Nonlinear network model analysis of vibrational energy transfer and localisation in the Fenna-Matthews-Olson complex

Collective protein modes are expected to be important for facilitating energy transfer in the Fenna-Matthews-Olson (FMO) complex of photosynthetic green sulphur bacteria, however to date little work has focussed on the microscopic details of these vibrations. The nonlinear network model (NNM) provides a computationally inexpensive approach to studying vibrational modes at the microscopic level in large protein structures, whilst incorporating anharmonicity in the inter-residue interactions which can influence protein dynamics. We apply the NNM to the entire trimeric FMO complex and find evidence for the existence of nonlinear discrete breather modes. These modes tend to transfer energy to the highly connected core pigments, potentially opening up alternative excitation energy transfer routes through their influence on pigment properties. Incorporating localised modes based on these discrete breathers in the optical spectra calculations for FMO using ab initio site energies and excitonic couplings can substantially improve their agreement with experimental results.A.W.C. and S.E.M. acknowledge support from the Winton Programme for the Physics of Sustainability. S.E.M. is also supported by an EPSRC doctoral training award. D.J.C. is supported by a Marie Curie International Outgoing Fellowship within the seventh European Community Framework Programme

Chapter 10 The effect of topography on ash-cloud surge generation and propagation

AbstractThe relationship between valley morphology and ash-cloud surge development for 12 pyroclastic density currents (PDCs) at Soufrière Hills Volcano (SHV), Montserrat is investigated. Channel slope, sinuosity and cross-sectional area were measured from high-resolution digital elevation models (DEMs) using geographical information system (GIS) software; and were compared to geometric parameters of the deposits. The data illustrate three surge-generation regimes: a proximal area of rapid expansion; a medial deflation zone; and a steadier distal surge ‘fringe'. The extent to which these regimes develop varies with flow volume. For larger flows, within the proximal and medial regimes, a strong inverse correlation exists between surge detachment and valley cross-sectional area. Surge detachment is also correlated with observed and modelled flow velocities. Areas of topography-induced increases in velocity are interpreted to result in more pervasive fragmentation and fluidization, and thus enhanced surge generation. Distally, surge deposits appear as fringes with decaying extents, indicative of more passive expansion and decreasing velocity. The results indicate that surge mobility and detachment are a complex product of flow mass flux and topography, and that future efforts to model dense–dilute coupled flows will need to account for and integrate several mechanisms acting on different parts of the flow.</jats:p

Chromium isotopes in marine hydrothermal sediments

Hydrothermal chromium (Cr) cycling contributes to marine Cr inventories and their Cr isotopic composition, yet Cr isotope effects associated with this cycling remain poorly documented. Here we determine the distribution, isotopic composition, and diagenetic mobility of Cr in hydrothermal sediments from the distal flank of the South East Pacific Rise (SEPR, DSDP-site 598). We find that Cr is primarily associated with the metalliferous iron (oxyhydr) oxide and detrital components of the sediment (0.4–3.6 mg kg⁻¹), whereas Cr concentrations are much lower in the dominant carbonate phase (80% Cr from the sediment relative to Fe. We propose this loss is tied to oxidation of authigenic Cr(III) to Cr(VI) followed by diagenetic remobilization and efflux from the sediment pile. The bulk δ⁵³Cr composition of the SEPR sediments is isotopically light (−0.24 to −0.57 ± 0.05‰) and the authigenic δ⁵³Cr is as light as −1.2 ± 0.2‰, and we argue that this light Cr isotopic composition results from the partial reduction of oxic seawater-bearing Cr(VI) by reduced hydrothermal vent fluids enriched in Fe(II)aq. Diagenetic oxidation of the reactive Cr pool by Mn-oxides and loss of Cr(VI) from the sediment may further deplete the sediment in ⁵³Cr during diagenesis. The δ⁵³Cr composition of the detrital Cr fraction of the sediment (average δ⁵³Cr composition = −0.05 ± 0.04‰) falls within the igneous silicate earth (ISE) range, revealing that detrital Cr delivered to this region of the Pacific ocean is unfractionated, and has carried a relatively constant δ⁵³Cr composition over the last 5.7 million years. Together our results show that light δ⁵³Cr compositions in hydrothermal sediments are imparted through a combination of processes previously overlooked in the marine Cr biogeochemical cycle, and that the δ⁵³Cr composition of such sediments may provide a rich source of information on paleo-marine redox conditions

The effectiveness of rehabilitation interventions including outdoor mobility on older adults' physical activity, endurance, outdoor mobility and falls-related self-efficacy: systematic review and meta-analysis.

