Time series — information and prediction

A time series Y _t can be transformed into another time series V _t by means of a linear transformation. Should the matrix of that transformation have an inverse, the pair (Y _t, V _t) is called invertible. Based on the decomposition procedure for stationary time series introduced in a previous paper it is shown that a sufficient condition for the invertibility of the pair (Y _t, V _t) is that V _t be the first component of Y _t, i.e. V _t = V _t ¹ . By the invertibility property V _t ¹ can be used for forecasting, that is, predictions are made on V _t ¹ which is then transformed into Y _t. This is accomplished by means of a special kind of predictor permitting to make one-step-ahead forecasts in a straightforward way. Since the first component depends on a parameter i.e. V _t ¹ = V _t ¹ (), a procedure is proposed that allows us to find the optimal parameter value, = ₀. Thus, it is shown that better forecasting accuracy may result by fitting a simple autoregression to the first component V _t ¹ (₀) than if the process Y _t were described by a more elaborate model. Model building is therefore no longer a prerequisite in forecasting. The forecasting procedure is then extended so as to cope with the homogeneous nonstationary case, and examples are given to illustrate the forecasting accuracy as compared to customary model-based approaches. In the light of these results the problem of the information conveyed by the values of the series is discussed in terms of the spreading rate concept, thus highlighting the role of the current time value, as well as that of the remote values of the series, in forecasting stationary and nonstationary time series.     

Psychocultural Studies: Has the Time Come?

Handbook of Cross-Cultural Psychology. Perspectives. Volume 1 . Harry C. Triandis and Willliam Wilson Lambert , eds.
Handbook of Cross-Cultural Psychology. Methodology. Volume 2 . Harry C. Triandis and John W. Berry eds.
Handbook of Cross-Cultural Psychology. Basic Processes. Volume 1 . Harry C. Triandis and Walter Lonner , eds.
Handbook of Cross-Cultural Psychology. Developmental Psychology. Volume 4 . Harry C. Triandis and Alastair Heron , eds.
Handbook of Cross-Cultural Psychology. Social Psychology. Volume 5 . Harry C. Triandis and Richard W. Brislin eds.
Handbook of Cross-Cultural Psychology. Psychopathology, Volume 6 . Harry C. Triandis and Juris G. Draguns eds.
Cross-cultural Contributions of Psychology . Lutz H. Echkensberger, Walter J. Lonner and Ype H. Poortinga eds.
Perspectives on Cross-Cultural Psychology . Anthony J. Marsella. Roland G. Tharp and Thomas J. Ciborowski. eds.
Studies in Cross-Culturla Psychology. Volume 2 . Neil Warren , ed.     

Time to recognise that mitochondria are bacteria?

The scientific community is comfortable with recognising mitochondria as organelles that happen to be descendants of bacteria. Here, I playfully explore the arguments for and against a phylogenetic fundamentalism that states that mitochondria are bacteria and should be given their own taxonomic family, the Mitochondriaceae. I also explore the consequences of recognizing mitochondria as bacteria for our understanding of the systemic response to trauma and for the prospects of creating transgenic mitochondria.     

Time for change in traditional working practices?

Consultants in Britain are under pressure to change the way they organise their work. Many rely on formal, but unwritten, rules and a culture of "learning by doing." Unlike their counterparts in Sweden, they are often not well integrated into the management systems of their hospitals. The result is wide differences in the NHS workloads of individual consultants and, for a minority, conflicts of interest with their private work. The training received by junior doctors varies because it is largely left to individual consultants. Clinical directorates should provide a more effective mechanism for consultants to influence trust policies and for consultants to implement these policies. Consultants must not only recognise the need for change but also seize the initiative.     

Time perception: brain time or event time?

Recent experiments show that synchronous events can appear to an observer to occur at different times. Neural processing time delays are offered as an explanation of these temporal illusions, but equating perceived time with processing time leads to some thorny philosophical problems.     

Brain Evolution: Getting Better All the Time?

