Semiparametric regression analysis of failure time data with dependent interval censoring.

PubMed

Chen, Chyong-Mei; Shen, Pao-Sheng

2017-09-20

Interval-censored failure-time data arise when subjects are examined or observed periodically such that the failure time of interest is not examined exactly but only known to be bracketed between two adjacent observation times. The commonly used approaches assume that the examination times and the failure time are independent or conditionally independent given covariates. In many practical applications, patients who are already in poor health or have a weak immune system before treatment usually tend to visit physicians more often after treatment than those with better health or immune system. In this situation, the visiting rate is positively correlated with the risk of failure due to the health status, which results in dependent interval-censored data. While some measurable factors affecting health status such as age, gender, and physical symptom can be included in the covariates, some health-related latent variables cannot be observed or measured. To deal with dependent interval censoring involving unobserved latent variable, we characterize the visiting/examination process as recurrent event process and propose a joint frailty model to account for the association of the failure time and visiting process. A shared gamma frailty is incorporated into the Cox model and proportional intensity model for the failure time and visiting process, respectively, in a multiplicative way. We propose a semiparametric maximum likelihood approach for estimating model parameters and show the asymptotic properties, including consistency and weak convergence. Extensive simulation studies are conducted and a data set of bladder cancer is analyzed for illustrative purposes. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Reduced birth intervals following the birth of children with long-term illness: evidence supporting a conditional evolved response.

PubMed

Waynforth, David

2015-10-01

Human birth interval length is indicative of the level of parental investment that a child will receive: a short interval following birth means that parental resources must be split with a younger sibling during a period when the older sibling remains highly dependent on their parents. From a life-history theoretical perspective, it is likely that there are evolved mechanisms that serve to maximize fitness depending on context. One context that would be expected to result in short birth intervals, and lowered parental investment, is after a child with low expected fitness is born. Here, data drawn from a longitudinal British birth cohort study were used to test whether birth intervals were shorter following the birth of a child with a long-term health problem. Data on the timing of 4543 births were analysed using discrete-time event history analysis. The results were consistent with the hypothesis: birth intervals were shorter following the birth of a child diagnosed by a medical professional with a severe but non-fatal medical condition. Covariates in the analysis were also significantly associated with birth interval length: births of twins or multiple births, and relationship break-up were associated with significantly longer birth intervals. © 2015 The Author(s).

Nonlogarithmic magnetization relaxation at the initial time intervals and magnetic field dependence of the flux creep rate in Bi2Sr2Ca(sub I)Cu2Ox single crystals

NASA Technical Reports Server (NTRS)

Moshchalcov, V. V.; Zhukov, A. A.; Kuznetzov, V. D.; Metlushko, V. V.; Leonyuk, L. I.

1990-01-01

At the initial time intervals, preceding the thermally activated flux creep regime, fast nonlogarithmic relaxation is found. The fully magnetic moment Pm(t) relaxation curve is shown. The magnetic measurements were made using SQUID-magnetometer. Two different relaxation regimes exist. The nonlogarithmic relaxation for the initial time intervals may be related to the viscous Abrikosov vortices flow with j is greater than j(sub c) for high enough temperature T and magnetic field induction B. This assumption correlates with Pm(t) measurements. The characteristic time t(sub O) separating two different relaxation regimes decreases as temperature and magnetic field are lowered. The logarithmic magnetization relaxation curves Pm(t) for fixed temperature and different external magnetic field inductions B are given. The relaxation rate dependence on magnetic field, R(B) = dPm(B, T sub O)/d(1nt) has a sharp maximum which is similar to that found for R(T) temperature dependences. The maximum shifts to lower fields as temperature goes up. The observed sharp maximum is related to a topological transition in shielding critical current distribution and, consequently, in Abrikosov vortices density. The nonlogarithmic magnetization relaxation for the initial time intervals is found. This fast relaxation has almost an exponentional character. The sharp relaxation rate R(B) maximum is observed. This maximum corresponds to a topological transition in Abrikosov vortices distribution.

Linear quadratic tracking problems in Hilbert space - Application to optimal active noise suppression

NASA Technical Reports Server (NTRS)

Banks, H. T.; Silcox, R. J.; Keeling, S. L.; Wang, C.

1989-01-01

A unified treatment of the linear quadratic tracking (LQT) problem, in which a control system's dynamics are modeled by a linear evolution equation with a nonhomogeneous component that is linearly dependent on the control function u, is presented; the treatment proceeds from the theoretical formulation to a numerical approximation framework. Attention is given to two categories of LQT problems in an infinite time interval: the finite energy and the finite average energy. The behavior of the optimal solution for finite time-interval problems as the length of the interval tends to infinity is discussed. Also presented are the formulations and properties of LQT problems in a finite time interval.

Outcome-Dependent Sampling with Interval-Censored Failure Time Data

PubMed Central

Zhou, Qingning; Cai, Jianwen; Zhou, Haibo

2017-01-01

Summary Epidemiologic studies and disease prevention trials often seek to relate an exposure variable to a failure time that suffers from interval-censoring. When the failure rate is low and the time intervals are wide, a large cohort is often required so as to yield reliable precision on the exposure-failure-time relationship. However, large cohort studies with simple random sampling could be prohibitive for investigators with a limited budget, especially when the exposure variables are expensive to obtain. Alternative cost-effective sampling designs and inference procedures are therefore desirable. We propose an outcome-dependent sampling (ODS) design with interval-censored failure time data, where we enrich the observed sample by selectively including certain more informative failure subjects. We develop a novel sieve semiparametric maximum empirical likelihood approach for fitting the proportional hazards model to data from the proposed interval-censoring ODS design. This approach employs the empirical likelihood and sieve methods to deal with the infinite-dimensional nuisance parameters, which greatly reduces the dimensionality of the estimation problem and eases the computation difficulty. The consistency and asymptotic normality of the resulting regression parameter estimator are established. The results from our extensive simulation study show that the proposed design and method works well for practical situations and is more efficient than the alternative designs and competing approaches. An example from the Atherosclerosis Risk in Communities (ARIC) study is provided for illustration. PMID:28771664

Multifactor analysis of multiscaling in volatility return intervals.

PubMed

Wang, Fengzhong; Yamasaki, Kazuko; Havlin, Shlomo; Stanley, H Eugene

2009-01-01

We study the volatility time series of 1137 most traded stocks in the U.S. stock markets for the two-year period 2001-2002 and analyze their return intervals tau , which are time intervals between volatilities above a given threshold q . We explore the probability density function of tau , P_(q)(tau) , assuming a stretched exponential function, P_(q)(tau) approximately e;(-tau;(gamma)) . We find that the exponent gamma depends on the threshold in the range between q=1 and 6 standard deviations of the volatility. This finding supports the multiscaling nature of the return interval distribution. To better understand the multiscaling origin, we study how gamma depends on four essential factors, capitalization, risk, number of trades, and return. We show that gamma depends on the capitalization, risk, and return but almost does not depend on the number of trades. This suggests that gamma relates to the portfolio selection but not on the market activity. To further characterize the multiscaling of individual stocks, we fit the moments of tau , mu_(m) identical with(tautau);(m);(1m) , in the range of 10

Multifactor analysis of multiscaling in volatility return intervals

NASA Astrophysics Data System (ADS)

Wang, Fengzhong; Yamasaki, Kazuko; Havlin, Shlomo; Stanley, H. Eugene

2009-01-01

We study the volatility time series of 1137 most traded stocks in the U.S. stock markets for the two-year period 2001-2002 and analyze their return intervals τ , which are time intervals between volatilities above a given threshold q . We explore the probability density function of τ , Pq(τ) , assuming a stretched exponential function, Pq(τ)˜e-τγ . We find that the exponent γ depends on the threshold in the range between q=1 and 6 standard deviations of the volatility. This finding supports the multiscaling nature of the return interval distribution. To better understand the multiscaling origin, we study how γ depends on four essential factors, capitalization, risk, number of trades, and return. We show that γ depends on the capitalization, risk, and return but almost does not depend on the number of trades. This suggests that γ relates to the portfolio selection but not on the market activity. To further characterize the multiscaling of individual stocks, we fit the moments of τ , μm≡⟨(τ/⟨τ⟩)m⟩1/m , in the range of 10<⟨τ⟩⩽100 by a power law, μm˜⟨τ⟩δ . The exponent δ is found also to depend on the capitalization, risk, and return but not on the number of trades, and its tendency is opposite to that of γ . Moreover, we show that δ decreases with increasing γ approximately by a linear relation. The return intervals demonstrate the temporal structure of volatilities and our findings suggest that their multiscaling features may be helpful for portfolio optimization.

A new variable interval schedule with constant hazard rate and finite time range.

PubMed

Bugallo, Mehdi; Machado, Armando; Vasconcelos, Marco

2018-05-27

We propose a new variable interval (VI) schedule that achieves constant probability of reinforcement in time while using a bounded range of intervals. By sampling each trial duration from a uniform distribution ranging from 0 to 2 T seconds, and then applying a reinforcement rule that depends linearly on trial duration, the schedule alternates reinforced and unreinforced trials, each less than 2 T seconds, while preserving a constant hazard function. © 2018 Society for the Experimental Analysis of Behavior.

Temporal Integration of Auditory Information Is Invariant to Temporal Grouping Cues

PubMed

Liu, Andrew S K; Tsunada, Joji; Gold, Joshua I; Cohen, Yale E

2015-01-01

Auditory perception depends on the temporal structure of incoming acoustic stimuli. Here, we examined whether a temporal manipulation that affects the perceptual grouping also affects the time dependence of decisions regarding those stimuli. We designed a novel discrimination task that required human listeners to decide whether a sequence of tone bursts was increasing or decreasing in frequency. We manipulated temporal perceptual-grouping cues by changing the time interval between the tone bursts, which led to listeners hearing the sequences as a single sound for short intervals or discrete sounds for longer intervals. Despite these strong perceptual differences, this manipulation did not affect the efficiency of how auditory information was integrated over time to form a decision. Instead, the grouping manipulation affected subjects' speed-accuracy trade-offs. These results indicate that the temporal dynamics of evidence accumulation for auditory perceptual decisions can be invariant to manipulations that affect the perceptual grouping of the evidence.

Time‐dependent renewal‐model probabilities when date of last earthquake is unknown

USGS Publications Warehouse

Field, Edward H.; Jordan, Thomas H.

2015-01-01

We derive time-dependent, renewal-model earthquake probabilities for the case in which the date of the last event is completely unknown, and compare these with the time-independent Poisson probabilities that are customarily used as an approximation in this situation. For typical parameter values, the renewal-model probabilities exceed Poisson results by more than 10% when the forecast duration exceeds ~20% of the mean recurrence interval. We also derive probabilities for the case in which the last event is further constrained to have occurred before historical record keeping began (the historic open interval), which can only serve to increase earthquake probabilities for typically applied renewal models.We conclude that accounting for the historic open interval can improve long-term earthquake rupture forecasts for California and elsewhere.

Baseline-dependent sampling and windowing for radio interferometry: data compression, field-of-interest shaping, and outer field suppression

NASA Astrophysics Data System (ADS)

Atemkeng, M.; Smirnov, O.; Tasse, C.; Foster, G.; Keimpema, A.; Paragi, Z.; Jonas, J.

2018-07-01

Traditional radio interferometric correlators produce regular-gridded samples of the true uv-distribution by averaging the signal over constant, discrete time-frequency intervals. This regular sampling and averaging then translate to be irregular-gridded samples in the uv-space, and results in a baseline-length-dependent loss of amplitude and phase coherence, which is dependent on the distance from the image phase centre. The effect is often referred to as `decorrelation' in the uv-space, which is equivalent in the source domain to `smearing'. This work discusses and implements a regular-gridded sampling scheme in the uv-space (baseline-dependent sampling) and windowing that allow for data compression, field-of-interest shaping, and source suppression. The baseline-dependent sampling requires irregular-gridded sampling in the time-frequency space, i.e. the time-frequency interval becomes baseline dependent. Analytic models and simulations are used to show that decorrelation remains constant across all the baselines when applying baseline-dependent sampling and windowing. Simulations using MeerKAT telescope and the European Very Long Baseline Interferometry Network show that both data compression, field-of-interest shaping, and outer field-of-interest suppression are achieved.

Impurity transport in fractal media in the presence of a degrading diffusion barrier

NASA Astrophysics Data System (ADS)

Kondratenko, P. S.; Leonov, K. V.

2017-08-01

We have analyzed the transport regimes and the asymptotic forms of the impurity concentration in a randomly inhomogeneous fractal medium in the case when an impurity source is surrounded by a weakly permeable degrading barrier. The systematization of transport regimes depends on the relation between the time t 0 of emergence of impurity from the barrier and time t * corresponding to the beginning of degradation. For t 0 < t *, degradation processes are immaterial. In the opposite situation, when t 0 > t *, the results on time intervals t < t * can be formally reduced to the problem with a stationary barrier. The characteristics of regimes with t * < t < t 0 depend on the scenario of barrier degradation. For an exponentially fast scenario, the interval t * < t < t 0 is very narrow, and the transport regime occurring over time intervals t < t * passes almost jumpwise to the regime of the problem without a barrier. In the slow power-law scenario, the transport over long time interval t * < t < t 0 occurs in a new regime, which is faster as compared to the problem with a stationary barrier, but slower than in the problem without a barrier. The asymptotic form of the concentration at large distances from the source over time intervals t < t 0 has two steps, while for t > t 0, it has only one step. The more remote step for t < t 0 and the single step for t > t 0 coincide with the asymptotic form in the problem without a barrier.

[Estimation of the atrioventricular time interval by pulse Doppler in the normal fetal heart].

PubMed

Hamela-Olkowska, Anita; Dangel, Joanna

2009-08-01

To assess normative values of the fetal atrioventricular (AV) time interval by pulse-wave Doppler methods on 5-chamber view. Fetal echocardiography exams were performed using Acuson Sequoia 512 in 140 singleton fetuses at 18 to 40 weeks of gestation with sinus rhythm and normal cardiac and extracardiac anatomy. Pulsed Doppler derived AV intervals were measured from left ventricular inflow/outflow view using transabdominal convex 3.5-6 MHz probe. The values of AV time interval ranged from 100 to 150 ms (mean 123 +/- 11.2). The AV interval was negatively correlated with the heart rhythm (p<0.001). Fetal heart rate decreased as gestation progressed (p<0.001). Thus, the AV intervals increased with the age of gestation (p=0.007). However, in the same subgroup of the fetal heart rate there was no relation between AV intervals and gestational age. Therefore, the AV intervals showed only the heart rate dependence. The 95th percentiles of AV intervals according to FHR ranged from 135 to 148 ms. 1. The AV interval duration was negatively correlated with the heart rhythm. 2. Measurement of AV time interval is easy to perform and has a good reproducibility. It may be used for the fetal heart block screening in anti-Ro and anti-La positive pregnancies. 3. Normative values established in the study may help obstetricians in assessing fetal abnormalities of the AV conduction.

Temporal Integration of Auditory Information Is Invariant to Temporal Grouping Cues1,2,3

PubMed Central

Tsunada, Joji

2015-01-01

Abstract Auditory perception depends on the temporal structure of incoming acoustic stimuli. Here, we examined whether a temporal manipulation that affects the perceptual grouping also affects the time dependence of decisions regarding those stimuli. We designed a novel discrimination task that required human listeners to decide whether a sequence of tone bursts was increasing or decreasing in frequency. We manipulated temporal perceptual-grouping cues by changing the time interval between the tone bursts, which led to listeners hearing the sequences as a single sound for short intervals or discrete sounds for longer intervals. Despite these strong perceptual differences, this manipulation did not affect the efficiency of how auditory information was integrated over time to form a decision. Instead, the grouping manipulation affected subjects’ speed−accuracy trade-offs. These results indicate that the temporal dynamics of evidence accumulation for auditory perceptual decisions can be invariant to manipulations that affect the perceptual grouping of the evidence. PMID:26464975

Determination of the Time-Space Magnetic Correlation Functions in the Solar Wind

NASA Astrophysics Data System (ADS)

Weygand, J. M.; Matthaeus, W. H.; Kivelson, M.; Dasso, S.

2013-12-01

Magnetic field data from many different intervals and 7 different solar wind spacecraft are employed to estimate the scale-dependent time decorrelation function in the interplanetary magnetic field in both the slow and fast solar wind. This estimation requires correlations varying with both space and time lags. The two point correlation function with no time lag is determined by correlating time series data from multiple spacecraft separated in space and for complete coverage of length scales relies on many intervals with different spacecraft spatial separations. In addition we employ single spacecraft time-lagged correlations, and two spacecraft time lagged correlations to access different spatial and temporal correlation data. Combining these data sets gives estimates of the scale-dependent time decorrelation function, which in principle tells us how rapidly time decorrelation occurs at a given wavelength. For static fields the scale-dependent time decorrelation function is trivially unity, but in turbulence the nonlinear cascade process induces time-decorrelation at a given length scale that occurs more rapidly with decreasing scale. The scale-dependent time decorrelation function is valuable input to theories as well as various applications such as scattering, transport, and study of predictability. It is also a fundamental element of formal turbulence theory. Our results are extension of the Eulerian correlation functions estimated in Matthaeus et al. [2010], Weygand et al [2012; 2013].

Waking and scrambling in holographic heating up

NASA Astrophysics Data System (ADS)

Ageev, D. S.; Aref'eva, I. Ya.

2017-10-01

Using holographic methods, we study the heating up process in quantum field theory. As a holographic dual of this process, we use absorption of a thin shell on a black brane. We find the explicit form of the time evolution of the quantum mutual information during heating up from the temperature Ti to the temperature T f in a system of two intervals in two-dimensional space-time. We determine the geometric characteristics of the system under which the time dependence of the mutual information has a bell shape: it is equal to zero at the initial instant, becomes positive at some subsequent instant, further attains its maximum, and again decreases to zero. Such a behavior of the mutual information occurs in the process of photosynthesis. We show that if the distance x between the intervals is less than log 2/2π T i, then the evolution of the holographic mutual information has a bell shape only for intervals whose lengths are bounded from above and below. For sufficiently large x, i.e., for x < log 2/2π T i, the bell-like shape of the time dependence of the quantum mutual information is present only for sufficiently large intervals. Moreover, the zone narrows as T i increases and widens as T f increases.

Filling the blanks in temporal intervals: the type of filling influences perceived duration and discrimination performance

PubMed Central

Horr, Ninja K.; Di Luca, Massimiliano

2015-01-01

In this work we investigate how judgments of perceived duration are influenced by the properties of the signals that define the intervals. Participants compared two auditory intervals that could be any combination of the following four types: intervals filled with continuous tones (filled intervals), intervals filled with regularly-timed short tones (isochronous intervals), intervals filled with irregularly-timed short tones (anisochronous intervals), and intervals demarcated by two short tones (empty intervals). Results indicate that the type of intervals to be compared affects discrimination performance and induces distortions in perceived duration. In particular, we find that duration judgments are most precise when comparing two isochronous and two continuous intervals, while the comparison of two anisochronous intervals leads to the worst performance. Moreover, we determined that the magnitude of the distortions in perceived duration (an effect akin to the filled duration illusion) is higher for tone sequences (no matter whether isochronous or anisochronous) than for continuous tones. Further analysis of how duration distortions depend on the type of filling suggests that distortions are not only due to the perceived duration of the two individual intervals, but they may also be due to the comparison of two different filling types. PMID:25717310

Optimal control of lift/drag ratios on a rotating cylinder

NASA Technical Reports Server (NTRS)

Ou, Yuh-Roung; Burns, John A.

1992-01-01

We present the numerical solution to a problem of maximizing the lift to drag ratio by rotating a circular cylinder in a two-dimensional viscous incompressible flow. This problem is viewed as a test case for the newly developing theoretical and computational methods for control of fluid dynamic systems. We show that the time averaged lift to drag ratio for a fixed finite-time interval achieves its maximum value at an optimal rotation rate that depends on the time interval.

Time-order errors and standard-position effects in duration discrimination: An experimental study and an analysis by the sensation-weighting model.

PubMed

Hellström, Åke; Rammsayer, Thomas H

2015-10-01

Studies have shown that the discriminability of successive time intervals depends on the presentation order of the standard (St) and the comparison (Co) stimuli. Also, this order affects the point of subjective equality. The first effect is here called the standard-position effect (SPE); the latter is known as the time-order error. In the present study, we investigated how these two effects vary across interval types and standard durations, using Hellström's sensation-weighting model to describe the results and relate them to stimulus comparison mechanisms. In Experiment 1, four modes of interval presentation were used, factorially combining interval type (filled, empty) and sensory modality (auditory, visual). For each mode, two presentation orders (St-Co, Co-St) and two standard durations (100 ms, 1,000 ms) were used; half of the participants received correctness feedback, and half of them did not. The interstimulus interval was 900 ms. The SPEs were negative (i.e., a smaller difference limen for St-Co than for Co-St), except for the filled-auditory and empty-visual 100-ms standards, for which a positive effect was obtained. In Experiment 2, duration discrimination was investigated for filled auditory intervals with four standards between 100 and 1,000 ms, an interstimulus interval of 900 ms, and no feedback. Standard duration interacted with presentation order, here yielding SPEs that were negative for standards of 100 and 1,000 ms, but positive for 215 and 464 ms. Our findings indicate that the SPE can be positive as well as negative, depending on the interval type and standard duration, reflecting the relative weighting of the stimulus information, as is described by the sensation-weighting model.

Place avoidance learning and memory in a jumping spider.

PubMed

Peckmezian, Tina; Taylor, Phillip W

2017-03-01

Using a conditioned passive place avoidance paradigm, we investigated the relative importance of three experimental parameters on learning and memory in a salticid, Servaea incana. Spiders encountered an aversive electric shock stimulus paired with one side of a two-sided arena. Our three parameters were the ecological relevance of the visual stimulus, the time interval between trials and the time interval before test. We paired electric shock with either a black or white visual stimulus, as prior studies in our laboratory have demonstrated that S. incana prefer dark 'safe' regions to light ones. We additionally evaluated the influence of two temporal features (time interval between trials and time interval before test) on learning and memory. Spiders exposed to the shock stimulus learned to associate shock with the visual background cue, but the extent to which they did so was dependent on which visual stimulus was present and the time interval between trials. Spiders trained with a long interval between trials (24 h) maintained performance throughout training, whereas spiders trained with a short interval (10 min) maintained performance only when the safe side was black. When the safe side was white, performance worsened steadily over time. There was no difference between spiders tested after a short (10 min) or long (24 h) interval before test. These results suggest that the ecological relevance of the stimuli used and the duration of the interval between trials can influence learning and memory in jumping spiders.

Time-dependent influence of sensorimotor set on automatic responses in perturbed stance

NASA Technical Reports Server (NTRS)

Chong, R. K.; Horak, F. B.; Woollacott, M. H.; Peterson, B. W. (Principal Investigator)

1999-01-01

These experiments tested the hypothesis that the ability to change sensorimotor set quickly for automatic responses depends on the time interval between successive surface perturbations. Sensorimotor set refers to the influence of prior experience or context on the state of the sensorimotor system. Sensorimotor set for postural responses was influenced by first giving subjects a block of identical backward translations of the support surface, causing forward sway and automatic gastrocnemius responses. The ability to change set quickly was inferred by measuring the suppression of the stretched antagonist gastrocnemius responses to toes-up rotations causing backward sway, following the translations. Responses were examined under short (10-14 s) and long (19-24 s) inter-trial intervals in young healthy subjects. The results showed that subjects in the long-interval group changed set immediately by suppressing gastrocnemius to 51% of translation responses within the first rotation and continued to suppress them over succeeding rotations. In contrast, subjects in the short-interval group did not change set immediately, but required two or more rotations to suppress gastrocnemius responses. By the last rotation, the short-interval group suppressed gastrocnemius responses to 33%, similar to the long-interval group of 29%. Associated surface plantarflexor torque resulting from these responses showed similar results. When rotation and translation perturbations alternated, however, the short-interval group was not able to suppress gastrocnemius responses to rotations as much as the long-interval group, although they did suppress more than in the first rotation trial after a series of translations. Set for automatic responses appears to linger, from one trial to the next. Specifically, sensorimotor set is more difficult to change when surface perturbations are given in close succession, making it appear as if set has become progressively stronger. A strong set does not mean that responses become larger over consecutive trials. Rather, it is inferred by the extent of difficulty in changing a response when it is appropriate to do so. These results suggest that the ability to change sensorimotor set quickly is sensitive to whether the change is required after a long or a short series of a prior different response, which in turn depends on the time interval between successive trials. Different rate of gastrocnemius suppression to toes-up rotation of the support surface have been reported in previous studies. This may be partially explained by different inter-trial time intervals demonstrated in this study.

Time-dependent limited penetrable visibility graph analysis of nonstationary time series

NASA Astrophysics Data System (ADS)

Gao, Zhong-Ke; Cai, Qing; Yang, Yu-Xuan; Dang, Wei-Dong

2017-06-01

Recent years have witnessed the development of visibility graph theory, which allows us to analyze a time series from the perspective of complex network. We in this paper develop a novel time-dependent limited penetrable visibility graph (TDLPVG). Two examples using nonstationary time series from RR intervals and gas-liquid flows are provided to demonstrate the effectiveness of our approach. The results of the first example suggest that our TDLPVG method allows characterizing the time-varying behaviors and classifying heart states of healthy, congestive heart failure and atrial fibrillation from RR interval time series. For the second example, we infer TDLPVGs from gas-liquid flow signals and interestingly find that the deviation of node degree of TDLPVGs enables to effectively uncover the time-varying dynamical flow behaviors of gas-liquid slug and bubble flow patterns. All these results render our TDLPVG method particularly powerful for characterizing the time-varying features underlying realistic complex systems from time series.

Fast transfer of crossmodal time interval training.

PubMed

Chen, Lihan; Zhou, Xiaolin

2014-06-01

Sub-second time perception is essential for many important sensory and perceptual tasks including speech perception, motion perception, motor coordination, and crossmodal interaction. This study investigates to what extent the ability to discriminate sub-second time intervals acquired in one sensory modality can be transferred to another modality. To this end, we used perceptual classification of visual Ternus display (Ternus in Psychol Forsch 7:81-136, 1926) to implicitly measure participants' interval perception in pre- and posttests and implemented an intra- or crossmodal sub-second interval discrimination training protocol in between the tests. The Ternus display elicited either an "element motion" or a "group motion" percept, depending on the inter-stimulus interval between the two visual frames. The training protocol required participants to explicitly compare the interval length between a pair of visual, auditory, or tactile stimuli with a standard interval or to implicitly perceive the length of visual, auditory, or tactile intervals by completing a non-temporal task (discrimination of auditory pitch or tactile intensity). Results showed that after fast explicit training of interval discrimination (about 15 min), participants improved their ability to categorize the visual apparent motion in Ternus displays, although the training benefits were mild for visual timing training. However, the benefits were absent for implicit interval training protocols. This finding suggests that the timing ability in one modality can be rapidly acquired and used to improve timing-related performance in another modality and that there may exist a central clock for sub-second temporal processing, although modality-specific perceptual properties may constrain the functioning of this clock.

Timing and Causality in the Generation of Learned Eyelid Responses

PubMed Central

Sánchez-Campusano, Raudel; Gruart, Agnès; Delgado-García, José M.

2011-01-01

The cerebellum-red nucleus-facial motoneuron (Mn) pathway has been reported as being involved in the proper timing of classically conditioned eyelid responses. This special type of associative learning serves as a model of event timing for studying the role of the cerebellum in dynamic motor control. Here, we have re-analyzed the firing activities of cerebellar posterior interpositus (IP) neurons and orbicularis oculi (OO) Mns in alert behaving cats during classical eyeblink conditioning, using a delay paradigm. The aim was to revisit the hypothesis that the IP neurons (IPns) can be considered a neuronal phase-modulating device supporting OO Mns firing with an emergent timing mechanism and an explicit correlation code during learned eyelid movements. Optimized experimental and computational tools allowed us to determine the different causal relationships (temporal order and correlation code) during and between trials. These intra- and inter-trial timing strategies expanding from sub-second range (millisecond timing) to longer-lasting ranges (interval timing) expanded the functional domain of cerebellar timing beyond motor control. Interestingly, the results supported the above-mentioned hypothesis. The causal inferences were influenced by the precise motor and pre-motor spike timing in the cause-effect interval, and, in addition, the timing of the learned responses depended on cerebellar–Mn network causality. Furthermore, the timing of CRs depended upon the probability of simulated causal conditions in the cause-effect interval and not the mere duration of the inter-stimulus interval. In this work, the close relation between timing and causality was verified. It could thus be concluded that the firing activities of IPns may be related more to the proper performance of ongoing CRs (i.e., the proper timing as a consequence of the pertinent causality) than to their generation and/or initiation. PMID:21941469

Fast temporal neural learning using teacher forcing

NASA Technical Reports Server (NTRS)

Toomarian, Nikzad (Inventor); Bahren, Jacob (Inventor)

1992-01-01

A neural network is trained to output a time dependent target vector defined over a predetermined time interval in response to a time dependent input vector defined over the same time interval by applying corresponding elements of the error vector, or difference between the target vector and the actual neuron output vector, to the inputs of corresponding output neurons of the network as corrective feedback. This feedback decreases the error and quickens the learning process, so that a much smaller number of training cycles are required to complete the learning process. A conventional gradient descent algorithm is employed to update the neural network parameters at the end of the predetermined time interval. The foregoing process is repeated in repetitive cycles until the actual output vector corresponds to the target vector. In the preferred embodiment, as the overall error of the neural network output decreasing during successive training cycles, the portion of the error fed back to the output neurons is decreased accordingly, allowing the network to learn with greater freedom from teacher forcing as the network parameters converge to their optimum values. The invention may also be used to train a neural network with stationary training and target vectors.

Fast temporal neural learning using teacher forcing

NASA Technical Reports Server (NTRS)

Toomarian, Nikzad (Inventor); Bahren, Jacob (Inventor)

1995-01-01

A neural network is trained to output a time dependent target vector defined over a predetermined time interval in response to a time dependent input vector defined over the same time interval by applying corresponding elements of the error vector, or difference between the target vector and the actual neuron output vector, to the inputs of corresponding output neurons of the network as corrective feedback. This feedback decreases the error and quickens the learning process, so that a much smaller number of training cycles are required to complete the learning process. A conventional gradient descent algorithm is employed to update the neural network parameters at the end of the predetermined time interval. The foregoing process is repeated in repetitive cycles until the actual output vector corresponds to the target vector. In the preferred embodiment, as the overall error of the neural network output decreasing during successive training cycles, the portion of the error fed back to the output neurons is decreased accordingly, allowing the network to learn with greater freedom from teacher forcing as the network parameters converge to their optimum values. The invention may also be used to train a neural network with stationary training and target vectors.

Discrimination of Variable Schedules Is Controlled by Interresponse Times Proximal to Reinforcement

ERIC Educational Resources Information Center

Tanno, Takayuki; Silberberg, Alan; Sakagami, Takayuki

2012-01-01

In Experiment 1, food-deprived rats responded to one of two schedules that were, with equal probability, associated with a sample lever. One schedule was always variable ratio, while the other schedule, depending on the trial within a session, was: (a) a variable-interval schedule; (b) a tandem variable-interval,…

Simulating transient dynamics of the time-dependent time fractional Fokker-Planck systems

NASA Astrophysics Data System (ADS)

Kang, Yan-Mei

2016-09-01

For a physically realistic type of time-dependent time fractional Fokker-Planck (FP) equation, derived as the continuous limit of the continuous time random walk with time-modulated Boltzmann jumping weight, a semi-analytic iteration scheme based on the truncated (generalized) Fourier series is presented to simulate the resultant transient dynamics when the external time modulation is a piece-wise constant signal. At first, the iteration scheme is demonstrated with a simple time-dependent time fractional FP equation on finite interval with two absorbing boundaries, and then it is generalized to the more general time-dependent Smoluchowski-type time fractional Fokker-Planck equation. The numerical examples verify the efficiency and accuracy of the iteration method, and some novel dynamical phenomena including polarized motion orientations and periodic response death are discussed.

Experiment Description and Results for Arrival Operations Using Interval Management with Spacing to Parallel Dependent Runways (IMSPiDR)

NASA Technical Reports Server (NTRS)

Baxley, Brian T.; Murdoch, Jennifer L.; Swieringa, Kurt A.; Barmore, Bryan E.; Capron, William R.; Hubbs, Clay E.; Shay, Richard F.; Abbott, Terence S.

2013-01-01

The predicted increase in the number of commercial aircraft operations creates a need for improved operational efficiency. Two areas believed to offer increases in aircraft efficiency are optimized profile descents and dependent parallel runway operations. Using Flight deck Interval Management (FIM) software and procedures during these operations, flight crews can achieve by the runway threshold an interval assigned by air traffic control (ATC) behind the preceding aircraft that maximizes runway throughput while minimizing additional fuel consumption and pilot workload. This document describes an experiment where 24 pilots flew arrivals into the Dallas Fort-Worth terminal environment using one of three simulators at NASA?s Langley Research Center. Results indicate that pilots delivered their aircraft to the runway threshold within +/- 3.5 seconds of their assigned time interval, and reported low workload levels. In general, pilots found the FIM concept, procedures, speeds, and interface acceptable. Analysis of the time error and FIM speed changes as a function of arrival stream position suggest the spacing algorithm generates stable behavior while in the presence of continuous (wind) or impulse (offset) error. Concerns reported included multiple speed changes within a short time period, and an airspeed increase followed shortly by an airspeed decrease.

The time dependent association of adrenaline administration and survival from out-of-hospital cardiac arrest.

PubMed

Ewy, Gordon A; Bobrow, Bentley J; Chikani, Vatsal; Sanders, Arthur B; Otto, Charles W; Spaite, Daniel W; Kern, Karl B

2015-11-01

Recommended for decades, the therapeutic value of adrenaline (epinephrine) in the resuscitation of patients with out-of-hospital cardiac arrest (OHCA) is controversial. To investigate the possible time-dependent outcomes associated with adrenaline administration by Emergency Medical Services personnel (EMS). A retrospective analysis of prospectively collected data from a near statewide cardiac resuscitation database between 1 January 2005 and 30 November 2013. Multivariable logistic regression was used to analyze the effect of the time interval between EMS dispatch and the initial dose of adrenaline on survival. The primary endpoints were survival to hospital discharge and favourable neurologic outcome. Data from 3469 patients with witnessed OHCA were analyzed. Their mean age was 66.3 years and 69% were male. An initially shockable rhythm was present in 41.8% of patients. Based on a multivariable logistic regression model with initial adrenaline administration time interval (AATI) from EMS dispatch as the covariate, survival was greatest when adrenaline was administered very early but decreased rapidly with increasing (AATI); odds ratio 0.94 (95% Confidence Interval (CI) 0.92-0.97). The AATI had no significant effect on good neurological outcome (OR=0.96, 95% CI=0.90-1.02). In patients with OHCA, survival to hospital discharge was greater in those treated early with adrenaline by EMS especially in the subset of patients with a shockable rhythm. However survival rapidly decreased with increasing adrenaline administration time intervals (AATI). Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Sleep-dependent consolidation benefits fast transfer of time interval training.

PubMed

Chen, Lihan; Guo, Lu; Bao, Ming

2017-03-01

Previous study has shown that short training (15 min) for explicitly discriminating temporal intervals between two paired auditory beeps, or between two paired tactile taps, can significantly improve observers' ability to classify the perceptual states of visual Ternus apparent motion while the training of task-irrelevant sensory properties did not help to improve visual timing (Chen and Zhou in Exp Brain Res 232(6):1855-1864, 2014). The present study examined the role of 'consolidation' after training of temporal task-irrelevant properties, or whether a pure delay (i.e., blank consolidation) following pretest of the target task would give rise to improved ability of visual interval timing, typified in visual Ternus display. A procedure of pretest-training-posttest was adopted, with the probe of discriminating Ternus apparent motion. The extended implicit training of timing in which the time intervals between paired auditory beeps or paired tactile taps were manipulated but the task was discrimination of the auditory pitches or tactile intensities, did not lead to the training benefits (Exps 1 and 3); however, a delay of 24 h after implicit training of timing, including solving 'Sudoku puzzles,' made the otherwise absent training benefits observable (Exps 2, 4, 5 and 6). The above improvements in performance were not due to a practice effect of Ternus motion (Exp 7). A general 'blank' consolidation period of 24 h also made improvements of visual timing observable (Exp 8). Taken together, the current findings indicated that sleep-dependent consolidation imposed a general effect, by potentially triggering and maintaining neuroplastic changes in the intrinsic (timing) network to enhance the ability of time perception.

Efficiency of time-lapse intervals and simple baits for camera surveys of wild pigs

USGS Publications Warehouse

Williams, B.L.; Holtfreter, R.W.; Ditchkoff, S.S.; Grand, J.B.

2011-01-01

Growing concerns surrounding established and expanding populations of wild pigs (Sus scrofa) have created the need for rapid and accurate surveys of these populations. We conducted surveys of a portion of the wild pig population on Fort Benning, Georgia, to determine if a longer time-lapse interval than had been previously used in surveys of wild pigs would generate similar detection results. We concurrently examined whether use of soured corn at camera sites affected the time necessary for pigs to locate a new camera site or the time pigs remained at a site. Our results suggest that a 9-min time-lapse interval generated dependable detection results for pigs and that soured corn neither attracted pigs to a site any quicker than plain, dry, whole-kernel corn, nor held them at a site longer. Maximization of time-lapse interval should decrease data and processing loads, and use of a simple, available bait should decrease cost and effort associated with more complicated baits; combination of these concepts should increase efficiency of wild pig surveys. ?? 2011 The Wildlife Society.

Delay-Dependent Stability Criterion for Bidirectional Associative Memory Neural Networks with Interval Time-Varying Delays

NASA Astrophysics Data System (ADS)

Park, Ju H.; Kwon, O. M.

In the letter, the global asymptotic stability of bidirectional associative memory (BAM) neural networks with delays is investigated. The delay is assumed to be time-varying and belongs to a given interval. A novel stability criterion for the stability is presented based on the Lyapunov method. The criterion is represented in terms of linear matrix inequality (LMI), which can be solved easily by various optimization algorithms. Two numerical examples are illustrated to show the effectiveness of our new result.

Relative frequencies of seismic main shocks after strong shocks in Italy

NASA Astrophysics Data System (ADS)

Gasperini, Paolo; Lolli, Barbara; Vannucci, Gianfranco

2016-10-01

We analysed a catalogue of Italian earthquakes, covering 55 yr of data from 1960 to 2014 with magnitudes homogeneously converted to Mw, to compute the time-dependent relative frequencies with which strong seismic shocks (4.0 ≤ Mw < 5.0), widely felt by the population, have been followed by main shocks (Mw ≥ 5.0) that threatened the health and the properties of the persons living in the epicentral area. Assuming the stationarity of the seismic release properties, such frequencies are estimates of the probabilities of potentially destructive shocks after the occurrence of future strong shocks. We compared them with the time-independent relative frequencies of random occurrence in terms of the frequency gain that is the ratio between the time-dependent and time-independent relative frequencies. The time-dependent relative frequencies vary from less than 1 per cent to about 20 per cent, depending on the magnitudes of the shocks and the time windows considered (ranging from minutes to years). They remain almost constant for a few hours after the strong shock and then decrease with time logarithmically. Strong earthquakes (with Mw ≥ 6.0) mainly occurred within two or three months of the strong shock. The frequency gains vary from about 10 000 for very short time intervals to less than 10 for a time interval of 2 yr. Only about 1/3 of main shocks were preceded by at least a strong shock in the previous day and about 1/2 in the previous month.

A Role for Memory in Prospective Timing informs Timing in Prospective Memory

PubMed Central

Waldum, Emily R; Sahakyan, Lili

2014-01-01

Time-based prospective memory (TBPM) tasks require the estimation of time in passing – known as prospective timing. Prospective timing is said to depend on an attentionally-driven internal clock mechanism, and is thought to be unaffected by memory for interval information (for reviews see, Block, Hancock, & Zakay, 2010; Block & Zakay, 1997). A prospective timing task that required a verbal estimate following the entire interval (Experiment 1) and a TBPM task that required production of a target response during the interval (Experiment 2) were used to test an alternative view that episodic memory does influence prospective timing. In both experiments, participants performed an ongoing lexical decision task of fixed duration while a varying number of songs were played in the background. Experiment 1 results revealed that verbal time estimates became longer the more songs participants remembered from the interval, suggesting that memory for interval information influences prospective time estimates. In Experiment 2, participants who were asked to perform the TBPM task without the aid of an external clock made their target responses earlier as the number of songs increased, indicating that prospective estimates of elapsed time increased as more songs were experienced. For participants who had access to a clock, changes in clock-checking coincided with the occurrence of song boundaries, indicating that participants used both song information and clock information to estimate time. Finally, ongoing task performance and verbal reports in both experiments further substantiate a role for episodic memory in prospective timing. PMID:22984950

Modeling the Formation of Hydrate-Filled Veins in Fine-Grained Sediments from in Situ Microbial Methane

NASA Astrophysics Data System (ADS)

Malinverno, A.; Cook, A.; Daigle, H.

2016-12-01

Continental margin sediments are dominantly fine-grained silt and clay, and methane hydrates in these sediments are often found in semi-vertical veins and fractures. In several instances, these hydrate veins occupy discrete depth intervals that are a few tens of meters thick and are surrounded by hydrate-free sediments. As they are not connected with gas sources beneath the base of the gas hydrate stability zone (GHSZ), these isolated hydrate-bearing intervals have been interpreted as formed by in situ microbial methane. To investigate the formation of these hydrate deposits, we applied a time-dependent advection-diffusion-reaction model that includes the effects of sedimentation, compaction, solute diffusion, and microbial methane generation. Microbial methane generation depends on the amount of metabolizable organic carbon deposited at the seafloor, whose progressive degradation produces methane beneath the sulfate reduction zone. If the amount of organic carbon entering the methanogenic zone is kept constant in time, we found that the computed amounts of hydrate formed in discrete intervals within the GHSZ are well below those estimated from observations. On the other hand, if the deposition of organic carbon is higher in a given time interval, methane generation during burial is more intense in the corresponding sediment interval, resulting in enhanced hydrate formation. With variations in organic carbon deposition comparable to those generally observed in continental margins, our model was able to reproduce the methane hydrate contents that were estimated from drilling. These results support the suggestion that in situ microbial generation associated with transient organic carbon deposition is the source of methane that forms isolated intervals of hydrate-filled veins in fine-grained sediments.

Modeling the Formation of Hydrate-Filled Veins in Fine-Grained Sediments from in Situ Microbial Methane

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

Malinverno, Alberto; Cook, Ann; Daigle, Hugh

Continental margin sediments are dominantly fine-grained silt and clay, and methane hydrates in these sediments are often found in semi-vertical veins and fractures. In several instances, these hydrate veins occupy discrete depth intervals that are a few tens of meters thick and are surrounded by hydrate-free sediments. As they are not connected with gas sources beneath the base of the gas hydrate stability zone (GHSZ), these isolated hydrate-bearing intervals have been interpreted as formed by in situ microbial methane. To investigate the formation of these hydrate deposits, we applied a time-dependent advection-diffusion-reaction model that includes the effects of sedimentation, compaction,more » solute diffusion, and microbial methane generation. Microbial methane generation depends on the amount of metabolizable organic carbon deposited at the seafloor, whose progressive degradation produces methane beneath the sulfate reduction zone. If the amount of organic carbon entering the methanogenic zone is kept constant in time, we found that the computed amounts of hydrate formed in discrete intervals within the GHSZ are well below those estimated from observations. On the other hand, if the deposition of organic carbon is higher in a given time interval, methane generation during burial is more intense in the corresponding sediment interval, resulting in enhanced hydrate formation. With variations in organic carbon deposition comparable to those generally observed in continental margins, our model was able to reproduce the methane hydrate contents that were estimated from drilling. These results support the suggestion that in situ microbial generation associated with transient organic carbon deposition is the source of methane that forms isolated intervals of hydrate-filled veins in fine-grained sediments.« less

Fall risk as a function of time after admission to sub-acute geriatric hospital units.

PubMed

Rapp, Kilian; Ravindren, Johannes; Becker, Clemens; Lindemann, Ulrich; Jaensch, Andrea; Klenk, Jochen

2016-10-07

There is evidence about time-dependent fracture rates in different settings and situations. Lacking are data about underlying time-dependent fall risk patterns. The objective of the study was to analyse fall rates as a function of time after admission to sub-acute hospital units and to evaluate the time-dependent impact of clinical factors at baseline on fall risk. This retrospective cohort study used data of 5,255 patients admitted to sub-acute units in a geriatric rehabilitation clinic in Germany between 2010 and 2014. Falls, personal characteristics and functional status at admission were extracted from the hospital information system. The rehabilitation stay was divided in 3-day time-intervals. The fall rate was calculated for each time-interval in all patients combined and in subgroups of patients. To analyse the influence of covariates on fall risk over time multivariate negative binomial regression models were applied for each of 5 time-intervals. The overall fall rate was 10.2 falls/1,000 person-days with highest fall risks during the first week and decreasing risks within the following weeks. A particularly pronounced risk pattern with high fall risks during the first days and decreasing risks thereafter was observed in men, disoriented people, and people with a low functional status or impaired cognition. In disoriented patients, for example, the fall rate decreased from 24.6 falls/1,000 person-days in day 2-4 to about 13 falls/1,000 person-days 2 weeks later. The incidence rate ratio of baseline characteristics changed also over time. Fall risk differs considerably over time during sub-acute hospitalisation. The strongest association between time and fall risk was observed in functionally limited patients with high risks during the first days after admission and declining risks thereafter. This should be considered in the planning and application of fall prevention measures.

Battery and capacitor technology for uniform charge time in implantable cardioverter-defibrillators

NASA Astrophysics Data System (ADS)

Skarstad, Paul M.

Implantable cardioverter-defibrillators (ICDs) are implantable medical devices designed to treat ventricular fibrillation by administering a high-voltage shock directly to the heart. Minimizing the time a patient remains in fibrillation is an important goal of this therapy. Both batteries and high-voltage capacitors used in these devices can display time-dependency in performance, resulting in significant extension of charge time. Altering the electrode balance in lithium/silver vanadium oxide batteries used to power these devices has minimized time-dependent changes in battery resistance. Charge-interval dependent changes in capacitor cycling efficiency have been minimized for stacked-plate aluminum electrolytic capacitors by a combination of material and processing factors.

A Variable Oscillator Underlies the Measurement of Time Intervals in the Rostral Medial Prefrontal Cortex during Classical Eyeblink Conditioning in Rabbits.

PubMed

Caro-Martín, C Rocío; Leal-Campanario, Rocío; Sánchez-Campusano, Raudel; Delgado-García, José M; Gruart, Agnès

2015-11-04

We were interested in determining whether rostral medial prefrontal cortex (rmPFC) neurons participate in the measurement of conditioned stimulus-unconditioned stimulus (CS-US) time intervals during classical eyeblink conditioning. Rabbits were conditioned with a delay paradigm consisting of a tone as CS. The CS started 50, 250, 500, 1000, or 2000 ms before and coterminated with an air puff (100 ms) directed at the cornea as the US. Eyelid movements were recorded with the magnetic search coil technique and the EMG activity of the orbicularis oculi muscle. Firing activities of rmPFC neurons were recorded across conditioning sessions. Reflex and conditioned eyelid responses presented a dominant oscillatory frequency of ≈12 Hz. The firing rate of each recorded neuron presented a single peak of activity with a frequency dependent on the CS-US interval (i.e., ≈12 Hz for 250 ms, ≈6 Hz for 500 ms, and≈3 Hz for 1000 ms). Interestingly, rmPFC neurons presented their dominant firing peaks at three precise times evenly distributed with respect to CS start and also depending on the duration of the CS-US interval (only for intervals of 250, 500, and 1000 ms). No significant neural responses were recorded at very short (50 ms) or long (2000 ms) CS-US intervals. rmPFC neurons seem not to encode the oscillatory properties characterizing conditioned eyelid responses in rabbits, but are probably involved in the determination of CS-US intervals of an intermediate range (250-1000 ms). We propose that a variable oscillator underlies the generation of working memories in rabbits. The way in which brains generate working memories (those used for the transient processing and storage of newly acquired information) is still an intriguing question. Here, we report that the firing activities of neurons located in the rostromedial prefrontal cortex recorded in alert behaving rabbits are controlled by a dynamic oscillator. This oscillator generated firing frequencies in a variable band of 3-12 Hz depending on the conditioned stimulus-unconditioned stimulus intervals (1 s, 500 ms, 250 ms) selected for classical eyeblink conditioning of behaving rabbits. Shorter (50 ms) and longer (2 s) intervals failed to activate the oscillator and prevented the acquisition of conditioned eyelid responses. This is an unexpected mechanism to generate sustained firing activities in neural circuits generating working memories. Copyright © 2015 the authors 0270-6474/15/3514809-13$15.00/0.

C-reactive protein-to-albumin ratio is a predictor of hepatitis B virus related decompensated cirrhosis: time-dependent receiver operating characteristics and decision curve analysis.

PubMed

Huang, Si-Si; Xie, Dong-Mei; Cai, Yi-Jing; Wu, Jian-Min; Chen, Rui-Chong; Wang, Xiao-Dong; Song, Mei; Zheng, Ming-Hua; Wang, Yu-Qun; Lin, Zhuo; Shi, Ke-Qing

2017-04-01

Hepatitis B virus (HBV) infection remains a major health problem and HBV-related-decompensated cirrhosis (HBV-DC) usually leads to a poor prognosis. Our aim was to determine the utility of inflammatory biomarkers in predicting mortality of HBV-DC. A total of 329 HBV-DC patients were enrolled. Survival estimates for the entire study population were generated using the Kaplan-Meier method. The prognostic values for model for end-stage liver disease (MELD) score, Child-Pugh score, and inflammatory biomarkers neutrophil/lymphocyte ratio, C-reactive protein-to-albumin ratio (CAR), and lymphocyte-to-monocyte ratio (LMR) for HBV-DC were compared using time-dependent receiver operating characteristic curves and time-dependent decision curves. The survival time was 23.1±15.8 months. Multivariate analysis identified age, CAR, LMR, and platelet count as prognostic independent risk factors. Kaplan-Meier analysis indicated that CAR of at least 1.0 (hazard ratio, 7.19; 95% confidence interval, 4.69-11.03), and LMR less than 1.9 (hazard ratio, 2.40; 95% confidence interval, 1.69-3.41) were independently associated with mortality of HBV-DC. The time-dependent receiver operating characteristic indicated that CAR showed the best performance in predicting mortality of HBV-DC compared with LMR, MELD score, and Child-Pugh score. The results were also confirmed by time-dependent decision curves. CAR and LMR were associated with the prognosis of HBV-DC. CAR was superior to LMR, MELD score, and Child-Pugh score in HBV-DC mortality prediction.

Cryptocurrency price drivers: Wavelet coherence analysis revisited

PubMed Central

2018-01-01

Cryptocurrencies have experienced recent surges in interest and price. It has been discovered that there are time intervals where cryptocurrency prices and certain online and social media factors appear related. In addition it has been noted that cryptocurrencies are prone to experience intervals of bubble-like price growth. The hypothesis investigated here is that relationships between online factors and price are dependent on market regime. In this paper, wavelet coherence is used to study co-movement between a cryptocurrency price and its related factors, for a number of examples. This is used alongside a well-known test for financial asset bubbles to explore whether relationships change dependent on regime. The primary finding of this work is that medium-term positive correlations between online factors and price strengthen significantly during bubble-like regimes of the price series; this explains why these relationships have previously been seen to appear and disappear over time. A secondary finding is that short-term relationships between the chosen factors and price appear to be caused by particular market events (such as hacks / security breaches), and are not consistent from one time interval to another in the effect of the factor upon the price. In addition, for the first time, wavelet coherence is used to explore the relationships between different cryptocurrencies. PMID:29668765

Cryptocurrency price drivers: Wavelet coherence analysis revisited.

PubMed

Phillips, Ross C; Gorse, Denise

2018-01-01

Cryptocurrencies have experienced recent surges in interest and price. It has been discovered that there are time intervals where cryptocurrency prices and certain online and social media factors appear related. In addition it has been noted that cryptocurrencies are prone to experience intervals of bubble-like price growth. The hypothesis investigated here is that relationships between online factors and price are dependent on market regime. In this paper, wavelet coherence is used to study co-movement between a cryptocurrency price and its related factors, for a number of examples. This is used alongside a well-known test for financial asset bubbles to explore whether relationships change dependent on regime. The primary finding of this work is that medium-term positive correlations between online factors and price strengthen significantly during bubble-like regimes of the price series; this explains why these relationships have previously been seen to appear and disappear over time. A secondary finding is that short-term relationships between the chosen factors and price appear to be caused by particular market events (such as hacks / security breaches), and are not consistent from one time interval to another in the effect of the factor upon the price. In addition, for the first time, wavelet coherence is used to explore the relationships between different cryptocurrencies.

Linear time-dependent reference intervals where there is measurement error in the time variable-a parametric approach.

PubMed

Gillard, Jonathan

2015-12-01

This article re-examines parametric methods for the calculation of time specific reference intervals where there is measurement error present in the time covariate. Previous published work has commonly been based on the standard ordinary least squares approach, weighted where appropriate. In fact, this is an incorrect method when there are measurement errors present, and in this article, we show that the use of this approach may, in certain cases, lead to referral patterns that may vary with different values of the covariate. Thus, it would not be the case that all patients are treated equally; some subjects would be more likely to be referred than others, hence violating the principle of equal treatment required by the International Federation for Clinical Chemistry. We show, by using measurement error models, that reference intervals are produced that satisfy the requirement for equal treatment for all subjects. © The Author(s) 2011.

ELECTRICAL LOAD ANTICIPATOR AND RECORDER

DOEpatents

Werme, J.E.

1961-09-01

A system is described in which an indication of the prevailing energy consumption in an electrical power metering system and a projected power demand for one demand in terval is provided at selected increments of time within the demand interval. Each watt-hour meter in the system is provided with an impulse generator that generates two impulses for each revolution of the meter disc. In each demand interval, for example, one half-hour, of the metering system, the total impulses received from all of the meters are continuously totaled for each 5-minute interval and multiplied by a number from 6 to 1 depending upon which 5- minute interval the impulses were received. This value is added to the total pulses received in the intervals preceding the current 5-minute interval within the half-hour demand interval tc thereby provide an indication of the projected power demand every 5 minutes in the demand interval.

Thermomechanical treatment of alloys

DOEpatents

Bates, John F.; Brager, Howard R.; Paxton, Michael M.

1983-01-01

An article of an alloy of AISI 316 stainless steel is reduced in size to predetermined dimensions by cold working in repeated steps. Before the last reduction step the article is annealed by heating within a temperature range, specifically between 1010.degree. C. and 1038.degree. C. for a time interval between 90 and 60 seconds depending on the actual temperature. By this treatment the swelling under neutron bombardment by epithermal neutrons is reduced while substantial recrystallization does not occur in actual use for a time interval of at least of the order of 5000 hours.

An informational transition in conditioned Markov chains: Applied to genetics and evolution.

PubMed

Zhao, Lei; Lascoux, Martin; Waxman, David

2016-08-07

In this work we assume that we have some knowledge about the state of a population at two known times, when the dynamics is governed by a Markov chain such as a Wright-Fisher model. Such knowledge could be obtained, for example, from observations made on ancient and contemporary DNA, or during laboratory experiments involving long term evolution. A natural assumption is that the behaviour of the population, between observations, is related to (or constrained by) what was actually observed. The present work shows that this assumption has limited validity. When the time interval between observations is larger than a characteristic value, which is a property of the population under consideration, there is a range of intermediate times where the behaviour of the population has reduced or no dependence on what was observed and an equilibrium-like distribution applies. Thus, for example, if the frequency of an allele is observed at two different times, then for a large enough time interval between observations, the population has reduced or no dependence on the two observed frequencies for a range of intermediate times. Given observations of a population at two times, we provide a general theoretical analysis of the behaviour of the population at all intermediate times, and determine an expression for the characteristic time interval, beyond which the observations do not constrain the population's behaviour over a range of intermediate times. The findings of this work relate to what can be meaningfully inferred about a population at intermediate times, given knowledge of terminal states. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modeling the formation of methane hydrate-bearing intervals in fine-grained sediments

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

Malinverno, Alberto; Cook, Ann; Daigle, Hugh

Sediment grain size exerts a fundamental control on how methane hydrates are distributed within the pore space. Fine-grained muds are the predominant sediments in continental margins, and hydrates in these sediments have often been observed in semi-vertical veins and fractures. In several instances, these hydrate veins/fractures are found in discrete depth intervals a few tens meters thick within the gas hydrate stability zone (GHSZ) surrounded by hydrate-free sediments above and below. As they are not obviously connected with free gas occurring beneath the base of the GHSZ, these isolated hydrate-bearing intervals have been interpreted as formed by microbial methane generatedmore » in situ. To investigate further the formation of these hydrate deposits, we applied a time-dependent advection-diffusion-reaction model that includes the effects of sedimentation, solute diffusion, and microbial methane generation. The microbial methane generation term depends on the amount of metabolizable organic carbon deposited at the seafloor, which is degraded at a prescribed rate resulting in methane formation beneath the sulfate reduction zone. In the model, methane hydrate precipitates once the dissolved methane concentration is greater than solubility, or hydrate dissolves if concentration goes below solubility. If the deposition of organic carbon at the seafloor is kept constant in time, we found that the predicted amounts of hydrate formed in discrete intervals within the GHSZ are much less than those estimated from observations. We then investigated the effect of temporal variations in the deposition of organic carbon. If greater amounts of organic carbon are deposited during some time interval, methane generation is enhanced during burial in the corresponding sediment interval. With variations in organic carbon deposition that are consistent with observations in continental margin sediments, we were able to reproduce the methane hydrate contents estimated in discrete depth intervals. Our results support the suggestion that in situ microbial methane generation is the source for hydrates within fine-grained sediments.« less

Predictors of Functional Dependence Despite Successful Revascularization in Large-Vessel Occlusion Strokes

PubMed Central

Shi, Zhong-Song; Liebeskind, David S.; Xiang, Bin; Ge, Sijian Grace; Feng, Lei; Albers, Gregory W.; Budzik, Ronald; Devlin, Thomas; Gupta, Rishi; Jansen, Olav; Jovin, Tudor G.; Killer-Oberpfalzer, Monika; Lutsep, Helmi L.; Macho, Juan; Nogueira, Raul G.; Rymer, Marilyn; Smith, Wade S.; Wahlgren, Nils; Duckwiler, Gary R.

2014-01-01

Background and Purpose High revascularization rates in large-vessel occlusion strokes treated by mechanical thrombectomy are not always associated with good clinical outcomes. We evaluated predictors of functional dependence despite successful revascularization among patients with acute ischemic stroke treated with thrombectomy. Methods We analyzed the pooled data from the Multi Mechanical Embolus Removal in Cerebral Ischemia (MERCI), Thrombectomy Revascularization of Large Vessel Occlusions in Acute Ischemic Stroke (TREVO), and TREVO 2 trials. Successful revascularization was defined as thrombolysis in cerebral infarction score 2b or 3. Functional dependence was defined as a score of 3 to 6 on the modified Rankin Scale at 3 months. We assessed relationship of demographic, clinical, angiographic characteristics, and hemorrhage with functional dependence despite successful revascularization. Results Two hundred and twenty-eight patients with successful revascularization had clinical outcome follow-up. The rates of functional dependence with endovascular success were 48.6% for Trevo thrombectomy and 58.0% for Merci thrombectomy. Age (odds ratio, 1.04; 95% confidence interval, 1.02–1.06 per 1-year increase), National Institutes of Health Stroke Scale score (odds ratio, 1.08; 95% confidence interval, 1.02–1.15 per 1-point increase), and symptom onset to endovascular treatment time (odds ratio, 1.11; 95% confidence interval, 1.01–1.22 per 30-minute delay) were predictors of functional dependence despite successful revascularization. Symptom onset to reperfusion time beyond 5 hours was associated with functional dependence. All subjects with symptomatic intracranial hemorrhage had functional dependence. Conclusions One half of patients with successful mechanical thrombectomy do not have good outcomes. Age, severe neurological deficits, and delayed endovascular treatment were associated with functional dependence despite successful revascularization. Our data support efforts to minimize delays to endovascular therapy in patients with acute ischemic stroke to improve outcomes. PMID:24876082

Tobacco smoking trajectory and associated ethnic differences among adolescent smokers seeking cessation treatment.

PubMed

Robinson, Miqun L; Berlin, Ivan; Moolchan, Eric T

2004-09-01

To examine smoking trajectories in a clinical sample of adolescent smokers seeking cessation treatment, including: (a) smoking onset (initial, daily) and time intervals from initial to daily smoking and from daily smoking to treatment request, (b) associations between current level of tobacco dependence and smoking history, and (c) differences in smoking trajectory between African-American and non-African-American youth. Four hundred and thirty-two adolescent smokers (aged 13-17 years, 61.8% female, 32% African-American) responding to various media advertisement completed a telephone interview as part of pre-eligibility screening for a smoking cessation trial. Smoking trajectory data included age at onset of initial and daily smoking, intervals between those time points, and cigarettes smoked per day (CPD). Tobacco dependence was assessed using the Fagerström Test for Nicotine Dependence (FTND). Data were analyzed using regression models and multiple analyses of covariance. Initial smoking occurred at a mean age of less than 12 years and daily smoking at age 13 years. Earlier onset of daily smoking was associated with higher FTND scores and longer duration from daily smoking to treatment request. For the entire sample, the time interval from initial to daily smoking was 1.14 years. When the sample was divided into early (before age 14 years) and later (at or after age 14 years) initiators, early initiators showed a slower progression from initial to daily smoking compared with late initiators (16 months vs. 6 months). Compared with non-African-American teen smokers, African-American youth reported a 1-year delay in onset of both initial and daily smoking. Early age of daily smoking and short time interval from initial to daily smoking highlight a brief window of opportunity to prevent the development of tobacco addiction and its consequences. Ethnic differences in smoking trajectory uncovered in this report call for ethnically tailored interventions to reduce youth smoking.

Aging Effects on Cardiac and Respiratory Dynamics in Healthy Subjects across Sleep Stages

PubMed Central

Schumann, Aicko Y.; Bartsch, Ronny P.; Penzel, Thomas; Ivanov, Plamen Ch.; Kantelhardt, Jan W.

2010-01-01

Study Objectives: Respiratory and heart rate variability exhibit fractal scaling behavior on certain time scales. We studied the short-term and long-term correlation properties of heartbeat and breathing-interval data from disease-free subjects focusing on the age-dependent fractal organization. We also studied differences across sleep stages and night-time wake and investigated quasi-periodic variations associated with cardiac risk. Design: Full-night polysomnograms were recorded during 2 nights, including electrocardiogram and oronasal airflow. Setting: Data were collected in 7 laboratories in 5 European countries. Participants: 180 subjects without health complaints (85 males, 95 females) aged from 20 to 89 years. Interventions: None. Measurements and Results: Short-term correlations in heartbeat intervals measured by the detrended fluctuation analysis (DFA) exponent α1 show characteristic age dependence with a maximum around 50–60 years disregarding the dependence on sleep and wake states. Long-term correlations measured by α2 differ in NREM sleep when compared with REM sleep and wake, besides weak age dependence. Results for respiratory intervals are similar to those for α2 of heartbeat intervals. Deceleration capacity (DC) decreases with age; it is lower during REM and deep sleep (compared with light sleep and wake). Conclusion: The age dependence of α1 should be considered when using this value for diagnostic purposes in post-infarction patients. Pronounced long-term correlations (larger α2) for heartbeat and respiration during REM sleep and wake indicate an enhanced control of higher brain regions, which is absent during NREM sleep. Reduced DC possibly indicates an increased cardiovascular risk with aging and during REM and deep sleep. Citation: Schumann AY; Bartsch RP; Penzel T; Ivanov PC; Kantelhardt JW. Aging effects on cardiac and respiratory dynamics in healthy subjects across sleep stages. SLEEP 2010;33(7):943-955. PMID:20614854

Recent progresses in outcome-dependent sampling with failure time data.

PubMed

Ding, Jieli; Lu, Tsui-Shan; Cai, Jianwen; Zhou, Haibo

2017-01-01

An outcome-dependent sampling (ODS) design is a retrospective sampling scheme where one observes the primary exposure variables with a probability that depends on the observed value of the outcome variable. When the outcome of interest is failure time, the observed data are often censored. By allowing the selection of the supplemental samples depends on whether the event of interest happens or not and oversampling subjects from the most informative regions, ODS design for the time-to-event data can reduce the cost of the study and improve the efficiency. We review recent progresses and advances in research on ODS designs with failure time data. This includes researches on ODS related designs like case-cohort design, generalized case-cohort design, stratified case-cohort design, general failure-time ODS design, length-biased sampling design and interval sampling design.

Recent progresses in outcome-dependent sampling with failure time data

PubMed Central

Ding, Jieli; Lu, Tsui-Shan; Cai, Jianwen; Zhou, Haibo

2016-01-01

An outcome-dependent sampling (ODS) design is a retrospective sampling scheme where one observes the primary exposure variables with a probability that depends on the observed value of the outcome variable. When the outcome of interest is failure time, the observed data are often censored. By allowing the selection of the supplemental samples depends on whether the event of interest happens or not and oversampling subjects from the most informative regions, ODS design for the time-to-event data can reduce the cost of the study and improve the efficiency. We review recent progresses and advances in research on ODS designs with failure time data. This includes researches on ODS related designs like case–cohort design, generalized case–cohort design, stratified case–cohort design, general failure-time ODS design, length-biased sampling design and interval sampling design. PMID:26759313

Seasonal variation in size-dependent survival of juvenile Atlantic salmon (Salmo salar): Performance of multistate capture-mark-recapture models

USGS Publications Warehouse

Letcher, B.H.; Horton, G.E.

2008-01-01

We estimated the magnitude and shape of size-dependent survival (SDS) across multiple sampling intervals for two cohorts of stream-dwelling Atlantic salmon (Salmo salar) juveniles using multistate capture-mark-recapture (CMR) models. Simulations designed to test the effectiveness of multistate models for detecting SDS in our system indicated that error in SDS estimates was low and that both time-invariant and time-varying SDS could be detected with sample sizes of >250, average survival of >0.6, and average probability of capture of >0.6, except for cases of very strong SDS. In the field (N ??? 750, survival 0.6-0.8 among sampling intervals, probability of capture 0.6-0.8 among sampling occasions), about one-third of the sampling intervals showed evidence of SDS, with poorer survival of larger fish during the age-2+ autumn and quadratic survival (opposite direction between cohorts) during age-1+ spring. The varying magnitude and shape of SDS among sampling intervals suggest a potential mechanism for the maintenance of the very wide observed size distributions. Estimating SDS using multistate CMR models appears complementary to established approaches, can provide estimates with low error, and can be used to detect intermittent SDS. ?? 2008 NRC Canada.

Intertime jump statistics of state-dependent Poisson processes.

PubMed

Daly, Edoardo; Porporato, Amilcare

2007-01-01

A method to obtain the probability distribution of the interarrival times of jump occurrences in systems driven by state-dependent Poisson noise is proposed. Such a method uses the survivor function obtained by a modified version of the master equation associated to the stochastic process under analysis. A model for the timing of human activities shows the capability of state-dependent Poisson noise to generate power-law distributions. The application of the method to a model for neuron dynamics and to a hydrological model accounting for land-atmosphere interaction elucidates the origin of characteristic recurrence intervals and possible persistence in state-dependent Poisson models.

A new time calibration method for switched-capacitor-array-based waveform samplers

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

Kim, H.; Chen, C. -T.; Eclov, N.

2014-08-24

Here we have developed a new time calibration method for the DRS4 waveform sampler that enables us to precisely measure the non-uniform sampling interval inherent in the switched-capacitor cells of the DRS4. The method uses the proportionality between the differential amplitude and sampling interval of adjacent switched-capacitor cells responding to a sawtooth-shape pulse. In the experiment, a sawtooth-shape pulse with a 40 ns period generated by a Tektronix AWG7102 is fed to a DRS4 evaluation board for calibrating the sampling intervals of all 1024 cells individually. The electronic time resolution of the DRS4 evaluation board with the new time calibrationmore » is measured to be ~2.4 ps RMS by using two simultaneous Gaussian pulses with 2.35 ns full-width at half-maximum and applying a Gaussian fit. The time resolution dependencies on the time difference with the new time calibration are measured and compared to results obtained by another method. Ultimately, the new method could be applicable for other switched-capacitor-array technology-based waveform samplers for precise time calibration.« less

A new time calibration method for switched-capacitor-array-based waveform samplers

NASA Astrophysics Data System (ADS)

Kim, H.; Chen, C.-T.; Eclov, N.; Ronzhin, A.; Murat, P.; Ramberg, E.; Los, S.; Moses, W.; Choong, W.-S.; Kao, C.-M.

2014-12-01

We have developed a new time calibration method for the DRS4 waveform sampler that enables us to precisely measure the non-uniform sampling interval inherent in the switched-capacitor cells of the DRS4. The method uses the proportionality between the differential amplitude and sampling interval of adjacent switched-capacitor cells responding to a sawtooth-shape pulse. In the experiment, a sawtooth-shape pulse with a 40 ns period generated by a Tektronix AWG7102 is fed to a DRS4 evaluation board for calibrating the sampling intervals of all 1024 cells individually. The electronic time resolution of the DRS4 evaluation board with the new time calibration is measured to be 2.4 ps RMS by using two simultaneous Gaussian pulses with 2.35 ns full-width at half-maximum and applying a Gaussian fit. The time resolution dependencies on the time difference with the new time calibration are measured and compared to results obtained by another method. The new method could be applicable for other switched-capacitor-array technology-based waveform samplers for precise time calibration.

A New Time Calibration Method for Switched-capacitor-array-based Waveform Samplers.

PubMed

Kim, H; Chen, C-T; Eclov, N; Ronzhin, A; Murat, P; Ramberg, E; Los, S; Moses, W; Choong, W-S; Kao, C-M

2014-12-11

We have developed a new time calibration method for the DRS4 waveform sampler that enables us to precisely measure the non-uniform sampling interval inherent in the switched-capacitor cells of the DRS4. The method uses the proportionality between the differential amplitude and sampling interval of adjacent switched-capacitor cells responding to a sawtooth-shape pulse. In the experiment, a sawtooth-shape pulse with a 40 ns period generated by a Tektronix AWG7102 is fed to a DRS4 evaluation board for calibrating the sampling intervals of all 1024 cells individually. The electronic time resolution of the DRS4 evaluation board with the new time calibration is measured to be ~2.4 ps RMS by using two simultaneous Gaussian pulses with 2.35 ns full-width at half-maximum and applying a Gaussian fit. The time resolution dependencies on the time difference with the new time calibration are measured and compared to results obtained by another method. The new method could be applicable for other switched-capacitor-array technology-based waveform samplers for precise time calibration.

A New Time Calibration Method for Switched-capacitor-array-based Waveform Samplers

PubMed Central

Kim, H.; Chen, C.-T.; Eclov, N.; Ronzhin, A.; Murat, P.; Ramberg, E.; Los, S.; Moses, W.; Choong, W.-S.; Kao, C.-M.

2014-01-01

We have developed a new time calibration method for the DRS4 waveform sampler that enables us to precisely measure the non-uniform sampling interval inherent in the switched-capacitor cells of the DRS4. The method uses the proportionality between the differential amplitude and sampling interval of adjacent switched-capacitor cells responding to a sawtooth-shape pulse. In the experiment, a sawtooth-shape pulse with a 40 ns period generated by a Tektronix AWG7102 is fed to a DRS4 evaluation board for calibrating the sampling intervals of all 1024 cells individually. The electronic time resolution of the DRS4 evaluation board with the new time calibration is measured to be ~2.4 ps RMS by using two simultaneous Gaussian pulses with 2.35 ns full-width at half-maximum and applying a Gaussian fit. The time resolution dependencies on the time difference with the new time calibration are measured and compared to results obtained by another method. The new method could be applicable for other switched-capacitor-array technology-based waveform samplers for precise time calibration. PMID:25506113

Effect of insertion method and postinsertion time interval prior to force application on the removal torque of orthodontic miniscrews.

PubMed

Sharifi, Maryam; Ghassemi, Amirreza; Bayani, Shahin

2015-01-01

Success of orthodontic miniscrews in providing stable anchorage is dependent on their stability. The purpose of this study was to assess the effect of insertion method and postinsertion time interval on the removal torque of miniscrews as an indicator of their stability. Seventy-two miniscrews (Jeil Medical) were inserted into the femoral bones of three male German Shepherd dogs and assigned to nine groups of eight miniscrews. Three insertion methods, including hand-driven, motor-driven with 5.0-Ncm insertion torque, and motor-driven with 20.0-Ncm insertion torque, were tested. Three time intervals of 0, 2, and 6 weeks between miniscrew insertion and removal were tested as well. Removal torque values were measured in newton centimeters by a removal torque tester (IMADA). Data were analyzed by one-way analysis of variance (ANOVA) followed by the Bonferroni post hoc test at a .05 level of significance. A miniscrew survival rate of 93% was observed in this study. The highest mean value of removal torque among the three postinsertion intervals (2.4 ± 0.59 Ncm) was obtained immediately after miniscrew insertion with a statistically significant difference from the other two time intervals (P < .001). Insertion were observed in this regard (P = .46). The stability of miniscrews was not affected by the insertion method. However, of the postinsertion time intervals, the highest removal torque values were obtained immediately after insertion.

Circadian Clocks for All Meal-Times: Anticipation of 2 Daily Meals in Rats

PubMed Central

Mistlberger, Ralph E.; Kent, Brianne A.; Chan, Sofina; Patton, Danica F.; Weinberg, Alexander; Parfyonov, Maksim

2012-01-01

Anticipation of a daily meal in rats has been conceptualized as a rest-activity rhythm driven by a food-entrained circadian oscillator separate from the pacemaker generating light-dark (LD) entrained rhythms. Rats can also anticipate two daily mealtimes, but whether this involves independently entrained oscillators, one ‘continuously consulted’ clock, cue-dependent non-circadian interval timing or a combination of processes, is unclear. Rats received two daily meals, beginning 3-h (meal 1) and 13-h (meal 2) after lights-on (LD 14∶10). Anticipatory wheel running began 68±8 min prior to meal 1 and 101±9 min prior to meal 2 but neither the duration nor the variability of anticipation bout lengths exhibited the scalar property, a hallmark of interval timing. Meal omission tests in LD and constant dark (DD) did not alter the timing of either bout of anticipation, and anticipation of meal 2 was not altered by a 3-h advance of meal 1. Food anticipatory running in this 2-meal protocol thus does not exhibit properties of interval timing despite the availability of external time cues in LD. Across all days, the two bouts of anticipation were uncorrelated, a result more consistent with two independently entrained oscillators than a single consulted clock. Similar results were obtained for meals scheduled 3-h and 10-h after lights-on, and for a food-bin measure of anticipation. Most rats that showed weak or no anticipation to one or both meals exhibited elevated activity at mealtime during 1 or 2 day food deprivation tests in DD, suggesting covert operation of circadian timing in the absence of anticipatory behavior. A control experiment confirmed that daytime feeding did not shift LD-entrained rhythms, ruling out displaced nocturnal activity as an explanation for daytime activity. The results favor a multiple oscillator basis for 2-meal anticipatory rhythms and provide no evidence for involvement of cue-dependent interval timing. PMID:22355393

A Semiparametric Approach for Composite Functional Mapping of Dynamic Quantitative Traits

PubMed Central

Yang, Runqing; Gao, Huijiang; Wang, Xin; Zhang, Ji; Zeng, Zhao-Bang; Wu, Rongling

2007-01-01

Functional mapping has emerged as a powerful tool for mapping quantitative trait loci (QTL) that control developmental patterns of complex dynamic traits. Original functional mapping has been constructed within the context of simple interval mapping, without consideration of separate multiple linked QTL for a dynamic trait. In this article, we present a statistical framework for mapping QTL that affect dynamic traits by capitalizing on the strengths of functional mapping and composite interval mapping. Within this so-called composite functional-mapping framework, functional mapping models the time-dependent genetic effects of a QTL tested within a marker interval using a biologically meaningful parametric function, whereas composite interval mapping models the time-dependent genetic effects of the markers outside the test interval to control the genome background using a flexible nonparametric approach based on Legendre polynomials. Such a semiparametric framework was formulated by a maximum-likelihood model and implemented with the EM algorithm, allowing for the estimation and the test of the mathematical parameters that define the QTL effects and the regression coefficients of the Legendre polynomials that describe the marker effects. Simulation studies were performed to investigate the statistical behavior of composite functional mapping and compare its advantage in separating multiple linked QTL as compared to functional mapping. We used the new mapping approach to analyze a genetic mapping example in rice, leading to the identification of multiple QTL, some of which are linked on the same chromosome, that control the developmental trajectory of leaf age. PMID:17947431

The steady part of the secular variation of the Earth's magnetic field

NASA Technical Reports Server (NTRS)

Bloxham, Jeremy

1992-01-01

The secular variation of the Earth's magnetic field results from the effects of magnetic induction in the fluid outer core and from the effects of magnetic diffusion in the core and the mantle. Adequate observations to map the magnetic field at the core-mantle boundary extend back over three centuries, providing a model of the secular variation at the core-mantle boundary. Here we consider how best to analyze this time-dependent part of the field. To calculate steady core flow over long time periods, we introduce an adaptation of our earlier method of calculating the flow in order to achieve greater numerical stability. We perform this procedure for the periods 1840-1990 and 1690-1840 and find that well over 90 percent of the variance of the time-dependent field can be explained by simple steady core flow. The core flows obtained for the two intervals are broadly similar to each other and to flows determined over much shorter recent intervals.

