bluuebunny/crossref_metadata_2025 huggingface dataset:
Process length scales and longitudinal damping in karst conduits
Authors: Covington M. D. , Luhmann A. J. , Wicks C. M. , Saar M. O.
Published: February 2012

Simple mathematical models often allow an intuitive grasp of the function of physical systems. We develop a mathematical framework to investigate reactive or dissipative transport processes within karst conduits. Specifically, we note that for processes that occur within a characteristic timescale, advection along the conduit produces a characteristic process length scale. We calculate characteristic length scales for the propagation of thermal and electrical conductivity signals along karst conduits. These process lengths provide a quantitative connection between karst conduit geometry and the signals observed at a karst spring. We show that water input from the porous/fractured matrix is also characterized by a length scale and derive an approximation that accounts for the influence of matrix flow on the transmission of signals through the aquifer. The single conduit model is then extended to account for conduits with changing geometries and conduit flow networks, demonstrating how these concepts can be applied in more realistic conduit geometries. We introduce a recharge density function, ϕR, which determines the capability of an aquifer to damp a given signal, and cast previous explanations of spring variability within this framework. Process lengths are a general feature of karst conduits and surface streams, and we conclude with a discussion of other potential applications of this conceptual and mathematical framework.
Dynamic Radiation Environment Assimilation Model: DREAM
Authors: Reeves G. D. , Chen Y. , Cunningham G. S. , Friedel R. W. H. , Henderson M. G. , Jordanova V. K. , Koller J. , Morley S. K. , Thomsen M. F. , Zaharia S.
Published: February 2012

The Dynamic Radiation Environment Assimilation Model (DREAM) was developed to provide accurate, global specification of the Earth's radiation belts and to better understand the physical processes that control radiation belt structure and dynamics. DREAM is designed using a modular software approach in order to provide a computational framework that makes it easy to change components such as the global magnetic field model, radiation belt dynamics model, boundary conditions, etc. This paper provides a broad overview of the DREAM model and a summary of some of the principal results to date. We describe the structure of the DREAM model, describe the five major components, and illustrate the various options that are available for each component. We discuss how the data assimilation is performed and the data preprocessing and postprocessing that are required for producing the final DREAM outputs. We describe how we apply global magnetic field models for conversion between flux and phase space density and, in particular, the benefits of using a self‐consistent, coupled ring current–magnetic field model. We discuss some of the results from DREAM including testing of boundary condition assumptions and effects of adding a source term to radial diffusion models. We also describe some of the testing and validation of DREAM and prospects for future development.
All Chinese to me
Authors: Jacobs Howy
Published: February 2012

English is nowadays the universal language of science. Howy argues that, to maximize their career prospects, prospective science students worldwide could benefit from English‐language immersion schooling from a young age.
Control of Brain Capillary Blood Flow
Authors: Itoh Yoshiaki , Suzuki Norihiro
Published: February 2012

While it has been widely confirmed that cerebral blood flow is closely coupled with brain metabolism, it remains a matter of controversy whether capillary flow is directly controlled to meet the energy demands of the parenchyma. Since the capillary is known to lack smooth muscle cells, it has generally been considered that capillary flow is not regulated in situ. However, we now have increasing data supporting the physiological control of capillary flow. The observation of heterogeneity in the microcirculation in vivo has suggested that intravascular factors may be involved in the flow control, including non-Newtonian rheology, red blood cell flow, leukocyte adhesion, release of vasoactive mediators, and expression of glycoproteins on the endothelial cells. Astrocytes, a key mediator of the neurovascular unit, and intrinsic innervation may also regulate capillary flow. In addition, recent findings on pericyte contractility have attracted the attention of many researchers. Finally, based on these findings, we present a new model of flow control, the proximal integration model, in which localized neural activity is detected at nearby capillaries and the vasodilation signal is transmitted proximally along the vessel. Signals are then integrated at the precapillary arterioles and other arterioles further upstream and regulate the capillary flow.
Limits to the detection of early warning signals of population collapse
Authors: Boettiger Carl , Hastings Alan
Published: February 2012

Background/Question/Methods

The recog-ni-tion that ecosys-tems can undergo sud-den shifts to alter-nate, less desir-able sta-ble states has led to the desire to iden-tify early warn-ing signs of these impend-ing col-lapses. This search has been moti-vated by the math-e-mat-ics of bifur-ca-tions, in which sud-den shifts result not from direct per-tur-ba-tions to the state (i.e. the pop-u-la-tion abun-dance, through mech-a-nisms such as over-harvesting) but to a slowly chang-ing para-me-ter that impacts the sys-tem sta-bil-ity. While these col-lapses can-not be antic-i-pated by observ-ing only the mean dynam-ics (as described by a deter-min-is-tic model), signs of the impend-ing col-lapse are expressed in the ran-dom per-tur-ba-tions, or noise, inher-ent in real sys-tems. The math-e-mat-i-cal the-ory of early warn-ing signs exploits this fact by seek-ing to detect pat-terns such as “crit-i-cal slow-ing down” of these per-tur-ba-tions due to the grad-ual loss of sta-bil-ity which leads to a bifurcation.While much atten-tion has been given to empha-siz-ing the exis-tence both of sud-den col-lapses and of signs of crit-i-cal slow-ing down, lit-tle atten-tion has been paid to its detec-tion. Faced with only finite data, any method risks both false alarms and failed detec-tion events. We believe that weigh-ing these risks must be the bur-den of man-age-ment pol-icy, while research must first pro-vide a reli-able way to quan-tify the rel-a-tive risks of each. We present a method which quan-ti-fies this risk and show how to decrease the uncer-tainty inher-ent in com-mon summary-statistic approaches through the use of a like-li-hood based mod-el-ing approach.