Recent studies on bats, goats and hominids suggest that some mammalian brains may have undergone dramatic evolutionary reductions in size. These studies emphasise the importance of selective pressures upon mammalian brain evolution and the need to integrate studies of neuroanatomy, neurophysiology and behaviour.     

Animal Cognition: An Insect's Sense of Time?

For Immanuel Kant, time was the very form of the inner sense, the bedrock of our consciousness and also the origin of arithmetic ability. New research on bumblebees has shown that even an invertebrate with a brain the size of a pinhead can actively sense the passage of elapsed time, allowing it to predict when certain salient events will occur in the future.     

Does Weight Loss Maintenance Become Easier Over Time?

Objective: Studies of health‐related behaviors, including weight loss, have shown that risk of relapse decreases over time, although reasons for this relationship are unclear. The purpose of this cross‐sectional study was to determine if subjects who have maintained weight losses for varying periods of time report different strategies for weight loss maintenance or differences in the effort and pleasure associated with weight maintenance behaviors. Research Methods and Procedures: Subjects were 758 women and 173 men who had maintained losses of at least 30 lb (mean = 60 lb) for 2 years or longer (mean = 6.8 ± 7.0 years). Self‐administered questionnaires assessed subjects’ use of weight maintenance strategies in the past year and their perceptions of the effort, attention, and pleasure associated with weight maintenance. Results: Subjects who had maintained weight losses longer used fewer weight maintenance strategies and reported that less effort was required to diet and maintain weight and that less attention was required to maintain weight. The pleasure derived from exercise, low‐fat eating, and maintaining weight was unrelated to duration of weight loss maintenance. Discussion: As duration increases, a shift in the balance between the effort and pleasure of weight maintenance may occur. This shift may increase the likelihood of continued maintenance.     

Does Feeding Competition Influence Tammar Wallaby Time Allocation?

Animals may aggregate to reduce predation risk, but this potentially incurs the cost of increased competition. We studied the degree to which competition for food influenced the time tammar wallabies (Macropus eugenii) allocate to foraging and vigilance by experimentally manipulating access to food, while holding other factors constant. Groups of six wallabies were observed when they had access to either one or six non‐depleting bins of supplemental food. Food availability had no effect on the time allocated to foraging, looking or affiliative interactions, and this was true whether individuals or groups were treated as the unit of analysis. However, wallabies engaged in substantially more aggressive acts in the high‐competition treatment. These results, when combined with other findings, suggest that the moderately social tammar wallaby receives an antipredator benefit by aggregating with conspecifics which is not reduced significantly by foraging competition.     

Determinants of Change in Children’s Sedentary Time

Background

Understanding the determinants of sedentary time during childhood contributes to the development of effective intervention programmes.

Purpose

To examine family and home-environmental determinants of 1-year change in objectively measured sedentary time after-school and at the weekend.

Methods

Participants wore accelerometers at baseline and 1 year later. Longitudinal data for after-school and weekend analyses were available for 854 (41.5%male, mean±SD age 10.2±0.3years) and 718 (41.8%male, age 10.2±0.3years) participants. Information on 26 candidate determinants, including socioeconomic status (SES), availability of electronic media and parental rules for sedentary behaviours was self-reported by children or their parents at baseline. Change in the proportion of registered time spent sedentary was used as the outcome variable in multi-level linear regression models, adjusted for age, sex, body mass index and baseline sedentary time. Simple and multiple models were run and interactions with sex explored.

Results

Children from higher socioeconomic status families exhibited greater increases in after-school (beta; 95% CI for change in % time spent sedentary 1.02; 0.37, 1.66) and weekend (1.42; 0.65, 2.18) sedentary time. Smaller increases in after-school sedentary time were observed in children with more siblings (−1.00; −1.69, −0.30), greater availability of electronic media (−0.81; −1.29, −0.33) and, for boys, more frequent family visits to the park (−1.89; −3.28, −0.51) and family participation in sport (−1.28; −2.54, −0.02). Greater maternal weekend screen-time (0.45; 0.08, 0.83) and, in girls, greater parental restriction on playing outside (0.91; 0.08, 1.74) were associated with larger increases in weekend sedentary time. The analytical sample was younger, more likely to be female, had lower BMI and was of higher SES than the original baseline sample.

