bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental weathering of (linear low‐density polyethylene)/(soya powder) blends compatibilized with polyethylene‐grafted maleic anhydride
Authors: Ting Sam Sung , Ismail Hanafi , Ahmad Zulkifli
Published: February 2012

Blends containing various percentages of linear low‐density polyethylene and soya powder were prepared. The effects of polyethylene‐graft‐(maleic anhydride) (PE‐g‐MA) as a compatibilizer and soya powder content on the natural weathering were investigated. Blends without PE‐g‐MA were used as controls. The soya powder was varied from 5 to 40 wt% of the blends, and PE‐g‐MA was used at 50 wt% based on soya powder content. The samples were exposed to natural weathering in the northern part of Malaysia for 1 year. Higher decreases in tensile strength and elongation at break of the controls were observed as compared to those of the PE‐g‐MA compatibilized blends after the natural weathering. The Young's modulus of both controls and compatibilized blends increased over the environmental exposure period. A control sample lost 8.8% of its original weight after 1 year of weathering, whereas a compatibilized blend lost 7.5 wt% during the same period. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers
Anisotropic pressure correlation spectra in turbulent shear flow
Authors: Tsuji Yoshiyuki , Kaneda Yukio
Published: February 2012

We measured the correlation spectrum ${\hat {Q} }_{p} (\mathbi{k})$ of pressure fluctuations in a driving mixing layer with a Taylor-scale Reynolds number ${R}_{\lambda } $ up to ${\simeq }700$ by a newly developed pressure probe with spatial and temporal resolutions that are sufficient to analyse inertial-subrange statistics. The influence of the mean velocity gradient tensor ${S}_{ij} $ in the mixing layer, which is almost constant near its centreline, is studied using an idea similar to that underlying the linear response theory developed in statistical mechanics for systems at or near thermal equilibrium. If we write the spectrum ${\hat {Q} }_{p} (\mathbi{k})$ as ${\hat {Q} }_{p} (\mathbi{k})= { \hat {Q} }_{p}^{(0)} (\mathbi{k})+ \mrm{\Delta} {\hat {Q} }_{p} (\mathbi{k})$, where ${ \hat {Q} }_{p}^{(0)} (\mathbi{k})$ is the isotropic Kolmogorov spectrum in the absence of mean shear, then for small ${S}_{ij} $ the deviation $ \mrm{\Delta} {\hat {Q} }_{p} (\mathbi{k})$ due to the shear is approximately linear and is determined by a few non-dimensional universal constants in addition to ${S}_{ij} $, $k$ and the mean energy dissipation rate. We also measured the pressure–velocity and velocity–velocity correlation spectra. Deviations from isotropy due to shear are shown to be approximately proportional to ${S}_{ij} $ at large ${R}_{\lambda } $.
Ice ripple formation at large Reynolds numbers
Authors: Camporeale Carlo , Ridolfi Luca
Published: February 2012

A free-surface-induced morphological instability is studied in the laminar regime at large Reynolds numbers ($\mathit{Re}= 1\text{{\ndash}} 1{0}^{3} $) and on sub-horizontal walls ($\vartheta \lt 3{0}^{\ensuremath{\circ} } $). We analytically and numerically develop the stability analysis of an inclined melting–freezing interface bounding a free-surface laminar flow. The complete solution of both the linearized flow field and the heat conservation equations allows the exact derivation of the upper and lower temperature gradients at the interface, as required by the Stefan condition, from which the dispersion relationship is obtained. The eigenstructure is obtained and discussed. Free-surface dynamics appears to be crucial for the triggering of upstream propagating ice ripples, which grow at the liquid–solid interface. The kinematic and the dynamic conditions play a key role in controlling the formation of the free-surface fluctuations; these latter induce a streamline distortion with an increment of the wall-normal velocities and a destabilizing phase shift in the net heat transfer to the interface. Three-dimensional effects appear to be crucial at high Reynolds numbers. The role of inertia forces, vorticity, and thermal boundary conditions are also discussed.
Wetting front dynamics in an isotropic porous medium
Authors: Shikhmurzaev Yulii D. , Sprittles James E.
Published: February 2012

A new approach to the modelling of wetting fronts in porous media on the Darcy scale is developed, based on considering the types (modes) of motion the menisci go through on the pore scale. This approach is illustrated using a simple model case of imbibition of a viscous incompressible liquid into an isotropic porous matrix with two modes of motion for the menisci, the wetting mode and the threshold mode. The latter makes it necessary to introduce an essentially new technique of conjugate problems that allows one to link threshold phenomena on the pore scale with the motion on the Darcy scale. The developed approach (a) makes room for incorporating the actual physics of wetting on the pore scale, (b) brings in the physics associated with pore-scale thresholds, which determine when sections of the wetting front will be brought to a halt (pinned), and, importantly, (c) provides a regular framework for constructing models of increasing complexity.
The effect of asymmetric large-scale dissipation on energy and potential enstrophy injection in two-layer quasi-geostrophic turbulence
Authors: Gkioulekas Eleftherios
Published: February 2012

