Sample records for strong spatial dependency

  1. Spatial occupancy models applied to atlas data show Southern Ground Hornbills strongly depend on protected areas.

    PubMed

    Broms, Kristin M; Johnson, Devin S; Altwegg, Res; Conquest, Loveday L

    2014-03-01

    Determining the range of a species and exploring species--habitat associations are central questions in ecology and can be answered by analyzing presence--absence data. Often, both the sampling of sites and the desired area of inference involve neighboring sites; thus, positive spatial autocorrelation between these sites is expected. Using survey data for the Southern Ground Hornbill (Bucorvus leadbeateri) from the Southern African Bird Atlas Project, we compared advantages and disadvantages of three increasingly complex models for species occupancy: an occupancy model that accounted for nondetection but assumed all sites were independent, and two spatial occupancy models that accounted for both nondetection and spatial autocorrelation. We modeled the spatial autocorrelation with an intrinsic conditional autoregressive (ICAR) model and with a restricted spatial regression (RSR) model. Both spatial models can readily be applied to any other gridded, presence--absence data set using a newly introduced R package. The RSR model provided the best inference and was able to capture small-scale variation that the other models did not. It showed that ground hornbills are strongly dependent on protected areas in the north of their South African range, but less so further south. The ICAR models did not capture any spatial autocorrelation in the data, and they took an order, of magnitude longer than the RSR models to run. Thus, the RSR occupancy model appears to be an attractive choice for modeling occurrences at large spatial domains, while accounting for imperfect detection and spatial autocorrelation. PMID:24689147

  2. Spatial dependence of the strong optogalvanic effects due to metastable quenching in a DC helium discharge

    SciTech Connect

    Tam, A.C.

    1982-12-01

    The optogalvanic effects of the He 2.058-..mu..m line (2/sup 1/P-2/sup 1/ S) from He lamps illuminating a weak dc He discharge (current density less than or equal to 10 ..mu..A/cm/sup 2/, field/pressure about 25 V/cm - torr) are reported. For illumination at the positive column, the authors have made quantitative measurements of the decreases in the discharge current, electron density, and metastable densities, as well as the increase in the electric field in the positive column, as the intensity of illumination increases. They have also observed that for sufficiently strong illumination (using He lamps only), the optogalvanic effect is catastrophic, i.e., the discharge is switched off; this clearly shows that a sufficiently large metastable density (which is reduced by the illumination) is necessary to maintain a weak He discharge. For illumination at the cathode regions, the optogalvanic effects are ''anomalous'': the discharge current is strongly suppressed by illumination at the cathode dark space next to the cathode, but is enhanced by illumination at the adjacent negative glow region.

  3. Spatial Structure of Seagrass Suggests That Size-Dependent Plant Traits Have a Strong Influence on the Distribution and Maintenance of Tropical Multispecies Meadows

    PubMed Central

    Ooi, Jillian L. S.; Van Niel, Kimberly P.; Kendrick, Gary A.; Holmes, Karen W.

    2014-01-01

    Background Seagrass species in the tropics occur in multispecies meadows. How these meadows are maintained through species co-existence and what their ecological drivers may be has been an overarching question in seagrass biogeography. In this study, we quantify the spatial structure of four co-existing species and infer potential ecological processes from these structures. Methods and Results Species presence/absence data were collected using underwater towed and dropped video cameras in Pulau Tinggi, Malaysia. The geostatistical method, utilizing semivariograms, was used to describe the spatial structure of Halophila spp, Halodule uninervis, Syringodium isoetifolium and Cymodocea serrulata. Species had spatial patterns that were oriented in the along-shore and across-shore directions, nested with larger species in meadow interiors, and consisted of multiple structures that indicate the influence of 2–3 underlying processes. The Linear Model of Coregionalization (LMC) was used to estimate the amount of variance contributing to the presence of a species at specific spatial scales. These distances were <2.5 m (micro-scale), 2.5–50 m (fine-scale) and >50 m (broad-scale) in the along-shore; and <2.5 m (micro-scale), 2.5–140 m (fine-scale) and >140 m (broad-scale) in the across-shore. The LMC suggests that smaller species (Halophila spp and H. uninervis) were most influenced by broad-scale processes such as hydrodynamics and water depth whereas large, localised species (S. isoetifolium and C. serrulata) were more influenced by finer-scale processes such as sediment burial, seagrass colonization and growth, and physical disturbance. Conclusion In this study, we provide evidence that spatial structure is distinct even when species occur in well-mixed multispecies meadows, and we suggest that size-dependent plant traits have a strong influence on the distribution and maintenance of tropical marine plant communities. This study offers a contrast from previous spatial models of seagrasses which have largely focused on monospecific temperate meadows. PMID:24497978

  4. Incorporating spatial dependence in regional frequency analysis

    PubMed Central

    Wang, Zhuo; Yan, Jun; Zhang, Xuebin

    2014-01-01

    The efficiency of regional frequency analysis (RFA) is undermined by intersite dependence, which is usually ignored in parameter estimation. We propose a spatial index flood model where marginal generalized extreme value distributions are joined by an extreme-value copula characterized by a max-stable process for the spatial dependence. The parameters are estimated with a pairwise likelihood constructed from bivariate marginal generalized extreme value distributions. The estimators of model parameters and return levels can be more efficient than those from the traditional index flood model when the max-stable process fits the intersite dependence well. Through simulation, we compared the pairwise likelihood method with an L-moment method and an independence likelihood method under various spatial dependence models and dependence levels. The pairwise likelihood method was found to be the most efficient in mean squared error if the dependence model was correctly specified. When the dependence model was misspecified within the max-stable models, the pairwise likelihood method was still competitive relative to the other two methods. When the dependence model was not a max-stable model, the pairwise likelihood method led to serious bias in estimating the shape parameter and return levels, especially when the dependence was strong. In an illustration with annual maximum precipitation data from Switzerland, the pairwise likelihood method yielded remarkable reduction in the standard errors of return level estimates in comparison to the L-moment method. PMID:25745273

  5. Simple diagnostic tests for spatial dependence

    Microsoft Academic Search

    Luc Anselin; Anil K. Bera; Raymond Florax; Mann J. Yoon

    1996-01-01

    In this paper we propose simple diagnostic tests, based on ordinary least-squares (OLS) residuals, for spatial error autocorrelation in the presence of a spatially lagged dependent variable and for spatial lag dependence in the presence of spatial error autocorrelation, applying the modified Lagrange multiplier (LM) test developed by Bera and Yoon (Econometric Theory, 1993, 9, 649–658). Our new tests may

  6. NON-PARAMETRIC ESTIMATION UNDER STRONG DEPENDENCE

    PubMed Central

    Zhao, Zhibiao; Zhang, Yiyun; Li, Runze

    2014-01-01

    We study non-parametric regression function estimation for models with strong dependence. Compared with short-range dependent models, long-range dependent models often result in slower convergence rates. We propose a simple differencing-sequence based non-parametric estimator that achieves the same convergence rate as if the data were independent. Simulation studies show that the proposed method has good finite sample performance. PMID:25018572

  7. A Bayesian Probit Model with Spatial Dependencies

    E-print Network

    Smith, Tony E.

    A Bayesian Probit Model with Spatial Dependencies Tony E. Smith Department of Systems Engineering of Economics University of Toledo Toledo, Ohio 43606 phone: (419) 530­4754 e-mail: jlesage@spatial-econometrics.com April 8, 2002 Abstract A Bayesian probit model with individual effects that exhibit spatial dependencies

  8. Spatially: resolved heterogeneous dynamics in a strong colloidal gel

    NASA Astrophysics Data System (ADS)

    Buzzaccaro, Stefano; Alaimo, Matteo David; Secchi, Eleonora; Piazza, Roberto

    2015-05-01

    We re-examine the classical problem of irreversible colloid aggregation, showing that the application of Digital Fourier Imaging (DFI), a class of optical correlation methods that combine the power of light scattering and imaging, allows one to pick out novel useful evidence concerning the restructuring processes taking place in a strong colloidal gel. In particular, the spatially-resolved displacement fields provided by DFI strongly suggest that the temporally-intermittent local rearrangements taking place in the course of gel ageing are characterized by very long-ranged spatial correlations.

  9. Spatial Dependencies between Large-Scale Brain Networks

    PubMed Central

    Leech, Robert; Scott, Gregory; Carhart-Harris, Robin; Turkheimer, Federico; Taylor-Robinson, Simon D.; Sharp, David J.

    2014-01-01

    Functional neuroimaging reveals both increases (task-positive) and decreases (task-negative) in neural activation with many tasks. Many studies show a temporal relationship between task positive and task negative networks that is important for efficient cognitive functioning. Here we provide evidence for a spatial relationship between task positive and negative networks. There are strong spatial similarities between many reported task negative brain networks, termed the default mode network, which is typically assumed to be a spatially fixed network. However, this is not the case. The spatial structure of the DMN varies depending on what specific task is being performed. We test whether there is a fundamental spatial relationship between task positive and negative networks. Specifically, we hypothesize that the distance between task positive and negative voxels is consistent despite different spatial patterns of activation and deactivation evoked by different cognitive tasks. We show significantly reduced variability in the distance between within-condition task positive and task negative voxels than across-condition distances for four different sensory, motor and cognitive tasks - implying that deactivation patterns are spatially dependent on activation patterns (and vice versa), and that both are modulated by specific task demands. We also show a similar relationship between positively and negatively correlated networks from a third ‘rest’ dataset, in the absence of a specific task. We propose that this spatial relationship may be the macroscopic analogue of microscopic neuronal organization reported in sensory cortical systems, and that this organization may reflect homeostatic plasticity necessary for efficient brain function. PMID:24887067

  10. Strong, Time-Dependent Electromagnetic Fields in the

    E-print Network

    Maryland at College Park, University of

    Strong, Time-Dependent Electromagnetic Fields in the Presence of Strong, Time- Dependent Gravity hydrodynamic model for the hot spots and lobes has withstood the test of time: With only the HR74 map of Cyg A to go on, they deduced that FR II sources were powered by jets produced a strong reverse "Mach disk

  11. Spatial Heterogeneity Induces Scale Dependent Rock Friction

    NASA Astrophysics Data System (ADS)

    Yamashita, F.; Fukuyama, E.; Xu, S.; Takizawa, S.; Mizoguchi, K.; Kawakata, H.; Passelègue, F. X.; Schubnel, A.

    2014-12-01

    We carried out large-scale biaxial friction experiments (Fukuyama et al., 2012; 2014) using a pair of meter-sized Indian gabbro as specimens, whose contacting area was 1.5 × 0.1 m2, normal stress was up to 6.7 MPa and loading velocity was up to 3 × 10-2 m/s. After each experiment, we found localized damages (i.e. grooves) were generated on the fault surface and gouges were distributed around them. We confirmed work rate dependency of rock friction as revealed by centimeter-sized rock samples (Di Toro et al., 2011), but further found that the meter-sized rock friction starts to decrease at one order of magnitude smaller work rate than that of the centimeter sized rock (Yamashita et al., 2013, AGU fall meeting). Here, we concluded that this difference is caused by stress localization and associated increase in heterogeneity on the fault as shown by: 1) Total amount of deviations of each local shear stress from the average, which were monitored by strain gauge array, increased with the decrease in friction. 2) Friction coefficients were negatively correlated with degree of spatial heterogeneity evaluated from the distribution of grooves and gouges. 3) Melt textures were found in the collected gouges by microscopic observation using HRSEM. Based on these observations, we propose a stress localization model; the fault surfaces are composed of patched and non-patched areas with high and low normal stress, respectively. The high normal stress patch leads to high shear stress, high mechanical work and thus production of much wear material (gouge), which further causes additional increase in normal stress. Assuming that the local friction follows the results by centimeter-sized gabbro experiments, we numerically simulated a slip-dependent friction for both patched and non-patched areas, and successively reproduced a weakening in macroscopic friction. We confirmed that the work rate dependency of simulated friction was consistent with that of biaxial experiments (Fig. 1). This result suggests this scale dependency should be taken into consideration since such heterogeneity should be common in nature.

  12. Corresponding delay-dependent biases in spatial language and spatial memory

    Microsoft Academic Search

    John Lipinski; John P. Spencer; Larissa K. Samuelson

    2010-01-01

    The present study addresses the relationship between linguistic and non-linguistic spatial representations. In three experiments\\u000a we probe spatial language and spatial memory at the same time points in the task sequence. Experiments 1 and 2 show analogous\\u000a delay-dependent biases in spatial language and spatial memory. Experiment 3 extends this correspondence, showing that additional\\u000a perceptual structure along the vertical axis reduces

  13. Spatial dependencies in wind-related housing damage

    Microsoft Academic Search

    Dakshina G. De Silva; Jamie B. Kruse; Yongsheng Wang

    2008-01-01

    This article examines the spatial dependence among housing losses due to tornadoes using data from the May 1999 Oklahoma City\\u000a tornado. In order to examine the existence of spatial dependence and its impacts on the damage analysis, we compare an estimation\\u000a based on a traditional ordinary least square model with the general spatial model. The results show that housing damage

  14. Task-Dependent Spatial Selectivity in the Primate Amygdala

    PubMed Central

    Peck, Ellen L.; Peck, Christopher J.

    2014-01-01

    Humans and other animals routinely encounter visual stimuli that indicate whether future reward delivery depends upon the identity or location of a stimulus, or the performance of a particular action. These reinforcement contingencies can influence how much attention is directed toward a stimulus. Neurons in the primate amygdala encode information about the association between visual stimuli and reinforcement as well as about the location of reward-predictive stimuli. Amygdala neural activity also predicts variability in spatial attention. In principle, the spatial properties of amygdala neurons may be present independent of spatial attention allocation. Alternatively, the encoding of spatial information may require attention. We trained monkeys to perform tasks that engaged spatial attention to varying degrees to understand the genesis of spatial processing in the amygdala. During classical conditioning tasks, conditioned stimuli appeared at different locations; amygdala neurons responded selectively to the location of stimuli. These spatial signals diminished rapidly upon stimulus disappearance and were unrelated to selectivity for expected reward. In contrast, spatial selectivity was sustained in time when monkeys performed a delayed saccade task that required sustained spatial attention. This temporally extended spatial signal was correlated with signals encoding reward expectation. Furthermore, variability in firing rates was correlated with variability in spatial attention, as measured by reaction time. These results reveal two types of spatial signals in the amygdala: one that is tied to initial visual responses and a second that reflects coordination between spatial and reinforcement information and that relates to the engagement of spatial attention. PMID:25471563

  15. Task-dependent spatial selectivity in the primate amygdala.

    PubMed

    Peck, Ellen L; Peck, Christopher J; Salzman, C Daniel

    2014-12-01

    Humans and other animals routinely encounter visual stimuli that indicate whether future reward delivery depends upon the identity or location of a stimulus, or the performance of a particular action. These reinforcement contingencies can influence how much attention is directed toward a stimulus. Neurons in the primate amygdala encode information about the association between visual stimuli and reinforcement as well as about the location of reward-predictive stimuli. Amygdala neural activity also predicts variability in spatial attention. In principle, the spatial properties of amygdala neurons may be present independent of spatial attention allocation. Alternatively, the encoding of spatial information may require attention. We trained monkeys to perform tasks that engaged spatial attention to varying degrees to understand the genesis of spatial processing in the amygdala. During classical conditioning tasks, conditioned stimuli appeared at different locations; amygdala neurons responded selectively to the location of stimuli. These spatial signals diminished rapidly upon stimulus disappearance and were unrelated to selectivity for expected reward. In contrast, spatial selectivity was sustained in time when monkeys performed a delayed saccade task that required sustained spatial attention. This temporally extended spatial signal was correlated with signals encoding reward expectation. Furthermore, variability in firing rates was correlated with variability in spatial attention, as measured by reaction time. These results reveal two types of spatial signals in the amygdala: one that is tied to initial visual responses and a second that reflects coordination between spatial and reinforcement information and that relates to the engagement of spatial attention. PMID:25471563

  16. Uncertainty Quantification for Characterizing Spatial Tail Dependence under Statistical Framework

    NASA Astrophysics Data System (ADS)

    Jeon, S.; Paciorek, C. J.; Prabhat, M.; Byna, S.; Collins, W.; Wehner, M. F.

    2014-12-01

    Large-scale weather systems such as Atmospheric Rivers (ARs) may affect extreme climate events, in particular resulting in high spatial coherence across regions. We use methods from statistical extreme value theory to characterize the spatial dependence of extremes as a function of spatial distance. Our focus in this work is characterizing uncertainty in our understanding of how the spatial dependence of extremes in climate models We investigate the influence of ARs on the spatial dependence structure of extreme precipitation from CMIP5 simulations under climate change. We fit statistical models that treat initial condition ensemble members as independent data replicates and uses bootstrapping (across yearlong blocks of data) to estimate uncertainty from having only limited model runs. We also focus on multi-model ensembles as random draws of CMIP5 model runs and approximate the uncertainty for simulating the behavior of tail dependence across models. Preliminary results from four CMIP5 models show that projected AR events bring more severe rainfall with less dependent pattern between locations under high emissions scenario (RCP8.5) during 2076-2100 than for the historical run during 1981-2005. Within the UQ framework, spatial dependence between nearby locations is estimated more precisely, showing narrower confidence intervals, than the spatial dependence measure for locations further apart.

  17. Verifying the Dependence of Fractal Coefficients on Different Spatial Distributions

    SciTech Connect

    Gospodinov, Dragomir [Plovdiv University 'Paisii Hilendarski', 24, Tsar Asen Str., Plovdiv (Bulgaria); Geophysical Institute of Bulgarian Academy of Sciences, Akad. G. Bonchev Str., bl.3, Sofia (Bulgaria); Marekova, Elisaveta; Marinov, Alexander [Plovdiv University 'Paisii Hilendarski', 24, Tsar Asen Str., Plovdiv (Bulgaria)

    2010-01-21

    A fractal distribution requires that the number of objects larger than a specific size r has a power-law dependence on the size N(r) = C/r{sup D}propor tor{sup -D} where D is the fractal dimension. Usually the correlation integral is calculated to estimate the correlation fractal dimension of epicentres. A 'box-counting' procedure could also be applied giving the 'capacity' fractal dimension. The fractal dimension can be an integer and then it is equivalent to a Euclidean dimension (it is zero of a point, one of a segment, of a square is two and of a cube is three). In general the fractal dimension is not an integer but a fractional dimension and there comes the origin of the term 'fractal'. The use of a power-law to statistically describe a set of events or phenomena reveals the lack of a characteristic length scale, that is fractal objects are scale invariant. Scaling invariance and chaotic behavior constitute the base of a lot of natural hazards phenomena. Many studies of earthquakes reveal that their occurrence exhibits scale-invariant properties, so the fractal dimension can characterize them. It has first been confirmed that both aftershock rate decay in time and earthquake size distribution follow a power law. Recently many other earthquake distributions have been found to be scale-invariant. The spatial distribution of both regional seismicity and aftershocks show some fractal features. Earthquake spatial distributions are considered fractal, but indirectly. There are two possible models, which result in fractal earthquake distributions. The first model considers that a fractal distribution of faults leads to a fractal distribution of earthquakes, because each earthquake is characteristic of the fault on which it occurs. The second assumes that each fault has a fractal distribution of earthquakes. Observations strongly favour the first hypothesis.The fractal coefficients analysis provides some important advantages in examining earthquake spatial distribution, which are: - Simple way to quantify scale-invariant distributions of complex objects or phenomena by a small number of parameters. - It is becoming evident that the applicability of fractal distributions to geological problems could have a more fundamental basis. Chaotic behaviour could underlay the geotectonic processes and the applicable statistics could often be fractal.The application of fractal distribution analysis has, however, some specific aspects. It is usually difficult to present an adequate interpretation of the obtained values of fractal coefficients for earthquake epicenter or hypocenter distributions. That is why in this paper we aimed at other goals - to verify how a fractal coefficient depends on different spatial distributions. We simulated earthquake spatial data by generating randomly points first in a 3D space - cube, then in a parallelepiped, diminishing one of its sides. We then continued this procedure in 2D and 1D space. For each simulated data set we calculated the points' fractal coefficient (correlation fractal dimension of epicentres) and then checked for correlation between the coefficients values and the type of spatial distribution.In that way one can obtain a set of standard fractal coefficients' values for varying spatial distributions. These then can be used when real earthquake data is analyzed by comparing the real data coefficients values to the standard fractal coefficients. Such an approach can help in interpreting the fractal analysis results through different types of spatial distributions.

  18. Detection error exponent for spatially dependent samples in random networks

    E-print Network

    Tong, Lang

    The problem of binary hypothesis testing is considered when the measurements are drawn from a Markov random field (MRF) under each hypothesis. Spatial dependence of the measurements is incorporated by explicitly modeling ...

  19. Parity-dependent localization in N strongly coupled chains

    NASA Astrophysics Data System (ADS)

    Weinmann, Dietmar; Evangelou, S. N.

    2014-10-01

    Anderson localization of wave functions at zero energy in quasi-one-dimensional (1D) systems of N disordered chains with interchain coupling t is examined. Localization becomes weaker than for the 1D disordered chain (t =0) when t is smaller than the longitudinal hopping t'=1, and localization becomes usually much stronger when t ?t'. This is not so for all N. We find "immunity" to strong localization for open (periodic) lateral boundary conditions when N is odd (a multiple of 4), with localization that is weaker than for t =0 and rather insensitive to t when t ?t'. The peculiar N dependence and a critical scaling with N are explained by a perturbative treatment in t'/t, and the correspondence to a weakly disordered effective chain is shown. Our results could be relevant for experimental studies of localization in photonic waveguide arrays.

  20. Spatially Dependent Polya Tree Modeling for Survival Data

    PubMed Central

    Zhao, Luping; Hanson, Timothy E.

    2010-01-01

    Summary With the proliferation of spatially oriented time-to-event data, spatial modeling in the survival context has received increased recent attention. A traditional way to capture a spatial pattern is to introduce frailty terms in the linear predictor of a semiparametric model, such as proportional hazards or accelerated failure time. We propose a new methodology to capture the spatial pattern by assuming a prior based on a mixture of spatially dependent Polya trees for the baseline survival in the proportional hazards model. Thanks to modern Markov chain Monte Carlo (MCMC) methods, this approach remains computationally feasible in a fully hierarchical Bayesian framework. We compare the spatially dependent mixture of Polya trees (MPT) approach to the traditional spatial frailty approach, and illustrate the usefulness of this method with an analysis of Iowan breast cancer survival data from the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute. Our method provides better goodness of fit over the traditional alternatives as measured by log pseudo marginal likelihood (LPML), the deviance information criterion (DIC) and full sample score (FSS) statistics. PMID:20731644

  1. Localized attacks on spatially embedded networks with dependencies

    PubMed Central

    Berezin, Yehiel; Bashan, Amir; Danziger, Michael M.; Li, Daqing; Havlin, Shlomo

    2015-01-01

    Many real world complex systems such as critical infrastructure networks are embedded in space and their components may depend on one another to function. They are also susceptible to geographically localized damage caused by malicious attacks or natural disasters. Here, we study a general model of spatially embedded networks with dependencies under localized attacks. We develop a theoretical and numerical approach to describe and predict the effects of localized attacks on spatially embedded systems with dependencies. Surprisingly, we find that a localized attack can cause substantially more damage than an equivalent random attack. Furthermore, we find that for a broad range of parameters, systems which appear stable are in fact metastable. Though robust to random failures—even of finite fraction—if subjected to a localized attack larger than a critical size which is independent of the system size (i.e., a zero fraction), a cascading failure emerges which leads to complete system collapse. Our results demonstrate the potential high risk of localized attacks on spatially embedded network systems with dependencies and may be useful for designing more resilient systems. PMID:25757572

  2. Finite mixture models for mapping spatially dependent disease counts.

    PubMed

    Alfó, Marco; Nieddu, Luciano; Vicari, Donatella

    2009-02-01

    A vast literature has recently been concerned with the analysis of variation in disease counts recorded across geographical areas with the aim of detecting clusters of regions with homogeneous behavior. Most of the proposed modeling approaches have been discussed for the univariate case and only very recently spatial models have been extended to predict more than one outcome simultaneously. In this paper we extend the standard finite mixture models to the analysis of multiple, spatially correlated, counts. Dependence among outcomes is modeled using a set of correlated random effects and estimation is carried out by numerical integration through an EM algorithm without assuming any specific parametric distribution for the random effects. The spatial structure is captured by the use of a Gibbs representation for the prior probabilities of component membership through a Strauss-like model. The proposed model is illustrated using real data. PMID:19219904

  3. Strong Spatial Mixing and Rapid Mixing with Five Colours for the Kagome Lattice

    E-print Network

    Markus Jalsenius

    2009-03-31

    We consider proper 5-colourings of the kagome lattice. Proper q-colourings correspond to configurations in the zero-temperature q-state anti-ferromagnetic Potts model. Salas and Sokal have given a computer assisted proof of strong spatial mixing on the kagome lattice for q>=6 under any temperature, including zero temperature. It is believed that there is strong spatial mixing for q>=4. Here we give a computer assisted proof of strong spatial mixing for q=5 and zero temperature. It is commonly known that strong spatial mixing implies that there is a unique infinite-volume Gibbs measure and that the Glauber dynamics is rapidly mixing. We give a proof of rapid mixing of the Glauber dynamics on any finite subset of the vertices of the kagome lattice, provided that the boundary is free (not coloured). The Glauber dynamics is not necessarily irreducible if the boundary is chosen arbitrarily for q=5 colours. The Glauber dynamics can be used to uniformly sample proper 5-colourings. Thus, a consequence of rapidly mixing Glauber dynamics is that there is fully polynomial randomised approximation scheme for counting the number of proper 5-colourings.

  4. Strongly enhanced field-dependent single-molecule electroluminescence.

    PubMed

    Lee, Tae-Hee; Gonzalez, Jose I; Dickson, Robert M

    2002-08-01

    Individual, strongly electroluminescent Ag(n) molecules (n = 2 approximately 8 atoms) have been electrically written within otherwise nonemissive silver oxide films. Exhibiting characteristic single-molecule behavior, these individual room-temperature molecules exhibit extreme electroluminescence enhancements (>10(4) vs. bulk and dc excitation on a per molecule basis) when excited with specific ac frequencies. Occurring through field extraction of electrons with subsequent reinjection and radiative recombination, single-molecule electroluminescence is enhanced by a general mechanism that avoids slow bulk material response. Thus, while we detail strong electroluminescence from single, highly fluorescent Ag(n) molecules, this mechanism also yields strong ac-excited electroluminescence from similarly prepared, but otherwise nonemissive, individual Cu nanoclusters. PMID:12149468

  5. Temperature Dependence of Thermopower in Strongly Correlated Multiorbital Systems

    SciTech Connect

    Sekino, M [Japan Atomic Energy Agency (JAEA)] [Japan Atomic Energy Agency (JAEA); Okamoto, Satoshi [ORNL] [ORNL; Koshibae, W [RIKEN, Japan] [RIKEN, Japan; Mori, Michiyasu [Japan Atomic Energy Agency (JAEA)] [Japan Atomic Energy Agency (JAEA); Maekawa, Sadamichi [Japan Atomic Energy Agency (JAEA)] [Japan Atomic Energy Agency (JAEA)

    2014-01-01

    Temperature dependence of thermopower in the multiorbital Hubbard model is studied by using the dynamical mean-field theory with the non-crossing approximation impurity solver. It is found that the Coulomb interaction, the Hund coupling, and the crystal filed splitting bring about nonmonotonic temperature dependence of the hermopower, including its sign reversal. The implication of our theoretical results to some materials is discussed.

  6. The Analysis of Tempo-Spatial Correlation Characteristics between Strong Earthquakes Based on Parallel Computing

    Microsoft Academic Search

    Li Jinsong; Gao Pengdong; Zhang Xiaolai; Wang Jintao

    2010-01-01

    A modified earthquake prediction model based on At-value is introduced in this paper, which is improved by using the parallel computing techniques. The At-value is employed to analyze and compare the strain energy that is released in an earthquake, and gives the tempo-spatial correlation characteristics between strong earthquakes. After calculation, a picture of At-value distribution can be drawn and provide

  7. Modelling land cover transitions: A solution to the problem of spatial dependence in data

    Microsoft Academic Search

    Kevin Weaver; Ajith H. Perera

    2004-01-01

    Raster-based spatial land cover transition models (LCTMs) are widely used in landscape ecology. However, many LCTMs do not account for spatial dependence of the input data, which may artificially fragment the output spatial configuration. We demonstrate the consequences of ignoring spatial dependence, thus assigning probabilities randomly in space, using a simple LCTM. We ran the model from four different initial

  8. Incorporating spatial dependence into a multicellular tumor spheroid growth model

    NASA Astrophysics Data System (ADS)

    Garner, Allen L.; Lau, Y. Y.; Jackson, Trachette L.; Uhler, Michael D.; Jordan, David W.; Gilgenbach, Ronald M.

    2005-12-01

    Recent models for organism and tumor growth yield simple scaling laws based on conservation of energy. Here, we extend such a model to include spatial dependence to model necrotic core formation. We adopt the allometric equation for tumor volume with a reaction-diffusion equation for nutrient concentration. In addition, we assume that the total metabolic energy and average cellular metabolic rate depend on nutrient concentration in a Michaelis-Menten-like manner. From experimental results, we relate the necrotic volume to nutrient consumption and estimate both the time and nutrient concentration at necrotic core formation. Based on experimental results, we demand that the necrotic core radius varies linearly with tumor radius after core formation and extend the equations for tumor volume and nutrient concentration to the postnecrotic core regime. In particular, we obtain excellent agreement with experimental data and the final steady-state viable rim thickness.

  9. TUG-OF-WAR GAMES AND THE INFINITY LAPLACIAN WITH SPATIAL DEPENDENCE

    E-print Network

    Rossi, Julio D.

    TUG-OF-WAR GAMES AND THE INFINITY LAPLACIAN WITH SPATIAL DEPENDENCE IVANA G´OMEZ AND JULIO D. ROSSI v · Jx(Dv); Jx(Dv) (x) = 0, that is, an infinity Laplacian with spatial dependence. Here Jx call a natural way of defining a infinity Laplacian with spatial dependence. First, let us recall

  10. Spin-orientation-dependent spatial structure of a magnetic acceptor state in a zinc-blende semiconductor

    E-print Network

    Flatte, Michael E.

    in semiconductor systems. Here we describe calculations of the dependence of the LDOS near a Mn dopant in GaAs-blende semiconductor Jian-Ming Tang and Michael E. Flatté Department of Physics and Astronomy, University of Iowa, Iowa of a magnetic dopant in a zinc-blende semiconductor strongly influences the spatial structure of an acceptor

  11. Strong dependence of ultracold chemical rates on electric dipole moments

    SciTech Connect

    Quemener, Goulven; Bohn, John L. [JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States)

    2010-02-15

    We use the quantum threshold laws combined with a classical capture model to provide an analytical estimate of the chemical quenching cross sections and rate coefficients of two colliding particles at ultralow temperatures. We apply this quantum threshold model (QT model) to indistinguishable fermionic polar molecules in an electric field. At ultracold temperatures and in weak electric fields, the cross sections and rate coefficients depend only weakly on the electric dipole moment d induced by the electric field. In stronger electric fields, the quenching processes scale as d{sup 4(L+(1/2))} where L>0 is the orbital angular-momentum quantum number between the two colliding particles. For p-wave collisions (L=1) of indistinguishable fermionic polar molecules at ultracold temperatures, the quenching rate thus scales as d{sup 6}. We also apply this model to pure two-dimensional collisions and find that chemical rates vanish as d{sup -4} for ultracold indistinguishable fermions. This model provides a quick and intuitive way to estimate chemical rate coefficients of reactions occuring with high probability.

  12. Spatially dependent relative diffusion of nanoparticles in polymer melts

    NASA Astrophysics Data System (ADS)

    Yamamoto, Umi; Schweizer, Kenneth S.

    2013-08-01

    We formulate and apply a microscopic statistical-mechanical theory for the non-hydrodynamic relative diffusion coefficient of a pair of spherical nanoparticles in entangled polymer melts based on a combination of Brownian motion, mode-coupling, and polymer physics ideas. The focus is on the mesoscopic regime where particles are larger than the entanglement spacing. The dependence of the non-hydrodynamic friction on interparticle separation, degree of entanglement, and tube diameter is systematically studied. The overall magnitude of the relative diffusivity is controlled by the ratio of the particle to tube diameter and the number of entanglements in a manner reminiscent of single-particle self-diffusion and Stokes-Einstein violations. A rich spatial separation dependence of mobility enhancement relative to the hydrodynamic behavior is predicted even for very large particles, and the asymptotic dependence is derived analytically in the small and large separation limits. Particle separations in excess of 100 nm are sometimes required to recover the hydrodynamic limit. The effects of local polymer-particle packing correlations are found to be weak, and the non-hydrodynamic effects are also small for unentangled melts.

  13. Modeling Spatial Dependencies for Mining Geospatial Data: An Introduction

    Microsoft Academic Search

    Sanjay Chawla; Shashi Shekhar; Weili Wu; Uygar Ozesmi

    2001-01-01

    this paper we first review spatial statistical methods which explictly modelspatial autocorrelation and we propose PLUMS (Predicting Locations Using MapSimilarity), a new approach for supervised spatial data mining problems. PLUMSsearches the parameter space of models using a map-similarity measure which ismore appropriate in the context of spatial data. We will show that compared tostate-of-the-art spatial statistics approaches, PLUMS achives comparable

  14. Spatial Visualization Abilities of Field Dependent/Independent Preservice Teachers

    ERIC Educational Resources Information Center

    Yazici, Ersen

    2014-01-01

    Introduction: Spatial skills have been a significant area of research in educational psychology for more years and it has two major dimensions as spatial visualization and spatial orientation. Mathematics educators acknowledge the influence of cognitive styles in the learning of mathematics. There are various recognized cognitive styles in the…

  15. A spatially filtered multilevel model to account for spatial dependency: application to self-rated health status in South Korea

    PubMed Central

    2014-01-01

    Background This study aims to suggest an approach that integrates multilevel models and eigenvector spatial filtering methods and apply it to a case study of self-rated health status in South Korea. In many previous health-related studies, multilevel models and single-level spatial regression are used separately. However, the two methods should be used in conjunction because the objectives of both approaches are important in health-related analyses. The multilevel model enables the simultaneous analysis of both individual and neighborhood factors influencing health outcomes. However, the results of conventional multilevel models are potentially misleading when spatial dependency across neighborhoods exists. Spatial dependency in health-related data indicates that health outcomes in nearby neighborhoods are more similar to each other than those in distant neighborhoods. Spatial regression models can address this problem by modeling spatial dependency. This study explores the possibility of integrating a multilevel model and eigenvector spatial filtering, an advanced spatial regression for addressing spatial dependency in datasets. Methods In this spatially filtered multilevel model, eigenvectors function as additional explanatory variables accounting for unexplained spatial dependency within the neighborhood-level error. The specification addresses the inability of conventional multilevel models to account for spatial dependency, and thereby, generates more robust outputs. Results The findings show that sex, employment status, monthly household income, and perceived levels of stress are significantly associated with self-rated health status. Residents living in neighborhoods with low deprivation and a high doctor-to-resident ratio tend to report higher health status. The spatially filtered multilevel model provides unbiased estimations and improves the explanatory power of the model compared to conventional multilevel models although there are no changes in the signs of parameters and the significance levels between the two models in this case study. Conclusions The integrated approach proposed in this paper is a useful tool for understanding the geographical distribution of self-rated health status within a multilevel framework. In future research, it would be useful to apply the spatially filtered multilevel model to other datasets in order to clarify the differences between the two models. It is anticipated that this integrated method will also out-perform conventional models when it is used in other contexts. PMID:24571639

  16. Bose representation for a strongly coupled nonequilibrium fermionic superfluid in a time-dependent trap

    NASA Astrophysics Data System (ADS)

    Tokatly, I. V.

    2004-10-01

    Using the functional integral formulation of nonequilibrium quantum many-body theory we develop a regular description of a Fermi system with a strong attractive interaction in the presence of an external time-dependent potential. In the strong coupling limit this fermionic system is equivalent to a nonequilibrium dilute Bose gas of diatomic molecules. We also consider nonequilibrium strongly coupled Bardeen-Cooper-Schrieffer theory and show that it reduces to the full nonlinear time-dependent Gross-Pitaevski equation, which determines the evolution of the condensate wave function.

  17. Spatially resolved x-ray studies of liquid crystals with strongly developed bond-orientational order.

    PubMed

    Zaluzhnyy, I A; Kurta, R P; Sulyanova, E A; Gorobtsov, O Y; Shabalin, A G; Zozulya, A V; Menushenkov, A P; Sprung, M; Ostrovskii, B I; Vartanyants, I A

    2015-04-01

    We present an x-ray study of freely suspended hexatic films of the liquid crystal 3(10)OBC. Our results reveal spatial inhomogeneities of the bond-orientational (BO) order in the vicinity of the hexatic-smectic phase transition and the formation of large-scale hexatic domains at lower temperatures. Deep in the hexatic phase up to 25 successive sixfold BO order parameters have been directly determined by means of angular x-ray cross-correlation analysis (XCCA). Such strongly developed hexatic order allowed us to determine higher order correction terms in the scaling relation predicted by the multicritical scaling theory over a full temperature range of the hexatic phase existence. PMID:25974515

  18. Non-monotonic temperature dependence of thermopower in strongly correlated electron systems

    SciTech Connect

    Matsuo, M [Japan Atomic Energy Agency (JAEA); Okamoto, Satoshi [ORNL; Koshibae, W [RIKEN, Japan; Mori, Michiyasu [Japan Atomic Energy Agency (JAEA); Maekawa, Sadamichi [Japan Atomic Energy Agency (JAEA)

    2011-01-01

    We examine the temperature dependence of thermopower in the single-band Hubbard model using dynamical mean-field theory. The strong Coulomb interaction brings about the coherent-to-incoherent crossover as temperature increases. As a result, the thermopower exhibits nonmonotonic temperature dependence and asymptotically approaches values given by the Mott-Heikes formula. In the light of our theoretical result, we discuss the thermopower in some transition metal oxides. The magnetic field dependence of the thermopower is also discussed.

  19. Modeling Spatial Dependencies in High-Resolution Overhead Imagery

    SciTech Connect

    Cheriyadat, Anil M [ORNL] [ORNL; Bright, Eddie A [ORNL] [ORNL; Vatsavai, Raju [ORNL] [ORNL

    2011-01-01

    Human settlement regions with different physical and socio-economic attributes exhibit unique spatial characteristics that are often illustrated in high-resolution overhead imageries. For example- size, shape and spatial arrangements of man-made structures are key attributes that vary with respect to the socioeconomic profile of the neighborhood. Successfully modeling these attributes is crucial in developing advanced image understanding systems for interpreting complex aerial scenes. In this paper we present three different approaches to model the spatial context in the overhead imagery. First, we show that the frequency domain of the image can be used to model the spatial context [1]. The shape of the spectral energy contours characterize the scene context and can be exploited as global features. Secondly, we explore a discriminative framework based on the Conditional Random Fields (CRF) [2] to model the spatial context in the overhead imagery. The features derived from the edge orientation distribution calculated for a neighborhood and the associated class labels are used as input features to model the spatial context. Our third approach is based on grouping spatially connected pixels based on the low-level edge primitives to form support-regions [3]. The statistical parameters generated from the support-region feature distributions characterize different geospatial neighborhoods. We apply our approaches on high-resolution overhead imageries. We show that proposed approaches characterize the spatial context in overhead imageries.

  20. The Effect of Exposure Duration on Stereopsis and Its Dependency on Spatial Frequency

    NASA Astrophysics Data System (ADS)

    Lee, Seungbae; Shioiri, Satoshi; Yaguchi, Hirohisa

    2004-07-01

    To investigate the effect of exposure duration on stereopsis and its spatial frequency dependency, we measured disparity threshold for the depth discrimination varying stimulus exposure duration between 0.05 and 2 s for three spatial frequencies (0.23, 0.94 and 3.75 c/deg). The results showed that disparity threshold decreased with increase in exposure duration up to a certain duration, beyond which it was approximately constant (the duration is called critical duration). The critical duration was about 150 ms for gratings with low and middle spatial frequencies (0.23 and 0.94 c/deg) while the duration was about 750 ms for gratings with high spatial frequency (3.75 c/deg). This suggests that temporal integration property varies dependently on stimulus spatial frequency. We also attempted to relate the spatial frequency dependency of the temporal integration property to the differences in temporal frequency tuning to different spatial frequency stimuli.

  1. Exchange and spin states in quantum dots under strong spatial correlations. Computer simulation by the Feynman path integral method

    NASA Astrophysics Data System (ADS)

    Shevkunov, S. V.

    2013-10-01

    The fundamental laws in the behavior of electrons in model quantum dots that are caused by exchange and strong Coulomb correlations are studied. The ab initio path integral method is used to numerically simulate systems of two, three, four, and six interacting identical electrons confined in a three-dimensional spherical potential well with a parabolic confining potential against the background of thermal fluctuations. The temperature dependences of spin and collective spin magnetic susceptibility are calculated for model quantum dots of various spatial sizes. A basically exact procedure is proposed for taking into account the permutation symmetry and the spin state of electrons, which makes it possible to perform numerical calculations using modern computer facilities. The conditions of applicability of a virial energy estimator and its optimum form in exchange systems are determined. A correlation estimator of kinetic energy, which is an alternative to a basic estimator, is suggested. A fundamental relation between the kinetic energy of a quantum particle and the character of its virtual diffusion in imaginary time is demonstrated. The process of natural "pairing" of electron spins during the compression of a quantum dot and cooling of a system is numerically reproduced in terms of path integrals. The temperature dependences of the spin magnetic susceptibility of electron pairs with a characteristic maximum caused by spin pairing are obtained.

  2. [Scale-dependency of spatial variability of soil available nutrients].

    PubMed

    Yang, Qi-Yong; Yang, Jing-Song; Liu, Guang-Ming

    2011-02-01

    With the support of GIS and by using classical statistics and geostatistics methods, the spatial variability of soil available P (AP) and available K (AK) in cultivated lands in Yucheng City of Shandong Province was approached at county and township scales. The results showed that both the soil AP and AK followed the logarithmic normal distribution, with the coefficient of variation (CV) at the two scales being 26.5% - 36.6% and presenting a moderate variation. With the decrease of the scale, the CV of the soil AP and AK increased. Both the soil AP and AK were spatially correlated with scale. At county scale, the soil AP and AK had a larger spatial correlation distance, being 9.0 km and 26.5 km, respectively; while at township scale, the soil AP and AK had a smaller spatial correlation distance, being 1.7 km and 2.8 km, respectively. The spatial distribution of the soil AP and AK at the two scales was obviously different, which was mainly affected by structural factors and random factors. PMID:21608258

  3. Strong impact parameter dependence of hard photon production in intermediate energy heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Migneco, E.; Agodi, C.; Alba, R.; Bellia, G.; Coniglione, R.; Del Zoppo, A.; Finocchiaro, P.; Maiolino, C.; Piattelli, P.; Russo, G.; Sapienza, P.; Badalá, A.; Barbera, R.; Palmeri, A.; Pappalardo, G. S.; Riggi, F.; Russo, A. C.; Peghaire, A.; Bonasera, A.

    1993-01-01

    The dependence of the high energy photon production on the impact parameter has been investigated in the reaction 129Xe+ 197Au at 44 MeV/u using the multidetector array MEDEA. A strong dependence of the high energy photon production probability on the impact parameter has been observed, while the slope parameter of the photon spectrum is almost constant. The data support the interpretation of the hard photon production in terms of first chance n-p collisions.

  4. Retrieval Induces Hippocampal-Dependent Reconsolidation of Spatial Memory

    ERIC Educational Resources Information Center

    Rossato, Janine I.; Medina, Jorge H.; Izquierdo, Ivan; Cammarota, Martin; Bevilaqua, Lia R. M.

    2006-01-01

    Nonreinforced retrieval can cause extinction and/or reconsolidation, two processes that affect subsequent retrieval in opposite ways. Using the Morris water maze task we show that, in the rat, repeated nonreinforced expression of spatial memory causes extinction, which is unaffected by inhibition of protein synthesis within the CA1 region of the…

  5. History-dependent effects in subcycle-waveform strong-field ionization

    NASA Astrophysics Data System (ADS)

    Kolesik, M.; Brown, J. M.; Moloney, J. V.; Faccio, D.

    2014-09-01

    Recent developments in laser sources allow one to shape the precise electric-field waveform oscillation at the subcycle level. These waveforms may then be used to drive and control ultrafast nonlinear phenomena at the attosecond timescale. By utilizing numerical solutions of time-dependent Schrödinger equations and exact solutions of a simple quantum-mechanical system, we show that an atom driven by such sources exhibit coherent history-dependent effects. These manifest themselves in "macroscopic" quantities such as the yield in multicolor, strong-field ionization. We argue that weakly bound, metastable electronic states may enable the dependence on the system history even in long-duration, relatively weak driving waveforms.

  6. Emotional modulation of hippocampus-dependent spatial learning 

    E-print Network

    Elliott, Audrea Elizabeth

    2006-10-30

    by the amygdala. Anxiogenic drugs administered during acquisition in a task that can be acquired either through hippocampus-dependent �place� learning or caudate dependent �response� learning, resulted in the predominant use of response...

  7. Copulas for the description of non-Gaussian spatial dependence (Invited)

    NASA Astrophysics Data System (ADS)

    Bardossy, A.; Guthke, P.

    2013-12-01

    Many natural processes lead to spatially distributed variables which exhibit considerable spatial variability and heterogeneous structures. The statistical description, interpolation or simulation of such fields can be done by geostatistical tools. Geostatistical methods use second order statistics, variograms and covariance functions for the description of spatial variability and the subsequent interpolation and simulation. However natural structures often exhibit non-Gaussian features both in their distributions and in their dependence. One of these is the different spatial dependence of high and low values. This kind of asymmetrical dependence is a clear sign of a non-Gaussian organization of the structure. Asymmetrical dependence is a feature which is independent of the distribution and thus can be related to the dependence described using copulas. Copulas offer a comprehensive description of spatial variability offering a framework to describe and to model asymmetrical behavior. A third order statistical function can describe asymmetrical behavior. Theoretical models allow interpolation and simulation of spatial fields. They differ from those obtained using geostatistics mainly in their uncertainty quantification. Examples from different spatial fields including topographical surfaces, rainfall and groundwater quality fields illustrate the methodology. Consequences of the models with respect to spatial scaling are also discussed.

  8. Spatial, Temporal, and Density-Dependent Components of Habitat Quality for a Desert Owl

    PubMed Central

    Flesch, Aaron D.; Hutto, Richard L.; van Leeuwen, Willem J. D.; Hartfield, Kyle; Jacobs, Sky

    2015-01-01

    Spatial variation in resources is a fundamental driver of habitat quality but the realized value of resources at any point in space may depend on the effects of conspecifics and stochastic factors, such as weather, which vary through time. We evaluated the relative and combined effects of habitat resources, weather, and conspecifics on habitat quality for ferruginous pygmy-owls (Glaucidium brasilianum) in the Sonoran Desert of northwest Mexico by monitoring reproductive output and conspecific abundance over 10 years in and around 107 territory patches. Variation in reproductive output was much greater across space than time, and although habitat resources explained a much greater proportion of that variation (0.70) than weather (0.17) or conspecifics (0.13), evidence for interactions among each of these components of the environment was strong. Relative to habitat that was persistently low in quality, high-quality habitat buffered the negative effects of conspecifics and amplified the benefits of favorable weather, but did not buffer the disadvantages of harsh weather. Moreover, the positive effects of favorable weather at low conspecific densities were offset by intraspecific competition at high densities. Although realized habitat quality declined with increasing conspecific density suggesting interference mechanisms associated with an Ideal Free Distribution, broad spatial heterogeneity in habitat quality persisted. Factors linked to food resources had positive effects on reproductive output but only where nest cavities were sufficiently abundant to mitigate the negative effects of heterospecific enemies. Annual precipitation and brooding-season temperature had strong multiplicative effects on reproductive output, which declined at increasing rates as drought and temperature increased, reflecting conditions predicted to become more frequent with climate change. Because the collective environment influences habitat quality in complex ways, integrated approaches that consider habitat resources, stochastic factors, and conspecifics are necessary to accurately assess habitat quality. PMID:25786257

  9. Spatial, temporal, and density-dependent components of habitat quality for a desert owl.

    PubMed

    Flesch, Aaron D; Hutto, Richard L; van Leeuwen, Willem J D; Hartfield, Kyle; Jacobs, Sky

    2015-01-01

    Spatial variation in resources is a fundamental driver of habitat quality but the realized value of resources at any point in space may depend on the effects of conspecifics and stochastic factors, such as weather, which vary through time. We evaluated the relative and combined effects of habitat resources, weather, and conspecifics on habitat quality for ferruginous pygmy-owls (Glaucidium brasilianum) in the Sonoran Desert of northwest Mexico by monitoring reproductive output and conspecific abundance over 10 years in and around 107 territory patches. Variation in reproductive output was much greater across space than time, and although habitat resources explained a much greater proportion of that variation (0.70) than weather (0.17) or conspecifics (0.13), evidence for interactions among each of these components of the environment was strong. Relative to habitat that was persistently low in quality, high-quality habitat buffered the negative effects of conspecifics and amplified the benefits of favorable weather, but did not buffer the disadvantages of harsh weather. Moreover, the positive effects of favorable weather at low conspecific densities were offset by intraspecific competition at high densities. Although realized habitat quality declined with increasing conspecific density suggesting interference mechanisms associated with an Ideal Free Distribution, broad spatial heterogeneity in habitat quality persisted. Factors linked to food resources had positive effects on reproductive output but only where nest cavities were sufficiently abundant to mitigate the negative effects of heterospecific enemies. Annual precipitation and brooding-season temperature had strong multiplicative effects on reproductive output, which declined at increasing rates as drought and temperature increased, reflecting conditions predicted to become more frequent with climate change. Because the collective environment influences habitat quality in complex ways, integrated approaches that consider habitat resources, stochastic factors, and conspecifics are necessary to accurately assess habitat quality. PMID:25786257

  10. Temperature dependence, spatial scale, and tree species diversity in eastern Asia and North America

    E-print Network

    Brown, James H.

    Temperature dependence, spatial scale, and tree species diversity in eastern Asia and North America in eastern Asia and North America to investigate the roles of environmental temperature and spatial scale and temperature is much steeper in eastern Asia than in North America: in cold climates at high latitudes

  11. Bimodal voltage dependence of TRPA1: mutations of a key pore helix residue reveal strong intrinsic voltage-dependent inactivation.

    PubMed

    Wan, Xia; Lu, Yungang; Chen, Xueqin; Xiong, Jian; Zhou, Yuanda; Li, Ping; Xia, Bingqing; Li, Min; Zhu, Michael X; Gao, Zhaobing

    2014-07-01

    Transient receptor potential A1 (TRPA1) is implicated in somatosensory processing and pathological pain sensation. Although not strictly voltage-gated, ionic currents of TRPA1 typically rectify outwardly, indicating channel activation at depolarized membrane potentials. However, some reports also showed TRPA1 inactivation at high positive potentials, implicating voltage-dependent inactivation. Here we report a conserved leucine residue, L906, in the putative pore helix, which strongly impacts the voltage dependency of TRPA1. Mutation of the leucine to cysteine (L906C) converted the channel from outward to inward rectification independent of divalent cations and irrespective to stimulation by allyl isothiocyanate. The mutant, but not the wild-type channel, displayed exclusively voltage-dependent inactivation at positive potentials. The L906C mutation also exhibited reduced sensitivity to inhibition by TRPA1 blockers, HC030031 and ruthenium red. Further mutagenesis of the leucine to all natural amino acids individually revealed that most substitutions at L906 (15/19) resulted in inward rectification, with exceptions of three amino acids that dramatically reduced channel activity and one, methionine, which mimicked the wild-type channel. Our data are plausibly explained by a bimodal gating model involving both voltage-dependent activation and inactivation of TRPA1. We propose that the key pore helix residue, L906, plays an essential role in responding to the voltage-dependent gating. PMID:24092046

  12. The Butcher-Oemler Effect in 295 Clusters: Strong Redshift Evolution and Cluster Richness Dependence

    Microsoft Academic Search

    V. E. Margoniner; R. R. de Carvalho; R. R. Gal; S. G. Djorgovski

    2000-01-01

    We examine the Butcher-Oemler effect and its cluster richness dependence in\\u000athe largest sample studied to date: 295 Abell clusters. We find a strong\\u000acorrelation between cluster richness and the fraction of blue galaxies, f_B, at\\u000aevery redshift. The slope of the f_B(z) relation is similar for all richnesses,\\u000abut at a given redshift, f_B is systematically higher for poor

  13. The Butcher-Oemler Effect in 295 Clusters: Strong Redshift Evolution and Cluster Richness Dependence

    Microsoft Academic Search

    V. E. Margoniner; R. R. de Carvalho; R. R. Gal; S. G. Djorgovski

    2001-01-01

    We examine the Butcher-Oemler effect and its cluster richness dependence in the largest sample studied to date: 295 Abell clusters. We find a strong correlation between cluster richness and the fraction of blue galaxies, fB, at every redshift. The slope of the fB(z) relation is similar for all richnesses, but at a given redshift, fB is systematically higher for poor

  14. Field-dependent ac susceptibility of amorphous ?: the strongly frustrated regime

    Microsoft Academic Search

    Anita G. Berndt; H. P. Kunkel; Gwyn Williams

    1998-01-01

    Detailed measurements of the field- and temperature-dependent ac susceptibility 0953-8984\\/10\\/38\\/014\\/img2 of amorphous 0953-8984\\/10\\/38\\/014\\/img3 for x = 0.30-0.41, a composition regime that has been characterized as strongly frustrated by previous neutron depolarization and electron microscopy studies, are presented. Whereas the x = 0.41 specimen appears to exhibit a single paramagnetic-spin-glass transition on cooling, this detailed analysis indicates that samples with x

  15. Large-Sample Properties of Parameter Estimates for Strongly Dependent Stationary Gaussian Time Series

    Microsoft Academic Search

    Robert Fox; Murad S. Taqqu

    1986-01-01

    A strongly dependent Gaussian sequence has a spectral density $f(x, \\\\theta)$ satisfying $f(x, \\\\theta) \\\\sim |x|^{-\\\\alpha(\\\\theta)} L_\\\\theta(x)$ as $x \\\\rightarrow 0$, where $0 < \\\\alpha(\\\\theta) < 1$ and $L_\\\\theta(x)$ varies slowly at 0. Here $\\\\theta$ is a vector of unknown parameters. An estimator for $\\\\theta$ is proposed and shown to be consistent and asymptotically normal under appropriate conditions. These conditions

  16. Magnetic field dependent specific heat and enhanced Wilson ratio in strongly correlated layered cobalt oxide

    Microsoft Academic Search

    P. Limelette; H. Muguerra; S. Hébert

    2010-01-01

    We have investigated the low-temperature specific-heat properties as a function of magnetic field in the strongly correlated layered cobalt oxide [BiBa0.66K0.36O2]CoO2 . These measurements reveal two kinds of magnetic field dependent contributions in qualitative agreement with the presence of a previously inferred magnetic quantum critical point (QCP). First, the coefficient of the low-temperature T3 behavior of the specific heat turns

  17. The time dependent machine makespan problem is strongly NP-complete

    Microsoft Academic Search

    T. C. Edwin Cheng; Qing Ding

    1999-01-01

    The computational complexity of the problem of scheduling a set of start-time dependent tasks with deadlines and identical decreasing rates of processing times on a single machine to minimize the makespan is open. In this paper we show that the problem is strongly NP-complete by a reduction from 3-Partition.Scope and purposeThere has been increasing interest in scheduling models where the

  18. Spatially dependent heating and ionization: From CME to ICME

    NASA Astrophysics Data System (ADS)

    Lepri, S. T.; Laming, J.; Rakowski, C. E.

    2010-12-01

    The January 21st 2005 Interplanetary Coronal Mass Ejection (ICME) observed by multiple spacecraft at L1 was also observed further out in the heliosphere at Ulysses (~3.25 AU). Previous multi-spacecraft studies of this ICME found evidence suggesting that the flanks of a magnetic cloud like structure associated with this ICME were observed at L1 while a more central cut through the associated magnetic cloud was observed at Ulysses. This event presents a unique opportunity to study the spatial variation of the ionic composition contained within a single ICME and relate it to the eruption at the Sun. Using SWICS, we compare and contrast the heavy ion composition across the two different observations cuts through the ICME. We will compare the results from ACE and Ulysses with predictions from ionization models in the corona and with remote observations of phenomena indicative of electron heating in the inner corona.

  19. Intensity dependent waiting time for strong electron trapping events in speckle stimulated raman scatter

    SciTech Connect

    Rose, Harvey [Los Alamos National Laboratory; Daughton, W [Los Alamos National Laboratory; Yin, L [Los Alamos National Laboratory

    2009-01-01

    The onset of Stimulated Raman scatter from an intense laser speckle is the simplest experimentally realizable laser-plasma-interaction environment. Despite this data and recent 3D particle simulations, the controlling mechanism at the onset of backscatter in the kinetic regime when strong electron trapping in the daughter Langmuir wave is a dominant nonlinearity is not understood. This paper explores the consequences of assuming that onset is controlled by large thermal fluctuations. A super exponential dependence of mean reflectivity on speckle intensity in the onset regime is predicted.

  20. Measuring time-dependent Greens Functions of strongly correlated gases in optical lattices

    NASA Astrophysics Data System (ADS)

    Kantian, Adrian; Schollwöck, Ulrich; Giamarchi, Thierry

    2015-03-01

    Recent advances in single-site addressing in optical-lattice confined strongly correlated ultracold gases promise to deliver entirely new capabilities for these systems to serve as quantum simulators. We show how these advances may be employed to design in-situ measurements of both local and nonlocal time-dependent Greens functions as well as higher-order correlators. Using analytics side-by-side with time-dependent DMRG we quantify the practically available resolutions of these schemes - which can be applied for practically any 1D and 2D system of lattice-confined ultracold atoms - for several examples of interest, such as the mobile impurity problem and the superfluid-Mott insulator transition. This work was supported in part by the Swiss NSF under Division II.

  1. Surface second harmonic generation from silicon pillar arrays with strong geometrical dependence.

    PubMed

    Dev Choudhury, B; Sahoo, Pankaj K; Sanatinia, R; Andler, Guillermo; Anand, S; Swillo, M

    2015-05-01

    We present experimental demonstration and analysis of enhanced surface second harmonic generation (SHG) from hexagonal arrays of silicon pillars. Three sets of Si pillar samples with truncated cone-shaped pillar arrays having periods of 500, 1000, and 2000 nm, and corresponding average diameters of 200, 585 and 1550 nm, respectively, are fabricated by colloidal lithography and plasma dry etching. We have observed strong dependence of SHG intensity on the pillar geometry. Pillar arrays with a 1000 nm period and a 585 nm average diameter give more than a one order of magnitude higher SHG signal compared to the other two samples. We theoretically verified the dependence of SHG intensity on pillar geometry by finite difference time domain simulations in terms of the surface normal E-field component. The enhanced surface SHG light can be useful for nonlinear silicon photonics, surface/interface characterization, and optical biosensing. PMID:25927787

  2. Spatial dependence of phenotype-environment associations for tadpoles in natural ponds

    Microsoft Academic Search

    Matt J. Michel

    2011-01-01

    Within natural habitats, phenotypes are shaped by many environmental factors. Consequently, heterogeneity of these factors\\u000a can promote phenotypic divergence. However, because environments exhibit heterogeneity at different spatial scales, phenotypic\\u000a divergence should also exhibit such scale-dependence. Using hierarchical linear models, I determined how multiple environmental\\u000a factors at two spatial scales affected the morphology of wood frog (Rana (Lithobates) sylvatica) tadpoles collected

  3. Strong density-dependent competition and acquired immunity constrain parasite establishment: implications for parasite aggregation.

    PubMed

    Luong, Lien T; Vigliotti, Beth A; Hudson, Peter J

    2011-04-01

    The vast majority of parasites exhibit an aggregated frequency distribution within their host population, such that most hosts have few or no parasites while only a minority of hosts are heavily infected. One exception to this rule is the trophically transmitted parasite Pterygodermatites peromysci of the white-footed mouse (Peromyscus leucopus), which is randomly distributed within its host population. Here, we ask: what are the factors generating the random distribution of parasites in this system when the majority of macroparasites exhibit non-random patterns? We hypothesise that tight density-dependent processes constrain parasite establishment and survival, preventing the build-up of parasites within individual hosts, and preclude aggregation within the host population. We first conducted primary infections in a laboratory experiment using white-footed mice to test for density-dependent parasite establishment and survival of adult worms. Secondary or challenge infection experiments were then conducted to investigate underlying mechanisms, including intra-specific competition and host-mediated restrictions (i.e. acquired immunity). The results of our experimental infections show a dose-dependent constraint on within-host-parasite establishment, such that the proportion of mice infected rose initially with exposure, and then dropped off at the highest dose. Additional evidence of density-dependent competition comes from the decrease in worm length with increasing levels of exposure. In the challenge infection experiment, previous exposure to parasites resulted in a lower prevalence and intensity of infection compared with primary infection of naïve mice; the magnitude of this effect was also density-dependent. Host immune response (IgG levels) increased with the level of exposure, but decreased with the number of worms established. Our results suggest that strong intra-specific competition and acquired host immunity operate in a density-dependent manner to constrain parasite establishment, driving down aggregation and ultimately accounting for the observed random distribution of parasites. PMID:21215747

  4. Response of a galactic disc to vertical perturbations: strong dependence on density distribution

    NASA Astrophysics Data System (ADS)

    Pranav, Pratyush; Jog, Chanda J.

    2010-07-01

    We study the self-consistent, linear response of a galactic disc to non-axisymmetric perturbations in the vertical direction as due to a tidal encounter, and show that the density distribution near the disc mid-plane has a strong impact on the radius beyond which distortions like warps develop. The self-gravity of the disc resists distortion in the inner parts. Applying this approach to a galactic disc with an exponential vertical profile, Saha & Jog showed that warps develop beyond 4-6 disc scalelengths, which could hence be only seen in HI. The real galactic discs, however, have less steep vertical density distributions that lie between a sech and an exponential profile. Here we calculate the disc response for such a general sec h2/n density distribution, and show that the warps develop from a smaller radius of 2-4 disc scalelengths. This naturally explains why most galaxies show stellar warps that start within the optical radius. Thus, a qualitatively different picture of ubiquitous optical warps emerges for the observed less steep density profiles. The surprisingly strong dependence on the density profile is due to the fact that the disc self-gravity depends crucially on its mass distribution close to the mid-plane. General results for the radius of onset of warps, obtained as a function of the disc scalelength and the vertical scaleheight, are presented as contour plots which can be applied to any galaxy.

  5. Strong seasonality produces spatial asynchrony in the outbreak of infectious diseases

    PubMed Central

    Duke-Sylvester, Scott M.; Bolzoni, Luca; Real, Leslie A.

    2011-01-01

    Models for infectious diseases usually assume a fixed demographic structure. Yet, a disease can spread over a region encountering different local demographic variations that may significantly alter local dynamics. Spatial heterogeneity in the resulting dynamics can lead to important differences in the design of surveillance and control strategies. We illustrate this by exploring the north–south gradient in the seasonal demography of raccoon rabies over the eastern USA. We find that the greater variance in the timing of spring births characteristic of southern populations can lead to the spatial synchronization of southern epidemics, while the narrow birth-pulse associated with northern populations can lead to an irregular patchwork of epidemics. These results indicate that surveillance in the southern states can be reduced relative to northern locations without loss of detection ability. This approach could yield significant savings in vaccination programmes. The importance of seasonality in many widely distributed diseases indicates that our findings will find applications beyond raccoon rabies. PMID:20961894

  6. Strong terahertz radiation by beating of spatial-triangular lasers in a plasma

    SciTech Connect

    Malik, Anil K.; Malik, Hitendra K. [Plasma Waves and Particle Acceleration Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi-110 016 (India); Stroth, Ulrich [Institute fuer Plasmaforschung, Universitaet Stuttgart, Stuttgart-70569 (Germany)

    2011-08-15

    Resonant excitation of terahertz (THz) radiation by beating of two spatial-triangular laser beams having different frequencies and wave numbers but the same electric fields is proposed, where the ponderomotive force in the transverse direction is realized due to the beating and spatial variation of the lasers' fields. This gives rise to a stronger transient transverse current due to a sharp gradient in the laser field, and subsequently THz radiation is excited resonantly in the presence of a periodic density structure. The present scheme yields the THz field {approx}10{sup 5} kV/cm and the efficiency {approx}10{sup -2} for the laser intensity {approx}10{sup 14} W/cm{sup 2}.

  7. Restricted dispersal reduces the strength of spatial density dependence in a tropical bird population

    PubMed Central

    Burgess, Malcolm D; Nicoll, Malcolm A.C; Jones, Carl G; Norris, Ken

    2008-01-01

    Spatial processes could play an important role in density-dependent population regulation because the disproportionate use of poor quality habitats as population size increases is widespread in animal populations—the so-called buffer effect. While the buffer effect patterns and their demographic consequences have been described in a number of wild populations, much less is known about how dispersal affects distribution patterns and ultimately density dependence. Here, we investigated the role of dispersal in spatial density dependence using an extraordinarily detailed dataset from a reintroduced Mauritius kestrel (Falco punctatus) population with a territorial (despotic) breeding system. We show that recruitment rates varied significantly between territories, and that territory occupancy was related to its recruitment rate, both of which are consistent with the buffer effect theory. However, we also show that restricted dispersal affects the patterns of territory occupancy with the territories close to release sites being occupied sooner and for longer as the population has grown than the territories further away. As a result of these dispersal patterns, the strength of spatial density dependence is significantly reduced. We conclude that restricted dispersal can modify spatial density dependence in the wild, which has implications for the way population dynamics are likely to be impacted by environmental change. PMID:18285284

  8. Dependence of Empirical Fundamental Diagram on Spatial-Temporal Traffic Patterns Features

    Microsoft Academic Search

    Boris S. Kerner

    2003-01-01

    It is shown that the branch of the empirical fundamental diagram for congested traffic strongly depends both on the type of the congested pattern at a freeway bottleneck and on the freeway location where the fundamental diagram is measured. Since the type of the pattern at the same bottleneck can depend on traffic demand, a qualitative form of the empirical

  9. A comparison of egocentric and allocentric age-dependent spatial learning in the beagle dog.

    PubMed

    Christie, Lori-Ann; Studzinski, Christa M; Araujo, Joseph A; Leung, Cleo S K; Ikeda-Douglas, Candace J; Head, Elizabeth; Cotman, Carl W; Milgram, Norton W

    2005-03-01

    Spatial discriminations can be performed using either egocentric information based on body position or allocentric information based on the position of landmarks in the environment. Beagle dogs ranging from 2 to 16 years of age were tested for their ability to learn a novel egocentric spatial discrimination task that used two identical blocks paired in three possible spatial positions (i.e. left, center and right). Dogs were rewarded for responding to an object furthest to either their left or right side. Therefore, when the center location was used, it was correct on half of the trials and incorrect on the other half. Upon successful acquisition of the task, the reward contingencies were reversed, and the dogs were rewarded for responding to the opposite side. A subset of dogs was also tested on an allocentric spatial discrimination task, landmark discrimination. Egocentric spatial reversal learning and allocentric discrimination learning both showed a significant age-dependent decline, while initial egocentric learning appeared to be age-insensitive. Intra-subject correlation analyses revealed a significant relationship between egocentric reversal learning and allocentric learning. However, the correlation only accounted for a small proportion of the variance, suggesting that although there might be some common mechanism underlying acquisition of the two tasks, additional unique neural substrates were involved depending on whether allocentric or egocentric spatial information processing was required. PMID:15795044

  10. Pressures at larger spatial scales strongly influence the ecological status of heavily modified river water bodies in Germany.

