Two nonlinear systems from mathematical physics

The dissertation is divided into two chapters. In the first one, we consider the 2-Vortex problem for two point vortices in a complex domain. The Hamiltonian of the system contains the regular part of a hydrodynamic Green’s function, the Robin function h and two coefficinets which are the strengths of the point vortices. We prove the existence of infinitely many periodic solutions with minimal period T which are a superposition of a slow motion of the center of vorticity along a level line of h and of a fast rotation of the two vortices around their center of vorticity. These vortices move in a prescribed subset of the domain that has to satisfy a geometric condition. The minimal period can be any T in a certain interval. Subsets to which our results apply can be found in any generic bounded domain. The proofs are based on a recent higher dimensional version of the Poincaré-Birkhoff theorem due to Fonda and Ureña. In the second part, we study bifurcations of a multi-component Schrödinger system. We construct a solution branch synchronized to a positive solution of a simpler system. From this branch, we find a sequence of local bifurcation values in the one dimensional case and also in the general case provided that the positive solution is nondegenerate

The Chronology of the Ross Sea II glaciation, an Antarctic glaciation of Illinoian Age

A meltwater stream in the Marshall Valley, southern Victoria Land, Antarctica has revealed a stratigraphy of glacial drift and lacustrine lake beds. The sequence has been differentiated by U/Th dating into the Ross Sea I Glaciation (15-30,000 years B.P.), represented by a gypsum bed and the Ross Sea II(?) Glaciation (130-180,000 years B.P.), represented by three calcium carbonate and gypsum beds. The three Ross Sea II(?) lake beds may be differentiated from one another by an increasing calcite content with age, and a systematic change in the crystal type and morphology of the carbonates. Chemical analysis of the lake beds reveals that their components have differing sources. The freezing on of seawater and/or frozen out seawater precipitates can quantitatively provide the salts required. However U isotope studies shows that a weathered crustal component is present in the lake beds. Stable isotope analysis indicates that the meltwaters were formed at high altitudes of 1,900 m (Ross Sea I) and 2,500 m (Ross Sea II(?)), and originated as snow, precipitated approximately 5,000 km to the south. Ice sheet incursion into the valley created a proglacial lake. Calcium carbonate and gypsum were precipitated due to increased lake saturation conditions. Stable isotope studies show that the calcium carbonate deposition was triggered biologically by phytoplankton. The morphology of the calcium carbonate and the presence of gypsum indicates that evaporitic conditions were also necessary for lake bed deposition, with the distribution of gypsum and calcium carbonate within the lake being controlled by depth of water. Correlation of lake bed geochronology and geochemistry, together with the stratigraphy of the stream sections provides a glacial history of Marshall Valley for the last 180,000 years B.P. The last two Ross Sea glacial sequences rest upon an unconformably eroded glacial surface. The Ross Sea II(?) Glaciation commenced at 180,000 years with a glacial ice incursion into the valley, a stillstand, proglacial lake occupation and deposition of a lake bed. The ice front then advance farther up the valley, depositing large terminal loop moraines between Sections III and IV. The ice then retreated at least 2 km. A second glacial advance commenced prior to 160,000 years, stillstanded and produced the 160,000 year lake bed, before retreating. A minor fluctuation and readvance, deposited another lake bed (160,000 years) or reworked the previous lake bed into the overlying stratigraphy, before the ice retreat. The deposition of the 130,000 year lake bed was also a the result of a stillstand, before the retreat and cessation of the Ross Sea II(?) glaciation. The Ross Sea I Glaciation involved the advance of a glacier front from an ice sheet occupying the McMurdo Sound and the deposition of a gypsum lake bed (15-30,000 years B.P.). With the retreat of the ice front, downwasting of ice-cored moraines in the mouth of the valley began, and currently continues. The geochronology of the Ross Sea II(?) Glaciation correlates with eustatic sea level lowering in the Illinoian (Isotope Stage 6). Subsurface drilling indicates that the calcium carbonate deposition was a unique event but at least 8 earlier glacial incursions had occurred in the Marshall Valley. The geochronology of the Ross Sea I Glaciation correlates with the eustatic sea level lowering in the Wisconsin (Isotope Stage 2). The chronology and isotopic composition of the proglacial lake deposits can be matched to those in other ice-free valleys exposed to McMurdo Sound

When nutritional guidelines and life collide: family fruit and vegetable socialisation practices in low socioeconomic communities

