293 research outputs found

    Non-dipole recollision-gated double ionization and observable effects

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    Using a three-dimensional semiclassical model, we study double ionization for strongly-driven He fully accounting for magnetic field effects. For linearly and slightly elliptically polarized laser fields, we show that recollisions and the magnetic field combined act as a gate. This gate favors more transverse - with respect to the electric field - initial momenta of the tunneling electron that are opposite to the propagation direction of the laser field. In the absence of non-dipole effects, the transverse initial momentum is symmetric with respect to zero. We find that this asymmetry in the transverse initial momentum gives rise to an asymmetry in a double ionization observable. Finally, we show that this asymmetry in the transverse initial momentum of the tunneling electron accounts for a recently-reported unexpectedly large average sum of the electron momenta parallel to the propagation direction of the laser field.Comment: Amended the focus of the paper and discussion. 9 pages, 7 figure

    Capture into Rydberg states and momentum distributions of ionized electrons

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    The yield of neutral excited atoms and low-energy photoelectrons generated by the electron dynamics in the combined Coulomb and laser field after tunneling is investigated. We present results of Monte-Carlo simulations built on the two-step semiclassical model, as well as analytic estimates and scaling relations for the population trapping into the Rydberg states. It is shown that mainly those electrons are captured into bound states of the neutral atom that due to their initial conditions (i) have moderate drift momentum imparted by the laser field and (ii) avoid strong interaction ("hard" collision) with the ion. In addition, it is demonstrated that the channel of capture, when accounted for in semiclassical calculations, has a pronounced effect on the momentum distribution of electrons with small positive energy. For the parameters that we investigated its presence leads to a dip at zero momentum in the longitudinal momentum distribution of the ionized electrons.Comment: 9 pages, 8 figures in one zip-archiv

    The failure of suicide prevention in primary care: family and GP perspectives - a qualitative study

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    Background Although Primary care is crucial for suicide prevention, clinicians tend to report completed suicides in their care as non-preventable. We aimed to examine systemic inadequacies in suicide prevention from the perspectives of bereaved family members and GPs.Methods Qualitative study of 72 relatives or close friends bereaved by suicide and 19 General Practitioners who have experienced the suicide of patients.Results Relatives highlight failures in detecting symptoms and behavioral changes and the inability of GPs to understand the needs of patients and their social contexts. A perceived overreliance on anti-depressant treatment is a major source of criticism by family members. GPs tend to lack confidence in the recognition and management of suicidal patients, and report structural inadequacies in service provision.Conclusions Mental health and primary care services must find innovative and ethical ways to involve families in the decision-making process for patients at risk of suicide

    Wavelet Based Fractal Analysis of Airborne Pollen

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    The most abundant biological particles in the atmosphere are pollen grains and spores. Self protection of pollen allergy is possible through the information of future pollen contents in the air. In spite of the importance of airborne pol len concentration forecasting, it has not been possible to predict the pollen concentrations with great accuracy, and about 25% of the daily pollen forecasts have resulted in failures. Previous analysis of the dynamic characteristics of atmospheric pollen time series indicate that the system can be described by a low dimensional chaotic map. We apply the wavelet transform to study the multifractal characteristics of an a irborne pollen time series. We find the persistence behaviour associated to low pollen concentration values and to the most rare events of highest pollen co ncentration values. The information and the correlation dimensions correspond to a chaotic system showing loss of information with time evolution.Comment: 11 pages, 7 figure

    The influence of hydrological regimes on sex ratios and spatial segregation of the sexes in two dioecious riparian shrub species in northern Sweden

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    River management practices have altered the hydrological regimes of many rivers and also altered the availability of regeneration niches for riparian species. We investigated the impact of changed hydrological regimes on the sex ratios and the Spatial Segregation of the Sexes (SSS) in the dioecious species Salix myrsinifolia Salisb.–phylicifolia L. and S. lapponum L. by studying the free-flowing Vindel River and the regulated Ume River in northern Sweden. We surveyed sex ratios of these species in 12 river reaches on the Vindel River and in 17 reaches on the Ume River. In addition, we surveyed the sex and location above mean river stage of 1,002 individuals across both river systems to investigate the SSS of both species. Cuttings were collected from male and female individuals of S. myrsinifolia–phylicifolia from both rivers and subjected to four different water table regimes in a greenhouse experiment to investigate growth response between the sexes. We found an M/F sex ratio in both river systems similar to the regional norm of 0.62 for S. myrsinifolia–phylicifolia and of 0.42 for S. lapponum. We found no evidence of SSS in either the free-flowing Vindel River or the regulated Ume River. In the greenhouse experiment, hydrological regime had a significant effect on shoot and root dry weight and on root length. Significantly higher shoot dry weights were found in females than in males and significantly different shoot and root dry weights were found between cuttings taken from the two rivers. We concluded that changed hydrological regimes are likely to alter dimensions of the regeneration niche and therefore to influence sex ratios and SSS at an early successional stage, making it difficult to find clear spatial patterns once these species reach maturity and can be sexed