OBJECTIVE: To determine the effectiveness of community-based rehabilitation interventions which incorporate outdoor mobility on physical activity, endurance, outdoor mobility and falls-related self-efficacy in older adults. DESIGN: MEDLINE, Embase, CINAHL, PEDro and OpenGrey were searched systematically from inception to June 2021 for randomised controlled trials (RCTs) of community-based rehabilitation incorporating outdoor mobility on physical activity, endurance, outdoor mobility and/or falls-related self-efficacy in older adults. Duplicate screening, selection, extraction and appraisal were completed. Results were reported descriptively and with random-effects meta-analyses stratified by population (proactive [community-dwelling], reactive [illness/injury]). RESULTS: A total of 29 RCTs with 7,076 participants were identified (66% high bias for at least one domain). The outdoor mobility component was predominantly a walking programme with behaviour change. Rehabilitation for reactive populations increased physical activity (seven RCTs, 587 participants. Hedge's g 1.32, 95% CI: 0.31, 2.32), endurance (four RCTs, 392 participants. Hedges g 0.24; 95% CI: 0.04, 0.44) and outdoor mobility (two RCTs with 663 participants. Go out as much as wanted, likelihood of a journey) at intervention end versus usual care. Where reported, effects were preserved at follow-up. One RCT indicated a benefit of rehabilitation for proactive populations on moderate-to-vigorous activity and outdoor mobility. No effect was noted for falls-related self-efficacy, or other outcomes following rehabilitation for proactive populations. CONCLUSION: Reactive rehabilitation for older adults may include walking programmes with behaviour change techniques. Future research should address the potential benefit of a walking programme for proactive populations and address mobility-related anxiety as a barrier to outdoor mobility for both proactive and reactive populations

Amblyopia and quality of life: a systematic review

Background/Aims Amblyopia is a common condition which can affect up to 5% of the general population. The health-related quality of life (HRQoL) implications of amblyopia and/or its treatment have been explored in the literature. Methods A systematic literature search was undertaken (16th-30th January 2007) to identify the HRQoL implications of amblyopia and/or its treatment. Results A total of 25 papers were included in the literature review. The HRQoL implications of amblyopia related specifically to amblyopia treatment, rather than the condition itself. These included the impact upon family life; social interactions; difficulties undertaking daily activities; and feelings and behaviour. The identified studies adopted a number of methodologies. The study populations included; children with the condition; parents of children with amblyopia; and adults who had undertaken amblyopia treatment as a child. Some studies developed their own measures of HRQoL, and others determined HRQoL through proxy measures. Conclusions The reported findings of the HRQoL implications are of importance when considering the management of cases of amblyopia. Further research is required to assess the immediate and long-term effects of amblyopia and/or its treatment upon HRQoL using a more standardised approach

Fundamental Strings, Holography, and Nonlinear Superconformal Algebras

We discuss aspects of holography in the AdS_3 \times S^p near string geometry of a collection of straight fundamental heterotic strings. We use anomalies and symmetries to determine general features of the dual CFT. The symmetries suggest the appearance of nonlinear superconformal algebras, and we show how these arise in the framework of holographic renormalization methods. The nonlinear algebras imply intricate formulas for the central charge, and we show that in the bulk these correspond to an infinite series of quantum gravity corrections. We also makes some comments on the worldsheet sigma-model for strings on AdS_3\times S^2, which is the holographic dual geometry of parallel heterotic strings in five dimensions.Comment: 25 page

Serotonin tranporter methylation and response to cognitive behaviour therapy in children with anxiety disorders

Anxiety disorders that are the most commonly occurring psychiatric disorders in childhood, are associated with a range of social and educational impairments and often continue into adulthood. Cognitive behaviour therapy (CBT) is an effective treatment option for the majority of cases, although up to 35-45% of children do not achieve remission. Recent research suggests that some genetic variants may be associated with a more beneficial response to psychological therapy. Epigenetic mechanisms such as DNA methylation work at the interface between genetic and environmental influences. Furthermore, epigenetic alterations at the serotonin transporter (SERT) promoter region have been associated with environmental influences such as stressful life experiences. In this study, we measured DNA methylation upstream of SERT in 116 children with an anxiety disorder, before and after receiving CBT. Change during treatment in percentage DNA methylation was significantly different in treatment responders vs nonresponders. This effect was driven by one CpG site in particular, at which responders increased in methylation, whereas nonresponders showed a decrease in DNA methylation. This is the first study to demonstrate differences in SERT methylation change in association with response to a purely psychological therapy. These findings confirm that biological changes occur alongside changes in symptomatology following a psychological therapy such as CBT