In the Nastrom–Gage spectrum of atmospheric turbulence, we observe a${k}^{\ensuremath{-} 3} $energy spectrum that transitions into a${k}^{\ensuremath{-} 5/ 3} $spectrum, with increasing wavenumber$k$. The transition occurs near a transition wavenumber${k}_{t} $, located near the Rossby deformation wavenumber${k}_{R} $. The Tung–Orlando theory interprets this spectrum as a double downscale cascade of potential enstrophy and energy, from large scales to small scales, in which the downscale potential enstrophy cascade coexists with the downscale energy cascade over the same length scale range. We show that, in a temperature-forced two-layer quasi-geostrophic model, the rates with which potential enstrophy and energy are injected place the transition wavenumber${k}_{t} $near${k}_{R} $. We also show that, if the potential energy dominates the kinetic energy in the forcing range, then the Ekman term suppresses the upscale cascading potential enstrophy more than it suppresses the upscale cascading energy, a behaviour contrary to what occurs in two-dimensional turbulence. As a result, the ratio$\eta / \varepsilon $of injected potential enstrophy over injected energy, in the downscale direction, decreases, thereby tending to decrease the transition wavenumber${k}_{t} $further. Using a random Gaussian forcing model, we reach the same conclusion, under the modelling assumption that the asymmetric Ekman term predominantly suppresses the bottom layer forcing, thereby disregarding a possible entanglement between the Ekman term and the nonlinear interlayer interaction. Based on these results, we argue that the Tung–Orlando theory can account for the approximate coincidence between${k}_{t} $and${k}_{R} $. We also identify certain open questions that require further investigation via numerical simulations.
Straight and linearly tapered capillaries produced by femtosecond laser micromachining
Authors: WIGGINS S. M. , REIJNDERS M. P. , ABUAZOUM S. , HART K. , VIEUX G. , WELSH G. H. , ISSAC R. C. , YANG X. , JONES D. R. , JAROSZYNSKI D. A.
Published: February 2012

Gas-filled capillary discharge waveguides are a commonly employed medium in laser–plasma interaction applications, such as the laser wakefield accelerator, because they can simultaneously guide high-power laser pulses while acting as the medium for acceleration. In this paper, the production of both straight and linearly tapered capillaries using a femtosecond laser micromachining technique is presented. A tapered capillary is shown to possess a smooth variation in diameter (from 305 μm to 183 μm) along its entire 40 mm length, which would lead to a longitudinal plasma density gradient, thereby dramatically improving the laser–plasma interaction efficiency in applications. Efficient guiding with up to 82% energy transmission of the fundamental Gaussian mode of a low intensity, 50 fs duration laser pulse is shown for both types of capillary waveguide.
Nonlinear theory of longitudinal dust-lattice wave in a magnetic dusty plasma crystal
Authors: SHAHMANSOURI M. , FAROKHI B.
Published: February 2012

The propagation of dust-lattice waves in two-dimensional hexagonal dusty plasma crystals in the presence of an external weak magnetic field is considered. Linear and nonlinear properties of the longitudinal dust-lattice waves are investigated. Dispersion relation, group velocity and evolution equation are found. The influence of the magnetic field on the propagation of dust-lattice waves is studied. We obtain the envelope evolution equation for longitudinal modes in the presence of a weak magnetic field, which is in the form of the Gross–Pitaevskii equation.
Approximating entropy for a class of ℤ2Markov random fields and pressure for a class of functions on ℤ2shifts of finite type
Authors: MARCUS BRIAN , PAVLOV RONNIE
Published: February 2012

For a class of ℤ2Markov Random Fields (MRFs)μ, we show that the sequence of successive differences of entropies of induced MRFs on strips of heightnconverges exponentially fast (inn) to the entropy ofμ. These strip entropies can be computed explicitly whenμis a Gibbs state given by a nearest-neighbor interaction on a strongly irreducible nearest-neighbor ℤ2shift of finite typeX. We state this result in terms of approximations to the (topological) pressures of certain functions on such anX, and we show that these pressures are computable if the values taken on by the functions are computable. Finally, we show that our results apply to the hard core model and Ising model for certain parameter values of the corresponding interactions, as well as to the topological entropy of certain nearest-neighbor ℤ2shifts of finite type, generalizing a result in [R. Pavlov. Approximating the hard square entropy constant with probabilistic methods.Ann. Probab.to appear].
A coding theoretic study of MLL proof nets
Authors: MATSUOKA SATOSHI
Published: February 2012

In this paper we propose a novel approach for analysing proof nets of Multiplicative Linear Logic (MLL) using coding theory. We define families of proof structures called PS-families and introduce a metric space for each family. In each family:

(1)

an MLL proof net is a true code element; and

(2)

a proof structure that is not an MLL proof net is a false (or corrupted) code element.

