Showing papers by "University of Manchester published in 2008"

Fine Structure Constant Defines Visual Transparency of Graphene

Abstract: There are few phenomena in condensed matter physics that are defined only by the fundamental constants and do not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is Planck's constant and e the electron charge), that appears in a variety of transport experiments and the magnetic flux quantum, h/e, playing an important role in the physics of superconductivity. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure constant, a = e2/hc feminine 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally associated with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (pa = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure.

Revised Definitions of Invasive Fungal Disease from the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) Consensus Group

Abstract: BACKGROUND: Invasive fungal diseases are important causes of morbidity and mortality. Clarity and uniformity in defining these infections are important factors in improving the quality of clinical studies. A standard set of definitions strengthens the consistency and reproducibility of such studies. METHODS: After the introduction of the original European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) Consensus Group definitions, advances in diagnostic technology and the recognition of areas in need of improvement led to a revision of this document. The revision process started with a meeting of participants in 2003, to decide on the process and to draft the proposal. This was followed by several rounds of consultation until a final draft was approved in 2005. This was made available for 6 months to allow public comment, and then the manuscript was prepared and approved. RESULTS: The revised definitions retain the original classifications of "proven," "probable," and "possible" invasive fungal disease, but the definition of "probable" has been expanded, whereas the scope of the category "possible" has been diminished. The category of proven invasive fungal disease can apply to any patient, regardless of whether the patient is immunocompromised, whereas the probable and possible categories are proposed for immunocompromised patients only. CONCLUSIONS: These revised definitions of invasive fungal disease are intended to advance clinical and epidemiological research and may serve as a useful model for defining other infections in high-risk patients.

Allergic rhinitis and its impact on asthma (ARIA) 2008 update (in collaboration with the World Health Organization, GA(2)LEN and AllerGen)

Abstract: Allergic rhinitis is a symptomatic disorder of the nose induced after allergen exposure by an IgE-mediated inflammation of the membranes lining the nose. It is a global health problem that causes major illness and disability worldwide. Over 600 million patients from all countries, all ethnic groups and of all ages suffer from allergic rhinitis. It affects social life, sleep, school and work and its economic impact is substantial. Risk factors for allergic rhinitis are well identified. Indoor and outdoor allergens as well as occupational agents cause rhinitis and other allergic diseases. The role of indoor and outdoor pollution is probably very important, but has yet to be fully understood both for the occurrence of the disease and its manifestations. In 1999, during the Allergic Rhinitis and its Impact on Asthma (ARIA) WHO workshop, the expert panel proposed a new classification for allergic rhinitis which was subdivided into 'intermittent' or 'persistent' disease. This classification is now validated. The diagnosis of allergic rhinitis is often quite easy, but in some cases it may cause problems and many patients are still under-diagnosed, often because they do not perceive the symptoms of rhinitis as a disease impairing their social life, school and work. The management of allergic rhinitis is well established and the ARIA expert panel based its recommendations on evidence using an extensive review of the literature available up to December 1999. The statements of evidence for the development of these guidelines followed WHO rules and were based on those of Shekelle et al. A large number of papers have been published since 2000 and are extensively reviewed in the 2008 Update using the same evidence-based system. Recommendations for the management of allergic rhinitis are similar in both the ARIA workshop report and the 2008 Update. In the future, the GRADE approach will be used, but is not yet available. Another important aspect of the ARIA guidelines was to consider co-morbidities. Both allergic rhinitis and asthma are systemic inflammatory conditions and often co-exist in the same patients. In the 2008 Update, these links have been confirmed. The ARIA document is not intended to be a standard-of-care document for individual countries. It is provided as a basis for physicians, health care professionals and organizations involved in the treatment of allergic rhinitis and asthma in various countries to facilitate the development of relevant local standard-of-care documents for patients.