Results/Conclusions

We demon-strate that com-monly used cor-re-la-tion tests applied to sum-mary sta-tis-tics such as auto-cor-re-la-tion and vari-ance are both inap-pro-pri-ate and insuf-fi-cient tests of early warn-ing signals.Our method esti-mates directly the para-me-ters of a gen-er-al-ized model of the bifur-ca-tion pos-tu-lated by early warn-ing sig-nals the-ory, with and with-out the pres-ence of a grad-ual change lead-ing towards col-lapse. Using Monte Carlo sim-u-la-tion we gen-er-ate the dis-tri-b-u-tion of warning-signal sta-tis-tics expected under each model. From this we can quan-tify the risk of false alarms and missed detec-tion. We then show how apply-ing this approach to the data directly rather than the sum-mary sta-tis-tic increases the power of detec-tion. We illus-trate the approach in both sim-u-lated and empir-i-cal data of sud-den eco-log-i-cal shifts.
Rhodaninecarboxylic acids as novel inhibitors of histoneacetyltransferases
Authors: Furdas Silviya D. , Shekfeh Suhaib , Kannan Srinivasaraghavan , Sippl Wolfgang , Jung Manfred
Published: February 2012

Virtual screening has identified rhodanine containing carboxylic acids as new inhibitors of histone acetyltransferases.
A tapered channel microfluidic device for comprehensive cell adhesion analysis, using measurements of detachment kinetics and shear stress-dependent motion
Authors: Rupprecht Peter , Golé Laurent , Rieu Jean-Paul , Vézy Cyrille , Ferrigno Rosaria , Mertani Hichem C. , Rivière Charlotte
Published: February 2012

We have developed a method for studying cellular adhesion by using a custom-designed microfluidic device with parallel non-connected tapered channels. The design enables investigation of cellular responses to a large range of shear stress (ratio of 25) with a single input flow-rate. For each shear stress, a large number of cells are analyzed (500–1500 cells), providing statistically relevant data within a single experiment. Besides adhesion strength measurements, the microsystem presented in this paper enables in-depth analysis of cell detachment kinetics by real-time videomicroscopy. It offers the possibility to analyze adhesion-associated processes, such as migration or cell shape change, within the same experiment. To show the versatility of our device, we examined quantitatively cell adhesion by analyzing kinetics, adhesive strength and migration behaviour or cell shape modifications of the unicellular model cell organism Dictyostelium discoideum at 21 °C and of the human breast cancer cell line MDA-MB-231 at 37 °C. For both cell types, we found that the threshold stresses, which are necessary to detach the cells, follow lognormal distributions, and that the detachment process follows first order kinetics. In addition, for particular conditions’ cells are found to exhibit similar adhesion threshold stresses, but very different detachment kinetics, revealing the importance of dynamics analysis to fully describe cell adhesion. With its rapid implementation and potential for parallel sample processing, such microsystem offers a highly controllable platform for exploring cell adhesion characteristics in a large set of environmental conditions and cell types, and could have wide applications across cell biology, tissue engineering, and cell screening.
Symmetry chaotic attractors and bursting dynamics of semiconductor lasers subjected to optical injection
Authors: Mengue A. D. , Essimbi B. Z.
Published: February 2012

This paper presents the nonlinear dynamics and bifurcations of optically injected semiconductor lasers in the frame of relative high injection strength. The behavior of the system is explored by means of bifurcation diagrams; however, the exact nature of the involved dynamics is well described by a detailed study of the dynamics evolutions as a function of the effective gain coefficient. As results, we notice the different types of symmetry chaotic attractors with the riddled basins, supercritical pitchfork and Hopf bifurcations, crisis of attractors, instability of chaos, symmetry breaking and restoring bifurcations, and the phenomena of the bursting behavior as well as two connected parts of the same chaotic attractor which merge in a periodic orbit.
Dipolophoresis of dielectric spheroids under asymmetric fields
Authors: Frankel Itzchak , Yossifon Gilad , Miloh Touvia
Published: February 2012

