bluuebunny/crossref_metadata_2025 huggingface dataset:
Histamine infused into basolateral amygdala enhances memory consolidation of inhibitory avoidance
Authors: Benetti Fernando , Izquierdo Ivan
Published: January 2013

The role of the basolateral amygdala (BLA) in the consolidation of aversive memory is well established. Here we investigate the involvement of the histaminergic system in BLA on this variable. Rats were chronically implanted with bilateral cannulae in the BLA and after recovery were trained in a one-trial step-down inhibitory avoidance task. Immediately after training histaminergic compounds either alone or in combination were infused through the cannulae. Memory was assessed in test sessions carried out 24 h after the training session. Post-training histamine (1–10 nmol; 0.5 µl/side) enhanced consolidation and the histamine H3 receptor antagonist thioperamide (50 nmol; 0.5 µl/side) impaired memory consolidation. The effect was shared by the histamine N-methyltransferase inhibitor SKF-91844 (50 nmol; 0.5 µl/side) as well as by the H3 receptor agonist imetit (10 nmol; 0.5 µl/side). The promnesic action of histamine was unaffected by the H1 receptor antagonist pyrilamine (50 nmol; 0.5 µl/side). The H1 receptor agonist pyridylethylamine (10 nmol; 0.5 µl/side), the H2 agonist dimaprit (10 nmol; 0.5 µl/side) and the H2 antagonist ranitidine (50 nmol; 0.5 µl/side) were ineffective. Histaminergic compounds infused into the BLA had no effect on open-field or elevated plus-maze behaviour. The data show that histamine induces a dose-dependent mnemonic effect in rats and indicate that this reflects a role of endogenous histamine in the BLA mediated by H3 receptors.
Critical agrarianism
Authors: Carlisle Liz
Published: January 2013

This paper develops the concept of ‘critical agrarianism’ to describe and advance the pursuit of land-based work as a means of realizing social justice and environmental sustainability. Encouraging new agrarianism to more carefully scrutinize its agenda, critical agrarianism celebrates the promise of a close working relationship with the natural world while insisting that a return to the land—per se—is insufficient. In the practice of linking people and land, past and present, critical agrarianism continually questions and reshapes the very category of agrarian, toward a more equitable and enduring prosperity. I revisit both canonical agrarian writing and its critics, pulling out ‘back-pocket tools’ that can keep critical agrarians on track in building our alternative futures. I then offer several case studies of critical agrarianism in practice, encouraging a move beyond idealized models of agrarian ties, toward an empirical account of who has actually been doing the work to put food on the table. Noting the historical gap between working the landscape and having a property or citizenship right, I call for an agrarianism in which practices—not land title—are the basis of material and social community. Furthermore, I suggest that agrarianism must extend its web outward rather than inward, forging connections to the work of land tenure reform, education, community development, immigrant advocacy and trade policy. To be a critical agrarian is not to preserve fixed social-natural ties, but rather to practice a powerfully open and dialogical engagement with the world and one another.
Evolution and control of H5N1
Authors: Watanabe Yohei , Ibrahim Madiha S , Ikuta Kazuyoshi
Published: January 2013

The evolutionary dynamics of the H5N1 virus present a challenge for conventional control measures. Efforts must consider the regional aspects of endemic H5N1.
On twistors and conformal field theories from six dimensions
Authors: Sämann Christian , Wolf Martin
Published: January 2013

We discuss chiral zero-rest-mass field equations on six-dimensional space-time from a twistorial point of view. Specifically, we present a detailed cohomological analysis, develop both Penrose and Penrose–Ward transforms, and analyse the corresponding contour integral formulæ. We also give twistor space action principles. We then dimensionally reduce the twistor space of six-dimensional space-time to obtain twistor formulations of various theories in lower dimensions. Besides well-known twistor spaces, we also find a novel twistor space amongst these reductions, which turns out to be suitable for a twistorial description of self-dual strings. For these reduced twistor spaces, we explain the Penrose and Penrose–Ward transforms as well as contour integral formulæ.
Doping incorporation paths in catalyst-free Be-doped GaAs nanowires
Authors: Casadei Alberto , Krogstrup Peter , Heiss Martin , Röhr Jason A. , Colombo Carlo , Ruelle Thibaud , Upadhyay Shivendra , Sørensen Claus B. , Nygård Jesper , Fontcuberta i Morral Anna
Published: January 2013

The incorporation paths of Be in GaAs nanowires grown by the Ga-assisted method in molecular beam epitaxy have been investigated by electrical measurements of nanowires with different doping profiles. We find that Be atoms incorporate preferentially via the nanowire side facets, while the incorporation path through the Ga droplet is negligible. We also show that Be can diffuse into the volume of the nanowire giving an alternative incorporation path. This work is an important step towards controlled doping of nanowires and will serve as a help for designing future devices based on nanowires.
Translational diffusion in paramagnetic liquids by 1H NMR relaxometry: Nitroxide radicals in solution
Authors: Kruk D. , Korpała A. , Kubica A. , Meier R. , Rössler E. A. , Moscicki J.
Published: January 2013

