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1

Syllable acoustics, temporal patterns, and call composition vary with behavioral context in Mexican free-tailed bats  

PubMed Central

Recent research has shown that some bat species have rich vocal repertoires with diverse syllable acoustics. Few studies, however, have compared vocalizations across different behavioral contexts or examined the temporal emission patterns of vocalizations. In this paper, a comprehensive examination of the vocal repertoire of Mexican free-tailed bats, T. brasiliensis, is presented. Syllable acoustics and temporal emission patterns for 16 types of vocalizations including courtship song revealed three main findings. First, although in some cases syllables are unique to specific calls, other syllables are shared among different calls. Second, entire calls associated with one behavior can be embedded into more complex vocalizations used in entirely different behavioral contexts. Third, when different calls are composed of similar syllables, distinctive temporal emission patterns may facilitate call recognition. These results indicate that syllable acoustics alone do not likely provide enough information for call recognition; rather, the acoustic context and temporal emission patterns of vocalizations may affect meaning.

Bohn, Kirsten M.; Schmidt-French, Barbara; Ma, Sean T.; Pollak, George D.

2008-01-01

2

Writing magnetic patterns with surface acoustic waves  

NASA Astrophysics Data System (ADS)

A novel patterning technique that creates magnetization patterns in a continuous magnetostrictive film with surface acoustic waves is demonstrated. Patterns of 10 ?m wide stripes of alternating magnetization and a 3 ?m dot of reversed magnetization are written using standing and focusing acoustic waves, respectively. The magnetization pattern is size-tunable, erasable, and rewritable by changing the magnetic field and acoustic power. This versatility, along with its solid-state implementation (no moving parts) and electronic control, renders it as a promising technique for application in magnetic recording, magnonic signal processing, magnetic particle manipulation, and spatial magneto-optical modulation.

Li, Weiyang; Buford, Benjamin; Jander, Albrecht; Dhagat, Pallavi

2014-05-01

3

Segregation of complex acoustic scenes based on temporal coherence  

PubMed Central

In contrast to the complex acoustic environments we encounter everyday, most studies of auditory segregation have used relatively simple signals. Here, we synthesized a new stimulus to examine the detection of coherent patterns (‘figures’) from overlapping ‘background’ signals. In a series of experiments, we demonstrate that human listeners are remarkably sensitive to the emergence of such figures and can tolerate a variety of spectral and temporal perturbations. This robust behavior is consistent with the existence of automatic auditory segregation mechanisms that are highly sensitive to correlations across frequency and time. The observed behavior cannot be explained purely on the basis of adaptation-based models used to explain the segregation of deterministic narrowband signals. We show that the present results are consistent with the predictions of a model of auditory perceptual organization based on temporal coherence. Our data thus support a role for temporal coherence as an organizational principle underlying auditory segregation. DOI: http://dx.doi.org/10.7554/eLife.00699.001

Teki, Sundeep; Chait, Maria; Kumar, Sukhbinder; Shamma, Shihab; Griffiths, Timothy D

2013-01-01

4

Analysis of Temporal Pattern of Swallowing Mechanism  

Microsoft Academic Search

This paper presents an objective method for analysis of temporal pattern of swallowing mechanism based on analysis of swallowing sounds and submental surface electromyogram (EMG). In this study, swallowing sound signal and submental EMG of 12 healthy subjects were recorded. Swallowing sound signals were divided into 25 millisecond segments each of which was represented by waveform fractal dimension (WED). Temporal

Mohammad Aboofazeli; Zahra Moussavi

2006-01-01

5

Spontaneous pattern formation in an acoustical resonator  

NASA Astrophysics Data System (ADS)

A dynamical system of equations describing parametric sound generation (PSG) in a dispersive large aspect ratio resonator is derived. The model generalizes previously proposed descriptions of PSG by including diffraction effects and is analogous to the model used in theoretical studies of optical parametric oscillation. A linear stability analysis of the solution below the threshold of subharmonic generation reveals the existence of a pattern forming instability, which is confirmed by numerical integration. The conditions of emergence of periodic patterns in transverse space are discussed in the acoustical context.

Sánchez-Morcillo, V. J.

2004-01-01

6

Auditory analysis of spectro-temporal information in acoustic signals  

Microsoft Academic Search

Acoustic signals are often characterized by pitch, timbre, loudness, forms of modulation, and onset\\/offset instants. These descriptors of sound quality have a close relationship to the instantaneous spectral properties of the sound waves. The auditory system has developed elegant mechanisms to extract and represent this spectro-temporal information through noise-robust perceptual features. After decades of research, the anatomical organization and functional

Kuansan Wang; Shihab A. Shamma

1995-01-01

7

Auditory Temporal Pattern Discrimination and Reading Ability  

ERIC Educational Resources Information Center

The relation between reading ability and performance on an auditory temporal pattern discrimination task was investigated in children who were either good or delayed readers. The stimuli in the primary task consisted of sequences of tones, alternating between high and low frequencies. The threshold interstimulus interval (ISI) for discrimination…

McAnally, Ken I.; Castles, Anne; Bannister, Susan

2004-01-01

8

SOME TEMPORAL CHARACTERISTICS OF VISUAL PATTERN PERCEPTION  

Microsoft Academic Search

VISUAL STIMULI WERE CONSTRUCTED SO THAT ANY GIVEN STIMULUS BY ITSELF APPEARED TO BE A RANDOM COLLECTION OF DOTS. HOWEVER, WHEN 2 CORRESPONDING STIMULI WERE SUPERIMPOSED BY MEANS OF A 2-FIELD TACHISTOSCOPE, A 3-LETTER NONSENSE SYLLABLE WAS PERCEIVED. TEMPORAL ORGANIZATION IN PERCEPTION WAS STUDIED IN EXP. I BY VARYING THE INTERVAL BETWEEN THE PRESENTATION OF THE 2 CORRESPONDING PATTERNS OVER

CHARLES W. ERIKSEN; JAMES F. COLLINS

1967-01-01

9

Mining Surprising Patterns Using Temporal Description Length  

Microsoft Academic Search

We propose a new notion of surprising temporal patternsin market basket data, and algorithms to find suchpatterns. This is distinct from finding frequent patterns asaddressed in the common mining literature. We argue thatonce the analyst is already familiar with prevalent patternsin the data, the greatest incremental benefit is likely to befrom changes in the relationship between item frequenciesover time.A simple

Soumen Chakrabarti; Sunita Sarawagi; Byron Dom

1998-01-01

10

Spatial and temporal analysis of landscape patterns  

Microsoft Academic Search

A variety of ecological questions now require the study of large regions and the understanding of spatial heterogeneity. Methods\\u000a for spatial-temporal analyses are becoming increasingly important for ecological studies. A grid cell based spatial analysis\\u000a program (SPAN) is described and results of landscape pattern analysis using SPAN are presentedd. Several ecological topics\\u000a in which geographic information systems (GIS) can play

Monica G. Turner

1990-01-01

11

Effective vertical beam patterns for ocean acoustic reverberation calculations  

Microsoft Academic Search

A description is given of a concept for using effective vertical beam patterns to perform reverberation calculations in underwater acoustics when the source or receiver has both horizontal and vertical directivity. The concept involves integrating the 3-D beam pattern B (?, ?) over azimuthal angles ? to obtain an effective vertical beam pattern that depends only on the vertical angle

Dale D. Ellis

1991-01-01

12

A Pattern Mining Approach for Classifying Multivariate Temporal Data.  

PubMed

We study the problem of learning classification models from complex multivariate temporal data encountered in electronic health record systems. The challenge is to define a good set of features that are able to represent well the temporal aspect of the data. Our method relies on temporal abstractions and temporal pattern mining to extract the classification features. Temporal pattern mining usually returns a large number of temporal patterns, most of which may be irrelevant to the classification task. To address this problem, we present the minimal predictive temporal patterns framework to generate a small set of predictive and non-spurious patterns. We apply our approach to the real-world clinical task of predicting patients who are at risk of developing heparin induced thrombocytopenia. The results demonstrate the benefit of our approach in learning accurate classifiers, which is a key step for developing intelligent clinical monitoring systems. PMID:22267987

Batal, Iyad; Valizadegan, Hamed; Cooper, Gregory F; Hauskrecht, Milos

2011-11-12

13

Temporal Patterns of Behavior from the Scheduling of Psychology Quizzes  

ERIC Educational Resources Information Center

Temporal patterns of behavior have been observed in real-life performances such as bill passing in the U.S. Congress, in-class studying, and quiz taking. However, the practical utility of understanding these patterns has not been evaluated. The current study demonstrated the presence of temporal patterns of quiz taking in a university-level…

Jarmolowicz, David P.; Hayashi, Yusuke; St. Peter Pipkin, Claire

2010-01-01

14

Investigation of acoustic streaming patterns around oscillating sharp edges.  

PubMed

Oscillating sharp edges have been employed to achieve rapid and homogeneous mixing in microchannels using acoustic streaming. Here, we used a perturbation approach to study the flow around oscillating sharp edges in a microchannel. This work extends prior experimental studies to numerically characterize the effect of various parameters on the acoustically induced flow. Our numerical results match well with the experimental results. We investigated multiple device parameters such as the tip angle, oscillation amplitude, and channel dimensions. Our results indicate that, due to the inherent nonlinearity of acoustic streaming, the channel dimensions could significantly impact the flow patterns and device performance. PMID:24903475

Nama, Nitesh; Huang, Po-Hsun; Huang, Tony Jun; Costanzo, Francesco

2014-08-01

15

Temporal patterns of behavior from the scheduling of psychology quizzes.  

PubMed

Temporal patterns of behavior have been observed in real-life performances such as bill passing in the U.S. Congress, in-class studying, and quiz taking. However, the practical utility of understanding these patterns has not been evaluated. The current study demonstrated the presence of temporal patterns of quiz taking in a university-level introductory psychology course and used these patterns to manage the traffic of quiz takers in a computerized testing lab. Results are discussed in terms of the applications of tracking temporal response patterns. PMID:21119904

Jarmolowicz, David P; Hayashi, Yusuke; Pipkin, Claire St Peter

2010-01-01

16

Mining temporal patterns in popularity of web items  

Microsoft Academic Search

Huge amounts of various web items (e.g., images, keywords, and web pages) are being made available on the Web. The popularity of such web items continuously changes over time, and mining for temporal patterns in the popularity of web items is an important problem that is useful for several Web applications; for example, the temporal patterns in the popularity of

Woong-Kee Loh; Sandeep Mane; Jaideep Srivastava

2011-01-01

17

Temporal pattern mining for multivarite clinical decision support.  

PubMed

Multivariate temporal data are collections of contiguous data values that reflect complex temporal changes over a given duration. Technological advances have resulted in significant amounts of such data in high-throughput disciplines, including EEG and iEEG data for effective and efficient healthcare informatics, and decision support. Most data analytics and data-mining algorithms are effective in capturing global trends, but fail to capture localized behavioral changes in large temporal data sets. We present a two-step algorithmic methodology to uncover temporal patterns and exploiting them for an efficient and accurate decision support system. This methodology aids the discovery of previously unknown, nontrivial, and potentially useful temporal patterns for enhanced patient-specific clinical decision support with high degrees of sensitivity and specificity. Classification results on multivariate time series iEEG data for epileptic seizure detection also demonstrate the efficacy and accuracy of the technique to uncover interesting and effective domain class-specific temporal patterns. PMID:23921002

Saini, Sheetal; Dua, Sumeet

2013-01-01

18

Gradient sensitivity to acoustic detail and temporal integration of phonetic cues  

NASA Astrophysics Data System (ADS)

Speech contains systematic covariation at the subphonemic level that could be used to integrate information over time (McMurray et al., 2003; Gow, 2001). Previous research has established sensitivity to this variation: activation for lexical competitors is sensitive to within-category variation in voice-onset-time (McMurray et al., 2002). This study extends this investigation to other subphonemic speech cues by examining formant transitions (r/l and d/g), formant slope (b/w) and VOT (b/p) in an eye-tracking paradigm similar to McMurray et al. (2002). Vowel length was also varied to examine temporal organization (e.g., VOT precedes the vowel). Subjects heard a token from each continua and selected the target from a screen containing pictures of the target, competitor and unrelated items. Fixations to the competitor increased with distance from the boundary along each of the speech continua. Unlike prior work, there was also an effect on fixations to the target. There was no effect of vowel length on the d/g or r/l continua, but rate dependent continua (b/w and b/p) showed length effects. Importantly, the temporal order of cues was reflected in the pattern of looks to competitors, providing an important window into the processes by which acoustic detail is temporally integrated.

McMurray, Bob; Clayards, Meghan A.; Aslin, Richard N.; Tanenhaus, Michael K.

2001-05-01

19

Detection of temporal patterns in dog–human interaction  

Microsoft Academic Search

A new time structure model and pattern detection procedures developed by (Magnusson, M.S., 1996. Hidden real-time patterns in intra- and inter-individual behaviour description and detection. Eur. J. Psychol. Assess. 12, 112–123; Magnusson, M.S., 2000. Discovering hidden time patterns in behaviour: T-patterns and their detection. Behav. Res. Methods, Instrum. Comput. 32, 93–110) enables us to detect complex temporal patterns in behaviour.

A. Kerepesi; G. K. Jonsson; Á. Miklósi; J. Topál; V. Csányi; M. S. Magnusson

2005-01-01

20

How temporal frequency affects global form coherence in Glass patterns.  

PubMed

Glass patterns are textural moirés from random dots. Sequential presentation of Glass patterns induces a sense of illusory motion. We evaluated how changes in temporal frequency affected the detection of global form in Glass patterns. We found linear improvement in coherence thresholds with increasing temporal frequency (Experiment 1), particularly in stimuli with large dot-pair separations (Experiment 2). These results support the notion that temporal and orientation information sum to boost sensitivity to visually obscure objects, and are discussed within the framework of "motion streak" detectors. PMID:24325849

Day, Annie M; Palomares, Melanie

2014-02-01

21

1987 WET DEPOSITION TEMPORAL AND SPATIAL PATTERNS IN NORTH AMERICA  

EPA Science Inventory

The focus of this report is on North American wet deposition temporal patterns from 1979 to 1987 and spatial patterns for 1987. he report investigates the patterns of annual precipitation-weighted average concentration and annual deposition for nine ion species: hydrogen, sulfate...

22

Tunable Nanowire Patterning Using Standing Surface Acoustic Waves  

PubMed Central

Patterning of nanowires in a controllable, tunable manner is important for the fabrication of functional nanodevices. Here we present a simple approach for tunable nanowire patterning using standing surface acoustic waves (SSAW). This technique allows for the construction of large-scale nanowire arrays with well-controlled patterning geometry and spacing within 5 seconds. In this approach, SSAWs were generated by interdigital transducers (IDTs), which induced a periodic alternating current (AC) electric field on the piezoelectric substrate and consequently patterned metallic nanowires in suspension. The patterns could be deposited onto the substrate after the liquid evaporated. By controlling the distribution of the SSAW field, metallic nanowires were assembled into different patterns including parallel and perpendicular arrays. The spacing of the nanowire arrays could be tuned by controlling the frequency of the surface acoustic waves. Additionally, we observed 3D spark-shape nanowire patterns in the SSAW field. The SSAW-based nanowire-patterning technique presented here possesses several advantages over alternative patterning approaches, including high versatility, tunability, and efficiency, making it promising for device applications.

Chen, Yuchao; Ding, Xiaoyun; Lin, Sz-Chin Steven; Yang, Shikuan; Huang, Po-Hsun; Nama, Nitesh; Zhao, Yanhui; Nawaz, Ahmad Ahsan; Guo, Feng; Wang, Wei; Gu, Yeyi; Mallouk, Thomas E.; Huang, Tony Jun

2014-01-01

23

Dynamic perfusion patterns in temporal lobe epilepsy  

Microsoft Academic Search

Purpose  To investigate dynamic ictal perfusion changes during temporal lobe epilepsy (TLE).\\u000a \\u000a \\u000a \\u000a Methods  We investigated 37 patients with TLE by ictal and interictal SPECT. All ictal injections were performed within 60 s of seizure\\u000a onset. Statistical parametric mapping was used to analyse brain perfusion changes and temporal relationships with injection\\u000a time and seizure duration as covariates.\\u000a \\u000a \\u000a \\u000a Results  The analysis revealed significant ictal hyperperfusion in

Patrick Dupont; John J. Zaknun; Alex Maes; Supatporn Tepmongkol; Silvia Vasquez; C. S. Bal; Wim Van Paesschen; Silvina Carpintiero; Chaichon Locharernkul; Maurizio Dondi

2009-01-01

24

Finding Spatio-Temporal Patterns in Large Sensor Datasets  

ERIC Educational Resources Information Center

Spatial or temporal data mining tasks are performed in the context of the relevant space, defined by a spatial neighborhood, and the relevant time period, defined by a specific time interval. Furthermore, when mining large spatio-temporal datasets, interesting patterns typically emerge where the dataset is most dynamic. This dissertation is…

McGuire, Michael Patrick

2010-01-01

25

Information flow and temporal coding in primate pattern vision  

Microsoft Academic Search

We perform time-resolved calculations of the information transmitted about visual patterns by neurons in primary visual and inferior temporal cortices. All measurable information is carried in an effective time-varying firing rate, obtained by averaging the neuronal response with a resolution no finer than about 25 ms in primary visual cortex and around twice that in inferior temporal cortex. We found

Joshua Heller; John A. Hertz; Troels W. Kjær; Barry J. Richmond

1995-01-01

26

Temporal Patterns of Communication in the Workplace  

ERIC Educational Resources Information Center

In this dissertation, we report on results of an in-depth observational study to understand the temporal dimension of communication in the workplace. By employing the "shadowing" method for in situ to-the-second data gathering of information workers' behaviors, we gained a detailed snapshot of informants' workdays, "warts and all." Our…

Su, Norman Makoto

2009-01-01

27

Spatial, Temporal and Spatio-Temporal Patterns of Maritime Piracy  

PubMed Central

Objectives: To examine patterns in the timing and location of incidents of maritime piracy to see whether, like many urban crimes, attacks cluster in space and time. Methods: Data for all incidents of maritime piracy worldwide recorded by the National Geospatial Intelligence Agency are analyzed using time-series models and methods originally developed to detect disease contagion. Results: At the macro level, analyses suggest that incidents of pirate attacks are concentrated in five subregions of the earth’s oceans and that the time series for these different subregions differ. At the micro level, analyses suggest that for the last 16 years (or more), pirate attacks appear to cluster in space and time suggesting that patterns are not static but are also not random. Conclusions: Much like other types of crime, pirate attacks cluster in space, and following an attack at one location the risk of others at the same location or nearby is temporarily elevated. The identification of such regularities has implications for the understanding of maritime piracy and for predicting the future locations of attacks.

Marchione, Elio

2013-01-01

28

VISUALIZATION OF SPATIO-TEMPORAL PATTERNS IN PUBLIC TRANSPORT DATA  

Microsoft Academic Search

In this paper, we discuss geovisualization techniques to explore spatio-temporal patterns formed by people traveling through public transport system (PTS). The Spatio-temporal reasoning by PTS operators\\/policy makers to extract patterns from public transport system data is studied. The resulting questions are related to basic visual tasks like locate, identify, associate and compare. These visual tasks are incorporated in a set

Menno-Jan Kraak

29

Perfusion patterns during temporal lobe seizures: relationship to surgical outcome.  

PubMed

We sought to determine whether patterns of ictal hyperfusion demonstrated using [99mTC]HMPAO (hexamethylpropylene amine oxime) single photon emission computed tomography (SPECT) predict outcome of temporal lobectomy; in particular, whether the more extensive patterns of ictal hyperperfusion are associated with poor outcome. We studied 63 patients who had ictal SPECT studies prior to temporal lobectomy. Hyperperfusion on ictal SPECT scans was lateralized, and classified into: (i) 'typical', (ii) 'typical with posterior extension', (iii) 'bilateral' and (iv) 'atypical' patterns. Outcome (minimum of 2 years follow-up) was classified as either seizure free, or not seizure free. Actuarial analysis was used to test the relationship of SPECT patterns with outcome. There were 35 cases with the typical ictal SPECT pattern, 13 posterior, nine bilateral and six atypical cases. The atypical pattern was associated with lack of pathology in the surgical specimen. Outcome was similar for the typical, posterior and bilateral with 60%, 69% and 67% seizure free, respectively. In contrast, the atypical group had a worse outcome with only 33% seizure free. Actuarial analysis showed a significant difference in outcome between patients with the typical pattern, and patients with the atypical pattern (P = 0.04). We conclude that extended patterns of ictal perfusion in temporal lobe epilepsy do not predict poor outcome, indicating that extended hyperperfusion probably represents seizure propagation pathways rather than intrinsically epileptogenic tissue. Atypical patterns of hyperperfusion are associated with poor outcome and may indicate diffuse or extra-temporal epileptogenicity. PMID:9397011

Ho, S S; Newton, M R; McIntosh, A M; Kalnins, R M; Fabinyi, G C; Brazenor, G A; McKay, W J; Bladin, P F; Berkovic, S F

1997-11-01

30

Learning of timing patterns and the development of temporal expectations.  

PubMed

The present study investigated the learning of a culturally unfamiliar musical rhythm, leading to the development of temporal expectations, and it explored the potential for generalization across tempi and tasks. With that aim, we adapted the serial reaction time task to examine the learning of temporal structures by an indirect method. The temporal pattern employed was based on a complex interval ratio (2:3) and compared to one based on a simple interval ratio (1:2). In the exposure phase, non-musician participants performed a two-choice speeded discrimination task that required responding by key press to each event of the simple or complex auditory pattern. Participants were not informed about the temporal regularities; their task solely concerned the discrimination task. During exposure (Experiments 1-3), response times decreased over time for both temporal patterns, but particularly for the events following the longer interval of the more complex 2:3 pattern. Exposure further influenced performance in subsequent testing phases, notably the precision of tap timing in a production task (Experiment 2) and temporal expectations in a perception task (Experiment 3). Our findings promote the new paradigm introduced here as a method to investigate the learning of temporal structures. PMID:20683612

Tillmann, Barbara; Stevens, Catherine; Keller, Peter E

2011-05-01

31

Sequential temporo-fronto-temporal activation during monitoring of the auditory environment for temporal patterns.  

PubMed

Subjects detected rarely occurring shifts between two simple tone-patterns, in a paradigm that dissociated the effects of rarity from those of pitch, habituation, and attention. Whole-head magnetoencephalography suggested that rare attended pattern-shifts evoked activity first in the superior temporal plane (sTp, peak ~100 ms), then superior temporal sulcus (sTs, peak ~130 ms), then posteroventral prefrontal (pvpF, peak ~230 ms), and anterior temporal cortices (aT, peak ~370 ms). Activity was more prominent in the right hemisphere. After subtracting the effects of nonshift tones (balanced for pitch and habituation status), weak but consistent differential effects of pattern-shifts began in aT at 90-130 ms, spread to sTs and sTp at ?130 ms, then pvpF, and finally returned to aT. Cingulate activity resembled prefrontal. Responses to pattern shifts were greatly attenuated when the same stimuli were ignored, suggesting that the initial superior temporal activity reflected an attention-related mismatch negativity. The prefrontal activity at ~230 ms corresponded in latency and task correlates with simultaneously recorded event-related potential components N2b and P3a; the subsequent temporal activity corresponded to the P3b. These results were confirmed in sensors specific for frontal or temporal cortex, and thus are independent of the inverse method used. Overall, these results suggest that auditory working memory for temporal patterns begins with detection of the pattern change by an interaction of anterior and superior temporal structures, followed by identification of the event and its consequences led by posteroventral prefrontal and cingulate cortices, and finally, definitive encoding of the event in anterior temporal areas. PMID:20665718

Halgren, Eric; Sherfey, Jason; Irimia, Andrei; Dale, Anders M; Marinkovic, Ksenija

2011-08-01

32

Identification of cylindrical shells with sets of reinforcing ribs by their acoustic Bragg diffraction (grating) patterns  

Microsoft Academic Search

The authors present a basic study of the acoustic Bragg diffraction patterns produced by gratings with various types of slits, which are insonified by (monochromatic) acoustic waves of various frequencies. Given the spacing in between the slits, the (Bragg) angular diffraction pattern generated by the grating can be predicted by the method of physical optics (acoustics), and can be numerically

Donald Brill; Guillermo C. Gaunaurd

1995-01-01

33

Temporal and Spatial Patterns of Gene Profiles during Chondrogenic Differentiation.  

PubMed

Clustering analysis based on temporal profile of genes may provide new insights in particular biological processes or conditions. We report such an integrative clustering analysis which is based on the expression patterns but is also influenced by temporal changes. The proposed platform is illustrated with a temporal gene expression dataset comprised of pellet culture-conditioned human primary chondrocytes and human bone marrow-derived mesenchymal stem cells (MSCs). We derived three clusters in each cell type and compared the content of these classes in terms of temporal changes. We further considered the induced biological processes and the gene-interaction networks formed within each cluster and discuss their biological significance. Our proposed methodology provides a consistent tool that facilitates both the statistical and biological validation of temporal profiles through spatial gene network profiles. PMID:24808223

Skreti, G; Bei, E S; Kalantzaki, K; Zervakis, M

2014-05-01

34

Temporal integration of acoustic stimulation obtained in reflex inhibition in rats and humans  

Microsoft Academic Search

Investigated whether inhibition provided by initial stimuli of various durations conforms to established temporal integration functions. Initial stimuli (S1) were noise bursts varying in duration (2, 20, or 200 msec) and intensity (55 or 85 db). Eliciting stimuli (S2) for 6 Holtzman rats were intense tone bursts, which elicited the acoustic startle reflex, and for 9 19–24 yr old humans

Benjamin M. Dykman; James R. Ison

1979-01-01

35

Detecting Multineuronal Temporal Patterns in Parallel Spike Trains  

PubMed Central

We present a non-parametric and computationally efficient method that detects spatiotemporal firing patterns and pattern sequences in parallel spike trains and tests whether the observed numbers of repeating patterns and sequences on a given timescale are significantly different from those expected by chance. The method is generally applicable and uncovers coordinated activity with arbitrary precision by comparing it to appropriate surrogate data. The analysis of coherent patterns of spatially and temporally distributed spiking activity on various timescales enables the immediate tracking of diverse qualities of coordinated firing related to neuronal state changes and information processing. We apply the method to simulated data and multineuronal recordings from rat visual cortex and show that it reliably discriminates between data sets with random pattern occurrences and with additional exactly repeating spatiotemporal patterns and pattern sequences. Multineuronal cortical spiking activity appears to be precisely coordinated and exhibits a sequential organization beyond the cell assembly concept.

Gansel, Kai S.; Singer, Wolf

2012-01-01

36

Detecting multineuronal temporal patterns in parallel spike trains.  

PubMed

We present a non-parametric and computationally efficient method that detects spatiotemporal firing patterns and pattern sequences in parallel spike trains and tests whether the observed numbers of repeating patterns and sequences on a given timescale are significantly different from those expected by chance. The method is generally applicable and uncovers coordinated activity with arbitrary precision by comparing it to appropriate surrogate data. The analysis of coherent patterns of spatially and temporally distributed spiking activity on various timescales enables the immediate tracking of diverse qualities of coordinated firing related to neuronal state changes and information processing. We apply the method to simulated data and multineuronal recordings from rat visual cortex and show that it reliably discriminates between data sets with random pattern occurrences and with additional exactly repeating spatiotemporal patterns and pattern sequences. Multineuronal cortical spiking activity appears to be precisely coordinated and exhibits a sequential organization beyond the cell assembly concept. PMID:22661942

Gansel, Kai S; Singer, Wolf

2012-01-01

37

Finding Spatio-Temporal Patterns in Earth Science Data  

Microsoft Academic Search

This paper presents preliminary work in using data mining techniques to find interesting spatio-temporal patterns from Earth Science data. The data consists of time series measurements for various Earth science and climate variables (e.g. soil moisture, temperature, and precipitation), along with additional data from existing ecosystem models (e.g. Net Primary Production). The ecological patterns of interest include associations, clusters, predictive

Pang-Ning Tan; Michael Steinbach; Vipin Kumar; Christopher Potter; Steven Klooster; Alicia Torregrosa

2001-01-01

38

1988 Wet deposition temporal and spatial patterns in North America  

SciTech Connect

The focus of this report is on North American wet deposition temporal patterns from 1979 to 1988 and spatial patterns for 1988. It is the third in a series of reports that investigate the patterns of annual precipitation-weighted average concentration and annual deposition for nine ion species: hydrogen, sulfate, nitrate, ammonium, calcium, chloride, sodium, potassium, and magnesium. Mosaic maps, based on surface estimation using kriging, display concentration and deposition spatial patterns of pH, hydrogen, sulfate, nitrate, ammonium, and calcium ion species for 1988 annual, winter, and summer periods. Temporal pattern analyses use a subset of 35 sites over a 10-year (1979--1988) period and an expanded subset of 137 sites, with greater spatial coverage, over a 7-year (1982--1988) period. The 10-year period represents the longest period with wet deposition monitoring data available that has a sufficient number of sites with data of known quality to allow a descriptive summary of annual temporal patterns. Sen`s median trend estimate and Kendall`s seasonal tau (KST) test are calculated for each ion species concentration and deposition at each site in both subsets.

Simpson, J.C.; Olsen, A.R.; Bittner, E.A.

1992-03-01

39

1988 Wet deposition temporal and spatial patterns in North America  

SciTech Connect

The focus of this report is on North American wet deposition temporal patterns from 1979 to 1988 and spatial patterns for 1988. It is the third in a series of reports that investigate the patterns of annual precipitation-weighted average concentration and annual deposition for nine ion species: hydrogen, sulfate, nitrate, ammonium, calcium, chloride, sodium, potassium, and magnesium. Mosaic maps, based on surface estimation using kriging, display concentration and deposition spatial patterns of pH, hydrogen, sulfate, nitrate, ammonium, and calcium ion species for 1988 annual, winter, and summer periods. Temporal pattern analyses use a subset of 35 sites over a 10-year (1979--1988) period and an expanded subset of 137 sites, with greater spatial coverage, over a 7-year (1982--1988) period. The 10-year period represents the longest period with wet deposition monitoring data available that has a sufficient number of sites with data of known quality to allow a descriptive summary of annual temporal patterns. Sen's median trend estimate and Kendall's seasonal tau (KST) test are calculated for each ion species concentration and deposition at each site in both subsets.

Simpson, J.C.; Olsen, A.R.; Bittner, E.A.

1992-03-01

40

A SIMPLE HETERODYNE TEMPORAL SPECKLE-PATTERN INTERFEROMETER  

SciTech Connect

A common light path design of heterodyne speckle pattern interferometer based on temporal speckle pattern interferometry is proposed for non-contact, full-field and real-time continuous displacement measurement. Double frequency laser is produced by rotating a half wave plate. An experiment was carried out to measure the dynamic displacement of a cantilever plate for testing the proposed common path heterodyne speckle pattern interferometer. The accuracy of displacement measurement was checked by measuring the motion at the mid-point of the plate with a point displacement sensor.

Wong, W. O.; Gao, Z.; Lu, J. [Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong)

2010-05-28

41

1986 wet deposition temporal and spatial patterns in North America  

SciTech Connect

The focus of this report is on North American wet deposition temporal patterns from 1979 to 1986 and spatial patterns for 1986. The report provides statistical distribution summaries of annual precipitation-weighted average concentration and annual deposition for nine ion species: hydrogen, sulfate, nitrate, ammonium, calcium, chloride, sodium, potassium, and magnesium. The data in the report are from the Acid Depositing System (ADS) for the statistical reporting of North American deposition data. Isopleth maps, based on surface estimation using kriging, display concentration and deposition spatial patterns of pH, hydrogen, sulfate, nitrate, ammonium, and calcium ion species for 1986 annual, winter, and summer periods. The temporal pattern analyses use a subset of 30 sites over an 8-year (1979-1986) period and an expanded subset of 137 sites with greater spatial coverage over a 5-year (1982-1986) period. The 8-year period represents the longest period with wet deposition monitoring data unavailable that has a sufficient number of sites with data of known quality to allow a descriptive summary of annual temporal patterns. 19 refs., 105 figs., 29 tabs.

Olsen, A.R.

1989-07-01

42

High-frequency acoustic observations of benthic spatial and temporal variability  

NASA Astrophysics Data System (ADS)

A bottom-mounted sonar operating at 40 kHz has been used to measure the variation of bottom acoustic scattering over extended time intervals at two shallow sites as part of the Coastal Benthic Boundary Layer Special Research Project. The acoustic data were analyzed using a correlation method that measures the spatial and temporal dependence of benthic change. The rate of decorrelation was two orders of magnitude more rapid at a sandy site near Panama City, Florida, USA, than at a silty site in Eckernförde Bay, Germany, and both sites were characterized by hot spots or localized regions of activity.

Jackson, Darrell R.; Williams, Kevin L.; Briggs, Kevin B.

1996-09-01

43

Spatial and temporal patterns in conterminous United States streamflow characteristics  

NASA Astrophysics Data System (ADS)

Spatial and temporal patterns in annual and seasonal minimum, mean, and maximum daily streamflow values were examined for a set of 516 reference streamgages located throughout the conterminous United States for the period 1950 to 2010. First, cluster analysis was used to classify the streamgages into eight groups according to similarity in their temporal patterns. Standardized departure values (z-scores) of the flow metrics then were computed for each region and the associations between the annual metrics and well-known climate indices (NINO3.4, PDO, PNA, AMO, NAO) were determined. The results indicated that the temporal patterns in flow metrics (1) have strong spatial coherence within each region; (2) vary significantly among the regions; (3) are similar among the three annual flow metrics and the four seasonal flow metrics within each region; and (4) are only weakly associated with the tested climate indices. We conclude that most of the temporal variability in flow is unpredictable in terms of relations to climate indices and infer that future changes in flow characteristics cannot be predicted by these indices.

Wolock, D.; McCabe, G. J.

2012-12-01

44

Spatio-temporal characteristics of acoustic emission during the deformation of rock samples with compressional and extensional en-echelon faults  

Microsoft Academic Search

The spatio-temporal characteristics of acoustic emission (AE) during the deformation of rock samples with compressional and\\u000a extensional en-echelon faults have been studied. The results show that the pre-existing structure can significantly influence\\u000a the patterns of AE spatial distribution. With increasing of differential stress, AE events firstly cluster around the two\\u000a ends of pre-existing faults inside the jog and then along

Hai-Kun Jiang; Shengli Ma; Liu Zhang; Hai-Feng Hou; Wen-Hai Cao

2002-01-01

45

Speaker recognition with temporal cues in acoustic and electric hearing  

NASA Astrophysics Data System (ADS)

Natural spoken language processing includes not only speech recognition but also identification of the speaker's gender, age, emotional, and social status. Our purpose in this study is to evaluate whether temporal cues are sufficient to support both speech and speaker recognition. Ten cochlear-implant and six normal-hearing subjects were presented with vowel tokens spoken by three men, three women, two boys, and two girls. In one condition, the subject was asked to recognize the vowel. In the other condition, the subject was asked to identify the speaker. Extensive training was provided for the speaker recognition task. Normal-hearing subjects achieved nearly perfect performance in both tasks. Cochlear-implant subjects achieved good performance in vowel recognition but poor performance in speaker recognition. The level of the cochlear implant performance was functionally equivalent to normal performance with eight spectral bands for vowel recognition but only to one band for speaker recognition. These results show a disassociation between speech and speaker recognition with primarily temporal cues, highlighting the limitation of current speech processing strategies in cochlear implants. Several methods, including explicit encoding of fundamental frequency and frequency modulation, are proposed to improve speaker recognition for current cochlear implant users.

Vongphoe, Michael; Zeng, Fan-Gang

2005-08-01

46

Impaired extraction of speech rhythm from temporal modulation patterns in speech in developmental dyslexia  

PubMed Central

Dyslexia is associated with impaired neural representation of the sound structure of words (phonology). The “phonological deficit” in dyslexia may arise in part from impaired speech rhythm perception, thought to depend on neural oscillatory phase-locking to slow amplitude modulation (AM) patterns in the speech envelope. Speech contains AM patterns at multiple temporal rates, and these different AM rates are associated with phonological units of different grain sizes, e.g., related to stress, syllables or phonemes. Here, we assess the ability of adults with dyslexia to use speech AMs to identify rhythm patterns (RPs). We study 3 important temporal rates: “Stress” (~2 Hz), “Syllable” (~4 Hz) and “Sub-beat” (reduced syllables, ~14 Hz). 21 dyslexics and 21 controls listened to nursery rhyme sentences that had been tone-vocoded using either single AM rates from the speech envelope (Stress only, Syllable only, Sub-beat only) or pairs of AM rates (Stress + Syllable, Syllable + Sub-beat). They were asked to use the acoustic rhythm of the stimulus to identity the original nursery rhyme sentence. The data showed that dyslexics were significantly poorer at detecting rhythm compared to controls when they had to utilize multi-rate temporal information from pairs of AMs (Stress + Syllable or Syllable + Sub-beat). These data suggest that dyslexia is associated with a reduced ability to utilize AMs <20 Hz for rhythm recognition. This perceptual deficit in utilizing AM patterns in speech could be underpinned by less efficient neuronal phase alignment and cross-frequency neuronal oscillatory synchronization in dyslexia. Dyslexics' perceptual difficulties in capturing the full spectro-temporal complexity of speech over multiple timescales could contribute to the development of impaired phonological representations for words, the cognitive hallmark of dyslexia across languages.

Leong, Victoria; Goswami, Usha

2014-01-01

47

Impaired extraction of speech rhythm from temporal modulation patterns in speech in developmental dyslexia.  

PubMed

Dyslexia is associated with impaired neural representation of the sound structure of words (phonology). The "phonological deficit" in dyslexia may arise in part from impaired speech rhythm perception, thought to depend on neural oscillatory phase-locking to slow amplitude modulation (AM) patterns in the speech envelope. Speech contains AM patterns at multiple temporal rates, and these different AM rates are associated with phonological units of different grain sizes, e.g., related to stress, syllables or phonemes. Here, we assess the ability of adults with dyslexia to use speech AMs to identify rhythm patterns (RPs). We study 3 important temporal rates: "Stress" (~2 Hz), "Syllable" (~4 Hz) and "Sub-beat" (reduced syllables, ~14 Hz). 21 dyslexics and 21 controls listened to nursery rhyme sentences that had been tone-vocoded using either single AM rates from the speech envelope (Stress only, Syllable only, Sub-beat only) or pairs of AM rates (Stress + Syllable, Syllable + Sub-beat). They were asked to use the acoustic rhythm of the stimulus to identity the original nursery rhyme sentence. The data showed that dyslexics were significantly poorer at detecting rhythm compared to controls when they had to utilize multi-rate temporal information from pairs of AMs (Stress + Syllable or Syllable + Sub-beat). These data suggest that dyslexia is associated with a reduced ability to utilize AMs <20 Hz for rhythm recognition. This perceptual deficit in utilizing AM patterns in speech could be underpinned by less efficient neuronal phase alignment and cross-frequency neuronal oscillatory synchronization in dyslexia. Dyslexics' perceptual difficulties in capturing the full spectro-temporal complexity of speech over multiple timescales could contribute to the development of impaired phonological representations for words, the cognitive hallmark of dyslexia across languages. PMID:24605099

Leong, Victoria; Goswami, Usha

2014-01-01

48

Network-based comparison of temporal gene expression patterns  

PubMed Central

Motivation: In the pursuits of mechanistic understanding of cell differentiation, it is often necessary to compare multiple differentiation processes triggered by different external stimuli and internal perturbations. Available methods for comparing temporal gene expression patterns are limited to a gene-by-gene approach, which ignores co-expression information and thus is sensitive to measurement noise. Methods: We present a method for co-expression network based comparison of temporal expression patterns (NACEP). NACEP compares the temporal patterns of a gene between two experimental conditions, taking into consideration all of the possible co-expression modules that this gene may participate in. The NACEP program is available at http://biocomp.bioen.uiuc.edu/nacep. Results: We applied NACEP to analyze retinoid acid (RA)-induced differentiation of embryonic stem (ES) cells. The analysis suggests that RA may facilitate neural differentiation by inducing the shh and insulin receptor pathways. NACEP was also applied to compare the temporal responses of seven RNA inhibition (RNAi) experiments. As proof of concept, we demonstrate that the difference in the temporal responses to RNAi treatments can be used to derive interaction relationships of transcription factors (TFs), and therefore infer regulatory modules within a transcription network. In particular, the analysis suggested a novel regulatory relationship between two pluripotency regulators, Esrrb and Tbx3, which was supported by in vivo binding of Esrrb to the promoter of Tbx3. Availability: The NACEP program and the supplementary documents are available at http://biocomp.bioen.uiuc.edu/nacep. Contact: szhong@illinois.edu Supplementary information: Supplementary data are available at Bioinformatics online.

Huang, Wei; Cao, Xiaoyi; Zhong, Sheng

2010-01-01

49

Atherosclerotic plaque characterization by spatial and temporal speckle pattern analysis  

NASA Astrophysics Data System (ADS)

Improved methods are needed to identify the vulnerable coronary plaques responsible for acute myocardial infraction or sudden cardiac death. We describe a method for characterizing the structure and biomechanical properties of atherosclerotic plaques based on speckle pattern fluctuations. Near-field speckle images were acquired from five human aortic specimens ex vivo. The speckle decorrelation time constant varied significantly for vulnerable aortic plaques (? = 40 ms) versus stable plaques (? = 400 ms) and normal aorta (? = 500 ms). These initial results indicate that different atherosclerotic plaque types may be distinguished by analysis of temporal and spatial speckle pattern fluctuations.

Tearney, Guillermo J.; Bouma, Brett E.

2002-04-01

50

1987 wet deposition temporal and spatial patterns in North America  

SciTech Connect

The focus of this report is on North American wet deposition temporal patterns from 1979 to 1987 and spatial patterns for 1987. The report investigates the patterns of annual precipitation-weighted average concentration and annual deposition for nine ion species: hydrogen, sulfate, nitrate, ammonium, calcium, chloride, sodium, potassium, and magnesium. Data are from the Acid Deposition System (ADS) for the statistical reporting of North American deposition data which includes the National Atmospheric Deposition Program/National Trends Network (NADP/NTN), the MAP3S precipitation chemistry network, the Utility Acid Precipitation Study Program (UAPSP), the Canadian Precipitation Monitoring Network (CAPMoN), and the daily and 4-weekly Acidic Precipitation in Ontario Study (APIOS-D and APIOS-C). Mosaic maps, based on surface estimation using kriging, display concentration and deposition spatial patterns of pH, hydrogen, sulfate, nitrate, ammonium, and calcium ion species for 1987 annual, winter, and summer periods. The temporal pattern analyses use a subset of 39 sites over a 9-year (1979--1987) period and an expanded subset of 140 sites with greater spatial coverage over a 6-year (1982--1987) period. 68 refs., 15 figs., 15 tabs.

Simpson, J.C.; Olsen, A.R.

1990-03-01

51

Spatiotemporal patterns of acoustic emission (AE) activity in salt mine  

NASA Astrophysics Data System (ADS)

Assessing the magnitude of completeness (Mc) is essential for the correct interpretation of earthquake catalogs. Knowledge on the spatiotemporal variation of Mc allows the mapping of other seismicity parameters, such as b-values. Spatial and temporal variations of b-values can indicate structural heterogeneities, stress perturbations and time-dependent fracturing processes. In order to precisely estimate Mc in strongly heterogeneous media, we propose a 3D development of the probabilistic magnitude of completeness (PMC) method, which relies on the analysis of network detection capabilities, to study spatial distribution of the Mc and b-value estimations for mining networks. We used a large dataset including more than 1 million acoustic emissions (AE), recorded at the Morsleben salt mine, Germany. Our study shows that the PMC estimations strongly depend on the source-receiver direction, and cannot be correctly accounted using a standard approach. The comparison between Mc using the 3D PMC method and Gutenberg-Richter methods show agreements for two reference depth ranges. Following our approach, we estimate Mc ranging between 1.25 (AE ,relative acoustic magnitude), at the center of the network, and 3.5, at further distances outside the network. Our method provides small-scale details about the capability of sensors to detect an AE event, and spatial distributions of Mc and b-value, which can be linked to the presence of structural heterogeneities or cavities in specific directions. Effects of heterogeneities on detection analysis are confirmed by synthetic tests using waveform modeling in heterogeneous media. This work has been funded by the German BMBF "Geotechnologien" project MINE (BMBF03G0737A).

Maghsoudi, S.; Cesca, S.; Hainzl, S.; Kaiser, D.; Dahm, T.

2012-04-01

52

Acoustic droplet-hydrogel composites for spatial and temporal control of growth factor delivery and scaffold stiffness  

PubMed Central

Wound healing is regulated by temporally and spatially restricted patterns of growth factor signaling, but there are few delivery vehicles capable of the “on-demand” release necessary for recapitulating these patterns. Recently we described a perfluorocarbon double emulsion that selectively releases a protein payload upon exposure to ultrasound through a process known as acoustic droplet vaporization (ADV). In this study, we describe a delivery system composed of fibrin hydrogels doped with growth factor-loaded double emulsion for applications in tissue regeneration. Release of immunoreactive basic fibroblast growth factor (bFGF) from the composites increased up to 5-fold following ADV and delayed release was achieved by delaying exposure to ultrasound. Releasates of ultrasound-treated materials significantly increased the proliferation of endothelial cells compared to sham controls, indicating that the released bFGF was bioactive. ADV also triggered changes in the ultrastructure and mechanical properties of the fibrin as bubble formation and consolidation of the fibrin in ultrasound-treated composites were accompanied by up to a 22-fold increase in shear stiffness. ADV did not reduce the viability of cells suspended in composite scaffolds. These results demonstrate that an acoustic droplet–hydrogel composite could have broad utility in promoting wound healing through on-demand control of growth factor release and/or scaffold architecture.

Fabiilli, Mario L.; Wilson, Christopher G.; Padilla, Frederic; Martin-Saavedra, Francisco M.; Fowlkes, J. Brian; Franceschi, Renny T.

2013-01-01

53

Acoustic droplet-hydrogel composites for spatial and temporal control of growth factor delivery and scaffold stiffness.  

PubMed

Wound healing is regulated by temporally and spatially restricted patterns of growth factor signaling, but there are few delivery vehicles capable of the "on-demand" release necessary for recapitulating these patterns. Recently we described a perfluorocarbon double emulsion that selectively releases a protein payload upon exposure to ultrasound through a process known as acoustic droplet vaporization (ADV). In this study, we describe a delivery system composed of fibrin hydrogels doped with growth factor-loaded double emulsion for applications in tissue regeneration. Release of immunoreactive basic fibroblast growth factor (bFGF) from the composites increased up to 5-fold following ADV and delayed release was achieved by delaying exposure to ultrasound. Releasates of ultrasound-treated materials significantly increased the proliferation of endothelial cells compared to sham controls, indicating that the released bFGF was bioactive. ADV also triggered changes in the ultrastructure and mechanical properties of the fibrin as bubble formation and consolidation of the fibrin in ultrasound-treated composites were accompanied by up to a 22-fold increase in shear stiffness. ADV did not reduce the viability of cells suspended in composite scaffolds. These results demonstrate that an acoustic droplet-hydrogel composite could have broad utility in promoting wound healing through on-demand control of growth factor release and/or scaffold architecture. PMID:23535233

Fabiilli, Mario L; Wilson, Christopher G; Padilla, Frédéric; Martín-Saavedra, Francisco M; Fowlkes, J Brian; Franceschi, Renny T

2013-07-01

54

Melatonin affects the temporal pattern of vocal signatures in birds.  

PubMed

In humans and other animals, melatonin is involved in the control of circadian biological rhythms. Here, we show that melatonin affects the temporal pattern of behavioral sequences in a noncircadian manner. The zebra finch (Taeniopygia guttata) song and the crow of the Japanese quail (Coturnix japonica) are courtship vocalizations composed of a stereotyped sequence of syllables. The zebra finch song is learned from conspecifics during infancy, whereas the Japanese quail crow develops normally without auditory input. We recorded and analyzed the complete vocal activity of adult birds of both species kept in social isolation for several weeks. In both species, we observed a shortening of signal duration following the transfer from a light-dark (LD) cycle to constant light (LL), a condition known to abolish melatonin production and to disrupt circadian rhythmicity. This effect was reversible because signal duration increased when the photoperiod was returned to the previous LD schedule. We then tested whether this effect was directly related to melatonin by removal of the pineal gland, which is the main production site of circulating melatonin. A shortening of the song duration was observed following pinealectomy in LD. Likewise, melatonin treatment induced changes in the temporal structure of the song. In a song learning experiment, young pinealectomized finches and young finches raised in LL failed to copy the temporal pattern of their tutor's song. Taken together, these results suggest that melatonin is involved in the control of motor timing of noncircadian behavioral sequences through an evolutionary conserved neuroendocrine pathway. PMID:22506964

Derégnaucourt, Sébastien; Saar, Sigal; Gahr, Manfred

2012-10-01

55

Temporal patterns of transient-evoked otoacoustic emissions in normal and impaired cochleae.  

PubMed

The spatial distribution of outer hair cells that participate in generating transient-EOE frequency-components has been investigated in man. According to several models (e.g. Wilson (1990) Hear. Res. 2, 527-532; Zwicker (1986) J. Acoust. Soc. Am. 80, 154-162; Wilson and Kemp (Eds.), Cochlear Mechanisms, Structures, Functions and Models, Plenum Press, NY), EOEs result from interferences between broadly distributed contributions, responsible for their long frequency-dependent delay. This work presents an analysis of the temporal patterns of click- and tone-burst-EOEs in human ears when contributions to EOEs are reduced by noise-induced lesions with audiometric notches centred around 4 kHz (N = 46). Although the auditory thresholds at the frequencies of the studied EOE-components were always normal, these components exhibited drastic and predictable changes compared to normal control ears (N = 40). (1) Their temporal pattern at the highest EOE frequency fmax just below the audiometric notch appeared to be determined by the cochlear state at high frequencies (6 to 8 kHz). Either it was normal and the EOE exhibited a complicated beat-structure, or it was impaired and the time envelope of the EOE was simple. In contrast, any type of time pattern could be observed in normal ears. (2) The temporal patterns of EOEs one octave below fmax always presented many beats and short delays. The proposed interpretation is that contributions to a transient-EOE component at frequency f can come from distant basal cochlear areas, i.e. more than 1 and sometimes 1.5 octaves from the place tuned to f. Therefore, the possible relationships between transient-EOEs and tuning mechanisms which presumably involve only a small number of OHC need further investigations. PMID:8276727

Avan, P; Bonfils, P; Loth, D; Wit, H P

1993-10-01

56

A temporal fourth-order scheme for the first-order acoustic wave equations  

NASA Astrophysics Data System (ADS)

In this paper, we propose a temporal fourth-order scheme for solving the 2-D first-order acoustic wave equations with perfectly matched layers in time domain. For the temporal discretization, we approximate the velocity at mid-points and the pressure at grid points, then expand the velocity and pressure by Taylor series and replace the high-order temporal derivatives by spatial derivatives. For the spatial discretization, we apply the Fourier pseudospectral method based on conventional and staggered-grid schemes. The dispersion and stability of the new scheme are analysed, and numerical simulations are presented to confirm the robustness and efficiency of the scheme. The new scheme is eventually applied for the wavefield modelling and reverse time migration in bilayered and heterogeneous media to further verify its accuracy and efficiency.

Long, Guihua; Zhao, Yubo; Zou, Jun

2013-09-01

57

Patterns of Urban Violent Injury: A Spatio-Temporal Analysis  

PubMed Central

Objectives Injury related to violent acts is a problem in every society. Although some authors have examined the geography of violent crime, few have focused on the spatio-temporal patterns of violent injury and none have used an ambulance dataset to explore the spatial characteristics of injury. The purpose of this study was to describe the combined spatial and temporal characteristics of violent injury in a large urban centre. Methodology/Principal Findings Using a geomatics framework and geographic information systems software, we studied 4,587 ambulance dispatches and 10,693 emergency room admissions for violent injury occurrences among adults (aged 18–64) in Toronto, Canada, during 2002 and 2004, using population-based datasets. We created kernel density and choropleth maps for 24-hour periods and four-hour daily time periods and compared location of ambulance dispatches and patient residences with local land use and socioeconomic characteristics. We used multivariate regressions to control for confounding factors. We found the locations of violent injury and the residence locations of those injured were both closely related to each other and clearly clustered in certain parts of the city characterised by high numbers of bars, social housing units, and homeless shelters, as well as lower household incomes. The night and early morning showed a distinctive peak in injuries and a shift in the location of injuries to a “nightlife” district. The locational pattern of patient residences remained unchanged during those times. Conclusions/Significance Our results demonstrate that there is a distinctive spatio-temporal pattern in violent injury reflected in the ambulance data. People injured in this urban centre more commonly live in areas of social deprivation. During the day, locations of injury and locations of residences are similar. However, later at night, the injury location of highest density shifts to a “nightlife” district, whereas the residence locations of those most at risk of injury do not change.

Cusimano, Michael; Marshall, Sean; Rinner, Claus; Jiang, Depeng; Chipman, Mary

2010-01-01

58

Inferring Synaptic Connectivity from Spatio-Temporal Spike Patterns  

PubMed Central

Networks of well-known dynamical units but unknown interaction topology arise across various fields of biology, including genetics, ecology, and neuroscience. The collective dynamics of such networks is often sensitive to the presence (or absence) of individual interactions, but there is usually no direct way to probe for their existence. Here we present an explicit method for reconstructing interaction networks of leaky integrate-and-fire neurons from the spike patterns they exhibit in response to external driving. Given the dynamical parameters are known, the approach works well for networks in simple collective states but is also applicable to networks exhibiting complex spatio-temporal spike patterns. In particular, stationarity of spiking time series is not required.

Van Bussel, Frank; Kriener, Birgit; Timme, Marc

2011-01-01

59

Reconstructing spatial and temporal patterns of paleoglaciation across Central Asia  

NASA Astrophysics Data System (ADS)

Understanding the behaviour of mountain glaciers and ice caps, the evolution of mountain landscapes, and testing global climate models all require well-constrained information on past spatial and temporal patterns of glacier change. Particularly important are transitional regions that have high spatial and temporal variation in glacier activity and that can provide a sensitive record of past climate change. Central Asia is an extreme continental location with glaciers that have responded sensitively to variations in major regional climate systems. As an international team, we are reconstructing glacial histories of several areas of the Tibetan Plateau as well as along the Tian Shan, Altai and Kunlun Mountains. Building on previous work, we are using remote sensing-based geomorphological mapping augmented with field observations to map out glacial landforms and the maximum distributions of erratics. We then use cosmogenic nuclide Be-10 and Al-26, optically stimulated luminescence, and electron spin resonance dating of moraines and other landforms to compare dating techniques and to constrain the ages of defined extents of paleo-glaciers and ice caps. Comparing consistently dated glacial histories across central Asia provides an opportunity to examine shifts in the dominance patterns of climate systems over time in the region. Results to date show significant variations in the timing and extent of glaciation, including areas in the southeast Tibetan Plateau and Tian Shan with extensive valley and small polythermal ice cap glaciation during the global last glacial maximum in contrast to areas in central and northeast Tibetan Plateau that had very limited valley glacier expansion then. Initial numerical modelling attempting to simulate mapped and dated paleoglacial extents indicates that relatively limited cooling is sufficient to produce observed past expansions of glaciers across the Tibetan Plateau, and predicts complex basal thermal regimes in some locations that match patterns of past glacial erosion inferred from landform patterns and ages. Future modelling will examine glacier behaviour along major mountain ranges across central Asia.

Stroeven, Arjen P.

2014-05-01

60

Simulating component-to-pattern dynamic effects with a computer model of middle temporal pattern neurons.  

