Biogeochemical modelling of dissolved oxygen in a changing ocean

Secular decreases in dissolved oxygen concentration have been observed within the tropical oxygen minimum zones (OMZs) and at mid- to high latitudes over the last approximately 50 years. Earth system model projections indicate that a reduction in the oxygen inventory of the global ocean, termed ocean deoxygenation, is a likely consequence of on-going anthropogenic warming. Current models are, however, unable to consistently reproduce the observed trends and variability of recent decades, particularly within the established tropical OMZs. Here, we conduct a series of targeted hindcast model simulations using a state-of-the-art global ocean biogeochemistry model in order to explore and review biases in model distributions of oceanic oxygen. We show that the largest magnitude of uncertainty is entrained into ocean oxygen response patterns due to model parametrization of pCO2-sensitive C : N ratios in carbon fixation and imposed atmospheric forcing data. Inclusion of a pCO2-sensitive C : N ratio drives historical oxygen depletion within the ocean interior due to increased organic carbon export and subsequent remineralization. Atmospheric forcing is shown to influence simulated interannual variability in ocean oxygen, particularly due to differences in imposed variability of wind stress and heat fluxes

Prototype of a bistable polariton field-effect transistor switch

This work has been supported by the State of Bavaria.Microcavity exciton polaritons are promising candidates to build a new generation of highly nonlinear and integrated optoelectronic devices. Such devices range from novel coherent light emitters to reconfigurable potential landscapes for electrooptical polariton-lattice based quantum simulators as well as building blocks of optical logic architectures. Especially for the latter, the strongly interacting nature of the light-matter hybrid particles has been used to facilitate fast and efficient switching of light by light, something which is very hard to achieve with weakly interacting photons. We demonstrate here that polariton transistor switches can be fully integrated in electro-optical schemes by implementing a one-dimensional polariton channel which is operated by an electrical gate rather than by a control laser beam. The operation of the device, which is the polariton equivalent to a field-effect transistor, relies on combining electro-optical potential landscape engineering with local exciton ionization to control the scattering dynamics underneath the gate. We furthermore demonstrate that our device has a region of negative differential resistance and features a completely new way to create bistable behavior.Publisher PDFPeer reviewe

Runaway Events Dominate the Heavy Tail of Citation Distributions

Statistical distributions with heavy tails are ubiquitous in natural and social phenomena. Since the entries in heavy tail have disproportional significance, the knowledge of its exact shape is very important. Citations of scientific papers form one of the best-known heavy tail distributions. Even in this case there is a considerable debate whether citation distribution follows the log-normal or power-law fit. The goal of our study is to solve this debate by measuring citation distribution for a very large and homogeneous data. We measured citation distribution for 418,438 Physics papers published in 1980-1989 and cited by 2008. While the log-normal fit deviates too strong from the data, the discrete power-law function with the exponent $\gamma=3.15$ does better and fits 99.955% of the data. However, the extreme tail of the distribution deviates upward even from the power-law fit and exhibits a dramatic "runaway" behavior. The onset of the runaway regime is revealed macroscopically as the paper garners 1000-1500 citations, however the microscopic measurements of autocorrelation in citation rates are able to predict this behavior in advance.Comment: 6 pages, 5 Figure

Thermoelectric Response of an Interacting Two-Dimensional Electron Gas in Quantizing Magnetic Field

We present a discussion of the linear thermoelectric response of an interacting electron gas in a quantizing magnetic field. Boundary currents can carry a significant fraction of the net current passing through the system. We derive general expressions for the bulk and boundary components of the number and energy currents. We show that the local current density may be described in terms of ``transport'' and ``internal magnetization'' contributions. The latter carry no net current and are not observable in standard transport experiments. We show that although Onsager relations cannot be applied to the local current, they are valid for the transport currents and hence for the currents observed in standard transport experiments. We relate three of the four thermoelectric response coefficients of a disorder-free interacting two-dimensional electron gas to equilibrium thermodynamic quantities. In particular, we show that the diffusion thermopower is proportional to the entropy per particle, and we compare this result with recent experimental observations.Comment: 18 pages, 2 postscript figures included. Revtex with epsf.tex and multicol.sty. In the revised version, the comparison with experimental observations at $\nu=1/2, 3/2$ is extended to include the possibility of corrections due to weak impurity scattering. The conclusions that we reach regarding the applicability of the composite fermion model at these filling fractions are not affecte

Holistic services for people with advanced disease and chronic or refractory breathlessness: a mixed-methods evidence synthesis

