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1

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

PubMed

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

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

2014-03-01

2

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

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

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

2014-01-01

3

Incorporating spatial dependence in regional frequency analysis  

NASA Astrophysics Data System (ADS)

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.

Wang, Zhuo; Yan, Jun; Zhang, Xuebin

2014-12-01

4

Strong-field spatial interference in a tailored electromagnetic bath  

E-print Network

Light scattered by a regular structure of atoms can exhibit interference signatures, similar to the classical double-slit. These first-order interferences, however, vanish for strong light intensities, restricting potential applications. Here, we show how to overcome these limitations to quantum interference in strong fields. First, we recover the first-order interference in strong fields via a tailored electromagnetic bath with a suitable frequency dependence. At strong driving, the optical properties for different spectral bands are distinct, thus extending the set of observables. We further show that for a two-photon detector as, e.g., in lithography, increasing the field intensity leads to twice the spatial resolution of the second-order interference pattern compared to the weak-field case.

M. Macovei; J. Evers; G. -x. Li; C. H. Keitel

2006-06-19

5

Strong-field spatial interference in a tailored electromagnetic bath.  

PubMed

Light scattered by a regular structure of atoms can exhibit interference signatures, similar to the classical double-slit. These first-order interferences, however, vanish for strong light intensities, restricting potential applications. Here, we show how to overcome these limitations to quantum interference in strong fields. First, we recover the first-order interference in strong fields via a tailored electromagnetic bath with a suitable frequency dependence. At strong driving, the optical properties for different spectral bands are distinct, thus extending the set of observables. We further show that for a two-photon detector as, e.g., in lithography, increasing the field intensity leads to twice the spatial resolution of the second-order interference pattern compared to the weak-field case. PMID:17358766

Macovei, Mihai; Evers, Jörg; Li, Gao-xiang; Keitel, Christoph H

2007-01-26

6

Strongly scale-dependent non-Gaussianity  

SciTech Connect

We discuss models of primordial density perturbations where the non-Gaussianity is strongly scale dependent. In particular, the non-Gaussianity may have a sharp cutoff and be very suppressed on large cosmological scales, but sizable on small scales. This may have an impact on probes of non-Gaussianity in the large-scale structure and in the cosmic microwave background radiation anisotropies.

Riotto, Antonio [INFN, Sezione di Padova, Via Marzolo 8, I-35131 Padua (Italy); CERN, PH-TH Division, CH-1211, Geneve 23 (Switzerland); Sloth, Martin S. [CERN, PH-TH Division, CH-1211, Geneve 23 (Switzerland)

2011-02-15

7

Spatial Dependency of Tuberculosis Incidence in Taiwan  

PubMed Central

Tuberculosis (TB) disease can be caused by either recent transmission from infectious patients or reactivation of remote latent infection. Spatial dependency (correlation between nearby geographic areas) in tuberculosis incidence is a signature for chains of recent transmission with geographic diffusion. To understand the contribution of recent transmission in the TB endemic in Taiwan, where reactivation has been assumed to be the predominant mode of pathogenesis, we used spatial regression analysis to examine whether there was spatial dependency between the TB incidence in each township and in its neighbors. A total of 90,661 TB cases from 349 townships in 2003–2008 were included in this analysis. After adjusting for the effects of confounding socioeconomic variables, including the percentages of aboriginals and average household income, the results show that the spatial lag parameter remains positively significant (0.43, p<0.001), which indicates that the TB incidences of neighboring townships had an effect on the TB incidence in each township. Townships with substantial spatial spillover effects were mainly located in the northern, western and eastern parts of Taiwan. Spatial dependency implies that recent transmission plays a significant role in the pathogenesis of TB in Taiwan. Therefore, in addition to the current focus on improving the cure rate under directly observed therapy programs, more resource need to be allocated to active case finding in order to break the chain of transmission. PMID:23226371

Ng, In-Chan; Wen, Tzai-Hung; Wang, Jann-Yuan; Fang, Chi-Tai

2012-01-01

8

Spatial Dependencies between Large-Scale Brain Networks  

PubMed Central

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

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

2014-01-01

9

Coexisting orchid species have distinct mycorrhizal communities and display strong spatial segregation.  

PubMed

Because orchids are dependent on mycorrhizal fungi for germination and establishment of seedlings, differences in the mycorrhizal communities associating with orchids can be expected to mediate the abundance, spatial distribution and coexistence of terrestrial orchids in natural communities. We assessed the small-scale spatial distribution of seven orchid species co-occurring in 25 × 25 m plots in two Mediterranean grasslands. In order to characterize the mycorrhizal community associating with each orchid species, 454 pyrosequencing was used. The extent of spatial clustering was assessed using techniques of spatial point pattern analysis. The community of mycorrhizal fungi consisted mainly of members of the Tulasnellaceae, Thelephoraceae and Ceratobasidiaceae, although sporadically members of the Sebacinaceae, Russulaceae and Cortinariaceae were observed. Pronounced differences in mycorrhizal communities were observed between species, whereas strong clustering and significant segregation characterized the spatial distribution of orchid species. However, spatial segregation was not significantly related to phylogenetic dissimilarity of fungal communities. Our results indicate that co-occurring orchid species have distinctive mycorrhizal communities and show strong spatial segregation, suggesting that mycorrhizal fungi are important factors driving niche partitioning in terrestrial orchids and may therefore contribute to orchid coexistence. PMID:24325257

Jacquemyn, Hans; Brys, Rein; Merckx, Vincent S F T; Waud, Michael; Lievens, Bart; Wiegand, Thorsten

2014-04-01

10

Strong Neutral Spatial Effects Shape Tree Species Distributions across Life Stages at Multiple Scales  

PubMed Central

Traditionally, ecologists use lattice (regional summary) count data to simulate tree species distributions to explore species coexistence. However, no previous study has explicitly compared the difference between using lattice count and basal area data and analyzed species distributions at both individual species and community levels while simultaneously considering the combined scenarios of life stage and scale. In this study, we hypothesized that basal area data are more closely related to environmental variables than are count data because of strong environmental filtering effects. We also address the contribution of niche and the neutral (i.e., solely dependent on distance) factors to species distributions. Specifically, we separately modeled count data and basal area data while considering life stage and scale effects at the two levels with simultaneous autoregressive models and variation partitioning. A principal coordinates of neighbor matrix (PCNM) was used to model neutral spatial effects at the community level. The explained variations of species distribution data did not differ significantly between the two types of data at either the individual species level or the community level, indicating that the two types of data can be used nearly identically to model species distributions. Neutral spatial effects represented by spatial autoregressive parameters and the PCNM eigenfunctions drove species distributions on multiple scales, different life stages and individual species and community levels in this plot. We concluded that strong neutral spatial effects are the principal mechanisms underlying the species distributions and thus shape biodiversity spatial patterns. PMID:22666497

Hu, Yue-Hua; Lan, Guo-Yu; Sha, Li-Qing; Cao, Min; Tang, Yong; Li, Yi-De; Xu, Da-Ping

2012-01-01

11

Investigating possible regional dependence in strong ground motions  

E-print Network

Investigating possible regional dependence in strong ground motions John Douglas, Ph.D. Earthquake.douglas@hi.is. On teaching leave from BRGM, Orléans, France. Abstract It is common practice to use ground-motion models dependence of ground motions on geographical region, i.e., are me- dian ground motions in the (target) region

Paris-Sud XI, Université de

12

ON DP-MINIMALITY, STRONG DEPENDENCE AND ALF ONSHUUS  

E-print Network

-minimality is equivalent (for an arbitrary dependent theory) to every 1-type having weight 1. Even though we startedON DP-MINIMALITY, STRONG DEPENDENCE AND WEIGHT ALF ONSHUUS AND ALEXANDER USVYATSOV Abstract. We and weight. 1. Introduction and Preliminaries 1.1. Introduction. The original goal of this paper

Edmundo, Mário Jorge

13

Corresponding delay-dependent biases in spatial language and spatial memory  

Microsoft Academic Search

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

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

2010-01-01

14

Strongly modified angular dependence of emission from OLEDs  

NASA Astrophysics Data System (ADS)

The emission pattern of organic light-emitting diodes (OLEDs) is usually close to Lambertian. This paper explores the factors controlling the angular dependence of the emission from OLEDs. In particular it considers the question of how far from Lambertian can the emission of an OLED be? We have examined how wavelength-scale microstructure can modify the pattern of light emission from OLEDs. We demonstrate OLEDs in which emission is strongly directed towards, or away from, the forward direction. We consider the relative importance of scattering of waveguide modes, surface plasmons and microcavity effects in the strongly modified emission patterns which we observe.

Zhang, Shuyu; Turnbull, Graham A.; Samuel, Ifor D. W.

2012-09-01

15

Perceived time is spatial frequency dependent  

Microsoft Academic Search

We investigated whether changes in low-level image characteristics, in this case spatial frequency, were capable of generating a well-known expansion in the perceived duration of an infrequent “oddball” stimulus relative to a repeatedly-presented “standard” stimulus. Our standard and oddball stimuli were Gabor patches that differed from each other in spatial frequency by two octaves. All stimuli were equated for visibility.

C. Aaen-Stockdale; J. Hotchkiss; J. Heron; D. Whitaker

2011-01-01

16

Spatial dependencies in wind-related housing damage  

Microsoft Academic Search

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

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

2008-01-01

17

Task-dependent spatial selectivity in the primate amygdala.  

PubMed

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

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

2014-12-01

18

Verifying the Dependence of Fractal Coefficients on Different Spatial Distributions  

SciTech Connect

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.

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

19

Spatial dependencies mining based on fuzzy neural networks  

NASA Astrophysics Data System (ADS)

Spatial dependency describes the relationship between one dependent spatial variable and other related spatial variables. This paper constructs two kinds of Fuzzy Neural Networks for spatial dependency mining, the modified fuzzy neural network model and the fuzzy comprehensive assessment network model. The first model is built from general fuzzy neural network model. It has four layers, input layer, fuzzy membership function layer, fuzzy reasoning layer and output layer. The second model is built based on a fuzzy comprehensive assessment algorithm. It has five layers. The first three layers are same as the first model, the fourth and the fifth layer are used to find the maximum membership degree and give the output. We develop the training algorithm for these two models based BP algorithm and genetic algorithm, respectively. This paper adopts a thematic spatial database of land evaluation to test these models. We use experiential knowledge as original rules to build initial FNN models. We can see that original rules (spatial dependencies) are corrected after training. It can be seen that these two models get almost the same revised dependencies, and this indicates that these two models both correct the original ones and get the more objective spatial dependencies. Experiments also indicate these two models are efficient.

Jiao, L. M.; Liu, Y. L.

2008-12-01

20

Chain Graphs for Spatial Dependence in Ecological Data  

E-print Network

Chain Graphs for Spatial Dependence in Ecological Data Alix I Gitelman1 & Alan Herlihy2 1-BERN is a Bayes network model implemented on the Neuse River Estuary in NC; it connects chlorophyll concentration

21

Subject dependent transfer functions in spatial hearing  

Microsoft Academic Search

Head Related Transfer Functions (HRTF's) characterize the transformation of pressure waves from the sound source to the listener's eardrums. They are of central interest to binaural hearing and to sound localization. The HRTF is a function of the azimuth and elevation of the sound source, and may vary from subject to subject. The functional dependence of the HRTF on azimuth

V. Ralph Algazi; Pierre L. Divenyi; V. A. Martinez; R. O. Duda

1997-01-01

22

Spatial Transport of Magnetic Flux Surfaces in Strongly Anisotropic Turbulence  

NASA Astrophysics Data System (ADS)

Magnetic flux surfaces afford familiar descriptions of spatial structure, dynamics, and connectivity of magnetic fields, with particular relevance in contexts such as solar coronal flux tubes, magnetic field connectivity in the interplanetary and interstellar medium, as well as in laboratory plasmas and dynamo problems [1-4]. Typical models assume that field-lines are orderly, and flux tubes remain identifiable over macroscopic distances; however, a previous study has shown that flux tubes shred in the presence of fluctuations, typically losing identity after several correlation scales [5]. Here, the structure of magnetic flux surfaces is numerically investigated in a reduced magnetohydrodynamic (RMHD) model of homogeneous turbulence. Short and long-wavelength behavior is studied statistically by propagating magnetic surfaces along the mean field. At small scales magnetic surfaces become complex, experiencing an exponential thinning. At large scales, instead, the magnetic flux undergoes a diffusive behavior. The link between the diffusion of the coarse-grained flux and field-line random walk is established by means of a multiple scale analysis. Both large and small scales limits are controlled by the Kubo number. These results have consequences for understanding and interpreting processes such as magnetic reconnection and field-line diffusion in plasmas [6]. [1] E. N. Parker, Cosmical Magnetic Fields (Oxford Univ. Press, New York, 1979). [2] J. R. Jokipii and E. N. Parker, Phys. Rev. Lett. 21, 44 (1968). [3] R. Bruno et al., Planet. Space Sci. 49, 1201 (2001). [4] M. N. Rosenbluth et al., Nuclear Fusion 6, 297 (1966). [5] W. H. Matthaeus et al., Phys. Rev. Lett. 75, 2136 (1995). [6] S. Servidio et al., submitted (2013).

Matthaeus, W. H.; Servidio, S.; Wan, M.; Ruffolo, D. J.; Rappazzo, A. F.; Oughton, S.

2013-12-01

23

Parity-dependent localization in N strongly coupled chains  

NASA Astrophysics Data System (ADS)

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.

Weinmann, Dietmar; Evangelou, S. N.

2014-10-01

24

Efficient Estimation of Mutual Information for Strongly Dependent Variables  

E-print Network

We demonstrate that a popular class of nonparametric mutual information (MI) estimators based on k-nearest-neighbor graphs requires number of samples that scales exponentially with the true MI. Consequently, accurate estimation of MI between two strongly dependent variables is possible only for prohibitively large sample size. This important yet overlooked shortcoming of the existing estimators is due to their implicit reliance on local uniformity of the underlying joint distribution. We introduce a new estimator that is robust to local non-uniformity, works well with limited data, and is able to capture relationship strengths over many orders of magnitude. We demonstrate the superior performance of the proposed estimator on both synthetic and real-world data.

Gao, Shuyang; Galstyan, Aram

2014-01-01

25

Spatial dependence of the pairing gap in superfluid nuclei  

SciTech Connect

The spatial structure of pairing correlations in {sup 120}Sn is investigated making use of both the bare nucleon-nucleon potential and the interaction induced by the exchange of collective vibrations, taking into account self-energy effects. The resulting pairing gap is strongly peaked on the nuclear surface.

Vigezzi, E.; Pastore, A.; Potel, G. [INFN, Sezione di Milano and Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milano (Italy); Barranco, F. [Departamento de Fisica Aplicada III, Universidad de Sevilla, Escuela Superior de Ingenieros, Sevilla, 41092 Camino de los Descubrimientos s/n (Spain); Broglia, R. A. [INFN, Sezione di Milano and Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milano (Italy); Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen Oe (Denmark)

2009-05-04

26

Modeling Spatial Dependencies and Semantic Concepts in Data Mining  

SciTech Connect

Data mining is the process of discovering new patterns and relationships in large datasets. However, several studies have shown that general data mining techniques often fail to extract meaningful patterns and relationships from the spatial data owing to the violation of fundamental geospatial principles. In this tutorial, we introduce basic principles behind explicit modeling of spatial and semantic concepts in data mining. In particular, we focus on modeling these concepts in the widely used classification, clustering, and prediction algorithms. Classification is the process of learning a structure or model (from user given inputs) and applying the known model to the new data. Clustering is the process of discovering groups and structures in the data that are ``similar,'' without applying any known structures in the data. Prediction is the process of finding a function that models (explains) the data with least error. One common assumption among all these methods is that the data is independent and identically distributed. Such assumptions do not hold well in spatial data, where spatial dependency and spatial heterogeneity are a norm. In addition, spatial semantics are often ignored by the data mining algorithms. In this tutorial we cover recent advances in explicitly modeling of spatial dependencies and semantic concepts in data mining.

Vatsavai, Raju [ORNL] [ORNL

2012-01-01

27

The combination of vision and touch depends on spatial proximity  

E-print Network

The combination of vision and touch depends on spatial proximity Vision Science Program, School combines visual and haptic information about object properties such that the combined estimate is more precise than with vision or haptics alone. We examined how the system determines when to combine

Burge, Johannes

28

Level dependence of spatial processing in the primate auditory cortex  

PubMed Central

Sound localization in both humans and monkeys is tolerant to changes in sound levels. The underlying neural mechanism, however, is not well understood. This study reports the level dependence of individual neurons' spatial receptive fields (SRFs) in the primary auditory cortex (A1) and the adjacent caudal field in awake marmoset monkeys. We found that most neurons' excitatory SRF components were spatially confined in response to broadband noise stimuli delivered from the upper frontal sound field. Approximately half the recorded neurons exhibited little change in spatial tuning width over a ?20-dB change in sound level, whereas the remaining neurons showed either expansion or contraction in their tuning widths. Increased sound levels did not alter the percent distribution of tuning width for neurons collected in either cortical field. The population-averaged responses remained tuned between 30- and 80-dB sound pressure levels for neuronal groups preferring contralateral, midline, and ipsilateral locations. We further investigated the spatial extent and level dependence of the suppressive component of SRFs using a pair of sequentially presented stimuli. Forward suppression was observed when the stimuli were delivered from “far” locations, distant to the excitatory center of an SRF. In contrast to spatially confined excitation, the strength of suppression typically increased with stimulus level at both the excitatory center and far regions of an SRF. These findings indicate that although the spatial tuning of individual neurons varied with stimulus levels, their ensemble responses were level tolerant. Widespread spatial suppression may play an important role in limiting the sizes of SRFs at high sound levels in the auditory cortex. PMID:22592309

Wang, Xiaoqin

2012-01-01

29

Graphene Oxidation: Thickness-Dependent Etching and Strong Chemical Doping  

Microsoft Academic Search

Patterned graphene shows substantial potential for applications in future molecular-scale integrated electronics. Environmental effects are a critical issue in a single layer material where every atom is on the surface. Especially intriguing is the variety of rich chemical interactions shown by molecular oxygen with aromatic molecules. We find that O2 etching kinetics vary strongly with the number of graphene layers

Li Liu; Sunmin Ryu; Michelle R. Tomasik; Elena Stolyarova; Naeyoung Jung; Mark S. Hybertsen; Michael L. Steigerwald; Louis E. Brus; George W. Flynn

2008-01-01

30

Improved dependent component analysis for hyperspectral unmixing with spatial correlations  

NASA Astrophysics Data System (ADS)

In highly mixed hyerspectral datasets, dependent component analysis (DECA) has shown its superiority over other traditional geometric based algorithms. This paper proposes a new algorithm that incorporates DECA with the infinite hidden Markov random field (iHMRF) model, which can efficiently exploit spatial dependencies between image pixels and automatically determine the number of classes. Expectation Maximization algorithm is derived to infer the model parameters, including the endmembers, the abundances, the dirichlet distribution parameters of each class and the classification map. Experimental results based on synthetic and real hyperspectral data show the effectiveness of the proposed algorithm.

Tang, Yi; Wan, Jianwei; Huang, Bingchao; Lan, Tian

2014-11-01

31

Reference frames in virtual spatial navigation are viewpoint dependent  

PubMed Central

Spatial navigation in the mammalian brain relies on a cognitive map of the environment. Such cognitive maps enable us, for example, to take the optimal route from a given location to a known target. The formation of these maps is naturally influenced by our perception of the environment, meaning it is dependent on factors such as our viewpoint and choice of reference frame. Yet, it is unknown how these factors influence the construction of cognitive maps. Here, we evaluated how various combinations of viewpoints and reference frames affect subjects' performance when they navigated in a bounded virtual environment without landmarks. We measured both their path length and time efficiency and found that (1) ground perspective was associated with egocentric frame of reference, (2) aerial perspective was associated with allocentric frame of reference, (3) there was no appreciable performance difference between first and third person egocentric viewing positions and (4) while none of these effects were dependent on gender, males tended to perform better in general. Our study provides evidence that there are inherent associations between visual perspectives and cognitive reference frames. This result has implications about the mechanisms of path integration in the human brain and may also inspire designs of virtual reality applications. Lastly, we demonstrated the effective use of a tablet PC and spatial navigation tasks for studying spatial and cognitive aspects of human memory. PMID:25249956

Török, Ágoston; Nguyen, T. Peter; Kolozsvári, Orsolya; Buchanan, Robert J.; Nadasdy, Zoltan

2014-01-01

32

Strong discontinuities in spatial stationary long-wave flows of an ideal incompressible fluid  

Microsoft Academic Search

Spatial stationary flows over an even bottom of a heavy ideal fluid with a free surface are considered. Jump relations for\\u000a flows with a strong discontinuity are studied. It is shown that the flow parameters behind the jump are defined by a certain\\u000a curve which is an analog of the (?, p) diagram in gas dynamics. A shock polar and

A. K. Khe

2009-01-01

33

Strong-field spatial intensity-intensity correlations of light scattered from regular structures of atoms  

E-print Network

Photon correlations and cross-correlations of light scattered by a regular structure of strongly driven atoms are investigated. At strong driving, the scattered light separates into distinct spectral bands, such that each band can be treated as independent, thus extending the set of observables. We focus on second-order intensity-intensity correlation functions in two- and multi-atom systems. We demonstrate that for a single two-photon detector as, e.g., in lithography, increasing the driving field intensity leads to an increased spatial resolution of the second-order two-atom interference pattern. We show that the cross-correlations between photons emitted in the spectral sidebands violate Cauchy-Schwartz inequalities, and that their emission ordering cannot be predicted. Finally, the results are generalized for multi-particle structures, where we find results different from those in a Dicke-type sample.

M. Macovei; J. Evers; C. H. Keitel

2007-02-14

34

Temporal and spatial characteristics of the formation of strong noctilucent clouds  

NASA Astrophysics Data System (ADS)

The 3-D Lagrangian model LIMA/ICE is used to track ice particles forming noctilucent clouds (NLC). Fifty strong NLC events at three different latitudes are analyzed. Visible particles are traced back to their nucleation sites as well as traced forward until sublimation. Particle nucleation occurs in bursts within areas of high supersaturation. We characterize NLC particle growth and vertical transport: Slow growth occurs below the mesopause up to ?6 h before observation. It is followed by rapid growth within the high water vapor zone around 83 km during phases of upward winds. At the same time temperature perturbations in these cold phases of waves lead to a high supersaturation. Sublimation occurs quickly after maximum brightness, since sedimentation into subsaturated altitudes is accelerated by downward winds. The duration of particle visibility (?>10% of observed backscatter) is only ?5 h. The mean particle age of all NLC events at 69°N is around 36 h, but particle age varies by more than 24 h for the different events studied. Although the age of particles in strong NLC depends on latitude, the visibility period does not. The brightness of strong NLC depends mainly on background conditions during the last 3 h before observation. This implies that local measurements, e.g. by lidar, are representative for the morphology of strong NLC on scales of several hundred kilometers.

Kiliani, J.; Baumgarten, G.; Lübken, F.-J.; Berger, U.; Hoffmann, P.

2013-11-01

35

Spatial Visualization Abilities of Field Dependent/Independent Preservice Teachers  

ERIC Educational Resources Information Center

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…

Yazici, Ersen

2014-01-01

36

Near-field spatial mapping of strongly interacting multiple plasmonic infrared antennas.  

PubMed

Near-field dipolar plasmon interactions of multiple infrared antenna structures in the strong coupling limit are studied using scattering-type scanning near-field optical microscope (s-SNOM) and theoretical finite-difference time-domain (FDTD) calculations. We monitor in real-space the evolution of plasmon dipolar mode of a stationary antenna structure as multiple resonantly matched dipolar plasmon particles are closely approaching it. Interparticle separation, length and polarization dependent studies show that the cross geometry structure favors strong interparticle charge-charge, dipole-dipole and charge-dipole Coulomb interactions in the nanometer scale gap region, which results in strong field enhancement in cross-bowties and further allows these structures to be used as polarization filters. The nanoscale local field amplitude and phase maps show that due to strong interparticle Coulomb coupling, cross-bowtie structures redistribute and highly enhance the out-of-plane (perpendicular to the plane of the sample) plasmon near-field component at the gap region relative to ordinary bowties. PMID:24097054

Grefe, Sarah E; Leiva, Daan; Mastel, Stefan; Dhuey, Scott D; Cabrini, Stefano; Schuck, P James; Abate, Yohannes

2013-11-21

37

Morphological dependence in the spatial orientations of Local Supercluster galaxies  

NASA Astrophysics Data System (ADS)

We have compiled a database of 4073 morphologically identified galaxies with radial velocity <3000 km s-1 and examined the alignments of the spin vectors of these galaxies in the Local Supercluster (LSC). Our aim is to test the morphological dependence of galaxy orientation. The “position angle - inclination” method is used to find the polar and azimuthal angles of the galaxy rotation axes. The spatial isotropic distribution is assumed to examine the non-random effects. We have carried out chi-square, Fourier, and auto correlation tests to examine non-random effects in the distributions of the polar and azimuthal angles of the galaxy rotation axes. We suspect that the orientations of galaxies in the LSC could be closely related to galactic morphology. The spiral galaxies exhibit anisotropy although not at a very high significance level. It is found that the spin vector orientations of the spiral galaxies in the LSC tend to lie perpendicular to the LSC plane. No preferred orientation is found in the spin vector orientations of barred spiral and irregular galaxies. The orientations of early-type and late-type spirals and barred spirals are discussed.

Aryal, B.; Saurer, W.

2005-03-01

38

DENSITY DEPENDENCE IN MARINE FISH POPULATIONS REVEALED AT SMALL AND LARGE SPATIAL SCALES  

Microsoft Academic Search

Experimental manipulation of population density has frequently been used to demonstrate demographic density dependence. However, such studies are usually small scale and typically provide evidence of spatial (within-generation) density dependence. It is often unclear whether small-scale, experimental tests of spatial density dependence will accurately describe temporal (between-generation) density dependence required for pop- ulation regulation. Understanding the mechanisms generating density dependence

DARREN W. J OHNSON

2006-01-01

39

Overcoming Spatial Dilution and Frequency Dependent Biases in Statistical Downscaling  

NASA Astrophysics Data System (ADS)

The impact of climate change on regional hydrology is a key component of adaptation and vulnerability studies. Yet downscaling global climate models to provide forcing fields for the necessary hydrological simulations is challenging because the distributed sources and non-linear nature of runoff renders such simulations highly sensitive to inaccuracies in spatial structure and other biases. For this reason bias correction is an integral part of the downscaling process. Biases in annual or monthly mean fields of precipitation and temperature have received considerable attention, but other biases remain that produce errors in hydrological applications. One such bias that occurs in some downscaling schemes is an increase in the spatial coherence of the daily downscaled precipitation. In evaluating this bias, it is useful to quantify the effects of low spatial variability and develop an understanding of how this bias affects hydrological simulations. An accurate representation of spatial precipitation variability is particularly important in simulating flood events; if simulated heavy precipitation is too spatially coherent, the volume of runoff from adjacent portions of a watershed may be artificially high. We illustrate a scale selective constructed analogues technique that ameliorates the spatial dilution found in other analogue schemes. Besides these spatial biases, another downscaling issue is that climate models produce substantial biases in frequency space, so that a given model can be deficient in variability in one frequency band yet have too much variability in another. Standard bias-correction methods such as quantile mapping and CDF-t do not address this problem. We show that bias correction in frequency space prior to quantile mapping or CDF-t can reduce these errors, leading to an overall improved agreement with observations.

Pierce, D. W.; Cayan, D. R.

2013-12-01

40

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

41

Static Dependency Pair Method Based on Strong Computability for Higher-Order Rewrite Systems  

NASA Astrophysics Data System (ADS)

Higher-order rewrite systems (HRSs) and simply-typed term rewriting systems (STRSs) are computational models of functional programs. We recently proposed an extremely powerful method, the static dependency pair method, which is based on the notion of strong computability, in order to prove termination in STRSs. In this paper, we extend the method to HRSs. Since HRSs include ?-abstraction but STRSs do not, we restructure the static dependency pair method to allow ?-abstraction, and show that the static dependency pair method also works well on HRSs without new restrictions.

Kusakari, Keiichirou; Isogai, Yasuo; Sakai, Masahiko; Blanqui, Frédéric

42

Retrieval Induces Hippocampal-Dependent Reconsolidation of Spatial Memory  

ERIC Educational Resources Information Center

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…

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

2006-01-01

43

Non-perturbative particle production mechanism in time-dependent strong non-Abelian fields  

SciTech Connect

Non-perturbative production of quark-antiquarks is investigated in the early stage of heavy-ion collisions. The time-dependent study is based on a kinetic description of the fermion-pair production in strong non-Abelian fields. We introduce time-dependent chromo-electric external field with a pulse-like time evolution to simulate the overlap of two colliding heavy ions. We have found that the small inverse duration time of the field pulse determines the efficiency of the quark-pair production. The expected suppression for heavy quark production, as follows from the Schwinger formula for a constant field, is not seen, but an enhanced heavy quark production appears at ultrarelativistic energies. We convert our pulse duration time-dependent results into collisional energy dependence and introduce energy and flavour-dependent string tensions, which can be used in string based model calculations at RHIC and LHC energies.

Levai, Peter [MTA KFKI RMKI, Konkoly-Thege Miklos 29-33, H-1121 Budapest (Hungary); Skokov, Vladimir V. [GSI, Planckstr. 1, D-64291 Darmstadt (Germany)

2011-04-26

44

Pulse-shape-dependent strong-field ionization viewed with velocity-map imaging  

SciTech Connect

We explore strong field molecular ionization with velocity map imaging of fragment ions produced by dissociation following ionization. Our measurements and ab initio electronic structure calculations allow us to identify various electronic states of the molecular cation populated during ionization, with multiple pathways to individual states highlighted by the pulse shape dependence. In addition, we show that relative populations can be reconstructed from our measurements. The results illustrate how strong field molecular ionization can be complicated by the presence and interaction of multiple cationic states during ionization.

Geissler, Dominik; Weinacht, Thomas C. [Department of Physics, Stony Brook University, Stony Brook, New York 11794 (United States); Rozgonyi, Tamas [Chemical Research Center of the Hungarian Academy of Sciences, Pusztaszeri u't 59-67, Budapest, HU-1025 (Hungary); Gonzalez-Vazquez, Jesus [Instituto de Quimica Fisica Rocasolano, CSIC, C/Serrano 119, ES-28006 Madrid (Spain); Gonzalez, Leticia; Marquetand, Philipp [Institute of Theoretical Chemistry, University of Vienna, Waehringer Str. 17, 1090 Vienna (Austria)

2011-11-15

45

Atmospheric Moisture Budget and Spatial Resolution Dependence of Precipitation Extremes in Aquaplanet Simulations  

SciTech Connect

This study investigates the resolution dependency of precipitation extremes in an aqua-planet framework. Strong resolution dependency of precipitation extremes is seen over both tropics and extra-tropics, and the magnitude of this dependency also varies with dynamical cores. Moisture budget analyses based on aqua-planet simulations with the Community Atmosphere Model (CAM) using the Model for Prediction Across Scales (MPAS) and High Order Method Modeling Environment (HOMME) dynamical cores but the same physics parameterizations suggest that during precipitation extremes moisture supply for surface precipitation is mainly derived from advective moisture convergence. The resolution dependency of precipitation extremes mainly originates from advective moisture transport in the vertical direction. At most vertical levels over the tropics and in the lower atmosphere over the subtropics, the vertical eddy transport of mean moisture field dominates the contribution to precipitation extremes and its resolution dependency. Over the subtropics, the source of moisture, its associated energy, and the resolution dependency during extremes are dominated by eddy transport of eddies moisture at the mid- and upper-troposphere. With both MPAS and HOMME dynamical cores, the resolution dependency of the vertical advective moisture convergence is mainly explained by dynamical changes (related to vertical velocity or omega), although the vertical gradients of moisture act like averaging kernels to determine the sensitivity of the overall resolution dependency to the changes in omega at different vertical levels. The natural reduction of variability with coarser resolution, represented by areal data averaging (aggregation) effect, largely explains the resolution dependency in omega. The thermodynamic changes, which likely result from non-linear feedback in response to the large dynamical changes, are small compared to the overall changes in dynamics (omega). However, after excluding the data aggregation effect in omega, thermodynamic changes become relatively significant in offsetting the effect of dynamics leading to reduce differences between the simulated and aggregated results. Compared to MPAS, the simulated stronger vertical motion with HOMME also results in larger resolution dependency. Compared to the simulation at fine resolution, the vertical motion during extremes is insufficiently resolved/parameterized at the coarser resolution even after accounting for the natural reduction in variability with coarser resolution, and this is more distinct in the simulation with HOMME. To reduce uncertainties in simulated precipitation extremes, future development in cloud parameterizations must address their sensitivity to spatial resolution as well as dynamical cores.

Yang, Qing; Leung, Lai-Yung R.; Rauscher, Sara; Ringler, Todd; Taylor, Mark

2014-05-01

46

Spatial Characterization of Strong Fiber Bragg Gratings Using Thermal Chirp and Optical-Frequency-Domain Reflectometry  

NASA Astrophysics Data System (ADS)

A method that can spatially characterize gratings with grating strength |k|L up to 10 is presented. The grating is thermally chirped, which increases the transmissivity through the grating. The complex reflectivity spectrum is measured using optical-frequency-domain reflectometry, and the spatial profile is reconstructed using the time-domain layer-peeling algorithm. The spatial profiles of a uniform grating with grating strength |k|L = 8.25 (-66-dB minimum transmissivity) and a distributed-feedback fiber laser grating with grating strength |k|L = 7.5 are accurately reconstructed from the measured complex reflection spectrum.

Waagaard, Ole Henrik

2005-02-01

47

Model for atomic dielectric response in strong, time-dependent laser fields  

NASA Astrophysics Data System (ADS)

A nonlocal quantum-mechanical model is presented for calculating the atomic dielectric response to a strong laser electric field. By replacing the Coulomb potential with a nonlocal potential in the Schrödinger equation, a 3 + 1-dimensional calculation of the time-dependent electric dipole moment can be reformulated as a 0 + 1-dimensional integral equation that retains the three-dimensional dynamics, while offering significant computational savings. The model is benchmarked against an established ionization model and ab initio simulation of the time-dependent Schrödinger equation. The reduced computational overhead makes the model a promising candidate to incorporate full quantum-mechanical time dynamics in laser pulse propagation simulations.

Rensink, T. C.; Antonsen, T. M.; Palastro, J. P.; Gordon, D. F.

2014-03-01

48

The time dependent machine makespan problem is strongly NP-complete  

Microsoft Academic Search

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

T. C. Edwin Cheng; Qing Ding

1999-01-01

49

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

E-print Network

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

Brown, James H.

50

Acute Effects of Alcohol on Intrusive Memory Development and Viewpoint Dependence in Spatial  

E-print Network

Words: Alcohol, allocentric, hippocampus, intrusions, post- traumatic stress disorder (PTSD) A primaryAcute Effects of Alcohol on Intrusive Memory Development and Viewpoint Dependence in Spatial Memory the effect of alcohol on intrusive memories and, concurrently, on egocentric and allocentric spatial memory

Burgess, Neil

51

Horizontal resolution ~5 m (stage dependent) Spatial chemical analysis of biologically active  

E-print Network

MALDI-TOF Horizontal resolution ~5 µm (stage dependent) Spatial chemical analysis of biologically spectroscopy Energy-dispersive X-ray spectroscopy, Auger, and X-ray photoelectron spectroscopy Optical

52

Emotional modulation of hippocampus-dependent spatial learning  

E-print Network

Experiment 4??????????????????????. 16 RESULTS?????????????????????????????. 18 Effects of Peripheral Injections or Intra-Amygdala Infusions of RS 79948-197 Prior to Memory... Retrieval?????????.... 18 Effects of Peripheral Injections or Intra-Amygdala Infusions of RS 79948-197 on Memory System Use: Role for State Dependency...

Elliott, Audrea Elizabeth

2006-10-30

53

Temporal and spatial dependence of hydrodynamic correlations: Simulation and experiment  

SciTech Connect

Time-dependent hydrodynamic interactions in a colloidal suspension of hard spheres are studied, both experimentally and through computer simulation. The focus is on the behavior at small wave vectors, which directly probes the temporal evolution of hydrodynamic interactions between nearby particles. The computer simulations show that the time-dependent diffusion coefficient has the same functional form for all wave vectors, with a single characteristic scaling time for each length scale and for each volume fraction. Wave-vector-averaged effective diffusion coefficients, measured experimentally using diffusing wave spectroscopy, also scale to the same functional form. In this case, the scaling time is dependent on both volume fraction and particle size; it decreases sharply with decreasing particle radius, reflecting the greater contribution from smaller wave vectors that is contained in the scattering from the smaller particles. For a direct comparison of simulation and experiment, we simulate the experimentally observed correlation functions, by averaging the wave-vector-dependent computer-simulation data with the weighting appropriate to the experimental technique. Although the overall scaling is similar, there are quantitative differences in the simulated and measured relaxation times. We suggest these differences are due to the compressibility of the suspension, and that the resultant pressure waves make an unexpectedly significant contribution to the hydrodynamic interactions. (c) 1995 The American Physical Society

Ladd, A.J.C. [Department of Theoretical and Applied Mechanics, Cornell University, Ithaca, New York 14853 (United States)] [Department of Theoretical and Applied Mechanics, Cornell University, Ithaca, New York 14853 (United States); Gang, H. [Exxon Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801 (United States)] [Exxon Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801 (United States); Zhu, J.X. [Department of Chemical Engineering, Princeton University, Princeton, New Jersey 07954 (United States)] [Department of Chemical Engineering, Princeton University, Princeton, New Jersey 07954 (United States); Weitz, D.A. [Exxon Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801 (United States)] [Exxon Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801 (United States)

1995-12-01

54

Spatially dependent cluster dynamics model of He plasma surface interaction in tungsten for fusion relevant conditions  

NASA Astrophysics Data System (ADS)

In fusion reactors, plasma facing components (PFC) and, in particular, the divertor will be irradiated with high fluxes of low-energy (?100 eV) helium and hydrogen ions. Tungsten is one of the leading candidate divertor materials for ITER and DEMO fusion reactors. However, the behaviour of tungsten under high dose, coupled helium/hydrogen exposure remains to be fully understood. The PFC response and performance changes are intimately related to microstructural changes, such as the formation of point defect clusters, helium and hydrogen bubbles or dislocation loops. Computational materials' modelling results are described here that investigate the mechanisms controlling microstructural evolution in tungsten. The aim of this study is to understand and predict sub-surface helium bubble growth under high flux helium ion implantation (?1022 m?2 s?1) at high temperatures (>1000 K). We report results from a spatially dependent cluster dynamics model based on reaction–diffusion rate theory to describe the evolution of the microstructure under these conditions. The key input parameters to the model (diffusion coefficients, migration and binding energies, initial defect production) are determined from a combination of atomistic modelling and available experimental data. The results are in good agreement with results of an analytical model that is presented in a separate paper. In particular, it is found that the sub-surface evolution with respect to bubble size and concentration of the helium bubbles strongly depends on the flux and temperature.

Faney, T.; Krasheninnikov, S. I.; Wirth, B. D.

2015-01-01

55

STRONG GRAVITATIONAL LENS MODELING WITH SPATIALLY VARIANT POINT-SPREAD FUNCTIONS  

SciTech Connect

Astronomical instruments generally possess spatially variant point-spread functions, which determine the amount by which an image pixel is blurred as a function of position. Several techniques have been devised to handle this variability in the context of the standard image deconvolution problem. We have developed an iterative gravitational lens modeling code called Mirage that determines the parameters of pixelated source intensity distributions for a given lens model. We are able to include the effects of spatially variant point-spread functions using the iterative procedures in this lensing code. In this paper, we discuss the methods to include spatially variant blurring effects and test the results of the algorithm in the context of gravitational lens modeling problems.

Rogers, Adam; Fiege, Jason D. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, R3T-2N2 (Canada)

2011-12-10

56

Numbers are associated with different types of spatial information depending on the task.  

PubMed

In this study, we examined the nature of the spatial-numerical associations underlying the SNARC-effect by imposing a verbal or spatial working memory load during a parity judgment and a magnitude comparison task. The results showed a double dissociation between the type of working memory load and type of task. The SNARC-effect disappeared under verbal load in parity judgment and under spatial load in magnitude comparison. These findings provide the first direct empirical evidence against the view that all behavioral signatures of spatial-numerical associations have their origin in a common spatial code. Instead they show that numbers are associated with different spatial codes which, depending on the task, have a visuospatial or verbally mediated nature. PMID:19726035

van Dijck, Jean-Philippe; Gevers, Wim; Fias, Wim

2009-11-01

57

The Redshift Dependence of Gamma-Ray Absorption in the Environments of Strong-Line AGNs  

SciTech Connect

The case of {gamma}-ray absorption due to photon-photon pair production of jet photons in the external photon environments, such as the accretion disk and the broad-line region radiation fields, of {gamma}-ray--loud active galactic nuclei (AGNs) that exhibit strong emission lines is considered. I demonstrate that this 'local opacity,' if detected, will almost unavoidably be redshift-dependent in the sub-TeV range. This introduces nonnegligible biases and complicates approaches for studying the evolution of the extragalactic background light with contemporary GeV instruments such as the Gamma-Ray Large Area Space Telescope (GLAST ), where the {gamma}-ray horizon is probed by means of statistical analysis of absorption features (e.g., the Fazio-Stecker relation) in AGN spectra at various redshifts. It particularly applies to strong-line quasars, where external photon fields are potentially involved in {gamma}-ray production.

Reimer, A.; /Stanford U., HEPL /KIPAC, Menlo Park

2007-11-12

58

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

SciTech Connect

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.

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

2009-01-01

59

Survivorship of juvenile barnacles and mussels: spatial dependence and the origin of  

E-print Network

Survivorship of juvenile barnacles and mussels: spatial dependence and the origin of alternative 2003 Abstract Mussels, barnacles, and rockweeds often form a distinct mosaic of patches on rocky- dependent, but it is not known if juvenile survivorships of mussels and barnacles are, in fact, scale

Plotkin, Joshua B.

60

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

PubMed

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

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

2011-06-01

61

Strong seasonality produces spatial asynchrony in the outbreak of infectious diseases  

PubMed Central

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

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

2011-01-01

62

Strong Spatial Influence on Colonization Rates in a Pioneer Zooplankton Metacommunity  

PubMed Central

The magnitude of community-wide dispersal is central to metacommunity models, yet dispersal is notoriously difficult to quantify in passive and cryptic dispersers such as many freshwater invertebrates. By overcoming the problem of quantifying dispersal rates, colonization rates into new habitats can provide a useful estimate of the magnitude of effective dispersal. Here we study the influence of spatial and local processes on colonization rates into new ponds that indicate differential dispersal limitation of major zooplankton taxa, with important implications for metacommunity dynamics. We identify regional and local factors that affect zooplankton colonization rates and spatial patterns in a large-scale experimental system. Our study differs from others in the unique setup of the experimental pond area by which we were able to test spatial and environmental variables at a large spatial scale. We quantified colonization rates separately for the Copepoda, Cladocera and Rotifera from samples collected over a period of 21 months in 48 newly constructed temporary ponds of 0.18–2.95 ha distributed in a restored wetland area of 2,700 ha in Doñana National Park, Southern Spain. Species richness upon initial sampling of new ponds was about one third of that in reference ponds, although the rate of detection of new species from thereon were not significantly different, probably owing to high turnover in the dynamic, temporary reference ponds. Environmental heterogeneity had no detectable effect on colonization rates in new ponds. In contrast, connectivity, space (based on latitude and longitude) and surface area were key determinants of colonization rates for copepods and cladocerans. This suggests dispersal limitation in cladocerans and copepods, but not in rotifers, possibly due to differences in propagule size and abundance. PMID:22792241

Frisch, Dagmar; Cottenie, Karl; Badosa, Anna; Green, Andy J.

