bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser ceilometer measurements of Australian dust storm highlight need for reassessment of atmospheric dust plume loads
Authors: McGowan Hamish A. , Soderholm Joshua
Published: December 2011

The wide ranging impacts of atmospheric dust have received much attention over the past two decades. This research has been driven by need to better resolve the roles of dusts in atmospheric processes; biogeochemical cycles, particularly in response to changing land use and climate; and impacts on human health. Global dust emissions are estimated to range from 1000 and 2000 Mt yr−1. These estimates have been derived from sediment budgets based on surface monitoring of dust concentrations, analyses of palaeo‐dust deposits and satellite monitoring of dust plumes. However, significant discrepancies remain between estimated dust transport rates and dust deposition measured directly, or constructed from sediment records. Here we present the first surface based laser ceilometer measurements of a major dust plume in eastern Australia, the largest dust source of the Southern Hemisphere. Results indicate that previous estimates of dust plume loads may have been overestimated by up to 120%. We conclude that new research is required to accurately quantify dust plume loads to enable the highest confidence of modelled dust emissions and their impacts, particularly on climate at this time of unprecedented uncertainty of future climate.
Latitude dependency of the geomagnetic secular variation S parameter: A mathematical artifact
Authors: Linder Julia , Gilder Stuart A.
Published: December 2011

Secular variation, the change in the Earth's magnetic field through time, reflects the energy state of the geodynamo. Secular variation is commonly quantified by paleomagnetists as the standard deviation of the angular distances of the virtual geomagnetic poles to their mean pole, known as the S value. This parameter has long been thought to exhibit latitude dependence [S(λ)], whose origin is widely attributed to a combination of time‐varying dipole and non‐dipole components. The slope and magnitude ofS(λ) are taken as a basis to understand the geomagnetic field and its evolution. Here we show that S(λ) stems from a mathematical aberration of the conversion from directions to poles, hence directional populations better quantify local estimates of paleosecular variation.
Effect of sudden stratospheric warming on lunar tidal modulation of the equatorial electrojet
Authors: Park Jaeheung , Lühr Hermann , Kunze Markus , Fejer Bela G. , Min Kyoung Wook
Published: December 2011

Using the equatorial electrojet (EEJ) peak current intensity as deduced from CHAMP magnetic observations from the years 2001 through 2009, we investigated the relationship between sudden stratospheric warming (SSW) and lunitidal signatures in the tropical ionosphere. There is a practically one‐to‐one correspondence between midwinter SSW periods and the strongest 13 day modulation of the EEJ strength as observed by CHAMP. That is, all the midwinter SSW periods from December 2001 to August 2009 were accompanied by an enhanced 13 day modulation of the EEJ strength. No other geophysical phenomenon brought about as strong a 13 day modulation as those of the midwinter SSW periods. During each midwinter SSW period the amplified 13 day modulation of the EEJ strengths starts roughly within ±1 week around the first peak in stratospheric temperature difference. An oscillation with a period of 13.26 days is predicted by the lunitidal equation when considering the precession of the CHAMP orbit. When fitting the lunitidal equation to the EEJ modulations during the midwinter SSW periods, consistent phase delays of 4.4 ± 0.3 days of the tidal signal emerge for all the cases. The results suggest that the pronounced 13 day modulation of the EEJ strength is related to an enhancement of the lunar tide in the ionosphere by the SSW effect.
Key role of time-delay and connection topology in shaping the dynamics of noisy genetic regulatory networks
Authors: Yang X. L. , Senthilkumar D. V. , Sun Z. K. , Kurths J.
Published: December 2011

This paper focuses on a paced genetic regulatory small-world network with time-delayed coupling. How the dynamical behaviors including temporal resonance and spatial synchronization evolve under the influence of time-delay and connection topology is explored through numerical simulations. We reveal the phenomenon of delay-induced resonance when the network topology is fixed. For a fixed time-delay, temporal resonance is shown to be degraded by increasing the rewiring probability of the network. On the other hand, for small rewiring probability, temporal resonance can be enhanced by an appropriately tuned small delay but degraded by a large delay, while conversely, temporal resonance is always reduced by time-delay for large rewiring probability. Finally, an optimal spatial synchrony is detected by a proper combination of time-delay and connection topology.
Synchronization analysis of voltage-sensitive dye imaging during focal seizures in the rat neocortex
Authors: Takeshita Daisuke , Bahar Sonya
Published: December 2011

