Reversible electron-hole separation in a hot carrier solar cell

Hot-carrier solar cells are envisioned to utilize energy filtering to extract power from photogenerated electron-hole pairs before they thermalize with the lattice, and thus potentially offer higher power conversion efficiency compared to conventional, single absorber solar cells. The efficiency of hot-carrier solar cells can be expected to strongly depend on the details of the energy filtering process, a relationship which to date has not been satisfactorily explored. Here, we establish the conditions under which electron-hole separation in hot-carrier solar cells can occur reversibly, that is, at maximum energy conversion efficiency. We thus focus our analysis on the internal operation of the hot-carrier solar cell itself, and in this work do not consider the photon-mediated coupling to the sun. After deriving an expression for the voltage of a hot-carrier solar cell valid under conditions of both reversible and irreversible electrical operation, we identify separate contributions to the voltage from the thermoelectric effect and the photovoltaic effect. We find that, under specific conditions, the energy conversion efficiency of a hot-carrier solar cell can exceed the Carnot limit set by the intra-device temperature gradient alone, due to the additional contribution of the quasi-Fermi level splitting in the absorber. We also establish that the open-circuit voltage of a hot-carrier solar cell is not limited by the band gap of the absorber, due to the additional thermoelectric contribution to the voltage. Additionally, we find that a hot-carrier solar cell can be operated in reverse as a thermally driven solid-state light emitter. Our results help explore the fundamental limitations of hot-carrier solar cells, and provide a first step towards providing experimentalists with a guide to the optimal configuration of devices.Comment: 31 pages, 5 figure

A comparison of the use of vacuum metal deposition versus cyanoacrylate fuming for visualisation of fingermarks and grab impressions on fabrics

Both vacuum metal deposition (VMD) and cyanoacrylate fuming (CAF) are techniques used to visualise latent fingermarks on smooth non-porous surfaces such as plastic and glass. VMD was initially investigated in the 1970s as to its effectiveness for visualising prints on fabrics, but was abandoned when radioactive sulphur dioxide was found to be more effective. However, interest in VMD was resurrected in the 1990s when CAF was also used routinely. We now report on studies to determine whether VMD or CAF is the more effective technique for the detection of marks on fabrics. Four different fabrics, nylon, polyester, polycotton and cotton, were utilised during this study, along with 15 donors who ranged in their age and ability to leave fingermarks, from good to medium to poor, thus reflecting the general population. Once samples were collected they were kept for a determined time (1, 2, 3, 4, 5, 6, 7, 14, 21 or 28 days) and then treated using either the gold and zinc metal VMD process or standard cyanoacrylate fuming.The smoother fabrics, such as nylon, consistently produced greater ridge detail whereas duller fabrics, like cotton tended only to show empty prints and impressions of where the fabric had been touched, rather than any ridge details. The majority of fabrics did however allow the development of touch marks that could be targeted for DNA taping which potentially could lead to a DNA profile. Of the two techniques VMD was around 5 times more effective than CAF, producing a greater amount of ridge detail, palmar flexion creases and target areas on more samples and fabrics

Cascade diagrams for depicting complex interventions in randomised trials

Clarity about how trial interventions are delivered is important for researchers and those who might want to use their results. A new graphical representation aims to help make complex interventions clearer. Many medical interventions—particularly non-pharmacological ones—are complex, consisting of multiple interacting components targeted at different organisational levels. Published descriptions of complex interventions often do not contain enough detail to enable their replication. Reports of behaviour change interventions should include descriptions of setting, mode, intensity, and duration, and characteristics of the participants. Graphical methods, such as that showing the relative timing of assessments and intervention components, may improve clarity of reporting. However, these approaches do not reveal the connections between the different “actors” in a complex intervention.8 Different audiences may want different things from a description of an intervention, but visualising relationships between actors can clarify crucial features such as the fidelity with which the intervention is passed down a chain of actors and possible routes of contamination between treatment arms. Here we describe a new graphical approach—the cascade diagram—that highlights these potential problems

Visualisation of fingermarks and grab impressions on fabrics. Part 1: gold/zinc vacuum metal deposition

Vacuum metal deposition (VMD) is a highly sensitive technique originally introduced for detecting latent fingermarks on smooth non-porous surfaces such as carrier bags, plastics and glass. The current study explores whether VMD can be used in the examination of clothing from physical and sexual assault cases in order to visualise identifiable fingermark ridge detail and/or palmar flexion crease detail, thus allowing potential areas to be indicated for DNA swabbing and/or to determine the sequence of events. Four different fabrics were utilised during this study – nylon, polyester, polycotton and cotton, along with 15 donors who ranged in their age and propensity to leave fingermarks, from good to medium to poor as determined by results obtained from test runs using paper and plastic carrier bags processed with VMD. Once samples were collected they were kept for a determined time (1, 2, 3, 4, 5, 6, 7, 14, 21 or 28 days) and then treated using the gold/zinc metal VMD process. From the results, it appears that greater ridge detail is visible on the smoother non-porous fabrics, such as nylon whereas on rougher porous fabrics, such as cotton, only empty prints and impressions, rather than any ridge details, were visible. All fabrics did however allow the development of touch marks that could be targeted for DNA taping thus potentially leading to a DNA profile and possible identification of a suspect