2012-01-01

63

Microscopic calculation and local approximation of the spatial dependence of the pairing field with bare and induced interactions  

SciTech Connect

The bare nucleon-nucleon interaction is essential for the production of pair correlations in nuclei, but an important contribution also arises from the induced interaction resulting from the exchange of collective vibrations between nucleons moving in time reversal states close to the Fermi energy. The pairing field resulting from the summed interaction is strongly peaked at the nuclear surface. It is possible to reproduce the detailed spatial dependence of this field by using either a local approximation, which fully takes into account finite size effects, or a contact interaction, with parameters that are quite different from those commonly used in more phenomenological approaches.

Pastore, A. [Dipartimento di Fisica, Universita degli Studi di Milano, via Celoria 16, I-20133 Milano (Italy); INFN, Sezione di Milano, via Celoria 16, I-20133 Milano (Italy); Barranco, F. [Departamento de Fisica Aplicada III, Escuela Superior de Ingenieros, Camino de los Descubrimientos s/n, E-41092 Sevilla (Spain); Broglia, R. A. [Dipartimento di Fisica, Universita degli Studi di Milano, via Celoria 16, I-20133 Milano (Italy); INFN, Sezione di Milano, via Celoria 16, I-20133 Milano (Italy); Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100 Copenhagen O (Denmark); Vigezzi, E. [INFN, Sezione di Milano, via Celoria 16, I-20133 Milano (Italy)

2008-08-15

64

Strong pressure-dependent electron-phonon coupling in FeSe  

NASA Astrophysics Data System (ADS)

We have computed the correlated electronic structure of FeSe and its dependence on the A1g mode versus compression. Using the self-consistent density functional theory-dynamical mean field theory (DFT-DMFT) with continuous time quantum Monte Carlo, we find that there is greatly enhanced coupling between some correlated electron states and the A1g lattice distortion. Superconductivity in FeSe shows a very strong sensitivity to pressure, with an increase in Tc of almost a factor of 5 within a few GPa, followed by a drop, despite monotonic pressure dependence of almost all electronic properties. We find that the maximum A1g deformation potential behaves similar to the experimental Tc. In contrast, the maximum deformation potential in DFT for this mode increases monotonically with increasing pressure.

Mandal, Subhasish; Cohen, R. E.; Haule, K.

2014-06-01

65

A doubly alkynylpyrene-threaded [4]rotaxane that exhibits strong circularly polarized luminescence from the spatially restricted excimer.  

PubMed

The Sonogashira coupling of ?-CD-encapsulated alkynylpyrenes with terphenyl-type stopper molecules gave a doubly alkynylpyrene-threaded [4]rotaxane. The rotaxane showed only excimer emission, with a high fluorescence quantum yield of ?f =0.37, arising from the spatially restricted excimer within the cavity of the ?-CD. The excimer emission suffered little from self-quenching up to a concentration of 1.5×10(-5) ?M and was circularly polarized with a high glum ?value of -1.5×10(-2) . The strong circularly polarized luminescence may result from the two stacked pyrenes existing in the rotaxane in an asymmetrically twisted manner. PMID:25349047

Inouye, Masahiko; Hayashi, Koichiro; Yonenaga, Yuki; Itou, Tatsuya; Fujimoto, Kazuhisa; Uchida, Taka-Aki; Iwamura, Munetaka; Nozaki, Koichi

2014-12-22

66

Extraordinary photoluminescence and strong temperature/angle-dependent Raman responses in few-layer phosphorene.  

PubMed

Phosphorene is a new family member of two-dimensional materials. We observed strong and highly layer-dependent photoluminescence in few-layer phosphorene (two to five layers). The results confirmed the theoretical prediction that few-layer phosphorene has a direct and layer-sensitive band gap. We also demonstrated that few-layer phosphorene is more sensitive to temperature modulation than graphene and MoS2 in Raman scattering. The anisotropic Raman response in few-layer phosphorene has enabled us to use an optical method to quickly determine the crystalline orientation without tunneling electron microscopy or scanning tunneling microscopy. Our results provide much needed experimental information about the band structures and exciton nature in few-layer phosphorene. PMID:25188827

Zhang, Shuang; Yang, Jiong; Xu, Renjing; Wang, Fan; Li, Weifeng; Ghufran, Muhammad; Zhang, Yong-Wei; Yu, Zongfu; Zhang, Gang; Qin, Qinghua; Lu, Yuerui

2014-09-23

67

Anomalous temperature dependent transport through single colloidal nanorods strongly coupled to metallic leads.  

PubMed

We report wiring of individual colloidal nanorods (NRs), 30-60 nm long by 3.5-5 nm diameter. Strong electrical coupling is achieved by electron beam induced deposition (EBID) of metallic lines targeting NR tips with nanometric precision. At T = 4 K many devices exhibit smooth I(V) curves with no sharp onset features, which remarkably fit a Fowler-Nordheim tunneling model. All devices exhibit an anomalous exponential temperature dependence of the form I approximately exp(T/T(0)). This irregular behavior cannot be explained by any hopping or activation model and is interpreted by accounting for the lowering of the NR conduction band due to lattice dilation and phonon coupling. PMID:19691333

Steinberg, Hadar; Lilach, Yigal; Salant, Asaf; Wolf, Omri; Faust, Adam; Millo, Oded; Banin, Uri

2009-11-01

68

On the measurement of frequency-dependent ultrasonic attenuation in strongly heterogeneous materials.  

PubMed

This paper deals with the measurement of frequency-dependent ultrasonic attenuation in strongly heterogeneous materials, such as cementitious materials. To improve the measurement of this parameter on this kind of materials, a linear swept-frequency signal is used to drive an emitter transducer to conduct a through-transmission inspection in immersion. To filter out undesirable frequency content, time-frequency filtering and detection process are performed. The use of this method has been compared with two excitation techniques, the broadband and the narrowband pulses. The results obtained using the swept-frequency excitation together with the time-frequency filtering, allows the determination of the attenuation curves with high accuracy over a wide frequency range without the need for complicated equipment, and improves the effective bandwidth by using a unique pair of transducers. PMID:20537363

Molero, M; Segura, I; Aparicio, S; Hernández, M G; Izquierdo, M A G

2010-08-01

69

Need for Space: The Key Distance Effect Depends on Spatial Stimulus Configurations  

PubMed Central

In numerous psychological experiments, participants classify stimuli by pressing response keys. According to Lakens, Schneider, Jostmann, and Schubert (2011), classification performance is affected by physical distance between response keys – indicating a cognitive tendency to represent categories in spatial code. However, previous evidence for a key distance effect (KDE) from a color-naming Stroop task is inconclusive as to whether: (a) key separation automatically leads to an internal spatial representation of non-spatial stimulus characteristics in participants, or if the KDE rather depends on physical spatial characteristics of the stimulus configuration; (b) the KDE attenuates the Stroop interference effect. We therefore first adopted the original Stroop task in Experiment 1, confirming that wider key distance facilitated responses, but did not modulate the Stroop effect as was previously found. In Experiments 2 and 3 we controlled potential mediator variables in the original design. When we did not display instructions about stimulus-response mappings, thereby removing the unintended spatial context from the Stroop stimuli, no KDE emerged. Presenting the instructions at a central position in Experiment 4 confirmed that key separation alone is not sufficient for a KDE, but correspondence between spatial configurations of stimuli and responses is also necessary. Evidence indicates that the KDE on Stroop performance is due to known mechanisms of stimulus-response compatibility and response discriminability. The KDE does, however, not demonstrate a general disposition to represent any stimulus in spatial code. PMID:24642888

Stephan, Julia; Franz, Volker H.

2014-01-01

70

Reversible lesion of the rat’s orbitofrontal cortex interferes with hippocampus-dependent spatial memory  

Microsoft Academic Search

In this study, tetrodotoxin (TTX) inactivation was employed to evaluate the involvement of the rat’s orbitofrontal cortex (OFC) in hippocampus-dependent spatial memory using Morris water maze (MWM) and place avoidance learning (PAL) tasks. In Experiment 1, rats trained in MWM task with two blocks of four trials per day for 3 consecutive days received bilateral injections of either TTX or

Abbas Ali Vafaei; Ali Rashidy-Pour

2004-01-01

71

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

E-print Network

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

German, Donovan P.

72

Thermal maps of Jupiter - Spatial organization and time dependence of stratospheric temperatures, 1980 to 1990  

Microsoft Academic Search

The spatial organization and time dependence of Jupiter's stratospheric temperatures have been measured by observing thermal emission from the 7.8-micrometer CH4 band. These temperatures, observed through the greater part of a Jovian year, exhibit the influence of seasonal radiative forcing. Distinct bands of high temperature are located at the poles and midlatitudes, while the equator alternates between warm and cold

G. S. Orton; A. J. Friedson; J. Caldwell; H. B. Hammel; K. H. Baines; J. T. Bergstralh; T. Z. Martin; M. E. Malcom; R. A. West; W. F. Golisch; D. M. Griep; C. D. Kaminski; A. T. Tokunaga; R. Baron; M. Shure

1991-01-01

73

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

E-print Network

that simulate the Earth's atmosphere, ocean and land processes are the primary tool to study how climate maySpatial Analysis to Quantify Numerical Model Bias and Dependence: How Many Climate Models Are There is that these climate models are random samples from a distribution of possible models centered around the true climate

Jun, Mikyoung

74

ASSESSING FINGERPRINT INDIVIDUALITY USING EPIC: A CASE STUDY IN THE ANALYSIS OF SPATIALLY DEPENDENT MARKED  

E-print Network

ASSESSING FINGERPRINT INDIVIDUALITY USING EPIC: A CASE STUDY IN THE ANALYSIS OF SPATIALLY DEPENDENT MARKED PROCESSES By Chae Young Lim and Sarat C. Dass Michigan State University Fingerprint individuality refers to the extent of uniqueness of finger- prints and is governed by the distribution of fingerprint

Dass, Sarat C.

75

Time-dependent spatial amplitude patterns of harmonic tremor at Arenal volcano, Costa Rica  

E-print Network

Time-dependent spatial amplitude patterns of harmonic tremor at Arenal volcano, Costa Rica: seismic´afico Nacional, 28014 Madrid, Spain 4 Escuela Centroamericana de Geolog´ia, Universidad de Costa Rica, AP 214-2060 San Jos´e, Costa Rica 5 Institut des Sciences de la Terre, Universit´e de Savoie, CNRS, F-73376 Le

Paris-Sud XI, Université de

76

Gaze-dependent spatial updating of tactile targets in a localization task  

PubMed Central

There is concurrent evidence that visual reach targets are represented with respect to gaze. For tactile reach targets, we previously showed that an effector movement leads to a shift from a gaze-independent to a gaze-dependent reference frame. Here we aimed to unravel the influence of effector movement (gaze shift) on the reference frame of tactile stimuli using a spatial localization task (yes/no paradigm). We assessed how gaze direction (fixation left/right) alters the perceived spatial location (point of subjective equality) of sequentially presented tactile standard and visual comparison stimuli while effector movement (gaze fixed/shifted) and stimulus order (vis-tac/tac-vis) were varied. In the fixed-gaze condition, subjects maintained gaze at the fixation site throughout the trial. In the shifted-gaze condition, they foveated the first stimulus, then made a saccade toward the fixation site where they held gaze while the second stimulus appeared. Only when an effector movement occurred after the encoding of the tactile stimulus (shifted-gaze, tac-vis), gaze similarly influenced the perceived location of the tactile and the visual stimulus. In contrast, when gaze was fixed or a gaze shift occurred before encoding of the tactile stimulus, gaze differentially affected the perceived spatial relation of the tactile and the visual stimulus suggesting gaze-dependent coding of only one of the two stimuli. Consistent with previous findings this implies that visual stimuli vary with gaze irrespective of whether gaze is fixed or shifted. However, a gaze-dependent representation of tactile stimuli seems to critically depend on an effector movement (gaze shift) after tactile encoding triggering spatial updating of tactile targets in a gaze-dependent reference frame. Together with our recent findings on tactile reaching, the present results imply similar underlying reference frames for tactile spatial perception and action. PMID:24575060

Mueller, Stefanie; Fiehler, Katja

2014-01-01

77

Gaze-dependent spatial updating of tactile targets in a localization task.  

PubMed

There is concurrent evidence that visual reach targets are represented with respect to gaze. For tactile reach targets, we previously showed that an effector movement leads to a shift from a gaze-independent to a gaze-dependent reference frame. Here we aimed to unravel the influence of effector movement (gaze shift) on the reference frame of tactile stimuli using a spatial localization task (yes/no paradigm). We assessed how gaze direction (fixation left/right) alters the perceived spatial location (point of subjective equality) of sequentially presented tactile standard and visual comparison stimuli while effector movement (gaze fixed/shifted) and stimulus order (vis-tac/tac-vis) were varied. In the fixed-gaze condition, subjects maintained gaze at the fixation site throughout the trial. In the shifted-gaze condition, they foveated the first stimulus, then made a saccade toward the fixation site where they held gaze while the second stimulus appeared. Only when an effector movement occurred after the encoding of the tactile stimulus (shifted-gaze, tac-vis), gaze similarly influenced the perceived location of the tactile and the visual stimulus. In contrast, when gaze was fixed or a gaze shift occurred before encoding of the tactile stimulus, gaze differentially affected the perceived spatial relation of the tactile and the visual stimulus suggesting gaze-dependent coding of only one of the two stimuli. Consistent with previous findings this implies that visual stimuli vary with gaze irrespective of whether gaze is fixed or shifted. However, a gaze-dependent representation of tactile stimuli seems to critically depend on an effector movement (gaze shift) after tactile encoding triggering spatial updating of tactile targets in a gaze-dependent reference frame. Together with our recent findings on tactile reaching, the present results imply similar underlying reference frames for tactile spatial perception and action. PMID:24575060

Mueller, Stefanie; Fiehler, Katja

2014-01-01

78

Strongly Composition-Dependent Partial Molar Compressibility of Water in Silicate Glasses  

NASA Astrophysics Data System (ADS)

Water and other volatiles have long been known to play a fundamental role in igneous processes, yet their influence on the physical properties of melts are still not well enough understood. Of particular interest is the density contrast between liquid and solid phases, which facilitates melt extraction and migration. Owing to its low molecular weight, dissolved water must decrease magma density, but the way it does so as a function of pressure remains largely to be determined. Studies on quenched melts (glasses) provide useful information because the glass has the same structure as the melt. We measured compressional and shear wave velocities of seven series of hydrous aluminosilicate glasses by Brillouin scattering at room temperature and pressure. The glasses were quenched from high temperature and 2 or 3 kbar pressure. The dry end-members range from highly polymerized albitic and granitic compositions, to depolymerized synthetic analogues of mantle-derived melts. For each set of glasses, the adiabatic shear and bulk moduli have been calculated from the measured sound velocities and densities. These moduli are linear functions of water content up to 5 wt % H2O, the highest concentration investigated, indicating that both are independent of water speciation in all series. For water-free glasses, the bulk modulus decreases from about 65 to 35 GPa with increasing degree of polymerization. Sympathetically, the partial molar bulk modulus of the water component decreases from 114 to 8 GPa, such that dissolved water amplifies the differences in rigidity between the anhydrous glasses. This strong variation indicates that the solubility mechanisms of water depend strongly on silicate composition. Depolymerized liquids are also much less compressible than their polymerized counterparts, suggesting that the partial molar compressibility of dissolved water approaches zero in depolymerized liquids. If this is correct, hydrous mantle melts formed beneath volcanic arcs would be more buoyant at depth than previously thought, facilitating their extraction and rapid ascent.

Whittington, A. G.; Richet, P.; Polian, A.

2010-12-01

79

Energy dependence of (p,t) analyzing powers arising from strong, sequential, two-step processes with j dependence  

NASA Astrophysics Data System (ADS)

A marked variation of the analyzing power A(?) with incident proton energy for the ground-state (0+g.s.) transition of 92Zr(p,t)90Zr(0+g.s. was observed over a proton-energy range from 17.0 to 28.5 MeV in the angular region around ?~=20° where the corresponding (p,t) cross section ?(?) yields the first minimum. On the other hand, no such an energy variation was observed at all in the analyzing power for the ground-state transition of 138Ba(p,t)136Ba(0g.s. +) over the same energy range. The former analyzing power shows an ``anomalous'' angular distribution which deviates essentially from the derivative rule \\{A(?)=[d?(?)/d?]/?(?)\\}, while the latter analyzing power shows a ``normal'' angular distribution. In contrast to the analyzing-power angular distributions, the cross-section angular distributions of the two reactions are quite similar and do not show any remarkable energy variation. All these characteristic features of the two reactions are explained by taking account of strong, sequential (p,d) (d,t) two-step processes in addition to a (p,t) one-step process in terms of the first- and second-order distorted-wave Born approximation. The nuclear-shell orbit dependence ( j dependence) of the analyzing powers for the (p,d) (d,t) two-step process plays an essential role in producing the distinguished difference in the energy dependence of the observed analyzing powers for the two reactions. When two neutrons are picked up sequentially from a j>=l+(1/2) ( j<=l-(1/2)) orbit, such as a d5/2 (d3/2) orbit in the case of the 92Zr(p,t)90Zr [138Ba(p,t)136Ba] reaction, the two-step analyzing power is quite different from (similar to) the one-step analyzing power so that the total analyzing power shows a completely different (similar) angular distribution from (to) the one-step analyzing power in the forward angles. The interference effect between the one- and two-step processes is thus quite sensitive to (quite stable against) the relative phase between the transition amplitudes of the two processes. Therefore 92Zr(p,t) [138Ba(p,t)] analyzing power shows a marked (no marked) change with incident energy. The nuclear structure involved in the reaction 138Ba(p,t)136Ba is calculated on the basis of the monopole-pairing vibrational model. The cross section of the (p,d) (d,t) two-step processes is as large as that of the one-step process, so that the resultant total cross section obtained from the coherent sum of the two processes can reproduce the absolute magnitude of the experimental cross sections for the 0+g.s.-->0+g.s.(p,t) reactions well. The derivative rule for 0+g.s.-->0+g.s.(p,t) reactions is derived within the framework of the first-order distorted-wave Born approximation.

Yagi, K.; Iida, H.; Aoki, Y.; Hashimoto, K.; Tagishi, Y.

1985-01-01

80

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

PubMed

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

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

2012-01-01

81

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

PubMed Central

Background The hybridization of nucleic acid targets with surface-immobilized probes is a widely used assay for the parallel detection of multiple targets in medical and biological research. Despite its widespread application, DNA microarray technology still suffers from several biases and lack of reproducibility, stemming in part from an incomplete understanding of the processes governing surface hybridization. In particular, non-random spatial variations within individual microarray hybridizations are often observed, but the mechanisms underpinning this positional bias remain incompletely explained. Methodology/Principal Findings This study identifies and rationalizes a systematic spatial bias in the intensity of surface hybridization, characterized by markedly increased signal intensity of spots located at the boundaries of the spotted areas of the microarray slide. Combining observations from a simplified single-probe block array format with predictions from a mathematical model, the mechanism responsible for this bias is found to be a position-dependent variation in lateral diffusion of target molecules. Numerical simulations reveal a strong influence of microarray well geometry on the spatial bias. Conclusions Reciprocal adjustment of the size of the microarray hybridization chamber to the area of surface-bound probes is a simple and effective measure to minimize or eliminate the diffusion-based bias, resulting in increased uniformity and accuracy of quantitative DNA microarray hybridization. PMID:21858215

Haider, Susanne; Horn, Matthias; Wagner, Michael; Stocker, Roman; Loy, Alexander

2011-01-01

82

Age-dependent effects of environmental enrichment on brain networks and spatial memory in Wistar rats.  

PubMed

We assessed the effect of 3h of environmental enrichment (EE) exposure per day started at different ages (3 and 18months old) on the performance in a spatial memory task and on brain regions involved in the spatial learning (SPL) process using the principal component analysis (PCA). The animals were tested in the four-arm radial water maze (4-RAWM) for 4days, with six daily trials. We used cytochrome c oxidase (COx) histochemistry to determine the brain oxidative metabolic changes related to age, SPL and EE. Behavioural results showed that the enriched groups, regardless of their age, achieved better performance in the spatial task. Interestingly, in the case of the distance travelled in the 4-RAWM, the effect of the EE was dependent on the age, so the young enriched group travelled a shorter distance compared to the aged enriched group. Respect to COx histochemistry results, we found that different brain mechanisms are triggered in aged rats to solve the spatial task, compared to young rats. PCA revealed the same brain functional network in both age groups, but the contribution of the brain regions involved in this network was slightly different depending on the age of the rats. Thus, in the aged group, brain regions involved in anxiety-like behaviour, such as the amygdala or the bed nucleus of the stria terminalis had more relevance; whereas in the young enriched group the frontal and the hippocampal subregions had more contribution. PMID:23769820

Sampedro-Piquero, P; Begega, A; Zancada-Menendez, C; Cuesta, M; Arias, J L

2013-09-17

83

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

PubMed Central

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

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

2013-01-01

84

Spatial dependence, dispersion, and sequential sampling of Anaphothrips obscurus (Thysanoptera: Thripidae) in timothy.  

PubMed

The spatial distribution and dispersion of Anaphothrips obscurus (Müller) (Thysanoptera: Thripidae) was examined with the goal of establishing a sequential sampling plan for this pest in timothy, Phleum pratense L. (Poaceae). Approximately 16 different California timothy fields were sampled twice yearly from 2006 to 2008 using direct observation and the beat cup method. For direct observation, the number of thrips on each leaf of the plant was counted. For the beat cup method, tillers were tapped into a cup and dislodged thrips were counted. Samples were separated by ?3 m in 2006 and 2007 and exactly 3 m in 2008. Spatial autocorrelation of intrafield population distribution was tested for significance in 2008 using Moran's I, but autocorrelation was not detected. The population dispersion was assessed by Taylor's power law and was determined to be aggregated and density-dependent. Intraplant population dispersion and distribution for each year were also evaluated for adults, larvae, and total thrips. All lifestages were highly spatially dependent and more thrips were found near the top of the plant than the bottom. Direct observation proved to be a more accurate and precise method than the beat cup method, especially when thrips abundances were greater than one. However, the number of samples required to provide an accurate level of precision was unrealistic for both methods. A sequential sampling plan was evaluated, but was not practical for the beat cup method because few thrips were found using this method. Because there was no spatial autocorrelation at sampling distances of 3 m, samples can be taken at intervals at 3 m to obtain spatially independent population abundance estimates. PMID:22251648

Reisig, Dominic D; Godfrey, Larry D; Marcum, Daniel B

2011-06-01

85

Neural correlates of reward-based spatial learning in persons with cocaine dependence.  

PubMed

Dysfunctional learning systems are thought to be central to the pathogenesis of and impair recovery from addictions. The functioning of the brain circuits for episodic memory or learning that support goal-directed behavior has not been studied previously in persons with cocaine dependence (CD). Thirteen abstinent CD and 13 healthy participants underwent MRI scanning while performing a task that requires the use of spatial cues to navigate a virtual-reality environment and find monetary rewards, allowing the functional assessment of the brain systems for spatial learning, a form of episodic memory. Whereas both groups performed similarly on the reward-based spatial learning task, we identified disturbances in brain regions involved in learning and reward in CD participants. In particular, CD was associated with impaired functioning of medial temporal lobe (MTL), a brain region that is crucial for spatial learning (and episodic memory) with concomitant recruitment of striatum (which normally participates in stimulus-response, or habit, learning), and prefrontal cortex. CD was also associated with enhanced sensitivity of the ventral striatum to unexpected rewards but not to expected rewards earned during spatial learning. We provide evidence that spatial learning in CD is characterized by disturbances in functioning of an MTL-based system for episodic memory and a striatum-based system for stimulus-response learning and reward. We have found additional abnormalities in distributed cortical regions. Consistent with findings from animal studies, we provide the first evidence in humans describing the disruptive effects of cocaine on the coordinated functioning of multiple neural systems for learning and memory. PMID:23917430

Tau, Gregory Z; Marsh, Rachel; Wang, Zhishun; Torres-Sanchez, Tania; Graniello, Barbara; Hao, Xuejun; Xu, Dongrong; Packard, Mark G; Duan, Yunsuo; Kangarlu, Alayar; Martinez, Diana; Peterson, Bradley S

2014-02-01

86

Scale dependency of fracture energy and estimates thereof via dynamic rupture solutions with strong thermal weakening  

NASA Astrophysics Data System (ADS)

Seismological estimates of fracture energy show a scaling with the total slip of an earthquake [e.g., Abercrombie and Rice, GJI 2005]. Potential sources for this scale dependency are coseismic fault strength reductions that continue with increasing slip or an increasing amount of off-fault inelastic deformation with dynamic rupture propagation [e.g., Andrews, JGR 2005; Rice, JGR 2006]. Here, we investigate the former mechanism by solving for the slip dependence of fracture energy at the crack tip of a dynamically propagating rupture in which weakening takes place by strong reductions of friction via flash heating of asperity contacts and thermal pressurization of pore fluid leading to reductions in effective normal stress. Laboratory measurements of small characteristic slip evolution distances for friction (~10 ?m at low slip rates of ?m-mm/s, possibly up to 1 mm for slip rates near 0.1 m/s) [e.g., Marone and Kilgore, Nature 1993; Kohli et al., JGR 2011] imply that flash weakening of friction occurs at small slips before any significant thermal pressurization and may thus have a negligible contribution to the total fracture energy [Brantut and Rice, GRL 2011; Garagash, AGU 2011]. The subsequent manner of weakening under thermal pressurization (the dominant contributor to fracture energy) spans a range of behavior from the deformation of a finite-thickness shear zone in which diffusion is negligible (i.e., undrained-adiabatic) to that in which large-scale diffusion obscures the existence of a thin shear zone and thermal pressurization effectively occurs by the heating of slip on a plane. Separating the contribution of flash heating, the dynamic rupture solutions reduce to a problem with a single parameter, which is the ratio of the undrained-adiabatic slip-weakening distance (?c) to the characteristic slip-on-a-plane slip-weakening distance (L*). However, for any value of the parameter, there are two end-member scalings of the fracture energy: for small slip, the undrained-adiabatic behavior expectedly results in fracture energy scaling as G ~ ?^2, and for large slip (where TP approaches slip on a plane) we find that G ~ ?^(2/3). This last result is a slight correction to estimates made assuming a constant, kinematically imposed slip rate and slip-on-a-plane TP resulting in G ~ ?^(1/2) [Rice, JGR 2006]. We compile fracture energy estimates of both continental and subduction zone earthquakes. In doing so, we incorporate independent estimates of fault prestress to distinguish fracture energy G from the parameter G' defined by Abercrombie and Rice [2005], which represents the energetic quantity that is most directly inferred following seismological estimates of radiated energy, seismic moment and source radius. We find that the dynamic rupture solutions (which account for the variable manner of thermal pressurization and result in a self-consistent slip rate history) allow for a close match of the estimated fracture energy over several orders of total event slip, further supporting the proposed explanation that fracture energy scaling may largely be attributed to a fault strength that weakens gradually with slip, and additionally, the potential prevalence of thermal pressurization.

Viesca, R. C.; Garagash, D.

2013-12-01

87

High-Tc superconductivity originated from strong spin-charge correlation: indication from linear temperature dependence of resistivity  

E-print Network

Both the highest- and the linear temperature dependence of the resistivity in wide temperature range appear at the optimally doped regions of Cu-based superconductors1,2,3,4,5, and the highest- of Fe-based superconductors6,7 are also associated with the linear temperature dependence of the resistivity in normal states near superconducting states. This means that the high temperature superconductivity and the linear temperature dependence of the resistivity should be dominated by the same mechanism. This letter on theoretic calculation clearly shows that strong spin-charge correlation dominated resistivity behaves the linear temperature dependence, thus high-temperature superconductivity should be induced by strong spin-charge correlation.

Tian De Cao

2007-06-01

88

Transport lattice models of heat transport in skin with spatially heterogeneous, temperature-dependent perfusion  

PubMed Central

Background Investigation of bioheat transfer problems requires the evaluation of temporal and spatial distributions of temperature. This class of problems has been traditionally addressed using the Pennes bioheat equation. Transport of heat by conduction, and by temperature-dependent, spatially heterogeneous blood perfusion is modeled here using a transport lattice approach. Methods We represent heat transport processes by using a lattice that represents the Pennes bioheat equation in perfused tissues, and diffusion in nonperfused regions. The three layer skin model has a nonperfused viable epidermis, and deeper regions of dermis and subcutaneous tissue with perfusion that is constant or temperature-dependent. Two cases are considered: (1) surface contact heating and (2) spatially distributed heating. The model is relevant to the prediction of the transient and steady state temperature rise for different methods of power deposition within the skin. Accumulated thermal damage is estimated by using an Arrhenius type rate equation at locations where viable tissue temperature exceeds 42°C. Prediction of spatial temperature distributions is also illustrated with a two-dimensional model of skin created from a histological image. Results The transport lattice approach was validated by comparison with an analytical solution for a slab with homogeneous thermal properties and spatially distributed uniform sink held at constant temperatures at the ends. For typical transcutaneous blood gas sensing conditions the estimated damage is small, even with prolonged skin contact to a 45°C surface. Spatial heterogeneity in skin thermal properties leads to a non-uniform temperature distribution during a 10 GHz electromagnetic field exposure. A realistic two-dimensional model of the skin shows that tissue heterogeneity does not lead to a significant local temperature increase when heated by a hot wire tip. Conclusions The heat transport system model of the skin was solved by exploiting the mathematical analogy between local thermal models and local electrical (charge transport) models, thereby allowing robust, circuit simulation software to obtain solutions to Kirchhoff's laws for the system model. Transport lattices allow systematic introduction of realistic geometry and spatially heterogeneous heat transport mechanisms. Local representations for both simple, passive functions and more complex local models can be easily and intuitively included into the system model of a tissue. PMID:15548324

Gowrishankar, TR; Stewart, Donald A; Martin, Gregory T; Weaver, James C

2004-01-01

89

Early visual processing deficits in patients with schizophrenia during spatial frequency-dependent facial affect processing.  

PubMed

Abnormal facial emotion recognition is considered as one of the key symptoms of schizophrenia. Only few studies have considered deficits in the spatial frequency (SF)-dependent visual pathway leading to abnormal facial emotion recognition in schizophrenia. Twenty-one patients with schizophrenia and 19 matched healthy controls (HC) were recruited for this study. Event-related potentials (ERP) were measured during presentation of SF-modulated face stimuli and their source imaging was analyzed. The patients showed reduced P100 amplitude for low-spatial frequency (LSF) pictures of fearful faces compared with the HC group. The P100 amplitude for high-spatial frequency (HSF) pictures of neutral faces was increased in the schizophrenia group, but not in the HC group. The neural source activities of the LSF fearful faces and HSF neutral faces led to hypo- and hyperactivation of the frontal lobe of subjects from the schizophrenia group and HC group, respectively. In addition, patients with schizophrenia showed enhanced N170 activation in the right hemisphere in the LSF condition, while the HC group did not. Our results suggest that deficits in the LSF-dependent visual pathway, which involves magnocellular neurons, impair early visual processing leading to dysfunctional facial emotion recognition in schizophrenia. Moreover, it suggests impaired bottom-up processing rather than top-down dysfunction for facial emotion recognition in these patients. PMID:25553978

Kim, Do-Won; Shim, Miseon; Song, Myeong Ju; Im, Chang-Hwan; Lee, Seung-Hwan

2015-02-01

90

Natal departure timing from spatially varying environments is dependent of individual ontogenetic status  

NASA Astrophysics Data System (ADS)

Natal departure timing represents one of the first crucial decisions for juveniles born in spatially varying environments that ultimately disappear, but our knowledge on its determinants is limited. The present study aimed at understanding the determinants of juvenile natal departure by releasing individually tagged juvenile pike ( Esox lucius L.) with variable body size and trophic position in a temporary flooded grassland. Specifically, we investigated whether natal departure depends on individual competitive status (`competition hypothesis'), physiological tolerance to environmental conditions (`physiological hypothesis') or individual trophic position and the spatial heterogeneity of trophic resources (`trophic hypothesis'). The results indicated that departure timing was negatively correlated with body size at release, showing that the dominance status among competing individuals was not the main trigger of juvenile departure. A positive correlation between departure timing and individual body size at departure was observed, suggesting that inter-individual variability in physiological tolerance did not explain departure patterns. While individual growth performances were similar irrespective of the timing of natal departure, stable isotope analyses revealed that juveniles with higher trophic position departed significantly earlier than individuals with lower trophic position. Therefore, the trade-off driving the use of spatially varying environments was most likely dependent upon the benefits associated with energetic returns than the costs associated with inter-individual competition or physiological stress. This result highlighted how ontogeny, and particularly ontogenetic niche shift, can play a central role in juvenile's decision to depart from natal habitats in a predatory species.

Cucherousset, Julien; Paillisson, Jean-Marc; Roussel, Jean-Marc

2013-08-01

91

Natal departure timing from spatially varying environments is dependent of individual ontogenetic status.  

PubMed

Natal departure timing represents one of the first crucial decisions for juveniles born in spatially varying environments that ultimately disappear, but our knowledge on its determinants is limited. The present study aimed at understanding the determinants of juvenile natal departure by releasing individually tagged juvenile pike (Esox lucius L.) with variable body size and trophic position in a temporary flooded grassland. Specifically, we investigated whether natal departure depends on individual competitive status ('competition hypothesis'), physiological tolerance to environmental conditions ('physiological hypothesis') or individual trophic position and the spatial heterogeneity of trophic resources ('trophic hypothesis'). The results indicated that departure timing was negatively correlated with body size at release, showing that the dominance status among competing individuals was not the main trigger of juvenile departure. A positive correlation between departure timing and individual body size at departure was observed, suggesting that inter-individual variability in physiological tolerance did not explain departure patterns. While individual growth performances were similar irrespective of the timing of natal departure, stable isotope analyses revealed that juveniles with higher trophic position departed significantly earlier than individuals with lower trophic position. Therefore, the trade-off driving the use of spatially varying environments was most likely dependent upon the benefits associated with energetic returns than the costs associated with inter-individual competition or physiological stress. This result highlighted how ontogeny, and particularly ontogenetic niche shift, can play a central role in juvenile's decision to depart from natal habitats in a predatory species. PMID:23812603

Cucherousset, Julien; Paillisson, Jean-Marc; Roussel, Jean-Marc

2013-08-01

92

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

PubMed

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

Dyhr, Jonathan P; Higgins, Charles M

2010-05-01

93

3D Rheological Modeling of NW Intraplate Europe, Deciphering Spatial Integrated strength patterns, Mechanical Strong Layering and EET  

NASA Astrophysics Data System (ADS)

Better understanding of 3D rheological heterogeneity of the European Lithosphere provide the key to tie the recorded intraplate deformation pattern to stress fields transmitted into plate interior from plate boundary forces. The first order strain patterns result from stresses transmitted through the European lithosphere that is marked by a patchwork of high strength variability from inherited structural and compositional heterogeneities and upper mantle thermal perturbations. As the lithospheric rheology depends primarily on its spatial structure, composition and thermal estate, the 3D strength model for the European lithosphere relies on a 3D compositional model that yields the compositional heterogeneities and an iteratively calculated thermal cube using Fouriers law for heat conduction. The accurate appraisal of spatial strength variability results from proper mapping and integration of the geophysical compositional and thermal input parameters. Therefore, much attention has been paid to a proper description of first order structural and tectonic features that facilitate compilation of the compositional and thermal input models. As such, the 3D strength model reflects the thermo-mechanical structure inherited from the Europeans polyphase deformation history. Major 3D spatial mechanical strength variability has been revealed. The East-European and Fennoscandian Craton to the NE exhibit high strength (30-50 1012 N/m) from low mantle temperatures and surface heatflow of 35-60 mW/m2 while central and western Europe reflect a polyphase Phanerozoic thermo- tectonic history. Here, regions with high rigidity are formed primarily by patches of thermally stabilized Variscan Massifs (e.g. Rhenish, Armorican, Bohemian, and Iberian Massif) with low heatflow and lithospheric thickness values (50-65 mW/m2; 110-150 km) yielding strengths of ~15-25 1012 N/m. In contrast, major axis of weakened lithosphere coincides with Cenozoic Rift System (e.g. Upper and Lower Rhine Grabens, Pannonian Basin and Massif Central) attributed to the presence of tomographically imaged plumes. This study has elucidated the memory of the present-days Europeans lithosphere induced by compositional and thermal heterogeneities. The resulting lateral strength variations has a clear signature of the pst lithospheres polyphase deformation and also entails active tectonics, tectonically induced topography and surface processes.

Beekman, F.; Hardebol, N.; Cloetingh, S.; Tesauro, M.

2006-12-01

94

Pressure Dependence of Fragile-to-Strong Transition and a Possible Second Critical Point in Supercooled Confined Water  

E-print Network

Pressure Dependence of Fragile-to-Strong Transition and a Possible Second Critical Point the crystallization and study the pressure effect on the dynamical behavior in deeply supercooled state using neutron that the transition temperature decreases steadily with an increasing pressure, until it intersects the homogenous

Chen, Sow-Hsin

95

Novel scatter compensation of list-mode PET data using spatial and energy dependent corrections.  

PubMed

With the widespread use of positron emission tomography (PET) crystals with greatly improved energy resolution (e.g., 11.5% with LYSO as compared to 20% with BGO) and of list-mode acquisitions, the use of the energy of individual events in scatter correction schemes becomes feasible. We propose a novel scatter approach that incorporates the energy of individual photons in the scatter correction and reconstruction of list-mode PET data in addition to the spatial information presently used in clinical scanners. First, we rewrite the Poisson likelihood function of list-mode PET data including the energy distributions of primary and scatter coincidences and show that this expression yields an MLEM reconstruction algorithm containing both energy and spatial dependent corrections. To estimate the spatial distribution of scatter coincidences we use the single scatter simulation (SSS). Next, we derive two new formulae which allow estimation of the 2-D (coincidences) energy probability density functions (E-PDF) of primary and scatter coincidences from the 1-D (photons) E-PDFs associated with each photon. We also describe an accurate and robust object-specific method for estimating these 1-D E-PDFs based on a decomposition of the total energy spectra detected across the scanner into primary and scattered components. Finally, we show that the energy information can be used to accurately normalize the scatter sinogram to the data. We compared the performance of this novel scatter correction incorporating both the position and energy of detected coincidences to that of the traditional approach modeling only the spatial distribution of scatter coincidences in 3-D Monte Carlo simulations of a medium cylindrical phantom and a large, nonuniform NCAT phantom. Incorporating the energy information in the scatter correction decreased bias in the activity distribution estimation by ~20% and ~40% in the cold regions of the large NCAT phantom at energy resolutions 11.5% and 20% at 511 keV, respectively, compared to when using the spatial information alone. PMID:21118770

Guérin, Bastien; El Fakhri, Georges

2011-03-01

96

Dependency of parameter values of a crop model on the spatial scale of simulation  

NASA Astrophysics Data System (ADS)

regional-scale representation of crop growth and yields has been increasingly important in earth system modeling for the simulation of atmosphere-vegetation-soil interactions in managed ecosystems. While the parameter values in many crop models are location specific or cultivar specific, the validity of such values for regional simulation is in question. We present the scale dependency of likely parameter values that are related to the responses of growth rate and yield to temperature, using the paddy rice model applied to Japan as an example. For all regions, values of the two parameters that determine the degree of yield response to low temperature (the base temperature for calculating cooling degree days and the curvature factor of spikelet sterility caused by low temperature) appeared to change relative to the grid interval. Two additional parameters (the air temperature at which the developmental rate is half of the maximum rate at the optimum temperature and the value of developmental index at which point the crop becomes sensitive to the photoperiod) showed scale dependency in a limited region, whereas the remaining three parameters that determine the phenological characteristics of a rice cultivar and the technological level show no clear scale dependency. These results indicate the importance of using appropriate parameter values for the spatial scale at which a crop model operates. We recommend avoiding the use of location-specific or cultivar-specific parameter values for regional crop simulation, unless a rationale is presented suggesting these values are insensitive to spatial scale.

Iizumi, Toshichika; Tanaka, Yukiko; Sakurai, Gen; Ishigooka, Yasushi; Yokozawa, Masayuki

2014-09-01

97

Anharmonic properties of fragile and strong liquids: temperature dependence of the mode Grüneisen parameter  

Microsoft Academic Search

Brillouin spectroscopy, dilatometry and calorimetry results have been used to investigate the temperature anomaly of the mode and thermal Grüneisen parameters around the glass transition of the fragile liquid poly(vinyl acetate). These results are compared with those of the strong liquids 0953-8984\\/8\\/50\\/012\\/img6 and 4-cyano-4-6-alkylbiphenyl.

J. K. Krüger; K.-P. Bohn; M. Pietralla; J. Schreiber

1996-01-01

98

Spatial organization and time dependence of Jupiter's tropospheric temperatures, 1980-1993  

NASA Technical Reports Server (NTRS)

The spatial organization and time dependence of Jupiter's temperature near 250-millibar pressure were measured through a jovian year by imaging thermal emission at 18 micrometers. The temperature field is influenced by seasonal radiative forcing, and its banded organization is closely correlated with the visible cloud field. Evidence was found for a quasi-periodic oscillation of temperatures in the Equatorial Zone, a correlation between tropospheric and stratospheric waves in the North Equatorial Belt, and slowly moving thermal features in the North and South Equatorial Belts. There appears to be no common relation between temporal changes of temperature and changes in the visual albedo of the various axisymmetric bands.

Orton, Glenn S.; Friedson, A. James; Yanamandra-Fisher, Padmavati A.; Caldwell, John; Hammel, Heidi B.; Baines, Kevin H.; Bergstralh, Jay T.; Martin, Terry Z.; West, Robert A.; Veeder, Glenn J., Jr.

1994-01-01

99

Relativistic particle scattering states with tensor potential and spatially-dependent mass  

NASA Astrophysics Data System (ADS)

We investigate the relativistic equation for particles with spin 1/2 in the q-parameter modified Pöschl-Teller potential, including Coulomb-like tensor interaction with spatially-dependent mass for the D-dimension. We present approximate solutions of the Dirac equation with these potentials for any spin-orbit quantum number ? under spin symmetry. The normalized wave functions are expressed in terms of the hyper-geometric series of the scattering states on the k/2? scale. We also give the formula for the phase shifts, and use the Nikiforov-Uvarov method to obtain the energy eigen-values equation.

Eshghi, M.; R. Abdi, M.

2013-05-01

100

Relative spatial frequency tuning and its contrast dependency in human perception.  

PubMed

Several physiological studies in cats and monkeys have reported that the spatial frequency (SF) tuning of visual neurons varies depending on the luminance contrast and size of stimulus. However, comparatively little is known about the effect of changing the stimulus contrast and size on SF tuning in human perception. In the present study, we investigated the effects of stimulus size and luminance contrast on human SF tuning using the subspace-reverse-correlation method. Measuring SF tunings at six different stimulus sizes and three different luminance contrast conditions (90%, 10%, and 1%), we found that human perception exhibits significant stimulus-size-dependent SF tunings. At 90% and 10% contrast, participants exhibited relative SF tuning (cycles/image) rather than absolute SF tuning (cycles/°) at response peak latency. On the other hand, at 1% contrast, the magnitude of the size-dependent-peak SF shift was too small for strictly relative SF tuning. These results show that human SF tuning is not fixed, but varies depending on the stimulus size and contrast. This dependency may contribute to size-invariant object recognition within an appropriate contrast rage. PMID:25413628

Naito, Tomoyuki; Suematsu, Naofumi; Matsumoto, Eriko; Sato, Hiromichi

2014-01-01

101

Spin-1/2 Particle in Scalar-Vector-Pseudoscalar Spatially Dependent Mass Coulomb Fields: 1 + 1 Dimensions  

NASA Astrophysics Data System (ADS)

In this letter, we present exact solutions of the Dirac equation with the mixed scalar-vector-pseudoscalar spatially dependent mass Coulomb potential under spin and pseudospin (p-spin) symmetry limits in 1+1 dimensions.