The definition of our metrics elegantly reflects the duality of the multiplicative connectives. We show that in our framework one-error-detection is always possible but one-error-correction is always impossible. We also demonstrate the importance of our main result by presenting two proof-net enumeration algorithms for a given PS-family: the first searches proof nets naively and exhaustively without help from our main result, while the second uses our main result to carry out an intelligent search. In some cases, the first algorithm visits proof structures exponentially, while the second does so only polynomially.
My Friend and Colleague, Richard Schelp
Authors: Faudree Ralph J.
Published: February 2012

Richard Schelp completed his PhD in lattice theory in 1970 at Kansas State University. However, he did not take a traditional route to a PhD in mathematics and an outstanding career as a professor and a mathematical researcher. He grew up in rural northeast Missouri. He received his BS in mathematics and physics from the University of Central Missouri. After the completion of his master's degree in mathematics from Kansas State University, he assumed a position as an associate mathematician in the Applied Science Laboratory at Johns Hopkins University for five years. To start his PhD programme at Kansas State University, he had to quit a well-paying position. Also, he was already married to his wife Billie (Swopes) Schelp and he had a family – a daughter Lisa and a son Rick. This was a courageous step to take, but it says something about who Dick Schelp was.
Role of phospholipase A2pathway in regulating activation ofBufo arenarumoocytes
Authors: Ajmat M.T. , Bonilla F. , Hermosilla P.C. , Zelarayán L. , Bühler M.I.
Published: February 2012

Transient increases in the concentration of cytosolic Ca2+are essential for triggering egg activation events. Increased Ca2+results from its rapid release from intracellular stores, mainly mediated by one or both intracellular calcium channels: the inositol trisphosphate receptor (IP3R) and the ryanodine receptor (RyR). Several regulatory pathways that tailor the response of these channels to the specific cell type have been proposed. Among its many modulatory actions, calcium can serve as an activator of a cytosolic phospholipase A2(cPLA2), which releases arachidonic acid from phospholipids of the endoplasmic reticulum as well as from the nuclear envelope. Previous studies have suggested that arachidonic acid and/or its metabolites were able to modulate the activity of several ion channels. Based on these findings, we have studied the participation of the phospholipase A2(PLA2) pathway in the process ofBufo arenarumoocyte activation and the interrelation between any of its metabolites and the ion channels involved in the calcium release from the intracellular reservoirs at fertilization. We found that addition of both melittin, a potent PLA2activator, and arachidonic acid, the main PLA2reaction metabolite, was able to induce activation events in a bell-shaped manner. Differential regulation of IP3Rs and RyRs by arachidonic acid and its products could explain melittin and arachidonic acid behaviour inBufo arenarumegg activation. The concerted action of arachidonic acid and/or its metabolites could provide controlled mobilization of calcium from intracellular reservoirs and useful tools for understanding calcium homeostasis in eggs that express both types of receptors.
Abnormal methylation of KCNQ1OT1 and differential methylation of H19 imprinting control regions in human ICSI embryos
Authors: Khoueiry Rita , Ibala-Romdhane Samira , Al-Khtib Mohamed , Blachère Thierry , Lornage Jacqueline , Guérin Jean-.François , Lefèvre Annick
Published: February 2012

To evaluate the integrity of genomic imprinting in embryos that failed to develop normally following intracytoplasmic sperm injection (ICSI), we analysed the methylation profile of H19 and KCNQ1OT1 imprinting control regions, H19DMR and KvDMR1 respectively, in high-grade blastocysts and in embryos that exhibited developmental anomalies. Significant hypomethylation of KvDMR1 was specifically observed in 5/5 atypical blastocysts graded BC, which probably reflected the vulnerability of the imprint in the inner cell mass during the methylation remodelling phase in the early embryo. In addition, KvDMR1 was hypermethylated in 2/5 CC graded atypical blastocysts and in 2/8 embryos that exhibited developmental delay. H19DMR appeared differentially methylated in all groups of embryos. DNA methyltransfersase 1 (DNMT1) expression was similar in most of the tested embryos and could not account for the abnormal methylation patterns of KvDMR1 observed.
Surfactant effects in global simulations of cloud droplet activation
Authors: Prisle N. L. , Asmi A. , Topping D. , Partanen A.‐I. , Romakkaniemi S. , Dal Maso M. , Kulmala M. , Laaksonen A. , Lehtinen K. E. J. , McFiggans G. , Kokkola H.
Published: February 2012

Atmospheric aerosols often contain surface active organics. We study the influence of these surfactants on predictions of particle cloud activation potential and aerosol indirect climate effects, by implementing different parametrizations of surfactant effects in the global circulation model ECHAM5.5–HAM2. A parametrization based only on droplet surface tension reduction produces significantly larger effects on predicted cloud droplet numbers than novel parametrizations based on detailed considerations of organic surface activity. It seems better to disregard surfactant effects altogether than employing parametrizations accounting only for effects on surface tension. We strongly recommend not using only the surface tension reduction to represent the surfactant effects in climate models.
Western European cold spells in current and future climate
Authors: de Vries Hylke , Haarsma Reindert J. , Hazeleger Wilco
Published: February 2012

This paper discusses western European cold spells (where temperature falls below the 10% quantile of the winter temperature distribution) in current and future climate. It is demonstrated that many of the projected future changes in cold‐spell statistics (duration, return period, intensity) can be explained by changes in the mean (increase) and variance (decrease) of the winter temperature distribution. After correcting for these changes (by subtracting the mean temperature and by dividing by the standard deviation), future cold‐spell statistics display no major changes outside estimated error bounds. In absolute terms however, the future cold spells are projected to become ∼5°C warmer (and remain above freezing point), thus having a significant climatic impact. An important contributor to the projected future decrease of temperature variance is shown to be the reduction of the mean zonal temperature gradient (land‐sea contrast). These results have been obtained using a 17‐member ensemble of climate‐model simulations with current and future concentration of greenhouse gases.
Three‐dimensional numerical simulations of equatorial spread F: Results and observations in the Pacific sector
Authors: Aveiro H. C. , Hysell D. L. , Caton R. G. , Groves K. M. , Klenzing J. , Pfaff R. F. , Stoneback R. , Heelis R. A.
Published: February 2012