Monitoring dopants by Raman scattering in an electrochemically top-gated graphene transistor

Abstract: The recent discovery of graphene has led to many advances in two-dimensional physics and devices. The graphene devices fabricated so far have relied on $SiO_2$ back gating. Electrochemical top gating is widely used for polymer transistors, and has also been successfully applied to carbon nanotubes. Here we demonstrate a top-gated graphene transistor that is able to reach doping levels of up to $5\times 10^{13} cm^{-2}$, which is much higher than those previously reported. Such high doping levels are possible because the nanometre-thick Debye layer in the solid polymer electrolyte gate provides a much higher gate capacitance than the commonly used $SiO_2$ back gate, which is usually about 300 nm thick. In situ Raman measurements monitor the doping. The G peak stiffens and sharpens for both electron and hole doping, but the 2D peak shows a different response to holes and electrons. The ratio of the intensities of the G and 2D peaks shows a strong dependence on doping, making it a sensitive parameter to monitor the doping.

Giant intrinsic carrier mobilities in graphene and its bilayer

Abstract: We have studied temperature dependences of electron transport in graphene and its bilayer and found extremely low electron-phonon scattering rates that set the fundamental limit on possible charge carrier mobilities at room temperature. Our measurements show that mobilities higher than 200 000 cm2/V s are achievable, if extrinsic disorder is eliminated. A sharp (thresholdlike) increase in resistivity observed above approximately 200 K is unexpected but can qualitatively be understood within a model of a rippled graphene sheet in which scattering occurs on intraripple flexural phonons.

What we can do and what we cannot do with fMRI

Abstract: Functional magnetic resonance imaging (fMRI) is currently the mainstay of neuroimaging in cognitive neuroscience. Advances in scanner technology, image acquisition protocols, experimental design, and analysis methods promise to push forward fMRI from mere cartography to the true study of brain organization. However, fundamental questions concerning the interpretation of fMRI data abound, as the conclusions drawn often ignore the actual limitations of the methodology. Here I give an overview of the current state of fMRI, and draw on neuroimaging and physiological data to present the current understanding of the haemodynamic signals and the constraints they impose on neuroimaging data interpretation.

Treatment of Aspergillosis: Clinical Practice Guidelines of the Infectious Diseases Society of America