PubMed

Some primate motion-sensitive middle temporal (MT) neurons respond best to motion orthogonal to a contour's orientation (component types) whereas another class (pattern type) responds maximally to the overall pattern motion. We have previously developed a model of the pattern-type neurons using integration of the activity generated in speed- and direction-tuned subunits. However, a number of other models have also been able to replicate MT neuron pattern-like behavior using a diverse range of mechanisms. This basic property does not really challenge or help discriminate between the different model types. There exist two sets of findings that we believe provide a better yardstick against which to assess MT pattern models. Some MT neurons have been shown to change from component to pattern behavior over brief time intervals. MT neurons have also been observed to switch from component- to pattern-like behavior when the intensity of the intersections in a plaid pattern stimulus changes. These properties suggest more complex time- and contrast-sensitive internal mechanisms underlying pattern motion extraction, which provide a real challenge for modelers. We have now replicated these two component-to-pattern effects using our MT pattern model. It incorporates two types of V1 neurons (sustained and transient), and these have slightly different time delays; this initially favors the component response, thus mimicking the temporal effects. We also discovered that some plaid stimuli contain a contrast asymmetry that depends on the plaid direction and the intensity of the intersections. This causes the model MT pattern units to act as component units. PMID:24453345

Perrone, John A; Krauzlis, Richard J

2014-01-01

61

Bacterial colonization of Hydra hatchlings follows a robust temporal pattern  

PubMed Central

Animals are colonized by complex bacterial communities. The processes controlling community membership and influencing the establishment of the microbial ecosystem during development are poorly understood. Here we aimed to explore the assembly of bacterial communities in Hydra with the broader goal of elucidating the general rules that determine the temporal progression of bacterial colonization of animal epithelia. We profiled the microbial communities in polyps at various time points after hatching in four replicates. The composition and temporal patterns of the bacterial communities were strikingly similar in all replicates. Distinct features included high diversity of community profiles in the first week, a remarkable but transient adult-like profile 2 weeks after hatching, followed by progressive emergence of a stable adult-like pattern characterized by low species diversity and the preponderance of the Betaproteobacterium Curvibacter. Intriguingly, this process displayed important parallels to the assembly of human fecal communities after birth. In addition, a mathematical modeling approach was used to uncover the organizational principles of this colonization process, suggesting that both, local environmental or host-derived factor(s) modulating the colonization rate, as well as frequency-dependent interactions of individual bacterial community members are important aspects in the emergence of a stable bacterial community at the end of development.

Franzenburg, Soren; Fraune, Sebastian; Altrock, Philipp M; Kunzel, Sven; Baines, John F; Traulsen, Arne; Bosch, Thomas CG

2013-01-01

62

Measurement resolution of noise directivity patterns from acoustic flight tests  

NASA Technical Reports Server (NTRS)

The measurement resolution of noise directivity patterns from acoustic flight tests was investigated. Directivity angle resolution is affected by the data reduction parameters, the aircraft velocity and flyover altitude, and by deviations of the aircraft from the desired flight path. Equations are developed which determine bounds for the lateral and longitudinal directivity angle resolution as a function of the nominal directivity angle. The equations are applied to a flight test data base and the effects of several flight conditions and data reduction parameters on the directivity angle resolution are presented. The maximum directivity angle resolution typically occurs when the aircraft is at or near the overhead position. In general, directivity angle resolution improves with decreasing velocity, increasing altitude, increasing sampling rate, decreasing block size, and decreasing block averages. Deviations from the desired ideal flight path will increase the resolution. For the flight experiment considered in this study, an average of two flyovers were required at each test condition to obtain an acceptable flight path. The ability of the pilot to maintain the flight track improved with decreasing altitude, decreasing velocity, and practice. Due to the prevailing wind conditions, yaw angles of as much as 20 deg were required to maintain the desired flight path.

Conner, David A.

1989-01-01

63

Acoustic temporal modulation detection and speech perception in cochlear implant listeners1  

PubMed Central

The goals of the present study were to measure acoustic temporal modulation transfer functions (TMTFs) in cochlear implant listeners and examine the relationship between modulation detection and speech recognition abilities. The effects of automatic gain control, presentation level and number of channels on modulation detection thresholds (MDTs) were examined using the listeners’ clinical sound processor. The general form of the TMTF was low-pass, consistent with previous studies. The operation of automatic gain control had no effect on MDTs when the stimuli were presented at 65 dBA. MDTs were not dependent on the presentation levels (ranging from 50 to 75 dBA) nor on the number of channels. Significant correlations were found between MDTs and speech recognition scores. The rates of decay of the TMTFs were predictive of speech recognition abilities. Spectral-ripple discrimination was evaluated to examine the relationship between temporal and spectral envelope sensitivities. No correlations were found between the two measures, and 56% of the variance in speech recognition was predicted jointly by the two tasks. The present study suggests that temporal modulation detection measured with the sound processor can serve as a useful measure of the ability of clinical sound processing strategies to deliver clinically pertinent temporal information.

Won, Jong Ho; Drennan, Ward R.; Nie, Kaibao; Jameyson, Elyse M.; Rubinstein, Jay T.

2011-01-01

64

Acoustic measurements during holmium:YAG laser ablation of cadaveric human temporal bone: preliminary observations  

NASA Astrophysics Data System (ADS)

Pulsed IR and UV lasers have been suggested for use in middle ear surgery due to decreased thermal trauma, precise ablation characteristics, and potential fiberoptic delivery. While there has been much focus on the thermal and photoacoustic events that occur during pulsed laser ablation of hard tissue, there are few studies that look at the acoustic energy generated from these devices from an audiologic standpoint. In this study, the mastoid cavities of cadaveric human temporal bones were irradiated with a Ho:YAG laser (lambda equals 2.12 micrometer) with the following parameters: 5, 10, and 15 Hz pulse repetition rate and 1, 2, 4, 6, 8, and 10 W average power. During ablation, acoustic measurements were made using a sound level meter held 5 cm away from the target site. With each set of laser parameters, the sound intensity (dB SPL) exceeded 85 dB. Peak intensity measurements of 125 dB were measured, and a saturation effect was noted above 4 W or 500 mJ/pulse. The clinical significance of these findings is discussed and the acoustical aspects of middle ear function and noise trauma are reviewed.

Wong, Brian J.; Gibbs, Lisa; Neev, Joseph; Shanks, Janet

1997-05-01

65

Spatial and Temporal Patterns of Eastern Australia Subtropical Coral Communities  

PubMed Central

Despite increases in the frequency and intensity of disturbances on coral reefs over the past few decades, the response of subtropical coral assemblages to climate change is poorly understood. To address this knowledge gap on Australian reefs and provide a baseline for future comparisons, we quantified spatial (10-100’s of kilometres) and temporal (decadal) patterns of benthic assemblages across a latitudinal gradient along the east Australian coastline (23.5° S to 31.5° S). Benthic community composition was quantified at six locations from the southern Great Barrier Reef, Queensland (Heron Reef, 23.5° S, 152° E) to northern New South Wales (31° S, 153.1° E) and at Lord Howe Island (31.5° S, 159.1° E). Our results indicate significant latitudinal differences in benthic assemblages, while community composition at some sites was more similar to those hundreds of kilometres away than to that of neighbouring reefs. A general trend was observed with decreasing cover of Acroporidae with increasing latitude, corresponding with an increasing cover of Pocilloporidae and Dendrophylliidae. Heron Reef comprised a high proportion of Acropora corals (43% total coral cover) and coralline algae (44%). In contrast, high-latitude reefs were dominated by mixed coral assemblages (0-52%) and high macroalgal cover (16-27%). Decadal comparisons of high-latitude reefs showed regional stability of benthic assemblages (9 out of 11 assemblages remained stable at > 75% similarity), during a period of warming oceans (0.15-0.24°C per decade). Such temporal stability suggests that eastern Australian subtropical communities may be more resistant than tropical reef communities that have experienced assembly shifts caused by perturbations associated with recent global climate change. Despite the clear differences in the structure of coral assemblages evident in our spatial surveys, we suggest that the temporal stability of high-latitude reefs may provide a limited refuge for tropical coral populations in an increasingly uncertain future.

Dalton, Steven J.; Roff, George

2013-01-01

66

Temporal patterns of solar eclipses on areostationary relay satellites  

NASA Astrophysics Data System (ADS)

Mars Areostationary Relay Satellites are considered robust candidates to meet the telecommunications needs of the coming set of Mars science missions. Orbital station-keeping manoeuvres are required to compensate natural perturbations on the areostationary orbit. This paper deals on the pattern description of solar eclipses in the areostationary orbit to allow to test the constrain imposed by the impossibility to perform manoeuvres at the eclipse times. We present here the models used to characterize the two eclipse epochs around the spring and autumn equinoxes over a Martian year. In average, each eclipse season lasts 90 sols in eclipse with a daily maxima duration of about 1 h 18 min plus 2 min 54 s of penumbra. Temporal duration of solar eclipses with different values near to zero inclination and different satellite orbit nodes has been also analyzed.

Romero, P.; Antolín, R.

2014-09-01

67

Spatio-Temporal Pattern of Saturn's Equatorial Oscillation  

NASA Technical Reports Server (NTRS)

Recent ground-based and Cassini CIRS thermal-infrared data have characterized the spatial and temporal characteristics of an equatorial oscillation in the middle atmosphere of Saturn above the 100-mbar level. The CIRS data [I] indicated a pattern of warm and cold anomalies near the equator, stacked vertically in alternating fashion. The ground-based observations s2, although not having the altitude range or vertical resolution of the CIRS observations, covered several years and indicated an oscillation cycle of approx.15 years, roughly half of Saturn's year. In Earth's middle atmosphere, both the quasi-biennial (approx.26 months) and semi-annual equatorial oscillations have been extensively observed and studied (see e.g., [3]), These exhibit a pattern of alternating warmer and cooler zonal-mean temperatures with altitude, relative to those at subtropical latitudes. Consistent with the thermal wind equation, this is also associated with an alternating pattern of westerly and easterly zonal winds. Moreover, the pattern of winds and temperatures descends with time. Momentum deposition by damped vertically propagating waves is thought to play a key role m forcing both types of oscillation, and it can plausibly account for the descent. Here we report the direct observation of this descent in Saturn's equatorial atmosphere from Cassini radio occultation soundings in 2005 and 2009. The retrieved temperatures are consistent with a descent of 0.7 x the pressure scale height. The descent rate is related to the magnitude of the wave forcing, radiative damping, and induced meridional circulations. We discuss possible implications.

Flasar, F. M.; Schnider, P. J.; Marouf, E. A.; McGhee, C. A.; Kliore, A. J.; Rappaport, N. J.

2010-01-01

68

A Visual Interface for Multivariate Temporal Data: Finding Patterns of Events across Multiple Histories  

Microsoft Academic Search

Finding patterns of events over time is important in searching patient histories, web logs, news stories, and criminal activities. This paper presents PatternFinder, an integrated interface for query and result-set visualization for search and discovery of temporal patterns within multivariate and categorical data sets. We define temporal patterns as sequences of events with inter- event time spans. PatternFinder allows users

Jerry Alan Fails; Amy K. Karlson; Layla Shahamat; Ben Shneiderman

2006-01-01

69

Tunable patterning of microparticles and cells using standing surface acoustic waves  

PubMed Central

We have developed an acoustic-based tunable patterning technique by which microparticles or cells can be arranged into reconfigurable patterns in microfluidic channels. In our approach, we use pairs of slanted-finger interdigital transducers (SFITs) to generate a tunable standing surface acoustic wave field, which in turn patterns microparticles or cells in one/two-dimensional arrays inside the microfluidic channels—all without the assistance of fluidic flow. By tuning the frequency of the input signal applied to the SFITs, we have shown that the cell pattern can be controlled with the tunability of up to 72%. This acoustic-based tunable patterning technique has the advantages of wide tunability, non-invasiveness, and ease of integration to lab-on-a-chip systems, and shall be valuable in many biological and colloidal studies.

Ding, Xiaoyun; Shi, Jinjie; Lin, Sz-Chin Steven; Yazdi, Shahrzad; Kiraly, Brian; Huang, Tony Jun

2014-01-01

70

The BMP signaling gradient patterns dorsoventral tissues in a temporally progressive manner along the anteroposterior axis  

PubMed Central

Summary Patterning of the vertebrate anteroposterior (AP) axis proceeds temporally from anterior to posterior. How dorsoventral (DV) axial patterning relates to AP temporal patterning is unknown. We examined the temporal activity of BMP signaling in patterning ventrolateral cell fates along the AP axis, using transgenes that rapidly turn ‘off’ or ‘on’ BMP signaling. We show that BMP signaling patterns rostral DV cell fates at the onset of gastrulation, while progressively more caudal DV cell fates are patterned at progressively later intervals during gastrulation. Increased BMP signal duration is not required to pattern more caudal DV cell fates, rather distinct temporal intervals of signaling are required. This progressive action is regulated downstream of, or in parallel to BMP signal transduction at the level of Smad1/5 phosphorylation. We propose that a temporal cue regulates a cell's competence to respond to BMP signaling, allowing the acquisition of a cell's DV and AP identity simultaneously.

Tucker, Jennifer A.; Mintzer, Keith A.; Mullins, Mary C.

2008-01-01

71

Spatio-Temporal Pattern Recognition Using Hidden Markov Models.  

National Technical Information Service (NTIS)

A new spatio-temporal method for identifying 3D objects found in 2D image sequences is presented. The Hidden Markov Model technique is used as a spatio-temporal classification algorithm to identify 3D objects by the temporal changes in observed shape feat...

K. H. Fielding

1994-01-01

72

Theoretical Analysis of Shear Wave Interference Patterns by Means of Dynamic Acoustic Radiation Forces  

PubMed Central

Acoustic radiation forces associated with high intensity focused ultrasound stimulate shear wave propagation allowing shear wave speed and shear viscosity estimation of tissue structures. As wave speeds are meters per second, real time displacement tracking over an extend field-of-view using ultrasound is problematic due to very high frame rate requirements. However, two spatially separated dynamic external sources can stimulate shear wave motion leading to shear wave interference patterns. Advantages are shear waves can be imaged at lower frame rates and local interference pattern spatial properties reflect tissue’s viscoelastic properties. Here a theoretical analysis of shear wave interference patterns by means of dynamic acoustic radiation forces is detailed. Using a viscoelastic Green’s function analysis, tissue motion due to a pair of focused ultrasound beams and associated radiation forces are presented. Overall, this paper theoretically demonstrates shear wave interference patterns can be stimulated using dynamic acoustic radiation forces and tracked using conventional ultrasound imaging.

Hoyt, Kenneth

2011-01-01

73

Temporal coherent and total intensity fluctuation of mid-frequency acoustic wave propagation during SWAT 2000 experiment  

NASA Astrophysics Data System (ADS)

Temporal coherent and total intensity fluctuations of acoustic wave propagation have been measured during SWAT (Shallow Water Acoustic Technology) 2000 Experiment data. The objective of this paper is to investigate the effect of the temporal fluctuation of an acoustic signal in shallow water. The acoustic propagation experiment was carried out among the three bottom mounted sonar towers, that were located in a triangle formed by 3, 4 and 5 km ranges. The center frequency of the acoustic signal is 5.5 kHz. A total of 32 hours acoustic data was sampled by a 2 min or 20 min sampling interval. In addition, oceanographic data including current velocity profile data and sound speed data is used to estimate the internal wave activity on the observation triangle. The time series of coherent intensity quickly attenuates, while the total intensity is maintained with weak fluctuation. According to the reciprocal transmission data, the reciprocity of coherent intensity is significantly distorted by the existence of a large internal wave, while the total intensity retains the reciprocity. The characteristics of these quantities are discussed by using the PE (Parabolic Equation) model. [Work supported by ONR 321OA, NIRE, and MEST.

Yamaoka, Haruhiko; Yamamoto, Tokuo

2003-04-01

74

Detection of Acoustic Temporal Fine Structure by Cochlear Implant Listeners: Behavioral Results and Computational Modeling  

PubMed Central

A test of within-channel detection of acoustic temporal fine structure (aTFS) cues is presented. Eight cochlear implant listeners (CI) were asked to discriminate between two Schroeder-phase (SP) complexes using a two-alternative, forced-choice task. Because differences between the acoustic stimuli are primarily constrained to their aTFS, successful discrimination reflects a combination of the subjects’ perception of and the strategy’s ability to deliver aTFS cues. Subjects were mapped with single-channel Continuous Interleaved Sampling (CIS) and Simultaneous Analog Stimulation (SAS) strategies. To compare within- and across- channel delivery of aTFS cues, a 16-channel clinical HiRes strategy was also fitted. Throughout testing, SAS consistently outperformed the CIS strategy (p ? 0.002). For SP stimuli with F0 =50 Hz, the highest discrimination scores were achieved with the HiRes encoding, followed by scores with the SAS and the CIS strategies, respectively. At 200 Hz, single-channel SAS performed better than HiRes (p = 0.022), demonstrating that under a more challenging testing condition, discrimination performance with a single-channel analog encoding can exceed that of a 16-channel pulsatile strategy. To better understand the intermediate steps of discrimination, a biophysical model was used to examine the neural discharges evoked by the SP stimuli. Discrimination estimates calculated from simulated neural responses successfully tracked the behavioral performance trends of single-channel CI listeners.

Imennov, Nikita S.; Won, Jong Ho; Drennan, Ward R.; Jameyson, Elyse; Rubinstein, Jay T.

2013-01-01

75

Temporal Patterns of Diversification across Global Cichlid Biodiversity (Acanthomorpha: Cichlidae)  

PubMed Central

The contrasting distribution of species diversity across the major lineages of cichlids makes them an ideal group for investigating macroevolutionary processes. In this study, we investigate whether different rates of diversification may explain the disparity in species richness across cichlid lineages globally. We present the most taxonomically robust time-calibrated hypothesis of cichlid evolutionary relationships to date. We then utilize this temporal framework to investigate whether both species-rich and depauperate lineages are associated with rapid shifts in diversification rates and if exceptional species richness can be explained by clade age alone. A single significant rapid rate shift increase is detected within the evolutionary history of the African subfamily Pseudocrenilabrinae, which includes the haplochromins of the East African Great Lakes. Several lineages from the subfamilies Pseudocrenilabrinae (Australotilapiini, Oreochromini) and Cichlinae (Heroini) exhibit exceptional species richness given their clade age, a net rate of diversification, and relative rates of extinction, indicating that clade age alone is not a sufficient explanation for their increased diversity. Our results indicate that the Neotropical Cichlinae includes lineages that have not experienced a significant rapid burst in diversification when compared to certain African lineages (rift lake). Neotropical cichlids have remained comparatively understudied with regard to macroevolutionary patterns relative to African lineages, and our results indicate that of Neotropical lineages, the tribe Heroini may have an elevated rate of diversification in contrast to other Neotropical cichlids. These findings provide insight into our understanding of the diversification patterns across taxonomically disparate lineages in this diverse clade of freshwater fishes and one of the most species-rich families of vertebrates.

McMahan, Caleb D.; Chakrabarty, Prosanta; Sparks, John S.; Smith, Wm. Leo; Davis, Matthew P.

2013-01-01

76

The temporal pattern of vitellogenin synthesis in Drosophila grimshawi  

SciTech Connect

The temporal pattern of protein production and, in particular, vitellogenin protein synthesis during the sexual maturation of Drosophila grimshawi females has been studied in vivo by briefly feeding the flies with 35S-methionine and 3H-amino acids. The overall level of incorporation was very low in young flies; it then progressively increased to reach a maximum with the onset of sexual maturity at 13-15 days. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analyses revealed three classes of proteins: those synthesized throughout the age spectrum, which constitute the majority of protein species; proteins synthesized primarily or only in young flies; and proteins synthesized only by the older flies. In this Drosophila species, the three vitellogenins (V1, V2, and V3) appeared to be synthesized in a two-phase pattern. In the first phase, small quantities of V1 and V2 were detected immunologically in the fat body and hemolymph of newly emerged and 1 day-old flies. These proteins did not accumulate in the hemolymph or the ovaries, apparently being unstable proteins. The second phase commenced in early vitellogenesis (7-9 days of age) with synthesis in the fat body of small quantities of V1 and V2, followed by V3 proteins. These proteins were secreted and accumulated in the hemolymph and 24 h later were found in the ovaries. Their quantities increased rapidly and a steady state of synthesis, release into the hemolymph, and uptake by the ovaries was reached by days 13-15. We have estimated that during the steady state of vitellogenin synthesis, a fly can synthesize in 24 h at least 152 micrograms of vitellogenins, which is more than 2% of its body weight, at an average rate of about 6.3 micrograms vitellogenins/h. About 2 micrograms of this are synthesized in the fat body, and about 4 micrograms in the ovaries.

Kambysellis, M.P.; Hatzopoulos, P.; Craddock, E.M. (New York Univ., New York City (USA))

1989-09-01

77

Temporal patterns of diversification across global cichlid biodiversity (Acanthomorpha: Cichlidae).  

PubMed

The contrasting distribution of species diversity across the major lineages of cichlids makes them an ideal group for investigating macroevolutionary processes. In this study, we investigate whether different rates of diversification may explain the disparity in species richness across cichlid lineages globally. We present the most taxonomically robust time-calibrated hypothesis of cichlid evolutionary relationships to date. We then utilize this temporal framework to investigate whether both species-rich and depauperate lineages are associated with rapid shifts in diversification rates and if exceptional species richness can be explained by clade age alone. A single significant rapid rate shift increase is detected within the evolutionary history of the African subfamily Pseudocrenilabrinae, which includes the haplochromins of the East African Great Lakes. Several lineages from the subfamilies Pseudocrenilabrinae (Australotilapiini, Oreochromini) and Cichlinae (Heroini) exhibit exceptional species richness given their clade age, a net rate of diversification, and relative rates of extinction, indicating that clade age alone is not a sufficient explanation for their increased diversity. Our results indicate that the Neotropical Cichlinae includes lineages that have not experienced a significant rapid burst in diversification when compared to certain African lineages (rift lake). Neotropical cichlids have remained comparatively understudied with regard to macroevolutionary patterns relative to African lineages, and our results indicate that of Neotropical lineages, the tribe Heroini may have an elevated rate of diversification in contrast to other Neotropical cichlids. These findings provide insight into our understanding of the diversification patterns across taxonomically disparate lineages in this diverse clade of freshwater fishes and one of the most species-rich families of vertebrates. PMID:23990936

McMahan, Caleb D; Chakrabarty, Prosanta; Sparks, John S; Smith, W M Leo; Davis, Matthew P

2013-01-01

78

Multimodal Far-Field Acoustic Radiation Pattern: An Approximate Equation.  

National Technical Information Service (NTIS)

The far-field sound radiation theory for a circular duct was studied for both single mode and multimodal inputs. The investigation was intended to develop a method to determine the acoustic power produced by turbofans as a function of mode cut-off ratio. ...

E. J. Rice

1977-01-01

79

Temporal prediction of epidemic patterns in community networks  

NASA Astrophysics Data System (ADS)

Most previous studies of epidemic dynamics on complex networks suppose that the disease will eventually stabilize at either a disease-free state or an endemic one. In reality, however, some epidemics always exhibit sporadic and recurrent behaviour in one region because of the invasion from an endemic population elsewhere. In this paper we address this issue and study a susceptible-infected-susceptible epidemiological model on a network consisting of two communities, where the disease is endemic in one community but alternates between outbreaks and extinctions in the other. We provide a detailed characterization of the temporal dynamics of epidemic patterns in the latter community. In particular, we investigate the time duration of both outbreak and extinction, and the time interval between two consecutive inter-community infections, as well as their frequency distributions. Based on the mean-field theory, we theoretically analyse these three timescales and their dependence on the average node degree of each community, the transmission parameters and the number of inter-community links, which are in good agreement with simulations, except when the probability of overlaps between successive outbreaks is too large. These findings aid us in better understanding the bursty nature of disease spreading in a local community, and thereby suggesting effective time-dependent control strategies.

Peng, Xiao-Long; Small, Michael; Xu, Xin-Jian; Fu, Xinchu

2013-11-01

80

Patterns of subregional mesiotemporal disease progression in temporal lobe epilepsy  

PubMed Central

Objective: Evidence for disease progression in the mesiotemporal lobe is mainly derived from global volumetry of the hippocampus. In this study, we tracked progressive structural changes in the hippocampus, amygdala, and entorhinal cortex in drug-resistant temporal lobe epilepsy at a subregional level. Furthermore, we evaluated the relation between disease progression and surgical outcome. Methods: We combined cross-sectional modeling of disease duration in a large cohort of patients (n = 134) and longitudinal analysis in a subset that delayed surgery (n = 31). To track subregional pathology, we applied surface-shape analysis techniques on manual mesiotemporal labels. Results: Longitudinal and cross-sectional designs showed consistent patterns of progressive atrophy in hippocampal CA1, anterolateral entorhinal, and the amygdalar laterobasal group bilaterally. These regions also exhibited more marked age-related volume loss in patients compared with controls. We found a faster progression of hippocampal atrophy in patients with a seizure frequency ?6 per month. High rates of contralateral entorhinal cortex atrophy predicted postsurgical seizure relapse. Conclusion: We observed progressive atrophy in hippocampal, amygdalar, and entorhinal subregions that frequently display neuronal loss on histology. The bilateral character of cumulative atrophy highlights the importance of early surgery. In patients who nevertheless delay this procedure, serial scanning may provide markers of surgical outcome.

Bernhardt, Boris C.; Kim, Hosung

2013-01-01

81

Spatial and Temporal Patterns of Global Onshore Wind Speed Distribution  

SciTech Connect

Wind power, a renewable energy source, can play an important role in electrical energy generation. Information regarding wind energy potential is important both for energy related modeling and for decision-making in the policy community. While wind speed datasets with high spatial and temporal resolution are often ultimately used for detailed planning, simpler assumptions are often used in analysis work. An accurate representation of the wind speed frequency distribution is needed in order to properly characterize wind energy potential. Using a power density method, this study estimated global variation in wind parameters as fitted to a Weibull density function using NCEP/CFSR reanalysis data. The estimated Weibull distribution performs well in fitting the time series wind speed data at the global level according to R2, root mean square error, and power density error. The spatial, decadal, and seasonal patterns of wind speed distribution were then evaluated. We also analyzed the potential error in wind power estimation when a commonly assumed Rayleigh distribution (Weibull k = 2) is used. We find that the assumption of the same Weibull parameter across large regions can result in substantial errors. While large-scale wind speed data is often presented in the form of average wind speeds, these results highlight the need to also provide information on the wind speed distribution.

Zhou, Yuyu; Smith, Steven J.

2013-09-09

82

Measurement of the temporal patterns of school bag carriage using activity monitoring and structured interview  

Microsoft Academic Search

The primary objective of the current study was to quantify the temporal patterns of school bag carriage over an actual school day using activity monitoring and structured interviews, in order to better understand the physical demands of school bag carriage. The temporal patterns of 40 students' school bag carriage over a 24-h period were defined by total school bag carrying

H. W. Mackie; S. J. Legg

2007-01-01

83

Numerical simulations of acoustic cavitation noise with the temporal fluctuation in the number of bubbles.  

PubMed

Numerical simulations of cavitation noise have been performed under the experimental conditions reported by Ashokkumar et al. (2007) [26]. The results of numerical simulations have indicated that the temporal fluctuation in the number of bubbles results in the broad-band noise. "Transient" cavitation bubbles, which disintegrate into daughter bubbles mostly in a few acoustic cycles, generate the broad-band noise as their short lifetimes cause the temporal fluctuation in the number of bubbles. Not only active bubbles in light emission (sonoluminescence) and chemical reactions but also inactive bubbles generate the broad-band noise. On the other hand, "stable" cavitation bubbles do not generate the broad-band noise. The weaker broad-band noise from a low-concentration surfactant solution compared to that from pure water observed experimentally by Ashokkumar et al. is caused by the fact that most bubbles are shape stable in a low-concentration surfactant solution due to the smaller ambient radii than those in pure water. For a relatively high number density of bubbles, the bubble-bubble interaction intensifies the broad-band noise. Harmonics in cavitation noise are generated by both "stable" and "transient" cavitation bubbles which pulsate nonlinearly with the period of ultrasound. PMID:19751988

Yasui, Kyuichi; Tuziuti, Toru; Lee, Judy; Kozuka, Teruyuki; Towata, Atsuya; Iida, Yasuo

2010-02-01

84

Spatial and Temporal Patterns of Aerosol-Cloud Interactions  

NASA Astrophysics Data System (ADS)

This study determines the spatial and temporal distribution of regions with frequent aerosol-cloud interactions (aci) and identifies their meteorological determinants based on CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) and ECMWF (European Centre for Medium-Range Weather Forecasts) data products. Atmospheric aerosols influence the microphysical structure of clouds, while both also respond to meteorological conditions. The potential radiative adjustments to changes in a cloud system associated with aerosol-cloud interactions are grouped and termed as effective radiative forcing due to aerosol-cloud interactions (ERFaci). It is difficult to distinguish, to what extent radiative forcing and precipitation patterns of clouds are a result of cloud feedbacks to aerosols or the existing meteorological conditions. A complete understanding of aerosol-cloud-meteorology interactions is crucial as the uncertainty range of ERFaci in climate change modeling could be significantly reduced. In the present study it is suggested that presence of hydrated aerosols is an implication for aci. Knowledge of their vertical and horizontal distribution and frequency over the globe would be important for understanding ERFaci. To identify regions with aerosol-cloud transitions the CAD score (cloud-aerosol discrimination) of the CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) instrument on the CALIPSO satellite is used. It separates aerosols and clouds according to the probability distribution functions of 5 parameters (attenuated backscatter, total color ratio, volume depolarization ratio, altitude and latitude) and assigns the likelihood of cloud or aerosol presence. This parameter is used to calculate relative frequencies of aci on a global scale from 2006 to 2013.

Fuchs, Julia; Cermak, Jan

2014-05-01

85

Match analysis and temporal patterns of fatigue in rugby sevens.  

PubMed

Rugby sevens is a rapidly growing sport. Match analysis is increasingly being used by sport scientists and coaches to improve the understanding of the physical demands of this sport. This study investigated the physical and physiological demands of elite men's rugby sevens, with special reference to the temporal patterns of fatigue during match play. Nine players, 4 backs and 5 forwards (age 25.1 ± 3.1 years) participated during 2 "Roma 7" international tournaments (2010 and 2011). All the players were at the professional level in the highest Italian rugby union, and 5 of these players also competed at the international level. During the matches (n = 15), the players were filmed to assess game performance. Global positioning system, heart rate (HR), and blood lactate (BLa) concentration data were measured and analyzed. The mean total distance covered throughout matches was 1,221 ± 118 m (first half = 643 ± 70 m and second half = 578 ± 77 m; with a decrease of 11.2%, p > 0.05, Effect Size [ES] = 0.29). The players achieved 88.3 ± 4.2 and 87.7 ± 3.4% of the HRmax during the first and second halves, respectively. The BLa for the first and second halves was 3.9 ± 0.9 and 11.2 ± 1.4 mmol·L, respectively. The decreases in performance occurred consistently in the final 3 minutes of the matches (-40.5% in the distance covered per minute). The difference found in relation to the playing position, although not statistically significant (p = 0.11), showed a large ES (? = 0.20), suggesting possible practical implications. These results demonstrate that rugby sevens is a demanding sport that places stress on both the anaerobic glycolytic and aerobic oxidative energy systems. Strength and conditioning programs designed to train these energy pathways may prevent fatigue-induced reductions in physical performance. PMID:23722109

Granatelli, Giampietro; Gabbett, Tim J; Briotti, Gianluca; Padulo, Johnny; Buglione, Antonio; D'Ottavio, Stefano; Ruscello, Bruno M

2014-03-01

86

Spatio-Temporal Rainfall Patterns in Northern Ghana, West Africa  

NASA Astrophysics Data System (ADS)

Rainfall reliability in West Africa has important societal consequences. However, our understanding of the rainfall generating processes in this region remains incomplete. This study aims at the detection of different rainfall producing processes and their characteristics during the later part of the rainy season in Northern Ghana. Rainfall in this region has three main origins: monsoonal advection, local convection, and squall lines. Different processes dominate during different parts of the rainy season, which runs from May through October. Rainfall measurements were taken with tipping-bucket rain gages with high temporal resolution. A total of 16 rain gages were used, organized in two nested grids covering areas of 9x9 km and 3x3 km, respectively. The recorded rainfall events were classified according to their origin primarily on the basis of intensity, duration, and spatial pattern and distribution. As local convective and squall line rainfall show similar characteristics, TRMM Precipitation Radar imagery was analyzed visually to help further distinguish between these two types. The main result is a procedure that allows to differentiate rainfall origins and a set of characteristic rainfall events. Special attention is paid to squall line induced rainfall. Squall lines are crescent shaped atmospheric disturbances that move from East to West over the sub-continent and are associated with violent wind gusts and high rainfall intensities of up to 300 mm/h. These squall lines are mainly caused by interaction between the monsoonal air layer and the African Easterly Jet. In Northern Ghana, line squalls produce most of the annual rainfall. At the end of the wet season, rain almost exclusively originates from squall lines. Because of their high intensities, squall lines and convective storms are hydrologically important for understanding runoff generation.

Friesen, J.; van de Giesen, N.

2002-12-01

87

Acoustics.  

National Technical Information Service (NTIS)

The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or...

F. Grosveld J. R. Goodman

2007-01-01

88

Cell patterning with a heptagon acoustic tweezer - application in neurite guidance.  

PubMed

Accurate control over positioning of cells is a highly desirable feature in tissue engineering applications since it allows, for example, population of substrates in a controlled fashion, rather than relying on random seeding. Current methods to achieve a differential distribution of cells mostly use passive patterning methods to change chemical, mechanical or topographic properties of surfaces, making areas differentially permissive to the adhesion of cells. However, these methods have no ad hoc control over the actual deposition of cells. Direct patterning methods like bioprinting offer good control over cell position, but require sophisticated instrumentation and are often cost- and time-intensive. Here, we present a novel electronically controlled method of generating dynamic cell patterns by acoustic trapping of cells at a user-determined position, with a heptagonal acoustic tweezer device. We demonstrate the capability of the device to create complex patterns of cells using the device's ability to re-position acoustic traps by using a phase shift in the acoustic wave, and by switching the configuration of active piezoelectric transducers. Furthermore, we show that by arranging Schwann cells from neonatal rats in a linear pattern we are able to create Bands of Büngner-like structures on a non-structured surface and demonstrate that these features are able to guide neurite outgrowth from neonatal rat dorsal root ganglia. PMID:24817215

Gesellchen, F; Bernassau, A L; Déjardin, T; Cumming, D R S; Riehle, M O

2014-07-01

89

Effects of internal solitary waves on the invariance of acoustic intensity striation patterns  

NASA Astrophysics Data System (ADS)

Effects of Internal Solitary Waves (ISWs) on the acoustic intensity striation patterns are studied using a unique data set collected in the South China Sea during the ONR Asian Seas International Acoustics Experiment (ASIAEx). The data set contains measured broadband (270-330 Hz) acoustic fields on a 32-element, ~400 m aperture horizontal array describing two regimes where the ISW packet being present and not present in a 19 km long propagation track. The geometry of the ISW packet was captured by a Synthetic Aperture Radar (SAR) image when it entered the propagation track at a 50 deg angle. It has been observed that ISWs introduce larger intensity fluctuations as well as frequency-shifts in the striation patterns when they are in the propagation track. However, the slope of the striations seems to be less affected by the presence of ISWs. Results from several broadband simulations are also presented to describe both acoustic intensity fluctuations and variations in the striation patterns in terms of acoustic mode coupling and mode refraction induced by ISWs. [Work supported by ONR.

Turgut, Altan; Orr, Marshall; Rouseff, Daniel; Lynch, James; Chiu, Ching Sang

2003-04-01

90

Accuracy of spatial and temporal averaging of acoustic Doppler current profiler (ADCP) moving boat measurements  

NASA Astrophysics Data System (ADS)

Characterization of mean velocity, turbulence levels and secondary currents in rivers and tidal flow is crucial for the annual energy production estimation and structural design of MHK devices. A moving vessel deployment of an acoustic Doppler current profiler (ADCP) can obtain 3D velocity data in a large spatial region in an open channel cross-section within a significantly shorter time than other methods currently available. When using such a deployment method, the ADCP measures only a single velocity value at each bin, and therefore the data contain a significant amount of fluctuations due to turbulence velocity fluctuation and instrument's noise. Several researchers have proposed spatial and temporal averaging methodologies for ADCP moving boat (transects) data to deal with this issue. However, little is known about the accuracy of this technique. The effects of spatial and temporal averaging (STA) of ADCP transects data are investigated in the St. Anthony Falls laboratory flume. ADCP transects were obtained upstream and downstream of a 1:10 scale MHK horizontal axis turbine at various bin sizes. The MHK turbine generates a helical vortex flow with its axis parallel to the flume longitudinal direction, similar to the Prandtl's secondary flow of the first and second kind observed in open channels. The ADCP is attached to a computerized cart capable of traversing the ADCP at various speeds and recording the ADCP positions up to 1 mm accuracy. Accuracy of the STA of ADCP transects data with various bin size is assessed against ADCP fixed vessel and ADV point measurements. The accuracy of the STA of ADCP transects in representing the magnitude and direction of the helical vortex flow is also assessed.

Gunawan, B.; Neary, V. S.; Hill, C.; Chamorro, L. P.

2011-12-01

91

A note on the radiative directivity patterns of duct acoustic modes  

Microsoft Academic Search

The classical solution for the external radiative pattern of acoustic modes in an unflanged circular duct has been presented in a form more suitable for practical computations. This expression predicts the same locations for the principal lobe and zeroes as would be obtained from the baffled model, and has the added advantage of being able to predict sideline and aft

G. F. Homicz; J. A. Lordi

1975-01-01

92

Experimental validation of acoustic radiation force induced shear wave interference patterns  

Microsoft Academic Search

A novel elasticity imaging system founded on the use of acoustic radiation forces from a dual beam arrangement to generate shear wave interference patterns is described. Acquired pulse-echo data and correlation-based techniques were used to estimate the resultant deformation and to visualize tissue viscoelastic response. The use of normal versus axicon focal configurations was investigated for effects on shear wave

Kenneth Hoyt; Zaegyoo Hah; Chris Hazard; Kevin J Parker

2012-01-01

93

Acoustic Processing of Temporally Modulated Sounds in Infants: Evidence from a Combined Near-Infrared Spectroscopy and EEG Study  

PubMed Central

Speech perception requires rapid extraction of the linguistic content from the acoustic signal. The ability to efficiently process rapid changes in auditory information is important for decoding speech and thereby crucial during language acquisition. Investigating functional networks of speech perception in infancy might elucidate neuronal ensembles supporting perceptual abilities that gate language acquisition. Interhemispheric specializations for language have been demonstrated in infants. How these asymmetries are shaped by basic temporal acoustic properties is under debate. We recently provided evidence that newborns process non-linguistic sounds sharing temporal features with language in a differential and lateralized fashion. The present study used the same material while measuring brain responses of 6 and 3?month old infants using simultaneous recordings of electroencephalography (EEG) and near-infrared spectroscopy (NIRS). NIRS reveals that the lateralization observed in newborns remains constant over the first months of life. While fast acoustic modulations elicit bilateral neuronal activations, slow modulations lead to right-lateralized responses. Additionally, auditory-evoked potentials and oscillatory EEG responses show differential responses for fast and slow modulations indicating a sensitivity for temporal acoustic variations. Oscillatory responses reveal an effect of development, that is, 6 but not 3?month old infants show stronger theta-band desynchronization for slowly modulated sounds. Whether this developmental effect is due to increasing fine-grained perception for spectrotemporal sounds in general remains speculative. Our findings support the notion that a more general specialization for acoustic properties can be considered the basis for lateralization of speech perception. The results show that concurrent assessment of vascular based imaging and electrophysiological responses have great potential in the research on language acquisition.

Telkemeyer, Silke; Rossi, Sonja; Nierhaus, Till; Steinbrink, Jens; Obrig, Hellmuth; Wartenburger, Isabell

2010-01-01

94

Temporal motifs reveal homophily, gender-specific patterns, and group talk in call sequences  

PubMed Central

Recent studies on electronic communication records have shown that human communication has complex temporal structure. We study how communication patterns that involve multiple individuals are affected by attributes such as sex and age. To this end, we represent the communication records as a colored temporal network where node color is used to represent individuals’ attributes, and identify patterns known as temporal motifs. We then construct a null model for the occurrence of temporal motifs that takes into account the interaction frequencies and connectivity between nodes of different colors. This null model allows us to detect significant patterns in call sequences that cannot be observed in a static network that uses interaction frequencies as link weights. We find sex-related differences in communication patterns in a large dataset of mobile phone records and show the existence of temporal homophily, the tendency of similar individuals to participate in communication patterns beyond what would be expected on the basis of their average interaction frequencies. We also show that temporal patterns differ between dense and sparse neighborhoods in the network. Because also this result is independent of interaction frequencies, it can be seen as an extension of Granovetter’s hypothesis to temporal networks.

Kovanen, Lauri; Kaski, Kimmo; Kertesz, Janos; Saramaki, Jari

2013-01-01

95

Effects of length and linguistic complexity on temporal acoustic measures in apraxia of speech.  

PubMed

The purpose of this study was to examine the effects of varying length and linguistic utterance types on temporal acoustic characteristics of the imitative speech of apraxic speakers. Vowel duration and two between-word segment durations were examined during the production of three response types: words, word-strings, and sentences. Three length conditions were studied in words, two length conditions for word-strings, and three length conditions for sentences, yielding eight experimental conditions. Apraxic speakers exhibited significantly longer vowel and between-word segment durations than control speakers in all conditions. Apraxic speakers consistently produced longer vowel and between-word segment durations in sentence contexts than in word contexts. Further, intrasubject and intersubject variability for between-word segment durations were substantially greater for the apraxic speakers in sentences compared to word conditions, whereas control speakers exhibited greater homogeneity in sentence production. The differences in duration and variability in sentence production versus word or word-string production imply different mechanisms for executing motor programs for varying linguistic stimuli. PMID:8898255

Strand, E A; McNeil, M R

1996-10-01

96

Discovering evolutionary theme patterns from text: an exploration of temporal text mining  

Microsoft Academic Search

Temporal Text Mining (TTM) is concerned with discovering temporal patterns in text information collected over time. Since most text information bears some time stamps, TTM has many applications in multiple domains, such as summarizing events in news articles and revealing research trends in scientific literature. In this paper, we study a particular TTM task -- discovering and summarizing the evolutionary

Qiaozhu Mei; ChengXiang Zhai

2005-01-01

97

General asymmetric neutral networks and structure design by genetic algorithms: A learning rule for temporal patterns  

SciTech Connect

A learning algorithm based on genetic algorithms for asymmetric neural networks with an arbitrary structure is presented. It is suited for the learning of temporal patterns and leads to stable neural networks with feedback.

Bornholdt, S. [Heidelberg Univ., (Germany). Inst., fuer Theoretische Physik; Graudenz, D. [Lawrence Berkeley Lab., CA (United States)

1993-07-01

98

Flow patterns and transport in Rayleigh surface acoustic wave streaming: combined finite element method and raytracing numerics versus experiments.  

PubMed

This work presents an approach for determining the streaming patterns that are generated by Rayleigh surface acoustic waves in arbitrary 3-D geometries by finite element method (FEM) simulations. An efficient raytracing algorithm is applied on the acoustic subproblem to avoid the unbearable memory demands and computational time of a conventional FEM acoustics simulation in 3-D. The acoustic streaming interaction is modeled by a body force term in the Stokes equation. In comparisons between experiments and simulated flow patterns, we demonstrate the quality of the proposed technique. PMID:18986877

Frommelt, Thomas; Gogel, Daniel; Kostur, Marcin; Talkner, Peter; Hänggi, Peter; Wixforth, Achim

2008-10-01

99

Experimental validation of acoustic radiation force induced shear wave interference patterns.  

PubMed

A novel elasticity imaging system founded on the use of acoustic radiation forces from a dual beam arrangement to generate shear wave interference patterns is described. Acquired pulse-echo data and correlation-based techniques were used to estimate the resultant deformation and to visualize tissue viscoelastic response. The use of normal versus axicon focal configurations was investigated for effects on shear wave generation. Theoretical models were introduced and shown in simulation to accurately predict shear wave propagation and interference pattern properties. In a tissue-mimicking phantom, experimental results are in congruence with theoretical predictions. Using dynamic acoustic radiation force excitation, results confirm that shear wave interference patterns can be produced remotely in a particular tissue region of interest (ROI). Overall, preliminary results are encouraging and the system described may prove feasible for interrogating the viscoelastic properties of normal and diseased tissue types. PMID:22127377

Hoyt, Kenneth; Hah, Zaegyoo; Hazard, Chris; Parker, Kevin J

2012-01-01

100

Development and Implementation of Nearfield Acoustical Holography for Wideband Sources  

Microsoft Academic Search

The acoustic radiation patterns above a controlled source have been studied using the nearfield acoustical holography (NAH) technique as the temporal and spatial coherence of the source was systematically degraded. To permit the application of the NAH technique to the study of temporally and spatially incoherent sources, a high -speed data acquisition system which provides virtually simultaneous sampling of the

Donald John Bowen

1986-01-01

101

Temporal changes in colony cuticular hydrocarbon patterns of Solenopsis invicta  

Microsoft Academic Search

Heritable cuticular hydrocarbon patterns ofSolenopsis invicta workers are consistent within colonies for a given sampling time but vary sufficiently from colony to colony to distinguish the colonies from each other. In addition, cuticular hydrocarbon patterns change within colonies over time. Nestmate recognition cues found on the individual's cuticle, can be from heritable or environmental sources, and are a subset of

Robert K. vander Meer; David Saliwanchik; Barry Lavine

1989-01-01

102

Spatial and Temporal Patterns of Tidal Dissipation in Synchronous Satellites  

NASA Technical Reports Server (NTRS)

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

Bills, Bruce G.; Aharonson, Oded

2003-01-01

103

Temporal and Durational Patterns Associating Respiration and Swallowing  

Microsoft Academic Search

.   This study obtained initial normative data on the temporal coordination of respiration and swallowing events in 12 young\\u000a adults using a first-generation Respirodeglutometer. In addition, direction of airflow before and after deglutive apnea was\\u000a obtained. Three swallows of two viscosities of bolus material were performed by each subject, yielding a total of 72 swallows.\\u000a Qualitative and quanitative analyses were

Matthew S. Klahn; Adrienne L. Perlman

1999-01-01

104

Hemispatial PCA dissociates temporal from parietal ERP generator patterns  

PubMed Central

Event-related potentials (31-channel ERPs) were recorded from 38 depressed, unmedicated outpatients and 26 healthy adults (all right-handed) in tonal and phonetic oddball tasks developed to exploit the perceptual challenge of a dichotic stimulation. Tonal nontargets were pairs of complex tones (corresponding to musical notes G and B above middle C) presented simultaneously to each ear (L/R) in an alternating series (G/B or B/G; 2-s fixed SOA). A target tone (note A) replaced one of the pair on 20% of the trials (A/B, G/A, B/A, A/G). Phonetic nontargets were L/R pairs of syllables (/ba/, /da/) with a short voice onset time (VOT), and targets contained a syllable (/ta/) with a long VOT. Subjects responded with a left or right button press to targets (counterbalanced across blocks). Target detection was poorer in patients than controls and for tones than syllables. Reference-free current source densities (CSDs; spherical spline Laplacian) derived from ERP waveforms were simplified and measured using temporal, covariance-based PCA followed by unrestricted Varimax rotation. Target-related N2 sinks and mid-parietal P3 sources were represented by CSD factors peaking at 245 and 440 ms. The P3 source topography included a secondary, left-lateralized temporal lobe maximum for both targets and nontargets. However, a subsequent hemispheric spatiotemporal PCA disentangled temporal lobe N1 and P3 sources as distinct factors. P3 sources were reduced in patients compared with controls, even after using performance as a covariate. Results are consistent with prior reports of P3 reduction in depression and implicate distinct parietal and temporal generators of P3 when using a dichotic oddball paradigm.

Tenke, Craig E.; Kayser, Jurgen; Shankman, Stewart A.; Griggs, Carlye B.; Leite, Paul; Stewart, Jonathan W.; Bruder, Gerard E.

2008-01-01

105

Observation of spatio-temporal pattern in magnetised rf plasmas  

NASA Astrophysics Data System (ADS)

We address an experimental observation of pattern formation in a magnetised rf plasma. The experiments are carried out in a electrically grounded aluminium chamber which is housed inside a rotatable superconducting magnetic coil. The plasma is formed by applying a rf voltage in parallel plate electrodes in push-pull mode under the background of argon gas. The time evolution of plasma intensity shows that a homogeneous plasma breaks into several concentric radial spatiotemoral bright and dark rings. These rings propagate radially at considerably low pressure and a constant magnetic field. These patterns are observed to trap small dust particles/grains in their potential. Exploiting this property of the patterns, a novel technique to measure the electric field associated with the patterns is described. The resulting estimates of the corresponding field intensity are presented. At other specific discharge parameters the plasma shows a range of special type of characteristic structures observed in certain other chemical, mechanical and biological systems.

Bandyopadhyay, P.; Sharma, D.; Konopka, U.; Morfill, G.

2014-02-01

106

Cultural and environmental influences on temporal-spectral development patterns of corn and soybeans  

NASA Technical Reports Server (NTRS)

A technique for evaluating crop temporal-spectral development patterns is described and applied to the analysis of cropping practices and environmental conditions as they affect reflectance characteristics of corn and soybean canopies. Typical variations in field conditions are shown to exert significant influences on the spectral development patterns, and thereby to affect the separability of the two crops.

Crist, E. P.

1982-01-01

107

Spatio-temporal patterns of soil available nutrients following experimental disturbance in a pine forest  

Microsoft Academic Search

Although disturbance is known to alter soil nutrient heterogeneity, it remains unclear whether spatial patterns in soil nutrients after disturbance follow predictable temporal changes that reflect underlying processes. This study examined the effects of tree harvesting and girdling on overall variability, geostatistical patterns, and resource congruence of soil available nutrients in a mature Pinus elliottii Engelm. forest. The two disturbances

Dali Guo; Pu Mou; Robert H. Jones; Robert J. Mitchell

2004-01-01

108

Avian Incubation Patterns Reflect Temporal Changes in Developing Clutches  

PubMed Central

Incubation conditions for eggs influence offspring quality and reproductive success. One way in which parents regulate brooding conditions is by balancing the thermal requirements of embryos with time spent away from the nest for self-maintenance. Age related changes in embryo thermal tolerance would thus be expected to shape parental incubation behavior. We use data from unmanipulated Black-capped Chickadee (Poecile atricapillus) nests to examine the temporal dynamics of incubation, testing the prediction that increased heat flux from eggs as embryos age influences female incubation behavior and/or physiology to minimize temperature fluctuations. We found that the rate of heat loss from eggs increased with embryo age. Females responded to increased egg cooling rates by altering incubation rhythms (more frequent, shorter on- and off- bouts), but not brood patch temperature. Consequently, as embryos aged, females were able to increase mean egg temperature and decrease variation in temperature. Our findings highlight the need to view full incubation as more than a static rhythm; rather, it is a temporally dynamic and finely adjustable parental behavior. Furthermore, from a methodological perspective, intra- and inter-specific comparisons of incubation rhythms and average egg temperatures should control for the stage of incubation.

2013-01-01

109

Temporal patterns in air pollution and hospital admissions.  

PubMed

A 6-year data set of daily counts of admissions to 79 acute care hospitals in Southern Ontario was analyzed in relation to concurrent measurements of air pollution and weather pooled over the same regions, using progressively more sophisticated statistical techniques. The diagnoses studied included a group of respiratory causes and two control diagnoses: accidents and gastrointestinal causes. The 6-year period (1979-1985) was subdivided into six 2-month "seasons" and the area of study was divided into three subregions. Bivariate correlations were found to be significant more often than expected due to chance for all three admissions variables, but accounting for the temporal variation within the 60-day seasons greatly reduced the significance of the control diagnoses. Twenty-four-hour averages for air quality were found to yield more significant associations than peak hourly concentrations. July-August was the only period not having important within-season temporal trends and also had the lowest daily counts for respiratory admissions. Based on a model which accounted for serial correlation, SO2, ozone, and sulfate aerosol were found to be significant predictors of respiratory admissions during July-August. Using cumulative lags increased the magnitude of the estimated response to about 20% of summer respiratory admissions, but no consistent relationships were found which could identify the "responsible" pollutant(s) with certainty. Average pollutant concentrations were generally within U.S. ambient standards. PMID:1464290

Lipfert, F W; Hammerstrom, T

1992-12-01

110

Temporal patterns in air pollution and hospital admissions  

SciTech Connect

A 6-year data set of daily counts of admissions to 79 acute care hospitals in Southern Ontario was analyzed in relation to concurrent measurements of air pollution and weather pooled over the same regions, using progressively more sophisticated statistical techniques. The diagnoses studied included a group of respiratory causes and two control diagnoses: accidents and gastrointestinal causes. The 6-year period (1979-1985) was subdivided into six 2-month seasons and the area of study was divided into three subregions. Bivariate correlations were found to be significant more often than expected due to chance for all three admissions variables, but accounting for the temporal variation within the 60-day seasons greatly reduced the significance of the control diagnoses. Twenty-four-hour averages for air quality were found to yield more significant associations than peak hourly concentrations. July-August was the only period not having important within-season temporal trends and also had the lowest daily counts for respiratory admissions. Based on a model which accounted for serial correlation, SO2, ozone, and sulfate aerosol were found to be significant predictors of respiratory admissions during July-August. Using cumulative lags increased the magnitude of the estimated response to about 20% of summer respiratory admissions, but no consistent relationships were found which could identify the responsible pollutant(s) with certainty. Average pollutant concentrations were generally within U.S. ambient standards.

Lipfert, F.W.; Hammerstrom, T. (Roth Associates, Inc., Rockville, MD (United States))

1992-12-01

111

DIRECTIVITY PATTERNS OF THE TRANSDUCERS FOR THE CORRELATIVE PASSIVE ACOUSTIC THERMOTOMOGRAPHY 1 Scientific Research Centre of Electronic Diagnostic Systems \\  

Microsoft Academic Search

Passive acoustic thermotomography is a method of reconstructio n of 2-D and 3-D distributions of temperature at the depth of any objects. The method is based on measurements of intrinsic thermal acoustic radiation of the investigated object. Directivity patterns of two piezotransducers (PTs) for measurement of the spatial correlation function of the sound pressure generated by a source of the

V. I. Passechnik; A. A. Anosov; Yu. N. Barabanenkov; L. R. Gavrilov

112

Experimental quiescent drifting dusty plasmas and temporal dust acoustic wave growth  

SciTech Connect

We report on dust acoustic wave growth rate measurements taken in a dc (anode glow) discharge plasma device. By introducing a mesh with a variable bias 12-17 cm from the anode, we developed a technique to produce a drifting dusty plasma. A secondary dust cloud, free of dust acoustic waves, was trapped adjacent to the anode side of the mesh. When the mesh was returned to its floating potential, the secondary cloud was released and streamed towards the anode and primary dust cloud, spontaneously exciting dust acoustic waves. The amplitude growth of the excited dust acoustic waves was measured directly along with the wavelength and Doppler shifted frequency. These measurements were compared to fluid and kinetic dust acoustic wave theories. As the wave growth saturated a transition from linear to nonlinear waves was observed. The merging of the secondary and primary dust clouds was also observed.

Heinrich, J. R.; Kim, S.-H.; Meyer, J. K.; Merlino, R. L. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)

2011-11-15

113

Storage of auditory temporal patterns in the songbird telencephalon  

Microsoft Academic Search

A quantitative model of auditory learning is presented to predict how auditory patterns are stored in the songbird auditory forebrain. This research focuses on the caudomedial nidopallium (NCM) in the songbird telencephalon, a candidate site for song perception and the formation of song auditory memories. The objective is to introduce simplified features of bird song that could be used by

Patrick D. Roberts; Roberto Santiago; Tarciso Velho; Claudio V. Mello

2007-01-01

114

SPATIAL AND TEMPORAL PATTERNS OF ACID PRECIPITATION AND THEIR INTERPRETATION  

EPA Science Inventory

Using data compiled from seven nationwide precipitation chemistry networks in the U.S. and Canada, the spatial distribution of hydrogen, sulfate, and nitrate ions in North America is discussed. Geographic patterns of concentration and deposition are characterized using isopleth m...

115

Life between clocks: daily temporal patterns of human chronotypes.  