Parents play a critical role in promoting fruit and vegetable consumption, for eating patterns established early in life tend to persist into adulthood. Despite this, the factors that facilitate or inhibit parents’ capacity to socialise fruit and vegetable consumption into their children’s daily diets remain poorly defined. Thirty-eight semi-structured interviews with residents, allied healthcare professionals, community leaders, community programme leaders and a local government leader living or working in two low socioeconomic suburbs were consequently conducted to ascertain factors exogenous and endogenous to the family unit that shaped parental food socialisation practices. Budgetary and time constraints emerged as exogenous factors that constrained fruit and vegetable socialisation. Constraining effects were also found for a range of endogenous factors, including commensal experiences, children’s food fussiness and the feeding styles employed by parents. As such, while many caregivers may wish to socialise fruit and vegetable consumption into their children’s daily diets, their capacity to do so is often inhibited by factors beyond their volitional control. Failure to take heed of these factors could therefore result in the development of social marketing campaigns that are ineffective at best or give rise to unintentionally harmful outcomes at worst

Help-seeking by rural residents for mental health problems: The importance of agrarian values

Objective: To examine the role of stoicism, self-efficacy and perceived stigma in predicting help-seeking by rural residents, for mental health problems. Method: A cross-sectional community survey was conducted with a sample of 467 rural residents (58% female), who completed self-report questionnaires assessing current levels of symptomatology, disability, perceived stigma, self-efficacy, stoicism, attitudes towards and experience of seeking help for psychological problems. Results: Overall, 7.6% (n = 129) of respondents had sought help from a general practitioner and/or mental health professional for psychological problems or a mental health issue. More women than men reported having sought such help. Lifetime help-seeking for a psychological problem or mental health issue was positively associated with higher levels of distress and lower levels of stoicism and, to a lesser extent, lower levels of self-efficacy. Conclusions: Efforts to improve help-seeking by rural residents for mental health problems should focus on understanding and addressing attitudes, such as stoicism which act as barriers to help-seeking. © 2006 The Authors; Journal compilation © 2006 The Royal Australian and New Zealand College of Psychiatrists.C

Neurobehaviour between birth and 40 weeks’ gestation in infants born <30 weeks’ gestation and parental psychological wellbeing: predictors of brain development and child outcomes

BACKGROUND: Infants born <30 weeks’ gestation are at increased risk of long term neurodevelopmental problems compared with term born peers. The predictive value of neurobehavioural examinations at term equivalent age in very preterm infants has been reported for subsequent impairment. Yet there is little knowledge surrounding earlier neurobehavioural development in preterm infants prior to term equivalent age, and how it relates to perinatal factors, cerebral structure, and later developmental outcomes. In addition, maternal psychological wellbeing has been associated with child development. Given the high rate of psychological distress reported by parents of preterm children, it is vital we understand maternal and paternal wellbeing in the early weeks and months after preterm birth and how this influences the parent–child relationship and children’s outcomes. Therefore this study aims to examine how 1) early neurobehaviour and 2) parental mental health relate to developmental outcomes for infants born preterm compared with infants born at term. METHODS/DESIGN: This prospective cohort study will describe the neurobehaviour of 150 infants born at <30 weeks’ gestational age from birth to term equivalent age, and explore how early neurobehavioural deficits relate to brain growth or injury determined by magnetic resonance imaging, perinatal factors, parental mental health and later developmental outcomes measured using standardised assessment tools at term, one and two years’ corrected age. A control group of 150 healthy term-born infants will also be recruited for comparison of outcomes. To examine the effects of parental mental health on developmental outcomes, both parents of preterm and term-born infants will complete standardised questionnaires related to symptoms of anxiety, depression and post-traumatic stress at regular intervals from the first week of their child’s birth until their child’s second birthday. The parent–child relationship will be assessed at one and two years’ corrected age. DISCUSSION: Detailing the trajectory of infant neurobehaviour and parental psychological distress following very preterm birth is important not only to identify infants most at risk, further understand the parental experience and highlight potential times for intervention for the infant and/or parent, but also to gain insight into the effect this has on parent–child interaction and child development

