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PubMed2001

How urban African American young adolescents spend their time: time budgets for locations, activities, and companionship.

The time budgets of a population of youth provide important information about their daily experience and socialization. This study reports data on the time budgets of a sample of 253 urban African American poor to working- and middle-class 5th-8th graders in Chicago. These youth were found to spend less time in school than other postindustrial adolescent populations, but spent no less time doing homework than White suburban U.S. young adolescents. They spent large quantities of time at home and with their families--at rates comparable to rates for young adolescents in a society with collectivist values like India. Unlike with other populations, early adolescence was not associated with major age changes in time allocations. Amount of time in schoolwork did not differ by grade, and amount of time with family did not show the decline with age that has been found for European American suburban adolescents.

Adolescent↗
PubMedDate not supplied

Precision of neural timing: effects of convergence and time-windowing.

We study the improvement in timing accuracy in a neural system having n identical input neurons projecting to one target neuron. The n input neurons receive the same stimulus but fire at stochastic times selected from one of four specified probability densities, f, each with standard deviation 1.0 msec. The target cell fires if and when it receives m inputs within a time window of epsilon msec. Let sigma(n,m,epsilon) denote the standard deviation of the time of firing of the target neuron (i.e. the standard deviation of the target neuron's latency relative to the arrival time of the stimulus). Mathematical analysis shows that sigma(n,m,epsilon) is a very complicated function of n, m, and epsilon. Typically, sigma(n,m,epsilon) is a non-monotone function of m and epsilon and the improvement of timing accuracy is highly dependent of the shape of the probability density for the time of firing of the input neurons. For appropriate choices of m, epsilon, and f, the standard deviation sigma(n,m,epsilon) may be as low as 1/n. Thus, depending on these variables, remarkable improvements in timing accuracy of such a stochastic system may occur.

Animals↗
PubMed2000

Expecting a break in time estimation: attentional time-sharing without concurrent processing.

The interference from nontemporal processing on concurrent time estimation is usually attributed to disruption in timing caused by attentional requirements of nontemporal processing. Here, we examined interruption in timing without concurrent nontemporal processing. Empty breaks of various durations, during time-interval production, lengthened produced intervals. Moreover, an effect of break location was observed: Intervals lengthened proportionally to prebreak duration. When cued and uncued uninterrupted trials were introduced, the lengthening was proportional to the duration for which a break was expected. It was concluded that attentional time-sharing between time estimation and expectation of its interruption contributed to the interference effect in time-estimation research, independently of any concurrent processing requirements during time estimation.

Adolescent↗
PubMed1998

Output loss or rehearsal loop? Output-time versus pronunciation-time limits in immediate recall for forgetting-matched materials.

Forgetting during recall may be one limit on memory span. Output time and accuracy of immediate serial recall using spoken and keypress responses were measured for digit, letter, and word sets approximately matched in phonemic discriminability and in immediate recognition memory. Nonetheless, the materials differed from one another in recall span, in output time during recall, and in pronunciation time (speech rate). Recall output times accounted precisely and completely for the measured memory span for these matched materials. Pronunciation times are correlated with recall output times, but output time gives a slightly better account of recall accuracy. The output time equivalent to the rule that short-term memory span corresponds to the number of items that can be said in about 1.5-2 s is that span corresponds to the number of items that can be recalled in about 4-6 s. Additional variations in span reflect differential item interference.

Attention↗
PubMed2007

Hard gelatin and hypromellose (HPMC) capsules: estimation of rupture time by real-time dissolution spectroscopy.

The objective of this study was to measure rupture time of gelatin and hypromellose (hydroxypropyl methylcellulose or HPMC) capsules using a novel approach based on real-time dissolution spectroscopy. Rupture time was measured in standard dissolution apparatus at a constant temperature using a dip-type fiber-optic probe. Labrasol released from the capsules was treated as the marker of the rupture process. Light scatter generated by the emulsified labrasol was detected by an ultrafast monochromator at scan rates approximating 24,000 nm/min. This technique was validated by measuring the dissolution time of gelatin capsules. Rupture times of hypromellose capsules were studied as a function of capsule size, capsule grade, and dissolution medium. Statistical correlations were analyzed by ANOVA. Rupture time of hypromellose capsules was dependent on both the medium and the grade of the capsule, and was independent of capsule size. The composition of the dissolution medium contributes to the rupture time of the capsules and should be considered when fast release and quick biological response is desired. Release delay, however, may not manifest itself in vivo and the time to maximum plasma concentration may not be significant.