Non-spherical particles are common in colloidal science. Spheroidal shapes are particularly convenient for the analysis of the pertinent electrostatic and hydrodynamic problems and are thus widely used to model the manipulation of biological cells as well as deformed drops and bubbles. We study the rotary motion of a dielectric spheroidal micro-particle which is freely suspended in an unbounded electrolyte solution in the presence of a uniform applied electric field, assuming a thin Debye layer. For the common case of a uniform distribution of the native surface-charge density, the rotary motion of the particle is generated by the contributions of the induced-charge electro-osmotic (ICEO) slip and the dielectrophoresis associated with the distribution of the Maxwell stress, respectively. Series solutions are obtained by using spheroidal (prolate or oblate) coordinates. Explicit results are presented for the angular velocity of particles spanning the entire spectrum from rod-like to disk-like shapes. These results demonstrate the non-monotonic variation of the angular speed with the eccentricity of particle shape and the singularity of the multiple limits corresponding to conducting (ideally polarizable) particles of extreme eccentricity (e ≈ 1). The non-monotonic variation of the angular speed with the particle dielectric permittivity is related to the induced-charge contribution. We apply these results to describe the motion of particles subject to a uniform field rotating in the plane. For a sufficiently slow rotation rate, prolate particles eventually become “locked” to the external field with their stationary relative orientation in the plane of rotation being determined by the particle eccentricity and dielectric constant. This effect may be of potential use in the manipulation of poly-disperse suspensions of dielectric non-spherical particles. Oblate spheroids invariably approach a uniform orientation with their symmetry axes directed normal to the external-field plane of rotation.
Magnetohydrodynamic instabilities in radial foil configurations
Authors: Gourdain P.-A. , Greenly J. B. , Hammer D. A. , Kusse B. R. , Pikuz S. A. , Seyler C. E. , Shelkovenko T. C. , Knapp P. F.
Published: February 2012

While detrimental to plasma performance, magnetohydrodynamic plasma instabilities in radial foil configurations do not preclude intense x-ray radiations from the central plasma column. As most of the plasma current flows there, the column pinches generating x-rays. However, pinch comes with a kink instability which twists the column and prevents homogeneous compression. This instability leads to the disruption of the plasma bubble surrounding the central plasma column. Loss of symmetry in the resulting plasma expansion has been recorded. It is possible to reduce the impact of instabilities by increasing the initial plasma mass. The central column can also be stabilized by using a central rod, delaying the formation of the kink.
Low-dimensional model of spatial shear layers
Authors: Wei Mingjun , Qawasmeh Bashar R. , Barone Matthew , van Bloemen Waanders Bart G. , Zhou Lin
Published: February 2012

The aim of this work is to develop nonlinear low-dimensional models to describe vortex dynamics in spatially developing shear layers with periodicity in time. By allowing a free variable g(x) to dynamically describe downstream thickness spreading, we are able to obtain basis functions in a scaled reference frame and construct effective models with only a few modes in the new space. To apply this modified version of proper orthogonal decomposition (POD)/Galerkin projection, we first scale the flow along y dynamically to match a template function as it is developing downstream. In the scaled space, the first POD mode can capture more than 80% energy for each frequency. However, to construct a Galerkin model, the second POD mode plays a critical role and needs to be included. Finally, a reconstruction equation for the scaling variable g is derived to relate the scaled space to physical space, where downstream spreading of shear thickness occurs. Using only two POD modes at each frequency, our models capture the basic dynamics of shear layers, such as vortex roll-up (from a one-frequency model) and vortex-merging (from a two-frequency model). When arbitrary excitation at different harmonics is added to the model, we can clearly observe the promoting or delaying/eliminating vortex merging events as a result of mode competition, which is commonly demonstrated in experiments and numerical simulations of shear layers.
Decaying versus stationary turbulence in particle-laden isotropic turbulence: Turbulence modulation mechanism
Authors: Abdelsamie Abouelmagd H. , Lee Changhoon
Published: February 2012

The objective of the current paper is to clarify the physical distinction between turbulence modulations by laden particles in decaying isotropic turbulence and stationary isotropic turbulence. Direct numerical simulations of stationary and decaying isotropic turbulence were carried out using 1283 grid points at a Taylor micro-scale Reynolds number of Rλ ∼ 70. The effect of O(106) solid particles with a different Stokes number (St) was implemented as a point-force approximation in the Navier-Stokes equation. Turbulent kinetic energy, acceleration, enstrophy, strain rate, and various spectra were examined to determine the distinctions. Turbulence modulation in decaying turbulence is qualitatively and quantitatively inconsistent compared to that in stationary turbulence, particularly when the particles have St ≤ 1, mainly due to the artificial forcing necessary for stationary status. For the particles with St > 1, however, decaying and stationary turbulence are qualitatively similar. A simple analysis confirms that stationary turbulence is not appropriate for the study of turbulence modulation by particles with St ≤ 1. Furthermore, the injection perturbation of particles has a significant effect on turbulence modulation in decaying turbulence. An investigation of the correlation between turbulence field zones and the two-way interaction energy was conducted to gain a better understanding of the modulation mechanism.
Combined depletion and electrostatic forces in polymer-induced membrane adhesion: A theoretical model
Authors: Raudino Antonio , Pannuzzo Martina , Karttunen Mikko
Published: February 2012