    PubMed

    Kail, Jochem; Wolter, Christian

    2013-06-01

    River biota are influenced by anthropogenic pressures that operate at different spatial scales. Understanding which pressures at which spatial scales affect biota is essential to manage and restore degraded rivers. In Europe, many river reaches were designated as Heavily Modified Water Bodies (HMWB) according to the European Water Framework Directive (WFD), where the ecological potential might mainly be determined by pressures at larger spatial scales outside the HMWB (e.g. hydromorphological alterations at the river network and land use at the catchment scale). In Germany, hydromorphological alterations and diffuse pollution were the main pressures. Therefore, the three objectives of this study were to (i) identify the hydromorphological pressures at the site, reach, and river network scale, and land use categories at the catchment scale which significantly affect the ecological status of HMWB in Germany, (ii) quantify the relative importance of these pressures at different spatial scales, and (iii) analyse the differences in response between fish and macroinvertebrates. The results indicated that: (i) At the reach scale, fish were most strongly influenced by channel-bank conditions whilst the naturalness of channel-planform was the best proxy for the ecological status of macroinvertebrates. At the catchment scale, urbanization was the most detrimental land use. (ii) The pressures at larger spatial scales (catchment land use and hydromorphological alterations in the river network) generally were more important than hydromorphological alterations at the reach scale. (iii) Fish were affected equally by both, hydromorphological alterations at the reach scale and large-scale pressures whereas the latter were far more important for the ecological status of macroinvertebrates. In conclusion, these results indicated that large-scale pressures may often limit the efficiency of reach-scale restoration, especially for macroinvertebrates, even in the absence of saprobic pollution, and have to be considered for the management and restoration of HMWB in Germany and comparable degraded river reaches. PMID:23542480

  11. On the Spatial Dependence Structure of Isotropic Pairwise Gaussian-Markov Random Field Models

    E-print Network

    Levada, Alexandre L M

    2011-01-01

    Markov Random Field (MRF) models are powerful tools for contextual modeling. However, little is known about how the spatial dependence between its elements is encoded in terms of statistical information, more precisely, information-theoretic measures. In this paper, we enlight the connection between Fisher information, Shannon entropy and spatial properties of the random field in the case of Gaussian variables (a Gaussian Markov random field), by defining analytical expressions to compute the local and global versions of these measures using Besag's pseudo-likelihood function (conditional independence assumption). Besides, we use the derived expressions to define an exact expression for the asymptotic variance of the maximum pseudo-likelihood estimator of the spatial dependence parameter, showing that it does not reach the Cramer-R\\'ao lower bound, since information equality fails. The obtained results provide a rich framework for extraction of relevant statistical information in a variety of MRF applications...

  12. THE WAVELET-GALERKIN METHOD FOR SOLVING PDE'S WITH SPATIALLY DEPENDENT VARIABLES

    E-print Network

    Paris-Sud XI, Université de

    THE WAVELET-GALERKIN METHOD FOR SOLVING PDE'S WITH SPATIALLY DEPENDENT VARIABLES Simon Jones, Montreal, Quebec, Canada e-mail: simon.jones2@mcgill.ca Discrete orthogonal wavelets are a family of functions with compact support which form a ba- sis on a bounded domain. Use of these wavelet families

  13. Drivers of bacterial -diversity depend on spatial scale Jennifer B. H. Martinya,1

    E-print Network

    German, Donovan P.

    whether the mechanisms that underlie bacterial -diversity vary over centimeters to continental spatial diversification of ammonia-oxidizing bacteria taxa at the continental scale, de- spite an overall relationship-decay | Nitrosomonadales | ecological drift Biodiversity supports the ecosystem processes upon which so- ciety depends (1

  14. A symplectic, symmetric algorithm for spatial evolution of particles in a time-dependent field6

    E-print Network

    Boyer, Edmond

    evolution in a time-dependent field with a fixed spatial step. The scheme is implemented in one space dimension and tested, showing excellent adequacy to experiment analysis. Keywords: symplectic integrator, wave-particle interaction, hamiltonian chaos, resonance overlap, traveling wave tube PACS: 52.65.Cc, 05

  15. Evolution of rotated anomalous hollow Gaussian beams in nonlinear media with a strongly spatial nonlocality

    NASA Astrophysics Data System (ADS)

    Dai, Zhiping; Yang, Zhenjun; Ling, Xiaohui; Pang, Zhaoguang; Zhang, Shumin

    2015-06-01

    In this paper, using the rotating coordinates, we take the anomalous hollow Gaussian beam as an example to investigate the evolution of an ellipse-symmetric beam in strongly nonlocal nonlinear media. A set of analytical expressions are obtained and some numerical simulations are carried out to illustrate the relation between the evolution characteristics and the rotation angle. It is found that the evolution properties, such as the critical powers, beam widths, and intensity distributions in x and y directions, are all variational with the rotation angle.

  16. Renormalization-scheme dependence of the strong coupling constantin quantum chromodynamics

    SciTech Connect

    Blumenfeld, A.; Moshe, M.

    1982-08-01

    Quantum chromodynamics (QCD) lacks a limit analogous to the Thomson limit of quantum electrodynamics (QED) for defining its coupling constant. Nevertheless, the strong coupling constant in QCD can be determined from measurable quantities in an approximately scheme-independent manner as -q/sup 2/..-->..infinity. At finite q/sup 2/, however, high-order terms in the renormalization-group functions introduce scheme-dependent terms into ..cap alpha../sub s/(q/sup 2/). A recently suggested method for estimating high-order terms in solutions of Callan-Symanzik equation, which is similar in nature to techniques employed in QED, enables us to determine the size of these scheme-dependent terms. We also discuss a modified minimal-subtraction (MS) scheme which is very appealing. It has the same ..beta.. function as the MS scheme (to all orders) but it equals the momentum-subtraction (MOM) scheme up to two-loop calculations and differs from it at higher orders. We denote this scheme as MOM.

  17. Aphid and ladybird beetle abundance depend on the interaction of spatial effects and genotypic diversity.

    PubMed

    Genung, Mark A; Crutsinger, Gregory M; Bailey, Joseph K; Schweitzer, Jennifer A; Sanders, Nathan J

    2012-01-01

    Intraspecific variation and genotypic diversity of host-plants can affect the structure of associated arthropod communities and the dynamics of populations. Similarly, neighboring plants can also affect interactions between host-plants and their associated arthropods. However, most studies on the effects of host-plant genotypes have largely ignored the potential effects of neighboring host-plants on arthropod communities. In this study, we used a common garden experiment to ask how spatial effects of neighboring patches, along with genotype identity and genotypic diversity in tall goldenrod (Solidago altissima), affect the abundances of a common goldenrod herbivore (Uroleucon nigrotuberculatum) and their dominant predator (Harmonia axyridis, a ladybird beetle). Aphid abundance varied 80-fold among genotypes, while ladybird beetle abundance was not affected by genotype identity. Additionally, there were strong effects of neighboring plots: aphid abundance in a focal plot was positively correlated to aphid abundance in nearby plots, suggesting strong spatial patterning in the abundance of aphids. Neither aphid nor ladybird beetle abundance was affected by genotypic diversity. However, focal plot genotypic diversity mediated the strength of the neighborhood effect (i.e., strong effects for genotype polyculture focal plots and weak effects for genotype monoculture focal plots). Our results show that aphids were directly influenced by host-plant genotype identity while ladybird beetles responded mainly to prey abundance, and suggest that genotypic diversity can influence the effects of spatial processes on the plant-herbivore interactions. PMID:21805301

  18. Frequency Dependence of Signal Power and Spatial Reach of the Local Field Potential

    PubMed Central

    ??ski, Szymon; Lindén, Henrik; Tetzlaff, Tom; Pettersen, Klas H.; Einevoll, Gaute T.

    2013-01-01

    Despite its century-old use, the interpretation of local field potentials (LFPs), the low-frequency part of electrical signals recorded in the brain, is still debated. In cortex the LFP appears to mainly stem from transmembrane neuronal currents following synaptic input, and obvious questions regarding the ‘locality’ of the LFP are: What is the size of the signal-generating region, i.e., the spatial reach, around a recording contact? How far does the LFP signal extend outside a synaptically activated neuronal population? And how do the answers depend on the temporal frequency of the LFP signal? Experimental inquiries have given conflicting results, and we here pursue a modeling approach based on a well-established biophysical forward-modeling scheme incorporating detailed reconstructed neuronal morphologies in precise calculations of population LFPs including thousands of neurons. The two key factors determining the frequency dependence of LFP are the spatial decay of the single-neuron LFP contribution and the conversion of synaptic input correlations into correlations between single-neuron LFP contributions. Both factors are seen to give low-pass filtering of the LFP signal power. For uncorrelated input only the first factor is relevant, and here a modest reduction (<50%) in the spatial reach is observed for higher frequencies (>100 Hz) compared to the near-DC () value of about . Much larger frequency-dependent effects are seen when populations of pyramidal neurons receive correlated and spatially asymmetric inputs: the low-frequency () LFP power can here be an order of magnitude or more larger than at 60 Hz. Moreover, the low-frequency LFP components have larger spatial reach and extend further outside the active population than high-frequency components. Further, the spatial LFP profiles for such populations typically span the full vertical extent of the dendrites of neurons in the population. Our numerical findings are backed up by an intuitive simplified model for the generation of population LFP. PMID:23874180

  19. Informing surveillance programmes by investigating spatial dependency of subclinical Salmonella infection.

    PubMed

    Benschop, J; Stevenson, M A; Dahl, J; Morris, R S; French, N P

    2009-09-01

    The aim of this paper is to investigate local spatial dependency with regard to Salmonella seropositivity in data from the Danish swine salmonellosis control programme and its application in informing surveillance strategies. We applied inhomogeneous and observed-difference K-function estimation, and geo-statistical modelling to data from the Danish swine salmonellosis control programme. Slaughter-pig farm density showed large variation at both the country-wide and local level in Denmark (median 0.23, range 0.02-0.47 farms/km(2)). The spatial distribution of pig farms followed a random inhomogeneous Poisson process but was not aggregated. We found evidence for aggregation of Salmonella case farms over that of all farms at distances of up to 6 km and semivariogram analyses of Salmonella seropositivity revealed spatial dependency between pairs of farms up to 4 km apart. The strength of the spatial dependency was positively associated with slaughter-pig farm density. We proposed sampling more intensively those farms within a 4 km radius of farms that were identified with a high Salmonella status, and reduced sampling of farms that are within this radius of 'Salmonella-free' farms. Our approach has the potential to optimize sampling strategies while maintaining consumer confidence in food safety and also has potential to be used for other zoonotic disease surveillance systems. PMID:19224653

  20. Compton scattering in strong magnetic fields: Spin-dependent influences at the cyclotron resonance

    NASA Astrophysics Data System (ADS)

    Gonthier, Peter L.; Baring, Matthew G.; Eiles, Matthew T.; Wadiasingh, Zorawar; Taylor, Caitlin A.; Fitch, Catherine J.

    2014-08-01

    The quantum electrodynamical (QED) process of Compton scattering in strong magnetic fields is commonly invoked in atmospheric and inner magnetospheric models of x-ray and soft gamma-ray emission in high-field pulsars and magnetars. A major influence of the field is to introduce resonances at the cyclotron frequency and its harmonics, where the incoming photon accesses thresholds for the creation of virtual electrons or positrons in intermediate states with excited Landau levels. At these resonances, the effective cross section typically exceeds the classical Thomson value by over 2 orders of magnitude. Near and above the quantum critical magnetic field of 44.13 TeraGauss, relativistic corrections must be incorporated when computing this cross section. This profound enhancement underpins the anticipation that resonant Compton scattering is a very efficient process in the environs of highly magnetized neutron stars. This paper presents formalism for the QED magnetic Compton differential cross section valid for both subcritical and supercritical fields, yet restricted to scattered photons that are below pair creation threshold. Calculations are developed for the particular case of photons initially propagating along the field, and in the limit of zero vacuum dispersion, mathematically simple specializations that are germane to interactions involving relativistic electrons frequently found in neutron star magnetospheres. This exposition of relativistic, quantum, magnetic Compton cross sections treats electron spin dependence fully, since this is a critical feature for describing the finite decay lifetimes of the intermediate states. Such lifetimes are introduced to truncate the resonant cyclotronic divergences via standard Lorentz profiles. The formalism employs both the traditional Johnson and Lippmann (JL) wave functions and the Sokolov and Ternov (ST) electron eigenfunctions of the magnetic Dirac equation. The ST states are formally correct for self-consistently treating spin-dependent effects that are so important in the resonances. It is found that the values of the polarization-dependent differential cross section depend significantly on the choice of ST or JL eigenstates when in the fundamental resonance but not outside of it, a characteristic that is naturally expected. Relatively compact analytic forms for the cross sections are presented that will prove useful for astrophysical modelers.

  1. ?9-Tetrahydrocannabinol-dependent mice undergoing withdrawal display impaired spatial memory

    PubMed Central

    Wise, Laura E.; Varvel, Stephen A.; Selley, Dana E.; Wiebelhaus, Jason M.; Long, Kelly A.; Middleton, Lisa S.; Sim-Selley, Laura J.

    2012-01-01

    Rationale Cannabis users display a constellation of withdrawal symptoms upon drug discontinuation, including sleep disturbances, irritability, and possibly memory deficits. In cannabinoid-dependent rodents, the CB1 antagonist rimona-bant precipitates somatic withdrawal and enhances forskolin-stimulated adenylyl cyclase activity in cerebellum, an effect opposite that of acutely administered ?9-tetrahydrocannabinol (THC), the primary constituent in cannabis. Objectives Here, we tested whether THC-dependent mice undergoing rimonabant-precipitated withdrawal display short-term spatial memory deficits, as assessed in the Morris water maze. We also evaluated whether rimonabant would precipitate adenylyl cyclase superactivation in hippocampal and cerebellar tissue from THC-dependent mice. Results Rimonabant significantly impaired spatial memory of THC-dependent mice at lower doses than those necessary to precipitate somatic withdrawal behavior. In contrast, maze performance was near perfect in the cued task, suggesting sensorimotor function and motivational factors were unperturbed by the withdrawal state. Finally, rimonabant increased adenylyl cyclase activity in cerebellar, but not in hippocampal, membranes. Conclusions The memory disruptive effects of THC undergo tolerance following repeated dosing, while the withdrawal state leads to a rebound deficit in memory. These results establish spatial memory impairment as a particularly sensitive component of cannabinoid withdrawal, an effect that may be mediated through compensatory changes in the cerebellum. PMID:21559804

  2. Field-dependent ac susceptibility of amorphous ?: the strongly frustrated regime

    NASA Astrophysics Data System (ADS)

    Berndt, Anita G.; Kunkel, H. P.; Williams, Gwyn

    1998-09-01

    Detailed measurements of the field- and temperature-dependent ac susceptibility 0953-8984/10/38/014/img2 of amorphous 0953-8984/10/38/014/img3 for x = 0.30-0.41, a composition regime that has been characterized as strongly frustrated by previous neutron depolarization and electron microscopy studies, are presented. Whereas the x = 0.41 specimen appears to exhibit a single paramagnetic-spin-glass transition on cooling, this detailed analysis indicates that samples with x = 0.30 and x = 0.32 display two transitions. In both latter specimens, 0953-8984/10/38/014/img2 near the upper transition exhibits a line of maxima which decrease in amplitude but increase in temperature as the field is increased; the locus of these maxima delineates a crossover line consistent with the presence of critical fluctuations accompanying a (continuous) paramagnetic-ferromagnetic transition. At lower temperature the non-linear response of these same two samples exhibits a distinct (but not divergent) anomaly, in contrast to the behaviour reported for specimens with lower values for x. Indeed, for the first time, we report the observation (for the x = 0.32 sample) of a more pronounced anomaly in this non-linear behaviour near the lower-temperature transition than that observed at the upper transition. On the basis of these new data, a modified phase diagram for the amorphous FeMn system is constructed.

  3. Dependence of Empirical Fundamental Diagram on Spatial-Temporal Traffic Patterns Features

    Microsoft Academic Search

    Boris S. Kerner

    2003-01-01

    It is shown that the branch of the empirical fundamental diagram for\\u000acongested traffic strongly depends both on the type of the congested pattern at\\u000aa freeway bottleneck and on the freeway location where the fundamental diagram\\u000ais measured. Since the type of the pattern at the same bottleneck can depend on\\u000atraffic demand, a qualitative form of the empirical

  4. DASPK: A new high order and adaptive time-integration technique with applications to mantle convection with strongly temperature-and pressure-dependent rheology

    NASA Astrophysics Data System (ADS)

    van Keken, P. E.; Yuen, D. A.; Petzold, L. R.

    A new technique is presented for the efficient time-integration of the equations that describe the slow deformation in the Earth's mantle. This method is based on the adaptive, high order implicit solver for differential-algebraic equations (DASPK) and is independent of the choice of spatial discretization technique. Using a standard finite element package for the spatial discretization, it is shown that the solution of the 2-D convection-diffusion equation for temperature can be performed at much lower computational cost, but at the same or higher accuracy, compared to a traditional implicit second-order method. The solution to the full set of 2-D mantle convection equations is 3 to 4 times more efficient. Both in 2-D and 3-D, the memory and CPU-usage of this implementation depends linearly on the number of grid points and has good properties with respect to vectorization and parallelization. As an application of this technique, convection in the Earth's mantle with strongly temperature and pressure dependent rheology is studied in axisymmetric geometry. Models are developed that are consistent with current estimates of surface heat flow and radial viscosity distribution. General characteristics are: a dynamic upper mantle overlying a near-stationary lower mantle; strong plumes rising from the core-mantle boundary, even at high rates of internal heating; and an effective Rayleigh number of nearly two orders of magnitudes lower than commonly used values in the range of 107 to 108.

  5. k-dependent optics of nanostructures: Spatial dispersion of metallic nanorings and split-ring resonators

    NASA Astrophysics Data System (ADS)

    Gompf, Bruno; Krausz, Barbara; Frank, Bettina; Dressel, Martin

    2012-08-01

    The response of matter on an electromagnetic wave at a certain point and time depends on the field strength prior to this time and at places close to this point. Hence the material parameters are functions of the frequency ? and the wave vector k?, in general. While the temporal dispersion is common knowledge, spatial dispersion in usually disregarded. However it becomes crucial in the optical response of nanostructures. Here we map the complete k?-dependent optical response of a split-ring-resonator array over a broad frequency range via Mueller-matrix spectroscopic ellipsometry at different angles of incidence and all azimuthal orientations. The comparison with a closed-ring structure elucidates the rule of spatial dispersion in metal-dielectric nanostructures.

  6. Relativistic scattering with a spatially dependent effective mass in the Dirac equation

    SciTech Connect

    Alhaidari, A. D. [Shura Council, Riyadh 11212 (Saudi Arabia); Bahlouli, H.; Abdelmonem, M. S. [Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Al-Hasan, A. [Samba Financial Group, Riyadh 11421 (Saudi Arabia)

    2007-06-15

    We formulate a relativistic algebraic method of scattering for systems with spatially dependent mass based on the J-matrix method. The reference Hamiltonian is the three-dimensional Dirac Hamiltonian but with a mass that is position-dependent with a constant asymptotic limit. Additionally, this effective mass distribution is locally represented in a finite dimensional function subspace. The spinor couples to spherically symmetric vector and pseudo scalar potentials that are short-range such that they are accurately represented by their matrix elements in the same finite dimensional subspace. We calculate the relativistic phase shift as a function of energy for a given configuration and study the effect of spatial variation of the mass on the energy resonance structure.

  7. Selective temporal resections and spatial memory impairment: cue dependent lateralization effects.

    PubMed

    Barkas, Lisa J; Henderson, Jenni L; Hamilton, Derek A; Redhead, Edward S; Gray, William P

    2010-04-01

    Patients who had undergone a unilateral trans-sylvian selective amygdalohippocampectomy as treatment for chronic intractable epilepsy were tested in a virtual Morris Water Maze (MWM) task where they were required to locate a hidden platform as a measure of spatial learning. These individuals' performance on spatial tasks was compared to age-matched healthy controls and drug-matched healthy controls. Training occurred in two different maze environments, one with conventional cues such as windows and doors, and another with abstract cues, such as colours and patterns. Participants searched for a hidden platform in the virtual pool, guided by either the conventional or abstract cues. There was a significant impairment in the surgery group compared to the control groups in all environments, however in the abstract environment only the patients with right-sided lesions were significantly worse than the controls. There was no difference between the groups on a control egocentric navigation task. These results suggest that people who have had right-sided surgery are impaired in spatial tasks, and that the level of impairment on the spatial task may be dependent on the characteristics of the cues such as how easily the cues are verbalised. These results support the notion of the functional lateralization of specific elements of spatial memory and functional lateralization, and may shed light on previous inconsistencies in this area of research. PMID:20064564

  8. Temperature dependence of spatial noise in InSb focal plane arrays

    Microsoft Academic Search

    Lior Shkedy; Ornit Amir; Zipora Calahorra; Joelle Oiknine-Schlesinger; Igor Szafranek

    2000-01-01

    Performance of InSb focal plane array (FPA) detectors depends to a great extent on both the absolute temperature and the temperature fluctuations of the detector. The residual spatial noise, which can be achieved and maintained after a two-point non-uniformity correction (NUC), increases with the FPA temperature changes relative to that at which the NUC procedure was performed. A model is

  9. Spatial dependence of the sheath power transmission factor in DIII-D

    SciTech Connect

    Futch, A.H.; Hill, D.N.; Porter, G.D. (Lawrence Livermore National Lab., CA (USA)); Matthews, G.F. (UKAEA Culham Lab., Abingdon (UK)); Buchenauer, D. (Sandia National Labs., Livermore, CA (USA))

    1991-02-01

    The spatial dependence of the power transmission factor, d, associated with an ion-electron pair passing through the sheath at the DIII-D divertor plate has been determined by sweeping the edge plasma across Langmuir probe detectors. Our results show that d decreases from the classically expected value of eight near the low density edge of the scrape-off-layer plasma to values less than unity at the peak of the profile. 13 refs., 16 figs.

  10. An energy- and spatial-dependent effective mass approach for resonant interband tunneling devices

    Microsoft Academic Search

    M. P. Houng; Y. H. Wang; H. H. Chen

    1993-01-01

    A theoretical study of resonant interband tunneling in GaAs ?-doped inducing homostructure and polytype GaSb\\/AlSb\\/InAs heterostructure is presented in this article. The resonant interband tunneling in such homo- and heterostructures is modeled by an energy- and spatial-dependent effective mass equation incorporating the general transfer matrix method. The present formalism is based on the envelope function approximation as done to date,

  11. Spatial and frequency dependence of plasma currents in a 300 mm capacitively coupled plasma reactor

    Microsoft Academic Search

    Paul A. Miller; Edward V. Barnat; Gregory A. Hebner; Alex M. Paterson; John P. Holland

    2006-01-01

    There is much interest in scaling rf-excited capacitively coupled plasma reactors to larger sizes and to higher frequencies. As the size approaches operating wavelength, concerns arise about non-uniformity across the work piece, particularly in light of the well-documented slow-surface-wave phenomenon. We present measurements and calculations of spatial and frequency dependence of rf magnetic fields inside argon plasma in an industrially

  12. Visualisation of structural inhomogeneities in strongly scattering media using the method of spatially-resolved reflectometry: Monte Carlo simulation

    SciTech Connect

    Bykov, A V; Priezzhev, A V; Myllylae, Risto A

    2011-06-30

    Two-dimensional spatial intensity distributions of diffuse scattering of near-infrared laser radiation from a strongly scattering medium, whose optical properties are close to those of skin, are obtained using Monte Carlo simulation. The medium contains a cylindrical inhomogeneity with the optical properties, close to those of blood. It is shown that stronger absorption and scattering of light by blood compared to the surrounding medium leads to the fact that the intensity of radiation diffusely reflected from the surface of the medium under study and registered at its surface has a local minimum directly above the cylindrical inhomogeneity. This specific feature makes the method of spatially-resolved reflectometry potentially applicable for imaging blood vessels and determining their sizes. It is also shown that blurring of the vessel image increases almost linearly with increasing vessel embedment depth. This relation may be used to determine the depth of embedment provided that the optical properties of the scattering media are known. The optimal position of the sources and detectors of radiation, providing the best imaging of the vessel under study, is determined. (biophotonics)

  13. Native Birds and Alien Insects: Spatial Density Dependence in Songbird Predation of Invading Oak Gallwasps

    PubMed Central

    Schönrogge, Karsten; Begg, Tracey; Stone, Graham N.

    2013-01-01

    Revealing the interactions between alien species and native communities is central to understanding the ecological consequences of range expansion. Much has been learned through study of the communities developing around invading herbivorous insects. Much less, however, is known about the significance of such aliens for native vertebrate predators for which invaders may represent a novel food source. We quantified spatial patterns in native bird predation of invading gall-inducing Andricus wasps associated with introduced Turkey oak (Quercus cerris) at eight sites across the UK. These gallwasps are available at high density before the emergence of caterpillars that are the principle spring food of native insectivorous birds. Native birds showed positive spatial density dependence in gall attack rates at two sites in southern England, foraging most extensively on trees with highest gall densities. In a subsequent study at one of these sites, positive spatial density dependence persisted through four of five sequential week-long periods of data collection. Both patterns imply that invading galls are a significant resource for at least some native bird populations. Density dependence was strongest in southern UK bird populations that have had longest exposure to the invading gallwasps. We hypothesise that this pattern results from the time taken for native bird populations to learn how to exploit this novel resource. PMID:23342048

  14. On Spatial Processes and Asymptotic Inference under Near-Epoch Dependence.

    PubMed

    Jenish, Nazgul; Prucha, Ingmar R

    2012-09-01

    The development of a general inferential theory for nonlinear models with cross-sectionally or spatially dependent data has been hampered by a lack of appropriate limit theorems. To facilitate a general asymptotic inference theory relevant to economic applications, this paper first extends the notion of near-epoch dependent (NED) processes used in the time series literature to random fields. The class of processes that is NED on, say, an ?-mixing process, is shown to be closed under infinite transformations, and thus accommodates models with spatial dynamics. This would generally not be the case for the smaller class of ?-mixing processes. The paper then derives a central limit theorem and law of large numbers for NED random fields. These limit theorems allow for fairly general forms of heterogeneity including asymptotically unbounded moments, and accommodate arrays of random fields on unevenly spaced lattices. The limit theorems are employed to establish consistency and asymptotic normality of GMM estimators. These results provide a basis for inference in a wide range of models with spatial dependence. PMID:22984323

  15. Suppressing an Anti-Inflammatory Cytokine Reveals a Strong Age-Dependent Survival Cost in Mice

    PubMed Central

    Belloni, Virginia; Faivre, Bruno; Guerreiro, Romain; Arnoux, Emilie; Bellenger, Jérôme; Sorci, Gabriele

    2010-01-01

    Background The central paradigm of ecological immunology postulates that selection acts on immunity as to minimize its cost/benefit ratio. Costs of immunity may arise because the energetic requirements of the immune response divert resources that are no longer available for other vital functions. In addition to these resource-based costs, mis-directed or over-reacting immune responses can be particularly harmful for the host. In spite of the potential importance of immunopathology, most studies dealing with the evolution of the immune response have neglected such non resource-based costs. To keep the immune response under control, hosts have evolved regulatory pathways that should be considered when studying the target of the selection pressures acting on immunity. Indeed, variation in regulation may strongly modulate the negative outcome of immune activation, with potentially important fitness consequences. Methodology/Principal Findings Here, we experimentally assessed the survival costs of reduced immune regulation by inhibiting an anti-inflammatory cytokine (IL-10) with anti-IL-10 receptor antibodies (anti-IL-10R) in mice that were either exposed to a mild inflammation or kept as control. The experiment was performed on young (3 months) and old (15 months) individuals, as to further assess the age-dependent cost of suppressing immune regulation. IL-10 inhibition induced high mortality in old mice exposed to the mild inflammatory insult, whereas no mortality was observed in young mice. However, young mice experienced a transitory lost in body mass when injected with the anti-IL-10R antibodies, showing that the treatment was to a lesser extent also costly for young individuals. Conclusions These results suggest a major role of immune regulation that deserves attention when investigating the evolution of immunity, and indicate that the capacity to down-regulate the inflammatory response is crucial for late survival and longevity. PMID:20886083

  16. CONCERNING THE CLASSICAL CEPHEID VI{sub C} WESENHEIT FUNCTION'S STRONG METALLICITY DEPENDENCE

    SciTech Connect

    Majaess, D.; Turner, D. [Department of Astronomy and Physics, Saint Mary's University, Halifax, NS (Canada); Gieren, W., E-mail: dmajaess@cygnus.smu.ca [Departamento de Astronomia, Universidad de Concepcion, Concepcion (Chile)

    2011-11-10

    Evidence is presented which supports findings that the classical Cepheid VI{sub C} period Wesenheit function is relatively insensitive to metallicity. The viability of a recently advocated strong metallicity dependence was evaluated by applying the proposed correction ({gamma} = -0.8 mag dex{sup -1}) to distances established for the Magellanic Clouds via a Galactic VI{sub C} Wesenheit calibration, which is anchored to 10 nearby classical Cepheids with measured Hubble Space Telescope (HST) parallaxes. The resulting {gamma}-corrected distances for the Magellanic Clouds (e.g., Small Magellanic Cloud, {mu}{sub 0,{gamma}} {approx} 18.3) are in significant disagreement with that established from a mean of >300 published estimates (NED-D), and a universal Wesenheit template featuring 11 {delta} Scuti, SX Phe, RR Lyrae, and Type II Cepheid variables with HST/Hipparcos parallaxes. Conversely, adopting a null correction (i.e., {gamma} = 0 mag dex{sup -1}) consolidates the estimates. In tandem with existing evidence, the results imply that variations in chemical composition among Cepheids are a comparatively negligible source of uncertainty for W{sub VIc}-based extragalactic distances and determinations of H{sub 0}. A new approach is described which aims to provide additional Galactic Cepheid calibrators to facilitate subsequent assessments of the VI{sub C} Wesenheit function's relative (in) sensitivity to abundance changes. VVV/UKIDSS/Two Micron All Sky Survey JHK{sub s} photometry for clusters in spiral arms shall be employed to establish a precise galactic longitude-distance relation, which can be applied in certain cases to determine the absolute Wesenheit magnitudes for younger Cepheids.

  17. Effects of reverberant spatial cues on attention-dependent object formation.

    PubMed

    Lee, Adrian K C; Shinn-Cunningham, Barbara G

    2008-03-01

    A recent study showed that when a sound mixture has ambiguous spectrotemporal structure, spatial cues alone are sufficient to change the balance of grouping cues and affect the perceptual organization of the auditory scene. The current study synthesizes similar stimuli in a reverberant setting to see whether the interaural decorrelation caused by reverberant energy reduces the influence of spatial cues on perceptual organization. Results suggest that reverberant spatial cues are less influential on perceptual segregation than anechoic spatial cues. In addition, results replicate an interesting finding from the earlier study, where an ambiguous tone that could logically belong to either a repeating tone sequence or a simultaneous harmonic complex can sometimes "disappear" and never be heard as part of the perceptual foreground, no matter which object a listener attends. As in the previous study, the perceived energy of the ambiguous element does not "trade" between the objects in a complex scene (i.e., the element does not necessarily contribute more to one object when it contributes less to a competing object). Results are consistent with the idea that the perceptual organization of an acoustic mixture depends on what object a listener attends. PMID:18214613

  18. Colour cues or spatial cues? Context-dependent preferences in the European greenfinch (Carduelis chloris).

    PubMed

    Herborn, Katherine; Alexander, Lucille; Arnold, Kathryn E

    2011-03-01

    Using featural cues such as colour to identify ephemeral food can increase foraging efficiency. Featural cues may change over time however; therefore, animals should use spatial cues to relocate food that occurs in a temporally stable position. We tested this hypothesis by measuring the cue preferences of captive greenfinches Carduelis chloris when relocating food hidden in a foraging tray. In these standardised associative learning trials, greenfinches favoured colour cues when returning to a foraging context that they had encountered before only once ("one-trial test") but switched to spatial cues when they had encountered that scenario on ten previous occasions ("repeated-trial test"). We suggest that repeated encounters generated a context in which individuals had a prior expectation of temporal stability, and hence context-dependent cue selection. Next, we trained birds to find food in the absence of colour cues but tested them in the presence of visual distracters. Birds were able to learn spatial cues after one encounter, but only when visual distracters were identical in colouration. When a colourful distracter was present in the test phase, cue selection was random. Unlike the first one-trial test, birds were not biased towards this colourful visual distracter. Together, these results suggest that greenfinches are able to learn both cue types, colour cue biases represent learning, not simply distraction, and spatial cues are favoured over colour cues only in temporally stable contexts. PMID:21170666

  19. The spatial frequency tuning of optic-flow-dependent behaviors in the bumblebee Bombus impatiens.

    PubMed

    Dyhr, Jonathan P; Higgins, Charles M

    2010-05-01

    Insects use visual estimates of flight speed for a variety of behaviors, including visual navigation, odometry, grazing landings and flight speed control, but the neuronal mechanisms underlying speed detection remain unknown. Although many models and theories have been proposed for how the brain extracts the angular speed of the retinal image, termed optic flow, we lack the detailed electrophysiological and behavioral data necessary to conclusively support any one model. One key property by which different models of motion detection can be differentiated is their spatiotemporal frequency tuning. Numerous studies have suggested that optic-flow-dependent behaviors are largely insensitive to the spatial frequency of a visual stimulus, but they have sampled only a narrow range of spatial frequencies, have not always used narrowband stimuli, and have yielded slightly different results between studies based on the behaviors being investigated. In this study, we present a detailed analysis of the spatial frequency dependence of the centering response in the bumblebee Bombus impatiens using sinusoidal and square wave patterns. PMID:20435814

  20. A gender- and sexual orientation-dependent spatial attentional effect of invisible images

    PubMed Central

    Jiang, Yi; Costello, Patricia; Fang, Fang; Huang, Miner; He, Sheng

    2006-01-01

    Human observers are constantly bombarded with a vast amount of information. Selective attention helps us to quickly process what is important while ignoring the irrelevant. In this study, we demonstrate that information that has not entered observers' consciousness, such as interocularly suppressed (invisible) erotic pictures, can direct the distribution of spatial attention. Furthermore, invisible erotic information can either attract or repel observers' spatial attention depending on their gender and sexual orientation. While unaware of the suppressed pictures, heterosexual males' attention was attracted to invisible female nudes, heterosexual females' attention was attracted to invisible male nudes, gay males behaved similarly to heterosexual females, and gay/bisexual females performed in-between heterosexual males and females. PMID:17075055

  1. A gender- and sexual orientation-dependent spatial attentional effect of invisible images.

    PubMed

    Jiang, Yi; Costello, Patricia; Fang, Fang; Huang, Miner; He, Sheng

    2006-11-01

    Human observers are constantly bombarded with a vast amount of information. Selective attention helps us to quickly process what is important while ignoring the irrelevant. In this study, we demonstrate that information that has not entered observers' consciousness, such as interocularly suppressed (invisible) erotic pictures, can direct the distribution of spatial attention. Furthermore, invisible erotic information can either attract or repel observers' spatial attention depending on their gender and sexual orientation. While unaware of the suppressed pictures, heterosexual males' attention was attracted to invisible female nudes, heterosexual females' attention was attracted to invisible male nudes, gay males behaved similarly to heterosexual females, and gay/bisexual females performed in-between heterosexual males and females. PMID:17075055

  2. Folding Study of Venus Reveals a Strong Ion Dependence of Its Yellow Fluorescence under Mildly Acidic Conditions*S

    E-print Network

    Jackson, Sophie

    Folding Study of Venus Reveals a Strong Ion Dependence of Its Yellow Fluorescence under Mildly- cencethatisrelativelyinsensitivetochangesinpHandionconcen- trations. Here, we present a detailed study of the stability and fold- ing of Venus. By following hydrogen-deuterium exchange of 15 N-labeled Venus using NMR spectroscopy over 13 months, residue

  3. Low-frequency ac electroporation shows strong frequency dependence and yields comparable transfection results to dc electroporation

    E-print Network

    Lu, Chang

    Low-frequency ac electroporation shows strong frequency dependence and yields comparable in the frequency range of 10 kHz­1 MHz. Based on Schwan equation, it was thought that with low ac frequencies (10 24061, USA d School of Public Health, Nantong University, Nantong, 226019, PR China e Department

  4. Spatial hierarchical approach in community ecology: a way beyond high context-dependency and low predictability in local phenomena

    Microsoft Academic Search

    Takashi Noda

    2004-01-01

    Patterns and functioning of communities, which are determined by a set of processes operating at a large variety of spatial and temporal scales, exhibit quite high context-dependency and low predictability at the fine spatial scales at which recent studies have concentrated. More attention to broader scale and across-scale phenomena may be useful to search for general patterns and rules in

  5. Strong configurational dependence of elastic properties for a binary model metallic glass

    E-print Network

    Goddard III, William A.

    in a Cu­Zr binary metallic glass assessed by molecular dynamics simulations is reported. By directly evaluating the temperature dependence and configurational potential energy dependence of elastic constants-Rahman formalism22 to calculate elastic stiffness coefficients by con- stant temperature and constant volume nvt

  6. Temperature dependence, spatial scale, and tree species diversity in eastern Asia and North America

    PubMed Central

    Wang, Zhiheng; Brown, James H.; Tang, Zhiyao; Fang, Jingyun

    2009-01-01

    The increase of biodiversity from poles to equator is one of the most pervasive features of nature. For 2 centuries since von Humboldt, Wallace, and Darwin, biogeographers and ecologists have investigated the environmental and historical factors that determine the latitudinal gradient of species diversity, but the underlying mechanisms remain poorly understood. The recently proposed metabolic theory of ecology (MTE) aims to explain ecological patterns and processes, including geographical patterns of species richness, in terms of the effects of temperature and body size on the metabolism of organisms. Here we use 2 comparable databases of tree distributions in eastern Asia and North America to investigate the roles of environmental temperature and spatial scale in shaping geographical patterns of species diversity. We find that number of species increases exponentially with environmental temperature as predicted by the MTE, and so does the rate of spatial turnover in species composition (slope of the species-area relationship). The magnitude of temperature dependence of species richness increases with spatial scale. Moreover, the relationship between species richness and temperature is much steeper in eastern Asia than in North America: in cold climates at high latitudes there are more tree species in North America, but the reverse is true in warmer climates at lower latitudes. These patterns provide evidence that the kinetics of ecological and evolutionary processes play a major role in the latitudinal pattern of biodiversity. PMID:19628692

  7. Strong spin-dependent negative differential resistance in composite graphene superlattices

    NASA Astrophysics Data System (ADS)

    Munárriz, J.; Gaul, C.; Malyshev, A. V.; Orellana, P. A.; Müller, C. A.; Domínguez-Adame, F.

    2013-10-01

    We find clear signatures of spin-dependent negative differential resistance in compound systems comprising a graphene nanoribbon and a set of ferromagnetic insulator strips deposited on top of it. The periodic array of ferromagnetic strips induces a proximity exchange splitting of the electronic states in graphene, resulting in the appearance of a superlattice with a spin-dependent energy spectrum. The electric current through the device can be highly polarized and both the current and its polarization manifest nonmonotonic dependence on the bias voltage. The device operates therefore as an Esaki spin diode, which opens possibilities to design new spintronic circuits.

  8. Submitted to the Annals of Probability STRONG INVARIANCE PRINCIPLES FOR DEPENDENT RANDOM

    E-print Network

    Wu, Wei-Biao

    By Wei Biao Wu University of Chicago We establish strong invariance principles for sums of stationary Merlev`ede and Peligrad (2003), Wu and Woodroofe (2004) and Peligrad and Utev (2005), where the central. WU measurable function for which E[g(0)] = 0; let the the filtration Fk = (. . . , k-1, k), k Z

  9. SPATIALLY DEPENDENT HEATING AND IONIZATION IN AN ICME OBSERVED BY BOTH ACE AND ULYSSES

    SciTech Connect

    Lepri, Susan T. [Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109-2143 (United States); Laming, J. Martin; Rakowski, Cara E. [Space Science Division, Naval Research Laboratory, Code 7674L, Washington, DC 20375-5321 (United States); Von Steiger, Rudolf [International Space Science Institute, Bern CH-3012 (Switzerland)

    2012-12-01

    The 2005 January 21 interplanetary coronal mass ejection (ICME) observed by multiple spacecraft at L1 was also observed from January 21-February 4 at Ulysses (5.3 AU). Previous studies of this ICME have found evidence suggesting that the flanks of a magnetic cloud like structure associated with this ICME were observed at L1 while a more central cut through the associated magnetic cloud was observed at Ulysses. This event allows us to study spatial variation across the ICME and relate it to the eruption at the Sun. In order to examine the spatial dependence of the heating in this ICME, we present an analysis and comparison of the heavy ion composition observed during the passage of the ICME at L1 and at Ulysses. Using SWICS, we compare the heavy ion composition across the two different observation cuts through the ICME and compare it with predictions for heating during the eruption based on models of the time-dependent ionization balance throughout the event.

  10. Strongly bias-dependent tunnel magnetoresistance in manganite spin filter tunnel junctions.

    PubMed

    Prasad, Bhagwati; Zhang, Wenrui; Jian, Jie; Wang, Haiyan; Blamire, Mark G

    2015-05-01

    A highly unconventional bias-dependent tunnel magnetoresistance (TMR) response is observed in Sm0.75 Sr0.25 MnO3 -based nanopillar spin filter tunnel junctions (SFTJs) with two different behaviors in two different thickness regimes of the barrier layer. Thinner barrier devices exhibit conventional SFTJ behaviors; however, for larger barrier thicknesses, the TMR-bias dependence is more complex and reverses sign at higher bias. PMID:25845706

  11. Strong magnetic field dependence of laser emission from quantum wires formed by cleaved edge overgrowth

    Microsoft Academic Search

    W. Wegscheider; L. N. Pfeiffer; K. W. West; P. Littlewood; O. Narayan; M. Hagn; M. M. Dignam; R. E. Leibenguth

    1996-01-01

    Characteristics of GaAsAlGaAs quantum wire (QWR) lasers are studied for the first time under strong magnetic fields up to 12T. The QWR laser diodes have been fabricated by the molecular beam epitaxy technique, we call “cleaved edge overgrowth” (CEO), which combines conventional layer growth along the [001] crystal axis with high-quality regrowth on the (110) crystal face formed by an

  12. The Temperature Dependence of Optical Phonon Scattering in Graphene under Strong Magnetic Field

    NASA Astrophysics Data System (ADS)

    Wang, Zi-Wu; Liu, Lei; Shi, Lin; Gong, Xiao-Jing; Li, Wei-Ping; Xu, Ke

    2013-09-01

    We theoretically investigate the electron relaxation mechanism assisted by optical phonon scattering among Landau levels in graphene. The relaxation rate displays a Gaussian distribution by considering the effect of lattice relaxation that arises from the electron-deformation potential acoustic phonon coupling. We find that the present model can gives both increasing and decreasing temperature dependence of the relaxation process mediated by phonon emission. Moreover, the deformation potential constant of the acoustic phonon plays an important role in determining the temperature dependence of relaxation rate.

  13. Defining neighborhood boundaries in studies of spatial dependence in child behavior problems

    PubMed Central

    2013-01-01

    Background The purpose of this study was to extend the analysis of neighborhood effects on child behavioral outcomes in two ways: (1) by examining the geographic extent of the relationship between child behavior and neighborhood physical conditions independent of standard administrative boundaries such as census tracts or block groups and (2) by examining the relationship and geographic extent of geographic peers’ behavior and individual child behavior. Methods The study neighborhood was a low income, ethnic minority neighborhood of approximately 20,000 residents in a large city in the southwestern United States. Observational data were collected for 11,552 parcels and 1,778 face blocks in the neighborhood over a five week period. Data on child behavior problems were collected from the parents of 261 school-age children (81% African American, 14% Latino) living in the neighborhood. Spatial analysis methods were used to examine the spatial dependence of child behavior problems in relation to physical conditions in the neighborhood for areas surrounding the child’s home ranging from a radius of 50 meters to a radius of 1000 meters. Likewise, the spatial dependence of child behavior problems in relation to the behavior problems of neighborhood peers was examined for areas ranging from a radius 255 meters to a radius of 600 meters around the child’s home. Finally, we examined the joint influence of neighborhood physical conditions and geographic peers. Results Poor conditions of the physical environment of the neighborhood were related to more behavioral problems, and the geographic extent of the physical environment that mattered was an area with a radius between 400 and 800 meters surrounding the child’s home. In addition, the average level of behavior problems of neighborhood peers within 255 meters of the child’s home was also positively associated with child behavior problems. Furthermore, these effects were independent of one another. Conclusions These findings demonstrate that using flexible geographies in the study of neighborhood effects can provide important insights into spatial influences on health outcomes. With regards to child behavioral outcomes, specifically, these findings support the importance of addressing the physical and social environment when planning community-level interventions to reduce child behavior problems. PMID:23642001

  14. Input-Dependent Frequency Modulation of Cortical Gamma Oscillations Shapes Spatial Synchronization and Enables Phase Coding

    PubMed Central

    Lowet, Eric; Roberts, Mark; Hadjipapas, Avgis; Peter, Alina; van der Eerden, Jan; De Weerd, Peter

    2015-01-01

    Fine-scale temporal organization of cortical activity in the gamma range (?25–80Hz) may play a significant role in information processing, for example by neural grouping (‘binding’) and phase coding. Recent experimental studies have shown that the precise frequency of gamma oscillations varies with input drive (e.g. visual contrast) and that it can differ among nearby cortical locations. This has challenged theories assuming widespread gamma synchronization at a fixed common frequency. In the present study, we investigated which principles govern gamma synchronization in the presence of input-dependent frequency modulations and whether they are detrimental for meaningful input-dependent gamma-mediated temporal organization. To this aim, we constructed a biophysically realistic excitatory-inhibitory network able to express different oscillation frequencies at nearby spatial locations. Similarly to cortical networks, the model was topographically organized with spatially local connectivity and spatially-varying input drive. We analyzed gamma synchronization with respect to phase-locking, phase-relations and frequency differences, and quantified the stimulus-related information represented by gamma phase and frequency. By stepwise simplification of our models, we found that the gamma-mediated temporal organization could be reduced to basic synchronization principles of weakly coupled oscillators, where input drive determines the intrinsic (natural) frequency of oscillators. The gamma phase-locking, the precise phase relation and the emergent (measurable) frequencies were determined by two principal factors: the detuning (intrinsic frequency difference, i.e. local input difference) and the coupling strength. In addition to frequency coding, gamma phase contained complementary stimulus information. Crucially, the phase code reflected input differences, but not the absolute input level. This property of relative input-to-phase conversion, contrasting with latency codes or slower oscillation phase codes, may resolve conflicting experimental observations on gamma phase coding. Our modeling results offer clear testable experimental predictions. We conclude that input-dependency of gamma frequencies could be essential rather than detrimental for meaningful gamma-mediated temporal organization of cortical activity. PMID:25679780

  15. Input-dependent frequency modulation of cortical gamma oscillations shapes spatial synchronization and enables phase coding.

    PubMed

    Lowet, Eric; Roberts, Mark; Hadjipapas, Avgis; Peter, Alina; van der Eerden, Jan; De Weerd, Peter

    2015-02-01

    Fine-scale temporal organization of cortical activity in the gamma range (?25-80Hz) may play a significant role in information processing, for example by neural grouping ('binding') and phase coding. Recent experimental studies have shown that the precise frequency of gamma oscillations varies with input drive (e.g. visual contrast) and that it can differ among nearby cortical locations. This has challenged theories assuming widespread gamma synchronization at a fixed common frequency. In the present study, we investigated which principles govern gamma synchronization in the presence of input-dependent frequency modulations and whether they are detrimental for meaningful input-dependent gamma-mediated temporal organization. To this aim, we constructed a biophysically realistic excitatory-inhibitory network able to express different oscillation frequencies at nearby spatial locations. Similarly to cortical networks, the model was topographically organized with spatially local connectivity and spatially-varying input drive. We analyzed gamma synchronization with respect to phase-locking, phase-relations and frequency differences, and quantified the stimulus-related information represented by gamma phase and frequency. By stepwise simplification of our models, we found that the gamma-mediated temporal organization could be reduced to basic synchronization principles of weakly coupled oscillators, where input drive determines the intrinsic (natural) frequency of oscillators. The gamma phase-locking, the precise phase relation and the emergent (measurable) frequencies were determined by two principal factors: the detuning (intrinsic frequency difference, i.e. local input difference) and the coupling strength. In addition to frequency coding, gamma phase contained complementary stimulus information. Crucially, the phase code reflected input differences, but not the absolute input level. This property of relative input-to-phase conversion, contrasting with latency codes or slower oscillation phase codes, may resolve conflicting experimental observations on gamma phase coding. Our modeling results offer clear testable experimental predictions. We conclude that input-dependency of gamma frequencies could be essential rather than detrimental for meaningful gamma-mediated temporal organization of cortical activity. PMID:25679780

  16. Strong strain dependence of ferroelectric coercivity in a BiFeO3 film

    SciTech Connect

    Biegalski, Michael D [ORNL; Kim, Dae Ho [Tulane University; Dorr, Kathrin [IFW Dresden; Christen, Hans M [ORNL

    2011-01-01

    The ferroelectric polarization loop of an epitaxial BiFeO3 film on a piezoelectric substrate has been measured as a function of the continuously and reversibly varied biaxial strain of e = 0.36 0.51 %. Over this range, the ferroelectric coercive field (Ec) at 80 K increases reversibly by 36 % with the increasing tensile strain. The strain dependence of the remanent polarization agrees with previous experimental results and simulations based on thermodynamic considerations. In contrast, such calculations predict dEc/de <0, contradicting our experiments. Thus, the strain dependence of kinetic barriers influencing the rates of domain wall nucleation and propagation which are neglected in thermodynamic models may dominate the observed positive dEc/de.

  17. Seed harvesting by a generalist consumer is context-dependent: Interactive effects across multiple spatial scales

    USGS Publications Warehouse

    Ostoja, Steven M.; Schupp, Eugene W.; Klinger, Rob

    2013-01-01

    Granivore foraging decisions affect consumer success and determine the quantity and spatial pattern of seed survival. These decisions are influenced by environmental variation at spatial scales ranging from landscapes to local foraging patches. In a field experiment, the effects of seed patch variation across three spatial scales on seed removal by western harvester ants Pogonomyrmex occidentalis were evaluated. At the largest scale we assessed harvesting in different plant communities, at the intermediate scale we assessed harvesting at different distances from ant mounds, and at the smallest scale we assessed the effects of interactions among seed species in local seed neighborhoods on seed harvesting (i.e. resource–consumer interface). Selected seed species were presented alone (monospecific treatment) and in mixture with Bromus tectorum (cheatgrass; mixture treatment) at four distances from P. occidentalis mounds in adjacent intact sagebrush and non-native cheatgrass-dominated communities in the Great Basin, Utah, USA. Seed species differed in harvest, with B. tectorum being least preferred. Large and intermediate scale variation influenced harvest. More seeds were harvested in sagebrush than in cheatgrass-dominated communities (largest scale), and the quantity of seed harvested varied with distance from mounds (intermediate-scale), although the form of the distance effect differed between plant communities. At the smallest scale, seed neighborhood affected harvest, but the patterns differed among seed species considered. Ants harvested fewer seeds from mixed-seed neighborhoods than from monospecific neighborhoods, suggesting context dependence and potential associational resistance. Further, the effects of plant community and distance from mound on seed harvest in mixtures differed from their effects in monospecific treatments. Beyond the local seed neighborhood, selection of seed resources is better understood by simultaneously evaluating removal at multiple scales. Associational effects provide a useful theoretical basis for better understanding harvester ant foraging decisions. These results demonstrate the importance of ecological context for seed removal, which has implications for seed pools, plant populations and communities.

  18. Temperature dependence of resistivity and Hall coefficient in strongly disordered NbN thin films

    Microsoft Academic Search

    Madhavi Chand; Archana Mishra; Y. M. Xiong; Anand Kamlapure; S. P. Chockalingam; John Jesudasan; Vivas Bagwe; Mintu Mondal; P. W. Adams; Vikram Tripathi; Pratap Raychaudhuri

    2009-01-01

    We report the temperature dependence of resistivity (rho) and Hall coefficient (RH) in the normal state of homogeneously disordered epitaxial NbN thin films with kFl˜1.68-10.12 . The superconducting transition temperature (Tc) of these films varies from 2.7 to 16.8 K. While our least disordered film displays usual metallic behavior, for all the films with kFl<=8.13 , both (drho)\\/(dT) and (dRH)\\/(dT)

  19. Do adjustments in search behavior depend on the precision of spatial memory?

    PubMed

    Pfuhl, G; Barrera, L B G; Living, M; Biegler, R

    2013-03-01

    Various forms of uncertainty are important for decision making. How aware are we of the precision of knowledge, and how accessible it is? In three experiments, an assessment of the precision of spatial memory was needed to make optimal decisions. First, we examined search strategies in a search task in which the most efficient strategy was to head to one side of the target by a margin depending on the precision of spatial information, the "where to start" task. We found that nine out of of our 20 human subjects adapted the margin according to precision. Second, we let the subjects search for the location of a sample picture. On one-third of the trials, the target was not present, making it a "when to stop searching" task. We found that the subjects did not adjust their investment in search according to their precision. In the third experiment, we looked at whether there was transfer between the two tasks. Subjects who had been reminded of the relevance of uncertainty by the "where to start" task increased their search effort more in the "when to stop searching" task. Thus, the results show that the use of information about precision is not automatic, but can be triggered. PMID:22886715

  20. Representational momentum in spatial hearing does not depend on eye movements.

    PubMed

    Getzmann, Stephan

    2005-08-01

    The perceived final position of a moving object usually seems to be displaced in the direction of motion. This displacement effect, termed representational momentum, has been reported for both visual and acoustic targets. This study investigated whether representational momentum in the auditory modality depends on oculomotor behavior during target presentation. In a dark anechoic environment, subjects localized the final position of a horizontally moving acoustic target (continuous noise) by using a hand pointer. Subjects were instructed to pursue the acoustic target with their eyes, to maintain central gaze direction, or to fixate a central visual fixation point. Forward displacements of the perceived final target position occurred irrespective of the eye-movement condition. This result is not consistent with previous findings in the visual modality indicating a reduction of forward displacement for continuously moving targets with fixation. It is suggested that factors other than oculomotor behavior are the source of representational momentum in spatial hearing. PMID:15942739

  1. Spatial dependent van der Waals energy between graphene and boron-nitride

    NASA Astrophysics Data System (ADS)

    Neek-Amal, Mehdi; Peeters, Francois; Condensed Matter Group, University of Antwerp Collaboration

    2014-03-01

    The small mismatch between the honeycomb lattices of graphene (GE) and boron nitrate (h-BN) leads to long wavelength Moiré patterns. In order to describe such patterns it will require large size unit cells that are unattainable with ab-initio calculations. Earlier density functional theory calculations imposed lattice matching between graphene and h-BN which induces strain and opens a gap of 4 meV. In previous works the Moiré pattern in GE/h-BN was connected to the van der Waals interaction, but a clear theoretical microscopic analysis is still missing. We used atomistic simulations with very large unit cells to investigate quantitative aspects of the connection between the vdW interaction and the Moiré patterns. The value and symmetry of the spatial dependent vdW energy is obtained which agrees with the recently reported Moiré patterns. Acknowledgement: This work was supported by FWO-Vl, EU-Marie Curie and the Methusalem foundation.

  2. Laser based imaging of time depending microscopic scenes with strong light emission

    NASA Astrophysics Data System (ADS)

    Hahlweg, Cornelius; Wilhelm, Eugen; Rothe, Hendrik

    2011-10-01

    Investigating volume scatterometry methods based on short range LIDAR devices for non-static objects we achieved interesting results aside the intended micro-LIDAR: the high speed camera recording of the illuminated scene of an exploding wire -intended for Doppler LIDAR tests - delivered a very effective method of observing details of objects with extremely strong light emission. As a side effect a schlieren movie is gathered without any special effort. The fact that microscopic features of short time processes with high emission and material flow might be imaged without endangering valuable equipment makes this technique at least as interesting as the intended one. So we decided to present our results - including latest video and photo material - instead of a more theoretical paper on our progress concerning the primary goal.

  3. The hippocampus mediates glucocorticoid-induced impairment of spatial memory retrieval: Dependence on the basolateral amygdala

    PubMed Central

    Roozendaal, Benno; Griffith, Qyana K.; Buranday, Jason; de Quervain, Dominique J.-F.; McGaugh, James L.

    2003-01-01

    Previous studies have indicated that stress-activated glucocorticoid hormones induce temporary memory retrieval impairment. The present study examined whether adrenal steroid receptors in the hippocampus mediate such glucocorticoid effects on spatial memory retrieval. The specific glucocorticoid receptor (GR) agonist 11?, 17?-dihydroxy-6,21-dimethyl-17?-pregna-4,6-trien-20yn-3-one (RU 28362; 5 or 15 ng) infused into the hippocampus of male Sprague–Dawley rats 60 min before water-maze retention testing, 24 h after training, dose-dependently impaired probe-trial retention performance, as assessed both by time spent in the training quadrant and initial latency to cross the platform location. The GR agonist did not affect circulating corticosterone levels immediately after the probe trial, indicating that RU 28362 infusions did not influence retention by altering glucocorticoid feedback mechanisms. As infusions of the GR agonist into the hippocampus 60 min before training did not influence water-maze acquisition or immediate recall, the findings indicated that the GR agonist-induced retention impairment was induced selectively by an influence on information retrieval. In contrast, pretest infusions of the GR agonist administered into the basolateral complex of the amygdala (BLA; 2 or 6 ng) did not alter retention performance in the water maze. However, N-methyl-d-aspartate-induced lesions of the BLA, made 1 week before training, blocked the memory retrieval impairment induced by intrahippocampal infusions of RU 28362 given 60 min before the retention test. These findings indicate that the effects of glucocorticoids on retrieval of long-term spatial memory depend on the hippocampus and, additionally, that neuronal input from the BLA is critical in enabling hippocampal glucocorticoid effects on memory retrieval. PMID:12538851

  4. Up, down, and all around: scale-dependent spatial variation in rocky-shore communities of Fildes Peninsula, King George Island, Antarctica.

    PubMed

    Valdivia, Nelson; Díaz, María J; Holtheuer, Jorge; Garrido, Ignacio; Huovinen, Pirjo; Gómez, Iván

    2014-01-01

    Understanding the variation of biodiversity along environmental gradients and multiple spatial scales is relevant for theoretical and management purposes. Hereby, we analysed the spatial variability in diversity and structure of intertidal and subtidal macrobenthic Antarctic communities along vertical environmental stress gradients and across multiple horizontal spatial scales. Since biotic interactions and local topographic features are likely major factors for coastal assemblages, we tested the hypothesis that fine-scale processes influence the effects of the vertical environmental stress gradients on the macrobenthic diversity and structure. We used nested sampling designs in the intertidal and subtidal habitats, including horizontal spatial scales ranging from few centimetres to 1000s of metres along the rocky shore of Fildes Peninsula, King George Island. In both intertidal and subtidal habitats, univariate and multivariate analyses showed a marked vertical zonation in taxon richness and community structure. These patterns depended on the horizontal spatial scale of observation, as all analyses showed a significant interaction between height (or depth) and the finer spatial scale analysed. Variance and pseudo-variance components supported our prediction for taxon richness, community structure, and the abundance of dominant species such as the filamentous green alga Urospora penicilliformis (intertidal), the herbivore Nacella concinna (intertidal), the large kelp-like Himantothallus grandifolius (subtidal), and the red crustose red alga Lithothamnion spp. (subtidal). We suggest that in coastal ecosystems strongly governed by physical factors, fine-scale processes (e.g. biotic interactions and refugia availability) are still relevant for the structuring and maintenance of the local communities. The spatial patterns found in this study serve as a necessary benchmark to understand the dynamics and adaptation of natural assemblages in response to observed and predicted environmental changes in Antarctica. PMID:24956114

  5. Strong field ionization rates simulated with time-dependent configuration interaction and an absorbing potential

    SciTech Connect

    Krause, Pascal; Sonk, Jason A.; Schlegel, H. Bernhard [Department of Chemistry, Wayne State University, Detroit, Michigan 48202-3489 (United States)] [Department of Chemistry, Wayne State University, Detroit, Michigan 48202-3489 (United States)

    2014-05-07

    Ionization rates of molecules have been modeled with time-dependent configuration interaction simulations using atom centered basis sets and a complex absorbing potential. The simulations agree with accurate grid-based calculations for the ionization of hydrogen atom as a function of field strength and for charge resonance enhanced ionization of H{sub 2}{sup +} as the bond is elongated. Unlike grid-based methods, the present approach can be applied to simulate electron dynamics and ionization in multi-electron polyatomic molecules. Calculations on HCl{sup +} and HCO{sup +} demonstrate that these systems also show charge resonance enhanced ionization as the bonds are stretched.

  6. Temperature dependence of resistivity and Hall-coefficient in a strongly disordered metal: NbN

    Microsoft Academic Search

    Madhavi Chand; Archana Mishra; Y. M. Xiong; Anand Kamlapure; S. P. Chockalingam; John Jesudasan; Vivas Bagwe; Mintu Mondal; P. W. Adams; Vikram Tripathi; Pratap Raychaudhuri

    2009-01-01

    We report the temperature dependence of resistivity (rho) and Hall\\u000acoefficient (R_H) in the normal state of homogeneously disordered epitaxial NbN\\u000athin films with kFl~3.27-10.12. The superconducting transition temperature (Tc)\\u000aof these films varies from 8.13K to 16.8K. While our least disordered film\\u000adisplays usual metallic behavior, for all the films with kFl<8.13, both and are\\u000anegative up to 300K.

  7. Strong Orientation Dependence of Multinucleon Transfer Processes in $^{238}$U+$^{124}$Sn Reaction

    E-print Network

    Kazuyuki Sekizawa; Kazuhiro Yabana

    2014-09-30

    We theoretically investigate multinucleon transfer (MNT) processes in $^{238}$U+$^{124}$Sn reaction at $E_\\mathrm{lab}=5.7$ MeV/$A$ using the time-dependent Hartree-Fock (TDHF) theory. For this reaction, measurements of MNT processes have been reported, showing substantial MNT cross sections accompanying more than ten protons. From the calculation, we find that the amount of transferred nucleons depends much on the relative orientation between the deformation axis of $^{238}$U and the relative vector connecting centers of $^{238}$U and $^{124}$Sn nuclei. We find a formation of thick neck when the $^{238}$U collides from its tip with $^{124}$Sn. However, the neck formation is substantially suppressed when $^{238}$U collides from its side. We have found that a large number of protons are transferred in the tip collision. This is caused by the breaking of the neck and subsequent absorption of nucleons in the neck region. We thus conclude that the measured MNT processes involving about ten protons originate from the neck breaking dynamics in the tip collisions of a deformed $^{238}$U nucleus.

  8. Sensitive Polarization Dependence for Helium Rydberg Atoms Driven by Strong Microwave Fields

    NASA Astrophysics Data System (ADS)

    Zelazny, S. A.; Bellermann, M. R. W.; Smith, L. L.; Koch, P. M.

    1996-05-01

    We prepare n^3S He Rydberg atoms with selected values n>=25 in a fast beam using CO2 lasers and double-resonance excitation. They then fly through a TE_121 mode cavity, exposing them to a half-sine pulse (about 350 field osc.) of 9.904 GHz electric field whose polarization can be varied: linear (LP), elliptical (EP), and circular (CP). Making EP close to LP can lead to substantial changes in microwave-power-dependent transitions to nearby bound states. In at least one case, a sharp dip in the LP signal( W. van de Water et al., Phys. Rev. A 42), 572 (1990) is transformed by EP into a pattern reminiscent of Stueckelberg oscillations, previously observed with LP at higher frequencies.( S. Yoakum et al., Phys. Rev. Lett. 69), 1919 (1992) Calculations suggest that pulse-shape-induced dynamics at Floquet avoided-crossing(s) explain the LP behavior. Changing the field to EP clearly must modify this behavior. We will discuss this kind of data as well as the polarization dependence of microwave ionization of n^3S He Rydberg atoms.

  9. Sensitive polarization dependence for helium Rydberg atoms driven by strong microwave fields

    SciTech Connect

    Zelazny, S.A.; Bellermann, M.R.W.; Smith, L.L.; Koch, P.M.

    1996-05-01

    The authors prepare n{sup 3}S He Rydberg atoms with selected values n {ge} 25 in a fast beam using CO{sub 2} lasers and double-resonance excitation. They then fly through a TE{sub 121} mode cavity, exposing them to a half-sine pulse (about 350 field osc.) of 9.904 GHz electric field whose polarization can be varied; linear (LP), elliptical (EP), and circular (CP). Making EP close to LP can lead to substantial changes in microwave-power-dependent transitions to nearby bound states. In at least one case, a sharp dip in the LP signal is transformed by EP into a pattern reminiscent of Stueckelberg oscillations, previously observed with LP at higher frequencies. Calculations suggest that pulse-shape-induced dynamics at Floquet avoided-crossing(s) explain the LP behavior. Changing the field to EP clearly must modify this behavior. The authors will discuss this kind of data as well as the polarization dependence of microwave ionization of n{sup 3}S He Rydberg atoms.

