bluuebunny/crossref_metadata_2025 huggingface dataset:
Forcing the TIEGCM model with Birkeland currents from the Active Magnetosphere and Planetary Electrodynamics Response Experiment
Authors: Marsal S. , Richmond A. D. , Maute A. , Anderson B. J.
Published: April 2012

Geomagnetic field‐aligned currents from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) satellite mission are used to drive the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM). We present a comparison between ground magnetic signatures computed by the model and observations at four different geomagnetic observatories, for different magnetic disturbance levels. Results show the ability of the model to pick up the gross features of the magnetic variations, improving its performance with increasing disturbance level and from low to high latitudes. During geomagnetically quiescent conditions a baseline noise of about 5 nT is evident in reconstructed ground magnetic field signatures, which we attribute to the baseline noise level in the AMPERE currents. For variations shorter than about 30 min the modeled signals are often significantly lower than observed by a factor up to 3 to 4, possibly reflecting localized ionization structures not captured in the TIEGCM conductance modules, or missing small‐scale and rapid temporal variations in auroral currents. While the observed horizontal field variations are reflected in the model, the vertical component is consistently underestimated, possibly indicating errors in the estimates for ground induction currents. Comparison with the standard version of the TIEGCM is also carried out, showing that time variations shorter than 6 h and down to the 10 min resolution of the AMPERE data (which do not appear in the standard version of TIEGCM) are now reflected in the AMPERE‐driven model.
Significant reduction of the Loop Current in the 21st century and its impact on the Gulf of Mexico
Authors: Liu Yanyun , Lee Sang‐Ki , Muhling Barbara A. , Lamkin John T. , Enfield David B.
Published: April 2012

This study examines the potential impact of future anthropogenic global warming on the Gulf of Mexico (GoM) by using a downscaled high‐resolution ocean model constrained with the surface forcing fields and initial and boundary conditions obtained from the IPCC‐AR4 model simulations under A1B scenario. The simulated volume transport by the Loop Current (LC) is reduced considerably by 20–25% during the 21st century, consistent with a similar rate of reduction in the Atlantic Meridional Overturning Circulation. The effect of the LC in the present climate is to warm the GoM, therefore the reduced LC and the associated weakening of the warm LC eddy have a cooling impact in the GoM, particularly in the northern basin. Due to this cooling influence, the northern GoM is characterized as the region of minimal warming. Low‐resolution models, such as the IPCC‐AR4 models, underestimate the reduction of the LC and its cooling effect, thus fail to simulate the reduced warming feature in the northern GoM. The potential implications of the reduced warming in the northern GoM on pelagic fish species and their spawning patterns are also discussed.
A numerical study of the Magellan Plume
Authors: Palma Elbio D. , Matano Ricardo P.
Published: April 2012

In this modeling study we investigate the dynamical mechanisms controlling the spreading of the Magellan Plume, which is a low‐salinity tongue that extends along the Patagonian Shelf. Our results indicate that the overall characteristics of the plume (width, depth, spreading rate, etc.) are primarily influenced by tidal forcing, which manifests through tidal mixing and tidal residual currents. Tidal forcing produces a homogenization of the plume's waters and an offshore displacement of its salinity front. The interaction between tidal and wind‐forcing reinforces the downstream and upstream buoyancy transports of the plume. The influence of the Malvinas Current on the Magellan Plume is more dominant north of 50°S, where it increases the along‐shelf velocities and generates intrusions of saltier waters from the outer shelf, thus causing a reduction of the downstream buoyancy transport. Our experiments also indicate that the northern limit of the Magellan Plume is set by a high salinity discharge from the San Matias Gulf. Sensitivity experiments show that increments of the wind stress cause a decrease of the downstream buoyancy transport and an increase of the upstream buoyancy transport. Variations of the magnitude of the discharge produce substantial modifications in the downstream penetration of the plume and buoyancy transport. The Magellan discharge generates a northeastward current in the middle shelf, a recirculation gyre south of the inlet and a region of weak currents father north.
Physical processes controlling ice concentrations in cold cirrus near the tropical tropopause
Authors: Jensen E. J. , Pfister L. , Bui T. P.
Published: April 2012

Previous ice nucleation calculations have suggested that in the presence of wave‐driven temperature perturbations typical of the tropical tropopause layer (TTL), homogeneous freezing should produce ice concentrations well in excess of measured values. A statistical ice cloud parameterization that includes effects of sedimentation was recently used to show that if the wave amplitudes are not too large, a quasi steady state may be established wherein loss of ice crystals by sedimentation is balanced by nucleation of new ice crystals, and the resulting cloud ice concentrations agree well with observations. Here, we use numerical models to further evaluate the evolution of ice concentrations in TTL cirrus, including a range of cloud physical processes (homogeneous and heterogeneous ice nucleation, sedimentation, and radiatively driven dynamics). We use a one‐dimensional microphysical model with bin microphysics to show that as a result of gravitational size sorting, the mean ice concentrations over the life cycle of the clouds are considerably smaller than the peak ice concentrations produced by ice nucleation events. However, the mean ice concentrations predicted here are considerably higher than either those reported based on the statistical model or those indicated by the observations. With the baseline wave amplitudes, ice crystals nucleated heterogeneously do not quench rising supersaturation in cooling air parcels and prevent homogeneous nucleation that produces high ice concentrations. We also use a three‐dimensional cloud resolving model to show that radiatively driven internal circulations and entrainment do slowly shift the ice concentrations toward lower values, but the time required to dilute ice concentrations produced by homogeneous freezing to values comparable to measured ice concentrations is of the order of 12–24 h, which may be longer than typical TTL cirrus lifetimes.
Local sea surface temperatures add to extreme precipitation in northeast Australia during La Niña
Authors: Evans Jason P. , Boyer‐Souchet Irène
Published: April 2012

