The Cohen Macaulay property for noncommutative rings

Let R be a noetherian ring which is a finite module over its centre Z(R). This paper studies the consequences for R of the hypothesis that it is a maximal Cohen Macaulay Z(R)-module. Old results are reviewed and a number of new results are proved. The additional hypothesis of homological grade symmetry is proposed as the appropriate extra lever needed to extend the classical commutative homological hierarchy to this setting, and results are given offering evidence in support of this proposal.Comment: Preliminary version; comments welcom

Radio-frequency reflectometry on an undoped AlGaAs/GaAs single electron transistor

Radio frequency reflectometry is demonstrated in a sub-micron undoped AlGaAs/GaAs device. Undoped single electron transistors (SETs) are attractive candidates to study single electron phenomena due to their charge stability and robust electronic properties after thermal cycling. However these devices require a large top-gate which is unsuitable for the fast and sensitive radio frequency reflectometry technique. Here we demonstrate rf reflectometry is possible in an undoped SET.Comment: Four pages, three figures, one supplementary fil

Mechanisms to improve integrative research at the science-policy interface for sustainable catchment management

Greater integration between researchers and policy makers is required to provide an evidence base that is transparent, integrated, and adaptive to support the complexities of sustainable catchment management. Opening-up and closing-down mechanisms are equally important in creating and establishing such an evidence base. We provide examples of both types based on our recent research and knowledge-transfer activities at the science-policy interface. Through our coordination role for the United Kingdom government we provide opening up physical and virtual forums for researchers and government science and policy staff to learn about and assess the gaps and uncertainties of the evidence base. Closing-down mechanisms are vital to policy cycles, in that they distil what is known and what is unknown. The Diffuse Pollution User Manual provides a valuable tool for policy and catchment management staff to assess the potential effectiveness of different combinations of remedial diffuse-pollution mitigation methods. It is vital that that opening-up and closing-down mechanisms are iteratively linked given the complexity and uncertainty of the science and policy cycles. Advances in integrative research at the science-policy interface are vital if there is to be a move to more deliberative policy making

The effect of estrogen on intracellular Ca2+ and Na+ regulation in heart failure

Background: Under-representation of women in heart failure (HF) trials and contradictory findings of estrogen supplementation highlight the need to investigate the involvement of estrogen in the progression of heart failure. Objectives: To characterize the influence of estrogen on cardiac function during the onset of heart failure in a controlled animal model that lacks traditional comorbidities. Methods: HF was induced by aortic constriction (AC) in female guinea pigs. Selected AC animals were ovariectomized (ACOV) and a group of these received 17β-estradiol (ACOV+E) supplementation. 150 days post-AC surgery, left ventricular myocytes were isolated and their electrophysiology and Ca2+ and Na+ regulation examined. Results: ACOV animals heart weight/body weight ratios increased by 11% and in vivo fractional shortening decreased by 14% compared with the AC group, suggesting greater impairment of cardiac function in the absence of estrogen. Action potential duration increased in all three HF groups, the extent of the changes being estrogen-dependent. Myocytes from ACOV animals had reduced Ca2+ transient amplitudes, slower transient decay kinetics, decreased SR Ca2+ contents but increased Ca2+ spark frequencies and spark-mediated SR leak compared with the AC and ACOV+E groups. The Na+/K+ ATPase current densities and Na+ extrusion rates were reduced by 13% and 19%, respectively, in parallel with a 17% increase in INa,L current densities in the ACOV group compared with the AC group. Conclusions: Long-term absence of ovarian hormones exacerbates the decline in cardiac function during the progression to HF. Estrogen supplementation reverses these aggravating effects

GPER limits adverse changes to Ca2+ signalling and arrhythmogenic activity in ovariectomised guinea pig cardiomyocytes