Abstract: Aspergillus species have emerged as an important cause of life-threatening infections in immunocompromised patients. This expanding population is composed of patients with prolonged neutropenia, advanced HIV infection, and inherited immunodeficiency and patients who have undergone allogeneic hematopoietic stem cell transplantation (HSCT) and/or lung transplantation. This document constitutes the guidelines of the Infectious Diseases Society of America for treatment of aspergillosis and replaces the practice guidelines for Aspergillus published in 2000 [1]. The objective of these guidelines is to summarize the current evidence for treatment of different forms of aspergillosis. The quality of evidence for treatment is scored according to a standard system used in other Infectious Diseases Society of America guidelines. This document reviews guidelines for management of the 3 major forms of aspergillosis: invasive aspergillosis, chronic (and saprophytic) forms of aspergillosis, and allergic forms of aspergillosis. Given the public health importance of invasive aspergillosis, emphasis is placed on the diagnosis, treatment, and prevention of the different forms of invasive aspergillosis, including invasive pulmonary aspergillosis, sinus aspergillosis, disseminated aspergillosis, and several types of single-organ invasive aspergillosis. There are few randomized trials on the treatment of invasive aspergillosis. The largest randomized controlled trial demonstrates that voriconazole is superior to deoxycholate amphotericin B (D-AMB) as primary treatment for invasive aspergillosis. Voriconazole is recommended for the primary treatment of invasive aspergillosis in most patients (A-I). Although invasive pulmonary aspergillosis accounts for the preponderance of cases treated with voriconazole, voriconazole has been used in enough cases of extrapulmonary and disseminated infection to allow one to infer that voriconazole is effective in these cases. A randomized trial comparing 2 doses of liposomal amphotericin B (L-AMB) showed similar efficacy in both arms, suggesting that liposomal therapy could be considered as alternative primary therapy in some patients (A-I). For salvage therapy, agents include lipid formulations of amphotericin (LFAB; A-II), posaconazole (B-II), itraconazole (B-II), caspofungin (B-II), or micafungin (B-II). Salvage therapy for invasive aspergillosis poses important challenges with significant gaps in knowledge. In patients whose aspergillosis is refractory to voriconazole, a paucity of data exist to guide management. Therapeutic options include a change of class using an amphotericin B (AMB) formulation or an echinocandin, such as caspofungin (B-II); further use of azoles should take into account host factors and pharmacokinetic considerations. Refractory infection may respond to a change to another drug class (B-II) or to a combination of agents (B-II). The role of combination therapy in the treatment of invasive aspergillosis as primary or salvage therapy is uncertain and warrants a prospective, controlled clinical trial. Assessment of patients with refractory aspergillosis may be difficult. In evaluating such patients, the diagnosis of invasive aspergillosis should be established if it was previously uncertain and should be confirmed if it was previously known. The drug dosage should be considered. Management options include a change to intravenous (IV) therapy, therapeutic monitoring of drug levels, change of drug class, and/or combination therapy. Antifungal prophylaxis with posaconazole can be recommended in the subgroup of HSCT recipients with graft-versus-host disease (GVHD) who are at high risk for invasive aspergillosis and in neutropenic patients with acute myelogenous leukemia or myelodysplastic syndrome who are at high risk for invasive aspergillosis (A-I). Management of breakthrough invasive aspergillosis in the context of mould-active azole prophylaxis is not defined by clinical trial data. The approach to such patients should be individualized on the basis of clinical criteria, including host immunosuppression, underlying disease, and site of infection, as well as consideration of antifungal dosing, therapeutic monitoring of drug levels, a switch to IV therapy, and/or a switch to another drug class (B-III). Certain conditions of invasive aspergillosis warrant consideration for surgical resection of the infected focus. These include but are not limited to pulmonary lesions contiguous with the heart or great vessels, invasion of the chest wall, osteomyelitis, pericardial infection, and endocarditis (B-III). Restoration of impaired host defenses is critical for improved outcome of invasive aspergillosis (A-III). Recovery from neutropenia in a persistently neutropenic host or reduction of corticosteroids in a patient receiving high-dose glucocorticosteroids is paramount for improved outcome in invasive aspergillosis. A special consideration is made concerning recommendations for therapy of aspergillosis in uncommon sites, such as osteomyelitis and endocarditis. There are very limited data on these infections, and most involve D-AMB as primary therapy simply because of its long-standing availability. Based on the strength of the randomized study, the panel recommends voriconazole for primary treatment of these very uncommon manifestations of invasive aspergillosis (B-III). Management of the chronic or saprophytic forms of aspergillosis varies depending on the condition. Single pulmonary aspergillomas may be best managed by surgical resection (B-III), whereas chronic cavitary and chronic necrotizing pulmonary aspergillosis require long-term medical therapy (B-III). The management of allergic forms of aspergillosis involves a combination of medical and anti-inflammatory therapy. For example, management of allergic bronchopulmonary aspergillosis (ABPA) involves the administration of itraconazole and corticosteroids (A-I). © 2008 by the Infectious Diseases Society of America. All rights reserved.

Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study.

Abstract: Carbon nanotubes have distinctive characteristics, but their needle-like fibre shape has been compared to asbestos, raising concerns that widespread use of carbon nanotubes may lead to mesothelioma, cancer of the lining of the lungs caused by exposure to asbestos. Here we show that exposing the mesothelial lining of the body cavity of mice, as a surrogate for the mesothelial lining of the chest cavity, to long multiwalled carbon nanotubes results in asbestos-like, length-dependent, pathogenic behaviour. This includes inflammation and the formation of lesions known as granulomas. This is of considerable importance, because research and business communities continue to invest heavily in carbon nanotubes for a wide range of products under the assumption that they are no more hazardous than graphite. Our results suggest the need for further research and great caution before introducing such products into the market if long-term harm is to be avoided.