Capsules↗
PubMed2001

Aligning gene expression time series with time warping algorithms.

UNLABELLED: motivation: Increasingly, biological processes are being studied through time series of RNA expression data collected for large numbers of genes. Because common processes may unfold at varying rates in different experiments or individuals, methods are needed that will allow corresponding expression states in different time series to be mapped to one another. RESULTS: We present implementations of time warping algorithms applicable to RNA and protein expression data and demonstrate their application to published yeast RNA expression time series. Programs executing two warping algorithms are described, a simple warping algorithm and an interpolative algorithm, along with programs that generate graphics that visually present alignment information. We show time warping to be superior to simple clustering at mapping corresponding time states. We document the impact of statistical measurement noise and sample size on the quality of time alignments, and present issues related to statistical assessment of alignment quality through alignment scores. We also discuss directions for algorithm improvement including development of multiple time series alignments and possible applications to causality searches and non-temporal processes ('concentration warping').

Algorithms↗
PubMed2006

BTW: a web server for Boltzmann time warping of gene expression time series.

UNLABELLED: Dynamic time warping (DTW) is a well-known quadratic time algorithm to determine the smallest distance and optimal alignment between two numerical sequences, possibly of different length. Originally developed for speech recognition, this method has been used in data mining, medicine and bioinformatics. For gene expression time series data, time warping distance is arguably a more flexible tool to determine genes having similar temporal expression, hence possibly related biological function, than either Euclidean distance or correlation coefficient--especially since time warping accommodates sequences of different length. The BTW web server allows a user to upload two tab-separated text files A,B of gene expression data, each possibly having a different number of time intervals of different durations. BTW then computes time warping distance between each gene of A with each gene of B, using a recently developed symmetric algorithm which additionally computes the Boltzmann partition function and outputs Boltzmann pair probabilities. The Boltzmann pair probabilities, not available with any other existent software, suggest possible biological significance of certain positions in an optimal time warping alignment. AVAILABILITY: http://bioinformatics.bc.edu/clotelab/BTW/.

Algorithms↗
PubMed2005

Estimating the incidence of prolonged turnover times and delays by time of day.

BACKGROUND: Prolonged turnover times cause frustration and can thereby reduce professional satisfaction and the workload surgeons bring to a hospital. METHODS: The authors analyzed 1 yr of operating room information system data from two academic, tertiary hospitals and Monte-Carlo simulations of a 15-operating room hospital surgical suite. RESULTS: Confidence interval widths for the mean turnover times at the hospitals were negligible when compared with the variation in sample mean turnover times among 31 hospitals. The authors developed a statistical method to estimate the proportion of all turnovers that were prolonged (> 15 min beyond mean) and that occurred during specified hours of the day. Confidence intervals for the proportions corrected for the effect of multiple comparisons. Statistical assumptions were satisfied at the two studied hospitals. The confidence intervals achieved family-wise type I error rates accurate to within 0.5% when applied to between five and nineteen 4-week periods of data. The diurnal pattern in the proportions of all turnovers that were prolonged provided different, more managerially relevant information than the time course throughout the day in the percentage of turnovers at each hour that were prolonged. CONCLUSIONS: Benchmarking sample mean turnover times among hospitals, without the use of confidence intervals, can be valid and useful. The authors successfully developed and validated a statistical method to estimate the percentage of turnover times at a surgical suite that are prolonged and occur at specified times of the day. Managers can target their quality improvement efforts on times of the day with the largest percentages of prolonged turnovers.

Academic Medical Centers↗
PubMed1996

Replacing time since human immunodeficiency virus infection by marker values in predicting residual time to acquired immunodeficiency syndrome diagnosis. Multicenter AIDS Cohort Study.