Time, rate, and conditioning.

PubMed

Gallistel, C R; Gibbon, J

2000-04-01

The authors draw together and develop previous timing models for a broad range of conditioning phenomena to reveal their common conceptual foundations: First, conditioning depends on the learning of the temporal intervals between events and the reciprocals of these intervals, the rates of event occurrence. Second, remembered intervals and rates translate into observed behavior through decision processes whose structure is adapted to noise in the decision variables. The noise and the uncertainties consequent on it have both subjective and objective origins. A third feature of these models is their timescale invariance, which the authors argue is a very important property evident in the available experimental data. This conceptual framework is similar to the psychophysical conceptual framework in which contemporary models of sensory processing are rooted. The authors contrast it with the associative conceptual framework.

A review of statistical issues with progression-free survival as an interval-censored time-to-event endpoint.

PubMed

Sun, Xing; Li, Xiaoyun; Chen, Cong; Song, Yang

2013-01-01

Frequent rise of interval-censored time-to-event data in randomized clinical trials (e.g., progression-free survival [PFS] in oncology) challenges statistical researchers in the pharmaceutical industry in various ways. These challenges exist in both trial design and data analysis. Conventional statistical methods treating intervals as fixed points, which are generally practiced by pharmaceutical industry, sometimes yield inferior or even flawed analysis results in extreme cases for interval-censored data. In this article, we examine the limitation of these standard methods under typical clinical trial settings and further review and compare several existing nonparametric likelihood-based methods for interval-censored data, methods that are more sophisticated but robust. Trial design issues involved with interval-censored data comprise another topic to be explored in this article. Unlike right-censored survival data, expected sample size or power for a trial with interval-censored data relies heavily on the parametric distribution of the baseline survival function as well as the frequency of assessments. There can be substantial power loss in trials with interval-censored data if the assessments are very infrequent. Such an additional dependency controverts many fundamental assumptions and principles in conventional survival trial designs, especially the group sequential design (e.g., the concept of information fraction). In this article, we discuss these fundamental changes and available tools to work around their impacts. Although progression-free survival is often used as a discussion point in the article, the general conclusions are equally applicable to other interval-censored time-to-event endpoints.

Photoinduced diffusion molecular transport

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

Rozenbaum, Viktor M., E-mail: vik-roz@mail.ru, E-mail: litrakh@gmail.com; Dekhtyar, Marina L.; Lin, Sheng Hsien

2016-08-14

We consider a Brownian photomotor, namely, the directed motion of a nanoparticle in an asymmetric periodic potential under the action of periodic rectangular resonant laser pulses which cause charge redistribution in the particle. Based on the kinetics for the photoinduced electron redistribution between two or three energy levels of the particle, the time dependence of its potential energy is derived and the average directed velocity is calculated in the high-temperature approximation (when the spatial amplitude of potential energy fluctuations is small relative to the thermal energy). The thus developed theory of photoinduced molecular transport appears applicable not only to conventionalmore » dichotomous Brownian motors (with only two possible potential profiles) but also to a much wider variety of molecular nanomachines. The distinction between the realistic time dependence of the potential energy and that for a dichotomous process (a step function) is represented in terms of relaxation times (they can differ on the time intervals of the dichotomous process). As shown, a Brownian photomotor has the maximum average directed velocity at (i) large laser pulse intensities (resulting in short relaxation times on laser-on intervals) and (ii) excited state lifetimes long enough to permit efficient photoexcitation but still much shorter than laser-off intervals. A Brownian photomotor with optimized parameters is exemplified by a cylindrically shaped semiconductor nanocluster which moves directly along a polar substrate due to periodically photoinduced dipole moment (caused by the repetitive excited electron transitions to a non-resonant level of the nanocylinder surface impurity).« less

Influence of the time scale on the construction of financial networks.

PubMed

Emmert-Streib, Frank; Dehmer, Matthias

2010-09-30

In this paper we investigate the definition and formation of financial networks. Specifically, we study the influence of the time scale on their construction. For our analysis we use correlation-based networks obtained from the daily closing prices of stock market data. More precisely, we use the stocks that currently comprise the Dow Jones Industrial Average (DJIA) and estimate financial networks where nodes correspond to stocks and edges correspond to none vanishing correlation coefficients. That means only if a correlation coefficient is statistically significant different from zero, we include an edge in the network. This construction procedure results in unweighted, undirected networks. By separating the time series of stock prices in non-overlapping intervals, we obtain one network per interval. The length of these intervals corresponds to the time scale of the data, whose influence on the construction of the networks will be studied in this paper. Numerical analysis of four different measures in dependence on the time scale for the construction of networks allows us to gain insights about the intrinsic time scale of the stock market with respect to a meaningful graph-theoretical analysis.

The Estimation of Short Time Intervals as a Function of Age and Metronome Pacing.

ERIC Educational Resources Information Center

Kline, Donald W.; And Others

1980-01-01

The time judgments of the older participants were significantly and systematically determined by a metronome rate. Results are consistent with the notion of increased field-dependence among older persons and suggest that their greater social conformity and their inability to ignore irrelevant stimuli might also be explicable. (Author)

Time-dependent Reliability of Dynamic Systems using Subset Simulation with Splitting over a Series of Correlated Time Intervals

DTIC Science & Technology

2013-08-01

cost due to potential warranty costs, repairs and loss of market share. Reliability is the probability that the system will perform its intended...MCMC and splitting sampling schemes. Our proposed SS/ STP method is presented in Section 4, including accuracy bounds and computational effort

Suppressive and Facilitative Effects of Shock Intensity and Interresponse Times Followed by Shock

ERIC Educational Resources Information Center

Everly, Jessica B.; Perone, Michael

2012-01-01

Although response-dependent shock often suppresses responding, response facilitation can occur. In two experiments, we examined the suppressive and facilitative effects of shock by manipulating shock intensity and the interresponse times that produced shock. Rats' lever presses were reinforced on a variable-interval 40-s schedule of food…

The effect of various morphine weaning regimens on the sequelae of opioid tolerance involving physical dependency, anxiety and hippocampus cell neurodegeneration in rats.

PubMed

Motaghinejad, Majid; Karimian, Seyed Morteza; Motaghinejad, Ozra; Shabab, Behnaz; Asadighaleni, Majid; Fatima, Sulail

2015-06-01

Chronic consumption of morphine induces physical dependency, anxiety, and neurodegeneration. In this study, morphine on its own has been used for the management of morphine-induced dependency, oxidative stress, and apoptosis. Forty-eight male rats were randomly divided into six groups. Rats in groups 1-5 were made morphine dependent by an increasing manner of morphine for 7 days (15-45 mg/kg). For the next 14 days, morphine was administered using the following regimen: (i) once daily 45 mg/kg (positive controls), (ii) the same dose at additional intervals (6 h longer than the previous intervals each time), (iii) 45 mg/kg of morphine at irregular intervals like of 12, 24, 36 h, (iv) decreasing dose once daily (every time 2.5 mg/kg less than the former dosage). Group 5 received 45 mg/kg of morphine and 10 mg/kg of SOD mimetic agent (M40401) injection per day. Group 6 (negative control) received saline solution only. On day 22, all animals received naloxone (3 mg/kg) and their Total Withdrawal Index (TWI) and blood cortisol levels were measured. After drug treatment, hippocampus cells were isolated, and oxidative, antioxidative, and apoptotic factors were evaluated. Various regimens of morphine reduced TWI, cortisol levels, Bax activity, caspase-3, caspase-9, TNF-α, and IL-1β and lipid peroxidation. In all treatment groups, GSH level, superoxide dismutase, glutathione peroxidase, and Bcl-2 activity were significantly increased. Furthermore, SOD mimetic agent c diminished morphine effect on SOD activity. Thus, varying the dosage regimen of morphine can reduce the severity of morphine-induced dependency and neurodegeneration. © 2015 Société Française de Pharmacologie et de Thérapeutique.

Controls on the long term earthquake behavior of an intraplate fault revealed by U-Th and stable isotope analyses of syntectonic calcite veins

NASA Astrophysics Data System (ADS)

Williams, Randolph; Goodwin, Laurel; Sharp, Warren; Mozley, Peter

2017-04-01

U-Th dates on calcite precipitated in coseismic extension fractures in the Loma Blanca normal fault zone, Rio Grande rift, NM, USA, constrain earthquake recurrence intervals from 150-565 ka. This is the longest direct record of seismicity documented for a fault in any tectonic environment. Combined U-Th and stable isotope analyses of these calcite veins define 13 distinct earthquake events. These data show that for more than 400 ka the Loma Blanca fault produced earthquakes with a mean recurrence interval of 40 ± 7 ka. The coefficient of variation for these events is 0.40, indicating strongly periodic seismicity consistent with a time-dependent model of earthquake recurrence. Stochastic statistical analyses further validate the inference that earthquake behavior on the Loma Blanca was time-dependent. The time-dependent nature of these earthquakes suggests that the seismic cycle was fundamentally controlled by a stress renewal process. However, this periodic cycle was punctuated by an episode of clustered seismicity at 430 ka. Recurrence intervals within the earthquake cluster were as low as 5-11 ka. Breccia veins formed during this episode exhibit carbon isotope signatures consistent with having formed through pronounced degassing of a CO2 charged brine during post-failure, fault-localized fluid migration. The 40 ka periodicity of the long-term earthquake record of the Loma Blanca fault is similar in magnitude to recurrence intervals documented through paleoseismic studies of other normal faults in the Rio Grande rift and Basin and Range Province. We propose that it represents a background rate of failure in intraplate extension. The short-term, clustered seismicity that occurred on the fault records an interruption of the stress renewal process, likely by elevated fluid pressure in deeper structural levels of the fault, consistent with fault-valve behavior. The relationship between recurrence interval and inferred fluid degassing suggests that pore fluid pressure along the fault may have been driven by variations in CO2 content, thereby fundamentally affecting earthquake frequency. Thus, the Loma Blanca fault provides a record of "naturally induced" seismicity, with lessons for better understanding anthropogenic induced seismicity.

Seismic hazard assessment over time: Modelling earthquakes in Taiwan

NASA Astrophysics Data System (ADS)

Chan, Chung-Han; Wang, Yu; Wang, Yu-Ju; Lee, Ya-Ting

2017-04-01

To assess the seismic hazard with temporal change in Taiwan, we develop a new approach, combining both the Brownian Passage Time (BPT) model and the Coulomb stress change, and implement the seismogenic source parameters by the Taiwan Earthquake Model (TEM). The BPT model was adopted to describe the rupture recurrence intervals of the specific fault sources, together with the time elapsed since the last fault-rupture to derive their long-term rupture probability. We also evaluate the short-term seismicity rate change based on the static Coulomb stress interaction between seismogenic sources. By considering above time-dependent factors, our new combined model suggests an increased long-term seismic hazard in the vicinity of active faults along the western Coastal Plain and the Longitudinal Valley, where active faults have short recurrence intervals and long elapsed time since their last ruptures, and/or short-term elevated hazard levels right after the occurrence of large earthquakes due to the stress triggering effect. The stress enhanced by the February 6th, 2016, Meinong ML 6.6 earthquake also significantly increased rupture probabilities of several neighbouring seismogenic sources in Southwestern Taiwan and raised hazard level in the near future. Our approach draws on the advantage of incorporating long- and short-term models, to provide time-dependent earthquake probability constraints. Our time-dependent model considers more detailed information than any other published models. It thus offers decision-makers and public officials an adequate basis for rapid evaluations of and response to future emergency scenarios such as victim relocation and sheltering.

Changes in corticospinal excitability and the direction of evoked movements during motor preparation: A TMS study

PubMed Central

van Elswijk, Gijs; Schot, Willemijn D; Stegeman, Dick F; Overeem, Sebastiaan

2008-01-01

Background Preparation of the direction of a forthcoming movement has a particularly strong influence on both reaction times and neuronal activity in the primate motor cortex. Here, we aimed to find direct neurophysiologic evidence for the preparation of movement direction in humans. We used single-pulse transcranial magnetic stimulation (TMS) to evoke isolated thumb-movements, of which the direction can be modulated experimentally, for example by training or by motor tasks. Sixteen healthy subjects performed brisk concentric voluntary thumb movements during a reaction time task in which the required movement direction was precued. We assessed whether preparation for the thumb movement lead to changes in the direction of TMS-evoked movements and to changes in amplitudes of motor-evoked potentials (MEPs) from the hand muscles. Results When the required movement direction was precued early in the preparatory interval, reaction times were 50 ms faster than when precued at the end of the preparatory interval. Over time, the direction of the TMS-evoked thumb movements became increasingly variable, but it did not turn towards the precued direction. MEPs from the thumb muscle (agonist) were differentially modulated by the direction of the precue, but only in the late phase of the preparatory interval and thereafter. MEPs from the index finger muscle did not depend on the precued direction and progressively decreased during the preparatory interval. Conclusion Our data show that the human corticospinal movement representation undergoes progressive changes during motor preparation. These changes are accompanied by inhibitory changes in corticospinal excitability, which are muscle specific and depend on the prepared movement direction. This inhibition might indicate a corticospinal braking mechanism that counteracts any preparatory motor activation. PMID:18559096

Real Time Correction of Aircraft Flight Fonfiguration

NASA Technical Reports Server (NTRS)

Schipper, John F. (Inventor)

2009-01-01

Method and system for monitoring and analyzing, in real time, variation with time of an aircraft flight parameter. A time-dependent recovery band, defined by first and second recovery band boundaries that are spaced apart at at least one time point, is constructed for a selected flight parameter and for a selected time recovery time interval length .DELTA.t(FP;rec). A flight parameter, having a value FP(t=t.sub.p) at a time t=t.sub.p, is likely to be able to recover to a reference flight parameter value FP(t';ref), lying in a band of reference flight parameter values FP(t';ref;CB), within a time interval given by t.sub.p.ltoreq.t'.ltoreq.t.sub.p.DELTA.t(FP;rec), if (or only if) the flight parameter value lies between the first and second recovery band boundary traces.

Conditioned [corrected] stimulus informativeness governs conditioned stimulus-unconditioned stimulus associability.

PubMed

Ward, Ryan D; Gallistel, C R; Jensen, Greg; Richards, Vanessa L; Fairhurst, Stephen; Balsam, Peter D

2012-07-01

In a conditioning protocol, the onset of the conditioned stimulus ([CS]) provides information about when to expect reinforcement (unconditioned stimulus [US]). There are two sources of information from the CS in a delay conditioning paradigm in which the CS-US interval is fixed. The first depends on the informativeness, the degree to which CS onset reduces the average expected time to onset of the next US. The second depends only on how precisely a subject can represent a fixed-duration interval (the temporal Weber fraction). In three experiments with mice, we tested the differential impact of these two sources of information on rate of acquisition of conditioned responding (CS-US associability). In Experiment 1, we showed that associability (the inverse of trials to acquisition) increased in proportion to informativeness. In Experiment 2, we showed that fixing the duration of the US-US interval or the CS-US interval or both had no effect on associability. In Experiment 3, we equated the increase in information produced by varying the C/T ratio with the increase produced by fixing the duration of the CS-US interval. Associability increased with increased informativeness, but, as in Experiment 2, fixing the CS-US duration had no effect on associability. These results are consistent with the view that CS-US associability depends on the increased rate of reward signaled by CS onset. The results also provide further evidence that conditioned responding is temporally controlled when it emerges.

CS Informativeness Governs CS-US Associability

PubMed Central

Ward, Ryan D.; Gallistel, C. R.; Jensen, Greg; Richards, Vanessa L.; Fairhurst, Stephen; Balsam, Peter D

2012-01-01

In a conditioning protocol, the onset of the conditioned stimulus (CS) provides information about when to expect reinforcement (the US). There are two sources of information from the CS in a delay conditioning paradigm in which the CS-US interval is fixed. The first depends on the informativeness, the degree to which CS onset reduces the average expected time to onset of the next US. The second depends only on how precisely a subject can represent a fixed-duration interval (the temporal Weber fraction). In three experiments with mice, we tested the differential impact of these two sources of information on rate of acquisition of conditioned responding (CS-US associability). In Experiment 1, we show that associability (the inverse of trials to acquisition) increases in proportion to informativeness. In Experiment 2, we show that fixing the duration of the US-US interval or the CS-US interval or both has no effect on associability. In Experiment 3, we equated the increase in information produced by varying the C̅/T̅ ratio with the increase produced by fixing the duration of the CS-US interval. Associability increased with increased informativeness, but, as in Experiment 2, fixing the CS-US duration had no effect on associability. These results are consistent with the view that CS-US associability depends on the increased rate of reward signaled by CS onset. The results also provide further evidence that conditioned responding is temporally controlled when it emerges. PMID:22468633

Triggering up states in all-to-all coupled neurons

NASA Astrophysics Data System (ADS)

Ngo, H.-V. V.; Köhler, J.; Mayer, J.; Claussen, J. C.; Schuster, H. G.

2010-03-01

Slow-wave sleep in mammalians is characterized by a change of large-scale cortical activity currently paraphrased as cortical Up/Down states. A recent experiment demonstrated a bistable collective behaviour in ferret slices, with the remarkable property that the Up states can be switched on and off with pulses, or excitations, of same polarity; whereby the effect of the second pulse significantly depends on the time interval between the pulses. Here we present a simple time-discrete model of a neural network that exhibits this type of behaviour, as well as quantitatively reproduces the time dependence found in the experiments.

Effects of an Approach Spacing Flight Deck Tool on Pilot Eyescan

DOT National Transportation Integrated Search

2004-02-01

An airborne tool has been developed based on the concept of an aircraft maintaining a time-based spacing interval from the preceding aircraft. The : Advanced Terminal Area Approach Spacing (ATAAS) tool uses Automatic : Dependent Surveillance-Broadcas...

Poststimulation time interval-dependent effects of motor cortex anodal tDCS on reaction-time task performance.

PubMed

Molero-Chamizo, Andrés; Alameda Bailén, José R; Garrido Béjar, Tamara; García López, Macarena; Jaén Rodríguez, Inmaculada; Gutiérrez Lérida, Carolina; Pérez Panal, Silvia; González Ángel, Gloria; Lemus Corchero, Laura; Ruiz Vega, María J; Nitsche, Michael A; Rivera-Urbina, Guadalupe N

2018-02-01

Anodal transcranial direct current stimulation (tDCS) induces long-term potentiation-like plasticity, which is associated with long-lasting effects on different cognitive, emotional, and motor performances. Specifically, tDCS applied over the motor cortex is considered to improve reaction time in simple and complex tasks. The timing of tDCS relative to task performance could determine the efficacy of tDCS to modulate performance. The aim of this study was to compare the effects of a single session of anodal tDCS (1.5 mA, for 15 min) applied over the left primary motor cortex (M1) versus sham stimulation on performance of a go/no-go simple reaction-time task carried out at three different time points after tDCS-namely, 0, 30, or 60 min after stimulation. Performance zero min after anodal tDCS was improved during the whole course of the task. Performance 30 min after anodal tDCS was improved only in the last block of the reaction-time task. Performance 60 min after anodal tDCS was not significantly different throughout the entire task. These findings suggest that the motor cortex excitability changes induced by tDCS can improve motor responses, and these effects critically depend on the time interval between stimulation and task performance.

The influence of prior experience and expected timing on vibrotactile discrimination

PubMed Central

Karim, Muhsin; Harris, Justin A.; Langdon, Angela; Breakspear, Michael

2013-01-01

Vibrotactile discrimination tasks involve perceptual judgements on stimulus pairs separated by a brief interstimulus interval (ISI). Despite their apparent simplicity, decision making during these tasks is biased by prior experience in a manner that is not well understood. A striking example is when participants perform well on trials where the first stimulus is closer to the mean of the stimulus-set than the second stimulus, and perform comparatively poorly when the first stimulus is further from the stimulus mean. This “time-order effect” suggests that participants implicitly encode the mean of the stimulus-set and use this internal standard to bias decisions on any given trial. For relatively short ISIs, the magnitude of the time-order effect typically increases with the distance of the first stimulus from the global mean. Working from the premise that the time-order effect reflects the loss of precision in working memory representations, we predicted that the influence of the time-order effect, and this superimposed “distance” effect, would monotonically increase for trials with longer ISIs. However, by varying the ISI across four intervals (300, 600, 1200, and 2400 ms) we instead found a complex, non-linear dependence of the time-order effect on both the ISI and the distance, with the time-order effect being paradoxically stronger at short ISIs. We also found that this relationship depended strongly on participants' prior experience of the ISI (from previous task titration). The time-order effect not only depends on participants' expectations concerning the distribution of stimuli, but also on the expected timing of the trials. PMID:24399927

Human-in-the-Loop Assessment of Alternative Clearances in Interval Management Arrival Operations

NASA Technical Reports Server (NTRS)

Baxley, Brian T.; Wilson, Sara R.; Swieringa, Kurt A.; Johnson, William C.; Roper, Roy D.; Hubbs, Clay E.; Goess, Paul A.; Shay, Richard F.

2016-01-01

Interval Management Alternative Clearances (IMAC) was a human-in-the-loop simulation experiment conducted to explore the Air Traffic Management (ATM) Technology Demonstration (ATD-1) Concept of Operations (ConOps), which combines advanced arrival scheduling, controller decision support tools, and aircraft avionics to enable multiple time deconflicted, efficient arrival streams into a high-density terminal airspace. Interval Management (IM) is designed to support the ATD-1 concept by having an "Ownship" (IM-capable) aircraft achieve or maintain a specific time or distance behind a "Target" (preceding) aircraft. The IM software uses IM clearance information and the Ownship data (route of flight, current location, and wind) entered by the flight crew, and the Target aircraft's Automatic Dependent Surveillance-Broadcast state data, to calculate the airspeed necessary for the IM-equipped aircraft to achieve or maintain the assigned spacing goal.

Detection of density dependence requires density manipulations and calculation of lambda.

PubMed

Fowler, N L; Overath, R Deborah; Pease, Craig M

2006-03-01

To investigate density-dependent population regulation in the perennial bunchgrass Bouteloua rigidiseta, we experimentally manipulated density by removing adults or adding seeds to replicate quadrats in a natural population for three annual intervals. We monitored the adjacent control quadrats for 14 annual intervals. We constructed a population projection matrix for each quadrat in each interval, calculated lambda, and did a life table response experiment (LTRE) analysis. We tested the effects of density upon lambda by comparing experimental and control quadrats, and by an analysis of the 15-year observational data set. As measured by effects on lambda and on N(t+1/Nt in the experimental treatments, negative density dependence was strong: the population was being effectively regulated. The relative contributions of different matrix elements to treatment effect on lambda differed among years and treatments; overall the pattern was one of small contributions by many different life cycle stages. In contrast, density dependence could not be detected using only the observational (control quadrats) data, even though this data set covered a much longer time span. Nor did experimental effects on separate matrix elements reach statistical significance. These results suggest that ecologists may fail to detect density dependence when it is present if they have only descriptive, not experimental, data, do not have data for the entire life cycle, or analyze life cycle components separately.

Long-term cardiovascular risk of nonsteroidal anti-inflammatory drug use according to time passed after first-time myocardial infarction: a nationwide cohort study.

PubMed

Olsen, Anne-Marie Schjerning; Fosbøl, Emil L; Lindhardsen, Jesper; Folke, Fredrik; Charlot, Mette; Selmer, Christian; Bjerring Olesen, Jonas; Lamberts, Morten; Ruwald, Martin H; Køber, Lars; Hansen, Peter R; Torp-Pedersen, Christian; Gislason, Gunnar H

2012-10-16

The cardiovascular risk after the first myocardial infarction (MI) declines rapidly during the first year. We analyzed whether the cardiovascular risk associated with using nonsteroidal anti-inflammatory drugs (NSAIDs) was associated with the time elapsed following first-time MI. We identified patients aged 30 years or older admitted with first-time MI in 1997 to 2009 and subsequent NSAID use by individual-level linkage of nationwide registries of hospitalization and drug dispensing from pharmacies in Denmark. We calculated the incidence rates of death and a composite end point of coronary death or nonfatal recurrent MIs associated with NSAID use in 1-year time intervals up to 5 years after inclusion and analyzed risk by using multivariable adjusted time-dependent Cox proportional hazards models. Of the 99 187 patients included, 43 608 (44%) were prescribed NSAIDs after the index MI. There were 36 747 deaths and 28 693 coronary deaths or nonfatal recurrent MIs during the 5 years of follow-up. Relative to noncurrent treatment with NSAIDs, the use of any NSAID in the years following MI was persistently associated with an increased risk of death (hazard ratio 1.59 [95% confidence interval, 1.49-1.69]) after 1 year and hazard ratio 1.63 [95% confidence interval, 1.52-1.74] after 5 years) and coronary death or nonfatal recurrent MI (hazard ratio, 1.30 [95% confidence interval,l 1.22-1.39] and hazard ratio, 1.41 [95% confidence interval, 1.28-1.55]). The use of NSAIDs is associated with persistently increased coronary risk regardless of time elapsed after first-time MI. We advise long-term caution in the use of NSAIDs for patients after MI.

Fixed-Time Schedule Effects in Combination with Response-Dependent Schedules

ERIC Educational Resources Information Center

Borrero, John C.; Bartels-Meints, Jamie A.; Sy, Jolene R.; Francisco, Monica T.

2011-01-01

We evaluated the effects of fixed-interval (FI), fixed-time (FT), and conjoint (combined) FI FT reinforcement schedules on the responding of 3 adults who had been diagnosed with schizophrenia. Responding on vocational tasks decreased for 2 of 3 participants under FT alone relative to FI alone. Responding under FI FT resulted in response…

Proceedings of the 30th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting

DTIC Science & Technology

1999-01-01

roa.es C. Tomis RedIRIS, Centro Comunicaciones CSIC RedIRIS Serrano 142, 28006 Madrid, Spain tel + 34-91-585-5150 fax +34-91-564-7421 e-mail...I&D) and managed by the Centro de Comunicaciones CSIC RedIRIS, which depends on the Scientific Research Council (Consejo Superior de Investigaciones

Evaluation of a Tool for Airborne-Managed In-Trail Approach Spacing

DOT National Transportation Integrated Search

2005-08-01

The Advanced Terminal Area Approach Spacing (ATAAS) tool uses Automatic Dependent Surveillance-Broadcast aircraft state data to compute a speed command for an ATAAS-equipped aircraft to follow and obtain a required time interval behind another aircra...

Scaling of seismic memory with earthquake size

NASA Astrophysics Data System (ADS)

Zheng, Zeyu; Yamasaki, Kazuko; Tenenbaum, Joel; Podobnik, Boris; Tamura, Yoshiyasu; Stanley, H. Eugene

2012-07-01

It has been observed that discrete earthquake events possess memory, i.e., that events occurring in a particular location are dependent on the history of that location. We conduct an analysis to see whether continuous real-time data also display a similar memory and, if so, whether such autocorrelations depend on the size of earthquakes within close spatiotemporal proximity. We analyze the seismic wave form database recorded by 64 stations in Japan, including the 2011 “Great East Japan Earthquake,” one of the five most powerful earthquakes ever recorded, which resulted in a tsunami and devastating nuclear accidents. We explore the question of seismic memory through use of mean conditional intervals and detrended fluctuation analysis (DFA). We find that the wave form sign series show power-law anticorrelations while the interval series show power-law correlations. We find size dependence in earthquake autocorrelations: as the earthquake size increases, both of these correlation behaviors strengthen. We also find that the DFA scaling exponent α has no dependence on the earthquake hypocenter depth or epicentral distance.

In situ time-series measurements of subseafloor sediment properties

USGS Publications Warehouse

Wheatcroft, R.A.; Stevens, A.W.; Johnson, R.V.

2007-01-01

The capabilities and diversity of subsurface sediment sensors lags significantly from what is available for the water column, thereby limiting progress in understanding time-dependent seabed exchange and high-frequency acoustics. To help redress this imbalance, a new instrument, the autonomous sediment profiler (ASP), is described herein. ASP consists of a four-electrode, Wenner-type resistivity probe and a thermistor that log data at 0.1-cm vertical intervals over a 58-cm vertical profile. To avoid resampling the same spot on the seafloor, the probes are moved horizontally within a 20 times 100-cm-2 area in one of three preselected patterns. Memory and power capacities permit sampling at hourly intervals for up to 3-mo duration. The system was tested in a laboratory tank and shown to be able to resolve high-frequency sediment consolidation, as well as changes in sediment roughness. In a field test off the southern coast of France, the system collected resistivity and temperature data at hourly intervals for 16 d. Coupled with environmental data collected on waves, currents, and suspended sediment, the ASP is shown to be useful for understanding temporal evolution of subsurface sediment porosity, although no large depositional or erosional events occurred during the deployment. Following a rapid decrease in bottom-water temperature, the evolution of the subsurface temperature field was consistent with the 1-D thermal diffusion equation coupled with advection in the upper 3-4 cm. Collectively, the laboratory and field tests yielded promising results on time-dependent seabed change.

Effects of an Approach Spacing Flight Deck Tool on Pilot Eyescan

NASA Technical Reports Server (NTRS)

Oseguera-Lohr, Rosa M.; Nadler, Eric D.

2004-01-01

An airborne tool has been developed based on the concept of an aircraft maintaining a time-based spacing interval from the preceding aircraft. The Advanced Terminal Area Approach Spacing (ATAAS) tool uses Automatic Dependent Surveillance-Broadcast (ADS-B) aircraft state data to compute a speed command for the ATAAS-equipped aircraft to obtain a required time interval behind another aircraft. The tool and candidate operational procedures were tested in a high-fidelity, full mission simulator with active airline subject pilots flying an arrival scenario using three different modes for speed control. Eyetracker data showed only slight changes in instrument scan patterns, and no significant change in the amount of time spent looking out the window with ATAAS, versus standard ILS procedures.

Dynamic response analysis of structure under time-variant interval process model

NASA Astrophysics Data System (ADS)

Xia, Baizhan; Qin, Yuan; Yu, Dejie; Jiang, Chao

2016-10-01

Due to the aggressiveness of the environmental factor, the variation of the dynamic load, the degeneration of the material property and the wear of the machine surface, parameters related with the structure are distinctly time-variant. Typical model for time-variant uncertainties is the random process model which is constructed on the basis of a large number of samples. In this work, we propose a time-variant interval process model which can be effectively used to deal with time-variant uncertainties with limit information. And then two methods are presented for the dynamic response analysis of the structure under the time-variant interval process model. The first one is the direct Monte Carlo method (DMCM) whose computational burden is relative high. The second one is the Monte Carlo method based on the Chebyshev polynomial expansion (MCM-CPE) whose computational efficiency is high. In MCM-CPE, the dynamic response of the structure is approximated by the Chebyshev polynomials which can be efficiently calculated, and then the variational range of the dynamic response is estimated according to the samples yielded by the Monte Carlo method. To solve the dependency phenomenon of the interval operation, the affine arithmetic is integrated into the Chebyshev polynomial expansion. The computational effectiveness and efficiency of MCM-CPE is verified by two numerical examples, including a spring-mass-damper system and a shell structure.

Communication: Coordinate-dependent diffusivity from single molecule trajectories

NASA Astrophysics Data System (ADS)

Berezhkovskii, Alexander M.; Makarov, Dmitrii E.

2017-11-01

Single-molecule observations of biomolecular folding are commonly interpreted using the model of one-dimensional diffusion along a reaction coordinate, with a coordinate-independent diffusion coefficient. Recent analysis, however, suggests that more general models are required to account for single-molecule measurements performed with high temporal resolution. Here, we consider one such generalization: a model where the diffusion coefficient can be an arbitrary function of the reaction coordinate. Assuming Brownian dynamics along this coordinate, we derive an exact expression for the coordinate-dependent diffusivity in terms of the splitting probability within an arbitrarily chosen interval and the mean transition path time between the interval boundaries. This formula can be used to estimate the effective diffusion coefficient along a reaction coordinate directly from single-molecule trajectories.

IEEE-1588(Trademark) Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems

DTIC Science & Technology

2002-12-01

34th Annual Precise Time and Time Interval (PTTI) Meeting 243 IEEE-1588™ STANDARD FOR A PRECISION CLOCK SYNCHRONIZATION PROTOCOL FOR... synchronization . 2. Cyclic-systems. In cyclic-systems, timing is periodic and is usually defined by the characteristics of a cyclic network or bus...incommensurate, timing schedules for each device are easily implemented. In addition, synchronization accuracy depends on the accuracy of the common

Bimodal stimulus timing-dependent plasticity in primary auditory cortex is altered after noise exposure with and without tinnitus

PubMed Central

Koehler, Seth D.; Shore, Susan E.

2015-01-01

Central auditory circuits are influenced by the somatosensory system, a relationship that may underlie tinnitus generation. In the guinea pig dorsal cochlear nucleus (DCN), pairing spinal trigeminal nucleus (Sp5) stimulation with tones at specific intervals and orders facilitated or suppressed subsequent tone-evoked neural responses, reflecting spike timing-dependent plasticity (STDP). Furthermore, after noise-induced tinnitus, bimodal responses in DCN were shifted from Hebbian to anti-Hebbian timing rules with less discrete temporal windows, suggesting a role for bimodal plasticity in tinnitus. Here, we aimed to determine if multisensory STDP principles like those in DCN also exist in primary auditory cortex (A1), and whether they change following noise-induced tinnitus. Tone-evoked and spontaneous neural responses were recorded before and 15 min after bimodal stimulation in which the intervals and orders of auditory-somatosensory stimuli were randomized. Tone-evoked and spontaneous firing rates were influenced by the interval and order of the bimodal stimuli, and in sham-controls Hebbian-like timing rules predominated as was seen in DCN. In noise-exposed animals with and without tinnitus, timing rules shifted away from those found in sham-controls to more anti-Hebbian rules. Only those animals with evidence of tinnitus showed increased spontaneous firing rates, a purported neurophysiological correlate of tinnitus in A1. Together, these findings suggest that bimodal plasticity is also evident in A1 following noise damage and may have implications for tinnitus generation and therapeutic intervention across the central auditory circuit. PMID:26289461

What measure of interpersonal dependency predicts changes in social support?

PubMed

Shahar, Golan

2008-01-01

One of the most intriguing characteristics of interpersonal dependency is its ability to predict elevated levels of social support. Yet studies of interpersonal dependency use various measures to assess this effect. In this study, I compared 3 commonly used measures of interpersonal dependency in terms of their prediction of social support: Hirschfield's Interpersonal Dependency Inventory (IDI; Hirschfeld et al., 1977), the dependency factor of the Depressive Experiences Questionnaire (DEQ; Blatt, D'Afflitti, & Quinlan, 1976), and the Dependency subscale of the Personal Style Inventory (PSI; Robins et al., 1994). A total of 152 undergraduates were administered these measures as well as measures of depressive symptoms and social support a week prior to their first exam period and a week after this period (interval time = 8 weeks). DEQ-dependency predicted an increase in social support, whereas PSI-Dependency and IDI predicted a decrease in social support over time. DEQ-dependency appears to capture better than the other 2 measures the dialectic tension between risk and resilience in interpersonal dependency.

Temporal Prediction Errors Affect Short-Term Memory Scanning Response Time.

PubMed

Limongi, Roberto; Silva, Angélica M

2016-11-01

The Sternberg short-term memory scanning task has been used to unveil cognitive operations involved in time perception. Participants produce time intervals during the task, and the researcher explores how task performance affects interval production - where time estimation error is the dependent variable of interest. The perspective of predictive behavior regards time estimation error as a temporal prediction error (PE), an independent variable that controls cognition, behavior, and learning. Based on this perspective, we investigated whether temporal PEs affect short-term memory scanning. Participants performed temporal predictions while they maintained information in memory. Model inference revealed that PEs affected memory scanning response time independently of the memory-set size effect. We discuss the results within the context of formal and mechanistic models of short-term memory scanning and predictive coding, a Bayes-based theory of brain function. We state the hypothesis that our finding could be associated with weak frontostriatal connections and weak striatal activity.

The contributions of encoding, retention, and recall to the Hebb effect.

PubMed

Oberauer, Klaus; Meyer, Nadine

2009-10-01

The article reports an experiment testing whether the Hebb repetition effect-the gradual improvement of immediate serial recall when the same list is repeated several times-depends on overt recall of the repeated lists. Previous reports which suggest that recall is critical confound the recall manipulation with retention interval. The present experiment orthogonally varies retention interval (0 or 9 s) and whether the list is to be recalled after the retention interval. Hebb repetition learning is assessed in a final test phase. A repetition effect was obtained in all four experimental conditions; it was larger for recalled than non-recalled lists, whereas retention interval had no effect. The results show that encoding is sufficient to generate cumulative long-term learning, which is strengthened by recall. Rehearsal, if it takes place in the retention interval at all, does not have the same effect on long-term learning as overt recall.

On the long-period evolution of the sun-synchronous orbits

NASA Astrophysics Data System (ADS)

Kuznetsov, E. D.; Jasim, A. T.

2016-05-01

The dynamic evolution of sun-synchronous orbits at a time interval of 20 years is considered. The numerical motion simulation has been carried out using the Celestial Mechanics software package developed at the Institute of Astronomy of the University of Bern. The dependence of the dynamic evolution on the initial value of the ascending node longitude is examined for two families of sun-synchronous orbits with altitudes of 751 and 1191 km. Variations of the semimajor axis and orbit inclination are obtained depending on the initial value of the ascending node longitude. Recommendations on the selection of orbits, in which spent sun-synchronous satellites can be moved, are formulated. Minimal changes of elements over a time interval of 20 years have been observed for orbits in which at the initial time the angle between the orbit ascending node and the direction of the Sun measured along the equator have been close to 90° or 270°. In this case, the semimajor axis of the orbit is not experiencing secular perturbations arising from the satellite's passage through the Earth's shadow.

Rationale choosing interval of a piecewise-constant approximation of input rate of non-stationary queue system

NASA Astrophysics Data System (ADS)

Korelin, Ivan A.; Porshnev, Sergey V.

2018-01-01

The paper demonstrates the possibility of calculating the characteristics of the flow of visitors to objects carrying out mass events passing through checkpoints. The mathematical model is based on the non-stationary queuing system (NQS) where dependence of requests input rate from time is described by the function. This function was chosen in such way that its properties were similar to the real dependencies of speed of visitors arrival on football matches to the stadium. A piecewise-constant approximation of the function is used when statistical modeling of NQS performing. Authors calculated the dependencies of the queue length and waiting time for visitors to service (time in queue) on time for different laws. Time required to service the entire queue and the number of visitors entering the stadium at the beginning of the match were calculated too. We found the dependence for macroscopic quantitative characteristics of NQS from the number of averaging sections of the input rate.

Spectral-based propagation schemes for time-dependent quantum systems with application to carbon nanotubes

NASA Astrophysics Data System (ADS)

Chen, Zuojing; Polizzi, Eric

2010-11-01

Effective modeling and numerical spectral-based propagation schemes are proposed for addressing the challenges in time-dependent quantum simulations of systems ranging from atoms, molecules, and nanostructures to emerging nanoelectronic devices. While time-dependent Hamiltonian problems can be formally solved by propagating the solutions along tiny simulation time steps, a direct numerical treatment is often considered too computationally demanding. In this paper, however, we propose to go beyond these limitations by introducing high-performance numerical propagation schemes to compute the solution of the time-ordered evolution operator. In addition to the direct Hamiltonian diagonalizations that can be efficiently performed using the new eigenvalue solver FEAST, we have designed a Gaussian propagation scheme and a basis-transformed propagation scheme (BTPS) which allow to reduce considerably the simulation times needed by time intervals. It is outlined that BTPS offers the best computational efficiency allowing new perspectives in time-dependent simulations. Finally, these numerical schemes are applied to study the ac response of a (5,5) carbon nanotube within a three-dimensional real-space mesh framework.

Influence of the Time Scale on the Construction of Financial Networks

PubMed Central

Emmert-Streib, Frank; Dehmer, Matthias

2010-01-01

Background In this paper we investigate the definition and formation of financial networks. Specifically, we study the influence of the time scale on their construction. Methodology/Principal Findings For our analysis we use correlation-based networks obtained from the daily closing prices of stock market data. More precisely, we use the stocks that currently comprise the Dow Jones Industrial Average (DJIA) and estimate financial networks where nodes correspond to stocks and edges correspond to none vanishing correlation coefficients. That means only if a correlation coefficient is statistically significant different from zero, we include an edge in the network. This construction procedure results in unweighted, undirected networks. By separating the time series of stock prices in non-overlapping intervals, we obtain one network per interval. The length of these intervals corresponds to the time scale of the data, whose influence on the construction of the networks will be studied in this paper. Conclusions/Significance Numerical analysis of four different measures in dependence on the time scale for the construction of networks allows us to gain insights about the intrinsic time scale of the stock market with respect to a meaningful graph-theoretical analysis. PMID:20949124

A cross-syndrome study of the differential effects of sleep on declarative memory consolidation in children with neurodevelopmental disorders.

PubMed

Ashworth, Anna; Hill, Catherine M; Karmiloff-Smith, Annette; Dimitriou, Dagmara

2017-03-01

Sleep plays an active role in memory consolidation. Because children with Down syndrome (DS) and Williams syndrome (WS) experience significant problems with sleep and also with learning, we predicted that sleep-dependent memory consolidation would be impaired in these children when compared to typically developing (TD) children. This is the first study to provide a cross-syndrome comparison of sleep-dependent learning in school-aged children. Children with DS (n = 20) and WS (n = 22) and TD children (n = 33) were trained on the novel Animal Names task where they were taught pseudo-words as the personal names of ten farm and domestic animals, e.g. Basco the cat, with the aid of animal picture flashcards. They were retested following counterbalanced retention intervals of wake and sleep. Overall, TD children remembered significantly more words than both the DS and WS groups. In addition, their performance improved following night-time sleep, whereas performance over the wake retention interval remained stable, indicating an active role of sleep for memory consolidation. Task performance of children with DS did not significantly change following wake or sleep periods. However, children with DS who were initially trained in the morning continued to improve on the task at the following retests, so that performance on the final test was greater for children who had initially trained in the morning than those who trained in the evening. Children with WS improved on the task between training and the first retest, regardless of whether sleep or wake occurred during the retention interval. This suggests time-dependent rather than sleep-dependent learning in children with WS, or tiredness at the end of the first session and better performance once refreshed at the start of the second session, irrespective of the time of day. Contrary to expectations, sleep-dependent learning was not related to baseline level of performance. The findings have significant implications for educational strategies, and suggest that children with DS should be taught more important or difficult information in the morning when they are better able to learn, whilst children with WS should be allowed a time delay between learning phases to allow for time-dependent memory consolidation, and frequent breaks from learning so that they are refreshed and able to perform at their best. © 2015 The Authors. Developmental Science Published by John Wiley & Sons Ltd.

Working disability in Norwegian patients with vestibular schwannoma: vertigo predicts future dependence.

PubMed

Breivik, Cathrine Nansdal; Nilsen, Roy Miodini; Myrseth, Erling; Finnkirk, Monica Katrine; Lund-Johansen, Morten

2013-12-01

We examined whether reduced hearing, tinnitus, dizziness, and unsteadiness affected the patients' ability to maintain work within a time frame of 2-10 years after diagnosis. A total of 434 consecutive patients were followed at regular intervals. Data on symptoms were scored prospectively and dichotomized by visual analog scales for tinnitus and vertigo. Study design is retrospective. Hearing acuity was scored according to the Gardner-Robertson scale, and unsteadiness was measured on a balance platform. Patients were asked about working status, and scored as receiving governmental compensation for disability. Two hundred six patients were eligible for study. Of these, one died and nine were lost to follow-up. Ninety-seven patients received conservative management, 49 patients recieved gamma knife radiosurgery, and 50 patients were treated by microsurgery. Mean follow-up time was 58.7 months (range, 20-132 months). There was a significant increase in the number of individuals receiving compensation during the study period (P < 0.0001). At baseline, the proportion of pension receivers was within same range as that of the age- and sex-matched Norwegian population (5.61% vs. 6.91%; case-control odds ratio, 0.82; 95% confidence interval 0.45-1.49; P = 0.51, not significant). At the final time point, the increase in the number of receivers deviated significantly from the reference population (case-control odds ratio, 3.80; 95% confidence interval 2.71-5.33; P ≤ 0.001). Examining symptoms at first presentation as predictors of future dependence revealed that vertigo and higher mean age were associated with a higher risk (P < 0.001 and P = 0.015, respectively). No other symptoms were predictive of dependence. In a prospectively followed cohort of Norwegian patients with vestibular schwannoma, vestibular complaints were significant predictors for becoming dependant of disability pension. Copyright © 2013 Elsevier Inc. All rights reserved.

The effect of temperature on development of Sarconesia chlorogaster, a blowfly of forensic importance.

PubMed

Lecheta, Melise Cristine; Thyssen, Patricia Jacqueline; Moura, Mauricio Osvaldo

2015-12-01

The blowfly Sarconesia chlorogaster (Diptera: Calliphoridae) is of limited forensic use in South America, due to the poorly known relationship between development time and temperature. The purpose of this study was to determine development time of S. chlorogaster at different constant temperatures, thereby enabling the forensic use of this fly. Development time of this species was examined by observing larval development at six temperatures (10, 15, 20, 25, 30, 35 °C). The thermal constant (K), the minimum development threshold (t 0), and development rate were calculated using linear regressions of the development time interval at five temperatures (10-30 °C). Development interval from egg to adult varied from 14.2 to 95.2 days, depending on temperature. The t0 calculated for total immature development is 6.33 °C and the overall thermal constant is 355.51 degree-days (DD). Temperature affected the viability of pupae, at 35 °C 100 % mortality was observed. Understanding development rate across these temperatures now makes development of S. chlorogaster a forensically useful tool for estimating postmortem interval.

Mixed-mode oscillations and interspike interval statistics in the stochastic FitzHugh-Nagumo model

NASA Astrophysics Data System (ADS)

Berglund, Nils; Landon, Damien

2012-08-01

We study the stochastic FitzHugh-Nagumo equations, modelling the dynamics of neuronal action potentials in parameter regimes characterized by mixed-mode oscillations. The interspike time interval is related to the random number of small-amplitude oscillations separating consecutive spikes. We prove that this number has an asymptotically geometric distribution, whose parameter is related to the principal eigenvalue of a substochastic Markov chain. We provide rigorous bounds on this eigenvalue in the small-noise regime and derive an approximation of its dependence on the system's parameters for a large range of noise intensities. This yields a precise description of the probability distribution of observed mixed-mode patterns and interspike intervals.

Associative spike timing-dependent potentiation of the basal dendritic excitatory synapses in the hippocampus in vivo.

PubMed

Fung, Thomas K; Law, Clayton S; Leung, L Stan

2016-06-01

Spike timing-dependent plasticity in the hippocampus has rarely been studied in vivo. Using extracellular potential and current source density analysis in urethane-anesthetized adult rats, we studied synaptic plasticity at the basal dendritic excitatory synapse in CA1 after excitation-spike (ES) pairing; E was a weak basal dendritic excitation evoked by stratum oriens stimulation, and S was a population spike evoked by stratum radiatum apical dendritic excitation. We hypothesize that positive ES pairing-generating synaptic excitation before a spike-results in long-term potentiation (LTP) while negative ES pairing results in long-term depression (LTD). Pairing (50 pairs at 5 Hz) at ES intervals of -10 to 0 ms resulted in significant input-specific LTP of the basal dendritic excitatory sink, lasting 60-120 min. Pairing at +10- to +20-ms ES intervals, or unpaired 5-Hz stimulation, did not induce significant basal dendritic or apical dendritic LTP or LTD. No basal dendritic LTD was found after stimulation of stratum oriens with 200 pairs of high-intensity pulses at 25-ms interval. Pairing-induced LTP was abolished by pretreatment with an N-methyl-d-aspartate receptor antagonist, 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), which also reduced spike bursting during 5-Hz pairing. Pairing at 0.5 Hz did not induce spike bursts or basal dendritic LTP. In conclusion, ES pairing at 5 Hz resulted in input-specific basal dendritic LTP at ES intervals of -10 ms to 0 ms but no LTD at ES intervals of -20 to +20 ms. Associative LTP likely occurred because of theta-rhythmic coincidence of subthreshold excitation with a backpropagated spike burst, which are conditions that can occur naturally in the hippocampus. Copyright © 2016 the American Physiological Society.

Associative spike timing-dependent potentiation of the basal dendritic excitatory synapses in the hippocampus in vivo

PubMed Central

Fung, Thomas K.; Law, Clayton S.

2016-01-01

Spike timing-dependent plasticity in the hippocampus has rarely been studied in vivo. Using extracellular potential and current source density analysis in urethane-anesthetized adult rats, we studied synaptic plasticity at the basal dendritic excitatory synapse in CA1 after excitation-spike (ES) pairing; E was a weak basal dendritic excitation evoked by stratum oriens stimulation, and S was a population spike evoked by stratum radiatum apical dendritic excitation. We hypothesize that positive ES pairing—generating synaptic excitation before a spike—results in long-term potentiation (LTP) while negative ES pairing results in long-term depression (LTD). Pairing (50 pairs at 5 Hz) at ES intervals of −10 to 0 ms resulted in significant input-specific LTP of the basal dendritic excitatory sink, lasting 60–120 min. Pairing at +10- to +20-ms ES intervals, or unpaired 5-Hz stimulation, did not induce significant basal dendritic or apical dendritic LTP or LTD. No basal dendritic LTD was found after stimulation of stratum oriens with 200 pairs of high-intensity pulses at 25-ms interval. Pairing-induced LTP was abolished by pretreatment with an N-methyl-d-aspartate receptor antagonist, 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), which also reduced spike bursting during 5-Hz pairing. Pairing at 0.5 Hz did not induce spike bursts or basal dendritic LTP. In conclusion, ES pairing at 5 Hz resulted in input-specific basal dendritic LTP at ES intervals of −10 ms to 0 ms but no LTD at ES intervals of −20 to +20 ms. Associative LTP likely occurred because of theta-rhythmic coincidence of subthreshold excitation with a backpropagated spike burst, which are conditions that can occur naturally in the hippocampus. PMID:27052581

Asymptotic expansion of pair production probability in a time-dependent electric field

NASA Astrophysics Data System (ADS)

Arai, Takashi

2015-12-01

We study particle creation in a single pulse of an electric field in scalar quantum electrodynamics. We investigate the parameter condition for the case where the dynamical pair creation and Schwinger mechanism respectively dominate. Then, an asymptotic expansion for the particle distribution in terms of the time interval of the applied electric field is derived. We compare our result with particle creation in a constant electric field with a finite-time interval. These results coincide in an extremely strong field, however they differ in general field strength. We interpret the reason of this difference as a nonperturbative effect of high-frequency photons in external electric fields. Moreover, we find that the next-to-leading-order term in our asymptotic expansion coincides with the derivative expansion of the effective action.

Long-Term Memory: A Natural Mechanism for the Clustering of Extreme Events and Anomalous Residual Times in Climate Records

NASA Astrophysics Data System (ADS)

Bunde, Armin; Eichner, Jan F.; Kantelhardt, Jan W.; Havlin, Shlomo

2005-01-01

We study the statistics of the return intervals between extreme events above a certain threshold in long-term persistent records. We find that the long-term memory leads (i)to a stretched exponential distribution of the return intervals, (ii)to a pronounced clustering of extreme events, and (iii)to an anomalous behavior of the mean residual time to the next event that depends on the history and increases with the elapsed time in a counterintuitive way. We present an analytical scaling approach and demonstrate that all these features can be seen in long climate records. The phenomena should also occur in heartbeat records, Internet traffic, and stock market volatility and have to be taken into account for an efficient risk evaluation.

Scale Dependence of Oak Woodland Historical Fire Intervals: Contrasting the Barrens of Tennessee and Cross Timbers of Oklahoma, USA

Treesearch

Michael C. Stambaugh; Richard P. Guyette; Joseph M. Marschall; Daniel C. Dey

2016-01-01

Characterization of scale dependence of fire intervals could inform interpretations of fire history and improve fire prescriptions that aim to mimic historical fire regime conditions. We quantified the temporal variability in fire regimes and described the spatial dependence of fire intervals through the analysis of multi-century fire scar records (8 study sites, 332...

Constraining the Long-Term Average of Earthquake Recurrence Intervals From Paleo- and Historic Earthquakes by Assimilating Information From Instrumental Seismicity

NASA Astrophysics Data System (ADS)

Zoeller, G.

2017-12-01

Paleo- and historic earthquakes are the most important source of information for the estimationof long-term recurrence intervals in fault zones, because sequences of paleoearthquakes cover more than one seismic cycle. On the other hand, these events are often rare, dating uncertainties are enormous and the problem of missing or misinterpreted events leads to additional problems. Taking these shortcomings into account, long-term recurrence intervals are usually unstable as long as no additional information are included. In the present study, we assume that the time to the next major earthquake depends on the rate of small and intermediate events between the large ones in terms of a ``clock-change'' model that leads to a Brownian Passage Time distribution for recurrence intervals. We take advantage of an earlier finding that the aperiodicity of this distribution can be related to the Gutenberg-Richter-b-value, which is usually around one and can be estimated easily from instrumental seismicity in the region under consideration. This allows to reduce the uncertainties in the estimation of the mean recurrence interval significantly, especially for short paleoearthquake sequences and high dating uncertainties. We present illustrative case studies from Southern California and compare the method with the commonly used approach of exponentially distributed recurrence times assuming a stationary Poisson process.

CACA-2: revised version of CACA-a heavy isotope and fission-product concentration calculational code for experimental irradiation capsules

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

Allen, E.J.

1976-02-01

A computer program is described which calculates nuclide concentration histories, power or neutron flux histories, burnups, and fission-product birthrates for fueled experimental capsules subjected to neutron irradiations. Seventeen heavy nuclides in the chain from $sup 232$Th to $sup 242$Pu and a user- specified number of fission products are treated. A fourth-order Runge-Kutta calculational method solves the differential equations for nuclide concentrations as a function of time. For a particular problem, a user-specified number of fuel regions may be treated. A fuel region is described by volume, length, and specific irradiation history. A number of initial fuel compositions may be specifiedmore » for each fuel region. The irradiation history for each fuel region can be divided into time intervals, and a constant power density or a time-dependent neutron flux is specified for each time interval. Also, an independent cross- section set may be selected for each time interval in each irradiation history. The fission-product birthrates for the first composition of each fuel region are summed to give the total fission-product birthrates for the problem.« less

Exponential synchronization of neural networks with discrete and distributed delays under time-varying sampling.

PubMed

Wu, Zheng-Guang; Shi, Peng; Su, Hongye; Chu, Jian

2012-09-01

This paper investigates the problem of master-slave synchronization for neural networks with discrete and distributed delays under variable sampling with a known upper bound on the sampling intervals. An improved method is proposed, which captures the characteristic of sampled-data systems. Some delay-dependent criteria are derived to ensure the exponential stability of the error systems, and thus the master systems synchronize with the slave systems. The desired sampled-data controller can be achieved by solving a set of linear matrix inequalitys, which depend upon the maximum sampling interval and the decay rate. The obtained conditions not only have less conservatism but also have less decision variables than existing results. Simulation results are given to show the effectiveness and benefits of the proposed methods.

Application of an Entropic Approach to Assessing Systems Integration

DTIC Science & Technology

2012-03-01

two econometrical measures of information efficiency – Shannon entropy and Hurst exponent . Shannon entropy (which is explained in Chapter III) can be...applied to evaluate long-term correlation of time series, while Hurst exponent can be applied to classify the time series in accordance to existence...of trend. Hurst exponent is the statistical measure of time series long-range dependence, and its value falls in the interval [0, 1] – a value in

Dynamic symmetries and quantum nonadiabatic transitions

DOE PAGES

Li, Fuxiang; Sinitsyn, Nikolai A.

2016-05-30

Kramers degeneracy theorem is one of the basic results in quantum mechanics. According to it, the time-reversal symmetry makes each energy level of a half-integer spin system at least doubly degenerate, meaning the absence of transitions or scatterings between degenerate states if the Hamiltonian does not depend on time explicitly. Here we generalize this result to the case of explicitly time-dependent spin Hamiltonians. We prove that for a spin system with the total spin being a half integer, if its Hamiltonian and the evolution time interval are symmetric under a specifically defined time reversal operation, the scattering amplitude between anmore » arbitrary initial state and its time reversed counterpart is exactly zero. Lastly, we also discuss applications of this result to the multistate Landau–Zener (LZ) theory.« less

Delay-distribution-dependent H∞ state estimation for delayed neural networks with (x,v)-dependent noises and fading channels.

PubMed

Sheng, Li; Wang, Zidong; Tian, Engang; Alsaadi, Fuad E

2016-12-01

This paper deals with the H ∞ state estimation problem for a class of discrete-time neural networks with stochastic delays subject to state- and disturbance-dependent noises (also called (x,v)-dependent noises) and fading channels. The time-varying stochastic delay takes values on certain intervals with known probability distributions. The system measurement is transmitted through fading channels described by the Rice fading model. The aim of the addressed problem is to design a state estimator such that the estimation performance is guaranteed in the mean-square sense against admissible stochastic time-delays, stochastic noises as well as stochastic fading signals. By employing the stochastic analysis approach combined with the Kronecker product, several delay-distribution-dependent conditions are derived to ensure that the error dynamics of the neuron states is stochastically stable with prescribed H ∞ performance. Finally, a numerical example is provided to illustrate the effectiveness of the obtained results. Copyright © 2016 Elsevier Ltd. All rights reserved.

On cell resistance and immune response time lag in a model for the HIV infection

NASA Astrophysics Data System (ADS)

Solovey, Guillermo; Peruani, Fernando; Ponce Dawson, Silvina; Maria Zorzenon dos Santos, Rita

2004-11-01

Recently, a cellular automata model has been introduced (Phys. Rev. Lett. 87 (2001) 168102) to describe the spread of the HIV infection among target cells in lymphoid tissues. The model reproduces qualitatively the entire course of the infection displaying, in particular, the two time scales that characterize its dynamics. In this work, we investigate the robustness of the model against changes in three of its parameters. Two of them are related to the resistance of the cells to get infected. The other one describes the time interval necessary to mount specific immune responses. We have observed that an increase of the cell resistance, at any stage of the infection, leads to a reduction of the latency period, i.e., of the time interval between the primary infection and the onset of AIDS. However, during the early stages of the infection, when the cell resistance increase is combined with an increase in the initial concentration of infected cells, the original behavior is recovered. Therefore we find a long and a short latency regime (eight and one year long, respectively) depending on the value of the cell resistance. We have obtained, on the other hand, that changes on the parameter that describes the immune system time lag affects the time interval during which the primary infection occurs. Using different extended versions of the model, we also discuss how the two-time scale dynamics is affected when we include inhomogeneities on the cells properties, as for instance, on the cell resistance or on the time interval to mount specific immune responses.

A Bimodal Hybrid Model for Time-Dependent Probabilistic Seismic Hazard Analysis

NASA Astrophysics Data System (ADS)

Yaghmaei-Sabegh, Saman; Shoaeifar, Nasser; Shoaeifar, Parva

2018-03-01

The evaluation of evidence provided by geological studies and historical catalogs indicates that in some seismic regions and faults, multiple large earthquakes occur in cluster. Then, the occurrences of large earthquakes confront with quiescence and only the small-to-moderate earthquakes take place. Clustering of large earthquakes is the most distinguishable departure from the assumption of constant hazard of random occurrence of earthquakes in conventional seismic hazard analysis. In the present study, a time-dependent recurrence model is proposed to consider a series of large earthquakes that occurs in clusters. The model is flexible enough to better reflect the quasi-periodic behavior of large earthquakes with long-term clustering, which can be used in time-dependent probabilistic seismic hazard analysis with engineering purposes. In this model, the time-dependent hazard results are estimated by a hazard function which comprises three parts. A decreasing hazard of last large earthquake cluster and an increasing hazard of the next large earthquake cluster, along with a constant hazard of random occurrence of small-to-moderate earthquakes. In the final part of the paper, the time-dependent seismic hazard of the New Madrid Seismic Zone at different time intervals has been calculated for illustrative purpose.

Metastasis-free interval in breast cancer patients: Thirty-year trends and time dependency of prognostic factors. A retrospective analysis based on a single institution experience.

PubMed

Houzé de l'Aulnoit, A; Rogoz, B; Pinçon, C; Houzé de l'Aulnoit, D

2018-02-01

Breast cancer remains the leading cause of cancer death in French women in spite of continuously improving management. The objectives of this study were to analyse trends in the metastasis-free interval over the past 30 years and to identify the prognostic factors of survival, while accounting for time dependency. A total of 1613 patients diagnosed with invasive non-metastatic breast cancer at Saint Vincent de Paul Hospital, Lille, France between 1977 and 2013, were followed for outcome (metastasis-free interval). Cohort entry time delay, a continuous temporal covariate, was defined to assess improvement of outcome. Data were analysed using the Cox proportional hazards model and presented as hazard ratio (HR). Metastatic disease developed during follow-up in 446 (27.6%) patients. Cohort entry time delay exhibited strong independent prognostic value while accounting for multiple prognostic factors including: tumour size (HR = 1.62, 95 %CI 1.37-1.91); rapid tumour growth (HR = 1.59, 95%CI 1.17-2.16); lymph node ratio (HR = 2.29, 95%CI 1.97-2.66); histological grade (grade 2 was significant only during the first 10 years after diagnosis, grade 3 and progesterone receptor status only during the first 5 years after diagnosis); and oestrogen receptor status (significant only during the first 8 years (HR = 0.75, 95%CI 0.58-0.96)). The current study showed an improvement in the prognosis of breast cancer patients over the past 30 years and pointed to the importance of evaluating covariates with time-varying effects. Copyright © 2017 Elsevier Ltd. All rights reserved.

Parental Smoking Exposure and Adolescent Smoking Trajectories

PubMed Central

Gilman, Stephen E.; Rende, Richard; Luta, George; Tercyak, Kenneth P.; Niaura, Raymond S.

2014-01-01

OBJECTIVE: In a multigenerational study of smoking risk, the objective was to investigate the intergenerational transmission of smoking by examining if exposure to parental smoking and nicotine dependence predicts prospective smoking trajectories among adolescent offspring. METHODS: Adolescents (n = 406) ages 12 to 17 and a parent completed baseline interviews (2001–2004), and adolescents completed up to 2 follow-up interviews 1 and 5 years later. Baseline interviews gathered detailed information on parental smoking history, including timing and duration, current smoking, and nicotine dependence. Adolescent smoking and nicotine dependence were assessed at each time point. Latent Class Growth Analysis identified prospective smoking trajectory classes from adolescence into young adulthood. Logistic regression was used to examine relationships between parental smoking and adolescent smoking trajectories. RESULTS: Four adolescent smoking trajectory classes were identified: early regular smokers (6%), early experimenters (23%), late experimenters (41%), and nonsmokers (30%). Adolescents with parents who were nicotine-dependent smokers at baseline were more likely to be early regular smokers (odds ratio 1.18, 95% confidence interval 1.05–1.33) and early experimenters (odds ratio 1.04, 95% confidence interval 1.04–1.25) with each additional year of previous exposure to parental smoking. Parents’ current non-nicotine–dependent and former smoking were not associated with adolescent smoking trajectories. CONCLUSIONS: Exposure to parental nicotine dependence is a critical factor influencing intergenerational transmission of smoking. Adolescents with nicotine-dependent parents are susceptible to more intense smoking patterns and this risk increases with longer duration of exposure. Research is needed to optimize interventions to help nicotine-dependent parents quit smoking early in their children’s lifetime to reduce these risks. PMID:24819567

A Lyapunov and Sacker–Sell spectral stability theory for one-step methods

DOE PAGES

Steyer, Andrew J.; Van Vleck, Erik S.

2018-04-13

Approximation theory for Lyapunov and Sacker–Sell spectra based upon QR techniques is used to analyze the stability of a one-step method solving a time-dependent (nonautonomous) linear ordinary differential equation (ODE) initial value problem in terms of the local error. Integral separation is used to characterize the conditioning of stability spectra calculations. The stability of the numerical solution by a one-step method of a nonautonomous linear ODE using real-valued, scalar, nonautonomous linear test equations is justified. This analysis is used to approximate exponential growth/decay rates on finite and infinite time intervals and establish global error bounds for one-step methods approximating uniformly,more » exponentially stable trajectories of nonautonomous and nonlinear ODEs. A time-dependent stiffness indicator and a one-step method that switches between explicit and implicit Runge–Kutta methods based upon time-dependent stiffness are developed based upon the theoretical results.« less

A Lyapunov and Sacker–Sell spectral stability theory for one-step methods

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

Steyer, Andrew J.; Van Vleck, Erik S.

Approximation theory for Lyapunov and Sacker–Sell spectra based upon QR techniques is used to analyze the stability of a one-step method solving a time-dependent (nonautonomous) linear ordinary differential equation (ODE) initial value problem in terms of the local error. Integral separation is used to characterize the conditioning of stability spectra calculations. The stability of the numerical solution by a one-step method of a nonautonomous linear ODE using real-valued, scalar, nonautonomous linear test equations is justified. This analysis is used to approximate exponential growth/decay rates on finite and infinite time intervals and establish global error bounds for one-step methods approximating uniformly,more » exponentially stable trajectories of nonautonomous and nonlinear ODEs. A time-dependent stiffness indicator and a one-step method that switches between explicit and implicit Runge–Kutta methods based upon time-dependent stiffness are developed based upon the theoretical results.« less

A model-free characterization of recurrences in stationary time series

NASA Astrophysics Data System (ADS)

Chicheportiche, Rémy; Chakraborti, Anirban

2017-05-01

Study of recurrences in earthquakes, climate, financial time-series, etc. is crucial to better forecast disasters and limit their consequences. Most of the previous phenomenological studies of recurrences have involved only a long-ranged autocorrelation function, and ignored the multi-scaling properties induced by potential higher order dependencies. We argue that copulas is a natural model-free framework to study non-linear dependencies in time series and related concepts like recurrences. Consequently, we arrive at the facts that (i) non-linear dependences do impact both the statistics and dynamics of recurrence times, and (ii) the scaling arguments for the unconditional distribution may not be applicable. Hence, fitting and/or simulating the intertemporal distribution of recurrence intervals is very much system specific, and cannot actually benefit from universal features, in contrast to the previous claims. This has important implications in epilepsy prognosis and financial risk management applications.

Active, capable, and potentially active faults - a paleoseismic perspective

USGS Publications Warehouse

Machette, M.N.

2000-01-01

Maps of faults (geologically defined source zones) may portray seismic hazards in a wide range of completeness depending on which types of faults are shown. Three fault terms - active, capable, and potential - are used in a variety of ways for different reasons or applications. Nevertheless, to be useful for seismic-hazards analysis, fault maps should encompass a time interval that includes several earthquake cycles. For example, if the common recurrence in an area is 20,000-50,000 years, then maps should include faults that are 50,000-100,000 years old (two to five typical earthquake cycles), thus allowing for temporal variability in slip rate and recurrence intervals. Conversely, in more active areas such as plate boundaries, maps showing faults that are <10,000 years old should include those with at least 2 to as many as 20 paleoearthquakes. For the International Lithosphere Programs' Task Group II-2 Project on Major Active Faults of the World our maps and database will show five age categories and four slip rate categories that allow one to select differing time spans and activity rates for seismic-hazard analysis depending on tectonic regime. The maps are accompanied by a database that describes evidence for Quaternary faulting, geomorphic expression, and paleoseismic parameters (slip rate, recurrence interval and time of most recent surface faulting). These maps and databases provide an inventory of faults that would be defined as active, capable, and potentially active for seismic-hazard assessments.

Reliability-based management of buried pipelines considering external corrosion defects

NASA Astrophysics Data System (ADS)

Miran, Seyedeh Azadeh

Corrosion is one of the main deteriorating mechanisms that degrade the energy pipeline integrity, due to transferring corrosive fluid or gas and interacting with corrosive environment. Corrosion defects are usually detected by periodical inspections using in-line inspection (ILI) methods. In order to ensure pipeline safety, this study develops a cost-effective maintenance strategy that consists of three aspects: corrosion growth model development using ILI data, time-dependent performance evaluation, and optimal inspection interval determination. In particular, the proposed study is applied to a cathodic protected buried steel pipeline located in Mexico. First, time-dependent power-law formulation is adopted to probabilistically characterize growth of the maximum depth and length of the external corrosion defects. Dependency between defect depth and length are considered in the model development and generation of the corrosion defects over time is characterized by the homogenous Poisson process. The growth models unknown parameters are evaluated based on the ILI data through the Bayesian updating method with Markov Chain Monte Carlo (MCMC) simulation technique. The proposed corrosion growth models can be used when either matched or non-matched defects are available, and have ability to consider newly generated defects since last inspection. Results of this part of study show that both depth and length growth models can predict damage quantities reasonably well and a strong correlation between defect depth and length is found. Next, time-dependent system failure probabilities are evaluated using developed corrosion growth models considering prevailing uncertainties where three failure modes, namely small leak, large leak and rupture are considered. Performance of the pipeline is evaluated through failure probability per km (or called a sub-system) where each subsystem is considered as a series system of detected and newly generated defects within that sub-system. Sensitivity analysis is also performed to determine to which incorporated parameter(s) in the growth models reliability of the studied pipeline is most sensitive. The reliability analysis results suggest that newly generated defects should be considered in calculating failure probability, especially for prediction of long-term performance of the pipeline and also, impact of the statistical uncertainty in the model parameters is significant that should be considered in the reliability analysis. Finally, with the evaluated time-dependent failure probabilities, a life cycle-cost analysis is conducted to determine optimal inspection interval of studied pipeline. The expected total life-cycle costs consists construction cost and expected costs of inspections, repair, and failure. The repair is conducted when failure probability from any described failure mode exceeds pre-defined probability threshold after each inspection. Moreover, this study also investigates impact of repair threshold values and unit costs of inspection and failure on the expected total life-cycle cost and optimal inspection interval through a parametric study. The analysis suggests that a smaller inspection interval leads to higher inspection costs, but can lower failure cost and also repair cost is less significant compared to inspection and failure costs.

Comparison of the Chebyshev Method and the Generalized Crank-Nicholson Method for time Propagation in Quantum Mechanics

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

Formanek, Martin; Vana, Martin; Houfek, Karel

2010-09-30

We compare efficiency of two methods for numerical solution of the time-dependent Schroedinger equation, namely the Chebyshev method and the recently introduced generalized Crank-Nicholson method. As a testing system the free propagation of a particle in one dimension is used. The space discretization is based on the high-order finite diferences to approximate accurately the kinetic energy operator in the Hamiltonian. We show that the choice of the more effective method depends on how many wave functions must be calculated during the given time interval to obtain relevant and reasonably accurate information about the system, i.e. on the choice of themore » time step.« less

Investigating the correlation between paediatric stride interval persistence and gross energy expenditure.

PubMed

Fairley, Jillian A; Sejdić, Ervin; Chau, Tom

2010-02-26

Stride interval persistence, a term used to describe the correlation structure of stride interval time series, is thought to provide insight into neuromotor control, though its exact clinical meaning has not yet been realized. Since human locomotion is shaped by energy efficient movements, it has been hypothesized that stride interval dynamics and energy expenditure may be inherently tied, both having demonstrated similar sensitivities to age, disease, and pace-constrained walking. This study tested for correlations between stride interval persistence and measures of energy expenditure including mass-specific gross oxygen consumption per minute (VO₂), mass-specific gross oxygen cost per meter (VO₂) and heart rate (HR). Metabolic and stride interval data were collected from 30 asymptomatic children who completed one 10-minute walking trial under each of the following conditions: (i) overground walking, (ii) hands-free treadmill walking, and (iii) handrail-supported treadmill walking. Stride interval persistence was not significantly correlated with (p > 0.32), VO₂ (p > 0.18) or HR (p > 0.56). No simple linear dependence exists between stride interval persistence and measures of gross energy expenditure in asymptomatic children when walking overground and on a treadmill.

Age of platelet concentrates and time to the next transfusion.

PubMed

Caram-Deelder, Camila; van der Bom, Johanna G; Putter, Hein; Leyte, Anja; Kerkhof, Daan van de; Evers, Dorothea; Beckers, Erik A; Weerkamp, Floor; Hudig, Francisca; Zwaginga, Jaap Jan; Rondeel, Jan M M; de Vooght, Karen M K; Péquériaux, Nathalie C V; Visser, Otto; Wallis, Jonathan P; Middelburg, Rutger A

2018-01-01

Storage time of platelet (PLT) concentrates has been negatively associated with clinical efficacy outcomes. The aim of this study was to quantify the association between storage time of PLT concentrates and interval to the next PLT transfusion for different types of PLT components, stored for up to 7 days and transfused to transfusion-dependent hematooncology patients with thrombocytopenia. From a cohort of patients from 10 major Dutch hospitals, patients were selected whose transfusion patterns were compatible with PLT transfusion dependency due to hematooncologic disease. Mean time to the next transfusion and mean differences in time to the next transfusion for different storage time categories (i.e., fresh, <4 days; intermediate, 4-5 days; and old, >5 days) were estimated, per component type, using multilevel mixed-effects linear models. Among a cohort of 29,761 patients who received 140,896 PLT transfusions we selected 4441 hematooncology patients who had received 12,724 PLT transfusions during periods of PLT transfusion dependency. Transfusion of fresh, compared to old, buffy coat-derived PLTs in plasma was associated with a delay to the next transfusion of 6.2 hours (95% confidence interval [CI], 4.5-8.0 hr). For buffy coat-derived PLTs in PAS-B and -C this difference was 7.7 hours (95% CI, 2.2-13.3 hr) and 3.9 hours (95% CI, -2.1 to 9.9 hr) while for apheresis PLTs in plasma it was only 1.8 hours (95% CI, -3.5 to 7.1 hr). Our results indicate that the time to the next transfusion shortens with increasing age of transfused buffy coat-derived PLT concentrates. This association was not observed for apheresis PLTs. © 2017 AABB.

The Time Dependent Propensity Function for Acceleration of Spatial Stochastic Simulation of Reaction-Diffusion Systems

PubMed Central

Wu, Sheng; Li, Hong; Petzold, Linda R.

2015-01-01

The inhomogeneous stochastic simulation algorithm (ISSA) is a fundamental method for spatial stochastic simulation. However, when diffusion events occur more frequently than reaction events, simulating the diffusion events by ISSA is quite costly. To reduce this cost, we propose to use the time dependent propensity function in each step. In this way we can avoid simulating individual diffusion events, and use the time interval between two adjacent reaction events as the simulation stepsize. We demonstrate that the new algorithm can achieve orders of magnitude efficiency gains over widely-used exact algorithms, scales well with increasing grid resolution, and maintains a high level of accuracy. PMID:26609185

The time-domain behavior of power-law noises. [of many geophysical phenomena

NASA Technical Reports Server (NTRS)

Agnew, Duncan C.

1992-01-01

The power spectra of many geophysical phenomena are well approximated by a power-law dependence on frequency or wavenumber. A simple expression for the root-mean-square variability of a process with such a spectrum over an interval of time or space is derived. The resulting expression yields the powerlaw time dependence characteristic of fractal processes, but can be generalized to give the temporal variability for more general spectral behaviors. The method is applied to spectra of crustal strain (to show what size of strain events can be detected over periods of months to seconds) and of sea level (to show the difficulty of extracting long-term rates from short records).

Have the temperature time series a structural change after 1998?

NASA Astrophysics Data System (ADS)

Werner, Rolf; Valev, Dimitare; Danov, Dimitar

2012-07-01

The global and hemisphere temperature GISS and Hadcrut3 time series were analysed for structural changes. We postulate the continuity of the preceding temperature function depending from the time. The slopes are calculated for a sequence of segments limited by time thresholds. We used a standard method, the restricted linear regression with dummy variables. We performed the calculations and tests for different number of thresholds. The thresholds are searched continuously in determined time intervals. The F-statistic is used to obtain the time points of the structural changes.

Response of single bacterial cells to stress gives rise to complex history dependence at the population level

PubMed Central

Mathis, Roland; Ackermann, Martin

2016-01-01

Most bacteria live in ever-changing environments where periods of stress are common. One fundamental question is whether individual bacterial cells have an increased tolerance to stress if they recently have been exposed to lower levels of the same stressor. To address this question, we worked with the bacterium Caulobacter crescentus and asked whether exposure to a moderate concentration of sodium chloride would affect survival during later exposure to a higher concentration. We found that the effects measured at the population level depended in a surprising and complex way on the time interval between the two exposure events: The effect of the first exposure on survival of the second exposure was positive for some time intervals but negative for others. We hypothesized that the complex pattern of history dependence at the population level was a consequence of the responses of individual cells to sodium chloride that we observed: (i) exposure to moderate concentrations of sodium chloride caused delays in cell division and led to cell-cycle synchronization, and (ii) whether a bacterium would survive subsequent exposure to higher concentrations was dependent on the cell-cycle state. Using computational modeling, we demonstrated that indeed the combination of these two effects could explain the complex patterns of history dependence observed at the population level. Our insight into how the behavior of single cells scales up to processes at the population level provides a perspective on how organisms operate in dynamic environments with fluctuating stress exposure. PMID:26960998

The contribution of disengagement to temporal discriminability.