A three‐dimensional numerical simulation of plasma density irregularities in the postsunset equatorial F region ionosphere leading to equatorial spread F (ESF) is described. The simulation evolves under realistic background conditions including bottomside plasma shear flow and vertical current. It also incorporates C/NOFS satellite data which partially specify the forcing. A combination of generalized Rayleigh‐Taylor instability (GRT) and collisional shear instability (CSI) produces growing waveforms with key features that agree with C/NOFS satellite and ALTAIR radar observations in the Pacific sector, including features such as gross morphology and rates of development. The transient response of CSI is consistent with the observation of bottomside waves with wavelengths close to 30 km, whereas the steady state behavior of the combined instability can account for the 100+ km wavelength waves that predominate in the F region.
Fluctuations in the direction of propagation of intermittent low‐frequency ionospheric waves
Authors: Sato H. , Pécseli H. L. , Trulsen J.
Published: February 2012

Low‐frequency (8–28 Hz), long‐wavelength electrostatic waves in the ionospheric E region over northern Scandinavia are studied by using data obtained from an instrumented rocket having four probes mounted on two perpendicular booms. Two data sets are available, one for upleg and one for downleg conditions with somewhat different ionospheric parameters. The ionospheric plasma is unstable with respect to the electrostatic Farley‐Buneman instability in both cases, but the DC electric field is somewhat enhanced during the downleg part of the flight. We find that the direction of wave propagation as given by the local normalized fluctuating electrostatic field vector varies randomly within an interval of aspect angles. The distribution of the directional change per time unit is determined. The waves propagate predominantly in the electrojet direction, but significant variations in directions can be found, both with respect to the magnetic field (the aspect angle) and with respect to the electrojet direction. Some of our results are in variance with related radar observations in the electrojet near the equator. Indications of significant spatial intermittency of the signal is demonstrated. Large‐amplitude electrostatic fluctuations are confined to spatially localized regions and have a narrower aspect angle distribution with reduced directional fluctuations. We introduce an intermittency measure based on average excess time statistics for the record for the absolute value of the detected time‐varying electric fields. We thus determine the average of time intervals spent above a prescribed amplitude threshold level. The results are compared with an analytical expression obtained for a reference nonintermittent Gaussian signal. The general analysis requires the joint probability density of signal amplitude and its time derivative to be known. The analytical models for quantifying the intermittency effects were tested by synthetic time series allowing study of the transition from non‐Gaussian to Gaussian random signals.
Dissolved iron in the Arctic Ocean: Important role of hydrothermal sources, shelf input and scavenging removal
Authors: Klunder M. B. , Laan P. , Middag R. , de Baar H. J. W. , Bakker K.
Published: February 2012

Arctic Ocean waters exchange with the North Atlantic, and thus dissolved iron (DFe) in the Arctic has implications for the global Fe cycle. We present deep water (>250 m) DFe concentrations of the Central Arctic Ocean (Nansen, Amundsen and Makarov Basins). The DFe concentration in the deep waters varies considerably between these basins, with the lowest DFe concentrations (0.2–0.4 nM) in the Makarov Basin, higher concentrations (∼0.45 nM) in the Amundsen Basin and highest concentrations (∼0.6–0.7 nM) in the Nansen Basin. Atlantic input from the shelf seas and slopes enhances the DFe concentration in the Nansen Basin. Moreover, hydrothermal activity at the Gakkel Ridge causes a significant and widespread enrichment of DFe in the Eurasian Basins, at a depth of 2000–3000 m. Below this maximum, the important role of scavenging and absence of input sources are reflected in a strong relation with dissolved Mn (DMn) and in very low (<0.25 nM) DFe concentrations in the deepest (>3000 m) Amundsen and Makarov Basins. The depth profiles of DFe in the Arctic Ocean, notably in the Makarov Basin, deviate from the DFe distribution pattern observed in other parts of the world ocean.
One year ozonesonde measurements at Kerguelen Island (49.2°S, 70.1°E): Influence of stratosphere‐to‐troposphere exchange and long‐range transport of biomass burning plumes
Authors: Baray Jean‐Luc , Duflot Valentin , Posny Françoise , Cammas Jean‐Pierre , Thompson Anne M. , Gabarrot Franck , Bonne Jean‐Louis , Zeng Guang
Published: February 2012

