How to Couple from the Past Using a Read-Once Source of Randomness

We give a new method for generating perfectly random samples from the stationary distribution of a Markov chain. The method is related to coupling from the past (CFTP), but only runs the Markov chain forwards in time, and never restarts it at previous times in the past. The method is also related to an idea known as PASTA (Poisson arrivals see time averages) in the operations research literature. Because the new algorithm can be run using a read-once stream of randomness, we call it read-once CFTP. The memory and time requirements of read-once CFTP are on par with the requirements of the usual form of CFTP, and for a variety of applications the requirements may be noticeably less. Some perfect sampling algorithms for point processes are based on an extension of CFTP known as coupling into and from the past; for completeness, we give a read-once version of coupling into and from the past, but it remains unpractical. For these point process applications, we give an alternative coupling method with which read-once CFTP may be efficiently used.Comment: 28 pages, 2 figure

Functional Incapacity and Physical and Psychological Symptoms: How They Interconnect in Chronic Fatigue Syndrome

Background: It has been argued that perceived functional incapacity might be a primary characteristic of chronic fatigue syndrome ( CFS) and could be explained by physical symptoms. If so, it could be expected to be closely associated with physical, but not psychological symptoms. The study tests this hypothesis. Sampling and Methods: The sample consisted of 73 patients, with a diagnosis of CFS according to the Oxford criteria, randomly selected from clinics in the Departments of Immunology and Psychiatry at St. Bartholomew's Hospital, London. The degree of fatigue experienced by patients was assessed using the Chalder Fatigue Questionnaire and a visual analogue scale. Self-rated instruments were used to measure physical and social functioning, quality of life, and physical and psychological symptoms. Results: Principal-component analysis of all scale scores revealed 2 distinct components, explaining 53% of the total variance. One component was characterized by psychological symptoms and generic quality of life indicators, whilst the other component was made up of physical symptoms, social and physical functioning and indicators of fatigue. Conclusions: The findings suggest that perceived functional incapacity is a primary characteristic of CFS, which is manifested and/or explained by physical symptoms. Copyright (C) 2008 S. Karger AG, Base

CARDIOVASCULAR EFFECTS OF DILTIAZEM IN THE DOG

SUMMARY The effects of two bolus injections (0.2 mg kg−1) and two infusion rates (0.2 mg min−1 and 0.4 mg min−1) ofdiltiazem on global and regional left (LV) and right ventricular (RV) performance (ultrasonic dimension technique), on coronary (electromagnetic flow meters) and systemic haemodynamics, and on electrophysiology (PR, QRS, QTC intervals) were studied in eight open-chest dogs anaesthetized with droperidol and fentanyl. The two bolus injections of diltiazem resulted in plasma concentrations of 688 ± 115 and 650 ± 85 ng ml−1 (means ± SE), respectively, and caused substantial decreases in systemic and coronary vascular resistances, and in aortic pressure, and increases in LV segment shortening, stroke volume and aortic flow. Electro -physiological variables were little affected. At the low infusion rate (plasma concentration 140 ± 23 ng ml−1) coronary and systemic vaso-dilatation occurred, but global and regional RV and LV performance were little affected. PR interval increased by 15%. At the higher infusion rate (plasma concentration 282 ± 33 ng ml−1) coronary and systemic vasodilatation were maintained. Aortic pressure decreased slightly. Whereas LV end-diastolic and end-systolic dimensions remained unchanged, they increased in the RV. In addition, the PR interval increased by 35%, and three animals developed atrio-ventricular block type I. The data indicate that diltiazem is a potent coronary and systemic vasodilator with little effect on global RV and L V performance. However, at a higher infusion rate RV dimensions clearly tend to increase, and conduction abnormalities develo

Can mental health interventions change social networks? A systematic review

KA was previously funded by East London NHS Foundation Trust, and is a PhD research fellow in the Netherlands at the time of print. SP was funded by Queen Mary University of London, and NL was funded by East London NHS Foundation Trust

How do psychiatrists address delusions in first meetings in acute care? A qualitative study

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Do long-term hospitalised patients benefit from discharge into the community?