Seizures are often assumed to result from an excess of synchronized neural activity. However, various recent studies have suggested that this is not necessarily the case. We investigate synchronization during focal neocortical seizures induced by injection of 4-aminopyridine (4AP) in the rat neocortex in vivo. Neocortical activity is monitored by field potential recording and by the fluorescence of the voltage-sensitive dye RH-1691. After removal of artifacts, the voltage-sensitive dye (VSD) signal is analyzed using the nonlinear dynamics-based technique of stochastic phase synchronization in order to determine the degree of synchronization within the neocortex during the development and spread of each seizure event. Results show a large, statistically significant increase in synchronization during seizure activity. Synchrony is typically greater between closer pixel pairs during a seizure event; the entire seizure region is synchronized almost exactly in phase. This study represents, to our knowledge, the first application of synchronization analysis methods to mammalian VSD imaging in vivo. Our observations indicate a clear increase in synchronization in this model of focal neocortical seizures across a large area of the neocortex; a sharp increase in synchronization during seizure events was observed in all 37 seizures imaged. The results are consistent with a recent computational study which simulates the effect of 4AP in a neocortical neuron model.
A common repressor pool results in indeterminacy of extrinsic noise
Authors: Stamatakis Michail , Adams Rhys M. , Balázsi Gábor
Published: December 2011

For just over a decade, stochastic gene expression has been the focus of many experimental and theoretical studies. It is now widely accepted that noise in gene expression can be decomposed into extrinsic and intrinsic components, which have orthogonal contributions to the total noise. Intrinsic noise stems from the random occurrence of biochemical reactions and is inherent to gene expression. Extrinsic noise originates from fluctuations in the concentrations of regulatory components or random transitions in the cell’s state and is imposed to the gene of interest by the intra- and extra-cellular environment. The basic assumption has been that extrinsic noise acts as a pure input on the gene of interest, which exerts no feedback on the extrinsic noise source. Thus, multiple copies of a gene would be uniformly influenced by an extrinsic noise source. Here, we report that this assumption falls short when multiple genes share a common pool of a regulatory molecule. Due to the competitive utilization of the molecules existing in this pool, genes are no longer uniformly influenced by the extrinsic noise source. Rather, they exert negative regulation on each other and thus extrinsic noise cannot be determined by the currently established method.
Biased Brownian motion in extremely corrugated tubes
Authors: Martens S. , Schmid G. , Schimansky-Geier L. , Hänggi P.
Published: December 2011

Biased Brownian motion of point-size particles in a three-dimensional tube with varying cross-section is investigated. In the fashion of our recent work, Martens et al. [Phys. Rev. E 83, 051135 (2011)] we employ an asymptotic analysis to the stationary probability density in a geometric parameter of the tube geometry. We demonstrate that the leading order term is equivalent to the Fick-Jacobs approximation. Expression for the higher order corrections to the probability density is derived. Using this expansion orders, we obtain that in the diffusion dominated regime the average particle current equals the zeroth order Fick-Jacobs result corrected by a factor including the corrugation of the tube geometry. In particular, we demonstrate that this estimate is more accurate for extremely corrugated geometries compared with the common applied method using a spatially-dependent diffusion coefficient D(x, f) which substitutes the constant diffusion coefficient in the common Fick-Jacobs equation. The analytic findings are corroborated with the finite element calculation of a sinusoidal-shaped tube.
Numerically exact, time-dependent treatment of vibrationally coupled electron transport in single-molecule junctions
Authors: Wang Haobin , Pshenichnyuk Ivan , Härtle Rainer , Thoss Michael
Published: December 2011

The multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) theory within second quantization representation of the Fock space, a novel numerically exact methodology to treat many-body quantum dynamics for systems containing identical particles, is applied to study the effect of vibrational motion on electron transport in a generic model for single-molecule junctions. The results demonstrate the importance of electronic-vibrational coupling for the transport characteristics. For situations where the energy of the bridge state is located close to the Fermi energy, the simulations show the time-dependent formation of a polaron state that results in a pronounced suppression of the current corresponding to the phenomenon of phonon blockade. We show that this phenomenon cannot be explained solely by the polaron shift of the energy but requires methods that incorporate the dynamical effect of the vibrations on the transport. The accurate results obtained with the ML-MCTDH in this parameter regime are compared to results of nonequilibrium Green's function theory.
Reduction of internal polarization fields in InGaN quantum wells by InGaN/AlGaN ultra-thin superlattice barriers with different indium composition
Authors: Noh Young-Kyun , Kim Moon-Deock , Oh Jae-Eung
Published: December 2011

The internal well polarization field in InGaN quantum wells (QWs), surrounded by strain-compensated (InxGa1−xN)/(Al0.065Ga0.935N) ultra-thin superlattice (SC-SL) barriers with different indium composition, is investigated. The indium composition of InGaN constituent of superlattice barriers has been varied in the range from 0.04 to 0.18. It is observed that the increase of indium composition of InGaN into the barrier results in a strong blue-shift of the peak wavelength of the room-temperature photoluminescence (RT-PL) and the significant increase in the intensity of the luminescence emission until too much indium is added into InGaN layers of superlattice barriers. From the bias-dependent photoluminescence measurements, it is determined that the blue-shift and intensity increase of the emission are caused by the decrease of well polarization field as the indium composition in InGaN of SC-SL barrier increases. In case of In0.16Ga0.84N containing SC-SL barriers, the well internal polarization field is greatly reduced to −0.33 MV/cm from −1.5 MV/cm with respect to typical GaN barriers, indicating that the internal field reduction similar to that obtained in semi-polar InGaN/GaN quantum wells can be obtained by applying the strain-compensating barrier to polar substrates.
Temperature-dependent stochastic dynamics of the Huber-Braun neuron model
Authors: Finke Christian , Freund Jan A. , Rosa Epaminondas , Bryant Paul H. , Braun Hans A. , Feudel Ulrike
Published: December 2011