Chaotic Dirac billiard in graphene quantum dots.

Abstract: The exceptional electronic properties of graphene, with its charge carriers mimicking relativistic quantum particles and its formidable potential in various applications, have ensured a rapid growth of interest in this new material. We report on electron transport in quantum dot devices carved entirely from graphene. At large sizes (>100 nanometers), they behave as conventional single-electron transistors, exhibiting periodic Coulomb blockade peaks. For quantum dots smaller than 100 nanometers, the peaks become strongly nonperiodic, indicating a major contribution of quantum confinement. Random peak spacing and its statistics are well described by the theory of chaotic neutrino billiards. Short constrictions of only a few nanometers in width remain conductive and reveal a confinement gap of up to 0.5 electron volt, demonstrating the possibility of molecular-scale electronics based on graphene.

Herwig++ Physics and Manual

Abstract: In this paper we describe Herwig++ version 2.3, a general-purpose Monte Carlo event generator for the simulation of hard lepton-lepton, lepton-hadron and hadron-hadron collisions. A number of important hard scattering processes are available, together with an interface via the Les Houches Accord to specialized matrix element generators for additional processes. The simulation of Beyond the Standard Model (BSM) physics includes a range of models and allows new models to be added by encoding the Feynman rules of the model. The parton-shower approach is used to simulate initial- and final-state QCD radiation, including colour coherence effects, with special emphasis on the correct description of radiation from heavy particles. The underlying event is simulated using an eikonal multiple parton-parton scattering model. The formation of hadrons from the quarks and gluons produced in the parton shower is described using the cluster hadronization model. Hadron decays are simulated using matrix elements, where possible including spin correlations and off-shell effects. Comment: 153 pages, program and additional information available from http://projects.hepforge.org/herwig . Updated description to Herwig++ version 2.3 and added one author

Graphene-based liquid crystal device.

Abstract: Graphene is only one atom thick, optically transparent, chemically inert, and an excellent conductor. These properties seem to make this material an excellent candidate for applications in various photonic devices that require conducting but transparent thin films. In this letter, we demonstrate liquid crystal devices with electrodes made of graphene that show excellent performance with a high contrast ratio. We also discuss the advantages of graphene compared to conventionally used metal oxides in terms of low resistivity, high transparency and chemical stability.

Global production networks: realizing the potential

Abstract: Understanding and conceptualizing the complexities of the contemporary global economy is a challenging but vitally important task. In this article, we critically evaluate the potential of one interpretive framework—the global production networks (GPN) perspective—for analysing the global economy and its impacts on territorial development. After situating the approach in relation to other cognate chain/network approaches, the article proceeds to review and evaluate a number of underdeveloped areas that need to be understood and incorporated more fully if the framework is to deliver on its early potential. The article concludes with a consideration of the key research issues facing work in this area.

Evaluating the successful implementation of evidence into practice using the PARIHS framework: theoretical and practical challenges