It is widely assumed that the time since human immunodeficiency virus (HIV) infection is an important indicator of HIV disease stage, yet for most infected individuals the date of infection is unknown. We consider whether marker values, such as CD4 lymphocyte number or percent and levels of serum beta2 microglobulin or serum neopterin, render time since infection unimportant for predicting the residual time to acquired immunodeficiency syndrome (AIDS) diagnosis. The Multicenter AIDS Cohort Study (MACS) contains a subsample of homosexual men whose date of HIV seroconversion is known within +/-6 months and who provide data for this analysis. From this subsample, we extract two overlapping data subsets. The first subset consists of 370 persons whose 3,723 study visits include complete data on the cellular markers CD4 lymphocyte number and percent for a period of 9 years. The second consists of 272 persons whose 1,593 visits include complete information on cellular markers and on the serological markers beta2-microglobulin and neopterin for a period of 5 1/2 years. We model the residual time to AIDS diagnosis with a regression model, in which cellular and serologic markers are the explanatory covariates (independent variables) and the residual time to AIDS is the responses variable (dependent variable). A robust estimate of the variance-covariance matrix corrects for the dependence of repeated measurements in the same individual. In the case of CD4 number and percent, the results indicate that time since infection is of none or at most little importance if the marker value is known, suggesting that time since infection can be adequately replaced by the combination of marker values. However, the serological markers alone do not eliminate the importance of the time since infection.

Acquired Immunodeficiency Syndrome↗
PubMed1975

Comparative study of sinoatrial conduction time and sinus node recovery time.

Atrial stimulation were performed in 5 normal patients (group A) and 4 patients with electrocardiographic evidence of sinoatrial disease (group B). The technique of premature atrial stimulation was used to calculate sinoatrial conduction time. Rapid atrial pacing was applied to measure maximum sinus node recovery time. In 4 cases both stimulation methods were repeated after intravenous administration of atropine Group A had a sinoatrial conduction time of 56 ms +/- 11 (SD) and a maximum sinus node recovery time of 1122 ms +/- 158. In 3 out of 4 patients with sinus node dysfunction a prolongation of sinoatrial conduction time could be demonstrated (145, 105, and 150 ms). In addition, one showed probable sinus node exit block after premature atrial stimulation. Sinus node recovery time was excessively prolonged in 2 (3880 and 3215 ms) and normal in the other 2 patients with sinoatrial disease (1330 and 1275 ms). Atropine leads to a decrease of sinoatrial conduction time. Results indicate that sinus node recovery time may not be a reliable indicator of sinus node automaticity if sinoatrial conduction is disturbed. The premature atrial stimulation technique makes it possible to study the pattern of sinoatrial conduction and to evaluate its reaction to therapeutic drugs.

Adult↗
PubMed2000

Mono- and biphasic plasma concentration-time curves of mesalazine from a 500 mg suppository in healthy male volunteers controlled by the time of defecation before dosing.

This study was based on data from a bioequivalence study (n=24) of two different formulations of suppositories containing 500 mg mesalazine (formulation I and II), with a similar dissolution profile in phosphate buffer pH 6.8. There was a large intra- and intersubject variability in the plasma concentration-time curves of mesalazine from both suppositories. The aim of the investigation was to identify the parameters that caused the observed large variations in release and absorption of mesalazine in the rectum. Plasma mesalazine and acetylmesalazine, and urine acetylmesalazine concentrations were determined according to validated methods involving HPLC analysis with coulometric detection. Lower limit of quantitation values were respectively 10.4 and 19.4 ng mL(-1) in plasma and 0.96 microg mL(-1) in urine. The time of defecation before and after insertion was recorded. There was a clear distinction between subjects who showed monophasic mesalazine release/absorption and those who showed biphasic and more extended release/absorption. With formulation I there was a correlation between time of defecation before dosing and the type of absorption, monophasic and biphasic absorbers showed a significant difference in the time of defecation, e.g. 9.7+/-5.6 h vs 18.8+/-11.9 h (P = 0.0218). The impact of time of defecation before dosing was non-significant with formulation II, 16.7+/-7.2 h vs 15.1+/-4.2 h (P = 0.67). The impact of the time elapsed between administration and time of defecation after the insertion of the suppository was not significant for the type of release/absorption. The plasma concentration-time curves of the metabolite ran parallel to that of the parent drug, the more parent drug was released/absorbed, the more was acetylated (P = 0.0013) and excreted into the urine (P = 0.0004). After absorption the compound was metabolized into acetylmesalazine, and renally excreted (12-13% of the dose). Monophasic release/ absorption resulted in 7.1% metabolite with I and 10.3% with II (P = 0.0004), while biphasic release/absorption gave 16.8% metabolite with I and 15.5% with II. The renal clearance of the metabolite acetylmesalazine was independent of the observed defecation patterns (300 mL min(-1), P > 0.8), stool composition, and type of absorption.