This study examines the role played by high sea surface temperatures around northern Australia, in producing the extreme precipitation which occurred during the strong La Niña in December 2010. These extreme rains produced floods that impacted almost 1,300,000 km2, caused billions of dollars in damage, led to the evacuation of thousands of people and resulted in 35 deaths. Through the use of regional climate model simulations the contribution of the observed high sea surface temperatures to the rainfall is quantified. Results indicate that the large‐scale atmospheric circulation changes associated with the La Niña event, while associated with above average rainfall in northeast Australia, were insufficient to produce the extreme rainfall and subsequent flooding observed. The presence of high sea surface temperatures around northern Australia added ∼25% of the rainfall total.
Regulation of angiotensin II receptors beyond the classical pathway
Authors: Horiuchi Masatsugu , Iwanami Jun , Mogi Masaki
Published: April 2012

The RAS (renin–angiotensin system) plays a role not only in the cardiovascular system, including blood pressure regulation, but also in the central nervous system. AngII (angiotensin II) binds two major receptors: the AT1 receptor (AngII type 1 receptor) and AT2 receptor (AngII type 2 receptor). It has been recognized that AT2 receptor activation not only opposes AT1 receptor actions, but also has unique effects beyond inhibitory cross-talk with AT1 receptor signalling. Novel pathways beyond the classical actions of RAS, the ACE (angiotensin-converting enzyme)/AngII/AT1 receptor axis, have been highlighted: the ACE2/Ang-(1–7) [angiotensin-(1–7)]/Mas receptor axis as a new opposing axis against the ACE/AngII/AT1 receptor axis, novel AngII-receptor-interacting proteins and various AngII-receptor-activation mechanisms including dimer formation. ATRAP (AT1-receptor-associated protein) and ATIP (AT2-receptor-interacting protein) are well-characterized AngII-receptor-associated proteins. These proteins could regulate the functions of AngII receptors and thereby influence various pathophysiological states. Moreover, the possible cross-talk between PPAR (peroxisome-proliferator-activated receptor)-γ and AngII receptor subtypes is an intriguing issue to be addressed in order to understand the roles of RAS in the metabolic syndrome, and interestingly some ARBs (AT1-receptor blockers) have been reported to have an AT1-receptor-blocking action with a partial PPAR-γ agonistic effect. These emerging concepts concerning the regulation of AngII receptors are discussed in the present review.
Anisotropic behavior of organic molecules on prepatterned surfaces
Authors: Hopp Stefan Frieder , Heuer Andreas
Published: April 2012

The nucleation of organic molecules on surfaces, prepatterned with stripes, is investigated with emphasis on anisotropy effects. Representing the molecules as ellipsoids, the related particle-particle interaction is modeled by means of a generalized Gay-Berne potential for similar biaxial particles. The orientation behavior of these ellipsoidal molecules induced by the stripe pattern is studied for the first monolayer by performing kinetic Monte Carlo simulations. It is shown how the properties of the particle alignment depend on energy scales, temperature, and flux. Based on the fact the particles strictly arrange in rows, it is furthermore instructive to analyze the orientation behavior within the different rows. Finally, the transfer of orientation from a preset row of molecules with fixed orientation to other nucleating particles is examined.
Pattern formation and mixing in three-dimensional film flow
Authors: Heining C. , Pollak T. , Aksel N.
Published: April 2012

The effect of inertia on gravity-driven free surface flow over different three-dimensional periodic corrugations is considered analytically, numerically and experimentally. In the case of high bottom amplitudes, compared to the film thickness, the results predict complex free surface structures especially in cases where the topography is not fully flooded by the liquid film. The investigation of the flow field shows a rich variety of pattern formation phenomena depending on the interplay between the geometry of the topography and the inertia of the film. Finally, we show how the complex topographical structure enhances the laminar mixing within the film.
Photo-origami—Bending and folding polymers with light
Authors: Ryu Jennie , D’Amato Matteo , Cui Xiaodong , Long Kevin N. , Jerry Qi H. , Dunn Martin L.
Published: April 2012

Photo-origami uses the dynamic control of the molecular architecture of a polymer by a combination of mechanical and non-contact optical stimuli to design and program spatially and temporally variable mechanical and optical fields into a material. The fields are essentially actuators, embedded in the material at molecular resolution, designed to enable controllable, sequenced, macroscopic bending and folding to create three-dimensional material structures. Here, we demonstrate, through a combination of theory, simulation-based design, synthesis, and experiment, the operative phenomena and capabilities of photo-origami that highlight its potential as a powerful, and potentially manufacturable, approach to create three-dimensional material structures.
An integrated, multiparametric flow cytometry chip using “microfluidic drifting” based three-dimensional hydrodynamic focusing
Authors: Mao Xiaole , Nawaz Ahmad Ahsan , Lin Sz-Chin Steven , Lapsley Michael Ian , Zhao Yanhui , McCoy J. Philip , El-Deiry Wafik S. , Huang Tony Jun
Published: April 2012

