Economic agglomerations and spatio-temporal cycles in a spatial growth model with capital transport cost

NASA Astrophysics Data System (ADS)

Juchem Neto, J. P.; Claeyssen, J. C. R.; Pôrto Júnior, S. S.

2018-03-01

In this paper we introduce capital transport cost in a unidimensional spatial Solow-Swan model of economic growth with capital-induced labor migration, considered in an unbounded domain. Proceeding with a stability analysis, we show that there is a critical value for the capital transport cost where the dynamic behavior of the economy changes, provided that the intensity of capital-induced labor migration is strong enough. On the one hand, if the capital transport cost is higher than this critical value, the spatially homogeneous equilibrium of coexistence of the model is stable, and the economy converges to this spatially homogeneous state in the long run; on the other hand, if transport cost is lower than this critical value, the equilibrium is unstable, and the economy may develop different spatio-temporal dynamics, including the formation of stable economic agglomerations and spatio-temporal economic cycles, depending on the other parameters in the model. Finally, numerical simulations support the results of the stability analysis, and illustrate the spatio-temporal dynamics generated by the model, suggesting that the economy as a whole benefits from the formation of economic agglomerations and cycles, with a higher capital transport cost reducing this gain.

Synchronisation and stability in river metapopulation networks.

PubMed

Yeakel, J D; Moore, J W; Guimarães, P R; de Aguiar, M A M

2014-03-01

Spatial structure in landscapes impacts population stability. Two linked components of stability have large consequences for persistence: first, statistical stability as the lack of temporal fluctuations; second, synchronisation as an aspect of dynamic stability, which erodes metapopulation rescue effects. Here, we determine the influence of river network structure on the stability of riverine metapopulations. We introduce an approach that converts river networks to metapopulation networks, and analytically show how fluctuation magnitude is influenced by interaction structure. We show that river metapopulation complexity (in terms of branching prevalence) has nonlinear dampening effects on population fluctuations, and can also buffer against synchronisation. We conclude by showing that river transects generally increase synchronisation, while the spatial scale of interaction has nonlinear effects on synchronised dynamics. Our results indicate that this dual stability - conferred by fluctuation and synchronisation dampening - emerges from interaction structure in rivers, and this may strongly influence the persistence of river metapopulations. © 2013 John Wiley & Sons Ltd/CNRS.

Phenotypic selection in natural populations: what limits directional selection?

PubMed

Kingsolver, Joel G; Diamond, Sarah E

2011-03-01

Studies of phenotypic selection document directional selection in many natural populations. What factors reduce total directional selection and the cumulative evolutionary responses to selection? We combine two data sets for phenotypic selection, representing more than 4,600 distinct estimates of selection from 143 studies, to evaluate the potential roles of fitness trade-offs, indirect (correlated) selection, temporally varying selection, and stabilizing selection for reducing net directional selection and cumulative responses to selection. We detected little evidence that trade-offs among different fitness components reduced total directional selection in most study systems. Comparisons of selection gradients and selection differentials suggest that correlated selection frequently reduced total selection on size but not on other types of traits. The direction of selection on a trait often changes over time in many temporally replicated studies, but these fluctuations have limited impact in reducing cumulative directional selection in most study systems. Analyses of quadratic selection gradients indicated stabilizing selection on body size in at least some studies but provided little evidence that stabilizing selection is more common than disruptive selection for most traits or study systems. Our analyses provide little evidence that fitness trade-offs, correlated selection, or stabilizing selection strongly constrains the directional selection reported for most quantitative traits.

Temporal Stability and Authenticity of Self-Representations in Adulthood

PubMed Central

Diehl, Manfred; Jacobs, Laurie M.; Hastings, Catherine T.

2008-01-01

The temporal stability of role-specific self-representations was examined in a sample of 188 young, middle-aged, and older adults. Considerable stability was observed for all self-representations. Central self-descriptors showed significantly greater temporal stability than peripheral self-descriptors. Temporal stability of self-representations was positively associated with self-concept clarity, self-esteem, and positive affect (PA). Age differences were obtained for three of the five self-representations, with older adults showing significantly lower stabilities for self with family, self with friend, and self with significant other compared to young and middle-aged adults. Assessment of the authenticity of adults’ role-specific self-representations showed that greater authenticity tended to be associated with greater temporal stability. Authenticity and the number of positive daily events were significant positive predictors of the stability of self-representations. PMID:18820732

Spatial and Temporal Dynamics of Pacific Oyster Hemolymph Microbiota across Multiple Scales

PubMed Central

Lokmer, Ana; Goedknegt, M. Anouk; Thieltges, David W.; Fiorentino, Dario; Kuenzel, Sven; Baines, John F.; Wegner, K. Mathias

2016-01-01

Unveiling the factors and processes that shape the dynamics of host associated microbial communities (microbiota) under natural conditions is an important part of understanding and predicting an organism's response to a changing environment. The microbiota is shaped by host (i.e., genetic) factors as well as by the biotic and abiotic environment. Studying natural variation of microbial community composition in multiple host genetic backgrounds across spatial as well as temporal scales represents a means to untangle this complex interplay. Here, we combined a spatially-stratified with a longitudinal sampling scheme within differentiated host genetic backgrounds by reciprocally transplanting Pacific oysters between two sites in the Wadden Sea (Sylt and Texel). To further differentiate contingent site from host genetic effects, we repeatedly sampled the same individuals over a summer season to examine structure, diversity and dynamics of individual hemolymph microbiota following experimental removal of resident microbiota by antibiotic treatment. While a large proportion of microbiome variation could be attributed to immediate environmental conditions, we observed persistent effects of antibiotic treatment and translocation suggesting that hemolymph microbial community dynamics is subject to within-microbiome interactions and host population specific factors. In addition, the analysis of spatial variation revealed that the within-site microenvironmental heterogeneity resulted in high small-scale variability, as opposed to large-scale (between-site) stability. Similarly, considerable within-individual temporal variability was in contrast with the overall temporal stability at the site level. Overall, our longitudinal, spatially-stratified sampling design revealed that variation in hemolymph microbiota is strongly influenced by site and immediate environmental conditions, whereas internal microbiome dynamics and oyster-related factors add to their long-term stability. The combination of small and large scale resolution of spatial and temporal observations therefore represents a crucial but underused tool to study host-associated microbiome dynamics. PMID:27630625

Temporal variability of foliar nutrients: responses to nitrogen deposition and prescribed fire in a temperate steppe

USGS Publications Warehouse

Lü, Xiao-Tao; Reed, Sasha C.; Hou, Shuang-Li; Hu, Yan-Yu; Wei, Hai-Wei; Lü, Fu-Mei; Cui, Qiang; Han, Xing Guo

2017-01-01

Plant nutrient concentrations and stoichiometry drive fundamental ecosystem processes, with important implications for primary production, diversity, and ecosystem sustainability. While a range of evidence exists regarding how plant nutrients vary across spatial scales, our understanding of their temporal variation remains less well understood. Nevertheless, we know nutrients regulate plant function across time, and that important temporal controls could strongly interact with environmental change. Here, we report results from a 3-year assessment of inter-annual changes of foliar nitrogen (N) and phosphorus (P) concentrations and stoichiometry in three dominant grasses in response to N deposition and prescribed fire in a temperate steppe of northern China. Foliar N and P concentrations and their ratios varied greatly among years, with this temporal variation strongly related to inter-annual variation in precipitation. Nitrogen deposition significantly increased foliar N concentrations and N:P ratios in all species, while fire significantly altered foliar N and P concentrations but had no significant impacts on N:P ratios. Generally, N addition enhanced the temporal stability of foliar N and decreased that of foliar P and of N:P ratios. Our results indicate that plant nutrient status and response to environmental change are temporally dynamic and that there are differential effects on the interactions between environmental change drivers and timing for different nutrients. These responses have important implications for consideration of global change effects on plant community structure and function, management strategies, and the modeling of biogeochemical cycles under global change scenarios.

Plant functional traits improve diversity-based predictions of temporal stability of grassland productivity

USDA-ARS?s Scientific Manuscript database

Aboveground net primary productivity (ANPP) varies in response to temporal fluctuations in weather. Temporal stability (mean/standard deviation) of community ANPP may be increased, on average, by increasing plant species richness, but stability also may differ widely at a given richness level imply...

Enhanced temporal stability of cholinergic hippocampal gamma oscillations following respiratory alkalosis in vitro.

PubMed

Stenkamp, K; Palva, J M; Uusisaari, M; Schuchmann, S; Schmitz, D; Heinemann, U; Kaila, K

2001-05-01

The decrease in brain CO(2) partial pressure (pCO(2)) that takes place both during voluntary and during pathological hyperventilation is known to induce gross alterations in cortical functions that lead to subjective sensations and altered states of consciousness. The mechanisms that mediate the effects of the decrease in pCO(2) at the neuronal network level are largely unexplored. In the present work, the modulation of gamma oscillations by hypocapnia was studied in rat hippocampal slices. Field potential oscillations were induced by the cholinergic agonist carbachol under an N-methyl-D-aspartate (NMDA)-receptor blockade and were recorded in the dendritic layer of the CA3 region with parallel measurements of changes in interstitial and intraneuronal pH (pH(o) and pH(i), respectively). Hypocapnia from 5 to 1% CO(2) led to a stable monophasic increase of 0.5 and 0.2 units in pH(o) and pH(i), respectively. The mean oscillation frequency increased slightly but significantly from 32 to 34 Hz and the mean gamma-band amplitude (20 to 80 Hz) decreased by 20%. Hypocapnia induced a dramatic enhancement of the temporal stability of the oscillations, as was indicated by a two-fold increase in the exponential decay time constant fitted to the autocorrelogram. A rise in pH(i) evoked by the weak base trimethylamine (TriMA) was associated with a slight increase in oscillation frequency (37 to 39 Hz) and a decrease in amplitude (30%). Temporal stability, on the other hand, was decreased by TriMA, which suggests that its enhancement in 1% CO(2) was related to the rise in pH(o). In 1% CO(2), the decay-time constant of the evoked monosynaptic pyramidal inhibitory postsynaptic current (IPSC) was unaltered but its amplitude was enhanced. This increase in IPSC amplitude seems to significantly contribute to the enhancement of temporal stability because the enhancement was almost fully reversed by a low concentration of bicuculline. These results suggest that changes in brain pCO(2) can have a strong influence on the temporal modulation of gamma rhythms.

Spatio-temporal patterns of key exploited marine species in the Northwestern Mediterranean Sea.

PubMed

Morfin, Marie; Fromentin, Jean-Marc; Jadaud, Angélique; Bez, Nicolas

2012-01-01

This study analyzes the temporal variability/stability of the spatial distributions of key exploited species in the Gulf of Lions (Northwestern Mediterranean Sea). To do so, we analyzed data from the MEDITS bottom-trawl scientific surveys from 1994 to 2010 at 66 fixed stations and selected 12 key exploited species. We proposed a geostatistical approach to handle zero-inflated and non-stationary distributions and to test for the temporal stability of the spatial structures. Empirical Orthogonal Functions and other descriptors were then applied to investigate the temporal persistence and the characteristics of the spatial patterns. The spatial structure of the distribution (i.e. the pattern of spatial autocorrelation) of the 12 key species studied remained highly stable over the time period sampled. The spatial distributions of all species obtained through kriging also appeared to be stable over time, while each species displayed a specific spatial distribution. Furthermore, adults were generally more densely concentrated than juveniles and occupied areas included in the distribution of juveniles. Despite the strong persistence of spatial distributions, we also observed that the area occupied by each species was correlated to its abundance: the more abundant the species, the larger the occupation area. Such a result tends to support MacCall's basin theory, according to which density-dependence responses would drive the expansion of those 12 key species in the Gulf of Lions. Further analyses showed that these species never saturated their habitats, suggesting that they are below their carrying capacity; an assumption in agreement with the overexploitation of several of these species. Finally, the stability of their spatial distributions over time and their potential ability to diffuse outside their main habitats give support to Marine Protected Areas as a potential pertinent management tool.

Resilience and stability of Cymodocea nodosa seagrass meadows over the last four decades in a Mediterranean lagoon

NASA Astrophysics Data System (ADS)

Garrido, Marie; Lafabrie, Céline; Torre, Franck; Fernandez, Catherine; Pasqualini, Vanina

2013-09-01

Understanding what controls the capacity of a coastal lagoon ecosystem to recover following climatic and anthropogenic perturbations and how these perturbations can alter this capacity is critical to efficient environmental management. The goal of this study was to examine the resilience and stability of Cymodocea nodosa-dominated seagrass meadows in Urbino lagoon (Corsica, Mediterranean Sea) by characterizing the spatio-temporal dynamics of seagrass meadows over a 40-year period and comparing (anthropogenic and climatic) environmental fluctuations. The spatio-temporal evolution of seagrass meadows was investigated using previous maps (1973, 1979, 1990, 1994, 1996, 1999) and a 2011 map realized by aerial photography-remote sensing combined with GIS technology. Environmental fluctuation was investigated via physical-chemical parameters (rainfall, water temperature, salinity, turbidity, dissolved oxygen) and human-impact changes (aquaculture, artificial channel). The results showed a severe decline (estimated at -49%) in seagrass meadows between 1973 and 1994 followed by a period of strong recovery (estimated to +42%) between 1994 and 2011. Increased turbidity, induced either by rainfall events, dredging or phytoplankton growth, emerged as the most important driver of the spatio-temporal evolution of Cymodocea nodosa-dominated meadows in Urbino lagoon over the last four decades. Climate events associated to increased turbidity and reduced salinity and temperature could heavily impact seagrass dynamics. This study shows that Urbino lagoon, a system relatively untouched by human impact, shelters seagrass meadows that exhibit high resilience and stability.

Baseline study of the spatio-temporal patterns of reef fish assemblages prior to a major mining project in New Caledonia (South Pacific).

PubMed

Chabanet, Pascale; Guillemot, Nicolas; Kulbicki, Michel; Vigliola, Laurent; Sarramegna, Sébastien

2010-01-01

From 2008 onwards, the coral reefs of Koné (New Caledonia) will be subjected to a major anthropogenic perturbation linked to development of a nickel mine. Dredging and sediment runoff may directly damage the reef environment whereas job creation should generate a large demographic increase and thus a rise in fishing activities. This study analyzed reef fish assemblages between 2002 and 2007 with a focus on spatio-temporal variability. Our results indicate strong spatial structure of fish assemblages through time. Total species richness, density and biomass were highly variable between years but temporal variations were consistent among biotopes. A remarkable spatio-temporal stability was observed for trophic (mean 4.6% piscivores, 53.1% carnivores, 30.8% herbivores and 11.4% planktivores) and home range structures of species abundance contributions. These results are discussed and compared with others sites of the South Pacific. For monitoring perspectives, some indicators related to expected disturbances are proposed. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Spatial–temporal changes in potential evaporation patterns based on the Cloud model and their possible causes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Yuelu; Huang, Shengzhi; Chang, Jianxia

It is of importance to comprehensively investigate the spatial-temporal changes in potential evaporation patterns, which helps guide the long-term water resource allocation and irrigation managements. In this study, the Cloud model was adopted to quantify the average, uniformity, and stability of annual potential evaporation in the Wei River Basin (WRB), a typical arid and semi-arid region in China.. The cross wavelet analysis was then applied to explore the correlations between potential evaporation and Arctic Oscillation (AO)/El Niño Southern Oscillation (ENSO) with an aim to determine the possible causes of potential evaporation variations. Results indicated that: (1) the average of annualmore » potential evaporation in the WRB first declined and then increased, which was similar with its stability, whilst its dispersion degree exhibited a decreasing trend, implying that potential evaporation has a small inter-annual variation; (2) the average of potential evaporation in the western basin was obviously smaller than that in the other areas, while its uniformity and stability in the Guanzhong plain and the Loess Plateau areas are larger than those in other areas, particularly in the western basin where the uniformity and stability are the smallest; (3) both AO and ENSO exhibited strong correlations with potential evaporation variations, indicating that both AO and ENSO have played an important role in the annual potential evaporation variations in the WRB.« less

Local adaptation in transgenerational responses to predators

PubMed Central

Walsh, Matthew R.; Castoe, Todd; Holmes, Julian; Packer, Michelle; Biles, Kelsey; Walsh, Melissa; Munch, Stephan B.; Post, David M.

2016-01-01

Environmental signals can induce phenotypic changes that span multiple generations. Along with phenotypic responses that occur during development (i.e. ‘within-generation’ plasticity), such ‘transgenerational plasticity’ (TGP) has been documented in a diverse array of taxa spanning many environmental perturbations. New theory predicts that temporal stability is a key driver of the evolution of TGP. We tested this prediction using natural populations of zooplankton from lakes in Connecticut that span a large gradient in the temporal dynamics of predator-induced mortality. We reared more than 120 clones of Daphnia ambigua from nine lakes for multiple generations in the presence/absence of predator cues. We found that temporal variation in mortality selects for within-generation plasticity while consistently strong (or weak) mortality selects for increased TGP. Such results provide us the first evidence for local adaptation in TGP and argue that divergent ecological conditions select for phenotypic responses within and across generations. PMID:26817775

Elevated CO2 and water addition enhance nitrogen turnover in grassland plants with implications for temporal stability.

PubMed

Dijkstra, Feike A; Carrillo, Yolima; Blumenthal, Dana M; Mueller, Kevin E; LeCain, Dan R; Morgan, Jack A; Zelikova, Tamara J; Williams, David G; Follett, Ronald F; Pendall, Elise

2018-05-01

Temporal variation in soil nitrogen (N) availability affects growth of grassland communities that differ in their use and reuse of N. In a 7-year-long climate change experiment in a semi-arid grassland, the temporal stability of plant biomass production varied with plant N turnover (reliance on externally acquired N relative to internally recycled N). Species with high N turnover were less stable in time compared to species with low N turnover. In contrast, N turnover at the community level was positively associated with asynchrony in biomass production, which in turn increased community temporal stability. Elevated CO 2 and summer irrigation, but not warming, enhanced community N turnover and stability, possibly because treatments promoted greater abundance of species with high N turnover. Our study highlights the importance of plant N turnover for determining the temporal stability of individual species and plant communities affected by climate change. © 2018 John Wiley & Sons Ltd/CNRS.

Exposure of Water Ice in the Northern Mid-lattitudes of Mars

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; Kanner, Lisa C.

2007-01-01

Water ice is exposed in the martian north polar cap, and is occasionally exposed beyond the cap boundary. Orbital gamma ray spectrometry data strongly imply the presence of water ice within meters of the surface at latitudes north of approximately 60 deg. We have examined midlatitude areas of the northern plains displaying evidence of residual ice-rich layers, and report possible present-day exposures of ice. These exposures, if confirmed, could constrain the latitudinal and temporal stability of surface ice on Mars.

[Age structure and dynamics of Quercus wutaishanica population in Lingkong Mountain of Shanxi Province, China].

PubMed

Zhang, Jie; Shangguan, Tie-Liang; Duan, Yi-Hao; Guo, Wei; Liu, Wei-Hua; Guo, Dong-Gang

2014-11-01

Using the plant survivorship theory, the age structure, and the relationship between tree height and diameter (DBH) of Quercus wutaishanica population in Lingkong Mountain were analyzed, and the static life table was compiled and the survival curve plotted. The shuttle shape in age structure of Q. wutaishanica population suggested its temporal stability. The linear regression significantly fitted the positive correlation between tree height and DBH. The maximal life expectancy was observed among the trees beyond the age of the highest mortality and coincided with the lowest point of mortality density, suggesting the strong vitality of the seedlings and young trees that survived in the natural selection and intraspecific competition. The population stability of the Q. wutaishanica population was characterized by the Deevey-II of the survival curve. The dynamic pattern was characterized by the recession in the early phase, growth in the intermediate phase, and stability in the latter phase.

Concurrent temporal stability of the apparent electrical conductivity and soil water content

USDA-ARS?s Scientific Manuscript database

Knowledge of spatio-temporal soil water content (SWC) variability within agricultural fields is useful to improve crop management. Spatial patterns of soil water contents can be characterized using the temporal stability analysis, however high density sampling is required. Soil apparent electrical c...

Detergent Isolation Stabilizes and Activates the Shigella Type III Secretion System Translocator Protein IpaC.

PubMed

Bernard, Abram R; Duarte, Shari M; Kumar, Prashant; Dickenson, Nicholas E

2016-07-01

Shigella rely on a type III secretion system as the primary virulence factor for invasion and colonization of human hosts. Although there are an estimated 90 million Shigella infections, annually responsible for more than 100,000 deaths worldwide, challenges isolating and stabilizing many type III secretion system proteins have prevented a full understanding of the Shigella invasion mechanism and additionally slowed progress toward a much needed Shigella vaccine. Here, we show that the non-denaturing zwitterionic detergent N, N-dimethyldodecylamine N-oxide (LDAO) and non-ionic detergent n-octyl-oligo-oxyethylene efficiently isolated the hydrophobic Shigella translocator protein IpaC from the co-purified IpaC/IpgC chaperone-bound complex. Both detergents resulted in monomeric IpaC that exhibits strong membrane binding and lysis characteristics while the chaperone-bound complex does not, suggesting that the stabilizing detergents provide a means of following IpaC "activation" in vitro. Additionally, biophysical characterization found that LDAO provides significant thermal and temporal stability to IpaC, protecting it for several days at room temperature and brief exposure to temperatures reaching 90°C. In summary, this work identified and characterized conditions that provide stable, membrane active IpaC, providing insight into key interactions with membranes and laying a strong foundation for future vaccine formulation studies taking advantage of the native immunogenicity of IpaC and the stability provided by LDAO. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Decreased gastrocnemius temporal muscle activation during gait in elderly women with history of recurrent falls.

PubMed

Kirkwood, Renata Noce; Trede, Renato Guilherme; Moreira, Bruno de Souza; Kirkwood, Scott Alexander; Pereira, Leani Souza Máximo

2011-05-01

Gait dysfunction is a strong issue in elderly women with a history of falls. The purpose of this study was to compare the temporal activity of the ankle muscles during gait in elderly women with and without a history of recurrent falls. Eighty-nine (89) elderly women - one group with a history of falls (45) and another group without (44) - participated in the study. The mean range of temporal activation of the gastrocnemius, tibialis anterior and soleus muscles during gait was obtained using electromyography. The muscles were considered active when the signal magnitude surpassed two standard deviations of the minimal magnitude of the average signal per individual. The results showed that the mean range of gastrocnemius muscle activation of the group of recurrent fallers was significantly shorter, 2.9% (16.9±5.7%) compared to the group without recurrent falls (19.8±6.6%) (p=0.004). The shorter duration in the gastrocnemius muscle activation during stance could possibly affect stability in the support phase, since the gastrocnemius is the main decelerator of the trunk. Clinically, this finding shows the importance of rehabilitation programs for elderly women that focus on strengthening the plantar flexor musculature aiming to reestablish the function and stability of gait and possibly avoiding falls. Copyright © 2011 Elsevier B.V. All rights reserved.

Experimental research on time-resolved evolution of cathode plasma expansion velocity in a long pulsed magnetically insulated coaxial diode

NASA Astrophysics Data System (ADS)

Zhu, Danni; Zhang, Jun; Zhong, Huihuang; Ge, Xingjun; Gao, Jingming

2018-02-01

Unlike planar diodes, separate research of the axial and radial plasma expansion velocities is difficult for magnetically insulated coaxial diodes. Time-resolved electrical diagnostic which is based on the voltage-ampere characteristics has been employed to study the temporal evolution of the axial and radial cathode plasma expansion velocities in a long pulsed magnetically insulated coaxial diode. Different from a planar diode with a "U" shaped profile of temporal velocity evolution, the temporal evolution trend of the axial expansion velocity is proved to be a "V" shaped profile. Apart from the suppression on the radial expansion velocity, the strong magnetic field is also conducive to slowing down the axial expansion velocity. Compared with the ordinary graphite cathode, the carbon velvet and graphite composite cathode showed superior characteristics as judged by the low plasma expansion velocity and long-term electrical stability as a promising result for applications where long-pulsed and reliable operation at high power is required.

Linear temporal and spatio-temporal stability analysis of a binary liquid film flowing down an inclined uniformly heated plate

NASA Astrophysics Data System (ADS)

Hu, Jun; Hadid, Hamda Ben; Henry, Daniel; Mojtabi, Abdelkader

Temporal and spatio-temporal instabilities of binary liquid films flowing down an inclined uniformly heated plate with Soret effect are investigated by using the Chebyshev collocation method to solve the full system of linear stability equations. Seven dimensionless parameters, i.e. the Kapitza, Galileo, Prandtl, Lewis, Soret, Marangoni, and Biot numbers (Ka, G, Pr, L, ) are used to control the flow system. In the case of pure spanwise perturbations, thermocapillary S- and P-modes are obtained. It is found that the most dangerous modes are stationary for positive Soret numbers (0), and oscillatory for =0 remains so for >0 and even merges with the long-wave S-mode. In the case of streamwise perturbations, a long-wave surface mode (H-mode) is also obtained. From the neutral curves, it is found that larger Soret numbers make the film flow more unstable as do larger Marangoni numbers. The increase of these parameters leads to the merging of the long-wave H- and S-modes, making the situation long-wave unstable for any Galileo number. It also strongly influences the short-wave P-mode which becomes the most critical for large enough Galileo numbers. Furthermore, from the boundary curves between absolute and convective instabilities (AI/CI) calculated for both the long-wave instability (S- and H-modes) and the short-wave instability (P-mode), it is shown that for small Galileo numbers the AI/CI boundary curves are determined by the long-wave instability, while for large Galileo numbers they are determined by the short-wave instability.

Temporal Variability and Stability in Infant-Directed Sung Speech: Evidence for Language-Specific Patterns

ERIC Educational Resources Information Center

Falk, Simone

2011-01-01

In this paper, sung speech is used as a methodological tool to explore temporal variability in the timing of word-internal consonants and vowels. It is hypothesized that temporal variability/stability becomes clearer under the varying rhythmical conditions induced by song. This is explored cross-linguistically in German--a language that exhibits a…

Present-day Exposures of Water Ice in the Northern Mid-latitudes of Mars

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; Kanner, Lisa C.

2007-01-01

Water ice is exposed in the martian north polar cap, but is rarely exposed beyond the cap boundary. Orbital gamma ray spectrometry data strongly imply the presence of water ice within meters of the surface at latitudes north of approximately 60deg. We have examined mid-latitude areas of the northern plains displaying residual ice-rich layers, and report evidence of present-day surface exposures of water ice. These exposures, if confirmed, could con-strain the latitudinal and temporal stability of surface ice on Mars.

Biodiversity and ecosystem stability in a decade-long grassland experiment.

PubMed

Tilman, David; Reich, Peter B; Knops, Johannes M H

2006-06-01

Human-driven ecosystem simplification has highlighted questions about how the number of species in an ecosystem influences its functioning. Although biodiversity is now known to affect ecosystem productivity, its effects on stability are debated. Here we present a long-term experimental field test of the diversity-stability hypothesis. During a decade of data collection in an experiment that directly controlled the number of perennial prairie species, growing-season climate varied considerably, causing year-to-year variation in abundances of plant species and in ecosystem productivity. We found that greater numbers of plant species led to greater temporal stability of ecosystem annual aboveground plant production. In particular, the decadal temporal stability of the ecosystem, whether measured with intervals of two, five or ten years, was significantly greater at higher plant diversity and tended to increase as plots matured. Ecosystem stability was also positively dependent on root mass, which is a measure of perenniating biomass. Temporal stability of the ecosystem increased with diversity, despite a lower temporal stability of individual species, because of both portfolio (statistical averaging) and overyielding effects. However, we found no evidence of a covariance effect. Our results indicate that the reliable, efficient and sustainable supply of some foods (for example, livestock fodder), biofuels and ecosystem services can be enhanced by the use of biodiversity.

Temporal Stability of Multiple Response Systems to 7.5% Carbon Dioxide Challenge

PubMed Central

Roberson-Nay, Roxann; Gorlin, Eugenia I.; Beadel, Jessica R.; Cash, Therese; Vrana, Scott; Teachman, Bethany A.

2017-01-01

Self-reported anxiety, and potentially physiological response, to maintained inhalation of carbon dioxide (CO2) enriched air shows promise as a putative marker of panic reactivity and vulnerability. Temporal stability of response systems during low-dose, steady-state CO2 breathing challenge is lacking. Outcomes on multiple levels were measured two times, one week apart, in 93 individuals. Stability was highest during the CO2 breathing phase compared to pre-CO2 and recovery phases, with anxiety ratings, respiratory rate, skin conductance level, and heart rate demonstrating good to excellent temporal stability (ICCs ≥ 0.71). Cognitive symptoms tied to panic were somewhat less stable (ICC = 0.58) than physical symptoms (ICC = 0.74) during CO2 breathing. Escape/avoidance behaviors and DSM-5 panic attacks were not stable. Large effect sizes between task phases also were observed. Overall, results suggest good-excellent levels of temporal stability for multiple outcomes during respiratory stimulation via 7.5% CO2. PMID:28163046

Temporal stability in the genetic structure of Sarcoptes scabiei under the host-taxon law: empirical evidences from wildlife-derived Sarcoptes mite in Asturias, Spain

PubMed Central

2011-01-01

Background Implicitly, parasite molecular studies assume temporal genetic stability. In this study we tested, for the first time to our knowledge, the extent of changes in genetic diversity and structure of Sarcoptes mite populations from Pyrenean chamois (Rupicapra pyrenaica) in Asturias (Spain), using one multiplex of 9 microsatellite markers and Sarcoptes samples from sympatric Pyrenean chamois, red deer (Cervus elaphus), roe deer (Capreolus capreolus) and red fox (Vulpes vulpes). Results The analysis of an 11-years interval period found little change in the genetic diversity (allelic diversity, and observed and expected heterozygosity). The temporal stability in the genetic diversity was confirmed by population structure analysis, which was not significantly variable over time. Population structure analysis revealed temporal stability in the genetic diversity of Sarcoptes mite under the host-taxon law (herbivore derived- and carnivore derived-Sarcoptes mite) among the sympatric wild animals from Asturias. Conclusions The confirmation of parasite temporal genetic stability is of vital interest to allow generalizations to be made, which have further implications regarding the genetic structure, epidemiology and monitoring protocols of the ubiquitous Sarcoptes mite. This could eventually be applied to other parasite species. PMID:21794141

On the measurement of stability in over-time data.

PubMed

Kenny, D A; Campbell, D T

1989-06-01

In this article, autoregressive models and growth curve models are compared. Autoregressive models are useful because they allow for random change, permit scores to increase or decrease, and do not require strong assumptions about the level of measurement. Three previously presented designs for estimating stability are described: (a) time-series, (b) simplex, and (c) two-wave, one-factor methods. A two-wave, multiple-factor model also is presented, in which the variables are assumed to be caused by a set of latent variables. The factor structure does not change over time and so the synchronous relationships are temporally invariant. The factors do not cause each other and have the same stability. The parameters of the model are the factor loading structure, each variable's reliability, and the stability of the factors. We apply the model to two data sets. For eight cognitive skill variables measured at four times, the 2-year stability is estimated to be .92 and the 6-year stability is .83. For nine personality variables, the 3-year stability is .68. We speculate that for many variables there are two components: one component that changes very slowly (the trait component) and another that changes very rapidly (the state component); thus each variable is a mixture of trait and state. Circumstantial evidence supporting this view is presented.

Diversity promotes temporal stability across levels of ecosystem organization in experimental grasslands.

PubMed

Proulx, Raphaël; Wirth, Christian; Voigt, Winfried; Weigelt, Alexandra; Roscher, Christiane; Attinger, Sabine; Baade, Jussi; Barnard, Romain L; Buchmann, Nina; Buscot, François; Eisenhauer, Nico; Fischer, Markus; Gleixner, Gerd; Halle, Stefan; Hildebrandt, Anke; Kowalski, Esther; Kuu, Annely; Lange, Markus; Milcu, Alex; Niklaus, Pascal A; Oelmann, Yvonne; Rosenkranz, Stephan; Sabais, Alexander; Scherber, Christoph; Scherer-Lorenzen, Michael; Scheu, Stefan; Schulze, Ernst-Detlef; Schumacher, Jens; Schwichtenberg, Guido; Soussana, Jean-François; Temperton, Vicky M; Weisser, Wolfgang W; Wilcke, Wolfgang; Schmid, Bernhard

2010-10-13

The diversity-stability hypothesis states that current losses of biodiversity can impair the ability of an ecosystem to dampen the effect of environmental perturbations on its functioning. Using data from a long-term and comprehensive biodiversity experiment, we quantified the temporal stability of 42 variables characterizing twelve ecological functions in managed grassland plots varying in plant species richness. We demonstrate that diversity increases stability i) across trophic levels (producer, consumer), ii) at both the system (community, ecosystem) and the component levels (population, functional group, phylogenetic clade), and iii) primarily for aboveground rather than belowground processes. Temporal synchronization across studied variables was mostly unaffected with increasing species richness. This study provides the strongest empirical support so far that diversity promotes stability across different ecological functions and levels of ecosystem organization in grasslands.

Computational Software to Fit Seismic Data Using Epidemic-Type Aftershock Sequence Models and Modeling Performance Comparisons

NASA Astrophysics Data System (ADS)

Chu, A.

2016-12-01

Modern earthquake catalogs are often analyzed using spatial-temporal point process models such as the epidemic-type aftershock sequence (ETAS) models of Ogata (1998). My work implements three of the homogeneous ETAS models described in Ogata (1998). With a model's log-likelihood function, my software finds the Maximum-Likelihood Estimates (MLEs) of the model's parameters to estimate the homogeneous background rate and the temporal and spatial parameters that govern triggering effects. EM-algorithm is employed for its advantages of stability and robustness (Veen and Schoenberg, 2008). My work also presents comparisons among the three models in robustness, convergence speed, and implementations from theory to computing practice. Up-to-date regional seismic data of seismic active areas such as Southern California and Japan are used to demonstrate the comparisons. Data analysis has been done using computer languages Java and R. Java has the advantages of being strong-typed and easiness of controlling memory resources, while R has the advantages of having numerous available functions in statistical computing. Comparisons are also made between the two programming languages in convergence and stability, computational speed, and easiness of implementation. Issues that may affect convergence such as spatial shapes are discussed.

Vortex Analysis of Intra-Aneurismal Flow in Cerebral Aneurysms

PubMed Central

Sunderland, Kevin; Haferman, Christopher; Chintalapani, Gouthami

2016-01-01

This study aims to develop an alternative vortex analysis method by measuring structure ofIntracranial aneurysm (IA) flow vortexes across the cardiac cycle, to quantify temporal stability of aneurismal flow. Hemodynamics were modeled in “patient-specific” geometries, using computational fluid dynamics (CFD) simulations. Modified versions of known λ 2 and Q-criterion methods identified vortex regions; then regions were segmented out using the classical marching cube algorithm. Temporal stability was measured by the degree of vortex overlap (DVO) at each step of a cardiac cycle against a cycle-averaged vortex and by the change in number of cores over the cycle. No statistical differences exist in DVO or number of vortex cores between 5 terminal IAs and 5 sidewall IAs. No strong correlation exists between vortex core characteristics and geometric or hemodynamic characteristics of IAs. Statistical independence suggests this proposed method may provide novel IA information. However, threshold values used to determine the vortex core regions and resolution of velocity data influenced analysis outcomes and have to be addressed in future studies. In conclusions, preliminary results show that the proposed methodology may help give novel insight toward aneurismal flow characteristic and help in future risk assessment given more developments. PMID:27891172

Vortex Analysis of Intra-Aneurismal Flow in Cerebral Aneurysms.

PubMed

Sunderland, Kevin; Haferman, Christopher; Chintalapani, Gouthami; Jiang, Jingfeng

2016-01-01

This study aims to develop an alternative vortex analysis method by measuring structure ofIntracranial aneurysm (IA) flow vortexes across the cardiac cycle, to quantify temporal stability of aneurismal flow. Hemodynamics were modeled in "patient-specific" geometries, using computational fluid dynamics (CFD) simulations. Modified versions of known λ 2 and Q -criterion methods identified vortex regions; then regions were segmented out using the classical marching cube algorithm. Temporal stability was measured by the degree of vortex overlap (DVO) at each step of a cardiac cycle against a cycle-averaged vortex and by the change in number of cores over the cycle. No statistical differences exist in DVO or number of vortex cores between 5 terminal IAs and 5 sidewall IAs. No strong correlation exists between vortex core characteristics and geometric or hemodynamic characteristics of IAs. Statistical independence suggests this proposed method may provide novel IA information. However, threshold values used to determine the vortex core regions and resolution of velocity data influenced analysis outcomes and have to be addressed in future studies. In conclusions, preliminary results show that the proposed methodology may help give novel insight toward aneurismal flow characteristic and help in future risk assessment given more developments.

Temporal Stability of DSM-5 Posttraumatic Stress Disorder Criteria in a Problem Drinking Sample

PubMed Central

Keane, Terence M.; Rubin, Amy; Lachowicz, Mark; Brief, Deborah; Enggasser, Justin L.; Roy, Monica; Hermos, John; Helmuth, Eric; Rosenbloom, David

2014-01-01

The Diagnostic and Statistical Manual-5 (DSM-5) reformulated Posttraumatic Stress Disorder (PTSD) based partially on research showing there were four main factors that underlie the symptoms of the disorder. The primary aim of this study was to examine the temporal stability of the DSM-5 factors as measured by the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5; Weathers et al., 2010). Confirmatory factor analyses were conducted to examine the structure of DSM-5 PTSD, and temporal stability over three time points was examined to determine if the measure reflects a consistent construct over time. Our sample was 507 combat-exposed veterans of Iraq and Afghanistan who enrolled in an online intervention for problem drinking and combat-related stress (masked for review). We administered the PCL-5 at baseline, 8-week post intervention, and 3-month follow-up assessments. The DSM-5 model provided an adequate fit to the data at baseline. Tests of equality of form and equality of factor loadings demonstrated stability of the factor structure over time, indicating temporal stability. This study confirms the results of previous research supporting the DSM-5 model of PTSD symptoms (Elhai et al., 2012; Miller et al., 2012). This is the first study to demonstrate the temporal stability of the PCL-5, indicating its use in longitudinal studies will measure the same construct over time. PMID:24932642

Diversity Promotes Temporal Stability across Levels of Ecosystem Organization in Experimental Grasslands

PubMed Central

Proulx, Raphaël; Wirth, Christian; Voigt, Winfried; Weigelt, Alexandra; Roscher, Christiane; Attinger, Sabine; Baade, Jussi; Barnard, Romain L.; Buchmann, Nina; Buscot, François; Eisenhauer, Nico; Fischer, Markus; Gleixner, Gerd; Halle, Stefan; Hildebrandt, Anke; Kowalski, Esther; Kuu, Annely; Lange, Markus; Milcu, Alex; Niklaus, Pascal A.; Oelmann, Yvonne; Rosenkranz, Stephan; Sabais, Alexander; Scherber, Christoph; Scherer-Lorenzen, Michael; Scheu, Stefan; Schulze, Ernst-Detlef; Schumacher, Jens; Schwichtenberg, Guido; Soussana, Jean-François; Temperton, Vicky M.; Weisser, Wolfgang W.; Wilcke, Wolfgang; Schmid, Bernhard

2010-01-01

The diversity–stability hypothesis states that current losses of biodiversity can impair the ability of an ecosystem to dampen the effect of environmental perturbations on its functioning. Using data from a long-term and comprehensive biodiversity experiment, we quantified the temporal stability of 42 variables characterizing twelve ecological functions in managed grassland plots varying in plant species richness. We demonstrate that diversity increases stability i) across trophic levels (producer, consumer), ii) at both the system (community, ecosystem) and the component levels (population, functional group, phylogenetic clade), and iii) primarily for aboveground rather than belowground processes. Temporal synchronization across studied variables was mostly unaffected with increasing species richness. This study provides the strongest empirical support so far that diversity promotes stability across different ecological functions and levels of ecosystem organization in grasslands. PMID:20967213

Preparation of pH-sensitive anionic liposomes designed for drug delivery system (DDS) application.

PubMed

Aoki, Asami; Akaboshi, Hikaru; Ogura, Taku; Aikawa, Tatsuo; Kondo, Takeshi; Tobori, Norio; Yuasa, Makoto

2015-01-01

We prepared pH-sensitive anionic liposomes composed solely of anionic bilayer membrane components that were designed to promote efficient release of entrapped agents in response to acidic pH. The pH-sensitive anionic liposomes showed high dispersion stability at neutral pH, but the fluidity of the bilayer membrane was enhanced in an acidic environment. These liposomes were rather simple and were composed of dimyristoylphosphatidylcholine (DMPC), an anionic bilayer membrane component, and polyoxyethylene sorbitan monostearate (Tween 80). In particular, the present pH-sensitive anionic liposomes showed higher temporal stability than those of conventional DMPC/DPPC liposomes. We found that pHsensitive properties strongly depended on the molecular structure, pKa value, and amount of an incorporated anionic bilayer membrane component, such as sodium oleate (SO), dimyristoylphosphatidylserine (DMPS), or sodium β-sitosterol sulfate (SS). These results provide an opportunity to manipulate liposomal stability in a pH-dependent manner, which could lead to the formulation of a high performance drug delivery system (DDS).

Linear stability analysis of particle-laden hypopycnal plumes

NASA Astrophysics Data System (ADS)

Farenzena, Bruno Avila; Silvestrini, Jorge Hugo

2017-12-01

Gravity-driven riverine outflows are responsible for carrying sediments to the coastal waters. The turbulent mixing in these flows is associated with shear and gravitational instabilities such as Kelvin-Helmholtz, Holmboe, and Rayleigh-Taylor. Results from temporal linear stability analysis of a two-layer stratified flow are presented, investigating the behavior of settling particles and mixing region thickness on the flow stability in the presence of ambient shear. The particles are considered suspended in the transport fluid, and its sedimentation is modeled with a constant valued settling velocity. Three scenarios, regarding the mixing region thickness, were identified: the poorly mixed environment, the strong mixed environment, and intermediate scenario. It was observed that Kelvin-Helmholtz and settling convection modes are the two fastest growing modes depending on the particles settling velocity and the total Richardson number. The second scenario presents a modified Rayleigh-Taylor instability, which is the dominant mode. The third case can have Kelvin-Helmholtz, settling convection, and modified Rayleigh-Taylor modes as the fastest growing mode depending on the combination of parameters.

Soil Water Holding Capacity Mitigates Downside Risk and Volatility in US Rainfed Maize: Time to Invest in Soil Organic Matter?

PubMed Central

Williams, Alwyn; Hunter, Mitchell C.; Kammerer, Melanie; Kane, Daniel A.; Jordan, Nicholas R.; Mortensen, David A.; Smith, Richard G.; Snapp, Sieglinde

2016-01-01

Yield stability is fundamental to global food security in the face of climate change, and better strategies are needed for buffering crop yields against increased weather variability. Regional- scale analyses of yield stability can support robust inferences about buffering strategies for widely-grown staple crops, but have not been accomplished. We present a novel analytical approach, synthesizing 2000–2014 data on weather and soil factors to quantify their impact on county-level maize yield stability in four US states that vary widely in these factors (Illinois, Michigan, Minnesota and Pennsylvania). Yield stability is quantified as both ‘downside risk’ (minimum yield potential, MYP) and ‘volatility’ (temporal yield variability). We show that excessive heat and drought decreased mean yields and yield stability, while higher precipitation increased stability. Soil water holding capacity strongly affected yield volatility in all four states, either directly (Minnesota and Pennsylvania) or indirectly, via its effects on MYP (Illinois and Michigan). We infer that factors contributing to soil water holding capacity can help buffer maize yields against variable weather. Given that soil water holding capacity responds (within limits) to agronomic management, our analysis highlights broadly relevant management strategies for buffering crop yields against climate variability, and informs region-specific strategies. PMID:27560666

Investigating local controls on soil moisture temporal stability using an inverse modeling approach

NASA Astrophysics Data System (ADS)

Bogena, Heye; Qu, Wei; Huisman, Sander; Vereecken, Harry

2013-04-01

A better understanding of the temporal stability of soil moisture and its relation to local and nonlocal controls is a major challenge in modern hydrology. Both local controls, such as soil and vegetation properties, and non-local controls, such as topography and climate variability, affect soil moisture dynamics. Wireless sensor networks are becoming more readily available, which opens up opportunities to investigate spatial and temporal variability of soil moisture with unprecedented resolution. In this study, we employed the wireless sensor network SoilNet developed by the Forschungszentrum Jülich to investigate soil moisture variability of a grassland headwater catchment in Western Germany within the framework of the TERENO initiative. In particular, we investigated the effect of soil hydraulic parameters on the temporal stability of soil moisture. For this, the HYDRUS-1D code coupled with a global optimizer (DREAM) was used to inversely estimate Mualem-van Genuchten parameters from soil moisture observations at three depths under natural (transient) boundary conditions for 83 locations in the headwater catchment. On the basis of the optimized parameter sets, we then evaluated to which extent the variability in soil hydraulic conductivity, pore size distribution, air entry suction and soil depth between these 83 locations controlled the temporal stability of soil moisture, which was independently determined from the observed soil moisture data. It was found that the saturated hydraulic conductivity (Ks) was the most significant attribute to explain temporal stability of soil moisture as expressed by the mean relative difference (MRD).

Self-recovery of stressed nanomembranes

NASA Astrophysics Data System (ADS)

Jiang, Chaoyang; Rybak, Beth M.; Markutsya, Sergiy; Kladitis, Paul E.; Tsukruk, Vladimir V.

2005-03-01

Long-term stability and self-recovery properties were studied for the compliant nanomembranes with a thickness of 55nm free suspended over openings of several hundred microns across. These nanomembranes were assembled with spin-assisted layer-by-layer routines and were composed of polymer multilayers and gold nanoparticles. In a wide pressure range, the membranes behave like completely elastic freely suspended plates. Temporal stability was tested under extreme deformational conditions close to ultimate strain and very modest creep behavior was observed. A unique "self-recovery" ability of these nanomembranes was revealed in these tests. We observed a complete restoration of the initial nanomembrane shape and properties after significant inelastic deformation. These unique micromechanical properties are suggested to be the result of strong Coulombic interaction between the polyelectrolyte layers combined with a high level of biaxial orientation of polymer chains and in-plane prestretching stresses.

Can shallow-layer measurements at a single location be used to predict deep soil water storage at the slope scale?

NASA Astrophysics Data System (ADS)

Gao, Lei; Lv, Yujuan; Wang, Dongdong; Tahir, Muhammad; Peng, Xinhua

2015-12-01

Knowing the amount of soil water storage (SWS) in agricultural soil profiles is important for understanding physical, chemical, and biological soil processes. However, measuring the SWS in deep soil layers is more expensive and time consuming than in shallower layers. Whether deep SWS can be predicted from shallow-layer measurements through temporal stability analysis (TSA) remains unclear. To address this issue, the soil water content was measured at depths of 0-1.6 m (0.2-m depth intervals) at 79 locations along an agricultural slope on 28 occasions between July 2013 and October 2014. SWSs values were then calculated for the 0-0.4, 0.4-0.8, 0.8-1.2, 1.2-1.6, and 0-1.6 m soil layers. The SWS exhibited strong temporal stability, with mean Spearman's ranking coefficients (rs) of 0.83, 0.92, 0.83, and 0.79 in the 0-0.4, 0.4-0.8, 0.8-1.2, and 1.2-1.6 m soil layers, respectively. As expected, the most temporally stable location (MTSL1) accurately predicted the average SWS of the corresponding soil layer, and the values of absolute bias relative to mean (ARB) were lower than 3% for all of the investigated soil layers. Using TSA, deep-layer SWS information could be predicted using a single-location measurement in the 0-0.4 m soil layer. The mean ARB values between the observed and predicted mean SWS values were 2.9%, 4.3%, 3.9%, and 2.7% in the 0.4-0.8, 0.8-1.2, 1.2-1.6, and 0-1.6 m soil layers, respectively. The prediction accuracy of the spatial distribution generally decreased with increasing depth, with linear determination coefficients (R2) of 0.93, 0.79, 0.72, and 0.84 for the four soil layers, respectively. The proposed method could further expand the application of the temporal stability technique in the estimation of SWS.

Soil internal drainage: temporal stability and spatial variability in succession bean-black oat

NASA Astrophysics Data System (ADS)

Salvador, M. M. S.; Libardi, P. L.; Moreira, N. B.; Sousa, H. H. F.; Neiverth, C. A.

2012-04-01

There are a variety of studies considering the soil water content, but those who consider the flow of water, which are translated by deep drainage and capillary rise are scarce, especially those who assess their spatio-temporal variability, due to its laborious obtaining. Large areas have been considered homogeneous, but show considerable spatial variability inherent in the soil, causing the appearance of zones of distinct physical properties. In deep, sandy soils where the groundwater level is far below the root zone of interference, internal drainage is one of the factors limiting the supply of water to the soil surface, and possibly one of the biggest factors that determines what kinds satisfactory development of plants present in a given landscape. The forms of relief may also be indicators of changes in soil properties, because this variability is caused by small changes that affect the slope of the pedogenetic processes and the transport and storage of water in the soil profile, i.e., the different trajectories of water flow in different forms of the landscape, is the cause of variability. The objectives of this research were: i) evaluate the spatial and temporal stability of internal soil water drainage in a place near and another distant from the root system in a bean-black-oat succession and ii) verify their spatial variability in relation to relief. With the hydraulic conductivity obtained by the instantaneous profile method and the total potential gradient obtained from the difference in readings of tensiometers installed at depths of 0.35 and 0.45 and 0.75 and 0.85 m in 60 sampling points totaling 1680 and 1200 observations during the cultivation of beans and oats, respectively, was obtained so the internal drainage / capillary rise through the Darcy-Buckingham equation. To evaluate the temporal stability the method used was the relative difference and Spearman correlation test and the spatial variability was analyzed as geostatistical methodology. During the period when the water flow in soil is higher, there is strong temporal stability in the depth of 0.40 m, which is the opposite for the periods of drying. The lowest relative difference and standard deviation for the internal drainage obtained during the cultivation of beans and depth of 0.40 m confirm the hypothesis that the research carried out during periods of soil water recharge have less variability than those in the drying period. Temporal stability was due to the topographic position of selected points, since the points chosen for the depth of 0.40 m in both growing seasons, are located on the lower portion of the relief, and the nominees for the depth of 0,80 m, the highest portion. There were differences in the spatial pattern of water flow in the soil along the crop succession, i.e. the seasonal demand for water by plants and evaporation from the soil at the time of drying, changed their distribution model with internal drainage phases and stages capillary rise.

Abstract Profiles of Structural Stability Point to Universal Tendencies, Family-Specific Factors, and Ancient Connections between Languages

PubMed Central

Dediu, Dan; Levinson, Stephen C.

2012-01-01

Language is the best example of a cultural evolutionary system, able to retain a phylogenetic signal over many thousands of years. The temporal stability (conservatism) of basic vocabulary is relatively well understood, but the stability of the structural properties of language (phonology, morphology, syntax) is still unclear. Here we report an extensive Bayesian phylogenetic investigation of the structural stability of numerous features across many language families and we introduce a novel method for analyzing the relationships between the “stability profiles” of language families. We found that there is a strong universal component across language families, suggesting the existence of universal linguistic, cognitive and genetic constraints. Against this background, however, each language family has a distinct stability profile, and these profiles cluster by geographic area and likely deep genealogical relationships. These stability profiles seem to show, for example, the ancient historical relationships between the Siberian and American language families, presumed to be separated by at least 12,000 years, and possible connections between the Eurasian families. We also found preliminary support for the punctuated evolution of structural features of language across families, types of features and geographic areas. Thus, such higher-level properties of language seen as an evolutionary system might allow the investigation of ancient connections between languages and shed light on the peopling of the world. PMID:23028843

Abstract profiles of structural stability point to universal tendencies, family-specific factors, and ancient connections between languages.

PubMed

Dediu, Dan; Levinson, Stephen C

2012-01-01

Language is the best example of a cultural evolutionary system, able to retain a phylogenetic signal over many thousands of years. The temporal stability (conservatism) of basic vocabulary is relatively well understood, but the stability of the structural properties of language (phonology, morphology, syntax) is still unclear. Here we report an extensive Bayesian phylogenetic investigation of the structural stability of numerous features across many language families and we introduce a novel method for analyzing the relationships between the "stability profiles" of language families. We found that there is a strong universal component across language families, suggesting the existence of universal linguistic, cognitive and genetic constraints. Against this background, however, each language family has a distinct stability profile, and these profiles cluster by geographic area and likely deep genealogical relationships. These stability profiles seem to show, for example, the ancient historical relationships between the Siberian and American language families, presumed to be separated by at least 12,000 years, and possible connections between the Eurasian families. We also found preliminary support for the punctuated evolution of structural features of language across families, types of features and geographic areas. Thus, such higher-level properties of language seen as an evolutionary system might allow the investigation of ancient connections between languages and shed light on the peopling of the world.

Optimal exploitation of spatially distributed trophic resources and population stability

USGS Publications Warehouse

Basset, A.; Fedele, M.; DeAngelis, D.L.

2002-01-01

The relationships between optimal foraging of individuals and population stability are addressed by testing, with a spatially explicit model, the effect of patch departure behaviour on individual energetics and population stability. A factorial experimental design was used to analyse the relevance of the behavioural factor in relation to three factors that are known to affect individual energetics; i.e. resource growth rate (RGR), assimilation efficiency (AE), and body size of individuals. The factorial combination of these factors produced 432 cases, and 1000 replicate simulations were run for each case. Net energy intake rates of the modelled consumers increased with increasing RGR, consumer AE, and consumer body size, as expected. Moreover, through their patch departure behaviour, by selecting the resource level at which they departed from the patch, individuals managed to substantially increase their net energy intake rates. Population stability was also affected by the behavioural factors and by the other factors, but with highly non-linear responses. Whenever resources were limiting for the consumers because of low RGR, large individual body size or low AE, population density at the equilibrium was directly related to the patch departure behaviour; on the other hand, optimal patch departure behaviour, which maximised the net energy intake at the individual level, had a negative influence on population stability whenever resource availability was high for the consumers. The consumer growth rate (r) and numerical dynamics, as well as the spatial and temporal fluctuations of resource density, which were the proximate causes of population stability or instability, were affected by the behavioural factor as strongly or even more strongly than by the others factors considered here. Therefore, patch departure behaviour can act as a feedback control of individual energetics, allowing consumers to optimise a potential trade-off between short-term individual fitness and long-term population stability. ?? 2002 Elsevier Science B.V. All rights reserved.

Longitudinal progression of frontal and temporal lobe changes in schizophrenia

PubMed Central

Cobia, Derin J.; Smith, Matthew J.; Wang, Lei; Csernansky, John G.

2012-01-01

Cortical abnormalities are considered a neurobiological characteristic of schizophrenia. However, the pattern of such deficits as they progress over the illness remains poorly understood. The goal of this project was to assess the progression of cortical thinning in frontal and temporal cortical regions in schizophrenia, and determine whether relationships exist between them and neuropsychological and clinical symptom profiles. As part of a larger longitudinal 2-year follow-up study, schizophrenia (n=20) and healthy participants (n=20) group-matched for age, gender, and recent-alcohol use, were selected. Using MRI, estimates of gray matter thickness were derived from primary anatomical gyri of the frontal and temporal lobes using surface-based algorithms. These values were entered into repeated-measures analysis of variance models to determine group status and time effects. Change values in cortical regions were correlated with changes in neuropsychological functioning and clinical symptomatology. Results revealed exaggerated cortical thinning of the middle frontal, superior temporal, and middle temporal gyri in schizophrenia participants. These thickness changes strongly influenced volumetric reductions, but were not related to shrinking surface area. Neuropsychological and clinical symptom profiles were stable in the schizophrenia participants despite these neuroanatomic changes. Overall it appears ongoing abnormalities in the cerebral cortex continue after initial onset of schizophrenia, particularly the lateral aspects of frontal and temporal regions, and do not relate to neuropsychological or clinical measures over time. Maintenance of neuropsychological performance and clinical stability in the face of changing neuroanatomical structure suggests the involvement of alternative compensatory mechanisms. PMID:22647883

Temporal Stability and Convergent Validity of the Behavior Assessment System for Children.

ERIC Educational Resources Information Center

Merydith, Scott P.

2001-01-01

Assesses the temporal stability and convergent validity of the Behavioral Assessment System for Children (BASC). Teachers and parents rated kindergarten and first-grade students using BASC. Teachers were more stable in rating children's externalizing behaviors and attention problems. Discusses results in terms of the accuracy of information…

Biodiversity, productivity and the temporal stability of productivity: patterns and processes

USDA-ARS?s Scientific Manuscript database

Theory predicts that the temporal stability of productivity, measured as the ratio of the mean to the standard deviation of community biomass, increases with species richness and evenness. We used experimental species mixtures of grassland plants to test this hypothesis and identify the mechanisms i...

Temporal (In)Stability of Employee Preferences for Rewards

ERIC Educational Resources Information Center

Wine, Byron; Gilroy, Shawn; Hantula, Donald A.

2012-01-01

This study examined the temporal stability of employee preferences for rewards over seven monthly evaluations. Participants completed a ranking stimulus preference assessment monthly, and the latter six monthly assessments were compared to the initial assessment. Correlations of preferences from month to month ranged from r = -0.89 to 0.99.…

Joint Video Stitching and Stabilization from Moving Cameras.

PubMed

Guo, Heng; Liu, Shuaicheng; He, Tong; Zhu, Shuyuan; Zeng, Bing; Gabbouj, Moncef

2016-09-08

In this paper, we extend image stitching to video stitching for videos that are captured for the same scene simultaneously by multiple moving cameras. In practice, videos captured under this circumstance often appear shaky. Directly applying image stitching methods for shaking videos often suffers from strong spatial and temporal artifacts. To solve this problem, we propose a unified framework in which video stitching and stabilization are performed jointly. Specifically, our system takes several overlapping videos as inputs. We estimate both inter motions (between different videos) and intra motions (between neighboring frames within a video). Then, we solve an optimal virtual 2D camera path from all original paths. An enlarged field of view along the virtual path is finally obtained by a space-temporal optimization that takes both inter and intra motions into consideration. Two important components of this optimization are that (1) a grid-based tracking method is designed for an improved robustness, which produces features that are distributed evenly within and across multiple views, and (2) a mesh-based motion model is adopted for the handling of the scene parallax. Some experimental results are provided to demonstrate the effectiveness of our approach on various consumer-level videos and a Plugin, named "Video Stitcher" is developed at Adobe After Effects CC2015 to show the processed videos.

Stabilizing effects in temporal fluctuations: management, traits, and species richness in high-diversity communities.

PubMed

Lepš, Jan; Májeková, Maria; Vítová, Alena; Doležal, Jiří; de Bello, Francesco

2018-02-01

The loss of biodiversity is thought to have adverse effects on multiple ecosystem functions, including the decline of community stability. Decreased diversity reduces the strength of the portfolio effect, a mechanism stabilizing community temporal fluctuations. Community stability is also expected to decrease with greater variability in individual species populations and with synchrony of their fluctuations. In semi-natural meadows, eutrophication is one of the most important drivers of diversity decline; it is expected to increase species fluctuations and synchrony among them, all effects leading to lower community stability. With a 16-year time series of biomass data from a temperate species-rich meadow with fertilization and removal of the dominant species, we assessed population biomass temporal (co)variation under different management types and competition intensity, and in relation to species functional traits and to species diversity. Whereas the effect of dominant removal was relatively small (with a tendency toward lower stability), fertilization markedly decreased community stability (i.e., increased coefficient of variation in the total biomass) and species diversity. On average, the fluctuations of individual populations were mutually independent, with a slight tendency toward synchrony in unfertilized plots, and a tendency toward compensatory dynamics in fertilized plots and no effects of removal. The marked decrease of synchrony with fertilization, contrary to the majority of the results reported previously, follows the predictions of increased compensatory dynamics with increased asymmetric competition for light in a more productive environment. Synchrony increased also with species functional similarity stressing the importance of shared ecological strategies in driving similar species responses to weather fluctuations. As expected, the decrease of temporal stability of total biomass was mainly related to the decrease of species richness, with its effect remaining significant also after accounting for fertilization. The weakening of the portfolio effect with species richness decline is a crucial driver of community destabilization. However, the positive effect of species richness on temporal stability of total biomass was not due to increased compensatory dynamics, since synchrony increased with species richness. This shows that the negative effect of eutrophication on community stability does not operate through increasing synchrony, but through the reduction of diversity. © 2017 by the Ecological Society of America.

Continuous and lurching traveling pulses in neuronal networks with delay and spatially decaying connectivity

PubMed Central

Golomb, David; Ermentrout, G. Bard

1999-01-01

Propagation of discharges in cortical and thalamic systems, which is used as a probe for examining network circuitry, is studied by constructing a one-dimensional model of integrate-and-fire neurons that are coupled by excitatory synapses with delay. Each neuron fires only one spike. The velocity and stability of propagating continuous pulses are calculated analytically. Above a certain critical value of the constant delay, these pulses lose stability. Instead, lurching pulses propagate with discontinuous and periodic spatio-temporal characteristics. The parameter regime for which lurching occurs is strongly affected by the footprint (connectivity) shape; bistability may occur with a square footprint shape but not with an exponential footprint shape. For strong synaptic coupling, the velocity of both continuous and lurching pulses increases logarithmically with the synaptic coupling strength gsyn for an exponential footprint shape, and it is bounded for a step footprint shape. We conclude that the differences in velocity and shape between the front of thalamic spindle waves in vitro and cortical paroxysmal discharges stem from their different effective delay; in thalamic networks, large effective delay between inhibitory neurons arises from their effective interaction via the excitatory cells which display postinhibitory rebound. PMID:10557346

Vision-based flight control in the hawkmoth Hyles lineata

PubMed Central

Windsor, Shane P.; Bomphrey, Richard J.; Taylor, Graham K.

2014-01-01

Vision is a key sensory modality for flying insects, playing an important role in guidance, navigation and control. Here, we use a virtual-reality flight simulator to measure the optomotor responses of the hawkmoth Hyles lineata, and use a published linear-time invariant model of the flight dynamics to interpret the function of the measured responses in flight stabilization and control. We recorded the forces and moments produced during oscillation of the visual field in roll, pitch and yaw, varying the temporal frequency, amplitude or spatial frequency of the stimulus. The moths’ responses were strongly dependent upon contrast frequency, as expected if the optomotor system uses correlation-type motion detectors to sense self-motion. The flight dynamics model predicts that roll angle feedback is needed to stabilize the lateral dynamics, and that a combination of pitch angle and pitch rate feedback is most effective in stabilizing the longitudinal dynamics. The moths’ responses to roll and pitch stimuli coincided qualitatively with these functional predictions. The moths produced coupled roll and yaw moments in response to yaw stimuli, which could help to reduce the energetic cost of correcting heading. Our results emphasize the close relationship between physics and physiology in the stabilization of insect flight. PMID:24335557

Vision-based flight control in the hawkmoth Hyles lineata.

PubMed

Windsor, Shane P; Bomphrey, Richard J; Taylor, Graham K

2014-02-06

Vision is a key sensory modality for flying insects, playing an important role in guidance, navigation and control. Here, we use a virtual-reality flight simulator to measure the optomotor responses of the hawkmoth Hyles lineata, and use a published linear-time invariant model of the flight dynamics to interpret the function of the measured responses in flight stabilization and control. We recorded the forces and moments produced during oscillation of the visual field in roll, pitch and yaw, varying the temporal frequency, amplitude or spatial frequency of the stimulus. The moths' responses were strongly dependent upon contrast frequency, as expected if the optomotor system uses correlation-type motion detectors to sense self-motion. The flight dynamics model predicts that roll angle feedback is needed to stabilize the lateral dynamics, and that a combination of pitch angle and pitch rate feedback is most effective in stabilizing the longitudinal dynamics. The moths' responses to roll and pitch stimuli coincided qualitatively with these functional predictions. The moths produced coupled roll and yaw moments in response to yaw stimuli, which could help to reduce the energetic cost of correcting heading. Our results emphasize the close relationship between physics and physiology in the stabilization of insect flight.

Glacigenic sedimentation pulses triggered post-glacial gas hydrate dissociation.

PubMed

Karstens, Jens; Haflidason, Haflidi; Becker, Lukas W M; Berndt, Christian; Rüpke, Lars; Planke, Sverre; Liebetrau, Volker; Schmidt, Mark; Mienert, Jürgen

2018-02-12

Large amounts of methane are stored in continental margins as gas hydrates. They are stable under high pressure and low, but react sensitively to environmental changes. Bottom water temperature and sea level changes were considered as main contributors to gas hydrate dynamics after the last glaciation. However, here we show with numerical simulations that pulses of increased sedimentation dominantly controlled hydrate stability during the end of the last glaciation offshore mid-Norway. Sedimentation pulses triggered widespread gas hydrate dissociation and explains the formation of ubiquitous blowout pipes in water depths of 600 to 800 m. Maximum gas hydrate dissociation correlates spatially and temporally with the formation or reactivation of pockmarks, which is constrained by radiocarbon dating of Isorropodon nyeggaensis bivalve shells. Our results highlight that rapid changes of sedimentation can have a strong impact on gas hydrate systems affecting fluid flow and gas seepage activity, slope stability and the carbon cycle.

Resilience and stability of a pelagic marine ecosystem

PubMed Central

Lindegren, Martin; Checkley, David M.; Ohman, Mark D.; Koslow, J. Anthony; Goericke, Ralf

2016-01-01

The accelerating loss of biodiversity and ecosystem services worldwide has accentuated a long-standing debate on the role of diversity in stabilizing ecological communities and has given rise to a field of research on biodiversity and ecosystem functioning (BEF). Although broad consensus has been reached regarding the positive BEF relationship, a number of important challenges remain unanswered. These primarily concern the underlying mechanisms by which diversity increases resilience and community stability, particularly the relative importance of statistical averaging and functional complementarity. Our understanding of these mechanisms relies heavily on theoretical and experimental studies, yet the degree to which theory adequately explains the dynamics and stability of natural ecosystems is largely unknown, especially in marine ecosystems. Using modelling and a unique 60-year dataset covering multiple trophic levels, we show that the pronounced multi-decadal variability of the Southern California Current System (SCCS) does not represent fundamental changes in ecosystem functioning, but a linear response to key environmental drivers channelled through bottom-up and physical control. Furthermore, we show strong temporal asynchrony between key species or functional groups within multiple trophic levels caused by opposite responses to these drivers. We argue that functional complementarity is the primary mechanism reducing community variability and promoting resilience and stability in the SCCS. PMID:26763697

Can we bet on negative emissions to achieve the 2°C target even under strong carbon cycle feedbacks?

NASA Astrophysics Data System (ADS)

Tanaka, K.; Yamagata, Y.; Yokohata, T.; Emori, S.; Hanaoka, T.

2015-12-01

Negative emission technologies such as Bioenergy with Carbon dioxide Capture and Storage (BioCCS) play an ever more crucial role in meeting the 2°C stabilization target. However, such technologies are currently at their infancy and their future penetrations may fall short of the scale required to stabilize the warming. Furthermore, the overshoot in the mid-century prior to a full realization of negative emissions would give rise to a risk because such a temporal but excessive warming above 2°C might amplify itself by strengthening climate-carbon cycle feedbacks. It has not been extensively assessed yet how carbon cycle feedbacks might play out during the overshoot in the context of negative emissions. This study explores how 2°C stabilization pathways, in particular those which undergo overshoot, can be influenced by carbon cycle feedbacks and asks their climatic and economic consequences. We compute 2°C stabilization emissions scenarios under a cost-effectiveness principle, in which the total abatement costs are minimized such that the global warming is capped at 2°C. We employ a reduced-complexity model, the Aggregated Carbon Cycle, Atmospheric Chemistry, and Climate model (ACC2), which comprises a box model of the global carbon cycle, simple parameterizations of the atmospheric chemistry, and a land-ocean energy balance model. The total abatement costs are estimated from the marginal abatement cost functions for CO2, CH4, N2O, and BC.Our preliminary results show that, if carbon cycle feedbacks turn out to be stronger than what is known today, it would incur substantial abatement costs to keep up with the 2°C stabilization goal. Our results also suggest that it would be less expensive in the long run to plan for a 2°C stabilization pathway by considering strong carbon cycle feedbacks because it would cost more if we correct the emission pathway in the mid-century to adjust for unexpectedly large carbon cycle feedbacks during overshoot. Furthermore, our tentative results point to a key policy message: do not rely on negative emissions to achieve the 2°C target. It would make more sense to gear climate mitigation actions toward the stabilization target without betting on negative emissions because negative emissions might create large overshoot in case of strong feedbacks.

Temporal Stability of Strength-Based Assessments: Test-Retest Reliability of Student and Teacher Reports

ERIC Educational Resources Information Center

Romer, Natalie; Merrell, Kenneth W.

2013-01-01

This study focused on evaluating the temporal stability of self-reported and teacher-reported perceptions of students' social and emotional skills and assets. We used a test-retest reliability procedure over repeated administrations of the child, adolescent, and teacher versions of the "Social-Emotional Assets and Resilience Scales".…

The impact of turbulent renewable energy production on power grid stability and quality

NASA Astrophysics Data System (ADS)

Schmietendorf, Katrin; Peinke, Joachim; Kamps, Oliver

2017-11-01

Feed-in fluctuations induced by renewables are one of the key challenges to the stability and quality of electrical power grids. In particular short-term fluctuations disturb the system on a time scale, on which load balancing does not operate yet and the system is intrinsically governed by self-organized synchronization. Wind and solar power are known to be strongly non-Gaussian with intermittent increment statistics in these time scales. We investigate the impact of short-term wind fluctuations on the basis of a Kuramoto-like power grid model considering stability in terms of desynchronization and frequency and voltage quality aspects. We present a procedure to generate realistic feed-in fluctuations with temporal correlations, Kolmogorov power spectrum and intermittent increments. By comparison to correlated Gaussian noise of the same spectrum and Gaussian white noise, we found out that while the correlations are essential to capture the likelihood of severe outages, the intermittent nature of wind power has significant consequences on power quality: intermittency is directly transferred into frequency and voltage fluctuations yielding a novel type of fluctuations, which is beyond engineering status of knowledge.

Long-range propagation of nonlinear infrasound waves through an absorbing atmosphere.

PubMed

de Groot-Hedlin, C D

2016-04-01

The Navier-Stokes equations are solved using a finite-difference, time-domain (FDTD) approach for axi-symmetric environmental models, allowing three-dimensional acoustic propagation to be simulated using a two-dimensional Cylindrical coordinate system. A method to stabilize the FDTD algorithm in a viscous medium at atmospheric densities characteristic of the lower thermosphere is described. The stabilization scheme slightly alters the governing equations but results in quantifiable dispersion characteristics. It is shown that this method leaves sound speeds and attenuation unchanged at frequencies that are well resolved by the temporal sampling rate but strongly attenuates higher frequencies. Numerical experiments are performed to assess the effect of source strength on the amplitudes and spectral content of signals recorded at ground level at a range of distances from the source. It is shown that the source amplitudes have a stronger effect on a signal's dominant frequency than on its amplitude. Applying the stabilized code to infrasound propagation through realistic atmospheric profiles shows that nonlinear propagation alters the spectral content of low amplitude thermospheric signals, demonstrating that nonlinear effects are significant for all detectable thermospheric returns.

Temporal stability and rates of post-depositional change in geochemical signatures of brown trout Salmo trutta scales.

PubMed

Ryan, D; Shephard, S; Kelly, F L

2016-09-01

This study investigates temporal stability in the scale microchemistry of brown trout Salmo trutta in feeder streams of a large heterogeneous lake catchment and rates of change after migration into the lake. Laser-ablation inductively coupled plasma mass spectrometry was used to quantify the elemental concentrations of Na, Mg, Mn, Cu, Zn, Ba and Sr in archived (1997-2002) scales of juvenile S. trutta collected from six major feeder streams of Lough Mask, County Mayo, Ireland. Water-element Ca ratios within these streams were determined for the fish sampling period and for a later period (2013-2015). Salmo trutta scale Sr and Ba concentrations were significantly (P < 0·05) correlated with stream water sample Sr:Ca and Ba:Ca ratios respectively from both periods, indicating multi-annual stability in scale and water-elemental signatures. Discriminant analysis of scale chemistries correctly classified 91% of sampled juvenile S. trutta to their stream of origin using a cross-validated classification model. This model was used to test whether assumed post-depositional change in scale element concentrations reduced correct natal stream classification of S. trutta in successive years after migration into Lough Mask. Fish residing in the lake for 1-3 years could be reliably classified to their most likely natal stream, but the probability of correct classification diminished strongly with longer lake residence. Use of scale chemistry to identify natal streams of lake S. trutta should focus on recent migrants, but may not require contemporary water chemistry data. © 2016 The Fisheries Society of the British Isles.

Operating characteristics of HTS power supply for and improving temporal stability of coated conductor magnet in liquid helium

NASA Astrophysics Data System (ADS)

Park, D. K.; Kim, Y. J.; Yang, S. E.; Kwon, N. Y.; Lee, H. G.; Ko, T. K.

2009-10-01

High temperature superconducting (HTS) magnets have been studied for insert coils of high field nuclear magnetic resonance (NMR) magnets but the temporal stability required for NMR is hard to achieve due to low index value and high joint resistance. In this research, the HTS power supply with magnets using coated conductor (CC) was investigated and tested in helium cryogenic system. All joints were conducted by soldering after etching stabilizer of the CC to minimize joint resistance. The pumping rate was determined by current amplitude and timing sequential control of heaters and the electromagnet. Operating characteristics were analyzed to enhance charging efficiency and the feasibility of temporally stable CC magnet during persistent mode was studied.

Temporal variatiions of Sea ice cover in the Baltic Sea derived from operational sea ice products used in NWP.