  10. Hepcidin Induction by Pathogens and Pathogen-Derived Molecules Is Strongly Dependent on Interleukin-6

    PubMed Central

    Rodriguez, Richard; Jung, Chun-Ling; Gabayan, Victoria; Deng, Jane C.; Ganz, Tomas; Nemeth, Elizabeta

    2014-01-01

    Hepcidin, the iron-regulatory hormone, is increased during infection or inflammation, causing hypoferremia. This response is thought to be a host defense mechanism that restricts iron availability to invading pathogens. It is not known if hepcidin is differentially induced by bacterial versus viral infections, whether the stimulation of pattern recognition receptors directly regulates hepcidin transcription, or which of the proposed signaling pathways are essential for hepcidin increase during infection. We analyzed hepcidin induction and its dependence on interleukin-6 (IL-6) in response to common bacterial or viral infections in mice or in response to a panel of pathogen-derived molecules (PAMPs) in mice and human primary hepatocytes. In wild-type (WT) mice, hepcidin mRNA was induced several hundred-fold both by a bacterial (Streptococcus pneumoniae) and a viral infection (influenza virus PR8) within 2 to 5 days. Treatment of mice and human primary hepatocytes with most Toll-like receptor ligands increased hepcidin mRNA within 6 h. Hepcidin induction by microbial stimuli was IL-6 dependent. IL-6 knockout mice failed to increase hepcidin in response to S. pneumoniae or influenza infection and had greatly diminished hepcidin response to PAMPs. In vitro, hepcidin induction by PAMPs in primary human hepatocytes was abolished by the addition of neutralizing IL-6 antibodies. Our results support the key role of IL-6 in hepcidin regulation in response to a variety of infectious and inflammatory stimuli. PMID:24478088

  11. How well do regional climate models simulate the spatial dependence of precipitation? An application of pair-copula constructions

    NASA Astrophysics Data System (ADS)

    Hobæk Haff, Ingrid; Frigessi, Arnoldo; Maraun, Douglas

    2015-04-01

    We investigate how well a suite of regional climate models (RCMs) from the ENSEMBLES project represents the residual spatial dependence of daily precipitation. The study area we consider is a 200 km × 200 km region in south central Norway, with RCMs driven by ERA-40 boundary conditions at a horizontal resolution of approximately 25 km × 25 km. We model the residual spatial dependence with pair-copula constructions, which allows us to assess both the overall and tail dependence in precipitation, including uncertainty estimates. The selected RCMs reproduce the overall dependence rather well, though the discrepancies compared to observations are substantial. All models overestimate the overall dependence in the west-east direction. They also overestimate the upper tail dependence in the north-south direction during winter, and in the west-east direction during summer, whereas they tend to underestimate this dependence in the north-south direction in summer. Moreover, many of the climate models do not simulate the small-scale dependence patterns caused by the pronounced orography well. However, the misrepresented residual spatial dependence does not seem to affect estimates of high quantiles of extreme precipitation aggregated over a few grid boxes. The underestimation of the area-aggregated extreme precipitation is due mainly to the well-known underestimation of the univariate margins for individual grid boxes, suggesting that the correction of RCM biases in precipitation might be feasible.

  12. Strong Asymmetric Charge Carrier Dependence in Inelastic Electron Tunneling Spectroscopy of Graphene Phonons

    NASA Astrophysics Data System (ADS)

    Natterer, Fabian D.; Zhao, Yue; Wyrick, Jonathan; Chan, Yang-Hao; Ruan, Wen-Ying; Chou, Mei-Yin; Watanabe, Kenji; Taniguchi, Takashi; Zhitenev, Nikolai B.; Stroscio, Joseph A.

    2015-06-01

    The observation of phonons in graphene by inelastic electron tunneling spectroscopy has been met with limited success in previous measurements arising from weak signals and other spectral features which inhibit a clear distinction between phonons and miscellaneous excitations. Utilizing a back-gated graphene device that allows adjusting the global charge carrier density, we introduce an averaging method where individual tunneling spectra at varying charge carrier density are combined into one representative spectrum. This method improves the signal for inelastic transitions while it suppresses dispersive spectral features. We thereby map the total graphene phonon density of states, in good agreement with density functional calculations. Unexpectedly, an abrupt change in the phonon intensity is observed when the graphene charge carrier type is switched through a variation of the back-gate electrode potential. This sudden variation in phonon intensity is asymmetric in the carrier type, depending on the sign of the tunneling bias.

  13. Space- and time-dependent quantum dynamics of spatially indirect excitons in semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Grasselli, Federico; Bertoni, Andrea; Goldoni, Guido

    2015-01-01

    We study the unitary propagation of a two-particle one-dimensional Schrödinger equation by means of the Split-Step Fourier method, to study the coherent evolution of a spatially indirect exciton (IX) in semiconductor heterostructures. The mutual Coulomb interaction of the electron-hole pair and the electrostatic potentials generated by external gates and acting on the two particles separately are taken into account exactly in the two-particle dynamics. As relevant examples, step/downhill and barrier/well potential profiles are considered. The space- and time-dependent evolutions during the scattering event as well as the asymptotic time behavior are analyzed. For typical parameters of GaAs-based devices, the transmission or reflection of the pair turns out to be a complex two-particle process, due to comparable and competing Coulomb, electrostatic, and kinetic energy scales. Depending on the intensity and anisotropy of the scattering potentials, the quantum evolution may result in excitation of the IX internal degrees of freedom, dissociation of the pair, or transmission in small periodic IX wavepackets due to dwelling of one particle in the barrier region. We discuss the occurrence of each process in the full parameter space of the scattering potentials and the relevance of our results for current excitronic technologies.

  14. Space- and time-dependent quantum dynamics of spatially indirect excitons in semiconductor heterostructures.

    PubMed

    Grasselli, Federico; Bertoni, Andrea; Goldoni, Guido

    2015-01-21

    We study the unitary propagation of a two-particle one-dimensional Schrödinger equation by means of the Split-Step Fourier method, to study the coherent evolution of a spatially indirect exciton (IX) in semiconductor heterostructures. The mutual Coulomb interaction of the electron-hole pair and the electrostatic potentials generated by external gates and acting on the two particles separately are taken into account exactly in the two-particle dynamics. As relevant examples, step/downhill and barrier/well potential profiles are considered. The space- and time-dependent evolutions during the scattering event as well as the asymptotic time behavior are analyzed. For typical parameters of GaAs-based devices, the transmission or reflection of the pair turns out to be a complex two-particle process, due to comparable and competing Coulomb, electrostatic, and kinetic energy scales. Depending on the intensity and anisotropy of the scattering potentials, the quantum evolution may result in excitation of the IX internal degrees of freedom, dissociation of the pair, or transmission in small periodic IX wavepackets due to dwelling of one particle in the barrier region. We discuss the occurrence of each process in the full parameter space of the scattering potentials and the relevance of our results for current excitronic technologies. PMID:25612719

  15. Spatial learning impairments in PLB1Triple knock-in Alzheimer mice are task-specific and age-dependent.

    PubMed

    Ryan, D; Koss, D; Porcu, E; Woodcock, H; Robinson, L; Platt, B; Riedel, G

    2013-07-01

    We recently generated an advanced mouse model of Alzheimer's disease (AD) by targeted knock-in of single-copy mutated human amyloid precursor-protein (APP) and tau genes, crossed with a non-symptomatic presenilin (PS1A246E) over-expressing mouse line. These PLB1Triple mice presented with age-dependent and AD-relevant phenotypes. Homozygous PLB1Triple mice aged 4-12 months were assessed here in a battery of spatial learning tasks: Exp.1 radial-arm water maze (spatial reference and working memory) Exp.2 open-field water maze (spatial reference memory); Exp.3 home cage observation system with spatial learning (IntelliCage); Exp.4 spontaneous object recognition (SOR; novel object and spatial object shift). A separate test with high-expression transgenic APP mice matching the design of experiment 1 was also performed. Spatial deficits in PLB1Triple mice were confirmed at 12, but not 4 months in both water maze tasks. PSAPP mice, by contrast, presented with severe yet non-progressive spatial learning deficits already at 4 months. During tests of spatial learning in SOR and IntelliCage, PLB1Triple mice neither acquired the location of the water-rewarded corner, nor recognize novel or spatially shifted objects at 4 months, indicating these protocols to be more sensitive than the water maze. Collectively and in line with AD symptomatology, PLB1Triple mice present with a graded and progressive age-dependent loss of spatial memory that can be revealed by the use of a battery of tasks. With the emergence of subtle deficits progressively increasing in severity, PLB1Triple mice may offer a more patho-physiologically relevant model of dementia than aggressive expression models. PMID:23535719

  16. Angular Dependence of Jet Quenching Indicates Its Strong Enhancement Near the QCD Phase Transition

    SciTech Connect

    Liao, Jinfeng; Shuryak, Edward

    2008-10-22

    We study dependence of jet quenching on matter density, using 'tomography' of the fireball provided by RHIC data on azimuthal anisotropy v{sub 2} of high p{sub t} hadron yield at different centralities. Slicing the fireball into shells with constant (entropy) density, we derive a 'layer-wise geometrical limit' v{sub 2}{sup max} which is indeed above the data v{sub 2} < v{sub x}{sup max}. Interestingly, the limit is reached only if quenching is dominated by shells with the entropy density exactly in the near-T{sub c} region. We show two models that simultaneously describe the high p{sub t} v{sub 2} and R{sub AA} data and conclude that such a description can be achieved only if the jet quenching is few times stronger in the near-T{sub c} region relative to QGP at T > T{sub c}. One possible reason for that may be recent indications that the near-T{sub c} region is a magnetic plasma of relatively light color-magnetic monopoles.

  17. Light-dependent induction of strongly increased microalgal growth by methanol.

    PubMed

    Theodoridou, A; Dörnemann, D; Kotzabasis, K

    2002-11-14

    Low methanol concentrations (about 0.5% v/v) induce biomass production in cultures of the unicellular green alga Scenedesmus obliquus by more than 300%, compared to controls without this solvent. This effect on the microalgal growth was found to be dependent on the solvent concentration, the packed cell volume (PCV), light intensity and light quality. It could be shown that methanol addition leads to a decrease in size of the light harvesting complex (LHC) on the basis of chlorophylls and proteins, and thus to changes in structure and functioning of the photosynthetic apparatus. These alterations lead to enhanced photosynthesis and respiration rates. The action of methanol on the photosynthetic apparatus is thus comparable to the effect of enhanced CO(2) concentrations. These findings support the previously proposed pathway for methanol metabolization with CO(2) as the final product. We conclude that the subsequent assimilation of the increased CO(2) amounts by the Calvin-Benson cycle is a possible explanation for the methanol-mediated increase in biomass production in terms of PCV. The methanol effect is observed only in the light and in the presence of a functioning photosynthetic apparatus. Preliminary action spectra suggest that the primary photoreceptor is a chlorophyll-protein complex with two absorption maxima at 680 and 430 nm, which may possibly be attributed to the reaction center of photosystem II (PSII). PMID:12399030

  18. Spatially resolved frequency-dependent elasticity measured with pulsed force microscopy and nanoindentation.

    PubMed

    Sweers, Kim K M; van der Werf, Kees O; Bennink, Martin L; Subramaniam, Vinod

    2012-03-21

    Recently several atomic force microscopy (AFM)-based surface property mapping techniques like pulsed force microscopy (PFM), harmonic force microscopy or Peakforce QNM® have been introduced to measure the nano- and micro-mechanical properties of materials. These modes all work at different operating frequencies. However, complex materials are known to display viscoelastic behavior, a combination of solid and fluid-like responses, depending on the frequency at which the sample is probed. In this report, we show that the frequency-dependent mechanical behavior of complex materials, such as polymer blends that are frequently used as calibration samples, is clearly measurable with AFM. Although this frequency-dependent mechanical behavior is an established observation, we demonstrate that the new high frequency mapping techniques enable AFM-based rheology with nanoscale spatial resolution over a much broader frequency range compared to previous AFM-based studies. We further highlight that it is essential to account for the frequency-dependent variation in mechanical properties when using these thin polymer samples as calibration materials for elasticity measurements by high-frequency surface property mapping techniques. These results have significant implications for the accurate interpretation of the nanomechanical properties of polymers or complex biological samples. The calibration sample is composed of a blend of soft and hard polymers, consisting of low-density polyethylene (LDPE) islands in a polystyrene (PS) surrounding, with a stiffness of 0.2 GPa and 2 GPa respectively. The spring constant of the AFM cantilever was selected to match the stiffness of LDPE. From 260 Hz to 1100 Hz the sample was imaged with the PFM method. At low frequencies (0.5-35 Hz), single-point nanoindentation was performed. In addition to the material's stiffness, the relative heights of the LDPE islands (with respect to the PS) were determined as a function of the frequency. At the lower operation frequencies for PFM, the islands exhibited lower heights than when measured with tapping mode at 120 kHz. Both spring constants and heights at the different frequencies clearly show a frequency-dependent behavior. PMID:22331128

  19. Propagation of sound waves through a spatially homogeneous but smoothly time-dependent medium

    SciTech Connect

    Hayrapetyan, A.G., E-mail: armen@physi.uni-heidelberg.de [Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg (Germany); Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Grigoryan, K.K.; Petrosyan, R.G. [Yerevan State University, 1 Alex Manoogian Str., 0025 Yerevan (Armenia)] [Yerevan State University, 1 Alex Manoogian Str., 0025 Yerevan (Armenia); Fritzsche, S. [Helmholtz-Institut Jena, Fröbelstieg 3, D-07743 Jena (Germany) [Helmholtz-Institut Jena, Fröbelstieg 3, D-07743 Jena (Germany); Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)

    2013-06-15

    The propagation of sound through a spatially homogeneous but non-stationary medium is investigated within the framework of fluid dynamics. For a non-vortical fluid, especially, a generalized wave equation is derived for the (scalar) potential of the fluid velocity distribution in dependence of the equilibrium mass density of the fluid and the sound wave velocity. A solution of this equation for a finite transition period ? is determined in terms of the hypergeometric function for a phenomenologically realistic, sigmoidal change of the mass density and sound wave velocity. Using this solution, it is shown that the energy flux of the sound wave is not conserved but increases always for the propagation through a non-stationary medium, independent of whether the equilibrium mass density is increased or decreased. It is found, moreover, that this amplification of the transmitted wave arises from an energy exchange with the medium and that its flux is equal to the (total) flux of the incident and the reflected wave. An interpretation of the reflected wave as a propagation of sound backward in time is given in close analogy to Feynman and Stueckelberg for the propagation of anti-particles. The reflection and transmission coefficients of sound propagating through a non-stationary medium is analyzed in more detail for hypersonic waves with transition periods ? between 15 and 200 ps as well as the transformation of infrasound waves in non-stationary oceans. -- Highlights: •Analytically exact study of sound propagation through a non-stationary medium. •Energy exchange between the non-stationary medium and the sound wave. •Transformation of hypersonic and ultrasound frequencies in non-stationary media. •Propagation of sound backward in time in close analogy to anti-particles. •Prediction of tsunamis both in spatially and temporally inhomogeneous oceans.

  20. Spatial distribution of electronic spins in a quasi-one-dimensional tight-binding model with spin-dependent hopping

    NASA Astrophysics Data System (ADS)

    Kawai, Ryota; Suzuura, Hidekatsu; Tomio, Yuh

    2012-12-01

    We have theoretically studied intrinsic spin Hall effect in a quantum wire with spin-orbit interaction. Our numerical calculations show that the current-induced distribution of electronic spins has characteristic spatial dependence in a quasi-one-dimensional tight-binding model with spin-dependent hopping. The difference between the chemical potentials of electrons with up and down spins shows spatial oscillation in a direction perpendicular to the charge current and reaches the maximum around one edge and the minimum around the other edge, which suggests spin accumulation around edges of the quantum wire.

  1. Strong localization induced anomalous temperature dependence exciton emission above 300 K from SnO2 quantum dots

    NASA Astrophysics Data System (ADS)

    Pan, S. S.; Li, F. D.; Liu, Q. W.; Xu, S. C.; Luo, Y. Y.; Li, G. H.

    2015-05-01

    SnO2 quantum dots (QDs) are potential materials for deep ultraviolet (DUV) light emitting devices. In this study, we report the temperature and excitation power-dependent exciton luminescence from SnO2 QDs. The exciton emission exhibits anomalous blue shift, accompanied with band width reduction with increasing temperature and excitation power above 300 K. The anomalous temperature dependences of the peak energy and band width are well interpreted by the strongly localized carrier thermal hopping process and Gaussian shape of band tails states, respectively. The localized wells and band tails at conduction minimum are considered to be induced by the surface oxygen defects and local potential fluctuation in SnO2 QDs.

  2. Soil microbial community variation correlates most strongly with plant species identity, followed by soil chemistry, spatial location and plant genus

    PubMed Central

    Burns, Jean H.; Anacker, Brian L.; Strauss, Sharon Y.; Burke, David J.

    2015-01-01

    Soil ecologists have debated the relative importance of dispersal limitation and ecological factors in determining the structure of soil microbial communities. Recent evidence suggests that ‘everything is not everywhere’, and that microbial communities are influenced by both dispersal limitation and ecological factors. However, we still do not understand the relative explanatory power of spatial and ecological factors, including plant species identity and even plant relatedness, for different fractions of the soil microbial community (i.e. bacterial and fungal communities). To ask whether factors such as plant species, soil chemistry, spatial location and plant relatedness influence rhizosphere community composition, we examined field-collected rhizosphere soil of seven congener pairs that occur at Bodega Bay Marine Reserve, CA, USA. We characterized differences in bacterial and fungal communities using terminal-restriction fragment length polymorphism. Plant species identity was the single best statistical predictor of both bacterial and fungal community composition in the root zone. Soil microbial community structure was also correlated with soil chemistry. The third best predictor of bacterial and fungal communities was spatial location, confirming that everything is not everywhere. Variation in microbial community composition was also related to combinations of spatial location, soil chemistry and plant relatedness, suggesting that these factors do not act independently. Plant relatedness explained less of the variation than plant species, soil chemistry, or spatial location. Despite some congeners occupying different habitats and being spatially distant, rhizosphere fungal communities of plant congeners were more similar than expected by chance. Bacterial communities from the same samples were only weakly similar between plant congeners. Thus, plant relatedness might influence soil fungal, more than soil bacterial, community composition. PMID:25818073

  3. Spatial evolution of a quasi-two-dimensional Kármán vortex street subjected to a strong uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Hamid, Ahmad H. A.; Hussam, Wisam K.; Pothérat, Alban; Sheard, Gregory J.

    2015-05-01

    A vortex decay model for predicting spatial evolution of peak vorticity in a wake behind a cylinder is presented. For wake vortices in the stable region behind the formation region, results have shown that the presented model has a good capability of predicting spatial evolution of peak vorticity within an advecting vortex across 0.1 ? ? ? 0.4, 500 ? H ? 5000, and 1500 ? ReL ? 8250. The model is also generalized to predict the decay behaviour of wake vortices in a class of quasi-two-dimensional magnetohydrodynamic duct flows. Comparison with published data demonstrates remarkable consistency.

  4. Spatial Dependence of Physical Attributes and Mechanical Properties of Ultisol in a Sugarcane Field

    PubMed Central

    Tavares, Uilka Elisa; Monteiro Rolim, Mário; Souza de Oliveira, Veronildo; Maria Regis Pedrosa, Elvira; Siqueira, Glécio Machado; Guedes Magalhães, Adriana

    2015-01-01

    This study investigates the effect of conventional tillage and application of the monoculture of sugar cane on soil health. Variables like density, moisture, texture, consistency limits, and preconsolidation stress were taken as indicators of soil quality. The measurements were made at a 120 × 120?m field cropped with sugar cane under conventional tillage. The objective of this work was to characterize the soil and to study the spatial dependence of the physical and mechanical attributes. Then, undisturbed soil samples were collected to measure bulk density, moisture content and preconsolidation stress and disturbed soil samples for classification of soil texture, and consistency limits. The soil texture indicated that soil can be characterized as sandy clay soil and a sandy clay loam soil, and the consistency limits indicated that the soil presents an inorganic low plasticity clay. The preconsolidation tests tillage in soil moisture content around 19% should be avoided or should be chosen a management of soil with lighter vehicles in this moisture content, to avoid risk of compaction. Using geostatistical techniques mapping was possible to identify areas of greatest conservation soil and greater disturbance of the ground. PMID:26167528

  5. Spatial and body-size dependent response of marine pelagic communities to projected global climate change.

    PubMed

    Lefort, Stelly; Aumont, Olivier; Bopp, Laurent; Arsouze, Thomas; Gehlen, Marion; Maury, Olivier

    2015-01-01

    Temperature, oxygen, and food availability directly affect marine life. Climate models project a global warming of the ocean's surface (~+3 °C), a de-oxygenation of the ocean's interior (~-3%) and a decrease in total marine net primary production (~-8%) under the 'business as usual' climate change scenario (RCP8.5). We estimated the effects of these changes on biological communities using a coupled biogeochemical (PISCES)--ecosystems (APECOSM) model forced by the physical outputs of the last generation of the IPSL-CM Earth System Model. The APECOSM model is a size-structured bio-energetic model that simulates the 3D dynamical distributions of three interactive pelagic communities (epipelagic, mesopelagic, and migratory) under the effects of multiple environmental factors. The PISCES-APECOSM model ran from 1850 to 2100 under historical forcing followed by RCP8.5. Our RCP8.5 simulation highlights significant changes in the spatial distribution, biomass, and maximum body-size of the simulated pelagic communities. Biomass and maximum body-size increase at high latitude over the course of the century, reflecting the capacity of marine organisms to respond to new suitable environment. At low- and midlatitude, biomass and maximum body-size strongly decrease. In those regions, large organisms cannot maintain their high metabolic needs because of limited and declining food availability. This resource reduction enhances the competition and modifies the biomass distribution among and within the three communities: the proportion of small organisms increases in the three communities and the migrant community that initially comprised a higher proportion of small organisms is favored. The greater resilience of small body-size organisms resides in their capacity to fulfill their metabolic needs under reduced energy supply and is further favored by the release of predation pressure due to the decline of large organisms. These results suggest that small body-size organisms might be more resilient to climate change than large ones. PMID:25044507

  6. Effect of the spatial structure of an acoustic field on Bragg's acoustooptic diffraction under strong acoustic anisotropy conditions

    NASA Astrophysics Data System (ADS)

    Antonov, S. N.; Vainer, A. V.; Proklov, V. V.; Rezvov, Yu. G.

    2010-03-01

    Bragg’s acoustooptic diffraction in an acoustically anisotropic medium is considered taking into account the two-dimensional spatial diffraction structure of the acoustic beam. The conditions are determined under which reverse transfer of optical power from the diffracted to the transmitted beam in the regime of 100% efficiency of diffraction is considerably suppressed. It is shown that this effect is due to diffraction bending of wave fronts of the acoustic beam in the acoustooptic diffraction plane. The problem of optimization of the piezoelectric transducer size and the spatial position of the input light beam is solved using the criterion of the minimal required power of the acoustic field. The results of simulation in a wide range of the acoustooptic interaction parameters for a Gaussian light beam are reported. The correctness of the model is confirmed experimentally. Recommendations for designers of acoustooptic devices are formulated.

  7. He?2++ molecular ion in a strong time-dependent magnetic field: a current-density functional study.

    PubMed

    Vikas

    2011-08-01

    The He?2++ molecular ion exposed to a strong ultrashort time-dependent (TD) magnetic field of the order of 10(9) G is investigated through a quantum fluid dynamics (QFD) and current-density functional theory (CDFT) based approach using vector exchange-correlation (XC) potential and energy density functional that depend not only on the electronic charge-density but also on the current density. The TD-QFD-CDFT computations are performed in a parallel internuclear-axis and magnetic field-axis configuration at the field-free equilibrium internuclear separation R = 1.3 au with the field-strength varying between 0 and 10(11) G. The TD behavior of the exchange- and correlation energy of the He?2++ is analyzed and compared with that obtained using a [B-TD-QFD-density functional theory (DFT)] approach based on the conventional TD-DFT under similar computational constraints but using only scalar XC potential and energy density functional dependent on the electronic charge-density alone. The CDFT based approach yields TD exchange- and correlation energy and TD electronic charge-density significantly different from that obtained using the conventional TD-DFT based approach, particularly, at typical magnetic field strengths and during a typical time period of the TD field. This peculiar behavior of the CDFT-based approach is traced to the TD current-density dependent vector XC potential, which can induce nonadiabatic effects causing retardation of the oscillating electronic charge density. Such dissipative electron dynamics of the He?2++ molecular ion is elucidated by treating electronic charge density as an electron-"fluid" in the terminology of QFD. PMID:21598275

  8. Strong-field ionization rates of linear polyenes simulated with time-dependent configuration interaction with an absorbing potential

    SciTech Connect

    Krause, Pascal; Schlegel, H. Bernhard [Department of Chemistry, Wayne State University, Detroit, Michigan 48202-3489 (United States)

    2014-11-07

    The strong field ionization rates for ethylene, trans 1,3-butadiene, and trans,trans 1,3,5-hexatriene have been calculated using time-dependent configuration interaction with single excitations and a complex absorbing potential (TDCIS-CAP). The calculations used the aug-cc-pVTZ basis set with a large set of diffuse functions (3 s, 2 p, 3 d, and 1 f) on each atom. The absorbing boundary was placed 3.5 times the van der Waals radius from each atom. The simulations employed a seven-cycle cosine squared pulse with a wavelength of 800 nm. Ionization rates were calculated for intensities ranging from 0.3 × 10{sup 14} W/cm{sup 2} to 3.5 × 10{sup 14} W/cm{sup 2}. Ionization rates along the molecular axis increased markedly with increasing conjugation length. By contrast, ionization rates perpendicular to the molecular axis were almost independent of the conjugation length.

  9. Spatial Dependence and Heterogeneity in Bayesian Factor Analysis: A Cross-National Investigation of Schwartz Values

    ERIC Educational Resources Information Center

    Stakhovych, Stanislav; Bijmolt, Tammo H. A.; Wedel, Michel

    2012-01-01

    In this article, we present a Bayesian spatial factor analysis model. We extend previous work on confirmatory factor analysis by including geographically distributed latent variables and accounting for heterogeneity and spatial autocorrelation. The simulation study shows excellent recovery of the model parameters and demonstrates the consequences…

  10. Three-Point Correlation Function of Galaxy Clusters in Cosmological Models - a Strong Dependence on Triangle Shapes

    NASA Astrophysics Data System (ADS)

    Jing, Y. P.; Borner, G.; Valdarnini, R.

    1995-11-01

    In this paper, we use large P^3^M N-body simulations to study the three- point correlation function {? of clusters in two theoretical models. The first model (LCDM) is a low-density flat model of {OMEGA}_0_ = 0.3, {LAMBDA}_0_ = 0.7 and h = 0.75, and the second model (PIM) is an Einstein-de Sitter model with its linear power spectrum obtained from observations We find that the scaled function Q(r, u, v), which is defined as the ratio of ?(r, ru, ru + rv) to the hierarchical sum ?(r)?(ru) + ?(ru)?(ru + rv) + ?(ru + rv)?(r) (where ? is the two-point correlation function of clusters), depends weakly on r and u, but very strongly on v. Q(r, u, v) is about 0.2 at v = 0.1 and 1.8 at v = 0.9. A model of Q(r, u, v) = {THETA}10^1.3_v_^2^ can fit the data of ? very nicely with {THETA} ~ 0.14. This model is found to be universal for the LCDM clusters and for the PIM clusters. Furthermore, Q(r, u, v) is found to be insensitive to the cluster richness. We compare our N-body results with simple analytical theories of cluster formation, like the peak theories or the local maxima theories. We find that these theories do not provide an adequate description for the three-point function of clusters. We also examine the observational data of ? presently available, and do not find any contradiction between the observations and our model predictions. The v- dependence of 4 in a projected catalogue of clusters is shown to be much weaker than the v-dependence of Q found in the three-dimensional case. This is probably the reason why the v-dependence of Q has not been found in an angular correlation function analysis of the Abell catalogue. The v-dependence found in this paper might be an important feature of clusters formed in the Gaussian gravitational instability theories. Therefore it would be important to search for the v-dependence on Q in redshift samples of rich clusters.

  11. Spatially dependent Rabi oscillations: An approach to sub-diffraction-limited coherent anti-Stokes Raman-scattering microscopy

    SciTech Connect

    Beeker, Willem P.; Lee, Chris J.; Boller, Klaus-Jochen; Gross, Petra; Cleff, Carsten; Fallnich, Carsten; Offerhaus, Herman L.; Herek, Jennifer L. [Laser Physics and Nonlinear Optics Group, MESA Research Institute for Nanotechnology, University of Twente, P.O. Box 217, Enschede NL-7500 AE (Netherlands); Institut fuer Angewandte Physik, Westfaelische Wilhelms-Universitaet, D-48149 Muenster (Germany); Optical Sciences Group, MESA Research Institute for Nanotechnology, University of Twente, P.O. Box 217, Enschede NL-7500 AE (Netherlands)

    2010-01-15

    We present a theoretical investigation of coherent anti-Stokes Raman scattering (CARS) that is modulated by periodically depleting the ground-state population through Rabi oscillations driven by an additional control laser. We find that such a process generates optical sidebands in the CARS spectrum and that the frequency of the sidebands depends on the intensity of the control laser light field. We show that analyzing the sideband frequency upon scanning the beams across the sample allows one to spatially resolve emitter positions where a spatial resolution of 65 nm, which is well below the diffraction limit, can be obtained.

  12. Strong topographic sheltering effects lead to spatially complex treeline advance and increased forest density in a subtropical mountain region.

    PubMed

    Greenwood, Sarah; Chen, Jan-Chang; Chen, Chaur-Tzuhn; Jump, Alistair S

    2014-12-01

    Altitudinal treelines are typically temperature limited such that increasing temperatures linked to global climate change are causing upslope shifts of treelines worldwide. While such elevational increases are readily predicted based on shifting isotherms, at the regional level the realized response is often much more complex, with topography and local environmental conditions playing an important modifying role. Here, we used repeated aerial photographs in combination with forest inventory data to investigate changes in treeline position in the Central Mountain Range of Taiwan over the last 60 years. A highly spatially variable upslope advance of treeline was identified in which topography is a major driver of both treeline form and advance. The changes in treeline position that we observed occurred alongside substantial increases in forest density, and lead to a large increase in overall forest area. These changes will have a significant impact on carbon stocking in the high altitude zone, while the concomitant decrease in alpine grassland area is likely to have negative implications for alpine species. The complex and spatially variable changes that we report highlight the necessity for considering local factors such as topography when attempting to predict species distributional responses to warming climate. PMID:25141823

  13. Binding constants of membrane-anchored receptors and ligands depend strongly on the nanoscale roughness of membranes

    PubMed Central

    Hu, Jinglei; Lipowsky, Reinhard; Weikl, Thomas R.

    2013-01-01

    Cell adhesion and the adhesion of vesicles to the membranes of cells or organelles are pivotal for immune responses, tissue formation, and cell signaling. The adhesion processes depend sensitively on the binding constant of the membrane-anchored receptor and ligand proteins that mediate adhesion, but this constant is difficult to measure in experiments. We have investigated the binding of membrane-anchored receptor and ligand proteins with molecular dynamics simulations. We find that the binding constant of the anchored proteins strongly decreases with the membrane roughness caused by thermally excited membrane shape fluctuations on nanoscales. We present a theory that explains the roughness dependence of the binding constant for the anchored proteins from membrane confinement and that relates this constant to the binding constant of soluble proteins without membrane anchors. Because the binding constant of soluble proteins is readily accessible in experiments, our results provide a useful route to compute the binding constant of membrane-anchored receptor and ligand proteins. PMID:24006364

  14. Three-dimensional electromagnetic strong turbulence: Dependence of the statistics and dynamics of strong turbulence on the electron to ion temperature ratio

    NASA Astrophysics Data System (ADS)

    Graham, D. B.; Cairns, Iver H.; Skjaeraasen, O.; Robinson, P. A.

    2012-02-01

    The temperature ratio Ti/Te of ions to electrons affects both the ion-damping rate and the ion-acoustic speed in plasmas. The effects of changing the ion-damping rate and ion-acoustic speed are investigated for electrostatic strong turbulence and electromagnetic strong turbulence in three dimensions. When ion damping is strong, density wells relax in place and act as nucleation sites for the formation of new wave packets. In this case, the density perturbations are primarily density wells supported by the ponderomotive force. For weak ion damping, corresponding to low Ti/Te, ion-acoustic waves are launched radially outwards when wave packets dissipate at burnout, thereby increasing the level of density perturbations in the system and thus raising the level of scattering of Langmuir waves off density perturbations. Density wells no longer relax in place so renucleation at recent collapse sites no longer occurs, instead wave packets form in background low density regions, such as superpositions of troughs of propagating ion-acoustic waves. This transition is found to occur at Ti/Te ? 0.1. The change in behavior with Ti/Te is shown to change the bulk statistical properties, scaling behavior, spectra, and field statistics of strong turbulence. For Ti/Te>rsim0.1, the electrostatic results approach the predictions of the two-component model of Robinson and Newman, and good agreement is found for Ti/Te>rsim0.15.

  15. Frequency-dependent spatial distribution of human somatosensory evoked neuromagnetic fields

    Microsoft Academic Search

    Masayuki Hirata; Amami Kato; Masaaki Taniguchi; Hirotomo Ninomiya; Douglas Cheyne; Stephen E. Robinson; Motohiko Maruno; Eiji Kumura; Ryouhei Ishii; Norio Hirabuki; Hironobu Nakamura; Toshiki Yoshimine

    2002-01-01

    Using synthetic aperture magnetometry (SAM), we examined the spatial distribution of frequency changes in magnetoencephalography signal rhythms on individual magnetic resonance images following somatosensory stimulation. SAM is a novel statistical spatial filtering method that uses an adaptive beamformer. Electrical stimulation of the right median nerve demonstrated high-frequency event-related synchronization (ERS) in the 50–200-Hz range, consistently localized in the contralateral primary

  16. Spatial scale-dependent land-atmospheric methane exchanges in the northern high latitudes from 1993 to 2004

    NASA Astrophysics Data System (ADS)

    Zhu, X.; Zhuang, Q.; Lu, X.; Song, L.

    2014-04-01

    Effects of various spatial scales of water table dynamics on land-atmospheric methane (CH4) exchanges have not yet been assessed for large regions. Here we used a coupled hydrology-biogeochemistry model to quantify daily CH4 exchanges over the pan-Arctic from 1993 to 2004 at two spatial scales of 100 km and 5 km. The effects of sub-grid spatial variability of the water table depth (WTD) on CH4 emissions were examined with a TOPMODEL-based parameterization scheme for the northern high latitudes. We found that both WTD and CH4 emissions are better simulated at a 5 km spatial resolution. By considering the spatial heterogeneity of WTD, net regional CH4 emissions at a 5 km resolution are 38.1-55.4 Tg CH4 yr-1 from 1993 to 2004, which are on average 42% larger than those simulated at a 100 km resolution using a grid-cell-mean WTD scheme. The difference in annual CH4 emissions is attributed to the increased emitting area and enhanced flux density with finer resolution for WTD. Further, the inclusion of sub-grid WTD spatial heterogeneity also influences the inter-annual variability of CH4 emissions. Soil temperature plays an important role in the 100 km estimates, while the 5 km estimates are mainly influenced by WTD. This study suggests that previous macro-scale biogeochemical models using a grid-cell-mean WTD scheme might have underestimated the regional CH4 emissions. The spatial scale-dependent effects of WTD should be considered in future quantification of regional CH4 emissions.

  17. Spatially dependent parameter estimation and nonlinear data assimilation by autosynchronization of a system of partial differential equations

    NASA Astrophysics Data System (ADS)

    Kramer, Sean; Bollt, Erik M.

    2013-09-01

    Given multiple images that describe chaotic reaction-diffusion dynamics, parameters of a partial differential equation (PDE) model are estimated using autosynchronization, where parameters are controlled by synchronization of the model to the observed data. A two-component system of predator-prey reaction-diffusion PDEs is used with spatially dependent parameters to benchmark the methods described. Applications to modeling the ecological habitat of marine plankton blooms by nonlinear data assimilation through remote sensing are discussed.

  18. Spatial and age-dependent tree-ring growth responses of Larix gmelinii to climate in northeastern China

    Microsoft Academic Search

    Xiaochun Wang; Yuandong Zhang; Douglas J. McRae

    2009-01-01

    Tree-ring width chronologies from 276 Larix gmelinii cores taken in northeastern China were used to analyze spatial and age-dependent growth–climate response relationships. Tree\\u000a radial growth from five localities showed similar patterns, while exhibiting different tree-ring growth responses to local\\u000a climate. The rotated principal component analysis (RPCA) indicated that tree age, growing season moisture conditions, and\\u000a ambient air temperature variations resulted

  19. Scale-dependent predictability of DEM-based landform attributes for soil spatial variability in a coastal dune system

    Microsoft Academic Search

    Daehyun Kim; Yanbing Zheng

    2011-01-01

    Much soil–landform modeling has shown that the predictability of topographic parameters derived from digital elevation models (DEM) for soil spatial variability is influenced by the selection of DEM's grid size. This study investigates soil–terrain relationships in a coastal dune at multiple DEM resolutions to examine if such scale-dependence is a ubiquitous phenomenon even in low-relief systems with relatively homogeneous substrates.

  20. Strong motion characteristics of the M w 6.6 Lushan earthquake, Sichuan, China — an insight into the spatial difference of a typical thrust fault earthquake

    NASA Astrophysics Data System (ADS)

    Hu, Jinjun; Zhang, Wenbo; Xie, Lili; Zhang, Qi; Jiang, Zhijun

    2015-06-01

    Near-field strong ground motions are useful for engineering seismology studies and seismic design, but dense observation networks of damaging earthquakes are still rare. In this study, based on the strong-motion data from the M w 6.6 Lushan earthquake, the ground motion parameters in different spatial regions are systematically analyzed, and the contributions from different effects, like the hanging-wall effect, directivity effect, and attenuation effect are separated to the extent possible. Different engineering parameters from the observed ground motions are compared with the local design response spectra and a new attenuation relation of Western China. General results indicate that the high frequency ground motion, like the peak ground acceleration, on two sides of the fault plane is sensitive to the hanging-wall effect, whereas the low frequency ground motion, like the long period spectral acceleration, in the rupture propagation direction is affected by the directivity effect. Moreover, although the M w 6.6 Lushan earthquake is not a large magnitude event, the spatial difference of ground motion is still obvious; thus, for a thrust faulting earthquake, in addition to the hanging effect, the directivity effect should also be considered.

  1. Site-dependent spectra from the 1999 Turkey earthquakes considering different sets of strong-motion data

    NASA Astrophysics Data System (ADS)

    Schwarz, J.; Ende, C.; Habenberger, J.; Lang, D. H.

    2003-04-01

    In the last decade extensive strong-motion measurements were carried out by the reconnaissance team of the German TaskForce for Earthquakes. Aftershocks were recorded by a mesh of temporarily installed strong-motion recorders during the field surveys to Turkey in 1998 (Adana/Ceyhan), 1999 (Izmit/Kocaeli and Duezce/Bolu) and 2002 (Sultandagi/Afyon). Particularly the two missions in 1999 provided a unique and comprehensive database of recorded aftershocks at sites where building damage occurred. In addition, post-earthquake investigations were initiated around the provinces Adana and Kocaeli in October 2000 to gain more insight into the effect of local site conditions. Therefore, microtremors were recorded at sites of the previously installed strong-motion accelerographs and locations of evident concentration or remarkable scatter of building damage. By applying H/V-spectral ratio method on microtremor data, a classification of the recording sites (into soft soil, stiff soil, rock-type conditions) was performed. For the derivation of attenuation laws different databases were applied. In addition to the aftershock records of the strong-motion stations of German TaskForce for Earthquakes (Schwarz et al., 2002), a small dataset of main- and aftershocks from the 1999 Turkey earthquakes provided by the Kandilli Observatory (KOERI, 2002) and the General Directorate of Disaster Affairs (AFET) could be implied. The magnitude-distance composition of both datasets are quite different in terms of the covered magnitude and distance range. While the dataset of the German TaskForce mainly consists of small magnitude aftershocks (at the present state of elaboration: Ml <= 4.9) being recorded in epicentral distances Re < 70 km, the KOERI dataset is featured by larger magnitudes (Ml = 4.8-7.2) and by a distance range of about 10--250 km. The aftershock database of German TaskForce consists of 538 triaxial acceleration records (rock 53, stiff 52, soft 433), while that of KOERI comprises 145 triaxial acceleration records (rock 6, stiff 36, soft 103). On this basis, three sets of strong motion records were investigated by an one-step as well as a two-step regression analysis (similar to the approach by Ambraseys et al., 1996). Furthermore, parametric studies with respect to the lower bounds of magnitude and source depth were performed. Results indicate that the composition of the dataset and in particular the decision on the lower bound magnitude significantly determine the qualitative spectrum shape. In comparison to the spectra determined by Ambraseys et al. (1996) attenuation functions, the recorded data lead to significant lower accelerations for the borizontal as well as for the vertical components. Furthermore, no significant differences between data from soft and stiff soil recording sites can be observed, supporting the authors opinion that the severity of ground motion during earthquakes is less responsible for the high extent of building damage than the vulnerability of the building stock (which seem to be quite different for one particular building type in dependence on the date of construction). Therefore more attention should be attributed to the investigation of the building inventory.

  2. Model-dependent spatial skill in pseudoproxy experiments testing climate field reconstruction methods for the Common Era

    NASA Astrophysics Data System (ADS)

    Smerdon, Jason E.; Coats, Sloan; Ault, Toby R.

    2015-06-01

    The spatial skill of four climate field reconstruction (CFR) methods is investigated using pseudoproxy experiments (PPEs) based on five last millennium and historical simulations from the Coupled and Paleo Model Intercomparison Projects Phases 5 and 3 (CMIP5/PMIP3) data archives. These simulations are used for the first time in a PPE context, the frameworks of which are constructed to test a recently assembled multiproxy network and multiple CFR techniques. The experiments confirm earlier findings demonstrating consistent methodological performance across the employed methods and spatially dependent reconstruction errors in all of the derived CFRs. Spectral biases in the reconstructed fields demonstrate that CFR methods can alone alter the ratio of spectral power at all locations in the field, independent of whether there are any spectral biases inherent in the underlying pseudoproxy series. The patterns of spectral biases are model dependent and indicate the potential for regions in the derived CFRs to be biased by changes in either low or high-frequency spectral power. CFR methods are also shown to alter the pattern of mean differences in the tropical Pacific during the Medieval Climate Anomaly and the Little Ice Age, with some model experiments indicating that CFR methodologies enhance the statistical likelihood of achieving larger mean differences between independent 300-year periods in the region. All of the characteristics of CFR performance are model dependent, indicating that CFR methods must be evaluated across multiple models and that conclusions from PPEs should be carefully connected to the spatial statistics of real-world climatic fields.

  3. Fitness Effects of Chlorpyrifos in the Damselfly Enallagma cyathigerum Strongly Depend upon Temperature and Food Level and Can Bridge Metamorphosis

    PubMed Central

    Janssens, Lizanne; Stoks, Robby

    2013-01-01

    Interactions between pollutants and suboptimal environmental conditions can have severe consequences for the toxicity of pollutants, yet are still poorly understood. To identify patterns across environmental conditions and across fitness-related variables we exposed Enallagma cyathigerum damselfly larvae to the pesticide chlorpyrifos at two food levels or at two temperatures and quantified four fitness-related variables (larval survival, development time, mass at emergence and adult cold resistance). Food level and temperature did not affect survival in the absence of the pesticide, yet the pesticide reduced survival only at the high temperature. Animals reacted to the pesticide by accelerating their development but only at the high food level and at the low temperature; at the low food level, however, pesticide exposure resulted in a slower development. Chlorpyrifos exposure resulted in smaller adults except in animals reared at the high food level. Animals reared at the low food level and at the low temperature had a higher cold resistance which was not affected by the pesticide. In summary our study highlight that combined effects of exposure to chlorpyrifos and the two environmental conditions (i) were mostly interactive and sometimes even reversed in comparison with the effect of the environmental condition in isolation, (ii) strongly differed depending on the fitness-related variable under study, (iii) were not always predictable based on the effect of the environmental condition in isolation, and (iv) bridged metamorphosis depending on which environmental condition was combined with the pesticide thereby potentially carrying over from aquatic to terrestrial ecosystems. These findings are relevant when extrapolating results of laboratory tests done under ideal environmental conditions to natural communities. PMID:23840819

  4. Electrochemistry of transition metal dichalcogenides: strong dependence on the metal-to-chalcogen composition and exfoliation method.

    PubMed

    Eng, Alex Yong Sheng; Ambrosi, Adriano; Sofer, Zden?k; Šimek, Petr; Pumera, Martin

    2014-12-23

    Beyond MoS2 as the first transition metal dichalcogenide (TMD) to have gained recognition as an efficient catalyst for the hydrogen evolution reaction (HER), interest in other TMD nanomaterials is steadily beginning to proliferate. This is particularly true in the field of electrochemistry, with a myriad of emerging applications ranging from catalysis to supercapacitors and solar cells. Despite this rise, current understanding of their electrochemical characteristics is especially lacking. We therefore examine the inherent electroactivities of various chemically exfoliated TMDs (MoSe2, WS2, WSe2) and their implications for sensing and catalysis of the hydrogen evolution and oxygen reduction reactions (ORR). The TMDs studied are found to possess distinctive inherent electroactivities and together with their catalytic effects for the HER are revealed to strongly depend on the chemical exfoliation route and metal-to-chalcogen composition particularly in MoSe2. Despite its inherent activity exhibiting large variations depending on the exfoliation procedure, it is also the most efficient HER catalyst with a low overpotential of -0.36 V vs RHE (at 10 mA cm(-2) current density) and fairly low Tafel slope of ?65 mV/dec after BuLi exfoliation. In addition, it demonstrates a fast heterogeneous electron transfer rate with a k0obs of 9.17×10(-4) cm s(-1) toward ferrocyanide, better than that seen for conventional glassy carbon electrodes. Knowledge of TMD electrochemistry is essential for the rational development of future applications; inherent TMD activity may potentially limit certain purposes, but intended objectives can nonetheless be achieved by careful selection of TMD compositions and exfoliation methods. PMID:25453501

  5. Mycolactone-Dependent Depletion of Endothelial Cell Thrombomodulin Is Strongly Associated with Fibrin Deposition in Buruli Ulcer Lesions

    PubMed Central

    Ogbechi, Joy; Ruf, Marie-Thérèse; Hall, Belinda S.; Bodman-Smith, Katherine; Vogel, Moritz; Wu, Hua-Lin; Stainer, Alexander; Esmon, Charles T.; Ahnström, Josefin; Pluschke, Gerd; Simmonds, Rachel E.

    2015-01-01

    A well-known histopathological feature of diseased skin in Buruli ulcer (BU) is coagulative necrosis caused by the Mycobacterium ulcerans macrolide exotoxin mycolactone. Since the underlying mechanism is not known, we have investigated the effect of mycolactone on endothelial cells, focussing on the expression of surface anticoagulant molecules involved in the protein C anticoagulant pathway. Congenital deficiencies in this natural anticoagulant pathway are known to induce thrombotic complications such as purpura fulimans and spontaneous necrosis. Mycolactone profoundly decreased thrombomodulin (TM) expression on the surface of human dermal microvascular endothelial cells (HDMVEC) at doses as low as 2ng/ml and as early as 8hrs after exposure. TM activates protein C by altering thrombin’s substrate specificity, and exposure of HDMVEC to mycolactone for 24 hours resulted in an almost complete loss of the cells’ ability to produce activated protein C. Loss of TM was shown to be due to a previously described mechanism involving mycolactone-dependent blockade of Sec61 translocation that results in proteasome-dependent degradation of newly synthesised ER-transiting proteins. Indeed, depletion from cells determined by live-cell imaging of cells stably expressing a recombinant TM-GFP fusion protein occurred at the known turnover rate. In order to determine the relevance of these findings to BU disease, immunohistochemistry of punch biopsies from 40 BU lesions (31 ulcers, nine plaques) was performed. TM abundance was profoundly reduced in the subcutis of 78% of biopsies. Furthermore, it was confirmed that fibrin deposition is a common feature of BU lesions, particularly in the necrotic areas. These findings indicate that there is decreased ability to control thrombin generation in BU skin. Mycolactone’s effects on normal endothelial cell function, including its ability to activate the protein C anticoagulant pathway are strongly associated with this. Fibrin-driven tissue ischemia could contribute to the development of the tissue necrosis seen in BU lesions. PMID:26181660

  6. Spatial and time-dependent distribution of plasma parameters in the metal-halide arc lamp

    E-print Network

    Khakhaev, A; Ekimov, K; Soloviev, A; Khakhaev, Anatoly; Luizova, Lidia; Ekimov, Konstantin; Soloviev, Alexey

    2004-01-01

    It was shown by several authors that closed high pressure arc a.c. discharge in mercury vapors with addition of metal halide cannot be described in frames of the local thermodynamic equilibrium (LTE) model. However some plasma parameters (electron and high lying excited states densities as well as Hg metastable levels densities) are assumed to be in equilibrium with electron temperature and these assumptions are applied in plasma diagnostics. To verify these supposition the method of local plasma spectroscopy based on spatial and temporal distribution of spectral line profiles was developed. The experimental set up is based on diffraction spectrometer with large aperture, spatial scanning device and photodetector, which allows to carry out the measurements in chosen phases of current period. The software for data acquisition and processing is based on LabVIEW system. The original method of joint data processing was applied to data arrays containing spatial, spectral and temporal distribution of a source surfa...

  7. Facile synthesis and strongly microstructure-dependent electrochemical properties of graphene/manganese dioxide composites for supercapacitors

    PubMed Central

    2014-01-01

    Graphene has attracted much attention since it was firstly stripped from graphite by two physicists in 2004, and the supercapacitor based on graphene has obtained wide attention and much investment as well. For practical applications of graphene-based supercapacitors, however, there are still many challenges to solve, for instance, to simplify the technological process, to lower the fabrication cost, and to improve the electrochemical performance. In this work, graphene/MnO2 composites are prepared by a microwave sintering method, and we report here a relatively simple method for the supercapacitor packaging, i.e., dipping Ni-foam into a graphene/MnO2 composite solution directly for a period of time to coat the active material on a current collector. It is found that the microwave reaction time has a significant effect on the microstructure of graphene/MnO2 composites, and consequently, the electrochemical properties of the supercapacitors based on graphene/MnO2 composites are strongly microstructure dependent. An appropriately longer microwave reaction time, namely, 15 min, facilitates a very dense and homogeneous microstructure of the graphene/MnO2 composites, and thus, excellent electrochemical performance is achieved in the supercapacitor device, including a high specific capacitance of 296 F/g and a high capacitance retention of 93% after 3,000 times of charging/discharging cycles. PACS 81.05.ue; 78.67.Sc; 88.80.fh PMID:25258609

  8. Respiration of the external mycelium in the arbuscular mycorrhizal symbiosis shows strong dependence on recent photosynthates and acclimation to temperature.

    PubMed

    Heinemeyer, A; Ineson, P; Ostle, N; Fitter, A H

    2006-01-01

    * Although arbuscular mycorrhizal (AM) fungi are a major pathway in the global carbon cycle, their basic biology and, in particular, their respiratory response to temperature remain obscure. * A pulse label of the stable isotope (13)C was applied to Plantago lanceolata, either uninoculated or inoculated with the AM fungus Glomus mosseae. The extra-radical mycelium (ERM) of the fungus was allowed to grow into a separate hyphal compartment excluding roots. We determined the carbon costs of the ERM and tested for a direct temperature effect on its respiration by measuring total carbon and the (13)C:(12)C ratio of respired CO(2). With a second pulse we tested for acclimation of ERM respiration after 2 wk of soil warming. * Root colonization remained unchanged between the two pulses but warming the hyphal compartment increased ERM length. delta(13)C signals peaked within the first 10 h and were higher in mycorrhizal treatments. The concentration of CO(2) in the gas samples fluctuated diurnally and was highest in the mycorrhizal treatments but was unaffected by temperature. Heating increased ERM respiration only after the first pulse and reduced specific ERM respiration rates after the second pulse; however, both pulses strongly depended on radiation flux. * The results indicate a fast ERM acclimation to temperature, and that light is the key factor controlling carbon allocation to the fungus. PMID:16771991

  9. Hypercycles versus parasites in the origin of life: model dependence in spatial hypercycle systems

    NASA Astrophysics Data System (ADS)

    Cronhjort, Mikael B.

    1995-06-01

    Spatial hypercycle systems can be modelled by means of cellular automata or partial differential equations. In either model, two dimensional spirals or clusters can be formed. Different models give rise to slightly different spatial structures, but the response to parasites is fundamentally different: In cellular automata the hypercycle is resistant to parasites that are fatal in a partial differential equations model. In three dimensions scroll rings correspond to the two dimensional spirals. Numerical simulations on a partial differential equations model indicate that the scroll rings are unstable: The contract by a power law and disappear. Therefore, in three dimensions clusters seem to be the best candidate for the hypercycle resistant to parasites.

  10. Epidemic West Nile virus encephalomyelitis: A temperature-dependent, spatial model of disease dynamics

    Microsoft Academic Search

    Michael P. Ward

    2005-01-01

    Since first being detected in New York in 1999, West Nile virus (WNV) has spread throughout the United States and more than 20,000 cases of equine WNV encephalomyelitis have been reported. A spatial model of disease occurrence was developed, using data from an outbreak of serologically confirmed disease in an unvaccinated population of horses at 108 locations in northern Indiana

  11. SPATIAL HETEROGENEITY EXPLAINS THE SCALE DEPENDENCE OF THE NATIVE–EXOTIC DIVERSITY RELATIONSHIP

    Microsoft Academic Search

    Kendi F. Davies; Peter Chesson; Susan Harrison; Brian D. Inouye; Brett A. Melbourne; Kevin J. Rice

    2005-01-01

    While small-scale studies show that more diverse native communities are less invasible by exotics, studies at large spatial scales often find positive correlations between native and exotic diversity. This large-scale pattern is thought to arise because landscapes with favorable conditions for native species also have favorable conditions for exotic species. From theory, we proposed an alternative hypothesis: the positive relationship

  12. Multisensory integration for spatial orientation in trait anxiety subjects: absence of visual dependence

    Microsoft Academic Search

    I Viaud-Delmon; A Berthoz; R Jouvent

    2002-01-01

    Studies suggest a greater reliance on visual information for maintaining balance in anxious subjects. Nevertheless, links between this supposed preferred visual processing and spatial orientation have not yet been evaluated. Two groups of subjects differing in their level of trait anxiety were formed. Equipped with a head-mounted visual display, they learned a virtual corridor using passive translation but active rotation,

  13. Spatial Dependence and Heterogeneity in Patterns of Hardship: An Intra-Urban Analysis

    Microsoft Academic Search

    Paul A. Longley; Carolina Tobón

    2004-01-01

    Developments in the provision and quality of digital data are creating possibilities for spatial and temporal measurement of the properties of socioeconomic systems at finer levels of granularity. In this article, we suggest that the “lifestyles” datasets collected by private sector organizations in the U.K. and the U.S. provide one such prospect for better inferring the structure, composition, and heterogeneity

  14. Systematic Spatial Bias in DNA Microarray Hybridization Is Caused by Probe Spot Position-Dependent Variability

    E-print Network

    Entekhabi, Dara

    Systematic Spatial Bias in DNA Microarray Hybridization Is Caused by Probe Spot Position research. Despite its widespread application, DNA microarray technology still suffers from several biases uniformity and accuracy of quantitative DNA microarray hybridization. Citation: Steger D, Berry D, Haider S

  15. Nonparametric image interpolation and dictionary learning using spatially-dependent Dirichlet and beta process priors

    Microsoft Academic Search

    John William Paisley; Mingyuan Zhou; Guillermo Sapiro; Lawrence Carin

    2010-01-01

    We present a Bayesian model for image interpolation and dictionary learning that uses two nonparametric priors for sparse signal representations: the beta process and the Dirichlet process. Additionally, the model uses spatial information within the image to encourage sharing of information within image subregions. We derive a hybrid MAP\\/Gibbs sampler, which performs Gibbs sampling for the latent indicator variables and

  16. Effects of Reverberant Spatial Cues on Attention-dependent Object Formation

    E-print Network

    Lee, Adrian KC

    , Cambridge, MA, USA 3 Department of Cognitive and Neural Systems, Boston University, 677 Beacon St., Room 311 on perceptual segregation than anechoic spatial cues. In addition, results repli- cate an interesting finding and Neural Systems & Boston University & 677 Beacon St., Room 311, Boston, MA 02215, USA. Telephone: +1

  17. Can inverse density dependence at small spatial scales produce dynamic instability in animal populations?

    Microsoft Academic Search

    J. Wilson White

    All else being equal, inversely density-dependent (IDD) mortality destabilizes population dynamics. However, stability has\\u000a not been investigated for cases in which multiple types of density dependence act simultaneously. To determine whether IDD\\u000a mortality can destabilize populations that are otherwise regulated by directly density-dependent (DDD) mortality, I used scale\\u000a transition approximations to model populations with IDD mortality at smaller “aggregation” scales

  18. Spatial distribution of intertidal fishes: a pattern dependent on body size and predation risk?

    Microsoft Academic Search

    José M. Rojas; F. Patricio Ojeda

    2010-01-01

    Traditionally, heterogeneity levels have been associated with refuge availability and, consequently, with security areas for\\u000a prey. Hence, there is assumed to be a positive correlation between the spatial distribution of potential victims and habitat\\u000a heterogeneity levels. Among fish, the magnitude of predator-prey interaction has been associated with their size ratio, which\\u000a includes body size as a central variable for individual

  19. Temperature Dependence of Spatially Resolved Picosecond Laser Induced Transients in a Deep Submicron CMOS Inverter

    Microsoft Academic Search

    Jamie S. Laird; Yuan Chen; Tuan Vo; Larry Edmonds; Leif Scheick; Philippe Adell

    2009-01-01

    Spatially-resolved picosecond laser induced transients have been measured in a 0.18 mum CMOS inverter test structure as a function of temperature. Sensitive n-drain and p-drain nodes have been scaled in size to accommodate characteristic differences between ion and laser tracks. Images based on pulse characteristics have been collected from 325 K to 400 K and transient currents extracted from laser

  20. Tunneling spectroscopy on silver clusters at T=5 K: size dependence and spatial energy shifts

    Microsoft Academic Search

    H. Hövel; B. Grimm; M. Bödecker; K. Fieger; B. Reihl

    2000-01-01

    We have studied silver clusters grown in nanopits on a graphite surface using low-temperature scanning tunneling spectroscopy (STS) at T=5K. The pronounced peak structure measured in the STS data of the clusters is interpreted to have its origin in the quantized electronic structure of the cluster–surface system. Additionally, a systematic spatial energy shift was observed for some spectral features in

  1. Determination of the spatial TDR-sensor characteristics in strong dispersive subsoil using 3D-FEM frequency domain simulations in combination with microwave dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Wagner, Norman; Trinks, Eberhard; Kupfer, Klaus

    2007-04-01

    The spatial sensor characteristics of a 6 cm TDR flat band cable sensor section was simulated with finite element modelling (high frequency structure simulator—HFSS) under certain conditions: (i) in direct contact with the surrounding material (air, water of different salinities, different synthetic and natural soils (sand-silt-clay mixtures)), (ii) with consideration of a defined gap of different size filled with air or water and (iii) the cable sensor pressed at a borehole-wall. The complex dielectric permittivity ?sstarf(?, ?i) or complex electrical conductivity ?sstarf(?, ?i) = i??sstarf(?, ?i) of the investigated saturated and unsaturated soils was examined in the frequency range 50 MHz-20 GHz at room temperature and atmospheric pressure with a HP8720D-network analyser. Three soil-specific relaxation processes are assumed to act in the investigated frequency-temperature-pressure range: one primary ?-process (main water relaxation) and two secondary (?', ?)-processes due to clay-water-ion interactions (bound water relaxation and the Maxwell-Wagner effect). The dielectric relaxation behaviour of every process is described with the use of a simple fractional relaxation model. 3D finite element simulation is performed with a ?/3 based adaptive mesh refinement at a solution frequency of 1 MHz, 10 MHz, 0.1 GHz, 1 GHz and 12.5 GHz. The electromagnetic field distribution, S-parameter and step responses were examined. The simulation adequately reproduces the spatial and temporal electrical and magnetic field distribution. High-lossy soils cause, as a function of increasing gravimetric water content and bulk density, an increase in TDR signal rise time as well as a strong absorption of multiple reflections. An air or water gap works as a quasi-waveguide, i.e. the influence of the surrounding medium is strongly reduced. Appropriate TDR-travel-time distortions can be quantified.

  2. Spatial heterogeneity in the effects of climate and density-dependence on dispersal in a house sparrow metapopulation

    PubMed Central

    Pärn, Henrik; Ringsby, Thor Harald; Jensen, Henrik; Sæther, Bernt-Erik

    2012-01-01

    Dispersal plays a key role in the response of populations to climate change and habitat fragmentation. Here, we use data from a long-term metapopulation study of a non-migratory bird, the house sparrow (Passer domesticus), to examine the influence of increasing spring temperature and density-dependence on natal dispersal rates and how these relationships depend on spatial variation in habitat quality. The effects of spring temperature and population size on dispersal rate depended on the habitat quality. Dispersal rate increased with temperature and population size on poor-quality islands without farms, where house sparrows were more exposed to temporal fluctuations in weather conditions and food availability. By contrast, dispersal rate was independent of spring temperature and population size on high-quality islands with farms, where house sparrows had access to food and shelter all the year around. This illustrates large spatial heterogeneity within the metapopulation in how population density and environmental fluctuations affect the dispersal process. PMID:21613299

  3. Spatial Analysis to Quantify Numerical Model Bias and Dependence: How Many Climate Models Are There?

    E-print Network

    Jun, Mikyoung

    the Earth's atmosphere, ocean, and land processes are the primary tool to study how climate may change over detailed knowledge of potential future climate change comes from coupled atmosphere ocean general circu are not strongly related. KEY WORDS: Cross-covariance model; Intergovernmental Panel on Climate Change; Kernel

  4. Model-Dependent Spatial Skill in Pseudoproxy Experiments Testing Climate Field Reconstruction Methods for the Common Era

    NASA Astrophysics Data System (ADS)

    Smerdon, Jason; Coats, Sloan; Ault, Toby

    2015-04-01

    The spatial skill of four climate field reconstruction (CFR) methods is investigated using pseudoproxy experiments (PPEs) based on five Last Millennium (LM) and historical simulations from the Coupled and Paleo Model Intercomparison Projects Phases 5 and 3 (CMIP5/PMIP3) data archives. These simulations are used for the first time in a PPE context, the pseudoproxy frameworks of which are constructed to test a recently assembled multiproxy network and multiple CFR techniques. The experiments confirm earlier findings demonstrating consistent methodological performance across all of the employed methods and spatially dependent reconstruction errors in the derived CFRs. Spectral biases in the reconstructed fields demonstrate that reconstruction methods can alone alter the ratio of spectral power at all locations in the field, independent of whether there are spectral biases inherent in the underlying proxy series. The patterns of spectral biases are model dependent and indicate the potential for regions in the derived CFRs to be biased by changes in either low or high-frequency spectral power. CFR methods are also shown to alter the pattern of mean differences in the tropical Pacific during the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA), with some model experiments indicating that CFR methodologies enhance the statistical likelihood of achieving a larger mean difference between the MCA and LIA in the region. All of the characteristics of reconstruction performance are model dependent, indicating that CFR methods must be evaluated across multiple models and that conclusions from PPEs should be carefully connected to the spatial statistics of real-world climatic fields.

  5. Exact Klein-Gordon equation with spatially-dependent masses for unequal scalar-vector Coulomb-like potentials

    E-print Network

    Sameer M. Ikhdair

    2009-03-23

    We study the effect of spatially dependent mass functions over the solution of the Klein-Gordon equation in the (3+1)-dimensions for spinless bosonic particles where the mixed scalar-vector Coulomb-like field potentials and masses are directly proportional and inversely proportional to the distance from force center. The exact bound state energy eigenvalues and the corresponding wave functions of the Klein-Gordon equation for mixed scalar-vector and pure scalar Coulomb-like field potentials are obtained by means of the Nikiforov-Uvarov (NU) method. The energy spectrum is discussed for different scalar-vector potential mixing cases and also for constant mass case.

  6. SPATIAL AND FREQUENCY DEPENDENCIES OF LOCAL PHOTORESPONSE OF HTS STRIP-LINE RESONATOR IN THE REGIME OF TWO-TONE MICROWAVE

    E-print Network

    Anlage, Steven

    SPATIAL AND FREQUENCY DEPENDENCIES OF LOCAL PHOTORESPONSE OF HTS STRIP-LINE RESONATOR IN THE REGIME resonators. The approach is based on frequency and spatial uniqueness of LSM images that can be extracted) response with respect to pumping power. This manifests itself as global intermodulation product distortion

  7. Chromosome aberration induction is dependent on the spatial distribution of energy deposition through a cell nucleus.

    PubMed

    Hill, M A; Griffin, C S; Pyke, E L; Stevens, D L

    2011-02-01

    The importance of the spatial distribution of energy deposition through the nucleus in determining the resultant chromosome rearrangements was investigated using fluorescent in situ hybridisation technique following either uniform or partial irradiation of HF19 human fibroblast cells with low-LET 1.5 keV ultrasoft X-rays. Irradiations were performed with and without a copper irradiation mask with a Poisson distribution of micron-sized holes immediately below the irradiation dish and the results are compared with previous results obtained following exposure to a Poisson distribution of alpha particles. For the same radiation quality, the spatial distribution of energy deposition within the nucleus was found to be important in determining the ultimate biological response, with an increased ratio of complex-to-simple aberrations observed for partial compared to uniform irradiation. Comparisons between low-LET ultrasoft X-rays and high-LET alpha particles indicate that the sub-micron clustering of damage along the alpha particle track is more important than just the total number of double-strand breaks produced. PMID:21183544

  8. Delay-dependent impairment of spatial working memory with inhibition of NR2B-containing NMDA receptors in hippocampal CA1 region of rats

    PubMed Central

    2013-01-01

    Hippocampal N-methyl-D-aspartate receptor (NMDAR) is required for spatial working memory. Although evidence from genetic manipulation mice suggests an important role of hippocampal NMDAR NR2B subunits (NR2B-NMDARs) in spatial working memory, it remains unclear whether or not the requirement of hippocampal NR2B-NMDARs for spatial working memory depends on the time of spatial information maintained. Here, we investigate the contribution of hippocampal NR2B-NMDARs to spatial working memory on delayed alternation task in T-maze (DAT task) and delayed matched-to-place task in water maze (DMP task). Our data show that infusions of the NR2B-NMDAR selective antagonists, Ro25-6981 or ifenprodil, directly into the CA1 region, impair spatial working memory in DAT task with 30-s delay (not 5-s delay), but severely impair error-correction capability in both 5-s and 30-s delay task. Furthermore, intra-CA1 inhibition of NR2B-NMDARs impairs spatial working memory in DMP task with 10-min delay (not 30-s delay). Our results suggest that hippocampal NR2B-NMDARs are required for spatial working memory in long-delay task, whereas spare for spatial working memory in short-delay task. We conclude that the requirement of NR2B-NMDARs for spatial working memory is delay-dependent in the CA1 region. PMID:23497405

  9. Blood oxygenation level-dependent functional MRI signal turbulence caused by ultrahigh spatial resolution: numerical simulation and theoretical explanation.

