bluuebunny/crossref_metadata_2025 huggingface dataset:
The Galactic Centre - a laboratory for starburst galaxies (?)
Authors: Crocker Roland M.
Published: August 2012

The Galactic centre – as the closest galactic nucleus – holds both intrinsic interest and possibly represents a useful analogue to starburst nuclei which we can observe with orders of magnitude finer detail than these external systems. The environmental conditions in the GC – here taken to mean the inner 200 pc in diameter of the Milky Way – are extreme with respect to those typically encountered in the Galactic disk. The energy densities of the various GC ISM components are typically ~two orders of magnitude larger than those found locally and the star-formation rate density ~three orders of magnitude larger. Unusually within the Galaxy, the Galactic centre exhibits hard-spectrum, diffuse TeV (=1012 eV) gamma-ray emission spatially coincident with the region's molecular gas. Recently the nuclei of local starburst galaxies NGC 253 and M82 have also been detected in gamma-rays of such energies. We have embarked on an extended campaign of modelling the broadband (radio continuum to TeV gamma-ray), non- thermal signals received from the inner 200 pc of the Galaxy. On the basis of this modelling we find that star-formation and associated supernova activity is the ultimate driver of the region's non-thermal activity. This activity drives a large-scale wind of hot plasma and cosmic rays out of the GC. The wind advects the locally-accelerated cosmic rays quickly, before they can lose much energy in situ or penetrate into the densest molecular gas cores where star-formation occurs. The cosmic rays can, however, heat/ionize the lower density/warm H2 phase enveloping the cores. On very large scales (~10 kpc) the non-thermal signature of the escaping GC cosmic rays has probably been detected recently as the spectacular ‘Fermi bubbles’ and corresponding ‘YWMAP haze’.
Constraints on the optical-IR extragalactic background from γ-ray absorption studies
Authors: Costamante Luigi
Published: August 2012

Very high energy (VHE ≳0.1 TeV) gamma-rays from extragalactic sources, interacting by γ-γ collisions with diffuse intergalactic radiation fields, provide an alternative way to constrain the diffuse background light, completely independent of direct measurements. The limits depend however on our knowledge of the physics of the gamma-ray sources. After clarifying the interplay between background light and VHE spectra, I summarize the extent and validity of the obtainable limits, and where future improvements can be expected.
Cosmic Optical Background: the view from Pioneer 10/11
Authors: Matsuoka Y. , Ienaka N. , Kawara K. , Oyabu S.
Published: August 2012

We present the new constraints on the cosmic optical background (COB) obtained from an analysis of the Pioneer 10/11 Imaging Photopolarimeter (IPP) data. After careful examination of data quality, the usable measurements free from the zodiacal light are integrated into sky maps at the blue (~0.44 μm) and red (~0.64 μm) bands. Accurate starlight subtraction is achieved by referring to all-sky star catalogs and a Galactic stellar population synthesis model down to 32.0 mag. We find that the residual light is separated into two components: one component shows a clear correlation with thermal 100 μm brightness, while another betrays a constant level in the lowest 100 μm brightness region. Presence of the second component is significant after all the uncertainties and possible residual light in the Galaxy are taken into account, thus it most likely has the extragalactic origin (i.e., the COB). The derived COB brightness is (1.8 ± 0.9) × 10−9 and (1.2 ± 0.9) × 10−9 erg s−1 cm−2 sr−1 Å−1 at the blue and red band, respectively, or 7.9 ± 4.0 and 7.7 ± 5.8 nW m−2 sr−1. Based on a comparison with the integrated brightness of galaxies, we conclude that the bulk of the COB is comprised of normal galaxies which have already been resolved by the current deepest observations. There seems to be little room for contributions of other populations including “first stars” at these wavelengths. On the other hand, the first component of the IPP residual light represents the diffuse Galactic light (DGL)---scattered starlight by the interstellar dust. We derive the mean DGL-to-100 μm brightness ratios of 2.1 × 10−3 and 4.6 × 10−3 at the two bands, which are roughly consistent with the previous observations toward denser dust regions. Extended red emission in the diffuse interstellar medium is also confirmed.
Evolutionary Map of the Universe
Authors: Norris Ray P.
Published: August 2012

EMU is a wide-field radio continuum survey planned for the new Australian Square Kilometre Array Pathfinder (ASKAP) telescope, due to be completed in 2012. The primary goal of EMU is to make a deep (~10μJy/bm rms) radio continuum survey of the entire Southern Sky at 1.4 GHz, extending as far North as +30° declination, with a 10 arcsec resolution. EMU is expected to detect and catalog about 70 million galaxies, including typical star-forming galaxies up to z = 1, powerful starbursts to even greater redshifts, and AGNs to the edge of the Universe. EMU will undoubtedly discover new classes of object. Here I present the science goals and survey parameters.
Effect of photo‐dissociation on the spreading of OH and O clouds in Saturn's inner magnetosphere
Authors: Tadokoro Hiroyasu , Misawa Hiroaki , Tsuchiya Fuminori , Katoh Yuto , Morioka Akira , Yoneda Mizuki
Published: August 2012

