Simulating Induced Interdigitation in Membranes

AbstractIn this study we introduce a mesoscopic lipid-water-alcohol model. Dissipative particle dynamics (DPD) simulations have been used to investigate the induced interdigitation of bilayers consisting of double-tail lipids by adding alcohol molecules to the bilayer. Our simulations nicely reproduce the experimental phase diagrams. We find that alcohol can induce an interdigitated structure where the common bilayer structure changes into monolayer in which the alcohol molecules screen the hydrophobic tails from the water phase. At low concentrations of alcohol the membrane has domains of the interdigitated phase that are in coexistence with the common membrane phase. We compute the effect of the chain length of the alcohol on the phase behavior of the membrane and show that the stability of the interdigitated phase depends on the length of the alcohol. We show that we can reproduce the experimental hydrophobic thickness of the bilayer for various combinations of lipids and alcohols. We use our model to clarify some of the experimental questions related to the structure of the interdigitated phase and put forward a simple model that explains the alcohol chain length dependence of the stability of this interdigitated phase

Recruiting Young and Urban Groups into a Probability-Based Online Panel by Promoting Smartphone Use

A sizable minority of all web surveys are nowadays completed on smartphones. People who choose a smartphone for Internet-related tasks are different from people who mainly use a PC or tablet. Smartphone use is particularly high among the young and urban. We have to make web surveys attractive for smartphone completion in order not to lose these groups of smartphone users. In this paper we study how to encourage people to complete surveys on smartphones in order to attract hard-to-reach subgroups of the population. We experimentally test new features of a survey-friendly design: we test two versions of an invitation letter to a survey, a new questionnaire lay-out, and autoforwarding. The goal of the experiment is to evaluate whether the new survey design attracts more smartphone users, leads to a better survey experience on smartphones and results in more respondents signing up to become a member of a probability-based online panel. Our results show that the invitation letter that emphasizes the possibility for smartphone completion does not yield a higher response rate than the control condition, nor do we find differences in the socio-demographic background of respondents. We do find that slightly more respondents choose a smartphone for survey completion. The changes in the layout of the questionnaire do lead to a change in survey experience on the smartphone. Smartphone respondents need 20% less time to complete the survey when the questionnaire includes autoforwarding. However, we do not find that respondents evaluate the survey better, nor are they more likely to become a member of the panel when asked at the end of the survey. We conclude with a discussion of autoforwarding in web surveys and methods to attract smartphone users to web surveys

Histories of Social Functioning and Mental Healthcare in Severely Dysfunctional Dual-Diagnosis Psychiatric Patients

Abstract Disengagement from mental health services is a major obstacle to the treatment of homeless dual-diagnosis patients (i.e., those with severe mental illness and substance-use disorder). A subgroup of these patients is considered to be treatment resistant and we aim to explore whether patients’ reasons for disengagement may stem from negative experiences in their lives and treatment histories. This retrospective, explorative study examined the medical files of 183 severely dysfunctional dual-diagnosis patients who had been admitted involuntarily to a new specialized clinic for long-term treatment. Most patients shared common negative experiences with respect to childhood adversities, low school achievement, high levels of unemployment, discontinuity of care, and problems with the judicial system. The lifetime histories of treatment-resistant, severely dysfunctional dual-diagnosis patients showed a common pattern of difficulties that may have contributed to treatment resistance and disengagement from services. If these adversities are targeted, disengagement may be prevented and outcome improved