NASA Astrophysics Data System (ADS)

Lange, Martin; Paul, Gerhard; Potthast, Roland

2014-05-01

Sea ice cover is a crucial parameter for surface fluxes of heat and moisture over water areas. The isolating effect and the much higher albedo strongly reduces the turbulent exchange of heat and moisture from the surface to the atmosphere and allows for cold and dry air mass flow with strong impact on the stability of the whole boundary layer and consequently cloud formation as well as precipitation in the downstream regions. Numerical weather centers as, ECMWF, MetoFrance or DWD use external products to initialize SST and sea ice cover in their NWP models. To the knowledge of the author there are mainly two global sea ice products well established with operational availability, one from NOAA NCEP that combines measurements with satellite data, and the other from OSI-SAF derived from SSMI/S sensors. The latter one is used in the Ostia product. DWD additionally uses a regional product for the Baltic Sea provided by the national center for shipping and hydrografie which combines observations from ships (and icebreakers) for the German part of the Baltic Sea and model analysis from the hydrodynamic HIROMB model of the Swedish meteorological service for the rest of the domain. The temporal evolution of the three different products are compared for a cold period in Februar 2012. Goods and bads will be presented and suggestions for a harmonization of strong day to day jumps over large areas are suggested.

Quantifying auditory temporal stability in a large database of recorded music.

PubMed

Ellis, Robert J; Duan, Zhiyan; Wang, Ye

2014-01-01

"Moving to the beat" is both one of the most basic and one of the most profound means by which humans (and a few other species) interact with music. Computer algorithms that detect the precise temporal location of beats (i.e., pulses of musical "energy") in recorded music have important practical applications, such as the creation of playlists with a particular tempo for rehabilitation (e.g., rhythmic gait training), exercise (e.g., jogging), or entertainment (e.g., continuous dance mixes). Although several such algorithms return simple point estimates of an audio file's temporal structure (e.g., "average tempo", "time signature"), none has sought to quantify the temporal stability of a series of detected beats. Such a method--a "Balanced Evaluation of Auditory Temporal Stability" (BEATS)--is proposed here, and is illustrated using the Million Song Dataset (a collection of audio features and music metadata for nearly one million audio files). A publically accessible web interface is also presented, which combines the thresholdable statistics of BEATS with queryable metadata terms, fostering potential avenues of research and facilitating the creation of highly personalized music playlists for clinical or recreational applications.

Longitudinal progression of frontal and temporal lobe changes in schizophrenia.

PubMed

Cobia, Derin J; Smith, Matthew J; Wang, Lei; Csernansky, John G

2012-08-01

Cortical abnormalities are considered a neurobiological characteristic of schizophrenia. However, the pattern of such deficits as they progress over the illness remains poorly understood. The goal of this project was to assess the progression of cortical thinning in frontal and temporal cortical regions in schizophrenia, and determine whether relationships exist between them and neuropsychological and clinical symptom profiles. As part of a larger longitudinal 2-year follow-up study, schizophrenia (n=20) and healthy participants (n=20) group-matched for age, gender, and recent-alcohol use, were selected. Using MRI, estimates of gray matter thickness were derived from primary anatomical gyri of the frontal and temporal lobes using surface-based algorithms. These values were entered into repeated-measures analysis of variance models to determine group status and time effects. Change values in cortical regions were correlated with changes in neuropsychological functioning and clinical symptomatology. Results revealed exaggerated cortical thinning of the middle frontal, superior temporal, and middle temporal gyri in schizophrenia participants. These thickness changes strongly influenced volumetric reductions, but were not related to shrinking surface area. Neuropsychological and clinical symptom profiles were stable in the schizophrenia participants despite these neuroanatomic changes. Overall it appears that ongoing abnormalities in the cerebral cortex continue after initial onset of schizophrenia, particularly the lateral aspects of frontal and temporal regions, and do not relate to neuropsychological or clinical measures over time. Maintenance of neuropsychological performance and clinical stability in the face of changing neuroanatomical structure suggests the involvement of alternative compensatory mechanisms. Copyright © 2012 Elsevier B.V. All rights reserved.

Temporal variation in pelagic food chain length in response to environmental change

PubMed Central

Ruiz-Cooley, Rocio I.; Gerrodette, Tim; Fiedler, Paul C.; Chivers, Susan J.; Danil, Kerri; Ballance, Lisa T.

2017-01-01

Climate variability alters nitrogen cycling, primary productivity, and dissolved oxygen concentration in marine ecosystems. We examined the role of this variability (as measured by six variables) on food chain length (FCL) in the California Current (CC) by reconstructing a time series of amino acid–specific δ15N values derived from common dolphins, an apex pelagic predator, and using two FCL proxies. Strong declines in FCL were observed after the 1997–1999 El Niño Southern Oscillation (ENSO) event. Bayesian models revealed longer FCLs under intermediate conditions for surface temperature, chlorophyll concentration, multivariate ENSO index, and total plankton volume but not for hypoxic depth and nitrate concentration. Our results challenge the prevalent paradigm that suggested long-term stability in the food web structure in the CC and, instead, reveal that pelagic food webs respond strongly to disturbances associated with ENSO events, local oceanography, and ongoing changes in climate. PMID:29057322

Assessing Temporal Stability for Coarse Scale Satellite Moisture Validation in the Maqu Area, Tibet

PubMed Central

Bhatti, Haris Akram; Rientjes, Tom; Verhoef, Wouter; Yaseen, Muhammad

2013-01-01

This study evaluates if the temporal stability concept is applicable to a time series of satellite soil moisture images so to extend the common procedure of satellite image validation. The area of study is the Maqu area, which is located in the northeastern part of the Tibetan plateau. The network serves validation purposes of coarse scale (25–50 km) satellite soil moisture products and comprises 20 stations with probes installed at depths of 5, 10, 20, 40, 80 cm. The study period is 2009. The temporal stability concept is applied to all five depths of the soil moisture measuring network and to a time series of satellite-based moisture products from the Advance Microwave Scanning Radiometer (AMSR-E). The in-situ network is also assessed by Pearsons's correlation analysis. Assessments by the temporal stability concept proved to be useful and results suggest that probe measurements at 10 cm depth best match to the satellite observations. The Mean Relative Difference plot for satellite pixels shows that a RMSM pixel can be identified but in our case this pixel does not overlay any in-situ station. Also, the RMSM pixel does not overlay any of the Representative Mean Soil Moisture (RMSM) stations of the five probe depths. Pearson's correlation analysis on in-situ measurements suggests that moisture patterns over time are more persistent than over space. Since this study presents first results on the application of the temporal stability concept to a series of satellite images, we recommend further tests to become more conclusive on effectiveness to broaden the procedure of satellite validation. PMID:23959237

Home ranges of lions in the Kalahari, Botswana exhibit vast sizes and high temporal variability.

PubMed

Zehnder, André; Henley, Stephen; Weibel, Robert

2018-06-01

The central Kalahari region in Botswana is one of the few remaining ecosystems with a stable lion population. Yet, relatively little is known about the ecology of the lions there. As an entry point, home range estimations provide information about the space utilization of the studied animals. The home ranges of eight lions in this region were determined to investigate their spatial overlaps and spatiotemporal variations. We found that, except for MCP, all home range estimators yielded comparable results regarding size and shape. The home ranges of all individuals were located predominantly inside the protected reserves. Their areas were among the largest known for lions with 1131 - 4314km 2 (95%), with no significant differences between males and females. Numerous overlaps between lions of different sexes were detected, although these originate from different groups. A distance chart confirmed that most of these lions directly encountered each other once or several times. Strong temporal variations of the home ranges were observed that did not match a seasonal pattern. The exceptionally large home ranges are likely to be caused by the sparse and dynamic prey populations. Since the ungulates in the study area move in an opportunistic way, too, strong spatiotemporal home range variations emerge. This can lead to misleading home ranges. We therefore recommend clarifying the stability of the home ranges by applying several levels of temporal aggregation. The lack of strict territoriality is likely an adaptation to the variable prey base and the high energetic costs associated with defending a large area. Copyright © 2018 Elsevier GmbH. All rights reserved.

The efficacy of a panel study for assessing the temporal stability of hunting participation and constraints

Treesearch

Ellen B. Drogin Rodgers; Brett A. Wright; Kenneth F. Backman

2003-01-01

The intent of this study of Virginia hunters/nonhunters was to test the efficacy of panel research for assessing the temporal stability of hunting participation and constraints. Findings suggest that participation/nonparticipation patterns were stable across time periods for the population, yet dynamic at the individual level. Although the structure of perceived...

Examination of the Psychometric Properties of the Adult Manifest Anxiety Scale-Elderly Version Scores

ERIC Educational Resources Information Center

Lowe, Patricia A.; Reynolds, Cecil R.

2006-01-01

The psychometric properties of the Adult Manifest Anxiety Scale-Elderly Version (AMAS-E) scores were evaluated in two studies. In Study 1, the temporal stability and construct validity of the AMAS-E test scores were examined in a group of 226 older adults, aged 60 years and older. Results indicated adequate to excellent temporal stability (2-week…

The Structure and Temporal Stability of the Child and Adolescent Perfectionism Scale

ERIC Educational Resources Information Center

O'Connor, Rory C.; Dixon, Diane; Rasmussen, Susan

2009-01-01

In this study, the authors examined the factor structure and temporal stability of the Child and Adolescent Perfectionism Scale (CAPS; G. L. Flett, P. L. Hewitt, D. J. Boucher, L. A. Davidson, & Y. Munro, 1997) in 2 samples of adolescents (15-16 years old). In Sample 1 (n = 624), confirmatory factor analysis did not support a 2-factor structure…

Psychometric Properties of Eating Disorder Instruments in Black and White Young Women: Internal Consistency, Temporal Stability, and Validity

ERIC Educational Resources Information Center

Bardone-Cone, Anna M.; Boyd, Clarissa A.

2007-01-01

Most of the major instruments in the eating disorder field have documented psychometric support only in predominantly White samples. The current study examined the internal consistency, temporal stability, and convergent and discriminant validity of a variety of eating disorder measures in Black (n = 97) and White (n = 179) female undergraduates.…

Attention-Deficit/Hyperactivity Disorder and Sluggish Cognitive Tempo throughout Childhood: Temporal Invariance and Stability from Preschool through Ninth Grade

ERIC Educational Resources Information Center

Leopold, Daniel R.; Christopher, Micaela E.; Burns, G. Leonard; Becker, Stephen P.; Olson, Richard K.; Willcutt, Erik G.

2016-01-01

Background: Although multiple cross-sectional studies have shown symptoms of sluggish cognitive tempo (SCT) and attention-deficit/hyperactivity disorder (ADHD) to be statistically distinct, studies have yet to examine the temporal stability and measurement invariance of SCT in a longitudinal sample. To date, only six studies have assessed SCT…

Temporal Stability of Genetic Variability and Differentiation in the Three-Spined Stickleback (Gasterosteus aculeatus)

PubMed Central

DeFaveri, Jacquelin; Merilä, Juha

2015-01-01

Temporal variation in allele frequencies, whether caused by deterministic or stochastic forces, can inform us about interesting demographic and evolutionary phenomena occurring in wild populations. In spite of the continued surge of interest in the genetics of three-spined stickleback (Gasterosteus aculeatus) populations, little attention has been paid towards the temporal stability of allele frequency distributions, and whether there are consistent differences in effective size (Ne) of local populations. We investigated temporal stability of genetic variability and differentiation in 15 microsatellite loci within and among eight collection sites of varying habitat type, surveyed twice over a six-year time period. In addition, Nes were estimated with the expectation that they would be lowest in isolated ponds, intermediate in larger lakes and largest in open marine sites. In spite of the marked differences in genetic variability and differentiation among the study sites, the temporal differences in allele frequencies, as well as measures of genetic diversity and differentiation, were negligible. Accordingly, the Ne estimates were temporally stable, but tended to be lower in ponds than in lake or marine habitats. Hence, we conclude that allele frequencies in putatively neutral markers in three-spined sticklebacks seem to be temporally stable – at least over periods of few generations – across a wide range of habitat types differing markedly in levels of genetic variability, effective population size and gene flow. PMID:25853707

Temporal stability of genetic variability and differentiation in the three-spined stickleback (Gasterosteus aculeatus).

PubMed

DeFaveri, Jacquelin; Merilä, Juha

2015-01-01

Temporal variation in allele frequencies, whether caused by deterministic or stochastic forces, can inform us about interesting demographic and evolutionary phenomena occurring in wild populations. In spite of the continued surge of interest in the genetics of three-spined stickleback (Gasterosteus aculeatus) populations, little attention has been paid towards the temporal stability of allele frequency distributions, and whether there are consistent differences in effective size (Ne) of local populations. We investigated temporal stability of genetic variability and differentiation in 15 microsatellite loci within and among eight collection sites of varying habitat type, surveyed twice over a six-year time period. In addition, Nes were estimated with the expectation that they would be lowest in isolated ponds, intermediate in larger lakes and largest in open marine sites. In spite of the marked differences in genetic variability and differentiation among the study sites, the temporal differences in allele frequencies, as well as measures of genetic diversity and differentiation, were negligible. Accordingly, the Ne estimates were temporally stable, but tended to be lower in ponds than in lake or marine habitats. Hence, we conclude that allele frequencies in putatively neutral markers in three-spined sticklebacks seem to be temporally stable - at least over periods of few generations - across a wide range of habitat types differing markedly in levels of genetic variability, effective population size and gene flow.

Transverse distribution of beam current oscillations of a 14 GHz electron cyclotron resonance ion source.

PubMed

Tarvainen, O; Toivanen, V; Komppula, J; Kalvas, T; Koivisto, H

2014-02-01

The temporal stability of oxygen ion beams has been studied with the 14 GHz A-ECR at JYFL (University of Jyvaskyla, Department of Physics). A sector Faraday cup was employed to measure the distribution of the beam current oscillations across the beam profile. The spatial and temporal characteristics of two different oscillation "modes" often observed with the JYFL 14 GHz ECRIS are discussed. It was observed that the low frequency oscillations below 200 Hz are distributed almost uniformly. In the high frequency oscillation "mode," with frequencies >300 Hz at the core of the beam, carrying most of the current, oscillates with smaller amplitude than the peripheral parts of the beam. The results help to explain differences observed between the two oscillation modes in terms of the transport efficiency through the JYFL K-130 cyclotron. The dependence of the oscillation pattern on ion source parameters is a strong indication that the mechanisms driving the fluctuations are plasma effects.

Functional or constructive attitudes: Which type drives consumers' evaluation of meat products?

PubMed

Hamlin, Robert

2016-07-01

Consumer attitudes towards meat can be divided up into two types: Functional attitudes which are stable and exist over long periods of time, and constructive attitudes which are ephemeral and usually constructed at the point of sale. This research investigated the temporal and situational stability of meat consumers' attitudes by using the same established functional, multidimensional attitude instrument to generate attitude profiles for the four meat types: chicken/beef/lamb/poultry both as an abstracted construct and as a cue on a range of meat and meat-based products. The results showed that strong attitude profile was generated by the meat types as abstracted constructs, but that this profile broke down completely when the food products carrying the same meat types were evaluated. This result indicates that consumer attitudes may not be temporally or situationally stable, which in turn suggests that consumers' evaluation and choice of meat products may be driven to a greater or lesser extent by constructive rather than functional attitudes. Copyright © 2016 Elsevier Ltd. All rights reserved.

An evolutionary model to predict the frequency of antibiotic resistance under seasonal antibiotic use, and an application to Streptococcus pneumoniae

PubMed Central

Lehtinen, Sonja; Fraser, Christophe

2017-01-01

The frequency of resistance to antibiotics in Streptococcus pneumoniae has been stable over recent decades. For example, penicillin non-susceptibility in Europe has fluctuated between 12% and 16% without any major time trend. In spite of long-term stability, resistance fluctuates over short time scales, presumably in part due to seasonal fluctuations in antibiotic prescriptions. Here, we develop a model that describes the evolution of antibiotic resistance under selection by multiple antibiotics prescribed at seasonally changing rates. This model was inspired by, and fitted to, published data on monthly antibiotics prescriptions and frequency of resistance in two communities in Israel over 5 years. Seasonal fluctuations in antibiotic usage translate into small fluctuations of the frequency of resistance around the average value. We describe these dynamics using a perturbation approach that encapsulates all ecological and evolutionary forces into a generic model, whose parameters quantify a force stabilizing the frequency of resistance around the equilibrium and the sensitivity of the population to antibiotic selection. Fitting the model to the data revealed a strong stabilizing force, typically two to five times stronger than direct selection due to antibiotics. The strong stabilizing force explains that resistance fluctuates in phase with usage, as antibiotic selection alone would result in resistance fluctuating behind usage with a lag of three months when antibiotic use is seasonal. While most antibiotics selected for increased resistance, intriguingly, cephalosporins selected for decreased resistance to penicillins and macrolides, an effect consistent in the two communities. One extra monthly prescription of cephalosporins per 1000 children decreased the frequency of penicillin-resistant strains by 1.7%. This model emerges under minimal assumptions, quantifies the forces acting on resistance and explains up to 43% of the temporal variation in resistance. PMID:28566489

Self-Management and Transition Readiness Assessment: Development, Reliability, and Factor Structure of the STARx Questionnaire.

PubMed

Ferris, M; Cohen, S; Haberman, C; Javalkar, K; Massengill, S; Mahan, J D; Kim, S; Bickford, K; Cantu, G; Medeiros, M; Phillips, A; Ferris, M T; Hooper, S R

2015-01-01

The Self-Management and Transition to Adulthood with Rx=Treatment (STARx) Questionnaire was developed to collect information on self-management and health care transition (HCT) skills, via self-report, in a broad population of adolescents and young adults (AYAs) with chronic conditions. Over several iterations, the STARx questionnaire was created with AYA, family, and health provider input. The development and pilot testing of the STARx Questionnaire took place with the assistance of 1219 AYAs with different chronic health conditions, in multiple institutions and settings over three phases: item development, pilot testing, reliability and factor structuring. The three development phases resulted in a final version of the STARx Questionnaire. The exploratory factor analysis of the third version of the 18-item STARx identified six factors that accounted for about 65% of the variance: Medication management, Provider communication, Engagement during appointments, Disease knowledge, Adult health responsibilities, and Resource utilization. Reliability estimates revealed good internal consistency and temporal stability, with the alpha coefficient for the overall scale being .80. The STARx was developmentally sensitive, with older patients scoring significantly higher on nearly every factor than younger patients. The STARx Questionnaire is a reliable, self-report tool with adequate internal consistency, temporal stability, and a strong, multidimensional factor structure. It provides another assessment strategy to measure self-management and transition skills in AYAs with chronic conditions. Copyright © 2015 Elsevier Inc. All rights reserved.

Spatial and Temporal Patterns of Throughfall Amounts and Solutes in a Tropical Montane Forest - Comparisons with Findings From Lowland Rain Forests

NASA Astrophysics Data System (ADS)

Zimmermann, A.

2007-05-01

The diverse tree species composition, irregular shaped tree crowns and a multi-layered forest structure affect the redistribution of rainfall in lower montane rain forests. In addition, abundant epiphyte biomass and associated canopy humus influence spatial patterns of throughfall. The spatial variability of throughfall amounts controls spatial patterns of solute concentrations and deposition. Moreover, the living and dead biomass interacts with the rainwater during the passage through the canopy and creates a chemical variability of its own. Since spatial and temporal patterns are intimately linked, the analysis of temporal solute concentration dynamics is an important step to understand the emerging spatial patterns. I hypothesized that: (1) the spatial variability of volumes and chemical composition of throughfall is particularly high compared with other forests because of the high biodiversity and epiphytism, (2) the temporal stability of the spatial pattern is high because of stable structures in the canopy (e.g. large epiphytes) that show only minor changes during the short term observation period, and (3) the element concentrations decrease with increasing rainfall because of exhausting element pools in the canopy. The study area at 1950 m above sea level is located in the south Ecuadorian Andes far away from anthropogenic emission sources and marine influences. Rain and throughfall were collected from August to October 2005 on an event and within-event basis for five precipitation periods and analyzed for pH, K, Na, Ca, Mg, NH4+, Cl-, NO3-, PO43-, TN, TP and TOC. Throughfall amounts and most of the solutes showed a high spatial variability, thereby the variability of H+, K, Ca, Mg, Cl- and NO3- exceeded those from a Brazilian tropical rain forest. The temporal persistence of the spatial patterns was high for throughfall amounts and varied depending on the solute. Highly persistent time stability patterns were detected for K, Mg and TOC concentrations. Time stability patterns of solute deposition were somewhat weaker than for concentrations for most of the solutes. Epiphytes strongly affected time stability patterns in that collectors situated below thick moss mats or arboreal bromeliads were in large part responsible for the extreme persistence with low throughfall amounts and high ion concentrations (H+ showed low concentrations). Rainfall solute concentrations were low compared with a variety of other tropical lowland and montane forest sites and showed a small temporal variability during the study period for both between and within-event dynamics, respectively. Throughfall solute concentrations were more within the range when compared with other sites and showed highly variable within-event dynamics. For most of the solutes, within-event concentrations did not reach low, constant concentrations in later event stages, rather concentrations fluctuated (e.g. Cl-) or increased (e.g. K and TOC). The within-event throughfall solute concentration dynamics in this lower montane rain forest contrast to recent observations from lowland tropical rain forests in Panama and Brazil. The observed within-event patterns are attributed (1) to the influence of epiphytes and associated canopy humus, and (2) to low rainfall intensities.

Three year stability of Five-Factor Model personality traits in relation to changes in symptom levels in patients with schizophrenia or related disorders.

PubMed

Boyette, Lindy-Lou; Nederlof, Jan; Meijer, Carin; de Boer, Froukje; de Haan, Lieuwe

2015-09-30

Five-Factor Model (FFM) personality traits are related to a wide range of clinical outcome in patients with psychotic disorders. However, it is not sufficiently clear whether psychotic illness, particularly fluctuation in negative symptoms and psychotic relapse, affects personality. The current study examined the 3-year temporal stability of FFM traits in 91 patients with non-affective psychotic disorders with a maximum duration of illness of 10 years and 32 control subjects without a (family member with) a diagnosis of psychotic illness. In patients, change in negative symptoms predicted changes in Neuroticism and (inversely) in Extraversion and Openness. However, when correcting for depressive symptoms, negative symptoms no longer predicted change in any FFM trait. Clinical characteristics, such as psychotic relapse, were also not found to be related to change in FFM traits. Patients showed a slight increase in Conscientiousness levels, the other FFM traits showed mean-level stability. Rank-order stability of the FFM traits was moderate to strong, although weaker for Neuroticism in patients. Our findings indicate that psychotic symptoms exert limited effect on the stability of FFM traits in patients with psychotic disorders. Consistent with general population findings, one should guard against state-trait confusion between Neuroticism/Extraversion and depression. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

High nutrient availability reduces the diversity and stability of the equine caecal microbiota

PubMed Central

Hansen, Naja C. K.; Avershina, Ekaterina; Mydland, Liv T.; Næsset, Jon A.; Austbø, Dag; Moen, Birgitte; Måge, Ingrid; Rudi, Knut

2015-01-01

Background It is well known that nutrient availability can alter the gut microbiota composition, while the effect on diversity and temporal stability remains largely unknown. Methods Here we address the equine caecal microbiota temporal stability, diversity, and functionality in response to diets with different levels of nutrient availability. Hay (low and slower nutrient availability) versus a mixture of hay and whole oats (high and more rapid nutrient availability) were used as experimental diets. Results We found major effects on the microbiota despite that the caecal pH was far from sub-clinical acidosis. We found that the low nutrient availability diet was associated with a higher level of both diversity and temporal stability of the caecal microbiota than the high nutrient availability diet. These observations concur with general ecological theories, suggesting a stabilising effect of biological diversity and that high nutrient availability has a destabilising effect through reduced diversity. Conclusion Nutrient availability does not only change the composition but also the ecology of the caecal microbiota. PMID:26246403

Phase stabilization of multidimensional amplification architectures for ultrashort pulses

NASA Astrophysics Data System (ADS)

Müller, M.; Kienel, M.; Klenke, A.; Eidam, T.; Limpert, J.; Tünnermann, A.

2015-03-01

The active phase stabilization of spatially and temporally combined ultrashort pulses is investigated theoretically and experimentally. Particularly, considering a combining scheme applying 2 amplifier channels and 4 divided-pulse replicas a bistable behavior is observed. The reason is mutual influence of the optical error signals that is intrinsic to temporal polarization beam combining. A successful mitigation strategy is proposed and is analyzed theoretically and experimentally.

Big Five personality stability, change, and codevelopment across adolescence and early adulthood.

PubMed

Borghuis, Jeroen; Denissen, Jaap J A; Oberski, Daniel; Sijtsma, Klaas; Meeus, Wim H J; Branje, Susan; Koot, Hans M; Bleidorn, Wiebke

2017-10-01

Using data from 2 large and overlapping cohorts of Dutch adolescents, containing up to 7 waves of longitudinal data each (N = 2,230), the present study examined Big Five personality trait stability, change, and codevelopment in friendship and sibling dyads from age 12 to 22. Four findings stand out. First, the 1-year rank-order stability of personality traits was already substantial at age 12, increased strongly from early through middle adolescence, and remained rather stable during late adolescence and early adulthood. Second, we found linear mean-level increases in girls' conscientiousness, in both genders' agreeableness, and in boys' openness. We also found temporal dips (i.e., U-shaped mean-level change) in boys' conscientiousness and in girls' emotional stability and extraversion. We did not find a mean-level change in boys' emotional stability and extraversion, and we found an increase followed by a decrease in girls' openness. Third, adolescents showed substantial individual differences in the degree and direction of personality trait changes, especially with respect to conscientiousness, extraversion, and emotional stability. Fourth, we found no evidence for personality trait convergence, for correlated change, or for time-lagged partner effects in dyadic friendship and sibling relationships. This lack of evidence for dyadic codevelopment suggests that adolescent friends and siblings tend to change independently from each other and that their shared experiences do not have uniform influences on their personality traits. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Marine protected areas increase temporal stability of community structure, but not density or diversity, of tropical seagrass fish communities

PubMed Central

Jiddawi, Narriman S.; Eklöf, Johan S.

2017-01-01

Marine protected areas (MPAs) have been shown to increase long-term temporal stability of fish communities and enhance ecosystem resilience to anthropogenic disturbance. Yet, the potential ability of MPAs to buffer effects of environmental variability at shorter time scales remains widely unknown. In the tropics, the yearly monsoon cycle is a major natural force affecting marine organisms in tropical regions, and its timing and severity are predicted to change over the coming century, with potentially severe effects on marine organisms, ecosystems and ecosystem services. Here, we assessed the ability of MPAs to buffer effects of monsoon seasonality on seagrass-associated fish communities, using a field survey in two MPAs (no-take zones) and two unprotected (open-access) sites around Zanzibar (Tanzania). We assessed the temporal stability of fish density and community structure within and outside MPAs during three monsoon seasons in 2014–2015, and investigated several possible mechanisms that could regulate temporal stability. Our results show that MPAs did not affect fish density and diversity, but that juvenile fish densities were temporally more stable within MPAs. Second, fish community structure was more stable within MPAs for juvenile and adult fish, but not for subadult fish or the total fish community. Third, the observed effects may be due to a combination of direct and indirect (seagrass-mediated) effects of seasonality and, potentially, fluctuating fishing pressure outside MPAs. In summary, these MPAs may not have the ability to enhance fish density and diversity and to buffer effects of monsoon seasonality on the whole fish community. However, they may increase the temporal stability of certain groups, such as juvenile fish. Consequently, our results question whether MPAs play a general role in the maintenance of biodiversity and ecosystem functioning under changing environmental conditions in tropical seagrass fish communities. PMID:28854231

Perspectives on the geographic stability and mobility of people in cities

PubMed Central

Hanson, Susan

2005-01-01

A class of questions in the human environment sciences focuses on the relationship between individual or household behavior and local geographic context. Central to these questions is the nature of people's geographic mobility as well as the duration of their locational stability at varying spatial and temporal scales. The problem for researchers is that the processes of mobility/stability are temporally and spatially dynamic and therefore difficult to measure. Whereas time and space are continuous, analysts must select levels of aggregation for both length of time in place and spatial scale of place that fit with the problem in question. Previous work has emphasized mobility and suppressed stability as an analytic category. I focus here on stability and show how analyzing individuals' stability requires also analyzing their mobility. Through an empirical example centered on the relationship between entrepreneurship and place, I demonstrate how a spotlight on stability illuminates a resolution to the measurement problem by highlighting the interdependence between the time and space dimensions of stability/mobility. PMID:16230616

Repeated burning of eastern tallgrass prairie increases richness and diversity, stabilizing late successional vegetation.

PubMed

Bowles, Marlin L; Jones, Michael D

2013-03-01

Understanding temporal effects of fire frequency on plant species diversity and vegetation structure is critical for managing tallgrass prairie (TGP), which occupies a mid-continental longitudinal precipitation and productivity gradient. Eastern TGP has contributed little information toward understanding whether vegetation-fire interactions are uniform or change across this biome. We resampled 34 fire-managed mid- and late-successional ungrazed TGP remnants occurring across a dry to wet-mesic moisture gradient in the Chicago region of Illinois, USA. We compared hypotheses that burning acts either as a stabilizing force or causes change in diversity and structure, depending upon fire frequency and successional stage. Based on western TGP, we expected a unimodal species richness distribution across a cover-productivity gradient, variable functional group responses to fire frequency, and a negative relationship between fire frequency and species richness. Species diversity was unimodal across the cover gradient and was more strongly humpbacked in stands with greater fire frequency. In support of a stabilizing hypothesis, temporal similarity of late-successional vegetation had a logarithmic relationship with increasing fire frequency, while richness and evenness remained stable. Temporal similarity within mid-successional stands was not correlated with fire frequency, while richness increased and evenness decreased over time. Functional group responses to fire frequency were variable. Summer forb richness increased under high fire frequency, while C4 grasses, spring forbs, and nitrogen-fixing species decreased with fire exclusion. On mesic and wet-mesic sites, vegetation structure measured by the ratio of woody to graminoid species was negatively correlated with abundance of forbs and with fire frequency. Our findings that species richness responds unimodally to an environmental-productivity gradient, and that fire exclusion increases woody vegetation and leads to loss of C4 and N-fixing species, suggest that these processes are uniform across the TGP biome and not affected by its rainfall-productivity gradient. However, increasing fire frequency in eastern TGP appears to increase richness of summer forbs and stabilize late-successional vegetation in the absence of grazing, and these processes may differ across the longitudinal axis of TGP. Managing species diversity in ungrazed eastern TGP may be dependent upon high fire frequency that removes woody vegetation and prevents biomass accumulation.

Feasibility study of basic characterization of MAGAT polymer gel using CBCT attached in linear accelerator: Preliminary study

NASA Astrophysics Data System (ADS)

Sathiyaraj, P.; Samuel, E. James jebaseelan

2018-01-01

The aim of this study is to evaluate the methacrylic acid, gelatin and tetrakis (hydroxymethyl) phosphonium chloride gel (MAGAT) by cone beam computed tomography (CBCT) attached with modern linear accelerator. To compare the results of standard diagnostic computed tomography (CT) with CBCT, different parameters such as linearity, sensitivity and temporal stability were checked. MAGAT gel showed good linearity for both diagnostic CT and CBCT measurements. Sensitivity and temporal stability were also comparable with diagnostic CT measurements. In both the modalities, the sensitivity of the MAGAT increased to 4 days and decreased till the 10th day of post irradiation. Since all measurements (linearity, sensitivity and temporal stability) from diagnostic CT and CBCT were comparable, CBCT could be a potential tool for dose analysis study for polymer gel dosimeter.

Iron Redox Dynamics in Humid Tropical Forest Soils: Carbon Stabilization vs. Degradation?

NASA Astrophysics Data System (ADS)

Hall, S. J.; Silver, W. L.; Hammel, K.

2015-12-01

Most terrestrial soils exhibit a patchwork of oxygen (O2) availability that varies over spatial scales of microsites to catenas to landscapes, and over temporal scales of minutes to seasons. Oxygen fluctuations often drive microbial iron (Fe) reduction and abiotic/biotic Fe oxidation at the microsite scale, contributing to anaerobic carbon (C) mineralization and changes in soil physical and chemical characteristics, especially the dissolution and precipitation of short-range ordered Fe phases thought to stabilize C. Thus, O2 fluctuations and Fe redox cycling may have multiple nuanced and opposing impacts on different soil C pools, illustrated by recent findings from Fe-rich Oxisols and Ultisols in the Luquillo Experimental Forest, Puerto Rico. Spatial patterns in surface soil C stocks at the landscape scale correlated strongly (R2 = 0.98) with concentrations of reduced Fe (Fe(II)), reflecting constitutive differences in reducing conditions within and among sites that promote C accumulation in mineral soil horizons. Similarly, turnover times of a decadal-cycling pool of mineral-associated organic matter increased with Fe(II) across a catena, possibly reflecting the role of anaerobic microsites in long-term C stabilization. However, two different indices of short-range order Fe showed highly significant opposing relationships (positive and negative) with spatial variation in soil C concentrations, possibly reflecting a dual role of Fe in driving C stabilization via co-precipitation, and C solubilization and loss following dissimilatory Fe reduction. Consistent with the field data, laboratory incubations demonstrated that redox fluctuations can increase the contribution of biochemically recalcitrant C (lignin) to soil respiration, whereas addition of short-range order Fe dramatically suppressed lignin mineralization but had no impact on bulk soil respiration. Thus, understanding spatial and temporal patterns of Fe redox cycling may provide insight into explaining the relatively rapid turnover of biochemically recalcitrant and mineral-associated C in soils.

Protection Enhances Community and Habitat Stability: Evidence from a Mediterranean Marine Protected Area

PubMed Central

Fraschetti, Simonetta; Guarnieri, Giuseppe; Bevilacqua, Stanislao; Terlizzi, Antonio; Boero, Ferdinando

2013-01-01

Rare evidences support that Marine Protected Areas (MPAs) enhance the stability of marine habitats and assemblages. Based on nine years of observation (2001–2009) inside and outside a well managed MPA, we assessed the potential of conservation and management actions to modify patterns of spatial and/or temporal variability of Posidonia oceanica meadows, the lower midlittoral and the shallow infralittoral rock assemblages. Significant differences in both temporal variations and spatial patterns were observed between protected and unprotected locations. A lower temporal variability in the protected vs. unprotected assemblages was found in the shallow infralittoral, demonstrating that, at least at local scale, protection can enhance community stability. Macrobenthos with long-lived and relatively slow-growing invertebrates and structurally complex algal forms were homogeneously distributed in space and went through little fluctuations in time. In contrast, a mosaic of disturbed patches featured unprotected locations, with small-scale shifts from macroalgal stands to barrens, and harsh temporal variations between the two states. Opposite patterns of spatial and temporal variability were found for the midlittoral assemblages. Despite an overall clear pattern of seagrass regression through time, protected meadows showed a significantly higher shoot density than unprotected ones, suggesting a higher resistance to local human activities. Our results support the assumption that the exclusion/management of human activities within MPAs enhance the stability of the structural components of protected marine systems, reverting or arresting threat-induced trajectories of change. PMID:24349135

Incidental rewarding cues influence economic decisions in people with obesity.

PubMed

Simmank, Jakob; Murawski, Carsten; Bode, Stefan; Horstmann, Annette

2015-01-01

Recent research suggests that obesity is linked to prominent alterations in learning and decision-making. This general difference may also underlie the preference for immediately consumable, highly palatable but unhealthy and high-calorie foods. Such poor food-related inter-temporal decision-making can explain weight gain; however, it is not yet clear whether this deficit can be generalized to other domains of inter-temporal decision-making, for example financial decisions. Further, little is known about the stability of decision-making behavior in obesity, especially in the presence of rewarding cues. To answer these questions, obese and lean participants (n = 52) completed two sessions of a novel priming paradigm including a computerized monetary delay discounting task. In the first session, general differences between groups in financial delay discounting were measured. In the second session, we tested the general stability of discount rates. Additionally, participants were primed by affective visual cues of different contextual categories before making financial decisions. We found that the obese group showed stronger discounting of future monetary rewards than the lean group, but groups did not differ in their general stability between sessions nor in their sensitivity toward changes in reward magnitude. In the obese group, a fast decrease of subjective value over time was directly related to a higher tendency for opportunistic eating. Obese in contrast to lean people were primed by the affective cues, showing a sex-specific pattern of priming direction. Our findings demonstrate that environments rich of cues, aiming at inducing unhealthy consumer decisions, can be highly detrimental for obese people. It also underscores that obesity is not merely a medical condition but has a strong cognitive component, meaning that current dietary and medical treatment strategies may fall too short.

Incidental rewarding cues influence economic decisions in people with obesity

PubMed Central

Simmank, Jakob; Murawski, Carsten; Bode, Stefan; Horstmann, Annette

2015-01-01

Recent research suggests that obesity is linked to prominent alterations in learning and decision-making. This general difference may also underlie the preference for immediately consumable, highly palatable but unhealthy and high-calorie foods. Such poor food-related inter-temporal decision-making can explain weight gain; however, it is not yet clear whether this deficit can be generalized to other domains of inter-temporal decision-making, for example financial decisions. Further, little is known about the stability of decision-making behavior in obesity, especially in the presence of rewarding cues. To answer these questions, obese and lean participants (n = 52) completed two sessions of a novel priming paradigm including a computerized monetary delay discounting task. In the first session, general differences between groups in financial delay discounting were measured. In the second session, we tested the general stability of discount rates. Additionally, participants were primed by affective visual cues of different contextual categories before making financial decisions. We found that the obese group showed stronger discounting of future monetary rewards than the lean group, but groups did not differ in their general stability between sessions nor in their sensitivity toward changes in reward magnitude. In the obese group, a fast decrease of subjective value over time was directly related to a higher tendency for opportunistic eating. Obese in contrast to lean people were primed by the affective cues, showing a sex-specific pattern of priming direction. Our findings demonstrate that environments rich of cues, aiming at inducing unhealthy consumer decisions, can be highly detrimental for obese people. It also underscores that obesity is not merely a medical condition but has a strong cognitive component, meaning that current dietary and medical treatment strategies may fall too short. PMID:26528158

2017 Update on the WFC3/UVIS Stability and Contamination Monitor

NASA Astrophysics Data System (ADS)

Shanahan, C. E.; Gosmeyer, C. M.; Baggett, S.

2017-06-01

The photometric throughput of the UVIS detector on WFC3 is monitored each cycle for its stability as a function of time, wavelength, as well as to check for any evidence of contamination on the CCD windows, which would manifest as a decrease in throughput strongest in the bluest filters. This program has been in place since the installation of WFC3 in 2009, historically making periodic observations of the spectrophotometric standard GRW+70d5824 (GRW70) in several key filters from 200 nm to 600 nm, with red filters acting as a control. This is a follow up report to the last analysis of the temporal stability of UVIS (Gosmeyer et al., 2014), since which several major changes to the program and data analysis have been implemented. Due to recent work suggesting a low-level, long-term variability for GRW70, another spectrophotometric standard star - GD153 - has been added to the program and is now analyzed in conjunction with GRW70. Data are now processed with the latest version of the CALWF3 calibration pipeline (v. 3.4), which has several new features that represent a paradigm shift in calibration methodology. Finally, the data analysis software, which was previously entirely IRAF based, was re-written in Python. We find a steady decline in the count rate for most filters but no evidence for contamination, which would manifest as a wavelength-dependent effect, impacting bluer filters more strongly. These declines range from 0.01% to 0.3% per year, and are stronger in longer wavelength filters. Similar temporal changes are found for both stars, and the long-term trends in throughput agree with previous trends derived in 2014.

Spatio-temporal and kinematic gait analysis in patients with Frontotemporal dementia and Alzheimer's disease through 3D motion capture.

PubMed

Rucco, Rosaria; Agosti, Valeria; Jacini, Francesca; Sorrentino, Pierpaolo; Varriale, Pasquale; De Stefano, Manuela; Milan, Graziella; Montella, Patrizia; Sorrentino, Giuseppe

2017-02-01

Alzheimer's disease (AD) and behavioral variant of Frontotemporal Dementia (bvFTD) are characterized respectively by atrophy in the medial temporal lobe with memory loss and prefrontal and anterior temporal degeneration with dysexecutive syndrome. In this study, we hypothesized that specific gait patterns are induced by either frontal or temporal degeneration. To test this hypothesis, we studied the gait pattern in bvFTD (23) and AD (22) patients in single and dual task ("motor" and "cognitive") conditions. To detect subtle alterations, we performed motion analysis estimating both spatio-temporal parameters and joint excursions. In the single task condition, the bvFTD group was more unstable and slower compared to healthy subjects, while only two stability parameters were compromised in the AD group. During the motor dual task, both velocity and stability parameters worsened further in the bvFTD group. In the same experimental conditions, AD patients showed a significantly lower speed and stride length than healthy subjects. During the cognitive dual task, a further impairment of velocity and stability parameters was observed in the bvFTD group. Interestingly, during the cognitive dual task, the gait performance of the AD group markedly deteriorated, as documented by the impairment of more indices of velocity and stability. Finally, the kinematic data of thigh, knee, and ankle were more helpful in revealing gait impairment than the spatio-temporal parameters alone. In conclusion, our data showed that the dysexecutive syndrome induces specific gait alterations. Furthermore, our results suggest that the gait worsens in the AD patients when the cognitive resources are stressed. Copyright © 2016 Elsevier B.V. All rights reserved.

Longitudinal structure in temperate stream fish communities: evaluating conceptual models with temporal data

USGS Publications Warehouse

Roberts, James H.; Hitt, Nathaniel P.

2010-01-01

Five conceptual models of longitudinal fish community organization in streams were examined: (1) niche diversity model (NDM), (2) stream continuum model (SCM), (3) immigrant accessibility model (IAM), (4) environmental stability model (ESM), and (5) adventitious stream model (ASM). We used differences among models in their predictions about temporal species turnover, along with five spatiotemporal fish community data sets, to evaluate model applicability. Models were similar in predicting a positive species richness–stream size relationship and longitudinal species nestedness, but differed in predicting either similar temporal species turnover throughout the stream continuum (NDM, SCM), higher turnover upstream (IAM, ESM), or higher turnover downstream (ASM). We calculated measures of spatial and temporal variation from spatiotemporal fish data in five wadeable streams in central and eastern North America spanning 34–68 years (French Creek [New York], Piasa Creek [Illinois], Spruce Run [Virginia], Little Stony Creek [Virginia], and Sinking Creek [Virginia]). All streams exhibited substantial species turnover (i.e., at least 27% turnover in stream-scale species pools), in contrast to the predictions of the SCM. Furthermore, community change was greater in downstream than upstream reaches in four of five streams. This result is most consistent with the ASM and suggests that downstream communities are strongly influenced by migrants to and from species pools outside the focal stream. In Sinking Creek, which is isolated from external species pools, temporal species turnover (via increased richness) was higher upstream than downstream, which is a pattern most consistent with the IAM or ESM. These results corroborate the hypothesis that temperate stream habitats and fish communities are temporally dynamic and that fish migration and environmental disturbances play fundamental roles in stream fish community organization.

The temporal stability and predictive validity of affect-based and cognition-based intentions.

PubMed

Keer, Mario; Conner, Mark; Van den Putte, Bas; Neijens, Peter

2014-06-01

Recent research has revealed individual differences in the extent to which people base their intentions on affect and cognition. Two studies are presented that assess whether such differences predict the strength of individuals' intention-behaviour relationships. Participants completed measures of affect, cognition, intention, and behaviour regarding a range of health behaviours. Study 1 (N = 300) found that the strength of the intention-behaviour relationship was significantly related to the extent to which individuals based their intentions on affect, but not to the extent they based them on cognition. Study 2 (N = 387) replicated the findings of the first study. In addition, Study 2 revealed that intention stability mediated the relationship between the degree people based their intentions on affect and the strength of the intention-behaviour relationship. Thus, individuals who base their intentions strongly on affect have more stable intentions, and are therefore more likely to enact them. © 2013 The British Psychological Society.

Blood Flow in the Stenotic Carotid Bifurcation

NASA Astrophysics Data System (ADS)

Rayz, Vitaliy

2005-11-01

The carotid artery is prone to atherosclerotic disease and the growth of plaque in the vessel, leading often to severe occlusion or plaque rupture, resulting in emboli and thrombus, and, possibly, stroke. Modeling the flow in stenotic blood vessels can elucidate the influence of the flow on plaque growth and stability. Numerical simulations are carried out to model the complex flows in anatomically realistic, patient-specific geometries constructed from magnetic resonance images. The 3-D unsteady Navier-Stokes equations are solved in a finite-volume formulation, using an iterative pressure-correction algorithm. The flow field computed is highly three-dimensional, with high-speed jets and strong recirculating secondary flows. Sharp spatial and temporal variations of the velocities and shear stresses are observed. The results are in a good agreement with the available experimental and clinical data. The influence of non-Newtonian blood behavior and arterial wall compliance are considered. Transitional and turbulent regimes have been looked at using LES. This work supports the conjecture that numerical simulations can provide a diagnostic tool for assessing plaque stability.

Dual Gamma Rhythm Generators Control Interlaminar Synchrony in Auditory Cortex

PubMed Central

Ainsworth, Matthew; Lee, Shane; Cunningham, Mark O.; Roopun, Anita K.; Traub, Roger D.; Kopell, Nancy J.; Whittington, Miles A.

2013-01-01

Rhythmic activity in populations of cortical neurons accompanies, and may underlie, many aspects of primary sensory processing and short-term memory. Activity in the gamma band (30 Hz up to > 100 Hz) is associated with such cognitive tasks and is thought to provide a substrate for temporal coupling of spatially separate regions of the brain. However, such coupling requires close matching of frequencies in co-active areas, and because the nominal gamma band is so spectrally broad, it may not constitute a single underlying process. Here we show that, for inhibition-based gamma rhythms in vitro in rat neocortical slices, mechanistically distinct local circuit generators exist in different laminae of rat primary auditory cortex. A persistent, 30 – 45 Hz, gap-junction-dependent gamma rhythm dominates rhythmic activity in supragranular layers 2/3, whereas a tonic depolarization-dependent, 50 – 80 Hz, pyramidal/interneuron gamma rhythm is expressed in granular layer 4 with strong glutamatergic excitation. As a consequence, altering the degree of excitation of the auditory cortex causes bifurcation in the gamma frequency spectrum and can effectively switch temporal control of layer 5 from supragranular to granular layers. Computational modeling predicts the pattern of interlaminar connections may help to stabilize this bifurcation. The data suggest that different strategies are used by primary auditory cortex to represent weak and strong inputs, with principal cell firing rate becoming increasingly important as excitation strength increases. PMID:22114273

Temporal and spatial correlation patterns of air pollutants in Chinese cities

PubMed Central

Dai, Yue-Hua

2017-01-01

As a huge threat to the public health, China’s air pollution has attracted extensive attention and continues to grow in tandem with the economy. Although the real-time air quality report can be utilized to update our knowledge on air quality, questions about how pollutants evolve across time and how pollutants are spatially correlated still remain a puzzle. In view of this point, we adopt the PMFG network method to analyze the six pollutants’ hourly data in 350 Chinese cities in an attempt to find out how these pollutants are correlated temporally and spatially. In terms of time dimension, the results indicate that, except for O3, the pollutants have a common feature of the strong intraday patterns of which the daily variations are composed of two contraction periods and two expansion periods. Besides, all the time series of the six pollutants possess strong long-term correlations, and this temporal memory effect helps to explain why smoggy days are always followed by one after another. In terms of space dimension, the correlation structure shows that O3 is characterized by the highest spatial connections. The PMFGs reveal the relationship between this spatial correlation and provincial administrative divisions by filtering the hierarchical structure in the correlation matrix and refining the cliques as the tinny spatial clusters. Finally, we check the stability of the correlation structure and conclude that, except for PM10 and O3, the other pollutants have an overall stable correlation, and all pollutants have a slight trend to become more divergent in space. These results not only enhance our understanding of the air pollutants’ evolutionary process, but also shed lights on the application of complex network methods into geographic issues. PMID:28832599

Increasing frequency of low summer precipitation synchronizes dynamics and compromises metapopulation stability in the Glanville fritillary butterfly

PubMed Central

Tack, Ayco J. M.; Mononen, Tommi; Hanski, Ilkka

2015-01-01

Climate change is known to shift species' geographical ranges, phenologies and abundances, but less is known about other population dynamic consequences. Here, we analyse spatio-temporal dynamics of the Glanville fritillary butterfly (Melitaea cinxia) in a network of 4000 dry meadows during 21 years. The results demonstrate two strong, related patterns: the amplitude of year-to-year fluctuations in the size of the metapopulation as a whole has increased, though there is no long-term trend in average abundance; and there is a highly significant increase in the level of spatial synchrony in population dynamics. The increased synchrony cannot be explained by increasing within-year spatial correlation in precipitation, the key environmental driver of population change, or in per capita growth rate. On the other hand, the frequency of drought during a critical life-history stage (early larval instars) has increased over the years, which is sufficient to explain the increasing amplitude and the expanding spatial synchrony in metapopulation dynamics. Increased spatial synchrony has the general effect of reducing long-term metapopulation viability even if there is no change in average metapopulation size. This study demonstrates how temporal changes in weather conditions can lead to striking changes in spatio-temporal population dynamics. PMID:25854888

Age-Related Differences in Motor Coordination during Simultaneous Leg Flexion and Finger Extension: Influence of Temporal Pressure

PubMed Central

Hussein, Tarek; Yiou, Eric; Larue, Jacques

2013-01-01

Although the effect of temporal pressure on spatio-temporal aspects of motor coordination and posture is well established in young adults, there is a clear lack of data on elderly subjects. This work examined the aging-related effects of temporal pressure on movement synchronization and dynamic stability. Sixteen young and eleven elderly subjects performed series of simultaneous rapid leg flexions in an erect posture paired with ipsilateral index-finger extensions, minimizing the difference between heel and finger movement onsets. This task was repeated ten times under two temporal conditions (self-initiated [SI] vs. reaction-time [RT]). Results showed that, first, temporal pressure modified movement synchronization; the finger extension preceded swing heel-off in RT, and inversely in SI. Synchronization error and associated standard deviation were significantly greater in elderly than in young adults in SI only, i.e. in the condition where proprioception is thought to be crucial for temporal coordination. Secondly, both groups developed a significantly shorter mediolateral (ML) anticipatory postural adjustment duration in RT (high temporal pressure) than in SI. In both groups, this shortening was compensated by an increase in the anticipatory peak of centre-of-gravity (CoG) acceleration towards the stance-leg so that ML dynamic stability at foot-off, quantified with the “extrapolated centre-of-mass”, remained unchanged across temporal conditions. This increased CoG acceleration was associated with an increased anticipatory peak of ML centre-of-pressure shift towards the swing-leg in young adults only. This suggested that the ability to accelerate the CoG with the centre-of-pressure shift was degraded in elderly, probably due to weakness in the lower limb muscles. Dynamic stability at foot-off was also degraded in elderly, with a consequent increased risk of ML imbalance and falling. The present study provides new insights into the ability of elderly adults to deal with temporal pressure constraints in adapting whole-body coordination of postural and focal components of paired movement. PMID:24340080

Age-related differences in motor coordination during simultaneous leg flexion and finger extension: influence of temporal pressure.

PubMed

Hussein, Tarek; Yiou, Eric; Larue, Jacques

2013-01-01

Although the effect of temporal pressure on spatio-temporal aspects of motor coordination and posture is well established in young adults, there is a clear lack of data on elderly subjects. This work examined the aging-related effects of temporal pressure on movement synchronization and dynamic stability. Sixteen young and eleven elderly subjects performed series of simultaneous rapid leg flexions in an erect posture paired with ipsilateral index-finger extensions, minimizing the difference between heel and finger movement onsets. This task was repeated ten times under two temporal conditions (self-initiated [SI] vs. reaction-time [RT]). Results showed that, first, temporal pressure modified movement synchronization; the finger extension preceded swing heel-off in RT, and inversely in SI. Synchronization error and associated standard deviation were significantly greater in elderly than in young adults in SI only, i.e. in the condition where proprioception is thought to be crucial for temporal coordination. Secondly, both groups developed a significantly shorter mediolateral (ML) anticipatory postural adjustment duration in RT (high temporal pressure) than in SI. In both groups, this shortening was compensated by an increase in the anticipatory peak of centre-of-gravity (CoG) acceleration towards the stance-leg so that ML dynamic stability at foot-off, quantified with the "extrapolated centre-of-mass", remained unchanged across temporal conditions. This increased CoG acceleration was associated with an increased anticipatory peak of ML centre-of-pressure shift towards the swing-leg in young adults only. This suggested that the ability to accelerate the CoG with the centre-of-pressure shift was degraded in elderly, probably due to weakness in the lower limb muscles. Dynamic stability at foot-off was also degraded in elderly, with a consequent increased risk of ML imbalance and falling. The present study provides new insights into the ability of elderly adults to deal with temporal pressure constraints in adapting whole-body coordination of postural and focal components of paired movement.

Stability Switches, Hopf Bifurcations, and Spatio-temporal Patterns in a Delayed Neural Model with Bidirectional Coupling

NASA Astrophysics Data System (ADS)

Song, Yongli; Zhang, Tonghua; Tadé, Moses O.

2009-12-01

The dynamical behavior of a delayed neural network with bi-directional coupling is investigated by taking the delay as the bifurcating parameter. Some parameter regions are given for conditional/absolute stability and Hopf bifurcations by using the theory of functional differential equations. As the propagation time delay in the coupling varies, stability switches for the trivial solution are found. Conditions ensuring the stability and direction of the Hopf bifurcation are determined by applying the normal form theory and the center manifold theorem. We also discuss the spatio-temporal patterns of bifurcating periodic oscillations by using the symmetric bifurcation theory of delay differential equations combined with representation theory of Lie groups. In particular, we obtain that the spatio-temporal patterns of bifurcating periodic oscillations will alternate according to the change of the propagation time delay in the coupling, i.e., different ranges of delays correspond to different patterns of neural activities. Numerical simulations are given to illustrate the obtained results and show the existence of bursts in some interval of the time for large enough delay.

[Sustainability analysis of an evaluation policy: the case of primary health care in Brazil].

PubMed

Felisberto, Eronildo; Freese, Eduardo; Bezerra, Luciana Caroline Albuquerque; Alves, Cinthia Kalyne de Almeida; Samico, Isabella

2010-06-01

This study analyzes the sustainability of Brazil's National Policy for the Evaluation of Primary Health Care, based on the identification and categorization of representative critical events in the institutionalization process. This was an evaluative study of two analytical units: Federal Management of Primary Health Care and State Health Secretariats, using multiple case studies with data collected through interviews and institutional documents, using the critical incidents technique. Events that were temporally classified as specific to implementation, sustainability, and mixed were categorized analytically as pertaining to memory, adaptation, values, and rules. Federal management and one of the State Health Secretariats showed medium-level sustainability, while the other State Secretariat showed strong sustainability. The results indicate that the events were concurrent and suggest a weighting process, since the adaptation of activities, adequacy, and stabilization of resources displayed a strong influence on the others. Innovations and the development of technical capability are considered the most important results for sustainability.

Asynchrony among local communities stabilises ecosystem function of metacommunities.

PubMed

Wilcox, Kevin R; Tredennick, Andrew T; Koerner, Sally E; Grman, Emily; Hallett, Lauren M; Avolio, Meghan L; La Pierre, Kimberly J; Houseman, Gregory R; Isbell, Forest; Johnson, David Samuel; Alatalo, Juha M; Baldwin, Andrew H; Bork, Edward W; Boughton, Elizabeth H; Bowman, William D; Britton, Andrea J; Cahill, James F; Collins, Scott L; Du, Guozhen; Eskelinen, Anu; Gough, Laura; Jentsch, Anke; Kern, Christel; Klanderud, Kari; Knapp, Alan K; Kreyling, Juergen; Luo, Yiqi; McLaren, Jennie R; Megonigal, Patrick; Onipchenko, Vladimir; Prevéy, Janet; Price, Jodi N; Robinson, Clare H; Sala, Osvaldo E; Smith, Melinda D; Soudzilovskaia, Nadejda A; Souza, Lara; Tilman, David; White, Shannon R; Xu, Zhuwen; Yahdjian, Laura; Yu, Qiang; Zhang, Pengfei; Zhang, Yunhai

2017-12-01

Temporal stability of ecosystem functioning increases the predictability and reliability of ecosystem services, and understanding the drivers of stability across spatial scales is important for land management and policy decisions. We used species-level abundance data from 62 plant communities across five continents to assess mechanisms of temporal stability across spatial scales. We assessed how asynchrony (i.e. different units responding dissimilarly through time) of species and local communities stabilised metacommunity ecosystem function. Asynchrony of species increased stability of local communities, and asynchrony among local communities enhanced metacommunity stability by a wide range of magnitudes (1-315%); this range was positively correlated with the size of the metacommunity. Additionally, asynchronous responses among local communities were linked with species' populations fluctuating asynchronously across space, perhaps stemming from physical and/or competitive differences among local communities. Accordingly, we suggest spatial heterogeneity should be a major focus for maintaining the stability of ecosystem services at larger spatial scales. © 2017 The Authors. Ecology Letters published by CNRS and John Wiley & Sons Ltd.

Direct evidence that density-dependent regulation underpins the temporal stability of abundant species in a diverse animal community

PubMed Central

Henderson, Peter A.; Magurran, Anne E.

2014-01-01

To understand how ecosystems are structured and stabilized, and to identify when communities are at risk of damage or collapse, we need to know how the abundances of the taxa in the entire assemblage vary over ecologically meaningful timescales. Here, we present an analysis of species temporal variability within a single large vertebrate community. Using an exceptionally complete 33-year monthly time series following the dynamics of 81 species of fishes, we show that the most abundant species are least variable in terms of temporal biomass, because they are under density-dependent (negative feedback) regulation. At the other extreme, a relatively large number of low abundance transient species exhibit the greatest population variability. The high stability of the consistently common high abundance species—a result of density-dependence—is reflected in the observation that they consistently represent over 98% of total fish biomass. This leads to steady ecosystem nutrient and energy flux irrespective of the changes in species number and abundance among the large number of low abundance transient species. While the density-dependence of the core species ensures stability under the existing environmental regime, the pool of transient species may support long-term stability by replacing core species should environmental conditions change. PMID:25100702

Community temporal variability increases with fluctuating resource availability

PubMed Central

Li, Wei; Stevens, M. Henry H.

2017-01-01

An increase in the quantity of available resources is known to affect temporal variability of aggregate community properties. However, it is unclear how might fluctuations in resource availability alter community-level temporal variability. Here we conduct a microcosm experiment with laboratory protist community subjected to manipulated resource pulses that vary in intensity, duration and time of supply, and examine the impact of fluctuating resource availability on temporal variability of the recipient community. The results showed that the temporal variation of total protist abundance increased with the magnitude of resource pulses, as protist community receiving infrequent resource pulses (i.e., high-magnitude nutrients per pulse) was relatively more unstable than community receiving multiple resource pulses (i.e., low-magnitude nutrients per pulse), although the same total amounts of nutrients were added to each community. Meanwhile, the timing effect of fluctuating resources did not significantly alter community temporal variability. Further analysis showed that fluctuating resource availability increased community temporal variability by increasing the degree of community-wide species synchrony and decreasing the stabilizing effects of dominant species. Hence, the importance of fluctuating resource availability in influencing community stability and the regulatory mechanisms merit more attention, especially when global ecosystems are experiencing high rates of anthropogenic nutrient inputs. PMID:28345592

Community temporal variability increases with fluctuating resource availability

NASA Astrophysics Data System (ADS)

Li, Wei; Stevens, M. Henry H.

2017-03-01

An increase in the quantity of available resources is known to affect temporal variability of aggregate community properties. However, it is unclear how might fluctuations in resource availability alter community-level temporal variability. Here we conduct a microcosm experiment with laboratory protist community subjected to manipulated resource pulses that vary in intensity, duration and time of supply, and examine the impact of fluctuating resource availability on temporal variability of the recipient community. The results showed that the temporal variation of total protist abundance increased with the magnitude of resource pulses, as protist community receiving infrequent resource pulses (i.e., high-magnitude nutrients per pulse) was relatively more unstable than community receiving multiple resource pulses (i.e., low-magnitude nutrients per pulse), although the same total amounts of nutrients were added to each community. Meanwhile, the timing effect of fluctuating resources did not significantly alter community temporal variability. Further analysis showed that fluctuating resource availability increased community temporal variability by increasing the degree of community-wide species synchrony and decreasing the stabilizing effects of dominant species. Hence, the importance of fluctuating resource availability in influencing community stability and the regulatory mechanisms merit more attention, especially when global ecosystems are experiencing high rates of anthropogenic nutrient inputs.

Morphometric changes in Yellow-headed Blackbirds during summer in central North Dakota

USGS Publications Warehouse

Twedt, D.J.; Linz, G.M.

2002-01-01

Temporal stability of morphometric measurements is desirable when using avian morphology as a predictor of geographic origin. Therefore, to assess their temporal stability, we examined changes in morphology of Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) from central North Dakota during summer. Measurements differed among age classes and between sexes. As expected, due to growth and maturation, measurements on hatching-year birds increased over summer. Measurements of adult plumage fluctuated with prebasic molt and exhibited age-specific discontinuities. Body mass of adult birds increased over summer, whereas both culmen length and skull length decreased. Only body length and length of internal skeletal elements were temporally stable in adult Yellow-headed Blackbirds.

Temporal stability of novelty exploration in mice exposed to different open field tests.

PubMed

Kalueff, Allan V; Keisala, Tiina; Minasyan, Anna; Kuuslahti, Marianne; Tuohimaa, Pentti

2006-03-01

We investigated behavioural activity and temporal distribution (patterning) of mouse exploration in different open field (OF) arenas. Mice of 129S1 (S1) strain were subjected in parallel to three different OF arenas (Experiment 1), two different OF arenas in two trials (Experiment 2) or two trials of the same OF test (Experiment 3). Overall, mice demonstrated a high degree of similarity in the temporal profile of novelty-induced horizontal and vertical exploration (regardless of the size, colour and shape of the OF), which remained stable in subsequent OF exposures. In Experiments 4 and 5, we tested F1 hybrid mice (BALB/c-S1; NMRI-S1), and Vitamin D receptor knockout mice (generated on S1 genetic background), again showing strikingly similar temporal patterns of their OF exploration, despite marked behavioural strain differences in anxiety and activity. These results suggest that mice are characterised by stability of temporal organization of their exploration in different OF novelty situations.

An in situ USAXS-SAXS-WAXS study of precipitate size distribution evolution in a model Ni-based alloy.

PubMed

Andrews, Ross N; Serio, Joseph; Muralidharan, Govindarajan; Ilavsky, Jan

2017-06-01

Intermetallic γ' precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS-SAXS-WAXS) analysis can be used to evaluate the temporal evolution of an alloy's precipitate size distribution (PSD) and phase structure during in situ heat treatment. Analysis of PSDs from USAXS-SAXS data employs either least-squares fitting of a preordained PSD model or a maximum entropy (MaxEnt) approach, the latter avoiding a priori definition of a functional form of the PSD. However, strong low- q scattering from grain boundaries and/or structure factor effects inhibit MaxEnt analysis of typical alloys. This work describes the extension of Bayesian-MaxEnt analysis methods to data exhibiting structure factor effects and low- q power law slopes and demonstrates their use in an in situ study of precipitate size evolution during heat treatment of a model Ni-Al-Si alloy.

An in situ USAXS–SAXS–WAXS study of precipitate size distribution evolution in a model Ni-based alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrews, Ross N.; Serio, Joseph A.; Muralidharan, Govindarajan

Intermetallic γ' precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS–SAXS–WAXS) analysis can be used to evaluate the temporal evolution of an alloy's precipitate size distribution (PSD) and phase structure duringin situheat treatment. Analysis of PSDs from USAXS–SAXS data employs either least-squares fitting of a preordained PSD model or a maximum entropy (MaxEnt) approach, the latter avoidinga prioridefinition of a functional form of the PSD. However, strong low-qscattering from grain boundaries and/or structuremore » factor effects inhibit MaxEnt analysis of typical alloys. Lastly, this work describes the extension of Bayesian–MaxEnt analysis methods to data exhibiting structure factor effects and low-qpower law slopes and demonstrates their use in anin situstudy of precipitate size evolution during heat treatment of a model Ni–Al–Si alloy.« less

An in situ USAXS–SAXS–WAXS study of precipitate size distribution evolution in a model Ni-based alloy1

PubMed Central

Andrews, Ross N.; Serio, Joseph; Muralidharan, Govindarajan; Ilavsky, Jan

2017-01-01

Intermetallic γ′ precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS–SAXS–WAXS) analysis can be used to evaluate the temporal evolution of an alloy’s precipitate size distribution (PSD) and phase structure during in situ heat treatment. Analysis of PSDs from USAXS–SAXS data employs either least-squares fitting of a preordained PSD model or a maximum entropy (MaxEnt) approach, the latter avoiding a priori definition of a functional form of the PSD. However, strong low-q scattering from grain boundaries and/or structure factor effects inhibit MaxEnt analysis of typical alloys. This work describes the extension of Bayesian–MaxEnt analysis methods to data exhibiting structure factor effects and low-q power law slopes and demonstrates their use in an in situ study of precipitate size evolution during heat treatment of a model Ni–Al–Si alloy. PMID:28656039

An in situ USAXS–SAXS–WAXS study of precipitate size distribution evolution in a model Ni-based alloy

DOE PAGES

Andrews, Ross N.; Serio, Joseph A.; Muralidharan, Govindarajan; ...

2017-05-30

Intermetallic γ' precipitates typically strengthen nickel-based superalloys. The shape, size and spatial distribution of strengthening precipitates critically influence alloy strength, while their temporal evolution characteristics determine the high-temperature alloy stability. Combined ultra-small-, small- and wide-angle X-ray scattering (USAXS–SAXS–WAXS) analysis can be used to evaluate the temporal evolution of an alloy's precipitate size distribution (PSD) and phase structure duringin situheat treatment. Analysis of PSDs from USAXS–SAXS data employs either least-squares fitting of a preordained PSD model or a maximum entropy (MaxEnt) approach, the latter avoidinga prioridefinition of a functional form of the PSD. However, strong low-qscattering from grain boundaries and/or structuremore » factor effects inhibit MaxEnt analysis of typical alloys. Lastly, this work describes the extension of Bayesian–MaxEnt analysis methods to data exhibiting structure factor effects and low-qpower law slopes and demonstrates their use in anin situstudy of precipitate size evolution during heat treatment of a model Ni–Al–Si alloy.« less

Newton's method applied to finite-difference approximations for the steady-state compressible Navier-Stokes equations

NASA Technical Reports Server (NTRS)

Bailey, Harry E.; Beam, Richard M.

1991-01-01

Finite-difference approximations for steady-state compressible Navier-Stokes equations, whose two spatial dimensions are written in generalized curvilinear coordinates and strong conservation-law form, are presently solved by means of Newton's method in order to obtain a lifting-airfoil flow field under subsonic and transonnic conditions. In addition to ascertaining the computational requirements of an initial guess ensuring convergence and the degree of computational efficiency obtainable via the approximate Newton method's freezing of the Jacobian matrices, attention is given to the need for auxiliary methods assessing the temporal stability of steady-state solutions. It is demonstrated that nonunique solutions of the finite-difference equations are obtainable by Newton's method in conjunction with a continuation method.

A Meta-Analysis for the Efficacy of Hypnotherapy in Alleviating PTSD Symptoms.

PubMed

Rotaru, Tudor-Ștefan; Rusu, Andrei

2016-01-01

A systematic review and meta-analysis of the efficacy of hypnotherapy in the treatment of PTSD used literature searches to obtain 47 articles. However, only 6 were experiments testing the efficacy of hypnosis-based treatments. A fixed-effects meta-analysis was applied to postintervention assessment results and 4-week follow-ups. A large effect in favor of hypnosis-based (especially manualized abreactive hypnosis) treatment was found for the studies that reported the posttest results (d = 1.17). The temporal stability of the effect remains strong, as reflected by the 4-week follow-up assessments (d = 1.58) and also by long-term evaluations (e.g., 12 months). Hypnosis appears to be effective in alleviating PTSD symptoms.

Soil-Structural Stability as Affected by Clay Mineralogy, Soil Texture and Polyacrylamide Application

USDA-ARS?s Scientific Manuscript database

Soil-structural stability (expressed in terms of aggregate stability and pore size distribution) depends on (i) soil inherent properties, (ii) extrinsic condition prevailing in the soil that may vary temporally and spatially, and (iii) addition of soil amendments. Different soil management practices...

a Simple Spatially Weighted Measure of Temporal Stability for Data with Limited Temporal Observations

NASA Astrophysics Data System (ADS)

Piburn, J.; Stewart, R.; Morton, A.

2017-10-01

Identifying erratic or unstable time-series is an area of interest to many fields. Recently, there have been successful developments towards this goal. These new developed methodologies however come from domains where it is typical to have several thousand or more temporal observations. This creates a challenge when attempting to apply these methodologies to time-series with much fewer temporal observations such as for socio-cultural understanding, a domain where a typical time series of interest might only consist of 20-30 annual observations. Most existing methodologies simply cannot say anything interesting with so few data points, yet researchers are still tasked to work within in the confines of the data. Recently a method for characterizing instability in a time series with limitedtemporal observations was published. This method, Attribute Stability Index (ASI), uses an approximate entropy based method tocharacterize a time series' instability. In this paper we propose an explicitly spatially weighted extension of the Attribute StabilityIndex. By including a mechanism to account for spatial autocorrelation, this work represents a novel approach for the characterizationof space-time instability. As a case study we explore national youth male unemployment across the world from 1991-2014.

The relative importance of pollinator abundance and species richness for the temporal variance of pollination services.

PubMed

Genung, Mark A; Fox, Jeremy; Williams, Neal M; Kremen, Claire; Ascher, John; Gibbs, Jason; Winfree, Rachael

2017-07-01

The relationship between biodiversity and the stability of ecosystem function is a fundamental question in community ecology, and hundreds of experiments have shown a positive relationship between species richness and the stability of ecosystem function. However, these experiments have rarely accounted for common ecological patterns, most notably skewed species abundance distributions and non-random extinction risks, making it difficult to know whether experimental results can be scaled up to larger, less manipulated systems. In contrast with the prolific body of experimental research, few studies have examined how species richness affects the stability of ecosystem services at more realistic, landscape scales. The paucity of these studies is due in part to a lack of analytical methods that are suitable for the correlative structure of ecological data. A recently developed method, based on the Price equation from evolutionary biology, helps resolve this knowledge gap by partitioning the effect of biodiversity into three components: richness, composition, and abundance. Here, we build on previous work and present the first derivation of the Price equation suitable for analyzing temporal variance of ecosystem services. We applied our new derivation to understand the temporal variance of crop pollination services in two study systems (watermelon and blueberry) in the mid-Atlantic United States. In both systems, but especially in the watermelon system, the stronger driver of temporal variance of ecosystem services was fluctuations in the abundance of common bee species, which were present at nearly all sites regardless of species richness. In contrast, temporal variance of ecosystem services was less affected by differences in species richness, because lost and gained species were rare. Thus, the findings from our more realistic landscapes differ qualitatively from the findings of biodiversity-stability experiments. © 2017 by the Ecological Society of America.

Temporal genetic stability of Stegomyia aegypti (= Aedes aegypti) populations.

PubMed

Gloria-Soria, A; Kellner, D A; Brown, J E; Gonzalez-Acosta, C; Kamgang, B; Lutwama, J; Powell, J R

2016-06-01

The mosquito Stegomyia aegypti (= Aedes aegypti) (Diptera: Culicidae) is the primary vector of viruses that cause yellow fever, dengue and Chikungunya fever. In the absence of effective vaccines, the reduction of these diseases relies on vector control strategies. The success of these strategies is tightly linked to the population dynamics of target populations. In the present study, 14 collections from St. aegypti populations separated by periods of 1-13 years were analysed to determine their temporal genetic stability. Although temporal structure is discernible in most populations, the degree of temporal differentiation is dependent on the population and does not obscure the geographic structure of the various populations. The results suggest that performing detailed studies in the years prior to and after population reduction- or modification-based control interventions at each target field site may be useful in assessing the probability of success. © 2016 The Royal Entomological Society.

Ultra-low-power hybrid light–matter solitons

PubMed Central

Walker, P. M.; Tinkler, L.; Skryabin, D. V.; Yulin, A.; Royall, B.; Farrer, I.; Ritchie, D. A.; Skolnick, M. S.; Krizhanovskii, D. N.

2015-01-01

New functionalities in nonlinear optics will require systems with giant optical nonlinearity as well as compatibility with photonic circuit fabrication techniques. Here we introduce a platform based on strong light–matter coupling between waveguide photons and quantum-well excitons. On a sub-millimetre length scale we generate picosecond bright temporal solitons at a pulse energy of only 0.5 pJ. From this we deduce a nonlinear refractive index three orders of magnitude larger than in any other ultrafast system. We study both temporal and spatio-temporal nonlinear effects and observe dark–bright spatio-temporal polariton solitons. Theoretical modelling of soliton formation in the strongly coupled system confirms the experimental observations. These results show the promise of our system as a high speed, low power, integrated platform for physics and devices based on strong interactions between photons. PMID:26400748

Ultra-low-power hybrid light-matter solitons.

PubMed

Walker, P M; Tinkler, L; Skryabin, D V; Yulin, A; Royall, B; Farrer, I; Ritchie, D A; Skolnick, M S; Krizhanovskii, D N

2015-09-24

New functionalities in nonlinear optics will require systems with giant optical nonlinearity as well as compatibility with photonic circuit fabrication techniques. Here we introduce a platform based on strong light-matter coupling between waveguide photons and quantum-well excitons. On a sub-millimetre length scale we generate picosecond bright temporal solitons at a pulse energy of only 0.5 pJ. From this we deduce a nonlinear refractive index three orders of magnitude larger than in any other ultrafast system. We study both temporal and spatio-temporal nonlinear effects and observe dark-bright spatio-temporal polariton solitons. Theoretical modelling of soliton formation in the strongly coupled system confirms the experimental observations. These results show the promise of our system as a high speed, low power, integrated platform for physics and devices based on strong interactions between photons.