PubMed

Human behavior shows large interindividual variation in temporal organization. Extreme "larks" wake up when extreme "owls" fall asleep. These chronotypes are attributed to differences in the circadian clock, and in animals, the genetic basis of similar phenotypic differences is well established. To better understand the genetic basis of temporal organization in humans, the authors developed a questionnaire to document individual sleep times, self-reported light exposure, and self-assessed chronotype, considering work and free days separately. This report summarizes the results of 500 questionnaires completed in a pilot study individual sleep times show large differences between work and free days, except for extreme early types. During the workweek, late chronotypes accumulate considerable sleep debt, for which they compensate on free days by lengthening their sleep by several hours. For all chronotypes, the amount of time spent outdoors in broad daylight significantly affects the timing of sleep: Increased self-reported light exposure advances sleep. The timing of self-selected sleep is multifactorial, including genetic disposition, sleep debt accumulated on workdays, and light exposure. Thus, accurate assessment of genetic chronotypes has to incorporate all of these parameters. The dependence of human chronotype on light, that is, on the amplitude of the light:dark signal, follows the known characteristics of circadian systems in all other experimental organisms. Our results predict that the timing of sleep has changed during industrialization and that a majority of humans are sleep deprived during the workweek. The implications are far ranging concerning learning, memory, vigilance, performance, and quality of life. PMID:12568247

Roenneberg, Till; Wirz-Justice, Anna; Merrow, Martha

2003-02-01

116

X-ray diffraction pattern of a Gulyaev-Bleustein surface acoustic wave in grazing geometry  

SciTech Connect

The X ray diffraction pattern of a Gulyaev-Bleustein surface acoustic wave (SAW) under grazing angles of incidence in noncoplanar symmetric Laue geometry has been considered. It is supposed that the propagation direction of an SAW makes a small angle with the diffraction vector. It is shown that small deviations from the Bragg angle ({approx}0.01'' induced by the SAW and do not affect the reflection coefficient lead to the formation of diffraction satellites both in the cases of standing and traveling SAWs. It has been established that the recorded diffraction pattern, which is a time-averaged intensity distribution, has characteristic profiles for odd and even satellites.

Levonyan, L. V., E-mail: gurgen@iapp.sci.am; Khachaturyan, G. K. [Academy of Sciences of Armenia, Institute of Applied Physics Problems (Armenia)

2006-12-15

117

Regulation and Temporal Expression Patterns of Vibrio cholerae Virulence Genes during Infection  

Microsoft Academic Search

The temporal expression patterns of the critical Vibrio cholerae virulence genes, tcpA and ctxA, were determined during infection using a recombinase reporter. TcpA was induced biphasically in two temporally and spatially separable events in the small intestine, whereas ctxA was induced monophasically only after, and remarkably, dependent upon, tcpA expression; however, this dependence was not observed during in vitro growth.

Sang Ho Lee; David L Hava; Matthew K Waldor; Andrew Camilli

1999-01-01

118

Spatio-Temporal Characterization of Bio-Acoustic Scatterers in Complex Media.  

National Technical Information Service (NTIS)

Characterization of biologically-induced ocean reverberation features is key to effectively parametrize acoustic models and thus ultimately improve the detection performance of long-range SONAR systems. In particular, scattering from fish schools can sign...

K. G. Sabra

2012-01-01

119

Different temporal patterns of vector soliton bunching induced by polarization-dependent saturable absorber  

NASA Astrophysics Data System (ADS)

A fiber laser with either a polarization-independent semiconductor saturable absorption mirror (PID-SESAM) or a polarization-dependent SESAM (PD-SESAM) as a passive mode-locker is constructed for obtaining the vector soliton bunching. The temporal patterns of the soliton bunching generated from the fiber laser with a PD-SESAM are much more abundant than that in fiber laser with a PID-SESAM. Only the vibrating soliton bunching is generated from the fiber laser with a PID-SESAM. However, there are another three interesting temporal patterns of the soliton bunching generated from the fiber laser with a PD-SESAM except for the vibrating soliton bunching. They are variable length soliton bunching, breathing soliton bunching and stable soliton bunching along the slow axis induced by polarization instability. It is found that the polarization property of the saturable absorber plays a pivotal role for achieving different temporal patterns of the soliton bunching.

Chen, Wei-Cheng; Chen, Guo-Jie; Han, Ding-An; Li, Bin

2014-06-01

120

Spatial and temporal patterns of nitrogen deposition in China  

NASA Astrophysics Data System (ADS)

Anthropogenic nitrous pollutant emission in China significantly increased during the last decades, which also contributed to the accelerated N deposition. In order to characterize spatial pattern of nitrogen deposition, we employed kriging technique to interpolate sampling data of precipitation chemistry and ambient air concentration from site-network observation over China. Due to the range of national-scale measurements, the estimation of wet deposition in China was limited to aqueous NO3- and NH4+, while ambient NO2 was the only species involved in the predicted dry deposition fluxes. To obtain wet deposition fluxes, precipitation concentration was multiplied by 30-year mean precipitation amounts with a resolution of 0.5 0.5 degree, and dry deposition fluxes were products of the interpolated ambient NO2 concentration and deposition velocity modeled for the main vegetation types in China. The total deposition rates of wet and dry deposition peaked over the central south China, with maximum values of 64.81 kg N·ha-1·yr-1, and an average value of 19.08 kg N·ha-1·yr-1. With ambient NO2 concentration data spanning from the year 1990 through 2003, we detected and evaluated trends in the time series of the annual values of atmospheric NO2 concentration. Significant upward trends at 21 of 102 sites were exhibited, with median percent change of 61.45% over the period 1990-2003. In addition, spatially continuous patterns of dry deposition fluxes based on ambient NO2 measurements in two 5-year phases, 9 years apart, were carried out. And comparison of the two maps indicated the percent changes of deposition fluxes in every grid cell at national scale. On average, there was small rise of 7.66% in NO2 dry deposition during 9 years throughout China.

Lu, C.; Tian, H.

2006-05-01

121

Spatial and Temporal Patterns in Carbon Emissions to the Atmosphere  

NASA Astrophysics Data System (ADS)

Data on global fossil-fuel emissions of CO2 to the atmosphere for year 2000 show that the range of national average per capita emissions, in metric tons of carbon per person, includes values of 5.40 for the United States, 2.61 for Germany, 0.29 for India and 0.04 for Liberia. This range is more than two orders of magnitude. Similar data on national fossil-fuel emissions for the United States vary by more than an order of magnitude, from 34.18 metric tons of carbon per person for Wyoming to 2.70 for California. The state data also show differing patterns of change over time. The Kyoto Protocol would require ratifying developed countries to reduce greenhouse gas emissions to quantified negotiated targets. The concept of contraction and convergence (C&C) has been widely touted as a possible basis for ultimate, more strict limits on greenhouse gas emissions. The idea of C&C is that per-capita emissions of CO2 for all countries would converge toward some common value that is consistent with stabilization of global climate. The U.S., on the other hand, has proposed intensity-based emissions targets whereby goals would be defined in terms of emissions per unit of gross domestic product, or perhaps emissions per unit of output for specific activities. This paper describes the data set on U.S. CO2 emissions by state, and begins to explore the patterns between states and over time.

Broniak, C. T.; Blasing, T. J.; Marland, G.

2003-12-01

122

Acoustics  

NASA Technical Reports Server (NTRS)

The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

Goodman, Jerry R.; Grosveld, Ferdinand

2007-01-01

123

Predictability of spatio-temporal patterns in a lattice of coupled FitzHugh-Nagumo oscillators  

PubMed Central

In many biological systems, variability of the components can be expected to outrank statistical fluctuations in the shaping of self-organized patterns. In pioneering work in the late 1990s, it was hypothesized that a drift of cellular parameters (along a ‘developmental path’), together with differences in cell properties (‘desynchronization’ of cells on the developmental path) can establish self-organized spatio-temporal patterns (in their example, spiral waves of cAMP in a colony of Dictyostelium discoideum cells) starting from a homogeneous state. Here, we embed a generic model of an excitable medium, a lattice of diffusively coupled FitzHugh–Nagumo oscillators, into a developmental-path framework. In this minimal model of spiral wave generation, we can now study the predictability of spatio-temporal patterns from cell properties as a function of desynchronization (or ‘spread’) of cells along the developmental path and the drift speed of cell properties on the path. As a function of drift speed and desynchronization, we observe systematically different routes towards fully established patterns, as well as strikingly different correlations between cell properties and pattern features. We show that the predictability of spatio-temporal patterns from cell properties contains important information on the pattern formation process as well as on the underlying dynamical system.

Grace, Miriam; Hutt, Marc-Thorsten

2013-01-01

124

Geochemical and temporal patterns of felsic volcanism in Ethiopia  

SciTech Connect

At least three major geochemical groups characterize late Cenozoic felsic volcanism exposed in the central Ethiopian Rift graben or along its uplifted margins. Each group is distinguished by age and/or position with distinctive compositional traits that are probably tectonically controlled. They include: (1) large-volume Pliocene tholeiitic to calcalkaline rhyolitic ignimbrites that form >500m thick exposures along the rift margins. These have moderate FeO/sub T/ (1.5-3.0%), low CaO (<0.5%) and moderately steep REE slopes (Ce/Yb = 21-24) with large negative Eu anomalies (Eu/Eu* = 0.2-0.4). K/Ar ages range from 4.5 to 3.0 Ma. These ignimbrites must have been associated with major caldera-forming events, but no calderas of this age or chemistry have yet been found; (2) Plio-Pleistocene trachytic volcanoes occur on the Ethiopian Highland, parallel to the rift axis. These have low SiO/sub 2/ (60-70%), high FeO/sub T/ (4-8%) and steep REE patterns (Ce/Yb = 25-37) with very small negative Eu anomalies (0.8-0.9). The volcanoes of Chilalo, Kaka, Hunkulu and the Bada Range are of this group. K/Ar ages range from 3.5 to 1.0 Ma; (3) Pleistocene peralkaline rhyolitic volcanoes of the Ethiopian Rift graben have high FeO/sub T/ (5-8%), high Na/sub 2/O (6-8%) and shallow REE profiles (Ce/Yb = 14-21) with small Eu anomalies (0.5 to 0.6). K/Ar ages range from 0.5 to <0.05 Ma. The volcanoes of Aluto and Dofen are of this group. Eruption of Group 1 signaled the modern rapid development of the present rift; Group 2 overlapped in time and mainly was confined to the Plateau margins; and Group 3 represents the present mature stage of rift floor volcanism.

Walter, R.C.; Westgate, J.A.; Giday, W.G.; Aronson, J.L.; Hart, W.K.

1985-01-01

125

Temporal variability of vertical nontidal circulation pattern in a partially mixed estuary: Comparison of self-organizing map and empirical orthogonal functions  

NASA Astrophysics Data System (ADS)

On the basis of a 233-day moored acoustic Doppler current profiler data set in an estuarine strait, temporal variability of vertical estuarine circulation is examined using self-organizing map (SOM) and empirical orthogonal functions (EOF). The SOM identifies a continuum of patterns of which eight have been selected. The best matching unit (BMU) time series shows distinct seasonal variation which separates the data set into three seasonal segments. Also, monthly variation can be discerned by BMU sequences, and the data set is further separated into seven monthly segments. The EOF analysis of the whole record identifies only four patterns which are contained in the SOM patterns. However, EOF analysis of the seven monthly segments shows distinct monthly variation of the first two EOF modes. Moreover, those EOF modes are compatible with the SOM patterns showing consistency between the two techniques. The synoptic variability is described by four selected events which correspond to particular BMU sequences and represent filling and draining processes. The pattern-forcing relationships are explored with EOF principle components. Long-term variations of circulation patterns are dominated by river discharge and winds. Short-term variations explored within seasonal and monthly segments indicate that the flow patterns are results of combined effect of forcing. Officer's (1976) analytical solutions of estuarine circulation are applied, and the results support the flow patterns and pattern-forcing relationship revealed by SOM and EOF analysis.

Cheng, Peng; Wilson, Robert E.

2006-12-01

126

Spatio-temporal diffusion pattern and hotspot detection of dengue in Chachoengsao province, Thailand.  

PubMed

In recent years, dengue has become a major international public health concern. In Thailand it is also an important concern as several dengue outbreaks were reported in last decade. This paper presents a GIS approach to analyze the spatial and temporal dynamics of dengue epidemics. The major objective of this study was to examine spatial diffusion patterns and hotspot identification for reported dengue cases. Geospatial diffusion pattern of the 2007 dengue outbreak was investigated. Map of daily cases was generated for the 153 days of the outbreak. Epidemiological data from Chachoengsao province, Thailand (reported dengue cases for the years 1999-2007) was used for this study. To analyze the dynamic space-time pattern of dengue outbreaks, all cases were positioned in space at a village level. After a general statistical analysis (by gender and age group), data was subsequently analyzed for temporal patterns and correlation with climatic data (especially rainfall), spatial patterns and cluster analysis, and spatio-temporal patterns of hotspots during epidemics. The results revealed spatial diffusion patterns during the years 1999-2007 representing spatially clustered patterns with significant differences by village. Villages on the urban fringe reported higher incidences. The space and time of the cases showed outbreak movement and spread patterns that could be related to entomologic and epidemiologic factors. The hotspots showed the spatial trend of dengue diffusion. This study presents useful information related to the dengue outbreak patterns in space and time and may help public health departments to plan strategies to control the spread of disease. The methodology is general for space-time analysis and can be applied for other infectious diseases as well. PMID:21318014

Jeefoo, Phaisarn; Tripathi, Nitin Kumar; Souris, Marc

2011-01-01

127

Reconstruction of missing data in social networks based on temporal patterns of interactions  

NASA Astrophysics Data System (ADS)

We discuss a mathematical framework based on a self-exciting point process aimed at analyzing temporal patterns in the series of interaction events between agents in a social network. We then develop a reconstruction model that allows one to predict the unknown participants in a portion of those events. Finally, we apply our results to the Los Angeles gang network.

Stomakhin, Alexey; Short, Martin B.; Bertozzi, Andrea L.

2011-11-01

128

Shadowing - Tracking - Interviewing: How to Explore Human Spatio-Temporal Behaviour Patterns  

Microsoft Academic Search

The complexity of pedestrian spatio-temporal behaviour calls for the combination of several complementary empirical methods in order to comprehen- sively understand human motion behaviour patterns and underlying motives, habits and intentions. This is essential for the development of mobile spatial information technologies, as the huge amount of potentially available information has to be fil- tered and customised to individual needs.

Alexandra Millonig; Georg Gartner

2008-01-01

129

Acoustic droplet vaporization for temporal and spatial control of tissue occlusion: a kidney study  

Microsoft Academic Search

Acoustic droplet vaporization (ADV) has been introduced with the potential application of tumor treatment via occlusion and subsequent necrosis. New Zealand White rabbits were anesthetized, and their left kidney was externalized. An imaging array and single-element transducer were positioned in a tank with direct access to the kidney's vasculature and renal artery. Filtered droplet emulsions (diameter 90% and an average

Oliver D. Kripfgans; C. M. Orifici; P. L. Carson; K. A. Ives; O. P. Eldevik; J. B. Fowlkes

2005-01-01

130

Spatio-temporal patterns of soil available nutrients following experimental disturbance in a pine forest.  

PubMed

Although disturbance is known to alter soil nutrient heterogeneity, it remains unclear whether spatial patterns in soil nutrients after disturbance follow predictable temporal changes that reflect underlying processes. This study examined the effects of tree harvesting and girdling on overall variability, geostatistical patterns, and resource congruence of soil available nutrients in a mature Pinus elliottii Engelm. forest. The two disturbances led to different patterns of vegetation removal, forest floor redistribution, and revegetation, but showed similar post-disturbance changes in overall soil nutrient variability. Soil nutrient variability increased after both disturbances by more than 5-fold, and then decreased, returning to the undisturbed level in 4 years. Spatial structures assessed using geostatistics did not show predictable temporal trends. However, girdled plots showed more persistent spatial structures in soil nutrients than harvested plots, and had semivariogram ranges mostly equal to or less than 10 m, reflecting effects of persistent and spatially stable patches of undisturbed hardwoods that had an average patch size of 10 m. Resource congruence examined with Spearman rank correlations was nil before disturbance, increased after disturbance and then became nil again by the 4th year post-disturbance. The timing of the increase was related to treatment, occurring in the 1st year after disturbance in the girdled plots, but not until the 2nd year in the harvested plots. These two patterns of congruence were potentially caused by different rates of nutrient patch formation and resource uptake by plants during early succession. Although temporal changes in soil heterogeneity have been documented previously, the present study indicates that temporal trends in nutrient variability after disturbance may be predictable, and that the marked changes in spatio-temporal patterns of soil nutrients as a result of disturbance are ephemeral. PMID:14689301

Guo, Dali; Mou, Pu; Jones, Robert H; Mitchell, Robert J

2004-03-01

131

Temporal feeding pattern may influence reproduction efficiency, the example of breeding mares.  

PubMed

Discomfort in farm animals may be induced by inappropriate types or timing of food supplies. Thus, time restriction of meals and lack of roughage have been shown to be one source of emergence of oral stereotypies and abnormal behaviour in horses which have evolved to eat high-fibre diets in small amounts over long periods of time. This feeding pattern is often altered in domestic environment where horses are often fed low fibre meals that can be rapidly consumed. This study aimed at determining the effect of the temporal pattern of feeding on reproductive efficiency of breeding mares, One hundred Arab breeding mares were divided into two groups that differed only in the temporal pattern of roughage availability: only at night for the standard feeding pattern group (SFP mares), night and day for the "continuous feeding" group (CF mares). The total amount of roughage provided was the same as the CF mares received half of the hay during the day while in paddock (haynets). Mares were tested for oestrus detection by teasing with one stallion and were then examined clinically by rectal palpations and ultrasound before being mated naturally or inseminated by fresh or frozen semen. Multivariate logistic regression was used to analyse data. The treatment affected significantly the reproductive efficiency of the mares with fewer oestrus abnormalities (p?=?0.0002) and more fertility (p?=?0.024) in CF mares (conception rate?=?81% versus 55% in SFP mares). Ensuring semi-continous feeding by providing roughage may be a way of fulfilling the basic physiological needs of the horses' digestive system, reducing stress and associated inhibitors of reproduction. To our knowledge, this study provides the first evidence of an impact of temporal feeding patterns on reproductive success in a Mammal. Temporal patterns of feeding may be a major and underestimated factor in breeding. PMID:24098636

Benhajali, Haifa; Ezzaouia, Mohammed; Lunel, Christophe; Charfi, Faouzia; Hausberger, Martine

2013-01-01

132

Temporal Feeding Pattern May Influence Reproduction Efficiency, the Example of Breeding Mares  

PubMed Central

Discomfort in farm animals may be induced by inappropriate types or timing of food supplies. Thus, time restriction of meals and lack of roughage have been shown to be one source of emergence of oral stereotypies and abnormal behaviour in horses which have evolved to eat high-fibre diets in small amounts over long periods of time. This feeding pattern is often altered in domestic environment where horses are often fed low fibre meals that can be rapidly consumed. This study aimed at determining the effect of the temporal pattern of feeding on reproductive efficiency of breeding mares, One hundred Arab breeding mares were divided into two groups that differed only in the temporal pattern of roughage availability: only at night for the standard feeding pattern group (SFP mares), night and day for the “continuous feeding” group (CF mares). The total amount of roughage provided was the same as the CF mares received half of the hay during the day while in paddock (haynets). Mares were tested for oestrus detection by teasing with one stallion and were then examined clinically by rectal palpations and ultrasound before being mated naturally or inseminated by fresh or frozen semen. Multivariate logistic regression was used to analyse data. The treatment affected significantly the reproductive efficiency of the mares with fewer oestrus abnormalities (p?=?0.0002) and more fertility (p?=?0.024) in CF mares (conception rate?=?81% versus 55% in SFP mares). Ensuring semi-continous feeding by providing roughage may be a way of fulfilling the basic physiological needs of the horses' digestive system, reducing stress and associated inhibitors of reproduction. To our knowledge, this study provides the first evidence of an impact of temporal feeding patterns on reproductive success in a Mammal. Temporal patterns of feeding may be a major and underestimated factor in breeding.

Benhajali, Haifa; Ezzaouia, Mohammed; Lunel, Christophe; Charfi, Faouzia; Hausberger, Martine

2013-01-01

133

Developmental regulation of spatio-temporal patterns of cortical circuit activation  

PubMed Central

Neural circuits are refined in an experience-dependent manner during early postnatal development. How development modulates the spatio-temporal propagation of activity through cortical circuits is poorly understood. Here we use voltage-sensitive dye imaging (VSD) to show that there are significant changes in the spatio-temporal patterns of intracortical signals in primary visual cortex (V1) from postnatal day 13 (P13), eye opening, to P28, the peak of the critical period for rodent visual cortical plasticity. Upon direct stimulation of layer 4 (L4), activity spreads to L2/3 and to L5 at all ages. However, while from eye opening to the peak of the critical period, the amplitude and persistence of the voltage signal decrease, peak activation is reached more quickly and the interlaminar gain increases with age. The lateral spread of activation within layers remains unchanged throughout the time window under analysis. These developmental changes in spatio-temporal patterns of intracortical circuit activation are mediated by differences in the contributions of excitatory and inhibitory synaptic components. Our results demonstrate that after eye opening the circuit in V1 is refined through a progression of changes that shape the spatio-temporal patterns of circuit activation. Signals become more efficiently propagated across layers through developmentally regulated changes in interlaminar gain.

Griffen, Trevor C.; Wang, Lang; Fontanini, Alfredo; Maffei, Arianna

2013-01-01

134

Temporal and Spatial Patterns of Habitat Use by Juveniles of a Small Coastal Shark (Mustelus lenticulatus) in an Estuarine Nursery  

PubMed Central

Juvenile rig (Mustelus lenticulatus) were internally tagged with acoustic transmitters and tracked with acoustic receivers deployed throughout two arms of Porirua Harbour, a small (7 km2) estuary in New Zealand. Ten rig were tracked for up to four months during summer–autumn to determine their spatial and temporal use of the habitat. The overall goal was to estimate the size of Marine Protected Areas required to protect rig nursery areas from direct human impacts. Rig showed clear site preferences, but those preferences varied among rig and over time. They spent most of their time in large basins and on shallow sand and mud flats around the margins, and avoided deep channels. Habitat range increased during autumn for many of the rig. Only one shark spent time in both harbour arms, indicating that there was little movement between the two. Rig home ranges were 2–7 km2, suggesting that an effective MPA would need to cover the entire Porirua Harbour. They moved to outer harbour sites following some high river flow rates, and most left the harbour permanently during or soon after a river spike, suggesting that they were avoiding low salinity water. Rig showed strong diel movements during summer, although the diel pattern weakened in autumn. Persistent use of the same day and night sites indicates that diel movements are directed rather than random. Further research is required to determine the sizes of rig home ranges in larger harbours where nursery habitat is more extensive. Marine Protected Areas do not control land-based impacts such as accelerated sedimentation and heavy metal pollution, so integration of marine and terrestrial management tools across a range of government agencies is essential to fully protect nursery areas.

Francis, Malcolm P.

2013-01-01

135

Finding motifs in birdsong data in the presence of acoustic noise and temporal jitter.  

PubMed

Here we present a novel approach to quickly and reliably find long (200 ms - 2 s) stereotyped sequences of sounds ("motifs") in acoustic recordings of birdsong. Robust and time-efficient identification of such sequences is a crucial first step in many studies ranging from development to neuronal basis of motor behavior. Accurately identifying motifs is usually hindered by the presence of animal-intrinsic variability in execution and tempo, and by extrinsic acoustic noise (e.g., movement artifacts, ambient noise). The algorithm we describe in this report has been optimized to work in bird species that sing stereotyped syllable sequences (such as the zebra finch), and requires minimal user involvement (? 5 min for over 1,000 motifs). Importantly, it is transparent and robust to the choice of parameters. PMID:24773442

Fantana, Antoniu L; Kozhevnikov, Alexay

2014-04-01

136

[Spatio-temporal change and gradient differentiation of landscape pattern in Guangzhou City during its urbanization].  

PubMed

Guangzhou City is a rapidly urbanizing city in China, and a constructed city with holistic planning. By using the remote sensing images of 1985, 1990, 1995, 2000 and 2004, this paper studied the 20 years spatio-temporal changes of landscape pattern in Guangzhou, and analyzed the relationships between these changes and urbanization. The landscape and class-level pattern indices of whole Guangzhou City and its five districts were compared, and the results indicated that the landscape pattern in Guangzhou had an obvious spatio-temporal variation, and an increase of diversity and fractal dimension. The landscape structural complexity and fragmentation increased gradually from 1985 to 2004, and the variation intensity and tendency varied during four comparative stages 1985-1990, 1990-1995, 1995-2000, and 2000-2004. It was a rapid development period from 1985 to 1995 in Guangzhou. The represents of ten districts varied in their spatio-temporal landscape pattern, because of the different development progress and planning motive. The urbanization of Panyu was from 1990 to 2000, and its natural landscape was seriously disturbed by human activities. The represents of Conghua and Zengcheng districts were of integrative disturbance, and also, the urbanization process mainly took place during 1990-2000. In the city center consisting of 8 official constructed districts, the urbanization process happened earlier. In Huadu district, the landscape change revealed the frequent and severe human disturbance. PMID:17147179

Guo, Luo; Xia, Beicheng; Liu, Weiqiu; Jiang, Xueding

2006-09-01

137

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

NASA Astrophysics Data System (ADS)

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

Bergström, Per; Lindegarth, Susanne; Lindegarth, Mats

2013-10-01

138

Three Eurasian teleconnection patterns: spatial structures, temporal variability, and associated winter climate anomalies  

NASA Astrophysics Data System (ADS)

The Eurasian (EU) pattern is a distinct teleconnection pattern observed in boreal winter. Since the EU pattern was first identified, three types have been reported in the literature: the conventional EU pattern; the type 1 EU pattern, or Scandinavian (SCAND) pattern; and the type 2 EU pattern, or East Atlantic/West Russia (EATL/WRUS) pattern. Based on several reanalysis and observational datasets, the three EU patterns are extracted using the rotated empirical orthogonal function method. In order to provide a further distinction and understanding of the three EU patterns, a comprehensive side-by-side comparison is performed among them including their temporal variability, horizontal and vertical structure, related stationary Rossby wave activity, impact on climate, and possible driving factors associated with external forcing. The results reveal that all three EU patterns are characterised by a clear quasi-barotropic wave-train structure, but each has a distinct source and centre of action. Accordingly, their impacts on the precipitation and surface air temperature also differ from one other. Further evidence suggests that the conventional EU pattern is likely driven by anomalous sea surface temperatures (SST) over the North Atlantic, in which process the transient eddies are actively involved. The SCAND pattern is partly maintained by the vorticity source over Western Europe, which arises from the anomalous convergence/divergence over the Mediterranean and is efficiently driven by the tropical and southern Indian Ocean SST via divergent circulation. The EATL/WRUS pattern shows some linkage to the North American snow cover, and the involved process remains unclear and needs further investigation.

Liu, Yuyun; Wang, Lin; Zhou, Wen; Chen, Wen

2014-06-01

139

Three Eurasian teleconnection patterns: spatial structures, temporal variability, and associated winter climate anomalies  

NASA Astrophysics Data System (ADS)

The Eurasian (EU) pattern is a distinct teleconnection pattern observed in boreal winter. Since the EU pattern was first identified, three types have been reported in the literature: the conventional EU pattern; the type 1 EU pattern, or Scandinavian (SCAND) pattern; and the type 2 EU pattern, or East Atlantic/West Russia (EATL/WRUS) pattern. Based on several reanalysis and observational datasets, the three EU patterns are extracted using the rotated empirical orthogonal function method. In order to provide a further distinction and understanding of the three EU patterns, a comprehensive side-by-side comparison is performed among them including their temporal variability, horizontal and vertical structure, related stationary Rossby wave activity, impact on climate, and possible driving factors associated with external forcing. The results reveal that all three EU patterns are characterised by a clear quasi-barotropic wave-train structure, but each has a distinct source and centre of action. Accordingly, their impacts on the precipitation and surface air temperature also differ from one other. Further evidence suggests that the conventional EU pattern is likely driven by anomalous sea surface temperatures (SST) over the North Atlantic, in which process the transient eddies are actively involved. The SCAND pattern is partly maintained by the vorticity source over Western Europe, which arises from the anomalous convergence/divergence over the Mediterranean and is efficiently driven by the tropical and southern Indian Ocean SST via divergent circulation. The EATL/WRUS pattern shows some linkage to the North American snow cover, and the involved process remains unclear and needs further investigation.

Liu, Yuyun; Wang, Lin; Zhou, Wen; Chen, Wen

2014-05-01

140

Exploratory Analysis of Spatial-Temporal Patterns of Air Pollution in the City  

NASA Astrophysics Data System (ADS)

Air pollution in the city is an important problem influencing environment, well-being of society, economy, management of urban zones, etc. The problem is extremely difficult due to a very complex distribution of the pollution sources, morphology of the city and dispersion processes leading to multivariate nature of the phenomena and high local spatial-temporal variability. The task of understanding, modelling and prediction of spatial-temporal patterns of air pollution in urban zones is an interesting and challenging topic having many research axes from science-based modelling to geostatistics and data mining. The present research mainly deals with a comprehensive exploratory analysis of spatial-temporal air pollution data using statistical, geostatistical and machine learning tools. This analysis helps to 1) understand and model spatial-temporal correlations using variography, 2) explore the temporal evolution of spatial correlation matrix; 3) analyse and visualize an interconnection between measurement stations using network science tools; 4) quantify the availability and predictability of structured patterns. The real data case study deals with spatial-temporal air pollution data of canton Geneva (2002-2011). Carbon dioxide (NO2) have caught our attention. It has effects on health: nitrogen dioxide can irritate the lungs, effects on plants; NO2 contributes to the phenomenon of acid rain. The negative effects of nitrogen dioxides on plants are reducing the growth, production and pesticide resistance. And finally the effects on materials: nitrogen dioxides increase the corrosion. Well-defined patterns of spatial-temporal correlations were detected. The analysis and visualization of spatial correlation matrix for 91 stations were carried out using the network science tools and high levels of clustering were revealed. Moving Window Correlation Matrix and Spatio-temporal variography methods were applied to define and explore the dynamic of our data. More than just exploratory of data analysis, this study brings to front the high complexity of air pollution in the city. This approach allowed the definition, parameterisation and analysis of the air pollution data in the city with the future goal of integrating this knowledge in the development of different models of air pollution diffusion. Keywords: space-time environmental data, variography, moving window correlation matrix, network science

Champendal, Alexandre; Kanevski, Mikhail; Huguenot, Pierre-Emmanuel; Golay, Jean

2013-04-01

141

Distinct roles for onset and sustained activity in the neuronal code for temporal periodicity and acoustic envelope shape  

PubMed Central

Auditory neurons are selective for temporal sound information that is important for rhythm, pitch, and timbre perception. Traditional models assume that periodicity information is represented either by the discharge rate of tuned modulation filters or synchrony in the discharge pattern. Compelling evidence for an invariant rate or synchrony code, however, is lacking and neither of these models account for how the sound envelope shape is encoded. We examined the neuronal representation for envelope shape and periodicity in the cat central nucleus of the inferior colliculus (CNIC) with modulated broadband noise that lack spectral cues and produce a periodicity pitch percept solely based on timing information. The modulation transfer functions of CNIC neurons differed dramatically across stimulus conditions with identical periodicity but different envelope shapes implying that shape contributed significantly to the neuronal response. We therefore devised a shuffled correlation procedure to quantify how periodicity and envelope shape contribute to the temporal discharge pattern. Sustained responses faithfully encode envelope shape at low modulation rates but deteriorate and fail to account for timing and envelope information at high rates. Surprisingly, onset responses accurately entrained to the stimulus and provided a means of encoding repetition information at high rates. Finally, we demonstrate that envelope shape information is accurately reflected in the population discharge pattern such that shape is readily discriminated for repetition frequencies up to ~100 Hz. These results argue against conventional rate or synchrony based codes and provides two complementary temporal mechanisms by which CNIC neurons can encode envelope shape and repetition information in natural sounds.

Zheng, Yi; Escabi, Monty A.

2009-01-01

142

Empirical macroscopic features of spatial-temporal traffic patterns at highway bottlenecks.  

PubMed

Results of an empirical study of congested patterns measured during 1995-2001 at German highways are presented. Based on this study, various types of congested patterns at on and off ramps have been identified, their macroscopic spatial-temporal features have been derived, and an evolution of those patterns and transformations between different types of the patterns over time has been found out. It has been found that at an isolated bottleneck (a bottleneck that is far enough from other effective bottlenecks) either the general pattern (GP) or the synchronized flow pattern (SP) can be formed. In GP, synchronized flow occurs and wide moving jams spontaneously emerge in that synchronized flow. In SP, no wide moving jams emerge, i.e., SP consists of synchronized flow only. An evolution of GP into SP when the flow rate to the on ramp decreases has been found and investigated. Spatial-temporal features of complex patterns that occur if two or more effective bottlenecks exist on a highway have been found out. In particular, the expanded pattern where synchronized flow covers two or more effective bottlenecks can be formed. It has been found that the spatial-temporal structure of congested patterns possesses predictable, i.e., characteristic, unique, and reproducible features, for example, the most probable types of patterns that are formed at a given bottleneck. According to the empirical investigations the cases of the weak and the strong congestion should be distinguished. In contrast to the weak congestion, the strong congestion possesses the following characteristic features: (i) the flow rate in synchronized flow is self-maintaining near a limit flow rate; (ii) the mean width of the region of synchronized flow in GP does not depend on traffic demand; (iii) there is a correlation between the parameters of synchronized flow and wide moving jams: the higher the flow rate out from a wide moving jam is, the higher is the limit flow rate in the synchronized flow. The strong congestion often occurs in GP whereas the weak congestion is usual for SP. The weak congestion is often observed at off ramps whereas the strong congestion much more often occurs at on ramps. Under the weak congestion diverse transformations between different congested patterns can occur. PMID:12005957

Kerner, Boris S

2002-04-01

143

Temporal patterns of native Mandarin Chinese speakers' productions of English stop-vowel syllable  

NASA Astrophysics Data System (ADS)

Second language (L2) production can be a kind of interlanguage, a relatively stable system bearing the nature of both the native language (L1) and L2. Within such a system sound components of a syllable may bear their own interlanguage characteristics and yet interact with the other component sounds. The present study investigates temporal patterns of L1-L2 interaction at the syllable level. Audio recordings were made of English stop-vowel syllables produced by native speakers of Mandarin who were fluent in English (ChE). Native English productions (AmE) of these syllables and native productions of Mandarin (ChM) stop-vowel syllables were acquired as native norms. Temporal measures included stop closure duration, voice-onset time (VOT), vowel duration, and syllable duration. Results show that the internal timing components of ChE often deviate from AmE, with the closure duration, VOT, and vowel duration being intermediate to AmE and ChM. However, at the syllable level, ChE productions tend to follow the overall patterns of AmE. Temporal deviations were often compensated by temporal compensation of other components in the syllable, maintaining a balanced consonant/vowel distribution. These findings have implications for a broader understanding of L2 productions.

Wang, Yue; Behne, Dawn M.

2001-05-01

144

Automatic classification of acetowhite temporal patterns to identify precursor lesions of cervical cancer  

NASA Astrophysics Data System (ADS)

Cervical cancer has remained, until now, as a serious public health problem in developing countries. The most common method of screening is the Pap test or cytology. When abnormalities are reported in the result, the patient is referred to a dysplasia clinic for colposcopy. During this test, a solution of acetic acid is applied, which produces a color change in the tissue and is known as acetowhitening phenomenon. This reaction aims to obtaining a sample of tissue and its histological analysis let to establish a final diagnosis. During the colposcopy test, digital images can be acquired to analyze the behavior of the acetowhitening reaction from a temporal approach. In this way, we try to identify precursor lesions of cervical cancer through a process of automatic classification of acetowhite temporal patterns. In this paper, we present the performance analysis of three classification methods: kNN, Naïve Bayes and C4.5. The results showed that there is similarity between some acetowhite temporal patterns of normal and abnormal tissues. Therefore we conclude that it is not sufficient to only consider the temporal dynamic of the acetowhitening reaction to establish a diagnosis by an automatic method. Information from cytologic, colposcopic and histopathologic disciplines should be integrated as well.

Gutiérrez-Fragoso, K.; Acosta-Mesa, H. G.; Cruz-Ramírez, N.; Hernández-Jiménez, R.

2013-12-01

145

Active processing of spatio-temporal input patterns in silicon dendrites.  

PubMed

Capturing the functionality of active dendritic processing into abstract mathematical models will help us to understand the role of complex biophysical neurons in neuronal computation and to build future useful neuromorphic analog Very Large Scale Integrated (aVLSI) neuronal devices. Previous work based on an aVLSI multi-compartmental neuron model demonstrates that the compartmental response in the presence of either of two widely studied classes of active mechanisms, is a nonlinear sigmoidal function of the degree of either input temporal synchrony OR input clustering level. Using the same silicon model, this work expounds the interaction between both active mechanisms in a compartment receiving input patterns of varying temporal AND spatial clustering structure and demonstrates that this compartmental response can be captured by a combined sigmoid and radial-basis function over both input dimensions. This paper further shows that the response to input spatio-temporal patterns in a one-dimensional multi-compartmental dendrite, can be described by a radial-basis like function of the degree of temporal synchrony between the inter-compartmental inputs. PMID:23853330

Wang, Yingxue; Liu, Shih-Chii

2013-06-01

146

The selective control of glycolysis, gluconeogenesis and glycogenesis by temporal insulin patterns  

PubMed Central

Insulin governs systemic glucose metabolism, including glycolysis, gluconeogenesis and glycogenesis, through temporal change and absolute concentration. However, how insulin-signalling pathway selectively regulates glycolysis, gluconeogenesis and glycogenesis remains to be elucidated. To address this issue, we experimentally measured metabolites in glucose metabolism in response to insulin. Step stimulation of insulin induced transient response of glycolysis and glycogenesis, and sustained response of gluconeogenesis and extracellular glucose concentration (GLCex). Based on the experimental results, we constructed a simple computational model that characterises response of insulin-signalling-dependent glucose metabolism. The model revealed that the network motifs of glycolysis and glycogenesis pathways constitute a feedforward (FF) with substrate depletion and incoherent feedforward loop (iFFL), respectively, enabling glycolysis and glycogenesis responsive to temporal changes of insulin rather than its absolute concentration. In contrast, the network motifs of gluconeogenesis pathway constituted a FF inhibition, enabling gluconeogenesis responsive to absolute concentration of insulin regardless of its temporal patterns. GLCex was regulated by gluconeogenesis and glycolysis. These results demonstrate the selective control mechanism of glucose metabolism by temporal patterns of insulin.

Noguchi, Rei; Kubota, Hiroyuki; Yugi, Katsuyuki; Toyoshima, Yu; Komori, Yasunori; Soga, Tomoyoshi; Kuroda, Shinya

2013-01-01

147

Spatio-temporal patterns and dynamics of net primary productivity for Kazakhstan  

NASA Astrophysics Data System (ADS)

Monitoring of net primary productivity (NPP) is especially important for the fragile ecosystems in arid and semi-arid regions. Great interest exists in observing large-scale vegetation dynamics and understanding spatial and temporal patterns of NPP in these areas. In this study we present results of NPP obtained with the model BETHY/DLR for Kazakhstan for 2003–2011 and its spatial and temporal dynamics. The spatial distribution of vegetation productivity shows a gradient from North to South and clear differences between individual vegetation classes. The monthly NPP values show the highest productivity in June. Differences between rain-fed and irrigated areas indicate the dependency on water availability. Annual NPP variability was high for agricultural areas, but showed low values for natural vegetation. The analysis of different patterns in vegetation productivity provides valuable information for the identification of regions that are vulnerable to a possible climate change. This information may thus substantially support a sustainable land management.

Eisfelder, C.; Klein, I.; Huth, J.; Niklaus, M.; Kuenzer, C.

2014-03-01

148

Multi-scale patterning of microparticles using a combination of surface acoustic waves and ultrasonic bulk waves  

NASA Astrophysics Data System (ADS)

Standing surface acoustic waves (SAWs) and standing bulk waves (BWs) are combined to pattern two populations of particles with differing sizes. Patterns with large differences in wavelength in each direction and simultaneous generation of different patterns for each population are demonstrated. Particles are trapped at nodal positions of orthogonal standing wave fields in patterns determined by device voltage amplitudes and frequencies. 10-?m beads are trapped at points at the intersection of the pressure nodes of the SAW and BW fields, and 1-?m beads are trapped in lines at the pressure nodes of the SAW field, producing a multi-scale pattern.

Zhang, Jie; Meng, Long; Cai, Feiyan; Zheng, Hairong; Courtney, Charles R. P.

2014-06-01

149

Mechanisms for spatio-temporal pattern formation in highway traffic models  

Microsoft Academic Search

A key qualitative requirement for highway traffic models is the ability to replicate a type of traffic jam popularly referred to as a phantom jam, shock wave or stop-and-go wave. Despite over 50 years of modelling, the precise mechanisms for the generation and propagation of stop-and-go waves and the associated spatio-temporal patterns are in dispute. However, the increasing availability of

R. Eddie Wilson

2008-01-01

150

Analysis of Spatio-Temporal Patterns in Associative Networks of Spiking Neurons  

Microsoft Academic Search

: A neural network is presentedthat stores spatio-temporal patterns (synfirechains)in associative networks of spikingneurons and replays them at a controlablespeed. An implicit equation is derived andsolved numerically which relates the averagespeed to the network parameters. The replayspeed can be controled by unspecific backgroundsignals and also depends on the numberof co-activated synfire-chains. Balancedinhibition can prevent the latter dependency.Simulation results confirm the...

Thomas Wennekers

1999-01-01

151

Discovering Interpretable Muscle Activation Patterns with the Temporal Data Mining Method  

Microsoft Academic Search

\\u000a The understanding of complex muscle coordination is an important goal in human movement science. There are numerous applications\\u000a in medicine, sports, and robotics. The coordination process can be studied by observing complex, often cyclic movements, which\\u000a are dynamically repeated in an almost identical manner. In this paper we demonstrate how interpretable temporal patterns can\\u000a be discovered within raw EMG measurements

Fabian Mörchen; Alfred Ultsch; Olaf Hoos

152

Spatio-temporal pattern formation on spherical surfaces: numerical simulation and application to solid tumour growth  

Microsoft Academic Search

.   In this paper we examine spatio-temporal pattern formation in reaction-diffusion systems on the surface of the unit sphere\\u000a in 3D. We first generalise the usual linear stability analysis for a two-chemical system to this geometrical context. Noting\\u000a the limitations of this approach (in terms of rigorous prediction of spatially heterogeneous steady-states) leads us to develop,\\u000a as an alternative, a

M. A. J. Chaplain; M. Ganesh; I. G. Graham

2001-01-01

153

A Sequence Identification Measurement Model to Investigate the Implicit Learning of Metrical Temporal Patterns  

PubMed Central

Implicit learning (IL) occurs unconsciously and without intention. Perceptual fluency is the ease of processing elicited by previous exposure to a stimulus. It has been assumed that perceptual fluency is associated with IL. However, the role of perceptual fluency following IL has not been investigated in temporal pattern learning. Two experiments by Schultz, Stevens, Keller, and Tillmann demonstrated the IL of auditory temporal patterns using a serial reaction-time task and a generation task based on the process dissociation procedure. The generation task demonstrated that learning was implicit in both experiments via motor fluency, that is, the inability to suppress learned information. With the aim to disentangle conscious and unconscious processes, we analyze unreported recognition data associated with the Schultz et al. experiments using the sequence identification measurement model. The model assumes that perceptual fluency reflects unconscious processes and IL. For Experiment 1, the model indicated that conscious and unconscious processes contributed to recognition of temporal patterns, but that unconscious processes had a greater influence on recognition than conscious processes. In the model implementation of Experiment 2, there was equal contribution of conscious and unconscious processes in the recognition of temporal patterns. As Schultz et al. demonstrated IL in both experiments using a generation task, and the conditions reported here in Experiments 1 and 2 were identical, two explanations are offered for the discrepancy in model and behavioral results based on the two tasks: 1) perceptual fluency may not be necessary to infer IL, or 2) conscious control over implicitly learned information may vary as a function of perceptual fluency and motor fluency.

Schultz, Benjamin G.; Stevens, Catherine J.; Keller, Peter E.; Tillmann, Barbara

2013-01-01

154

Temporal coherence among tropical coastal lagoons: a search for patterns and mechanisms.  

PubMed

Temporal coherence (i.e., the degree of synchronicity of a given variable among ecological units within a predefined space) has been shown for several limnological features among temperate lakes, allowing predictions about the structure and function of ecosystems. However, there is little evidence of temporal coherence among tropical aquatic systems, where the climatic variability among seasons is less pronounced. Here, we used data from long-term monitoring of physical, chemical and biological variables to test the degree of temporal coherence among 18 tropical coastal lagoons. The water temperature and chlorophyll-a concentration had the highest and lowest temporal coherence among the lagoons, respectively, whereas the salinity and water colour had intermediate temporal coherence. The regional climactic factors were the main factors responsible for the coherence patterns in the water temperature and water colour, whereas the landscape position and morphometric characteristics explained much of the variation of the salinity and water colour among the lagoons. These results indicate that both local (lagoon morphometry) and regional (precipitation, air temperature) factors regulate the physical and chemical conditions of coastal lagoons by adjusting the terrestrial and marine subsidies at a landscape-scale. On the other hand, the chlorophyll-a concentration appears to be primarily regulated by specific local conditions resulting in a weak temporal coherence among the ecosystems. We concluded that temporal coherence in tropical ecosystems is possible, at least for some environmental features, and should be evaluated for other tropical ecosystems. Our results also reinforce that aquatic ecosystems should be studied more broadly to accomplish a full understanding of their structure and function. PMID:21085785

Caliman, A; Carneiro, L S; Santangelo, J M; Guariento, R D; Pires, A P F; Suhett, A L; Quesado, L B; Scofield, V; Fonte, E S; Lopes, P M; Sanches, L F; Azevedo, F D; Marinho, C C; Bozelli, R L; Esteves, F A; Farjalla, V F

2010-10-01

155

Groundwater-Surface Water Interactions along a Lake Shore: Spatial Patterns and Temporal Dynamics  

NASA Astrophysics Data System (ADS)

In this study the spatial and temporal variability of groundwater-surface water interactions along a lake shore is investigated by combining different experimental methods. Study area is Lake Hinnensee, situated in the lake district north of Berlin in Germany. The lake is a seepage lake with no surface inflows or outflows. To investigate the spatial patterns of groundwater surface water interactions as well as their temporal dynamics we applied a number of different techniques: snapshots of spatial patterns were determined by gridded measurements of temperature profiles in the lake sediment as well as with distributed temperature sensing (DTS), using a fiber optic cable placed at the sediment surface. The spatial resolution of measurements adequate for pattern detection was determined by comparing experimental designs at various spatial scales and resolutions. Continuous time series of water levels and temperature time series in piezometer transects at different locations along the lake shore give insight into both spatial variability and temporal dynamics of vertical hydraulic gradients and heat transport. Exfiltration rates of groundwater into the lake were estimated with 3 different approaches. The experimental methodologies were evaluated in a "cost-benefit" analysis, comparing effort with scientific benefit. The results show that groundwater exfiltration into the lake is to some extent variable in time and is highly variable in space: there is a strong gradient perpendicular to the lake shore as well as high heterogeneity along the lake shore.

Blume, T.; Tecklenburg, C.; Krause, S.; Lewandowski, J.

2012-12-01

156

Can acoustic emissions patterns signal imminence of avalanche events in a growing sand pile?  

NASA Astrophysics Data System (ADS)

Gravity driven mass release is often triggered abruptly with limited precursory cues to indicate imminent failure and thus limiting early warning. Evidence suggests that with increased mechanical loading of a slope, numerous local damage events marking friction between rearranged particles or breakage of roots release strain energy as elastic waves measurable as acoustic emissions. We examined the potential predictability of mass release events from preceding acoustic emission (AE) signatures in a well-known and simple model system of a growing sand pile. We installed four AE-sensors within the core of a 30 cm (diameter) sand pile fed by a constant input of grains and mounted on a balance. Subsequent to the convergence of the slope to dynamic angle of repose, sand avalanche across the bottom boundary were monitored by abrupt mass change and by the amplitudes and number of AE events (recorded at high frequency and averaged to 0.2 s). We detected a systematic change of AE-patterns characterized by systematically decreasing AE standard deviation prior to each mass release. Although the lead time following minimum AE standard deviation was relatively short (10s of seconds), the AE signature already started to change minutes before the mass release. Accordingly the information embedded in AE signal dynamics could potentially offer larger lead times for systems of practical interest.

Vögtli, Melanie; Lehmann, Peter; Breitenstein, Daniel; Or, Dani

2014-05-01

157

Spatio-temporal patterns of forest fires: a comprehensive application of the K-function  

NASA Astrophysics Data System (ADS)

The spatial distribution of uncontrolled hazardous events, such as forest fires, is largely investigated from the scientific community with the purpose of finding out the more vulnerable areas. Mapping the location of spatio-temporal sequences for a given environmental dataset is of great impact; however, the majority of the studies miss the analysis of the aggregation over time. Nonetheless discovering unusual temporal pattern for a given time sequence is fundamental to understand the phenomena and underlying processes. The present study aims investigating both the spatial and the temporal cluster behaviour of forest fires occurrences registered in Canton Ticino (Switzerland) over a period of about 40 years and testing if space and time interact in generate clusters. To do this, the purely spatial, the time and the space-time extensions of the Ripley's K-function were applied. The Ripley's K-function is a statistic exploratory method which enables detecting whether or not a point process (e.g. the location of the ignition points) is randomly distributed. The purely spatial K-function K(r) is defined as the expected number of further events within an area of radius r around an arbitrary point of the pattern, divided by the intensity of the phenomenon. Under completely spatial randomness, the value of the K(r) is equal to the area around the point (=?r2), while observations above this theoretical value imply a clustering behaviour at the corresponding distance r. For the purely time analysis, the Ripley's K-function K(t) can be taught as a reformulation of the spatial version to detect unexpected aggregation of events over the temporal scale. For its computation, the value of the intensity used in K(r) is replaced by the total duration of the time sequence divided by the total number of observed events, and the distance r is replaced by the time interval t. Under time-regularity, K(t) equals 2t, whereas, observed measures above this theoretical value indicate a temporal cluster behaviour at the corresponding temporal scale t. For the analysis of the space-time clustering, we applied the spatio-temporal (bivariate) K-function K(r,t), which evaluates if events are closer in both space and time. Intuitively, if there is no space-time interaction K(r,t) = K(r) * K(t). Accordingly, if K(r,t) minus K(r) * K(t) is positive, this indicates an interaction between space and time in producing clusters, which arise from a well detectable spatial and temporal scales. This study allowed detecting: 1) the purely spatial and the purely temporal scales at which the registered forest fires events are clustered, given by the results of the K(r) and the K(t) computations; and 2) the time period where spatial clusters take place at a given distance scale, exhibited by the results of the K(r,t) computation. Key words: spatio-temporal sequences, cluster, Ripley's K-function, forest fires. Acknowledgements This work was partly supported by the SNFS Project No. 200021-140658, "Analysis and Modelling of Space-Time Patterns in Complex Regions". References - Bivand R., Rowlingson B., and Diggle P. (2012) - splancs package in R project - Diggle P., Chetwynd A., Haggkvist R. and Morris S. (1995) Second-order analysis of space-time clustering. Statistical Methods in Medical Research, vol. 4(2): 124-136. - R Development Core Team (2012). R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. URL: http://www.R-project.org/. - Vega Orozco C., Tonini M., Conedera M., Kanveski M. (2012) Cluster recognition in spatial-temporal sequences: the case of forest fires, GeoInformatica, vol. 16(4): 653-673.

Tonini, Marj; Vega Orozco, Carmen; Kanevski, Mikhaïl; Conedera, Marco

2013-04-01

158

Temporal variability of thermal refuges and water temperature patterns in an Atlantic salmon river  

NASA Astrophysics Data System (ADS)

River basins in northern latitudes are predicted to experience increased water temperatures under future climate change. This will have a negative impact on most salmonid populations which are highly intolerant of temperatures in excess of 23° C. In response to summer heat stress, salmonids thermoregulate in discrete units of cold water. Termed thermal refuges, these are of great significance to the ability of salmon and trout to survive increased water temperatures. Although previous research has documented links between the spatial patterns of thermal refuges and salmonid distribution and behaviour, the temporal variability of these cold water units has never been studied. In this investigation, airborne thermal infrared (TIR) imagery acquired six times between 2009 and 2011 was used to characterise temporal variability of thermal refuges and broader scale patterns of water temperature in the Rivière Ouelle, an Atlantic salmon river in Québec, Canada. Thermal refuges detected from TIR imagery were classified into a series of categories, revealing notable inter-survey variability between the absolute counts of each refuge type. Broader-scale longitudinal temperature profiles of river temperature were also extracted. Temporal variability in the absolute counts of lateral groundwater seeps (the most frequently observed thermal refuge class) was shown to correlate strongly with long duration hydrometeorological metrics such as seasonal mean discharge (R2 = 0.94, p < 0.01). Conversely, thermal refuges resulting from cold water tributaries were more temporally stable. Downstream temperature complexity was shown to correlate best with short duration metrics such as cumulative precipitation depth within a 5-day period prior to each survey (R2 = 0.90, p < 0.01). This study is the first of its kind to link thermal refuge dynamics and water temperature patterns to hydrometeorological conditions and may offer valuable insights into how changing hydrometeorological regimes could influence these important cold water units in the future.

Dugdale, S.; Bergeron, N.; St-Hilaire, A.

2013-12-01

159

Temporal stability of soil moisture patterns measured by proximal ground-penetrating radar  

NASA Astrophysics Data System (ADS)

We analyzed the temporal stability of soil moisture patterns acquired using a proximal ground-penetrating radar (GPR) in a 2.5 ha agricultural field at five different dates over three weeks. The GPR system was mounted on a mobile platform, allowing for real-time mapping of soil moisture with a high spatial resolution (2-5 m). The spatio-temporal soil moisture patterns were in accordance with the meteorological data and with soil moisture measurements from soil core sampling. Time-stable areas showing the field-average moisture could be revealed by two methods: (1) by the computation of temporal stability indicators based on relative differences of soil moisture to the field-average and (2) by the spatial intersection of the areas showing the field-average. Locations where the mean relative difference was below 0.02 m3 m-3 extended up to 10% of the field area whereas the intersection of areas showing the field-average within a tolerance of 0.02 m3 m-3 covered 5% of the field area. Compared to most of the previous studies about temporal stability of soil moisture, time-stable areas and their spatial patterns could be revealed instead of single point locations, owing to the advanced GPR method for real-time mapping. It is believed that determining spatially coherent time-stable areas is more informative rather than determining time-stable points. Other acquisitions over larger time periods would be necessary to assert the robustness of the time-stable areas.

Minet, J.; Verhoest, N. E. C.; Lambot, S.; Vanclooster, M.

2013-04-01

160

Spatio-temporal pattern recognizers using spiking neurons and spike-timing-dependent plasticity  

PubMed Central

It has previously been shown that by using spike-timing-dependent plasticity (STDP), neurons can adapt to the beginning of a repeating spatio-temporal firing pattern in their input. In the present work, we demonstrate that this mechanism can be extended to train recognizers for longer spatio-temporal input signals. Using a number of neurons that are mutually connected by plastic synapses and subject to a global winner-takes-all mechanism, chains of neurons can form where each neuron is selective to a different segment of a repeating input pattern, and the neurons are feed-forwardly connected in such a way that both the correct input segment and the firing of the previous neurons are required in order to activate the next neuron in the chain. This is akin to a simple class of finite state automata. We show that nearest-neighbor STDP (where only the pre-synaptic spike most recent to a post-synaptic one is considered) leads to “nearest-neighbor” chains where connections only form between subsequent states in a chain (similar to classic “synfire chains”). In contrast, “all-to-all spike-timing-dependent plasticity” (where all pre- and post-synaptic spike pairs matter) leads to multiple connections that can span several temporal stages in the chain; these connections respect the temporal order of the neurons. It is also demonstrated that previously learnt individual chains can be “stitched together” by repeatedly presenting them in a fixed order. This way longer sequence recognizers can be formed, and potentially also nested structures. Robustness of recognition with respect to speed variations in the input patterns is shown to depend on rise-times of post-synaptic potentials and the membrane noise. It is argued that the memory capacity of the model is high, but could theoretically be increased using sparse codes.

Humble, James; Denham, Susan; Wennekers, Thomas

2012-01-01

161

Spatio-temporal pattern recognizers using spiking neurons and spike-timing-dependent plasticity.  