For nitroxide radicals in solution one can identify three frequency regimes in which 1H spin-lattice relaxation rate of solvent molecules depend linearly on square root of the 1H resonance frequency. Combining a recently developed theory of nuclear (proton) spin-lattice relaxation in solutions of nitroxide radicals [D. Kruk et al., J. Chem. Phys. 137, 044512 (2012)]10.1063/1.4736854 with properties of the spectral density function associated with translational dynamics, relationships between the corresponding linear changes of the relaxation rate (for 14N spin probes) and relative translational diffusion coefficient of the solvent and solute molecules have been derived (in analogy to 15N spin probes [E. Belorizky et al., J. Phys. Chem. A 102, 3674 (1998)]10.1021/jp980397h). This method allows a simple and straightforward determination of diffusion coefficients in spin-labeled systems, by means of 1H nuclear magnetic resonance (NMR) relaxometry. The approach has thoroughly been tested by applying to a large set of experimental data—1H spin-lattice relaxation dispersion results for solutions of different viscosity (decalin, glycerol, propylene glycol) of 14N and 15N spin probes. The experiments have been performed versus temperature (to cover a broad range of translational diffusion coefficients) using field cycling spectrometer which covers three decades in 1H resonance frequency, 10 kHz–20 MHz. The limitations of NMR relaxometry caused by the time scale of the translational dynamics as well as electron spin relaxation have been discussed. It has been shown that for spin-labeled systems NMR relaxometry gives access to considerably faster diffusion processes than for diamagnetic systems.
Force fields for divalent cations based on single-ion and ion-pair properties
Authors: Mamatkulov Shavkat , Fyta Maria , Netz Roland R.
Published: January 2013

We develop force field parameters for the divalent cations Mg2+, Ca2+, Sr2+, and Ba2+ for molecular dynamics simulations with the simple point charge-extended (SPC/E) water model. We follow an approach introduced recently for the optimization of monovalent ions, based on the simultaneous optimization of single-ion and ion-pair properties. We consider the solvation free energy of the divalent cations as the relevant single-ion property. As a probe for ion-pair properties we compute the activity derivatives of the salt solutions. The optimization of the ionic force fields is done in two consecutive steps. First, the cation solvation free energy is determined as a function of the Lennard-Jones (LJ) parameters. The peak in the ion-water radial distribution function (RDF) is used as a check of the structural properties of the ions. Second, the activity derivatives of the electrolytes MgY2, CaY2, BaY2, SrY2 are determined through Kirkwood-Buff solution theory, where Y = Cl−, Br−, I−. The activity derivatives are determined for the restricted set of LJ parameters which reproduce the exact solvation free energy of the divalent cations. The optimal ion parameters are those that match the experimental activity data and therefore simultaneously reproduce single-ion and ion-pair thermodynamic properties. For Ca2+, Ba2+, and Sr2+ such LJ parameters exist. On the other hand, for Mg2+ the experimental activity derivatives can only be reproduced if we generalize the combination rule for the anion-cation LJ interaction and rescale the effective cation-anion LJ radius, which is a modification that leaves the cation solvation free energy invariant. The divalent cation force fields are transferable within acceptable accuracy, meaning the same cation force field is valid for all halide ions Cl−, Br−, I− tested in this study.
On asymptotic completeness of scattering in the nonlinear Lamb system, II
Authors: Komech A. I. , Merzon A. E.
Published: January 2013

We establish the asymptotic completeness in the nonlinear Lamb system for hyperbolic stationary states. For the proof we construct a trajectory of a reduced equation (which is a nonlinear nonautonomous ordinary differential equation) converging to a hyperbolic stationary point using the inverse function theorem in a Banach space. We give counterexamples which show nonexistence of such trajectories for nonhyperbolic stationary points.
Selective homopolymer adsorption on structured surfaces as a model for pattern recognition
Authors: Gemünden Patrick , Behringer Hans
Published: January 2013

Homopolymer adsorption onto chemically structured periodic surfaces and its potential for pattern recognition is investigated using Monte Carlo simulations. To analyze the surface-induced selective adsorption on a fundamental geometric level polymer chains are represented by freely jointed chains with a fixed bond length whose monomers are attracted by the sites of regular lattice patterns. The structural properties of the adsorbed low-temperature state are comprehensively discussed for different lattices by looking at the radius of gyration and the inter bond angle distributions. These observables show a non-trivial dependence on the commensurability of characteristic lengths given by the lattice constant and by the bond length. Reasons for this behavior are given by exploiting geometric and entropic arguments. The findings are examined in the context of pattern recognition by polymer adsorption. Furthermore, the adsorption transition is discussed briefly. For certain incommensurable situations the adsorption occurs in two steps due to entropic restrictions.
Optical properties of fully and partially fluorinated rubrene in films and solution
Authors: Anger F. , Scholz R. , Adamski E. , Broch K. , Gerlach A. , Sakamoto Y. , Suzuki T. , Schreiber F.
Published: January 2013

We present the optical properties of fully (C42F28, PF-RUB) and half-fluorinated (C42F14H14, F14-RUB) rubrene, both in thin films and as monomers in solution and compare them to hydrogenated rubrene (C42H28, RUB). All three compounds show similar optical absorption bands and photoluminescence line shapes. The results are interpreted with density functional calculations of the orbital energies and time-dependent density functional theory for the HOMO-LUMO transition. Red shifts induced by the surrounding solvent or organic thin films remain much smaller than for polyacenes, in keeping with previous observations for rubrene and existing models for the solvatochromic shifts.
Correlation effects in the optical spectra of porphyrin oligomer chains: Exciton confinement and length dependence
Authors: Hogan Conor , Palummo Maurizia , Gierschner Johannes , Rubio Angel
Published: January 2013

