Fluctuating-friction molecular motors

We show that the correlated stochastic fluctuation of the friction coefficient can give rise to long-range directional motion of a particle undergoing Brownian random walk in a constant periodic energy potential landscape. The occurrence of this motion requires the presence of two additional independent bodies interacting with the particle via friction and via the energy potential, respectively, which can move relative to each other. Such three-body system generalizes the classical Brownian ratchet mechanism, which requires only two interacting bodies. In particular, we describe a simple two-level model of fluctuating-friction molecular motor that can be solved analytically. In our previous work [M.K., L.M and D.P. 2000 J. Nonlinear Opt. Phys. Mater. vol. 9, 157] this model has been first applied to understanding the fundamental mechanism of the photoinduced reorientation of dye-doped liquid crystals. Applications of the same idea to other fields such as molecular biology and nanotechnology can however be envisioned. As an example, in this paper we work out a model of the actomyosin system based on the fluctuating-friction mechanism.Comment: to be published in J. Physics Condensed Matter (http://www.iop.org/Journals/JPhysCM

Electron density stratification in two-dimensional structures tuned by electric field

A new kinetic instability which results in formation of charge density waves is proposed. The instability is of a purely classical nature. A spatial period of arising space-charge and field configuration is inversely proportional to electric field and can be tuned by applied voltage. The instability has no interpretation in the framework of traditional hydrodynamic approach, since it arises from modulation of an electron distribution function both in coordinate and energy spaces. The phenomenon can be observed in thin 2D nanostructures at relatively low electron density.Comment: 4 pages, 2 figure

Perceived need of, and interest in, HIV pre-exposure prophylaxis amongst men who have sex with men attending three sexual health clinics in London, UK

HIV pre-exposure prophylaxis (PrEP) has proven efficacy in reducing the risk of HIV infection in men who have sex with men (MSM), but has not yet been commissioned in the UK. The aim of this study was to investigate perceived need and benefit (or experience of) PrEP among HIV-negative MSM attending sexual health clinics. HIV-negative MSM attending three sexual health centres in London, UK were opportunistically invited to complete a questionnaire. Data collected comprised demographic data and sexual and drug use behaviours as well as questions regarding perceptions of risk and need for PrEP. Logistic regression analysis was undertaken to identify variables predicting acceptability of, and intention to use, PrEP. In addition, data were gathered in respondents already taking PrEP. Eight hundred and thirty-nine questionnaires were analysed. The median age of respondents was 35 years (IQR 28–41, range 18–78), 650 (77%) were of white ethnicity and 649 (77%) had a university education. Four hundred and fifty-six (54%) reported at least one episode of condomless anal sex in the preceding three months, 437 (52%) reported recreational drug use in the preceding three months and 311 (37%) had been diagnosed with a sexually transmitted infection within the preceding six months. Four hundred and sixty-three (64%) of 726 strongly agreed with the statement ‘I think I would benefit from PrEP’. Multivariate logistic regression analysis demonstrated that having receptive anal intercourse (RAI) without condoms, having an awareness of the risk of unprotected RAI and having belief in the effectiveness of PrEP were independent predictors for someone thinking they would benefit from taking PrEP. Eight percent of respondents (59/724) had already taken or were currently taking PrEP. The results suggest that individuals at risk are likely to perceive themselves as benefiting from PrEP. The majority perceived their risk of acquiring HIV and benefit from PrEP accurately. Overall they appeared to have little concern over the use of PrEP and generally positive attitudes. Further investigation is warranted to understand why those at risk do not perceive benefit from PrEP

Phytochemical Screening and Antioxidant Activity of Selekop (Lepisanthes Amoena) Fruit

Selekop (Lepisanthes amoena (Hassk.) Leenh.) plant leaves are used by the Dayak tribe of East Kalimantan as traditional cosmetics. Selekop fruit is also edible, but not well known. This study was conducted to obtain the phytochemical content and antioxidant assay in flesh, seed and pericarp extracts from the fruit of Selekop. Phytochemical analysis was conducted on ethanol extract for identification of flavonoid, alkaloid, tannin, saponin, triterpenoid and steroid. The antioxidant activity was done by DPPH assay with ascorbic acid as positive control. The flesh contained flavonoid, saponin, and tannin; the seed contained flavonoid, alkaloid, saponin, triterpenoid, and tannin; and the pericarp contained flavonoid, alkaloid, saponin, triterpenoid, and tannin. Analysis of antioxidant activity revealed the following Inhibitory Concentration (IC50 values): 122.51 ppm of flesh, 63.30 ppm of seed, 53.21 ppm of pericarp and 3.06 ppm of ascorbic acid. Based on these results, the ethanol extract of the seed and the flesh had a phytochemical content and antioxidant activity which was better than the flesh extract from Selekop fuit

An unfolding signifier: London's Baltic Exchange in Tallinn

In the summer of 2007 an unusual cargo arrived at Muuga and Paldiski harbors outside Tallinn. It consisted of nearly 50 containers holding over 1,000 tons of building material ranging from marble columns, staircases and fireplaces, to sculpted allegorical figures, wooden paneling and old-fashioned telephone booths. They were once part of the Baltic Exchange in the City of London. Soon they will become facets of the landscape of Tallinn. The following article charts this remarkable story and deploys this fragmented monument to analyze three issues relating to the Estonian capital: the relocation of the ‘Bronze Soldier’, the demolition of the Sakala Culture Center, and Tallinn’s future role as European Cultural Capital in 2011

Project20: Does continuity of care and community-based antenatal care improve maternal and neonatal birth outcomes for women with social risk factors? A prospective, observational study.