Strong and Long Makes Short: Strong-Pump Strong-Probe Spectroscopy.

PubMed

Gelin, Maxim F; Egorova, Dassia; Domcke, Wolfgang

2011-01-20

We propose a new time-domain spectroscopic technique that is based on strong pump and probe pulses. The strong-pump strong-probe (SPSP) technique provides temporal resolution that is not limited by the durations of the pump and probe pulses. By numerically exact simulations of SPSP signals for a multilevel vibronic model, we show that the SPSP signals exhibit electronic and vibrational beatings on time scales which are significantly shorter than the pulse durations. This suggests the possible application of SPSP spectroscopy for the real-time investigation of molecular processes that cannot be temporally resolved by pump-probe spectroscopy with weak pump and probe pulses.

Nonlocal elasticity tensors in dislocation and disclination cores

DOE PAGES

Taupin, V.; Gbemou, K.; Fressengeas, C.; ...

2017-01-07

We introduced nonlocal elastic constitutive laws for crystals containing defects such as dislocations and disclinations. Additionally, the pointwise elastic moduli tensors adequately reflect the elastic response of defect-free regions by relating stresses to strains and couple-stresses to curvatures, elastic cross-moduli tensors relating strains to couple-stresses and curvatures to stresses within convolution integrals are derived from a nonlocal analysis of strains and curvatures in the defects cores. Sufficient conditions are derived for positive-definiteness of the resulting free energy, and stability of elastic solutions is ensured. The elastic stress/couple stress fields associated with prescribed dislocation/disclination density distributions and solving the momentum andmore » moment of momentum balance equations in periodic media are determined by using a Fast Fourier Transform spectral method. Here, the convoluted cross-moduli bring the following results: (i) Nonlocal stresses and couple stresses oppose their local counterparts in the defects core regions, playing the role of restoring forces and possibly ensuring spatio-temporal stability of the simulated defects, (ii) The couple stress fields are strongly affected by nonlocality. Such effects favor the stability of the simulated grain boundaries and allow investigating their elastic interactions with extrinsic defects, (iii) Driving forces inducing grain growth or refinement derive from the self-stress and couple stress fields of grain boundaries in nanocrystalline configurations.« less

Quantifying full phenological event distributions reveals simultaneous advances, temporal stability and delays in spring and autumn migration timing in long-distance migratory birds.

PubMed

Miles, Will T S; Bolton, Mark; Davis, Peter; Dennis, Roy; Broad, Roger; Robertson, Iain; Riddiford, Nick J; Harvey, Paul V; Riddington, Roger; Shaw, Deryk N; Parnaby, David; Reid, Jane M

2017-04-01

Phenological changes in key seasonally expressed life-history traits occurring across periods of climatic and environmental change can cause temporal mismatches between interacting species, and thereby impact population and community dynamics. However, studies quantifying long-term phenological changes have commonly only measured variation occurring in spring, measured as the first or mean dates on which focal traits or events were observed. Few studies have considered seasonally paired events spanning spring and autumn or tested the key assumption that single convenient metrics accurately capture entire event distributions. We used 60 years (1955-2014) of daily bird migration census data from Fair Isle, Scotland, to comprehensively quantify the degree to which the full distributions of spring and autumn migration timing of 13 species of long-distance migratory bird changed across a period of substantial climatic and environmental change. In most species, mean spring and autumn migration dates changed little. However, the early migration phase (≤10th percentile date) commonly got earlier, while the late migration phase (≥90th percentile date) commonly got later. Consequently, species' total migration durations typically lengthened across years. Spring and autumn migration phenologies were not consistently correlated within or between years within species and hence were not tightly coupled. Furthermore, different metrics quantifying different aspects of migration phenology within seasons were not strongly cross-correlated, meaning that no single metric adequately described the full pattern of phenological change. These analyses therefore reveal complex patterns of simultaneous advancement, temporal stability and delay in spring and autumn migration phenologies, altering species' life-history structures. Additionally, they demonstrate that this complexity is only revealed if multiple metrics encompassing entire seasonal event distributions, rather than single metrics, are used to quantify phenological change. Existing evidence of long-term phenological changes detected using only one or two metrics should consequently be interpreted cautiously because divergent changes occurring simultaneously could potentially have remained undetected. © 2016 John Wiley & Sons Ltd.

A unified nonlinear stochastic time series analysis for climate science

PubMed Central

Moon, Woosok; Wettlaufer, John S.

2017-01-01

Earth’s orbit and axial tilt imprint a strong seasonal cycle on climatological data. Climate variability is typically viewed in terms of fluctuations in the seasonal cycle induced by higher frequency processes. We can interpret this as a competition between the orbitally enforced monthly stability and the fluctuations/noise induced by weather. Here we introduce a new time-series method that determines these contributions from monthly-averaged data. We find that the spatio-temporal distribution of the monthly stability and the magnitude of the noise reveal key fingerprints of several important climate phenomena, including the evolution of the Arctic sea ice cover, the El Nio Southern Oscillation (ENSO), the Atlantic Nio and the Indian Dipole Mode. In analogy with the classical destabilising influence of the ice-albedo feedback on summertime sea ice, we find that during some time interval of the season a destabilising process operates in all of these climate phenomena. The interaction between the destabilisation and the accumulation of noise, which we term the memory effect, underlies phase locking to the seasonal cycle and the statistical nature of seasonal predictability. PMID:28287128

Hydrothermal circulation at Mount St. Helens determined by self-potential measurements

USGS Publications Warehouse

Bedrosian, P.A.; Unsworth, M.J.; Johnston, M.J.S.

2007-01-01

The distribution of hydrothermal circulation within active volcanoes is of importance in identifying regions of hydrothermal alteration which may in turn control explosivity, slope stability and sector collapse. Self-potential measurements, indicative of fluid circulation, were made within the crater of Mount St. Helens in 2000 and 2001. A strong dipolar anomaly in the self-potential field was detected on the north face of the 1980-86 lava dome. This anomaly reaches a value of negative one volt on the lower flanks of the dome and reverses sign toward the dome summit. The anomaly pattern is believed to result from a combination of thermoelectric, electrokinetic, and fluid disruption effects within and surrounding the dome. Heat supplied from a cooling dacite magma very likely drives a shallow hydrothermal convection cell within the dome. The temporal stability of the SP field, low surface recharge rate, and magmatic component to fumarole condensates and thermal waters suggest the hydrothermal system is maintained by water vapor exsolved from the magma and modulated on short time scales by surface recharge. ?? 2006 Elsevier B.V. All rights reserved.

A unified nonlinear stochastic time series analysis for climate science.

PubMed

Moon, Woosok; Wettlaufer, John S

2017-03-13

Earth's orbit and axial tilt imprint a strong seasonal cycle on climatological data. Climate variability is typically viewed in terms of fluctuations in the seasonal cycle induced by higher frequency processes. We can interpret this as a competition between the orbitally enforced monthly stability and the fluctuations/noise induced by weather. Here we introduce a new time-series method that determines these contributions from monthly-averaged data. We find that the spatio-temporal distribution of the monthly stability and the magnitude of the noise reveal key fingerprints of several important climate phenomena, including the evolution of the Arctic sea ice cover, the El Nio Southern Oscillation (ENSO), the Atlantic Nio and the Indian Dipole Mode. In analogy with the classical destabilising influence of the ice-albedo feedback on summertime sea ice, we find that during some time interval of the season a destabilising process operates in all of these climate phenomena. The interaction between the destabilisation and the accumulation of noise, which we term the memory effect, underlies phase locking to the seasonal cycle and the statistical nature of seasonal predictability.

A unified nonlinear stochastic time series analysis for climate science

NASA Astrophysics Data System (ADS)

Moon, Woosok; Wettlaufer, John

2017-04-01

Earth's orbit and axial tilt imprint a strong seasonal cycle on climatological data. Climate variability is typically viewed in terms of fluctuations in the seasonal cycle induced by higher frequency processes. We can interpret this as a competition between the orbitally enforced monthly stability and the fluctuations/noise induced by weather. Here we introduce a new time-series method that determines these contributions from monthly-averaged data. We find that the spatio-temporal distribution of the monthly stability and the magnitude of the noise reveal key fingerprints of several important climate phenomena, including the evolution of the Arctic sea ice cover, the El Niño Southern Oscillation (ENSO), the Atlantic Niño and the Indian Dipole Mode. In analogy with the classical destabilising influence of the ice-albedo feedback on summertime sea ice, we find that during some period of the season a destabilising process operates in all of these climate phenomena. The interaction between the destabilisation and the accumulation of noise, which we term the memory effect, underlies phase locking to the seasonal cycle and the statistical nature of seasonal predictability.

A three-wavelength multi-channel brain functional imager based on digital lock-in photon-counting technique

NASA Astrophysics Data System (ADS)

Ding, Xuemei; Wang, Bingyuan; Liu, Dongyuan; Zhang, Yao; He, Jie; Zhao, Huijuan; Gao, Feng

2018-02-01

During the past two decades there has been a dramatic rise in the use of functional near-infrared spectroscopy (fNIRS) as a neuroimaging technique in cognitive neuroscience research. Diffuse optical tomography (DOT) and optical topography (OT) can be employed as the optical imaging techniques for brain activity investigation. However, most current imagers with analogue detection are limited by sensitivity and dynamic range. Although photon-counting detection can significantly improve detection sensitivity, the intrinsic nature of sequential excitations reduces temporal resolution. To improve temporal resolution, sensitivity and dynamic range, we develop a multi-channel continuous-wave (CW) system for brain functional imaging based on a novel lock-in photon-counting technique. The system consists of 60 Light-emitting device (LED) sources at three wavelengths of 660nm, 780nm and 830nm, which are modulated by current-stabilized square-wave signals at different frequencies, and 12 photomultiplier tubes (PMT) based on lock-in photon-counting technique. This design combines the ultra-high sensitivity of the photon-counting technique with the parallelism of the digital lock-in technique. We can therefore acquire the diffused light intensity for all the source-detector pairs (SD-pairs) in parallel. The performance assessments of the system are conducted using phantom experiments, and demonstrate its excellent measurement linearity, negligible inter-channel crosstalk, strong noise robustness and high temporal resolution.

The environmental influence on tropical cyclone precipitation

NASA Technical Reports Server (NTRS)

Rodgers, Edward B.; Baik, Jong-Jin; Pierce, Harold F.

1994-01-01

The intensity, spatial, and temporal changes in precipitation were examined in three North Atlantic hurricanes during 1989 (Dean, Gabrielle, and Hugo) using precipitation estimates made from Special Sensor Microwave/Imager (SSM/I) measurements. In addition, analyses from a barotropic hurricane forecast model and the European Centre for Medium-Range Weather Forecast model were used to examine the relationship between the evolution of the precipitation in these tropical cyclones and external forcing. The external forcing parameters examined were (1) mean climatological sea surface temperatures, (2) vertical wind shear, (3) environmental tropospheric water vapor flux, and (4) upper-tropospheric eddy relative angular momentum flux convergence. The analyses revealed that (1) the SSM/I precipitation estimates were able to delineate and monitor convective ring cycles similar to those observed with land-based and aircraft radar and in situ measurements; (2) tropical cyclone intensification was observed to occur when these convective rings propagated into the inner core of these systems (within 111 km of the center) and when the precipitation rates increased; (3) tropical cyclone weakening was observed to occur when these inner-core convective rings dissipated; (4) the inward propagation of the outer convective rings coincided with the dissipation of the inner convective rings when they came within 55 km of each other; (5) in regions with the combined warm sea surface temperatures (above 26 C) and low vertical wind shear (less than 5 m/s), convective rings outside the region of strong lower-tropospheric inertial stability could be initiated by strong surges of tropospheric moisture, while convective rings inside the region of strong lower-tropospheric inertial stability could be enhanced by upper-tropospheric eddy relative angular momentum flux convergence.

The Environmental Influence on Tropical Cyclone Precipitation.

NASA Astrophysics Data System (ADS)

Rodgers, Edward B.; Baik, Jong-Jin; Pierce, Harold F.

1994-05-01

The intensity, spatial, and temporal changes in precipitation were examined in three North Atlantic hurricanes during 1989 (Dean, Gabrielle, and Hugo) using precipitation estimates made from Special Sensor Microwave/Imager (SSM/I) measurements. In addition, analyses from a barotropic hurricane forecast model and the European Centre for Medium-Range Weather Forecast model were used to examine the relationship between the evolution of the precipitation in these tropical cyclones and external forcing. The external forcing parameters examined were 1) mean climatological sea surface temperatures, 2) vertical wind shear, 3) environmental tropospheric water vapor flux, and 4) upper-tropospheric eddy relative angular momentum flux convergence.The analyses revealed that 1) the SSM/I precipitation estimates were able to delineate and monitor convective ring cycles similar to those observed with land-based and aircraft radar and in situ measurements; 2) tropical cyclone intensification was observed to occur when these convective rings propagated into the inner core of these systems (within 111 km of the center) and when the precipitation rates increased; 3) tropical cyclone weakening was observed to occur when these inner-core convective rings dissipated; 4) the inward propagation of the outer convective rings coincided with the dissipation of the inner convective rings when they came within 55 km of each other; 5) in regions with the combined warm sea surface temperatures (above 26°C) and low vertical wind shear (less than 5 m s1), convective rings outside the region of strong lower-tropospheric inertial stability could be initiated by strong surges of tropospheric moisture, while convective rings inside the region of strong lower-tropospheric inertial stability could be enhanced by upper-tropospheric eddy relative angular momentum flux convergence.

A Study of Strong Stability of Distributed Systems. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Cataltepe, Tayfun

1989-01-01

The strong stability of distributed systems is studied and the problem of characterizing strongly stable semigroups of operators associated with distributed systems is addressed. Main emphasis is on contractive systems. Three different approaches to characterization of strongly stable contractive semigroups are developed. The first one is an operator theoretical approach. Using the theory of dilations, it is shown that every strongly stable contractive semigroup is related to the left shift semigroup on an L(exp 2) space. Then, a decomposition for the state space which identifies strongly stable and unstable states is introduced. Based on this decomposition, conditions for a contractive semigroup to be strongly stable are obtained. Finally, extensions of Lyapunov's equation for distributed parameter systems are investigated. Sufficient conditions for weak and strong stabilities of uniformly bounded semigroups are obtained by relaxing the equivalent norm condition on the right hand side of the Lyanupov equation. These characterizations are then applied to the problem of feedback stabilization. First, it is shown via the state space decomposition that under certain conditions a contractive system (A,B) can be strongly stabilized by the feedback -B(*). Then, application of the extensions of the Lyapunov equation results in sufficient conditions for weak, strong, and exponential stabilizations of contractive systems by the feedback -B(*). Finally, it is shown that for a contractive system, the first derivative of x with respect to time = Ax + Bu (where B is any linear bounded operator), there is a related linear quadratic regulator problem and a corresponding steady state Riccati equation which always has a bounded nonnegative solution.

Tracking Human Mobility Using WiFi Signals.

PubMed

Sapiezynski, Piotr; Stopczynski, Arkadiusz; Gatej, Radu; Lehmann, Sune

2015-01-01

We study six months of human mobility data, including WiFi and GPS traces recorded with high temporal resolution, and find that time series of WiFi scans contain a strong latent location signal. In fact, due to inherent stability and low entropy of human mobility, it is possible to assign location to WiFi access points based on a very small number of GPS samples and then use these access points as location beacons. Using just one GPS observation per day per person allows us to estimate the location of, and subsequently use, WiFi access points to account for 80% of mobility across a population. These results reveal a great opportunity for using ubiquitous WiFi routers for high-resolution outdoor positioning, but also significant privacy implications of such side-channel location tracking.

Understanding the Effect of Stratification on Vertical and Temporal Heterogenieties of Cyanobacteria Blooms in Lakes Using a Long Term in-situ Monitoring Station

NASA Astrophysics Data System (ADS)

Wilkinson, A.; Guala, M.; Hondzo, M.

2017-12-01

Harmful Algal Blooms (HAB) are made up of potentially toxic freshwater microorganisms called cyanobacteria, because of this they are a ecological and public health hazard. The occurrences of toxic HAB are unpredictable and highly spatially and temporary variable in freshwater ecosystems. To study the abiotic drivers for toxic HAB, a floating research station has been deployed in a hyper-eutrophic lake in Madison Lake, Minnesota, from June-October 2016. This research station provides full depth water quality (hourly) and meteorological monitoring (5 minutes). Water quality monitoring is performed by an autonomously traversed water quality sonde that provides chemical, physical and biological measurements; including phycocyanin, a photosynthetic pigment distinct to cyanobacteria. A bloom of cyanobacteria recorded in the epiliminion in mid-July was driven by prolonged strong thermal stratification in the water column, high surface water temperatures and high phosphate concentrations in the epiliminion. The high biovolume (BV) persisted until late September and was sustained below the surface after stratification weakened, when the thermocline did not confine cyanobacteria-rich layers any more, and cyanobacteria vertical heterogeneities decayed in the water column. High correlations among BV stratification, surface water temperature, and stratification stability informed the development of a quantitative relationship to determine how BV heterogeneities vary with thermal structure in the water column. The BV heterogeneity decreased with thermal stratification stability and surface water temperature, and the dynamic lake stability described by the Lake Number. Finally the location of maximum BV accumulation showed diurnal patterns ie. BV peaks were observed at 1 m depth during the day and deeper layers during the night, which followed patterns in light penetration and thermocline depth. These findings capture cyanobacteria vertical and temporal heterogeneities on a on full depth, seasonal scale and quantify BV distribution throughout the water column under different stratification conditions, which can be important for mitigating risks of contamination of drinking water and recreational exposure.

Comparison of spatially and temporally resolved diffuse transillumination measurement systems for extraction of optical properties of scattering media.

PubMed

Ortiz-Rascón, E; Bruce, N C; Garduño-Mejía, J; Carrillo-Torres, R; Hernández-Paredes, J; Álvarez-Ramos, M E

2017-11-20

This paper discusses the main differences between two different methods for determining the optical properties of tissue optical phantoms by fitting the spatial and temporal intensity distribution functions to the diffusion approximation theory. The consistency in the values of the optical properties is verified by changing the width of the recipient containing the turbid medium; as the optical properties are an intrinsic value of the scattering medium, independently of the recipient width, the stability in these values for different widths implies a better measurement system for the acquisition of the optical properties. It is shown that the temporal fitting method presents higher stability than the spatial fitting method; this is probably due to the addition of the time of flight parameter into the diffusion theory.

Dynamic semantic cognition: Characterising coherent and controlled conceptual retrieval through time using magnetoencephalography and chronometric transcranial magnetic stimulation.

PubMed

Teige, Catarina; Mollo, Giovanna; Millman, Rebecca; Savill, Nicola; Smallwood, Jonathan; Cornelissen, Piers L; Jefferies, Elizabeth

2018-06-01

Distinct neural processes are thought to support the retrieval of semantic information that is (i) coherent with strongly-encoded aspects of knowledge, and (ii) non-dominant yet relevant for the current task or context. While the brain regions that support readily coherent and more controlled patterns of semantic retrieval are relatively well-characterised, the temporal dynamics of these processes are not well-understood. This study used magnetoencephalography (MEG) and dual-pulse chronometric transcranial magnetic stimulation (cTMS) in two separate experiments to examine temporal dynamics during the retrieval of strong and weak associations. MEG results revealed a dissociation within left temporal cortex: anterior temporal lobe (ATL) showed greater oscillatory response for strong than weak associations, while posterior middle temporal gyrus (pMTG) showed the reverse pattern. Left inferior frontal gyrus (IFG), a site associated with semantic control and retrieval, showed both patterns at different time points. In the cTMS experiment, stimulation of ATL at ∼150 msec disrupted the efficient retrieval of strong associations, indicating a necessary role for ATL in coherent conceptual activations. Stimulation of pMTG at the onset of the second word disrupted the retrieval of weak associations, suggesting this site may maintain information about semantic context from the first word, allowing efficient engagement of semantic control. Together these studies provide converging evidence for a functional dissociation within the temporal lobe, across both tasks and time. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Stability of Synchronization Clusters and Seizurability in Temporal Lobe Epilepsy

PubMed Central

Palmigiano, Agostina; Pastor, Jesús; García de Sola, Rafael; Ortega, Guillermo J.

2012-01-01

Purpose Identification of critical areas in presurgical evaluations of patients with temporal lobe epilepsy is the most important step prior to resection. According to the “epileptic focus model”, localization of seizure onset zones is the main task to be accomplished. Nevertheless, a significant minority of epileptic patients continue to experience seizures after surgery (even when the focus is correctly located), an observation that is difficult to explain under this approach. However, if attention is shifted from a specific cortical location toward the network properties themselves, then the epileptic network model does allow us to explain unsuccessful surgical outcomes. Methods The intraoperative electrocorticography records of 20 patients with temporal lobe epilepsy were analyzed in search of interictal synchronization clusters. Synchronization was analyzed, and the stability of highly synchronized areas was quantified. Surrogate data were constructed and used to statistically validate the results. Our results show the existence of highly localized and stable synchronization areas in both the lateral and the mesial areas of the temporal lobe ipsilateral to the clinical seizures. Synchronization areas seem to play a central role in the capacity of the epileptic network to generate clinical seizures. Resection of stable synchronization areas is associated with elimination of seizures; nonresection of synchronization clusters is associated with the persistence of seizures after surgery. Discussion We suggest that synchronization clusters and their stability play a central role in the epileptic network, favoring seizure onset and propagation. We further speculate that the stability distribution of these synchronization areas would differentiate normal from pathologic cases. PMID:22844524

An Expanded Model of the Temporal Stability of Condom Use Intentions: Gender-Specific Predictors among High-Risk Adolescents

PubMed Central

Schmiege, Sarah J.; Bryan, Angela D.

2011-01-01

Background Adolescents involved with the criminal justice system are at particularly high-risk for the Human Immunodeficiency Virus and sexually transmitted infections. Purpose The purpose of this study was to longitudinally examine gender-specific models of condom use, incorporating temporal stability of intentions. Methods Adolescents on probation (N=728) were recruited to complete longitudinal surveys including measures of Theory of Planned Behavior and gender-specific constructs, relationship length, and condom use. Results Gender-specific models of condom use behavior suggested by previous research were mostly replicated. For young women, the effect of baseline intentions on subsequent condom use behavior was stronger when intentions were either stable or increasing. For young men, more stable, increasing intentions were directly associated with more condom use. There was preliminary evidence to suggest an association between temporal stability of intentions and decreasing condom use in stable relationships. Conclusions Intervention efforts should be tailored by gender and aim to forestall decreasing intentions and condom use over time by addressing difficulties in maintaining condom use. PMID:21347619

One-year temporal stability and predictive and incremental validity of the body, eating, and exercise comparison orientation measure (BEECOM) among college women.

PubMed

Fitzsimmons-Craft, Ellen E; Bardone-Cone, Anna M

2014-01-01

This study examined the one-year temporal stability and the predictive and incremental validity of the Body, Eating, and Exercise Comparison Measure (BEECOM) in a sample of 237 college women who completed study measures at two time points about one year apart. One-year temporal stability was high for the BEECOM total and subscale (i.e., Body, Eating, and Exercise Comparison Orientation) scores. Additionally, the BEECOM exhibited predictive validity in that it accounted for variance in body dissatisfaction and eating disorder symptomatology one year later. These findings held even after controlling for body mass index and existing measures of social comparison orientation. However, results regarding the incremental validity of the BEECOM, or its ability to predict change in these constructs over time, were more mixed. Overall, this study demonstrated additional psychometric properties of the BEECOM among college women, further establishing the usefulness of this measure for more comprehensively assessing eating disorder-related social comparison. Copyright © 2013 Elsevier Ltd. All rights reserved.

Different forms of effective connectivity in primate frontotemporal pathways.

PubMed

Petkov, Christopher I; Kikuchi, Yukiko; Milne, Alice E; Mishkin, Mortimer; Rauschecker, Josef P; Logothetis, Nikos K

2015-01-23

It is generally held that non-primary sensory regions of the brain have a strong impact on frontal cortex. However, the effective connectivity of pathways to frontal cortex is poorly understood. Here we microstimulate sites in the superior temporal and ventral frontal cortex of monkeys and use functional magnetic resonance imaging to evaluate the functional activity resulting from the stimulation of interconnected regions. Surprisingly, we find that, although certain earlier stages of auditory cortical processing can strongly activate frontal cortex, downstream auditory regions, such as voice-sensitive cortex, appear to functionally engage primarily an ipsilateral temporal lobe network. Stimulating other sites within this activated temporal lobe network shows strong activation of frontal cortex. The results indicate that the relative stage of sensory processing does not predict the level of functional access to the frontal lobes. Rather, certain brain regions engage local networks, only parts of which have a strong functional impact on frontal cortex.

Different forms of effective connectivity in primate frontotemporal pathways

PubMed Central

Petkov, Christopher I.; Kikuchi, Yukiko; Milne, Alice E.; Mishkin, Mortimer; Rauschecker, Josef P.; Logothetis, Nikos K.

2015-01-01

It is generally held that non-primary sensory regions of the brain have a strong impact on frontal cortex. However, the effective connectivity of pathways to frontal cortex is poorly understood. Here we microstimulate sites in the superior temporal and ventral frontal cortex of monkeys and use functional magnetic resonance imaging to evaluate the functional activity resulting from the stimulation of interconnected regions. Surprisingly, we find that, although certain earlier stages of auditory cortical processing can strongly activate frontal cortex, downstream auditory regions, such as voice-sensitive cortex, appear to functionally engage primarily an ipsilateral temporal lobe network. Stimulating other sites within this activated temporal lobe network shows strong activation of frontal cortex. The results indicate that the relative stage of sensory processing does not predict the level of functional access to the frontal lobes. Rather, certain brain regions engage local networks, only parts of which have a strong functional impact on frontal cortex. PMID:25613079

Emotional cues enhance the attentional effects on spatial and temporal resolution.

PubMed

Bocanegra, Bruno R; Zeelenberg, René

2011-12-01

In the present study, we demonstrated that the emotional significance of a spatial cue enhances the effect of covert attention on spatial and temporal resolution (i.e., our ability to discriminate small spatial details and fast temporal flicker). Our results indicated that fearful face cues, as compared with neutral face cues, enhanced the attentional benefits in spatial resolution but also enhanced the attentional deficits in temporal resolution. Furthermore, we observed that the overall magnitudes of individuals' attentional effects correlated strongly with the magnitude of the emotion × attention interaction effect. Combined, these findings provide strong support for the idea that emotion enhances the strength of a cue's attentional response.

Microwave Radiometer and Lidar Synergy for High Vertical Resolution Thermodynamic Profiling in a Cloudy Scenario

NASA Astrophysics Data System (ADS)

Barrera Verdejo, M.; Crewell, S.; Loehnert, U.; Di Girolamo, P.

2016-12-01

Continuous monitoring of thermodynamic atmospheric profiles is important for many applications, e.g. assessment of atmospheric stability and cloud formation. Nowadays there is a wide variety of ground-based sensors for atmospheric profiling. However, no single instrument is able to simultaneously provide measurements with complete vertical coverage, high vertical and temporal resolution, and good performance under all weather conditions. For this reason, instrument synergies of a wide range of complementary measurements are more and more considered for improving the quality of atmospheric observations. The current work presents synergetic use of a microwave radiometer (MWR) and Raman lidar (RL) within a physically consistent optimal estimation approach. On the one hand, lidar measurements provide humidity and temperature measurements with a high vertical resolution albeit with limited vertical coverage, due to overlapping function problems, sunlight contamination and the presence of clouds. On the other hand, MWRs obtain humidity, temperature and cloud information throughout the troposphere, with however only a very limited vertical resolution. The benefits of MWR+RL synergy have been previously demonstrated for clear sky cases. This work expands this approach to cloudy scenarios. Consistent retrievals of temperature, absolute and relative humidity as well as liquid water path are analyzed. In addition, different measures are presented to demonstrate the improvements achieved via the synergy compared to individual retrievals, e.g. degrees of freedom or theoretical error. We also demonstrate that, compared to the lidar, the higher temporal resolution of the MWR presents a strong advantage for capturing the high temporal variability of the liquid water cloud.. Finally, the results are compared with independent information sources, e.g. GPS or radiosondes, showing good consistency. The study demonstrates the benefits of the sensor combination, being especially strong in regions where lidar data is not available, whereas if both instruments are available, the lidar measurements dominate the retrieval.

Intraseasonal asynchrony as a factor boosting isolation within a metapopulation: The case of the clouded apollo.

PubMed

Adamski, Paweł; Ćmiel, Adam M; M Lipińska, Anna

2018-03-23

This article discusses the influence of phenology-related intraseasonal asynchrony on metapopulation dynamics and stability. As the part played by intraseasonal asynchrony is as yet unclear and poorly described, greater account of it should be taken in both metapopulation research and conservation practice. The subpopulations of the Parnassius mnemosyne metapopulation studied here are strongly isolated because of the phenological shift between them, despite the relatively small physical distances between them. This isolation is the result of a significant temporal shift in the species' flight periods in the main metapopulation centers: in some seasons its flight times in the different subpopulations did not overlap at all. The predicted results of such strong intraseasonal asynchrony are not altogether clear. On the one hand, they reduce the vulnerability of the entire metapopulation to the effects of short-term random disasters. On the other, the ever-greater isolation of subpopulations may cause the metapopulation to become a nonequilibrium one, which will have a serious impact on its long-term survival. © 2018 Institute of Zoology, Chinese Academy of Sciences.

Enhanced attosecond pulse generation in the vacuum ultraviolet using a two-colour driving field for high harmonic generation

NASA Astrophysics Data System (ADS)

Matía-Hernando, P.; Witting, T.; Walke, D. J.; Marangos, J. P.; Tisch, J. W. G.

2018-03-01

High-harmonic radiation in the extreme ultraviolet and soft X-ray spectral regions can be used to generate attosecond pulses and to obtain structural and dynamic information in atoms and molecules. However, these sources typically suffer from a limited photon flux. An additional issue at lower photon energies is the appearance of satellites in the time domain, stemming from insufficient temporal gating and the spectral filtering required for the isolation of attosecond pulses. Such satellites limit the temporal resolution. The use of multi-colour driving fields has been proven to enhance the harmonic yield and provide additional control, using the relative delays between the different spectral components for waveform shaping. We describe here a two-colour high-harmonic source that combines a few-cycle near-infrared pulse with a multi-cycle second harmonic pulse, with both relative phase and carrier-envelope phase stabilization. We observe strong modulations in the harmonic flux, and present simulations and experimental results supporting the suppression of satellites in sub-femtosecond pulses at 20 eV compared to the single colour field case, an important requirement for attosecond pump-probe measurements.

Patterns of resource exploitation in four coexisting globeflower fly species ( Chiastocheta sp.)

NASA Astrophysics Data System (ADS)

Pompanon, François; Pettex, Emeline; Després, Laurence

2006-03-01

Life history and spatio-temporal patterns of resource utilisation were characterised in four Chiastocheta (Diptera: Anthomyiidae) species, whose larvae compete as seed predators on Trollius europaeus fruits. Interspecific co-occurrence was observed in 80% of the resource patches (= Trollius fruits) in the two communities studied. Isolated larvae from all species had a similar food intake, but differed in development time and size at emergence. Different species exhibit contrasting resource exploitation strategies with specific mining patterns and a partial temporal shift. Two species exhibited particularly singular strategies. C. rotundiventris escaped from strong interactions with other species because it was the first species to develop and the only one to exploit the central pith of Trollius fruits. The key role of this species as the main pollinator of the host-plant appears to be a by-product of constraints imposed by occupying a restricted niche. Although the resource is ephemeral due to seed dispersal, C. dentifera, the last species to oviposit, is not disadvantaged because it has a short development time and rapid food intake. The different patterns can partly explain the stability of Chiastocheta communities, but do not prevent competition to occur at high larval densities.

Does Timing Matter? Temporal Stability of Soil-Magnetic Climate Proxies

NASA Astrophysics Data System (ADS)

Geiss, C. E.

2013-12-01

Numerous studies have shown that the rock-magnetic properties of soils can serve as valuable proxies of continental climates. Many studies average the magnetic properties of several closely spaced sites to reconstruct regional climate signals, but little is known about the temporal variability of soil-magnetic properties. We analyzed the magnetic properties of five, closely spaced (within 20 m from each other) soil profiles that were sampled over a period of five years between 2002 and 2006. The soil profiles are well-developed and display strong magnetic enhancement. According to land records, agricultural influence was minimal as the site had never been plowed and solely been used as pasture. Detailed soil descriptions and measurements of magnetic susceptibility (χ), anhysteretic and isothermal remanent magnetization (ARM, IRM), as well as coercivity parameters show that all studied profiles have very similar horizination and magnetic properties are virtually unchanged from year to year. The only differences between the soil profiles are the position and strength of redoximorphic features. These nanocrystalline iron-oxide deposits have little influence on the magnetic properties of the soils and the timing of soil sampling for magnetic analyses is not a critical factor when sampling for climatic reconstructions.

Investigation into the temporal stability of aqueous standard solutions of psilocin and psilocybin using high performance liquid chromatography.

PubMed

Anastos, N; Barnett, N W; Pfeffer, F M; Lewis, S W

2006-01-01

This paper reports an investigation into the temporal stability of aqueous solutions of psilocin and psilocybin reference drug standards over a period of fourteen days. This study was performed using high performance liquid chromatography utilising a (95:5% v/v) methanol: 10 mM ammonium formate, pH 3.5 mobile phase and absorption detection at 269 nm. It was found that the exclusion of light significantly prolonged the useful life of standards, with aqueous solutions of both psilocin and psilocybin being stable over a period of seven days.

Spatial and temporal variability of throughfall and soil moisture in a deciduous forest in the low mountain ranges (Hesse, Germany)

NASA Astrophysics Data System (ADS)

Chifflard, Peter; Weishaupt, Philipp; Reiss, Martin

2017-04-01

Spatial and temporal patterns of throughfall can affect the heterogeneity of ecological, biogeochemical and hydrological processes at a forest floor and further the underlying soil. Previous research suggests different factors controlling the spatial and temporal patterns of throughfall, but most studies focus on coniferous forest, where the vegetation coverage is more or less constant over time. In deciduous forests the leaf area index varies due to the leaf fall in autumn which implicates a specific spatial and temporal variability of throughfall and furthermore of the soil moisture. Therefore, in the present study, the measurements of throughfall and soil moisture in a deciduous forest in the low mountain ranges focused especially on the period of leaf fall. The aims of this study were: 1) to detect the spatial and temporal variability of both the throughfall and the soil moisture, 2) to examine the temporal stability of the spatial patterns of the throughfall and soil moisture and 3) relate the soil moisture patterns to the throughfall patterns and further to the canopy characteristics. The study was carried out in a small catchment on middle Hesse (Germany) which is covered by beech forest. Annual mean air temperature is 9.4°C (48.9˚F) and annual mean precipitation is 650 mm. Base materials for soil genesis is greywacke and clay shale from Devonian deposits. The soil type at the study plot is a shallow cambisol. The study plot covers an area of about 150 m2 where 77 throughfall samplers where installed. The throughfall and the soil moisture (FDR-method, 20 cm depth) was measured immediately after every rainfall event at the 77 measurement points. During the period of October to December 2015 altogether 7 events were investigated. The geostatistical method kriging was used to interpolate between the measurements points to visualize the spatial patterns of each investigated parameter. Time-stability-plots were applied to examine temporal scatters of each investigated parameter. The spearmen and pearson correlation coefficients were applied to detect the relationship between the different investigated parameters. First results show that the spatial variability of throughfall decreases if the total amount of the throughfall increases. The soil moisture shows a similar behavior. It`s spatial variability decreases if higher soil moisture values were measured. Concerning the temporal stability of throughfall it can be shown that it is very high during the leaf-free period, although the rainfall events have different total througfall amounts. The soil moisture patterns consists of a low temporal stability and additionally only during one event a significant correlations between throughfall and soil moisture patterns exists. This implies that other factors than the throughfall patterns control the spatial patterns of soil moisture.

Quantifying Auditory Temporal Stability in a Large Database of Recorded Music

PubMed Central

Ellis, Robert J.; Duan, Zhiyan; Wang, Ye

2014-01-01

“Moving to the beat” is both one of the most basic and one of the most profound means by which humans (and a few other species) interact with music. Computer algorithms that detect the precise temporal location of beats (i.e., pulses of musical “energy”) in recorded music have important practical applications, such as the creation of playlists with a particular tempo for rehabilitation (e.g., rhythmic gait training), exercise (e.g., jogging), or entertainment (e.g., continuous dance mixes). Although several such algorithms return simple point estimates of an audio file’s temporal structure (e.g., “average tempo”, “time signature”), none has sought to quantify the temporal stability of a series of detected beats. Such a method-a “Balanced Evaluation of Auditory Temporal Stability” (BEATS)–is proposed here, and is illustrated using the Million Song Dataset (a collection of audio features and music metadata for nearly one million audio files). A publically accessible web interface is also presented, which combines the thresholdable statistics of BEATS with queryable metadata terms, fostering potential avenues of research and facilitating the creation of highly personalized music playlists for clinical or recreational applications. PMID:25469636

Beyond Group-Threat: Temporal Dynamics of International Migration and Linkages to Anti-Foreigner Sentiment.

PubMed

DeWaard, Jack

2015-07-01

Prior research on the association between country-level patterns of international migration and anti-foreigner sentiment shows that larger foreign-born concentrations increase perceptions of threat among native-born individuals in receiving countries, which, in turn, give rise to exclusionary preferences. While recent work has assembled a list of limiting conditions that shape the strength of this association, I argue that these efforts are premature because they are based on a narrow way of conceptualising and measuring international migration. In contrast to concepts and measures privileging the size of the foreign-born population in receiving countries, I draw from other literatures highlighting the temporal dynamics of migration. In considering the role of the temporal dynamics of international migration in explaining variation in anti-foreigner sentiment, the question is whether and how the temporal stability of the foreign-born population in receiving countries matters. My results suggest that it does. The size and temporal stability of the foreign-born population play opposing roles in aggravating and ameliorating anti-foreigner sentiment, respectively, with each operating via different pathways at the individual level. My work thus breaks new ground by challenging existing theoretical constructs and operationalisations in the group-threat literature.

Beyond Group-Threat: Temporal Dynamics of International Migration and Linkages to Anti-Foreigner Sentiment

PubMed Central

DeWaard, Jack

2014-01-01

Prior research on the association between country-level patterns of international migration and anti-foreigner sentiment shows that larger foreign-born concentrations increase perceptions of threat among native-born individuals in receiving countries, which, in turn, give rise to exclusionary preferences. While recent work has assembled a list of limiting conditions that shape the strength of this association, I argue that these efforts are premature because they are based on a narrow way of conceptualising and measuring international migration. In contrast to concepts and measures privileging the size of the foreign-born population in receiving countries, I draw from other literatures highlighting the temporal dynamics of migration. In considering the role of the temporal dynamics of international migration in explaining variation in anti-foreigner sentiment, the question is whether and how the temporal stability of the foreign-born population in receiving countries matters. My results suggest that it does. The size and temporal stability of the foreign-born population play opposing roles in aggravating and ameliorating anti-foreigner sentiment, respectively, with each operating via different pathways at the individual level. My work thus breaks new ground by challenging existing theoretical constructs and operationalisations in the group-threat literature. PMID:26146481

Soil Communities Promote Temporal Stability and Species Asynchrony in Experimental Grassland Communities

PubMed Central

Pellkofer, Sarah; van der Heijden, Marcel G. A.; Schmid, Bernhard; Wagg, Cameron

2016-01-01

Background Over the past two decades many studies have demonstrated that plant species diversity promotes primary productivity and stability in grassland ecosystems. Additionally, soil community characteristics have also been shown to influence the productivity and composition of plant communities, yet little is known about whether soil communities also play a role in stabilizing the productivity of an ecosystem. Methodology/Principal Findings Here we use microcosms to assess the effects of the presence of soil communities on plant community dynamics and stability over a one-year time span. Microcosms were filled with sterilized soil and inoculated with either unaltered field soil or field soil sterilized to eliminate the naturally occurring soil biota. Eliminating the naturally occurring soil biota not only resulted in lower plant productivity, and reduced plant species diversity, and evenness, but also destabilized the net aboveground productivity of the plant communities over time, which was largely driven by changes in abundance of the dominant grass Lolium perenne. In contrast, the grass and legumes contributed more to net aboveground productivity of the plant communities in microcosms where soil biota had been inoculated. Additionally, the forbs exhibited compensatory dynamics with grasses and legumes, thus lowering temporal variation in productivity in microcosms that received the unaltered soil inocula. Overall, asynchrony among plant species was higher in microcosms where an unaltered soil community had been inoculated, which lead to higher temporal stability in community productivity. Conclusions/Significance Our results suggest that soil communities increase plant species asynchrony and stabilize plant community productivity by equalizing the performance among competing plant species through potential antagonistic and facilitative effects on individual plant species. PMID:26829481

Temporal stability of E. coli concentration patterns in two irrigation ponds in Maryland

USDA-ARS?s Scientific Manuscript database

There are about nine millions ponds in USA, and many of them serve as an important agricultural surface water source. E. coli concentrations are commonly used as indicator organisms to evaluate microbial water quality for irrigation and recreation. Our hypothesis was that there exists a temporally ...

Temporal stability of Escherichia coli concentration patterns in two irrigation ponds in Maryland

USDA-ARS?s Scientific Manuscript database

Fecal contamination of water sources is an important water quality issue for agricultural irrigation ponds. Escherichia coli is a common microbial indicator used to evaluate recreational and irrigation water quality. We hypothesized that there is a temporally stable pattern of E.coli concentrations ...

[Simulation of CO2 exchange between forest canopy and atmosphere].

PubMed

Diao, Yiwei; Wang, Anzhi; Jin, Changjie; Guan, Dexin; Pei, Tiefan

2006-12-01

Estimating the scalar source/sink distribution of CO2 and its vertical fluxes within and above forest canopy continues to be a critical research problem in biosphere-atmosphere exchange processes and plant ecology. With broad-leaved Korean pine forest in Changbai Mountains as test object, and based on Raupach's localized near field theory, the source/sink and vertical flux distribution of CO2 within and above forest canopy were modeled through an inverse Lagrangian dispersion analysis. This model correctly predicted a strong positive CO2 source strength in the deeper layers of the canopy due to soil-plant respiration, and a strong CO2 sink in the upper layers of the canopy due to the assimilation by sunlit foliage. The foliage in the top layer of canopy changed from a CO2 source in the morning to a CO2 sink in the afternoon, while the soil constituted a strong CO2 source all the day. The simulation results accorded well with the eddy covariance CO2 flux measurements within and above the canopy, and the average precision was 89%. The CO2 exchange predicted by the analysis was averagely 15% higher than that of the eddy correlation, but exhibited identical temporal trend. Atmospheric stability remarkably affected the CO2 exchange between forest canopy and atmosphere.

SU-E-T-410: Fringe Stability and Phase Shift Measurements in a Michelson Interferometer for Optical Calorimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flores-Martinez, E; Malin, M; DeWerd, L

2014-06-01

Purpose: To identify the variables limiting the resolution of a Michelson interferometer used to measure phase shifts (PS) in water as part of a radiometric calorimeter. Methods: We investigated the output stability of a He-Ne laser and a laser diode. The short and long term stability of the fringe pattern in a Michelson interferometer was tested with different types of lasers, thermal insulation arrangements, damping systems and optical mounts to optimize system performance. PS were induced by electrically heating water in a 1 cm quartz cuvette located in one of the interferometer arms. The PS was calculated from fringe intensitymore » changes and compared to a calculated PS using thermocouple-measured temperature changes in the water. Results: The intensity of the laser diode is more stable, but the gas laser’s profile is more suitable for fringe analysis and has better temporal coherence. The laser requires a warm-up time of 4 hours before its output is stabilized (SNR>95). The fringe’s stability strongly depends on the thermal insulation. When the interferometer is exposed to ambient temperature swings of 0.7 K, it is not possible to stabilize the fringe pattern. Enclosing the system in a 2.5 cm-thick Styrofoam box improves the SNR, but further insulation will be needed to increase the SNR above 50. High frequency noise is significantly reduced by damping the system.Inducing a temperature rise in water, starting at 299 K, the average temperature increase for a 2π PS is 0.29 ± 0.02 K and the proportionality constant is -21.1 ± 0.8 radians/K. This is 5.8% lower than the calculated value using the thermocouple. Conclusion: Interferometric PS measurements of temperature may provide an alternative to thermistors for water calorimetry. The resolution of the current prototype is limited by ambient temperature stability. Calculated and measured thermally-induced PS in water agreed to within 5.8%.« less

Three-dimensional modelling of slope stability using the Local Factor of Safety concept

NASA Astrophysics Data System (ADS)

Moradi, Shirin; Huisman, Sander; Beck, Martin; Vereecken, Harry; Class, Holger

2017-04-01

Slope stability is governed by coupled hydrological and mechanical processes. The slope stability depends on the effective stress, which in turn depends on the weight of the soil and the matrix potential. Therefore, changes in water content and matrix potential associated with infiltration will affect slope stability. Most available models describing these coupled hydro-mechanical processes either rely on a one- or two-dimensional representation of hydrological and mechanical properties and processes, which obviously is a strong simplification in many applications. Therefore, the aim of this work is to develop a three-dimensional hydro-mechanical model that is able to capture the effect of spatial and temporal variability of both mechanical and hydrological parameters on slope stability. For this, we rely on DuMux, which is a free and open-source simulator for flow and transport processes in porous media that facilitates coupling of different model approaches and offers flexibility for model development. We use the Richards equation to model unsaturated water flow. The simulated water content and matrix potential distribution is used to calculate the effective stress. We only consider linear elasticity and solve for statically admissible fields of stress and displacement without invoking failure or the redistribution of post-failure stress or displacement. The Local Factor of Safety concept is used to evaluate slope stability in order to overcome some of the main limitations of commonly used methods based on limit equilibrium considerations. In a first step, we compared our model implementation with a 2D benchmark model that was implemented in COMSOL Multiphysics. In a second step, we present in-silico experiments with the newly developed 3D model to show the effect of slope morphology, spatial variability in hydraulic and mechanical material properties, and spatially variable soil depth on simulated slope stability. It is expected that this improved physically-based three-dimensional hydro-mechanical model is able to provide more reliable slope instability predictions in more complex situations.

Spatial and temporal patterns of neutral and adaptive genetic variation in the endangered African wild dog (Lycaon pictus).

PubMed

Marsden, Clare D; Woodroffe, Rosie; Mills, Michael G L; McNutt, J Weldon; Creel, Scott; Groom, Rosemary; Emmanuel, Masenga; Cleaveland, Sarah; Kat, Pieter; Rasmussen, Gregory S A; Ginsberg, Joshua; Lines, Robin; André, Jean-Marc; Begg, Colleen; Wayne, Robert K; Mable, Barbara K

2012-03-01

Deciphering patterns of genetic variation within a species is essential for understanding population structure, local adaptation and differences in diversity between populations. Whilst neutrally evolving genetic markers can be used to elucidate demographic processes and genetic structure, they are not subject to selection and therefore are not informative about patterns of adaptive variation. As such, assessments of pertinent adaptive loci, such as the immunity genes of the major histocompatibility complex (MHC), are increasingly being incorporated into genetic studies. In this study, we combined neutral (microsatellite, mtDNA) and adaptive (MHC class II DLA-DRB1 locus) markers to elucidate the factors influencing patterns of genetic variation in the African wild dog (Lycaon pictus); an endangered canid that has suffered extensive declines in distribution and abundance. Our genetic analyses found all extant wild dog populations to be relatively small (N(e)  < 30). Furthermore, through coalescent modelling, we detected a genetic signature of a recent and substantial demographic decline, which correlates with human expansion, but contrasts with findings in some other African mammals. We found strong structuring of wild dog populations, indicating the negative influence of extensive habitat fragmentation and loss of gene flow between habitat patches. Across populations, we found that the spatial and temporal structure of microsatellite diversity and MHC diversity were correlated and strongly influenced by demographic stability and population size, indicating the effects of genetic drift in these small populations. Despite this correlation, we detected signatures of selection at the MHC, implying that selection has not been completely overwhelmed by genetic drift. © 2012 Blackwell Publishing Ltd.

Temporal Stability of Gifted Children's Intelligence.

ERIC Educational Resources Information Center

Spangler, Robert S.; Sabatino, David A.

1995-01-01

The longitudinal stability of the Wechsler Intelligence Scale for Children-Revised was examined for consistency in determining eligibility for gifted programs among 66 elementary children. All subtest scales except one remained extremely stable, producing less than one scale score point difference across three test administrations. Children…

The effects of psammophilous plants on sand dune dynamics

NASA Astrophysics Data System (ADS)

Bel, Golan; Ashkenazy, Yosef

2014-07-01

Mathematical models of sand dune dynamics have considered different types of sand dune cover. However, despite the important role of psammophilous plants (plants that flourish in moving-sand environments) in dune dynamics, the incorporation of their effects into mathematical models of sand dunes remains a challenging task. Here we propose a nonlinear physical model for the role of psammophilous plants in the stabilization and destabilization of sand dunes. There are two main mechanisms by which the wind affects these plants: (i) sand drift results in the burial and exposure of plants, a process that is known to result in an enhanced growth rate, and (ii) strong winds remove shoots and rhizomes and seed them in nearby locations, enhancing their growth rate. Our model describes the temporal evolution of the fractions of surface cover of regular vegetation, biogenic soil crust, and psammophilous plants. The latter reach their optimal growth under either (i) specific sand drift or (ii) specific wind power. The model exhibits complex bifurcation diagrams and dynamics, which explain observed phenomena, and it predicts new dune stabilization scenarios. Depending on the climatological conditions, it is possible to obtain one, two, or, predicted here for the first time, three stable dune states. Our model shows that the development of the different cover types depends on the precipitation rate and the wind power and that the psammophilous plants are not always the first to grow and stabilize the dunes.

A study of the temporal stability of multiple cell vortices

NASA Technical Reports Server (NTRS)

Khorrami, Mehdi R.

1989-01-01

The effect of initial mean velocity field on the stability characteristics of longitudinal vortices is documented in detail. The temporal stability of isolated multiple cell vortices is considered. The types of vortices studied include single cell as well as two and three cell vortices. It is shown that cell multiplicity in the vortex core has drastic effects on the stability characteristics. On the basis of numerical calculations, it is concluded that the growth rates of instabilities in multiple cell vortices are substantially larger (two to threefold increases are observed) than those of a single cell vortex. It is also determined that there is a substantial increase in the effective range of axial and azimuthal wavenumbers where instabilities are present. But most importantly, there is the appearance of a variety of viscous modes of instability. In the case of vortices, these latter instabilities which highlight the importance of viscous forces have never been reported before. These effects are discussed in detail for the case of a two cell vortex.

Characterization of the dimensional stability of advanced metallic materials using an optical test bench structure

NASA Technical Reports Server (NTRS)

Hsieh, Cheng; O'Donnell, Timothy P.

1991-01-01

The dimensional stability of low-density high specific-strength metal-matrix composites (including 30 vol pct SiC(p)/SXA 24-T6 Al, 25 vol pct SiC(p)/6061-T6 Al, 40 vol pct graphite P100 fiber/6061 Al, 50 vol pct graphite P100 fiber/6061 Al, and 40 vol pct P100 graphite fiber/AZ91D Mg composites) and an Al-Li-Mg metal alloy was evaluated using a specially designed five-strut optical test bench structure. The structure had 30 thermocouple locations, one retroreflector, one linear interferometer multilayer insulation, and various strip heaters. It was placed in a 10 exp -7 torr capability vacuum chamber with a laser head positioned at a window port, and a laser interferometer system for collecting dimensional change data. It was found that composite materials have greater 40-C temporal dimensional stability than the AL-Li-Mg alloy. Aluminum-based composites demonstrated better 40-C temporal stability than Mg-based composites.

Temporal genetic analysis of the endangered tidewater goby: extinction-colonization dynamics or drift in isolation?

PubMed

Kinziger, Andrew P; Hellmair, Michael; McCraney, W Tyler; Jacobs, David K; Goldsmith, Greg

2015-11-01

Extinction and colonization dynamics are critical to understanding the evolution and conservation of metapopulations. However, traditional field studies of extinction-colonization are potentially fraught with detection bias and have rarely been validated. Here, we provide a comparison of molecular and field-based approaches for assessment of the extinction-colonization dynamics of tidewater goby (Eucyclogobius newberryi) in northern California. Our analysis of temporal genetic variation across 14 northern California tidewater goby populations failed to recover genetic change expected with extinction-colonization cycles. Similarly, analysis of site occupancy data from field studies (94 sites) indicated that extinction and colonization are very infrequent for our study populations. Comparison of the approaches indicated field data were subject to imperfect detection, and falsely implied extinction-colonization cycles in several instances. For northern California populations of tidewater goby, we interpret the strong genetic differentiation between populations and high degree of within-site temporal stability as consistent with a model of drift in the absence of migration, at least over the past 20-30 years. Our findings show that tidewater goby exhibit different population structures across their geographic range (extinction-colonization dynamics in the south vs. drift in isolation in the north). For northern populations, natural dispersal is too infrequent to be considered a viable approach for recolonizing extirpated populations, suggesting that species recovery will likely depend on artificial translocation in this region. More broadly, this work illustrates that temporal genetic analysis can be used in combination with field data to strengthen inference of extinction-colonization dynamics or as a stand-alone tool when field data are lacking. © 2015 John Wiley & Sons Ltd.

Combustion stability with baffles, absorbers and velocity sensitive combustion. [liquid propellant rocket combustors

NASA Technical Reports Server (NTRS)

Mitchell, C. E.

1980-01-01

Analytical and computational techniques were developed to predict the stability behavior of liquid propellant rocket combustors using damping devices such as acoustic liners, slot absorbers, and injector face baffles. Models were developed to determine the frequency and decay rate of combustor oscillations, the spatial and temporal pressure waveforms, and the stability limits in terms of combustion response model parameters.

Reproductive niche conservatism in the isolated New Zealand flora over 23 million years

PubMed Central

Conran, John G.; Lee, William G.; Lee, Daphne E.; Bannister, Jennifer M.; Kaulfuss, Uwe

2014-01-01

The temporal stability of plant reproductive features on islands has rarely been tested. Using flowers, fruits/cones and seeds from a well-dated (23 Ma) Miocene Lagerstätte in New Zealand, we show that across 23 families and 30 genera of forest angiosperms and conifers, reproductive features have remained constant for more than 20 Myr. Insect-, wind- and bird-pollinated flowers and wind- and bird-dispersed diaspores all indicate remarkable reproductive niche conservatism, despite widespread environmental and biotic change. In the past 10 Myr, declining temperatures and the absence of low-latitude refugia caused regional extinction of thermophiles, while orogenic processes steepened temperature, precipitation and nutrient gradients, limiting forest niches. Despite these changes, the palaeontological record provides empirical support for evidence from phylogeographical studies of strong niche conservatism within lineages and biomes. PMID:25319820

Tracking Human Mobility Using WiFi Signals

PubMed Central

Sapiezynski, Piotr; Stopczynski, Arkadiusz; Gatej, Radu; Lehmann, Sune

2015-01-01

We study six months of human mobility data, including WiFi and GPS traces recorded with high temporal resolution, and find that time series of WiFi scans contain a strong latent location signal. In fact, due to inherent stability and low entropy of human mobility, it is possible to assign location to WiFi access points based on a very small number of GPS samples and then use these access points as location beacons. Using just one GPS observation per day per person allows us to estimate the location of, and subsequently use, WiFi access points to account for 80% of mobility across a population. These results reveal a great opportunity for using ubiquitous WiFi routers for high-resolution outdoor positioning, but also significant privacy implications of such side-channel location tracking. PMID:26132115

Temporal Dynamics of the Human Vaginal Microbiota

PubMed Central

Gajer, Pawel; Brotman, Rebecca M.; Bai, Guoyun; Sakamoto, Joyce; Schütte, Ursel M.E.; Zhong, Xue; Koenig, Sara S.K.; Fu, Li; Ma, Zhanshan; Zhou, Xia; Abdo, Zaid; Forney, Larry J.; Ravel, Jacques

2012-01-01

Elucidating the factors that impinge on the stability of bacterial communities in the vagina may help in predicting the risk of diseases that affect women’s health. Here, we describe the temporal dynamics of the composition of vaginal bacterial communities in 32 reproductive age women over a 16-week period. The analysis revealed the dynamics of five major classes of bacterial communities and showed that some communities change markedly over short time periods, whereas others are relatively stable. Modeling community stability using new quantitative measures indicates that deviation from stability correlates with time in the menstrual cycle, bacterial community composition and sexual activity. The women studied are healthy, thus it appears that neither variation in community composition per se, nor higher levels of observed diversity (co-dominance) are necessarily indicative of dysbiosis, in which there is microbial imbalance accompanied by symptoms. PMID:22553250

Temporal windows in visual processing: "prestimulus brain state" and "poststimulus phase reset" segregate visual transients on different temporal scales.

PubMed

Wutz, Andreas; Weisz, Nathan; Braun, Christoph; Melcher, David

2014-01-22

Dynamic vision requires both stability of the current perceptual representation and sensitivity to the accumulation of sensory evidence over time. Here we study the electrophysiological signatures of this intricate balance between temporal segregation and integration in vision. Within a forward masking paradigm with short and long stimulus onset asynchronies (SOA), we manipulated the temporal overlap of the visual persistence of two successive transients. Human observers enumerated the items presented in the second target display as a measure of the informational capacity read-out from this partly temporally integrated visual percept. We observed higher β-power immediately before mask display onset in incorrect trials, in which enumeration failed due to stronger integration of mask and target visual information. This effect was timescale specific, distinguishing between segregation and integration of visual transients that were distant in time (long SOA). Conversely, for short SOA trials, mask onset evoked a stronger visual response when mask and targets were correctly segregated in time. Examination of the target-related response profile revealed the importance of an evoked α-phase reset for the segregation of those rapid visual transients. Investigating this precise mapping of the temporal relationships of visual signals onto electrophysiological responses highlights how the stream of visual information is carved up into discrete temporal windows that mediate between segregated and integrated percepts. Fragmenting the stream of visual information provides a means to stabilize perceptual events within one instant in time.

Stability of strongly nonlinear normal modes

NASA Astrophysics Data System (ADS)

Recktenwald, Geoffrey; Rand, Richard

2007-10-01

It is shown that a transformation of time can allow the periodic solution of a strongly nonlinear oscillator to be written as a simple cosine function. This enables the stability of strongly nonlinear normal modes in multidegree of freedom systems to be investigated by standard procedures such as harmonic balance.

Observations of upper ocean stability and heat fluxes in the Antarctic from under-ice Argo float profile data.

NASA Astrophysics Data System (ADS)

Wilson, E. A.; Riser, S.

2016-12-01

Sea ice growth around Antarctica is intimately linked to the stability and thermohaline structure of the underlying ocean. As sea ice grows, the resulting brine triggers convective instabilities that deepen the mixed layer and entrain warm water from the weakly stratified pycnocline. The heat released from this process acts as a strong negative feedback to ice growth which, under the right scenarios, can exceed the initial atmospheric heat loss. Much of our current understanding of this ice-ocean interaction comes from a handful of relatively short field campaigns in the Weddell Sea. Here, we supplement those observations with an analysis of over 9000 under-ice Argo float profiles, collected between 2006-2015. These profiles provide an unprecedented view of the temporal and spatial variability of the upper ocean structure throughout the Antarctic region. With these observations and a theoretical understanding of the coupled ice-ocean system, we assess the ocean's potential to limit thermodynamic ice growth as well as its susceptibility to deep convection in different regions. Using these results, we infer how recent climatic changes may influence Antarctic sea ice growth and deep ocean ventilation in the near future.

Visual contribution to the multistable perception of speech.

PubMed

Sato, Marc; Basirat, Anahita; Schwartz, Jean-Luc

2007-11-01

The multistable perception of speech, or verbal transformation effect, refers to perceptual changes experienced while listening to a speech form that is repeated rapidly and continuously. In order to test whether visual information from the speaker's articulatory gestures may modify the emergence and stability of verbal auditory percepts, subjects were instructed to report any perceptual changes during unimodal, audiovisual, and incongruent audiovisual presentations of distinct repeated syllables. In a first experiment, the perceptual stability of reported auditory percepts was significantly modulated by the modality of presentation. In a second experiment, when audiovisual stimuli consisting of a stable audio track dubbed with a video track that alternated between congruent and incongruent stimuli were presented, a strong correlation between the timing of perceptual transitions and the timing of video switches was found. Finally, a third experiment showed that the vocal tract opening onset event provided by the visual input could play the role of a bootstrap mechanism in the search for transformations. Altogether, these results demonstrate the capacity of visual information to control the multistable perception of speech in its phonetic content and temporal course. The verbal transformation effect thus provides a useful experimental paradigm to explore audiovisual interactions in speech perception.

Stabilized linear semi-implicit schemes for the nonlocal Cahn-Hilliard equation

NASA Astrophysics Data System (ADS)

Du, Qiang; Ju, Lili; Li, Xiao; Qiao, Zhonghua

2018-06-01

Comparing with the well-known classic Cahn-Hilliard equation, the nonlocal Cahn-Hilliard equation is equipped with a nonlocal diffusion operator and can describe more practical phenomena for modeling phase transitions of microstructures in materials. On the other hand, it evidently brings more computational costs in numerical simulations, thus efficient and accurate time integration schemes are highly desired. In this paper, we propose two energy-stable linear semi-implicit methods with first and second order temporal accuracies respectively for solving the nonlocal Cahn-Hilliard equation. The temporal discretization is done by using the stabilization technique with the nonlocal diffusion term treated implicitly, while the spatial discretization is carried out by the Fourier collocation method with FFT-based fast implementations. The energy stabilities are rigorously established for both methods in the fully discrete sense. Numerical experiments are conducted for a typical case involving Gaussian kernels. We test the temporal convergence rates of the proposed schemes and make a comparison of the nonlocal phase transition process with the corresponding local one. In addition, long-time simulations of the coarsening dynamics are also performed to predict the power law of the energy decay.

Spatio-temporal response of maize yield to edaphic and meteorological conditions in a saline farmland

USDA-ARS?s Scientific Manuscript database

Spatio-temporal variability of crop production strongly depends on soil heterogeneity, meteorological conditions, and their interaction. Canopy reflectance can be used to describe crop status and yield spatial variability. The objectives of this work were to understand the spatio-temporal variabilit...

Test Score Stability and Construct Validity of the Adult Manifest Anxiety Scale-College Version Scores among College Students: A Brief Report

ERIC Educational Resources Information Center

Lowe, Patricia A.; Papanastasiou, Elena C.; DeRuyck, Kimberly A.; Reynolds, Cecil R.

2005-01-01

In this study, the authors investigated the temporal stability and construct validity of the Adult Manifest Anxiety Scale-College Version (AMAS-C; C. R. Reynolds, B. O. Richmond, & P. A. Lowe, 2003b) scores. Results indicated that the AMAS-C scores had adequate to excellent test score stability, and evidence supported the construct validity of the…

Stability of the Orca Basin Brine Interface Determined Using Radium Isotopes

NASA Astrophysics Data System (ADS)

Peterson, R. N.; Peterson, L.; Montoya, J. P.; Joye, S. B.

2016-02-01

The Orca Basin is an intraslope basin in the northern continental slope of the Gulf of Mexico, and contains a deep (up to 220 m) anoxic, hypersaline brine lake. The brine interface extends from ocean salinity (at a water depth of 2125 m) to a constant salinity of 215 psu below a depth of 2250 m. This interface is considered to be among the most stable interfaces on the planet, and contains distinct zones of macrofaunal and microbial assemblages. The brine lake is supported by continued dissolution of exposed rock salt at an estimated rate of 0.5 million t/yr. Such dissolution of salt should serve as a source of radium isotopes, and given their range of half-lives, these isotopes can serve as unique proxies to the location and rate of salt dissolution into this basin. We have collected a series of radon and radium isotope profiles through this brine lake over the past 4 years, which allow us to assess the spatial and temporal stability of this interface. Throughout the brine lake, we observe strong enrichments in unsupported Ra-224, Rn-222, and Ra-226 in a 10 m thick zone near the base of the brine interface, between 2232 m and 2242 m. The strong enrichment in unsupported Ra-224 in this layer must be supported by a continuous source, presumably the dissolution of exposed salt rock. Various degrees of isotopic enrichment throughout the lake provide an assessment of the rates of lateral and vertical dispersion of salt and associated chemical constituents.

Bundle Adjustment-Based Stability Analysis Method with a Case Study of a Dual Fluoroscopy Imaging System

NASA Astrophysics Data System (ADS)

Al-Durgham, K.; Lichti, D. D.; Detchev, I.; Kuntze, G.; Ronsky, J. L.

2018-05-01

A fundamental task in photogrammetry is the temporal stability analysis of a camera/imaging-system's calibration parameters. This is essential to validate the repeatability of the parameters' estimation, to detect any behavioural changes in the camera/imaging system and to ensure precise photogrammetric products. Many stability analysis methods exist in the photogrammetric literature; each one has different methodological bases, and advantages and disadvantages. This paper presents a simple and rigorous stability analysis method that can be straightforwardly implemented for a single camera or an imaging system with multiple cameras. The basic collinearity model is used to capture differences between two calibration datasets, and to establish the stability analysis methodology. Geometric simulation is used as a tool to derive image and object space scenarios. Experiments were performed on real calibration datasets from a dual fluoroscopy (DF; X-ray-based) imaging system. The calibration data consisted of hundreds of images and thousands of image observations from six temporal points over a two-day period for a precise evaluation of the DF system stability. The stability of the DF system - for a single camera analysis - was found to be within a range of 0.01 to 0.66 mm in terms of 3D coordinates root-mean-square-error (RMSE), and 0.07 to 0.19 mm for dual cameras analysis. It is to the authors' best knowledge that this work is the first to address the topic of DF stability analysis.

Earthworms are associated with subpopulations of Gammaproteobacteria irrespective of the total soil microbiota composition and stability.

PubMed

Fjøsne, Trine; Myromslien, Frøydis D; Wilson, Robert C; Rudi, Knut

2018-05-01

Soil represents one of the most complex microbial ecosystems on earth. It is well-known that invertebrates such as earthworms have a major impact on transformations of organic material in soil, while their effect on the soil microbiota remains largely unknown. The aim of our work was therefore to investigate the association of earthworms with temporal stability, composition and diversity in two soil microbiota experimental series. We found that earthworms were consistently associated with an increase in subgroups of Gammaproteobacteria, despite major differences in microbiota composition and temporal stability across the experimental series. Our results therefore suggest that earthworms can affect subpopulation dynamics in the soil microbiota, irrespective of the total microbiota composition. If the soil microbiota is comprised of independent microbiota components, this can contribute to our general understanding of the complexity of the soil microbiota.

Insights into soil carbon dynamics across climatic and geologic gradients from temporally-resolved radiocarbon measurements

NASA Astrophysics Data System (ADS)

van der Voort, T. S.; Hagedorn, F.; Mannu, U.; Walthert, L.; McIntyre, C.; Eglinton, T. I.

2016-12-01

Soil carbon constitutes the largest terrestrial reservoir of organic carbon, and therefore quantifying soil organic matter dynamics (carbon turnover, stocks and fluxes) across spatial gradients is essential for an understanding of the carbon cycle and the impacts of global change. In particular, links between soil carbon dynamics and different climatic and compositional factors remains poorly understood. Radiocarbon constitutes a powerful tool for unraveling soil carbon dynamics. Temporally-resolved radiocarbon measurements, which take advantage of "bomb-radiocarbon"-driven changes in atmospheric 14C, enable further constraints to be placed on C turnover times. These in turn can yield more precise flux estimates for both upper and deeper soil horizons. This project combines bulk radiocarbon measurements on a suite of soil profiles spanning strong climatic (MAT 1.3-9.2°C, MAP 600 to 2100 mm m-2y-1) and geologic gradients with a more in-depth approach for a subset of locations. For this subset, temporal and carbon-fraction specific radiocarbon data has been acquired for both topsoil and deeper soils. These well-studied sites are part of the Long-Term Forest Ecosystem Research (LWF) program of the Swiss Federal Institute for Forest, Snow and Landscape research (WSL). Resulting temporally-resolved turnover estimates are coupled to carbon stocks, fluxes across this wide range of forest ecosystems and are examined in the context of environmental drivers (temperature, precipitation, primary production and soil moisture) as well as composition (sand, silt and clay content). Statistical analysis on the region-scale - correlating radiocarbon signature with climatic variables such as temperature, precipitation, primary production and elevation - indicates that composition rather than climate is a key driver of ­­Δ14C signatures. Estimates of carbon turnover, stocks and fluxes derived from temporally-resolved measurements highlight the pivotal role of soil moisture as a key driver of soil carbon turnover and associated fluxes. Overall, this study has afforded a uniquely comprehensive dataset that improves our understanding of controls on carbon dynamics across spatial and temporal scales, as well as the pool-specific and long-term trends in soil carbon (de)stabilization and vulnerability.

Functional differentiation of macaque visual temporal cortical neurons using a parametric action space.

PubMed

Vangeneugden, Joris; Pollick, Frank; Vogels, Rufin

2009-03-01

Neurons in the rostral superior temporal sulcus (STS) are responsive to displays of body movements. We employed a parametric action space to determine how similarities among actions are represented by visual temporal neurons and how form and motion information contributes to their responses. The stimulus space consisted of a stick-plus-point-light figure performing arm actions and their blends. Multidimensional scaling showed that the responses of temporal neurons represented the ordinal similarity between these actions. Further tests distinguished neurons responding equally strongly to static presentations and to actions ("snapshot" neurons), from those responding much less strongly to static presentations, but responding well when motion was present ("motion" neurons). The "motion" neurons were predominantly found in the upper bank/fundus of the STS, and "snapshot" neurons in the lower bank of the STS and inferior temporal convexity. Most "motion" neurons showed strong response modulation during the course of an action, thus responding to action kinematics. "Motion" neurons displayed a greater average selectivity for these simple arm actions than did "snapshot" neurons. We suggest that the "motion" neurons code for visual kinematics, whereas the "snapshot" neurons code for form/posture, and that both can contribute to action recognition, in agreement with computation models of action recognition.

Long-lived groupers require structurally stable reefs in the face of repeated climate change disturbances

NASA Astrophysics Data System (ADS)

Karkarey, R.; Kelkar, N.; Lobo, A. Savio; Alcoverro, T.; Arthur, R.

2014-06-01

Benthic recovery from climate-related disturbances does not always warrant a commensurate functional recovery for reef-associated fish communities. Here, we examine the distribution of benthic groupers (family Serranidae) in coral reef communities from the Lakshadweep archipelago (Arabian Sea) in response to structural complexity and long-term habitat stability. These coral reefs that have been subject to two major El Niño Southern Oscillation-related coral bleaching events in the last decades (1998 and 2010). First, we employ a long-term (12-yr) benthic-monitoring dataset to track habitat structural stability at twelve reef sites in the archipelago. Structural stability of reefs was strongly driven by exposure to monsoon storms and depth, which made deeper and more sheltered reefs on the eastern aspect more stable than the more exposed (western) and shallower reefs. We surveyed groupers (species richness, abundance, biomass) in 60 sites across the entire archipelago, representing both exposures and depths. Sites were selected along a gradient of structural complexity from very low to high. Grouper biomass appeared to vary with habitat stability with significant differences between depth and exposure; sheltered deep reefs had a higher grouper biomass than either sheltered shallow or exposed (deep and shallow) reefs. Species richness and abundance showed similar (though not significant) trends. More interestingly, average grouper biomass increased exponentially with structural complexity, but only at the sheltered deep (high stability) sites, despite the availability of recovered structure at exposed deep and shallow sites (lower-stability sites). This trend was especially pronounced for long-lived groupers (life span >10 yrs). These results suggest that long-lived groupers may prefer temporally stable reefs, independent of the local availability of habitat structure. In reefs subject to repeated disturbances, the presence of structurally stable reefs may be critical as refuges for functionally important, long-lived species like groupers.

The effects of the mineral phase on C stabilization mechanisms and the microbial community along an eroding slope transect

NASA Astrophysics Data System (ADS)

Doetterl, S.; Opfergelt, S.; Cornelis, J.; Boeckx, P. F.; van oost, K.; Six, J.

2013-12-01

An increasing number of studies show the importance of including soil redistribution processes in understanding carbon (C) dynamics in eroding landscapes. The quality and quantity of soil organic carbon in sloping cropland differs with topographic position. These differences are commonly more visible in the subsoil, while the size and composition of topsoil C pools are similar along the hillslope. The type (plant- or microbial-derived) and quality (level of degradation) of C found in a specific soil fraction depends on the interplay between the temporal dynamic of the specific mechanism and it's strength to protect C from decomposition. Here, we present an analysis that aims to clarify the bio/geo-chemical and mineralogical components involved in stabilizing C at various depths and slope positions and how they affect the microbial community and the degradation of C. For this we analyzed soil samples from different soil depths along a slope transect applying (i) a sequential extraction of the reactive soil phase using pyrophosphate, oxalate and dithionite-citrate-bicarbonate, (ii) a semi-quantitative and qualitative analysis of the clay mineralogy, (iii) an analysis of the microbial community using amino sugars and (iv) an analysis of the level of degradation of C in different soil fractions focusing on the soil Lignin signature. The results show that the pattern of minerals and their relative importance in stabilizing C varies greatly along the transect. In the investigated soils, pyrophosphate extractable Manganese, and not Iron or Aluminum as often observed, is strongly correlated to C in the bulk soil and in the non-aggregated silt and clay fractions. This suggests a certain role of Manganese for C stabilization where physical protection is absent. In contrast, pyrophosphate extractable Iron and Aluminum components are largely abundant in water-stable soil aggregates but not correlated to C, suggesting importance of these extracts to stabilize aggregates and, hence, providing physical protection of C. Oxalate extractable amorphous and poorly crystalline minerals are correlated to C, especially for the more recalcitrant C fractions, but only at the depositional site. However, decreasing contents of oxalate extractable elements with depth indicate a temporal limitation of this stabilization mechanism and this is also supported by the results of our lignin extraction. Non-expandable clay minerals experience a relative enrichment at the depositional site while expandable clay minerals experience the same at the eroding site. These changes in clay mineralogy along the slope are partly responsible for the abundance of silt and clay associated C. The changes in soil mineralogy and micro-scale environmental conditions led to an adaptation of the microbial community in comparison to sites not affected by soil redistribution.