Rajabi, A. A.; Hamzavi, M.

2013-11-01

102

Existence of Strong Solutions for Incompressible Fluids with Shear Dependent Viscosities  

NASA Astrophysics Data System (ADS)

Certain rheological behavior of non-Newtonian fluids in engineering sciences is often modeled by a power law ansatz with p ? (1, 2]. In the present paper the local in time existence of strong solutions is studied. The main result includes also the degenerate case (? = 0) of the extra stress tensor and thus improves previous results of [L. Diening and M. R?ži?ka, J. Math. Fluid Mech., 7 (2005), pp. 413-450].

Berselli, Luigi C.; Diening, Lars; R?ži?ka, Michael

2010-03-01

103

Observations of the spatial evolution of a potential hump into a strong double layer in a high-voltage straight plasma discharge  

Microsoft Academic Search

Data on the spatial evolution of an explosively generated potential hump into a strong double layer in the current-limiting phase of a high-voltage linear plasma discharge are reported. Correlation measurements were made of the electric field component parallel to the magnetic field using floating double probes and optically isolated transmission systems. The presence of high energy electrons was verified by

Y. Takeda; K. Yamagiwa

1985-01-01

104

Nicotine dependence more strongly correlates with psychological distress in disadvantaged areas of Kazakhstan than Germany.  

PubMed

The aim of this study was to describe the association of current smoking and nicotine dependence with psychological distress in socially disadvantaged urban areas of Germany and Kazakhstan. Random samples of people living in disadvantaged areas of Berlin, Germany, and Almaty, Kazakhstan, were assessed using the General Health Questionnaire with 28 items and the Fagerström Test for Nicotine Dependence. The association of both current smoking and nicotine dependence with psychological distress was assessed for each sample using linear regression analyses and compared between the two samples calculating t-values for the comparison of B-coefficients. Current smoking was equally associated with psychological distress in both countries, whereas the association of nicotine dependence and psychological distress was only seen for the Kazakh sample and significantly stronger than for the German sample. The results could not be explained by social characteristics. Possibly due to the lack of outpatient community mental health services for the treatment of common mental disorders, nicotine dependence was associated with psychological distress in the disadvantaged area of Kazakhstan. PMID:23807567

Ignatyev, Yuriy; Mundt, Adrian P

2014-10-01

105

Spatial dependency of cholera prevalence on potential cholera reservoirs in an urban area, Kumasi, Ghana  

NASA Astrophysics Data System (ADS)

Cholera has been a public health burden in Ghana since the early 1970s. Between 1999 and 2005, a total of 25,636 cases and 620 deaths were officially reported to the WHO. In one of the worst affected urban cities, fecal contamination of surface water is extremely high, and the disease is reported to be prevalent among inhabitants living in close proximity to surface water bodies. Surface runoff from dump sites is a major source of fecal and bacterial contamination of rivers and streams in the study area. This study aims to determine (a) the impacts of surface water contamination on cholera infection and (b) detect and map arbitrary shaped clusters of cholera. A Geographic Information System (GIS) based spatial analysis is used to delineate potential reservoirs of the cholera vibrios; possibly contaminated by surface runoff from open space refuse dumps. Statistical modeling using OLS model reveals a significant negative association between (a) cholera prevalence and proximity to all the potential cholera reservoirs ( R2 = 0.18, p < 0.001) and (b) cholera prevalence and proximity to upstream potential cholera reservoirs ( R2 = 0.25, p < 0.001). The inclusion of spatial autoregressive coefficients in the OLS model reveals the dependency of the spatial distribution of cholera prevalence on the spatial neighbors of the communities. A flexible scan statistic identifies a most likely cluster with a higher relative risk (RR = 2.04, p < 0.01) compared with the cluster detected by circular scan statistic (RR = 1.60, p < 0.01). We conclude that surface water pollution through runoff from waste dump sites play a significant role in cholera infection.

Osei, Frank B.; Duker, Alfred A.; Augustijn, Ellen-Wien; Stein, Alfred

2010-10-01

106

The maturation of global motion perception depends on the spatial and temporal offsets of the stimulus.  

PubMed

The typical development of motion perception is commonly assessed with tests of global motion integration using random dot kinematograms. There are discrepancies, however, with respect to when typically-developing children reach adult-like performance on this task, ranging from as early as 3 years to as late as 12 years. To address these discrepancies, the current study measured the effect of frame duration (?t) and signal dot spatial offset (?x) on motion coherence thresholds in adults and children. Two ?t values were used in combination with seven ?x values, for a range of speeds (0.3-38 deg/s). Developmental comparisons showed that for the longer ?t, children performed as well as adults for larger ?x, and were immature for smaller ?x. When parameters were expressed as speed, there was a range of intermediate speeds (4-12 deg/s) for which maturity was dependent on the values of ?x and ?t tested. These results resolve previous discrepancies by showing that motion sensitivity to a given speed may be mature, or not, depending on the underlying spatial and temporal properties of the motion stimulus. PMID:24368221

Meier, Kimberly; Giaschi, Deborah

2014-02-01

107

Physiological Mechanisms of the Effectiveness of Bilateral Stereotactic Cingulotomy against Strong Psychological Dependence in Drug Addicts  

Microsoft Academic Search

It is now generally believed that psychological dependence in drug addicts is determined not only socially, but also physiologically. At the Institute of the Human Brain (Russian Academy of Sciences), bilateral stereotactic cryocingulotomy has been used for treatment of drug addiction since 1998. To date, the surgery has been performed on 348 patients, which has made it possible to study

S. V. Medvedev; A. D. Anichkov; Yu. I. Polyakov

2003-01-01

108

Strong polarization dependence in the optical transmission through a bull's eye with an elliptical sub-wavelength aperture.  

PubMed

Strong polarization dependence in the optical transmission through a bull's eye with a central elliptical aperture in a thin Au film is analyzed numerically by finite difference time domain (FDTD) method. Focusing on the impacts of the structural anisotropy, detailed investigation of polarization dependent enhanced optical transmission (EOT) of light is discussed in terms of the resonance intensity variations caused by the incident light polarization and the geometrical parameters of bull's eye. We found that the light polarized along the minor axis of the elliptic aperture has significantly larger EOT by more than three orders of magnitude than the other orthogonal polarization, which can be further utilized in polarized EOT devices. PMID:23187534

Pournoury, Marzieh; Arabi, Hesam Edin; Oh, Kyunghwan

2012-11-19

109

Ideal gas in a strong gravitational field: Area dependence of entropy  

SciTech Connect

We study the thermodynamic parameters like entropy, energy etc. of a box of gas made up of indistinguishable particles when the box is kept in various static background spacetimes having a horizon. We compute the thermodynamic variables using both statistical mechanics as well as by solving the hydrodynamical equations for the system. When the box is far away from the horizon, the entropy of the gas depends on the volume of the box except for small corrections due to background geometry. As the box is moved closer to the horizon with one (leading) edge of the box at about Planck length (L{sub p}) away from the horizon, the entropy shows an area dependence rather than a volume dependence. More precisely, it depends on a small volume A{sub perpendicular}L{sub p}/2 of the box, up to an order O(L{sub p}/K){sup 2} where A{sub perpendicular} is the transverse area of the box and K is the (proper) longitudinal size of the box related to the distance between leading and trailing edge in the vertical direction (i.e. in the direction of the gravitational field). Thus the contribution to the entropy comes from only a fraction O(L{sub p}/K) of the matter degrees of freedom and the rest are suppressed when the box approaches the horizon. Near the horizon all the thermodynamical quantities behave as though the box of gas has a volume A{sub perpendicular}L{sub p}/2 and is kept in a Minkowski spacetime. These effects are: (i) purely kinematic in their origin and are independent of the spacetime curvature (in the sense that the Rindler approximation of the metric near the horizon can reproduce the results) and (ii) observer dependent. When the equilibrium temperature of the gas is taken to be equal to the horizon temperature, we get the familiar A{sub perpendicular}/L{sub p}{sup 2} dependence in the expression for entropy. All these results hold in a D+1 dimensional spherically symmetric spacetime. The analysis based on methods of statistical mechanics and the one based on thermodynamics applied to the gas treated as a fluid in static geometry, lead to the same results showing the consistency. The implications are discussed.

Kolekar, Sanved; Padmanabhan, T. [IUCAA, Pune University Campus, Ganeshkhind, Pune 411007 (India)

2011-03-15

110

A local limit theorem for strongly dependent random variables and its application to a chaotic configuration of atoms  

Microsoft Academic Search

We investigate one-dimensional chaotic configurations of atoms, which are generated by the Baker transformation or, equivalently, by the Bernoulli shift. The problem of calculating the distribution of the jth nearest-neighbor distances of these configurations is shown to be equivalent to the task of finding the limit distribution of the sum of the strongly dependent random variables Xl:([0,1),?L)?[0,1), x?(2lx)mod 1 (l?N0,

P. Reichert; R. Schilling

1985-01-01

111

How strongly does dating meteorites constrain the time-dependence of the fine-structure constant?  

E-print Network

We review our argument on the nature of the so-called meteorite constraint on the possible time-dependence of the fine-structure constant, emphasizing that dating meteorites at the present time is different in principle from searching directly for the traces in the past, as in the Oklo phenomenon and the QSO absorption lines. In the related literature, we still find some arguments not necessarily consistent with this difference to be taken properly into account. It does not immediately follow that any model-dependent approaches are useless in practice, though we cannot help suspecting that dating meteorites is no match for the Oklo and the QSO in probing the time-variability of the fine-structure constant, at this moment. Some of the relevance to the QSO data particularly in terms of the scalar field will be discussed.

Yasunori Fujii; Akira Iwamoto

2005-08-06

112

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

PubMed Central

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

2013-01-01

113

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

SciTech Connect

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.

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

114

Spatial organization of the cell cytoplasm by position-dependent phase separation.  

PubMed

During asymmetric cell division, cytoplasmic components are segregated to opposite sides of the cell. We discuss how the observed segregation can be achieved by a position-dependent phase separation mechanism controlled by a protein concentration gradient. We show that effects of even a weak gradient can be amplified by the phase transition to achieve strong segregation. We compare our theory to the segregation of germ granules observed during the divisions in the C. elegans embryo. Our study demonstrates how liquid-liquid phase separation can play a key role in the organization of the cytoplasm. PMID:24010479

Lee, Chiu Fan; Brangwynne, Clifford P; Gharakhani, Jöbin; Hyman, Anthony A; Jülicher, Frank

2013-08-23

115

Spatial Organization of the Cell Cytoplasm by Position-Dependent Phase Separation  

NASA Astrophysics Data System (ADS)

During asymmetric cell division, cytoplasmic components are segregated to opposite sides of the cell. We discuss how the observed segregation can be achieved by a position-dependent phase separation mechanism controlled by a protein concentration gradient. We show that effects of even a weak gradient can be amplified by the phase transition to achieve strong segregation. We compare our theory to the segregation of germ granules observed during the divisions in the C. elegans embryo. Our study demonstrates how liquid-liquid phase separation can play a key role in the organization of the cytoplasm.

Lee, Chiu Fan; Brangwynne, Clifford P.; Gharakhani, Jöbin; Hyman, Anthony A.; Jülicher, Frank

2013-08-01

116

Strong asymmetrical bias dependence of magnetoresistance in organic spin valves: the role of ferromagnetic/organic interfaces  

NASA Astrophysics Data System (ADS)

We report a highly asymmetric magnetoresistance (MR) bias dependence, with the inverse MR peaking at a negative bias and a sign reversal occurring at a positive bias in prototypical La0.7Sr0.3MnO3 (LSMO)/Alq3/Co organic spin valve (OSV) with a tunnel barrier between LSMO and Alq3. This behavior is in strong contrast with the commonly found inverse MR in entire bias range for LSMO/Alq3/Co OSVs. The MR bias voltage dependence is independent on the type of the tunnel barrier, either SrTiO3 or Al2O3. Together with first-principle calculations, we demonstrate that the strongly hybridized Co d-states with Alq3 molecules at the interface are responsible for the efficient d-states spin injection and the observed MR bias dependence is originated from the energy dependent density of states of Co d-states. These findings open up new possibilities to engineer interfacial bonding between ferromagnetic materials and a wide variety of molecule selections for the desired spin transport properties.

Jiang, S. W.; Shu, D. J.; Lin, L.; Shi, Y. J.; Shi, J.; Ding, H. F.; Du, J.; Wang, M.; Wu, D.

2014-01-01

117

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

PubMed Central

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

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

2014-01-01

118

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

E-print Network

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 ...

Sekizawa, Kazuyuki

2014-01-01

119

A Simulation Methodology for Assessing the Impact of Spatial/Pattern Dependent Interconnect Parameter Variation on Circuit Performance  

E-print Network

A Simulation Methodology for Assessing the Impact of Spatial/Pattern Dependent Interconnect *PDF Solutions, Inc, San Jose, CA 95110 Abstract In this paper, we illustrate a methodology for determining the impact of interconnect pattern dependent variation on circuit performance. The methodology

Boning, Duane S.

120

Plant adaptation to fluctuating environment and biomass production are strongly dependent on guard cell potassium channels  

PubMed Central

At least four genes encoding plasma membrane inward K+ channels (Kin channels) are expressed in Arabidopsis guard cells. A double mutant plant was engineered by disruption of a major Kin channel gene and expression of a dominant negative channel construct. Using the patch-clamp technique revealed that this mutant was totally deprived of guard cell Kin channel (GCKin) activity, providing a model to investigate the roles of this activity in the plant. GCKin activity was found to be an essential effector of stomatal opening triggered by membrane hyperpolarization and thereby of blue light-induced stomatal opening at dawn. It improved stomatal reactivity to external or internal signals (light, CO2 availability, and evaporative demand). It protected stomatal function against detrimental effects of Na+ when plants were grown in the presence of physiological concentrations of this cation, probably by enabling guard cells to selectively and rapidly take up K+ instead of Na+ during stomatal opening, thereby preventing deleterious effects of Na+ on stomatal closure. It was also shown to be a key component of the mechanisms that underlie the circadian rhythm of stomatal opening, which is known to gate stomatal responses to extracellular and intracellular signals. Finally, in a meteorological scenario with higher light intensity during the first hours of the photophase, GCKin activity was found to allow a strong increase (35%) in plant biomass production. Thus, a large diversity of approaches indicates that GCKin activity plays pleiotropic roles that crucially contribute to plant adaptation to fluctuating and stressing natural environments. PMID:18367672

Lebaudy, Anne; Vavasseur, Alain; Hosy, Eric; Dreyer, Ingo; Leonhardt, Nathalie; Thibaud, Jean-Baptiste; Véry, Anne-Aliénor; Simonneau, Thierry; Sentenac, Hervé

2008-01-01

121

Morphological dependence in the spatial orientations of galaxies around the Local Supercluster  

NASA Astrophysics Data System (ADS)

We study the spatial orientation of 5 169 galaxies that have radial velocity 3 000 to 5 000 km s-1. The ‘position angle inclination’ method is used to find the spin vector and the projections of spin vector of the galaxy rotation axes. The spatial isotropic distribution is assumed to examine the non-random effects. For this, we have performed chi-square, Fourier, and auto-correlation tests. We found a random alignment of spin vectors of total galaxies with respect to the equatorial coordinate system. The spin vector projections of total galaxies is found to be oriented tangentially with respect to the equatorial center. The spiral galaxies show a similar orientation as shown by the total sample. Five subsamples of barred spiral (late-type) galaxies show a preferred alignment. However, early-type barred spirals show a random orientation. A weak morphological dependence is noticed in the subsamples of late type barred spirals. A comparison with the previous works and the possible explanation of the results will be presented.

Aryal, B.; Neupane, D.; Saurer, W.

2008-04-01

122

Angular Dependence of Jet Quenching Indicates Its Strong Enhancement near the QCD Phase Transition  

NASA Astrophysics Data System (ADS)

We study dependence of jet quenching on matter density, using “tomography” of the fireball provided by RHIC data on azimuthal anisotropy v2 of high pt hadron yield at different centralities. Slicing the fireball into shells with constant (entropy) density, we derive a “layer-wise geometrical limit” v2max? which is indeed above the data v2Tc. One possible reason for such enhancement may be recent indications that the near-Tc region is a magnetic plasma of relatively light color-magnetic monopoles.

Liao, Jinfeng; Shuryak, Edward

2009-05-01

123

Textural parameters based on the Spatial Gray Level Dependence Method applied to melanocytic nevi.  

PubMed

The purpose of this study is to evaluate the Spatial Gray Level Dependence Method (SGLDM) of texture analysis with respect to its ability to discriminate between melanocytic nevi and normal skin. Thirteen textural features based on the SGLDM were evaluated with respect to their relative sensitivities to both texture and tone. Ten features were found to be more sensitive to texture than tone and were selected for further study. Twenty-four digitized images of benign melanocytic nevi were obtained from six volunteers. Ten textural features were analyzed for each nevus and for surrounding sections of normal skin. Of these 10 features, 8 features can distinguish between textural properties of melanocytic nevi and surrounding skin. PMID:9012567

Pope, T W; Williams, W L; Wilkinson, S B; Gordon, M A

1996-12-01

124

Generalization of visuomotor adaptation depends on the spatial characteristic of visual workspace.  

PubMed

The present study aims to address a novel aspect of visuomotor adaptation and its generalization. It is based on the assumption that the spatial structure of the distal action space is crucial for generalization. In the experiments, the distal action spaces could manifest either a symmetric or parallel structure. The imposed visuomotor rotations in the adaptation and the following generalization were either the same or opposing each other. In the generalization phase, motor bias resulting from prior adaptation was observed, and it turned out to substantially depend on the property of the workspace. In Experiment 1 with a parallel workspace, preceding adaptation to the same rotation was more advantageous than adaptation to an opposing rotation. This observation was reversed in Experiment 2 with the symmetrical workspace: prior adaptation to an opposing rotation was more advantageous for the generalization than prior adaptation to the same rotation. Mechanisms possibly underlying the observed influence of the workspace configuration were discussed. PMID:22990294

Wang, Lei; Müsseler, Jochen

2012-11-01

125

Spin dependence of k-mixing, strong configuration mixing and electromagnetic properties of {sup 178}Hf.  

SciTech Connect

The combined data of two Coulomb excitation experiments has verified the purely electromagnetic population of the K{pi} = 4{sup +}, 6{sup +}, 8{sup -}, and 16{sup +} rotational bands in {sup 178}Hf via 2 {le} {nu} {le} 14 K-forbidden transitions, quantifying the breakdown of the K-selection rule with increasing spin in the low-K bands. The {gamma}{sup -}, 4{sup +}, and 6{sup +} bands were extended, and four new states in a rotational band were tentatively assigned to a previously known K{pi} = 0{sup +} band. The quasiparticle structure of the 6{sup +} (t 1/2 = 77 ns) and 8{sup -} (t 1/2 = 4s) isomer bands were evaluated, showing that the gyromagnetic ratios of the 6{sup +} isomer band are consistent with a pure {pi} 7/2{sup +}[404],{pi} 5/2{sup +}[402] structure. The 8{sup -} isomer band at 1147 keV and the second 8{sup -} band at 1479 keV, thought to be predominantly {nu} 7/2{sup -}[514], {nu} 9/2{sup +}[624] and {pi} 9/2{sup -}[514], {pi}7/2{sup +}[404], respectively, are mixed to a degree approaching the strong-mixing limit. Based on measured matrix elements, it was shown that heavy-ion bombardment could depopulate the 16{sup +} isomer at the {approx}1% level, although no states were found that would mediate photodeexcitation of the isomer via low-energy x-ray absorption.

Hayes, A.B.; Cline, D.; Wu, C.Y.; Ai, H.; Amro, H.; Beausang, C.; Casten, R.F.; Gerl, J.; Hecht, A.A.; Heinz, A.; Hua, H.; Hughes, R.; Janssens, R.V.F; Lister, C.J.; Macchiavelli, A.O.; Meyer, D.A.; Moore, E.F.; Napiorkowski, P.; Pardo, R.C.; Schlegel, Ch.; Seweryniak, D.; Simon, W.M.; Srebrny, J.; Teng, R.; Vetter, K.; Physics; Univ. of Rochester; LLNL; Yale Univ.; Univ. of Richmond; GSI; Peking Univ.; Lawrence Berkeley National Lab.; Warsaw Univ.

2007-01-01

126

Spin dependence of K mixing, strong configuration mixing, and electromagnetic properties of {sup 178}Hf  

SciTech Connect

The combined data of two Coulomb excitation experiments has verified the purely electromagnetic population of the K{sup {pi}}=4{sup +},6{sup +},8{sup -}, and 16{sup +} rotational bands in {sup 178}Hf via 2{<=}{nu}{<=}14 K-forbidden transitions, quantifying the breakdown of the K-selection rule with increasing spin in the low-K bands. The {gamma}-, 4{sup +}, and 6{sup +} bands were extended, and four new states in a rotational band were tentatively assigned to a previously known K{sup {pi}}=0{sup +} band. The quasiparticle structure of the 6{sup +} (t{sub (1/2)}=77 ns) and 8{sup -} (t{sub (1/2)}=4 s) isomer bands were evaluated, showing that the gyromagnetic ratios of the 6{sup +} isomer band are consistent with a pure {pi}(7/2){sup +}[404],{pi}(5/2){sup +}[402] structure. The 8{sup -} isomer band at 1147 keV and the second 8{sup -} band at 1479 keV, thought to be predominantly {nu}(7/2){sup -}[514],{nu}(9/2){sup +}[624] and {pi}(9/2){sup -}[514],{pi}(7/2){sup +}[404], respectively, are mixed to a degree approaching the strong-mixing limit. Based on measured matrix elements, it was shown that heavy-ion bombardment could depopulate the 16{sup +} isomer at the {approx}1% level, although no states were found that would mediate photodeexcitation of the isomer via low-energy x-ray absorption.

Hayes, A. B.; Cline, D.; Hua, H.; Simon, M. W.; Teng, R. [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Wu, C. Y. [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Ai, H.; Amro, H.; Casten, R. F.; Hecht, A. A.; Heinz, A.; Hughes, R.; Meyer, D. A. [Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520 (United States); Beausang, C. [Physics Department, University of Richmond, Richmond, Virginia 23173 (United States); Gerl, J.; Schlegel, Ch.; Wollersheim, H. J. [GSI, Gesellschaft fuer Schwerionenforschung, Planckstrasse 1, D-64291 Darmstadt (Germany); Janssens, R. V. F.; Lister, C. J.; Moore, E. F. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] (and others)

2007-03-15

127

Angular dependence of jet quenching indicates its strong enhancement near the QCD phase transition.  

PubMed

We study dependence of jet quenching on matter density, using "tomography" of the fireball provided by RHIC data on azimuthal anisotropy v_{2} of high p_{t} hadron yield at different centralities. Slicing the fireball into shells with constant (entropy) density, we derive a "layer-wise geometrical limit" v_{2};{max} which is indeed above the data v_{2} < v_{2};{max}. Interestingly, the limit is reached only if quenching is dominated by shells with the entropy density exactly in the near-T_{c} region. We show two models that simultaneously describe the high p_{t} v_{2} and R_{A-A} data and conclude that such a description can be achieved only if the jet quenching is few times stronger in the near-T_{c} region relative to QGP at T > T_{c}. One possible reason for such enhancement may be recent indications that the near-T_{c} region is a magnetic plasma of relatively light color-magnetic monopoles. PMID:19519022

Liao, Jinfeng; Shuryak, Edward

2009-05-22

128

Angular Dependence of Jet Quenching Indicates Its Strong Enhancement near the QCD Phase Transition  

SciTech Connect

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}T{sub c}. One possible reason for such enhancement may be recent indications that the near-T{sub c} region is a magnetic plasma of relatively light color-magnetic monopoles.

Liao Jinfeng [Department of Physics and Astronomy, State University of New York, Stony Brook, New York 11794 (United States); Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Shuryak, Edward [Department of Physics and Astronomy, State University of New York, Stony Brook, New York 11794 (United States)

2009-05-22

129

Ciprofloxacin Metalloantibiotic: An Effective Antibiotic with an Influx Route Strongly Dependent on Lipid Interaction?  

PubMed

Fluoroquinolones are antibiotics that have a large spectrum of action against bacteria, especially Gram-negative. A strategy to enhance their pharmacological behavior, and try to counteract bacterial resistance, is their coordination to divalent metal ions and 1,10-phenanthroline. These stable complexes modify fluoroquinolones potency and specificity, possibly due to their alternative translocation through the bacterial membranes. In this work, we determined the interaction of ciprofloxacin and its copper(II) ternary complex with unilamellar liposomes of DMPC, POPE/POPG (0.75:0.25), POPE/POPG/cardiolipin (0.67:0.23:0.10), and E. coli total extract, using time-resolved and steady-state fluorescence spectroscopy. The association constants determined show that the interaction of both compounds depends on membrane lipids composition and is always higher for the metalloantibiotic, a trend already observed for other fluoroquinolone metalloantibiotics. Nevertheless, the interaction of ciprofloxacin metalloantibiotic is, normally, higher, which reflects the fluoroquinolone species that are present in solution at physiological pH. In overall, the results obtained suggest that ciprofloxacin and its metalloantibiotic have different translocation pathways, proposing that the diffusion of the metalloantibiotic is a hydrophobic mechanism and suggesting that this new metalloantibiotic may be a good choice to replace the pure ciprofloxacin and bypass, at least, one of the mechanisms of the bacterial resistance to fluoroquinolones. PMID:25378125

Ferreira, Mariana; Gameiro, Paula

2014-11-01

130

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

SciTech Connect

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.

Liao, Jinfeng; Shuryak, Edward

2008-10-22

131

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

PubMed

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

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

2014-01-01

132

Angular dependence of magnetoresistance in strongly anisotropic quasi-two-dimensional metals: Influence of Landau-level shape  

NASA Astrophysics Data System (ADS)

We present the quantum-mechanical calculation of the angular dependence of interlayer conductivity ?zz(? ) in a tilted magnetic field in quasi-two-dimensional (quasi-2D) layered metals. Our calculation is applicable for arbitrary density of electron states and shows that the shape of Landau levels (LLs) is important for this angular dependence. We derive simple analytical formulas for ?zz(? ) in the particular cases of Gaussian and dome-shaped LLs. Since in strongly anisotropic quasi-two-dimensional metals in a high magnetic field the LL shape is closer to dome-like or Gaussian, this analytical formula replaces the traditionally used one, derived for Lorentzian LL shape. The amplitude of angular magnetoresistance oscillations (AMRO) is considerably stronger for the dome-like or Gaussian than for the traditionally used Lorentzian LL shape. The ratio ?zz(? =0)/?zz(? ?±90?) is also several times smaller for the Lorentzian LL shape at the same LL width. The field dependence of ?zz(? ?±90?) provides useful information about the electron mean free time. AMRO and Zeeman energy splitting lead to a spin current. For typical organic metals and for a medium magnetic field of 10 T this spin current is only a few percent of the charge current. However, the spin current may almost reach the charge current for special tilt angles of the magnetic field. The spin current has strong angular oscillations, which are phase-shifted as compared to the usual AMRO.

Grigoriev, P. D.; Mogilyuk, T. I.

2014-09-01

133

Time-dependent density-functional theory of strong-field ionization of atoms by soft x rays  

NASA Astrophysics Data System (ADS)

We demonstrate the capabilities of time-dependent density functional theory (TDDFT) for strong-field, short-wavelength (soft x-ray) physics, as compared to a formalism based on rate equations. We find that TDDFT provides a very good description of the total and individual ionization yields for Ne and Ar atoms exposed to strong laser pulses. We assess the reliability of different adiabatic density functionals and conclude that an accurate description of long-range interactions by the exchange and correlation potential is crucial for obtaining the correct ionization yield over a wide range of intensities (from 1013 to 5×1015W/cm2). Our TDDFT calculations disentangle the contribution from each ionization channel based on the Kohn-Sham wave functions.

Crawford-Uranga, A.; De Giovannini, U.; Räsänen, E.; Oliveira, M. J. T.; Mowbray, D. J.; Nikolopoulos, G. M.; Karamatskos, E. T.; Markellos, D.; Lambropoulos, P.; Kurth, S.; Rubio, A.

2014-09-01

134

Comparison of strong gravitational lens model software I. Redshift and model dependence of time delay and mass calculations  

NASA Astrophysics Data System (ADS)

Analysis of strong gravitational lensing depends on software analysis of observational data. The purpose of this study is to evaluate the behavior of strong gravitational lens modeling software with changes in redshift. Four different strong gravitational lens software modeling codes are directly compared (Lenstool/glafic, two light traces mass codes, and GRALE/PixeLens, two non-light traces mass codes) in the analysis of a mock model as well as analysis of SDSSJ1004 + 4112. The calculated time delay is proportional to DdDs /Dds. The percent change in time delays calculated at each redshift tested is compared with percent change in DdDs /Dds. A mock model with a singular isothermal ellipsoid and four images is tested with each code. Five models are used with a constant zlens and a varying zsource, and five models with a constant zsource and a varying zlens. The effects of changing geometry are similarly investigated for SDSSJ1004 + 4112. In general, the changes in time delay are of a similar magnitude and direction, although some calculated time delays did not follow changes in DdDs /Dds. This variation is explained by changes in image position calculated by glafic and GRALE, which varied according to Dds /Ds. Changes in enclosed mass for the mock model with a constant zsource are similar to changes in DdDs /Dds for three of the four codes tested. These data demonstrate the effect of changes in redshift on parameters calculated by each of the codes as compared to changes in DdDs /Dds. The paucity of comparative studies in strong gravitational lensing suggests the need for further studies. These results show that small changes in redshift affect the calculated time delay and mass, and that the effect on the calculations is dependent on the particular software used.

Lefor, A. T.; Futamase, T.

2014-10-01

135

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

PubMed

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

Grasselli, Federico; Bertoni, Andrea; Goldoni, Guido

2015-01-21

136

Time-dependent density-functional theory for strong-field multiphoton processes: Application to the study of the role of dynamical electron correlation  

E-print Network

Time-dependent density-functional theory for strong-field multiphoton processes: Application 1997 We present a self-interaction-free time-dependent density-functional theory TDDFT. The theory is based on the extension of the time-dependent Kohn-Sham formalism. The time-dependent exchange

Chu, Shih-I

137

Spatial variation in the plasma sheet composition: Dependence on geomagnetic and solar activity  

NASA Astrophysics Data System (ADS)

study the spatial distribution of plasma sheet O+ and H+ ions using data from the COmposition and DIstribution Function (CODIF) instrument on board the Cluster spacecraft from 2001 to 2005. The densities are mapped along magnetic field lines to produce bidimensional density maps at the magnetospheric equatorial plane for various geomagnetic and solar activity levels (represented by the Kp and F10.7 indexes). We analyze the correlation of the O+ and H+ density with Kp and F10.7 in the midtail region at geocentric distances between 15 and 20 RE and in the near-Earth regions at radial distances between 7 and 8 RE. Near Earth the H+ density slightly increases with Kp and F10.7 while in the midtail region it is not correlated with Kp and F10.7. On the contrary, the amount of O+ ions significantly increases with Kp and F10.7 independently of the region. In the near-Earth region, the effects of solar EUV and geomagnetic activity on the O+ density are comparable. In the midtail region, the O+ density increases at a lower rate with solar EUV flux but strongly increases with geomagnetic activity although the effect is modulated by the solar EUV flux level. We also evidence a strong increase of the proportion of O+ ions with decreasing geocentric distance below ~10 RE. These results confirm the direct entry of O+ ions into the near-Earth plasma sheet and suggest that both energetic outflows from the auroral zone and cold outflow from the high-latitude ionosphere may contribute to feed the near-Earth plasma sheet with ionospheric ions.

Maggiolo, R.; Kistler, L. M.

2014-04-01

138

Orientation-dependent ionization yields from strong-field ionization of fixed-in-space linear and asymmetric top molecules  

NASA Astrophysics Data System (ADS)

The yield of strong-field ionization, by a linearly polarized probe pulse, is studied experimentally and theoretically as a function of the relative orientation between the laser field and the molecule. Experimentally, carbonyl sulphide (OCS), benzonitrile and naphthalene molecules are aligned in one or three dimensions before being singly ionized by a 30 fs laser pulse centred at 800 nm. Theoretically, we address the behaviour of these three molecules. We consider the degree of alignment and orientation and model the angular dependence of the total ionization yield by molecular tunnelling theory accounting for the Stark shift of the energy level of the ionizing orbital. For naphthalene and benzonitrile, the orientational dependence of the ionization yield agrees well with the calculated results, in particular, we observe that ionization is maximized when the probe laser is polarized along the most polarizable axis. For OCS the observation of the maximum ionization yield when the probe is perpendicular to the internuclear axis contrasts the theoretical results.

Hansen, Jonas L.; Holmegaard, Lotte; Nielsen, Jens H.; Stapelfeldt, Henrik; Dimitrovski, Darko; Bojer Madsen, Lars

2012-01-01

139

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

SciTech Connect

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.

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

140

P/Halley - Effects of time-dependent production rates on spatial emission profiles  

NASA Astrophysics Data System (ADS)

Spatial profiles of C2, CN, NH2, and O(D-1) in Comet P/Halley taken on 1986 March 1.54 and 2.55 and April 14.32 and 15.30 clearly show the effect of the 7 day periodic variation seen in photometric observations. With a time-dependent model based upon the light curve and employing standard scale lengths for each species reduced to the appropriate heliocentric distance, we are able to reproduce the highly variable profiles for all species. We computed the phase lag and amplitude correction between the actual gas production at the nucleus and the temporal/spatial filter imposed by the finite aperture photometry. For early March we find a phase lag and amplitude correction of 12 hr and -9 percent, respectively, whereas in mid-April the values are 6 hr and -27 percent. The same phase lag and amplitude correction work equally well for all four species despite their wide variation in photochemical lifetimes for production and decay. The same model integrated over circular apertures is able to reproduce the entire published March and April photometric light curves for C2. Our results require the use of the 7.60 day period for the March data as opposed to the 7.37 day period that is relevant for the April data, in agreement with the published analysis of the photometric data. Our results will help to reconcile the placement of active areas on the surface of Halley's comet with various remote observations and spacecraft images of the nucleus.

Combi, M. R.; Fink, U.

1993-06-01

141

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

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

142

Linking the Allee Effect, Sexual Reproduction, and Temperature?Dependent Sex Determination Via Spatial Dynamics  

Microsoft Academic Search

We develop a spatially explicit, two-sex, individual-based model (IBM) and a derived spatially homogeneous model (SHM) to describe the Allee effect due to scarcity of mating possibilities at low population sizes or densities. The SHM, based on coupled difference equations, represents the first spatially homogeneous approach to this phenomenon, which differentiates between sexes and relies only on measurable population parameters.

Lud?k Berec; David S. Boukal; Michal Berec

2001-01-01

143

Spatially dependent cluster dynamics modeling of microstructure evolution in low energy helium irradiated tungsten  

NASA Astrophysics Data System (ADS)

In fusion reactors, plasma facing components (PFC) and in particular the divertor will be irradiated with high fluxes of low energy (˜100 eV) helium and hydrogen ions. Tungsten is one of the leading candidate divertor materials for ITER and DEMO fusion reactors. However, the behavior of tungsten under high dose, coupled helium/hydrogen exposure remains to be fully understood. The PFC response and performance changes are intimately related to microstructural changes, such as the formation of point defect clusters, helium and hydrogen bubbles or dislocation loops. Computational materials modeling has been used to investigate the mechanisms controlling microstructural evolution in tungsten following high dose, high temperature helium exposure. The aim of this study is to understand and predict helium implantation, primary defect production and defect diffusion, helium-defect clustering and interactions below a tungsten surface exposed to low energy helium irradiation. The important defects include interstitial clusters, vacancy clusters, helium interstitials and helium-vacancy clusters. We report results from a one-dimensional, spatially dependent cluster dynamics model based on the continuum reaction-diffusion rate theory to describe the evolution in space and time of all these defects. The key parameter inputs to the model (diffusion coefficients, migration and binding energies, initial defect production) are determined from a combination of atomistic materials modeling and available experimental data.

Faney, T.; Wirth, B. D.

2014-09-01

144

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

PubMed

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

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

2015-01-01

145

Characterizing structural conditions in mature managed red pine: Spatial dependency of metrics and adequacy of plot size  

Microsoft Academic Search

Restoration of the range of forest types and stages that once composed the landscape mosaic of the Upper Great Lakes region of North America will involve manipulating managed red pine stands to recreate now rare structural conditions. Because many of the attributes used to characterize structural condition depend upon spatial arrangement, sampling schemes to assess condition must match sampling extent

Eric K. Zenner; JeriLynn E. Peck

2009-01-01

146

Frequency distributions and spatially dependent variability of ammonium and nitrate concentrations in soil under grazed and ungrazed grassland  

Microsoft Academic Search

The frequency distributions of soil NO3- and NH4+ concentrations under grazed and ungrazed grassland were found to be lognormal, irrespective of time of year or soil depth. The variance and skewness of the sample values increased with stocking density and use of N fertilizer. An analysis of the spatial dependence of the variability using the semivariogram showed a high ‘nugget’

RE White; Rosalyn A Haigh; Jh Macduff

1987-01-01

147

Spatial heterogeneity, frequency-dependent selection and polymorphism in host-parasite interactions  

PubMed Central

Background Genomic and pathology analysis has revealed enormous diversity in genes involved in disease, including those encoding host resistance and parasite effectors (also known in plant pathology as avirulence genes). It has been proposed that such variation may persist when an organism exists in a spatially structured metapopulation, following the geographic mosaic of coevolution. Here, we study gene-for-gene relationships governing the outcome of plant-parasite interactions in a spatially structured system and, in particular, investigate the population genetic processes which maintain balanced polymorphism in both species. Results Following previous theory on the effect of heterogeneous environments on maintenance of polymorphism, we analysed a model with two demes in which the demes have different environments and are coupled by gene flow. Environmental variation is manifested by different coefficients of natural selection, the costs to the host of resistance and to the parasite of virulence, the cost to the host of being diseased and the cost to an avirulent parasite of unsuccessfully attacking a resistant host. We show that migration generates negative direct frequency-dependent selection, a condition for maintenance of stable polymorphism in each deme. Balanced polymorphism occurs preferentially if there is heterogeneity for costs of resistance and virulence alleles among populations and to a lesser extent if there is variation in the cost to the host of being diseased. We show that the four fitness costs control the natural frequency of oscillation of host resistance and parasite avirulence alleles. If demes have different costs, their frequencies of oscillation differ and when coupled by gene flow, there is amplitude death of the oscillations in each deme. Numerical simulations show that for a multiple deme island model, costs of resistance and virulence need not to be present in each deme for stable polymorphism to occur. Conclusions Our theoretical results confirm the importance of empirical studies for measuring the environmental heterogeneity for genetic costs of resistance and virulence alleles. We suggest that such studies should be developed to investigate the generality of this mechanism for the long-term maintenance of genetic diversity at host and parasite genes. PMID:22044632

2011-01-01

148

A Spatial Dependency and Causality Analysis of Crime in Savannah, Georgia, 2000  

Microsoft Academic Search

Abstract: This article examines,the spatial variability in the distribution of crime in the City of Savannah, GA, where a total of 12,458 crimes were reported in 2000. All crimes were geocoded,and the same numbers,of control locations were generated under the assumption that the spatial distribution of crime is a realization of an inhomogeneous Poisson process (spatially random). The control locations

Naresh Kumar

149

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

PubMed

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

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

2014-12-01

150

Strong dependence of surface plasmon resonance and surface enhanced Raman scattering on the composition of Au-Fe nanoalloys  

NASA Astrophysics Data System (ADS)

Nanoalloys of noble metals with transition metals are crucial components for the integration of plasmonics with magnetic and catalytic properties, as well as for the production of low-cost photonic devices. However, due to synthetic challenges in the realization of nanoscale solid solutions of noble metals and transition metals, very little is known about the composition dependence of plasmonic response in nanoalloys. Here we demonstrate for the first time that the elemental composition of Au-Fe nanoalloys obtained by laser ablation in liquid solution can be tuned by varying the liquid environment. Due to surface passivation and reaction with thiolated ligands, the nanoalloys obtained by our synthetic protocol are structurally and colloidally stable. Hence, we studied the dependence of the surface plasmon resonance (SPR) on the iron fraction and, for the first time, we observed surface enhanced Raman scattering (SERS) in Au-Fe nanoalloys. SPR and SERS performances are strongly affected by the iron content and are investigated using analytical and numerical models. By demonstrating the strong modification of plasmonic properties on the composition, our results provide important insights into the exploitation of Au-Fe nanoalloys in photonics, nanomedicine, magneto-plasmonic and plasmon-enhanced catalysis. Moreover, our findings show that several other plasmonic materials exist beyond gold and silver nanostructures.Nanoalloys of noble metals with transition metals are crucial components for the integration of plasmonics with magnetic and catalytic properties, as well as for the production of low-cost photonic devices. However, due to synthetic challenges in the realization of nanoscale solid solutions of noble metals and transition metals, very little is known about the composition dependence of plasmonic response in nanoalloys. Here we demonstrate for the first time that the elemental composition of Au-Fe nanoalloys obtained by laser ablation in liquid solution can be tuned by varying the liquid environment. Due to surface passivation and reaction with thiolated ligands, the nanoalloys obtained by our synthetic protocol are structurally and colloidally stable. Hence, we studied the dependence of the surface plasmon resonance (SPR) on the iron fraction and, for the first time, we observed surface enhanced Raman scattering (SERS) in Au-Fe nanoalloys. SPR and SERS performances are strongly affected by the iron content and are investigated using analytical and numerical models. By demonstrating the strong modification of plasmonic properties on the composition, our results provide important insights into the exploitation of Au-Fe nanoalloys in photonics, nanomedicine, magneto-plasmonic and plasmon-enhanced catalysis. Moreover, our findings show that several other plasmonic materials exist beyond gold and silver nanostructures. Electronic supplementary information (ESI) available: DDA calculations of phase-segregated bimetallic Au-Fe nanoparticles and XPS study of Ar+ irradiation on the Fe 2p peak of iron oxide standard. See DOI: 10.1039/c3nr04995g

Amendola, Vincenzo; Scaramuzza, Stefano; Agnoli, Stefano; Polizzi, Stefano; Meneghetti, Moreno

2014-01-01

151

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)

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.

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

2012-02-01

152

Numbers Are Associated with Different Types of Spatial Information Depending on the Task  

ERIC Educational Resources Information Center

In this study, we examined the nature of the spatial-numerical associations underlying the SNARC-effect by imposing a verbal or spatial working memory load during a parity judgment and a magnitude comparison task. The results showed a double dissociation between the type of working memory load and type of task. The SNARC-effect disappeared under…

van Dijck, Jean-Philippe; Gevers, Wim; Fias, Wim

2009-01-01

153

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

ERIC Educational Resources Information Center

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…

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

2012-01-01

154

Order-dependent mappings: Strong-coupling behavior from weak-coupling expansions in non-Hermitian theories  

SciTech Connect

A long time ago, it has been conjectured that a Hamiltonian with a potential of the form x{sup 2}+ivx{sup 3}, v real, has a real spectrum. This conjecture has been generalized to a class of the so-called PT symmetric Hamiltonians and some proofs have been given. Here, we show by numerical investigation that the divergent perturbation series can be summed efficiently by an order-dependent mapping (ODM) in the whole complex plane of the coupling parameter v{sup 2}, and that some information about the location of level-crossing singularities can be obtained in this way. Furthermore, we discuss to which accuracy the strong-coupling limit can be obtained from the initially weak-coupling perturbative expansion, by the ODM summation method. The basic idea of the ODM summation method is the notion of order-dependent 'local' disk of convergence and analytic continuation by an ODM of the domain of analyticity augmented by the local disk of convergence onto a circle. In the limit of vanishing local radius of convergence, which is the limit of high transformation order, convergence is demonstrated both by numerical evidence as well as by analytic estimates.