We analyze a 1 year campaign of 17 ozonesondes launched in 2008–2009 at Kerguelen Island (49.2°S, 70.1°E), the first such soundings performed at this location. Tropospheric ozone presents a large variability in austral summer (December to February) and austral winter (June to September). The baseline tropospheric ozone is higher in winter (between 30 and 50 ppbv) than in summer (between 20 and 40 ppbv). We compare these observations to a data set obtained during the same period at Lauder (45.0°S, 169.7°E), which presents a marked seasonal pattern. The analysis of trajectory runs and reanalysis output help identify two significant contributors to the tropospheric ozone level at Kerguelen: the stratosphere‐to‐troposphere air mass transport and the long‐range transport of biomass burning plumes. The stratosphere‐to‐troposphere transport is exemplified by a case study of a dry and enriched ozone layer over Kerguelen (70 ppbv at an altitude of 6 km on 28 February 2009). Using Lagrangian model simulations, we show that wintertime enhancement of the tropospheric ozone baseline can be partially attributed to the long‐range transport of ozone precursors from biomass burning plumes originating in southern America and Africa. However, owing to limited data and to the many factors that can cause this wintertime baseline ozone enhancement, further investigations are needed to fully explain it. Additional measurements are also needed to establish an ozone climatology, to further characterize the ozone annual cycle and wintertime enhancement, and to better compare Kerguelen with other midlatitude sites.
Isotopic constraints on the formation pathways of sulfate aerosol in the marine boundary layer of the subtropical northeast Atlantic Ocean
Authors: Alexander B. , Allman D. J. , Amos H. M. , Fairlie T. D. , Dachs J. , Hegg Dean A. , Sletten Ronald S.
Published: February 2012

We use observations of the oxygen‐17 excess of non‐sea salt sulfate aerosol (Δ17O(nssSO42−)) collected from two ship cruises in the subtropical northeast Atlantic Ocean in August 2006 and February 2007 to quantify the formation pathways of sulfate in the marine boundary layer (MBL). The large observed Δ17O(nssSO42−) values up to 7.3‰ suggest a large role for sulfate formation via S(IV) oxidation by O3 in the MBL. Model simulations with the GEOS‐Chem global chemical transport model suggest that in‐cloud oxidation of S(IV) by O3 represents over one‐third (36–37%) of total in‐cloud sulfate production on average. A model parameterization accounting for the impacts of sea salt aerosol on cloud droplet chemical heterogeneity and resulting impacts on in‐cloud sulfate production rates improves the model's agreement with the Δ17O(nssSO42−) observations in the MBL. Including this parameterization in the model had little impact on the global sulfur budget due to the dominant role of continental anthropogenic emissions for global sulfur emissions in the present‐day. The large observed Δ17O(nssSO42−) argue against a significant role of hypobromous (HOBr) or hypochlorous (HOCl) acid for sulfate formation in the remote MBL of the wintertime subtropical northeast Atlantic, but S(IV) oxidation by HOBr/HOCl on the order of 20% of total sulfate abundance is consistent with the summertime Δ17O(nssSO42−) observations in the more polluted coastal region of the Iberian Peninsula. Additional measurements of Δ17O(nssSO42−) are needed to quantify sulfate production mechanisms in the MBL over larger spatial and temporal scales.
Mapping of CO2at high spatiotemporal resolution using satellite observations: Global distributions from OCO‐2
Authors: Hammerling Dorit M. , Michalak Anna M. , Kawa S. Randolph
Published: February 2012

Satellite observations of CO2offer new opportunities to improve our understanding of the global carbon cycle. Using such observations to infer global maps of atmospheric CO2and their associated uncertainties can provide key information about the distribution and dynamic behavior of CO2, through comparison to atmospheric CO2distributions predicted from biospheric, oceanic, or fossil fuel flux emissions estimates coupled with atmospheric transport models. Ideally, these maps should be at temporal resolutions that are short enough to represent and capture the synoptic dynamics of atmospheric CO2. This study presents a geostatistical method that accomplishes this goal. The method can extract information about the spatial covariance structure of the CO2field from the available CO2retrievals, yields full coverage (Level 3) maps at high spatial resolutions, and provides estimates of the uncertainties associated with these maps. The method does not require information about CO2fluxes or atmospheric transport, such that the Level 3 maps are informed entirely by available retrievals. The approach is assessed by investigating its performance using synthetic OCO‐2 data generated from the PCTM/GEOS‐4/CASA‐GFED model, for time periods ranging from 1 to 16 days and a target spatial resolution of 1° latitude × 1.25° longitude. Results show that global CO2fields from OCO‐2 observations can be predicted well at surprisingly high temporal resolutions. Even one‐day Level 3 maps reproduce the large‐scale features of the atmospheric CO2distribution, and yield realistic uncertainty bounds. Temporal resolutions of two to four days result in the best performance for a wide range of investigated scenarios, providing maps at an order of magnitude higher temporal resolution relative to the monthly or seasonal Level 3 maps typically reported in the literature.
Advances in the simulation and automated measurement of well‐sorted granular material: 1. Simulation
Authors: Buscombe D. , Rubin D. M.
Published: February 2012

In this, the first of a pair of papers which address the simulation and automated measurement of well‐sorted natural granular material, a method is presented for simulation of two‐phase (solid, void) assemblages of discrete non‐cohesive particles. The purpose is to have a flexible, yet computationally and theoretically simple, suite of tools with well constrained and well known statistical properties, in order to simulate realistic granular material as a discrete element model with realistic size and shape distributions, for a variety of purposes. The stochastic modeling framework is based on three‐dimensional tessellations with variable degrees of order in particle‐packing arrangement. Examples of sediments with a variety of particle size distributions and spatial variability in grain size are presented. The relationship between particle shape and porosity conforms to published data. The immediate application is testing new algorithms for automated measurements of particle properties (mean and standard deviation of particle sizes, and apparent porosity) from images of natural sediment, as detailed in the second of this pair of papers. The model could also prove useful for simulating specific depositional structures found in natural sediments, the result of physical alterations to packing and grain fabric, using discrete particle flow models. While the principal focus here is on naturally occurring sediment and sedimentary rock, the methods presented might also be useful for simulations of similar granular or cellular material encountered in engineering, industrial and life sciences.
Cretaceous deep‐water formation in the Indian sector of the Southern Ocean
Authors: Murphy Daniel P. , Thomas Deborah J.
Published: February 2012