Background: The increased risk of post-menopausal women developing abnormalities of heart function emphasises the requirement to understand the effect of declining oestrogen levels on cardiac electrophysiology and structure, and investigate possible therapeutic targets, namely the G protein-coupled oestrogen receptor 1 (GPER). Methods: Female guinea pigs underwent sham or ovariectomy (OVx) surgeries. Cardiomyocytes were isolated 150-days post-operatively. Membrane structure was assessed using di-8-ANEPPs staining and scanning ion conductance microscopy. Imunnohistochemistry (IHC) determined the localisation of oestrogen receptors. The effect of GPER activation on excitation-contraction coupling mechanisms were assessed using electrophysiological and fluorescence techniques. Downstream signalling proteins were investigated by western blot. Results: IHC staining confirmed the presence of nuclear oestrogen receptors and GPER, the latter prominently localised to the peri-nuclear region and having a clear striated pattern elsewhere in the cells. Following OVx, GPER expression increased and its activation reduced Ca2+ transient amplitude (by 40%) and sarcomere shortening (by 32%). In these cells, GPER activation reduced abnormal spontaneous Ca2+ activity, shortened action potential duration and limited drug-induced early after-depolarisation formation. Conclusion: In an animal species with comparable steroidogenesis and cardiac physiology to humans, we show the expression and localisation of all three oestrogen receptors in cardiac myocytes. We found that following oestrogen withdrawal, GPER expression increased and its activation limited arrhythmogenic behaviours in this low oestrogen state, indicating a potential cardioprotective role of this receptor in post-menopausal women

Sociomateriality: A Theoretical Framework for Studying Distributed Medical Education

Distributed medical education (DME) is a type of distance learning in which students participate in medical education from diverse geographic locations using Web conferencing, videoconferencing, e-learning, and similar tools. DME is becoming increasingly widespread in North America and around the world. Although relatively new to medical education, distance learning has a long history in the broader field of education and a related body of literature that speaks to the importance of engaging in rigorous and theoretically informed studies of distance learning. The existing DME literature is helpful, but it has been largely descriptive and lacks a critical "lens"-that is, a theoretical perspective from which to rigorously conceptualize and interrogate DME's social (relationships, people) and material (technologies, tools) aspects. The authors describe DME and theories about distance learning and show that such theories focus on social, pedagogical, and cognitive considerations without adequately taking into account material factors. They address this gap by proposing sociomateriality as a theoretical framework allowing researchers and educators to study DME and (1) understand and consider previously obscured actors, infrastructure, and other factors that, on the surface, seem unrelated and even unimportant; (2) see clearly how the social and material components of learning are intertwined in fluid, messy, and often uncertain ways; and (3) perhaps think differently, even in ways that disrupt traditional approaches, as they explore DME. The authors conclude that DME brings with it substantial investments of social and material resources, and therefore needs careful study, using approaches that embrace its complexity

Diesel exhaust-gas reforming for H2 addition to an aftertreatment unit

This is the post-print version of the final paper published in Chemical Engineering Journal. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2008 Elsevier B.V.The work described in this paper has been undertaken as part of the design of an integrated system comprising a diesel engine, an exhaust-gas fuel reformer and a NOx aftertreatment unit. The exhaust-gas reformer is used to provide hydrogen-rich reformate to the NOx aftertreatment unit, containing a hydrocarbon-SCR catalyst, in order to improve its NOx reduction activity at low exhaust-gas temperatures. The reformer configuration and operating parameters have been examined in order to optimise the performance of the hydrocarbon-SCR catalyst, which is promoted by the presence of H2 but inhibited by CO. The length of the catalyst bed inside the reformer is a key factor in determining the extent to which the water-gas shift reaction can contribute to the reforming process, and therefore strongly influences the proportions of CO and H2 in the reformate. However, it is also necessary for the reactant ratios at the reformer inlet to be controlled in response to changes in the engine operating conditions. In practice, this means that the rate of fuel addition to the reformer needs to be optimised for different exhaust gas compositions and space velocities

Methanol Masers as Tracers of Circumstellar Disks

We show that in many methanol maser sources the masers are located in lines, with a velocity gradient along them which suggests that the masers are situated in edge-on circumstellar, or protoplanetary, disks. We present VLBI observations of the methanol maser source G309.92+0.48, in the 12.2 GHz transition, which confirm previous observations that the masers in this source lie along a line. We show that such sources are not only linear in space but, in many cases, also have a linear velocity gradient. We then model these and other data in both the 6.7 GHz and the 12.2 GHz transition from a number of star formation regions, and show that the observed spatial and velocity distribution of methanol masers, and the derived Keplerian masses, are consistent with a circumstellar disk rotating around an OB star. We consider this and other hypotheses, and conclude that about half of these methanol masers are probably located in edge-on circumstellar disks around young stars. This is of particular significance for studies of circumstellar disks because of the detailed velocity information available from the masers.Comment: 38 pages, 13 figures accepted by Ap