Zinn-Justin, Jean [CEA, IRFU, Centre de Saclay, 91191 Gif-sur-Yvette Cedex (France); Jentschura, Ulrich D. [Missouri University of Science and Technology, Rolla, Missouri 65409-0640 (United States)

2010-07-15

155

Orientation-dependent ionization yields from strong-field ionization of fixed-in-space linear and asymmetric top molecules  

NASA Astrophysics Data System (ADS)

The ionization step leading to single ionization in the multiphoton or tunnel ionization regime is a fundamental process which is thought to be well understood for atoms; however, for larger molecules much less is known. Of particular importance is the understanding of the dependence of the initial ionization step on the molecular orientation with respect to the external field. To fully test existing theories and to guide the way for new theory development, we here extend these experiments to larger and more complex molecular systems: Carbonyl sulphide (OCS), benzonitrile and naphthalene. In particular we investigate the yield of strong-field ionization, by a linearly polarized probe pulse, as a function of the relative orientation between the laser field and the molecule. This is achieved using standard laser alignment techniques to produce 1D or 3D aligned molecular ensembles before a femtosecond laser probe pulse singly ionizes the target molecules. For naphthalene and benzonitrile, the orientational dependence of the ionization yield agrees well with the calculated results, in particular, we observe that ionization is maximized when the probe laser is polarized along the most polarizable axis. For OCS the observation of the maximum ionization yield when the probe is perpendicular to the internuclear axis contrasts the theoretical results.

Hansen, J. L.; Dimitrovski, D.; Madsen, L. B.; Stapelfeldt, H.

2012-06-01

156

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

SciTech Connect

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.

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

157

Field Observations Of The 29 September Tsunami In American Samoa: Spatial Variability And Indications Of Strong Return Flow  

NASA Astrophysics Data System (ADS)

The 29 September 2009 tsunami caused 181 fatalities and displaced more than 5000 people on the islands of Samoa, American Samoa, and Tonga. This is the first tsunami to cause significant damage and fatalities on U.S. soil in more than 30 years. Scientists from around the world quickly mobilized to help document the tsunami water levels before this ephemeral data was forever lost as recovery activities and natural processes overtook the effected area. A USGS team collected data in American Samoa from October 6-22 and November 5-12, 2009. The tsunami was large, reaching elevations of greater than 15 m, however wave heights and devastation varied from village to village in American Samoa. Even within villages, some structures were completely destroyed, some flooded and left standing, and others barely touched. Wave heights, flow depths, runup heights, inundation distances, and flow directions were collected for use in ground-truthing inundation models. The team also collected nearshore bathymetry, topography and reef flat elevation, sediment samples, and documented the distribution and characteristics of both sand and boulder deposits. Eyewitness accounts of the tsunami were also videotaped. One striking aspect of this tsunami was the abundance of indicators of strong return flow. For example at Poloa in the northwest of Tutuila, where the runup was greater than 11 m along a 300-m stretch of coast and flow depths exceeded 4 m, the coral reef flat was strewn with debris including chairs, desks, and books from a school. On land, River channels were excavated and new channels formed as return flow scoured sediment and transported it offshore. Possible causes for the strong return flow and the relation between the stength of the return flow, inundation distance, and runup in American Samoa are presented. These relationships and others based on data collected by field survey teams will ultimately reduce loss of life and destruction from tsunamis in the Pacific and elsewhere.

Jaffe, B. E.; Richmond, B. M.; Gelfenbaum, G. R.; Watt, S.; Apotsos, A. A.; Buckley, M. L.; Dudley, W. C.; Peck, B.

2009-12-01

158

Transport lattice models of heat transport in skin with spatially heterogeneous, temperature-dependent perfusion  

E-print Network

Background: Investigation of bioheat transfer problems requires the evaluation of temporal and spatial distributions of temperature. This class of problems has been traditionally addressed using the Pennes bioheat equation. ...

Martin, Gregory T

159

SPATIAL AGGREGATION IN A FOREST FLOOR INSECT DEPENDS ON SEASONAL CONGREGATION AND SCATTERING EFFECTS OF PREDATORS  

EPA Science Inventory

Spatial aggregations arising from gregarious behavior are common in nature and have important implications for population dynamics, community stability, and conservation. However, the translation of aggregation behaviors into emergent properties of populations and communities de...

160

Reconstructing land use drivers and their spatial scale dependence for Costa Rica (1973 and 1984)  

Microsoft Academic Search

Costa Rican land use and cover (in 1973 and 1984) were investigated using a nested scale analysis. Spatial distributions of potential biophysical and human land use\\/cover drivers were statistically related to the distribution of pastures, arable lands, permanent crops, natural and secondary vegetation, for 0.1° grid units and five artificially aggregated spatial scales. Multiple regression models describing land use\\/cover variability

A. Veldkamp; L. O. Fresco

1997-01-01

161

Categorical and coordinate processing in object recognition depends on different spatial frequencies.  

PubMed

Previous studies have suggested that processing categorical spatial relations requires high spatial frequency (HSF) information, while coordinate spatial relations require low spatial frequency (LSF) information. The aim of the present study was to determine whether spatial frequency influences categorical and coordinate processing in object recognition. Participants performed two object-matching tasks for novel, non-nameable objects consisting of "geons" (c.f. Brain Cogn 71:181-186, 2009). For each original stimulus, categorical and coordinate transformations were applied to create comparison stimuli. These stimuli were high-pass/low-cut-filtered or low-pass/high-cut-filtered by a filter with a 2D Gaussian envelope. The categorical task consisted of the original and categorical-transformed objects. The coordinate task consisted of the original and coordinate-transformed objects. The non-filtered object image was presented on a CRT monitor, followed by a comparison object (non-filtered, high-pass-filtered, and low-pass-filtered stimuli). The results showed that the removal of HSF information from the object image produced longer reaction times (RTs) in the categorical task, while removal of LSF information produced longer RTs in the coordinate task. These results support spatial frequency processing theory, specifically Kosslyn's hypothesis and the double filtering frequency model. PMID:25236965

Saneyoshi, Ayako; Michimata, Chikashi

2015-02-01

162

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

NASA Astrophysics Data System (ADS)

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.

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

2003-04-01

163

Casimir dependence of transverse distribution of pairs produced from a strong constant chromo-electric background field  

SciTech Connect

Recently the transverse distribution of particle production from strong constant chromo-electric fields has been explicitly calculated in Ref. 1 for soft-gluon production and in Ref. 2 for quark (antiquark) production. This particle production method, originally discussed by Heisenberg and Euler, Schwinger and Weisskopf, has a long history as a model of the production of the quark gluon plasma following a relativistic heavy ion collision. The physical picture considered here is that of two relativistic heavy nuclei colliding and leaving behind a semi-classical gluon field which then non-perturbatively produces gluon and quark-antiquark pairs via the Schwinger mechanism. At high energy large hadron colliders, such as RHIC (Au-Au collisions at {radical}{ovr s} = 200 GeV) and LHC (Pb-Pb collisions at {radical}{ovr s} = 5.5 TeV), about half the total center-of-mass energy, E{sub cm}, goes into the production of a semi-classical gluon field, which can be thought to be initially in a Lorentz contracted disc. The gluon field in SU(3) is described by two Casimir invariants, the first one, C{sub 1} = E{sup a}E{sup a}, being related to the energy density of the initial field, where the second one, C{sub 2} = [d{sub abc}E{sup a}E{sup b}E{sup c}]{sup 2}, is related to the SU(3) color hypercharge left behind by the leading particles. So the question we want to study in this short note is how sensitive the transverse distribution is to this second Casimir invariant C{sub 2}. We have considered the dependence of the pair production rate of quarks and gluons from a strong chromo-electric field and have discovered that the effect of the second Casimir invariant of SU(3), which was not present in the electric field problem, effects the distribution by less than 15%. This event by event dependence of the transverse momentum distribution of jets on C{sub 2} may be something of interest at heavy ion colliders.

Cooper, Fred M [Los Alamos National Laboratory; Mihaila, Bogdan [Los Alamos National Laboratory; Dawson, John F [UNIV OF NH

2008-01-01

164

Electrochemistry of Transition Metal Dichalcogenides: Strong Dependence on the Metal-to-Chalcogen Composition and Exfoliation Method.  

PubMed

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 k(0)obs 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

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

2014-12-23

165

Strong Spatial Clustering of UV-selected Galaxies with Magnitude Ks<20.5 and Redshift Z~2  

E-print Network

We obtained deep 8.5'x8.5' near-infrared images within four high-redshift survey fields, measured the Ks magnitudes of 300 optically selected galaxies with spectroscopic redshift 1.820.5. We found at greater than 95% confidence that the brighter galaxies cluster more strongly. The best-fit correlation lengths for the bright and faint samples are 10+-3 and 4+-0.8 comoving Mpc/h, respectively (1sigma), although the unusual density of bright QSOs in one of our survey fields may imply that the result is not representative of the universe as a whole. Neglecting this possibility, the correlation length for the optically selected sample with Ks<20.5 agrees well with that reported for comparably bright near-IR-selected samples. The differences in correlation length between optically selected and near-IR-selected samples have been presented as evidence that the two techniques find orthogonal populations of high-redshift galaxies. Our results favor a more nuanced view.

Kurt L. Adelberger; Dawn K. Erb; Charles C. Steidel; Naveen A. Reddy; Max Pettini; Alice E. Shapley

2005-01-17

166

Strong Decoherence  

Microsoft Academic Search

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

Murray Gell-Mann; James B. Hartle

1995-01-01

167

Spatially resolved emission using a geometry-dependent system function and its application to excitation temperature profile measurement  

NASA Astrophysics Data System (ADS)

As typical emission spectroscopy involves chord integration along the line of sight, a local measurement with high spatial resolution is attempted using simple lens optics in this work. In the experiment, chord integrated optical plasma emission profile was measured by moving a scanning lens located outside the plasma. The measured emission intensities were spatially reconstructed by employing a geometry-dependent system function, and the local (i.e., only from the lens focal point) emission intensities were obtained with all out-focused emissions subtracted. The 34 different Ar I emission lines spatially reconstructed in this way were used to determine excitation temperature ( Texc) of the argon plasma by the Boltzmann plot method. Being different from the plasma driven at 13.56 MHz where a rather uniform profile was obtained, the spatial profile of Texc from the plasma driven at 90 MHz showed a hollow profile, which is similar to that of the electron temperature ( Te) measured by a Langmuir probe. This hollow profile is attributed from the electromagnetic phenomena such as skin effect and standing wave effect. The similar spatial tendency of Texc and Te implies that Texc can be a representative of Te. This is particularly useful for the cases in which conventional Langmuir probe measurements are limited, such as in large size plasmas.

Park, Hoyong; Choe, Wonho; Yoo, S. J.

2010-12-01

168

Time-dependent density-functional-theory calculation of strong-field ionization rates of H{sub 2}  

SciTech Connect

We report a numerical study of strong-field ionization rates of the H{sub 2} molecule using time-dependent density-functional theory (TDDFT). In the dc field limit, TDDFT results for the rate of tunneling ionization agree with molecular Ammosov-Delone-Kralnov (MO-ADK) predictions, as well as results from a complex scaling method at the full configuration interaction level. Our study demonstrates the effect of photon energy, molecular vibration, and orientation on the ionization. Calculated rates for 800-nm lasers are about four times greater than the values predicted by the slowly varying field approximation for tunneling ionization. The rate for the ground vibrational state is higher than that of the fixed nuclei value at the equilibrium distance. This difference decreases with increasing field intensity. When the field intensity is sufficiently high, the two rates are very similar, and the fixed nuclear distance rate may be used to approximate the ground-vibrational-state rate. TDDFT methods predict an anisotropy slightly larger than the prediction obtained from the MO-ADK method. We also find that the field intensity plays a role in the anisotropy, which the MO-ADK results do not show.

Chu Xi [Department of Chemistry and Biochemistry, The University of Montana, Missoula, Montana 59812 (United States)

2010-08-15

169

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

NASA Astrophysics Data System (ADS)

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.

Zhang, Caiyun; Zhu, Xiaohong; Wang, Zhongxing; Sun, Ping; Ren, Yinjuan; Zhu, Jiliang; Zhu, Jianguo; Xiao, Dingquan

2014-09-01

170

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

Microsoft Academic Search

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

Xiaochun Wang; Yuandong Zhang; Douglas J. McRae

2009-01-01

171

Population change and farm dependence: Temporal and spatial variation in the U.S. great plains, 1900–2000  

Microsoft Academic Search

I investigate the relationship between county population change and farm dependence in the Great Plains region during the\\u000a twentieth century, using spatial data analysis techniques. This research is rooted in a long-standing sociological and demographic\\u000a interest in population responses to economic transitions and informs the theoretical understanding of urbanization processes.\\u000a Using census and environmental data, the analysis challenges earlier assertions

Katherine J. Curtis White

2008-01-01

172

Task-Dependent Viscoelasticity of Human Multijoint Arm and Its Spatial Characteristics for Interaction with Environments  

E-print Network

mechanisms of the human arm, we studied the controllability and spatial characteristics of viscoelastic interactions with objects. Key words: human arm mechanical impedance; arm stiffness; arm viscosity; muscle control; arm control; environmental inter- action; isometric force control In all manipulation tasks

Osu, Rieko

173

Representing genetic variation as continuous surfaces: an approach for identifying spatial dependency in landscape genetic studies  

E-print Network

, migration, effective population size) and used ancestry (q) values from STRUCTURE to interpolate a genetic surface. Using a spatially adjusted Pearson's correlation coefficient to test the significance of testing landscape influence on genetic structure. Finally, we apply genetic surfacing to analyze

Storfer, Andrew

174

Patterns of spatial dependence and heterogeneity and the scale of urban deprivation  

Microsoft Academic Search

The scale and pace of change in urban systems is without historic precedent. Today's increasingly affluent populations have ever more diverse lifestyles, and it is increasingly untenable to think of intra urban social patterning by analogy to an inert mosaic of internally homogeneous statistical reporting zones (Johnston, 1999). Small area spatial differentiation in physical and social conditions thus remains an

Carolina Tobón; Paul Longley

175

Assessments of habitat preferences and quality depend on spatial scale and metrics of fitness  

USGS Publications Warehouse

1. Identifying the habitat features that influence habitat selection and enhance fitness is critical for effective management. Ecological theory predicts that habitat choices should be adaptive, such that fitness is enhanced in preferred habitats. However, studies often report mismatches between habitat preferences and fitness consequences across a wide variety of taxa based on a single spatial scale and/or a single fitness component. 2. We examined whether habitat preferences of a declining shrub steppe songbird, the Brewer's sparrow Spizella breweri, were adaptive when multiple reproductive fitness components and spatial scales (landscape, territory and nest patch) were considered. 3. We found that birds settled earlier and in higher densities, together suggesting preference, in landscapes with greater shrub cover and height. Yet nest success was not higher in these landscapes; nest success was primarily determined by nest predation rates. Thus landscape preferences did not match nest predation risk. Instead, nestling mass and the number of nesting attempts per pair increased in preferred landscapes, raising the possibility that landscapes were chosen on the basis of food availability rather than safe nest sites. 4. At smaller spatial scales (territory and nest patch), birds preferred different habitat features (i.e. density of potential nest shrubs) that reduced nest predation risk and allowed greater season-long reproductive success. 5. Synthesis and applications. Habitat preferences reflect the integration of multiple environmental factors across multiple spatial scales, and individuals may have more than one option for optimizing fitness via habitat selection strategies. Assessments of habitat quality for management prescriptions should ideally include analysis of diverse fitness consequences across multiple ecologically relevant spatial scales. ?? 2007 The Authors.

Chalfoun, A.D.; Martin, T.E.

2007-01-01

176

Spatial Memory Deficits and Motor Coordination Facilitation in cGMP-Dependent Protein Kinase Type II-deficient Mice  

PubMed Central

Activity-dependent trafficking of AMPA receptors to synapses regulates synaptic strength. Activation of the NMDA receptor induces several second messenger pathways that contribute to receptor trafficking-dependent plasticity, including the NO pathway, which elevates cGMP. In turn, cGMP activates the cGMP-dependent protein kinase type II (cGKII), which phosphorylates the AMPA receptor subunit GluA1 at serine 845, a critical step facilitating synaptic delivery in the mechanism of activity-dependent synaptic potentiation. Since cGKII is expressed in the striatum, amygdala, cerebral cortex, and hippocampus, it has been proposed that mice lacking cGKII may present phenotypic differences compared to their wild-type littermates in emotion-dependent tasks, learning and memory, and drug reward salience. Previous studies have shown that cGKII KO mice ingest higher amounts of ethanol as well as exhibit elevated anxiety levels compared to wild-type (WT) littermates. Here, we show that cGKII KO mice are significantly deficient in spatial learning while exhibiting facilitated motor coordination, demonstrating a clear dependence of memory-based tasks on cGKII. We also show diminished GluA1 phosphorylation in the postsynaptic density (PSD) of cGKII KO prefrontal cortex while in hippocampal PSD fractions, phosphorylation was not significantly altered. These data suggest that the role of cGKII may be more robust in particular brain regions, thereby impacting complex behaviors dependent on these regions differently. PMID:23103773

Wincott, Charlotte M.; Kim, Seonil; Titcombe, Roseann F.; Tukey, David S.; Girma, Hiwot K.; Pick, Joseph E.; DeVito, Loren M.; Hofmann, Franz; Hoeffer, Charles; Ziff, Edward

2012-01-01

177

Role of space-time-dependent eddy viscosity on the spatial pattern of tidal and residual flow in estuaries  

NASA Astrophysics Data System (ADS)

Several field studies in estuaries show non-logarithmic profiles of the tidal flow amplitude over the water column and complex patterns of residual flow. To gain fundamental understanding about these phenomena, a semi-analytical 3D model is designed and analysed, with focus on the sensitivity of the spatial pattern of tidal (semi-diurnal) and residual (tidally-averaged) flow to formulations of eddy viscosity that account for spatial and temporal variations. To allow comparison of model results with field observations measured in sigma-levels, the model is formulated in sigma-coordinates. The residual flow is decomposed into individual contributions induced by river discharge (including discharge due to Stokes return flow), horizontal density gradient, tidal rectification, wind, depth-dependent friction and asymmetric tidal mixing due to temporal covariance between eddy viscosity and velocity shear. By using scaling and perturbation techniques, new analytical solutions for semi-diurnal tide and residual flows are found for space-time-dependent eddy viscosity. The model reveals that "Surface Velocity Jumps" (tidal flow amplitude non-logarithmically increasing near the surface of water column) and "Subsurface Velocity Jets" (maximum tidal flow amplitude shows at subsurface of water column) occur for relatively low mixing conditions. Model output is subsequently compared with field data collected at an estuarine cross-section in the North Passage of the Yangtze (Changjiang) estuary. It is found that the modelled tidal velocity shear agrees better with observations when using space-time-dependent eddy viscosity instead of a constant eddy viscosity. Moreover, the spatial patterns of individual residual flow components on along-estuary direction are more spread over the cross section, which agrees with observations. With space-time-dependent eddy viscosity, it turns out that density gradient and time-varying mixing are key forcing agents of residual flow.

Chen, Wei; de Swart, Huib

2014-05-01

178

Spatial hearing in Cope’s gray treefrog: II. Frequency-dependent directionality in the amplitude and phase of tympanum vibrations  

PubMed Central

Anuran ears function as pressure difference receivers, and the amplitude and phase of tympanum vibrations are inherently directional, varying with sound incident angle. We quantified the nature of this directionality for Cope’s gray treefrog, Hyla chrysoscelis. We presented subjects with pure tones, advertisement calls, and frequency-modulated sweeps to examine the influence of frequency, signal level, lung inflation, and sex on ear directionality. Interaural differences in the amplitude of tympanum vibrations were 1–4 dB greater than sound pressure differences adjacent to the two tympana, while interaural differences in the phase of tympanum vibration were similar to or smaller than those in sound phase. Directionality in the amplitude and phase of tympanum vibration were highly dependent on sound frequency, and directionality in amplitude varied slightly with signal level. Directionality in the amplitude and phase of tone- and call-evoked responses did not differ between sexes. Lung inflation strongly affected tympanum directionality over a narrow frequency range that, in females, included call frequencies. This study provides a foundation for further work on the biomechanics and neural mechanisms of spatial hearing in H. chrysoscelis, and lends valuable perspective to behavioral studies on the use of spatial information by this species and other frogs. PMID:24504183

Lee, Norman; Schrode, Katrina M.; Johns, Anastasia R.; Christensen-Dalsgaard, Jakob; Bee, Mark A.

2014-01-01

179

Spatial dependence of polycrystalline FTO's conductance analyzed by conductive atomic force microscope (C-AFM)  

NASA Astrophysics Data System (ADS)

Fluorine-doped Tin oxide (FTO) is a highly transparent, electrically conductive polycrystalline material frequently used as an electrode in organic solar cells and optical-electronic devices [1-2]. In this work a spatial analysis of the conductive behavior of FTO was carried out by Conductive-mode Atomic Force Microscopy (C-AFM). Rare highly oriented grains sample give us an opportunity to analyze the top portion of polycrystalline FTO and compare with the border one. It is shown that the current flow essentially takes place through the polycrystalline edge at grain boundaries.

Peixoto, Alexandre Pessoa; da Costa, J. C.

2014-05-01

180

The spatial scale dependence of water vapor variability inferred from observations from a very tall tower  

NASA Astrophysics Data System (ADS)

Recent studies have established that atmospheric water vapor fields exhibit spatial spectra that take the form of power laws and hence can be compactly characterized by scaling exponents. The power law scaling exponents have been shown to exhibit substantial vertical variability. In this work, Taylor's frozen turbulence hypothesis is used to infer the first-order spatial structure function and generalized detrended fluctuation function scaling exponents for scales between 1 km and 100 km. Both methods are used to estimate the Hurst exponent (H) using 10 Hz time series of water vapor measured at 396 m altitude from an Ameriflux tower in Wisconsin. Due to the diurnal cycle in the boundary layer height at the 396 m observational level, H may be estimated for both the daytime convective mixed layer and the nocturnal residual layer. Values of H?1/3 are obtained for the convective mixed layer, while values of H>1/2 apply in the nocturnal residual layer. The results are shown to be remarkably consistent with a similar analysis from satellite-based observations as reported in Pressel and Collins (2012).

Pressel, Kyle G.; Collins, William D.; Desai, Ankur R.

2014-08-01

181

The influence of acute intense exercise on exogenous spatial attention depends on physical fitness level.  

PubMed

We investigated the effect of a previous bout of intense exercise on exogenous spatial attention. In Experiment 1, a group of participants performed an exogenous spatial task at rest (without prior effort), immediately after intense exercise, and after recovering from an intense exercise. The analyses revealed that the typical "facilitation effect" (i.e., faster reaction times on cued than on uncued trials) immediately after exercise was positively correlated with participants' fitness level. In Experiment 2, a high-fit and a low-fit group performed the same task at rest (without prior effort) and immediately after an intense exercise. Results revealed that, after the bout of exercise, only low-fit participants showed reduced attentional effects compared to the rest condition. We argue that the normal functioning of exogenous attention was influenced by intense effort, affecting low-fit participants to a larger extent than to high-fit participants. As a consequence, target processing was prioritized over irrelevant stimuli. PMID:25270559

Llorens, Francesc; Sanabria, Daniel; Huertas, Florentino

2015-01-01

182

Single-Virus Tracking Reveals a Spatial Receptor-Dependent Search Mechanism  

PubMed Central

Viral infection begins with the binding of a virus to a specific target on the surface of the host cell, followed by viral genome delivery into the host and a continuation of the infection process. Before binding occurs, the virus must first find its receptor by a process whose details are largely unknown. We applied high-resolution fluorescence microscopy and single-particle tracking to elucidate the target-finding process in bacteriophage ? as it infects an Escherichia coli cell. By monitoring the motion of individual viruses through the early stages of infection, we identified a unique spatial focusing process that allows a virus to arrive from its initial random landing site to its destination at the cell pole. The search process is governed by the interaction between the virus and the LamB receptors, and by the spatial organization of the receptor network on the cell surface. Our findings allowed us to develop a theoretical model for the target-finding process that reproduces the key features observed in experiment. We discuss the possible implications of our findings for the process of viral receptor-finding in higher systems. PMID:21689520

Rothenberg, Eli; Sepúlveda, Leonardo A.; Skinner, Samuel O.; Zeng, Lanying; Selvin, Paul R.; Golding, Ido

2011-01-01

183

Strong decoherence  

E-print Network

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 wha...

Gell-Mann, Murray; Gell-Mann, Murray; Hartle, James B

1997-01-01

184

Nanoparticle-rich diesel exhaust affects hippocampal-dependent spatial learning and NMDA receptor subunit expression in female mice.  

PubMed

We investigated the effect of exposure to nanoparticle-rich diesel exhaust (NRDE) on hippocampal-dependent spatial learning and memory function-related gene expressions in female mice. Female BALB/c mice were exposed to clean air, middle-dose NRDE (M-NRDE), high-dose NRDE (H-NRDE) or filtered diesel exhaust (F-DE) for three months. A Morris water maze apparatus was used to examine spatial learning. The expression levels of the N-methyl-D-aspartate (NMDA) receptor subunit, proinflammatory cytokines and neurotrophin mRNAs in the hippocampus were then investigated using real-time RT-PCR. Mice exposed to H-NRDE required a longer time to reach the hidden platform and showed higher mRNA expression levels of the NMDA receptor subunit NR2A, the proinflammatory cytokine CCL3, and brain-derived neurotrophic factor (BDNF) in the hippocampus, compared with the findings in the control group. These results indicate that three months of exposure to NRDE affected spatial learning and memory function-related gene expressions in the female mouse hippocampus. PMID:21663545

Win-Shwe, Tin-Tin; Yamamoto, Shoji; Fujitani, Yuji; Hirano, Seishiro; Fujimaki, Hidekazu

2012-08-01

185

Temperature-dependent linewidth of charged excitons in semiconductor quantum dots: Strongly broadened ground state transitions due to acoustic phonon scattering  

E-print Network

Temperature-dependent linewidth of charged excitons in semiconductor quantum dots: Strongly and therefore the extent to which the quantum dot properties are influenced by the surrounding semiconductor of temperature for excitons in single semiconductor quantum dots as they are charged with excess electrons. Our

Ludwig-Maximilians-Universität, München

186

PRELIMINARY ANALYSIS OF THE PEAKS OF STRONG EARTHQUAKE GROUND MOTION--DEPENDENCE OF PEAKS ON EARTHQUAKE MAGNITUDE, EPICENTRAL DISTANCE, AND RECORDING SITE CONDITIONS  

Microsoft Academic Search

Analyses of peak amplitudes of strong earthquake ground motion have been carried out with the emphasis on their dependence on earthquake magnitude, epicen- tral distance, and geological conditions at the recording site. Approximate empirical scaling functions have been developed which, for a selected confidence level, yield an estimate of an upper bound of peak accelerations, velocities, and displacements. The parameters

M. D. TRIFUNAC

1976-01-01

187

Benchmark solutions for the galactic ion transport equations: Energy and spatially dependent problems  

NASA Technical Reports Server (NTRS)

Nontrivial benchmark solutions are developed for the galactic ion transport (GIT) equations in the straight-ahead approximation. These equations are used to predict potential radiation hazards in the upper atmosphere and in space. Two levels of difficulty are considered: (1) energy independent, and (2) spatially independent. The analysis emphasizes analytical methods never before applied to the GIT equations. Most of the representations derived have been numerically implemented and compared to more approximate calculations. Accurate ion fluxes are obtained (3 to 5 digits) for nontrivial sources. For monoenergetic beams, both accurate doses and fluxes are found. The benchmarks presented are useful in assessing the accuracy of transport algorithms designed to accommodate more complex radiation protection problems. In addition, these solutions can provide fast and accurate assessments of relatively simple shield configurations.

Ganapol, Barry D.; Townsend, Lawrence W.; Wilson, John W.

1989-01-01

188

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

PubMed

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

Chen, Zikuan; Chen, Zeyuan; Calhoun, Vince

2013-03-01

189

Automatic knee cartilage segmentation from multi-contrast MR images using support vector machine classification with spatial dependencies.  

PubMed

Accurate segmentation of knee cartilage is required to obtain quantitative cartilage measurements, which is crucial for the assessment of knee pathology caused by musculoskeletal diseases or sudden injuries. This paper presents an automatic knee cartilage segmentation technique which exploits a rich set of image features from multi-contrast magnetic resonance (MR) images and the spatial dependencies between neighbouring voxels. The image features and the spatial dependencies are modelled into a support vector machine (SVM)-based association potential and a discriminative random field (DRF)-based interaction potential. Subsequently, both potentials are incorporated into an inference graphical model such that the knee cartilage segmentation is cast into an optimal labelling problem which can be efficiently solved by loopy belief propagation. The effectiveness of the proposed technique is validated on a database of multi-contrast MR images. The experimental results show that using diverse forms of image and anatomical structure information as the features are helpful in improving the segmentation, and the joint SVM-DRF model is superior to the classification models based solely on DRF or SVM in terms of accuracy when the same features are used. The developed segmentation technique achieves good performance compared with gold standard segmentations and obtained higher average DSC values than the state-of-the-art automatic cartilage segmentation studies. PMID:23867282

Zhang, Kunlei; Lu, Wenmiao; Marziliano, Pina

2013-12-01

190

Personality-dependent dispersal: characterization, ontogeny and consequences for spatially structured populations  

PubMed Central

Dispersal is one of the most fundamental components of ecology, and affects processes as diverse as population growth, metapopulation dynamics, gene flow and adaptation. Although the act of moving from one habitat to another entails major costs to the disperser, empirical and theoretical studies suggest that these costs can be reduced by having morphological, physiological or behavioural specializations for dispersal. A few recent studies on different systems showed that individuals exhibit personality-dependent dispersal, meaning that dispersal tendency is associated with boldness, sociability or aggressiveness. Indeed, in several species, dispersers not only develop behavioural differences at the onset of dispersal, but display these behavioural characteristics through their life cycle. While personality-dependent dispersal has been demonstrated in only a few species, we believe that it is a widespread phenomenon with important ecological consequences. Here, we review the evidence for behavioural differences between dispersers and residents, to what extent they constitute personalities. We also examine how a link between personality traits and dispersal behaviours can be produced and how personality-dependent dispersal affects the dynamics of metapopulations and biological invasions. Finally, we suggest future research directions for population biologists, behavioural ecologists and conservation biologists such as how the direction and the strength of the relationship between personality traits and dispersal vary with ecological contexts. PMID:21078658

Cote, J.; Clobert, J.; Brodin, T.; Fogarty, S.; Sih, A.

2010-01-01

191

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

E-print Network

We perform an ab initio study of multiphoton ionization (MPI) of carbon dioxide in intense linearly polarized laser pulses with arbitrary molecular orientation by means of a time-dependent density-functional theory (TDDFT) with proper long...

Son, Sang-Kil; Chu, Shih-I

2009-07-24

192

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)

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.

Krishnan, Prabu; Sriram Kumar, D.

2014-12-01

193

Imaging Self-assembly Dependent Spatial Distribution of Small Molecules in Cellular Environment  

PubMed Central

Self-assembly of small molecules, as a more common phenomenon than one previously thought, can be either beneficial or detrimental to cells. Despite its profound biological implications, how the self-assembly of small molecules behave in cellular environment is largely unknown and barely explored. This work studies four fluorescent molecules that consist of the same peptidic backbone (e.g., Phe-Phe-Lys) and enzyme trigger (e.g., a phosphotyrosine residue), but bear different fluorophores on the side chain of the lysine residue of the peptidic motif. These molecules, however, exhibit different ability of self-assembly before and after enzymatic transformation (e.g., dephosphorylation). Fluorescent imaging reveals that self-assembly directly affects the distribution of these small molecules in cellular environment. Moreover, cell viability tests suggest that the states and the location of the molecular assemblies in the cellular environment control the phenotypes of the cells. For example, the molecular nanofibers of one of the small molecules apparently stabilize actin filaments and alleviate the insult of an F-actin toxin (e.g., latrunculin A). Combining fluorescent imaging and enzyme-instructed self-assembly of small peptidic molecules, this work not only demonstrates that self-assembly as a key factor for dictating the spatial distribution of small molecules in cellular environment. In addition, it illustrates a useful approach, based on enzyme-instructed self-assembly of small molecules, to modulate spatiotemporal profiles of small molecules in cellular environment, which allows the use of the emergent properties of small molecules to control the fate of cells. PMID:24266765

Gao, Yuan; Kuang, Yi; Du, Xuewen; Zhou, Jie; Chandran, Preethi; Horkay, Ferenc; Xu, Bing

2014-01-01

194

Numerical Volumetric Analysis of Spatially Dependent Transmissivity and Storativity in Heterogeneous Aquifers  

NASA Astrophysics Data System (ADS)

Aquifer transmissivity (T) and storativity (S) values control the rate and areal extent of propagation of the cone of depression from a pumped well. It has been documented recently that transmissivity and storativity, reflect the geometric and arithmetic means, respectively, of the area contacted by the cone of depression. However, these findings do not reflect a volumetric evaluation of the cone of depression within the heterogenities. Analysis of spatial, volumetric variations within the cone of depression expressed at the potentiometric surface, offers a more general solution to evaluate the meaning of T and S values. Log-normal and normal distributions of hydraulic conductivity as block heterogeneities were established within model domains for simulated aquifer tests. By analyzing the volumetric evolution of the cone of depression observed in the potentiometric surface, we are able to illustrate the averaging of transmissivity as a function of time, and distance from the pumping well for the entire affected aquifer. Volumetric analysis of simulated aquifer tests show an exponential decrease in the arithmetic, harmonic, and geometric weighted mean transmissivity within the evolving cone of depression through time, approaching steady, basin-wide averages. Transmissivity estimates derived for single observation wells by conventional testing methods (i.e., Theis, 1935; Cooper and Jacob, 1946) are found to increase with increasing radial distance from the pumping well. However, when the same observation well drawdown data are plotted together with, and constrained by, the drawdown curve for the pumping well, a family of drawdown curves is derived that yields transmissivity values that are consistent with the volumetric, weighted, mean transmissivity values calculated for the entire cone of depression for specific periods of time (i.e., areal extent).

Rhode, K.; Osiensky, J.

2005-12-01

195

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

PubMed Central

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

Keating, Peter; King, Andrew J.

2013-01-01

196

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

E-print Network

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

Iyengar, Srinivasan S.

197

Battery life and performance depend strongly on temperature; thus there exists a need for thermal conditioning in plug-in  

E-print Network

of the battery such as its technology and design. Currently, PHEVs use Li-ion chemistries due to superior power among different type of Li-ion batteries, depending on the cell design and the material chemistries used used anode material is graphite. Therefore, in the literature, Li-ion chemistry is often specified

Michalek, Jeremy J.

198

Systemic lipopolysaccharide administration impairs retrieval of context-object discrimination, but not spatial, memory: Evidence for selective disruption of specific hippocampus-dependent memory functions during acute neuroinflammation.  

PubMed

Neuroinflammation is implicated in impairments in neuronal function and cognition that arise with aging, trauma, and/or disease. Therefore, understanding the underlying basis of the effect of immune system activation on neural function could lead to therapies for treating cognitive decline. Although neuroinflammation is widely thought to preferentially impair hippocampus-dependent memory, data on the effects of cytokines on cognition are mixed. One possible explanation for these inconsistent results is that cytokines may disrupt specific neural processes underlying some forms of memory but not others. In an earlier study, we tested the effect of systemic administration of bacterial lipopolysaccharide (LPS) on retrieval of hippocampus-dependent context memory and neural circuit function in CA3 and CA1 (Czerniawski and Guzowski, 2014). Paralleling impairment in context discrimination memory, we observed changes in neural circuit function consistent with disrupted pattern separation function. In the current study we tested the hypothesis that acute neuroinflammation selectively disrupts memory retrieval in tasks requiring hippocampal pattern separation processes. Male Sprague-Dawley rats given LPS systemically prior to testing exhibited intact performance in tasks that do not require hippocampal pattern separation processes: novel object recognition and spatial memory in the water maze. By contrast, memory retrieval in a task thought to require hippocampal pattern separation, context-object discrimination, was strongly impaired in LPS-treated rats in the absence of any gross effects on exploratory activity or motivation. These data show that LPS administration does not impair memory retrieval in all hippocampus-dependent tasks, and support the hypothesis that acute neuroinflammation impairs context discrimination memory via disruption of pattern separation processes in hippocampus. PMID:25451612

Czerniawski, Jennifer; Miyashita, Teiko; Lewandowski, Gail; Guzowski, John F

2015-02-01

199

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

PubMed

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

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

200

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

PubMed Central

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

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

201

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

NASA Astrophysics Data System (ADS)

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.

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.

2014-10-01

202

Pressure Dependence of Fragile-to-Strong Transition and a Possible Second Critical Point in Supercooled Confined Water  

E-print Network

By confining water in nano-pores of silica glass, we can bypass the crystallization and study the pressure effect on the dynamical behavior in deeply supercooled state using neutron scattering. We observe a clear evidence of a cusp-like fragile-to-strong (F-S) dynamic transition. Here we show that the transition temperature decreases steadily with an increasing pressure, until it intersects the homogenous nucleation temperature line of bulk water at a pressure of 1600 bar. Above this pressure, it is no longer possible to discern the characteristic feature of the F-S transition. Identification of this end point with the possible second critical point is discussed.

Li Liu; Sow-Hsin Chen; Antonio Faraone; Chun-Wan Yen; Chung-Yuan Mou

2005-08-16

203

Quantum fluid dynamics based current-density functional study of a helium atom in a strong time-dependent magnetic field  

Microsoft Academic Search

.  \\u000a Evolution of the helium atom in a strong time-dependent (TD) magnetic field\\u000a (B) of strength up to 1011 G is investigated through a quantum fluid\\u000a dynamics (QFD) based current-density functional theory (CDFT). The\\u000a TD-QFD-CDFT computations are performed through numerical solution of a\\u000a single generalized nonlinear Schrödinger equation employing vector\\u000a exchange-correlation potentials and scalar exchange-correlation density\\u000a functionals that depend both on

2011-01-01

204

Detection of smoothelin expression in the urinary bladder is strongly dependent on pretreatment conditions: a critical analysis with possible consequences for cancer staging.  

PubMed

Distinguishing urinary bladder muscularis propria (MP) from muscularis mucosae (MM) is crucial in bladder cancer staging. Immunohistochemical staining for the smooth muscle-specific protein smoothelin has been reported to be a robust marker for MP. The aim of this study was to investigate how smoothelin immunostaining in the bladder varies with pretreatment techniques and if it can be used to discriminate between MM and MP. Immunohistochemistry (IHC) for smoothelin was performed on nontumoral sections from 18 cystectomy specimens using three different pretreatment protocols. The immunoreactivity of MM, MP and blood vessels was scored semiquantitatively. Staining intensity depended strongly on the different pretreatment protocols used. Heat-induced epitope retrieval (HIER) in alkaline buffer resulted in the strongest staining with a moderate or strong immunostaining of the MP in 18/18 (100%) of cases, but in 11/18 (61%), the MM was moderately or strongly stained. HIER in acidic buffer resulted in a suboptimal staining of the MP. Enzymatic pretreatment resulted in absent or weak staining. In conclusion, smoothelin IHC is strongly dependent on epitope retrieval, and smoothelin staining did not discriminate reliably between MP and MM with any of the tested pretreatment protocols. PMID:21494761

Lindh, Claes; Nilsson, Robert; Lindstrom, Marie Louise; Lundin, Lilian; Elmberger, Goran

2011-06-01

205

Discussion paper: Strong dependence of whole animal absorption on polarization and frequency or radio-frequency energy.  

PubMed

A two-plate stripline is used to determine wide-band radio-frequency (285-4000 MHz) absorption characteristics of 96-390-g rats and brain-phantom prolate spheroidal bodies. The results compare well to those for free space irradiation. At resonance, for E along the long dimension (â), a power deposition nine times higher than that for the H parallel â orientation is observed. For rats in the k parallel â configuration, the frequencies of peak absorption and the maximum absorption at these values demonstrate W-1/3 and W 2/3 dependencies, respectively, upon the weight W of the animal. This finding implies that whole animal absorption is a size- and shape-dependent phenomenon. PMID:1054254

Gandhi, O P

1975-02-28

206

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

207

Tract-based spatial statistics (TBSS) of diffusion tensor imaging data in alcohol dependence: abnormalities of the motivational neurocircuitry  

PubMed Central

Previous diffusion tensor imaging (DTI) studies indicated microstructural disruption of white matter in alcohol dependence. To investigate the microstructure of primary neurocircuitry involved in alcohol use disorders, the present study used Tract-Based Spatial Statistics (TBSS) of DTI measures as well as probabilistic tractography. Eleven recovering alcoholics in their first week of abstinence from alcohol were compared with ten light drinking controls; diffusion measures were correlated with measures of neurocognition and drinking severity. Regions characterized by low fractional anisotropy and high mean diffusivity included cortico-striatal fibers and those in frontal white matter and limbic pathways. Greater diffusion abnormalities in sections of commissural fibers (inter-hemispheric connections) were associated with stronger drinking severity, and lower fractional anisotropy measures in frontal and limbic fiber tracts correlated with lower visuospatial memory performance. These study findings provide direct evidence of compromised integrity of the motivational brain circuitry in alcohol use disorders. These abnormalities in fiber connections could be partially responsible for deficiencies in executive functions, behavioral regulation, and impulse control commonly described in alcohol dependence. PMID:19442492

Yeh, Ping-Hong; Simpson, Ken; Durazzo, Timothy C.; Gazdzinski, Stefan; Meyerhoff, Dieter J.

2009-01-01

208

Magnetic-field dependence of energy levels of superconducting nano-scale mettalic grains with strong spin-orbit scattering  

NASA Astrophysics Data System (ADS)

We study the Zeeman splitting of discrete energy levels of superconducting nano-scale metallic grains whose single-electron dynamics is chaotic [1]. In the absence of spin-orbit scattering the Zeeman splitting of a single-electron level is trivial; it is the same for all levels and linear in magnetic field. Spin-orbit coupling suppresses this splitting, induces level-to-level fluctuations and non-linear corrections to the energies. We investigate the combined effect of pairing correlations, which lead to superconductivity in the bulk limit, and spin-orbit scattering on the many-electron energy levels in a weak magnetic field. In particular, we focus our studies on the linear (g-factor) and quadratic (zero-field level curvature) corrections and their mesoscopic fluctuations. The single-electron part of the Hamiltonian follows the statistics of the Gaussian symplectic ensemble of random matrix theory, which is applicable in the limit of strong spin-orbit scattering and a large dimensionless Thouless conductance. The interaction is given by a BCS-like pairing term and the magnetic field coupling is described by a Zeeman term. [1] K. Nesterov and Y. Alhassid, to be published.

Nesterov, Konstantin; Alhassid, Yoram

2012-02-01

209

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)

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.

