Physical activity, leisure-time screen use and depression among children and young adolescents

Objectives:
Adolescent mental disorders remain a relatively neglected area of research, despite evidence that these conditions affect youth disproportionately. We examined associations between physical activity, leisure-time screen use and depressive symptoms among Australian children and adolescents.

Design:
Large cross-sectional observational study.

Methods:
Self-reported physical activity and leisure-time screen behaviours, and depressive symptoms using the Short Mood and Feeling Questionnaire were assessed in 8256 students aged 10–16 years (mean age = 11.5 years, SD = 0.8).

Results:
Thirty three percent of the sample reported moderate to high depressive symptoms, with rates higher among females (OR = 1.18; 95% CI: 1.02, 1.36; p = 0.001). Increased opportunities to be active at school outside class (OR = 0.70; 0.58, 0.85; p < 0.001), being active in physical education classes (OR = 0.77; 0.69, 0.86; p < 0.001), greater involvement in sports teams at school (OR = 0.77; 0.67, 0.88; p < 0.001) and outside of school (OR = 0.84; 0.73, 0.96; p = 0.01) were all independently associated with lower odds for depressive symptoms. Meeting recommended guidelines for physical activity (OR = 0.62; 0.44, 0.88; p = 0.007) and, for 12–14 year olds, leisure-time screen use (OR = 0.77; 0.59, 0.99; p = 0.04) were also independently associated with lower odds for depressive symptoms.

Conclusions:
Higher levels of physical activity among children and young adolescents, and lower levels of leisure-time screen use among young adolescents, are associated with lower depressive symptoms. Longitudinal studies are needed to understand the causal relationships between these variables.

Presleep activities and time of sleep onset in children

OBJECTIVE: Presleep activities have been implicated in the declining sleep duration of young people. A use-of-time approach may be used to describe the presleep period. The study aims were to describe the activities undertaken 90 minutes before sleep onset and to examine the association between activities and time of sleep onset in New Zealand young people. METHODS: Participants (N = 2017; 5-18 years) self-reported their time use as part of a national survey. All activities reported in the 90 minutes before sleep were extracted. The top 20 activities were grouped into 3 behavioral sets: screen sedentary time, nonscreen sedentary time, and self-care. An adjusted regression model was used to estimate presleep time spent in each behavioral set for 4 distinct categories of sleep onset (very early, early, late, or very late), and the differences between sleep onset categories were tested. RESULTS: In the entire sample, television watching was the most commonly reported activity, and screen sedentary time accounted for ∼30 minutes of the 90-minute presleep period. Participants with a later sleep onset had significantly greater engagement in screen time than those with an earlier sleep onset. Conversely, those with an earlier sleep onset spent significantly greater time in nonscreen sedentary activities and self-care. CONCLUSIONS: Screen sedentary time dominated the presleep period in this sample and was associated with a later sleep onset. The development of interventions to reduce screen-based behaviors in the presleep period may promote earlier sleep onset and ultimately improved sleep duration in young people.

The relationship between time of founding and the composition of the workforce in Australian workplaces

This paper presents the results of an analysis of the relationship between organisational age and two specific aspects of labour flexibility-numerical
flexibility and workforce skill composition (as one facet of functional flexibility)that extends earlier work in two ways. First, it uses data from a large-scale national survey (the Australian Workplace Industrial Relations Survey [AWIRS)1995). Second. it focuses on two widely studied facets of labour flexibility, numerical flexibility and functional flexibility. Previous research has investigated the relationship between organisational age and aspects of organisation such as strategy and structure (Baum and Oliver, 1991; Henderson, 1999; Reed and Blunsdon, 1998). Henderson (1999) found that age effects were contingent on different organisational strategies and process. Reed and Blunsdon (1998) found that organisational maturity is associated with goal directed, or strategic flexibility characterised by low levels of formal rules and regulations but clarity a/purpose. But a more complex relationship was also identified - for example; very young organisations (founded in the 1990,) appear to have higher levels of formalisation at founding than organisations established in earlier periods. This paper investigates these questions further. The results show that the relationship between age; numerical flexibility and workforce skill composition is non-linear, but the data do not make it possible to separate age effects associated with aging, time of founding and changing environmental conditions.