Excited states of ethylene-linked free-base porphyrin oligomers and polymer are studied using many-body perturbation theory (MBPT) within the GW approximation and the Bethe-Salpeter equation. Trends in the electronic levels with oligomer length are analysed and the correct long-range behaviour in the band gap is obtained. High polarizabilities and strong redshifts in the optical absorption peaks are predicted in agreement with observations on other strongly conjugated oligoporphyrins. We explain these trends by means of spatial and spectral analyses of the exciton character. Although Wannier-Mott and charge-transfer excitons are identified in the optical spectra, the strongest polarizabilities are actually associated with small, tightly bound excitons (Frenkel-like), in contrast to expectations. Furthermore, the common procedure of extrapolating polymer properties from oligomer calculations is examined from a MBPT perspective.
Asymptotically minimal uncertainty states for time-dependent oscillators
Authors: Punoševac Predrag , Robinson Sam L.
Published: January 2013

We consider the time-dependent Schrödinger equation in one spatial dimension with a time-dependent quadratic Hamiltonian and, under appropriate assumptions on the coefficient functions in the Hamiltonian, construct solutions that approach minimal uncertainty states for large times.
Dynamics of micro-bubble sonication inside a phantom vessel
Authors: Qamar Adnan , Samtaney Ravi , Bull Joseph L.
Published: January 2013

A model for sonicated micro-bubble oscillations inside a phantom vessel is proposed. The model is not a variant of conventional Rayleigh-Plesset equation and is obtained from reduced Navier-Stokes equations. The model relates the micro-bubble oscillation dynamics with geometric and acoustic parameters in a consistent manner. It predicts micro-bubble oscillation dynamics as well as micro-bubble fragmentation when compared to the experimental data. For large micro-bubble radius to vessel diameter ratios, predictions are damped, suggesting breakdown of inherent modeling assumptions for these cases. Micro-bubble response with acoustic parameters is consistent with experiments and provides physical insight to the micro-bubble oscillation dynamics.
Dynamics of exploding plasmas in a large magnetized plasma
Authors: Niemann C. , Gekelman W. , Constantin C. G. , Everson E. T. , Schaeffer D. B. , Clark S. E. , Winske D. , Zylstra A. B. , Pribyl P. , Tripathi S. K. P. , Larson D. , Glenzer S. H. , Bondarenko A. S.
Published: January 2013

The dynamics of an exploding laser-produced plasma in a large ambient magneto-plasma was investigated with magnetic flux probes and Langmuir probes. Debris-ions expanding at super-Alfvénic velocity (up to MA=1.5) expel the ambient magnetic field, creating a large (>20 cm) diamagnetic cavity. We observe a field compression of up to B/B0=1.5 as well as localized electron heating at the edge of the bubble. Two-dimensional hybrid simulations reproduce these measurements well and show that the majority of the ambient ions are energized by the magnetic piston and swept outside the bubble volume. Nonlinear shear-Alfvén waves (δB/B0>25%) are radiated from the cavity with a coupling efficiency of 70% from magnetic energy in the bubble to the wave.
Spin-dependent transport through a quantum wire on a graphene surface
Authors: Yang Fu-Bin , Cheng Yan , Liu Fu-Ti , Chen Xiang-Rong
Published: January 2013

Electron transport through a quantum wire coupled with ferromagnetic leads on a graphene sheet is studied by the Keldysh nonequilibrium Green's function method. We investigate the dependence of the transport properties on the wire-graphene coupling strength in detail. It is found that the peaks of the density of states fade away and the current is suppressed with the increasing wire–graphene coupling strength. The spin polarized strength of the two leads can effectively suppress the current and the transmission. The results obtained provide valuable theoretical guidance to the spintronics experiment.
Sound attenuation using microelectromechanical systems fabricated acoustic metamaterials
Authors: Yunker William N. , Stevens Colin B. , Flowers George T. , Dean Robert N.
Published: January 2013

Unlike traditional rotational gyroscopes, microelectromechanical systems (MEMS) gyroscopes use a vibrating proof mass rather than a rotational mass to sense changes in angular rate. They are also smaller and less expensive than traditional gyroscopes. MEMS gyroscopes are known to be susceptible to the effects of acoustic noise, in particular high frequency and high power acoustic noise. Most notably, this has been proven true in aerospace applications where the noise can reach levels in excess of 120 dB and the noise frequency can exceed 20 kHz. The typical resonant frequency for the proof mass of a MEMS gyroscope is between 3 and 20 kHz. High power, high frequency acoustic noise can disrupt the output signal of the gyroscope to the point that the output becomes unreliable. In recent years, considerable research has focused on the fascinating properties found in metamaterials. A metamaterial is an artificially fabricated device or structure that is engineered to produce desired material responses that can either mimic known behaviors or produce responses that do not occur naturally in materials found in nature. Acoustic metamaterials, in particular, have shown great promise in the field of sound attenuation. This paper proposes a method to mitigate the performance degradation of the MEMS gyroscope in the presence of high power, high frequency acoustic noise by using a new acoustic metamaterial in the form of a two-dimensional array of micromachined Helmholtz resonators. The Helmholtz resonators are fabricated in a silicon wafer using standard MEMS manufacturing techniques and are designed to attenuate sound at the resonant frequency of the gyroscope proof mass. The resonator arrays were diced from the silicon wafer in one inch squares and assembled into a box open on one end in a manner to attenuate sound on all sides of the gyroscope, and to seal the gyroscope inside the box. The resulting acoustic metamaterial device was evaluated in an acoustic chamber and was found to successfully attenuate sound as much as 18 dB. This attenuation is in the form of a notch filter at and around 14.5 kHz, which was the target frequency of attenuation. The notch filter attenuation occurred over a 700 Hz frequency band with 18 dB being the largest attenuation in the band.
The equation of state of flexible chains of tangent hard spheres at high-density region from simulation and thermodynamic perturbation theory
Authors: Alavi Farzad , Feyzi Farzaneh
Published: January 2013