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

2002-01-01

210

Temporal and spatial distribution of tropospheric NO2 over arid areas of Central Asia by OMI Satellite observations: Evidence for a strong contribution of soil biogenic nitric oxide  

NASA Astrophysics Data System (ADS)

We present results observations of tropospheric NO2 carried out by Ozone Monitoring Instrument (OMI) over the Central Asian arid areas from 2005 to 2011. We selected 8 oases (Ruoqiang, Milan, Waxxari, Qiemo, Minfeng, Shache, Awati and Kuche) in Taklimakan desert (part of the great Central Asian deserts). For these, spatial distributions, seasonal variations, and trends of tropospheric NO2 Vertical Column Densities (VCDs) retrieved are discussed. In the Taklimakan desert, oases are the centers of all human activities and the economy of the selected oases are dominated by oasis agriculture. Irrigation and fertilization favor the microbial production of nitric oxide in soils, which after emission is converted to NO2 by ozone. Consequently, tropospheric NO2-VCDs are a good proxy for biogenic NO emissions from soils. For contrast, we examined also the NO2-VCDs in the area of the growing megacity Urumqi (43.85°N, 87.62°E), which is known as an anthropogenic highly polluted city in the Central Asian deserts. For 2005-2011, all selected oases are hot spots of NO/NO2 in the Taklimakan desert. Higher NO2-VCDs were observed during growing seasons over all 8 oases. NO2-VCDs observed in summer generally increased from 2005 to 2011. NO2-VCDs over Urumqi were generally at least 1 order of magnitude higher than those over the oases. In contrast to the oases, wintertime NO2-VCDs over Urumqi are higher than in summer. We evaluated governmental statistical agricultural data of the 8 oasis, and compared the trends with corresponding summertime NO2-VCDs. Inter-annual trends of NO2-VCDs over the oases show similar patterns to those of N-fertilizer application and sown (and irrigated) areas. Highest NO2-VCDs observed in summer for agriculturally dominated oases are a strong indication that soil biogenic NO emission is the main contributor to the tropospheric NO2 over all 8 oases, while in Urumqi fossil fuel combustion, particularly during winter, is the main source for NO/NO2. With regard to recent/future agriculture development in the Taklimakan oases (80% of the current Chinese cotton production originates from there), biogenic NO emission from soils will provide an increasing contribution to tropospheric NO2 over Central Asia.

Mamtimin, Buhalqem; Qi, Yue; Beirle, Steffen; Wagner, Thomas; Meixner, Franz X.

2013-04-01

211

Nonlinear frequency-dependent effects in the dc magnetization of uniaxial magnetic nanoparticles in superimposed strong alternating current and direct current fields  

NASA Astrophysics Data System (ADS)

The dc component of the magnetization of noninteracting fine magnetic particles possessing simple uniaxial anisotropy and subjected to strong ac and dc bias magnetic fields is calculated via the magnetic Langevin equation. In the presence of an ac driving field, the dc component of the magnetization of uniaxial particles alters drastically leading to new nonlinear effects; in particular, it becomes frequency-dependent. In axial symmetry, where the strong ac field is parallel to the easy axis of a particle, two distinct dispersion regions in the dc magnetization at low and mid-frequencies emerge, corresponding to longitudinal overbarrier and intrawell relaxation modes. Such frequency-dependent behavior allows one to estimate the magnetization reversal time via the half-width of the low-frequency dispersion band. Otherwise, by applying the strong ac field at an angle to the easy axis of a particle so breaking the axial symmetry, a third high-frequency nonlinear resonant dispersion in the dc component of the magnetization appears accompanied by parametric resonance behavior due to excitation of transverse modes with frequencies close to the precession frequency.

Wei, Nijun; Byrne, Declan; Coffey, William T.; Kalmykov, Yuri P.; Titov, Serguey V.

2014-11-01

212

Frequency-dependent time delays for strong outbursts in selected blazars from the Metsähovi and UMRAO monitoring data bases - II  

NASA Astrophysics Data System (ADS)

We analyse the radio light curves of the blazars 1308+326, 2223-052 and 2251+158 using University of Michigan Radio Observatory and Metsähovi Radio Observatory multifrequency monitoring data combined with high-resolution very long baseline interferometry (VLBI) observations in order to extract the properties of prominent outbursts. The outbursts are classified as `core' and `jet' events according to their behaviour at different frequencies and their associations with features appearing in the VLBI jet. We define the activity cycle for each blazar as the time interval between successive `core' outbursts. The durations of the activity cycle derived in this way are >=14 yr for 1308+326, ~12 yr for 2223-052 and 12.4 +/- 0.6 yr for 2251+158. We find an unusual frequency dependence for the time profiles for a major flare in 1308+326, which may provide evidence for acceleration or bending of the jet flow in the optically thick part of the emission region. Analysis of these activity cycles, combined with our earlier results, leads us to suggest that more luminous blazars possess shorter activity cycles, consistent with the accretion rates being higher in more powerful sources (relative to the Eddington rate).

Pyatunina, T. B.; Kudryavtseva, N. A.; Gabuzda, D. C.; Jorstad, S. G.; Aller, M. F.; Aller, H. D.; Teräsranta, H.

2007-10-01

213

Adaptive Time-Dependent Density-Matrix Renormalization-Group Technique for Calculating the Conductance of Strongly Correlated Nanostructures  

SciTech Connect

A procedure based on the recently developed ''adaptive'' time-dependent density-matrix-renormalization-group (DMRG) technique is presented to calculate the zero temperature conductance of nanostructures, such as quantum dots (QDs) or molecular conductors, when represented by a small number of active levels. The leads are modeled using noninteracting tight-binding Hamiltonians. The ground state at time zero is calculated at zero bias. Then, a small bias is applied between the two leads, the wave function is DMRG evolved in time, and currents are measured as a function of time. Typically, the current is expected to present periodicities over long times, involving intermediate well-defined plateaus that resemble steady states. The conductance can be obtained from those steady-state-like currents. To test this approach, several cases of interacting and noninteracting systems have been studied. Our results show excellent agreement with exact results in the noninteracting case. More importantly, the technique also reproduces quantitatively well-established results for the conductance and local density of states in both the cases of one and two coupled interacting QDs. The technique also works at finite bias voltages, and it can be extended to include interactions in the leads.

Al Hassanieh, Khaled A [ORNL; Feiguin, Adrian E [ORNL; Riera, Jose Alejandro [ORNL; Busser, Carlos A [ORNL; Dagotto, Elbio R [ORNL

2006-01-01

214

Determination of Earths transient and equilibrium climate sensitivities from observations over the twentieth century: Strong dependence on assumed forcing  

SciTech Connect

Relations among observed changes in global mean surface temperature, ocean heat content, ocean heating rate, and calculated radiative forcing, all as a function of time over the twentieth century, that are based on a two-compartment energy balance model, are used to determine key properties of Earth's climate system. The increase in heat content of the world ocean, obtained as the average of several recent compilations, is found to be linearly related to the increase in global temperature over the period 1965-2009; the slope, augmented to account for additional heat sinks, which is an effective heat capacity of the climate system, is 21.8 {+-} 2.1 W year m{sup -2} K{sup -1} (one sigma), equivalent to the heat capacity of 170 m of seawater (for the entire planet) or 240 m for the world ocean. The rate of planetary heat uptake, determined from the time derivative of ocean heat content, is found to be proportional to the increase in global temperature relative to the beginning of the twentieth century with proportionality coefficient 1.05 {+-} 0.06 W m{sup -2} K{sup -1}. Transient and equilibrium climate sensitivities were evaluated for six published data sets of forcing mainly by incremental greenhouse gases and aerosols over the twentieth century as calculated by radiation transfer models; these forcings ranged from 1.1 to 2.1 W m{sup -2}, spanning much of the range encompassed by the 2007 assessment of the Intergovernmental Panel on Climate Change (IPCC). For five of the six forcing data sets, a rather robust linear proportionality obtains between the observed increase in global temperature and the forcing, allowing transient sensitivity to be determined as the slope. Equilibrium sensitivities determined by two methods that account for the rate of planetary heat uptake range from 0.31 {+-} 0.02 to 1.32 {+-} 0.31 K (W m{sup -2}){sup -1} (CO{sub 2} doubling temperature 1.16 {+-} 0.09-4.9 {+-} 1.2 K), more than spanning the IPCC estimated 'likely' uncertainty range, and strongly anticorrelated with the forcing used to determine the sensitivities. Transient sensitivities, relevant to climate change on the multidecadal time scale, are considerably lower, 0.23 {+-} 0.01 to 0.51 {+-} 0.04 K (W m{sup -2}){sup -1}. The time constant characterizing the response of the upper ocean compartment of the climate system to perturbations is estimated as about 5 years, in broad agreement with other recent estimates, and much shorter than the time constant for thermal equilibration of the deep ocean, about 500 years.

Schwartz S. E.

2012-05-04

215

Magnetic hyperthermia properties of nanoparticles inside lysosomes using kinetic Monte Carlo simulations: Influence of key parameters and dipolar interactions, and evidence for strong spatial variation of heating power  

NASA Astrophysics Data System (ADS)

Understanding the influence of dipolar interactions in magnetic hyperthermia experiments is of crucial importance for fine optimization of nanoparticle (NP) heating power. In this study we use a kinetic Monte Carlo algorithm to calculate hysteresis loops that correctly account for both time and temperature. This algorithm is shown to correctly reproduce the high-frequency hysteresis loop of both superparamagnetic and ferromagnetic NPs without any ad hoc or artificial parameters. The algorithm is easily parallelizable with a good speed-up behavior, which considerably decreases the calculation time on several processors and enables the study of assemblies of several thousands of NPs. The specific absorption rate (SAR) of magnetic NPs dispersed inside spherical lysosomes is studied as a function of several key parameters: volume concentration, applied magnetic field, lysosome size, NP diameter, and anisotropy. The influence of these parameters is illustrated and comprehensively explained. In summary, magnetic interactions increase the coercive field, saturation field, and hysteresis area of major loops. However, for small amplitude magnetic fields such as those used in magnetic hyperthermia, the heating power as a function of concentration can increase, decrease, or display a bell shape, depending on the relationship between the applied magnetic field and the coercive/saturation fields of the NPs. The hysteresis area is found to be well correlated with the parallel or antiparallel nature of the dipolar field acting on each particle. The heating power of a given NP is strongly influenced by a local concentration involving approximately 20 neighbors. Because this local concentration strongly decreases upon approaching the surface, the heating power increases or decreases in the vicinity of the lysosome membrane. The amplitude of variation reaches more than one order of magnitude in certain conditions. This transition occurs on a thickness corresponding to approximately 1.3 times the mean distance between two neighbors. The amplitude and sign of this variation is explained. Finally, implications of these various findings are discussed in the framework of magnetic hyperthermia optimization. It is concluded that feedback on two specific points from biology experiments is required for further advancement of the optimization of magnetic NPs for magnetic hyperthermia. The present simulations will be an advantageous tool to optimize magnetic NPs heating power and interpret experimental results.

Tan, R. P.; Carrey, J.; Respaud, M.

2014-12-01

216

Configuration-interaction-based time-dependent orbital approach for ab initio treatment of electronic dynamics in a strong optical laser field  

NASA Astrophysics Data System (ADS)

The time-dependent configuration interaction singles (TDCIS) method—an ab initio electronic-structure technique with predictive character—is reformulated in terms of an effective one-electron theory with coupled channels. In this form, the TDCIS equations of motion may be evaluated using standard wave-packet propagation techniques in real space. The time-dependent orbital formulation of TDCIS has computational and conceptual advantages for studying strong-field phenomena in many-electron systems. A simplified version of this theory, referred to as the determinantal single-active-electron (d-SAE) method, is derived. TDCIS and d-SAE are tested by their application to a one-dimensional two-electron model in a strong laser field. The numerically exact time-dependent dipole moment of the interacting system is found to be very well reproduced with TDCIS. The d-SAE method is less accurate, but still provides superior performance in comparison to the standard single-active-electron approach.

Rohringer, Nina; Gordon, Ariel; Santra, Robin

2006-10-01

217

Comparison of the strong-field ionization of N{sub 2} and F{sub 2}: A time-dependent density-functional-theory study  

SciTech Connect

We compare strong-field ionization probabilities of N{sub 2} and F{sub 2} molecules using time-dependent density functional theory calculations. Accurate nuclear potentials and ground vibrational wave functions are incorporated into our study. For both molecules, the effect of molecular vibration is small, while that of the molecular orientation is significant. When compared to the ionization probability of a molecule at the equilibrium geometry, we estimate the effect of the ground state vibration to be within 3% for N{sub 2} and within 6% for F{sub 2} in the intensity range from 1 to 5x10{sup 14} W/cm{sup 2}. The molecular-orientation-dependent ionization probabilities for both molecules at various intensities are presented. They are strongly dependent on the laser intensity, and the anisotropy diminishes when the laser intensity is high. For laser intensities of 1.6 and 2.2x10{sup 14} W/cm{sup 2} we find ionization probability ratios of 5.9 and 4.3, respectively, for the parallel versus perpendicular orientation of N{sub 2}. This is reasonably consistent with experimental measurements. For randomly oriented molecules, the ratio of the probabilities for N{sub 2} and F{sub 2} increases from about 1 at 10{sup 14} W/cm{sup 2} to 2 at 4x10{sup 14} W/cm{sup 2}, which agrees well with experimental results.

Chu Xi; McIntyre, Melissa [Department of Chemistry and Biochemistry, University of Montana, Missoula, Montana 59812 (United States)

2011-01-15

218

Statistical analyses of spatial and time dependence of lightning whistlers observed by VLF/WBA onboard AKEBONO  

NASA Astrophysics Data System (ADS)

AKEBONO (EXOS-D) has been continuously operated for more than 24 years since 1989 to observe particles and plasma waves in the auroral region and the plasmasphere. It covers altitude region from 300 km to about 10,000 km with an inclination of 75 degree. Therefore, analyses of the data obtained by AKEBONO enable us to study how the magnetosphere varies depending on the local time, season and solar activity. The WBA (Wide Band Analyzer) is one of subsystems of the VLF instruments onboard AKEBONO. It measures one component of electric or magnetic analogue waveform at frequency band of 50 Hz - 15 kHz. Lightning whistler is one of typical waves frequently observed by the WBA. It is generated by lightning discharge and propagates along the geomagnetic field lines from northern to southern hemisphere and vice-versa. Their dispersions depend on their path length and electron density profile along their propagation path. We have been developed an automatic detection system of lightning whistlers from the spectrogram of the WBA receiver. In the present study, we statistically analyzed the data received at Uchinoura Space Center from 1989 to 2005, and got spatial and time distribution of lightning whistlers by the system. First, we found that lightning whistlers were mainly observed only inside the plasmasphere with L-value below 4. Next, we studied MLT (Magnetic Local Time) and seasonal dependences of occurrence frequency of the lightning whistlers. It is noted that the coverage of MLT and season of the AKEBONO orbit changes simultaneously, but we could successfully identified the MLT and seasonal dependences separately analyzing the long term observation data. Consequently lightning whistlers were mainly observed in the night-side (from 16 to 4 in MLT), while their occurrence frequency becomes quite small in the dayside (from 7 to 15 in MLT). Presumably this is caused by the condition of the ionosphere. In the dayside, it is difficult for whistler-mode wave to propagate into the plasmasphere but it can easily propagate in the night-side. About the seasonal dependence, we found two peaks of occurrence frequency of lightning whistlers. One is from December to January and another is from June to July. The source of lightning whistler is lightning discharge, whose occurrence frequency is known to become maximum in summer. Thus we can find two peaks of occurrence frequency which correspond to the lightning whistlers propagating from summer hemisphere to winter hemisphere. As a future work, we will study solar activity dependence of lightning whistlers. By normalizing the bias caused by MLT and seasonal dependences of lightning whistler based on the results derived in the present study, it is expected to clarify the solar activity dependence independent of the MLT and seasonal variation. It is also interesting to estimate the electron density profile using trends of whistler dispersion. The propagation time of whistler mode wave can be theoretically calculated using ray tracing technique under assumption of electron density profile model. By comparing the observed trends of dispersion along the AKEBONO trajectories with those theoretically derived, we can determine an appropriate electron density profile, and we can know the time variation of the electron density profile in the plasmasphere statistically.

Oike, Y.; Kasahara, Y.; Goto, Y.

2013-12-01

219

Strong electron correlation effects on first- and second-order hyperpolarizabilities in zwitterionic sigma-conjugated systems: its dependence on substituents, conformations, spacer size, and basis sets.  

PubMed

Nonlinear optical properties of zwitterionic sigma-conjugated systems were theoretically investigated with relation to the electron correlation effects at the ab initio molecular orbital level. We examined the strong electron correlation effects on the first- and second-order hyperpolarizabilities in the specific systems with effective "pi-sigma-pi" and (or) "pi-sigma-n" interactions. The electron correlation effects on the hyperpolarizabilities strongly depend on the type of substituents, conformations, spacer size, and basis sets. It was found that the Hartree-Fock level calculations qualitatively predict the behavior of the hyperpolarizabilities after considering the correlation effects. Through-space/-bond interaction analysis quantitatively revealed that the electron correlation effects on the hyperpolarizabilities were induced mainly by the sigma-conjugations on the spacer unit in the zwitterionic sigma-systems. PMID:17665881

Orimoto, Yuuichi; Aoki, Yuriko

2007-08-23

220

Observation of a strong inverse temperature dependence for the opacity of atmospheric water vapor in the mm continuum near 280 GHz  

NASA Technical Reports Server (NTRS)

Results are presented of the field measurements of atmospheric opacity at 278 GHz (9.3/cm) conducted at the McMurdo Station (Antarctica) during the austral springs of 1986 and 1987, in conjunction with balloon measurements of water vapor profile and total column density, showing a strong inverse temperature dependence when normalized to precipitable water vapor. The value of measured opacity per mm of precipitable water vapor (PWV) is roughly two times greater at -35 C than at -10 C and three times greater than measurements at +25 C reported by Zammit and Ade (1981). Various theories proposed to explain excess absorption in continuum regions are reviewed.

Emmons, Louisa K.; De Zafra, Robert L.

1990-01-01

221

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

222

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

SciTech Connect

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.

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

2011-09-16

223

Strong pressure dependence of the magnetic penetration depth in single crystals of the heavy-fermion superconductor CeCoIn5 studied by muon spin rotation.  

PubMed

In the tetragonal heavy fermion system CeCoIn(5) the unconventional superconducting state is probed by means of muon spin rotation. The pressure dependence (0-1 GPa) of the basal-plane magnetic penetration depth (?(a)), the penetration depth anisotropy (? = ?(c)/?(a)) and the temperature dependence of 1/?(i)(2) (i = a, c) were studied in single crystals. A strong decrease of ?(a) with pressure was observed, while ? and ?(i)(2)(0)/?(i)(2)(T) are pressure independent. A linear relationship between 1/?(a)(2)(270 mK) and T(c) was also found. The large decrease of ?(a) with pressure is the signature of an increase of the number of superconducting quasiparticles by a factor of about 2. PMID:23383830

Howald, L; Maisuradze, A; de Réotier, P Dalmas; Yaouanc, A; Baines, C; Lapertot, G; Mony, K; Brison, J-P; Keller, H

2013-01-01

224

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

- vorable state. The measurement of strain-dependent coercivity Strong strain dependence of ferroelectric coercivity in a BiFeO3 film M. D. Biegalski, D. H. Kim, S subject to AIP license or copyright; see http://apl.aip.org/about/rights_and_permissions #12;Strong strain

Chen, Long-Qing

225

The roles of scene gist and spatial dependency among objects in the semantic guidance of attention in real-world scenes.  

PubMed

A previous study (Vision Research 51 (2011) 1192-1205) found evidence for semantic guidance of visual attention during the inspection of real-world scenes, i.e., an influence of semantic relationships among scene objects on overt shifts of attention. In particular, the results revealed an observer bias toward gaze transitions between semantically similar objects. However, this effect is not necessarily indicative of semantic processing of individual objects but may be mediated by knowledge of the scene gist, which does not require object recognition, or by known spatial dependency among objects. To examine the mechanisms underlying semantic guidance, in the present study, participants were asked to view a series of displays with the scene gist excluded and spatial dependency varied. Our results show that spatial dependency among objects seems to be sufficient to induce semantic guidance. Scene gist, on the other hand, does not seem to affect how observers use semantic information to guide attention while viewing natural scenes. Extracting semantic information mainly based on spatial dependency may be an efficient strategy of the visual system that only adds little cognitive load to the viewing task. PMID:25199610

Wu, Chia-Chien; Wang, Hsueh-Cheng; Pomplun, Marc

2014-12-01

226

Low levels of realized seed and pollen gene flow and strong spatial genetic structure in a small, isolated and fragmented population of the tropical tree Copaifera langsdorffii Desf  

Microsoft Academic Search

Over the past century, the Brazilian Atlantic forest has been reduced to small, isolated fragments of forest. Reproductive isolation theories predict a loss of genetic diversity and increases in inbreeding and spatial genetic structure (SGS) in such populations. We analysed eight microsatellite loci to investigate the pollen and seed dispersal patterns, genetic diversity, inbreeding and SGS of the tropical tree

A M Sebbenn; A C M Carvalho; M L M Freitas; S M B Moraes; A P S C Gaino; J M da Silva; C Jolivet; M L T Moraes

2011-01-01

227

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

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.

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

2006-06-01

228

Time-integrated and time-dependent angular analyses of B?J/?K?: A measurement of cos(2? with no sign ambiguity from strong phases  

NASA Astrophysics Data System (ADS)

We present results on B?J/?K? decays using e+e-annihilation data collected with the BABAR detector at the ?(4S) resonance. The detector is located at the PEP-II asymmetric-energy storage ring facility at the Stanford Linear Accelerator Center. Using approximately 88×106 BB¯ pairs, we measure the decay amplitudes for the flavor eigenmodes and observe strong-phase differences indicative of final-state interactions with a significance of 7.6 standard deviations. We use the interference between the K? S-wave and P-wave amplitudes in the region of the K*(892) to resolve the ambiguity in the determination of these strong phases. We then perform an ambiguity-free measurement of cos(2? using the angular and time-dependent asymmetry in B?J/?K*0(K0S?0) decays. With sin(2? fixed at its measured value and cos(2? treated as an independent parameter, we find cos(2?=2.72+0.50-0.79(stat)±0.27(syst), determining the sign of cos(2? to be positive at 86% C.L.

Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Gaillard, J.-M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Tisserand, V.; Zghiche, A.; Palano, A.; Pompili, A.; Chen, J. C.; Qi, N. D.; Rong, G.; Wang, P.; Zhu, Y. S.; Eigen, G.; Ofte, I.; Stugu, B.; Abrams, G. S.; Borgland, A. W.; Breon, A. B.; Brown, D. N.; Button-Shafer, J.; Cahn, R. N.; Charles, E.; Day, C. T.; Gill, M. S.; Gritsan, A. V.; Groysman, Y.; Jacobsen, R. G.; Kadel, R. W.; Kadyk, J.; Kerth, L. T.; Kolomensky, Yu. G.; Kukartsev, G.; Lynch, G.; Mir, L. M.; Oddone, P. J.; Orimoto, T. J.; Pripstein, M.; Roe, N. A.; Ronan, M. T.; Shelkov, V. G.; Wenzel, W. A.; Barrett, M.; Ford, K. E.; Harrison, T. J.; Hart, A. J.; Hawkes, C. M.; Morgan, S. E.; Watson, A. T.; Fritsch, M.; Goetzen, K.; Held, T.; Koch, H.; Lewandowski, B.; Pelizaeus, M.; Steinke, M.; Boyd, J. T.; Chevalier, N.; Cottingham, W. N.; Kelly, M. P.; Latham, T. E.; Wilson, F. F.; Cuhadar-Donszelmann, T.; Hearty, C.; Knecht, N. S.; Mattison, T. S.; McKenna, J. A.; Thiessen, D.; Khan, A.; Kyberd, P.; Teodorescu, L.; Blinov, A. E.; Blinov, V. E.; Druzhinin, V. P.; Golubev, V. B.; Ivanchenko, V. N.; Kravchenko, E. A.; Onuchin, A. P.; Serednyakov, S. I.; Skovpen, Yu. I.; Solodov, E. P.; Yushkov, A. N.; Best, D.; Bruinsma, M.; Chao, M.; Eschrich, I.; Kirkby, D.; Lankford, A. J.; Mandelkern, M.; Mommsen, R. K.; Roethel, W.; Stoker, D. P.; Buchanan, C.; Hartfiel, B. L.; Foulkes, S. D.; Gary, J. W.; Shen, B. C.; Wang, K.; del Re, D.; Hadavand, H. K.; Hill, E. J.; Macfarlane, D. B.; Paar, H. P.; Rahatlou, Sh.; Sharma, V.; Cunha, J. Adam; Berryhill, J. W.; Campagnari, C.; Dahmes, B.; Hong, T. M.; Long, O.; Lu, A.; Mazur, M. A.; Richman, J. D.; Verkerke, W.; Beck, T. W.; Eisner, A. M.; Heusch, C. A.; Kroseberg, J.; Lockman, W. S.; Nesom, G.; Schalk, T.; Schumm, B. A.; Seiden, A.; Spradlin, P.; Williams, D. C.; Wilson, M. G.; Albert, J.; Chen, E.; Dubois-Felsmann, G. P.; Dvoretskii, A.; Hitlin, D. G.; Narsky, I.; Piatenko, T.; Porter, F. C.; Ryd, A.; Samuel, A.; Yang, S.; Jayatilleke, S.; Mancinelli, G.; Meadows, B. T.; Sokoloff, M. D.; Blanc, F.; Bloom, P.; Chen, S.; Ford, W. T.; Nauenberg, U.; Olivas, A.; Rankin, P.; Smith, J. G.; Zhang, J.; Zhang, L.; Chen, A.; Harton, J. L.; Soffer, A.; Toki, W. H.; Wilson, R. J.; Zeng, Q.; Altenburg, D.; Brandt, T.; Brose, J.; Dickopp, M.; Feltresi, E.; Hauke, A.; Lacker, H. M.; Müller-Pfefferkorn, R.; Nogowski, R.; Otto, S.; Petzold, A.; Schubert, J.; Schubert, K. R.; Schwierz, R.; Spaan, B.; Sundermann, J. E.; Bernard, D.; Bonneaud, G. R.; Brochard, F.; Grenier, P.; Schrenk, S.; Thiebaux, Ch.; Vasileiadis, G.; Verderi, M.; Bard, D. J.; Clark, P. J.; Lavin, D.; Muheim, F.; Playfer, S.; Xie, Y.; Andreotti, M.; Azzolini, V.; Bettoni, D.; Bozzi, C.; Calabrese, R.; Cibinetto, G.; Luppi, E.; Negrini, M.; Piemontese, L.; Sarti, A.; Treadwell, E.; Anulli, F.; Baldini-Ferroli, R.; Calcaterra, A.; de Sangro, R.; Finocchiaro, G.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Zallo, A.; Buzzo, A.; Capra, R.; Contri, R.; Crosetti, G.; Vetere, M. Lo; Macri, M.; Monge, M. R.; Passaggio, S.; Patrignani, C.; Robutti, E.; Santroni, A.; Tosi, S.; Bailey, S.; Brandenburg, G.; Chaisanguanthum, K. S.; Morii, M.; Won, E.; Dubitzky, R. S.; Langenegger, U.; Marks, J.; Uwer, U.; Bhimji, W.; Bowerman, D. A.; Dauncey, P. D.; Egede, U.; Gaillard, J. R.; Morton, G. W.; Nash, J. A.; Nikolich, M. B.; Taylor, G. P.; Charles, M. J.; Grenier, G. J.; Mallik, U.; Cochran, J.; Crawley, H. B.; Lamsa, J.; Meyer, W. T.; Prell, S.; Rosenberg, E. I.; Rubin, A. E.; Yi, J.; Biasini, M.; Covarelli, R.; Pioppi, M.; Davier, M.; Giroux, X.; Grosdidier, G.; Höcker, A.; Laplace, S.; Le Diberder, F.; Lepeltier, V.; Lutz, A. M.; Petersen, T. C.; Plaszczynski, S.; Schune, M. H.; Tantot, L.; Wormser, G.; Cheng, C. H.; Lange, D. J.; Simani, M. C.; Wright, D. M.; Bevan, A. J.; Chavez, C. A.; Coleman, J. P.; Forster, I. J.; Fry, J. R.; Gabathuler, E.; Gamet, R.; Hutchcroft, D. E.; Parry, R. J.; Payne, D. J.; Sloane, R. J.; Touramanis, C.; Cormack, C. M.; Di Lodovico, F.; Brown, C. L.; Cowan, G.; Flack, R. L.; Flaecher, H. U.; Green, M. G.; Jackson, P. S.; McMahon, T. R.; Ricciardi, S.; Salvatore, F.; Winter, M. A.; Brown, D.; Davis, C. L.; Allison, J.; Barlow, N. R.; Barlow, R. J.; Hodgkinson, M. C.; Lafferty, G. D.; Lyon, A. J.; Williams, J. C.; Farbin, A.; Hulsbergen, W. D.; Jawahery, A.; Kovalskyi, D.; Lae, C. K.; Lillard, V.; Roberts, D. A.; Blaylock, G.; Dallapiccola, C.; Hertzbach, S. S.; Kofler, R.; Koptchev, V. B.; Moore, T. B.; Saremi, S.; Staengle, H.; Willocq, S.; Cowan, R.; Sciolla, G.; Sekula, S. J.; Taylor, F.; Yamamoto, R. K.; Mangeol, D. J.; Patel, P. M.; Robertson, S. H.; Lazzaro, A.; Lombardo, V.; Palombo, F.; Bauer, J. M.; Cremaldi, L.; Eschenburg, V.; Godang, R.; Kroeger, R.

2005-02-01

229

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

SciTech Connect

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.

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

230

CLASSSTRONG: Classical simulations of strong field processes  

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

231

CaMKII-dependent dendrite ramification and spine generation promote spatial training-induced memory improvement in a rat model of sporadic Alzheimer's disease.  

PubMed

Participation in cognitively stimulating activities can preserve memory capacities in patients with Alzheimer's disease (AD), but the mechanism is not fully understood. Here, we used a rat model with hyperhomocysteinemia, an independent risk factor of AD, to study whether spatial training could remodel the synaptic and/or dendritic plasticity and the key molecular target(s) involved. We found that spatial training in water maze remarkably improved the subsequent short-term and long-term memory performance in contextual fear conditioning and Barnes maze. The trained rats showed an enhanced dendrite ramification, spine generation and plasticity in dentate gyrus (DG) neurons, and stimulation of long-term potentiation between perforant path and DG circuit. Spatial training also increased the levels of postsynaptic GluA1, GluN2A, GluN2B, and PSD93 with selective activation of calcium/calmodulin-dependent protein kinase II (CaMKII), although inhibition of CaMKII by stereotaxic injection of KN93 into hippocampal DG, abolished the training-induced cognitive improvement, dendrite ramification, and spine generation. We conclude that spatial training can preserve the cognitive function by CaMKII-dependent remodeling of dendritic plasticity in hyperhomocysteinemia-induced sporadic AD-like rats. PMID:25457025

Jiang, Xia; Chai, Gao-Shang; Wang, Zhi-Hao; Hu, Yu; Li, Xiao-Guang; Ma, Zhi-Wei; Wang, Qun; Wang, Jian-Zhi; Liu, Gong-Ping

2014-10-16

232

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

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

Micha? Malinga; Piotr Szefer; Geir W. Gabrielsen

2010-01-01

233

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

Microsoft Academic Search

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

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

2002-01-01

234

Low levels of realized seed and pollen gene flow and strong spatial genetic structure in a small, isolated and fragmented population of the tropical tree Copaifera langsdorffii Desf  

PubMed Central

Over the past century, the Brazilian Atlantic forest has been reduced to small, isolated fragments of forest. Reproductive isolation theories predict a loss of genetic diversity and increases in inbreeding and spatial genetic structure (SGS) in such populations. We analysed eight microsatellite loci to investigate the pollen and seed dispersal patterns, genetic diversity, inbreeding and SGS of the tropical tree Copaifera langsdorffii in a small (4.8?ha), isolated population. All 112 adult trees and 128 seedlings found in the stand were sampled, mapped and genotyped. Seedlings had significantly lower levels of genetic diversity (A=16.5±0.45, mean±95% s.e.; He=0.838±0.006) than did adult trees (A=23.2±0.81; He=0.893±0.030). Parentage analysis did not indicate any seed immigration (mseeds=0) and the pollen immigration rate was very low (mpollen=0.047). The average distance of realized pollen dispersal within the stand was 94?m, with 81% of the pollen travelling <150?m. A significant negative correlation was found between the frequency and distance of pollen dispersal (r=?0.79, P<0.01), indicating that short-distance pollinations were more frequent. A significant SGS for both adults (?50?m) and seedlings (?20?m) was also found, indicating that most of the seeds were dispersed over short distances. The results suggested that the spatial isolation of populations by habitat fragmentation can restrict seed and pollen gene flow, increase SGS and affect the genetic diversity of future generations. PMID:20372183

Sebbenn, A M; Carvalho, A C M; Freitas, M L M; Moraes, S M B; Gaino, A P S C; da Silva, J M; Jolivet, C; Moraes, M L T

2011-01-01

235

Spatial variability of nitrous oxide and methane emissions from an MBT landfill in operation: Strong N{sub 2}O hotspots at the working face  

SciTech Connect

Highlights: ? First measurements of N{sub 2}O and CH{sub 4} emissions from an MBT landfill. ? High N{sub 2}O emissions from recently deposited material. ? N{sub 2}O emissions associated with aeration and the occurrence of nitrite and nitrate. ? Strong negative correlation between CH{sub 4} and N{sub 2}O production activity. - Abstract: Mechanical biological treatment (MBT) is an effective technique, which removes organic carbon from municipal solid waste (MSW) prior to deposition. Thereby, methane (CH{sub 4}) production in the landfill is strongly mitigated. However, direct measurements of greenhouse gas emissions from full-scale MBT landfills have not been conducted so far. Thus, CH{sub 4} and nitrous oxide (N{sub 2}O) emissions from a German MBT landfill in operation as well as their concentrations in the landfill gas (LFG) were measured. High N{sub 2}O emissions of 20–200 g CO{sub 2} eq. m{sup ?2} h{sup ?1} magnitude (up to 428 mg N m{sup ?2} h{sup ?1}) were observed within 20 m of the working face. CH{sub 4} emissions were highest at the landfill zone located at a distance of 30–40 m from the working face, where they reached about 10 g CO{sub 2} eq. m{sup ?2} h{sup ?1}. The MBT material in this area has been deposited several weeks earlier. Maximum LFG concentration for N{sub 2}O was 24.000 ppmv in material below the emission hotspot. At a depth of 50 cm from the landfill surface a strong negative correlation between N{sub 2}O and CH{sub 4} concentrations was observed. From this and from the distribution pattern of extractable ammonium, nitrite, and nitrate it has been concluded that strong N{sub 2}O production is associated with nitrification activity and the occurrence of nitrite and nitrate, which is initiated by oxygen input during waste deposition. Therefore, CH{sub 4} mitigation measures, which often employ aeration, could result in a net increase of GHG emissions due to increased N{sub 2}O emissions, especially at MBT landfills.

Harborth, Peter, E-mail: p.harborth@tu-bs.de [Department of Waste and Resource Management, Leichtweiß-Institute for Hydraulic Engineering and Water Resources, Technische Universität Braunschweig, Braunschweig (Germany); Fuß, Roland [Institute of Climate-Smart Agriculture, Johann Heinrich von Thünen Institute, Braunschweig (Germany); Münnich, Kai [Department of Waste and Resource Management, Leichtweiß-Institute for Hydraulic Engineering and Water Resources, Technische Universität Braunschweig, Braunschweig (Germany); Flessa, Heinz [Institute of Climate-Smart Agriculture, Johann Heinrich von Thünen Institute, Braunschweig (Germany); Fricke, Klaus [Department of Waste and Resource Management, Leichtweiß-Institute for Hydraulic Engineering and Water Resources, Technische Universität Braunschweig, Braunschweig (Germany)

2013-10-15

236

Behavioral assessment of emotional and motivational appraisal during visual processing of emotional scenes depending on spatial frequencies.  

PubMed

Previous studies performed on visual processing of emotional stimuli have revealed preference for a specific type of visual spatial frequencies (high spatial frequency, HSF; low spatial frequency, LSF) according to task demands. The majority of studies used a face and focused on the appraisal of the emotional state of others. The present behavioral study investigates the relative role of spatial frequencies on processing emotional natural scenes during two explicit cognitive appraisal tasks, one emotional, based on the self-emotional experience and one motivational, based on the tendency to action. Our results suggest that HSF information was the most relevant to rapidly identify the self-emotional experience (unpleasant, pleasant, and neutral) while LSF was required to rapidly identify the tendency to action (avoidance, approach, and no action). The tendency to action based on LSF analysis showed a priority for unpleasant stimuli whereas the identification of emotional experience based on HSF analysis showed a priority for pleasant stimuli. The present study confirms the interest of considering both emotional and motivational characteristics of visual stimuli. PMID:23954668

Fradcourt, B; Peyrin, C; Baciu, M; Campagne, A

2013-10-01

237

Foraging behavior of field populations of Diadegma spp. (Hymenoptera: Ichneumonidae): testing for density-dependence at two spatial scales  

Technology Transfer Automated Retrieval System (TEKTRAN)

The foraging behavior of populations of Diadegma sp. (Hymenoptera: Ichneumonidae) attacking the diamondback moth, Plutella xylostella L. (Lepidoptera: Pyralidae) was studied in the field. The effect of host density on percentage parasitism was investigated at two spatial scales: that of the individu...

238

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

PubMed

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

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

2014-08-01

239

Speech cues contribute to audiovisual spatial integration.  

PubMed

Speech is the most important form of human communication but ambient sounds and competing talkers often degrade its acoustics. Fortunately the brain can use visual information, especially its highly precise spatial information, to improve speech comprehension in noisy environments. Previous studies have demonstrated that audiovisual integration depends strongly on spatiotemporal factors. However, some integrative phenomena such as McGurk interference persist even with gross spatial disparities, suggesting that spatial alignment is not necessary for robust integration of audiovisual place-of-articulation cues. It is therefore unclear how speech-cues interact with audiovisual spatial integration mechanisms. Here, we combine two well established psychophysical phenomena, the McGurk effect and the ventriloquist's illusion, to explore this dependency. Our results demonstrate that conflicting spatial cues may not interfere with audiovisual integration of speech, but conflicting speech-cues can impede integration in space. This suggests a direct but asymmetrical influence between ventral 'what' and dorsal 'where' pathways. PMID:21909378

Bishop, Christopher W; Miller, Lee M

2011-01-01

240

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)

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.

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

2014-03-01

241

Glucuronidation converts clopidogrel to a strong time-dependent inhibitor of CYP2C8: a phase II metabolite as a perpetrator of drug-drug interactions.  

PubMed

Cerivastatin and repaglinide are substrates of cytochrome P450 (CYP)2C8, CYP3A4, and organic anion-transporting polypeptide (OATP)1B1. A recent study revealed an increased risk of rhabdomyolysis in patients using cerivastatin with clopidogrel, warranting further studies on clopidogrel interactions. In healthy volunteers, repaglinide area under the concentration-time curve (AUC(0-?)) was increased 5.1-fold by a 300-mg loading dose of clopidogrel and 3.9-fold by continued administration of 75?mg clopidogrel daily. In vitro, we identified clopidogrel acyl-?-D-glucuronide as a potent time-dependent inhibitor of CYP2C8. A physiologically based pharmacokinetic model indicated that inactivation of CYP2C8 by clopidogrel acyl-?-D-glucuronide leads to uninterrupted 60-85% inhibition of CYP2C8 during daily clopidogrel treatment. Computational modeling resulted in docking of clopidogrel acyl-?-D-glucuronide at the CYP2C8 active site with its thiophene moiety close to heme. The results indicate that clopidogrel is a strong CYP2C8 inhibitor via its acyl-?-D-glucuronide and imply that glucuronide metabolites should be considered potential inhibitors of CYP enzymes. PMID:24971633

Tornio, A; Filppula, A M; Kailari, O; Neuvonen, M; Nyrönen, T H; Tapaninen, T; Neuvonen, P J; Niemi, M; Backman, J T

2014-10-01

242

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

PubMed Central

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

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

2013-01-01

243

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

PubMed

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

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

2014-11-01

244

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

PubMed

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

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

2010-04-01

245

Endogenous Proteolytic Cleavage of Disease-associated Prion Protein to Produce C2 Fragments Is Strongly Cell- and Tissue-dependent*  

PubMed Central

The abnormally folded form of the prion protein (PrPSc) 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 PrPSc 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, PrPSc 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 PrPSc 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 PrPSc 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 PrPSc and cell pathogenesis of prion infection. PMID:20154089

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

2010-01-01

246

Full energy expression of a uniaxial nematic phase with spatially dependent density and order parameters: From microscopic to macroscopic theory  

NASA Astrophysics Data System (ADS)

We present a microscopic derivation of the full macroscopic energy expression of a spatially bounded uniaxial nematic phase. The surface is described by spatial variations of the density and scalar order parameters of all even orders. The method developed in the paper allowed us to unambiguously separate the surface elastic K24 and K13 terms and isotropic and anisotropic surface tension (anchoring). The full energy expression incorporating variations of the director, scalar order parameters, and density is obtained. The macroscopic coefficients are derived in terms of the isotropic and anisotropic fractions of the microscopic intermolecular interaction. An important physical consequence of the obtained formulas, in particular, is that the observed considerable difference K33-K11 between the bend and splay elastic constants unambiguously indicates that (i) the intermolecular interaction has a large anisotropic fraction, and thus, the effective constant K13 and intrinsic anchoring are considerable; (ii) at least some scalar order parameters of order four and higher are essentially nonzero. Relation of the developed theory with the Nehring-Saupe theory and Landau-de Gennes approach is considered.

Pergamenshchik, V. M.; Chernyshuk, S. B.

2002-11-01

247

Quantitative spatial comparison of diffuse optical imaging with blood oxygen level-dependent and arterial spin labeling-based functional magnetic resonance imaging  

PubMed Central

Akin to functional magnetic resonance imaging (fMRI), diffuse optical imaging (DOI) is a noninvasive method for measuring localized changes in hemoglobin levels within the brain. When combined with fMRI methods, multimodality approaches could offer an integrated perspective on the biophysics, anatomy, and physiology underlying each of the imaging modalities. Vital to the correct interpretation of such studies, control experiments to test the consistency of both modalities must be performed. Here, we compare DOI with blood oxygen level-dependent (BOLD) and arterial spin labeling fMRI-based methods in order to explore the spatial agreement of the response amplitudes recorded by these two methods. Rather than creating optical images by regularized, tomographic reconstructions, we project the fMRI image into optical measurement space using the optical forward problem. We report statistically better spatial correlation between the fMRI-BOLD response and the optically measured deoxyhemoglobin (R=0.71, p=1 × 10?7) than between the BOLD and oxyhemoglobin or total hemoglobin measures (R=0.38, p=0.04|0.37, p=0.05, respectively). Similarly, we find that the correlation between the ASL measured blood flow and optically measured total and oxyhemoglobin is stronger (R=0.73, p=5 × 10?6 and R=0.71, p=9 × 10?6, respectively) than the flow to deoxyhemoglobin spatial correlation (R=0.26, p=0.10). PMID:17212541

Huppert, Theodore J.; Hoge, Rick D.; Dale, Anders M.; Franceschini, Maria A.; Boas, David A.