We develop a semi-quantitative analytical theory to describe adhesion between two identical planar charged surfaces embedded in a polymer-containing electrolyte solution. Polymer chains are uncharged and differ from the solvent by their lower dielectric permittivity. The solution mimics physiological fluids: It contains 0.1 M of monovalent ions and a small number of divalent cations that form tight bonds with the headgroups of charged lipids. The components have heterogeneous spatial distributions. The model was derived self-consistently by combining: (a) a Poisson-Boltzmann like equation for the charge densities, (b) a continuum mean-field theory for the polymer profile, (c) a solvation energy forcing the ions toward the polymer-poor regions, and (d) surface interactions of polymers and electrolytes. We validated the theory via extensive coarse-grained Molecular Dynamics (MD) simulations. The results confirm our analytical model and reveal interesting details not detected by the theory. At high surface charges, polymer chains are mainly excluded from the gap region, while the concentration of ions increases. The model shows a strong coupling between osmotic forces, surface potential and salting-out effects of the slightly polar polymer chains. It highlights some of the key differences in the behaviour of monomeric and polymeric mixed solvents and their responses to Coulomb interactions. Our main findings are: (a) the onset of long-ranged ion-induced polymer depletion force that increases with surface charge density and (b) a polymer-modified repulsive Coulomb force that increases with surface charge density. Overall, the system exhibits homeostatic behaviour, resulting in robustness against variations in the amount of charges. Applications and extensions of the model are briefly discussed.
Bouncing, coalescence, and separation in head-on collision of unequal-size droplets
Authors: Tang Chenglong , Zhang Peng , Law Chung K.
Published: February 2012

The dynamics of head-on collision of unequal-size droplets were experimentally and theoretically investigated, with emphasis on identifying distinct collision outcomes and interpreting the size-ratio dependence. A unified regime diagram in terms of bouncing, permanent coalescence, and separation after coalescence was identified for hydrocarbon and water droplets in the parameter space of the size ratio and a collision Weber number. Experimental results show that the transition Weber number, Web-c, that separates the bouncing and permanent coalescence regimes, weakly depends on the size ratio, while the transition Weber number, Wec-s, that separates permanent coalescence and separation regimes, significantly increases with the size ratio. A theoretical model based on energy balance and scaling analysis was developed to explain the size-ratio dependence of Wec-s. The theoretical results show good agreement with the experimental data for tetradecane and decane droplets, with a moderate discrepancy for water droplets.
Simple electronics for inertial and Pan-type piezoelectric positioners used in scanning probe microscopes
Authors: Chen LeuJen , Kim Seong Heon , Lee Alfred K. H. , de Lozanne Alex
Published: February 2012

We describe a new type of circuit designed for driving piezoelectric positioners that rely on the stick-slip phenomenon. The circuit can be used for inertial positioners that have only one piezoelectric element (or multiple elements that are moved simultaneously) or for designs using a sequential movement of independent piezoelectric elements. A relay switches the piezoelectric elements between a high voltage source and ground, thus creating a fast voltage step followed by a slow ramp produced by the exponential discharging of the piezoelectric elements through a series resistor. A timing cascade is generated by having each relay power the next relay in the sequence. This design is simple and inexpensive. While it was developed for scanning probe microscopes, it may be useful for any piezoelectric motor based on a fast jump followed by a slow relaxation.
Cutoff probe using Fourier analysis for electron density measurement
Authors: Na Byung-Keun , You Kwang-Ho , Kim Dae-Woong , Chang Hong-Young , You Shin-Jae , Kim Jung-Hyung
Published: February 2012

This paper proposes a new method for cutoff probe using a nanosecond impulse generator and an oscilloscope, instead of a network analyzer. The nanosecond impulse generator supplies a radiating signal of broadband frequency spectrum simultaneously without frequency sweeping, while frequency sweeping method is used by a network analyzer in a previous method. The transmission spectrum (S21) was obtained through a Fourier analysis of the transmitted impulse signal detected by the oscilloscope and was used to measure the electron density. The results showed that the transmission frequency spectrum and the electron density obtained with a new method are very close to those obtained with a previous method using a network analyzer. And also, only 15 ns long signal was necessary for spectrum reconstruction. These results were also compared to the Langmuir probe's measurements with satisfactory results. This method is expected to provide not only fast measurement of absolute electron density, but also function in other diagnostic situations where a network analyzer would be used (a hairpin probe and an impedance probe) by replacing the network analyzer with a nanosecond impulse generator and an oscilloscope.
Online in situ x-ray diffraction setup for structural modification studies during swift heavy ion irradiation
Authors: Grygiel C. , Lebius H. , Bouffard S. , Quentin A. , Ramillon J. M. , Madi T. , Guillous S. , Been T. , Guinement P. , Lelièvre D. , Monnet I.
Published: February 2012

The high energy density of electronic excitations due to the impact of swift heavy ions can induce structural modifications in materials. We present an x-ray diffractometer called ALIX (“Analyse en Ligne sur IRRSUD par diffraction de rayons X”), which has been set up at the low-energy beamline (IRRadiation SUD - IRRSUD) of the Grand Accélérateur National d’Ions Lourds facility, to allow the study of structural modification kinetics as a function of the ion fluence. The x-ray setup has been modified and optimized to enable irradiation by swift heavy ions simultaneously to x-ray pattern recording. We present the capability of ALIX to perform simultaneous irradiation–diffraction by using energy discrimination between x-rays from diffraction and from ion-target interaction. To illustrate its potential, results of sequential or simultaneous irradiation–diffraction are presented in this article to show radiation effects on the structural properties of ceramics. Phase transition kinetics have been studied during xenon ion irradiation of polycrystalline MgO and SrTiO3. We have observed that MgO oxide is radiation-resistant to high electronic excitations, contrary to the high sensitivity of SrTiO3, which exhibits transition from the crystalline to the amorphous state during irradiation. By interpreting the amorphization kinetics of SrTiO3, defect overlapping models are discussed as well as latent track characteristics. Together with a transmission electron microscopy study, we conclude that a single impact model describes the phase transition mechanism.
Dynamic thermomechanical response of bimaterial microcantilevers to periodic heating by infrared radiation
Authors: Kwon Beomjin , Rosenberger Matthew , Bhargava Rohit , Cahill David G. , King William P.
Published: February 2012