Radial and triplet correlation functions of the reference hard sphere system are determined at several solid densities by canonical Monte Carlo (MC) simulations. These customized data are used to extend the second order thermodynamic perturbation theory (TPT) to the solid phase of flexible hard chain systems. In order to test the accuracy of the TPT equation of state (EOS) for hard chains, MC simulations are carried out for systems of chain length 4 to 15. Several simulations are performed in the isobaric-isothermal ensemble to obtain the high-density EOS of hard chains in the fluid and solid phases. To determine solid-fluid equilibrium (SFE), Helmholtz free energies of solid crystals at a reference density are determined in a series of canonical MC simulations. As the chain length increases, asymptotic behaviors are observed in the coexistence pressure and densities of fluid and solid phases. It is found that the accuracy of TPT for EOS and SFE in systems of hard chains greatly improves by extending it to second order.
Implementation of quantum logic gates using polar molecules in pendular states
Authors: Zhu Jing , Kais Sabre , Wei Qi , Herschbach Dudley , Friedrich Bretislav
Published: January 2013

We present a systematic approach to implementation of basic quantum logic gates operating on polar molecules in pendular states as qubits for a quantum computer. A static electric field prevents quenching of the dipole moments by rotation, thereby creating the pendular states; also, the field gradient enables distinguishing among qubit sites. Multi-target optimal control theory is used as a means of optimizing the initial-to-target transition probability via a laser field. We give detailed calculations for the SrO molecule, a favorite candidate for proposed quantum computers. Our simulation results indicate that NOT, Hadamard and CNOT gates can be realized with high fidelity, as high as 0.985, for such pendular qubit states.
Chirped fiber Bragg grating detonation velocity sensing
Authors: Rodriguez G. , Sandberg R. L. , McCulloch Q. , Jackson S. I. , Vincent S. W. , Udd E.
Published: January 2013

An all optical-fiber-based approach to measuring high explosive detonation front position and velocity is described. By measuring total light return using an incoherent light source reflected from a linearly chirped fiber Bragg grating sensor in contact with the explosive, dynamic mapping of the detonation front position and velocity versus time is obtained. We demonstrate two calibration procedures and provide several examples of detonation front measurements: PBX 9502 cylindrical rate stick, radial detonation front in PBX 9501, and PBX 9501 detonation along curved meridian line. In the cylindrical rate stick measurement, excellent agreement with complementary diagnostics (electrical pins and streak camera imaging) is achieved, demonstrating accuracy in the detonation front velocity to below the 0.3% level when compared to the results from the pin data. Finally, an estimate on the linear spatial and temporal resolution of the system shows that sub-mm and sub-μs levels are attainable with proper consideration of the recording speed, detection sensitivity, spectrum, and chirp properties of the grating.
An experimental study on SrB4O7:Sm2+ as a pressure sensor
Authors: Jing Qiumin , Wu Qiang , Liu Lei , Xu Ji-an , Bi Yan , Liu Yonggang , Chen Haihua , Liu Shenggang , Zhang Yi , Xiong Lun , Li Yanchun , Liu Jing
Published: January 2013

A pressure sensor of SrB4O7:Sm2+ has been synthesized and the pressure shift of its 7D0-5F0 fluorescence line has been recalibrated at room temperature up to 48 GPa and 127 GPa hydrostatically and non-hydrostatically, respectively. Different from previous study, our results show that the calibrated relation in the quasi-hydrostatic pressure environment is quite different from that in the non-hydrostatic pressure environment. The yield strength of SrB4O7:Sm2+ as a function of the pressure has been determined by the pressure gradient method in a diamond anvil cell. The results show that the yield strength of SrB4O7:Sm2+ increases from 2.85 GPa at a pressure of 7.9 GPa to 4.22 GPa at 25.4 GPa and is much smaller than that of ruby. The relatively small high-pressure yield strength of SrB4O7:Sm2+ is at the same level of the most sample materials. This would result in a small pressure difference with the coexisting sample, thus lead to a small error in the pressure measurement. The smaller yield strength and excellent fluorescent spectral characters of SrB4O7:Sm2+ make it a good substitute for ruby as a pressure scale in high-pressure experiments, especially under non-hydrostatic pressure environments.
Ferroelectric ceramic tunability in transversely oriented static and transient electric fields
Authors: Semikin D. A. , Tagantsev A. K. , Kanareykin A. D.
Published: January 2013

The dielectric tunability of ferroelectric ceramics in the paraelectric phase is studied theoretically for the case where the dc bias electric field is orthogonal to the ac electric field of a signal. Results are obtained in the most general form and then applied to a treatment of Landau-Ginzburg-Devonshire-based models. Relationships are derived between the “transverse” (dc electric field is normal to the ac electric field) and “longitudinal” (dc and ac electric fields are parallel) tunabilities. The relevant available experimental data are discussed in the context of these results.
Rapid reversible electromigration of intercalated K ions within individual MoO3 nanobundle
Authors: Hu Zhibin , Zhou Chenggang , Ramanujam Prabhakar Rajiv , Xiaodai Lim Sharon , Wang Yinghui , van Kan Jeroen A. , Cheng Hansong , Mhaisalkar Subodh G. , Sow Chorng-Haur
Published: January 2013