PubMed

Shipstead, Zach; Nespodzany, Ashley

2018-05-01

The present study examines the idea that time-based forgetting of outdated information can lead to better memory of currently relevant information. This was done using the visual arrays task, along with a between-subjects manipulation of both the retention interval (1 s vs. 4 s) and the time between two trials (1 s vs. 4 s). Consistent with prior work [Shipstead, Z., & Engle, R. W. (2013). Interference within the focus of attention: Working memory tasks reflect more than temporary maintenance. Journal of Experimental Psychology: Learning, Memory, and Cognition, 39, 277-289; Experiment 1], longer retention intervals did not lead to diminished memory of currently relevant information. However, we did find that longer periods of time between two trials improved memory for currently relevant information. This replicates findings that indicate proactive interference affects visual arrays performance and extends previous findings to show that reduction of proactive interference can occur in a time-dependent manner.

Are EUR and GBP different words for the same currency?

NASA Astrophysics Data System (ADS)

Ivanova, K.; Ausloos, M.

2002-05-01

The British Pound (GBP) is not part of the Euro (EUR) monetary system. In order to find out arguments on whether GBP should join the EUR or not correlations are calculated between GBP exchange rates with respect to various currencies: USD, JPY, CHF, DKK, the currencies forming EUR and a reconstructed EUR for the time interval from 1993 till June 30, 2000. The distribution of fluctuations of the exchange rates is Gaussian for the central part of the distribution, but has fat tails for the large size fluctuations. Within the Detrended Fluctuation Analysis (DFA) statistical method the power law behavior describing the root-mean-square deviation from a linear trend of the exchange rate fluctuations is obtained as a function of time for the time interval of interest. The time-dependent exponent evolution of the exchange rate fluctuations is given. Statistical considerations imply that the GBP is already behaving as a true EUR.

Human's choices in situations of time-based diminishing returns.

PubMed Central

Hackenberg, T D; Axtell, S A

1993-01-01

Three experiments examined adult humans' choices in situations with contrasting short-term and long-term consequences. Subjects were given repeated choices between two time-based schedules of points exchangeable for money: a fixed schedule and a progressive schedule that began at 0 s and increased by 5 s with each point delivered by that schedule. Under "reset" conditions, choosing the fixed schedule not only produced a point but it also reset the requirements of the progressive schedule to 0 s. In the first two experiments, reset conditions alternated with "no-reset" conditions, in which progressive-schedule requirements were independent of fixed-schedule choices. Experiment 1 entailed choices between a progressive-interval schedule and a fixed-interval schedule, the duration of which varied across conditions. Switching from the progressive- to the fixed-interval schedule was systematically related to fixed-interval size in 4 of 8 subjects, and in all subjects occurred consistently sooner in the progressive-schedule sequence under reset than under no-reset procedures. The latter result was replicated in a second experiment, in which choices between progressive- and fixed-interval schedules were compared with choices between progressive- and fixed-time schedules. In Experiment 3, switching patterns under reset conditions were unrelated to variations in intertrial interval. In none of the experiments did orderly choice patterns depend on verbal descriptions of the contingencies or on schedule-controlled response patterns in the presence of the chosen schedules. The overall pattern of results indicates control of choices by temporarily remote consequences, and is consistent with versions of optimality theory that address performance in situations of diminishing returns. PMID:8315364

Recurrence Interval and Event Age Data for Type A Faults

USGS Publications Warehouse

Dawson, Timothy E.; Weldon, Ray J.; Biasi, Glenn P.

2008-01-01

This appendix summarizes available recurrence interval, event age, and timing of most recent event data for Type A faults considered in the Earthquake Rate Model 2 (ERM 2) and used in the ERM 2 Appendix C analysis as well as Appendix N (time-dependent probabilities). These data have been compiled into an Excel workbook named Appendix B A-fault event ages_recurrence_V5.0 (herein referred to as the Appendix B workbook). For convenience, the Appendix B workbook is attached to the end of this document as a series of tables. The tables within the Appendix B workbook include site locations, event ages, and recurrence data, and in some cases, the interval of time between earthquakes is also reported. The Appendix B workbook is organized as individual worksheets, with each worksheet named by fault and paleoseismic site. Each worksheet contains the site location in latitude and longitude, as well as information on event ages, and a summary of recurrence data. Because the data has been compiled from different sources with different presentation styles, descriptions of the contents of each worksheet within the Appendix B spreadsheet are summarized.

Developing Empirical Lightning Cessation Forecast Guidance for the Cape Canaveral Air Force Station and Kennedy Space Center

NASA Technical Reports Server (NTRS)

Stano, Geoffrey T.; Fuelberg, Henry E.; Roeder, William P.

2010-01-01

This research addresses the 45th Weather Squadron's (45WS) need for improved guidance regarding lightning cessation at Cape Canaveral Air Force Station and Kennedy Space Center (KSC). KSC's Lightning Detection and Ranging (LDAR) network was the primary observational tool to investigate both cloud-to-ground and intracloud lightning. Five statistical and empirical schemes were created from LDAR, sounding, and radar parameters derived from 116 storms. Four of the five schemes were unsuitable for operational use since lightning advisories would be canceled prematurely, leading to safety risks to personnel. These include a correlation and regression tree analysis, three variants of multiple linear regression, event time trending, and the time delay between the greatest height of the maximum dBZ value to the last flash. These schemes failed to adequately forecast the maximum interval, the greatest time between any two flashes in the storm. The majority of storms had a maximum interval less than 10 min, which biased the schemes toward small values. Success was achieved with the percentile method (PM) by separating the maximum interval into percentiles for the 100 dependent storms.

Use of Data Comm by Flight Crew to Conduct Interval Management Operations to Parallel Dependent Runways

NASA Technical Reports Server (NTRS)

Baxley, Brian T.; Hubbs, Clay; Shay, Rick; Karanian, James

2011-01-01

The Interval Management (IM) concept is being developed as a method to maintain or increase high traffic density airport arrival throughput while allowing aircraft to conduct near idle thrust descents. The Interval Management with Spacing to Parallel Dependent Runways (IMSPiDR1) experiment at NASA Langley Research Center used 24 commercial pilots to examine IM procedures to conduct parallel dependent runway arrival operations while maintaining safe but efficient intervals behind the preceding aircraft. The use of IM procedures during these operations requires a lengthy and complex clearance from Air Traffic Control (ATC) to the participating aircraft, thereby making the use of Controller Pilot Data Link Communications (CPDLC) highly desirable as the communication method. The use of CPDLC reduces the need for voice transmissions between controllers and flight crew, and enables automated transfer of IM clearance elements into flight management systems or other aircraft avionics. The result is reduced crew workload and an increase in the efficiency of crew procedures. This paper focuses on the subset of data collected related to the use of CPDLC for IM operations into a busy airport. Overall, the experiment and results were very successful, with the mean time under 43 seconds for the flight crew to load the clearance into the IM spacing tool, review the calculated speed, and respond to ATC. An overall mean rating of Moderately Agree was given when the crews were asked if the use of CPDLC was operationally acceptable as simulated in this experiment. Approximately half of the flight crew reported the use of CPDLC below 10,000 for IM operations was unacceptable, with 83% reporting below 5000 was unacceptable. Also described are proposed modifications to the IM operations that may reduce CPDLC Respond time to less than 30 seconds and should significantly reduce the complexity of crew procedures, as well as follow-on research issues for operational use of CPDLC during IM operations.

Estimating degradation in real time and accelerated stability tests with random lot-to-lot variation: a simulation study.

PubMed

Magari, Robert T

2002-03-01

The effect of different lot-to-lot variability levels on the prediction of stability are studied based on two statistical models for estimating degradation in real time and accelerated stability tests. Lot-to-lot variability is considered as random in both models, and is attributed to two sources-variability at time zero, and variability of degradation rate. Real-time stability tests are modeled as a function of time while accelerated stability tests as a function of time and temperatures. Several data sets were simulated, and a maximum likelihood approach was used for estimation. The 95% confidence intervals for the degradation rate depend on the amount of lot-to-lot variability. When lot-to-lot degradation rate variability is relatively large (CV > or = 8%) the estimated confidence intervals do not represent the trend for individual lots. In such cases it is recommended to analyze each lot individually. Copyright 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91: 893-899, 2002

A model of partial differential equations for HIV propagation in lymph nodes

NASA Astrophysics Data System (ADS)

Marinho, E. B. S.; Bacelar, F. S.; Andrade, R. F. S.

2012-01-01

A system of partial differential equations is used to model the dissemination of the Human Immunodeficiency Virus (HIV) in CD4+T cells within lymph nodes. Besides diffusion terms, the model also includes a time-delay dependence to describe the time lag required by the immunologic system to provide defenses to new virus strains. The resulting dynamics strongly depends on the properties of the invariant sets of the model, consisting of three fixed points related to the time independent and spatial homogeneous tissue configurations in healthy and infected states. A region in the parameter space is considered, for which the time dependence of the space averaged model variables follows the clinical pattern reported for infected patients: a short scale primary infection, followed by a long latency period of almost complete recovery and third phase characterized by damped oscillations around a value with large HIV counting. Depending on the value of the diffusion coefficient, the latency time increases with respect to that one obtained for the space homogeneous version of the model. It is found that same initial conditions lead to quite different spatial patterns, which depend strongly on the latency interval.

Time-dependent neo-deterministic seismic hazard scenarios for the 2016 Central Italy earthquakes sequence

NASA Astrophysics Data System (ADS)

Peresan, Antonella; Kossobokov, Vladimir; Romashkova, Leontina; Panza, Giuliano F.

2017-04-01

Predicting earthquakes and related ground shaking is widely recognized among the most challenging scientific problems, both for societal relevance and intrinsic complexity of the problem. The development of reliable forecasting tools requires their rigorous formalization and testing, first in retrospect, and then in an experimental real-time mode, which imply a careful application of statistics to data sets of limited size and different accuracy. Accordingly, the operational issues of prospective validation and use of time-dependent neo-deterministic seismic hazard scenarios are discussed, reviewing the results in their application in Italy and surroundings. Long-term practice and results obtained for the Italian territory in about two decades of rigorous prospective testing, support the feasibility of earthquake forecasting based on the analysis of seismicity patterns at the intermediate-term middle-range scale. Italy is the only country worldwide where two independent, globally tested, algorithms are simultaneously applied, namely CN and M8S, which permit to deal with multiple sets of seismic precursors to allow for a diagnosis of the intervals of time when a strong event is likely to occur inside a given region. Based on routinely updated space-time information provided by CN and M8S forecasts, an integrated procedure has been developed that allows for the definition of time-dependent seismic hazard scenarios, through the realistic modeling of ground motion by the neo-deterministic approach (NDSHA). This scenario-based methodology permits to construct, both at regional and local scale, scenarios of ground motion for the time interval when a strong event is likely to occur within the alerted areas. CN and M8S predictions, as well as the related time-dependent ground motion scenarios associated with the alarmed areas, are routinely updated since 2006. The issues and results from real-time testing of the integrated NDSHA scenarios are illustrated, with special emphasis on the sequence of destructive earthquakes that struck Central Italy starting on August 2016. The results obtained so far evidence the validity of the proposed methodology in anticipating ground shaking from approaching strong earthquakes and prove that the information provided by time-dependent NDSHA can be useful in assigning priorities for timely and effective mitigation actions.

Are Earthquake Clusters/Supercycles Real or Random?

NASA Astrophysics Data System (ADS)

Salditch, L.; Brooks, E. M.; Stein, S.; Spencer, B. D.

2016-12-01

Long records of earthquakes at plate boundaries such as the San Andreas or Cascadia often show that large earthquakes occur in temporal clusters, also termed supercycles, separated by less active intervals. These are intriguing because the boundary is presumably being loaded by steady plate motion. If so, earthquakes resulting from seismic cycles - in which their probability is small shortly after the past one, and then increases with time - should occur quasi-periodically rather than be more frequent in some intervals than others. We are exploring this issue with two approaches. One is to assess whether the clusters result purely by chance from a time-independent process that has no "memory." Thus a future earthquake is equally likely immediately after the past one and much later, so earthquakes can cluster in time. We analyze the agreement between such a model and inter-event times for Parkfield, Pallet Creek, and other records. A useful tool is transformation by the inverse cumulative distribution function, so the inter-event times have a uniform distribution when the memorylessness property holds. The second is via a time-variable model in which earthquake probability increases with time between earthquakes and decreases after an earthquake. The probability of an event increases with time until one happens, after which it decreases, but not to zero. Hence after a long period of quiescence, the probability of an earthquake can remain higher than the long-term average for several cycles. Thus the probability of another earthquake is path dependent, i.e. depends on the prior earthquake history over multiple cycles. Time histories resulting from simulations give clusters with properties similar to those observed. The sequences of earthquakes result from both the model parameters and chance, so two runs with the same parameters look different. The model parameters control the average time between events and the variation of the actual times around this average, so models can be strongly or weakly time-dependent.

Adaptation to visual or auditory time intervals modulates the perception of visual apparent motion

PubMed Central

Zhang, Huihui; Chen, Lihan; Zhou, Xiaolin

2012-01-01

It is debated whether sub-second timing is subserved by a centralized mechanism or by the intrinsic properties of task-related neural activity in specific modalities (Ivry and Schlerf, 2008). By using a temporal adaptation task, we investigated whether adapting to different time intervals conveyed through stimuli in different modalities (i.e., frames of a visual Ternus display, visual blinking discs, or auditory beeps) would affect the subsequent implicit perception of visual timing, i.e., inter-stimulus interval (ISI) between two frames in a Ternus display. The Ternus display can induce two percepts of apparent motion (AM), depending on the ISI between the two frames: “element motion” for short ISIs, in which the endmost disc is seen as moving back and forth while the middle disc at the overlapping or central position remains stationary; “group motion” for longer ISIs, in which both discs appear to move in a manner of lateral displacement as a whole. In Experiment 1, participants adapted to either the typical “element motion” (ISI = 50 ms) or the typical “group motion” (ISI = 200 ms). In Experiments 2 and 3, participants adapted to a time interval of 50 or 200 ms through observing a series of two paired blinking discs at the center of the screen (Experiment 2) or hearing a sequence of two paired beeps (with pitch 1000 Hz). In Experiment 4, participants adapted to sequences of paired beeps with either low pitches (500 Hz) or high pitches (5000 Hz). After adaptation in each trial, participants were presented with a Ternus probe in which the ISI between the two frames was equal to the transitional threshold of the two types of motions, as determined by a pretest. Results showed that adapting to the short time interval in all the situations led to more reports of “group motion” in the subsequent Ternus probes; adapting to the long time interval, however, caused no aftereffect for visual adaptation but significantly more reports of group motion for auditory adaptation. These findings, suggesting amodal representation for sub-second timing across modalities, are interpreted in the framework of temporal pacemaker model. PMID:23133408

Long-term engagement in smoking cessation counseling among rural smokers.

PubMed

Cupertino, A Paula; Mahnken, Jonathan D; Richter, Kimber; Cox, Lisa Sanderson; Casey, Genevieve; Resnicow, Ken; Ellerbeck, Edward F

2007-11-01

Effective smoking cessation treatment requires active patient engagement. This may be particularly important for rural smokers who have less access to smoking cessation resources than others. This study describes long-term engagement in counseling for smoking cessation and factors associated with engagement. As part of a randomized trial, 231 rural smokers received up to 6 telephone-based counseling sessions at 6-month intervals over 24 months. Engagement in treatment was categorized according to the number of counseling calls each interval. During the final 6-month interval, more than 60% of continuing smokers remained engaged in treatment. Call completion varied over time; while levels of engagement dropped after the first interval, many continuing smokers remained engaged throughout the study. Education, age, motivation, income, diabetes, and health insurance status were predictors of treatment engagement. This study demonstrates that smokers will remain engaged in long-term counseling designed to address the chronic nature of nicotine dependence.

Efficacy and safety of tranexamic acid as an emetic in dogs.

PubMed

Kakiuchi, Hitoshi; Kawarai-Shimamura, Asako; Fujii, Yoko; Aoki, Takuma; Yoshiike, Masaki; Arai, Hayato; Nakamura, Atsushi; Orito, Kensuke

2014-12-01

To determine dose dependency of tranexamic acid-induced emesis and the time course of the antifibrinolytic potency of tranexamic acid in dogs. 10 Beagles. In a dose-escalating experiment, ascending doses of tranexamic acid (10, 20, and 30 mg/kg, IV) were administered at 5-minute intervals until vomiting was observed. In a separate single-dose experiment, ascending doses of tranexamic acid (20, 30, 40, and 50 mg/kg, IV) were administered at 1-week intervals until vomiting was observed. Time to onset of vomiting and number of vomiting episodes were measured in both experiments. In a coagulation experiment, a single 50 mg/kg bolus of tranexamic acid was administered, and blood was obtained 1 hour before and 20 minutes, 3 hours, and 24 hours after administration. Antifibrinolytic potency of tranexamic acid was evaluated by use of a modified rotational thromboelastography method. Tranexamic acid induced vomiting in a dose-dependent manner. Vomiting frequency was ≤ 2 episodes, and vomiting concluded ≤ 250 seconds after administration. Antifibrinolytic potency of tranexamic acid was significantly higher at 20 minutes following administration, but not different by 24 hours, when compared with the potency measured before administration. No adverse effects were observed in any experiment. IV administration of tranexamic acid induced emesis in a dose-dependent manner. The antifibrinolytic potency of tranexamic acid decreased in a time-dependent manner and was resolved ≤ 24 hours after administration. Further studies are warranted to investigate the emetic and other adverse effects of tranexamic acid in dogs of various breeds and ages.

Alternative Confidence Interval Methods Used in the Diagnostic Accuracy Studies

PubMed Central

Gülhan, Orekıcı Temel

2016-01-01

Background/Aim. It is necessary to decide whether the newly improved methods are better than the standard or reference test or not. To decide whether the new diagnostics test is better than the gold standard test/imperfect standard test, the differences of estimated sensitivity/specificity are calculated with the help of information obtained from samples. However, to generalize this value to the population, it should be given with the confidence intervals. The aim of this study is to evaluate the confidence interval methods developed for the differences between the two dependent sensitivity/specificity values on a clinical application. Materials and Methods. In this study, confidence interval methods like Asymptotic Intervals, Conditional Intervals, Unconditional Interval, Score Intervals, and Nonparametric Methods Based on Relative Effects Intervals are used. Besides, as clinical application, data used in diagnostics study by Dickel et al. (2010) has been taken as a sample. Results. The results belonging to the alternative confidence interval methods for Nickel Sulfate, Potassium Dichromate, and Lanolin Alcohol are given as a table. Conclusion. While preferring the confidence interval methods, the researchers have to consider whether the case to be compared is single ratio or dependent binary ratio differences, the correlation coefficient between the rates in two dependent ratios and the sample sizes. PMID:27478491

Alternative Confidence Interval Methods Used in the Diagnostic Accuracy Studies.

PubMed

Erdoğan, Semra; Gülhan, Orekıcı Temel

2016-01-01

Background/Aim. It is necessary to decide whether the newly improved methods are better than the standard or reference test or not. To decide whether the new diagnostics test is better than the gold standard test/imperfect standard test, the differences of estimated sensitivity/specificity are calculated with the help of information obtained from samples. However, to generalize this value to the population, it should be given with the confidence intervals. The aim of this study is to evaluate the confidence interval methods developed for the differences between the two dependent sensitivity/specificity values on a clinical application. Materials and Methods. In this study, confidence interval methods like Asymptotic Intervals, Conditional Intervals, Unconditional Interval, Score Intervals, and Nonparametric Methods Based on Relative Effects Intervals are used. Besides, as clinical application, data used in diagnostics study by Dickel et al. (2010) has been taken as a sample. Results. The results belonging to the alternative confidence interval methods for Nickel Sulfate, Potassium Dichromate, and Lanolin Alcohol are given as a table. Conclusion. While preferring the confidence interval methods, the researchers have to consider whether the case to be compared is single ratio or dependent binary ratio differences, the correlation coefficient between the rates in two dependent ratios and the sample sizes.

Effects of a temperature-dependent rheology on large scale continental extension

NASA Technical Reports Server (NTRS)

Sonder, Leslie J.; England, Philip C.

1988-01-01

The effects of a temperature-dependent rheology on large-scale continental extension are investigated using a thin viscous sheet model. A vertically-averaged rheology is used that is consistent with laboratory experiments on power-law creep of olivine and that depends exponentially on temperature. Results of the calculations depend principally on two parameters: the Peclet number, which describes the relative rates of advection and diffusion of heat, and a dimensionless activation energy, which controls the temperature dependence of the rheology. At short times following the beginning of extension, deformation occurs with negligible change in temperature, so that only small changes in lithospheric strength occur due to attenuation of the lithosphere. However, after a certain critical time interval, thermal diffusion lowers temperatures in the lithosphere, strongly increasing lithospheric strength and slowing the rate of extension. This critical time depends principally on the Peclet number and is short compared with the thermal time constant of the lithosphere. The strength changes cause the locus of high extensional strain rates to shift with time from regions of high strain to regions of low strain. Results of the calculations are compared with observations from the Aegean, where maximum extensional strains are found in the south, near Crete, but maximum present-day strain rates are largest about 300 km further north.

Evaluation of a Tool for Airborne-Managed In-Trail Approach Spacing

NASA Technical Reports Server (NTRS)

Oseguera-Lohr, Rosa M.; Lohr, Gary W.; Abbott, Terence S.; Nadler, Eric D.; Eischeid, Todd

2005-01-01

The Advanced Terminal Area Approach Spacing (ATAAS) tool uses Automatic Dependent Surveillance-Broadcast aircraft state data to compute a speed command for an ATAAS-equipped aircraft to follow and obtain a required time interval behind another aircraft. The ATAAS tool and candidate operational procedures were tested in a high-fidelity, full mission simulator with active airline subject pilots flying an arrival scenario to obtain pilot perceptions of acceptability and workload for the concept. The aircraft consistently achieved the target spacing interval within 1 s when the ATAAS speed guidance was autothrottle-coupled and a slightly greater (4 - 5 s) but consistent interval with pilot-controlled speed changes. The subject pilots rated the ATAAS workload as similar to one with standard procedures for a nominal Instrument Landing System (ILS) approach. They also rated highly various procedural aspects (including amount of head-down time required). Eyetracker data showed only slight changes in instrument scan patterns for ATAAS versus standard ILS procedures.

Effects of psilocybin on time perception and temporal control of behaviour in humans.

PubMed

Wittmann, Marc; Carter, Olivia; Hasler, Felix; Cahn, B Rael; Grimberg, Ulrike; Spring, Philipp; Hell, Daniel; Flohr, Hans; Vollenweider, Franz X

2007-01-01

Hallucinogenic psilocybin is known to alter the subjective experience of time. However, there is no study that systematically investigated objective measures of time perception under psilocybin. Therefore, we studied dose-dependent effects of the serotonin (5-HT)2A/1A receptor agonist psilocybin (4-phosphoryloxy-N, N-dimethyltryptamine) on temporal processing, employing tasks of temporal reproduction, sensorimotor synchronization and tapping tempo. To control for cognitive and subjective changes, we assessed spatial working memory and conscious experience. Twelve healthy human volunteers were tested under placebo, medium (115 microg/kg), and high (250 microg/kg) dose conditions, in a double-blind experimental design. Psilocybin was found to significantly impair subjects' ability to (1) reproduce interval durations longer than 2.5 sec, (2) to synchronize to inter-beat intervals longer than 2 sec and (3) caused subjects to be slower in their preferred tapping rate. These objective effects on timing performance were accompanied by working-memory deficits and subjective changes in conscious state, namely increased reports of 'depersonalization' and 'derealization' phenomena including disturbances in subjective 'time sense.' Our study is the first to systematically assess the impact of psilocybin on timing performance on standardized measures of temporal processing. Results indicate that the serotonin system is selectively involved in duration processing of intervals longer than 2 to 3 seconds and in the voluntary control of the speed of movement. We speculate that psilocybin's selective disruption of longer intervals is likely to be a product of interactions with cognitive dimensions of temporal processing -presumably via 5-HT2A receptor stimulation.

Evaluation of Operational Procedures for Using a Time-Based Airborne Inter-arrival Spacing Tool

NASA Technical Reports Server (NTRS)

Oseguera-Lohr, Rosa M.; Lohr, Gary W.; Abbott, Terence S.; Eischeid, Todd M.

2002-01-01

An airborne tool has been developed based on the concept of an aircraft maintaining a time-based spacing interval from the preceding aircraft. The Advanced Terminal Area Approach Spacing (ATAAS) tool uses Automatic Dependent Surveillance-Broadcast (ADS-B) aircraft state data to compute a speed command for the ATAAS-equipped aircraft to obtain a required time interval behind another aircraft. The tool and candidate operational procedures were tested in a high-fidelity, full mission simulator with active airline subject pilots flying an arrival scenario using three different modes for speed control. The objectives of this study were to validate the results of a prior Monte Carlo analysis of the ATAAS algorithm and to evaluate the concept from the standpoint of pilot acceptability and workload. Results showed that the aircraft was able to consistently achieve the target spacing interval within one second (the equivalent of approximately 220 ft at a final approach speed of 130 kt) when the ATAAS speed guidance was autothrottle-coupled, and a slightly greater (4-5 seconds), but consistent interval with the pilot-controlled speed modes. The subject pilots generally rated the workload level with the ATAAS procedure as similar to that with standard procedures, and also rated most aspects of the procedure high in terms of acceptability. Although pilots indicated that the head-down time was higher with ATAAS, the acceptability of head-down time was rated high. Oculometer data indicated slight changes in instrument scan patterns, but no significant change in the amount of time spent looking out the window between the ATAAS procedure versus standard procedures.

A note on windowing for the waveform relaxation

NASA Technical Reports Server (NTRS)

Zhang, Hong

1994-01-01

The technique of windowing has been often used in the implementation of the waveform relaxations for solving ODE's or time dependent PDE's. Its efficiency depends upon problem stiffness and operator splitting. Using model problems, the estimates for window length and convergence rate are derived. The electiveness of windowing is then investigated for non-stiff and stiff cases respectively. lt concludes that for the former, windowing is highly recommended when a large discrepancy exists between the convergence rate on a time interval and the ones on its subintervals. For the latter, windowing does not provide any computational advantage if machine features are disregarded. The discussion is supported by experimental results.

Consideration of computer limitations in implementing on-line controls. M.S. Thesis

NASA Technical Reports Server (NTRS)

Roberts, G. K.

1976-01-01

A formal statement of the optimal control problem which includes the interval of dicretization as an optimization parameter, and extend this to include selection of a control algorithm as part of the optimization procedure, is formulated. The performance of the scalar linear system depends on the discretization interval. Discrete-time versions of the output feedback regulator and an optimal compensator, and the use of these results in presenting an example of a system for which fast partial-state-feedback control better minimizes a quadratic cost than either a full-state feedback control or a compensator, are developed.

The date-delay framing effect in temporal discounting depends on substance abuse.

PubMed

Klapproth, Florian

2012-07-01

In the present study, individuals with substance use disorders (n=30) and non-addicted controls (n=30) were presented with a delay-discounting task with time being described either as dates or as temporal intervals. Three main results were obtained. First, in both groups reward size had a large impact on discounting future rewards, with discount rates becoming larger with smaller reward sizes. Second, participants discounted future rewards less strongly when their time of delivery was presented as a date instead of a temporal distance. Third, whereas discount rates of individuals with substance use disorders varied substantially with regard to the presentation of time in the task, the controls changed their choices depending on time presentation only slightly. Copyright © 2012 Elsevier B.V. All rights reserved.

The Cutaneous Rabbit Revisited

ERIC Educational Resources Information Center

Flach, Rudiger; Haggard, Patrick

2006-01-01

In the cutaneous rabbit effect (CRE), a tactile event (so-called attractee tap) is mislocalized toward an adjacent attractor tap. The effect depends on the time interval between the taps. The authors delivered sequences of taps to the forearm and asked participants to report the location of one of the taps. The authors replicated the original CRE…

Radiocarbon content in the annual tree rings during last 150 years and time variation of cosmic rays

NASA Technical Reports Server (NTRS)

Kocharov, G. E.; Metskvarishvili, R. Y.; Tsereteli, S. L.

1985-01-01

The results of the high accuracy measurements of radiocarbon abundance in precisely dated tree rings in the interval 1800 to 1950 yrs are discussed. Radiocarbon content caused by solar activity is established. The temporal dependence of cosmic rays is constructed, by use of radio abundance data.

Prospective Memory in HIV-associated Neurocognitive Disorders (HAND): The Neuropsychological Dynamics of Time Monitoring

PubMed Central

Doyle, Katie L.; Loft, Shayne; Morgan, Erin E.; Weber, Erica; Cushman, Clint; Johnston, Elaine; Grant, Igor; Woods, Steven Paul

2013-01-01

Strategic monitoring during a delay interval is theorized to be an essential feature of time-based prospective memory (TB PM), the cognitive architecture of which is thought to rely heavily on frontostriatal systems and executive functions. This hypothesis was examined in 55 individuals with HIV-associated neurocognitive disorders (HAND) and 108 seronegative comparison participants who were administered the Memory for Intentions Screening Test (MIST), during which time monitoring (clock checking) behavior was measured. Results revealed a significant interaction between HAND group and the frequency of clock checking, in which individuals with HAND monitored checked the clock significantly less often than the comparison group across the TB PM retention intervals of the MIST. Subsequent analyses in the HAND sample revealed that the frequency of clocking checking was positively related to overall TB performance, as well as to standard clinical measures of retrospective memory and verbal fluency. These findings add support to a growing body of research elucidating TB PM’s reliance on strategic monitoring processes dependent upon intact frontostriatal systems. HIV-associated TB strategic time monitoring deficits may manifest in poorer functioning outcomes, including medication non-adherence and dependence in activities of daily living. Future research is needed to further delineate the cognitive mechanisms underlying strategic time monitoring in order to advise rehabilitation strategies for reducing HAND related TB PM deficits. PMID:23465043

In vivo gamma-rays induced initial DNA damage and the effect of famotidine in mouse leukocytes as assayed by the alkaline comet assay.

PubMed

Mozdarani, Hossein; Nasirian, Borzo; Haeri, S Abolghasem

2007-03-01

Ionizing radiation induces a variety of lesions in DNA, each of which can be used as a bio-indicator for biological dosimetry or the study of the radioprotective effects of substances. To assess gamma ray-induced DNA damage in vivo in mouse leukocytes at various doses and the effect of famotidine, blood was collected from Balb/c male mice after irradiation with 4 Gy gamma-rays at different time intervals post-irradiation. To assess the response, mice were irradiated with doses of gamma-rays at 1 to 4 Grays. Famotidine was injected intra-peritoneally (i.p) at a dose of 5 mg/kg at various time intervals before irradiation. Four slides were prepared from each sample and alkaline comet assay was performed using standard protocols. Results obtained show that radiation significantly increases DNA damage in leukocytes in a dose dependent manner (p < 0.01) when using appropriate sampling time after irradiation, because increasing sampling time after irradiation resulted in a time dependent disappearance of DNA damage. Treatment with only 5 mg/kg famotidine before 4 Gy irradiation led to almost 50% reduction in DNA damage when compared with those animals which received radiation alone. The radioprotective capability of famotidine might be attributed to radical scavenging properties and an anti-oxidation mechanism.

Reasoning about real-time systems with temporal interval logic constraints on multi-state automata

NASA Technical Reports Server (NTRS)

Gabrielian, Armen

1991-01-01

Models of real-time systems using a single paradigm often turn out to be inadequate, whether the paradigm is based on states, rules, event sequences, or logic. A model-based approach to reasoning about real-time systems is presented in which a temporal interval logic called TIL is employed to define constraints on a new type of high level automata. The combination, called hierarchical multi-state (HMS) machines, can be used to model formally a real-time system, a dynamic set of requirements, the environment, heuristic knowledge about planning-related problem solving, and the computational states of the reasoning mechanism. In this framework, mathematical techniques were developed for: (1) proving the correctness of a representation; (2) planning of concurrent tasks to achieve goals; and (3) scheduling of plans to satisfy complex temporal constraints. HMS machines allow reasoning about a real-time system from a model of how truth arises instead of merely depending of what is true in a system.

Cathepsin B is a novel gender-dependent determinant of cholesterol absorption from the intestine[S

PubMed Central

Wong, Winifred P. S.; Altemus, Jessica B.; Hester, James F.; Chan, Ernest R.; Côté, Jean-François; Serre, David; Sehayek, Ephraim

2013-01-01

We used a mouse C57BL/6J×CASA/Rk intercross to map a locus on chromosome 14 that displayed a gender-dependent effect on cholesterol absorption from the intestine. Studies in congenic animals revealed a complex locus with multiple operating genetic determinants resulting in alternating gender-dependent phenotypic effects. Fine-mapping narrowed the locus to a critical 6.3 Mb interval. Female subcongenics, but not males, of the critical interval displayed a decrease of 33% in cholesterol absorption. RNA-Seq analysis of female subcongenic jejunum revealed that cysteine protease cathepsin B (Ctsb) is a candidate to explain the interval effect. Consistent with the phenotype in critical interval subcongenics, female Ctsb knockout mice, but not males, displayed a decrease of 31% in cholesterol absorption. Although studies in Ctsb knockouts revealed a gender-dependent effect on cholesterol absorption, further fine-mapping dismissed a role for Ctsb in determining the effect of the critical 6.3 Mb interval on cholesterol absorption. PMID:23248330

Using complexity metrics with R-R intervals and BPM heart rate measures.

PubMed

Wallot, Sebastian; Fusaroli, Riccardo; Tylén, Kristian; Jegindø, Else-Marie

2013-01-01

Lately, growing attention in the health sciences has been paid to the dynamics of heart rate as indicator of impending failures and for prognoses. Likewise, in social and cognitive sciences, heart rate is increasingly employed as a measure of arousal, emotional engagement and as a marker of interpersonal coordination. However, there is no consensus about which measurements and analytical tools are most appropriate in mapping the temporal dynamics of heart rate and quite different metrics are reported in the literature. As complexity metrics of heart rate variability depend critically on variability of the data, different choices regarding the kind of measures can have a substantial impact on the results. In this article we compare linear and non-linear statistics on two prominent types of heart beat data, beat-to-beat intervals (R-R interval) and beats-per-min (BPM). As a proof-of-concept, we employ a simple rest-exercise-rest task and show that non-linear statistics-fractal (DFA) and recurrence (RQA) analyses-reveal information about heart beat activity above and beyond the simple level of heart rate. Non-linear statistics unveil sustained post-exercise effects on heart rate dynamics, but their power to do so critically depends on the type data that is employed: While R-R intervals are very susceptible to non-linear analyses, the success of non-linear methods for BPM data critically depends on their construction. Generally, "oversampled" BPM time-series can be recommended as they retain most of the information about non-linear aspects of heart beat dynamics.

Using complexity metrics with R-R intervals and BPM heart rate measures

PubMed Central

Wallot, Sebastian; Fusaroli, Riccardo; Tylén, Kristian; Jegindø, Else-Marie

2013-01-01

Lately, growing attention in the health sciences has been paid to the dynamics of heart rate as indicator of impending failures and for prognoses. Likewise, in social and cognitive sciences, heart rate is increasingly employed as a measure of arousal, emotional engagement and as a marker of interpersonal coordination. However, there is no consensus about which measurements and analytical tools are most appropriate in mapping the temporal dynamics of heart rate and quite different metrics are reported in the literature. As complexity metrics of heart rate variability depend critically on variability of the data, different choices regarding the kind of measures can have a substantial impact on the results. In this article we compare linear and non-linear statistics on two prominent types of heart beat data, beat-to-beat intervals (R-R interval) and beats-per-min (BPM). As a proof-of-concept, we employ a simple rest-exercise-rest task and show that non-linear statistics—fractal (DFA) and recurrence (RQA) analyses—reveal information about heart beat activity above and beyond the simple level of heart rate. Non-linear statistics unveil sustained post-exercise effects on heart rate dynamics, but their power to do so critically depends on the type data that is employed: While R-R intervals are very susceptible to non-linear analyses, the success of non-linear methods for BPM data critically depends on their construction. Generally, “oversampled” BPM time-series can be recommended as they retain most of the information about non-linear aspects of heart beat dynamics. PMID:23964244

Methane oxidation behind reflected shock waves: Ignition delay times measured by pressure and flame band emission

NASA Technical Reports Server (NTRS)

Brabbs, T. A.; Robertson, T. F.

1986-01-01

Ignition delay data were recorded for three methane-oxygen-argon mixtures (phi = 0.5, 1.0, 2.0) for the temperature range 1500 to 1920 K. Quiet pressure trances enabled us to obtain delay times for the start of the experimental pressure rise. These times were in good agreement with those obtained from the flame band emission at 3700 A. The data correlated well with the oxygen and methane dependence of Lifshitz, but showed a much stronger temperature dependence (phi = 0.5 delta E = 51.9, phi = 1.0 delta = 58.8, phi = 2.0 delta E = 58.7 Kcal). The effect of probe location on the delay time measurement was studied. It appears that the probe located 83 mm from the reflecting surface measured delay times which may not be related to the initial temperature and pressure. It was estimated that for a probe located 7 mm from the reflecting surface, the measured delay time would be about 10 microseconds too short, and it was suggested that delay times less than 100 microsecond should not be used. The ignition period was defined as the time interval between start of the experimental pressure rise and 50 percent of the ignition pressure. This time interval was measured for three gas mixtures and found to be similar (40 to 60 micro sec) for phi = 1.0 and 0.5 but much longer (100 to 120) microsecond for phi = 2.0. It was suggested that the ignition period would be very useful to the kinetic modeler in judging the agreement between experimental and calculated delay times.

Electrocardiographic Predictors of Long-Term Cardiac Pacing Dependency Following Transcatheter Aortic Valve Implantation.

PubMed

Naveh, Sivan; Perlman, Gidon Y; Elitsur, Yair; Planer, David; Gilon, Dan; Leibowitz, David; Lotan, Chaim; Danenberg, Haim; Alcalai, Ronny

2017-02-01

Conduction disorders requiring permanent pacemaker (PPM) implantation are a known complication of transcatheter aortic valve implantation (TAVI). Indications for permanent pacing in this setting are still controversial. The study aim was to characterize the natural history of conduction disorders related to TAVI, and to identify predictors for long-term pacing dependency. Consecutive patients who underwent TAVI were included in this prospective observational study. The conduction system was investigated by reviewing 12-lead ECGs during hospitalization and up to 1-year follow-up and by analyzing pacemaker interrogation data. Multivariate analysis was performed in order to identify independent predictors for pacemaker dependency. Of 110 patients included in the analysis, 38 (34.5%) underwent PPM implantation. Of those, 26 (68.4%) had a long-term pacing dependency (required PPM), while 12 (31.6%) did not (not-required PPM). Logistic regression revealed that baseline RBBB (P = 0.01, OR = 18.0), baseline PR interval (P = 0.019, OR = 1.14), post-TAVI PR interval and the change in PR interval from baseline (P < 0.001 for both, OR = 1.17 for each 10 milliseconds increment) were independent predictors for long-term pacing dependency. A PR interval increment of greater than 28 milliseconds had the best accuracy in predicting pacemaker dependency. Increased pre- and postprocedural PR intervals and pre-existing RBBB are reliable predictors for long-term PPM dependency, while left bundle branch block or QRS width are misleading factors. Our study suggests that the decision for implanting PPM after TAVI should be based mostly on the prolongation of the PR interval. © 2016 Wiley Periodicals, Inc.

Motor Timing Deficits in Sequential Movements in Parkinson Disease Are Related to Action Planning: A Motor Imagery Study

PubMed Central

Avanzino, Laura; Pelosin, Elisa; Martino, Davide; Abbruzzese, Giovanni

2013-01-01

Timing of sequential movements is altered in Parkinson disease (PD). Whether timing deficits in internally generated sequential movements in PD depends also on difficulties in motor planning, rather than merely on a defective ability to materially perform the planned movement is still undefined. To unveil this issue, we adopted a modified version of an established test for motor timing, i.e. the synchronization–continuation paradigm, by introducing a motor imagery task. Motor imagery is thought to involve mainly processes of movement preparation, with reduced involvement of end-stage movement execution-related processes. Fourteen patients with PD and twelve matched healthy volunteers were asked to tap in synchrony with a metronome cue (SYNC) and then, when the tone stopped, to keep tapping, trying to maintain the same rhythm (CONT-EXE) or to imagine tapping at the same rhythm, rather than actually performing it (CONT-MI). We tested both a sub-second and a supra-second inter-stimulus interval between the cues. Performance was recorded using a sensor-engineered glove and analyzed measuring the temporal error and the interval reproduction accuracy index. PD patients were less accurate than healthy subjects in the supra-second time reproduction task when performing both continuation tasks (CONT-MI and CONT-EXE), whereas no difference was detected in the synchronization task and on all tasks involving a sub-second interval. Our findings suggest that PD patients exhibit a selective deficit in motor timing for sequential movements that are separated by a supra-second interval and that this deficit may be explained by a defect of motor planning. Further, we propose that difficulties in motor planning are of a sufficient degree of severity in PD to affect also the motor performance in the supra-second time reproduction task. PMID:24086534

Reliability of patient-reported outcomes in rheumatoid arthritis patients: an observational prospective study.

PubMed

Studenic, Paul; Stamm, Tanja; Smolen, Josef S; Aletaha, Daniel

2016-01-01

Patient-reported outcomes (PROs) such as pain, patient global assessment (PGA) and fatigue are regularly assessed in RA patients. In the present study, we aimed to explore the reliability and smallest detectable differences (SDDs) of these PROs, and whether the time between assessments has an impact on reliability. Forty RA patients on stable treatment reported the three PROs daily over two subsequent months. We assessed the reliability of these measures by calculating intraclass correlation coefficients (ICCs) and the SDDs for 1-, 7-, 14- and 28-day test-retest intervals. Overall, SDD and ICC were 25 mm and 0.67 for pain, 25 mm and 0.71 for PGA and 30 mm and 0.66 for fatigue, respectively. SDD was higher with longer time period between assessments, ranging from 19 mm (1-day intervals) to 30 mm (28-day intervals) for pain, 19 to 33 mm for PGA, and 26 to 34 mm for fatigue; correspondingly, ICC was smaller with longer intervals, and ranged between the 1- and the 28-day interval from 0.80 to 0.50 for pain, 0.83 to 0.57 for PGA and 0.76 to 0.58 for fatigue. The baseline simplified disease activity index did not have any influence on reliability. Lower baseline PRO scores led to smaller SDDs. Reliability of pain, PGA and fatigue measurements is dependent on the tested time interval and the baseline levels. The relatively high SDDs, even for patients in the lowest tertiles of their PROs, indicate potential issues for assessment of the presence of remission. © The Author 2015. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The Lambert-Beer law in time domain form and its application.

PubMed

Mosorov, Volodymyr

2017-10-01

The majority of current radioisotope gauges utilize measurements of intensity for a chosen sampling time interval using a detector. Such an approach has several disadvantages: temporal resolution of the gauge is fixed and the accuracy of the measurements is not the same for different count rate. The solution can be the use of a stronger radioactive source, but it will be conflicted with ALARA (As Low As Reasonably Achievable) principle. Therefore, the article presents an alternative approach which is based on modified Lambert-Beer law. The basis of the approach is the registration of time intervals instead of the registration of counts. It allows to increase the temporal resolution of a gauge without the necessity of using a stronger radioactive source and the accuracy of the measurements will not depend on count rate. Copyright © 2017 Elsevier Ltd. All rights reserved.

(U) Physics Validation of the RMI-Based Ejecta Source Model Implementation in FLAG: L2 Milestone #6035 Report

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

Tregillis, I. L.

The Los Alamos Physics and Engineering Models (PEM) program has developed a model for Richtmyer-Meshkov instability (RMI) based ejecta production from shock-melted surfaces, along with a prescription for a self-similar velocity distribution (SSVD) of the resulting ejecta particles. We have undertaken an effort to validate this source model using data from explosively driven tin coupon experiments. The model’s current formulation lacks a crucial piece of physics: a method for determining the duration of the ejecta production interval. Without a mechanism for terminating ejecta production, the model is not predictive. Furthermore, when the production interval is hand-tuned to match time-integrated massmore » data, the predicted time-dependent mass accumulation on a downstream sensor rises too sharply at early times and too slowly at late times because the SSVD overestimates the amount of mass stored in the fastest particles and underestimates the mass stored in the slowest particles. The functional form of the resulting m(t) is inconsistent with the available time-dependent data; numerical simulations and analytic studies agree on this point. Simulated mass tallies are highly sensitive to radial expansion of the ejecta cloud. It is not clear if the same effect is present in the experimental data but if so, depending on the degree, this may challenge the model’s compatibility with tin coupon data. The current implementation of the model in FLAG is sensitive to the detailed interaction between kinematics (hydrodynamic methods) and thermodynamics (material models); this sensitivity prohibits certain physics modeling choices. The appendices contain an extensive analytic study of piezoelectric ejecta mass measurements, along with test problems, excerpted from a longer work (LA-UR-17-21218).« less

Daily home gardening improved survival for older people with mobility limitations: an 11-year follow-up study in Taiwan.

PubMed

Lêng, Chhian Hūi; Wang, Jung-Der

2016-01-01

To test the hypothesis that gardening is beneficial for survival after taking time-dependent comorbidities, mobility, and depression into account in a longitudinal middle-aged (50-64 years) and older (≥65 years) cohort in Taiwan. The cohort contained 5,058 nationally sampled adults ≥50 years old from the Taiwan Longitudinal Study on Aging (1996-2007). Gardening was defined as growing flowers, gardening, or cultivating potted plants for pleasure with five different frequencies. We calculated hazard ratios for the mortality risks of gardening and adjusted the analysis for socioeconomic status, health behaviors and conditions, depression, mobility limitations, and comorbidities. Survival models also examined time-dependent effects and risks in each stratum contingent upon baseline mobility and depression. Sensitivity analyses used imputation methods for missing values. Daily home gardening was associated with a high survival rate (hazard ratio: 0.82; 95% confidence interval: 0.71-0.94). The benefits were robust for those with mobility limitations, but without depression at baseline (hazard ratio: 0.64, 95% confidence interval: 0.48-0.87) when adjusted for time-dependent comorbidities, mobility limitations, and depression. Chronic or relapsed depression weakened the protection of gardening. For those without mobility limitations and not depressed at baseline, gardening had no effect. Sensitivity analyses using different imputation methods yielded similar results and corroborated the hypothesis. Daily gardening for pleasure was associated with reduced mortality for Taiwanese >50 years old with mobility limitations but without depression.

Reaction front barriers in time aperiodic fluid flows

NASA Astrophysics Data System (ADS)

Locke, Rory; Mitchell, Kevin

2016-11-01

Many chemical and biological systems can be characterized by the propagation of a front that separates different phases or species. One approach to formalizing a general theory is to apply frameworks developed in nonlinear dynamics. It has been shown that invariant manifolds form barriers to passive transport in time-dependent or time-periodic fluid flows. More recently, analogous manifolds termed burning- invariant-manifolds (BIMs), have been shown to form one-sided barriers to reaction fronts in advection-reaction-diffusion (ARD) systems. To model more realistic time-aperiodic systems, recent theoretical work has suggested that similar one-sided barriers, termed burning Lagrangian coherent structures (bLCSs), exist for fluid velocity data prescribed over a finite time interval. In this presentation, we use a stochastic "wind" to generate time dependence in a double-vortex channel flow and demonstrate the (locally) most attracting or repelling curves are the bLCSs.

Music enhances performance and perceived enjoyment of sprint interval exercise.

PubMed

Stork, Matthew J; Kwan, Matthew Y W; Gibala, Martin J; Martin Ginis, Kathleen A

2015-05-01

Interval exercise training can elicit physiological adaptations similar to those of traditional endurance training, but with reduced time. However, the intense nature of specific protocols, particularly the "all-out" efforts characteristic of sprint interval training (SIT), may be perceived as being aversive. The purpose of this study was to determine whether listening to self-selected music can reduce the potential aversiveness of an acute session of SIT by improving affect, motivation, and enjoyment, and to examine the effects of music on performance. Twenty moderately active adults (22 ± 4 yr) unfamiliar with interval exercise completed an acute session of SIT under two different conditions: music and no music. The exercise consisted of four 30-s "all-out" Wingate Anaerobic Test bouts on a cycle ergometer, separated by 4 min of rest. Peak and mean power output, RPE, affect, task motivation, and perceived enjoyment of the exercise were measured. Mixed-effects models were used to evaluate changes in dependent measures over time and between the two conditions. Peak and mean power over the course of the exercise session were higher in the music condition (coefficient = 49.72 [SE = 13.55] and coefficient = 23.65 [SE = 11.30]; P < 0.05). A significant time by condition effect emerged for peak power (coefficient = -12.31 [SE = 4.95]; P < 0.05). There were no between-condition differences in RPE, affect, or task motivation. Perceived enjoyment increased over time and was consistently higher in the music condition (coefficient = 7.00 [SE = 3.05]; P < 0.05). Music enhances in-task performance and enjoyment of an acute bout of SIT. Listening to music during intense interval exercise may be an effective strategy for facilitating participation in, and adherence to, this form of training.

Association mining of dependency between time series

NASA Astrophysics Data System (ADS)

Hafez, Alaaeldin

2001-03-01

Time series analysis is considered as a crucial component of strategic control over a broad variety of disciplines in business, science and engineering. Time series data is a sequence of observations collected over intervals of time. Each time series describes a phenomenon as a function of time. Analysis on time series data includes discovering trends (or patterns) in a time series sequence. In the last few years, data mining has emerged and been recognized as a new technology for data analysis. Data Mining is the process of discovering potentially valuable patterns, associations, trends, sequences and dependencies in data. Data mining techniques can discover information that many traditional business analysis and statistical techniques fail to deliver. In this paper, we adapt and innovate data mining techniques to analyze time series data. By using data mining techniques, maximal frequent patterns are discovered and used in predicting future sequences or trends, where trends describe the behavior of a sequence. In order to include different types of time series (e.g. irregular and non- systematic), we consider past frequent patterns of the same time sequences (local patterns) and of other dependent time sequences (global patterns). We use the word 'dependent' instead of the word 'similar' for emphasis on real life time series where two time series sequences could be completely different (in values, shapes, etc.), but they still react to the same conditions in a dependent way. In this paper, we propose the Dependence Mining Technique that could be used in predicting time series sequences. The proposed technique consists of three phases: (a) for all time series sequences, generate their trend sequences, (b) discover maximal frequent trend patterns, generate pattern vectors (to keep information of frequent trend patterns), use trend pattern vectors to predict future time series sequences.

Echolocating Big Brown Bats, Eptesicus fuscus, Modulate Pulse Intervals to Overcome Range Ambiguity in Cluttered Surroundings

PubMed Central

Wheeler, Alyssa R.; Fulton, Kara A.; Gaudette, Jason E.; Simmons, Ryan A.; Matsuo, Ikuo; Simmons, James A.

2016-01-01

Big brown bats (Eptesicus fuscus) emit trains of brief, wideband frequency-modulated (FM) echolocation sounds and use echoes of these sounds to orient, find insects, and guide flight through vegetation. They are observed to emit sounds that alternate between short and long inter-pulse intervals (IPIs), forming sonar sound groups. The occurrence of these strobe groups has been linked to flight in cluttered acoustic environments, but how exactly bats use sonar sound groups to orient and navigate is still a mystery. Here, the production of sound groups during clutter navigation was examined. Controlled flight experiments were conducted where the proximity of the nearest obstacles was systematically decreased while the extended scene was kept constant. Four bats flew along a corridor of varying widths (100, 70, and 40 cm) bounded by rows of vertically hanging plastic chains while in-flight echolocation calls were recorded. Bats shortened their IPIs for more rapid spatial sampling and also grouped their sounds more tightly when flying in narrower corridors. Bats emitted echolocation calls with progressively shorter IPIs over the course of a flight, and began their flights by emitting shorter starting IPI calls when clutter was denser. The percentage of sound groups containing 3 or more calls increased with increasing clutter proximity. Moreover, IPI sequences having internal structure become more pronounced when corridor width narrows. A novel metric for analyzing the temporal organization of sound sequences was developed, and the results indicate that the time interval between echolocation calls depends heavily on the preceding time interval. The occurrence of specific IPI patterns were dependent upon clutter, which suggests that sonar sound grouping may be an adaptive strategy for coping with pulse-echo ambiguity in cluttered surroundings. PMID:27445723

A Study of Transport in the Near-Earth Plasma Sheet During A Substorm Using Time-Dependent Large Scale Kinetics

NASA Technical Reports Server (NTRS)

El-Alaoui, M.; Ashour-Abdalla, M.; Raeder, J.; Frank, L. A.; Paterson, W. R.

1998-01-01

In this study we investigate the transport of H+ ions that made up the complex ion distribution function observed by the Geotail spacecraft at 0740 UT on November 24, 1996. This ion distribution function, observed by Geotail at approximately 20 R(sub E) downtail, was used to initialize a time-dependent large-scale kinetic (LSK) calculation of the trajectories of 75,000 ions forward in time. Time-dependent magnetic and electric fields were obtained from a global magnetohydrodynamic (MHD) simulation of the magnetosphere and its interaction with the solar wind and the interplanetary magnetic field (IMF) as observed during the interval of the observation of the distribution function. Our calculations indicate that the particles observed by Geotail were scattered across the equatorial plane by the multiple interactions with the current sheet and then convected sunward. They were energized by the dawn-dusk electric field during their transport from Geotail location and ultimately were lost at the ionospheric boundary or into the magnetopause.

Earthquake stress drop and laboratory-inferred interseismic strength recovery

USGS Publications Warehouse

Beeler, N.M.; Hickman, S.H.; Wong, T.-F.

2001-01-01

We determine the scaling relationships between earthquake stress drop and recurrence interval tr that are implied by laboratory-measured fault strength. We assume that repeating earthquakes can be simulated by stick-slip sliding using a spring and slider block model. Simulations with static/kinetic strength, time-dependent strength, and rate- and state-variable-dependent strength indicate that the relationship between loading velocity and recurrence interval can be adequately described by the power law VL ??? trn, where n=-1. Deviations from n=-1 arise from second order effects on strength, with n>-1 corresponding to apparent time-dependent strengthening and n<-1 corresponding to weakening. Simulations with rate and state-variable equations show that dynamic shear stress drop ????d scales with recurrence as d????d/dlntr ??? ??e(b-a), where ??e is the effective normal stress, ??=??/??e, and (a-b)=d??ss/dlnV is the steady-state slip rate dependence of strength. In addition, accounting for seismic energy radiation, we suggest that the static shear stress drop ????s scales as d????s/dlntr ??? ??e(1+??)(b-a), where ?? is the fractional overshoot. The variation of ????s with lntr for earthquake stress drops is somewhat larger than implied by room temperature laboratory values of ?? and b-a. However, the uncertainty associated with the seismic data is large and the discrepancy between the seismic observations and the rate of strengthening predicted by room temperature experiments is less than an order of magnitude. Copyright 2001 by the American Geophysical Union.

Long-interval Cytapheresis as a Novel Therapeutic Strategy Leading to Dosage Reduction and Discontinuation of Steroids in Steroid-dependent Ulcerative Colitis

PubMed Central

Iizuka, Masahiro; Etou, Takeshi; Kumagai, Makoto; Matsuoka, Atsushi; Numata, Yuka; Sagara, Shiho

2017-01-01

Objective This study was performed to confirm the efficacy of long-interval cytapheresis on steroid-dependent ulcerative colitis (UC). Methods To discontinue steroids in patients with steroid-dependent UC, we previously designed a novel regimen of cytapheresis (CAP), which we termed “long-interval cytapheresis (LI-CAP)”, in which CAP was performed as one session every two or three weeks and continued during the whole period of tapering steroid dosage. In this study, we performed LI-CAP therapy 20 times (11 male and 9 female; mean age 41.8 years) between April 2010 and April 2015 for 14 patients with steroid-dependent UC. We evaluated the effectiveness of LI-CAP by examining the improvement in Lichtiger's clinical activity index (CAI), the rate of clinical remission, and the rate of steroid discontinuation. We further examined the rate of sustained steroid-free clinical remission at 6 and 12 months after LI-CAP in patients who successfully discontinued steroid-use after LI-CAP. The primary endpoint was the rate of discontinuation of steroids after LI-CAP. Results The mean CAI score before LI-CAP (7.550) significantly decreased to 1.65 after LI-CAP (p<0.0001). The rate of clinical remission after LI-CAP was 80%. The rate of steroid discontinuation after LI-CAP was 60.0%. The mean dose of daily prednisolone was significantly decreased after LI-CAP (2.30 mg) compared with that before therapy (17.30 mg) (p=0.0003). The rate of sustained steroid-free clinical remission after LI-CAP was 66.7% at 6 months and 66.7% at 12 months. Conclusion We confirmed that LI-CAP has therapeutic effects on reducing the dosage and discontinuing steroids in patients with steroid-dependent UC. PMID:28924114

Long-interval Cytapheresis as a Novel Therapeutic Strategy Leading to Dosage Reduction and Discontinuation of Steroids in Steroid-dependent Ulcerative Colitis.

PubMed

Iizuka, Masahiro; Etou, Takeshi; Kumagai, Makoto; Matsuoka, Atsushi; Numata, Yuka; Sagara, Shiho

2017-10-15

Objective This study was performed to confirm the efficacy of long-interval cytapheresis on steroid-dependent ulcerative colitis (UC). Methods To discontinue steroids in patients with steroid-dependent UC, we previously designed a novel regimen of cytapheresis (CAP), which we termed "long-interval cytapheresis (LI-CAP)", in which CAP was performed as one session every two or three weeks and continued during the whole period of tapering steroid dosage. In this study, we performed LI-CAP therapy 20 times (11 male and 9 female; mean age 41.8 years) between April 2010 and April 2015 for 14 patients with steroid-dependent UC. We evaluated the effectiveness of LI-CAP by examining the improvement in Lichtiger's clinical activity index (CAI), the rate of clinical remission, and the rate of steroid discontinuation. We further examined the rate of sustained steroid-free clinical remission at 6 and 12 months after LI-CAP in patients who successfully discontinued steroid-use after LI-CAP. The primary endpoint was the rate of discontinuation of steroids after LI-CAP. Results The mean CAI score before LI-CAP (7.550) significantly decreased to 1.65 after LI-CAP (p<0.0001). The rate of clinical remission after LI-CAP was 80%. The rate of steroid discontinuation after LI-CAP was 60.0%. The mean dose of daily prednisolone was significantly decreased after LI-CAP (2.30 mg) compared with that before therapy (17.30 mg) (p=0.0003). The rate of sustained steroid-free clinical remission after LI-CAP was 66.7% at 6 months and 66.7% at 12 months. Conclusion We confirmed that LI-CAP has therapeutic effects on reducing the dosage and discontinuing steroids in patients with steroid-dependent UC.

Shoulder pain and time dependent structure in wheelchair propulsion variability

PubMed Central

Jayaraman, Chandrasekaran; Moon, Yaejin; Sosnoff, Jacob J.

2016-01-01

Manual wheelchair propulsion places considerable repetitive mechanical strain on the upper limbs leading to shoulder injury and pain. While recent research indicates that the amount of variability in wheelchair propulsion and shoulder pain may be related. There has been minimal inquiry into the fluctuation over time (i.e. time-dependent structure) in wheelchair propulsion variability. Consequently the purpose of this investigation was to examine if the time-dependent structure in the wheelchair propulsion parameters are related to shoulder pain. 27 experienced wheelchair users manually propelled their own wheelchair fitted with a SMARTWheel on a roller at 1.1 m/s for 3 minutes. Time-dependent structure of cycle-to-cycle fluctuations in contact angle and inter push time interval was quantified using sample entropy (SampEn) and compared between the groups with/without shoulder pain using non-parametric statistics. Overall findings were, (1) variability observed in contact angle fluctuations during manual wheelchair propulsion is structured (Z=3.15;p<0.05), (2) individuals with shoulder pain exhibited higher SampEn magnitude for contact angle during wheelchair propulsion than those without pain (χ2(1)=6.12;p<0.05); and (3) SampEn of contact angle correlated significantly with self-reported shoulder pain (rs (WUSPI) =0.41;rs (VAS)=0.56;p<0.05). It was concluded that the time-dependent structure in wheelchair propulsion may provide novel information for tracking and monitoring shoulder pain. PMID:27134151

Block Constraints in Age-Period-Cohort Models with Unequal-Width Intervals

ERIC Educational Resources Information Center

Luo, Liying; Hodges, James S.

2016-01-01

Age-period-cohort (APC) models are designed to estimate the independent effects of age, time periods, and cohort membership. However, APC models suffer from an identification problem: There are no unique estimates of the independent effects that fit the data best because of the exact linear dependency among age, period, and cohort. Among methods…

Time Determines the Neural Circuit Underlying Associative Fear Learning

PubMed Central

Guimarãis, Marta; Gregório, Ana; Cruz, Andreia; Guyon, Nicolas; Moita, Marta A.

2011-01-01

Ultimately associative learning is a function of the temporal features and relationships between experienced stimuli. Nevertheless how time affects the neural circuit underlying this form of learning remains largely unknown. To address this issue, we used single-trial auditory trace fear conditioning and varied the length of the interval between tone and foot-shock. Through temporary inactivation of the amygdala, medial prefrontal-cortex (mPFC), and dorsal-hippocampus in rats, we tested the hypothesis that different temporal intervals between the tone and the shock influence the neuronal structures necessary for learning. With this study we provide the first experimental evidence showing that temporarily inactivating the amygdala before training impairs auditory fear learning when there is a temporal gap between the tone and the shock. Moreover, imposing a short interval (5 s) between the two stimuli also relies on the mPFC, while learning the association across a longer interval (40 s) becomes additionally dependent on a third structure, the dorsal-hippocampus. Thus, our results suggest that increasing the interval length between tone and shock leads to the involvement of an increasing number of brain areas in order for the association between the two stimuli to be acquired normally. These findings demonstrate that the temporal relationship between events is a key factor in determining the neuronal mechanisms underlying associative fear learning. PMID:22207842

Detection of abnormal item based on time intervals for recommender systems.

PubMed

Gao, Min; Yuan, Quan; Ling, Bin; Xiong, Qingyu

2014-01-01

With the rapid development of e-business, personalized recommendation has become core competence for enterprises to gain profits and improve customer satisfaction. Although collaborative filtering is the most successful approach for building a recommender system, it suffers from "shilling" attacks. In recent years, the research on shilling attacks has been greatly improved. However, the approaches suffer from serious problem in attack model dependency and high computational cost. To solve the problem, an approach for the detection of abnormal item is proposed in this paper. In the paper, two common features of all attack models are analyzed at first. A revised bottom-up discretized approach is then proposed based on time intervals and the features for the detection. The distributions of ratings in different time intervals are compared to detect anomaly based on the calculation of chi square distribution (χ(2)). We evaluated our approach on four types of items which are defined according to the life cycles of these items. The experimental results show that the proposed approach achieves a high detection rate with low computational cost when the number of attack profiles is more than 15. It improves the efficiency in shilling attacks detection by narrowing down the suspicious users.

The economics and timing of preoperative antibiotics for orthopaedic procedures.

PubMed

Norman, B A; Bartsch, S M; Duggan, A P; Rodrigues, M B; Stuckey, D R; Chen, A F; Lee, B Y

2013-12-01

The efficacy of antibiotics in preventing surgical site infections (SSIs) depends on the timing of administration relative to the start of surgery. However, currently, both the timing of and recommendations for administration vary substantially. To determine how the economic value from the hospital perspective of preoperative antibiotics varies with the timing of administration for orthopaedic procedures. Computational decision and operational models were developed from the hospital perspective. Baseline analyses looked at current timing of administration, while additional analyses varied the timing of administration, compliance with recommended guidelines, and the goal time-interval. Beginning antibiotic administration within 0-30 min prior to surgery resulted in the lowest costs and SSIs. Operationally, linking to a pre-surgical activity, administering antibiotics prior to incision but after anaesthesia-ready time was optimal, as 92.1% of the time, antibiotics were administered in the optimal time-interval (0-30 min prior to incision). Improving administration compliance from 80% to 90% for this pre-surgical activity results in cost savings of $447 per year for a hospital performing 100 orthopaedic operations a year. This study quantifies the potential cost-savings when antibiotic administration timing is improved, which in turn can guide the amount hospitals should invest to address this issue.

Financial factor influence on scaling and memory of trading volume in stock market

NASA Astrophysics Data System (ADS)

Li, Wei; Wang, Fengzhong; Havlin, Shlomo; Stanley, H. Eugene

2011-10-01

We study the daily trading volume volatility of 17 197 stocks in the US stock markets during the period 1989-2008 and analyze the time return intervals τ between volume volatilities above a given threshold q. For different thresholds q, the probability density function Pq(τ) scales with mean interval <τ> as Pq(τ)=<τ>-1f(τ/<τ>), and the tails of the scaling function can be well approximated by a power law f(x)˜x-γ. We also study the relation between the form of the distribution function Pq(τ) and several financial factors: stock lifetime, market capitalization, volume, and trading value. We find a systematic tendency of Pq(τ) associated with these factors, suggesting a multiscaling feature in the volume return intervals. We analyze the conditional probability Pq(τ|τ0) for τ following a certain interval τ0, and find that Pq(τ|τ0) depends on τ0 such that immediately following a short (long) return interval a second short (long) return interval tends to occur. We also find indications that there is a long-term correlation in the daily volume volatility. We compare our results to those found earlier for price volatility.

tOWL: a temporal Web Ontology Language.

PubMed

Milea, Viorel; Frasincar, Flavius; Kaymak, Uzay

2012-02-01

Through its interoperability and reasoning capabilities, the Semantic Web opens a realm of possibilities for developing intelligent systems on the Web. The Web Ontology Language (OWL) is the most expressive standard language for modeling ontologies, the cornerstone of the Semantic Web. However, up until now, no standard way of expressing time and time-dependent information in OWL has been provided. In this paper, we present a temporal extension of the very expressive fragment SHIN(D) of the OWL Description Logic language, resulting in the temporal OWL language. Through a layered approach, we introduce three extensions: 1) concrete domains, which allow the representation of restrictions using concrete domain binary predicates; 2) temporal representation , which introduces time points, relations between time points, intervals, and Allen's 13 interval relations into the language; and 3) timeslices/fluents, which implement a perdurantist view on individuals and allow for the representation of complex temporal aspects, such as process state transitions. We illustrate the expressiveness of the newly introduced language by using an example from the financial domain.

Cascaded processing in written compound word production

PubMed Central

Bertram, Raymond; Tønnessen, Finn Egil; Strömqvist, Sven; Hyönä, Jukka; Niemi, Pekka

2015-01-01

In this study we investigated the intricate interplay between central linguistic processing and peripheral motor processes during typewriting. Participants had to typewrite two-constituent (noun-noun) Finnish compounds in response to picture presentation while their typing behavior was registered. As dependent measures we used writing onset time to assess what processes were completed before writing and inter-key intervals to assess what processes were going on during writing. It was found that writing onset time was determined by whole word frequency rather than constituent frequencies, indicating that compound words are retrieved as whole orthographic units before writing is initiated. In addition, we found that the length of the first syllable also affects writing onset time, indicating that the first syllable is fully prepared before writing commences. The inter-key interval results showed that linguistic planning is not fully ready before writing, but cascades into the motor execution phase. More specifically, inter-key intervals were largest at syllable and morpheme boundaries, supporting the view that additional linguistic planning takes place at these boundaries. Bigram and trigram frequency also affected inter-key intervals with shorter intervals corresponding to higher frequencies. This can be explained by stronger memory traces for frequently co-occurring letter sequences in the motor memory for typewriting. These frequency effects were even larger in the second than in the first constituent, indicating that low-level motor memory starts to become more important during the course of writing compound words. We discuss our results in the light of current models of morphological processing and written word production. PMID:25954182

Cascaded processing in written compound word production.

PubMed

Bertram, Raymond; Tønnessen, Finn Egil; Strömqvist, Sven; Hyönä, Jukka; Niemi, Pekka

2015-01-01

In this study we investigated the intricate interplay between central linguistic processing and peripheral motor processes during typewriting. Participants had to typewrite two-constituent (noun-noun) Finnish compounds in response to picture presentation while their typing behavior was registered. As dependent measures we used writing onset time to assess what processes were completed before writing and inter-key intervals to assess what processes were going on during writing. It was found that writing onset time was determined by whole word frequency rather than constituent frequencies, indicating that compound words are retrieved as whole orthographic units before writing is initiated. In addition, we found that the length of the first syllable also affects writing onset time, indicating that the first syllable is fully prepared before writing commences. The inter-key interval results showed that linguistic planning is not fully ready before writing, but cascades into the motor execution phase. More specifically, inter-key intervals were largest at syllable and morpheme boundaries, supporting the view that additional linguistic planning takes place at these boundaries. Bigram and trigram frequency also affected inter-key intervals with shorter intervals corresponding to higher frequencies. This can be explained by stronger memory traces for frequently co-occurring letter sequences in the motor memory for typewriting. These frequency effects were even larger in the second than in the first constituent, indicating that low-level motor memory starts to become more important during the course of writing compound words. We discuss our results in the light of current models of morphological processing and written word production.

Data series embedding and scale invariant statistics.

PubMed

Michieli, I; Medved, B; Ristov, S

2010-06-01

Data sequences acquired from bio-systems such as human gait data, heart rate interbeat data, or DNA sequences exhibit complex dynamics that is frequently described by a long-memory or power-law decay of autocorrelation function. One way of characterizing that dynamics is through scale invariant statistics or "fractal-like" behavior. For quantifying scale invariant parameters of physiological signals several methods have been proposed. Among them the most common are detrended fluctuation analysis, sample mean variance analyses, power spectral density analysis, R/S analysis, and recently in the realm of the multifractal approach, wavelet analysis. In this paper it is demonstrated that embedding the time series data in the high-dimensional pseudo-phase space reveals scale invariant statistics in the simple fashion. The procedure is applied on different stride interval data sets from human gait measurements time series (Physio-Bank data library). Results show that introduced mapping adequately separates long-memory from random behavior. Smaller gait data sets were analyzed and scale-free trends for limited scale intervals were successfully detected. The method was verified on artificially produced time series with known scaling behavior and with the varying content of noise. The possibility for the method to falsely detect long-range dependence in the artificially generated short range dependence series was investigated. (c) 2009 Elsevier B.V. All rights reserved.

Joint cross-correlation analysis reveals complex, time-dependent functional relationship between cortical neurons and arm electromyograms

PubMed Central

Zhuang, Katie Z.; Lebedev, Mikhail A.

2014-01-01

Correlation between cortical activity and electromyographic (EMG) activity of limb muscles has long been a subject of neurophysiological studies, especially in terms of corticospinal connectivity. Interest in this issue has recently increased due to the development of brain-machine interfaces with output signals that mimic muscle force. For this study, three monkeys were implanted with multielectrode arrays in multiple cortical areas. One monkey performed self-timed touch pad presses, whereas the other two executed arm reaching movements. We analyzed the dynamic relationship between cortical neuronal activity and arm EMGs using a joint cross-correlation (JCC) analysis that evaluated trial-by-trial correlation as a function of time intervals within a trial. JCCs revealed transient correlations between the EMGs of multiple muscles and neural activity in motor, premotor and somatosensory cortical areas. Matching results were obtained using spike-triggered averages corrected by subtracting trial-shuffled data. Compared with spike-triggered averages, JCCs more readily revealed dynamic changes in cortico-EMG correlations. JCCs showed that correlation peaks often sharpened around movement times and broadened during delay intervals. Furthermore, JCC patterns were directionally selective for the arm-reaching task. We propose that such highly dynamic, task-dependent and distributed relationships between cortical activity and EMGs should be taken into consideration for future brain-machine interfaces that generate EMG-like signals. PMID:25210153

Measurements of time-dependent CP violation in B0→ωKS0, f0(980)KS0, KS0π0 and K+K-KS0 decays

NASA Astrophysics Data System (ADS)

Chao, Y.; Chen, K.-F.; Miyake, H.; Tajima, O.; Trabelsi, K.; Abe, K.; Abe, K.; Adachi, I.; Aihara, H.; Anipko, D.; Bakich, A. M.; Barberio, E.; Bitenc, U.; Bizjak, I.; Blyth, S.; Bondar, A.; Bračko, M.; Browder, T. E.; Chang, M.-C.; Chang, P.; Chen, A.; Chen, W. T.; Cheon, B. G.; Chistov, R.; Choi, Y.; Choi, Y. K.; Cole, S.; Dalseno, J.; Danilov, M.; Dash, M.; Dragic, J.; Drutskoy, A.; Eidelman, S.; Fratina, S.; Gabyshev, N.; Golob, B.; Ha, H.; Haba, J.; Hara, K.; Hara, T.; Hastings, N. C.; Hayashii, H.; Hazumi, M.; Heffernan, D.; Higuchi, T.; Hokuue, T.; Hoshi, Y.; Hou, W.-S.; Hsiung, Y. B.; Iijima, T.; Ikado, K.; Inami, K.; Ishikawa, A.; Ishino, H.; Itoh, R.; Iwasaki, M.; Iwasaki, Y.; Kaji, H.; Kang, J. H.; Kapusta, P.; Kawai, H.; Kawasaki, T.; Kim, H. J.; Kim, H. O.; Kim, Y. J.; Kinoshita, K.; Korpar, S.; Križan, P.; Krokovny, P.; Kulasiri, R.; Kumar, R.; Kuo, C. C.; Kuzmin, A.; Kwon, Y.-J.; Lee, M. J.; Lesiak, T.; Limosani, A.; Lin, S.-W.; Liventsev, D.; Matsumoto, T.; McOnie, S.; Miyabayashi, K.; Miyata, H.; Miyazaki, Y.; Mizuk, R.; Mohapatra, D.; Moloney, G. R.; Nakahama, Y.; Nakano, E.; Nakao, M.; Natkaniec, Z.; Nishida, S.; Nitoh, O.; Ogawa, S.; Okuno, S.; Olsen, S. L.; Onuki, Y.; Ozaki, H.; Pakhlov, P.; Pakhlova, G.; Park, C. W.; Pestotnik, R.; Piilonen, L. E.; Sakai, Y.; Satoyama, N.; Schietinger, T.; Schneider, O.; Schwartz, A. J.; Seidl, R.; Senyo, K.; Sevior, M. E.; Shapkin, M.; Shibuya, H.; Singh, J. B.; Somov, A.; Soni, N.; Stanič, S.; Starič, M.; Stoeck, H.; Sumisawa, K.; Sumiyoshi, T.; Suzuki, S.; Takasaki, F.; Tamai, K.; Tanaka, M.; Taylor, G. N.; Teramoto, Y.; Tian, X. C.; Tikhomirov, I.; Tsukamoto, T.; Uehara, S.; Ueno, K.; Unno, Y.; Uno, S.; Ushiroda, Y.; Usov, Y.; Varner, G.; Varvell, K. E.; Villa, S.; Vinokurova, A.; Wang, C. H.; Watanabe, Y.; Won, E.; Yabsley, B. D.; Yamaguchi, A.; Yamashita, Y.; Yamauchi, M.; Yusa, Y.; Zhilich, V.; Zhulanov, V.; Zupanc, A.

2007-11-01

We present measurements of time-dependent CP asymmetries in B0→ωKS0, f0(980)KS0, KS0π0 and K+K-KS0 decays based on a sample of 535×106 BB¯ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. One neutral B meson is fully reconstructed in one of the specified decay channels, and the flavor of the accompanying B meson is identified from its decay products. CP-violation parameters for each of the decay modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays.

Finite horizon EOQ model for non-instantaneous deteriorating items with price and advertisement dependent demand and partial backlogging under inflation

NASA Astrophysics Data System (ADS)

Palanivel, M.; Uthayakumar, R.

2015-07-01

This paper deals with an economic order quantity (EOQ) model for non-instantaneous deteriorating items with price and advertisement dependent demand pattern under the effect of inflation and time value of money over a finite planning horizon. In this model, shortages are allowed and partially backlogged. The backlogging rate is dependent on the waiting time for the next replenishment. This paper aids the retailer in minimising the total inventory cost by finding the optimal interval and the optimal order quantity. An algorithm is designed to find the optimum solution of the proposed model. Numerical examples are given to demonstrate the results. Also, the effect of changes in the different parameters on the optimal total cost is graphically presented and the implications are discussed in detail.

Statistical Characteristics of the Gaussian-Noise Spikes Exceeding the Specified Threshold as Applied to Discharges in a Thundercloud

NASA Astrophysics Data System (ADS)

Klimenko, V. V.

2017-12-01

We obtain expressions for the probabilities of the normal-noise spikes with the Gaussian correlation function and for the probability density of the inter-spike intervals. As distinct from the delta-correlated noise, in which the intervals are distributed by the exponential law, the probability of the subsequent spike depends on the previous spike and the interval-distribution law deviates from the exponential one for a finite noise-correlation time (frequency-bandwidth restriction). This deviation is the most pronounced for a low detection threshold. Similarity of the behaviors of the distributions of the inter-discharge intervals in a thundercloud and the noise spikes for the varying repetition rate of the discharges/spikes, which is determined by the ratio of the detection threshold to the root-mean-square value of noise, is observed. The results of this work can be useful for the quantitative description of the statistical characteristics of the noise spikes and studying the role of fluctuations for the discharge emergence in a thundercloud.