We examine the contribution of photo‐dissociation under quiet solar conditions to the global OH and O distributions in Saturn's inner magnetosphere by performing a Monte Carlo simulation. We first calculate the H2O distribution generated by H2O sources, namely Enceladus' cryo‐volcanic plumes, satellite sputtering, and E ring sputtering. We calculate the OH distribution through photo‐dissociation reactions using the calculated H2O distribution and then calculate the O distribution from the obtained H2O and OH distributions. We quantitatively evaluate the role of the energy increment of produced OH and O particles due to photo‐dissociation by comparing the resultant distribution of OH and O particles with and without the energy increment. To quantitatively examine the effect of photo‐dissociation on the spreading of OH and O clouds, we use the H2O model including charge exchange and neutral/neutral collisions based on Cassidy and Johnson (2010), as the initial distribution. For the OH (O) density in the region outside 5 Rs (6 Rs), the density with energy increment is greater than that without energy increment. The contribution of calculated OH density with energy increment to the observation is more than ∼10%. The OH ratio outside 6 Rs decreases with radial distance from Saturn. On the other hand, the contribution of calculated O density with energy increment to the observation is less than 10% except for around Enceladus.
Can time domain and source area tracers reduce uncertainty in rainfall‐runoff models in larger heterogeneous catchments?
Authors: Capell R. , Tetzlaff D. , Soulsby C.
Published: August 2012

We used both time domain (deuterium) and source area (alkalinity) tracers to reduce uncertainty in simple conceptual rainfall‐runoff models applied to a larger (749 km2) heterogeneous catchment with both upland and lowland headwaters. Stepwise, tracer‐aided model development resulted in different model structures for the uplands and lowlands as representative elementary watersheds (REWs). These were differentiated by the parameterization of a nonlinear overland flow mechanism in the former, and the incorporation of high soil moisture storage capacity in the latter. Use of tracers and recession characteristics also helped to reduce parameter uncertainty and provided models that could simulate flows and tracer responses reasonably well over a full hydrological year. However, it was apparent that other processes (e.g., more complex mixing, fractionation, etc.) would need to be parameterized to explain the full variation in isotope dynamics. It is also evident that the information content of tracer data declines as the intensity of sampling decreases, particularly in the lowlands. The models of the REWs were coupled to provide plausible simulations of the up‐scaled flow and tracer response at the outfall of the 749 km2catchment, though the usefulness of source area tracers decreased markedly at this larger scale. Whereas the approach provides a step toward simple models that are likely to give the “right answer for the right reasons,” further improvements appear to require increased parameterization and/or higher‐resolution tracer data.
Biological productivity along Line P in the subarctic northeast Pacific: In situ versus incubation‐based methods
Authors: Giesbrecht Karina E. , Hamme Roberta C. , Emerson Steven R.
Published: August 2012

We compared net community production determined from an in situ O2/Ar mass balance (O2/Ar‐NCP) with incubation measurements of new and primary production in the subarctic northeast Pacific. In situ O2/Ar‐NCP was strongly correlated to new production from 24‐h15NO3− uptake integrated over the mixed layer (15N‐NewP), if measurements were separated into high and low‐productivity conditions. Under high‐productivity conditions, O2/Ar‐NCP estimates were similar to15N‐NewP, whereas under low productivity conditions O2/Ar‐NCP was up to two times higher than15N‐NewP. The relationship between O2/Ar‐NCP and 24‐h13C primary production (13C‐PP) was more variable, but with a consistent mean O2/Ar‐NCP:13C‐PP ratio of 0.52 ± 0.17 when only low‐productivity, summer measurements were considered. This relationship with primary production is perturbed by high productivity events such as a late‐summer, iron‐stimulated bloom observed at the offshore stations. Finally, we show that diapycnal mixing usually dominates the O2/Ar mass balance in winter in the subarctic Pacific, preventing the determination of NCP by the O2/Ar method at that time, except for one unusual stratification event in February 2007.
Slow‐slip evolves into megathrust earthquakes in 2D numerical simulations
Authors: Segall Paul , Bradley Andrew M.
Published: August 2012

Slow slip events (SSE) in many subduction zones incrementally stress the adjacent locked megathrust, suggesting that they could potentially either trigger or evolve into damaging earthquakes. We explore this with 2D quasi‐dynamic simulations with rate‐state friction, dilatancy, and coupled 1D pore‐fluid and heat transport. Steady‐state weakening friction allows transient slip to nucleate, but is inhibited by dilatant strengthening and destabilized by thermal pressurization. SSE spontaneously nucleate in Low Effective‐Stress Velocity‐Weakening (LESVW) regions. If the dimension of the LESVW is relatively small the SSE are trapped at its updip end, imparting a strong stress concentration in the locked zone. After several centuries SSE penetrate into the region of higher effective stress, where thermal pressurization eventually leads to dynamic rupture. For larger LESVW regions SSE tend to increase in length with time; ultimately higher slip speeds enhance thermal weakening, leading to dynamic instability within the SSE zone. In both cases the onset of the ultimate SSE is essentially indistinguishable from preceding events.
Quantifying the impact of dust on heterogeneous ice generation in midlevel supercooled stratiform clouds
Authors: Zhang Damao , Wang Zhien , Heymsfield Andrew , Fan Jiwen , Liu Dong , Zhao Ming
Published: August 2012