Conclusions

Intervention strategies aimed at reducing parents’ weekend screen-time, increasing family participation in sports or recreation (boys) and promoting freedom to play outside (girls) may contribute towards preventing the age-related increase in sedentary time.     

Recalibrating Time: When Did I Do that?

A recent study has shown that illusory inversion of temporal order can be induced by the 'intentional binding' of an action with its consequence, and that this is associated with increased activation in a brain area implicated in conflict monitoring.     

Time Regained: When People Stop a Physical Activity Program,How Does Their Time Use Change? A Randomised Controlled Trial

The aim of this study was to investigate how previously inactive adults who had participated in a structured, partly supervised 6-week exercise program restructured their time budgets when the program ended. Using a randomised controlled trial design, 129 previously inactive adults were recruited and randomly allocated to one of three groups: a Moderate or Extensive six-week physical activity intervention (150 and 300 additional minutes of exercise per week, respectively) or a Control group. Additional physical activity was accumulated through both group and individual exercise sessions with a wide range of activities. Use of time and time spent in energy expenditure zones was measured using a computerised 24-h self-report recall instrument, the Multimedia Activity Recall for Children and Adults, and accelerometry at baseline, mid- and end-program and at 3- and 6-months follow up. At final follow up, all significant changes in time use domains had returned to within 20 minutes of baseline levels (Physical Activity 1-2 min/d, Active Transport 3-9 min/d, Self-Care 0-2 min/d, Television/Videogames 13-18 min/d in the Moderate and Extensive group, relative to Controls, respectively, p>0.05). Similarly, all significant changes in time spent in the moderate energy expenditure zone had returned to within 1-3 min/d baseline levels (p>0.05), however time spent in vigorous physical activity according to accelerometry estimates remained elevated, although the changes were small in magnitude (1 min/d in the Moderate and Extensive groups, relative to Controls, p=0.01). The results of this study demonstrate strong recidivist patterns in physical activity, but also in other aspects of time use. In designing and determining the effectiveness of exercise interventions, future studies would benefit from considering the whole profile of time use, rather than focusing on individual activities.

Trial Registration

Australian New Zealand Clinical Trials Registry ACTRN12610000248066     

Sex Determination: Time for Meiosis? The Gonad Decides

Germ cell sex determination is directed by the gonad and is characterized by a difference in the timing of entry into meiosis. Recent data show that retinoic acid signalling is responsible for the induction of germ cell meiosis in the developing ovary. In the fetal testis, this process is inhibited by a retinoic acid metabolizing enzyme.     

HIV/AID Research in China： Chasing against Time

The spread of HIV in China has lasted for over 20 years,and is marked by three periods:sporadic period(1984-1988),localized epidemic period(1989-1994),     

Does Time Really Slow Down during a Frightening Event?

Observers commonly report that time seems to have moved in slow motion during a life-threatening event. It is unknown whether this is a function of increased time resolution during the event, or instead an illusion of remembering an emotionally salient event. Using a hand-held device to measure speed of visual perception, participants experienced free fall for 31 m before landing safely in a net. We found no evidence of increased temporal resolution, in apparent conflict with the fact that participants retrospectively estimated their own fall to last 36% longer than others' falls. The duration dilation during a frightening event, and the lack of concomitant increase in temporal resolution, indicate that subjective time is not a single entity that speeds or slows, but instead is composed of separable subcomponents. Our findings suggest that time-slowing is a function of recollection, not perception: a richer encoding of memory may cause a salient event to appear, retrospectively, as though it lasted longer.     

Microring Plasmonic Circuit Characteristics Using Space–Time Modulation Control

Plasmonics - The biased plasmonic circuit is proposed using a Panda-ring infinitesimal space–time function control. The circuit has two small rings alongside the main microring. The small...