    Maternal childhood abuse and neglect predicts offspring development in early childhood: the roles of reflective functioning and child sex

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    Background: Recent evidence suggests that offspring of mothers having been exposed to childhood abuse and neglect (CA&N) are at increased risk of developmental problems and that boys are more affected by maternal CA&N than girls. Since impairments in reflective functioning (RF) have been associated with maternal CA&N and offspring development, RF could represent a key mechanism in these intergenerational risk trajectories. Objective: This study evaluated mediating (RF) and moderating (child sex) mechanisms in the association between maternal CA&N and child development. Participants and setting: In a longitudinal setting, 111 mothers completed measures during pregnancy and between 11 and 36 months postpartum. Methods: CA&N and impairments in RF were assessed during pregnancy and offspring development was measured during the longitudinal follow-up using the Ages and Stages Questionnaires (ASQ-3). Child development was operationalized in two ways: using the global score at the ASQ-3 and using a dichotomous score of accumulation of delays across domains of development. Results: Structural equation modeling indicated that RF mediated the association between maternal CA&N and offspring development. Child sex moderated the association between CA&N and the clustering of developmental problems (Wald = 5.88, p = 0.02), with boys being particularly likely to accumulate developmental delays when their mother experienced CA&N (RR = 2.62). Accumulation of developmental problems was associated with impairments in maternal RF in girls and with maternal exposure to CA&N in boys. Conclusions: Results provide novel insights on the role of mentalization and child sex in the association between maternal CA&N and child development. © 2021 The Author

    Incidence and prevalence of drug-resistant epilepsy : a systematic review and meta-analysis

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    Objective To evaluate the incidence and prevalence of drug-resistant epilepsy (DRE) as well as its predictors and correlates, we conducted a systematic review and meta-analysis of observational studies. Methods Our protocol was registered with PROSPERO, and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Meta-analysis of Observational Studies in Epidemiology reporting standards were followed. We searched MEDLINE, Embase, and Web of Science. We used a double arcsine transformation and random-effects models to perform our meta-analyses. We performed random-effects meta-regressions using study-level data. Results Our search strategy identified 10,794 abstracts. Of these, 103 articles met our eligibility criteria. There was high interstudy heterogeneity and risk of bias. The cumulative incidence of DRE was 25.0% (95% confidence interval [CI]: 16.8–34.3) in child studies but 14.6% (95% CI: 8.8–21.6) in adult/mixed age studies. The prevalence of DRE was 13.7% (95% CI: 9.2–19.0) in population/community-based populations but 36.3% (95% CI: 30.4–42.4) in clinic-based cohorts. Meta-regression confirmed that the prevalence of DRE was higher in clinic-based populations and in focal epilepsy. Multiple predictors and correlates of DRE were identified. The most reported of these were having a neurologic deficit, an abnormal EEG, and symptomatic epilepsy. The most reported genetic predictors of DRE were polymorphisms of the ABCB1 gene. Conclusions Our observations provide a basis for estimating the incidence and prevalence of DRE, which vary between populations. We identified numerous putative DRE predictors and correlates. These findings are important to plan epilepsy services, including epilepsy surgery, a crucial treatment option for people with disabling seizures and DRE

    Socioemotional development in infants of pregnant women during the COVID-19 pandemic : The role of prenatal and postnatal maternal distress

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    Background An upsurge in psychological distress was documented in pregnant women during the COVID-19 pandemic. We investigated with a longitudinal design whether prenatal and postnatal maternal distress during the COVID-19 pandemic was associated with lower infant socioemotional development. Methods Pregnant women (N = 468, Mage = 30,00, 97.6% White) were recruited during the first COVID-19 mandatory lockdown in Quebec, Canada, from April 2nd to April 13th 2020 and were re-contacted at two months postpartum to complete self-reported measures of general (i.e. not specifically related to the COVID-19 pandemic) anxio-depressive symptoms and infant development. Structural equation modeling analyses were performed using maximum likelihood parameter estimation. Results Higher maternal prenatal distress significantly contributed to poorer infant socioemotional development. A mediation model showed that postnatal distress significantly mediated the association between prenatal distress and infant socioemotional development, whereas the direct effect of prenatal distress was no longer significant. Prenatal and postnatal maternal distress accounted for 13.7% of the variance in infant socioemotional development. Conclusion Our results call for special means of clinical surveillance in mothers and for innovative (online) interventions aiming to support maternal mental health during pregnancy and after delivery
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