Dust aerosols have been regarded as effective ice nuclei (IN), but large uncertainties regarding their efficiencies remain. Here, four years of collocated CALIPSO and CloudSat measurements are used to quantify the impact of dust on heterogeneous ice generation in midlevel supercooled stratiform clouds (MSSCs) over the ‘dust belt’. The results show that the dusty MSSCs have an up to 20% higher mixed‐phase cloud occurrence, up to 8 dBZ higher mean maximum Ze (Ze_max), and up to 11.5 g/m2 higher ice water path (IWP) than similar MSSCs under background aerosol conditions. Assuming similar ice growth and fallout history in similar MSSCs, the significant differences in Ze_max between dusty and non‐dusty MSSCs reflect ice particle number concentration differences. Therefore, observed Ze_max differences indicate that dust could enhance ice particle concentration in MSSCs by a factor of 2 to 6 at temperatures colder than −12°C. The enhancements are strongly dependent on the cloud top temperature, large dust particle concentration and chemical compositions. These results imply an important role of dust particles in modifying mixed‐phase cloud properties globally.
Improving the responses of the Australian community land surface model (CABLE) to seasonal drought
Authors: Li Longhui , Wang Ying‐Ping , Yu Qiang , Pak Bernard , Eamus Derek , Yan Junhua , van Gorsel Eva , Baker Ian T.
Published: August 2012

Correct representations of root functioning, such as root water uptake and hydraulic redistribution, are critically important for modeling the responses of vegetation to droughts and seasonal changes in soil moisture content. However, these processes are poorly represented in global land surface models. In this study, we incorporated two root functions: a root water uptake function which assumes root water uptake efficiency varies with rooting depth, and a hydraulic redistribution function into a global land surface model, CABLE. The water uptake function developed by Lai and Katul (2000) was also compared with the default one (see Wang et al., 2010) that assumes that efficiency of water uptake per unit root length is constant. Using eddy flux measurements of CO2 and water vapor fluxes at three sites experiencing different patterns of seasonal changes in soil water content, we showed that the two root functions significantly improved the agreement between the simulated fluxes of net ecosystem exchange and latent heat flux and soil moisture dynamics with those observed during the dry season while having little impact on the model simulation during the wet seasons at all three sites. Sensitivity analysis showed that varying several model parameters influencing soil water dynamics in CABLE did not significantly affect the model's performance. We conclude that these root functions represent a valuable improvement for land surface modeling and should be implemented into CABLE and other land surface models for studying carbon and water dynamics where rainfall varies seasonally or interannually.
Amino-derivatives of the sesquiterpene lactone class of natural products as prodrugs
Authors: Woods James R. , Mo Huaping , Bieberich Andrew A. , Alavanja Tanja , Colby David A.
Published: August 2012

The medicinal chemistry of amino-derivatives of the sesquiterpene lactones is described, beginning with synthetic development, moving into pharmacological applications, and finishing with clinical translation.
Muscarinic receptors stimulate AC2 by novel phosphorylation sites, whereas Gβγ subunits exert opposing effects depending on the G-protein source
Authors: Shen Jia X. , Wachten Sebastian , Halls Michelle L. , Everett Katy L. , Cooper Dermot M. F.
Published: August 2012

Direct phosphorylation of AC2 (adenylyl cyclase 2) by PKC (protein kinase C) affords an opportunity for AC2 to integrate signals from non-canonical pathways to produce the second messenger, cyclic AMP. The present study shows that stimulation of AC2 by pharmacological activation of PKC or muscarinic receptor activation is primarily the result of phosphorylation of Ser490 and Ser543, as opposed to the previously proposed Thr1057. A double phosphorylation-deficient mutant (S490/543A) of AC2 was insensitive to PMA (phorbol myristic acid) and CCh (carbachol) stimulation, whereas a double phosphomimetic mutant (S490/543D) mimicked the activity of PKC-activated AC2. Putative Gβγ-interacting sites are in the immediate environment of these PKC phosphorylation sites (Ser490 and Ser543) that are located within the C1b domain of AC2, suggesting a significant regulatory importance of this domain. Consequently, we examined the effect of both Gq-coupled muscarinic and Gi-coupled somatostatin receptors. Employing pharmacological and FRET (fluorescence resonance energy transfer)-based real-time single cell imaging approaches, we found that Gβγ released from the Gq-coupled muscarinic receptor or Gi-coupled somatostatin receptors exert inhibitory or stimulatory effects respectively. These results underline the sophisticated regulatory capacities of AC2, in not only being subject to regulation by PKC, but also and in an opposite manner to Gβγ subunits, depending on their source.
Concept to diagnose mix with imaging x-ray Thomson scattering
Authors: Keiter Paul A. , Gamboa Eliseo J. , Huntington Channing M. , Kuranz Carolyn C.
Published: August 2012