Stable and simple quantitative phase-contrast imaging by Fresnel biprism

NASA Astrophysics Data System (ADS)

Ebrahimi, Samira; Dashtdar, Masoomeh; Sánchez-Ortiga, Emilio; Martínez-Corral, Manuel; Javidi, Bahram

2018-03-01

Digital holographic (DH) microscopy has grown into a powerful nondestructive technique for the real-time study of living cells including dynamic membrane changes and cell fluctuations in nanometer and sub-nanometer scales. The conventional DH microscopy configurations require a separately generated coherent reference wave that results in a low phase stability and a necessity to precisely adjust the intensity ratio between two overlapping beams. In this work, we present a compact, simple, and very stable common-path DH microscope, employing a self-referencing configuration. The microscope is implemented by a diode laser as the source and a Fresnel biprism for splitting and recombining the beams simultaneously. In the overlapping area, linear interference fringes with high contrast are produced. The frequency of the interference pattern could be easily adjusted by displacement of the biprism along the optical axis without a decrease in fringe contrast. To evaluate the validity of the method, the spatial noise and temporal stability of the setup are compared with the common off-axis DH microscope based on a Mach-Zehnder interferometer. It is shown that the proposed technique has low mechanical noise as well as superb temporal stability with sub-nanometer precision without any external vibration isolation. The higher temporal stability improves the capabilities of the microscope for studying micro-object fluctuations, particularly in the case of biological specimens. Experimental results are presented using red blood cells and silica microspheres to demonstrate the system performance.

Some theoretical aspects of boundary layer stability theory

NASA Technical Reports Server (NTRS)

Hall, Philip

1990-01-01

Increased understanding in recent years of boundary layer transition has been made possible by the development of strongly nonlinear stability theories. After some twenty or so years when nonlinear stability theory was restricted to the application of the Stuart-Watson method (or less formal amplitude expansion procedures), there now exist strongly nonlinear theories which can describe processes which have an 0(1) effect on the basic state. These strongly nonlinear theories and their possible role in pushing theoretical understanding of transition ever further into the nonlinear regime are discussed.

The Intertemporal Stability of Teacher Effect Estimates. Working Paper 2008-22

ERIC Educational Resources Information Center

McCaffrey, Daniel F.; Sass, Tim R.; Lockwood, J.R.

2008-01-01

Recently, a number of school districts have begun using measures of teachers' contributions to student test scores or teacher "value added" to determine salaries and other monetary rewards. In this paper we investigate the precision of value-added measures by analyzing their inter-temporal stability. We find that these measures of…

The dynamics of gas bubbles in conduits of vascular plants and implications for embolism repair.

PubMed

Konrad, W; Roth-Nebelsick, A

2003-09-07

Pressure-induced tensions in the xylem, the water conducting tissue of vascular plants, can lead to embolism in the water-conducting cells. The details and mechanisms of embolism repair in vascular plants are still not well understood. In particular, experimental results which indicate that embolism repair may occur during xylem tension cause great problems with respect to current paradigms of plant water transport. The present paper deals with a theoretical analysis of interfacial effects at the pits (pores in the conduit walls), because it was suggested that gas-water interfaces at the pit pores may be involved in the repair process by hydraulically isolating the embolized conduit. The temporal behaviour of bubbles at the pit pores was especially studied since the question of whether these pit bubbles are able to persist is of crucial importance for the suggested mechanism to work. The results indicate that (1) the physical preconditions which are necessary for the suggested mechanism appear to be satisfied, (2) pit bubbles can achieve temporal stability and therefore persist and (3) dissolving of bubbles in the conduit lumen may lead to the final breakdown of the hydraulic isolation. The whole process is, however, complex and strongly dependent on the detailed anatomy of the pit and the contact angle.

Genetic evolution, plasticity, and bet-hedging as adaptive responses to temporally autocorrelated fluctuating selection: A quantitative genetic model.

PubMed

Tufto, Jarle

2015-08-01

Adaptive responses to autocorrelated environmental fluctuations through evolution in mean reaction norm elevation and slope and an independent component of the phenotypic variance are analyzed using a quantitative genetic model. Analytic approximations expressing the mutual dependencies between all three response modes are derived and solved for the joint evolutionary outcome. Both genetic evolution in reaction norm elevation and plasticity are favored by slow temporal fluctuations, with plasticity, in the absence of microenvironmental variability, being the dominant evolutionary outcome for reasonable parameter values. For fast fluctuations, tracking of the optimal phenotype through genetic evolution and plasticity is limited. If residual fluctuations in the optimal phenotype are large and stabilizing selection is strong, selection then acts to increase the phenotypic variance (bet-hedging adaptive). Otherwise, canalizing selection occurs. If the phenotypic variance increases with plasticity through the effect of microenvironmental variability, this shifts the joint evolutionary balance away from plasticity in favor of genetic evolution. If microenvironmental deviations experienced by each individual at the time of development and selection are correlated, however, more plasticity evolves. The adaptive significance of evolutionary fluctuations in plasticity and the phenotypic variance, transient evolution, and the validity of the analytic approximations are investigated using simulations. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

Electromagnetic eigenmodes of collisional and collisionless plasmas and their stability to stimulated Brillouin scattering

NASA Astrophysics Data System (ADS)

Pathak, Vishwa Bandhu; Tripathi, V. K.

2007-02-01

Nonlinear electromagnetic eigenmodes of collisional and collisionless plasmas, when the temporal extent of the modes is longer than the ambipolar diffusion time, have been investigated. The nonlinearity in a collisionless plasma arises through ponderomotive force, whereas in collisional plasmas Ohmic nonlinearity prevails. The mode structure in both cases, representing a balance between the nonlinearity-induced self-convergence and diffraction-induced divergence, closely resembles Gaussian form. The spot size of the mode decreases with the increasing axial amplitude of the laser, attains a minimum, and then rises very gradually. The modes are susceptible to stimulated Brillouin backscattering. The growth rate of the Brillouin process initially increases with mode amplitude, attains a maximum, and then decreases. The reduction in the growth rate is caused by strong electron evacuation from the axial region by the ponderomotive force and thermal pressure gradient force created by nonuniform Ohmic heating.

Clk post-transcriptional control denoises circadian transcription both temporally and spatially.

PubMed

Lerner, Immanuel; Bartok, Osnat; Wolfson, Victoria; Menet, Jerome S; Weissbein, Uri; Afik, Shaked; Haimovich, Daniel; Gafni, Chen; Friedman, Nir; Rosbash, Michael; Kadener, Sebastian

2015-05-08

The transcription factor CLOCK (CLK) is essential for the development and maintenance of circadian rhythms in Drosophila. However, little is known about how CLK levels are controlled. Here we show that Clk mRNA is strongly regulated post-transcriptionally through its 3' UTR. Flies expressing Clk transgenes without normal 3' UTR exhibit variable CLK-driven transcription and circadian behaviour as well as ectopic expression of CLK-target genes in the brain. In these flies, the number of the key circadian neurons differs stochastically between individuals and within the two hemispheres of the same brain. Moreover, flies carrying Clk transgenes with deletions in the binding sites for the miRNA bantam have stochastic number of pacemaker neurons, suggesting that this miRNA mediates the deterministic expression of CLK. Overall our results demonstrate a key role of Clk post-transcriptional control in stabilizing circadian transcription, which is essential for proper development and maintenance of circadian rhythms in Drosophila.

Reproductive niche conservatism in the isolated New Zealand flora over 23 million years.

PubMed

Conran, John G; Lee, William G; Lee, Daphne E; Bannister, Jennifer M; Kaulfuss, Uwe

2014-10-01

The temporal stability of plant reproductive features on islands has rarely been tested. Using flowers, fruits/cones and seeds from a well-dated (23 Ma) Miocene Lagerstätte in New Zealand, we show that across 23 families and 30 genera of forest angiosperms and conifers, reproductive features have remained constant for more than 20 Myr. Insect-, wind- and bird-pollinated flowers and wind- and bird-dispersed diaspores all indicate remarkable reproductive niche conservatism, despite widespread environmental and biotic change. In the past 10 Myr, declining temperatures and the absence of low-latitude refugia caused regional extinction of thermophiles, while orogenic processes steepened temperature, precipitation and nutrient gradients, limiting forest niches. Despite these changes, the palaeontological record provides empirical support for evidence from phylogeographical studies of strong niche conservatism within lineages and biomes. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Body-force-driven multiplicity and stability of combined free and forced convection in rotating curved ducts: Coriolis force

NASA Astrophysics Data System (ADS)

Yang, T.; Wang, L.

A numerical study is made on the fully developed bifurcation structure and stability of forced convection in a rotating curved duct of square cross-section. Solution structure is determined as variation of a parameter that indicates the effect of rotation (Coriolis-force-driven multiplicity). Three solutions for the flows in a stationary curved duct obtained in the work of Yang and Wang [1] are used as initial solutions of continuation calculations to unfold the solution branches. Twenty-one solution branches are found comparing with five obtained by Selmi and Nandakumar [2]. Dynamic responses of the multiple solutions to finite random disturbances are examined by the direct transient computation. Results show that characteristics of physically realizable fully developed flows changes significantly with variation of effect of rotation. Fourteen sub-ranges are identified according to characteristics of physically realizable solutions. As rotation effect changes, possible physically realizable fully-developed flows can be stable steady 2-cell state, stable multi-cell state, temporal periodic oscillation between symmetric/asymmetric 2-cell/4-cell flows, temporal oscillation with intermittency, temporal chaotic oscillation and temporal oscillation with pseudo intermittency. Among these possible physically realizable fully developed flows, stable multi-cell state and stable steady 2-cell state exist as dual stable. And oscillation with pseudo intermittency is a new phenomenon. In addition to the temporal oscillation with intermittency, sudden shift from stationary stable solution to temporal chaotic oscillation is identified to be another way of onset of chaos.

Validation of prediction models: examining temporal and geographic stability of baseline risk and estimated covariate effects

PubMed Central

Austin, Peter C.; van Klaveren, David; Vergouwe, Yvonne; Nieboer, Daan; Lee, Douglas S.; Steyerberg, Ewout W.

2018-01-01

Background Stability in baseline risk and estimated predictor effects both geographically and temporally is a desirable property of clinical prediction models. However, this issue has received little attention in the methodological literature. Our objective was to examine methods for assessing temporal and geographic heterogeneity in baseline risk and predictor effects in prediction models. Methods We studied 14,857 patients hospitalized with heart failure at 90 hospitals in Ontario, Canada, in two time periods. We focussed on geographic and temporal variation in baseline risk (intercept) and predictor effects (regression coefficients) of the EFFECT-HF mortality model for predicting 1-year mortality in patients hospitalized for heart failure. We used random effects logistic regression models for the 14,857 patients. Results The baseline risk of mortality displayed moderate geographic variation, with the hospital-specific probability of 1-year mortality for a reference patient lying between 0.168 and 0.290 for 95% of hospitals. Furthermore, the odds of death were 11% lower in the second period than in the first period. However, we found minimal geographic or temporal variation in predictor effects. Among 11 tests of differences in time for predictor variables, only one had a modestly significant P value (0.03). Conclusions This study illustrates how temporal and geographic heterogeneity of prediction models can be assessed in settings with a large sample of patients from a large number of centers at different time periods. PMID:29350215

Temporal and spatial influences incur reconfiguration of Arctic heathland soil bacterial community structure.

PubMed

Hill, Richard; Saetnan, Eli R; Scullion, John; Gwynn-Jones, Dylan; Ostle, Nick; Edwards, Arwyn

2016-06-01

Microbial responses to Arctic climate change could radically alter the stability of major stores of soil carbon. However, the sensitivity of plot-scale experiments simulating climate change effects on Arctic heathland soils to potential confounding effects of spatial and temporal changes in soil microbial communities is unknown. Here, the variation in heathland soil bacterial communities at two survey sites in Sweden between spring and summer 2013 and at scales between 0-1 m and, 1-100 m and between sites (> 100 m) were investigated in parallel using 16S rRNA gene T-RFLP and amplicon sequencing. T-RFLP did not reveal spatial structuring of communities at scales < 100 m in any site or season. However, temporal changes were striking. Amplicon sequencing corroborated shifts from r- to K-selected taxon-dominated communities, influencing in silico predictions of functional potential. Network analyses reveal temporal keystone taxa, with a spring betaproteobacterial sub-network centred upon a Burkholderia operational taxonomic unit (OTU) and a reconfiguration to a summer sub-network centred upon an alphaproteobacterial OTU. Although spatial structuring effects may not confound comparison between plot-scale treatments, temporal change is a significant influence. Moreover, the prominence of two temporally exclusive keystone taxa suggests that the stability of Arctic heathland soil bacterial communities could be disproportionally influenced by seasonal perturbations affecting individual taxa. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Influences of spatial and temporal variation on fish-habitat relationships defined by regression quantiles

USGS Publications Warehouse

Dunham, J.B.; Cade, B.S.; Terrell, J.W.

2002-01-01

We used regression quantiles to model potentially limiting relationships between the standing crop of cutthroat trout Oncorhynchus clarki and measures of stream channel morphology. Regression quantile models indicated that variation in fish density was inversely related to the width:depth ratio of streams but not to stream width or depth alone. The spatial and temporal stability of model predictions were examined across years and streams, respectively. Variation in fish density with width:depth ratio (10th-90th regression quantiles) modeled for streams sampled in 1993-1997 predicted the variation observed in 1998-1999, indicating similar habitat relationships across years. Both linear and nonlinear models described the limiting relationships well, the latter performing slightly better. Although estimated relationships were transferable in time, results were strongly dependent on the influence of spatial variation in fish density among streams. Density changes with width:depth ratio in a single stream were responsible for the significant (P < 0.10) negative slopes estimated for the higher quantiles (>80th). This suggests that stream-scale factors other than width:depth ratio play a more direct role in determining population density. Much of the variation in densities of cutthroat trout among streams was attributed to the occurrence of nonnative brook trout Salvelinus fontinalis (a possible competitor) or connectivity to migratory habitats. Regression quantiles can be useful for estimating the effects of limiting factors when ecological responses are highly variable, but our results indicate that spatiotemporal variability in the data should be explicitly considered. In this study, data from individual streams and stream-specific characteristics (e.g., the occurrence of nonnative species and habitat connectivity) strongly affected our interpretation of the relationship between width:depth ratio and fish density.

Synaptic consolidation as a temporally variable process: Uncovering the parameters modulating its time-course.

PubMed

Casagrande, Mirelle A; Haubrich, Josué; Pedraza, Lizeth K; Popik, Bruno; Quillfeldt, Jorge A; de Oliveira Alvares, Lucas

2018-04-01

Memories are not instantly created in the brain, requiring a gradual stabilization process called consolidation to be stored and persist in a long-lasting manner. However, little is known whether this time-dependent process is dynamic or static, and the factors that might modulate it. Here, we hypothesized that the time-course of consolidation could be affected by specific learning parameters, changing the time window where memory is susceptible to retroactive interference. In the rodent contextual fear conditioning paradigm, we compared weak and strong training protocols and found that in the latter memory is susceptible to post-training hippocampal inactivation for a shorter period of time. The accelerated consolidation process triggered by the strong training was mediated by glucocorticoids, since this effect was blocked by pre-training administration of metyrapone. In addition, we found that pre-exposure to the training context also accelerates fear memory consolidation. Hence, our results demonstrate that the time window in which memory is susceptible to post-training interferences varies depending on fear conditioning intensity and contextual familiarity. We propose that the time-course of memory consolidation is dynamic, being directly affected by attributes of the learning experiences. Copyright © 2018 Elsevier Inc. All rights reserved.

Spatio-Temporal Evolution and Scaling Properties of Human Settlements (Invited)

NASA Astrophysics Data System (ADS)

Small, C.; Milesi, C.; Elvidge, C.; Baugh, K.; Henebry, G. M.; Nghiem, S. V.

2013-12-01

Growth and evolution of cities and smaller settlements is usually studied in the context of population and other socioeconomic variables. While this is logical in the sense that settlements are groups of humans engaged in socioeconomic processes, our means of collecting information about spatio-temporal distributions of population and socioeconomic variables often lack the spatial and temporal resolution to represent the processes at scales which they are known to occur. Furthermore, metrics and definitions often vary with country and through time. However, remote sensing provides globally consistent, synoptic observations of several proxies for human settlement at spatial and temporal resolutions sufficient to represent the evolution of settlements over the past 40 years. We use several independent but complementary proxies for anthropogenic land cover to quantify spatio-temporal (ST) evolution and scaling properties of human settlements globally. In this study we begin by comparing land cover and night lights in 8 diverse settings - each spanning gradients of population density and degree of land surface modification. Stable anthropogenic night light is derived from multi-temporal composites of emitted luminance measured by the VIIRS and DMSP-OLS sensors. Land cover is represented as mixtures of sub-pixel fractions of rock, soil and impervious Substrates, Vegetation and Dark surfaces (shadow, water and absorptive materials) estimated from Landsat imagery with > 94% accuracy. Multi-season stability and variability of land cover fractions effectively distinguishes between spectrally similar land covers that corrupt thematic classifications based on single images. We find that temporal stability of impervious substrates combined with persistent shadow cast between buildings results in temporally stable aggregate reflectance across seasons at the 30 m scale of a Landsat pixel. Comparison of night light brightness with land cover composition, stability and variability yields several consistent relationships that persist across a variety of settlement types and physical environments. We use the multiple threshold method of Small et al (2011) to represent a continuum of settlement density by segmenting both night light brightness and multi-season land cover characteristics. Rank-size distributions of spatially contiguous segments quantify scaling and connectivity of land cover. Spatial and temporal evolution of rank-size distributions is consistent with power laws as suggested by Zipf's Law for city size based on population. However, unlike Zipf's Law, the observed distributions persist to global scales in which the larger agglomerations are much larger than individual cities. The scaling relations observed extend from the scale of cities and smaller settlements up to vast spatial networks of interconnected settlements.

Temporal and spatial stability of red-tailed hawk territories in the Luquillo Experimental Forest, Puerto Rico

USGS Publications Warehouse

Boal, C.W.; Snyder, H.A.; Bibles, Brent D.; Estabrook, T.S.

2003-01-01

We mapped Red-tailed Hawk (Buteo jamaicensis) territories in the Luquillo Experimental Forest (LEF) of Puerto Rico in 1998. We combined our 1998 data with that collected during previous studies of Red-tailed Hawks in the LEF to examine population numbers and spatial stability of territorial boundaries over a 26-yr period. We also investigated potential relationships between Red-tailed Hawk territory sizes and topographic and climatic factors. Mean size of 16 defended territories during 1998 was 124.3 ?? 12.0 ha, which was not significantly different from our calculations of mean territory sizes derived from data collected in 1974 and 1984. Aspect and slope influenced territory size with the smallest territories having high slope and easterly aspects. Territory size was small compared to that reported for other parts of the species' range. In addition, there was remarkably little temporal change in the spatial distribution, area, and boundaries of Red-tailed Hawk territories among the study periods. Further, there was substantial boundary overlap (21-27%) between defended territories among the different study periods. The temporal stability of the spatial distribution of Red-tailed Hawk territories in the study area leads us to believe the area might be at or near saturation.

Algorithm for Stabilizing a POD-Based Dynamical System

NASA Technical Reports Server (NTRS)

Kalb, Virginia L.

2010-01-01

This algorithm provides a new way to improve the accuracy and asymptotic behavior of a low-dimensional system based on the proper orthogonal decomposition (POD). Given a data set representing the evolution of a system of partial differential equations (PDEs), such as the Navier-Stokes equations for incompressible flow, one may obtain a low-dimensional model in the form of ordinary differential equations (ODEs) that should model the dynamics of the flow. Temporal sampling of the direct numerical simulation of the PDEs produces a spatial time series. The POD extracts the temporal and spatial eigenfunctions of this data set. Truncated to retain only the most energetic modes followed by Galerkin projection of these modes onto the PDEs obtains a dynamical system of ordinary differential equations for the time-dependent behavior of the flow. In practice, the steps leading to this system of ODEs entail numerically computing first-order derivatives of the mean data field and the eigenfunctions, and the computation of many inner products. This is far from a perfect process, and often results in the lack of long-term stability of the system and incorrect asymptotic behavior of the model. This algorithm describes a new stabilization method that utilizes the temporal eigenfunctions to derive correction terms for the coefficients of the dynamical system to significantly reduce these errors.

Mode instability in one-dimensional anharmonic lattices: Variational equation approach

NASA Astrophysics Data System (ADS)

Yoshimura, K.

1999-03-01

The stability of normal mode oscillations has been studied in detail under the single-mode excitation condition for the Fermi-Pasta-Ulam-β lattice. Numerical experiments indicate that the mode stability depends strongly on k/N, where k is the wave number of the initially excited mode and N is the number of degrees of freedom in the system. It has been found that this feature does not change when N increases. We propose an average variational equation - approximate version of the variational equation - as a theoretical tool to facilitate a linear stability analysis. It is shown that this strong k/N dependence of the mode stability can be explained from the view point of the linear stability of the relevant orbits. We introduce a low-dimensional approximation of the average variational equation, which approximately describes the time evolution of variations in four normal mode amplitudes. The linear stability analysis based on this four-mode approximation demonstrates that the parametric instability mechanism plays a crucial role in the strong k/N dependence of the mode stability.

Age-Related Neural Oscillation Patterns During the Processing of Temporally Manipulated Speech.

PubMed

Rufener, Katharina S; Oechslin, Mathias S; Wöstmann, Malte; Dellwo, Volker; Meyer, Martin

2016-05-01

This EEG-study aims to investigate age-related differences in the neural oscillation patterns during the processing of temporally modulated speech. Viewing from a lifespan perspective, we recorded the electroencephalogram (EEG) data of three age samples: young adults, middle-aged adults and older adults. Stimuli consisted of temporally degraded sentences in Swedish-a language unfamiliar to all participants. We found age-related differences in phonetic pattern matching when participants were presented with envelope-degraded sentences, whereas no such age-effect was observed in the processing of fine-structure-degraded sentences. Irrespective of age, during speech processing the EEG data revealed a relationship between envelope information and the theta band (4-8 Hz) activity. Additionally, an association between fine-structure information and the gamma band (30-48 Hz) activity was found. No interaction, however, was found between acoustic manipulation of stimuli and age. Importantly, our main finding was paralleled by an overall enhanced power in older adults in high frequencies (gamma: 30-48 Hz). This occurred irrespective of condition. For the most part, this result is in line with the Asymmetric Sampling in Time framework (Poeppel in Speech Commun 41:245-255, 2003), which assumes an isomorphic correspondence between frequency modulations in neurophysiological patterns and acoustic oscillations in spoken language. We conclude that speech-specific neural networks show strong stability over adulthood, despite initial processes of cortical degeneration indicated by enhanced gamma power. The results of our study therefore confirm the concept that sensory and cognitive processes undergo multidirectional trajectories within the context of healthy aging.

Carrier-envelope phase control of femtosecond mode-locked lasers and direct optical frequency synthesis

PubMed

Jones; Diddams; Ranka; Stentz; Windeler; Hall; Cundiff

2000-04-28

We stabilized the carrier-envelope phase of the pulses emitted by a femtosecond mode-locked laser by using the powerful tools of frequency-domain laser stabilization. We confirmed control of the pulse-to-pulse carrier-envelope phase using temporal cross correlation. This phase stabilization locks the absolute frequencies emitted by the laser, which we used to perform absolute optical frequency measurements that were directly referenced to a stable microwave clock.

Unreliability and error in the military's "gold standard" measure of sexual harassment by education and gender.

PubMed

Murdoch, Maureen; Pryor, John B; Griffin, Joan M; Ripley, Diane Cowper; Gackstetter, Gary D; Polusny, Melissa A; Hodges, James S

2011-01-01

The Department of Defense's "gold standard" sexual harassment measure, the Sexual Harassment Core Measure (SHCore), is based on an earlier measure that was developed primarily in college women. Furthermore, the SHCore requires a reading grade level of 9.1. This may be higher than some troops' reading abilities and could generate unreliable estimates of their sexual harassment experiences. Results from 108 male and 96 female soldiers showed that the SHCore's temporal stability and alternate-forms reliability was significantly worse (a) in soldiers without college experience compared to soldiers with college experience and (b) in men compared to women. For men without college experience, almost 80% of the temporal variance in SHCore scores was attributable to error. A plain language version of the SHCore had mixed effects on temporal stability depending on education and gender. The SHCore may be particularly ill suited for evaluating population trends of sexual harassment in military men without college experience.

Testing the limits of temporal stability: Willingness to pay values among Grand Canyon whitewater boaters across decades

USGS Publications Warehouse

Neher, Chris J.; Duffield, John; Bair, Lucas S.; Patterson, David A.; Neher, Katherine

2017-01-01

We directly compare trip willingness to pay (WTP) values between 1985 and 2015 stated preference surveys of private party Grand Canyon boaters using identically designed valuation methods. The temporal gap of 30 years between these two studies is well beyond that of any tests of WTP temporal stability in the literature. Comparisons were made of mean WTP estimates for four hypothetical Colorado River flow level scenarios. WTP values from the 1985 survey were adjusted to 2015 levels using the consumer price index. Mean WTP precision was estimated through simulation. No statistically significant differences were detected between the adjusted Bishop et al. (1987) and the current study mean WTP estimates. Examination of pooled models of the data from the studies suggest that while the estimated WTP values are stable over time, the underlying valuation functions may not be, particularly when the data and models are corrected to account for differing bid structures and possible panel effects.

Composition and temporal stability of turf sediments on inner-shelf coral reefs.

PubMed

Gordon, Sophie E; Goatley, Christopher H R; Bellwood, David R

2016-10-15

Elevated sediment loads within the epilithic algal matrix (EAM) of coral reefs can increase coral mortality and inhibit herbivory. Yet the composition, distribution and temporal variability of EAM sediment loads are poorly known, especially on inshore reefs. This study quantified EAM sediment loads (including organic particulates) and algal length across the reef profile of two bays at Orpheus Island (inner-shelf Great Barrier Reef) over a six month period. We examined the total sediment mass, organic load, carbonate and silicate content, and the particle sizes of EAM sediments. Throughout the study period, all EAM sediment variables exhibited marked variation among reef zones. However, EAM sediment loads and algal length were consistent between bays and over time, despite major seasonal variation in climate including a severe tropical cyclone. This study provides a comprehensive description of EAM sediments on inshore reefs and highlights the exceptional temporal stability of EAM sediments on coral reefs. Copyright © 2016 Elsevier Ltd. All rights reserved.

Testing the Limits of Temporal Stability: Willingness to Pay Values among Grand Canyon Whitewater Boaters Across Decades

NASA Astrophysics Data System (ADS)

Neher, Chris; Duffield, John; Bair, Lucas; Patterson, David; Neher, Katherine

2017-12-01

We directly compare trip willingness to pay (WTP) values between 1985 and 2015 stated preference surveys of private party Grand Canyon boaters using identically designed valuation methods. The temporal gap of 30 years between these two studies is well beyond that of any tests of WTP temporal stability in the literature. Comparisons were made of mean WTP estimates for four hypothetical Colorado River flow level scenarios. WTP values from the 1985 survey were adjusted to 2015 levels using the consumer price index. Mean WTP precision was estimated through simulation. No statistically significant differences were detected between the adjusted Bishop et al. (1987) and the current study mean WTP estimates. Examination of pooled models of the data from the studies suggest that while the estimated WTP values are stable over time, the underlying valuation functions may not be, particularly when the data and models are corrected to account for differing bid structures and possible panel effects.

Discordant Temporal Turnovers of Sediment Bacterial and Eukaryotic Communities in Response to Dredging: Nonresilience and Functional Changes.

PubMed

Zhang, Na; Xiao, Xian; Pei, Meng; Liu, Xiang; Liang, Yuting

2017-01-01

To study the stability and succession of sediment microbial and macrobenthic communities in response to anthropogenic disturbance, a time-series sampling was conducted before, during, and 1 year after dredging in the Guan River in Changzhou, China, which was performed with cutter suction dredgers from 10 April to 20 May 2014. The microbial communities were analyzed by sequencing bacterial 16S rRNA and eukaryotic 18S rRNA gene amplicons with Illumina MiSeq, and the macrobenthic community was identified using a morphological approach simultaneously. The results indicated that dredging disturbance significantly altered the composition and structures of sediment communities. The succession rates of communities were estimated by comparing the slopes of time-decay relationships. The temporal turnover of microeukaryotes (w = 0.3251, P < 0.001 [where w is a measure of the rate of log(species turnover) across log(time)]) was the highest, followed by that of bacteria (w = 0.2450, P < 0.001), and then macrobenthos (w = 0.1273, P < 0.001). During dredging, the alpha diversities of both bacterial and microeukaryotic communities were more resistant, but their beta diversities were less resistant than that of macrobenthos. After recovery for 1 year, all three sediment communities were not resilient and had reached an alternative state. The alterations in sediment community structure and stability resulted in functional changes in nitrogen and carbon cycling in sediments. Sediment pH, dissolved oxygen, redox potential, and temperature were the most important factors influencing the stability of sediment communities and ecosystem multifunctionality. This study suggests that discordant temporal turnovers and nonresilience of sediment communities under dredging resulted in functional changes, which are important for predicting sediment ecosystem functions under anthropogenic disturbances. Understanding the temporal turnover and stability of biotic communities is crucial for predicting the responses of sediment ecosystems to dredging disturbance. Most studies to date focused on the bacterial or macrobenthic community, only at two discontinuous time points, before and after dredging, and hence, it was difficult to analyze the community succession. This study first compared the stabilities and temporal changes of sediment bacterial, microeukaryotic, and macrobenthic communities at a continuous time course. The results showed that discordant responses of the three communities are mainly related to their different biological inherent attributes, and sensitivities to sediment geochemical variables change with dredging, resulting in changes in sediment ecosystem multifunctionality. Copyright © 2016 American Society for Microbiology.

Discordant Temporal Turnovers of Sediment Bacterial and Eukaryotic Communities in Response to Dredging: Nonresilience and Functional Changes

PubMed Central

Zhang, Na; Xiao, Xian; Pei, Meng; Liu, Xiang

2016-01-01

ABSTRACT To study the stability and succession of sediment microbial and macrobenthic communities in response to anthropogenic disturbance, a time-series sampling was conducted before, during, and 1 year after dredging in the Guan River in Changzhou, China, which was performed with cutter suction dredgers from 10 April to 20 May 2014. The microbial communities were analyzed by sequencing bacterial 16S rRNA and eukaryotic 18S rRNA gene amplicons with Illumina MiSeq, and the macrobenthic community was identified using a morphological approach simultaneously. The results indicated that dredging disturbance significantly altered the composition and structures of sediment communities. The succession rates of communities were estimated by comparing the slopes of time-decay relationships. The temporal turnover of microeukaryotes (w = 0.3251, P < 0.001 [where w is a measure of the rate of log(species turnover) across log(time)]) was the highest, followed by that of bacteria (w = 0.2450, P < 0.001), and then macrobenthos (w = 0.1273, P < 0.001). During dredging, the alpha diversities of both bacterial and microeukaryotic communities were more resistant, but their beta diversities were less resistant than that of macrobenthos. After recovery for 1 year, all three sediment communities were not resilient and had reached an alternative state. The alterations in sediment community structure and stability resulted in functional changes in nitrogen and carbon cycling in sediments. Sediment pH, dissolved oxygen, redox potential, and temperature were the most important factors influencing the stability of sediment communities and ecosystem multifunctionality. This study suggests that discordant temporal turnovers and nonresilience of sediment communities under dredging resulted in functional changes, which are important for predicting sediment ecosystem functions under anthropogenic disturbances. IMPORTANCE Understanding the temporal turnover and stability of biotic communities is crucial for predicting the responses of sediment ecosystems to dredging disturbance. Most studies to date focused on the bacterial or macrobenthic community, only at two discontinuous time points, before and after dredging, and hence, it was difficult to analyze the community succession. This study first compared the stabilities and temporal changes of sediment bacterial, microeukaryotic, and macrobenthic communities at a continuous time course. The results showed that discordant responses of the three communities are mainly related to their different biological inherent attributes, and sensitivities to sediment geochemical variables change with dredging, resulting in changes in sediment ecosystem multifunctionality. PMID:27793828

Continuity of character neurosis from childhood to adulthood. A prospective longitudinal study.

PubMed

Parnas, J; Teasdale, T W; Schulsinger, H

1982-12-01

In a prospective longitudinal study, stability of personality traits was examined between the age of 15 and the age of 25. Scales, derived from an Adjective Check List, intending to predict obsessive-compulsive character neurosis, anti-aggressive character neurosis and non-neurotic personality have been utilized. Temporal stability of the examined personality traits was demonstrated.

Evaluating a process-based model for use in streambank stabilization and stream restoration: insights on the bank stability and toe erosion model (BSTEM)

USDA-ARS?s Scientific Manuscript database

Streambank retreat is a complex cyclical process involving subaerial processes, fluvial erosion, seepage erosion, and geotechnical failures and is driven by several soil properties that themselves are temporally and spatially variable. Therefore, it can be extremely challenging to predict and model ...

In silico selection of expression reference genes with demonstrated stability in barley among a diverse set of tissues and cultivars

USDA-ARS?s Scientific Manuscript database

Premise of the study: Reference genes are selected based on the assumption of temporal and spatial expression stability and on their widespread use in model species. They are often used in new target species without validation, presumed as stable. For barley, reference gene validation is lacking, bu...

Pulse shaping of on-chip microresonator frequency combs: investigation of temporal coherence

NASA Astrophysics Data System (ADS)

Ferdous, F.; Miao, H.; Leaird, D. E.; Srinivasan, K.; Chen, L.; Aksyuk, V.; Weiner, A. M.

2013-03-01

We use pulse shaping to investigate the temporal coherence of frequency combs generated in microresonators pumped by a strong CW laser. We observe that different groups of comb lines have different mutual coherence.

Species dispersal rates alter diversity and ecosystem stability in pond metacommunities.

PubMed

Howeth, Jennifer G; Leibold, Mathew A

2010-09-01

Metacommunity theory suggests that relationships between diversity and ecosystem stability can be determined by the rate of species dispersal among local communities. The predicted relationships, however, may depend upon the relative strength of local environmental processes and disturbance. Here we evaluate the role of dispersal frequency and local predation perturbations in affecting patterns of diversity and stability in pond plankton metacommunities. Pond metacommunities were composed of three mesocosm communities: one of the three communities maintained constant "press" predation from a selective predator, bluegill sunfish (Lepomis macrochirus); the second community maintained "press" conditions without predation; and the third community experienced recurrent "pulsed" predation from bluegill sunfish. The triads of pond communities were connected at either no, low (0.7%/d), or high (20%/d) planktonic dispersal. Richness and composition of zooplankton and stability of plankton biomass and ecosystem productivity were measured at local and regional spatial scales. Dispersal significantly affected diversity such that local and regional biotas at the low dispersal rate maintained the greatest number of species. The unimodal local dispersal-diversity relationship was predator-dependent, however, as selective press predation excluded species regardless of dispersal. Further, there was no effect of dispersal on beta diversity because predation generated local conditions that selected for distinct community assemblages. Spatial and temporal ecosystem stability responded to dispersal frequency but not predation. Low dispersal destabilized the spatial stability of producer biomass but stabilized temporal ecosystem productivity. The results indicate that selective predation can prevent species augmentation from mass effects but has no apparent influence on stability. Dispersal rates, in contrast, can have significant effects on both species diversity and ecosystem stability at multiple spatial scales in metacommunities.

Relations between productivity, climate, and normalized difference vegetation index in the central Great Plains

NASA Astrophysics Data System (ADS)

Wang, Jue

Understanding the influences of climate on productivity remains a major challenge in landscape ecology. Satellite remote sensing of normalized difference vegetation index (NDVI) provides a useful tool to study landscape patterns, based on generalization of local measurements, and to examine relations between climate and variation in productivity. This dissertation examines temporal and spatial relations between NDVI, productivity, and climatic factors over the course of nine years in the central Great Plains. Two general findings emerge: (1) integrated NDVI is a reliable measure of production, as validated with ground-based productivity measurements; and (2) precipitation is the primary factor that determines spatial and temporal patterns of NDVI. NDVI, integrated over appropriate time intervals, is strongly correlated with ground productivity measurements in forests, grasslands, and croplands. Most tree productivity measurements (tree ring size, tree diameter growth, and seed production) are strongly correlated with NDVI integrated for a period during the early growing season; foliage production is most strongly correlated with NDVI integrated over the entire growing season; and tree height growth corresponds with NDVI integrate during the previous growing season. Similarly, productivity measurements for herbaceous plants (grassland biomass and crop yield) are strongly correlated with NDVI. Within the growing season, the temporal pattern of grassland biomass production covaries with NDVI, with a four-week lag time. Across years, grassland biomass production covaries with NDVI integrated from part to all of the current growing season. Corn and wheat yield are most strongly related to NDVI integrated from late June to early August and from late April to mid-May, respectively. Precipitation strongly influences both temporal and spatial patterns of NDVI, while temperature influences NDVI only during the early and late growing season. In terms of temporal patterns, NDVI integrated over the growing season is strongly correlated with precipitation received during the current growing season plus the seven preceding months (fifteen month period); NDVI within the growing season responds to changes in precipitation with a four to eight week lag time; and major precipitation events lead to changes in NDVI with a two to four week lag time. Temperature has a positive correlation with NDVI during the early and late growing season, and a weak negative correlation during the middle of the growing season. In terms of spatial patterns, average precipitation is a strong predictor of the major east-west gradient of NDVI. Deviation from average precipitation explains most of the year-to-year variation in spatial patterns. NDVI and precipitation deviations from average covary (both positive or both negative) for 60--95% of the total land area in Kansas. Minimum and average temperatures are positively correlated with NDVI, but temperature deviation from average is generally not correlated with NDVI deviation from average. The strong relationships between NDVI and productivity, and between precipitation and NDVI, along with detailed analysis of the temporal and spatial patterns for our study region, provides the basis for prediction of productivity at landscape scales under different climate regimes.

Power law analysis of the human microbiome.

PubMed

Ma, Zhanshan Sam

2015-11-01

Taylor's (1961, Nature, 189:732) power law, a power function (V = am(b) ) describing the scaling relationship between the mean and variance of population abundances of organisms, has been found to govern the population abundance distributions of single species in both space and time in macroecology. It is regarded as one of few generalities in ecology, and its parameter b has been widely applied to characterize spatial aggregation (i.e. heterogeneity) and temporal stability of single-species populations. Here, we test its applicability to bacterial populations in the human microbiome using extensive data sets generated by the US-NIH Human Microbiome Project (HMP). We further propose extending Taylor's power law from the population to the community level, and accordingly introduce four types of power-law extensions (PLEs): type I PLE for community spatial aggregation (heterogeneity), type II PLE for community temporal aggregation (stability), type III PLE for mixed-species population spatial aggregation (heterogeneity) and type IV PLE for mixed-species population temporal aggregation (stability). Our results show that fittings to the four PLEs with HMP data were statistically extremely significant and their parameters are ecologically sound, hence confirming the validity of the power law at both the population and community levels. These findings not only provide a powerful tool to characterize the aggregations of population and community in both time and space, offering important insights into community heterogeneity in space and/or stability in time, but also underscore the three general properties of power laws (scale invariance, no average and universality) and their specific manifestations in our four PLEs. © 2015 John Wiley & Sons Ltd.

Pheromone responsiveness threshold depends on temporal integration by antennal lobe projection neurons

PubMed Central

Tabuchi, Masashi; Sakurai, Takeshi; Mitsuno, Hidefumi; Namiki, Shigehiro; Minegishi, Ryo; Shiotsuki, Takahiro; Uchino, Keiro; Sezutsu, Hideki; Tamura, Toshiki; Haupt, Stephan Shuichi; Nakatani, Kei; Kanzaki, Ryohei

2013-01-01

The olfactory system of male moths has an extreme sensitivity with the capability to detect and recognize conspecific pheromones dispersed and greatly diluted in the air. Just 170 molecules of the silkmoth (Bombyx mori) sex pheromone bombykol are sufficient to induce sexual behavior in the male. However, it is still unclear how the sensitivity of olfactory receptor neurons (ORNs) is relayed through the brain to generate high behavioral responsiveness. Here, we show that ORN activity that is subthreshold in terms of behavior can be amplified to suprathreshold levels by temporal integration in antennal lobe projection neurons (PNs) if occurring within a specific time window. To control ORN inputs with high temporal resolution, channelrhodopsin-2 was genetically introduced into bombykol-responsive ORNs. Temporal integration in PNs was only observed for weak inputs, but not for strong inputs. Pharmacological dissection revealed that GABAergic mechanisms inhibit temporal integration of strong inputs, showing that GABA signaling regulates PN responses in a stimulus-dependent fashion. Our results show that boosting of the PNs’ responses by temporal integration of olfactory information occurs specifically near the behavioral threshold, effectively defining the lower bound for behavioral responsiveness. PMID:24006366

Predicting safe sex: Assessment of autoregressive and cross-lagged effects within the Theory of Planned Behavior.

PubMed

Eggers, Sander M; Taylor, Myra; Sathiparsad, Reshma; Bos, Arjan Er; de Vries, Hein

2015-11-01

Despite its popularity, few studies have assessed the temporal stability and cross-lagged effects of the Theory of Planned Behavior factors: Attitude, subjective norms and self-efficacy. For this study, 298 adolescent learners from KwaZulu-Natal, South Africa, filled out a Theory of Planned Behavior questionnaire on teenage pregnancy at baseline and after 6 months. Structural equation modeling showed that there were considerable cross-lagged effects between attitude and subjective norms. Temporal stability was moderate with test-retest correlations ranging from 0.37 to 0.51 and the model was able to predict intentions to have safe sex (R2 = 0.69) Implications for practice and future research are discussed. © The Author(s) 2013.

Trapped Field Characteristics of Stacked YBCO Thin Plates for Compact NMR Magnets: Spatial Field Distribution and Temporal Stability

PubMed Central

Hahn, Seungyong; Kim, Seok Beom; Ahn, Min Cheol; Voccio, John; Bascuñán, Juan; Iwasa, Yukikazu

2010-01-01

This paper presents experimental and analytical results of trapped field characteristics of a stack of square YBCO thin film plates for compact NMR magnets. Each YBCO plate, 40 mm × 40 mm × 0.08 mm, has a 25-mm diameter hole at its center. A total of 500 stacked plates were used to build a 40-mm long magnet. Its trapped field, in a bath of liquid nitrogen, was measured for spatial field distribution and temporal stability. Comparison of measured and analytical results is presented: the effects on trapped field characteristics of the unsaturated nickel substrate and the non-uniform current distribution in the YBCO plate are discussed. PMID:20585463

Superoxide Stabilization and a Universal KO2 Growth Mechanism in Potassium-Oxygen Batteries.

PubMed

Wang, Wanwan; Lai, Nien-Chu; Liang, Zhuojian; Wang, Yu; Lu, Yi-Chun

2018-04-23

Rechargeable potassium-oxygen (K-O 2 ) batteries promise to provide higher round-trip efficiency and cycle life than other alkali-oxygen batteries with satisfactory gravimetric energy density (935 Wh kg -1 ). Exploiting a strong electron-donating solvent, for example, dimethyl sulfoxide (DMSO) strongly stabilizes the discharge product (KO 2 ), resulting in significant improvement in electrode kinetics and chemical/electrochemical reversibility. The first DMSO-based K-O 2 battery demonstrates a much higher energy efficiency and stability than the glyme-based electrolyte. A universal KO 2 growth model is developed and it is demonstrated that the ideal solvent for K-O 2 batteries should strongly stabilize superoxide (strong donor ability) to obtain high electrode kinetics and reversibility while providing fast oxygen diffusion to achieve high discharge capacity. This work elucidates key electrolyte properties that control the efficiency and reversibility of K-O 2 batteries. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural Coherence and Temporal Stability of Psychopathic Personality Features During Emerging Adulthood

PubMed Central

Hawes, Samuel W.; Mulvey, Edward P.; Schubert, Carol A.; Pardini, Dustin A.

2015-01-01

Psychopathy is a complex personality disorder characterized by affective, interpersonal, and behavioral dimensions. Although features of psychopathy have been extended downwardly to earlier developmental periods, there is a discerning lack of studies that have focused on critically important issues such as longitudinal invariance and stability/change in these features across time. The current study examines these issues using a large sample of male adolescent offenders (N = 1,170) assessed across 7 annual time points during the transition into emerging adulthood (ages ~ 17 to 24 years). Findings demonstrated that features of psychopathy remained longitudinally invariant across this developmental period, and showed temporally consistent and theoretically coherent associations with other measures of personality, psychopathology, and criminal behaviors. Results also demonstrated that mean levels of psychopathic personality features tended to decrease into emerging adulthood and showed relatively modest rank-order stability across assessments with 7-year lags. These findings suggest that reductions in maladaptive personality features seem to parallel the well-documented decreases in offending that occur during the early 20s. PMID:24978692

Differences in stability of seed-associated microbial assemblages in response to invasion by phytopathogenic microorganisms.

PubMed

Rezki, Samir; Campion, Claire; Iacomi-Vasilescu, Beatrice; Preveaux, Anne; Toualbia, Youness; Bonneau, Sophie; Briand, Martial; Laurent, Emmanuelle; Hunault, Gilles; Simoneau, Philippe; Jacques, Marie-Agnès; Barret, Matthieu

2016-01-01

Seeds are involved in the vertical transmission of microorganisms from one plant generation to another and consequently act as reservoirs for the plant microbiota. However, little is known about the structure of seed-associated microbial assemblages and the regulators of assemblage structure. In this work, we have assessed the response of seed-associated microbial assemblages of Raphanus sativus to invading phytopathogenic agents, the bacterial strain Xanthomonas campestris pv. campestris (Xcc) 8004 and the fungal strain Alternaria brassicicola Abra43. According to the indicators of bacterial (16S rRNA gene and gyrB sequences) and fungal (ITS1) diversity employed in this study, seed transmission of the bacterial strain Xcc 8004 did not change the overall composition of resident microbial assemblages. In contrast seed transmission of Abra43 strongly modified the richness and structure of fungal assemblages without affecting bacterial assemblages. The sensitivity of seed-associated fungal assemblage to Abra43 is mostly related to changes in relative abundance of closely related fungal species that belong to the Alternaria genus. Variation in stability of the seed microbiota in response to Xcc and Abra43 invasions could be explained by differences in seed transmission pathways employed by these micro-organisms, which ultimately results in divergence in spatio-temporal colonization of the seed habitat.

Differences in stability of seed-associated microbial assemblages in response to invasion by phytopathogenic microorganisms

PubMed Central

Rezki, Samir; Campion, Claire; Iacomi-Vasilescu, Beatrice; Preveaux, Anne; Toualbia, Youness; Bonneau, Sophie; Briand, Martial; Laurent, Emmanuelle; Hunault, Gilles; Simoneau, Philippe; Jacques, Marie-Agnès

2016-01-01

Seeds are involved in the vertical transmission of microorganisms from one plant generation to another and consequently act as reservoirs for the plant microbiota. However, little is known about the structure of seed-associated microbial assemblages and the regulators of assemblage structure. In this work, we have assessed the response of seed-associated microbial assemblages of Raphanus sativus to invading phytopathogenic agents, the bacterial strain Xanthomonas campestris pv. campestris (Xcc) 8004 and the fungal strain Alternaria brassicicola Abra43. According to the indicators of bacterial (16S rRNA gene and gyrB sequences) and fungal (ITS1) diversity employed in this study, seed transmission of the bacterial strain Xcc 8004 did not change the overall composition of resident microbial assemblages. In contrast seed transmission of Abra43 strongly modified the richness and structure of fungal assemblages without affecting bacterial assemblages. The sensitivity of seed-associated fungal assemblage to Abra43 is mostly related to changes in relative abundance of closely related fungal species that belong to the Alternaria genus. Variation in stability of the seed microbiota in response to Xcc and Abra43 invasions could be explained by differences in seed transmission pathways employed by these micro-organisms, which ultimately results in divergence in spatio-temporal colonization of the seed habitat. PMID:27077013

Humidity-Induced Photoluminescence Hysteresis in Variable Cs/Br Ratio Hybrid Perovskites.

PubMed

Howard, John M; Tennyson, Elizabeth M; Barik, Sabyasachi; Szostak, Rodrigo; Waks, Edo; Toney, Michael F; Nogueira, Ana F; Neves, Bernardo R A; Leite, Marina S

2018-06-21

Hybrid organic-inorganic perovskites containing Cs are a promising new material for light-absorbing and light-emitting optoelectronics. However, the impact of environmental conditions on their optical properties is not fully understood. Here, we elucidate and quantify the influence of distinct humidity levels on the charge carrier recombination in Cs x FA 1- x Pb(I y Br 1- y ) 3 perovskites. Using in situ environmental photoluminescence (PL), we temporally and spectrally resolve light emission within a loop of critical relative humidity (rH) levels. Our measurements show that exposure up to 35% rH increases the PL emission for all Cs (10-17%) and Br (17-38%) concentrations investigated here. Spectrally, samples with larger Br concentrations exhibit PL redshift at higher humidity levels, revealing water-driven halide segregation. The compositions considered present hysteresis in their PL intensity upon returning to a low-moisture environment due to partially reversible hydration of the perovskites. Our findings demonstrate that the Cs/Br ratio strongly influences both the spectral stability and extent of light emission hysteresis. We expect our method to become standard when testing the stability of emerging perovskites, including lead-free options, and to be combined with other parameters known for affecting material degradation, e.g., oxygen and temperature.

Size-Dependent Protein-Nanoparticle Interactions in Citrate-Stabilized Gold Nanoparticles: The Emergence of the Protein Corona.

PubMed

Piella, Jordi; Bastús, Neus G; Puntes, Víctor

2017-01-18

Surface modifications of highly monodisperse citrate-stabilized gold nanoparticles (AuNPs) with sizes ranging from 3.5 to 150 nm after their exposure to cell culture media supplemented with fetal bovine serum were studied and characterized by the combined use of UV-vis spectroscopy, dynamic light scattering, and zeta potential measurements. In all the tested AuNPs, a dynamic process of protein adsorption was observed, evolving toward the formation of an irreversible hard protein coating known as Protein Corona. Interestingly, the thickness and density of this protein coating were strongly dependent on the particle size, making it possible to identify different transition regimes as the size of the particles increased: (i) NP-protein complexes (or incomplete corona), (ii) the formation of a near-single dense protein corona layer, and (iii) the formation of a multilayer corona. In addition, the different temporal patterns in the evolution of the protein coating came about more quickly for small particles than for the larger ones, further revealing the significant role that size plays in the kinetics of this process. Since the biological identity of the NPs is ultimately determined by the protein corona and different NP-biological interactions take place at different time scales, these results are relevant to biological and toxicological studies.

Longitudinal Stability of Social Competence Indicators in a Portuguese Sample: Q-Sort Profiles of Social Competence, Measures of Social Engagement, and Peer Sociometric Acceptance

ERIC Educational Resources Information Center

Santos, António J.; Vaughn, Brian E.; Peceguina, Inês; Daniel, João R.

2014-01-01

This study examines the temporal stability (over 3 years) of individual differences in 3 domains relevant to preschool children's social competence: social engagement/motivation, profiles of behavior and personality attributes characteristic of socially competent young children, and peer acceptance. Each domain was measured with multiple…

Maintenance of Genetic Variability under Strong Stabilizing Selection: A Two-Locus Model

PubMed Central

Gavrilets, S.; Hastings, A.

1993-01-01

We study a two locus model with additive contributions to the phenotype to explore the relationship between stabilizing selection and recombination. We show that if the double heterozygote has the optimum phenotype and the contributions of the loci to the trait are different, then any symmetric stabilizing selection fitness function can maintain genetic variability provided selection is sufficiently strong relative to linkage. We present results of a detailed analysis of the quadratic fitness function which show that selection need not be extremely strong relative to recombination for the polymorphic equilibria to be stable. At these polymorphic equilibria the mean value of the trait, in general, is not equal to the optimum phenotype, there exists a large level of negative linkage disequilibrium which ``hides'' additive genetic variance, and different equilibria can be stable simultaneously. We analyze dependence of different characteristics of these equilibria on the location of optimum phenotype, on the difference in allelic effect, and on the strength of selection relative to recombination. Our overall result that stabilizing selection does not necessarily eliminate genetic variability is compatible with some experimental results where the lines subject to strong stabilizing selection did not have significant reductions in genetic variability. PMID:8514145

Structural stability as a consistent predictor of phenological events.

PubMed

Song, Chuliang; Saavedra, Serguei

2018-06-13

The timing of the first and last seasonal appearance of a species in a community typically follows a pattern that is governed by temporal factors. While it has been shown that changes in the environment are linked to phenological changes, the direction of this link appears elusive and context-dependent. Thus, finding consistent predictors of phenological events is of central importance for a better assessment of expected changes in the temporal dynamics of ecological communities. Here we introduce a measure of structural stability derived from species interaction networks as an estimator of the expected range of environmental conditions compatible with the existence of a community. We test this measure as a predictor of changes in species richness recorded on a daily basis in a high-arctic plant-pollinator community during two spring seasons. We find that our measure of structural stability is the only consistent predictor of changes in species richness among different ecological and environmental variables. Our findings suggest that measures based on the notion of structural stability can synthesize the expected variation of environmental conditions tolerated by a community, and explain more consistently the phenological changes observed in ecological communities. © 2018 The Author(s).

Quantitative characterization of non-classic polarization of cations on clay aggregate stability.

PubMed

Hu, Feinan; Li, Hang; Liu, Xinmin; Li, Song; Ding, Wuquan; Xu, Chenyang; Li, Yue; Zhu, Longhui

2015-01-01

Soil particle interactions are strongly influenced by the concentration, valence and ion species and the pH of the bulk solution, which will also affect aggregate stability and particle transport. In this study, we investigated clay aggregate stability in the presence of different alkali ions (Li+, Na+, K+, and Cs+) at concentrations from10-5 to 10-1 mol L-1. Strong specific ion effects on clay aggregate stability were observed, and showed the order Cs+>K+>Na+>Li+. We found that it was not the effects of ion size, hydration, and dispersion forces in the cation-surface interactions but strong non-classic polarization of adsorbed cations that resulted in these specific effects. In this study, the non-classic dipole moments of each cation species resulting from the non-classic polarization were estimated. By comparing non-classic dipole moments with classic values, the observed dipole moments of adsorbed cations were up to 104 times larger than the classic values for the same cation. The observed non-classic dipole moments sharply increased with decreasing electrolyte concentration. We conclude that strong non-classic polarization could significantly suppress the thickness of the diffuse layer, thereby weakening the electric field near the clay surface and resulting in improved clay aggregate stability. Even though we only demonstrated specific ion effects on aggregate stability with several alkali ions, our results indicate that these effects could be universally important in soil aggregate stability.

Quantitative Characterization of Non-Classic Polarization of Cations on Clay Aggregate Stability

PubMed Central

Hu, Feinan; Li, Hang; Liu, Xinmin; Li, Song; Ding, Wuquan; Xu, Chenyang; Li, Yue; Zhu, Longhui

2015-01-01

Soil particle interactions are strongly influenced by the concentration, valence and ion species and the pH of the bulk solution, which will also affect aggregate stability and particle transport. In this study, we investigated clay aggregate stability in the presence of different alkali ions (Li+, Na+, K+, and Cs+) at concentrations from10−5 to 10−1 mol L−1. Strong specific ion effects on clay aggregate stability were observed, and showed the order Cs+>K+>Na+>Li+. We found that it was not the effects of ion size, hydration, and dispersion forces in the cation–surface interactions but strong non-classic polarization of adsorbed cations that resulted in these specific effects. In this study, the non-classic dipole moments of each cation species resulting from the non-classic polarization were estimated. By comparing non-classic dipole moments with classic values, the observed dipole moments of adsorbed cations were up to 104 times larger than the classic values for the same cation. The observed non-classic dipole moments sharply increased with decreasing electrolyte concentration. We conclude that strong non-classic polarization could significantly suppress the thickness of the diffuse layer, thereby weakening the electric field near the clay surface and resulting in improved clay aggregate stability. Even though we only demonstrated specific ion effects on aggregate stability with several alkali ions, our results indicate that these effects could be universally important in soil aggregate stability. PMID:25874864

Spatio-Temporal Dynamics of Exploited Groundfish Species Assemblages Faced to Environmental and Fishing Forcings: Insights from the Mauritanian Exclusive Economic Zone

PubMed Central

Kidé, Saïkou Oumar; Manté, Claude; Dubroca, Laurent; Demarcq, Hervé; Mérigot, Bastien

2015-01-01

Environmental changes and human activities can have strong impacts on biodiversity and ecosystem functioning. This study investigates how, from a quantitative point of view, simultaneously both environmental and anthropogenic factors affect species composition and abundance of exploited groundfish assemblages (i.e. target and non-target species) at large spatio-temporal scales. We aim to investigate (1) the spatial and annual stability of groundfish assemblages, (2) relationships between these assemblages and structuring factors in order to better explain the dynamic of the assemblages’ structure. The Mauritanian Exclusive Economic Zone (MEEZ) is of particular interest as it embeds a productive ecosystem due to upwelling, producing abundant and diverse resources which constitute an attractive socio-economic development. We applied the multi-variate and multi-table STATICO method on a data set consisting of 854 hauls collected during 14-years (1997–2010) from scientific trawl surveys (species abundance), logbooks of industrial fishery (fishing effort), sea surface temperature and chlorophyll a concentration as environmental variables. Our results showed that abiotic factors drove four main persistent fish assemblages. Overall, chlorophyll a concentration and sea surface temperature mainly influenced the structure of assemblages of coastal soft bottoms and those of the offshore near rocky bottoms where upwellings held. While highest levels of fishing effort were located in the northern permanent upwelling zone, effects of this variable on species composition and abundances of assemblages were relatively low, even if not negligible in some years and areas. The temporal trajectories between environmental and fishing conditions and assemblages did not match for all the entire time series analyzed in the MEEZ, but interestingly for some specific years and areas. The quantitative approach used in this work may provide to stakeholders, scientists and fishers a useful assessment for the spatio-temporal dynamics of exploited assemblages under stable or changing conditions in fishing and environment. PMID:26505198

Effects of a cognitive dual task on variability and local dynamic stability in sustained repetitive arm movements using principal component analysis: a pilot study.

PubMed

Longo, Alessia; Federolf, Peter; Haid, Thomas; Meulenbroek, Ruud

2018-06-01

In many daily jobs, repetitive arm movements are performed for extended periods of time under continuous cognitive demands. Even highly monotonous tasks exhibit an inherent motor variability and subtle fluctuations in movement stability. Variability and stability are different aspects of system dynamics, whose magnitude may be further affected by a cognitive load. Thus, the aim of the study was to explore and compare the effects of a cognitive dual task on the variability and local dynamic stability in a repetitive bimanual task. Thirteen healthy volunteers performed the repetitive motor task with and without a concurrent cognitive task of counting aloud backwards in multiples of three. Upper-body 3D kinematics were collected and postural reconfigurations-the variability related to the volunteer's postural change-were determined through a principal component analysis-based procedure. Subsequently, the most salient component was selected for the analysis of (1) cycle-to-cycle spatial and temporal variability, and (2) local dynamic stability as reflected by the largest Lyapunov exponent. Finally, end-point variability was evaluated as a control measure. The dual cognitive task proved to increase the temporal variability and reduce the local dynamic stability, marginally decrease endpoint variability, and substantially lower the incidence of postural reconfigurations. Particularly, the latter effect is considered to be relevant for the prevention of work-related musculoskeletal disorders since reduced variability in sustained repetitive tasks might increase the risk of overuse injuries.

Hydrodynamic Stability Analysis of Multi-jet Effects in Swirling Jet Combustors

NASA Astrophysics Data System (ADS)

Emerson, Benjamin; Lieuwen, Tim

2016-11-01

Many practical combustion devices use multiple swirling jets to stabilize flames. However, much of the understanding of swirling jet dynamics has been generated from experimental and computational studies of single reacting, swirling jets. A smaller body of literature has begun to explore the effects of multi-jet systems and the role of jet-jet interactions on the macro-system dynamics. This work uses local temporal and spatio-temporal stability analyses to isolate the hydrodynamic interactions of multiple reacting, swirling jets, characterized by jet diameter, D, and spacing, L. The results first identify the familiar helical modes in the single jet. Comparison to the multi-jet configuration reveals these same familiar modes simultaneously oscillating in each of the jets. Jet-jet interaction is mostly limited to a spatial synchronization of each jet's oscillations at the jet spacing values analyzed here (L/D =3.5). The presence of multiple jets vs a single jet has little influence on the temporal and absolute growth rates. The biggest difference between the single and multi-jet configurations is the presence of nearly degenerate pairs of hydrodynamic modes in the multi-jet case, with one mode dominated by oscillations in the inner jet, and the other in the outer jets. The close similarity between the single and multi-jet hydrodynamics lends insight into experiments from our group.

Two baselines are better than one: Improving the reliability of computerized testing in sports neuropsychology.

PubMed

Bruce, Jared; Echemendia, Ruben; Tangeman, Lindy; Meeuwisse, Willem; Comper, Paul; Hutchison, Michael; Aubry, Mark

2016-01-01

Computerized neuropsychological tests are frequently used to assist in return-to-play decisions following sports concussion. However, due to concerns about test reliability, the Centers for Disease Control and Prevention recommends yearly baseline testing. The standard practice that has developed in baseline/postinjury comparisons is to examine the difference between the most recent baseline test and postconcussion performance. Drawing from classical test theory, the present study investigated whether temporal stability could be improved by taking an alternate approach that uses the aggregate of 2 baselines to more accurately estimate baseline cognitive ability. One hundred fifteen English-speaking professional hockey players with 3 consecutive Immediate Postconcussion Assessment and Testing (ImPACT) baseline tests were extracted from a clinical program evaluation database overseen by the National Hockey League and National Hockey League Players' Association. The temporal stability of ImPACT composite scores was significantly increased by aggregating test performance during Sessions 1 and 2 to predict performance during Session 3. Using this approach, the 2-factor Memory (r = .72) and Speed (r = .79) composites of ImPACT showed acceptable long-term reliability. Using the aggregate of 2 baseline scores significantly improves temporal stability and allows for more accurate predictions of cognitive change following concussion. Clinicians are encouraged to estimate baseline abilities by taking into account all of an athlete's previous baseline scores.

Proportional spike-timing precision and firing reliability underlie efficient temporal processing of periodicity and envelope shape cues

PubMed Central

Zheng, Y.

2013-01-01

Temporal sound cues are essential for sound recognition, pitch, rhythm, and timbre perception, yet how auditory neurons encode such cues is subject of ongoing debate. Rate coding theories propose that temporal sound features are represented by rate tuned modulation filters. However, overwhelming evidence also suggests that precise spike timing is an essential attribute of the neural code. Here we demonstrate that single neurons in the auditory midbrain employ a proportional code in which spike-timing precision and firing reliability covary with the sound envelope cues to provide an efficient representation of the stimulus. Spike-timing precision varied systematically with the timescale and shape of the sound envelope and yet was largely independent of the sound modulation frequency, a prominent cue for pitch. In contrast, spike-count reliability was strongly affected by the modulation frequency. Spike-timing precision extends from sub-millisecond for brief transient sounds up to tens of milliseconds for sounds with slow-varying envelope. Information theoretic analysis further confirms that spike-timing precision depends strongly on the sound envelope shape, while firing reliability was strongly affected by the sound modulation frequency. Both the information efficiency and total information were limited by the firing reliability and spike-timing precision in a manner that reflected the sound structure. This result supports a temporal coding strategy in the auditory midbrain where proportional changes in spike-timing precision and firing reliability can efficiently signal shape and periodicity temporal cues. PMID:23636724

Compensatory dynamics stabilize aggregate community properties in response to multiple types of perturbations.

PubMed

Brown, Bryan L; Downing, Amy L; Leibold, Mathew A

2016-08-01

Compensatory dynamics are an important suite of mechanisms that can stabilize community and ecosystem attributes in systems subject to environmental fluctuations. However, few experimental investigations of compensatory dynamics have addressed these mechanisms in systems of real-world complexity, and existing evidence relies heavily on correlative analyses, retrospective examination, and experiments in simple systems. We investigated the potential for compensatory dynamics to stabilize plankton communities in plankton mesocosm systems of real-world complexity. We employed four types of perturbations including two types of nutrient pulses, shading, and acidification. To quantify how communities responded to these perturbations, we used a measure of community-wide synchrony combined with spectral analysis that allowed us to assess timescale-specific community dynamics, for example, whether dynamics were synchronous at some timescales but compensatory at others. The 150-d experiment produced 32-point time series of all zooplankton taxa in the mesocosms. We then used those time series to evaluate total zooplankton biomass as an aggregate property and to evaluate community dynamics. For three of our four perturbation types, total zooplankton biomass was significantly less variable in systems with environmental variation than in constant environments. For the same three perturbation types, community-wide synchrony was much lower in fluctuating environments than in the constant environment, particularly at longer timescales (periods ≈ 60 d). Additionally, there were strong negative correlations between population temporal variances and the level of community-wide synchrony. Taken together, these results strongly imply that compensatory interactions between species stabilized total biomass in response to perturbations. Diversity did not differ significantly across either treatments or perturbation types, thus ruling out several classes of mechanisms driven by changes in diversity. We also used several pieces of secondary evidence to evaluate the particular mechanism behind compensatory responses since a wide variety of mechanisms are hypothesized to produce compensatory dynamics. We concluded that fluctuation dependent endogenous cycles that occur as a consequence of consumer-resource interactions in competitive communities were the most likely explanation for the compensatory dynamics observed in our experiment. As with our previous work, scale-dependent dynamics were also a key to understanding compensatory dynamics in these experimental communities. © 2016 by the Ecological Society of America.

Community ecology in 3D: Tensor decomposition reveals spatio-temporal dynamics of large ecological communities.

PubMed

Frelat, Romain; Lindegren, Martin; Denker, Tim Spaanheden; Floeter, Jens; Fock, Heino O; Sguotti, Camilla; Stäbler, Moritz; Otto, Saskia A; Möllmann, Christian

2017-01-01

Understanding spatio-temporal dynamics of biotic communities containing large numbers of species is crucial to guide ecosystem management and conservation efforts. However, traditional approaches usually focus on studying community dynamics either in space or in time, often failing to fully account for interlinked spatio-temporal changes. In this study, we demonstrate and promote the use of tensor decomposition for disentangling spatio-temporal community dynamics in long-term monitoring data. Tensor decomposition builds on traditional multivariate statistics (e.g. Principal Component Analysis) but extends it to multiple dimensions. This extension allows for the synchronized study of multiple ecological variables measured repeatedly in time and space. We applied this comprehensive approach to explore the spatio-temporal dynamics of 65 demersal fish species in the North Sea, a marine ecosystem strongly altered by human activities and climate change. Our case study demonstrates how tensor decomposition can successfully (i) characterize the main spatio-temporal patterns and trends in species abundances, (ii) identify sub-communities of species that share similar spatial distribution and temporal dynamics, and (iii) reveal external drivers of change. Our results revealed a strong spatial structure in fish assemblages persistent over time and linked to differences in depth, primary production and seasonality. Furthermore, we simultaneously characterized important temporal distribution changes related to the low frequency temperature variability inherent in the Atlantic Multidecadal Oscillation. Finally, we identified six major sub-communities composed of species sharing similar spatial distribution patterns and temporal dynamics. Our case study demonstrates the application and benefits of using tensor decomposition for studying complex community data sets usually derived from large-scale monitoring programs.

Coherence properties of the radiation from FLASH

NASA Astrophysics Data System (ADS)

Schneidmiller, E. A.; Yurkov, M. V.

2016-02-01

Free electron LASer in Hamburg is the first free electron laser user facility operating in the vacuum ultraviolet and soft X-ray wavelength range. Many user experiments require knowledge of the spatial and temporal coherence properties of the radiation. In this paper, we present a theoretical analysis of the coherence properties of the radiation for the fundamental and for the higher odd frequency harmonics. We show that temporal and spatial coherence reach their maxima close to the free electron laser (FEL) saturation but may degrade significantly in the post-saturation regime. We also find that the pointing stability of short FEL pulses is limited due to the fact that nonazimuthal FEL eigenmodes are not sufficiently suppressed. We discuss possible ways for improving the degree of transverse coherence and the pointing stability.

Stability and sensitivity of ABR flow control protocols

NASA Astrophysics Data System (ADS)

Tsai, Wie K.; Kim, Yuseok; Chiussi, Fabio; Toh, Chai-Keong

1998-10-01

This tutorial paper surveys the important issues in stability and sensitivity analysis of ABR flow control of ATM networks. THe stability and sensitivity issues are formulated in a systematic framework. Four main cause of instability in ABR flow control are identified: unstable control laws, temporal variations of available bandwidth with delayed feedback control, misbehaving components, and interactions between higher layer protocols and ABR flow control. Popular rate-based ABR flow control protocols are evaluated. Stability and sensitivity is shown to be the fundamental issues when the network has dynamically-varying bandwidth. Simulation result confirming the theoretical studies are provided. Open research problems are discussed.

Characteristics of attention-related body sensations. Temporal stability and associations with measures of body focus, affect, sustained attention, and heart rate variability.

PubMed

Tihanyi, Benedek T; Ferentzi, Eszter; Köteles, Ferenc

2017-09-01

This study investigated the temporal stability and correlates of attention-related body sensations that emerge without external stimulation during rest and due to focused attention on a body part. To assess attention-related body sensations, participants were asked to focus on a freely chosen body area with closed eyes, and had to report whether the sensation of that area had changed. Self-report questionnaires were used to assess various aspects of body focus (body awareness, body responsiveness, somatosensory amplification, subjective somatic symptoms), and positive and negative affectivity. Previous experiences in body-mind therapies were also measured. PEBL Continuous Performance Test was used to assess sustained attention. Heart rate variability scores were based on a 3-minute long resting heart rate measurement. Fifty-eight university students (22.3 ± 3.95 years; 34 females) participated in the study. The stability of attention-related body sensations was measured 8 weeks later on a randomly chosen sub-group (n = 28). Attention-related body sensations showed a mediocre temporal stability (r ρ  = 0.47, p = 0.012). People reporting attention-related body sensations showed significantly higher body awareness, somatosensory amplification, and resting heart rate; and marginally higher somatic symptoms. No relation was found with body-mind practice, body responsiveness, positive and negative affect, the vagal component of heart rate variability, and performance in the sustained attention task. Attention-related sensations are relatively stable over time. They are connected to some, but not to all of the aspects of body focus. Further studies are needed to elaborate the influencing stable and situational factors.

Does stability in local community composition depend on temporal variation in rates of dispersal and connectivity?

NASA Astrophysics Data System (ADS)

Valanko, Sebastian; Norkko, Joanna; Norkko, Alf

2015-04-01

In ecology understanding variation in connectivity is central for how biodiversity is maintained. Field studies on dispersal and temporal dynamics in community regulating processes are, however, rare. We test the short-term temporal stability in community composition in a soft-sediment benthic community by determining among-sampling interval similarity in community composition. We relate stability to in situ measures of connectivity (wind, wave, current energy) and rates of dispersal (quantified in different trap types). Waves were an important predictor of when local community taxa are most likely to disperse in different trap-types, suggesting that wave energy is important for connectivity in a region. Community composition at the site was variable and changed stochastically over time. We found changes in community composition (occurrence, abundance, dominance) to be greater at times when connectivity and rates of dispersal were low. In response to periods of lower connectedness dominant taxa in the local community only exhibited change in their relative abundance. In contrast, locally less abundant taxa varied in both their presence, as well as in relative abundance. Constancy in connectivity and rates of dispersal promotes community stability and persistence, suggesting that local community composition will be impacted by changes in the spatial extent over which immigration and emigration operates in the region. Few empirical studies have actually measured dispersal directly in a multi-species context to demonstrate the role it plays in maintaining local community structure. Even though our study does not evaluate coexistence over demographic time scales, it importantly demonstrates that dispersal is not only important in initial recruitment or following a disturbance, but also key in maintaining local community composition.

Age-Related Changes in Visual Temporal Order Judgment Performance: Relation to Sensory and Cognitive Capacities

PubMed Central

Busey, Thomas; Craig, James; Clark, Chris; Humes, Larry

2010-01-01

Five measures of temporal order judgments were obtained from 261 participants, including 146 elder, 44 middle aged, and 71 young participants. Strong age group differences were observed in all five measures, although the group differences were reduced when letter discriminability was matched for all participants. Significant relations were found between these measures of temporal processing and several cognitive and sensory assays, and structural equation modeling revealed the degree to which temporal order processing can be viewed as a latent factor that depends in part on contributions from sensory and cognitive capacities. The best-fitting model involved two different latent factors representing temporal order processing at same and different locations, and the sensory and cognitive factors were more successful predicting performance in the different location factor than the same-location factor. Processing speed, even measured using high-contrast symbols on a paper-and-pencil test, was a surprisingly strong predictor of variability in both latent factors. However, low-level sensory measures also made significant contributions to the latent factors. The results demonstrate the degree to which temporal order processing relates to other perceptual and cognitive capacities, and address the question of whether age-related declines in these capacities share a common cause. PMID:20580644

Age-related changes in visual temporal order judgment performance: Relation to sensory and cognitive capacities.

