Formation and interaction of resonance chains in the open 3-disk system

In ballistic open quantum systems one often observes that the resonances in the complex-energy plane form a clear chain structure. Taking the open 3-disk system as a paradigmatic model system, we investigate how this chain structure is reflected in the resonance states and how it is connected to the underlying classical dynamics. Using an efficient scattering approach we observe that resonance states along one chain are clearly correlated while resonance states of different chains show an anticorrelation. Studying the phase space representations of the resonance states we find that their localization in phase space oscillate between different regions of the classical trapped set as one moves along the chains and that these oscillations are connected to a modulation of the resonance spacing. A single resonance chain is thus no WKB quantization of a single periodic orbits, but the structure of several oscillating chains arises from the interaction of several periodic orbits. We illuminate the physical mechanism behind these findings by combining the semiclassical cycle expansion with a quantum graph model.Comment: 25 pages, 15 figure

Experimental Observation of the Spectral Gap in Microwave n-Disk Systems

Symmetry reduced three-disk and five-disk systems are studied in a microwave setup. Using harmonic inversion the distribution of the imaginary parts of the resonances is determined. With increasing opening of the systems, a spectral gap is observed for thick as well as for thin repellers and for the latter case it is compared with the known topological pressure bounds. The maxima of the distributions are found to coincide for a large range of the distance to radius parameter with half of the classical escape rate. This confirms theoretical predictions based on rigorous mathematical analysis for the spectral gap and on numerical experiments for the maxima of the distributions.Comment: 5 pages, 4 figure

Primary group size, social support, gender and future mental health status in a prospective study of people living in private households throughout Great Britain

Background. Structural characteristics of social networks such as primary group size have received less attention than measures of perceived social support. Previous research suggests that associations between social network size and later common mental disorder status may differ according to sex and initial mental state. Method. Adults participating in the 2000 British National Household Survey of psychiatric morbidity were randomly selected for follow-up 18 months later. The revised Clinical Interview Schedule (CIS-R) and the Interview Measure of Social Relations (IMSR) were administered at baseline and follow-up. Primary group size was defined as the total number of close relatives and friends. A four-level scale of common mental disorder was modelled with ordinal logistic regression, based on weighted data (n=2413). Findings. After adjusting for confounders, a primary group size of three or less at time 1 predicted worse mental health at time 2. This effect was greatest in men who were initially non-cases at baseline (averaged odds 4.5) and in women who were initially cases at baseline (average odds 2.9). Primary group size at time 2 was significantly predicted by level of common mental disorder at time 1 in women but not in men. Thus, confounding by baseline disorder does not explain risk of developing poor mental health in socially isolated men. Conclusion. This study replicates the strong effects of primary group size on future mental health that emerge when men and women are studied separately and when subjects are categorized according to baseline mental health status

The population impact of common mental disorders and long-term physical conditions on disability and hospital admission

Background: Long-term physical conditions (LTCs) consume the largest share of healthcare budgets. Although common mental disorders (CMDs) and LTCs often co-occur, the potential impact of improved mental health treatment on severe disability and hospital admissions for physical health problems remains unknown. Method: A cross-sectional study of 7403 adults aged 16–95 years living in private households in England was performed. LTCs were ascertained by prompted self-report. CMDs were ascertained by structured clinical interview. Disability was assessed using questions about problems with activities of daily living. Population impact and potential preventive gain were estimated using population-attributable fraction (PAF), and conservative estimates were obtained using ‘treated non-cases’ as the reference group. Results: Of the respondents, 20.7% reported at least one LTC. The prevalence of CMDs increased with the number of LTCs, but over two-thirds (71.2%) of CMD cases in people with LTCs were untreated. Statistically significant PAFs were found for CMDs and recent hospital admission [13.5%, 95% confidence intervals (CI) 6.6–20.0] and severe disability (31.3%, 95% CI 27.1–35.2) after adjusting for LTCs and other confounders. Only the latter remained significant when using the most conservative estimate of PAF (21.8%, 95% CI 14.0–28.9), and this was reduced only slightly when considering only participants with LTCs (18.5%, 95% CI 7.9–27.9). Conclusions: Better treatments for CMDs in people with LTCs could achieve almost the same population health gain in terms of reducing severe disability as those targeted at the entire population. Interventions to reduce the prevalence of CMDs among people with LTCs should be part of routine medical care