Turbulent mixing of two fluid species is a ubiquitous problem, prevalent in systems such as inertial confinement fusion (ICF) capsule implosions, supernova remnants, and other astrophysical systems. In complex, high Reynolds number compressible high energy density (HED) flows such as these, hydrodynamic instabilities initiate the turbulent mixing process, which can then feedback and alter the mean hydrodynamic motion through nonlinear processes. In order to predict how these systems evolve under turbulent conditions, models are used. However, these models require detailed quantitative data to validate and constrain their detailed physics models as well as improve them. Providing this much needed data is currently at the forefront of HED research but is proving elusive due to a lack of available diagnostics capable of directly measuring detailed flow variables. Thomson scattering is a promising technique in this regard as it provides fundamental conditions of the flow (ρ, T, Zbar) due to its direct interaction with the small scales of the fluid or plasma and was recently considered as a possible mix diagnostic. With the development of imaging x-ray Thomson scattering (IXRTS) obtaining spatial profiles of these variables is within reach. We propose a novel use of the IXRTS technique that will provide more detailed quantitative data required for model validation in mix experiments.
Disorder-activated Raman spectra of cubic rocksalt-type Li(1−x)/2Ga(1−x)/2MxO (M = Mg, Zn) alloys
Authors: Lei Li , Ohfuji Hiroaki , Irifune Tetsuo , Qin Jiaqian , Zhang Xinyu , Shinmei Toru
Published: August 2012

Disorder-activated phonon behaviors of the cubic rocksalt-type semiconductor alloy Li(1−x)/2Ga(1−x)/2MxO (M = Mg, Zn) prepared by high-pressure and high-temperature method has been studied by Raman scattering analysis. The LO Raman phonon in Li(1−x)/2Ga(1−x)/2MxO was found to exhibit a distinct two-mode behavior. The compositional dependence of Raman frequency, peak-width, and intensity has been discussed. A model associated with a composite mode of the Brillouin zone center and edge phonons combined with phonon dispersion curves determined by first-principle calculations were employed to explain the asymmetric broadening of the LO phonon mode. The broadening and asymmetric Raman line-shape in Li(1−x)/2Ga(1−x)/2MxO can be interpreted as a composite mode of the softening Brillouin zone center mode and the Brillouin zone edge mode.
The contribution of diffusion to gas microflow: An experimental study
Authors: Veltzke Thomas , Baune Michael , Thöming Jorg
Published: August 2012

Moderately rarefied gas flows are clearly distinguished from viscous flow in the continuum regime and from molecular diffusion at high rarefaction. They are an intermediate of the two border cases referred to as slip flow and transition regime flow. Here, we present a new pencil-and-paper approach for modeling flows in these regimes by a superposition of convection and Fickian diffusion. It allows us to predict mass flows for helium, argon, nitrogen, and carbon dioxide in microducts with parallel walls and with slightly varying cross section. The model was validated by measurement series taken from literature and by own permeation experiments on tapered microchannels. Analytical investigation of the approach showed that the diffusive flow is proportional to the cross-sectional area at the channel entrance. Hence, the mass flow in a tapered channel is unequal in both directions when diffusion dominates due to increased rarefaction. In contrary to the common Maxwellian slip approach the superposition model describes the data reliably. From this we conclude that deviations from continuum behavior in the intermediate cannot be explained by slip flow at the walls and tangential momentum accommodation, but by Fickian diffusion. Now predictions are possible without any usage of fitted parameters such as the tangential momentum accommodation coefficient.
On self-similarity in the drop-filament corner region formed during pinch-off of viscoelastic fluid threads
Authors: Bhat Pradeep P. , Appathurai Santosh , Harris Michael T. , Basaran Osman A.
Published: August 2012

A characteristic feature of pinch-off of fluid threads is the formation of drops connected to thinning filaments. This phenomenon is encountered in a number of widely used applications requiring the production of drops such as electronics microfabrication via inkjet printing, spray coating/drying, and microarraying. In pinch-off of viscoelastic fluid threads, the region that connects the drops to the filaments develops into a sharp corner. Recently, Clasen et al. [J. Fluid Mech. 556, 283–308 (2006)]10.1017/S0022112006009633 showed that such a corner evolves self-similarly. They, however, neglected the capillary pressure in the drop. A modified similarity solution is presented here that incorporates the drop capillary-pressure term, and transient simulations of corner region profiles are shown to converge onto the new similarity solution better than that of Clasen et al. Indeed, the new similarity solution is valid in all the three regions: the drop, the corner, and the filament regions. Similarity solutions, so obtained, are particularly useful in capillary-breakup rheometry where they are employed to estimate a fluid's extensional viscosity—a material property of viscoelastic fluids that influences greatly the drop formation process.
Absolute calibration method for nanosecond-resolved, time-streaked, fiber optic light collection, spectroscopy systems
Authors: Johnston Mark D. , Oliver Bryan V. , Droemer Darryl W. , Frogget Brent , Crain Marlon D. , Maron Yitzhak
Published: August 2012