PubMed

Busey, Thomas; Craig, James; Clark, Chris; Humes, Larry

2010-08-06

Five measures of temporal order judgments were obtained from 261 participants, including 146 elder, 44 middle aged, and 71 young participants. Strong age group differences were observed in all five measures, although the group differences were reduced when letter discriminability was matched for all participants. Significant relations were found between these measures of temporal processing and several cognitive and sensory assays, and structural equation modeling revealed the degree to which temporal order processing can be viewed as a latent factor that depends in part on contributions from sensory and cognitive capacities. The best-fitting model involved two different latent factors representing temporal order processing at same and different locations, and the sensory and cognitive factors were more successful predicting performance in the different location factor than the same-location factor. Processing speed, even measured using high-contrast symbols on a paper-and-pencil test, was a surprisingly strong predictor of variability in both latent factors. However, low-level sensory measures also made significant contributions to the latent factors. The results demonstrate the degree to which temporal order processing relates to other perceptual and cognitive capacities, and address the question of whether age-related declines in these capacities share a common cause. Copyright 2010 Elsevier Ltd. All rights reserved.

Thermal structure and minor species distribution of Venus mesosphere by ALMA submm observations

NASA Astrophysics Data System (ADS)

Piccialli, Arianna; Moreno, Raphael; Encrenaz, Therese; Fouchet, Thierry; Lellouch, Emmanuel; Moullet, Arielle; Widemann, Thomas

2015-11-01

Venus upper atmosphere (70-150 km altitude) is a transition region characterized by a complex dynamics: strong retrograde zonal winds dominate the lower mesosphere while a solar-to-antisolar circulation is observed in the upper mesosphere/lower thermosphere. In addition, photochemical processes play an important role at these altitudes and affect the thermal structure and chemical stability of the entire atmosphere. Sulfur dioxide and water vapor are key species in the photochemical cycles taking place in the troposphere and mesosphere of Venus. They are carried by convective transport, together with the Hadley circulation, up to about 60 km where SO2 is photodissociated and oxydated, leading to the formation of H2SO4 which condenses in the clouds enshrouding the planet. Previous observations obtained by several instruments on board Venus Express and during ground-based campaigns have shown evidence of strong temporal variations, both on day-to-day as well as longer timescales, of density, temperature and SO2 abundance. Such strong variability is still not well understood.Submillimeter observations obtained with the Atacama Large Millimeter Array (ALMA) offer the possibility of probing Venus upper mesosphere and of monitoring minor species, winds and the thermal structure. A first set of observations was obtained on November 14, 15, 26 and 27, 2011 during the first ALMA Early Science observation cycle. These observations targeted SO2, SO, HDO and CO transitions around 345 GHz during four sequences of 30 minutes each. The Venus’ disk was about 11” with an illumination factor of 90%, so that mostly the dayside of the planet was mapped.Assuming nominal night-time and dayside CO abundance profiles from Clancy et al. 2013, we retrieved vertical temperature profiles over the entire disk as a function of latitude and local time for the four days of observation. Temperature profiles were later used to derive the abundances of minor species (HDO, SO, SO2) in each pixel of the disk in order to study their spatial and temporal variability.

Spatio-temporal dynamics in phytobenthos structural properties reveal insights into agricultural catchment dynamics and nutrient fluxes

NASA Astrophysics Data System (ADS)

Reaney, S. M.; Snell, M. A.; Barker, P. A.; Aftab, A.; Barber, N. J.; Benskin, C.; Burke, S.; Cleasby, W.; Haygarth, P.; Jonczyk, J. C.; Owen, G. J.; Perks, M. T.; Quinn, P. F.; Surridge, B.

2016-12-01

Low order streams are spatially extensive, temporally dynamic, systems within the agricultural landscape. This dynamism extends to the aquatic communities within these streams, including the phytobentos, which demonstrates considerable resilience to diffuse anthropogenic nutrient pressures and changing climate dynamics. The phytobenthos community can substantially contribute to the food web, in particular diatoms, which dominate photo-autotrophic assemblages in low order streams. Diatoms are widely used in ecological monitoring because of their high sensitivity to environmental condition, but knowledge is limited on the ecological effects of winter disturbances and variance introduced by multiple and interacting pressures (N, P, sediment), introducing bias in understanding temporal dynamics in benthic diatom communities. Using the environmental time series data from long term monitoring within the River Eden Demonstration Test Catchment programme, we assess the impact of multiple hydro-chemical stressors on phytobenthic community resilience, and synthesize the impact of an extreme winter event. Monthly data from diatom communities collected in the Eden DTC from March 2011 to present show that river flow, strongly coupled to precipitation, is a key driver of these communities. Discharge has a direct effect on communities through scouring, but is also tightly correlated to nutrient delivery, such that 80% of the annual TP load arrives in 10% of the time. Trophic Diatom Index (TDI) values demonstrated considerable resilience by the stability of inter-monthly TDI scores over 5 seasonal cycles against the characterised highly variable hydrological regime. This research demonstrates that well characterised winter disturbances are critical to understanding drivers of aquatic dynamics. This has implications for catchment diffuse pollution policy, farm management and economics, given the climate projections of increases in frequency and intensity of extreme winter events, which may alter instream nutrient fluxes.

Assessing the temporal stability of spatial patterns of soil apparent electrical conductivity using geophysical methods

NASA Astrophysics Data System (ADS)

De Caires, Sunshine A.; Wuddivira, Mark N.; Bekele, Isaac

2014-10-01

Cocoa remains in the same field for decades, resulting in plantations dominated with aging trees growing on variable and depleted soils. We determined the spatio-temporal variability of key soil properties in a (5.81 ha) field from the International Cocoa Genebank, Trinidad using geophysical methods. Multi-year (2008-2009) measurements of apparent electrical conductivity at 0-0.75 m (shallow) and 0.75-1.5 m (deep) were conducted. Apparent electrical conductivity at deep and shallow gave the strongest linear correlation with clay-silt content (R = 0.67 and R = 0.78, respectively) and soil solution electrical conductivity (R = 0.76 and R = 0.60, respectively). Spearman rank correlation coefficients ranged between 0.89-0.97 and 0.81- 0.95 for apparent electrical conductivity at deep and shallow, respectively, signifying a strong linear dependence between measurement days. Thus, in the humid tropics, cocoa fields with thick organic litter layer and relatively dense understory cover, experience minimal fluctuations in transient properties of soil water and temperature at the topsoil resulting in similarly stable apparent electrical conductivity at shallow and deep. Therefore, apparent electrical conductivity at shallow, which covers the depth where cocoa feeder roots concentrate, can be used as a fertility indicator and to develop soil zones for efficient application of inputs and management of cocoa fields.

Understanding thermal circulations and near-surface turbulence processes in a small mountain valley

NASA Astrophysics Data System (ADS)

Pardyjak, E.; Dupuy, F.; Durand, P.; Gunawardena, N.; Thierry, H.; Roubin, P.

2017-12-01

The interaction of turbulence and thermal circulations in complex terrain can be significantly different from idealized flat terrain. In particular, near-surface horizontal spatial and temporal variability of winds and thermodynamic variables can be significant event over very small spatial scales. The KASCADE (KAtabatic winds and Stability over CAdarache for Dispersion of Effluents) 2017 conducted from January through March 2017 was designed to address these issues and to ultimately improve prediction of dispersion in complex terrain, particularly during stable atmospheric conditions. We have used a relatively large number of sensors to improve our understanding of the spatial and temporal development, evolution and breakdown of topographically driven flows. KASCADE 2017 consisted of continuous observations and fourteen Intensive Observation Periods (IOPs) conducted in the Cadarache Valley located in southeastern France. The Cadarache Valley is a relatively small valley (5 km x 1 km) with modest slopes and relatively small elevation differences between the valley floor and nearby hilltops ( 100 m). During winter, winds in the valley are light and stably stratified at night leading to thermal circulations as well as complex near-surface atmospheric layering. In this presentation we present results quantifying spatial variability of thermodynamic and turbulence variables as a function of different large -scale forcing conditions (e.g., quiescent conditions, strong westerly flow, and Mistral flow). In addition, we attempt to characterize highly-regular nocturnal horizontal wind meandering and associated turbulence statistics.

Temporal acceleration of spatially distributed kinetic Monte Carlo simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, Abhijit; Vlachos, Dionisios G.

The computational intensity of kinetic Monte Carlo (KMC) simulation is a major impediment in simulating large length and time scales. In recent work, an approximate method for KMC simulation of spatially uniform systems, termed the binomial {tau}-leap method, was introduced [A. Chatterjee, D.G. Vlachos, M.A. Katsoulakis, Binomial distribution based {tau}-leap accelerated stochastic simulation, J. Chem. Phys. 122 (2005) 024112], where molecular bundles instead of individual processes are executed over coarse-grained time increments. This temporal coarse-graining can lead to significant computational savings but its generalization to spatially lattice KMC simulation has not been realized yet. Here we extend the binomial {tau}-leapmore » method to lattice KMC simulations by combining it with spatially adaptive coarse-graining. Absolute stability and computational speed-up analyses for spatial systems along with simulations provide insights into the conditions where accuracy and substantial acceleration of the new spatio-temporal coarse-graining method are ensured. Model systems demonstrate that the r-time increment criterion of Chatterjee et al. obeys the absolute stability limit for values of r up to near 1.« less

Improving carrier-envelope phase stability in optical parametric chirped-pulse amplifiers by control of timing jitter.

PubMed

Hädrich, S; Rothhardt, J; Krebs, M; Demmler, S; Limpert, J; Tünnermann, A

2012-12-01

It is shown that timing jitter in optical parametric chirped-pulse amplification induces spectral drifts that transfer to carrier-envelope phase (CEP) instabilities via dispersion. Reduction of this effect requires temporal synchronization, which is realized with feedback obtained from the angularly dispersed idler. Furthermore, a novel method to measure the CEP drifts by utilizing parasitic second harmonic generation within parametric amplifiers is presented. Stabilization of the timing allows the obtainment of a CEP stability of 86 mrad over 40 min at 150 kHz repetition rate.

Interannual Variability of OLR as Observed by AIRS and CERES

NASA Technical Reports Server (NTRS)

Susskind, Joel; Molnar, Gyula I.; Iredell, Lena F.; Loeb, Norman G.

2012-01-01

The paper examines spatial anomaly time series of Outgoing Longwave Radiation (OLR) and Clear Sky OLR (OLR(sub CLR)) as determined using observations from CERES Terra and AIRS over the time period September 2002 through June 2011. We find excellent agreement of the two OLR data sets in almost every detail down to the x11deg spatial grid point level. The extremely close agreement of OLR anomaly time series derived from observations by two different instruments implies high stability of both sets of results. Anomalies of global mean, and especially tropical mean, OLR are shown to be strongly correlated with an El Nino index. These correlations explain that the recent global and tropical mean decreases in OLR over the time period studied are primarily the result of a transition from an El Nino condition at the beginning of the data record to La Nina conditions toward the end of the data period. We show that the close correlation of mean OLR anomalies with the El Nino Index can be well accounted for by temporal changes of OLR within two spatial regions, one to the east of, and one to the west of, the NOAA Nino-4 region. Anomalies of OLR in these two spatial regions are both strongly correlated with the El Nino Index as a result of the strong anti-correlation of anomalies of cloud cover and mid-tropospheric water vapor in these two regions with the El Nino Index.

Acoustical Survey of Methane Plumes on North Hydrate Ridge: Constraining Temporal and Spatial Characteristics.

NASA Astrophysics Data System (ADS)

Kannberg, P. K.; Trehu, A. M.

2008-12-01

While methane plumes associated with hydrate formations have been acoustically imaged before, little is known about their temporal characteristics. Previous acoustic surveys have focused on determining plume location, but as far as we know, multiple, repeated surveys of the same plume have not been done prior to the survey presented here. In July 2008, we acquired sixteen identical surveys within 19 hours over the northern summit of Hydrate Ridge in the Cascadia accretionary complex using the onboard 3.5 and 12 kHz echosounders. As in previous studies, the plumes were invisible to the 3.5 kHz echosounder and clearly imaged with 12 kHz. Seafloor depth in this region is ~600 m. Three distinct plumes were detected close to where plumes were located by Heeschen et al. (2003) a decade ago. Two of the plumes disappeared at ~520 m water depth, which is the depth of the top of the gas hydrate stability as determined from CTD casts obtained during the cruise. This supports the conclusion of Heeschen et al. (2003) that the bubbles are armored by gas hydrate and that they dissolve in the water column when they leave the hydrate stability zone. One of the plumes near the northern summit, however, extended through this boundary to at least 400 m (the shallowest depth recorded). A similar phenomenon was observed in methane plumes in the Gulf of Mexico, where the methane was found to be armored by an oil skin. In addition to the steady plumes, two discrete "burps" were observed. One "burp" occurred approximately 600 m to the SSW of the northern summit. This was followed by a second strong event 300m to the north an hour later. To evaluate temporal and spatial patterns, we summed the power of the backscattered signal in different depth windows for each survey. We present the results as a movie in which the backscatter power is shown in map view as a function of time. The surveys encompassed two complete tidal cycles, but no correlation between plume location or intensity and tides is apparent in the data. Additional analyses will constrain plume strength as a function of water depth. Heeschen et al., GRL, v. 30, 2003.

Long-term historical analysis of benthic communities and physical habitat in an agricultural stream in California's San Joaquin River watershed.

PubMed

Hall, Lenwood W; Killen, William D; Alden, Raymond

2009-05-01

This study was designed to characterize long-term annual temporal and spatial trends (2001 to 2007) in physical habitat and benthic communities and to determine relationships of habitat and benthic communities during this 7-year period in an agricultural stream in the San Joaquin River watershed in California (Del Puerto Creek). The canonical discriminant analysis indicated that there were no overall significant temporal patterns for the habitat metrics although spatial patterns were prominent for nearly all the habitat metrics. Channel alteration, riparian vegetative zone, bank stability, vegetative protection and frequency of riffles/bends were the primary habitat metrics associated with these site effects. Approximately 3,700 to 4,500 individual macroinvertebrates were picked and identified from five Del Puerto Creek sites sampled annually from 2001 to 2007. The total number of taxa by year ranged from 81 in 2003 to 106 in 2007. These benthic assemblages were generally comprised of tolerant to moderately tolerant taxa such as blackflies, oligochaetes, snails and chironomids. The metrics % predators, % EPT index, % collectors/filterers and % shredders were the benthic metrics that were most associated with the temporal effects. Ephemeroptera taxa, trichoptera taxa, and % sensitive EPT index were the benthic metrics that were most associated with the site effects. The most upstream site in Del Puerto Creek had the most robust and healthy benthic communites. Strong statistical relationships were reported between certain benthic metrics and habitat metrics. Overall, samples taken from site-year combinations with sediments that were qualitatively less muddy (less fines) and that had higher habitat metric scores for embeddedness, riparian vegetative zone, and channel alteration tended to have benthic communities characterized by higher values of the benthic metrics such as EPT taxa, Ephemeroptera taxa, EPT index, abundance, and taxonomic richness, among others. Conversely, tolerance value and % tolerant taxa, the indicators of stressed benthic communities, were found to be inversely related to Bank Stability and Riparian vegetative zone (respectively), both indicators of habitat quality. Relationships between the quality of the physical habitat and the health of the benthic communities in aquatic systems, such as agricultural streams, needs to be considered before the impact of anthropogenic agents (e.g., pesticides, metals, and other potential toxicants) or other man-made perturbations may be understood. Otherwise, the interpretation of patterns of environmental conditions or causalities may be confounded.

On the temporal stability of personality: evidence for differential stability and the role of life experiences.

PubMed

Vaidya, Jatin G; Gray, Elizabeth K; Haig, Jeffrey; Watson, David

2002-12-01

The authors investigated the stability of personality and trait affect in young adults. In Studies 1 and 2, young adults were retested on a Big Five personality measure and a trait affect inventory over a 2.5-year and a 2-month period, respectively. Results from Study 1 point to positive mean-level changes; participants scored higher on Extraversion, Openness, Agreeableness, and Conscientiousness at Time 2. Affectively, participants experienced less negative affect and more positive affect at Time 2. Results from both retests provide clear evidence of differential stability. Affective traits were consistently less stable than the Big Five. Other analyses suggest that life events influence the stability of affective traits more than the Big Five.

Surface water and groundwater interactions in coastal wetlands

NASA Astrophysics Data System (ADS)

Li, Ling; Xin, Pei; Shen, Chengji

2014-05-01

Salt marshes are an important wetland system in the upper intertidal zone, interfacing the land and coastal water. Dominated by salt-tolerant plants, these wetlands provide essential eco-environmental services for maintaining coastal biodiversity. They also act as sediment traps and help stabilize the coastline. While they play an active role in moderating greenhouse gas emissions, these wetlands have become increasingly vulnerable to the impact of global climate change. Salt marshes are a complex hydrological system characterized by strong, dynamic interactions between surface water and groundwater, which underpin the wetland's eco-functionality. Bordered with coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur at different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil aeration conditions, which in turn affect marsh plant growth. This talk presents results and findings from recent numerical and experimental studies, focusing on the pore-water flow behaviour in the marsh soil under the influence of tides and density-gradients.

Long-range intercellular Ca2+ wave patterns

NASA Astrophysics Data System (ADS)

Tabi, C. B.; Maïna, I.; Mohamadou, A.; Ekobena, H. P. F.; Kofané, T. C.

2015-10-01

Modulational instability is utilized to investigate intercellular Ca2+ wave propagation in an array of diffusively coupled cells. Cells are supposed to be connected via paracrine signaling, where long-range effects, due to the presence of extracellular messengers, are included. The multiple-scale expansion is used to show that the whole dynamics of Ca2+ waves, from the endoplasmic reticulum to the cytosol, can be reduced to a single differential-difference nonlinear equation whose solutions are assumed to be plane waves. Their linear stability analysis is studied, with emphasis on the impact of long-range coupling, via the range parameter s. It is shown that s, as well as the number of interacting cells, importantly modifies the features of modulational instability, as small values of s imply a strong coupling, and increasing its value rather reduces the problem to a first-neighbor one. Our theoretical findings are numerically tested, as the generic equations are fully integrated, leading to the emergence of nonlinear patterns of Ca2+ waves. Strong long-range coupling is pictured by extended trains of breather-like structures whose frequency decreases with increasing s. We also show numerically that the number of interacting cells plays on the spatio-temporal formation of Ca2+ patterns, whilst the quasi-perfect intercellular communication depends on the paracrine coupling parameter.

Climate velocity and the future global redistribution of marine biodiversity

NASA Astrophysics Data System (ADS)

García Molinos, Jorge; Halpern, Benjamin S.; Schoeman, David S.; Brown, Christopher J.; Kiessling, Wolfgang; Moore, Pippa J.; Pandolfi, John M.; Poloczanska, Elvira S.; Richardson, Anthony J.; Burrows, Michael T.

2016-01-01

Anticipating the effect of climate change on biodiversity, in particular on changes in community composition, is crucial for adaptive ecosystem management but remains a critical knowledge gap. Here, we use climate velocity trajectories, together with information on thermal tolerances and habitat preferences, to project changes in global patterns of marine species richness and community composition under IPCC Representative Concentration Pathways (RCPs) 4.5 and 8.5. Our simple, intuitive approach emphasizes climate connectivity, and enables us to model over 12 times as many species as previous studies. We find that range expansions prevail over contractions for both RCPs up to 2100, producing a net local increase in richness globally, and temporal changes in composition, driven by the redistribution rather than the loss of diversity. Conversely, widespread invasions homogenize present-day communities across multiple regions. High extirpation rates are expected regionally (for example, Indo-Pacific), particularly under RCP8.5, leading to strong decreases in richness and the anticipated formation of no-analogue communities where invasions are common. The spatial congruence of these patterns with contemporary human impacts highlights potential areas of future conservation concern. These results strongly suggest that the millennial stability of current global marine diversity patterns, against which conservation plans are assessed, will change rapidly over the course of the century in response to ocean warming.

Stabilization and Structure of wave packets in Rydberg atoms ionized by a strong light field.

PubMed

Fedorov, M; Fedorov, S

1998-09-28

New features of the phenomenon of interference stabilization of Rydberg atoms are found to exist. The main of them are: (i) dynamical stabilization, which means that in case of pulses with a smooth envelope the time-dependent residual probability for an atom to survive in bound states remains almost constant in the middle part of a pulse (at the strongest fields); (ii) existence of the strong-field stabilization of the after-pulse residual probability in case of pulses longer than the classical Kepler period; and (iii) pulsation of the time-dependent Rydberg wave packet formed in the process of photoionization.

Menstrual cycle and the temporal discrimination threshold.

PubMed

Mc Govern, Eavan M; O'Connor, Emer; Beiser, Ines; Williams, Laura; Butler, John S; Quinlivan, Brendan; Narasimham, Shruti; Beck, Rebecca; Reilly, Richard B; O'Riordan, Sean; Hutchinson, Michael

2017-02-01

The temporal discrimination threshold (TDT) is a proposed pre-clinical biomarker (endophenotype) for adult onset isolated focal dystonia (AOIFD). Age- and sex-related effects on temporal discrimination demonstrate that women, before the age of 40 years, have faster temporal discrimination than men but their TDTs worsen with age at almost three times the rate of men. Thus after 40 years the TDT in women is progressively worse than in men. AOIFD is an increasingly female-predominant disorder after the age of 40; it is not clear whether this age-related sexually-dimorphic difference observed for both the TDT and sex ratio at disease onset in AOIFD is a hormonal or chromosomal effect. The aim of this study was to examine temporal discrimination at weekly intervals during two consecutive menstrual cycles in 14 healthy female volunteers to determine whether physiological hormonal changes affected temporal discrimination. We observed no significant differences in weekly temporal discrimination threshold values during the menstrual cycles and no significant correlation with the menstrual cycle stage. This observed stability of temporal discrimination during cyclical hormonal change raises interesting questions concerning the age-related sexually-dimorphic decline observed in temporal discrimination. Our findings pave the way for future studies exploring potential pathomechanisms for this age-related deterioration.

Brain volume change and cognitive trajectories in aging.

PubMed

Fletcher, Evan; Gavett, Brandon; Harvey, Danielle; Farias, Sarah Tomaszewski; Olichney, John; Beckett, Laurel; DeCarli, Charles; Mungas, Dan

2018-05-01

Examine how longitudinal cognitive trajectories relate to brain baseline measures and change in lobar volumes in a racially/ethnically and cognitively diverse sample of older adults. Participants were 460 older adults enrolled in a longitudinal aging study. Cognitive outcomes were measures of episodic memory, semantic memory, executive function, and spatial ability derived from the Spanish and English Neuropsychological Assessment Scales (SENAS). Latent variable multilevel modeling of the four cognitive outcomes as parallel longitudinal processes identified intercepts for each outcome and a second order global change factor explaining covariance among the highly correlated slopes. We examined how baseline brain volumes (lobar gray matter, hippocampus, and white matter hyperintensity) and change in brain volumes (lobar gray matter) were associated with cognitive intercepts and global cognitive change. Lobar volumes were dissociated into global and specific components using latent variable methods. Cognitive change was most strongly associated with brain gray matter volume change, with strong independent effects of global gray matter change and specific temporal lobe gray matter change. Baseline white matter hyperintensity and hippocampal volumes had significant incremental effects on cognitive decline beyond gray matter change. Baseline lobar gray matter was related to cognitive decline, but did not contribute beyond gray matter change. Cognitive decline was strongly influenced by gray matter volume change and, especially, temporal lobe change. The strong influence of temporal lobe gray matter change on cognitive decline may reflect involvement of temporal lobe structures that are critical for late life cognitive health but also are vulnerable to diseases of aging. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Multiscale responses of soil stability and invasive plants to removal of non-native grazers from an arid conservation reserve

USGS Publications Warehouse

Beever, E.A.; Huso, M.; Pyke, D.A.

2006-01-01

Disturbances and ecosystem recovery from disturbance both involve numerous processes that operate on multiple spatial and temporal scales. Few studies have investigated how gradients of disturbance intensity and ecosystem responses are distributed across multiple spatial resolutions and also how this relationship changes through time during recovery. We investigated how cover of non-native species and soil-aggregate stability (a measure of vulnerability to erosion by water) in surface and subsurface soils varied spatially during grazing by burros and cattle and whether patterns in these variables changed after grazer removal from Mojave National Preserve, California, USA. We compared distance from water and number of ungulate defecations - metrics of longer-term and recent grazing intensity, respectively, - as predictors of our response variables. We used information-theoretic analyses to compare hierarchical linear models that accounted for important covariates and allowed for interannual variation in the disturbance-response relationship at local and landscape scales. Soil stability was greater under perennial vegetation than in bare interspaces, and surface soil stability decreased with increasing numbers of ungulate defecations. Stability of surface samples was more affected by time since removal of grazers than was stability of subsurface samples, and subsurface soil stability in bare spaces was not related to grazing intensity, time since removal, or any of our other predictors. In the high rainfall year (2003) after cattle had been removed for 1-2 years, cover of all non-native plants averaged nine times higher than in the low-rainfall year (2002). Given the heterogeneity in distribution of large-herbivore impacts that we observed at several resolutions, hierarchical analyses provided a more complete understanding of the spatial and temporal complexities of disturbance and recovery processes in arid ecosystems. ?? 2006 Blackwell Publishing Ltd.

Multi-scale responses of soil stability and invasive plants to removal of non-native grazers from an arid conservation reserve

USGS Publications Warehouse

Beever, Erik A.; Huso, Manuela M. P.; Pyke, David A.

2006-01-01

Disturbances and ecosystem recovery from disturbance both involve numerous processes that operate on multiple spatial and temporal scales. Few studies have investigated how gradients of disturbance intensity and ecosystem responses are distributed across multiple spatial resolutions and also how this relationship changes through time during recovery. We investigated how cover of non-native species and soil-aggregate stability (a measure of vulnerability to erosion by water) in surface and subsurface soils varied spatially during grazing by burros and cattle and whether patterns in these variables changed after grazer removal from Mojave National Preserve, California, USA. We compared distance from water and number of ungulate defecations — metrics of longer-term and recent grazing intensity, respectively, — as predictors of our response variables. We used information-theoretic analyses to compare hierarchical linear models that accounted for important covariates and allowed for interannual variation in the disturbance–response relationship at local and landscape scales. Soil stability was greater under perennial vegetation than in bare interspaces, and surface soil stability decreased with increasing numbers of ungulate defecations. Stability of surface samples was more affected by time since removal of grazers than was stability of subsurface samples, and subsurface soil stability in bare spaces was not related to grazing intensity, time since removal, or any of our other predictors. In the high rainfall year (2003) after cattle had been removed for 1–2 years, cover of all non-native plants averaged nine times higher than in the low-rainfall year (2002). Given the heterogeneity in distribution of large-herbivore impacts that we observed at several resolutions, hierarchical analyses provided a more complete understanding of the spatial and temporal complexities of disturbance and recovery processes in arid ecosystems.

Pitch and time, tonality and meter: how do musical dimensions combine?

PubMed

Prince, Jon B; Thompson, William F; Schmuckler, Mark A

2009-10-01

The authors examined how the structural attributes of tonality and meter influence musical pitch-time relations. Listeners heard a musical context followed by probe events that varied in pitch class and temporal position. Tonal and metric hierarchies contributed additively to the goodness-of-fit of probes, with pitch class exerting a stronger influence than temporal position (Experiment 1), even when listeners attempted to ignore pitch (Experiment 2). Speeded classification tasks confirmed this asymmetry. Temporal classification was biased by tonal stability (Experiment 3), but pitch classification was unaffected by temporal position (Experiment 4). Experiments 5 and 6 ruled out explanations based on the presence of pitch classes and temporal positions in the context, unequal stimulus quantity, and discriminability. The authors discuss how typical Western music biases attention toward pitch and distinguish between dimensional discriminability and salience. PsycINFO Database Record (c) 2009 APA, all rights reserved.

Tear thinning time and topical anesthesia as assessed using the HIRCAL grid and the NCCA.

PubMed

Blades, K J; Murphy, P J; Patel, S

1999-03-01

The literature contains conflicting reports of the effects of topical anesthetics on tear film stability, with some consensus that unpreserved topical anesthetics are less likely to reduce tear film stability than preserved preparations. This experiment investigated the effect of unpreserved 0.4% benoxinate hydrochloride on tear thinning time (TTT), in parallel with "real time" corneal sensitivity assessment. Tear film stability was assessed (HIRCAL grid) in parallel with real time assessment of the pharmacological activity (NCCA) of unpreserved 0.4% benoxinate hydrochloride in normal eyes. The anesthetic used did not significantly affect tear film stability. This finding is in agreement with previous investigators. Unpreserved 0.4% benoxinate hydrochloride could be used to facilitate tear film stability assessment. The experimental protocol used could also be applied to investigate the temporal relationship between anesthesia and tear film stability with preserved topical anesthetics that have been found to decrease tear film stability.

Long-term stability and temporal trends of organic contaminants in four collections of mussel tissue frozen standard reference materials.

PubMed

Schantz, Michele M; Pugh, Rebecca S; Pol, Stacy S Vander; Wise, Stephen A

2015-04-01

The stability of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and chlorinated pesticides in frozen mussel tissue Standard Reference Materials (SRMs) stored at -80 °C was assessed by analyzing samples of SRM 1974, SRM 1974a, and SRM 1974b Organics in Mussel Tissue (Mytilus edulis) periodically over 25 y, 20 y, and 12 y, respectively. The most recent analyses were performed during the certification of the fourth release of this material, SRM 1974c. Results indicate the concentrations of these persistent organic pollutants have not changed during storage at -80 °C. In addition, brominated diphenyl ethers (BDEs) were quantified in each of the materials during this study. The stability information is important for on-going monitoring studies collecting large quantities of samples for future analyses (i.e., formally established specimen banking programs). Since all four mussel tissue SRMs were prepared from mussels collected at the same site in Dorchester Bay, MA, USA, the results provide a temporal trend study for these contaminants over a 17 year period (1987 to 2004).

Preservation of perceptual integration improves temporal stability of bimanual coordination in the elderly: an evidence of age-related brain plasticity.

PubMed

Blais, Mélody; Martin, Elodie; Albaret, Jean-Michel; Tallet, Jessica

2014-12-15

Despite the apparent age-related decline in perceptual-motor performance, recent studies suggest that the elderly people can improve their reaction time when relevant sensory information are available. However, little is known about which sensory information may improve motor behaviour itself. Using a synchronization task, the present study investigates how visual and/or auditory stimulations could increase accuracy and stability of three bimanual coordination modes produced by elderly and young adults. Neurophysiological activations are recorded with ElectroEncephaloGraphy (EEG) to explore neural mechanisms underlying behavioural effects. Results reveal that the elderly stabilize all coordination modes when auditory or audio-visual stimulations are available, compared to visual stimulation alone. This suggests that auditory stimulations are sufficient to improve temporal stability of rhythmic coordination, even more in the elderly. This behavioural effect is primarily associated with increased attentional and sensorimotor-related neural activations in the elderly but similar perceptual-related activations in elderly and young adults. This suggests that, despite a degradation of attentional and sensorimotor neural processes, perceptual integration of auditory stimulations is preserved in the elderly. These results suggest that perceptual-related brain plasticity is, at least partially, conserved in normal aging. Copyright © 2014 Elsevier B.V. All rights reserved.

Does Repeated Testing Impact Concordance Between Genital and Self-Reported Sexual Arousal in Women?

PubMed

Velten, Julia; Chivers, Meredith L; Brotto, Lori A

2018-04-01

Women show a substantial variability in their genital and subjective responses to sexual stimuli. The level of agreement between these two aspects of response is termed sexual concordance and has been increasingly investigated because of its implications for understanding models of sexual response and as a potential endpoint in clinical trials of treatments to improve women's sexual dysfunction. However, interpreting changes in sexual concordance may be problematic because, to date, it still is unclear how repeated testing itself influences sexual concordance in women. We are aware of only one study that evaluated temporal stability of concordance in women, and it found no evidence of stability. However, time stability would be necessary for arguing that concordance is a stable individual difference. The main goal of this study was to investigate the test-retest reliability of sexual concordance in a sample of 30 women with sexual difficulties. Using hierarchical linear modeling, we found that sexual concordance was not influenced by repeated testing 12 weeks later, but showed test-retest reliability suggesting temporal stability. Our findings support the hypothesis that sexual concordance is a relatively stable individual difference and that changes in sexual concordance after treatment or experimental conditions could, therefore, be attributed to effects of those conditions.

Community ecology in 3D: Tensor decomposition reveals spatio-temporal dynamics of large ecological communities

PubMed Central

Lindegren, Martin; Denker, Tim Spaanheden; Floeter, Jens; Fock, Heino O.; Sguotti, Camilla; Stäbler, Moritz; Otto, Saskia A.; Möllmann, Christian

2017-01-01

Understanding spatio-temporal dynamics of biotic communities containing large numbers of species is crucial to guide ecosystem management and conservation efforts. However, traditional approaches usually focus on studying community dynamics either in space or in time, often failing to fully account for interlinked spatio-temporal changes. In this study, we demonstrate and promote the use of tensor decomposition for disentangling spatio-temporal community dynamics in long-term monitoring data. Tensor decomposition builds on traditional multivariate statistics (e.g. Principal Component Analysis) but extends it to multiple dimensions. This extension allows for the synchronized study of multiple ecological variables measured repeatedly in time and space. We applied this comprehensive approach to explore the spatio-temporal dynamics of 65 demersal fish species in the North Sea, a marine ecosystem strongly altered by human activities and climate change. Our case study demonstrates how tensor decomposition can successfully (i) characterize the main spatio-temporal patterns and trends in species abundances, (ii) identify sub-communities of species that share similar spatial distribution and temporal dynamics, and (iii) reveal external drivers of change. Our results revealed a strong spatial structure in fish assemblages persistent over time and linked to differences in depth, primary production and seasonality. Furthermore, we simultaneously characterized important temporal distribution changes related to the low frequency temperature variability inherent in the Atlantic Multidecadal Oscillation. Finally, we identified six major sub-communities composed of species sharing similar spatial distribution patterns and temporal dynamics. Our case study demonstrates the application and benefits of using tensor decomposition for studying complex community data sets usually derived from large-scale monitoring programs. PMID:29136658

[INVITED] Control of femtosecond pulsed laser ablation and deposition by temporal pulse shaping

NASA Astrophysics Data System (ADS)

Garrelie, Florence; Bourquard, Florent; Loir, Anne--Sophie; Donnet, Christophe; Colombier, Jean-Philippe

2016-04-01

This study explores the effects of temporal laser pulse shaping on femtosecond pulsed laser deposition (PLD). The potential of laser pulses temporally tailored on ultrafast time scales is used to control the expansion and the excitation degree of ablation products including atomic species and nanoparticles. The ablation plume generated by temporally shaped femtosecond pulsed laser ablation of aluminum and graphite targets is studied by in situ optical diagnostic methods. Taking advantage of automated pulse shaping techniques, an adaptive procedure based on spectroscopic feedback regulates the irradiance for the enhancement of typical plasma features. Thin films elaborated by unshaped femtosecond laser pulses and by optimized sequence indicate that the nanoparticles generation efficiency is strongly influenced by the temporal shaping of the laser irradiation. The ablation processes leading either to the generation of the nanoparticles either to the formation of plasma can be favored by using a temporal shaping of the laser pulse. Insights are given on the possibility to control the quantity of the nanoparticles. The temporal laser pulse shaping is shown also to strongly modify the laser-induced plasma contents and kinetics for graphite ablation. Temporal pulse shaping proves its capability to reduce the number of slow radicals while increasing the proportion of monomers, with the addition of ionized species in front of the plume. This modification of the composition and kinetics of plumes in graphite ablation using temporal laser pulse shaping is discussed in terms of modification of the structural properties of deposited Diamond-Like Carbon films (DLC). This gives rise to a better understanding of the growth processes involved in femtosecond-PLD and picosecond-PLD of DLC suggesting the importance of neutral C atoms, which are responsible for the subplantation process.

Rapid and tunable method to temporally control gene editing based on conditional Cas9 stabilization. | Office of Cancer Genomics

Cancer.gov

The CRISPR/Cas9 system is a powerful tool for studying gene function. Here, we describe a method that allows temporal control of CRISPR/Cas9 activity based on conditional Cas9 destabilization. We demonstrate that fusing an FKBP12-derived destabilizing domain to Cas9 (DD-Cas9) enables conditional Cas9 expression and temporal control of gene editing in the presence of an FKBP12 synthetic ligand. This system can be easily adapted to co-express, from the same promoter, DD-Cas9 with any other gene of interest without co-modulation of the latter.

Reduced Orbitofrontal and Temporal Grey Matter in a Community Sample of Maltreated Children

ERIC Educational Resources Information Center

De Brito, Stephane A.; Viding, Essi; Sebastian, Catherine L.; Kelly, Philip A.; Mechelli, Andrea; Maris, Helen; McCrory, Eamon J.

2013-01-01

Background: Childhood maltreatment is strongly associated with increased risk of psychiatric disorder. Previous neuroimaging studies have reported atypical neural structure in the orbitofrontal cortex, temporal lobe, amygdala, hippocampus and cerebellum in maltreated samples. It has been hypothesised that these structural differences may relate to…

The impact of climate change on photovoltaic power generation in Europe

PubMed Central

Jerez, Sonia; Tobin, Isabelle; Vautard, Robert; Montávez, Juan Pedro; López-Romero, Jose María; Thais, Françoise; Bartok, Blanka; Christensen, Ole Bøssing; Colette, Augustin; Déqué, Michel; Nikulin, Grigory; Kotlarski, Sven; van Meijgaard, Erik; Teichmann, Claas; Wild, Martin

2015-01-01

Ambitious climate change mitigation plans call for a significant increase in the use of renewables, which could, however, make the supply system more vulnerable to climate variability and changes. Here we evaluate climate change impacts on solar photovoltaic (PV) power in Europe using the recent EURO-CORDEX ensemble of high-resolution climate projections together with a PV power production model and assuming a well-developed European PV power fleet. Results indicate that the alteration of solar PV supply by the end of this century compared with the estimations made under current climate conditions should be in the range (−14%;+2%), with the largest decreases in Northern countries. Temporal stability of power generation does not appear as strongly affected in future climate scenarios either, even showing a slight positive trend in Southern countries. Therefore, despite small decreases in production expected in some parts of Europe, climate change is unlikely to threaten the European PV sector. PMID:26658608

Likelihood testing of seismicity-based rate forecasts of induced earthquakes in Oklahoma and Kansas

USGS Publications Warehouse

Moschetti, Morgan P.; Hoover, Susan M.; Mueller, Charles

2016-01-01

Likelihood testing of induced earthquakes in Oklahoma and Kansas has identified the parameters that optimize the forecasting ability of smoothed seismicity models and quantified the recent temporal stability of the spatial seismicity patterns. Use of the most recent 1-year period of earthquake data and use of 10–20-km smoothing distances produced the greatest likelihood. The likelihood that the locations of January–June 2015 earthquakes were consistent with optimized forecasts decayed with increasing elapsed time between the catalogs used for model development and testing. Likelihood tests with two additional sets of earthquakes from 2014 exhibit a strong sensitivity of the rate of decay to the smoothing distance. Marked reductions in likelihood are caused by the nonstationarity of the induced earthquake locations. Our results indicate a multiple-fold benefit from smoothed seismicity models in developing short-term earthquake rate forecasts for induced earthquakes in Oklahoma and Kansas, relative to the use of seismic source zones.

Laser Speckle Strain Imaging reveals the origin of delayed fracture in a soft solid

PubMed Central

Dussi, Simone; Frijns, Raoul A. M.; van der Gucht, Jasper; Sprakel, Joris

2018-01-01

Stresses well below the critical fracture stress can lead to highly unpredictable delayed fracture after a long period of seemingly quiescent stability. Delayed fracture is a major threat to the lifetime of materials, and its unpredictability makes it difficult to prevent. This is exacerbated by the lack of consensus on the microscopic mechanisms at its origin because unambiguous experimental proof of these mechanisms remains absent. We present an experimental approach to measure, with high spatial and temporal resolution, the local deformations that precipitate crack nucleation. We apply this method to study delayed fracture in an elastomer and find that a delocalized zone of very small strains emerges as a consequence of strongly localized damage processes. This prefracture deformation zone grows exponentially in space and time, ultimately culminating in the nucleation of a crack and failure of the material as a whole. Our results paint a microscopic picture of the elusive origins of delayed fracture and open the way to detect damage well before it manifests macroscopically. PMID:29736415

Estimation of the limit of detection in semiconductor gas sensors through linearized calibration models.

PubMed

Burgués, Javier; Jiménez-Soto, Juan Manuel; Marco, Santiago

2018-07-12

The limit of detection (LOD) is a key figure of merit in chemical sensing. However, the estimation of this figure of merit is hindered by the non-linear calibration curve characteristic of semiconductor gas sensor technologies such as, metal oxide (MOX), gasFETs or thermoelectric sensors. Additionally, chemical sensors suffer from cross-sensitivities and temporal stability problems. The application of the International Union of Pure and Applied Chemistry (IUPAC) recommendations for univariate LOD estimation in non-linear semiconductor gas sensors is not straightforward due to the strong statistical requirements of the IUPAC methodology (linearity, homoscedasticity, normality). Here, we propose a methodological approach to LOD estimation through linearized calibration models. As an example, the methodology is applied to the detection of low concentrations of carbon monoxide using MOX gas sensors in a scenario where the main source of error is the presence of uncontrolled levels of humidity. Copyright © 2018 Elsevier B.V. All rights reserved.

Two-dimensional nanowires on homoepitaxial interfaces: Atomic-scale mechanism of breakdown and disintegration

NASA Astrophysics Data System (ADS)

Michailov, Michail; Ranguelov, Bogdan

2018-03-01

We present a model for hole-mediated spontaneous breakdown of ahomoepitaxial two-dimensional (2D) flat nanowire based exclusively on random, thermally-activated motion of atoms. The model suggests a consecutive three-step mechanism driving the rupture and complete disintegration of the nanowire on a crystalline surface. The breakdown scenario includes: (i) local narrowing of a part of the stripe to a monatomic chain, (ii) formation of a recoverable single vacancy or a 2D vacancy cluster that causes temporary nanowire rupture, (iii) formation of a non-recoverable 2D hole leading to permanent nanowire breakdown. These successive events in the temporal evolution of the nanowire morphology bring the nanowire stripe into an irreversible unstable state, leading to a dramatic change in its peculiar physical properties and conductivity. The atomistic simulations also reveal a strong increase of the nanowire lifetime with an enlargement of its width and open up a way for a fine atomic-scale control of the nanowire lifetime and structural, morphological and thermodynamic stability.

Modeling Effects of Local Extinctions on Culture Change and Diversity in the Paleolithic

PubMed Central

Premo, L. S.; Kuhn, Steven L.

2010-01-01

The persistence of early stone tool technologies has puzzled archaeologists for decades. Cognitively based explanations, which presume either lack of ability to innovate or extreme conformism, do not account for the totality of the empirical patterns. Following recent research, this study explores the effects of demographic factors on rates of culture change and diversification. We investigate whether the appearance of stability in early Paleolithic technologies could result from frequent extinctions of local subpopulations within a persistent metapopulation. A spatially explicit agent-based model was constructed to test the influence of local extinction rate on three general cultural patterns that archaeologists might observe in the material record: total diversity, differentiation among spatially defined groups, and the rate of cumulative change. The model shows that diversity, differentiation, and the rate of cumulative cultural change would be strongly affected by local extinction rates, in some cases mimicking the results of conformist cultural transmission. The results have implications for understanding spatial and temporal patterning in ancient material culture. PMID:21179418

The Tropopause Inversion Layer: New Observations, New Theories

NASA Astrophysics Data System (ADS)

Tandon, N.; Randel, W. J.; Pan, L.; Son, S.; Polvani, L. M.

2009-12-01

There is now great interest in the tropopause inversion inversion layer (TIL), a 1-2 km region just above the tropopause where there is a spike in static stability. Radio occultation data from the COSMIC GPS mission are providing an unprecedented level of spatial and temporal resolution with which to analyze the TIL. We start by showing the agreement between GPS data and radiosondes. We then examine the causes and consequences of the TIL. Observations from the ACE satellite and fixed dynamical heating calculations suggest strong roles for water vapor and ozone in the formation and modulation of the TIL. This agrees with observations showing a large TIL in the polar winter, where water vapor levels are persistently high. It is also clear that TIL strength is related to vorticity, but observations and models have important differences that need to be reconciled. These dynamical considerations dovetail with observations showing high TIL variability in the storm-track regions. Finally there is evidence from ozonesonde data that the TIL may be coupled to transport across the tropopause.

A Continuous Labour Supply Model in Microsimulation: A Life-Cycle Modelling Approach with Heterogeneity and Uncertainty Extension

PubMed Central

Li, Jinjing; Sologon, Denisa Maria

2014-01-01

This paper advances a structural inter-temporal model of labour supply that is able to simulate the dynamics of labour supply in a continuous setting and addresses two main drawbacks of most existing models. The first limitation is the inability to incorporate individual heterogeneity as every agent is sharing the same parameters of the utility function. The second one is the strong assumption that individuals make decisions in a world of perfect certainty. Essentially, this paper offers an extension of marginal-utility-of-wealth-constant labour supply functions known as “Frisch functions” under certainty and uncertainty with homogenous and heterogeneous preferences. The lifetime models based on the fixed effect vector decomposition yield the most stable simulation results, under both certain and uncertain future wage assumptions. Due to its improved accuracy and stability, this lifetime labour supply model is particularly suitable for enhancing the performance of the life cycle simulation models, thus providing a better reference for policymaking. PMID:25391021

Blood Flow in Stenotic Carotid Bifurcation

NASA Astrophysics Data System (ADS)

Rayz, Vitaliy L.; Williamson, Shobha Devi; Berger, Stanley A.; Saloner, David

2004-11-01

Mechanical forces induced by blood flow on an arterial wall play an important role in the development and growth of atherosclerotic plaque. To assess vulnerability of a plaque it is important to model the flow in a realistic, patient-specific geometry. Three-dimensional models of stenotic carotid bifurcations were obtained from MR images and grids were generated for the flow domains. The unsteady, incompressible Navier-Stokes equations were solved numerically using physiological boundary conditions. The results obtained by computations were compared with in-vivo ultrasound measurements and flow visualization experiments carried out for the same geometry. The simulations show a high velocity jet forming at the stenotic throat and a strong recirculation zone downstream of the stenosis. The jet grows rapidly during the systolic part of the pulse. During diastole the flow is more stagnant. The flow is highly three-dimensional and unsteady which is clearly demonstrated by the flow streamlines. These unsteady flows cause rapid temporal and spatial changes of the forces acting on the atherosclerotic plaque, which has important effects on its growth and stability.

"Signal" search for intelligence in the galactic nucleus with the array of the Lowlands.

PubMed

Shostak, G S; Tarter, J

1985-01-01

In August, 1981, the Westerbork Synthesis Radio Telescope was used for 4 h to search for narrowband pulsing radio beacons in the direction of the Galactic Center. By using both the spatial discrimination and temporal stability available to an interferometric measurement, weak intermittent signals can be detected even in the face of the strong, naturally caused radiation from this region. A radio beacon within our bandwidth, centered on the 21 cm neutral hydrogen line, would be recognizable if it had a repetition period between 40 sec and 1/2 h. The rms sensitivity to point sources was approximately 50 mJy/cycle, and the detection limit was 500 mJy/cycle. The limit degrades for pulse widths < 0.02s. No repetitive signals were found. For a swept, narrow-band radio beacon constrained to the Galactic Disk (beamwidth = 0.02 rad), our detection limit corresponds to a transmitter power of 10(11) MW at the Galactic Center.

Advances in the stability of high precision crystal resonators

NASA Technical Reports Server (NTRS)

Ballato, A.; Vig, J. R.

1979-01-01

Advances in technology directed toward minimizing the temporal changes in frequency of crystal resonators are described. Specific emphasis is placed on reducing their susceptibility to temperature, acceleration, and other environmental effects.

Felder-Soloman's Index of Learning Styles: internal consistency, temporal stability, and factor structure.

PubMed

Hosford, Charles C; Siders, William A

2010-10-01

Strategies to facilitate learning include using knowledge of students' learning style preferences to inform students and their teachers. Aims of this study were to evaluate the factor structure, internal consistency, and temporal stability of medical student responses to the Index of Learning Styles (ILS) and determine its appropriateness as an instrument for medical education. The ILS assesses preferences on four dimensions: sensing/intuitive information perceiving, visual/verbal information receiving, active/reflective information processing, and sequential/global information understanding. Students entering the 2002-2007 classes completed the ILS; some completed the ILS again after 2 and 4 years. Analyses of responses supported the ILS's intended structure and moderate reliability. Students had moderate preferences for sensing and visual learning. This study provides evidence supporting the appropriateness of the ILS for assessing learning style preferences in medical students.

Representations of temporal information in short-term memory: Are they modality-specific?

PubMed

Bratzke, Daniel; Quinn, Katrina R; Ulrich, Rolf; Bausenhart, Karin M

2016-10-01

Rattat and Picard (2012) reported that the coding of temporal information in short-term memory is modality-specific, that is, temporal information received via the visual (auditory) modality is stored as a visual (auditory) code. This conclusion was supported by modality-specific interference effects on visual and auditory duration discrimination, which were induced by secondary tasks (visual tracking or articulatory suppression), presented during a retention interval. The present study assessed the stability of these modality-specific interference effects. Our study did not replicate the selective interference pattern but rather indicated that articulatory suppression not only impairs short-term memory for auditory but also for visual durations. This result pattern supports a crossmodal or an abstract view of temporal encoding. Copyright © 2016 Elsevier B.V. All rights reserved.

Focus expansion and stability of the spread parameter estimate of the power law model for dispersal gradients

PubMed Central

Gent, David H.; Mehra, Lucky K.; Christie, David; Magarey, Roger

2017-01-01

Empirical and mechanistic modeling indicate that pathogens transmitted via aerially dispersed inoculum follow a power law, resulting in dispersive epidemic waves. The spread parameter (b) of the power law model, which is an indicator of the distance of the epidemic wave front from an initial focus per unit time, has been found to be approximately 2 for several animal and plant diseases over a wide range of spatial scales under conditions favorable for disease spread. Although disease spread and epidemic expansion can be influenced by several factors, the stability of the parameter b over multiple epidemic years has not been determined. Additionally, the size of the initial epidemic area is expected to be strongly related to the final epidemic extent for epidemics, but the stability of this relationship is also not well established. Here, empirical data of cucurbit downy mildew epidemics collected from 2008 to 2014 were analyzed using a spatio-temporal model of disease spread that incorporates logistic growth in time with a power law function for dispersal. Final epidemic extent ranged from 4.16 ×108 km2 in 2012 to 6.44 ×108 km2 in 2009. Current epidemic extent became significantly associated (P < 0.0332; 0.56 < R2 < 0.99) with final epidemic area beginning near the end of April, with the association increasing monotonically to 1.0 by the end of the epidemic season in July. The position of the epidemic wave-front became exponentially more distant with time, and epidemic velocity increased linearly with distance. Slopes from the temporal and spatial regression models varied with about a 2.5-fold range across epidemic years. Estimates of b varied substantially ranging from 1.51 to 4.16 across epidemic years. We observed a significant b ×time (or distance) interaction (P < 0.05) for epidemic years where data were well described by the power law model. These results suggest that the spread parameter b may not be stable over multiple epidemic years. However, b ≈ 2 may be considered the lower limit of the distance traveled by epidemic wave-fronts for aerially transmitted pathogens that follow a power law dispersal function. PMID:28649473

Enhanced effect of temporal variation of the fine structure constant and the strong interaction in 229Th.

PubMed

Flambaum, V V

2006-09-01

The relative effects of the variation of the fine structure constant alpha = e2/variant Planck's over 2pi c and the dimensionless strong interaction parameter m(q)/LambdaQCD are enhanced by 5-6 orders of magnitude in a very narrow ultraviolet transition between the ground and the first excited states in the 229Th nucleus. It may be possible to investigate this transition with laser spectroscopy. Such an experiment would have the potential of improving the sensitivity to temporal variation of the fundamental constants by many orders of magnitude.

Influence of temporal pressure constraint on the biomechanical organization of gait initiation made with or without an obstacle to clear.

PubMed

Yiou, Eric; Fourcade, Paul; Artico, Romain; Caderby, Teddy

2016-06-01

Many daily motor tasks have to be performed under a temporal pressure constraint. This study aimed to explore the influence of such constraint on motor performance and postural stability during gait initiation. Young healthy participants initiated gait at maximal velocity under two conditions of temporal pressure: in the low-pressure condition, gait was self-initiated (self-initiated condition, SI); in the high-pressure condition, it was initiated as soon as possible after an acoustic signal (reaction-time condition, RT). Gait was initiated with and without an environmental constraint in the form of an obstacle to be cleared placed in front of participants. Results showed that the duration of postural adjustments preceding swing heel-off ("anticipatory postural adjustments", APAs) was shorter, while their amplitude was larger in RT compared to SI. These larger APAs allowed the participants to reach equivalent postural stability and motor performance in both RT and SI. In addition, the duration of the execution phase of gait initiation increased greatly in the condition with an obstacle to be cleared (OBST) compared to the condition without an obstacle (NO OBST), thereby increasing lateral instability and thus involving larger mediolateral APA. Similar effects of temporal pressure were obtained in NO OBST and OBST. This study shows the adaptability of the postural system to temporal pressure in healthy young adults initiating gait. The outcome of this study may provide a basis for better understanding the aetiology of balance impairments with the risk of falling in frail populations while performing daily complex tasks involving a whole-body progression.

Spatial Distribution of a Large Herbivore Community at Waterholes: An Assessment of Its Stability over Years in Hwange National Park, Zimbabwe.

PubMed

Chamaillé-Jammes, Simon; Charbonnel, Anaïs; Dray, Stéphane; Madzikanda, Hillary; Fritz, Hervé

2016-01-01

The spatial structuring of populations or communities is an important driver of their functioning and their influence on ecosystems. Identifying the (in)stability of the spatial structure of populations is a first step towards understanding the underlying causes of these structures. Here we studied the relative importance of spatial vs. interannual variability in explaining the patterns of abundance of a large herbivore community (8 species) at waterholes in Hwange National Park (Zimbabwe). We analyzed census data collected over 13 years using multivariate methods. Our results showed that variability in the census data was mostly explained by the spatial structure of the community, as some waterholes had consistently greater herbivore abundance than others. Some temporal variability probably linked to Park-scale migration dependent on annual rainfall was noticeable, however. Once this was accounted for, little temporal variability remained to be explained, suggesting that other factors affecting herbivore abundance over time had a negligible effect at the scale of the study. The extent of spatial and temporal variability in census data was also measured for each species. This study could help in projecting the consequences of surface water management, and more generally presents a methodological framework to simultaneously address the relative importance of spatial vs. temporal effects in driving the distribution of organisms across landscapes.

Temporal stability of an endemic Mexican treefrog

PubMed Central

Cruz-Ruiz, Griselda; Venegas-Barrera, Crystian S.; Sanchez-Sanchez, Hermilo

2015-01-01

The demographic characteristics of an amphibian population fluctuate independently over time, mainly in response to the temporal variation of environmental factors, especially precipitation and temperature. These temporal fluctuations may contribute to the size of an amphibian population and could be used to determine the current conservation status of a species. During a five year (2004–2008) period, we studied the relative abundance, sex ratio, and age-sex structure of a population of metamorphosed individuals of the endemic treefrog Hyla eximia in Central Mexico. We also studied the species’ relationship with climatic variables such as temperature and precipitation. We found an interannual constant abundance during the study period. However, interannual differences were observed in the population structure by age-sex category (males, females, or juveniles), with decreased abundance of males and juveniles during the rainy months (August–November). The annual abundance of H. eximia was positively correlated with rainfall, but negatively with monthly temperature. We found the sex ratio was male-biased (2:1), except for year 2008. Also, differences in snout-vent length (SVL) were found between years, suggesting changes in recruitment of new individuals. We conclude that variations in abundance, and frequencies by age-sex category, of H. eximia are related to seasonal variations in temperature and precipitation characteristics of temperate zones. However, this temporal stability may suggest that anurans have an unusual capacity to persist even in the face of human-induced habitat change. PMID:26421242

Linear Temporal Stability Analysis of a Low-Density Round Gas Jet Injected into a High-Density Gas

NASA Technical Reports Server (NTRS)

Lawson, Anthony L.; Parthasarathy, Ramkumar N.

2002-01-01

It has been observed in previous experimental studies that round helium jets injected into air display a repetitive structure for a long distance, somewhat similar to the buoyancy-induced flickering observed in diffusion flames. In order to investigate the influence of gravity on the near-injector development of the flow, a linear temporal stability analysis of a round helium jet injected into air was performed. The flow was assumed to be isothermal and locally parallel; viscous and diffusive effects were ignored. The variables were represented as the sum of the mean value and a normal-mode small disturbance. An ordinary differential equation governing the amplitude of the pressure disturbance was derived. The velocity and density profiles in the shear layer, and the Froude number (signifying the effects of gravity) were the three important parameters in this equation. Together with the boundary conditions, an eigenvalue problem was formulated. Assuming that the velocity and density profiles in the shear layer to be represented by hyperbolic tangent functions, the eigenvalue problem was solved for various values of Froude number. The temporal growth rates and the phase velocity of the disturbances were obtained. The temporal growth rates of the disturbances increased as the Froude number was reduced (i.e. gravitational effects increased), indicating the destabilizing role played by gravity.

Spatial Distribution of a Large Herbivore Community at Waterholes: An Assessment of Its Stability over Years in Hwange National Park, Zimbabwe

PubMed Central

Chamaillé-Jammes, Simon; Charbonnel, Anaïs; Dray, Stéphane; Madzikanda, Hillary; Fritz, Hervé

2016-01-01

The spatial structuring of populations or communities is an important driver of their functioning and their influence on ecosystems. Identifying the (in)stability of the spatial structure of populations is a first step towards understanding the underlying causes of these structures. Here we studied the relative importance of spatial vs. interannual variability in explaining the patterns of abundance of a large herbivore community (8 species) at waterholes in Hwange National Park (Zimbabwe). We analyzed census data collected over 13 years using multivariate methods. Our results showed that variability in the census data was mostly explained by the spatial structure of the community, as some waterholes had consistently greater herbivore abundance than others. Some temporal variability probably linked to Park-scale migration dependent on annual rainfall was noticeable, however. Once this was accounted for, little temporal variability remained to be explained, suggesting that other factors affecting herbivore abundance over time had a negligible effect at the scale of the study. The extent of spatial and temporal variability in census data was also measured for each species. This study could help in projecting the consequences of surface water management, and more generally presents a methodological framework to simultaneously address the relative importance of spatial vs. temporal effects in driving the distribution of organisms across landscapes. PMID:27074044

Local Stability of the Trunk in Patients with Degenerative Cerebellar Ataxia During Walking.

PubMed

Chini, Giorgia; Ranavolo, Alberto; Draicchio, Francesco; Casali, Carlo; Conte, Carmela; Martino, Giovanni; Leonardi, Luca; Padua, Luca; Coppola, Gianluca; Pierelli, Francesco; Serrao, Mariano

2017-02-01

This study aims to evaluate trunk local stability in a group of patients with degenerative primary cerebellar ataxia and to correlate it with spatio-temporal parameters, clinical variables, and history of falls. Sixteen patients affected by degenerative cerebellar ataxia and 16 gender- and age-matched healthy adults were studied by means of an inertial sensor to measure trunk kinematics and spatio-temporal parameters during over-ground walking. Trunk local dynamic stability was quantified by the maximum Lyapunov exponent with short data series of the acceleration data. According to this index, low values indicate more stable trunk dynamics, while high values denote less stable trunk dynamics. Disease severity was assessed by means of International Cooperative Ataxia Rating Scale (ICARS) according to which higher values correspond to more severe disease, while lower values correspond to less severe disease.Patients displayed a higher short-term maximum Lyapunov exponent than controls in all three spatial planes, which was correlated with the age, onset of the disease, and history of falls. Furthermore, the maximum Lyapunov exponent was negatively correlated with ICARS balance, ICARS posture, and ICARS total scores.These findings indicate that trunk local stability during gait is lower in patients with cerebellar degenerative ataxia than that in healthy controls and that this may increase the risk of falls. Local dynamic stability of the trunk seems to be an important aspect in patients with ataxia and could be a useful tool in the evaluation of rehabilitative and pharmacological treatment outcomes.

Adaptive correlation filter-based video stabilization without accumulative global motion estimation

NASA Astrophysics Data System (ADS)

Koh, Eunjin; Lee, Chanyong; Jeong, Dong Gil

2014-12-01

We present a digital video stabilization approach that provides both robustness and efficiency for practical applications. In this approach, we adopt a stabilization model that maintains spatio-temporal information of past input frames efficiently and can track original stabilization position. Because of the stabilization model, the proposed method does not need accumulative global motion estimation and can recover the original position even if there is a failure in interframe motion estimation. It can also intelligently overcome the situation of damaged or interrupted video sequences. Moreover, because it is simple and suitable to parallel scheme, we implement it on a commercial field programmable gate array and a graphics processing unit board with compute unified device architecture in a breeze. Experimental results show that the proposed approach is both fast and robust.

Synchronization of mobile chaotic oscillator networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujiwara, Naoya, E-mail: fujiwara@csis.u-tokyo.ac.jp; Kurths, Jürgen; Díaz-Guilera, Albert

We study synchronization of systems in which agents holding chaotic oscillators move in a two-dimensional plane and interact with nearby ones forming a time dependent network. Due to the uncertainty in observing other agents' states, we assume that the interaction contains a certain amount of noise that turns out to be relevant for chaotic dynamics. We find that a synchronization transition takes place by changing a control parameter. But this transition depends on the relative dynamic scale of motion and interaction. When the topology change is slow, we observe an intermittent switching between laminar and burst states close to themore » transition due to small noise. This novel type of synchronization transition and intermittency can happen even when complete synchronization is linearly stable in the absence of noise. We show that the linear stability of the synchronized state is not a sufficient condition for its stability due to strong fluctuations of the transverse Lyapunov exponent associated with a slow network topology change. Since this effect can be observed within the linearized dynamics, we can expect such an effect in the temporal networks with noisy chaotic oscillators, irrespective of the details of the oscillator dynamics. When the topology change is fast, a linearized approximation describes well the dynamics towards synchrony. These results imply that the fluctuations of the finite-time transverse Lyapunov exponent should also be taken into account to estimate synchronization of the mobile contact networks.« less

Highly stable and finely tuned magnetic fields generated by permanent magnet assemblies.

PubMed

Danieli, E; Perlo, J; Blümich, B; Casanova, F

2013-05-03

Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays.

Synthesis and characterization of an Fe(i) cage complex with high stability towards strong H-acids.

PubMed

Voloshin, Yan Z; Novikov, Valentin V; Nelyubina, Yulia V; Belov, Alexander S; Roitershtein, Dmitrii M; Savitsky, Anton; Mokhir, Andriy; Sutter, Jörg; Miehlich, Matthias E; Meyer, Karsten

2018-04-03

The first synthesized and X-ray structurally characterized "classical" iron(i) dioximate showed an unrivaled stability towards strong acids, thus calling for a reassessment of the origins of the electrocatalytic activity of similar low-valent cobalt and iron cage complexes with electron-withdrawing ribbed substituents, shown previously to be effective electrocatalysts of the HER.

Equilibrium, confinement and stability of runaway electrons in tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spong, D A

1976-03-01

Some of the ramifications of the runaway population in tokamak experiments are investigated. Consideration is given both to the normal operating regime of tokamaks where only a small fraction of high energy runaways are present and to the strong runaway regime where runaways are thought to carry a significant portion of the toroidal current. In particular, the areas to be examined are the modeling of strong runaway discharges, single particle orbit characteristics of runaways, macroscopic beam-plasma equilibria, and stability against kink modes. A simple one-dimensional, time-dependent model has been constructed in relation to strong runaway discharges. Single particle orbits aremore » analyzed in relation to both the strong runaway regime and the weak regime. The effects of vector E x vector B drifts are first considered in strong runaway discharges and are found to lead to a slow inward shrinkage of the beam. Macroscopic beam-plasma equilibria are treated assuming a pressureless relativistic beam with inertia and using an ideal MHD approximation for the plasma. The stability of a toroidal relativistic beam against kink perturbations is examined using several models. (MOW)« less

Contribution of the frontal eye field to gaze shifts in the head-unrestrained rhesus monkey: neuronal activity.

PubMed

Knight, T A

2012-12-06

The frontal eye field (FEF) has a strong influence on saccadic eye movements with the head restrained. With the head unrestrained, eye saccades combine with head movements to produce large gaze shifts, and microstimulation of the FEF evokes both eye and head movements. To test whether the dorsomedial FEF provides commands for the entire gaze shift or its separate eye and head components, we recorded extracellular single-unit activity in monkeys trained to make large head-unrestrained gaze shifts. We recorded 80 units active during gaze shifts, and closely examined 26 of these that discharged a burst of action potentials that preceded horizontal gaze movements. These units were movement or visuomovement related and most exhibited open movement fields with respect to amplitude. To reveal the relations of burst parameters to gaze, eye, and/or head movement metrics, we used behavioral dissociations of gaze, eye, and head movements and linear regression analyses. The burst number of spikes (NOS) was strongly correlated with movement amplitude and burst temporal parameters were strongly correlated with movement temporal metrics for eight gaze-related burst neurons and five saccade-related burst neurons. For the remaining 13 neurons, the NOS was strongly correlated with the head movement amplitude, but burst temporal parameters were most strongly correlated with eye movement temporal metrics (head-eye-related burst neurons, HEBNs). These results suggest that FEF units do not encode a command for the unified gaze shift only; instead, different units may carry signals related to the overall gaze shift or its eye and/or head components. Moreover, the HEBNs exhibit bursts whose magnitude and timing may encode a head displacement signal and a signal that influences the timing of the eye saccade, thereby serving as a mechanism for coordinating the eye and head movements of a gaze shift. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Organic matter exploitation in a highly turbid environment: Planktonic food web in the Charente estuary, France

NASA Astrophysics Data System (ADS)

Modéran, Julien; David, Valérie; Bouvais, Pierre; Richard, Pierre; Fichet, Denis

2012-02-01

Estuaries are highly dynamic systems where multiple organic matter sources coexist and where complex biogeochemical processes greatly affect their fate. Although zooplankton plays a key role of in the energy fluxes between primary sources and exploited macrofauna, there is still a critical lack of field information concerning the spatio-temporal variability of the trophic pathways supporting its high biomasses in estuaries. From January 2007 to January 2008, suspended matter, microphytobenthos and zooplankton were sampled along the salinity gradient of the Charente estuary to determine their carbon and nitrogen stable isotope composition. The relative homogeneity of the δ 13C values of particulate organic matter (POM) all along the estuary (-23.6 to -26.5‰ except in March and June, ˜ -28.5‰) was attributed to physical mixing of marine and terrestrially derived organic matter with the great load of tidally resuspended particles. The five zooplankton taxa analysed displayed a wide range of δ 13C (from -34.9 to -17.4‰) and δ 15N values (3.4-15.2‰) over the year, providing strong evidence for high selectivity toward different organic matter sources and reinforcing the idea that a spatio-temporal succession of species assemblages lead to multiple trophic pathways and may stabilize the estuarine trophic network. The high δ 15N values of Eurytemora affinis in the maximum turbidity zone were believed to reflect a higher carnivorous tendency as a functional response to the strong decrease of phytoplankton availability. Conversely, Acartia spp. appeared unable to change their diet in the same way and was thus unable to colonize upstream areas. Stable isotope analysis also revealed that Mesopodopsis slabberi mostly relied on fresh phytoplankton and microphytobenthos while Neomysis integer presented a clear carnivorous tendency toward copepods, at least during the warm period. Additionally evidence was provided for passive (downstream advection of freshwater cladocerans with river runoffs) and active (coast-estuary seasonal migration of M. slabberi) longitudinal movements in estuarine organisms.

Stochastic and deterministic processes regulate spatio-temporal variation in seed bank diversity

Treesearch

Alejandro A. Royo; Todd E. Ristau

2013-01-01

Seed banks often serve as reservoirs of taxonomic and genetic diversity that buffer plant populations and influence post-disturbance vegetation trajectories; yet evaluating their importance requires understanding how their composition varies within and across spatial and temporal scales (α- and β-diversity). Shifts in seed bank diversity are strongly...

Auditory Temporal Processing and Working Memory: Two Independent Deficits for Dyslexia

ERIC Educational Resources Information Center

Fostick, Leah; Bar-El, Sharona; Ram-Tsur, Ronit

2012-01-01

Dyslexia is a neuro-cognitive disorder with a strong genetic basis, characterized by a difficulty in acquiring reading skills. Several hypotheses have been suggested in an attempt to explain the origin of dyslexia, among which some have suggested that dyslexic readers might have a deficit in auditory temporal processing, while others hypothesized…

Nighttime atmospheric stability changes and their effects on the temporal intensity of a mesoscale convective complex

NASA Technical Reports Server (NTRS)

Hovis, Jeffrey S.; Brundidge, Kenneth C.

1987-01-01

A method of interpolating atmospheric soundings while reducing the errors associated with simple time interpolation was developed. The purpose of this was to provide a means to determine atmospheric stability at times between standard soundings and to relate changes in stability to intensity changes in an MCC. Four MCC cases were chosen for study with this method with four stability indices being included. The discussion centers on three aspects for each stability parameter examined: the stability field in the vicinity of the storm and its changes in structure and magnitude during the lifetime of the storm, the average stability within the storm boundary as a function of time and its relation to storm intensity, and the apparent flux of stability parameter into the storm as a consequence of low-level storm relative flow. It was found that the results differed among the four stability parameters, sometimes in a conflicting fashion. Thus, an interpolation of how the storm intensity is related to the changing environmental stability depends upon the particular index utilized. Some explanation for this problem is offered.

Characterization of nano-porosity in molecular layer deposited films.

PubMed

Perrotta, Alberto; Poodt, Paul; van den Bruele, F J Fieke; Kessels, W M M Erwin; Creatore, Mariadriana

2018-06-12

Molecular layer deposition (MLD) delivers (ultra-) thin organic and hybrid materials, with atomic-level thickness control. However, such layers are often reported to be unstable under ambient conditions, due to the interaction of water and oxygen with the hybrid structure, consequently limiting their applications. In this contribution, we investigate the impact of porosity in MLD layers on their degradation. Alucone layers were deposited by means of trimethylaluminium and ethylene glycol, adopting both temporal and spatial MLD and characterized by means of FT-IR spectroscopy, spectroscopic ellipsometry, and ellipsometric porosimetry. The highest growth per cycle (GPC) achieved by spatial MLD resulted in alucone layers with very low stability in ambient air, leading to their conversion to AlOx. Alucones deposited by means of temporal MLD, instead, showed a lower GPC and a higher ambient stability. Ellipsometric porosimetry showed the presence of open nano-porosity in pristine alucone layers. Pores with a diameter in the range of 0.42-2 nm were probed, with a relative content between 1.5% and 5%, respectively, which are attributed to the temporal and spatial MLD layers. We concluded that a correlation exists between the process GPC, the open-porosity relative content, and the degradation of alucone layers.

Strong Temporal Variation Over One Saturnian Year: From Voyager to Cassini

NASA Technical Reports Server (NTRS)

Li, Liming; Achterberg, Richard K.; Conrath, Barney J.; Gierasch, Peter J.; Smith, Mark A.; Simon-Miller, Amy A.; Nixon, Conor A.; Orton, Glenn S.; Flasar, F. Michael; Jiang, Xun;

Strong Temporal Variation Over One Saturnian Year: From Voyager to Cassini

PubMed Central

Li, Liming; Achterberg, Richard K.; Conrath, Barney J.; Gierasch, Peter J.; Smith, Mark A.; Simon-Miller, Amy A.; Nixon, Conor A.; Orton, Glenn S.; Flasar, F. Michael; Jiang, Xun; Baines, Kevin H.; Morales-Juberías, Raúl; Ingersoll, Andrew P.; Vasavada, Ashwin R.; Del Genio, Anthony D.; West, Robert A.; Ewald, Shawn P.

2013-01-01

Here we report the combined spacecraft observations of Saturn acquired over one Saturnian year (~29.5 Earth years), from the Voyager encounters (1980–81) to the new Cassini reconnaissance (2009–10). The combined observations reveal a strong temporal increase of tropic temperature (~10 Kelvins) around the tropopause of Saturn (i.e., 50 mbar), which is stronger than the seasonal variability (~a few Kelvins). We also provide the first estimate of the zonal winds at 750 mbar, which is close to the zonal winds at 2000 mbar. The quasi-consistency of zonal winds between these two levels provides observational support to a numerical suggestion inferring that the zonal winds at pressures greater than 500 mbar do not vary significantly with depth. Furthermore, the temporal variation of zonal winds decreases its magnitude with depth, implying that the relatively deep zonal winds are stable with time. PMID:23934437

Dispersive optical solitons and modulation instability analysis of Schrödinger-Hirota equation with spatio-temporal dispersion and Kerr law nonlinearity

NASA Astrophysics Data System (ADS)

Inc, Mustafa; Aliyu, Aliyu Isa; Yusuf, Abdullahi; Baleanu, Dumitru

2018-01-01

This paper obtains the dark, bright, dark-bright or combined optical and singular solitons to the perturbed nonlinear Schrödinger-Hirota equation (SHE) with spatio-temporal dispersion (STD) and Kerr law nonlinearity in optical fibers. The integration algorithm is the Sine-Gordon equation method (SGEM). Furthermore, the modulation instability analysis (MI) of the equation is studied based on the standard linear-stability analysis and the MI gain spectrum is got.