Abstract: The PARiHS framework (Promoting Action on Research Implementation in Health Services) has proved to be a useful practical and conceptual heuristic for many researchers and practitioners in framing their research or knowledge translation endeavours. However, as a conceptual framework it still remains untested and therefore its contribution to the overall development and testing of theory in the field of implementation science is largely unquantified. This being the case, the paper provides an integrated summary of our conceptual and theoretical thinking so far and introduces a typology (derived from social policy analysis) used to distinguish between the terms conceptual framework, theory and model – important definitional and conceptual issues in trying to refine theoretical and methodological approaches to knowledge translation. Secondly, the paper describes the next phase of our work, in particular concentrating on the conceptual thinking and mapping that has led to the generation of the hypothesis that the PARiHS framework is best utilised as a two-stage process: as a preliminary (diagnostic and evaluative) measure of the elements and sub-elements of evidence (E) and context (C), and then using the aggregated data from these measures to determine the most appropriate facilitation method. The exact nature of the intervention is thus determined by the specific actors in the specific context at a specific time and place. In the process of refining this next phase of our work, we have had to consider the wider issues around the use of theories to inform and shape our research activity; the ongoing challenges of developing robust and sensitive measures; facilitation as an intervention for getting research into practice; and finally to note how the current debates around evidence into practice are adopting wider notions that fit innovations more generally. The paper concludes by suggesting that the future direction of the work on the PARiHS framework is to develop a two-stage diagnostic and evaluative approach, where the intervention is shaped and moulded by the information gathered about the specific situation and from participating stakeholders. In order to expedite the generation of new evidence and testing of emerging theories, we suggest the formation of an international research implementation science collaborative that can systematically collect and analyse experiences of using and testing the PARiHS framework and similar conceptual and theoretical approaches. We also recommend further refinement of the definitions around conceptual framework, theory, and model, suggesting a wider discussion that embraces multiple epistemological and ontological perspectives.

Criteria for Annotation of Plant MicroRNAs

Abstract: MicroRNAs (miRNAs) are ∼21 nucleotide noncoding RNAs produced by Dicer-catalyzed excision from stem-loop precursors. Many plant miRNAs play critical roles in development, nutrient homeostasis, abiotic stress responses, and pathogen responses via interactions with specific target mRNAs. miRNAs are not the only Dicer-derived small RNAs produced by plants: A substantial amount of the total small RNA abundance and an overwhelming amount of small RNA sequence diversity is contributed by distinct classes of 21- to 24-nucleotide short interfering RNAs. This fact, coupled with the rapidly increasing rate of plant small RNA discovery, demands an increased rigor in miRNA annotations. Herein, we update the specific criteria required for the annotation of plant miRNAs, including experimental and computational data, as well as refinements to standard nomenclature.

The minimum information about a genome sequence (MIGS) specification.

Abstract: With the quantity of genomic data increasing at an exponential rate, it is imperative that these data be captured electronically, in a standard format. Standardization activities must proceed within the auspices of open-access and international working bodies. To tackle the issues surrounding the development of better descriptions of genomic investigations, we have formed the Genomic Standards Consortium (GSC). Here, we introduce the minimum information about a genome sequence (MIGS) specification with the intent of promoting participation in its development and discussing the resources that will be required to develop improved mechanisms of metadata capture and exchange. As part of its wider goals, the GSC also supports improving the 'transparency' of the information contained in existing genomic databases.

Metacognitive Therapy for Anxiety and Depression

Abstract: Theory and Nature of Metacognitive Therapy. Assessment. Foundation Metacognitive Therapy Skills. Attention Training Techniques. Detached Mindfulness Techniques. Generalized Anxiety Disorder. Posttraumatic Stress Disorder. Obsessive-Compulsive Disorder. Major Depressive Disorder. The Evidence for Metacognitive Theory and Therapy. Concluding Thoughts. Appendices. Metacognitions Questionnaire 30 (MCQ-30). Meta-Worry Questionnaire (MWQ). Thought Fusion Instrument (TFI). Attention Training Technique Summary Sheet. Self-attention Rating Scale. CAS-1. Generalized Anxiety Disorder Scale - Revised (GADS-R). Posttraumatic Stress Disorder Scale (PTSD-S). Obsessive-Compulsive Disorder Scale (OCD-S). Major Depressive Disorder Scale (MDD-S). GAD Case Formulation Interview. PTSD Case Formulation Interview. OCD Case Formulation Interview. Depression Case Formulation Interview. GAD Treatment Plan. PTSD Treatment Plan. OCD Treatment Plan. Depression Treatment Plan. New Plan Summary Sheet.