The response of a four-dimensional mammalian cold receptor model to different implementations of noise is studied across a wide temperature range. It is observed that for noisy activation kinetics, the parameter range decomposes into two regions in which the system reacts qualitatively completely different to small perturbations through noise, and these regions are separated by a homoclinic bifurcation. Noise implemented as an additional current yields a substantially different system response at low temperature values, while the response at high temperatures is comparable to activation-kinetic noise. We elucidate how this phenomenon can be understood in terms of state space dynamics and gives quantitative results on the statistics of interspike interval distributions across the relevant parameter range.
Sensory coding in oscillatory electroreceptors of paddlefish
Authors: Neiman Alexander B. , Russell David F.
Published: December 2011

Coherence and information theoretic analyses were applied to quantitate the response properties and the encoding of time-varying stimuli in paddlefish electroreceptors (ERs), studied in vivo. External electrical stimuli were Gaussian noise waveforms of varied frequency band and strength, including naturalistic waveforms derived from zooplankton prey. Our coherence analyses elucidated the role of internal oscillations and transduction processes in shaping the 0.5–20 Hz best frequency tuning of these electroreceptors, to match the electrical signals emitted by zooplankton prey. Stimulus-response coherence fell off above approximately 20 Hz, apparently due to intrinsic limits of transduction, but was detectable up to 40–50 Hz. Aligned with this upper fall off was a narrow band of intense internal noise at ∼25 Hz, due to prominent membrane potential oscillations in cells of sensory epithelia, which caused a narrow deadband of external insensitivity. Using coherence analysis, we showed that more than 76% of naturalistic stimuli of weak strength, ∼1 μV/cm, was linearly encoded into an afferent spike train, which transmitted information at a rate of ∼30 bits/s. Stimulus transfer to afferent spike timing became essentially nonlinear as the stimulus strength was increased to induce bursting firing. Strong stimuli, as from nearby zooplankton prey, acted to synchronize the bursting responses of afferents, including across populations of electroreceptors, providing a plausible mechanism for reliable information transfer to higher-order neurons through noisy synapses.
Accurate ab initio quartic force fields of cyclic and bent HC2N isomers
Authors: Inostroza Natalia , Huang Xinchuan , Lee Timothy J.
Published: December 2011

Highly correlated ab initio quartic force fields (QFFs) are used to calculate the equilibrium structures and predict the spectroscopic parameters of three HC2N isomers. Specifically, the ground state quasilinear triplet and the lowest cyclic and bent singlet isomers are included in the present study. Extensive treatment of correlation effects were included using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, denoted as CCSD(T). Dunning's correlation-consistent basis sets cc-pVXZ, X = 3,4,5, were used, and a three-point formula for extrapolation to the one-particle basis set limit was used. Core-correlation and scalar relativistic corrections were also included to yield highly accurate QFFs. The QFFs were used together with second-order perturbation theory (PT) (with proper treatment of Fermi resonances) and variational methods to solve the nuclear Schrödinger equation. The quasilinear nature of the triplet isomer is problematic, and it is concluded that a QFF is not adequate to describe properly all of the fundamental vibrational frequencies and spectroscopic constants (though some constants not dependent on the bending motion are well reproduced by PT). On the other hand, this procedure (a QFF together with either PT or variational methods) leads to highly accurate fundamental vibrational frequencies and spectroscopic constants for the cyclic and bent singlet isomers of HC2N. All three isomers possess significant dipole moments, 3.05 D, 3.06 D, and 1.71 D, for the quasilinear triplet, the cyclic singlet, and the bent singlet isomers, respectively. It is concluded that the spectroscopic constants determined for the cyclic and bent singlet isomers are the most accurate available, and it is hoped that these will be useful in the interpretation of high-resolution astronomical observations or laboratory experiments.
Field emission in ordered arrays of ZnO nanowires prepared by nanosphere lithography and extended Fowler-Nordheim analyses
Authors: McCarthy E. , Garry S. , Byrne D. , McGlynn E. , Mosnier J.-P.
Published: December 2011

A multistage chemical method based on nanosphere lithography was used to produce hexagonally patterned arrays of ZnO vertical nanowires, with 1 μm interspacing and aspect ratio ∼20, with a view to study the effects of emitter uniformity on the current emitted upon application of a dc voltage across a 250 μm vacuum gap. A new treatment, based on the use of analytical expressions for the image-potential correction functions, was applied to the linear region below 2000 V of the Fowler-Nordheim (FN) plot and showed the most suitable value of the work function φ in the range 3.3–4.5 eV (conduction band emission) with a Schottky lowering parameter y ∼ 0.72 and a field enhancement factor γ in the 700–1100 range. A modeled γ value of ∼200 was calculated for an emitter shape of a prolate ellipsoid of revolution and also including the effect of nanowire screening, in fair agreement with the experimental value. The Fowler-Nordheim current densities and effective emission areas were derived as 1011 Am−2 and 10−17 m2, respectively, showing that field emission likely takes place in an area of atomic dimensions at the tip of the emitter. Possible causes for the observed departure from linear FN plot behavior above 2000 V were discussed.
Tb3+-Yb3+ cooperative down and up conversion processes in Tb0.81Ca0.19F2.81:Yb3+ single crystals
Authors: Molina P. , Vasyliev V. , Víllora E. G. , Shimamura K.
Published: December 2011