BACKGROUND: Social factors associated with poor childbirth outcomes and experiences of maternity care include minority ethnicity, poverty, young motherhood, homelessness, difficulty speaking or understanding English, migrant or refugee status, domestic violence, mental illness and substance abuse. It is not known what specific aspects of maternity care work to improve the maternal and neonatal outcomes for these under-served, complex populations. METHODS: This study aimed to compare maternal and neonatal clinical birth outcomes for women with social risk factors accessing different models of maternity care. Quantitative data on pregnancy and birth outcome measures for 1000 women accessing standard care, group practice and specialist models of care at two large, inner-city maternity services were prospectively collected and analysed using multinominal regression. The level of continuity of care and place of antenatal care were used as independent variables to explore these potentially influential aspects of care. Outcomes adjusted for women's social and medical risk factors and the service attended. RESULTS: Women who received standard maternity care were significantly less likely to use water for pain relief in labour (RR 0.11, CI 0.02-0.62) and have skin to skin contact with their baby shortly after birth (RR 0.34, CI 0.14-0.80) compared to the specialist model of care. Antenatal care based in the hospital setting was associated with a significant increase in preterm birth (RR 2.38, CI 1.32-4.27) and low birth weight (RR 2.31, CI 1.24-4.32), and a decrease in induction of labour (RR 0.65, CI 0.45-0.95) compared to community-based antenatal care, this was despite women's medical risk factors. A subgroup analysis found that preterm birth was increased further for women with the highest level of social risk accessing hospital-based antenatal care (RR 3.11, CI1.49-6.50), demonstrating the protective nature of community-based antenatal care. CONCLUSIONS: This research highlights how community-based antenatal care, with a focus on continuity of carer reduced health inequalities and improved maternal and neonatal clinical outcomes for women with social risk factors. The findings support the current policy drive to increase continuity of midwife-led care, whilst adding that community-based care may further improve outcomes for women at increased risk of health inequalities. The relationship between community-based models of care and neonatal outcomes require further testing in future research. The identification of specific mechanisms such as help-seeking and reduced anxiety, to explain these findings are explored in a wider evaluation

Project20: maternity care mechanisms that improve access and engagement for women with social risk factors in the UK - a mixed-methods, realist evaluation

OBJECTIVES: To evaluate how women access and engage with different models of maternity care, whether specialist models improve access and engagement for women with social risk factors, and if so, how? DESIGN: Realist evaluation. SETTING: Two UK maternity service providers. PARTICIPANTS: Women accessing maternity services in 2019 (n=1020). METHODS: Prospective observational cohort with multinomial regression analysis to compare measures of access and engagement between models and place of antenatal care. Realist informed, longitudinal interviews with women accessing specialist models of care were analysed to identify mechanisms. MAIN OUTCOME MEASURES: Measures of access and engagement, healthcare-seeking experiences. RESULTS: The number of social risk factors women were experiencing increased with deprivation score, with the most deprived more likely to receive a specialist model that provided continuity of care. Women attending hospital-based antenatal care were more likely to access maternity care late (risk ratio (RR) 2.51, 95% CI 1.33 to 4.70), less likely to have the recommended number of antenatal appointments (RR 0.61, 95% CI 0.38 to 0.99) and more likely to have over 15 appointments (RR 4.90, 95% CI 2.50 to 9.61) compared with community-based care. Women accessing standard care (RR 0.02, 95% CI 0.00 to 0.11) and black women (RR 0.02, 95% CI 0.00 to 0.11) were less likely to have appointments with a known healthcare professional compared with the specialist model. Qualitative data revealed mechanisms for improved access and engagement including self-referral, relational continuity with a small team of midwives, flexibility and situating services within deprived community settings. CONCLUSION: Inequalities in access and engagement with maternity care appears to have been mitigated by the community-based specialist model that provided continuity of care. The findings enabled the refinement of a realist programme theory to inform those developing maternity services in line with current policy

Incorporating organic matter alters soil greenhouse gas emissions and increases grain yield in a semi-arid climate

© 2016 The Authors Increasing soil organic matter (OM) is promoted as a strategy for improving the resilience of coarse-textured cropping soils in semi-arid climates. While increasing soil OM can benefit crop productivity, it can also enhance nitrous oxide (N2O) emissions in temperate climates. Our objective was to investigate if increasing soil OM affected soil greenhouse gas (GHG) fluxes and grain production in a semi-arid region in south-western Australia. We firstly measured N2O and methane (CH4) fluxes from a free-draining sandy soil with contrasting soil OM content for 2.5 years using automated soil chambers. The randomized block design included two OM additions (no OM, plus OM) by two nitrogen (N) fertilizer rates (0, 0N; 100 kg N ha-1 yr-1, +N) by three replicate plots. Organic matter (chaff) had been applied to the plus OM treatments every three years since 2003, with 80 t OM ha-1applied in total. Secondly, we investigated the interaction between soil OM content and N fertilizer addition on grain yield for two growing seasons. The randomized split-plot design included two OM treatments by five N fertilizer rates (0, 25, 50, 75 and 100 kg N ha-1), by three replicates. Increasing soil OM increased grain yields and soil mineral N, but also enhanced soil N2O emissions. Nitrous oxide emissions were low by international standards (<0.12% of the N fertilizer applied), with total N2O emissions after two years ranked: plus OM (+N; 427 g N2O-N ha-1) > plus OM (0N; 194 g N2O-N ha-1) > no OM (+N; 41 g N2O-N ha-1) = no OM (0N; 14 g N2O-N ha-1). Increasing soil OM also decreased CH4uptake by 30%. Management practices that increase soil OM in sandy-textured rainfed, cropping soils in semi-arid regions should be encouraged as they can improve grain yield without substantial increases in soil N2O or CH4emissions