Stability and Noise in the Cyanobacterial Circadian Clock

NASA Astrophysics Data System (ADS)

Mihalcescu, Irina

2008-03-01

Accuracy in cellular function has to be achieved despite random fluctuations (noise) in the concentrations of different molecular constituents inside and outside the cell. Single cell in vivo monitoring reveals that individual cells generate autonomous circadian rhythms in protein abundance. In multi-cellular organisms, the individual cell rhythms appear to be noisy with drifting phases and frequencies. However, the whole organism is significantly more accurate, the temporal precision being achieved most probably via intercellular coupling of the individual noisy oscillators. In cyanobacteria, we have shown that single cell oscillators are impressively stable and a first estimation rules out strong intercellular coupling. Interestingly, these prokaryotes also have the simplest molecular mechanism at the heart of their circadian clock. In the absence of transcriptional activity in vivo, as well alone in vitro, the three clock proteins KaiA, KaiB and KaiC generate a self-sustained circadian oscillation of autophosphorylation and dephosphorylation. Recent chemical kinetics models provide a possible understanding of the three-protein oscillator, but the measured in vivo stability remains yet unexplained. Is the clock stability a built-in property for each bacterium or does a weak intercellular coupling, make them appear like that? To address this question we first theoretically designed our experiment to be able to distinguish coupling, even weak, from phase diffusion. As the precision of our evaluation increases with the length of the experiments, we continuously monitor, for a couple of weeks, mixtures of cell populations with different initial phases. The inherent experimental noise contribution, initially dominant, is reduced by enhanced statistics. In addition, in situ entrainment experiments confirm our ability to detect a coupling of the circadian oscillator to an external force and to describe explicitly the dynamic change of the mean phase. We report a value of the coupling constant that is small compared to the diffusion constant. These results therefore confirm that the cyanobacterial clock stability is a built-in property: the cyanobacterian clock mechanism is not only the simplest but also the most robust.

Turbulent pipe flows subjected to temporal decelerations

NASA Astrophysics Data System (ADS)

Jeong, Wongwan; Lee, Jae Hwa

2016-11-01

Direct numerical simulations of temporally decelerating turbulent pipe flows were performed to examine effects of temporal decelerations on turbulence. The simulations were started with a fully developed turbulent pipe flow at a Reynolds number, ReD =24380, based on the pipe radius (R) and the laminar centerline velocity (Uc 0). Three different temporal decelerations were imposed to the initial flow with f= | d Ub / dt | =0.00127, 0.00625 and 0.025, where Ub is the bulk mean velocity. Comparison of Reynolds stresses and turbulent production terms with those for steady flow at a similar Reynolds number showed that turbulence is highly intensified with increasing f due to delay effects. Furthermore, inspection of the Reynolds shear stress profiles showed that strong second- and fourth-quadrant Reynolds shear stresses are greatly increased, while first- and third-quadrant components are also increased. Decomposition of streamwise Reynolds normal stress with streamwise cutoff wavelength (λx) 1 R revealed that the turbulence delay is dominantly originated from delay of strong large-scale turbulent structures in the outer layer, although small-scale motions throughout the wall layer adjusted more rapidly to the temporal decelerations. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2014R1A1A2057031).

Effect of risk perception on epidemic spreading in temporal networks

NASA Astrophysics Data System (ADS)

Moinet, Antoine; Pastor-Satorras, Romualdo; Barrat, Alain

2018-01-01

Many progresses in the understanding of epidemic spreading models have been obtained thanks to numerous modeling efforts and analytical and numerical studies, considering host populations with very different structures and properties, including complex and temporal interaction networks. Moreover, a number of recent studies have started to go beyond the assumption of an absence of coupling between the spread of a disease and the structure of the contacts on which it unfolds. Models including awareness of the spread have been proposed, to mimic possible precautionary measures taken by individuals that decrease their risk of infection, but have mostly considered static networks. Here, we adapt such a framework to the more realistic case of temporal networks of interactions between individuals. We study the resulting model by analytical and numerical means on both simple models of temporal networks and empirical time-resolved contact data. Analytical results show that the epidemic threshold is not affected by the awareness but that the prevalence can be significantly decreased. Numerical studies on synthetic temporal networks highlight, however, the presence of very strong finite-size effects, resulting in a significant shift of the effective epidemic threshold in the presence of risk awareness. For empirical contact networks, the awareness mechanism leads as well to a shift in the effective threshold and to a strong reduction of the epidemic prevalence.

Audio-visual temporal perception in children with restored hearing.

PubMed

Gori, Monica; Chilosi, Anna; Forli, Francesca; Burr, David

2017-05-01

It is not clear how audio-visual temporal perception develops in children with restored hearing. In this study we measured temporal discrimination thresholds with an audio-visual temporal bisection task in 9 deaf children with restored audition, and 22 typically hearing children. In typically hearing children, audition was more precise than vision, with no gain in multisensory conditions (as previously reported in Gori et al. (2012b)). However, deaf children with restored audition showed similar thresholds for audio and visual thresholds and some evidence of gain in audio-visual temporal multisensory conditions. Interestingly, we found a strong correlation between auditory weighting of multisensory signals and quality of language: patients who gave more weight to audition had better language skills. Similarly, auditory thresholds for the temporal bisection task were also a good predictor of language skills. This result supports the idea that the temporal auditory processing is associated with language development. Copyright © 2017. Published by Elsevier Ltd.

Location, sidedness, and sex distribution of intracranial arachnoid cysts in a population-based sample.

PubMed

Helland, Christian A; Lund-Johansen, Morten; Wester, Knut

2010-11-01

The aim of this study was to examine the distribution of intracranial arachnoid cysts in a large and unselected patient population with special emphasis on sidedness and sex distribution. In total, 299 patients with 305 arachnoid cysts were studied. These patients were consecutively referred to our department during a 20-year period from a well-defined geographical area with a stable population. There was a strong predilection (198 patients [66.2%]) for intracranial arachnoid cysts in the temporal fossa. Forty-two patients had cysts overlying the frontal convexity, 36 had cysts in the posterior fossa, and 23 patients had cysts in other, different locations. Of 269 cysts with clearly unilateral distribution, 163 were located on the left side and 106 on the right side. This difference resulted from the marked preponderance of temporal fossa cysts on the left side (left-to-right ratio 2.5:1; p < 0.0001 [adjusted < 0.0005]). For cysts in the cerebellopontine angle (CPA), there was preponderance on the right side (p = 0.001 [adjusted = 0.005]). Significantly more males than females had cysts in the temporal fossa (p = 0.002 [adjusted = 0.004]), whereas in the CPA a significant female preponderance was found (p = 0.016 [adjusted = 0.032]). For all other cyst locations, there was no difference between the 2 sexes. Arachnoid cysts have a strong predilection for the temporal fossa. There is a sex dependency for some intracranial locations of arachnoid cysts, with temporal cysts occurring more frequently in men, and CPA cysts found more frequently in women. Furthermore, there is a strong location-related sidedness for arachnoid cysts, independent of patient sex. These findings and reports from the literature suggest a possible genetic component in the development of some arachnoid cysts.

Contribution to the assessment of the imminent seismic hazard: Geophysical, statistical (and more) challenges in the territory of Greece

NASA Astrophysics Data System (ADS)

Adamaki, Angeliki K.; Papadimitriou, Eleftheria E.; Karakostas, Vassilis G.; Tsaklidis, George M.

2013-04-01

The necessity of the imminent seismic hazard assessment stems from a strong social component which is the outcome of the need of people to inquire more in order to understand nature exhaustively and not partially, either to satisfy their inner curiosity or in favor of their self preservation instinct against the physical phenomena that the human kind cannot control. Choosing this path to follow, many seismologists have focused on forecasting the temporal and spatial distribution of earthquakes in short time scales. The possibility of knowing with a degree of certainty the way an earthquake sequence evolves proves to be an important object of research. Being more specific, the present work summarizes applications of seismicity and statistical models on seismic catalogues of areas that are specified by their tectonic structures and their past seismicity, providing information on the temporal and spatial evolution of local seismic activity, which can point out seismicity rate "irregularities" or changes as precursors of strong events, either in case of a main shock or a strong aftershock. In order to study these rate changes both preceding and following a strong earthquake, seismicity models are applied in order to estimate the Coulomb stress changes resulting from the occurrence of a strong earthquake and their results are combined with the application of a Restricted Epidemic Type Aftershock Sequence model. There are many active tectonic structures in the territory of Greece that are related with the occurrence of strong earthquakes, especially near populated areas, and the aim of this work is to contribute to the assessment of the imminent seismic hazard by applying the aforementioned models and techniques and studying the temporal evolution of several seismic sequences that occurred in the Aegean area in the near past.

RSS Fingerprint Based Indoor Localization Using Sparse Representation with Spatio-Temporal Constraint

PubMed Central

Piao, Xinglin; Zhang, Yong; Li, Tingshu; Hu, Yongli; Liu, Hao; Zhang, Ke; Ge, Yun

2016-01-01

The Received Signal Strength (RSS) fingerprint-based indoor localization is an important research topic in wireless network communications. Most current RSS fingerprint-based indoor localization methods do not explore and utilize the spatial or temporal correlation existing in fingerprint data and measurement data, which is helpful for improving localization accuracy. In this paper, we propose an RSS fingerprint-based indoor localization method by integrating the spatio-temporal constraints into the sparse representation model. The proposed model utilizes the inherent spatial correlation of fingerprint data in the fingerprint matching and uses the temporal continuity of the RSS measurement data in the localization phase. Experiments on the simulated data and the localization tests in the real scenes show that the proposed method improves the localization accuracy and stability effectively compared with state-of-the-art indoor localization methods. PMID:27827882

Global Stability and Dynamics of Strongly Nonlinear Systems Using Koopman Operator Theory

DTIC Science & Technology

2017-03-01

calculus, applied mathematics, Director’s Research Initiative 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18... research of Svenkeson et al.4 Section 2 is Accomplishments and Section 3 is the Conclusion. 2. Accomplishments 2.1 Prescribed External Forcing To study ...ARL-TR-7959 MAR 2017 US Army Research Laboratory Global Stability and Dynamics of Strongly Nonlinear Systems Using Koopman

Intestinal Microbiota in Healthy Adults: Temporal Analysis Reveals Individual and Common Core and Relation to Intestinal Symptoms

PubMed Central

Nikkilä, Janne; Immonen, Outi; Kekkonen, Riina; Lahti, Leo; Palva, Airi; de Vos, Willem M.

2011-01-01

Background While our knowledge of the intestinal microbiota during disease is accumulating, basic information of the microbiota in healthy subjects is still scarce. The aim of this study was to characterize the intestinal microbiota of healthy adults and specifically address its temporal stability, core microbiota and relation with intestinal symptoms. We carried out a longitudinal study by following a set of 15 healthy Finnish subjects for seven weeks and regularly assessed their intestinal bacteria and archaea with the Human Intestinal Tract (HIT)Chip, a phylogenetic microarray, in conjunction with qPCR analyses. The health perception and occurrence of intestinal symptoms was recorded by questionnaire at each sampling point. Principal Findings A high overall temporal stability of the microbiota was observed. Five subjects showed transient microbiota destabilization, which correlated not only with the intake of antibiotics but also with overseas travelling and temporary illness, expanding the hitherto known factors affecting the intestinal microbiota. We identified significant correlations between the microbiota and common intestinal symptoms, including abdominal pain and bloating. The most striking finding was the inverse correlation between Bifidobacteria and abdominal pain: subjects who experienced pain had over five-fold less Bifidobacteria compared to those without pain. Finally, a novel computational approach was used to define the common core microbiota, highlighting the role of the analysis depth in finding the phylogenetic core and estimating its size. The in-depth analysis suggested that we share a substantial number of our intestinal phylotypes but as they represent highly variable proportions of the total community, many of them often remain undetected. Conclusions/Significance A global and high-resolution microbiota analysis was carried out to determine the temporal stability, the associations with intestinal symptoms, and the individual and common core microbiota in healthy adults. The findings provide new approaches to define intestinal health and to further characterize the microbial communities inhabiting the human gut. PMID:21829582

Model-Based Speech Signal Coding Using Optimized Temporal Decomposition for Storage and Broadcasting Applications

NASA Astrophysics Data System (ADS)

Athaudage, Chandranath R. N.; Bradley, Alan B.; Lech, Margaret

2003-12-01

A dynamic programming-based optimization strategy for a temporal decomposition (TD) model of speech and its application to low-rate speech coding in storage and broadcasting is presented. In previous work with the spectral stability-based event localizing (SBEL) TD algorithm, the event localization was performed based on a spectral stability criterion. Although this approach gave reasonably good results, there was no assurance on the optimality of the event locations. In the present work, we have optimized the event localizing task using a dynamic programming-based optimization strategy. Simulation results show that an improved TD model accuracy can be achieved. A methodology of incorporating the optimized TD algorithm within the standard MELP speech coder for the efficient compression of speech spectral information is also presented. The performance evaluation results revealed that the proposed speech coding scheme achieves 50%-60% compression of speech spectral information with negligible degradation in the decoded speech quality.

Flower diversity and bee reproduction in an arid ecosystem.

PubMed

Dorado, Jimena; Vázquez, Diego P

2016-01-01

Diverse flower communities are more stable in floral resource production along the flowering season, but the question about how the diversity and stability of resources affect pollinator reproduction remains open. High plant diversity could favor short foraging trips, which in turn would enhance bee fitness. In addition to plant diversity, greater temporal stability of floral resources in diverse communities could favor pollinator fitness because such communities are likely to occupy the phenological space more broadly, increasing floral availability for pollinators throughout the season. In addition, this potential effect of flower diversity on bee reproduction could be stronger for generalist pollinators because they can use a broader floral spectrum. Based on above arguments we predicted that pollinator reproduction would be positively correlated to flower diversity, and to temporal stability in flower production, and that this relationship would be stronger for the most generalized pollinator species. Using structural equation models, we evaluated the effect of these variables and other ecological factors on three estimates of bee reproduction (average number of brood cells per nest per site, total number of brood cells per site, and total number of nests per site), and whether such effects were modulated by bee generalization on floral resources. Contrary to our expectations, flower diversity had no effect on bee reproduction, stability in flower production had a weakly negative effect on one of the bee reproductive variables, and the strength of the fitness-diversity relationship was unrelated to bee generalization. In contrast, elevation had a negative effect on bee reproduction, despite the narrow elevation range encompassed by our sites. Flower diversity did not affect the reproduction of the solitary bees studied here. This result could stem from the context dependence of the diversity-stability relationship, given that elevation had a positive effect on flower diversity but a negative effect on bee reproduction. Although high temporal stability in flower production is expected to enhance pollinator reproduction, in our study it had a weakly negative-instead of positive-effect on the average number of brood cells per nest. Other environmental factors that vary with elevation could influence bee reproduction. Our study focused on a small group of closely-related bee species, which cautions against generalization of our findings to other groups of pollinators. More studies are clearly needed to assess the extent to which pollinator demography is influenced by the diversity of floral resources.

Managing risk in an unstable world.

PubMed

Bremmer, Ian

2005-06-01

With emerging markets like China and politically unstable countries like Saudi Arabia figuring more than ever into companies' investment calculations, business leaders are turning to political risk analysis to measure the impact of politics on potential markets, minimize risks, and make the most of global opportunities. But political risk is more subjective than its economic counterpart. It is influenced by the passage of laws, the foibles of government leaders, and the rise of popular movements. So corporate leaders must grapple not just with broad, easily observable trends but also with nuances of society and even quirks of personality. And those hard-to-quantify factors must constantly be pieced together into an ongoing narrative within historical and regional contexts. As goods, services, information, ideas, and people cross borders today with unprecedented velocity, corporations debating operational or infrastructural investments abroad increasingly need objective, rigorous assessments. One tool for measuring and presenting stability data, for example, incorporates 20 composite indicators of risk in emerging markets and scores risk variables according to both their structural and their temporal components. The indicators are then organized into four equally weighted subcategories whose ratings are aggregated into a single stability score. Countries are ranked on a scale of zero (a failed state) to100 (a fully institutionalized, stable democracy). Companies can buy political risk analyses from consultants or, as some large energy and financial services organizations have done, develop them in-house. Either way, a complete and accurate picture of any country's risk requires analysts with strong reportorial skills; timely, accurate data on a variety of social and political trends; and a framework for evaluating the impact of individual risks on stability.

Stability characteristics of the mesopause region above the Andes

NASA Astrophysics Data System (ADS)

Yang, F.; Liu, A. Z.

2017-12-01

The structure and seasonal variations of static and dynamic (shear) instabilities in the upper atmosphere (80 to 110 km) are examined using 3-year high-resolution wind and temperature data obtained with the Na Lidar at Andes Lidar Observatory (30S,71W). The stabilities are primarily determined by background temperature and wind, but strongly affected by tidal and gravity wave variations. Gravity waves perturb the atmosphere, causing intermittent unstable layers. The stabilities are characterized by their vertical and seasonal distributions of probability of instabilities. As have been found in previous studies, there is a correlation between high static stability (large N2) and strong vertical wind shear. The mechanism for this relationship is investigated in the context of gravity waves interacting with varying background.

Observation of discrete time-crystalline order in a disordered dipolar many-body system

NASA Astrophysics Data System (ADS)

Choi, Soonwon; Choi, Joonhee; Landig, Renate; Kucsko, Georg; Zhou, Hengyun; Isoya, Junichi; Jelezko, Fedor; Onoda, Shinobu; Sumiya, Hitoshi; Khemani, Vedika; von Keyserlingk, Curt; Yao, Norman Y.; Demler, Eugene; Lukin, Mikhail D.

2017-03-01

Understanding quantum dynamics away from equilibrium is an outstanding challenge in the modern physical sciences. Out-of-equilibrium systems can display a rich variety of phenomena, including self-organized synchronization and dynamical phase transitions. More recently, advances in the controlled manipulation of isolated many-body systems have enabled detailed studies of non-equilibrium phases in strongly interacting quantum matter; for example, the interplay between periodic driving, disorder and strong interactions has been predicted to result in exotic ‘time-crystalline’ phases, in which a system exhibits temporal correlations at integer multiples of the fundamental driving period, breaking the discrete time-translational symmetry of the underlying drive. Here we report the experimental observation of such discrete time-crystalline order in a driven, disordered ensemble of about one million dipolar spin impurities in diamond at room temperature. We observe long-lived temporal correlations, experimentally identify the phase boundary and find that the temporal order is protected by strong interactions. This order is remarkably stable to perturbations, even in the presence of slow thermalization. Our work opens the door to exploring dynamical phases of matter and controlling interacting, disordered many-body systems.

Psychometric Properties of a Self-Report Instrument for the Assessment of Tic Severity in Adults With Tic Disorders.

PubMed

Abramovitch, Amitai; Reese, Hannah; Woods, Douglas W; Peterson, Alan; Deckersbach, Thilo; Piacentini, John; Scahill, Lawrence; Wilhelm, Sabine

2015-11-01

The gold-standard measure of tic severity in tic disorders (TD), the Yale Global Tic Severity Scale (YGTSS), is a semistructured clinician-administered interview that can be time consuming and requires highly trained interviewers. Moreover, the YGTSS does not provide information regarding frequency and intensity of specific tics because all motor and all vocal tics are rated as a group. The aim of the present study is to describe and test the Adult Tic Questionnaire (ATQ), a measure for the assessment of tic severity in adults, and to report its preliminary psychometric properties. The ATQ is a brief self-report questionnaire that provides information regarding frequency, intensity, and severity of 27 specific tics. In addition, the ATQ produces total frequency, intensity, and severity scores for vocal and motor tics, as well as a global total tic severity score. Results showed that the ATQ demonstrated very good internal consistency and temporal stability. The total, vocal, and motor tic severity scales of the ATQ showed strong correlation with corresponding subscales of the YGTSS, indicating strong convergent validity. Weak correlations with measures of severity of obsessive-compulsive disorder and attention deficit/hyperactivity disorder, indicated strong discriminant validity. The ATQ, a promising measure for the assessment of tic severity in adults with TD, may be a valuable supplement to the current recommended assessment battery for TD. Furthermore, the ATQ enables clinicians and researchers to track changes in the frequency and intensity of specific tics, which is important given their complex and dynamic nature. Copyright © 2015. Published by Elsevier Ltd.

Psychometric Properties of a Self-Report Instrument for the Assessment of Tic Severity in Adults with Tic Disorders

PubMed Central

Abramovitch, Amitai; Reese, Hannah; Woods, Douglas W.; Peterson, Alan; Deckersbach, Thilo; Piacentini, John; Scahill, Lawrence; Wilhelm, Sabine

2017-01-01

The gold-standard measure of tic severity in Tic Disorders (TD), the Yale Global Tic Severity Scale (YGTSS), is a semi-structured clinician-administered interview that can be time consuming and requires highly trained interviewers. Moreover, the YGTSS does not provide information regarding frequency and intensity of specific tics as all motor, and all vocal tics are rated as a group. The aim of the present study is to describe and test the Adult Tic Questionnaire (ATQ), a measure for the assessment of tic severity in adults, and to report its preliminary psychometric properties. The ATQ is a brief self-report questionnaire that provides information regarding frequency, intensity, and severity of 27 specific tics. In addition, the ATQ produces total frequency, intensity, and severity scores for vocal, and motor tics, as well as a global total tic severity score. Results showed that the ATQ demonstrated very good internal consistency and temporal stability. The total, vocal, and motor tic severity scales of the ATQ showed strong correlation with corresponding subscales of the YGTSS, indicating strong convergent validity. Weak correlations with measures of severity of obsessive-compulsive disorder and attention deficit/hyperactivity disorder, indicated strong discriminant validity. The ATQ is a promising measure for the assessment of tic severity in adults with TD which may be a valuable supplement to the current recommended assessment battery for TD. Furthermore, the ATQ enables clinicians and researchers to track changes in the frequency and intensity of specific tics, which is important given their complex and dynamic nature. PMID:26520221

Augmented feedback of COM and COP modulates the regulation of quiet human standing relative to the stability boundary.

PubMed

Kilby, Melissa C; Slobounov, Semyon M; Newell, Karl M

2016-06-01

The experiment manipulated real-time kinematic feedback of the motion of the whole body center of mass (COM) and center of pressure (COP) in anterior-posterior (AP) and medial-lateral (ML) directions to investigate the variables actively controlled in quiet standing of young adults. The feedback reflected the current 2D postural positions within the 2D functional stability boundary that was scaled to 75%, 30% and 12% of its original size. The findings showed that the distance of both COP and COM to the respective stability boundary was greater during the feedback trials compared to a no feedback condition. However, the temporal safety margin of the COP, that is, the virtual time-to-contact (VTC), was higher without feedback. The coupling relation of COP-COM showed stable in-phase synchronization over all of the feedback conditions for frequencies below 1Hz. For higher frequencies (up to 5Hz), there was progressive reduction of COP-COM synchronization and local adaptation under the presence of augmented feedback. The findings show that the augmented feedback of COM and COP motion differentially and adaptively influences spatial and temporal properties of postural motion relative to the stability boundary while preserving the organization of the COM-COP coupling in postural control. Copyright © 2016. Published by Elsevier B.V.

Reconstructing the rise of recent coastal anoxia; molybdenum in Chesapeake Bay sediments

USGS Publications Warehouse

Adelson, J.M.; Helz, G.R.; Miller, C.V.

2001-01-01

Sporadic, direct observations over a 50 yr period inadequately characterize the history of seasonal hypoxia and anoxia in Chesapeake Bay, alarge estuary threatened by eutrophication. Here, we undertake a reconstruction of 20th century oxygen depletion in this estuary using Mo concentrations in 210Pb-dated sediments; Cu concentrations are used to control for anthropogenic influences. Cores from the central channel display mild Mo enrichments above crustal backgrounds (up to 5 ??g/g) and strong Cu enrichments (up to 35 ??g/g). Temporally, Cu enrichment (mostly anthropogenic) began earlier and stabilized in the last two thirds of the 20th century. In contrast, Mo enrichment has grown during the last two thirds of the century. Molybdenum enrichment is mostly hydrogenic, except in a section of the channel that receives additional Mo from erosion of Early Miocene shore deposits. Two geochemical mechanisms promote Mo enrichment: Manganese refluxing concentrates dissolved MoO24- at the sediment-water interface and sulfide substitution into MoO24- produces thiomolybdates, which can be fixed by particles. The Mo enrichment mechanisms operate primarily during periods when bottom waters are anoxic and thiomolybdate formation can occur near the sediment-water interface. This implies a temporal coupling between water-column anoxia and Mo fixation even though fixation occurs only within sediments. The Mo enrichment profiles suggest that Chesapeake Bay has experienced growing O2 depletion since the first half of the 20th century, but especially after 1960. Copyright ?? 2001 Elsevier Science Ltd.

A space-time lower-upper symmetric Gauss-Seidel scheme for the time-spectral method

NASA Astrophysics Data System (ADS)

Zhan, Lei; Xiong, Juntao; Liu, Feng

2016-05-01

The time-spectral method (TSM) offers the advantage of increased order of accuracy compared to methods using finite-difference in time for periodic unsteady flow problems. Explicit Runge-Kutta pseudo-time marching and implicit schemes have been developed to solve iteratively the space-time coupled nonlinear equations resulting from TSM. Convergence of the explicit schemes is slow because of the stringent time-step limit. Many implicit methods have been developed for TSM. Their computational efficiency is, however, still limited in practice because of delayed implicit temporal coupling, multiple iterative loops, costly matrix operations, or lack of strong diagonal dominance of the implicit operator matrix. To overcome these shortcomings, an efficient space-time lower-upper symmetric Gauss-Seidel (ST-LU-SGS) implicit scheme with multigrid acceleration is presented. In this scheme, the implicit temporal coupling term is split as one additional dimension of space in the LU-SGS sweeps. To improve numerical stability for periodic flows with high frequency, a modification to the ST-LU-SGS scheme is proposed. Numerical results show that fast convergence is achieved using large or even infinite Courant-Friedrichs-Lewy (CFL) numbers for unsteady flow problems with moderately high frequency and with the use of moderately high numbers of time intervals. The ST-LU-SGS implicit scheme is also found to work well in calculating periodic flow problems where the frequency is not known a priori and needed to be determined by using a combined Fourier analysis and gradient-based search algorithm.

Diversifying Selection Underlies the Origin of Allozyme Polymorphism at the Phosphoglucose Isomerase Locus in Tigriopus californicus

PubMed Central

Schoville, Sean D.; Flowers, Jonathan M.; Burton, Ronald S.

2012-01-01

The marine copepod Tigriopus californicus lives in intertidal rock pools along the Pacific coast, where it exhibits strong, temporally stable population genetic structure. Previous allozyme surveys have found high frequency private alleles among neighboring subpopulations, indicating that there is limited genetic exchange between populations. Here we evaluate the factors responsible for the diversification and maintenance of alleles at the phosphoglucose isomerase (Pgi) locus by evaluating patterns of nucleotide variation underlying previously identified allozyme polymorphism. Copepods were sampled from eleven sites throughout California and Baja California, revealing deep genetic structure among populations as well as genetic variability within populations. Evidence of recombination is limited to the sample from Pescadero and there is no support for linkage disequilibrium across the Pgi locus. Neutrality tests and codon-based models of substitution suggest the action of natural selection due to elevated non-synonymous substitutions at a small number of sites in Pgi. Two sites are identified as the charge-changing residues underlying allozyme polymorphisms in T. californicus. A reanalysis of allozyme variation at several focal populations, spanning a period of 26 years and over 200 generations, shows that Pgi alleles are maintained without notable frequency changes. Our data suggest that diversifying selection accounted for the origin of Pgi allozymes, while McDonald-Kreitman tests and the temporal stability of private allozyme alleles suggests that balancing selection may be involved in the maintenance of amino acid polymorphisms within populations. PMID:22768211

Gender-specific effects of emotional modulation on visual temporal order thresholds.

PubMed

Liang, Wei; Zhang, Jiyuan; Bao, Yan

2015-09-01

Emotions affect temporal information processing in the low-frequency time window of a few seconds, but little is known about their effect in the high-frequency domain of some tens of milliseconds. The present study aims to investigate whether negative and positive emotional states influence the ability to discriminate the temporal order of visual stimuli, and whether gender plays a role in temporal processing. Due to the hemispheric lateralization of emotion, a hemispheric asymmetry between the left and the right visual field might be expected. Using a block design, subjects were primed with neutral, negative and positive emotional pictures before performing temporal order judgment tasks. Results showed that male subjects exhibited similarly reduced order thresholds under negative and positive emotional states, while female subjects demonstrated increased threshold under positive emotional state and reduced threshold under negative emotional state. Besides, emotions influenced female subjects more intensely than male subjects, and no hemispheric lateralization was observed. These observations indicate an influence of emotional states on temporal order processing of visual stimuli, and they suggest a gender difference, which is possibly associated with a different emotional stability.

Pitting temporal against spatial integration in schizophrenic patients.

PubMed

Herzog, Michael H; Brand, Andreas

2009-06-30

Schizophrenic patients show strong impairments in visual backward masking possibly caused by deficits on the early stages of visual processing. The underlying aberrant mechanisms are not clearly understood. Spatial as well as temporal processing deficits have been proposed. Here, by combining a spatial with a temporal integration paradigm, we show further evidence that temporal but not spatial processing is impaired in schizophrenic patients. Eleven schizophrenic patients and ten healthy controls were presented with sequences composed of Vernier stimuli. Patients needed significantly longer presentation times for sequentially presented Vernier stimuli to reach a performance level comparable to that of healthy controls (temporal integration deficit). When we added spatial contextual elements to some of the Vernier stimuli, performance changed in a complex but comparable manner in patients and controls (intact spatial integration). Hence, temporal but not spatial processing seems to be deficient in schizophrenia.

Polyethylenimine Interfacial Layers in Inverted Organic Photovoltaic Devices: Effects of Ethoxylation and Molecular Weight on Efficiency and Temporal Stability.

PubMed

Courtright, Brett A E; Jenekhe, Samson A

2015-12-02

We report a comparative study of polyethylenimine (PEI) and ethoxylated-polyethylenimine (PEIE) cathode buffer layers in high performance inverted organic photovoltaic devices. The work function of the indium-tin oxide (ITO)/zinc oxide (ZnO) cathode was reduced substantially (Δφ = 0.73-1.09 eV) as the molecular weight of PEI was varied from 800 g mol(-1) to 750 000 g mol(-1) compared with the observed much smaller reduction when using a PEIE thin film (Δφ = 0.56 eV). The reference inverted polymer solar cells based on the small band gap polymer PBDTT-FTTE (ITO/ZnO/PBDTT-FTTE:PC70BM/MoO3/Ag), without a cathode buffer layer, had an average power conversion efficiency (PCE) of 6.06 ± 0.22%. Incorporation of a PEIE cathode buffer layer in the same PBDTT-FTTE:PC70BM blend devices gave an enhanced performance with a PCE of 7.37 ± 0.53%. In contrast, an even greater photovoltaic efficiency with a PCE of 8.22 ± 0.10% was obtained in similar PBDTT-FTTE:PC70BM blend solar cells containing a PEI cathode buffer layer. The temporal stability of the inverted polymer solar cells was found to increase with increasing molecular weight of the cathode buffer layer. The results show that PEI is superior to PEIE as a cathode buffer layer in high performance organic photovoltaic devices and that the highest molecular weight PEI interlayer provides the highest temporal stability.

Cross-cultural Adaptation of the Self-care of Hypertension Inventory Into Brazilian Portuguese.

PubMed

Silveira, Luana Claudia Jacoby; Rabelo-Silva, Eneida Rejane; Ávila, Christiane Whast; Beltrami Moreira, Leila; Dickson, Victoria Vaughan; Riegel, Barbara

Lifestyle changes and treatment adherence still constitute a challenge to healthcare providers involved in the care of persons with hypertension. The lack of validated instruments measuring the ability of hypertensive patients to manage their disease has slowed research progress in this area. The Self-care of Hypertension Inventory, originally developed in the United States, consists of 23 items divided across 3 scales: Self-care Maintenance, Self-care Management, and Self-care Confidence. These scales measure how well patients with hypertension adhere to treatment and manage elevated blood pressure, as well as their confidence in their ability to perform self-care. A rigorous cross-cultural adaptation and validation process is required before this instrument can be used in other countries. The aims of this study were to translate the Self-care of Hypertension Inventory into Brazilian Portuguese with cross-cultural adaptation and to evaluate interobserver reliability and temporal stability. This methodological study involved forward translation, synthesis of forward translations, back-translation, synthesis of back-translations, expert committee review, and pretesting. Interobserver agreement and the temporal stability of the scales were assessed. The expert committee proposed semantic and cultural modifications to some items and the addition of guidance statements to facilitate administration of the scale. Interobserver analysis demonstrated substantial agreement. Analysis of temporal stability showed near-perfect agreement. Cross-cultural adaptation of the Self-care of Hypertension Inventory successfully produced a Portuguese-language version of the instrument for further evaluation of psychometric properties. Once that step is completed, the scale can be used in Brazil.

Nursing Intensive-Care Satisfaction Scale [NICSS]: Development and validation of a patient-centred instrument.

PubMed

Romero-García, Marta; de la Cueva-Ariza, Laura; Benito-Aracil, Llucia; Lluch-Canut, Teresa; Trujols-Albet, Joan; Martínez-Momblan, Maria Antonia; Juvé-Udina, Maria-Eulàlia; Delgado-Hito, Pilar

2018-06-01

The aim of this study was to develop and validate the Nursing Intensive-Care Satisfaction Scale to measures satisfaction with nursing care from the critical care patient's perspective. Instruments that measure satisfaction with nursing cares have been designed and validated without taking the patient's perspective into consideration. Despite the benefits and advances in measuring satisfaction with nursing care, none instrument is specifically designed to assess satisfaction in intensive care units. Instrument development. The population were all discharged patients (January 2013 - January 2015) from three Intensive Care Units of a third level hospital (N = 200). All assessment instruments were given to discharged patients and 48 hours later, to analyse the temporal stability, only the questionnaire was given again. The validation process of the scale included the analysis of internal consistency, temporal stability; validity of construct through a confirmatory factor analysis; and criterion validity. Reliability was 0.95. The intraclass correlation coefficient for the total scale was 0.83 indicating a good temporal stability. Construct validity showed an acceptable fit and factorial structure with four factors, in accordance with the theoretical model, being Consequences factor the best correlated with other factors. Criterion validity, presented a correlation between low and high (range: 0.42-0.68). The scale has been designed and validated incorporating the perspective of critical care patients. Thanks to its reliability and validity, this questionnaire can be used both in research and in clinical practice. The scale offers a possibility to assess and develop interventions to improve patient satisfaction with nursing care. © 2018 John Wiley & Sons Ltd.

A Critical Test of Temporal and Spatial Accuracy of the Tobii T60XL Eye Tracker

ERIC Educational Resources Information Center

Morgante, James D.; Zolfaghari, Rahman; Johnson, Scott P.

2012-01-01

Infant eye tracking is becoming increasingly popular for its presumed precision relative to traditional looking time paradigms and potential to yield new insights into developmental processes. However, there is strong reason to suspect that the temporal and spatial resolution of popular eye tracking systems is not entirely accurate, potentially…

Speckle temporal stability in XAO coronagraphic images. II. Refine model for quasi-static speckle temporal evolution for VLT/SPHERE

NASA Astrophysics Data System (ADS)

Martinez, P.; Kasper, M.; Costille, A.; Sauvage, J. F.; Dohlen, K.; Puget, P.; Beuzit, J. L.

2013-06-01

Context. Observing sequences have shown that the major noise source limitation in high-contrast imaging is the presence of quasi-static speckles. The timescale on which quasi-static speckles evolve is determined by various factors, mechanical or thermal deformations, among others. Aims: Understanding these time-variable instrumental speckles and, especially, their interaction with other aberrations, referred to as the pinning effect, is paramount for the search for faint stellar companions. The temporal evolution of quasi-static speckles is, for instance, required for quantifying the gain expected when using angular differential imaging (ADI) and to determining the interval on which speckle nulling techniques must be carried out. Methods: Following an early analysis of a time series of adaptively corrected, coronagraphic images obtained in a laboratory condition with the high-order test bench (HOT) at ESO Headquarters, we confirm our results with new measurements carried out with the SPHERE instrument during its final test phase in Europe. The analysis of the residual speckle pattern in both direct and differential coronagraphic images enables the characterization of the temporal stability of quasi-static speckles. Data were obtained in a thermally actively controlled environment reproducing realistic conditions encountered at the telescope. Results: The temporal evolution of the quasi-static wavefront error exhibits a linear power law, which can be used to model quasi-static speckle evolution in the context of forthcoming high-contrast imaging instruments, with implications for instrumentation (design, observing strategies, data reduction). Such a model can be used for instance to derive the timescale on which non-common path aberrations must be sensed and corrected. We found in our data that quasi-static wavefront error increases with ~0.7 Å per minute.

A Numerical Study of Wind-Turbine Wakes for Three Atmospheric Stability Conditions

NASA Astrophysics Data System (ADS)

Xie, Shengbai; Archer, Cristina L.

2017-10-01

The effects of atmospheric stability on wind-turbine wakes are studied via large-eddy simulations. Three stability conditions are considered: stable, neutral, and unstable, with the same geostrophic wind speed aloft and the same Coriolis frequency. Both a single 5-MW turbine and a wind farm of five turbines are studied. The single-turbine wake is strongly correlated with stability, in terms of velocity deficit, turbulence kinetic energy (TKE) and temperature distribution. Because of the Coriolis effect, the wake shape deviates from a Gaussian distribution. For the wind-farm simulations, the separation of the core region and outer region is clear for the stable and neutral cases, but less distinct for the unstable case. The unstable case exhibits strong horizontal variations in wind speed. Local accelerations such as related to aisle jets are also observed, whose features depend on stability. The added TKE in the wind farm increases with stability. The highest power extraction and lowest power deficit are observed for the unstable case.

Issues with Strong Compression of Plasma Target by Stabilized Imploding Liner

NASA Astrophysics Data System (ADS)

Turchi, Peter; Frese, Sherry; Frese, Michael

2017-10-01

Strong compression (10:1 in radius) of an FRC by imploding liquid metal liners, stabilized against Rayleigh-Taylor modes, using different scalings for loss based on Bohm vs 100X classical diffusion rates, predict useful compressions with implosion times half the initial energy lifetime. The elongation (length-to-diameter ratio) near peak compression needed to satisfy empirical stability criterion and also retain alpha-particles is about ten. The present paper extends these considerations to issues of the initial FRC, including stability conditions (S*/E) and allowable angular speeds. Furthermore, efficient recovery of the implosion energy and alpha-particle work, in order to reduce the necessary nuclear gain for an economical power reactor, is seen as an important element of the stabilized liner implosion concept for fusion. We describe recent progress in design and construction of the high energy-density prototype of a Stabilized Liner Compressor (SLC) leading to repetitive laboratory experiments to develop the plasma target. Supported by ARPA-E ALPHA Program.

[Study on stability of curcumine, demethoxycurcumin and bisdemethoxycurcumin].

PubMed

Han, Gang; Cui, Jing-jing; Bi, Rui; Zhao, Lin-lin; Zhang, Wei-guo

2008-11-01

To investigate the stability of curcumin, demethoxycurcumin and bisdemethoxycurcumin in different buffer solution. To determine concentration of curcumin by HPLC when added curcumin, demethoxycurcumin and bisdemethoxycurcumin into the buffer solution the equation of degradation was established. The sequence of stability are bisdemethoxycurcumin > or = demethoxycurcumin > or =curcumin at the same condition. The demethoxycurcumin can stabilize curcumin more strong than the others. The demethoxycurcumin is a nature stabilizing agent for curcumin.

Speech Perception in Tones and Noise via Cochlear Implants Reveals Influence of Spectral Resolution on Temporal Processing

PubMed Central

Kreft, Heather A.

2014-01-01

Under normal conditions, human speech is remarkably robust to degradation by noise and other distortions. However, people with hearing loss, including those with cochlear implants, often experience great difficulty in understanding speech in noisy environments. Recent work with normal-hearing listeners has shown that the amplitude fluctuations inherent in noise contribute strongly to the masking of speech. In contrast, this study shows that speech perception via a cochlear implant is unaffected by the inherent temporal fluctuations of noise. This qualitative difference between acoustic and electric auditory perception does not seem to be due to differences in underlying temporal acuity but can instead be explained by the poorer spectral resolution of cochlear implants, relative to the normally functioning ear, which leads to an effective smoothing of the inherent temporal-envelope fluctuations of noise. The outcome suggests an unexpected trade-off between the detrimental effects of poorer spectral resolution and the beneficial effects of a smoother noise temporal envelope. This trade-off provides an explanation for the long-standing puzzle of why strong correlations between speech understanding and spectral resolution have remained elusive. The results also provide a potential explanation for why cochlear-implant users and hearing-impaired listeners exhibit reduced or absent masking release when large and relatively slow temporal fluctuations are introduced in noise maskers. The multitone maskers used here may provide an effective new diagnostic tool for assessing functional hearing loss and reduced spectral resolution. PMID:25315376

Continental drift and climate change drive instability in insect assemblages

NASA Astrophysics Data System (ADS)

Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk

2015-06-01

Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region—one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale.

Continental drift and climate change drive instability in insect assemblages

PubMed Central

Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk

2015-01-01

Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region—one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale. PMID:26081036

Continental drift and climate change drive instability in insect assemblages.

PubMed

Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk

2015-06-17

Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region--one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale.

Effects of Mean Flow Profiles on Instability of a Low-Density Gas Jet Injected into a High-Density Gas

NASA Technical Reports Server (NTRS)

Vedantam, Nanda Kishore

2003-01-01

The objective of this study was to investigate the effects of the mean flow profiles on the instability characteristics in the near-injector region of low-density gas jets injected into high-density ambient gas mediums. To achieve this, a linear temporal stability analysis and a spatio-temporal stability analysis of a low-density round gas jet injected vertically upwards into a high-density ambient gas were performed by assuming three different sets of mean velocity and density profiles. The flow was assumed to be isothermal and locally parallel. Viscous and diffusive effects were ignored. The mean flow parameters were represented as the sum of the mean value and a small normal-mode fluctuation. A second order differential equation governing the pressure disturbance amplitude was derived from the basic conservation equations. The first set of mean velocity and density profiles assumed were those used by Monkewitz and Sohn for investigating absolute instability in hot jets. The second set of velocity and density profiles assumed for this study were the ones used by Lawson. And the third set of mean profiles included a parabolic velocity profile and a hyperbolic tangent density profile. The effects of the inhomogeneous shear layer and the Froude number (signifying the effects of gravity) on the temporal and spatio-temporal results for each set of mean profiles were delineated. Additional information is included in the original extended abstract.

Cyclical Dynamics and Control of a Neuromechanical System

DTIC Science & Technology

2012-01-01

of the membrane potentials and synaptic conductances of neurons in the CPG model, or the lengths, velocities, and calcium concentrations in a muscle...empirical data. • We found that muscle is strongly self-stabilizing when activated cyclically, possibly because of the nonlinearity in how calcium binds and...only its natural calcium dynamics and length, velocity, and tension relationships, is strongly self-stabilizing. I plan to submit these results as an

The inviscid stability of supersonic flow past axisymmetric bodies

NASA Technical Reports Server (NTRS)

Duck, Peter W.

1990-01-01

The supersonic flow past a sharp cone is studied. The associated boundary layer flow (i.e., the velocity and temperature field) is computed. The inviscid linear temporal stability of axisymmetric boundary layers in general is considered, and in particular, a so-called 'triply generalized' inflection condition for 'subsonic' nonaxisymmetric neutral modes is presented. Preliminary numerical results for the stability of the cone boundary layer are presented for a freestream Mach number of 3.8. In particular, a new inviscid mode of instability is seen to occur in certain regimes, and this is shown to be related to a viscous mode found by Duck and Hall (1988).

Exceptionally Strong Electron-Donating Ability of Bora-Ylide Substituent vis-à-vis Silylene and Silylium Ion.

PubMed

Rosas-Sánchez, Alfredo; Alvarado-Beltran, Isabel; Baceiredo, Antoine; Saffon-Merceron, Nathalie; Massou, Stéphane; Branchadell, Vicenç; Kato, Tsuyoshi

2017-08-21

Electropositive boron-based substituent (phosphonium bora-ylide) with an exceptionally strong π- and σ-electron donating character dramatically increases the stability of a new type of N-heterocyclic silylene 2 featuring amino- and bora-ylide-substituents. Moreover, the related silylium ion 4 and transition-metal-silylene complexes, with trigonal-planar geometries around the silicon center, are also well stabilized. Therefore, the N,B-heterocyclic silylene 2 can be used as a strongly electron-donating innocent ligand in coordination chemistry similarly to N-heterocyclic carbenes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Decadal features of heavy rainfall events in eastern China

NASA Astrophysics Data System (ADS)

Chen, Huopo; Sun, Jianqi; Fan, Ke

2012-06-01

Based on daily precipitation data, the spatial-temporal features of heavy rainfall events (HREs) during 1960-2009 are investigated. The results indicate that the HREs experienced strong decadal variability in the past 50 years, and the decadal features varied across regions. More HRE days are observed in the 1960s, 1980s, and 1990s over Northeast China (NEC); in the 1960s, 1970s, and 1990s over North China (NC); in the early 1960s, 1980s, and 2000s over the Huaihe River basin (HR); in the 1970s-1990s over the mid-lower reaches of the Yangtze River valley (YR); and in the 1970s and 1990s over South China (SC). These decadal changes of HRE days in eastern China are closely associated with the decadal variations of water content and stratification stability of the local atmosphere. The intensity of HREs in each sub-region is also characterized by strong decadal variability. The HRE intensity and frequency co-vary on the long-term trend, and show consistent variability over NEC, NC, and YR, but inconsistent variability over SC and HR. Further analysis of the relationships between the annual rainfall and HRE frequency as well as intensity indicates that the HRE frequency is the major contributor to the total rainfall variability in eastern China, while the HRE intensity shows only relative weak contribution.

LSPV+7, a branch-point-tolerant reconstructor for strong turbulence adaptive optics.

PubMed

Steinbock, Michael J; Hyde, Milo W; Schmidt, Jason D

2014-06-20

Optical wave propagation through long paths of extended turbulence presents unique challenges to adaptive optics (AO) systems. As scintillation and branch points develop in the beacon phase, challenges arise in accurately unwrapping the received wavefront and optimizing the reconstructed phase with respect to branch cut placement on a continuous facesheet deformable mirror. Several applications are currently restricted by these capability limits: laser communication, laser weapons, remote sensing, and ground-based astronomy. This paper presents a set of temporally evolving AO simulations comparing traditional least-squares reconstruction techniques to a complex-exponential reconstructor and several other reconstructors derived from the postprocessing congruence operation. The reconstructors' behavior in closed-loop operation is compared and discussed, providing several insights into the fundamental strengths and limitations of each reconstructor type. This research utilizes a self-referencing interferometer (SRI) as the high-order wavefront sensor, driving a traditional linear control law in conjunction with a cooperative point source beacon. The SRI model includes practical optical considerations and frame-by-frame fiber coupling effects to allow for realistic noise modeling. The "LSPV+7" reconstructor is shown to offer the best performance in terms of Strehl ratio and correction stability-outperforming the traditional least-squares reconstructed system by an average of 120% in the studied scenarios. Utilizing a continuous facesheet deformable mirror, these reconstructors offer significant AO performance improvements in strong turbulence applications without the need for segmented deformable mirrors.

The three-dimensional evolution of a plane mixing layer. Part 1: The Kelvin-Helmholtz roll-up

NASA Technical Reports Server (NTRS)

Rogers, Michael M.; Moser, Robert D.

1991-01-01

The Kelvin Helmholtz roll up of three dimensional, temporally evolving, plane mixing layers were simulated numerically. All simulations were begun from a few low wavenumber disturbances, usually derived from linear stability theory, in addition to the mean velocity profile. The spanwise disturbance wavelength was taken to be less than or equal to the streamwise wavelength associated with the Kelvin Helmholtz roll up. A standard set of clean structures develop in most of the simulations. The spanwise vorticity rolls up into a corrugated spanwise roller, with vortex stretching creating strong spanwise vorticity in a cup shaped region at the vends of the roller. Predominantly streamwise rib vortices develop in the braid region between the rollers. For sufficiently strong initial three dimensional disturbances, these ribs collapse into compact axisymmetric vortices. The rib vortex lines connect to neighboring ribs and are kinked in the opposite direction of the roller vortex lines. Because of this, these two sets of vortex lines remain distinct. For certain initial conditions, persistent ribs do not develop. In such cases the development of significant three dimensionality is delayed. When the initial three dimensional disturbance energy is about equal to, or less than, the two dimensional fundamental disturbance energy, the evolution of the three dimensional disturbance is nearly linear (with respect to the mean and the two dimensional disturbances), at least until the first Kelvin Helmholtz roll up is completed.

Long-times series of infrasonic records at open-vents volcanoes (Yasur volcano, Vanuatu, 2003-2014): the remarkable temporal stability of magma viscosity

NASA Astrophysics Data System (ADS)

Vergniolle, S.; Souty, V.; Zielinski, C.; Bani, P.; LE Pichon, A.; Lardy, M.; Millier, P.; Herry, P.; Todman, S.; Garaebiti, E.

2017-12-01

Open-vents volcanoes, often presenting series of Strombolian explosions of various intensity, are responding, although with a delay, to any changes in the degassing pattern, providing a quasi-direct route to processes at depth. Open-vents volcanoes display a persistent volcanic activity, although of variable intensity. Long-times series at open-vents volcanoes could therefore be key measurements to unravel physical processes at the origin of Strombolian explosions and be crucial for monitoring. Continuous infrasonic records can be used to estimate the gas volume expelled at the vent during explosions (bursting of a long slug). The gas volume of each explosion is deduced from a series of two successive integrations of acoustic pressure (monopole). Here we analysed more than 4 years of infrasonic records at Yasur volcano (Vanuatu), spanning between 2003 and 2014 and organised into 8 main quasi-continuous periods. The relationship between the gas volume of each explosion and its associated maximum positive acoustic pressure, a proxy for the inner gas overpressure at bursting, shows a remarkably stable trend over the 8 periods. Two main trends exists, one which covers the full range of acoustic pressures (called « strong explosions ») and the second which represents explosions with a large gas volume and mild acoustic pressure. The class of « strong explosions » clearly follows the model of Del Bello et al. (2012), which shows that the inner gas overpressure at bursting, here empirically measured by the maximum acoustic pressure, is proportional to the gas volume. Constrains on magma viscosity and conduit radius, are deduced from this trend and from the gas volume at the transition passive-active degassing. The remarkable stability of this trend over time suggests that 1) the magma viscosity is stable at the depth where gas overpressure is produced within the slug and 2) any potential changes in magma viscosity occur very close to the top of the magma column.

Drivers of inter-year variability of plant production and decomposers across contrasting island ecosystems.

PubMed

Wardle, David A; Jonsson, Micael; Kalela-Brundin, Maarit; Lagerström, Anna; Bardgett, Richard D; Yeates, Gregor W; Nilsson, Marie-Charlotte

2012-03-01

Despite the likely importance of inter-year dynamics of plant production and consumer biota for driving community- and ecosystem-level processes, very few studies have explored how and why these dynamics vary across contrasting ecosystems. We utilized a well-characterized system of 30 lake islands in the boreal forest zone of northern Sweden across which soil fertility and productivity vary considerably, with larger islands being more fertile and productive than smaller ones. In this system we assessed the inter-year dynamics of several measures of plant production and the soil microbial community (primary consumers in the decomposer food web) for each of nine years, and soil microfaunal groups (secondary and tertiary consumers) for each of six of those years. We found that, for measures of plant production and each of the three consumer trophic levels, inter-year dynamics were strongly affected by island size. Further, many variables were strongly affected by island size (and thus bottom-up regulation by soil fertility and resources) in some years, but not in other years, most likely due to inter-year variation in climatic conditions. For each of the plant and microbial variables for which we had nine years of data, we also determined the inter-year coefficient of variation (CV), an inverse measure of stability. We found that CVs of some measures of plant productivity were greater on large islands, whereas those of other measures were greater on smaller islands; CVs of microbial variables were unresponsive to island size. We also found that the effects of island size on the temporal dynamics of some variables were related to inter-year variability of macroclimatic variables. As such, our results show that the inter-year dynamics of both plant productivity and decomposer biota across each of three trophic levels, as well as the inter-year stability of plant productivity, differ greatly across contrasting ecosystems, with potentially important but largely overlooked implications for community and ecosystem processes.

Learning and disrupting invariance in visual recognition with a temporal association rule

PubMed Central

Isik, Leyla; Leibo, Joel Z.; Poggio, Tomaso

2012-01-01

Learning by temporal association rules such as Foldiak's trace rule is an attractive hypothesis that explains the development of invariance in visual recognition. Consistent with these rules, several recent experiments have shown that invariance can be broken at both the psychophysical and single cell levels. We show (1) that temporal association learning provides appropriate invariance in models of object recognition inspired by the visual cortex, (2) that we can replicate the “invariance disruption” experiments using these models with a temporal association learning rule to develop and maintain invariance, and (3) that despite dramatic single cell effects, a population of cells is very robust to these disruptions. We argue that these models account for the stability of perceptual invariance despite the underlying plasticity of the system, the variability of the visual world and expected noise in the biological mechanisms. PMID:22754523

Spatial-temporal variability of soil moisture and its estimation across scales

NASA Astrophysics Data System (ADS)

Brocca, L.; Melone, F.; Moramarco, T.; Morbidelli, R.

2010-02-01

The soil moisture is a quantity of paramount importance in the study of hydrologic phenomena and soil-atmosphere interaction. Because of its high spatial and temporal variability, the soil moisture monitoring scheme was investigated here both for soil moisture retrieval by remote sensing and in view of the use of soil moisture data in rainfall-runoff modeling. To this end, by using a portable Time Domain Reflectometer, a sequence of 35 measurement days were carried out within a single year in seven fields located inside the Vallaccia catchment, central Italy, with area of 60 km2. Every sampling day, soil moisture measurements were collected at each field over a regular grid with an extension of 2000 m2. The optimization of the monitoring scheme, with the aim of an accurate mean soil moisture estimation at the field and catchment scale, was addressed by the statistical and the temporal stability. At the field scale, the number of required samples (NRS) to estimate the field-mean soil moisture within an accuracy of 2%, necessary for the validation of remotely sensed soil moisture, ranged between 4 and 15 for almost dry conditions (the worst case); at the catchment scale, this number increased to nearly 40 and it refers to almost wet conditions. On the other hand, to estimate the mean soil moisture temporal pattern, useful for rainfall-runoff modeling, the NRS was found to be lower. In fact, at the catchment scale only 10 measurements collected in the most "representative" field, previously determined through the temporal stability analysis, can reproduce the catchment-mean soil moisture with a determination coefficient, R2, higher than 0.96 and a root-mean-square error, RMSE, equal to 2.38%. For the "nonrepresentative" fields the accuracy in terms of RMSE decreased, but similar R2 coefficients were found. This insight can be exploited for the sampling in a generic field when it is sufficient to know an index of soil moisture temporal pattern to be incorporated in conceptual rainfall-runoff models. The obtained results can address the soil moisture monitoring network design from which a reliable soil moisture temporal pattern at the catchment scale can be derived.

An experimental test of a fundamental food web motif.

PubMed

Rip, Jason M K; McCann, Kevin S; Lynn, Denis H; Fawcett, Sonia

2010-06-07

Large-scale changes to the world's ecosystem are resulting in the deterioration of biostructure-the complex web of species interactions that make up ecological communities. A difficult, yet crucial task is to identify food web structures, or food web motifs, that are the building blocks of this baroque network of interactions. Once identified, these food web motifs can then be examined through experiments and theory to provide mechanistic explanations for how structure governs ecosystem stability. Here, we synthesize recent ecological research to show that generalist consumers coupling resources with different interaction strengths, is one such motif. This motif amazingly occurs across an enormous range of spatial scales, and so acts to distribute coupled weak and strong interactions throughout food webs. We then perform an experiment that illustrates the importance of this motif to ecological stability. We find that weak interactions coupled to strong interactions by generalist consumers dampen strong interaction strengths and increase community stability. This study takes a critical step by isolating a common food web motif and through clear, experimental manipulation, identifies the fundamental stabilizing consequences of this structure for ecological communities.

Structural Technology Evaluation Analysis Program (STEAP). Task Order 0029: Thermal Stability of Fatigue Life-Enhanced Structures

DTIC Science & Technology

2012-01-01

and c, we were able to obtain Figure 21: Intensity and Pressure Temporal Profiles Calculated from Pressure Model 0 20 40 60 80 100 0 2 4 6 8...August 2008 – 31 January 2012 4 . TITLE AND SUBTITLE STRUCTURAL TECHNOLOGY EVALUATION ANALYSIS PROGRAM (STEAP) Task Order 0029: Thermal...Stability of Fatigue Life-Enhanced Structures 5a. CONTRACT NUMBER FA8650-04-D-3446-0029 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62201F 6

Nineteen-month stability of Revised NEO Personality Inventory domain and facet scores in patients with personality disorders.

PubMed

Wilberg, Theresa; Karterud, Sigmund; Pedersen, Geir; Urnes, Øyvind; Costa, Paul T

2009-03-01

We lack knowledge of the temporal stability of major personality dimensions in patients with personality disorders (PDs). The Revised NEO Personality Inventory (NEO-PI-R) is a self-report instrument that operationalizes the Five-Factor Model of personality. This study investigated the relative stability, mean level stability, and individual level stability of the NEO-PI-R scores in patients with PDs (n = 393) and patients with symptom disorders only (n = 131). The NEO-PI-R was administered at admission to short-term day treatment and after an average of 19 months. The results showed a moderate to high degree of stability of NEO-PI-R scale scores with no substantial difference in stability between patients with and without PD. Changes in NEO-PI-R scores were associated with changes in symptom distress. Neuroticism was the least stable domain. The study indicates that the Five-Factor Model of personality dimensions and traits are fairly stable in patients with PDs. The lower stability of Neuroticism may partly be explained by its inherent state aspects.

Probabilistic stability analysis: the way forward for stability analysis of sustainable power systems.

PubMed

Milanović, Jovica V

2017-08-13

Future power systems will be significantly different compared with their present states. They will be characterized by an unprecedented mix of a wide range of electricity generation and transmission technologies, as well as responsive and highly flexible demand and storage devices with significant temporal and spatial uncertainty. The importance of probabilistic approaches towards power system stability analysis, as a subsection of power system studies routinely carried out by power system operators, has been highlighted in previous research. However, it may not be feasible (or even possible) to accurately model all of the uncertainties that exist within a power system. This paper describes for the first time an integral approach to probabilistic stability analysis of power systems, including small and large angular stability and frequency stability. It provides guidance for handling uncertainties in power system stability studies and some illustrative examples of the most recent results of probabilistic stability analysis of uncertain power systems.This article is part of the themed issue 'Energy management: flexibility, risk and optimization'. © 2017 The Author(s).

Full-frame video stabilization with motion inpainting.

PubMed

Matsushita, Yasuyuki; Ofek, Eyal; Ge, Weina; Tang, Xiaoou; Shum, Heung-Yeung

2006-07-01

Video stabilization is an important video enhancement technology which aims at removing annoying shaky motion from videos. We propose a practical and robust approach of video stabilization that produces full-frame stabilized videos with good visual quality. While most previous methods end up with producing smaller size stabilized videos, our completion method can produce full-frame videos by naturally filling in missing image parts by locally aligning image data of neighboring frames. To achieve this, motion inpainting is proposed to enforce spatial and temporal consistency of the completion in both static and dynamic image areas. In addition, image quality in the stabilized video is enhanced with a new practical deblurring algorithm. Instead of estimating point spread functions, our method transfers and interpolates sharper image pixels of neighboring frames to increase the sharpness of the frame. The proposed video completion and deblurring methods enabled us to develop a complete video stabilizer which can naturally keep the original image quality in the stabilized videos. The effectiveness of our method is confirmed by extensive experiments over a wide variety of videos.

Temporal Ordering Effects of Adolescent Depression, Relational Aggression, and Victimization over Six Waves: Fully Latent Reciprocal Effects Models

ERIC Educational Resources Information Center

Marsh, Herbert W.; Craven, Rhonda G.; Parker, Philip D.; Parada, Roberto H.; Guo, Jiesi; Dicke, Theresa; Abduljabbar, Adel Salah

2016-01-01

The temporal ordering of depression, aggression, and victimization has important implications for theory, policy, and practice. For a representative sample of high school students (Grades 7-10; N = 3,793) who completed the same psychometrically strong, multiitem scales 6 times over a 2-year period, there were reciprocal effects between…

The Relationship between Age Structure and Homicide Rates in the United States, 1970 to 1999

ERIC Educational Resources Information Center

Phillips, Julie A.

2006-01-01

The nature of the temporal association between age structure and homicide rates between 1970 and 1999 is examined using U.S. county data. Specifically, the following questions are asked: (a) does the strong temporal association between the relative size of the young population and homicide rates demonstrated at the U.S. national level hold at a…

Flicker sensitivity as a function of target area with and without temporal noise.

PubMed

Rovamo, J; Donner, K; Näsänen, R; Raninen, A

2000-01-01

Flicker sensitivities (1-30 Hz) in foveal, photopic vision were measured as functions of stimulus area with and without strong external white temporal noise. Stimuli were circular, sinusoidally flickering sharp-edged spots of variable diameters (0.25-4 degrees ) but constant duration (2 s), surrounded by a uniform equiluminant field. The data was described with a model comprising (i) low-pass filtering in the retina (R), with a modulation transfer function (MTF) of a form derived from responses of cones; (ii) normalisation of the temporal luminance distribution by the average luminance; (iii) high-pass filtering by postreceptoral neural pathways (P), with an MTF proportional to temporal frequency; (iv) addition of internal white neural noise (N(i)); (v) integration over a spatial window; and (vi) detection by a suboptimal temporal matched filter of efficiency eta. In strong external noise, flicker sensitivity was independent of spot area. Without external noise, sensitivity increased with the square root of stimulus area (Piper's law) up to a critical area (A(c)), where it reaches a maximum level (S(max)). Both A(c) and eta were monotonic functions of temporal frequency (f), such that log A(c) increased and log eta decreased linearly with log f. Remarkably, the increase in spatial integration area and the decrease in efficiency were just balanced, so A(c)(f)eta(f) was invariant against f. Thus the bandpass characteristics of S(max)(f) directly reflected the composite effect of the distal filters R(f) and P(f). The temporal equivalent (N(it)) of internal neural noise (N(i)) decreased in inverse proportion to spot area up to A(c) and then stayed constant indicating that spatially homogeneous signals and noise are integrated over the same area.

MONSTIR II: A 32-channel, multispectral, time-resolved optical tomography system for neonatal brain imaging

NASA Astrophysics Data System (ADS)

Cooper, Robert J.; Magee, Elliott; Everdell, Nick; Magazov, Salavat; Varela, Marta; Airantzis, Dimitrios; Gibson, Adam P.; Hebden, Jeremy C.

2014-05-01

We detail the design, construction and performance of the second generation UCL time-resolved optical tomography system, known as MONSTIR II. Intended primarily for the study of the newborn brain, the system employs 32 source fibres that sequentially transmit picosecond pulses of light at any four wavelengths between 650 and 900 nm. The 32 detector channels each contain an independent photo-multiplier tube and temporally correlated photon-counting electronics that allow the photon transit time between each source and each detector position to be measured with high temporal resolution. The system's response time, temporal stability, cross-talk, and spectral characteristics are reported. The efficacy of MONSTIR II is demonstrated by performing multi-spectral imaging of a simple phantom.

Quality assurance of temporal variability of natural decay chain and neutron induced background for low-level NORM analysis

DOE PAGES

Yoho, Michael; Porterfield, Donivan R.; Landsberger, Sheldon

2015-09-22

In this study, twenty-one high purity germanium (HPGe) background spectra were collected over 2 years at Los Alamos National Laboratory. A quality assurance methodology was developed to monitor spectral background levels from thermal and fast neutron flux levels and naturally occurring radioactive material decay series radionuclides. 238U decay products above 222Rn demonstrated minimal temporal variability beyond that expected from counting statistics. 238U and 232Th progeny below Rn gas displayed at most twice the expected variability. Further, an analysis of the 139 keV 74Ge(n, γ) and 691 keV 72Ge(n, n') spectral features demonstrated temporal stability for both thermal and fastmore » neutron fluxes.« less

Comparative leaching of six toxic metals from raw and chemically stabilized MSWI fly ash using citric acid.

PubMed

Wang, Huawei; Fan, Xinxiu; Wang, Ya-Nan; Li, Weihua; Sun, Yingjie; Zhan, Meili; Wu, Guizhi

2018-02-15

The leaching behavior of six typical toxic metals (Pb, Zn, Cr, Cd, Cu and Ni) from raw and chemically stabilized (phosphate and chelating agent) municipal solid waste incineration (MSWI) fly ash were investigated using citric acid. Leaching tests indicated that phosphate stabilization can effectively decrease the leaching of Zn, Cd and Cr; whereas chelating agent stabilization shows a strong ability to lower the release of Pb, Cd and Cu, but instead increases the solubility of Zn and Cr at low pH conditions. Sequential extraction results suggested that the leaching of Pb, Zn and Cd in both the stabilized MSWI fly ash samples led to the decrease in Fe/Mn oxide fraction and the increase in exchangeable and carbonate fractions. The leaching of Cr was due to the decrease in exchangeable, carbonate and Fe/Mn oxide fractions in phosphate-stabilized and chelating agent-stabilized MSWI fly ash. The leaching of Cu in both stabilized MSWI fly ash was greatly ascribed to the decrease in Fe/Mn oxide and oxidisable fractions. Moreover, predicted curves by geochemical model indicated that both stabilized MSWI fly ash have the risk of releasing toxic metals under strong acid environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Reconciling spatial and temporal soil moisture effects on afternoon rainfall

PubMed Central

Guillod, Benoit P.; Orlowsky, Boris; Miralles, Diego G.; Teuling, Adriaan J.; Seneviratne, Sonia I.

2015-01-01

Soil moisture impacts on precipitation have been strongly debated. Recent observational evidence of afternoon rain falling preferentially over land parcels that are drier than the surrounding areas (negative spatial effect), contrasts with previous reports of a predominant positive temporal effect. However, whether spatial effects relating to soil moisture heterogeneity translate into similar temporal effects remains unknown. Here we show that afternoon precipitation events tend to occur during wet and heterogeneous soil moisture conditions, while being located over comparatively drier patches. Using remote-sensing data and a common analysis framework, spatial and temporal correlations with opposite signs are shown to coexist within the same region and data set. Positive temporal coupling might enhance precipitation persistence, while negative spatial coupling tends to regionally homogenize land surface conditions. Although the apparent positive temporal coupling does not necessarily imply a causal relationship, these results reconcile the notions of moisture recycling with local, spatially negative feedbacks. PMID:25740589

Temporal Integration of Auditory Information Is Invariant to Temporal Grouping Cues

PubMed

Liu, Andrew S K; Tsunada, Joji; Gold, Joshua I; Cohen, Yale E

2015-01-01

Auditory perception depends on the temporal structure of incoming acoustic stimuli. Here, we examined whether a temporal manipulation that affects the perceptual grouping also affects the time dependence of decisions regarding those stimuli. We designed a novel discrimination task that required human listeners to decide whether a sequence of tone bursts was increasing or decreasing in frequency. We manipulated temporal perceptual-grouping cues by changing the time interval between the tone bursts, which led to listeners hearing the sequences as a single sound for short intervals or discrete sounds for longer intervals. Despite these strong perceptual differences, this manipulation did not affect the efficiency of how auditory information was integrated over time to form a decision. Instead, the grouping manipulation affected subjects' speed-accuracy trade-offs. These results indicate that the temporal dynamics of evidence accumulation for auditory perceptual decisions can be invariant to manipulations that affect the perceptual grouping of the evidence.

Understanding the tropical cloud feedback from an analysis of the circulation and stability regimes simulated from an upgraded multiscale modeling framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Kuan-Man; Cheng, Anning

As revealed from studies using conventional general circulation models (GCMs), the thermodynamic contribution to the tropical cloud feedback dominates the dynamic contribution, but these models have difficulty in simulating the subsidence regimes in the tropics. In this study, we analyze the tropical cloud feedback from a 2 K sea surface temperature (SST) perturbation experiment performed with a multiscale modeling framework (MMF). The MMF explicitly represents cloud processes using 2-D cloud-resolving models with an advanced higher-order turbulence closure in each atmospheric column of the host GCM. We sort the monthly mean cloud properties and cloud radiative effects according to circulation andmore » stability regimes. Here, we find that the regime-sorted dynamic changes dominate the thermodynamic changes in terms of the absolute magnitude. The dynamic changes in the weak subsidence regimes exhibit strong negative cloud feedback due to increases in shallow cumulus and deep clouds while those in strongly convective and moderate-to-strong subsidence regimes have opposite signs, resulting in a small contribution to cloud feedback. On the other hand, the thermodynamic changes are large due to decreases in stratocumulus clouds in the moderate-to-strong subsidence regimes with small opposite changes in the weak subsidence and strongly convective regimes, resulting in a relatively large contribution to positive cloud feedback. The dynamic and thermodynamic changes contribute equally to positive cloud feedback and are relatively insensitive to stability in the moderate-to-strong subsidence regimes. But they are sensitive to stability changes from the SST increase in convective and weak subsidence regimes. Lastly, these results have implications for interpreting cloud feedback mechanisms.« less

Understanding the tropical cloud feedback from an analysis of the circulation and stability regimes simulated from an upgraded multiscale modeling framework

DOE PAGES

Xu, Kuan-Man; Cheng, Anning

2016-11-15

As revealed from studies using conventional general circulation models (GCMs), the thermodynamic contribution to the tropical cloud feedback dominates the dynamic contribution, but these models have difficulty in simulating the subsidence regimes in the tropics. In this study, we analyze the tropical cloud feedback from a 2 K sea surface temperature (SST) perturbation experiment performed with a multiscale modeling framework (MMF). The MMF explicitly represents cloud processes using 2-D cloud-resolving models with an advanced higher-order turbulence closure in each atmospheric column of the host GCM. We sort the monthly mean cloud properties and cloud radiative effects according to circulation andmore » stability regimes. Here, we find that the regime-sorted dynamic changes dominate the thermodynamic changes in terms of the absolute magnitude. The dynamic changes in the weak subsidence regimes exhibit strong negative cloud feedback due to increases in shallow cumulus and deep clouds while those in strongly convective and moderate-to-strong subsidence regimes have opposite signs, resulting in a small contribution to cloud feedback. On the other hand, the thermodynamic changes are large due to decreases in stratocumulus clouds in the moderate-to-strong subsidence regimes with small opposite changes in the weak subsidence and strongly convective regimes, resulting in a relatively large contribution to positive cloud feedback. The dynamic and thermodynamic changes contribute equally to positive cloud feedback and are relatively insensitive to stability in the moderate-to-strong subsidence regimes. But they are sensitive to stability changes from the SST increase in convective and weak subsidence regimes. Lastly, these results have implications for interpreting cloud feedback mechanisms.« less

Linear stability of compressible Taylor-Couette flow

NASA Technical Reports Server (NTRS)

Kao, Kai-Hsiung; Chow, Chuen-Yen

1992-01-01

A temporal stability analysis of compressible Taylor-Couette flow is presented. The viscous flow studied in this paper is contained between two concentric cylinders of infinite length, which are rotating with different angular velocities and are kept at different surface temperatures. The effects of differential rotation and temperature difference on the stability of Taylor-Couette flow are contrasted for a range of Mach numbers ranging from incompressible to Mach 3.0. The relative motion of the cylinders dramatically affects the characteristics of the Couette flow at the onset of instability. The flow is stabilized or destabilized depending upon the temperature ratio and speeds of the two cylinders. Independent of Mach number and temperature ratio, increasing Reynolds number generally promotes a destabilizing effect, indicating the inviscid nature of the Taylor-Couette flow.

Stability of matter-wave solitons in optical lattices

NASA Astrophysics Data System (ADS)

Ali, Sk. Golam; Roy, S. K.; Talukdar, B.

2010-08-01

We consider localized states of both single- and two-component Bose-Einstein condensates (BECs) confined in a potential resulting from the superposition of linear and nonlinear optical lattices and make use of Vakhitov-Kolokolov criterion to investigate the effect of nonlinear lattice on the stability of the soliton solutions in the linear optical lattice (LOL). For the single-component case we show that a weak nonlinear lattice has very little effect on the stability of such solitons while sufficiently strong nonlinear optical lattice (NOL) squeezes them to produce narrow bound states. For two-component condensates we find that when the strength of the NOL (γ1) is less than that of the LOL (V0) a relatively weak intra-atomic interaction (IAI) has little effect on the stability of the component solitons. This is true for both attractive and repulsive IAI. A strong attractive IAI, however, squeezes the BEC solitons while a similar repulsive IAI makes the component solitons wider. For γ1 > V0, only a strong attractive IAI squeezes the BEC solitons but the squeezing effect is less prominent than that found for γ1 < V0. We make useful checks on the results of our semianalytical stability analysis by solving the appropriate Gross-Pitaevskii equations numerically.

Robust Video Stabilization Using Particle Keypoint Update and l1-Optimized Camera Path

PubMed Central

Jeon, Semi; Yoon, Inhye; Jang, Jinbeum; Yang, Seungji; Kim, Jisung; Paik, Joonki

2017-01-01

Acquisition of stabilized video is an important issue for various type of digital cameras. This paper presents an adaptive camera path estimation method using robust feature detection to remove shaky artifacts in a video. The proposed algorithm consists of three steps: (i) robust feature detection using particle keypoints between adjacent frames; (ii) camera path estimation and smoothing; and (iii) rendering to reconstruct a stabilized video. As a result, the proposed algorithm can estimate the optimal homography by redefining important feature points in the flat region using particle keypoints. In addition, stabilized frames with less holes can be generated from the optimal, adaptive camera path that minimizes a temporal total variation (TV). The proposed video stabilization method is suitable for enhancing the visual quality for various portable cameras and can be applied to robot vision, driving assistant systems, and visual surveillance systems. PMID:28208622

Sequential bottom-up assembly of mechanically stabilized synthetic cells by microfluidics

NASA Astrophysics Data System (ADS)

Weiss, Marian; Frohnmayer, Johannes Patrick; Benk, Lucia Theresa; Haller, Barbara; Janiesch, Jan-Willi; Heitkamp, Thomas; Börsch, Michael; Lira, Rafael B.; Dimova, Rumiana; Lipowsky, Reinhard; Bodenschatz, Eberhard; Baret, Jean-Christophe; Vidakovic-Koch, Tanja; Sundmacher, Kai; Platzman, Ilia; Spatz, Joachim P.