Absorption↗
PubMed2003

Unconventional ventral attachment of time-depth recorders as a new method for investigating time budget and diving behaviour of seabirds.

We tested the use of commercially available electronic time-depth recorders (TDRs) to quantify activities and thus total time budgets of seabirds. This new method involved first fitting TDRs onto the birds' bellies (not on their backs), and, secondly, analysing continuous recordings of temperature, light and pressure to differentiate activities on land and at sea. The birds studied were 12 common guillemots (Uria aalge) rearing chicks at Hornøya, in northern Norway. The method successfully recorded five different activities: at the colony, flying, diving, and resting or active at the sea surface. Overall, common guillemots spent 68% of their time at the colony and 32% at sea. While at sea, the birds spent the majority (77%) of their time at the surface, during which they were active 64% of the time, and rested only 13%. Birds engaged in the costly behaviours of flying and diving for shorter times (11% and 12% of their time at sea, respectively). The method allowed us to differentiate between two types of trips to sea based on the presence (foraging trips: 77% of the total number of trips) or absence (non-foraging trips: 23%) of dives. On average, foraging trips lasted 3.2 h, but most trips were shorter (<1 h), during which the mean estimated travel distance from the colony was 11 km. Diving occurred in bouts of 7.7+/-6.6 dives (mean +/- S.D.). The mean maximum dive depth was 10.2+/-7.6 m (deepest dive: 37 m), and the mean dive duration and post-dive intervals were 38.7+/-21.3 s (longest dive: 119 s) and 20+/-12 s, respectively. Direct and indirect evidence suggests that common guillemots had no difficulty in finding food during the study period, and that the TDRs had minimal effects on the birds' behaviour and physiology. The method is easy to use in the field and is applicable to many other flying seabird species; it is therefore an efficient way of collecting information on time budgets and diving behaviour in the context of various ecological and monitoring studies.

Animals↗
PubMed1991

Effect of time of feeding on oviposition time and production parameters in broiler breeders.

In Experiment 1, four pens of 90 Ross dwarf broiler breeder hens and 9 cocks each were assigned to feeding times of 0830, 1130, and 1430 h. Eggs were collected hourly from 0800 to 1600 h, 5 days/wk for 4 wk. In Experiment 2, five pens of 30 Arbor Acres and 3 cocks each were assigned to feeding times of 0830, 1130, 1430, and 1730 h. Eggs were collected hourly from 0700 to 1600 for Days 6 through 10 of a 10-day treatment period. Feeding time did not significantly change oviposition time in dwarf broiler breeders, except for an increase in oviposition at 1600 h for hens fed at 1130 and 1430 h. Peak oviposition times were 1000 and 1100 h with distribution of ovipositions throughout the day. Egg weight, shell thickness, and egg production were not significantly affected by feeding time. In the standard-sized strain, afternoon feeding times significantly increased the proportion of afternoon ovipositions. The incidence of floor, dirty, cracked, and abnormal eggs was not significantly changed by feeding time in either experiment.

Analysis of Variance↗
PubMed1994

[Effects of goal setting and real-time feedback on performance and time estimation during VDT operation].

The problem of serious occupational fatigue of software operators has come up for discussion. Along with the outcome of a survey showing that their working hours are longer than those of other types of workers, with the former reporting for duty unconsciously early in the morning, it is pointed out that their time estimation and crookedness of time cognition are reduced. As a result of the survey, it was also found that in visual display terminal task, the work is carried on while receiving real-time feedback, and those engaged in development work, set their goal to complete a specific amount of work within a specific time-limit. Thus, in order to examine the effects of these two factors on these workers' performance and their subjective time estimation, 76 subjects (undergraduate students) were asked to engage in task of six terms. The results indicated that the group with its goal set and real-time feedback given had higher performance and motivation for task, and showed more time reduction than did other groups to a significant extent. It is noteworthy that it was proved that the subjects were not conscious of this time reduction.