The role that meridional overturning circulation (MOC) patterns played in poleward heat transport during the extreme warmth of the Early to Late Cretaceous is a fundamental and unresolved question in climate dynamics. In order to address this question we must determine where deep waters formed, and how they may have circulated during periods of extreme warmth. Here we present late Albian through Maastrichtian (105 to 65 Ma) Nd isotope records from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) sites in the proto‐Indian Ocean and the tropical Pacific. Comparison of these data with previously published records indicates deep‐water formation in the Indian sector of the Southern Ocean began at least ∼105 Ma, extending the record of high‐latitude convection back into the Early Cretaceous prior to the peak warmth of the mid‐Cretaceous. The growing body of data supports a mode of MOC in part characterized by high‐latitude downwelling during the peak of greenhouse warmth of the Mesozoic and Cenozoic. However, this mode of MOC likely was characterized by numerous locations of deep convection that were regionally important, but not significant in terms of a globally overturning circulation due to paleogeographic and bathymetric barriers.
Surface expression of eastern Mediterranean slab dynamics: Neogene topographic and structural evolution of the southwest margin of the Central Anatolian Plateau, Turkey
Authors: Schildgen T. F. , Cosentino D. , Caruso A. , Buchwaldt R. , Yıldırım C. , Bowring S. A. , Rojay B. , Echtler H. , Strecker M. R.
Published: February 2012

The southwest margin of the Central Anatolian Plateau has experienced multiple phases of topographic growth, including the formation of localized highs prior to the Late Miocene that were later affected by wholesale uplift of the plateau margin. Our new biostratigraphic data limit the age of uplifted marine sediments at the southwest plateau margin at 1.5 km elevation to <7.17 Ma, and regional lithostratigraphic correlations imply that the age is <6.7 Ma. Single‐grain CA‐TIMS U‐Pb zircon analyses from a reworked ash within the marine sediments yield dates as young as 10.6 Ma, indicating a maximum age that is consistent with the biostratigraphy. Our structural measurements within the uplifted region and fault inversion modeling agree with previous findings in surrounding regions, with early contraction followed by strike‐slip and extensional deformation during uplift. Focal mechanisms from shallow earthquakes show that the extensional phase has continued to the present. Broad similarities in the change in the tectonic stress regime (after 8 Ma) and the onset of surface uplift (after 7 Ma) imply that deep‐seated process(es) caused post‐7 Ma uplift. The geometry of lithospheric slabs beneath the plateau margin, Pliocene to recent alkaline volcanism, and the uplift pattern with accompanying normal faulting point toward slab tearing and localized heating at the base of the lithosphere as a probable mechanism for post‐7 Ma uplift of the southwest margin. Considering previous work in the region, there appears to be an important link between slab dynamics and surface uplift throughout the Anatolian Plateau's southern margin.
A closed‐form analytical solution for thermal single‐well injection‐withdrawal tests
Authors: Jung Yoojin , Pruess Karsten
Published: February 2012

Thermal single‐well injection‐withdrawal (SWIW) tests entail pumping cold water into a hot and usually fractured reservoir, and monitoring the temperature recovery during subsequent backflow. Such tests have been proposed as a potential means to characterize properties of enhanced geothermal systems (EGS), such as fracture spacing, connectivity, and porosity. In this paper we develop an analytical solution for thermal SWIW tests, using an idealized model of a single vertical fracture with linear flow geometry embedded in impermeable conductive wall rocks. The analytical solution shows that the time dependence of temperature recovery is dominated by the heat exchange between fracture and matrix rock, but strong thermal diffusivities of rocks as compared to typical solute diffusivities are not necessarily advantageous for characterizing fracture‐matrix interactions. The effect of fracture aperture on temperature recovery during backflow is weak, particularly when the fracture aperture is smaller than 0.1 cm. The solution also shows that temperature recovery during backflow is independent of the applied injection and backflow rates. This surprising result implies that temperature recovery is independent of the height of the fracture, or the specific fracture‐matrix interface areas per unit fracture length, suggesting that thermal SWIW tests will not be able to characterize fracture growth that may be achieved by stimulation treatments.
A naturally occurring nonapeptide functionally compensates for the CP1 domain of leucyl-tRNA synthetase to modulate aminoacylation activity
Authors: Tan Min , Yan Wei , Liu Ru-Juan , Wang Meng , Chen Xin , Zhou Xiao-Long , Wang En-Duo
Published: February 2012