2018-01-01

Compartments for the spatially and temporally controlled assembly of biological processes are essential towards cellular life. Synthetic mimics of cellular compartments based on lipid-based protocells lack the mechanical and chemical stability to allow their manipulation into a complex and fully functional synthetic cell. Here, we present a high-throughput microfluidic method to generate stable, defined sized liposomes termed `droplet-stabilized giant unilamellar vesicles (dsGUVs)’. The enhanced stability of dsGUVs enables the sequential loading of these compartments with biomolecules, namely purified transmembrane and cytoskeleton proteins by microfluidic pico-injection technology. This constitutes an experimental demonstration of a successful bottom-up assembly of a compartment with contents that would not self-assemble to full functionality when simply mixed together. Following assembly, the stabilizing oil phase and droplet shells are removed to release functional self-supporting protocells to an aqueous phase, enabling them to interact with physiologically relevant matrices.

Temporal Stability of the Human Skin Microbiome.

PubMed

Oh, Julia; Byrd, Allyson L; Park, Morgan; Kong, Heidi H; Segre, Julia A

2016-05-05

Biogeography and individuality shape the structural and functional composition of the human skin microbiome. To explore these factors' contribution to skin microbial community stability, we generated metagenomic sequence data from longitudinal samples collected over months and years. Analyzing these samples using a multi-kingdom, reference-based approach, we found that despite the skin's exposure to the external environment, its bacterial, fungal, and viral communities were largely stable over time. Site, individuality, and phylogeny were all determinants of stability. Foot sites exhibited the most variability; individuals differed in stability; and transience was a particular characteristic of eukaryotic viruses, which showed little site-specificity in colonization. Strain and single-nucleotide variant-level analysis showed that individuals maintain, rather than reacquire, prevalent microbes from the environment. Longitudinal stability of skin microbial communities generates hypotheses about colonization resistance and empowers clinical studies exploring alterations observed in disease states. Copyright © 2016 Elsevier Inc. All rights reserved.

Grouping and Segregation of Sensory Events by Actions in Temporal Audio-Visual Recalibration.

PubMed

Ikumi, Nara; Soto-Faraco, Salvador

2016-01-01

Perception in multi-sensory environments involves both grouping and segregation of events across sensory modalities. Temporal coincidence between events is considered a strong cue to resolve multisensory perception. However, differences in physical transmission and neural processing times amongst modalities complicate this picture. This is illustrated by cross-modal recalibration, whereby adaptation to audio-visual asynchrony produces shifts in perceived simultaneity. Here, we examined whether voluntary actions might serve as a temporal anchor to cross-modal recalibration in time. Participants were tested on an audio-visual simultaneity judgment task after an adaptation phase where they had to synchronize voluntary actions with audio-visual pairs presented at a fixed asynchrony (vision leading or vision lagging). Our analysis focused on the magnitude of cross-modal recalibration to the adapted audio-visual asynchrony as a function of the nature of the actions during adaptation, putatively fostering cross-modal grouping or, segregation. We found larger temporal adjustments when actions promoted grouping than segregation of sensory events. However, a control experiment suggested that additional factors, such as attention to planning/execution of actions, could have an impact on recalibration effects. Contrary to the view that cross-modal temporal organization is mainly driven by external factors related to the stimulus or environment, our findings add supporting evidence for the idea that perceptual adjustments strongly depend on the observer's inner states induced by motor and cognitive demands.

Grouping and Segregation of Sensory Events by Actions in Temporal Audio-Visual Recalibration

PubMed Central

Ikumi, Nara; Soto-Faraco, Salvador

2017-01-01

Perception in multi-sensory environments involves both grouping and segregation of events across sensory modalities. Temporal coincidence between events is considered a strong cue to resolve multisensory perception. However, differences in physical transmission and neural processing times amongst modalities complicate this picture. This is illustrated by cross-modal recalibration, whereby adaptation to audio-visual asynchrony produces shifts in perceived simultaneity. Here, we examined whether voluntary actions might serve as a temporal anchor to cross-modal recalibration in time. Participants were tested on an audio-visual simultaneity judgment task after an adaptation phase where they had to synchronize voluntary actions with audio-visual pairs presented at a fixed asynchrony (vision leading or vision lagging). Our analysis focused on the magnitude of cross-modal recalibration to the adapted audio-visual asynchrony as a function of the nature of the actions during adaptation, putatively fostering cross-modal grouping or, segregation. We found larger temporal adjustments when actions promoted grouping than segregation of sensory events. However, a control experiment suggested that additional factors, such as attention to planning/execution of actions, could have an impact on recalibration effects. Contrary to the view that cross-modal temporal organization is mainly driven by external factors related to the stimulus or environment, our findings add supporting evidence for the idea that perceptual adjustments strongly depend on the observer's inner states induced by motor and cognitive demands. PMID:28154529

Characterization of high temporal resolution prr acquisition by fast comtec card: Deadtime, PRR desaturation, temperature calibration and retrieval.

NASA Astrophysics Data System (ADS)

Martucci, Giovanni; Simeonov, Valentin; Renaud, Ludovic; Haefele, Alexander

2018-04-01

RAman Lidar for Meteorological Observations (RALMO) is operated at MeteoSwiss and provides continuous measurements of water vapor and temperature since 2010. While the water vapor has been acquired by a Licel acquisition system since 2008, the temperature channels have been migrated to a Fastcom P7888 acquisition system, since August 2015. We present a characterization of this new acquisition system, namely its dead-time, desaturation, temporal stability of the Pure Rotational Raman signals and the retrieval of the PRR-temperature.

TH-CD-BRA-11: Implementation and Evaluation of a New 3D Dosimetry Protocol for Validating MRI Guided Radiation Therapy Treatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mein, S; Rankine, L; Department of Radiation Oncology, Washington University School of Medicine

Purpose: To develop, evaluate and apply a novel high-resolution 3D remote dosimetry protocol for validation of MRI guided radiation therapy treatments (MRIdian by ViewRay™). We demonstrate the first application of the protocol (including two small but required new correction terms) utilizing radiochromic 3D plastic PRESAGE™ with optical-CT readout. Methods: A detailed study of PRESAGE™ dosimeters (2kg) was conducted to investigate the temporal and spatial stability of radiation induced optical density change (ΔOD) over 8 days. Temporal stability was investigated on 3 dosimeters irradiated with four equally-spaced square 6MV fields delivering doses between 10cGy and 300cGy. Doses were imaged (read-out) bymore » optical-CT at multiple intervals. Spatial stability of ΔOD response was investigated on 3 other dosimeters irradiated uniformly with 15MV extended-SSD fields with doses of 15cGy, 30cGy and 60cGy. Temporal and spatial (radial) changes were investigated using CERR and MATLAB’s Curve Fitting Tool-box. A protocol was developed to extrapolate measured ΔOD readings at t=48hr (the typical shipment time in remote dosimetry) to time t=1hr. Results: All dosimeters were observed to gradually darken with time (<5% per day). Consistent intra-batch sensitivity (0.0930±0.002 ΔOD/cm/Gy) and linearity (R2=0.9996) was observed at t=1hr. A small radial effect (<3%) was observed, attributed to curing thermodynamics during manufacture. The refined remote dosimetry protocol (including polynomial correction terms for temporal and spatial effects, CT and CR) was then applied to independent dosimeters irradiated with MR-IGRT treatments. Excellent line profile agreement and 3D-gamma results for 3%/3mm, 10% threshold were observed, with an average passing rate 96.5%± 3.43%. Conclusion: A novel 3D remote dosimetry protocol is presented capable of validation of advanced radiation treatments (including MR-IGRT). The protocol uses 2kg radiochromic plastic dosimeters read-out by optical-CT within a week of treatment. The protocol requires small corrections for temporal and spatially-dependent behaviors observed between irradiation and readout.« less

Dynamic Control of Plans with Temporal Uncertainty

NASA Technical Reports Server (NTRS)

Morris, Paul; Muscettola, Nicola; Vidal, Thierry

2001-01-01

Certain planning systems that deal with quantitative time constraints have used an underlying Simple Temporal Problem solver to ensure temporal consistency of plans. However, many applications involve processes of uncertain duration whose timing cannot be controlled by the execution agent. These cases require more complex notions of temporal feasibility. In previous work, various "controllability" properties such as Weak, Strong, and Dynamic Controllability have been defined. The most interesting and useful Controllability property, the Dynamic one, has ironically proved to be the most difficult to analyze. In this paper, we resolve the complexity issue for Dynamic Controllability. Unexpectedly, the problem turns out to be tractable. We also show how to efficiently execute networks whose status has been verified.

Spatial and temporal analysis of postural control in dyslexic children.

PubMed

Gouleme, Nathalie; Gerard, Christophe Loic; Bui-Quoc, Emmanuel; Bucci, Maria Pia

2015-07-01

The aim of this study is to examine postural control of dyslexic children using both spatial and temporal analysis. Thirty dyslexic (mean age 9.7±0.3years) and thirty non-dyslexic age-matched children participated in the study. Postural stability was evaluated using Multitest Equilibre from Framiral®. Posture was recorded in the following conditions: eyes open fixating a target (EO) and eyes closed (EC) on stable (-S-) and unstable (-U-) platforms. The findings of this study showed poor postural stability in dyslexic children with respect to the non-dyslexic children group, as demonstrated by both spatial and temporal analysis. In both groups of children postural control depends on the condition, and improves when the eyes are open on a stable platform. Dyslexic children have spectral power indices that are higher than in non-dyslexic children and they showed a shorter cancelling time. Poor postural control in dyslexic children could be due to a deficit in using sensory information most likely caused by impairment in cerebellar activity. The reliability of brain activation patterns, namely in using sensory input and cerebellar activity may explain the deficit in postural control in dyslexic children. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Temporal distribution of intertidal macrozoobenthic assemblages in a Nanozostera noltii-dominated area (Lagoon of Venice).

PubMed

Tagliapietra, D; Pessa, G; Cornello, M; Zitelli, A; Magni, P

2016-03-01

We describe the temporal distribution of intertidal macrozoobenthic assemblages in a small marsh pond of the Lagoon of Venice colonized by the seagrass Nanozostera noltii (Hornemman) Tomlinson et Posluzny. Three stations ranging in the degree of N. noltii cover were selected about 100 m apart and sampled 9 times at regular intervals from March 1996 to March 1997. We applied the concepts of resistance and resilience to "natural stress" (e.g. extent of protection from seagrass meadows, exposure of macrozoobenthic assemblages to high temperatures in summer) with the aim to assess the stability of a community along a gradient of seagrass coverage. Results showed that the most structured and taxa-rich macrozoobenthic assemblage occurred at the station covered by a continuous stand of N. noltii, where permanent taxa (i.e. found in 100% of samples) were almost double than those found at the other stations. During the annual cycle, the macrozoobenthic assemblages showed a cyclical pattern, with temporal fluctuations increasing as they moved further away from the seagrass beds. We propose the role of N. noltii offering structural complexity and stability as the more probable explanation to the observed differences between stations in the intertidal assemblages. Copyright © 2015 Elsevier Ltd. All rights reserved.

A commentary on the Atlantic meridional overturning circulation stability in climate models

NASA Astrophysics Data System (ADS)

Gent, Peter R.

2018-02-01

The stability of the Atlantic meridional overturning circulation (AMOC) in ocean models depends quite strongly on the model formulation, especially the vertical mixing, and whether it is coupled to an atmosphere model. A hysteresis loop in AMOC strength with respect to freshwater forcing has been found in several intermediate complexity climate models and in one fully coupled climate model that has very coarse resolution. Over 40% of modern climate models are in a bistable AMOC state according to the very frequently used simple stability criterion which is based solely on the sign of the AMOC freshwater transport across 33° S. In a recent freshwater hosing experiment in a climate model with an eddy-permitting ocean component, the change in the gyre freshwater transport across 33° S is larger than the AMOC freshwater transport change. This casts very strong doubt on the usefulness of this simple AMOC stability criterion. If a climate model uses large surface flux adjustments, then these adjustments can interfere with the atmosphere-ocean feedbacks, and strongly change the AMOC stability properties. AMOC can be shut off for many hundreds of years in modern fully coupled climate models if the hosing or carbon dioxide forcing is strong enough. However, in one climate model the AMOC recovers after between 1000 and 1400 years. Recent 1% increasing carbon dioxide runs and RCP8.5 future scenario runs have shown that the AMOC reduction is smaller using an eddy-resolving ocean component than in the comparable standard 1° ocean climate models.

On the Temporal Variability of Low-Mode Internal Tides in the Deep Ocean

NASA Technical Reports Server (NTRS)

Ray, Richard D.; Zaron, E. D.

2010-01-01

In situ measurements of internal tides are typically characterized by high temporal variability, with strong dependence on stratification, mesoscale eddies, and background currents commonly observed. Thus, it is surprising to find phase-locked internal tides detectable by satellite altimetry. An important question is how much tidal variability is missed by altimetry. We address this question in several ways. We subset the altimetry by season and find only very small changes -- an important exception being internal tides in the South China Sea where we observe strong seasonal dependence. A wavenumber-domain analysis confirms that throughout most of the global ocean there is little temporal variability in altimetric internal-tide signals, at least in the first baroclinic mode, which is the mode that dominates surface elevation. The analysis shows higher order modes to be significantly more variable. The results of this study have important practical implications for the anticipated SWOT wide-swath altimeter mission, for which removal of internal tide signals is critical for observing non-tidal submesoscale phenomena.

Contributions of local speech encoding and functional connectivity to audio-visual speech perception

PubMed Central

Giordano, Bruno L; Ince, Robin A A; Gross, Joachim; Schyns, Philippe G; Panzeri, Stefano; Kayser, Christoph

2017-01-01

Seeing a speaker’s face enhances speech intelligibility in adverse environments. We investigated the underlying network mechanisms by quantifying local speech representations and directed connectivity in MEG data obtained while human participants listened to speech of varying acoustic SNR and visual context. During high acoustic SNR speech encoding by temporally entrained brain activity was strong in temporal and inferior frontal cortex, while during low SNR strong entrainment emerged in premotor and superior frontal cortex. These changes in local encoding were accompanied by changes in directed connectivity along the ventral stream and the auditory-premotor axis. Importantly, the behavioral benefit arising from seeing the speaker’s face was not predicted by changes in local encoding but rather by enhanced functional connectivity between temporal and inferior frontal cortex. Our results demonstrate a role of auditory-frontal interactions in visual speech representations and suggest that functional connectivity along the ventral pathway facilitates speech comprehension in multisensory environments. DOI: http://dx.doi.org/10.7554/eLife.24763.001 PMID:28590903

Ultra-Rapid Vision in Birds.

PubMed

Boström, Jannika E; Dimitrova, Marina; Canton, Cindy; Håstad, Olle; Qvarnström, Anna; Ödeen, Anders

2016-01-01

Flying animals need to accurately detect, identify and track fast-moving objects and these behavioral requirements are likely to strongly select for abilities to resolve visual detail in time. However, evidence of highly elevated temporal acuity relative to non-flying animals has so far been confined to insects while it has been missing in birds. With behavioral experiments on three wild passerine species, blue tits, collared and pied flycatchers, we demonstrate temporal acuities of vision far exceeding predictions based on the sizes and metabolic rates of these birds. This implies a history of strong natural selection on temporal resolution. These birds can resolve alternating light-dark cycles at up to 145 Hz (average: 129, 127 and 137, respectively), which is ca. 50 Hz over the highest frequency shown in any other vertebrate. We argue that rapid vision should confer a selective advantage in many bird species that are ecologically similar to the three species examined in our study. Thus, rapid vision may be a more typical avian trait than the famously sharp vision found in birds of prey.

Varus-valgus stability at 90° flexion correlates with the stability at midflexion range more widely than that at 0° extension in posterior-stabilized total knee arthroplasty.

PubMed

Hino, Kazunori; Kutsuna, Tatsuhiko; Watamori, Kunihiko; Kiyomatsu, Hiroshi; Ishimaru, Yasumitsu; Takeba, Jun; Watanabe, Seiji; Shiraishi, Yoshitaka; Miura, Hiromasa

2017-10-01

Midflexion stability can potentially improve the outcome of total knee arthroplasty (TKA). The purpose of this study was to evaluate the correlation between varus-valgus stability at 0° of extension and 90° of flexion and that at the midflexion range in posterior-stabilized (PS)-TKA. Forty-three knees that underwent PS-TKA were evaluated. Manual mild passive varus-valgus stress was applied to the knees, and the postoperative maximum varus-valgus stability was measured every 10° throughout range of motion, using a navigation system. Correlations between the stability at 0°, 90° of flexion, and that at each midflexion angle were evaluated using Spearman's correlation coefficients. The stability of 0° modestly correlated with that of 10°-20°, but it did not significantly correlate with that of 30°-80°. However, the stability of 90° strongly correlated with that of 60°-80°, modestly correlated with that of 40°-50°, weakly correlated with that of 20°-30°, and did not correlate with that of 10°. The present study confirmed the importance of acquiring stability at 90° flexion to achieve midflexion stability in PS-TKA. However, initial flexion stability did not strongly correlate with the stability at either 0° or 90°. Our findings can provide useful information for understanding varus-valgus stability throughout the range of motion in PS-TKA. Attention to soft tissue balancing is necessary to stabilize a knee at the initial flexion range in PS-TKA.

Characterization of peeling modes in a low aspect ratio tokamak

NASA Astrophysics Data System (ADS)

Bongard, M. W.; Thome, K. E.; Barr, J. L.; Burke, M. G.; Fonck, R. J.; Hinson, E. T.; Redd, A. J.; Schlossberg, D. J.

2014-11-01

Peeling modes are observed at the plasma edge in the Pegasus Toroidal Experiment under conditions of high edge current density (Jedge ˜ 0.1 MA m-2) and low magnetic field (B ˜ 0.1 T) present at near-unity aspect ratio. Their macroscopic properties are measured using external Mirnov coil arrays, Langmuir probes and high-speed visible imaging. The modest edge parameters and short pulse lengths of Pegasus discharges permit direct measurement of the internal magnetic field structure with an insertable array of Hall-effect sensors, providing the current profile and its temporal evolution. Peeling modes generate coherent, edge-localized electromagnetic activity with low toroidal mode numbers n ⩽ 3 and high poloidal mode numbers, in agreement with theoretical expectations of a low-n external kink structure. Coherent MHD fluctuation amplitudes are found to be strongly dependent on the experimentally measured Jedge/B peeling instability drive, consistent with theory. Peeling modes nonlinearly generate ELM-like, field-aligned filamentary structures that detach from the edge and propagate radially outward. The KFIT equilibrium code is extended with an Akima spline profile parameterization and an improved model for induced toroidal wall current estimation to obtain a reconstruction during peeling activity with its current profile constrained by internal Hall measurements. It is used to test the analytic peeling stability criterion and numerically evaluate ideal MHD stability. Both approaches predict instability, in agreement with experiment, with the latter identifying an unstable external kink.

Stability of a behavioural syndrome vs. plasticity in individual behaviours over the breeding cycle: Ultimate and proximate explanations.

PubMed

Trnka, Alfréd; Samaš, Peter; Grim, Tomáš

2018-08-01

Animals often show correlated suites of consistent behavioural traits, i.e., personality or behavioural syndromes. Does this conflict with potential phenotypic plasticity which should be adaptive for animals facing various contexts and situations? This fundamental question has been tested predominantly in studies which were done in non-breeding contexts and under laboratory conditions. Therefore, in the present study we examined the temporal stability of behavioural correlations in a breeding context and under natural conditions. We found that in the great reed warbler (Acrocephalus arundinaceus) females, the intensity of their nest defence formed a behavioural syndrome with two other traits: their aggression during handling (self-defence) and stress responses during handling (breath rate). This syndrome was stable across the nesting cycle: each of the three behavioural traits was highly statistically repeatable between egg and nestling stages and the traits were strongly correlated with each other during both the egg stage and the nestling stage. Despite this consistency (i.e., rank order between stages) the individual behaviours changed their absolute values significantly during the same period. This shows that stable behavioural syndromes might be based on behaviours that are themselves unstable. Thus, syndromes do not inevitably constrain phenotypic plasticity. We suggest that the observed behavioural syndrome is the product of interactions between behavioural and life history trade-offs and that crucial proximate mechanisms for the plasticity and correlations between individual behaviours are hormonally-regulated. Copyright © 2018 Elsevier B.V. All rights reserved.

Self-biased broadband magnet-free linear isolator based on one-way space-time coherency

NASA Astrophysics Data System (ADS)

Taravati, Sajjad

2017-12-01

This paper introduces a self-biased broadband magnet-free and linear isolator based on one-way space-time coherency. The incident wave and the space-time-modulated medium share the same temporal frequency and are hence temporally coherent. However, thanks to the unidirectionally of the space-time modulation, the space-time-modulated medium and the incident wave are spatially coherent only in the forward direction and not in the opposite direction. As a consequence, the energy of the medium strongly couples to the propagating wave in the forward direction, while it conflicts with the propagating wave in the opposite direction, yielding strong isolation. We first derive a closed-form solution for the wave scattering from a spatiotemporally coherent medium and then show that a perfectly coherent space-time-modulated medium provides a moderate isolation level which is also subject to one-way transmission gain. To overcome this issue, we next investigate the effect of space-coherency imperfection between the medium and the wave, while they are still perfectly temporally coherent. Leveraging the spatial-coherency imperfection, the medium exhibits a quasiarbitrary and strong nonreciprocal transmission. Finally, we present the experimental demonstration of the self-biased version of the proposed broadband isolator, exhibiting more than 122 % fractional operation bandwidth.

Optical emission and nanoparticle generation in Al plasmas using ultrashort laser pulses temporally optimized by real-time spectroscopic feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guillermin, M.; Colombier, J. P.; Audouard, E.

2010-07-15

With an interest in pulsed laser deposition and remote spectroscopy techniques, we explore here the potential of laser pulses temporally tailored on ultrafast time scales to control the expansion and the excitation degree of various ablation products including atomic species and nanoparticulates. Taking advantage of automated pulse-shaping techniques, an adaptive procedure based on spectroscopic feedback is applied to regulate the irradiance and enhance the optical emission of monocharged aluminum ions with respect to the neutral signal. This leads to optimized pulses usually consisting in a series of femtosecond peaks distributed on a longer picosecond sequence. The ablation features induced bymore » the optimized pulse are compared with those determined by picosecond pulses generated by imposed second-order dispersion or by double pulse sequences with adjustable picosecond separation. This allows to analyze the influence of fast- and slow-varying envelope features on the material heating and the resulting plasma excitation degree. Using various optimal pulse forms including designed asymmetric shapes, we analyze the establishment of surface pre-excitation that enables conditions of enhanced radiation coupling. Thin films elaborated by unshaped femtosecond laser pulses and by optimized, stretched, or double pulse sequences are compared, indicating that the nanoparticles generation efficiency is strongly influenced by the temporal shaping of the laser irradiation. A thermodynamic scenario involving supercritical heating is proposed to explain enhanced ionization rates and lower particulates density for optimal pulses. Numerical one-dimensional hydrodynamic simulations for the excited matter support the interpretation of the experimental results in terms of relative efficiency of various relaxation paths for excited matter above or below the thermodynamic stability limits. The calculation results underline the role of the temperature and density gradients along the ablated plasma plume which lead to the spatial distinct locations of excited species. Moreover, the nanoparticles sizes are computed based on liquid layer ejection followed by a Rayleigh and Taylor instability decomposition, in good agreement with the experimental findings.« less

Mapping permafrost change hot-spots with Landsat time-series

NASA Astrophysics Data System (ADS)

Grosse, G.; Nitze, I.

2016-12-01

Recent and projected future climate warming strongly affects permafrost stability over large parts of the terrestrial Arctic with local, regional and global scale consequences. The monitoring and quantification of permafrost and associated land surface changes in these areas is crucial for the analysis of hydrological and biogeochemical cycles as well as vegetation and ecosystem dynamics. However, detailed knowledge of the spatial distribution and the temporal dynamics of these processes is scarce and likely key locations of permafrost landscape dynamics may remain unnoticed. As part of the ERC funded PETA-CARB and ESA GlobPermafrost projects, we developed an automated processing chain based on data from the entire Landsat archive (excluding MSS) for the detection of permafrost change related processes and hotspots. The automated method enables us to analyze thousands of Landsat scenes, which allows for a multi-scaled spatio-temporal analysis at 30 meter spatial resolution. All necessary processing steps are carried out automatically with minimal user interaction, including data extraction, masking, reprojection, subsetting, data stacking, and calculation of multi-spectral indices. These indices, e.g. Landsat Tasseled Cap and NDVI among others, are used as proxies for land surface conditions, such as vegetation status, moisture or albedo. Finally, a robust trend analysis is applied to each multi-spectral index and each pixel over the entire observation period of up to 30 years from 1985 to 2015, depending on data availability. Large transects of around 2 million km² across different permafrost types in Siberia and North America have been processed. Permafrost related or influencing landscape dynamics were detected within the trend analysis, including thermokarst lake dynamics, fires, thaw slumps, and coastal dynamics. The produced datasets will be distributed to the community as part of the ERC PETA-CARB and ESA GlobPermafrost projects. Users are encouraged to provide feedback and ground truth data for a continuous improvement of our methodology and datasets, which will lead to a better understanding of the spatial and temporal distribution of changes within the vulnerable permafrost zone.

Psychometric properties of a new questionnaire to assess eating in the absence of hunger in children and adolescents.

PubMed

Tanofsky-Kraff, Marian; Ranzenhofer, Lisa M; Yanovski, Susan Z; Schvey, Natasha A; Faith, Myles; Gustafson, Jennifer; Yanovski, Jack A

2008-07-01

Eating in the absence of hunger (EAH), studied in the context of laboratory paradigms, has been associated with obesity and is predictive of excess weight gain in children. However, no easily administered questionnaire exists to assess for EAH in children. We developed an Eating in the Absence of Hunger Questionnaire to be administered to children and adolescents (EAH-C) and examined psychometric properties of the measure. Two-hundred and twenty-six obese (BMI > or = 95th percentile for age and sex, n=73) and non-obese (BMI<95th percentile, n=153) youth (mean age+/-S.D., 14.4+/-2.5 y) completed the EAH-C and measures of loss of control and emotional eating, and general psychopathology. Temporal stability was assessed in a subset of participants. Factor analysis generated three subscales for the EAH-C: Negative Affect, External Eating, and Fatigue/Boredom. Internal consistency for all subscales was established (Cronbach's alphas: 0.80-0.88). The EAH-C subscales had good convergent validity with emotional eating and loss of control episodes (p's<0.01). Obese children reported higher Negative Affect subscale scores than non-obese children (p

Temporal Stability and the Effect of Transgenerational Transfer on Fecal Microbiota Structure in a Long Distance Migratory Bird

PubMed Central

Kreisinger, Jakub; Kropáčková, Lucie; Petrželková, Adéla; Adámková, Marie; Tomášek, Oldřich; Martin, Jean-François; Michálková, Romana; Albrecht, Tomáš

2017-01-01

Animal bodies are inhabited by a taxonomically and functionally diverse community of symbiotic and commensal microorganisms. From an ecological and evolutionary perspective, inter-individual variation in host-associated microbiota contributes to physiological and immune system variation. As such, host-associated microbiota may be considered an integral part of the host’s phenotype, serving as a substrate for natural selection. This assumes that host-associated microbiota exhibits high temporal stability, however, and that its composition is shaped by trans-generational transfer or heritable host-associated microbiota modulators encoded by the host genome. Although this concept is widely accepted, its crucial assumptions have rarely been tested in wild vertebrate populations. We performed 16S rRNA metabarcoding on an extensive set of fecal microbiota (FM) samples from an insectivorous, long-distance migratory bird, the barn swallow (Hirundo rustica). Our data revealed clear differences in FM among juveniles and adults as regards taxonomic and functional composition, diversity and co-occurrence network complexity. Multiple FM samples from the same juvenile or adult collected within single breeding seasons exhibited higher similarity than expected by chance, as did adult FM samples over two consecutive years. Despite low effect sizes for FM stability over time at the community level, we identified an adult FM subset with relative abundances exhibiting significant temporal consistency, possibly inducing long-term effects on the host phenotype. Our data also indicate a slight maternal (but not paternal) effect on FM composition in social offspring, though this is unlikely to persist into adulthood. We discuss our findings in the context of both evolution and ecology of microbiota vs. host interactions and barn swallow biology. PMID:28220109

Temporal Variability of Oral Microbiota over 10 Months and the Implications for Future Epidemiologic Studies.

PubMed

Vogtmann, Emily; Hua, Xing; Zhou, Liang; Wan, Yunhu; Suman, Shalabh; Zhu, Bin; Dagnall, Casey L; Hutchinson, Amy; Jones, Kristine; Hicks, Belynda D; Sinha, Rashmi; Shi, Jianxin; Abnet, Christian C

2018-05-01

Background: Few studies have prospectively evaluated the association between oral microbiota and health outcomes. Precise estimates of the intrasubject microbial metric stability will allow better study planning. Therefore, we conducted a study to evaluate the temporal variability of oral microbiota. Methods: Forty individuals provided six oral samples using the OMNIgene ORAL kit and Scope mouthwash oral rinses approximately every two months over 10 months. DNA was extracted using the QIAsymphony and the V4 region of the 16S rRNA gene was amplified and sequenced using the MiSeq. To estimate temporal variation, we calculated intraclass correlation coefficients (ICCs) for a variety of metrics and examined stability after clustering samples into distinct community types using Dirichlet multinomial models (DMMs). Results: The ICCs for the alpha diversity measures were high, including for number of observed bacterial species [0.74; 95% confidence interval (CI): 0.65-0.82 and 0.79; 95% CI: 0.75-0.94] from OMNIgene ORAL and Scope mouthwash, respectively. The ICCs for the relative abundance of the top four phyla and beta diversity matrices were lower. Three clusters provided the best model fit for the DMM from the OMNIgene ORAL samples, and the probability of remaining in a specific cluster was high (59.5%-80.7%). Conclusions: The oral microbiota appears to be stable over time for multiple metrics, but some measures, particularly relative abundance, were less stable. Impact: We used this information to calculate stability-adjusted power calculations that will inform future field study protocols and experimental analytic designs. Cancer Epidemiol Biomarkers Prev; 27(5); 594-600. ©2018 AACR . ©2018 American Association for Cancer Research.

Psychometric Properties of a New Questionnaire to Assess Eating in the Absence of Hunger in Children and Adolescents

PubMed Central

Tanofsky-Kraff, Marian; Ranzenhofer, Lisa M.; Yanovski, Susan Z.; Schvey, Natasha A.; Faith, Myles; Gustafson, Jennifer; Yanovski, Jack A.

2008-01-01

Background Eating in the absence of hunger (EAH), studied in the context of laboratory paradigms, has been associated with obesity and is predictive of excess weight gain in children. However, no easily administered questionnaire exists to assess for EAH in children. Objective We developed an Eating in the Absence of Hunger questionnaire to be administered to children and adolescents (EAH-C) and examined psychometric properties of the measure. Design Two-hundred-twenty-six obese (BMI ≥ 95th percentile for age and sex, n = 73) and non-obese (BMI <95th percentile, n = 153) youth (mean age ± SD, 14.4 ± 2.5y) completed the EAH-C and measures of loss of control and emotional eating, and general psychopathology. Temporal stability was assessed in a subset of participants. Results Factor analysis generated three subscales for the EAH-C: Negative Affect, External Eating, and Fatigue/Boredom. Internal consistency for all subscales was established (Cronbach's alphas: 0.80 to 0.88). The EAH-C subscales had good convergent validity with emotional eating and loss of control episodes (p's < 0.01). Obese children reported higher Negative Affect subscale scores than non-obese children (p ≤ 0.05). All three subscales were positively correlated with measures of general psychopathology. Intra-class correlation coefficients revealed temporal stability for all subscales (ranging from 0.65 to 0.70, p's < 0.01). We conclude that the EAH-C had internally consistent subscales with good convergent validity and temporal stability, but may have limited discriminant validity. Further investigations examining the EAH-C in relation to laboratory feeding studies are required to determine whether reported EAH is related to actual energy intake or to the development of excess weight gain. PMID:18342988

The relation between circadian asynchrony, functional redundancy, and trophic performance in tropical ant communities.

PubMed

Houadria, Mickal; Blüthgen, Nico; Salas-Lopez, Alex; Schmitt, Mona-Isabel; Arndt, Johanna; Schneider, Eric; Orivel, Jérôme; Menzel, Florian

2016-01-01

The diversity-stability relationship has been under intense scrutiny for the past decades, and temporal asynchrony is recognized as an important aspect of ecosystem stability. In contrast to relatively well-studied interannual and seasonal asynchrony, few studies investigate the role of circadian cycles for ecosystem stability. Here, we studied multifunctional redundancy of diurnal and nocturnal ant communities in four tropical rain forest sites. We analyzed how it was influenced by species richness, functional performance, and circadian asynchrony. In two neotropical sites, species richness and functional redundancy were lower at night. In contrast, these parameters did not differ in the two paleotropical sites we studied. Circadian asynchrony between species was pronounced in the neotropical sites, and increased circadian functional redundancy. In general, species richness positively affected functional redundancy, but the effect size depended on the temporal and spatial breadth of the species with highest functional performance. Our analysis shows that high levels of trophic performance were only reached through the presence of such high-performing species, but not by even contributions of multiple, less-efficient species. Thus, these species can increase current functional performance, but reduce overall functional redundancy. Our study highlights that diurnal and nocturnal ecosystem properties of the very same habitat can markedly differ in terms of species richness and functional redundancy. Consequently, like the need to study multiple ecosystem functions, multiple periods of the circadian cycle need to be assessed in order to fully understand the diversity-stability relationship in an ecosystem.

Goal orientations, motivational climate, and prosocial and antisocial behaviour in youth football: exploring their temporal stability and reciprocal relationships.

PubMed

Sage, Luke D; Kavussanu, Maria

2008-05-01

In this study, we examined the temporal stability and reciprocal relationships among task and ego orientation, task- and ego-involving climates, and prosocial and antisocial behaviour in youth football. Male (n = 156) and female (n = 24) footballers (mean age 14.1 years, s = 1.8) completed questionnaires towards the beginning and end of a regular season. Questionnaires measured goal orientation, perceived motivational climate, and frequency of prosocial and antisocial behaviours. Structural equation modelling indicated moderate covariance stability between the beginning and end of the season. Subsequent analyses revealed a significant decrease only in perceptions of task-involving climate. In the cross-lagged analyses, prosocial behaviour at the beginning of the season positively predicted task-involving climate at the end of the season. Antisocial behaviour at the beginning of the season positively predicted both ego orientation and ego-involving climate at the end of the season and a reciprocal relationship was revealed whereby ego orientation at the beginning of the season positively predicted antisocial behaviour at the end of the season. Task orientation at the beginning of the season negatively predicted ego-involving climate at the end of the season. All cross-lagged relationships were weak. This exploratory study offers limited support for bi-directional relationships between personal, environmental, and behavioural variables but provides useful insight into the covariance stability, change, and interrelationships between motivational and moral constructs over a competitive season.

Figure–ground discrimination behavior in Drosophila. I. Spatial organization of wing-steering responses

PubMed Central

Fox, Jessica L.; Aptekar, Jacob W.; Zolotova, Nadezhda M.; Shoemaker, Patrick A.; Frye, Mark A.

2014-01-01

The behavioral algorithms and neural subsystems for visual figure–ground discrimination are not sufficiently described in any model system. The fly visual system shares structural and functional similarity with that of vertebrates and, like vertebrates, flies robustly track visual figures in the face of ground motion. This computation is crucial for animals that pursue salient objects under the high performance requirements imposed by flight behavior. Flies smoothly track small objects and use wide-field optic flow to maintain flight-stabilizing optomotor reflexes. The spatial and temporal properties of visual figure tracking and wide-field stabilization have been characterized in flies, but how the two systems interact spatially to allow flies to actively track figures against a moving ground has not. We took a systems identification approach in flying Drosophila and measured wing-steering responses to velocity impulses of figure and ground motion independently. We constructed a spatiotemporal action field (STAF) – the behavioral analog of a spatiotemporal receptive field – revealing how the behavioral impulse responses to figure tracking and concurrent ground stabilization vary for figure motion centered at each location across the visual azimuth. The figure tracking and ground stabilization STAFs show distinct spatial tuning and temporal dynamics, confirming the independence of the two systems. When the figure tracking system is activated by a narrow vertical bar moving within the frontal field of view, ground motion is essentially ignored despite comprising over 90% of the total visual input. PMID:24198267

Dose-response characteristics of an amorphous silicon EPID.

PubMed

Winkler, Peter; Hefner, Alfred; Georg, Dietmar

2005-10-01

Electronic portal imaging devices (EPIDs) were originally developed for the purpose of patient setup verification. Nowadays, they are increasingly used as dosimeters (e.g., for IMRT verification and linac-specific QA). A prerequisite for any clinical dosimetric application is a detailed understanding of the detector's dose-response behavior. The aim of this study is to investigate the dosimetric properties of an amorphous silicon EPID (Elekta IVIEWGT) with respect to three photon beam qualities: 6, 10, and 25 MV. The EPID showed an excellent temporal stability on short term as well as on long term scales. The stability throughout the day was strongly influenced by warming up, which took several hours and affected EPID response by 2.5%. Ghosting effects increased the sensitivity of the EPID. They became more pronounced with decreasing time intervals between two exposures as well as with increasing dose. Due to ghosting, changes in pixel sensitivity amounted up to 16% (locally) for the 25 MV photon beam. It was observed that the response characteristics of our EPID depended on dose as well as on dose rate. Doubling the dose rate increased the EPID sensitivity by 1.5%. This behavior was successfully attributed to a dose per frame effect, i.e., a nonlinear relationship between the EPID signal and the dose which was delivered to the panel between two successive readouts. The sensitivity was found to vary up to 10% in the range of 1 to 1000 monitor units. This variation was governed by two independent effects. For low doses, the EPID signal was reduced due to the linac's changing dose rate during startup. Furthermore, the detector reading was influenced by intrabeam variations of EPID sensitivity, namely, an increase of detector response during uniform exposure. For the beam qualities which were used, the response characteristics of the EPID did not depend on energy. Differences in relative dose-response curves resulted from energy dependent temporal output characteristics of the accelerator. If ghosting is prevented from affecting the results and all dose-response effects are properly corrected for, the EPID signal becomes independent of dose rate, dose, and exposure time.

Towards Adaptive Educational Assessments: Predicting Student Performance using Temporal Stability and Data Analytics in Learning Management Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thakur, Gautam; Olama, Mohammed M; McNair, Wade

Data-driven assessments and adaptive feedback are becoming a cornerstone research in educational data analytics and involve developing methods for exploring the unique types of data that come from the educational context. For example, predicting college student performance is crucial for both the students and educational institutions. It can support timely intervention to prevent students from failing a course, increasing efficacy of advising functions, and improving course completion rate. In this paper, we present our efforts in using data analytics that enable educationists to design novel data-driven assessment and feedback mechanisms. In order to achieve this objective, we investigate temporal stabilitymore » of students grades and perform predictive analytics on academic data collected from 2009 through 2013 in one of the most commonly used learning management systems, called Moodle. First, we have identified the data features useful for assessments and predicting student outcomes such as students scores in homework assignments, quizzes, exams, in addition to their activities in discussion forums and their total Grade Point Average(GPA) at the same term they enrolled in the course. Second, time series models in both frequency and time domains are applied to characterize the progression as well as overall projections of the grades. In particular, the model analyzed the stability as well as fluctuation of grades among students during the collegiate years (from freshman to senior) and disciplines. Third, Logistic Regression and Neural Network predictive models are used to identify students as early as possible who are in danger of failing the course they are currently enrolled in. These models compute the likelihood of any given student failing (or passing) the current course. The time series analysis indicates that assessments and continuous feedback are critical for freshman and sophomores (even with easy courses) than for seniors, and those assessments may be provided using the predictive models. Numerical results are presented to evaluate and compare the performance of the developed models and their predictive accuracy. Our results show that there are strong ties associated with the first few weeks for coursework and they have an impact on the design and distribution of individual modules.« less

On confidence and consequence: the certainty and importance of self-knowledge.

PubMed

Pelham, B W

1991-04-01

Belief certainty and belief importance represent 2 relatively independent forms of investment in the self-concept. Three studies suggested that whereas certainty is associated with epistemic (i.e., rational or informational) factors, importance is more closely associated with emotive (i.e., emotional and motivational) factors. A 4th study explored the implications of certainty and importance for the temporal stability of people's self-views and revealed that whereas belief certainty was associated with the stability of both positive and negative beliefs, belief importance was associated with the stability of positive beliefs only. The implications of belief investment for the verification-enhancement debate and for the structure and measurement of the self-concept are discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanz, J.; Betti, R.

A sharp boundary model for the deceleration phase of imploding capsules in inertial confinement fusion, in both direct and indirect drive, has been developed. The model includes heat conduction, local {alpha}-particle energy deposition, and shell compressibility effects. A differential equation for the temporal evolution of the modal amplitude interface is obtained. It is found that the {alpha}-particle energy has a strong influence on the evolution of the low l modes, via the compressibility of the shell. The modes are damped by vorticity convection, fire polishing, and {alpha}-particle energy deposition. The existence of a cutoff l number arises from the highmore » blow of velocity into the hot region (rocket effect) if density gradient scale length effects are taken into account at the interface. The differential equation for the modal amplitude is used as a postprocessor to the results of 1D-SARA code [J. J. Honrubia, J. Quant. Spectrosc. Radiat. Transfer. 49, 491 (1993)] in a typical capsule for indirect-drive ignition designed on the National Ignition Facility. It is found that modes with l>180 are completely stabilized. The results are in agreement with two-dimensional simulations.« less

The Italian version of the Depression Anxiety Stress Scales-21: Factor structure and psychometric properties on community and clinical samples.

PubMed

Bottesi, Gioia; Ghisi, Marta; Altoè, Gianmarco; Conforti, Erica; Melli, Gabriele; Sica, Claudio

2015-07-01

The Depression Anxiety Stress Scales-21 (DASS-21) is the short version of a self-report measure that was originally developed to provide maximum differentiation between depressive and anxious symptoms. Despite encouraging evidence, the factor structure and other features of the DASS-21 are yet to be firmly established. A community sample of 417 participants and two clinical groups (32 depressive patients and 25 anxious patients) completed the Italian version of the DASS-21 along with several measures of psychopathology. Confirmatory factor analyses suggested that the DASS-21 is a measure of general distress plus three additional orthogonal dimensions (anxiety, depression, and stress). The internal consistency and temporal stability of the measure were good; each DASS-21 scale correlated more strongly with a measure of a similar construct, demonstrating good convergent and divergent validity. Lastly, the DASS-21 demonstrated good criterion-oriented validity. The validity of the Italian DASS-21 and its utility, both for community and clinical individuals, are supported. Copyright © 2015 Elsevier Inc. All rights reserved.

Six centuries of May-July precipitation in Cyprus from tree rings

NASA Astrophysics Data System (ADS)

Touchan, Ramzi; Christou, Andreas K.; Meko, David M.

2014-12-01

A May-July precipitation nested reconstruction for the period AD 1415-2010 was developed from multi-century tree-ring records of Pinus nigra, Pinus brutia, and Cedrus brevifolia for Cyprus. Calibration and verification statistics for the period 1917-2010 show a good level of skill, and split-sample validation over 1917-2010 supports temporal stability of the tree-ring signal for precipitation. Smoothed annual time series of reconstructed precipitation and a tally of drought events in a moving time window indicate that the calibration period is not representative of the full range of drought variability. While convective precipitation in the warm season may be driven strongly by local factors, composite maps of geopotential height anomaly for dry years and wet years support large-scale atmospheric-flow influence related to height anomalies over the broader region of northeast Africa and the eastern Mediterranean. Emerging positive trend in reconstruction residuals may be an early sign of exacerbation of drought stress on trees by recent warming in May-July. Future warming expected from increases in greenhouse gases poses a threat to forest resources in Cyprus and elsewhere in the Mediterranean.

Spray formation processes of impinging jet injectors

NASA Technical Reports Server (NTRS)

Anderson, W. E.; Ryan, H. M.; Pal, S.; Santoro, R. J.

1993-01-01

A study examining impinging liquid jets has been underway to determine physical mechanisms responsible for combustion instabilities in liquid bi-propellant rocket engines. Primary atomization has been identified as an important process. Measurements of atomization length, wave structure, and drop size and velocity distribution were made under various ambient conditions. Test parameters included geometric effects and flow effects. It was observed that pre-impingement jet conditions, specifically whether they were laminar or turbulent, had the major effect on primary atomization. Comparison of the measurements with results from a two dimensional linear aerodynamic stability model of a thinning, viscous sheet were made. Measured turbulent impinging jet characteristics were contrary to model predictions; the structure of waves generated near the point of jet impingement were dependent primarily on jet diameter and independent of jet velocity. It has been postulated that these impact waves are related to pressure and momentum fluctuations near the impingement region and control the eventual disintegration of the liquid sheet into ligaments. Examination of the temporal characteristics of primary atomization (ligament shedding frequency) strongly suggests that the periodic nature of primary atomization is a key process in combustion instability.

Computed tomographic analysis of temporal maxillary stability and pterygomaxillary generate formation following pediatric Le Fort III distraction advancement.

PubMed

Hopper, Richard A; Sandercoe, Gavin; Woo, Albert; Watts, Robyn; Kelley, Patrick; Ettinger, Russell E; Saltzman, Babette

2010-11-01

Le Fort III distraction requires generation of bone in the pterygomaxillary region. The authors performed retrospective digital analysis on temporal fine-cut computed tomographic images to quantify both radiographic evidence of pterygomaxillary region bone formation and relative maxillary stability. Fifteen patients with syndromic midface hypoplasia were included in the study. The average age of the patients was 8.7 years; 11 had either Crouzon or Apert syndrome. The average displacement of the maxilla during distraction was 16.2 mm (range, 7 to 31 mm). Digital analysis was performed on fine-cut computed tomographic scans before surgery, at device removal, and at annual follow-up. Seven patients also had mid-consolidation computed tomographic scans. Relative maxillary stability and density of radiographic bone in the pterygomaxillary region were calculated between each scan. There was no evidence of clinically significant maxillary relapse, rotation, or growth between the end of consolidation and 1-year follow-up, other than a relatively small 2-mm subnasal maxillary vertical growth. There was an average radiographic ossification of 0.5 mm/mm advancement at the time of device removal, with a 25th percentile value of 0.3 mm/mm. The time during consolidation that each patient reached the 25th percentile of pterygomaxillary region bone density observed in this series of clinically stable advancements ranged from 1.3 to 9.8 weeks (average, 3.7 weeks). There was high variability in the amount of bone formed in the pterygomaxillary region associated with clinical stability of the advanced Le Fort III segment. These data suggest that a subsection of patients generate the minimal amount of pterygomaxillary region bone formation associated with advancement stability as early as 4 weeks into consolidation.

Hydration Repulsion between Carbohydrate Surfaces Mediated by Temperature and Specific Ions

PubMed Central

Chen, Hsieh; Cox, Jason R.; Ow, Hooisweng; Shi, Rena; Panagiotopoulos, Athanassios Z.

2016-01-01

Stabilizing colloids or nanoparticles in solution involves a fine balance between surface charges, steric repulsion of coating molecules, and hydration forces against van der Waals attractions. At high temperature and electrolyte concentrations, the colloidal stability of suspensions usually decreases rapidly. Here, we report a new experimental and simulation discovery that the polysaccharide (dextran) coated nanoparticles show ion-specific colloidal stability at high temperature, where we observed enhanced colloidal stability of nanoparticles in CaCl2 solution but rapid nanoparticle-nanoparticle aggregation in MgCl2 solution. The microscopic mechanism was unveiled in atomistic simulations. The presence of surface bound Ca2+ ions increases the carbohydrate hydration and induces strongly polarized repulsive water structures beyond at least three hydration shells which is farther-reaching than previously assumed. We believe leveraging the binding of strongly hydrated ions to macromolecular surfaces represents a new paradigm in achieving absolute hydration and colloidal stability for a variety of materials, particularly under extreme conditions. PMID:27334145

Convergence and stability of the exponential Euler method for semi-linear stochastic delay differential equations.

PubMed

Zhang, Ling

2017-01-01

The main purpose of this paper is to investigate the strong convergence and exponential stability in mean square of the exponential Euler method to semi-linear stochastic delay differential equations (SLSDDEs). It is proved that the exponential Euler approximation solution converges to the analytic solution with the strong order [Formula: see text] to SLSDDEs. On the one hand, the classical stability theorem to SLSDDEs is given by the Lyapunov functions. However, in this paper we study the exponential stability in mean square of the exact solution to SLSDDEs by using the definition of logarithmic norm. On the other hand, the implicit Euler scheme to SLSDDEs is known to be exponentially stable in mean square for any step size. However, in this article we propose an explicit method to show that the exponential Euler method to SLSDDEs is proved to share the same stability for any step size by the property of logarithmic norm.

Hydration Repulsion between Carbohydrate Surfaces Mediated by Temperature and Specific Ions

NASA Astrophysics Data System (ADS)

Chen, Hsieh; Cox, Jason R.; Ow, Hooisweng; Shi, Rena; Panagiotopoulos, Athanassios Z.

2016-06-01

Stabilizing colloids or nanoparticles in solution involves a fine balance between surface charges, steric repulsion of coating molecules, and hydration forces against van der Waals attractions. At high temperature and electrolyte concentrations, the colloidal stability of suspensions usually decreases rapidly. Here, we report a new experimental and simulation discovery that the polysaccharide (dextran) coated nanoparticles show ion-specific colloidal stability at high temperature, where we observed enhanced colloidal stability of nanoparticles in CaCl2 solution but rapid nanoparticle-nanoparticle aggregation in MgCl2 solution. The microscopic mechanism was unveiled in atomistic simulations. The presence of surface bound Ca2+ ions increases the carbohydrate hydration and induces strongly polarized repulsive water structures beyond at least three hydration shells which is farther-reaching than previously assumed. We believe leveraging the binding of strongly hydrated ions to macromolecular surfaces represents a new paradigm in achieving absolute hydration and colloidal stability for a variety of materials, particularly under extreme conditions.

Long-Term IQ Stability Using the WISC-IV and WAIS-IV among a Sample of Special Education Students

ERIC Educational Resources Information Center

Spector, Hayley

2013-01-01

The present study investigated the stability of scores on the WISC-IV and WAIS-IV over an approximate six-year period. Previous research using older versions of the WISC and WAIS have suggested that these scales demonstrate strong stability of scores. Since research that has compared the stability of scores between the WISC-IV and the WAIS-IV is…

Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices.

PubMed

Li, Zhe; Ho Chiu, Kar; Shahid Ashraf, Raja; Fearn, Sarah; Dattani, Rajeev; Cheng Wong, Him; Tan, Ching-Hong; Wu, Jiaying; Cabral, João T; Durrant, James R

2015-10-15

Morphological stability is a key requirement for outdoor operation of organic solar cells. We demonstrate that morphological stability and lifetime of polymer/fullerene based solar cells under thermal stress depend strongly on the substrate interface on which the active layer is deposited. In particular, we find that the stability of benchmark PCDTBT/PCBM solar cells under modest thermal stress is substantially increased in inverted solar cells employing a ZnO substrate compared to conventional devices employing a PSS substrate. This improved stability is observed to correlate with PCBM nucleation at the 50 nm scale, which is shown to be strongly influenced by different substrate interfaces. Employing this approach, we demonstrate remarkable thermal stability for inverted PCDTBT:PC70BM devices on ZnO substrates, with negligible (<2%) loss of power conversion efficiency over 160 h under 85 °C thermal stress and minimal thermally induced "burn-in" effect. We thus conclude that inverted organic solar cells, in addition to showing improved environmental stability against ambient humidity exposure as widely reported previously, can also demonstrate enhanced morphological stability. As such we show that the choice of suitable substrate interfaces may be a key factor in achieving prolonged lifetimes for organic solar cells under thermal stress conditions.

Flower diversity and bee reproduction in an arid ecosystem

PubMed Central

Vázquez, Diego P.

2016-01-01

Background: Diverse flower communities are more stable in floral resource production along the flowering season, but the question about how the diversity and stability of resources affect pollinator reproduction remains open. High plant diversity could favor short foraging trips, which in turn would enhance bee fitness. In addition to plant diversity, greater temporal stability of floral resources in diverse communities could favor pollinator fitness because such communities are likely to occupy the phenological space more broadly, increasing floral availability for pollinators throughout the season. In addition, this potential effect of flower diversity on bee reproduction could be stronger for generalist pollinators because they can use a broader floral spectrum. Based on above arguments we predicted that pollinator reproduction would be positively correlated to flower diversity, and to temporal stability in flower production, and that this relationship would be stronger for the most generalized pollinator species. Materials and Methods: Using structural equation models, we evaluated the effect of these variables and other ecological factors on three estimates of bee reproduction (average number of brood cells per nest per site, total number of brood cells per site, and total number of nests per site), and whether such effects were modulated by bee generalization on floral resources. Results: Contrary to our expectations, flower diversity had no effect on bee reproduction, stability in flower production had a weakly negative effect on one of the bee reproductive variables, and the strength of the fitness-diversity relationship was unrelated to bee generalization. In contrast, elevation had a negative effect on bee reproduction, despite the narrow elevation range encompassed by our sites. Discussion: Flower diversity did not affect the reproduction of the solitary bees studied here. This result could stem from the context dependence of the diversity-stability relationship, given that elevation had a positive effect on flower diversity but a negative effect on bee reproduction. Although high temporal stability in flower production is expected to enhance pollinator reproduction, in our study it had a weakly negative—instead of positive—effect on the average number of brood cells per nest. Other environmental factors that vary with elevation could influence bee reproduction. Our study focused on a small group of closely-related bee species, which cautions against generalization of our findings to other groups of pollinators. More studies are clearly needed to assess the extent to which pollinator demography is influenced by the diversity of floral resources. PMID:27547556

Stability measures in arid ecosystems

NASA Astrophysics Data System (ADS)

Nosshi, M. I.; Brunsell, N. A.; Koerner, S.

2015-12-01

Stability, the capacity of ecosystems to persist in the face of change, has proven its relevance as a fundamental component of ecological theory. Here, we would like to explore meaningful and quantifiable metrics to define stability, with a focus on highly variable arid and semi-arid savanna ecosystems. Recognizing the importance of a characteristic timescale to any definition of stability, our metrics will be focused scales from annual to multi-annual, capturing different aspects of stability. Our three measures of stability, in increasing order of temporal scale, are: (1) Ecosystem resistance, quantified as the degree to which the system maintains its mean state in response to a perturbation (drought), based on inter-annual variability in Normalized Difference Vegetation Index (NDVI). (2) An optimization approach, relevant to arid systems with pulse dynamics, that models vegetation structure and function based on a trade off between the ability to respond to resource availability and avoid stress. (3) Community resilience, measured as species turnover rate (β diversity). Understanding the nature of stability in structurally-diverse arid ecosystems, which are highly variable, yields theoretical insight which has practical implications.

Transport and deposition of carbon at catchment scale: stabilization mechanisms approach

NASA Astrophysics Data System (ADS)

Martínez-Mena, María; Almagro, María; Díaz-Pereira, Elvira; García-Franco, Noelia; Boix-Fayos, Carolina

2016-04-01

Terrestrial sedimentation buries large amounts of organic carbon (OC) annually, contributing to the terrestrial carbon sink. The temporal significance of this sink will strongly depend on the attributes of the depositional environment, but also on the characteristics of the OC reaching these sites and its stability upon deposition. The fate of the redistributed OC will ultimately depend on the mechanisms of its physical and chemical protection against decomposition, its turnover rates and the conditions under which the OC is stored in sedimentary settings. This framework is more complex in Mediterranean river basins where sediments are often redistributed under a range of environmental conditions in ephemeral, intermittent and perennial fluvial courses, sometimes within the same catchment. The OC stabilization mechanisms and their relations with aggregation at different transport and sedimentary deposits is under those conditions highly uncertain. The main objective of this work was to characterize the stabilization and mineralization of OC in sediments in transit (suspended load), at a range of depositional settings (alluvial bars, reservoir sediments) and soils from the source areas in a sub-catchment (111 km2) at the headwaters of the Segura catchment in South East Spain. In order to obtain a deeper knowledge on the predominant stabilization mechanism corresponding to each erosional phase, the following organic carbon fractionation method was carried out: Four aggregate size classes were distinguished by sieving (large and small macroaggregates, free microaggregates, and free silt plus clay fraction), and the microaggregates occluded within macroaggregates (SMm) were isolated. As a further step, an oxidation of the OC occluded in silt plus clay fraction and that of the free silt plus clay fraction was performed to estimate the oxidant resistant OC pool. Measured OC in these fractions can be related to three functional pools: active (free particulate organic matter), slow (carbon associated to clay and silt or stabilized in aggregates) and passive (oxidation-resistant OC). In addition, the potential mineralized C (incubation method) in each deposit and soil was determined. Preliminary results indicate a higher OC content in the suspended sediments in transit and in the reservoir deposited sediments than in the alluvial bars, being in all sediments the total OC content lower than in the source soils. Slow and passive pools prevailed in suspended sediments and in reservoir sediments compared to alluvial bars, indicating different OC stabilization mechanisms. In addition, in the alluvial bars, mineralization rates were higher in bars located in channels with ephemeral flow conditions and vegetated areas than in bars located in channels with perennial flow conditions.

Psychometric Evaluation of the Chinese Virtues Questionnaire

ERIC Educational Resources Information Center

Duan, Wenjie; Ho, Samuel M. Y.; Bai, Yu; Tang, Xiaoqing

2013-01-01

Objectives: The present study examined the psychometric properties of the Chinese Virtues Questionnaire (CVQ). The reliability, factor structure, construct validity, and temporal stability of the inventory were examined. Method: A university student sample ("n" = 878) and a working adult sample ("n" = 153) were recruited.…

Ct Anatomy of Buccal Fat Pad and its Role in Volumetric Alterations of Face

NASA Astrophysics Data System (ADS)

Guryanov, R. A.; Guryanov, A. S.

2015-05-01

The aim of our study is the revision of the anatomy of buccal fat pad and its role in a volumetric pattern of face. Bichat fat pad is a fatty anatomical structure with body and numerous process enclosed between the bony and muscular structures in temporal, pterygopalatine fossae and extents to the cheek area. Nevertheless, the opinion about its structure and role in forming of volume pattern of face sometimes could be controversial. The Bichat fat pad consists on predominately hormone insensitive fat tissue with underdeveloped stroma, this leads to the stability of the fat pad volume and lesser radiodensity in contrast to the subcutaneous fat. Moreover, the buccal fat pad is delimited from the subcutaneous fat of cheek area by the strong capsule. This feature allows us to use CT to divide the Bichat fat pad from the surrounding tissues. The thorough embryological data provide the distinction of Bichat fat pad from the subcutaneous fat of cheek area even at the stage of development. On the other hand, the border between the masticatory muscles and the processes of the fat pad is not evident and resembles cellular spaces in the other anatomical areas. To elicit the role of the buccal fat pad in volume pattern of face and its function we have performed the several experiments, analyzed the postoperative results after Bichat fat pad resection using surface scanner and CT data. At first, we have performed the gravity test: the patient's face photogrammetry scanning in horizontal and vertical position of head and it revealed the excess of volume in temporal area in horizontal position. To exclude mechanism of overflowing of the skin and subcutaneous fat over the zygomatic arch we have placed the markers on the skin surface at the different areas of face including the projection of ligaments and found out that the migration of soft tissue over the zygomatic arch is about 3-5 mm and almost the same in temporal area. However, the acquired result was unsatisfying because cannot exclude completely the migration of superficial tissues. In following experiments it was shown that the intensive pressure on the cheek area in vertical position produce the volume excess in the temporal area similar and more exaggerate than in gravity test. To correlate the excess of tissue with underlying anatomical structures we had acquired the CT's of some probationers, performed 3D reconstruction of bony structures, Bichat fat pad, and aligned with the previous surface scans. The projection of this excess in both experiments corresponds with the temporal process of Bichat fat pad. That means that the leading mechanism of these changes is protrusion of temporal process of Bichat fat pad through the leaves of temporal fascia due to pressure on the buccal extension: in these conditions, the buccal fat pad works as a communicating vessel between the cheek area and temporal fossa. This fact has suggested us that the phenomenon of the deepening of temporal area during the ageing could be produced as by the atrophy of buccal fat pad as by the migration of the fat pad to the cheek area due to ptosis.

Dynamic strain aging and plastic instabilities

NASA Astrophysics Data System (ADS)

Mesarovic, Sinisa Dj.

1995-05-01

A constitutive model proposed by McCormick [(1988) Theory of flow localization due to dynamic strain ageing. Acta. Metall.36, 3061-3067] based on dislocation-solute interaction and describing dynamic strain aging behavior, is analyzed for the simple loading case of uniaxial tension. The model is rate dependent and includes a time-varying state variable, representing the local concentration of the impurity atoms at dislocations. Stability of the system and its post-instability behavior are considered. The methods used include analytical and numerical stability and bifurcation analysis with a numerical continuation technique. Yield point behavior and serrated yielding are found to result for well defined intervals of temperature and strain rate. Serrated yielding emerges as a branch of periodic solutions of the relaxation oscillation type, similar to frictional stick-slip. The distinction between the temporal and spatial (loss of homogeneity of strain) instability is emphasized. It is found that a critical machine stiffness exists above which a purely temporal instability cannot occur. The results are compared to the available experimental data.

Development of a self-report questionnaire designed for population-based surveillance of gingivitis in adolescents: assessment of content validity and reliability.

PubMed

Quiroz, Viviana; Reinero, Daniela; Hernández, Patricia; Contreras, Johanna; Vernal, Rolando; Carvajal, Paola

2017-01-01

This study aimed to develop and assess the content validity and reliability of a cognitively adapted self-report questionnaire designed for surveillance of gingivitis in adolescents. Ten predetermined self-report questions evaluating early signs and symptoms of gingivitis were preliminary assessed by a panel of clinical experts. Eight questions were selected and cognitively tested in 20 adolescents aged 12 to 18 years from Santiago de Chile. The questionnaire was then conducted and answered by 178 Chilean adolescents. Internal consistency was measured using the Cronbach's alpha and temporal stability was calculated using the Kappa-index. A reliable final self-report questionnaire consisting of 5 questions was obtained, with a total Cronbach's alpha of 0.73 and a Kappa-index ranging from 0.41 to 0.77 between the different questions. The proposed questionnaire is reliable, with an acceptable internal consistency and a temporal stability from moderate to substantial, and it is promising for estimating the prevalence of gingivitis in adolescents.

[Validity and reliability of a scale to assess self-efficacy for physical activity in elderly].

PubMed

Borges, Rossana Arruda; Rech, Cassiano Ricardo; Meurer, Simone Teresinha; Benedetti, Tânia Rosane Bertoldo

2015-04-01

This study aimed to analyze the confirmatory factor validity and reliability of a self-efficacy scale for physical activity in a sample of 118 elderly (78% women) from 60 to 90 years of age. Mplus 6.1 was used to evaluate the confirmatory factor analysis. Reliability was tested by internal consistency and temporal stability. The original scale consisted of five items with dichotomous answers (yes/no), independently for walking and moderate and vigorous physical activity. The analysis excluded the item related to confidence in performing physical activities when on vacation. Two constructs were identified, called "self-efficacy for walking" and "self-efficacy for moderate and vigorous physical activity", with a factor load ≥ 0.50. Internal consistency was adequate both for walking (> 0.70) and moderate and vigorous physical activity (> 0.80), and temporal stability was adequate for all the items. In conclusion, the self-efficacy scale for physical activity showed adequate validity, reliability, and internal consistency for evaluating this construct in elderly Brazilians.

Temporal variability of bacterial communities in cryoconite on an alpine glacier.

PubMed

Franzetti, Andrea; Navarra, Federico; Tagliaferri, Ilario; Gandolfi, Isabella; Bestetti, Giuseppina; Minora, Umberto; Azzoni, Roberto Sergio; Diolaiuti, Guglielmina; Smiraglia, Claudio; Ambrosini, Roberto

2017-04-01

Cryoconite holes, that is, small ponds that form on glacier surface, are considered the most biologically active environments on glaciers. Bacterial communities in these environments have been extensively studied, but often through snapshot studies based on the assumption of a general stability of community structure. In this study, the temporal variation of bacterial communities in cryoconite holes on the Forni Glacier (Italian Alps) was investigated by high throughput DNA sequencing. A temporal change of bacterial communities was observed with autotrophic Cyanobacteria populations dominating communities after snowmelt, and heterotrophic Sphingobacteriales populations increasing in abundance later in the season. Bacterial communities also varied according to hole depth and area, amount of organic matter in the cryoconite and oxygen concentration. However, variation in environmental features explained a lower fraction of the variation in bacterial communities than temporal variation. Temporal change along ablation season seems therefore more important than local environmental conditions in shaping bacterial communities of cryoconite of the Forni Glacier. These findings challenge the assumption that bacterial communities of cryoconite holes are stable. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Assessment of microscale spatio-temporal variation of air pollution at an urban hotspot in Madrid (Spain) through an extensive field campaign

NASA Astrophysics Data System (ADS)

Borge, Rafael; Narros, Adolfo; Artíñano, Begoña; Yagüe, Carlos; Gómez-Moreno, Francisco Javier; de la Paz, David; Román-Cascón, Carlos; Díaz, Elías; Maqueda, Gregorio; Sastre, Mariano; Quaassdorff, Christina; Dimitroulopoulou, Chrysanthi; Vardoulakis, Sotiris

2016-09-01

Poor urban air quality is one of the main environmental concerns worldwide due to its implications for population exposure and health-related issues. However, the development of effective abatement strategies in cities requires a consistent and holistic assessment of air pollution processes, taking into account all the relevant scales within a city. This contribution presents the methodology and main results of an intensive experimental campaign carried out in a complex pollution hotspot in Madrid (Spain) under the TECNAIRE-CM research project, which aimed at understanding the microscale spatio-temporal variation of ambient concentration levels in areas where high pollution values are recorded. A variety of instruments were deployed during a three-week field campaign to provide detailed information on meteorological and micrometeorological parameters and spatio-temporal variations of the most relevant pollutants (NO2 and PM) along with relevant information needed to simulate pedestrian fluxes. The results show the strong dependence of ambient concentrations on local emissions and meteorology that turns out in strong spatial and temporal variations, with gradients up to 2 μg m-3 m-1 for NO2 and 55 μg m-3 min-1 for PM10. Pedestrian exposure to these pollutants also presents strong variations temporally and spatially but it concentrates on pedestrian crossings and bus stops. The analysis of the results show that the high concentration levels found in urban hotspots depend on extremely complex dynamic processes that cannot be captured by routinely measurements made by air quality monitoring stations used for regulatory compliance assessment. The large influence from local traffic in the concentration fields highlights the need for a detailed description of specific variables that determine emissions and dispersion at microscale level. This also indicates that city-scale interventions may be complemented with local control measures and exposure management, to improve air quality and reduce air pollution health effects more effectively.

Learning State Space Dynamics in Recurrent Networks

NASA Astrophysics Data System (ADS)

Simard, Patrice Yvon

Fully recurrent (asymmetrical) networks can be used to learn temporal trajectories. The network is unfolded in time, and backpropagation is used to train the weights. The presence of recurrent connections creates internal states in the system which vary as a function of time. The resulting dynamics can provide interesting additional computing power but learning is made more difficult by the existence of internal memories. This study first exhibits the properties of recurrent networks in terms of convergence when the internal states of the system are unknown. A new energy functional is provided to change the weights of the units in order to the control the stability of the fixed points of the network's dynamics. The power of the resultant algorithm is illustrated with the simulation of a content addressable memory. Next, the more general case of time trajectories on a recurrent network is studied. An application is proposed in which trajectories are generated to draw letters as a function of an input. In another application of recurrent systems, a neural network certain temporal properties observed in human callosally sectioned brains. Finally the proposed algorithm for stabilizing dynamics around fixed points is extended to one for stabilizing dynamics around time trajectories. Its effects are illustrated on a network which generates Lisajous curves.

The role of oxygen in the photostimulation luminescence process of europium doped potassium chloride

PubMed Central

Xiao, Zhiyan; Mazur, Thomas R.; Driewer, Joseph P.; Li, H. Harold

2015-01-01

A recent suggestion that europium doped potassium chloride (KCl:Eu2+) has the potential to significantly advance the state-of-the-art in radiation therapy dosimetry has generated a renewed interest in a classic storage phosphor material. The purposes of this work are to investigate the role of oxygen in the photostimulation luminescence (PSL) process and to determine if both increased PSL yield and improved temporal stability could be realized in KCl:Eu2+ by incorporating oxygen in the material fabrication process. Regardless of synthesis atmosphere, air or pure nitrogen, PSL amplitude shows a maximum at 1.0 mol % Eu. Depending on europium concentration, dosimeters fabricated in air exhibit stronger PSL by a factor of 2 to 4 compared to those made in N2. There is no change in PSL stimulation spectrum while noticeable shifts in both photoluminescence and PSL emission spectra are observed for air versus nitrogen. Almost all charge-storage centers are spatially correlated, suggesting oxygen’s stabilization role in the PSL process. However, oxygen alone does not improve material’s temporal stability in the first few hours post irradiation at room temperature, probably because a significant portion of radiation-induced holes are stored in the Vk centers which are mobile. PMID:25897274

Temporal and voltage stress stability of high performance indium-zinc-oxide thin film transistors

NASA Astrophysics Data System (ADS)

Song, Yang; Katsman, Alexander; Butcher, Amy L.; Paine, David C.; Zaslavsky, Alexander

2017-10-01

Thin film transistors (TFTs) based on transparent oxide semiconductors, such as indium zinc oxide (IZO), are of interest due to their improved characteristics compared to traditional a-Si TFTs. Previously, we reported on top-gated IZO TFTs with an in-situ formed HfO2 gate insulator and IZO active channel, showing high performance: on/off ratio of ∼107, threshold voltage VT near zero, extracted low-field mobility μ0 = 95 cm2/V·s, and near-perfect subthreshold slope at 62 mV/decade. Since device stability is essential for technological applications, in this paper we report on the temporal and voltage stress stability of IZO TFTs. Our devices exhibit a small negative VT shift as they age, consistent with an increasing carrier density resulting from an increasing oxygen vacancy concentration in the channel. Under gate bias stress, freshly annealed TFTs show a negative VT shift during negative VG gate bias stress, while aged (>1 week) TFTs show a positive VT shift during negative VG stress. This indicates two competing mechanisms, which we identify as the field-enhanced generation of oxygen vacancies and the field-assisted migration of oxygen vacancies, respectively. A simplified kinetic model of the vacancy concentration evolution in the IZO channel under electrical stress is provided.

Temporal Stability of Stated Preferences: The Case of Junior Nursing Jobs.

PubMed

Doiron, Denise; Yoo, Hong Il

2017-06-01

With the growing use of discrete choice experiments (DCEs) in health workforce research, the reliability of elicited job preferences is a growing concern. We provide the first empirical evidence on the temporal stability of such preferences using a unique longitudinal survey of Australian nursing students and graduate nurses. The respondents completed DCEs on nursing positions in two survey waves. Each position is described by salary and 11 non-salary attributes, and the two waves are spaced 15months apart on average. Between the waves, most final-year students finished their degrees and started out as graduate nurses. Thus, the survey covers a long timespan that includes an important period of career transition. The relative importance of different job attributes appears stable enough to support the use of DCEs to identify key areas of policy intervention. There is virtually no change in the groupings of influential job characteristics. Conclusions regarding the stability of willingness-to-pay, however, are different because of unstable preferences for salary. The instability of preferences for salary was also found previously in the context of comparing alternative elicitation methods. This prompts us to push for further work on the reliability of stated preferences over monetary attributes. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Phase stability in fMRI time series: effect of noise regression, off-resonance correction and spatial filtering techniques.

PubMed

Hagberg, Gisela E; Bianciardi, Marta; Brainovich, Valentina; Cassara, Antonino Mario; Maraviglia, Bruno

2012-02-15

Although the majority of fMRI studies exploit magnitude changes only, there is an increasing interest regarding the potential additive information conveyed by the phase signal. This integrated part of the complex number furnished by the MR scanners can also be used for exploring direct detection of neuronal activity and for thermography. Few studies have explicitly addressed the issue of the available signal stability in the context of phase time-series, and therefore we explored the spatial pattern of frequency specific phase fluctuations, and evaluated the effect of physiological noise components (heart beat and respiration) on the phase signal. Three categories of retrospective noise reduction techniques were explored and the temporal signal stability was evaluated in terms of a physiologic noise model, for seven fMRI measurement protocols in eight healthy subjects at 3T, for segmented CSF, gray and white matter voxels. We confirmed that for most processing methods, an efficient use of the phase information is hampered by the fact that noise from physiological and instrumental sources contributes significantly more to the phase than to the magnitude instability. Noise regression based on the phase evolution of the central k-space point, RETROICOR, or an orthonormalized combination of these were able to reduce their impact, but without bringing phase stability down to levels expected from the magnitude signal. Similar results were obtained after targeted removal of scan-to-scan variations in the bulk magnetic field by the dynamic off-resonance in k-space (DORK) method and by the temporal off-resonance alignment of single-echo time series technique (TOAST). We found that spatial high-pass filtering was necessary, and in vivo a Gaussian filter width of 20mm was sufficient to suppress physiological noise and bring the phase fluctuations to magnitude levels. Stronger filters brought the fluctuations down to levels dictated by thermal noise contributions, and for 62.5mm(3) voxels the phase stability was as low as 5 mrad (0.27°). In conditions of low SNR(o) and high temporal sampling rate (short TR); we achieved an upper bound for the phase instabilities at 0.0017 ppm, which is close to the dHb contribution to the GM/WM phase contrast. Copyright © 2011 Elsevier Inc. All rights reserved.