PubMed

It has previously been shown that by using spike-timing-dependent plasticity (STDP), neurons can adapt to the beginning of a repeating spatio-temporal firing pattern in their input. In the present work, we demonstrate that this mechanism can be extended to train recognizers for longer spatio-temporal input signals. Using a number of neurons that are mutually connected by plastic synapses and subject to a global winner-takes-all mechanism, chains of neurons can form where each neuron is selective to a different segment of a repeating input pattern, and the neurons are feed-forwardly connected in such a way that both the correct input segment and the firing of the previous neurons are required in order to activate the next neuron in the chain. This is akin to a simple class of finite state automata. We show that nearest-neighbor STDP (where only the pre-synaptic spike most recent to a post-synaptic one is considered) leads to "nearest-neighbor" chains where connections only form between subsequent states in a chain (similar to classic "synfire chains"). In contrast, "all-to-all spike-timing-dependent plasticity" (where all pre- and post-synaptic spike pairs matter) leads to multiple connections that can span several temporal stages in the chain; these connections respect the temporal order of the neurons. It is also demonstrated that previously learnt individual chains can be "stitched together" by repeatedly presenting them in a fixed order. This way longer sequence recognizers can be formed, and potentially also nested structures. Robustness of recognition with respect to speed variations in the input patterns is shown to depend on rise-times of post-synaptic potentials and the membrane noise. It is argued that the memory capacity of the model is high, but could theoretically be increased using sparse codes. PMID:23087641

Humble, James; Denham, Susan; Wennekers, Thomas

2012-01-01

162

Spatio-Temporal Patterns of Barmah Forest Virus Disease in Queensland, Australia  

PubMed Central

Background Barmah Forest virus (BFV) disease is a common and wide-spread mosquito-borne disease in Australia. This study investigated the spatio-temporal patterns of BFV disease in Queensland, Australia using geographical information system (GIS) tools and geostatistical analysis. Methods/Principal Findings We calculated the incidence rates and standardised incidence rates of BFV disease. Moran's I statistic was used to assess the spatial autocorrelation of BFV incidences. Spatial dynamics of BFV disease was examined using semi-variogram analysis. Interpolation techniques were applied to visualise and display the spatial distribution of BFV disease in statistical local areas (SLAs) throughout Queensland. Mapping of BFV disease by SLAs reveals the presence of substantial spatio-temporal variation over time. Statistically significant differences in BFV incidence rates were identified among age groups (?2?=?7587, df?=?7327,p<0.01). There was a significant positive spatial autocorrelation of BFV incidence for all four periods, with the Moran's I statistic ranging from 0.1506 to 0.2901 (p<0.01). Semi-variogram analysis and smoothed maps created from interpolation techniques indicate that the pattern of spatial autocorrelation was not homogeneous across the state. Conclusions/Significance This is the first study to examine spatial and temporal variation in the incidence rates of BFV disease across Queensland using GIS and geostatistics. The BFV transmission varied with age and gender, which may be due to exposure rates or behavioural risk factors. There are differences in the spatio-temporal patterns of BFV disease which may be related to local socio-ecological and environmental factors. These research findings may have implications in the BFV disease control and prevention programs in Queensland.

Naish, Suchithra; Hu, Wenbiao; Mengersen, Kerrie; Tong, Shilu

2011-01-01

163

Temporal Analysis of Feeding Patterns of Culex erraticus in Central Alabama  

PubMed Central

Abstract Host blood meals in seven mosquito species previously shown to be infected with eastern equine encephalitis virus at a site in the Tuskegee National Forest in southcentral Alabama were investigated. Of 1374 blood meals derived from 88 different host species collected over 6 years from these seven mosquito species, 1099 were derived from Culex erraticus. Analysis of the temporal pattern of Cx. erraticus meals using a Runs test revealed that the patterns of feeding upon avian and mammalian hosts from March to September of each year were not randomly distributed over time. Similarly, meals taken from the three most commonly targeted host species (yellow-crowned night heron, great blue heron, and white-tailed deer) were not randomly distributed. A Tukey's two-way analysis of variance test demonstrated that although the temporal pattern of meals taken from avian hosts were consistent over the years, the patterns of meals taken from the individual host species were not consistent from year to year.

Katholi, Charles R.; Burkett-Cadena, Nathan; Hassan, Hassan K.; Kristensen, Sibylle

2011-01-01

164

Discrimination and Comprehension of Synthetic Speech by Students with Visual Impairments: The Case of Similar Acoustic Patterns  

ERIC Educational Resources Information Center

This study examined the perceptions held by sighted students and students with visual impairments of the intelligibility and comprehensibility of similar acoustic patterns produced by synthetic speech. It determined the types of errors the students made and compared the performance of the two groups on auditory discrimination and comprehension.

Papadopoulos, Konstantinos; Argyropoulos, Vassilios S.; Kouroupetroglou, Georgios

2008-01-01

165

Temporal investigation of acoustic wave pressure spectrum of high repetition rate TEA-CO 2 lasers by using a three-dimensional mathematical model  

NASA Astrophysics Data System (ADS)

The production of acoustic wave is one of the most important factors on the action of High Repetition Rate TEA-CO 2 lasers. In this paper a three-dimensional mathematical modeling has been considered for investigation of temporal and spatial variations of acoustic waves in the laser cavity and its effect on the output of HRR lasers. By calculation of equations obtained from this model and plotting the pressure spectrum in different states, the effect of electrodes dimensions, cavity dimensions, gas flow velocity and repetition rate of laser in different times have been acquired. At last, optimum conditions for performance of laser action and having a good output have been arrived.

Rahimi, M.; Baghshahi, H. R.; Marashi, S. M. B.

2011-04-01

166

Temporal reiteration of a precise gene expression pattern during nematode development.  

PubMed Central

The nematode Caenorhabditis elegans is contained within a multifunctional exoskeleton, the cuticle, that contains a large number of distinct collagens. As the nematode proceeds from the egg through four larval stages to the adult, transition between larval stages is marked by synthesis of a new cuticle and subsequent moulting of the old one. This is a cyclically repeated developmental event, frequently described as the moulting cycle. We have examined the temporal expression of a group of six genes encoding distinct cuticular collagens. As expected, mRNA abundance for each of the six genes tested is found to oscillate, peaking once during each larval stage. Unexpectedly, the periods of abundance for each gene do not coincide, different genes being expressed at different times relative to one another within the moulting cycle. We detect a programme of temporally distinct waves of collagen gene expression, the precise pattern of which is repeated during each of the four larval stages. This multiphasic pattern of oscillating cuticular collagen gene expression indicates an unexpected complexity of temporal control during the nematode moulting cycle and has implications for collagen trimerization and cuticle synthesis. Images

Johnstone, I L; Barry, J D

1996-01-01

167

Microscopic theory of spatial-temporal congested traffic patterns at highway bottlenecks.  

PubMed

A microscopic theory of spatial-temporal congested traffic patterns at highway bottlenecks due to on-ramps, merge bottlenecks (a reduction of highway lanes), and off-ramps is presented. The basic postulate of three-phase traffic theory is used, which claims that homogeneous (in space and time) model solutions (steady states) of synchronized flow cover a two dimensional region in the flow-density plane [B. S. Kerner, Phys. Rev. Lett. 81, 3797 (1998); Trans. Res. Rec. 1678, 160 (1999)]. Phase transitions leading to diverse congested patterns, pattern evolution, and pattern nonlinear features have been found. Diagrams of congested patterns, i.e., regions of the pattern emergence dependent on traffic demand, have been derived. Diverse effects of metastability with respect to the pattern formation have been found. The microscopic theory allows us to explain the main empirical pattern features at on-ramps and off-ramps which have recently been found [B. S. Kerner, Phys. Rev. E 65, 046138 (2002)]. (i) Rather than moving jams, synchronized flow first occurs at bottlenecks if the flow rate is slowly increasing. Wide moving jams can spontaneously occur only in synchronized flow. (ii) General patterns (GP) and synchronized flow patterns (SP) can spontaneously emerge at the bottlenecks. There can be the widening SP (WSP), the moving SP (MSP), and the localized SP. (iii) At on-ramps cases of "weak" and "strong" congestion should be distinguished. In contrast to weak congestion, under strong congestion the flow rate in synchronized flow in GP reaches a limit flow rate, the frequency of the moving jam emergence reaches a maximum, i.e., the GP characteristics under strong congestion do not depend on traffic demand. (iv) At the off-ramp GP with weak congestion occur. (v) A study of the pattern formation on a highway with two bottlenecks shows that diverse expanded patterns can occur, which cover both bottlenecks. SP first emerged at the downstream bottleneck can be caught at the upstream bottleneck (the catch effect). MSP, WSP, or wide moving jams first emerged at the downstream bottleneck induce diverse patterns at the upstream bottleneck. The onset of congestion at the upstream bottleneck can lead to an intensification of congestion at the downstream bottleneck. This causes a change in the pattern type and/or the pattern features. PMID:14524855

Kerner, Boris S; Klenov, Sergey L

2003-09-01

168

Similarity breeds proximity: pattern similarity within and across contexts is related to later mnemonic judgments of temporal proximity.  

PubMed

Experiences unfold over time, but little is known about the mechanisms that support the formation of coherent episodic memories for temporally extended events. Recent work in animals has provided evidence for signals in hippocampus that could link events across temporal gaps; however, it is unknown whether and how such signals might be related to later memory for temporal information in humans. We measured patterns of fMRI BOLD activity as people encoded items that were separated in time and manipulated the presence of shared or distinct context across items. We found that hippocampal pattern similarity in the BOLD response across trials predicted later temporal memory decisions when context changed. By contrast, pattern similarity in lateral occipital cortex was related to memory only when context remained stable. These data provide evidence in humans that representational stability in hippocampus across time may be a mechanism for temporal memory organization. PMID:24607235

Ezzyat, Youssef; Davachi, Lila

2014-03-01

169

Temporal Changes in Eruptive Behavior at Fuego Volcano, Guatemala Identified with Seismic Coda Wave Interferometry and Seismo-acoustic Observations  

NASA Astrophysics Data System (ADS)

Fuego Volcano (14°29'N, 90°53'W, 3800m) is the southernmost vent of the north-south trending Fuego-Acatenango volcanic complex. A basaltic-andesite stratovolcano, Fuego has had more than 60 sub-plinian eruptions since 1524 AD, making it one of the most active volcanoes in the world. Since 1999 Fuego has exhibited continuous low-level activity, which alternates between periods of lava effusion with strombolian explosions and periods of discrete explosions with no lava effusion. We analyzed 138 explosions recorded on a broadband seismometer and infrasonic microphones from 7 to 14 June 2008 at a distance of 7.5 km from the vent. During the observation period, a new lava flow began. Additional observations were made at a distance of 1 km between 27 June and 1 July 2008. The explosions were identified through a combination of visual field observations and the examination of infrasound records. Acoustic waveform cross-correlation indicated a highly repetitive source appropriate for investigating temporal variations in the wavefield. We measured variations in seismic and acoustic wave arrival time differences in the range of 0.5 s for the more distant station, which might occur as a result of variations in source depth, for example. However, after examining a wind speed model for the region, we find that wind speed variations are more likely to explain the delays. We also detected short-term relative changes in the velocity structure ranging from -0.23% to 0.61% at the distant station and -0.8% to 0.7% at the closer station using seismic coda wave interferometry. This rapid variation, sometimes changing by 0.23% in 90 minutes, may indicate minor fluctuations in volatile content.

Erdem, J.; Waite, G. P.

2011-12-01

170

Temporal and spatial patterns in vegetation and atmospheric properties from AVIRIS  

SciTech Connect

Little research has focused on the use of imaging spectrometry for change detection. In this paper, the authors apply Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data to the monitoring of seasonal changes in atmospheric water vapor, liquid water, and surface cover in the vicinity of the Jasper Ridge, CA, for three dates in 1992. Apparent surface reflectance was retrieved and water vapor and liquid water mapped by using a radiative-transfer-based inversion that accounts for spatially variable atmospheres. Spectral mixture analysis (SMA) was used to model reflectance data as mixtures of green vegetation (GV), nonphotosynthetic vegetation (NPV), soil, and shade. Temporal and spatial patterns in endmember fractions and liquid water were compared to the normalized difference vegetation index (NDVI). The reflectance retrieval algorithm was tested by using a temporally invariant target.

Roberts, D.A. [Univ. of California, Santa Barbara, CA (United States). Dept. of Geography] [Univ. of California, Santa Barbara, CA (United States). Dept. of Geography; Green, R.O. [Univ. of California, Santa Barbara, CA (United States). Dept. of Geography] [Univ. of California, Santa Barbara, CA (United States). Dept. of Geography; [Jet Propulsion Labs., Pasadena, CA (United States); Adams, J.B. [Univ. of Washington, Seattle, WA (United States). Dept. of Geological Sciences] [Univ. of Washington, Seattle, WA (United States). Dept. of Geological Sciences

1997-12-01

171

Different patterns of famous people recognition disorders in patients with right and left anterior temporal lesions: a systematic review.  

PubMed

Selective disorders in recognition of familiar people have been described in patients with right and left anterior temporal lesions, but the exact nature of these cognitive impairments remains controversial. A clarification of this issue could have theoretical implications, because, according to Snowden et al. [Snowden, J. S., Thompson, J. C., & Neary, D. (2004). Knowledge of famous faces and names in semantic dementia. Brain, 127, 860-872], the pattern of impairment shown by patients with right and left anterior temporal atrophy is inconsistent with unitary, abstract, amodal models of semantic memory. This pattern could, on the contrary suggest a multimodal network, in which the right and left temporal lobes would mainly process and store visual and, respectively, verbal information. I tried to clarify this issue by systematically reviewing: (a) all published individual cases of patients showing a prevalent damage of the anterior parts of the right or left temporal lobes and a selective disorder of famous people recognition; (b) all group studies of patients with right or left temporal lobe epilepsy, which had investigated aspects of famous people recognition impairment. Results of these reviews consistently showed that different patterns of impaired recognition of familiar people can be observed in patients with right and left anterior temporal pathology. These patterns consist of a loss of familiarity feelings and of person specific information retrieval from face stimuli, when the right temporal lobe is damaged and of a prevalent impairment in finding their names when the anterior parts of the left temporal lobe are selectively damaged. PMID:17275042

Gainotti, Guido

2007-04-01

172

TEMPORAL PATTERNS IN THREE-DIMENSIONAL STRUCTURE AND ACTIVITY OF SCHOOLS OF THE ATLANTIC SILVERSIDE 'MENIDIA MENIDIA'  

EPA Science Inventory

Temporal patterns in the structure and activity of schools of the Atlantic silverside Menidia menidia were investigated under laboratory conditions using a new computerized video technique for three-dimensional analysis. Fish were collected by seining at Middle Bridge, Pettaquans...

173

Analysing spatio-temporal pattern of changing farmland in China's arid zone  

NASA Astrophysics Data System (ADS)

Multi-temporal imagery has been used for landuse and land cover change detection since the very early stage of remote sensing technology. As large amount of remotely sensed data have been collected, historical land cover changes and change patterns can be reconstructed by a time series recorded by images. This paper reports a study on the methodology for quantifying spatial pattern of land cover changes in an arid zone during a 13-year period and the attempts to identify the key factors for these changes. The approach is based on the post-classification method. Multi-temporal images were independently classified to establish change trajectories for the farmland land cover type. A set of class-level metrics is then calculated on the trajectory classes, including Percentage of Landscape (PLAND), Normalized Landscape Shape Index (NLSI), Interspersion and Juxtaposition Index (IJI) and Area Weighted Fractal Dimension Index (FRAC_AM). These metrics and their relationship were shown as good indicators on the environmental impact in the fragile ecosystem due to the rapid expansion of farmland accompanied with the limited water resources. The results show that spatial pattern metrics of land cover change trajectories provide an effective measurement on landscape changes, which can further be interpreted for agriculture planning and management.

Zhou, Qiming; Sun, Bo

2008-10-01

174

Phenol oxidases from Rhodnius prolixus: temporal and tissue expression pattern and regulation by ecdysone.  

PubMed

Rhodnius prolixus 5th instar nymphs have significant PO enzymatic activity in the anterior midgut, fat body and hemolymph. The tissue with the major amount of PO activity is the anterior midgut while those with higher specific activities are the fat body and hemolymph. In this work the temporal pattern of PO enzymatic activity in different tissues was investigated. In fat body, PO peaks occur at 7, 12 and 16 days after a blood meal. In hemolymph, PO diminishes until day 7, and then recovers by day 14. In the anterior midgut tissue, PO peaks on day 9 and just before ecdysis; a similar pattern was observed in the anterior midgut contents. Some of these activities are dependent on the release of ecdysone, as feeding blood meal containing azadirachtin suppresses them and ecdysone treatment counteracts this effect. These results suggest that during the development of the 5th instar, the insect has natural regulating cycles of basal PO expression and activation, which could be related to the occurrence of natural infections. The differences in temporal patterns of activity and the effects of azadirachtin and ecdysone in each organ suggest that, at least in R. prolixus, different tissues are expressing different PO genes. PMID:20361973

Genta, F A; Souza, R S; Garcia, E S; Azambuja, P

2010-09-01

175

Spatial patterns of water diffusion along white matter tracts in temporal lobe epilepsy  

PubMed Central

Objectives: Diffusion tensor imaging (DTI) tractography has shown tract-specific pathology in temporal lobe epilepsy (TLE). This technique normally yields a single value per diffusion parameter per tract, potentially reducing the sensitivity for the detection of focal changes. Our goal was to spatially characterize diffusion abnormalities of fasciculi carrying temporal lobe connections. Methods: We studied 30 patients with drug-resistant TLE and 21 healthy control subjects. Twenty-four patients underwent DTI toward the end of video-EEG telemetry, with an average of 50 ± 54 hours between the last seizure and DTI examination. After manual dissection of the uncinate and inferior longitudinal and arcuate bundle, they were spatially matched based on their distance to the temporal lobe, providing between-subject correspondence of tract segments. We evaluated point-wise differences in diffusion parameters along each tract at group and subject levels. Results: Our approach localized increased mean diffusivity restricted to or more prominent within the ipsilateral temporal lobe. These abnormalities tapered off as tracts exited the temporal lobe. We observed that the shorter the interval between the last seizure and DTI, the higher the mean diffusivity (MD) of the ipsilateral tracts. Linear discriminant analysis of tract segments correctly lateralized 87% of patients. Conclusions: The centrifugal pattern of white matter diffusion abnormalities probably reflects astrogliosis and microstructure derangement related to seizure activity in the vicinity of the focus. The negative correlation between the interval from last seizure and MD suggests a role for postictal vasogenic edema. The ability to assess tracts segmentally may contribute to a better understanding of the extent of white matter pathology in epilepsy and assist in the presurgical evaluation of patients with TLE, particularly those with unremarkable conventional imaging results.

Concha, Luis; Kim, Hosung; Bernasconi, Andrea; Bernhardt, Boris C.

2012-01-01

176

Temporal pattern of skeletal muscle gene expression following endurance exercise in Alaskan sled dogs.  

PubMed

Muscle responses to exercise are complex and include acute responses to exercise-induced injury, as well as longer term adaptive training responses. Using Alaskan sled dogs as an experimental model, changes in muscle gene expression were analyzed to test the hypotheses that important regulatory elements of the muscle's adaptation to exercise could be identified based on the temporal pattern of gene expression. Dogs were randomly assigned to undertake a 160-km run (n=9), or to remain at rest (n=4). Biceps femoris muscle was obtained from the unexercised dogs and two dogs at each of 2, 6, and 12 h after the exercise, and from three dogs 24 h after exercise. RNA was extracted and microarray analysis used to define gene transcriptional changes. The changes in gene expression after exercise occurred in a temporal pattern. Overall, 569, 469, 316, and 223 transcripts were differentially expressed at 2, 6, 12, and 24 h postexercise, respectively, compared with unexercised dogs (based on Por=1.5). Increases in a number of known transcriptional regulators, including peroxisome proliferator-activated receptor-alpha, cAMP-responsive element modulator, and CCAAT enhancer binding protein-delta, and potential signaling molecules, including brain-derived neurotrophic factor, dermokine, and suprabasin, were observed 2 h after exercise. Biological functional analysis suggested changes in expression of genes with known functional relationships, including genes involved in muscle remodeling and growth, intermediary metabolism, and immune regulation. Sustained endurance exercise by Alaskan sled dogs induces coordinated changes in gene expression with a clear temporal pattern. RNA expression profiling has the potential to identify novel regulatory mechanisms and responses to exercise stimuli. PMID:19498091

Brass, Eric P; Peters, Mette A; Hinchcliff, Kenneth W; He, Yudong D; Ulrich, Roger G

2009-08-01

177

The impact of spatial and temporal patterns on multi-cellular behavior  

NASA Astrophysics Data System (ADS)

What makes a fruit fly a fruit fly? Essentially this question stems from one of the most fascinating problems in biology: how a single cell (fertilized egg) can give rise to a fully grown animal. To be able to answer this question, the importance to how spatial and temporal patterns of gene and protein expression influence the development of an organism must be understood. After all, fruit fly larvae are segmented, while fertilized eggs are not. Pattern formation is fundamental to establishing this organization of the developing embryo with the ultimate goal being the precise arrangements of specialized cells and tissues within each organ in an adult organism. The research presented here showcases the examples of studies that assess the impact spatial and temporal protein patterns have on the behavior of a collection of cells. By introducing new experimental, non-traditional techniques we developed model systems that allowed us to examine the dependence of the strength of adhesion of cells on the protein organization on sub-cellular, micron length scales, and to investigate how epithelial cell sheets coordinate their migration incorporating individual cell locomotion, molecular signal propagation and different boundary conditions. The first part of this dissertation presents a photolithography-based silanization patterning technique that allowed us to homogeneously pattern large areas with high precision. This method is then applied to organizing cell adhesion-promoting proteins on surfaces for the purposes of studying and manipulating cell behavior. We show how the strength of adhesion is dependent on high local density of an adhesive extracellular matrix protein fibronectin. The varied appeal of this technique is exhibited by showing its applicability to pattern stretched DNA, too. The second part of this dissertation focuses on the impact of spatial and temporal propagation of a molecular signal (ERK 1/2 MAPK) in migrating epithelial sheets during wound healing. By tracking the motion of individual cells within the sheet under the three constructed conditions, we show how the dynamics of the individual cells' motion is responsible for the coordinated migration of the sheet in accordance with the activation of ERK 1/2 MAPK.

Nikolic, Djordje L.

178

Spontaneous firings of carnivorous aquatic Utricularia traps: temporal patterns and mechanical oscillations.  

PubMed

Aquatic species of Utricularia are carnivorous plants living in environments poor in nutrients. Their trapping mechanism has fascinated generations of scientists and is still debated today. It was reported recently that Utricularia traps can fire spontaneously. We show here that these spontaneous firings follow an unexpected diversity of temporal patterns, from "metronomic" traps which fire at fixed time intervals to "random" patterns, displaying more scattered firing times. Some "bursting" traps even combine both aspects, with groups of fast regular firings separated by a variable amount of time. We propose a physical model to understand these very particular behaviors, showing that a trap of Utricularia accomplishes mechanical oscillations, based on continuous pumping and sudden opening of the trap door (buckling). We isolate the key parameters governing these oscillations and discuss the effect of their fluctuations. PMID:21647417

Vincent, Olivier; Roditchev, Ivan; Marmottant, Philippe

2011-01-01

179

Spatial and temporal coherence of broadband acoustic transmissions in the Straits of Florida  

NASA Astrophysics Data System (ADS)

Month-long time series of broadband coherent measurements of channel pulse responses in the Florida Straits allow for estimation of signal coherence under a great variety of signal parameters and environmental conditions. Two 32-element arrays, one vertical and another horizontal (bottomed) along the path of propagation allow for comparison of spatial coherency and single phone temporal coherencies. The transmitted signals cover 5 octaves from 100 through 3200 Hz. Coherencies for single resolved SRBR arrivals are compared with those for unresolved multipath BRB focused arrivals. Many factors are at play including the complication of coherent reception from nearby shipping and multipath interference. However, the time series are long enough to sort out and explain most relations to the environmental variability. Vertical and horizontal coherence lengths are compared over a wide range of frequencies. Generally, SBRB paths are found to be far more stable and coherent than RBR paths especially at higher frequencies suggesting that sound-speed variability near turning RBR rays/modes is more destructive to coherency. The loss of signal coherency for RBR paths is accompanied by a significant loss of signal intensity-as much as 10 to 15 dB.

Deferrari, Harry A.; Williams, Neil; Nguyen, Hien

2003-04-01

180

Spatial and temporal patterns of hydrologic connectivity between upland landscapes and stream networks (Invited)  

NASA Astrophysics Data System (ADS)

Congress enacted the Clean Water Act (CWA) 'to restore and maintain the chemical, physical, and biological integrity of the Nation's waters'. A recent Supreme Court decision further described protection for waters with 'a significant nexus to navigable waters" if they are in the same watershed and have an effect on the chemical, physical, or biological integrity of traditional navigable waters or interstate waters that is more than 'speculative or insubstantial.' Evolving interpretation of the CWA and 'significant nexus' (connectivity) requires investigation and understanding of the spatial and temporal patterns of hydrologic connectivity between upland landscapes and stream networks that mediate streamflow magnitude and composition. While hydrologic connectivity is a continuum, strong non-linearities including the shift from unsaturated to saturated flow conditions lead to threshold or transient connectivity behavior and orders of magnitude changes in flow velocities and source water compositions. Here we illustrate the spatial and temporal dynamics of hydrologic connectivity between upland landscapes and stream networks that provide direct and proximate links between streamflow composition and its watershed sources. We suggest that adjacency alone does not determine influence on hydrologic response and streamwater composition and that new understanding and communication of the temporal and spatial dynamics of watershed connectivity are required to address urgent needs at the interface of the CWA, science, and society.

Ma, L.; Qi, Z.; Helmers, M. J.; Ahuja, L. R.; Malone, R. W.

2011-12-01

181

Spatial and temporal patterns of hydrologic connectivity between upland landscapes and stream networks  

NASA Astrophysics Data System (ADS)

Congress enacted the Clean Water Act (CWA) "to restore and maintain the chemical, physical, and biological integrity of the Nation's waters". A recent Supreme Court decision further described protection for waters with "a significant nexus to navigable waters" if they are in the same watershed and have an effect on the chemical, physical, or biological integrity of traditional navigable waters or interstate waters that is more than "speculative or insubstantial." Evolving interpretation of the CWA and "significant nexus" (connectivity) requires investigation and understanding of the spatial and temporal patterns of hydrologic connectivity between upland landscapes and stream networks that mediate streamflow magnitude and composition. While, hydrologic connectivity is a continuum, strong non-linearities including the shift from unsaturated to saturated flow conditions lead to threshold or transient connectivity behavior and orders of magnitude changes in flow velocities. Here we illustrate the spatial and temporal dynamics of hydrologic connectivity between upland landscapes and stream networks that provide direct and proximate links between streamflow composition and its watershed sources. New understanding and communication of the temporal and spatial scales of watershed connectivity are required to address urgent needs at the interface of the CWA, science, and society.

McGlynn, B. L.; Jencso, K. G.; Nippgen, F.; Emanuel, R. E.; Marshall, L. A.; Gooseff, M. N.

2012-12-01

182

Learning complex temporal patterns with resource-dependent spike timing-dependent plasticity  

PubMed Central

Studies of spike timing-dependent plasticity (STDP) have revealed that long-term changes in the strength of a synapse may be modulated substantially by temporal relationships between multiple presynaptic and postsynaptic spikes. Whereas long-term potentiation (LTP) and long-term depression (LTD) of synaptic strength have been modeled as distinct or separate functional mechanisms, here, we propose a new shared resource model. A functional consequence of our model is fast, stable, and diverse unsupervised learning of temporal multispike patterns with a biologically consistent spiking neural network. Due to interdependencies between LTP and LTD, dendritic delays, and proactive homeostatic aspects of the model, neurons are equipped to learn to decode temporally coded information within spike bursts. Moreover, neurons learn spike timing with few exposures in substantial noise and jitter. Surprisingly, despite having only one parameter, the model also accurately predicts in vitro observations of STDP in more complex multispike trains, as well as rate-dependent effects. We discuss candidate commonalities in natural long-term plasticity mechanisms.

Chan, Victor H.; Froemke, Robert C.

2012-01-01

183

Altered temporal patterns of anxiety in aged and amyloid precursor protein (APP) transgenic mice.  

PubMed

Both normal aging and dementia are associated with dysregulation of the biological clock, which contributes to disrupted circadian organization of physiology and behavior. Diminished circadian organization in conjunction with the loss of cholinergic input to the cortex likely contributes to impaired cognition and behavior. One especially notable and relatively common circadian disturbance among the aged is "sundowning syndrome," which is characterized by exacerbated anxiety, agitation, locomotor activity, and delirium during the hours before bedtime. Sundowning has been reported in both dementia patients and cognitively intact elderly individuals living in institutions; however, little is known about temporal patterns in anxiety and agitation, and the neurobiological basis of these rhythms remains unspecified. In the present study, we explored the diurnal pattern of anxiety-like behavior in aged and amyloid precursor protein (APP) transgenic mice. We then attempted to treat the observed behavioral disturbances in the aged mice using chronic nightly melatonin treatment. Finally, we tested the hypothesis that time-of-day differences in acetylcholinesterase and choline acetyltransferase expression and general neuronal activation (i.e., c-Fos expression) coincide with the behavioral symptoms. Our results show a temporal pattern of anxiety-like behavior that emerges in elderly mice. This behavioral pattern coincides with elevated locomotor activity relative to adult mice near the end of the dark phase, and with time-dependent changes in basal forebrain acetylcholinesterase expression. Transgenic APP mice show a similar behavioral phenomenon that is not observed among age-matched wild-type mice. These results may have useful applications to the study and treatment of age- and dementia-related circadian behavioral disturbances, namely, sundowning syndrome. PMID:21709248

Bedrosian, Tracy A; Herring, Kamillya L; Weil, Zachary M; Nelson, Randy J

2011-07-12

184

Dynamic evolving spiking neural networks for on-line spatio- and spectro-temporal pattern recognition.  

PubMed

On-line learning and recognition of spatio- and spectro-temporal data (SSTD) is a very challenging task and an important one for the future development of autonomous machine learning systems with broad applications. Models based on spiking neural networks (SNN) have already proved their potential in capturing spatial and temporal data. One class of them, the evolving SNN (eSNN), uses a one-pass rank-order learning mechanism and a strategy to evolve a new spiking neuron and new connections to learn new patterns from incoming data. So far these networks have been mainly used for fast image and speech frame-based recognition. Alternative spike-time learning methods, such as Spike-Timing Dependent Plasticity (STDP) and its variant Spike Driven Synaptic Plasticity (SDSP), can also be used to learn spatio-temporal representations, but they usually require many iterations in an unsupervised or semi-supervised mode of learning. This paper introduces a new class of eSNN, dynamic eSNN, that utilise both rank-order learning and dynamic synapses to learn SSTD in a fast, on-line mode. The paper also introduces a new model called deSNN, that utilises rank-order learning and SDSP spike-time learning in unsupervised, supervised, or semi-supervised modes. The SDSP learning is used to evolve dynamically the network changing connection weights that capture spatio-temporal spike data clusters both during training and during recall. The new deSNN model is first illustrated on simple examples and then applied on two case study applications: (1) moving object recognition using address-event representation (AER) with data collected using a silicon retina device; (2) EEG SSTD recognition for brain-computer interfaces. The deSNN models resulted in a superior performance in terms of accuracy and speed when compared with other SNN models that use either rank-order or STDP learning. The reason is that the deSNN makes use of both the information contained in the order of the first input spikes (which information is explicitly present in input data streams and would be crucial to consider in some tasks) and of the information contained in the timing of the following spikes that is learned by the dynamic synapses as a whole spatio-temporal pattern. PMID:23340243

Kasabov, Nikola; Dhoble, Kshitij; Nuntalid, Nuttapod; Indiveri, Giacomo

2013-05-01

185

BaySTDetect: detecting unusual temporal patterns in small area data via Bayesian model choice.  

PubMed

Space-time modeling of small area data is often used in epidemiology for mapping chronic disease rates and by government statistical agencies for producing local estimates of, for example, unemployment or crime rates. Although there is typically a general temporal trend, which affects all areas similarly, abrupt changes may occur in a particular area, e.g. due to emergence of localized predictors/risk factor(s) or impact of a new policy. Detection of areas with "unusual" temporal patterns is therefore important as a screening tool for further investigations. In this paper, we propose BaySTDetect, a novel detection method for short-time series of small area data using Bayesian model choice between two competing space-time models. The first model is a multiplicative decomposition of the area effect and the temporal effect, assuming one common temporal pattern across the whole study region. The second model estimates the time trends independently for each area. For each area, the posterior probability of belonging to the common trend model is calculated, which is then used to classify the local time trend as unusual or not. Crucial to any detection method, we provide a Bayesian estimate of the false discovery rate (FDR). A comprehensive simulation study has demonstrated the consistent good performance of BaySTDetect in detecting various realistic departure patterns in addition to estimating well the FDR. The proposed method is applied retrospectively to mortality data on chronic obstructive pulmonary disease (COPD) in England and Wales between 1990 and 1997 (a) to test a hypothesis that a government policy increased the diagnosis of COPD and (b) to perform surveillance. While results showed no evidence supporting the hypothesis regarding the policy, an identified unusual district (Tower Hamlets in inner London) was later recognized to have higher than national rates of hospital readmission and mortality due to COPD by the National Health Service, which initiated various local enhanced services to tackle the problem. Our method would have led to an early detection of this local health issue. PMID:22452805

Li, Guangquan; Best, Nicky; Hansell, Anna L; Ahmed, Ismaïl; Richardson, Sylvia

2012-09-01

186

Spatial and temporal patterns of bioindicator mercury in pennsylvania oak forest.  

PubMed

We monitored spatial and temporal patterns of total Hg in forest bioindicators to assess possible local, regional, and global changes in atmospheric Hg deposition. Total Hg concentrations were monitored in leaves and fresh litterfall of northern red oak ( L.), on an epiphytic moss ( Hedw.) on northern red oak stems, and in surface soil organic matter (O and O horizons) in Pennsylvania oak-dominated forests. Variously configured plots were used to monitor Hg deposition near local coal-fired generating stations and an industrial city and along an extended regional transect. Linearly decreasing temporal trends in Hg concentrations occurred in leaves, litterfall, moss, and soil O and O. Mean annual Hg concentrations were often greater near local emissions sources compared with remote areas, especially in the initial monitoring period. Decreasing time trends for different impact areas tended to converge due to greater rates of Hg decrease where initial bioindicator Hg levels were higher. Fresh litter and soil O showed the greatest overall potential as Hg bioindicators. We conclude that Hg deposition has been significantly decreasing over time throughout the study area as a result of locally and regionally declining Hg emissions. Reductions in Hg emissions are likely a co-benefit of the 1990 Clean Air Act regulations and changing industrial activities. Recent leveling of several bioindicator Hg time trends may foretell a shift in Hg depositional patterns. Mercury monitoring studies such as this fulfill a need for documenting local and regional effects of emissions reduction. PMID:23673822

McClenahen, James R; Hutnik, Russell J; Davis, Donald D

2013-01-01

187

Spatial and temporal patterns of Ambystoma tigrinum virus (ATV) prevalence in tiger salamanders Ambystoma tigrinum nebulosum.  

PubMed

Amphibian ranaviruses have been documented as causes of mass mortality in amphibian populations throughout the world. The temporal and spatial dynamics of ranavirus infections when epidemics are not apparent remains unclear. To address this question, we collected tissue samples from 2003 to 2006 in 4 geographically separated tiger salamander Ambystoma tigrinum nebulosum host populations on the Kaibab Plateau in northern Arizona. We tested for Ambystoma tigrinum virus (ATV), a lethal ranavirus of tiger salamanders, calculated ATV prevalence for each sampling date, and examined temporal and spatial patterns by quantifying the annual level of ATV synchrony among populations using the intraclass correlation coefficient. Salamander populations were commonly infected with ATV. We observed no morbidity or mortality in these populations even as ATV prevalence values varied from 0 to 57%. Infection prevalence across the landscape was more similar within a given year than between years. There was no statistically significant spatial pattern in prevalence across the landscape. Our findings highlight the need to explore new hypotheses regarding the population level impact of these pathogens on amphibian communities. PMID:19593927

Greer, Amy L; Brunner, Jesse L; Collins, James P

2009-05-27

188

Temporal patterns of human behaviour: are there signs of deterministic 1/ f scaling?  

NASA Astrophysics Data System (ADS)

Temporal patterns apparently exhibiting scaling properties may originate either from fractal stochastic processes or from causal (i.e., deterministic) dynamics. In general, the distinction between the possible two origins remains a non-trivial task. This holds especially for the interpretation of properties derived from temporal patterns of various types of human behaviour, which were reported repeatedly. We propose here a computational scheme based on a generic intermittency model to test predictability (thus determinism) of a part of a time series with knowledge gathered from another part. The method is applied onto psychodynamic time series related to turns from non-psychosis to psychosis. A nonrandom correlation ( ?=0.76) between prediction and real outcome is found. Our scheme thus provides a particular kind of fractal risk-assessment for this possibly deterministic process. We briefly discuss possible implications of these findings to evaluate the risk to undergo a state transition, in our case a patients risk to enter a next psychotic state. We further point to some problems concerning data sample pecularities and equivalence between data and model setup.

Dünki, Rudolf M.; Keller, Elvira; Meier, Peter F.; Ambühl, Brigitte

2000-02-01

189

Hyperpigmentation in North Sea dab Limanda limanda. I. Spatial and temporal patterns and host effects.  

PubMed

Hyperpigmentation is a term describing a specific pigment anomaly affecting common dab Limanda limanda in the North Sea and, less frequently, in adjacent areas, e.g. the English Channel, Irish and Celtic Seas, western Baltic Sea and Icelandic waters. Other North Sea flatfish species are also affected, but at a markedly lower prevalence. The condition is characterised by the occurrence of varying degrees of green to black patchy pigment spots in the skin of the upper (ocular) body side and pearly-white pigment spots in the skin of the lower (abocular) body side. In the course of fish disease monitoring programmes carried out by Germany and the UK (England and Scotland), a pronounced spatial pattern of hyperpigmentation has been detected in the North Sea. An increase in prevalence has been recorded in almost all North Sea areas studied in the past 2 decades. The prevalence recorded in hot spot areas of the condition increased from 5 to >40% between 1988 and 2009. Analysis of the German data indicates that the prevalence and intensity (degree of discolouration) of hyperpigmentation increase with size and age, indicating a temporal progression of the condition with size and age. Intense hyperpigmentation is associated with increased growth (length) and decreased condition factor. Potential causes of the condition (UV-B radiation nutrition, water temperature increase, demographic changes) and, in particular, of the spatial/temporal patterns recorded as well as the relationship to host-specific factors (sex, age, length, growth, condition factor) are discussed. PMID:23482381

Grütjen, F; Lang, T; Feist, S; Bruno, D; Noguera, P; Wosniok, W

2013-03-13

190

Local Temporal Correlation Common Spatial Patterns for Single Trial EEG Classification during Motor Imagery  

PubMed Central

Common spatial pattern (CSP) is one of the most popular and effective feature extraction methods for motor imagery-based brain-computer interface (BCI), but the inherent drawback of CSP is that the estimation of the covariance matrices is sensitive to noise. In this work, local temporal correlation (LTC) information was introduced to further improve the covariance matrices estimation (LTCCSP). Compared to the Euclidean distance used in a previous CSP variant named local temporal CSP (LTCSP), the correlation may be a more reasonable metric to measure the similarity of activated spatial patterns existing in motor imagery period. Numerical comparisons among CSP, LTCSP, and LTCCSP were quantitatively conducted on the simulated datasets by adding outliers to Dataset IVa of BCI Competition III and Dataset IIa of BCI Competition IV, respectively. Results showed that LTCCSP achieves the highest average classification accuracies in all the outliers occurrence frequencies. The application of the three methods to the EEG dataset recorded in our laboratory also demonstrated that LTCCSP achieves the highest average accuracy. The above results consistently indicate that LTCCSP would be a promising method for practical motor imagery BCI application.

Xu, Peng; Liu, Tiejun; Zhang, Yangsong; Guo, Lanjin; Li, Peiyang; Yao, Dezhong

2013-01-01

191

Temporal recruitment patterns and gene flow in kelp rockfish (Sebastes atrovirens).  

PubMed

Pelagic dispersal of marine organisms provides abundant opportunity for gene flow and presumably inhibits population genetic divergence. However, ephemeral, fine-scale, temporal and spatial genetic heterogeneity is frequently observed in settled propagules of marine species that otherwise exhibit broad-scale genetic homogeneity. A large variance in reproductive success is one explanation for this phenomenon. Here, genetic analyses of 16 microsatellite loci are used to examine temporal patterns of variation in young-of-year kelp rockfish (Sebastes atrovirens) recruiting to nearshore habitat in Monterey Bay, California, USA. Population structure of adults from central California is also evaluated to determine if spatial structure exists and might potentially contribute to recruitment patterns. Genetic homogeneity was found among 414 young-of-year sampled throughout the entire 1998 recruitment season. No substantial adult population structure was found among seven populations spanning 800 km of coastline that includes the Point Conception marine biogeographic boundary. Comparison of young-of-year and adult samples revealed no genetic differentiation and no measurable reduction in genetic variation of offspring, indicating little variance in reproductive success and no reduction in effective population size for this year class. Simulation analyses determined that the data set was sufficiently powerful to detect both slight population structure among adults and a small reduction in effective number of breeders contributing to this year class. The findings of high gene flow and low genetic drift have important implications for fisheries management and conservation efforts. PMID:17032275

Gilbert-Horvath, Elizabeth A; Larson, Ralph J; Garza, John Carlos

2006-10-01

192

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

PubMed

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. PMID:22655079

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

2012-01-01

193

Spatio-Temporal Patterns of Key Exploited Marine Species in the Northwestern Mediterranean Sea  

PubMed Central

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.

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

2012-01-01

194

Spatial and temporal patterns in the contribution of fish from their nursery habitats.  

PubMed

Because anthropogenic influences threaten the degradation of many ecosystems, determining where organisms live during early life-history stages and the extent to which different areas contribute individuals to adult populations is critical for the management and conservation of a species. Working in Puget Sound, Washington State in the United States, and using a common flatfish (English sole, Parophrys vetulus), we sought to establish (using otolith chemistry) which areas contribute age-0 fish to age-1 population(s), the extent to which this pattern was consistent between two years, and whether this spatial pattern of contribution coincides with surveys of age-0 fish and/or the available area of nearshore habitat. Our study indicated completely different spatial patterns of fish nursery use between the two years of sampling. We highlight that the contribution of individuals from nursery areas is not related to density of recently settled English sole or the available area of nearshore habitat (depth <10 m) in Puget Sound, nor can we draw conclusions based on environmental data (precipitation, water salinity, light transmission, pH, dissolved oxygen, and water temperature). The results of this study highlight (1) the need for assessing the temporal patterns of nursery habitat use, and (2) that, in order to conservatively manage a species and its population(s), it may be necessary to protect several areas that are used intermittently by that species. PMID:19214587

Chittaro, Paul M; Finley, Rachel J; Levin, Phillip S

2009-05-01

195

Cluster analysis of linear model coefficients under contiguity constraints for identifying spatial and temporal fishing effort patterns  

Microsoft Academic Search

For fisheries management purposes, it is essential to take into account spatial and seasonal characteristics of fishing activities to allow a reliable assessment of fishing impact on resource. This paper presents a novel technique for describing spatial and temporal patterns in fishing effort. The spatial and seasonal fishing activity patterns of the French trawler fleet in the Celtic Sea during

Stéphanie Mahévas; Lise Bellanger; Verena M. Trenkel

2008-01-01

196

[Spatial and temporal patterns of stream fish assemblages in the Qiupu Headwaters National Wetland Park].  

PubMed

Identifying and clarifying how stream fish assemblage patterns vary spatially and temporally are basic measures for the conservation and management of fish species. Based on data collected from 24 wadeable reaches within the Qiupu Headwaters National Wetland Park between May and October 2012, we examined the spatial and temporal patterns of the assemblage structures and diversities, collecting a total of 29 fish species belonging to four orders and ten families. The results of our survey showed influences of local habitat and tributary spatial position variables on fish assemblages. Fish diversity showed significant variations across stream-orders and seasons, which were higher in the second-order streams than in first-order streams and higher in October than in May. Habitat factors such as substrate coarseness and heterogeneity, water temperature and water depth, as well as tributary position factor-link, showed significant effects on fish diversity. Fish assemblages fitted the nested pattern that upstream assemblages presented as a nested subset of downstream assemblages. Fish assemblage structures did not vary significantly across seasons but did across stream-orders; fish assemblages between first- and second-order streams showed significant differences despite some overlap. These spatial differences mainly resulted from spatial variations of the relative abundance of Cobitis rarus, Ctenogobius sp., Zacco platypus, Phoxinus oxycephalus, Rhodeus ocellatus and Vanmanenia stenosoma, among which P. oxycephalus had higher abundance in first-order than in second-order streams but the other five species were more abundant in second-order streams. Fish assemblage structures were significantly related to substrate heterogeneity, water depth, stream order, link and C-link. PMID:23913894

Wang, Wen-Jian; Chu, Ling; Si, Chun; Zhu, Ren; Chen, Wen-Hao; Chen, Fang-Ming; Yan, Yun-Zhi

2013-08-01

197

Benefiting from a migratory prey: spatio-temporal patterns in allochthonous subsidization of an Arctic predator.  

PubMed

1.?Flows of nutrients and energy across ecosystem boundaries have the potential to subsidize consumer populations and modify the dynamics of food webs, but how spatio-temporal variations in autochthonous and allochthonous resources affect consumers' subsidization remains largely unexplored. 2.?We studied spatio-temporal patterns in the allochthonous subsidization of a predator living in a relatively simple ecosystem. We worked on Bylot Island (Nunavut, Canada), where arctic foxes (Vulpes lagopus L.) feed preferentially on lemmings (Lemmus trimucronatus and Dicrostonyx groenlandicus Traill), and alternatively on colonial greater snow geese (Anser caerulescens atlanticus L.). Geese migrate annually from their wintering grounds (where they feed on farmlands and marshes) to the Canadian Arctic, thus generating a strong flow of nutrients and energy across ecosystem boundaries. 3.?We examined the influence of spatial variations in availability of geese on the diet of fox cubs (2003-2005) and on fox reproductive output (1996-2005) during different phases of the lemming cycle. 4.?Using stable isotope analysis and a simple statistical routine developed to analyse the outputs of a multisource mixing model (SIAR), we showed that the contribution of geese to the diet of arctic fox cubs decreased with distance from the goose colony. 5.?The probability that a den was used for reproduction by foxes decreased with distance from the subsidized goose colony and increased with lemming abundance. When lemmings were highly abundant, the effect of distance from the colony disappeared. The goose colony thus generated a spatial patterning of reproduction probability of foxes, while the lemming cycle generated a strong temporal variation of reproduction probability of foxes. 6.?This study shows how the input of energy owing to the large-scale migration of prey affects the functional and reproductive responses of an opportunistic consumer, and how this input is spatially and temporally modulated through the foraging behaviour of the consumer. Thus, perspectives of both landscape and foraging ecology are needed to fully resolve the effects of subsidies on animal demographic processes and population dynamics. PMID:22268371

Giroux, Marie-Andrée; Berteaux, Dominique; Lecomte, Nicolas; Gauthier, Gilles; Szor, Guillaume; Bêty, Joël

2012-05-01

198

Effect of shallow water internal waves on ocean acoustic striation patterns  

Microsoft Academic Search

Contour plots of underwater acoustic intensity, mapped in range and frequency, often exhibit striations. It has been claimed that a scalar parameter `beta', defined in terms of the slope of the striations, is invariant to the details of the acoustic waveguide. In shallow water, the canonical value is beta = 1. In the present paper, the waveguide invariant is modelled

Daniel Rouseff

2001-01-01

199

Lacustrine Groundwater Discharge at Lake Hinnensee - Spatial Patterns and their Temporal Stability  

NASA Astrophysics Data System (ADS)

Lacustrine groundwater discharge (LGD) can play an important role for the lake water balance and lake water quality of enclosed lakes. Measuring groundwater- lake interactions is generally challenging and spatial exchange patterns are seldom explored in detail. This study aims at a) identifying spatial patterns of lacustrine groundwater discharge along the shoreline of Lake Hinnensee, b) identifying spatial patterns of LGD along several cross-sections through the lake and c) investigating the temporal dynamics of these flow patterns for both the seasonal and event time scales. The lake under investigation is located in the lowlands of northeast Germany. The lake has a surface area of 49 ha and the length of the shore line is about 4 km. To monitor LGD at Lake Hinnensee short piezometer transects (2-4 piezometers) were installed every 250 m around the lake. Additional piezometers were installed where major inflow was expected. Vertical hydraulic gradients indicating strength and direction of exchange are measured continuously with pressure sensors. To identify small scale spatial variability vertical temperature profiles were measured every 10 m along 2.35 km of the total shoreline. LGD rates can be determined by fitting the heat transport equation to these profiles. Measurements were repeated in summer 2011, 2012, 2013 and winter 2013 to investigate the temporal stability of the observed patterns. It is generally assumed that the majority of groundwater inflow occurs in the immediate vicinity of the shore line (the focus area of the temperature surveys and piezometer transects). Strength of hydraulic gradients measured in the piezometers decrease considerably within the first few meters from shore und thus support the general assumption, but no information on groundwater discharge is available within the lake basin itself. To test the hypothesis of minimal off-shore groundwater inflows we installed a 500 m long distributed-temperature-sensing cable on the lake sediment resulting in several transects across the northern part of the lake. Measurements will be carried out in February when temperature differences between lake and groundwater are expected to be strongest.

Tecklenburg, Christina; Blume, Theresa

2014-05-01

200

Spatial and temporal patterns of seagrass habitat use by fishes at the Ryukyu Islands, Japan  

NASA Astrophysics Data System (ADS)

To investigate whether or not regional-temporal patterns of seagrass habitat use by fishes existed at the Ryukyu Islands (southern Japan), visual surveys were conducted in seagrass beds and adjacent coral reefs in northern, central, and southern Ryukyu Islands, in November 2004, and May, August, and November 2005, the northern region having less extensive seagrass beds compared with the central and southern regions. During the study period, the seagrass beds were utilized primarily by 31 species, the densities of some of the latter differing significantly among regions. With the exception of Apogonidae and Holocentridae, all species were diurnal and could be divided into 6 groups based on seagrass habitat use patterns; (1) permanent residents A (10 species, e.g. Stethojulis strigiventer), juveniles and adults living in seagrass beds as well as other habitats; (2) permanent residents B (5 species, e.g. Calotomus spinidens), juveniles and adults living only or mainly in seagrass beds; (3) seasonal residents A (4 species, e.g. Cheilodipterus quinquelineatus), juveniles living in seagrass beds as well as other habitats; (4) seasonal residents B (6 species, e.g. Lethrinus atkinsoni), juveniles living only or mainly in seagrass beds; (5) transients (5 species, e.g. Parupeneus indicus), occurring in seagrass beds in the course of foraging over a variety of habitats; and (6) casual species (1 species, Acanthurus blochii), occurring only occasionally in seagrass beds. Regarding temporal differences, juvenile densities in each group were high in May and August compared with November in each region, whereas adult densities did not differ drastically in each month. For regional differences, juvenile and adult densities of permanent residents A and B were higher in the southern and central regions than in the northern region. Moreover, some seasonal residents showed possible ontogenetic habitat shift from seagrass beds to coral reefs in each region. These results indicated that seagrass habitat use patterns by fishes changed temporally and regionally and there may be habitat connectivity between seagrass beds and coral reefs via ontogenetic migration in the Ryukyu Islands.

Nakamura, Yohei; Tsuchiya, Makoto

2008-01-01

201

The temporal pattern of stimulation may be important to the mechanism of deep brain stimulation  

PubMed Central

Deep brain stimulation (DBS) has emerged as an important and potentially powerful treatment option for the management of carefully selected patients with advanced Parkinson's disease (PD) who are not adequately controlled by standard medication therapy. Though considerable advances have been made, the mechanisms underlying the therapeutic effects of DBS remain unclear despite its clinical efficacy. It is now widely held that both excitation and inhibition can occur secondary to stimulation, and it is suspected that abnormal synchronized oscillations may also be important in the mechanism of DBS. Other potentially important processes, including blood flow changes, local and upstream neurogenesis, and the modulation of neurotransmitters through stimulation of bordering astrocytes are also being investigated. Recent research has suggested that the temporal pattern of DBS stimulation is also an important variable in DBS neuromodulation, yet the extent of its influence on DBS efficacy has yet to be determined. As high stimulation frequency alone does not appear to be sufficient for optimal symptom suppression, attention to stimulation pattern might lead to more effective symptom control and reduced side effects, possibly at a lower frequency. Stimulation pattern may be potentially amenable to therapeutic modulation and its role in the clinical efficacy of DBS should be addressed through further focus and research.

Hess, Christopher W.; Vaillancourt, David E.; Okun, Michael S.

2013-01-01

202

Temporal matching among diurnal photosynthetic patterns within the crown of the evergreen sclerophyll Olea europaea L.  

PubMed

Trees are modular organisms that adjust their within-crown morphology and physiology in response to within-crown light gradients. However, whether within-plant variation represents a strategy for optimizing light absorption has not been formally tested. We investigated the arrangement of the photosynthetic surface throughout one day and its effects on the photosynthetic process, at the most exposed and most sheltered crown layers of a wild olive tree (Olea europaea L.). Similar measurements were made for cuttings taken from this individual and grown in a greenhouse at contrasted irradiance-levels (100 and 20% full sunlight). Diurnal variations in light interception, carbon fixation and carbohydrate accumulation in sun leaves were negatively correlated with those in shade leaves under field conditions when light intensity was not limiting. Despite genetic identity, these complementary patterns were not found in plants grown in the greenhouse. The temporal disparity among crown positions derived from specialization of the photosynthetic behaviour at different functional and spatial scales: architectural structure (crown level) and carbon budget (leaf level). Our results suggest that the profitability of producing a new module may not only respond to construction costs or light availability, but also rely on its spatio-temporal integration within the productive processes at the whole-crown level. PMID:21276011

Granado-Yela, C; García-Verdugo, C; Carrillo, K; Rubio DE Casas, R; Kleczkowski, L A; Balaguer, L

2011-05-01

203

Radio-frequency discharges in oxygen: II. Spatio-temporally resolved optical emission pattern  

NASA Astrophysics Data System (ADS)

Axially and temporally resolved optical emission structures were investigated in the rf sheath region of a parallel plate capacitively coupled rf discharge (13.56 MHz) in pure oxygen and tetrafluoromethane. The rf discharge was driven at total pressures of between 10 and 100 Pa, gas flow rate of 3 sccm and rf power in the range 5-100 W. In particular, the emission of the atomic oxygen at 844.6 nm (3p3P ? 3s3S0) and the atomic carbon at 193 nm (3s1P0 ? 2p1D) were imaged with a lens onto the entrance slit of a spectrometer and detected by a fast ICCD-camera. The spatio-temporally resolved analysis of the emission intensity during the rf cycle (73.75 ns) provides two significant excitation processes inside the rf sheath: the electron impact excitation at the sheath edge, and heavy particle impact excitation in front of the powered electrode. In oxygen plasma the emission of atomic oxygen was found in both regions whereas in tetrafluoromethane the emission of atomic carbon was observed only in front of the powered electrode. The experimental results reveal characteristic dependence of the emission pattern in front of the powered electrode on plasma process parameters (self-bias voltage, pressure) and allow an estimation of the excitation threshold energy and effective cross section of energetic heavy particle loss.

Dittmann, K.; Drozdov, D.; Krames, B.; Meichsner, J.

2007-11-01

204

Mosses as biomonitors of atmospheric heavy metal deposition: spatial patterns and temporal trends in Europe.  