    PubMed

    Chen, Zikuan; Chen, Zeyuan; Calhoun, Vince

    2013-03-01

    High-spatial-resolution functional MRI (fMRI) can enhance image contrast and improve spatial specificity for brain activity mapping. As the voxel size is reduced, an irregular magnetic fieldmap will emerge as a result of less local averaging, and will lead to abnormal fMRI signal evolution with respect to the image acquisition TE. In this article, we report this signal turbulence phenomenon observed in simulations of ultrahigh-spatial-resolution blood oxygenation level-dependent (BOLD) fMRI (voxel size of less than 50?×?50?×?50 µm³). We present a four-level coarse-to-fine multiresolution BOLD fMRI signal simulation. Based on the statistical histogram of an intravoxel fieldmap, we reformulate the intravoxel dephasing summation (a form of Riemann sum) into a new formula that is a discrete Fourier transformation of the intravoxel fieldmap histogram (a form of Lebesgue sum). We interpret the BOLD signal formation by relating its magnitude (phase) to the even (odd) symmetry of the fieldmap histogram. Based on multiresolution BOLD signal simulation, we find that the signal turbulence mainly emerges at the vessel boundary, and that there are only a few voxels (less than 10%) in an ultrahigh-resolution image that reveal turbulence in the form of sparse point noise. Our simulation also shows that, for typical human brain imaging of the cerebral cortex with millimeter resolution, TE?< 30 ms and B? ?=?3 T, we are unlikely to observe BOLD signal turbulence. Overall, the main causes of voxel signal turbulence include a high spatial resolution, high field, long TE and large vessel. PMID:22927163

  10. Early life inflammatory pain induces long-lasting deficits in hippocampal-dependent spatial memory in male and female rats.

    PubMed

    Henderson, Yoko O; Victoria, Nicole C; Inoue, Kiyoshi; Murphy, Anne Z; Parent, Marise B

    2015-02-01

    The present experiment tested the hypothesis that neonatal injury disrupts adult hippocampal functioning and that normal aging or chronic stress during adulthood, which are known to have a negative impact on hippocampal function, exacerbate these effects. Male and female Sprague-Dawley rats were given an intraplantar injection of the inflammatory agent carrageenan (1%) on the day of birth and their memory was tested in the hippocampal-dependent spatial water maze in adulthood and again in middle age. We found that neonatal injury impaired hippocampal-dependent memory in adulthood, that the effects of injury on memory were more pronounced in middle-aged male rats, and that chronic stress accelerated the onset of these memory deficits. Neonatal injury also decreased glucocorticoid receptor mRNA in the dorsal CA1 area of middle-aged rats, a brain region critical for spatial memory. Morphine administration at the time of injury completely reversed injury-induced memory deficits, but neonatal morphine treatments in the absence of injury produced significant memory impairments in adulthood. Collectively, these findings are consistent with our hypothesis that neonatal injury produces long-lasting disruption in adult hippocampal functioning. PMID:25451312

  11. Bound state of solution of Dirac-Coulomb problem with spatially dependent mass

    E-print Network

    Eser Olgar; Hayder M. Dhahir; H. Mutaf

    2014-09-24

    The bound state solution of Coulomb Potentials in the Dirac equation is calculated for position dependent mass function M(r) within the framework of asymptotic iteration method (AIM). The eigenfunctions are derived in terms of hypergeometric function and function generator equation of AIM.

  12. Phase Transitions in Ferromagnetic Ising Models with Spatially Dependent Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Bissacot, Rodrigo; Cassandro, Marzio; Cioletti, Leandro; Presutti, Errico

    2015-07-01

    In this paper we study the nearest neighbor Ising model with ferromagnetic interactions in the presence of a space dependent magnetic field that vanishes as , , as . We prove that in dimensions for all ? large enough, if there is a phase transition, while if there is a unique DLR state.

  13. Observation of Fermi-energy dependent unitary impurity resonances in a strong topological insulator Bi2Se3 with scanning tunneling

    E-print Network

    Faraon, Andrei

    Observation of Fermi-energy dependent unitary impurity resonances in a strong topological insulator of topological insulators against high- density impurities that preserve time reversal symmetry. PACS: 73.20.-r, 68.37.Ef, 72.10.Fk Keywords: topological insulators; Dirac fermions; impurity resonances; scanning

  14. Spatial distribution of gravity-dependent gain changes in the vestibuloocular reflex.

    PubMed

    Yakushin, Sergei B; Xiang, Yongqing; Raphan, Theodore; Cohen, Bernard

    2005-06-01

    This study determined whether dependence of angular vestibuloocular reflex (aVOR) gain adaptation on gravity is a fundamental property in three dimensions. Horizontal aVOR gains were adaptively increased or decreased in two cynomolgus monkeys in upright, side down, prone, and supine positions, and aVOR gains were tested in darkness by yaw rotation with the head in a wide variety of orientations. Horizontal aVOR gain changes peaked at the head position in which the adaptation took place and gradually decreased as the head moved away from this position in any direction. The gain changes were plotted as a function of head tilt and fit with a sinusoid plus a bias to obtain the gravity-dependent (amplitude) and gravity-independent (bias) components. Peak-to-peak gravity-dependent gain changes in planes containing the position of adaptation and the magnitude of the gravity-independent components were both approximately 25%. We assumed that gain changes over three-dimensional space could be described by a sinusoid the amplitude of which also varied sinusoidally. Using gain changes obtained from the head position in which the gains were adapted, a three-dimensional surface was generated that was qualitatively similar to a surface obtained from the experimental data. This extends previous findings on vertical aVOR gain adaptation in one plane and introduces a conceptual framework for understanding plasticity in three dimensions: aVOR gain changes are composed of two components, one of which depends on head position relative to gravity. It is likely that this gravitational dependence optimizes the stability of retinal images during movement in three-dimensional space. PMID:15689386

  15. Phase Transitions in Ferromagnetic Ising Models with spatially dependent magnetic fields

    E-print Network

    Rodrigo Bissacot; Marzio Cassandro; Leandro Cioletti; Errico Presutti

    2014-08-18

    In this paper we study the nearest neighbor Ising model with ferromagnetic interactions in the presence of a space dependent magnetic field which vanishes as $|x|^{-\\alpha}$, $\\alpha >0$, as $|x|\\to \\infty$. We prove that in dimensions $d\\ge 2$ for all $\\beta$ large enough if $\\alpha>1$ there is a phase transition while if $\\alpha<1$ there is a unique DLR state.

  16. Task-dependent calibration of auditory spatial perception through environmental visual observation

    PubMed Central

    Tonelli, Alessia; Brayda, Luca; Gori, Monica

    2015-01-01

    Visual information is paramount to space perception. Vision influences auditory space estimation. Many studies show that simultaneous visual and auditory cues improve precision of the final multisensory estimate. However, the amount or the temporal extent of visual information, that is sufficient to influence auditory perception, is still unknown. It is therefore interesting to know if vision can improve auditory precision through a short-term environmental observation preceding the audio task and whether this influence is task-specific or environment-specific or both. To test these issues we investigate possible improvements of acoustic precision with sighted blindfolded participants in two audio tasks [minimum audible angle (MAA) and space bisection] and two acoustically different environments (normal room and anechoic room). With respect to a baseline of auditory precision, we found an improvement of precision in the space bisection task but not in the MAA after the observation of a normal room. No improvement was found when performing the same task in an anechoic chamber. In addition, no difference was found between a condition of short environment observation and a condition of full vision during the whole experimental session. Our results suggest that even short-term environmental observation can calibrate auditory spatial performance. They also suggest that echoes can be the cue that underpins visual calibration. Echoes may mediate the transfer of information from the visual to the auditory system. PMID:26082692

  17. Task-dependent calibration of auditory spatial perception through environmental visual observation.

    PubMed

    Tonelli, Alessia; Brayda, Luca; Gori, Monica

    2015-01-01

    Visual information is paramount to space perception. Vision influences auditory space estimation. Many studies show that simultaneous visual and auditory cues improve precision of the final multisensory estimate. However, the amount or the temporal extent of visual information, that is sufficient to influence auditory perception, is still unknown. It is therefore interesting to know if vision can improve auditory precision through a short-term environmental observation preceding the audio task and whether this influence is task-specific or environment-specific or both. To test these issues we investigate possible improvements of acoustic precision with sighted blindfolded participants in two audio tasks [minimum audible angle (MAA) and space bisection] and two acoustically different environments (normal room and anechoic room). With respect to a baseline of auditory precision, we found an improvement of precision in the space bisection task but not in the MAA after the observation of a normal room. No improvement was found when performing the same task in an anechoic chamber. In addition, no difference was found between a condition of short environment observation and a condition of full vision during the whole experimental session. Our results suggest that even short-term environmental observation can calibrate auditory spatial performance. They also suggest that echoes can be the cue that underpins visual calibration. Echoes may mediate the transfer of information from the visual to the auditory system. PMID:26082692

  18. Epidemic West Nile virus encephalomyelitis: a temperature-dependent, spatial model of disease dynamics.

    PubMed

    Ward, Michael P

    2005-10-12

    Since first being detected in New York in 1999, West Nile virus (WNV) has spread throughout the United States and more than 20,000 cases of equine WNV encephalomyelitis have been reported. A spatial model of disease occurrence was developed, using data from an outbreak of serologically confirmed disease in an unvaccinated population of horses at 108 locations in northern Indiana between 3 August and 17 October 2002. Daily maximum temperature data were recorded at meteorological stations surrounding the study area. The distribution of the total number of degree-days elapsing between July 4 and the date of diagnosis of each case was best described by a normal distribution (mean=5243 degrees F, S.D.=1047). The days on which the average risk was >25, >50 and >75% were predicted (versus observed) to occur on August 23 (August 9), August 31 (September 2) and September 9 (September 9). The epidemic was predicted to occur 3 days earlier, or 4 days later, than observed if temperatures in the study area were uniformly increased, or decreased, by 5 degrees F, respectively. Maps indicated that WNV encephalomyelitis risk always remained greater in the northwest quadrant of the study area. Since WNV might exist at a hypoendemic level of infection, and occasionally re-emerge as a cause of epidemics in equine populations, by identifying factors that contributed to this epidemic, the potential impact of future epidemics can be reduced. Such studies rely on a GIS framework, availability of meteorological and possibly remotely sensed data and information on host and landscape factors. An early-warning system for WNV transmission in equine populations could be developed. PMID:16112761

  19. Strong Decoherence

    E-print Network

    Murray Gell-Mann; James B. Hartle

    1995-11-23

    We introduce a condition for the strong decoherence of a set of alternative histories of a closed quantum-mechanical system such as the universe. The condition applies, for a pure initial state, to sets of homogeneous histories that are chains of projections, generally branch-dependent. Strong decoherence implies the consistency of probability sum rules but not every set of consistent or even medium decoherent histories is strongly decoherent. Two conditions characterize a strongly decoherent set of histories: (1) At any time the operators that effectively commute with generalized records of history up to that moment provide the pool from which -- with suitable adjustment for elapsed time -- the chains of projections extending history to the future may be drawn. (2) Under the adjustment process, generalized record operators acting on the initial state of the universe are approximately unchanged. This expresses the permanence of generalized records. The strong decoherence conditions (1) and (2) guarantee what we call ``permanence of the past'' -- in particular the continued decoherence of past alternatives as the chains of projections are extended into the future. Strong decoherence is an idealization capturing in a general way this and other aspects of realistic physical mechanisms that destroy interference, as we illustrate in a simple model. We discuss the connection between the reduced density matrices that have often been used to characterize mechanisms of decoherence and the more general notion of strong decoherence. The relation between strong decoherence and a measure of classicality is briefly described.

  20. Developmental plasticity of spatial hearing following asymmetric hearing loss: context-dependent cue integration and its clinical implications

    PubMed Central

    Keating, Peter; King, Andrew J.

    2013-01-01

    Under normal hearing conditions, comparisons of the sounds reaching each ear are critical for accurate sound localization. Asymmetric hearing loss should therefore degrade spatial hearing and has become an important experimental tool for probing the plasticity of the auditory system, both during development and adulthood. In clinical populations, hearing loss affecting one ear more than the other is commonly associated with otitis media with effusion, a disorder experienced by approximately 80% of children before the age of two. Asymmetric hearing may also arise in other clinical situations, such as after unilateral cochlear implantation. Here, we consider the role played by spatial cue integration in sound localization under normal acoustical conditions. We then review evidence for adaptive changes in spatial hearing following a developmental hearing loss in one ear, and show that adaptation may be achieved either by learning a new relationship between the altered cues and directions in space or by changing the way different cues are integrated in the brain. We next consider developmental plasticity as a source of vulnerability, describing maladaptive effects of asymmetric hearing loss that persist even when normal hearing is provided. We also examine the extent to which the consequences of asymmetric hearing loss depend upon its timing and duration. Although much of the experimental literature has focused on the effects of a stable unilateral hearing loss, some of the most common hearing impairments experienced by children tend to fluctuate over time. We therefore propose that there is a need to bridge this gap by investigating the effects of recurring hearing loss during development, and outline recent steps in this direction. We conclude by arguing that this work points toward a more nuanced view of developmental plasticity, in which plasticity may be selectively expressed in response to specific sensory contexts, and consider the clinical implications of this. PMID:24409125

  1. Transcription-dependent spatial arrangements of CFTR and adjacent genes in human cell nuclei

    PubMed Central

    Zink, Daniele; Amaral, Margarida D.; Englmann, Andreas; Lang, Susanne; Clarke, Luka A.; Rudolph, Carsten; Alt, Felix; Luther, Kathrin; Braz, Carla; Sadoni, Nicolas; Rosenecker, Joseph; Schindelhauer, Dirk

    2004-01-01

    We investigated in different human cell types nuclear positioning and transcriptional regulation of the functionally unrelated genes GASZ, CFTR, and CORTBP2, mapping to adjacent loci on human chromosome 7q31. When inactive, GASZ, CFTR, and CORTBP2 preferentially associated with the nuclear periphery and with perinuclear heterochromatin, whereas in their actively transcribed states the gene loci preferentially associated with euchromatin in the nuclear interior. Adjacent genes associated simultaneously with these distinct chromatin fractions localizing at different nuclear regions, in accordance with their individual transcriptional regulation. Although the nuclear localization of CFTR changed after altering its transcription levels, the transcriptional status of CFTR was not changed by driving this gene into a different nuclear environment. This implied that the transcriptional activity affected the nuclear positioning, and not vice versa. Together, the results show that small chromosomal subregions can display highly flexible nuclear organizations that are regulated at the level of individual genes in a transcription-dependent manner. PMID:15364959

  2. Bit error rate analysis of free-space optical system with spatial diversity over strong atmospheric turbulence channel with pointing errors

    NASA Astrophysics Data System (ADS)

    Krishnan, Prabu; Sriram Kumar, D.

    2014-12-01

    Free-space optical communication (FSO) is emerging as a captivating alternative to work out the hindrances in the connectivity problems. It can be used for transmitting signals over common lands and properties that the sender or receiver may not own. The performance of an FSO system depends on the random environmental conditions. The bit error rate (BER) performance of differential phase shift keying FSO system is investigated. A distributed strong atmospheric turbulence channel with pointing error is considered for the BER analysis. Here, the system models are developed for single-input, single-output-FSO (SISO-FSO) and single-input, multiple-output-FSO (SIMO-FSO) systems. The closed-form mathematical expressions are derived for the average BER with various combining schemes in terms of the Meijer's G function.

  3. Spatially-resolved mapping of history-dependent coupled electrochemical and electronical behaviors of electroresistive NiO

    PubMed Central

    Sugiyama, Issei; Kim, Yunseok; Jesse, Stephen; Strelcov, Evgheni; Kumar, Amit; Tselev, Alexander; Rahani, Ehasan Kabiri; Shenoy, Vivek B.; Yamamoto, Takahisa; Shibata, Naoya; Ikuhara, Yuichi; Kalinin, Sergei V.

    2014-01-01

    Bias-induced oxygen ion dynamics underpins a broad spectrum of electroresistive and memristive phenomena in oxide materials. Although widely studied by device-level and local voltage-current spectroscopies, the relationship between electroresistive phenomena, local electrochemical behaviors, and microstructures remains elusive. Here, the interplay between history-dependent electronic transport and electrochemical phenomena in a NiO single crystalline thin film with a number of well-defined defect types is explored on the nanometer scale using an atomic force microscopy-based technique. A variety of electrochemically-active regions were observed and spatially resolved relationship between the electronic and electrochemical phenomena was revealed. The regions with pronounced electroresistive activity were further correlated with defects identified by scanning transmission electron microscopy. Using fully coupled mechanical-electrochemical modeling, we illustrate that the spatial distribution of strain plays an important role in electrochemical and electroresistive phenomena. These studies illustrate an approach for simultaneous mapping of the electronic and ionic transport on a single defective structure level such as dislocations or interfaces, and pave the way for creating libraries of defect-specific electrochemical responses. PMID:25335689

  4. Time-dependent density-functional study of the alignment-dependent ionization of acetylene and ethylene by strong laser pulses

    NASA Astrophysics Data System (ADS)

    Russakoff, Arthur; Bubin, Sergiy; Xie, Xinhua; Erattupuzha, Sonia; Kitzler, Markus; Varga, Kálmán

    2015-02-01

    The alignment-dependent ionization of acetylene and ethylene in short laser pulses is investigated in the framework of the time-dependent density-functional theory coupled with Ehrenfest dynamics. The molecular alignment is found to have a substantial effect on the total ionization. Bond stretching is shown to cause an increase of the ionization efficiency, i.e., enhanced ionization, in qualitative agreement with previous theoretical investigations. It is also demonstrated that the enhanced ionization mechanism greatly enhances the ionization from the inner valence orbitals, and the ionization of the inner orbitals is primarily due to their extended weakly bound density tails.

  5. On the similar spatial arrangement of active site residues in PAPS-dependent and phenolic sulfate-utilizing sulfotransferases.

    PubMed

    Teramoto, Takamasa; Adachi, Rumi; Sakakibara, Yoichi; Liu, Ming-Cheh; Suiko, Masahito; Kimura, Makoto; Kakuta, Yoshimitsu

    2009-09-17

    Mammalian sulfotransferases (STs) utilize exclusively the sulfuryl group donor 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to catalyze the sulfurylation reactions based on a sequential transfer mechanism. In contrast, the commensal intestinal bacterial arylsulfate sulfotransferases (ASSTs) do not use PAPS as the sulfuryl group donor, but instead catalyze sulfuryl transfer from phenolic sulfate to a phenol via a Ping-Pong mechanism. Interestingly, structural comparison revealed a similar spatial arrangement of the active site residues as well as the cognate substrates in mouse ST (mSULT1D1) and Escherichia coli CFT073 ASST, despite that their overall structures bear no discernible relationship. These observations suggest that the active sites of PAPS-dependent SULT1D1 and phenolic sulfate-utilizing ASST represent an example of convergent evolution. PMID:19695253

  6. Isotope dependent, temperature regulated, energy repartitioning in a low-barrier, short-strong hydrogen bonded cluster

    E-print Network

    Iyengar, Srinivasan S.

    Isotope dependent, temperature regulated, energy repartitioning in a low-barrier, short/deuterium isotope effects, in a fundamental organic hydrogen bonded system using multiple experimental infrared the isotopically labeled systems arises from an analysis of the simulated cluster spectroscopy and leads

  7. A new method to simulate convection with strongly temperature- and pressure-dependent viscosity in a spherical shell: Applications to the Earth's mantle

    Microsoft Academic Search

    K. Stemmer; H. Harder; U. Hansen

    2006-01-01

    We present a new finite volume code for modeling three-dimensional thermal convection in a spherical shell with strong temperature- and pressure-dependent viscosity. A new discretization formulation of the viscous term, tailored to the finite volume method on a colocated grid, enables laterally variable viscosity. A smoothed cubed–sphere grid is used to avoid pole problems which occur in latitude–longitude grids with

  8. Spatial dependence and mitigation of radiation damage by a line-focus mini-beam.

    SciTech Connect

    Finfrock, Y.; Stern, E.; Yacoby, Y.; Alkire, R.; Evans-Lutterodt, K.; Stein, A.; Isakovic, A. F.; Kas, J.; Joachimiak, A.; Biosciences Division; Univ. of Washington; Hebrew Univ.; BNL

    2010-12-01

    Recently, strategies to reduce primary radiation damage have been proposed which depend on focusing X-rays to dimensions smaller than the penetration depth of excited photoelectrons. For a line focus as used here the penetration depth is the maximum distance from the irradiated region along the X-ray polarization direction that the photoelectrons penetrate. Reported here are measurements of the penetration depth and distribution of photoelectron damage excited by 18.6 keV photons in a lysozyme crystal. The experimental results showed that the penetration depth of {approx}17.35 keV photoelectrons is 1.5 {+-} 0.2 {micro}m, which is well below previous theoretical estimates of 2.8 {micro}m. Such a small penetration depth raises challenging technical issues in mitigating damage by line-focus mini-beams. The optimum requirements to reduce damage in large crystals by a factor of 2.0-2.5 are Gaussian line-focus mini-beams with a root-mean-square width of 0.2 {micro}m and a distance between lines of 2.0 {micro}m. The use of higher energy X-rays (>26 keV) would help to alleviate some of these requirements by more than doubling the penetration depth. It was found that the X-ray dose has a significant contribution from the crystal's solvent, which initially contained 9.0%(w/v) NaCl. The 15.8 keV photoelectrons of the Cl atoms and their accompanying 2.8 keV local dose from the decay of the resulting excited atoms more than doubles the dose deposited in the X-ray-irradiated region because of the much greater cross-section and higher energy of the excited atom, degrading the mitigation of radiation damage from 2.5 to 2.0. Eliminating heavier atoms from the solvent and data collection far from heavy-atom absorption edges will significantly improve the mitigation of damage by line-focus mini-beams.

  9. Spatial Dependence and Mitigation of Radiation Damage by a Line Focus Mini Beam

    SciTech Connect

    Finfrock, Y.Z.; Evans-Lutterodt, K.; Stern, E.A.; Yacoby, Y.; Alkire, R.W.; Stein, A.; Isakovic, A.F.; Kas, J. J.; Joachimiak, A.

    2010-09-14

    Recently, strategies to reduce primary radiation damage have been proposed which depend on focusing X-rays to dimensions smaller than the penetration depth of excited photoelectrons. For a line focus as used here the penetration depth is the maximum distance from the irradiated region along the X-ray polarization direction that the photoelectrons penetrate. Reported here are measurements of the penetration depth and distribution of photoelectron damage excited by 18.6 keV photons in a lysozyme crystal. The experimental results showed that the penetration depth of {approx}17.35 keV photoelectrons is 1.5 {+-} 0.2 {micro}m, which is well below previous theoretical estimates of 2.8 {micro}m. Such a small penetration depth raises challenging technical issues in mitigating damage by line-focus mini-beams. The optimum requirements to reduce damage in large crystals by a factor of 2.0-2.5 are Gaussian line-focus mini-beams with a root-mean-square width of 0.2 {micro}m and a distance between lines of 2.0 {micro}m. The use of higher energy X-rays (>26 keV) would help to alleviate some of these requirements by more than doubling the penetration depth. It was found that the X-ray dose has a significant contribution from the crystal's solvent, which initially contained 9.0%(w/v) NaCl. The 15.8 keV photoelectrons of the Cl atoms and their accompanying 2.8 keV local dose from the decay of the resulting excited atoms more than doubles the dose deposited in the X-ray-irradiated region because of the much greater cross-section and higher energy of the excited atom, degrading the mitigation of radiation damage from 2.5 to 2.0. Eliminating heavier atoms from the solvent and data collection far from heavy-atom absorption edges will significantly improve the mitigation of damage by line-focus mini-beams.

  10. A new method to simulate convection with strongly temperature- and pressure-dependent viscosity in a spherical shell: Applications to the Earth's mantle

    NASA Astrophysics Data System (ADS)

    Stemmer, K.; Harder, H.; Hansen, U.

    2006-08-01

    We present a new finite volume code for modeling three-dimensional thermal convection in a spherical shell with strong temperature- and pressure-dependent viscosity. A new discretization formulation of the viscous term, tailored to the finite volume method on a colocated grid, enables laterally variable viscosity. A smoothed cubed-sphere grid is used to avoid pole problems which occur in latitude-longitude grids with spherical coordinates. The spherical shell is topologically divided into six cubes. The equations are formulated in primitive variables, and are treated in the Cartesian cubes. In order to ensure mass conservation a SIMPLER pressure correction procedure is applied and to handle strong viscosity variations of ? ? = 10 7 and high Rayleigh numbers of Ra = 10 8 the pressure correction algorithm is combined with a pressure weighted interpolation method to satisfy the incompressibility condition and to avoid oscillatory pressure solutions. The model is validated by a comparison of diagnostical parameters of steady-state cubic and tetrahedral convection with other published spherical models and a detailed convergence test on successively refined grids. Lateral variable fluid properties have a significant influence on the convection pattern and heat flow dynamics. The influence of temperature- and pressure-dependent viscosity on the flow is systematically analyzed for basal and mixed-mode heated thermal convection in the spherical shell. A new method to classify the simulations to the mobile, transitional or stagnant-lid regime is given by means of a comparison of selected diagnostical parameters, a significantly improved classification as compared to the common surface layer mobility criterion. A scaling law for the interior temperature and viscosity in the stagnant-lid regime is given. Purely basal heating and strongly temperature-dependent rheology stabilize plume positions and yield with a weak time dependence of the convecting system, while the amount of additional internal heating controls the strength of time dependence. Strength and partitioning of basal and internal heat sources in the mantle seems to be of major importance to specify the dynamics of the flow field and therefore the evolution of the Earth and other planets. Additional pressure dependence strongly influences the dynamics even if the magnitude of pressure variation is relatively small. For an appropriate combination of pressure and temperature dependence we observe a kind of low and high viscosity zone in the asthenosphere and deep in the mantle. The viscosity-depth profile of such a flow shows striking similarities to viscosity profiles from inversion of seismic, geoid and post-glacial rebound data.

  11. Electronic Coupling between Heme Electron-Transfer Centers and Its Decay with Distance Depends Strongly on Relative Orientation

    SciTech Connect

    Smith, Dayle MA; Rosso, Kevin M.; Dupuis, Michel; Valiev, Marat; Straatsma, TP

    2006-08-10

    A method for calculating the electron-transfer matrix element VRP using density functional theory Kohn-Sham orbitals is presented and applied to heme dimers of varying relative orientation. The electronic coupling decays with increased iron separation according to VRP ) V0RP exp(-?r/2) with a distance dependence parameter ? ? 2 Å-1 for hemes with parallel porphyrins and either 1.1 or 4.0 Å-1 when the porphyrin planes are perpendicular, depending on the alignment of the iron d? orbital. These findings are used to interpret the observed orientation of the hemes in tetraheme redox proteins such as Flavocytochrome c3 fumarate reductase (Ifc3, PDB code 1QJD) of Shewanella frigidimarina, another flavocytochrome from the same bacterium (Fcc3, 1E39) and a small tetraheme cytochrome of Shewanella oneidensis strain MR1 (1M1P). Our results show that shifting and rotating the hemes controls the adiabaticity of the three electron hopping steps.

  12. Multielectron effects on the orientation dependence and photoelectron angular distribution of multiphoton ionization of CO2 in strong laser fields

    E-print Network

    Son, Sang-Kil; Chu, Shih-I

    2009-07-24

    #3;6,26#4;. We note that a recent study using the strong- field approximation model predicts that the peak maximum occurs at 37° #3;27#4;. We now examine contributions of individual orbitals on the total ionization probability. The total ionization..., 023411 #2;2001#1;. #3;26#4; A.-T. Le et al., J. Mod. Opt. 54, 967 #2;2007#1;. #3;27#4; V.-H. Le et al., J. Phys. B 41, 085603 #2;2008#1;. #3;28#4; A. S. Alnaser et al., Phys. Rev. A 71, 031403#2;R#1; #2;2005#1;. #3;29#4; A. Jaro?-Becker et al., J. Phys. B...

  13. Abnormal dependence of strong-field-ionization-induced nitrogen lasing on polarization ellipticity of the driving field

    NASA Astrophysics Data System (ADS)

    Zhang, Haisu; Jing, Chenrui; Li, Guihua; Xie, Hongqiang; Yao, Jinping; Zeng, Bin; Chu, Wei; Ni, Jielei; Xu, Huailiang; Cheng, Ya

    2013-12-01

    We experimentally investigate lasing behaviors of population-inverted N2+ ions for the transitions between the vibrational level (v' = 0) of excited electronic B 2?u+ state and the two lowest vibrational levels (v = 0, 1) of the ground X 2?g+ state in an elliptically polarized laser field. It is found that, as the polarization of the pump laser evolves from linear to circular, the lasing signal for the 0 ? 0 transition at 391 nm first increases with a maximum enhancement of ˜40% at the ellipticity of 0.3 and then decreases, whereas for the 0 ? 1 transition at 428 nm, the lasing signal decreases monotonically. This difference between the 391- and 428-nm lasing signals is ascribed to the high sensitivity of the strong-field response of the molecular ion to molecular vibrations, which indicates the possibility to control the vibrational state distribution of molecules by tuning the ellipticity of the laser pulse.

  14. Anomalous pressure dependence of the superconductivity in noncentrosymmetric LaNi C2 : Evidence of strong electronic correlations

    NASA Astrophysics Data System (ADS)

    Katano, Susumu; Nakagawa, Hideya; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya; Soeda, Hideto; Tomita, Takahiro; Takahashi, Hiroki

    2014-12-01

    The superconductivity of the noncentrosymmetric system LaNi C2 has been studied under high pressures up to 30 GPa with electrical resistivity measurements. For this superconducting state, the breaking of time-reversal symmetry was shown recently in a muon spin relaxation (? SR ) experiment, which leads to nonunitary spin-triplet superconductive pairings. The present experiments on this superconductor reveal that the transition temperature Tc greatly increases at the rate of 0.25 (±0.01) K/GPa up to 3 GPa. However, above this pressure, Tc gradually decreases; and at the pressures over 8 GPa, the superconductivity disappears completely. With this disappearance of the superconductivity, a different state with a high-energy scale dramatically emerges. These results indicate that the system is not a simple normal metal, but is rather highly correlated with strong electronic interactions which would contribute to its superconductivity.

  15. Scale Dependence of Statistics of Spatially Averaged Rain Rate Seen in TOGA COARE Comparison with Predictions from a Stochastic Model

    NASA Technical Reports Server (NTRS)

    Kundu, Prasun K.; Bell, T. L.; Lau, William K. M. (Technical Monitor)

    2002-01-01

    A characteristic feature of rainfall statistics is that they in general depend on the space and time scales over which rain data are averaged. As a part of an earlier effort to determine the sampling error of satellite rain averages, a space-time model of rainfall statistics was developed to describe the statistics of gridded rain observed in GATE. The model allows one to compute the second moment statistics of space- and time-averaged rain rate which can be fitted to satellite or rain gauge data to determine the four model parameters appearing in the precipitation spectrum - an overall strength parameter, a characteristic length separating the long and short wavelength regimes and a characteristic relaxation time for decay of the autocorrelation of the instantaneous local rain rate and a certain 'fractal' power law exponent. For area-averaged instantaneous rain rate, this exponent governs the power law dependence of these statistics on the averaging length scale $L$ predicted by the model in the limit of small $L$. In particular, the variance of rain rate averaged over an $L \\times L$ area exhibits a power law singularity as $L \\rightarrow 0$. In the present work the model is used to investigate how the statistics of area-averaged rain rate over the tropical Western Pacific measured with ship borne radar during TOGA COARE (Tropical Ocean Global Atmosphere Coupled Ocean Atmospheric Response Experiment) and gridded on a 2 km grid depends on the size of the spatial averaging scale. Good agreement is found between the data and predictions from the model over a wide range of averaging length scales.

  16. Quantitative evaluation of the lactate signal loss and its spatial dependence in press localized (1)H NMR spectroscopy.

    PubMed

    Jung, W I; Bunse, M; Lutz, O

    2001-10-01

    Localized (1)H NMR spectroscopy using the 90 degrees -t(1)-180 degrees -t(1)+t(2)-180 degrees -t(2)-Acq. PRESS sequence can lead to a signal loss for the lactate doublet compared with signals from uncoupled nuclei which is dependent on the choice of t(1) and t(2). The most striking signal loss of up to 78% of the total signal occurs with the symmetrical PRESS sequence (t(1)=t(2)) at an echo time of 2/J (approximately 290 ms). Calculations have shown that this signal loss is related to the pulse angle distributions produced by the two refocusing pulses which leads to the creation of single quantum polarization transfer (PT) as well as to not directly observable states (NDOS) of the lactate AX(3) spin system: zero- and multiple-quantum coherences, and longitudinal spin orders. In addition, the chemical shift dependent voxel displacement (VOD) leads to further signal loss. By calculating the density operator for various of the echo times TE=n/J, n=1, 2, 3,..., we calculated quantitatively the contributions of these effects to the signal loss as well as their spatial distribution. A maximum signal loss of 75% can be expected from theory for the symmetrical PRESS sequence and TE=2/J for Hamming filtered sinc pulses, whereby 47% are due to the creation of NDOS and up to 28% arise from PT. Taking also the VOD effect into account (2 mT/m slice selection gradients, 20-mm slices) leads to 54% signal loss from NDOS and up to 24% from PT, leading to a maximum signal loss of 78%. Using RE-BURP pulses with their more rectangular pulse angle distributions reduces the maximum signal loss to 44%. Experiments at 1.5 T using a lactate solution demonstrated a maximum lactate signal loss for sinc pulses of 82% (52% NDOS, 30% PT) at TE=290 ms using the symmetrical PRESS sequence. The great signal loss and its spatial distribution is of importance for investigations using a symmetrical PRESS sequence at TE=2/J. PMID:11567573

  17. Quantitative Evaluation of the Lactate Signal Loss and Its Spatial Dependence in PRESS Localized 1H NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Jung, Wulf-Ingo; Bunse, Michael; Lutz, Otto

    2001-10-01

    Localized 1H NMR spectroscopy using the 90°-t1-180°-t1+t2-180°-t2-Acq. PRESS sequence can lead to a signal loss for the lactate doublet compared with signals from uncoupled nuclei which is dependent on the choice of t1 and t2. The most striking signal loss of up to 78% of the total signal occurs with the symmetrical PRESS sequence (t1=t2) at an echo time of 2/J (?290 ms). Calculations have shown that this signal loss is related to the pulse angle distributions produced by the two refocusing pulses which leads to the creation of single quantum polarization transfer (PT) as well as to not directly observable states (NDOS) of the lactate AX3 spin system: zero- and multiple-quantum coherences, and longitudinal spin orders. In addition, the chemical shift dependent voxel displacement (VOD) leads to further signal loss. By calculating the density operator for various of the echo times TE=n/J, n=1, 2, 3, …, we calculated quantitatively the contributions of these effects to the signal loss as well as their spatial distribution. A maximum signal loss of 75% can be expected from theory for the symmetrical PRESS sequence and TE=2/J for Hamming filtered sinc pulses, whereby 47% are due to the creation of NDOS and up to 28% arise from PT. Taking also the VOD effect into account (2 mT/m slice selection gradients, 20-mm slices) leads to 54% signal loss from NDOS and up to 24% from PT, leading to a maximum signal loss of 78%. Using RE-BURP pulses with their more rectangular pulse angle distributions reduces the maximum signal loss to 44%. Experiments at 1.5 T using a lactate solution demonstrated a maximum lactate signal loss for sinc pulses of 82% (52% NDOS, 30% PT) at TE=290 ms using the symmetrical PRESS sequence. The great signal loss and its spatial distribution is of importance for investigations using a symmetrical PRESS sequence at TE=2/J.

  18. Amplitude of the actomyosin power stroke depends strongly on the isoform of the myosin essential light chain.

    PubMed

    Guhathakurta, Piyali; Prochniewicz, Ewa; Thomas, David D

    2015-04-14

    We have used time-resolved fluorescence resonance energy transfer (TR-FRET) to determine the role of myosin essential light chains (ELCs) in structural transitions within the actomyosin complex. Skeletal muscle myosins have two ELC isoforms, A1 and A2, which differ by an additional 40-45 residues at the N terminus of A1, and subfragment 1 (S1) containing A1 (S1A1) has higher catalytic efficiency and higher affinity for actin than S1A2. ELC's location at the junction between the catalytic and light-chain domains gives it the potential to play a central role in the force-generating power stroke. Therefore, we measured site-directed TR-FRET between a donor on actin and an acceptor near the C terminus of ELC, detecting directly the rotation of the light-chain domain (lever arm) relative to actin (power stroke), induced by the interaction of ATP-bound myosin with actin. TR-FRET resolved the weakly bound (W) and strongly bound (S) states of actomyosin during the W-to-S transition (power stroke). We found that the W states are essentially the same for the two isoenzymes, but the S states are quite different, indicating a much larger movement of S1A1. FRET from actin to a probe on the N-terminal extension of A1 showed close proximity to actin. We conclude that the N-terminal extension of A1-ELC modulates the W-to-S structural transition of acto-S1, so that the light-chain domain undergoes a much larger power stroke in S1A1 than in S1A2. These results have profound implications for understanding the contractile function of actomyosin, as needed in therapeutic design for muscle disorders. PMID:25825773

  19. Strong Association of The Alcohol Dehydrogenase 1B Gene (ADH1B) With Alcohol Dependence And Alcohol-induced Medical Diseases

    PubMed Central

    Li, Dawei; Zhao, Hongyu; Gelernter, Joel

    2011-01-01

    Background The alcohol dehydrogenase 1B gene (ADH1B) is hypothesized to affect predisposition to alcohol dependence (AD) and abuse. A variant of the ADH1B gene (rs1229984 or Arg48His; previously referred to as Arg (*1) and His (*2)) has been reported to be associated with reduced rates of alcohol and drug dependence. Different studies have produced inconclusive results regarding association between rs1229984 (or rs2066702) and substance dependence. Methods Using the cumulative association study literature from the past 21 years from both English and Chinese-language publications, this meta-analysis seeks to clarify the contradictory findings and to examine whether the aggregate data provide new evidence of significant association. Results The results, based on a large sample size (9,638 cases and 9,517 controls), suggested strong associations with alcohol dependence and abuse as well as alcohol-induced liver diseases, with an allelic (Arg vs. His) P value being 1×10?36 and odds ratio (OR) 2.06 (1.84, 2.31) under the random effects model. The dominant and recessive models produced larger ORs of 2.17 and 3.05, respectively. When more stringent criteria and sub-group analyses were imposed, the associations remained consistent, and were strongest in various Asian groups (allelic P = 7×10?42 and OR = 2.24 (1.99, 2.51) with ORs of 2.16 and 4.11 for dominant and recessive models, respectively). Conclusions Our findings provide further strong evidence for the involvement of the ADH1B gene in the pathogenesis of alcohol dependence and abuse as well as for some alcohol-induced medical diseases in the multiple ethnic populations, in particular, in certain Asian populations. PMID:21497796

  20. HLA-system in Chinese children with insulin-dependent diabetes mellitus: a strong association with DR3.

    PubMed

    Lee, B W; Chan, S H; Tan, S H; Wee, G B; Yap, H K; Wong, H B; Tan, C L; Tan, K W

    1984-12-01

    We studied the distribution of HLA-A, B, and DR and MT1, MT2, MT3 genotypes in all 20 Chinese children with insulin-dependent diabetes mellitus (IDDM) attending the four government pediatric units in Singapore. We found an increase in HLA BW22 but the corrected probability value was not statistically significant. AW33 and B17 were observed in 50% and 55% of IDDM children, respectively, compared with 11% and 13% of normal controls, respectively. The values for AW33 were as follows: corrected P = 0.00094 and relative risk (RR) = 8.17; for B17 they were corrected P = 0.001 and RR = 7.55. In addition, the frequency of DR3 was 50% in IDDM children compared with 14% of normal controls (corrected P = 0.0019, RR = 6.20). AW33, B17, and DR3 are in linkage disequilibrium in our normal Chinese population. All ten patients who were positive for DR3 also had B17. The frequency of DR4 was not increased, and there were no protection IDDM related antigens found. These differences compared with the results in Western populations may contribute to the relative rarity of IDDM among Chinese children. PMID:6334218

  1. The Min Oscillator Uses MinD-Dependent Conformational Changes in MinE to Spatially Regulate Cytokinesis.

    SciTech Connect

    Park, Kyung-Tase; Wu, Wei; Battaile, Kevin P.; Lovell, Scott; Holyoak, Todd; Lutkenhaus, Joe (Kansas); (HWMRI)

    2011-09-16

    In E. coli, MinD recruits MinE to the membrane, leading to a coupled oscillation required for spatial regulation of the cytokinetic Z ring. How these proteins interact, however, is not clear because the MinD-binding regions of MinE are sequestered within a six-stranded {beta} sheet and masked by N-terminal helices. minE mutations that restore interaction between some MinD and MinE mutants were isolated. These mutations alter the MinE structure leading to release of the MinD-binding regions and the N-terminal helices that bind the membrane. Crystallization of MinD-MinE complexes revealed a four-stranded {beta} sheet MinE dimer with the released {beta} strands (MinD-binding regions) converted to {alpha} helices bound to MinD dimers. These results identify the MinD-dependent conformational changes in MinE that convert it from a latent to an active form and lead to a model of how MinE persists at the MinD-membrane surface.

  2. Quantum confinement in nonadditive space with a spatially dependent effective mass for Si and Ge quantum wells

    NASA Astrophysics Data System (ADS)

    Barbagiovanni, E. G.; Filho, R. N. Costa

    2014-09-01

    We calculate the effect of a spatially dependent effective mass (SPDEM) [adapted from Costa Filho et al. (2011)] on an electron and a hole confined in a quantum well (QW). In the work of Costa Filho et al., the translation operator is modified to include an inverse character length scale, ?, which defines the SPDEM. The introduction of ? means that translations are no longer additive. In nonadditive space, we choose a ‘skewed' Gaussian confinement potential defined by the replacement x??-1ln(1+?x) in the usual Gaussian potential. Within the parabolic approximation ? is inversely related to the QW thickness and we obtain analytic solutions to our confinement Hamiltonian. Our calculation yields a reduced dispersion relation for the gap energy (EG) as a function of QW thickness, D: EG~D-1, compared to the effective mass approximation: EG~D-2. Additionally, nonadditive space contracts the position space metric thus increasing the occupied momentum space and reducing the effective mass, in agreement with the relation: mo*-1??2E/?k2. The change in the effective mass is shown to be a function of the confinement potential via a point canonical transformation. Our calculation agrees with experimental measurements of EG for Si and Ge QWs.

  3. Pushing the Limits: Strongly-Driven Laser Plasma Coupling

    NASA Astrophysics Data System (ADS)

    Kruer, William L.; Campbell, E. Michael; Decker, Christopher D.; Wilks, Scott C.; Moody, John D.; Orzechowski, Thaddeus J.; Suter, Laurance J.; Afeyan, Bedros B.; Dague, N.

    1998-11-01

    An improved understanding of strongly-driven laser plasma coupling is important for a variety of advanced applications. We discuss a novel model for the scaling of strongly-driven stimulated Brillouin and Raman scattering. This model postulates an intensity-dependent correlation length associated with spatial incoherence due to filamentation and stimulated forward scattering. Particular attention is paid to high temperature hohlraum experiments, which exhibited low to modest stimulated Brillouin scattering even though this instability was very strongly driven.

  4. Involvement of NADPH-Dependent and cAMP-PKA Sensitive H+ Channels in the Chorda Tympani Nerve Responses to Strong Acids

    PubMed Central

    DeSimone, John A.; T. Phan, Tam-Hao; Heck, Gerard L.; Ren, ZuoJun; Coleman, Jamison; Mummalaneni, Shobha; Melone, Pamela

    2011-01-01

    To investigate if chorda tympani (CT) taste nerve responses to strong (HCl) and weak (CO2 and acetic acid) acidic stimuli are dependent upon NADPH oxidase–linked and cAMP-sensitive proton conductances in taste cell membranes, CT responses were monitored in rats, wild-type (WT) mice, and gp91phox knockout (KO) mice in the absence and presence of blockers (Zn2+ and diethyl pyrocarbonate [DEPC]) or activators (8-(4-chlorophenylthio)-cAMP; 8-CPT-cAMP) of proton channels and activators of the NADPH oxidase enzyme (phorbol 12-myristate 13-acetate [PMA], H2O2, and nitrazepam). Zn2+ and DEPC inhibited and 8-CPT-cAMP, PMA, H2O2, and nitrazepam enhanced the tonic CT responses to HCl without altering responses to CO2 and acetic acid. In KO mice, the tonic HCl CT response was reduced by 64% relative to WT mice. The residual CT response was insensitive to H2O2 but was blocked by Zn2+. Its magnitude was further enhanced by 8-CPT-cAMP treatment, and the enhancement was blocked by 8-CPT-adenosine-3?-5?-cyclic monophospho-rothioate, a protein kinase A (PKA) inhibitor. Under voltage-clamp conditions, before cAMP treatment, rat tonic HCl CT responses demonstrated voltage-dependence only at ±90 mV, suggesting the presence of H+ channels with voltage-dependent conductances. After cAMP treatment, the tonic HCl CT response had a quasi-linear dependence on voltage, suggesting that the cAMP-dependent part of the HCl CT response has a quasi-linear voltage dependence between +60 and ?60 mV, only becoming sigmoidal when approaching +90 and ?90 mV. The results suggest that CT responses to HCl involve 2 proton entry pathways, an NADPH oxidase–dependent proton channel, and a cAMP-PKA sensitive proton channel. PMID:21339339

  5. Polarization Dependence of the Optical Interband Transition Defined by the Spatial Variation of the Valence p-Orbital Bloch Functions in Quantum Wires

    Microsoft Academic Search

    Shinichi Watanabe; Masahiro Yoshita; Shyun Koshiba; Hidefumi Akiyama

    2002-01-01

    We develope a method to express wave functions of hole states in semiconductor quantum wire (QWR) structures based on spatial variation of the valence p-orbital Bloch functions, to show how envelope wave functions relate to polarization-dependent interband transition. A wave function of a hole state is obtained solving the Schrödinger equation based on the 4× 4 Luttinger Hamiltonian, and then

  6. Alteration of ocean crust provides a strong temperature dependent feedback on the geological carbon cycle and is a primary driver of the Sr-isotopic composition of seawater

    NASA Astrophysics Data System (ADS)

    Coogan, Laurence A.; Dosso, Stan E.

    2015-04-01

    On geological timescales there is a temperature dependent feedback that means that increased degassing of CO2 into the atmosphere leads to increased CO2 drawdown into rocks stabilizing Earth's climate. It is widely considered that this thermostat largely comes from continental chemical weathering. An alternative, or additional, feedback comes from dissolution of seafloor basalt in low-temperature (tens of °C), off-axis, hydrothermal systems. Carbonate minerals precipitated in these systems provide strong evidence that increased bottom water temperature (traced by their O-isotopic compositions) leads to increased basalt dissolution (traced by their Sr-isotopic compositions). Inversion of a simple probabilistic model of fluid-rock interaction allows us to determine the apparent activation energy of rock dissolution in these systems. The high value we find (92 ± 7 kJmol-1) indicates a strong temperature dependence of rock dissolution. Because deep-ocean temperature is sensitive to global climate, and the fluid temperature in the upper oceanic crust is strongly influenced by bottom water temperature, increased global temperature must lead to increased basalt dissolution. In turn, through the generation of alkalinity by rock dissolution, this leads to a negative feedback on planetary warming; i.e. off-axis, hydrothermal systems play an important role in the planetary thermostat. Changes in the extent of rock dissolution, due to changes in bottom water temperature, also lead to changes in the flux of unradiogenic Sr into the ocean. The decreased flux of unradiogenic Sr into the ocean due to the cooling of ocean bottom water over the last 35 Myr is sufficient to explain most of the increase in seawater 87Sr/86Sr over this time.

  7. Spatial Pattern Analysis of Heavy Metals in Beijing Agricultural Soils Based on Spatial Autocorrelation Statistics

    PubMed Central

    Huo, Xiao-Ni; Zhang, Wei-Wei; Sun, Dan-Feng; Li, Hong; Zhou, Lian-Di; Li, Bao-Guo

    2011-01-01

    This study explored the spatial pattern of heavy metals in Beijing agricultural soils using Moran’s I statistic of spatial autocorrelation. The global Moran’s I result showed that the spatial dependence of Cr, Ni, Zn, and Hg changed with different spatial weight matrixes, and they had significant and positive global spatial correlations based on distance weight. The spatial dependence of the four metals was scale-dependent on distance, but these scale effects existed within a threshold distance of 13 km, 32 km, 50 km, and 29 km, respectively for Cr, Ni, Zn, and Hg. The maximal spatial positive correlation range was 57 km, 70 km, 57 km, and 55 km for Cr, Ni, Zn, and Hg, respectively and these were not affected by sampling density. Local spatial autocorrelation analysis detected the locations of spatial clusters and spatial outliers and revealed that the pollution of these four metals occurred in significant High-high spatial clusters, Low-high, or even High-low spatial outliers. Thus, three major areas were identified and should be receiving more attention: the first was the northeast region of Beijing, where Cr, Zn, Ni, and Hg had significant increases. The second was the southeast region of Beijing where wastewater irrigation had strongly changed the content of metals, particularly of Cr and Zn, in soils. The third area was the urban fringe around city, where Hg showed a significant increase. PMID:21776217

  8. DEFINITION OF MULTIVARIATE GEOCHEMICAL ASSOCIATIONS WITH POLYMETALLIC MINERAL OCCURRENCES USING A SPATIALLY DEPENDENT CLUSTERING TECHNIQUE AND RASTERIZED STREAM SEDIMENT DATA - AN ALASKAN EXAMPLE.

    USGS Publications Warehouse

    Jenson, Susan K.; Trautwein, C.M.

    1984-01-01

    The application of an unsupervised, spatially dependent clustering technique (AMOEBA) to interpolated raster arrays of stream sediment data has been found to provide useful multivariate geochemical associations for modeling regional polymetallic resource potential. The technique is based on three assumptions regarding the compositional and spatial relationships of stream sediment data and their regional significance. These assumptions are: (1) compositionally separable classes exist and can be statistically distinguished; (2) the classification of multivariate data should minimize the pair probability of misclustering to establish useful compositional associations; and (3) a compositionally defined class represented by three or more contiguous cells within an array is a more important descriptor of a terrane than a class represented by spatial outliers.

  9. Directional biases and resource-dependence in dispersal generate spatial patterning in a consumer-producer model.

    PubMed

    Anderson, Kurt E; Hilker, Frank M; Nisbet, Roger M

    2012-03-01

    Directional dispersal plays a large role in shaping ecological processes in diverse systems such as rivers, coastlines and vegetation communities. We describe an instability driven by directional dispersal in a spatially explicit consumer-producer model where spatial patterns emerge in the absence of external environmental variation. Dispersal of the consumer has both undirected and directed components that are functions of producer biomass. We demonstrate that directional dispersal is required for the instability, while undirected diffusive dispersal sets a lower bound to the spatial scale of emerging patterns. Furthermore, instability requires indirect feedbacks affecting consumer per capita dispersal rates, and not activator-inhibitor dynamics affecting production and mortality as is described in previous theory. This novel and less-restrictive mechanism for generating spatial patterns can arise over realistic parameter values, which we explore using an empirically inspired model and data on stream macroinvertebrates. PMID:22248081

  10. Strong excitation intensity dependence of the photoluminescence line shape in GaAs{sub 1-x}Bi{sub x} single quantum well samples

    SciTech Connect

    Mazur, Yu. I.; Dorogan, V. G.; Ware, M. E.; Salamo, G. J. [Department of Physics, University of Arkansas, 226 Physics Building, Fayetteville, Arkansas 72701 (United States); Schmidbauer, M. [Leibniz-Institute for Crystal Growth, Max-Born-Str. 2, D-12489 Berlin (Germany); Tarasov, G. G. [Institute of Semiconductor Physics, National Academy of Sciences, pr. Nauki 45, Kiev 03028 (Ukraine); Johnson, S. R.; Lu, X. [Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287-6206 (United States); Yu, S.-Q. [Department of Electrical Engineering, University of Arkansas, 3217 Bell Engineering, Fayetteville, Arkansas 72701 (United States); Tiedje, T. [Department of Electrical and Computer Engineering, University of Victoria, Victoria, British Columbia V8W 3P6 (Canada)

    2013-04-14

    A set of high quality single quantum well samples of GaAs{sub 1-x}Bi{sub x} with bismuth concentrations not exceeding 6% and well widths ranging from 7.5 to 13 nm grown by molecular beam epitaxy on a GaAs substrate at low temperature is studied by means of photoluminescence (PL). It is shown that the PL line shape changes when the exciton reduced mass behavior changes from an anomalous increase (x < 5%) to a conventional decrease (x > 5%). Strongly non-monotonous PL bandwidth dependence on the excitation intensity is revealed and interpreted in terms of optically unresolved contributions from the saturable emission of bound free excitons.

  11. Verification test problems for the calculation of probability of loss of assured safety in temperature-dependent systems with multiple weak and strong links.

    SciTech Connect

    Johnson, Jay Dean (ProStat, Mesa, AZ); Oberkampf, William Louis; Helton, Jon Craig (Arizona State University, Tempe, AZ)

    2006-06-01

    Four verification test problems are presented for checking the conceptual development and computational implementation of calculations to determine the probability of loss of assured safety (PLOAS) in temperature-dependent systems with multiple weak links (WLs) and strong links (SLs). The problems are designed to test results obtained with the following definitions of loss of assured safety: (1) Failure of all SLs before failure of any WL, (2) Failure of any SL before failure of any WL, (3) Failure of all SLs before failure of all WLs, and (4) Failure of any SL before failure of all WLs. The test problems are based on assuming the same failure properties for all links, which results in problems that have the desirable properties of fully exercising the numerical integration procedures required in the evaluation of PLOAS and also possessing simple algebraic representations for PLOAS that can be used for verification of the analysis.

  12. Neuroprotective Mechanism of Lycium barbarum Polysaccharides against Hippocampal-Dependent Spatial Memory Deficits in a Rat Model of Obstructive Sleep Apnea

    PubMed Central

    Lam, Chun-Sing; Tipoe, George Lim; So, Kwok-Fai; Fung, Man-Lung

    2015-01-01

    Chronic intermittent hypoxia (CIH) is a hallmark of obstructive sleep apnea (OSA), which induces hippocampal injuries mediated by oxidative stress. This study aims to examine the neuroprotective mechanism of Lycium barbarum polysaccharides (LBP) against CIH-induced spatial memory deficits. Adult Sprague–Dawley rats were exposed to hypoxic treatment resembling a severe OSA condition for a week. The animals were orally fed with LBP solution (1mg/kg) daily 2 hours prior to hypoxia or in air for the control. The effect of LBP on the spatial memory and levels of oxidative stress, inflammation, endoplasmic reticulum (ER) stress, apoptosis and neurogenesis in the hippocampus was examined. There was a significant deficit in the spatial memory and an elevated level of malondialdehyde with a decreased expression of antioxidant enzymes (SOD, GPx-1) in the hypoxic group when compared with the normoxic control. In addition, redox-sensitive nuclear factor kappa B (NF?B) canonical pathway was activated with a translocation of NF?B members (p65, p50) and increased expression levels of NF?B-dependent inflammatory cytokines and mediator (TNF?, IL-1?, COX-2); also, a significantly elevated level of ER stress (GRP78/Bip, PERK, CHOP) and autophagic flux in the hypoxic group, leading to neuronal apoptosis in hippocampal subfields (DG, CA1, CA3). Remarkably, LBP administration normalized the elevated level of oxidative stress, neuroinflammation, ER stress, autophagic flux and apoptosis induced by hypoxia. Moreover, LBP significantly mitigated both the caspase-dependent intrinsic (Bax, Bcl2, cytochrome C, cleaved caspase-3) and extrinsic (FADD, cleaved caspase-8, Bid) signaling apoptotic cascades. Furthermore, LBP administration prevented the spatial memory deficit and enhanced the hippocampal neurogenesis induced by hypoxia. Our results suggest that LBP is neuroprotective against CIH-induced hippocampal-dependent spatial memory deficits by promoting hippocampal neurogenesis and negatively modulating the apoptotic signaling cascades activated by oxidative stress and inflammation. PMID:25714473

  13. Neuroprotective mechanism of Lycium barbarum polysaccharides against hippocampal-dependent spatial memory deficits in a rat model of obstructive sleep apnea.

    PubMed

    Lam, Chun-Sing; Tipoe, George Lim; So, Kwok-Fai; Fung, Man-Lung

    2015-01-01

    Chronic intermittent hypoxia (CIH) is a hallmark of obstructive sleep apnea (OSA), which induces hippocampal injuries mediated by oxidative stress. This study aims to examine the neuroprotective mechanism of Lycium barbarum polysaccharides (LBP) against CIH-induced spatial memory deficits. Adult Sprague-Dawley rats were exposed to hypoxic treatment resembling a severe OSA condition for a week. The animals were orally fed with LBP solution (1 mg/kg) daily 2 hours prior to hypoxia or in air for the control. The effect of LBP on the spatial memory and levels of oxidative stress, inflammation, endoplasmic reticulum (ER) stress, apoptosis and neurogenesis in the hippocampus was examined. There was a significant deficit in the spatial memory and an elevated level of malondialdehyde with a decreased expression of antioxidant enzymes (SOD, GPx-1) in the hypoxic group when compared with the normoxic control. In addition, redox-sensitive nuclear factor kappa B (NF?B) canonical pathway was activated with a translocation of NF?B members (p65, p50) and increased expression levels of NF?B-dependent inflammatory cytokines and mediator (TNF?, IL-1?, COX-2); also, a significantly elevated level of ER stress (GRP78/Bip, PERK, CHOP) and autophagic flux in the hypoxic group, leading to neuronal apoptosis in hippocampal subfields (DG, CA1, CA3). Remarkably, LBP administration normalized the elevated level of oxidative stress, neuroinflammation, ER stress, autophagic flux and apoptosis induced by hypoxia. Moreover, LBP significantly mitigated both the caspase-dependent intrinsic (Bax, Bcl2, cytochrome C, cleaved caspase-3) and extrinsic (FADD, cleaved caspase-8, Bid) signaling apoptotic cascades. Furthermore, LBP administration prevented the spatial memory deficit and enhanced the hippocampal neurogenesis induced by hypoxia. Our results suggest that LBP is neuroprotective against CIH-induced hippocampal-dependent spatial memory deficits by promoting hippocampal neurogenesis and negatively modulating the apoptotic signaling cascades activated by oxidative stress and inflammation. PMID:25714473

  14. SU-E-T-299: Small Fields Profiles Correction Through Detectors Spatial Response Functions and Field Size Dependence Analysis

    SciTech Connect

    Filipuzzi, M; Garrigo, E; Venencia, C [Instituto de Radioterapia - Fundacion Marie Curie, Cordoba, Cordoba (Spain); Germanier, A [CEPROCOR, Cordoba, Cordoba (Spain)

    2014-06-01

    Purpose: To calculate the spatial response function of various radiation detectors, to evaluate the dependence on the field size and to analyze the small fields profiles corrections by deconvolution techniques. Methods: Crossline profiles were measured on a Novalis Tx 6MV beam with a HDMLC. The configuration setup was SSD=100cm and depth=5cm. Five fields were studied (200×200mm2,100×100mm2, 20×20mm2, 10×10mm2and 5×5mm2) and measured were made with passive detectors (EBT3 radiochromic films and TLD700 thermoluminescent detectors), ionization chambers (PTW30013, PTW31003, CC04 and PTW31016) and diodes (PTW60012 and IBA SFD). The results of passive detectors were adopted as the actual beam profile. To calculate the detectors kernels, modeled by Gaussian functions, an iterative process based on a least squares criterion was used. The deconvolutions of the measured profiles were calculated with the Richardson-Lucy method. Results: The profiles of the passive detectors corresponded with a difference in the penumbra less than 0.1mm. Both diodes resolve the profiles with an overestimation of the penumbra smaller than 0.2mm. For the other detectors, response functions were calculated and resulted in Gaussian functions with a standard deviation approximate to the radius of the detector in study (with a variation less than 3%). The corrected profiles resolve the penumbra with less than 1% error. Major discrepancies were observed for cases in extreme conditions (PTW31003 and 5×5mm2 field size). Conclusion: This work concludes that the response function of a radiation detector is independent on the field size, even for small radiation beams. The profiles correction, using deconvolution techniques and response functions of standard deviation equal to the radius of the detector, gives penumbra values with less than 1% difference to the real profile. The implementation of this technique allows estimating the real profile, freeing from the effects of the detector used for the acquisition.

  15. Simultaneous fluorescence light-up and selective multicolor nucleobase recognition based on sequence-dependent strong binding of berberine to DNA abasic site.

    PubMed

    Wu, Fei; Shao, Yong; Ma, Kun; Cui, Qinghua; Liu, Guiying; Xu, Shujuan

    2012-04-28

    Label-free DNA nucleobase recognition by fluorescent small molecules has received much attention due to its simplicity in mutation identification and drug screening. However, sequence-dependent fluorescence light-up nucleobase recognition and multicolor emission with individual emission energy for individual nucleobases have been seldom realized. Herein, an abasic site (AP site) in a DNA duplex was employed as a binding field for berberine, one of isoquinoline alkaloids. Unlike weak binding of berberine to the fully matched DNAs without the AP site, strong binding of berberine to the AP site occurs and the berberine's fluorescence light-up behaviors are highly dependent on the target nucleobases opposite the AP site in which the targets thymine and cytosine produce dual emission bands, while the targets guanine and adenine only give a single emission band. Furthermore, more intense emissions are observed for the target pyrimidines than purines. The flanking bases of the AP site also produce some modifications of the berberine's emission behavior. The binding selectivity of berberine at the AP site is also confirmed by measurements of fluorescence resonance energy transfer, excited-state lifetime, DNA melting and fluorescence quenching by ferrocyanide and sodium chloride. It is expected that the target pyrimidines cause berberine to be stacked well within DNA base pairs near the AP site, which results in a strong resonance coupling of the electronic transitions to the particular vibration mode to produce the dual emissions. The fluorescent signal-on and emission energy-modulated sensing for nucleobases based on this fluorophore is substantially advantageous over the previously used fluorophores. We expect that this approach will be developed as a practical device for differentiating pyrimidines from purines by positioning an AP site toward a target that is available for readout by this alkaloid probe. PMID:22410866

  16. Strong spin-orbit coupling and Zeeman spin splitting in angle dependent magnetoresistance of Bi{sub 2}Te{sub 3}

    SciTech Connect

    Dey, Rik, E-mail: rikdey@utexas.edu; Pramanik, Tanmoy; Roy, Anupam; Rai, Amritesh; Guchhait, Samaresh; Sonde, Sushant; Movva, Hema C. P.; Register, Leonard F.; Banerjee, Sanjay K. [Microelectronics Research Center, University of Texas at Austin, Austin, Texas 78758 (United States); Colombo, Luigi [Texas Instruments, Dallas, Texas 75243 (United States)

    2014-06-02

    We have studied angle dependent magnetoresistance of Bi{sub 2}Te{sub 3} thin film with field up to 9?T over 2–20?K temperatures. The perpendicular field magnetoresistance has been explained by the Hikami-Larkin-Nagaoka theory alone in a system with strong spin-orbit coupling, from which we have estimated the mean free path, the phase coherence length, and the spin-orbit relaxation time. We have obtained the out-of-plane spin-orbit relaxation time to be small and the in-plane spin-orbit relaxation time to be comparable to the momentum relaxation time. The estimation of these charge and spin transport parameters are useful for spintronics applications. For parallel field magnetoresistance, we have confirmed the presence of Zeeman effect which is otherwise suppressed in perpendicular field magnetoresistance due to strong spin-orbit coupling. The parallel field data have been explained using both the contributions from the Maekawa-Fukuyama localization theory for non-interacting electrons and Lee-Ramakrishnan theory of electron-electron interactions. The estimated Zeeman g-factor and the strength of Coulomb screening parameter agree well with the theory. Finally, the anisotropy in magnetoresistance with respect to angle has been described by the Hikami-Larkin-Nagaoka theory. This anisotropy can be used in anisotropic magnetic sensor applications.

  17. CLASSSTRONG: Classical simulations of strong field processes

    NASA Astrophysics Data System (ADS)

    Ciappina, M. F.; Pérez-Hernández, J. A.; Lewenstein, M.

    2014-01-01

    A set of Mathematica functions is presented to model classically two of the most important processes in strong field physics, namely high-order harmonic generation (HHG) and above-threshold ionization (ATI). Our approach is based on the numerical solution of the Newton-Lorentz equation of an electron moving on an electric field and takes advantage of the symbolic languages features and graphical power of Mathematica. Like in the Strong Field Approximation (SFA), the effects of atomic potential on the motion of electron in the laser field are neglected. The SFA was proven to be an essential tool in strong field physics in the sense that it is able to predict with great precision the harmonic (in the HHG) and energy (in the ATI) limits. We have extended substantially the conventional classical simulations, where the electric field is only dependent on time, including spatial nonhomogeneous fields and spatial and temporal synthesized fields. Spatial nonhomogeneous fields appear when metal nanosystems interact with strong and short laser pulses and temporal synthesized fields are routinely generated in attosecond laboratories around the world. Temporal and spatial synthesized fields have received special attention nowadays because they would allow to exceed considerably the conventional harmonic and electron energy frontiers. Classical simulations are an invaluable tool to explore exhaustively the parameters domain at a cheap computational cost, before massive quantum mechanical calculations, absolutely indispensable for the detailed analysis, are performed.