This paper investigates the dynamic thermomechanical response of bimaterial microcantilevers to periodic heating by an infrared laser operating at a wavelenegth of 10.35 μm. A model relates incident radiation, heat transfer, temperature distribution in the cantilever, and thermal expansion mismatch to find the cantilever displacement. Experiments were conducted on two custom-fabricated bimaterial cantilevers and two commercially available bimaterial microcantilevers. The cantilever response was measured as a function of the modulation frequency of the laser over the range of 0.01–30 kHz. The model and the method of cantilever displacement calibration can be applied for bimaterial cantilever with thick coating layer. The sensitivity and signal-to-noise of bimaterial cantilevers were evaluated in terms of either total incident power or incident flux. The custom-fabricated bimaterial cantilevers showed 9X or 190X sensitivity improvement compared to commercial cantilevers. The detection limit on incident flux is as small as 0.10 pW μm−2 Hz−1/2.
Using high-intensity laser-generated energetic protons to radiograph directly driven implosions
Authors: Zylstra A. B. , Li C. K. , Rinderknecht H. G. , Séguin F. H. , Petrasso R. D. , Stoeckl C. , Meyerhofer D. D. , Nilson P. , Sangster T. C. , Le Pape S. , Mackinnon A. , Patel P.
Published: February 2012

The recent development of petawatt-class lasers with kilojoule-picosecond pulses, such as OMEGA EP [L. Waxer et al., Opt. Photonics News 16, 30 (2005)10.1364/OPN.16.7.000030], provides a new diagnostic capability to study inertial-confinement-fusion (ICF) and high-energy-density (HED) plasmas. Specifically, petawatt OMEGA EP pulses have been used to backlight OMEGA implosions with energetic proton beams generated through the target normal sheath acceleration (TNSA) mechanism. This allows time-resolved studies of the mass distribution and electromagnetic field structures in ICF and HED plasmas. This principle has been previously demonstrated using Vulcan to backlight six-beam implosions [A. J. Mackinnon et al., Phys. Rev. Lett. 97, 045001 (2006)10.1103/PhysRevLett.97.045001]. The TNSA proton backlighter offers better spatial and temporal resolution but poorer spatial uniformity and energy resolution than previous D3He fusion-based techniques [C. Li et al., Rev. Sci. Instrum. 77, 10E725 (2006)10.1063/1.2228252]. A target and the experimental design technique to mitigate potential problems in using TNSA backlighting to study full-energy implosions is discussed. The first proton radiographs of 60-beam spherical OMEGA implosions using the techniques discussed in this paper are presented. Sample radiographs and suggestions for troubleshooting failed radiography shots using TNSA backlighting are given, and future applications of this technique at OMEGA and the NIF are discussed.
From mesoscopic to global polar order in the uniaxial relaxor ferroelectric Sr0.8Ba0.2Nb2O6
Authors: Dec J. , Kleemann W. , Shvartsman V. V. , Lupascu D. C. , Łukasiewicz T.
Published: February 2012

In the relaxor ferroelectric Sr0.8Ba0.2Nb2O6 (SBN80) the relaxation of polar nanoregions (PNRs) reveals an anisotropic breathing mode when approaching the transition temperature, TC ≈ 289 K, on cooling. Two distinct dispersion steps and peaks, respectively, of the complex susceptibility components in the milli- and megahertz frequency range reflect their large length-to-width aspect ratio. Below TC power-law frequency dispersion characterizes the creep motion of the emerging ferroelectric domain walls and the fractal dimension D ≈ 2 of their contour lines. Piezoforce micrographs reveal nanometric jagged domains in accordance with the large disorder and random field magnitude in the extreme relaxor SBN80.
Non-equilibrium umbrella sampling applied to force spectroscopy of soft matter
Authors: Gao Y. X. , Wang G. M. , Williams D. R. M. , Williams Stephen R. , Evans Denis J. , Sevick E. M.
Published: February 2012

Physical systems often respond on a timescale which is longer than that of the measurement. This is particularly true in soft matter where direct experimental measurement, for example in force spectroscopy, drives the soft system out of equilibrium and provides a non-equilibrium measure. Here we demonstrate experimentally for the first time that equilibrium physical quantities (such as the mean square displacement) can be obtained from non-equilibrium measurements via umbrella sampling. Our model experimental system is a bead fluctuating in a time-varying optical trap. We also show this for simulated force spectroscopy on a complex soft molecule—a piston-rotaxane.
Optical detection of melting point depression for silver nanoparticles via in situ real time spectroscopic ellipsometry
Authors: Little S. A. , Begou T. , Collins R. W. , Marsillac S.
Published: February 2012

