The influence of turbulent ocean mixing transcends its inherently small scales to affect large scale ocean processes including water‐mass transformation, stratification maintenance, and the ...overturning circulation. However, the distribution of ocean mixing is not well described by sparse ship‐based observations since this mixing is both spatially patchy and temporally intermittent. We use strain information from Argo float profiles in the upper 2,000 m of the ocean to generate over 400,000 estimates of the energy dissipation rate, indicative of ocean mixing. These estimates rely on numerous assumptions, and do not take the place of direct measurement methods. Temporally averaged estimates reveal clear spatial patterns in the parameterized dissipation rate and diffusivity distribution across all the oceans. They corroborate previous observations linking elevated dissipation rates to regions of rough topography. We also observe heightened estimated dissipation rates in areas of high eddy kinetic energy, as well as heightened diffusivity in high latitudes where stratification is weak. The seasonal dependence of mixing is observed in the Northwest Pacific, suggesting a wind‐forced response in the upper ocean.
Key Points
Argo floats can be used to estimate the turbulent mixing in the global ocean
Spatial patterns of mixing are apparent (e.g., elevation over rough topography)
Temporal patterns of mixing are also apparent (e.g., seasonal cycles)
An increase in time spent on screen-based technologies has been suggested to underlie recent increases in mental health problems among young people. However, this hypothesis has primarily been based ...on the findings of cross-sectional studies. The aim of the current review was to provide a comprehensive overview of longitudinal studies examining the relationship between screen time and internalising mental health symptoms. PsycINFO, PubMed/Medline and EMBASE were systematically searched for articles published up to August 2020. Thirty-five studies, with sample sizes ranging from 126 to 12,866 participants, met inclusion criteria. The association between screen time and subsequent depressive symptoms was found to be small to very small in size. There was limited evidence of any reverse association between depressive symptoms and subsequent screen time. The association between screen time and depressive symptoms varied between different devices and uses. In contrast to depressive symptoms, evidence to support longitudinal associations between screen time and other internalising mental health symptoms, including anxiety, self-esteem, and general internalising problems, was lacking. Together, these results suggest that the impact of increased screen time on the prevalence of mental health problems among young people is likely to be negligible or small. Further longitudinal studies that examine screen content and motivations underlying screen use are required to better discern any relationship between screen time and internalising mental health symptoms.
•Total screen time has small to very small effects on subsequent depressive symptoms.•The association between screen time and depression depends on device type and use.•There is limited evidence linking screen time with other internalising symptoms.•Longitudinal studies examining screen content and motivations for screen use are needed.
Selection Landscape of Malaria Parasites Mackinnon, M.J; Marsh, K
Science (American Association for the Advancement of Science),
05/2010, Letnik:
328, Številka:
5980
Journal Article
Recenzirano
Malaria parasites have to survive and transmit within a highly selective and ever-changing host environment. Because immunity to malaria is nonsterilizing and builds up slowly through repeated ...infections, commonly the parasite invades a host that is immunologically and physiologically different from its previous host. During the course of infection, the parasite must also keep pace with changes in host immune responses and red-blood-cell physiology. Here, we describe the "selection landscape" of the most virulent of the human malaria parasites, Plasmodium falciparum, and the adaptive mechanisms it uses to navigate through that landscape. Taking a cost-benefit view of parasite fitness, we consider the evolutionary outcomes of the most important forces of selection operating on the parasite, namely immunity, host death, drugs, mosquito availability, and coinfection. Given the huge potential for malaria parasite evolution in the context of the recently renewed effort to eradicate malaria, a deeper understanding of P. falciparum adaptation is essential.
A series of cryogenic, layered deuterium-tritium (DT) implosions have produced, for the first time, fusion energy output twice the peak kinetic energy of the imploding shell. These experiments at the ...National Ignition Facility utilized high density carbon ablators with a three-shock laser pulse (1.5 MJ in 7.5 ns) to irradiate low gas-filled (0.3 mg/cc of helium) bare depleted uranium hohlraums, resulting in a peak hohlraum radiative temperature ∼290 eV. The imploding shell, composed of the nonablated high density carbon and the DT cryogenic layer, is, thus, driven to velocity on the order of 380 km/s resulting in a peak kinetic energy of ∼21 kJ, which once stagnated produced a total DT neutron yield of 1.9×10^{16} (shot N170827) corresponding to an output fusion energy of 54 kJ. Time dependent low mode asymmetries that limited further progress of implosions have now been controlled, leading to an increased compression of the hot spot. It resulted in hot spot areal density (ρr∼0.3 g/cm^{2}) and stagnation pressure (∼360 Gbar) never before achieved in a laboratory experiment.