2009-01-01

248

Spatial scale-dependent habitat heterogeneity influences submarine canyon macrofaunal abundance and diversity off the Main and Northwest Hawaiian Islands  

NASA Astrophysics Data System (ADS)

The mapping of biodiversity on continental margins on landscape scales is highly relevant to marine spatial planning and conservation. Submarine canyons are widespread topographic features on continental and island margins that enhance benthic biomass across a range of oceanic provinces and productivity regimes. However, it remains unclear whether canyons enhance faunal biodiversity on landscape scales relevant to marine protected area (MPA) design. Furthermore, it is not known which physical attributes and heterogeneity metrics can provide good surrogates for large-scale mapping of canyon benthic biodiversity. To test mechanistic hypotheses evaluating the role of different canyon-landscape attributes in enhancing benthic biodiversity at different spatial scales we conducted 34 submersible dives in six submarine canyons and nearby slopes in the Hawaiian archipelago, sampling infaunal macrobenthos in a depth-stratified sampling design. We employed multivariate multiple regression models to evaluate sediment and topographic heterogeneity, canyon transverse profiles, and overall water mass variability as potential drivers of macrobenthic community structure and species richness. We find that variables related to habitat heterogeneity at medium (0.13 km2) and large (15-33 km2) spatial scales such as slope, backscatter reflectivity and canyon transverse profiles are often good predictors of macrobenthic biodiversity, explaining 16-30% of the variance. Particulate organic carbon (POC) flux and distance from shore are also important variables, implicating food supply as a major predictor of canyon biodiversity. Canyons off the high Main Hawaiian Islands (Oahu and Moloka'i) are significantly affected by organic enrichment, showing enhanced infaunal macrobenthos abundance, whereas this effect is imperceptible around the low Northwest Hawaiian Islands (Nihoa and Maro Reef). Variable canyon alpha-diversity and high rates of species turnover (beta-diversity), particularly for polychaetes, suggest that canyons play important roles in maintaining high levels of regional biodiversity in the extremely oligotrophic system of the North Pacific Subtropical Gyre. This information is of key importance to the process of MPA design, suggesting that canyon habitats be explicitly included in marine spatial planning. The low-islands of Nihoa and Maro Reef in the NWHI showed a lack of sustained input of terrestrial and macrolagae detritus, likely having an influence on the observed low macrofaunal abundances (see further discussion of ‘canyon effects’ in Section 4.3), and showing the fundamental role of coastal landscape characteristics in determining the amount and nature of allochthonous organic matter entering the system. Total and highly-mobile invertebrate megafauna abundances were two to three times higher in the submarine canyons and slopes of the MHI contrasted with the NWHI (Vetter et al., 2010), also demonstrating the role of this larger contribution of terrestrial and coastal organic enrichment in the MHI contrasted with the NWHI.

De Leo, Fabio C.; Vetter, Eric W.; Smith, Craig R.; Rowden, Ashley A.; McGranaghan, Matthew

2014-06-01

249

Seismicity on a fault controlled by rate- and state-dependent friction with spatial variations of the critical slip distance  

NASA Astrophysics Data System (ADS)

We perform systematic simulations of slip using a quasi-dynamic continuum model of a two-dimensional (2-D) strike-slip fault governed by rate- and state-dependent friction. The depth dependence of the a - b and L frictional parameters are treated in an innovative way that is consistent with available laboratory data and multidisciplinary field observations. Various realizations of heterogeneous L distributions are used to study effects of structural variations of fault zones on spatiotemporal evolution of slip. We demonstrate that such realizations can produce within the continuum class of models realistic features of seismicity and slip distributions on a fault. We explore effects of three types of variable L distributions: (1) a depth-dependent L profile accounting for the variable width of fault zones with depth, (2) uncorrelated 2-D random distributions of L with different degrees of heterogeneity, and (3) a hybrid distribution combining the depth-dependent L profile with the 2-D random L distributions. The first type of L distribution, with relatively small L over the depth range corresponding to the seismogenic zone and larger L elsewhere, generates stick-slip events in the seismogenic zone and ongoing creep above and below that region. The 2-D heterogeneous parameterizations generate frequency-size statistics with event sizes spanning 4 orders of magnitude. Our results indicate that different degrees of heterogeneity of L distributions control (1) the number of simulated events and (2) the overall stress level and fluctuations. Other observable trends are (3) the dependency of hypocenter location on L and (4) different nucleation phases for small and large events in heterogeneous distributions.

Hillers, G.; Ben-Zion, Y.; Mai, P. M.

2006-01-01

250

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

PubMed

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

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

251

Conflict of spatial development and water supply under climate change in case of water dependent ecosystem of Ljubljana Moor  

NASA Astrophysics Data System (ADS)

Water resources are vulnerable to climate change and to many other socio-economic drivers of change. A key aspect of vulnerability is that it is spatially variable, reflecting variations of physical and socio-economic conditions. Given the real representation of vulnerability and a set of climate change adaptation options there is need to develop a common transnational strategy for vulnerability reduction. The latter is the goal of SEE CC-WARE project. Among others, ecosystem services, land use change, improving water use efficiency and economic incentives for water management have large potentials to decrease water resources vulnerability. Especially, forests, wetlands and grasslands are important ecosystems, which together with their management emerged as an important means for a sustainable future drinking water supply. The Ljubljana Moor is one of the biggest and most important complexes of wet meadows in Slovenia, which have, due to land use high biodiversity. The Ljubljana Moor extends from the southern part of Ljubljana, the capital of Slovenia, where in the last two centuries extensive irrigation and river regulation projects were implemented to develop agricultural land. Biodiversity of the area is high due to large zones of wet meadows, some flood forest patches, bog areas, and open water courses habitats. The Ljubljana Moor is therefore protected as Natura 2000 site. The Ljubljana Moor is changing very fast and impacts are especially intense in the present years, mostly due to spreading of urbanization and monocultures. In this area the water well field Brest has been designed as important future drinking water source for Ljubljana, pumping mainly water from confined aquifer. The pressure from urbanisation and agriculture and high subsidence that are noticed in the central and eastern part of the aquifer, those two phenomena pose high risk to stable drinking water supply and wetland habitats that are protected as NATURA 2000. Water protection areas with limitation of land use were delineated for protection of drinking water from Brest pumping station. A part of Ljubljana Moor area is also protected as Landscape Park. These legal acts are in conflict with existing agricultural practices, spatial development plans and further urbanisation processes (including new and larger roads, flood areas disconnections and destruction). No attention has been given yet to integrated water management and there is no consideration of long term hydrological and hydrogeological processes.

Bra?i? Železnik, Branka; Souvent, Petra; ?en?ur Curk, Barbara

2013-04-01

252

Using Multivariate Geostatistics to Assess Patterns of Spatial Dependence of Apparent Soil Electrical Conductivity and Selected Soil Properties  

PubMed Central

The apparent soil electrical conductivity (ECa) was continuously recorded in three successive dates using electromagnetic induction in horizontal (ECa-H) and vertical (ECa-V) dipole modes at a 6 ha plot located in Northwestern Spain. One of the ECa data sets was used to devise an optimized sampling scheme consisting of 40 points. Soil was sampled at the 0.0–0.3?m depth, in these 40 points, and analyzed for sand, silt, and clay content; gravimetric water content; and electrical conductivity of saturated soil paste. Coefficients of correlation between ECa and gravimetric soil water content (0.685 for ECa-V and 0.649 for ECa-H) were higher than those between ECa and clay content (ranging from 0.197 to 0.495, when different ECa recording dates were taken into account). Ordinary and universal kriging have been used to assess the patterns of spatial variability of the ECa data sets recorded at successive dates and the analyzed soil properties. Ordinary and universal cokriging methods have improved the estimation of gravimetric soil water content using the data of ECa as secondary variable with respect to the use of ordinary kriging. PMID:25614893

Siqueira, Glécio Machado; Dafonte, Jorge Dafonte; Valcárcel Armesto, Montserrat; Silva, Ênio Farias França e

2014-01-01

253

MinD-dependent conformational changes in MinE required for the Min oscillator to spatially regulate cytokinesis  

PubMed Central

Summary MinD recruits MinE to the membrane leading to a coupled oscillation required for spatial regulation of the cytokinetic Z ring in E. coli. How these proteins interact, however, is not clear since the MinD binding regions of MinE are sequestered within a 6-stranded ?-sheet and masked by N-terminal helices. Here, minE mutations are isolated that restore interaction to some MinD and MinE mutants. These mutations alter the MinE structure releasing the MinD binding regions and N-terminal helices that bind MinD and the membrane, respectively. Crystallization of MinD-MinE complexes reveals a 4-stranded ?-sheet MinE dimer with the released ? strands (MinD binding regions) converted to ?-helices bound to MinD dimers. These results suggest a 6 stranded, ?-sheet dimer of MinE ‘senses’ MinD and switches to a 4-stranded ?-sheet dimer that binds MinD and contributes to membrane binding. Also, the results indicate how MinE persists at the MinD-membrane surface. PMID:21816275

Park, Kyung-Tae; Wu, Wei; Battaile, Kevin P.; Lovell, Scott; Holyoak, Todd; Lutkenhaus, Joe

2011-01-01

254

Impaired hippocampus-dependent spatial flexibility and sociability represent autism-like phenotypes in GluK2 mice.  

PubMed

Autism is a complex neurodevelopmental disorder with high heritability. grik2 (which encodes the GluK2 subunit of kainate receptors) has been identified as a susceptibility gene in Autism Spectrum Disorders (ASD), but its role in the core and associated symptoms of ASD still remains elusive. We used mice lacking GluK2 (GluK2 KO) to examine their endophenotype with a view to modeling aspects of autism, including social deficits, stereotyped and repetitive behavior and decreased cognitive abilities. Anxiety was recorded in the elevated plus maze, social behavior in a three-chamber apparatus, and cognition in different water maze protocols. Deletion of the GluK2 gene reduced locomotor activity and sociability as indicated by the social interaction task. In addition, GluK2 KO mice learnt to locate a hidden platform in a water maze surrounded by a curtain with hanging cues faster than wild-type mice. They maintained a bias toward the target quadrant when some of these cues were removed, at which point wild-types orthogonalized the behavior and showed no memory. However, GluK2 KO mice were impaired in spatial reversal learning. These behavioral data together with previously published electrophysiology showing severe anomalies in CA3 network activity, suggest a computational shift in this network for enhanced propensity of pattern completion that would explain the loss of behavioral flexibility in GluK2 KO mice. Although a single mutation cannot recapitulate the entire core symptoms of ASD, our data provide evidence for glutamatergic dysfunction underlying a number of social- and cognition-related phenotypes relevant to ASD. PMID:24753134

Micheau, Jacques; Vimeney, Alice; Normand, Elisabeth; Mulle, Christophe; Riedel, Gernot

2014-09-01

255

Volume and Quark Mass Dependence of the Chiral Phase Transition  

E-print Network

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.

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

2006-06-23

256

Strong-field Kapitza-Dirac scattering of neutral atoms.  

PubMed

Laser induced strong-field phenomena in atoms and molecules on the femtosecond (fs) time scale have been almost exclusively investigated with traveling wave fields. In almost all cases, approximation of the strong electromagnetic field by an electric field purely oscillating in time suffices to describe experimental observations. Spatially dependent electromagnetic fields, as they occur in a standing light wave, allow for strong energy and momentum transfer and are expected to extend strong-field dynamics profoundly. Here we report a strong-field version of the Kapitza-Dirac effect for neutral atoms where we scatter neutral He atoms in an intense short pulse standing light wave with fs duration and intensities well in the strong-field tunneling regime. We observe substantial longitudinal momentum transfer concomitant with an unprecedented atomic photon scattering rate greater than 10(16)s(-1). PMID:24702358

Eilzer, S; Zimmermann, H; Eichmann, U

2014-03-21

257

Infection dynamics of endemic malaria in a wild bird population: parasite species-dependent drivers of spatial and temporal variation in transmission rates.  

PubMed

1.?Investigating the ecological context in which host-parasite interactions occur and the roles of biotic and abiotic factors in forcing infection dynamics is essential to understanding disease transmission, spread and maintenance. 2.?Despite their prominence as model host-pathogen systems, the relative influence of environmental heterogeneity and host characteristics in influencing the infection dynamics of avian blood parasites has rarely been assessed in the wild, particularly at a within-population scale. 3.?We used a novel multievent modelling framework (an extension of multistate mark-recapture modelling) that allows for uncertainty in disease state, to estimate transmission parameters and assess variation in the infection dynamics of avian malaria in a large, longitudinally sampled data set of breeding blue tits infected with two divergent species of Plasmodium parasites. 4.?We found striking temporal and spatial heterogeneity in the disease incidence rate and the likelihood of recovery within this single population and demonstrate marked differences in the relative influence of environmental and host factors in forcing the infection dynamics of the two Plasmodium species. 5.?Proximity to a permanent water source greatly influenced the transmission rates of P. circumflexum, but not of P. relictum, suggesting that these parasites are transmitted by different vectors. 6.?Host characteristics (age/sex) were found to influence infection rates but not recovery rates, and their influence on infection rates was also dependent on parasite species: P. relictum infection rates varied with host age, whilst P. circumflexum infection rates varied with host sex. 7.?Our analyses reveal that transmission of endemic avian malaria is a result of complex interactions between biotic and abiotic components that can operate on small spatial scales and demonstrate that knowledge of the drivers of spatial and temporal heterogeneity in disease transmission will be crucial for developing accurate epidemiological models and a thorough understanding of the evolutionary implications of pathogens. PMID:21848864

Lachish, Shelly; Knowles, Sarah C L; Alves, Ricardo; Wood, Matthew J; Sheldon, Ben C

2011-11-01

258

Using contextual analysis to investigate the nature of spatial memory  

PubMed Central

The present study investigated the properties of episodic spatial memory by conducting contextual analysis on spatial memory tasks in a large sample of individuals (N = 778) between the ages of 18 and 92. The results suggest that episodic spatial memory as measured by a dot location task is not uniquely influenced by memory but is strongly influenced by fluid ability (Gf). The spatial memory–Gf relationship is evident and robust even when spatial memory is operationalized with a very simple single-dot location task, suggesting that allocation of attention across space may play a role in the relationship. Results also indicate that the spatial memory–Gf relations are not dependent on complexity of processing, because Gf has a similar magnitude of relations with a more complex version of the dot location task. Collectively, the results suggest that spatial memory likely represents some aspect of fluid intelligence and is not uniquely related to measures of verbal memory. PMID:24234277

Salthouse, Timothy A.

2015-01-01

259

The level of cAMP-dependent protein kinase A activity strongly affects osmotolerance and osmo-instigated gene expression changes in Saccharomyces cerevisiae.  

PubMed

The influence of cAMP-dependent protein kinase (PKA) on protein expression during exponential growth under osmotic stress was studied by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). The responses of isogenic strains (tpk2Deltatpk3Delta) with either constitutively low (tpk1(w1)), regulated (TPK1) or constitutively high (TPK1bcy1Delta) PKA activity were compared. The activity of cAMP-dependent protein kinase (PKA) was shown to be a major determinant of osmotic shock tolerance. Proteins with increased expression during growth under sodium chloride stress could be grouped into three classes with respect to PKA activity, with the glycerol metabolic proteins GPD1, GPP2 and DAK1 standing out as independent of PKA. The other osmotically induced proteins displayed a variable dependence on PKA activity; fully PKA-dependent genes were TPS1 and GCY1, partly PKA-dependent genes were ENO1, TDH1, ALD3 and CTT1. The proteins repressed by osmotic stress also fell into distinct classes of PKA-dependency. Ymr116c was PKA-independent, while Pgi1p, Sam1p, Gdh1p and Vma1p were fully PKA-dependent. Hxk2p, Pdc1p, Ssb1p, Met6p, Atp2p and Hsp60p displayed a partially PKA-dependent repression. The promotors of all induced PKA-dependent genes have STRE sites in their promotors suggestive of a mechanism acting via Msn2/4p. The mechanisms governing the expression of the other classes are unknown. From the protein expression data we conclude that a low PKA activity causes a protein expression resembling that of osmotically stressed cells, and furthermore makes cells tolerant to this type of stress. PMID:10641035

Norbeck, J; Blomberg, A

2000-01-30

260

Are Automatic Conceptual Cores the Gold Standard of Semantic Processing? The Context-Dependence of Spatial Meaning in Grounded Congruency Effects.  

PubMed

According to grounded cognition, words whose semantics contain sensory-motor features activate sensory-motor simulations, which, in turn, interact with spatial responses to produce grounded congruency effects (e.g., processing the spatial feature of up for sky should be faster for up vs. down responses). Growing evidence shows these congruency effects do not always occur, suggesting instead that the grounded features in a word's meaning do not become active automatically across contexts. Researchers sometimes use this as evidence that concepts are not grounded, further concluding that grounded information is peripheral to the amodal cores of concepts. We first review broad evidence that words do not have conceptual cores, and that even the most salient features in a word's meaning are not activated automatically. Then, in three experiments, we provide further evidence that grounded congruency effects rely dynamically on context, with the central grounded features in a concept becoming active only when the current context makes them salient. Even when grounded features are central to a word's meaning, their activation depends on task conditions. PMID:25243925

Lebois, Lauren A M; Wilson-Mendenhall, Christine D; Barsalou, Lawrence W

2014-09-22

261

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

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

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

2014-07-18

262

Mechanism of the ultraviolet photodissociation of chloroethylenes determined from the Doppler profiles, spatial anisotropy, and power dependence of the photofragments  

NASA Astrophysics Data System (ADS)

Doppler profiles of chlorine and hydrogen atomic fragments produced in the photodissociation of mono- and dichloroethylenes at 193 nm have been measured in a pump-and-probe experiment using 2+1 resonance-enhanced multiphoton ionization. In a second experiment, the angular distributions of the Cl fragments produced from chloroethylenes at 235 and 238 nm were measured using a perfect-focusing mass spectrometer. In a third experiment, we measured the power dependence of the relative yields of H, Cl, HCl, and HCl+ produced from vinyl chloride at 193 nm. For Cl detachment, two primary processes have been confirmed. One produces an isotropic angular distribution of photofragments, while the other produces an anisotropic distribution. For H atom detachment, an isotropic angular distribution and a Boltzmann velocity distribution were found. The ratio of yields of the Cl and H fragments was found to be 4±1 for CH2CCl2 and higher than 10 for t-CHClCHCl and CCl2CClH. The H, Cl, and HCl yields were found to be first order in laser intensity, while the HCl+ yield was found to be third order. Saturation measurements of the ion yield indicate that the latter results from a 1+1+1 resonance-enhanced process involving a bound state of the parent molecule. This intermediate state may also be responsible for producing the statistical component of the Cl atom product.

Mo, Yuxiang; Tonokura, Kenichi; Matsumi, Yutaka; Kawasaki, Masahiro; Sato, Tetsuya; Arikawa, Tatsuo; Reilly, Peter T. A.; Xie, Yongjin; Yang, Yung-an; Huang, Yibo; Gordon, Robert J.

1992-10-01

263

Spatially distributed assessment of solar resources for energy applications in Slovakia  

Microsoft Academic Search

Spatial and temporal distribution of available solar energy depends on several factors. Besides latitude and astronomical factors it is strongly influenced by climate factors (e.g. cloudiness, turbidity) and topography. This paper presents a solar database of Slovakia containing spatially-distributed solar energy resource data necessary for planning, sitting and forecasting of solar device installations. The database consists of several data sets

Jaroslav HOFIERKA

2008-01-01

264

Histone deacetylase inhibitors strongly sensitise neuroblastoma cells to TRAIL-induced apoptosis by a caspases-dependent increase of the pro- to anti-apoptotic proteins ratio  

Microsoft Academic Search

BACKGROUND: Neuroblastoma (NB) is the second most common solid childhood tumour, an aggressive disease for which new therapeutic strategies are strongly needed. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) selectively induces apoptosis in most tumour cells, but not in normal tissues and therefore represents a valuable candidate in apoptosis-inducing therapies. Caspase-8 is silenced in a subset of highly malignant NB cells,

Annick Mühlethaler-Mottet; Marjorie Flahaut; Katia Balmas Bourloud; Katya Auderset; Roland Meier; Jean-Marc Joseph; Nicole Gross

2006-01-01

265

CoFe alloy as middle layer for strong spin dependent quantum well resonant tunneling in double barrier magnetic tunnel junctions  

SciTech Connect

We report the spin-dependent quantum well resonant tunneling effect in CoFe/MgO/CoFe/MgO/CoFeB (CoFe) double barrier magnetic tunnel junctions. The dI/dV spectra reveal clear resonant peaks for the parallel magnetization configurations, which can be matched to quantum well resonances obtained from calculation. The differential TMR exhibits an oscillatory behavior with a sign change due to the formation of the spin-dependent QW states in the middle CoFe layer. Also, we observe pronounced TMR enhancement at resonant voltages at room temperature, suggesting that it is very promising to achieve high TMR using the spin-dependent QW resonant tunneling effect.

Liu, R. S. [IBM Corporation, Almaden Research Center; Yang, See-Hun [IBM Corporation, Almaden Research Center; Jiang, Xin [IBM Corporation, Almaden Research Center; Zhang, Xiaoguang [ORNL; Rice, Philip M. [IBM Corporation, Almaden Research Center; Canali, Carlo M. [Kalmar University; Parkin, S. S. P. [IBM Corporation, Almaden Research Center

2013-01-01

266

Strongly coupled quantum field theory  

SciTech Connect

I analyze numerically a two-dimensional {lambda}{phi}{sup 4} theory showing that in the limit of a strong coupling {lambda}{yields}{infinity} just the homogeneous solutions for time evolution are relevant in agreement with the duality principle in perturbation theory as presented in [M. Frasca, Phys. Rev. A 58, 3439 (1998)], being negligible the contribution of the spatial varying parts of the dynamical equations. A consequence is that the Green function method works for this nonlinear problem in the large coupling limit as in a linear theory. A numerical proof is given for this. With these results at hand, I built a strongly coupled quantum field theory for a {lambda}{phi}{sup 4} interacting field computing the first order correction to the generating functional. Mass spectrum of the theory is obtained turning out to be that of a harmonic oscillator with no dependence on the dimensionality of space-time. The agreement with the Lehmann-Kaellen representation of the perturbation series is then shown at the first order.

Frasca, Marco

2006-01-15

267

Anisotropic model of kinetic roughening: the strong-coupling regime.  

PubMed

We study the strong coupling (SC) limit of the anisotropic Kardar-Parisi-Zhang (KPZ) model. A systematic mapping of the continuum model to its lattice equivalent shows that in the SC limit, anisotropic perturbations destroy all spatial correlations but retain a temporal scaling which shows a remarkable crossover along one of the two spatial directions, the choice of direction depending on the relative strength of anisotropicity. The results agree with exact numerics and are expected to settle the long-standing SC problem of a KPZ model in the infinite range limit. PMID:18233612

Chattopadhyay, Amit K

2007-11-01

268

Anisotropic model of kinetic roughening: The strong-coupling regime  

NASA Astrophysics Data System (ADS)

We study the strong coupling (SC) limit of the anisotropic Kardar-Parisi-Zhang (KPZ) model. A systematic mapping of the continuum model to its lattice equivalent shows that in the SC limit, anisotropic perturbations destroy all spatial correlations but retain a temporal scaling which shows a remarkable crossover along one of the two spatial directions, the choice of direction depending on the relative strength of anisotropicity. The results agree with exact numerics and are expected to settle the long-standing SC problem of a KPZ model in the infinite range limit.

Chattopadhyay, Amit K.

2007-11-01

269

From repulsion to attraction: species- and spatial context-dependent threat sensitive response of the spider mite Tetranychus urticae to predatory mite cues  

NASA Astrophysics Data System (ADS)

Prey perceiving predation risk commonly change their behavior to avoid predation. However, antipredator strategies are costly. Therefore, according to the threat-sensitive predator avoidance hypothesis, prey should match the intensity of their antipredator behaviors to the degree of threat, which may depend on the predator species and the spatial context. We assessed threat sensitivity of the two-spotted spider mite, Tetranychus urticae, to the cues of three predatory mites, Phytoseiulus persimilis, Neoseiulus californicus, and Amblyseius andersoni, posing different degrees of risk in two spatial contexts. We first conducted a no-choice test measuring oviposition and activity of T. urticae exposed to chemical traces of predators or traces plus predator eggs. Then, we tested the site preference of T. urticae in choice tests, using artificial cages and leaves. In the no-choice test, T. urticae deposited their first egg later in the presence of cues of P. persimilis than of the other two predators and cue absence, indicating interspecific threat-sensitivity. T. urticae laid also fewer eggs in the presence of cues of P. persimilis and A. andersoni than of N. californicus and cue absence. In the artificial cage test, the spider mites preferred the site with predator traces, whereas in the leaf test, they preferentially resided on leaves without traces. We argue that in a nonplant environment, chemical predator traces do not indicate a risk for T. urticae, and instead, these traces function as indirect habitat cues. The spider mites were attracted to these cues because they associated them with the existence of a nearby host plant.

Fernández Ferrari, M. Celeste; Schausberger, Peter

2013-06-01

270

Vestibular modulation of spatial perception  

PubMed Central

Vestibular inputs make a key contribution to the sense of one’s own spatial location. While the effects of vestibular stimulation on visuo-spatial processing in neurological patients have been extensively described, the normal contribution of vestibular inputs to spatial perception remains unclear. To address this issue, we used a line bisection task to investigate the effects of galvanic vestibular stimulation (GVS) on spatial perception, and on the transition between near and far space. Brief left-anodal and right-cathodal GVS or right-anodal and left-cathodal GVS were delivered. A sham stimulation condition was also included. Participants bisected lines of different lengths at six distances from the body using a laser pointer. Consistent with previous results, our data showed an overall shift in the bisection bias from left to right as viewing distance increased. This pattern suggests leftward bias in near space, and rightward bias in far space. GVS induced strong polarity dependent effects in spatial perception, broadly consistent with those previously reported in patients: left-anodal and right-cathodal GVS induced a leftward bisection bias, while right-anodal and left-cathodal GVS reversed this effect, and produced bisection bias toward the right side of the space. Interestingly, the effects of GVS were comparable in near and far space. We speculate that vestibular-induced biases in space perception may optimize gathering of information from different parts of the environment. PMID:24133440

Ferrè, Elisa R.; Longo, Matthew R.; Fiori, Federico; Haggard, Patrick

2013-01-01

271

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

PubMed

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

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

2010-10-01

272

Drug-, dose- and sex-dependent effects of chronic fluoxetine, reboxetine and venlafaxine on open-field behavior and spatial memory in rats.  

PubMed

In an effort to address the need to include both sexes in studies of effects of the SSRI fluoxetine, the NRI reboxetine and the SNRI venlafaxine on anxiety-related behavior and memory along with the use of chronic drug administration, male and female PVG/c rats were fed diets containing two doses of each drug for 21 days. The rats' anxiety level was then assessed in an open field. Short-term spatial memory for a brightness change in a Y maze was also measured. While there was little evidence of anxiolytic effects of any of the drugs, both fluoxetine and, to a lesser extent, venlafaxine appeared to be mainly anxiogenic in their action depending on both dose and sex. Reboxetine was relatively ineffective in this respect. Ability to locate the Y-maze arm that had changed (from white to black) seemed to be impaired for male (but not female) rats by both fluoxetine and venlafaxine and, to a much lesser extent, by reboxetine. Given the relative ineffectiveness of reboxetine in either test, it is possible that the effects of the other two drugs on both anxiety and memory were mainly due to their serotonin reuptake inhibiting properties. The differences that occurred between males and females in responsiveness to all three drugs supported the long-held view that both sexes should be investigated in studies of this sort, especially in view of reports of sex differences in effects of clinically prescribed antidepressants. PMID:25523028

Gray, Vanessa C; Hughes, Robert N

2015-03-15

273

Task Dependence, Tissue Specificity, and Spatial Distribution of Widespread Activations in Large Single-Subject Functional MRI Datasets at 7T.  

PubMed

It was recently shown that when large amounts of task-based blood oxygen level-dependent (BOLD) data are combined to increase contrast- and temporal signal-to-noise ratios, the majority of the brain shows significant hemodynamic responses time-locked with the experimental paradigm. Here, we investigate the biological significance of such widespread activations. First, the relationship between activation extent and task demands was investigated by varying cognitive load across participants. Second, the tissue specificity of responses was probed using the better BOLD signal localization capabilities of a 7T scanner. Finally, the spatial distribution of 3 primary response types-namely positively sustained (pSUS), negatively sustained (nSUS), and transient-was evaluated using a newly defined voxel-wise waveshape index that permits separation of responses based on their temporal signature. About 86% of gray matter (GM) became significantly active when all data entered the analysis for the most complex task. Activation extent scaled with task load and largely followed the GM contour. The most common response type was nSUS BOLD, irrespective of the task. Our results suggest that widespread activations associated with extremely large single-subject functional magnetic resonance imaging datasets can provide valuable information about the functional organization of the brain that goes undetected in smaller sample sizes. PMID:25405938

Gonzalez-Castillo, Javier; Hoy, Colin W; Handwerker, Daniel A; Roopchansingh, Vinai; Inati, Souheil J; Saad, Ziad S; Cox, Robert W; Bandettini, Peter A

2014-07-01

274

Topics in strong Langmuir turbulence  

NASA Technical Reports Server (NTRS)

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.

Nicholson, D. R.

1982-01-01

275

Topics in strong Langmuir turbulence  

NASA Technical Reports Server (NTRS)

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.

Nicholson, D. R.

1983-01-01

276

Size- and temperature-dependent epitaxy for a strong film-substrate mismatch: The case of Pt/MgO(001)  

SciTech Connect

The growth of platinum film on MgO(001) was analyzed in a combined experimental and theoretical study. Experiments were performed by grazing-incidence x-ray diffraction at small [grazing-incidence small-angle x-ray scattering (GISAXS)] and wide [grazing-incidence x-ray scattering (GIXS)] angles, and the theory coupled ab initio calculations on model Pt/MgO(001) systems and large-scale simulations of supported Pt clusters using a coordination-dependent interaction potential. GISAXS data showed that the cluster aspect ratio is constant at all studied temperatures with a tendency to faceting at 1000 K. The cluster spacing at the early stage of the growth is characteristic of a growth on defects, while the particle size obeys a d{approx}t{sup 0.5} power law assigned to dynamic coalescence. All Pt films deposited at 1000 K show the [100](001){sub Pt} parallel [100](001){sub MgO} epitaxy. As the cluster size increases, the in-plane Pt-Pt distance increases above the bulk value (0.393 nm), passes through a maximum (0.398 nm) at a thickness of t=0.6 nm, and then relaxes back to the bulk value through interfacial dislocations, a behavior predicted by calculation and which appears typical of (001) epitaxy. Finally, the formation of dislocations arising from the Pt/MgO(001) mismatch of -6.83% is evidenced. Below 1000 K, due to a minimization of the surface energy of the film, the (111){sub Pt} parallel (001){sub MgO} epitaxy dominates. Beside the expected [110](111){sub Pt} parallel [110](001){sub MgO} orientation, another epitaxy is revealed, i.e., [110](111){sub Pt} parallel [100](001){sub MgO}. Moreover, families of orientations slightly rotated relative to the former epitaxy are evidenced. Calculations reveal that intermediate minima in energy appear at angles that depend on the size of the particles. Comparison between Ni/, Pd/, Pt/, and Ag/MgO(001) shows that the progressive weakening of the metal-MgO bonding in this order explains the decrease in adhesion energy as well as in metal-MgO distance, which are experimentally and/or theoretically observed through that series.

Olander, J.; Lazzari, R.; Jupille, J.; Mangili, B.; Goniakowski, J.; Renaud, G. [Institut des NanoSciences de Paris, CNRS UMR 7588-Universites Pierre et Marie Curie (Paris 6) et Denis Diderot (Paris 7), Campus Boucicaut, 140 Rue de Lourmel, 75015 Paris (France); CEA-Grenoble, Departement de Recherche Fondamentale sur la Matiere Condensee, Service de Physique des Materiaux et Microstructures, Nanostructures et Rayonnement Synchrotron, 17 Avenue des Martyrs, F-38054 Grenoble, Cedex 9 (France)

2007-08-15

277

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

SciTech Connect

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.

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

2009-07-27

278

Spatial Econometrics and Political Science  

Microsoft Academic Search

Abstract Many theories in political science predict the spatial clustering of similar behaviors among,neighboring units of observation. This spatial autocorrelation poses implications for both inference and modeling that are distinct from the more familiar serial dependence in time series analysis. In this paper, I examine how political scientists can diagnose and model the spatial dependence that is predicted by our

David Darmofal

279

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

SciTech Connect

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.

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

280

Inelastic X-ray Scattering Study of SmFeAs(O1?xFy) Single Crystals: Evidence for Strong Momentum-Dependent Doping-Induced Renormalizations of Optical Phonons  

SciTech Connect

We report inelastic x-ray scattering experiments on the lattice dynamics in SmFeAsO and superconducting SmFeAsO{sub 0.60}F{sub 0.35} single crystals. Particular attention was paid to the dispersions along the [100] direction of three optical modes close to 23 meV, polarized out of the FeAs planes. Remarkably, two of these modes are strongly renormalized upon fluorine doping. These results provide significant insight into the energy and momentum dependence of the coupling of the lattice to the electron system and underline the importance of spin-phonon coupling in the superconducting iron pnictides.

Hill, J.P.; Le Tacon, M.; Forrest, T.R.; Ruegg, Ch.; Bosak, A.; Walters, A.C.; Mittal, R.; Rønnow, H.M.; Zhigadlo, N.D.; Katrych, S.; Karpinski, J.; Krisch, M.; McMorrow, D.F.

2009-12-01

281

Spatial dependency of soil nutrient availability and microbial properties in a mixed forest of Tsuga heterophylla and Pseudotsuga menziesii, in coastal British Columbia, Canada  

Microsoft Academic Search

Spatial variations in nutrient concentrations and turnover may contribute to variations in productivity within forest ecosystems and be responsible for creating and maintaining diversity of plant species. The aim of this study was to relate spatial patterns in soil nutrient availability and microbial properties in the forest floor and mineral soil in order to explore the controls on variations in

Per Bengtson; Nathan Basiliko; Cindy E. Prescott; Susan J. Grayston

2007-01-01

282

Diurnal pattern of stomatal conductance in the large-leaved temperate liana Aristolochia macrophylla depends on spatial position within the leaf lamina  

PubMed Central

Background and Aims The large distance between peripheral leaf regions and the petiole in large leaves is expected to cause stronger negative water potentials at the leaf apex and marginal zones compared with more central or basal leaf regions. Leaf zone-specific differences in water supply and/or gas exchange may therefore be anticipated. In this study, an investigation was made to see whether zonal differences in gas exchange regulation can be detected in large leaves. Methods The diurnal course of stomatal conductance, gs, was monitored at defined lamina zones during two consecutive vegetation periods in the liana Aristolochia macrophylla that has large leaves. Local climate and stem water potential were also monitored to include parameters involved in stomatal response. Additionally, leaf zonal vein densities were measured to assess possible trends in local hydraulic supply. Key Results It was found that the diurnal pattern of gs depends on the position within a leaf in A. macrophylla. The highest values during the early morning were shown by the apical region, with subsequent decline later in the morning and a further gradual decline towards the evening. The diurnal pattern of gs at the marginal regions was similar to that of the leaf tip but showed a time lag of about 1 h. At the leaf base, the diurnal pattern of gs was similar to that of the margins but with lower maximum gs. At the the leaf centre regions, gs tended to show quite constant moderate values during most of the day. Densities of minor veins were lower at the margin and tip compared with the centre and base. Conclusions Gas exchange regulation appears to be zone specific in A. macrophylla leaves. It is suggested that the spatial–diurnal pattern of gs expressed by A. macrophylla leaves represents a strategy to prevent leaf zonal water stress and subsequent vein embolism. PMID:23606681

Miranda, Tatiana; Ebner, Martin; Traiser, Christopher; Roth-Nebelsick, Anita

2013-01-01

283

Spatial decoupling of agricultural production and consumption: quantifying dependences of countries on food imports due to domestic land and water constraints  

NASA Astrophysics Data System (ADS)

In our globalizing world, the geographical locations of food production and consumption are becoming increasingly disconnected, which increases reliance on external resources and their trade. We quantified to what extent water and land constraints limit countries’ capacities, at present and by 2050, to produce on their own territory the crop products that they currently import from other countries. Scenarios of increased crop productivity and water use, cropland expansion (excluding areas prioritized for other uses) and population change are accounted for. We found that currently 16% of the world population use the opportunities of international trade to cover their demand for agricultural products. Population change may strongly increase the number of people depending on ex situ land and water resources up to about 5.2 billion (51% of world population) in the SRES A2r scenario. International trade will thus have to intensify if population growth is not accompanied by dietary change towards less resource-intensive products, by cropland expansion, or by productivity improvements, mainly in Africa and the Middle East. Up to 1.3 billion people may be at risk of food insecurity in 2050 in present low-income economies (mainly in Africa), if their economic development does not allow them to afford productivity increases, cropland expansion and/or imports from other countries.

Fader, Marianela; Gerten, Dieter; Krause, Michael; Lucht, Wolfgang; Cramer, Wolfgang

2013-03-01

284

Dissecting the age-related decline on spatial learning and memory tasks in rodent models: N-methyl-D-aspartate receptors and voltage-dependent Ca2+ channels in senescent synaptic plasticity  

PubMed Central

In humans, heterogeneity in the decline of hippocampal-dependent episodic memory is observed during aging. Rodents have been employed as models of age-related cognitive decline and the spatial water maze has been used to show variability in the emergence and extent of impaired hippocampal-dependent memory. Impairment in the consolidation of intermediate-term memory for rapidly acquired and flexible spatial information emerges early, in middle-age. As aging proceeds, deficits may broaden to include impaired incremental learning of a spatial reference memory. The extent and time course of impairment has been be linked to senescence of calcium (Ca2+) regulation and Ca2+-dependent synaptic plasticity mechanisms in region CA1. Specifically, aging is associated with altered function of N-methyl-D-aspartate receptors (NMDARs), voltage-dependent Ca2+ channels (VDCCs), and ryanodine receptors (RyRs) linked to intracellular Ca2+ stores (ICS). In young animals, NMDAR activation induces long-term potentiation of synaptic transmission (NMDAR-LTP), which is thought to mediate the rapid consolidation of intermediate-term memory. Oxidative stress, starting in middle-age, reduces NMDAR function. In addition, VDCCs and ICS can actively inhibit NMDAR-dependent LTP and oxidative stress enhances the role of VDCC and RyR-ICS in regulating synaptic plasticity. Blockade of L-type VDCCs promotes NMDAR-LTP and memory in older animals. Interestingly, pharmacological or genetic manipulations to reduce hippocampal NMDAR function readily impair memory consolidation or rapid learning, generally leaving incremental learning intact. Finally, evidence is mounting to indicate a role for VDCC-dependent synaptic plasticity in associative learning and the consolidation of remote memories. Thus, VDCC-dependent synaptic plasticity and extrahippocampal systems may contribute to incremental learning deficits observed with advanced aging. PMID:22307057

Foster, Thomas C.

2012-01-01

285

Explaining foreign diplomatic presence in the U.S. with spatial models: a liberal spatial perspective  

Microsoft Academic Search

This paper examines the effect of economic interdependence, intergovernmental organizations, political freedom, and spatial relationship on foreign diplomatic presence in the U.S. from 1980 to 2000. Spatial perspective is largely missing in the mainstream international theories. Spatial relationship has three measures: spatial proximity measured as distance, spatial dependency measured as neighborhood effect, and spatial heterogeneity measured as regional effect. We

Imam M. Xierali; Lin Liu

2006-01-01

286

Spatial Autoregression Techniques for Real Estate Data  

Microsoft Academic Search

This paper describes how spatial techniques can be used to improve the accuracy of market value estimates obtained using multiple regression analysis. Rather than eliminating the problem of spatial residual dependencies through the inclusion of many independent variables, spatial statistical methods typically keep fewer independent variables and augment these with a simple model of the spatial error dependence. We discuss

Robin Dubin; R. Kelley Pace; Thomas G. Thibodeau

1999-01-01

287

Spatially and Temporally Varying Associations between Temporary Outmigration and Natural Resource Availability in Resource-Dependent Rural Communities in South Africa: A Modeling Framework  

PubMed Central

Migration-environment models tend to be aspatial within chosen study regions, although associations between temporary outmigration and environmental explanatory variables likely vary across the study space. This research extends current approaches by developing migration models considering spatial non-stationarity and temporal variation – through examination of the migration-environment association at nested geographic scales (i.e. whole-population, village, and subvillage) within a specific study site. Demographic survey data from rural South Africa, combined with indicators of natural resource availability from satellite imagery, are employed in a nested modeling approach that brings out distinct patterns of spatial variation in model associations derived at finer geographic scales. Given recent heightened public and policy concern with the human migratory implications of climate change, we argue that consideration of spatial variability adds important nuance to scientific understanding of the migration-environment association. PMID:23008525

Leyk, Stefan; Maclaurin, Galen J.; Hunter, Lori M.; Nawrotzki, Raphael; Twine, Wayne; Collinson, Mark; Erasmus, Barend

2012-01-01

288

Modelling Spatial Relations by Generalized Proximity Matrices  

Microsoft Academic Search

One of the main challenges for the development of spatial information theory is the formalization of the concepts of space and spatial relations. Currently, most spatial data structures and spatial analytical methods used in GIS embody the notion of space as a set of absolute locations in a Cartesian coordinate system, thus failing to incorporate spatial relations which are dependent

Ana Paula Dutra De Aguiar; Gilberto Câmara; Antônio Miguel Vieira Monteiro; Ricardo Cartaxo Modesto De Souza

2003-01-01

289

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

PubMed

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

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

2013-03-01

290

Spatial correlation of probabilistic earthquake ground motion and loss  

USGS Publications Warehouse

Spatial correlation of annual earthquake ground motions and losses can be used to estimate the variance of annual losses to a portfolio of properties exposed to earthquakes A direct method is described for the calculations of the spatial correlation of earthquake ground motions and losses. Calculations for the direct method can be carried out using either numerical quadrature or a discrete, matrix-based approach. Numerical results for this method are compared with those calculated from a simple Monte Carlo simulation. Spatial correlation of ground motion and loss is induced by the systematic attenuation of ground motion with distance from the source, by common site conditions, and by the finite length of fault ruptures. Spatial correlation is also strongly dependent on the partitioning of the variability, given an event, into interevent and intraevent components. Intraevent variability reduces the spatial correlation of losses. Interevent variability increases spatial correlation of losses. The higher the spatial correlation, the larger the variance in losses to a port-folio, and the more likely extreme values become. This result underscores the importance of accurately determining the relative magnitudes of intraevent and interevent variability in ground-motion studies, because of the strong impact in estimating earthquake losses to a portfolio. The direct method offers an alternative to simulation for calculating the variance of losses to a portfolio, which may reduce the amount of calculation required.

Wesson, R.L.; Perkins, D.M.

2001-01-01

291

Spatially embedded growing small-world networks  

PubMed Central

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

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

2014-01-01

292

Spatially embedded growing small-world networks  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

293

Spared unconscious influences of spatial memory in diencephalic amnesia  

PubMed Central

Spatial memory is crucial to our daily lives and in part strongly depends on automatic, implicit memory processes. This study investigates the neurocognitive basis of conscious and unconscious influences of object–location memory in amnesic patients with Korsakoff’s syndrome (N = 23) and healthy controls (N = 18) using a process-dissociation procedure in a computerized spatial memory task. As expected, the patients performed substantially worse on the conscious memory measures but showed even slightly stronger effects of unconscious influences than the controls. Moreover, a delayed test administered after 1 week revealed a strong decline in conscious influences in the patients, while unconscious influences were not affected. The presented results suggest that conscious and unconscious influences of spatial memory can be clearly dissociated in Korsakoff’s syndrome. PMID:18560813

Antonides, Rémy; Wester, Arie J.; Kessels, Roy P. C.

2008-01-01

294

Spatial-visual skills and engineering design  

E-print Network

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 ...