Silver nanoparticle films were deposited by sputtering at room temperature and were annealed while monitoring by real time spectroscopic ellipsometry (SE). The nanoparticle dielectric functions (0.75 eV–6.5 eV) obtained by SE were modeled using Lorentz and generalized oscillators for the nanoparticle plasmon polariton (NPP) and interband transitions, respectively. The nanoparticle melting point could be identified from variations in the oscillator parameters during annealing, and this identification was further confirmed after cooling through significant, irreversible changes in these parameters relative to the as-deposited film. The variation in melting point with physical thickness, and thus average nanoparticle diameter, as measured by SE enables calculation of the surface energy density.
Functional plasma polymers deposited in capacitively and inductively coupled plasmas
Authors: Hegemann Dirk , Körner Enrico , Chen Shang , Benedikt Jan , von Keudell Achim
Published: February 2012

Capacitively and inductively coupled plasmas were investigated in order to deposit functional plasma polymers. Considering plasma chemical and surface processes, comparable films can be obtained with both plasma sources yielding distinctly higher deposition rates for ICP. While the gas phase processes scaled with the energy input into the plasma, the surface processes were controlled by the energy dissipated during film growth (ion bombardment).
Understanding metal doping for organic electron transport layers
Authors: Mityashin Alexander , Cheyns David , Rand Barry P. , Heremans Paul
Published: February 2012

This work concerns the physical mechanisms of metal n-doping in charge transport layers for optoelectronic devices, for which the doping level is constrained by transparency requirements so as to avoid parasitic absorption. Comparing various metal dopants, we claim that enhanced conductivity at low doping is initiated by the electrical doping effect, namely, metal-semiconductor charge donation. Electrical measurements show that doping effects at low concentration strongly depend on the work function of the introduced metal, and not every metal works as an efficient dopant. Practical applicability is demonstrated by introducing doped transport layers in prototypical bilayer solar cells in conventional and inverted architectures.
ZnS-nanocrystals/polypyrrole nanocomposite film based immunosensor
Authors: Mishra Sujeet K. , Pasricha Renu , Biradar Ashok M , Rajesh
Published: February 2012

We report an electrochemically synthesized ZnS nanocrystals modified polypyrrole (PPy) nanocomposite film based immunosensor for the detection of C-reactive protein (αCRP). The ZnS-PPy composite film was characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and electrochemical techniques. The modified film showed good biocompatibility with efficient binding to protein antibody (αCRP-Ab) molecules through ZnS nanocrystals, exhibited an attractive platform for immunosensor fabrication. The electrical and sensing properties of the polymer composite film of different thickness towards protein antigen (αCRP-Ag) were delineated. The immunosensor exhibited an impedance response to αCRP-Ag concentration in a linear range from 10 ng to 10 μg mL−1.
Plasma enables edge-to-center-oriented graphene nanoarrays on Si nanograss
Authors: Kumar S. , Levchenko I. , Cheng Q. J. , Shieh J. , Ostrikov K.
Published: February 2012

The formation of clearly separated vertical graphene nanosheets on silicon nanograss support is demonstrated. The plasma-enabled, two-stage mask-free process produced self-organized vertical graphenes of a few carbon layers (as confirmed by advanced microanalysis), prominently oriented in the substrate center–substrate edge direction. It is shown that the width of the alignment zone depends on the substrate conductivity, and thus the electric field in the vicinity of the growth surface is responsible for the graphene alignment. This finding is confirmed by the Monte Carlo simulations of the ion flux distribution in the silicon nanograss pattern.
All-metallic lateral spin valves using Co2Fe(Ge0.5Ga0.5) Heusler alloy with a large spin signal
Authors: Takahashi Y. K. , Kasai S. , Hirayama S. , Mitani S. , Hono K.
Published: February 2012

A large spin signal (ΔRs) of 12.8 mΩ at room temperature is demonstrated in an all-metallic lateral spin valve (LSV) device comprising of ferromagnetic wire of a highly spin-polarized Co2Fe(Ge0.5Ga0.5) Heusler alloy and a Cu wire. From the results on multi-terminal LSV devices, the origin of the large ΔRs was concluded to be the high spin polarization of Co2Fe(Ge0.5Ga0.5) and the resultant small spin absorption. The all-metallic LSV device without MgO barrier has low contact resistance, which is considered to be beneficial for a high frequency ultrathin read sensor for the next generation ultrahigh density magnetic recording.
Anaerobic fermentation hydrogen production from apple residue: Effects of sludge pretreatments
Authors: Wang Hui , Xu Hui , Ma Shenghua , Zhi Zelun , Wang Xiaofang , Fang Zhong , Fang Ming , Bai Jintao
Published: February 2012