PubMed

In recent decades, mosses have been used successfully as biomonitors of atmospheric deposition of heavy metals. Since 1990, the European moss survey has been repeated at five-yearly intervals. Although spatial patterns were metal-specific, in 2005 the lowest concentrations of metals in mosses were generally found in Scandinavia, the Baltic States and northern parts of the UK; the highest concentrations were generally found in Belgium and south-eastern Europe. The recent decline in emission and subsequent deposition of heavy metals across Europe has resulted in a decrease in the heavy metal concentration in mosses for the majority of metals. Since 1990, the concentration in mosses has declined the most for arsenic, cadmium, iron, lead and vanadium (52-72%), followed by copper, nickel and zinc (20-30%), with no significant reduction being observed for mercury (12% since 1995) and chromium (2%). However, temporal trends were country-specific with sometimes increases being found. PMID:20674112

Harmens, H; Norris, D A; Steinnes, E; Kubin, E; Piispanen, J; Alber, R; Aleksiayenak, Y; Blum, O; Co?kun, M; Dam, M; De Temmerman, L; Fernández, J A; Frolova, M; Frontasyeva, M; González-Miqueo, L; Grodzi?ska, K; Jeran, Z; Korzekwa, S; Krmar, M; Kvietkus, K; Leblond, S; Liiv, S; Magnússon, S H; Mankovská, B; Pesch, R; Rühling, A; Santamaria, J M; Schröder, W; Spiric, Z; Suchara, I; Thöni, L; Urumov, V; Yurukova, L; Zechmeister, H G

2010-10-01

205

Spatial and temporal patterns in sulfate aerosol acidity and neutralization within a metropolitan area  

SciTech Connect

Measurements of atmospheric acidity are relatively new and not routine. The influences and variability due to local phenomena have not been investigated heretofore. As part of a U.S. EPA-sponsored air pollution-health effects study in metropolitan Toronto (population 2.3 million), aerosol acidity was monitored at three sites. This study is discussed in the book. The primary objective was to document human exposures to acidic aerosol during the study period. Because of its chemical reactivity, it was not known whether substantial variations in acidic aerosol concentrations would be found within the subregion (area 60 km{sup 2}). A network of three acidic aerosol monitoring sites was used. Hence, this study design offered the first opportunity to compare spatial and temporal patterns of acidic aerosol levels within a large, receptor region.

Waldman, J.M.; Lloy, P.J. (UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ (US)); Thurston, G.D.; Lippmann, M. (New York Univ. Medical Center, Tuxedo, NY (US))

1988-01-01

206

SWI/SNF complex prevents lineage reversion and induces temporal patterning in neural stem cells.  

PubMed

Members of the SWI/SNF chromatin-remodeling complex are among the most frequently mutated genes in human cancer, but how they suppress tumorigenesis is currently unclear. Here, we use Drosophila neuroblasts to demonstrate that the SWI/SNF component Osa (ARID1) prevents tumorigenesis by ensuring correct lineage progression in stem cell lineages. We show that Osa induces a transcriptional program in the transit-amplifying population that initiates temporal patterning, limits self-renewal, and prevents dedifferentiation. We identify the Prdm protein Hamlet as a key component of this program. Hamlet is directly induced by Osa and regulates the progression of progenitors through distinct transcriptional states to limit the number of transit-amplifying divisions. Our data provide a mechanistic explanation for the widespread tumor suppressor activity of SWI/SNF. Because the Hamlet homologs Evi1 and Prdm16 are frequently mutated in cancer, this mechanism could well be conserved in human stem cell lineages. PAPERCLIP: PMID:24630726

Eroglu, Elif; Burkard, Thomas R; Jiang, Yanrui; Saini, Nidhi; Homem, Catarina C F; Reichert, Heinrich; Knoblich, Juergen A

2014-03-13

207

Precision phenotyping of biomass accumulation in triticale reveals temporal genetic patterns of regulation  

PubMed Central

To extend agricultural productivity by knowledge-based breeding and tailor varieties adapted to specific environmental conditions, it is imperative to improve our ability to assess the dynamic changes of the phenome of crops under field conditions. To this end, we have developed a precision phenotyping platform that combines various sensors for a non-invasive, high-throughput and high-dimensional phenotyping of small grain cereals. This platform yielded high prediction accuracies and heritabilities for biomass of triticale. Genetic variation for biomass accumulation was dissected with 647 doubled haploid lines derived from four families. Employing a genome-wide association mapping approach, two major quantitative trait loci (QTL) for biomass were identified and the genetic architecture of biomass accumulation was found to be characterized by dynamic temporal patterns. Our findings highlight the potential of precision phenotyping to assess the dynamic genetics of complex traits, especially those not amenable to traditional phenotyping.

Busemeyer, Lucas; Ruckelshausen, Arno; Moller, Kim; Melchinger, Albrecht E.; Alheit, Katharina V.; Maurer, Hans Peter; Hahn, Volker; Weissmann, Elmar A.; Reif, Jochen C.; Wurschum, Tobias

2013-01-01

208

Secondary metabolite and inorganic contents in Cystodytes sp. (Ascidiacea): temporal patterns and association with reproduction and growth  

Microsoft Academic Search

Temporal variation is one of the least known components of defence production in marine organisms. Here we examined whether\\u000a there is a predictable temporal pattern in the production of chemical and structural defences by a marine invertebrate. To\\u000a assess the seasonal variation in chemical defence, we measured ascididemin, the main pyridoacridine alkaloid in the blue Mediterranean\\u000a morph of the ascidian

Susanna López-Legentil; Nataly Bontemps-Subielos; Xavier Turon; Bernard Banaigs

2007-01-01

209

Temporal patterns of odorant receptor gene expression in adult and aged mice.  

PubMed

In the mouse, the sense of smell relies predominantly on the expression of ~1200 odorant receptor (OR) genes in the main olfactory epithelium (MOE). Each mature olfactory sensory neuron (OSN) in the MOE is thought to express just one of these OR genes; conversely, an OR gene is expressed in thousands to tens of thousands of OSNs per mouse. Here, we have characterized temporal patterns of OR gene expression in a cohort of inbred C57BL6/N mice from the Aged Rodent Colonies of the National Institute on Aging. We applied the NanoString multiplex platform to quantify RNA abundance for 531 OR genes in whole olfactory mucosa (WOM) tissue samples. The five study groups were females aged 2, 6, 12, 18, and 31 months (mo). We classified the 531 temporal patterns using a step-down quadratic regression method for time course analysis. The majority of OR genes (58.4%) are classified as flat: there is no significant difference from a horizontal line within this time window. There are 32.8% of OR genes with a downward profile, 7.2% with an upward profile, and 1.7% with a convex or concave profile. But the magnitude of these decreases and increases tends to be small: only 4.3% of OR genes are differentially expressed (DE) at 31 mo compared to 2 mo. Interestingly, the variances of NanoString counts for individual OR genes are homogeneous among the age groups. Our analyses of these 15,930 OR gene expression data of C57BL6/N mice that were raised and housed under well-controlled conditions indicate that OR gene expression at the MOE level is intrinsically stable. PMID:23962816

Khan, Mona; Vaes, Evelien; Mombaerts, Peter

2013-11-01

210

Epibacterial community patterns on marine macroalgae are host-specific but temporally variable.  

PubMed

Marine macroalgae are constantly exposed to epibacterial colonizers. The epiphytic bacterial patterns and their temporal and spatial variability on host algae are poorly understood. To investigate the interaction between marine macroalgae and epiphytic bacteria, this study tested if the composition of epibacterial communities on different macroalgae was specific and persisted under varying biotic and abiotic environmental conditions over a 2-year observation time frame. Epibacterial communities on the co-occurring macroalgae Fucus vesiculosus, Gracilaria vermiculophylla and Ulva intestinalis were repeatedly sampled in summer and winter of 2007 and 2008. The epibacterial community composition was analysed by denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene libraries. Epibacterial community profiles did not only differ significantly at each sampling interval among algal species, but also showed consistent seasonal differences on each algal species at a bacterial phylum level. These compositional patterns re-occurred at the same season of two consecutive years. Within replicates of the same algal species, the composition of bacterial phyla was subject to shifts at the bacterial species level, both within the same season but at different years and between different seasons. However, 7-16% of sequences were identified as species specific to the host alga. These findings demonstrate that marine macroalgae harbour species-specific and temporally adapted epiphytic bacterial biofilms on their surfaces. Since several algal host-specific bacteria were highly similar to other bacteria known to either avoid subsequent colonization by eukaryotic larvae or to exhibit potent antibacterial activities, algal host-specific bacterial associations are expected to play an important role for marine macroalgae. PMID:21078035

Lachnit, Tim; Meske, Diana; Wahl, Martin; Harder, Tilmann; Schmitz, Ruth

2011-03-01

211

Reconstructing spatial and temporal patterns of paleoglaciation along the Tian Shan  

NASA Astrophysics Data System (ADS)

Testing and calibrating global climate models require well-constrained information on past climates of key regions around the world. Particularly important are transitional regions that provide a sensitive record of past climate change. Central Asia is an extreme continental location with glaciers and rivers that respond sensitively to temporal variations in the dominance of several major climate systems. As an international team initiative, we are reconstructing the glacial history of the Kyrgyz and Chinese Tian Shan, based on mapping and dating of key localities along the range. Remote-sensing-based geomorphological mapping, building on previous maps produced by Kyrgyz, Russian, Chinese and German scholars, is being augmented with field observations of glacial geomorphology and the maximum distribution of erratics. We are using cosmogenic nuclide (CN) 10Be dating of moraines and other landforms that constrain the former maximum extents of glaciers. Study sites include the Ala-Archa, Ak-Shyrak and Inylchek/Sary-Dzaz areas in Kyrgyzstan and the Urumqi valley (as well as its upland and southern slopes), and the Tumur and Bogeda peak areas in China. Comparing consistently dated glacial histories along and across the range will allow us to examine potential shifts in the dominance patterns of climate systems over time in Central Asia. We are also comparing ages based on CN with optically stimulated luminescence (OSL) and electron spin resonance (ESR) dates. The final stage of this project will use intermediate complexity glacier flow models to examine paleoclimatic implications of the observed spatial and temporal patterns of glacier changes across Central Asia and eastern Tibet, focused in particular on the last glacial cycle.

Harbor, J.; Stroeven, A. P.; Beel, C.; Blomdin, R.; Caffee, M. W.; Chen, Y.; Codilean, A.; Gribenski, N.; Hattestrand, C.; Heyman, J.; Ivanov, M.; Kassab, C.; Li, Y.; Lifton, N. A.; Liu, G.; Petrakov, D.; Rogozhina, I.; Usubaliev, R.

2012-12-01

212

Buoyancy characteristics of the bloater (Coregonus hoyi) in relation to patterns of vertical migration and acoustic backscattering  

USGS Publications Warehouse

Acoustic studies in Lake Michigan found that bloaters (Coregonus hoyi) were less reflective per size than the other major pelagic species. This difference in in situ acoustic backscattering could indicate that the deep-water bloaters have compressed swimbladders for much of their vertical range with related implications on buoyancy. To test this hypothesis, the buoyancy characteristics of bloaters were determined with fish placed in a cage that was lowered to bottom and monitored with an underwater camera. We found bloaters were positively buoyant near surface, neutrally buoyant at intermediate strata, and negatively buoyant near bottom. This pattern was consistent for the range of depths bloaters occur. The depth of neutral buoyancy (near the 50-n strata) corresponds with the maximum extent of vertical migration for bloaters observed in acoustic surveys. Fish below this depth would be negatively buoyant which supports our contention that bloaters deeper in the water column have compressed swimbladders. Understanding the buoyancy characteristics of pelagic fishes will help to predict the effects of vertical migration on target strength measurement and confirms the use of acoustics as a tool to identify and quantify the ecological phenomenon of vertical migration.

Fleischer, Guy W.; TeWinkel, Leslie M.

1998-01-01

213

The spatial and temporal patterns of falciparum and vivax malaria in Per?: 1994-2006  

PubMed Central

Background Malaria is the direct cause of approximately one million deaths worldwide each year, though it is both preventable and curable. Increasing the understanding of the transmission dynamics of falciparum and vivax malaria and their relationship could suggest improvements for malaria control efforts. Here the weekly number of malaria cases due to Plasmodium falciparum (1994–2006) and Plasmodium vivax (1999–2006) in Perú at different spatial scales in conjunction with associated demographic, geographic and climatological data are analysed. Methods Malaria periodicity patterns were analysed through wavelet spectral analysis, studied patterns of persistence as a function of community size and assessed spatial heterogeneity via the Lorenz curve and the summary Gini index. Results Wavelet time series analyses identified annual cycles in the incidence of both malaria species as the dominant pattern. However, significant spatial heterogeneity was observed across jungle, mountain and coastal regions with slightly higher levels of spatial heterogeneity for P. vivax than P. falciparum. While the incidence of P. falciparum has been declining in recent years across geographic regions, P. vivax incidence has remained relatively steady in jungle and mountain regions with a slight decline in coastal regions. Factors that may be contributing to this decline are discussed. The time series of both malaria species were significantly synchronized in coastal (? = 0.9, P < 0.0001) and jungle regions (? = 0.76, P < 0.0001) but not in mountain regions. Community size was significantly associated with malaria persistence due to both species in jungle regions, but not in coastal and mountain regions. Conclusion Overall, findings highlight the importance of highly refined spatial and temporal data on malaria incidence together with demographic and geographic information in improving the understanding of malaria persistence patterns associated with multiple malaria species in human populations, impact of interventions, detection of heterogeneity and generation of hypotheses.

Chowell, Gerardo; Munayco, Cesar V; Escalante, Ananias A; McKenzie, F Ellis

2009-01-01

214

Migratory patterns of exotic brown trout Salmo trutta in south-western Hokkaido, Japan, on the basis of otolith Sr:Ca ratios and acoustic telemetry.  

PubMed

Acoustic telemetry and microchemical analysis of otolith strontium-calcium ratios were used to evaluate how exotic brown trout Salmo trutta have responded to Japanese riverine environments of south-western Hokkaido by observing their migratory patterns. The existence of anadromous S. trutta was also verified. Most S. trutta caught in rivers for otolith analysis were freshwater residents (95·6%), whereas those caught in the sea were mainly smolts (91·3%), which had just migrated from rivers during spring. Anadromous S. trutta (n = 6) were captured in rivers and in the sea, confirming the existence of mature pre- and post-spawning fish. According to telemetry results, both mature and immature S. trutta used the river in winter, and their estimated sea-run timings showed individual differences. Through the combination of these two methods, migratory patterns on various spatio-temporal scales were observed. This first documentation of the presence of both male and female anadromous S. trutta in the same region within Japan indicated the risk of further colonization of exotic S. trutta via oceanic migration. PMID:22268438

Honda, K; Arai, T; Kobayashi, S; Tsuda, Y; Miyashita, K

2012-02-01

215

Temporal patterns in count-to-ten fetal movement charts and their associations with pregnancy characteristics: a prospective cohort study  

PubMed Central

Background Fetal movement counting has long been suggested as a screening tool to identify impaired placental function. However, quantitative limits for decreased fetal movement perform poorly for screening purposes, indicating the need for methodological refinement. We aimed to identify the main individual temporal patterns in fetal movement counting charts, and explore their associations with pregnancy characteristics. Methods In a population-based prospective cohort in Norway, 2009–2011, women with singleton pregnancies counted fetal movements daily from pregnancy week 24 until delivery using a modified "count-to-ten” procedure. To account for intra-woman correlation of observations, we used functional data analysis and corresponding functional principal component analysis to identify the main individual temporal patterns in fetal movement count data. The temporal patterns are described by continuous functional principal component (FPC) curves, with an individual score on each FPC for each woman. These scores were later used as outcome variables in multivariable linear regression analyses, with pregnancy characteristics as explanatory variables. Results Fetal movement charts from 1086 pregnancies were included. Three FPC curves explained almost 99% of the variation in the temporal data, with the first FPC, representing the individual overall counting time, accounting for 91% alone. There were several statistically significant associations between the FPCs and various pregnancy characteristics. However, the effects were small and of limited clinical value. Conclusions This statistical approach for analyzing fetal movement counting data successfully captured clinically meaningful individual temporal patterns and how these patterns vary between women. Maternal body mass index, gestational age and placental site explained little of the variation in the temporal fetal movement counting patterns. Thus, a perceived decrease in fetal movement should not be attributed to a woman’s basic pregnancy characteristics, but assessed as a potential marker of risk.

2012-01-01

216

Rapid Generation of Multiplexed Cell Cocultures Using Acoustic Droplet Ejection Followed by Aqueous Two-Phase Exclusion Patterning  

PubMed Central

The development of tools for patterning cocultures of cells is a fundamental interest among cell biologists and tissue engineers. Although a variety of systems exist for micropatterning cells, the methods used to generate cell micropatterns are often cumbersome and difficult to adapt for tissue engineering purposes. This study combines acoustic droplet ejection and aqueous two-phase system exclusion patterning to introduce a method for patterning cocultures of cells in multiplexed arrays. This new method uses focused acoustic radiation pressure to eject discrete droplets of uniform size from the surface of a dextran solution containing cells. The size of droplets is controlled by adjusting ultrasound parameters, such as pulse, duration, and amplitude. The ejected dextran droplets are captured on a cell culture substrate that is manipulated by a computer-controlled 3D positioning system according to predesigned patterns. Polyethylene glycol solution containing an additional cell type is then added to the culture dish to produce a two-phase system capable of depositing different types of cells around the initial pattern of cells. We demonstrate that our method can produce patterns of islands or lines with two or more cell types. Further, we demonstrate that patterns can be multiplexed for studies involving combinations of multiple cell types. This method offers a tool to transfer cell-containing samples in a contact-free, nozzle-less manner, avoiding sample cross-contamination. It can be used to pattern cell cocultures without complicated fabrication of culture substrates. These capabilities were used to examine the response of cancer cells to the presence of a ligand (CXCL12) secreted from surrounding cocultured cells.

Fang, Yu; Frampton, John P.; Raghavan, Shreya; Sabahi-Kaviani, Rahman; Luker, Gary

2012-01-01

217

Optimization of the temporal pattern of applied dose for a single fraction of radiation: Implications for radiation therapy  

NASA Astrophysics Data System (ADS)

The increasing prevalence of intensity modulated radiation therapy (IMRT) as a treatment modality has led to a renewed interest in the potential for interaction between prolonged treatment time, as frequently associated with IMRT, and the underlying radiobiology of the irradiated tissue. A particularly relevant aspect of radiobiology is cell repair capacity, which influences cell survival, and thus directly relates to the ability to control tumors and spare normal tissues. For a single fraction of radiation, the linear quadratic (LQ) model is commonly used to relate the radiation dose to the fraction of cells surviving. The LQ model implies a dependence on two time-related factors which correlate to radiobiological effects: the duration of radiation application, and the functional form of how the dose is applied over that time (the "temporal pattern of applied dose"). Although the former has been well studied, the latter has not. Thus, the goal of this research is to investigate the impact of the temporal pattern of applied dose on the survival of human cells and to explore how the manipulation of this temporal dose pattern may be incorporated into an IMRT-based radiation therapy treatment planning scheme. The hypothesis is that the temporal pattern of applied dose in a single fraction of radiation can be optimized to maximize or minimize cell kill. Furthermore, techniques which utilize this effect could have clinical ramifications. In situations where increased cell kill is desirable, such as tumor control, or limiting the degree of cell kill is important, such as the sparing of normal tissue, temporal sequences of dose which maximize or minimize cell kill (temporally "optimized" sequences) may provide greater benefit than current clinically used radiation patterns. In the first part of this work, an LQ-based modeling analysis of effects of the temporal pattern of dose on cell kill is performed. Through this, patterns are identified for maximizing cell kill for a given radiation pattern by concentrating the highest doses in the middle of a fraction (a "Triangle" pattern), or minimizing cell kill by placing the highest doses near the beginning and end (a "V-shaped" pattern). The conditions under which temporal optimization effects are most acute are also identified: irradiation of low alpha/beta tissues, long fraction durations, and high doses/fx. An in vitro study is then performed which verifies that the temporal effects and trends predicted by the modeling study are clearly manifested in human cells. Following this a phantom which could allow similar in vitro radiobiological experiments in a 3-dimensional clinically-based environment is designed, created, and dosimetrically assessed using TLDs, film, and biological assay-based techniques. The phantom is found to be a useful and versatile tool for such experiments. A scheme for utilizing the phantom in a clinical treatment environment is then developed. This includes a demonstration of prototype methods for optimizing the temporal pattern of applied dose in clinical IMRT plans to manipulate tissue-dependent effects. Looking toward future experimental validation of such plans using the phantom, an analysis of the suitability of biological assays for use in phantom-based in vitro experiments is performed. Finally, a discussion is provided about the steps necessary to integrate temporal optimization into in vivo experiments and ultimately into a clinical radiation therapy environment. If temporal optimization is ultimately shown to have impact in vivo, the successful implementation of the methods developed in this study could enhance the efficacy and care of thousands of patients receiving radiotherapy.

Altman, Michael B.

218

Spatio-temporal patterns of soil water storage under dryland agriculture at the watershed scale  

NASA Astrophysics Data System (ADS)

SummarySpatio-temporal patterns of soil water are major determinants of crop yield potential in dryland agriculture and can serve as the basis for delineating precision management zones. Soil water patterns can vary significantly due to differences in seasonal precipitation, soil properties and topographic features. In this study we used empirical orthogonal function (EOF) analysis to characterize the spatial variability of soil water at the Washington State University Cook Agronomy Farm (CAF) near Pullman, WA. During the period 1999-2006, the CAF was divided into three roughly equal blocks (A, B, and C), and soil water at 0.3 m intervals to a depth of 1.5 m measured gravimetrically at approximately one third of the 369 geo-referenced points on the 37-ha watershed. These data were combined with terrain attributes, soil bulk density and apparent soil conductivity (EC a). The first EOF generated from the three blocks explained 73-76% of the soil water variability. Field patterns of soil water based on EOF interpolation varied between wet and dry conditions during spring and fall seasons. Under wet conditions, elevation and wetness index were the dominant factors regulating the spatial patterns of soil water. As soil dries out during summer and fall, soil properties (EC a and bulk density) become more important in explaining the spatial patterns of soil water. The EOFs generated from block B, which represents average topographic and soil properties, provided better estimates of soil water over the entire watershed with larger Nash-Sutcliffe Coefficient of Efficiency (NSCE) values, especially when the first two EOFs were retained. Including more than the first two EOFs did not significantly increase the NSCE of soil water estimate. The EOF interpolation method to estimate soil water variability worked slightly better during spring than during fall, with average NSCE values of 0.23 and 0.20, respectively. The predictable patterns of stored soil water in the spring could serve as the basis for delineating precision management zones as yield potential is largely driven by water availability. The EOF-based method has the advantage of estimating the soil water variability based on soil water data from several measurement times, whereas in regression methods only soil water measurement at a single time are used. The EOF-based method can also be used to estimate soil water at any time other than measurement times, assuming the average soil water of the watershed is known at that time.

Ibrahim, Hesham M.; Huggins, David R.

2011-07-01

219

Temporal patterns and processes of retreat of drumlin coastal cliffs — Strangford Lough, Northern Ireland  

NASA Astrophysics Data System (ADS)

Monthly measurements of erosion pins at sixteen sites around the very low energy marine environment of Strangford Lough, Northern Ireland, were used to investigate temporal patterns and processes of retreat of low cliffs of glacial material. Erosion rates were extremely varied: the mean was 76 ± 49.03 mm a - 1 . Erosion is strongly seasonal with 86.6% of the total erosion occurring during 'winter' (September to March) periods. This seasonal pattern was most exaggerated in some of the more rapidly-eroding sites on the exposed eastern side of the lough. 'Preparatory processes' - heavy rainfall, desiccation and frost action - reduce the compressive strength of the cliff materials and act as important forcing of the erodibility of the cliffs. Direct wave attack on cliffs around the lough takes place when threshold conditions of wind speed and tidal heights are met (tidal levels > 1.50 m above O.D. with wind speed of 15.4 m s - 1 (30 knots), maintaining for more than 4 h). During the study period eighteen events exceeding the above criteria were identified. Extremely low atmospheric pressure has also been identified as important in raising water levels. Slumps, falls, topples and slides were the forms of cliff failure observed.

Greenwood, Richard O.; Orford, Julian D.

2008-02-01

220

Distinct temporal pattern of T cell receptor signals during positive versus negative selection in situ  

PubMed Central

The recognition by the T cell receptor (TCR) of self peptides presented by the major histocompatibility complex (MHC) controls T cell fate in the thymus, with weak signals inducing survival (the process of positive selection) and stronger signals inducing death (negative selection). In vitro studies have indicated that ligands that give rise to positive selection induce a low, but sustained, pattern of TCR signaling; however, the temporal pattern of TCR signaling in thymocytes that are presented peptide by MHC class I (MHC class I restriction) in they thymus, under conditions that support positive selection, are unknown. Here, we addressed this question by examining intracellular calcium (Ca2+) dynamics and migratory changes in thymocytes undergoing positive and negative selection in thymic slices. We found that brief, serial signaling events that were separated by migratory periods and low cytosolic Ca2+ correlated with the positive selection of MHC class I–restricted thymocytes, whereas sustained signaling and arrest of thymocytes were associated with negative selection. Low avidity peptides and the presentation of peptides by cortical thymic epithelial cells failed to induce strong migratory arrest of thymocytes, which led to transient TCR signaling. Thus, we provide a comparison of positive and negative selection signals in situ and suggest that the absence of strong stop signals is an important feature that distinguishes between positive and negative selection.

Melichar, Heather J.; Ross, Jenny O.; Herzmark, Paul; Hogquist, Kristin A.; Robey, Ellen A.

2014-01-01

221

Spatial and temporal expression patterns of chitinase genes in developing zebrafish embryos.  

PubMed

Chitinases and chitinase like proteins play an important role in mammalian immunity and functions in early zebrafish development have been suggested. Here we report identification of six zebrafish chitinases and chitinase like proteins (called CHIA.1-6) belonging to the glycoside hydrolase family 18, and determine their spatial and temporal expression at 10 stages of zebrafish development. CHIA.4 is highly maternally expressed and it is expressed 100 fold above any other CHIA gene at zygote through to blastula stage. Later, after the maternal to zygotic transition, CHIA.4 expression decreases to the same level as CHIA.5 and CHIA.6. Subsequently, CHIA.1, CHIA.2, CHIA.3 and CHIA.4, CHIA.5, CHIA.6 each follow distinct paths in terms of expression levels. Until 4 days post fertilization the spatial expression patterns of all six CHIA genes overlap extensively, with expression detected predominantly in vascular, ocular and intestinal tissues. At 5 days post fertilization CHIA.1, CHIA.2 and CHIA.3 are expressed almost exclusively in the stomach, whereas CHIA.4, CHIA.5 and CHIA.6 are also prominently expressed in the liver. These different expression patterns may contribute to the establishment of a basis on which functional analysis in older larvae may be founded. PMID:24418193

Koch, Bjørn E V; Stougaard, Jens; Spaink, Herman P

2014-03-01

222

The spatio-temporal pattern of testis organogenesis in mammals - insights from the mole.  

PubMed

Some cellular events are crucial in testis organogenesis, including Sertoli and Leydig cell differentiation, mesonephric cell migration and testis cord formation. These processes are controlled by transcription factors, paracrine signalling and hormones. Using the mole species Talpa occidentalis as an alternative animal model, we report the expression patterns of nine genes during testis differentiation and analyse their implications in the above-mentioned cellular processes. We show that: 1) Sertoli cell differentiation occurs very early and precedes mesonephric cell migration, indicating that the latter is not needed for the endocrine cytodifferentiation of Sertoli cells; 2) the time of Leydig cell differentiation is consistent with the participation of PDGFR-alpha in promoting the migration and/or proliferation of Leydig cell precursors, and with that of WNT4 signalling in inhibiting Leydig cell differentiation and 3) the formation of the tunica albuginea involves intragonadal cell migration/movement. These results demonstrate that testicular organogenesis in the mole differs from that in the mouse in some particular aspects, thus providing evidence that the spatio-temporal pattern of testis development is not highly conserved during mammalian evolution. PMID:19598120

Carmona, Francisco D; Lupiáñez, Darío G; Martín, José-Ezequiel; Burgos, Miguel; Jiménez, Rafael; Zurita, Federico

2009-01-01

223

Spatial and Temporal Patterns of Biocide Action against Staphylococcus epidermidis Biofilms? ‡  

PubMed Central

The dynamic antimicrobial action of chlorine, a quaternary ammonium compound, glutaraldehyde, and nisin within biofilm cell clusters of Staphylococcus epidermidis was investigated using time-lapse confocal scanning laser microscopy. The technique allowed for the simultaneous imaging of changes in biofilm structure and disruption of cellular membrane integrity through the loss of an unbound fluorophore loaded into bacterial cells prior to antimicrobial challenge. Each of the four antimicrobial agents produced distinct spatial and temporal patterns of fluorescence loss. The antimicrobial action of chlorine was localized around the periphery of biofilm cell clusters. Chlorine was the only antimicrobial agent that caused any biofilm removal. Treatment with the quaternary ammonium compound caused membrane permeabilization that started at the periphery of cell clusters, then migrated steadily inward. A secondary pattern superimposed on the penetration dynamic suggested a subpopulation of less-susceptible cells. These bacteria lost fluorescence much more slowly than the majority of the population. Nisin caused a rapid and uniform loss of green fluorescence from all parts of the biofilm without any removal of biofilm. Glutaraldehyde caused no biofilm removal and also no loss of membrane integrity. Measurements of biocide penetration and action time at the center of cell clusters yielded 46 min for 10 mg liter?1 chlorine, 21 min for 50 mg liter?1 chlorine, 25 min for the quaternary ammonium compound, and 4 min for nisin. These results underscore the distinction between biofilm removal and killing and reinforce the critical role of biocide reactivity in determining the rate of biofilm penetration.

Davison, William M.; Pitts, Betsey; Stewart, Philip S.

2010-01-01

224

Temporal and histological evaluation of melatonin patterns in a 'basal' metazoan.  

PubMed

While recent advances suggest functional pleiotropy of melatonin in higher organisms, an understanding of the biological significance of this ancient molecule in early evolutionary groups is lacking. Here, endogenous melatonin production was identified for the first time in the sea anemone Actinia equina, a nonsymbiotic hexacorallian cnidarian. Day/night activity profiles of melatonin in this anemone indicated that melatonin levels oscillate with significant nocturnal peaks. However, dynamic changes in melatonin concentration did not persist under constant dark conditions and therefore were not circadian in nature. Thus, the oscillating pattern of melatonin in A. equina is presumed to be the result of alternative, simpler melatonin control mechanism that likely involves direct regulation by the daily photocycle. As nocturnal melatonin signals still potentially provide 'time-of-day' information and can illustrate the seasonally changing length of the biological night, we hypothesize that melatonin may be relevant to temporal coordination of timed processes also in anthozoans. Spatial patterns of melatonin distribution found in this study indicate abundant melatonin distribution in the endodermal filaments wrapped around gametes. This finding supports the possibility that one of the melatonin-responsive processes in this basal metazoan species may involve reproductive functions. PMID:22506978

Roopin, Modi; Levy, Oren

2012-10-01

225

Precipitation extremes in the Yangtze River Basin, China: regional frequency and spatial-temporal patterns  

NASA Astrophysics Data System (ADS)

Regional frequency analysis and spatial-temporal patterns of precipitation extremes are investigated based on daily precipitation data covering 1960-2009 using the index-flood L-moments method together with some advanced statistical tests and spatial analysis techniques. The results indicate that: (1) the entire Yangtze River basin can be divided into six homogeneous regions in terms of extreme daily precipitation index. Goodness-of-fit test indicates that Pearson type III (PE3, three parameters), general extreme-value (GEV, three parameters), and general normal (GNO, three parameters) perform well in fitting regional precipitation extremes; (2) the regional growth curves for each homogeneous region with 99 % error bands show that the quantile estimates are reliable enough and can be used when return periods are less than 100 years, and the results indicate that extreme precipitation events are highly probable to occur in regions V and VI, and hence higher risk of floods and droughts; and (3) spatial patterns of annual extreme daily precipitation with return period of 20 years indicate that precipitation amount increases gradually from the upper to the lower Yangtze River basin, showing higher risks of floods and droughts in the middle and lower Yangtze River basin, and this result is in good agreement with those derived from regional growth curves.

Chen, Yongqin David; Zhang, Qiang; Xiao, Mingzhong; Singh, Vijay P.; Leung, Yee; Jiang, Luguang

2014-05-01

226

Temporal patterns in daily measurements of inorganic and organic speciated PM2.5 in Denver  

PubMed Central

Airborne particulate matter less than 2.5 ?m in aerodynamic diameter (PM2.5) has been linked to a wide range of adverse health effects and as a result is currently regulated by the U.S. Environmental Protection Agency. PM2.5 originates from a multitude of sources and has heterogeneous physical and chemical characteristics. These features complicate the link between PM2.5 emission sources, ambient concentrations and health effects. The goal of the Denver Aerosol Sources and Health (DASH) study is to investigate associations between sources and health using daily measurements of speciated PM2.5 in Denver. The datxa set being collected for the DASH study will be the longest daily speciated PM2.5 data set of its kind covering 5.5 years of daily inorganic and organic speciated measurements. As of 2008, 4.5 years of bulk measurements (mass, inorganic ions and total carbon) and 1.5 years of organic molecular marker measurements have been completed. Several techniques were used to reveal long-term and short-term temporal patterns in the bulk species and the organic molecular marker species. All species showed a strong annual periodicity, but their monthly and seasonal behavior varied substantially. Weekly periodicities appear in many compound classes with the most significant weekday/weekend effect observed for elemental carbon, cholestanes, hopanes, select polycyclic aromatic hydrocarbons (PAHs), heavy n-alkanoic acids and methoxyphenols. Many of the observed patterns can be explained by meteorology or anthropogenic activity patterns while others do not appear to have such obvious explanations. Similarities and differences in these findings compared to those reported from other cities are highlighted.

Dutton, Steven J.; Rajagopalan, Balaji; Vedal, Sverre; Hannigan, Michael P.

2013-01-01

227

Spatial and temporal patterns of forest disturbance in geographically distinct regions: rates, intensity, and size distribution  

NASA Astrophysics Data System (ADS)

Disturbance plays a critical role in shaping the structure and function of terrestrial forested ecosystems as well as the ecosystem services they provide such as the storage and transfer of carbon between the atmosphere and biosphere. Despite increased awareness and research on the importance of disturbance in shaping terrestrial ecosystems and the global carbon budget, large uncertainties and challenges remain. One area of large uncertainty is the role of natural and partial mortality disturbance events. The distribution of disturbance over space and time influence not only landscape and regional forest structure and function but also our ability to accurately monitor and model disturbance on the landscape under various sampling regimes. This study aims to quantify how disturbance events vary spatially, temporally and mechanistically within and between distinct regions of the conterminous US. Specifically we characterized the current and near past disturbance gap size frequency, severity, rates, variance and spatial patterns of disturbance using 30 m annual Landsat time-series data from 1984-2010 run through the highly automated Vegetation Change Tracker (VCT). Mapped forest change were broken down into land conversion (forest to non forest), severe disturbance (stand replacing), and non severe (partial clearing/ thinning). Local to national field and aerial inventories were used to both validate disturbance maps as well as inform disturbance mechanism classification. Results show strong distinctions in disturbance rates, gap sizes and patterns of disturbance between the northeast (p012r29*), northwest (p045r029), and southeast (p016r035) study regions as well as intra regional trends. The southeastern site had the highest average annual rate of disturbance at just over 1.5% forest area disturbed, followed by Northwest (~1%) and Northeast (~0.5%), with the northwest having the largest inter-annual variation. Within region strong patterns of disturbance could be observed between geopolitical boundaries. Results have implications on various sampling regimes ability to adequately capture disturbance across the regions and thus implications on estimates of forest carbon storage and flux.

Dolan, K. A.; Hurtt, G. C.; Huang, C.; Masek, J. G.; Fisk, J.

2013-12-01

228

Analysis of spatio-temporal brain imaging patterns by hidden markov models and serial MRI images.  

PubMed

Brain changes due to development and maturation, normal aging, or degenerative disease are continuous, gradual, and variable across individuals. To quantify the individual progression of brain changes, we propose a spatio-temporal methodology based on Hidden Markov Models (HMM), and apply it on four-dimensional structural brain magnetic resonance imaging series of older individuals. First, regional brain features are extracted in order to reduce image dimensionality. This process is guided by the objective of the study or the specific imaging patterns whose progression is of interest, for example, the evaluation of Alzheimer-like patterns of brain change in normal individuals. These regional features are used in conjunction with HMMs, which aim to measure the dynamic association between brain structure changes and progressive stages of disease over time. A bagging framework is used to obtain models with good generalization capability, since in practice the number of serial scans is limited. An application of the proposed methodology was to detect individuals with the risk of developing MCI, and therefore it was tested on modeling the progression of brain atrophy patterns in older adults. With HMM models, the state-transition paths corresponding to longitudinal brain changes were constructed from two completely independent datasets, the Alzheimer Disease Neuroimaging Initiative and the Baltimore Longitudinal Study of Aging. The statistical analysis of HMM-state paths among the normal, progressive MCI, and MCI groups indicates that, HMM-state index 1 is likely to be a predictor of the conversion from cognitively normal to MCI, potentially many years before clinical symptoms become measurable. Hum Brain Mapp 35:4777-4794, 2014. © 2014 Wiley Periodicals, Inc. PMID:24706564

Wang, Ying; Resnick, Susan M; Davatzikos, Christos

2014-09-01

229

Temporal patterns in daily measurements of inorganic and organic speciated PM 2.5 in Denver  

NASA Astrophysics Data System (ADS)

Airborne particulate matter less than 2.5 ?m in aerodynamic diameter (PM 2.5) has been linked to a wide range of adverse health effects and as a result is currently regulated by the U.S. Environmental Protection Agency. PM 2.5 originates from a multitude of sources and has heterogeneous physical and chemical characteristics. These features complicate the link between PM 2.5 emission sources, ambient concentrations and health effects. The goal of the Denver Aerosol Sources and Health (DASH) study is to investigate associations between sources and health using daily measurements of speciated PM 2.5 in Denver. The datxa set being collected for the DASH study will be the longest daily speciated PM 2.5 data set of its kind covering 5.5 years of daily inorganic and organic speciated measurements. As of 2008, 4.5 years of bulk measurements (mass, inorganic ions and total carbon) and 1.5 years of organic molecular marker measurements have been completed. Several techniques were used to reveal long-term and short-term temporal patterns in the bulk species and the organic molecular marker species. All species showed a strong annual periodicity, but their monthly and seasonal behavior varied substantially. Weekly periodicities appear in many compound classes with the most significant weekday/weekend effect observed for elemental carbon, cholestanes, hopanes, select polycyclic aromatic hydrocarbons (PAHs), heavy n-alkanoic acids and methoxyphenols. Many of the observed patterns can be explained by meteorology or anthropogenic activity patterns while others do not appear to have such obvious explanations. Similarities and differences in these findings compared to those reported from other cities are highlighted.

Dutton, Steven J.; Rajagopalan, Balaji; Vedal, Sverre; Hannigan, Michael P.

2010-03-01

230

Decoding Temporal Structure in Music and Speech Relies on Shared Brain Resources but Elicits Different Fine-Scale Spatial Patterns  

PubMed Central

Music and speech are complex sound streams with hierarchical rules of temporal organization that become elaborated over time. Here, we use functional magnetic resonance imaging to measure brain activity patterns in 20 right-handed nonmusicians as they listened to natural and temporally reordered musical and speech stimuli matched for familiarity, emotion, and valence. Heart rate variability and mean respiration rates were simultaneously measured and were found not to differ between musical and speech stimuli. Although the same manipulation of temporal structure elicited brain activation level differences of similar magnitude for both music and speech stimuli, multivariate classification analysis revealed distinct spatial patterns of brain responses in the 2 domains. Distributed neuronal populations that included the inferior frontal cortex, the posterior and anterior superior and middle temporal gyri, and the auditory brainstem classified temporal structure manipulations in music and speech with significant levels of accuracy. While agreeing with previous findings that music and speech processing share neural substrates, this work shows that temporal structure in the 2 domains is encoded differently, highlighting a fundamental dissimilarity in how the same neural resources are deployed.

Bhatara, Anjali; Ryali, Srikanth; Balaban, Evan; Levitin, Daniel J.; Menon, Vinod

2011-01-01

231

Decoding temporal structure in music and speech relies on shared brain resources but elicits different fine-scale spatial patterns.  

PubMed

Music and speech are complex sound streams with hierarchical rules of temporal organization that become elaborated over time. Here, we use functional magnetic resonance imaging to measure brain activity patterns in 20 right-handed nonmusicians as they listened to natural and temporally reordered musical and speech stimuli matched for familiarity, emotion, and valence. Heart rate variability and mean respiration rates were simultaneously measured and were found not to differ between musical and speech stimuli. Although the same manipulation of temporal structure elicited brain activation level differences of similar magnitude for both music and speech stimuli, multivariate classification analysis revealed distinct spatial patterns of brain responses in the 2 domains. Distributed neuronal populations that included the inferior frontal cortex, the posterior and anterior superior and middle temporal gyri, and the auditory brainstem classified temporal structure manipulations in music and speech with significant levels of accuracy. While agreeing with previous findings that music and speech processing share neural substrates, this work shows that temporal structure in the 2 domains is encoded differently, highlighting a fundamental dissimilarity in how the same neural resources are deployed. PMID:21071617

Abrams, Daniel A; Bhatara, Anjali; Ryali, Srikanth; Balaban, Evan; Levitin, Daniel J; Menon, Vinod

2011-07-01

232

Gender Differences in Speech Temporal Patterns Detected Using Lagged Co-occurrence Text-Analysis of Personal Narratives  

Microsoft Academic Search

This paper describes a novel methodology for the detection of speech patterns. Lagged co-occurrence analysis (LCA) utilizes\\u000a the likelihood that a target word will be uttered in a certain position after a trigger word. Using this methodology, it is\\u000a possible to uncover a statistically significant repetitive temporal patterns of word use, compared to a random choice of words.\\u000a To demonstrate

Shuki J. Cohen

2009-01-01

233

Spatial and temporal patterns of sea ice variations in Vilkitsky strait, Russian High Arctic  

NASA Astrophysics Data System (ADS)

The Arctic Ocean has been greatly affected by climate change. Future predications show an even more drastic reduction of the ice cap which will open new areas for the exploration of natural resources and maritime transportation.Shipping through the Arctic Ocean via the Northern Sea Route (NSR) could save about 40% of the sailing distance from Asia (Yokohama) to Europe (Rotterdam) compared to the traditional route via the Suez Canal. Vilkitsky strait is the narrowest and northest portion of the Northern Sea Route with heaviest traffic between the Taimyr Peninsular and the Severnaya Zemlya archipelago. The preliminary results of sea ice variations are presented by using moderate-resolution imaging spectro radiometer(MODIS) data with 250-m resolution in the Vilkitsky strait during 2009-2012. Temporally, the first rupture on sea ice in Vilkitsky strait usually comes up in April and sea ice completely break into pieces in early June. The strait would be ice-free between August and late September. The frequency of ice floes grows while temperature falls down in October. There are always one or two months suitable for transport. Spatially, Sea ice on Laptev sea side breaks earlier than that of Kara sea side while sea ice in central of strait breaks earlier than in shoreside. The phenomena are directly related with the direction of sea wind and ocean current. In summmary, study on Spatial and temporal patterns in this area is significant for the NSR. An additional research issue to be tackled is to seeking the trends of ice-free duration in the context of global warming. Envisat ASAR data will also be used in this study.

Ci, T.; Cheng, X.; Hui, F.

2013-12-01

234

Temporal and Spatial Patterns of Ambient Endotoxin Concentrations in Fresno, California  

PubMed Central

Background Endotoxins are found in indoor dust generated by human activity and pets, in soil, and adsorbed onto the surfaces of ambient combustion particles. Endotoxin concentrations have been associated with respiratory symptoms and the risk of atopy and asthma in children. Objective We characterized the temporal and spatial variability of ambient endotoxin in Fresno/Clovis, California, located in California’s Central Valley, to identify correlates and potential predictors of ambient endotoxin concentrations in a cohort of children with asthma [Fresno Asthmatic Children’s Environment Study (FACES)]. Methods Between May 2001 and October 2004, daily ambient endotoxin and air pollutants were collected at the central ambient monitoring site of the California Air Resources Board in Fresno and, for shorter time periods, at 10 schools and indoors and outdoors at 84 residences in the community. Analyses were restricted to May–October, the dry months during which endotoxin concentrations are highest. Results Daily endotoxin concentration patterns were determined mainly by meteorologic factors, particularly the degree of air stagnation. Overall concentrations were lowest in areas distant from agricultural activities. Highest concentrations were found in areas immediately downwind from agricultural/pasture land. Among three other measured air pollutants [fine particulate matter, elemental carbon (a marker of traffic in Fresno), and coarse particulate matter (PMc)], PMc was the only pollutant correlated with endotoxin. Endotoxin, however, was the most spatially variable. Conclusions Our data support the need to evaluate the spatial/temporal variability of endotoxin concentrations, rather than relying on a few measurements made at one location, in studies of exposure and and respiratory health effects, particularly in children with asthma and other chronic respiratory diseases.

Tager, Ira B.; Lurmann, Frederick W.; Haight, Thaddeus; Alcorn, Siana; Penfold, Bryan; Hammond, S. Katharine

2010-01-01

235

Spatial and temporal patterns of coexistence between competing Aedes mosquitoes in urban Florida  

PubMed Central

Understanding mechanisms fostering coexistence between invasive and resident species is important in predicting ecological, economic, or health impacts of invasive species. The mosquito Aedes aegypti coexists at some urban sites in southeastern United States with invasive Aedes albopictus, which is often superior in interspecific competition. We tested predictions for three hypotheses of species coexistence: seasonal condition-specific competition, aggregation among individual water-filled containers, and colonization–competition tradeoff across spatially partitioned habitat patches (cemeteries) that have high densities of containers. We measured spatial and temporal patterns of abundance for both species among water-filled resident cemetery vases and experimentally positioned standard cemetery vases and ovitraps in metropolitan Tampa, Florida. Consistent with the seasonal condition-specific competition hypothesis, abundances of both species in resident and standard cemetery vases were higher early in the wet season (June) versus late in the wet season (September), but the proportional increase of A. albopictus was greater than that of A. aegypti, presumably due to higher dry-season egg mortality and strong wet-season competitive superiority of larval A. albopictus. Spatial partitioning was not evident among cemeteries, a result inconsistent with the colonization-competition tradeoff hypothesis, but both species were highly independently aggregated among standard cemetery vases and ovitraps, which is consistent with the aggregation hypothesis. Densities of A. aegypti but not A. albopictus differed among land use categories, with A. aegypti more abundant in ovitraps in residential areas compared to industrial and commercial areas. Spatial partitioning among land use types probably results from effects of land use on conditions in both terrestrial and aquatic-container environments. These results suggest that both temporal and spatial variation may contribute to local coexistence between these Aedes in urban areas.

Juliano, S. A.

2009-01-01

236

Temporal patterns of nitrogenase gene (nifH) expression in the oligotrophic North Pacific Ocean.  

PubMed

Dinitrogen (N(2))-fixing microorganisms (diazotrophs) play important roles in ocean biogeochemistry and plankton productivity. In this study, we examined the presence and expression of specific planktonic nitrogenase genes (nifH) in the upper ocean (0 to 175 m) at Station ALOHA in the oligotrophic North Pacific Ocean. Clone libraries constructed from reverse-transcribed PCR-amplified mRNA revealed six unique phylotypes. Five of the nifH phylotypes grouped with sequences from unicellular and filamentous cyanobacteria, and one of the phylotypes clustered with gamma-proteobacteria. The cyanobacterial nifH phylotypes retrieved included two sequence types that phylogenetically grouped with unicellular cyanobacteria (termed groups A and B), several sequences closely related (97 to 99%) to Trichodesmium spp. and Katagnymene spiralis, and two previously unreported phylotypes clustering with heterocyst-forming nifH cyanobacteria. Temporal patterns of nifH expression were evaluated using reverse-transcribed quantitative PCR amplification of nifH gene transcripts. The filamentous and presumed unicellular group A cyanobacterial phylotypes exhibited elevated nifH transcription during the day, while members of the group B (closely related to Crocosphaera watsonii) unicellular phylotype displayed greater nifH transcription at night. In situ nifH expression by all of the cyanobacterial phylotypes exhibited pronounced diel periodicity. The gamma-proteobacterial phylotype had low transcript abundance and did not exhibit a clear diurnal periodicity in nifH expression. The temporal separation of nifH expression by the various phylotypes suggests that open ocean diazotrophic cyanobacteria have unique in situ physiological responses to daily fluctuations of light in the upper ocean. PMID:16151126

Church, Matthew J; Short, Cindy M; Jenkins, Bethany D; Karl, David M; Zehr, Jonathan P

2005-09-01

237

Interpreting the spatio-temporal patterns of sea turtle strandings: Going with the flow  

USGS Publications Warehouse

Knowledge of the spatial and temporal distribution of specific mortality sources is crucial for management of species that are vulnerable to human interactions. Beachcast carcasses represent an unknown fraction of at-sea mortalities. While a variety of physical (e.g., water temperature) and biological (e.g., decomposition) factors as well as the distribution of animals and their mortality sources likely affect the probability of carcass stranding, physical oceanography plays a major role in where and when carcasses strand. Here, we evaluate the influence of nearshore physical oceanographic and wind regimes on sea turtle strandings to decipher seasonal trends and make qualitative predictions about stranding patterns along oceanfront beaches. We use results from oceanic drift-bottle experiments to check our predictions and provide an upper limit on stranding proportions. We compare predicted current regimes from a 3D physical oceanographic model to spatial and temporal locations of both sea turtle carcass strandings and drift bottle landfalls. Drift bottle return rates suggest an upper limit for the proportion of sea turtle carcasses that strand (about 20%). In the South Atlantic Bight, seasonal development of along-shelf flow coincides with increased numbers of strandings of both turtles and drift bottles in late spring and early summer. The model also predicts net offshore flow of surface waters during winter - the season with the fewest relative strandings. The drift bottle data provide a reasonable upper bound on how likely carcasses are to reach land from points offshore and bound the general timeframe for stranding post-mortem (< two weeks). Our findings suggest that marine turtle strandings follow a seasonal regime predictable from physical oceanography and mimicked by drift bottle experiments. Managers can use these findings to reevaluate incidental strandings limits and fishery takes for both nearshore and offshore mortality sources. ?? 2005 Elsevier Ltd. All rights reserved.

Hart, K. M.; Mooreside, P.; Crowder, L. B.

2006-01-01

238

Spatial and temporal patterns of coexistence between competing Aedes mosquitoes in urban Florida.  

PubMed

Understanding mechanisms fostering coexistence between invasive and resident species is important in predicting ecological, economic, or health impacts of invasive species. The mosquito Aedes aegypti coexists at some urban sites in southeastern United States with invasive Aedes albopictus, which is often superior in interspecific competition. We tested predictions for three hypotheses of species coexistence: seasonal condition-specific competition, aggregation among individual water-filled containers, and colonization-competition tradeoff across spatially partitioned habitat patches (cemeteries) that have high densities of containers. We measured spatial and temporal patterns of abundance for both species among water-filled resident cemetery vases and experimentally positioned standard cemetery vases and ovitraps in metropolitan Tampa, Florida. Consistent with the seasonal condition-specific competition hypothesis, abundances of both species in resident and standard cemetery vases were higher early in the wet season (June) versus late in the wet season (September), but the proportional increase of A. albopictus was greater than that of A. aegypti, presumably due to higher dry-season egg mortality and strong wet-season competitive superiority of larval A. albopictus. Spatial partitioning was not evident among cemeteries, a result inconsistent with the colonization-competition tradeoff hypothesis, but both species were highly independently aggregated among standard cemetery vases and ovitraps, which is consistent with the aggregation hypothesis. Densities of A. aegypti but not A. albopictus differed among land use categories, with A. aegypti more abundant in ovitraps in residential areas compared to industrial and commercial areas. Spatial partitioning among land use types probably results from effects of land use on conditions in both terrestrial and aquatic-container environments. These results suggest that both temporal and spatial variation may contribute to local coexistence between these Aedes in urban areas. PMID:19263086

Leisnham, Paul T; Juliano, S A

2009-05-01

239

Spatial and temporal seismicity patterns from dynamic trigger by great earthquakes  

NASA Astrophysics Data System (ADS)

Questions remain regarding the dynamic triggering of large earthquakes at global distances and the role of earthquake nucleation times following dynamic stress perturbations on active faults. At distances beyond 2-3 fault lengths, transient stress changes as a result of seismic waves have been shown to trigger microseismicity in regions of geothermal activity, non-volcanic tremor, and small tectonic earthquakes, i.e. M<3, during the passage of seismic waves and subsequent days. Less frequently, immediate triggering of earthquakes ranging from 3 > M < 5 is detected during the passage of the surface wave train, whereas events M>5 are shown to experience no rate increase outside the aftershock zone of large-magnitude events. An exception to this magnitude threshold for dynamically triggered activity is the MW 8.6 2012 east Indian Ocean earthquake that resulted in above-average global seismicity for events >M5.5 in the 6 days following the mainshock (Pollitz et al., 2012 Nature) followed by a 95 day period of global quiescence for M>=6.5 events (Pollitz et al., 2013 submitted to BSSA). The activity observed following the 2012 event is an example of delayed dynamic triggering which suggests that the stress perturbations experienced during the teleseismic surface waves were large enough to advance the earthquake cycle of multiple >M5 events. Conversely, the same stress changes could suppress activity while earthquake rates return to equilibrium. Here we investigate the idea of global 'dynamic shadowing' in order to determine if a spatial and temporal relationship to large-magnitude events exists for periods of reduced global seismicity. We build on the previous work by Parsons and Velasco (2011 Nature Geoscience) who concluded that increases in M>5 seismicity are confined to within 2-3 fault lengths of the rupture and activity returned to background rates within 36 hours following a M>7 event. Using a similar methodology, we explore the suppression of global activity with respect to background earthquake activity following large magnitude events using 30 years of earthquake catalog data obtained from the Advanced National Seismic System. Our goal is to determine if a dynamic shadow effect results in a reduction of seismicity at a distinguishable level below the background seismicity over various temporal and spatial ranges following the largest cataloged earthquakes. We utilize spatial ranges consistent with maximum transient stress changes for different fault mechanisms in order to document the temporal characteristics of seismicity patterns.

Johnson, C. W.; Burgmann, R.

2013-12-01

240

Spatial and Temporal Variability of Zooplankton Thin Layers: The Effects of Composition and Orientation on Acoustic Detection of Layers.  

National Technical Information Service (NTIS)

Our primary long-term objective is to better understand the physical and biological mechanisms of formation and maintenance of thin layers of zooplankton. Because zooplankton can be strong sound scatterers, acoustic instruments are effective at detecting ...

A. Lavery C. Ashjian D. Fratantoni M. Sutor P. Wiebe

2006-01-01

241

Spatial and Temporal Variability of Zooplankton Thin Layers: The Effects of Composition and Orientation on Acoustic Detection of Layers.  

National Technical Information Service (NTIS)

Our primary long-term objective is to better understand the physical and biological mechanisms of formation and maintenance of thin layers of zooplankton. Because zooplankton can be strong sound scatterers, acoustic instruments are effective at detecting ...

A. Lavery C. Ashjian D. Fratantoni M. Sutor P. Wiebe

2008-01-01

242

Spatial and Temporal Variability of Zooplankton Thin Layers: The Effects of Composition and Orientation on Acoustic Detection of Layers.  

National Technical Information Service (NTIS)

Our primary long-term objective is to better understand the physical and biological mechanisms of formation and maintenance of thin layers of zooplankton. Because zooplankton can be strong sound scatterers, acoustic instruments are effective at detecting ...