Tseng, Tiffany

2009-01-01

295

A Spatial Hedonic Approach to Assess the Impact of Swine Production on Residential Property Values  

Microsoft Academic Search

A spatial hedonic model is developed to assess monetary harm of confined animal feeding operations (CAFOs) on property values, taking explicitly into account spatial dependence in property values. Spatial autocorrelation was found in the form of spatial lag dependence, not spatial error dependence. When spatial lag dependence is explicitly taken into account, on average the impact coefficient estimate of a

Jungik Kim; Peter Goldsmith

2008-01-01

296

Strongly Driven Crystallization Processes in a Metallic Glass  

SciTech Connect

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.

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

2009-02-09

297

High Order Strong Stability Preserving Time Discretizations  

Microsoft Academic Search

Strong stability preserving (SSP) high order time discretizations were developed to ensure nonlinear stability properties necessary in the numerical solution of hyperbolic par- tial differential equations with discontinuous solutions. SSP methods preserve the strong sta- bility properties---in any norm, seminorm or convex functional---of the spatial discretization coupled with first order Euler time stepping. This paper describes the development of SSP

Sigal Gottlieb; David I. Ketcheson; Chi-Wang Shu

2009-01-01

298

Spatial forms and mental imagery.  

PubMed

Four studies investigated how general mental imagery might be involved in mediating the phenomenon of 'synaesthetic' spatial forms - i.e., the experience that sequences such as months or numbers have spatial locations. In Study 1, people with spatial forms scored higher than controls on visual imagery self-report scales. This is consistent with the suggestion that strong general imagery is at least a necessary condition to experience spatial forms. However self-reported spatial imagery did not differ between groups, suggesting either that the spatial nature of forms is mediated by special synaesthetic mechanisms, or that forms are depictive visual images rather than explicit spatial models. A methodological implication of Study 1 was that a general tendency for people with spatial forms to use imagery strategies might account for some of their previously-reported behavioural differences with control groups. This concern was supported by Studies 2-4. Normal participants were encouraged to visually image the months in various spatial layouts, and spatial associations for months were tested using left/right key presses to classify month names as belonging to the first or second half of the year (Studies 2-3) or as odd/even (Study 4). Reaction times showed month-SNARC (Spatial Numerical Association of Response Codes) effects of similar magnitude to previously-reported data from spatial form participants (Price and Mentzoni, 2008). Additionally, reversing the spatial associations within instructed images was sufficient to reverse the direction of observed month-SNARC effects (i.e., positive vs negative slope), just as different spatial forms were previously shown to modulate the direction of effects (ibid.). Results challenge whether previously observed behavioural differences between spatial form and control groups need to be explained in terms of special synaesthetic mechanisms rather than intentional imagery strategies. It is argued that usually strong general imagery processes should complement synaesthetic mechanisms as possible explanations of spatial forms. PMID:19665116

Price, Mark C

2009-01-01

299

STRONG FERTILITY CENTER Strong Fertility Center  

E-print Network

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

Goldman, Steven A.

300

Spatial Inhibition and the Visual Cortex: A Magnetic Resonance Spectroscopy Imaging Study  

PubMed Central

Introduction Deficits in processing spatial information have been observed in clinical populations who have abnormalities within the dopamine (DA) system. As psychostimulants such as methamphetamine (MA) are particularly neurotoxic to the dopaminergic system it was of interest to examine the performance of MA-dependent individuals on a task of spatial attention. Method 51 MA-dependent subjects and 22 age-matched non-substance abusing control subjects were tested on a Spatial Stroop attention test. MR Spectroscopy (MRS) imaging data were analyzed from 32 MA abusers and 13 controls. Results No group differences in response time or accuracy emerged on the behavioral task with both groups exhibiting equivalent slowing when the word meaning and the spatial location of the word were in conflict. MRS imaging data from the MA abusers revealed a strong inverse correlation between NAA/Cr ratios in the primary visual cortex (PVC) and Spatial interference (p=0.0001). Moderate inverse correlations were also seen in the anterior cingulate cortex (ACC) (p = 0.02). No significant correlations were observed in the controls, perhaps due to the small sample of imaging data available (n=13). Discussion The strong correlation between spatial conflict suppression and NAA/Cr levels within the PVC in the MA-dependent individuals suggests that preserved neuronal integrity within the PVC of stimulant abusers may modulate cognitive mechanisms that process implicit spatial information. PMID:21237183

Salo, R; Nordahl, TE; Buonocore, MH; Natsuaki, YT; Moore, CD; Waters, C; Leamon, MH

2011-01-01

301

Double Dissociations in Visual and Spatial Short-Term Memory  

ERIC Educational Resources Information Center

A visual short-term memory task was more strongly disrupted by visual than spatial interference, and a spatial memory task was simultaneously more strongly disrupted by spatial than visual interference. This double dissociation supports a fractionation of visuospatial short-term memory into separate visual and spatial components. In 6 experiments,…

Klauer, Karl Christoph; Zhao, Zengmei

2004-01-01

302

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

SciTech Connect

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.

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

303

Testing the spatial distribution of economic activity in Jiangsu province by means of spatial association methods  

NASA Astrophysics Data System (ADS)

The new economic geography theory suggests that regional development is strongly dependent on market access. Due to a snowball effect, spatial clusters of employment and firms might induce regional income increases. In order to identify explicit patterns of regional development, this study makes the empirical attempts by applying spatial association methods for estimating and distinguishing various spatial patterns of economic activities for three county-level factors, namely income, employment and firms of Jiangsu in 2004. The conclusions in this study reveal that on the whole, there is significant, positive correlation of income, employment and firms between regions over the whole space in that year. Moreover, regional income can be to a large extent explained by the market potentials of its neighbors. Apart from market access, regional incomes might be affected by other factors such as local amenities or technology spillover. Also, highly agglomerated clusters of employment and firms give rise to high regional incomes. Strong spatial heterogeneity of employment and firms indicates that firms locate first, anticipating the subsequent consumers' locations and demand functions. Thus, the mobility of firms and employment can induce the highly agglomeration of income.

Ge, Ying; Wang, Weina; Zhang, Shuhui; Yan, Weibiao

2007-06-01

304

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

SciTech Connect

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.

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

305

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

PubMed

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

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

306

Comment on "Tracking an Invisible Target Reveals Spatial Tuning of Neurons in the Rostral Superior Colliculus Is Not Dependent on Visual Stimuli"  

E-print Network

Colliculus Is Not Dependent on Visual Stimuli" Ziad M. Hafed, Laurent Goffart, Richard J. Krauzlis We thank the monkeys were instructed to fixate, whereas the other cited experiments often involved bilateral "averaging" saccades when done in combination with visually guided eye movements (as also shown in Gandhi

Krauzlis, Richard J.

307

Spatial cognition  

NASA Technical Reports Server (NTRS)

Spatial cognition is the ability to reason about geometric relationships in the real (or a metaphorical) world based on one or more internal representations of those relationships. The study of spatial cognition is concerned with the representation of spatial knowledge, and our ability to manipulate these representations to solve spatial problems. Spatial cognition is utilized most critically when direct perceptual cues are absent or impoverished. Examples are provided of how human spatial cognitive abilities impact on three areas of space station operator performance: orientation, path planning, and data base management. A videotape provides demonstrations of relevant phenomena (e.g., the importance of orientation for recognition of complex, configural forms). The presentation is represented by abstract and overhead visuals only.

Kaiser, Mary Kister; Remington, Roger

1988-01-01

308

Higgs-induced spectroscopic shifts near strong gravity sources  

SciTech Connect

We explore the consequences of the mass generation due to the Higgs field in strong gravity astrophysical environments. The vacuum expectation value of the Higgs field is predicted to depend on the curvature of spacetime, potentially giving rise to peculiar spectroscopic shifts, named hereafter 'Higgs shifts'. Higgs shifts could be searched through dedicated multiwavelength and multispecies surveys with high spatial and spectral resolution near strong gravity sources such as Sagittarius A* or broad searches for signals due to primordial black holes. The possible absence of Higgs shifts in these surveys should provide limits to the coupling between the Higgs particle and the curvature of spacetime, a topic of interest for a recently proposed Higgs-driven inflationary model. We discuss some conceptual issues regarding the coexistence between the Higgs mechanism and gravity, especially for their different handling of fundamental and composite particles.

Onofrio, Roberto [Dipartimento di Fisica 'Galileo Galilei', Universita di Padova, Via Marzolo 8, Padova 35131 (Italy) and ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)

2010-09-15

309

Higgs-induced spectroscopic shifts near strong gravity sources  

E-print Network

We explore the consequences of the mass generation due to the Higgs field in strong gravity astrophysical environments. The vacuum expectation value of the Higgs field is predicted to depend on the curvature of spacetime, potentially giving rise to peculiar spectroscopic shifts, named hereafter "Higgs shifts." Higgs shifts could be searched through dedicated multiwavelength and multispecies surveys with high spatial and spectral resolution near strong gravity sources such as Sagittarius A* or broad searches for signals due to primordial black holes. The possible absence of Higgs shifts in these surveys should provide limits to the coupling between the Higgs particle and the curvature of spacetime, a topic of interest for a recently proposed Higgs-driven inflationary model. We discuss some conceptual issues regarding the coexistence between the Higgs mechanism and gravity, especially for their different handling of fundamental and composite particles.

Roberto Onofrio

2010-11-12

310

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)

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.

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

2008-12-01

311

Sequence independent interferon-? induction by multimerized phosphodiester DNA depends on spatial regulation of Toll-like receptor-9 activation in plasmacytoid dendritic cells  

PubMed Central

Single-stranded versus multimeric phosphorothioate-modified CpG oligodeoxynucleotides (ODNs) undergo differential endosomal trafficking upon uptake into plasmacytoid dendritic cells (pDCs), correlating with Toll-like receptor-9-dependent pDC maturation/activation (single-stranded B-type CpG ODN) or interferon-? (IFN-?) induction (multimeric A-type CpG ODN), respectively. As was recently shown, IFN-? production, other than by CpG ODNs, can also be induced in a sequence-independent manner by phosphodiester (PD) ODNs multimerized by 3? poly-guanosine (poly-G) tails. We investigate here the type of endosomal trafficking responsible for IFN-? induction by natural PD ODN ligands. We show that 3? extension with poly-G tails leads to multimerization of single-stranded PD ODNs and to enhanced cellular uptake into pDCs. While monomeric PD ODNs, which induce CpG-dependent Toll-like receptor-9 stimulation and pDC maturation/activation, localized to late endosomal/lysosomal compartments, the poly-G multimerized PD ODNs, which induce CpG-independent IFN-? production, located to vesicles with a distinct, ‘early’ endosomal phenotype. We conclude that poly-G-mediated multimerization of natural PD ODNs allows for sequence-independent, Toll-like receptor-9-dependent IFN-? induction in pDCs by combining three distinct effects: relative protection of sensitive PD ODNs from extracellular and intracellular DNase degradation, enhanced cellular uptake and preferential early endosomal compartmentation. PMID:19019086

Haas, Tobias; Schmitz, Frank; Heit, Antje; Wagner, Hermann

2009-01-01

312

Spatial Displays and Spatial Instruments  

NASA Technical Reports Server (NTRS)

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.

Ellis, Stephen R. (editor); Kaiser, Mary K. (editor); Grunwald, Arthur J. (editor)

1989-01-01

313

Approximate \\kappa -state solutions of the Dirac equation in spatially dependent mass for the Eckart potential including the Yukawa tensor interaction  

NASA Astrophysics Data System (ADS)

We investigate the analytical approximation to arbitrary \\kappa -state solutions of the Dirac equation with the position-dependent mass particle in the Eckart potential including the Yukawa tensor interaction in the framework of a parametric Nikiforov-Uvarov method. By taking a proper approximation to deal with the centrifugal term, the analytical relativistic energy eigenvalues and the corresponding normalized two-spinor components of the wave function are obtained in closed form. The relativistic and non-relativistic bound state solutions for some special cases, such as the Hulthén potential and the generalized Morse potential, are easily obtained from our general solution.

Ikhdair, Sameer M.

2013-12-01

314

Multielectron effects in strong-field dissociative ionization of molecules  

NASA Astrophysics Data System (ADS)

We study triple-ionization-induced, spatially asymmetric dissociation of N2 using angular streaking in an elliptically polarized laser pulse in conjunction with few-cycle pump-probe experiments. The kinetic-energy-release dependent directional asymmetry in the ion sum-momentum distribution reflects the internuclear distance dependence of the fragmentation mechanism. Our results show that for 5-35-fs near-infrared laser pulses with intensities reaching 1015 W/cm2, charge exchange between nuclei plays a minor role in the triple ionization of N2. We demonstrate that angular streaking provides a powerful tool for probing multielectron effects in strong-field dissociative ionization of small molecules.

Gong, X.; Kunitski, M.; Betsch, K. J.; Song, Q.; Schmidt, L. Ph. H.; Jahnke, T.; Kling, Nora G.; Herrwerth, O.; Bergues, B.; Senftleben, A.; Ullrich, J.; Moshammer, R.; Paulus, G. G.; Ben-Itzhak, I.; Lezius, M.; Kling, M. F.; Zeng, H.; Jones, R. R.; Wu, J.

2014-04-01

315

Nova Spatial  

NSDL National Science Digital Library

Nova Spatial is a software firm which has developed GIS software for the Android (TM) mobile device platform. Products include pcMapper Lite and extensions that allow for creation of GIS shape files using just a standard smartphone.

Llc, Nova S.

316

Spatial agraphia.  

PubMed

Twenty-one patients with right hemisphere damage were studied (11 men, 10 women; average age = 41.33; age range 19-65). Subjects were divided into two groups: pre-Rolandic (6) and retro-Rolandic (15) right hemisphere damaged patients. A special writing test was given to each patient. The writing errors observed included literal substitutions, feature omissions and additions, letter omissions and additions, inability to maintain horizontal writing, inappropriate grouping and fragmentation of elements, and changes in handwriting style. Associated disorders included left-hemiparesis, visual field defects, spatial hemi-neglect, constructional apraxia, spatial alexia, and spatial acalculia. It is proposed that spatial agraphia is related to: (1) left hemi-neglect, (2) constructional deficits, (3) general spatial defects, and (4) some motor disautomatization and tendency to perseverate. In cases of right frontal damage, motor-associated deficits (iterations of features and letters) predominated, whereas in cases of posterior right hemisphere damage, spatial defects (inappropriate distribution of written material in the space, grouping of letters belonging to different words, and splitting of words) were more evident. Writing impairments are in general more noticeable in cases of retro-Rolandic damage. PMID:8373568

Ardila, A; Rosselli, M

1993-07-01

317

Spatial dependence of a differential shading artifact in images from coil arrays with reactive cross-talk at 1.5 T.  

PubMed

Reactive cross-talk causes leakage of the reception signal between neighboring coils of a receiver array. We present here experimental and computer-simulated NMR images (based upon a simple theory) to show, for an array of two coils, that the leakage (or secondary) signal is combined phase sensitively with the primary signal in each coil, to produce (in certain geometries) a differential shading artifact, manifest as a divot of missing intensity in the image derived from one (and only one) of the two coils. The asymmetry of this effect arises from the sense of the nuclear precession, and the afflicted coil may be swapped with its mate by reversing the direction of the static magnetic field. The artifact appears most clearly in transaxial images and is shown to be forbidden in certain types of saggital images. In a simplified theory for an array of two meshes (i.e., with only two degrees of freedom) the severity of the artifact depends upon the normalized coefficient of coupling (denoted eta and related to the cross-talk in decibels, psi, by psi=-20 log eta.) While the presence of input trap circuits in a typical array doubles the degrees of freedom and complicates both the circuit theory and the circuit measurements, the cross-talk is nonetheless shown to be given by an expression of the form psi=-20 log eta', where the new primed parameter eta' embodies the impedance-matching capacitance and the resistance of the scanner's preamplifiers, as well as the mutual reactance responsible for the cross-talk. The values of cross-talk inferred from the computer simulations of the image artifact are somewhat higher (by an estimated 3 to 6 dB) than those obtained by bench top measurements; but, given that the simulations unmistakably reproduce the unique and highly characteristic visual appearance of the artifact, the proposed model for its formation is claimed to be essentially correct. Finally, it is suggested that the artifact could be corrected by means of the filtered, edge-completed, reception profile described by Wald and co-workers (Wald et al., Magn. Reson. Med. 34, 433 (1995)). PMID:11444950

Tropp, J; Schirmer, T

2001-07-01

318

Serial dependence in visual perception  

PubMed Central

Visual input often arrives in a noisy and discontinuous stream, owing to head and eye movements, occlusion, lighting changes, and many other factors. Yet the physical world is generally stable—objects and physical characteristics rarely change spontaneously. How then does the human visual system capitalize on continuity in the physical environment over time? Here we show that visual perception is serially dependent, using both prior and present input to inform perception at the present moment. Using an orientation judgment task, we found that even when visual input changes randomly over time, perceived orientation is strongly and systematically biased toward recently seen stimuli. Further, the strength of this bias is modulated by attention and tuned to the spatial and temporal proximity of successive stimuli. These results reveal a serial dependence in perception characterized by a spatiotemporally tuned, orientation-selective operator—which we call a continuity field—that may promote visual stability over time. PMID:24686785

Fischer, Jason; Whitney, David

2014-01-01

319

On Strong ( A )-Rings  

Microsoft Academic Search

In this paper, we introduce a strong property (A) as follows: A ring R is called satisfying strong property (A) if every finitely generated ideal of R which is generated by a finite number of zero-divisors elements of R, has a non zero annihilator. We study the transfer of property (A) and strong property (A) in trivial ring extensions and

Najib Mahdou; Aziza Rahmouni Hassani

320

Synesthesia: Strong and Weak  

Microsoft Academic Search

In this review, we distinguish strong and weak forms of synesthesia. Strong synesthesia is characterized by a vivid image in one sensory modality in response to stimulation in another one. Weak synesthesia is characterized by cross-sensory correspondences expressed through language, perceptual similarity, and perceptual interactions during information processing. Despite important phenomenological dissimilarities between strong and weak synesthesia, we maintain that

Gail Martino; Lawrence E. Marks

2001-01-01

321

Natural auditory scene statistics shapes human spatial hearing  

PubMed Central

Human perception, cognition, and action are laced with seemingly arbitrary mappings. In particular, sound has a strong spatial connotation: Sounds are high and low, melodies rise and fall, and pitch systematically biases perceived sound elevation. The origins of such mappings are unknown. Are they the result of physiological constraints, do they reflect natural environmental statistics, or are they truly arbitrary? We recorded natural sounds from the environment, analyzed the elevation-dependent filtering of the outer ear, and measured frequency-dependent biases in human sound localization. We find that auditory scene statistics reveals a clear mapping between frequency and elevation. Perhaps more interestingly, this natural statistical mapping is tightly mirrored in both ear-filtering properties and in perceived sound location. This suggests that both sound localization behavior and ear anatomy are fine-tuned to the statistics of natural auditory scenes, likely providing the basis for the spatial connotation of human hearing. PMID:24711409

Parise, Cesare V.; Knorre, Katharina; Ernst, Marc O.

2014-01-01

322

High-resolution delineation of chlorinated volatile organic compounds in a dipping, fractured mudstone: Depth- and strata-dependent spatial variability from rock-core sampling  

NASA Astrophysics Data System (ADS)

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.

Goode, Daniel J.; Imbrigiotta, Thomas E.; Lacombe, Pierre J.

2014-12-01

323

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

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.

Goode, Daniel J.; Imbrigiotta, Thomas E.; Lacombe, Pierre J.

2014-01-01

324

High-resolution delineation of chlorinated volatile organic compounds in a dipping, fractured mudstone: Depth- and strata-dependent spatial variability from rock-core sampling.  

PubMed

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 55years 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. PMID:25461882

Goode, Daniel J; Imbrigiotta, Thomas E; Lacombe, Pierre J

2014-12-15

325

SPATIAL TRANSFORMATIONS 1 Running head: Spatial transformations  

E-print Network

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

Zacks, Jeffrey M.

326

One spatial map or many? Spatial coding of connected environments.  

PubMed

We investigated how humans encode large-scale spatial environments using a virtual taxi game. We hypothesized that if 2 connected neighborhoods are explored jointly, people will form a single integrated spatial representation of the town. However, if the neighborhoods are first learned separately and later observed to be connected, people will form separate spatial representations; this should incur an accuracy cost when inferring directions from one neighborhood to the other. Interestingly, our data instead suggest that people have a very strong tendency to form local representations, regardless of whether the neighborhoods were learned together or separately. Only when all visible distinctions between neighborhoods were removed did people behave as if they formed one integrated spatial representation. These data are broadly consistent with evidence from rodent hippocampal place cell recordings in connected boxes, and with hierarchical models of spatial coding. PMID:24364723

Han, Xue; Becker, Suzanna

2014-03-01

327

Spatially confined assembly of nanoparticles.  

PubMed

The ability to assemble NPs into ordered structures that are expected to yield collective physical or chemical properties has afforded new and exciting opportunities in the field of nanotechnology. Among the various configurations of nanoparticle assemblies, two-dimensional (2D) NP patterns and one-dimensional (1D) NP arrays on surfaces are regarded as the ideal assembly configurations for many technological devices, for example, solar cells, magnetic memory, switching devices, and sensing devices, due to their unique transport phenomena and the cooperative properties of NPs in assemblies. To realize the potential applications of NP assemblies, especially in nanodevice-related applications, certain key issues must still be resolved, for example, ordering and alignment, manipulating and positioning in nanodevices, and multicomponent or hierarchical structures of NP assemblies for device integration. Additionally, the assembly of NPs with high precision and high levels of integration and uniformity for devices with scaled-down dimensions has become a key and challenging issue. Two-dimensional NP patterns and 1D NP arrays are obtained using traditional lithography techniques (top-down strategies) or interfacial assembly techniques (bottom-up strategies). However, a formidable challenge that persists is the controllable assembly of NPs in desired locations over large areas with high precision and high levels of integration. The difficulty of this assembly is due to the low efficiency of small features over large areas in lithography techniques or the inevitable structural defects that occur during the assembly process. The combination of self-assembly strategies with existing nanofabrication techniques could potentially provide effective and distinctive solutions for fabricating NPs with precise position control and high resolution. Furthermore, the synergistic combination of spatially mediated interactions between nanoparticles and prestructures on surfaces may play an increasingly important role in the controllable assembly of NPs. In this Account, we summarize our approaches and progress in fabricating spatially confined assemblies of NPs that allow for the positioning of NPs with high resolution and considerable throughput. The spatially selective assembly of NPs at the desired location can be achieved by various mechanisms, such as, a controlled dewetting process, electrostatically mediated assembly of particles, and confined deposition and growth of NPs. Three nanofabrication techniques used to produce prepatterns on a substrate are summarized: the Langmuir-Blodgett (LB) patterning technique, e-beam lithography (EBL), and nanoimprint lithography (NPL). The particle density, particle size, or interparticle distance in NP assemblies strongly depends on the geometric parameters of the template structure due to spatial confinement. In addition, with smart design template structures, multiplexed NPs can be assembled into a defined structure, thus demonstrating the structural and functional complexity required for highly integrated and multifunction applications. PMID:25244100

Jiang, Lin; Chen, Xiaodong; Lu, Nan; Chi, Lifeng

2014-10-21

328

Spatial anxiety relates to spatial abilities as a function of working memory in children  

Microsoft Academic Search

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

Gerardo Ramirez; Elizabeth A. Gunderson; Susan C. Levine; Sian L. Beilock

2012-01-01

329

Spatial complexity due to strong correlations in vanadium dioxide  

NASA Astrophysics Data System (ADS)

Near-field scanning infrared microscopy on the Mott metal-insulator system vanadium dioxide (VO2) has revealed complex nanoscale pattern formation in the form of insulating and metallic puddles near the insulator-to-metal transition [1]. We use and extend recently developed cluster techniques [2] in order to understand the fundamental physics driving this multiscale pattern formation. We map the observed metallic and insulating clusters to Ising variables by a rigorous choice of threshold amplitude, and quantify the statistics of the sizes and shapes of the geometric clusters. These in turn yield critical exponents including the cluster size distribution exponent ?, and the fractal dimensions associated with the cluster formation. These quantitative measures show power-law behavior over multiple decades, revealing a delicate interplay between interactions and disorder in the material. The cluster techniques employed here can be readily applied to 2D image data in the context of other materials and measurement techniques. [1] M. M. Qazilbash, et al., Science 318, 1750 (2007).[2] B. Phillabaum, E. W. Carlson, and K. A. Dahmen, Nat. Commun. 3, 915 (2012).

Liu, Shuo; Phillabaum, Benjamin; Carlson, Erica; Dahmen, Karin; Qazilbash, Mumtaz; Basov, Dmitri; Sudhindra, Vidhyadhiraja

2013-03-01

330

Spatial networks  

NASA Astrophysics Data System (ADS)

Complex systems are very often organized under the form of networks where nodes and edges are embedded in space. Transportation and mobility networks, Internet, mobile phone networks, power grids, social and contact networks, and neural networks, are all examples where space is relevant and where topology alone does not contain all the information. Characterizing and understanding the structure and the evolution of spatial networks is thus crucial for many different fields, ranging from urbanism to epidemiology. An important consequence of space on networks is that there is a cost associated with the length of edges which in turn has dramatic effects on the topological structure of these networks. We will thoroughly explain the current state of our understanding of how the spatial constraints affect the structure and properties of these networks. We will review the most recent empirical observations and the most important models of spatial networks. We will also discuss various processes which take place on these spatial networks, such as phase transitions, random walks, synchronization, navigation, resilience, and disease spread.

Barthélemy, Marc

2011-02-01

331

Implications of Strong-Rate-Weakening Friction  

E-print Network

Implications of Strong-Rate- Weakening Friction for the Length-Scale Dependence of the Strength · Rapid transitions between high static friction and very low dynamic friction · Leads to slip-pulse rupture · Slip pulses are extremely localized and have strong positive feedback between friction and slip

Greer, Julia R.

332

A Malthusian curb on spatial structure in microorganism populations.  

PubMed

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

Martin, A P

2004-10-01

333

Strongly Modified Plasmon-Matter Interaction with Mesoscopic Quantum Emitters  

E-print Network

Semiconductor quantum dots (QDs) provide an essential link between light and matter in emerging fields such as light-harvesting, all-solid-state quantum communication, and quantum computing. QDs are excellent single-photon sources and can store quantum bits for extended periods making them promising interconnects between light and matter in integrated quantum information networks. To this end the light-matter interaction strength must be strongly enhanced using nanophotonic structures such as photonic crystal cavities and waveguides or plasmonic nanowires. So far it has been assumed that QDs can be treated just like atomic photon emitters where the spatial properties of the wavefunction can be safely ignored. Here we demonstrate that the point-emitter description for QDs near plasmonic nanostructures breaks down. We observe that the QDs can excite plasmons eight times more efficiently depending on their orientation due to their mesoscopic character. Either enhancement or suppresion of the rate of plasmon exci...

Andersen, Mads Lykke; Sørensen, Anders Søndberg; Lodahl, Peter

2010-01-01

334

Discovering Sensor Space: Constructing Spatial Embeddings That Explain  

E-print Network

Discovering Sensor Space: Constructing Spatial Embeddings That Explain Sensor Correlations Joseph a sensor space from sensor correlations, namely the algorithm generates a spatial embedding of sensors where strongly correlated sensors will be neighbors in the embedding. The algorithm first infers

Modayil, Joseph

335

Strong Navajo Marriages  

ERIC Educational Resources Information Center

The purpose of this qualitative study, conducted in two Navajo Nation chapters, was to learn what makes Navajo marriages strong because no research has been done on this topic. Twenty-one Navajo couples (42 individuals) who felt they had strong marriages volunteered to participate in the study. Couples identified the following marital strengths:…

Skogrand, Linda; Mueller, Mary Lou; Arrington, Rachel; LeBlanc, Heidi; Spotted Elk, Davina; Dayzie, Irene; Rosenbrand, Reva

2008-01-01

336

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.

337

Strong quantum interference in strongly disordered bosonic insulators  

NASA Astrophysics Data System (ADS)

We study the model of variable-range hopping of bosons in an array of sites with short-range interactions and a large characteristic coordination number, which describes conduction in a broad class of insulators, such as strongly disordered superconductive films, systems close to the Anderson transition, Josephson networks, etc. Large coordination number leads to strong quantum interference phenomena yet allows for their analytical study. We develop a functional renormalization group scheme that repeatedly eliminates high-energy sites properly renormalizing the tunneling between the low-energy ones. Using this approach we determine the temperature and magnetic field dependence of the hopping conductivity and find a large positive magnetoresistance. With increasing magnetic field the behaviour of the conductivity crossovers from the Mott's law to an activational behaviour with the activation gap proportional to the magnetic field.

Syzranov, Sergey; Moor, Andreas; Efetov, Konstantin

2012-02-01

338

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

We present a time-dependent density-functional-theory approach for the ab initio study of the effect of correlated multielectron responses on the multiphoton ionization (MPI) of diatomic molecules N2, O2, and F2 in intense short laser pulse fields...

Chu, Shih-I; Telnov, Dmitry A.

2009-04-03

339

Spatial effects in real networks: measures, null models, and applications.  

PubMed

Spatially embedded networks are shaped by a combination of purely topological (space-independent) and space-dependent formation rules. While it is quite easy to artificially generate networks where the relative importance of these two factors can be varied arbitrarily, it is much more difficult to disentangle these two architectural effects in real networks. Here we propose a solution to this problem, by introducing global and local measures of spatial effects that, through a comparison with adequate null models, effectively filter out the spurious contribution of nonspatial constraints. Our filtering allows us to consistently compare different embedded networks or different historical snapshots of the same network. As a challenging application we analyze the World Trade Web, whose topology is known to depend on geographic distances but is also strongly determined by nonspatial constraints (degree sequence or gross domestic product). Remarkably, we are able to detect weak but significant spatial effects both locally and globally in the network, showing that our method succeeds in retrieving spatial information even when nonspatial factors dominate. We finally relate our results to the economic literature on gravity models and trade globalization. PMID:23368007

Ruzzenenti, Franco; Picciolo, Francesco; Basosi, Riccardo; Garlaschelli, Diego

2012-12-01

340

Spatial effects in real networks: Measures, null models, and applications  

NASA Astrophysics Data System (ADS)

Spatially embedded networks are shaped by a combination of purely topological (space-independent) and space-dependent formation rules. While it is quite easy to artificially generate networks where the relative importance of these two factors can be varied arbitrarily, it is much more difficult to disentangle these two architectural effects in real networks. Here we propose a solution to this problem, by introducing global and local measures of spatial effects that, through a comparison with adequate null models, effectively filter out the spurious contribution of nonspatial constraints. Our filtering allows us to consistently compare different embedded networks or different historical snapshots of the same network. As a challenging application we analyze the World Trade Web, whose topology is known to depend on geographic distances but is also strongly determined by nonspatial constraints (degree sequence or gross domestic product). Remarkably, we are able to detect weak but significant spatial effects both locally and globally in the network, showing that our method succeeds in retrieving spatial information even when nonspatial factors dominate. We finally relate our results to the economic literature on gravity models and trade globalization.

Ruzzenenti, Franco; Picciolo, Francesco; Basosi, Riccardo; Garlaschelli, Diego

2012-12-01

341

Competing valence-bond states of spin-3/2 fermions on a strongly coupled ladder  

NASA Astrophysics Data System (ADS)

We study the possible ground-state configurations of two strongly coupled chains of charge neutral spin-3/2 fermionic atoms interacting via short-range van der Waals interaction. The coupling between the two chains is realized by a relatively large hopping amplitude. Exploiting the fact that such a ladder configuration can be mapped to an effective one-band model, we analyze the emerging ground states of the system. We show that various spatially inhomogeneous states, valence-bond states, and plaquette states compete depending on the filling and the ratio of the interaction strengths in the singlet and quintet scattering channel. We find that a Luttinger liquid state is the ground state of the strongly coupled ladder in an extended region of the parameter space, and we also show that a topologically nontrivial charge Haldane state can emerge in the strongly coupled ladder at quarter and three-quarter fillings.

Szirmai, E.; Nonne, H.

2014-12-01

342

Explosion source strong ground motions in the Mississippi embayment  

USGS Publications Warehouse

Two strong-motion arrays were deployed for the October 2002 Embayment Seismic Excitation Experiment to study the spatial variation of strong ground motions in the deep, unconsolidated sediments of the Mississippi embayment because there are no comparable strong-motion data from natural earthquakes in the area. Each linear array consisted of eight three-component K2 accelerographs spaced 15 m apart situated 1.2 and 2.5 kin from 2268-kg and 1134-kg borehole explosion sources, respectively. The array data show distinct body-wave and surface-wave arrivals that propagate within the thick, unconsolidated sedimentary column, the high-velocity basement rocks, and small-scale structure near the surface. Time-domain coherence of body-wave and surface-wave arrivals is computed for acceleration, velocity, and displacement time windows. Coherence is high for relatively low-frequency verticalcomponent Rayleigh waves and high-frequency P waves propagating across the array. Prominent high-frequency PS conversions seen on radial components, a proxy for the direct S wave from earthquake sources, lose coherence quickly over the 105-m length of the array. Transverse component signals are least coherent for any ground motion and appear to be highly scattered. Horizontal phase velocity is computed by using the ratio of particle velocity to estimates of the strain based on a plane-wave-propagation model. The resulting time-dependent phase-velocity map is a useful way to infer the propagation mechanisms of individual seismic phases and time windows of three-component waveforms. Displacement gradient analysis is a complementary technique for processing general spatial-array data to obtain horizontal slowness information.

Langston, C.A.; Bodin, P.; Powell, C.; Withers, M.; Horton, S.; Mooney, W.

2006-01-01

343

An efficient algorithm for spatially-correlated random fields generation and its applications on the two-phase material  

NASA Astrophysics Data System (ADS)

The properties of material strongly depend on the microstructure, and the development of microstructure is closely related to the phase transition with the temperature-dependent spatial correlation. To consider more realistic microstructures, we have proposed an efficient and simple algorithm for generating the spatially-correlated random field, which is obtained by the weighted average of random fields without spatial correlation according to the spatially-correlated length and anisotropy parameter. By using a mesoscale finite element model with the microstructures generated by our algorithm, an application study on the effective elastic behavior of Al2O3-NiAl composite materials is given. Our numerical results are in agreement with the experimental measurements. The proposed method is general and robust, which can be extended to the multi-phase materials.

Tang, Xin-Wei; Yang, Xiao-Bao; Zhou, Yuan-De

2014-03-01

344

[Spatial neglect].  

PubMed

Unilateral spatial (hemi-)neglect or (hemi-)inattention are clinical terms used to describe a number of different clinical symptoms which have in common the patient's failure to attend to, respond adequately to, or orient voluntarily to people or objects in the contralesional space. Unilateral spatial neglect is most often observed following brain lesions affecting the right hemisphere, and in particular the right inferior parietal cortex (angular and supramarginal gyrus) and right temporoparietal junction. Importantly, the term hemineglect cannot be meaningfully used if the target behavior is explained by primary sensory or motor deficits only. Typically the patient's deficit is supramodal: patients with hemineglect fail to respond to novel or meaningful stimuli irrespective of whether they are presented in the visual, auditory, and somesthetic (somatosensory) domain. As adequate perception and spatial representation of both the body and the outside world are mandatory for almost all activities of daily living, hemineglect is known to limit the degree of active participation in rehabilitation programs and is thus commonly associated with poor functional recovery and less successful social reintegration. A number of new promising behavioral and pharmacological treatments may help to ameliorate neglect in the future. PMID:15048330

Fink, G R; Heide, W

2004-04-01

345

Scale matters: the impact of organic farming on biodiversity at different spatial scales.  

PubMed

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

Gabriel, Doreen; Sait, Steven M; Hodgson, Jenny A; Schmutz, Ulrich; Kunin, William E; Benton, Tim G

2010-07-01

346

Communication with spatially modulated Light through turbulent Air across Vienna  

E-print Network

The transverse spatial modes of light offer a large state-space with interesting physical properties. For exploiting it in future long-distance experiments, spatial modes will have to be transmitted over turbulent free-space links. Numerous recent lab-scale experiments have found significant degradation in the mode quality after transmission through simulated turbulence and consecutive coherent detection. Here we experimentally analyze the transmission of one prominent class of spatial modes, the orbital-angular momentum (OAM) modes, through 3 km of strong turbulence over the city of Vienna. Instead of performing a coherent phase-dependent measurement, we employ an incoherent detection scheme which relies on the unambiguous intensity patterns of the different spatial modes. We use a pattern recognition algorithm (an artificial neural network) to identify the characteristic mode pattern displayed on a screen at the receiver. We were able to distinguish between 16 different OAM mode superpositions with only ~1.7% error, and use them to encode and transmit small grey-scale images. Moreover, we found that the relative phase of the superposition modes is not affected by the atmosphere, establishing the feasibility for performing long-distance quantum experiments with the OAM of photons. Our detection method works for other classes of spatial modes with unambiguous intensity patterns as well, and can further be improved by modern techniques of pattern recognition.

Mario Krenn; Robert Fickler; Matthias Fink; Johannes Handsteiner; Mehul Malik; Thomas Scheidl; Rupert Ursin; Anton Zeilinger

2014-11-12

347

Spatial variation in the bacterial and denitrifying bacterial community in a biofilter treating subsurface agricultural drainage.  

PubMed

Denitrifying biofilters can remove agricultural nitrates from subsurface drainage, reducing nitrate pollution that contributes to coastal hypoxic zones. The performance and reliability of natural and engineered systems dependent upon microbially mediated processes, such as the denitrifying biofilters, can be affected by the spatial structure of their microbial communities. Furthermore, our understanding of the relationship between microbial community composition and function is influenced by the spatial distribution of samples.In this study we characterized the spatial structure of bacterial communities in a denitrifying biofilter in central Illinois. Bacterial communities were assessed using automated ribosomal intergenic spacer analysis for bacteria and terminal restriction fragment length polymorphism of nosZ for denitrifying bacteria.Non-metric multidimensional scaling and analysis of similarity (ANOSIM) analyses indicated that bacteria showed statistically significant spatial structure by depth and transect,while denitrifying bacteria did not exhibit significant spatial structure. For determination of spatial patterns, we developed a package of automated functions for the R statistical environment that allows directional analysis of microbial community composition data using either ANOSIM or Mantel statistics.Applying this package to the biofilter data, the flow path correlation range for the bacterial community was 6.4 m at the shallower, periodically in undated depth and 10.7 m at the deeper, continually submerged depth. These spatial structures suggest a strong influence of hydrology on the microbial community composition in these denitrifying biofilters. Understanding such spatial structure can also guide optimal sample collection strategies for microbial community analyses. PMID:24077652

Andrus, J Malia; Porter, Matthew D; Rodríguez, Luis F; Kuehlhorn, Timothy; Cooke, Richard A C; Zhang, Yuanhui; Kent, Angela D; Zilles, Julie L

2014-02-01

348

Spatial and Temporal Patterns of Tidal Dissipation in Synchronous Satellites  

NASA Technical Reports Server (NTRS)

Tidal heating is an important energy source for several solar system bodies, and there is a wide-spread perception that the pattern of surface heat flow is diagnostic of internal structure. We wish to clarify that situation. Our analysis depends upon two important assumptions: First, that heat transport is dominated by conduction. Second, that the body can be modeled by a sequence of spherically symmetric layers, each with a linear visco-elastic rheology. Under these assumptions, surface heat flow patterns in tidally dominated satellites will reflect radially integrated dissipation patterns. For synchronously rotating satellites with zero obliquity, this pattern depends quite strongly on orbital eccentricity but relatively little on purely radial variations in internal structure. The total amount of heat generated within the body does depend sensitively on internal structure, but the spatial pattern is rather insensitive to structure, especially at low orbital eccentricities.

Bills, Bruce G.; Aharonson, Oded

2003-01-01

349

Detecting the Amplitude Mode of Strongly Interacting Lattice Bosons by Bragg Scattering  

SciTech Connect

We report the first detection of the Higgs-type amplitude mode using Bragg spectroscopy in a strongly interacting condensate of ultracold atoms in an optical lattice. By the comparison of our experimental data with a spatially resolved, time-dependent bosonic Gutzwiller calculation, we obtain good quantitative agreement. This allows for a clear identification of the amplitude mode, showing that it can be detected with full momentum resolution by going beyond the linear response regime. A systematic shift of the sound and amplitude modes' resonance frequencies due to the finite Bragg beam intensity is observed.

Bissbort, Ulf; Hofstetter, Walter [Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, 60438 Frankfurt/Main (Germany); Goetze, Soeren; Heinze, Jannes; Krauser, Jasper S.; Weinberg, Malte; Becker, Christoph; Sengstock, Klaus [Institut fuer Laser-Physik, Universitaet Hamburg, 22761 Hamburg (Germany); Li Yongqiang [Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, 60438 Frankfurt/Main (Germany); Department of Physics, National University of Defense Technology, Changsha 410073 (China)

2011-05-20

350

The realization that the Red Queen and Court Jester models may be scale-dependent, and that  

E-print Network

, and the origin of novelties. Further, methods are shared by paleontologists and ne- ontologists, and this allows, genetic, and developmental factors and strongly dependent on historical contingencies. Using modeling approaches, we identify 10 general patterns concerning the temporal, spatial, and genetic

Losos, Jonathan B.

351

Temporal consistency of spatial pattern in growth of the mussel, Mytilus edulis: Implications for predictive modelling  

NASA Astrophysics Data System (ADS)

Human pressures on coastal seas are increasing and methods for sustainable management, including spatial planning and mitigative actions, are therefore needed. In coastal areas worldwide, the development of mussel farming as an economically and ecologically sustainable industry requires geographic information on the growth and potential production capacity. In practice this means that coherent maps of temporally stable spatial patterns of growth need to be available in the planning process and that maps need to be based on mechanistic or empirical models. Therefore, as a first step towards development of models of growth, we assessed empirically the fundamental requirement that there are temporally consistent spatial patterns of growth in the blue mussel, Mytilus edulis. Using a pilot study we designed and dimensioned a transplant experiment, where the spatial consistency in the growth of mussels was evaluated at two resolutions. We found strong temporal and scale-dependent spatial variability in growth but patterns suggested that spatial patterns were uncoupled between growth of shell and that of soft tissue. Spatial patterns of shell growth were complex and largely inconsistent among years. Importantly, however, the growth of soft tissue was qualitatively consistent among years at the scale of km. The results suggest that processes affecting the whole coastal area cause substantial differences in growth of soft tissue among years but that factors varying at the scale of km create strong and persistent spatial patterns of growth, with a potential doubling of productivity by identifying the most suitable locations. We conclude that the observed spatial consistency provides a basis for further development of predictive modelling and mapping of soft tissue growth in these coastal areas. Potential causes of observed patterns, consequences for mussel-farming as a tool for mitigating eutrophication, aspects of precision of modelling and sampling of mussel growth as well as ecological functions in general are discussed.

Bergström, Per; Lindegarth, Susanne; Lindegarth, Mats

2013-10-01

352

Kinetic Characterization of Strongly Coupled Systems  

SciTech Connect

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.

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

353

On Strong Anticipation  

PubMed Central

We examine Dubois's (2003) distinction between weak anticipation and strong anticipation. Anticipation is weak if it arises from a model of the system via internal simulations. Anticipation is strong if it arises from the system itself via lawful regularities embedded in the system's ordinary mode of functioning. The assumption of weak anticipation dominates cognitive science and neuroscience and in particular the study of perception and action. The assumption of strong anticipation, however, seems to be required by anticipation's ubiquity. It is, for example, characteristic of homeostatic processes at the level of the organism, organs, and cells. We develop the formal distinction between strong and weak anticipation by elaboration of anticipating synchronization, a phenomenon arising from time delays in appropriately coupled dynamical systems. The elaboration is conducted in respect to (a) strictly physical systems, (b) the defining features of circadian rhythms, often viewed as paradigmatic of biological behavior based in internal models, (c) Pavlovian learning, and (d) forward models in motor control. We identify the common thread of strongly anticipatory systems and argue for its significance in furthering understanding of notions such as “internal”, “model” and “prediction”. PMID:20191086

Stepp, N.; Turvey, M. T.

