Isotropic-nematic phase transition in suspensions of filamentous virus and the neutral polymer Dextran

We present an experimental study of the isotropic-nematic phase transition in an aqueous mixture of charged semi-flexible rods (fd virus) and neutral polymer (Dextran). A complete phase diagram is measured as a function of ionic strength and polymer molecular weight. At high ionic strength we find that adding polymer widens the isotropic-nematic coexistence region with polymers preferentially partitioning into the isotropic phase, while at low ionic strength the added polymer has no effect on the phase transition. The nematic order parameter is determined from birefringence measurements and is found to be independent of polymer concentration (or equivalently the strength of attraction). The experimental results are compared with the existing theoretical predictions for the isotropic-nematic transition in rods with attractive interactions.Comment: 8 Figures. To be published in Phys. Rev. E. For more information see http://www.elsie.brandeis.ed

A coil-globule transition of a semiflexible polymer driven by the addition of spherical particles

The phase behaviour of a single large semiflexible polymer immersed in a suspension of spherical particles is studied. All interactions are simple excluded volume interactions and the diameter of the spherical particles is an order of magnitude larger than the diameter of the polymer. The spherical particles induce a quite long ranged depletion attraction between the segments of the polymer and this induces a continuous coil-globule transition in the polymer. This behaviour gives an indication of the condensing effect of macromolecular crowding on DNA.Comment: 12 pages, 4 figure

Predicting phase equilibria in polydisperse systems

Many materials containing colloids or polymers are polydisperse: They comprise particles with properties (such as particle diameter, charge, or polymer chain length) that depend continuously on one or several parameters. This review focusses on the theoretical prediction of phase equilibria in polydisperse systems; the presence of an effectively infinite number of distinguishable particle species makes this a highly nontrivial task. I first describe qualitatively some of the novel features of polydisperse phase behaviour, and outline a theoretical framework within which they can be explored. Current techniques for predicting polydisperse phase equilibria are then reviewed. I also discuss applications to some simple model systems including homopolymers and random copolymers, spherical colloids and colloid-polymer mixtures, and liquid crystals formed from rod- and plate-like colloidal particles; the results surveyed give an idea of the rich phenomenology of polydisperse phase behaviour. Extensions to the study of polydispersity effects on interfacial behaviour and phase separation kinetics are outlined briefly.Comment: 48 pages, invited topical review for Journal of Physics: Condensed Matter; uses Institute of Physics style file iopart.cls (included

Nematic phase transitions in mixtures of thin and thick colloidal rods

Published versio

Research into the efficacy and cost-effectiveness of brief, free of charge and anonymous sex counselling to improve (mental) health in youth: Design of a randomised controlled trial

<p>Abstract</p> <p>Background</p> <p>The capacity to form romantic relationships and sexual health of adolescents in the Netherlands are compromised by several factors, including young age of first intercourse and adolescent depression. Several thresholds like own expenses, trust and embarrassment prevent adolescents to seek help for their sexual problems. To overcome these thresholds, brief sex counselling has been developed. It has been used since 2006 within the Rotterdam-Rijnmond Public Health Service, but there is lack of information about the (cost-) effectiveness. In the current study we will evaluate the (cost-) effectiveness of brief sex counselling for sexual problems in adolescents and young adults between 18 and 25 years of age.</p> <p>Methods</p> <p>In a randomised controlled trial we will compare (1) brief sex counselling with (2) intensive sexological treatment, and (3) delayed treatment (waiting list). Embedded in this RCT will be a trial-based economic evaluation, looking at the cost-effectiveness and cost-utility of brief sex counselling versus the two other interventions. Four hundred fifty adolescents (aged 18-25) with sexual problems will be recruited among the persons who visit the Public Health Service (PHS) and through various websites. After a screening procedure, eligible participants will be randomly allocated to one of the three intervention groups. Primary outcome measure of the clinical evaluation is the severity of sexual problems. Other outcomes include psychological distress, especially depression. The economic evaluation will be performed from a societal perspective. Costs will be assessed continuously by a retrospective questionnaire covering the last 3 month. All outcome assessments (including those for the economic evaluation) will take place via the internet at baseline, and at 3, 6, 9, and 12 months after baseline.</p> <p>Discussion</p> <p>The proposed research project will be the first study to provide preliminary data about the effect and cost-effectiveness of brief sex counselling in youth in comparison with intensive sexological treatment and delayed treatment. It is anticipated that positive results in (cost-) effectiveness of the proposed intervention will contribute to the improvement of sexual health care for adolescents and young adults.</p> <p>Trial registration</p> <p>The study has been registered at the Netherlands Trial Register, part of the Dutch Cochrane Centre (NTR1952)</p

Validation of the PHQ-9 as a screening instrument for depression in diabetes patients in specialized outpatient clinics