Selenium in reproduction

Selenium is an essential trace element of importance to human biology and health. Increasing evidence suggests that this mineral plays an important role in normal growth and reproduction in animals and humans, and selenium supplementation is now recommended as part of public health policy in geographical areas with severe selenium deficiency in soil. This review addresses the biological functions of selenium followed by a detailed review of associations between selenium status and reproductive health. In many countries, selenium dietary intake falls below the recommended nutrient intakes and is inadequate to support maximal expression of the selenoenzymes. Numerous reports implicate selenium deficiency in several reproductive and obstetric complications including male and female infertility, miscarriage, preeclampsia, fetal growth restriction, preterm labor, gestational diabetes, and obstetric cholestasis. Currently, there is inadequate information from the available small intervention studies to inform public health strategies. Larger intervention trials are required to reinforce or refute a beneficial role of selenium supplementation in disorders of reproductive health

The DARE study of relapse prevention in depression: design for a phase 1/2 translational randomised controlled trial involving mindfulness-based cognitive therapy and supported self monitoring

<p>Abstract</p> <p>Background</p> <p>Depression is a common condition that typically has a relapsing course. Effective interventions targeting relapse have the potential to dramatically reduce the point prevalence of the condition. Mindfulness-based cognitive therapy (MBCT) is a group-based intervention that has shown efficacy in reducing depressive relapse. While trials of MBCT to date have met the core requirements of phase 1 translational research, there is a need now to move to phase 2 translational research - the application of MBCT within real-world settings with a view to informing policy and clinical practice. The aim of this trial is to examine the clinical impact and health economics of MBCT under real-world conditions and where efforts have been made to assess for and prevent resentful demoralization among the control group. Secondary aims of the project involve extending the phase 1 agenda to an examination of the effects of co-morbidity and mechanisms of action.</p> <p>Methods/Design</p> <p>This study is designed as a prospective, multi-site, single-blind, randomised controlled trial using a group comparison design between involving the intervention, MBCT, and a self-monitoring comparison condition, Depression Relapse Active Monitoring (DRAM). Follow-up is over 2 years. The design of the study indicates recruitment from primary and secondary care of 204 participants who have a history of 3 or more episodes of Major Depression but who are currently well. Measures assessing depressive relapse/recurrence, time to first clinical intervention, treatment expectancy and a range of secondary outcomes and process variables are included. A health economics evaluation will be undertaken to assess the incremental cost of MBCT.</p> <p>Discussion</p> <p>The results of this trial, including an examination of clinical, functional and health economic outcomes, will be used to assess the role that this treatment approach may have in recommendations for treatment of depression in Australia and elsewhere. If the findings are positive, we expect that this research will consolidate the evidence base to guide the decision to fund MBCT and to seek to promote its availability to those who have experienced at least 3 episodes of depression.</p> <p>Trial Registration</p> <p>Australian New Zealand Clinical Trials Registry: <a href="http://www.anzctr.org.au/ACTRN12607000166471.aspx">ACTRN12607000166471</a></p

Long-term Mortality in HIV-Positive Individuals Virally Suppressed for >3 Years With Incomplete CD4 Recovery

Virally suppressed HIV-positive individuals on combination antiretroviral therapy who do not achieve a CD4 count >200 cells/µL have substantially increased long-term mortality. The increased mortality was seen across different patient groups and for all causes of deat

The physiological responses of cacao to the environment and the implications for climate change resilience. A review

Cacao (Theobroma cacao L.) is a tropical perennial crop which is of great economic importance to the confectionary industry and to the economies of many countries of the humid tropics where it is grown. Some recent studies have suggested climate change could severely impact cacao production in West Africa. It is essential to incorporate our understanding of the physiology and genetic variation within cacao germplasm when discussing the implications of climate change on cacao productivity and developing strategies for climate resilience in cacao production. Here we review the current research on the physiological responses of cacao to various climate factors. Our main findings are 1) water limitation causes significant yield reduction in cacao but genotypic variation in sensitivity is evident, 2) in the field cacao experiences higher temperatures than is often reported in the literature, 3) the complexity of the cacao/ shade tree interaction can lead to contradictory results, 4) elevated CO2 may alleviate some negative effects of climate change 5) implementation of mitigation strategies can help reduce environmental stress, 6) significant gaps in the research need addressing to accelerate the development of climate resilience. Harnessing the significant genetic variation apparent within cacao germplasm is essential to develop modern varieties capable of high yields in non-optimal conditions. Mitigation strategies will also be essential but to use shading to best effect shade tree selection is crucial to avoid resource competition. Cacao is often described as being sensitive to climate change but genetic variation, adaptive responses, appropriate mitigation strategies and interactive climate effects should all be considered when predicting the future of cacao production. Incorporating these physiological responses to various environmental conditions and developing a deeper understanding of the processes underlying these responses will help to accelerate the development of a more resource use efficient tree ensuring sustainable production into the future