aaRSs (aminoacyl-tRNA synthetases) establish the rules of the genetic code by catalysing the formation of aminoacyl-tRNA. The quality control for aminoacylation is achieved by editing activity, which is usually carried out by a discrete editing domain. For LeuRS (leucyl-tRNA synthetase), the CP1 (connective peptide 1) domain is the editing domain responsible for hydrolysing mischarged tRNA. The CP1 domain is universally present in LeuRSs, except MmLeuRS (Mycoplasma mobile LeuRS). The substitute of CP1 in MmLeuRS is a nonapeptide (MmLinker). In the present study, we show that the MmLinker, which is critical for the aminoacylation activity of MmLeuRS, could confer remarkable tRNA-charging activity on the inactive CP1-deleted LeuRS from Escherichia coli (EcLeuRS) and Aquifex aeolicus (AaLeuRS). Furthermore, CP1 from EcLeuRS could functionally compensate for the MmLinker and endow MmLeuRS with post-transfer editing capability. These investigations provide a mechanistic framework for the modular construction of aaRSs and their co-ordination to achieve catalytic efficiency and fidelity. These results also show that the pre-transfer editing function of LeuRS originates from its conserved synthetic domain and shed light on future study of the mechanism.
Configural Face Processing: A Meta-Analytic Survey
Authors: Bruyer Raymond
Published: February 2012

In the field of face processing, the configural hypothesis is defended by many researchers. It is often claimed that this thesis is robustly supported by a large number of experiments exploring the face-inversion effect, the composite face effect, the face superiority effect, and the negative face effect. However, this claim is generally based on a rudimentary and approximate vote-counting approach. In this paper, I use meta-analyses to examine the relevant literature in more depth. The analysis supports the vote-counting argument.
The Effect of Language on Visual Contrast Sensitivity
Authors: Pelekanos Vassilis , Moutoussis Konstantinos
Published: February 2012

Embodied cognition and perceptual symbol theories assume that higher cognition interacts with and is grounded in perception and action. Recent experiments have shown that language processing interacts with perceptual processing in various ways, indicating that linguistic representations have a strong perceptual character. In the present study, we have used signal detection theory to investigate whether the comprehension of written sentences, implying either horizontal or vertical orientation, could improve the participants' visual sensitivity for discriminating between horizontal or vertical square-wave gratings and noise. We tested this prediction by conducting one main and one follow-up experiment. Our results indicate that language can, indeed, affect perception at such a low level of the visual process and thus provide further support for the embodied theories of cognition.
Mapping the Perceptual Structure of Rectangles through Goodness-of-Fit Ratings
Authors: Palmer Stephen E , Guidi Stefano
Published: February 2012

Three experiments were carried out to investigate the internal structure of a rectangular frame to test Arnheim's (1974 Art and Visual Perception, 1988 The Power of the Center) proposals about its ‘structural skeleton’. Observers made subjective ratings of how well a small probe circle fit within a rectangle at different interior positions. In experiment 1, ratings of 77 locations were highest in the center, decreased with distance from the center, greatly elevated along vertical and horizontal symmetry axes, and somewhat elevated along the local symmetry axes. A linear regression model with six symmetry-related factors accounted for 95% of the variance. In experiment 2 we measured perceived fit along local symmetry axes versus global diagonals near the corners to determine which factor was relevant. 2AFC probabilities were elevated only along the local symmetry axes and were higher when the probe was closer to the vertex. In experiment 3 we examined the effect of dividing a rectangular frame into two rectangular ‘subframes’ using an additional line. The results show that the primary determinant of good fit is the position of the target circle within the local subframes. In general, the results are consistent with Arnheim's proposals about the internal structure of a rectangular frame, but an alternative interpretation is offered in terms of the Gestalt concept of figural goodness.
Skill Level and Graphical Detail Shape Perceptual Judgments in Tennis
Authors: Loffing Florian , Wilkes Timo , Hagemann Norbert
Published: February 2012

Reducing the representation of human actions from normal video to biological motion animation in perceptual tasks means removing a number of visual features from the scenery, thereby eliminating potentially useful information for successfully performing the task. To determine the impact of selected visual features on perceptual judgments in tennis, we invited skilled players and novices to predict baseline shot direction under four different display conditions (PL: point-light display; PL_TC: PL plus an animated tennis court; NV_NB: normal video without ball; NV: normal video). Skilled players clearly outperformed novices and prediction performance increased with more realistic display content. Both groups were similarly affected by display conditions and across groups significant differences between conditions were only found for PL vs NV, and PL_TC vs NV, respectively. Application of signal detection theory on response data revealed that, unlike novices, skilled players showed a bias towards preferentially expecting cross-court shots and this bias increased with enhancement in graphical detail. Results confirm previous research in that biological motion appears to provide the minimal essential information necessary for correctly predicting an opponent's intent, particularly in skilled players. In addition, findings indicate that a combination of player and scenery-related visual information is likely to facilitate visual anticipation; however, such information seems to impact skilled players' and novices' response behaviour differently.
Visual Influences on Interactive Speech Alignment
Authors: Dias James W , Rosenblum Lawrence D
Published: February 2012

Speech alignment describes the unconscious tendency to produce speech that shares characteristics with perceived speech (eg Goldinger, 1998 Psychological Review105 251 – 279). In the present study we evaluated whether seeing a talker enhances alignment over just hearing a talker. Pairs of participants performed an interactive search task which required them to repeatedly utter a series of keywords. Half of the pairs performed the task while hearing each other, while the other half could see and hear each other. Alignment was assessed by naive judges rating the similarity of interlocutors' keywords recorded before, during, and after the interactive task. Results showed that interlocutors aligned more when able to see one another suggesting that visual information enhances speech alignment.
Interactions between Intrinsic Principles of Similarity and Proximity and Extrinsic Principle of Common Region in Visual Perception
Authors: Luna Dolores , Montoro Pedro R
Published: February 2012