Visualisation of fingermarks and grab impressions on dark fabrics using silver vacuum metal deposition

Vacuum metal deposition (VMD) involves the thermal evaporation of metal (silver) in a vacuum, resulting in a uniform layer being deposited on the specimen being treated. This paper examines the use of silver on dark fabrics, thus offering a simpler operation and more obvious colouration to that of the traditional use of gold and zinc metals which must be evaporated separately. The aim of this study was to investigate the effect of fabric type, donor, mark age and method of fingermark deposition on the quality of marks visualised using silver VMD. This was achieved by collecting fingermark deposits from fifteen donors, of both sexes and various ages, by a grab or a press method. Four different fabrics: satin, polyester, polycotton and cotton were studied over a 10 day timeline of 1, 2, 3, 4, 5, 6, 7, 14, 21 and 28 + days. It was found that satin and polyester gave the most positive results, with polyester often producing excellent ridge detail. Cotton and polycotton were less successful with no ridge detail being observed. The donors also had an observable effect on the results obtained probably due to variations in secretions produced or pressures applied during specimen collection. The age of the mark or the method of mark deposition had little influence on the results obtained. Silver VMD is a viable process for visualising marks on certain dark fabrics and has the advantage over gold/zinc VMD in that the marks visualised are light in colour which contrasts well against the dark background

Discontinuing financial incentives for adherence to antipsychotic depot medication: long-term outcomes of a cluster randomised controlled trial

Objectives: In a cluster randomised controlled trial, offering financial incentives improved adherence to antipsychotic depot medication over a 1-year period. Yet, it is unknown whether this positive effect is sustained once the incentives stop. Methods and analyses: Patients in the intervention and control group were followed up for 2 years after the intervention. Primary and secondary outcomes were assessed at 6 months and 24 months post intervention. Assessments were conducted between September 2011 and November 2014. Results: After the intervention period, intervention and control groups did not show any statistically significant differences in adherence, neither in the first 6 months (71% and 77%, respectively) nor in the following 18 months (68%, 74%). There were no statistically significant differences in secondary outcomes, that is, adherence ≥95% and untoward incidents either. Conclusions: It may be concluded that incentives to improve adherence to antipsychotic maintenance medication are effective only for as long as they are provided. Once they are stopped, adherence returns to approximately baseline level with no sustained benefit. Trial registration number: ISRCTN77769281

Clinicians have several therapeutic relationships and patients only one: the effect on their assessments of relationships

Objectives Little attention has been given to the common assessment problem that clinicians assess outcomes of several patients and may rate them in comparison to one another, whereas patients assess only their own outcomes without any comparison. We explored empirically whether this would lead to a greater variability of clinician ratings as compared to patient ratings. Methods Data from two independent samples in which clinicians and patients, using consistent instruments, rated their therapeutic relationships. We present descriptive statistics of variability and intracluster correlation coefficients. Results The Helping Alliance Scale was completed at baseline and follow‐up by 20 clinicians and 103 patients in an observational study and by 88 clinicians and 431 patients in a trial. Patients tended to rate their relationship 5–10% more highly than their clinicians, but with 50–100% more variability. Intraclinician Helping Alliance Scale ratings were more correlated than those by patients (intracluster correlation coefficients 0.3–0.7 vs. 0.0–0.2). Conclusion Contrary to our assumption, clinicians' ratings of therapeutic relationships were in both samples less variable than those of their patients. When clinicians rate outcomes of several patients, a cluster effect of ratings may have to be considered in the design and analysis

Effectiveness and cost-effectiveness of a novel, group self-management course for adults with chronic musculoskeletal pain: study protocol for a multicentre, randomised controlled trial (COPERS)

Introduction: Chronic musculoskeletal pain is a common condition that often responds poorly to treatment. Self-management courses have been advocated as a non-drug pain management technique, although evidence for their effectiveness is equivocal. We designed and piloted a self-management course based on evidence for effectiveness for specific course components and characteristics. Methods/analysis: COPERS (coping with persistent pain, effectiveness research into self-management) is a pragmatic randomised controlled trial testing the effectiveness and cost-effectiveness of an intensive, group, cognitive behavioural-based, theoretically informed and manualised self-management course for chronic pain patients against a control of best usual care: a pain education booklet and a relaxation CD. The course lasts for 15 h, spread over 3 days, with a –2 h follow-up session 2 weeks later. We aim to recruit 685 participants with chronic musculoskeletal pain from primary, intermediate and secondary care services in two UK regions. The study is powered to show a standardised mean difference of 0.3 in the primary outcome, pain-related disability. Secondary outcomes include generic health-related quality of life, healthcare utilisation, pain self-efficacy, coping, depression, anxiety and social engagement. Outcomes are measured at 6 and 12 months postrandomisation. Pain self-efficacy is measured at 3 months to assess whether change mediates clinical effect. Ethics/dissemination: Ethics approval was given by Cambridgeshire Ethics 11/EE/046. This trial will provide robust data on the effectiveness and cost-effectiveness of an evidence-based, group self-management programme for chronic musculoskeletal pain. The published outcomes will help to inform future policy and practice around such self-management courses, both nationally and internationally. Trial registration: ISRCTN24426731