This paper describes a convenient and accurate method to calibrate fast (<1 ns resolution) streaked, fiber optic light collection, spectroscopy systems. Such systems are inherently difficult to calibrate due to the lack of sufficiently intense, calibrated light sources. Such a system is used to collect spectral data on plasmas generated in electron beam diodes fielded on the RITS-6 accelerator (8-12MV, 140-200kA) at Sandia National Laboratories. On RITS, plasma light is collected through a small diameter (200 μm) optical fiber and recorded on a fast streak camera at the output of a 1 meter Czerny-Turner monochromator. For this paper, a 300 W xenon short arc lamp (Oriel Model 6258) was used as the calibration source. Since the radiance of the xenon arc varies from cathode to anode, just the area around the tip of the cathode (“hotspot”) was imaged onto the fiber, to produce the highest intensity output. To compensate for chromatic aberrations, the signal was optimized at each wavelength measured. Output power was measured using 10 nm bandpass interference filters and a calibrated photodetector. These measurements give power at discrete wavelengths across the spectrum, and when linearly interpolated, provide a calibration curve for the lamp. The shape of the spectrum is determined by the collective response of the optics, monochromator, and streak tube across the spectral region of interest. The ratio of the spectral curve to the measured bandpass filter curve at each wavelength produces a correction factor (Q) curve. This curve is then applied to the experimental data and the resultant spectra are given in absolute intensity units (photons/sec/cm2/steradian/nm). Error analysis shows this method to be accurate to within +/– 20%, which represents a high level of accuracy for this type of measurement.
Light emission lifetimes in p-type δ-doped GaAs/AlAs multiple quantum wells near the Mott transition
Authors: Kundrotas J. , Čerškus A. , Valušis G. , Li L. H. , Linfield E. H. , Johannessen A. , Johannessen E.
Published: August 2012

The time resolved photoluminescence of beryllium δ-doped GaAs/AlAs multiple quantum wells have been studied over a range of doping concentrations, in order to investigate possible mechanisms for the carrier radiative recombination, both above and below the Mott metal-insulator transition. It was found that at doping concentrations near the Mott transition (NBe ∼ 3 × 1012 cm−2), the radiative recombination of excitons-bound-to-acceptor impurities as well as free electrons with acceptor impurities, dominated in the Be δ-doped GaAs/AlAs MQWs (LW = 15 nm) that were used in this study. Above the Mott transition, the major contribution was from radiative recombination of free electrons with a two-dimensional hole gas. The radiative lifetime would therefore exhibit different behavior with doping. In lightly doped GaAs/AlAs MQWs, this changed from 0.3–1 ns at 3.6 K to 8 ns at 300 K, whilst in quantum wells above the Mott transition, it changed from ∼0.36 ns at 3.6 K to ∼1 ns at 300 K, and was also weakly dependent on the concentrations of acceptor doping.
How a single stretched polymer responds coherently to a minute oscillation in fluctuating environments: An entropic stochastic resonance
Authors: Kim Won Kyu , Sung Wokyung
Published: August 2012

Within the cell, biopolymers are often situated in constrained, fluid environments, e.g., cytoskeletal networks, stretched DNAs in chromatin. It is of paramount importance to understand quantitatively how they, utilizing their flexibility, optimally respond to a minute signal, which is, in general, temporally fluctuating far away from equilibrium. To this end, we analytically study viscoelastic response and associated stochastic resonance in a stretched single semi-flexible chain to an oscillatory force or electric field. Including hydrodynamic interactions between chain segments, we evaluate dynamics of the polymer extension in coherent response to the force or field. We find power amplification factor of the response at a noise-strength (temperature) can attain the maximum that grows as the chain length increases, indicative of an entropic stochastic resonance (ESR). In particular for a charged chain under an electric field, we find that the maximum also occurs at an optimal chain length, a new feature of ESR. The hydrodynamic interaction is found to enhance the power amplification, representing unique polymer cooperativity which the fluid background imparts despite its overdamping nature. For the slow oscillatory force, the resonance behavior is explained by the chain undulation of the longest wavelength. This novel ESR phenomenon suggests how a biopolymer self-organizes in an overdamping environment, utilizing its flexibility and thermal fluctuations.
Finite temperature path integral Monte Carlo simulations of structural and dynamical properties of ArN−CO2 clusters
Authors: Wang Lecheng , Xie Daiqian
Published: August 2012

We report finite temperature quantum mechanical simulations of structural and dynamical properties of ArN−CO2 clusters using a path integral Monte Carlo algorithm. The simulations are based on a newly developed analytical Ar−CO2 interaction potential obtained by fitting ab initio results to an anisotropic two-dimensional Morse/Long-range function. The calculated distributions of argon atoms around the CO2 molecule in ArN−CO2 clusters with different sizes are consistent to the previous studies of the configurations of the clusters. A first-order perturbation theory is used to quantitatively predict the CO2 vibrational frequency shift in different clusters. The first-solvation shell is completed at N = 17. Interestingly, our simulations for larger ArN−CO2 clusters showed several different structures of the argon shell around the doped CO2 molecule. The observed two distinct peaks (2338.8 and 2344.5 cm−1) in the υ3 band of CO2 may be due to the different arrangements of argon atoms around the dopant molecule.
Cervical cancer screening and abnormalities among women in a residential drug-rehabilitation program
Authors: Tilley D. M. , Hristov S. , Templeton D. J. , Sharp N. C. , O'Connor C. C.
Published: August 2012

Women in a residential drug-rehabilitation program had lower rates of cervical screening attendance and higher rates of detected abnormalities than women attending a local Well Women’s Clinic. As a result of this study we plan to include a more comprehensive sexual health history into routine women’s health consultations.
Evaluation and optimization of mass transport of redox species in silicon microwire-array photoelectrodes
Authors: Xiang Chengxiang , Meng Andrew C. , Lewis Nathan S.
Published: August 2012