In this work, we demonstrate an integrated, single-layer, miniature flow cytometry device that is capable of multi-parametric particle analysis. The device integrates both particle focusing and detection components on-chip, including a “microfluidic drifting” based three-dimensional (3D) hydrodynamic focusing component and a series of optical fibers integrated into the microfluidic architecture to facilitate on-chip detection. With this design, multiple optical signals (i.e., forward scatter, side scatter, and fluorescence) from individual particles can be simultaneously detected. Experimental results indicate that the performance of our flow cytometry chip is comparable to its bulky, expensive desktop counterpart. The integration of on-chip 3D particle focusing with on-chip multi-parametric optical detection in a single-layer, mass-producible microfluidic device presents a major step towards low-cost flow cytometry chips for point-of-care clinical diagnostics.
Unipolar transport in bilayer graphene controlled by multiple p-n interfaces
Authors: Miyazaki Hisao , Li Song-Lin , Nakaharai Shu , Tsukagoshi Kazuhito
Published: April 2012

Unipolar transport is demonstrated in a bilayer graphene with a series of p-n junctions and is controlled by electrostatic biasing by a comb-shaped top gate. The OFF state is induced by multiple barriers in the p-n junctions, where the band gap is generated by applying a perpendicular electric field to the bilayer graphene, and the ON state is induced by the p-p or n-n configurations of the junctions. As the number of the junction increases, current suppression in the OFF state is pronounced. The multiple p-n junctions also realize the saturation of the drain current under relatively high source-drain voltages.
Perspective: Relativistic effects
Authors: Autschbach Jochen
Published: April 2012

This perspective article discusses some broadly-known and some less broadly-known consequences of Einstein's special relativity in quantum chemistry, and provides a brief outline of the theoretical methods currently in use, along with a discussion of recent developments and selected applications. The treatment of the electron correlation problem in relativistic quantum chemistry methods, and expanding the reach of the available relativistic methods to calculate all kinds of energy derivative properties, in particular spectroscopic and magnetic properties, requires on-going efforts.
Quantization and fractional quantization of currents in periodically driven stochastic systems. I. Average currents
Authors: Chernyak Vladimir Y. , Klein John R. , Sinitsyn Nikolai A.
Published: April 2012

This article studies Markovian stochastic motion of a particle on a graph with finite number of nodes and periodically time-dependent transition rates that satisfy the detailed balance condition at any time. We show that under general conditions, the currents in the system on average become quantized or fractionally quantized for adiabatic driving at sufficiently low temperature. We develop the quantitative theory of this quantization and interpret it in terms of topological invariants. By implementing the celebrated Kirchhoff theorem we derive a general and explicit formula for the average generated current that plays a role of an efficient tool for treating the current quantization effects.
Key experimental information on intermediate-range atomic structures in amorphous Ge2Sb2Te5 phase change material
Authors: Hosokawa Shinya , Pilgrim Wolf-Christian , Höhle Astrid , Szubrin Daniel , Boudet Nathalie , Bérar Jean-François , Maruyama Kenji
Published: April 2012

Laser-induced crystalline-amorphous phase change of Ge-Sb-Te alloys is the key mechanism enabling the fast and stable writing/erasing processes in rewritable optical storage devices, such as digital versatile disk (DVD) or blu-ray disk. Although the structural information in the amorphous phase is essential for clarifying this fast process, as well as long lasting stabilities of both the phases, experimental works were mostly limited to the short-range order by x ray absorption fine structure. Here we show both the short and intermediate-range atomic structures of amorphous DVD material, Ge2Sb2Te5 (GST), investigated by a combination of anomalous x ray scattering and reverse Monte Carlo modeling. From the obtained atomic configurations of amorphous GST, we have found that the Sb atoms and half of the Ge atoms play roles in the fast phase change process of order-disorder transition, while the remaining Ge atoms act for the proper activation energy of barriers between the amorphous and crystalline phases.
Time dependent stretching of aging dynamics in a generalized hydrodynamic model for supercooled liquids
Authors: Gupta Bhaskar Sen , Das Shankar P.
Published: April 2012

The nonequilibrium dynamics and aging behavior of a supercooled liquid is investigated from an analysis of the correlation of density fluctuations at two different times. The dynamic correlation functions are computed by solving numerically the equations of nonlinear fluctuating hydrodynamics. The aging time dependence follows a modified stretched exponential form with a relaxation time which is dependent on the aging time. This is similar to the behavior seen in the aging data of dielectric response functions of a typical glass forming liquid.
Three-step H2Se/Ar/H2S reaction of Cu-In-Ga precursors for controlled composition and adhesion of Cu(In,Ga)(Se,S)2 thin films
Authors: Kim Kihwan , Hanket Gregory M. , Huynh Trang , Shafarman William N.
Published: April 2012

