individual domains, we are able to perform a detailed study of the mechanisms of phase coarsening at each stage. We are able to directly test the condition for which bridges connecting both confining walls do not sever. Finally, we consider the role of hydrodynamics and of thermal interface fluctuations in our system.
Development of Monte Carlo configuration interaction: Natural orbitals and second-order perturbation theory
Authors: Coe J. P. , Paterson M. J.
Published: November 2012

Approximate natural orbitals are investigated as a way to improve a Monte Carlo configuration interaction (MCCI) calculation. We introduce a way to approximate the natural orbitals in MCCI and test these and approximate natural orbitals from Møller-Plesset perturbation theory and quadratic configuration interaction with single and double substitutions in MCCI calculations of single-point energies. The efficiency and accuracy of approximate natural orbitals in MCCI potential curve calculations for the double hydrogen dissociation of water, the dissociation of carbon monoxide, and the dissociation of the nitrogen molecule are then considered in comparison with standard MCCI when using full configuration interaction as a benchmark. We also use the method to produce a potential curve for water in an aug-cc-pVTZ basis. A new way to quantify the accuracy of a potential curve is put forward that takes into account all of the points and that the curve can be shifted by a constant. We adapt a second-order perturbation scheme to work with MCCI (MCCIPT2) and improve the efficiency of the removal of duplicate states in the method. MCCIPT2 is tested in the calculation of a potential curve for the dissociation of nitrogen using both Slater determinants and configuration state functions.
Hydration structure in concentrated aqueous lithium chloride solutions: A reverse Monte Carlo based combination of molecular dynamics simulations and diffraction data
Authors: Harsányi I. , Pusztai L.
Published: November 2012

We report on a comparison of three interaction potential models of water (SPC/E, TIP4P-2005, and SWM4-DP) for describing the structure of concentrated aqueous lithium chloride solutions. Classical molecular dynamics simulations have been carried out and total scattering structure factors, calculated from the particle configurations, were compared with experimental diffraction data. Later, reverse Monte Carlo structural modelling was applied for refining molecular dynamics results, so that particle configurations consistent with neutron and X-ray diffraction data could be prepared that, at the same time, were as close as possible to the final stage of the molecular dynamics simulations. Partial radial distribution functions, first neighbors, and angular correlations were analysed further from the best fitting particle configurations. It was found that none of the water potential models describe the structure perfectly; overall, the SWM4-DP model seems to be the most promising. At the highest concentrations the SPC/E model appears to provide the best approximation of the water structure, whereas the TIP4P-2005 model proved to be the most successful for estimating the lithium-oxygen partial radial distribution function at each concentration.
An efficient solution of Liouville-von Neumann equation that is applicable to zero and finite temperatures
Authors: Tian Heng , Chen GuanHua
Published: November 2012

Application of quantum dissipation theory to electronic dynamics has been limited to model systems with few energy levels, and its numerical solutions are mostly restricted to high temperatures. A highly accurate and efficient numerical algorithm, which is based on the Chebyshev spectral method, is developed to integrate a single-particle Liouville-von Neumann equation, and the two long-standing limitations of quantum dissipation theory are resolved in the context of quantum transport. Its computational time scales to \documentclass[12pt]{minimal}\begin{document}$\mathcal {O}(N^{3})$\end{document}O(N3) with N being the number of orbitals involved, which leads to a reality for the quantum mechanical simulation of real open systems containing hundreds or thousands of atomic orbitals. More importantly, the algorithm spans both finite and zero temperatures. Numerical calculations are carried out to simulate the transient current through a metallic wire containing up to 1000 orbitals.
Influence of buoyancy-driven flow on mass transfer in a two-stream microfluidic channel: Introduction of cryoprotective agents into cell suspensions
Authors: Bala Chandran Rohini , Reinhart Jennifer , Lemke Erin , Hubel Allison
Published: November 2012

A variety of methods have been used to introduce chemicals into a stream or to mix two or more streams of different compositions using microfluidic devices. In the following paper, the introduction of cryoprotective agents (CPAs) used during cryopreservation of cells in order to protect them from freezing injuries and increase viability post thaw is described. Dimethylsulphoxide (DMSO) is the most commonly used CPA. We aim to optimize the operating conditions of a two-stream microfluidic device to introduce a 10% vol/vol solution of DMSO into a cell suspension. Transport behavior of DMSO between two streams in the device has been experimentally characterized for a spectrum of flow conditions (0.7 < Re < 10), varying initial donor stream concentrations, (1% vol/vol < Co < 15% vol/vol) and different flow rate fractions (0.23 < fq < 0.77). The outlet cell stream concentration is analyzed for two different flow configurations: one with the cell stream flowing on top of the DMSO-rich donor stream, and the other with the cell stream flowing beneath the heavy DMSO-laden stream. We establish a transition from a diffusive mode of mass transfer to gravity-influenced convective currents for Atwood numbers (At) in the range of (1.7 × 10−3 < At < 3.1 × 10−3) for the latter configuration. Flow visualization with cells further our understanding of the effect of At on the nature of mass transport. Cell motion studies performed with Jurkat cells confirm a high cell recovery from the device while underscoring the need to collect both the streams at the outlet of the device and suggesting flow conditions that will help us achieve the target DMSO outlet concentration for clinical scale flow rates of the cell suspension.