Physical integration of a Ag electrical contact internally into a metal/substrate/microstructured Si wire array/oxide/Ag/electrolyte photoelectrochemical solar cell has produced structures that display relatively low ohmic resistance losses, as well as highly efficient mass transport of redox species in the absence of forced convection. Even with front-side illumination, such wire-array based photoelectrochemical solar cells do not require a transparent conducting oxide top contact. In contact with a test electrolyte that contained 50 mM/5.0 mM of the cobaltocenium
+/0
redox species in CH
3
CN–1.0 M LiClO
4
, when the counterelectrode was placed in the solution and separated from the photoelectrode, mass transport restrictions of redox species in the internal volume of the Si wire array photoelectrode produced low fill factors and limited the obtainable current densities to 17.6 mA cm
-2
even under high illumination. In contrast, when the physically integrated internal Ag film served as the counter electrode, the redox couple species were regenerated inside the internal volume of the photoelectrode, especially in regions where depletion of the redox species due to mass transport limitations would have otherwise occurred. This behavior allowed the integrated assembly to operate as a two-terminal, stand-alone, photoelectrochemical solar cell. The current density vs. voltage behavior of the integrated photoelectrochemical solar cell produced short-circuit current densities in excess of 80 mA cm
-2
at high light intensities, and resulted in relatively low losses due to concentration overpotentials at 1 Sun illumination. The integrated wire array-based device architecture also provides design guidance for tandem photoelectrochemical cells for solar-driven water splitting.
Meso-scale turbulence in living fluids
Authors: Wensink Henricus H. , Dunkel Jörn , Heidenreich Sebastian , Drescher Knut , Goldstein Raymond E. , Löwen Hartmut , Yeomans Julia M.
Published: August 2012

Turbulence is ubiquitous, from oceanic currents to small-scale biological and quantum systems. Self-sustained turbulent motion in microbial suspensions presents an intriguing example of collective dynamical behavior among the simplest forms of life and is important for fluid mixing and molecular transport on the microscale. The mathematical characterization of turbulence phenomena in active nonequilibrium fluids proves even more difficult than for conventional liquids or gases. It is not known which features of turbulent phases in living matter are universal or system-specific or which generalizations of the Navier–Stokes equations are able to describe them adequately. Here, we combine experiments, particle simulations, and continuum theory to identify the statistical properties of self-sustained meso-scale turbulence in active systems. To study how dimensionality and boundary conditions affect collective bacterial dynamics, we measured energy spectra and structure functions in dense
Bacillus subtilis
suspensions in quasi-2D and 3D geometries. Our experimental results for the bacterial flow statistics agree well with predictions from a minimal model for self-propelled rods, suggesting that at high concentrations the collective motion of the bacteria is dominated by short-range interactions. To provide a basis for future theoretical studies, we propose a minimal continuum model for incompressible bacterial flow. A detailed numerical analysis of the 2D case shows that this theory can reproduce many of the experimentally observed features of self-sustained active turbulence.
Sequence-based prediction of single nucleosome positioning and genome-wide nucleosome occupancy
Authors: van der Heijden Thijn , van Vugt Joke J.F.A. , Logie Colin , van Noort John
Published: August 2012

Nucleosome positioning dictates eukaryotic DNA compaction and access. To predict nucleosome positions in a statistical mechanics model, we exploited the knowledge that nucleosomes favor DNA sequences with specific periodically occurring dinucleotides. Our model is the first to capture both dyad position within a few base pairs, and free binding energy within 2 
k
B
T
, for all the known nucleosome positioning sequences. By applying Percus’s equation to the derived energy landscape, we isolate sequence effects on genome-wide nucleosome occupancy from other factors that may influence nucleosome positioning. For both in vitro and in vivo systems, three parameters suffice to predict nucleosome occupancy with correlation coefficients of respectively 0.74 and 0.66. As predicted, we find the largest deviations in vivo around transcription start sites. This relatively simple algorithm can be used to guide future studies on the influence of DNA sequence on chromatin organization.
A selective force favoring increased G+C content in bacterial genes
Authors: Raghavan Rahul , Kelkar Yogeshwar D. , Ochman Howard
Published: August 2012

Bacteria display considerable variation in their overall base compositions, which range from 13% to over 75% G+C. This variation in genomic base compositions has long been considered to be a strictly neutral character, due solely to differences in the mutational process; however, recent sequence comparisons indicate that mutational input alone cannot produce the observed base compositions, implying a role for natural selection. Because bacterial genomes have high gene content, forces that operate on the base composition of individual genes could help shape the overall genomic base composition. To explore this possibility, we tested whether genes that encode the same protein but vary only in their base compositions at synonymous sites have effects on bacterial fitness.
Escherichia coli
strains harboring G+C-rich versions of genes display higher growth rates, indicating that despite a pervasive mutational bias toward A+T, a selective force, independent of adaptive codon use, is driving genes toward higher G+C contents.
The Ndc80 kinetochore complex directly modulates microtubule dynamics
Authors: Umbreit Neil T. , Gestaut Daniel R. , Tien Jerry F. , Vollmar Breanna S. , Gonen Tamir , Asbury Charles L. , Davis Trisha N.
Published: August 2012