Control of the through-film composition and adhesion are critical issues for Cu(In,Ga)Se2 (CIGS) and/or Cu(In,Ga)(Se,S)2 (CIGSS) films formed by the reaction of Cu–In–Ga metal precursor films in H2Se or H2S. In this work, CIGSS films with homogenous Ga distribution and good adhesion were formed using a three-step reaction involving: (1) selenization in H2Se at 400 °C for 60 min, (2) temperature ramp-up to 550 °C and annealing in Ar for 20 min, and (3) sulfization in H2S at 550 °C for 10 min. The 1st selenization step led to fine grain microstructure with Ga accumulation near the Mo back contact, primarily in a Cu9(In1−xGax)4 phase. The 2nd Ar anneal step produces significant grain growth with homogenous through-film Ga distribution and the formation of an InSe binary compound near the Mo back contact. The 3rd sulfization step did not result in any additional change in Ga distribution or film microstructure but a small S incorporation near the CIGSS film surface and complete reaction of InSe to form CIGSS were observed. The three-step process facilitates good control of the film properties by separating different effects of the reaction process and a film growth model is proposed. Finally, CIGSS solar cells with the three-step reaction were fabricated and devices with efficiency = 14.2% and VOC = 599 mV were obtained.
Structure, magnetic, and dielectric properties of La2Ni(Mn1-xTix)O6 ceramics
Authors: Yang W. Z. , Liu X. Q. , Lin Y. Q. , Chen X. M.
Published: April 2012

In the present work, the effects of Ti-substitution for Mn upon the structure, magnetic and dielectric properties in La2NiMnO6 ceramics have been investigated. Ti-substitution for Mn strongly affects the crystallographic, magnetic, and dielectric properties of La2NiMnO6 double perovskite ceramics. Refinements of the x-ray diffraction data show that all compositions investigated here have the monoclinic perovskite structure in space group P21/n with a partially ordered arrangement of Ni and Mn/Ti cations. The magnetic nature of the present ceramics with x up to 0.8 is ferromagnetic (FM), while that is antiferromagnetic for La2NiTiO6. The Curie temperature and the spontaneous magnetization, or FM component, decrease with increasing x. These ferromagnetic states are attributed to the Ni2+-O-Mn4+ superexchange interaction. The dielectric constant monotonically decreases and the relaxor-like behavior is suppressed with x. The similar variation tendency of magnetic and dielectric properties with increasing x can be explained simply by the dilution effect.
Polarization and angular effects of femtosecond laser-induced conical microstructures on Ni
Authors: Yong Hwang Taek , Guo Chunlei
Published: April 2012

In this paper, through femtosecond laser pulse irradiation with various polarizations and incident angles, we create arrays of nanostructure-covered conical microstructures (NC-CMs) on Ni. We show that the shape of CMs depends significantly on the polarization and incident angle of the laser beam, and find that the size of nanostructures is distributed asymmetrically on the CMs at off normal incidence. We suggest that nonuniform energy deposition owing to the polarization and the incident angle of laser beam plays an important role in the asymmetric nanostructure distribution and shape of CMs on Ni.
Changes in structural and electronic properties of graphene grown on 6H-SiC(0001) induced by Na deposition
Authors: Watcharinyanon S. , Johansson L. I. , Xia C. , Virojanadara C.
Published: April 2012

The effects of Na deposited on monolayer graphene on SiC(001) were investigated by synchrotron-based photoelectron spectroscopy and angle resolved photoelectron spectroscopy. The experimental results show that Na prefers to adsorb on the graphene layer after deposition at room temperature. Nonetheless, part of the Na atoms are able to intercalate in between the graphene and the buffer layer and some go even further into the substrate interface as indicated by the shift of the bulk SiC component in the C 1s and Si 2p core level spectra. The ARPES spectrum exhibits a lowering of the Dirac point indicating increased n-type doping of the monolayer graphene induced by the deposited Na atoms. Upon subsequently heating the sample, we found that a slightly elevated temperature is essential in order to promote Na intercalation. A fully Na intercalation at the graphene-SiC interface is obtained after heating at a temperature of about 75 °C. The intercalated Na decouples the buffer layer and transforms it into a second graphene layer so two π-bands are observed in the ARPES spectra. Interestingly, the two bands show different locations of the Dirac point but both exhibit linear dispersion in the vicinity of the K¯ point and not the hyperbolic dispersion observed for AB stacked bi-layer graphene. When heating the sample to about 125 °C or higher, Na is found to leave the interface and the second graphene layer is transformed back to the carbon buffer layer.
Origin of preferential grain orientation in excimer laser-induced crystallization of silicon thin films
Authors: Weizman M. , Klimm C. , Nickel N. H. , Rech B.
Published: April 2012

The origin of the formation of {100} and {111} grain textures in polycrystalline silicon thin films prepared with multiple excimer laser shots at the super-lateral-growth crystallization regime is investigated in this study. Our results demonstrate that the type of texture formed is determined solely by the thickness of the silicon layer. At a critical value of 40 nm, a transition from {100} to {111} texture is observed with increasing layer thickness. It is therefore proposed that below this critical value, the texture formation is governed by surface energy anisotropy whereas above it, the kinetics of the solidification process predominate.
Elasticity of flexible and semiflexible polymers with extensible bonds in the Gibbs and Helmholtz ensembles
Authors: Manca Fabio , Giordano Stefano , Palla Pier Luca , Zucca Rinaldo , Cleri Fabrizio , Colombo Luciano
Published: April 2012