Abstract
Observational evidence is presented for transfer of energy from the internal tide to near-inertial motions near 29°N in the Pacific Ocean. The transfer is accomplished via parametric ...subharmonic instability (PSI), which involves interaction between a primary wave (the internal tide in this case) and two smaller-scale waves of nearly half the frequency. The internal tide at this location is a complex superposition of a low-mode waves propagating north from Hawaii and higher-mode waves generated at local seamounts, making application of PSI theory challenging. Nevertheless, a statistically significant phase locking is documented between the internal tide and upward- and downward-propagating near-inertial waves. The phase between those three waves is consistent with that expected from PSI theory. Calculated energy transfer rates from the tide to near-inertial motions are modest, consistent with local dissipation rate estimates. The conclusion is that while PSI does befall the tide near a critical latitude of 29°N, it does not do so catastrophically.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The diapycnal diffusivity of mass supported by turbulent events in the ocean interior plays a fundamental role in controlling the global overturning circulation. The conventional representation of ...this diffusivity, due to Osborn (1980), assumes a constant mixing efficiency. We replace this methodology by a generalized‐Osborn formula which involves a mixing efficiency that varies nonmonotonically with at least two nondimensional variables. Using these two variables, we propose dynamic parameterizations for mixing efficiency and turbulent Prandtl number (the latter quantifies the ratio of momentum to mass diapycnal diffusivities) based on the first synthesis of an extensive direct numerical simulation of inhomogeneously stratified shear‐induced turbulence. Data from Argo floats are employed to demonstrate the extent of the spatial and statistical variability to be expected in both the diapycnal diffusivities of mass and momentum. We therefore suggest that previous estimates of these important characteristics of the global ocean require reconsideration.
Key Points
The first multiparameter parameterizations of mixing efficiency and turbulent Prandtl number are proposed
Global maps of mixing efficiency suggest local estimates that may be grossly different from the canonical value of 0.2
Estimates of diapycnal diffusivity need to be reassessed based on the generalized‐Osborn formula
Abstract Background : Joiner's Interpersonal Theory of Suicide ( Van Orden et al., 2010; Joiner, 2005 ) predicts that suicide ideation is strongest in those experiencing both high perceived ...burdensomeness and thwarted belongingness, and that the combination of suicide ideation and acquired capability for suicide is critical in the development of suicide plans and attempts. However, few datasets exist which allow the examination of these predictions. The present study aimed to test predictions from the model in a population-based cohort. Methods : a survey was completed by 6133 participants from the PATH Through Life Project. Scales measuring perceived burdensomeness, thwarted belongingness, hopelessness, capability to self-injure, ideation, plans and attempts were developed using existing items. Regression models were used to predict the outcomes of ideation and of plans/attempts. Results : consistent with the Interpersonal Theory, interactions were found between perceived burdensomeness and thwarted belongingness predicting ideation, and interactions of capability and ideation for plans/attempts. However, some predictions of the theory were not fulfilled. Nevertheless, the Interpersonal Theory explained more variance than epidemiological models using mental disorders as predictors. Age differences were evident, with models of older cohorts accounting for less variance. Gender models suggested thwarted belongingness was a stronger predictor of ideation in males than females. Limitations : while the fit of the factors assessing the Interpersonal Theory was adequate, the findings will need to be confirmed using previously developed scales of these constructs. Conclusions : predictive models of suicide need to take into account multiple risk factors, gender differences and changes in associations over the life span.
Abstract
Background
Suicide is a major issue affecting communities around the world. Community-based suicide prevention approaches can tailor activities at a local level and are recognised as a key ...component of national suicide prevention strategies. Despite this, research exploring their effects on completed suicides is rare. This study examined the effect of a national program of community suicide prevention networks on suicide rates in catchment areas across Australia.
Methods
Australian suicide data from the National Coronial Information System for 2001–2017 were mapped to geographic catchment areas of community suicide prevention networks and matched control areas with similar characteristics. The effect of network establishment on suicide rates was evaluated using longitudinal models including fixed effects for site type (network or control), time, season, and intervention (network establishment), with site included as a random intercept.
Results
Sixty suicide prevention networks were included, servicing areas with a population of 3.5 million. Networks varied in when they were established, ranging from 2007 to 2016. Across the time-period, suicide rates per 100,000 per quarter averaged 3.73 (SD = 5.35). A significant reduction in the suicide rate of 7.0% was found after establishment of networks (IRR = 0.93, 95% CI 0.87 to 0.99, p = .025).
Conclusion
This study found evidence of an average reduction in suicide rates following the establishment of suicide prevention networks in Australian communities. These findings support the effectiveness of empowering local communities to take action to prevent suicide.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study examines the mental health trajectories of future/current undergraduate university students relative to their age-matched community peers from the ages of 15 to 21. It analysed data from ...the Household, Income and Labour Dynamics in Australia survey. The sample comprised 442 students and 1292 peers. Mental health was assessed with the five-item Mental Health Inventory from the Short Form 36. The results showed that students generally had better mental health than their peers. This was largely associated with better parental mental health and socio- economic position. However, the models also revealed reductions in the mental health of students relative to their peers at ages prior to major transitions in their student careers. This study contributes to the literature on university student mental health by comparing the mental health trajectories of students with their community peers and by identifying the ages when student mental health programmes may be of most benefit. Author abstract
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Turbulent mixing rates are inferred from measurements spanning 25°–37°N in the Pacific Ocean. The observations were made as part of the Internal Waves Across the Pacific experiment, designed ...to investigate the long-range fate of the low-mode internal tide propagating north from Hawaii. Previous and companion results argue that, near a critical latitude of 29°N, the internal tide loses energy to high-mode near-inertial motions through parametric subharmonic instability. Here, the authors estimate mixing from several variations of the finescale shear–strain parameterization, as well as Thorpe-scale analysis of overturns. Though all estimated diffusivities are modest in magnitude, average diffusivity in the top kilometer shows a factor of 2–4 elevation near and equatorward of 29°N. However, given intrinsic uncertainty and the strong temporal variability of diffusivity observed in long mooring records, the meridional mixing pattern is found to be near the edge of statistical significance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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