Debt income and mental disorder in the general population

Background The association between poor mental health and poverty is well known but its mechanism is not fully understood. This study tests the hypothesis that the association between low income and mental disorder is mediated by debt and its attendant financial hardship. Method The study is a cross-sectional nationally representative survey of private households in England, Scotland and Wales, which assessed 8580 participants aged 16–74 years living in general households. Psychosis, neurosis, alcohol abuse and drug abuse were identified by the Clinical Interview Schedule – Revised, the Schedule for Assessment in Neuropsychiatry (SCAN), the Alcohol Use Disorder Identification Test (AUDIT) and other measures. Detailed questions were asked about income, debt and financial hardship. Results Those with low income were more likely to have mental disorder [odds ratio (OR) 2.09, 95% confidence interval (CI) 1.68–2.59] but this relationship was attenuated after adjustment for debt (OR 1.58, 95% CI 1.25–1.97) and vanished when other sociodemographic variables were also controlled (OR 1.07, 95% CI 0.77–1.48). Of those with mental disorder, 23% were in debt (compared with 8% of those without disorder), and 10% had had a utility disconnected (compared with 3%). The more debts people had, the more likely they were to have some form of mental disorder, even after adjustment for income and other sociodemographic variables. People with six or more separate debts had a six-fold increase in mental disorder after adjustment for income (OR 6.0, 95% CI 3.5–10.3). Conclusions Both low income and debt are associated with mental illness, but the effect of income appears to be mediated largely by debt

Review Article: Medical management of opioid dependence in South Africa

Medical practitioners in South Africa are increasingly confronted with requests to treat patients with opioid use disorders. Many do not possess the required knowledge and skills to deal with these patients effectively. This overview of the medical treatment of opioid dependence was compiled by an elected working group of doctors working in the field of substance dependence. Recommendations are based on current best practice derived from scientific evidence and consensus of the working group, but should never replace individual clinical judgement.South African Medical Journal Vol. 98 (4) 2008: pp. 280-28

Weyl asymptotics: From closed to open systems

We present microwave experiments on the symmetry reduced 5-disk billiard studying the transition from a closed to an open system. The measured microwave reflection signal is analyzed by means of the harmonic inversion and the counting function of the resulting resonances is studied. For the closed system this counting function shows the Weyl asymptotic with a leading exponent equal to 2. By opening the system successively this exponent decreases smoothly to an non-integer value. For the open systems the extraction of resonances by the harmonic inversion becomes more challenging and the arising difficulties are discussed. The results can be interpreted as a first experimental indication for the fractal Weyl conjecture for resonances.Comment: 9 pages, 7 figure

Predictors of 1-year survival in South African transcatheter aortic valve implant candidates

Background. Transcatheter aortic valve implantation (TAVI) has undergone rapid expansion internationally over the past 15 years. In view of resource constraints in developing countries, a major challenge in applying this technology lies in identifying patients most likely to benefit. The development of a risk prediction model for TAVI has proved elusive, with a reported area under the curve (AUC) of 0.6 - 0.65. The available models were developed in a First-World setting and may not be applicable to South Africa (SA).Objectives. To evaluate novel indicators and to develop a TAVI risk prediction model unique to the SA context. The current work represents the important initial steps of derivation cohort risk model development and internal validation.Methods. Seven-year experience with 244 successive TAVI implants in three centres in Western Cape Province, SA, was used to derive risk parameters. All outcomes are reported in accordance with the Valve Academic Research Consortium definitions. Multiple preprocedural variables were assessed for their impact on 1-year survival using univariate and multivariate models.Results. Factors found not to correlate with 1-year survival included age, renal function and aortic valve gradients. The commonly used surgical risk prediction models (Society of Thoracic Surgeons score and EuroSCORE) showed no correlation with outcomes. Factors found to correlate best with 1-year survival on multivariate analysis were preprocedural body mass index (BMI) (favouring higher BMI), preprocedural left ventricular end-diastolic dimension (LVED) and ejection fraction (EF) (favouring smaller LVED and higher EF), absence of atrial fibrillation, and three novel parameters: independent living, ability to drive a car, and independent food acquisition/cooking. Discriminant analysis of these factors yielded an AUC of 0.8 (95% confidence interval 0.7 - 0.9) to predict 1-year survival, with resubstitution sensitivities and specificities of 72% and 71%, respectively.Conclusions. Apart from existing predictors, we identified three novel risk predictors (independent living, ability to drive a car, and independent food acquisition/cooking) for 1-year survival in TAVI candidates. These novel parameters performed well in this early evaluation, with an AUC for predicting 1-year survival higher than the AUCs for many of the internationally derived parameters. The parameters are inexpensive and easy to obtain at the initial patient visit. If validated prospectively in external cohorts, they may be applicable to other resource-constrained environments.

Chapter 3: Mental health treatment and services

In this chapter reported use of psychotropic medication and psychological therapy are examined, as well as the extent of use of health care services for a mental health reason (GP, inpatient and outpatient health care) and day and community service use. It should be noted that rates presented are based on participant self-reports, not health records. Misclassifications of type of treatment or service are possible, and which was the providing organisation was not established