Stretching experiments on single molecules of arbitrary length opened the way for studying the statistical mechanics of small systems. In many cases in which the thermodynamic limit is not satisfied, different macroscopic boundary conditions, corresponding to different statistical mechanics ensembles, yield different force-displacement curves. We formulate analytical expressions and develop Monte Carlo simulations to quantitatively evaluate the difference between the Helmholtz and the Gibbs ensembles for a wide range of polymer models of biological relevance. We consider generalizations of the freely jointed chain and of the worm-like chain models with extensible bonds. In all cases we show that the convergence to the thermodynamic limit upon increasing contour length is described by a suitable power law and a specific scaling exponent, characteristic of each model.
Bringing aptamers into technologies: Impact of spacer terminations
Authors: Brut M. , Trapaidze A. , Estève A. , Bancaud A. , Estève D. , Landa G. , Djafari-Rouhani M.
Published: April 2012

We propose a low cost modeling approach to screen the impact of aptamer structural modifications on their biomechanical stability. This responds to the current immature control of aptamer properties when integrated into bio-hybrid devices. We predict that common spacers (PEG, polythymine) disrupt aptamer rigidity, whereas alkyl chains have minimal incidence on its mechanical properties. We also observe that mutations in the active site are equally perturbative as PEG or polythymine. We suggest that the rational design of aptamer-based biosensing devices calls for a precise modeling of surface grafting and envision that our tool is readily adapted to face this challenge.
Resistive switching phenomenon driven by antiferromagnetic phase separation in an antiperovskite nitride Mn3ZnN
Authors: Sun Y. S. , Guo Y. F. , Wang X. X. , Tsujimoto Y. , Matsushita Y. , Shi Y. G. , Wang C. , Belik A. A. , Yamaura K.
Published: April 2012

A resistive-switching phenomenon driven by antiferromagnetic phase separation is observed for a manganese nitride Mn3ZnN, which crystallizes in the antiperovskite structure. Measurements of the lattice parameters, magnetic susceptibility, electrical resistivity, and specific heat from 2 K to 300 K reveal antiferromagnetic phase separation that appears below a temperature of approximately 190 K. The mechanism of the phase separation is highly complicated; nevertheless the accompanying resistive-switching phenomenon is useful for non-volatile memory applications.
Computer simulation of sedimentation of ionic systems using the Wolf method
Authors: Viveros-Méndez P. X. , Gil-Villegas Alejandro
Published: April 2012

We present computer simulation results for 1:1 and 2:1 electrolyte solutions in the presence of a gravitational field, using the Monte Carlo method in the NVT ensemble for the restrictive primitive model. Coulombic interactions were taken into account comparing the Ewald and Wolf methods. Three variations of Ewald summations were considered: the exact method for slab geometries (EW2D), and the three-dimensional (3D) versions with and without a dipolar correction (EW3DC and EW3D, respectively). The equivalent 3D Wolf protocols were applied under the same conditions (WF3DC and WF3D, respectively). The Wolf and Ewald methods agree accurately in the prediction of several thermodynamic and structural properties for these inhomogeneous systems: excess internal energies, isochoric heath capacities, and density and electrostatic potential profiles. The main advantage using the Wolf method is the significant saving in computing time, which is approximately six times faster than EW3D and EW3DC, and sixty times faster than EW2D.
Hofmeister effects in micromolar electrolyte solutions
Authors: Enami Shinichi , Mishra Himanshu , Hoffmann Michael R. , Colussi Agustín J.
Published: April 2012

Ions induce both specific (Hofmeister) and non-specific (Coulomb) effects at aqueous interfaces. More than a century after their discovery, the origin of specific ion effects (SIE) still eludes explanation because the causal electrostatic and non-electrostatic interactions are neither local nor separable. Since direct Coulomb effects essentially vanish below ∼10 μM (i.e., at >50 nm average ion separations in water), we decided to investigate whether SIE operate at, hitherto unexplored, lower concentrations. Herein, we report the detection of SIE above ∼0.1 μM in experiments where relative iodide/bromide populations, χ = I−/Br−, were determined on the surface of aqueous (NaI + NaBr) jets by online electrospray mass spectrometry in the presence of variable XCl (X = H, Na, K, Cs, NH4, and N(C4H9)4) and NaY (Y = OH, Cl, NO3, and ClO4) concentrations. We found that (1) all tested electrolytes begin to affect χ below ∼1 μM and (2) I− and Br− are preferentially suppressed by co-ions closely matching their interfacial affinities. We infer that these phenomena, by falling outside the reach of even the longest ranged electrostatic interactions, are dynamical in nature.
Kinetic simulations of the structures of magnetic island in multiple X line guide field reconnection
Authors: Huang Can , Lu Quanming , Zhang Hui , Wu Mingyu , Dong Quanli , Lu San , Wang Shui
Published: April 2012

Magnetic reconnection is one of the most important processes in astrophysical, space, and laboratory plasmas, and magnetic island is an important feature in reconnection. Therefore, identifying the structures of magnetic island is crucial to improving our understanding of magnetic reconnection. Using two-dimensional (2-D) particle-in-cell (PIC) simulations, we demonstrate that the out-of-plane magnetic field has a dip in the center of magnetic island, which is formed during multiple X line guide field reconnection. Such structures are considered to be produced by the current system in the magnetic island. At the edge of the magnetic island, there exists a current anti-parallel to the in-plane magnetic field, while the current is parallel to the in-plane magnetic field inside the magnetic island. Such a dual-ring current system, which is attributed to the electron dynamics in the magnetic island, leads to the dip of the out-of-plane magnetic field in the center of the island. The relevance between our simulations and crater flux transfer events (C-FTEs) is also discussed.
Exact folded-band chaotic oscillator
Authors: Corron Ned J. , Blakely Jonathan N.
Published: April 2012