Rapid and reversible electromigration of intercalated K ions within an individual layered single crystalline KxMoO3 nanobundle is observed. When an electric current was applied to a KxMoO3 nanobundle, the K ions migrated readily and rapidly in the flowing direction of electrons within the nanobundle and accumulated near an electrode. Upon reversal of the applied current, the accumulated K ions near one electrode were driven back and gathered near the opposite electrode. This observation is attributed to the unique structure of KxMoO3 where K ions occupy O vacancies in the nanobundle and the location of K ions is exactly the channel of high current density within the nanobundle. The duration required to induce significant accumulation of K ions and relaxation time of accumulated ions were significantly shorter than the value reported in other interstitial systems. The reversible ion movement was repeated for hundred times and remarkably there were no obvious sign of structural damage in the nanobundle.
Split-gate quantum point contacts with tunable channel length
Authors: Iqbal M. J. , de. Jong J. P. , Reuter D. , Wieck A. D. , van der Wal C. H.
Published: January 2013

We report on developing split-gate quantum point contacts (QPCs) that have a tunable length for the transport channel. The QPCs were realized in a GaAs/AlGaAs heterostructure with a two-dimensional electron gas (2DEG) below its surface. The conventional design uses 2 gate fingers on the wafer surface which deplete the 2DEG underneath when a negative gate voltage is applied, and this allows for tuning the width of the QPC channel. Our design has 6 gate fingers and this provides additional control over the form of the electrostatic potential that defines the channel. Our study is based on electrostatic simulations and experiments and the results show that we developed QPCs where the effective channel length can be tuned from about 200 nm to 600 nm. Length-tunable QPCs are important for studies of electron many-body effects because these phenomena show a nanoscale dependence on the dimensions of the QPC channel.
A composite-metamaterial-based terahertz-wave polarization rotator with an ultrathin thickness, an excellent conversion ratio, and enhanced transmission
Authors: Chiang Yi-Ju , Yen Ta-Jen
Published: January 2013

We integrated the polarization convertibility of asymmetric split-ring resonators with the polarization selectivity of S-shape resonators for realizing a composite-metamaterial-based 90-degree ultrathin polarization rotator (UTPR) with a 50.4-μm thickness in the terahertz-gap region. By introducing the Fabry-Perot resonance into the UTPR, the measured transmission is maximized to 0.48 at 1.04 THz, leading to the polarization-conversion ratio up to 97.7%. Compared to other waveplates composed by pile-stacking birefringent metamaterials, the UTPR possesses less loss from the intrinsic resonances because it comprises only two layers of the resonators, and can evade from dichroism effects due to the unique working mechanism.
Effects of lateral overgrowth on residual strain and In incorporation in a-plane InGaN/GaN quantum wells on r-sapphire substrates
Authors: Hong Moon-Taek , Kim Tae-Soo , Park Ki-Nam , Jung Sukkoo , Chang Younghak , Bang Gyu-Hyun , Kim Hyung-Gu , Jeon Jina , Choi Yoon-Ho , Hwang Sung-Min , Song Jung-Hoon
Published: January 2013

We investigated the effects of the patterned lateral over-growth on the residual strain in GaN templates and In incorporation in a-plane InGaN/GaN quantum wells grown on a r-sapphire substrate, by utilizing micro-photoluminescence and Raman scattering spectroscopy. Strong enhancement of emission intensity is observed from the wing area. We report a reduction in the residual strain and different In incorporation in the wing area. The InGaN quantum wells on the merged area have higher In composition with smaller residual strain of the GaN layers underneath.
Probing the mechanical properties of brain cancer cells using a microfluidic cell squeezer device
Authors: Khan Z. S. , Vanapalli S. A.
Published: January 2013

Despite being invasive within surrounding brain tissues and the central nervous system, little is known about the mechanical properties of brain tumor cells in comparison with benign cells. Here, we present the first measurements of the peak pressure drop due to the passage of benign and cancerous brain cells through confined microchannels in a “microfluidic cell squeezer” device, as well as the elongation, speed, and entry time of the cells in confined channels. We find that cancerous and benign brain cells cannot be differentiated based on speeds or elongation. We have found that the entry time into a narrow constriction is a more sensitive indicator of the differences between malignant and healthy glial cells than pressure drops. Importantly, we also find that brain tumor cells take a longer time to squeeze through a constriction and migrate more slowly than benign cells in two dimensional wound healing assays. Based on these observations, we arrive at the surprising conclusion that the prevailing notion of extraneural cancer cells being more mechanically compliant than benign cells may not apply to brain cancer cells.
Residual turbulence from velocity shear stabilized interchange instabilities
Authors: Hung C. P. , Hassam A. B.
Published: January 2013