Activated sludge from sewage treatment plant was tested for their suitability as inoculum source for the fermentation H2 production. A series of batch experiments were conducted to study the effects of various sludge pretreatments (domestication, boiling, acid, and alkali) on the fermentative H2 production from apple residue. The sludge domestication process markedly shortens the H2-producing lag time, and H2 gas was produced only 5 min after mixing the sludge and substrate. The boiling pretreatment of the sludge is better than the acid and alkali pretreatments in enhancing hydrogen yield from apple residue. The best domestication and boiling time for the sludge were 6 h and 30 min, respectively. A maximum cumulative H2 yield of 87.33 ml·g−1-TS with an average H2 production rate of 14.56 ml·g−1-TS·h−1 was obtained at the fermentation temperature of 37 °C, initial pH 7.0, and substrate concentrate of 20 g·l−1.
Enhancement of random lasing assisted by light scattering and resonance energy transfer based on ZnO/SnO nanocomposites
Authors: Wang C. S. , Lin H. Y. , Lin T. H. , Chen Y. F.
Published: February 2012

A new composite consisting of ZnO nanorods and SnO nanoparticles has been synthesized and characterized. It is found that the UV laser emission from ZnO NRs can be greatly enhanced and more easily achieved by the assistance of SnO NPs. The underlying mechanism is interpreted in terms of light scattering, charge carrier transfer and fluorescence resonance energy transfer (FRET) mediated by SnO NPs. Our strategy opens a promising route for improving the external conversion efficiency of optoelectronic devices.
Optical-fiber microcavities reach angstrom-scale precision
Authors: Wilson R. Mark
Published: February 2012

Using heat and light to subtly vary the local radius and refractive index of a glass fiber is a simple and surprisingly reproducible way to create and tune a microresonator.
From cells to limbs, UK center studies war injuries
Authors: Feder Toni
Published: February 2012

More people are surviving with worse injuries than ever before.
A century of cosmic rays
Authors: Carlson Per
Published: February 2012

Twenty years after puzzling atmospheric ionization led to the discovery of cosmic rays, their investigation opened up particle physics. Now they’re providing a window on extragalactic astrophysics.
Mikhail Lomonosov and the dawn of Russian science
Authors: Shiltsev Vladimir
Published: February 2012

Curiously unsung in the West, Lomonosov broke ground in physics, chemistry, and astronomy; won acclaim as a poet and historian; and was a key figure of the Russian Enlightenment.
Women in physics: A tale of limits
Authors: Ivie Rachel , Tesfaye Casey Langer
Published: February 2012

A newly completed survey of 15 000 physicists worldwide reveals that women physicists still do not have equal access to the career-advancing resources and opportunities enjoyed by their male colleagues.
Hydraulic connectivity from roots to branches depicted through sap flow: analysis on a Quercus suber tree
Authors: David Teresa S. , David Jorge S. , Pinto Clara A. , Cermak Jan , Nadezhdin Valery , Nadezhdina Nadezhda
Published: February 2012

The topology of the xylem network is likely to affect the transport of water, propagation of embolism and plant survival and growth. Few studies have been conducted on the hydraulics of the entire water pathway in trees. We evaluated the hydraulic connections from roots to branches in a mature Quercus suber L. tree, through sap flow responses upon branch severing. Sap flow was recorded in branches, stem and roots by the heat field deformation (HFD) method. Results showed that roots, except for the taproot, were hydraulically connected to all branches, but the rest of the tree (stem, branches and taproot) was highly sectored. In the large roots that showed an integrated response to branch severing, the outer xylem was preferentially connected to the same side branch and the inner xylem to the opposite branch. The hydraulic sectoriality in branches, stem and taproot may be regarded as an adaptive trait to water stress. The integrated hydraulic structure of roots is advantageous under patchy soil conditions, but may allow the spread of root diseases. The HFD sap flow method proved extremely useful to calculate xylem flux connectivity between different organs of a large tree, providing a comprehensive picture of its hydraulic architecture.
Postpartum emotional support: a qualitative study of women’s and men’s anticipated needs and preferred sources
Authors: Rowe Heather J. , Holton Sara , Fisher Jane R. W.
Published: February 2012

Australian health policy emphasises prevention, early intervention and improved pathways to treatment for perinatal mental disorders. Primary care is vital to achieving these aims. The aim of this study was to understand the anticipated needs and preferred sources of mental health information and support of men and women expecting their first baby. Nulliparous English-speaking expectant parents attending childbirth education programs in public and private hospitals participated in single sex small group discussions in late pregnancy. Discussions were audio-recorded, transcribed and analysed thematically using the group as the unit of analysis. Eight groups (22 women; 16 men) encompassing diverse socioeconomic circumstances were conducted. Analyses showed idealised fantasies consistently tempered with realistic expectations about adjustment to life with a baby. However, there were diverse and gendered views about whether primary care providers should discuss mental health with parents of infants and willingness to complete written questionnaires or be referred for specialist mental health care. Men regard primary family care as mother not father inclusive. Expectant parents readily anticipate realistic postnatal adjustment and need for emotional support. Increased provision of services that meet men’s needs and public understanding and acceptance of Australian integrated models of primary postnatal mental health care are needed.
The human circadian metabolome
Authors: Dallmann Robert , Viola Antoine U. , Tarokh Leila , Cajochen Christian , Brown Steven A.
Published: February 2012