A. Lavery C. Ashijian D. Fratantoni M. Sutor P. Wiebe

2007-01-01

243

Spatial and Temporal Patterns of Aspergillus flavus Strain Composition and Propagule Density in Yuma County, Arizona, Soils  

Microsoft Academic Search

Orum, T. V., Bigelow, D. M., Nelson, M. R., Howell, D. R., and Cotty, P. J. 1997. Spatial and temporal patterns of Aspergillus flavus strain composition and propagule density in Yuma County, Arizona, soils. Plant Dis. 81:911-916. Aspergillus flavus isolates from Arizona can be divided into S and L strains on the basis of scle- rotial morphology. These genetically distinct

Thomas V. Orum; Donna M. Bigelow; Merritt R. Nelson; Donald R. Howell; Peter J. Cotty

1997-01-01

244

Temporal trajectories of phosphorus and pedo-patterns mapped in Water Conservation Area 2, Everglades, Florida, USA  

Microsoft Academic Search

Documenting local change of soil properties over longer periods of time is critical to assess trends along trajectories. We present two types of temporal trajectories that document change in soil phosphorus (P) and pedo-patterns in Water Conservation Area 2, a subtropical wetland in the Everglades, Florida. Our specific objectives were to (i) quantify the spatial distribution of total P (TP)

S. Grunwald; T. Z. Osborne; K. R. Reddy

2008-01-01

245

The sooner, the better: temporal patterns in brief treatment of depression and their role in long-term outcome  

Microsoft Academic Search

To examine whether temporal patterns of change in brief treatment for depression are predictive of outcome at 18 months posttreatment, the authors used data from the National Institute of Mental Health-sponsored Treatment of Depression Collaborative Research Program. In accordance with their hypotheses, they found that (a) individuals whose level of distress does not decrease between intake and Week 4 of

Eva Gilboa-Schechtman; Golan Shahar

2006-01-01

246

Distribution and long-term temporal patterns of four invasive colonial ascidians in the Gulf of Maine  

Microsoft Academic Search

Invasive ascidians are a growing concern for ecologists and natural resource managers, yet few studies have documented their short- and long-term temporal patterns of abundance. This study focuses on the invasion of the Gulf of Maine by the colonial ascidians Botryllus schlosseri, Botrylloides violaceus, Diplosoma listerianum and Didemnum sp. A. We examined the time of arrival and potential vectors for

Jennifer Dijkstra; Larry G. Harris; Erica Westerman

2007-01-01

247

Single-unit analysis of pattern-motion selective properties in the middle temporal visual area (MT)  

Microsoft Academic Search

The middle temporal visual area (MT) in macaque extrastriate cortex is characterized by a high proportion of neurons selective for the direction of stimulus motion, and is thus thought to play an important role in motion perception. Previous studies identified a population of cells in MT that appeared capable of coding the motion of whole visual patterns independent of the

H. R. Rodman; T. D. Albright

1989-01-01

248

When to feed on gums: Temporal patterns of gummivory in wild tamarins,Saguinus mystaxand Saguinus fuscicollis(Callitrichinae)  

Microsoft Academic Search

This study examines the temporal patterning of gum feeding in two species of sympatric tamarin monkeys, Saguinus mystax and Saguinus fuscicollis, during the diurnal activity period. The number and duration of visits to gum sources and number of gum feeding records are used as parameters to analyze the gum feeding itinerary. Both visits to gum sources and gum feeding records

Eckhard W. Heymann; Andrew C. Smith

1999-01-01

249

Different Phases of Long-Term Memory Require Distinct Temporal Patterns of PKA Activity after Single-Trial Classical Conditioning  

ERIC Educational Resources Information Center

The cAMP-dependent protein kinase (PKA) is known to play a critical role in both transcription-independent short-term or intermediate-term memory and transcription-dependent long-term memory (LTM). Although distinct phases of LTM already have been demonstrated in some systems, it is not known whether these phases require distinct temporal patterns

Michel, Maximilian; Kemenes, Ildiko; Muller, Uli; Kemenes, Gyorgy

2008-01-01

250

Spatio-temporal patterns of fish assemblages in coastal West African rivers: a self-organizing map approach  

Microsoft Academic Search

We investigated spatio-temporal patterns of fish assemblages in four small coastal rivers in South-East Ivory Coast. The samples were collected between July 2003 and March 2005 at 8 sampling sites (2 per river: 1 upstream and 1 downstream). A total of 59 fish species belonging to 39 genera, 23 families and 11 orders were captured. Perci- forms (30% of the

Félix Koffi Konan; Fabien Leprieur; Allassane Ouattara; Sébastien Brosse; Gaël Grenouillet; Germain Gourène; Peter Winterton; Sovan Lek

2006-01-01

251

Composition, structural characteristics and temporal patterns of fish assemblages in non-tidal Mediterranean lagoons: A case study  

Microsoft Academic Search

The importance of transitional water ecosystems as nursery habitats and feeding grounds for fish species is well-known. Detailed studies of colonization patterns of fish guilds in response to biotic and abiotic drivers are however unevenly distributed among ecosystem types. We address here the temporal variability of fish assemblages in small non-tidal lagoons in the Mediterranean basin. The study was carried

S. Maci; A. Basset

2009-01-01

252

Spatio-temporal profile of DNA fragmentation and its relationship to patterns of epileptiform activity following focally evoked limbic seizures  

Microsoft Academic Search

The specific electrographic activity responsible for seizure-induced DNA damage remains little explored. We therefore examined the regional and temporal appearance of DNA fragmentation and cell death and its relationship to specific electrographic seizure patterns in a rat model of focally evoked limbic epilepsy. Animals received intra-amygdaloid injection of kainic acid (KA) to induce seizures for 45 min during continuous electroencephalographic

David C. Henshall; Jennifer Sinclair; Roger P. Simon

2000-01-01

253

Neuromolecular Imaging Shows Temporal Synchrony Patterns between Serotonin and Movement within Neuronal Motor Circuits in the Brain  

PubMed Central

The present discourse links the electrical and chemical properties of the brain with neurotransmitters and movement behaviors to further elucidate strategies to diagnose and treat brain disease. Neuromolecular imaging (NMI), based on electrochemical principles, is used to detect serotonin in nerve terminals (dorsal and ventral striata) and somatodendrites (ventral tegmentum) of reward/motor mesocorticolimbic and nigrostriatal brain circuits. Neuronal release of serotonin is detected at the same time and in the same animal, freely moving and unrestrained, while open-field behaviors are monitored via infrared photobeams. The purpose is to emphasize the unique ability of NMI and the BRODERICK PROBE® biosensors to empirically image a pattern of temporal synchrony, previously reported, for example, in Aplysia using central pattern generators (CPGs), serotonin and cerebral peptide-2. Temporal synchrony is reviewed within the context of the literature on central pattern generators, neurotransmitters and movement disorders. Specifically, temporal synchrony data are derived from studies on psychostimulant behavior with and without cocaine while at the same time and continuously, serotonin release in motor neurons within basal ganglia, is detected. The results show that temporal synchrony between the neurotransmitter, serotonin and natural movement occurs when the brain is NOT injured via, e.g., trauma, addictive drugs or psychiatric illness. In striking contrast, in the case of serotonin and cocaine-induced psychostimulant behavior, a different form of synchrony and also asynchrony can occur. Thus, the known dysfunctional movement behavior produced by cocaine may well be related to the loss of temporal synchrony, the loss of the ability to match serotonin in brain with motor activity. The empirical study of temporal synchrony patterns in humans and animals may be more relevant to the dynamics of motor circuits and movement behaviors than are studies of static parameters currently relied upon within the realms of science and medicine. There are myriad applications for the use of NMI to discover clinically relevant diagnoses and treatments for brain disease involving the motor system.

Broderick, Patricia A.

2013-01-01

254

Neuromolecular Imaging Shows Temporal Synchrony Patterns between Serotonin and Movement within Neuronal Motor Circuits in the Brain.  

PubMed

The present discourse links the electrical and chemical properties of the brain with neurotransmitters and movement behaviors to further elucidate strategies to diagnose and treat brain disease. Neuromolecular imaging (NMI), based on electrochemical principles, is used to detect serotonin in nerve terminals (dorsal and ventral striata) and somatodendrites (ventral tegmentum) of reward/motor mesocorticolimbic and nigrostriatal brain circuits. Neuronal release of serotonin is detected at the same time and in the same animal, freely moving and unrestrained, while open-field behaviors are monitored via infrared photobeams. The purpose is to emphasize the unique ability of NMI and the BRODERICK PROBE® biosensors to empirically image a pattern of temporal synchrony, previously reported, for example, in Aplysia using central pattern generators (CPGs), serotonin and cerebral peptide-2. Temporal synchrony is reviewed within the context of the literature on central pattern generators, neurotransmitters and movement disorders. Specifically, temporal synchrony data are derived from studies on psychostimulant behavior with and without cocaine while at the same time and continuously, serotonin release in motor neurons within basal ganglia, is detected. The results show that temporal synchrony between the neurotransmitter, serotonin and natural movement occurs when the brain is NOT injured via, e.g., trauma, addictive drugs or psychiatric illness. In striking contrast, in the case of serotonin and cocaine-induced psychostimulant behavior, a different form of synchrony and also asynchrony can occur. Thus, the known dysfunctional movement behavior produced by cocaine may well be related to the loss of temporal synchrony, the loss of the ability to match serotonin in brain with motor activity. The empirical study of temporal synchrony patterns in humans and animals may be more relevant to the dynamics of motor circuits and movement behaviors than are studies of static parameters currently relied upon within the realms of science and medicine. There are myriad applications for the use of NMI to discover clinically relevant diagnoses and treatments for brain disease involving the motor system. PMID:24961434

Broderick, Patricia A

2013-01-01

255

Spatio-temporal expression patterns of Arabidopsis thaliana and Medicago truncatula defensin-like genes.  

PubMed

Plant genomes contain several hundred defensin-like (DEFL) genes that encode short cysteine-rich proteins resembling defensins, which are well known antimicrobial polypeptides. Little is known about the expression patterns or functions of many DEFLs because most were discovered recently and hence are not well represented on standard microarrays. We designed a custom Affymetrix chip consisting of probe sets for 317 and 684 DEFLs from Arabidopsis thaliana and Medicago truncatula, respectively for cataloging DEFL expression in a variety of plant organs at different developmental stages and during symbiotic and pathogenic associations. The microarray analysis provided evidence for the transcription of 71% and 90% of the DEFLs identified in Arabidopsis and Medicago, respectively, including many of the recently annotated DEFL genes that previously lacked expression information. Both model plants contain a subset of DEFLs specifically expressed in seeds or fruits. A few DEFLs, including some plant defensins, were significantly up-regulated in Arabidopsis leaves inoculated with Alternaria brassicicola or Pseudomonas syringae pathogens. Among these, some were dependent on jasmonic acid signaling or were associated with specific types of immune responses. There were notable differences in DEFL gene expression patterns between Arabidopsis and Medicago, as the majority of Arabidopsis DEFLs were expressed in inflorescences, while only a few exhibited root-enhanced expression. By contrast, Medicago DEFLs were most prominently expressed in nitrogen-fixing root nodules. Thus, our data document salient differences in DEFL temporal and spatial expression between Arabidopsis and Medicago, suggesting distinct signaling routes and distinct roles for these proteins in the two plant species. PMID:23527067

Tesfaye, Mesfin; Silverstein, Kevin At; Nallu, Sumitha; Wang, Lin; Botanga, Christopher J; Gomez, S Karen; Costa, Liliana M; Harrison, Maria J; Samac, Deborah A; Glazebrook, Jane; Katagiri, Fumiaki; Gutierrez-Marcos, Jose F; Vandenbosch, Kathryn A

2013-01-01

256

Convergence and Divergence in the Evolution of Cat Skulls: Temporal and Spatial Patterns of Morphological Diversity  

PubMed Central

Background Studies of biological shape evolution are greatly enhanced when framed in a phylogenetic perspective. Inclusion of fossils amplifies the scope of macroevolutionary research, offers a deep-time perspective on tempo and mode of radiations, and elucidates life-trait changes. We explore the evolution of skull shape in felids (cats) through morphometric analyses of linear variables, phylogenetic comparative methods, and a new cladistic study of saber-toothed cats. Methodology/Principal Findings A new phylogenetic analysis supports the monophyly of saber-toothed cats (Machairodontinae) exclusive of Felinae and some basal felids, but does not support the monophyly of various saber-toothed tribes and genera. We quantified skull shape variation in 34 extant and 18 extinct species using size-adjusted linear variables. These distinguish taxonomic group membership with high accuracy. Patterns of morphospace occupation are consistent with previous analyses, for example, in showing a size gradient along the primary axis of shape variation and a separation between large and small-medium cats. By combining the new phylogeny with a molecular tree of extant Felinae, we built a chronophylomorphospace (a phylogeny superimposed onto a two-dimensional morphospace through time). The evolutionary history of cats was characterized by two major episodes of morphological divergence, one marking the separation between saber-toothed and modern cats, the other marking the split between large and small-medium cats. Conclusions/Significance Ancestors of large cats in the ‘Panthera’ lineage tend to occupy, at a much later stage, morphospace regions previously occupied by saber-toothed cats. The latter radiated out into new morphospace regions peripheral to those of extant large cats. The separation between large and small-medium cats was marked by considerable morphologically divergent trajectories early in feline evolution. A chronophylomorphospace has wider applications in reconstructing temporal transitions across two-dimensional trait spaces, can be used in ecophenotypical and functional diversity studies, and may reveal novel patterns of morphospace occupation.

Sakamoto, Manabu; Ruta, Marcello

2012-01-01

257

Areal and Temporal Analysis of Precipitation Patterns In Slovakia Using Spectral Analysis  

NASA Astrophysics Data System (ADS)

Harmonic analysis as an objective method of precipitation seasonality studying is ap- plied to the 1901-2000 monthly precipitation averages at five stations in the low-land part of Slovakia with elevation less than 800 m a.s.l. The significant harmonics of long-term precipitation series have been separately computed for eight 30-year peri- ods, which cover the 20th century and some properties and the variations are com- pared to 100-year monthly precipitation averages. The selected results show that the first and the second harmonics pre-dominantly influence on the annual distribution and climatic seasonal regimes of pre-cipitation that contribute to the precipitation am- plitude/pattern with about 20% and 10%, respectively. These indicate annual and half year variations. The rest harmon-ics often have each less than 5% contribution on the Fourier interpolation course. Maximum in yearly precipitation course, which oc- curs approximately at the begin-ning of July, because of phase changing shifts then to the middle of June. Some probable reasons regarding to Fourier components are discussed. In addition, a tem-poral analysis over precipitation time series belonging to the Hurbanovo Observa-tory as the longest observational series on the territory of Slovakia (with 130-year precipitation records) has been individually performed and possible meteorological factors responsible for the observed patterns are suggested. A comparison of annual precipitation course obtained from daily precipitation totals analysis and polynomial trends with Fourier interpolation has been done too. Daily precipitation data in the latest period are compared for some stations in Slovakia as well. Only selected results are pre-sented in the poster.

Pishvaei, M. R.

258

Spatio-temporal patterns of weekend effects in surface air temperatures in China, 1978-2008  

NASA Astrophysics Data System (ADS)

Spatio-temporal patterns of weekend effects of surface air temperature variables over the continental area of China during the period 1978-2008 were analyzed by statistics and spatial analysis of the homogenized time series from the selected 615 surface meteorological stations of China Meteorological Administration (CMA). Results indicate that (1) there is an evident warming trend over China from 1978 to 2008, with the linear trend rates of Tmean, Tmax, Tmin and DTR being 0.43, 0.41, 0.48, and -0.07 °C/10 a, respectively; (2) weekend temperature effects are statistically significant (? = 0.05) in the annual and seasonal mean (Tmean) and maximum (Tmax) temperatures, but not in the minimum temperature (Tmin) or diurnal temperature range (DTR); And (3) for seasonal time series, Tmean, Tmax and Tmin show negative weekend effect anomalies in spring, summer and autumn, while they have opposite signals — positive weekend effect anomalies in winter. Spatial statistics show that only a minority (less than 30%) of the 615 stations demonstrate weekend effects in all four temperature variables at the ? = 0.10 confidence level. Tmean, Tmax and Tmin have negative weekend effects only in southern-central and southwestern China, while DTR has a positive weekend effect in northwestern and southwestern China. The weekend effects of temperature variables vary with season and region over China. There are different spatial distribution patterns of weekend effect in different temperature variables for different seasons and no evidently opposite signals of weekend effects for winter and summer in Tmean, Tmax, Tmin and DTR over China, 1978-2008.; Fig.1 Spatial distribution map of weekend effects in DTR over China, 1978-2008. Shown as the average for Saturday through Monday minus the average for Wednesday through Friday for each station. Stations significant at ? = 0.05 and 0.10 are filled with dark and light colors, respectively.

Xiong, Y.

2012-12-01

259

Spatial pattern and temporal dynamics of groundwater-surface water interaction in heterogeneous alluvial fan system  

NASA Astrophysics Data System (ADS)

As a key component of the hydrologic system, groundwater and surface water interaction in aquifer-aquitard complexes has not received adequate study. It has long been realized that the heterogeneity of geologic sediments strongly affects the groundwater flow and solute transport. In large scale deep heterogeneous vadose zone system, it remains numerically challenging to model the interplay between surface water and groundwater because of the highly non-linear aspect of partially saturated flow, three-dimensional heterogeneity requiring large systems of equations, and the sharp contrast in permeability between aquifer and aquitard in geologic systems. In this study, the spatial pattern of groundwater and surface water interaction and their temporal dynamics are investigated in a regional scale model (36.2 km by 45.4 km by 600 m) with high resolution (200 m by 200 m by 1 m) and detailed geo-structure with the fully parallel code, ParFlow, which solves three dimensional Richard's Equation in a fully mass conservative manner. This model makes it possible to study the groundwater dynamics, perched aquifer system, spatial pattern of surface water infiltration on a scale that is appropriate for investigating regional interplay between groundwater pumping, streamflow, and water resources management. The findings of this study will benefit large coupled hydrologic modeling, such as hydro-climate modeling, in the sense of better understanding the mechanism of feedbacks between groundwater and surface water, as well as provide strategic solutions on water resource management, especially as the climate variability drives year to year change in surface water and groundwater conjunctive usage.

Liu, Y.; Newcomb, N. J.; Fogg, G. E.

2013-12-01

260

Capturing spatial and temporal patterns of widespread, extreme flooding across Europe  

NASA Astrophysics Data System (ADS)

Statistical characterisation of physical hazards is an integral part of probabilistic catastrophe models used by the reinsurance industry to estimate losses from large scale events. Extreme flood events are not restricted by country boundaries which poses an issue for reinsurance companies as their exposures often extend beyond them. We discuss challenges and solutions that allow us to appropriately capture the spatial and temporal dependence of extreme hydrological events on a continental-scale, which in turn enables us to generate an industry-standard stochastic event set for estimating financial losses for widespread flooding. By presenting our event set methodology, we focus on explaining how extreme value theory (EVT) and dependence modelling are used to account for short, inconsistent hydrological data from different countries, and how to make appropriate statistical decisions that best characterise the nature of flooding across Europe. The consistency of input data is of vital importance when identifying historical flood patterns. Collating data from numerous sources inherently causes inconsistencies and we demonstrate our robust approach to assessing the data and refining it to compile a single consistent dataset. This dataset is then extrapolated using a parameterised EVT distribution to estimate extremes. Our method then captures the dependence of flood events across countries using an advanced multivariate extreme value model. Throughout, important statistical decisions are explored including: (1) distribution choice; (2) the threshold to apply for extracting extreme data points; (3) a regional analysis; (4) the definition of a flood event, which is often linked with reinsurance industry's hour's clause; and (5) handling of missing values. Finally, having modelled the historical patterns of flooding across Europe, we sample from this model to generate our stochastic event set comprising of thousands of events over thousands of years. We then briefly illustrate how this is applied within a probabilistic model to estimate catastrophic loss curves used by the reinsurance industry.

Busby, Kathryn; Raven, Emma; Liu, Ye

2013-04-01

261

Spatial, temporal, and interspecies patterns in fine particulate matter in Texas  

SciTech Connect

The Big Bend Regional Aerosol and Visibility Observational (BRAVO) field study was conducted from July to October 1999 and was followed by several years of modeling and data analyses to examine the causes of haze at Big Bend National Park TX (BBNP). During BRAVO, daily speciated fine (diameter <2.5 {mu}m) particulate concentrations were measured at 37 sites throughout Texas. At the primary receptor site, K-Bar Ranch, there were many additional measurements including a 'high-sensitivity' version of the 24-hr fine particulate elemental data. The spatial, temporal, and interspecies patterns in these data are examined here to qualitatively investigate source regions and source types influencing the fine particulate concentrations in Texas with an emphasis on sources of sulfates, the largest contributor to fine mass and light extinction. Peak values of particulate sulfur (S) varied spatially and seasonally. Maximum S was in Northeast Texas during the summer, whereas peak S at BBNP was in the fall. Sulfate acidity at BBNP also varied by month. Sources of Se were evident in Northeast Texas and from the Carbon I and II coal-fired plants. High S episodes at BBNP during BRAVO had several different trace element characteristics. Carbon concentrations at BBNP during BRAVO were probably mostly urban-related, with arrival from the Houston area likely. The Houston artificial tracer released during the second half of BRAVO was highly correlated with some carbon fractions. There was evidence of the influence of African dust at sites throughout Texas during the summer. Patterns in several trace elements were also examined. Vanadium was associated with air masses from Mexico. Lead concentrations in southern Texas have dropped dramatically over the past several years. 23 refs., 9 figs., 2 tabs.

Kristi A. Gebhart; William C. Malm; Lowell L. Ashbaugh [Colorado State University, Fort Collins, CO (United States). National Park Service

2005-11-01

262

Spatial and temporal variability of subsurface flow patterns at the hillslope scale: an experimental analysis  

NASA Astrophysics Data System (ADS)

Despite the importance of subsurface flow in regulating catchment runoff and slope stability, the dominant controls on the spatial and temporal variability of subsurface flow patterns on hillslopes of headwater catchments are still poorly understood. In this work, we used groundwater data from spatially distributed piezometric wells on two alpine hillslopes to investigate the main factors controlling the water table response to precipitation. Particularly, we tested the following hypotheses: i) piezometric response triggering is jointly controlled by antecedent moisture condition and rainfall depth; ii) contrasting hillslope topographic features affect the magnitude and dynamics of piezometric response, and iii) soil depth controls the timing of piezometric response. Two steep hillslopes of similar size, soil properties and vegetation cover but contrasting topography (divergent-convex and relatively planar morphology) in the 0.14 km2 Bridge Creek Catchment (Dolomites, Central-Eastern Italian Alps) were instrumented with 24 piezometric wells, ranging in depth between 0.7 m and 1.5 m from the soil surface. The analysis was conducted for 63 rainfall-runoff events selected over three years in the snow-free months. Results show that piezometric response, although very variable both in space and in time, was clearly distinct for events that occurred during wet or dry conditions, distinguished on the basis of a threshold relation between stormflow and an index combining antecedent soil moisture and rainfall depth. Correlation analysis based on two metrics of transient water table response (percentage of well activation and piezometric peak) revealed that antecedent soil water content alone was the poorest predictor of piezometric response whereas the highest degree of variance was explained by the combination of rainfall and antecedent soil moisture. Hillslope topography played a significant role on water table peak only for the site characterized by an overall convex-divergent morphology. As at other experimental sites, groundwater was found to not rise in unison throughout the hillslope, violating the steady-state assumption. However, in contrast with many other studies, we observed that water table level at the top of the hillslope typically peaked earlier and was less variable than at the hillslope toe. We related this behaviour to the control exerted by soil depth that increased in downslope direction. The temporal structure of the piezometric response, mainly driven by the soil depth and hillslope topography, led to consistent hysteretic behaviour, characterized by the highest variability for intermediate groundwater levels and the lowest during wet conditions. On the one hand, this work contributes to improve the comprehension of the hydrological behaviour of the study catchment, adding new information on the effect of topography of individual hillslopes and of soil depth on the spatial and temporal dynamics of subsurface flow patterns. On the other hand, these results offer insights, previously missing, on the main controls governing the water table response in alpine hillslopes, and likely in other hillslopes of humid catchments worldwide, that are generally poorly investigated due to practical difficulties in monitoring groundwater variations. Keywords: water table dynamics; hillslope topography; antecedent conditions; hysteresis; soil depth, steady state.

Penna, Daniele; Hopp, Luisa; Dalla Fontana, Giancarlo; Borga, Marco

2014-05-01

263

Spatial and Temporal Patterns of Lin-12 Expression during C. Elegans Hermaphrodite Development  

PubMed Central

The lin-12 gene encodes a receptor that mediates certain cell-cell interactions during Caenorhabditis elegans development. We have examined the expression of a lin-12::lacZ reporter gene in individual cells during the development of C. elegans hermaphrodites. lin-12::lacZ is expressed in a discrete spatial and temporal pattern during development and the lin-12::lacZ reporter gene will provide a useful marker for other studies, particularly of somatic gonadal and vulval development. In general, the cells that express lin-12::lacZ correspond to cells whose fates are known to be altered in lin-12 mutants implying that restriction of lin-12 expression may be an important regulatory mechanism; the exceptions to this statement may reveal the cellular defects that underlie aspects of the lin-12 phenotype that have not been previously explained. For decisions that are not naturally variable, lin-12::lacZ expression does not appear to change before or upon commitment to a cell fate implying that in these cases posttranscriptional regulation of lin-12 activity may control cell fate specification.

Wilkinson, H. A.; Greenwald, IVA.

1995-01-01

264

Temporal patterns of infiltration into a water repellent soil under field conditions  

NASA Astrophysics Data System (ADS)

Water repellency causes substantial economic losses for farmers in southern Australia through impacts on crop growth and weed germination. However, recent research has demonstrated that laboratory measurements of water repellency may not be a reliable indicator of the severity of symptoms experienced in the field. In particular, crop residue retention and minimal soil disturbance led to increased water repellency, but was also associated with higher soil water contents measured at strategic times of the year. Little is known about the temporal patterns of soil water storage close to the soil surface in a water repellent sand. In this research we measured soil water content at a depth of 0.05 m at 15-minute intervals from June 2011 to October 2012, under various treatment combinations of residue retention and soil disturbance. Measurements were made in both 'crop row' and 'crop inter-row' positions. For a rainfall event (9.2 mm) in March 2012, prior to crop seeding, plots previously established with no-till absorbed significantly more water (increase in soil water content of 0.074 v/v) than plots conventionally cultivated (0.038 v/v). In June 2012 (12.6 mm), 4 weeks after crop seeding, tillage was again significant, and there was a significant interaction between tillage and 'row' or 'inter-row' position. These results demonstrate the importance of crop management in modifying the response of water repellent soils to rainfall in the field.

Ward, Phil; Roper, Margaret; Micin, Shayne; Jongepier, Ramona

2014-05-01

265

We'll Meet Again: Revealing Distributional and Temporal Patterns of Social Contact  

PubMed Central

What are the dynamics and regularities underlying social contact, and how can contact with the people in one's social network be predicted? In order to characterize distributional and temporal patterns underlying contact probability, we asked 40 participants to keep a diary of their social contacts for 100 consecutive days. Using a memory framework previously used to study environmental regularities, we predicted that the probability of future contact would follow in systematic ways from the frequency, recency, and spacing of previous contact. The distribution of contact probability across the members of a person's social network was highly skewed, following an exponential function. As predicted, it emerged that future contact scaled linearly with frequency of past contact, proportionally to a power function with recency of past contact, and differentially according to the spacing of past contact. These relations emerged across different contact media and irrespective of whether the participant initiated or received contact. We discuss how the identification of these regularities might inspire more realistic analyses of behavior in social networks (e.g., attitude formation, cooperation).

Pachur, Thorsten; Schooler, Lael J.; Stevens, Jeffrey R.

2014-01-01

266

CT Scans in Young People in Great Britain: Temporal and Descriptive Patterns, 1993-2002  

PubMed Central

Background. Although using computed tomography (CT) can be greatly beneficial, the associated relatively high radiation doses have led to growing concerns in relation to potential associations with risk of future cancer. Very little has been published regarding the trends of CT use in young people. Therefore, our objective was to assess temporal and other patterns in CT usage among patients aged under 22 years in Great Britain from 1993 to 2002. Methods. Electronic data were obtained from the Radiology Information Systems of 81 hospital trusts within Great Britain. All included patients were aged under 22 years and examined using CT between 1993 and 2002, with accessible radiology records. Results. The number of CT examinations doubled over the study period. While increases in numbers of recorded examinations were seen across all age groups, the greatest increases were in the older patients, most notably those aged 15–19 years of age. Sixty percent of CT examinations were of the head, with the percentages varying with calendar year and patient age. Conclusions. In contrast to previous data from the North of England, the doubling of CT use was not accompanied by an increase in numbers of multiple examinations to the same individual.

Pearce, Mark S.; Salotti, Jane A.; Howe, Nicola L.; McHugh, Kieran; Kim, Kwang Pyo; Lee, Choonsik; Craft, Alan W.; Berrington de Gonzalez, Amy; Parker, Louise

2012-01-01

267

Temporal-Spatial Neural Activation Patterns Linked to Perceptual Encoding of Emotional Salience  

PubMed Central

It is well known that we continuously filter incoming sensory information, selectively allocating attention to what is important while suppressing distracting or irrelevant information. Yet questions remain about spatiotemporal patterns of neural processes underlying attentional biases toward emotionally significant aspects of the world. One index of affectively biased attention is an emotional variant of an attentional blink (AB) paradigm, which reveals enhanced perceptual encoding for emotionally salient over neutral stimuli under conditions of limited executive attention. The present study took advantage of the high spatial and temporal resolution of magnetoencephalography (MEG) to investigate neural activation related to emotional and neutral targets in an AB task. MEG data were collected while participants performed a rapid stimulus visual presentation task in which two target stimuli were embedded in a stream of distractor words. The first target (T1) was a number and the second (T2) either an emotionally salient or neutral word. Behavioural results replicated previous findings of greater accuracy for emotionally salient than neutral T2 words. MEG source analyses showed that activation in orbitofrontal cortex, characterized by greater power in the theta and alpha bands, and dorsolateral prefrontal activation were associated with successful perceptual encoding of emotionally salient relative to neutral words. These effects were observed between 250 and 550 ms, latencies associated with discrimination of perceived from unperceived stimuli. These data suggest that important nodes of both emotional salience and frontoparietal executive systems are associated with the emotional modulation of the attentional blink.

Todd, Rebecca M.; Taylor, Margot J.; Robertson, Amanda; Cassel, Daniel B.; Doesberg, Sam M.; Lee, Daniel H.; Shek, Pang N.; Pang, Elizabeth W.

2014-01-01

268

Temporally patterned pulse trains affect duration tuning characteristics of bat inferior collicular neurons.  

PubMed

This study examines the effect of temporally patterned pulse trains on duration tuning characteristics of inferior collicular neurons of the big brown bat. Eptesicus fuscus, under free-field stimulation conditions. Using a 50% difference between maximal and minimal responses as a criterion, the duration tuning characteristics of inferior collicular neurons determined with pulse trains of different pulse durations are described as band-pass, long-pass, short-pass, and all-pass. Each band-pass neuron discharged maximally to a specific pulse duration that was at least 50% larger than the neuron's responses to a long- and a short-duration pulse. In contrast, each long- or short-pass neuron discharged maximally to a range of long- or short-duration pulses that were at least 50% larger than the minimal responses. The number of impulses of an all-pass neuron never differed by more than 50%. When pulse trains were delivered at different pulse repetition rates, the number of short-pass and band-pass neurons progressively increased with increasing pulse repetition rates. The slope of the duration tuning curves also became sharper when determined with pulse trains at high pulse repetition rates. Possible mechanisms underlying these findings are discussed. PMID:10573869

Jen, P H; Zhou, X M

1999-11-01

269

Patterns of spatial and temporal distribution of the asparagus miner (Diptera: Agromyzidae): implications for management.  

PubMed

The asparagus miner is an obligatory feeder on asparagus and a putative vector for pathogenic fungi implicated in the early decline of asparagus fields. To date, the distribution of the asparagus miner over space and time is poorly understood. Our study evaluated the spatial and temporal pattern of adult asparagus miners in commercial asparagus fields in Michigan in 2011 and 2012. We sampled adults and damage weekly during the growing season using yellow sticky traps outside, at the edge, and inside commercial fields. Yellow sticky traps at each trapping location were placed at the canopy and ground level to determine vertical distribution of adults. During the first generation, adults were more evenly distributed throughout the field. In the second generation, adults were more commonly found on the edge of the field. Overall, there was a greater percent of mining damage near the edge of the field. Additionally, three times as many asparagus miners were found in the canopy compared with ground-level traps. There were 12 times as many asparagus miner adults on edges bordered by another asparagus field than on ones bordered by forest. Taken together, our results indicate that while asparagus miner management in the beginning of the growing season should focus on the entire field, in the latter half of the season, growers could save money and resources by targeting miner adults at the edges of fields. Finally, conserving the remaining naturally forested landscape and planting borders of trees may help ameliorate pest pressure in asparagus fields. PMID:23865186

Morrison, William R; Szendrei, Zsofia

2013-06-01

270

Temporal patterns of gene expression in developing maize endosperm identified through transcriptome sequencing.  

PubMed

Endosperm is a filial structure resulting from a second fertilization event in angiosperms. As an absorptive storage organ, endosperm plays an essential role in support of embryo development and seedling germination. The accumulation of carbohydrate and protein storage products in cereal endosperm provides humanity with a major portion of its food, feed, and renewable resources. Little is known regarding the regulatory gene networks controlling endosperm proliferation and differentiation. As a first step toward understanding these networks, we profiled all mRNAs in the maize kernel and endosperm at eight successive stages during the first 12 d after pollination. Analysis of these gene sets identified temporal programs of gene expression, including hundreds of transcription-factor genes. We found a close correlation of the sequentially expressed gene sets with distinct cellular and metabolic programs in distinct compartments of the developing endosperm. The results constitute a preliminary atlas of spatiotemporal patterns of endosperm gene expression in support of future efforts for understanding the underlying mechanisms that control seed yield and quality. PMID:24821765

Li, Guosheng; Wang, Dongfang; Yang, Ruolin; Logan, Kyle; Chen, Hao; Zhang, Shanshan; Skaggs, Megan I; Lloyd, Alan; Burnett, William J; Laurie, John D; Hunter, Brenda G; Dannenhoffer, Joanne M; Larkins, Brian A; Drews, Gary N; Wang, Xiangfeng; Yadegari, Ramin

2014-05-27

271

Temporal and spatial patterns of anthropogenic disturbance at McMurdo Station, Antarctica  

NASA Astrophysics Data System (ADS)

Human visitations to Antarctica have increased in recent decades, raising concerns about preserving the continent's environmental quality. To understand the spatial and temporal patterns of anthropogenic disturbances at the largest scientific station in Antarctica, McMurdo Station, a long-term monitoring program has been implemented. Results from the first nine years (1999-2007) of monitoring are reported. Most physical disturbance of land surfaces occurred prior to 1970 during initial establishment of the station. Hydrocarbons from fuel and anthropogenic metals occur in patches of tens to hundreds of square meters in areas of fuel usage and storage. Most soil contaminant concentrations are not expected to elicit biological responses. Past disposal practices have contaminated marine sediments with polychlorinated biphenyls (PCBs), petroleum hydrocarbons, and metals in close proximity to the station that often exceed concentrations expected to elicit biological responses. Chemical contamination and organic enrichment reduced marine benthic ecological integrity within a few hundred meters offshore of the station. Contaminants were detected in marine benthic organisms confirming bioavailability and uptake. PCBs in sediments are similar to suspected source materials, indicating minimal microbial degradation decades after release. Anthropogenic disturbance of the marine environment is likely to persist for decades. A number of monitoring design elements, indicators and methodologies used in temperate climates were effective and provide guidance for monitoring programs elsewhere in Antarctica.

Kennicutt, Mahlon C., II; Klein, Andrew; Montagna, Paul; Sweet, Stephen; Wade, Terry; Palmer, Terence; Sericano, Jose; Denoux, Guy

2010-07-01

272

Temporal and spatial patterns in [alpha]- and [gamma]-hexachlorocyclohexane concentrations in industrially contaminated rivers  

SciTech Connect

Fluxes of HCH isomers [alpha]- and [gamma]-HCH dynamics were determined in four industrial UK rivers feeding the North Sea. Sampling was conducted weekly basis over a 2-year period. This was complemented by discrete studies of events where two hourly sampling periods were used to investigate the fine time scale dynamics of fluxes. Two intensively industrialized rivers had average isomer concentrations of [approximately] 20 ng L[sup [minus]1] for both isomers, while average concentrations in the two less industrialized rivers ranged between 1.5 and 5.0 ng L[sup [minus]1]. [alpha]-HCH concentrations showed no strong temporal patterns on any river, which contrasts with [gamma]-HCH levels that increased considerably during late summer/early autumn following sustained periods of low river flow. Sampling during high river flow events on rivers with differing HCH pollution histories both showed the same dynamics in HCH isomer concentrations. [gamma]-HCH concentrations decreased 4-fold during events while [alpha]-HCH concentrations stayed constant. The increases in [gamma]-HCH concentrations under low flow conditions and the rapid dilution of this isomer during events indicate that [gamma]-HCH has current inputs to these river systems. It was calculated that these four rivers export 30.8 kg yr[sup [minus]1] of [gamma]-HCH and 14.8 kg yr[sup [minus]1] of [alpha]-HCH to the North Sea.

Meharg, A.A.; Wright, J.; Osborn, D. (Inst. of Terrestrial Ecology, Huntingdon (United Kingdom)); Leeks, G.J.L.; Wass, P.D. (Inst. of Hydrology, Wallingford (United Kingdom))

1999-06-15

273

Spatial and temporal patterns of transcription of a wound-induced gene in potato.  

PubMed Central

Transcriptional fusions between the gene encoding win2 from potato and the reporter gene encoding beta-glucuronidase (GUS) have been used to study the spatial and temporal patterns of wound induced gene activity in transgenic potato and tobacco plants. Gene fusions containing a full length win2 promoter were found to be correctly regulated in response to mechanical wounding in transgenic potato, but not in the heterologous host, tobacco. Sequences greater than 560 bp upstream of the transcription start site of win2 were shown to be important for wound inducibility. The dramatic induction of GUS activity detected using fluorometric assays of extracts of wounded and aged leaves of several independent win2--GUS transformants was consistent with the kinetics of win2 mRNA accumulation. Histochemical analysis of wounded leaves showed that transcription first occurred in cells immediately adjacent to the wound, and was then progressively induced in cells associated with the vascular system at a distance from the wound site. In tubers, a localized response to wounding was observed, and this only spread to other parts of the tuber if it had started to sprout. It was concluded that active vascular transport was necessary for the spread of wound response. Win2--GUS fusions were also expressed as part of normal plant development, as GUS activity was detected in the developing buds and in a layer of cells associated with the lenticels of unwounded tubers. Images Fig. 2. Fig. 3. Fig. 4. Fig. 5.

Stanford, A C; Northcote, D H; Bevan, M W

1990-01-01

274

Temporal patterns of gene expression in developing maize endosperm identified through transcriptome sequencing  

PubMed Central

Endosperm is a filial structure resulting from a second fertilization event in angiosperms. As an absorptive storage organ, endosperm plays an essential role in support of embryo development and seedling germination. The accumulation of carbohydrate and protein storage products in cereal endosperm provides humanity with a major portion of its food, feed, and renewable resources. Little is known regarding the regulatory gene networks controlling endosperm proliferation and differentiation. As a first step toward understanding these networks, we profiled all mRNAs in the maize kernel and endosperm at eight successive stages during the first 12 d after pollination. Analysis of these gene sets identified temporal programs of gene expression, including hundreds of transcription-factor genes. We found a close correlation of the sequentially expressed gene sets with distinct cellular and metabolic programs in distinct compartments of the developing endosperm. The results constitute a preliminary atlas of spatiotemporal patterns of endosperm gene expression in support of future efforts for understanding the underlying mechanisms that control seed yield and quality.

Li, Guosheng; Wang, Dongfang; Yang, Ruolin; Logan, Kyle; Chen, Hao; Zhang, Shanshan; Skaggs, Megan I.; Lloyd, Alan; Burnett, William J.; Laurie, John D.; Hunter, Brenda G.; Dannenhoffer, Joanne M.; Larkins, Brian A.; Drews, Gary N.; Wang, Xiangfeng; Yadegari, Ramin

2014-01-01

275

Temporal pattern of locomotor activity recuperation after administration of propofol in Japanese quail (Coturnix coturnix japonica).  

PubMed

The present study evaluates the organization and complexity of the temporal pattern of locomotion after an acute administration of propofol in Japanese quail by using traditional and fractal analysis. Birds were administered with propofol 0, 10, 20, 40 or 80 mg/kg. Ten min after administration, they were placed in an open-field apparatus and their locomotor activity was recorded during 45 min at a resolution of 0.5 s. A significant dose dependant increase in the latency to initiate ambulation was observed for doses of 20, 40 and 80 mg/kg when compared to the control group. A rapid recuperation of normal locomotor activity was observed after sedation with 20 mg/kg. Birds administered with propofol 40 mg/kg showed signs of recuperation of normal locomotion after 30 and 40 min (males and females, respectively) of propofol administration, that was not observed in quail treated with propofol 80 mg/kg. Our results suggest that depending on the dose, propofol administration in quail may allow full locomotor recovery of a sedative/anesthetic dose as early as 30 min post-administration. PMID:21724216

Kembro, J M; Guzman, D A; Perillo, M A; Marin, R H

2012-08-01

276

Acoustic Modal Patterns and Striations (AMPS) experiment G-325, Norfolk Public Schools  

NASA Technical Reports Server (NTRS)

This paper will describe how high school students with the guidance of volunteer mentors were able to successfully complete an acoustics space experiment. Some of the NORSTAR program strategies used to effectively accomplish this goal will be discussed. The experiment and present status of results will be explained.

Young, Joy W.

1995-01-01

277

Hierarchical Bayesian modeling of spatio-temporal patterns of lung cancer incidence risk in Georgia, USA: 2000-2007  

NASA Astrophysics Data System (ADS)

Lung cancer is the second most commonly diagnosed cancer in both men and women in Georgia, USA. However, the spatio-temporal patterns of lung cancer risk in Georgia have not been fully studied. Hierarchical Bayesian models are used here to explore the spatio-temporal patterns of lung cancer incidence risk by race and gender in Georgia for the period of 2000-2007. With the census tract level as the spatial scale and the 2-year period aggregation as the temporal scale, we compare a total of seven Bayesian spatio-temporal models including two under a separate modeling framework and five under a joint modeling framework. One joint model outperforms others based on the deviance information criterion. Results show that the northwest region of Georgia has consistently high lung cancer incidence risk for all population groups during the study period. In addition, there are inverse relationships between the socioeconomic status and the lung cancer incidence risk among all Georgian population groups, and the relationships in males are stronger than those in females. By mapping more reliable variations in lung cancer incidence risk at a relatively fine spatio-temporal scale for different Georgian population groups, our study aims to better support healthcare performance assessment, etiological hypothesis generation, and health policy making.

Yin, Ping; Mu, Lan; Madden, Marguerite; Vena, John E.

2014-05-01

278

Spatial-temporal patterns in Mediterranean carnivore road casualties: Consequences for mitigation  

USGS Publications Warehouse

Many carnivores have been seriously impacted by the expansion of transportation systems and networks; however we know little about carnivore response to the extent and magnitude of road mortality, or which age classes may be disproportionately impacted. Recent research has demonstrated that wildlife-vehicle-collisions (WVC) involving carnivores are modulated by temporal and spatial factors. Thus, we investigated road mortality on a guild of small and medium-sized carnivores in southern Portugal using road-kill data obtained from a systematic 36 months monitoring period along highways (260 km) and national roads (314 km) by addressing the following questions: (a) which species and age class are most vulnerable to WVC? (b) are there temporal and/or spatial patterns in road-kill? and (c) which life-history and/or spatial factors influence the likelihood of collisions? We recorded a total of 806 carnivore casualties, which represented an average of 47 ind./100 km/year. Red fox and stone marten had the highest mortality rates. Our findings highlight three key messages: (1) the majority of road-killed individuals were adults of common species; (2) all carnivores, except genets, were more vulnerable during specific life-history phenological periods: higher casualties were observed when red fox and stone marten were provisioning young, Eurasian badger casualties occurred more frequently during dispersal, and higher Egyptian mongoose mortality occurred during the breeding period; and (3) modeling demonstrated that favorable habitat, curves in the road, and low human disturbance were major contributors to the deadliest road segments. Red fox carcasses were more likely to be found on road sections with passages distant from urban areas. Conversely, stone marten mortalities were found more often on national roads with high of cork oak woodland cover; Egyptian mongoose and genet road-kills were found more often on road segments close to curves. Based on our results, two key mitigation measures should help to reduce WVC in Portugal. The first involves the improvement of existing crossings with buried and small mesh size fence to guide the individuals towards to the passages, in road segments with high traffic volume (>1200 vehicles/night) and located in preferred carnivore habitats. The second mitigation involves cutting or removal of dense vegetation in verges of road segments with curves to aid motorists in seeing animals about to cross. ?? 2008 Elsevier Ltd.

Grilo, C.; Bissonette, J. A.; Santos-Reis, M.

2009-01-01

279

Spatial and Temporal Pattern of Rift Valley Fever Outbreaks in Tanzania; 1930 to 2007  

PubMed Central

Background Rift Valley fever (RVF)-like disease was first reported in Tanzania more than eight decades ago and the last large outbreak of the disease occurred in 2006–07. This study investigates the spatial and temporal pattern of RVF outbreaks in Tanzania over the past 80 years in order to guide prevention and control strategies. Materials and Methods A retrospective study was carried out based on disease reporting data from Tanzania at district or village level. The data were sourced from the Ministries responsible for livestock and human health, Tanzania Meteorological Agency and research institutions involved in RVF surveillance and diagnosis. The spatial distribution of outbreaks was mapped using ArcGIS 10. The space-time permutation model was applied to identify clusters of cases, and a multivariable logistic regression model was used to identify risk factors associated with the occurrence of outbreaks in the district. Principal Findings RVF outbreaks were reported between December and June in 1930, 1947, 1957, 1960, 1963, 1968, 1977–79, 1989, 1997–98 and 2006–07 in 39.2% of the districts in Tanzania. There was statistically significant spatio-temporal clustering of outbreaks. RVF occurrence was associated with the eastern Rift Valley ecosystem (OR?=?6.14, CI: 1.96, 19.28), total amount of rainfall of >405.4 mm (OR?=?12.36, CI: 3.06, 49.88), soil texture (clay [OR?=?8.76, CI: 2.52, 30.50], and loam [OR?=?8.79, CI: 2.04, 37.82]). Conclusion/Significance RVF outbreaks were found to be distributed heterogeneously and transmission dynamics appeared to vary between areas. The sequence of outbreak waves, continuously cover more parts of the country. Whenever infection has been introduced into an area, it is likely to be involved in future outbreaks. The cases were more likely to be reported from the eastern Rift Valley than from the western Rift Valley ecosystem and from areas with clay and loam rather than sandy soil texture.

Sindato, Calvin; Karimuribo, Esron D.; Pfeiffer, Dirk U.; Mboera, Leonard E. G.; Kivaria, Fredrick; Dautu, George; Bernard, Bett; Paweska, Janusz T.

2014-01-01

280

Geospatial and temporal patterns of annual cholera outbreaks in Matlab, Bangladesh  

NASA Astrophysics Data System (ADS)

Cholera is a waterborne diarrheal disease endemic to Bangladesh, resulting in 1 million diagnoses annually. Such disease burden results in incalculable lost wages and treatment expenses, taken from the pockets of an already impoverished society. Two seasonally correlated outbreaks of cholera occur in Bangladesh every year. In the spring and early summer, the Bay of Bengal - which serves as a natural reservoir for the cholera bacteria - flows inland, causing the first outbreak amongst coastal communities. Waste containing the cholera bacteria enters the sewage system and remains untreated due to poor water and sanitation infrastructure. Therefore, during the following monsoon season, flooding of cholera-contaminated sewage into drinking water sources results in a second outbreak. Though considered common knowledge among local populations, this geographic and temporal progression has not been empirically verified in the current literature. The aim of our ongoing study is to systematically analyze the seasonal trajectory of endemic cholera in Bangladesh. This paper discusses the results obtained from a comprehensive survey of available cholera data from the International Centre of Diarrheal Disease Research, Bangladesh (ICDDR,B) in Matlab, Bangladesh. Matlab thana is a near-coastal community that consists of 142 villages. Monsoon season takes place from June through October. Due to its proximity to the Meghna River, which opens into the Bay of Bengal, the area experiences significant flooding during these months. Using 10 years of geographically referenced cholera data, cases were plotted in time and space. Preliminary patterns suggest that villages closer to the Meghna River experience the majority of the area's cholera outbreaks and that case count is highest in late spring and late fall. April/May and November/December represent 25% and 23% of total annual case counts respectively. Moreover, villages further from the coastline demonstrate 57% higher relative prevalence in fall than in the spring. Such initial results demonstrate great promise in advancing our present knowledge of endemic cholera in Bangladesh. By improving our understanding of cholera proliferating in time and space, disease mitigation resources can be distributed to the most susceptible areas when they need them most. The next step forward for our ongoing study involves the use of mobile health (mHealth) case surveillance and cloud computing for real-time geographic and temporal cholera data acquisition.

Majumder, M. S.; de Klerk, K.; Meyers, D.

2012-12-01

281

Soft computing analysis of the possible correlation between temporal and energy release patterns in seismic activity  

NASA Astrophysics Data System (ADS)

This paper is a preliminary investigation of the possible correlation of temporal and energy release patterns of seismic activity involving the preparation processes of consecutive sizeable seismic events [1,2]. The background idea is that during periods of low-level seismic activity, stress processes in the crust accumulate energy at the seismogenic area whilst larger seismic events act as a decongesting mechanism releasing considerable energy [3,4]. A dynamic algorithm is being developed aiming to identify and cluster pre- and post- seismic events to the main earthquake following on research carried out by Zubkov [5] and Dobrovolsky [6,7]. This clustering technique along with energy release equations dependent on Richter's scale [8,9] allow for an estimate to be drawn regarding the amount of the energy being released by the seismic sequence. The above approach is being implemented as a monitoring tool to investigate the behaviour of the underlying energy management system by introducing this information to various neural [10,11] and soft computing models [1,12,13,14]. The incorporation of intelligent systems aims towards the detection and simulation of the possible relationship between energy release patterns and time-intervals among consecutive sizeable earthquakes [1,15]. Anticipated successful training of the imported intelligent systems may result in a real-time, on-line processing methodology [1,16] capable to dynamically approximate the time-interval between the latest and the next forthcoming sizeable seismic event by monitoring the energy release process in a specific seismogenic area. Indexing terms: pattern recognition, long-term earthquake precursors, neural networks, soft computing, earthquake occurrence intervals References [1] Konstantaras A., Vallianatos F., Varley M.R. and Makris J. P.: ‘Soft computing modelling of seismicity in the southern Hellenic arc', IEEE Geoscience and Remote Sensing Letters, vol. 5 (3), pp. 323-327, 2008 [2] Eneva M. and Ben-Zion Y.: ‘Techniques and parameters to analyze seismicity patterns associated with large earthquakes', Geophysics Res., vol. 102, pp. 17785-17795, 1997a [3] Habermann R. E.: ‘Precursory seismic quiescence: past, present and future', Pure Applied Geophysics, vol. 126, pp. 279-318, 1988 [4] Matthews M. V. and Reasenberg P. A.: ‘Statistical methods for investigating quiescence and other temporal seismicity patterns', Pure Applied Geophysics, vol. 126, pp. 357-372, 1988 [5] Zubkov S. I.: ‘The appearance times of earthquake precursors', Izv. Akad. Nauk SSSR Fiz. Zemli (Solid Earth), No. 5, pp. 87-91, 1987 [6] Dobrovolsky I. P., Zubkov S. I. and Miachkin V. I.: ‘Estimation of the size of earthquake preparation zones', Pageoph, vol. 117, pp. 1025-1044, 1979 [7] Dobrovolsky I. P., Gershenzon N. I. And Gokhberg M. B.: ‘Theory of electrokinetic effects occurring at the final stage in the preparation of a tectonic earthquake', Physics of the Earth and Planetary Interiors, vol. 57, pp. 144-156, 1989 [8] Richter C. F.: ‘Elementary Seismology', W.H.Freeman and Co., San Francisco, 1958 [9] Choy G. L. and Boatwright J. L.: ‘Global patterns of radiated seismic energy and apparent stress', Journal of Geophysical Research, vol. 84 (B5), pp. 2348-2350, 1995 [10] Haykin S.: ‘Neural Networks', 2nd Edition, Prentice Hall, 1999 [11] Jang J., Sun T. and Mizutany E.: ‘Neuro-fuzzy and soft computing', Prentice Hall, Upper Saddle River, NJ, 1997 [12] Konstantaras A., Varley M.R., Vallianatos F., Collins G. and Holifield P.: ‘Detection of weak seismo-electric signals upon the recordings of the electrotelluric field by means of neuron-fuzzy technology', IEEE Geoscience and Remote Sensing Letters, vol. 4 (1), 2007 [13] Konstantaras A., Varley M.R., Vallianatos F., Collins G. and Holifield P.: ‘Neuro-fuzzy prediction-based adaptive filtering applied to severely distorted magnetic field recordings', IEEE Geoscience and Remote Sensing Letters, vol. 3 (4), 2006 [14] Maravelakis E., Bilalis N., Keith J. and Antoniadis A.: ‘Measuring and Benchmarking the Innovativene

Konstantaras, Anthony; Katsifarakis, Emmanouil; Artzouxaltzis, Xristos; Makris, John; Vallianatos, Filippos; Varley, Martin

2010-05-01

282

Using Conditional Analysis to Investigate Spatial and Temporal patterns in Upland Rainfall  

NASA Astrophysics Data System (ADS)

The seasonality and characteristics of rainfall in the UK are altering under a changing climate. Summer rainfall is generally decreasing whereas winter rainfall is increasing, particularly in northern and western areas (Maraun et al., 2008) and recent research suggests these rainfall increases are amplified in upland areas (Burt and Ferranti, 2010). Conditional analysis has been used to investigate these rainfall patterns in Cumbria, an upland area in northwest England. Cumbria was selected as an example of a topographically diverse mid-latitude region that has a predominately maritime and westerly-defined climate. Moreover it has a dense network of more than 400 rain gauges that have operated for periods between 1900 and present day. Cumbria has experienced unprecedented flooding in the past decade and understanding the spatial and temporal changes in this and other upland regions is important for water resource and ecosystem management. The conditional analysis method examines the spatial and temporal variations in rainfall under different synoptic conditions and in different geographic sub-regions (Ferranti et al., 2009). A daily synoptic typing scheme, the Lamb Weather Catalogue, was applied to classify rainfall into different weather types, for example: south-westerly, westerly, easterly or cyclonic. Topographic descriptors developed using GIS were used to classify rain gauges into 6 directionally-dependant geographic sub-regions: coastal, windward-lowland, windward-upland, leeward-upland, leeward-lowland, secondary upland. Combining these classification methods enabled seasonal rainfall climatologies to be produced for specific weather types and sub-regions. Winter rainfall climatologies were constructed for all 6 sub-regions for 3 weather types - south-westerly (SW), westerly (W), and cyclonic (C); these weather types contribute more than 50% of total winter rainfall. The frequency of wet-days (>0.3mm), the total winter rainfall and the average wet day rainfall amount were analysed for each rainfall sub-region and weather type from 1961-2007 (Ferranti et al., 2010). The conditional analysis showed total rainfall under SW and W weather types to be increasing, with the greatest increases observed in the upland sub-regions. The increase in total SW rainfall is driven by a greater occurrence of SW rain days, and there has been little change to the average wet-day rainfall amount. The increase in total W rainfall is driven in part by an increase in the frequency of wet-days, but more significantly by an increase in the average wet-day rainfall amount. In contrast, total rainfall under C weather types has decreased. Further analysis will investigate how spring, summer and autumn rainfall climatologies have changed for the different weather types and sub-regions. Conditional analysis that combines GIS and synoptic climatology provides greater insights into the processes underlying readily available meteorological data. Dissecting Cumbrian rainfall data under different synoptic and geographic conditions showed the observed changes in winter rainfall are not uniform for the different weather types, nor for the different geographic sub-regions. These intricate details are often lost during coarser resolution analysis, and conditional analysis will provide a detailed synopsis of Cumbrian rainfall processes against which Regional Climate Model (RCM) performance can be tested. Conventionally RCMs try to simulate composite rainfall over many different weather types and sub-regions and by undertaking conditional validation the model performance for individual processes can be tested. This will help to target improvements in model performance, and ultimately lead to better simulation of rainfall in areas of complex topography. BURT, T. P. & FERRANTI, E. J. S. (2010) Changing patterns of heavy rainfall in upland areas: a case study from northern England. Atmospheric Environment, [in review]. FERRANTI, E. J. S., WHYATT, J. D. & TIMMIS, R. J. (2009) Development and application of topographic descriptors for conditional a

Sakamoto Ferranti, Emma Jayne; Whyatt, James Duncan; Timmis, Roger James

2010-05-01

283

Analysis and Monitoring of the Spatio-temporal Aerosol Patterns over Bangladesh  

NASA Astrophysics Data System (ADS)

Nowadays climate change is the burning issue and atmospheric aerosols are vital parameter of the global climate system. So, atmospheric aerosols are one of the hot topics for present scientific research. Most remote sensing methods retrieve aerosol optical depth (AOD) to assess the aerosols and their various effects on environmental and climate system. However, there is lack of studies dealing with monitoring of aerosol patterns over Bangladesh. In this research, we have analyzed the spatial and temporal variations in aerosol load over Bangladesh, using MODerate resolution Imaging Spectroradiometer (MODIS) Level 3 remote sensing data. A Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to generate a backward trajectory in order to identify the origins of air masses, with the aim of understanding these spatial and temporal variabilities in aerosol concentrations. During the last decade, AODs have increased across Bangladesh and revealed a higher AOD concentration in western part but a much cleaner environment in eastern part. An assessment of monthly mean variations in AOD has exhibited maximum AODs in June and minimum AODs in October. Looking over seasonal variations during the last decade over Bangladesh showed maximum AOD values during the summer, while minimum AOD values showed during the post monsoon also an evidence of a decreasing AOD trend showed during the monsoon can be owing to an increase in monsoonal rainfall in Bangladesh, while all other seasons showed increasing trends. Northwestern part of Bangladesh has showed at the top of AOD concentration in winter season during the year 2010. Dense fog activities in northern part of Bangladesh may be the causes of this high AOD distribution. We also documented, the regional AOD variations over seven different divisions of Bangladesh, for which Dhaka and Sylhet divisions showed decreasing trends where all others showed increasing trends. Annual mean AODs have highest levels in Rajshahi and Khulna and lowest level in Sylhet. Back trajectory analysis indicates that Bangladesh is mainly affected by the pollutions and desert dust of India combining with sea salt particles blown from the Arabian Sea. The sources of air masses were arriving at lower altitudes (500m, 1500m) mainly in western India and Indian subcontinent but higher altitude (2500m) air masses were loading especially in winter season from far western regions, such as Europe and various sub-Sahara region of Africa. However, an exceptional result was observed in post monsoon of 2010 that different flow patterns of air masses were observed that the air masses were arriving in Sylhet from southeast in the direction, the sources of air masses were in coastal region of Thailand and the boarder region of Myanmar and China. The air masses were arriving at several divisions in different seasons from different distances and directions owing to the variations of wind velocities and wind directions. These studies become important and useful to proceed about climate change in Bangladesh. However, more and more studies are required to understand about atmospheric aerosol properties and their climate impacts.