The stabilizing effect of velocity shear on the macroscopic, broad bandwidth, ideal interchange instability is studied in linear and nonlinear regimes. A 2D dissipative magnetohydrodynamic (MHD) code is employed to simulate the system. For a given flow shear, V′, linear growth rates are shown to be suppressed to below the shear-free level at both the small and large wavelengths. With increasing V′, the unstable band in wavenumber-space shrinks so that the peak growth results for modes that correspond to relatively high wavenumbers, on the scale of the density gradient. In the nonlinear turbulent steady state, a similar turbulent spectrum obtains, and the convection cells are roughly circular. In addition, the density fluctuation level and the degree of flattening of the initial inverted density profile are found to decrease as V′ increases; in fact, unstable modes are almost completely stabilized and the density profile reverts to laminar when V′ is a few times the classic interchange growth rate. Moreover, the turbulent particle flux diminishes with increasing velocity shear such that all the flux is carried by the classical diffusive flux in the asymptotic limit. The simulations are compared with measurements of magnetic fluctuations from the Maryland Centrifugal Experiment, MCX, which investigated interchange modes in the presence of velocity shear. The experimental spectral data, taken in the plasma edge, are in general agreement with the numerical data obtained in higher viscosity simulations for which the level of viscosity is chosen consistent with MCX Reynolds numbers at the edge. In particular, the residual turbulence in both cases is dominated by elongated convection cells. Finally, concomitant Kelvin-Helmholtz instabilities in the system are also examined. Complete stability to interchanges is obtained only in the parameter space wherein the generalized Rayleigh inflexion theorem is satisfied.
Correlation between physical, electrical, and optical properties of Cu2ZnSnSe4 based solar cells
Authors: Brammertz G. , Buffière M. , Mevel Y. , Ren Y. , Zaghi A. E. , Lenaers N. , Mols Y. , Koeble C. , Vleugels J. , Meuris M. , Poortmans J.
Published: January 2013

We report on the physical, electrical, and optical properties of Cu2ZnSnSe4 (CZTSe) solar cells based on an absorber layer fabricated by selenization of sputtered Cu, Zn, Sn multilayers. It is shown that the doping density as measured by drive level capacitance profiling is correlated exponentially to the Zn/Sn ratio of the CZTSe absorber as measured by energy dispersive X-ray spectroscopy. Furthermore, it is shown that the open circuit voltage of the cells, minority carrier lifetime, and peak position of the photoluminescence response of the absorber all correlate with the doping level and, therefore, with the Zn/Sn ratio measured in the absorber.
Optimization of thickness and doping of heterojunction unipolar barrier layer for dark current suppression in long wavelength strain layer superlattice infrared detectors
Authors: Baril Neil , Billman Curtis , Maloney Patrick , Nallon Eric , Tidrow Meimei , Pellegrino Joseph , Bandara Sumith
Published: January 2013

Suppression of generation-recombination dark current and bias stability in long wavelength infrared (LWIR) strained layer superlattice (SLS) detectors, consisting of a lightly doped p-type absorber layer and a wide bandgap hole barrier, are investigated with respect to the wide bandgap barrier layer thickness and doping profile. Dark current IV, photoresponse, and theoretical modeling are used to correlate device performance with the widegap barrier design parameters. Decreased dark current density and increased operating bias were observed as the barrier thickness was increased. This study also identifies key device parameters responsible for optimal performance of heterojunction based SLS LWIR detector.
Synchrotron radiation study of VO2 crystal film epitaxial growth on sapphire substrate with intrinsic multi-domains
Authors: Fan L. L. , Wu Y. F. , Si C. , Pan G. Q. , Zou C. W. , Wu Z. Y.
Published: January 2013

The growth behavior of VO2 crystal film deposited on Al2O3 (0001) monocrystalline substrate by pulsed laser deposition was investigated by high-resolution synchrotron radiation X-ray diffraction (XRD). φ-scan XRD confirmed the in-plane epitaxial matching relation. Furthermore, fine structures observed in the φ-scan indicated that each main peak contained two additional satellites in both the inclined (220) plane and some other vertical planes. A growth model for this observation was proposed based on the intrinsic multi-domain growth of the VO2 crystal at the interface. This observation will give some insights in VO2 epitaxial growth on the hexagonal substrate system.
Frequency effects on the production of reactive oxygen species in atmospheric radio frequency helium-oxygen discharges
Authors: Zhang Yuantao T. , He Jin
Published: January 2013

Several experimental and computational studies have shown that increasing frequency can effectively enhance the discharge stability in atmospheric radio-frequency (rf) discharges, but the frequency effects on the reactivity of rf discharges, represented by the densities of reactive oxygen species (ROS), are still far from fully understood. In this paper, a one-dimensional fluid model with 17 species and 65 reactions taken into account is used to explore the influences of the driving frequency on the production and destruction of ROS in atmospheric rf helium-oxygen discharges. From the computational results, with an increase in the frequency the densities of ROS decrease always at a constant power density, however, in the relatively higher frequency discharges the densities of ROS can be effectively improved by increasing the input power density with an expanded oxygen admixture range, while the discharges operate in the α mode, and the numerical data also show the optimal oxygen admixture for ground state atomic oxygen, at which the peak atomic oxygen density can be obtained, increases with the driving frequency.
Laser ablation and deposition of aluminium with a specially configured target-substrate arrangement
Authors: Perrone A. , Cultrera L. , Lorusso A. , Maiolo B. , Strafella F.
Published: January 2013

The deposition process of Al thin films by nanosecond laser irradiation with a special hemi-cylindrical holder, containing an array of silicon substrates, is studied. The experimental results, obtained by scanning electron microscopy investigation, show that the ablated material produces an unexpected component in a direction that is approximately specular to that of the incident direction of the laser beam. This component, never before reported in the literature, is mainly formed of micrometer droplets. Simple calculations and qualitative assessments show that the forces induced by radiation pressure, thermoelastic waves, or shockwave formation cannot explain the direction of this new component.
Gyrokinetic simulations of reverse shear Alfvén eigenmodes in DIII-D plasmas
Authors: Chen Y. , Munsat T. , Parker S. E. , Heidbrink W. W. , Van Zeeland M. A. , Tobias B. J. , Domier C. W.
Published: January 2013