Monte Carlo Method for Determining Earthquake Recurrence Parameters from Short Paleoseismic Catalogs: Example Calculations for California

USGS Publications Warehouse

Parsons, Tom

2008-01-01

Paleoearthquake observations often lack enough events at a given site to directly define a probability density function (PDF) for earthquake recurrence. Sites with fewer than 10-15 intervals do not provide enough information to reliably determine the shape of the PDF using standard maximum-likelihood techniques [e.g., Ellsworth et al., 1999]. In this paper I present a method that attempts to fit wide ranges of distribution parameters to short paleoseismic series. From repeated Monte Carlo draws, it becomes possible to quantitatively estimate most likely recurrence PDF parameters, and a ranked distribution of parameters is returned that can be used to assess uncertainties in hazard calculations. In tests on short synthetic earthquake series, the method gives results that cluster around the mean of the input distribution, whereas maximum likelihood methods return the sample means [e.g., NIST/SEMATECH, 2006]. For short series (fewer than 10 intervals), sample means tend to reflect the median of an asymmetric recurrence distribution, possibly leading to an overestimate of the hazard should they be used in probability calculations. Therefore a Monte Carlo approach may be useful for assessing recurrence from limited paleoearthquake records. Further, the degree of functional dependence among parameters like mean recurrence interval and coefficient of variation can be established. The method is described for use with time-independent and time-dependent PDF?s, and results from 19 paleoseismic sequences on strike-slip faults throughout the state of California are given.

Monte Carlo method for determining earthquake recurrence parameters from short paleoseismic catalogs: Example calculations for California

USGS Publications Warehouse

Parsons, T.

2008-01-01

Paleoearthquake observations often lack enough events at a given site to directly define a probability density function (PDF) for earthquake recurrence. Sites with fewer than 10-15 intervals do not provide enough information to reliably determine the shape of the PDF using standard maximum-likelihood techniques (e.g., Ellsworth et al., 1999). In this paper I present a method that attempts to fit wide ranges of distribution parameters to short paleoseismic series. From repeated Monte Carlo draws, it becomes possible to quantitatively estimate most likely recurrence PDF parameters, and a ranked distribution of parameters is returned that can be used to assess uncertainties in hazard calculations. In tests on short synthetic earthquake series, the method gives results that cluster around the mean of the input distribution, whereas maximum likelihood methods return the sample means (e.g., NIST/SEMATECH, 2006). For short series (fewer than 10 intervals), sample means tend to reflect the median of an asymmetric recurrence distribution, possibly leading to an overestimate of the hazard should they be used in probability calculations. Therefore a Monte Carlo approach may be useful for assessing recurrence from limited paleoearthquake records. Further, the degree of functional dependence among parameters like mean recurrence interval and coefficient of variation can be established. The method is described for use with time-independent and time-dependent PDFs, and results from 19 paleoseismic sequences on strike-slip faults throughout the state of California are given.

Modeling the safety impacts of driving hours and rest breaks on truck drivers considering time-dependent covariates.

PubMed

Chen, Chen; Xie, Yuanchang

2014-12-01

Driving hours and rest breaks are closely related to driver fatigue, which is a major contributor to truck crashes. This study investigates the effects of driving hours and rest breaks on commercial truck driver safety. A discrete-time logistic regression model is used to evaluate the crash odds ratios of driving hours and rest breaks. Driving time is divided into 11 one hour intervals. These intervals and rest breaks are modeled as dummy variables. In addition, a Cox proportional hazards regression model with time-dependent covariates is used to assess the transient effects of rest breaks, which consists of a fixed effect and a variable effect. Data collected from two national truckload carriers in 2009 and 2010 are used. The discrete-time logistic regression result indicates that only the crash odds ratio of the 11th driving hour is statistically significant. Taking one, two, and three rest breaks can reduce drivers' crash odds by 68%, 83%, and 85%, respectively, compared to drivers who did not take any rest breaks. The Cox regression result shows clear transient effects for rest breaks. It also suggests that drivers may need some time to adjust themselves to normal driving tasks after a rest break. Overall, the third rest break's safety benefit is very limited based on the results of both models. The findings of this research can help policy makers better understand the impact of driving time and rest breaks and develop more effective rules to improve commercial truck safety. Copyright © 2014 National Safety Council and Elsevier Ltd. All rights reserved.

Inverse analysis and regularisation in conditional source-term estimation modelling

NASA Astrophysics Data System (ADS)

Labahn, Jeffrey W.; Devaud, Cecile B.; Sipkens, Timothy A.; Daun, Kyle J.

2014-05-01

Conditional Source-term Estimation (CSE) obtains the conditional species mass fractions by inverting a Fredholm integral equation of the first kind. In the present work, a Bayesian framework is used to compare two different regularisation methods: zeroth-order temporal Tikhonov regulatisation and first-order spatial Tikhonov regularisation. The objectives of the current study are: (i) to elucidate the ill-posedness of the inverse problem; (ii) to understand the origin of the perturbations in the data and quantify their magnitude; (iii) to quantify the uncertainty in the solution using different priors; and (iv) to determine the regularisation method best suited to this problem. A singular value decomposition shows that the current inverse problem is ill-posed. Perturbations to the data may be caused by the use of a discrete mixture fraction grid for calculating the mixture fraction PDF. The magnitude of the perturbations is estimated using a box filter and the uncertainty in the solution is determined based on the width of the credible intervals. The width of the credible intervals is significantly reduced with the inclusion of a smoothing prior and the recovered solution is in better agreement with the exact solution. The credible intervals for temporal and spatial smoothing are shown to be similar. Credible intervals for temporal smoothing depend on the solution from the previous time step and a smooth solution is not guaranteed. For spatial smoothing, the credible intervals are not dependent upon a previous solution and better predict characteristics for higher mixture fraction values. These characteristics make spatial smoothing a promising alternative method for recovering a solution from the CSE inversion process.

How preservation time changes the linear viscoelastic properties of porcine liver.

PubMed

Wex, C; Stoll, A; Fröhlich, M; Arndt, S; Lippert, H

2013-01-01

The preservation time of a liver graft is one of the crucial factors for the success of a liver transplantation. Grafts are kept in a preservation solution to delay cell destruction and cellular edema and to maximize organ function after transplantation. However, longer preservation times are not always avoidable. In this paper we focus on the mechanical changes of porcine liver with increasing preservation time, in order to establish an indicator for the quality of a liver graft dependent on preservation time. A time interval of 26 h was covered and the rheological properties of liver tissue studied using a stress-controlled rheometer. For samples of 1 h preservation time 0.8% strain was found as the limit of linear viscoelasticity. With increasing preservation time a decrease in the complex shear modulus as an indicator for stiffness was observed for the frequency range from 0.1 to 10 Hz. A simple fractional derivative representation of the Kelvin Voigt model was applied to gain further information about the changes of the mechanical properties of liver with increasing preservation time. Within the small shear rate interval of 0.0001-0.01 s⁻¹ the liver showed Newtonian-like flow behavior.

Finite-time barriers to reaction front propagation

NASA Astrophysics Data System (ADS)

Locke, Rory; Mahoney, John; Mitchell, Kevin

2015-11-01

Front propagation in advection-reaction-diffusion systems gives rise to rich geometric patterns. It has been shown for time-independent and time-periodic fluid flows that invariant manifolds, termed burning invariant manifolds (BIMs), serve as one-sided dynamical barriers to the propagation of reaction front. More recently, theoretical work has suggested that one-sided barriers, termed burning Lagrangian Coherent structures (bLCSs), exist for fluid velocity data prescribed over a finite time interval, with no assumption on the time-dependence of the flow. In this presentation, we use a time-varying fluid ``wind'' in a double-vortex channel flow to demonstrate that bLCSs form the (locally) most attracting or repelling fronts.

The prelaying interval of emperor geese on the Yukon-Kuskokwim Delta, Alaska

USGS Publications Warehouse

Hupp, Jerry W.; Schmutz, J.A.; Ely, Craig R.

2006-01-01

We marked 136 female Emperor Geese (Chen canagica) in western Alaska with VHF or satellite (PTT) transmitters from 1999 to 2003 to monitor their spring arrival and nest initiation dates on the Yukon Delta, and to estimate prelaying interval lengths once at the nesting area. Ninety-two females with functional transmitters returned to the Yukon Delta in the spring after they were marked, and we located the nests of 35 of these individuals. Prelaying intervals were influenced by when snow melted in the spring and individual arrival dates on the Yukon Delta. The median prelaying interval was 15 days (range = 12-19 days) in a year when snow melted relatively late, and 11 days (range = 4-16 days) in two warmer years when snow melted earlier. In years when snow melted earlier, prelaying intervals of <12 days for 11 of 15 females suggested they initiated rapid follicle development on spring staging areas. The prelaying interval declined by approximately 0.4 days and nest initiation date increased approximately 0.5 days for each day a female delayed her arrival. Thus, females that arrived first on the Yukon Delta had prelaying intervals up to four days longer, yet they nested up to five days earlier, than females that arrived last. The proximity of spring staging areas on the Alaska Peninsula to nesting areas on the Yukon Delta may enable Emperor Geese to alter timing of follicle development depending on annual conditions, and to invest nutrients acquired from both areas in eggs during their formation. Plasticity in timing of follicle development is likely advantageous in a variable environment where melting of snow cover in the spring can vary by 2-3 weeks annually. ?? The Cooper Ornithological Society 2006.

Representation of time interval entrained by periodic stimuli in the visual thalamus of pigeons

PubMed Central

Wang, Shu-Rong

2017-01-01

Animals use the temporal information from previously experienced periodic events to instruct their future behaviors. The retina and cortex are involved in such behavior, but it remains largely unknown how the thalamus, transferring visual information from the retina to the cortex, processes the periodic temporal patterns. Here we report that the luminance cells in the nucleus dorsolateralis anterior thalami (DLA) of pigeons exhibited oscillatory activities in a temporal pattern identical to the rhythmic luminance changes of repetitive light/dark (LD) stimuli with durations in the seconds-to-minutes range. Particularly, after LD stimulation, the DLA cells retained the entrained oscillatory activities with an interval closely matching the duration of the LD cycle. Furthermore, the post-stimulus oscillatory activities of the DLA cells were sustained without feedback inputs from the pallium (equivalent to the mammalian cortex). Our study suggests that the experience-dependent representation of time interval in the brain might not be confined to the pallial/cortical level, but may occur as early as at the thalamic level. PMID:29284554

Estimation of time-delayed mutual information and bias for irregularly and sparsely sampled time-series

PubMed Central

Albers, D. J.; Hripcsak, George

2012-01-01

A method to estimate the time-dependent correlation via an empirical bias estimate of the time-delayed mutual information for a time-series is proposed. In particular, the bias of the time-delayed mutual information is shown to often be equivalent to the mutual information between two distributions of points from the same system separated by infinite time. Thus intuitively, estimation of the bias is reduced to estimation of the mutual information between distributions of data points separated by large time intervals. The proposed bias estimation techniques are shown to work for Lorenz equations data and glucose time series data of three patients from the Columbia University Medical Center database. PMID:22536009

System implications of the ambulance arrival-to-patient contact interval on response interval compliance.

PubMed

Campbell, J P; Gratton, M C; Salomone, J A; Lindholm, D J; Watson, W A

1994-01-01

In some emergency medical services (EMS) system designs, response time intervals are mandated with monetary penalties for noncompliance. These times are set with the goal of providing rapid, definitive patient care. The time interval of vehicle at scene-to-patient access (VSPA) has been measured, but its effect on response time interval compliance has not been determined. To determine the effect of the VSPA interval on the mandated code 1 (< 9 min) and code 2 (< 13 min) response time interval compliance in an urban, public-utility model system. A prospective, observational study used independent third-party riders to collect the VSPA interval for emergency life-threatening (code 1) and emergency nonlife-threatening (code 2) calls. The VSPA interval was added to the 9-1-1 call-to-dispatch and vehicle dispatch-to-scene intervals to determine the total time interval from call received until paramedic access to the patient (9-1-1 call-to-patient access). Compliance with the mandated response time intervals was determined using the traditional time intervals (9-1-1 call-to-scene) plus the VSPA time intervals (9-1-1 call-to-patient access). Chi-square was used to determine statistical significance. Of the 216 observed calls, 198 were matched to the traditional time intervals. Sixty-three were code 1, and 135 were code 2. Of the code 1 calls, 90.5% were compliant using 9-1-1 call-to-scene intervals dropping to 63.5% using 9-1-1 call-to-patient access intervals (p < 0.0005). Of the code 2 calls, 94.1% were compliant using 9-1-1 call-to-scene intervals. Compliance decreased to 83.7% using 9-1-1 call-to-patient access intervals (p = 0.012). The addition of the VSPA interval to the traditional time intervals impacts system response time compliance. Using 9-1-1 call-to-scene compliance as a basis for measuring system performance underestimates the time for the delivery of definitive care. This must be considered when response time interval compliances are defined.

Effects of environmental support on overt and covert visuospatial rehearsal.

PubMed

Lilienthal, Lindsey; Myerson, Joel; Abrams, Richard A; Hale, Sandra

2018-09-01

People can rehearse to-be-remembered locations either overtly, using eye movements, or covertly, using only shifts of spatial attention. The present study examined whether the effectiveness of these two strategies depends on environmental support for rehearsal. In Experiment 1, when environmental support (i.e., the array of possible locations) was present and participants could engage in overt rehearsal during retention intervals, longer intervals resulted in larger spans, whereas in Experiment 2, when support was present but participants could only engage in covert rehearsal, longer intervals resulted in smaller spans. When environmental support was absent, however, longer retention intervals resulted in smaller memory spans regardless of which rehearsal strategies were available. In Experiment 3, analyses of participants' eye movements revealed that the presence of support increased participants' fixations of to-be-remembered target locations more than fixations of non-targets, and that this was associated with better memory performance. Further, although the total time fixating targets increased, individual target fixations were actually briefer. Taken together, the present findings suggest that in the presence of environmental support, overt rehearsal is more effective than covert rehearsal at maintaining to-be-remembered locations in working memory, and that having more time for overt rehearsal can actually increase visuospatial memory spans.

Time perception, pacing and exercise intensity: maximal exercise distorts the perception of time.

PubMed

Edwards, A M; McCormick, A

2017-10-15

Currently there are no data examining the impact of exercise on the perception of time, which is surprising as optimal competitive performance is dependent on accurate pacing using knowledge of time elapsed. With institutional ethics approval, 12 recreationally active adult participants (f=7, m=5) undertook both 30s Wingate cycles and 20min (1200s) rowing ergometer bouts as short and long duration self-paced exercise trials, in each of three conditions on separate occasions: 1) light exertion: RPE 11, 2) heavy exertion: RPE 15, 3) maximal exertion: RPE 20. Participants were unaware of exercise duration and were required to verbally indicate when they perceived (subjective time) 1) 25%, 2) 50%, 3) 75% and 4) 100% of each bout's measured (chronological) time had elapsed. In response to the Wingate task, there was no difference between durations of subjective time at the 25%, nor at the 50% interval. However, at the 75% and 100% intervals, the estimate for the RPE 20 condition was shortest (P<0.01). In response to rowing, there were no differences at the 25% interval, but there was some evidence that the RPE 20 condition was perceived shorter at 50%. At 75% and 100%, the RPE 20 condition was perceived to be shorter than both RPE 15 (P=0.04) and RPE 11 (P=0.008) conditions. This study is the first to empirically demonstrate that exercise intensity distorts time perception, particularly during maximal exercise. Consequently external feedback of chronological time may be an important factor for athletes undertaking maximal effort tasks or competitions. Copyright © 2017 Elsevier Inc. All rights reserved.

Temporal properties of compensation for positive and negative spectacle lenses in chicks.

PubMed

Zhu, Xiaoying; Wallman, Josh

2009-01-01

Chicks' eyes rapidly compensate for defocus imposed by spectacle lenses by changing their rate of elongation and their choroidal thickness. Compensation may involve internal emmetropization signals that rise and become saturated during episodes of lens wear and decline between episodes. The time constants of these signals were measured indirectly by measuring the magnitude of lens compensation in refractive error and ocular dimensions as a function of the duration of episodes and the intervals between the episodes. First, in a study of how quickly the signals rose, chicks were subjected to episodes of lens-wear of various durations (darkness otherwise), and the duration required to cause a half-maximum effect (rise-time) was estimated. Second, in a study of how quickly the signals declined, various dark intervals were imposed between episodes of lens-wear, and the interval required to reduce the maximum effect by half (fall-time) was estimated. The rise-times for the rate of ocular elongation and choroidal thickness were approximately 3 minutes for positive and negative lenses. The fall-times had a broad range of time courses: Positive lenses caused an enduring inhibition of ocular elongation with a fall-time of 24 hours. In contrast, negative lenses caused a transient stimulation of ocular elongation with a fall-time of 0.4 hour. The effects of episodes of defocus rise rapidly with episode duration to an asymptote and decline between episodes, with the time course depending strongly on the sign of defocus and the ocular component. The complex etiology of human myopia may reflect these temporal properties.

Sleep Can Reduce the Testing Effect: It Enhances Recall of Restudied Items but Can Leave Recall of Retrieved Items Unaffected

ERIC Educational Resources Information Center

Bäuml, Karl-Heinz T.; Holterman, Christoph; Abel, Magdalena

2014-01-01

The testing effect refers to the finding that retrieval practice in comparison to restudy of previously encoded contents can improve memory performance and reduce time-dependent forgetting. Naturally, long retention intervals include both wake and sleep delay, which can influence memory contents differently. In fact, sleep immediately after…

Dopaminergic Actions of D-Amphetamine on Schedule-Induced Polydipsia in Rats

ERIC Educational Resources Information Center

Pellon, Ricardo; Ruiz, Ana; Rodriguez, Cilia; Flores, Pilar

2007-01-01

Schedule-induced polydipsia in rats was developed by means of a fixed-time 60-s schedule of food presentation. The acute administration of d-amphetamine sulfate (0.1-3.0 mg/kg) produced a dose-dependent decrease in the rate of licking. D-Amphetamine shifted to the left the temporal distribution of adjunctive drinking within interfood intervals.…

Modeling of the static recrystallization for 7055 aluminum alloy by cellular automaton

NASA Astrophysics Data System (ADS)

Zhang, Tao; Lu, Shi-hong; Zhang, Jia-bin; Li, Zheng-fang; Chen, Peng; Gong, Hai; Wu, Yun-xin

2017-09-01

In order to simulate the flow behavior and microstructure evolution during the pass interval period of the multi-pass deformation process, models of static recovery (SR) and static recrystallization (SRX) by the cellular automaton (CA) method for the 7055 aluminum alloy were established. Double-pass hot compression tests were conducted to acquire flow stress and microstructure variation during the pass interval period. With the basis of the material constants obtained from the compression tests, models of the SR, incubation period, nucleation rate and grain growth were fitted by least square method. A model of the grain topology and a statistical computation of the CA results were also introduced. The effects of the pass interval time, temperature, strain, strain rate and initial grain size on the microstructure variation for the SRX of the 7055 aluminum alloy were studied. The results show that a long pass interval time, large strain, high temperature and large strain rate are beneficial for finer grains during the pass interval period. The stable size of the static recrystallized grain is not concerned with the initial grain size, but mainly depends on the strain rate and temperature. The SRX plays a vital role in grain refinement, while the SR has no effect on the variation of microstructure morphology. Using flow stress and microstructure comparisons of the simulated and experimental CA results, the established CA models can accurately predict the flow stress and microstructure evolution during the pass interval period, and provide guidance for the selection of optimized parameters for the multi-pass deformation process.

Measurements of geomagnetically trapped alpha particles, 1968-1970. I - Quiet time distributions

NASA Technical Reports Server (NTRS)

Krimigis, S. M.; Verzariu, P.

1973-01-01

Results of observations of geomagnetically trapped alpha particles over the energy range from 1.18 to 8 MeV performed with the aid of the Injun 5 polar-orbiting satellite during the period from September 1968 to May 1970. Following a presentation of a time history covering this entire period, a detailed analysis is made of the magnetically quiet period from Feb. 11 to 28, 1970. During this period the alpha particle fluxes and the intensity ratio of alpha particles to protons attained their lowest values in approximately 20 months; the alpha particle intensity versus L profile was most similar to the proton profile at the same energy per nucleon interval; the intensity ratio was nearly constant as a function of L in the same energy per nucleon representation, but rose sharply with L when computed in the same total energy interval; the variation of alpha particle intensity with B suggested a steep angular distribution at small equatorial pitch angles, while the intensity ratio showed little dependence on B; and the alpha particle spectral parameter showed a markedly different dependence on L from the equivalent one for protons.

The Impact of Surgical Timing in Acute Traumatic Spinal Cord Injury

DTIC Science & Technology

2016-10-01

However, their study was con - ducted with a small sample of 63 patients and only cer- vical T-SCI, and did not account for other possible factors that... con - tributors are the time of transfer from the site of trauma to the SCI center, the interval between the first medical assessment and surgical plan...requiring surgery will depend upon the availability of the operating rooms and of the spine surgeons, con - sidering the high number of elective cases

Noncommutative FRW Apparent Horizon and Hawking Radiation

NASA Astrophysics Data System (ADS)

Bouhallouf, H.; Mebarki, N.; Aissaoui, H.

2017-11-01

In the context of noncommutative (NCG) gauge gravity, and using a cosmic time power law formula for the scale factor, a Friedman-Robertson-Walker (FRW) like metric is obtained. Within the fermions tunneling effect approach and depending on the various intervals of the power parameter, expressions of the apparent horizon are also derived. It is shown that in some regions of the parameter space, a pure NCG trapped horizon does exist leading to new interpretation of the role played by the noncommutativity of the space-time.

Interplanetary propagation of flare-associated energetic particles

NASA Technical Reports Server (NTRS)

Masung, L. L.; Earl, J. A.

1978-01-01

A propagation model which combines a Gaussian profile for particle release from the sun, with interplanetary particle densities predicted by focused diffusion, was proposed to explain the propagation history of flare associated energetic particles. This model, which depends on only two parameters, successfully describes the time-intensity profiles of 30 proton and electron events originating from the western hemisphere of the sun. Generally, particles are released from the sun over a finite interval. In almost all events, particle release begins at the time of flare acceleration.

Time-varying nonstationary multivariate risk analysis using a dynamic Bayesian copula

NASA Astrophysics Data System (ADS)

Sarhadi, Ali; Burn, Donald H.; Concepción Ausín, María.; Wiper, Michael P.

2016-03-01

A time-varying risk analysis is proposed for an adaptive design framework in nonstationary conditions arising from climate change. A Bayesian, dynamic conditional copula is developed for modeling the time-varying dependence structure between mixed continuous and discrete multiattributes of multidimensional hydrometeorological phenomena. Joint Bayesian inference is carried out to fit the marginals and copula in an illustrative example using an adaptive, Gibbs Markov Chain Monte Carlo (MCMC) sampler. Posterior mean estimates and credible intervals are provided for the model parameters and the Deviance Information Criterion (DIC) is used to select the model that best captures different forms of nonstationarity over time. This study also introduces a fully Bayesian, time-varying joint return period for multivariate time-dependent risk analysis in nonstationary environments. The results demonstrate that the nature and the risk of extreme-climate multidimensional processes are changed over time under the impact of climate change, and accordingly the long-term decision making strategies should be updated based on the anomalies of the nonstationary environment.

Prediction of hemoglobin in blood donors using a latent class mixed-effects transition model.

PubMed

Nasserinejad, Kazem; van Rosmalen, Joost; de Kort, Wim; Rizopoulos, Dimitris; Lesaffre, Emmanuel

2016-02-20

Blood donors experience a temporary reduction in their hemoglobin (Hb) value after donation. At each visit, the Hb value is measured, and a too low Hb value leads to a deferral for donation. Because of the recovery process after each donation as well as state dependence and unobserved heterogeneity, longitudinal data of Hb values of blood donors provide unique statistical challenges. To estimate the shape and duration of the recovery process and to predict future Hb values, we employed three models for the Hb value: (i) a mixed-effects models; (ii) a latent-class mixed-effects model; and (iii) a latent-class mixed-effects transition model. In each model, a flexible function was used to model the recovery process after donation. The latent classes identify groups of donors with fast or slow recovery times and donors whose recovery time increases with the number of donations. The transition effect accounts for possible state dependence in the observed data. All models were estimated in a Bayesian way, using data of new entrant donors from the Donor InSight study. Informative priors were used for parameters of the recovery process that were not identified using the observed data, based on results from the clinical literature. The results show that the latent-class mixed-effects transition model fits the data best, which illustrates the importance of modeling state dependence, unobserved heterogeneity, and the recovery process after donation. The estimated recovery time is much longer than the current minimum interval between donations, suggesting that an increase of this interval may be warranted. Copyright © 2015 John Wiley & Sons, Ltd.

Daily home gardening improved survival for older people with mobility limitations: an 11-year follow-up study in Taiwan

PubMed Central

Lêng, Chhian Hūi; Wang, Jung-Der

2016-01-01

Aims To test the hypothesis that gardening is beneficial for survival after taking time-dependent comorbidities, mobility, and depression into account in a longitudinal middle-aged (50–64 years) and older (≥65 years) cohort in Taiwan. Methods The cohort contained 5,058 nationally sampled adults ≥50 years old from the Taiwan Longitudinal Study on Aging (1996–2007). Gardening was defined as growing flowers, gardening, or cultivating potted plants for pleasure with five different frequencies. We calculated hazard ratios for the mortality risks of gardening and adjusted the analysis for socioeconomic status, health behaviors and conditions, depression, mobility limitations, and comorbidities. Survival models also examined time-dependent effects and risks in each stratum contingent upon baseline mobility and depression. Sensitivity analyses used imputation methods for missing values. Results Daily home gardening was associated with a high survival rate (hazard ratio: 0.82; 95% confidence interval: 0.71–0.94). The benefits were robust for those with mobility limitations, but without depression at baseline (hazard ratio: 0.64, 95% confidence interval: 0.48–0.87) when adjusted for time-dependent comorbidities, mobility limitations, and depression. Chronic or relapsed depression weakened the protection of gardening. For those without mobility limitations and not depressed at baseline, gardening had no effect. Sensitivity analyses using different imputation methods yielded similar results and corroborated the hypothesis. Conclusion Daily gardening for pleasure was associated with reduced mortality for Taiwanese >50 years old with mobility limitations but without depression. PMID:27486315

Emergency department patient satisfaction survey in Imam Reza Hospital, Tabriz, Iran

PubMed Central

2011-01-01

Introduction Patient satisfaction is an important indicator of the quality of care and service delivery in the emergency department (ED). The objective of this study was to evaluate patient satisfaction with the Emergency Department of Imam Reza Hospital in Tabriz, Iran. Methods This study was carried out for 1 week during all shifts. Trained researchers used the standard Press Ganey questionnaire. Patients were asked to complete the questionnaire prior to discharge. The study questionnaire included 30 questions based on a Likert scale. Descriptive and analytical statistics were used throughout data analysis in a number of ways using SPSS version 13. Results Five hundred patients who attended our ED were included in this study. The highest satisfaction rates were observed in the terms of physicians' communication with patients (82.5%), security guards' courtesy (78.3%) and nurses' communication with patients (78%). The average waiting time for the first visit to a physician was 24 min 15 s. The overall satisfaction rate was dependent on the mean waiting time. The mean waiting time for a low rate of satisfaction was 47 min 11 s with a confidence interval of (19.31, 74.51), and for very good level of satisfaction it was 14 min 57 s with a (10.58, 18.57) confidence interval. Approximately 63% of the patients rated their general satisfaction with the emergency setting as good or very good. On the whole, the patient satisfaction rate at the lowest level was 7.7 with a confidence interval of (5.1, 10.4), and at the low level it was 5.8% with a confidence interval of (3.7, 7.9). The rate of satisfaction for the mediocre level was 23.3 with a confidence interval of (19.1, 27.5); for the high level of satisfaction it was 28.3 with a confidence interval of (22.9, 32.8), and for the very high level of satisfaction, this rate was 32.9% with a confidence interval of (28.4, 37.4). Conclusion The study findings indicated the need for evidence-based interventions in emergency care services in areas such as medical care, nursing care, courtesy of staff, physical comfort and waiting time. Efforts should focus on shortening waiting intervals and improving patients' perceptions about waiting in the ED, and also improving the overall cleanliness of the emergency room. PMID:21407998

Feasibility of Ecological Momentary Assessment Using Cellular Telephones in Methamphetamine Dependent Subjects

PubMed Central

Galloway, Gantt P; Didier, Ryne; Garrison, Kathleen; Mendelson, John

2008-01-01

Background Predictors of relapse to methamphetamine use are poorly understood. State variables may play an important role in relapse, but they have been difficult to measure at frequent intervals in outpatients. Methods We conducted a feasibility study of the use of cellular telephones to collect state variable data from outpatients. Six subjects in treatment for methamphetamine dependence were called three times per weekday for approximately seven weeks. Seven questionnaires were administered that assessed craving, stress, affect and current type of location and social environment. Results 395/606 (65%) of calls attempted were completed. The mean time to complete each call was 4.9 (s.d. 1.8) minutes and the mean time to complete each item was 8.4 (s.d. 4.8) seconds. Subjects rated the acceptability of the procedures as good. All six cellular phones and battery chargers were returned undamaged. Conclusion Cellular telephones are a feasible method for collecting state data from methamphetamine dependent outpatients. PMID:19997532

Evaluation of confidence intervals for a steady-state leaky aquifer model

USGS Publications Warehouse

Christensen, S.; Cooley, R.L.

1999-01-01

The fact that dependent variables of groundwater models are generally nonlinear functions of model parameters is shown to be a potentially significant factor in calculating accurate confidence intervals for both model parameters and functions of the parameters, such as the values of dependent variables calculated by the model. The Lagrangian method of Vecchia and Cooley [Vecchia, A.V. and Cooley, R.L., Water Resources Research, 1987, 23(7), 1237-1250] was used to calculate nonlinear Scheffe-type confidence intervals for the parameters and the simulated heads of a steady-state groundwater flow model covering 450 km2 of a leaky aquifer. The nonlinear confidence intervals are compared to corresponding linear intervals. As suggested by the significant nonlinearity of the regression model, linear confidence intervals are often not accurate. The commonly made assumption that widths of linear confidence intervals always underestimate the actual (nonlinear) widths was not correct. Results show that nonlinear effects can cause the nonlinear intervals to be asymmetric and either larger or smaller than the linear approximations. Prior information on transmissivities helps reduce the size of the confidence intervals, with the most notable effects occurring for the parameters on which there is prior information and for head values in parameter zones for which there is prior information on the parameters.The fact that dependent variables of groundwater models are generally nonlinear functions of model parameters is shown to be a potentially significant factor in calculating accurate confidence intervals for both model parameters and functions of the parameters, such as the values of dependent variables calculated by the model. The Lagrangian method of Vecchia and Cooley was used to calculate nonlinear Scheffe-type confidence intervals for the parameters and the simulated heads of a steady-state groundwater flow model covering 450 km2 of a leaky aquifer. The nonlinear confidence intervals are compared to corresponding linear intervals. As suggested by the significant nonlinearity of the regression model, linear confidence intervals are often not accurate. The commonly made assumption that widths of linear confidence intervals always underestimate the actual (nonlinear) widths was not correct. Results show that nonlinear effects can cause the nonlinear intervals to be asymmetric and either larger or smaller than the linear approximations. Prior information on transmissivities helps reduce the size of the confidence intervals, with the most notable effects occurring for the parameters on which there is prior information and for head values in parameter zones for which there is prior information on the parameters.

Shoulder pain and time dependent structure in wheelchair propulsion variability.

PubMed

Jayaraman, Chandrasekaran; Moon, Yaejin; Sosnoff, Jacob J

2016-07-01

Manual wheelchair propulsion places considerable repetitive mechanical strain on the upper limbs leading to shoulder injury and pain. While recent research indicates that the amount of variability in wheelchair propulsion and shoulder pain may be related. There has been minimal inquiry into the fluctuation over time (i.e. time-dependent structure) in wheelchair propulsion variability. Consequently the purpose of this investigation was to examine if the time-dependent structure in the wheelchair propulsion parameters are related to shoulder pain. 27 experienced wheelchair users manually propelled their own wheelchair fitted with a SMARTWheel on a roller at 1.1m/s for 3min. Time-dependent structure of cycle-to-cycle fluctuations in contact angle and inter push time interval was quantified using sample entropy (SampEn) and compared between the groups with/without shoulder pain using non-parametric statistics. Overall findings were, (1) variability observed in contact angle fluctuations during manual wheelchair propulsion is structured (Z=3.15;p<0.05), (2) individuals with shoulder pain exhibited higher SampEn magnitude for contact angle during wheelchair propulsion than those without pain (χ(2)(1)=6.12;p<0.05); and (3) SampEn of contact angle correlated significantly with self-reported shoulder pain (rs (WUSPI) =0.41;rs (VAS)=0.56;p<0.05). It was concluded that the time-dependent structure in wheelchair propulsion may provide novel information for tracking and monitoring shoulder pain. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Dividing traffic cluster into parts by signal control

NASA Astrophysics Data System (ADS)

Nagatani, Takashi

2018-02-01

When a cluster of vehicles with various speeds moves through the series of signals, the cluster breaks down by stopping at signals and results in smaller groups of vehicles. We present the nonlinear-map model of the motion of vehicles controlled by the signals. We study the breakup of a cluster of vehicles through the series of signals. The cluster of vehicles is divided into various groups by controlling the cycle time of signals. The vehicles within each group move with the same mean velocity. The breakup of the traffic cluster depends highly on the signal control. The dependence of dividing on both cycle time and vehicular speed is clarified. Also, we investigate the effect of the irregular interval between signals on dividing.

Gonadal morphogenesis and gene expression in reptiles with temperature-dependent sex determination.

PubMed

Merchant-Larios, H; Díaz-Hernández, V; Marmolejo-Valencia, A

2010-01-01

In reptiles with temperature-dependent sexual determination, the thermosensitive period (TSP) is the interval in which the sex is defined during gonadal morphogenesis. One-shift experiments in a group of eggs define the onset and the end of the TSP as all and none responses, respectively. Timing for sex-undetermined (UG) and -determined gonads (DG) differs at male- (MPT) or female-producing temperatures (FPT). During the TSP a decreasing number of embryos respond to temperature shifts indicating that in this period embryos with both UG and DG exist. Although most UG correspond to undifferentiated gonads, some embryos extend UG after the onset of histological differentiation. Thus, temperature affects gonadal cells during the process of morphogenesis, but timing of commitment depends on individual embryos. A correlation between gonadal morphogenesis, TSP, and gene expression suggests that determination of the molecular pathways modulated by temperature in epithelial cells (surface epithelium and medullary cords) holds the key for a unifying hypothesis on temperature-dependent sex determination. (c) 2010 S. Karger AG, Basel.

Petahertz optical oscilloscope

NASA Astrophysics Data System (ADS)

Kim, Kyung Taec; Zhang, Chunmei; Shiner, Andrew D.; Schmidt, Bruno E.; Légaré, François; Villeneuve, D. M.; Corkum, P. B.

2013-12-01

The time-dependent field of an electromagnetic pulse can be measured if there is a fast enough gate. For terahertz radiation, femtosecond photoinjection of free carriers into a semiconductor in the presence of the terahertz radiation can serve as the gate. For visible or infrared radiation, attosecond photoionization of a gas target in the presence of the optical field is a direct analogue. Here, we show that nonlinear optical mixing in a medium in which attosecond pulses are being generated can also be used to measure the time-dependent field of an optical pulse. The gate is the phase accumulated by the recollision electron during the subcycle time interval between ionization and recombination. We show that the instantaneous field of an unknown pulse is imprinted onto the deflection of the attosecond extreme ultraviolet pulse using an all-optical set-up with a bandwidth up to 1 PHz.

Absorption of subcutaneously infused insulin: influence of the basal rate pulse interval.

PubMed

Hildebrandt, P; Birch, K; Jensen, B M; Kühl, C; Brange, J

1985-01-01

Eight insulin-dependent diabetic patients were given two constant infusions (each 1 IU/h) of 125I-labeled insulin into the abdominal subcutaneous tissue for about 12 h. Insulin was infused in pulses into one side of the abdomen in 6-min intervals (by means of an Auto-Syringe pump) and in the other side of the abdomen, insulin was infused in 1-h intervals (by means of a Medix pump). The size of the subcutaneous depots was continuously measured by counting the radioactivity at the infusion sites. After starting the infusions, the two depots were built up to steady-state levels at the same time and of the same size (approximately 3 IU) and with similar absorption rates. Thus, during basal rate insulin infusion, identical insulin absorption kinetics was achieved, irrespective of a 10-fold difference in the pulse rate.

Dissociating movement from movement timing in the rat primary motor cortex.

PubMed

Knudsen, Eric B; Powers, Marissa E; Moxon, Karen A

2014-11-19

Neural encoding of the passage of time to produce temporally precise movements remains an open question. Neurons in several brain regions across different experimental contexts encode estimates of temporal intervals by scaling their activity in proportion to the interval duration. In motor cortex the degree to which this scaled activity relies upon afferent feedback and is guided by motor output remains unclear. Using a neural reward paradigm to dissociate neural activity from motor output before and after complete spinal transection, we show that temporally scaled activity occurs in the rat hindlimb motor cortex in the absence of motor output and after transection. Context-dependent changes in the encoding are plastic, reversible, and re-established following injury. Therefore, in the absence of motor output and despite a loss of afferent feedback, thought necessary for timed movements, the rat motor cortex displays scaled activity during a broad range of temporally demanding tasks similar to that identified in other brain regions. Copyright © 2014 the authors 0270-6474/14/3415576-11$15.00/0.

Optimizing some 3-stage W-methods for the time integration of PDEs

NASA Astrophysics Data System (ADS)

Gonzalez-Pinto, S.; Hernandez-Abreu, D.; Perez-Rodriguez, S.

2017-07-01

The optimization of some W-methods for the time integration of time-dependent PDEs in several spatial variables is considered. In [2, Theorem 1] several three-parametric families of three-stage W-methods for the integration of IVPs in ODEs were studied. Besides, the optimization of several specific methods for PDEs when the Approximate Matrix Factorization Splitting (AMF) is used to define the approximate Jacobian matrix (W ≈ fy(yn)) was carried out. Also, some convergence and stability properties were presented [2]. The derived methods were optimized on the base that the underlying explicit Runge-Kutta method is the one having the largest Monotonicity interval among the thee-stage order three Runge-Kutta methods [1]. Here, we propose an optimization of the methods by imposing some additional order condition [7] to keep order three for parabolic PDE problems [6] but at the price of reducing substantially the length of the nonlinear Monotonicity interval of the underlying explicit Runge-Kutta method.

Interactions between sleeping position and feeding on cardiorespiratory activity in preterm infants.

PubMed

Fifer, William P; Myers, Michael M; Sahni, Rakesh; Ohira-Kist, Kiyoko; Kashyap, Sudha; Stark, Raymond I; Schulze, Karl F

2005-11-01

Infants sleeping in the prone position are at greater risk for sudden infant death syndrome (SIDS). Sleep position-dependent changes in cardiorespiratory activity may contribute to this increased risk. Cardiorespiratory activity is also affected by feeding. Twenty prematurely-born infants were studied at 31-36 weeks postconceptional age while sleeping in the prone and supine positions. Heart rate, respiratory rate, and patterns of variability were recorded during interfeed intervals, and effects of position and time after feeding were analyzed by repeated measures analyses of variance. There were significant effects of both sleeping position and time after feeding. Heart rate is higher and heart period variability is lower in the prone position, and the effects of sleeping position on cardiac functioning are more pronounced during the middle of the intrafeed interval. In preterm infants, autonomic responses to nutrient processing modulate the cardiorespiratory effects of sleeping position. Prone sleeping risk may vary with time after feeding. Copyright 2005 Wiley Periodicals, Inc.

Analysis of noise-induced temporal correlations in neuronal spike sequences

NASA Astrophysics Data System (ADS)

Reinoso, José A.; Torrent, M. C.; Masoller, Cristina

2016-11-01

We investigate temporal correlations in sequences of noise-induced neuronal spikes, using a symbolic method of time-series analysis. We focus on the sequence of time-intervals between consecutive spikes (inter-spike-intervals, ISIs). The analysis method, known as ordinal analysis, transforms the ISI sequence into a sequence of ordinal patterns (OPs), which are defined in terms of the relative ordering of consecutive ISIs. The ISI sequences are obtained from extensive simulations of two neuron models (FitzHugh-Nagumo, FHN, and integrate-and-fire, IF), with correlated noise. We find that, as the noise strength increases, temporal order gradually emerges, revealed by the existence of more frequent ordinal patterns in the ISI sequence. While in the FHN model the most frequent OP depends on the noise strength, in the IF model it is independent of the noise strength. In both models, the correlation time of the noise affects the OP probabilities but does not modify the most probable pattern.

Allan deviation analysis of financial return series

NASA Astrophysics Data System (ADS)

Hernández-Pérez, R.

2012-05-01

We perform a scaling analysis for the return series of different financial assets applying the Allan deviation (ADEV), which is used in the time and frequency metrology to characterize quantitatively the stability of frequency standards since it has demonstrated to be a robust quantity to analyze fluctuations of non-stationary time series for different observation intervals. The data used are opening price daily series for assets from different markets during a time span of around ten years. We found that the ADEV results for the return series at short scales resemble those expected for an uncorrelated series, consistent with the efficient market hypothesis. On the other hand, the ADEV results for absolute return series for short scales (first one or two decades) decrease following approximately a scaling relation up to a point that is different for almost each asset, after which the ADEV deviates from scaling, which suggests that the presence of clustering, long-range dependence and non-stationarity signatures in the series drive the results for large observation intervals.

The impact of peritoneal dialysis-related peritonitis on mortality in peritoneal dialysis patients.

PubMed

Ye, Hongjian; Zhou, Qian; Fan, Li; Guo, Qunying; Mao, Haiping; Huang, Fengxian; Yu, Xueqing; Yang, Xiao

2017-06-05

Results concerning the association between peritoneal dialysis-related peritonitis and mortality in peritoneal dialysis patients are inconclusive, with one potential reason being that the time-dependent effect of peritonitis has rarely been considered in previous studies. This study aimed to evaluate whether peritonitis has a negative impact on mortality in a large cohort of peritoneal dialysis patients. We also assessed the changing impact of peritonitis on patient mortality with respect to duration of follow-up. This retrospective cohort study included incident patients who started peritoneal dialysis from 1 January 2006 to 31 December 2011. Episodes of peritonitis were recorded at the time of onset, and peritonitis was parameterized as a time-dependent variable for analysis. We used the Cox regression model to assess whether peritonitis has a negative impact on mortality. A total of 1321 patients were included. The mean age was 48.1 ± 15.3 years, 41.3% were female, and 23.5% with diabetes mellitus. The median (interquartile) follow-up time was 34 (21-48) months. After adjusting for confounders, peritonitis was independently associated with 95% increased risk of all-cause mortality (hazard ratio, 1.95; 95% confidence interval: 1.46-2.60), 90% increased risk of cardiovascular mortality (hazard ratio, 1.90; 95% confidence interval: 1.28-2.81) and near 4-fold increased risk of infection-related mortality (hazard ratio, 4.94; 95% confidence interval: 2.47-9.86). Further analyses showed that peritonitis was not significantly associated with mortality within 2 years of peritoneal dialysis initiation, but strongly influenced mortality in patients dialysed longer than 2 years. Peritonitis was independently associated with higher risk of all-cause, cardiovascular and infection-related mortality in peritoneal dialysis patients, and its impact on mortality was more significant in patients with longer peritoneal dialysis duration.

Does major depression result in lasting personality change?

PubMed

Shea, M T; Leon, A C; Mueller, T I; Solomon, D A; Warshaw, M G; Keller, M B

1996-11-01

Individuals with a history of depression are characterized by high levels of certain personality traits, particularly neuroticism, introversion, and interpersonal dependency. The authors examined the "scar hypothesis," i.e., the possibility that episodes of major depression result in lasting personality changes that persist beyond recovery from the depression. A large sample of first-degree relatives, spouses, and comparison subjects ascertained in connection with the proband sample from the National Institute of Mental Health Collaborative Program on the Psychobiology of Depression were assessed at two points in time separated by an interval of 6 years. Subjects with a prospectively observed first episode of major depression during the interval were compared with subjects remaining well in terms of change from time 1 to time 2 in self-reported personality traits. All subjects studied were well (had no mental disorders) at the time of both assessments. There was no evidence of negative change from premorbid to postmorbid assessment in any of the personality traits for subjects with a prospectively observed first episode of major depression during the interval. The results suggested a possible association of number and length of episodes with increased levels of emotional reliance and introversion, respectively. The findings suggest that self-reported personality traits do not change after a typical episode of major depression. Future studies are needed to determine whether such change occurs following more severe, chronic, or recurrent episodes of depression.

The solar wind effect on cosmic rays and solar activity

NASA Technical Reports Server (NTRS)

Fujimoto, K.; Kojima, H.; Murakami, K.

1985-01-01

The relation of cosmic ray intensity to solar wind velocity is investigated, using neutron monitor data from Kiel and Deep River. The analysis shows that the regression coefficient of the average intensity for a time interval to the corresponding average velocity is negative and that the absolute effect increases monotonously with the interval of averaging, tau, that is, from -0.5% per 100km/s for tau = 1 day to -1.1% per 100km/s for tau = 27 days. For tau 27 days the coefficient becomes almost constant independently of the value of tau. The analysis also shows that this tau-dependence of the regression coefficiently is varying with the solar activity.

Birth spacing and fertility limitation: a behavioral analysis of a nineteenth century frontier population.

PubMed

Anderton, D L; Bean, L L

1985-05-01

Our analysis of changing birth interval distributions over the course of a fertility transition from natural to controlled fertility has examined three closely related propositions. First, within both natural fertility populations (identified at the aggregate level) and cohorts following the onset of fertility limitation, we hypothesized that substantial groups of women with long birth intervals across the individually specified childbearing careers could be identified. That is, even during periods when fertility behavior at the aggregate level is consistent with a natural fertility regime, birth intervals at all parities are inversely related to completed family size. Our tabular analysis enables us to conclude that birth spacing patterns are parity dependent; there is stability in CEB-parity specific mean and birth interval variance over the entire transition. Our evidence does not suggest that the early group of women limiting and spacing births was marked by infecundity. Secondly, the transition appears to be associated with an increasingly larger proportion of women shifting to the same spacing schedules associated with smaller families in earlier cohorts. Thirdly, variations in birth spacing by age of marriage indicate that changes in birth intervals over time are at least indirectly associated with age of marriage, indicating an additional compositional effect. The evidence we have presented on spacing behavior does not negate the argument that parity-dependent stopping behavior was a powerful factor in the fertility transition. Our data also provide evidence of attempts to truncate childbearing. Specifically, the smaller the completed family size, the longer the ultimate birth interval; and ultimate birth intervals increase across cohorts controlling CEB and parity. But spacing appears to represent an additional strategy of fertility limitation. Thus, it may be necessary to distinguish spacing and stopping behavior if one wishes to clarify behavioral patterns within a population (Edlefsen, 1981; Friedlander et al., 1980; Rodriguez and Hobcraft, 1980). Because fertility transition theories imply increased attempts to limit family sizes, it is important to examine differential behavior within subgroups achieving different family sizes. It is this level of analysis which we have attempted to achieve in utilizing parity-specific birth intervals controlled by children ever born.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluating Protocol Lifecycle Time Intervals in HIV/AIDS Clinical Trials

PubMed Central

Schouten, Jeffrey T.; Dixon, Dennis; Varghese, Suresh; Cope, Marie T.; Marci, Joe; Kagan, Jonathan M.

2014-01-01

Background Identifying efficacious interventions for the prevention and treatment of human diseases depends on the efficient development and implementation of controlled clinical trials. Essential to reducing the time and burden of completing the clinical trial lifecycle is determining which aspects take the longest, delay other stages, and may lead to better resource utilization without diminishing scientific quality, safety, or the protection of human subjects. Purpose In this study we modeled time-to-event data to explore relationships between clinical trial protocol development and implementation times, as well as identify potential correlates of prolonged development and implementation. Methods We obtained time interval and participant accrual data from 111 interventional clinical trials initiated between 2006 and 2011 by NIH’s HIV/AIDS Clinical Trials Networks. We determined the time (in days) required to complete defined phases of clinical trial protocol development and implementation. Kaplan-Meier estimates were used to assess the rates at which protocols reached specified terminal events, stratified by study purpose (therapeutic, prevention) and phase group (pilot/phase I, phase II, and phase III/ IV). We also examined several potential correlates to prolonged development and implementation intervals. Results Even though phase grouping did not determine development or implementation times of either therapeutic or prevention studies, overall we observed wide variation in protocol development times. Moreover, we detected a trend toward phase III/IV therapeutic protocols exhibiting longer developmental (median 2 ½ years) and implementation times (>3years). We also found that protocols exceeding the median number of days for completing the development interval had significantly longer implementation. Limitations The use of a relatively small set of protocols may have limited our ability to detect differences across phase groupings. Some timing effects present for a specific study phase may have been masked by combining protocols into phase groupings. Presence of informative censoring, such as withdrawal of some protocols from development if they began showing signs of lost interest among investigators, complicates interpretation of Kaplan-Meier estimates. Because this study constitutes a retrospective examination over an extended period of time, it does not allow for the precise identification of relative factors impacting timing. Conclusions Delays not only increase the time and cost to complete clinical trials, but they also diminish their usefulness by failing to answer research questions in time. We believe that research analyzing the time spent traversing defined intervals across the clinical trial protocol development and implementation continuum can stimulate business process analyses and reengineering efforts that could lead to reductions in the time from clinical trial concept to results, thereby accelerating progress in clinical research. PMID:24980279

Modeling and quantification of repolarization feature dependency on heart rate.

PubMed

Minchole, A; Zacur, E; Pueyo, E; Laguna, P

2014-01-01

This article is part of the Focus Theme of Methods of Information in Medicine on "Biosignal Interpretation: Advanced Methods for Studying Cardiovascular and Respiratory Systems". This work aims at providing an efficient method to estimate the parameters of a non linear model including memory, previously proposed to characterize rate adaptation of repolarization indices. The physiological restrictions on the model parameters have been included in the cost function in such a way that unconstrained optimization techniques such as descent optimization methods can be used for parameter estimation. The proposed method has been evaluated on electrocardiogram (ECG) recordings of healthy subjects performing a tilt test, where rate adaptation of QT and Tpeak-to-Tend (Tpe) intervals has been characterized. The proposed strategy results in an efficient methodology to characterize rate adaptation of repolarization features, improving the convergence time with respect to previous strategies. Moreover, Tpe interval adapts faster to changes in heart rate than the QT interval. In this work an efficient estimation of the parameters of a model aimed at characterizing rate adaptation of repolarization features has been proposed. The Tpe interval has been shown to be rate related and with a shorter memory lag than the QT interval.

Precise time and time interval applications to electric power systems

NASA Technical Reports Server (NTRS)

Wilson, Robert E.

1992-01-01

There are many applications of precise time and time interval (frequency) in operating modern electric power systems. Many generators and customer loads are operated in parallel. The reliable transfer of electrical power to the consumer partly depends on measuring power system frequency consistently in many locations. The internal oscillators in the widely dispersed frequency measuring units must be syntonized. Elaborate protection and control systems guard the high voltage equipment from short and open circuits. For the highest reliability of electric service, engineers need to study all control system operations. Precise timekeeping networks aid in the analysis of power system operations by synchronizing the clocks on recording instruments. Utility engineers want to reproduce events that caused loss of service to customers. Precise timekeeping networks can synchronize protective relay test-sets. For dependable electrical service, all generators and large motors must remain close to speed synchronism. The stable response of a power system to perturbations is critical to continuity of electrical service. Research shows that measurement of the power system state vector can aid in the monitoring and control of system stability. If power system operators know that a lightning storm is approaching a critical transmission line or transformer, they can modify operating strategies. Knowledge of the location of a short circuit fault can speed the re-energizing of a transmission line. One fault location technique requires clocks synchronized to one microsecond. Current research seeks to find out if one microsecond timekeeping can aid and improve power system control and operation.

Bayesian lead time estimation for the Johns Hopkins Lung Project data.

PubMed

Jang, Hyejeong; Kim, Seongho; Wu, Dongfeng

2013-09-01

Lung cancer screening using X-rays has been controversial for many years. A major concern is whether lung cancer screening really brings any survival benefits, which depends on effective treatment after early detection. The problem was analyzed from a different point of view and estimates were presented of the projected lead time for participants in a lung cancer screening program using the Johns Hopkins Lung Project (JHLP) data. The newly developed method of lead time estimation was applied where the lifetime T was treated as a random variable rather than a fixed value, resulting in the number of future screenings for a given individual is a random variable. Using the actuarial life table available from the United States Social Security Administration, the lifetime distribution was first obtained, then the lead time distribution was projected using the JHLP data. The data analysis with the JHLP data shows that, for a male heavy smoker with initial screening ages at 50, 60, and 70, the probability of no-early-detection with semiannual screens will be 32.16%, 32.45%, and 33.17%, respectively; while the mean lead time is 1.36, 1.33 and 1.23 years. The probability of no-early-detection increases monotonically when the screening interval increases, and it increases slightly as the initial age increases for the same screening interval. The mean lead time and its standard error decrease when the screening interval increases for all age groups, and both decrease when initial age increases with the same screening interval. The overall mean lead time estimated with a random lifetime T is slightly less than that with a fixed value of T. This result is hoped to be of benefit to improve current screening programs. Copyright © 2013 Ministry of Health, Saudi Arabia. Published by Elsevier Ltd. All rights reserved.

Mutual information identifies spurious Hurst phenomena in resting state EEG and fMRI data

NASA Astrophysics Data System (ADS)

von Wegner, Frederic; Laufs, Helmut; Tagliazucchi, Enzo

2018-02-01

Long-range memory in time series is often quantified by the Hurst exponent H , a measure of the signal's variance across several time scales. We analyze neurophysiological time series from electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) resting state experiments with two standard Hurst exponent estimators and with the time-lagged mutual information function applied to discretized versions of the signals. A confidence interval for the mutual information function is obtained from surrogate Markov processes with equilibrium distribution and transition matrix identical to the underlying signal. For EEG signals, we construct an additional mutual information confidence interval from a short-range correlated, tenth-order autoregressive model. We reproduce the previously described Hurst phenomenon (H >0.5 ) in the analytical amplitude of alpha frequency band oscillations, in EEG microstate sequences, and in fMRI signals, but we show that the Hurst phenomenon occurs without long-range memory in the information-theoretical sense. We find that the mutual information function of neurophysiological data behaves differently from fractional Gaussian noise (fGn), for which the Hurst phenomenon is a sufficient condition to prove long-range memory. Two other well-characterized, short-range correlated stochastic processes (Ornstein-Uhlenbeck, Cox-Ingersoll-Ross) also yield H >0.5 , whereas their mutual information functions lie within the Markovian confidence intervals, similar to neural signals. In these processes, which do not have long-range memory by construction, a spurious Hurst phenomenon occurs due to slow relaxation times and heteroscedasticity (time-varying conditional variance). In summary, we find that mutual information correctly distinguishes long-range from short-range dependence in the theoretical and experimental cases discussed. Our results also suggest that the stationary fGn process is not sufficient to describe neural data, which seem to belong to a more general class of stochastic processes, in which multiscale variance effects produce Hurst phenomena without long-range dependence. In our experimental data, the Hurst phenomenon and long-range memory appear as different system properties that should be estimated and interpreted independently.

MK-801 and memantine act differently on short-term memory tested with different time-intervals in the Morris water maze test.

PubMed

Duda, Weronika; Wesierska, Malgorzata; Ostaszewski, Pawel; Vales, Karel; Nekovarova, Tereza; Stuchlik, Ales

2016-09-15

N-methyl-d-aspartate receptors (NMDARs) play a crucial role in spatial memory formation. In neuropharmacological studies their functioning strongly depends on testing conditions and the dosage of NMDAR antagonists. The aim of this study was to assess the immediate effects of NMDAR block by (+)MK-801 or memantine on short-term allothetic memory. Memory was tested in a working memory version of the Morris water maze test. In our version of the test, rats underwent one day of training with 8 trials, and then three experimental days when rats were injected intraperitoneally with low- 5 (MeL), high - 20 (MeH) mg/kg memantine, 0.1mg/kg MK-801 or 1ml/kg saline (SAL) 30min before testing, for three consecutive days. On each experimental day there was just one acquisition and one test trial, with an inter-trial interval of 5 or 15min. During training the hidden platform was relocated after each trial and during the experiment after each day. The follow-up effect was assessed on day 9. Intact rats improved their spatial memory across the one training day. With a 5min interval MeH rats had longer latency then all rats during retrieval. With a 15min interval the MeH rats presented worse working memory measured as retrieval minus acquisition trial for path than SAL and MeL and for latency than MeL rats. MK-801 rats had longer latency than SAL during retrieval. Thus, the high dose of memantine, contrary to low dose of MK-801 disrupts short-term memory independent on the time interval between acquisition and retrieval. This shows that short-term memory tested in a working memory version of water maze is sensitive to several parameters: i.e., NMDA receptor antagonist type, dosage and the time interval between learning and testing. Copyright © 2016. Published by Elsevier B.V.

Setting Thresholds to Varying Blood Pressure Monitoring Intervals Differentially Affects Risk Estimates Associated With White-Coat and Masked Hypertension in the Population

PubMed Central

Asayama, Kei; Thijs, Lutgarde; Li, Yan; Gu, Yu-Mei; Hara, Azusa; Liu, Yan-Ping; Zhang, Zhenyu; Wei, Fang-Fei; Lujambio, Inés; Mena, Luis J.; Boggia, José; Hansen, Tine W.; Björklund-Bodegård, Kristina; Nomura, Kyoko; Ohkubo, Takayoshi; Jeppesen, Jørgen; Torp-Pedersen, Christian; Dolan, Eamon; Stolarz-Skrzypek, Katarzyna; Malyutina, Sofia; Casiglia, Edoardo; Nikitin, Yuri; Lind, Lars; Luzardo, Leonella; Kawecka-Jaszcz, Kalina; Sandoya, Edgardo; Filipovský, Jan; Maestre, Gladys E.; Wang, Jiguang; Imai, Yutaka; Franklin, Stanley S.; O’Brien, Eoin; Staessen, Jan A.

2015-01-01

Outcome-driven recommendations about time intervals during which ambulatory blood pressure should be measured to diagnose white-coat or masked hypertension are lacking. We cross-classified 8237 untreated participants (mean age, 50.7 years; 48.4% women) enrolled in 12 population studies, using ≥140/≥90, ≥130/≥80, ≥135/≥85, and ≥120/≥70 mm Hg as hypertension thresholds for conventional, 24-hour, daytime, and nighttime blood pressure. White-coat hypertension was hypertension on conventional measurement with ambulatory normotension, the opposite condition being masked hypertension. Intervals used for classification of participants were daytime, nighttime, and 24 hours, first considered separately, and next combined as 24 hours plus daytime or plus nighttime, or plus both. Depending on time intervals chosen, white-coat and masked hypertension frequencies ranged from 6.3% to 12.5% and from 9.7% to 19.6%, respectively. During 91 046 person-years, 729 participants experienced a cardiovascular event. In multivariable analyses with normotension during all intervals of the day as reference, hazard ratios associated with white-coat hypertension progressively weakened considering daytime only (1.38; P=0.033), nighttime only (1.43; P=0.0074), 24 hours only (1.21; P=0.20), 24 hours plus daytime (1.24; P=0.18), 24 hours plus nighttime (1.15; P=0.39), and 24 hours plus daytime and nighttime (1.16; P=0.41). The hazard ratios comparing masked hypertension with normotension were all significant (P<0.0001), ranging from 1.76 to 2.03. In conclusion, identification of truly low-risk white-coat hypertension requires setting thresholds simultaneously to 24 hours, daytime, and nighttime blood pressure. Although any time interval suffices to diagnose masked hypertension, as proposed in current guidelines, full 24-hour recordings remain standard in clinical practice. PMID:25135185

A comparative analysis of spectral exponent estimation techniques for 1/fβ processes with applications to the analysis of stride interval time series

PubMed Central

Schaefer, Alexander; Brach, Jennifer S.; Perera, Subashan; Sejdić, Ervin

2013-01-01

Background The time evolution and complex interactions of many nonlinear systems, such as in the human body, result in fractal types of parameter outcomes that exhibit self similarity over long time scales by a power law in the frequency spectrum S(f) = 1/fβ. The scaling exponent β is thus often interpreted as a “biomarker” of relative health and decline. New Method This paper presents a thorough comparative numerical analysis of fractal characterization techniques with specific consideration given to experimentally measured gait stride interval time series. The ideal fractal signals generated in the numerical analysis are constrained under varying lengths and biases indicative of a range of physiologically conceivable fractal signals. This analysis is to complement previous investigations of fractal characteristics in healthy and pathological gait stride interval time series, with which this study is compared. Results The results of our analysis showed that the averaged wavelet coefficient method consistently yielded the most accurate results. Comparison with Existing Methods: Class dependent methods proved to be unsuitable for physiological time series. Detrended fluctuation analysis as most prevailing method in the literature exhibited large estimation variances. Conclusions The comparative numerical analysis and experimental applications provide a thorough basis for determining an appropriate and robust method for measuring and comparing a physiologically meaningful biomarker, the spectral index β. In consideration of the constraints of application, we note the significant drawbacks of detrended fluctuation analysis and conclude that the averaged wavelet coefficient method can provide reasonable consistency and accuracy for characterizing these fractal time series. PMID:24200509

A comparative analysis of spectral exponent estimation techniques for 1/f(β) processes with applications to the analysis of stride interval time series.

PubMed

Schaefer, Alexander; Brach, Jennifer S; Perera, Subashan; Sejdić, Ervin

2014-01-30

The time evolution and complex interactions of many nonlinear systems, such as in the human body, result in fractal types of parameter outcomes that exhibit self similarity over long time scales by a power law in the frequency spectrum S(f)=1/f(β). The scaling exponent β is thus often interpreted as a "biomarker" of relative health and decline. This paper presents a thorough comparative numerical analysis of fractal characterization techniques with specific consideration given to experimentally measured gait stride interval time series. The ideal fractal signals generated in the numerical analysis are constrained under varying lengths and biases indicative of a range of physiologically conceivable fractal signals. This analysis is to complement previous investigations of fractal characteristics in healthy and pathological gait stride interval time series, with which this study is compared. The results of our analysis showed that the averaged wavelet coefficient method consistently yielded the most accurate results. Class dependent methods proved to be unsuitable for physiological time series. Detrended fluctuation analysis as most prevailing method in the literature exhibited large estimation variances. The comparative numerical analysis and experimental applications provide a thorough basis for determining an appropriate and robust method for measuring and comparing a physiologically meaningful biomarker, the spectral index β. In consideration of the constraints of application, we note the significant drawbacks of detrended fluctuation analysis and conclude that the averaged wavelet coefficient method can provide reasonable consistency and accuracy for characterizing these fractal time series. Copyright © 2013 Elsevier B.V. All rights reserved.

Time, Not Sleep, Unbinds Contexts from Item Memory

PubMed Central

Cox, Roy; Tijdens, Ron R.; Meeter, Martijn M.; Sweegers, Carly C. G.; Talamini, Lucia M.

2014-01-01

Contextual cues are known to benefit memory retrieval, but whether and how sleep affects this context effect remains unresolved. We manipulated contextual congruence during memory retrieval in human volunteers across 12 h and 24 h intervals beginning with either sleep or wakefulness. Our data suggest that whereas contextual cues lose their potency with time, sleep does not modulate this process. Furthermore, our results are consistent with the idea that sleep's beneficial effect on memory retention depends on the amount of waking time that has passed between encoding and sleep onset. The findings are discussed in the framework of competitive consolidation theory. PMID:24498441

A tale of two timescales: Mixing, mass generation, and phase transitions in the early universe

NASA Astrophysics Data System (ADS)

Dienes, Keith R.; Kost, Jeff; Thomas, Brooks

2016-02-01

Light scalar fields such as axions and string moduli can play an important role in early-universe cosmology. However, many factors can significantly impact their late-time cosmological abundances. For example, in cases where the potentials for these fields are generated dynamically—such as during cosmological mass-generating phase transitions—the duration of the time interval required for these potentials to fully develop can have significant repercussions. Likewise, in scenarios with multiple scalars, mixing amongst the fields can also give rise to an effective timescale that modifies the resulting late-time abundances. Previous studies have focused on the effects of either the first or the second timescale in isolation. In this paper, by contrast, we examine the new features that arise from the interplay between these two timescales when both mixing and time-dependent phase transitions are introduced together. First, we find that the effects of these timescales can conspire to alter not only the total late-time abundance of the system—often by many orders of magnitude—but also its distribution across the different fields. Second, we find that these effects can produce large parametric resonances which render the energy densities of the fields highly sensitive to the degree of mixing as well as the duration of the time interval over which the phase transition unfolds. Finally, we find that these effects can even give rise to a "reoverdamping" phenomenon which causes the total energy density of the system to behave in novel ways that differ from those exhibited by pure dark matter or vacuum energy. All of these features therefore give rise to new possibilities for early-universe phenomenology and cosmological evolution. They also highlight the importance of taking into account the time dependence associated with phase transitions in cosmological settings.

The Influence of Pituitary Size on Outcome After Transsphenoidal Hypophysectomy in a Large Cohort of Dogs with Pituitary-Dependent Hypercortisolism.

PubMed

van Rijn, S J; Galac, S; Tryfonidou, M A; Hesselink, J W; Penning, L C; Kooistra, H S; Meij, B P

2016-07-01

Transsphenoidal hypophysectomy is one of the treatment strategies in the comprehensive management of dogs with pituitary-dependent hypercortisolism (PDH). To describe the influence of pituitary size at time of pituitary gland surgery on long-term outcome. Three-hundred-and-six dogs with PDH. Survival and disease-free fractions were analyzed and related to pituitary size; dogs with and without recurrence were compared. Four weeks after surgery, 91% of dogs were alive and remission was confirmed in 92% of these dogs. The median survival time was 781 days, median disease-free interval was 951 days. Over time, 27% of dogs developed recurrence of hypercortisolism after a median period of 555 days. Dogs with recurrence had significantly higher pituitary height/brain area (P/B) ratio and pre-operative basal urinary corticoid-to-creatinine ratio (UCCR) than dogs without recurrence. Survival time and disease-free interval of dogs with enlarged pituitary glands was significantly shorter than that of dogs with a non-enlarged pituitary gland. Pituitary size at the time of surgery significantly increased over the 20-year period. Although larger tumors have a less favorable prognosis, outcome in larger tumors improved over time. Transsphenoidal hypophysectomy is an effective treatment for PDH in dogs, with an acceptable long-term outcome. Survival time and disease-free fractions are correlated negatively with pituitary gland size, making the P/B ratio an important pre-operative prognosticator. However, with increasing experience, and for large tumors, pituitary gland surgery remains an option to control the pituitary mass and hypercortisolism. Copyright © 2016 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

[Study on effect of aqueous extracts from aconite on "dose-time-toxicity" relationships in mice hearts].

PubMed

Feng, Qun; Li, Xiao-yu; Luan, Yong-fu; Sun, Sai-nan; Sun, Rong

2015-03-01

To study the effect of single administration of aqueous extracts from aconite on "dose-toxicity" relationship and "time-toxicity" relationship of mice hearts, through changes in electrocardiogram (ECG) and serum biochemical indexes. Mice were grouped according to different drug doses and time points, and orally administered with water extracts from aconite for once to observe the changes of mice ECG before and after the administration, calculate visceral indexes heart, liver and kidney, and detect levels of CK, LDH, BNP and CTn-I in serum. According to the "time-toxicity" relationship study, at 5 min after oral administration with aqueous extracts from aconite in mice, the heart rate of mice began rising, reached peak at 60 min and then slowly reduced; QRS, R amplitude, T duration and amplitude and QT interval declined at 5 min, reduced to the bottom at 60 min and then gradually elevated. The levels of CK, LDH, BNP and CTn-I in serum elevated at 5 min and reached the peak at 60 min, with no significant change in ratios of organs to body at different time points. On the basis of the "dose-toxicity" relationship, with the increase in single dose of aqueous extracts from aconite, the heart rate of mice. QRS, T duration and amplitude and QT interval declined gradually, and levels of CK, LDH, BNP and CTn-I in serum slowly elevated, with a certain dose dependence and no significant change in ratios of organs to body in mice. Single oral administration of different doses of aqueous extracts from aconite could cause different degrees of heart injury at different time points, with a certain dose dependence. Its peak time of toxicity is at 60 min after the administration of aqueous extracts from aconite.

Time-dependent impact of glutamatergic modulators on the promnesiant effect of 5-HT6R blockade on mice recognition memory.

PubMed

Asselot, Rachel; Simon-O'Brien, Emmanuelle; Lebourgeois, Sophie; Nee, Gérald; Delaunay, Virgile; Duchatelle, Pascal; Bouet, Valentine; Dauphin, François

2017-04-01

Selective antagonists at serotonin 5-HT 6 receptors (5-HT 6 R) improve memory performance in rodents and are currently under clinical investigations. If blockade of 5-HT 6 R is known to increase glutamate release, only two studies have so far demonstrated an interaction between 5-HT 6 R and glutamate transmission, but both, using the non-competitive NMDA antagonist MK-801, insensitive to variations of glutamate concentrations. In a place recognition task, we investigated here in mice the role of glutamate transmission in the beneficial effects of 5-HT 6 R blockade (SB-271046). Through the use of increasing intervals (2, 4 and 6h) between acquisition and retrieval, we investigated the time-dependent impact of two different glutamatergic modulators. NMDAR-dependant glutamate transmission (NMDA Receptors) was either blocked by the competitive antagonist at NMDAR, CGS 19755, or potentiated by the glycine transporter type 1 (GlyT1) inhibitor, NFPS. Results showed that neither SB-271046, nor CGS 19755, nor NFPS, alter behavioural performances after short intervals, i.e. when control mice displayed significant memory performances (2h and 4h) (respectively 10, 3, and 0.625mg.kg -1 ). Conversely, with the 6h-interval, a situation in which spontaneous forgetting is observed in control mice, SB-271046 improved recognition memory performances. This beneficial effect was prevented when co-administered with either CGS 19755 or NFPS, which themselves had no effect. Interestingly, a dose-dependent effect was observed with NFPS, with promnesic effect observed at lower dose (0.156mg.kg -1 ) when administrated alone, whereas it did no modify promnesic effect of SB-271046. These results demonstrate that promnesiant effect induced by 5-HT 6 R blockade is sensitive to the competitive blockade of NMDAR and underline the need of a fine adjustment of the inhibition of GlyT1. Overall, our findings support the idea of a complex crosstalk between serotonergic and glutamatergic systems in the promnesic properties of 5-HT 6 R antagonists. Copyright © 2016 Elsevier Ltd. All rights reserved.

Prediction of future asset prices

NASA Astrophysics Data System (ADS)

Seong, Ng Yew; Hin, Pooi Ah; Ching, Soo Huei

2014-12-01

This paper attempts to incorporate trading volumes as an additional predictor for predicting asset prices. Denoting r(t) as the vector consisting of the time-t values of the trading volume and price of a given asset, we model the time-(t+1) asset price to be dependent on the present and l-1 past values r(t), r(t-1), ....., r(t-1+1) via a conditional distribution which is derived from a (2l+1)-dimensional power-normal distribution. A prediction interval based on the 100(α/2)% and 100(1-α/2)% points of the conditional distribution is then obtained. By examining the average lengths of the prediction intervals found by using the composite indices of the Malaysia stock market for the period 2008 to 2013, we found that the value 2 appears to be a good choice for l. With the omission of the trading volume in the vector r(t), the corresponding prediction interval exhibits a slightly longer average length, showing that it might be desirable to keep trading volume as a predictor. From the above conditional distribution, the probability that the time-(t+1) asset price will be larger than the time-t asset price is next computed. When the probability differs from 0 (or 1) by less than 0.03, the observed time-(t+1) increase in price tends to be negative (or positive). Thus the above probability has a good potential of being used as a market indicator in technical analysis.

Surface microhardness of a resin composite exposed to a "first-generation" LED curing lamp, in vitro.

PubMed

Keogh, Pauraic; Ray, Noel J; Lynch, Christopher D; Burke, Francis M; Hannigan, Ailish

2004-12-01

This investigation determined the minimum exposure times consistent with optimised surface microhardness parameters for a commercial resin composite cured using a "first-generation" light-emitting diode activation lamp. Disk specimens were exposed and surface microhardness numbers measured at the top and bottom surfaces for elapsed times of 1 hour and 24 hours. Bottom/top microhardness number ratios were also calculated. Most microhardness data increased significantly over the elapsed time interval but microhardness ratios (bottom/top) were dependent on exposure time only. A minimum exposure of 40 secs is appropriate to optimise microhardness parameters for the combination of resin composite and lamp investigated.

QT interval correction for drug-induced changes in body temperature during integrated cardiovascular safety assessment in regulatory toxicology studies in dogs: A case study.

PubMed

El Amrani, Abdel-Ilah; El Amrani-Callens, Francine; Loriot, Stéphane; Singh, Pramila; Forster, Roy

2016-01-01

Cardiovascular safety assessment requires accurate evaluation of QT interval, which depends on the length of the cardiac cycle and also on core body temperature (BT). Increases in QT interval duration have been shown to be associated with decreases in BT in dogs. An example of altered QT interval duration associated with changes in body temperature observed during a 4-week regulatory toxicology study in dogs is presented. Four groups of Beagle dogs received the vehicle or test item once on Day 1, followed by a 4-week observation period. Electrocardiogram (ECG) parameters were continuously recorded on Days 1 and 26 by jacketed external telemetry (JET). Core body temperature (BT) was measured with a conventional rectal thermometer at appropriate time-points during the Day 1 recording period. Decreased BT was observed approximately 2h after treatment on Day 1, along with increased QT interval duration corrected according to the Van de Water formula (QTcV), but the effect was no longer observed after correction for changes in BT [QTcVcT=QTcV-14(37.5-BT)] according to the Van der Linde formula. No significant changes in QTcV were reported at the end of the observation period, on Day 26. The present study demonstrates that core body (rectal) temperature can easily be monitored at appropriate time-points during JET recording in regulatory toxicology studies in dogs, in order to correct QT interval duration values for treatment-related changes in BT. The successful application of the Van der Linde formula to correct QTc prolongation for changes in BT was demonstrated. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

CALCULATION OF NONLINEAR CONFIDENCE AND PREDICTION INTERVALS FOR GROUND-WATER FLOW MODELS.

USGS Publications Warehouse

Cooley, Richard L.; Vecchia, Aldo V.

1987-01-01

A method is derived to efficiently compute nonlinear confidence and prediction intervals on any function of parameters derived as output from a mathematical model of a physical system. The method is applied to the problem of obtaining confidence and prediction intervals for manually-calibrated ground-water flow models. To obtain confidence and prediction intervals resulting from uncertainties in parameters, the calibrated model and information on extreme ranges and ordering of the model parameters within one or more independent groups are required. If random errors in the dependent variable are present in addition to uncertainties in parameters, then calculation of prediction intervals also requires information on the extreme range of error expected. A simple Monte Carlo method is used to compute the quantiles necessary to establish probability levels for the confidence and prediction intervals. Application of the method to a hypothetical example showed that inclusion of random errors in the dependent variable in addition to uncertainties in parameters can considerably widen the prediction intervals.

A case of time-dependent anisotropy of low-field susceptibility (AMS)

NASA Astrophysics Data System (ADS)

Borradaile, Graham J.; Geneviciene, Ieva

2007-07-01

A suite of non-tectonized, Meso-Proterozoic siliceous crystal tuffs and volcanic breccia with a visible stratification has a modal bulk susceptibility ( k) ˜ 160 μSI [mean; S.D. = 141 μSI; 44 μSI]. Normally, such susceptibilities suffice to make reliable measurements of anisotropy of low field susceptibility (AMS) using AC induction-coil instruments. However, for this suite, time-dependent susceptibility - variations during measurement are large in comparison to susceptibility - differences along different axes through a specimen. Thus, in many specimens, AMS axes determined by routine induction coil measurement in a (Sapphire Instruments SI2B; 19,200 Hz, 60 A/m) measurement procedures are not reproducible. The apparent variation of specimen susceptibility during a single, four minute AMS measurement can > 2 μSI whereas in the same interval the noise-level of our instrument is < 0.2 μSI. Thus, the time-dependence of the specimen-susceptibility is an intrinsic phenomenon due to the characteristics (grain size, domain structure) of the magnetite which dominates susceptibility during measurement and handling. Two procedures improved the reproducibility and stability of AMS axial orientations in some specimens. First, for some specimens, one or two cycles of LTD or AF demagnetization (≤ 15 mT) stabilized AMS axes. (Previous workers have observed that LTD and AF demagnetization may change slightly the AMS of polydomainal magnetite). Of course, exposure to alternating fields is preferably avoided before any AMS study. Second, for some specimens AMS measurement were improved by shielding the induction coil instrument in a large magnetically shielded space (ambient field < 5 nT). Further improvements were achieved by permitting the specimens to relax in side a magnetic shield for 24 h before measurement. The occurrence of time-dependent bulk susceptibility, especially noticeable in its AMS axial orientations is certainly a rare phenomenon and the procedures we used to improve measurement are excessive and unnecessary safeguards in routine AMS work; in any case, they mostly failed to produce a desirable degree of reproducibility. However, a simple test to detect for the presence of such time-dependent AMS is to repeat measurements at intervals of several hours, between which the specimen is permitted to relax in different orientations with respect to the geomagnetic field, or in a shielded space.