The conserved Ndc80 complex is an essential microtubule-binding component of the kinetochore. Recent findings suggest that the Ndc80 complex influences microtubule dynamics at kinetochores in vivo. However, it was unclear if the Ndc80 complex mediates these effects directly, or by affecting other factors localized at the kinetochore. Using a reconstituted system in vitro, we show that the human Ndc80 complex directly stabilizes the tips of disassembling microtubules and promotes rescue (the transition from microtubule shortening to growth). In vivo, an N-terminal domain in the Ndc80 complex is phosphorylated by the Aurora B kinase. Mutations that mimic phosphorylation of the Ndc80 complex prevent stable kinetochore-microtubule attachment, and mutations that block phosphorylation damp kinetochore oscillations. We find that the Ndc80 complex with Aurora B phosphomimetic mutations is defective at promoting microtubule rescue, even when robustly coupled to disassembling microtubule tips. This impaired ability to affect dynamics is not simply because of weakened microtubule binding, as an N-terminally truncated complex with similar binding affinity is able to promote rescue. Taken together, these results suggest that in addition to regulating attachment stability, Aurora B controls microtubule dynamics through phosphorylation of the Ndc80 complex.
Reproductive queue without overt conflict in the primitively eusocial wasp
Ropalidia marginata
Authors: Bang Alok , Gadagkar Raghavendra
Published: August 2012

Colonies of the primitively eusocial wasp
Ropalidia marginata
consist of a single egg layer (queen) and a number of non–egg-laying workers. Although the queen is a docile individual, not at the top of the behavioral dominance hierarchy of the colony, she maintains complete reproductive monopoly. If the queen is lost or removed, one and only one of the workers [potential queen (PQ)] becomes hyperaggressive and will become the next queen of the colony. The PQ is almost never challenged because she first becomes hyperaggressive and then gradually loses her aggression, develops her ovaries, and starts laying eggs. Although we are unable to identify the PQ when the queen is present, she appears to be a “cryptic heir designate.” Here, we show that there is not just one heir designate but a long reproductive queue and that PQs take over the role of egg-laying, successively, without overt conflict, as the queen or previous PQs are removed. The dominance rank of an individual is not a significant predictor of its position in the succession hierarchy. The age of an individual is a significant predictor, but it is not a perfect predictor because PQs often bypass older individuals to become successors. We suggest that such a predesignated reproductive queue that is implemented without overt conflict is adaptive in the tropics, where conspecific usurpers from outside the colony, which can take advantage of the anarchy prevailing in a queenless colony and invade it, are likely to be present throughout the year.
Translocating Adult Pacific Lamprey within the Columbia River Basin: State of the Science
Authors: Ward David L , Clemens Benjamin J , Clugston David , Jackson Aaron D , Moser Mary L , Peery Chris , Statler David P
Published: August 2012

The Pacific lamprey (Entosphenus tridentatus) is in decline in the Columbia River Basin, and translocating adult lamprey to bypass difficult migration corridors has been implemented since 2000. We describe and report results from two current translocation programs, provide context for use of translocation, and discuss potential benefits, risks, and uncertainties. Both translocation programs appear to have increased the number of spawning adults and the presence of larvae and juveniles; however, any subsequent increase in naturally spawning adults will require at least one, and likely more, generations to be realized. It was seen that the number of adults entering the Umatilla River increased beginning four years after the first translocations. Potential benefits of translocation programs are increased pheromone production by ammocoetes to attract adults, increased lamprey distribution and abundance in target areas, increased marine-derived nutrients, and promotion of tribal culture. Potential risks include disruption of population structure and associated genetic adaptations, disease transmission, and depletion of donor stocks.

RESUMEN

Las poblaciones de la lamprea del Pacífico (Entosphenus tridentatus) están declinando en la cuenca del Río Columbia, y desde el año 2000 se ha implementado la translocación de individuos adultos para restablecer los corredores migratorios de esta especie. Se describen y reportan los resultados de dos programas recientes de translocación, se contextualiza el uso de la translocación y se discuten sus beneficios potenciales, riesgos e incertidumbre. Ambos programas de translocación parecen haber incrementado el número de adultos desovantes y la presencia tanto de larvas como de juveniles; sin embargo, para que sea posible cualquier incremento ulterior en el stock natural de reproductores se requerirá de al menos una, aunque muy probablemente de más, generaciones. Se observó que el número de adultos que ingresó al Río Umatilla aumentó en los primeros cuatro años después de la primera translocación. Los beneficios potenciales de los programas de translocación son un aumento en la producción de feromonas por parte de larvas ammocoetes para atraer adultos, incremento en la distribución y abundancia de lampreas en áreas objetivas, incremento en la cantidad de nutrientes derivados del medio marino y la promoción de culturas tribales. Los riesgos potenciales incluyen modificación de la estructura poblacional y las adaptaciones genéticas asociadas, transmisión de enfermedades y agotamiento de los stocks donadores.
Physiological characteristics of elite dancers of different dance styles
Authors: Liiv Helena , Jürimäe Toivo , Mäestu Jarek , Purge Priit , Hannus Aave , Jürimäe Jaak
Published: August 2012