An exactly solvable chaotic oscillator with folded-band dynamics is shown. The oscillator is a hybrid dynamical system containing a linear ordinary differential equation and a nonlinear switching condition. Bounded oscillations are provably chaotic, and successive waveform maxima yield a one-dimensional piecewise-linear return map with segments of both positive and negative slopes. Continuous-time dynamics exhibit a folded-band topology similar to Rössler’s oscillator. An exact solution is written as a linear convolution of a fixed basis pulse and a discrete binary sequence, from which an equivalent symbolic dynamics is obtained. The folded-band topology is shown to be dependent on the symbol grammar.
Communication: The highest frequency hydrogen bond vibration and an experimental value for the dissociation energy of formic acid dimer
Authors: Kollipost F. , Larsen R. Wugt , Domanskaya A. V. , Nörenberg M. , Suhm M. A.
Published: April 2012

The highest frequency hydrogen bond fundamental of formic acid dimer, ν24 (Bu), is experimentally located at 264 cm−1. FTIR spectra of this in-plane bending mode of (HCOOH)2 and band centers of its symmetric D isotopologues (isotopomers) recorded in a supersonic slit jet expansion are presented. Comparison to earlier studies at room temperature reveals the large influence of thermal excitation on the band maximum. Together with three Bu combination states involving hydrogen bond fundamentals and with recent progress for the Raman-active modes, this brings into reach an accurate statistical thermodynamics treatment of the dimerization process up to room temperature. We obtain D0 = 59.5(5) kJ/mol as the best experimental estimate for the dimer dissociation energy at 0 K. Further improvements have to wait for a more consistent determination of the room temperature equilibrium constant.
Resonant Auger spectroscopy at the carbon and nitrogen K-edges of pyrimidine
Authors: Bolognesi P. , O'Keeffe P. , Ovcharenko Y. , Avaldi L. , Carravetta V.
Published: April 2012

The resonant Auger electron spectra obtained after photoexcitation below the C and N 1s ionization thresholds in the pyrimidine molecule have been measured at several photon energies. The results show the relevance of the localization of the inner hole and of the matching between the symmetries of the intermediate and final states in the decay spectra via participator transitions. The comparison with the Auger electron spectra suggests some assignment for the two-hole-one-particle states reached via spectator transitions. The analysis of the participator decay is supported by state-of-the art density functional theory calculations.
Passive harmonic mode-locking in Er-doped fiber laser based on graphene saturable absorber with repetition rates scalable to 2.22 GHz
Authors: Sobon Grzegorz , Sotor Jaroslaw , Abramski Krzysztof M.
Published: April 2012

Passive harmonic-mode locking of erbium-doped fiber laser with atomic multilayer graphene is presented. The laser could operate at several harmonics (from 2nd to 21st) of the fundamental repetition frequency of the ring resonator (106 MHz). The highest achieved repetition rate was 2.22 GHz (which corresponds to the 21st harmonic) with sub-picosecond pulse durations and over 40 dB of the supermode noise suppression. The saturable absorber was formed by multilayer graphene, mechanically exfoliated from pure graphite block through Scotch-tape and deposited on the fiber ferrule.
Gate-dependent photoconductivity of single layer graphene grafted with metalloporphyrin molecules
Authors: Choi M. S. , Lee D. J. , Lee S. J. , Hwang D. H. , Lee J. H. , Aoki N. , Ochiai Y. , Kim H.-J. , Whang D. , Kim S. , Hwang S. W.
Published: April 2012

We present the gate-dependent photoconductivity measurements of single layer graphene ribbons grafted with zinc porphyrin molecules Zn(OEP). The Zn(OEP)-graphene showed a maximum 610% increase in its photo-sensitivity compared to the bare graphene samples. Furthermore, the measured photocurrent exhibited strong dependence on the gate bias, light power, and light wavelength. These dependences showed clear evidence of the excitation of the carriers in Zn(OEP) and their energy transfer to graphene.
Negative normal stress differences in graphene/polycarbonate composites
Authors: Il Jun Sang , Sang Lee Heon
Published: April 2012

We measured the negative normal stress differences in graphene (0.5 wt. %)/polycarbonate composites during shear flow. The Peclet number in graphene/PC melt is estimated to be 105 ∼ 108, indicating the graphene sheets are non-Brownian. The negative normal stress is related with the deformations of gel-like structure of graphene sheets in PC. The storage modulus of graphene/PC composite melts approaches to a solid-like plateau in the terminal region at low concentration of 0.05 ∼ 0.70 wt. % graphene.
Nonthermal ATP-dependent fluctuations contribute to the in vivo motion of chromosomal loci
Authors: Weber Stephanie C. , Spakowitz Andrew J. , Theriot Julie A.
Published: April 2012