The energy transfer processes between Tb3+ and Yb3+ ions are studied in Tb-based fluoride single crystals. These are very transparent from the UV to the IR wavelength regions, except for the characteristic absorption lines of the rare-earth ions under study. In contrast with previously reported Tb3+-doped glasses and oxide powders, these crystals containing a high Tb3+ concentration present two major advantages for the study of the energy transfer processes in the Tb3+-Yb3+ ion pair. Firstly, the adverse influence of host defects is minimized with the use of high quality crystals. Secondly, the high Tb3+ concentration guarantees a much higher absorption cross-section of UV light, and consequently these crystals have real potential for practical applications. Photoluminescence spectra in the visible-IR wavelength region demonstrate the existence of efficient down and up conversion processes by crossed excitation and emission characteristics of Tb3+ and Yb3+ ions. In the down conversion process, Tb3+(5D4) → 2Yb3+(2F5/2), two IR photons are emitted for each Tb3+ ion deexcited by second-order energy transfer to two Yb3+ ions. The total quantum efficiency of the down conversion process in the fluoride system is shown to increase linearly with the Yb3+ concentration, reaching its maximum at the Yb3+ solubility limit in the fluoride host. Further, efficient up conversion by two- and three-IR photon absorption is observed.
X-transport of ions in diverted tokamaks, with application to DIII-D
Authors: Stacey Weston M.
Published: December 2011

A calculation model for X-transport due to the radially outward grad-B and curvature drift of ions trapped poloidally in the null-Bθ X-region just inside the X-point in diverted tokamaks is presented. Calculations are presented for two representative DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] shots which indicate that X-transport effects are significant and should be taken into account in calculations of present and future experiments.
Mechanisms of the rotational dynamics of C70 in C70-cubane heteromolecular crystals
Authors: Faro Tatiana M. C. , Skaf Munir S. , Coluci Vitor R.
Published: December 2011

Fullerenes and cubane (C8H8) can be arranged to form heteromolecular crystals that exhibit interesting crystal phases. Experimental measurements indicate a rotor-stator phase for C60-cubane crystals in which the C60 molecules rotate freely whereas cubane molecules are essentially static. A similar phase is found for C70-cubane crystals but, due to C70’s asymmetry, hindered rotations can be observed in specific crystal phases. Details of the rotational dynamics of the fullerenes in these heteromolecular crystals are difficult to be completely assessed by experiments. To this end, we have performed classical molecular dynamics simulations of C70-cubane crystals to investigate the behavior of C70 fullerenes and cubanes in the face-centered cubic and body-centered tetragonal crystallographic phases. Our simulations show that, in the cubic phase, C70 molecules are allowed to freely rotate whereas cubanes act as molecular bearings. In the tetragonal phase, the cubane molecules also remain practically fixed and the rotation of C70 fullerenes becomes hindered. In this phase, C70 molecules rotate around the fivefold axis, which in turn precesses about the c crystallographic direction of the unit cell. Details regarding the dynamics (e.g., energy barriers, reorientational relaxation processes, and phonon-libration coupling) of the C70 molecules in both crystal phases are discussed. In general, our results agree with previous experimental findings for C70-cubane crystals.
Terahertz generation from laser filaments in the presence of a static electric field in a plasma
Authors: Bhasin Lalita , Tripathi V. K.
Published: December 2011

Two femtosecond laser pulses with frequencies ω1 and ω2 that undergo filamentation in a plasma couple nonlinearly in the presence of a transverse, static electric field to generate terahertz wave at the frequency ω1-ω2. The coupling is enhanced in the presence of the static electric field. We develop a theoretical model and observe over 30 times increase in the magnitude of normalized terahertz amplitude by applying a dc electric field ~50kV/cm.
A novel method to describe the interaction pressure between charged plates with application of the weighted correlation approach
Authors: Wang Zhao , Liu Longcheng , Neretnieks Ivars
Published: December 2011