The present investigation was aimed to study international level dancesport dancer's aerobic capacity during incremental test and competition simulation in relation to the gender, dance style and international ranking. A total of 30 couples (12 Standard, 7 Latin American and 11 Ten Dance; aged 22.8±6.6 years male and 22.0±6.4 years female) performed an incremental treadmill test and competition simulation. In this study for the first time we carried out longer than one round competition simulation and compared three different dancesport styles (Standard, Latin American and Ten Dance). The results showed that dancers of these three dance styles had similar aerobic capacity values. The average maximal oxygen consumption ([Vdot]O2max) values were 59.6±5.1 and 51.2±6.2 ml·min−1·kg−1 for male and female dancers, respectively. Competition simulation showed that Latin American Dance discipline is physiologically more intensive compared to Standard and Ten Dance styles especially for the female dancers. It appeared that male and female Standard dancers tended to perform at lower intensity than anaerobic threshold (AT) during competition simulation (male 97.3±2.9%; female 97.9±3.6%), while Latin (male 101.4±2.9%; female 106.7±5.9%) and Ten Dance (male 100.7±6.4%; female 99.2±5.6%) competition intensity was higher compared to AT level of athletes. The highest heart rate during competition simulation was always found during the last dances (Paso Double, Jive or Quickstep) and in the last round of each dance style. No significant relationship between [Vdot]O2max values and international rankings was registered.
Is overall similarity classification less effortful than single-dimension classification?
Authors: Wills Andy J. , Milton Fraser , Longmore Christopher A. , Hester Sarah , Robinson Jo
Published: August 2012

It is sometimes argued that the implementation of an overall similarity classification is less effortful than the implementation of a single-dimension classification. In the current article, we argue that the evidence securely in support of this view is limited, and report additional evidence in support of the opposite proposition—overall similarity classification is more effortful than single-dimension classification. Using a match-to-standards procedure, Experiments 1A, 1B and 2 demonstrate that concurrent load reduces the prevalence of overall similarity classification, and that this effect is robust to changes in the concurrent load task employed, the level of time pressure experienced, and the short-term memory requirements of the classification task. Experiment 3 demonstrates that participants who produced overall similarity classifications from the outset have larger working memory capacities than those who produced single-dimension classifications initially, and Experiment 4 demonstrates that instructions to respond meticulously increase the prevalence of overall similarity classification.
Phonological decoding or direct access? Regularity effects in lexical decisions of Grade 3 and 4 children
Authors: Schmalz Xenia , Marinus Eva , Castles Anne
Published: August 2012

Learning to read fluently involves moving from an effortful phonological decoding strategy to automatic recognition of familiar words. However, little is known about the timing of this transition, or the extent to which children continue to be influenced by phonological factors when recognizing words even as they progress in reading. We explored this question by examining regularity effects in a lexical decision task, as opposed to the more traditionally used reading-aloud task. Children in Grades 3 and 4 made go/no-go lexical decisions on high- and low-frequency regular and irregular words that had been matched for consistency. The children showed regularity effects in their accuracy for low-frequency words, indicating that they were using phonological decoding strategies to recognize unfamiliar words. The size of this effect was correlated with measures of reading ability. However, we found no regularity effects on accuracy for high-frequency words or on response times for either word type, suggesting that even 8-year-old children are already relying predominantly on a direct lexical strategy in their silent reading of familiar words.
The influence of action on episodic memory: A virtual reality study
Authors: Plancher Gaën , Barra Julien , Orriols Eric , Piolino Pascale
Published: August 2012

A range of empirical findings suggest that active learning is important for memory. However, few studies have focused on the mechanisms underlying this enactment effect in episodic memory using complex environments. Research using virtual reality has yielded inconsistent results. We postulated that the effect of action depends on the degree of interaction with the environment and freedom in the planning of an itinerary. To test these hypotheses, we disentangled the interaction and planning components of action to investigate whether each enhances factual and spatial memory. Seventy-two participants (36 male and 36 female) explored a virtual town in one of three experimental conditions: (a) a passive condition where participants were immersed as passenger of the car (no interaction, no planning); (b) a planning-only condition (the subject chose the itinerary but did not drive the car); (c) an interaction-only condition (the subject drove the car but the itinerary was fixed). We found that itinerary choice and motor control both enhanced spatial memory, while factual memory was impaired by online motor control. The role of action in memory is discussed.
Syllabic pseudohomophone priming in tip-of-the-tongue states resolution: The role of syllabic position and number of syllables
Authors: Pureza Rita , Soares Ana Paula , Comesaña Montserrat
Published: August 2012

The tip-of-the-tongue (TOT) state is a common experience, usually coupled with a frustrating feeling caused by the incapability of retrieving a familiar word. It is thought that TOTs occur when the semantic and syntactic information of the word is retrieved but not its phonology. This study aims to further understand the role of phonology in TOT resolution. Specifically, using a syllabic pseudohomophone priming paradigm, we aim to analyse the role of the phonological syllabic position (first vs. last) and the number of syllables in TOT states resolution. TOT was elicited by a picture naming task, after which a lexical decision task was presented. Here, first, last, or none of the phonological syllables of the target word were embedded in pseudohomophone primes. Results showed a significant syllabic pseudohomophone priming effect facilitating TOT resolution. The effect was stronger for four-syllable words, especially when the last syllable was used as prime. These results seem to reinforce the importance of phonology in TOT states resolution, particularly the role of the syllable as an important sublexical unit in speech processing.