A gyrokinetic ion/mass-less fluid electron hybrid model as implemented in the GEM code [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 837 (2007)] is used to study the reverse shear Alfvén eigenmodes (RSAE) observed in DIII-D, discharge #142111. This is a well diagnosed case with measurement of the core-localized RSAE mode structures and the mode frequency, which can be used to compare with simulations. Simulations reproduce many features of the observation, including the mode frequency up-sweeping in time and the sweeping range. A new algorithmic feature is added to the GEM code for this study. Instead of the gyrokinetic Poisson equation itself, its time derivative, or the vorticity equation, is solved to obtain the electric potential. This permits a numerical scheme that ensures the E × B convection of the equilibrium density profiles of each species cancel each other in the absence of any finite-Larmor-radius effects. These nonlinear simulations generally result in an electron temperature fluctuation level that is comparable to measurements, and a mode frequency spectrum broader than the experimental spectrum. The spectral width from simulations can be reduced if less steep beam density profiles are used, but then the experimental fluctuation level can be reproduced only if a collision rate above the classical level is assumed.
Communication: Theoretical prediction of the structure and spectroscopic properties of the $\tilde{\mathrm{X}}$X̃ and $\tilde{\mathrm{A}}$Ã states of hydroxymethyl peroxy (HOCH2OO) radical
Authors: Delcey Mickael G. , Lindh Roland , Linguerri Roberto , Hochlaf Majdi , Francisco Joseph S.
Published: January 2013

The hydroxymethyl peroxy (HMOO) radical is a radical product from the oxidation of non-methane hydrocarbons. The present study provides theoretical prediction of critical spectroscopic features of this radical that should aid in its experimental characterization. Structure, rotational constants, and harmonic frequencies are presented for the ground and first excited electronic states of HMOO. The adiabatic transition energy for the \documentclass[12pt]{minimal}\begin{document}$\tilde{\mathrm{A}} \leftarrow \tilde{\mathrm{X}}$\end{document}Ã←X̃ process is 7360 cm−1, suggesting that this transition, occurring in the mid to near infrared, is the most promising candidate for observing the radical spectroscopically. The band origin of the \documentclass[12pt]{minimal}\begin{document}$\tilde{\mathrm{A}} \leftarrow \tilde{\mathrm{X}}$\end{document}Ã←X̃ transition of HMOO is calibrated and benchmarked with the corresponding state of the HOO radical, which is experimentally and theoretically well characterized.
Communication: Paramagnetic NMR chemical shift in a spin state subject to zero-field splitting
Authors: Soncini Alessandro , Van den Heuvel Willem
Published: January 2013

We derive a general formula for the paramagnetic NMR nuclear shielding tensor of an open-shell molecule in a pure spin state, subject to a zero-field splitting (ZFS). Our findings are in contradiction with a previous proposal. We present a simple application of the newly derived formula to the case of a triplet ground state split by an easy-plane ZFS spin Hamiltonian. When kT is much smaller than the ZFS gap, thus a single non-degenerate level is thermally populated, our approach correctly predicts a temperature-independent paramagnetic shift, while the previous theory leads to a Curie temperature dependence.
Caspase-11 stimulates rapid flagellin-independent pyroptosis in response to
Legionella pneumophila
Authors: Case Christopher L. , Kohler Lara J. , Lima Jonilson B. , Strowig Till , de Zoete Marcel R. , Flavell Richard A. , Zamboni Dario S. , Roy Craig R.
Published: January 2013

A flagellin-independent caspase-1 activation pathway that does not require NAIP5 or NRLC4 is induced by the intracellular pathogen
Legionella pneumophila
. Here we demonstrate that this pathway requires caspase-11. Treatment of macrophages with LPS up-regulated the host components required for this caspase-11 activation pathway. Activation by
Legionella
differed from caspase-11 activation using previously described agonists in that
Legionella
caspase-11 activation was rapid and required bacteria with a functional type IV secretion system called Dot/Icm.
Legionella
activation of caspase-11 induced pyroptosis by a mechanism independent of the NAIP/NLRC4 and caspase-1 axis.
Legionella
activation of caspase-11 stimulated activation of caspase-1 through NLRP3 and ASC. Induction of caspase-11–dependent responses occurred in macrophages deficient in the adapter proteins TRIF or MyD88 but not in macrophages deficient in both signaling factors. Although caspase-11 was produced in macrophages deficient in the type-I IFN receptor, there was a severe defect in caspase-11–dependent pyroptosis in these cells. These data indicate that macrophages respond to microbial signatures to produce proteins that mediate a capsase-11 response and that the caspase-11 system provides an alternative pathway for rapid detection of an intracellular pathogen capable of evading the canonical caspase-1 activation system that responds to bacterial flagellin.
NTP-mediated nucleotide excision activity of hepatitis C virus RNA-dependent RNA polymerase
Authors: Jin Zhinan , Leveque Vincent , Ma Han , Johnson Kenneth A. , Klumpp Klaus
Published: January 2013