Spatial and temporal changes in abundance of the infaunal bivalve Soletellina alba (Lamark, 1818) during a time of drought in the seasonally-closed Hopkins River Estuary, Victoria Australia

The infaunal bivalve Soletellina alba is susceptible to mass mortalities during annual winter flooding in the Hopkins River Estuary, southern Australia. Periods of low salinity (≤1) are the likely cause of these mass mortality events, which can occur in seasonally-closed estuaries when high winter flows are sufficient to flush all salt water from the estuary. Core samples of S. alba were collected from two water depths across four times and at three sites near the mouth of the estuary. Minimal to zero abundances of large S. alba (>1 mm) were expected to be sampled, particularly at the shallower water depth, during a typical winter flood event. However, the present study occurred during a period of drought, which led to the absence of winter flooding. This absence of winter flooding prevented the occurrence of lethal salinities (i.e. ≤1) in the estuary during this period and a greater number of living S. alba adults were sampled. Abundances of juvenile and adult S. alba were still variable, even in the absence of winter flooding, and reflected an interaction between date, site and water depth. However, no mass mortalities of adults were observed during the drought conditions in contrast to what occurs during typical winter flood events and provides support for the hypothesis that winter flooding is responsible for past mass mortalities.

Optimality analysis of sensor-target geometries in passive localization: Part 2 - time-of-arrival based localization

In this paper we characterize the relative sensor-target geometry in R2 in terms of potential localization performance for time-of-arrival based localization. Our aim is to characterize those relative sensor-target geometries which minimize the relative Cramer-Rao lower bound.

It's academic : American studies in a time of crisis

My archive- the collection of resources I have drawn upon for my comments- includes, among other sources, a panel on international American studies held at the American Studies Association conference in Montreal in November 1999, the Wednesday Higher Education supplement of the Australian newspaper, and another supplement- this is one in the Derridean sense of the word- the Howard government. I hope to draw these threads together to focus on the present crisis facing American studies and, not coincidentally, this Association. To arrive at this point I take a tour through theoretical and disciplinary responses to the prevailing situation.

Patterns of use and exchange of genetic resources of the striped catfish Pangasianodon hypophthalmus (Sauvage 1878)

The present paper reviews the use and exchange of genetic resources of the migratory freshwater fish Pangasianodon hypophthalmus (Sauvage 1878) (the striped or sutchi catfish). This species is naturally distributed in the Mekong River and Chao Phraya River basins, and is cultured in several countries, but current production occurs predominantly in the Mekong Delta, Vietnam. Catfish aquaculture in Vietnam has evolved from extensive systems using wild-caught seed to an intensified farming system that is entirely dependent on hatchery-produced seed. Genetic improvement programmes on catfish have started in Vietnam, but are still in their infancy. Genetic studies have revealed several subpopulations of the species. Apart from selective breeding and the production of hybrids with closely related species, no other technologies have been applied to improve the performance of catfish. The use and exchange of P. hypophthalmus genetic resources have brought benefits to rural communities. Aquaculture development of catfish has evolved from being seen as an exploitation of natural resources to an activity that can reduce pressure on wild fish populations. Management of aquaculture stocks need to be rationalised to minimise the potential impacts it might cause to wild populations.

Conservative discourse at the time of the Korean War. 1950-52

This thesis identifies the rhetorical strategies by which the Menzies government reconciled acceptance of full employment, the welfare state and government intervention with a defence of liberalism. It argues that the Korean War offered the Menzies government an opportunity to reconstitute these key aspects of the postwar state as "liberal" rather than social democratic.