Adult↗
PubMed1999

[Time of consciousness, consciousness of time].

Time shapes our behavior: we must estimate the duration of events in our environment in order to anticipate changes and time our activity in function of these changes. However, there is no sensory modality devoted to the perception of time, therefore the question is to know which mechanisms underlie the consciousness that time flows and allow us to estimate time precisely. This article proposes a brief overview of psychological, neuropsychological and brain imaging studies which rely on theoretical models postulating the existence of an internal timer. These studies examine the different components--time base, counter and memory--of this timer: particularly they are aimed at characterising the relationships between the evolution of these components with age or their pathological alterations and changes in temporal judgements. They also attempt to specify the neural bases of these components. From this brief overview comes the idea that, if an internal timer exits, it does not mark objective time but a multitude of subjective times.

Biological Clocks↗
PubMed1999

Benchmarking cardiac catheterization laboratories: the impact of patient age, gender and risk factors on variable costs, device costs, total time and procedural time in 53 catheterization laboratories.

Coronary catheterization laboratories (CCLs) are the cornerstones of the delivery system for many cardiovascular procedures performed in the United States. However, few comprehensive data exist benchmarking physician activities in CCLs. This study benchmarks cost and time data on 82,548 consecutive patient encounters in 53 CCLs for the 18-month period of January 1997 through June 1998. The data are compiled from the OEP program, a relational database developed by Boston Scientific/Scimed (Maple Grove, Minnesota) for use in CCLs. CCL productivity (total time and procedure time) and cost (variable costs and device costs) benchmarks are created for: 1) left heart catheterization; 2) right and left heart catheterization; 3) percutaneous transluminal coronary balloon angioplasty (PTCA); 4) atherectomy; and 5) coronary stents. Results show the variable costs (those costs that vary in direct proportion to changes in CCL activities) for the five procedures are: $308, left heart catheterization; $395, right and left heart catheterization; $841, PTCA; $2,768, atherectomy; and $3,186, coronary stent. These variable costs are lower than the typical average costs reported for these procedures because they do not include hospital, laboratory, and physician costs, only the procedure-specific activity-related costs most directly controlled and/or influenced by CCL physicians or administrators. The total time for the left heart catheterization averaged 64 minutes and 84 minutes for the right and left heart catheterization, respectively, and procedural times averaged 25 and 32 minutes, respectively. For the major interventional procedures N PTCA, atherectomy, and coronary stents, total times averages were 102, 135, and 117 minutes, respectively. Procedural times for these procedures averaged between 60 and 65 percent of the total time. The major implications of these findings are discussed and limitations noted.

Age Factors↗
PubMed2002

Traveling in time: a time-left analogue for humans.

Two experiments studied normal humans in an analogue of the time-left procedure of J. Gibbon and R. M. Church (1981). In Experiment 1 the "standard" alternative (S) was always half the length of the "comparison" time-left link (C), and S ranged from 4 to 8 s. Humans showed an increasing preference for the time-left alternative with increasing elapsed time in the interval, and indifference points strongly supported the idea of a linear, rather than a logarithmic, time scale. Experiment 2 used some conditions in which S was greater or less than C/2, and preference for the time-left alternative varied systematically with the S/C ratio. Data from both experiments showed reasonable superposition, suggesting underlying scalar timing processes in time left in humans.

Choice Behavior↗
PubMed2004

Reaction-time measurement and real-time data acquisition for neuroscientific experiments in virtual environments.

This paper describes an approach to neuroscientific reaction-time experiments and resulting methods for data processing under real-time constraints in virtual environments (VE). Immersive VEs produce huge amounts of data, which has to be processed in real-time to meet the interactivity requirement of VE. Furthermore, data is needed often with a timing resolution and even more crucial with an accuracy in the range of milliseconds. Unfortunately recent operating systems do not in general guarantee timing precision in this range. For these purposes we have researched possibilities for reaction-time measurement and real-time data acquisition. Our system enables neuroscientists to perform reaction-time experiments in platform-independent virtual environments.

Neurosciences↗