The interactions between intrinsic grouping principles (by proximity or by similarity in shape or luminance) and extrinsic grouping by common region were examined by presenting both principles acting alone or conjoined with another principle in visual patterns. The procedure used in our study closely mirrored that of Quinlan and Wilton (1998 Perception27 417 – 430). However, in the present experiment, the intrinsic and extrinsic grouping principles involved had similar relative salience in order to avoid their possible effects on interactions. The results showed that the grouping effect of conjoined cooperating principles was greater than that of either principle acting alone, and the grouping effect of conjoined competing principles was lower than that of either principle operating alone. Compatibility of data with additive effects of grouping principles has been examined.
Phylogeography of the rare Gymnocarpos przewalskii (Caryophyllaceae): indications of multiple glacial refugia in north-western China
Authors: Ma S. M. , Zhang M. L. , Sanderson S. C.
Published: February 2012

We investigated the phylogeography of Gymnocarpos przewalskii Maxim. (Caryophyllaceae), a rare relictual shrub restricted to north-western China, in the context of Quaternary climate oscillations. Three cpDNA regions (psbA–trnH, ycf6–psbM and rpl32–trnL (UAG)) were sequenced for 160 individuals from 16 populations. High genetic diversity (hT = 0.930, hS = 0.425) and a significant phylogeographic structure (NST > GST, P < 0.01) were identified; 31 different cpDNA haplotypes were detected. Phylogenetic analyses showed that the haplotypes were clustered into five clades, consistent with their distributions in the following four geographic regions: the Tarim Basin, Hami Basin, the western Yumen of Gansu Province and an easternmost region, consisting of populations in the Wulate Rear Banner region in Inner Mongolia, the Jinta and Jingyuan regions in Gansu Province and the Zhongwei region in Ningxia. The existence of regional divergence was supported by AMOVA, which revealed that ~63% of variation was due to differences among the four geographic regions. Four independent glacial refugia were inferred, in the western Tarim Basin, Hami Basin, the Liuyuan region in western Gansu and the easternmost region mentioned. Population bottlenecks and postglacial recolonisation were identified in the northern Tarim Basin, western Yumen and the Jinta region in Gansu Province.
Non-structural carbohydrates of immature seeds of Caesalpinia echinata (Leguminosae) are involved in the induction of desiccation tolerance
Authors: Leduc Simone Nadur Motta , Silva João Paulo Naldi , Gaspar Maríia , Barbedo Claudio José , Figueiredo-Ribeiro Rita de Cássia Leone
Published: February 2012

Seeds of Caesalpinia echinata fill up to physiological maturation phase ~60 days after anthesis (DAA) in the field. These seeds are desiccation tolerant to 0.08 gH2O gDW–1 and can be stored for 2 years under freezing temperatures without losing germinability. Starch (40–50%), soluble carbohydrates (10–15%, mainly sucrose and cyclitols), in addition to traces of raffinose and stachyose detected early at maturation, are supposed to be related to the acquisition of desiccation tolerance. In the present work we demonstrate that desiccation-intolerant immature seeds (45 DAA) of C. echinata can be dried until 0.14 gH2O gDW–1 when previously soaked in polyethylene glycol (PEG) solution, maintaining high germination percentage. In contrast, seeds of 55 DAA tolerated drying until 0.14 gH2O gDW–1 without previous PEG treatment, indicating that they have already reached desiccation tolerance at this developmental stage. High-performance anion exchange chromatography analysis revealed that cyclitols and sucrose increased markedly in the embryonic axes at 45 DAA after PEG treatment, reaching levels found in embryos at 55 DAA. These results suggest that PEG treatment mimics the natural maturation drying of C. echinata seeds, changing carbohydrate metabolism and triggering processes involved in desiccation tolerance.
Hungarian cultural autonomy in Vojvodina from the 1974 Socialist Constitution to the 2009 Statute of Autonomy: path dependence dynamics against the reversal of minority policies
Authors: Tolvaišis Leonas
Published: February 2012

Applying a historical institutionalist theoretical perspective to the ethnic minority policy domain, the article attempts to explain why state policies toward minorities may be difficult to reverse once introduced. Focusing on a case study of the cultural status of the Vojvodina Hungarian minority in Serbia, the article attempts to find out the forms taken by self-reinforcing dynamics associated with minority-related policies, once they are de-institutionalized. The paper deals with the evolution of the concept of Hungarian cultural autonomy in Vojvodina in the context of the transition from the socialist framework of minority rights protection, applied in the Socialist Autonomous Province of Vojvodina under the 1974 Constitution, to the system established by the Law on National Councils of National Minorities and the Statute of the Autonomous Province of Vojvodina adopted in 2009, after the interim period of state centralization in the 1990s. The Vojvodina case study exemplifies the costs faced by governments aspiring to reverse these policies and allows the identification of path-dependent factors behind the collective action processes related to the main principles of these policies, and conditions that allow these principles to outlive the abolishment of respective institutional arrangements, persist across radical political and social changes over time, and re-emerge at later historical stages, in new institutional settings.