Hepatitis C virus (HCV) RNA-dependent RNA polymerase replicates the viral genomic RNA and is a primary drug target for antiviral therapy. Previously, we described the purification of an active and stable polymerase–primer–template elongation complex. Here, we show that, unexpectedly, the polymerase elongation complex can use NTPs to excise the terminal nucleotide in nascent RNA. Mismatched ATP, UTP, or CTP could mediate excision of 3′-terminal CMP to generate the dinucleoside tetraphosphate products Ap
4
C, Up
4
C, and Cp
4
C, respectively. Pre–steady-state kinetic studies showed that the efficiency of NTP-mediated excision was highest with ATP. A chain-terminating inhibitor, 3′deoxy-CMP, could also be excised through this mechanism, suggesting important implications for nucleoside drug potency and resistance. The nucleotide excision reaction catalyzed by recombinant hepatitis C virus polymerase was 100-fold more efficient than the corresponding reaction observed with HIV reverse transcriptase.
Reference-assisted chromosome assembly
Authors: Kim Jaebum , Larkin Denis M. , Cai Qingle , Asan  , Zhang Yongfen , Ge Ri-Li , Auvil Loretta , Capitanu Boris , Zhang Guojie , Lewin Harris A. , Ma Jian
Published: January 2013

One of the most difficult problems in modern genomics is the assembly of full-length chromosomes using next generation sequencing (NGS) data. To address this problem, we developed “reference-assisted chromosome assembly” (RACA), an algorithm to reliably order and orient sequence scaffolds generated by NGS and assemblers into longer chromosomal fragments using comparative genome information and paired-end reads. Evaluation of results using simulated and real genome assemblies indicates that our approach can substantially improve genomes generated by a wide variety of de novo assemblers if a good reference assembly of a closely related species and outgroup genomes are available. We used RACA to reconstruct 60 Tibetan antelope (
Pantholops hodgsonii
) chromosome fragments from 1,434 SOAPdenovo sequence scaffolds, of which 16 chromosome fragments were homologous to complete cattle chromosomes. Experimental validation by PCR showed that predictions made by RACA are highly accurate. Our results indicate that RACA will significantly facilitate the study of chromosome evolution and genome rearrangements for the large number of genomes being sequenced by NGS that do not have a genetic or physical map.
Recognition of microbial and mammalian phospholipid antigens by NKT cells with diverse TCRs
Authors: Tatituri Raju V. V. , Watts Gerald F. M. , Bhowruth Veemal , Barton Nathaniel , Rothchild Alissa , Hsu Fong-Fu , Almeida Catarina F. , Cox Liam R. , Eggeling Lothar , Cardell Susanna , Rossjohn Jamie , Godfrey Dale I. , Behar Samuel M. , Besra Gurdyal S. , Brenner Michael B. , Brigl Manfred
Published: January 2013

CD1d-restricted natural killer T (NKT) cells include two major subgroups. The most widely studied are Vα14Jα18+invariant NKT (iNKT) cells that recognize the prototypical α-galactosylceramide antigen, whereas the other major group uses diverse T-cell receptor (TCR) α-and β-chains, does not recognize α-galactosylceramide, and is referred to as diverse NKT (dNKT) cells. dNKT cells play important roles during infection and autoimmunity, but the antigens they recognize remain poorly understood. Here, we identified phosphatidylglycerol (PG), diphosphatidylglycerol (DPG, or cardiolipin), and phosphatidylinositol fromMycobacterium tuberculosisorCorynebacterium glutamicumas microbial antigens that stimulated various dNKT, but not iNKT, hybridomas. dNKT hybridomas showed distinct reactivities for diverse antigens. Stimulation of dNKT hybridomas by microbial PG was independent of Toll-like receptor-mediated signaling by antigen-presenting cells and required lipid uptake and/or processing. Furthermore, microbial PG bound to CD1d molecules and plate-bound PG/CD1d complexes stimulated dNKT hybridomas, indicating direct recognition by the dNKT cell TCR. Interestingly, despite structural differences in acyl chain composition between microbial and mammalian PG and DPG, lipids from both sources stimulated dNKT hybridomas, suggesting that presentation of microbial lipids and enhanced availability of stimulatory self-lipids may both contribute to dNKT cell activation during infection.
Level of emotional awareness in the general French population: Effects of gender, age, and education level
Authors: Nandrino Jean‐Louis , Baracca Margaret , Antoine Pascal , Paget Virginie , Bydlowski Sarah , Carton Solange
Published: January 2013

The Levels of Emotional Awareness Scale (LEAS) developed by Lane et al. (1990) measures the ability of a subject to discriminate his or her own emotional state and that of others. The scale is based on a cognitive‐developmental model in which emotional awareness increases in a similar fashion to intellectual functions. Because studies performed using North American and German populations have demonstrated an effect of age, gender, and level of education on the ability to differentiate emotional states, our study attempts to evaluate whether these factors have the same effects in a general French population. 750 volunteers (506 female, 244 male), who were recruited from three regions of France (Lille, Montpellier, Paris), completed the LEAS. The sample was divided into five age groups and three education levels. The results of the LEAS scores for self and others and the total score showed a difference in the level of emotional awareness for different age groups, by gender and education level. A higher emotional level was observed for younger age groups, suggesting that emotional awareness depends on the cultural context and generational societal teachings. Additionally, the level of emotional awareness was higher in women than in men and lower in individuals with less education. This result might be explained by an educational bias linked to gender and higher education whereby expressive ability is reinforced. In addition, given the high degree of variability in previously observed scores in the French population, we propose a standard based on our French sample.