Based on the Euler–Lagrange equation for ion density distribution in an inhomogeneous, charged, and hard-sphere fluid, a novel method is proposed to determine the interaction pressure between charged plates. The resulting expression is a sum of distinct physical contributions to the pressure, which involves different contributions to the single-particle direct correlation function. It can, therefore, be conveniently used in any density functional approach to facilitate analysis of the pressure components. In this study, the so-called fundamental measure theory (FMT)/weighted correlation approach (WCA) approach is applied to estimate both the hard-sphere and the electric residual contributions to the single-particle direct correlation function, upon the calculation of the ionic density profiles between charged plates. The results, against the Monte Carlo simulations, show that the FMT/WCA approach is superior to the typical FMT/mean spherical approximation approach of the density functional theory in predicting the interaction pressure between charged plates immersed in an electrolyte solution upon various conditions in the primitive model. The FMT/WCA approach can well capture the fine features of the pressure-separation dependence, to reproduce not only the shoulder shape and the weak attractions in monovalent electrolytes but also the strongly oscillatory behavior of pressure in divalent electrolytes where pronounced attractions are observed. In addition, it is found that the FMT/WCA approach even has an advantage over the anisotropic, hyper-netted chain approach in that it agrees with the Monte Carlo results to a very good extent with, however, much less computational effort.
High temperature thermal properties of thin tantalum nitride films
Authors: Bozorg-Grayeli Elah , Li Zijian , Asheghi Mehdi , Delgado Gil , Pokrovsky Alexander , Panzer Matthew , Wack Daniel , Goodson Kenneth E.
Published: December 2011

Tantalum Nitride (TaN) films carry high heat fluxes in a variety of applications including diffusion barriers in magnetoresistive random access memory and buffer/absorbers in extreme ultraviolet masks. The thicknesses of these films are usually of the same order as the thermal energy carrier mean free path, which complicates the study of heat conduction. This paper presents thermal (cross-plane) and electrical (in-plane) conductivity measurements on TaN films with thicknesses of 50, 75, and 100 nm. Picosecond thermoreflectance is used to extract the thermal boundary resistance between TaN and Al and the intrinsic thermal conductivity of TaN for temperatures of 300–700 K. The data and the relative importance of boundary resistances, electron-boundary scattering, and electron-defect scattering are interpreted using the electrical and thermal transport data. These data facilitate comparison of the phonon and electron contributions to thermal conduction in TaN.
Slow dynamics in a liquid crystal: 1H and 19F NMR relaxometry
Authors: Rajeswari M. , Molugu Trivikram R. , Dhara Surajit , Sastry V. S. S. , Venu K. , Dabrowski R.
Published: December 2011

Spin-lattice relaxation rates (R1H and R1F) of two nuclear species (1H and 19F) are measured at different temperatures in the isotropic phase of a liquid crystal (4′-butoxy-3′-fluoro-4-isothiocyanatotolane–4OFTOL), over a wide range of Larmor frequency (10 kHz–50 MHz). Their dispersion profiles are found to be qualitatively very different, and the R1F in particular shows significant dispersion (varying over two orders of magnitude) in the entire isotropic range, unlike R1H. The proton spin-lattice relaxation, as has been established, is mediated by time modulation of magnetic dipolar interactions with other protons (case of like spins), and the discernable dispersion in the mid-frequency range, observed as the isotropic to nematic transition is approached on cooling, is indicative of the critical slowing of the time fluctuations of the nematic order. Significant dispersion seen in the R1F extending to very low frequencies suggests a distinctly different relaxation path which is exclusively sensitive to the ultra slow modes apparently present in the system. We find that under the conditions of our experiment at low Zeeman fields, spin-rotation coupling of the fluorine with the molecular angular momentum is the dominant mechanism, and the observed dispersion is thus attributed to the presence of slow torques experienced by the molecules, arising clearly from collective modes. Following the arguments advanced to explain similar slow processes inferred from earlier detailed ESR measurements in liquid crystals, we propose that slowly relaxing local structures representing such dynamic processes could be the likely underlying mechanism providing the necessary slow molecular angular momentum correlations to manifest as the observed low frequency dispersion. We also find that the effects of the onset of cross-relaxation between the two nuclear species when their resonance lines start overlapping at very low Larmor frequencies (below ∼ 400 kHz), provide an additional relaxation contribution.
On-chip single photon emission from an integrated semiconductor quantum dot into a photonic crystal waveguide
Authors: Schwagmann Andre , Kalliakos Sokratis , Farrer Ian , Griffiths Jonathan P. , Jones Geb A. C. , Ritchie David A. , Shields Andrew J.
Published: December 2011

We demonstrate the in-plane emission of highly polarized single photons from an InAs quantum dot embedded into a photonic crystal waveguide. The spontaneous emission rates are Purcell-enhanced by the coupling of the quantum dot to a slow-light mode of the waveguide. Photon-correlation measurements confirm the sub-Poissonian statistics of the in-plane emission. Under optical pulse excitation, single photon emission rates of up to 19 MHz into the guided mode are demonstrated, which corresponds to a device efficiency of 24%. These results herald the monolithic integration of sources in photonic quantum circuits.
Structural variability in La0.5Sr0.5TiO3±δ thin films
Authors: Gu Meng , Dearden Craig R. , Song Chengyu , Browning Nigel D. , Takamura Yayoi
Published: December 2011