Development of an adaptive harvest management program for Taiga bean geese

USGS Publications Warehouse

Johnson, Fred A.; Alhainen, Mikko; Fox, Anthony D.; Madsen, Jesper

2016-01-01

This report describes recent progress in specifying the elements of an adaptive harvest program for taiga bean goose. It describes harvest levels appropriate for first rebuilding the population of the Central Management Unit and then maintaining it near the goal specified in the AEWA International Single Species Action Plan (ISSAP). This report also provides estimates of the length of time it would take under ideal conditions (no density dependence and no harvest) to rebuild depleted populations in the Western and Eastern Management Units. We emphasize that our estimates are a first approximation because detailed demographic information is lacking for taiga bean geese. Using allometric relationships, we estimated parameters of a thetalogistic matrix population model. The mean intrinsic rate of growth was estimated as r = 0.150 (90% credible interval: 0.120 – 0.182). We estimated the mean form of density dependence as   2.361 (90% credible interval: 0.473 – 11.778), suggesting the strongest density dependence occurs when the population is near its carrying capacity. Based on expert opinion, carrying capacity (i.e., population size expected in the absence of hunting) for the Central Management Unit was estimated as K  87,900 (90% credible interval: 82,000 – 94,100). The ISSAP specifies a population goal for the Central Management Unit of 60,000 – 80,000 individuals in winter; thus, we specified a preliminary objective function as one which would minimize the difference between this goal and population size. Using the concept of stochastic dominance to explicitly account for uncertainty in demography, we determined that optimal harvest rates for 5, 10, 15, and 20-year time horizons were h = 0.00, 0.02, 0.05, and 0.06, respectively. These optima represent a tradeoff between the harvest rate and the time required to achieve and maintain a population size within desired bounds. We recognize, however, that regulation of absolute harvest rather than harvest rate is more practical, but our matrix model does not permit one to calculate an exact harvest associated with a specific harvest rate. Approximate harvests for current population size in the Central Management Unit are 0, 1,200, 2,300, and 3,500 for the 5, 10, 15, and 20-year time horizons, respectively. Populations of taiga bean geese in the Western and Eastern Units would require at least 10 and 13 years, respectively, to reach their minimum goals under the most optimistic of scenarios. The presence of harvest, density dependence, or environmental variation could extend these time frames considerably. Finally, we stress that development and implementation of internationally coordinated monitoring programs will be essential to further development and implementation of an adaptive harvest management program.

Reliability, resilience and vulnerability criteria for the evaluation of time-dependent health risks: A hypothetical case study of wellhead protection

NASA Astrophysics Data System (ADS)

Rodak, C. M.; Silliman, S. E.; Bolster, D.

2012-12-01

A hypothetical case study of groundwater contaminant protection was carried out using time-dependent health risk calculations. The case study focuses on a hypothetical zoning project for parcels of land around a well field in northern Indiana, where the control of cancer risk relative to a mandated cancer risk threshold is of concern in the management strategy. Within our analysis, we include both uncertainty in the subsurface transport and variability in population behavior in the calculation of time-dependent health risks. From these results we introduce risk maps, a visual representation of the probability of an unacceptable health risk as a function of population behavior and the time at which exposure to the contaminant begins. We also evaluate the time-dependent risks with three criteria from water resource literature: reliability, resilience, and vulnerability (RRV). With respect to health risk from a groundwater well, the three criteria determine: the probability that a well produces safe water (reliability), the probability that a contaminated well returns to an uncontaminated state within a specified time interval (resilience), and the overall severity in terms of health impact of the contamination at a well head (vulnerability). The results demonstrate that the distributions of RRV values for each parcel of land are linked to the time-dependent concentration profile of the contaminant at the well, and the toxicological characteristics of the contaminant. The proposed time-dependent risk calculation expands on current techniques to include a continuous exposure start time, capable of reproducing the maximum risk while providing information on the severity and duration of health risks. Overall this study suggests that, especially in light of the inherent complexity of health-groundwater systems, RRV are viable criteria for relatively simple and effective evaluation of time-dependent health risk. It is argued that the RRV approach, as applied to consideration of potential health impact, allows for more informed, health-based decisions regarding zoning for wellhead protection.

Formation of Load Parameters of Destroyed Massife in Explosion of Multicharge Composition with Separation of its Parts by Profile Inert Interval

NASA Astrophysics Data System (ADS)

Paramonov, G. P.; Mysin, A. V.; Babkin, R. S.

2017-10-01

The paper introduces construction of multicharge composition with separation of parts by the profile inert interval. On the basis of the previous researches, the pulse-forming process at explosion of the borehole multicharge taking into account the offered design is considered. The physical model for definition of reflected wavelet taking into account an increment of radius of cross section of a charging cavity and the expiration of detonation products is offered. A technique is developed for numerical modeling of gas-dynamic processes in a borehole with a change in the axial channel of a profile inert interval caused by a high-temperature flow of gaseous products of an explosion. The authors obtained the dependence of the change in mean pressure on the borehole wall on time for each of the parts of the multicharge. To blast a series of charges of the proposed design, taking into account optimization of the stress fields of neighboring charges, the delay interval is determined for a short-delayed explosion.

Stability analysis for discrete-time stochastic memristive neural networks with both leakage and probabilistic delays.

PubMed

Liu, Hongjian; Wang, Zidong; Shen, Bo; Huang, Tingwen; Alsaadi, Fuad E

2018-06-01

This paper is concerned with the globally exponential stability problem for a class of discrete-time stochastic memristive neural networks (DSMNNs) with both leakage delays as well as probabilistic time-varying delays. For the probabilistic delays, a sequence of Bernoulli distributed random variables is utilized to determine within which intervals the time-varying delays fall at certain time instant. The sector-bounded activation function is considered in the addressed DSMNN. By taking into account the state-dependent characteristics of the network parameters and choosing an appropriate Lyapunov-Krasovskii functional, some sufficient conditions are established under which the underlying DSMNN is globally exponentially stable in the mean square. The derived conditions are made dependent on both the leakage and the probabilistic delays, and are therefore less conservative than the traditional delay-independent criteria. A simulation example is given to show the effectiveness of the proposed stability criterion. Copyright © 2018 Elsevier Ltd. All rights reserved.

Interval Timing Is Preserved Despite Circadian Desynchrony in Rats: Constant Light and Heavy Water Studies.

PubMed

Petersen, Christian C; Mistlberger, Ralph E

2017-08-01

The mechanisms that enable mammals to time events that recur at 24-h intervals (circadian timing) and at arbitrary intervals in the seconds-to-minutes range (interval timing) are thought to be distinct at the computational and neurobiological levels. Recent evidence that disruption of circadian rhythmicity by constant light (LL) abolishes interval timing in mice challenges this assumption and suggests a critical role for circadian clocks in short interval timing. We sought to confirm and extend this finding by examining interval timing in rats in which circadian rhythmicity was disrupted by long-term exposure to LL or by chronic intake of 25% D 2 O. Adult, male Sprague-Dawley rats were housed in a light-dark (LD) cycle or in LL until free-running circadian rhythmicity was markedly disrupted or abolished. The rats were then trained and tested on 15- and 30-sec peak-interval procedures, with water restriction used to motivate task performance. Interval timing was found to be unimpaired in LL rats, but a weak circadian activity rhythm was apparently rescued by the training procedure, possibly due to binge feeding that occurred during the 15-min water access period that followed training each day. A second group of rats in LL were therefore restricted to 6 daily meals scheduled at 4-h intervals. Despite a complete absence of circadian rhythmicity in this group, interval timing was again unaffected. To eliminate all possible temporal cues, we tested a third group of rats in LL by using a pseudo-randomized schedule. Again, interval timing remained accurate. Finally, rats tested in LD received 25% D 2 O in place of drinking water. This markedly lengthened the circadian period and caused a failure of LD entrainment but did not disrupt interval timing. These results indicate that interval timing in rats is resistant to disruption by manipulations of circadian timekeeping previously shown to impair interval timing in mice.

Exact Scheffé-type confidence intervals for output from groundwater flow models: 2. Combined use of hydrogeologic information and calibration data

USGS Publications Warehouse

Cooley, Richard L.

1993-01-01

Calibration data (observed values corresponding to model-computed values of dependent variables) are incorporated into a general method of computing exact Scheffé-type confidence intervals analogous to the confidence intervals developed in part 1 (Cooley, this issue) for a function of parameters derived from a groundwater flow model. Parameter uncertainty is specified by a distribution of parameters conditioned on the calibration data. This distribution was obtained as a posterior distribution by applying Bayes' theorem to the hydrogeologically derived prior distribution of parameters from part 1 and a distribution of differences between the calibration data and corresponding model-computed dependent variables. Tests show that the new confidence intervals can be much smaller than the intervals of part 1 because the prior parameter variance-covariance structure is altered so that combinations of parameters that give poor model fit to the data are unlikely. The confidence intervals of part 1 and the new confidence intervals can be effectively employed in a sequential method of model construction whereby new information is used to reduce confidence interval widths at each stage.

Evolution of motion uncertainty in rectal cancer: implications for adaptive radiotherapy

NASA Astrophysics Data System (ADS)

Kleijnen, Jean-Paul J. E.; van Asselen, Bram; Burbach, Johannes P. M.; Intven, Martijn; Philippens, Marielle E. P.; Reerink, Onne; Lagendijk, Jan J. W.; Raaymakers, Bas W.

2016-01-01

Reduction of motion uncertainty by applying adaptive radiotherapy strategies depends largely on the temporal behavior of this motion. To fully optimize adaptive strategies, insight into target motion is needed. The purpose of this study was to analyze stability and evolution in time of motion uncertainty of both the gross tumor volume (GTV) and clinical target volume (CTV) for patients with rectal cancer. We scanned 16 patients daily during one week, on a 1.5 T MRI scanner in treatment position, prior to each radiotherapy fraction. Single slice sagittal cine MRIs were made at the beginning, middle, and end of each scan session, for one minute at 2 Hz temporal resolution. GTV and CTV motion were determined by registering a delineated reference frame to time-points later in time. The 95th percentile of observed motion (dist95%) was taken as a measure of motion. The stability of motion in time was evaluated within each cine-MRI separately. The evolution of motion was investigated between the reference frame and the cine-MRIs of a single scan session and between the reference frame and the cine-MRIs of several days later in the course of treatment. This observed motion was then converted into a PTV-margin estimate. Within a one minute cine-MRI scan, motion was found to be stable and small. Independent of the time-point within the scan session, the average dist95% remains below 3.6 mm and 2.3 mm for CTV and GTV, respectively 90% of the time. We found similar motion over time intervals from 18 min to 4 days. When reducing the time interval from 18 min to 1 min, a large reduction in motion uncertainty is observed. A reduction in motion uncertainty, and thus the PTV-margin estimate, of 71% and 75% for CTV and tumor was observed, respectively. Time intervals of 15 and 30 s yield no further reduction in motion uncertainty compared to a 1 min time interval.

An institutional study of time delays for symptomatic carotid endarterectomy.

PubMed

Charbonneau, Philippe; Bonaventure, Paule Lessard; Drudi, Laura M; Beaudoin, Nathalie; Blair, Jean-François; Elkouri, Stéphane

2016-12-01

The aim of this study was to assess time delays between first cerebrovascular symptoms and carotid endarterectomy (CEA) at a single center and to systematically evaluate causes of these delays. Consecutive adult patients who underwent CEAs between January 2010 and September 2011 at a single university-affiliated center (Centre Hospitalier de l'Université Montréal-Hôtel-Dieu Hospital, Montreal) were identified from a clinical database and operative records. Covariates of interest were extracted from electronic medical records. Timing and nature of the first cerebrovascular symptoms were also documented. The first medical contact and pathway of referral were also assessed. When possible, the ABCD 2 score (age, blood pressure, clinical features, duration of symptoms, and diabetes) was calculated to calculate further risk of stroke. The nonparametric Wilcoxon test was used to assess differences in time intervals between two variables. The Kruskal-Wallis test was used to assess differences in time intervals in comparing more than two variables. A multivariate linear regression analysis was performed using covariates that were determined to be statistically significant in our sensitivity analyses. The cohort consisted of 111 patients with documented symptomatic carotid stenosis undergoing surgical intervention. Thirty-nine percent of all patients were operated on within 2 weeks from the first cerebrovascular symptoms. The median time between the occurrence of the first neurologic symptom and the CEA procedure was 25 (interquartile range [IQR], 11-85) days. The patient-dependent delay, defined as the median delay between the first neurologic symptom and the first medical contact, was 1 (IQR, 0-14) day. The medical-dependent delay was defined as the time interval between the first medical contact and CEA. This included the delay between the first medical contact and the request for surgery consultation (median, 3 [IQR, 1-10] days). The multivariate regression model demonstrated that the emergency physician as referral source (P = .0002) was statistically significant for reducing CEA delay. Patients who were investigated as an outpatient (P = .02), first medical contact with a general practitioner (P = .0002), and hospital center I as referral center (P = .045) were also found to be statistically significant to extend CEA delay when the model was adjusted over all covariates. In this center, there was no correlation between ABCD 2 risk score and waiting time for surgery. The majority of our cohort falls short of the recommended 2-week interval to perform CEA. Factors contributing to reduced CEA delay were presentation to an emergency department, in-patient investigations, and a stroke center where a vascular surgeon is available. Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Catalytic Reduction of 4-Nitrophenol: A Quantitative Assessment of the Role of Dissolved Oxygen in Determining the Induction Time.

PubMed

Menumerov, Eredzhep; Hughes, Robert A; Neretina, Svetlana

2016-12-14

The reduction of 4-nitrophenol to 4-aminophenol by borohydride is one of the foremost model catalytic reactions because it allows for a straightforward assessment of catalysts using the kinetic parameters extracted from the real-time spectroscopic monitoring of an aqueous solution. Crucial to its standing as a model reaction is a comprehensive mechanistic framework able to explain the entire time evolution of the reaction. While much of this framework is in place, there is still much debate over the cause of the induction period, an initial time interval where no reaction seemingly occurs. Here, we report on the simultaneous monitoring of the spectroscopic signal and the dissolved oxygen content within the aqueous solution. It reveals that the induction period is the time interval required for the level of dissolved oxygen to fall below a critical value that is dependent upon whether Au, Ag, or Pd nanoparticles are used as the catalyst. With this understanding, we are able to exert complete control over the induction period, being able to eliminate it, extend it indefinitely, or even induce multiple induction periods over the course of a single reaction. Moreover, we have determined that the reaction product, 4-aminophenol, in the presence of the same catalyst reacts with dissolved oxygen to form 4-nitrophenolate. The implication of these results is that the induction period relates, not to some activation of the catalyst, but to a time interval where the reaction product is being rapidly transformed back into a reactant by a side reaction.

Response to a periodic stimulus in a perfect integrate-and-fire neuron model driven by colored noise.

PubMed

Mankin, Romi; Rekker, Astrid

2016-12-01

The output interspike interval statistics of a stochastic perfect integrate-and-fire neuron model driven by an additive exogenous periodic stimulus is considered. The effect of temporally correlated random activity of synaptic inputs is modeled by an additive symmetric dichotomous noise. Using a first-passage-time formulation, exact expressions for the output interspike interval density and for the serial correlation coefficient are derived in the nonsteady regime, and their dependence on input parameters (e.g., the noise correlation time and amplitude as well as the frequency of an input current) is analyzed. It is shown that an interplay of a periodic forcing and colored noise can cause a variety of nonequilibrium cooperation effects, such as sign reversals of the interspike interval correlations versus noise-switching rate as well as versus the frequency of periodic forcing, a power-law-like decay of oscillations of the serial correlation coefficients in the long-lag limit, amplification of the output signal modulation in the instantaneous firing rate of the neural response, etc. The features of spike statistics in the limits of slow and fast noises are also discussed.

Response to a periodic stimulus in a perfect integrate-and-fire neuron model driven by colored noise

NASA Astrophysics Data System (ADS)

Mankin, Romi; Rekker, Astrid

2016-12-01

The output interspike interval statistics of a stochastic perfect integrate-and-fire neuron model driven by an additive exogenous periodic stimulus is considered. The effect of temporally correlated random activity of synaptic inputs is modeled by an additive symmetric dichotomous noise. Using a first-passage-time formulation, exact expressions for the output interspike interval density and for the serial correlation coefficient are derived in the nonsteady regime, and their dependence on input parameters (e.g., the noise correlation time and amplitude as well as the frequency of an input current) is analyzed. It is shown that an interplay of a periodic forcing and colored noise can cause a variety of nonequilibrium cooperation effects, such as sign reversals of the interspike interval correlations versus noise-switching rate as well as versus the frequency of periodic forcing, a power-law-like decay of oscillations of the serial correlation coefficients in the long-lag limit, amplification of the output signal modulation in the instantaneous firing rate of the neural response, etc. The features of spike statistics in the limits of slow and fast noises are also discussed.

Changes in intensity of precipitation extremes in Romania on very hight temporal scale and implications on the validity of the Clausius-Clapeyron relation

NASA Astrophysics Data System (ADS)

Busuioc, Aristita; Baciu, Madalina; Breza, Traian; Dumitrescu, Alexandru; Stoica, Cerasela; Baghina, Nina

2016-04-01

Many observational, theoretical and based on climate model simulation studies suggested that warmer climates lead to more intense precipitation events, even when the total annual precipitation is slightly reduced. In this way, it was suggested that extreme precipitation events may increase at Clausius-Clapeyron (CC) rate under global warming and constraint of constant relative humidity. However, recent studies show that the relationship between extreme rainfall intensity and atmospheric temperature is much more complex than would be suggested by the CC relationship and is mainly dependent on precipitation temporal resolution, region, storm type and whether the analysis is conducted on storm events rather than fixed data. The present study presents the dependence between the very hight temporal scale extreme rainfall intensity and daily temperatures, with respect to the verification of the CC relation. To solve this objective, the analysis is conducted on rainfall event rather than fixed interval using the rainfall data based on graphic records including intensities (mm/min.) calculated over each interval with permanent intensity per minute. The annual interval with available a such data (April to October) is considered at 5 stations over the interval 1950-2007. For Bucuresti-Filaret station the analysis is extended over the longer interval (1898-2007). For each rainfall event, the maximum intensity (mm/min.) is retained and these time series are considered for the further analysis (abbreviated in the following as IMAX). The IMAX data were divided based on the daily mean temperature into bins 2oC - wide. The bins with less than 100 values were excluded. The 90th, 99th and 99.9th percentiles were computed from the binned data using the empirical distribution and their variability has been compared to the CC scaling (e.g. exponential relation given by a 7% increase per temperature degree rise). The results show a dependence close to double the CC relation for temperatures less than ~ 220C and negative scaling rates for higher temperatures. This behaviour is similar for all the 5 analysed stations over the common interval 1950-2007. This scaling is more exactly for the 90th percentile, while for the higher percentiles the rainfall intensity in response to warming exceeds sometimes the CC rate. For Bucuresti-Filaret station, the results are similar over a longer interval (1898-2007) showing that these findings are robust. Similar techniques has been previously applied to the hourly rainfall intensities recorded at 9 stations (including the 5 ones) and the results are slightly different: the 90th percentile shows dependence close to the CC relation for all temperatures; the 99th and 99.9th percentiles exhibit rates close to double the CC rate for temperatures between ~ 100C and ~ 220C and negative scaling rates for higher temperatures. In conclusion, these results show that the dependence between the extreme precipitation intensity and atmospheric temperature in Romania is mainly dependent on the temporal precipitation resolution and the degree of the extreme precipitation event (moderate or stronger); these findings are mainly in agreenment with the conclusions presented by previous international studies (mentioned above), with some regional specific features, showing the importance of the regional studies. The results presented is this study were funded by the Executive Agency for Higher Education, Research, Development and Innovation Funding (UEFISCDI) through the research project CLIMHYDEX, "Changes in climate extremes and associated impact in hydrological events in Romania", code PNII-ID-2011-2-0073 (http://climhydex.meteoromania.ro).

Application of point kinetics equations to the design of a reactivity meter

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

Binney, S.E.; Bakir, A.J.M.

1988-01-01

The time-dependent reactivity of a nuclear reactor is obviously one of the most important reactor parameters that describes the state of the reactor. Although several different types of techniques exist to measure reactivity, only the kinetic method is described here. The paper illustrates the measured reactor power and calculated reactivity for a 70 cents step change in reactivity. These data were taken at 1-s time intervals. It is seen that the reactivity, initially at zero, rises rapidly to a predetermined value (determined by the reactivity change induced in the system) and then returns to zero as the reactor is reestablishedmore » in a critical situation by insertion of another control rod. It is concluded that the method of Tuttle has been adapted to produce a reliable, on-line calculation of reactivity from a time-dependent reactor power signal.« less

Forecasting Epidemics Through Nonparametric Estimation of Time-Dependent Transmission Rates Using the SEIR Model.

PubMed

Smirnova, Alexandra; deCamp, Linda; Chowell, Gerardo

2017-05-02

Deterministic and stochastic methods relying on early case incidence data for forecasting epidemic outbreaks have received increasing attention during the last few years. In mathematical terms, epidemic forecasting is an ill-posed problem due to instability of parameter identification and limited available data. While previous studies have largely estimated the time-dependent transmission rate by assuming specific functional forms (e.g., exponential decay) that depend on a few parameters, here we introduce a novel approach for the reconstruction of nonparametric time-dependent transmission rates by projecting onto a finite subspace spanned by Legendre polynomials. This approach enables us to effectively forecast future incidence cases, the clear advantage over recovering the transmission rate at finitely many grid points within the interval where the data are currently available. In our approach, we compare three regularization algorithms: variational (Tikhonov's) regularization, truncated singular value decomposition (TSVD), and modified TSVD in order to determine the stabilizing strategy that is most effective in terms of reliability of forecasting from limited data. We illustrate our methodology using simulated data as well as case incidence data for various epidemics including the 1918 influenza pandemic in San Francisco and the 2014-2015 Ebola epidemic in West Africa.

A general strategy for performing temperature-programming in high performance liquid chromatography--further improvements in the accuracy of retention time predictions of segmented temperature gradients.

PubMed

Wiese, Steffen; Teutenberg, Thorsten; Schmidt, Torsten C

2012-01-27

In the present work it is shown that the linear elution strength (LES) model which was adapted from temperature-programming gas chromatography (GC) can also be employed for systematic method development in high-temperature liquid chromatography (HT-HPLC). The ability to predict isothermal retention times based on temperature-gradient as well as isothermal input data was investigated. For a small temperature interval of ΔT=40°C, both approaches result in very similar predictions. Average relative errors of predicted retention times of 2.7% and 1.9% were observed for simulations based on isothermal and temperature-gradient measurements, respectively. Concurrently, it was investigated whether the accuracy of retention time predictions of segmented temperature gradients can be further improved by temperature dependent calculation of the parameter S(T) of the LES relationship. It was found that the accuracy of retention time predictions of multi-step temperature gradients can be improved to around 1.5%, if S(T) was also calculated temperature dependent. The adjusted experimental design making use of four temperature-gradient measurements was applied for systematic method development of selected food additives by high-temperature liquid chromatography. Method development was performed within a temperature interval from 40°C to 180°C using water as mobile phase. Two separation methods were established where selected food additives were baseline separated. In addition, a good agreement between simulation and experiment was observed, because an average relative error of predicted retention times of complex segmented temperature gradients less than 5% was observed. Finally, a schedule of recommendations to assist the practitioner during systematic method development in high-temperature liquid chromatography was established. Copyright © 2011 Elsevier B.V. All rights reserved.

Determination of Time Dependent Virus Inactivation Rates

NASA Astrophysics Data System (ADS)

Chrysikopoulos, C. V.; Vogler, E. T.

2003-12-01

A methodology is developed for estimating temporally variable virus inactivation rate coefficients from experimental virus inactivation data. The methodology consists of a technique for slope estimation of normalized virus inactivation data in conjunction with a resampling parameter estimation procedure. The slope estimation technique is based on a relatively flexible geostatistical method known as universal kriging. Drift coefficients are obtained by nonlinear fitting of bootstrap samples and the corresponding confidence intervals are obtained by bootstrap percentiles. The proposed methodology yields more accurate time dependent virus inactivation rate coefficients than those estimated by fitting virus inactivation data to a first-order inactivation model. The methodology is successfully applied to a set of poliovirus batch inactivation data. Furthermore, the importance of accurate inactivation rate coefficient determination on virus transport in water saturated porous media is demonstrated with model simulations.

A computational model for telomere-dependent cell-replicative aging.

PubMed

Portugal, R D; Land, M G P; Svaiter, B F

2008-01-01

Telomere shortening provides a molecular basis for the Hayflick limit. Recent data suggest that telomere shortening also influence mitotic rate. We propose a stochastic growth model of this phenomena, assuming that cell division in each time interval is a random process which probability decreases linearly with telomere shortening. Computer simulations of the proposed stochastic telomere-regulated model provides good approximation of the qualitative growth of cultured human mesenchymal stem cells.

Effect of Light/Dark Cycle on Wheel Running and Responding Reinforced by the Opportunity to Run Depends on Postsession Feeding Time

ERIC Educational Resources Information Center

Belke, T. W.; Mondona, A. R.; Conrad, K. M.; Poirier, K. F.; Pickering, K. L.

2008-01-01

Do rats run and respond at a higher rate to run during the dark phase when they are typically more active? To answer this question, Long Evans rats were exposed to a response-initiated variable interval 30-s schedule of wheel-running reinforcement during light and dark cycles. Wheel-running and local lever-pressing rates increased modestly during…

Acute haemodynamic effects of felodipine and verapamil in man, singly and with metoprolol.

PubMed

Rönn, O; Bengtsson, B; Edgar, B; Raner, S

1985-01-01

In a single-blind randomised study in 9 healthy men we compared the acute haemodynamic effects of the calcium antagonists felodipine and verapamil, singly and in combination with metoprolol. Three different cumulative intravenous doses of 0.25, 0.75 and 1.5 mg felodipine and of 2.0, 4.0 and 8.0 mg verapamil or placebo were given as constant infusions over 5 minutes on 3 occasions and were followed by intravenous metoprolol (15 mg). Felodipine caused a significant and dose-dependent decrease in the total peripheral resistance, and an increase in the forearm blood flow by 8, 48 and 163% with progressively increasing doses showing that the drug is a potent arteriolar vasodilator. A significant and dose-dependent increase in heart rate and a decrease in the pre-ejection period/left ventricular ejection time (PEP/LVET) ratio of up to 15% was also recorded, mainly reflecting a reflexogenic increase in the sympathetic tone. Total peripheral resistance, forearm blood flow, heart rate and the systolic time intervals were mainly unchanged after verapamil, whereas the PQ interval was prolonged. Metoprolol given after the 2 calcium antagonists caused a decrease in heart rate and blood flow and an increase in the total peripheral resistance and PEP/LVET ratio. The tolerability was good to all infusions.

Imaging galectin-3 dependent endocytosis with lattice light-sheet microscopy

NASA Astrophysics Data System (ADS)

Baek, Jongho; Lou, Jieqiong; Coelho, Simao; Lim, Yean Jin; Seidlitz, Silvia; Nicovich, Philip R.; Wunder, Christian; Johannes, Ludger; Gaus, Katharina

2017-04-01

Lattice light-sheet (LLS) microscopy provides ultrathin light sheets of a two-dimensional optical lattice that allows us imaging three-dimensional (3D) objects for hundreds of time points at sub-second intervals and at or below the diffraction limit. Galectin-3 (Gal3), a carbohydrate-binding protein, triggers glycosphingolipid (GSL)-dependent biogenesis of morphologically distinct endocytic vesicles that are cargo specific and clathrin independent. In this study, we apply LLS microscopy to study the dynamics of Gal3 dependent endocytosis in live T cells. This will allow us to observe Gal3-mediated endocytosis at high temporal and excellent 3D spatial resolution, which may shed light on our understanding of the mechanism and physiological function of Gal3-induced endocytosis.

Vibrational relaxation of a molecule in strong interaction with a reservoir: Nonmonotonic temperature dependence

NASA Astrophysics Data System (ADS)

Kenkre, V. M.; Ierides, A. A.

2018-06-01

This theoretical study of the vibrational relaxation of a molecule in interaction with a reservoir uncovers a noteworthy temperature (T) dependence of the time evolution of the relaxation. Its rate increases with T in one interval but decreases in another. The feature arises not for a weak molecule-reservoir interaction but only for coupling strong enough to require polaronic dressing transformations. Our treatment, based on a recent generalization of the well-known Montroll-Shuler equation for relaxation and an explicit calculation of bath correlations from the microscopically specified Hamiltonian, could provide an alternative explanation of an "inverted" T-dependence of relaxation in an experimental report by Fayer and collaborators on W(CO)6 dissolved in CHCl3.

Empirical Model of the Location of the Main Ionospheric Trough

NASA Astrophysics Data System (ADS)

Deminov, M. G.; Shubin, V. N.

2018-05-01

The empirical model of the location of the main ionospheric trough (MIT) is developed based on an analysis of data from CHAMP satellite measured at the altitudes of 350-450 km during 2000-2007; the model is presented in the form of the analytical dependence of the invariant latitude of the trough minimum Φm on the magnetic local time (MLT), the geomagnetic activity, and the geographical longitude for the Northern and Southern Hemispheres. The time-weighted average index Kp(τ), the coefficient of which τ = 0.6 is determined by the requirement of the model minimum deviation from experimental data, is used as an indicator of geomagnetic activity. The model has no limitations, either in local time or geomagnetic activity. However, the initial set of MIT minima mainly contains data dealing with an interval of 16-08 MLT for Kp(τ) < 6; therefore, the model is rather qualitative outside this interval. It is also established that (a) the use of solar local time (SLT) instead of MLT increases the model error no more than by 5-10%; (b) the amplitude of the longitudinal effect at the latitude of MIT minimum in geomagnetic (invariant) coordinates is ten times lower than that in geographical coordinates.

Opioid Analgesics and Adverse Outcomes among Hemodialysis Patients.

PubMed

Ishida, Julie H; McCulloch, Charles E; Steinman, Michael A; Grimes, Barbara A; Johansen, Kirsten L

2018-05-07

Patients on hemodialysis frequently experience pain and may be particularly vulnerable to opioid-related complications. However, data evaluating the risks of opioid use in patients on hemodialysis are limited. Using the US Renal Data System, we conducted a cohort study evaluating the association between opioid use (modeled as a time-varying exposure and expressed in standardized oral morphine equivalents) and time to first emergency room visit or hospitalization for altered mental status, fall, and fracture among 140,899 Medicare-covered adults receiving hemodialysis in 2011. We evaluated risk according to average daily total opioid dose (>60 mg, ≤60 mg, and per 60-mg dose increment) and specific agents (per 60-mg dose increment). The median age was 61 years old, 52% were men, and 50% were white. Sixty-four percent received opioids, and 17% had an episode of altered mental status (15,658 events), fall (7646 events), or fracture (4151 events) in 2011. Opioid use was associated with risk for all outcomes in a dose-dependent manner: altered mental status (lower dose: hazard ratio, 1.28; 95% confidence interval, 1.23 to 1.34; higher dose: hazard ratio, 1.67; 95% confidence interval, 1.56 to 1.78; hazard ratio, 1.29 per 60 mg; 95% confidence interval, 1.26 to 1.33), fall (lower dose: hazard ratio, 1.28; 95% confidence interval, 1.21 to 1.36; higher dose: hazard ratio, 1.45; 95% confidence interval, 1.31 to 1.61; hazard ratio, 1.04 per 60 mg; 95% confidence interval, 1.03 to 1.05), and fracture (lower dose: hazard ratio, 1.44; 95% confidence interval, 1.33 to 1.56; higher dose: hazard ratio, 1.65; 95% confidence interval, 1.44 to 1.89; hazard ratio, 1.04 per 60 mg; 95% confidence interval, 1.04 to 1.05). All agents were associated with a significantly higher hazard of altered mental status, and several agents were associated with a significantly higher hazard of fall and fracture. Opioids were associated with adverse outcomes in patients on hemodialysis, and this risk was present even at lower dosing and for agents that guidelines have recommended for use. Copyright © 2018 by the American Society of Nephrology.

Interaction of inhibitory and facilitatory effects of conditioning trials on long-term memory formation

PubMed Central

Hosono, Shouhei; Matsumoto, Yukihisa

2016-01-01

Animals learn through experience and consolidate the memories into long-time storage. Conditioning parameters to induce protein synthesis-dependent long-term memory (LTM) have been the subject of extensive studies in many animals. Here we found a case in which a conditioning trial inhibits or facilitates LTM formation depending on the intervals from preceding trials. We studied the effects of conditioning parameters on LTM formation in olfactory conditioning of maxillary-palpi extension response with sucrose reward in the cockroach Periplaneta americana. We found, at first, that translation- and transcription-dependent LTM forms 1 h after training, the fastest so far reported in insects. Second, we observed that multiple-trial training with an intertrial interval (ITI) of 20 or 30 sec, often called massed training, is more effective than spaced training for LTM formation, an observation that differs from the results of most studies in other animals. Third, we found that a conditioning trial inhibits LTM formation when the intervals from preceding trials were in the range of 10–16 min. This inhibitory effect is pairing-specific and is not due to decreased motivation for learning (overtraining effect). To our knowledge, no similar inhibition of LTM formation by a conditioning trial has been reported in any animals. We propose a model to account for the effects of trial number and ITIs on LTM formation. Olfactory conditioning in cockroaches should provide pertinent materials in which to study neuronal and molecular mechanisms underlying the inhibitory and facilitatory processes for LTM formation. PMID:27918270

Volumetric Security Alarm Based on a Spherical Ultrasonic Transducer Array

NASA Astrophysics Data System (ADS)

Sayin, Umut; Scaini, Davide; Arteaga, Daniel

Most of the existent alarm systems depend on physical or visual contact. The detection area is often limited depending on the type of the transducer, creating blind spots. Our proposition is a truly volumetric alarm system that can detect any movement in the intrusion area, based on monitoring the change over time of the impulse response of the room, which acts as an acoustic footprint. The device depends on an omnidirectional ultrasonic transducer array emitting sweep signals to calculate the impulse response in short intervals. Any change in the room conditions is monitored through a correlation function. The sensitivity of the alarm to different objects and different environments depends on the sweep duration, sweep bandwidth, and sweep interval. Successful detection of intrusions also depends on the size of the monitoring area and requires an adjustment of emitted ultrasound power. Strong air flow affects the performance of the alarm. A method for separating moving objects from strong air flow is devised using an adaptive thresholding on the correlation function involving a series of impulse response measurements. The alarm system can be also used for fire detection since air flow sourced from heating objects differ from random nature of the present air flow. Several measurements are made to test the integrity of the alarm in rooms sizing from 834-2080m3 with irregular geometries and various objects. The proposed system can efficiently detect intrusion whilst adequate emitting power is provided.

Exhibition of veiled features in diffusion bonding of titanium alloy and stainless steel via copper

NASA Astrophysics Data System (ADS)

Thirunavukarasu, Gopinath; Kundu, Sukumar; Laha, Tapas; Roy, Deb; Chatterjee, Subrata

2017-11-01

An investigation was carried out to know the extent of influence of bonding-time on the interface structure and mechanical properties of diffusion bonding (DB) of TiA|Cu|SS. DB of Ti6Al4V (TiA) and 304 stainless steel (SS) using pure copper (Cu) of 200-μm thickness were processed in vacuum using 4-MPa bonding-pressure at 1123 K from 15 to 120 min in steps of 15 min. Preparation of DB was not possible when bonding-time was less than 60 min as the bonding at Cu|SS interface was unsuccessful in spite of effective bonding at TiA|Cu interface; however, successful DB were produced when the bonding-time was 60 min and beyond. DB processed for 60 and 75 min (classified as shorter bonding-time interval) showed distinctive characteristics (structural, mechanical, and fractural) as compared to the DB processed for 90, 105, and 120 min (classified as longer bonding-time interval). DB processed for 60 and 75 min exhibited layer-wise Cu-Ti-based intermetallics at TiA|Cu interface, whereas Cu|SS interface was completely free from reaction products. The layer-wise structure of Cu-Ti-based intermetallics were not observed at TiA|Cu interface in the DB processed for longer bonding-time; however, the Cu|SS interface had layer-wise ternary intermetallic compounds (T1, T2, and T3) of Cu-Fe-Ti-based along with σ phase depending upon the bonding-time chosen. Diffusivity of Ti-atoms in Cu-layer (DTi in Cu-layer) was much greater than the diffusivity of Fe-atoms in Cu-layer (DFe in Cu-layer). Ti-atoms reached Cu|SS interface but Fe-atoms were unable to reach TiA|Cu interface. It was observed that DB fractured at Cu|SS interface when processed for shorter bonding-time interval, whereas the DB processed for longer bonding-time interval fractured apparently at the middle of Cu-foil region predominantly due to the existence of brittle Cu-Fe-Ti-based intermetallics.

Association between congenital anomalies and paternal exposure to agricultural pesticides depending on mother's employment status.

PubMed

Ronda, Elena; Regidor, Enrique; García, Ana M; Domínguez, Vicente

2005-08-01

We analyzed the association between fetal death from congenital anomalies and paternal agricultural occupation in mothers who were employed and in housewives. The data consist of individual records from the Spanish Birth Register (1995-1999). The adjusted relative risk of fetal death in agricultural workers compared with nonagricultural was 1.24 (95% confidence interval = 0.38- 4.02) in mothers who were employed and 1.68 (95% confidence interval = 1.03-2.73) in housewives. The risk of fetal death in the offspring of agricultural workers exposed to pesticides around the time of conception was higher than in the offspring of nonagricultural workers in mothers who were housewives but not in mothers who worked outside the home.

Properties of behavior under different random ratio and random interval schedules: A parametric study.

PubMed

Dembo, M; De Penfold, J B; Ruiz, R; Casalta, H

1985-03-01

Four pigeons were trained to peck a key under different values of a temporally defined independent variable (T) and different probabilities of reinforcement (p). Parameter T is a fixed repeating time cycle and p the probability of reinforcement for the first response of each cycle T. Two dependent variables were used: mean response rate and mean postreinforcement pause. For all values of p a critical value for the independent variable T was found (T=1 sec) in which marked changes took place in response rate and postreinforcement pauses. Behavior typical of random ratio schedules was obtained at T 1 sec and behavior typical of random interval schedules at T 1 sec. Copyright © 1985. Published by Elsevier B.V.

Improving 24-Month Abstinence and Employment Outcomes for Substance-Dependent Women Receiving Temporary Assistance for Needy Families With Intensive Case Management

PubMed Central

Neighbors, Charles J.; Kuerbis, Alexis; Riordan, Annette; Blanchard, Kimberly A.; McVeigh, Katharine H.; Morgan, Thomas J.; McCrady, Barbara

2009-01-01

Objective. We examined abstinence rates among substance-dependent women receiving Temporary Assistance for Needy Families (TANF) in intensive case management (ICM) over 24 months and whether ICM yielded significantly better employment outcomes compared with a screen-and-refer program (i.e., usual care). Methods. Substance-dependent (n = 302) and non–substance dependent (n = 150) TANF applicants in Essex County, New Jersey, were recruited. We randomly assigned substance-dependent women to ICM or usual care. We interviewed all women at 3, 9, 15, and 24 months. Results. Abstinence rates were higher for the ICM group than for the usual care group through 24 months of follow-up (odds ratio [OR] = 2.11; 95% confidence interval [CI] = 1.36, 3.29). A statistically significant interaction between time and group on number of days employed indicated that the rate of improvement over time in employment was greater for the ICM group than for the usual care group (incidence rate ratio = 1.03; 95% CI = 1.02, 1.04). Additionally, there were greater odds of being employed full time for those in the ICM group (OR = 1.68; 95% CI = 1.12, 2.51). Conclusions. ICM is a promising intervention for managing substance dependence among women receiving TANF and for improving employment rates among this vulnerable population. PMID:19059855

The effects of time of disease occurrence, milk yield, and body condition on fertility of dairy cows.

PubMed

Loeffler, S H; de Vries, M J; Schukken, Y H

1999-12-01

The associations between occurrence of diseases, milk yield, and body condition score on conception risk after first artificial insemination (AI) were analyzed in an observational study on a convenience sample of 43 farms participating in a herd health program. Data were taken from 9369 lactations, from 4382 cows inseminated between 20 and 180 d in milk from 1990 to 1996. Two logistic regression models, one containing data from all lactations and a subset containing data from 1762 lactations with body condition scoring, were used to determine pregnancy risk at first AI. The effects of herd deviation in test-day milk yield, body condition score loss, and milk fat to protein ratio changes in early lactation were significant predictors of pregnancy risk, independent of disease; days in milk; farm; and seasonal factors. Three different methods of disease parameterization (incidence rates, binomial classes dependent on the interval in days since last occurrence with respect to AI, and a linear variable weighted for this interval) produced similar results. Metritis, cystic ovarian disease, lameness, and mastitis gave odds ratios for pregnancy risk ranging from 0.35 to 1.15, largely dependent on the interval in days from final disease occurrence to first AI. Displaced abomasum, milk fever, and retained fetal membranes resulted in odds ratios for pregnancy risk of 0.25, 0.85, and 0.55, respectively. These diseases showed little relationship between fertility and the number of days since last occurrence. Results of this study confirm the negative effects of milk yield, body score condition loss, and disease on dairy cow fertility. The effects of some diseases on first service conception were strongly dependent on the interval since last disease occurrence. This was especially valid for clinical mastitis, which has an extremely weak effect on conception if occurring prior to AI and is associated with > 50% reduction in pregnancy risk if occurring in the 3 wk directly after AI.

Comparative evaluation of nickel discharge from brackets in artificial saliva at different time intervals.

PubMed

Jithesh, C; Venkataramana, V; Penumatsa, Narendravarma; Reddy, S N; Poornima, K Y; Rajasigamani, K

2015-08-01

To determine and compare the potential difference of nickel release from three different orthodontic brackets, in different artificial pH, in different time intervals. Twenty-seven samples of three different orthodontic brackets were selected and grouped as 1, 2, and 3. Each group was divided into three subgroups depending on the type of orthodontic brackets, salivary pH and the time interval. The Nickel release from each subgroup were analyzed by using inductively coupled plasma-Atomic Emission Spectrophotometer (Perkin Elmer, Optima 2100 DV, USA) model. Quantitative analysis of nickel was performed three times, and the mean value was used as result. ANOVA (F-test) was used to test the significant difference among the groups at 0.05 level of significance (P < 0.05). The descriptive method of statistics was used to calculate the mean, standard deviation, minimum and maximum. SPSS 18 software ((SPSS.Ltd, Quarry bay, Hong Kong, PASW-statistics 18) was used to analyze the study. The analysis shows a significant difference between three groups. The study shows that the nickel releases from the recycled stainless steel brackets have the highest at all 4.2 pH except in 120 h. The study result shows that the nickel release from the recycled stainless steel brackets is highest. Metal slot ceramic bracket release significantly less nickel. So, recycled stainless steel brackets should not be used for nickel allergic patients. Metal slot ceramic brackets are advisable.

Comparative evaluation of nickel discharge from brackets in artificial saliva at different time intervals

PubMed Central

Jithesh, C.; Venkataramana, V.; Penumatsa, Narendravarma; Reddy, S. N.; Poornima, K. Y.; Rajasigamani, K.

2015-01-01

Objectives: To determine and compare the potential difference of nickel release from three different orthodontic brackets, in different artificial pH, in different time intervals. Materials and Methods: Twenty-seven samples of three different orthodontic brackets were selected and grouped as 1, 2, and 3. Each group was divided into three subgroups depending on the type of orthodontic brackets, salivary pH and the time interval. The Nickel release from each subgroup were analyzed by using inductively coupled plasma-Atomic Emission Spectrophotometer (Perkin Elmer, Optima 2100 DV, USA) model. Quantitative analysis of nickel was performed three times, and the mean value was used as result. ANOVA (F-test) was used to test the significant difference among the groups at 0.05 level of significance (P < 0.05). The descriptive method of statistics was used to calculate the mean, standard deviation, minimum and maximum. SPSS 18 software ((SPSS.Ltd, Quarry bay, Hong Kong, PASW-statistics 18) was used to analyze the study. Result: The analysis shows a significant difference between three groups. The study shows that the nickel releases from the recycled stainless steel brackets have the highest at all 4.2 pH except in 120 h. Conclusion: The study result shows that the nickel release from the recycled stainless steel brackets is highest. Metal slot ceramic bracket release significantly less nickel. So, recycled stainless steel brackets should not be used for nickel allergic patients. Metal slot ceramic brackets are advisable. PMID:26538924

Integrated stratigraphy and astronomical tuning of Smirra cores, lower Eocene, Umbria-Marche basin, Italy.

NASA Astrophysics Data System (ADS)

Lauretano, Vittoria; Turtù, Antonio; Hilgen, Frits; Galeotti, Simone; Catanzariti, Rita; Reichart, Gert Jan; Lourens, Lucas J.

2016-04-01

The early Eocene represents an ideal case study to analyse the impact of increase global warming on the ocean-atmosphere system. During this time interval, the Earth's surface experienced a long-term warming trend that culminated in a period of sustained high temperatures called the Early Eocene Climatic Optimum (EECO). These perturbations of the ocean-atmosphere system involved the global carbon cycle and global temperatures and have been linked to orbital forcing. Unravelling this complex climatic system strictly depends on the availability of high-quality suitable geological records and accurate age models. However, discrepancies between the astrochronological and radioisotopic dating techniques complicate the development of a robust time scale for the early Eocene (49-54 Ma). Here we present the first magneto-, bio-, chemo- and cyclostratigraphic results of the drilling of the land-based Smirra section, in the Umbria Marche Basin. The sediments recovered at Smirra provide a remarkably well-preserved and undisturbed succession of the early Palaeogene pelagic stratigraphy. Bulk stable carbon isotope and X-Ray Fluorescence (XRF) scanning records are employed in the construction of an astronomically tuned age model for the time interval between ~49 and ~54 Ma based on the tuning to long-eccentricity. These results are then compared to the astronomical tuning of the benthic carbon isotope record of ODP Site 1263 to evaluate the different age model options and improve the time scale of the early Eocene by assessing the precise number of eccentricity-related cycles comprised in this critical interval.

Stabilization of memory States by stochastic facilitating synapses.

PubMed

Miller, Paul

2013-12-06

Bistability within a small neural circuit can arise through an appropriate strength of excitatory recurrent feedback. The stability of a state of neural activity, measured by the mean dwelling time before a noise-induced transition to another state, depends on the neural firing-rate curves, the net strength of excitatory feedback, the statistics of spike times, and increases exponentially with the number of equivalent neurons in the circuit. Here, we show that such stability is greatly enhanced by synaptic facilitation and reduced by synaptic depression. We take into account the alteration in times of synaptic vesicle release, by calculating distributions of inter-release intervals of a synapse, which differ from the distribution of its incoming interspike intervals when the synapse is dynamic. In particular, release intervals produced by a Poisson spike train have a coefficient of variation greater than one when synapses are probabilistic and facilitating, whereas the coefficient of variation is less than one when synapses are depressing. However, in spite of the increased variability in postsynaptic input produced by facilitating synapses, their dominant effect is reduced synaptic efficacy at low input rates compared to high rates, which increases the curvature of neural input-output functions, leading to wider regions of bistability in parameter space and enhanced lifetimes of memory states. Our results are based on analytic methods with approximate formulae and bolstered by simulations of both Poisson processes and of circuits of noisy spiking model neurons.

Profile local linear estimation of generalized semiparametric regression model for longitudinal data.

PubMed

Sun, Yanqing; Sun, Liuquan; Zhou, Jie

2013-07-01

This paper studies the generalized semiparametric regression model for longitudinal data where the covariate effects are constant for some and time-varying for others. Different link functions can be used to allow more flexible modelling of longitudinal data. The nonparametric components of the model are estimated using a local linear estimating equation and the parametric components are estimated through a profile estimating function. The method automatically adjusts for heterogeneity of sampling times, allowing the sampling strategy to depend on the past sampling history as well as possibly time-dependent covariates without specifically model such dependence. A [Formula: see text]-fold cross-validation bandwidth selection is proposed as a working tool for locating an appropriate bandwidth. A criteria for selecting the link function is proposed to provide better fit of the data. Large sample properties of the proposed estimators are investigated. Large sample pointwise and simultaneous confidence intervals for the regression coefficients are constructed. Formal hypothesis testing procedures are proposed to check for the covariate effects and whether the effects are time-varying. A simulation study is conducted to examine the finite sample performances of the proposed estimation and hypothesis testing procedures. The methods are illustrated with a data example.

Solar flare and galactic cosmic ray studies of Apollo 14 and 15 samples.

NASA Technical Reports Server (NTRS)

Crozaz, G.; Drozd, R.; Hohenberg, C. M.; Hoyt, H. P., Jr.; Ragan, D.; Walker, R. M.; Yuhas, D.

1972-01-01

Thermoluminescence (TL) measurements in rock 14310 show a strong depth dependence consistent with that expected from solar flares. This effect should prove useful in studying solar flare fluctuations in the time interval of 100 to 100,000 years. Rare gas spallation ages for rock 14301, 14306, and 14311 are respectively 102 plus or minus 30, 25 plus or minus 2, and 661 plus or minus 72 m.y. The 14306 value supports the idea that Cone Crater was formed 25 million years ago. Groupings of exposure ages suggest the dates of other major cratering events. Galactic track data in 14310 show little depth dependence.

Comparison between volatility return intervals of the S&P 500 index and two common models

NASA Astrophysics Data System (ADS)

Vodenska-Chitkushev, I.; Wang, F. Z.; Weber, P.; Yamasaki, K.; Havlin, S.; Stanley, H. E.

2008-01-01

We analyze the S&P 500 index data for the 13-year period, from January 1, 1984 to December 31, 1996, with one data point every 10 min. For this database, we study the distribution and clustering of volatility return intervals, which are defined as the time intervals between successive volatilities above a certain threshold q. We find that the long memory in the volatility leads to a clustering of above-median as well as below-median return intervals. In addition, it turns out that the short return intervals form larger clusters compared to the long return intervals. When comparing the empirical results to the ARMA-FIGARCH and fBm models for volatility, we find that the fBm model predicts scaling better than the ARMA-FIGARCH model, which is consistent with the argument that both ARMA-FIGARCH and fBm capture the long-term dependence in return intervals to a certain extent, but only fBm accounts for the scaling. We perform the Student's t-test to compare the empirical data with the shuffled records, ARMA-FIGARCH and fBm. We analyze separately the clusters of above-median return intervals and the clusters of below-median return intervals for different thresholds q. We find that the empirical data are statistically different from the shuffled data for all thresholds q. Our results also suggest that the ARMA-FIGARCH model is statistically different from the S&P 500 for intermediate q for both above-median and below-median clusters, while fBm is statistically different from S&P 500 for small and large q for above-median clusters and for small q for below-median clusters. Neither model can fully explain the entire regime of q studied.

Serum phosphate optimal timing and range associated with patients survival in haemodialysis: the COSMOS study.

PubMed

Fernández-Martín, José L; Dusso, Adriana; Martínez-Camblor, Pablo; Dionisi, Maria P; Floege, Jürgen; Ketteler, Markus; London, Gérard; Locatelli, Francesco; Górriz, José L; Rutkowski, Boleslaw; Bos, Willem-Jan; Tielemans, Christian; Martin, Pierre-Yves; Wüthrich, Rudolf P; Pavlovic, Drasko; Benedik, Miha; Rodríguez-Puyol, Diego; Carrero, Juan J; Zoccali, Carmine; Cannata-Andía, Jorge B

2018-05-07

Serum phosphate is a key parameter in the management of chronic kidney disease-mineral and bone disorder (CKD-MBD). The timing of phosphate measurement is not standardized in the current guidelines. Since the optimal range of these biomarkers may vary depending on the duration of the interdialytic interval, in this analysis of the Current management of secondary hyperparathyroidism: a multicentre observational study (COSMOS), we assessed the influence of a 2- (midweek) or 3-day (post-weekend) dialysis interval for blood withdrawal on serum levels of CKD-MBD biomarkers and their association with mortality risk. The COSMOS cohort (6797 patients, CKD Stage 5D) was divided into two groups depending upon midweek or post-weekend blood collection. Univariate and multivariate Cox's models adjusted hazard ratios (HRs) by demographics and comorbidities, treatments and biochemical parameters from a patient/centre database collected at baseline and every 6 months for 3 years. There were no differences in serum calcium or parathyroid hormone levels between midweek and post-weekend patients. However, in post-weekend patients, the mean serum phosphate levels were higher compared with midweek patients (5.5 ± 1.4 versus 5.2 ± 1.4 mg/dL, P < 0.001). Also, the range of serum phosphate with the lowest mortality risk [HR ≤ 1.1; midweek: 3.5-4.9 mg/dL (95% confidence interval, CI: 2.9-5.2 mg/dL); post-weekend: 3.8-5.7 mg/dL (95% CI: 3.0-6.4 mg/dL)] showed significant differences in the upper limit (P = 0.021). Midweek and post-weekend serum phosphate levels and their target ranges associated with the lowest mortality risk differ. Thus, clinical guidelines should consider the timing of blood withdrawal when recommending optimal target ranges for serum phosphate and therapeutic strategies for phosphate control.

Low thermal dependence of the contractile properties of a wing muscle in the bat Carollia perspicillata.

PubMed

Rummel, Andrea D; Swartz, Sharon M; Marsh, Richard L

2018-05-29

Temperature affects contractile rate properties in muscle, which may affect locomotor performance. Endotherms are known to maintain high core body temperatures, but temperatures in the periphery of the body can fluctuate. Such a phenomenon occurs in bats, whose wing musculature is relatively poorly insulated, resulting in substantially depressed temperatures in the distal wing. We examined a wing muscle in the small-bodied tropical bat Carollia perspicillata and a hindlimb muscle in the laboratory mouse at 5°C intervals from 22 to 42°C to determine the thermal dependence of the contractile properties of both muscles. We found that the bat ECRL had low thermal dependence from near body temperature to 10°C lower, with Q 10 values of less than 1.5 for relaxation from contraction and shortening velocities in that interval, and with no significant difference in some rate properties in the interval between 32 and 37°C. In contrast, for all temperature intervals below 37°C, Q 10 values for the mouse EDL were 1.5 or higher, and rate properties differed significantly across successive temperature intervals from 37 to 22°C. An ANCOVA analysis found that the thermal dependencies of all measured isometric and isotonic rate processes were significantly different between the bat and mouse muscles. The relatively low thermal dependence of the bat muscle likely represents a downward shift of its optimal temperature and may be functionally significant in light of the variable operating temperatures of bat wing muscles. © 2018. Published by The Company of Biologists Ltd.

Modeling short duration extreme precipitation patterns using copula and generalized maximum pseudo-likelihood estimation with censoring

NASA Astrophysics Data System (ADS)

Bargaoui, Zoubeida Kebaili; Bardossy, Andràs

2015-10-01

The paper aims to develop researches on the spatial variability of heavy rainfall events estimation using spatial copula analysis. To demonstrate the methodology, short time resolution rainfall time series from Stuttgart region are analyzed. They are constituted by rainfall observations on continuous 30 min time scale recorded over a network composed by 17 raingages for the period July 1989-July 2004. The analysis is performed aggregating the observations from 30 min up to 24 h. Two parametric bivariate extreme copula models, the Husler-Reiss model and the Gumbel model are investigated. Both involve a single parameter to be estimated. Thus, model fitting is operated for every pair of stations for a giving time resolution. A rainfall threshold value representing a fixed rainfall quantile is adopted for model inference. Generalized maximum pseudo-likelihood estimation is adopted with censoring by analogy with methods of univariate estimation combining historical and paleoflood information with systematic data. Only pairs of observations greater than the threshold are assumed as systematic data. Using the estimated copula parameter, a synthetic copula field is randomly generated and helps evaluating model adequacy which is achieved using Kolmogorov Smirnov distance test. In order to assess dependence or independence in the upper tail, the extremal coefficient which characterises the tail of the joint bivariate distribution is adopted. Hence, the extremal coefficient is reported as a function of the interdistance between stations. If it is less than 1.7, stations are interpreted as dependent in the extremes. The analysis of the fitted extremal coefficients with respect to stations inter distance highlights two regimes with different dependence structures: a short spatial extent regime linked to short duration intervals (from 30 min to 6 h) with an extent of about 8 km and a large spatial extent regime related to longer rainfall intervals (from 12 h to 24 h) with an extent of 34 to 38 km.

Absence of equifinality of hand position in a double-step unloading task.

PubMed

Norouzi-Gheidari, Nahid; Archambault, Philippe

2010-08-01

Equifinality, during arm reaching movements, relates to the capacity of the neuromuscular system to attain the same final position in the presence or absence of transient perturbations. There have been several controversies regarding equifinality in the literature. A brief elastic perturbation, applied during a fast arm movement or just before its initiation, typically does not affect final arm position. On the other hand, several experiments have shown that velocity-dependent perturbations, such as Coriolis force or negative damping, while transient in nature, have a significant effect on final arm position when compared to unperturbed movements. In this study, an unloading paradigm was used to study the role of reflexes with respect to equifinality. The effects on final arm position of suddenly decreasing a static load maintained by fourteen subjects were analyzed. Subjects maintained an initial load produced by a double-joint manipulandum moving in the horizontal plane. The load was suddenly decreased, either in one or in two successive steps with different time intervals, resulting in a rapid reflex-mediated change in arm position. Unloading led to short-latency changes in the activity of shoulder and elbow muscles and significant variations in tonic activity. It was found that the final hand position was shorter for double- versus single-step unloading if the time between two successive changes in load was greater than 100 ms. With a shorter time interval, the final hand positions were the same. This difference in final hand positions was inversely proportional to the hand velocity at the time of the second change in load. Further, agonist/antagonist co-activation increased in double-step unloading. Thus, the change in both the load and the movement velocity may influence the magnitude of the unloading reflex. This may be indicative of a dependence of stretch reflexes on velocity. Perturbation may cause a reflex-mediated increase in joint stiffness, which could explain why equifinality is not preserved after some perturbations, such as velocity-dependant external forces.

High resolution data acquisition

DOEpatents

Thornton, G.W.; Fuller, K.R.

1993-04-06

A high resolution event interval timing system measures short time intervals such as occur in high energy physics or laser ranging. Timing is provided from a clock, pulse train, and analog circuitry for generating a triangular wave synchronously with the pulse train (as seen in diagram on patent). The triangular wave has an amplitude and slope functionally related to the time elapsed during each clock pulse in the train. A converter forms a first digital value of the amplitude and slope of the triangle wave at the start of the event interval and a second digital value of the amplitude and slope of the triangle wave at the end of the event interval. A counter counts the clock pulse train during the interval to form a gross event interval time. A computer then combines the gross event interval time and the first and second digital values to output a high resolution value for the event interval.

High resolution data acquisition

DOEpatents

Thornton, Glenn W.; Fuller, Kenneth R.

1993-01-01

A high resolution event interval timing system measures short time intervals such as occur in high energy physics or laser ranging. Timing is provided from a clock (38) pulse train (37) and analog circuitry (44) for generating a triangular wave (46) synchronously with the pulse train (37). The triangular wave (46) has an amplitude and slope functionally related to the time elapsed during each clock pulse in the train. A converter (18, 32) forms a first digital value of the amplitude and slope of the triangle wave at the start of the event interval and a second digital value of the amplitude and slope of the triangle wave at the end of the event interval. A counter (26) counts the clock pulse train (37) during the interval to form a gross event interval time. A computer (52) then combines the gross event interval time and the first and second digital values to output a high resolution value for the event interval.

Timescale dependent deformation of orogenic belts?

NASA Astrophysics Data System (ADS)

Hoth, S.; Friedrich, A. M.; Vietor, T.; Hoffmann-Rothe, A.; Kukowski, N.; Oncken, O.

2004-12-01

The principle aim to link geodetic, paleoseismologic and geologic estimates of fault slip is to extrapolate the respective rates from one timescale to the other to finally predict the recurrence interval of large earthquakes, which threat human habitats. This approach however, is based on two often implicitly made assumptions: a uniform slip distribution through time and space and no changes of the boundary conditions during the time interval of interest. Both assumptions are often hard to verify. A recent study, which analysed an exceptionally complete record of seismic slip for the Wasatch and related faults (Basin and Range province), ranging from 10 yr to 10 Myr suggests that such a link between geodetic and geologic rates might not exist, i.e., that our records of fault displacement may depend on the timescale over which they were measured. This view derives support from results of scaled 2D sandbox experiments, as well as numerical simulations with distinct elements, both of which investigated the effect of boundary conditions such as flexure, mechanic stratigraphy and erosion on the spatio-temporal distribution of deformation within bivergent wedges. We identified three types of processes based on their distinct spatio-temporal distribution of deformation. First, incremental strain and local strain rates are very short-lived are broadly distributed within the bivergent wedge and no temporal pattern could be established. Second, footwall shortcuts and the re-activation of either internal thrusts or of the retro shear-zone are irregularly distributed in time and are thus not predictable either, but last for a longer time interval. Third, the stepwise initiation and propagation of the deformation front is very regular in time, since it depends on the thickness of the incoming layer and on its internal and basal material properties. We consider the propagation of the deformation front as an internal clock of a thrust belt, which is therefore predictable. A deformation front advance cycle requires the longest timescale. Thus, despite known and constant boundary conditions during the simulations, we found only one regular temporal pattern of deformation in a steady active bivergent-wedge. We therefore propose that the structural inventory of an orogenic belt is hierarchically ordered with respect to accumulated slip, in analogy to the discharge pattern in a drainage network. The deformation front would have the highest, a branching splay the lowest order. Since kinematic boundary conditions control deformation front advance, its timing and the related maximum magnitude of finite strain, i.e. throw on the frontal thrust are predictable. However, the number of controlling factors, such as the degree of strain softening, the orientation of faults or fluid flow and resulting cementation of faults, responsible for the reactivation of faults increases with increasing distance from the deformation front. Since it is rarely possible to determine the complete network of forces within a wedge, the reactivation of lower order structures is not predictable in time and space. Two implications for field studies may emerge: A change of the propagation of deformation can only be determined, if at least two accretion cycles are sampled. The link between geodetic, paleoseismologic and geologic fault slip estimates can only be successfully derived if the position of the investigated fault within the hierarchical order has not changed over the time interval of interest.

Effects of a pretarget distractor on saccade reaction times across space and time in monkeys and humans

PubMed Central

Khan, Aarlenne Z.; Munoz, Douglas P.; Takahashi, Naomi; Blohm, Gunnar; McPeek, Robert M.

2016-01-01

Previous studies have shown that the influence of a behaviorally irrelevant distractor on saccade reaction times (SRTs) varies depending on the temporal and spatial relationship between the distractor and the saccade target. We measured distractor influence on SRTs to a subsequently presented target, varying the spatial location and the timing between the distractor and the target. The distractor appeared at one of four equally eccentric locations, followed by a target (either 50 ms or 200 ms after) at one of 136 different locations encompassing an area of 20° square. We extensively tested two humans and two monkeys on this task to determine interspecies similarities and differences, since monkey neurophysiology is often used to interpret human behavioral findings. Results were similar across species; for the short interval (50 ms), SRTs were shortest to a target presented close to or at the distractor location and increased primarily as a function of the distance from the distractor. There was also an effect of distractor-target direction and visual field. For the long interval (200 ms) the results were inverted; SRTs were longest for short distances between the distractor and target and decreased as a function of distance from distractor. Both SRT patterns were well captured by a two-dimensional dynamic field model with short-distance excitation and long-distance inhibition, based upon known functional connectivity found in the superior colliculus that includes wide-spread excitation and inhibition. Based on these findings, we posit that the different time-dependent patterns of distractor-related SRTs can emerge from the same underlying neuronal mechanisms common to both species. PMID:27148697

Nonpreemptive run-time scheduling issues on a multitasked, multiprogrammed multiprocessor with dependencies, bidimensional tasks, folding and dynamic graphs

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

Miller, Allan Ray

1987-05-01

Increases in high speed hardware have mandated studies in software techniques to exploit the parallel capabilities. This thesis examines the effects a run-time scheduler has on a multiprocessor. The model consists of directed, acyclic graphs, generated from serial FORTRAN benchmark programs by the parallel compiler Parafrase. A multitasked, multiprogrammed environment is created. Dependencies are generated by the compiler. Tasks are bidimensional, i.e., they may specify both time and processor requests. Processor requests may be folded into execution time by the scheduler. The graphs may arrive at arbitrary time intervals. The general case is NP-hard, thus, a variety of heuristics aremore » examined by a simulator. Multiprogramming demonstrates a greater need for a run-time scheduler than does monoprogramming for a variety of reasons, e.g., greater stress on the processors, a larger number of independent control paths, more variety in the task parameters, etc. The dynamic critical path series of algorithms perform well. Dynamic critical volume did not add much. Unfortunately, dynamic critical path maximizes turnaround time as well as throughput. Two schedulers are presented which balance throughput and turnaround time. The first requires classification of jobs by type; the second requires selection of a ratio value which is dependent upon system parameters. 45 refs., 19 figs., 20 tabs.« less

Prior Design for Dependent Dirichlet Processes: An Application to Marathon Modeling

PubMed Central

F. Pradier, Melanie; J. R. Ruiz, Francisco; Perez-Cruz, Fernando

2016-01-01

This paper presents a novel application of Bayesian nonparametrics (BNP) for marathon data modeling. We make use of two well-known BNP priors, the single-p dependent Dirichlet process and the hierarchical Dirichlet process, in order to address two different problems. First, we study the impact of age, gender and environment on the runners’ performance. We derive a fair grading method that allows direct comparison of runners regardless of their age and gender. Unlike current grading systems, our approach is based not only on top world records, but on the performances of all runners. The presented methodology for comparison of densities can be adopted in many other applications straightforwardly, providing an interesting perspective to build dependent Dirichlet processes. Second, we analyze the running patterns of the marathoners in time, obtaining information that can be valuable for training purposes. We also show that these running patterns can be used to predict finishing time given intermediate interval measurements. We apply our models to New York City, Boston and London marathons. PMID:26821155

Does Tinnitus Depend on Time-of-Day? An Ecological Momentary Assessment Study with the “TrackYourTinnitus” Application

PubMed Central

Probst, Thomas; Pryss, Rüdiger C.; Langguth, Berthold; Rauschecker, Josef P.; Schobel, Johannes; Reichert, Manfred; Spiliopoulou, Myra; Schlee, Winfried; Zimmermann, Johannes

2017-01-01

Only few previous studies used ecological momentary assessments to explore the time-of-day-dependence of tinnitus. The present study used data from the mobile application “TrackYourTinnitus” to explore whether tinnitus loudness and tinnitus distress fluctuate within a 24-h interval. Multilevel models were performed to account for the nested structure of assessments (level 1: 17,209 daily life assessments) nested within days (level 2: 3,570 days with at least three completed assessments), and days nested within participants (level 3: 350 participants). Results revealed a time-of-day-dependence of tinnitus. In particular, tinnitus was perceived as louder and more distressing during the night and early morning hours (from 12 a.m. to 8 a.m.) than during the upcoming day. Since previous studies suggested that stress (and stress-associated hormones) show a circadian rhythm and this might influence the time-of-day-dependence of tinnitus, we evaluated whether the described results change when statistically controlling for subjectively reported stress-levels. Correcting for subjective stress-levels, however, did not change the result that tinnitus (loudness and distress) was most severe at night and early morning. These results show that time-of-day contributes to the level of both tinnitus loudness and tinnitus distress. Possible implications of our results for the clinical management of tinnitus are that tailoring the timing of therapeutic interventions to the circadian rhythm of individual patients (chronotherapy) might be promising. PMID:28824415

Measuring the EMS patient access time interval and the impact of responding to high-rise buildings.

PubMed

Morrison, Laurie J; Angelini, Mark P; Vermeulen, Marian J; Schwartz, Brian

2005-01-01

To measure the patient access time interval and characterize its contribution to the total emergency medical services (EMS) response time interval; to compare the patient access time intervals for patients located three or more floors above ground with those less than three floors above or below ground, and specifically in the apartment subgroup; and to identify barriers that significantly impede EMS access to patients in high-rise apartments. An observational study of all patients treated by an emergency medical technician paramedics (EMT-P) crew was conducted using a trained independent observer to collect time intervals and identify potential barriers to access. Of 118 observed calls, 25 (21%) originated from patients three or more floors above ground. The overall median and 90th percentile (95% confidence interval) patient access time intervals were 1.61 (1.27, 1.91) and 3.47 (3.08, 4.05) minutes, respectively. The median interval was 2.73 (2.22, 3.03) minutes among calls from patients located three or more stories above ground compared with 1.25 (1.07, 1.55) minutes among those at lower levels. The patient access time interval represented 23.5% of the total EMS response time interval among calls originating less than three floors above or below ground and 32.2% of those located three or more stories above ground. The most frequently encountered barriers to access included security code entry requirements, lack of directional signs, and inability to fit the stretcher into the elevator. The patient access time interval is significantly long and represents a substantial component of the total EMS response time interval, especially among ambulance calls originating three or more floors above ground. A number of barriers appear to contribute to delayed paramedic access.

Time-scale effects on the gain-loss asymmetry in stock indices

NASA Astrophysics Data System (ADS)

Sándor, Bulcsú; Simonsen, Ingve; Nagy, Bálint Zsolt; Néda, Zoltán

2016-08-01

The gain-loss asymmetry, observed in the inverse statistics of stock indices is present for logarithmic return levels that are over 2 % , and it is the result of the non-Pearson-type autocorrelations in the index. These non-Pearson-type correlations can be viewed also as functionally dependent daily volatilities, extending for a finite time interval. A generalized time-window shuffling method is used to show the existence of such autocorrelations. Their characteristic time scale proves to be smaller (less than 25 trading days) than what was previously believed. It is also found that this characteristic time scale has decreased with the appearance of program trading in the stock market transactions. Connections with the leverage effect are also established.

Temporal binding function of dorsal CA1 is critical for declarative memory formation

PubMed Central

Sellami, Azza; Al Abed, Alice Shaam; Brayda-Bruno, Laurent; Etchamendy, Nicole; Valério, Stéphane; Oulé, Marie; Pantaléon, Laura; Lamothe, Valérie; Potier, Mylène; Bernard, Katy; Jabourian, Maritza; Herry, Cyril; Mons, Nicole; Piazza, Pier-Vincenzo; Eichenbaum, Howard; Marighetto, Aline

2017-01-01

Temporal binding, the process that enables association between discontiguous stimuli in memory, and relational organization, a process that enables the flexibility of declarative memories, are both hippocampus-dependent and decline in aging. However, how these two processes are related in supporting declarative memory formation and how they are compromised in age-related memory loss remain hypothetical. We here identify a causal link between these two features of declarative memory: Temporal binding is a necessary condition for the relational organization of discontiguous events. We demonstrate that the formation of a relational memory is limited by the capability of temporal binding, which depends on dorsal (d)CA1 activity over time intervals and diminishes in aging. Conversely, relational representation is successful even in aged individuals when the demand on temporal binding is minimized, showing that relational/declarative memory per se is not impaired in aging. Thus, bridging temporal intervals by dCA1 activity is a critical foundation of relational representation, and a deterioration of this mechanism is responsible for the age-associated memory impairment. PMID:28874586

Temporal binding function of dorsal CA1 is critical for declarative memory formation.

PubMed

Sellami, Azza; Al Abed, Alice Shaam; Brayda-Bruno, Laurent; Etchamendy, Nicole; Valério, Stéphane; Oulé, Marie; Pantaléon, Laura; Lamothe, Valérie; Potier, Mylène; Bernard, Katy; Jabourian, Maritza; Herry, Cyril; Mons, Nicole; Piazza, Pier-Vincenzo; Eichenbaum, Howard; Marighetto, Aline

2017-09-19

Temporal binding, the process that enables association between discontiguous stimuli in memory, and relational organization, a process that enables the flexibility of declarative memories, are both hippocampus-dependent and decline in aging. However, how these two processes are related in supporting declarative memory formation and how they are compromised in age-related memory loss remain hypothetical. We here identify a causal link between these two features of declarative memory: Temporal binding is a necessary condition for the relational organization of discontiguous events. We demonstrate that the formation of a relational memory is limited by the capability of temporal binding, which depends on dorsal (d)CA1 activity over time intervals and diminishes in aging. Conversely, relational representation is successful even in aged individuals when the demand on temporal binding is minimized, showing that relational/declarative memory per se is not impaired in aging. Thus, bridging temporal intervals by dCA1 activity is a critical foundation of relational representation, and a deterioration of this mechanism is responsible for the age-associated memory impairment.

Measurement of the timing behaviour of off-the-shelf cameras

NASA Astrophysics Data System (ADS)

Schatz, Volker

2017-04-01

This paper presents a measurement method suitable for investigating the timing properties of cameras. A single light source illuminates the camera detector starting with a varying defined delay after the camera trigger. Pixels from the recorded camera frames are summed up and normalised, and the resulting function is indicative of the overlap between illumination and exposure. This allows one to infer the trigger delay and the exposure time with sub-microsecond accuracy. The method is therefore of interest when off-the-shelf cameras are used in reactive systems or synchronised with other cameras. It can supplement radiometric and geometric calibration methods for cameras in scientific use. A closer look at the measurement results reveals deviations from the ideal camera behaviour of constant sensitivity limited to the exposure interval. One of the industrial cameras investigated retains a small sensitivity long after the end of the nominal exposure interval. All three investigated cameras show non-linear variations of sensitivity at O≤ft({{10}-3}\\right) to O≤ft({{10}-2}\\right) during exposure. Due to its sign, the latter effect cannot be described by a sensitivity function depending on the time after triggering, but represents non-linear pixel characteristics.

A physical model for earthquakes. I - Fluctuations and interactions. II - Application to southern California

NASA Technical Reports Server (NTRS)

Rundle, John B.

1988-01-01

The idea that earthquakes represent a fluctuation about the long-term motion of plates is expressed mathematically through the fluctuation hypothesis, under which all physical quantities which pertain to the occurance of earthquakes are required to depend on the difference between the present state of slip on the fault and its long-term average. It is shown that under certain circumstances the model fault dynamics undergo a sudden transition from a spatially ordered, temporally disordered state to a spatially disordered, temporally ordered state, and that the latter stages are stable for long intervals of time. For long enough faults, the dynamics are evidently chaotic. The methods developed are then used to construct a detailed model for earthquake dynamics in southern California. The result is a set of slip-time histories for all the major faults, which are similar to data obtained by geological trenching studies. Although there is an element of periodicity to the events, the patterns shift, change and evolve with time. Time scales for pattern evolution seem to be of the order of a thousand years for average recurring intervals of about a hundred years.

Evaluating Independent Proportions for Statistical Difference, Equivalence, Indeterminacy, and Trivial Difference Using Inferential Confidence Intervals

ERIC Educational Resources Information Center

Tryon, Warren W.; Lewis, Charles

2009-01-01

Tryon presented a graphic inferential confidence interval (ICI) approach to analyzing two independent and dependent means for statistical difference, equivalence, replication, indeterminacy, and trivial difference. Tryon and Lewis corrected the reduction factor used to adjust descriptive confidence intervals (DCIs) to create ICIs and introduced…

Response-reinforcer dependency and resistance to change.

PubMed

Cançado, Carlos R X; Abreu-Rodrigues, Josele; Aló, Raquel Moreira; Hauck, Flávia; Doughty, Adam H

2018-01-01

The effects of the response-reinforcer dependency on resistance to change were studied in three experiments with rats. In Experiment 1, lever pressing produced reinforcers at similar rates after variable interreinforcer intervals in each component of a two-component multiple schedule. Across conditions, in the fixed component, all reinforcers were response-dependent; in the alternative component, the percentage of response-dependent reinforcers was 100, 50 (i.e., 50% response-dependent and 50% response-independent) or 10% (i.e., 10% response-dependent and 90% response-independent). Resistance to extinction was greater in the alternative than in the fixed component when the dependency in the former was 10%, but was similar between components when this dependency was 100 or 50%. In Experiment 2, a three-component multiple schedule was used. The dependency was 100% in one component and 10% in the other two. The 10% components differed on how reinforcers were programmed. In one component, as in Experiment 1, a reinforcer had to be collected before the scheduling of other response-dependent or independent reinforcers. In the other component, response-dependent and -independent reinforcers were programmed by superimposing a variable-time schedule on an independent variable-interval schedule. Regardless of the procedure used to program the dependency, resistance to extinction was greater in the 10% components than in the 100% component. These results were replicated in Experiment 3 in which, instead of extinction, VT schedules replaced the baseline schedules in each multiple-schedule component during the test. We argue that the relative change in dependency from Baseline to Test, which is greater when baseline dependencies are high rather than low, could account for the differential resistance to change in the present experiments. The inconsistencies in results across the present and previous experiments suggest that the effects of dependency on resistance to change are not well understood. Additional systematic analyses are important to further understand the effects of the response-reinforcer relation on resistance to change and to the development of a more comprehensive theory of behavioral persistence. © 2017 Society for the Experimental Analysis of Behavior.