Mamun, M.; Islam, M.

2012-12-01

284

Contribution of NMDA and AMPA Receptors to Temporal Patterning of Auditory Responses in the Inferior Colliculus  

PubMed Central

Although NMDA receptors (NMDARs) are associated with synaptic plasticity, they form an essential part of responses to sensory stimuli. We compared contributions of glutamatergic NMDARs and AMPA receptors (AMPARs) to auditory responses in the inferior colliculus (IC) of awake, adult mustached bats. We examined the magnitude and temporal pattern of responses to tonal signals in single units before, during, and after local micro-iontophoretic application of selective antagonists to AMPARs (NBQX) and NMDARs (CPP). Combined blockade of AMPARs and NMDARs eliminated excitatory responses in nearly all neurons, while separate blockade of each receptor was quantitatively similar, causing substantial (>50%) spike reductions in ~75% of units. The major result was that effects of receptor blockade were most closely related to a unit’s first-spike latency. Thus, AMPAR blockade substantially reduced spikes in all short-latency units (<12 ms), but never in long-latency units (?12 ms). NMDAR blockade had variable effects on short-latency units but reduced spikes substantially for all long-latency units. There were no distinct contributions of AMPARs and NMDARs to early and later elements of responses. Thus, AMPAR blockade reduced early (onset) spikes somewhat more effectively than NMDAR blockade in short-latency units, but NMDAR blockade reduced onset spikes more effectively in long-latency units. AMPAR and NMDAR blockade were equally effective in reducing later elements of sustained responses in short-latency units, while NMDAR blockade was much more effective in long-latency units. These results indicate that NMDARs play multiple roles for signal processing in adult IC neurons.

Sanchez, Jason Tait; Gans, Donald; Wenstrup, Jeffrey J.

2007-01-01

285

Spatial and temporal patterns of dissolved organic matter optical properties across large rivers in Africa  

NASA Astrophysics Data System (ADS)

Tropical rivers have disproportionally high carbon transport and outgassing compared to temperate and Arctic rivers. Yet the cycling of dissolved organic matter (DOM) within these systems is still poorly studied with the exception of the Amazon basin. The chromophoric or colored dissolved organic matter (CDOM) is the fraction of DOM that absorbs ultraviolet and visible light. As the biochemical nature of DOM (and CDOM) defines its optical properties, optical measurements are particularly useful to assess the composition of DOM in freshwater and hence can be applied as proxies for assessments of DOM sources and its biogeochemical role. However, less is known on how specific optical characteristics can be applied as proxies and how these proxies vary from one system to another. In this study we compared concentrations and stable isotopic signature of dissolved organic carbon with optical properties of DOM from diverse tropical river systems across the African continent including the Congo basin, the Zambezi basin, the Ogooué basin and the Niger basin. These major rivers of the African continent were monitored for long period (from 1-3 years) at biweekly frequency. This large dataset allowed us to compare the spatial and temporal patterns of DOM quality along various environmental gradients, including hydrology, river size, terrestrial vegetation and connectivity to terrestrial inputs. The optical proxies presented and discussed in this study include absorption coefficients a(?) at different wavelength (254, 300, 350 and 440 nm), spectral slopes (S275-295and S350-400), the spectral slope ratio (SR=S275-295:S350-400) and the a(250):a(365) ratio.

Lambert, Thibault; Darchambeau, François; Vieira Borges, Alberto; Alhou, Bassirou; Mbega, Jean-Daniel; Teodoru, Cristian; Marwick, Trent Richard; Bouillon, Steven

2014-05-01

286

Spatial and Temporal Patterns of Soil Organic Carbon in Mangrove Forest Ecosystems (Invited)  

NASA Astrophysics Data System (ADS)

Wetlands are recognized as potentially important carbon sinks, but few studies have focused on tropical and sub-tropical systems that accumulate organic carbon. Soil organic carbon (SOC) density was analyzed in multiple mangrove forests, representing 30 geographic locations and six forest types (total of 230 study plots overall). SOC density varied from 0.002 to 0.1 g cm-3, with an overall average of 0.019 and 0.058 g cm-3 in mineral and organic soils, respectively. Sites spanned a latitudinal range from 37° S to 29° N, and carbon density was correlated with average annual temperature. However, high variation in SOC density within latitude indicated additional influences. At a regional scale, SOC density varied with forest type and generally increased with hydrologic energy. At a site in Panama, SOC density varied spatially with soil pore space, which influenced bulk density and soil temperature—indicating an influence of compaction and/or degree of decomposition. Carbon sequestration rates estimated from surface accretion of organic C were similar in organic (216 g C m-2 yr-1) and mineral (145 g C m-2 yr-1) soil types, but varied across geographic locations (41 to 591 g C m-2 yr-1). Subsurface inputs of carbon, which were estimated using measured rates of root matter accumulation and root carbon content, averaged 121 g m-2 yr-1, but exceeded 400 g m-2 yr-1 at several sites. Depths of mangrove peat varied across sites from < 1 m to over 10 m, indicating the potentially large carbon stores that can develop under certain conditions. Rates of carbon accretion at a site in Belize have varied from 90 to 300 g C m-2 yr-1 over 8000 yr. These patterns indicate spatial and temporal variability in SOC and suggest multiple controls on rates of carbon accumulation in mangrove ecosystems.

McKee, K. L.

2010-12-01

287

Temporal Pattern of the Repeated Bout Effect of Eccentric Exercise on Delayed-Onset Muscle Soreness  

PubMed Central

Objective: To determine the temporal pattern of the repeated bout effect of eccentric exercise on perceived pain and muscular tenderness associated with delayed-onset muscle soreness (DOMS). Design and Setting: Subjects completed 2 identical eccentric exercise bouts separated by 6, 7, 8, or 9 weeks. The experiment was conducted in a biokinetics research laboratory. Subjects: Sixteen male and 15 female untrained subjects (age = 24.59 ± 4.42 years, height = 171.71 ± 7.81 cm, weight = 73.00 ± 11.20 kg). Measurements: Two physiologic characteristics of DOMS were measured immediately before and 0, 24, 48, and 72 hours after each eccentric exercise bout. Perceived pain was measured using a visual analog scale (VAS), and muscular tenderness was measured using a punctate tenderness gauge (PTG). Results: Two 4 × 2 × 5 (group × bout × time) analyses of variance with repeated measures on the bout and time factors were performed on the VAS and PTG data. Significant (P < .05) main effects were found for group, bout, and time for the VAS and the PTG data. No significant interactions were detected. Post hoc analysis revealed significantly less perceived pain for the 9-week group than the 8-week group. The 7-week group had significantly less and the 8-week group had significantly more muscular tenderness than any other group. Perceived pain and muscular tenderness were significantly less after exercise bout 2 than after exercise bout 1. All subjects had significantly less perceived pain and muscular tenderness pre-exercise than 0 and 24 hours after the eccentric exercise bouts. Conclusions: An effective prophylaxis for perceived pain and muscular tenderness associated with DOMS is the performance of an eccentric exercise bout 6 to 9 weeks before a similar exercise bout.

Cleary, Michelle A.; Kimura, Iris F.; Sitler, Michael R.; Kendrick, Zebulon V.

2002-01-01

288

Patterns of temporal lobe atrophy in semantic dementia and Alzheimer's disease  

Microsoft Academic Search

Volumetric magnetic resonance imaging analyses of 30 subjects were undertaken to quantify the global and temporal lobe atrophy in semantic dementia and Alzheimer's disease. Three groups of 10 subjects were studied: semantic dementia patients, Alzheimer's disease patients, and control subjects. The temporal lobe structures measured were the amygdala, hippocampus, entorhinal cortex, parahippocampal gyrus, fusiform gyrus, and superior, middle, and inferior

Dennis Chan; Nick C. Fox; Rachael I. Scahill; William R. Crum; Jennifer L. Whitwell; Guy Leschziner; Alex M. Rossor; John M. Stevens; Lisa Cipolotti; Martin N. Rossor

2001-01-01

289

Rates and patterns of land use change in the Upper Great Lakes States, USA: A framework for spatial temporal analysis  

Microsoft Academic Search

Land use\\/cover maps derived from aerial photography for five areas in the Upper Great Lake States were analyzed for rates and patterns of change using our framework for spatial–temporal analysis. The Detroit (1978–2000), Chicago (1990–2000), Milwaukee (1963–2000), and Twin Cities (1990–1997) Metropolitan Areas, along with the Muskegon River Watershed (1978–1998), were examined for five spatial levels (global, regional, zonal, landscape,

Bryan C. Pijanowski; Kimberly D. Robinson

2011-01-01

290

Temporal and spatial patterns of organic carbon are linked to egg deposition by beach spawning horseshoe crabs ( Limulus polyphemus )  

Microsoft Academic Search

The spring spawning by the American horseshoe crab (Limulus polyphemus L.) results in temporally and spatially discrete inputs of eggs onto sandy beaches in Delaware Bay, USA. We tested the hypothesis\\u000a that seasonal patterns of sediment organic carbon on Delaware Bay beaches is linked to this pulsed input of horseshoe crab\\u000a eggs. At a location with minimal horseshoe crab spawning

Mark L. Botton; Robert E. Loveland

2011-01-01

291

Spatio-temporal Patterning of Small Area Low Birth Weight Incidence and Its Correlates: A Latent Spatial Structure Approach  

PubMed Central

Low birth weight (LBW) defined as infant weight at birth of less than 2500g is a useful health outcome for exploring spatio-temporal variation and the role of covariates. LBW is a key measure of population health used by local, national and international health organizations. Yet its spatio-temporal patterns and their dependence structures are poorly understood. In this study we examine the use of flexible latent structure models for the analysis of spatio-temporal variation in LBW. Beyond the explanatory capabilities of well-known predictors, we observe spatio-temporal effects, which are not directly observable using conventional modeling approaches. Our analysis shows that for county-level counts of LBW in Georgia and South Carolina the proportion of black population is a positive risk factor while high-income is a negative risk factor. Two dominant residual temporal components are also estimated. Finally our proposed method provides a better goodness-of-fit to these data than the conventional space-time models.

Kirby, Russell S.; Liu, Jihong; Lawson, Andrew B.; Choi, Jungsoon; Cai, Bo; Hossain, Md Monir

2011-01-01

292

Temporal patterns and selectivity in the unitary responses of olfactory receptors in the tiger salamander to odor stimulation  

PubMed Central

Temporal patterns and selectivity in unitary responses of 100 single olfactory receptors in the tiger salamander to odor stimulation were investigated. An olfactometer which permitted control of stimulus concentration, duration, and flow rate was calibrated with a gas chromatograph. Stimulus pulses were monitored by recording the electroolfactogram from the surface of the olfactory epithelium. Both diphasic and triphasic spikes were recorded extracellularly. No discernible differences in types of responses, reproducibility of responses, and cross-unit distribution of spontaneous rates distinguished diphasic from triphasic units. The cross-unit selectivity in responses to the seven olfactory stimulants used and the range of odorant concentrations which effectively evoked these responses suggest variations in types and number of types of receptive sites on each cell. Temporal patterns in the unitary responses were generally less complex than those observed in the olfactory bulb. Phasic stimulations evoked phasic patterns. Tonic stimulations evoked phasic/tonic patterns. Occasionally poststimulus depressions or elevations in firing rates were observed. The nature of these patterns varied somewhat with odorant concentration for a particular unit.

1979-01-01

293

Depth Depending Pattern Recognition (DDPR) - a tool for visualization of spatial and temporal similarities of properties in sediment cores  

NASA Astrophysics Data System (ADS)

Depth Depending Pattern Recognition (DDPR) is a new simple tool for the visualization of spatial and temporal similarities of measured parameters in a set of sediment cores. It was developed to support the multivariate analysis of data of sediment cores taken in a still water area of the River Elbe [1]. The idea behind is the assumption that correlations in spatial or temporal distributions of environmental parameters can be visualized by different ways and that a distance between two patterns can be defined with mathematical methods. So the similarity of two patterns can be quantified and assessed by a catalog of subjective rules. Generally, defining one reference pattern, the computation of a distance matrix for different parameter distributions is easily possible. Consequently, the three main steps of the algorithm are a) the creation of the pattern from the measurements, b) the definition of the distance calculation and c) the interpretation and assessment of the distance matrix. The method can be used in addition to classical uni- or multivariate statistical methods like regression analysis, principal component analysis, correlation analysis etc. DDPR supports hypothesis testing and explanation of relationships. In the poster DDPR is explained and the method is presented for two examples, an artificial one and one with data from sediment cores. Reference [1] Baborowski M., Büttner O., Morgenstern P., Jancke T., Westrich B. (2012) Spatial variability of metal pollution in groyne fields of the Middle Elbe - Implications for sediment monitoring, Environmental Pollution, 167,115-123

Büttner, Olaf; Baborowski, Martina

2013-04-01

294

Temporal patterns of deep brain stimulation generated with a true random number generator and the logistic equation: effects on CNS arousal in mice  

PubMed Central

Deep brain stimulation (DBS) has shown promise in the treatment of many neurological and psychiatric disorders as well as a disorder of consciousness, the minimally conscious state (MCS). In the clinic, DBS is always monotonic standard pulses; however, we have hypothesized that temporally patterned pulses might be more efficient in achieving desired behavioral responses. Here we present two experiments on DBS of the central thalamus to increase arousal, as measured by motor activity, and to affect the electroencephalogram (EEG). In the first, we optimized amplitude and frequency in standard stimulation of the central thalamus in intact mice. In the second, the optimized fixed frequency was compared to two alternative temporal patterns, chaotic and random, which were physically identical to each other and fixed frequency in all ways except temporal pattern. In both experiments and with all types of stimulation, DBS of the central thalamus increased arousal as measured by motor activity. These data also revealed that temporal patterning of pulses can modulate response to stimulation. That temporal patterns in DBS of the central thalamus were found to alter motor activity response implies possible usefulness of temporal patterns in DBS of other contexts. More investigation into exactly how temporally patterned stimulation may affect neuronal circuit dynamics is necessary.

Quinkert, A. W.; Pfaff, D. W.

2012-01-01

295

Representation of interval timing by temporally scalable firing patterns in rat prefrontal cortex.  

PubMed

Perception of time interval on the order of seconds is an essential component of cognition, but the underlying neural mechanism remains largely unknown. In rats trained to estimate time intervals, we found that many neurons in the medial prefrontal cortex (PFC) exhibited sustained spiking activity with diverse temporal profiles of firing-rate modulation during the time-estimation period. Interestingly, in tasks involving different intervals, each neuron exhibited firing-rate modulation with the same profile that was temporally scaled by a factor linearly proportional to the instructed intervals. The behavioral variability across trials within each task also correlated with the intertrial variability of the temporal scaling factor. Local cooling of the medial PFC, which affects neural circuit dynamics, significantly delayed behavioral responses. Thus, PFC neuronal activity contributes to time perception, and temporally scalable firing-rate modulation may reflect a general mechanism for neural representation of interval timing. PMID:24367075

Xu, Min; Zhang, Si-yu; Dan, Yang; Poo, Mu-ming

2014-01-01

296

Representation of interval timing by temporally scalable firing patterns in rat prefrontal cortex  

PubMed Central

Perception of time interval on the order of seconds is an essential component of cognition, but the underlying neural mechanism remains largely unknown. In rats trained to estimate time intervals, we found that many neurons in the medial prefrontal cortex (PFC) exhibited sustained spiking activity with diverse temporal profiles of firing-rate modulation during the time-estimation period. Interestingly, in tasks involving different intervals, each neuron exhibited firing-rate modulation with the same profile that was temporally scaled by a factor linearly proportional to the instructed intervals. The behavioral variability across trials within each task also correlated with the intertrial variability of the temporal scaling factor. Local cooling of the medial PFC, which affects neural circuit dynamics, significantly delayed behavioral responses. Thus, PFC neuronal activity contributes to time perception, and temporally scalable firing-rate modulation may reflect a general mechanism for neural representation of interval timing.

Xu, Min; Zhang, Si-yu; Dan, Yang; Poo, Mu-ming

2014-01-01

297

Patterns of venom production and temporal polyethism in workers of Jerdon's jumping ant, Harpegnathos saltator.  

PubMed

Ants are chemical factories, and among their more noticeable products are their venoms. Though many studies have addressed the properties and activities of ant venoms, basic venom-related physiological questions, such as how venom production and replacement may vary with age, are rarely addressed. The answers to these questions are fundamental to understanding the physiological capabilities of these organisms, as well as the parameters within which potential optimization of their investment in venom production must take place. The only previous investigation into venom production in ants found it to be limited to early life in workers of the fire ant, Solenopsis invicta (Haight and Tschinkel, 2003). Because similar studies have not been conducted for comparison, it is unclear whether or not this is a common physiological pattern in ants. As a parsimonious way to address this question, and, more generally, to increase the currently scant information available regarding the venom-producing capabilities of ants, the longevity, temporal polyethism, age-related venom production, and age-related venom replacement capabilities of workers of Jerdon's jumping ant, Harpegnathos saltator were investigated. Longevity varied from 10 days to nearly 2 years, with a median lifespan of 206 days. Workers remained in the nest when young, transitioned to outside work (foraging) after 50 days of age, and reached a plateau in their tendency to be outside the nest at 74 days of age. They eclosed with empty venom sacs, filled them by about 57 days of age, and were able to replace venom at all three ages tested (though at a higher rate when aged 100 days than 30 and 206). So, venom-production ability is not limited to early life in H. saltator workers, and aspects of venom physiology and exploratory behavior appear to coincide in a manner likely to result in foraging efficiency benefits; venom sacs reach fullness around the age workers begin their foraging careers, and venom replacement rate is highest around the age workers become the most dedicated foragers. PMID:23041374

Haight, Kevin L

2012-12-01

298

Spatial and temporal patterns of Pleistocene biogenic sediment accumulation in the Gulf of Alaska  

NASA Astrophysics Data System (ADS)

Reconstructing the timing and nature of past changes in aquatic productivity in the Gulf of Alaska (GoA) can shed light on the primary processes driving biogeochemical cycling over geologic timescales. Today, Fe is an important micronutrient that limits primary productivity in surface waters beyond the continental shelf in much of the GoA. However, we have a relatively poor understanding of how Fe-delivery processes, combined with changing climate, environmental, and oceanographic conditions, interact to influence primary production over glacial-interglacial timescales. An important first step is to identify the spatial and temporal patterns of increased productivity in the sediment record. Here, we present sedimentologic and physical property data from IODP Expedition 341 and identify intervals where diatom ooze and diatom-rich mud lithofacies are prevalent during the Pleistocene. Among the Expedition 341 recovered cores, were high-recovery intervals in the outer (Site U1417) and inner (U1418) Surveyor Fan, and from a small slope basin at the edge of the continental shelf (Site U1419). In general, greenish gray diatomaceous ooze (containing >50 % diatoms in smear slides) and diatom-rich mud (>25% diatoms) is found in beds ranging in thickness from 20 to 150 cm, interbedded with gray mud that commonly contains lonestones. Ooze is occasionally found immediately overlying volcanic ash. Compared to non-biogenic mud, diatomaceous sediments are generally characterized by lower magnetic susceptibility, natural gamma ray, bulk density, and higher b* color reflectance. At Site U1417, we observe a frequent occurrence of diatomaceous ooze during the middle Pleistocene relative to the early and late Pleistocene. At Site U1418, intervals containing diatom ooze are less common than at U1417 and biogenic sediments are mainly observed within the late Pleistocene portion of the record. However, higher sedimentation rates at U1418 relative to U1417, and the co-occurrence of sand and interbedded mud and silt indicate that clastic sediment dilution may obscure biogenic sediment contribution. At Site U1419, two prominent ~5 m thick intervals of diatomaceous ooze are found (within the uppermost 5 m and between 80 and 90 m composite depth, respectively). Between these intervals are numerous 20 cm thick intervals of biogenic sediment that were likely deposited during the middle or late Pleistocene based on preliminary shipboard age models. Biogenic intervals observed at Expedition 341 sites may be related to increased productivity driven by a combination of the aforementioned processes, but additional chronological and geochemical constraints are needed from all sites to rule out the role that changing sedimentation rates and/or silica dissolution plays in controlling the distribution of ooze in these records.

Moy, C. M.; Bahlburg, H.; Childress, L. B.; Cowan, E. A.; Forwick, M.; Müller, J.; Ribeiro, F.; Ridgway, K. D.; Mix, A. C.

2013-12-01

299

Temporal pattern in the effect of postnatal blood lead level on intellectual development of young children.  

PubMed

To determine the temporal pattern of the effect of postnatal blood lead level on the General Cognitive Index (GCI) of the McCarthy Scales of Children's Abilities, we used data from 112 children of the Mexico City Prospective Lead Study with complete evaluations from 36 to 60 months of age at 6-month intervals. We measured blood lead level every 6 months from 6 to 54 months. We controlled for 5-min Apgar, birth weight, birth order, sex, socioeconomic level, maternal IQ, and maximum maternal educational level in a repeated measures ANCOVA using child blood lead level grouped by 6-18 month (geometric mean 10.1 microg/dl, range 3.5-37.0 microg/dl), 24-36 month (geometric mean 9.7 microg/dl, range 3.0-42.7 microg/dl), and 42-54 month (geometric mean 8.4 microg/dl, range 2.5-44.8 microg/dl) averages. There were significant interactions between the 6-18 month blood lead level and age with GCI as the endpoint and between 24-36 month blood lead level and age. The regression coefficient of blood lead at 6-18 months became more negative with age until 48 months, when the rate of decline moderated (linear polynomial contrast p=0. 047). The regression coefficient of blood lead at 24-36 months with CGI became more negative as well from 36 to 48 months but then started decreasing toward zero from 48 to 60 months (quadratic polynomial contrast p=0.019). Significant between-subjects lead effects on GCI were found for 24-36 month blood lead level at 48 months (p=0.021) and at 54 months (p=0.073). The greatest effect (at 48 months) was a 5.8-point GCI decrease with each natural log unit increase in blood lead. Significant between-subjects lead effects on GCI were found for 42-54 month blood lead level at 54 months (p=0. 040) and at 60 months (p=0.060). The effect of postnatal blood lead level on GCI reaches its maximum approximately 1-3 years later, and then becomes less evident. Four to five years of age appears to be a critical period for the manifestation of the earlier postnatal blood lead level effects. PMID:11120385

Schnaas, L; Rothenberg, S J; Perroni, E; Martínez, S; Hernández, C; Hernández, R M

2000-01-01

300

GABAergic disinhibition affects responses of bat inferior collicular neurons to temporally patterned sound pulses.  

PubMed

Using the big brown bat, Eptesicus fuscus, as a model mammalian auditory system, we studied the effect of GABAergic disinhibition by bicuculline on the responses of inferior collicular (IC) neurons to temporally patterned trains of sound pulses delivered at different pulse repetition rates (PRRs) under free-field stimulation conditions. All 66 neurons isolated from eight bats either discharged one to two impulses (phasic on responders, n = 41, 62%), three to eight impulses (phasic bursters, n = 19, 29%), or many impulses throughout the entire duration of the stimulus (tonic responders, n = 6, 9%). Whereas 50 neurons responded vigorously to frequency-modulated (FM) pulses, 16 responded poorly or not at all to FM pulses. Bicuculline application increased the number of impulses of all 66 neurons in response to 4 ms pulses by 15-1,425%. The application also changed most phasic on responders into phasic bursters or tonic responders, resulting in 12 (18%) phasic on responders, 34 (52%) phasic bursters, and 20 (30%) tonic responders. Response latencies of these neurons were either shortened (n = 25, 38%) by 0.5-6.0 ms, lengthened (n = 9, 14%) by 0. 5-2.5 ms or not changed (n = 32, 48%) on bicuculline application. Each neuron had a highest response repetition rate beyond which the neuron failed to respond. Bicuculline application increased the highest response repetition rates of 62 (94%) neurons studied. The application also increased the highest 100% pulse-locking repetition rates of 21 (32%) neurons and facilitated 27 (41%) neurons in response to more pulses at the same PRR than predrug conditions. According to average rate-based modulation transfer functions (average rate MTFs), all 66 neurons had low-pass filtering characteristics both before and after bicuculline application. According to total discharge rate-based modulation transfer functions (total rate MTFs), filtering characteristics of these neurons can be described as band-pass (n = 52, 79%), low-pass (n = 12, 18%), or high-pass (n = 2, 3%) before bicuculline application. Bicuculline application changed the filtering characteristics of 14 (21%) neurons. According to synchronization coefficient-based modulation transfer functions, filtering characteristics of these neurons can be described as low-pass (n = 41, 62%), all-pass (n = 11, 17%), band-suppression (n = 7, 10.5%), and band-suppression-band-pass filters (n = 7, 10.5%). Bicuculline application changed filtering characteristics of 19 (29%) neurons. PMID:9582206

Lu, Y; Jen, P H; Wu, M

1998-05-01

301

Spatial-temporal excess mortality patterns of the 1918-1919 influenza pandemic in Spain  

PubMed Central

Background The impact of socio-demographic factors and baseline health on the mortality burden of seasonal and pandemic influenza remains debated. Here we analyzed the spatial-temporal mortality patterns of the 1918 influenza pandemic in Spain, one of the countries of Europe that experienced the highest mortality burden. Methods We analyzed monthly death rates from respiratory diseases and all-causes across 49 provinces of Spain, including the Canary and Balearic Islands, during the period January-1915 to June-1919. We estimated the influenza-related excess death rates and risk of death relative to baseline mortality by pandemic wave and province. We then explored the association between pandemic excess mortality rates and health and socio-demographic factors, which included population size and age structure, population density, infant mortality rates, baseline death rates, and urbanization. Results Our analysis revealed high geographic heterogeneity in pandemic mortality impact. We identified 3 pandemic waves of varying timing and intensity covering the period from Jan-1918 to Jun-1919, with the highest pandemic-related excess mortality rates occurring during the months of October-November 1918 across all Spanish provinces. Cumulative excess mortality rates followed a south–north gradient after controlling for demographic factors, with the North experiencing highest excess mortality rates. A model that included latitude, population density, and the proportion of children living in provinces explained about 40% of the geographic variability in cumulative excess death rates during 1918–19, but different factors explained mortality variation in each wave. Conclusions A substantial fraction of the variability in excess mortality rates across Spanish provinces remained unexplained, which suggests that other unidentified factors such as comorbidities, climate and background immunity may have affected the 1918–19 pandemic mortality rates. Further archeo-epidemiological research should concentrate on identifying settings with combined availability of local historical mortality records and information on the prevalence of underlying risk factors, or patient-level clinical data, to further clarify the drivers of 1918 pandemic influenza mortality.

2014-01-01

302

Spatio-temporal recharge patterns in a semi-arid alluvial basin with irrigated crops  

NASA Astrophysics Data System (ADS)

Recharge in semi-arid regions with irrigated crops is predominantly driven by irrigation technology and cropping patterns, but also by the seasonal distribution of rainfall and the availability of irrigation water. A significant amount of basin recharge occurs from ephemeral streams and unlined irrigation canals. A spatially distributed, GIS-based hydrologic model of water application and water use at the land-atmosphere interface was developed to estimate transient recharge to the deep vadose zone and into the unconfined alluvial aquifer. The spatial basis for the hydrologic model are individual landuse units (diffuse recharge) and a network of streams and canals with water seepage (lineal recharge). The land-atmosphere interface and unsaturated zone model component (LAIUZ) is coupled to a surface water supply model component (SWSM) that provides surface water deliveries by district or sub-district, depending on available information. Using LAIUZ and SWSM, we investigate the regional behavior and spatio-temporal variability of deep vadose zone recharge in the 3,800 square kilometer Tule groundwater basin of the San Joaquin Valley, California. Surface water management in the topographically flat basin is divided between two dozen irrigation and water districts. All surface water is imported or is natural discharge into the basin. Groundwater extractions are managed by landowners on a field-by-field basis. Monthly varying recharge and groundwater pumping rates are computed for the hydrologic years 1970 through 2000. The average size of the GIS landuse units is 0.4 sq. kilometers. The GIS coverage distinguishes over 60 landuse types. Applied and consumptive water use are computed based on actual evapotranspiration and known irrigation or water use efficiencies for each landuse unit. Seepage from streams is computed by mass balance. The resulting model estimates of groundwater recharge and pumping are in good agreement with measured groundwater level changes for the thirty-year period (model validation). Throughout the region, the deep vadose zone (up to 30 m deep) is found to account for a significant amount of intermediate-term basin storage, particularly during wet year cycles. The hydrologic model demonstrates that practically all of the annual precipitation (230 mm) is available for intermediate storage in the root zone, crop water uptake, or deep percolation. No direct losses to evaporation occur, presumably because most precipitation occurs during the winter months. Diffuse recharge is 110 mm/year (range: 38 - 200 mm/year). Lineal recharge accounts for one-third of the total recharge (170 mm/year) in the basin. In wet years, lineal recharge along streams and in intentional recharge basins may account for over 50% of the total recharge, whereas in dry years it may be as little as 8%.

Ruud, N. C.; Harter, T.; Naugle, A. W.

2001-12-01

303

Spatial and temporal patterns of larval dispersal in a coral-reef fish metapopulation: evidence of variable reproductive success.  

PubMed

Many marine organisms can be transported hundreds of kilometres during their pelagic larval stage, yet little is known about spatial and temporal patterns of larval dispersal. Although traditional population-genetic tools can be applied to infer movement of larvae on an evolutionary timescale, large effective population sizes and high rates of gene flow present serious challenges to documenting dispersal patterns over shorter, ecologically relevant, timescales. Here, we address these challenges by combining direct parentage analysis and indirect genetic analyses over a 4-year period to document spatial and temporal patterns of larval dispersal in a common coral-reef fish: the bicolour damselfish (Stegastes partitus). At four island locations surrounding Exuma Sound, Bahamas, including a long-established marine reserve, we collected 3278 individuals and genotyped them at 10 microsatellite loci. Using Bayesian parentage analysis, we identified eight parent-offspring pairs, thereby directly documenting dispersal distances ranging from 0 km (i.e., self-recruitment) to 129 km (i.e., larval connectivity). Despite documenting substantial dispersal and gene flow between islands, we observed more self-recruitment events than expected if the larvae were drawn from a common, well-mixed pool (i.e., a completely open population). Additionally, we detected both spatial and temporal variation in signatures of sweepstakes and Wahlund effects. The high variance in reproductive success (i.e., 'sweepstakes') we observed may be influenced by seasonal mesoscale gyres present in the Exuma Sound, which play a prominent role in shaping local oceanographic patterns. This study documents the complex nature of larval dispersal in a coral-reef fish, and highlights the importance of sampling multiple cohorts and coupling both direct and indirect genetic methods in order disentangle patterns of dispersal, gene flow and variable reproductive success. PMID:24917250

Pusack, Timothy J; Christie, Mark R; Johnson, Darren W; Stallings, Christopher D; Hixon, Mark A

2014-07-01

304

River-floodplain Hydrologic Connectivity: Impact on Temporal and Spatial Floodplain Water Quality and Productivity Patterns  

NASA Astrophysics Data System (ADS)

Nutrient spiraling and cycling are critical processes for floodplain systems, but these have not been well studied in western North America. Floodplain production and function relies on the integrity of river-floodplain interactions, particularly during periods of hydrologic connectivity. The purpose of this study was to: (1) determine the importance of the timing and duration of river-floodplain hydrologic connectivity, (2) link flood event water quality to subsequent primary and secondary production, and (3) identify temporal and spatial patterns of floodplain production. The Cosumnes River watershed transports surface runoff and snowmelt from the Sierra Nevadas to the Sacramento-San Joaquin Delta. It is one of the few watersheds in California that has no major water diversions or impoundments; therefore the river responds to the natural watershed hydrology. The study site in southern Sacramento County is an unmanaged experimental floodplain, one of the few remaining floodplains in California. Weekly and flood-event water quality and macroinvertebrate sampling was conducted during the flood season from January through June in 2001 and 2002. Both water years were characterized by historically low river flows. On average, volatile suspended solids in the water column increased from 5 mg/l to 10 mg/l during early season periods of hydrologic connectivity (December - February), suggesting that during watershed flushing flood events, the river acts as a source of nutrients and organic matter to the floodplain. Following a flood event, invertebrate concentrations decreased on average from 26,000 individuals/m3 to 9,000 individuals/m3 for zooplankton and from 350 individuals/m2 to 65 individuals/m2 for benthic macro-invertebrate, suggesting a net dilution of invertebrates during flood events. Chlorophyll a (chl-a) levels were also diluted during flood events, on average from 25 ppb to 5 ppb. Zooplankton densities and chl-a levels quickly rose after flood events. On average, zooplankton densities and chl-a concentrations exceeded 150,000 individulas/m3 and 30 ppb respectively. However, as hydrologic residence time increased, chl-a levels decreased and were generally lowest following periods when macroinvertebrate population densities were highest, suggesting grazing pressure on planktonic algae. Total nitrogen to total phosphorous ratios (TN:TP) tended to be greater than 10 during periods of high hydrologic residence time, suggesting P limitation during periods of hydrologic disconnection, which coincides with the highest zooplankton densities and lowest chl-a levels observed. Following a flood event, TN:TP dramatically decreased, suggesting that during periods of river-floodplain connectivity, N tends to be the limiting nutrient. These data suggest that nutrients are replenished to the floodplain during periods of hydrologic connectivity, followed by periods of resource uptake and subsequent nutrient limitation. These patterns suggests that efforts directed towards restoration of river floodplain systems should attempt to reconstruct the naturally irregular and periodic connection cycle to enhance primary and secondary production.

Gallo, E. L.; Ahearn, D.; Dahlgren, R. A.; Grosholz, E.

2003-12-01

305

Composition, structural characteristics and temporal patterns of fish assemblages in non-tidal Mediterranean lagoons: A case study  

NASA Astrophysics Data System (ADS)

The importance of transitional water ecosystems as nursery habitats and feeding grounds for fish species is well-known. Detailed studies of colonization patterns of fish guilds in response to biotic and abiotic drivers are however unevenly distributed among ecosystem types. We address here the temporal variability of fish assemblages in small non-tidal lagoons in the Mediterranean basin. The study was carried out at the Acquatina lagoon (Lecce, Italy) where four stations, situated in two habitat types along a confinement gradient, were sampled twice per month for one year with fyke nets. Forty-five taxa ranging across 20 families were collected, with the most abundant species, Atherina boyeri, accounting for more than 95% of total abundance. Pooling all species together (excluding sand smelt), the structural features of the assemblage, relative abundance of families, and abundance of individual species all showed significant temporal patterns. Mean abundance peaked in Summer and Autumn and fell in Winter, whereas taxonomic richness and diversity were highest in Summer and lowest in Spring. Within the fish assemblage, multivariate ordination showed temporal segregation of species belonging to the same family or genus and expected to be functionally similar, suggesting that they avoid competition for space and resources by timing inward migration and peak occurrence differently. Of the environmental driving forces, which also showed temporal patterns of variation, salinity was the main factor affecting the distribution of individuals and species. The catch of young individuals of several marine species confirmed the role of this small lagoon as a nursery and feeding area, and emphasized the need for further studies.

Maci, S.; Basset, A.

2009-08-01

306

Spatio-temporal pattern formation in a lateral high-frequency glow discharge system  

Microsoft Academic Search

In a two-dimensional lateral high frequency glow discharge system pattern formation has been investigated experimentally. We observe, e.g., Turing patterns, isolated solitary like filaments, filament clusters, coexisting stationary and nonstationary structures and various kinds of rotating filamentary patterns.

E. Ammelt; D. Schweng; H.-G. Purwins

1993-01-01

307

Analysis of the meter of acoustic musical signals  

Microsoft Academic Search

A method is decribed which analyzes the basic pattern of beats in a piece of music, the musical meter. The analysis is performed jointly at three different time scales: at the temporally atomic tatum pulse level, at the tactus pulse level which corresponds to the tempo of a piece, and at the musical measure level. Acoustic signals from arbitrary musical

Anssi P. Klapuri; Antti J. Eronen; Jaakko T. Astola

2006-01-01

308

From patterned optical near-fields to high symmetry acoustic vibrations in gold crystalline platelets.  

PubMed

Noble metal particles allow enhanced interaction with light and efficient light to heat conversion. In the present paper, we report on non-linear optical spectroscopy of individual gold crystalline platelets and address two of the energy relaxation steps following optical excitation of the metallic nano-objects. In particular, at short timescales we show that optical excitation yields intense two-photon photoluminescence at particular locations of the gold platelets. Our experimental results are interpreted with numerical simulations based on the Green Dyadic Method. Subsequent conversion from optical to thermal energy triggers acoustic vibrations that modulate the optical response of the nano-object on a 10 ps-100 ps timescale. We address the different contributions to the damping of the associated mechanical oscillations focusing on the high frequency thickness vibrations (100 GHz) of these nanometer-thin metallic structures. PMID:23264962

Fedou, J; Viarbitskaya, S; Marty, R; Sharma, J; Paillard, V; Dujardin, E; Arbouet, A

2013-03-28

309

Spatial and temporal patterns of large-scale droughts between 1951 and 2000 in the Valencia region (east Spain)  

NASA Astrophysics Data System (ADS)

We have analyzed the spatial distribution patterns of temporal evolution of large scale drought in the eastern coast of Iberian peninsula (Valencia Region) by using the Standardized Precipitation Index in 95 monthly rainfall series from 1951 to 2000. The general spatial distribution patterns of drought are recognized using EOF analysis. Four EOFs are extracted from the drought series that does not overlap in the space. The 1st EOF represents the temporal evolution of drought in the NE coastland area; the 2nd one is related to drought in the middle mountainous area. The 3th component describes the inland mountains and the 4th is related to the southern semiarid-arid area. Evolution of these components is not syncronic in time. The area (in percentage values) affected by intensity drought categories is analyzed, and presents an increase in the moderate to severe drought categories during the last decades. Trend analysis of temporal drought index in the area shows a very contrasting spatial distribution of the signs. Drought trend is positive in 39 observatories, in 10 negative and in 46 cases were not significant (Spearman rho, p < 0.05). The spatial distribution of these trends is quite contrasted.

Vicente, S. M.; González-Hidalgo, J. C.; de Luis, M.; Cuadrat, J. M.; Raventós, J.

2003-04-01

310

Separation of spatial-temporal patterns ('climatic modes') by combined analysis of really measured and generated numerically vector time series  

NASA Astrophysics Data System (ADS)

The new method of decomposition of the Earth's climate system into well separated spatial-temporal patterns ('climatic modes') is discussed. The method is based on: (i) generalization of the MSSA (Multichannel Singular Spectral Analysis) [1] for expanding vector (space-distributed) time series in basis of spatial-temporal empirical orthogonal functions (STEOF), which makes allowance delayed correlations of the processes recorded in spatially separated points; (ii) expanding both real SST data, and longer by several times SST data generated numerically, in STEOF basis; (iii) use of the numerically produced STEOF basis for exclusion of 'too slow' (and thus not represented correctly) processes from real data. The application of the method allows by means of vector time series generated numerically by the INM RAS Coupled Climate Model [2] to separate from real SST anomalies data [3] two climatic modes possessing by noticeably different time scales: 3-5 and 9-11 years. Relations of separated modes to ENSO and PDO are investigated. Possible applications of spatial-temporal climatic patterns concept to prognosis of climate system evolution is discussed. 1. Ghil, M., R. M. Allen, M. D. Dettinger, K. Ide, D. Kondrashov, et al. (2002) "Advanced spectral methods for climatic time series", Rev. Geophys. 40(1), 3.1-3.41. 2. http://83.149.207.89/GCM_DATA_PLOTTING/GCM_INM_DATA_XY_en.htm 3. http://iridl.ldeo.columbia.edu/SOURCES/.KAPLAN/.EXTENDED/.v2/.ssta/

Feigin, A. M.; Mukhin, D.; Volodin, E. M.; Gavrilov, A.; Loskutov, E. M.

2013-12-01

311

The social organization of resident-type killer whales ( Orcinus orca) in Avacha Gulf, Northwest Pacific, as revealed through association patterns and acoustic similarity  

Microsoft Academic Search

Northeast Pacific resident-type killer whales (Orcinus orca) are known to form stable associations based on kinship between maternal relatives (matrilines) with a system of vocal dialects thought to reflect kinship relationships. We analyzed association patterns and acoustic similarity to study the social organization of killer whales in Avacha Gulf (Kamchatka, Russia), in the Northwest Pacific. The resident-type killer whales of

Tatiana Ivkovich; Olga A. Filatova; Alexandr M. Burdin; Hal Sato; Erich Hoyt

2010-01-01

312

Tinnitus behavior and hearing function correlate with the reciprocal expression patterns of BDNF and Arg3.1\\/arc in auditory neurons following acoustic trauma  

Microsoft Academic Search

The molecular changes following sensory trauma and the subsequent response of the CNS are poorly understood. We focused on finding a molecular tool for monitoring the features of excitability which occur following acoustic trauma to the auditory system. Of particular interest are genes that alter their expression pattern during activity-induced changes in synaptic efficacy and plasticity. The expression of brain-derived

J. Tan; L. Rüttiger; R. Panford-Walsh; W. Singer; H. Schulze; S. B. Kilian; S. Hadjab; U. Zimmermann; I. Köpschall; K. Rohbock; M. Knipper

2007-01-01

313

Spatial and Temporal Patterns of Nitrogen Transport in a Subtropical Urban Coastal Watershed  

NASA Astrophysics Data System (ADS)

Non-point source pollution is the dominant pathway of nitrogen (N) transport in agriculture as well as urban watersheds. Very little is known about N transport in urban watersheds located in the subtropics. Our objective was to evaluate the spatial and temporal evolution patterns of N forms in streams draining sub-basins, ranging in size from 19 to 350 km2, of an urban watershed located in the Tampa Bay region. We used long-term monthly (1991-2009) and weekly (2009) stream water N concentration data collected from these sub-basins to evaluate the impact of urban development on N transport. Sub-basins were separated in two groups based on urban land uses: developed (18-24% residential, 1-14% built up) and undeveloped (3-11% residential, 1-3% built up). Mean monthly total N concentrations during 1991-2009 were 0.8-2.4 mg L-1 at all sites and were greatest in streams draining developed (1.7-2.4 mg L-1) than undeveloped (0.8-1.2 mg L-1) sub-basins. All the developed and undeveloped sub-basins had a narrow range of organic N concentration (0.60-0.77 mg L-1) in streams; however, percent organic N was about twice as much in streams draining undeveloped (66-71% of total N) than developed (30-44% of total N) sub-basins. On the other hand, both NO3-N concentration and percentage of total N were much greater in developed (0.89-1.66 mg L-1; 53-68% of total N) than undeveloped (0.21-0.37 mg L-1; 25-30% of total N) sub-basins. Among all N forms, mean monthly concentrations of NH4-N were lowest (<0.1 mg L-1; 2-5% of total N). Compared with long-term monthly total N concentrations, weekly total N concentrations were much higher (1.90-2.90 mg L-1) during 2009 high-flow period (June to September), with greater concentrations in developed (2.40-2.95 mg L-1) as compared to undeveloped (1.90-2.06 mg L-1) sub-basins. Concentrations of organic N mirrored a similar trend as total N at all sites. The weekly inorganic N (NO3-N, NH4-N) trends were similar to long-term data, with greater proportions in developed (26-39% of total N) than undeveloped (13-23% of total N) sub-basins. Percent weekly organic N was much greater (65-85% of total N) across all sites as compared to 1991-2009 monthly data (30-71% of total N). Organic N approached 77-85% of total N in undeveloped and 71-75% of total N in developed sub-basins. Organic N forms consists of dissolved organic N (DON; humic substances, amino acids, amino sugars, and tannins) and particulate organic N (PON; partially decomposed organic matter); these forms were measured in weekly samples. The undeveloped sub-basins had much greater concentrations of DON (0.97-1.05 mg L-1, 50-53% of total N) as compared to PON (0.56-0.64 mg L-1, 27-34% of total N). The transport of a specific organic N form whether DON or PON will be determined by the duration and intensity of rainfall-runoff events. For example, high-rainfall events may transport leaf litter and organic matter (that are components of PON) to streams, whereas low-rainfall events may not have enough hydrologic power to transport particulates from land to streams but can mobilize and carry DON to streams.

Toor, G.; Banger, K.; Inglett, P.; Stanley, C.

2010-12-01

314

Spatial and temporal patterns of recent area change of glacier systems on the Antarctic Peninsula  

NASA Astrophysics Data System (ADS)

Glaciers on the Antarctic Peninsula (AP) have recently shown changes in extent, velocity and thickness. Understanding the response of glaciers to warming air temperatures and ocean circulation changes in this region is critical for understanding future mass balance changes, and yet there is little quantification of change in the mass balance of individual basins and the processes controlling changes in their extent. One reason for this is that the AP is a complex mountainous glacier system and without a topographic model at sufficient resolution the boundaries between individual glacier systems have been difficult to identify. With outlines it becomes possible to calculate changes in area and compare characteristics of individual glaciers. We present a new Digital Elevation Model (DEM) and a new drainage basin data set for the Antarctic Peninsula, along with an assessment of changes in area of marine-terminating glacier systems from the 1940s to 2010. We explain the methodology used in producing the new 100-m DEM of the region using ASTER GDEM, and the semi-automated drainage basin delineation method based on this DEM. This approach has resulted in outlines for 1598 glacier systems: these include outlet and mountain glaciers, ice caps, piedmonts, ice-covered islands and 'ice walls'. Of these, 903 are marine-terminating glaciers, all of which have coastal-change data at various time periods since the 1940s. Area calculations, along with other attributes, were assigned to individual basins, thus enabling comparative statistical analyses. We give a summary of these changes both by overall area change and by change in extent at 5-year time intervals, and describe patterns of ice loss both spatially (by latitude and by specific regions) and temporally (trends across time intervals). Although 90% of the 903 glaciers have reduced in size since the earliest recorded date, the area lost varies considerably between glaciers. Largest area loss has occurred to glaciers flowing into Wordie Bay, where the largest basin on the AP lost 329 km2 between 1997 and 2010. Large losses also occurred to the glaciers which once flowed into the Larsen B Ice Shelf (up to 131 km2), and to the large ice piedmont on Adelaide Island (60 km2). In total, 21 glaciers lost > 10 km2 since their earliest recorded position, 209 glaciers lost between 1-10 km2 and 672 showed minimal change (<1 km2). The relative area change is generally inversely correlated with basin size although there are a number of outliers. We examine spatial differences in ice loss and compare regions that differ in consistency of retreat. A statistical analysis of glacier changes alongside glaciological controls obtained from the drainage basin outlines and the DEM can help us to understand why some glaciers behave anomalously, and here we discuss initial findings.

Cook, Alison; Murray, Tavi; Luckman, Adrian; Vaughan, David

2013-04-01

315

Spatial and temporal patterns of porcine reproductive and respiratory syndrome virus (PRRSV) genotypes in Ontario, Canada, 2004-2007  

PubMed Central

Background The spread of PRRSV among pig herds has been investigated experimentally, but few observational studies have investigated this subject. Because PRRSV is endemic and live modified vaccines are used in Ontario, the spatial and temporal distributions of 6 PRRSV genotypes were investigated in the province during the period from 2004–2007. The purpose was to find evidence of spread of PRRSV genotypes and determine if spread could be attributed to supplier or ownership connections between herds. Sequence information from PRRSV ORF5 and related source-herd demographic information were obtained from diagnostic submissions to the Animal Health Laboratory, University of Guelph. Results A spatial cluster that could not be attributed to supplier or ownership connections among herds in the cluster was detected for RFLP type 1-3-4. Because of genetic dissimilarity among members of the cluster, it was considered to be a result of past spread of the RFLP type. A spatio-temporal cluster detected for RFLP type 1-18-4 was attributed to a shared gilt supplier among the herds in the cluster. Significant spatio-temporal patterns detected for RFLP type 2-5-2, which is considered to be a vaccine-type virus were most likely due to grouping of herds in an ownership that used the corresponding vaccine. Clustering within herd-ownership was a risk factor for presence of five of the six genotypes investigated in the present study. Conclusions Although the literature indicates that PRRSV can spread via aerosol between pig herds, the present study found no strong evidence of this occurring in Ontario. The evidence pointed toward transmission of PRRSV occurring in this population by common sources of animals or similarity of herd ownership, which is a proxy measure for other connections between herds. It is also apparent that the recognition and testing of these connections between herds is a necessary part of interpreting spatio-temporal patterns of PRRSV genotypes.

2014-01-01

316

Clusters of Temporal Discordances Reveal Distinct Embryonic Patterning Mechanisms in Drosophila and Anopheles  

PubMed Central

Evolutionary innovations can be driven by spatial and temporal changes in gene expression. Several such differences have been documented in the embryos of lower and higher Diptera. One example is the reduction of the ancient extraembryonic envelope composed of amnion and serosa as seen in mosquitoes to the single amnioserosa of fruit flies. We used transcriptional datasets collected during the embryonic development of the fruit fly, Drosophila melanogaster, and the malaria mosquito, Anopheles gambiae, to search for whole-genome changes in gene expression underlying differences in their respective embryonic morphologies. We found that many orthologous gene pairs could be clustered based on the presence of coincident discordances in their temporal expression profiles. One such cluster contained genes expressed specifically in the mosquito serosa. As shown previously, this cluster is redeployed later in development at the time of cuticle synthesis. In addition, there is a striking difference in the temporal expression of a subset of maternal genes. Specifically, maternal transcripts that exhibit a sharp reduction at the time of the maternal-zygotic transition in Drosophila display sustained expression in the Anopheles embryo. We propose that gene clustering by local temporal discordance can be used for the de novo identification of the gene batteries underlying morphological diversity.

Papatsenko, Dmitri; Levine, Michael; Goltsev, Yury

2011-01-01

317

TEMPORAL GENE INDUCTION PATTERNS IN SHEEPSHEAD MINNOWS EXPOSED TO 17-ESTRADIOL  

EPA Science Inventory

Gene arrays provide a powerful method to examine changes in gene expression in fish due to chemical exposures in the environment. In this study, we expanded an existing gene array for sheepshead minnows (Cyprinodon variegatus) (SHM) and used it to examine temporal changes in gene...

318

SPATIAL AND TEMPORAL PATTERNS IN MERCURY CONTAMINATION IN SEDIMENTS OF THE LAURENTIAL GREAT LAKES  

EPA Science Inventory

Data from recent sediment surveys have been collated and mapped in order to determine the spatial distribution of mercury in sediments across the entire Great Lakes basin. Information from historical surveys has also been collated in order to evaluate temporal trends. Lake Huron ...

319

Habitat overlap of enemies: temporal patterns and the role of spatial complexity  

Microsoft Academic Search

Environmental heterogeneity can promote coexistence of conflicting species by providing spatial or temporal refuges from strong interactions (e.g., intraguild predation, competition). However, in many systems, refuge availability and effectiveness may change through time and space because of variability in habitat use by either species. Here I consider how the intensity of intraguild predation risk varies from day to night for

Stephanie E. Hampton

2004-01-01

320

Temporal patterns of fire sequences observed in Canton of Ticino (southern Switzerland)  

NASA Astrophysics Data System (ADS)

Temporal dynamical analysis in fire sequences recorded from 1969 to 2008 in Canton Ticino (Switzerland) was carried out by using the Allan Factor statistics. The obtained results show the presence of daily periodicities, superimposed to two time-scaling regimes. The daily cycle vanishes for sequences of higher altitude fires, for which a single scaling behaviour is observed.

Telesca, L.; Kanevski, M.; Tonini, M.; Pezzatti, G. B.; Conedera, M.

2010-04-01

321

Aoristic Signatures and the Spatio-Temporal Analysis of High Volume Crime Patterns  

Microsoft Academic Search

The spatial analysis of crime and the current focus on hotspots has pushed the area of crime mapping to the fore, especially in regard to high volume offenses such as vehicle theft and burglary. Hotspots also have a temporal component, yet police recorded crime databases rarely record the actual time of offense as this is seldom known. Police crime data

Jerry H. Ratcliffe

2002-01-01

322

Emergence of spatio-temporal patterns in forest-fire sequences  

Microsoft Academic Search

Temporal variation of spatial clustering in fire data recorded from 1997 to 2003 in Tuscany region, central Italy, has been investigated using the Voronoï polygon area, the Morishita index and the fractal dimension. Our findings reveal that the spatial clustering of fire events changes with time, showing an enhancement of the clustering degree before the largest events.

Devis Tuia; Rosa Lasaponara; Luciano Telesca; Mikhail Kanevski

2008-01-01

323

Querying Spatio-temporal Patterns in Mobile Phone-Call Databases  

Microsoft Academic Search

Call Detail Record (CDR) databases contain many millions of records with information about mobile phone calls, including the users' location when the call was made\\/received. This huge amount of spatio-temporal data opens the door for the study of human trajectories on a large scale without the bias that other sources, like GPS or WLAN networks, introduce in the population studied.

Marcos R. Vieira; Enrique Frías-Martínez; Petko Bakalov; Vanessa Frías-Martínez; Vassilis J. Tsotras

2010-01-01

324

Spatio-temporal interfacial potential patterns during the electrocatalyzed oxidation of formic acid on Bi-modified Pt  

NASA Astrophysics Data System (ADS)

We report experimental observations of the spatio-temporal dynamics in the electro-oxidation of formic acid on a Pt ring electrode modified by bismuth adatoms. Bismuth modification significantly enhanced the current density and it was found to considerably increase the existence range of oscillations and spatio-temporal self-organization. Hidden negative differential resistance and the existence of a Hopf bifurcation were deduced from the electrochemical impedance spectra and the occurrence of galvanostatic oscillations. The pattern formation resulted from hybrid effects of the nonlinear chemistry during formic acid oxidation and the long-range coupling of the interfacial potential induced by the chosen geometry (ring type) of the working electrode. Reversible transitions between traveling pulses and oscillating standing waves were observed when the outer potential or the formic acid concentration near the electrode were used as control parameters. Experimental results were compared with computer simulations of a reaction-migration system. The role of electrode inhomogeneities in pattern formation and the transform between patterns were discussed.