Molecular doping of graphene

Abstract: Graphene is considered as one of the most promising materials for post silicon electronics, as it combines high electron mobility with atomic thickness [Novoselov et al. Science 2004, 306, 666−669. Novoselov et al. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 10451−10453]. The possibility of chemical doping and related excellent chemical sensor properties of graphene have been demonstrated experimentally [Schedin et al. Nat. Mater. 2007, 6, 652−655], but a microscopic understanding of these effects has been lacking, so far. In this letter, we present the first joint experimental and theoretical investigation of adsorbate-induced doping of graphene. A general relation between the doping strength and whether adsorbates are open- or closed-shell systems is demonstrated with the NO2 system: The single, open shell NO2 molecule is found to be a strong acceptor, whereas its closed shell dimer N2O4 causes only weak doping. This effect is pronounced by graphene's peculiar density of states (DOS), which provides an id...

Investigation, treatment and monitoring of late-onset hypogonadism in males: ISA, ISSAM, EAU, EAA and ASA recommendations

Abstract: Demographic data clearly demonstrate that the percentage of the population in the older age group is increasing. Androgen deficiency in the aging male has become a topic of increasing interest and debate throughout the world. Cross-sectional and longitudinal data indicate that the testosterone falls progressively with age and that a significant percentage of men over the age of 60 years have serum testosterone levels that are below the lower limits of young adult (age 20–30 years) men (1–4). The principal questions raised by these observations are whether older hypogonadal men will benefit from testosterone treatment and what will be the risks associated with such intervention. The past decade has brought evidence of benefit of androgen treatment of hypogonadal men on multiple target organs and the recent studies show short-term beneficial effects of testosterone in older men that are similar to those in younger men. This has been comprehensively reviewed and summarized by the Institute of Medicine in ‘Testosterone and Aging: Clinical Research Directions’ (5). Long-term data on the effects of testosterone treatment in the older population are limited mainly to effects on body composition and bone mass (6–11). Key questions of the effects of testosterone on patient reported outcomes and functional benefits that may retard physical or mental frailty of the elderly or improve the quality of life are not yet available. Specific risk data on the prostate and cardiovascular systems are needed.

Qualitative Research and Translation Dilemmas

Abstract: The focus of this article is an examination of translation dilemmas in qualitative research. Specifically it explores three questions: whether methodologically it matters if the act of translation ...

Neoliberalising nature: The logics of deregulation and reregulation

Abstract: This and a companion paper examine a new and fast-growing geographical research literature about neoliberal approaches to governing human interactions with the physical environment. This literature, authored by critical geographers for the most part, is largely case study based and focuses on a range of biophysical phenomena in different parts of the contemporary world. In an attempt to take stock of what has been learnt and what is left to do, the two papers survey the literature theoretically and empirically, cognitively and normatively. They are written for the benefit of readers trying to make some sense of this growing literature and for future researchers of the topic. Specifically, they aim to parse the critical studies of nature's neoliberalisation with a view to answering four key questions posed, variously, in many or most of them: what are the main reasons why all manner of qualitatively different nonhuman phenomena in different parts of the world are being ‘neoliberalised’? what are the princi...

Dark matter halo concentrations in the Wilkinson Microwave Anisotropy Probe year 5 cosmology

Abstract: We use a combination of three large N-body simulations to investigate the dependence of dark matter halo concentrations on halo mass and redshift in the Wilkinson Microwave Anisotropy Probe year 5 (WMAP5) cosmology. The median relation between concentration and mass is adequately described by a power law for halo masses in the range 1011–1015 h−1 M⊙ and redshifts z < 2, regardless of whether the halo density profiles are fitted using Navarro, Frenk & White or Einasto profiles. Compared with recent analyses of the Millennium Simulation, which uses a value of σ8 that is higher than allowed by WMAP5, z= 0 halo concentrations are reduced by factors ranging from 23 per cent at 1011 h−1 M⊙ to 16 per cent at 1014 h−1 M⊙. The predicted concentrations are much lower than inferred from X-ray observations of groups and clusters.