2009-01-01

354

Strongly nonlinear traveling waves in granular dimer chains  

NASA Astrophysics Data System (ADS)

This study is concerned with the dynamics of spatially periodic travelling waves supported by strongly nonlinear granular dimer chains with no pre-compression. In particular, we demonstrate numerically the formation of special families of travelling waves with spatially periodic waveforms that are realized in semi-infinite dimer chains. These traveling waves depend on a single system parameter defined as the mass ratio of the two granules forming each dimer pair of the chain. The dynamics of these families of traveling waves is systematically studied by considering finite dimer chains (termed the 'reduced systems') subject to periodic boundary conditions. In the present work we demonstrate that these waves may exhibit interesting bifurcations or loss of stability as the system parameter and the energy of the motion vary. In turn, these bifurcations and stability exchanges in infinite dimer chains are correlated to previous studies of pulse attenuation in finite dimer chains through efficient energy radiation from the propagating pulse to the far field, mainly in the form of traveling waves. Based on these results a new formulation of attenuation and propagation zones (stop and pass bands) in semi-infinite granular dimer chains is proposed.

Jayaprakash, K. R.; Vakakis, Alexander F.; Starosvetsky, Yuli

2013-08-01

355

How context dependent are species interactions?  

PubMed

The net effects of interspecific species interactions on individuals and populations vary in both sign (-, 0, +) and magnitude (strong to weak). Interaction outcomes are context-dependent when the sign and/or magnitude change as a function of the biotic or abiotic context. While context dependency appears to be common, its distribution in nature is poorly described. Here, we used meta-analysis to quantify variation in species interaction outcomes (competition, mutualism, or predation) for 247 published articles. Contrary to our expectations, variation in the magnitude of effect sizes did not differ among species interactions, and while mutualism was most likely to change sign across contexts (and predation least likely), mutualism did not strongly differ from competition. Both the magnitude and sign of species interactions varied the most along spatial and abiotic gradients, and least as a function of the presence/absence of a third species. However, the degree of context dependency across these context types was not consistent among mutualism, competition and predation studies. Surprisingly, study location and ecosystem type varied in the degree of context dependency, with laboratory studies showing the highest variation in outcomes. We urge that studying context dependency per se, rather than focusing only on mean outcomes, can provide a general method for describing patterns of variation in nature. PMID:24735225

Chamberlain, Scott A; Bronstein, Judith L; Rudgers, Jennifer A

2014-07-01

356

Microbial spatial variability: An example from the Celtic Sea  

NASA Astrophysics Data System (ADS)

In July 2004, dominant populations of microbial ultraplankton (<5 ?m), in the surface of the Celtic Sea (between UK and Eire), were repeatedly mapped using flow cytometry, at 1.5 km resolution over a region of diameter 100 km. The numerically dominant representatives of all basic functional types were enumerated including one group of phototrophic bacteria ( Syn), two groups of phytoplankton (PP, NP), three groups of heterotrophic bacterioplankton (HB) and the regionally dominant group of heterotrophic protists (HP). The distributions of all organisms showed strong spatial variability with little relation to variability in physical fields such as salinity and temperature. Furthermore, there was little agreement between distributions of different organisms. The only linear correlation consistently explaining more than 50% of the variance between any pairing of the organism groups enumerated is between two different groups of HB. Specifically, no linear, or non-linear, relationship is found between any pairings of SYB, PP or HB groups with their protist predators HP. Looking for multiple dependencies, factor analysis reveals three groupings: Syn, PP and low nucleic acid content HB (LNA); high nucleic acid content HB (HNA); HP and NP. Even the manner in which the spatial variability of Syn, PP and HB abundance varies as a function of lengthscale (represented by a semivariogram) differs significantly from that for HP. In summary, although all microbial planktonic groups enumerated are present and numerically dominant throughout the region studied, at face value the relationships between them seem weak. Nevertheless, the behaviour of a simple, illustrative ecological model, with strongly interacting phototrophs and heterotrophs, with stochastic forcing, is shown to be consistent with the observed poor correlations and differences in how spatial variability varies with lengthscale. Thus, our study suggests that a comparison of microbial abundances alone may not discern strong underlying trophic interactions. Specific knowledge of these processes, in particular grazing, will be required to explain the causes of the observed microbial spatial variability and its resulting consequences for the functioning of the ecosystem.

Martin, Adrian P.; Zubkov, Mikhail V.; Fasham, Michael J.; Burkill, Peter H.; Holland, Ross J.

2008-03-01

357

Networks of strong ties  

NASA Astrophysics Data System (ADS)

Social networks transmitting covert or sensitive information cannot use all ties for this purpose. Rather, they can only use a subset of ties that are strong enough to be “trusted”. This paper addresses whether it is still possible, under this restriction, for information to be transmitted widely and rapidly in social networks. We use transitivity as evidence of strong ties, requiring one or more shared contacts in order to count an edge as strong. We examine the effect of removing all non-transitive ties in two real social network data sets, imposing varying thresholds in the number of shared contacts. We observe that transitive ties occupy a large portion of the network and that removing all other ties, while causing some individuals to become disconnected, preserves the majority of the giant connected component. Furthermore, the average shortest path, important for the rapid diffusion of information, increases only slightly relative to the original network. We also evaluate the cost of forming transitive ties by modeling a random graph composed entirely of closed triads and comparing its connectivity and average shortest path with the equivalent Erdös-Renyi random graph. Both the empirical study and random model point to a robustness of strong ties with respect to the connectivity and small world property of social networks.

Shi, Xiaolin; Adamic, Lada A.; Strauss, Martin J.

2007-05-01

358

Finish strong Criminology &  

E-print Network

Finish strong with us. Criminology & Criminal Justice DEGREE COMPLETION PROGRAM Our new Criminology Justice/Criminology as well as professional in the field, so that you'll know what to expect on the job at Wittenberg twenty or twenty­one semester hours in CRCJ courses, including: CRCJ 370 Criminological Theory

Bogaerts, Steven

359

Strong Little Magnets  

ERIC Educational Resources Information Center

Did you know that some strong little cylindrical magnets available in local hardware stores can have an effective circumferential current of 2500 A? This intriguing information can be obtained by hanging a pair of magnets at the center of a coil, as shown in Fig. 1, and measuring the oscillation frequency as a function of coil current.

Moloney, Michael J.

2007-01-01

360

Strong Coupling Holography  

E-print Network

We show that whenever a 4-dimensional theory with N particle species emerges as a consistent low energy description of a 3-brane embedded in an asymptotically-flat (4+d)-dimensional space, the holographic scale of high-dimensional gravity sets the strong coupling scale of the 4D theory. This connection persists in the limit in which gravity can be consistently decoupled. We demonstrate this effect for orbifold planes, as well as for the solitonic branes and string theoretic D-branes. In all cases the emergence of a 4D strong coupling scale from bulk holography is a persistent phenomenon. The effect turns out to be insensitive even to such extreme deformations of the brane action that seemingly shield 4D theory from the bulk gravity effects. A well understood example of such deformation is given by large 4D Einstein term in the 3-brane action, which is known to suppress the strength of 5D gravity at short distances and change the 5D Newton's law into the four-dimensional one. Nevertheless, we observe that the scale at which the scalar polarization of an effective 4D-graviton becomes strongly coupled is again set by the bulk holographic scale. The effect persist in the gravity decoupling limit, when the full theory reduces to a 4D system in which the only memory about the high-dimensional holography is encoded in the strong coupling scale. The observed intrinsic connection between the high-dimensional flat space holography and 4D strong coupling suggests a possible guideline for generalization of AdS/CFT duality to other systems.

Gia Dvali; Cesar Gomez

2009-07-18

361

Strong rightward lateralization of the dorsal attentional network in left-handers with right sighting-eye: An evolutionary advantage.  

PubMed

Hemispheric lateralization for spatial attention and its relationships with manual preference strength and eye preference were studied in a sample of 293 healthy individuals balanced for manual preference. Functional magnetic resonance imaging was used to map this large sample while performing visually guided saccadic eye movements. This activated a bilateral distributed cortico-subcortical network in which dorsal and ventral attentional/saccadic pathways elicited rightward asymmetrical activation depending on manual preference strength and sighting eye. While the ventral pathway showed a strong rightward asymmetry irrespective of both manual preference strength and eye preference, the dorsal frontoparietal network showed a robust rightward asymmetry in strongly left-handers, even more pronounced in left-handed subjects with a right sighting-eye. Our findings brings support to the hypothesis that the origin of the rightward hemispheric dominance for spatial attention may have a manipulo-spatial origin neither perceptual nor motor per se but rather reflecting a mechanism by which a spatial context is mapped onto the perceptual and motor activities, including the exploration of the spatial environment with eyes and hands. Within this context, strongly left-handers with a right sighting-eye may benefit from the advantage of having the same right hemispheric control of their dominant hand and visuospatial attention processing. We suggest that this phenomenon explains why left-handed right sighting-eye athletes can outperform their competitors in sporting duels and that the prehistoric and historical constancy of the left-handers ratio over the general population may relate in part on the hemispheric specialization of spatial attention. Hum Brain Mapp 36:1151-1164, 2015. © 2014 Wiley Periodicals, Inc. PMID:25409934

Petit, Laurent; Zago, Laure; Mellet, Emmanuel; Jobard, Gaël; Crivello, Fabrice; Joliot, Marc; Mazoyer, Bernard; Tzourio-Mazoyer, Nathalie

2015-03-01

362

Regulation of Spatial Selectivity by Crossover Inhibition  

PubMed Central

Signals throughout the nervous system diverge into parallel excitatory and inhibitory pathways that later converge on downstream neurons to control their spike output. Converging excitatory and inhibitory synaptic inputs can exhibit a variety of temporal relationships. A common motif is feedforward inhibition, in which an increase (decrease) in excitatory input precedes a corresponding increase (decrease) in inhibitory input. The delay of inhibitory input relative to excitatory input originates from an extra synapse in the circuit shaping inhibitory input. Another common motif is push-pull or “crossover” inhibition, in which increases (decreases) in excitatory input occur together with decreases (increases) in inhibitory input. Primate On midget ganglion cells receive primarily feedforward inhibition and On parasol cells receive primarily crossover inhibition; this difference provides an opportunity to study how each motif shapes the light responses of cell types that play a key role in visual perception. For full-field stimuli, feedforward inhibition abbreviated and attenuated responses of On midget cells, while crossover inhibition, though plentiful, had surprisingly little impact on the responses of On parasol cells. Spatially structured stimuli, however, could cause excitatory and inhibitory inputs to On parasol cells to increase together, adopting a temporal relation very much like that for feedforward inhibition. In this case, inhibitory inputs substantially abbreviated a cell’s spike output. Thus inhibitory input shapes the temporal stimulus selectivity of both midget and parasol ganglion cells, but its impact on responses of parasol cells depends strongly on the spatial structure of the light inputs. PMID:23575830

Cafaro, Jon; Rieke, Fred

2013-01-01

363

Combining spatial and temporal expectations to improve visual perception  

PubMed Central

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

Rohenkohl, Gustavo; Gould, Ian C.; Pessoa, Jéssica; Nobre, Anna C.

2014-01-01

364

Strong Quantum Interference in Strongly Disordered Bosonic Insulators  

NASA Astrophysics Data System (ADS)

We study the variable-range hopping of bosons in an array of sites with short-range interactions and a large characteristic coordination number. The latter leads to strong quantum interference phenomena yet allows for their analytical study. We develop a functional renormalization-group scheme that repeatedly eliminates high-energy sites properly renormalizing the tunneling between the low-energy ones. Using this approach we determine the temperature and magnetic field dependence of the hopping conductivity and find a large positive magnetoresistance. With increasing magnetic field the behavior of the conductivity crossovers from the Mott’s law to an activational behavior with the activation gap proportional to the magnetic field.

Syzranov, S. V.; Moor, A.; Efetov, K. B.

2012-06-01

365

Dynamics of strongly correlated and strongly inhomogeneous plasmas  

NASA Astrophysics Data System (ADS)

Kinetic and fluid equations are derived for the dynamics of classical inhomogeneous trapped plasmas in the strong coupling regime. The starting point is an extended Singwi-Tosi-Land-Sjölander (STLS) ansatz for the dynamic correlation function, which is allowed to depend on time and both particle coordinates separately. The time evolution of the correlation function is determined from the second equation of the Bogolyubov-Born-Green-Kirkwood-Yvon hierarchy. We study the equations in the linear limit and derive a nonlocal equation for the fluid displacement field. Comparisons to first-principles molecular dynamics simulations reveal an excellent quality of our approach thereby overcoming the limitations of the broadly used STLS scheme.

Kählert, Hanno; Kalman, Gabor J.; Bonitz, Michael

2014-07-01

366

On the growth of locally interacting plants: differential equations for the dynamics of spatial moments.  

PubMed

Ecologists are faced with the challenge of how to scale up from the activities of individual plants and animals to the macroscopic dynamics of populations and communities. It is especially difficult to do this in communities of plants where the fate of individuals depends on their immediate neighbors rather than an average over a larger region. This has meant that algorithmic, agent-based models are typically used to understand their dynamics, although certain macroscopic models have been developed for neighbor-dependent, birth death processes. Here we present a macroscopic model that, for the first time, incorporates explicit, gradual, neighbor-dependent plant growth, as a third fundamental process of plant communities. The model is derived from a stochastic, agent-based model, and describes the dynamics of the first and second spatial moments of a multispecies, spatially structured plant community with neighbor-dependent growth, births, and deaths. A simple example shows that strong neighborhood space-filling during tree growth in an even-aged stand of Scots pine is well captured by the spatial-moment model. The space-filling has a spatial signature consistent with that observed in several field studies of forests. Small neighborhoods of interaction, nonuniform spacing of trees, and asymmetric competition all contribute to the buildup of a wide range of tree sizes with some large dominant individuals and many smaller ones. PMID:24597220

Adams, Thomas P; Holland, E Penelope; Law, Richard; Plank, Michael J; Raghib, Michael

2013-12-01

367

Strongly interacting Higgs bosons  

Microsoft Academic Search

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

Thomas Appelquist; Claude Bernard

1980-01-01

368

Optimal configurations of spatial scale for grid cell firing under noise and uncertainty  

PubMed Central

We examined the accuracy with which the location of an agent moving within an environment could be decoded from the simulated firing of systems of grid cells. Grid cells were modelled with Poisson spiking dynamics and organized into multiple ‘modules’ of cells, with firing patterns of similar spatial scale within modules and a wide range of spatial scales across modules. The number of grid cells per module, the spatial scaling factor between modules and the size of the environment were varied. Errors in decoded location can take two forms: small errors of precision and larger errors resulting from ambiguity in decoding periodic firing patterns. With enough cells per module (e.g. eight modules of 100 cells each) grid systems are highly robust to ambiguity errors, even over ranges much larger than the largest grid scale (e.g. over a 500 m range when the maximum grid scale is 264 cm). Results did not depend strongly on the precise organization of scales across modules (geometric, co-prime or random). However, independent spatial noise across modules, which would occur if modules receive independent spatial inputs and might increase with spatial uncertainty, dramatically degrades the performance of the grid system. This effect of spatial uncertainty can be mitigated by uniform expansion of grid scales. Thus, in the realistic regimes simulated here, the optimal overall scale for a grid system represents a trade-off between minimizing spatial uncertainty (requiring large scales) and maximizing precision (requiring small scales). Within this view, the temporary expansion of grid scales observed in novel environments may be an optimal response to increased spatial uncertainty induced by the unfamiliarity of the available spatial cues. PMID:24366144

Towse, Benjamin W.; Barry, Caswell; Bush, Daniel; Burgess, Neil

2014-01-01

369

Temperature compensated sub-metre spatial resolution distributed strain sensor  

Microsoft Academic Search

Temperature compensated strain sensor measurements are demonstrated with strain resolution of 86u? and spatial resolution of 26cms, utilising temperature dependence of spontaneous Raman scattering for temperature compensated sub-metre spatial resolution Brillouin frequency based strain sensor.

Mohammad Belal; Trevor P Newson

2010-01-01

370

Probability Densities in Strong Turbulence  

E-print Network

According to modern developments in turbulence theory, the "dissipation" scales (u.v. cut-offs) $\\eta$ form a random field related to velocity increments $\\delta_{\\eta}u$. In this work we, using Mellin's transform combined with the Gaussain large -scale boundary condition, calculate probability densities (PDFs) of velocity increments $P(\\delta_{r}u,r)$ and the PDF of the dissipation scales $Q(\\eta, Re)$, where $Re$ is the large-scale Reynolds number. The resulting expressions strongly deviate from the Log-normal PDF $P_{L}(\\delta_{r}u,r)$ often quoted in the literature. It is shown that the probability density of the small-scale velocity fluctuations includes information about the large (integral) scale dynamics which is responsible for deviation of $P(\\delta_{r}u,r)$ from $P_{L}(\\delta_{r}u,r)$. A framework for evaluation of the PDFs of various turbulence characteristics involving spatial derivatives is developed. The exact relation, free of spurious Logarithms recently discussed in Frisch et al (J. Fluid Mech. {\\bf 542}, 97 (2005)), for the multifractal probability density of velocity increments, not based on the steepest descent evaluation of the integrals is obtained and the calculated function $D(h)$ is close to experimental data. A novel derivation (Polyakov, 2005), of a well-known result of the multi-fractal theory [Frisch, "Turbulence. {\\it Legacy of A.N.Kolmogorov}", Cambridge University Press, 1995)), based on the concepts described in this paper, is also presented.

Victor Yakhot

2005-12-12

371

Spatial Statistics and Real Estate  

Microsoft Academic Search

Real estate has historically employed statistical tools designed for independent observations while simultaneously noting the violation of these assumptions in the form of clustering of same sign residuals by neighborhood, along roads, and near facilities such as airports. Spatial statistics takes these dependencies into account to provide more realistic inference (OLS has biased standard errors), better prediction, and more efficient

R. Kelley Pace; Ronald Barry; C. F. Sirmans

1998-01-01

372

EDITORIAL: Strongly correlated electron systems Strongly correlated electron systems  

NASA Astrophysics Data System (ADS)

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

Ronning, Filip; Batista, Cristian

2011-03-01

373

PREFACE: Strongly correlated electron systems Strongly correlated electron systems  

NASA Astrophysics Data System (ADS)

This special section is dedicated to the Strongly Correlated Electron Systems Conference (SCES) 2011, which was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 is dedicated to 100 years of superconductivity and covers a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The selected papers derived from invited presentations seek to deepen our understanding of the rich physical phenomena that arise from correlation effects. The focus is on quantum phase transitions, non-Fermi liquid phenomena, quantum magnetism, unconventional superconductivity and metal-insulator transitions. Both experimental and theoretical work is presented. Based on fundamental advances in the understanding of electronic materials, much of 20th century materials physics was driven by miniaturisation and integration in the electronics industry to the current generation of nanometre scale devices. The achievements of this industry have brought unprecedented advances to society and well-being, and no doubt there is much further to go—note that this progress is founded on investments and studies in the fundamentals of condensed matter physics from more than 50 years ago. Nevertheless, the defining challenges for the 21st century will lie in the discovery in science, and deployment through engineering, of technologies that can deliver the scale needed to have an impact on the sustainability agenda. Thus the big developments in nanotechnology may lie not in the pursuit of yet smaller transistors, but in the design of new structures that can revolutionise the performance of solar cells, batteries, fuel cells, light-weight structural materials, refrigeration, water purification, etc. The science presented in the papers of this special section also highlights the underlying interest in energy-dense materials, which make use of 'small' electrons packed to the highest possible density. These are by definition 'strongly correlated'. For example: good photovoltaics must be efficient optical absorbers, which means that photons will generate tightly bound electron-hole pairs (excitons) that must then be ionised at a heterointerface and transported to contacts; efficient solid state refrigeration depends on substantial entropy changes in a unit cell, with large local electrical or magnetic moments; efficient lighting is in a real sense the inverse of photovoltaics; the limit of an efficient battery is a supercapacitor employing mixed valent ions; fuel cells and solar to fuel conversion require us to understand electrochemistry on the scale of a single atom; and we already know that the only prospect for effective high temperature superconductivity involves strongly correlated materials. Even novel IT technologies are now seen to have value not just for novel function but also for efficiency. While strongly correlated electron systems continue to excite researchers and the public alike due to the fundamental science issues involved, it seems increasingly likely that support for the science will be leveraged by its impact on energy and sustainability. Strongly correlated electron systems contents Strongly correlated electron systemsSiddharth S Saxena and P B Littlewood Magnetism, f-electron localization and superconductivity in 122-type heavy-fermion metalsF Steglich, J Arndt, O Stockert, S Friedemann, M Brando, C Klingner, C Krellner, C Geibel, S Wirth, S Kirchner and Q Si High energy pseudogap and its evolution with doping in Fe-based superconductors as revealed by optical spectroscopyN L Wang, W Z Hu, Z G Chen, R H Yuan, G Li, G F Chen and T Xiang Structural investigations on YbRh2Si2: from the atomic to the macroscopic length scaleS Wirth, S Ernst, R Cardoso-Gil, H Borrmann, S Seiro, C Krellner, C Geibel, S Kirchner, U Burkhardt, Y Grin and F Steglich Confinement of chiral magnetic modulations in the precursor region of FeGeH Wilhelm, M Baenitz, M Schmidt, C Naylor, R Lortz, U

Saxena, Siddharth S.; Littlewood, P. B.

2012-07-01

374

Numerical micromagnetism of strong inhomogeneities  

E-print Network

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 $l_s$ and the magnetocrystalline exchange length $l_k$ 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...

Andreas, Christian; Hertel, Riccardo

2014-01-01

375

Electrophoresis in strong electric fields.  

PubMed

Two kinds of non-linear electrophoresis (ef) that can be detected in strong electric fields (several hundred V/cm) are considered. The first ("classical" non-linear ef) is due to the interaction of the outer field with field-induced ionic charges in the electric double layer (EDL) under conditions, when field-induced variations of electrolyte concentration remain to be small comparatively to its equilibrium value. According to the Shilov theory, the non-linear component of the electrophoretic velocity for dielectric particles is proportional to the cubic power of the applied field strength (cubic electrophoresis) and to the second power of the particles radius; it is independent of the zeta-potential but is determined by the surface conductivity of particles. The second one, the so-called "superfast electrophoresis" is connected with the interaction of a strong outer field with a secondary diffuse layer of counterions (space charge) that is induced outside the primary (classical) diffuse EDL by the external field itself because of concentration polarization. The Dukhin-Mishchuk theory of "superfast electrophoresis" predicts quadratic dependence of the electrophoretic velocity of unipolar (ionically or electronically) conducting particles on the external field gradient and linear dependence on the particle's size in strong electric fields. These are in sharp contrast to the laws of classical electrophoresis (no dependence of V(ef) on the particle's size and linear dependence on the electric field gradient). A new method to measure the ef velocity of particles in strong electric fields is developed that is based on separation of the effects of sedimentation and electrophoresis using videoimaging and a new flowcell and use of short electric pulses. To test the "classical" non-linear electrophoresis, we have measured the ef velocity of non-conducting polystyrene, aluminium-oxide and (semiconductor) graphite particles as well as Saccharomice cerevisiae yeast cells as a function of the electric field strength, particle size, electrolyte concentration and the adsorbed polymer amount. It has been shown that the electrophoretic velocity of the particles/cells increases with field strength linearly up to about 100 and 200 V/cm (for cells) without and with adsorbed polymers both in pure water and in electrolyte solutions. In line with the theoretical predictions, in stronger fields substantial non-linear effects were recorded (V(ef)~E(3)). The ef velocity of unipolar ion-type conducting (ion-exchanger particles and fibres), electron-type conducting (magnesium and Mg/Al alloy) and semiconductor particles (graphite, activated carbon, pyrite, molybdenite) increases significantly with the electric field (V(ef)~E(2)) and the particle's size but is almost independent of the ionic strength. These trends are inconsistent with Smoluchowski's equation for dielectric particles, but are consistent with the Dukhin-Mishchuk theory of superfast electrophoresis. PMID:19041962

Barany, Sandor

2009-01-01

376

Strongly Modified Plasmon-Matter Interaction with Mesoscopic Quantum Emitters  

E-print Network

Semiconductor quantum dots (QDs) provide an essential link between light and matter in emerging fields such as light-harvesting, all-solid-state quantum communication, and quantum computing. QDs are excellent single-photon sources and can store quantum bits for extended periods making them promising interconnects between light and matter in integrated quantum information networks. To this end the light-matter interaction strength must be strongly enhanced using nanophotonic structures such as photonic crystal cavities and waveguides or plasmonic nanowires. So far it has been assumed that QDs can be treated just like atomic photon emitters where the spatial properties of the wavefunction can be safely ignored. Here we demonstrate that the point-emitter description for QDs near plasmonic nanostructures breaks down. We observe that the QDs can excite plasmons eight times more efficiently depending on their orientation due to their mesoscopic character. Either enhancement or suppresion of the rate of plasmon excitation is observed depending on the geometry of the plasmonic nanostructure in full agreement with a new theory. This discovery has no equivalence in atomic systems and paves the way for novel nanophotonic devices that exploit the extended size of QDs as a resource for increasing the light-matter interaction strength.

Mads Lykke Andersen; Søren Stobbe; Anders Søndberg Sørensen; Peter Lodahl

2010-11-25

377

Numerical micromagnetism of strong inhomogeneities  

NASA Astrophysics Data System (ADS)

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.

Andreas, Christian; Gliga, Sebastian; Hertel, Riccardo

2014-08-01

378

Strongly intensive quantities  

SciTech Connect

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.

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

379

Spatial memory, recognition memory, and the hippocampus  

E-print Network

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

Squire, Larry R.

380

Improved Cloud and Snow Screening in MAIAC Aerosol Retrievals Using Spectral and Spatial Analysis  

NASA Technical Reports Server (NTRS)

An improved cloud/snow screening technique in the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm is described. It is implemented as part of MAIAC aerosol retrievals based on analysis of spectral residuals and spatial variability. Comparisons with AERONET aerosol observations and a large-scale MODIS data analysis show strong suppression of aerosol optical thickness outliers due to unresolved clouds and snow. At the same time, the developed filter does not reduce the aerosol retrieval capability at high 1 km resolution in strongly inhomogeneous environments, such as near centers of the active fires. Despite significant improvement, the optical depth outliers in high spatial resolution data are and will remain the problem to be addressed by the application-dependent specialized filtering techniques.

Lyapustin, A.; Wang, Y.; Laszlo, I.; Kokrkin, S.

2012-01-01

381

Strongly correlated materials.  

PubMed

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

Morosan, Emilia; Natelson, Douglas; Nevidomskyy, Andriy H; Si, Qimiao

2012-09-18

382

Spatially resolved measurement of high doses in microbeam radiation therapy using samarium doped fluorophosphate glasses  

SciTech Connect

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.

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

383

Beyond carbon K-edge harmonic emission using a spatial and temporal synthesized laser field.  

PubMed

We present numerical simulations of high-order harmonic generation in helium using a temporally synthesized and spatially nonhomogeneous strong laser field. The combination of temporal and spatial laser field synthesis results in a dramatic cutoff extension far beyond the usual semiclassical limit. Our predictions are based on the convergence of three complementary approaches: resolution of the three dimensional time dependent Schrödinger equation, time-frequency analysis of the resulting dipole moment, and classical trajectory extraction. A laser field synthesized both spatially and temporally has been proven capable of generating coherent extreme ultraviolet photons beyond the carbon K edge, an energy region of high interest as it can be used to initiate inner-shell dynamics and study time-resolved intramolecular attosecond spectroscopy. PMID:23414015

Pérez-Hernández, J A; Ciappina, M F; Lewenstein, M; Roso, L; Zaïr, A

2013-02-01

384

Spatially resolved measurement of high doses in microbeam radiation therapy using samarium doped fluorophosphate glasses  

NASA Astrophysics Data System (ADS)

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.

Okada, Go; Morrell, Brian; Koughia, Cyril; Edgar, Andy; Varoy, Chris; Belev, George; Wysokinski, Tomasz; Chapman, Dean; Kasap, Safa

2011-09-01

385

Spatial Uncertainty Analysis of Ecological Models  

SciTech Connect

The authors evaluated the sensitivity of a habitat model and a source-sink population model to spatial uncertainty in landscapes with different statistical properties and for hypothetical species with different habitat requirements. Sequential indicator simulation generated alternative landscapes from a source map. Their results showed that spatial uncertainty was highest for landscapes in which suitable habitat was rare and spatially uncorrelated. Although, they were able to exert some control over the degree of spatial uncertainty by varying the sampling density drawn from the source map, intrinsic spatial properties (i.e., average frequency and degree of spatial autocorrelation) played a dominant role in determining variation among realized maps. To evaluate the ecological significance of landscape variation, they compared the variation in predictions from a simple habitat model to variation among landscapes for three species types. Spatial uncertainty in predictions of the amount of source habitat depended on both the spatial life history characteristics of the species and the statistical attributes of the synthetic landscapes. Species differences were greatest when the landscape contained a high proportion of suitable habitat. The predicted amount of source habitat was greater for edge-dependent (interior) species in landscapes with spatially uncorrelated(correlated) suitable habitat. A source-sink model demonstrated that, although variation among landscapes resulted in relatively little variation in overall population growth rate, this spatial uncertainty was sufficient in some situations, to produce qualitatively different predictions about population viability (i.e., population decline vs. increase).

Jager, H.I.; Ashwood, T.L.; Jackson, B.L.; King, A.W.

2000-09-02

386

Spatial Thinking Strategies  

NSDL National Science Digital Library

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,

Susan Everett

2000-04-01

387

Testosterone influences spatial strategy preferences among adult male rats  

PubMed Central

Males outperform females on some spatial tasks, and this may be partially due to the effects of sex steroids on spatial strategy preferences. Previous work with rodents indicates that low estradiol levels bias females toward a striatum-dependent response strategy, whereas high estradiol levels bias them toward a hippocampus-dependent place strategy. We tested whether testosterone influenced the strategy preferences in male rats. All subjects were castrated and assigned to one of three daily injection doses of testosterone (0.125, 0.250, or 0.500 mg/rat) or a control group that received daily injections of the drug vehicle. Three different maze protocols were used to determine rats’ strategy preferences. A low dose of testosterone (0.125 mg) biased males toward a motor-response strategy on a T-maze task. In a water maze task in which the platform itself could be used intermittently as a visual cue, a low testosterone dose (0.125 mg) caused a significant increase in the use of a cued-response strategy relative to control males. Results from this second experiment also indicated that males receiving a high dose of testosterone (0.500 mg) were biased toward a place strategy. A third experiment indicated that testosterone dose did not have a strong influence on the ability of rats to use a nearby visual cue (floating ball) in the water maze. For this experiment, all groups seemed to use a combination of place and cued-response strategies. Overall, the results indicate that the effects of testosterone on spatial strategy preference are dose dependent and task dependent. PMID:23597827

Spritzer, Mark D.; Fox, Elliott C.; Larsen, Gregory D.; Batson, Christopher G.; Wagner, Benjamin A.; Maher, Jack

2013-01-01

388

Holographic display with tilted spatial light modulator.  

PubMed

In this paper, we analyze a holographic display system utilizing a phase-only spatial light modulator (SLM) based on liquid crystal on silicon (LCoS). An LCoS SLM works in reflection, and, in some applications, it is convenient to use with an inclined illumination. Even with a highly inclined illumination, the holographic display is capable of good-quality image generation. We show that the key to obtain high-quality reconstructions is the tilt-dependent calibration and algorithms. Typically, an LCoS SLM is illuminated with a plane wave with normal wave vector. We use inclined illumination, which requires development of new algorithms and display characterization. In this paper we introduce two algorithms. The first one is designed to process a digital hologram captured in CCD normal configuration, so it can be displayed in SLM tilted geometry, while the second one is capable of synthetic hologram generation for tilted SLM configuration. The inclined geometry asymmetrically changes the field of view of a holographic display. The presented theoretical analysis of the aliasing effect provides a formula for the field of view as a function of SLM tilt. The incidence angle affects SLM performance. Both elements of SLM calibration, i.e., pixel phase response and wavefront aberrations, strongly depend on SLM tilt angle. The effect is discussed in this paper. All of the discussions are accompanied with experimental results. PMID:21743569

Kozacki, Tomasz

2011-07-10

389

Strongly Coupled Cosmologies  

E-print Network

Models including an energy transfer from CDM to DE are widely considered in the literature, namely to allow DE a significant high-z density. Strongly Coupled cosmologies assume a much larger coupling between DE and CDM, together with the presence of an uncoupled warm DM component, as the role of CDM is mostly restricted to radiative eras. This allows us to preserve small scale fluctuations even if the warm particle, possibly a sterile neutrino, is quite light, O(100 eV). Linear theory and numerical simulations show that these cosmologies agree with LCDM on supergalactic scales; e.g., CMB spectra are substantially identical. Simultaneously, simulations show that they significantly ease problems related to the properties of MW satellites and cores in dwarfs. SC cosmologies also open new perspectives on early black hole formation, and possibly lead towards unificating DE and inflationary scalar fields.

Bonometto, S A; Musco, I; Mainini, R; Maccio', A V

2014-01-01

390

Strong, Lightweight, Porous Materials  

NASA Technical Reports Server (NTRS)

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.

Leventis, Nicholas; Meador, Mary Ann B.; Johnston, James C.; Fabrizio, Eve F.; Ilhan, Ulvi

2007-01-01

391

Strong-Field Electrodynamics  

E-print Network

Strong-Field Electrodynamics (SFE) is Maxwell theory with a certain Lorentz-covariant Ohm's law which uses only the electromagnetic degrees of freedom. We show that SFE is {\\it semi-dissipative}: while the dissipation rate of the electromagnetic energy is non-negative, it can be exactly zero for non-trivial electromagnetic fields. It appears that SFE is well-defined for arbitrary electromagnetic fields. It should be possible to calculate the dissipative pulsar magnetosphere and resolve the magnetic separatrix using SFE. We show that SFE reduces to Force-Free Electrodynamics (FFE) in the large conductivity limit. In the regions where the ideal FFE 4-current is space-like, SFE predicts small dissipative corrections. In the regions where the ideal FFE 4-current is time-like, SFE predicts a zero correction. This indicates that bright pulsars radiate primarily from the magnetic separatrix.

Andrei Gruzinov

2008-02-12

392

Strongly interacting astrophysical neutrinos  

NASA Astrophysics Data System (ADS)

The origin and chemical composition of ultrahigh energy cosmic rays is still an open question in astroparticle physics. The observed large-scale isotropy and also direct composition measurements can be interpreted as an extragalactic proton dominance above the ankle at about 1010 GeV. Photopion production of extragalactic protons in the cosmic microwave background predicts a cut-off at about 5×1010 GeV in conflict with excesses reported by some experiments. In this report we will outline a recent statistical analysis [M. Ahlers, A. Ringwald, H. Tu, Astropart. Phys. (in press). Preprint astro-ph/0506698] of cosmic ray data using strongly interacting neutrinos as primaries for these excesses.

Ahlers, Markus

2006-07-01

393

Effects of spatial variability of soil hydraulic properties on water dynamics  

NASA Astrophysics Data System (ADS)

Soil hydraulic properties may present spatial variability and dependence at the scale of watersheds or fields even in man-made single soil structures, such as cranberry fields. The saturated hydraulic conductivity (Ksat) and soil moisture curves were measured at two depths for three cranberry fields (about 2 ha) at three different sites near Québec city, Canada. Two of the three studied fields indicate strong spatial dependence for Ksat values and soil moisture curves both in horizontal and vertical directions. In the summer of 2012, the three fields were equipped with 55 tensiometers installed at a depth of 0.10 m in a regular grid. About 20 mm of irrigation water were applied uniformly by aspersion to the fields, raising soil water content to near saturation condition. Soil water tension was measured once every hour during seven days. Geostatistical techniques such as co-kriging and cross-correlograms estimations were used to investigate the spatial dependence between variables. The results show that soil tension varied faster in high Ksat zones than in low Ksatones in the cranberry fields. These results indicate that soil water dynamic is strongly affected by the variability of saturated soil hydraulic conductivity, even in a supposed homogenous anthropogenic soil. This information may have a strong impact in irrigation management and subsurface drainage efficiency as well as other water conservation issues. Future work will involve 3D numerical modeling of the field water dynamics with HYDRUS software. The anticipated outcome will provide valuable information for the understanding of the effect of spatial variability of soil hydraulic properties on soil water dynamics and its relationship with crop production and water conservation.

Gumiere, Silvio Jose; Caron, Jean; Périard, Yann; Lafond, Jonathan

2013-04-01

394

Achieving a Strongly Temperature-Dependent Casimir Effect  

E-print Network

We propose a method of achieving large temperature sensitivity in the Casimir force that involves measuring the stable separation between dielectric objects immersed in fluid. We study the Casimir force between slabs and spheres using realistic material models, and find large > 2nm/K variations in their stable separations (hundreds of nanometers) near room temperature. In addition, we analyze the effects of Brownian motion on suspended objects, and show that the average separation is also sensitive to changes in temperature . Finally, this approach also leads to rich qualitative phenomena, such as irreversible transitions, from suspension to stiction, as the temperature is varied.

Alejandro W. Rodriguez; David Woolf; Alexander P. McCauley; Federico Capasso; John D. Joannopoulos; Steven G. Johnson

2010-04-15

395

Achieving a Strongly Temperature-Dependent Casimir Effect  

SciTech Connect

We propose a method of achieving large temperature T sensitivity in the Casimir force that involves measuring the stable separation between dielectric objects immersed in a fluid. We study the Casimir force between slabs and spheres using realistic material models, and find large >2 nm/K variations in their stable separations (hundreds of nanometers) near room temperature. In addition, we analyze the effects of Brownian motion on suspended objects, and show that the average separation is also sensitive to changes in T. Finally, this approach also leads to rich qualitative phenomena, such as irreversible transitions, from suspension to stiction, as T is varied.

Rodriguez, Alejandro W. [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02139 (United States); Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Woolf, David; Capasso, Federico [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02139 (United States); McCauley, Alexander P.; Joannopoulos, John D. [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Johnson, Steven G. [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2010-08-06

396

Development of spatial coarse-to-fine processing in the visual pathway.  

PubMed

The sequential analysis of information in a coarse-to-fine manner is a fundamental mode of processing in the visual pathway. Spatial frequency (SF) tuning, arguably the most fundamental feature of spatial vision, provides particular intuition within the coarse-to-fine framework: low spatial frequencies convey global information about an image (e.g., general orientation), while high spatial frequencies carry more detailed information (e.g., edges). In this paper, we study the development of cortical spatial frequency tuning. As feedforward input from the lateral geniculate nucleus (LGN) has been shown to have significant influence on cortical coarse-to-fine processing, we present a firing-rate based thalamocortical model which includes both feedforward and feedback components. We analyze the relationship between various model parameters (including cortical feedback strength) and responses. We confirm the importance of the antagonistic relationship between the center and surround responses in thalamic relay cell receptive fields (RFs), and further characterize how specific structural LGN RF parameters affect cortical coarse-to-fine processing. Our results also indicate that the effect of cortical feedback on spatial frequency tuning is age-dependent: in particular, cortical feedback more strongly affects coarse-to-fine processing in kittens than in adults. We use our results to propose an experimentally testable hypothesis for the function of the extensive feedback in the corticothalamic circuit. PMID:24077933

Nirody, Jasmine A

2014-06-01

397

Strongly Correlated Electronic Systems  

NASA Astrophysics Data System (ADS)

This dissertation presents several explorations into the field of many-body physics. In chapters 1-3 the fundamental nature of many-body interactions in quantum antiferromagnets is scrutinized. Chapter 1 surveys the modern theory of magnetic insulators, focusing on quantum antiferromagnets. Chapter 2 presents an improved method for computing expectation values of local operators in fully Gutzwiller -projected variational states. This embedded cluster method allows accurate extrapolation to the thermodynamic limit when the correlations are sufficiently short-range. The method is used to calculate static spin-spin correlations in a variety of one- and two-dimensional variational states for quantum antiferromagnets. Section 2.3.3 presents a study of the Heisenberg spin Hamiltonian on several lattices using Gutzwiller-projected variational wavefunctions with non-zero Neel order. The variational energies are comparable to more sophisticated calculations, suggesting that these variational wavefunctions are close to the true ground state wavefunction of the Heisenberg antiferromagnet. Chapter 3 discusses Gutzwiller-projected variational wavefunctions for charged, spinless holon excitations in chiral spin liquids. We find that these states describe anyons, with a statistical phase Phi_ {s} that is continuously adjustable between 0 and pi/2, depending on a variational parameter. The statistical flux attached to each holon is localized to within a lattice constant. Chapters 4 and 5 consider a superconducting and a magnetically ordered system, respectively, with the aim of understanding the many-body effects phenomenologically. Chapter 4 presents a self-contained overview of solid Buckminsterfullerene, C_{60}, with an emphasis on those aspects relevant to superconductivity. A BCS theory for superconductivity based on phonon-mediated electron pairing is also presented in some detail. In this model, the isotope effect is the most direct experimental indicator of the role played by phonons in the electron-electron pairing. The superconducting transition temperature of doped C_{60 } is unusually sensitive to partial substitution of ^{13}C for the naturally abundant isotope ^{12}C. Section 4.6 presents the theoretical temperature -dependent resistivity rho(T) resulting from a complete theory of the phonons in rm K_3C_{60} and rm Rb_3C_{60}. The electron-phonon couplings are derived from the theory highlighted in chapter 4. The theory accounts for the unusual non -linear temperature dependence in rho(T). . Finally, chapter 5 reviews several experiments on a variety of magnetic multi-layer and sandwich structures are reviewed. These systems have revealed an indirect exchange coupling between layers of ferromagnets separated by nonmagnetic spacer layers. This coupling oscillates from ferromagnetic to antiferromagnetic depending on the thickness of the spacer layers, with an anomalously long period. (Abstract shortened by UMI.).

Deaven, David Matthew

398

Spatial and Temporal Activity of Migratory Bats at Landscape Features.  

E-print Network

??Geographical landmarks may be important features for navigation of migrating bats although spatial and temporal activity may depend on species-specific migration strategies. I predicted that… (more)

Hamilton, Rachel M

2012-01-01

399

Capacity of MIMO free space optical communications using multiple partially coherent beams propagation through non-Kolmogorov strong turbulence.  

PubMed

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

Deng, Peng; Kavehrad, Mohsen; Liu, Zhiwen; Zhou, Zhou; Yuan, Xiuhua

2013-07-01

400

Strong-interaction nonuniversality  

SciTech Connect

The universal QCD color theory is extended to an SU(3)/sub 1//direct product/SU(3)/sub 2//direct product/SU(3)/sub 3/ gauge theory, where quarks of the /ital i/th generation transform as triplets under SU(3)/sub /ital i// and singlets under the other two factors. The usual color group is then identified with the diagonal subgroup, which remains exact after symmetry breaking. The gauge bosons associated with the 16 broken generators then form two massive octets under ordinary color. The interactions between quarks and these heavy gluonlike particles are explicitly nonuniversal and thus an exploration of their physical implications allows us to shed light on the fundamental issue of strong-interaction universality. Nonuniversality and weak flavor mixing are shown to generate heavy-gluon-induced flavor-changing neutral currents. The phenomenology of these processes is studied, as they provide the major experimental constraint on the extended theory. Three symmetry-breaking scenarios are presented. The first has color breaking occurring at the weak scale, while the second and third divorce the two scales. The third model has the interesting feature of radiatively induced off-diagonal Kobayashi-Maskawa matrix elements.

Volkas, R. R.; Foot, R.; He, X.; Joshi, G. C.

1989-07-01