Lee, Jaeyoung; Christoph, Johannes; Strasser, Peter; Eiswirth, Markus; Ertl, Gerhard

2001-07-01

325

Spatial and temporal patterns of endocrine active chemicals in small streams indicate differential exposure to aquatic organisms  

USGS Publications Warehouse

Alkylphenolic chemicals (APCs) and hormones were measured six times from February through October 2007 in three Minnesota streams receiving wastewater to identify spatial and temporal patterns in concentrations and in estrogen equivalency. Fish were collected once during the study to evaluate endpoints indicative of endocrine disruption. The most commonly detected APCs were 4-tert-octylphenol and 4-nonylphenol and the most commonly detected hormones were estrone and androstenedione. Chemical concentrations were greatest for nonylphenol ethoxycarboxylates (NPECs) (5,000-140,000 ng/l), followed by 4-nonlylphenol and 4-nonylphenolethoxylates (50-880 ng/l), 4-tert-octylphenol and 4-tert-octylphenolethoxylates with concentrations as great as 130 ng/l, and hormones (0.1-54 ng/l). Patterns in chemicals and estrogen equivalency indicated that wastewater effluent is a pathway of APCs and hormones to downstream locations in this study. However, upstream contributions can be equally or more important indicating alternative sources. This study indicates that aquatic organisms experience both spatially and temporally variable exposures in the number of compounds, total concentrations, and estrogenicity. This variability was evident in fish collected from the three rivers as no clear upstream to downstream pattern of endocrine disruption endpoints emerged.

Lee, K. E.; Barber, L. B.; Schoenfuss, H. L.

2014-01-01

326

Spatial and Temporal Patterns of Locally-Acquired Dengue Transmission in Northern Queensland, Australia, 1993-2012  

PubMed Central

Background Dengue has been a major public health concern in Australia since it re-emerged in Queensland in 1992–1993. We explored spatio-temporal characteristics of locally-acquired dengue cases in northern tropical Queensland, Australia during the period 1993–2012. Methods Locally-acquired notified cases of dengue were collected for northern tropical Queensland from 1993 to 2012. Descriptive spatial and temporal analyses were conducted using geographic information system tools and geostatistical techniques. Results 2,398 locally-acquired dengue cases were recorded in northern tropical Queensland during the study period. The areas affected by the dengue cases exhibited spatial and temporal variation over the study period. Notified cases of dengue occurred more frequently in autumn. Mapping of dengue by statistical local areas (census units) reveals the presence of substantial spatio-temporal variation over time and place. Statistically significant differences in dengue incidence rates among males and females (with more cases in females) (?2?=?15.17, d.f.?=?1, p<0.01). Differences were observed among age groups, but these were not statistically significant. There was a significant positive spatial autocorrelation of dengue incidence for the four sub-periods, with the Moran's I statistic ranging from 0.011 to 0.463 (p<0.01). Semi-variogram analysis and smoothed maps created from interpolation techniques indicate that the pattern of spatial autocorrelation was not homogeneous across the northern Queensland. Conclusions Tropical areas are potential high-risk areas for mosquito-borne diseases such as dengue. This study demonstrated that the locally-acquired dengue cases have exhibited a spatial and temporal variation over the past twenty years in northern tropical Queensland, Australia. Therefore, this study provides an impetus for further investigation of clusters and risk factors in these high-risk areas.

Naish, Suchithra; Dale, Pat; Mackenzie, John S.; McBride, John; Mengersen, Kerrie; Tong, Shilu

2014-01-01

327

Multi-voxel pattern analysis of selective representation of visual working memory in ventral temporal and occipital regions.  

PubMed

While previous results from univariate analysis showed that the activity level of the parahippocampal gyrus (PHG) but not the fusiform gyrus (FG) reflects selective maintenance of the cued picture category, present results from multi-voxel pattern analysis (MVPA) showed that the spatial response patterns of both regions can be used to differentiate the selected picture category in working memory. The ventral temporal and occipital areas including the PHG and FG have been shown to be specialized in perceiving and processing different kinds of visual information, though their role in the representation of visual working memory remains unclear. To test whether the PHG and FG show spatial response patterns that reflect selective maintenance of task-relevant visual working memory in comparison with other posterior association regions, we reanalyzed data from a previous fMRI study of visual working memory with a cue inserted during the delay period of a delayed recognition task. Classification of FG and PHG activation patterns for the selected category (face or scene) during the cue phase was well above chance using classifiers trained with fMRI data from the cue or probe phase. Classification of activity in other temporal and occipital regions for the cued picture category during the cue phase was relatively less consistent even though classification of their activity during the probe recognition was comparable with the FG and PHG. In sum, these findings suggest that the FG and PHG carry information relevant to the cued visual category, and their spatial activation patterns during selective maintenance seem to match those during visual recognition. PMID:23380167

Han, Xufeng; Berg, Alexander C; Oh, Hwamee; Samaras, Dimitris; Leung, Hoi-Chung

2013-06-01

328

Obesity and chronic stress are able to desynchronize the temporal pattern of serum levels of leptin and triglycerides.  

PubMed

Disruption of the circadian system can lead to metabolic dysfunction as a response to environmental alterations. This study assessed the effects of the association between obesity and chronic stress on the temporal pattern of serum levels of adipogenic markers and corticosterone in rats. We evaluated weekly weight, delta weight, Lee index, and weight fractions of adipose tissue (mesenteric, MAT; subcutaneous, SAT; and pericardial, PAT) to control for hypercaloric diet-induced obesity model efficacy. Wistar rats were divided into four groups: standard chow (C), hypercaloric diet (HD), stress plus standard chow (S), and stress plus hypercaloric diet (SHD), and analyzed at three time points: ZT0, ZT12, and ZT18. Stressed animals were subjected to chronic stress for 1h per day, 5 days per week, during 80 days. The chronic exposure to a hypercaloric diet was an effective model for the induction of obesity and metabolic syndrome, increasing delta weight, Lee index, weight fractions of adipose tissue, and triglycerides and leptin levels. We confirmed the presence of a temporal pattern in the release of triglycerides, corticosterone, leptin, and adiponectin in naïve animals. Chronic stress reduced delta weight, MAT weight, and levels of triglycerides, total cholesterol, and leptin. There were interactions between chronic stress and obesity and serum total cholesterol levels, between time points and obesity and adiponectin and corticosterone levels, and between time points and chronic stress and serum leptin levels. In conclusion, both parameters were able to desynchronize the temporal pattern of leptin and triglyceride release, which could contribute to the development of metabolic diseases such as obesity and metabolic syndrome. PMID:24184591

de Oliveira, Carla; Scarabelot, Vanessa Leal; de Souza, Andressa; de Oliveira, Cleverson Moraes; Medeiros, Liciane Fernandes; de Macedo, Isabel Cristina; Marques Filho, Paulo Ricardo; Cioato, Stefania Giotti; Caumo, Wolnei; Torres, Iraci L S

2014-01-01

329

Investigation of the robustness of time reversal acoustics in solid media through the reconstruction of temporally symmetric sources  

NASA Astrophysics Data System (ADS)

We investigate some of the limitations of time reversal acoustics (TRA) in solid media with transducers attached to the surface. In particular, we consider the limitations due to the finite size of the transducers and elastic wave propagation. Using a theoretical approach, numerical simulations and validation from laboratory ultrasound experiments, we find that finite size transducers and the existence of longitudinal and shear waves play significant roles in perturbing the time reversal process. Despite these limitations, we show that TRA in solids is very robust, providing the means to reconstruct the main features of the source signal. The analysis of TRA retro-focusing properties in solid specimens is of foremost importance for the development of new non-destructive evaluation techniques.

Griffa, M.; Anderson, B. E.; Guyer, R. A.; Ulrich, T. J.; Johnson, P. A.

2008-04-01

330

Complex temporal and spatial patterns in nonequilibrium processes. Progress report, December 1, 1987--November 30, 1992  

SciTech Connect

We have used dynamical systems methods to study and characterize bifurcations and pattern formation in a variety of nonequilibrium systems. In this paper we describe our work on dynamical systems, chemical oscillations and chaos, chemical spatial patterns, instabilities in fluid dynamics, electrodeposition clusters, the ballast resistor, and crack propagation.

Swinney, H.L.

1992-10-01

331

Temporal and Spatial Patterns of Preferential Flow Occurrence in the Shale Hills Catchment: From the Hillslope to the Catchment Scales  

NASA Astrophysics Data System (ADS)

Understanding temporal and spatial patterns of preferential flow (PF) occurrence is important in revealing hillslope and catchment hydrologic and biogeochemical processes. Quantitative assessment of the frequency and control of PF occurrence in the field, however, has been limited, especially at the landscape scale of hillslope and catchment. By using 5.5-years' (2007-2012) real-time soil moisture at 10 sites response to 323 precipitation events, we tested the temporal consistency of PF occurrence at the hillslope scale in the forested Shale Hills Catchment; and by using 25 additional sites with at least 1-year data (2011-2012), we evaluated the spatial patterns of PF occurrence across the catchment. To explore the potential effects of PF occurrence on catchment hydrology, wavelet analysis was performed on the recorded time series of hydrological signals (i.e., precipitation, soil moisture, catchment discharge). Considerable temporal consistence was observed in both the frequency and the main controls of PF occurrence at the hillslope scale, which was attributed largely to the statistical stability of precipitation pattern over the monitoring period and the relatively stable subsurface preferential pathways. Preferential flow tended to occur more often in response to intense rainfall events, and favored the conditions at dry hilltop or wet valley floor sites. When upscaling to the entire catchment, topographic control on the PF occurrence was amplified remarkably, leading to the identification of a subsurface PF network in the catchment. Higher frequency of PF occurrence was observed at the valley floor (average 48%), hilltop (average 46%), and swales/hillslopes near the stream (average 40%), while the hillslopes in the eastern part of the catchment were least likely to experience PF (0-20%). No clear relationship, however, was observed between terrain attributes and PF occurrence, because the initiation and persistency of PF in this catchment was controlled jointly by complex interactions among landform units, soil types, initial soil moisture, precipitation features, and season. Through the wavelet method (coherence spectrum and phase differences), dual-pore filtering effects of soil system were proven, rendering it possible to further infer characteristic properties of the underlying hydrological processes in the subsurface. We found that preferential flow dominates the catchment discharge response at short-time periods (< 3 days), while the matrix flow may dominate the discharge response at the time scales of around 10-12 days. The temporal and spatial patterns of PF occurrence revealed in this study can help advance the modeling and prediction of complex PF dynamics in this and other similar landscapes.

Liu, H.; Lin, H.

2013-12-01

332

Spatial and temporal patterns of nutrient concentration and export in the tidal Hudson River  

Microsoft Academic Search

Spatial and temporal dynamics of N and P were examined in the tidal Hudson River between 1992 and 1996. For all seasons and\\u000a at all locations in the river nutrient concentrations were generally quite high. TN averaged 60 ?M and was above 50 ?M in\\u000a 75% of samples. TP averaged 1.7 ?M and was above 1.2 ?M in 75% of

G. G. Lampman; N. F. Caraco; J. J. Cole

1999-01-01

333

Computational intelligence in biomedical imaging: multidimensional analysis of spatio-temporal patterns  

Microsoft Academic Search

Technical innovations in radiology, such as advanced cross-sectional imaging methods, have opened up new vistas for the exploration\\u000a of structure and function of the human body enabling both high spatial and temporal resolution. However, these techniques\\u000a have led to vast amounts of data whose precise and reliable visual analysis by radiologists requires a considerable amount\\u000a of human intervention and expertise,

Axel Wismüller

2011-01-01

334

Spatio-temporal patterns of juvenile marine turtle occurrence in waters of the European continental shelf  

Microsoft Academic Search

We present data spanning approximately 100 years regarding the spatial and temporal occurrence of marine turtle sightings\\u000a and strandings in the northeast Atlantic from two public recording schemes and demonstrate potential signals of changing population\\u000a status. Records of loggerhead (n = 317) and Kemp’s ridley (n = 44) turtles occurring on the European continental shelf were most prevalent during the autumn and winter, when waters

Matthew J. Witt; Rod Penrose; Brendan J. Godley

2007-01-01

335

Temporal Asthma Patterns Using Repeated Questionnaires over 13 Years in a Large French Cohort of Women  

PubMed Central

Variable expression is one aspect of the heterogeneity of asthma. We aimed to define a variable pattern, which is relevant in general health epidemiological cohorts. Our objectives were to assess whether: 1) asthma patterns defined using simple asthma questions through repeated measurements could reflect disease variability 2) these patterns may further be classified according to asthma severity/control. Among 70,428 French women, we used seven questionnaires (1992–2005) and a comprehensive reimbursement database (2004–2009) to define three reliable asthma patterns based on repeated positive answers to the ever asthma attack question: “never asthma” (n?=?64,061); “inconsistent” (“yes” followed by “no”, n?=?3,514); “consistent” (fully consistent positive answers, n?=?2,853). The “Inconsistent” pattern was related to both long-term (childhood-onset asthma with remission in adulthood) and short-term (reported asthma attack in the last 12 months, associated with asthma medication) asthma variability, showing that repeated questions are relevant markers of the variable expression of asthma. Furthermore, in this pattern, the number of positive responses (1992–2005) predicted asthma drug consumption in subsequent years, a marker of disease severity. The “Inconsistent” pattern is a phenotype that may capture the variable expression of asthma. Repeated answers, even to a simple question, are too often neglected.

Sanchez, Margaux; Bousquet, Jean; Le Moual, Nicole; Jacquemin, Benedicte; Clavel-Chapelon, Francoise; Humbert, Marc; Kauffmann, Francine; Tubert-Bitter, Pascale; Varraso, Raphaelle

2013-01-01

336

Two distinct modes of forebrain circuit dynamics underlie temporal patterning in the vocalizations of young songbirds  

PubMed Central

Accurate timing is a critical aspect of motor control, yet the temporal structure of many mature behaviors emerges during learning from highly variable exploratory actions. How does a developing brain acquire the precise control of timing in behavioral sequences? To investigate the development of timing, we analyzed the songs of young juvenile zebra finches. These highly variable vocalizations, akin to human babbling, gradually develop into temporally-stereotyped adult songs. We find that the durations of syllables and silences in juvenile singing are formed by a mixture of two distinct modes of timing – a random mode producing broadly-distributed durations early in development, and a stereotyped mode underlying the gradual emergence of stereotyped durations. Using lesions, inactivations, and localized brain cooling we investigated the roles of neural dynamics within two premotor cortical areas in the production of these temporal modes. We find that LMAN (lateral magnocellular nucleus of the nidopallium) is required specifically for the generation of the random mode of timing, and that mild cooling of LMAN causes an increase in the durations produced by this mode. On the contrary, HVC (used as a proper name) is required specifically for producing the stereotyped mode of timing, and its cooling causes a slowing of all stereotyped components. These results show that two neural pathways contribute to the timing of juvenile songs, and suggest an interesting organization in the forebrain, whereby different brain areas are specialized for the production of distinct forms of neural dynamics.

Aronov, Dmitriy; Veit, Lena; Goldberg, Jesse H.; Fee, Michale S.

2011-01-01

337

Temporal variability of remotely sensed suspended sediment and sea surface temperature patterns in Mobile Bay, Alabama  

USGS Publications Warehouse

Distribution patterns of suspended sediments and sea surface temperatures in, Mobile Bay were derived from algorithms using digital data from the visible, near infrared, and infrared channels of the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-TIROS-N satellite. Closely spaced AVHRR scenes for January 20, 24, and 29, 1982, were compared with available environmental information taken during the same period. A complex interaction between river discharge, winds, and astronomical tides controlled the distribution patterns of suspended sediments. These same variables, coupled with air temperatures, also governed the distribution patterns of sea surface temperatures. ?? 1990 Estuarine Research Federation.

Rucker, J. B.; Stumpf, R. P.; Schroeder, W. W.

1990-01-01

338

Investigating univariate temporal patterns for intrinsic connectivity networks based on complexity and low-frequency oscillation: a test-retest reliability study.  

PubMed

Intrinsic connectivity networks (ICNs) are composed of spatial components and time courses. The spatial components of ICNs were discovered with moderate-to-high reliability. So far as we know, few studies focused on the reliability of the temporal patterns for ICNs based their individual time courses. The goals of this study were twofold: to investigate the test-retest reliability of temporal patterns for ICNs, and to analyze these informative univariate metrics. Additionally, a correlation analysis was performed to enhance interpretability. Our study included three datasets: (a) short- and long-term scans, (b) multi-band echo-planar imaging (mEPI), and (c) eyes open or closed. Using dual regression, we obtained the time courses of ICNs for each subject. To produce temporal patterns for ICNs, we applied two categories of univariate metrics: network-wise complexity and network-wise low-frequency oscillation. Furthermore, we validated the test-retest reliability for each metric. The network-wise temporal patterns for most ICNs (especially for default mode network, DMN) exhibited moderate-to-high reliability and reproducibility under different scan conditions. Network-wise complexity for DMN exhibited fair reliability (ICC<0.5) based on eyes-closed sessions. Specially, our results supported that mEPI could be a useful method with high reliability and reproducibility. In addition, these temporal patterns were with physiological meanings, and certain temporal patterns were correlated to the node strength of the corresponding ICN. Overall, network-wise temporal patterns of ICNs were reliable and informative and could be complementary to spatial patterns of ICNs for further study. PMID:24042040

Wang, X; Jiao, Y; Tang, T; Wang, H; Lu, Z

2013-12-19

339

Temporal Patterns of Ozone Pollution in West Virginia: Implications for High-Elevation Hardwood Forests  

Microsoft Academic Search

Hourly ozone (O3) data from one rural and four urban sites throughout West Virginia were analyzed for a three-year period (1987-1989) focusing on seasonal and diurnal patterns of O3 concentrations. Based on maximum hourly O3 concentrations (highest 1-hr maximum value per month), there were definite seasonal patterns with highest values from May to August and lowest values from December to

Frank S. Gilliam; Nicole L. Turrill

1995-01-01

340

Determining of spatial distribution patterns and temporal trends of an air pollutant using proper orthogonal decomposition basis functions  

NASA Astrophysics Data System (ADS)

This study aims to determine spatial patterns of an air pollutant dispersion and its temporal trends using proper orthogonal decomposition (POD) basis functions. The POD method is a model reduction technique for complex nonlinear problems and POD basis functions contain essential dynamics and physics of original problem. In the present work, the POD basis functions are applied to identify the dominant modes of carbon monoxide (CO) concentration in ambient air. For this purpose, CO concentration data for 15 monitoring stations over mega city of Tehran for 1339 days (1 Jan. 2006 to 31 Aug. 2009) are used. Data of monitoring stations are interpolated to generate 100 × 100 grid point network. Generated grid based data for all days create a time series of data that is the basic for constructing the POD basis functions. POD basis functions are obtained using eigenvectors of correlation matrix that is obtained using correlation of time series of data. The few number of the POD basis functions corresponding to the few first largest eigenvalues of correlation matrix are dominant modes. The results indicate that the first 7 largest eigenvalues of correlation matrix are 99 percent of the first 100 largest eigenvalues. This indicates that the first 7 POD basis functions out of 1339 capture the essential physics of CO distribution over region. Distribution of the first POD basis function over the city shows that the central and west-central parts of the city are more affected by CO pollutant. In addition, using the recorded data and the POD basis functions the temporal variation of each POD basis function is obtained. Results for the temporal variations of the POD basis functions show that the largest temporal trend belongs to the first POD basis function.

Ashrafi, Khosro

2012-02-01

341

Temporal downscaling of soil CO2 efflux survey measurements based on time-stable spatial patterns  

NASA Astrophysics Data System (ADS)

Chamber measurements of soil CO2 efflux are known to require repetitions at different points in space in order to achieve a high accuracy time series of the area average. In the absence of multiple gas analyzers, which are a limiting factor in most field studies, this is usually achieved either by automatic multiplexing or by manual surveys. As a trade-off, if t1 is the interval between two measurements and N the number of different measurement points used to reduce the error in determining the area average, the new improved-accuracy time series of the area average has a reduced temporal resolution characterised by the interval t2 = N * t1. However, if measurement points keep their (relative) deviation from the area average for a time considerably longer than t2, this additional information can be used to either reduce measurement effort or reconstruct an estimated unbiased time series of any resolution between t1 and t2. The former has already been demonstrated for soil moisture and soil CO2 efflux. Here, we give an overview of simple scaling methods that can be used to achieve the latter objective, i.e. temporal downscaling. The raw time series consisting of different measurement points is decomposed into a moving average over all points, a temporally stable deviation of each point from this, and a residual term comprising both fast temporal variability and random errors. By removing the second term, a time series of any resolution t3 = t1 *n,n = 1...N can be regained, which is subject to an increasing random error with decreasing n but not biased due to systematic deviations of single points from the area average. With respect to the time scale of stability and to the definition and removal of the stable deviation of each point from the area average, several variations of this method can be distinguished, e.g. constant offset, constant factor, constant relative offset or first order regression (offset and factor). We compared these methods for a dataset of circular repeated soil CO2 efflux measurements on transects of up to 30 points (t2 = 1.5 h). Rapid meteorological changes in environmental conditions are used to qualitatively assess the ability of the method to describe short-term changes in the area average of soil CO2 efflux.

Graf, A.; Prolingheuer, N.; Herbst, M.; Huisman, J. A.; Weihermüller, L.; Scharnagl, B.; Steenpass, C.; Harms, R.; Vereecken, H.

2009-04-01

342

Studies on the mechanism of retinoid-induced pattern duplications in the early chick limb bud: temporal and spatial aspects  

PubMed Central

All-trans-retinoic acid causes striking digit pattern changes when it is continuously released from a bead implanted in the anterior margin of an early chick wing bud. In addition to the normal set of digits (234), extra digits form in a mirror-symmetrical arrangement, creating digit patterns such as a 432234. These retinoic acid-induced pattern duplications closely mimic those found after grafts of polarizing region cells to the same positions with regard to dose-response, timing, and positional effects. To elucidate the mechanism by which retinoic acid induces these pattern duplications, we have studied the temporal and spatial distribution of all-trans-retinoic acid and its potent analogue TTNPB in these limb buds. We find that the induction process is biphasic: there is an 8-h lag phase followed by a 6-h duplication phase, during which additional digits are irreversibly specified in the sequence digit 2, digit 3, digit 4. On average, formation of each digit seems to require between 1 and 2 h. The tissue concentrations, metabolic pattern, and spatial distribution of all- trans-retinoic acid and TTNPB in the limb rapidly reach a steady state, in which the continuous release of the retinoid is balanced by loss from metabolism and blood circulation. Pulse-chase experiments reveal that the half-time of clearance from the bud is 20 min for all-trans- retinoic acid and 80 min for TTNPB. Manipulations that change the experimentally induced steep concentration gradient of TTNPB suggest that a graded distribution of retinoid concentrations across the limb is required during the duplication phase to induce changes in the digit pattern. The extensive similarities between results obtained with retinoids and with polarizing region grafts raise the possibility that retinoic acid serves as a natural "morphogen" in the limb.

1985-01-01

343

An investigation of acoustic beam patterns for the sonar localization problem using a beam based method.  

PubMed

Target localization can be accomplished through an ultrasonic sonar system equipped with an emitter and two receivers. Time of flight of the sonar echoes allows the calculation of the distance of the target. The orientation can be estimated from knowledge of the beam pattern of the receivers and the ratio, in the frequency domain, between the emitted and the received signals after compensation for distance effects and air absorption. The localization method is described and, as its performance strongly depends on the beam pattern, the search of the most appropriate sonar receiver in order to ensure the highest accuracy of target orientation estimations is developed in this paper. The structure designs considered are inspired by the ear shapes of some bat species. Parameters like flare rate, truncation angle, and tragus are considered in the design of the receiver structures. Simulations of the localization method allow us to state which combination of those parameters could provide the best real world implementation. Simulation results show the estimates of target orientations are, in the worst case, 2° with SNR?=?50?dB using the receiver structure chosen for a potential practical implementation of a sonar system. PMID:23742357

Guarato, Francesco; Windmill, James; Gachagan, Anthony; Harvey, Gerald

2013-06-01

344

Spatial-temporal analysis of drink-driving patterns in Hong Kong.  

PubMed

Normally, bars and restaurants are the preferred locations for drinking. Therefore, there is concern that the roads in bar and restaurant areas could have a higher probability of drink-drivers and alcohol-related road crashes. Many studies have been conducted to model the association between drinking locations and the prevalence of drink-driving, so that cost-effective enforcement strategies can be developed to combat drink-driving. In this study, a cluster analysis approach was applied to model the spatial-temporal variation of drink-driving distribution in Hong Kong. Six spatial-temporal clusters of drink-driving distribution emerged from the data: (i) bar and restaurant area, weekend-overnight; (ii) bar and restaurant area, other timespan; (iii) urban area, weekend-overnight; (iv) urban area, other timespans; (v) rural area, weekend-overnight; and (vi) rural area, other timespans. Next, separate zero-inflated regression models were established to identify the factors contributing to the prevalence of drink-driving for each of the six recognized clusters. The results indicated that drivers in rural areas tend to consume more alcohol than those in urban areas, regardless of the time period. In addition, both seasonal variation and vehicle class were found to determine the breath alcohol concentration (BrAC) levels among drivers. PMID:23896045

Li, Y C; Sze, N N; Wong, S C

2013-10-01

345

Defining temporal spatial patterns of mega city Istanbul to see the impacts of increasing population.  

PubMed

Rapid land use change has taken place over the last few decades in Istanbul. As most of the metropolitan areas, Istanbul faces increasing problems connected to increasing population and urbanisation. In this study, temporal changes of Istanbul's land use/cover were defined using remotely sensed data and post classification change detection method. For the aim of the study, relevant information was derived from different dated Landsat Thematic Mapper (TM) satellite data by using Unsupervised Iterative Self-Organizing Data Analysis Technique (ISODATA) and results were examined with matrix analysis method. Ground truth data were used for the classification and accuracy assessment of the classification. Temporal changes of land use/cover classes of the mega city Istanbul between the years of 1992, 1997 and 2005 were examined for the management and decision making process. Landsat TM images were classified into six land use/cover types: forest-green area, bare land, water surface, road, urban area, and mining area. The results show that urban areas and road categories are increased greatly by 13,630 and 5,018ha, respectively, but forest-green areas decreased by 77,722ha over 13years between 1992 and 2005. The reason for the decrease in green areas is mainly because of development of unplanned urbanization and unavoidable migration. PMID:18157736

Sanli, Fusun Balik; Balcik, Filiz Bektas; Goksel, Cigdem

2008-11-01

346

Decoupled temporal patterns of evolution and ecology in two post-Paleozoic clades  

NASA Technical Reports Server (NTRS)

Counts of taxonomic diversity are the prevailing standards for documenting large-scale patterns of evolution in the fossil record. However, the secular pattern of relative ecological importance between the bryozoan clades Cyclostomata and Cheilostomata is not reflected fully in compilations of generic diversity or within-fauna species richness, and the delayed ecological recovery of the Cheilostomata after the mass extinction at the Cretaceous-Tertiary boundary is missed entirely. These observations demonstrate that evolutionary success and ecological dominance can be decoupled and profoundly different, even over tens of millions of years.

McKinney, F. K.; Lidgard, S.; Sepkoski, J. J. Jr; Taylor, P. D.

1998-01-01

347

On the Relation Between Temporal Envelope Patterns at Two Different Points in the Cochlea.  

National Technical Information Service (NTIS)

A series of experiments was run to determine to what extent the auditory system can tell whether two envelope patterns at two different points on the basilar membrane are from the same random source or from two different sources. The signals were fabricat...

E. D. Schubert J. C. Nixon

1970-01-01

348

Mosses as biomonitors of atmospheric heavy metal deposition: Spatial patterns and temporal trends in Europe  

Microsoft Academic Search

In recent decades, mosses have been used successfully as biomonitors of atmospheric deposition of heavy metals. Since 1990, the European moss survey has been repeated at five-yearly intervals. Although spatial patterns were metal-specific, in 2005 the lowest concentrations of metals in mosses were generally found in Scandinavia, the Baltic States and northern parts of the UK; the highest concentrations were

H. Harmens; D. A. Norris; E. Steinnes; E. Kubin; J. Piispanen; R. Alber; Y. Aleksiayenak; O. Blum; M. Co?kun; M. Dam; L. De Temmerman; J. A. Fernández; M. Frolova; M. Frontasyeva; L. González-Miqueo; K. Grodzi?ska; Z. Jeran; S. Korzekwa; M. Krmar; K. Kvietkus; S. Leblond; S. Liiv; S. H. Magnússon; B. Ma?kovská; R. Pesch; Å. Rühling; J. M. Santamaria; W. Schröder; Z. Spiric; I. Suchara; L. Thöni; V. Urumov; L. Yurukova; H. G. Zechmeister

2010-01-01

349

Spatial and Temporal Patterns of Regional Seismicity Preceding the 1992 Landers California Earthquake  

Microsoft Academic Search

We investigate regional seismicity patterns as a function of space, time and magnitude preceding the 1992 Landers California earthquake using both raw and declustered catalogs. In addition to the previously documented increase of intermediate earthquakes (and associated acceleration of seismic moment release), the occurrence of small earthquakes down to M=1.8 selected from the declustered catalog also accelerated before the Landers

Y. Chen; C. G. Sammis

2002-01-01

350

Spatial and Temporal Patterns of Small-Scale Mixing in Drake Passage  

Microsoft Academic Search

Temperature and salinity profiles obtained with expendable CTD probes throughout Drake Passage between February 2002 and July 2005 are analyzed to estimate turbulent diapycnal eddy diffusivities to a depth of 1000 m. Diffusivity values are inferred from density\\/temperature inversions and internal wave vertical strain. Both methods reveal the same pattern of spatial variability across Drake Passage; diffusivity estimates from inversions

Andrew F. Thompson; Sarah T. Gille; J. A. MacKinnon; Janet Sprintall

2007-01-01

351

Spatial and temporal patterns of nitrogen deposition in China: Synthesis of observational data  

Microsoft Academic Search

Anthropogenic nitrous pollutant emissions in China significantly increased during the last decades, which contributed to the accelerated nitrogen (N) deposition. In order to characterize spatial pattern of nitrogen deposition, we employed the kriging technique to interpolate sampling data of precipitation chemistry and ambient air concentration from site-network observations over China. The estimation of wet deposition in China was limited to

Chaoqun Lü; Hanqin Tian

2007-01-01

352

Spatial and Temporal Patterns of Mercury Accumulation in Lacustrine Sediments Across the Laurentian Great Lakes Region  

EPA Science Inventory

Data from 103 sediment cores from the Great Lakes and inland lakes of the Great Lakes airshed were compiled to examine and provide a synthesis of patterns of historical and recent changes in mercury (Hg) deposition. Limited data from the lower Laurentian Great Lakes shows a lega...

353

Time Series Datamining: Identifying Temporal Patterns For Characterizationand Prediction Of Time Series Events  

Microsoft Academic Search

A new framework for analyzing time series data called Time Series Data Mining(TSDM) is introduced. This framework adapts and innovates data mining concepts toanalyzing time series data. In particular, it creates a set of methods that reveal hiddentemporal patterns that are characteristic and predictive of time series events. Traditionaltime series analysis methods are limited by the requirement of stationarity of

Richard J. Povinelli

1999-01-01

354

Estimating spatio-temporal patterns of agricultural productivity in fragmented landscapes using AVHRR NDVI time series  

Microsoft Academic Search

The characteristics of Normalized Difference Vegetation Index (NDVI) time series can be disaggregated into a set of quantitative metrics that may be used to derive information about vegetation phenology and land cover. In this paper, we examine the patterns observed in metrics calculated for a time series of 8 years over the southwest of Western Australia—an important crop and animal

Michael J Hill; Graham E Donald

2003-01-01

355

Diagnostic Patterns and Temporal Trends in the Evaluation of Adult Patients Hospitalized With Syncope  

Microsoft Academic Search

Background: Syncope is a common clinical problem that is often difficult and expensive to diagnose. We exam- ined diagnostic patterns and trends and use of specialty consultations in the evaluation of syncope. Methods: We retrospectively reviewed the medical rec- ords of consecutive adult patients hospitalized with the principal diagnosis of syncope (International Classifica- tion of Diseases, Ninth Revision, code 780.2)

L. A. Pires; Jangadeesh R. Ganji; Nalini Tarakeshwar; Robert Steele; Regina Jarandila; Daniel H. Solomon; Laura Van Houten; Robert J. Glynn; Lindsey Baden; Kelley Curtis; Harry Schrager; Jerry Avorn; Thomas P. Erlinger; Eliseo Guallar; Edgar R. Miller III; Rachael Stolzenberg-Solomon; Lawrence J. Appel; Pedro Redondo; Teresa Solano; Ana Bauza; Pedro Lloret; Sheila Feit; Mort Rubinstein; Ellen Remenchik; Walter M. Bortz II; William S. Nevin; Charles V. Allen; Karen Davis; Cathy Schoen; Stephen Schoenbaum

2001-01-01

356

SOX13 exhibits a distinct spatial and temporal expression pattern during chondrogenesis, neurogenesis, and limb development.  

PubMed

SOX13 is a member of the SOX family of transcription factors. SOX proteins play essential roles in development, and some are associated with human genetic diseases. SOX13 maps to a multi-disease locus on chromosome 1q31-32, yet its function is unknown. Here we describe the temporal and spatial expression of SOX13 protein during mouse organogenesis. SOX13 is expressed in the three embryonic cell lineages, suggesting that it may direct various developmental processes. SOX13 is expressed in the developing central nervous system including the neural tube and the developing brain. Expression is also detected in the condensing mesenchyme and cartilage progenitor cells during endochondral bone formation in the limb as well as the somite sclerotome and its derivatives. SOX13 is also detected in the developing kidney, pancreas, and liver as well as in the visceral mesoderm of the extra-embryonic yolk sac and spongiotrophoblast layer of the placenta. PMID:16835393

Wang, Yi; Ristevski, Sika; Harley, Vincent R

2006-12-01

357

Polycyclic aromatic hydrocarbons (PAHs) in the atmospheres of two French alpine valleys: sources and temporal patterns  

NASA Astrophysics Data System (ADS)

Alpine valleys represent some of the most important crossroads for international heavy-duty traffic in Europe, but the full impact of this traffic on air quality is not known due to a lack of data concerning these complex systems. As part of the program "Pollution des Vallées Alpines" (POVA), we performed two sampling surveys of polycyclic aromatic hydrocarbons (PAHs) in two sensitive valleys: the Chamonix and Maurienne Valleys, between France and Italy. Sampling campaigns were performed during the summer of 2000 and the winter of 2001, with both periods taking place during the closure of the "Tunnel du Mont-Blanc". The first objective of this paper is to describe the relations between PAH concentrations, external parameters (sampling site localization, meteorological parameters, sources), and aerosol characteristics, including its carbonaceous fraction (OC and EC). The second objective is to study the capacity of PAH profiles to accurately distinguish the different emission sources. Temporal evolution of the relative concentration of an individual PAH (CHR) and the PAH groups BghiP+COR and BbF+BkF is studied in order to differentiate wood combustion, gasoline, and diesel emissions, respectively. The results show that the total particulate PAH concentrations were higher in the Chamonix valley during both seasons, despite the cessation of international traffic. Seasonal cycles, with higher concentrations in winter, are also stronger in this valley. During winter, particulate PAH concentration can reach very high levels (up to 155 ng.m-3) in this valley during cold anticyclonic periods. The examination of sources shows the impact during summer of heavy-duty traffic in the Maurienne valley and of gasoline vehicles in the Chamonix valley. During winter, Chamonix is characterized by the strong influence of wood combustion in residential fireplaces, even if the temporal evolution of specific PAH ratios are difficult to interpret. Information on sources given by PAH profiles can only be considered in qualitative terms.

Marchand, N.; Besombes, J. L.; Chevron, N.; Masclet, P.; Aymoz, G.; Jaffrezo, J. L.

2004-08-01

358

Temporal album  

Microsoft Academic Search

Transient synchronization has been used as a mechanism of recognizing auditory patterns using integrate-and-fire neural networks. We first extend the mechanism to vision tasks and investigate the role of spike dependent learning. We show that such a temporal Hebbian learning rule significantly improves accuracy of detection. We demonstrate how multiple patterns can be identified by a single pattern selective neuron

Eleni Vasilaki; Jianfeng Feng; Hilary Buxton

2003-01-01

359

Effect of temporal distribution of calories on diurnal patterns of glucose levels and insulin secretion in NIDDM.  

PubMed

The effect of different temporal patterns of calorie intake on plasma glucose, serum insulin, and insulin secretion rates was examined in six patients with moderately well controlled non-insulin-dependent diabetes mellitus (NIDDM). Patients were studied on three separate occasions over 26 h. Total calories and food composition (50% carbohydrate, 15% protein, and 35% fat) were kept constant, but the pattern of calorie intake was varied. In study A (similar meal size), calories were distributed as 30, 40, and 30% at breakfast, lunch, and dinner, respectively. In study B (3 snacks, 3 meals), each subject ate three meals of 20, 20, and 30% of calories for breakfast, lunch, and dinner, respectively, and three snacks, each comprising 10% of calories, presented 2.5 h after the meal. In study C (large dinner), 10% of calories were consumed at breakfast, 20% at lunch, and 70% at dinner. Glucose, insulin, and C-peptide concentrations were measured at 15- to 30-min intervals. Insulin secretion rates were calculated from C-peptide levels with individually derived C-peptide clearance parameters. The different eating patterns were associated with only modest differences in overall levels of glucose and insulin secretion. Daytime insulin secretion was lowest when most of the daily calorie intake occurred in the form of a large dinner. Overnight levels of glucose and insulin secretion rates did not differ for the three eating patterns, and the morning glucose levels were also unaffected by the pattern of calorie intake on the previous day. A morning rise of glucose of greater than 0.28 mM occurred consistently only when dinner was of moderate size (30% of total calories).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2201497

Beebe, C A; Van Cauter, E; Shapiro, E T; Tillil, H; Lyons, R; Rubenstein, A H; Polonsky, K S

1990-07-01

360

Spatio-temporal patterns of beaked whale echolocation signals in the North Pacific.  

PubMed

At least ten species of beaked whales inhabit the North Pacific, but little is known about their abundance, ecology, and behavior, as they are elusive and difficult to distinguish visually at sea. Six of these species produce known species-specific frequency modulated (FM) echolocation pulses: Baird's, Blainville's, Cuvier's, Deraniyagala's, Longman's, and Stejneger's beaked whales. Additionally, one described FM pulse (BWC) from Cross Seamount, Hawai'i, and three unknown FM pulse types (BW40, BW43, BW70) have been identified from almost 11 cumulative years of autonomous recordings at 24 sites throughout the North Pacific. Most sites had a dominant FM pulse type with other types being either absent or limited. There was not a strong seasonal influence on the occurrence of these signals at any site, but longer time series may reveal smaller, consistent fluctuations. Only the species producing BWC signals, detected throughout the Pacific Islands region, consistently showed a diel cycle with nocturnal foraging. By comparing stranding and sighting information with acoustic findings, we hypothesize that BWC signals are produced by ginkgo-toothed beaked whales. BW43 signal encounters were restricted to Southern California and may be produced by Perrin's beaked whale, known only from Californian waters. BW70 signals were detected in the southern Gulf of California, which is prime habitat for Pygmy beaked whales. Hubb's beaked whale may have produced the BW40 signals encountered off central and southern California; however, these signals were also recorded off Pearl and Hermes Reef and Wake Atoll, which are well south of their known range. PMID:24465877

Baumann-Pickering, Simone; Roch, Marie A; Brownell, Robert L; Simonis, Anne E; McDonald, Mark A; Solsona-Berga, Alba; Oleson, Erin M; Wiggins, Sean M; Hildebrand, John A

2014-01-01

361

Temporal pattern of questing tick Ixodes ricinus density at differing elevations in the coastal region of western Norway  

PubMed Central

Background Climate change can affect the activity and distribution of species, including pathogens and parasites. The densities and distribution range of the sheep tick (Ixodes ricinus) and it’s transmitted pathogens appears to be increasing. Thus, a better understanding of questing tick densities in relation to climate and weather conditions is urgently needed. The aim of this study was to test predictions regarding the temporal pattern of questing tick densities at two different elevations in Norway. We predict that questing tick densities will decrease with increasing elevations and increase with increasing temperatures, but predict that humidity levels will rarely affect ticks in this northern, coastal climate with high humidity. Methods We described the temporal pattern of questing tick densities at ~100 and ~400 m a.s.l. along twelve transects in the coastal region of Norway. We used the cloth lure method at 14-day intervals during the snow-free season to count ticks in two consecutive years in 20 m2 plots. We linked the temporal pattern of questing tick densities to local measurements of the prevailing weather. Results The questing tick densities were much higher and the season was longer at ~100 compared to at ~400 m a.s.l. There was a prominent spring peak in both years and a smaller autumn peak in one year at ~100 m a.s.l.; but no marked peak at ~400 m a.s.l. Tick densities correlated positively with temperature, from low densities <5°C, then increasing and levelling off >15-17°C. We found no evidence for reduced questing densities during the driest conditions measured. Conclusions Tick questing densities differed even locally linked to elevation (on the same hillside, a few kilometers apart). The tick densities were strongly hampered by low temperatures that limited the duration of the questing seasons, whereas the humidity appeared not to be a limiting factor under the humid conditions at our study site. We expect rising global temperatures to increase tick densities and lead to a transition from a short questing season with low densities in the current cold and sub-optimal tick habitats, to longer questing seasons with overall higher densities and a marked spring peak.

2014-01-01

362

Temporal and spatial patterning of transgene expression by near-infrared irradiation.  

PubMed

We investigated whether near-infrared (NIR) light could be employed for patterning transgene expression in plasmonic cell constructs. Hollow gold nanoparticles with a plasmon surface band absorption peaking at ?750 nm, a wavelength within the so called "tissue optical window", were used as fillers in fibrin-based hydrogels. These composites, which efficiently transduce NIR photon energy into heat, were loaded with genetically-modified cells that harbor a heat-activated and ligand-dependent gene switch for regulating transgene expression. NIR laser irradiation in the presence of ligand triggered 3-dimensional patterns of transgene expression faithfully matching the illuminated areas of plasmonic cell constructs. This non-invasive technology was proven useful for remotely controlling in vivo the spatiotemporal bioavailability of transgenic vascular endothelial growth factor. The combination of spatial control by means of NIR irradiation along with safe and timed transgene induction presents a high application potential for engineering tissues in regenerative medicine scenarios. PMID:24957294

Martin-Saavedra, Francisco M; Cebrian, Virginia; Gomez, Leyre; Lopez, Daniel; Arruebo, Manuel; Wilson, Christopher G; Franceschi, Renny T; Voellmy, Richard; Santamaria, Jesus; Vilaboa, Nuria

2014-09-01

363

Microscopic fluctuations and spatio-temporal pattern formation in a supercitical oscillatory chemical system  

NASA Astrophysics Data System (ADS)

The spontaneous formation of order in the form of spatial concentration patterns in an unstirred chemical medium, supported by dissipation of chemical free energy, has been considered often since early work of Turing and Prigogine's group on non-equilibrium thermodynamics. The best-known experimental example is the oscillatory Belousov-Zhabotinskii reaction, in which target patterns of outward-moving concentric rings are readily observed. Question: can "microscopic" fluctuations nucleate targets, or is a catalytic, nucleating heterogeneous center is required? Vidal and Pagola observed spontaneous activity with no visible nucleating particles; however Zhang, Forster and Ross argued that fluctuations cannot nucleate targets far from bifurcation points. We describe an explicit model (using stochastic partial differential equations) that demonstrates how microscopic fluctuations can nucleate activity in a "supercritical" regime, extending the Oregonator of Field, Koros and Noyes. Partially supported by the NSF.

Hastings, Harold M.; Field, Richard J.; Sobel, Sabrina G.

2004-03-01

364

Spatial-temporal change in precipitation patterns based on the cloud model across the Wei River Basin, China  

NASA Astrophysics Data System (ADS)

It is of significant importance to investigate the spatial-temporal change in precipitation patterns due to its great effects on droughts, floods, soil erosion and water resource management. A complete investigation of precipitation structure and its distribution pattern based on daily precipitation covering 1960-2005 at 21 meteorological stations in the Wei River Basin has been performed. In order to comprehensively and objectively describe the changing pattern of precipitation, the cloud model is employed to quantitatively analyse the average, uniformity and stability of precipitation. Results indicate the following: (1) the occurrence of different precipitation durations exhibits a positive exponential curve with the decrease in precipitation durations, and 1-3-day events are the predominant precipitation events which have an increasing trend; (2) precipitation and its non-uniformity is increasingly reducing, while its stability increases initially then decreases; (3) mean precipitation reduces from southeast to northwest, and the precipitation of the Guanzhong Plain has a low uniformity and stability due to its location and increasingly intensifying human activities. The cloud model provides a new idea and quantitative measure for the evaluation of the uniformity and stability of precipitation.

Huang, Shengzhi; Hou, Beibei; Chang, Jianxia; Huang, Qiang; Chen, Yutong

2014-05-01

365

Vibration measurement of the tympanic membrane of guinea pig temporal bones using time-averaged speckle pattern interferometry  

NASA Astrophysics Data System (ADS)

``Time-averaged holography'' and ``holographic interferometry'' enable recording of the complete vibration pattern of a surface within several seconds. The results appear in the form of fringes. Vibration amplitudes smaller than 100 nm are not readily measurable by these techniques, because such small amplitudes produce variations in gray level, but not fringes. In practice, to obtain clear fringes in these measurements, stimulus sound pressures higher than 100 dB SPL must be used. The phase of motion is also not obtainable from such fringe techniques. In this study, a sinusoidal phase modulation technique is described, which allows detection of both small amplitudes of motion and their phase from time-averaged speckle pattern interferometry. In this technique, the laser injection current is modulated and digital image processing is used to analyze the measured patterns. When the sound-pressure level of stimuli is between 70 and 85 dB SPL, this system is applied to measure the vibratory response of the tympanic membrane (TM) of guinea pig temporal bones at frequencies up to 4 kHz where complicated vibration modes are observed. The effect of the bulla on TM displacements is also quantified. Results indicate that this system is capable of measuring the nanometer displacements of the TM, produced by stimuli of 70 dB SPL.

Wada, Hiroshi; Ando, Masayoshi; Takeuchi, Masataka; Sugawara, Hironori; Koike, Takuji; Kobayashi, Toshimitsu; Hozawa, Koji; Gemma, Takashi; Nara, Makoto

2002-05-01

366

REPEATED ETHANOL ADMINISTRATION MODIFIES THE TEMPORAL STRUCTURE OF SUCROSE INTAKE PATTERNS IN MICE: EFFECTS ASSOCIATED WITH BEHAVIORAL SENSITIZATION  

PubMed Central

Neuroadaptations supporting behavioral sensitization to abused drugs are suggested to underlie pathological, excessive motivation toward drugs and drug-associated stimuli. Drug-induced sensitization has also been linked to increased appetitive responses for non-drug, natural reinforcers. The present research investigated whether ethanol (EtOH)-induced neural changes, inferred from psychomotor sensitization, can modify consumption and intake dynamics for the natural reinforcer, sucrose. The effects of EtOH-induced sensitization in mice on the temporal structure of sucrose intake patterns were measured using a lickometer system. Sucrose intake dynamics were measured after sensitization for 1 h daily for 7 days and indicated more rapid initial approach and consumption of sucrose in EtOH-sensitized groups; animals showed a shorter latency to the first intake bout and an increased number of sucrose bottle licks during the initial 15 min of the 1-h sessions. This effect was associated with increased frequency and size of bouts. For the total 1-h session, sucrose intake and bout dynamics were not different between groups, indicating a change in patterns of sucrose intake but not total consumption. When sensitization was prevented by the GABAB receptor agonist baclofen, the increased rate of approach and consumption of sucrose were also prevented. Thus, EtOH-induced sensitization, and not the mere exposure to EtOH, was associated with changes in sucrose intake patterns. These data are consistent with current literature suggesting an enhancing effect of drug-induced sensitization on motivational processes involved in reinforcement.

Pastor, Raul; Kamens, Helen M.; McKinnon, Carrie S.; Ford, Matthew M.; Phillips, Tamara J.

2010-01-01

367

The influence of patch-delineation mismatches on multi-temporal landscape pattern analysis  

Microsoft Academic Search

Investigations of land-cover change often employ metrics designed to quantify changes in landscape structure through time,\\u000a using analyses of land cover maps derived from the classification of remote sensing images from two or more time periods.\\u000a Unfortunately, the validity of these landscape pattern analyses (LPA) can be compromised by the presence of spurious change, i.e., differences between map products caused

Julia Linke; Gregory J. McDermid; Alysha D. Pape; Adam J. McLane; David N. Laskin; Mryka Hall-Beyer; Steven E. Franklin

2009-01-01

368

Spatial and temporal patterns of intraspecific morphological variation in Dactylogyrus simplexus from fathead minnows in Nebraska.  

PubMed

Dactylogyrus simplexus Monaco and Mizelle, 1955, occurs on the gills of fathead minnows (Pimephales promelas). Previous research on parasites of fathead minnows from 3 converging Nebraska streams, Elk Creek, Oak Creek, and West Oak Creek, shows that fish in each stream constitute distinct populations. To determine whether their parasites had diverged structurally in response to such isolation, or in response to seasonal change, we searched for patterns of intraspecific morphometric variation among D. simplexus. Over 3 collection dates in fall 2007, spring 2008, and fall 2009, 203 D. simplexus were collected from Elk and West Oak Creeks. We ran 1-way ANOVA to compare differences in 15 distinct point-to-point measurements of sclerotized parts across sites and collection dates. Significant differences were found in some D. simplexus measurements between Elk and West Oak Creeks for all 3 collection dates, but the characteristics that differed and the trend of variation between the creeks were not consistent over time. Dactylogyrus simplexus from both Elk and West Oak Creeks showed consistent patterns of variation over time for 5 measurements, including hamulus gap width, bar length, marginal hook length, sickle length, and sickle width. In conclusion, D. simplexus demonstrate consistent patterns of seasonal variation, but not spatial. PMID:21721902

Bi, Mark; Janovy, John

2011-12-01

369

Spatio-temporal patterns in Lateglacial and Holocene vegetation and climate of Finnmark, northernmost Europe  

NASA Astrophysics Data System (ADS)

Precisely-dated records of palaeovegetation and reconstructed palaeoclimate are presented from three lakes in northernmost Finnmark. The lakes lie adjacent to the southern shore of the Barents Sea and are located along a west-east transect. The three records are used to reconstruct spatial patterns in regional vegetation and climatic history since 13,900 cal yr BP. Longer-term shifts in treeline position and in the position of the Pinus-Betula ecotone are recorded. In addition, especially during the regional Holocene thermal maximum, the latter exhibited strong periodic fluctuations. The number and strength of these fluctuations that were recorded at each of the three sites differed systematically, with fewer and weaker fluctuations seen at the easternmost site, in particular. The patterns revealed are used to test the hypothesis that variations in the strength of the North Cape Current have been of primary importance as the proximal driver of climatic variability in the region since deglaciation. The results provide strong support for this hypothesis during the Holocene, the strong periodic fluctuations during the regional Holocene thermal maximum in particular being consistent with the proposed mechanism. During the Lateglacial and earliest Holocene the patterns are less clear, but nonetheless also consistent with the proposed mechanism. Further work on precisely-dated marine sediment cores will be necessary to understand the factors leading to the periodic and longer-term variations in strength of the North Cape Current.

Huntley, Brian; Long, Antony J.; Allen, Judy R. M.

2013-06-01

370

Spatial and temporal patterns in the energy potential of surface water in Sweden  

NASA Astrophysics Data System (ADS)

Recent investigations show that land-use changes and hydropower regulation has caused significant changes in the annual runoff periodicity in Swedish rivers during the 20th century. Those changes in the annual periodicities are caused by structural alterations in river basins affected by intense agriculture and hydropower regulation. In addition, we found significant long-term (decadal) fluctuation in the available energy potential of surface runoff of Sweden, which has a significant impact on the planning of hydropower regulation and watershed management plans. Based on daily precipitation data in the period 1961 - 2005 we simulated using the HBV model the surface water runoff and the associated energy potential in 1001 watersheds covering the entire surface of Sweden. Comparisons were made with individual time-series of river discharge dating as far back as to the 1850s. As an average for the entire surface of Sweden, the five-year running mean of the energy potential of surface water varies between 115 TWh / year up to nearly 180 TWh / year with significant fluctuations on different periods extending up to at least 10 years. The 30-year running mean of the discharge of River Dalälven shows a decrease from 360 m3/s in the mid 19th century to 290 m3/s in 1965 and, thereafter, a significant increase. The more than century-long discharge time-series also shows decadal fluctuations that are well correlated with the fluctuations noted over the entire surface of Sweden. The fluctuations of energy potential show coherence up to 30 - 40% with the North Atlantic Oscillation index. The handling of these significant temporal variations in energy levels for hydropower purposes depends on the spatial coherence of river discharges. Consequently, we analysed the coherence spectrum of major rivers and found for the most separated rivers in Sweden that the coherence approaches asymptotically about 20 - 25 % for long-term variations. Neighbouring river basins could have coherence spectra starting at just few percents for weekly periods and increasing to over 90% for annual periods. The low coherences in river discharge on the national spatial scale is an important 'asset' for dealing with the significant temporal fluctuations in energy potential within hydropower production.

Worman, A. L.; Bottacin-Busolin, A.; Lindstrom, G.

2013-12-01

371

Patterns in the Composition of Microbial Communities from a Subtropical River: Effects of Environmental, Spatial and Temporal Factors  

PubMed Central

Microbes are key components of aquatic ecosystems and play crucial roles in global biogeochemical cycles. However, the spatiotemporal dynamics of planktonic microbial community composition in riverine ecosystems are still poorly understood. In this study, we used denaturing gradient gel electrophoresis of PCR-amplified 16S and 18S rRNA gene fragments and multivariate statistical methods to explore the spatiotemporal patterns and driving factors of planktonic bacterial and microbial eukaryotic communities in the subtropical Jiulong River, southeast China. Both bacterial and microbial eukaryotic communities varied significantly in time and were spatially structured according to upper stream, middle-lower stream and estuary. Among all the environmental factors measured, water temperature, conductivity, PO4-P and TN/TP were best related to the spatiotemporal distribution of bacterial community, while water temperature, conductivity, NOx-N and transparency were closest related to the variation of eukaryotic community. Variation partitioning, based on partial RDA, revealed that environmental factors played the most important roles in structuring the microbial assemblages by explaining 11.3% of bacterial variation and 17.5% of eukaryotic variation. However, pure spatial factors (6.5% for bacteria and 9.6% for eukaryotes) and temporal factors (3.3% for bacteria and 5.5% for eukaryotes) also explained some variation in microbial distribution, thus inherent spatial and temporal variation of microbial assemblages should be considered when assessing the impact of environmental factors on microbial communities.

Liu, Lemian; Yang, Jun; Yu, Xiaoqing; Chen, Guangjie; Yu, Zheng

2013-01-01

372

Temporal Processing Evaluation in Tinnitus Patients: Results on Analysis of Gap in Noise and Duration Pattern Test  

PubMed Central

Introduction: Tinnitus is a perception of sound without external source. For complete assessment of tinnitus, central auditory processing abilities should be considered in addition to the routine psychological evaluation of tinnitus characteristics. Temporal processing is one of the important auditory skills that are necessary for complex higher level auditory processing. Materials and Methods: 20 tinnitus patients and 20 healthy volunteers without tinnitus, all with normal auditory thresholds (? 20 dBnHL), were enrolled in present study. Pure Tone Audiometry (PTA), Tinnitus evaluation, Gap in Noise (GIN) test and Duration Pattern Test (DPT) were applied to all participants. Result: Analysis of GIN test revealed statistically significant increases in an approximate threshold value of gap detection in the patients group, both in right and left sides (P=0.007 and P=0.011, respectively). Comparison of percentage of correct responses in between two groups was also statistically meaningful in right and left ears (P=0.019 and P=0.026, respectively). The comparison of different parameters of DPT in two study groups revealed no significant differences in percentage of correct responses between two groups (P>0.05). Conclusion: GIN test results identified auditory temporal resolution difficulties in patients with tinnitus, meaning that in spite of normal auditory thresholds there may be some possibility of abnormality in central auditory processing functions.

Mehdizade Gilani, Vahid; Ruzbahani, Masumeh; Mahdi, Par