Fmoc-diphenylalanine self assembles to a hydrogel via a novel architecture based on π–π interlocked β-sheets

Abstract: The self assembly of peptide hydrogelators that carry aromatic substituents can be modeled by a novel nanocylindrical architecture. The proposed model suggests that the nanocylinders are formed by anti-parallel β-sheets interlocked by the π-stacking interactions of fluorenyl groups and phenyl rings. This explanation is consistent with the structures observed in TEM and the data obtained by a variety of spectroscopic techniques.

The Authentic Personality: A Theoretical and Empirical Conceptualization and the Development of the Authenticity Scale

Abstract: This article describes the development of a measure of dispositional authenticity and tests whether authenticity is related to well-being, as predicted by several counseling psychology perspectives. Scales were designed to measure a tripartite conception of authenticity, comprising self-alienation, authentic living, and accepting external influence, which was supported with exploratory factor analysis. Multi-group confirmatory factor analysis showed that the factor loadings were invariant across sample, ethnicity, and gender. The scale showed substantial discriminant validity from the Big Five personality traits, nonsignificant correlations with social desirability, and 2- and 4-week test-retest correlations ranging from r = .78 to .91. Each subscale was strongly related to self-esteem and aspects of both subjective and psychological well-being. This article provides the first direct test of several theoretical models that view authenticity as integral to well-being.

Secretion of Flavins by Shewanella Species and Their Role in Extracellular Electron Transfer

Abstract: Fe(III)-respiring bacteria such as Shewanella species play an important role in the global cycle of iron, manganese, and trace metals and are useful for many biotechnological applications, including microbial fuel cells and the bioremediation of waters and sediments contaminated with organics, metals, and radionuclides. Several alternative electron transfer pathways have been postulated for the reduction of insoluble extracellular subsurface minerals, such as Fe(III) oxides, by Shewanella species. One such potential mechanism involves the secretion of an electron shuttle. Here we identify for the first time flavin mononucleotide (FMN) and riboflavin as the extracellular electron shuttles produced by a range of Shewanella species. FMN secretion was strongly correlated with growth and exceeded riboflavin secretion, which was not exclusively growth associated but was maximal in the stationary phase of batch cultures. Flavin adenine dinucleotide was the predominant intracellular flavin but was not released by live cells. The flavin yields were similar under both aerobic and anaerobic conditions, with total flavin concentrations of 2.9 and 2.1 μmol per gram of cellular protein, respectively, after 24 h and were similar under dissimilatory Fe(III)-reducing conditions and when fumarate was supplied as the sole electron acceptor. The flavins were shown to act as electron shuttles and to promote anoxic growth coupled to the accelerated reduction of poorly crystalline Fe(III) oxides. The implications of flavin secretion by Shewanella cells living at redox boundaries, where these mineral phases can be significant electron acceptors for growth, are discussed.

Hypothalamic-pituitary-testicular axis disruptions in older men are differentially linked to age and modifiable risk factors: the European Male Aging Study.

Abstract: Context: The cause of declining testosterone (T) in aging men and their relationships with risk factors are unclear. Objective: The objective of the study was to investigate the relationships between lifestyle and health with reproductive hormones in aging men. Design: This was a baseline cross-sectional survey on 3200 community-dwelling men aged 40–79 yr from a prospective cohort study in eight European countries. Results: Four predictors were associated with distinct modes of altered function: 1) age: lower free T (FT; −3.12 pmol/liter·yr, P < 0.001) with raised LH, suggesting impaired testicular function; 2) obesity: lower total T (TT; −2.32 nmol/liter) and FT (−17.60 pmol/liter) for body mass index (BMI; ≥ 25 to < 30 kg/m2) and lower TT (−5.09 nmol/liter) and FT (−53.72 pmol/liter) for BMI 30 kg/m2 or greater (P < 0.001–0.01, referent: BMI < 25 kg/m2) with unchanged/decreased LH, indicating hypothalamus/pituitary dysfunction; 3) comorbidity: lower TT (−0.80 nmol/liter, P < 0.01) with unchanged LH in y...