The circadian clock orchestrates many aspects of human physiology, and disruption of this clock has been implicated in various pathologies, ranging from cancer to metabolic syndrome and diabetes. Although there is evidence that metabolism and the circadian clockwork are intimately linked on a transcriptional level, whether these effects are directly under clock control or are mediated by the rest–activity cycle and the timing of food intake is unclear. To answer this question, we conducted an unbiased screen in human subjects of the metabolome of blood plasma and saliva at different times of day. To minimize indirect effects, subjects were kept in a 40-h constant routine of enforced posture, constant dim light, hourly isocaloric meals, and sleep deprivation. Under these conditions, we found that ∼15% of all identified metabolites in plasma and saliva were under circadian control, most notably fatty acids in plasma and amino acids in saliva. Our data suggest that there is a strong direct effect of the endogenous circadian clock on multiple human metabolic pathways that is independent of sleep or feeding. In addition, they identify multiple potential small-molecule biomarkers of human circadian phase and sleep pressure.
Quantifying Mortal Injury of Juvenile Chinook Salmon Exposed to Simulated Hydro‐Turbine Passage
Authors: Brown Richard S. , Carlson Thomas J. , Gingerich Andrew J. , Stephenson John R. , Pflugrath Brett D. , Welch Abigail E. , Langeslay Mike J. , Ahmann Martin L. , Johnson Robert L. , Skalski John R. , Seaburg Adam G. , Townsend Richard L.
Published: February 2012

A proportion of juvenile Chinook salmon Oncorhynchus tshawytscha and other salmonids travel through one or more turbines during their seaward migration in the Columbia and Snake rivers. There is limited information on how these fish respond to the hydraulic pressures found during turbine passage events. We exposed juvenile Chinook salmon to varied acclimation pressures and subsequent exposure pressures to mimic the hydraulic pressures of large Kaplan turbines. Additionally, we varied abiotic (total dissolved gas and rate of pressure change) and biotic factors (condition factor, fish length, and fish weight) that may contribute to the incidence of mortal injury associated with fish passage through hydropower turbines. We determined that the main factor associated with the mortal injury of juvenile Chinook salmon during simulated turbine passage was the ratio between the acclimation pressure and the lowest exposure pressure. Condition factor, total dissolved gas, and rate of pressure change were found to only slightly increase the predictive power of the equations relating the probability of mortal injury to the conditions of exposure or the characteristics of the test fish during simulated turbine passage. This research should assist engineers and fisheries managers in operating and improving hydroelectric facilities while minimizing mortality and injury to turbine‐passed juvenile Chinook salmon. Using these data, models can be built that might determine how much mortal injury is present at different turbine operations as pressures change. Further, pressure data coupled with the mortal injury data should be useful to engineers and turbine manufacturers when designing new turbines, which could not only increase power generation and efficiency but also minimize barotrauma to the fish that pass through them.
Bioenergetics and Population Dynamics of Flannelmouth Sucker and Bluehead Sucker in Grand Canyon as Evidenced by Tag Recapture Observations
Authors: Walters Carl J. , van Poorten Brett T. , Coggins Lewis G.
Published: February 2012

Flannelmouth suckers Catostomus latipinnus and bluehead suckers C. discolobus in the Grand Canyon of the Colorado River are among the few native species to persist after river conditions changed with the completion of Glen Canyon Dam in 1963. To evaluate the effectiveness of adaptive management manipulations to the system for recovering native species, it is necessary to estimate basic demographic and population dynamic parameters for the species of interest, such as growth, mortality, and recruitment. With this in mind, we present a two‐stage analysis in which we first estimated growth and individual ages using a field‐based bioenergetics model and then input the age estimates into age‐structured mark–recapture (ASMR) models to estimate mortality and recruitment. The analysis was based on 18,500 flannelmouth suckers and 13,975 bluehead suckers that had been tagged with passive integrated transponder tags in the main‐stem Colorado River in Grand Canyon and its tributaries since 1989. The bioenergetics estimates of growth suggest that the growth of flannelmouth suckers is faster and that of bluehead suckers slower than in the tributaries reported in other studies. The results from the bioenergetics model provide necessary parameters for input into future ecosystem models. The ASMR models that include the effects of age‐specific gear vulnerability indicate that annual natural mortality rates are about 0.2 for flannelmouth suckers and 0.4 for bluehead suckers, which is in agreement with independent estimates from growth parameters and longevity. The estimates of age‐1 sucker recruitment and adult abundance correspond well with independent electrofishing catch rate data. The estimated recruitment and abundance estimates provide insights into the efficacy of adaptive management actions targeted to benefit native fishes over the past two decades.
Evaluation of Tannic Acid for Disinfection of Rainbow Trout Eggs
Authors: Wagner Eric J , Oplinger Randall W , Bartley Matthew
Published: February 2012

Because of its bactericidal properties, tannic acid was evaluated as a potential egg disinfectant for rainbow trout Oncorhynchus mykiss. After water hardening, eggs were disinfected with tannic acid (2, 20, or 200 mg/L for 5 or 15 min) or with iodine (100 mg/L for 10 min; control). Hatch (83.7–93.4%) and deformity percentages (<0.8%) did not significantly differ among treatments. Bacteriological data indicated that the percentage of eggs with no bacteria was significantly higher from the iodine treatment (87%) than from the tannic acid treatments (29.2–50.0%). Therefore, we found that tannic acid was safe to use on rainbow trout eggs at concentrations of up to 200 mg/L for 15 min, but the control of bacteria was inferior to that provided by the standard iodine treatment.