La0.5Sr0.5TiO3±δ films were grown by pulsed laser deposition and characterized using aberration-corrected scanning transmission electron microscopy. Single-phase films with low resistivity and a near Ti3+ valence state were stabilized by a large concentration of oxygen vacancies under reducing conductions. In contrast, single-phase films transformed into “superlattices” upon exposure to an oxygen rich environment through the formation of stacking faults and cation vacancies in order to reach the stable Ti4+ valence state. The resistivity of the superlattices exceeded that of single phase films by two orders of magnitude, indicating that the observed structural order had a significant effect on the overall film properties.
Direct observation of dynamic force propagation between focal adhesions of cells on microposts by atomic force microscopy
Authors: Okada Akinori , Mizutani Yusuke , Subagyo Agus , Hosoi Hirotaka , Nakamura Motonori , Sueoka Kazuhisa , Kawahara Koichi , Okajima Takaharu
Published: December 2011

We investigated dynamic force propagation between focal adhesions of fibroblast cells cultured on polydimethylsiloxane micropost substrates, by atomic force microscopy. Live cells were mechanically modulated by the atomic force microscopy probe bound to cell apical surfaces at 0.01–0.5 Hz, while microposts served as a force sensor at basal surfaces. We observed that cells exhibited rheological behavior at the apical surface but had no apparent out-of-phase response at the basal surface, indicating that the dynamic force propagating through cytoskeletal filaments behaves in an elastic manner. Moreover, the direction of the propagated force was observed to be intimately associated with the prestress.
All-electrical operation of magnetic vortex core memory cell
Authors: Nakano K. , Chiba D. , Ohshima N. , Kasai S. , Sato T. , Nakatani Y. , Sekiguchi K. , Kobayashi K. , Ono T.
Published: December 2011

A single vortex-core switching in a ferromagnetic disk is detected in real time by using a three-terminal device with the tunneling magnetoresistance junction. We show that the device works as a vortex core memory cell, where reading and writing can be done in an all-electrical way: binary data corresponding to the core direction can be read out electrically as the amplitude of the output, while the data can be written electrically by applying a pulsed current.
Simple spark erosion device based on optical disk or hard disk drive actuators
Authors: Kamer O.
Published: December 2011

We present the design of a compact electric discharge device incorporating hard disk or optical disk drive actuators. It is simple enough to be assembled in the absence of a mechanical workshop. The electronic circuit allows the adjustment of current, voltage, and discharge power. The system has been tested with organic dielectric liquids and deionized water and spark conditions; dynamic properties and machining characteristics were investigated. This device can be used to shape materials or to produce powdered samples with low material loss and minimal liquid consumption.
Negative effective dynamic mass-density and stiffness: Micro-architecture and phononic transport in periodic composites
Authors: Nemat-Nasser Sia , Srivastava Ankit
Published: December 2011

We report the results of the calculation of negative effective density and negative effective compliance for a layered composite. We show that the frequency-dependent effective properties remain positive for cases which lack the possibility of localized resonances (a 2-phase composite) whereas they may become negative for cases where there exists a possibility of local resonance below the length-scale of the wavelength (a 3-phase composite). We also show that the introduction of damping in the system considerably affects the effective properties in the frequency region close to the resonance. It is envisaged that this demonstration of doubly negative material characteristics for 1-D wave propagation would pave the way for the design and synthesis of doubly negative material response for full 3-D elastic wave propagation.
On chip complex signal processing devices using coupled phononic crystal slab resonators and waveguides
Authors: Mohammadi Saeed , Adibi Ali
Published: December 2011

In this paper, we report the evidence for the possibility of achieving complex signal processing functionalities such as multiplexing/demultiplexing at high frequencies using phononic crystal (PnC) slabs. It is shown that such functionalities can be obtained by appropriate cross-coupling of PnC resonators and waveguides. PnC waveguides and waveguide-based resonators are realized and cross-coupled through two different methods of mechanical coupling (i.e., direct coupling and side coupling). Waveguide-based PnC resonators are employed because of their high-Q, compactness, large spurious-free spectral ranges, and the possibility of better control over coupling to PnC waveguides. It is shown that by modifying the defects in the formation of the resonators, the frequency of the resonance can be tuned.
Bandwidth and resolution of super-resolution imaging with perforated solids
Authors: Liang Zixian , Li Jensen
Published: December 2011

Recent experiments on acoustic superlens and hyperlens found anisotropic metamaterials constructed from periodic perforated solids can be used for super-resolution imaging. Here, we present a theoretical study on the operational bandwidth of these imaging devices using the emerging framework of transformation acoustics. Within the transformation approach, both the microstructural superlens and hyperlens can be discussed using the transfer matrix method on the same footing. We show that the geometrical structure of the periodic metamaterials induces that an acoustics hyperlens has a very wide operational frequency bandwidth with its subwavelength resolution limited by the ratio of image magnification while an acoustics superlens has a very deep subwavelength resolution limited only by the periodicity of the perforations but intrinsically working at a narrow frequency bandwidth. Such investigation will become useful for designing future transformation acoustical imaging devices.
Band structures tunability of bulk 2D phononic crystals made of magneto-elastic materials
Authors: Vasseur J. O. , Matar O. Bou , Robillard J. F. , Hladky-Hennion A.-C. , Deymier P. A.
Published: December 2011