  18. Age, sex and spatial dependent variations in heavy metals levels in the Glaucous Gulls ( Larus hyperboreus ) from the Bjørnøya and Jan Mayen, Arctic

    Microsoft Academic Search

    Micha? Malinga; Piotr Szefer; Geir W. Gabrielsen

    2010-01-01

    Heavy metals (Cd, Cu, Fe, Mn and Zn) concentrations were determined in different tissues (muscle, kidney, liver, brain, gonads,\\u000a heart and feathers) of Glaucous Gulls (Larus hyperboreus) from Bjørnøya and Jan Mayen. The age and spatial dependent variations in heavy metals were quantified and interpreted in\\u000a view of the three chemometric techniques, i.e. non-parametric Mann–Whitney U test, redundancy gradient analysis

  19. Survival and spatial fidelity of moufl on ( Ovis gmelini ): A Bayesian analysis of an age-dependent capture-recapture model

    Microsoft Academic Search

    Jerôme Dupuis; Jacques Badia; Marie-Line Maublanc; Richard Bon

    2002-01-01

    We study the influence of age and sex on survival and spatial fidelity of moufl on (Ovis gmelini) in the Caroux-Espinouse massif. Survival and movement probabilities are estimated through a Bayesian analysis of an age-dependent\\u000a capture-recapture model. Prior information is based on external data, namely on radio-tracked animals. Recapture rates differed\\u000a between age, sexes, and areas. Whatever the area, survival

  20. Tuning magnetoresistance and magnetic-field-dependent electroluminescence through mixing a strong-spin-orbital-coupling molecule and a weak-spin-orbital-coupling polymer

    SciTech Connect

    Wu, Yue [University of Tennessee, Knoxville (UTK); Xu, Zhihua [University of Tennessee, Knoxville (UTK); Hu, Bin [University of Tennessee, Knoxville (UTK); Howe, Jane Y [ORNL

    2007-01-01

    We report a tunable magnetoresistance by uniformly mixing strong-spin-orbital-coupling molecule fac-tris (2-phenylpyridinato) iridium [Ir(ppy)3] and weak-spin-orbital-coupling polymer poly(N-vinyl carbazole) (PVK). Three possible mechanisms, namely charge transport distribution, energy transfer, and intermolecular spin-orbital interaction, are discussed to interpret the Ir(ppy)3 concentration-dependent magnetoresistance in the PVK+Ir(ppy)3 composite. The comparison between the magnetic field effects measured from energy-transfer and non-energy-transfer Ir(ppy)3 doped polymer composites indicates that energy transfer and intermolecular spin-orbital interaction lead to rough and fine tuning for the magnetoresistance, respectively. Furthermore, the photocurrent dependence of magnetic field implies that the excited states contribute to the magnetoresistance through dissociation. As a result, the modification of singlet or triplet ratio of excited states through energy transfer and intermolecular spin-orbital interaction form a mechanism to tune the magnetoresistance in organic semiconducting materials.

  1. Phase dependence of relativistic electron dynamics and emission spectra in the superposition of an ultraintense laser field and a strong uniform magnetic field.

    PubMed

    He, Xinkui; Shuai, B; Ge, X C; Li, R X; Xu, Z Z

    2003-11-01

    The phase dependence of the dynamics and emission spectra of a fully relativistic electron in the superposition of an ultraintense plane wave laser field and a strong uniform magnetic field has been investigated. It is found that the effect of changing the initial laser phase is quite different for circularly and linearly polarized laser fields. For circular polarization only the axis of the helical trajectory is changed with variation of the initial laser field phase. However, for linear polarization, the effect of changing the initial phase is opposite in the two parameter regions divided by the resonance condition r=1 (r stands for the ratio between the reduced cyclotron frequency and laser frequency). When r<1, with increase in the initial laser field phase eta(0) from 0 to pi/2, both the radius of the electron's helical trajectory and the height of the peak related to the uniform magnetic field are decreased, and these two physical values are increased with an increase in the laser initial phase when r>1. The phase dependence of the electron's energy and velocity components was also studied. Some beat structure is found when eta(0)=0 and this structure is absent when eta(0)=pi/2. PMID:14682898

  2. A linear stability analysis on the onset of thermal convection of a fluid with strongly temperature-dependent viscosity in a spherical shell

    NASA Astrophysics Data System (ADS)

    Kameyama, Masanori; Ichikawa, Hiroki; Miyauchi, Arata

    2013-02-01

    A linear stability analysis was performed in order to study the onset of thermal convection in the presence of a strong viscosity variation, with a special emphasis on the condition for the stagnant-lid (ST) convection where a convection takes place only in a sublayer beneath a highly viscous lid of cold fluid. We consider the temporal evolution (growth or decay) of an infinitesimal perturbation superimposed to a Boussinesq fluid with an infinite Prandtl number which is in a static (motionless) and conductive state in a basally heated planar layer or spherical shell. The viscosity of the fluid is assumed to be exponentially dependent on temperature. The linearized equations for conservations of mass, momentum, and internal (thermal) energy are numerically solved for the critical Rayleigh number, Ra c , as well as the radial profiles of eigenfunctions for infinitesimal perturbations. The above calculations are repeatedly carried out by systematically varying (i) the magnitude of the temperature dependence of viscosity, E, and (ii) the ratio of the inner and outer radii of the spherical shell, ?. A careful analysis of the vertical structure of incipient flows demonstrated that the dominance of the ST convection can be quantitatively identified by the vertical profile of ? h (a measure of conversion between horizontal and vertical flows), regardless of the model geometries. We also found that, in the spherical shell relevant to the Earth's mantle ( ? = 0.55), the transition into ST convection takes place at the viscosity contrast across the layer {r_?˜eq10^4} . Taken together with the fact that the threshold value of r ? falls in the range of r ? for a so-called sluggish-lid convection, our finding suggests that the ST-mode of convection with horizontally elongated convection cells is likely to arise in the Earth's mantle solely from the temperature-dependent viscosity.

  3. ?-Catenin-dependent pathway activation by both promiscuous "canonical" WNT3a-, and specific "noncanonical" WNT4- and WNT5a-FZD receptor combinations with strong differences in LRP5 and LRP6 dependency.

    PubMed

    Ring, Larisa; Neth, Peter; Weber, Christian; Steffens, Sabine; Faussner, Alexander

    2014-02-01

    The WNT/?-catenin signalling cascade is the best-investigated frizzled receptor (FZD) pathway, however, whether and how specific combinations of WNT/FZD and co-receptors LRP5 and LRP6 differentially affect this pathway are not well understood. This is mostly due to the fact that there are 19 WNTs, 10 FZDs and at least two co-receptors. In our attempt to identify the signalling capabilities of specific WNT/FZD/LRP combinations we made use of our previously reported TCF/LEF Gaussia luciferase reporter gene HEK293 cell line (Ring et al., 2011). Generation of WNT/FZD fusion constructs - but not their separate transfection - without or with additional isogenic overexpression of LRP5 and LRP6 in our reporter cells permitted the investigation of specific WNT/FZD/LRP combinations. The canonical WNT3a in fusion to almost all FZDs was able to induce ?-catenin-dependent signalling with strong dependency on LRP6 but not LRP5. Interestingly, noncanonical WNT ligands, WNT4 and WNT5a, were also able to act "canonically" but only in fusion with specific FZDs and with selective dependence on LRP5 or LRP6. These data and extension of this experimental setup to the poorly characterized other WNTs should facilitate deeper insight into the complex WNT/FZD signalling system and its function. PMID:24269653

  4. Prediction of strong ground state electron and hole wave function spatial overlap in nonpolar GaN/AlN quantum dots

    NASA Astrophysics Data System (ADS)

    Schulz, S.; Caro, M. A.; O'Reilly, E. P.

    2012-09-01

    We present a detailed analysis of the electrostatic built-in field, the electronic structure, and the optical properties of a-plane GaN/AlN quantum dots with an arrowhead-shaped geometry. This geometry is based on extensive experimental analysis given in the literature. Our results indicate that the spatial overlap of electron and hole ground state wave functions is significantly increased, compared to that of a c-plane system, when taking the experimentally suggested trapezoid-shaped dot base into account. This finding is in agreement with experimental data on the optical properties of a-plane GaN/AlN quantum dots.

  5. Does pattern electroretinogram spatial tuning alteration in Parkinson's disease depend on motor disturbances or retinal dopaminergic loss?

    Microsoft Academic Search

    A Peppe; P Stanzione; M Pierantozzi; R Semprini; A Bassi; A. M Santilli; R Formisano; M Piccolino; G Bernardi

    1998-01-01

    Systemic decrease of dopaminergic cells, such as in Parkinson's disease may produce visual alterations in humans. In order to show possible pattern electroretinogram (PERG) spatial tuning function (STF) alterations due to impaired dopaminergic transmission in humans, we studied a group of Parkinson's disease patients before and during treatment with the dopamine precursor, levodopa, and compared their performances with those of

  6. Dose reduction in CT with correlated-polarity noise reduction: context-dependent spatial resolution and noise properties demonstrating two-fold dose reduction with minimal artifacts

    NASA Astrophysics Data System (ADS)

    Dobbins, James T.; Wells, Jered R.; Segars, W. Paul

    2014-03-01

    Correlated-polarity noise reduction (CPNR) is a novel noise reduction technique that uses a statistical approach to reducing noise while maintaining excellent spatial resolution and a traditional noise appearance. It was demonstrated in application to CT imaging for the first time at SPIE 2013 and showed qualitatively excellent image quality at half of normal CT dose. In this current work, we measure quantitatively the spatial resolution and noise properties of CPNR in CT imaging. To measure the spatial resolution, we developed a metrology approach that is suitable for nonlinear algorithms such as CPNR. We introduce the formalism of Signal Modification Factor, SMF(u,v), which is the ratio in frequency space of the CPNR-processed image divided by the noise-free image, averaged over an ensemble of ROIs in a given anatomical context. SMF is a nonlinear analog to the MTF. We used XCAT computer-generated anthropomorphic phantom images followed by projection space processing with CPNR. The SMF revealed virtually no effect from CPNR on spatial resolution of the images (<7% degradation at all frequencies). Corresponding contextdependent NPS measurements generated with CPNR at half-dose were about equal to the NPS of full-dose images without CPNR. This result demonstrates for the first time the quantitative determination of a two-fold reduction in dose with CPNR with less than 7% reduction in spatial resolution. We conclude that CPNR shows strong promise as a method for reduction of noise (and hence, dose) in CT. CPNR may also be used in combination with iterative reconstruction techniques for yet further dose reduction, pending further investigation.

  7. Strong strain dependence of ferroelectric coercivity in a BiFeO3 film M. D. Biegalski, D. H. Kim, S. Choudhury, L. Q. Chen, H. M. Christen et al.

    E-print Network

    Chen, Long-Qing

    Strong strain dependence of ferroelectric coercivity in a BiFeO3 film M. D. Biegalski, D. H. Kim, S dependence of ferroelectric coercivity in a BiFeO3 film M. D. Biegalski,1,a D. H. Kim,1,2 S. Choudhury,3,4 L

  8. Excision efficiency is not strongly coupled to transgenic rate: cell type-dependent transposition efficiency of sleeping beauty and piggyBac DNA transposons.

    PubMed

    Kolacsek, Orsolya; Erdei, Zsuzsa; Apáti, Agota; Sándor, Sára; Izsvák, Zsuzsanna; Ivics, Zoltán; Sarkadi, Balázs; Orbán, Tamás I

    2014-08-01

    The Sleeping Beauty (SB) and piggyBac (PB) DNA transposons represent an emerging new gene delivery technology, potentially suitable for human gene therapy applications. Previous studies pointed to important differences between these transposon systems, depending on the cell types examined and the methodologies applied. However, efficiencies cannot always be compared because of differences in applications. In addition, "overproduction inhibition," a phenomenon believed to be a characteristic of DNA transposons, can remarkably reduce the overall transgenic rate, emphasizing the importance of transposase dose applied. Therefore, because of lack of comprehensive analysis, researchers are forced to optimize the technology for their own "in-house" platforms. In this study, we investigated the transposition of several SB (SB11, SB32, SB100X) and PB (mPB and hyPB) variants in various cell types at three levels: comparing the excision efficiency of the reaction by real-time PCR, testing the overall transgenic rate by detecting cells with stable integrations, and determining the average copy number when using different transposon systems and conditions. We concluded that high excision activity is not always followed by a higher transgenic rate, as exemplified by the hyperactive transposases, indicating that the excision and the integration steps of transposition are not strongly coupled as previously thought. In general, all levels of transposition show remarkable differences depending on the transposase used and cell lines examined, being the least efficient in human embryonic stem cells (hESCs). In spite of the comparably low activity in those special cell types, the hyperactive SB100X and hyPB systems could be used in hESCs with similar transgenic efficiency and with reasonably low (2-3) transgene copy numbers, indicating their potential applicability for gene therapy purposes in the future. PMID:25045962

  9. Hormonal regulation of gluconeogenesis in cereal aleurone is strongly cultivar-dependent and gibberellin action involves SLENDER1 but not GAMYB.

    PubMed

    Eastmond, Peter J; Jones, Russell L

    2005-11-01

    Storage oil is a major constituent in the cereal aleurone layer. The aim of this study was to investigate how gibberellin (GA) and abscisic acid (ABA) regulate conversion of oil to sugar in barley aleurone. The activity of the glyoxylate cycle enzyme isocitrate lyase (ICL) was surveyed in eight barley cultivars. Surprisingly, some cultivars do not require GA for the induction of ICL (e.g. Himalaya), whereas some do (e.g. Golden Promise). Furthermore, in Golden Promise, GA also stimulates triacylglycerol breakdown and enhances the net flux of carbon from acetate to sugar. In contrast, ABA strongly represses ICL activity and the flux of carbon from oil to sugar in both Golden Promise and Himalaya. Biolistics using a promoter reporter showed that GA and ABA regulate ICL at the level of transcription. Studies using barley and rice mutants and pharmacological agents show that GA-dependent induction of ICL activity is mediated by SLENDER1 and requires cGMP, but does not involve the transcription factor GAMYB. Gibberellin and ABA therefore act antagonistically to regulate gluconeogenesis in the aleurone layer as well as controlling the production and secretion of hydrolases into the starchy endosperm. We suggest that the variation between different barley cultivars might be a result of selective breeding to alter seed dormancy. PMID:16236157

  10. Time-dependent effects of transcription- and translation-halting drugs on the spatial distributions of the Escherichia coli chromosome and ribosomes.

    PubMed

    Bakshi, Somenath; Choi, Heejun; Mondal, Jagannath; Weisshaar, James C

    2014-11-01

    Previously observed effects of rifampicin and chloramphenicol indicate that transcription and translation activity strongly affect the coarse spatial organization of the bacterial cytoplasm. Single-cell, time-resolved, quantitative imaging of chromosome and ribosome spatial distributions and ribosome diffusion in live Escherichia coli provides insight into the underlying mechanisms. Monte Carlo simulations of model DNA-ribosome mixtures support a novel nucleoid-ribosome mixing hypothesis. In normal conditions, 70S-polysomes and the chromosomal DNA segregate, while 30S and 50S ribosomal subunits are able to penetrate the nucleoids. Growth conditions and drug treatments determine the partitioning of ribosomes into 70S-polysomes versus free 30S and 50S subunits. Entropic and excluded volume effects then dictate the resulting chromosome and ribosome spatial distributions. Direct observation of radial contraction of the nucleoids 0-5?min after treatment with either transcription- or translation-halting drugs supports the hypothesis that simultaneous transcription, translation, and insertion of proteins into the membrane ('transertion') exerts an expanding force on the chromosomal DNA. Breaking of the DNA-RNA polymerase-mRNA-ribosome-membrane chain in either of two ways causes similar nucleoid contraction on a similar timescale. We suggest that chromosomal expansion due to transertion enables co-transcriptional translation throughout the nucleoids. PMID:25250841

  11. Diagnostic differentiation of mild cognitive impairment due to Alzheimer's disease using a hippocampus-dependent test of spatial memory.

    PubMed

    Moodley, Kuven; Minati, Ludovico; Contarino, Valeria; Prioni, Sara; Wood, Ruth; Cooper, Rebecca; D'Incerti, Ludovico; Tagliavini, Fabrizio; Chan, Dennis

    2015-08-01

    The hippocampus is one of the earliest brain regions affected in Alzheimer's disease (AD) and tests of hippocampal function have the potential to detect AD in its earliest stages. Given that the hippocampus is critically involved in allocentric spatial memory, this study applied a short test of spatial memory, the 4 Mountains Test (4MT), to determine whether test performance can differentiate mild cognitive impairment (MCI) patients with and without CSF biomarker evidence of underlying AD and whether the test can distinguish patients with MCI and mild AD dementia when applied in different cultural settings. Healthy controls (HC), patients with MCI, and mild AD dementia were recruited from study sites in UK and Italy. Study numbers were: HC (UK 20, Italy 10), MCI (UK 21, Italy 14), and AD (UK 11, Italy 9). Nineteen UK MCI patients were grouped into CSF biomarker-positive (MCI+, n = 10) and biomarker-negative (MCI-, n = 9) subgroups. Behavioral data were correlated with hippocampal volume and cortical thickness of the precuneus and posterior cingulate gyrus. Spatial memory was impaired in both UK and Italy MCI and AD patients. Test performance additionally differentiated between MCI+ and MCI- subgroups (P = 0.001). A 4MT score of ?8/15 was associated with 100% sensitivity and 90% specificity for detection of early AD (MCI+ and mild AD dementia) in the UK population, and with 100% sensitivity and 50% specificity for detection of MCI and AD in the Italy sample. 4MT performance correlated with hippocampal volume in the UK population and cortical thickness of the precuneus in both study populations. In conclusion, performance on a hippocampus-sensitive test of spatial memory differentiates MCI due to AD with high diagnostic sensitivity and specificity. The observation that similar diagnostic sensitivity was obtained in two separate study populations, allied to the scalability and usability of the test in community memory clinics, supports future application of the 4MT in the diagnosis of pre-dementia due to AD. © 2015 Wiley Periodicals, Inc. PMID:25605659

  12. Quantitative PCR Reveals Strong Spatial and Temporal Variation of the Wasting Disease Pathogen, Labyrinthula zosterae in Northern European Eelgrass (Zostera marina) Beds

    PubMed Central

    Bockelmann, Anna-Christina; Tams, Verena; Ploog, Jana; Schubert, Philipp R.; Reusch, Thorsten B. H.

    2013-01-01

    Seagrass beds are the foundation species of functionally important coastal ecosystems worldwide. The world’s largest losses of the widespread seagrass Zostera marina (eelgrass) have been reported as a consequence of wasting disease, an infection with the endophytic protist Labyrinthula zosterae. During one of the most extended epidemics in the marine realm, ?90% of East and Western Atlantic eelgrass beds died-off between 1932 and 1934. Today, small outbreaks continue to be reported, but the current extent of L. zosterae in European meadows is completely unknown. In this study we quantify the abundance and prevalence of the wasting disease pathogen among 19 Z. marina populations in northern European coastal waters, using quantitative PCR (QPCR) with primers targeting a species specific portion of the internally transcribed spacer (ITS1) of L. zosterae. Spatially, we found marked variation among sites with abundances varying between 0 and 126 cells mg?1 Z. marina dry weight (mean: 5.7 L. zosterae cells mg?1 Z. marina dry weight ±1.9 SE) and prevalences ranged from 0–88.9%. Temporarily, abundances varied between 0 and 271 cells mg?1 Z. marina dry weight (mean: 8.5±2.6 SE), while prevalences ranged from zero in winter and early spring to 96% in summer. Field concentrations accessed via bulk DNA extraction and subsequent QPCR correlated well with prevalence data estimated via isolation and cultivation from live plant tissue. L. zosterae was not only detectable in black lesions, a sign of Labyrinthula-induced necrosis, but also occurred in green, apparently healthy tissue. We conclude that L. zosterae infection is common (84% infected populations) in (northern) European eelgrass populations with highest abundances during the summer months. In the light of global climate change and increasing rate of marine diseases our data provide a baseline for further studies on the causes of pathogenic outbreaks of L. zosterae. PMID:23658711

  13. Quantitative PCR reveals strong spatial and temporal variation of the wasting disease pathogen, Labyrinthula zosterae in northern European eelgrass (Zostera marina) beds.

    PubMed

    Bockelmann, Anna-Christina; Tams, Verena; Ploog, Jana; Schubert, Philipp R; Reusch, Thorsten B H

    2013-01-01

    Seagrass beds are the foundation species of functionally important coastal ecosystems worldwide. The world's largest losses of the widespread seagrass Zostera marina (eelgrass) have been reported as a consequence of wasting disease, an infection with the endophytic protist Labyrinthula zosterae. During one of the most extended epidemics in the marine realm, ?90% of East and Western Atlantic eelgrass beds died-off between 1932 and 1934. Today, small outbreaks continue to be reported, but the current extent of L. zosterae in European meadows is completely unknown. In this study we quantify the abundance and prevalence of the wasting disease pathogen among 19 Z. marina populations in northern European coastal waters, using quantitative PCR (QPCR) with primers targeting a species specific portion of the internally transcribed spacer (ITS1) of L. zosterae. Spatially, we found marked variation among sites with abundances varying between 0 and 126 cells mg(-1) Z. marina dry weight (mean: 5.7 L. zosterae cells mg(-1) Z. marina dry weight ±1.9 SE) and prevalences ranged from 0-88.9%. Temporarily, abundances varied between 0 and 271 cells mg(-1) Z. marina dry weight (mean: 8.5±2.6 SE), while prevalences ranged from zero in winter and early spring to 96% in summer. Field concentrations accessed via bulk DNA extraction and subsequent QPCR correlated well with prevalence data estimated via isolation and cultivation from live plant tissue. L. zosterae was not only detectable in black lesions, a sign of Labyrinthula-induced necrosis, but also occurred in green, apparently healthy tissue. We conclude that L. zosterae infection is common (84% infected populations) in (northern) European eelgrass populations with highest abundances during the summer months. In the light of global climate change and increasing rate of marine diseases our data provide a baseline for further studies on the causes of pathogenic outbreaks of L. zosterae. PMID:23658711

  14. Endogenous proteolytic cleavage of disease-associated prion protein to produce C2 fragments is strongly cell- and tissue-dependent.

    PubMed

    Dron, Michel; Moudjou, Mohammed; Chapuis, Jérôme; Salamat, Muhammad Khalid Farooq; Bernard, Julie; Cronier, Sabrina; Langevin, Christelle; Laude, Hubert

    2010-04-01

    The abnormally folded form of the prion protein (PrP(Sc)) accumulating in nervous and lymphoid tissues of prion-infected individuals can be naturally cleaved to generate a N-terminal-truncated fragment called C2. Information about the identity of the cellular proteases involved in this process and its possible role in prion biology has remained limited and controversial. We investigated PrP(Sc) N-terminal trimming in different cell lines and primary cultured nerve cells, and in the brain and spleen tissue from transgenic mice infected by ovine and mouse prions. We found the following: (i) the full-length to C2 ratio varies considerably depending on the infected cell or tissue. Thus, in primary neurons and brain tissue, PrP(Sc) accumulated predominantly as untrimmed species, whereas efficient trimming occurred in Rov and MovS cells, and in spleen tissue. (ii) Although C2 is generally considered to be the counterpart of the PrP(Sc) proteinase K-resistant core, the N termini of the fragments cleaved in vivo and in vitro can actually differ, as evidenced by a different reactivity toward the Pc248 anti-octarepeat antibody. (iii) In lysosome-impaired cells, the ratio of full-length versus C2 species dramatically increased, yet efficient prion propagation could occur. Moreover, cathepsin but not calpain inhibitors markedly inhibited C2 formation, and in vitro cleavage by cathepsins B and L produced PrP(Sc) fragments lacking the Pc248 epitope, strongly arguing for the primary involvement of acidic hydrolases of the endolysosomal compartment. These findings have implications on the molecular analysis of PrP(Sc) and cell pathogenesis of prion infection. PMID:20154089

  15. STUDY OF SPATIALLY RESOLVED IMPURITY DIFFUSION IN CdTe SOLAR CELLS USING VOLTAGE DEPENDENT QUANTUM EFFICIENCY

    Microsoft Academic Search

    D. L. Bätzner; G. Agostinelli; M. Campo; A. Romeo; J. Beier; H. Zogg; A. N. Tiwari

    2002-01-01

    The performance stability of CdTe\\/CdS solar cells is strongly determined by diffusion of impurities from the back contact into the absorber layer and hetero-junction. Impurity migration changes the effective carrier concentration and barriers in the device by compensation of donors or acceptors and by creation of defect centres. The CdS window layer is particularly affected by this phenomenon, since the

  16. Study of spatially resolved impurity diffusion in CdTe solar cells using voltage dependent quantum efficiency

    Microsoft Academic Search

    D. L. Bätzner; G. Agostinelli; M. Campo; A. Romeo; J. Beier; H. Zogg; A. N. Tiwari

    2003-01-01

    The performance stability of CdTe\\/CdS solar cells is strongly determined by diffusion of impurities from the back contact into the absorber layer and hetero-junction. Impurity migration changes the effective carrier concentration and barriers in the device by compensation of donors or acceptors and by creation of defect centres. The CdS window layer is particularly affected by this phenomenon, since the

  17. A nonlinear spatially variant object-dependent system model for prediction of partial volume effects and scatter in PET

    Microsoft Academic Search

    Chi-Hsien Chen; Raymond F. Muzic Jr.; A. Dennis Nelson; Lee P. Adler

    1998-01-01

    Accurate quantitation of small lesions with positron emission tomography (PET) requires correction for the partial volume effect. Traditional methods that use Gaussian models of the PET system were found to be insufficient. A new approach that models the non-Gaussian object-dependent scatter was developed. The model consists of eight simple functions with a total of 24 parameters. Images of line and

  18. Distance-dependence in two Amazonian palms: effects of spatial and temporal variation in seed predator communities

    Microsoft Academic Search

    Julie L. Wyatt; Miles R. Silman

    2004-01-01

    Animals aid population growth and fitness in tropical forest communities through dispersal and negatively impact populations through seed predation. The interaction between dispersal and seed predation can produce distance- or density-dependence; powerful mechanisms for maintaining species diversity incorporated in the Janzen–Connell model. Large mammals, the highest biomass seed predators of intact Amazonian communities and at risk due to human disturbance,

  19. Sex and dose-dependent effects of developmental exposure to bisphenol A on anxiety and spatial learning in deer mice (Peromyscus maniculatus bairdii) offspring.

    PubMed

    Jašarevi?, Eldin; Williams, Scott A; Vandas, Gregory M; Ellersieck, Mark R; Liao, Chunyang; Kannan, Kurunthachalam; Roberts, R Michael; Geary, David C; Rosenfeld, Cheryl S

    2013-01-01

    Bisphenol A (BPA) is a widely produced, endocrine disrupting compound that is pervasive in the environment. Data suggest that developmental exposure to BPA during sexual differentiation of the brain leads to later behavioral consequences in offspring. Outbred deer mice (Peromyscus maniculatus bairdii) are an excellent animal model for such studies as they exhibit well-defined sex- and steroid-dependent behaviors. Here, dams during gestation and lactation were fed with a phytoestrogen-free control diet, the same diet supplemented with either ethinyl estradiol (0.1 ppb), or one of the three doses of BPA (50 mg, 5 mg, 50 ?g/kg feed weight). After weaning, the pups were maintained on control diet until they reached sexual maturity and then assessed for both spatial learning capabilities and anxiety-like and exploratory behaviors. Relative to controls, males exposed to the two upper but not the lowest dose of BPA demonstrated similar impairments in spatial learning, increased anxiety and reduced exploratory behaviors as ethinyl estradiol-exposed males, while females exposed to ethinyl estradiol, but not to BPA, consistently exhibited masculinized spatial abilities. We also determined whether dams maintained chronically on the upper dose of BPA contained environmentally relevant concentrations of BPA in their blood. While serum concentrations of unconjugated BPA in controls were below the minimum level of detection, those from dams on the BPA diet were comparable (5.48±2.07 ng/ml) to concentrations that have been observed in humans. Together, these studies demonstrate that developmental exposure to environmentally relevant concentrations of BPA can disrupt adult behaviors in a dose- and sex-dependent manner. PMID:23051835

  20. Prey-predator dynamics in rotifers: density-dependent consequences of spatial heterogeneity due to surface attachment.

    PubMed

    Vadstein, Olav; Olsen, Lasse M; Andersen, Tom

    2012-08-01

    Classical models of prey-predator interactions assume that per capita prey consumption is dependent on prey density alone and that prey consumption (functional response) and consumer proliferation (numerical response) operate on the same timescales and without time lags. Several modifications have been proposed for resolving this timescale discrepancy, including variants where the functional response depends on both prey and predator densities. A microcosm system with the rotifer Brachionus 'Nevada' feeding on the prasinophyte Tetraselmis sp. showed significant (P < 0.0005) increases in steady-state biomasses of both prey and predators with increasing carrying capacity (represented by total phosphorus of the growth medium), which is inconsistent with predictions based on the traditional prey-only-dependent functional response. We provide data indicating that surfaces where the predator can attach provide a high-quality habitat for rotifers, which can result in a predator-dependent functional response. We also show that partitioning between the attached and free-swimming habitats was fast compared to the timescale of the numerical response. When attached to surfaces, rotifers maximized net energy gain by avoiding the high cost of swimming and by increased food capture due to reduced viscous drag. A mathematical model with prey-dependent functional response and wall-attached and free-swimming fractions of the population describes our data adequately. We discuss the implications of this finding for extrapolating microcosm experiments to systems with other surface-to-volume ratios, and to what extent our findings may apply to other popular model organisms for prey-predator interaction. PMID:22928408

  1. Volume and Quark Mass Dependence of the Chiral Phase Transition

    E-print Network

    J. Braun; B. Klein; H. -J. Pirner; A. H. Rezaeian

    2006-06-23

    We investigate chiral symmetry restoration in finite spatial volume and at finite temperature by calculating the dependence of the chiral phase transition temperature on the size of the spatial volume and the current-quark mass for the quark-meson model, using the proper-time Renormalization Group approach. We find that the critical temperature is weakly dependent on the size of the spatial volume for large current-quark masses, but depends strongly on it for small current-quark masses. In addition, for small volumes we observe a dependence on the choice of quark boundary conditions.

  2. Quantitative Evaluation of the Lactate Signal Loss and Its Spatial Dependence in PRESS Localized 1H NMR Spectroscopy

    Microsoft Academic Search

    Wulf-Ingo Jung; Michael Bunse; Otto Lutz

    2001-01-01

    Localized 1H NMR spectroscopy using the 90°?t1?180°?t1+t2?180°?t2?Acq. PRESS sequence can lead to a signal loss for the lactate doublet compared with signals from uncoupled nuclei which is dependent on the choice of t1 and t2. The most striking signal loss of up to 78% of the total signal occurs with the symmetrical PRESS sequence (t1=t2) at an echo time of

  3. Multiparity-induced enhancement of hippocampal neurogenesis and spatial memory depends on ovarian hormone status in middle age.

    PubMed

    Barha, Cindy K; Lieblich, Stephanie E; Chow, Carmen; Galea, Liisa A M

    2015-08-01

    Menopause is associated with cognitive decline, and previous parity can increase or delay the trajectory of cognitive aging. Furthermore, parity enables the hippocampus to respond to estrogens in middle age. The present study investigated how previous parity and estrogens influence cognition, neurogenesis, and neuronal activation in response to memory retrieval in the hippocampus of middle-aged females. Multiparous and nulliparous rats were ovariectomized (OVX) or received sham surgery and were treated with vehicle, 17?-estradiol, 17?-estradiol, or estrone. Rats were trained on the spatial working and reference memory versions of the Morris water maze. Multiparous rats had a significantly greater density of immature neurons in the hippocampus, enhanced acquisition of working memory, but poorer reference memory compared with nulliparous rats. Furthermore, OVX increased, while treatment with estrogens reduced, the density of immature neurons, regardless of parity. OVX improved reference memory only in nulliparous rats. Thus, motherhood has long-lasting effects on the neuroplasticity and function of the hippocampus. These findings have wide-ranging implications for the treatment of age-associated decline in women. PMID:25998101

  4. Strong Interaction

    SciTech Connect

    Karsch, F.; Vogelsang, V.

    2009-09-29

    We will give here an overview of our theory of the strong interactions, Quantum Chromo Dynamics (QCD) and its properties. We will also briefly review the history of the study of the strong interactions, and the discoveries that ultimately led to the formulation of QCD. The strong force is one of the four known fundamental forces in nature, the others being the electromagnetic, the weak and the gravitational force. The strong force, usually referred to by scientists as the 'strong interaction', is relevant at the subatomic level, where it is responsible for the binding of protons and neutrons to atomic nuclei. To do this, it must overcome the electric repulsion between the protons in an atomic nucleus and be the most powerful force over distances of a few fm (1fm=1 femtometer=1 fermi=10{sup -15}m), the typical size of a nucleus. This property gave the strong force its name.

  5. Endocytotic routes of cobra cardiotoxins depend on spatial distribution of positively charged and hydrophobic domains to target distinct types of sulfated glycoconjugates on cell surface.

    PubMed

    Lee, Shao-Chen; Lin, Chien-Chu; Wang, Chia-Hui; Wu, Po-Long; Huang, Hsuan-Wei; Chang, Chung-I; Wu, Wen-guey

    2014-07-18

    Cobra cardiotoxins (CTX) are a family of three-fingered basic polypeptides known to interact with diverse targets such as heparan sulfates, sulfatides, and integrins on cell surfaces. After CTX bind to the membrane surface, they are internalized to intracellular space and exert their cytotoxicity via an unknown mechanism. By the combined in vitro kinetic binding, three-dimensional x-ray structure determination, and cell biology studies on the naturally abundant CTX homologues from the Taiwanese cobra, we showed that slight variations on the spatial distribution of positively charged or hydrophobic domains among CTX A2, A3, and A4 could lead to significant changes in their endocytotic pathways and action mechanisms via distinct sulfated glycoconjugate-mediated processes. The intracellular locations of these structurally similar CTX after internalization are shown to vary between the mitochondria and lysosomes via either dynamin2-dependent or -independent processes with distinct membrane cholesterol sensitivity. Evidence is presented to suggest that the shifting between the sulfated glycoconjugates as distinct targets of CTX A2, A3, and A4 might play roles in the co-evolutionary arms race between venomous snake toxins to cope with different membrane repair mechanisms at the cellular levels. The sensitivity of endocytotic routes to the spatial distribution of positively charged or hydrophobic domains may provide an explanation for the diverse endocytosis pathways of other cell-penetrating basic polypeptides. PMID:24898246

  6. Library-dependent and library-independent microbial source tracking to identify spatial variation in faecal contamination sources along a Lake Ontario beach (Ontario, Canada).

    PubMed

    Edge, T A; Hill, S; Seto, P; Marsalek, J

    2010-01-01

    Multiple microbial source tracking methods were applied to investigate spatial variation in faecal pollution sources impacting a 1.7 km freshwater beach on Lake Ontario (Canada). The highest E. coli concentrations measured in the study area were from interstitial sand pore water at Sunnyside Beach, reaching 2.6 x 10(6) CFU/100 ml. These E. coli concentrations exceeded those in the nearby Humber River and Black Creek, which are impacted by combined sewer overflows containing municipal wastewater and by stormwater conveying washoff from the urban area. Library-independent Bacteroidales HF183 analyses identified the more frequent occurrence of municipal wastewater contamination in the Humber River and at a Sunnyside Beach location closest to the mouth of the river. Library-dependent E. coli antibiotic resistance and rep-PCR DNA fingerprinting analyses identified the more frequent occurrence of bird faecal contamination at Sunnyside Beach locations away from the river mouth. These microbial source tracking results raise caution about managing beaches with multiple sources of contamination as a single entity without considering spatial variability in faecal pollution sources and the need for more localized beach management practices. PMID:20706020

  7. PHYSICAL REVIEW A 82, 023407 (2010) Time-dependent density-functional-theory calculation of strong-field ionization rates of H2

    E-print Network

    Chu, Xi

    2010-01-01

    molecular physics. Strong-field atomic ionization models are mostly based on the single-active-electron (SAERevA.82.023407 PACS number(s): 33.80.Rv, 42.50.Hz, 33.90.+h I. INTRODUCTION Single-electron ionization of density-functional-theory (DFT) methods is that they are in general less costly in terms of computation

  8. Signatures of charmonium modification in spatial correlation functions

    E-print Network

    F. Karsch; E. Laermann; Swagato Mukherjee; P. Petreczky

    2012-05-30

    We study spatial correlation functions of charmonium in 2+1 flavor QCD using an improved staggered formulation. Contrary to the temporal correlation functions the spatial correlation functions exhibit a strong temperature dependence above the QCD transition temperature. Above this temperature they are sensitive to temporal boundary conditions. Both features become significant at a temperature close to 1.5 Tc and suggest corresponding modifications of charmonium spectral functions.

  9. Time-dependent effects of isoflurane and dexmedetomidine on functional connectivity, spectral characteristics, and spatial distribution of spontaneous BOLD fluctuations

    PubMed Central

    Magnuson, Matthew Evan; Thompson, Garth John; Pan, Wen-Ju; Keilholz, Shella Dawn

    2015-01-01

    Anesthesia is often necessary to perform fMRI experiments in the rodent model; however, commonly used anesthetic protocols may manifest changing brain conditions over the duration of the study. This possibility was explored in the current work. Eleven rats were anesthetized with 2% isoflurane anesthesia; four rats were anesthetized for a short period (30min, simulating induction and fMRI setup) and seven rats were anesthetized for a long period (3 h, simulating surgical preparation). Following the initial anesthetic period, isoflurane was discontinued, and a dexmedetomidine bolus (0.025 mg/kg) and continuous subcutaneous infusion (0.05 mg/kg/h) were administered. Blood-oxygen-level dependent resting state imaging was performed every 30 min from 0.75 h post dexmedetomidine bolus until 5.75 h post-bolus. Evaluation of power spectra obtained from time courses in the primary somatosensory cortex revealed, in general, a monotonic increase in low-frequency power (0.05–0.3 Hz) in both groups over the duration of resting state imaging. Greater low-band spectral power (0.05–0.15 Hz) is present in the short isoflurane group for the first 2.75 h, but the spectra become highly uniform at 3.25 h. The emergence of a ~0.18 Hz peak, beginning at the 3.75 h time point, exists in both groups and evolves similarly, increasing in strength as the duration of dexmedetomidine sedation (and time since isoflurane cessation) extends. In the long isoflurane group only, bilateral functional connectivity strengthens with anesthetic duration, and correlation is linearly linked to low-band spectral power. Convergence of connectivity and spectral metrics between the short and long isoflurane groups occurs at ~3.25 h, suggesting the effects of isoflurane have subsided. Researchers using dexmedetomidine following isoflurane for functional studies should be aware of the duration specific effects of the pre-scan isoflurane durations as well as the continuing influences of long-term imaging under dexmedetomidine. PMID:24449532

  10. Flexibility of spatial averaging in visual perception

    PubMed Central

    Lombrozo, Tania; Judson, Jeff; MacLeod, Donald I.A

    2005-01-01

    The classical receptive field (RF) concept—the idea that a visual neuron responds to fixed parts and properties of a stimulus—has been challenged by a series of recent physiological results. Here, we extend these findings to human vision, demonstrating that the extent of spatial averaging in contrast perception is also flexible, depending strongly on stimulus contrast and uniformity. At low contrast, spatial averaging is greatest (about 11?min of arc) within uniform regions such as edges, as expected if the relevant neurons have orientation-selective RFs. At high contrast, spatial averaging is minimal. These results can be understood if the visual system is balancing a trade-off between noise reduction, which favours large areas of averaging, and detail preservation, which favours minimal averaging. Two distinct populations of neurons with hard-wired RFs could account for our results, as could the more intriguing possibility of dynamic, contrast-dependent RFs. PMID:15870034

  11. Meta-ecosystem dynamics and functioning on finite spatial networks

    PubMed Central

    Marleau, Justin N.; Guichard, Frédéric; Loreau, Michel

    2014-01-01

    The addition of spatial structure to ecological concepts and theories has spurred integration between sub-disciplines within ecology, including community and ecosystem ecology. However, the complexity of spatial models limits their implementation to idealized, regular landscapes. We present a model meta-ecosystem with finite and irregular spatial structure consisting of local nutrient–autotrophs–herbivores ecosystems connected through spatial flows of materials and organisms. We study the effect of spatial flows on stability and ecosystem functions, and provide simple metrics of connectivity that can predict these effects. Our results show that high rates of nutrient and herbivore movement can destabilize local ecosystem dynamics, leading to spatially heterogeneous equilibria or oscillations across the meta-ecosystem, with generally increased meta-ecosystem primary and secondary production. However, the onset and the spatial scale of these emergent dynamics depend heavily on the spatial structure of the meta-ecosystem and on the relative movement rate of the autotrophs. We show how this strong dependence on finite spatial structure eludes commonly used metrics of connectivity, but can be predicted by the eigenvalues and eigenvectors of the connectivity matrix that describe the spatial structure and scale. Our study indicates the need to consider finite-size ecosystems in meta-ecosystem theory. PMID:24403323

  12. Meta-ecosystem dynamics and functioning on finite spatial networks.

    PubMed

    Marleau, Justin N; Guichard, Frédéric; Loreau, Michel

    2014-02-22

    The addition of spatial structure to ecological concepts and theories has spurred integration between sub-disciplines within ecology, including community and ecosystem ecology. However, the complexity of spatial models limits their implementation to idealized, regular landscapes. We present a model meta-ecosystem with finite and irregular spatial structure consisting of local nutrient-autotrophs-herbivores ecosystems connected through spatial flows of materials and organisms. We study the effect of spatial flows on stability and ecosystem functions, and provide simple metrics of connectivity that can predict these effects. Our results show that high rates of nutrient and herbivore movement can destabilize local ecosystem dynamics, leading to spatially heterogeneous equilibria or oscillations across the meta-ecosystem, with generally increased meta-ecosystem primary and secondary production. However, the onset and the spatial scale of these emergent dynamics depend heavily on the spatial structure of the meta-ecosystem and on the relative movement rate of the autotrophs. We show how this strong dependence on finite spatial structure eludes commonly used metrics of connectivity, but can be predicted by the eigenvalues and eigenvectors of the connectivity matrix that describe the spatial structure and scale. Our study indicates the need to consider finite-size ecosystems in meta-ecosystem theory. PMID:24403323

  13. Extremely strong temperature-dependent Davydow-splitting effects in the polarized IR spectra of the hydrogen bond: Pyrazole and quinolin-2(1H)-one crystals

    NASA Astrophysics Data System (ADS)

    Hachu?a, Barbara; Flakus, Henryk T.; Tyl, Aleksandra; Polasz, Anna

    2014-04-01

    Polarized IR spectra were recorded in the spectral range of the ?N-H and ?N-D proton stretching vibration bands for the isotopically neat and isotopically diluted crystals of pyrazole (Pzl) and quinolin-2(1H)-one (2HQ). The spectra measured in the temperature range of 77-293 K have shown that temperature extremely strongly influenced the magnitude of the Davydow-splitting effects in the crystalline spectra. Two different competing vibrational Davydow-coupling mechanisms involving hydrogen bonds, i.e., the ‘tail-to-head' and the ‘side-to-side', were responsible for the generation of the temperature effects in the polarized spectra.

  14. Remaking Memories: Reconsolidation Updates Positively Motivated Spatial Memory in Rats

    ERIC Educational Resources Information Center

    Jones, Bethany; Bukoski, Elizabeth; Nadel, Lynn; Fellous, Jean-Marc

    2012-01-01

    There is strong evidence that reactivation of a memory returns it to a labile state, initiating a restabilization process termed reconsolidation, which allows for updating of the memory. In this study we investigated reactivation-dependent updating using a new positively motivated spatial task in rodents that was designed specifically to model a…

  15. Spatial Knowledge Spatial representation

    E-print Network

    Pillow, Jonathan

    1 Spatial Knowledge · Spatial representation · Mental maps · Large-scale space · Small-scale space) ­ Cognitive geography · Maps of large-scale space ­ What is our sense of the locations of items in the world? Large-scale space · Which is further north: ­ Austin, TX or Chicago, IL? ­ Portland, OR or Portland, ME

  16. Age, sex and spatial dependent variations in heavy metals levels in the Glaucous Gulls (Larus hyperboreus) from the Bjørnøya and Jan Mayen, Arctic.

    PubMed

    Malinga, Micha?; Szefer, Piotr; Gabrielsen, Geir W

    2010-10-01

    Heavy metals (Cd, Cu, Fe, Mn and Zn) concentrations were determined in different tissues (muscle, kidney, liver, brain, gonads, heart and feathers) of Glaucous Gulls (Larus hyperboreus) from Bjørnøya and Jan Mayen. The age and spatial dependent variations in heavy metals were quantified and interpreted in view of the three chemometric techniques, i.e. non-parametric Mann-Whitney U test, redundancy gradient analysis and detrended correspondence analysis. The Glaucous Gulls from Bjørnøya contained significantly higher (p < 0.05) levels of Cd, Cu and Zn than those inhabited Jan Mayen. Adult birds were characterized by greater (p < 0.01) concentration of muscle, hepatic and renal heavy metals in comparison to chicks. Insignificantly higher slope constant Zn/Cd for the liver than for the kidney may reflect insignificant Cd exposure. Estimate of transfer factor (TF) allows us to assess variations in heavy metal concentrations during the individual development of Glaucous Gulls. It may be stated that there is a distinct increase of bioaccumulation of all the studied metals during subsequent stages of the bird life. PMID:19847662

  17. Self-intermediate scattering function of strongly interacting three-dimensional lattice gases: time- and wave-vector-dependent tracer diffusion coefficient.

    PubMed

    Skarpalezos, Loukas; Argyrakis, Panos; Vikhrenko, Vyacheslav S

    2014-05-01

    We investigate the self-intermediate scattering function (SISF) in a three-dimensional (3D) cubic lattice fluid (interacting lattice gas) with attractive nearest-neighbor interparticle interactions at a temperature slightly above the critical one by means of Monte Carlo simulations. A special representation of SISF as an exponent of the mean tracer diffusion coefficient multiplied by the geometrical factor and time is considered to highlight memory effects that are included in time and wave-vector dependence of the diffusion coefficient. An analytical expression for the diffusion coefficient is suggested to reproduce the simulation data. It is shown that the particles' mean-square displacement is equal to the time integral of the diffusion coefficient. We make a comparison with the previously considered 2D system on a square lattice. The main difference with the two-dimensional case is that the time dependence of particular characteristics of the tracer diffusion coefficient in the 3D case cannot be described by exponentially decreasing functions, but requires using stretched exponentials with rather small values of exponents, of the order of 0.2. The hydrodynamic values of the tracer diffusion coefficient (in the limit of large times and small wave vectors) defined through SIFS simulation results agree well with the results of its direct determination by the mean-square displacement of the particles in the entire range of concentrations and temperatures. PMID:25353925

  18. Spectral type dependent rotational braking and strong magnetic flux in three components of the late-M multiple system LHS 1070

    E-print Network

    Ansgar Reiners; Andreas Seifahrt; Hans Ulrich Käufl; Ralf Siebenmorgen; Alain Smette

    2007-07-11

    We show individual high resolution spectra of components A, B, and C of the nearby late-M type multiple system LHS 1070. Component A is a mid-M star, B and C are known to have masses at the threshold to brown dwarfs. From our spectra we measure rotation velocities and the mean magnetic field for all three components individually. We find magnetic flux on the order of several kilo-Gauss in all components. The rotation velocities of the two late-M objects B and C are similar (vsini = 16km/s), the earlier A component is spinning only at about half that rate. This suggests weakening of net rotational braking at late-M spectral type, and that the lack of slowly rotating late-M and L dwarfs is real. Furthermore, we found that magnetic flux in the B component is about twice as strong as in component C at similar rotation rate. This indicates that rotational braking is not proportional to magnetic field strength in fully convective objects, and that a different field topology is the reason for the weak braking in low mass objects.

  19. Anomalous decay of photon echo in a quantum dot ensemble in the strong excitation regime

    SciTech Connect

    Suemori, Ryosuke; Ishi-Hayase, Junko [Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522 (Japan); Akahane, Kouichi; Yamamoto, Naokatsu [National Institute of Information and Communications Technology (NICT), 4-2-1, Nukuikitamchi, Koganei, Tokyo 102-8554 (Japan)

    2013-12-04

    We investigated the coherent dynamics of exciton ground-state transitions in an 150-layer-stacked strain-compensated InAs quantum dot ensemble using photon echo (PE) technique in the strong excitation regime. The time delay dependence of PE signal intensity shows a drastic change depending on the excitation intensity and the aperture position placed in front of a detector. Our results suggest that the excitation-intensity-dependent spatial distribution of PE signal intensity plays an important role in observing PE signal decay in the strong excitation regime.

  20. Spatially pooled depth-dependent reservoir storage, elevation, and water-quality data for selected reservoirs in Texas, January 1965-January 2010

    USGS Publications Warehouse

    Burley, Thomas E.; Asquith, William H.; Brooks, Donald L.

    2011-01-01

    The U.S. Geological Survey (USGS), in cooperation with Texas Tech University, constructed a dataset of selected reservoir storage (daily and instantaneous values), reservoir elevation (daily and instantaneous values), and water-quality data from 59 reservoirs throughout Texas. The period of record for the data is as large as January 1965-January 2010. Data were acquired from existing databases, spreadsheets, delimited text files, and hard-copy reports. The goal was to obtain as much data as possible; therefore, no data acquisition restrictions specifying a particular time window were used. Primary data sources include the USGS National Water Information System, the Texas Commission on Environmental Quality Surface Water-Quality Management Information System, and the Texas Water Development Board monthly Texas Water Condition Reports. Additional water-quality data for six reservoirs were obtained from USGS Texas Annual Water Data Reports. Data were combined from the multiple sources to create as complete a set of properties and constituents as the disparate databases allowed. By devising a unique per-reservoir short name to represent all sites on a reservoir regardless of their source, all sampling sites at a reservoir were spatially pooled by reservoir and temporally combined by date. Reservoir selection was based on various criteria including the availability of water-quality properties and constituents that might affect the trophic status of the reservoir and could also be important for understanding possible effects of climate change in the future. Other considerations in the selection of reservoirs included the general reservoir-specific period of record, the availability of concurrent reservoir storage or elevation data to match with water-quality data, and the availability of sample depth measurements. Additional separate selection criteria included historic information pertaining to blooms of golden algae. Physical properties and constituents were water temperature, reservoir storage, reservoir elevation, specific conductance, dissolved oxygen, pH, unfiltered salinity, unfiltered total nitrogen, filtered total nitrogen, unfiltered nitrate plus nitrite, unfiltered phosphorus, filtered phosphorus, unfiltered carbon, carbon in suspended sediment, total hardness, unfiltered noncarbonate hardness, filtered noncarbonate hardness, unfiltered calcium, filtered calcium, unfiltered magnesium, filtered magnesium, unfiltered sodium, filtered sodium, unfiltered potassium, filtered potassium, filtered chloride, filtered sulfate, unfiltered fluoride, and filtered fluoride. When possible, USGS and Texas Commission on Environmental Quality water-quality properties and constituents were matched using the database parameter codes for individual physical properties and constituents, descriptions of each physical property or constituent, and their reporting units. This report presents a collection of delimited text files of source-aggregated, spatially pooled, depth-dependent, instantaneous water-quality data as well as instantaneous, daily, and monthly storage and elevation reservoir data.

  1. Topics in strong Langmuir turbulence

    NASA Technical Reports Server (NTRS)

    Nicholson, D. R.

    1983-01-01

    Progress in two approaches to the study of strong Langmuir turbulence is reported. In two spatial dimensions, numerical solution of the Zakharov equations yields a steady state involving linear growth, linear damping, and a collection of coherent, long-lived entities which might loosely be called solitons. In one spatial dimension, a statistical theory is applied to the cubically nonlinear Schroedinger equation and is solved analytically in a special case.

  2. Topics in strong Langmuir turbulence

    NASA Technical Reports Server (NTRS)

    Nicholson, D. R.

    1982-01-01

    Progress in two approaches to the study of strong Langmuir turbulence is reported. In two spatial dimensions, numerical solution of the Zakharov equations yields a steady state involving linear growth, linear damping, and a collection of coherent, long-lived entities which might loosely be called solitons. In one spatial dimension, a statistical theory is applied to the cubically nonlinear Schroedinger equation and is solved analytically in a special case.

  3. Polyphosphates strongly inhibit the tRNA dependent synthesis of poly(A) catalyzed by poly(A) polymerase from Saccharomyces cerevisiae.

    PubMed

    Sillero, María A Günther; de Diego, Anabel; Silles, Eduardo; Osorio, Hugo; Sillero, Antonio

    2003-08-28

    Polyphosphates of different chain lengths (P(3), P(4), P(15), P(35)), (1 microM) inhibited 10, 60, 90 and 100%, respectively, the primer (tRNA) dependent synthesis of poly(A) catalyzed poly(A) polymerase from Saccharomyces cerevisiae. The relative inhibition evoked by p(4)A and P(4) (1 microM) was 40 and 60%, respectively, whereas 1 microM Ap(4)A was not inhibitory. P(4) and P(15) were assayed as inhibitors of the enzyme in the presence of (a) saturating tRNA and variable concentrations of ATP and (b) saturating ATP and variable concentrations of tRNA. In (a), P(4) and P(15) behaved as competitive inhibitors, with K(i) values of 0.5 microM and 0.2 microM, respectively. In addition, P(4) (at 1 microM) and P(15) (at 0.3 microM) changed the Hill coefficient (n(H)) from 1 (control) to about 1.3 and 1.6, respectively. In (b), the inhibition by P(4) and P(15) decreased V and modified only slightly the K(m) values of the enzyme towards tRNA. PMID:12935883

  4. HER2 signaling pathway activation and response of breast cancer cells to HER2-targeting agents is dependent strongly on the 3D microenvironment

    SciTech Connect

    Weigelt, Britta; Lo, Alvin T; Park, Catherine C; Gray, Joe W; Bissell, Mina J

    2009-07-27

    Development of effective and durable breast cancer treatment strategies requires a mechanistic understanding of the influence of the microenvironment on response. Previous work has shown that cellular signaling pathways and cell morphology are dramatically influenced by three-dimensional (3D) cultures as opposed to traditional two-dimensional (2D) monolayers. Here, we compared 2D and 3D culture models to determine the impact of 3D architecture and extracellular matrix (ECM) on HER2 signaling and on the response of HER2-amplified breast cancer cell lines to the HER2-targeting agents Trastuzumab, Pertuzumab and Lapatinib. We show that the response of the HER2-amplified AU565, SKBR3 and HCC1569 cells to these anti-HER2 agents was highly dependent on whether the cells were cultured in 2D monolayer or 3D laminin-rich ECM gels. Inhibition of {beta}1 integrin, a major cell-ECM receptor subunit, significantly increased the sensitivity of the HER2-amplified breast cancer cell lines to the humanized monoclonal antibodies Trastuzumab and Pertuzumab when grown in a 3D environment. Finally, in the absence of inhibitors, 3D cultures had substantial impact on HER2 downstream signaling and induced a switch between PI3K-AKT- and RAS-MAPKpathway activation in all cell lines studied, including cells lacking HER2 amplification and overexpression. Our data provide direct evidence that breast cancer cells are able to rapidly adapt to different environments and signaling cues by activating alternative pathways that regulate proliferation and cell survival, events that may play a significant role in the acquisition of resistance to targeted therapies.

  5. The Strong In Vivo Anti-Tumor Effect of the UIC2 Monoclonal Antibody Is the Combined Result of Pgp Inhibition and Antibody Dependent Cell-Mediated Cytotoxicity

    PubMed Central

    Szalóki, Gábor; Krasznai, Zoárd T.; Tóth, Ágnes; Vízkeleti, Laura; Szöll?si, Attila G.; Trencsényi, György; Lajtos, Imre; Juhász, István; Krasznai, Zoltán; Márián, Teréz; Balázs, Margit; Szabó, Gábor; Goda, Katalin

    2014-01-01

    P-glycoprotein (Pgp) extrudes a large variety of chemotherapeutic drugs from the cells, causing multidrug resistance (MDR). The UIC2 monoclonal antibody recognizes human Pgp and inhibits its drug transport activity. However, this inhibition is partial, since UIC2 binds only to 10–40% of cell surface Pgps, while the rest becomes accessible to this antibody only in the presence of certain substrates or modulators (e.g. cyclosporine A (CsA)). The combined addition of UIC2 and 10 times lower concentrations of CsA than what is necessary for Pgp inhibition when the modulator is applied alone, decreased the EC50 of doxorubicin (DOX) in KB-V1 (Pgp+) cells in vitro almost to the level of KB-3-1 (Pgp-) cells. At the same time, UIC2 alone did not affect the EC50 value of DOX significantly. In xenotransplanted severe combined immunodeficient (SCID) mice co-treated with DOX, UIC2 and CsA, the average weight of Pgp+ tumors was only ?10% of the untreated control and in 52% of these animals we could not detect tumors at all, while DOX treatment alone did not decrease the weight of Pgp+ tumors. These data were confirmed by visualizing the tumors in vivo by positron emission tomography (PET) based on their increased 18FDG accumulation. Unexpectedly, UIC2+DOX treatment also decreased the size of tumors compared to the DOX only treated animals, as opposed to the results of our in vitro cytotoxicity assays, suggesting that immunological factors are also involved in the antitumor effect of in vivo UIC2 treatment. Since UIC2 binding itself did not affect the viability of Pgp expressing cells, but it triggered in vitro cell killing by peripheral blood mononuclear cells (PBMCs), it is concluded that the impressive in vivo anti-tumor effect of the DOX-UIC2-CsA treatment is the combined result of Pgp inhibition and antibody dependent cell-mediated cytotoxicity (ADCC). PMID:25238617

  6. Molecular rotational excitation by strong femtosecond laser pulses.

    PubMed

    Wu, Chengyin; Zeng, Guiping; Jiang, Hongyan; Gao, Yunan; Xu, Nan; Gong, Qihuang

    2009-10-01

    We study the rotational wave packet created by nonadiabatic rotational excitation of molecules with strong femtosecond laser pulses. The applicable condition of the Delta-Kick method is obtained by comparing the laser intensity and pulse duration dependences of the wave packet calculated with different methods. The wave packet evolution is traced analytically with the Delta-Kick method. The calculations demonstrate that the rotational populations can be controlled for the rotational wave packet created by two femtosecond laser pulses. The evolution of the rotational wave packet with controlled populations produces interference patterns with exotic spatial symmetries. These calculations are validated by comparing the theoretical calculations with our experimental measurements for the rotational wave packet created by thermal ensemble CO(2) and two strong femtosecond laser pulses. Potential applications in molecular science are also discussed for the rotational wave packet with controlled populations and spatial symmetries. PMID:19746946

  7. Molecular Rotational Excitation by Strong Femtosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Wu, Chengyin; Zeng, Guiping; Jiang, Hongyan; Gao, Yunan; Xu, Nan; Gong, Qihuang

    2009-09-01

    We study the rotational wave packet created by nonadiabatic rotational excitation of molecules with strong femtosecond laser pulses. The applicable condition of the Delta-Kick method is obtained by comparing the laser intensity and pulse duration dependences of the wave packet calculated with different methods. The wave packet evolution is traced analytically with the Delta-Kick method. The calculations demonstrate that the rotational populations can be controlled for the rotational wave packet created by two femtosecond laser pulses. The evolution of the rotational wave packet with controlled populations produces interference patterns with exotic spatial symmetries. These calculations are validated by comparing the theoretical calculations with our experimental measurements for the rotational wave packet created by thermal ensemble CO2 and two strong femtosecond laser pulses. Potential applications in molecular science are also discussed for the rotational wave packet with controlled populations and spatial symmetries.

  8. Strongly driven laser-plasma coupling

    NASA Astrophysics Data System (ADS)

    Kruer, W. L.; Campbell, E. M.; Decker, C. D.; Wilks, S. C.; Moody, J.; Orzechowski, T.; Powers, L.; Suter, L. J.; Afeyan, B. B.; Dague, N.

    1999-03-01

    An improved understanding of strongly driven laser-plasma coupling is important for optimal use of the National Ignition Facility (NIF) for both inertial fusion and for a variety of advanced applications. Such applications range from high-energy x-ray sources and high-temperature hohlraums to fast ignition and laser radiography. We discuss a novel model for the scaling of strongly driven stimulated Brillouin and Raman scattering. This model postulates an intensity-dependent correlation length associated with spatial incoherence due to filamentation and stimulated forward scattering. We first describe the model and then relate it to a variety of experiments. Particular attention is paid to high-temperature hohlraum experiments, which exhibit low to modest stimulated Brillouin scattering even though this instability is strongly driven. We also briefly discuss the strongly nonlinear interaction physics for efficient generation of high-energy electrons either by irradiating a large plasma with near quarter-critical density or by irradiating overdense targets with ultra-intense laser light.

  9. Strong temperature dependence of the {ital c}-axis gap parameter of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} intrinsic Josephson junctions

    SciTech Connect

    Yurgens, A. [Department of Physics, Chalmers University of Technology, S-412 96, Goeteborg (Sweden)] [Department of Physics, Chalmers University of Technology, S-412 96, Goeteborg (Sweden); [P. L. Kapitza Institute for Physical Problems, ul. Kosygina 2, Moscow, 117334 (Russia); Winkler, D. [Department of Physics, Chalmers University of Technology, S-412 96, Goeteborg (Sweden)] [Department of Physics, Chalmers University of Technology, S-412 96, Goeteborg (Sweden); Zavaritsky, N.V. [P. L. Kapitza Institute for Physical Problems, ul. Kosygina 2, Moscow, 117334 (Russia)] [P. L. Kapitza Institute for Physical Problems, ul. Kosygina 2, Moscow, 117334 (Russia); Claeson, T. [Department of Physics, Chalmers University of Technology, S-412 96, Goeteborg (Sweden)] [Department of Physics, Chalmers University of Technology, S-412 96, Goeteborg (Sweden)

    1996-04-01

    Stacked series arrays of intrinsic Josephson tunnel junctions have been fabricated on the surfaces of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single crystals using photolithography and Ar-ion milling together with {ital in} {ital situ} monitoring of the resulting current-voltage ({ital I}-{ital V}) characteristics. The number of junctions in the stack (along the {ital c} axis) is varied from 1{endash}5 to {approximately}200 in a controlled way. Both Josephson coupling and multiple branches with well developed gap features are seen in the {ital I}-{ital V} dependences of the arrays at {ital T}{approx_lt}90 K. The gap parameter {Delta}{sub {ital c}} is 10{endash}13 meV at 4.2 K, which is approximately half the value reported in the literature. The temperature dependence of {Delta}{sub {ital c}} deviates strongly from the BCS one. Proximity induced superconductivity of the Bi-O layers may possibly explain both the reduced gap parameter and its temperature dependence. {copyright} {ital 1996 The American Physical Society.}

  10. Strong Invariance Principle for Dependent Random Fields

    E-print Network

    Paris-Sud XI, Université de

    , r 0 as r , such that for any pair of disjoint finite sets I, J Zd and any pair of bounded(f)Lip(g)(|I| |J|)r. (1.1) Here and below |V | stands for the cardinality of a finite set V, r = dist(I, J) = min random field with finite second moments satisfies (1.1), provided that the Cox-Grimmett coefficient r

  11. Stimulus- and state-dependence of systematic bias in spatial attention: additive effects of stimulus-size and time-on-task.

    PubMed

    Benwell, Christopher S Y; Harvey, Monika; Gardner, Stephanie; Thut, Gregor

    2013-03-01

    Systematic biases in spatial attention are a common finding. In the general population, a systematic leftward bias is typically observed (pseudoneglect), possibly as a consequence of right hemisphere dominance for visuospatial attention. However, this leftward bias can cross-over to a systematic rightward bias with changes in stimulus and state factors (such as line length and arousal). The processes governing these changes are still unknown. Here we tested models of spatial attention as to their ability to account for these effects. To this end, we experimentally manipulated both stimulus and state factors, while healthy participants performed a computerized version of a landmark task. State was manipulated by time-on-task (>1 h) leading to increased fatigue and a reliable left- to rightward shift in spatial bias. Stimulus was manipulated by presenting either long or short lines which was associated with a shift of subjective midpoint from a reliable leftward bias for long to a more rightward bias for short lines. Importantly, we found time-on-task and line length effects to be additive suggesting a common denominator for line bisection across all conditions, which is in disagreement with models that assume that bisection decisions in long and short lines are governed by distinct processes (Magnitude estimation vs Global/local distinction). Our findings emphasize the dynamic rather than static nature of spatial biases in midline judgement. They are best captured by theories of spatial attention positing that spatial bias is flexibly modulated, and subject to inter-hemispheric balance which can change over time or conditions to accommodate task demands or reflect fatigue. PMID:22270326

  12. Momentum Dependence of Superconducting Gap, Strong-Coupling Dispersion Kink, And Tightly Bound Cooper Pairs in the High-T(C)(Sr,Ba)(1-X)(K,Na)(X)Fe(2) As(2) Superconductors

    SciTech Connect

    Wray, L.; Qian, D.; Hsieh, D.; Xia, Y.; Li, L.; Checkelsky, J.G.; Pasupathy, A.; Gomes, K.K.; Parker, C.V.; Fedorov, A.V.; Chen, G.F.; Luo, J.L.; Yazdani, A.; Ong, N.P.; Wang, N.L.; Hasan, M.Z.

    2009-05-28

    We present a systematic angle-resolved photoemission spectroscopic study of the high-T{sub c} superconductor class (Sr/Ba){sub 1-x}K{sub x}Fe{sub 2}As{sub 2}. By utilizing a photon-energy-modulation contrast and scattering geometry we report the Fermi surface and the momentum dependence of the superconducting gap, {triangle}(k{open_square}). A prominent quasiparticle dispersion kink reflecting strong scattering processes is observed in a binding-energy range of 25--55 meV in the superconducting state, and the coherence length or the extent of the Cooper pair wave function is found to be about 20 {angstrom}, which is uncharacteristic of a superconducting phase realized by the BCS-phonon-retardation mechanism. The observed 40{+-}15 meV kink likely reflects contributions from the frustrated spin excitations in a J{sub 1}-J{sub 2} magnetic background and scattering from the soft phonons. Results taken collectively provide direct clues to the nature of the pairing potential including an internal phase-shift factor in the superconducting order parameter which leads to a Brillouin zone node in a strong-coupling setting.