Local-in-Time Adjoint-Based Method for Optimal Control/Design Optimization of Unsteady Compressible Flows

NASA Technical Reports Server (NTRS)

Yamaleev, N. K.; Diskin, B.; Nielsen, E. J.

2009-01-01

.We study local-in-time adjoint-based methods for minimization of ow matching functionals subject to the 2-D unsteady compressible Euler equations. The key idea of the local-in-time method is to construct a very accurate approximation of the global-in-time adjoint equations and the corresponding sensitivity derivative by using only local information available on each time subinterval. In contrast to conventional time-dependent adjoint-based optimization methods which require backward-in-time integration of the adjoint equations over the entire time interval, the local-in-time method solves local adjoint equations sequentially over each time subinterval. Since each subinterval contains relatively few time steps, the storage cost of the local-in-time method is much lower than that of the global adjoint formulation, thus making the time-dependent optimization feasible for practical applications. The paper presents a detailed comparison of the local- and global-in-time adjoint-based methods for minimization of a tracking functional governed by the Euler equations describing the ow around a circular bump. Our numerical results show that the local-in-time method converges to the same optimal solution obtained with the global counterpart, while drastically reducing the memory cost as compared to the global-in-time adjoint formulation.

Fuel optimal maneuvers for spacecraft with fixed thrusters

NASA Technical Reports Server (NTRS)

Carter, T. C.

1982-01-01

Several mathematical models, including a minimum integral square criterion problem, were used for the qualitative investigation of fuel optimal maneuvers for spacecraft with fixed thrusters. The solutions consist of intervals of "full thrust" and "coast" indicating that thrusters do not need to be designed as "throttleable" for fuel optimal performance. For the primary model considered, singular solutions occur only if the optimal solution is "pure translation". "Time optimal" singular solutions can be found which consist of intervals of "coast" and "full thrust". The shape of the optimal fuel consumption curve as a function of flight time was found to depend on whether or not the initial state is in the region admitting singular solutions. Comparisons of fuel optimal maneuvers in deep space with those relative to a point in circular orbit indicate that qualitative differences in the solutions can occur. Computation of fuel consumption for certain "pure translation" cases indicates that considerable savings in fuel can result from the fuel optimal maneuvers.

Implementation of Automatic Clustering Algorithm and Fuzzy Time Series in Motorcycle Sales Forecasting

NASA Astrophysics Data System (ADS)

Rasim; Junaeti, E.; Wirantika, R.

2018-01-01

Accurate forecasting for the sale of a product depends on the forecasting method used. The purpose of this research is to build motorcycle sales forecasting application using Fuzzy Time Series method combined with interval determination using automatic clustering algorithm. Forecasting is done using the sales data of motorcycle sales in the last ten years. Then the error rate of forecasting is measured using Means Percentage Error (MPE) and Means Absolute Percentage Error (MAPE). The results of forecasting in the one-year period obtained in this study are included in good accuracy.

Time-dependent seismic tomography of the Coso geothermal area, 1996-2004

USGS Publications Warehouse

Julian, B.R.; Foulger, G.R.

2005-01-01

The permanent 18-station network of three-component digital seismometers at the seismically active Coso geothermal area, California, provides high-quality microearthquake (MEQ) data that are well suited to investigating temporal variations in structure related to processes within the geothermal reservoir. A preliminary study [Julian, et al., 2003; Julian, et al., 2004] comparing data from 1996 and 2003 found significant variations in the ratio of the seismic wave-speeds, Vp/Vs, at shallow depths over this time interval. This report describes results of a more detailed study of each year from 1996 through 2004.

Estimation of Neutrophil Infiltration into Hairless Guinea Pig Skin treated with 2,2’ -Dichlorodiethyl Sulfide

DTIC Science & Technology

1993-05-13

guinea pig (HPG) for evaluating sulfur mustard (2,2’dichlorodiethylsulfide, HD) skin injury, there are presently few antivesicant drug assessment endpoints validated in vivo for this model. We measured the activity of myeloperoxidase (MPO) to characterize the dose- and time-dependence of polymorphonuclear leukocyte (PMN) infiltration during development of the HD lesion. Biopsies were obtained from the dorsal thoracic-lumbar area of HGPs at successive 3 hr time intervals for up to 24 hrs following controlled exposure to either 5, 7, 8 or 10 min HD vapor. The presence

Periodicity in the autocorrelation function as a mechanism for regularly occurring zero crossings or extreme values of a Gaussian process.

PubMed

Wilson, Lorna R M; Hopcraft, Keith I

2017-12-01

The problem of zero crossings is of great historical prevalence and promises extensive application. The challenge is to establish precisely how the autocorrelation function or power spectrum of a one-dimensional continuous random process determines the density function of the intervals between the zero crossings of that process. This paper investigates the case where periodicities are incorporated into the autocorrelation function of a smooth process. Numerical simulations, and statistics about the number of crossings in a fixed interval, reveal that in this case the zero crossings segue between a random and deterministic point process depending on the relative time scales of the periodic and nonperiodic components of the autocorrelation function. By considering the Laplace transform of the density function, we show that incorporating correlation between successive intervals is essential to obtaining accurate results for the interval variance. The same method enables prediction of the density function tail in some regions, and we suggest approaches for extending this to cover all regions. In an ever-more complex world, the potential applications for this scale of regularity in a random process are far reaching and powerful.

Periodicity in the autocorrelation function as a mechanism for regularly occurring zero crossings or extreme values of a Gaussian process

NASA Astrophysics Data System (ADS)

Wilson, Lorna R. M.; Hopcraft, Keith I.

2017-12-01

The problem of zero crossings is of great historical prevalence and promises extensive application. The challenge is to establish precisely how the autocorrelation function or power spectrum of a one-dimensional continuous random process determines the density function of the intervals between the zero crossings of that process. This paper investigates the case where periodicities are incorporated into the autocorrelation function of a smooth process. Numerical simulations, and statistics about the number of crossings in a fixed interval, reveal that in this case the zero crossings segue between a random and deterministic point process depending on the relative time scales of the periodic and nonperiodic components of the autocorrelation function. By considering the Laplace transform of the density function, we show that incorporating correlation between successive intervals is essential to obtaining accurate results for the interval variance. The same method enables prediction of the density function tail in some regions, and we suggest approaches for extending this to cover all regions. In an ever-more complex world, the potential applications for this scale of regularity in a random process are far reaching and powerful.

Department of Defense Precise Time and Time Interval program improvement plan

NASA Technical Reports Server (NTRS)

Bowser, J. R.

1981-01-01

The United States Naval Observatory is responsible for ensuring uniformity in precise time and time interval operations including measurements, the establishment of overall DOD requirements for time and time interval, and the accomplishment of objectives requiring precise time and time interval with minimum cost. An overview of the objectives, the approach to the problem, the schedule, and a status report, including significant findings relative to organizational relationships, current directives, principal PTTI users, and future requirements as currently identified by the users are presented.

Recurrence and interoccurrence behavior of self-organized complex phenomena

NASA Astrophysics Data System (ADS)

Abaimov, S. G.; Turcotte, D. L.; Shcherbakov, R.; Rundle, J. B.

2007-08-01

The sandpile, forest-fire and slider-block models are said to exhibit self-organized criticality. Associated natural phenomena include landslides, wildfires, and earthquakes. In all cases the frequency-size distributions are well approximated by power laws (fractals). Another important aspect of both the models and natural phenomena is the statistics of interval times. These statistics are particularly important for earthquakes. For earthquakes it is important to make a distinction between interoccurrence and recurrence times. Interoccurrence times are the interval times between earthquakes on all faults in a region whereas recurrence times are interval times between earthquakes on a single fault or fault segment. In many, but not all cases, interoccurrence time statistics are exponential (Poissonian) and the events occur randomly. However, the distribution of recurrence times are often Weibull to a good approximation. In this paper we study the interval statistics of slip events using a slider-block model. The behavior of this model is sensitive to the stiffness α of the system, α=kC/kL where kC is the spring constant of the connector springs and kL is the spring constant of the loader plate springs. For a soft system (small α) there are no system-wide events and interoccurrence time statistics of the larger events are Poissonian. For a stiff system (large α), system-wide events dominate the energy dissipation and the statistics of the recurrence times between these system-wide events satisfy the Weibull distribution to a good approximation. We argue that this applicability of the Weibull distribution is due to the power-law (scale invariant) behavior of the hazard function, i.e. the probability that the next event will occur at a time t0 after the last event has a power-law dependence on t0. The Weibull distribution is the only distribution that has a scale invariant hazard function. We further show that the onset of system-wide events is a well defined critical point. We find that the number of system-wide events NSWE satisfies the scaling relation NSWE ∝(α-αC)δ where αC is the critical value of the stiffness. The system-wide events represent a new phase for the slider-block system.

Identifying Significant Changes in Cerebrovascular Reactivity to Carbon Dioxide.

PubMed

Sobczyk, O; Crawley, A P; Poublanc, J; Sam, K; Mandell, D M; Mikulis, D J; Duffin, J; Fisher, J A

2016-05-01

Changes in cerebrovascular reactivity can be used to assess disease progression and response to therapy but require discrimination of pathology from normal test-to-test variability. Such variability is due to variations in methodology, technology, and physiology with time. With uniform test conditions, our aim was to determine the test-to-test variability of cerebrovascular reactivity in healthy subjects and in patients with known cerebrovascular disease. Cerebrovascular reactivity was the ratio of the blood oxygen level-dependent MR imaging response divided by the change in carbon dioxide stimulus. Two standardized cerebrovascular reactivity tests were conducted at 3T in 15 healthy men (36.7 ± 16.1 years of age) within a 4-month period and were coregistered into standard space to yield voxelwise mean cerebrovascular reactivity interval difference measures, composing a reference interval difference atlas. Cerebrovascular reactivity interval difference maps were prepared for 11 male patients. For each patient, the test-retest difference of each voxel was scored statistically as z-values of the corresponding voxel mean difference in the reference atlas and then color-coded and superimposed on the anatomic images to create cerebrovascular reactivity interval difference z-maps. There were no significant test-to-test differences in cerebrovascular reactivity in either gray or white matter (mean gray matter, P = .431; mean white matter, P = .857; paired t test) in the healthy cohort. The patient cerebrovascular reactivity interval difference z-maps indicated regions where cerebrovascular reactivity increased or decreased and the probability that the changes were significant. Accounting for normal test-to-test differences in cerebrovascular reactivity enables the assessment of significant changes in disease status (stability, progression, or regression) in patients with time. © 2016 by American Journal of Neuroradiology.

The effect of laminar air flow and door openings on operating room contamination.

PubMed

Smith, Eric B; Raphael, Ibrahim J; Maltenfort, Mitchell G; Honsawek, Sittisak; Dolan, Kyle; Younkins, Elizabeth A

2013-10-01

We evaluate the association of laminar airflow (LAF) and OR traffic with intraoperative contamination rates. Two sterile basins were placed in each room during 81 cases, one inside and one outside the LAF. One Replicate Organism Detection and Counting (RODAC) plate from each basin was sent for culture at successive 30-minute intervals from incision time until wound closure. At successive 30-minute intervals more plates were contaminated outside than inside the LAF. A negative binomial model showed that the bacteria colony forming units (CFU) depended on whether there were any door openings (P=0.02) and the presence of LAF (P=0.003). LAF decreases CFU by 36.6%. LAF independently reduces the risk of contamination and microbial counts for surgeries lasting 90 minutes or less. © 2013.

On the motion of a rigid body with an internal moving point mass on a horizontal plane

NASA Astrophysics Data System (ADS)

Bardin, B. S.; Panev, A. S.

2018-05-01

We consider motions of a body carrying movable internal mass. The internal mass is a particle moving in a circle inside the body, which performs a rectilinear motion on a horizontal plane. We suppose that viscous and dry friction acts between the plane and the body. We also assume that the body moves without jumps on the plane. Our study has shown that depending on values of parameters the body moves either periodically stoping and resting for certain time intervals or it approaches a periodic mode of motion without quiescence intervals. The above conclusions are in good correspondence with results obtained in our previous papers, where the above problem has been studied under assumption that the viscous friction is absent.

Improvements in GPS precision: 10 Hz to one day

NASA Astrophysics Data System (ADS)

Choi, Kyuhong

Seeking to understand Global Positioning System (GPS) measurements and the positioning solutions in various time intervals, this dissertation improves the consistency of pseudorange measurements from different receiver types, processes 30 s interval data with optimized filtering techniques, and analyzes very-high-rate data with short arc lengths and baseline noise. The first project studies satellite-dependent biases between C/A and P1 codes. Calibrating these biases reduces the inconsistency of satellite clocks, improving the ambiguity resolution which allows for higher position precision. Receiver-dependent biases for two receivers are compared with the bias products of Center for Orbit Determination in Europe (CODE). Baseline lengths ranging up to ˜2,100km are tested with the receiver-specific biases; they resolve more phase ambiguity by 4.3% than using CODE's products. The second project analyzes 1 s and 30 s interval GPS data of the 2003 Tokachi-Oki earthquake. For 1 Hz positioning, Iterative Tropospheric Estimation (ITE) method improves vertical precision. While equalized sidereal filtering reduces noise for multipath-dominant 30--300 s periods, it can cause long-term drifts in the timeseries. A study of postseismic deformation after the Tokachi-Oki earthquake uses 30 s interval position estimations to test multiple filtering strategies to maximize precision using lower-rate data. On top of the residual stacking, estimation of a random walk constraint of sigmaDelta = 1.80 cm/ hr shows maximum noise reduction capability while retaining the real deformation signal. These techniques enhance our grasp of fault response in the aftermath of great earthquakes. The third project probes noise floor characteristics of very-high-rate (> 1 Hz) GPS data. A hybrid method, designed and tested to resolve phase biases, minimizes computational burdens while keeping the quality of ambiguity-fixed solutions. Noise characteristics are compared after an analysis of 5 and 10 Hz Ashtech MicroZ and ZFX as well as Trimble NetRS receivers. The Trimble NetRS receiver noise has a timeseries standard deviation double that of Ashtech MicroZ receivers. Also, the power spectral density function has a 0.1 Hz peak. Noise power shows white noise for the frequency range from 2 Hz and higher. Each research project assesses the methods to reduce the noises and/or biases in various time intervals. Each method considered in this dissertation will fulfill the needs for scientific applications.

Why trace and delay conditioning are sometimes (but not always) hippocampal dependent: A computational model

PubMed Central

Moustafa, Ahmed A.; Wufong, Ella; Servatius, Richard J.; Pang, Kevin C. H.; Gluck, Mark A.; Myers, Catherine E.

2013-01-01

A recurrent-network model provides a unified account of the hippocampal region in mediating the representation of temporal information in classical eyeblink conditioning. Much empirical research is consistent with a general conclusion that delay conditioning (in which the conditioned stimulus CS and unconditioned stimulus US overlap and co-terminate) is independent of the hippocampal system, while trace conditioning (in which the CS terminates before US onset) depends on the hippocampus. However, recent studies show that, under some circumstances, delay conditioning can be hippocampal-dependent and trace conditioning can be spared following hippocampal lesion. Here, we present an extension of our prior trial-level models of hippocampal function and stimulus representation that can explain these findings within a unified framework. Specifically, the current model includes adaptive recurrent collateral connections that aid in the representation of intra-trial temporal information. With this model, as in our prior models, we argue that the hippocampus is not specialized for conditioned response timing, but rather is a general-purpose system that learns to predict the next state of all stimuli given the current state of variables encoded by activity in recurrent collaterals. As such, the model correctly predicts that hippocampal involvement in classical conditioning should be critical not only when there is an intervening trace interval, but also when there is a long delay between CS onset and US onset. Our model simulates empirical data from many variants of classical conditioning, including delay and trace paradigms in which the length of the CS, the inter-stimulus interval, or the trace interval is varied. Finally, we discuss model limitations, future directions, and several novel empirical predictions of this temporal processing model of hippocampal function and learning. PMID:23178699

Rainfall disaggregation for urban hydrology: Effects of spatial consistence

NASA Astrophysics Data System (ADS)

Müller, Hannes; Haberlandt, Uwe

2015-04-01

For urban hydrology rainfall time series with a high temporal resolution are crucial. Observed time series of this kind are very short in most cases, so they cannot be used. On the contrary, time series with lower temporal resolution (daily measurements) exist for much longer periods. The objective is to derive time series with a long duration and a high resolution by disaggregating time series of the non-recording stations with information of time series of the recording stations. The multiplicative random cascade model is a well-known disaggregation model for daily time series. For urban hydrology it is often assumed, that a day consists of only 1280 minutes in total as starting point for the disaggregation process. We introduce a new variant for the cascade model, which is functional without this assumption and also outperforms the existing approach regarding time series characteristics like wet and dry spell duration, average intensity, fraction of dry intervals and extreme value representation. However, in both approaches rainfall time series of different stations are disaggregated without consideration of surrounding stations. This yields in unrealistic spatial patterns of rainfall. We apply a simulated annealing algorithm that has been used successfully for hourly values before. Relative diurnal cycles of the disaggregated time series are resampled to reproduce the spatial dependence of rainfall. To describe spatial dependence we use bivariate characteristics like probability of occurrence, continuity ratio and coefficient of correlation. Investigation area is a sewage system in Northern Germany. We show that the algorithm has the capability to improve spatial dependence. The influence of the chosen disaggregation routine and the spatial dependence on overflow occurrences and volumes of the sewage system will be analyzed.

Radial diffusion with outer boundary determined by geosynchronous measurements: Storm and post-storm intervals

NASA Astrophysics Data System (ADS)

Chu, F.; Haines, P.; Hudson, M.; Kress, B.; Freidel, R.; Kanekal, S.

2007-12-01

Work is underway by several groups to quantify diffusive radial transport of radiation belt electrons, including a model for pitch angle scattering losses to the atmosphere. The radial diffusion model conserves the first and second adiabatic invariants and breaks the third invariant. We have developed a radial diffusion code which uses the Crank Nicholson method with a variable outer boundary condition. For the radial diffusion coefficient, DLL, we have several choices, including the Brautigam and Albert (JGR, 2000) diffusion coefficient parameterized by Kp, which provides an ad hoc measure of the power level at ULF wave frequencies in the range of electron drift (mHz), breaking the third invariant. Other diffusion coefficient models are Kp-independent, fixed in time but explicitly dependent on the first invariant, or energy at a fixed L, such as calculated by Elkington et al. (JGR, 2003) and Perry et al. (JGR, 2006) based on ULF wave model fields. We analyzed three periods of electron flux and phase space density (PSD) enhancements inside of geosynchronous orbit: March 31 - May 31, 1991, and July 2004 and Nov 2004 storm intervals. The radial diffusion calculation is initialized with a computed phase space density profile for the 1991 interval using differential flux values from the CRRES High Energy Electron Fluxmeter instrument, covering 0.65 - 7.5 MeV. To calculate the initial phase space density, we convert Roederer L* to McIlwain's L- parameter using the ONERA-DESP program. A time averaged model developed by Vampola1 from the entire 14 month CRRES data set is applied to the July 2004 and Nov 2004 storms. The online CRESS data for specific orbits and the Vampola-model flux are both expressed in McIlwain L-shell, while conversion to L* conserves phase space density in a distorted non-dipolar magnetic field model. A Tsyganenko (T04) magnetic field model is used for conversion between L* and L. The outer boundary PSD is updated using LANL GEO satellite fluxes. After calculating the phase space density time evolution for the two storms and post-injection interval (March 31 - May 31, 1991), we compare results with SAMPEX measurements. A better match with SAMPEX measurements is obtained with a variable outer boundary, also with a Kp-dependent diffusion coefficient, and finally with an energy and L-dependent loss term (Summers et al., JGR, 2004), than with a time-independent diffusion coefficient and a simple Kp-parametrized loss rate and location of the plasmapause. Addition of a varying outer boundary which incorporates measured fluxes at geosynchronous orbit using L* has the biggest effect of the three parametrized variations studied. 1Vampola, A.L., 1996, The ESA Outer Zone Electron Model Update, Environment Modelling for Spaced-based Applications, ESA SP-392, ESTEC, Nordwijk, NL, pp. 151-158, W. Burke and T.-D. Guyenne, eds.

EPIDEMIOLOGY OF AGE-DEPENDENCE IN SLEEP DISORDERED BREATHING (SDB) IN OLD AGE: THE BAY AREA SLEEP COHORT (BASC).

PubMed

Bliwise, Donald L

2009-03-01

Sleep Disordered Breathing (SDB) is highly prevalent in elderly populations and is thought to reflect, at least in part, age-dependence. Several studies suggest that SDB in elderly populations may hold different functional outcomes relative to SDB in middle-aged populations. Risk factors for SDB specific for the elderly remain uncertain. In this report, we examined changes in SDB, body weight and pulmonary function in 103 individuals over an average interval of 7 years to determine whether changes in these measures covaried. In-lab polysomnography was performed on members of an elderly cohort (Bay Area Sleep Cohort) on two separate occasions (Time 1, Time 2) with multiple nights of measurement typically made on each occasion. Results indicated that: a) SDB progressed over time in both men and women; b) changes in body weight were unrelated to the progression in SDB; c) relative declines in lung volumes (Forced Vital Capacity, Forced Expiratory Volume in 1.0 second) were associated with relative increases in SDB, with the effects slightly stronger in men. These data suggest that age-dependence in one commonly ascribed aging biomarker (lung function) were coupled to increments in SDB. Maintenance of healthy lung function into old age may confer some protective benefits in the development of age-dependent SDB.

General intelligence predicts memory change across sleep.

PubMed

Fenn, Kimberly M; Hambrick, David Z

2015-06-01

Psychometric intelligence (g) is often conceptualized as the capability for online information processing but it is also possible that intelligence may be related to offline processing of information. Here, we investigated the relationship between psychometric g and sleep-dependent memory consolidation. Participants studied paired-associates and were tested after a 12-hour retention interval that consisted entirely of wake or included a regular sleep phase. We calculated the number of word-pairs that were gained and lost across the retention interval. In a separate session, participants completed a battery of cognitive ability tests to assess g. In the wake group, g was not correlated with either memory gain or memory loss. In the sleep group, we found that g correlated positively with memory gain and negatively with memory loss. Participants with a higher level of general intelligence showed more memory gain and less memory loss across sleep. Importantly, the correlation between g and memory loss was significantly stronger in the sleep condition than in the wake condition, suggesting that the relationship between g and memory loss across time is specific to time intervals that include sleep. The present research suggests that g not only reflects the capability for online cognitive processing, but also reflects capability for offline processes that operate during sleep.

Lateral masking in cycling displays: the relative importance of separation, flanker duration, and interstimulus interval for object-mediated updating.

PubMed

Hein, Elisabeth; Moore, Cathleen M

2010-01-01

A central bar repeatedly presented in alternation with two flanking bars can lead to the disappearance of the central bar. Recently it has been suggested that this masking effect could be explained by object-mediated updating: the information from the central bar is integrated into the representation of the flankers, leading not only to the disappearance of the central bar as a separate object, but also to the perception of the flankers in apparent motion between their real position and the position of the central bar. This account suggests that the visibility of the central bar should depend on the same factors as those that influence the construction and maintenance of object representations. Therefore separation between central bar and flankers should not influence visibility as long as the time interval between them is adequate to make an interpretation of the scene in terms of one object moving from one location to the other possible location. We found that if the time interval between the central bar and the flankers is neither too short nor too long, the central bar becomes invisible even at large separations. These findings are inconsistent with traditional accounts of the cycling lateral masking displays in terms of local inhibitory mechanisms.

The Kepler Light Curves of V1504 Cygni and V344 Lyrae: A Study of the Outburst Properties

NASA Technical Reports Server (NTRS)

Cannizzo, John K.; Smale, Alan P.; Still, Martin D.; Wood, Matt A.; Howell, Steve B.

2011-01-01

We examine the Kepler light curves of V1504 Cyg and V344 Lyr, encompassing approximately 460 d at 1 min cadence. During this span each system exhibited approximately 40 outbursts, including four superoutbursts. We find that, in both systems, the normal outbursts lying between two superoutbursts increase in duration by a factor approximately 1.2 - 1.7, and then reset to a small value after the following superoutburst. In V344 Lyr the trend of quiescent intervals between normal outbursts is to increase to a local maximum about half way through the supercycle the interval from one superoutburst to the next - and then to decrease back to a small value by the time of the next superoutburst, whereas for V1504 Cyg the quiescent intervals are relatively constant during the supercycle. Both of these trends are inconsistent with the Osaki's thermal-tidal model, which robustly predicts a secular increase in the quiescent intervals between normal outbursts during a supercycle. Also, most of the normal outbursts have an asymmetric, fast-rise/slower-decline shape, which would be consistent with outbursts triggered at large radii. The exponential rate of decay of the plateau phase of the superoutbursts is 8 d mag(sup -1) for approximately 1504 Cyg and 12 d mag(sup -1) for V344 Lyr. This time scale gives a direct measure of the VISCOUS time scale III the outer accretion disk given the expectation that the entire disk is in the hot, viscous state during superoutburst. The resulting constraint on the Shakura-Sunyaev parameter, alpha(sub hot) approximately equal to 0.1, is consistent with the value inferred from the fast dwarf nova decays. By looking at the slow decay rate for superoutbursts, which occur in systems below the period gap, in combination with the slow decay rate in one long outburst above the period gap (in U Gem), we infer a steep dependence of the decay rate on orbital period for long outbursts. We argue that this relation implies a steep dependence of alpha(sub cold) on orbital period, which may be consistent with recent findings of Patterson, and is consistent with tidal torquing as being the dominant angular momentum transport mechanism in quiescent disks in interacting binary systems.

Anxiety profile in morphine-dependent and withdrawn rats: effect of voluntary exercise.

PubMed

Miladi-Gorji, Hossein; Rashidy-Pour, Ali; Fathollahi, Yaghoub

2012-01-18

Withdrawal from chronic opiates is associated with an increase in anxiogenic-like behaviours, but the anxiety profile in the morphine-dependent animals is not clear. Thus, one of the aims of the present study was to examine whether morphine-dependent rats would increase the expression of anxiogenic-like behaviours in novel and stressful conditions. Additionally, recent studies have shown that voluntary exercise can reduce anxiety levels in rodents. Therefore, another aim of this study was to examine the effect of voluntary exercise on the anxiety profile in both morphine-dependent animals and animals experiencing withdrawal. Rats were injected with bi-daily doses (10 mg/kg, at 12 h intervals) of morphine over a period of 10 days in which they were also allowed voluntary exercise. Following these injections, anxiety-like behaviours were tested in the elevated plus-maze (EPM) model and the light/dark (L/D) box. We found reductions in time spent in, and entries into, the EPM open arms and reductions in time spent in the lit side of the L/D box for both sedentary morphine-dependent and withdrawn rats as compared to the sedentary control groups. The exercising morphine-dependent and withdrawn rats exhibited an increase in EPM open arm time and entries and L/D box lit side time as compared with the sedentary control groups. We conclude that voluntary exercise decreases the severity of the anxiogenic-like behaviours in both morphine-dependent and withdrawn rats. Thus, voluntary exercise could be a potential natural method to ameliorate some of the deleterious behavioural consequences of opiate abuse. Copyright © 2011 Elsevier Inc. All rights reserved.

Ratio-based lengths of intervals to improve fuzzy time series forecasting.

PubMed

Huarng, Kunhuang; Yu, Tiffany Hui-Kuang

2006-04-01

The objective of this study is to explore ways of determining the useful lengths of intervals in fuzzy time series. It is suggested that ratios, instead of equal lengths of intervals, can more properly represent the intervals among observations. Ratio-based lengths of intervals are, therefore, proposed to improve fuzzy time series forecasting. Algebraic growth data, such as enrollments and the stock index, and exponential growth data, such as inventory demand, are chosen as the forecasting targets, before forecasting based on the various lengths of intervals is performed. Furthermore, sensitivity analyses are also carried out for various percentiles. The ratio-based lengths of intervals are found to outperform the effective lengths of intervals, as well as the arbitrary ones in regard to the different statistical measures. The empirical analysis suggests that the ratio-based lengths of intervals can also be used to improve fuzzy time series forecasting.

Estimating equivalence with quantile regression

USGS Publications Warehouse

Cade, B.S.

2011-01-01

Equivalence testing and corresponding confidence interval estimates are used to provide more enlightened statistical statements about parameter estimates by relating them to intervals of effect sizes deemed to be of scientific or practical importance rather than just to an effect size of zero. Equivalence tests and confidence interval estimates are based on a null hypothesis that a parameter estimate is either outside (inequivalence hypothesis) or inside (equivalence hypothesis) an equivalence region, depending on the question of interest and assignment of risk. The former approach, often referred to as bioequivalence testing, is often used in regulatory settings because it reverses the burden of proof compared to a standard test of significance, following a precautionary principle for environmental protection. Unfortunately, many applications of equivalence testing focus on establishing average equivalence by estimating differences in means of distributions that do not have homogeneous variances. I discuss how to compare equivalence across quantiles of distributions using confidence intervals on quantile regression estimates that detect differences in heterogeneous distributions missed by focusing on means. I used one-tailed confidence intervals based on inequivalence hypotheses in a two-group treatment-control design for estimating bioequivalence of arsenic concentrations in soils at an old ammunition testing site and bioequivalence of vegetation biomass at a reclaimed mining site. Two-tailed confidence intervals based both on inequivalence and equivalence hypotheses were used to examine quantile equivalence for negligible trends over time for a continuous exponential model of amphibian abundance. ?? 2011 by the Ecological Society of America.

Importance of the Time Interval between Bowel Preparation and Colonoscopy in Determining the Quality of Bowel Preparation for Full-Dose Polyethylene Glycol Preparation

PubMed Central

Kim, Tae Kyung; Kim, Hyung Wook; Kim, Su Jin; Ha, Jong Kun; Jang, Hyung Ha; Hong, Young Mi; Park, Su Bum; Choi, Cheol Woong; Kang, Dae Hwan

2014-01-01

Background/Aims The quality of bowel preparation (QBP) is the important factor in performing a successful colonoscopy. Several factors influencing QBP have been reported; however, some factors, such as the optimal preparation-to-colonoscopy time interval, remain controversial. This study aimed to determine the factors influencing QBP and the optimal time interval for full-dose polyethylene glycol (PEG) preparation. Methods A total of 165 patients who underwent colonoscopy from June 2012 to August 2012 were prospectively evaluated. The QBP was assessed using the Ottawa Bowel Preparation Scale (Ottawa) score according to several factors influencing the QBP were analyzed. Results Colonoscopies with a time interval of 5 to 6 hours had the best Ottawa score in all parts of the colon. Patients with time intervals of 6 hours or less had the better QBP than those with time intervals of more than 6 hours (p=0.046). In the multivariate analysis, the time interval (odds ratio, 1.897; 95% confidence interval, 1.006 to 3.577; p=0.048) was the only significant contributor to a satisfactory bowel preparation. Conclusions The optimal time was 5 to 6 hours for the full-dose PEG method, and the time interval was the only significant contributor to a satisfactory bowel preparation. PMID:25368750

What Could Be Causing Global Ozone Depletion

NASA Technical Reports Server (NTRS)

Singer, S. Fred

1990-01-01

The reported decline trend in global ozone between 1970 and 1986 may be in part an artifact of the analysis; the trend value appears to depend on the time interval selected for analysis--in relation to the 11-year solar cycle. If so, then the decline should diminish as one approaches solar maximum and includes data from 1987 to 1990. If the decline is real, its cause could be the result of natural and human factors other than just chlorofluorocarbons.

Celestial mechanics solutions that escape

NASA Astrophysics Data System (ADS)

Gingold, Harry; Solomon, Daniel

2017-08-01

We establish the existence of an open set of initial conditions through which pass solutions without singularities to Newton's gravitational equations in R3 on a semi-infinite interval in forward time, for which every pair of particles separates like At , A > 0, as t → ∞. The solutions are constructable as series with rapid uniform convergence and their asymptotic behavior to any order is prescribed. We show that this family of solutions depends on 6N parameters subject to certain constraints.

Isotemporal Substitution Paradigm for Physical Activity Epidemiology and Weight Change

PubMed Central

Willett, Walter C.; Hu, Frank B.; Ding, Eric L.

2009-01-01

For a fixed amount of time engaged in physical activity, activity choice may affect body weight differently depending partly on other activities’ displacement. Typical models used to evaluate effects of physical activity on body weight do not directly address these substitutions. An isotemporal substitution paradigm was developed as a new analytic model to study the time-substitution effects of one activity for another. In 1991–1997, the authors longitudinally examined the associations of discretionary physical activities, with varying activity displacements, with 6-year weight loss maintenance among 4,558 healthy, premenopausal US women who had previously lost >5% of their weight. Results of isotemporal substitution models indicated widely heterogeneous relations with each physical activity type (P < 0.001) depending on the displaced activities. Notably, whereas 30 minutes/day of brisk walking substituted for 30 minutes/day of jogging/running was associated with weight increase (1.57 kg, 95% confidence interval: 0.33, 2.82), brisk walking was associated with lower weight when substituted for slow walking (−1.14 kg, 95% confidence interval: −1.75, −0.53) and with even lower weight when substituted for TV watching. Similar heterogeneous relations with weight change were found for each activity type (TV watching, slow walking, brisk walking, jogging/running) when displaced by other activities across these various models. The isotemporal substitution paradigm may offer new insights for future public health recommendations. PMID:19584129

Interresponse Time Structures in Variable-Ratio and Variable-Interval Schedules

ERIC Educational Resources Information Center

Bowers, Matthew T.; Hill, Jade; Palya, William L.

2008-01-01

The interresponse-time structures of pigeon key pecking were examined under variable-ratio, variable-interval, and variable-interval plus linear feedback schedules. Whereas the variable-ratio and variable-interval plus linear feedback schedules generally resulted in a distinct group of short interresponse times and a broad distribution of longer…

Tachycardia-dependent augmentation of "notched J waves" in a general patient population without ventricular fibrillation or cardiac arrest: not a repolarization but a depolarization abnormality?

PubMed

Aizawa, Yoshifusa; Sato, Masahito; Kitazawa, Hitoshi; Aizawa, Yoshiyasu; Takatsuki, Seiji; Oda, Eiji; Okabe, Masaaki; Fukuda, Keiichi

2015-02-01

J waves can be observed in individuals of the general population, but electrocardiographic characteristics are poorly understood. The purpose of this study was to examine the J-wave dynamicity in a general patient population. The responses of J waves (>0.1 mV above the isoelectric line in 2 contiguous leads) to varying RR intervals were analyzed. Patients with aborted sudden cardiac death, documented ventricular fibrillation, or a family history of sudden cardiac death were excluded. The J-wave amplitude was measured at baseline, in beats with short RR intervals in conducted atrial premature beats (APBs) or atrial stimulation during the electrophysiology study, and in the beats next to APBs with prolonged RR intervals. Mainly notched J waves were identified in 94 of 701 (24.5%) general patients (13.4%), and APBs were present in 23 of 94 (24.5%) patients. The mean baseline amplitude of J waves was 0.20 ± 0.06 mV at the baseline RR interval of 853 ± 152 ms, 0.25 ± 0.11 mV at the RR interval in the conducted APB of 545 ± 133 ms (P = .0018), and 0.19 ± 0.08 mV at the RR interval of 1146 ± 314 ms (P = .3102). The clinical characteristics were not different between patients with and without tachycardia-dependent augmentation of J waves. Augmentation of J waves was confirmed by the electrophysiology study: 0.28 ± 0.12 mV vs 0.42 ± 0.11 mV at baseline and in the beats of atrial stimulation, respectively (P = .0001). However, no bradycardia-dependent augmentation (>0.05 mV) was observed. Such tachycardia-dependent augmentation can represent depolarization abnormality rather than repolarization abnormality. J waves in a general patient population were augmented at shorter RR intervals, but not at prolonged RR intervals. Mechanistically, conduction delay is most likely responsible for this. Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Microstructural indicators of transition mechanisms in time-dependent fatigue crack growth in nickel base superalloys

NASA Astrophysics Data System (ADS)

Heeter, Ann E.

Gas turbine engines are an important part of power generation in modern society, especially in the field of aerospace. Aerospace engines are design to last approximately 30 years and the engine components must be designed to survive for the life of the engine or to be replaced at regular intervals to ensure consumer safety. Fatigue crack growth analysis is a vital component of design for an aerospace component. Crack growth modeling and design methods date back to an origin around 1950 with a high rate of accuracy. The new generation of aerospace engines is designed to be efficient as possible and require higher operating temperatures than ever seen before in previous generations. These higher temperatures place more stringent requirements on the material crack growth performance under creep and time dependent conditions. Typically the types of components which are subject to these requirements are rotating disk components which are made from advanced materials such as nickel base superalloys. Traditionally crack growth models have looked at high temperature crack growth purely as a function of temperature and assumed that all crack growth was either controlled by a cycle dependent or time dependent mechanism. This new analysis is trying to evaluate the transition between cycle-dependent and time-dependent mechanism and the microstructural markers that characterize this transitional behavior. The physical indications include both the fracture surface morphology as well as the shape of the crack front. The research will evaluate whether crack tunneling occurs and whether it consistently predicts a transition from cycle-dependent crack growth to time-dependent crack growth. The study is part of a larger research program trying to include the effects of geometry, mission profile and environmental effects, in addition to temperature effects, as a part of the overall crack growth system. The outcome will provide evidence for various transition types and correlate those physical attributes back to the material mechanisms to improve predictive modeling capability.

Mitigating the effects of in-vehicle distractions through use of the Psychological Refractory Period paradigm.

PubMed

Hibberd, Daryl L; Jamson, Samantha L; Carsten, Oliver M J

2013-01-01

Modern driving involves frequent and potentially detrimental interactions with distracting in-vehicle tasks. Distraction has been shown to slow brake reaction time and decrease lateral and longitudinal vehicle control. It is likely that these negative effects will become more prevalent in the future as advances are made in the functionality, availability, and number of in-vehicle systems. This paper addresses this problem by considering ways to manage in-vehicle task presentation to mitigate their distracting effects. A driving simulator experiment using 48 participants was performed to investigate the existence of the Psychological Refractory Period in the driving context and its effect on braking performance. Drivers were exposed to lead vehicle braking events in isolation (single-task) and with a preceding surrogate in-vehicle task (dual-task). In dual-task scenarios, the time interval between the in-vehicle and braking tasks was manipulated. Brake reaction time increased when drivers were distracted. The in-vehicle task interfered with the performance of the braking task in a manner that was dependent on the interval between the two tasks, with slower reactions following a shorter inter-task interval. This is the Psychological Refractory Period effect. These results have implications for driver safety during in-vehicle distraction. The findings are used to develop recommendations regarding the timing of in-vehicle task presentation so as to reduce their potentially damaging effects on braking performance. In future, these guidelines could be incorporated into a driver workload management system to minimise the opportunity for a driver to be distracted from the ongoing driving task. Copyright © 2012 Elsevier Ltd. All rights reserved.

Not All Prehospital Time is Equal: Influence of Scene Time on Mortality

PubMed Central

Brown, Joshua B.; Rosengart, Matthew R.; Forsythe, Raquel M.; Reynolds, Benjamin R.; Gestring, Mark L.; Hallinan, William M.; Peitzman, Andrew B.; Billiar, Timothy R.; Sperry, Jason L.

2016-01-01

Background Trauma is time-sensitive and minimizing prehospital (PH) time is appealing. However, most studies have not linked increasing PH time with worse outcomes, as raw PH times are highly variable. It is unclear whether specific PH time patterns affect outcomes. Our objective was to evaluate the association of PH time interval distribution with mortality. Methods Patients transported by EMS in the Pennsylvania trauma registry 2000-2013 with total prehospital time (TPT)≥20min were included. TPT was divided into three PH time intervals: response, scene, and transport time. The number of minutes in each PH time interval was divided by TPT to determine the relative proportion each interval contributed to TPT. A prolonged interval was defined as any one PH interval contributing ≥50% of TPT. Patients were classified by prolonged PH interval or no prolonged PH interval (all intervals<50% of TPT). Patients were matched for TPT and conditional logistic regression determined the association of mortality with PH time pattern, controlling for confounders. PH interventions were explored as potential mediators, and prehospital triage criteria used identify patients with time-sensitive injuries. Results There were 164,471 patients included. Patients with prolonged scene time had increased odds of mortality (OR 1.21; 95%CI 1.02–1.44, p=0.03). Prolonged response, transport, and no prolonged interval were not associated with mortality. When adjusting for mediators including extrication and PH intubation, prolonged scene time was no longer associated with mortality (OR 1.06; 0.90–1.25, p=0.50). Together these factors mediated 61% of the effect between prolonged scene time and mortality. Mortality remained associated with prolonged scene time in patients with hypotension, penetrating injury, and flail chest. Conclusions Prolonged scene time is associated with increased mortality. PH interventions partially mediate this association. Further study should evaluate whether these interventions drive increased mortality because they prolong scene time or by another mechanism, as reducing scene time may be a target for intervention. Level of Evidence IV, prognostic study PMID:26886000

Risk of metachronous ovarian cancer after ovarian conservation in young women with stage I cervical cancer.

PubMed

Matsuo, Koji; Machida, Hiroko; Horowitz, Max P; Shahzad, Mian M K; Guntupalli, Saketh R; Roman, Lynda D; Wright, Jason D

2017-11-01

While there is an increasing trend of ovarian conservation at the time of surgical treatment for young women with stage I cervical cancer, the risk for subsequent ovarian cancer after ovarian conservation has not been well studied. We sought to examine the incidence of and risk factors for metachronous ovarian cancer among young women with stage I cervical cancer who had ovarian conservation at the time of hysterectomy. The Surveillance, Epidemiology, and End Results Program was used to identify women aged <50 years who underwent hysterectomy with ovarian conservation for stage I cervical cancer from 1983 through 2013 (n = 4365). Time-dependent analysis was performed for ovarian cancer risk after cervical cancer diagnosis. Mean age at cervical cancer diagnosis was 37 years, and the majority of patients had stage IA disease (68.2%) and squamous histology (72.9%). Median follow-up time was 10.8 years, and there were 13 women who developed metachronous ovarian cancer. The 10- and 20-year cumulative incidences of metachronous ovarian cancer were 0.2% (95% confidence interval, 0.1-0.4) and 0.5% (95% confidence interval, 0.2-0.8), respectively. Mean age at the time of diagnosis of metachronous ovarian cancer was 47.5 years, and stage III-IV disease was seen in 55.6%. Age (≥45 vs <45 years, hazard ratio, 4.22; 95% confidence interval, 1.16-15.4; P = .018), ethnicity (non-white vs white, hazard ratio, 4.29; 95% confidence interval, 1.31-14.0; P = .009), cervical cancer histology (adenocarcinoma or adenosquamous vs squamous, hazard ratio, 3.50; 95% confidence interval, 1.17-10.5; P = .028), and adjuvant radiotherapy use (yes vs no, hazard ratio, 3.69; 95% confidence interval, 1.01-13.4; P = .034) were significantly associated with metachronous ovarian cancer risk. The presence of multiple risk factors was associated with a significantly increased risk of metachronous ovarian cancer compared to the no risk factor group: 1 risk factor (hazard ratio range, 2.96-8.43), 2 risk factors (hazard ratio range, 16.6-31.0), and 3-4 risk factors (hazard ratio range, 62.3-109), respectively. Metachronous ovarian cancer risk after ovarian conservation for women with stage I cervical cancer is <1%. Older age, non-white ethnicity, adenocarcinoma or adenosquamous histology, and adjuvant radiotherapy may be associated with an increased metachronous ovarian cancer risk. Copyright © 2017 Elsevier Inc. All rights reserved.

Time interval measurement device based on surface acoustic wave filter excitation, providing 1 ps precision and stability.

PubMed

Panek, Petr; Prochazka, Ivan

2007-09-01

This article deals with the time interval measurement device, which is based on a surface acoustic wave (SAW) filter as a time interpolator. The operating principle is based on the fact that a transversal SAW filter excited by a short pulse can generate a finite signal with highly suppressed spectra outside a narrow frequency band. If the responses to two excitations are sampled at clock ticks, they can be precisely reconstructed from a finite number of samples and then compared so as to determine the time interval between the two excitations. We have designed and constructed a two-channel time interval measurement device which allows independent timing of two events and evaluation of the time interval between them. The device has been constructed using commercially available components. The experimental results proved the concept. We have assessed the single-shot time interval measurement precision of 1.3 ps rms that corresponds to the time of arrival precision of 0.9 ps rms in each channel. The temperature drift of the measured time interval on temperature is lower than 0.5 ps/K, and the long term stability is better than +/-0.2 ps/h. These are to our knowledge the best values reported for the time interval measurement device. The results are in good agreement with the error budget based on the theoretical analysis.

Chromosome dynamics in the yeast interphase nucleus.

PubMed

Heun, P; Laroche, T; Shimada, K; Furrer, P; Gasser, S M

2001-12-07

Little is known about the dynamics of chromosomes in interphase nuclei. By tagging four chromosomal regions with a green fluorescent protein fusion to lac repressor, we monitored the movement and subnuclear position of specific sites in the yeast genome, sampling at short time intervals. We found that early and late origins of replication are highly mobile in G1 phase, frequently moving at or faster than 0.5 micrometers/10 seconds, in an energy-dependent fashion. The rapid diffusive movement of chromatin detected in G1 becomes constrained in S phase through a mechanism dependent on active DNA replication. In contrast, telomeres and centromeres provide replication-independent constraint on chromatin movement in both G1 and S phases.

Statistical evaluation of time-dependent metabolite concentrations: estimation of post-mortem intervals based on in situ 1H-MRS of the brain.

PubMed

Scheurer, Eva; Ith, Michael; Dietrich, Daniel; Kreis, Roland; Hüsler, Jürg; Dirnhofer, Richard; Boesch, Chris

2005-05-01

Knowledge of the time interval from death (post-mortem interval, PMI) has an enormous legal, criminological and psychological impact. Aiming to find an objective method for the determination of PMIs in forensic medicine, 1H-MR spectroscopy (1H-MRS) was used in a sheep head model to follow changes in brain metabolite concentrations after death. Following the characterization of newly observed metabolites (Ith et al., Magn. Reson. Med. 2002; 5: 915-920), the full set of acquired spectra was analyzed statistically to provide a quantitative estimation of PMIs with their respective confidence limits. In a first step, analytical mathematical functions are proposed to describe the time courses of 10 metabolites in the decomposing brain up to 3 weeks post-mortem. Subsequently, the inverted functions are used to predict PMIs based on the measured metabolite concentrations. Individual PMIs calculated from five different metabolites are then pooled, being weighted by their inverse variances. The predicted PMIs from all individual examinations in the sheep model are compared with known true times. In addition, four human cases with forensically estimated PMIs are compared with predictions based on single in situ MRS measurements. Interpretation of the individual sheep examinations gave a good correlation up to 250 h post-mortem, demonstrating that the predicted PMIs are consistent with the data used to generate the model. Comparison of the estimated PMIs with the forensically determined PMIs in the four human cases shows an adequate correlation. Current PMI estimations based on forensic methods typically suffer from uncertainties in the order of days to weeks without mathematically defined confidence information. In turn, a single 1H-MRS measurement of brain tissue in situ results in PMIs with defined and favorable confidence intervals in the range of hours, thus offering a quantitative and objective method for the determination of PMIs. Copyright 2004 John Wiley & Sons, Ltd.

Particle dynamics in a viscously decaying cat's eye: The effect of finite Schmidt numbers

NASA Astrophysics Data System (ADS)

Newton, P. K.; Meiburg, Eckart

1991-05-01

The dynamics and mixing of passive marker particles for the model problem of a decaying cat's eye flow is studied. The flow field corresponds to Stuart's one-parameter family of solutions [J. Fluid Mech. 29, 417 (1967)]. It is time dependent as a result of viscosity, which is modeled by allowing the free parameter to depend on time according to the self-similar solution of the Navier-Stokes equations for an isolated point vortex. Particle diffusion is numerically simulated by a random walk model. While earlier work had shown that, for small values of time over Reynolds number t/Re≪1, the interval length characterizing the formation of lobes of fluid escaping from the cat's eye scales as Re-1/2, the present study shows that, for the case of diffusive effects and t/Pe≪1, the scaling follows Pe-1/4. A simple argument, taking into account streamline convergence and divergence in different parts of the flow field, explains the Pe-1/4 scaling.

Bacterial detection using bacteriophages and gold nanorods by following time-dependent changes in Raman spectral signals.

PubMed

Moghtader, Farzaneh; Tomak, Aysel; Zareie, Hadi M; Piskin, Erhan

2018-03-27

This study attemps to develop bacterial detection strategies using bacteriophages and gold nanorods (GNRs) by Raman spectral analysis. Escherichia coli was selected as the target and its specific phage was used as the bioprobe. Target bacteria and phages were propagated/purified by traditional techniques. GNRs were synthesized by using hexadecyltrimethyl ammonium bromide (CTAB) as stabilizer. A two-step detection strategy was applied: Firstly, the target bacteria were interacted with GNRs in suspensions, and then they were dropped onto silica substrates for detection. It was possible to obtain clear surface-enchanced Raman spectroscopy (SERS) peaks of the target bacteria, even without using phages. In the second step, the phage nanoemulsions were droped onto the bacterial-GNRs complexes on those surfaces and time-dependent changes in the Raman spectra were monitored at different time intervals upto 40 min. These results demonstrated that how one can apply phages with plasmonic nanoparticles for detection of pathogenic bacteria very effectively in a quite simple test.

Effect of intravenous gadolinium-DTPA on diffusion-weighted imaging of brain tumors: a short temporal interval assessment.

PubMed

Li, Xiang; Qu, Jin-Rong; Luo, Jun-Peng; Li, Jing; Zhang, Hong-Kai; Shao, Nan-Nan; Kwok, Keith; Zhang, Shou-Ning; Li, Yan-le; Liu, Cui-Cui; Zee, Chi-Shing; Li, Hai-Liang

2014-09-01

To determine the effect of intravenous administration of gadolinium (Gd) contrast medium (Gd-DTPA) on diffusion-weighted imaging (DWI) for the evaluation of normal brain parenchyma vs. brain tumor following a short temporal interval. Forty-four DWI studies using b values of 0 and 1000 s/mm(2) were performed before, immediately after, 1 min after, 3 min after, and 5 min after the administration of Gd-DTPA on 62 separate lesions including 15 meningioma, 17 glioma and 30 metastatic lesions. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and apparent diffusion coefficient (ADC) values of the brain tumor lesions and normal brain tissues were measured on pre- and postcontrast images. Statistical analysis using paired t-test between precontrast and postcontrast data were obtained on three brain tumors and normal brain tissue. The SNR and CNR of brain tumors and the SNR of normal brain tissue showed no statistical differences between pre- and postcontrast (P > 0.05). The ADC values on the three cases of brain tumors demonstrated significant initial increase on the immediate time point (P < 0.01) and decrease on following the 1 min time point (P < 0.01) after contrast. Significant decrease of ADC value was still found at 3min and 5min time point in the meningioma group (P < 0.01) with gradual normalization over time. The ADC values of normal brain tissues demonstrated significant initial elevation on the immediately postcontrast DWI sequence (P < 0.01). Contrast medium can cause a slight but statistically significant change on the ADC value within a short temporal interval after the contrast administration. The effect is both time and lesion-type dependent. © 2013 Wiley Periodicals, Inc.

High-intensity Interval Training in Different Exercise Modes: Lessons from Time to Exhaustion.

PubMed

Sousa, Ana Catarina; Fernandes, Ricardo J; Boas, Joao Paulo Vilas; Figueiredo, Pedro

2018-06-20

To provide information for high-intensity interval training (HIIT) load, we compared the temporal variables of VO 2 response at, and after, a time sustained at the exercise intensity corresponding to VO 2max (Tlim) in different exercise modes. Forty-five trained male swimmers (11), rowers (13), runners (10) and cyclists (11) completed an incremental protocol to determine the velocity (vVO 2max ) or power (wVO 2max ) at VO 2max and a square wave exercise from rest to 100% of vVO 2max /wVO 2max . The temporal variables of VO 2 response were examined using a breath-by-breath gas analyzer. VO 2 responses were not different between exercise modes, except for the percentage of VO 2max at 50% of Tlim, which was ~6% higher in rowing compared to cycling (97.70±2.90 vs 92.40±5.69%, p =0.013). During the recovery period, both swimmers and rowers evidenced higher percentages of VO 2max compared to cyclists at 30 s (65.1±10.4 and 65.7±5.6 vs 52.7±5.6%) and 60 s (41.7±10.8 and 38.4±5.4 vs 30.4±1.8%) time periods, all for p< 0.01. Furthermore, swimmers presented higher time values to reach 50% VO 2max compared to runners and cyclists (51.1±15.6 vs 38.1±6.7 and 33.8±4.7%; p <0.001). When training at 100% of VO 2max intensity, fixed intervals for HIIT could be set freely. However, recovery periods based on time or intensity are exercise-mode dependent. © Georg Thieme Verlag KG Stuttgart · New York.

Algorithm for Compressing Time-Series Data

NASA Technical Reports Server (NTRS)

Hawkins, S. Edward, III; Darlington, Edward Hugo

2012-01-01

An algorithm based on Chebyshev polynomials effects lossy compression of time-series data or other one-dimensional data streams (e.g., spectral data) that are arranged in blocks for sequential transmission. The algorithm was developed for use in transmitting data from spacecraft scientific instruments to Earth stations. In spite of its lossy nature, the algorithm preserves the information needed for scientific analysis. The algorithm is computationally simple, yet compresses data streams by factors much greater than two. The algorithm is not restricted to spacecraft or scientific uses: it is applicable to time-series data in general. The algorithm can also be applied to general multidimensional data that have been converted to time-series data, a typical example being image data acquired by raster scanning. However, unlike most prior image-data-compression algorithms, this algorithm neither depends on nor exploits the two-dimensional spatial correlations that are generally present in images. In order to understand the essence of this compression algorithm, it is necessary to understand that the net effect of this algorithm and the associated decompression algorithm is to approximate the original stream of data as a sequence of finite series of Chebyshev polynomials. For the purpose of this algorithm, a block of data or interval of time for which a Chebyshev polynomial series is fitted to the original data is denoted a fitting interval. Chebyshev approximation has two properties that make it particularly effective for compressing serial data streams with minimal loss of scientific information: The errors associated with a Chebyshev approximation are nearly uniformly distributed over the fitting interval (this is known in the art as the "equal error property"); and the maximum deviations of the fitted Chebyshev polynomial from the original data have the smallest possible values (this is known in the art as the "min-max property").

Mechanism-based pharmacokinetic-pharmacodynamic modeling of the antinociceptive effect of buprenorphine in healthy volunteers.

PubMed

Yassen, Ashraf; Olofsen, Erik; Romberg, Raymonda; Sarton, Elise; Danhof, Meindert; Dahan, Albert

2006-06-01

The objective of this investigation was to characterize the pharmacokinetic-pharmacodynamic relation of buprenorphine's antinociceptive effect in healthy volunteers. Data on the time course of the antinociceptive effect after intravenous administration of 0.05-0.6 mg/70 kg buprenorphine in healthy volunteers was analyzed in conjunction with plasma concentrations by nonlinear mixed-effects analysis. A three-compartment pharmacokinetic model best described the concentration time course. Four structurally different pharmacokinetic-pharmacodynamic models were evaluated for their appropriateness to describe the time course of buprenorphine's antinociceptive effect: (1) E(max) model with an effect compartment model, (2) "power" model with an effect compartment model, (3) receptor association-dissociation model with a linear transduction function, and (4) combined biophase equilibration/receptor association-dissociation model with a linear transduction function. The latter pharmacokinetic-pharmacodynamic model described the time course of effect best and was used to explain time dependencies in buprenorphine's pharmacodynamics. The model converged, yielding precise estimation of the parameters characterizing hysteresis and the relation between relative receptor occupancy and antinociceptive effect. The rate constant describing biophase equilibration (k(eo)) was 0.00447 min(-1) (95% confidence interval, 0.00299-0.00595 min(-1)). The receptor dissociation rate constant (k(off)) was 0.0785 min(-1) (95% confidence interval, 0.0352-0.122 min(-1)), and k(on) was 0.0631 ml . ng(-1) . min(-1) (95% confidence interval, 0.0390-0.0872 ml . ng(-1) . min(-1)). This is consistent with observations in rats, suggesting that the rate-limiting step in the onset and offset of the antinociceptive effect is biophase distribution rather than slow receptor association-dissociation. In the dose range studied, no saturation of receptor occupancy occurred explaining the lack of a ceiling effect for antinociception.

Interval Timing Accuracy and Scalar Timing in C57BL/6 Mice

PubMed Central

Buhusi, Catalin V.; Aziz, Dyana; Winslow, David; Carter, Rickey E.; Swearingen, Joshua E.; Buhusi, Mona C.

2010-01-01

In many species, interval timing behavior is accurate—appropriate estimated durations—and scalar—errors vary linearly with estimated durations. While accuracy has been previously examined, scalar timing has not been yet clearly demonstrated in house mice (Mus musculus), raising concerns about mouse models of human disease. We estimated timing accuracy and precision in C57BL/6 mice, the most used background strain for genetic models of human disease, in a peak-interval procedure with multiple intervals. Both when timing two intervals (Experiment 1) or three intervals (Experiment 2), C57BL/6 mice demonstrated varying degrees of timing accuracy. Importantly, both at individual and group level, their precision varied linearly with the subjective estimated duration. Further evidence for scalar timing was obtained using an intraclass correlation statistic. This is the first report of consistent, reliable scalar timing in a sizable sample of house mice, thus validating the PI procedure as a valuable technique, the intraclass correlation statistic as a powerful test of the scalar property, and the C57BL/6 strain as a suitable background for behavioral investigations of genetically engineered mice modeling disorders of interval timing. PMID:19824777

Time dependent pre-treatment EPID dosimetry for standard and FFF VMAT.

PubMed

Podesta, Mark; Nijsten, Sebastiaan M J J G; Persoon, Lucas C G G; Scheib, Stefan G; Baltes, Christof; Verhaegen, Frank

2014-08-21

Methods to calibrate Megavoltage electronic portal imaging devices (EPIDs) for dosimetry have been previously documented for dynamic treatments such as intensity modulated radiotherapy (IMRT) using flattened beams and typically using integrated fields. While these methods verify the accumulated field shape and dose, the dose rate and differential fields remain unverified. The aim of this work is to provide an accurate calibration model for time dependent pre-treatment dose verification using amorphous silicon (a-Si) EPIDs in volumetric modulated arc therapy (VMAT) for both flattened and flattening filter free (FFF) beams. A general calibration model was created using a Varian TrueBeam accelerator, equipped with an aS1000 EPID, for each photon spectrum 6 MV, 10 MV, 6 MV-FFF, 10 MV-FFF. As planned VMAT treatments use control points (CPs) for optimization, measured images are separated into corresponding time intervals for direct comparison with predictions. The accuracy of the calibration model was determined for a range of treatment conditions. Measured and predicted CP dose images were compared using a time dependent gamma evaluation using criteria (3%, 3 mm, 0.5 sec). Time dependent pre-treatment dose verification is possible without an additional measurement device or phantom, using the on-board EPID. Sufficient data is present in trajectory log files and EPID frame headers to reliably synchronize and resample portal images. For the VMAT plans tested, significantly more deviation is observed when analysed in a time dependent manner for FFF and non-FFF plans than when analysed using only the integrated field. We show EPID-based pre-treatment dose verification can be performed on a CP basis for VMAT plans. This model can measure pre-treatment doses for both flattened and unflattened beams in a time dependent manner which highlights deviations that are missed in integrated field verifications.

Assessment of cardiac time intervals using high temporal resolution real-time spiral phase contrast with UNFOLDed-SENSE.

PubMed

Kowalik, Grzegorz T; Knight, Daniel S; Steeden, Jennifer A; Tann, Oliver; Odille, Freddy; Atkinson, David; Taylor, Andrew; Muthurangu, Vivek

2015-02-01

To develop a real-time phase contrast MR sequence with high enough temporal resolution to assess cardiac time intervals. The sequence utilized spiral trajectories with an acquisition strategy that allowed a combination of temporal encoding (Unaliasing by fourier-encoding the overlaps using the temporal dimension; UNFOLD) and parallel imaging (Sensitivity encoding; SENSE) to be used (UNFOLDed-SENSE). An in silico experiment was performed to determine the optimum UNFOLD filter. In vitro experiments were carried out to validate the accuracy of time intervals calculation and peak mean velocity quantification. In addition, 15 healthy volunteers were imaged with the new sequence, and cardiac time intervals were compared to reference standard Doppler echocardiography measures. For comparison, in silico, in vitro, and in vivo experiments were also carried out using sliding window reconstructions. The in vitro experiments demonstrated good agreement between real-time spiral UNFOLDed-SENSE phase contrast MR and the reference standard measurements of velocity and time intervals. The protocol was successfully performed in all volunteers. Subsequent measurement of time intervals produced values in keeping with literature values and good agreement with the gold standard echocardiography. Importantly, the proposed UNFOLDed-SENSE sequence outperformed the sliding window reconstructions. Cardiac time intervals can be successfully assessed with UNFOLDed-SENSE real-time spiral phase contrast. Real-time MR assessment of cardiac time intervals may be beneficial in assessment of patients with cardiac conditions such as diastolic dysfunction. © 2014 Wiley Periodicals, Inc.

The impacts of marijuana dispensary density and neighborhood ecology on marijuana abuse and dependence

PubMed Central

Mair, Christina; Freisthler, Bridget; Ponicki, William R.; Gaidus, Andrew

2015-01-01

Background As an increasing number of states liberalize cannabis use and develop laws and local policies, it is essential to better understand the impacts of neighborhood ecology and marijuana dispensary density on marijuana use, abuse, and dependence. We investigated associations between marijuana abuse/dependence hospitalizations and community demographic and environmental conditions from 2001–2012 in California, as well as cross-sectional associations between local and adjacent marijuana dispensary densities and marijuana hospitalizations. Methods We analyzed panel population data relating hospitalizations coded for marijuana abuse or dependence and assigned to residential ZIP codes in California from 2001 through 2012 (20,219 space-time units) to ZIP code demographic and ecological characteristics. Bayesian space-time misalignment models were used to account for spatial variations in geographic unit definitions over time, while also accounting for spatial autocorrelation using conditional autoregressive priors. We also analyzed cross-sectional associations between marijuana abuse/dependence and the density of dispensaries in local and spatially adjacent ZIP codes in 2012. Results An additional one dispensary per square mile in a ZIP code was cross-sectionally associated with a 6.8% increase in the number of marijuana hospitalizations (95% credible interval 1.033, 1.105) with a marijuana abuse/dependence code. Other local characteristics, such as the median household income and age and racial/ethnic distributions, were associated with marijuana hospitalizations in cross-sectional and panel analyses. Conclusions Prevention and intervention programs for marijuana abuse and dependence may be particularly essential in areas of concentrated disadvantage. Policy makers may want to consider regulations that limit the density of dispensaries. PMID:26154479

Spatial Distribution of the Coefficient of Variation for the Paleo-Earthquakes in Japan

NASA Astrophysics Data System (ADS)

Nomura, S.; Ogata, Y.

2015-12-01

Renewal processes, point prccesses in which intervals between consecutive events are independently and identically distributed, are frequently used to describe this repeating earthquake mechanism and forecast the next earthquakes. However, one of the difficulties in applying recurrent earthquake models is the scarcity of the historical data. Most studied fault segments have few, or only one observed earthquake that often have poorly constrained historic and/or radiocarbon ages. The maximum likelihood estimate from such a small data set can have a large bias and error, which tends to yield high probability for the next event in a very short time span when the recurrence intervals have similar lengths. On the other hand, recurrence intervals at a fault depend on the long-term slip rate caused by the tectonic motion in average. In addition, recurrence times are also fluctuated by nearby earthquakes or fault activities which encourage or discourage surrounding seismicity. These factors have spatial trends due to the heterogeneity of tectonic motion and seismicity. Thus, this paper introduces a spatial structure on the key parameters of renewal processes for recurrent earthquakes and estimates it by using spatial statistics. Spatial variation of mean and variance parameters of recurrence times are estimated in Bayesian framework and the next earthquakes are forecasted by Bayesian predictive distributions. The proposal model is applied for recurrent earthquake catalog in Japan and its result is compared with the current forecast adopted by the Earthquake Research Committee of Japan.

Gravity and Neuronal Adaptation. Neurophysiology of Reflexes from Hypo- to Hypergravity Conditions

NASA Astrophysics Data System (ADS)

Ritzmann, Ramona; Krause, Anne; Freyler, Kathrin; Gollhofer, Albert

2017-02-01

Introduction: For interplanetary and orbital missions in human space flight, knowledge about the gravity-sensitivity of the central nervous system (CNS) is required. The objective of this study was to assess neurophysiological correlates in variable hetero gravity conditions in regard to their timing and shaping. Methods: In ten subjects, peripheral nerve stimulation was used to elicit H-reflexes and M-waves in the M. soleus in Lunar, Martian, Earth and hypergravity. Gravity-dependencies were described by means of reflex latency, inter-peak-interval, duration, stimulation threshold and maximal amplitudes. Experiments were executed during the CNES/ESA/DLR JEPPFs. Results: H-reflex latency, inter-peak-interval and duration decreased with increasing gravitation (P<0.05); likewise, M-wave inter-peak-interval was diminished and latency prolonged with increasing gravity (P<0.05). Stimulation threshold of H-reflexes and M-waves decreased (P<0.05) while maximal amplitudes increased with an increase in gravitation (P<0.05). Conclusion: Adaptations in neurophysiological correlates in hetero gravity are associated with a shift in timing and shaping. For the first time, our results indicate that synaptic and axonal nerve conduction velocity as well as axonal and spinal excitability are diminished with reduced gravitational forces on the Moon and Mars and gradually increased when gravitation is progressively augmented up to hypergravity. Interrelated with the adaptation in threshold we conclude that neuronal circuitries are significantly affected by gravitation. As a consequence, movement control and countermeasures may be biased in extended space missions involving transitions between different force environments.

Electropermeabilization by uni- or bipolar nanosecond electric pulses: The impact of extracellular conductivity.

PubMed

Gianulis, Elena C; Casciola, Maura; Xiao, Shu; Pakhomova, Olga N; Pakhomov, Andrei G

2018-02-01

Cellular effects caused by nanosecond electric pulses (nsEP) can be reduced by an electric field reversal, a phenomenon known as bipolar cancellation. The reason for this cancellation effect remains unknown. We hypothesized that assisted membrane discharge is the mechanism for bipolar cancellation. CHO-K1 cells bathed in high (16.1mS/cm; HCS) or low (1.8mS/cm; LCS) conductivity solutions were exposed to either one unipolar (300-ns) or two opposite polarity (300+300-ns; bipolar) nsEP (4-40kV/cm) with increasing interpulse intervals (0.1-50μs). Time-lapse YO-PRO-1 (YP) uptake revealed enhanced membrane permeabilization in LCS compared to HCS at all tested voltages. The time-dependence of bipolar cancellation was similar in both solutions, using either identical (22kV/cm) or isoeffective nsEP treatments (12 and 32kV/cm for LCS and HCS, respectively). However, cancellation was significantly stronger in LCS when the bipolar nsEP had no, or very short (<1μs), interpulse intervals. Finally, bipolar cancellation was still present with interpulse intervals as long as 50μs, beyond the time expected for membrane discharge. Our findings do not support assisted membrane discharge as the mechanism for bipolar cancellation. Instead they exemplify the sustained action of nsEP that can be reversed long after the initial stimulus. Copyright © 2017 Elsevier B.V. All rights reserved.

Multi-Residential Activity Labelling in Smart Homes with Wearable Tags Using BLE Technology

PubMed Central

Mokhtari, Ghassem; Zhang, Qing; Karunanithi, Mohanraj

2018-01-01

Smart home platforms show promising outcomes to provide a better quality of life for residents in their homes. One of the main challenges that exists with these platforms in multi-residential houses is activity labeling. As most of the activity sensors do not provide any information regarding the identity of the person who triggers them, it is difficult to label the sensor events in multi-residential smart homes. To deal with this challenge, individual localization in different areas can be a promising solution. The localization information can be used to automatically label the activity sensor data to individuals. Bluetooth low energy (BLE) is a promising technology for this application due to how easy it is to implement and its low energy footprint. In this approach, individuals wear a tag that broadcasts its unique identity (ID) in certain time intervals, while fixed scanners listen to the broadcasting packet to localize the tag and the individual. However, the localization accuracy of this method depends greatly on different settings of broadcasting signal strength, and the time interval of BLE tags. To achieve the best localization accuracy, this paper studies the impacts of different advertising time intervals and power levels, and proposes an efficient and applicable algorithm to select optimal value settings of BLE sensors. Moreover, it proposes an automatic activity labeling method, through integrating BLE localization information and ambient sensor data. The applicability and effectiveness of the proposed structure is also demonstrated in a real multi-resident smart home scenario. PMID:29562666

Multi-Residential Activity Labelling in Smart Homes with Wearable Tags Using BLE Technology.

PubMed

Mokhtari, Ghassem; Anvari-Moghaddam, Amjad; Zhang, Qing; Karunanithi, Mohanraj

2018-03-19

Smart home platforms show promising outcomes to provide a better quality of life for residents in their homes. One of the main challenges that exists with these platforms in multi-residential houses is activity labeling. As most of the activity sensors do not provide any information regarding the identity of the person who triggers them, it is difficult to label the sensor events in multi-residential smart homes. To deal with this challenge, individual localization in different areas can be a promising solution. The localization information can be used to automatically label the activity sensor data to individuals. Bluetooth low energy (BLE) is a promising technology for this application due to how easy it is to implement and its low energy footprint. In this approach, individuals wear a tag that broadcasts its unique identity (ID) in certain time intervals, while fixed scanners listen to the broadcasting packet to localize the tag and the individual. However, the localization accuracy of this method depends greatly on different settings of broadcasting signal strength, and the time interval of BLE tags. To achieve the best localization accuracy, this paper studies the impacts of different advertising time intervals and power levels, and proposes an efficient and applicable algorithm to select optimal value settings of BLE sensors. Moreover, it proposes an automatic activity labeling method, through integrating BLE localization information and ambient sensor data. The applicability and effectiveness of the proposed structure is also demonstrated in a real multi-resident smart home scenario.

Relative time sharing: new findings and an extension of the resource allocation model of temporal processing.

PubMed

Buhusi, Catalin V; Meck, Warren H

2009-07-12

Individuals time as if using a stopwatch that can be stopped or reset on command. Here, we review behavioural and neurobiological data supporting the time-sharing hypothesis that perceived time depends on the attentional and memory resources allocated to the timing process. Neuroimaging studies in humans suggest that timekeeping tasks engage brain circuits typically involved in attention and working memory. Behavioural, pharmacological, lesion and electrophysiological studies in lower animals support this time-sharing hypothesis. When subjects attend to a second task, or when intruder events are presented, estimated durations are shorter, presumably due to resources being taken away from timing. Here, we extend the time-sharing hypothesis by proposing that resource reallocation is proportional to the perceived contrast, both in temporal and non-temporal features, between intruders and the timed events. New findings support this extension by showing that the effect of an intruder event is dependent on the relative duration of the intruder to the intertrial interval. The conclusion is that the brain circuits engaged by timekeeping comprise not only those primarily involved in time accumulation, but also those involved in the maintenance of attentional and memory resources for timing, and in the monitoring and reallocation of those resources among tasks.

VARIABLE TIME-INTERVAL GENERATOR

DOEpatents

Gross, J.E.

1959-10-31

This patent relates to a pulse generator and more particularly to a time interval generator wherein the time interval between pulses is precisely determined. The variable time generator comprises two oscillators with one having a variable frequency output and the other a fixed frequency output. A frequency divider is connected to the variable oscillator for dividing its frequency by a selected factor and a counter is used for counting the periods of the fixed oscillator occurring during a cycle of the divided frequency of the variable oscillator. This defines the period of the variable oscillator in terms of that of the fixed oscillator. A circuit is provided for selecting as a time interval a predetermined number of periods of the variable oscillator. The output of the generator consists of a first pulse produced by a trigger circuit at the start of the time interval and a second pulse marking the end of the time interval produced by the same trigger circuit.

The association between physical dependency and the presence of neuropsychiatric symptoms, with the admission of people with dementia to a long-term care institution: a prospective observational cohort study.

PubMed

Risco, Ester; Cabrera, Esther; Jolley, David; Stephan, Astrid; Karlsson, Staffan; Verbeek, Hilde; Saks, Kai; Hupli, Maija; Sourdet, Sandrine; Zabalegui, Adelaida

2015-05-01

Dementia is a progressive neurological disorder that causes a high degree of dependency. This dependency has been defined as an increased need for assistance due to deterioration in cognition and physical functioning, and changes in behavior. Highly dependent people with dementia are more likely to be institutionalized. To investigate the association between specific categories of physical dependency and the presence of neuropsychiatric symptoms in people with dementia admitted to a long-term care institution. A prospective observational cohort study. Home care and long-term care institutions in eight European countries. People with dementia living at home but at risk of institutionalization and recently institutionalized people with dementia. Baseline and 3-month follow-up interviews were performed between November, 2010 and April, 2012. The sample consisted of 116 recently institutionalized dementia sufferers and 949 people with dementia still living at home. Physical dependency was measured using the Katz Activity of Daily Living index, and neuropsychiatric symptoms were assessed through The Neuropsychiatric Inventory. Specific categories of dependency were analyzed by performing a logistic regression analysis. This followed examination of baseline characteristics to define the degree of physical dependency, as factors associated with institutionalization, and evaluation of the same characteristics at 3-month follow-up to detect changes in the degree of physical dependency and neuropsychiatric symptoms associated with recent admission to a long-term care institution. Toileting, dressing and continence dependency was higher in institutionalized people than in those receiving home-care. Delusion, hallucination, agitation, anxiety, apathy, motor-disturbances, night-time behavior and eating disorders were also worse in the institutionalized. Logistic regression analysis showed that independent factors significantly associated with being recently institutionalized were toileting (odds ratio=2.3; 95% confidence interval=1.43-3.71) and motor disturbances (odds ratio=1.81; 95% confidence interval=1.15-2.87). This study supports the association between type and degree of physical dependency in people with dementia and long-term institutionalization. Institutionalization is associated with physical dependency and the presence of neuropsychiatric symptoms. Copyright © 2015 Elsevier Ltd. All rights reserved.

Quantum field-theoretical description of neutrino and neutral kaon oscillations

NASA Astrophysics Data System (ADS)

Volobuev, Igor P.

2018-05-01

It is shown that the neutrino and neutral kaon oscillation processes can be consistently described in quantum field theory using only plane waves of the mass eigenstates of neutrinos and neutral kaons. To this end, the standard perturbative S-matrix formalism is modified so that it can be used for calculating the amplitudes of the processes passing at finite distances and finite time intervals. The distance-dependent and time-dependent parts of the amplitudes of the neutrino and neutral kaon oscillation processes are calculated and the results turn out to be in accordance with those of the standard quantum mechanical description of these processes based on the notion of neutrino flavor states and neutral kaon states with definite strangeness. However, the physical picture of the phenomena changes radically: now, there are no oscillations of flavor or definite strangeness states, but, instead of it, there is interference of amplitudes due to different virtual mass eigenstates.

Spontaneous Recovery After Extinction of the Conditioned Proboscis Extension Response in the Honeybee

PubMed Central

Sandoz, Jean-Christophe; Pham-Delègue, Minh-Hà

2004-01-01

In honeybees, the proboscis extension response (PER) can be conditioned by associating an odor stimulus (CS) to a sucrose reward (US). Conditioned responses to the CS, which are acquired by most bees after a single CS-US pairing, disappear after repeated unrewarded presentations of the CS, a process called extinction. Extinction is usually thought to be based either on (1) the disruption of the stored CS-US association, or (2) the formation of an inhibitory “CS-no US” association that is better retrieved than the initial CS-US association. The observation of spontaneous recovery, i.e., the reappearance of responses to the CS after time passes following extinction, is traditionally interpreted as a proof for the formation of a transient inhibitory association. To provide a better understanding of extinction in honeybees, we examined whether time intervals during training and extinction or the number of conditioning and extinction trials have an effect on the occurrence of spontaneous recovery. We found that spontaneous recovery mostly occurs when conditioning and testing took place in a massed fashion (1-min intertrial intervals). Moreover, spontaneous recovery depended on the time elapsed since extinction, 1 h being an optimum. Increasing the number of conditioning trials improved the spontaneous recovery level, whereas increasing the number of extinction trials reduced it. Lastly, we show that after single-trial conditioning, spontaneous recovery appears only once after extinction. These elements suggest that in honeybees extinction of the PER actually reflects the impairment of the CS-US association, but that depending on training parameters different memory substrates are affected. PMID:15466313

Intracalibration of particle detectors on a three-axis stabilized geostationary platform

NASA Astrophysics Data System (ADS)

Rowland, W.; Weigel, R. S.