The original publication is available at www.springerlink.co

Symptoms associated with victimization in patients with schizophrenia and related disorders

Background: Patients with psychoses have an increased risk of becoming victims of violence. Previous studies have suggested that higher symptom levels are associated with a raised risk of becoming a victim of physical violence. There has been, however, no evidence on the type of symptoms that are linked with an increased risk of recent victimization. Methods: Data was taken from two studies on involuntarily admitted patients, one national study in England and an international one in six other European countries. In the week following admission, trained interviewers asked patients whether they had been victims of physical violence in the year prior to admission, and assessed symptoms on the Brief Psychiatric Rating Scale (BPRS). Only patients with a diagnosis of schizophrenia or related disorders (ICD-10 F20–29) were included in the analysis which was conducted separately for the two samples. Symptom levels assessed on the BPRS subscales were tested as predictors of victimization. Univariable and multivariable logistic regression models were fitted to estimate adjusted odds ratios. Results: Data from 383 patients in the English sample and 543 patients in the European sample was analysed. Rates of victimization were 37.8% and 28.0% respectively. In multivariable models, the BPRS manic subscale was significantly associated with victimization in both samples. Conclusions: Higher levels of manic symptoms indicate a raised risk of being a victim of violence in involuntary patients with schizophrenia and related disorders. This might be explained by higher activity levels, impaired judgement or poorer self-control in patients with manic symptoms. Such symptoms should be specifically considered in risk assessments

Understanding psychiatric institutionalization: a conceptual review

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

General practice consultations with obese children-a missed opportunity? Cross-sectional study using linked national child measurement and primary care data

Meeting AbstractBackground A third of children leaving primary school are obese. Child weight status information from the National Child Measurement Programme (NCMP) is not routinely shared with general practitioners (GPs). We hypothesised that obese children were more likely to consult their GP for obesity or weight management than healthy-weight children. Methods NCMP data from 2013–16 for City and Hackney, London, were linked to coded GP data using pseudonymised National Health Service numbers, resulting in 13 663 linked records (93%). NCMP-assigned weight status was based on the UK90 clinical reference, and obesity and weight-management consultations identified (read codes C38..; 66C..; 8HHH%; 9N1yK; 22A%). The odds of one or more obesity or weight-management consultations in the school year of NCMP measurement among obese compared with healthy-weight children were estimated with logistic regression. Findings Obesity was identified in 624 (8·6%) of 7275 children aged 5 years (3721 boys [51·2%]; median age 5·01 years, IQR 4·76–5·27) and 1220 (19·1%) of 6388 children aged 11 (3297 [51·6%]; 10·87, 10·59–11·11). Obesity was more prevalent in boys than girls (9·5% [353/3721] vs 7·6% [271/3554] and 19·5% [643/3297] vs 18·7% [577/3091] at ages 5 and 11 years, respectively). Obese children were more likely than healthy-weight children to consult for obesity or weight management (respectively at age 5 years, boys 19·8% [70/353] vs 13·5% [391/2900]; girls 16·2% [44/271] vs 11·8% [342/2895] and at age 11 years, boys 17·0% [109/643] vs 12·6% [265/2111]; girls 19·9% [115/577] vs 10·0% [200/1996]). The odds of one or more obesity or weight-management consultations in obese boys and girls, respectively, were 1·59 (95% CI 1·20–2·10) and 1·45 (1·03–2·04) at age 5 years, and 1·42 (1·12–1·81) and 2·24 (1·74–2·87) at age 11 years. Interpretation Although more likely to consult their GP for obesity or weight management in the period before or after identification of obesity in the NCMP, fewer than a fifth of obese children attending primary schools in a London borough with one of the highest child obesity rates in England do so. This is, to our knowledge, the first study linking NCMP to primary care data. Further work is needed to evaluate routine sharing of NCMP data with GPs and primary care-initiated weight-management support for children and their families

Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy

Ultrafast electron and X-ray imaging and spectroscopy are the basis for an ongoing revolution in the understanding of dynamical atomic-scale processes in matter. The underlying technology relies heavily on laser science for the generation and characterization of ever shorter pulses. Recent findings suggest that ultrafast electron microscopy with attosecond-structured wavefunctions may be feasible. However, such future technologies call for means to both prepare and fully analyse the corresponding free-electron quantum states. Here, we introduce a framework for the preparation, coherent manipulation and characterization of free-electron quantum states, experimentally demonstrating attosecond electron pulse trains. Phase-locked optical fields coherently control the electron wavefunction along the beam direction. We establish a new variant of quantum state tomography—‘SQUIRRELS’—for free-electron ensembles. The ability to tailor and quantitatively map electron quantum states will promote the nanoscale study of electron–matter entanglement and new forms of ultrafast electron microscopy down to the attosecond regime