  13. Self-focusing suppression in a system of two nonlinear media and a spatial filter

    SciTech Connect

    Garanin, S G; L'vov, L V; Sukharev, S A [Russian Federal Nuclear Center 'All-Russian Scientific Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod Region (Russian Federation); Epatko, I V; Serov, R V [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2007-12-31

    It is shown that the rate of development of spatial instability caused by small-scale self-focusing strongly depends on the mutual arrangement of nonlinear media and spatial filters in a setup. The expressions are obtained for the arrangement of elements providing the minimal growth rate of intensity fluctuations. The results of two-dimensional calculations confirm the efficiency of this method of suppressing small-scale self-focusing. (nonlinear optical phenomena)

  14. Spatially embedded growing small-world networks.

    PubMed

    Zitin, Ari; Gorowara, Alexander; Squires, Shane; Herrera, Mark; Antonsen, Thomas M; Girvan, Michelle; Ott, Edward

    2014-01-01

    Networks in nature are often formed within a spatial domain in a dynamical manner, gaining links and nodes as they develop over time. Motivated by the growth and development of neuronal networks, we propose a class of spatially-based growing network models and investigate the resulting statistical network properties as a function of the dimension and topology of the space in which the networks are embedded. In particular, we consider two models in which nodes are placed one by one in random locations in space, with each such placement followed by configuration relaxation toward uniform node density, and connection of the new node with spatially nearby nodes. We find that such growth processes naturally result in networks with small-world features, including a short characteristic path length and nonzero clustering. We find no qualitative differences in these properties for two different topologies, and we suggest that results for these properties may not depend strongly on the topology of the embedding space. The results do depend strongly on dimension, and higher-dimensional spaces result in shorter path lengths but less clustering. PMID:25395180

  15. TOR-dependent reduction in the expression level of Rrn3p lowers the activity of the yeast RNA Pol I machinery, but does not account for the strong inhibition of rRNA production

    PubMed Central

    Philippi, Anja; Steinbauer, Robert; Reiter, Alarich; Fath, Stephan; Leger-Silvestre, Isabelle; Milkereit, Philipp; Griesenbeck, Joachim; Tschochner, Herbert

    2010-01-01

    Ribosome biogenesis is tightly linked to cellular growth. A crucial step in the regulation of ribosomal RNA (rRNA) gene transcription is the formation of the complex between RNA polymerase I (Pol I) and the Pol I-dependent transcription factor Rrn3p. We found that TOR inactivation leads to proteasome-dependent degradation of Rrn3p and a strong reduction in initiation competent Pol I–Rrn3p complexes affecting yeast rRNA gene transcription. Using a mutant expressing non-degradable Rrn3p or a strain in which defined endogenous Rrn3p levels can be adjusted by the Tet-off system, we can demonstrate that Rrn3p levels influence the number of Pol I–Rrn3p complexes and consequently rRNA gene transcription. However, our analysis reveals that the dramatic reduction of rRNA synthesis in the immediate cellular response to impaired TOR signalling cannot be explained by the simple down-regulation of Rrn3p and Pol I–Rrn3p levels. PMID:20421203

  16. Spatial-visual skills and engineering design

    E-print Network

    Tseng, Tiffany

    2009-01-01

    The purpose of this study was to determine whether students with strong spatial-visual skills tend to design more complex mechanisms for the undergraduate course Design and Manufacturing I. The Purdue Spatial Visualization ...

  17. Strongly Driven Crystallization Processes in a Metallic Glass

    SciTech Connect

    LaGrange, T; Grummon, D S; Reed, B W; Browning, N D; King, W E; Campbell, G H

    2009-02-09

    The crystallization of amorphous NiTi thin films was studied in situ using pulsed laser heating in a dynamic transmission electron microscope. A single pulse can crystallize small areas of the film within 2 {micro}s. The crystallized volume fraction and morphology depend strongly on the laser energy, the laser spatial profile, and the heat transport in the film. As compared to slower furnace and continuous wave laser annealing, pulsed laser heating produces a dramatically different microstructure. Higher than expected crystallization rates were observed under pulsed irradiation that do not correlate with kinetic data obtained from the slow-heating crystallization experiments.

  18. Discovering fuzzy spatial association rules

    NASA Astrophysics Data System (ADS)

    Kacar, Esen; Cicekli, Nihan K.

    2002-03-01

    Discovering interesting, implicit knowledge and general relationships in geographic information databases is very important to understand and use these spatial data. One of the methods for discovering this implicit knowledge is mining spatial association rules. A spatial association rule is a rule indicating certain association relationships among a set of spatial and possibly non-spatial predicates. In the mining process, data is organized in a hierarchical manner. However, in real-world applications it may not be possible to construct a crisp structure for this data, instead some fuzzy structures should be used. Fuzziness, i.e. partial belonging of an item to more than one sub-item in the hierarchy, could be applied to the data itself, and also to the hierarchy of spatial relations. This paper shows that, strong association rules can be mined from large spatial databases using fuzzy concept and spatial relation hierarchies.

  19. Spatial Modulation of the NMR Properties of the Cuprates

    NASA Astrophysics Data System (ADS)

    Haase, J.; Slichter, C. P.; Stern, R.; Milling, C. T.; Hinks, D. G.

    2000-11-01

    Substantial temperature dependent spatial modulation of the O and Cu NMR parameters of La 1.85Sr 0.15CuO 4 from 10 K to 300K are reported. The length scale of the modulations is only a few lattice distances. Analysis of the planar oxygen lineshape shows that modulations of the Knight shift and quadrupole coupling are correlated. The Cu spectra reveal a strong modulation of chemical shift. Similar results on other cuprates indicate universality of these phenomena.

  20. Spatial ordering in InP\\/InGaP nanostructures

    Microsoft Academic Search

    J. R. R. Bortoleto; H. R. Gutiérrez; M. A. Cotta; J. Bettini; L. P. Cardoso; M. M. G. de Carvalho

    2003-01-01

    We report the observation of a spatially-ordered bidimensional array of self-assembled InP quantum dots grown on slightly In-rich InGaP layers. The alignment of InP dots is observed along [100] and [010] directions. This effect is enhanced when 2° off vicinal substrates are used; it is also strongly dependent on growth temperature. Our results suggest that the density and size of

  1. Spatial and temporal characterisations of the degradation of dissolved humic substances in freshwater lake

    Microsoft Academic Search

    Stefania Mazzuoli; Silvia Focardi; Luca Bracchini; Margherita Falcucci; Steven A. Loiselle; Claudio Rossi

    2005-01-01

    Dissolved organic matter (DOM) is a key component in freshwater ecosystems, strongly influencing the optical, chemical and biological environment. The influence of the organic material on lake water depends on the molecular characteristics of the compounds. In the present study, the spatial distribution of dissolved organic matter and humic concentrations was determined together with the indices for optical colour (a440)

  2. Transient dynamics and nonlinear stability of spatially extended systems Andreas Handel

    E-print Network

    Grigoriev, Roman

    Transient dynamics and nonlinear stability of spatially extended systems Andreas Handel Department can be misleading, especially when the dynamics of disturbances is characterized by strong transient of transient amplification. In what follows we show that the power law exponent sensitively depends on the type

  3. Robustness of spatial micronetworks.

    PubMed

    McAndrew, Thomas C; Danforth, Christopher M; Bagrow, James P

    2015-04-01

    Power lines, roadways, pipelines, and other physical infrastructure are critical to modern society. These structures may be viewed as spatial networks where geographic distances play a role in the functionality and construction cost of links. Traditionally, studies of network robustness have primarily considered the connectedness of large, random networks. Yet for spatial infrastructure, physical distances must also play a role in network robustness. Understanding the robustness of small spatial networks is particularly important with the increasing interest in microgrids, i.e., small-area distributed power grids that are well suited to using renewable energy resources. We study the random failures of links in small networks where functionality depends on both spatial distance and topological connectedness. By introducing a percolation model where the failure of each link is proportional to its spatial length, we find that when failures depend on spatial distances, networks are more fragile than expected. Accounting for spatial effects in both construction and robustness is important for designing efficient microgrids and other network infrastructure. PMID:25974553

  4. Robustness of spatial micronetworks

    NASA Astrophysics Data System (ADS)

    McAndrew, Thomas C.; Danforth, Christopher M.; Bagrow, James P.

    2015-04-01

    Power lines, roadways, pipelines, and other physical infrastructure are critical to modern society. These structures may be viewed as spatial networks where geographic distances play a role in the functionality and construction cost of links. Traditionally, studies of network robustness have primarily considered the connectedness of large, random networks. Yet for spatial infrastructure, physical distances must also play a role in network robustness. Understanding the robustness of small spatial networks is particularly important with the increasing interest in microgrids, i.e., small-area distributed power grids that are well suited to using renewable energy resources. We study the random failures of links in small networks where functionality depends on both spatial distance and topological connectedness. By introducing a percolation model where the failure of each link is proportional to its spatial length, we find that when failures depend on spatial distances, networks are more fragile than expected. Accounting for spatial effects in both construction and robustness is important for designing efficient microgrids and other network infrastructure.

  5. Three-Dimensional Hermite—Bessel—Gaussian Soliton Clusters in Strongly Nonlocal Media

    NASA Astrophysics Data System (ADS)

    Jin, Hai-Qin; Liang, Jian-Chu; Cai, Ze-Bin; Liu, Fei; Yi, Lin

    2012-12-01

    We analytically and numerically demonstrate the existence of Hermite—Bessel—Gaussian spatial soliton clusters in three-dimensional strongly nonlocal media. It is found that the soliton clusters display the vortex, dipole azimuthon and quadrupole azimuthon in geometry, and the total number of solitons in the necklaces depends on the quantum number n and m of the Hermite functions and generalized Bessel polynomials. The numerical simulation is basically identical to the analytical solution, and white noise does not lead to collapse of the soliton, which confirms the stability of the soliton waves. The theoretical predictions may give new insights into low-energetic spatial soliton transmission with high fidelity.

  6. Phase states of a 2D easy-plane ferromagnet with strong inclined anisotropy

    SciTech Connect

    Fridman, Yu. A., E-mail: frid@tnu.crimea.ua; Klevets, F. N.; Gorelikov, G. A.; Meleshko, A. G. [Vernadskii Tavria National University (Ukraine)

    2012-12-15

    We investigate the spin states of a 2D film exhibiting easy-axis anisotropy and a strong single-ion inclined anisotropy whose axis forms a certain angle with the normal to the film surface. Such a system may have an angular ferromagnetic phase, a spatially inhomogeneous state, and a quadrupole phase, whose realization depends substantially on the inclined anisotropy and the orientation of the wavevector in the film plane.

  7. The spatial scaling of habitat selection by African elephants.

    PubMed

    de Knegt, Henrik J; van Langevelde, Frank; Skidmore, Andrew K; Delsink, Audrey; Slotow, Rob; Henley, Steve; Bucini, Gabriela; de Boer, Willem F; Coughenour, Michael B; Grant, Cornelia C; Heitkönig, Ignas M A; Henley, Michelle; Knox, Nicky M; Kohi, Edward M; Mwakiwa, Emmanuel; Page, Bruce R; Peel, Mike; Pretorius, Yolanda; van Wieren, Sipke E; Prins, Herbert H T

    2011-01-01

    1. Understanding and accurately predicting the spatial patterns of habitat use by organisms is important for ecological research, biodiversity conservation and ecosystem management. However, this understanding is complicated by the effects of spatial scale, because the scale of analysis affects the quantification of species-environment relationships. 2. We therefore assessed the influence of environmental context (i.e. the characteristics of the landscape surrounding a site), varied over a large range of scales (i.e. ambit radii around focal sites), on the analysis and prediction of habitat selection by African elephants in Kruger National Park, South Africa. 3. We focused on the spatial scaling of the elephants' response to their main resources, forage and water, and found that the quantification of habitat selection strongly depended on the scales at which environmental context was considered. Moreover, the inclusion of environmental context at characteristic scales (i.e. those at which habitat selectivity was maximized) increased the predictive capacity of habitat suitability models. 4. The elephants responded to their environment in a scale-dependent and perhaps hierarchical manner, with forage characteristics driving habitat selection at coarse spatial scales, and surface water at fine spatial scales. 5. Furthermore, the elephants exhibited sexual habitat segregation, mainly in relation to vegetation characteristics. Male elephants preferred areas with high tree cover and low herbaceous biomass, whereas this pattern was reversed for female elephants. 6. We show that the spatial distribution of elephants can be better understood and predicted when scale-dependent species-environment relationships are explicitly considered. This demonstrates the importance of considering the influence of spatial scale on the analysis of spatial patterning in ecological phenomena. PMID:21054380

  8. Toll-like receptor ligands sensitize B-cell receptor signalling by reducing actin-dependent spatial confinement of the receptor

    PubMed Central

    Freeman, Spencer A.; Jaumouillé, Valentin; Choi, Kate; Hsu, Brian E.; Wong, Harikesh S.; Abraham, Libin; Graves, Marcia L.; Coombs, Daniel; Roskelley, Calvin D.; Das, Raibatak; Grinstein, Sergio; Gold, Michael R.

    2015-01-01

    Integrating signals from multiple receptors allows cells to interpret the physiological context in which a signal is received. Here we describe a mechanism for receptor crosstalk in which receptor-induced increases in actin dynamics lower the threshold for signalling by another receptor. We show that the Toll-like receptor ligands lipopolysaccharide and CpG DNA, which are conserved microbial molecules, enhance signalling by the B-cell antigen receptor (BCR) by activating the actin-severing protein cofilin. Single-particle tracking reveals that increased severing of actin filaments reduces the spatial confinement of the BCR within the plasma membrane and increases BCR mobility. This allows more frequent collisions between BCRs and greater signalling in response to low densities of membrane-bound antigen. These findings implicate actin dynamics as a means of tuning receptor signalling and as a mechanism by which B cells distinguish inert antigens from those that are accompanied by indicators of microbial infection. PMID:25644899

  9. THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 7 SPECTROSCOPIC M DWARF CATALOG. III. THE SPATIAL DEPENDENCE OF MAGNETIC ACTIVITY IN THE GALAXY

    SciTech Connect

    Sebastian Pineda, J. [Department of Astronomy, California Institute of Technology, 1200 E. California Avenue, Pasadena, CA 91125 (United States); West, Andrew A. [Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Bochanski, John J. [Department of Physics and Astronomy, Haverford College, 370 Lancaster Avenue, Haverford, PA 19041 (United States); Burgasser, Adam J., E-mail: jspineda@astro.caltech.edu [Center of Astrophysics and Space Sciences, Department of Physics, University of California, San Diego, CA 92093 (United States)

    2013-09-15

    We analyze the magnetic activity of 59,318 M dwarfs from the Sloan Digital Sky Survey Data Release 7. This analysis explores the spatial distribution of M dwarf activity as a function of both vertical distance from the Galactic plane (Z) and planar distance from the Galactic center (R). We confirm the established trends of decreasing magnetic activity (as measured by H{alpha} emission) with increasing distance from the mid-plane of the disk and find evidence of a trend in Galactocentric radii. We measure a non-zero radial gradient in the activity fraction in our analysis of stars with spectral types dM3 and dM4. The activity fraction increases with R and can be explained by a decreasing mean stellar age with increasing distance from the Galactic center.

  10. The Sloan Digital Sky Survey Data Release 7 Spectroscopic M Dwarf Catalog. III. The Spatial Dependence of Magnetic Activity in the Galaxy

    NASA Astrophysics Data System (ADS)

    Pineda, J. Sebastian; West, Andrew A.; Bochanski, John J.; Burgasser, Adam J.

    2013-09-01

    We analyze the magnetic activity of 59,318 M dwarfs from the Sloan Digital Sky Survey Data Release 7. This analysis explores the spatial distribution of M dwarf activity as a function of both vertical distance from the Galactic plane (Z) and planar distance from the Galactic center (R). We confirm the established trends of decreasing magnetic activity (as measured by H? emission) with increasing distance from the mid-plane of the disk and find evidence of a trend in Galactocentric radii. We measure a non-zero radial gradient in the activity fraction in our analysis of stars with spectral types dM3 and dM4. The activity fraction increases with R and can be explained by a decreasing mean stellar age with increasing distance from the Galactic center.

  11. Flavin-dependent alcohol oxidase from the yeast Pichia pinus. Spatial localization of the coenzyme FAD in the protein structure: hot-tritium bombardment and ESR experiments.

    PubMed Central

    Averbakh, A Z; Pekel, N D; Seredenko, V I; Kulikov, A V; Gvozdev, R I; Rudakova, I P

    1995-01-01

    The spatial localization of the coenzyme FAD in the quaternary structure of the alcohol oxidase from the yeast Pichia pinus was studied by tritium planigraphy and ESR methods. In the present paper we measured the specific radioactivity of FAD labelled as a part of the alcohol oxidase complex. The specific-radioactivity ratio for two FAD portions (FMN and AMP) was calculated. ESR experiments show 4 A (0.4 nm) to be the depth of immersion of paramagnetic isoalloxazines into alcohol oxidase octamer molecules. It is suggested that FAD molecules are bound to the surface of the octamer, rather than to the subunit interfaces. The orientation of the prosthetic group FAD in the alcohol oxidase protein is discussed. PMID:7654201

  12. STRONG FERTILITY CENTER Strong Fertility Center

    E-print Network

    Goldman, Steven A.

    STRONG FERTILITY CENTER Strong Fertility Center Women's Lifestyle Center The Women's Lifestyle with the improved lifestyle. Also, we work together with the Strong Fertility Center to coordinate your fertility fertility treatments. · A complete nutritional consultation with our registered dietician, Tracy Cherry, RD

  13. Topographic Controls on Spatial Patterns of Soil Texture and Moisture in a Semi-arid Montane Catchment with Aspect-Dependent Vegetation

    NASA Astrophysics Data System (ADS)

    Lehman, B. M.; Niemann, J. D.

    2008-12-01

    Soil moisture exerts significant control over the partitioning of latent and sensible energy fluxes, the magnitude of both vertical and lateral water fluxes, the physiological and water-use characteristics of vegetation, and nutrient cycling. Considerable progress has been made in determining how soil characteristics, topography, and vegetation influence spatial patterns of soil moisture in humid environments at the catchment, hillslope, and plant scales. However, understanding of the controls on soil moisture patterns beyond the plant scale in semi-arid environments remains more limited. This study examines the relationships between the spatial patterns of near surface soil moisture (upper 5 cm), terrain indices, and soil properties in a small, semi-arid, montane catchment. The 8 ha catchment, located in the Cache La Poudre River Canyon in north-central Colorado, has a total relief of 115 m and an average elevation of 2193 m. It is characterized by steep slopes and shallow, gravelly/sandy soils with scattered granite outcroppings. Depth to bedrock ranges from 0 m to greater than 1 m. Vegetation in the catchment is highly correlated with topographic aspect. In particular, north-facing hillslopes are predominately vegetated by ponderosa pines, while south-facing slopes are mostly vegetated by several shrub species. Soil samples were collected at a 30 m resolution to characterize soil texture and bulk density, and several datasets consisting of more than 300 point measurements of soil moisture were collected using time domain reflectometry (TDR) between Fall 2007 and Summer 2008 at a 15 m resolution. Results from soil textural analysis performed with sieving and the ASTM standard hydrometer method show that soil texture is finer on the north-facing hillslope than on the south-facing hillslope. Cos(aspect) is the best univariate predictor of silts, while slope is the best predictor of coarser fractions up to fine gravel. Bulk density increases with depth but shows no significant relationship with topographic indices. When the catchment average soil moisture is low, the variance of soil moisture increases with the average. When the average is high, the variance remains relatively constant. Little of the variation in soil moisture is explained by topographic indices when the catchment is either very wet or dry; however, when the average soil moisture takes on intermediate values, cos(aspect) is consistently the best predictor among the terrain indices considered.

  14. Spatial Modes of a Squeezed Vacuum Field

    NASA Astrophysics Data System (ADS)

    Zhang, Mi; Lanning, R. Nicholas; Xiao, Zhihao; Dowling, Jonathan P.; Novikova, Irina; Mikhailov, Eugeniy E.

    2015-03-01

    We prepared a quantum noise suppressed squeezed vacuum field by propagating a beam with a wavelength of 795nm through a hot Rb cell. Observation of the quadrature noise showed that we achieved a noise suppression of -2.0 dB below the quantum noise limit. When a spatial mask was applied to the beam after its interaction with atoms, we observed that the detected quantum noise suppression strongly depended on the shape of the mask. An exploration of the spatial distribution of noise in the squeezed field illustrated that the squeezed field was in a different spatial mode from the pump field used as a local oscillator. Our research showed that the squeezed field consisted of several spatial modes with various squeezing parameters. If a pure squeezed mode could be extracted, it would enhance the signal to noise ratio, which would impact precision metrology and quantum memory applications. This project is supported by AFOSR Grant FA9550-13-1-0098.

  15. Kinematics of Strong Discontinuities

    NASA Technical Reports Server (NTRS)

    Peterson, K.; Nguyen, G.; Sulsky, D.

    2006-01-01

    Synthetic Aperture Radar (SAR) provides a detailed view of the Arctic ice cover. When processed with the RADARSAT Geophysical Processor System (RGPS), it provides estimates of sea ice motion and deformation over large regions of the Arctic for extended periods of time. The deformation is dominated by the appearance of linear kinematic features that have been associated with the presence of leads. The RGPS deformation products are based on the assumption that the displacement and velocity are smooth functions of the spatial coordinates. However, if the dominant deformation of multiyear ice results from the opening, closing and shearing of leads, then the displacement and velocity can be discontinuous. This presentation discusses the kinematics associated with strong discontinuities that describe possible jumps in displacement or velocity. Ice motion from SAR data are analyzed using this framework. It is assumed that RGPS cells deform due to the presence of a lead. The lead orientation is calculated to optimally account for the observed deformation. It is shown that almost all observed deformation can be represented by lead opening and shearing. The procedure used to reprocess motion data to account for leads will be described and applied to regions of the Beaufort Sea. The procedure not only provides a new view of ice deformation, it can be used to obtain information about the presence of leads for initialization and/or validation of numerical simulations.

  16. Lateral inhibition between spatially adjacent spatial-frequency channels?

    Microsoft Academic Search

    Dov Sagi; Shaul Hochstein

    1985-01-01

    A new lateral inhibitory phenomenon is suggested between spatially neighboring channels that detect similar spatial frequencies.\\u000a This mechanism tends to enhance the apparent contrast of gratings at their boundaries, and Mach-band-type effects are demonstrated\\u000a at the edge of a suprathreshold half-field grating. We studied the dependence of this effect on the grating parameters of\\u000a spatial frequency and contrast. The grating

  17. Spatial Displays and Spatial Instruments

    NASA Technical Reports Server (NTRS)

    Ellis, Stephen R. (editor); Kaiser, Mary K. (editor); Grunwald, Arthur J. (editor)

    1989-01-01

    The conference proceedings topics are divided into two main areas: (1) issues of spatial and picture perception raised by graphical electronic displays of spatial information; and (2) design questions raised by the practical experience of designers actually defining new spatial instruments for use in new aircraft and spacecraft. Each topic is considered from both a theoretical and an applied direction. Emphasis is placed on discussion of phenomena and determination of design principles.

  18. Local root abscisic acid (ABA) accumulation depends on the spatial distribution of soil moisture in potato: implications for ABA signalling under heterogeneous soil drying

    PubMed Central

    Puértolas, Jaime; Conesa, María R.; Ballester, Carlos; Dodd, Ian C.

    2015-01-01

    Patterns of root abscisic acid (ABA) accumulation ([ABA]root), root water potential (?root), and root water uptake (RWU), and their impact on xylem sap ABA concentration ([X-ABA]) were measured under vertical partial root-zone drying (VPRD, upper compartment dry, lower compartment wet) and horizontal partial root-zone drying (HPRD, two lateral compartments: one dry, the other wet) of potato (Solanum tuberosum L.). When water was withheld from the dry compartment for 0–10 d, RWU and ?root were similarly lower in the dry compartment when soil volumetric water content dropped below 0.22cm3 cm–3 for both spatial distributions of soil moisture. However, [ABA]root increased in response to decreasing ?root in the dry compartment only for HPRD, resulting in much higher ABA accumulation than in VPRD. The position of the sampled roots (~4cm closer to the surface in the dry compartment of VPRD than in HPRD) might account for this difference, since older (upper) roots may accumulate less ABA in response to decreased ?root than younger (deeper) roots. This would explain differences in root ABA accumulation patterns under vertical and horizontal soil moisture gradients reported in the literature. In our experiment, these differences in root ABA accumulation did not influence [X-ABA], since the RWU fraction (and thus ABA export to shoots) from the dry compartment dramatically decreased simultaneously with any increase in [ABA]root. Thus, HPRD might better trigger a long-distance ABA signal than VPRD under conditions allowing simultaneous high [ABA]root and relatively high RWU fraction. PMID:25547916

  19. The Organization of High-Affinity Ammonium Uptake in Arabidopsis Roots Depends on the Spatial Arrangement and Biochemical Properties of AMT1-Type Transporters[W

    PubMed Central

    Yuan, Lixing; Loqué, Dominique; Kojima, Soichi; Rauch, Sabine; Ishiyama, Keiki; Inoue, Eri; Takahashi, Hideki; von Wirén, Nicolaus

    2007-01-01

    The AMMONIUM TRANSPORTER (AMT) family comprises six isoforms in Arabidopsis thaliana. Here, we describe the complete functional organization of root-expressed AMTs for high-affinity ammonium uptake. High-affinity influx of 15N-labeled ammonium in two transposon-tagged amt1;2 lines was reduced by 18 to 26% compared with wild-type plants. Enrichment of the AMT1;2 protein in the plasma membrane and localization of AMT1;2 promoter activity in the endodermis and root cortex indicated that AMT1;2 mediates the uptake of ammonium entering the root via the apoplasmic transport route. An amt1;1 amt1;2 amt1;3 amt2;1 quadruple mutant (qko) showed severe growth depression under ammonium supply and maintained only 5 to 10% of wild-type high-affinity ammonium uptake capacity. Transcriptional upregulation of AMT1;5 in nitrogen-deficient rhizodermal and root hair cells and the ability of AMT1;5 to transport ammonium in yeast suggested that AMT1;5 accounts for the remaining uptake capacity in qko. Triple and quadruple amt insertion lines revealed in vivo ammonium substrate affinities of 50, 234, 61, and 4.5 ?M for AMT1;1, AMT1;2, AMT1;3, and AMT1;5, respectively, but no ammonium influx activity for AMT2;1. These data suggest that two principle means of achieving effective ammonium uptake in Arabidopsis roots are the spatial arrangement of AMT1-type ammonium transporters and the distribution of their transport capacities at different substrate affinities. PMID:17693533

  20. The Strong Distance Problems

    Microsoft Academic Search

    Justie Su-tzu Juan; Chun-ming Huang

    2004-01-01

    Suppose G = (V,E) is a graph and D = (V,F) is a strong orientation of G. Let u,v ? V, the strong distance sd(u,v) is the minimum size of strong subdigraph of D containing u and v, the strong eccentricity se(u) is the maximum strong distance sd(u,v) between u and v for all v ? V. The strong radius

  1. Spatial Concepts and Spatial Reasoning in the Social Sciences

    E-print Network

    Fabrikant, Sara Irina

    to measure understanding, learning, & skill development spatial@ucsb Focus: · Geospatial concepts in social: · Identify fundamental geospatial concepts · Context dependent applications (re: disciplines, theory;Geospatial Concepts in the Social Sciences · Location ­ Understanding formal & informal methods of specifying

  2. Spin-dependent transport in waveguides with spatially modulated strengths of the Rashba and Dresselhaus terms of the spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Krstaji?, P. M.; Rezasoltani, E.; Vasilopoulos, P.

    2010-04-01

    We study electron transport through waveguides (WGs) in which the strengths of the Rashba (?) and Dresselhaus (?) terms of the spin-orbit interaction (SOI) vary in space. Subband mixing, due to lateral confinement, is taken into account only between the two first subbands. For sufficiently narrow WGs the transmission T exhibits a squarelike shape as a function of ? or ? . Particular attention is paid to the case of equal SOI strengths, ?=? , for which spin-flip processes are expected to decrease. The transmission exhibits resonances as a function of the length of a SOI-free region separating two regions with SOI present, that are most pronounced for ?=? . The sign of ? strongly affects the spin-up and spin-down transmissions. The results show that the main effect of subband mixing is to shift the transmission resonances and to decrease the transmission from one spin state to another. The effect of possible band offsets between regions that have different SOI strengths and effective masses is also discussed.

  3. Near-Front Wave Profile on Shallow Water over a Rapidly Oscillating Bottom Generated by Time-Dependent Spatially Localized Source

    NASA Astrophysics Data System (ADS)

    Dobrokhotov, S.

    2012-04-01

    We consider the 2D wave equation with rapidly oscillating velocity and time-dependent right-hand side vanishing for large time and localized in a neighborhood of some point of the physical plane. We present asymptotic formulas describing the solutions of this problem and connecting the solution profile with the form of the right-hand side source. We show that for some specific sources these formulas can be expressed via special functions like the Airy functions Ai and Bi, Erf, Erfc, etc., which allow one to analyze the oscillations near the front generated by the bottom oscillation and time-oscillation of the source. We compare these oscillations with the oscillations due to water wave dispersion. Applications to tsunami wave propagation are discussed. This work was done together with B. Tirozzi and V. Nazaikinskii and was supported by RFBR grants nos. 11-01-00973 and 09-01-12063.

  4. Decrease in highly polysialylated neuronal cell adhesion molecules and in spatial learning during ageing are not correlated

    Microsoft Academic Search

    D. N. Abrous; M. F. Montaron; K. G. Petry; G. Rougon; M. Darnaudery; M. Le Moal; W. Mayo

    1997-01-01

    Age-dependent spatial memory impairments have been related to a decline in hippocampal plasticity. Highly polysialylated neuronal cell adhesion molecules (PSA-NCAM) show a strong expression during adulthood within regions associated with neuroplastic events. Furthermore, NCAM molecules have been proposed to mediate neuronal plasticity during learning and memory. The aim of the present study was to examine the effect of ageing on

  5. Coupled-cluster theory of a gas of strongly-interacting electrons in the dilute limit

    SciTech Connect

    Mihaila, Bodgan [Los Alamos National Laboratory; Cardenas, Andres L [Los Alamos National Laboratory

    2008-01-01

    We study the ground-state properties of a dilute gas of strongly-interacting fermions in the framework of the coupled-cluster expansion (CCE). We demonstrate that properties such as universality, opening of a gap in the excitation spectrum and applicability of s-wave approximations appear naturally in the CCE approach. In the zero-density limit, we show that the ground-state energy density depends on only one parameter which in turn may depend at most on the spatial dimensionality of the system.

  6. Relationships Between Tillage and Spatial Patterns of Heterodera glycines.

    PubMed

    Gavassoni, W L; Tylka, G L; Munkvold, G P

    2001-06-01

    ABSTRACT The dynamics of Heterodera glycines spatial patterns were studied under different tillage systems in two naturally infested soybean fields in Iowa from 1994 to 1997. At each location, there were four different tillage treatments (conventional tillage, reduced tillage, ridge tillage, and no tillage). Soil samples were taken from 98 contiguous quadrats (5.2 m(2)) per plot in the fall of 1994, before any tillage was performed, and in the spring of the following 3 years shortly after planting. Cysts were extracted from soil samples by elutriation and counted, and eggs were extracted from cysts and enumerated. Spatial patterns of H. glycines populations were characterized by geostatistical analysis and variance-to-mean (VM) ratios. Semivariance values were calculated for cyst and egg densities and semivariograms were constructed. In general, there was greater spatial dependence among cyst populations than egg populations. In one field with a strongly aggregated initial H. glycines population, tillage practices resulted in changes in spatial patterns of H. glycines populations, characterized by spherical-model semivariogram parameters (sill, nugget effect, and range of spatial dependence). These parameters indicated increasing aggregation over time in no tillage and ridge tillage treatments, but decreasing aggregation in reduced and conventional tillage treatments. There was an increase of 350% in sill values (maximum semivariance) for cyst populations after 3 years of no tillage, but in the conventional tillage treatment, sill values remained unchanged or decreased over time as tillage was implemented. Semivariograms for cyst and egg population densities revealed strong anisotropy (directional spatial dependence) along soybean rows, coincident with the direction of tillage practices. VM ratios for cyst counts increased each year in the no tillage and ridge tillage treatments, but decreased for 2 years in reduced tillage and conventional tillage treatments. Final VM ratios for cyst and egg counts were highest in the no tillage treatment. In a second field, with low initial aggregation of H. glycines populations, there was little measurable change in semivariogram parameters after 3 years of no tillage, but in the conventional tillage treatment, populations became less aggregated, as the range, sill, and the proportion of the sill explained by spatial dependence decreased for cyst population densities. Our results indicated that in soybean fields with initially aggregated populations of H. glycines, no tillage and ridge tillage systems promoted aggregation of the nematode population, whereas conventional and reduced tillage systems resulted in a less aggregated spatial pattern. PMID:18943941

  7. High-resolution delineation of chlorinated volatile organic compounds in a dipping, fractured mudstone: depth- and strata-dependent spatial variability from rock-core sampling

    USGS Publications Warehouse

    Goode, Daniel J.; Imbrigiotta, Thomas E.; Lacombe, Pierre J.

    2014-01-01

    Synthesis of rock-core sampling and chlorinated volatile organic compound (CVOC) analysis at five coreholes, with hydraulic and water-quality monitoring and a detailed hydrogeologic framework, was used to characterize the fine-scale distribution of CVOCs in dipping, fractured mudstones of the Lockatong Formation of Triassic age, of the Newark Basin in West Trenton, New Jersey. From these results, a refined conceptual model for more than 55 years of migration of CVOCs and depth- and strata-dependent rock-matrix contamination was developed. Industrial use of trichloroethene (TCE) at the former Naval Air Warfare Center (NAWC) from 1953 to 1995 resulted in dense non-aqueous phase liquid (DNAPL) TCE and dissolved TCE and related breakdown products, including other CVOCs, in underlying mudstones. Shallow highly weathered and fractured strata overlie unweathered, gently dipping, fractured strata that become progressively less fractured with depth. The unweathered lithology includes black highly fractured (fissile) carbon-rich strata, gray mildly fractured thinly layered (laminated) strata, and light-gray weakly fractured massive strata. CVOC concentrations in water samples pumped from the shallow weathered and highly fractured strata remain elevated near residual DNAPL TCE, but dilution by uncontaminated recharge, and other natural and engineered attenuation processes, have substantially reduced concentrations along flow paths removed from sources and residual DNAPL. CVOCs also were detected in most rock-core samples in source areas in shallow wells. In many locations, lower aqueous concentrations, compared to rock core concentrations, suggest that CVOCs are presently back-diffusing from the rock matrix. Below the weathered and highly fractured strata, and to depths of at least 50 meters (m), groundwater flow and contaminant transport is primarily in bedding-plane-oriented fractures in thin fissile high-carbon strata, and in fractured, laminated strata of the gently dipping mudstones. Despite more than 18 years of pump and treat (P&T) remediation, and natural attenuation processes, CVOC concentrations in aqueous samples pumped from these deeper strata remain elevated in isolated intervals. DNAPL was detected in one borehole during coring at a depth of 27 m. In contrast to core samples from the weathered zone, concentrations in core samples from deeper unweathered and unfractured strata are typically below detection. However, high CVOC concentrations were found in isolated samples from fissile black carbon-rich strata and fractured gray laminated strata. Aqueous-phase concentrations were correspondingly high in samples pumped from these strata via short-interval wells or packer-isolated zones in long boreholes. A refined conceptual site model considers that prior to P&T remediation groundwater flow was primarily subhorizontal in the higher-permeability near surface strata, and the bulk of contaminant mass was shallow. CVOCs diffused into these fractured and weathered mudstones. DNAPL and high concentrations of CVOCs migrated slowly down in deeper unweathered strata, primarily along isolated dipping bedding-plane fractures. After P&T began in 1995, using wells open to both shallow and deep strata, downward transport of dissolved CVOCs accelerated. Diffusion of TCE and other CVOCs from deeper fractures penetrated only a few centimeters into the unweathered rock matrix, likely due to sorption of CVOCs on rock organic carbon. Remediation in the deep, unweathered strata may benefit from the relatively limited migration of CVOCs into the rock matrix. Synthesis of rock core sampling from closely spaced boreholes with geophysical logging and hydraulic testing improves understanding of the controls on CVOC delineation and informs remediation design and monitoring.

  8. Phase transitions driven by state-dependent poisson noise.

    PubMed

    Porporato, Amilcare; D'Odorico, Paolo

    2004-03-19

    Nonlinear systems driven by state-dependent Poisson noise are introduced to model the persistence of climatic anomalies in land-atmosphere interaction caused by the soil-moisture dependence of the frequency of rainfall events. It is found that these systems may give rise to bimodal probability distributions, while the state variable randomly persists around the preferential states because of transient dynamics that are opposite to the long-term behavior. Mean-field analysis and numerical simulations of the spatially distributed systems reveal a symmetry-breaking bifurcation for sufficiently strong spatial diffusive couplings and intermediate noise intensities. In such conditions, the initial development of spatial patterns is followed by a stable configuration, selected on the bases of the initial conditions in correspondence of the remnants of the modes of the uncoupled system. PMID:15089118

  9. SPATIAL TRANSFORMATIONS 1 Running head: Spatial transformations

    E-print Network

    Zacks, Jeffrey M.

    SPATIAL TRANSFORMATIONS 1 Running head: Spatial transformations Multiple Systems for Spatial Imagery: Transformations of Objects and Bodies Jeffrey M. Zacks* and Barbara Tversky * Washington COGNITION & COMPUTATION #12;SPATIAL TRANSFORMATIONS 2 Abstract Problem-solving often requires imagining

  10. Physically-based modeling of topographic effects on spatial evapotranspiration and soil moisture patterns through radiation and wind

    NASA Astrophysics Data System (ADS)

    Liu, M.; Bárdossy, A.; Li, J.; Jiang, Y.

    2012-02-01

    In this paper, simulations with the Soil Water Atmosphere Plant (SWAP) model are performed to quantify the spatial variability of both potential and actual evapotranspiration (ET), and soil moisture content (SMC) caused by topography-induced spatial wind and radiation differences. To obtain the spatially distributed ET/SMC patterns, the field scale SWAP model is applied in a distributed way for both pointwise and catchment wide simulations. An adapted radiation model from r.sun and the physically-based meso-scale wind model METRAS PC are applied to obtain the spatial radiation and wind patterns respectively, which show significant spatial variation and correlation with aspect and elevation respectively. Such topographic dependences and spatial variations further propagate to ET/SMC. A strong spatial, seasonal-dependent, scale-relevant intra-catchment variability in daily/annual ET and less variability in SMC can be observed from the numerical experiments. The study concludes that topography has a significant effect on ET/SMC in the humid region where ET is a energy limited rather than water availability limited process. It affects the spatial runoff generation through spatial radiation and wind, therefore should be applied to inform hydrological model development. In addition, the methodology used in the study can serve as a general method for physically-based ET estimation for data sparse regions.

  11. Spatial anxiety relates to spatial abilities as a function of working memory in children

    Microsoft Academic Search

    Gerardo Ramirez; Elizabeth A. Gunderson; Susan C. Levine; Sian L. Beilock

    2012-01-01

    Spatial ability is a strong predictor of students' pursuit of higher education in science and mathematics. However, very little is known about the affective factors that influence individual differences in spatial ability, particularly at a young age. We examine the role of spatial anxiety in young children's performance on a mental rotation task. We show that even at a young

  12. Dynamical properties of strongly interacting Markov chains

    Microsoft Academic Search

    Nihat Ay; Thomas Wennekers

    2003-01-01

    Spatial interdependences of multiple stochastic units can be suitably quantified by the Kullback–Leibler divergence of the joint probability distribution from the corresponding factorized distribution. In the present paper, a generalized measure for stochastic interaction, which also captures temporal interdependences, is analysed within the setting of Markov chains. The dynamical properties of systems with strongly interacting stochastic units are analytically studied

  13. Spatial interpolation of precipitation distributions using copulas

    NASA Astrophysics Data System (ADS)

    Bàrdossy, Andràs; Pegram, Geoffrey

    2013-04-01

    The interpolation of precipitation distributions is important for example for climatological studies, interpolation of precipitation on different time scales and extreme value analyses. Spatial interpolation requires a certain degree of spatial continuity. This is in our case measured with the help of a Cramer- von Mises type statistic. Examples of daily precipitation measured over 4 regions with the number of stations ranging from 222 to 748 in South Germany, show a high degree of spatial continuity of the distributions. As a further step, the interpolation itself can be carried out by interpolating • The parameters of fitted Gamma or Weibull (or other appropriate) distributions • The moments of the distributions with a subsequent fit of parametric distributions • The quantiles of the distributions directly The interdependence between the variables to be interpolated makes this task extremely difficult in all three of the above cases. However a straightforward analysis of the higher quantiles shows that their interdependence is extremely strong, allowing simultaneous interpolation of quantiles using copulas. Lower quantiles are less well structured, but they are subject to higher observation errors and are likely to be of less importance in hydrology. Thus the interpolation was carried out on the basis of the quantiles corresponding to greater than 1mm/day values. Topographical influence on precipitation is considered as a covariate. The applied copula is a mixed truncated-Gaussian and Gaussian copula, which reflects the asymmetrical dependence between topography and precipitation quantiles. A split sampling and a cross validation methodology are used to evaluate the quality of the interpolation.

  14. Evaluating Spatial Data Quality in GIS Database

    Microsoft Academic Search

    Ying Su; Lei Yang; Zhanming Jin

    2007-01-01

    The quality of spatial data is often limited by the quality of their sources such as paper maps and satellite images. Spatial operations performed on database of geographical information systems (GIS) such as selection, projection, and Cartesian product, do not always work correctly because their accuracy and completeness depends on the quality of spatial data. The present paper suggests a

  15. A Malthusian curb on spatial structure in microorganism populations.

    PubMed

    Martin, A P

    2004-10-01

    That all organisms are born in the company of a parent but die alone is a fundamental biological asymmetry. It has been suggested that this provides a deep-rooted source of spatial pattern formation for microorganisms even at the scale of the population. Such a theory, however, neglects the strong influence in nature of the limited and spatially variable availability of food. The tendency, first recognized by Thomas Malthus in the 18th century, of a population to out-strip its food resources will eventually lead, through local starvation, to the suppression of a heterogeneity growing within a population. Using a generic model it is demonstrated that including local food limitation of breeding strongly dampens spatial structure otherwise resulting from birth and death. The extent of this damping is shown to be a function of the strength of the coupling between organisms and their food and of the total abundance of organic material. Moreover, this work provides an example of a density-dependent process acting to diminish spatial structure rather than to create it and highlights the rich variety of behaviour that is missed by continuum models which fail to represent such local dynamics. PMID:15302544

  16. Strongly Nonequilibrium Bose-Condensed Atomic Systems

    NASA Astrophysics Data System (ADS)

    Yukalov, V. I.; Novikov, A. N.; Bagnato, V. S.

    2015-07-01

    A trapped Bose-Einstein condensate, being strongly perturbed, exhibits several spatial structures. First, there appear quantum vortices. Increasing the amount of the injected energy leads to the formation of vortex tangles representing quantum vortex turbulence. Continuing energy injection makes the system so strongly perturbed that vortices become destroyed and there develops another kind of spatial structures with essentially heterogeneous spatial density. These structures consist of high-density droplets, or grains, surrounded by the regions of low density. The droplets are randomly distributed in space, where they can move; however they live sufficiently long time to be treated as a type of metastable creatures. Such structures have been observed in nonequilibrium trapped Bose gases of Rb subject to the action of an oscillatory perturbation modulating the trapping potential. Perturbing the system even stronger transforms the droplet structure into wave turbulence, where Bose condensate is destroyed. Numerical simulations are in good agreement with experimental observations.

  17. Spatial Mass

    E-print Network

    Benjamin Nachman; Ariel Schwartzman

    2014-07-08

    In analogy to the transverse mass constructed from two objects, we define the spatial mass constructed from the input objects 3-vector momenta. This observable is insensitive to jet mass scale and resolution uncertainties when constructed from small-radius hadronic jets. Thus it improves the effective resolution on multijet masses for searches and measurements in hadronic final states. To illustrate the efficacy of the spatial mass, we consider a top quark mass measurement at the Large Hadron Collider (LHC) in the 3-jet final state. The reduction in uncertainty comes with a negligible cost in sensitivity.

  18. Conductivity of Strong, Weak, and Nonelectrolyte Solutions

    NSDL National Science Digital Library

    Dr. Charles Ward

    This is a video clip of strong, weak, and nonelectrolyte solutions conducting electricity. Each solution is tested with the light bulb apparatus and the bulb glows brightly, dimly, or not at all depending on the solution.

  19. Time-dependent density-functional theory for strong-field multiphoton processes: Application to the study of the role of dynamical electron correlation in multiple high-order harmonic generation

    E-print Network

    Tong, Xiao-Min; Chu, Shih-I

    1998-01-01

    We present a self-interaction-free time-dependent density-functional theory (TDDFT) for nonperturbative treatment of multiphoton processes of many-electron atomic systems in intense laser fields. The theory is based on the ...

  20. Time-dependent density-functional theory for molecular processes in strong fields: Study of multiphoton processes and dynamical response of individual valence electrons of N2 in intense laser fields

    E-print Network

    Chu, Xi; Chu, Shih-I

    2001-11-14

    We present a time-dependent density-functional theory (TDDFT) with proper asymptotic long-range potential for nonperturbative treatment of multiphoton processes of many-electron molecular systems in intense laser fields. ...

  1. Spatially resolved PMD measurements

    Microsoft Academic Search

    Andrea Galtarossa; Luca Palmieri

    2004-01-01

    Spatially resolved measurements of polarization properties of fiber optic link-such as birefringence, polarization-mode dispersion (PMD) and polarization dependent loss (PDL)-may be effectively performed using polarization sensitive reflectometric techniques. In particular, this paper focuses on polarization-OTDR and reviews its theory and applications. Special emphasis is given to the use of optical reflectometry as a tool to characterize fiber birefringence. This allows

  2. LHC Phenomenology and Lattice Strong Dynamics

    NASA Astrophysics Data System (ADS)

    Fleming, G. T.

    2013-03-01

    While the LHC experimentalists work to find evidence of physics beyond the standard model, lattice gauge theorists are working as well to characterize the range of possible phenomena in strongly-coupled models of electroweak symmetry breaking. I will summarize the current progress of the Lattice Strong Dynamics (LSD) collaboration on the flavor dependence of SU(3) gauge theories.

  3. Spatial Dependence and House Price Index Construction

    Microsoft Academic Search

    Ay se Can; Isaac Megbolugbe

    1997-01-01

    Accurate estimation of prevailing metropolitan housing prices is important for both business and research investigations of housing and mortgage markets. This is typically done by constructing quality-adjusted house price indices from hedonic price regressions for given metropolitan areas. A major limitation of currently available indices is their insensitivity to the geographic location of dwellings within the metropolitan area. Indices are

  4. Scale matters: the impact of organic farming on biodiversity at different spatial scales.

    PubMed

    Gabriel, Doreen; Sait, Steven M; Hodgson, Jenny A; Schmutz, Ulrich; Kunin, William E; Benton, Tim G

    2010-07-01

    There is increasing recognition that ecosystems and their services need to be managed in the face of environmental change. However, there is little consensus as to the optimum scale for management. This is particularly acute in the agricultural environment given the level of public investment in agri-environment schemes (AES). Using a novel multiscale hierarchical sampling design, we assess the effect of land use at multiple spatial scales (from location-within-field to regions) on farmland biodiversity. We show that on-farm biodiversity components depend on farming practices (organic vs. conventional) at farm and landscape scales, but this strongly interacts with fine- and coarse-scale variables. Different taxa respond to agricultural practice at different spatial scales and often at multiple spatial scales. Hence, AES need to target multiple spatial scales to maximize effectiveness. Novel policy levers may be needed to encourage multiple land managers within a landscape to adopt schemes that create landscape-level benefits. PMID:20482572

  5. CMEIAS-aided microscopy of the spatial ecology of individual bacterial interactions involving cell-to-cell communication within biofilms.

    PubMed

    Dazzo, Frank B

    2012-01-01

    This paper describes how the quantitative analytical tools of CMEIAS image analysis software can be used to investigate in situ microbial interactions involving cell-to-cell communication within biofilms. Various spatial pattern analyses applied to the data extracted from the 2-dimensional coordinate positioning of individual bacterial cells at single-cell resolution indicate that microbial colonization within natural biofilms is not a spatially random process, but rather involves strong positive interactions between communicating cells that influence their neighbors' aggregated colonization behavior. Geostatistical analysis of the data provide statistically defendable estimates of the micrometer scale and interpolation maps of the spatial heterogeneity and local intensity at which these microbial interactions autocorrelate with their spatial patterns of distribution. Including in situ image analysis in cell communication studies fills an important gap in understanding the spatially dependent microbial ecophysiology that governs the intensity of biofilm colonization and its unique architecture. PMID:22969336

  6. CMEIAS-Aided Microscopy of the Spatial Ecology of Individual Bacterial Interactions Involving Cell-to-Cell Communication within Biofilms

    PubMed Central

    Dazzo, Frank B.

    2012-01-01

    This paper describes how the quantitative analytical tools of CMEIAS image analysis software can be used to investigate in situ microbial interactions involving cell-to-cell communication within biofilms. Various spatial pattern analyses applied to the data extracted from the 2-dimensional coordinate positioning of individual bacterial cells at single-cell resolution indicate that microbial colonization within natural biofilms is not a spatially random process, but rather involves strong positive interactions between communicating cells that influence their neighbors' aggregated colonization behavior. Geostatistical analysis of the data provide statistically defendable estimates of the micrometer scale and interpolation maps of the spatial heterogeneity and local intensity at which these microbial interactions autocorrelate with their spatial patterns of distribution. Including in situ image analysis in cell communication studies fills an important gap in understanding the spatially dependent microbial ecophysiology that governs the intensity of biofilm colonization and its unique architecture. PMID:22969336

  7. Spatial cluster detection for weighted outcomes using cumulative geographic residuals

    PubMed Central

    Cook, Andrea J.; Li, Yi; Arterburn, David; Tiwari, Ram C.

    2010-01-01

    Summary Spatial cluster detection is an important methodology for identifying regions with excessive numbers of adverse health events without making strong model assumptions on the underlying spatial dependence structure. Previous work has focused on point or individual-level outcome data and few advances have been made when the outcome data are reported at an aggregated level, e.g. at the county- or census tract-level. This paper proposes a new class of spatial cluster detecion methods for point or aggregate data, comprising of continuous, binary, and count data. Compared with the existing spatial cluster detection methods it has the following advantages. First, it readily incorporates region-specific weights, for example, based on a region’s population or a region’s outcome variance, which is key for aggregate data. Second, the established general framework allows for area-level and individual-level covariate adjustment. A simulation study is conducted to evaluate the performance of the method. The proposed method is then applied to assess spatial clustering of high Body Mass Index in a HMO population in the Seattle, Washington USA area. PMID:19751250

  8. A rainfall spatial interpolation algorithm based on inhomogeneous kernels

    NASA Astrophysics Data System (ADS)

    Campo, Lorenzo; Fiori, Elisabetta; Molini, Luca

    2015-04-01

    Rainfall fields constitute the main input of hydrological distributed models, both for long period water balance and for short period flood forecast and monitoring. The importance of an accurate reconstruction of the spatial pattern of rainfall is, thus, well recognized in several fields of application: agricultural planning, water balance at watershed scale, water management, flood monitoring. The latter case is particularly critical, due to the strong effect of the combination of the soil moisture pattern and of the rainfall pattern on the intensity peak of the flood. Despite the importance of the spatial characterization of the rainfall height, this variable still presents several difficulties when an interpolation is required. Rainfall fields present spatial and temporal alternance of large zero-values areas (no-rainfall) and complex pattern of non zero heights (rainfall events). Furthermore, the spatial patterns strongly depend on the type and the origin of rain event (convective, stratiform, orographic) and on the spatial scale. Different kind of rainfall measures and estimates (rainfall gauges, satellite estimates, meteo radar) are available, as well as large amount of literature for the spatial interpolation: from Thiessen polygons to Inverse Distance Weight (IDW) to different variants of kriging, neural network and other deterministic or geostatistic methods. In this work a kernel-based method for interpolation of point measures (raingauges) is proposed, in which spatially inhomogeneous kernel are used. For each gauge a particular kernel is fitted following the particular correlation structures between the rainfall time series of the given gauge and those of its neighbors. In this way the local features of the field are considered following the observed dependence spatial pattern. The kernel are assumed to be Gaussian, whose covariance matrices are fitted basing on the values of the correlation of the time series and the location. A similar approach is used on a binary variant to reconstruct the rainfall - no rainfall areas, to be used as mask of the continuous rainfall interpolated field. The method was applied on a set of 8 years of measurements (2006-2013) of raingauges in Northern Italy.

  9. Frequency dependent plasma characteristics in a capacitively coupled 300 mm wafer plasma processing chamber.

    SciTech Connect

    Hebner, Gregory Albert; Holland, J.P. (Applied Materials, Sunnyvale, CA); Paterson, A.M. (Applied Materials, Sunnyvale, CA); Barnat, Edward V.; Miller, Paul Albert

    2006-01-01

    Argon plasma characteristics in a dual-frequency, capacitively coupled, 300 mm-wafer plasma processing system were investigated for rf drive frequencies between 10 and 190 MHz. We report spatial and frequency dependent changes in plasma parameters such as line-integrated electron density, ion saturation current, optical emission and argon metastable density. For the conditions investigated, the line-integrated electron density was a nonlinear function of drive frequency at constant rf power. In addition, the spatial distribution of the positive ions changed from uniform to peaked in the centre as the frequency was increased. Spatially resolved optical emission increased with frequency and the relative optical emission at several spectral lines depended on frequency. Argon metastable density and spatial distribution were not a strong function of drive frequency. Metastable temperature was approximately 400 K.

  10. Partially strong WW scattering

    SciTech Connect

    Cheung Kingman [Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China); Physics Division, National Center for Theoretical Sciences, Hsinchu, Taiwan (China); Chiang Chengwei [Department of Physics and Center for Mathematics and Theoretical Physics, National Central University, Chung-Li, Taiwan (China); Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Yuan Tzuchiang [Physics Division, National Center for Theoretical Sciences, Hsinchu, Taiwan (China); Institute of Physics, Academia Sinica, Taipei, Taiwan (China)

    2008-09-01

    What if only a light Higgs boson is discovered at the CERN LHC? Conventional wisdom tells us that the scattering of longitudinal weak gauge bosons would not grow strong at high energies. However, this is generally not true. In some composite models or general two-Higgs-doublet models, the presence of a light Higgs boson does not guarantee complete unitarization of the WW scattering. After partial unitarization by the light Higgs boson, the WW scattering becomes strongly interacting until it hits one or more heavier Higgs bosons or other strong dynamics. We analyze how LHC experiments can reveal this interesting possibility of partially strong WW scattering.

  11. Spatial Hyperschematia without Spatial Neglect after Insulo-Thalamic Disconnection

    PubMed Central

    Saj, Arnaud; Wilcke, Juliane C.; Gschwind, Markus; Emond, Héloïse; Assal, Frédéric

    2013-01-01

    Different spatial representations are not stored as a single multipurpose map in the brain. Right brain-damaged patients can show a distortion, a compression of peripersonal and extrapersonal space. Here we report the case of a patient with a right insulo-thalamic disconnection without spatial neglect. The patient, compared with 10 healthy control subjects, showed a constant and reliable increase of her peripersonal and extrapersonal egocentric space representations - that we named spatial hyperschematia - yet left her allocentric space representations intact. This striking dissociation shows that our interactions with the surrounding world are represented and processed modularly in the human brain, depending on their frame of reference. PMID:24302992

  12. Spatial computation

    Microsoft Academic Search

    Mihai Budiu; Girish Venkataramani; Tiberiu Chelcea; Seth Copen Goldstein

    2004-01-01

    This paper describes a computer architecture, Spatial Computation (SC), which is based on the translation of high-level language programs directly into hardware structures. SC program implementations are completely distributed, with no centralized control. SC circuits are optimized for wires at the expense of computation units.In this paper we investigate a particular implementation of SC: ASH (Application-Specific Hardware). Under the assumption

  13. Spatial mode filtering of mid-infrared (mid-IR) laser beams with hollow core fiber optics

    NASA Astrophysics Data System (ADS)

    Kriesel, Jason M.; Hagglund, Gina M.; Gat, Nahum; Spagnolo, Vincenzo; Patimisco, Pietro

    2013-12-01

    Measurements characterizing spatial mode filtering of mid-infrared (mid-IR) laser beams using hollow core fiber optics are presented. The mode filtering depends strongly on the fiber diameter, with effective mode filtering demonstrated with bore diameters of d = 200 ?m and 300 ?m. In addition to mode filtering, beam profile measurements also demonstrate the strong dependence of the mode quality on the fiber coupling conditions. As predicted, optimal coupling is achieved using relatively slow optics that produce focused spots that nearly fill the fiber diameter. Examples of the utility of using hollow fibers for mode-filtering to improve molecular spectroscopy experiments are also discussed.

  14. Recruitment of SWI\\/SNF by Gcn4p Does Not Require Snf2p or Gcn5p but Depends Strongly on SWI\\/SNF Integrity, SRB Mediator, and SAGA

    Microsoft Academic Search

    Sungpil Yoon; Hongfang Qiu; Mark J. Swanson; Alan G. Hinnebusch

    2003-01-01

    The nucleosome remodeling complex SWI\\/SNF is a coactivator for yeast transcriptional activator Gcn4p. We provide strong evidence that Gcn4p recruits the entire SWI\\/SNF complex to its target genes ARG1 and SNZ1 but that SWI\\/SNF is dispensable for Gcn4p binding to these promoters. It was shown previously that Snf2p\\/Swi2p, Snf5p, and Swi1p interact directly with Gcn4p in vitro. However, we found

  15. BUILDING A STRONG FOUNDATION.

    E-print Network

    Linsley, Braddock K.

    information, including non-discriminatory policies, safety and security, Clery Act, etc., can be foundBUILDING A STRONG FOUNDATION. UALBANY FACTS. Enrollment: 12,822 undergraduates 4,516 graduate) (MAAC) #12;STUDY. LISTEN. CHALLENGE. LEARN. A STRONG FOUNDATION The University at Albany puts the world

  16. Strong Acids (GCMP)

    NSDL National Science Digital Library

    Strong Acids: this is a resource in the collection "General Chemistry Multimedia Problems". This problem will explore the properties of common strong acids. General Chemistry Multimedia Problems ask students questions about experiments they see presented using videos and images. The questions asked apply concepts from different parts of an introductory course, encouraging students to decompartmentalize the material.

  17. What Is Strong Correlation?

    ERIC Educational Resources Information Center

    Kozak, Marcin

    2009-01-01

    Interpretation of correlation is often based on rules of thumb in which some boundary values are given to help decide whether correlation is non-important, weak, strong or very strong. This article shows that such rules of thumb may do more harm than good, and instead of supporting interpretation of correlation--which is their aim--they teach a…

  18. Spatial Working Memory Interferes with Explicit, but Not Probabilistic Cuing of Spatial Attention

    ERIC Educational Resources Information Center

    Won, Bo-Yeong; Jiang, Yuhong V.

    2015-01-01

    Recent empirical and theoretical work has depicted a close relationship between visual attention and visual working memory. For example, rehearsal in spatial working memory depends on spatial attention, whereas adding a secondary spatial working memory task impairs attentional deployment in visual search. These findings have led to the proposal…

  19. Retinoic acid increases amount of phosphorylated raf; Ectopic expression of cFMS reveals that retinoic acid-induced differentiation is more strongly dependent on ERK2 signaling than induced go arrest is

    Microsoft Academic Search

    Andrew Yen; Rhonda Sturgill; Susi Varvayanis

    2000-01-01

    Summary  Retinoic acid is known to cause the myeloid differentiation and G1\\/0 cell cycle arrest of HL-60 cells in a process that requires\\u000a mitogen-activated protein\\/extracellular signal regulated kinase (MEK)-dependent extracellular signal regulated kinase (ERK)2\\u000a activation. It has also been shown that ectopic expression of cFMS, a platelet-derived growth factor (PDGF)-family transmembrane\\u000a tyrosine kinase receptor, enhances retinoic acid-induced differentiation and G1\\/0 arrest.

  20. Nonparametric regression estimation and prediction for continuous spatial processes

    Microsoft Academic Search

    Sophie Dabo-Niang; Anne-Francoise Yao

    2004-01-01

    The spatial regression estimation as well as prediction is an interesting and crucial problem in statistical inference for a number of applications, where the influence of a vector of covariates on some response variable is to be studied in a context of spatial dependence. Spatial data are modeled as finite realizations of random fields and are collected from dierent spatial

  1. Partially Strong WW Scattering

    E-print Network

    Kingman Cheung; Cheng-Wei Chiang; Tzu-Chiang Yuan

    2008-04-14

    What if only a light Higgs boson is discovered at the CERN LHC? Conventional wisdom tells us that the scattering of longitudinal weak gauge bosons would not grow strong at high energies. We show that this is not always true. In some composite models, two-Higgs-doublet models, or even supersymmetric models, the presence of a light Higgs boson does not guarantee the complete unitarization of the $WW$ scattering. After the partial unitarization by the light Higgs boson, the $WW$ scattering becomes strongly interacting until it hits one or more heavier Higgs bosons or other strong dynamics. We analyze how the LHC experiments can reveal this interesting possibility of partially strong $WW$ scattering.

  2. On aggregation in spatial econometric modelling

    NASA Astrophysics Data System (ADS)

    Paelinck, Jean H. P.

    The spatial aggregation problem - also termed the modifiable areal unit problem - has attracted regular attention in spatial statistics and econometrics. In this study econometric aggregation analysis is used to investigate the formal composition of meso-areal parameters given micro-areal underlying relations with spatial dependence. Impact on stochastic terms (possible meso-areal spatial autocorrelation) is also studied. Finally consequences for meso-areal estimation are derived, the general finding having been that spatial aggregation leads to meso-region specific parameter values, with the estimation problems this implies.

  3. Kinetic Characterization of Strongly Coupled Systems

    SciTech Connect

    Knapek, C. A.; Ivlev, A. V.; Klumov, B. A.; Morfill, G. E. [Max-Planck-Institute for Extraterrestrial Physics, 85741 Garching (Germany); Samsonov, D. [Department of Electrical Engineering and Electronics, The University of Liverpool, Liverpool L69 3GJ (United Kingdom)

    2007-01-05

    We propose a simple method to determine the local coupling strength {gamma} experimentally, by linking the individual particle dynamics with the local density and crystal structure of a 2D plasma crystal. By measuring particle trajectories with high spatial and temporal resolution we obtain the first maps of {gamma} and temperature at individual particle resolution. We employ numerical simulations to test this new method, and discuss the implications to characterize strongly coupled systems.

  4. Effects of electron structure and multielectron dynamical response on strong-field multiphoton ionization of diatomic molecules with arbitrary orientation: An all-electron time-dependent density-functional-theory approach

    E-print Network

    Chu, Shih-I; Telnov, Dmitry A.

    2009-04-03

    .2 19.0 #2;Ref. #3;18#4;#1; 1#7;g #2;HOMO#1; 16.0 15.7 #2;Ref. #3;18#4;#1; DMITRY A. TELNOV AND SHIH-I CHU PHYSICAL REVIEW A 79, 041401#2;R#1; #2;2009#1; RAPID COMMUNICATIONS 041401-2 total survival probability P#2;s#1; can be calculated as P#2;s#1... dominant over the highest-occupied molecular orbital, depending on detailed electronic structure and symmetry, laser field intensity, and orientation angle. DOI: 10.1103/PhysRevA.79.041401 PACS number#2;s#1;: 33.80.Rv, 31.15.ee Processes involving diatomic...

  5. Combining spatial and temporal expectations to improve visual perception.

    PubMed

    Rohenkohl, Gustavo; Gould, Ian C; Pessoa, Jéssica; Nobre, Anna C

    2014-01-01

    The importance of temporal expectations in modulating perceptual functions is increasingly recognized. However, the means through which temporal expectations can bias perceptual information processing remains ill understood. Recent theories propose that modulatory effects of temporal expectations rely on the co-existence of other biases based on receptive-field properties, such as spatial location. We tested whether perceptual benefits of temporal expectations in a perceptually demanding psychophysical task depended on the presence of spatial expectations. Foveally presented symbolic arrow cues indicated simultaneously where (location) and when (time) target events were more likely to occur. The direction of the arrow indicated target location (80% validity), while its color (pink or blue) indicated the interval (80% validity) for target appearance. Our results confirmed a strong synergistic interaction between temporal and spatial expectations in enhancing visual discrimination. Temporal expectation significantly boosted the effectiveness of spatial expectation in sharpening perception. However, benefits for temporal expectation disappeared when targets occurred at unattended locations. Our findings suggest that anticipated receptive-field properties of targets provide a natural template upon which temporal expectations can operate in order to help prioritize goal-relevant events from early perceptual stages. PMID:24722562

  6. Display method with compensation of the spatial frequency response of a liquid crystal spatial light modulator for holographic femtosecond laser processing

    Microsoft Academic Search

    Kota Chaen; Hidetomo Takahashi; Satoshi Hasegawa; Yoshio Hayasaki

    2007-01-01

    Liquid crystal spatial light modulators, which are widely used as display devices for computer-generated holograms, have modulation characteristics that depend on spatial frequency. We describe a method for displaying a computer-generated hologram on a liquid crystal spatial light modulator with compensation of its spatial frequency response. Using this method, we demonstrate a binary phase grating with smaller dependence on the

  7. Urban growth and strategic spatial planning in Johannesburg, South Africa

    Microsoft Academic Search

    Alison Todes

    The article examines the way strategic spatial planning in the City of Johannesburg has attempted to reshape existing and emerging spatial patterns of a divided sprawling city, focusing particularly on current initiatives to link spatial planning and infrastructure development through the growth management strategy. The strategy has been well institutionalised in the municipality, with strong political support and links to

  8. A model for predicting spatially and time resolved convective heat transfer in bowl-in-piston combustion chambers

    SciTech Connect

    Morel, T.; Keribar, R.