2012-11-01

We describe an algorithm for intracalibration of measurements from plasma or energetic particle detectors on a three-axis stabilized platform. Modeling and forecasting of Earth's radiation belt environment requires data from particle instruments, and these data depend on measurements which have an inherent calibration uncertainty. Pre-launch calibration is typically performed, but on-orbit changes in the instrument often necessitate adjustment of calibration parameters to mitigate the effect of these changes on the measurements. On-orbit calibration practices for particle detectors aboard spin-stabilized spacecraft are well established. Three-axis stabilized platforms, however, pose unique challenges even when comparisons are being performed between multiple telescopes measuring the same energy ranges aboard the same satellite. This algorithm identifies time intervals when different telescopes are measuring particles with the same pitch angles. These measurements are used to compute scale factors which can be multiplied by the pre-launch geometric factor to correct any changes. The approach is first tested using measurements from GOES-13 MAGED particle detectors over a 5-month time period in 2010. We find statistically significant variations which are generally on the order of 5% or less. These results do not appear to be dependent on Poisson statistics nor upon whether a dead time correction was performed. When applied to data from a 5-month interval in 2011, one telescope shows a 10% shift from the 2010 scale factors. This technique has potential for operational use to help maintain relative calibration between multiple telescopes aboard a single satellite. It should also be extensible to inter-calibration between multiple satellites.

Potentiation: Effect of Ballistic and Heavy Exercise on Vertical Jump Performance.

PubMed

Hester, Garrett M; Pope, Zachary K; Sellers, John H; Thiele, Ryan M; DeFreitas, Jason M

2017-03-01

Hester, GM, Pope, ZK, Sellers, JH, Thiele, RM, and DeFreitas, JM. Potentiation: Effect of ballistic and heavy exercise on vertical jump performance. J Strength Cond Res 31(3): 660-666, 2017-The purpose of this study was to compare the acute effects of heavy and ballistic conditioning protocols on vertical jump performance in resistance-trained men. Fourteen resistance-trained men (mean ± SD: age = 22 ± 2.1 years, body mass = 86.29 ± 9.95 kg, and height = 175.39 ± 9.34 cm) with an average relative full squat of 2.02 ± 0.28 times their body mass participated in this study. In randomized, counterbalanced order, subjects performed two countermovement vertical jumps before and 1, 3, 5, and 10 minutes after either performing 10 rapid jump squats or 5 heavy back squats. The back squat protocol consisted of 5 repetitions at 80% one repetition maximum (1RM), whereas the jump squat protocol consisted of 10 repetitions at 20% 1RM. Peak jump height (in centimeters) using a jump mat, along with power output (in Watts) and velocity (in meters per second) through a linear transducer, was recorded for each time interval. There was no significant condition × time interaction for any of the dependent variables (p = 0.066-0.127). In addition, there was no main effect for condition for any of the dependent variables (p = 0.457-0.899). Neither the ballistic nor heavy protocol used in this study enhanced vertical jump performance at any recovery interval. The use of these protocols in resistance-trained men to produce postactivation potentiation is not recommended.

ON ASYMMETRY OF MAGNETIC HELICITY IN EMERGING ACTIVE REGIONS: HIGH-RESOLUTION OBSERVATIONS

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

Tian Lirong; Alexander, David; Zhu Chunming

We employ the DAVE (differential affine velocity estimator) tracking technique on a time series of Michelson Doppler Imager (MDI)/1 minute high spatial resolution line-of-sight magnetograms to measure the photospheric flow velocity for three newly emerging bipolar active regions (ARs). We separately calculate the magnetic helicity injection rate of the leading and following polarities to confirm or refute the magnetic helicity asymmetry, found by Tian and Alexander using MDI/96 minute low spatial resolution magnetograms. Our results demonstrate that the magnetic helicity asymmetry is robust, being present in the three ARs studied, two of which have an observed balance of the magneticmore » flux. The magnetic helicity injection rate measured is found to depend little on the window size selected, but does depend on the time interval used between the two successive magnetograms being tracked. It is found that the measurement of the magnetic helicity injection rate performs well for a window size between 12 x 10 and 18 x 15 pixels and at a time interval {Delta}t = 10 minutes. Moreover, the short-lived magnetic structures, 10-60 minutes, are found to contribute 30%-50% of the magnetic helicity injection rate. Comparing with the results calculated by MDI/96 minute data, we find that the MDI/96 minute data, in general, can outline the main trend of the magnetic properties, but they significantly underestimate the magnetic flux in strong field regions and are not appropriate for quantitative tracking studies, so provide a poor estimate of the amount of magnetic helicity injected into the corona.« less

Lock-and-key mechanisms of cerebellar memory recall based on rebound currents.

PubMed

Wetmore, Daniel Z; Mukamel, Eran A; Schnitzer, Mark J

2008-10-01

A basic question for theories of learning and memory is whether neuronal plasticity suffices to guide proper memory recall. Alternatively, information processing that is additional to readout of stored memories might occur during recall. We formulate a "lock-and-key" hypothesis regarding cerebellum-dependent motor memory in which successful learning shapes neural activity to match a temporal filter that prevents expression of stored but inappropriate motor responses. Thus, neuronal plasticity by itself is necessary but not sufficient to modify motor behavior. We explored this idea through computational studies of two cerebellar behaviors and examined whether deep cerebellar and vestibular nuclei neurons can filter signals from Purkinje cells that would otherwise drive inappropriate motor responses. In eyeblink conditioning, reflex acquisition requires the conditioned stimulus (CS) to precede the unconditioned stimulus (US) by >100 ms. In our biophysical models of cerebellar nuclei neurons this requirement arises through the phenomenon of postinhibitory rebound depolarization and matches longstanding behavioral data on conditioned reflex timing and reliability. Although CS-US intervals<100 ms may induce Purkinje cell plasticity, cerebellar nuclei neurons drive conditioned responses only if the CS-US training interval was >100 ms. This bound reflects the minimum time for deinactivation of rebound currents such as T-type Ca2+. In vestibulo-ocular reflex adaptation, hyperpolarization-activated currents in vestibular nuclei neurons may underlie analogous dependence of adaptation magnitude on the timing of visual and vestibular stimuli. Thus, the proposed lock-and-key mechanisms link channel kinetics to recall performance and yield specific predictions of how perturbations to rebound depolarization affect motor expression.

Intact interval timing in circadian CLOCK mutants.

PubMed

Cordes, Sara; Gallistel, C R

2008-08-28

While progress has been made in determining the molecular basis for the circadian clock, the mechanism by which mammalian brains time intervals measured in seconds to minutes remains a mystery. An obvious question is whether the interval-timing mechanism shares molecular machinery with the circadian timing mechanism. In the current study, we trained circadian CLOCK +/- and -/- mutant male mice in a peak-interval procedure with 10 and 20-s criteria. The mutant mice were more active than their wild-type littermates, but there were no reliable deficits in the accuracy or precision of their timing as compared with wild-type littermates. This suggests that expression of the CLOCK protein is not necessary for normal interval timing.

Toxicity of iron oxide nanoparticles to grass litter decomposition in a sandy soil

NASA Astrophysics Data System (ADS)

Rashid, Muhammad Imtiaz; Shahzad, Tanvir; Shahid, Muhammad; Imran, Muhammad; Dhavamani, Jeyakumar; Ismail, Iqbal M. I.; Basahi, Jalal M.; Almeelbi, Talal

2017-02-01

We examined time-dependent effect of iron oxide nanoparticles (IONPs) at a rate of 2000 mg kg-1 soil on Cynodon dactylon litter (3 g kg-1) decomposition in an arid sandy soil. Overall, heterotrophic cultivable bacterial and fungal colonies, and microbial biomass carbon were significantly decreased in litter-amended soil by the application of nanoparticles after 90 and 180 days of incubation. Time dependent effect of nanoparticles was significant for microbial biomass in litter-amended soil where nanoparticles decreased this variable from 27% after 90 days to 49% after 180 days. IONPs decreased CO2 emission by 28 and 30% from litter-amended soil after 90 and 180 days, respectively. These observations indicated that time-dependent effect was not significant on grass-litter carbon mineralization efficiency. Alternatively, nanoparticles application significantly reduced mineral nitrogen content in litter-amended soil in both time intervals. Therefore, nitrogen mineralization efficiency was decreased to 60% after 180 days compared to that after 90 days in nanoparticles grass-litter amended soil. These effects can be explained by the presence of labile Fe in microbial biomass after 180 days in nanoparticles amendment. Hence, our results suggest that toxicity of IONPs to soil functioning should consider before recommending their use in agro-ecosystems.

Mycophenolic Acid Pharmacokinetics and Relapse in Children with Steroid–Dependent Idiopathic Nephrotic Syndrome

PubMed Central

Tellier, Stéphanie; Dallocchio, Aymeric; Guigonis, Vincent; Saint-Marcoux, Frank; Llanas, Brigitte; Ichay, Lydia; Bandin, Flavio; Godron, Astrid; Morin, Denis; Brochard, Karine; Gandia, Peggy; Bouchet, Stéphane; Marquet, Pierre; Decramer, Stéphane

2016-01-01

Background and objectives Therapeutic drug monitoring of mycophenolic acid can improve clinical outcome in organ transplantation and lupus, but data are scarce in idiopathic nephrotic syndrome. The aim of our study was to investigate whether mycophenolic acid pharmacokinetics are associated with disease control in children receiving mycophenolate mofetil for the treatment of steroid–dependent nephrotic syndrome. Design, setting, participants, & measurements This was a retrospective multicenter study including 95 children with steroid–dependent nephrotic syndrome treated with mycophenolate mofetil with or without steroids. Area under the concentration-time curve of mycophenolic acid was determined in all children on the basis of sampling times at 20, 60, and 180 minutes postdose, using Bayesian estimation. The association between a threshold value of the area under the concentration-time curve of mycophenolic acid and the relapse rate was assessed using a negative binomial model. Results In total, 140 areas under the concentration-time curve of mycophenolic acid were analyzed. The findings indicate individual dose adaptation in 53 patients (38%) to achieve an area under the concentration-time curve target of 30–60 mg·h/L. In a multivariable negative binomial model including sex, age at disease onset, time to start of mycophenolate mofetil, previous immunomodulatory treatment, and concomitant prednisone dose, a level of area under the concentration-time curve of mycophenolic acid >45 mg·h/L was significantly associated with a lower relapse rate (rate ratio, 0.65; 95% confidence interval, 0.46 to 0.89; P=0.01). Conclusions Therapeutic drug monitoring leading to individualized dosing may improve the efficacy of mycophenolate mofetil in steroid–dependent nephrotic syndrome. Additional prospective studies are warranted to determine the optimal target for area under the concentration-time curve of mycophenolic acid in this population. PMID:27445161

Mycophenolic Acid Pharmacokinetics and Relapse in Children with Steroid-Dependent Idiopathic Nephrotic Syndrome.

PubMed

Tellier, Stéphanie; Dallocchio, Aymeric; Guigonis, Vincent; Saint-Marcoux, Frank; Llanas, Brigitte; Ichay, Lydia; Bandin, Flavio; Godron, Astrid; Morin, Denis; Brochard, Karine; Gandia, Peggy; Bouchet, Stéphane; Marquet, Pierre; Decramer, Stéphane; Harambat, Jérôme

2016-10-07

Therapeutic drug monitoring of mycophenolic acid can improve clinical outcome in organ transplantation and lupus, but data are scarce in idiopathic nephrotic syndrome. The aim of our study was to investigate whether mycophenolic acid pharmacokinetics are associated with disease control in children receiving mycophenolate mofetil for the treatment of steroid-dependent nephrotic syndrome. This was a retrospective multicenter study including 95 children with steroid-dependent nephrotic syndrome treated with mycophenolate mofetil with or without steroids. Area under the concentration-time curve of mycophenolic acid was determined in all children on the basis of sampling times at 20, 60, and 180 minutes postdose, using Bayesian estimation. The association between a threshold value of the area under the concentration-time curve of mycophenolic acid and the relapse rate was assessed using a negative binomial model. In total, 140 areas under the concentration-time curve of mycophenolic acid were analyzed. The findings indicate individual dose adaptation in 53 patients (38%) to achieve an area under the concentration-time curve target of 30-60 mg·h/L. In a multivariable negative binomial model including sex, age at disease onset, time to start of mycophenolate mofetil, previous immunomodulatory treatment, and concomitant prednisone dose, a level of area under the concentration-time curve of mycophenolic acid >45 mg·h/L was significantly associated with a lower relapse rate (rate ratio, 0.65; 95% confidence interval, 0.46 to 0.89; P =0.01). Therapeutic drug monitoring leading to individualized dosing may improve the efficacy of mycophenolate mofetil in steroid-dependent nephrotic syndrome. Additional prospective studies are warranted to determine the optimal target for area under the concentration-time curve of mycophenolic acid in this population. Copyright © 2016 by the American Society of Nephrology.

Long‐term time‐dependent probabilities for the third Uniform California Earthquake Rupture Forecast (UCERF3)

USGS Publications Warehouse

Field, Edward; Biasi, Glenn P.; Bird, Peter; Dawson, Timothy E.; Felzer, Karen R.; Jackson, David A.; Johnson, Kaj M.; Jordan, Thomas H.; Madden, Christopher; Michael, Andrew J.; Milner, Kevin; Page, Morgan T.; Parsons, Thomas E.; Powers, Peter; Shaw, Bruce E.; Thatcher, Wayne R.; Weldon, Ray J.; Zeng, Yuehua

2015-01-01

The 2014 Working Group on California Earthquake Probabilities (WGCEP 2014) presents time-dependent earthquake probabilities for the third Uniform California Earthquake Rupture Forecast (UCERF3). Building on the UCERF3 time-independent model, published previously, renewal models are utilized to represent elastic-rebound-implied probabilities. A new methodology has been developed that solves applicability issues in the previous approach for un-segmented models. The new methodology also supports magnitude-dependent aperiodicity and accounts for the historic open interval on faults that lack a date-of-last-event constraint. Epistemic uncertainties are represented with a logic tree, producing 5,760 different forecasts. Results for a variety of evaluation metrics are presented, including logic-tree sensitivity analyses and comparisons to the previous model (UCERF2). For 30-year M≥6.7 probabilities, the most significant changes from UCERF2 are a threefold increase on the Calaveras fault and a threefold decrease on the San Jacinto fault. Such changes are due mostly to differences in the time-independent models (e.g., fault slip rates), with relaxation of segmentation and inclusion of multi-fault ruptures being particularly influential. In fact, some UCERF2 faults were simply too long to produce M 6.7 sized events given the segmentation assumptions in that study. Probability model differences are also influential, with the implied gains (relative to a Poisson model) being generally higher in UCERF3. Accounting for the historic open interval is one reason. Another is an effective 27% increase in the total elastic-rebound-model weight. The exact factors influencing differences between UCERF2 and UCERF3, as well as the relative importance of logic-tree branches, vary throughout the region, and depend on the evaluation metric of interest. For example, M≥6.7 probabilities may not be a good proxy for other hazard or loss measures. This sensitivity, coupled with the approximate nature of the model and known limitations, means the applicability of UCERF3 should be evaluated on a case-by-case basis.

Stimulus-dependent modulation of spike burst length in cat striate cortical cells.

PubMed

DeBusk, B C; DeBruyn, E J; Snider, R K; Kabara, J F; Bonds, A B

1997-07-01

Burst activity, defined by groups of two or more spikes with intervals of < or = 8 ms, was analyzed in responses to drifting sinewave gratings elicited from striate cortical neurons in anesthetized cats. Bursting varied broadly across a population of 507 simple and complex cells. Half of this population had > or = 42% of their spikes contained in bursts. The fraction of spikes in bursts did not vary as a function of average firing rate and was stationary over time. Peaks in the interspike interval histograms were found at both 3-5 ms and 10-30 ms. In many cells the locations of these peaks were independent of firing rate, indicating a quantized control of firing behavior at two different time scales. The activity at the shorter time scale most likely results from intrinsic properties of the cell membrane, and that at the longer scale from recurrent network excitation. Burst frequency (bursts per s) and burst length (spikes per burst) both depended on firing rate. Burst frequency was essentially linear with firing rate, whereas burst length was a nonlinear function of firing rate and was also governed by stimulus orientation. At a given firing rate, burst length was greater for optimal orientations than for nonoptimal orientations. No organized orientation dependence was seen in bursts from lateral geniculate nucleus cells. Activation of cortical contrast gain control at low response amplitudes resulted in no burst length modulation, but burst shortening at optimal orientations was found in responses characterized by supersaturation. At a given firing rate, cortical burst length was shortened by microinjection of gamma-aminobutyric acid (GABA), and bursts became longer in the presence of N-methyl-bicuculline, a GABA(A) receptor blocker. These results are consistent with a model in which responses are reduced at nonoptimal orientations, at least in part, by burst shortening that is mediated by GABA. A similar mechanism contributes to response supersaturation at high contrasts via recruitment of inhibitory responses that are tuned to adjacent orientations. Burst length modulation can serve as a form of coding by supporting dynamic, stimulus-dependent reorganization of the effectiveness of individual network connections.

Time-dependent Data System (TDDS); an interactive program to assemble, manage, and appraise input data and numerical output of flow/transport simulation models

USGS Publications Warehouse

Regan, R.S.; Schaffranek, R.W.; Baltzer, R.A.

1996-01-01

A system of functional utilities and computer routines, collectively identified as the Time-Dependent Data System CI DDS), has been developed and documented by the U.S. Geological Survey. The TDDS is designed for processing time sequences of discrete, fixed-interval, time-varying geophysical data--in particular, hydrologic data. Such data include various, dependent variables and related parameters typically needed as input for execution of one-, two-, and three-dimensional hydrodynamic/transport and associated water-quality simulation models. Such data can also include time sequences of results generated by numerical simulation models. Specifically, TDDS provides the functional capabilities to process, store, retrieve, and compile data in a Time-Dependent Data Base (TDDB) in response to interactive user commands or pre-programmed directives. Thus, the TDDS, in conjunction with a companion TDDB, provides a ready means for processing, preparation, and assembly of time sequences of data for input to models; collection, categorization, and storage of simulation results from models; and intercomparison of field data and simulation results. The TDDS can be used to edit and verify prototype, time-dependent data to affirm that selected sequences of data are accurate, contiguous, and appropriate for numerical simulation modeling. It can be used to prepare time-varying data in a variety of formats, such as tabular lists, sequential files, arrays, graphical displays, as well as line-printer plots of single or multiparameter data sets. The TDDB is organized and maintained as a direct-access data base by the TDDS, thus providing simple, yet efficient, data management and access. A single, easily used, program interface that provides all access to and from a particular TDDB is available for use directly within models, other user-provided programs, and other data systems. This interface, together with each major functional utility of the TDDS, is described and documented in this report.

The Anaesthetic-ECT Time Interval in Electroconvulsive Therapy Practice--Is It Time to Time?

PubMed

Gálvez, Verònica; Hadzi-Pavlovic, Dusan; Wark, Harry; Harper, Simon; Leyden, John; Loo, Colleen K

2016-01-01

Because most common intravenous anaesthetics used in ECT have anticonvulsant properties, their plasma-brain concentration at the time of seizure induction might affect seizure expression. The quality of ECT seizure expression has been repeatedly associated with efficacy outcomes. The time interval between the anaesthetic bolus injection and the ECT stimulus (anaesthetic-ECT time interval) will determine the anaesthetic plasma-brain concentration when the ECT stimulus is administered. The aim of this study was to examine the effect of the anaesthetic-ECT time interval on ECT seizure quality and duration. The anaesthetic-ECT time interval was recorded in 771 ECT sessions (84 patients). Right unilateral brief pulse ECT was applied. Anaesthesia given was propofol (1-2 mg/kg) and succinylcholine (0.5-1.0 mg/kg). Seizure quality indices (slow wave onset, amplitude, regularity, stereotypy and post-ictal suppression) and duration were rated through a structured rating scale by a single blinded trained rater. Linear Mixed Effects Models analysed the effect of the anaesthetic-ECT time interval on seizure quality indices, controlling for propofol dose (mg), ECT charge (mC), ECT session number, days between ECT, age (years), initial seizure threshold (mC) and concurrent medication. Longer anaesthetic-ECT time intervals lead to significantly higher quality seizures (p < 0.001 for amplitude, regularity, stereotypy and post-ictal suppression). These results suggest that the anaesthetic-ECT time interval is an important factor to consider in ECT practice. This time interval should be extended to as long as practically possible to facilitate the production of better quality seizures. Close collaboration between the anaesthetist and the psychiatrist is essential. Copyright © 2015 Elsevier Inc. All rights reserved.

Time-dependent magnetohydrodynamic simulations of the inner heliosphere

NASA Astrophysics Data System (ADS)

Merkin, V. G.; Lyon, J. G.; Lario, D.; Arge, C. N.; Henney, C. J.

2016-04-01

This paper presents results from a simulation study exploring heliospheric consequences of time-dependent changes at the Sun. We selected a 2 month period in the beginning of year 2008 that was characterized by very low solar activity. The heliosphere in the equatorial region was dominated by two coronal holes whose changing structure created temporal variations distorting the classical steady state picture of the heliosphere. We used the Air Force Data Assimilate Photospheric Flux Transport (ADAPT) model to obtain daily updated photospheric magnetograms and drive the Wang-Sheeley-Arge (WSA) model of the corona. This leads to a formulation of a time-dependent boundary condition for our three-dimensional (3-D) magnetohydrodynamic (MHD) model, LFM-helio, which is the heliospheric adaptation of the Lyon-Fedder-Mobarry MHD simulation code. The time-dependent coronal conditions were propagated throughout the inner heliosphere, and the simulation results were compared with the spacecraft located near 1 astronomical unit (AU) heliocentric distance: Advanced Composition Explorer (ACE), Solar Terrestrial Relations Observatory (STEREO-A and STEREO-B), and the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft that was in cruise phase measuring the heliospheric magnetic field between 0.35 and 0.6 AU. In addition, during the selected interval MESSENGER and ACE aligned radially allowing minimization of the effects of temporal variation at the Sun versus radial evolution of structures. Our simulations show that time-dependent simulationsreproduce the gross-scale structure of the heliosphere with higher fidelity, while on smaller spatial and faster time scales (e.g., 1 day) they provide important insights for interpretation of the data. The simulations suggest that moving boundaries of slow-fast wind transitions at 0.1 AU may result in the formation of inverted magnetic fields near pseudostreamers which is an intrinsically time-dependent process. Finally, we show that heliospheric current sheet corrugation, which may result in multiple sector boundary crossings when observed by spacecraft, is caused by solar wind velocity shears. Overall, our simulations demonstrate that time-dependent heliosphere modeling is a promising direction of research both for space weather applications and fundamental physics of the heliosphere.

Ultrafast magneto-optical spectroscopy of GaMnAs (Invited Paper)

NASA Astrophysics Data System (ADS)

Heroux, Jean Benoit; Kojima, Eiji; Ino, Y.; Hashimoto, Y.; Katsumoto, Shingo; Iye, Yasushiro; Kuwata-Gonokami, Makoto

2005-04-01

Spin dynamics in the III-V dilute magnetic semiconductor GaMnAs is investigated by photo-induced demagnetization. Experimental results obtained from two different time-dependent characterization techniques - "two color-probe" magneto-optical Kerr effect (TR-MOKE) and mid-infrared differential transmittance -- are compared. Upon photo-excitation with a 100 fs, 3.1 eV light pulse, a long demagnetization time in the hundreds of picoseconds timescale is found by TR-MOKE, indicating a spin-dependent band structure in this material. In mid-infrared measurements, a positive increase of the differential transmittance is observed in the same time interval when the sample is cooled below its Currie temperature. It is shown that this mid-infrared absorption feature is directly related to ferromagnetism in this material. The magnetism-related component of the broad DC mid-infrared absorption peak characteristic of this p-type material could be observed with this time-resolved measurement. Experimental results were simulated with a model describing the interaction between three thermal reservoirs (hole, spin and lattice) and taking thermal diffusion into account.

Support for the existence of invertible maps between electronic densities and non-analytic 1-body external potentials in non-relativistic time-dependent quantum mechanics

NASA Astrophysics Data System (ADS)

Mosquera, Martín A.

2017-10-01

Provided the initial state, the Runge-Gross theorem establishes that the time-dependent (TD) external potential of a system of non-relativistic electrons determines uniquely their TD electronic density, and vice versa (up to a constant in the potential). This theorem requires the TD external potential and density to be Taylor-expandable around the initial time of the propagation. This paper presents an extension without this restriction. Given the initial state of the system and evolution of the density due to some TD scalar potential, we show that a perturbative (not necessarily weak) TD potential that induces a non-zero divergence of the external force-density, inside a small spatial subset and immediately after the initial propagation time, will cause a change in the density within that subset, implying that the TD potential uniquely determines the TD density. In this proof, we assume unitary evolution of wavefunctions and first-order differentiability (which does not imply analyticity) in time of the internal and external force-densities, electronic density, current density, and their spatial derivatives over the small spatial subset and short time interval.

Dynamics of Bottlebrush Networks

NASA Astrophysics Data System (ADS)

Cao, Zhen; Daniel, William; Vatankhah-Varnosfaderani, Mohammad; Sheiko, Sergei; Dobrynin, Andrey

The deformation dynamics of bottlebrush networks in a melt state is studied using a combination of theoretical, computational, and experimental techniques. Three main molecular relaxation processes are identified in these systems: (i) relaxation of the side chains, (ii) relaxation of the bottlebrush backbones on length scales shorter than the bottlebrush Kuhn length (bK) , and (iii) relaxation of the bottlebrush network strands between cross-links. The relaxation of side chains having a degree of polymerization (DP), nsc, dominates the network dynamics on the time scales τ0 < t <=τsc , where τ0 and τsc τ0 (nsc + 1)2 are the characteristic relaxation times of monomeric units and side chains, respectively. In this time interval, the shear modulus at small deformations decays with time as G0BB (t) t - 1 / 2. On time scales t >τsc, bottlebrush elastomers behave as networks of filaments with a shear modulus G0BB (t) (nsc + 1)- 1 / 4t - 1 / 2 . Finally, the response of the bottlebrush networks becomes time independent at times scales longer than the Rouse time of the bottlebrush network strands. In this time interval, the network shear modulus depends on the network molecular parameters as G0BB (t) (nsc + 1)-1N-1 . Analysis of the simulation data shows that the stress evolution in the bottlebrush networks during constant strain-rate deformation can be described by a universal function. NSF DMR-1409710, DMR-1407645, DMR-1624569, DMR-1436201.

Scale-dependent Normalized Amplitude and Weak Spectral Anisotropy of Magnetic Field Fluctuations in the Solar Wind Turbulence

NASA Astrophysics Data System (ADS)

Wang, Xin; Tu, Chuanyi; Marsch, Eckart; He, Jiansen; Wang, Linghua

2016-01-01

Turbulence in the solar wind was recently reported to be anisotropic, with the average power spectral index close to -2 when sampling parallel to the local mean magnetic field B0 and close to -5/3 when sampling perpendicular to the local B0. This result was widely considered to be observational evidence for the critical balance theory (CBT), which is derived by making the assumption that the turbulence strength is close to one. However, this basic assumption has not yet been checked carefully with observational data. Here we present for the first time the scale-dependent magnetic-field fluctuation amplitude, which is normalized by the local B0 and evaluated for both parallel and perpendicular sampling directions, using two 30-day intervals of Ulysses data. From our results, the turbulence strength is evaluated as much less than one at small scales in the parallel direction. An even stricter criterion is imposed when selecting the wavelet coefficients for a given sampling direction, so that the time stationarity of the local B0 is better ensured during the local sampling interval. The spectral index for the parallel direction is then found to be -1.75, whereas the spectral index in the perpendicular direction remains close to -1.65. These two new results, namely that the value of the turbulence strength is much less than one in the parallel direction and that the angle dependence of the spectral index is weak, cannot be explained by existing turbulence theories, like CBT, and thus will require new theoretical considerations and promote further observations of solar-wind turbulence.

Risk of Cardiac Events Associated With Antidepressant Therapy in Patients With Long QT Syndrome.

PubMed

Wang, Meng; Szepietowska, Barbara; Polonsky, Bronislava; McNitt, Scott; Moss, Arthur J; Zareba, Wojciech; Auerbach, David S

2018-01-15

Patients with long QT syndrome (LQTS) are at a high risk of cardiac events. Many patients with LQTS are treated with antidepressant drugs (ADs). We investigated the LQTS genotype-specific risk of recurrent cardiac arrhythmic events (CAEs) associated with AD therapy. The study included 59 LQT1 and 72 LQT2 patients from the Rochester-based LQTS Registry with corrected QT (QT c ) prolongation and a history of AD therapy. Using multivariate Anderson-Gill models, we estimated the LQTS genotype-specific risk of recurrent CAEs (ventricular tachyarrhythmias, aborted cardiac arrest, or sudden cardiac death) associated with time-dependent ADs. Specifically, we examined the risk associated with all ADs, selective serotonin reuptake inhibitor (SSRI), and ADs classified on the CredibleMeds list (www.CredibleMeds.org) as "Conditional" or "Known risk of Torsades de pointes (TdP)." After adjusting for baseline QT c duration, sex, and time-dependent beta-blocker usage, there was an increased risk of recurrent CAEs associated with ADs in LQT1 patients (hazard ratio = 3.67, 95% confidence interval 1.98-6.82, p < 0.001) but not in LQT2 patients (hazard ratio = 0.89, 95% confidence interval 0.49-1.64, p = 0.716; LQT1 vs LQT2 interaction, p < 0.001). Similarly, LQT1 patients who were on SSRIs or ADs with "Known risk of TdP" had a higher risk of recurrent CAEs than those patients off all ADs, whereas there was no association in LQT2 patients. ADs with "Conditional risk of TdP" were not associated with the risk of recurrent CAEs in any of the groups. In conclusion, the risk of recurrent CAEs associated with time-dependent ADs is higher in LQT1 patients but not in LQT2 patients. Results suggest a LQTS genotype-specific effect of ADs on the risk of arrhythmic events. Copyright © 2017 Elsevier Inc. All rights reserved.

Reservoir zonation based on statistical analyses: A case study of the Nubian sandstone, Gulf of Suez, Egypt

NASA Astrophysics Data System (ADS)

El Sharawy, Mohamed S.; Gaafar, Gamal R.

2016-12-01

Both reservoir engineers and petrophysicists have been concerned about dividing a reservoir into zones for engineering and petrophysics purposes. Through decades, several techniques and approaches were introduced. Out of them, statistical reservoir zonation, stratigraphic modified Lorenz (SML) plot and the principal component and clustering analyses techniques were chosen to apply on the Nubian sandstone reservoir of Palaeozoic - Lower Cretaceous age, Gulf of Suez, Egypt, by using five adjacent wells. The studied reservoir consists mainly of sandstone with some intercalation of shale layers with varying thickness from one well to another. The permeability ranged from less than 1 md to more than 1000 md. The statistical reservoir zonation technique, depending on core permeability, indicated that the cored interval of the studied reservoir can be divided into two zones. Using reservoir properties such as porosity, bulk density, acoustic impedance and interval transit time indicated also two zones with an obvious variation in separation depth and zones continuity. The stratigraphic modified Lorenz (SML) plot indicated the presence of more than 9 flow units in the cored interval as well as a high degree of microscopic heterogeneity. On the other hand, principal component and cluster analyses, depending on well logging data (gamma ray, sonic, density and neutron), indicated that the whole reservoir can be divided at least into four electrofacies having a noticeable variation in reservoir quality, as correlated with the measured permeability. Furthermore, continuity or discontinuity of the reservoir zones can be determined using this analysis.

Early photosensitizer uptake kinetics predict optimum drug-light interval for photodynamic therapy

NASA Astrophysics Data System (ADS)

Sinha, Lagnojita; Elliott, Jonathan T.; Hasan, Tayyaba; Pogue, Brian W.; Samkoe, Kimberley S.; Tichauer, Kenneth M.

2015-03-01

Photodynamic therapy (PDT) has shown promising results in targeted treatment of cancerous cells by developing localized toxicity with the help of light induced generation of reactive molecular species. The efficiency of this therapy depends on the product of the intensity of light dose and the concentration of photosensitizer (PS) in the region of interest (ROI). On account of this, the dynamic and variable nature of PS delivery and retention depends on many physiological factors that are known to be heterogeneous within and amongst tumors (e.g., blood flow, blood volume, vascular permeability, and lymph drainage rate). This presents a major challenge with respect to how the optimal time and interval of light delivery is chosen, which ideally would be when the concentration of PS molecule is at its maximum in the ROI. In this paper, a predictive algorithm is developed that takes into consideration the variability and dynamic nature of PS distribution in the body on a region-by-region basis and provides an estimate of the optimum time when the PS concentration will be maximum in the ROI. The advantage of the algorithm lies in the fact that it predicts the time in advance as it takes only a sample of initial data points (~12 min) as input. The optimum time calculated using the algorithm estimated a maximum dose that was only 0.58 +/- 1.92% under the true maximum dose compared to a mean dose error of 39.85 +/- 6.45% if a 1 h optimal light deliver time was assumed for patients with different efflux rate constants of the PS, assuming they have the same plasma function. Therefore, if the uptake values of PS for the blood and the ROI is known for only first 12 minutes, the entire curve along with the optimum time of light radiation can be predicted with the help of this algorithm.

Studying DDT Susceptibility at Discriminating Time Intervals Focusing on Maximum Limit of Exposure Time Survived by DDT Resistant Phlebotomus argentipes (Diptera: Psychodidae): an Investigative Report.

PubMed

Rama, Aarti; Kesari, Shreekant; Das, Pradeep; Kumar, Vijay

2017-07-24

Extensive application of routine insecticide i.e., dichlorodiphenyltrichloroethane (DDT) to control Phlebotomus argentipes (Diptera: Psychodidae), the proven vector of visceral leishmaniasis in India, had evoked the problem of resistance/tolerance against DDT, eventually nullifying the DDT dependent strategies to control this vector. Because tolerating an hour-long exposure to DDT is not challenging enough for the resistant P. argentipes, estimating susceptibility by exposing sand flies to insecticide for just an hour becomes a trivial and futile task.Therefore, this bioassay study was carried out to investigate the maximum limit of exposure time to which DDT resistant P. argentipes can endure the effect of DDT for their survival. The mortality rate of laboratory-reared DDT resistant strain P. argentipes exposed to DDT was studied at discriminating time intervals of 60 min and it was concluded that highly resistant sand flies could withstand up to 420 min of exposure to this insecticide. Additionally, the lethal time for female P. argentipes was observed to be higher than for males suggesting that they are highly resistant to DDT's toxicity. Our results support the monitoring of tolerance limit with respect to time and hence points towards an urgent need to change the World Health Organization's protocol for susceptibility identification in resistant P. argentipes.

Insights from Smart Meters: Ramp-Up, Dependability, and Short-Term Persistence of Savings from Home Energy Reports

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

Todd, A.; Perry, M.; Smith, B.

2015-04-01

Smart meters, smart thermostats, and other new technologies provide previously unavailable high-frequency and location-specific energy usage data. Many utilities are now able to capture real-time, customer-specific hourly interval usage data for a large proportion of their residential and small commercial customers. These vast, constantly growing streams of rich data (or big data) have the potential to provide novel insights into key policy questions about how people make energy decisions.

Frequency analysis via the method of moment functionals

NASA Technical Reports Server (NTRS)

Pearson, A. E.; Pan, J. Q.

1990-01-01

Several variants are presented of a linear-in-parameters least squares formulation for determining the transfer function of a stable linear system at specified frequencies given a finite set of Fourier series coefficients calculated from transient nonstationary input-output data. The basis of the technique is Shinbrot's classical method of moment functionals using complex Fourier based modulating functions to convert a differential equation model on a finite time interval into an algebraic equation which depends linearly on frequency-related parameters.

Starting Circuit For Erasable Programmable Logic Device

NASA Technical Reports Server (NTRS)

Cole, Steven W.

1990-01-01

Voltage regulator bypassed to supply starting current. Starting or "pullup" circuit supplies large inrush of current required by erasable programmable logic device (EPLD) while being turned on. Operates only during such intervals of high demand for current and has little effect any other time. Performs needed bypass, acting as current-dependent shunt connecting battery or other source of power more nearly directly to EPLD. Input capacitor of regulator removed when starting circuit installed, reducing probability of damage to transistor in event of short circuit in or across load.

Shuttle program: OFT ascent/descent ancillary data requirements document

NASA Technical Reports Server (NTRS)

Bond, A. C., Jr.; Knoedler, J.

1980-01-01

Requirements are presented for the ascent/descent (A/D) navigation and attitude-dependent ancillary data products to be generated for the space shuttle orbiter in support of the orbital flight test (OFT) flight test requirements, MPAD guidance and navigation performance assessment, and the mission evaluation team. The A/D ancillary data support for OFT mission evaluation activities is confined to providing postflight position, velocity, attitude, and associated navigation and attitude derived parameters for the Orbiter over particular flight phases and time intervals.

Cardiac transient outward potassium current: a pulse chemistry model of frequency-dependent properties.

PubMed

Liu, L; Krinsky, V I; Grant, A O; Starmer, C F

1996-01-01

Recent voltage-clamp studies of isolated myocytes have demonstrated widespread occurrence of a transient outward current (I(to)) carried by potassium ions. In the canine ventricle, this current is well developed in epicardial cells but not in endocardial cells. The resultant spatial dispersion of refractoriness is potentially proarrhythmic and may be amplified by channel blockade. The inactivation and recovery time constants of this channel are in excess of several hundred milliseconds, and consequently channel availability is frequency dependent at physiological stimulation rates. When the time constants associated with transitions between different channel conformations are rapid relative to drug binding kinetics, the interactions between drugs and an ion channel can be approximated by a sequence of first-order reactions, in which binding occurs in pulses in response to pulse train stimulation (pulse chemistry). When channel conformation transition time constants do not meet this constraint, analytical characterizations of the drug-channel interaction must then be modified to reflect the channel time-dependent properties. Here we report that the rate and steady-state amount of frequency-dependent inactivation of I(to) are consistent with a generalization of the channel blockade model: channel availability is reduced in a pulsatile exponential pattern as the stimulation frequency is increased, and the rate of reduction is a linear function of the pulse train depolarizing and recovery intervals. I(to) was reduced in the presence of quinidine. After accounting for the use-dependent availability of I(to) channels, we found little evidence of an additional use-dependent component of block after exposure to quinidine, suggesting that quinidine reacts with both open and closed I(to) channels as though the binding site is continuously accessible. The model provides a useful tool for assessing drug-channel interactions when the reaction cannot be continuously monitored.

Functional and histological bladder damage in mice after photodynamic therapy: the influence of sensitiser dose and time of administration.

PubMed Central

Stewart, F. A.; Oussoren, Y.

1993-01-01

The bladders of anaesthetised mice were illuminated with red laser light (630 nm) at intervals of 1 day to 4 weeks after i.p. administration of Photofrin. Light was delivered intravesically by inserting a fibre optic, with a diffusing bulb tip, into the centre of fluid filled bladders. A single light dose of 11.3 J cm-2 applies 1 day after 10 mg kg-1 Photofrin caused a severe acute response, with increased urination frequency (five to seven times control) and hematuria. Recovery was good, however, and by 10 weeks only a mild (approximately two-fold) increase in frequency remained. There was no reduction in the amount of acute bladder damage or in the rate of healing when the interval between Photofrin and light was increased from 1 to 7 days but a 2 to 3 week interval lead to a significant reduction in damage. For an interval of 4 weeks there was only a mild (less than two-fold) increase in urination frequency during the first week. A drug dose of 2.5 mg kg-1 given 1 day before illumination caused transient haematuria but no increase in urination frequency. Doses of 5, 7.5 or 10 mg kg-1 all caused photosensitisation and the amount of bladder damage was drug dose dependent. The bladder seems to be well able to recover from severe acute damage induced by PDT. Occasional incidences of pyelonephritis were seen, however, suggesting that urinary tract infection during the acute period may lead to permanent renal damage. Images Figure 5 PMID:8398691

Temporal expectation in focal hand dystonia.

PubMed

Avanzino, Laura; Martino, Davide; Martino, Isadora; Pelosin, Elisa; Vicario, Carmelo M; Bove, Marco; Defazio, Gianni; Abbruzzese, Giovanni

2013-02-01

Patients with writer's cramp present sensory and representational abnormalities relevant to motor control, such as impairment in the temporal discrimination between tactile stimuli and in pure motor imagery tasks, like the mental rotation of corporeal and inanimate objects. However, only limited information is available on the ability of patients with dystonia to process the time-dependent features (e.g. speed) of movement in real time. The processing of time-dependent features of movement has a crucial role in predicting whether the outcome of a complex motor sequence, such as handwriting or playing a musical passage, will be consistent with its ultimate goal, or results instead in an execution error. In this study, we sought to evaluate the implicit ability to perceive the temporal outcome of different movements in a group of patients with writer's cramp. Fourteen patients affected by writer's cramp in the right hand and 17 age- and gender-matched healthy subjects were recruited for the study. Subjects were asked to perform a temporal expectation task by predicting the end of visually perceived human body motion (handwriting, i.e. the action performed by the human body segment specifically affected by writer's cramp) or inanimate object motion (a moving circle reaching a spatial target). Videos representing movements were shown in full before experimental trials; the actual tasks consisted of watching the same videos, but interrupted after a variable interval ('pre-dark') from its onset by a dark interval of variable duration. During the 'dark' interval, subjects were asked to indicate when the movement represented in the video reached its end by clicking on the space bar of the keyboard. We also included a visual working memory task. Performance on the timing task was analysed measuring the absolute value of timing error, the coefficient of variability and the percentage of anticipation responses. Patients with writer's cramp exhibited greater absolute timing error compared with control subjects in the human body motion task (whereas no difference was observed in the inanimate object motion task). No effect of group was documented on the visual working memory tasks. Absolute timing error on the human body motion task did not significantly correlate with symptom severity, disease duration or writing speed. Our findings suggest an alteration of the writing movement representation at a central level and are consistent with the view that dystonia is not a purely motor disorder, but it also involves non-motor (sensory, cognitive) aspects related to movement processing and planning.

Rapid fibrin plug formation within cutaneous ablative fractional CO2 laser lesions.

PubMed

Kositratna, Garuna; Evers, Michael; Sajjadi, Amir; Manstein, Dieter

2016-02-01

Ablative fractional laser procedures have been shown to facilitate topical drug delivery into the skin. Past studies have mainly used ex vivo models to demonstrate enhanced drug delivery and in vivo studies have investigated laser created channels over a time course of days and weeks rather than within the first few minutes and hours after exposures. We have noticed rapid in vivo fibrin plug formation within ablative fractional laser lesions impairing passage through the laser created channels. In vivo laser exposures were performed in a porcine model. A fractional CO2 laser (AcuPulse™ system, AcuScan 120™ handpiece, Lumenis, Inc., Yokneam, Israel) was programmed in quasi-continuous wave (QCW) mode, at 40W, 50 mJ per pulse, 5% coverage, nominal 120 µm spot size, 8 × 8 mm square pattern, 169 MTZs per scan. Six millimeters punch biopsies were procured at 0, 2, 5, 10, 15, 30, 60, 90 minutes after completion of each scan, then fixed in 10% formalin. 12 repeats were performed of each time point. Skin samples were processed for serial vertically cut paraffin sections (5 μm collected every 25 μm) then H&E and special immunohistochemistry staining for fibrin and platelet. Dimensions of Microscopic Treatment Zones (MTZs) and extent of fibrin plug were assessed and quantified histologically. Ex vivo laser exposures of the identical laser parameter were performed on porcine and human skin at different storage conditions. Histology procured at various predetermined time intervals after in vivo fractional CO2 laser exposures revealed a rapidly forming fibrin plug initiating at the bottom of the MTZ lesions. At longer time intervals, the fibrin plug was extending towards the superficial sections. Within the first 5 minutes, more than 25% length of the entire laser-ablated channel was filled with a fibrin plug. With increased time intervals, the cavity was progressively filled with a fibrin plug. At 90 minutes, more than 90% length of the entire laser-ablated channel was occluded. Ex vivo exposures failed to produce any significant fibrin plug formation. The current study has demonstrated rapid fibrin plug formation after ablative fractional laser procedures. It was shown that the passage through laser created pathways is critically time dependent for in vivo exposures. In contrast, ex vivo exposures do not exhibit such time dependent passage capacity. In particular, drug, substance, and cell delivery studies for ablative fractional laser treatments should take early fibrin plug formation into consideration and further investigate the impact on transdermal delivery. © 2015 Wiley Periodicals, Inc.

A simple method to calculate first-passage time densities with arbitrary initial conditions

NASA Astrophysics Data System (ADS)

Nyberg, Markus; Ambjörnsson, Tobias; Lizana, Ludvig

2016-06-01

Numerous applications all the way from biology and physics to economics depend on the density of first crossings over a boundary. Motivated by the lack of general purpose analytical tools for computing first-passage time densities (FPTDs) for complex problems, we propose a new simple method based on the independent interval approximation (IIA). We generalise previous formulations of the IIA to include arbitrary initial conditions as well as to deal with discrete time and non-smooth continuous time processes. We derive a closed form expression for the FPTD in z and Laplace-transform space to a boundary in one dimension. Two classes of problems are analysed in detail: discrete time symmetric random walks (Markovian) and continuous time Gaussian stationary processes (Markovian and non-Markovian). Our results are in good agreement with Langevin dynamics simulations.

The Unusual Wolf-Rayet Star EZ CMa

NASA Technical Reports Server (NTRS)

Skinner, Stephen L.

2002-01-01

The XMM-Newton observations were obtained on 29 - 30 October 2001 during the AO-1 Guest Observer program. Our X-ray analysis focused on data from the European Photon Imaging Camera (EPIC). The VLA observations were obtained during a 3.5 hour interval on 1999 Oct. 19 with the array in hybrid BnA configuration. Radio continuum data were acquired at five different frequencies 1.42 GHz (21 cm), 4.86 GHz (6 cm), 8.44 GHz (3.6 cm), 14.94 GHz (2 cm), and 22.46 GHz (1.3 cm). These radio data are unique since they provide an excellent snapshot picture of the dependence of the radio flux on frequency obtained over a short time interval and are thus immune to the variability effects which can distort results obtained from non-contemporaneous observations at different frequencies.

Double dynamic scaling in human communication dynamics

NASA Astrophysics Data System (ADS)

Wang, Shengfeng; Feng, Xin; Wu, Ye; Xiao, Jinhua

2017-05-01

In the last decades, human behavior has been deeply understanding owing to the huge quantities data of human behavior available for study. The main finding in human dynamics shows that temporal processes consist of high-activity bursty intervals alternating with long low-activity periods. A model, assuming the initiator of bursty follow a Poisson process, is widely used in the modeling of human behavior. Here, we provide further evidence for the hypothesis that different bursty intervals are independent. Furthermore, we introduce a special threshold to quantitatively distinguish the time scales of complex dynamics based on the hypothesis. Our results suggest that human communication behavior is a composite process of double dynamics with midrange memory length. The method for calculating memory length would enhance the performance of many sequence-dependent systems, such as server operation and topic identification.

Fuzzy rationality and parameter elicitation in decision analysis

NASA Astrophysics Data System (ADS)

Nikolova, Natalia D.; Tenekedjiev, Kiril I.

2010-07-01

It is widely recognised by decision analysts that real decision-makers always make estimates in an interval form. An overview of techniques to find an optimal alternative among such with imprecise and interval probabilities is presented. Scalarisation methods are outlined as most appropriate. A proper continuation of such techniques is fuzzy rational (FR) decision analysis. A detailed representation of the elicitation process influenced by fuzzy rationality is given. The interval character of probabilities leads to the introduction of ribbon functions, whose general form and special cases are compared with the p-boxes. As demonstrated, approximation of utilities in FR decision analysis does not depend on the probabilities, but the approximation of probabilities is dependent on preferences.

On the Determination of Poisson Statistics for Haystack Radar Observations of Orbital Debris

NASA Technical Reports Server (NTRS)

Stokely, Christopher L.; Benbrook, James R.; Horstman, Matt

2007-01-01

A convenient and powerful method is used to determine if radar detections of orbital debris are observed according to Poisson statistics. This is done by analyzing the time interval between detection events. For Poisson statistics, the probability distribution of the time interval between events is shown to be an exponential distribution. This distribution is a special case of the Erlang distribution that is used in estimating traffic loads on telecommunication networks. Poisson statistics form the basis of many orbital debris models but the statistical basis of these models has not been clearly demonstrated empirically until now. Interestingly, during the fiscal year 2003 observations with the Haystack radar in a fixed staring mode, there are no statistically significant deviations observed from that expected with Poisson statistics, either independent or dependent of altitude or inclination. One would potentially expect some significant clustering of events in time as a result of satellite breakups, but the presence of Poisson statistics indicates that such debris disperse rapidly with respect to Haystack's very narrow radar beam. An exception to Poisson statistics is observed in the months following the intentional breakup of the Fengyun satellite in January 2007.

Thermal comfort and safety of cotton blankets warmed at 130°F and 200°F.

PubMed

Kelly, Patricia A; Cooper, Susan K; Krogh, Mary L; Morse, Elizabeth C; Crandall, Craig G; Winslow, Elizabeth H; Balluck, Julie P

2013-12-01

In 2009, the ECRI Institute recommended warming cotton blankets in cabinets set at 130°F or less. However, there is limited research to support the use of this cabinet temperature. To measure skin temperatures and thermal comfort in healthy volunteers before and after application of blankets warmed in cabinets set at 130 and 200°F, respectively, and to determine the time-dependent cooling of cotton blankets after removal from warming cabinets set at the two temperatures. Prospective, comparative, descriptive. Participants (n = 20) received one or two blankets warmed in 130 or 200°F cabinets. First, skin temperatures were measured, and thermal comfort reports were obtained at fixed timed intervals. Second, blanket temperatures (n = 10) were measured at fixed intervals after removal from the cabinets. No skin temperatures approached levels reported in the literature that cause epidermal damage. Thermal comfort reports supported using blankets from the 200°F cabinet, and blankets lost heat quickly over time. We recommend warming cotton blankets in cabinets set at 200°F or less to improve thermal comfort without compromising patient safety. Copyright © 2013 American Society of PeriAnesthesia Nurses. Published by Elsevier Inc. All rights reserved.

Effects of a low-resistance, interval bicycling intervention in Parkinson's Disease.

PubMed

Uygur, Mehmet; Bellumori, Maria; Knight, Christopher A

2017-12-01

Previous studies have shown that people with Parkinson's disease (PD) benefit from a variety of exercise modalities with respect to symptom management and function. Among the possible exercise modalities, speedwork has been identified as a promising strategy, with direct implications for the rate and amplitude of nervous system involvement. Considering that previous speed-based exercise for PD has often been equipment, personnel and/or facility dependent, and often time intensive, our purpose was to develop a population-specific exercise program that could be self-administered with equipment that is readily found in fitness centers or perhaps the home. Fourteen individuals with PD (Hoehn-Yahr (H-Y) stage of 3.0 or less) participated in twelve 30-min sessions of low-resistance interval training on a stationary recumbent bicycle. Motor examination section of the Unified Parkinson's Disease Rating Scale (UPDRS), 10-meter walk (10mW), timed-up-and-go (TUG), functional reach, four-square step test (4SST), nine-hole peg test (9HPT) and simple reaction time scores all exhibited significant improvements (p < 0.05). These results add further support to the practice of speedwork for people with PD and outline a population-amenable program with high feasibility.

Intact Interval Timing in Circadian CLOCK Mutants

PubMed Central

Cordes, Sara; Gallistel, C. R.

2008-01-01

While progress has been made in determining the molecular basis for the circadian clock, the mechanism by which mammalian brains time intervals measured in seconds to minutes remains a mystery. An obvious question is whether the interval timing mechanism shares molecular machinery with the circadian timing mechanism. In the current study, we trained circadian CLOCK +/− and −/− mutant male mice in a peak-interval procedure with 10 and 20-s criteria. The mutant mice were more active than their wild-type littermates, but there were no reliable deficits in the accuracy or precision of their timing as compared with wild-type littermates. This suggests that expression of the CLOCK protein is not necessary for normal interval timing. PMID:18602902

Evaluation of family intervention through unobtrusive audio recordings: experiences in "bugging" children.

PubMed

Johnson, S M; Christensen, A; Bellamy, G T

1976-01-01

Five children referred to a child-family intervention program wore a radio transmitter in the home during pre-intervention and termination assessments. The transmitter broadcast to a receiver-recording apparatus in the home (either activated by an interval timer at predetermined "random" times or by parents at predetermined "picked" times). "Picked" times were parent-selected situations during which problems typically occurred (e.g., bedtime). Parents activated the recorder regularly whether or not problems occurred. Child-deviant, parent-negative, and parent-commanding behaviors were significantly higher at the picked times during pretest than at random times. At posttest, behaviors in all three classes were substantially reduced at picked times, but not at random times. For individual subject data, reductions occurred in at least two of the three dependent variables for three of the five cases during random time assessments. In general, the behavioral outcome data corresponded to parent-attitude reports and parent-collected observation data.

Left ventricular function determined by Doppler echocardiography in adolescents with type I (insulin-dependent) diabetes mellitus.

PubMed

Salazar, J; Rivas, A; Rodriguez, M; Felipe, J; Garcia, M D; Bone, J

1994-01-01

Sixty-one children with insulin-dependent diabetes mellitus and twenty-three healthy subjects were investigated. The patients with diabetes mellitus aged 4 to 20 years (13.4 +/- 4.0) had had diabetes for 1 to 16 years (6.4 +/- 3.5). There were no cardiovascular risk factor other than diabetes. Patients received no medication other than insulin. The following echocardiographic and Doppler parameters of the left ventricle were analyzed in both groups: systolic and diastolic dimensions, systolic time intervals, fractional shortening, mean velocity of circumferential fiber shortening, percent relaxation of the left ventricular posterior wall at 50% of diastole, peak velocity of early (E) and late atrial (A) mitral flow. E/A ratio, deceleration of the E-wave, and the isovolumetric relaxation time. None of the parameters were significantly different between the groups. There was no relation observed between duration of diabetes and any of the parameters analyzed. It is concluded that there is not echocardiographic data to support the concept of diabetic cardiomyopathy in adolescents with type I (insulin-dependent) diabetes mellitus.

Solutions for transients in arbitrarily branching cables: III. Voltage clamp problems.

PubMed

Major, G

1993-07-01

Branched cable voltage recording and voltage clamp analytical solutions derived in two previous papers are used to explore practical issues concerning voltage clamp. Single exponentials can be fitted reasonably well to the decay phase of clamped synaptic currents, although they contain many underlying components. The effective time constant depends on the fit interval. The smoothing effects on synaptic clamp currents of dendritic cables and series resistance are explored with a single cylinder + soma model, for inputs with different time courses. "Soma" and "cable" charging currents cannot be separated easily when the soma is much smaller than the dendrites. Subtractive soma capacitance compensation and series resistance compensation are discussed. In a hippocampal CA1 pyramidal neurone model, voltage control at most dendritic sites is extremely poor. Parameter dependencies are illustrated. The effects of series resistance compound those of dendritic cables and depend on the "effective capacitance" of the cell. Plausible combinations of parameters can cause order-of-magnitude distortions to clamp current waveform measures of simulated Schaeffer collateral inputs. These voltage clamp problems are unlikely to be solved by the use of switch clamp methods.

Apparatus and method for closed-loop control of reactor power in minimum time

DOEpatents

Bernard, Jr., John A.

1988-11-01

Closed-loop control law for altering the power level of nuclear reactors in a safe manner and without overshoot and in minimum time. Apparatus is provided for moving a fast-acting control element such as a control rod or a control drum for altering the nuclear reactor power level. A computer computes at short time intervals either the function: .rho.=(.beta.-.rho.).omega.-.lambda..sub.e '.rho.-.SIGMA..beta..sub.i (.lambda..sub.i -.lambda..sub.e ')+l* .omega.+l* [.omega..sup.2 +.lambda..sub.e '.omega.] or the function: .rho.=(.beta.-.rho.).omega.-.lambda..sub.e .rho.-(.lambda..sub.e /.lambda..sub.e)(.beta.-.rho.)+l* .omega.+l* [.omega..sup.2 +.lambda..sub.e .omega.-(.lambda..sub.e /.lambda..sub.e).omega.] These functions each specify the rate of change of reactivity that is necessary to achieve a specified rate of change of reactor power. The direction and speed of motion of the control element is altered so as to provide the rate of reactivity change calculated using either or both of these functions thereby resulting in the attainment of a new power level without overshoot and in minimum time. These functions are computed at intervals of approximately 0.01-1.0 seconds depending on the specific application.

Working times of elastomeric impression materials determined by dimensional accuracy.

PubMed

Tan, E; Chai, J; Wozniak, W T

1996-01-01

The working times of five poly(vinyl siloxane) impression materials were estimated by evaluating the dimensional accuracy of stone dies of impressions of a standard model made at successive time intervals. The stainless steel standard model was represented by two abutments having known distances between landmarks in three dimensions. Three dimensions in the x-, y-, and z-axes of the stone dies were measured with a traveling microscope. A time interval was rejected as being within the working time if the percentage change of the resultant dies, in any dimension, was statistically different from those measured from stone dies from previous time intervals. The absolute dimensions of those dies from the rejected time interval also must have exceeded all those from previous time intervals. Results showed that the working times estimated with this method generally were about 30 seconds longer than those recommended by the manufacturers.

A new strategy to analyze possible association structures between dynamic nocturnal hormone activities and sleep alterations in humans.

PubMed

Kalus, Stefanie; Kneib, Thomas; Steiger, Axel; Holsboer, Florian; Yassouridis, Alexander

2009-04-01

The human sleep process shows dynamic alterations during the night. Methods are needed to examine whether and to what extent such alterations are affected by internal, possibly time-dependent, factors, such as endocrine activity. In an observational study, we examined simultaneously sleep EEG and nocturnal levels of renin, growth hormone (GH), and cortisol (between 2300 and 0700) in 47 healthy volunteers comprising 24 women (41.67 +/- 2.93 yr of age) and 23 men (37.26 +/- 2.85 yr of age). Hormone concentrations were measured every 20 min. Conventional sleep stage scoring at 30-s intervals was applied. Semiparametric multinomial logit models are used to study and quantify possible time-dependent hormone effects on sleep stage transition courses. Results show that increased cortisol levels decrease the probability of transition from rapid-eye-movement (REM) sleep to wakefulness (WAKE) and increase the probability of transition from REM to non-REM (NREM) sleep, irrespective of the time in the night. Via the model selection criterion Akaike's information criterion, it was found that all considered hormone effects on transition probabilities with the initial state WAKE change with time. Similarly, transition from slow-wave sleep (SWS) to light sleep (LS) is affected by a "hormone-time" interaction for cortisol and renin, but not GH. For example, there is a considerable increase in the probability of SWS-LS transition toward the end of the night, when cortisol concentrations are very high. In summary, alterations in human sleep possess dynamic forms and are partially influenced by the endocrine activity of certain hormones. Statistical methods, such as semiparametric multinomial and time-dependent logit regression, can offer ambitious ways to investigate and estimate the association intensities between the nonstationary sleep changes and the time-dependent endocrine activities.

Single-channel autocorrelation functions: the effects of time interval omission.

PubMed Central

Ball, F G; Sansom, M S

1988-01-01

We present a general mathematical framework for analyzing the dynamic aspects of single channel kinetics incorporating time interval omission. An algorithm for computing model autocorrelation functions, incorporating time interval omission, is described. We show, under quite general conditions, that the form of these autocorrelations is identical to that which would be obtained if time interval omission was absent. We also show, again under quite general conditions, that zero correlations are necessarily a consequence of the underlying gating mechanism and not an artefact of time interval omission. The theory is illustrated by a numerical study of an allosteric model for the gating mechanism of the locust muscle glutamate receptor-channel. PMID:2455553

Application of a temperature-dependent fluorescent dye (Rhodamine B) to the measurement of radiofrequency radiation-induced temperature changes in biological samples.

PubMed

Chen, Yuen Y; Wood, Andrew W

2009-10-01

We have applied a non-contact method for studying the temperature changes produced by radiofrequency (RF) radiation specifically to small biological samples. A temperature-dependent fluorescent dye, Rhodamine B, as imaged by laser scanning confocal microscopy (LSCM) was used to do this. The results were calibrated against real-time temperature measurements from fiber optic probes, with a calibration factor of 3.4% intensity change degrees C(-1) and a reproducibility of +/-6%. This non-contact method provided two-dimensional and three-dimensional images of temperature change and distributions in biological samples, at a spatial resolution of a few micrometers and with an estimated absolute precision of around 1.5 degrees C, with a differential precision of 0.4 degree C. Temperature rise within tissue was found to be non-uniform. Estimates of specific absorption rate (SAR) from absorbed power measurements were greater than those estimated from rate of temperature rise, measured at 1 min intervals, probably because this interval is too long to permit accurate estimation of initial temperature rise following start of RF exposure. Future experiments will aim to explore this.

Effects of environmental and pharmacological manipulations on a novel delayed nonmatching-to-sample 'working memory' procedure in unrestrained rhesus monkeys.

PubMed

Hutsell, Blake A; Banks, Matthew L

2015-08-15

Working memory is a domain of 'executive function.' Delayed nonmatching-to-sample (DNMTS) procedures are commonly used to examine working memory in both human laboratory and preclinical studies. The aim was to develop an automated DNMTS procedure maintained by food pellets in rhesus monkeys using a touch-sensitive screen attached to the housing chamber. Specifically, the DNMTS procedure was a 2-stimulus, 2-choice recognition memory task employing unidimensional discriminative stimuli and randomized delay interval presentations. DNMTS maintained a delay-dependent decrease in discriminability that was independent of the retention interval distribution. Eliminating reinforcer availability during a single delay session or providing food pellets before the session did not systematically alter accuracy, but did reduce total choices. Increasing the intertrial interval enhanced accuracy at short delays. Acute Δ(9)-THC pretreatment produced delay interval-dependent changes in the forgetting function at doses that did not alter total choices. Acute methylphenidate pretreatment only decreased total choices. All monkeys were trained to perform NMTS at the 1s training delay within 60 days of initiating operant touch training. Furthermore, forgetting functions were reliably delay interval-dependent and stable over the experimental period (∼6 months). Consistent with previous studies, increasing the intertrial interval improved DNMTS performance, whereas Δ(9)-THC disrupted DNMTS performance independent of changes in total choices. Overall, the touchscreen-based DNMTS procedure described provides an efficient method for training and testing experimental manipulations on working memory in unrestrained rhesus monkeys. Copyright © 2015 Elsevier B.V. All rights reserved.

Two-key concurrent responding: response-reinforcement dependencies and blackouts1

PubMed Central

Herbert, Emily W.

1970-01-01

Two-key concurrent responding was maintained for three pigeons by a single variable-interval 1-minute schedule of reinforcement in conjunction with a random number generator that assigned feeder operations between keys with equal probability. The duration of blackouts was varied between keys when each response initiated a blackout, and grain arranged by the variable-interval schedule was automatically presented after a blackout (Exp. I). In Exp. II every key peck, except for those that produced grain, initiated a blackout, and grain was dependent upon a response following a blackout. For each pigeon in Exp. I and for one pigeon in Exp. II, the relative frequency of responding on a key approximated, i.e., matched, the relative reciprocal of the duration of the blackout interval on that key. In a third experiment, blackouts scheduled on a variable-interval were of equal duration on the two keys. For one key, grain automatically followed each blackout; for the other key, grain was dependent upon a response and never followed a blackout. The relative frequency of responding on the former key, i.e., the delay key, better approximated the negative exponential function obtained by Chung (1965) than the matching function predicted by Chung and Herrnstein (1967). PMID:16811458

Setting the Revisit Interval in Primary Care

PubMed Central

Schwartz, Lisa M; Woloshin, Steven; Wasson, John H; Renfrew, Roger A; Welch, H Gilbert

1999-01-01

OBJECTIVE Although longitudinal care constitutes the bulk of primary care, physicians receive little guidance on the fundamental question of how to time follow-up visits. We sought to identify important predictors of the revisit interval and to describe the variability in how physicians set these intervals when caring for patients with common medical conditions. DESIGN Cross-sectional survey of physicians performed at the end of office visits for consecutive patients with hypertension, angina, diabetes, or musculoskeletal pain. PARTICIPANTS/SETTING One hundred sixty-four patients under the care of 11 primary care physicians in the Dartmouth Primary Care Cooperative Research Network. MEASUREMENTS The main outcome measures were the variability in mean revisit intervals across physicians and the proportion of explained variance by potential determinants of revisit intervals. We assessed the relation between the revisit interval (dependent variable) and three groups of independent variables, patient characteristics (e.g., age, physician perception of patient health), identification of individual physician, and physician characterization of the visit (e.g., routine visit, visit requiring a change in management, or visit occurring on a “hectic” day), using multiple regression that accounted for the natural grouping of patients within physician. MAIN RESULTS Revisit intervals ranged from 1 week to over 1 year. The most common intervals were 12 and 16 weeks. Physicians’ perception of fair-poor health status and visits involving a change in management were most strongly related to shorter revisit intervals. In multivariate analyses, patient characteristics explained about 18% of the variance in revisit intervals, and adding identification of the individual provider doubled the explained variance to about 40%. Physician characterization of the visit increased explained variance to 57%. The average revisit interval adjusted for patient characteristics for each of the 11 physicians varied from 4 to 20 weeks. Although all physicians lengthened revisit intervals for routine visits and shortened them when changing management, the relative ranking of mean revisit intervals for each physician changed little for different visit characterizations—some physicians were consistently long and others were consistently short. CONCLUSION Physicians vary widely in their recommendations for office revisits. Patient factors accounted for only a small part of this variation. Although physicians responded to visits in predictable ways, each physician appeared to have a unique set point for the length of the revisits interval. PMID:10203635

Multi-component time, spatial and frequency analysis of Paleoclimatic Data

NASA Astrophysics Data System (ADS)

Cristiano, Luigia; Stampa, Johannes; Feeser, Ingo; Dörfler, Walter; Meier, Thomas

2017-04-01

The investigation of the paleoclimatic data offers a powerful tool for understanding the impact of extreme climatic events as well as gradual climatic variations on the human development and cultural changes. The current global record of paleoclimatic data is relatively rich but is not generally uniformly structured and regionally distributed. The general characteristic of the reconstructed time series of paleoclimatic data is a not constant sampling interval and data resolution together with the presence of gaps in the record. Our database consists of pollen concentration from annually laminated lake sediments in two sites in Northern Germany. Such data characteristic offers the possibility for high-resolution palynological and sedimentological analyses on a well constrained time scale. Specifically we are interested to investigate the time dependence of proxies, and time and spatial correlation of the different observables respect each other. We present here a quantitative analysis of the pollent data in the frequency and time. In particular we are interested to understand the complexity of the system and understand the cause of sudden as well as the slow changes in the time dependence of the observables. We show as well our approach for handling the not uniform sampling interval and the broad frequency content characterizing the paleoclimatic databases. In particular we worked to the development of a robust data analysis to answer the key questions about the correlation between rapid climatic changes and changes in the human habits and quantitatively elaborate a model for the processed data. Here we present the preliminary results on synthetics as well as on real data for the data visualization for the trend identification with a smoothing procedure, for the identification of sharp changes in the data as function of time with AutoRegressive approach. In addition to that we use the cross-correlation and cross spectrum by applying the Multiple Filtering Technique(MFT) of different pollen data from same location and same pollen data from different locations to identify the short and long period terms and to quantify the similarities in time and frequency domain.

Relaxation dynamics in the presence of pulse multiplicative noise sources with different correlation properties

NASA Astrophysics Data System (ADS)

Kargovsky, A. V.; Chichigina, O. A.; Anashkina, E. I.; Valenti, D.; Spagnolo, B.

2015-10-01

The relaxation dynamics of a system described by a Langevin equation with pulse multiplicative noise sources with different correlation properties is considered. The solution of the corresponding Fokker-Planck equation is derived for Gaussian white noise. Moreover, two pulse processes with regulated periodicity are considered as a noise source: the dead-time-distorted Poisson process and the process with fixed time intervals, which is characterized by an infinite correlation time. We find that the steady state of the system is dependent on the correlation properties of the pulse noise. An increase of the noise correlation causes the decrease of the mean value of the solution at the steady state. The analytical results are in good agreement with the numerical ones.

Relaxation dynamics in the presence of pulse multiplicative noise sources with different correlation properties.

PubMed

Kargovsky, A V; Chichigina, O A; Anashkina, E I; Valenti, D; Spagnolo, B

2015-10-01

The relaxation dynamics of a system described by a Langevin equation with pulse multiplicative noise sources with different correlation properties is considered. The solution of the corresponding Fokker-Planck equation is derived for Gaussian white noise. Moreover, two pulse processes with regulated periodicity are considered as a noise source: the dead-time-distorted Poisson process and the process with fixed time intervals, which is characterized by an infinite correlation time. We find that the steady state of the system is dependent on the correlation properties of the pulse noise. An increase of the noise correlation causes the decrease of the mean value of the solution at the steady state. The analytical results are in good agreement with the numerical ones.

Effects of Temporal Features and Order on the Apparent duration of a Visual Stimulus

PubMed Central

Bruno, Aurelio; Ayhan, Inci; Johnston, Alan

2012-01-01

The apparent duration of a visual stimulus has been shown to be influenced by its speed. For low speeds, apparent duration increases linearly with stimulus speed. This effect has been ascribed to the number of changes that occur within a visual interval. Accordingly, a higher number of changes should produce an increase in apparent duration. In order to test this prediction, we asked subjects to compare the relative duration of a 10-Hz drifting comparison stimulus with a standard stimulus that contained a different number of changes in different conditions. The standard could be static, drifting at 10 Hz, or mixed (a combination of variable duration static and drifting intervals). In this last condition the number of changes was intermediate between the static and the continuously drifting stimulus. For all standard durations, the mixed stimulus looked significantly compressed (∼20% reduction) relative to the drifting stimulus. However, no difference emerged between the static (that contained no changes) and the mixed stimuli (which contained an intermediate number of changes). We also observed that when the standard was displayed first, it appeared compressed relative to when it was displayed second with a magnitude that depended on standard duration. These results are at odds with a model of time perception that simply reflects the number of temporal features within an interval in determining the perceived passing of time. PMID:22461778

Effects of computing time delay on real-time control systems

NASA Technical Reports Server (NTRS)

Shin, Kang G.; Cui, Xianzhong

1988-01-01

The reliability of a real-time digital control system depends not only on the reliability of the hardware and software used, but also on the speed in executing control algorithms. The latter is due to the negative effects of computing time delay on control system performance. For a given sampling interval, the effects of computing time delay are classified into the delay problem and the loss problem. Analysis of these two problems is presented as a means of evaluating real-time control systems. As an example, both the self-tuning predicted (STP) control and Proportional-Integral-Derivative (PID) control are applied to the problem of tracking robot trajectories, and their respective effects of computing time delay on control performance are comparatively evaluated. For this example, the STP (PID) controller is shown to outperform the PID (STP) controller in coping with the delay (loss) problem.

Possible control of subduction zone slow-earthquake periodicity by silica enrichment.

PubMed

Audet, Pascal; Bürgmann, Roland

2014-06-19

Seismic and geodetic observations in subduction zone forearcs indicate that slow earthquakes, including episodic tremor and slip, recur at intervals of less than six months to more than two years. In Cascadia, slow slip is segmented along strike and tremor data show a gradation from large, infrequent slip episodes to small, frequent slip events with increasing depth of the plate interface. Observations and models of slow slip and tremor require the presence of near-lithostatic pore-fluid pressures in slow-earthquake source regions; however, direct evidence of factors controlling the variability in recurrence times is elusive. Here we compile seismic data from subduction zone forearcs exhibiting recurring slow earthquakes and show that the average ratio of compressional (P)-wave velocity to shear (S)-wave velocity (vP/vS) of the overlying forearc crust ranges between 1.6 and 2.0 and is linearly related to the average recurrence time of slow earthquakes. In northern Cascadia, forearc vP/vS values decrease with increasing depth of the plate interface and with decreasing tremor-episode recurrence intervals. Low vP/vS values require a large addition of quartz in a mostly mafic forearc environment. We propose that silica enrichment varying from 5 per cent to 15 per cent by volume from slab-derived fluids and upward mineralization in quartz veins can explain the range of observed vP/vS values as well as the downdip decrease in vP/vS. The solubility of silica depends on temperature, and deposition prevails near the base of the forearc crust. We further propose that the strong temperature dependence of healing and permeability reduction in silica-rich fault gouge via dissolution-precipitation creep can explain the reduction in tremor recurrence time with progressive silica enrichment. Lower gouge permeability at higher temperatures leads to faster fluid overpressure development and low effective fault-normal stress, and therefore shorter recurrence times. Our results also agree with numerical models of slip stabilization under fault zone dilatancy strengthening caused by decreasing fluid pressure as pore space increases. This implies that temperature-dependent silica deposition, permeability reduction and fluid overpressure development control dilatancy and slow-earthquake behaviour.

Surface deformation time series and source modeling for a volcanic complex system based on satellite wide swath and image mode interferometry: The Lazufre system, central Andes

NASA Astrophysics Data System (ADS)

Anderssohn, J.; Motagh, M.; Walter, T. R.; Rosenau, M.; Kaufmann, H.; Oncken, O.

2009-12-01

The variable spatio-temporal scales of Earth's surface deformation in potentially hazardous volcanic areas pose a challenge for observation and assessment. Here we used Envisat data acquired in Wide Swath Mode (WSM) and Image Mode (IM) from ascending and descending geometry, respectively, to study time-dependent ground uplift at the Lazufre volcanic system in Chile and Argentina. A least-squares adjustment was performed on 65 IM interferograms that covered the time period of 2003-2008. We obtained a clear trend of uplift reaching 15-16 cm in this 5-year interval. Using a joint inversion of ascending and descending interferograms, we evaluated the geometry and time-dependent progression of a horizontally extended pressurized source beneath the Lazufre volcanic system. Our results hence indicate that an extended magma body at a depth between 10 and 15 km would account for most of the ground uplift. The maximum inflation reached up to ~40 cm during 2003-2008. The lateral propagation velocity of the intrusion was estimated to be nearly constant at 5-10 km/yr during the observation time, which has important implications for the physical understanding of magma intrusion processes.

Climate modeling for Yamal territory using supercomputer atmospheric circulation model ECHAM5-wiso

NASA Astrophysics Data System (ADS)

Denisova, N. Y.; Gribanov, K. G.; Werner, M.; Zakharov, V. I.

2015-11-01

Dependences of monthly means of regional averages of model atmospheric parameters on initial and boundary condition remoteness in the past are the subject of the study. We used atmospheric general circulation model ECHAM5-wiso for simulation of monthly means of regional averages of climate parameters for Yamal region and different periods of premodeling. Time interval was varied from several months to 12 years. We present dependences of model monthly means of regional averages of surface temperature, 2 m air temperature and humidity for December of 2000 on duration of premodeling. Comparison of these results with reanalysis data showed that best coincidence with true parameters could be reached if duration of pre-modelling is approximately 10 years.

[EEG features during olfactory stimulation in drug dependence persons].

PubMed

Batukhtina, E I; Nevidimova, T I; Vetlugina, T P; Kokorina, N P; Bokhan, N A

2013-01-01

Power spectra analysis EEG was used for baseline interval and during olfactory stimulation in drug dependence and healthy persons. Intergroup differences of EEG spectra were related with enhancement of cortex biopotential power in narcological patients at parietal and temporal sites. Interhemispheres features of frequency bands contribution in EEG spectra were identified. Increased biopotential power in drug dependence persons was observed at left temporal hemisphere in high-frequency bands in baseline interval and during olfactory stimulation. Increased power of alpha activity was typical for right temporal hemisphere in narcological patients as compare to healthy persons. Detected neurophysiological patterns may be related with psychological and behavioral features of addictive disorders.

Finding Every Root of a Broad Class of Real, Continuous Functions in a Given Interval

NASA Technical Reports Server (NTRS)

Tausworthe, Robert C.; Wolgast, Paul A.

2011-01-01

One of the most pervasive needs within the Deep Space Network (DSN) Metric Prediction Generator (MPG) view period event generation is that of finding solutions to given occurrence conditions. While the general form of an equation expresses equivalence between its left-hand and right-hand expressions, the traditional treatment of the subject subtracts the two sides, leaving an expression of the form Integral of(x) = 0. Values of the independent variable x satisfying this condition are roots, or solutions. Generally speaking, there may be no solutions, a unique solution, multiple solutions, or a continuum of solutions to a given equation. In particular, all view period events are modeled as zero crossings of various metrics; for example, the time at which the elevation of a spacecraft reaches its maximum value, as viewed from a Deep Space Station (DSS), is found by locating that point at which the derivative of the elevation function becomes zero. Moreover, each event type may have several occurrences within a given time interval of interest. For example, a spacecraft in a low Moon orbit will experience several possible occultations per day, each of which must be located in time. The MPG is charged with finding all specified event occurrences that take place within a given time interval (or pass ), without any special clues from operators as to when they may occur, for the entire spectrum of missions undertaken by the DSN. For each event type, the event metric function is a known form that can be computed for any instant within the interval. A method has been created for a mathematical root finder to be capable of finding all roots of an arbitrary continuous function, within a given interval, to be subject to very lenient, parameterized assumptions. One assumption is that adjacent roots are separated at least by a given amount, xGuard. Any point whose function value is less than ef in magnitude is considered to be a root, and the function values at distances xGuard away from a root are larger than ef, unless there is another root located in this vicinity. A root is considered found if, during iteration, two root candidates differ by less than a pre-specified ex, and the optimum cubic polynomial matching the function at the end and at two interval points (that is within a relative error fraction L at its midpoint) is reliable in indicating whether the function has extrema within the interval. The robustness of this method depends solely on choosing these four parameters that control the search. The roots of discontinuous functions were also found, but at degraded performance.