Chromosomal loci jiggle in place between segregation events in prokaryotic cells and during interphase in eukaryotic nuclei. This motion seems random and is often attributed to Brownian motion. However, we show here that locus dynamics in live bacteria and yeast are sensitive to metabolic activity. When ATP synthesis is inhibited, the apparent diffusion coefficient decreases, whereas the subdiffusive scaling exponent remains constant. Furthermore, the magnitude of locus motion increases more steeply with temperature in untreated cells than in ATP-depleted cells. This “superthermal” response suggests that untreated cells have an additional source of molecular agitation, beyond thermal motion, that increases sharply with temperature. Such ATP-dependent fluctuations are likely mechanical, because the heat dissipated from metabolic processes is insufficient to account for the difference in locus motion between untreated and ATP-depleted cells. Our data indicate that ATP-dependent enzymatic activity, in addition to thermal fluctuations, contributes to the molecular agitation driving random (sub)diffusive motion in the living cell.
Metaproteomics of a gutless marine worm and its symbiotic microbial community reveal unusual pathways for carbon and energy use
Authors: Kleiner Manuel , Wentrup Cecilia , Lott Christian , Teeling Hanno , Wetzel Silke , Young Jacque , Chang Yun-Juan , Shah Manesh , VerBerkmoes Nathan C. , Zarzycki Jan , Fuchs Georg , Markert Stephanie , Hempel Kristina , Voigt Birgit , Becher Dörte , Liebeke Manuel , Lalk Michael , Albrecht Dirk , Hecker Michael , Schweder Thomas , Dubilier Nicole
Published: April 2012

Low nutrient and energy availability has led to the evolution of numerous strategies for overcoming these limitations, of which symbiotic associations represent a key mechanism. Particularly striking are the associations between chemosynthetic bacteria and marine animals that thrive in nutrient-poor environments such as the deep sea because the symbionts allow their hosts to grow on inorganic energy and carbon sources such as sulfide and CO
2
. Remarkably little is known about the physiological strategies that enable chemosynthetic symbioses to colonize oligotrophic environments. In this study, we used metaproteomics and metabolomics to investigate the intricate network of metabolic interactions in the chemosynthetic association between
Olavius algarvensis
, a gutless marine worm, and its bacterial symbionts. We propose previously undescribed pathways for coping with energy and nutrient limitation, some of which may be widespread in both free-living and symbiotic bacteria. These pathways include (
i
) a pathway for symbiont assimilation of the host waste products acetate, propionate, succinate and malate; (
ii
) the potential use of carbon monoxide as an energy source, a substrate previously not known to play a role in marine invertebrate symbioses; (
iii
) the potential use of hydrogen as an energy source; (
iv
) the strong expression of high-affinity uptake transporters; and (
v
) as yet undescribed energy-efficient steps in CO
2
fixation and sulfate reduction. The high expression of proteins involved in pathways for energy and carbon uptake and conservation in the
O
.
algarvensis
symbiosis indicates that the oligotrophic nature of its environment exerted a strong selective pressure in shaping these associations.
Tandem mass spectrometry identifies many mouse brain
O
-GlcNAcylated proteins including EGF domain-specific
O
-GlcNAc transferase targets
Authors: Alfaro Joshua F. , Gong Cheng-Xin , Monroe Matthew E. , Aldrich Joshua T. , Clauss Therese R. W. , Purvine Samuel O. , Wang Zihao , Camp David G. , Shabanowitz Jeffrey , Stanley Pamela , Hart Gerald W. , Hunt Donald F. , Yang Feng , Smith Richard D.
Published: April 2012

O
-linked
N
-acetylglucosamine (
O
-GlcNAc) is a reversible posttranslational modification of Ser and Thr residues on cytosolic and nuclear proteins of higher eukaryotes catalyzed by
O
-GlcNAc transferase (OGT).
O
-GlcNAc has recently been found on Notch1 extracellular domain catalyzed by EGF domain-specific OGT. Aberrant
O
-GlcNAc modification of brain proteins has been linked to Alzheimer's disease (AD). However, understanding specific functions of
O
-GlcNAcylation in AD has been impeded by the difficulty in characterization of
O
-GlcNAc sites on proteins. In this study, we modified a chemical/enzymatic photochemical cleavage approach for enriching
O
-GlcNAcylated peptides in samples containing ∼100 μg of tryptic peptides from mouse cerebrocortical brain tissue. A total of 274
O
-GlcNAcylated proteins were identified. Of these, 168 were not previously known to be modified by
O
-GlcNAc. Overall, 458
O
-GlcNAc sites in 195 proteins were identified. Many of the modified residues are either known phosphorylation sites or located proximal to known phosphorylation sites. These findings support the proposed regulatory cross-talk between
O
-GlcNAcylation and phosphorylation. This study produced the most comprehensive
O
-GlcNAc proteome of mammalian brain tissue with both protein identification and
O
-GlcNAc site assignment. Interestingly, we observed
O
-β-GlcNAc on EGF-like repeats in the extracellular domains of five membrane proteins, expanding the evidence for extracellular
O
-GlcNAcylation by the EGF domain-specific OGT. We also report a GlcNAc-β-1,3-Fuc-α-1-
O
-Thr modification on the EGF-like repeat of the versican core protein, a proposed substrate of Fringe β-1,3-
N
-acetylglucosaminyltransferases.
Direct observation of stick-slip movements of water nanodroplets induced by an electron beam
Authors: Mirsaidov Utkur M. , Zheng Haimei , Bhattacharya Dipanjan , Casana Yosune , Matsudaira Paul
Published: April 2012