The feasibility of contactless tunability of the band structure of two-dimensional phononic crystals is demonstrated by employing magnetostrictive materials and applying an external magnetic field. The influence of the amplitude and of the orientation with respect to the inclusion axis of the applied magnetic field are studied in details. Applications to tunable selective frequency filters with switching functionnality and to reconfigurable wave-guides and demultiplexing devices are then discussed.
Negative refraction of elastic waves in 2D phononic crystals: Contribution of resonant transmissions to the construction of the image of a point source
Authors: Hladky-Hennion Anne-Christine , Croënne Charles , Dubus Bertrand , Vasseur Jérôme , Haumesser Lionel , Manga Dimitri , Morvan Bruno
Published: December 2011

Negative refraction properties of a two-dimensional phononic crystal (PC), made of a triangular lattice of steel rods embedded in epoxy are investigated both experimentally and numerically. First, experiments have been carried out on a prism shaped PC immersed in water. Then, for focusing purposes, a flat lens is considered and the construction of the image of a point source is analyzed in details, when indices are matched between the PC and the surrounding fluid medium, whereas acoustic impedances are mismatched. Optimal conditions for focusing longitudinal elastic waves by such PC flat lens are then discussed.
Reducing system noise in copy number data using principal components of self-self hybridizations
Authors: Lee Yoon-ha , Ronemus Michael , Kendall Jude , Lakshmi B. , Leotta Anthony , Levy Dan , Esposito Diane , Grubor Vladimir , Ye Kenny , Wigler Michael , Yamrom Boris
Published: December 2011

Genomic copy number variation underlies genetic disorders such as autism, schizophrenia, and congenital heart disease. Copy number variations are commonly detected by array based comparative genomic hybridization of sample to reference DNAs, but probe and operational variables combine to create correlated system noise that degrades detection of genetic events. To correct for this we have explored hybridizations in which no genetic signal is expected, namely “self-self” hybridizations (SSH) comparing DNAs from the same genome. We show that SSH trap a variety of correlated system noise present also in sample-reference (test) data. Through singular value decomposition of SSH, we are able to determine the principal components (PCs) of this noise. The PCs themselves offer deep insights into the sources of noise, and facilitate detection of artifacts. We present evidence that linear and piecewise linear correction of test data with the PCs does not introduce detectable spurious signal, yet improves signal-to-noise metrics, reduces false positives, and facilitates copy number determination.
Medical publishing and the drug industry: is medical science for sale?
Authors: SISMONDO Sergio
Published: December 2011

The pharmaceutical industry produces an abundance of special‐purpose knowledge, flooding the markets it is most interested in. To gain the largest scientific impact and market value from research, drug company articles placed in medical journals are often written under the names of independent medical researchers. Pharmaceutical company statisticians, reviewers from a diverse array of company departments, medical writers, and publication planners are only rarely acknowledged in journal publications, and key company scientists only sometimes acknowledged. The public knowledge that results from this ghost‐managed research and publication is a marketing tool, providing bases for continuing medical education, buttressing sales pitches, and contributing to medical common sense and further research. In the pharmaceutical industry, knowledge is a resource to be accumulated, shaped, and deployed to best effect. In this paper, I describe this process and discuss ways in which it might be addressed.
Integrating social media in the marketing mix: the case of Best Practice
Authors: KENNEWAY Melinda , RAPPLE Charlie
Published: December 2011

In this case study we examine how Best Practice – a clinical decision support tool from the BMJ Evidence Centre – was successfully launched into a competitive market, with social media tactics at the heart of the campaign, fully integrated with more traditional approaches. Our campaign reached over 60% of the target market and attracted engagement in the order of 4–6% of that market. Usage of the site and time on the site increased greatly (by 33% and 81%, respectively). Clear processes are in place to track awareness (market exposure) through to interest (playing the game), desire (registering for a trial), and action (recommending or taking out a subscription). The campaign has been constructed in a modular manner to enable it to be localized and deployed around the world.
Online piracy of publishers' content: a primer
Authors: McCOYD Ed
Published: December 2011

Protection of copyrights owned by authors and publishers has grown significantly more complex in the Internet age. Digital piracy of published products is an expanding problem which must be continuously addressed. This article provides an overview of the scope and many current facets of online piracy affecting publishers, strategies being deployed to prevent the transmission of infringing content via the Internet, and legislative proposals to create enhanced enforcement mechanisms to combat the problem.
Journal article mining: the scholarly publishers' perspective
Authors: SMIT Eefke , VAN DER GRAAF Maurits
Published: December 2011