Ultrafast chirped optical waveform recording using referenced heterodyning and a time microscope

DOEpatents

Bennett, Corey Vincent

2010-06-15

A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. This invention expands upon previous work in temporal imaging by adding heterodyning, which can be self-referenced for improved precision and stability, to convert frequency chirp (the second derivative of phase with respect to time) into a time varying intensity modulation. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

Ultrafast chirped optical waveform recorder using referenced heterodyning and a time microscope

DOEpatents

Bennett, Corey Vincent [Livermore, CA

2011-11-22

A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. This invention expands upon previous work in temporal imaging by adding heterodyning, which can be self-referenced for improved precision and stability, to convert frequency chirp (the second derivative of phase with respect to time) into a time varying intensity modulation. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

Stabilization of beta-catenin impacts pancreas growth.

PubMed

Heiser, Patrick W; Lau, Janet; Taketo, Makoto M; Herrera, Pedro L; Hebrok, Matthias

2006-05-01

A recent study has shown that deletion of beta-catenin within the pancreatic epithelium results in a loss of pancreas mass. Here, we show that ectopic stabilization of beta-catenin within mouse pancreatic epithelium can have divergent effects on both organ formation and growth. Robust stabilization of beta-catenin during early organogenesis drives changes in hedgehog and Fgf10 signaling and induces a loss of Pdx1 expression in early pancreatic progenitor cells. Together, these perturbations in early pancreatic specification culminate in a severe reduction of pancreas mass and postnatal lethality. By contrast, inducing the stabilized form of beta-catenin at a later time point in pancreas development causes enhanced proliferation that results in a dramatic increase in pancreas organ size. Taken together, these data suggest a previously unappreciated temporal/spatial role for beta-catenin signaling in the regulation of pancreas organ growth.

The inviscid stability of supersonic flow past heated or cooled axisymmetric bodies

NASA Technical Reports Server (NTRS)

Shaw, Stephen J.; Duck, Peter W.

1992-01-01

The inviscid, linear, nonaxisymmetric, temporal stability of the boundary layer associated with the supersonic flow past axisymmetric bodies (with particular emphasis on long thin, straight circular cylinders), subject to heated or cooled wall conditions is investigated. The eigenvalue problem is computed in some detail for a particular Mach number or 3.8, revealing that the effect of curvature and the choice of wall conditions both have a significant effect on the stability of the flow. Both the asymptotic, large azimuthal wavenumber solution and the asymptotic, far downstream solution are obtained for the stability analysis and compared with numerical results. Additionally, asymptotic analyses valid for large radii of curvature with cooled/heated wall conditions are presented. In general, important differences were found to exist between the wall temperature conditions imposed and the adiabatic wall conditions considered previously.

The inviscid stability of supersonic flow past heated or cooled axisymmetric bodies

NASA Technical Reports Server (NTRS)

Shaw, Stephen J.; Duck, Peter W.

1990-01-01

The inviscid, linear, nonaxisymmetric, temporal stability of the boundary layer associated with the supersonic flow past axisymmetric bodies (with particular emphasis on long thin, straight circular cylinders), subject to heated or cooled wall conditions is investigated. The eigenvalue problem is computed in some detail for a particular Mach number or 3.8, revealing that the effect of curvature and the choice of wall conditions both have a significant effect on the stability of the flow. Both the asymptotic, large azimuthal wavenumber solution and the asymptotic, far downstream solution are obtained for the stability analysis and compared with numerical results. Additionally, asymptotic analyses valid for large radii of curvature with cooled/heated wall conditions, are presented. In general, important differences were found to exist between the wall temperature conditions imposed and the adiabatic wall conditions considered previously.

Factors associated with high heterogeneity of malaria at fine spatial scale in the Western Kenyan highlands.

PubMed

Baidjoe, Amrish Y; Stevenson, Jennifer; Knight, Philip; Stone, William; Stresman, Gillian; Osoti, Victor; Makori, Euniah; Owaga, Chrispin; Odongo, Wycliffe; China, Pauline; Shagari, Shehu; Kariuki, Simon; Drakeley, Chris; Cox, Jonathan; Bousema, Teun

2016-06-04

The East African highlands are fringe regions between stable and unstable malaria transmission. What factors contribute to the heterogeneity of malaria exposure on different spatial scales within larger foci has not been extensively studied. In a comprehensive, community-based cross-sectional survey an attempt was made to identify factors that drive the macro- and micro epidemiology of malaria in a fringe region using parasitological and serological outcomes. A large cross-sectional survey including 17,503 individuals was conducted across all age groups in a 100 km(2) area in the Western Kenyan highlands of Rachuonyo South district. Households were geo-located and prevalence of malaria parasites and malaria-specific antibodies were determined by PCR and ELISA. Household and individual risk-factors were recorded. Geographical characteristics of the study area were digitally derived using high-resolution satellite images. Malaria antibody prevalence strongly related to altitude (1350-1600 m, p < 0.001). A strong negative association with increasing altitude and PCR parasite prevalence was found. Parasite carriage was detected at all altitudes and in all age groups; 93.2 % (2481/2663) of malaria infections were apparently asymptomatic. Malaria parasite prevalence was associated with age, bed net use, house construction features, altitude and topographical wetness index. Antibody prevalence was associated with all these factors and distance to the nearest water body. Altitude was a major driver of malaria transmission in this study area, even across narrow altitude bands. The large proportion of asymptomatic parasite carriers at all altitudes and the age-dependent acquisition of malaria antibodies indicate stable malaria transmission; the strong correlation between current parasite carriage and serological markers of malaria exposure indicate temporal stability of spatially heterogeneous transmission.

Investigation of Kelvin-Helmholtz Instability in the boundary layer using Doppler lidar and radiosonde data

NASA Astrophysics Data System (ADS)

Das, Subrata Kumar; Das, Siddarth Shankar; Saha, Korak; Murali Krishna, U. V.; Dani, K. K.

2018-04-01

Characteristics of Kelvin Helmholtz Instability (KHI) using Doppler wind lidar observation have rarely been reported during the Indian summer monsoon season. In this paper, we present a case study of KHI near planetary boundary layer using Doppler wind lidar and radiosonde measurements at Mahabubnagar, a tropical Indian station. The data was collected during the Integrated Ground Observation Campaign (June-October 2011) under the Cloud Aerosol Interaction and Precipitation Enhancement EXperiment-2011. The continuous wind lidar observation during 10-16 August 2011 shows there is an increase in carrier-to-noise ratio values near planetary boundary layer from 03:00 to 11:00 LT on 13 August; reveals the formation of KHI. There is a strong power bursts pattern corresponding to high turbulence characteristics in the early half of the day. The KHI temporal evolution from initial to dissipating stage is observed with clear variation in the carrier-to-noise ratio values. The observed KHI billows are in the height between 600 and 1200 m and lasted for about 7.5 h. The vertical velocity from Doppler lidar measurement shows the presence of updrafts after breaking of KHI in the boundary layer. The presence of strong wind shear, high stability parameter, low Richardson number and high relative humidity during the enhanced carrier-to-noise ratio period indicates the ideal condition for the formation and persistence of this dynamic instability. A typical characteristic of trapped humidity above the KHI billows suggest the presence of strong inversion. A wavelet analysis of 3-dimensional wind components show dominant periodicity of 45-65 min and the periodicity in vertical wind is more prominent.

Super long-life supercapacitors based on the construction of nanohoneycomb-like strongly coupled CoMoO(4)-3D graphene hybrid electrodes.

PubMed

Yu, Xinzhi; Lu, Bingan; Xu, Zhi

2014-02-01

Nanohoneycomb-like strongly coupled CoMoO4 -3D graphene hybird electrodes are synthesized for supercapacitors which exhibit excellent specific capacitance and superior long-term cycle stability. The supercapacitor device can power a 5 mm-diameter LED efficiently for more than 3 min with a charging time of only 2 s, and shows high energy densities and good cycle stability. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced thermal stability of Cu alloy films by strong interaction between Ni and Zr (or Fe)

NASA Astrophysics Data System (ADS)

Zheng, Yuehong; Li, Xiaona; Cheng, Xiaotian; Li, Zhuming; Liu, Yubo; Dong, Chuang

2018-04-01

Low resistivity, phase stability and nonreactivity with surrounding dielectrics are the key to the application of Cu to ultra-large-scale integrated circuits. Here, a stable solid solution cluster model was introduced to design the composition of barrierless Cu-Ni-Zr (or Fe) seed layers. The third elements Fe and Zr were dissolved into Cu via a second element Ni, which is soluble in both Cu and Zr (or Fe). The films were prepared by magnetron sputtering on the single-crystal p-Si (1 0 0) wafers. Since the diffusion characteristics of the alloying elements are different, the effects of the strong interaction between Ni and Zr (or Fe) on the film’s stability and resistivity were studied. The results showed that a proper addition of Zr-Ni (Zr/Ni  ⩽  0.6/12) into Cu could form a large negative lattice distortion, which inhibits Cu-Si interdiffusion and enhances the stability of Cu film. When Fe-Ni was co-added into Cu, the lattice distortion of Cu reached a lower value, 0.0029 Å  ⩽  |Δa|  ⩽  0.0046 Å, and the films showed poor stability. Therefore, when the model is applied to the composition design of the films, the strong interaction between the elements and the addition ratio should be taken into consideration.

Enzyme architecture: optimization of transition state stabilization from a cation-phosphodianion pair.

PubMed

Reyes, Archie C; Koudelka, Astrid P; Amyes, Tina L; Richard, John P

2015-04-29

The side chain cation of R269 lies at the surface of l-glycerol 3-phosphate dehydrogenase (GPDH) and forms an ion pair to the phosphodianion of substrate dihydroxyacetone phosphate (DHAP), which is buried at the nonpolar protein interior. The R269A mutation of GPDH results in a 110-fold increase in K(m) (2.8 kcal/mol effect) and a 41,000-fold decrease in k(cat) (6.3 kcal/mol effect), which corresponds to a 9.1 kcal/mol destabilization of the transition state for GPDH-catalyzed reduction of DHAP by NADH. There is a 6.7 kcal/mol stabilization of the transition state for the R269A mutant GPDH-catalyzed reaction by 1.0 M guanidinium ion, and the transition state for the reaction of the substrate pieces is stabilized by an additional 2.4 kcal/mol by their covalent attachment at wildtype GPDH. These results provide strong support for the proposal that GPDH invests the 11 kcal/mol intrinsic phosphodianion binding energy of DHAP in trapping the substrate at a nonpolar active site, where strong electrostatic interactions are favored, and obtains a 9 kcal/mol return from stabilizing interactions between the side chain cation and transition state trianion. We propose a wide propagation for the catalytic motif examined in this work, which enables strong transition state stabilization from enzyme-phosphodianion pairs.

Discrete time-crystalline order in black diamond

NASA Astrophysics Data System (ADS)

Zhou, Hengyun; Choi, Soonwon; Choi, Joonhee; Landig, Renate; Kucsko, Georg; Isoya, Junichi; Jelezko, Fedor; Onoda, Shinobu; Sumiya, Hitoshi; Khemani, Vedika; von Keyserlingk, Curt; Yao, Norman; Demler, Eugene; Lukin, Mikhail D.

2017-04-01

The interplay of periodic driving, disorder, and strong interactions has recently been predicted to result in exotic ``time-crystalline'' phases, which spontaneously break the discrete time-translation symmetry of the underlying drive. Here, we report the experimental observation of such discrete time-crystalline order in a driven, disordered ensemble of 106 dipolar spin impurities in diamond at room-temperature. We observe long-lived temporal correlations at integer multiples of the fundamental driving period, experimentally identify the phase boundary and find that the temporal order is protected by strong interactions; this order is remarkably stable against perturbations, even in the presence of slow thermalization. Our work opens the door to exploring dynamical phases of matter and controlling interacting, disordered many-body systems.

[Temporo-mandibular joint. Morpho-functional considerations].

PubMed

Scutariu, M D; Indrei, Anca

2004-01-01

The temporo-mandibular joint is distinguished from most other synovial joints of the body by two features: 1. the two jointed components carry teeth whose position and occlusion introduce a very strong influence on the movements of the temporo-mandibular joint and 2. its articular surfaces are not covered by hyaline cartilage, but by a dense, fibrous tissue. This paper describes the parts of the temporo-mandibular joint: the articular surfaces (the condylar process of the mandible and the glenoid part of the temporal bone), the fibrocartilaginous disc which is interposed between the mandibular and the temporal surface, the fibrous capsule of the temporo-mandibular joint and the ligaments of this joint. All these parts present a very strong adaptation at the important functions of the temporo-mandibular joint.

Time stability of spring and superconducting gravimeters through the analysis of very long gravity records

NASA Astrophysics Data System (ADS)

Calvo, Marta; Hinderer, Jacques; Rosat, Severine; Legros, Hilaire; Boy, Jean-Paul; Ducarme, Bernard; Zürn, Walter

2014-10-01

Long gravity records are of great interest when performing tidal analyses. Indeed, long series enable to separate contributions of near-frequency waves and also to detect low frequency signals (e.g. long period tides and polar motion). In addition to the length of the series, the quality of the data and the temporal stability of the noise are also very important. We study in detail some of the longest gravity records available in Europe: 3 data sets recorded with spring gravimeters in Black Forest Observatory (Germany, 1980-2012), Walferdange (Luxemburg, 1980-1995) and Potsdam (Germany, 1974-1998) and several superconducting gravimeters (SGs) data sets, with at least 9 years of continuous records, at different European GGP (Global Geodynamics Project) sites (Bad Homburg, Brussels, Medicina, Membach, Moxa, Vienna, Wettzell and Strasbourg). The stability of each instrument is investigated using the temporal variations of tidal parameters (amplitude factor and phase difference) for the main tidal waves (O1, K1, M2 and S2) as well as the M2/O1 factor ratio, the later being insensitive to the instrumental calibration. The long term stability of the tidal observations is also dependent on the stability of the scale factor of the relative gravimeters. Therefore we also check the time stability of the scale factor for the superconducting gravimeter C026 installed at the J9 Gravimetric Observatory of Strasbourg (France), using numerous calibration experiments carried out by co-located absolute gravimeter (AG) measurements during the last 15 years. The reproducibility of the scale factor and the achievable precision are investigated by comparing the results of different calibration campaigns. Finally we present a spectrum of the 25 years of SG records at J9 Observatory, with special attention to small amplitude tides in the semi-diurnal and diurnal bands, as well as to the low frequency part.

Climate variability decreases species richness and community stability in a temperate grassland.

PubMed

Zhang, Yunhai; Loreau, Michel; He, Nianpeng; Wang, Junbang; Pan, Qingmin; Bai, Yongfei; Han, Xingguo

2018-06-26

Climate change involves modifications in both the mean and the variability of temperature and precipitation. According to global warming projections, both the magnitude and the frequency of extreme weather events are increasing, thereby increasing climate variability. The previous studies have reported that climate warming tends to decrease biodiversity and the temporal stability of community primary productivity (i.e., community stability), but the effects of the variability of temperature and precipitation on biodiversity, community stability, and their relationship have not been clearly explored. We used a long-term (from 1982 to 2014) field data set from a temperate grassland in northern China to explore the effects of the variability of mean temperature and total precipitation on species richness, community stability, and their relationship. Results showed that species richness promoted community stability through increases in asynchronous dynamics across species (i.e., species asynchrony). Both species richness and species asynchrony were positively associated with the residuals of community stability after controlling for its dependence on the variability of mean temperature and total precipitation. Furthermore, the variability of mean temperature reduced species richness, while the variability of total precipitation decreased species asynchrony and community stability. Overall, the present study revealed that species richness and species asynchrony promoted community stability, but increased climate variability may erode these positive effects and thereby threaten community stability.

A Novel Temporal Bone Simulation Model Using 3D Printing Techniques.

PubMed

Mowry, Sarah E; Jammal, Hachem; Myer, Charles; Solares, Clementino Arturo; Weinberger, Paul

2015-09-01

An inexpensive temporal bone model for use in a temporal bone dissection laboratory setting can be made using a commercially available, consumer-grade 3D printer. Several models for a simulated temporal bone have been described but use commercial-grade printers and materials to produce these models. The goal of this project was to produce a plastic simulated temporal bone on an inexpensive 3D printer that recreates the visual and haptic experience associated with drilling a human temporal bone. Images from a high-resolution CT of a normal temporal bone were converted into stereolithography files via commercially available software, with image conversion and print settings adjusted to achieve optimal print quality. The temporal bone model was printed using acrylonitrile butadiene styrene (ABS) plastic filament on a MakerBot 2x 3D printer. Simulated temporal bones were drilled by seven expert temporal bone surgeons, assessing the fidelity of the model as compared with a human cadaveric temporal bone. Using a four-point scale, the simulated bones were assessed for haptic experience and recreation of the temporal bone anatomy. The created model was felt to be an accurate representation of a human temporal bone. All raters felt strongly this would be a good training model for junior residents or to simulate difficult surgical anatomy. Material cost for each model was $1.92. A realistic, inexpensive, and easily reproducible temporal bone model can be created on a consumer-grade desktop 3D printer.

Non-steady wind turbine response to daytime atmospheric turbulence.

PubMed

Nandi, Tarak N; Herrig, Andreas; Brasseur, James G

2017-04-13

Relevant to drivetrain bearing fatigue failures, we analyse non-steady wind turbine responses from interactions between energy-dominant daytime atmospheric turbulence eddies and the rotating blades of a GE 1.5 MW wind turbine using a unique dataset from a GE field experiment and computer simulation. Time-resolved local velocity data were collected at the leading and trailing edges of an instrumented blade together with generator power, revolutions per minute, pitch and yaw. Wind velocity and temperature were measured upwind on a meteorological tower. The stability state and other atmospheric conditions during the field experiment were replicated with a large-eddy simulation in which was embedded a GE 1.5 MW wind turbine rotor modelled with an advanced actuator line method. Both datasets identify three important response time scales: advective passage of energy-dominant eddies (≈25-50 s), blade rotation (once per revolution (1P), ≈3 s) and sub-1P scale (<1 s) response to internal eddy structure. Large-amplitude short-time ramp-like and oscillatory load fluctuations result in response to temporal changes in velocity vector inclination in the aerofoil plane, modulated by eddy passage at longer time scales. Generator power responds strongly to large-eddy wind modulations. We show that internal dynamics of the blade boundary layer near the trailing edge is temporally modulated by the non-steady external flow that was measured at the leading edge, as well as blade-generated turbulence motions.This article is part of the themed issue 'Wind energy in complex terrains'. © 2017 The Author(s).

Non-steady wind turbine response to daytime atmospheric turbulence

PubMed Central

Nandi, Tarak N.; Herrig, Andreas

2017-01-01

Relevant to drivetrain bearing fatigue failures, we analyse non-steady wind turbine responses from interactions between energy-dominant daytime atmospheric turbulence eddies and the rotating blades of a GE 1.5 MW wind turbine using a unique dataset from a GE field experiment and computer simulation. Time-resolved local velocity data were collected at the leading and trailing edges of an instrumented blade together with generator power, revolutions per minute, pitch and yaw. Wind velocity and temperature were measured upwind on a meteorological tower. The stability state and other atmospheric conditions during the field experiment were replicated with a large-eddy simulation in which was embedded a GE 1.5 MW wind turbine rotor modelled with an advanced actuator line method. Both datasets identify three important response time scales: advective passage of energy-dominant eddies (≈25–50 s), blade rotation (once per revolution (1P), ≈3 s) and sub-1P scale (<1 s) response to internal eddy structure. Large-amplitude short-time ramp-like and oscillatory load fluctuations result in response to temporal changes in velocity vector inclination in the aerofoil plane, modulated by eddy passage at longer time scales. Generator power responds strongly to large-eddy wind modulations. We show that internal dynamics of the blade boundary layer near the trailing edge is temporally modulated by the non-steady external flow that was measured at the leading edge, as well as blade-generated turbulence motions. This article is part of the themed issue ‘Wind energy in complex terrains’. PMID:28265026

Spatial and temporal variations in the sediment state of North American dune fields

NASA Astrophysics Data System (ADS)

Halfen, Alan F.; Lancaster, Nicholas; Wolfe, Stephen

2015-04-01

This research evaluates geomorphic and chronologic data from the INQUA Dune Atlas for three areas of North America: 1) the Prairie, Parkland and Boreal ecozones of the northern Great Plains in Canada; 2) the Central Great Plains of the USA; and 3) the deserts of southwestern USA and northern Mexico. Chronometric data for periods of dune activity and stability are compared with palaeoenvironment reconstructions to assess dune system response to changes in sediment supply, availability, and mobility. Dune fields in the northern Great Plains were formed from glaciofluvial or glaciolacustrine sediments deposited during deglaciation 16-11 ka. Subsequent aeolian deposition occurred in Parkland and Prairie dune fields as a result of mid-Holocene (8-5 ka) and late-Holocene (< 3.5 ka) activity related to drought conditions. In the Central Great Plains, many dune fields are closely linked to fluvial sediment sources. Sediment supply was high in these dune fields during deglaciation of the Rocky Mountains and resulted in widespread dune construction 16-10 ka. Multiple periods of Holocene reactivation are recorded and reflect increased sediment availability during drought episodes. Dune fields in the southwestern deserts experienced periods of construction as a result of enhanced supply of sediment from fluvial and lacustrine sources during the period 11.8 - 8 ka and at short but repeated intervals during the late Holocene. Despite spatial and temporal gaps in chronometric data, the record from North American dune fields indicates the strong influence of sediment supply on dune construction, with changes in sediment availability, as a result of drought, being the primary driver of dune activity during the Holocene.

Host and parasite life history interplay to yield divergent population genetic structures in two ectoparasites living on the same bat species.

PubMed

van Schaik, J; Dekeukeleire, D; Kerth, G

2015-05-01

Host-parasite interactions are ubiquitous in nature. However, how parasite population genetic structure is shaped by the interaction between host and parasite life history remains understudied. Studies comparing multiple parasites infecting a single host can be used to investigate how different parasite life history traits interplay with host behaviour and life history. In this study, we used 10 newly developed microsatellite loci to investigate the genetic structure of a parasitic bat fly (Basilia nana). Its host, the Bechstein's bat (Myotis bechsteinii), has a social system and roosting behaviour that restrict opportunities for parasite transmission. We compared fly genetic structure to that of the host and another parasite, the wing-mite, Spinturnix bechsteini. We found little spatial or temporal genetic structure in B. nana, suggesting a large, stable population with frequent genetic exchange between fly populations from different bat colonies. This contrasts sharply with the genetic structure of the wing-mite, which is highly substructured between the same bat colonies as well as temporally unstable. Our results suggest that although host and parasite life history interact to yield similar transmission patterns in both parasite species, the level of gene flow and eventual spatiotemporal genetic stability is differentially affected. This can be explained by the differences in generation time and winter survival between the flies and wing-mites. Our study thus exemplifies that the population genetic structure of parasites on a single host can vary strongly as a result of how their individual life history characteristics interact with host behaviour and life history traits. © 2015 John Wiley & Sons Ltd.

The temporal deployment of emotion regulation strategies during negative emotional episodes.

PubMed

Kalokerinos, Elise K; Résibois, Maxime; Verduyn, Philippe; Kuppens, Peter

2017-04-01

Time is given a central place in theoretical models of emotion regulation (Gross, 1998, 2015), but key questions regarding the role of time remain unanswered. We investigated 2 such unanswered questions. First, we explored when different emotion regulation strategies were used within the course of an emotional episode in daily life. Second, we investigated the association between the temporal deployment of strategies and negative emotional experience. We conducted a daily diary study in which participants (N = 74) drew an intensity profile depicting the temporal unfolding of their negative emotional experience across daily events (N = 480), and mapped their usage of emotion regulation strategies onto this intensity profile. Strategies varied in their temporal deployment, with suppression and rumination occurring more at the beginning of the episode, and reappraisal and distraction occurring more toward the end of the episode. Strategies also varied in their association with negative emotion: rumination was positively associated with negative emotion, and reappraisal and distraction were negatively associated with negative emotion. Finally, both rumination and reappraisal interacted with time to predict negative emotional experience. Rumination was more strongly positively associated with negative emotions at the end of the episode than the beginning, but reappraisal was more strongly negatively associated with negative emotion at the beginning of the episode than the end. These findings highlight the importance of accounting for timing in the study of emotion regulation, as well as the necessity of studying these temporal processes in daily life. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

MODELED MESOSCALE METEOROLOGICAL FIELDS WITH FOUR-DIMENSIONAL DATA ASSIMILATION IN REGIONAL SCALE AIR QUALITY MODELS

EPA Science Inventory

This paper addresses the need to increase the temporal and spatial resolution of meteorological data currently used in air quality simulation models, AQSMs. ransport and diffusion parameters including mixing heights and stability used in regulatory air quality dispersion models a...

Specificity and Modifiability of Cognitive Biases in Hypochondriasis

ERIC Educational Resources Information Center

Gropalis, Maria; Bleichhardt, Gaby; Hiller, Wolfgang; Witthoft, Michael

2013-01-01

Objective: According to cognitive-behavioral models of hypochondriasis (HYP), biased attentional and memory processes related to health threat stimuli are crucial for the development and maintenance of severe health anxiety. Little is known about the specificity, temporal stability, and modifiability of these biases via psychotherapy. Method: In…

Temporal and spatial variability of wind resources in the United States as derived from the Climate Forecast System Reanalysis

Treesearch

Lejiang Yu; Shiyuan Zhong; Xindi Bian; Warren E. Heilman

2015-01-01

This study examines the spatial and temporal variability of wind speed at 80m above ground (the average hub height of most modern wind turbines) in the contiguous United States using Climate Forecast System Reanalysis (CFSR) data from 1979 to 2011. The mean 80-m wind exhibits strong seasonality and large spatial variability, with higher (lower) wind speeds in the...

Fractional Stability of Trunk Acceleration Dynamics of Daily-Life Walking: Toward a Unified Concept of Gait Stability

PubMed Central

Ihlen, Espen A. F.; van Schooten, Kimberley S.; Bruijn, Sjoerd M.; Pijnappels, Mirjam; van Dieën, Jaap H.

2017-01-01

Over the last decades, various measures have been introduced to assess stability during walking. All of these measures assume that gait stability may be equated with exponential stability, where dynamic stability is quantified by a Floquet multiplier or Lyapunov exponent. These specific constructs of dynamic stability assume that the gait dynamics are time independent and without phase transitions. In this case the temporal change in distance, d(t), between neighboring trajectories in state space is assumed to be an exponential function of time. However, results from walking models and empirical studies show that the assumptions of exponential stability break down in the vicinity of phase transitions that are present in each step cycle. Here we apply a general non-exponential construct of gait stability, called fractional stability, which can define dynamic stability in the presence of phase transitions. Fractional stability employs the fractional indices, α and β, of differential operator which allow modeling of singularities in d(t) that cannot be captured by exponential stability. The fractional stability provided an improved fit of d(t) compared to exponential stability when applied to trunk accelerations during daily-life walking in community-dwelling older adults. Moreover, using multivariate empirical mode decomposition surrogates, we found that the singularities in d(t), which were well modeled by fractional stability, are created by phase-dependent modulation of gait. The new construct of fractional stability may represent a physiologically more valid concept of stability in vicinity of phase transitions and may thus pave the way for a more unified concept of gait stability. PMID:28900400

MODIS comparisons with northeastern Pacific in situ stratocumulus microphysics

NASA Astrophysics Data System (ADS)

Noble, Stephen R.; Hudson, James G.

2015-08-01

Vertical sounding measurements within stratocumuli during two aircraft field campaigns, Marine Stratus/stratocumulus Experiment (MASE) and Physics of Stratocumulus Top (POST), are used to validate Moderate Resolution Imaging Spectroradiometer (MODIS) cloud optical thickness (COT), cloud liquid water path (LWP), and cloud effective radius (re). In situ COT, LWP, and re were calculated using 5 m vertically averaged droplet probe measurements of complete vertical cloud penetrations. MODIS COT, LWP, and re 1 km pixels were averaged along these penetrations. COT comparisons in POST showed strong correlations and a near 1:1 relationship. In MASE, comparisons showed strong correlations; however, MODIS COT exceeded in situ COT, likely due to larger temporal differences between MODIS and in situ measurements. LWP comparisons between two cloud probes show good agreement for POST but not MASE, giving confidence to POST data. Both projects provided strong LWP correlations but MODIS exceeded in situ by 14-36%. MODIS in situ re correlations were strong, but MODIS 2.1 µm re exceeded in situ re, which contributed to LWP bias; in POST, MODIS re was 20-30% greater than in situ re. Maximum in situ re near cloud top showed comparisons nearer 1:1. Other MODIS re bands (3.7 µm and 1.6 µm) showed similar comparisons. Temporal differences between MODIS and in situ measurements, airplane speed differences, and cloud probe artifacts were likely causes of weaker MASE correlations. POST COT comparison was best for temporal differences under 20 min. POST data validate MODIS COT but it also implies a positive MODIS re bias that propagates to LWP while still capturing variability.

Instability Analysis of a Low-Density Gas Jet Injected into a High-Density Gas

NASA Technical Reports Server (NTRS)

Lawson, Anthony Layiwola

2001-01-01

The objective of this study was to determine the effects of buoyancy on the absolute instability of low-density gas jets injected into high-density gas mediums. Most of the existing analyses of low-density gas jets injected into a high-density ambient have been carried out neglecting effects of gravity. In order to investigate the influence of gravity on the near-injector development of the flow, a linear temporal stability analysis and a spatio-temporal stability analysis of a low-density round jet injected into a high-density ambient gas were performed. The flow was assumed to be isothermal and locally parallel; viscous and diffusive effects were ignored. The variables were represented as the sum of the mean value and a normal-mode small disturbance. An ordinary differential equation governing the amplitude of the pressure disturbance was derived. The velocity and density profiles in the shear layer, and the Froude number (signifying the effects of gravity) were the three important parameters in this equation. Together with the boundary conditions, an eigenvalue problem was formulated. Assuming that the velocity and density profiles in the shear layer to be represented by hyperbolic tangent functions, the eigenvalue problem was solved for various values of Froude number. The temporal growth rates and the phase velocity of the disturbances were obtained. It was found that the presence of variable density within the shear layer resulted in an increase in the temporal amplification rate of the disturbances and an increase in the range of unstable frequencies, accompanied by a reduction in the phase velocities of the disturbances. Also, the temporal growth rates of the disturbances were increased as the Froude number was reduced (i.e. gravitational effects increased), indicating the destabilizing role played by gravity. The spatio-temporal stability analysis was performed to determine the nature of the absolute instability of the jet. The roles of the density ratio, Froude number, Schmidt number, and the lateral shift between the density and velocity profiles on the jet s absolute instability were determined. Comparisons of the results with previous experimental studies show good agreement when the effects of these variables are combined together. Thus, the combination of these variables determines how absolutely unstable the jet will be. Experiments were carried out to observe the qualitative differences between a round low-density gas jet injected into a high-density gas (helium jet injected into air) and a round constant density jet (air jet injected into air). Flow visualizations and velocity measurements in the near-injector region of the helium jet show more mixing and spreading of the helium jet than the air jet. The vortex structures develop and contribute to the jet spreading causing the helium jet to oscillate.

Engineering proteins with tunable thermodynamic and kinetic stabilities.

PubMed

Pey, Angel L; Rodriguez-Larrea, David; Bomke, Susanne; Dammers, Susanne; Godoy-Ruiz, Raquel; Garcia-Mira, Maria M; Sanchez-Ruiz, Jose M

2008-04-01

It is widely recognized that enhancement of protein stability is an important biotechnological goal. However, some applications at least, could actually benefit from stability being strongly dependent on a suitable environment variable, in such a way that enhanced stability or decreased stability could be realized as required. In therapeutic applications, for instance, a long shelf-life under storage conditions may be convenient, but a sufficiently fast degradation of the protein after it has performed the planned molecular task in vivo may avoid side effects and toxicity. Undesirable effects associated to high stability are also likely to occur in food-industry applications. Clearly, one fundamental factor involved here is the kinetic stability of the protein, which relates to the time-scale of the irreversible denaturation processes and which is determined to some significant extent by the free-energy barrier for unfolding (the barrier that "separates" the native state from the highly-susceptible-to-irreversible-alterations nonnative states). With an appropriate experimental model, we show that strong environment-dependencies of the thermodynamic and kinetic stabilities can be achieved using robust protein engineering. We use sequence-alignment analysis and simple computational electrostatics to design stabilizing and destabilizing mutations, the latter introducing interactions between like charges which are screened out at high salt. Our design procedures lead naturally to mutating regions which are mostly unstructured in the transition state for unfolding. As a result, the large salt effect on the thermodynamic stability of our consensus plus charge-reversal variant translates into dramatic changes in the time-scale associated to the unfolding barrier: from the order of years at high salt to the order of days at low salt. Certainly, large changes in salt concentration are not expected to occur in biological systems in vivo. Hence, proteins with strong salt-dependencies of the thermodynamic and kinetic stabilities are more likely to be of use in those cases in which high-stability is required only under storage conditions. A plausible scenario is that inclusion of high salt in liquid formulations will contribute to a long protein shelf-life, while the lower salt concentration under the conditions of the application will help prevent the side effects associated with high-stability which may potentially arise in some therapeutic and food-industry applications. From a more general viewpoint, this work shows that consensus engineering and electrostatic engineering can be readily combined and clarifies relevant aspects of the relation between thermodynamic stability and kinetic stability in proteins. (c) 2007 Wiley-Liss, Inc.

The Role of Inhibition in a Computational Model of an Auditory Cortical Neuron during the Encoding of Temporal Information

PubMed Central

Bendor, Daniel

2015-01-01

In auditory cortex, temporal information within a sound is represented by two complementary neural codes: a temporal representation based on stimulus-locked firing and a rate representation, where discharge rate co-varies with the timing between acoustic events but lacks a stimulus-synchronized response. Using a computational neuronal model, we find that stimulus-locked responses are generated when sound-evoked excitation is combined with strong, delayed inhibition. In contrast to this, a non-synchronized rate representation is generated when the net excitation evoked by the sound is weak, which occurs when excitation is coincident and balanced with inhibition. Using single-unit recordings from awake marmosets (Callithrix jacchus), we validate several model predictions, including differences in the temporal fidelity, discharge rates and temporal dynamics of stimulus-evoked responses between neurons with rate and temporal representations. Together these data suggest that feedforward inhibition provides a parsimonious explanation of the neural coding dichotomy observed in auditory cortex. PMID:25879843

Temporal Integration of Auditory Information Is Invariant to Temporal Grouping Cues1,2,3

PubMed Central

Tsunada, Joji

2015-01-01

Abstract Auditory perception depends on the temporal structure of incoming acoustic stimuli. Here, we examined whether a temporal manipulation that affects the perceptual grouping also affects the time dependence of decisions regarding those stimuli. We designed a novel discrimination task that required human listeners to decide whether a sequence of tone bursts was increasing or decreasing in frequency. We manipulated temporal perceptual-grouping cues by changing the time interval between the tone bursts, which led to listeners hearing the sequences as a single sound for short intervals or discrete sounds for longer intervals. Despite these strong perceptual differences, this manipulation did not affect the efficiency of how auditory information was integrated over time to form a decision. Instead, the grouping manipulation affected subjects’ speed−accuracy trade-offs. These results indicate that the temporal dynamics of evidence accumulation for auditory perceptual decisions can be invariant to manipulations that affect the perceptual grouping of the evidence. PMID:26464975

GRMHD/RMHD Simulations and Stability of Magnetized Spine-Sheath Relativistic Jets

NASA Technical Reports Server (NTRS)

Hardee, Philip; Mizuno, Yosuke; Nishikawa, Ken-Ichi

2007-01-01

A new general relativistic magnetohydrodynamics (GRMHD ) code "RAISHIN" used to simulate jet generation by rotating and non-rotating black holes with a geometrically thin Keplarian accretion disk finds that the jet develops a spine-sheath structure in the rotating black hole case. Spine-sheath structure and strong magnetic fields significantly modify the Kelvin-Helmholtz (KH) velocity shear driven instability. The RAISHIN code has been used in its relativistic magnetohydrodynamic (RMHD) configuration to study the effects of strong magnetic fields and weakly relativistic sheath motion, cl2, on the KH instability associated with a relativistic, Y = 2.5, jet spine-sheath interaction. In the simulations sound speeds up to ? c/3 and Alfven wave speeds up to ? 0.56 c are considered. Numerical simulation results are compared to theoretical predictions from a new normal mode analysis of the RMHD equations. Increased stability of a weakly magnetized system resulting from c/2 sheath speeds and stabilization of a strongly magnetized system resulting from d 2 sheath speeds is found.

Dynamic Stabilization of a Quantum Many-Body Spin System

NASA Astrophysics Data System (ADS)

Hoang, T. M.; Gerving, C. S.; Land, B. J.; Anquez, M.; Hamley, C. D.; Chapman, M. S.

2013-08-01

We demonstrate dynamic stabilization of a strongly interacting quantum spin system realized in a spin-1 atomic Bose-Einstein condensate. The spinor Bose-Einstein condensate is initialized to an unstable fixed point of the spin-nematic phase space, where subsequent free evolution gives rise to squeezing and quantum spin mixing. To stabilize the system, periodic microwave pulses are applied that rotate the spin-nematic many-body fluctuations and limit their growth. The stability diagram for the range of pulse periods and phase shifts that stabilize the dynamics is measured and compares well with a stability analysis.

Thalamocortical NMDA conductances and intracortical inhibition can explain cortical temporal tuning

NASA Technical Reports Server (NTRS)

Krukowski, A. E.; Miller, K. D.

2001-01-01

Cells in cerebral cortex fail to respond to fast-moving stimuli that evoke strong responses in the thalamic nuclei innervating the cortex. The reason for this behavior has remained a mystery. We study an experimentally motivated model of the thalamic input-recipient layer of cat primary visual cortex that accounts for many aspects of cortical orientation tuning. In this circuit, inhibition dominates over excitation, but temporal modulations of excitation and inhibition occur out of phase with one another, allowing excitation to transiently drive cells. We show that this circuit provides a natural explanation of cortical low-pass temporal frequency tuning, provided N-methyl-D-aspartate (NMDA) receptors are present in thalamocortical synapses in proportions measured experimentally. This suggests a new and unanticipated role for NMDA conductances in shaping the temporal response properties of cortical cells, and suggests that common cortical circuit mechanisms underlie both spatial and temporal response tuning.

A real-world size organization of object responses in occipito-temporal cortex

PubMed Central

Konkle, Talia; Oliva, Aude

2012-01-01

SUMMARY While there are selective regions of occipito-temporal cortex that respond to faces, letters, and bodies, the large-scale neural organization of most object categories remains unknown. Here we find that object representations can be differentiated along the ventral temporal cortex by their real-world size. In a functional neuroimaging experiment, observers were shown pictures of big and small real-world objects (e.g. table, bathtub; paperclip, cup), presented at the same retinal size. We observed a consistent medial-to-lateral organization of big and small object preferences in the ventral temporal cortex, mirrored along the lateral surface. Regions in the lateral-occipital, infero-temporal, and parahippocampal cortices showed strong peaks of differential real-world size selectivity, and maintained these preferences over changes in retinal size and in mental imagery. These data demonstrate that the real-world size of objects can provide insight into the spatial topography of object representation. PMID:22726840

Temporal Genetic Dynamics of an Invasive Species, Frankliniella occidentalis (Pergande), in an Early Phase of Establishment.

PubMed

Yang, Xian-Ming; Lou, Heng; Sun, Jing-Tao; Zhu, Yi-Ming; Xue, Xiao-Feng; Hong, Xiao-Yue

2015-07-03

Many species can successfully colonize new areas despite their propagules having low genetic variation. We assessed whether the decreased genetic diversity could result in temporal fluctuations of genetic parameters of the new populations of an invasive species, western flower thrips, Frankliniella occidentalis, using mitochondrial and microsatellite markers. This study was conducted in eight localities from four climate regions in China, where F. occidentalis was introduced in the year 2000 and had lower genetic diversity than its native populations. We also tested the level of genetic differentiation in these introduced populations. The genetic diversity of the samples at different years in the same locality was not significantly different from each other in most localities. FST and STRUCTURE analysis also showed that most temporal population comparisons from the same sites were not significantly differentiated. Our results showed that the invasive populations of F. occidentalis in China can maintain temporal stability in genetic composition at an early phase of establishment despite having lower genetic diversity than in their native range.

Characterization of temporal coherence of hard X-ray free-electron laser pulses with single-shot interferograms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osaka, Taito; Hirano, Takashi; Morioka, Yuki

Temporal coherence is one of the most fundamental characteristics of light, connecting to spectral information through the Fourier transform relationship between time and frequency. Interferometers with a variable path-length difference (PLD) between the two branches have widely been employed to characterize temporal coherence properties for broad spectral regimes. Hard X-ray interferometers reported previously, however, have strict limitations in their operational photon energies, due to the specific optical layouts utilized to satisfy the stringent requirement for extreme stability of the PLD at sub-ångström scales. The work presented here characterizes the temporal coherence of hard X-ray free-electron laser (XFEL) pulses by capturingmore » single-shot interferograms. Since the stability requirement is drastically relieved with this approach, it was possible to build a versatile hard X-ray interferometer composed of six separate optical elements to cover a wide photon energy range from 6.5 to 11.5 keV while providing a large variable delay time of up to 47 ps at 10 keV. A high visibility of up to 0.55 was observed at a photon energy of 10 keV. The visibility measurement as a function of time delay reveals a mean coherence time of 5.9 ± 0.7 fs, which agrees with that expected from the single-shot spectral information. In conclusion, this is the first result of characterizing the temporal coherence of XFEL pulses in the hard X-ray regime and is an important milestone towards ultra-high energy resolutions at micro-electronvolt levels in time-domain X-ray spectroscopy, which will open up new opportunities for revealing dynamic properties in diverse systems on timescales from femtoseconds to nanoseconds, associated with fluctuations from ångström to nanometre spatial scales.« less

Characterization of temporal coherence of hard X-ray free-electron laser pulses with single-shot interferograms

DOE PAGES

Osaka, Taito; Hirano, Takashi; Morioka, Yuki; ...

2017-10-13

Temporal coherence is one of the most fundamental characteristics of light, connecting to spectral information through the Fourier transform relationship between time and frequency. Interferometers with a variable path-length difference (PLD) between the two branches have widely been employed to characterize temporal coherence properties for broad spectral regimes. Hard X-ray interferometers reported previously, however, have strict limitations in their operational photon energies, due to the specific optical layouts utilized to satisfy the stringent requirement for extreme stability of the PLD at sub-ångström scales. The work presented here characterizes the temporal coherence of hard X-ray free-electron laser (XFEL) pulses by capturingmore » single-shot interferograms. Since the stability requirement is drastically relieved with this approach, it was possible to build a versatile hard X-ray interferometer composed of six separate optical elements to cover a wide photon energy range from 6.5 to 11.5 keV while providing a large variable delay time of up to 47 ps at 10 keV. A high visibility of up to 0.55 was observed at a photon energy of 10 keV. The visibility measurement as a function of time delay reveals a mean coherence time of 5.9 ± 0.7 fs, which agrees with that expected from the single-shot spectral information. In conclusion, this is the first result of characterizing the temporal coherence of XFEL pulses in the hard X-ray regime and is an important milestone towards ultra-high energy resolutions at micro-electronvolt levels in time-domain X-ray spectroscopy, which will open up new opportunities for revealing dynamic properties in diverse systems on timescales from femtoseconds to nanoseconds, associated with fluctuations from ångström to nanometre spatial scales.« less

Temporal stability of pathological scratchcard gambling among adult scratchcard buyers two years later.

PubMed

DeFuentes-Merillas, Laura; Koeter, Maarten W J; Schippers, Gerard M; van den Brink, Wim

2004-01-01

To estimate the 2-year cumulative incidence of pathological scratchcard gambling (PSG) among a representative sample of high-risk scratchcard buyers, to assess the 2-year temporal stability of PSG and scratchcard-related problems and to estimate the adjusted 1-year prevalence for PSG taking into account the temporal dynamics of this diagnosis. A prospective study with two assessments was applied to a non-proportional stratified random sample of 12,222 adult scratchcard buyers in the Netherlands. A cost-effective design was used and only those scratchcard buyers (n=201) who had already experienced some scratchcard-related problems at initial assessment were followed-up 2 years later. Two independent cohorts of buyers with scratchcard-related problems were followed-up: a cohort of 173 potential problematic scratchcard gamblers (PPSG) at increased risk for PSG and a cohort of 28 pathological scratchcard gamblers. Incidence and prevalence estimates were calculated for the total sample of adult scratchcard buyers and for the Dutch adult population. Of the PPSG group 6.72% (95% CI 2.30-8.90%) became addicted to scratchcards during the 2-year period. The 2-year cumulative incidence of PSG among Dutch adult scratchcard players was 0.24% (95% CI 0.16-0.34%). The stability of the Diagnostic and Statistical Manual 4th edition (DSM-IV) diagnosis of PSG ranged from 11.1% to 42.9%, depending on whether or not those lost to follow-up were considered to be cases of PSG. Taking into account the dynamics of this disorder, using the most conservative assumption, the adjusted 1-year prevalence of PSG for the total sample of adult scratchcard buyers was 0.33% (95% CI 0.23-0.45%). PSG proves to be a rare phenomenon among adult scratchcard buyers in the Netherlands. Both incidence and prevalence of the DSM-IV diagnosis PSG were low. Stability of the DSM-IV diagnosis PSG, DSM-IV criteria and South Oaks Gambling Screening-S (SOGS-S) problems were low. Prevalence was stable over the time because incidence and recovery rates were very similar.

Determining hydroclimatic extreme events over the south-central Andes

NASA Astrophysics Data System (ADS)

RamezaniZiarani, Maryam; Bookhagen, Bodo; Schmidt, Torsten; Wickert, Jens; de la Torre, Alejandro; Volkholz, Jan

2017-04-01

The south-central Andes in NW Argentina are characterized by a strong rainfall asymmetry. In the east-west direction exists one of the steepest rainfall gradients on Earth, resulting from the large topographic differences in this region. In addition, in the north-south direction the rainfall intensity varies as the climatic regime shifts from the tropical central Andes to the subtropical south-central Andes. In this study, we investigate hydroclimatic extreme events over the south-central Andes using ERA-Interim reanalysis data of the ECMWF (European Centre for Medium-Range Weather Forecasts), the high resolution regional climate model (COSMO-CLM) data and TRMM (Tropical Rainfall Measuring Mission) data. We divide the area in three different study regions based on elevation: The high-elevation Altiplano-Puna plateau, an intermediate area characterized by intramontane basins, and the foreland area. We analyze the correlations between climatic variables, such as specific humidity, zonal wind component, meridional wind component and extreme rainfall events in all three domains. The results show that there is a high positive temporal correlation between extreme rainfall events (90th and 99th percentile rainfall) and extreme specific humidity events (90th and 99th percentile specific humidity). In addition, the temporal variations analysis represents a trend of increasing specific humidity with time during time period (1994-2013) over the Altiplano-Puna plateau which is in agreement with rainfall trend. Regarding zonal winds, our results indicate that 99th percentile rainfall events over the Altiplano-Puna plateau coincide temporally with strong easterly winds from intermountain and foreland regions in the east. In addition, the results regarding the meridional wind component represent strong northerly winds in the foreland region coincide temporally with 99th percentile rainfall over the Altiplano-Puna plateau.

Do Older Listeners With Hearing Loss Benefit From Dynamic Pitch for Speech Recognition in Noise?

PubMed

Shen, Jing; Souza, Pamela E

2017-10-12

Dynamic pitch, the variation in the fundamental frequency of speech, aids older listeners' speech perception in noise. It is unclear, however, whether some older listeners with hearing loss benefit from strengthened dynamic pitch cues for recognizing speech in certain noise scenarios and how this relative benefit may be associated with individual factors. We first examined older individuals' relative benefit between natural and strong dynamic pitches for better speech recognition in noise. Further, we reported the individual factors of the 2 groups of listeners who benefit differently from natural and strong dynamic pitches. Speech reception thresholds of 13 older listeners with mild-moderate hearing loss were measured using target speech with 3 levels of dynamic pitch strength. Individuals' ability to benefit from dynamic pitch was defined as the speech reception threshold difference between speeches with and without dynamic pitch cues. The relative benefit of natural versus strong dynamic pitch varied across individuals. However, this relative benefit remained consistent for the same individuals across those background noises with temporal modulation. Those listeners who benefited more from strong dynamic pitch reported better subjective speech perception abilities. Strong dynamic pitch may be more beneficial than natural dynamic pitch for some older listeners to recognize speech better in noise, particularly when the noise has temporal modulation.

TRMM-TMI Satellite Observed Soil Moisture and Vegetation Density (1998-2005) Show Strong Connection with El Nino in Eastern Australia

NASA Technical Reports Server (NTRS)

Liu, Yi; van Dijk, Albert I.J.M.; Owe, Manfred

2007-01-01

Spatiotemporal patterns in soil moisture and vegetation water content across mainland Australia were investigated from 1998 through 2005, using TRMMITMI passive microwave observations. The Empirical Orthogonal Function technique was used to extract dominant spatial and temporal patterns in retrieved estimates of moisture content for the top 1-cm of soil (theta) and vegetation moisture content (via optical depth tau). The dominant temporal theta and tau patterns were strongly correlated to El Nino/Southern Oscillation (ENSO) in spring (3 = 0.90), and to a progressively lesser extent autumn, summer and winter. The Indian Ocean Dipole (IOD) index also explained part of the variation in spring 8 and z. Cluster analysis suggested that the regions most affected by ENS0 are mainly located in eastern Australia. The results suggest that the drought conditions experienced in eastern Australia since 2000 an clearly expressed in these satellite observations have a strong connection with ENSO patterns.

Stability studies of anticancer agent bis(4-fluorobenzyl)trisulfide and synthesis of related substances.

PubMed

Bao, Yimei; Mo, Xiaopeng; Xu, Xiaoying; He, Yuyu; Xu, Xiao; An, Haoyun

2008-11-04

Bis(4-fluorobenzyl)trisulfide, fluorapacin, has been extensively developed as a promising new anticancer drug candidate. Its degradation products were identified and verified by the newly synthesized compounds bis(4-fluorobenzyl)disulfide (A) and bis(4-fluorobenzyl)tetrasulfide (B) which were resulted from the disproportionation of fluorapacin under forced conditions. A stability-indicating HPLC method was used for the stability evaluation of active pharmaceutical ingredient (API) fluorapacin and finished pharmaceutical product (FPP) under various conditions. High recovery (99.57%) of API was found after three freeze-thaw cycle processes of fluorapacin FPP. Susceptibility of fluorapacin to oxidative degradation was studied by treating fluorapacin and FPP in 30% hydrogen peroxide aqueous solution, and the result verified the oxidative stability of fluorapacin. However, treatment of this drug candidate under strong light (4500 Lx+/-500 Lx) for 10 days showed substantial effect on the recovery of fluorapacin, especially from fluorapacin FPP. Strong acid (1.0M, HCl) did not affect the recovery of fluorapacin while strong basic condition (1.0M, NaOH) accelerated the disproportionation of fluorapacin to its related substances A and B. The stability of fluorapacin in its aqueous media at a pH range of 2.0-10.0 for up to 6h was further investigated, and 4.0-8.0 was found to be the most stable pH range. Fluorapacin and FPP were exposed to the elevated temperatures of 40 and 60 degrees C for 10 days without obvious impact on their stability. The thermal stability of fluorapacin API and FPP under constant humidity with light protection was also thoroughly investigated under accelerated (40+/-2 degrees C, RH 75+/-5%, 6 months) and long-term (25+/-2 degrees C, RH 60+/-10%, 24 months) conditions. There was no significant change except minor color change of fluorapacin FPP. Therefore, fluorapacin has excellent stability as a potential drug candidate for further clinical development investigation.

Dimensional stability. [of glass and glass-ceramic materials in diffraction telescopes

NASA Technical Reports Server (NTRS)

Hochen, R.; Justie, B.

1976-01-01

The temporal stability of glass and glass-ceramic materials is important to the success of a large diffraction-limited telescope. The results are presented of an experimental study of the dimensional stability of glasses and glass ceramics being considered for substrates of massive diffraction-limited mirrors designed for several years of service in earth orbit. The purpose of the study was to measure the relative change in length of the candidate substrate materials, to the order of 5 parts in 10 to the 8th power, as a function of several years time. The development of monolithic test etalons, the development and improvement of two types of ultra-high precision interferometers, and certain aspects of tests data presently achieved are discussed.

Frictional stability-permeability relationships for fractures in shales

NASA Astrophysics Data System (ADS)

Fang, Yi; Elsworth, Derek; Wang, Chaoyi; Ishibashi, Takuya; Fitts, Jeffrey P.

2017-03-01

There is wide concern that fluid injection in the subsurface, such as for the stimulation of shale reservoirs or for geological CO2 sequestration (GCS), has the potential to induce seismicity that may change reservoir permeability due to fault slip. However, the impact of induced seismicity on fracture permeability evolution remains unclear due to the spectrum of modes of fault reactivation (e.g., stable versus unstable). As seismicity is controlled by the frictional response of fractures, we explore friction-stability-permeability relationships through the concurrent measurement of frictional and hydraulic properties of artificial fractures in Green River shale (GRS) and Opalinus shale (OPS). We observe that carbonate-rich GRS shows higher frictional strength but weak neutral frictional stability. The GRS fracture permeability declines during shearing while an increased sliding velocity reduces the rate of permeability decline. By comparison, the phyllosilicate-rich OPS has lower friction and strong stability while the fracture permeability is reduced due to the swelling behavior that dominates over the shearing induced permeability reduction. Hence, we conclude that the friction-stability-permeability relationship of a fracture is largely controlled by mineral composition and that shale mineral compositions with strong frictional stability may be particularly subject to permanent permeability reduction during fluid infiltration.

Test-Retest Reliability of the Salutogenic Wellness Promotion Scale (SWPS)

ERIC Educational Resources Information Center

Anderson, L. M.; Moore, J. B.; Hayden, B. M.; Becker, C. M.

2014-01-01

Objective: This study examined the temporal stability (i.e. test-retest reliability) of the Salutogenic Wellness Promotion Scale (SWPS) using intraclass correlation coefficients (ICC). Current intraclass results were also compared to previously published interclass correlations to support the use of the intraclass method for test-retest…

Landslide susceptibility mapping using downscaled AMSR-E soil moisture: A case study from Cleveland Corral, California, US

USDA-ARS?s Scientific Manuscript database

As soil moisture increases, slope stability decreases. Remotely sensed soil moisture data can provide routine updates of slope conditions necessary for landslide predictions. For regional scale landslide investigations, only remote sensing methods have the spatial and temporal resolution required to...

Temporal Trends and Evidence of Preservation of Benzotriazoles in Coastal Sediments of the United States

EPA Science Inventory

Benzotriazoles (BZTs) are used in a wide range of commercial and industrial applications as well as consumer products. There are several categories of usage of these compounds, the major two being as an additive to provide ultraviolet (UV) stabilization for plastics and films an...

Variability in oak forest herb layer communities

Treesearch

J. R. McClenahen; R. P. Long

1995-01-01

This study evaluates forest herb-layer sensitivity to annual-scale environmental fluctuation. Specific objectives were to determine the between-year variation in herb-layer community biomass, and to contrast and evaluate the temporal stability of spatial relationships in herb-layer community structure and composition between successive years. Aboveground dry weights of...

Short-Term Temporal Stability in Observed Retail Food Characteristics

ERIC Educational Resources Information Center

Zenk, Shannon N.; Grigsby-Toussaint, Diana S.; Curry, Susan J.; Berbaum, Michael; Schneider, Linda

2010-01-01

Objective: Use of direct observation to characterize neighborhood retail food environments is increasing, but to date most studies have relied on a single observation. If food availability, prices, and quality vary over short time periods, repeated measures may be needed to portray these food characteristics. This study evaluated short-term…

The Vane Kindergarten Test: Temporal Stability And Ability to Predict Behavioral Criteria

ERIC Educational Resources Information Center

Powers, Sandra M.

1977-01-01

The Vane Kindergarten Test (VKT) is judged to have limited usefulness in early detection of learning handicaps for two reasons: (a) Its reliability is too low to allow discrimination between individuals, and (b) The ability of the VKT to predict problem behaviors is quite limited. (Author)

Evaluating the temporal stability of synthetically generated time-series for crop types in central Germany

USDA-ARS?s Scientific Manuscript database

Synthetically generated Landsat time-series based on the STARFM algorithm are increasingly used for applications in forestry or agriculture. Although successes in classification and derivation of phenological orbiomass parameters are evident, a thorough evaluation of the limits of the method is stil...

MOLECULAR TRACKING FECAL CONTAMINATION IN SURFACE WATERS: 16S RDNA VERSUS METAGENOMICS APPROACHES

EPA Science Inventory

Microbial source tracking methods need to be sensitive and exhibit temporal and geographic stability in order to provide meaningful data in field studies. The objective of this study was to use a combination of PCR-based methods to track cow fecal contamination in two watersheds....

Stability and Repeatability of the Distress Thermometer (DT) and the Edmonton Symptom Assessment System-Revised (ESAS-r) with Parents of Childhood Cancer Survivors.

PubMed

Leclair, Tatsiana; Carret, Anne-Sophie; Samson, Yvan; Sultan, Serge

2016-01-01

Parents report psychological distress in association with their child's cancer. Reliable tools are needed to screen parental distress over the cancer trajectory. This study aimed to estimate the stability and repeatability of the Distress Thermometer (DT) and the Depression and Anxiety items of the Edmonton Symptom Assessment System-revised (ESAS-r-D; -A) in parents of children diagnosed with cancer. Fifty parents (28 mothers, median age = 44) of clinically stable survivors of childhood solid and brain tumours completed questionnaires about their own distress (DT, ESAS-r-D; -A, Brief Symptom Inventory-18: BSI-18, Patient Health Questionnaire-9: PHQ-9, Generalized Anxiety Disorder-7: GAD-7) and their children's quality of life (QoL; Peds Quality of Life: PedsQL) twice, with a month interval between the two assessments. At retest, parents also evaluated life events that occurred between the two time points. Hierarchical regressions explored moderators for the temporal stability of test measures. Stability estimates were ICC = .78 for the DT, .55 for the ESAS-r-D, and .47 for the ESAS-r-A. Caseness agreement between test and retest was substantial for the DT, fair for the ESAS-r-D, and slight for the ESAS-r-A. Repeatability analyses indicated that the error range for the DT was more than 2 pts below/above actual measurement, whereas it was more than 3 pts for the ESAS-r-A, and 2.5 for the ESAS-r-D. Instability of the DT could be explained by changes in children's physical QoL, but not by other components of QoL or life events. No moderators of stability could be identified for the ESAS-r items. The DT appears to be a fairly stable measure when the respondent's condition is stable yet with a relatively wide error range. Fluctuations in distress-related constructs may affect the temporal stability of the DT. The lower stability of ESAS-r items may result from shorter time-lapse instructions resulting in a greater sensitivity to change. Findings support future research on the DT as a reliable instrument in caregivers.

Stability and Repeatability of the Distress Thermometer (DT) and the Edmonton Symptom Assessment System-Revised (ESAS-r) with Parents of Childhood Cancer Survivors

PubMed Central

Carret, Anne-Sophie; Samson, Yvan; Sultan, Serge

2016-01-01

Objective Parents report psychological distress in association with their child's cancer. Reliable tools are needed to screen parental distress over the cancer trajectory. This study aimed to estimate the stability and repeatability of the Distress Thermometer (DT) and the Depression and Anxiety items of the Edmonton Symptom Assessment System-revised (ESAS-r-D; -A) in parents of children diagnosed with cancer. Methods Fifty parents (28 mothers, median age = 44) of clinically stable survivors of childhood solid and brain tumours completed questionnaires about their own distress (DT, ESAS-r-D; -A, Brief Symptom Inventory-18: BSI-18, Patient Health Questionnaire-9: PHQ-9, Generalized Anxiety Disorder-7: GAD-7) and their children’s quality of life (QoL; Peds Quality of Life: PedsQL) twice, with a month interval between the two assessments. At retest, parents also evaluated life events that occurred between the two time points. Hierarchical regressions explored moderators for the temporal stability of test measures. Results Stability estimates were ICC = .78 for the DT, .55 for the ESAS-r-D, and .47 for the ESAS-r-A. Caseness agreement between test and retest was substantial for the DT, fair for the ESAS-r-D, and slight for the ESAS-r-A. Repeatability analyses indicated that the error range for the DT was more than 2 pts below/above actual measurement, whereas it was more than 3 pts for the ESAS-r-A, and 2.5 for the ESAS-r-D. Instability of the DT could be explained by changes in children’s physical QoL, but not by other components of QoL or life events. No moderators of stability could be identified for the ESAS-r items. Conclusions The DT appears to be a fairly stable measure when the respondent's condition is stable yet with a relatively wide error range. Fluctuations in distress-related constructs may affect the temporal stability of the DT. The lower stability of ESAS-r items may result from shorter time-lapse instructions resulting in a greater sensitivity to change. Findings support future research on the DT as a reliable instrument in caregivers. PMID:27454432

Diamond brecciation and annealing accompanying major metasomatism in eclogite xenoliths from the Sask Craton, Canada

NASA Astrophysics Data System (ADS)

Czas, Janina; Stachel, Thomas; Pearson, D. Graham; Stern, Richard A.; Read, George H.

2018-05-01

We studied eclogite xenoliths (diamond-free n = 28; diamondiferous n = 22) from the Cretaceous Fort à la Corne Kimberlite Field in Western Canada for their major element, trace element and oxygen isotope compositions to assess their origin and metasomatic history, and possible relationships between metasomatism and diamond formation. All eclogites have major element and oxygen isotope compositions consistent with a derivation from different levels of subducted, seawater altered oceanic crust. While barren xenoliths are more likely to be of gabbroic origin, diamond-bearing samples commonly have signatures consistent with shallow basaltic protoliths. The mineral chemistry in bimineralic diamond-free eclogites spans a wide compositional range, yet it is typically homogenous within individual xenoliths. Temperatures calculated from Mg-Fe exchange between garnet and clinopyroxene range widely for these eclogites, from 740 to 1300 °C, indicating the presence of eclogite through most of the lithospheric mantle. Diamondiferous samples are restricted to high temperatures (1180-1390 °C), consistent with derivation from the zone of diamond stability. Compositionally, diamond-bearing eclogites span a broad range similar to their barren counterparts, but there is also heterogeneity in mineral chemistry on the intra-sample level and in particular garnets are characterised by strong internal chemical gradients. This intra-sample heterogeneity is interpreted as the result of intense melt metasomatism, which occurred in temporal proximity to host kimberlite magmatism, strongly affected major, trace and even oxygen isotope values and resulted in diamond brecciation and annealing.

Development and validation of Big Four personality scales for the Schedule for Nonadaptive and Adaptive Personality--Second Edition (SNAP-2).

PubMed

Calabrese, William R; Rudick, Monica M; Simms, Leonard J; Clark, Lee Anna

2012-09-01

Recently, integrative, hierarchical models of personality and personality disorder (PD)--such as the Big Three, Big Four, and Big Five trait models--have gained support as a unifying dimensional framework for describing PD. However, no measures to date can simultaneously represent each of these potentially interesting levels of the personality hierarchy. To unify these measurement models psychometrically, we sought to develop Big Five trait scales within the Schedule for Nonadaptive and Adaptive Personality--Second Edition (SNAP-2). Through structural and content analyses, we examined relations between the SNAP-2, the Big Five Inventory (BFI), and the NEO Five-Factor Inventory (NEO-FFI) ratings in a large data set (N = 8,690), including clinical, military, college, and community participants. Results yielded scales consistent with the Big Four model of personality (i.e., Neuroticism, Conscientiousness, Introversion, and Antagonism) and not the Big Five, as there were insufficient items related to Openness. Resulting scale scores demonstrated strong internal consistency and temporal stability. Structural validity and external validity were supported by strong convergent and discriminant validity patterns between Big Four scale scores and other personality trait scores and expectable patterns of self-peer agreement. Descriptive statistics and community-based norms are provided. The SNAP-2 Big Four Scales enable researchers and clinicians to assess personality at multiple levels of the trait hierarchy and facilitate comparisons among competing big-trait models. PsycINFO Database Record (c) 2012 APA, all rights reserved.

Reliability and validity of the perspectives of Support From God Scale.

PubMed

Hamilton, Jill B; Crandell, Jamie L; Carter, J Kameron; Lynn, Mary R

2010-01-01

Existing spiritual support scales for use with cancer survivors focus on the support believed to come from a religious community, clergy, or health care providers. The objective of this study was to evaluate the reliability and validity of a new measure of spiritual support believed to come from God in older Christian African American cancer survivors. The Perceived Support From God Scale was administered to 317 African American cancer survivors aged 55-89 years. Psychometric evaluation involved identifying underlying factors, conducting item analysis and estimating reliability, and obtaining evidence on the relationship to other variables or the extent to which the Perceived Support From God Scale correlates with religious involvement and depression. The Perceived Support From God Scale consists of 15 items in two subscales (Support From God and God's Purpose for Me). The two subscales explained 59% of the variance. Cronbach's alpha coefficients were .94 and .86 for the Support From God and God's Purpose for Me subscales, respectively. Test-retest correlations were strong, supporting the temporal stability of the instrument. Pearson's correlations to an existing religious involvement and beliefs scale were moderate to strong. Subscale scores on Support From God were negatively correlated to depression. Initial support for reliability and validity was demonstrated for the Perceived Support From God Scale. The scale captures a facet of spirituality not emphasized in other measures. Further research is needed to evaluate the scale with persons of other racial/ethnic groups and to explore the relationship of spirituality to other outcome measures.

Development and Validation of Big Four Personality Scales for the Schedule for Nonadaptive and Adaptive Personality-2nd Edition (SNAP-2)

PubMed Central

Calabrese, William R.; Rudick, Monica M.; Simms, Leonard J.; Clark, Lee Anna

2012-01-01

Recently, integrative, hierarchical models of personality and personality disorder (PD)—such as the Big Three, Big Four and Big Five trait models—have gained support as a unifying dimensional framework for describing PD. However, no measures to date can simultaneously represent each of these potentially interesting levels of the personality hierarchy. To unify these measurement models psychometrically, we sought to develop Big Five trait scales within the Schedule for Adaptive and Nonadaptive Personality–2nd Edition (SNAP-2). Through structural and content analyses, we examined relations between the SNAP-2, Big Five Inventory (BFI), and NEO-Five Factor Inventory (NEO-FFI) ratings in a large data set (N = 8,690), including clinical, military, college, and community participants. Results yielded scales consistent with the Big Four model of personality (i.e., Neuroticism, Conscientiousness, Introversion, and Antagonism) and not the Big Five as there were insufficient items related to Openness. Resulting scale scores demonstrated strong internal consistency and temporal stability. Structural and external validity was supported by strong convergent and discriminant validity patterns between Big Four scale scores and other personality trait scores and expectable patterns of self-peer agreement. Descriptive statistics and community-based norms are provided. The SNAP-2 Big Four Scales enable researchers and clinicians to assess personality at multiple levels of the trait hierarchy and facilitate comparisons among competing “Big Trait” models. PMID:22250598

Watershed Scale Shear Stress From Tethersonde Wind Profile Measurements Under Near Neutral and Unstable Atmospheric Stability

NASA Astrophysics Data System (ADS)

Parlange, M. B.; Katul, G. G.

1995-04-01

Mean wind speed profiles were measured in the atmospheric surface layer, using a tethersonde system, above the Ojai Valley Watershed in southern California. The valley is mainly planted with mature avocado and orange trees. The surface shear stress and latent and sensible heat fluxes were measured above the trees which are up to 9 m in height. Near-neutral wind speed profile measurements allowed the determination of the watershed surface roughness (z0 = 1.4 m) and the momentum displacement height (d0 = 7.0 m). The wind speed measurements obtained under unstable atmospheric stability were analyzed using Monin-Obukhov similarity theory. New stability correction functions proposed based on theory and experiments of Kader-Yaglom as well as the now classic Businger-Dyer type functions were tested. The watershed shear stress values calculated using the surface layer wind speed profiles with the new Monin-Obukhov stability functions were found to be improved in comparison with the values obtained with the Businger-Dyer functions under strongly unstable stability conditions. The Monin-Obukhov model with the Businger-Dyer stability correction function underpredicted the momentum flux by 25% under strongly unstable stability conditions, while the new Kader-Yaglom formulation compared well on average (R2 = 0.77) with the surface eddy correlation measurements for all atmospheric stability conditions. The unstable 100-m drag coefficient was found to be u*2/V1002 = 0.0182.

Cortical Correlates of Binaural Temporal Processing Deficits in Older Adults.

PubMed

Eddins, Ann Clock; Eddins, David A

This study was designed to evaluate binaural temporal processing in young and older adults using a binaural masking level difference (BMLD) paradigm. Using behavioral and electrophysiological measures within the same listeners, a series of stimulus manipulations was used to evaluate the relative contribution of binaural temporal fine-structure and temporal envelope cues. We evaluated the hypotheses that age-related declines in the BMLD task would be more strongly associated with temporal fine-structure than envelope cues and that age-related declines in behavioral measures would be correlated with cortical auditory evoked potential (CAEP) measures. Thirty adults participated in the study, including 10 young normal-hearing, 10 older normal-hearing, and 10 older hearing-impaired adults with bilaterally symmetric, mild-to-moderate sensorineural hearing loss. Behavioral and CAEP thresholds were measured for diotic (So) and dichotic (Sπ) tonal signals presented in continuous diotic (No) narrowband noise (50-Hz wide) maskers. Temporal envelope cues were manipulated by using two different narrowband maskers; Gaussian noise (GN) with robust envelope fluctuations and low-noise noise (LNN) with minimal envelope fluctuations. The potential to use temporal fine-structure cues was controlled by varying the signal frequency (500 or 4000 Hz), thereby relying on the natural decline in phase-locking with increasing frequency. Behavioral and CAEP thresholds were similar across groups for diotic conditions, while the masking release in dichotic conditions was larger for younger than for older participants. Across all participants, BMLDs were larger for GN than LNN and for 500-Hz than for 4000-Hz conditions, where envelope and fine-structure cues were most salient, respectively. Specific age-related differences were demonstrated for 500-Hz dichotic conditions in GN and LNN, reflecting reduced binaural temporal fine-structure coding. No significant age effects were observed for 4000-Hz dichotic conditions, consistent with similar use of binaural temporal envelope cues across age in these conditions. For all groups, thresholds and derived BMLD values obtained using the behavioral and CAEP methods were strongly correlated, supporting the notion that CAEP measures may be useful as an objective index of age-related changes in binaural temporal processing. These results demonstrate an age-related decline in the processing of binaural temporal fine-structure cues with preserved temporal envelope coding that was similar with and without mild-to-moderate peripheral hearing loss. Such age-related changes can be reliably indexed by both behavioral and CAEP measures in young and older adults.

Implicit time accurate simulation of unsteady flow

NASA Astrophysics Data System (ADS)

van Buuren, René; Kuerten, Hans; Geurts, Bernard J.

2001-03-01

Implicit time integration was studied in the context of unsteady shock-boundary layer interaction flow. With an explicit second-order Runge-Kutta scheme, a reference solution to compare with the implicit second-order Crank-Nicolson scheme was determined. The time step in the explicit scheme is restricted by both temporal accuracy as well as stability requirements, whereas in the A-stable implicit scheme, the time step has to obey temporal resolution requirements and numerical convergence conditions. The non-linear discrete equations for each time step are solved iteratively by adding a pseudo-time derivative. The quasi-Newton approach is adopted and the linear systems that arise are approximately solved with a symmetric block Gauss-Seidel solver. As a guiding principle for properly setting numerical time integration parameters that yield an efficient time accurate capturing of the solution, the global error caused by the temporal integration is compared with the error resulting from the spatial discretization. Focus is on the sensitivity of properties of the solution in relation to the time step. Numerical simulations show that the time step needed for acceptable accuracy can be considerably larger than the explicit stability time step; typical ratios range from 20 to 80. At large time steps, convergence problems that are closely related to a highly complex structure of the basins of attraction of the iterative method may occur. Copyright

Transient hazard model using radar data for predicting debris flows in Madison County, Virginia

USGS Publications Warehouse

Morrissey, M.M.; Wieczorek, G.F.; Morgan, B.A.

2004-01-01

During the rainstorm of June 27, 1995, roughly 330-750 mm of rain fell within a 16-hour period, initiating floods and over 600 debris flows in a small area (130 km2) of Madison County, VA. We developed a distributed version of Iverson's transient response model for regional slope stability analysis for the Madison County debris flows. This version of the model evaluates pore-pressure head response and factor of safety on a regional scale in areas prone to rainfall-induced shallow (<2-3 m) landslides. These calculations used soil properties of shear strength and hydraulic conductivity from laboratory measurements of soil samples collected from field sites where debris flows initiated. Rainfall data collected by radar every 6 minutes provided a basis for calculating the temporal variation of slope stability during the storm. The results demonstrate that the spatial and temporal variation of the factor of safety correlates with the movement of the storm cell. When the rainstorm was treated as two separate rainfall events and a larger hydraulic conductivity and friction angle than the laboratory values were used, the timing and location of landslides predicted by the model were in closer agreement with eyewitness observations of debris flows. Application of spatially variable initial pre-storm water table depth and soil properties may improve both the spatial and temporal prediction of instability.