Background. For the treatment of depression in diabetes patients, it is important that depression is recognized at an early stage. A screening method for depression is the patient health questionnaire (PHQ-9). The aim of this study is to validate the 9-item Patient Health Questionnaire (PHQ-9) as a screening instrument for depression in diabetes patients in outpatient clinics. Methods. 197 diabetes patients from outpatient clinics in the Netherlands filled in the PHQ-9. Within 2 weeks they were approached for an interview with the Mini Neuropsychiatric Interview. DSM-IV diagnoses of Major Depressive Disorder (MDD) were the criterion for which the sensitivity, specificity, positive- and negative predictive values and Receiver Operator Curves (ROC) for the PHQ-9 were calculated. Results. The cut-off point of a summed score of 12 on the PHQ-9 resulted in a sensitivity of 75.7% and a specificity of 80.0%. Predictive values for negative and positive test results were respectively 93.4% and 46.7%. The ROC showed an area under the curve of 0.77. Conclusions. The PHQ-9 proved to be an efficient and well-received screening instrument for MDD in this sample of diabetes patients in a specialized outpatient clinic. The higher cut-off point of 12 that was needed and somewhat lower sensitivity than had been reported elsewhere may be due to the fact that the patients from a specialized diabetes clinic have more severe pathology and more complications, which could be recognized by the PHQ-9 as depression symptoms, while instead being diabetes symptom

Strategies to prevent intraoperative lung injury during cardiopulmonary bypass

During open heart surgery the influence of a series of factors such as cardiopulmonary bypass (CPB), hypothermia, operation and anaesthesia, as well as medication and transfusion can cause a diffuse trauma in the lungs. This injury leads mostly to a postoperative interstitial pulmonary oedema and abnormal gas exchange. Substantial improvements in all of the above mentioned factors may lead to a better lung function postoperatively. By avoiding CPB, reducing its time, or by minimizing the extracorporeal surface area with the use of miniaturized circuits of CPB, beneficial effects on lung function are reported. In addition, replacement of circuit surface with biocompatible surfaces like heparin-coated, and material-independent sources of blood activation, a better postoperative lung function is observed. Meticulous myocardial protection by using hypothermia and cardioplegia methods during ischemia and reperfusion remain one of the cornerstones of postoperative lung function. The partial restoration of pulmonary artery perfusion during CPB possibly contributes to prevent pulmonary ischemia and lung dysfunction. Using medication such as corticosteroids and aprotinin, which protect the lungs during CPB, and leukocyte depletion filters for operations expected to exceed 90 minutes in CPB-time appear to be protective against the toxic impact of CPB in the lungs. The newer methods of ultrafiltration used to scavenge pro-inflammatory factors seem to be protective for the lung function. In a similar way, reducing the use of cardiotomy suction device, as well as the contact-time between free blood and pericardium, it is expected that the postoperative lung function will be improved

The association between medically unexplained physical symptoms and health care use over two years and the influence of depressive and anxiety disorders and personality traits: a longitudinal study

Background Medically unexplained physical symptoms (MUPS) are highly prevalent and are associated with frequent health care use (HCU). MUPS frequently co-occur with psychiatric disorders. With this study we examined the longitudinal association between MUPS and HCU over 2 years and the influence of depressive and anxiety disorders and personality traits on this association. Methods We analysed follow-up data from 2045 to 2981 participants from the Netherlands Study of Depression and Anxiety (NESDA), a multisite cohort study. The study population included participants with a current depressive and/or anxiety disorder, participants with a lifetime risk and/or subthreshold symptoms for depressive and/or anxiety disorders and healthy controls. HCU, measured with the Trimbos and iMTA questionnaire on Costs associated with Psychiatric illness (TIC-P), was operationalized as the number of used medical services and the number of associated contacts. MUPS were measured with the Four Dimensional Symptoms Questionnaire, depressive and anxiety disorders with the Composite International Diagnostic Interview and personality traits with the NEO Five-Factory Inventory. Measurements were taken at baseline, 1 and 2 years follow-up. We used generalized estimating equations (GEE), using HCU at all three measurements as (multivariate) outcome. GEE also takes into account the dependency of observations within participants. Results MUPS were positively associated with HCU over 2 years (medical services: RR 1.020, 95 % CI 1.017–1.022; contacts: RR 1.037, 95 % CI 1.030–1.044). Neuroticism and depression had the strongest influence on the associations. After adjustment for these factors, the associations between MUPS and HCU weakened, but remained significant (services: RR 1.011, 95 % CI 1.008–1.014; contacts: RR 1.023, 95 % CI 1.015–1.032). Conclusions Our results show that MUPS were positively associated with HCU over 2 years, even after adjusting for depressive and anxiety disorders and personality traits