    1985-01-01

    A new model for convective in-cylinder heat transfer has been developed which calculates heat transfer coefficients based on a description of the in-cylinder flow field. The combustion chamber volume is divided into three regions in which differential equations for angular momentum, turbulent kinetic energy and turbulent dissipation are solved. The resultant heat transfer coefficients are strongly spatially non-uniform, unlike those calculated from standard correlations, which assume spatial uniformity. When spatially averaged, the heat transfer coefficient is much more peaked near TDC of the compression stroke as compared to that predicted by standard correlations. This is due to the model's dependence on gas velocity and turbulence, both of which are amplified near TDC. The new model allows a more accurate calculation of the spatial distribution of the heat fluxes. This capability is essential for calculation of heat transfer and of component thermal loading and temperatures.

  9. Strong mobile authentication

    Microsoft Academic Search

    M. Hassinen; K. Hypponen

    2005-01-01

    Our main contribution is a protocol that provides strong mobile authentication with non-repudiation using SMS messages. For ensuring these properties, governmentally controlled PKI, and SIM cards with electronic identity application are used. Moreover, our protocol provides confidentiality and integrity of transferred content. An application that implements this protocol was developed and tested in a partly simulated environment. Furthermore, we developed

  10. Partners: Forging Strong Relationships.

    ERIC Educational Resources Information Center

    Spears, Ellen, Ed.

    1999-01-01

    This newsletter issue asserts that sound, effective relationships in which diverse groups of people and organizations work together toward a common goal are the basis of the collaborative efforts in education that can accomplish change. The first article, "Partners: Forging Strong Relationships" (Sarah E. Torian), briefly describes the efforts of…

  11. Strong Ionizing Shock Waves

    Microsoft Academic Search

    Robert A. Gross

    1965-01-01

    The physical effects created by strong shock waves propagating in hydrogen are reviewed and theoretically studied for speeds up to relativistic conditions. In the progression from weak to relativistic shock speeds, various physical phenomena affect the shock wave. Dissociation, ionization, and the presence of an upstream electric field cause several important effects for slow (sub-Alfvénic speed) normal ionizing shock waves.

  12. Spatially resolved measurement of high doses in microbeam radiation therapy using samarium doped fluorophosphate glasses

    SciTech Connect

    Okada, Go; Morrell, Brian; Koughia, Cyril; Kasap, Safa [Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada); Edgar, Andy; Varoy, Chris [School of Chemical and Physical Sciences and MacDiarmid Institute, Victoria University of Wellington, Kelburn Parade (New Zealand); Belev, George; Wysokinski, Tomasz [Canadian Light Source Inc., University of Saskatchewan, Saskatoon, SK S7N 0X4 (Canada); Chapman, Dean [Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK S7N 5E5 (Canada)

    2011-09-19

    The measurement of spatially resolved high doses in microbeam radiation therapy has always been a challenging task, where a combination of high dose response and high spatial resolution (microns) is required for synchrotron radiation peaked around 50 keV. The x-ray induced Sm{sup 3+}{yields} Sm{sup 2+} valence conversion in Sm{sup 3+} doped fluorophosphates glasses has been tested for use in x-ray dosimetry for microbeam radiation therapy. The conversion efficiency depends almost linearly on the dose of irradiation up to {approx}5 Gy and saturates at doses exceeding {approx}80 Gy. The conversion shows strong correlation with x-ray induced absorbance of the glass which is related to the formation of phosphorus-oxygen hole centers. When irradiated through a microslit collimator, a good spatial resolution and high ''peak-to-valley'' contrast have been observed by means of confocal photoluminescence microscopy.

  13. Spatially resolved measurement of high doses in microbeam radiation therapy using samarium doped fluorophosphate glasses

    NASA Astrophysics Data System (ADS)

    Okada, Go; Morrell, Brian; Koughia, Cyril; Edgar, Andy; Varoy, Chris; Belev, George; Wysokinski, Tomasz; Chapman, Dean; Kasap, Safa

    2011-09-01

    The measurement of spatially resolved high doses in microbeam radiation therapy has always been a challenging task, where a combination of high dose response and high spatial resolution (microns) is required for synchrotron radiation peaked around 50 keV. The x-ray induced Sm3+ ? Sm2+ valence conversion in Sm3+ doped fluorophosphates glasses has been tested for use in x-ray dosimetry for microbeam radiation therapy. The conversion efficiency depends almost linearly on the dose of irradiation up to ˜5 Gy and saturates at doses exceeding ˜80 Gy. The conversion shows strong correlation with x-ray induced absorbance of the glass which is related to the formation of phosphorus-oxygen hole centers. When irradiated through a microslit collimator, a good spatial resolution and high "peak-to-valley" contrast have been observed by means of confocal photoluminescence microscopy.

  14. Spatial quantum correlations in multiple scattered light

    E-print Network

    P. Lodahl; A. P. Mosk; A. Lagendijk

    2005-11-10

    We predict a new spatial quantum correlation in light propagating through a multiple scattering random medium. The correlation depends on the quantum state of the light illuminating the medium, is infinite range, and dominates over classical mesoscopic intensity correlations. The spatial quantum correlation is revealed in the quantum fluctuations of the total transmission or reflection through the sample and should be readily observable experimentally.

  15. Spatial memory, recognition memory, and the hippocampus

    E-print Network

    Squire, Larry R.

    Spatial memory, recognition memory, and the hippocampus Nicola J. Broadbent*, Larry R. Squire. Squire, August 27, 2004 There is wide agreement that spatial memory is dependent on the integrity recognition memory is not as clear. We examined the relationship between hippocampal lesion size and both

  16. Improving Spatially Distributed Regional Recharge Estimation

    Microsoft Academic Search

    Zainab Zomlot; Okke Batelaan

    2010-01-01

    Spatial and temporal variability of groundwater recharge are key factors that need to be quantified to determine the sustainability of groundwater resources. In response to the need for better estimates of groundwater recharge the WetSpass spatially distributed water balance model was developed and applied for Flanders. This model aims to simulate long-term average recharge depending on land cover, soil texture,

  17. Strong-disorder renormalization for interacting non-Abelian anyon systems in two dimensions

    NASA Astrophysics Data System (ADS)

    Laumann, C. R.; Huse, D. A.; Ludwig, A. W. W.; Refael, G.; Trebst, S.; Troyer, M.

    2012-06-01

    We consider the effect of quenched spatial disorder on systems of interacting, pinned non-Abelian anyons as might arise in disordered Hall samples at filling fractions ?=5/2 or ?=12/5. In one spatial dimension, such disordered anyon models have previously been shown to exhibit a hierarchy of infinite randomness phases. Here, we address systems in two spatial dimensions and report on the behavior of Ising and Fibonacci anyons under the numerical strong-disorder renormalization group (SDRG). In order to manage the topology-dependent interactions generated during the flow, we introduce a planar approximation to the SDRG treatment. We characterize this planar approximation by studying the flow of disordered hard-core bosons and the transverse field Ising model, where it successfully reproduces the known infinite randomness critical point with exponent ??0.49. Our main conclusion for disordered anyon models in two spatial dimensions is that systems of Ising anyons as well as systems of Fibonacci anyons do not realize infinite randomness phases, but flow back to weaker disorder under the numerical SDRG treatment.

  18. Spatial Regression for Marked Point Processes

    Microsoft Academic Search

    KATJA ICKSTADT; ROBERT L. WOLPERT

    1998-01-01

    SUMMARY In a wide range of applications, dependence on smoothly-varying covariates leads spatial point count intensities to feature positive correlation for nearby loc ations. In applications where the points are \\

  19. Outage calculations for spatially multiplexed fiber links

    Microsoft Academic Search

    Peter J. Winzer; Gerard J. Foschini

    2011-01-01

    We calculate multiple-input-multiple-output (MIMO) outage probabilities for optical fiber links employing spatial multiplexing across linearly coupled propagation modes in the presence of mode-dependent loss and distributed optical noise. © 2010 Optical Society of America

  20. Strongly interacting Higgs bosons

    Microsoft Academic Search

    Thomas Appelquist; Claude Bernard

    1980-01-01

    The sensitivity of present-energy weak interactions to a strongly interacting heavy-Higgs-boson sector is discussed. The gauged nonlinear sigma model, which is the limit of the linear model as the Higgs-boson mass goes to infinity, is used to organize and catalogue all possible heavy-Higgs-boson effects. As long as the SU(2)L×SU(2)R symmetry of the Higgs sector is preserved, these effects are found

  1. PEER Strong Motion Database

    NSDL National Science Digital Library

    2000-01-01

    Processed by Dr. Walt Silva of Pacific Engineering and supported by the Pacific Earthquake Engineering Research Center (PEER) at the University of California Berkley, the PEER Strong Motion Database "contains 1557 records from 143 earthquakes from tectonically active regions." Searches can be done by earthquake, type of plate movement (e.g., strike slip), magnitude, and several other criteria. The correct browser and JAVA version even allows dynamic sorting and interactive plotting of data.

  2. EDITORIAL: Strongly correlated electron systems Strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Ronning, Filip; Batista, Cristian

    2011-03-01

    Strongly correlated electrons is an exciting and diverse field in condensed matter physics. This special issue aims to capture some of that excitement and recent developments in the field. Given that this issue was inspired by the 2010 International Conference on Strongly Correlated Electron Systems (SCES 2010), we briefly give some history in order to place this issue in context. The 2010 International Conference on Strongly Correlated Electron Systems was held in Santa Fe, New Mexico, a reunion of sorts from the 1989 International Conference on the Physics of Highly Correlated Electron Systems that also convened in Santa Fe. SCES 2010—co-chaired by John Sarrao and Joe Thompson—followed the tradition of earlier conferences, in this century, hosted by Buzios (2008), Houston (2007), Vienna (2005), Karlsruhe (2004), Krakow (2002) and Ann Arbor (2001). Every three years since 1997, SCES has joined the International Conference on Magnetism (ICM), held in Recife (2000), Rome (2003), Kyoto (2006) and Karlsruhe (2009). Like its predecessors, SCES 2010 topics included strongly correlated f- and d-electron systems, heavy-fermion behaviors, quantum-phase transitions, non-Fermi liquid phenomena, unconventional superconductivity, and emergent states that arise from electronic correlations. Recent developments from studies of quantum magnetism and cold atoms complemented the traditional subjects and were included in SCES 2010. 2010 celebrated the 400th anniversary of Santa Fe as well as the birth of astronomy. So what's the connection to SCES? The Dutch invention of the first practical telescope and its use by Galileo in 1610 and subsequent years overturned dogma that the sun revolved about the earth. This revolutionary, and at the time heretical, conclusion required innovative combinations of new instrumentation, observation and mathematics. These same combinations are just as important 400 years later and are the foundation of scientific discoveries that were discussed during SCES 2010. As we learned, past dogmas about strongly correlated materials and phenomena must be re-examined with an open and inquisitive mind. Invited speakers and respected leaders in the field were invited to contribute to this special issue and we have insisted that they present new data, ideas, or perspectives, as opposed to simply an overview of their past work. As with the conference, this special issue touches upon recent developments of strongly correlated electron systems in d-electron materials, such as Sr3Ru2O7, graphene, and the new Fe-based superconductors, but it is dominated by topics in f-electron compounds. Contributions reflect the growing appreciation for the influence of disorder and frustration, the need for organizing principles, as well as detailed investigations on particular materials of interest and, of course, new materials. As this special issue could not possibly capture the full breadth and depth that the conference had to offer, it is being published simultaneously with an issue of Journal of Physics: Conference Series containing 157 manuscripts in which all poster presenters at SCES 2010 were invited to contribute. Since this special issue grew out of the 2010 SCES conference, we take this opportunity to give thanks. This conference would not have been possible without the hard work of the SCES 2010 Program Committee, International and National Advisory Committees, Local Committee, and conference organizers, the New Mexico Consortium. We thank them as well as those organizations that generously provided financial support: ICAM-I2CAM, Quantum Design, Lakeshore, the National High Magnetic Field Laboratory and the Department of Energy National Laboratories at Argonne, Berkeley, Brookhaven, Los Alamos and Oak Ridge. Of course, we especially thank the participants for bringing new ideas and new results, without which SCES 2010 would not have been possible. Strongly correlated electron systems contents Spin-orbit coupling and k-dependent Zeeman splitting in strontium ruthenate Emil J Rozbicki, James F Annett, Jean-René Souquet an

  3. Spatial Encounters: Exercises in Spatial Awareness.

    ERIC Educational Resources Information Center

    New Mexico Univ., Albuquerque.

    This series of activities on spatial relationships was designed to help users acquire the skills of spatial visualization and orientation and to improve their effectiveness in applying those skills. The series contains an introduction to spatial orientation with several self-directed activities to help improve that skill. It also contains seven…

  4. Spatial Thinking Strategies

    NSDL National Science Digital Library

    Susan Everett

    2000-04-01

    While some people consider spatial thinking a "gift" that only some individuals have, many others view spatial thinking as a cognitive process that can be developed. Much research supports the developmental view of spatial thinking as a cognitive process,

  5. Spatially Modulated Structures in Convective Systems

    NASA Astrophysics Data System (ADS)

    Kao, Hsien-Ching

    This dissertation focuses on the study of spatially modulated structures in pattern forming systems. The work is motivated by recent interest in spatially localized states observed in convective systems. Weakly nonlinear analysis is applied to derive the modulation equations and systematic studies, both analytical and numerical, are then performed on the simplified equations. The following is a summary of this work: Weakly Subcritical Patterns: The transition from subcritical to supercritical periodic patterns is described by the one-dimensional cubic-quintic Ginzburg-Landau equation with cubic nonlinear gradient terms. The coefficients are real indicating that the system is spatially reversible. Properties of the equation such as well-posedness, gradient structure, and bifurcation behavior depend significantly on the coefficients of the cubic nonlinear gradient terms. In this system, periodic patterns may in turn become unstable through one of two different mechanisms, an Eckhaus instability or an oscillatory instability. Dynamics and bifurcations near the instability thresholds are analyzed. Among the stationary solutions, the front solution which connects the zero state to a spatially periodic state plays the most important role. The location of the front in the parameter mu is treated as a Maxwell point. The spatially modulated solutions which bifurcate from the periodic solutions demonstrate protosnaking behavior near this point. These results are used to shed light on both variational and non-variational systems exhibiting homoclinic snaking. Localized Patterns in Rotating Convection and Magnetoconvection: In two-dimensional rotating convection and magnetoconvection, the formation of spatially localized patterns is strongly affected by the interaction between convection and a large scale mode: zonal velocity in rotating convection and magnetic flux in magnetoconvection. A nonlocal fifth order Ginzburg-Landau theory is developed to describe the localization near a codimension-two point. The study of the fifth-order Ginzburg-Landau theory gives us better understanding of the appearance of spatially modulated solutions and their subsequent bifurcation behavior. These results are used to explain the properties of spatially localized convectons in the full convection problem. The effect of boundary conditions is also analyzed which shows how the bifurcation picture is modified in the presence of mixed boundary conditions. Exact Solutions of the Cubic-Quintic Swift-Hohenberg Equation: Meromorphic exact solutions of the cubic-quintic Swift-Hohenberg equation are studied and a one-parameter family of real exact solutions is derived. The solutions are of two types, differing in their symmetry properties, and are connected via an exact heteroclinic solution. These exact solutions are used as initial conditions for numerical continuation which shows that some of these lie on secondary branches while others fall on isolas. The approach substantially enhances our understanding of the solution space of this equation.

  6. Interactive spatial analysis of lineaments

    NASA Astrophysics Data System (ADS)

    Chandrasiri Ekneligoda, Thushan; Henkel, Herbert

    2010-08-01

    An interactive software tool, here called Spatial Analysis of Lineaments (SAL), has been developed for calculating the spatial properties azimuth, length, spacing, and unidirectional frequency of lineaments which are defined by their start and end coordinates. In a series of steps the user is guided by displays of relevant statistical distributions, which can be user designed. Statistical outliers can be excluded and the total sample of lineaments can be subdivided into azimuth sets and, if required, into spatial clusters. Special attention is given to the removal of spatial outliers in an interactive way. Several rule-based decisions are made to determine the nearest lineament in the spacing calculation. As a default procedure, the program defines a window whose size depends on the mode value of the length distribution of the lineaments in the study area. The software can accept a large amount of lineaments and can analyze the spatial properties of each azimuth set avoiding the repetitive calling of the original database. A simple rule was developed to derive the unidirectional lineament frequency. The spatial properties are presented as histograms for each azimuth set together with the mode, mean, standard deviation, and number of involved lineaments.

  7. Numerical micromagnetism of strong inhomogeneities

    NASA Astrophysics Data System (ADS)

    Andreas, Christian; Gliga, Sebastian; Hertel, Riccardo

    2014-08-01

    The size of micromagnetic structures, such as domain walls or vortices, is comparable to the exchange length of the ferromagnet. Both, the exchange length of the stray field ls and the magnetocrystalline exchange length lk, are material-dependent quantities that usually lie in the nanometer range. This emphasizes the theoretical challenges associated with the mesoscopic nature of micromagnetism: the magnetic structures are much larger than the atomic lattice constant, but at the same time much smaller than the sample size. In computer simulations, the smallest exchange length serves as an estimate for the largest cell size admissible to prevent appreciable discretization errors. This general rule is not valid in special situations where the magnetization becomes particularly inhomogeneous. When such strongly inhomogeneous structures develop, micromagnetic simulations inevitably contain systematic and numerical errors. It is suggested to combine micromagnetic theory with a Heisenberg model to resolve such problems. We analyze cases where strongly inhomogeneous structures pose limits to standard micromagnetic simulations, arising from fundamental aspects as well as from numerical drawbacks.

  8. Hydrological Networks and Associated Topographic Variation as Templates for the Spatial Organization of Tropical Forest Vegetation

    PubMed Central

    Detto, Matteo; Muller-Landau, Helene C.; Mascaro, Joseph; Asner, Gregory P.

    2013-01-01

    An understanding of the spatial variability in tropical forest structure and biomass, and the mechanisms that underpin this variability, is critical for designing, interpreting, and upscaling field studies for regional carbon inventories. We investigated the spatial structure of tropical forest vegetation and its relationship to the hydrological network and associated topographic structure across spatial scales of 10–1000 m using high-resolution maps of LiDAR-derived mean canopy profile height (MCH) and elevation for 4930 ha of tropical forest in central Panama. MCH was strongly associated with the hydrological network: canopy height was highest in areas of positive convexity (valleys, depressions) close to channels draining 1 ha or more. Average MCH declined strongly with decreasing convexity (transition to ridges, hilltops) and increasing distance from the nearest channel. Spectral analysis, performed with wavelet decomposition, showed that the variance in MCH had fractal similarity at scales of ?30–600 m, and was strongly associated with variation in elevation, with peak correlations at scales of ?250 m. Whereas previous studies of topographic correlates of tropical forest structure conducted analyses at just one or a few spatial grains, our study found that correlations were strongly scale-dependent. Multi-scale analyses of correlations of MCH with slope, aspect, curvature, and Laplacian convexity found that MCH was most strongly related to convexity measured at scales of 20–300 m, a topographic variable that is a good proxy for position with respect to the hydrological network. Overall, our results support the idea that, even in these mesic forests, hydrological networks and associated topographical variation serve as templates upon which vegetation is organized over specific ranges of scales. These findings constitute an important step towards a mechanistic understanding of these patterns, and can guide upscaling and downscaling. PMID:24204610

  9. Generic regimes of quantum many-body dynamics of trapped bosonic systems with strong repulsive interactions

    NASA Astrophysics Data System (ADS)

    Streltsova, Oksana I.; Alon, Ofir E.; Cederbaum, Lorenz S.; Streltsov, Alexej I.

    2014-06-01

    The nonequilibrium quantum dynamics of trapped bosons interacting by strong interparticle interaction of finite range in one, two, and three spatial dimensions is investigated on an accurate many-body level. We use different time-dependent processes to destabilize the systems' ground states: A sudden quench of the strength of the interparticle repulsion is accompanied by displacement of the trap. Two qualitatively different but otherwise generic dynamical quantum many-body behaviors are discovered. In the first, the overall "topology" of the ground-state density is preserved, whereas in the second the density totally "explodes." An intuitive many-body time-dependent model is devised to interpret and explain the observations. The generality of the discovered scenarios is explicitly confirmed in traps of various shapes and dimensionality, and interparticle interactions of different forms and ranges. Implications are briefly discussed.

  10. Spatial scale, rather than nature of task or locomotion, modulates the spatial reference frame of attention.

    PubMed

    Jiang, Yuhong V; Won, Bo-Yeong

    2015-06-01

    Visuospatial attention is strongly biased to locations that had frequently contained a search target before. However, the function of this bias depends on the reference frame in which attended locations are coded. Previous research has shown a striking difference between tasks administered on a computer monitor and those administered in a large environment, with the former inducing viewer-centered learning and the latter environment-centered learning. Why does environment-centered learning fail on a computer? Here, we tested 3 possibilities: differences in spatial scale, the nature of task, and locomotion may each influence the reference frame of attention. Participants searched for a target on a monitor placed flat on a stand. On each trial, they stood at a different location around the monitor. The target was frequently located in a fixed area of the monitor, but changes in participants' perspective rendered this area random relative to the participants. Under incidental learning conditions, participants failed to acquire environment-centered learning even when (a) the task and display resembled those of a large-scale task and (b) the search task required locomotion. The difficulty in inducing environment-centered learning on a computer underscores the egocentric nature of visual attention. It supports the idea that spatial scale modulates the reference frame of attention. (PsycINFO Database Record PMID:25867510

  11. Strongly Charged Polymer Brushes

    E-print Network

    Ben O'Shaughnessy; Qingbo Yang

    2005-08-10

    Charged polymer brushes are layers of surface-tethered chains. Experimental systems are frequently strongly charged. Here we calculate phase diagrams for such brushes in terms of salt concentration n_s, grafting density and polymer backbone charge density. Electrostatic stiffening and counterion condensation effects arise which are absent from weakly charged brushes. In various phases chains are locally or globally fully stretched and brush height H has unique scaling forms; at higher salt concentrations we find H ~ n_s^(-1/3), in good agreement with experiment.

  12. Strongly intensive quantities

    SciTech Connect

    Gorenstein, M. I. [Bogolyubov Institute for Theoretical Physics, Kiev (Ukraine); Frankfurt Institute for Advanced Studies, Frankfurt (Germany); Gazdzicki, M. [Institut fuer Kernphysik, University of Frankfurt, Frankfurt (Germany); Jan Kochanowski University, Kielce (Poland)

    2011-07-15

    Analysis of fluctuations of hadron production properties in collisions of relativistic particles profits from use of measurable intensive quantities which are independent of system size variations. The first family of such quantities was proposed in 1992; another is introduced in this paper. Furthermore we present a proof of independence of volume fluctuations for quantities from both families within the framework of the grand canonical ensemble. These quantities are referred to as strongly intensive ones. Influence of conservation laws and resonance decays is also discussed.

  13. Hot strong matter

    E-print Network

    Katarzyna Grebieszkow

    2014-07-14

    The recent results on relativistic heavy-ion collisions are discussed. The most convincing quark-gluon plasma signatures at the LHC and the top RHIC energies are presented. Moreover, the possible methods of evaluating the energy threshold for deconfinement (onset of deconfinement) are described, and the corresponding results from the RHIC Beam Energy Scan and the SPS programs are shown. Additionally, the first signatures of creating dense and collectively behaving systems in collisions of small nuclei (or even in elementary interactions) are discussed. Finally, the current status of experimental search for the critical point of strongly interacting matter is summarized.

  14. Capacity of MIMO free space optical communications using multiple partially coherent beams propagation through non-Kolmogorov strong turbulence.

    PubMed

    Deng, Peng; Kavehrad, Mohsen; Liu, Zhiwen; Zhou, Zhou; Yuan, Xiuhua

    2013-07-01

    We study the average capacity performance for multiple-input multiple-output (MIMO) free-space optical (FSO) communication systems using multiple partially coherent beams propagating through non-Kolmogorov strong turbulence, assuming equal gain combining diversity configuration and the sum of multiple gamma-gamma random variables for multiple independent partially coherent beams. The closed-form expressions of scintillation and average capacity are derived and then used to analyze the dependence on the number of independent diversity branches, power law ?, refractive-index structure parameter, propagation distance and spatial coherence length of source beams. Obtained results show that, the average capacity increases more significantly with the increase in the rank of MIMO channel matrix compared with the diversity order. The effect of the diversity order on the average capacity is independent of the power law, turbulence strength parameter and spatial coherence length, whereas these effects on average capacity are gradually mitigated as the diversity order increases. The average capacity increases and saturates with the decreasing spatial coherence length, at rates depending on the diversity order, power law and turbulence strength. There exist optimal values of the spatial coherence length and diversity configuration for maximizing the average capacity of MIMO FSO links over a variety of atmospheric turbulence conditions. PMID:23842307

  15. [Spatial variation characteristics of surface soil water content, bulk density and saturated hydraulic conductivity on Karst slopes].

    PubMed

    Zhang, Chuan; Chen, Hong-Song; Zhang, Wei; Nie, Yun-Peng; Ye, Ying-Ying; Wang, Ke-Lin

    2014-06-01

    Surface soil water-physical properties play a decisive role in the dynamics of deep soil water. Knowledge of their spatial variation is helpful in understanding the processes of rainfall infiltration and runoff generation, which will contribute to the reasonable utilization of soil water resources in mountainous areas. Based on a grid sampling scheme (10 m x 10 m) and geostatistical methods, this paper aimed to study the spatial variability of surface (0-10 cm) soil water content, soil bulk density and saturated hydraulic conductivity on a typical shrub slope (90 m x 120 m, projected length) in Karst area of northwest Guangxi, southwest China. The results showed that the surface soil water content, bulk density and saturated hydraulic conductivity had different spatial dependence and spatial structure. Sample variogram of the soil water content was fitted well by Gaussian models with the nugget effect, while soil bulk density and saturated hydraulic conductivity were fitted well by exponential models with the nugget effect. Variability of soil water content showed strong spatial dependence, while the soil bulk density and saturated hydraulic conductivity showed moderate spatial dependence. The spatial ranges of the soil water content and saturated hydraulic conductivity were small, while that of the soil bulk density was much bigger. In general, the soil water content increased with the increase of altitude while it was opposite for the soil bulk densi- ty. However, the soil saturated hydraulic conductivity had a random distribution of large amounts of small patches, showing high spatial heterogeneity. Soil water content negatively (P < 0.01) correlated with the bulk density and saturated hydraulic conductivity, while there was no significant correlation between the soil bulk density and saturated hydraulic conductivity. PMID:25223011

  16. Spatial variability characteristics of soil available N, P, and K and their influencing factors at the county scale

    NASA Astrophysics Data System (ADS)

    Pang, Su; Li, Tinxuan; Wang, Yongdong; Yu, Haiying

    2009-06-01

    Spatial variability, a major feature of soils, was generally influenced by various factors, relative studies on which laid solid foundations for precision agriculture. In this investigation, method of geostatistics combined with GIS was used to analyze the spatial variability characteristics of soil available nitrogen (SAN), soil available phosphorus (SAP) and soil available potassium (SAK) and their influencing factors in Shuangliu county Sichuan province, China. The results showed that, SAP and SAK were normally distributed through naturally logarithmic transformation. Semivariogram analysis revealed that SAN and SAK were highly spatial correlated, while SAP moderately spatial correlated, and the spatially dependent ranges of SAN, SAK and SAP contents were 21590m, 76903m and 23300m, respectively. Through ordinary Kriging interpolation, SAN, SAP and SAK presented different varying tendencies in the study area. SSR test indicated that SAN was significantly different depending on different soil types; SAP was significantly different depending on terrain conditions and soil parental materials; SAK was strongly affected by soil parental materials. The fertilizer application rate at the regions with high soil available N, P and K contents was obviously higher than that with low soil available nutrient contents.

  17. Spatial Wavelet Analysis of Calcium Oscillations in Developing Neurons

    PubMed Central

    Ruffinatti, Federico Alessandro; Gilardino, Alessandra; Lovisolo, Davide; Ferraro, Mario

    2013-01-01

    Calcium signals play a major role in the control of all key stages of neuronal development, and in particular in the growth and orientation of neuritic processes. These signals are characterized by high spatial compartmentalization, a property which has a strong relevance in the different roles of specific neuronal regions in information coding. In this context it is therefore important to understand the structural and functional basis of this spatial compartmentalization, and in particular whether the behavior at each compartment is merely a consequence of its specific geometry or the result of the spatial segregation of specific calcium influx/efflux mechanisms. Here we have developed a novel approach to separate geometrical from functional differences, regardless on the assumptions on the actual mechanisms involved in the generation of calcium signals. First, spatial indices are derived with a wavelet-theoretic approach which define a measure of the oscillations of cytosolic calcium concentration in specific regions of interests (ROIs) along a cell, in our case developing chick ciliary ganglion neurons. The resulting spatial profile demonstrates clearly that different ROIs along the neuron are characterized by specific patterns of calcium oscillations. Next we have investigated whether this inhomogeneity is due just to geometrical factors, namely the surface to volume ratio in the different subcompartments (e.g. soma vs. growth cone) or it depends on their specific biophysical properties. To this aim correlation functions are computed between the activity indices and the surface/volume ratio along the cell: the data thus obtained are validated by a statistical analysis on a dataset of different cells. This analysis shows that whereas in the soma calcium dynamics is highly correlated to the surface/volume ratio, correlations drop in the growth cone-neurite region, suggesting that in this latter case the key factor is the expression of specific mechanisms controlling calcium influx/efflux. PMID:24155880

  18. Strongly correlated materials.

    PubMed

    Morosan, Emilia; Natelson, Douglas; Nevidomskyy, Andriy H; Si, Qimiao

    2012-09-18

    Strongly correlated materials are profoundly affected by the repulsive electron-electron interaction. This stands in contrast to many commonly used materials such as silicon and aluminum, whose properties are comparatively unaffected by the Coulomb repulsion. Correlated materials often have remarkable properties and transitions between distinct, competing phases with dramatically different electronic and magnetic orders. These rich phenomena are fascinating from the basic science perspective and offer possibilities for technological applications. This article looks at these materials through the lens of research performed at Rice University. Topics examined include: Quantum phase transitions and quantum criticality in "heavy fermion" materials and the iron pnictide high temperature superconductors; computational ab initio methods to examine strongly correlated materials and their interface with analytical theory techniques; layered dichalcogenides as example correlated materials with rich phases (charge density waves, superconductivity, hard ferromagnetism) that may be tuned by composition, pressure, and magnetic field; and nanostructure methods applied to the correlated oxides VO? and Fe?O?, where metal-insulator transitions can be manipulated by doping at the nanoscale or driving the system out of equilibrium. We conclude with a discussion of the exciting prospects for this class of materials. PMID:22893361

  19. Spatial patterns of human papillomavirus-associated cancers within the state of Minnesota, 1998-2007.

    PubMed

    Nelson, Erik J; Hughes, John; Kulasingam, Shalini L

    2014-06-01

    Human papillomavirus (HPV) infection in women is a concern because it is considered a necessary cause of cervical cancer. Male HPV infection is also an important concern, both for the HPV-associated cancer burden in men and for the risk of transmission to women. Effective screening programs have greatly reduced cervical cancer incidence and mortality. HPV vaccines are expected to further reduce the burden of cervical cancer and other HPV-related cancers. However, disparities in terms of screening and HPV vaccination exist across the United States. In order to accurately identify areas of disparity, the spatial distributions of HPV-associated cancers has to be determined. To date, the geographic distribution and pattern exhibited by all HPV-associated cancers that accounts for spatial dependence have not been analyzed at a local level (i.e. county or ZIP code). This study analyzed the spatial dependence and pattern of HPV-associated cancers in Minnesota from 1998 to 2007 using sparse spatial generalized linear mixed models and scan statistics for cluster detection. A strong clustering pattern was seen in the northern region of Minnesota for both men and women. Separate cluster analyses by gender identified areas of overlapping disease burden. The patterns observed in this analysis demonstrate the need to account for spatial dependence when analyzing disease rates for geographic areas (i.e. county or ZIP codes) since spatial analyses of HPV-associated cancers have the potential to identify areas with the highest HPV disease burden and may serve to uncover areas where policies and HPV vaccination strategies can be most beneficial. PMID:24889990

  20. Limber equation for luminosity dependent correlations

    E-print Network

    A. Gardini; S. A. Bonometto; A. Maccio`

    1999-11-11

    The passage from angular to spatial correlations, in the case of spatial clustering length depending on the average distance between nearby objects is studied. We show that, in a number of cases, the scaling law of angular correlation amplitudes, which holds for constant spatial clustering length, is still true also for a luminosity dependent spatial correlation. If the Limber equation is then naively used to obtain `the' spatial clustering length from the angular function amplitude, a quantity close to the average object separation is obtained. The case of cluster clustering is explicitly considered.

  1. On Strong Cosmic Censorship

    E-print Network

    Isenberg, James

    2015-01-01

    For almost half of the one hundred year history of Einstein's theory of general relativity, Strong Cosmic Censorship has been one of its most intriguing conjectures. The SCC conjecture addresses the issue of the nature of the singularities found in most solutions of Einstein's gravitational field equations: Are such singularities generically characterized by unbounded curvature? Is the existence of a Cauchy horizon (and the accompanying extensions into spacetime regions in which determinism fails) an unstable feature of solutions of Einstein's equations? In this short review article, after briefly commenting on the history of the SCC conjecture, we survey some of the progress made in research directed either toward supporting SCC or toward uncovering some of its weaknesses. We focus in particular on model versions of SCC which have been proven for restricted families of spacetimes (e.g., the Gowdy spacetimes), and the role played by the generic presence of Asymptotically Velocity Term Dominated behavior in th...

  2. Strong, Lightweight, Porous Materials

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Meador, Mary Ann B.; Johnston, James C.; Fabrizio, Eve F.; Ilhan, Ulvi

    2007-01-01

    A new class of strong, lightweight, porous materials has been invented as an outgrowth of an effort to develop reinforced silica aerogels. The new material, called X-Aerogel is less hygroscopic, but no less porous and of similar density to the corresponding unmodified aerogels. However, the property that sets X-Aerogels apart is their mechanical strength, which can be as much as two and a half orders of magnitude stronger that the unmodified aerogels. X-Aerogels are envisioned to be useful for making extremely lightweight, thermally insulating, structural components, but they may also have applications as electrical insulators, components of laminates, catalyst supports, templates for electrode materials, fuel-cell components, and filter membranes.

  3. Intense or spatially heterogeneous predation can select against prey dispersal.

    PubMed

    Barraquand, Frederic; Murrell, David J

    2012-01-01

    Dispersal theory generally predicts kin competition, inbreeding, and temporal variation in habitat quality should select for dispersal, whereas spatial variation in habitat quality should select against dispersal. The effect of predation on the evolution of dispersal is currently not well-known: because predation can be variable in both space and time, it is not clear whether or when predation will promote dispersal within prey. Moreover, the evolution of prey dispersal affects strongly the encounter rate of predator and prey individuals, which greatly determines the ecological dynamics, and in turn changes the selection pressures for prey dispersal, in an eco-evolutionary feedback loop. When taken all together the effect of predation on prey dispersal is rather difficult to predict. We analyze a spatially explicit, individual-based predator-prey model and its mathematical approximation to investigate the evolution of prey dispersal. Competition and predation depend on local, rather than landscape-scale densities, and the spatial pattern of predation corresponds well to that of predators using restricted home ranges (e.g. central-place foragers). Analyses show the balance between the level of competition and predation pressure an individual is expected to experience determines whether prey should disperse or stay close to their parents and siblings, and more predation selects for less prey dispersal. Predators with smaller home ranges also select for less prey dispersal; more prey dispersal is favoured if predators have large home ranges, are very mobile, and/or are evenly distributed across the landscape. PMID:22247764

  4. Using the Spatial Configuration of the Data to Improve Estimation

    Microsoft Academic Search

    R. KELLEY PACE; OTIS W. GILLEY

    1997-01-01

    Using the well-known Harrison and Rubinfeld (1978) hedonic pricing data, this manuscript demonstrates the substantial benefits obtained by modeling the spatial dependence of the errors. Specifically, the estimated errors on the spatial autoregression fell by 44% relative to OLS. The spatial autoregression corrects predicted values by a nonparametric estimate of the error on nearby observations and thus mimics the behavior

  5. Enhanced spatial localization of collective scattering based on spatially varying electric fields (abstract)

    SciTech Connect

    Rettig, C.L.; Doyle, E.J.; Luhmann, N.C. Jr.; Peebles, W.A.; Philipona, R. (Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90024-1594 (United States)); Burrell, K.H.; Groebner, R.J. (General Atomics, San Diego, California 92186 (United States))

    1992-10-01

    Collective scattering measurements on DIII-D have been complicated by the large toroidal and polodial plasma rotation which results in a large spatially varying radial electric field, especially during neutral beam injection and H mode. This electric field produces a Doppler shift (via {bold E}{sub {ital r}}{times}B rotation) of the scattered spectra which usually dominates the measured phase velocity and depends strongly on plasma conditions and radial variations of the electric field. Measurements from charge exchange recombination spectroscopy allow the radial structure of {ital E}{sub {ital r}} to be independently determined. The strong variation of the radial electric field across the plasma has allowed unambiguous mapping of different frequency bands of the scattered spectra into different locations in the plasma. Thus, the characteristics of fluctuations originating from the plasma interior can be easily distinguished from the edge. Measurements of the radial variation of the turbulent fluctuations will be presented. This work is supported by the U.S. Department of Energy (DOE) under Grant No. DE-FG03-86-ER53225 and DOE Contract No. DE-AC03-89ER51114.

  6. Strongly Hyperbolic Extensions of the ADM Hamiltonian

    E-print Network

    J. David Brown

    2008-07-10

    The ADM Hamiltonian formulation of general relativity with prescribed lapse and shift is a weakly hyperbolic system of partial differential equations. In general weakly hyperbolic systems are not mathematically well posed. For well posedness, the theory should be reformulated so that the complete system, evolution equations plus gauge conditions, is (at least) strongly hyperbolic. Traditionally, reformulation has been carried out at the level of equations of motion. This typically destroys the variational and Hamiltonian structures of the theory. Here I show that one can extend the ADM formalism to (i) incorporate the gauge conditions as dynamical equations and (ii) affect the hyperbolicity of the complete system, all while maintaining a Hamiltonian description. The extended ADM formulation is used to obtain a strongly hyperbolic Hamiltonian description of Einstein's theory that is generally covariant under spatial diffeomorphisms and time reparametrizations, and has physical characteristics. The extended Hamiltonian formulation with 1+log slicing and gamma--driver shift conditions is weakly hyperbolic.

  7. Ability and Sex-Related Differences in Cognitive Strategies on Spatial Tasks

    Microsoft Academic Search

    Kathryn F. Cochran; Grayson H. Wheatley

    1989-01-01

    Individual differences in cognitive strategies and their relationships to spatial ability, sex, and handedness were investigated. Undergraduates (N = 165) were given two spatial ability tests and a spatial strategy questionnaire (SSQ). High spatial performance was significantly related to holistic\\/nonverbal strategies and was more strongly related to the reported difficulty of such strategies than to the frequency of their use.

  8. Taming Random Lasers through Active Spatial Control of the Pump

    NASA Astrophysics Data System (ADS)

    Bachelard, N.; Andreasen, J.; Gigan, S.; Sebbah, P.

    2012-07-01

    Active control of the spatial pump profile is proposed to exercise control over random laser emission. We demonstrate numerically the selection of any desired lasing mode from the emission spectrum. An iterative optimization method is employed, first in the regime of strong scattering where modes are spatially localized and can be easily selected using local pumping. Remarkably, this method works efficiently even in the weakly scattering regime, where strong spatial overlap of the modes precludes spatial selectivity. A complex optimized pump profile is found, which selects the desired lasing mode at the expense of others, thus demonstrating the potential of pump shaping for robust and controllable single mode operation of a random laser.

  9. Spatial filtering with photonic crystals

    NASA Astrophysics Data System (ADS)

    Maigyte, Lina; Staliunas, Kestutis

    2015-03-01

    Photonic crystals are well known for their celebrated photonic band-gaps—the forbidden frequency ranges, for which the light waves cannot propagate through the structure. The frequency (or chromatic) band-gaps of photonic crystals can be utilized for frequency filtering. In analogy to the chromatic band-gaps and the frequency filtering, the angular band-gaps and the angular (spatial) filtering are also possible in photonic crystals. In this article, we review the recent advances of the spatial filtering using the photonic crystals in different propagation regimes and for different geometries. We review the most evident configuration of filtering in Bragg regime (with the back-reflection—i.e., in the configuration with band-gaps) as well as in Laue regime (with forward deflection—i.e., in the configuration without band-gaps). We explore the spatial filtering in crystals with different symmetries, including axisymmetric crystals; we discuss the role of chirping, i.e., the dependence of the longitudinal period along the structure. We also review the experimental techniques to fabricate the photonic crystals and numerical techniques to explore the spatial filtering. Finally, we discuss several implementations of such filters for intracavity spatial filtering.

  10. Local spatial structure of forest biomass and its consequences for remote sensing of carbon stocks

    NASA Astrophysics Data System (ADS)

    Réjou-Méchain, M.; Muller-Landau, H. C.; Detto, M.; Thomas, S. C.; Le Toan, T.; Saatchi, S. S.; Barreto-Silva, J. S.; Bourg, N. A.; Bunyavejchewin, S.; Butt, N.; Brockelman, W. Y.; Cao, M.; Cárdenas, D.; Chiang, J.-M.; Chuyong, G. B.; Clay, K.; Condit, R.; Dattaraja, H. S.; Davies, S. J.; Duque, A.; Esufali, S.; Ewango, C.; Fernando, R. H. S.; Fletcher, C. D.; Gunatilleke, I. A. U. N.; Hao, Z.; Harms, K. E.; Hart, T. B.; Hérault, B.; Howe, R. W.; Hubbell, S. P.; Johnson, D. J.; Kenfack, D.; Larson, A. J.; Lin, L.; Lin, Y.; Lutz, J. A.; Makana, J.-R.; Malhi, Y.; Marthews, T. R.; McEwan, R. W.; McMahon, S. M.; McShea, W. J.; Muscarella, R.; Nathalang, A.; Noor, N. S. M.; Nytch, C. J.; Oliveira, A. A.; Phillips, R. P.; Pongpattananurak, N.; Punchi-Manage, R.; Salim, R.; Schurman, J.; Sukumar, R.; Suresh, H. S.; Suwanvecho, U.; Thomas, D. W.; Thompson, J.; Uríarte, M.; Valencia, R.; Vicentini, A.; Wolf, A. T.; Yap, S.; Yuan, Z.; Zartman, C. E.; Zimmerman, J. K.; Chave, J.

    2014-04-01

    Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDD+. Though broad scale mapping is based primarily on remote sensing data, the accuracy of resulting forest carbon stock estimates depends critically on the quality of field measurements and calibration procedures. The mismatch in spatial scales between field inventory plots and larger pixels of current and planned remote sensing products for forest biomass mapping is of particular concern, as it has the potential to introduce errors, especially if forest biomass shows strong local spatial variation. Here, we used 30 large (8-50 ha) globally distributed permanent forest plots to quantify the spatial variability in aboveground biomass (AGB) at spatial grains ranging from 5 to 250 m (0.025-6.25 ha), and we evaluate the implications of this variability for calibrating remote sensing products using simulated remote sensing footprints. We found that the spatial sampling error in AGB is large for standard plot sizes, averaging 46.3% for 0.1 ha subplots and 16.6% for 1 ha subplots. Topographically heterogeneous sites showed positive spatial autocorrelation in AGB at scales of 100 m and above; at smaller scales, most study sites showed negative or nonexistent spatial autocorrelation in AGB. We further show that when field calibration plots are smaller than the remote sensing pixels, the high local spatial variability in AGB leads to a substantial "dilution" bias in calibration parameters, a bias that cannot be removed with current statistical methods. Overall, our results suggest that topography should be explicitly accounted for in future sampling strategies and that much care must be taken in designing calibration schemes if remote sensing of forest carbon is to achieve its promise.

  11. Applying Spatial Statistics to Isolate the Effects of Fuels, Topography, and Weather on Burn Severity

    NASA Astrophysics Data System (ADS)

    Wimberly, M. C.; Cochrane, M. A.; Baer, A. D.; Zhu, Z.

    2007-12-01

    Fire severity datasets derived from satellite remote sensing data are now being used extensively in wildfire research and land management. Maps of burn severity based on the differenced normalized burn ratio (dNBR) are being produced and disseminated by the Monitoring Trends in Burn Severity (MTBS) project for all major wildfires in the United States from 1984 to present. This abundance of data presents unprecedented new opportunities for understanding how weather, terrain, and fuels interact to determine fire severity patterns, and for testing the effectiveness of fuel-reduction strategies for mitigating wildfire impacts. However, these datasets present challenges for statistical analysis because of their large sizes and the non-independence of spatially autocorrelated pixels. To explore the importance of spatial autocorrelation, we analyzed the spatial patterns of burn severity in two recent wildfires - the 2004 School Fire in the Blue Mountains of southeastern Washington and the 2005 Warm Fire on the Kaibab Plateau in northern Arizona. Conditional autoregressive (CAR) models were fitted with dNBR as the dependent variable and topography, fuels, and locations of recent fuel treatments as the independent variables. In both fires, elevation, slope, and aspect had strong effects on burn severity. Fuels had stronger effects on burn severity for the School fire than for the Warm Fire. In both fires, fuel treatments that combined thinning and prescribed burning resulted in statistically significant reductions in fire severity. The CAR models were then decomposed to isolate the spatial signal, which reflected spatially structured variability in dNBR that was not related to the independent variables. The spatial signals were correlated with the burn progression maps, reflecting spatial and temporal variability in weather and fire behavior (e.g. wind versus plume driven) over the course of the fire. These results suggest that spatial autocorrelation in the analysis of remotely- sensed burn severity datasets is not simply a nuisance, but in fact captures substantive and interpretable effects of weather and fire behavior on burn severity.

  12. A Generalized Spatial Two-Stage Least Squares Procedure for Estimating a Spatial Autoregressive Model with Autoregressive Disturbances

    Microsoft Academic Search

    Harry H. Kelejian; Ingmar R. Prucha

    1998-01-01

    Cross-sectional spatial models frequently contain a spatial lag of the dependent variable as a regressor or a disturbance term that is spatially autoregressive. In this article we describe a computationally simple procedure for estimating cross-sectional models that contain both of these characteristics. We also give formal large-sample results.

  13. X-ray microprobe of optical strong-field processes

    Microsoft Academic Search

    L. Young; R. W. Dunford; C. Hoehr; E. P. Kanter; B. Krässig; E. R. Peterson; S. H. Southworth; D. L. Ederer; J. Rudati; D. A. Arms; E. M. Dufresne; E. C. Landahl

    2006-01-01

    A time-resolved X-ray microprobe to study optical strong-field processes has been developed. Individual atoms or molecules located within the strong-field environment created by a focused ultrafast laser are probed by undulator-produced X-ray pulses to achieve spatial, temporal, spectral and polarization selectivity. Approximately 106 monochromatic X-rays per 100-ps pulse are focused into a ?10?m spot to selectively probe atoms in focal

  14. Scintillation of a laser beam propagation through non-Kolmogorov strong turbulence

    NASA Astrophysics Data System (ADS)

    Deng, Peng; Yuan, Xiu-Hua; Huang, Dexiu

    2012-03-01

    Atmospheric turbulence causes strong irradiance fluctuations of propagating optical wave under the severe weather conditions in long-distance free space optical communication. In this paper, the scintillation index for a Gaussian beam wave propagation through non-Kolmogorov turbulent atmosphere is derived in strong fluctuation regime, using non-Kolmogorov spectrum with a generalized power law exponent and the extended Rytov theory with a modified spatial filter function. The analytic expressions are obtained and then used to analyze the effect of power law, refractive-index structure parameter, propagation distance, phase radius of curvature, beam width and wavelength on scintillation index of Gaussian beam under the strong atmospheric turbulence. It shows that, with the increasing of structure parameter or propagation distance, scintillation index increases sharply up to the peak point and then decreases gradually toward unity at rates depending on power law. And there exist optimal value of radius of curvature and beam width for minimizing the value of scintillation index and long wavelength for mitigating the effect of non-Kolmogorov strong turbulence on link performance.

  15. Strongly correlated surface states

    NASA Astrophysics Data System (ADS)

    Alexandrov, Victor A.

    Everything has an edge. However trivial, this phrase has dominated theoretical condensed matter in the past half a decade. Prior to that, questions involving the edge considered to be more of an engineering problem rather than a one of fundamental science: it seemed self-evident that every edge is different. However, recent advances proved that many surface properties enjoy a certain universality, and moreover, are 'topologically' protected. In this thesis I discuss a selected range of problems that bring together topological properties of surface states and strong interactions. Strong interactions alone can lead to a wide spectrum of emergent phenomena: from high temperature superconductivity to unconventional magnetic ordering; interactions can change the properties of particles, from heavy electrons to fractional charges. It is a unique challenge to bring these two topics together. The thesis begins by describing a family of methods and models with interactions so high that electrons effectively disappear as particles and new bound states arise. By invoking the AdS/CFT correspondence we can mimic the physical systems of interest as living on the surface of a higher dimensional universe with a black hole. In a specific example we investigate the properties of the surface states and find helical spin structure of emerged particles. The thesis proceeds from helical particles on the surface of black hole to a surface of samarium hexaboride: an f-electron material with localized magnetic moments at every site. Interactions between electrons in the bulk lead to insulating behavior, but the surfaces found to be conducting. This observation motivated an extensive research: weather the origin of conduction is of a topological nature. Among our main results, we confirm theoretically the topological properties of SmB6; introduce a new framework to address similar questions for this type of insulators, called Kondo insulators. Most notably we introduce the idea of Kondo band banding (KBB): a modification of edges and their properties due to interactions. We study (chapter 5) a simplified 1D Kondo model, showing that the topology of its ground state is unstable to KBB. Chapter 6 expands the study to 3D: we argue that not only KBB preserves the topology but it could also explain the experimentally observed anomalously high Fermi velocity at the surface as the case of large KBB effect.

  16. Hyperon Stars in Strong Magnetic Fields

    E-print Network

    R. O. Gomes; V. Dexheimer; C. A. Z. Vasconcellos

    2013-07-29

    We investigate the effects of strong magnetic fields on the properties of hyperon stars. The matter is described by a hadronic model with parametric coupling. The matter is considered to be at zero temperature, charge neutral, beta-equilibrated, containing the baryonic octet, electrons and muons. The charged particles have their orbital motions Landau-quantized in the presence of strong magnetic fields (SMF). Two parametrisations of a chemical potential dependent static magnetic field are considered, reaching $1-2 \\times 10^{18}\\,G$ in the center of the star. Finally, the Tolman-Oppenheimer-Volkov (TOV) equations are solved to obtain the mass-radius relation and population of the stars.

  17. Electron Dynamics during Strong Field Molecular Ionization

    NASA Astrophysics Data System (ADS)

    Weinacht, Thomas

    2014-05-01

    Strong Field Ionization plays a central role in the study of ultrafast electron dynamics, both as the first step in attosecond pulse generation and in the launch of electron wave packets in atoms and molecules. This talk will focus on studies of strong field molecular ionization with shaped laser pulses, where the pulse shape dependence yields insight into the electron dynamics during ionization. Coincidence velocity map imaging and close collaboration with theory enable us to examine the role of both neutral and ionic resonances as well as electron correlation. We gratefully acknowledge support from the National Science Foundation under grant number 1205397.

  18. Spatial variability of trends in hydrological extremes induced by orographically enhanced rainfall events due to westerly atmospheric circulations.

    PubMed

    Pfister, L; Drogue, G; Poirier, C; Hoffmann, L

    2005-01-01

    Since the mid 1970s, the number of days with westerly atmospheric circulations has strongly increased during winter months. As a consequence, rainfall totals, rainfall event duration and intensity have been subject to significant positive trends throughout the Mosel river basin. However, the trends identified through the non-parametrical test named Kendall's tau have shown to be spatially varying. The intensity of the trends appears to be directly linked to orographic obstacles that are well known to have a strong influence on average rainfall totals. A direct consequence of the changes having affected winter rainfall under westerly atmospheric circulations on the one hand and the spatial variability of these changes on the other hand, is a spatially varying positive trend in maximum winter streamflow. Thus, even though a clear large-scale change has affected winter rainfall over the past decades, its intensity is either strongly moderated or enhanced by orographic obstacles. The related changes in streamflow are directly dependent on the spatial variability of the changed rainfall characteristics. PMID:15918354

  19. Spatial distributions at equilibrium under heterogeneous transient subdiffusion

    PubMed Central

    Berry, Hugues; Soula, Hédi A.

    2014-01-01

    Experimental measurements of the mobility of macromolecules, especially proteins, in cells and their membranes consistently report transient subdiffusion with possibly position-dependent—non-homogeneous—properties. However, the spatiotemporal dynamics of protein mobility when transient subdiffusion is restricted to a subregion of space is still unclear. Here, we investigated the spatial distribution at equilibrium of proteins undergoing transient subdiffusion due to continuous-time random walks (CTRW) in a restricted subregion of a two-dimensional space. Our Monte-Carlo simulations suggest that this process leads to a non-homogeneous spatial distribution of the proteins at equilibrium, where proteins increasingly accumulate in the CTRW subregion as its anomalous properties are increasingly marked. In the case of transient CTRW, we show that this accumulation is dictated by the asymptotic Brownian regime and not by the initial anomalous transient dynamics. Moreover, our results also show that this dominance of the asymptotic Brownian regime cannot be simply generalized to other scenarios of transient subdiffusion. In particular, non-homogeneous transient subdiffusion due to hindrance by randomly-located immobile obstacles does not lead to such a strong local accumulation. These results suggest that, even though they exhibit the same time-dependence of the mean-squared displacement, the different scenarios proposed to account for subdiffusion in the cell lead to different protein distribution in space, even at equilibrium and without coupling with reaction. PMID:25429273

  20. Spatial genetic structure of the ectoparasite Ixodes uriae within breeding cliffs of its colonial seabird host.

    PubMed

    McCoy, K D; Tirard, C; Michalakis, Y

    2003-10-01

    To examine the potential importance of the spatial subdivision of hosts for the functioning of parasite populations, we analysed patterns of local genetic structure within natural populations of the seabird ectoparasite, Ixodes uriae, at the scale of the host breeding cliff. The seabird hosts of this parasite nest in dense colonies with a hierarchical spatial organisation (individual nests-breeding cliffs-colony). Using eight microsatellite markers and samples from three breeding cliffs of the Black-legged kittiwake (Rissa tridactyla), we found that tick populations were indeed genetically structured at this spatial scale. However, the nature of this structuring depended on the characteristics of the cliffs considered. Both the host nest and cliff topography seemed to be important factors in the isolation of tick groups, but their relative roles may depend on the size of the local parasite population. We found no evidence of isolation by distance within a cliff suggesting that independent tick dispersal may not be a significant force influencing population structure in highly infested cliffs. However, genetic structure seemed to decrease with tick life stage, nymphal ticks being more strongly structured than adult ticks. These results may be related to the clustering of tick progeny combined with differential mortality and dispersal probabilities of each life stage. Overall, results indicate that the spatial organisation of hosts can indeed have important consequences for the population genetic structure of their parasites and, thus, may modify parasite dynamics and the scale at which local coevolutionary processes occur. PMID:14512959

  1. Modeling small-scale spatial interaction of shortgrass prairie species

    Microsoft Academic Search

    R. M. Reich; C. D. Bonham; K. L. Metzger

    1997-01-01

    Native grasses interact spatially with themselves and their environment and can therefore be thought of as a system of dependent random variables. One method of modeling the spatial dependence of a multi-species population is a Gibbsian pairwise potential model. Since natural selection operates at the level of individual plants, the information obtained from such a model should provide a greater

  2. Spatial asynchrony and periodic travelling waves in cyclic populations of field voles.

    PubMed Central

    Lambin, X; Elston, D A; Petty, S J; MacKinnon, J L

    1998-01-01

    We demonstrate evidence for the presence of travelling waves in a cyclic population of field voles in northern Britain by fitting simple, empirical models to spatially referenced time series data. Population cycles were broadly synchronous at all sites, but use of Mantel correlations suggested a strong spatial pattern along one axis at a projection line 72 degrees from North. We then fitted a generalized additive model to log population density assuming a fixed-form travelling wave in one spatial dimension for which the density at each site was offset in time by a constant amount from a standard density-time curve. We assumed that the magnitude of this offset would be proportional to the spatial separation between any given site and the centroid of the sampling sites, where separation is the distance between sites in a fixed direction. After fitting this model, we estimated that the wave moved at an average speed of 19 km yr-1, heading from West to East at an angle of 78 degrees from North. Nomadic avian predators which could synchronize populations over large areas are scarce and the travelling wave may be caused by density-dependent dispersal by field voles and/or predation by weasels, both of which act at a suitably small spatial scale. PMID:9744104

  3. The relative influence of habitat amount and configuration on genetic structure across multiple spatial scales.

    PubMed

    Millette, Katie L; Keyghobadi, Nusha

    2015-01-01

    Despite strong interest in understanding how habitat spatial structure shapes the genetics of populations, the relative importance of habitat amount and configuration for patterns of genetic differentiation remains largely unexplored in empirical systems. In this study, we evaluate the relative influence of, and interactions among, the amount of habitat and aspects of its spatial configuration on genetic differentiation in the pitcher plant midge, Metriocnemus knabi. Larvae of this species are found exclusively within the water-filled leaves of pitcher plants (Sarracenia purpurea) in a system that is naturally patchy at multiple spatial scales (i.e., leaf, plant, cluster, peatland). Using generalized linear mixed models and multimodel inference, we estimated effects of the amount of habitat, patch size, interpatch distance, and patch isolation, measured at different spatial scales, on genetic differentiation (F ST) among larval samples from leaves within plants, plants within clusters, and clusters within peatlands. Among leaves and plants, genetic differentiation appears to be driven by female oviposition behaviors and is influenced by habitat isolation at a broad (peatland) scale. Among clusters, gene flow is spatially restricted and aspects of both the amount of habitat and configuration at the focal scale are important, as is their interaction. Our results suggest that both habitat amount and configuration can be important determinants of genetic structure and that their relative influence is scale dependent. PMID:25628865

  4. Tomographic retrieval for scattered light limb measurements: multiple spectral fit windows to improve the spatial resolution

    NASA Astrophysics Data System (ADS)

    Pukite, Janis; Dörner, Steffen; Wagner, Thomas

    2015-04-01

    The Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite probed the atmosphere at the day side of Earth in alternating sequences of nadir and limb measurements from August 2002 to April 2012. Limb measurements allow the retrieval of stratospheric profiles of various trace gases on a global scale. It has been shown that combining measurements of the same air volume from different viewing positions along the orbit, 2D distribution fields of stratospheric trace gases can be acquired in one inversion step. Since the atmospheric scattering and absorption processes are wavelength dependent, the spatial sensitivity for limb observations also varies with wavelength. In general, for longer wavelengths, photons from more remote areas along the line of sight are contributing stronger to the measurement than for shorter wavelengths because of the lower probability of Rayleigh scattering. In addition, the radiative transfer is modified by the ozone absorption structures making longer light paths less probable within strong ozone absorption bands. In this study, additional information on the spatial distribution of NO2 is investigated by analysing results obtained by Differential Optical Absorption Spectroscopy (DOAS) in various spectral fit windows. Combing the fit results in one profile retrieval algorithm helps to improve the spatial sensitivity and resolution of the measurements. The largest improvements for the spatial resolution and sensitivity are expected for the upper troposphere/ lower stratosphere (UTLS) region where the variation of the spatial sensitivity with wavelength is strongest.

  5. The relative influence of habitat amount and configuration on genetic structure across multiple spatial scales

    PubMed Central

    Millette, Katie L; Keyghobadi, Nusha

    2015-01-01

    Despite strong interest in understanding how habitat spatial structure shapes the genetics of populations, the relative importance of habitat amount and configuration for patterns of genetic differentiation remains largely unexplored in empirical systems. In this study, we evaluate the relative influence of, and interactions among, the amount of habitat and aspects of its spatial configuration on genetic differentiation in the pitcher plant midge, Metriocnemus knabi. Larvae of this species are found exclusively within the water-filled leaves of pitcher plants (Sarracenia purpurea) in a system that is naturally patchy at multiple spatial scales (i.e., leaf, plant, cluster, peatland). Using generalized linear mixed models and multimodel inference, we estimated effects of the amount of habitat, patch size, interpatch distance, and patch isolation, measured at different spatial scales, on genetic differentiation (FST) among larval samples from leaves within plants, plants within clusters, and clusters within peatlands. Among leaves and plants, genetic differentiation appears to be driven by female oviposition behaviors and is influenced by habitat isolation at a broad (peatland) scale. Among clusters, gene flow is spatially restricted and aspects of both the amount of habitat and configuration at the focal scale are important, as is their interaction. Our results suggest that both habitat amount and configuration can be important determinants of genetic structure and that their relative influence is scale dependent. PMID:25628865

  6. Oracle Spatial Data Option Spatial Cartridge Oracle8i SpatialIBM ESRI DB2 Spatial ExtenderInformix Informix Spatial

    E-print Network

    Li, Xiang

    ; ---- Oracle Spatial Data Option Spatial Cartridge Oracle8i SpatialIBM ESRI DB2 Spatial ExtenderInformix Informix Spatial Datablade Oracle Oracle8i Spatial Oracle Spatial ----SDO_GEOMETRY SDO_GEOMETRY Oracle/cdrom/papers/coors1997 Oracle Co.Oracle Spatial White Paper2001.5 MapInfo Co. Spatial Database Standards

  7. DNS of Turbulent Boundary Layer Subject Strong Adverse Pressure Gradient

    Microsoft Academic Search

    Guillermo Araya; Luciano Castillo

    2010-01-01

    Direct Numerical Simulations of spatially evolving turbulent boundary layers with prescribed strong adverse pressure gradients are performed. The driven force behind this investigation is to analyze the interaction between the inner and outer layers in adverse pressure gradient with eventual separation. A method for prescribing realistic turbulent velocity inflow boundary conditions is employed. The approach is based on the rescaling-recycling

  8. Strong lensing optical depths in a LambdaCDM universe

    Microsoft Academic Search

    Stefan Hilbert; Simon D. M. White; Jan Hartlap; Peter Schneider

    2007-01-01

    We investigate strong gravitational lensing in the concordance LambdaCDM cosmology by carrying out ray tracing along past light cones through the Millennium Simulation, the largest simulation of cosmic structure formation ever carried out. We extend previous ray-tracing methods in order to take full advantage of the large volume and the excellent spatial and mass resolution of the simulation. As a

  9. Kubo conductivity of a strongly magnetized two-dimensional plasma.

    NASA Technical Reports Server (NTRS)

    Montgomery, D.; Tappert, F.

    1971-01-01

    The Kubo formula is used to evaluate the bulk electrical conductivity of a two-dimensional guiding-center plasma in a strong dc magnetic field. The particles interact only electrostatically. An ?anomalous' electrical conductivity is derived for this system, which parallels a recent result of Taylor and McNamara for the coefficient of spatial diffusion.

  10. Vacuum birefringence in strong inhomogeneous electromagnetic fields

    E-print Network

    Karbstein, Felix; Reuter, Maria; Zepf, Matt

    2015-01-01

    Birefringence is one of the fascinating properties of the vacuum of quantum electrodynamics (QED) in strong electromagnetic fields. The scattering of linearly polarized incident probe photons into a perpendicularly polarized mode provides a distinct signature of the optical activity of the quantum vacuum and thus offers an excellent opportunity for a precision test of non-linear QED. Precision tests require accurate predictions and thus a theoretical framework that is capable of taking the detailed experimental geometry into account. We derive analytical solutions for vacuum birefringence which include the spatio-temporal field structure of a strong optical pump laser field and an x-ray probe. We show that the angular distribution of the scattered photons depends strongly on the interaction geometry and find that scattering of the perpendicularly polarized scattered photons out of the cone of the incident probe x-ray beam is the key to making the phenomenon experimentally accessible with the current generatio...

  11. Spatial structure in the color of the dust coma of Comet P/Halley

    SciTech Connect

    Hoban, S.; A'Hearn, M.F.; Birch, P.V.; Martin, R. (Maryland Univ., College Park (USA); Perth Observatory, Bickley (Australia))

    1989-05-01

    Significant spatial variations are noted in the color of the dust in Comet Halley's dust coma, out to 156,000 km from the optocenter, in the present March 1-6, 1986 narrowband CCD images. In particular, the envelope of intermediate-mass particles formed around the nucleus by solar radiation pressure is redder than the rest of the dust coma, and a strong jet noted in the March 1 images is redder than both the dust envelope and the remainder of the dust coma. A wavelength-dependence model of the Comet Halley dust's color is developed on the basis of Mie theory. 28 refs.

  12. The strong Ekeland variational principle

    NASA Astrophysics Data System (ADS)

    Suzuki, Tomonari

    2006-08-01

    In this paper, we consider the strong Ekeland variational principle due to Georgiev [P.G. Georgiev, The strong Ekeland variational principle, the strong drop theorem and applications, J. Math. Anal. Appl. 131 (1988) 1-21]. We discuss it for functions defined on Banach spaces and on compact metric spaces. We also prove the [tau]-distance version of it.

  13. Spatial Information Management within Digital Libraries

    Microsoft Academic Search

    Christian Sallaberry; Christophe Marquesuzaà; Patrick Etcheverry

    2006-01-01

    Local cultural heritage document collections are characterized by contents strongly attached to a territory and its land history. Our contribution aims at enhancing such a content retrieval process efficiently each time a query includes geographic criteria. We propose a unified model for a formal representation of geographic information. This geographic model allows spatial features to be described independently of their

  14. Simulations of Dynamical Friction Including Spatially-Varying Magnetic Fields

    SciTech Connect

    Bell, G. I.; Bruhwiler, D. L.; Busby, R.; Abell, D. T.; Messmer, P.; Veitzer, S. [Tech-X Corp., Boulder, CO 80303 (United States); Litvinenko, V. N. [Brookhaven National Lab, Upton, NY 11973 (United States); Cary, J. R. [Tech-X Corp., Boulder, CO 80303 (United States); University of Colorado, Boulder, CO 80309 (United States)

    2006-03-20

    A proposed luminosity upgrade to the Relativistic Heavy Ion Collider (RHIC) includes a novel electron cooling section, which would use {approx}55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions. We consider the dynamical friction force exerted on individual ions due to a relevant electron distribution. The electrons may be focussed by a strong solenoid field, with sensitive dependence on errors, or by a wiggler field. In the rest frame of the relativistic co-propagating electron and ion beams, where the friction force can be simulated for nonrelativistic motion and electrostatic fields, the Lorentz transform of these spatially-varying magnetic fields includes strong, rapidly-varying electric fields. Previous friction force simulations for unmagnetized electrons or error-free solenoids used a 4th-order Hermite algorithm, which is not well-suited for the inclusion of strong, rapidly-varying external fields. We present here a new algorithm for friction force simulations, using an exact two-body collision model to accurately resolve close interactions between electron/ion pairs. This field-free binary-collision model is combined with a modified Boris push, using an operator-splitting approach, to include the effects of external fields. The algorithm has been implemented in the VORPAL code and successfully benchmarked.