Explaining the human resource management preferences of employees: A study of Chinese workers

The forces of globalization, technology and the differences or similarities in institutional systems place substantial pressure on convergence and divergence in HRM practices. Moreover, local customs and the responses from employees also pose serious constraints on the degree of convergence or divergence (Rowley and Benson 2002). In other words, there is what might be termed an upward influence coming from the employees. Although companies may benchmark HRM ‘best practices’, the actual adoption and success of these practices depends, to a large extent, on perceptions and acceptance from employees. However, the opinions of non-managerial employees have been largely neglected in the studies of HRM (Cooke 2009; Legge 1995; Guest 2002; Edgar and Geare 2005; Qiao, Khilji and Wang 2009). Cooke (2009), after reviewing studies on HRM in China published between 1998 and 2007 in major business and management journals, reported that two-thirds of the studies had collected data from managers and most of them relied on managers as the sole source for information. Since the information has mainly been provided by managers, there is the potential for bias because feedback from the managers probably reflects the ideal or ‘best practices’ of HRM that those managers want to implement, rather than the actual HR policies or practices being used in the organization. Thus Cooke (2009, p.19) argued that ‘unless we can broaden our research catchment to include views from the widest range of stakeholders, particularly the employees, our understanding of HRM in China remains partial, from management’s lens’. This study explores the HR preferences of Chinese employees, both non-managerial and managerial ones, based on a sample of 2852 questionnaires from companies in China. A number of questions are explored. For example, what do they think of a ‘promotion-from-within’ policy? Do they prefer an individual-based bonus or a group-based bonus? Do they prefer a ‘downward performance appraisal method’ or a ‘multi-source performance appraisal method’? The research findings shows a strong ‘group orientation’ and a great emphasis on ‘soft factors’ such as seniority, loyalty and connections in many HRM areas. The debate on whether Chinese HRM will converge or diverge towards the Western models is still ongoing. Many argue that there could be further convergence towards the Western practices because globalization may place substantial pressure on firms to standardize practices and policies (see Chen, Lawler and Bae 2005). Others argue that HRM is highly context specific in which institutional and cultural forces have enduring influences (see Rowley and Cooke 2010), which indicates a divergent perspective. The third group supports a ‘cross-vergence’ view which argues that there will be signs of convergence in certain areas but Chinese HRM will keep its ‘Chinese characteristics’ (Cooke 2005, 2010; Yeung, Warner and Rowley 2008; Warner 2009a, b). This study supports the ‘cross-vergence’ perspective. It is argued that certain areas of Chinese HRM are converging to the Western model, but the influence of traditional Chinese personnel practices remains strong. A ‘group orientation’, a major emphasis on ‘soft factors’ and a trade union presence is likely to remain as the three main features of Chinese HRM in the long-term

Brain age predicts mortality

Age-associated disease and disability are placing a growing burden on society. However, ageing does not affect people uniformly. Hence, markers of the underlying biological ageing process are needed to help identify people at increased risk of age-associated physical and cognitive impairments and ultimately, death. Here, we present such a biomarker, ‘brain-predicted age’, derived using structural neuroimaging. Brain-predicted age was calculated using machine-learning analysis, trained on neuroimaging data from a large healthy reference sample (N=2001), then tested in the Lothian Birth Cohort 1936 (N=669), to determine relationships with age-associated functional measures and mortality. Having a brain-predicted age indicative of an older-appearing brain was associated with: weaker grip strength, poorer lung function, slower walking speed, lower fluid intelligence, higher allostatic load and increased mortality risk. Furthermore, while combining brain-predicted age with grey matter and cerebrospinal fluid volumes (themselves strong predictors) not did improve mortality risk prediction, the combination of brain-predicted age and DNA-methylation-predicted age did. This indicates that neuroimaging and epigenetics measures of ageing can provide complementary data regarding health outcomes. Our study introduces a clinically-relevant neuroimaging ageing biomarker and demonstrates that combining distinct measurements of biological ageing further helps to determine risk of age-related deterioration and death