Dynamics of the first few nanometers of water at the interface are encountered in a wide range of physical, chemical, and biological phenomena. A simple but critical question is whether interfacial forces at these nanoscale dimensions affect an externally induced movement of a water droplet on a surface. At the bulk-scale water droplets spread on a hydrophilic surface and slip on a nonwetting, hydrophobic surface. Here we report the experimental description of the electron beam-induced dynamics of nanoscale water droplets by direct imaging the translocation of 10- to 80-nm-diameter water nanodroplets by transmission electron microscopy. These nanodroplets move on a hydrophilic surface not by a smooth flow but by a series of stick-slip steps. We observe that each step is preceded by a unique characteristic deformation of the nanodroplet into a toroidal shape induced by the electron beam. We propose that this beam-induced change in shape increases the surface free energy of the nanodroplet that drives its transition from stick to slip state.
Human fibrocytes coexpress thyroglobulin and thyrotropin receptor
Authors: Fernando Roshini , Atkins Stephen , Raychaudhuri Nupur , Lu Ying , Li Bin , Douglas Raymond S. , Smith Terry J.
Published: April 2012

Thyroglobulin (Tg) is the macromolecular precursor of thyroid hormones and is thought to be uniquely expressed by thyroid epithelial cells. Tg and the thyroid-stimulating hormone receptor (TSHR) are targets for autoantibody generation in the autoimmune disorder Graves disease (GD). Fully expressed GD is characterized by thyroid overactivity and orbital tissue inflammation and remodeling. This process is known as thyroid-associated ophthalmopathy (TAO). Early reports suggested that in TAO, both Tg and TSHR become overexpressed in orbital tissues. Previously, we found that CD34
+
progenitor cells, known as fibrocytes, express functional TSHR, infiltrate the orbit, and comprise a large subset of orbital fibroblasts in TAO. We now report that fibrocytes also express Tg, which resolves as a 305-kDa protein on Western blots. It can be immunoprecipitated with anti-Tg Abs. Further,
125
iodine and [
35
S]methionine are incorporated into Tg expressed by fibrocytes. De novo Tg synthesis is attenuated with a specific small interfering RNA targeting the protein. A fragment of the Tg gene promoter fused to a luciferase reporter exhibits substantial activity when transfected into fibrocytes. Unlike fibrocytes, GD orbital fibroblasts, which comprise a mixture of CD34
+
and CD34
−
cells, express much lower levels of Tg and TSHR. When sorted into pure CD34
+
and CD34
−
subsets, Tg and TSHR mRNA levels become substantially higher in CD34
+
cells. These findings indicate that human fibrocytes express multiple “thyroid-specific” proteins, the levels of which are reduced after they infiltrate tissue. Our observations establish the basis for Tg accumulation in orbital GD.
War of Creative Destruction: the central tendency in the globalized Arab revolutions (a study in the formation of the future)
Authors: al-ʿAfīfī Fatḥī
Published: April 2012

The Arab world in the 2010–2011 period was subject to a massive and unprecedented process of ‘creative destruction’. Despite its highly pernicious effects at numerous levels, including the distortion of political life and the stark polarization and increasing disparities between rich and poor, creative destruction is the instrument of choice in the process of globalization run by the major powers, and functions in place of more costly direct military interventions but can be used to serve similar ends. Major western powers engage in trafficking in protection, and American policies impose international axes conflicting by design for the purposes of managing their concerns whether such be through playing off political rivals against one another or running low-intensity wars that serve vested interests or grander imperial designs. Savage capitalism is an overt instrument and consequence of authoritarianism and corruption that justifies chaos, which also, in the context of globalization, gives just cause for revolution when it affirms social– Darwinian concepts that suggest ‘victims deserve their fate’ and ‘whoever can save himself does’. The Neo-liberalism derivative of Adam Smith that is at the core of globalization and its logic vigorously promotes individualism at the expense of collectivism and group interests and encourages individual initiatives—all of which led to the major global financial collapse of September 2008, and it is this same logic that underpins the strategy of creative destruction. This article provides a theoretical framework as well as specific means for analyzing the process of creative destruction specifically in the Arab world during the period of the so-called ‘Arab Spring’ and deals with the various social matrices and movements along with the role of Arab satellite media, electronic chaos and cyber-mobilization. Additionally projects, justifications for, and hierarchies of creative destruction are detailed across various axes and different modalities including the American mode, the Arab authoritarian state mode and the popular mode. The force of creative destruction in the Middle East, in the final analysis, is more than a US scheme for dismantling the old Arab order; the Arab revolts constitute the catalyst and central tendency towards taking responsibility—as a concept and plan for the unleashing of the tremendous power and mobilization that are permitting Arab peoples to do more than react, but to have their say in history.
Absolute atomic chlorine densities in a Cl2 inductively coupled plasma determined by two-photon laser-induced fluorescence with a new calibration method
Authors: Booth J P , Azamoum Y , Sirse N , Chabert P
Published: April 2012

Absolute densities of chlorine atoms were determined in an inductively coupled plasma in pure chlorine gas as a function of gas pressure and RF power by two-photon laser-induced fluorescence. A new technique is proposed to put the relative two-photon laser-induced fluorescence (TALIF) measurements on an absolute scale, based on photolysis of Cl2 gas (without plasma) with a tripled Nd : YAG laser at 355 nm. Because the dissociation cross-section and photo-dissociation laser beam energy density are well known, the absolute densities can be determined with high accuracy. We find that the ratio of the Cl atom density normalized to the Cl2 gas density without plasma

at the reactor centre increases with RF power and decreases with gas pressure, reaching 20% at 2 mTorr 500 WRF.