The essence of text mining and data mining is that a machine and software are used for content analysis of large digital corpora. The Publishing Research Consortium commissioned a study on content mining of scholarly journal articles with 29 expert interviews and an international survey among publishers. The main results are: (i) content mining developments appear to be accelerating with more applications in more areas; (ii) third‐party demand for content mining is widespread but still at low levels of frequency; (iii) publishers' permissions for content mining are quite liberal, especially for research‐driven mining requests; (iv) half of the publisher respondents undertake mining of their own content; and (v) content mining is on the rise – publishers and third parties both report an increase in planned mining activities. As content mining of journal articles spreads and intensifies, cross‐publisher solutions can better help facilitate content mining. The study investigated the interest and willingness of publishers to support a set of different solutions, from one shared content mining platform to commonly agreed access terms for mining and standardization of mining‐friendly content formats.
Book Reviews
Authors: CLARK Cindy
Published: December 2011

A Librarian's Guide on How to Publish Srećko Jelušić and Ivanka Stričević Oxford, Chandos Publishing, 2011, 166pp. 978‐1‐84334‐619‐7, £45.00/US$75.00/€55.00 pbk
Ultraconserved elements are novel phylogenomic markers that resolve placental mammal phylogeny when combined with species-tree analysis
Authors: McCormack John E. , Faircloth Brant C. , Crawford Nicholas G. , Gowaty Patricia Adair , Brumfield Robb T. , Glenn Travis C.
Published: December 2011

Phylogenomics offers the potential to fully resolve the Tree of Life, but increasing genomic coverage also reveals conflicting evolutionary histories among genes, demanding new analytical strategies for elucidating a single history of life. Here, we outline a phylogenomic approach using a novel class of phylogenetic markers derived from ultraconserved elements and flanking DNA. Using species-tree analysis that accounts for discord among hundreds of independent loci, we show that this class of marker is useful for recovering deep-level phylogeny in placental mammals. In broad outline, our phylogeny agrees with recent phylogenomic studies of mammals, including several formerly controversial relationships. Our results also inform two outstanding questions in placental mammal phylogeny involving rapid speciation, where species-tree methods are particularly needed. Contrary to most phylogenomic studies, our study supports a first-diverging placental mammal lineage that includes elephants and tenrecs (Afrotheria). The level of conflict among gene histories is consistent with this basal divergence occurring in or near a phylogenetic “anomaly zone” where a failure to account for coalescent stochasticity will mislead phylogenetic inference. Addressing a long-standing phylogenetic mystery, we find some support from a high genomic coverage data set for a traditional placement of bats (Chiroptera) sister to a clade containing Perissodactyla, Cetartiodactyla, and Carnivora, and not nested within the latter clade, as has been suggested recently, although other results were conflicting. One of the most remarkable findings of our study is that ultraconserved elements and their flanking DNA are a rich source of phylogenetic information with strong potential for application across Amniotes.
Comparative RNA sequencing reveals substantial genetic variation in endangered primates
Authors: Perry George H. , Melsted Páll , Marioni John C. , Wang Ying , Bainer Russell , Pickrell Joseph K. , Michelini Katelyn , Zehr Sarah , Yoder Anne D. , Stephens Matthew , Pritchard Jonathan K. , Gilad Yoav
Published: December 2011

Comparative genomic studies in primates have yielded important insights into the evolutionary forces that shape genetic diversity and revealed the likely genetic basis for certain species-specific adaptations. To date, however, these studies have focused on only a small number of species. For the majority of nonhuman primates, including some of the most critically endangered, genome-level data are not yet available. In this study, we have taken the first steps toward addressing this gap by sequencing RNA from the livers of multiple individuals from each of 16 mammalian species, including humans and 11 nonhuman primates. Of the nonhuman primate species, five are lemurs and two are lorisoids, for which little or no genomic data were previously available. To analyze these data, we developed a method for de novo assembly and alignment of orthologous gene sequences across species. We assembled an average of 5721 gene sequences per species and characterized diversity and divergence of both gene sequences and gene expression levels. We identified patterns of variation that are consistent with the action of positive or directional selection, including an 18-fold enrichment of peroxisomal genes among genes whose regulation likely evolved under directional selection in the ancestral primate lineage. Importantly, we found no relationship between genetic diversity and endangered status, with the two most endangered species in our study, the black and white ruffed lemur and the Coquerel's sifaka, having the highest genetic diversity among all primates. Our observations imply that many endangered lemur populations still harbor considerable genetic variation. Timely efforts to conserve these species alongside their habitats have, therefore, strong potential to achieve long-term success.
Cultural Complexity and Border Markers in Norwegian Kindergartens
Authors: Lauritsen Kirsten
Published: December 2011

This article has analysed practices towards and views on cultural diversity by staff in two Norwegian kindergartens. The article has focused on food traditions both among minorities and the Norwegian majority that serve as border markers and are used in differentiating processes among the staff. The analysis found concurrent processes towards cultural homogenisation and increased diversity and experienced that staff members are in the process of developing a perception about minority children that is complex, shifting and intersecting, rather than a straightforward perception based solely on minority status. However, the study also identified a tendency operating in parallel where, even though the ideal goal is equality in results, the outcome in practice is often a majority‐based equality practice that leaves little room for difference.