Background : Breathlessness is a common and distressing symptom of many advanced diseases, affecting around 2 million people in the UK. Breathlessness increases with disease progression and often becomes chronic or refractory. Breathlessness-triggered services that integrate holistic assessment and specialist palliative care input as part of a multiprofessional approach have been developed for this group, offering tailored interventions to support self-management and reduce distress. Objectives : The aim was to synthesise evidence on holistic breathlessness services for people with advanced disease and chronic or refractory breathlessness. The objectives were to describe the structure, organisation and delivery of services, determine clinical effectiveness, cost-effectiveness and acceptability, identify predictors of treatment response, and elicit stakeholders’ evidence-based priorities for clinical practice, policy and research. Design : The mixed-methods evidence synthesis comprised three components: (1) a systematic review to determine the clinical effectiveness, cost-effectiveness and acceptability of holistic breathlessness services; (2) a secondary analysis of pooled individual data from three trials to determine predictors of clinical response; and (3) a transparent expert consultation (TEC), comprising a stakeholder workshop and an online consensus survey, to identify stakeholders’ priorities. Results : Thirty-seven papers reporting on 18 holistic breathlessness services were included in the systematic review. Most studies enrolled people with thoracic cancer, were delivered over 4–6 weeks, and included breathing training, relaxation techniques and psychological support. Meta-analysis demonstrated significant reductions in the Numeric Rating Scale (NRS) distress due to breathlessness, significant reductions in the Hospital Anxiety and Depressions Scale (HADS) depression scores, and non-significant reductions in the Chronic Respiratory Disease Questionnaire (CRQ) mastery and HADS anxiety, favouring the intervention. Recipients valued education, self-management interventions, and expertise of the staff in breathlessness and person-centred care. Evidence for cost-effectiveness was limited and inconclusive. The responder analysis (n = 259) revealed baseline CRQ mastery and NRS distress to be strong predictors of the response to breathlessness services assessed by these same measures, and no significant influence from baseline breathlessness intensity, patient diagnosis, lung function, health status, anxiety or depression. The TEC elicited 34 priorities from stakeholders. Seven priorities received high agreement and consensus, reflecting stakeholders’ (n = 74) views that services should be person-centred and multiprofessional, share their breathlessness management skills with others, and recognise the roles and support needs of informal carers.  Limitations : The evidence synthesis draws predominantly from UK services and may not be generalisable to other settings. Some meta-analyses were restricted by reporting biases and statistical heterogeneity.  Conclusions : Despite heterogeneity in composition and delivery, holistic breathlessness services are highly valued by recipients and can lead to significant improvements in the distress caused by breathlessness and depression. Outcomes of improved mastery and reduced distress caused by breathlessness are not influenced by patient diagnosis, lung function or health status. Stakeholders highlighted the need for improved access to person-centred, multi professional breathlessness services and support for informal carers.  Future work : Our research suggests that key therapeutic components of holistic breathlessness services be considered in clinical practice and models of delivery and educational strategies to address stakeholders’ priorities tested

Synthesis of 4-methyl-5-arylpyrimidines and 4-arylpyrimidines: route speci®c markers for the Leuckardt preparation of amphetamine, 4-methoxyamphetamine, and 4-methylthioamphetamine

Abstract General synthetic routes to 4-methyl-5-arylpyrimidines and 5-arylpyrimidines are described. 4-Benzylpyrimidine, 4-methyl-5-phenylpyrimidine, 4-(4-methoxybenzyl)pyrimidine, and 4-methyl-5-(4-methoxyphenyl)pyrimidine have been positively identi®ed as route-speci®c by-products in the Leuckardt preparations of amphetamine and 4-methoxyamphetamine. Using headspace solid phase microextraction (SPME) 4-(4-methoxybenzyl)pyrimidine and 4-methyl-5-(4-methoxyphenyl)pyrimidine have been identi®ed in illicit tablets containing 4-methoxyamphetamine. This is an indication that illicit laboratories use the Leuckardt method for the preparation of 4-methoxyamphetamine. Flatliner tablets containing 4-methylthioamphetamine have been screened for the presence of 4-(4-methylthiobenzyl)pyrimidine and 4-methyl-5-(4-methylthiophenyl)pyrimidine using both headspace and aqueous phase SPME. As these pyrimidines were not detected it would appear likely that illicit laboratories are not using the Leuckardt method for the preparation of 4-methylthioamphetamine.

Towards a Phenomenology of Grief : insights from Merleau-Ponty

This paper shows how phenomenological research can enhance our understanding of what it is to experience grief. I focus specifically on themes in the work of Maurice Merleau-Ponty, in order to develop an account that emphasizes two importantly different ways of experiencing indeterminacy. This casts light on features of grief that are disorienting and difficult to describe, while also making explicit an aspect of experience upon which the possibility of phenomenological inquiry itself depends

A Small Conductance Calcium-Activated K⁺ Channel in C. elegans, KCNL-2, Plays a Role in the Regulation of the Rate of Egg-Laying

In the nervous system of mice, small conductance calcium-activated potassium (SK) channels function to regulate neuronal excitability through the generation of a component of the medium afterhyperpolarization that follows action potentials. In humans, irregular action potential firing frequency underlies diseases such as ataxia, epilepsy, schizophrenia and Parkinson's disease. Due to the complexity of studying protein function in the mammalian nervous system, we sought to characterize an SK channel homologue, KCNL-2, in C. elegans, a genetically tractable system in which the lineage of individual neurons was mapped from their early developmental stages. Sequence analysis of the KCNL-2 protein reveals that the six transmembrane domains, the potassium-selective pore and the calmodulin binding domain are highly conserved with the mammalian homologues. We used widefield and confocal fluorescent imaging to show that a fusion construct of KCNL-2 with GFP in transgenic lines is expressed in the nervous system of C. elegans. We also show that a KCNL-2 null strain, kcnl-2(tm1885), demonstrates a mild egg-laying defective phenotype, a phenotype that is rescued in a KCNL-2-dependent manner. Conversely, we show that transgenic lines that overexpress KCNL-2 demonstrate a hyperactive egg-laying phenotype. In this study, we show that the vulva of transgenic hermaphrodites is highly innervated by neuronal processes and by the VC4 and VC5 neurons that express GFP-tagged KCNL-2. We propose that KCNL-2 functions in the nervous system of C. elegans to regulate the rate of egg-laying. © 2013 Chotoo et al