  15. Spatial Interference Cancellation and Pairwise Error Probability Analysis

    E-print Network

    Gesbert, David

    Spatial Interference Cancellation and Pairwise Error Probability Analysis Rizwan Ghaffar, Raymond frequency reuse, adaptive modulation and coding schemes and diversified data services will be interference interference cancellation in the presence of one strong interferer. We derive an analytical upper bound

  16. Concentration dependence of rheological properties of telechelic associative polymer solutions.

    PubMed

    Uneyama, Takashi; Suzuki, Shinya; Watanabe, Hiroshi

    2012-09-01

    We consider concentration dependence of rheological properties of associative telechelic polymer solutions. Experimental results for model telechelic polymer solutions show rather strong concentration dependence of rheological properties. For solutions with relatively high concentrations, linear viscoelasticity deviates from the single Maxwell behavior. The concentration dependence of characteristic relaxation time and moduli is different in high- and low-concentration cases. These results suggest that there are two different concentration regimes. We expect that densely connected (well percolated) networks are formed in high-concentration solutions, whereas sparsely connected (weakly percolated) networks are formed in low-concentration solutions. We propose single chain type transient network models to explain experimental results. Our models incorporate the spatial correlation effect of micellar cores and average number of elastically active chains per micellar core (the network functionality). Our models can reproduce nonsingle Maxwellian relaxation and nonlinear rheological behavior such as the shear thickening and thinning. They are qualitatively consistent with experimental results. In our models, the linear rheological behavior is mainly attributable to the difference of network structures (functionalities). The nonlinear rheological behavior is attributable to the nonlinear flow rate dependence of the spatial correlation of micellar core positions. PMID:23030933

  17. Concentration Dependence of Rheological Properties of Telechelic Associative Polymer Solutions

    E-print Network

    Takashi Uneyama; Shinya Suzuki; Hiroshi Watanabe

    2012-08-24

    We consider concentration dependence of rheological properties of associative telechelic polymer solutions. Experimental results for model telechelic polymer solutions show rather strong concentration dependence of rheological properties. For solutions with relatively high concentrations, linear viscoelasticity deviates from the single Maxwell behavior. The concentration dependence of characteristic relaxation time and moduli is different in high and low concentration cases. These results suggest that there are two different concentration regimes. We expect that densely connected (well percolated) networks are formed in high-concentration solutions, whereas sparsely connected (weakly percolated) networks are formed in low-concentration solutions. We propose single chain type transient network models to explain experimental results. Our models incorporate the spatial correlation effect of micellar cores and average number of elastically active chains per micellar core (the network functionality). Our models can reproduce non-single Maxwellian relaxation and nonlinear rheological behavior such as the shear thickening and thinning. They are qualitatively consistent with experimental results. In our models, the linear rheological behavior is mainly attributable to the difference of network structures (functionalities). The nonlinear rheological behavior is attributable to the nonlinear flow rate dependence of the spatial correlation of micellar core positions.

  18. Resolution Improvement In Spect By Spatial Filtering

    Microsoft Academic Search

    Weishi Xia; Robert M. Lewitt; Paul R. Edholm

    1990-01-01

    In this paper, a method is presented for pre-processing projection data in single-photon emission computed tomography which are blurred by the collimator's spatially-variant point-response function. The algorithm developed to correct this kind of blumng is based on Fourier analysis of the sinogram. Special depth-dependent characteristics of the Fourier coefficients are used to achieve spatially-variant inverse filtering of the projection data

  19. UWB Spatial-Frequency Channel Characterization

    Microsoft Academic Search

    Wen Zhang; Thushara D. Abhayapala; Jian Zhang

    This paper investigates the spatial-frequency chan- nel characterization of Ultra-wideband (UWB) wireless commu- nication systems. Firstly, a novel frequency dependent UWB channel model is constructed based on the theory of electro- magnetic diffraction mechanism, which causes the field strength to vary with the frequency in each multipath. Secondly, we build a space-frequency model, which includes spatial characteristics such as angular

  20. Pattern Formation in Populations with Density-Dependent Movement and Two Interaction Scales

    E-print Network

    Martínez-García, Ricardo; Hernández-García, Emilio; López, Cristóbal

    2015-01-01

    We study the spatial patterns formed by a system of interacting particles where the mobility of any individual is determined by the population crowding at two different spatial scales. In this way we model the behavior of some biological organisms (like mussels) that tend to cluster at short ranges as a defensive strategy, and strongly disperse if there is a high population pressure at large ranges for optimizing foraging. We perform stochastic simulations of a particle-level model of the system, and derive and analyze a continuous density description (a nonlinear diffusion equation). In both cases we show that this interplay of scale-dependent-behaviors gives rise to a rich formation of spatial patterns ranging from labyrinths to periodic cluster arrangements. In most cases these clusters have the very peculiar appearance of ring-like structures, i.e., organisms arranging in the perimeter of the clusters, that we discuss in detail.

  1. Pattern Formation in Populations with Density-Dependent Movement and Two Interaction Scales

    PubMed Central

    Martínez-García, Ricardo; Murgui, Clara; Hernández-García, Emilio; López, Cristóbal

    2015-01-01

    We study the spatial patterns formed by a system of interacting particles where the mobility of any individual is determined by the population crowding at two different spatial scales. In this way we model the behavior of some biological organisms (like mussels) that tend to cluster at short ranges as a defensive strategy, and strongly disperse if there is a high population pressure at large ranges for optimizing foraging. We perform stochastic simulations of a particle-level model of the system, and derive and analyze a continuous density description (a nonlinear diffusion equation). In both cases we show that this interplay of scale-dependent-behaviors gives rise to a rich formation of spatial patterns ranging from labyrinths to periodic cluster arrangements. In most cases these clusters have the very peculiar appearance of ring-like structures, i.e., organisms arranging in the perimeter of the clusters, which we discuss in detail. PMID:26147351

  2. Deconstruction of spatial integrity in visual stimulus detected by modulation of synchronized activity in cat visual cortex.

    PubMed

    Zhou, Zhiyi; Bernard, Melanie R; Bonds, A B

    2008-04-01

    Spatiotemporal relationships among contour segments can influence synchronization of neural responses in the primary visual cortex. We performed a systematic study to dissociate the impact of spatial and temporal factors in the signaling of contour integration via synchrony. In addition, we characterized the temporal evolution of this process to clarify potential underlying mechanisms. With a 10 x 10 microelectrode array, we recorded the simultaneous activity of multiple cells in the cat primary visual cortex while stimulating with drifting sine-wave gratings. We preserved temporal integrity and systematically degraded spatial integrity of the sine-wave gratings by adding spatial noise. Neural synchronization was analyzed in the time and frequency domains by conducting cross-correlation and coherence analyses. The general association between neural spike trains depends strongly on spatial integrity, with coherence in the gamma band (35-70 Hz) showing greater sensitivity to the change of spatial structure than other frequency bands. Analysis of the temporal dynamics of synchronization in both time and frequency domains suggests that spike timing synchronization is triggered nearly instantaneously by coherent structure in the stimuli, whereas frequency-specific oscillatory components develop more slowly, presumably through network interactions. Our results suggest that, whereas temporal integrity is required for the generation of synchrony, spatial integrity is critical in triggering subsequent gamma band synchronization. PMID:18385334

  3. A spatial resolution threshold of land cover in estimating terrestrial carbon sequestration in four counties in Georgia and Alabama, USA

    USGS Publications Warehouse

    Zhao, S.Q.; Liu, S.; Li, Z.; Sohl, T.L.

    2010-01-01

    Changes in carbon density (i.e., carbon stock per unit area) and land cover greatly affect carbon sequestration. Previous studies have shown that land cover change detection strongly depends on spatial scale. However, the influence of the spatial resolution of land cover change information on the estimated terrestrial carbon sequestration is not known. Here, we quantified and evaluated the impact of land cover change databases at various spatial resolutions (250 m, 500 m, 1 km, 2 km, and 4 km) on the magnitude and spatial patterns of regional carbon sequestration in four counties in Georgia and Alabama using the General Ensemble biogeochemical Modeling System (GEMS). Results indicated a threshold of 1 km in the land cover change databases and in the estimated regional terrestrial carbon sequestration. Beyond this threshold, significant biases occurred in the estimation of terrestrial carbon sequestration, its interannual variability, and spatial patterns. In addition, the overriding impact of interannual climate variability on the temporal change of regional carbon sequestration was unrealistically overshadowed by the impact of land cover change beyond the threshold. The implications of these findings directly challenge current continental- to global-scale carbon modeling efforts relying on information at coarse spatial resolution without incorporating fine-scale land cover dynamics.

  4. Multichannel coherence in strong-field ionization

    SciTech Connect

    Rohringer, Nina [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Santra, Robin [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)

    2009-05-15

    Atomic and molecular ions generated by a strong optical laser pulse are not in general in the electronic ground state. The density matrix for such ions is characterized by the electronic quantum-state populations and by the coherences among the electronic quantum states. Nonvanishing coherences signal the presence of coherent electronic wave-packet dynamics in the laser-generated ions. For noble-gas atoms heavier than helium, the most important channels populated via strong-field ionization are the outer-valence single-hole states with a total angular momentum of j=3/2 or j=1/2. For this case, we develop a time-dependent multichannel theory of strong-field ionization. We derive the ion density matrix and express the hole density in terms of the elements of the ion density matrix. Our wave-packet calculations demonstrate that neon ions generated in a strong optical field (800 nm) are almost perfectly coherent. In strong-field-generated xenon ions, however, the coherence is substantially suppressed.

  5. Local spatial structure of forest biomass and its consequences for remote sensing of carbon stocks

    NASA Astrophysics Data System (ADS)

    Réjou-Méchain, M.; Muller-Landau, H. C.; Detto, M.; Thomas, S. C.; Le Toan, T.; Saatchi, S. S.; Barreto-Silva, J. S.; Bourg, N. A.; Bunyavejchewin, S.; Butt, N.; Brockelman, W. Y.; Cao, M.; Cárdenas, D.; Chiang, J.-M.; Chuyong, G. B.; Clay, K.; Condit, R.; Dattaraja, H. S.; Davies, S. J.; Duque, A.; Esufali, S.; Ewango, C.; Fernando, R. H. S.; Fletcher, C. D.; Gunatilleke, I. A. U. N.; Hao, Z.; Harms, K. E.; Hart, T. B.; Hérault, B.; Howe, R. W.; Hubbell, S. P.; Johnson, D. J.; Kenfack, D.; Larson, A. J.; Lin, L.; Lin, Y.; Lutz, J. A.; Makana, J.-R.; Malhi, Y.; Marthews, T. R.; McEwan, R. W.; McMahon, S. M.; McShea, W. J.; Muscarella, R.; Nathalang, A.; Noor, N. S. M.; Nytch, C. J.; Oliveira, A. A.; Phillips, R. P.; Pongpattananurak, N.; Punchi-Manage, R.; Salim, R.; Schurman, J.; Sukumar, R.; Suresh, H. S.; Suwanvecho, U.; Thomas, D. W.; Thompson, J.; Uríarte, M.; Valencia, R.; Vicentini, A.; Wolf, A. T.; Yap, S.; Yuan, Z.; Zartman, C. E.; Zimmerman, J. K.; Chave, J.

    2014-12-01

    Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDD+ (Reducing Emissions from Deforestation and Forest Degradation). Though broad-scale mapping is based primarily on remote sensing data, the accuracy of resulting forest carbon stock estimates depends critically on the quality of field measurements and calibration procedures. The mismatch in spatial scales between field inventory plots and larger pixels of current and planned remote sensing products for forest biomass mapping is of particular concern, as it has the potential to introduce errors, especially if forest biomass shows strong local spatial variation. Here, we used 30 large (8-50 ha) globally distributed permanent forest plots to quantify the spatial variability in aboveground biomass density (AGBD in Mg ha-1) at spatial scales ranging from 5 to 250 m (0.025-6.25 ha), and to evaluate the implications of this variability for calibrating remote sensing products using simulated remote sensing footprints. We found that local spatial variability in AGBD is large for standard plot sizes, averaging 46.3% for replicate 0.1 ha subplots within a single large plot, and 16.6% for 1 ha subplots. AGBD showed weak spatial autocorrelation at distances of 20-400 m, with autocorrelation higher in sites with higher topographic variability and statistically significant in half of the sites. We further show that when field calibration plots are smaller than the remote sensing pixels, the high local spatial variability in AGBD leads to a substantial "dilution" bias in calibration parameters, a bias that cannot be removed with standard statistical methods. Our results suggest that topography should be explicitly accounted for in future sampling strategies and that much care must be taken in designing calibration schemes if remote sensing of forest carbon is to achieve its promise.

  6. Implementation of marine spatial planning in shellfish aquaculture management: modeling studies in a Norwegian fjord.

    PubMed

    Filgueira, Ramon; Grant, Jon; Strand, Øivind

    2014-06-01

    Shellfish carrying capacity is determined by the interaction of a cultured species with its ecosystem, which is strongly influenced by hydrodynamics. Water circulation controls the exchange of matter between farms and the adjacent areas, which in turn establishes the nutrient supply that supports phytoplankton populations. The complexity of water circulation makes necessary the use of hydrodynamic models with detailed spatial resolution in carrying capacity estimations. This detailed spatial resolution also allows for the study of processes that depend on specific spatial arrangements, e.g., the most suitable location to place farms, which is crucial for marine spatial planning, and consequently for decision support systems. In the present study, a fully spatial physical-biogeochemical model has been combined with scenario building and optimization techniques as a proof of concept of the use of ecosystem modeling as an objective tool to inform marine spatial planning. The object of this exercise was to generate objective knowledge based on an ecosystem approach to establish new mussel aquaculture areas in a Norwegian fjord. Scenario building was used to determine the best location of a pump that can be used to bring nutrient-rich deep waters to the euphotic layer, increasing primary production, and consequently, carrying capacity for mussel cultivation. In addition, an optimization tool, parameter estimation (PEST), was applied to the optimal location and mussel standing stock biomass that maximize production, according to a preestablished carrying capacity criterion. Optimization tools allow us to make rational and transparent decisions to solve a well-defined question, decisions that are essential for policy makers. The outcomes of combining ecosystem models with scenario building and optimization facilitate planning based on an ecosystem approach, highlighting the capabilities of ecosystem modeling as a tool for marine spatial planning. PMID:24988780

  7. Changes in Auditory Frequency Guide Visual-Spatial Attention

    ERIC Educational Resources Information Center

    Mossbridge, Julia A.; Grabowecky, Marcia; Suzuki, Satoru

    2011-01-01

    How do the characteristics of sounds influence the allocation of visual-spatial attention? Natural sounds typically change in frequency. Here we demonstrate that the direction of frequency change guides visual-spatial attention more strongly than the average or ending frequency, and provide evidence suggesting that this cross-modal effect may be…

  8. Spatial Detect Technology Applied on Earthquake's Impending Forecast

    Microsoft Academic Search

    Guo Ziqi; Hu Guiwen; Qian Shuqing

    2001-01-01

    Impending forecast of strong earthquake is still an unsolvable scientific question in the world. Based on our analysis of the disadvantages of present earthquake forecasting, this article discussed the probability to use the Spatial Detect Technology in earthquake's forecasting, moreover summarized the status, extent and some unanswered questions of those new spatial detect techniques and methods. We can surely believe

  9. Spatial succession modeling of biological communities: a multi-model approach

    Microsoft Academic Search

    WenJun Zhang; Wu Wei

    2009-01-01

    Strong spatial correlation may exist in the spatial succession of biological communities, and the spatial succession can be\\u000a mathematically described. It was confirmed by our study on spatial succession of both plant and arthropod communities along\\u000a a linear transect of natural grassland. Both auto-correlation and cross-correlation analyses revealed that the succession\\u000a of plant and arthropod communities exhibited a significant spatial

  10. Spatial distribution of thermal energy in equilibrium

    NASA Astrophysics Data System (ADS)

    Bar-Sinai, Yohai; Bouchbinder, Eran

    2015-06-01

    The equipartition theorem states that in equilibrium, thermal energy is equally distributed among uncoupled degrees of freedom that appear quadratically in the system's Hamiltonian. However, for spatially coupled degrees of freedom, such as interacting particles, one may speculate that the spatial distribution of thermal energy may differ from the value predicted by equipartition, possibly quite substantially in strongly inhomogeneous or disordered systems. Here we show that for systems undergoing simple Gaussian fluctuations around an equilibrium state, the spatial distribution is universally bounded from above by 1/2 kBT . We further show that in one-dimensional systems with short-range interactions, the thermal energy is equally partitioned even for coupled degrees of freedom in the thermodynamic limit and that in higher dimensions nontrivial spatial distributions emerge. Some implications are discussed.

  11. Changes in ecological stability across realistic biodiversity gradients depend

    E-print Network

    Chalcraft, David R.

    RESEARCH PAPER Changes in ecological stability across realistic biodiversity gradients depend on spatial scale David R. Chalcraft* Department of Biology and North Carolina Center for Biodiversity, East ecosystems and populations varies with biodiversity at spatial scales relevant to resource managers

  12. Spatial coherence and the orbital angular momentum of light in astronomy

    NASA Astrophysics Data System (ADS)

    Hetharia, D.; van Exter, M. P.; Löffler, W.

    2014-12-01

    The orbital angular momentum (OAM) of light is potentially interesting for astronomical study of rotating objects such as black holes, but the effect of reduced spatial coherence of astronomical light sources like stars is largely unknown. In a laboratory-scale experiment, we find that the detected OAM spectrum depends strongly on the position of the light-twisting object along the line of sight. We develop a simple intuitive model to predict the influence of reduced spatial coherence on the propagating OAM spectrum for, e.g., astronomical observations. Further, we derive equations to predict the effect of line-of-sight misalignment and the received intensity in higher-order OAM modes for limited-size detectors such as telescopes.

  13. Spatial gain profiles of a continuous wave radio-frequency pumped atomic xenon laser

    SciTech Connect

    Tskhai, S.N.; Blok, F.J.; Udalov, Y.B.; Peters, P.J.; Witteman, W.J. [Department of Applied Physics, Quantum Electronics Group, University of Twente, 7500 AE Enschede (the Netherlands)] [Department of Applied Physics, Quantum Electronics Group, University of Twente, 7500 AE Enschede (the Netherlands); Ochkin, V.N. [Low Temperature Plasma Optics Department, P. N. Lebedev Physics Institute, Russian Academy of Sciences, 117924 Moscow (Russia)] [Low Temperature Plasma Optics Department, P. N. Lebedev Physics Institute, Russian Academy of Sciences, 117924 Moscow (Russia)

    1997-04-01

    Spatially dependent small signal gain measurements in a continuous wave rf excited Ar{endash}He{endash}Xe (59.5/40/0.5) gas discharge are presented. Maximum values for the small signal gain of the 2.03 and 2.65 {mu}m xenon transitions of about 22{percent} and 37{percent}/cm, respectively, were obtained at a total pressure of 120 mbar, an input power per unit electrode area of 20 W/cm{sup 2} and at a rf driving frequency of 115 MHz. With a spatial resolution better than 0.5 mm, a strongly inhomogeneous gain distribution in the transverse direction was measured. {copyright} {ital 1997 American Institute of Physics.}

  14. Nutritional deficits during early development affect hippocampal structure and spatial memory later in life.

    PubMed

    Pravosudov, Vladimir V; Lavenex, Pierre; Omanska, Alicja

    2005-10-01

    Development rates vary among individuals, often as a result of direct competition for food. Survival of young might depend on their learning abilities, but it remains unclear whether learning abilities are affected by nutrition during development. The authors demonstrated that compared with controls, 1-year-old Western scrub jays (Aphelocoma californica) that experienced nutritional deficits during early posthatching development had smaller hippocampi with fewer neurons and performed worse in a cache recovery task and in a spatial version of an associative learning task. In contrast, performance of nutritionally deprived birds was similar to that of controls in 2 color versions of an associative learning task. These findings suggest that nutritional deficits during early development have long-term consequences for hippocampal structure and spatial memory, which, in turn, are likely to have a strong impact on animals' future fitness. PMID:16300442

  15. [Prediction of spatial distribution of forest carbon storage in Heilongjiang Province using spatial error model].

    PubMed

    Liu, Chang; Li, Feng-Ri; Zhen, Zhen

    2014-10-01

    Abstract: Based on the data from Chinese National Forest Inventory (CNFI) and Key Ecological Benefit Forest Monitoring plots (5075 in total) in Heilongjiang Province in 2010 and concurrent meteorological data coming from 59 meteorological stations located in Heilongjiang, Jilin and Inner Mongolia, this paper established a spatial error model (SEM) by GeoDA using carbon storage as dependent variable and several independent variables, including diameter of living trees (DBH), number of trees per hectare (TPH), elevation (Elev), slope (Slope), and product of precipitation and temperature (Rain_Temp). Global Moran's I was computed for describing overall spatial autocorrelations of model results at different spatial scales. Local Moran's I was calculated at the optimal bandwidth (25 km) to present spatial distribution residuals. Intra-block spatial variances were computed to explain spatial heterogeneity of residuals. Finally, a spatial distribution map of carbon storage in Heilongjiang was visualized based on predictions. The results showed that the distribution of forest carbon storage in Heilongjiang had spatial effect and was significantly influenced by stand, topographic and meteorological factors, especially average DBH. SEM could solve the spatial autocorrelation and heterogeneity well. There were significant spatial differences in distribution of forest carbon storage. The carbon storage was mainly distributed in Zhangguangcai Mountain, Xiao Xing'an Mountain and Da Xing'an Mountain where dense, forests existed, rarely distributed in Songnen Plains, while Wanda Mountain had moderate-level carbon storage. PMID:25796882

  16. Ideal magnetohydrodynamic simulations of unmagnetized dense plasma jet injection into a hot strongly magnetized plasma

    E-print Network

    Liu, Wei

    2010-01-01

    We present results from three-dimensional ideal magnetohydrodynamic simulations of unmagnetized dense plasma jet injection into a hot strongly magnetized plasma, with the aim of providing insight into core fueling of a tokamak with parameters relevant for ITER (International Thermonuclear Experimental Reactor) and NSTX (National Spherical Torus Experiment). Unmagnetized jet injection is similar to compact toroid injection but with higher possible injection density and total mass, as well as a potentially smaller footprint for the injector hardware. Our simulation results show that the unmagnetized dense jet is quickly magnetized upon injection. The penetration depth of the jet into the tokamak plasma is mostly dependent on the jet's initial kinetic energy while the jet's magnetic field determines its interior evolution. A key requirement for spatially precise fueling is for the jet's slowing-down time to be less than the time for the perturbed tokamak magnetic flux to relax due to magnetic reconnection. Thus ...

  17. Bifurcations and interacting modes in coupled lasers : a strong coupling theory.

    SciTech Connect

    Chow, Weng Wah; Wieczorek, Sebastian Maciej

    2003-08-01

    The paper presents a theoretical study of synchronization between two coupled lasers. A theory valid for arbitrary coupling between lasers is used. Its key feature is that the laser field is decomposed in terms of the composite-cavity modes reflecting the spatial field dependence over the entire coupled-laser system. The ensuing multimode equations are reduced to class-B, and further to class-A equations which resemble competing species equations. Bifurcation analysis, supported by insight provided by analytical solutions, is used to investigate influences of pump, carrier decay rate, polarization decay rate, and coupling mirror losses on synchronization between lasers. Population pulsation is found to be an essential mode competition mechanism responsible for bistability in the synchronized solutions. Finally, we discovered that the mechanism leading to laser synchronization changes from strong composite-cavity mode competition in class-A regime to frequency locking of composite-cavity modes in class-B regime.

  18. Violation of the holographic viscosity bound in a strongly coupled anisotropic plasma.

    PubMed

    Rebhan, Anton; Steineder, Dominik

    2012-01-13

    We study the conductivity and shear viscosity tensors of a strongly coupled N=4 super-Yang-Mills plasma which is kept anisotropic by a ? parameter that depends linearly on one of the spatial dimensions. Its holographic dual is given by an anisotropic axion-dilaton-gravity background and has recently been proposed by Mateos and Trancanelli as a model for the preequilibrium stage of quark-gluon plasma in heavy-ion collisions. By applying the membrane paradigm which we also check by numerical evaluation of Kubo formula and lowest lying quasinormal modes, we find that the shear viscosity purely transverse to the direction of anisotropy saturates the holographic viscosity bound, whereas longitudinal shear viscosities are smaller, providing the first such example not involving higher-derivative theories of gravity and, more importantly, with fully known gauge-gravity correspondence. PMID:22324669

  19. Spatiotemporal properties of nanoshell plasmonic response for strong-field experiments

    NASA Astrophysics Data System (ADS)

    Weber, S. J.; Colas des Francs, G.; Girard, C.

    2015-05-01

    Field enhancement behavior of a SiO2/Au nanoshell is studied in the framework of strong-field physics. Localized plasmonic fields induce local electric field enhancement with the potential to lead to the strong-field regime without the use of costly amplified lasers. In this framework, electrons are tunnel ionized from the nanoshell and accelerated by the local field being spatially inhomogeneous in terms of spectral and polarization properties. These processes are happening within a single laser shot, and thermal effects are therefore neglected. We show that the localized response to ultrashort femtosecond pulses can be investigated by extending Mie theory to multilayer spherical particles. Nanoshell plasmonic resonances can be easily tuned depending on the volume ratio between core and whole particle. Optimum geometric parameters of the nanoshell are selected for use with ultrashort pulses centered at 800 nm where most femtosecond oscillators operate. It is shown that phase and amplitude reshaping of the incident pulse by the plasmonic resonance can be partially corrected using active shaping leading to ultrashort response of the medium. Finally, free electron classical trajectories are calculated to highlight the inhomogeneous nature of the local enhancement in a strong-field picture.

  20. Beryllium and Strong Hydrogen Bonds

    Microsoft Academic Search

    T. Mark McCleskey; Brian L. Scott

    2009-01-01

    We compare beryllium to H and show that beryllium can displace H in many “strong hydrogen bonds” where Be as a “tetrahedral proton” (O-Be-O angle is tetrahedral as opposed to the nearly linear O-H—O angle) is thermodynamically preferred. The strong hydrogen bond provides two advantages. First, the O–X distance in a strong hydrogen bond is in the range 2.4–2.8 Å,

  1. EDITORIAL: Strongly correlated electron systems Strongly correlated electron systems

    Microsoft Academic Search

    Filip Ronning; Cristian Batista

    2011-01-01

    Strongly correlated electrons is an exciting and diverse field in condensed matter physics. This special issue aims to capture some of that excitement and recent developments in the field. Given that this issue was inspired by the 2010 International Conference on Strongly Correlated Electron Systems (SCES 2010), we briefly give some history in order to place this issue in context.

  2. Spatial Variability Some Physical and Chemical Prpperties Soil surface In Dasht-e-Tabriz Different Landforms

    NASA Astrophysics Data System (ADS)

    Foroughifar, Hamed; Asghar Jafarzadeh, Ali; Torabi, Hosien; Aliasgharzad, Naser; Toomanian, Norair

    2010-05-01

    Spatial distribution of soil properties at the field and watershed scale(region scale) affect yield potential, hydrologic responses , and transport of herbicides and No3 to surface or groundwater.The present study aim was to evaluate some physical and chemical properties spatial variability and frequency distribution within and between landforms of Dash-e-Tabriz in the northwest of Iran.For this evaluation 98 samples from soils surface of layer according to grid sampling design and with 500-1000 meters distance based on soils variability were selected and analysed.Landforms were hill, piedmont plain, plain, river alluvial plain and lowland.The study of soil variables frequency distribution showed that Bd, CEC, Caco3, pH,clay and silt follow normal distribution ,which to study their variation one can use parametric statistical method.Variables such as MWD, N(total), SAR, EC, P(available) and sand showed log-normal distribution,that for their variation study,should first be transformed to a logarithmic scale.The variables frequency distribution increase within landforms,which in lowland, hill, and river alluvial plain they showed normal distribution and only EC in piedmont plain and sand, OC and N(total) in plain had log-normal distributions.The results indicate significantly differences of soil properties distribution among landforms,which clay ,pH, EC ,SAR and MWD, CEC, Bd, N(total), OC, P(available), sand, silt were strongly and moderately spatial dependent respectively and Caco3 had no spatial dependence and it is following nugget model.These results indicate that strong spatial dependence due to the effects of intrinsic factors such as parent material, relief and soil types. Also soil properties variations result from variation in depositional environments and or differences in pedogenic or hydrologic processes for different landform positions,and so it can be affected by the flood irrigation,fertilizeir addition,high watertable level or agriculture practices.These effects may cause data departure from normal distribution and cause skewness (positive or negative) for soil mapping unit. Key words : Spatial Variability , Frequency Distribution, Landform, EC, SAR, CEC, MWD, Dasht-e-Tabriz

  3. Flexible hydrological modeling - Disaggregation from lumped catchment scale to higher spatial resolutions

    NASA Astrophysics Data System (ADS)

    Tran, Quoc Quan; Willems, Patrick; Pannemans, Bart; Blanckaert, Joris; Pereira, Fernando; Nossent, Jiri; Cauwenberghs, Kris; Vansteenkiste, Thomas

    2015-04-01

    Based on an international literature review on model structures of existing rainfall-runoff and hydrological models, a generalized model structure is proposed. It consists of different types of meteorological components, storage components, splitting components and routing components. They can be spatially organized in a lumped way, or on a grid, spatially interlinked by source-to-sink or grid-to-grid (cell-to-cell) routing. The grid size of the model can be chosen depending on the application. The user can select/change the spatial resolution depending on the needs and/or the evaluation of the accuracy of the model results, or use different spatial resolutions in parallel for different applications. Major research questions addressed during the study are: How can we assure consistent results of the model at any spatial detail? How can we avoid strong or sudden changes in model parameters and corresponding simulation results, when one moves from one level of spatial detail to another? How can we limit the problem of overparameterization/equifinality when we move from the lumped model to the spatially distributed model? The proposed approach is a step-wise one, where first the lumped conceptual model is calibrated using a systematic, data-based approach, followed by a disaggregation step where the lumped parameters are disaggregated based on spatial catchment characteristics (topography, land use, soil characteristics). In this way, disaggregation can be done down to any spatial scale, and consistently among scales. Only few additional calibration parameters are introduced to scale the absolute spatial differences in model parameters, but keeping the relative differences as obtained from the spatial catchment characteristics. After calibration of the spatial model, the accuracies of the lumped and spatial models were compared for peak, low and cumulative runoff total and sub-flows (at downstream and internal gauging stations). For the distributed models, additional validation on spatial results was done for the groundwater head values at observation wells. To ensure that the lumped model can produce results as accurate as the spatially distributed models or close regardless to the number of parameters and implemented physical processes, it was checked whether the structure of the lumped models had to be adjusted. The concept has been implemented in a PCRaster - Python platform and tested for two Belgian case studies (catchments of the rivers Dijle and Grote Nete). So far, use is made of existing model structures (NAM, PDM, VHM and HBV). Acknowledgement: These results were obtained within the scope of research activities for the Flemish Environment Agency (VMM) - division Operational Water Management on "Next Generation hydrological modeling", in cooperation with IMDC consultants, and for Flanders Hydraulics Research (Waterbouwkundig Laboratorium) on "Effect of climate change on the hydrological regime of navigable watercourses in Belgium".

  4. Strong Gravitational Lensing with LSST

    Microsoft Academic Search

    Philip J. Marshall; M. Bradac; G. Chartas; G. Dobler; A. Eliasdottir; E. Falco; C. D. Fassnacht; M. J. Jee; C. R. Keeton; M. Oguri; J. A. Tyson

    2010-01-01

    LSST will find more strong gravitational lensing events than any other survey preceding it, and will monitor them all at a cadence of a few days to a few weeks. We can expect the biggest advances in strong lensing science made with LSST to be in those areas that benefit most from the large volume, and the high accuracy multi-filter

  5. Strong WW Interaction at LHC

    SciTech Connect

    Pelaez, Jose R

    1998-12-14

    We present a brief pedagogical introduction to the Effective Electroweak Chiral Lagrangians, which provide a model independent description of the WW interactions in the strong regime. When it is complemented with some unitarization or a dispersive approach, this formalism allows the study of the general strong scenario expected at the LHC, including resonances.

  6. Strong-back safety latch

    SciTech Connect

    DeSantis, G.N.

    1995-03-06

    The calculation decides the integrity of the safety latch that will hold the strong-back to the pump during lifting. The safety latch will be welded to the strong-back and will latch to a 1.5-in. dia cantilever rod welded to the pump baseplate. The static and dynamic analysis shows that the safety latch will hold the strong-back to the pump if the friction clamps fail and the pump become free from the strong-back. Thus, the safety latch will meet the requirements of the Lifting and Rigging Manual for under the hook lifting for static loading; it can withstand shock loads from the strong-back falling 0.25 inch.

  7. Quadratic spatial soliton interactions

    NASA Astrophysics Data System (ADS)

    Jankovic, Ladislav

    Quadratic spatial soliton interactions were investigated in this Dissertation. The first part deals with characterizing the principal features of multi-soliton generation and soliton self-reflection. The second deals with two beam processes leading to soliton interactions and collisions. These subjects were investigated both theoretically and experimentally. The experiments were performed by using potassium niobate (KNBO 3) and periodically poled potassium titanyl phosphate (KTP) crystals. These particular crystals were desirable for these experiments because of their large nonlinear coefficients and, more importantly, because the experiments could be performed under non-critical-phase-matching (NCPM) conditions. The single soliton generation measurements, performed on KNBO3 by launching the fundamental component only, showed a broad angular acceptance bandwidth which was important for the soliton collisions performed later. Furthermore, at high input intensities multi-soliton generation was observed for the first time. The influence on the multi-soliton patterns generated of the input intensity and beam symmetry was investigated. The combined experimental and theoretical efforts indicated that spatial and temporal noise on the input laser beam induced multi-soliton patterns. Another research direction pursued was intensity dependent soliton routing by using of a specially engineered quadratically nonlinear interface within a periodically poled KTP sample. This was the first time demonstration of the self-reflection phenomenon in a system with a quadratic nonlinearity. The feature investigated is believed to have a great potential for soliton routing and manipulation by engineered structures. A detailed investigation was conducted on two soliton interaction and collision processes. Birth of an additional soliton resulting from a two soliton collision was observed and characterized for the special case of a non-planar geometry. A small amount of spiraling, up to 30 degrees rotation, was measured in the experiments performed. The parameters relevant for characterizing soliton collision processes were also studied in detail. Measurements were performed for various collision angles (from 0.2 to 4 degrees), phase mismatch, relative phase between the solitons and the distance to the collision point within the sample (which affects soliton formation). Both the individual and combined effects of these collision variables were investigated. Based on the research conducted, several all-optical switching scenarios were proposed.

  8. Gutzwiller approximation in strongly correlated electron systems

    NASA Astrophysics Data System (ADS)

    Li, Chunhua

    Gutzwiller wave function is an important theoretical technique for treating local electron-electron correlations nonperturbatively in condensed matter and materials physics. It is concerned with calculating variationally the ground state wave function by projecting out multi-occupation configurations that are energetically costly. The projection can be carried out analytically in the Gutzwiller approximation that offers an approximate way of calculating expectation values in the Gutzwiller projected wave function. This approach has proven to be very successful in strongly correlated systems such as the high temperature cuprate superconductors, the sodium cobaltates, and the heavy fermion compounds. In recent years, it has become increasingly evident that strongly correlated systems have a strong propensity towards forming inhomogeneous electronic states with spatially periodic superstrutural modulations. A good example is the commonly observed stripes and checkerboard states in high- Tc superconductors under a variety of conditions where superconductivity is weakened. There exists currently a real challenge and demand for new theoretical ideas and approaches that treats strongly correlated inhomogeneous electronic states, which is the subject matter of this thesis. This thesis contains four parts. In the first part of the thesis, the Gutzwiller approach is formulated in the grand canonical ensemble where, for the first time, a spatially (and spin) unrestricted Gutzwiller approximation (SUGA) is developed for studying inhomogeneous (both ordered and disordered) quantum electronic states in strongly correlated electron systems. The second part of the thesis applies the SUGA to the t-J model for doped Mott insulators which led to the discovery of checkerboard-like inhomogeneous electronic states competing with d-wave superconductivity, consistent with experimental observations made on several families of high-Tc superconductors. In the third part of the thesis, new concepts and techniques are developed to study the Mott transition in inhomogeneous electronic superstructures. The latter is termed "SuperMottness" which is shown to be a general framework that unifies the two paradigms in the physics of strong electronic correlation: Mott transition and Wigner crystallization. A cluster Gutzwiller approximation (CGA) approach is developed that treats the local ( U) and extended Coulomb interactions (V) on equal footing. It is shown with explicit calculations that the Mott-Wigner metal-insulator transition can take place far away from half-filling. The mechanism by which a superlattice potential enhances the correlation effects and the tendency towards local moment formation is investigated and the results reveal a deeper connection among the strongly correlated inhomogeneous electronic states, the Wigner-Mott physics, and the multiorbital Mott physics that can all be united under the notion of SuperMottness. It is proposed that doping into a superMott insulator can lead to coexistence of local moment and itinerant carriers. The last part of the thesis studies the possible Kondo effect that couples the local moment and the itinerant carriers. In connection to the sodium rich phases of the cobaltates, a new Kondo lattice model is proposed where the itinerant carriers form a Stoner ferromagnet. The competition between the Kondo screening and the Stoner ferromagnetism is investigated when the conduction band is both at and away from half-filling.

  9. Spatial and Temporal Variation of Turbulence during Oscillatory Flow in Realistic Model Human Airways

    NASA Astrophysics Data System (ADS)

    Tanaka, Gaku; Hatori, Akihiro; Takano, Ryosuke

    Turbulence in the oscillatory flow in realistic model human central airways was measured by particle image velocimetry (PIV) to reveal the nature of turbulence in a lung. The transparent silicone model of multi-branching airways was fabricated from X-ray CT images by rapid prototyping. The multi-branching airways comprise trachea, and right and left bronchi, with airway diameters ranging from 14 to 2 mm, respectively. Experiments were performed for a Reynolds number from 1200 to 2200 and a Womersley number from 1.9 to 2.3 in the trachea. Results showed that spatial and temporal variations of turbulent intensity strongly depends on the airway geometry and on the phase of oscillatory flow, and that expiratory flow generates strong turbulence which explosively occurs in the entire cross-section especially in the right bronchi, whereas inspiratory flow generates relatively weak turbulence near the airway wall.

  10. Spatial cointegration and heteroscedasticity

    NASA Astrophysics Data System (ADS)

    Lauridsen, Jørgen; Kosfeld, Reinhold

    2007-09-01

    A two-step Lagrange Multiplier test strategy has recently been suggested as a tool to reveal spatial cointegration. The present paper generalises the test procedure by incorporating control for unobserved heteroscedasticity. Using Monte Carlo simulation, the behaviour of several relevant tests for spatial cointegration and/or heteroscedasticity is investigated. The two-step test for spatial cointegration appears to be robust towards heteroscedasticity. While several tests for heteroscedasticity prove to be inconclusive under certain circumstances, a Lagrange Multiplier test for heteroscedasticity based on spatially differenced variables is shown to serve well as an indication of heteroscedasticity irrespective of cointegration status.

  11. Spatial attention is attracted in a sustained fashion toward singular points in the optic flow.

    PubMed

    Wang, Shuo; Fukuchi, Masaki; Koch, Christof; Tsuchiya, Naotsugu

    2012-01-01

    While a single approaching object is known to attract spatial attention, it is unknown how attention is directed when the background looms towards the observer as s/he moves forward in a quasi-stationary environment. In Experiment 1, we used a cued speeded discrimination task to quantify where and how spatial attention is directed towards the target superimposed onto a cloud of moving dots. We found that when the motion was expansive, attention was attracted towards the singular point of the optic flow (the focus of expansion, FOE) in a sustained fashion. The effects were less pronounced when the motion was contractive. The more ecologically valid the motion features became (e.g., temporal expansion of each dot, spatial depth structure implied by distribution of the size of the dots), the stronger the attentional effects. Further, the attentional effects were sustained over 1000 ms. Experiment 2 quantified these attentional effects using a change detection paradigm by zooming into or out of photographs of natural scenes. Spatial attention was attracted in a sustained manner such that change detection was facilitated or delayed depending on the location of the FOE only when the motion was expansive. Our results suggest that focal attention is strongly attracted towards singular points that signal the direction of forward ego-motion. PMID:22905096

  12. Refined critical balance in strong Alfvénic turbulence

    NASA Astrophysics Data System (ADS)

    Mallet, A.; Schekochihin, A. A.; Chandran, B. D. G.

    2015-04-01

    We present numerical evidence that in strong Alfvénic turbulence, the critical balance principle - equality of the non-linear decorrelation and linear propagation times - is scale invariant, in the sense that the probability distribution of the ratio of these times is independent of scale. This result only holds if the local alignment of the Elsasser fields is taken into account in calculating the non-linear time. At any given scale, the degree of alignment is found to increase with fluctuation amplitude, supporting the idea that the cause of alignment is mutual dynamical shearing of Elsasser fields. The scale-invariance of critical balance (while all other quantities of interest are strongly intermittent, i.e. have scale-dependent distributions) suggests that it is the most robust of the scaling principles used to describe Alfvénic turbulence. The quality afforded by situ fluctuation measurements in the solar wind allows for direct verification of this fundamental principle.

  13. Peltier effect in strongly driven quantum wires

    NASA Astrophysics Data System (ADS)

    Mierzejewski, M.; Crivelli, D.; Prelovšek, P.

    2014-08-01

    We study a microscopic model of a thermocouple device with two connected correlated quantum wires driven by a constant electric field. In such a closed system we follow the time and position dependence of the entropy density using the concept of the reduced density matrix. At weak driving, the initial changes of the entropy at the junctions can be described by the linear Peltier response. At longer times the quasiequilibrium situation is reached with well defined local temperatures which increase due to an overall Joule heating. On the other hand, a strong electric field induces a nontrivial nonlinear thermoelectric response, e.g., the Bloch oscillations of the energy current. Moreover, we show for the doped Mott insulators that strong driving can reverse the Peltier effect.

  14. Strong lensing interferometry for compact binaries

    NASA Astrophysics Data System (ADS)

    Pen, Ue-Li; Yang, I.-Sheng

    2015-03-01

    We propose a possibility to improve the current precision measurements on compact binaries. When the orbital axis is almost perpendicular to our line of sight, a pulsar behind its companion can form two strong lensing images. These images cannot be resolved, but we can use multiwavelength interferometry to accurately determine the passage through superior conjunction. This method does not depend strongly on the stability of the pulse profile and applies equally well to both slow and fast pulsars. We discuss the possible improvement this can bring to the bound on stochastic gravitational wave background and to determine black hole spin. We also discuss the possibility of discovering a suitable binary system by the Square Kilometer Array to which our method can apply.

  15. Experimental study of spatial nonuniformities in 100 MHz capacitively coupled plasma using optical probe

    SciTech Connect

    Volynets, V. N.; Ushakov, A. G.; Sung, D.; Tolmachev, Y. N.; Pashkovsky, V. G.; Lee, J. B.; Kwon, T. Y.; Jeong, K. S. [Mechatronics and Manufacturing Technology Center, Samsung Electronics Co. Ltd., 416 Maetan-3 dong, Yeongtong-Gu, Suwon, Gyeonggi-Do 443-742 (Korea, Republic of)

    2008-05-15

    Plasma spatial nonuniformities in the 100 MHz rf driven capacitively coupled reactor used for reactive ion etching of 300 mm substrates were experimentally studied using a linear scanning optical emission spectroscopy probe. Radial profiles of plasma emission intensity were measured both in argon and fluorocarbon-containing gas mixtures in the pressure interval of 10-80 mTorr and the rf power range of 500-1250 W. It was demonstrated that the plasma emission profiles strongly depend on the working gas composition and pressure. The profiles have a bell-like shape at pressures about 10 mTorr for all gases. As the pressure increases, the profile shape becomes more complex with the central and peripheral peaks, and the amplitudes of the peaks strongly depend on the working gas composition. It is suggested that the emission profiles show plasma spatial nonuniformities that can influence the etching rate profiles obtained with such systems. According to the existing theoretical models, the most probable reasons for these plasma nonuniformities are charged particle radial diffusion at low pressures (about 10 mTorr), as well as the standing wave and skin and edge effects at higher pressures. Using the experimental emission profiles, the working conditions have been found that allow one to achieve the most uniform plasma for discharges in argon and fluorocarbon-containing gas mixtures.

  16. Recent advances of strong-strong beam-beam simulation

    SciTech Connect

    Qiang, Ji; Furman, Miguel A.; Ryne, Robert D.; Fischer, Wolfram; Ohmi,Kazuhito

    2004-09-15

    In this paper, we report on recent advances in strong-strong beam-beam simulation. Numerical methods used in the calculation of the beam-beam forces are reviewed. A new computational method to solve the Poisson equation on nonuniform grid is presented. This method reduces the computational cost by a half compared with the standard FFT based method on uniform grid. It is also more accurate than the standard method for a colliding beam with low transverse aspect ratio. In applications, we present the study of coherent modes with multi-bunch, multi-collision beam-beam interactions at RHIC. We also present the strong-strong simulation of the luminosity evolution at KEKB with and without finite crossing angle.

  17. Individual Differences in Spatial Text Processing: High Spatial Ability Can Compensate for Spatial Working Memory Interference

    ERIC Educational Resources Information Center

    Meneghetti, Chiara; Gyselinck, Valerie; Pazzaglia, Francesca; De Beni, Rossana

    2009-01-01

    The present study investigates the relation between spatial ability and visuo-spatial and verbal working memory in spatial text processing. In two experiments, participants listened to a spatial text (Experiments 1 and 2) and a non-spatial text (Experiment 1), at the same time performing a spatial or a verbal concurrent task, or no secondary task.…

  18. Spatial dynamics of large-scale, multistage crab (Callinectes sapidus) dispersal: Determinants and consequences for recruitment

    USGS Publications Warehouse

    Etherington, L.L.; Eggleston, D.B.

    2003-01-01

    We assessed determinants and consequences of multistage dispersal on spatial recruitment of the blue crab, Callinectes sapidus, within the Croatan, Albemarle, Pamlico Estuarine System (CAPES), North Carolina, U.S.A. Large-scale sampling of early juvenile crabs over 4 years indicated that spatial abundance patterns were size-dependent and resulted from primary post-larval dispersal (pre-settlement) and secondary juvenile dispersal (early post-settlement). In general, primary dispersal led to high abundances within more seaward habitats, whereas secondary dispersal (which was relatively consistent) expanded the distribution of juveniles, potentially increasing the estuarine nursery capacity. There were strong relationships between juvenile crab density and specific wind characteristics; however, these patterns were spatially explicit. Various physical processes (e.g., seasonal wind events, timing and magnitude of tropical cyclones) interacted to influence dispersal during multiple stages and determined crab recruitment patterns. Our results suggest that the nursery value of different habitats is highly dependent on the dispersal potential (primary and secondary dispersal) to and from these areas, which is largely determined by the relative position of habitats within the estuarine landscape.

  19. Users as essential contributors to spatial cyberinfrastructures

    PubMed Central

    Poore, Barbara S.

    2011-01-01

    Current accounts of spatial cyberinfrastructure development tend to overemphasize technologies to the neglect of critical social and cultural issues on which adoption depends. Spatial cyberinfrastructures will have a higher chance of success if users of many types, including nonprofessionals, are made central to the development process. Recent studies in the history of infrastructures reveal key turning points and issues that should be considered in the development of spatial cyberinfrastructure projects. These studies highlight the importance of adopting qualitative research methods to learn how users work with data and digital tools, and how user communities form. The author's empirical research on data sharing networks in the Pacific Northwest salmon crisis at the turn of the 21st century demonstrates that ordinary citizens can contribute critical local knowledge to global databases and should be considered in the design and construction of spatial cyberinfrastructures. PMID:21444825

  20. Hofstadter's Butterfly in the strongly interacting regime

    NASA Astrophysics Data System (ADS)

    Dean, Cory

    2015-03-01

    In 1976, Douglas Hofstadter predicted that in the presence of both a strong magnetic field, and a spatially varying periodic potential, Bloch electrons confined to a 2D quantum well exhibit a self-similar fractal energy spectrum known as the ``Hofstadter's Butterfly.'' In subsequent years, experimental discovery of the quantum Hall effect gave birth to an expansive field of research into 2D electronic systems in the presence of a magnetic field, however, direct confirmation of the fractal spectrum remained elusive. Recently we demonstrated that graphene, in which Bloch electrons can be described by Dirac fermions, provides a new opportunity to investigate this nearly 40 year old problem. In this talk I will discuss the experimental realization of Hofstader's butterfly by exploiting nano-scale interfacial effects between graphene and hexagonal boron nitride substrates, together with application of extremely high magnetic fields. Utilizing newly developed techniques to fabricate ultra-clean graphene devices, I will additionally demonstrate the capability to probe for the first time the effect of strong electron interactions within the fractal Hofstadter spectrum.

  1. Heat treatment modelling using strongly continuous semigroups.

    PubMed

    Malek, Alaeddin; Abbasi, Ghasem

    2015-07-01

    In this paper, mathematical simulation of bioheat transfer phenomenon within the living tissue is studied using the thermal wave model. Three different sources that have therapeutic applications in laser surgery, cornea laser heating and cancer hyperthermia are used. Spatial and transient heating source, on the skin surface and inside biological body, are considered by using step heating, sinusoidal and constant heating. Mathematical simulations describe a non-Fourier process. Exact solution for the corresponding non-Fourier bioheat transfer model that has time lag in its heat flux is proposed using strongly continuous semigroup theory in conjunction with variational methods. The abstract differential equation, infinitesimal generator and corresponding strongly continuous semigroup are proposed. It is proved that related semigroup is a contraction semigroup and is exponentially stable. Mathematical simulations are done for skin burning and thermal therapy in 10 different models and the related solutions are depicted. Unlike numerical solutions, which suffer from uncertain physical results, proposed analytical solutions do not have unwanted numerical oscillations. PMID:25912988

  2. Wavelength dependence in radio-wave scattering and specular-point theory

    NASA Technical Reports Server (NTRS)

    Tyler, G. L.

    1976-01-01

    Radio-wave scattering from natural surfaces contains a strong quasispecular component that at fixed wavelengths is consistent with specular-point theory, but often has a strong wavelength dependence that is not predicted by physical optics calculations under the usual limitations of specular-point models. Wavelength dependence can be introduced by a physical approximation that preserves the specular-point assumptions with respect to the radii of curvature of a fictitious, effective scattering surface obtained by smoothing the actual surface. A uniform low-pass filter model of the scattering process yields explicit results for the effective surface roughness versus wavelength. Interpretation of experimental results from planetary surfaces indicates that the asymptotic surface height spectral densities fall at least as fast as an inverse cube of spatial frequency. Asymptotic spectral densities for Mars and portions of the lunar surface evidently decrease more rapidly.

  3. Thermalization of Strongly Coupled Field Theories

    SciTech Connect

    Balasubramanian, V. [David Rittenhouse Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Bernamonti, A.; Copland, N.; Craps, B.; Staessens, W. [Theoretische Natuurkunde, Vrije Universiteit Brussel, and International Solvay Institutes, B-1050 Brussels (Belgium); Boer, J. de [Institute for Theoretical Physics, University of Amsterdam, 1090 GL Amsterdam (Netherlands); Keski-Vakkuri, E. [Helsinki Institute of Physics and Department of Physics, FIN-00014 University of Helsinki (Finland); Mueller, B. [Department of Physics and CTMS, Duke University, Durham, North Carolina 27708 (United States); Schaefer, A. [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); Shigemori, M. [Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan)

    2011-05-13

    Using the holographic mapping to a gravity dual, we calculate 2-point functions, Wilson loops, and entanglement entropy in strongly coupled field theories in d=2, 3, and 4 to probe the scale dependence of thermalization following a sudden injection of energy. For homogeneous initial conditions, the entanglement entropy thermalizes slowest and sets a time scale for equilibration that saturates a causality bound. The growth rate of entanglement entropy density is nearly volume-independent for small volumes but slows for larger volumes. In this setting, the UV thermalizes first.

  4. Community Invasibility Spatial Heterogeneity, Spatial Scale,

    E-print Network

    Davies, Kendi

    . Davies, University of Colorado, Boulder IntroDuCtIon: Why Are Some CommunItIeS more InvASIble thAn other, serpentine systems are very spatially heterogeneous in soil chemistry, texture, rockiness, and toxicity empirical studies that detected negative relation- ships between native and exotic diversity at small

  5. Biodiversity as spatial insurance in heterogeneous landscapes.

    PubMed

    Loreau, Michel; Mouquet, Nicolas; Gonzalez, Andrew

    2003-10-28

    The potential consequences of biodiversity loss for ecosystem functioning and services at local scales have received considerable attention during the last decade, but little is known about how biodiversity affects ecosystem processes and stability at larger spatial scales. We propose that biodiversity provides spatial insurance for ecosystem functioning by virtue of spatial exchanges among local systems in heterogeneous landscapes. We explore this hypothesis by using a simple theoretical metacommunity model with explicit local consumer-resource dynamics and dispersal among systems. Our model shows that variation in dispersal rate affects the temporal mean and variability of ecosystem productivity strongly and nonmonotonically through two mechanisms: spatial averaging by the intermediate-type species that tends to dominate the landscape at high dispersal rates, and functional compensations between species that are made possible by the maintenance of species diversity. The spatial insurance effects of species diversity are highest at the intermediate dispersal rates that maximize local diversity. These results have profound implications for conservation and management. Knowledge of spatial processes across ecosystems is critical to predict the effects of landscape changes on both biodiversity and ecosystem functioning and services. PMID:14569008

  6. Biodiversity as spatial insurance in heterogeneous landscapes

    PubMed Central

    Loreau, Michel; Mouquet, Nicolas; Gonzalez, Andrew

    2003-01-01

    The potential consequences of biodiversity loss for ecosystem functioning and services at local scales have received considerable attention during the last decade, but little is known about how biodiversity affects ecosystem processes and stability at larger spatial scales. We propose that biodiversity provides spatial insurance for ecosystem functioning by virtue of spatial exchanges among local systems in heterogeneous landscapes. We explore this hypothesis by using a simple theoretical metacommunity model with explicit local consumer–resource dynamics and dispersal among systems. Our model shows that variation in dispersal rate affects the temporal mean and variability of ecosystem productivity strongly and nonmonotonically through two mechanisms: spatial averaging by the intermediate-type species that tends to dominate the landscape at high dispersal rates, and functional compensations between species that are made possible by the maintenance of species diversity. The spatial insurance effects of species diversity are highest at the intermediate dispersal rates that maximize local diversity. These results have profound implications for conservation and management. Knowledge of spatial processes across ecosystems is critical to predict the effects of landscape changes on both biodiversity and ecosystem functioning and services. PMID:14569008

  7. Properties of second-order spatial frequency channels Michael S. Landy *, _IIpek Oruc

    E-print Network

    Landy, Michael S.

    Properties of second-order spatial frequency channels Michael S. Landy *, _IIpek Orucß Department response), and finally subsequent (``second-order'') linear spatial filters (to provide a strong response flat over a five-octave range of spatial frequency, but was bandpass when stated as efficiency

  8. Regulation mechanisms in spatial stochastic development models

    E-print Network

    Dmitri Finkelshtein; Yuri Kondratiev

    2008-09-04

    The aim of this paper is to analyze different regulation mechanisms in spatial continuous stochastic development models. We describe the density behavior for models with global mortality and local establishment rates. We prove that the local self-regulation via a competition mechanism (density dependent mortality) may suppress a unbounded growth of the averaged density if the competition kernel is superstable.

  9. The Interplay among Acorn Abundance and Rodent Behavior Drives the Spatial Pattern of Seedling Recruitment in Mature Mediterranean Oak Forests

    PubMed Central

    Boixadera, Ester; Bonal, Raúl

    2015-01-01

    The patterns of seedling recruitment in animal-dispersed plants result from the interactions among environmental and behavioral variables. However, we know little on the contribution and combined effect of both kinds of variables. We designed a field study to assess the interplay between environment (vegetation structure, seed abundance, rodent abundance) and behavior (seed dispersal and predation by rodents, and rooting by wild boars), and their contribution to the spatial patterns of seedling recruitment in a Mediterranean mixed-oak forest. In a spatially explicit design, we monitored intensively all environmental and behavioral variables in fixed points at a small spatial scale from autumn to spring, as well as seedling emergence and survival. Our results revealed that the spatial patterns of seedling emergence were strongly related to acorn availability on the ground, but not by a facilitationeffect of vegetation cover. Rodents changed seed shadows generated by mother trees by dispersing most seeds from shrubby to open areas, but the spatial patterns of acorn dispersal/predation had no direct effect on recruitment. By contrast, rodents had a strong impact on recruitment as pilferers of cached seeds. Rooting by wild boars also reduced recruitment by reducing seed abundance, but also by changing rodent’s behavior towards higher consumption of acorns in situ. Hence, seed abundance and the foraging behavior of scatter-hoarding rodents and wild boars are driving the spatial patterns of seedling recruitment in this mature oak forest, rather than vegetation features. The contribution of vegetation to seedling recruitment (e.g. facilitation by shrubs) may be context dependent, having a little role in closed forests, or being overridden by directed seed dispersal from shrubby to open areas. We warn about the need of using broad approaches that consider the combined action of environment and behavior to improve our knowledge on the dynamics of natural regeneration in forests. PMID:26070129

  10. Curriculum in Spatial Sciences

    E-print Network

    Curriculum in Spatial Sciences Catalog 12-13 University Core Curriculum Required Courses (Th-Pr) Cr.......................................................................................(3-0) 3 Mathematics electives (MATH prefix required) 1...............................................................................................................(3-2) 4 40 #12;Spatial Sciences Core Curriculum ESSM 444 Remote Sensing of the Environment

  11. SPATIAL ENCRYPTION A DISSERTATION

    E-print Network

    SPATIAL ENCRYPTION A DISSERTATION SUBMITTED TO THE DEPARTMENT OF COMPUTER SCIENCE AND THE COMMITTEE cryptography and guide my study of it, he also worked directly on spatial encryption. Finally, the credit and Generic Groups . . . . . . . . . . . . . . . . . . 9 2 Generalized Identity-Based Encryption 11 2

  12. SPATIAL INTERACTION DATA

    Microsoft Academic Search

    Derek Thompson

    1974-01-01

    The lack of good flow data is a handicap to spatial interaction researth, yet many published works provide little evaluation of such data. Good quality flow data should provide spatial coverage at a large scale with small sampling and other error components. Few generally available data series for interregional commodity flows, interregional population migration, and intercity person movement in the

  13. Strong anisotropy of ferroelectricity in lead-free bismuth silicate.

    PubMed

    Seol, Daehee; Taniguchi, Hiroki; Hwang, Jae-Yeol; Itoh, Mitsuru; Shin, Hyunjung; Kim, Sung Wng; Kim, Yunseok

    2015-07-21

    Bismuth silicate (Bi2SiO5) was recently suggested as a potential silicate based lead-free ferroelectric material. Here, we show the existence of ferroelectricity and explore the strong anisotropy of local ferroelectricity using piezoresponse force microscopy (PFM). Domain structures are reconstructed using angle-resolved PFM. Furthermore, piezoresponse hysteresis loops and piezoelectric coefficients are spatially investigated at the nanoscale. The obtained results confirm the existence of ferroelectricity with strong c-axis polarization. These results could provide basic information on the anisotropic ferroelectricity in Bi2SiO5 and furthermore suggest its considerable potential for lead-free ferroelectric applications with silicon technologies. PMID:26084633

  14. Resource heterogeneity and foraging behaviour of cattle across spatial scales

    PubMed Central

    Utsumi, Santiago A; Cangiano, Carlos A; Galli, Julio R; McEachern, Mary B; Demment, Montague W; Laca, Emilio A

    2009-01-01

    Background Understanding the mechanisms that influence grazing selectivity in patchy environments is vital to promote sustainable production and conservation of cultivated and natural grasslands. To better understand how patch size and spatial dynamics influence selectivity in cattle, we examined grazing selectivity under 9 different treatments by offering alfalfa and fescue in patches of 3 sizes spaced with 1, 4, and 8 m between patches along an alley. We hypothesized that (1) selectivity is driven by preference for the forage species that maximizes forage intake over feeding scales ranging from single bites to patches along grazing paths, (2) that increasing patch size enhances selectivity for the preferred species, and that (3) increasing distances between patches restricts selectivity because of the aggregation of scale-specific behaviours across foraging scales. Results Cows preferred and selected alfalfa, the species that yielded greater short-term intake rates (P < 0.0001) and greater daily intake potential. Selectivity was not affected by patch arrangement, but it was scale dependent. Selectivity tended to emerge at the scale of feeding stations and became strongly significant at the bite scale, because of differences in bite mass between plant species. Greater distance between patches resulted in longer patch residence time and faster speed of travel but lower overall intake rate, consistent with maximization of intake rate. Larger patches resulted in greater residence time and higher intake rate. Conclusion We conclude that patch size and spacing affect components of intake rate and, to a lesser extent, the selectivity of livestock at lower hierarchies of the grazing process, particularly by enticing livestock to make more even use of the available species as patches are spaced further apart. Thus, modifications in the spatial pattern of plant patches along with reductions in the temporal and spatial allocation of grazing may offer opportunities to improve uniformity of grazing by livestock and help sustain biodiversity and stability of plant communities. PMID:19393094

  15. Holography and strongly correlated systems

    E-print Network

    Iqbal, Nabil

    2011-01-01

    In this thesis we apply techniques arising from string theory - gauge-gravity/duality, or holography - to problems associated with strongly coupled quantum field theories under extreme conditions such as finite temperature ...

  16. Spatial contextual classification and prediction models for mining geospatial data

    Microsoft Academic Search

    Shashi Shekhar; Paul R. Schrater; Ranga Raju Vatsavai; Weili Wu; Sanjay Chawla

    2002-01-01

    Abstract: Modeling spatial context (e.g., autocorrelation) is akey challenge in classification problems that arise in geospatial domains.Markov random fields (MRF) is a popular model for incorporatingspatial context into image segmentation and land-useclassification problems. The spatial autoregression (SAR) model,which is an extension of the classical regression model for incorporatingspatial dependence, is popular for prediction and classificationof spatial data in regional economics,

  17. Environments of strong gravitational lenses

    Microsoft Academic Search

    Ivelina Gospodinova Momcheva

    2009-01-01

    This dissertation focuses on determining the properties of the environments and the line-of-sight mass distributions for a sample of strong gravitational lenses as well as establishing their effects on the observed lens properties and the Hubble constant. Strong gravitational lenses ought to be able to provide important constraints for cosmology, however the lack of understanding of their large-scale environments has

  18. Children's Spatial Thinking: Does Talk about the Spatial World Matter?

    ERIC Educational Resources Information Center

    Pruden, Shannon M.; Levine, Susan C.; Huttenlocher, Janellen

    2011-01-01

    In this paper we examine the relations between parent spatial language input, children's own production of spatial language, and children's later spatial abilities. Using a longitudinal study design, we coded the use of spatial language (i.e. words describing the spatial features and properties of objects; e.g. big, tall, circle, curvy, edge) from…

  19. Spatial distribution of pulmonary blood flow in dogs in increased force environments

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. F.; Ritman, E. L.; Chevalier, P. A.; Sass, D. J.; Wood, E. H.

    1978-01-01

    Spatial distribution of pulmonary blood flow during 2- to 3-min exposures to 6-8 Gy acceleration was studied, using radioactive microspheres in dogs, and compared to previously reported 1 Gy control distributions. Isotope distributions were measured by scintiscanning individual 1-cm-thick cross sections of excised, fixed lungs. Results indicate: (1) the fraction of cardiac output traversing left and right lungs did not change systematically with the duration and magnitude of acceleration; but (2) the fraction is strongly affected by the occurrence or absence of fast deep breaths, which cause an increase or decrease, respectively, in blood flow through the dependent lung; and (3) Gy acceleration caused a significant increase in relative pulmonary vascular resistance (PVR) in nondependent and dependent regions of the lung concurrent with a decrease in PVR in the midsagittal region of the thorax.

  20. Spatial patterns of tidal heating

    NASA Astrophysics Data System (ADS)

    Beuthe, Mikael

    2013-03-01

    In a body periodically strained by tides, heating produced by viscous friction is far from homogeneous. The spatial distribution of tidal heating depends in a complicated way on the tidal potential and on the internal structure of the body. I show here that the distribution of the dissipated power within a spherically stratified body is a linear combination of three angular functions. These angular functions depend only on the tidal potential whereas the radial weights are specified by the internal structure of the body. The 3D problem of predicting spatial patterns of dissipation at all radii is thus reduced to the 1D problem of computing weight functions. I compute spatial patterns in various toy models without assuming a specific rheology: a viscoelastic thin shell stratified in conductive and convective layers, an incompressible homogeneous body and a two-layer model of uniform density with a liquid or rigid core. For a body in synchronous rotation undergoing eccentricity tides, dissipation in a mantle surrounding a liquid core is highest at the poles. Within a soft layer (or asthenosphere) in contact with a more rigid layer, the same tides generate maximum heating in the equatorial region with a significant degree-four structure if the soft layer is thin. The asthenosphere can be a layer of partial melting in the upper mantle or, very differently, an icy layer in contact with a silicate mantle or solid core. Tidal heating patterns are thus of three main types: mantle dissipation (with the icy shell above an ocean as a particular case), dissipation in a thin soft layer and dissipation in a thick soft layer. Finally, I show that the toy models predict well patterns of dissipation in Europa, Titan and Io. The formalism described in this paper applies to dissipation within solid layers of planets and satellites for which internal spherical symmetry and viscoelastic linear rheology are good approximations.