Formation Flying Control Implementation in Highly Elliptical Orbits

NASA Technical Reports Server (NTRS)

Capo-Lugo, Pedro A.; Bainum, Peter M.

2009-01-01

The Tschauner-Hempel equations are widely used to correct the separation distance drifts between a pair of satellites within a constellation in highly elliptical orbits [1]. This set of equations was discretized in the true anomaly angle [1] to be used in a digital steady-state hierarchical controller [2]. This controller [2] performed the drift correction between a pair of satellites within the constellation. The objective of a discretized system is to develop a simple algorithm to be implemented in the computer onboard the satellite. The main advantage of the discrete systems is that the computational time can be reduced by selecting a suitable sampling interval. For this digital system, the amount of data will depend on the sampling interval in the true anomaly angle [3]. The purpose of this paper is to implement the discrete Tschauner-Hempel equations and the steady-state hierarchical controller in the computer onboard the satellite. This set of equations is expressed in the true anomaly angle in which a relation will be formulated between the time and the true anomaly angle domains.

The deployment of attention in short-term memory tasks: trade-offs between immediate and delayed deployment.

PubMed

Bunting, Michael F; Cowan, Nelson; Colflesh, Greg H

2008-06-01

Memory at times depends on attention, as when attention is used to encode incoming, serial verbal information. When encoding and rehearsal are difficult or when attention is divided during list presentation, more attention is needed in the time following the presentation and just preceding the response. Across 12 experimental conditions observed in several experiments, we demonstrated this by introducing a nonverbal task with three levels of effort (no task, a natural nonverbal task, or an unnatural version of the task) during a brief retention interval in a short-term digit recall task. Interference from the task during the retention interval was greater when resources were drawn away from the encoding of the stimuli by other factors, including unpredictability of the end point of the list, rapid presentation, and a secondary task during list presentation. When those conditions complicate encoding of the list, we argue, attention is needed after the list so that the contents of passive memory (i.e., postcategorical phonological storage and/or precategorical sensory memory) may be retrieved and become the focus of attention for recall.

Preharvest Interval Periods and their relation to fruit growth stages and pesticide formulations.

PubMed

Alister, Claudio; Araya, Manuel; Becerra, Kevin; Saavedra, Jorge; Kogan, Marcelo

2017-04-15

The aim of this study was to evaluate the effect of pesticide formulations and fruit growth stages on the Pre-harvest Interval Period (PHI). Results showed that pesticide formulations did not affect the initial deposit and dissipation rate. However, the fruit growth stage at the application time showed a significant effect on the above-mentioned parameters. Fruit diameter increases in one millimeter pesticide dissipation rates were reduced in -0.033mgkg -1 day -1 (R 2 =0.87; p<0.001) for grapes and -0.014mgkg -1 day -1 (R 2 =0.85; p<0.001) for apples. The relation between solar radiation, air humidity and temperature, and pesticide dissipation rates were dependent on fruit type. PHI could change according to the application time, because of the initial amount of pesticide deposit in the fruits and change in the dissipation rates. Because Maximum Residue Level are becoming more restrictive, it is more important to consider the fruit growth stage effects on pesticide when performing dissipation studies to define PHI. Copyright © 2016. Published by Elsevier Ltd.

The impacts of marijuana dispensary density and neighborhood ecology on marijuana abuse and dependence.

PubMed

Mair, Christina; Freisthler, Bridget; Ponicki, William R; Gaidus, Andrew

2015-09-01

As an increasing number of states liberalize cannabis use and develop laws and local policies, it is essential to better understand the impacts of neighborhood ecology and marijuana dispensary density on marijuana use, abuse, and dependence. We investigated associations between marijuana abuse/dependence hospitalizations and community demographic and environmental conditions from 2001 to 2012 in California, as well as cross-sectional associations between local and adjacent marijuana dispensary densities and marijuana hospitalizations. We analyzed panel population data relating hospitalizations coded for marijuana abuse or dependence and assigned to residential ZIP codes in California from 2001 through 2012 (20,219 space-time units) to ZIP code demographic and ecological characteristics. Bayesian space-time misalignment models were used to account for spatial variations in geographic unit definitions over time, while also accounting for spatial autocorrelation using conditional autoregressive priors. We also analyzed cross-sectional associations between marijuana abuse/dependence and the density of dispensaries in local and spatially adjacent ZIP codes in 2012. An additional one dispensary per square mile in a ZIP code was cross-sectionally associated with a 6.8% increase in the number of marijuana hospitalizations (95% credible interval 1.033, 1.105) with a marijuana abuse/dependence code. Other local characteristics, such as the median household income and age and racial/ethnic distributions, were associated with marijuana hospitalizations in cross-sectional and panel analyses. Prevention and intervention programs for marijuana abuse and dependence may be particularly essential in areas of concentrated disadvantage. Policy makers may want to consider regulations that limit the density of dispensaries. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Patient-specific Distraction Regimen to Avoid Growth-rod Failure.

PubMed

Agarwal, Aakash; Jayaswal, Arvind; Goel, Vijay K; Agarwal, Anand K

2018-02-15

A finite element study to establish the relationship between patient's curve flexibility (determined using curve correction under gravity) in juvenile idiopathic scoliosis and the required distraction frequency to avoid growth rod fracture, as a function of time. To perform a parametric analysis using a juvenile scoliotic spine model (single mid-thoracic curve with the apex at the eighth thoracic vertebra) and establish the relationship between curve flexibility (determined using curve correction under gravity) and the distraction interval that allows a higher factor of safety for the growth rods. Previous studies have shown that frequent distraction with smaller magnitude of distractions are less likely to result in rod failure. However there has not been any methodology or a chart provided to apply this knowledge on to the individual patients that undergo the treatment. This study aims to fill in that gap. The parametric study was performed by varying the material properties of the disc, hence altering the axial stiffness of the scoliotic spine model. The stresses on the rod were found to increase with increased axial stiffness of the spine, and this resulted in the increase of required optimal frequency to achieve a factor of safety of two for growth rods. A relationship between the percentage correction in Cobb's angle due to gravity alone, and the required distraction interval for limiting the maximum von Mises stress to 255 MPa on the growth rods was established. The distraction interval required to limit the stresses to the selected nominal value reduces with increase in stiffness of the spine. Furthermore, the appropriate distraction interval reduces for each model as the spine becomes stiffer with time (autofusion). This points to the fact the optimal distraction frequency is a time-dependent variable that must be achieved to keep the maximum von Mises stress under the specified factor of safety. The current study demonstrates the possibility of translating fundamental information from finite element modeling to the clinical arena, for mitigating the occurrence of growth rod fracture, that is, establishing a relationship between optimal distraction interval and curve flexibility (determined using curve correction under gravity). N/A.

Buffered coscheduling for parallel programming and enhanced fault tolerance

DOEpatents

Petrini, Fabrizio [Los Alamos, NM; Feng, Wu-chun [Los Alamos, NM

2006-01-31

A computer implemented method schedules processor jobs on a network of parallel machine processors or distributed system processors. Control information communications generated by each process performed by each processor during a defined time interval is accumulated in buffers, where adjacent time intervals are separated by strobe intervals for a global exchange of control information. A global exchange of the control information communications at the end of each defined time interval is performed during an intervening strobe interval so that each processor is informed by all of the other processors of the number of incoming jobs to be received by each processor in a subsequent time interval. The buffered coscheduling method of this invention also enhances the fault tolerance of a network of parallel machine processors or distributed system processors

Achilles tendinosis – a morphometrical study in a rat model

PubMed Central

Silva, Rafael Duarte; Glazebrook, Mark Anthony; Campos, Vinicius Castro; Vasconcelos, Anilton Cesar

2011-01-01

This study addresses the morphopathogenesis of Achilles tendinosis, using a rat model and presenting quantitative analysis of time-dependent histological changes. Thirty Wistar rats were used, randomly split in experimental and control groups. Animals of the experimental group were submitted to a treadmill running scheme. Five animals of each group were euthanized at four, eight and sixteen weeks. Achilles tendons were collected and processed routinely for histopath sections. Slides were stained by Hematoxylin-Eosin, Picrosirius Red, Alcian Blue, AgNOR, TUNEL and evaluated morphometrically. Cellular density decreased slightly along the time and was higher in the experimental group than in controls at fourth, eighth and sixteenth weeks. Fiber microtearing, percentual of reticular fibers and glycosaminoglycans content increased along the time and were higher in experimental group than in controls at all-time intervals. AgNOR labeling here interpreted as a marker of transcription activity was higher in the experimental groups than in controls at all-time intervals. Apoptotic cells were more frequent and diffusely distributed in tendinosis samples than in control groups. These results suggest that as mechanical overload is becoming chronic, cellular turnover and matrix deposition increases leading to tendinosis. The combination of staining techniques and morphometry used here to describe the evolution of lesions occurring in a rat model system has proved to be suited for the study of induced Achilles tendinosis. PMID:22076169

'Stroke Room': Diagnosis and Treatment at a Single Location for Rapid Intraarterial Stroke Treatment.

PubMed

Ragoschke-Schumm, Andreas; Yilmaz, Umut; Kostopoulos, Panagiotis; Lesmeister, Martin; Manitz, Matthias; Walter, Silke; Helwig, Stefan; Schwindling, Lenka; Fousse, Mathias; Haass, Anton; Garner, Dominique; Körner, Heiko; Roumia, Safwan; Grunwald, Iris; Nasreldein, Ali; Halmer, Ramona; Liu, Yang; Schlechtriemen, Thomas; Reith, Wolfgang; Fassbender, Klaus

2015-01-01

For patients with acute ischemic stroke, intra-arterial treatment (IAT) is considered to be an effective strategy for removing the obstructing clot. Because outcome crucially depends on time to treatment ('time-is-brain' concept), we assessed the effects of an intervention based on performing all the time-sensitive diagnostic and therapeutic procedures at a single location on the delay before intra-arterial stroke treatment. Consecutive acute stroke patients with large vessel occlusion who obtained IAT were evaluated before and after implementation (April 26, 2010) of an intervention focused on performing all the diagnostic and therapeutic measures at a single site ('stroke room'). After implementation of the intervention, the median intervals between admission and first angiography series were significantly shorter for 174 intervention patients (102 min, interquartile range (IQR) 85-120 min) than for 81 control patients (117 min, IQR 89-150 min; p < 0.05), as were the intervals between admission and clot removal or end of angiography (152 min, IQR 123-185 min vs. 190 min, IQR 163-227 min; p < 0.001). However, no significant differences in clinical outcome were observed. This study shows for the, to our knowledge, first time that for patients with acute ischemic stroke, stroke diagnosis and treatment at a single location ('stroke room') saves crucial time until IAT. © 2015 S. Karger AG, Basel.

Factors affecting red blood cell storage age at the time of transfusion.

PubMed

Dzik, Walter H; Beckman, Neil; Murphy, Michael F; Delaney, Meghan; Flanagan, Peter; Fung, Mark; Germain, Marc; Haspel, Richard L; Lozano, Miguel; Sacher, Ronald; Szczepiorkowski, Zbigniew; Wendel, Silvano

2013-12-01

Clinical trials are investigating the potential benefit resulting from a reduced maximum storage interval for red blood cells (RBCs). The key drivers that determine RBC age at the time of issue vary among individual hospitals. Although progressive reduction in the maximum storage period of RBCs would be expected to result in smaller hospital inventories and reduced blood availability, the magnitude of the effect is unknown. Data on current hospital blood inventories were collected from 11 hospitals and three blood centers in five nations. A general predictive model for the age of RBCs at the time of issue was developed based on considerations of demand for RBCs in the hospital. Age of RBCs at issue is sensitive to the following factors: ABO group, storage age at the time of receipt by the hospital, the restock interval, inventory reserve, mean demand, and variation in demand. A simple model, based on hospital demand, may serve as the basis for examining factors affecting the storage age of RBCs in hospital inventories. The model suggests that the age of RBCs at the time of their issue to the patient depends on factors external to the hospital transfusion service. Any substantial change in the expiration date of stored RBCs will need to address the broad variation in demand for RBCs while attempting to balance considerations of availability and blood wastage. © 2013 American Association of Blood Banks.

Effect of DA-8031, a novel oral compound for premature ejaculation, on male rat sexual behavior.

PubMed

Kang, Kyung Koo; Sung, Ji Hyun; Kim, Soon Hoe; Lee, Sukhyang

2014-03-01

DA-8031 is a potent and selective serotonin transporter inhibitor developed for the treatment of premature ejaculation. The aim of the present study was to investigate the effects of DA-8031 on male sexual behavior in a rat model. Sexual behavior was examined after an acute oral administration of 10, 30 or 100 mg/kg of DA-8031 in copulation studies with female rats. Pharmacokinetic parameters were calculated after oral administration of DA-8031 at a dose level of 30 mg/kg. DA-8031 treatment produced a dose-dependent increase in ejaculation latency time and showed statistical significance at 30 and 100 mg/kg dosage levels compared with the vehicle (P < 0.05). In addition, DA-8031 treatment reduced the mean number of ejaculations in a dose-dependent manner. No changes in post-ejaculatory interval, numbers of mounts, intromissions or ejaculations were observed at any dose. In pharmacokinetic study, the blood concentration of DA-8031 peaked at 0.38 ± 0.14 h after oral administration, and then rapidly declined with a half-life of 1.79 ± 0.32 h. Treatment with DA-8031 delays the ejaculation latency time without affecting the initiation of mounting behavior or post-ejaculatory interval in rats. Furthermore, DA-8031 is rapidly absorbed and eliminated after oral administration in rats. These preclinical findings provide a clue for the clinical testing of DA-8031 as an "on-demand" agent for premature ejaculation. © 2013 The Japanese Urological Association.

Quantifying economic fluctuations by adapting methods of statistical physics

NASA Astrophysics Data System (ADS)

Plerou, Vasiliki

2001-09-01

The first focus of this thesis is the investigation of cross-correlations between the price fluctuations of different stocks using the conceptual framework of random matrix theory (RMT), developed in physics to describe the statistical properties of energy-level spectra of complex nuclei. RMT makes predictions for the statistical properties of matrices that are universal, i.e., do not depend on the interactions between the elements comprising the system. In physical systems, deviations from the predictions of RMT provide clues regarding the mechanisms controlling the dynamics of a given system so this framework is of potential value if applied to economic systems. This thesis compares the statistics of cross-correlation matrix C-whose elements Cij are the correlation coefficients of price fluctuations of stock i and j-against the ``null hypothesis'' of a random matrix having the same symmetry properties. It is shown that comparison of the eigenvalue statistics of C with RMT results can be used to distinguish random and non-random parts of C. The non-random part of C which deviates from RMT results, provides information regarding genuine cross-correlations between stocks. The interpretations and potential practical utility of these deviations are also investigated. The second focus is the characterization of the dynamics of stock price fluctuations. The statistical properties of the changes G Δt in price over a time interval Δ t are quantified and the statistical relation between G Δt and the trading activity-measured by the number of transactions NΔ t in the interval Δt is investigated. The statistical properties of the volatility, i.e., the time dependent standard deviation of price fluctuations, is related to two microscopic quantities: NΔt and the variance W2Dt of the price changes for all transactions in the interval Δ t. In addition, the statistical relationship between G Δt and the number of shares QΔt traded in Δ t is investigated.

A Phase One Archaeological Survey of the Cottonwood, Redwood and Yellow Medicine Drainages in Southwestern Minnesota

DTIC Science & Technology

1989-03-01

and June 15, a three person field team conducted the archaeological survey in the Cottonwood, Redwood, and Yellow Medicine subbasins. The project...discovering sites that are exposed on the ground surface. A three- person survey team can examine between 100 and 150 acres per day, depending on field...results are dependent on the interval used between individual shovel tests. When 15 meter intervals between tests are used, we estimate that one person

Analysis of thickness dependent on crystallization kinetics in thin isotactic-polysterene films

NASA Astrophysics Data System (ADS)

Khairuddin

2016-11-01

Crystalliaztion kinetics of thin film of Isotactic Polysterene (it-PS) films has been studied. Thin PET films having thickness of 338, 533, 712, 1096, 1473, and 2185 A° were prepared by using spin-cast technique. The it-PS crystals were grown on Linkam-hostage in the temperature range 130-240°C with an interval of 10°C. The crystal growths are measured by optical microscopy in lateral direction. It was found that a substantial thickness dependence on crystallisation rate. The analysis using fitting technique based on theory crystal growth of Lauritzen-Hoffman showed that the fitting technique could not resolve to predict the mechanism controlling the thickness dependence on the rate of crystallisation. The possible reasons were due to the crystallisation rate varies with the type of crystals (smooth, rough, overgrowth terrace), and the crystallisation rate changes with the time of crystallisation.

Assessment of toxicity and coagulopathy of brodifacoum in Japanese quail and testing in wild owls.

PubMed

Webster, Kirstin H; Harr, Kendal E; Bennett, Darin C; Williams, Tony D; Cheng, Kimberly M; Maisonneuve, France; Elliott, John E

2015-07-01

Based on detection of hepatic residues, scavenging and predatory non-target raptors are widely exposed to second generation anticoagulant rodenticides (SGARs). A small proportion, generally <10%, of tested birds are diagnosed as acutely poisoned. Little is known, however, of sub-lethal effects of SGARs, such as interaction of clotting capacity with traumatic injury. Assessment of coagulation function of birds submitted live to wildlife rehabilitators or veterinarians may provide a means of establishing the proportion of animals suffering sub-lethal coagulopathies, as well as identifying individuals requiring treatment. As a first step in exploring the potential of this approach, we dosed Japanese quail (Coturnix japonica) with the SGAR, brodifacoum, at 0, 0.8, 1.4, 1.9, and 2.5 mg/kg and sampled birds at 1, 3, 5 and 7 days post-dosing. Prothrombin time (PT), which measures the extrinsic coagulation pathway, was significantly prolonged in 98% of brodifacoum-exposed quail in a dose- and time-dependent manner. 50-fold prolongation of PT occurred at higher brodifacoum dosages and correlated to hemorrhage found at necropsy. Activated clotting time (ACT), a measure of the intrinsic pathway also increased with dose and time. Hemoglobin (Hb) and hematocrit (Hct) decreased dose- and time-dependently at doses ≥1.4 mg/kg with no significant change at 0.8 mg/kg. Reference intervals for PT (10.0-16.2 s), ACT (30-180 s), Hb (9.6-18.4 g/dl), and Hct (34-55%) were established in Japanese quail. Species-specific reference intervals are required as barn owl PT (17-29 s) and quail PT were different. The proportion of brodifacoum-exposed quail with hemorrhage was not correlated with liver residues, but was correlated with PT, suggesting that this assay is a useful indicator of avian anticoagulant rodenticide exposure. PTs measured in free-living barn owls sampled between April 2009 and August 2010 in the lower Fraser Valley of BC do not suggest significant exposure to SGARs.

Priority queues with bursty arrivals of incoming tasks

NASA Astrophysics Data System (ADS)

Masuda, N.; Kim, J. S.; Kahng, B.

2009-03-01

Recently increased accessibility of large-scale digital records enables one to monitor human activities such as the interevent time distributions between two consecutive visits to a web portal by a single user, two consecutive emails sent out by a user, two consecutive library loans made by a single individual, etc. Interestingly, those distributions exhibit a universal behavior, D(τ)˜τ-δ , where τ is the interevent time, and δ≃1 or 3/2 . The universal behaviors have been modeled via the waiting-time distribution of a task in the queue operating based on priority; the waiting time follows a power-law distribution Pw(τ)˜τ-α with either α=1 or 3/2 depending on the detail of queuing dynamics. In these models, the number of incoming tasks in a unit time interval has been assumed to follow a Poisson-type distribution. For an email system, however, the number of emails delivered to a mail box in a unit time we measured follows a power-law distribution with general exponent γ . For this case, we obtain analytically the exponent α , which is not necessarily 1 or 3/2 and takes nonuniversal values depending on γ . We develop the generating function formalism to obtain the exponent α , which is distinct from the continuous time approximation used in the previous studies.

Reaction Event Counting Statistics of Biopolymer Reaction Systems with Dynamic Heterogeneity.

PubMed

Lim, Yu Rim; Park, Seong Jun; Park, Bo Jung; Cao, Jianshu; Silbey, Robert J; Sung, Jaeyoung

2012-04-10

We investigate the reaction event counting statistics (RECS) of an elementary biopolymer reaction in which the rate coefficient is dependent on states of the biopolymer and the surrounding environment and discover a universal kinetic phase transition in the RECS of the reaction system with dynamic heterogeneity. From an exact analysis for a general model of elementary biopolymer reactions, we find that the variance in the number of reaction events is dependent on the square of the mean number of the reaction events when the size of measurement time is small on the relaxation time scale of rate coefficient fluctuations, which does not conform to renewal statistics. On the other hand, when the size of the measurement time interval is much greater than the relaxation time of rate coefficient fluctuations, the variance becomes linearly proportional to the mean reaction number in accordance with renewal statistics. Gillespie's stochastic simulation method is generalized for the reaction system with a rate coefficient fluctuation. The simulation results confirm the correctness of the analytic results for the time dependent mean and variance of the reaction event number distribution. On the basis of the obtained results, we propose a method of quantitative analysis for the reaction event counting statistics of reaction systems with rate coefficient fluctuations, which enables one to extract information about the magnitude and the relaxation times of the fluctuating reaction rate coefficient, without a bias that can be introduced by assuming a particular kinetic model of conformational dynamics and the conformation dependent reactivity. An exact relationship is established between a higher moment of the reaction event number distribution and the multitime correlation of the reaction rate for the reaction system with a nonequilibrium initial state distribution as well as for the system with the equilibrium initial state distribution.

[Structure of maxillary sinus mucous membrane under normal conditions and in odontogenic perforative sinusitis].

PubMed

Baĭdik, O D; Logvinov, S V; Zubarev, S G; Sysoliatin, P G; Gurin, A A

2011-01-01

Methods of light, electron microscopy and immunohistochemistry were used to study the samples of maxillary sinus (MS) mucous membrane (MM) under normal conditions and in odontogenic sinusitis. To study the normal structure, the samples were obtained at autopsy from 26 human corpses 12-24 hours after death. Electron microscopic and immunohistochemical study was performed on biopsies of grossly morphologically unchanged MS MM, obtained during the operations for retention cysts in 6 patients. MS MM in perforative sinusitis was studied using the biopsies obtained from 43 patients. The material is broken into 4 groups depending on perforative sinusitis duration. Under normal conditions, MS MM is lined with a pseudostratified columnar ciliated epithelium. Degenerative changes of ciliated epithelial cells were already detected at short time intervals after MS perforations and become apparent due to reduction of specific volume of mitochondria and, rough endoplasmic reticulum, and increase of nuclear-cytoplasmic ratio. In the globlet cells, the reduction of nuclear-cytoplasmic ratio was associated with the disturbance of the secretory product release. At time intervals exceeding 3 months, epithelium underwent metaplasia into simple cuboidal and stratified squamous keratinized, while in MS MM lamina propria, cellular infiltration was increased. CD4+ cell content in sinus MM gradually increased, while at late periods after perforation occurrence it decreased. Low CD4+ cell count within the epithelium and the absence of muromidase on the surface of MS MM was detected. With the increase of the time interval since MS perforation, the number of CD8+ and CD20+ cells in MS MM was found to increase.

An empirical comparison of SPM preprocessing parameters to the analysis of fMRI data.

PubMed

Della-Maggiore, Valeria; Chau, Wilkin; Peres-Neto, Pedro R; McIntosh, Anthony R

2002-09-01

We present the results from two sets of Monte Carlo simulations aimed at evaluating the robustness of some preprocessing parameters of SPM99 for the analysis of functional magnetic resonance imaging (fMRI). Statistical robustness was estimated by implementing parametric and nonparametric simulation approaches based on the images obtained from an event-related fMRI experiment. Simulated datasets were tested for combinations of the following parameters: basis function, global scaling, low-pass filter, high-pass filter and autoregressive modeling of serial autocorrelation. Based on single-subject SPM analysis, we derived the following conclusions that may serve as a guide for initial analysis of fMRI data using SPM99: (1) The canonical hemodynamic response function is a more reliable basis function to model the fMRI time series than HRF with time derivative. (2) Global scaling should be avoided since it may significantly decrease the power depending on the experimental design. (3) The use of a high-pass filter may be beneficial for event-related designs with fixed interstimulus intervals. (4) When dealing with fMRI time series with short interstimulus intervals (<8 s), the use of first-order autoregressive model is recommended over a low-pass filter (HRF) because it reduces the risk of inferential bias while providing a relatively good power. For datasets with interstimulus intervals longer than 8 seconds, temporal smoothing is not recommended since it decreases power. While the generalizability of our results may be limited, the methods we employed can be easily implemented by other scientists to determine the best parameter combination to analyze their data.

Eliminating livelock by assigning the same priority state to each message that is input into a flushable routing system during N time intervals

DOEpatents

Faber, V.

1994-11-29

Livelock-free message routing is provided in a network of interconnected nodes that is flushable in time T. An input message processor generates sequences of at least N time intervals, each of duration T. An input register provides for receiving and holding each input message, where the message is assigned a priority state p during an nth one of the N time intervals. At each of the network nodes a message processor reads the assigned priority state and awards priority to messages with priority state (p-1) during an nth time interval and to messages with priority state p during an (n+1) th time interval. The messages that are awarded priority are output on an output path toward the addressed output message processor. Thus, no message remains in the network for a time longer than T. 4 figures.

Eliminating livelock by assigning the same priority state to each message that is inputted into a flushable routing system during N time intervals

DOEpatents

Faber, Vance

1994-01-01

Livelock-free message routing is provided in a network of interconnected nodes that is flushable in time T. An input message processor generates sequences of at least N time intervals, each of duration T. An input register provides for receiving and holding each input message, where the message is assigned a priority state p during an nth one of the N time intervals. At each of the network nodes a message processor reads the assigned priority state and awards priority to messages with priority state (p-1) during an nth time interval and to messages with priority state p during an (n+1) th time interval. The messages that are awarded priority are output on an output path toward the addressed output message processor. Thus, no message remains in the network for a time longer than T.

a New Approach for Accuracy Improvement of Pulsed LIDAR Remote Sensing Data

NASA Astrophysics Data System (ADS)

Zhou, G.; Huang, W.; Zhou, X.; He, C.; Li, X.; Huang, Y.; Zhang, L.

2018-05-01

In remote sensing applications, the accuracy of time interval measurement is one of the most important parameters that affect the quality of pulsed lidar data. The traditional time interval measurement technique has the disadvantages of low measurement accuracy, complicated circuit structure and large error. A high-precision time interval data cannot be obtained in these traditional methods. In order to obtain higher quality of remote sensing cloud images based on the time interval measurement, a higher accuracy time interval measurement method is proposed. The method is based on charging the capacitance and sampling the change of capacitor voltage at the same time. Firstly, the approximate model of the capacitance voltage curve in the time of flight of pulse is fitted based on the sampled data. Then, the whole charging time is obtained with the fitting function. In this method, only a high-speed A/D sampler and capacitor are required in a single receiving channel, and the collected data is processed directly in the main control unit. The experimental results show that the proposed method can get error less than 3 ps. Compared with other methods, the proposed method improves the time interval accuracy by at least 20 %.

Map of Pseudo-F-statistics of seismic noise parameters as an indicator of current seismic danger in Japan

NASA Astrophysics Data System (ADS)

Lyubushin, Alexey

2016-04-01

The problem of estimate of current seismic danger based on monitoring of seismic noise properties from broadband seismic network F-net in Japan (84 stations) is considered. Variations of the following seismic noise parameters are analyzed: multifractal singularity spectrum support width, generalized Hurst exponent, minimum Hölder-Lipschitz exponent and minimum normalized entropy of squared orthogonal wavelet coefficients. These parameters are estimated within adjacent time windows of the length 1 day for seismic noise waveforms from each station. Calculating daily median values of these parameters by all stations provides 4-dimensional time series which describes integral properties of the seismic noise in the region covered by the network. Cluster analysis is applied to the sequence of clouds of 4-dimensional vectors within moving time window of the length 365 days with mutual shift 3 days starting from the beginning of 1997 up to the current time. The purpose of the cluster analysis is to find the best number of clusters (BNC) from probe numbers which are varying from 1 up to the maximum value 40. The BNC is found from the maximum of pseudo-F-statistics (PFS). A 2D map could be created which presents dependence of PFS on the tested probe number of clusters and the right-hand end of moving time window which is rather similar to usual spectral time-frequency diagrams. In the paper [1] it was shown that the BNC before Tohoku mega-earthquake on March 11, 2011, has strongly chaotic regime with jumps from minimum up to maximum values in the time interval 1 year before the event and this time intervals was characterized by high PFS values. The PFS-map is proposed as the method for extracting time intervals with high current seismic danger. The next danger time interval after Tohoku mega-EQ began at the end of 2012 and was finished at the middle of 2013. Starting from middle of 2015 the high PFS values and chaotic regime of BNC variations were returned. This could be interpreted as the increasing of the danger of the next mega-EQ in Japan in the region of Nankai Trough [1] at the first half of 2016. References 1. Lyubushin, A., 2013. How soon would the next mega-earthquake occur in Japan? // Natural Science, 5 (8A1), 1-7. http://dx.doi.org/10.4236/ns.2013.58A1001

Effect of aspirin in pregnant women is dependent on increase in bleeding time.

PubMed

Dumont, A; Flahault, A; Beaufils, M; Verdy, E; Uzan, S

1999-01-01

Randomized trials with low-dose aspirin to prevent preeclampsia and intrauterine growth restriction have yielded conflicting results. In particular, 3 recent large trials were not conclusive. Study designs, however, varied greatly regarding selection of patients, dose of aspirin, and timing of treatment, all of which can be determinants of the results. Retrospectively analyzing the conditions associated with failure or success of aspirin may therefore help to draw up new hypotheses and prepare for more specific randomized trials. We studied a historical cohort of 187 pregnant women who were considered at high risk for preeclampsia, intrauterine growth restriction, or both and were therefore treated with low-dose aspirin between 1989 and 1994. Various epidemiologic, clinical, and laboratory data were extracted from the files. Univariate and multivariate analyses were performed to search for independent parameters associated with the outcome of pregnancy. Age, parity, weight, height, and race had no influence on the outcome. The success rate was higher when treatment was given because of previous poor pregnancy outcomes than when it was given for other indications, and the patients with successful therapy had started aspirin earlier than had those with therapy failure (17.7 vs 20.0 weeks' gestation, P =.04). After multivariate analysis an increase in Ivy bleeding time after 10 days of treatment by >2 minutes was an independent predictor of a better outcome (odds ratio 0.22, 95% confidence interval 0.09-0.51). Borderline statistical significance was observed for aspirin initiation before 17 weeks' gestation (odds ratio 0.44, 95% confidence interval 0.18-1. 08). Abnormal uterine artery Doppler velocimetric scan at 20-24 weeks' gestation (odds ratio 3.31, 95% confidence interval 1.41-7.7), abnormal umbilical artery Doppler velocimetric scan after 26 weeks' gestation (odds ratio 37.6, 95% confidence interval 3.96-357), and use of antihypertensive therapy (odds ratio 6.06, 95% confidence interval 2.45-15) were independent predictors of poor outcome. Efficacy of aspirin seems optimal when bleeding time increases >/=2 minutes with treatment, indicating a more powerful antiplatelet effect. This suggests that the dose of aspirin should be adjusted according to a biologic marker of the antiplatelet effect. A prospective trial is warranted to test this hypothesis.

A theoretically consistent stochastic cascade for temporal disaggregation of intermittent rainfall

NASA Astrophysics Data System (ADS)

Lombardo, F.; Volpi, E.; Koutsoyiannis, D.; Serinaldi, F.

2017-06-01

Generating fine-scale time series of intermittent rainfall that are fully consistent with any given coarse-scale totals is a key and open issue in many hydrological problems. We propose a stationary disaggregation method that simulates rainfall time series with given dependence structure, wet/dry probability, and marginal distribution at a target finer (lower-level) time scale, preserving full consistency with variables at a parent coarser (higher-level) time scale. We account for the intermittent character of rainfall at fine time scales by merging a discrete stochastic representation of intermittency and a continuous one of rainfall depths. This approach yields a unique and parsimonious mathematical framework providing general analytical formulations of mean, variance, and autocorrelation function (ACF) for a mixed-type stochastic process in terms of mean, variance, and ACFs of both continuous and discrete components, respectively. To achieve the full consistency between variables at finer and coarser time scales in terms of marginal distribution and coarse-scale totals, the generated lower-level series are adjusted according to a procedure that does not affect the stochastic structure implied by the original model. To assess model performance, we study rainfall process as intermittent with both independent and dependent occurrences, where dependence is quantified by the probability that two consecutive time intervals are dry. In either case, we provide analytical formulations of main statistics of our mixed-type disaggregation model and show their clear accordance with Monte Carlo simulations. An application to rainfall time series from real world is shown as a proof of concept.

How large a dataset should be in order to estimate scaling exponents and other statistics correctly in studies of solar wind turbulence

NASA Astrophysics Data System (ADS)

Rowlands, G.; Kiyani, K. H.; Chapman, S. C.; Watkins, N. W.

2009-12-01

Quantitative analysis of solar wind fluctuations are often performed in the context of intermittent turbulence and center around methods to quantify statistical scaling, such as power spectra and structure functions which assume a stationary process. The solar wind exhibits large scale secular changes and so the question arises as to whether the timeseries of the fluctuations is non-stationary. One approach is to seek a local stationarity by parsing the time interval over which statistical analysis is performed. Hence, natural systems such as the solar wind unavoidably provide observations over restricted intervals. Consequently, due to a reduction of sample size leading to poorer estimates, a stationary stochastic process (time series) can yield anomalous time variation in the scaling exponents, suggestive of nonstationarity. The variance in the estimates of scaling exponents computed from an interval of N observations is known for finite variance processes to vary as ~1/N as N becomes large for certain statistical estimators; however, the convergence to this behavior will depend on the details of the process, and may be slow. We study the variation in the scaling of second-order moments of the time-series increments with N for a variety of synthetic and “real world” time series, and we find that in particular for heavy tailed processes, for realizable N, one is far from this ~1/N limiting behavior. We propose a semiempirical estimate for the minimum N needed to make a meaningful estimate of the scaling exponents for model stochastic processes and compare these with some “real world” time series from the solar wind. With fewer datapoints the stationary timeseries becomes indistinguishable from a nonstationary process and we illustrate this with nonstationary synthetic datasets. Reference article: K. H. Kiyani, S. C. Chapman and N. W. Watkins, Phys. Rev. E 79, 036109 (2009).

Recurrence time statistics for finite size intervals

NASA Astrophysics Data System (ADS)

Altmann, Eduardo G.; da Silva, Elton C.; Caldas, Iberê L.

2004-12-01

We investigate the statistics of recurrences to finite size intervals for chaotic dynamical systems. We find that the typical distribution presents an exponential decay for almost all recurrence times except for a few short times affected by a kind of memory effect. We interpret this effect as being related to the unstable periodic orbits inside the interval. Although it is restricted to a few short times it changes the whole distribution of recurrences. We show that for systems with strong mixing properties the exponential decay converges to the Poissonian statistics when the width of the interval goes to zero. However, we alert that special attention to the size of the interval is required in order to guarantee that the short time memory effect is negligible when one is interested in numerically or experimentally calculated Poincaré recurrence time statistics.

Fine particulate air pollution and all-cause mortality within the Harvard Six-Cities Study: variations in risk by period of exposure.

PubMed

Villeneuve, Paul J; Goldberg, Mark S; Krewski, Daniel; Burnett, Richard T; Chen, Yue

2002-11-01

We used Poisson regression methods to examine the relation between temporal changes in the levels of fine particulate air pollution (PM(2.5)) and the risk of mortality among participants of the Harvard Six Cities longitudinal study. Our analyses were based on 1430 deaths that occurred between 1974 and 1991 in a cohort that accumulated 105,714 person-years of follow-up. For each city, indices of PM(2.5) were derived using daily samples. Individual level data were collected on several risk factors including: smoking, education, body mass index (BMI), and occupational exposure to dusts. Time-dependent indices of PM(2.5) were created across 13 calendar periods (< 1979, 1979, 1980, em leader, 1989, >/= 1990) to explore whether recent or chronic exposures were more important predictors of mortality. The relative risk (RR) of mortality calculated using Poisson regression based on average city-specific exposures that remained constant during follow-up was 1.31 [95% confidence interval (CI) = 1.12-1.52] per 18.6 microg/m(3) of PM(2.5). This result was similar to the risk calculated using the Cox model (RR = 1.26, 95% CI = 1.08-1.46). The RR of mortality was attenuated when the Poisson regression model included a time-dependent estimate of exposure (RR = 1.19, 95% CI = 1.04-1.36). There was little variation in RR across time-dependent indices of PM(2.5). The attenuated risk of mortality that was observed with a time-dependent index of PM(2.5) is due to the combined influence of city-specific variations in mortality rates and decreasing levels of air pollution that occurred during follow-up. The RR of mortality associated with PM(2.5) did not depend on when exposure occurred in relation to death, possibly because of little variation between the time-dependent city-specific exposure indices.

Glacial Cycles Influence Marine Methane Hydrate Formation

NASA Astrophysics Data System (ADS)

Malinverno, A.; Cook, A. E.; Daigle, H.; Oryan, B.

2018-01-01

Methane hydrates in fine-grained continental slope sediments often occupy isolated depth intervals surrounded by hydrate-free sediments. As they are not connected to deep gas sources, these hydrate deposits have been interpreted as sourced by in situ microbial methane. We investigate here the hypothesis that these isolated hydrate accumulations form preferentially in sediments deposited during Pleistocene glacial lowstands that contain relatively large amounts of labile particulate organic carbon, leading to enhanced microbial methanogenesis. To test this hypothesis, we apply an advection-diffusion-reaction model with a time-dependent organic carbon deposition controlled by glacioeustatic sea level variations. In the model, hydrate forms in sediments with greater organic carbon content deposited during the penultimate glacial cycle ( 120-240 ka). The model predictions match hydrate-bearing intervals detected in three sites drilled on the northern Gulf of Mexico continental slope, supporting the hypothesis of hydrate formation driven by enhanced organic carbon burial during glacial lowstands.

A comparison of analysis methods to estimate contingency strength.

PubMed

Lloyd, Blair P; Staubitz, Johanna L; Tapp, Jon T

2018-05-09

To date, several data analysis methods have been used to estimate contingency strength, yet few studies have compared these methods directly. To compare the relative precision and sensitivity of four analysis methods (i.e., exhaustive event-based, nonexhaustive event-based, concurrent interval, concurrent+lag interval), we applied all methods to a simulated data set in which several response-dependent and response-independent schedules of reinforcement were programmed. We evaluated the degree to which contingency strength estimates produced from each method (a) corresponded with expected values for response-dependent schedules and (b) showed sensitivity to parametric manipulations of response-independent reinforcement. Results indicated both event-based methods produced contingency strength estimates that aligned with expected values for response-dependent schedules, but differed in sensitivity to response-independent reinforcement. The precision of interval-based methods varied by analysis method (concurrent vs. concurrent+lag) and schedule type (continuous vs. partial), and showed similar sensitivities to response-independent reinforcement. Recommendations and considerations for measuring contingencies are identified. © 2018 Society for the Experimental Analysis of Behavior.

Permanent pacemaker implantation in octogenarians with unexplained syncope and positive electrophysiologic testing.

PubMed

Giannopoulos, Georgios; Kossyvakis, Charalampos; Panagopoulou, Vasiliki; Tsiachris, Dimitrios; Doudoumis, Konstantinos; Mavri, Maria; Vrachatis, Dimitrios; Letsas, Konstantinos; Efremidis, Michael; Katsivas, Apostolos; Lekakis, John; Deftereos, Spyridon

2017-05-01

Syncope is a common problem in the elderly, and a permanent pacemaker is a therapeutic option when a bradycardic etiology is revealed. However, the benefit of pacing when no association of symptoms to bradycardia has been shown is not clear, especially in the elderly. The aim of this study was to evaluate the effect of pacing on syncope-free mortality in patients aged 80 years or older with unexplained syncope and "positive" invasive electrophysiologic testing (EPT). This was an observational study. A positive EPT for the purposes of this study was defined by at least 1 of the following: a corrected sinus node recovery time of >525 ms, a basic HV interval of >55 ms, detection of infra-Hisian block, or appearance of second-degree atrioventricular block on atrial decremental pacing at a paced cycle length of >400 ms. Among the 2435 screened patients, 228 eligible patients were identified, 145 of whom were implanted with a pacemaker. Kaplan-Meier analysis determined that time to event (syncope or death) was 50.1 months (95% confidence interval 45.4-54.8 months) with a pacemaker vs 37.8 months (95% confidence interval 31.3-44.4 months) without a pacemaker (log-rank test, P = .001). The 4-year time-dependent estimate of the rate of syncope was 12% vs 44% (P < .001) and that of any-cause death was 41% vs 56% (P = .023), respectively. The multivariable odds ratio was 0.25 (95% confidence interval 0.15-0.40) after adjustment for potential confounders. In patients with unexplained syncope and signs of sinus node dysfunction or impaired atrioventricular conduction on invasive EPT, pacemaker implantation was independently associated with longer syncope-free survival. Significant differences were also shown in the individual components of the primary outcome measure (syncope and death from any cause). Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Estimation of the Undiagnosed Intervals of HIV-Infected Individuals by a Modified Back-Calculation Method for Reconstructing the Epidemic Curves.

PubMed

Wong, Ngai Sze; Wong, Ka Hing; Lee, Man Po; Tsang, Owen T Y; Chan, Denise P C; Lee, Shui Shan

2016-01-01

Undiagnosed infections accounted for the hidden proportion of HIV cases that have escaped from public health surveillance. To assess the population risk of HIV transmission, we estimated the undiagnosed interval of each known infection for constructing the HIV incidence curves. We used modified back-calculation methods to estimate the seroconversion year for each diagnosed patient attending any one of the 3 HIV specialist clinics in Hong Kong. Three approaches were used, depending on the adequacy of CD4 data: (A) estimating one's pre-treatment CD4 depletion rate in multilevel model;(B) projecting one's seroconversion year by referencing seroconverters' CD4 depletion rate; or (C) projecting from the distribution of estimated undiagnosed intervals in (B). Factors associated with long undiagnosed interval (>2 years) were examined in univariate analyses. Epidemic curves constructed from estimated seroconversion data were evaluated by modes of transmission. Between 1991 and 2010, a total of 3695 adult HIV patients were diagnosed. The undiagnosed intervals were derived from method (A) (28%), (B) (61%) and (C) (11%) respectively. The intervals ranged from 0 to 10 years, and were shortened from 2001. Heterosexual infection, female, Chinese and age >64 at diagnosis were associated with long undiagnosed interval. Overall, the peaks of the new incidence curves were reached 4-6 years ahead of reported diagnoses, while their contours varied by mode of transmission. Characteristically, the epidemic growth of heterosexual male and female declined after 1998 with slight rebound in 2004-2006, but that of MSM continued to rise after 1998. By determining the time of seroconversion, HIV epidemic curves could be reconstructed from clinical data to better illustrate the trends of new infections. With the increasing coverage of antiretroviral therapy, the undiagnosed interval can add to the measures for assessing HIV transmission risk in the population.

Estimation of postmortem interval based on colony development time for Anoplolepsis longipes (Hymenoptera: Formicidae).

PubMed

Goff, M L; Win, B H

1997-11-01

The postmortem interval for a set of human remains discovered inside a metal tool box was estimated using the development time required for a stratiomyid fly (Diptera: Stratiomyidae), Hermetia illucens, in combination with the time required to establish a colony of the ant Anoplolepsis longipes (Hymenoptera: Formicidae) capable of producing alate (winged) reproductives. This analysis resulted in a postmortem interval estimate of 14 + months, with a period of 14-18 months being the most probable time interval. The victim had been missing for approximately 18 months.

TIME-INTERVAL MEASURING DEVICE

DOEpatents

Gross, J.E.

1958-04-15

An electronic device for measuring the time interval between two control pulses is presented. The device incorporates part of a previous approach for time measurement, in that pulses from a constant-frequency oscillator are counted during the interval between the control pulses. To reduce the possible error in counting caused by the operation of the counter gating circuit at various points in the pulse cycle, the described device provides means for successively delaying the pulses for a fraction of the pulse period so that a final delay of one period is obtained and means for counting the pulses before and after each stage of delay during the time interval whereby a plurality of totals is obtained which may be averaged and multplied by the pulse period to obtain an accurate time- Interval measurement.

Monitoring molecular interactions using photon arrival-time interval distribution analysis

DOEpatents

Laurence, Ted A [Livermore, CA; Weiss, Shimon [Los Angels, CA

2009-10-06

A method for analyzing/monitoring the properties of species that are labeled with fluorophores. A detector is used to detect photons emitted from species that are labeled with one or more fluorophores and located in a confocal detection volume. The arrival time of each of the photons is determined. The interval of time between various photon pairs is then determined to provide photon pair intervals. The number of photons that have arrival times within the photon pair intervals is also determined. The photon pair intervals are then used in combination with the corresponding counts of intervening photons to analyze properties and interactions of the molecules including brightness, concentration, coincidence and transit time. The method can be used for analyzing single photon streams and multiple photon streams.

Time management in acute vertebrobasilar occlusion.

PubMed

Kamper, Lars; Rybacki, Konrad; Mansour, Michael; Winkler, Sven B; Kempkes, Udo; Haage, Patrick

2009-03-01

Acute vertebrobasilar occlusion (VBO) is associated with a high risk of stroke and death. Although local thrombolysis may achieve recanalization and improve outcome, mortality is still between 35% and 75%. However, without recanalization the chance of a good outcome is extremely poor, with mortality rates of 80-90%. Early treatment is a fundamental factor, but detailed studies of the exact time management of the diagnostic and interventional workflow are still lacking. Data on 18 patients were retrospectively evaluated. Time periods between symptom onset, admission to hospital, time of diagnosis, and beginning of intervention were correlated with postinterventional neurological status. The Glasgow Coma Scale and National Institute of Health Stroke Scale (NIHSS) were used to examine patients before and after local thrombolysis. Additionally, multivariate statistics were applied to reveal similarities between patients with neurological improvement. Primary recanalization was achieved in 77% of patients. The overall mortality was 55%. Major complications were intracranial hemorrhage and peripheral embolism. The time period from symptom onset to intervention showed a strong correlation with the postinterventional NIHSS as well as the patient's age, with the best results in a 4-h interval. Multivariate statistics revealed similarities among the patients. Evaluation of time management in acute VBO by multivariate statistics is a helpful tool for definition of similarities in this patient group. Similarly to the door-to-balloon time for acute coronary interventions, the chances for a good outcome depend on a short time interval between symptom onset and intervention. While the only manipulable time period starts with hospital admission, our results emphasize the necessity of efficient intrahospital workflow.

Low-Volume Intense Exercise Elicits Post-exercise Hypotension and Subsequent Hypervolemia, Irrespective of Which Limbs Are Exercised.

PubMed

Graham, Matthew J; Lucas, Samuel J E; Francois, Monique E; Stavrianeas, Stasinos; Parr, Evelyn B; Thomas, Kate N; Cotter, James D

2016-01-01

Exercise reduces arterial and central venous blood pressures during recovery, which contributes to its valuable anti-hypertensive effects and to facilitating hypervolemia. Repeated sprint exercise potently improves metabolic function, but its cardiovascular effects (esp. hematological) are less well-characterized, as are effects of exercising upper versus lower limbs. The purposes of this study were to identify the acute (<24 h) profiles of arterial blood pressure and blood volume for (i) sprint intervals versus endurance exercise, and (ii) sprint intervals using arms versus legs. Twelve untrained males completed three cycling exercise trials; 50-min endurance (legs), and 5(*)30-s intervals using legs or arms, in randomized and counterbalanced sequence, at a standardized time of day with at least 8 days between trials. Arterial pressure, hemoglobin concentration and hematocrit were measured before, during and across 22 h after exercise, the first 3 h of which were seated rest. The post-exercise hypotensive response was larger after leg intervals than endurance (AUC: 7540 ± 3853 vs. 3897 ± 2757 mm Hg·min, p = 0.049, 95% CI: 20 to 6764), whereas exercising different limbs elicited similar hypotension (arms: 6420 ± 3947 mm Hg·min, p = 0.48, CI: -1261 to 3896). In contrast, arterial pressure at 22 h was reduced after endurance but not after leg intervals (-8 ± 8 vs. 0 ± 7 mm Hg, p = 0.04, CI: 7 ± 7) or reliably after arm intervals (-4 ± 8 mm Hg, p = 0.18 vs. leg intervals). Regardless, plasma volume expansion at 22 h was similar between leg intervals and endurance (both +5 ± 5%; CI: -5 to 5%) and between leg and arm intervals (arms: +5 ± 7%, CI: -8 to 5%). These results emphasize the relative importance of central and/or systemic factors in post-exercise hypotension, and indicate that markedly diverse exercise profiles can induce substantive hypotension and subsequent hypervolemia. At least for endurance exercise, this hypervolemia may not depend on the volume of post-exercise hypotension. Finally, endurance exercise led to reduced blood pressure the following day, but sprint interval exercise did not.

Bayesian analyses of time-interval data for environmental radiation monitoring.

PubMed

Luo, Peng; Sharp, Julia L; DeVol, Timothy A

2013-01-01

Time-interval (time difference between two consecutive pulses) analysis based on the principles of Bayesian inference was investigated for online radiation monitoring. Using experimental and simulated data, Bayesian analysis of time-interval data [Bayesian (ti)] was compared with Bayesian and a conventional frequentist analysis of counts in a fixed count time [Bayesian (cnt) and single interval test (SIT), respectively]. The performances of the three methods were compared in terms of average run length (ARL) and detection probability for several simulated detection scenarios. Experimental data were acquired with a DGF-4C system in list mode. Simulated data were obtained using Monte Carlo techniques to obtain a random sampling of the Poisson distribution. All statistical algorithms were developed using the R Project for statistical computing. Bayesian analysis of time-interval information provided a similar detection probability as Bayesian analysis of count information, but the authors were able to make a decision with fewer pulses at relatively higher radiation levels. In addition, for the cases with very short presence of the source (< count time), time-interval information is more sensitive to detect a change than count information since the source data is averaged by the background data over the entire count time. The relationships of the source time, change points, and modifications to the Bayesian approach for increasing detection probability are presented.

Can We Draw General Conclusions from Interval Training Studies?

PubMed

Viana, Ricardo Borges; de Lira, Claudio Andre Barbosa; Naves, João Pedro Araújo; Coswig, Victor Silveira; Del Vecchio, Fabrício Boscolo; Ramirez-Campillo, Rodrigo; Vieira, Carlos Alexandre; Gentil, Paulo

2018-04-19

Interval training (IT) has been used for many decades with the purpose of increasing performance and promoting health benefits while demanding a relatively small amount of time. IT can be defined as intermittent periods of intense exercise separated by periods of recovery and has been divided into high-intensity interval training (HIIT), sprint interval training (SIT), and repeated sprint training (RST). IT use has resulted in the publication of many studies and many of them with conflicting results and positions. The aim of this article was to move forward and understand the studies' protocols in order to draw accurate conclusions, as well as to avoid previous mistakes and effectively reproduce previous protocols. When analyzing the literature, we found many inconsistencies, such as the controversial concept of 'supramaximal' effort, a misunderstanding with regard to the term 'high intensity,' and the use of different strategies to control intensity. The adequate definition and interpretation of training intensity seems to be vital, since the results of IT are largely dependent on it. These observations are only a few examples of the complexity involved in IT prescription, and are discussed to illustrate some problems with the current literature regarding IT. Therefore, it is our opinion that it is not possible to draw general conclusions about IT without considering all variables used in IT prescription, such as exercise modality, intensity, effort and rest times, and participants' characteristics. In order to help guide researchers and health professionals in their practices it is important that experimental studies report their methods in as much detail as possible and future reviews and meta-analyses should critically discuss the articles included in the light of their methods to avoid inappropriate generalizations.

Characteristic pulse trains of preliminary breakdown in four isolated small thunderstorms

NASA Astrophysics Data System (ADS)

Ma, Dong

2017-03-01

Using a low-frequency six-station local network, preliminary breakdown (PB) pulses not followed or followed by negative return stroke (RS), which are defined as PB-type and PB cloud-to-ground (PBCG)-type flashes, are analyzed based on four isolated small thunderstorms for the first time. On the basis of 22 PB-type flashes out of totally 2155 flashes, it indicates that the number of PB-type flashes is very small. At the early stage, PB-type flashes are observed in all four thunderstorms. At the active stage, PB-type flashes still can occur; meanwhile, there are few or no negative cloud-to-ground (CG) flashes. However, at the final stage no PB-type flashes occur. At the stage of distinct cell merging or splitting, PB-type flashes are also observed. Based on the 123 PBCG-type flashes, we discuss the percentage of PBCG-type flashes and also analyze the relationship between the electric field (E-field) amplitude of the largest pulse in the PB pulse train normalized to 100 km (PBA), the E-field amplitude of the first return stroke normalized to 100 km (RSA), the time interval between PBA and RSA (PB-RS interval), and the ratio between PBA and RSA (PB-RS ratio). We find that the percentage of PBCG-type flashes is not always dependent on PBA or PB-RS ratio; the type of thunderstorms may also have an impact on this percentage. None of the PB-RS intervals is less than 20 ms; we speculate that such long PB-RS interval is the feature of isolated small thunderstorms, but more observations are needed to further investigate this question.

Influence of heat and moisture exchanger respiratory load on transcutaneous oxygenation in laryngectomized individuals: a randomized crossover study.

PubMed

Zuur, J Karel; Muller, Sara H; Sinaasappel, Michiel; Hart, Guus A M; van Zandwijk, Nico; Hilgers, Frans J M

2007-12-01

High-resistance heat and moisture exchangers (HMEs) have been reported to increase transcutaneous oxygenation (tcpO(2)) values in laryngectomized individuals and to negatively influence patient compliance. The goal of the present study was to validate earlier published results on short-term transcutaneous oxygenation changes by high-resistance HMEs. We conducted a randomized crossover study, monitoring the influence of an HME on tcpO(2) over a 2-hour time interval in 20 subjects. No evidence of an immediate HME effect (95% CI: -14.9-13.3 mm Hg, p = .91), or a time-dependent HME effect (95% CI: -.121 - .172 mm Hg/minute, p = .74), on tcpO(2) was found. After fitting the statistical model without time dependency, again no evidence of HME presence was seen (95% CI: -.5 mm Hg - 3.6 mm Hg, p = .15). In contrast to earlier suggestions, there is no evidence of increased tcpO(2) levels by high-resistance HMEs in laryngectomized individuals. Thus, using such HMEs has no added clinical value in this respect.

Fixed-interval matching-to-sample: intermatching time and intermatching error runs1

PubMed Central

Nelson, Thomas D.

1978-01-01

Four pigeons were trained on a matching-to-sample task in which reinforcers followed either the first matching response (fixed interval) or the fifth matching response (tandem fixed-interval fixed-ratio) that occurred 80 seconds or longer after the last reinforcement. Relative frequency distributions of the matching-to-sample responses that concluded intermatching times and runs of mismatches (intermatching error runs) were computed for the final matching responses directly followed by grain access and also for the three matching responses immediately preceding the final match. Comparison of these two distributions showed that the fixed-interval schedule arranged for the preferential reinforcement of matches concluding relatively extended intermatching times and runs of mismatches. Differences in matching accuracy and rate during the fixed interval, compared to the tandem fixed-interval fixed-ratio, suggested that reinforcers following matches concluding various intermatching times and runs of mismatches influenced the rate and accuracy of the last few matches before grain access, but did not control rate and accuracy throughout the entire fixed-interval period. PMID:16812032

Improved confidence intervals when the sample is counted an integer times longer than the blank.

PubMed

Potter, William Edward; Strzelczyk, Jadwiga Jodi

2011-05-01

Past computer solutions for confidence intervals in paired counting are extended to the case where the ratio of the sample count time to the blank count time is taken to be an integer, IRR. Previously, confidence intervals have been named Neyman-Pearson confidence intervals; more correctly they should have been named Neyman confidence intervals or simply confidence intervals. The technique utilized mimics a technique used by Pearson and Hartley to tabulate confidence intervals for the expected value of the discrete Poisson and Binomial distributions. The blank count and the contribution of the sample to the gross count are assumed to be Poisson distributed. The expected value of the blank count, in the sample count time, is assumed known. The net count, OC, is taken to be the gross count minus the product of IRR with the blank count. The probability density function (PDF) for the net count can be determined in a straightforward manner.

The Time Is Up: Compression of Visual Time Interval Estimations of Bimodal Aperiodic Patterns

PubMed Central

Duarte, Fabiola; Lemus, Luis

2017-01-01

The ability to estimate time intervals subserves many of our behaviors and perceptual experiences. However, it is not clear how aperiodic (AP) stimuli affect our perception of time intervals across sensory modalities. To address this question, we evaluated the human capacity to discriminate between two acoustic (A), visual (V) or audiovisual (AV) time intervals of trains of scattered pulses. We first measured the periodicity of those stimuli and then sought for correlations with the accuracy and reaction times (RTs) of the subjects. We found that, for all time intervals tested in our experiment, the visual system consistently perceived AP stimuli as being shorter than the periodic (P) ones. In contrast, such a compression phenomenon was not apparent during auditory trials. Our conclusions are: first, the subjects exposed to P stimuli are more likely to measure their durations accurately. Second, perceptual time compression occurs for AP visual stimuli. Lastly, AV discriminations are determined by A dominance rather than by AV enhancement. PMID:28848406

Optimum testing intervals of building emergency power supply systems in tall buildings in the Hong Kong Special Administrative Region

NASA Astrophysics Data System (ADS)

Kwok, Yu Fat

The main objective of this study is to develop a model for the determination of optimum testing interval (OTI) of non-redundant standby plants. This study focuses on the emergency power generators in tall buildings in Hong Kong. The model for the reliability, which is developed, is applicable to any non-duplicated standby plant. In a tall building, the mobilisation of occupants is constrained by its height and the building internal layout. Occupant's safety, amongst other safety considerations, highly depends on the reliability of the fire detection and protection system, which in turn is dependent on the reliability of the emergency power generation plants. A thorough literature survey shows that the practice used in determining OTI in nuclear plants is generally applicable. Historically, the OTI in these plants is determined by balancing the testing downtime and reliability gained from frequent testing. However, testing downtime does not exist in plants like emergency power generator. Subsequently, sophisticated models have taken repairing downtime into consideration. In this study, the algorithms for the determination of OTI, and hence reliability of standby plants, are reconsidered. A new concept is introduced into the subject. A new model is developed for such purposes which embraces more realistic factors found in practice. System aging and the finite life cycle of the standby plant are considered. Somewhat more pragmatic is that the Optimum Overhauling Interval can also be determined from this new model. System unavailability grow with time, but can be reset by test or overhaul. Contrary to fixed testing intervals, OTI is determined whenever system point unavailability exceeds certain level, which depends on the reliability requirement of the standby system. An optimum testing plan for lowering this level to the 'minimum useful unavailability' level (see section 9.1 for more elaboration) can be determined by the new model presented. Cost effectiveness is accounted for by a new parameter 'tau min', the minimum testing interval (MTI). The MTI optimises the total number of tests and the total number of overhauls, when the costs for each are available. The model sets up criteria for test and overhaul and to 'announce' end of system life. The usefulness of the model is validated by a detailed analysis of the operating parameters from 8,500 maintenance records collected for emergency power generation plants in high rise buildings in Hong Kong. (Abstract shortened by UMI.)

Short-term variability in QT interval and ventricular arrhythmias induced by dofetilide are dependent on high-frequency autonomic oscillations

PubMed Central

Champeroux, P; Thireau, J; Judé, S; Laigot-Barbé, C; Maurin, A; Sola, M L; Fowler, J S L; Richard, S; Le Guennec, J Y

2015-01-01

Background and Purpose The present study was undertaken to investigate an effect of dofetilide, a potent arrhythmic blocker of the voltage-gated K+ channel, hERG, on cardiac autonomic control. Combined with effects on ardiomyocytes, these properties could influence its arrhythmic potency. Experimental Approach The short-term variability of beat-to-beat QT interval (STVQT), induced by dofetilide is a strong surrogate of Torsades de pointes liability. Involvement of autonomic modulation in STVQT was investigated in healthy cynomolgus monkeys and beagle dogs by power spectral analysis under conditions of autonomic blockade with hexamethonium. Key Results Increase in STVQT induced by dofetilide in monkeys and dogs was closely associated with an enhancement of endogenous heart rate and QT interval high-frequency (HF) oscillations. These effects were fully suppressed under conditions of autonomic blockade with hexamethonium. Ventricular arrhythmias, including Torsades de pointes in monkeys, were prevented in both species when HF oscillations were suppressed by autonomic blockade. Similar enhancements of heart rate HF oscillations were found in dogs with other hERG blockers described as causing Torsades de pointes in humans. Conclusions and Implications These results demonstrate for the first time that beat-to-beat ventricular repolarization variability and ventricular arrhythmias induced by dofetilide are dependent on endogenous HF autonomic oscillations in heart rate. When combined with evidence of hERG-blocking properties, enhancement of endogenous HF oscillations in heart rate could constitute an earlier and more sensitive biomarker than STVQT for Torsades de pointes liability, applicable to preclinical regulatory studies conducted in healthy animals. PMID:25625756

Short-term variability in QT interval and ventricular arrhythmias induced by dofetilide are dependent on high-frequency autonomic oscillations.

PubMed

Champeroux, P; Thireau, J; Judé, S; Laigot-Barbé, C; Maurin, A; Sola, M L; Fowler, J S L; Richard, S; Le Guennec, J Y

2015-06-01

The present study was undertaken to investigate an effect of dofetilide, a potent arrhythmic blocker of the voltage-gated K(+) channel, hERG, on cardiac autonomic control. Combined with effects on ardiomyocytes, these properties could influence its arrhythmic potency. The short-term variability of beat-to-beat QT interval (STVQT ), induced by dofetilide is a strong surrogate of Torsades de pointes liability. Involvement of autonomic modulation in STVQT was investigated in healthy cynomolgus monkeys and beagle dogs by power spectral analysis under conditions of autonomic blockade with hexamethonium. Increase in STVQT induced by dofetilide in monkeys and dogs was closely associated with an enhancement of endogenous heart rate and QT interval high-frequency (HF) oscillations. These effects were fully suppressed under conditions of autonomic blockade with hexamethonium. Ventricular arrhythmias, including Torsades de pointes in monkeys, were prevented in both species when HF oscillations were suppressed by autonomic blockade. Similar enhancements of heart rate HF oscillations were found in dogs with other hERG blockers described as causing Torsades de pointes in humans. These results demonstrate for the first time that beat-to-beat ventricular repolarization variability and ventricular arrhythmias induced by dofetilide are dependent on endogenous HF autonomic oscillations in heart rate. When combined with evidence of hERG-blocking properties, enhancement of endogenous HF oscillations in heart rate could constitute an earlier and more sensitive biomarker than STVQT for Torsades de pointes liability, applicable to preclinical regulatory studies conducted in healthy animals. © 2015 The British Pharmacological Society.

Comparing performance of multinomial logistic regression and discriminant analysis for monitoring access to care for acute myocardial infarction.

PubMed

Hossain, Monir; Wright, Steven; Petersen, Laura A

2002-04-01

One way to monitor patient access to emergent health care services is to use patient characteristics to predict arrival time at the hospital after onset of symptoms. This predicted arrival time can then be compared with actual arrival time to allow monitoring of access to services. Predicted arrival time could also be used to estimate potential effects of changes in health care service availability, such as closure of an emergency department or an acute care hospital. Our goal was to determine the best statistical method for prediction of arrival intervals for patients with acute myocardial infarction (AMI) symptoms. We compared the performance of multinomial logistic regression (MLR) and discriminant analysis (DA) models. Models for MLR and DA were developed using a dataset of 3,566 male veterans hospitalized with AMI in 81 VA Medical Centers in 1994-1995 throughout the United States. The dataset was randomly divided into a training set (n = 1,846) and a test set (n = 1,720). Arrival times were grouped into three intervals on the basis of treatment considerations: <6 hours, 6-12 hours, and >12 hours. One model for MLR and two models for DA were developed using the training dataset. One DA model had equal prior probabilities, and one DA model had proportional prior probabilities. Predictive performance of the models was compared using the test (n = 1,720) dataset. Using the test dataset, the proportions of patients in the three arrival time groups were 60.9% for <6 hours, 10.3% for 6-12 hours, and 28.8% for >12 hours after symptom onset. Whereas the overall predictive performance by MLR and DA with proportional priors was higher, the DA models with equal priors performed much better in the smaller groups. Correct classifications were 62.6% by MLR, 62.4% by DA using proportional prior probabilities, and 48.1% using equal prior probabilities of the groups. The misclassifications by MLR for the three groups were 9.5%, 100.0%, 74.2% for each time interval, respectively. Misclassifications by DA models were 9.8%, 100.0%, and 74.4% for the model with proportional priors and 47.6%, 79.5%, and 51.0% for the model with equal priors. The choice of MLR or DA with proportional priors, or DA with equal priors for monitoring time intervals of predicted hospital arrival time for a population should depend on the consequences of misclassification errors.

Ex vivo 12 h bactericidal activity of oral co-amoxiclav (1.125 g) against beta-lactamase-producing Haemophilus influenzae.

PubMed

Bronner, S; Pompei, D; Elkhaïli, H; Dhoyen, N; Monteil, H; Jehl, F

2001-10-01

The aim of the study was to evaluate the in vitro/ex vivo bactericidal activity of a new coamoxiclav single-dose sachet formulation (1 g amoxicillin + 0.125 g clavulanic acid) against a beta-lactamase-producing strain of Haemophilus influenzae. The evaluation covered the 12 h period after antibiotic administration. Serum specimens from the 12 healthy volunteers included in the pharmacokinetic study were pooled by time point and in equal volumes. Eight of 12 pharmacokinetic sampling time points were included in the study. At time points 0.5, 0.75, 1, 1.5, 2.5, 5, 8 and 12 h post-dosing, the kinetics of bactericidal activity were determined for each of the serial dilutions. Each specimen was serially diluted from 1:2 to 1:256. The index of surviving bacteria (ISB) was subsequently determined for each pharmacokinetic time point. For all the serum samples, bactericidal activity was fast (3-6 h), marked (3-6 log(10) reduction in the initial inoculum) and sustained over the 12 h between-dosing interval. The results obtained also confirmed that the potency of the amoxicillin plus clavulanic acid combination was time dependent against the species under study and that the time interval over which the concentrations were greater than the MIC (t > MIC) was 100% for the strain under study. The data thus generated constitute an interesting prerequisite with a view to using co-amoxiclav 1.125 g in a bd oral regimen.

Time estimation by patients with frontal lesions and by Korsakoff amnesics.

PubMed

Mimura, M; Kinsbourne, M; O'Connor, M

2000-07-01

We studied time estimation in patients with frontal damage (F) and alcoholic Korsakoff (K) patients in order to differentiate between the contributions of working memory and episodic memory to temporal cognition. In Experiment 1, F and K patients estimated time intervals between 10 and 120 s less accurately than matched normal and alcoholic control subjects. F patients were less accurate than K patients at short (< 1 min) time intervals whereas K patients increasingly underestimated durations as intervals grew longer. F patients overestimated short intervals in inverse proportion to their performance on the Wisconsin Card Sorting Test. As intervals grew longer, overestimation yielded to underestimation for F patients. Experiment 2 involved time estimation while counting at a subjective 1/s rate. F patients' subjective tempo, though relatively rapid, did not fully explain their overestimation of short intervals. In Experiment 3, participants produced predetermined time intervals by depressing a mouse key. K patients underproduced longer intervals. F patients produced comparably to normal participants, but were extremely variable. Findings suggest that both working memory and episodic memory play an individual role in temporal cognition. Turnover within a short-term working memory buffer provides a metric for temporal decisions. The depleted working memory that typically attends frontal dysfunction may result in quicker turnover, and this may inflate subjective duration. On the other hand, temporal estimation beyond 30 s requires episodic remembering, and this puts K patients at a disadvantage.

Ultrasonic filtration of industrial chemical solutions

NASA Technical Reports Server (NTRS)

Cosma, T.

1974-01-01

The practical results obtained as a result of filtering industrial chemical solutions under continuous flow conditions with the aid of an ultrasonic filter are presented. The main part of the assembly consists of an ultrasonic generator with an output power of about 400 W and the filtration assembly, in which there is a magnetostrictive amplifier constructed for 20.5 kHz. In addition to ensuring a continuous flow of filtered solution, ultrasonic filters can be replaced or cleaned at intervals of time that are 8-10 times greater than in the case of mechanical filters. They yield considerably better results as far as the size of the filtered particles is concerned. The parameters on which filtration quality depends are also presented.

Adaptation and survivors in a random Boolean network.

PubMed

Nakamura, Ikuo

2002-04-01

We introduce the competitive agent with imitation strategy in a random Boolean network, in which the agent plays a competitive game that rewards those in minority. After a long time interval, the worst performer changes its strategy to the one of the best and the process is repeated. The network, initially in a chaotic state, evolves to an intermittent state and finally reaches a frozen state. Time series of survived species (whose strategies are imitated by other agents) in the system depend on the connectivity of each agent. In a system with various connectivity groups, the low connectivity groups win the minority game over the high connectivity groups. We also compared the result with mutation strategy system.

A Newton-Krylov solver for fast spin-up of online ocean tracers

NASA Astrophysics Data System (ADS)

Lindsay, Keith

2017-01-01

We present a Newton-Krylov based solver to efficiently spin up tracers in an online ocean model. We demonstrate that the solver converges, that tracer simulations initialized with the solution from the solver have small drift, and that the solver takes orders of magnitude less computational time than the brute force spin-up approach. To demonstrate the application of the solver, we use it to efficiently spin up the tracer ideal age with respect to the circulation from different time intervals in a long physics run. We then evaluate how the spun-up ideal age tracer depends on the duration of the physics run, i.e., on how equilibrated the circulation is.

Modeling of cw OIL energy performance based on similarity criteria

NASA Astrophysics Data System (ADS)

Mezhenin, Andrey V.; Pichugin, Sergey Y.; Azyazov, Valeriy N.

2012-01-01

A simplified two-level generation model predicts that power extraction from an cw oxygen-iodine laser (OIL) with stable resonator depends on three similarity criteria. Criterion τd is the ratio of the residence time of active medium in the resonator to the O2(1Δ) reduction time at the infinitely large intraresonator intensity. Criterion Π is small-signal gain to the threshold ratio. Criterion Λ is the relaxation to excitation rate ratio for the electronically excited iodine atoms I(2P1/2). Effective power extraction from a cw OIL is achieved when the values of the similarity criteria are located in the intervals: τd=5-8, Π=3-8 and Λ<=0.01.

Deletion of chromosome 9p21 noncoding cardiovascular risk interval in mice alters Smad2 signaling and promotes vascular aneurysm.

PubMed

Loinard, Céline; Basatemur, Gemma; Masters, Leanne; Baker, Lauren; Harrison, James; Figg, Nichola; Vilar, José; Sage, Andrew P; Mallat, Ziad

2014-12-01

Vascular aneurysm is an abnormal local dilatation of an artery that can lead to vessel rupture and sudden death. The only treatment involves surgical or endovascular repair or exclusion. There is currently no approved medical therapy for this condition. Recent data established a strong association between genetic variants in the 9p21 chromosomal region in humans and the presence of cardiovascular diseases, including aneurysms. However, the mechanisms linking this 9p21 DNA variant to cardiovascular risk are still unknown. Here, we show that deletion of the orthologous 70-kb noncoding interval on mouse chromosome 4 (chr4(Δ70kb/Δ70kb) mice) is associated with reduced aortic expression of cyclin-dependent kinase inhibitor genes p19Arf and p15Inkb. Vascular smooth muscle cells from chr4(Δ70kb/Δ70kb) mice show reduced transforming growth factor-β-dependent canonical Smad2 signaling but increased cyclin-dependent kinase-dependent Smad2 phosphorylation at linker sites, a phenotype previously associated with tumor growth and consistent with the mechanistic link between reduced canonical transforming growth factor-β signaling and susceptibility to vascular diseases. We also show that targeted deletion of the 9p21 risk interval promotes susceptibility to aneurysm development and rupture when mice are subjected to a validated model of aneurysm formation. The vascular disease of chr4(Δ70kb/Δ70kb) mice is prevented by treatment with a cyclin-dependent kinase inhibitor. The results establish a direct mechanistic link between 9p21 noncoding risk interval and susceptibility to aneurysm and may have important implications for the understanding and treatment of vascular diseases. © 2014 American Heart Association, Inc.

Incorporating Duration Information in Activity Recognition

NASA Astrophysics Data System (ADS)

Chaurasia, Priyanka; Scotney, Bryan; McClean, Sally; Zhang, Shuai; Nugent, Chris

Activity recognition has become a key issue in smart home environments. The problem involves learning high level activities from low level sensor data. Activity recognition can depend on several variables; one such variable is duration of engagement with sensorised items or duration of intervals between sensor activations that can provide useful information about personal behaviour. In this paper a probabilistic learning algorithm is proposed that incorporates episode, time and duration information to determine inhabitant identity and the activity being undertaken from low level sensor data. Our results verify that incorporating duration information consistently improves the accuracy.

The role of breast-feeding beyond postpartum amenorrhoea on the return of fertility in India: a life table and hazards model analysis.

PubMed

Nath, D C; Land, K C; Singh, K K

1994-04-01

This paper investigates the effects of continued breast-feeding after resumption of menses on fertility, using data from two retrospective surveys in India and single decrement life table and multivariate time-dependent hazards analyses. Breast-feeding even after the return of menses is found to be associated with longer birth intervals. The interaction of breast-feeding duration after resumption of menses and postpartum amenorrhoea has a significant effect on the risk of conception after return of menses.

Peculiarity of Seismicity in the Balakend-Zagatal Region, Azerbaijan

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

Ismail-Zadeh, Tahir T.

2006-03-23

The study of seismicity in the Balakend-Zagatal region demonstrates a temporal correlation of small events in the region with the moderate events in Caucasus for the time interval of 1980 to 1990. It is shown that the processes resulting in deformation and tectonic movements of main structural elements of the Caucasus region are internal and are not related to large-scale tectonic processes. A week dependence of the regional movements on the large-scale motion of the lithospheric plates and microplates is apparent from another geological and geodetic data as well.

Fabrication of highly efficient ZnO nanoscintillators

NASA Astrophysics Data System (ADS)

Procházková, Lenka; Gbur, Tomáš; Čuba, Václav; Jarý, Vítězslav; Nikl, Martin

2015-09-01

Photo-induced synthesis of high-efficiency ultrafast nanoparticle scintillators of ZnO was demonstrated. Controlled doping with Ga(III) and La(III) ions together with the optimized method of ZnO synthesis and subsequent two-step annealing in air and under reducing atmosphere allow to achieve very high intensity of UV exciton luminescence, up to 750% of BGO intensity magnitude. Fabricated nanoparticles feature extremely short sub-nanosecond photoluminescence decay times. Temperature dependence of the photoluminescence spectrum within 8-340 K range was investigated and shows the absence of visible defect-related emission within all temperature intervals.

The Theory of Quantized Fields. III

DOE R&D Accomplishments Database

Schwinger, J.

1953-05-01

In this paper we discuss the electromagnetic field, as perturbed by a prescribed current. All quantities of physical interest in various situations, eigenvalues, eigenfunctions, and transformation probabilities, are derived from a general transformation function which is expressed in a non-Hermitian representation. The problems treated are: the determination of the energy-momentum eigenvalues and eigenfunctions for the isolated electromagnetic field, and the energy eigenvalues and eigenfunctions for the field perturbed by a time-independent current that departs from zero only within a finite time interval, and for a time-dependent current that assumes non-vanishing time-independent values initially and finally. The results are applied in a discussion of the intra-red catastrophe and of the adiabatic theorem. It is shown how the latter can be exploited to give a uniform formulation for all problems requiring the evaluation of transition probabilities or eigenvalue displacements.

Nonlinear effects in the time measurement device based on surface acoustic wave filter excitation.

PubMed

Prochazka, Ivan; Panek, Petr

2009-07-01

A transversal surface acoustic wave filter has been used as a time interpolator in a time interval measurement device. We are presenting the experiments and results of an analysis of the nonlinear effects in such a time interpolator. The analysis shows that the nonlinear distortion in the time interpolator circuits causes a deterministic measurement error which can be understood as the time interpolation nonlinearity. The dependence of this error on time of the measured events can be expressed as a sparse Fourier series thus it usually oscillates very quickly in comparison to the clock period. The theoretical model is in good agreement with experiments carried out on an experimental two-channel timing system. Using highly linear amplifiers in the time interpolator and adjusting the filter excitation level to the optimum, we have achieved the interpolation nonlinearity below 0.2 ps. The overall single-shot precision of the experimental timing device is 0.9 ps rms in each channel.