Line

Review of Line: A group exhibition at the Lisson Gallery, London. 22 January - 12 March 2016. Curated by: Mary Doyle and Kate Macfarlane

Irreversibility Measures in a Quantum Setting

A satisfactory understanding of macroscopic irreversibility has remained elusive since the advent of thermodynamics. Progress has nevertheless been made in understanding irreversibility measures classically; this work explores irreversibility in a quantum setting. Entropy production quantifies the irreversibility associated with open stochastic dynamical systems, and our main aim has been to extend this concept. Understanding the thermodynamics of open quantum systems better will eventually improve the efficiency of increasingly feasible nanoscale operations. An exact method to model the thermodynamic properties of open quantum systems is the stochastic Liouville-von Neumann (SLN) equation, based on unravelling Feynman-Vernon influence functionals. We extend its use from the one heat bath case to a system in a non-equilibrium stationary state due to coupling to more than one heat bath. An asymmetry in the probabilistic specification of a closed deterministic system can lead to a disparity between the likelihoods of a particular forward and corresponding backward behaviour starting from a specified time. Such a comparison is a test of a property denoted obversibility, quantified in terms of dissipation production – rather than entropy production – as a measure of irreversibility. We evaluate dissipation production in a deterministic two-level quantum system described by a statistical ensemble of state vectors. We identify the conditions under which the dissipation production fulfills an Evans-Searles Fluctuation Theorem and for which the system will display time-asymmetric average behaviour as it evolves. Finally, we use a Kraus operator formalism to present a minimal model for the random evolution in the Bloch sphere of individual trajectory realisations of the coherence vector of a qubit and use it to evaluate the entropy production associated with weak quantum measurement, with both one and two measurement operators, before speculating on the consequences of our results to our understanding of quantum measurement and the associated indeterminism

Guiding the adolescent girl

This item was digitized by the Internet Archive. Thesis (M.A.)--Boston Universityhttps://archive.org/details/guidingadolescen00cla

Evaluating the Variability of Static Carbon Dioxide Storage Capacity Estimates through Integrated Analysis of Reservoir Structure, Aquifer Performance and Thermodynamic Behaviour: Case Studies from Three Depleted Triassic Gas Fields on the UK Continental Shelf

Evaluation of the variability of theoretical and effective CO2 storage capacity estimation within depleted gas reservoirs is dependent on the integrated analysis of reservoir structure, aquifer performance and thermodynamic behaviour. Four published theoretical CO2 storage capacity methods and one effective method have been used to estimate the capacity and variability of two Triassic depletion drive reservoirs and two Triassic water drive reservoirs located within the UK Southern North Sea and East Irish Sea Basin. Input parameters to the storage capacity equations have shown a degree of natural variability whereas others are more accurately constrained. As such, attempts have been made to more accurately constrain the most variable input parameters. The geometric, petrophysical and production characteristics of the reservoirs are analysed. Material balance methods are used to assess the reservoir drive mechanism of the reservoirs. If reservoirs are found to experience a water drive, the aquifer strength is estimated. The gas compressibility factor, gas formation volume factor and CO2 density is estimated under initial reservoir temperature conditions using six equations of state for comparison of results. These results are then input to storage capacity equations producing a range of estimates. The most susceptible parameter to variability was the cumulative volume of water influx to a reservoir, We. Variability was also found to be the result of error in estimation of the original gas in place. As such, the water drive reservoirs made further use of aquifer modelling to achieve more precise estimates of OGIP and We. The effective capacity coefficients for the various reservoirs have been estimated to assess the proportion of pore space available for CO2 storage. The effective CO2 storage capacity constitutes a fraction of the theoretical CO2 storage capacity which ranges between 0 (no storage possible) and 1 (all theoretically accessible pore volume is occupied by CO2). Overall, it was found that depletion drive reservoirs have the potential to store greater volumes of CO2 than water drive reservoirs whose aquifer waters occupy the newly liberated pore space

Selenium supplementation for the primary prevention of cardiovascular disease

Background: Selenium is a key component of a number of selenoproteins which protect against oxidative stress and have the potential to prevent chronic diseases including cardiovascular disease (CVD). However, observational studies have shown inconsistent associations between selenium intake and CVD risk; in addition, there is concern around a possible increased risk of type 2 diabetes with high selenium exposure. Objectives: To determine the effectiveness of selenium only supplementation for the primary prevention of CVD and examine the potential adverse effect of type 2 diabetes. Search methods: The following electronic databases were searched: the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 10 of 12, October 2012) on The Cochrane Library; MEDLINE (Ovid) (1946 to week 2 October 2012); EMBASE Classic + EMBASE (Ovid) (1947 to 2012 Week 42); CINAHL (EBSCO) (to 24 October 2012); ISI Web of Science (1970 to 24 October 2012); PsycINFO (Ovid) (1806 to week 3 October 2012); Database of Abstracts of Reviews of Effects (DARE), Health Technology Assessment Database and Health Economics Evaluations Database (Issue 4 of 4, October 2012) on The Cochrane Library. Trial registers and reference lists of reviews and articles were searched and experts in the field were approached. No language restrictions were applied. Selection criteria: Randomised controlled trials on the effects of selenium only supplementation on major CVD end-points, mortality, changes in CVD risk factors, and type 2 diabetes were included both in adults of all ages from the general population and in those at high risk of CVD. Trials were only considered where the comparison group was placebo or no intervention. Only studies with at least three months follow-up were included in the meta-analyses, shorter term studies were dealt with descriptively. Data collection and analysis: Two review authors independently assessed trial quality and extracted data. Study authors were contacted for additional information. Main results: Twelve trials (seven with duration of at least three months) met the inclusion criteria, with 19,715 participants randomised. The two largest trials that were conducted in the USA (SELECT and NPC) reported clinical events. There were no statistically significant effects of selenium supplementation on all cause mortality (RR 0.97, 95% CI 0.88 to 1.08), CVD mortality (RR 0.97, 95% CI 0.79 to 1.2), non-fatal CVD events (RR 0.96, 95% CI 0.89 to 1.04) or all CVD events (fatal and non-fatal) (RR 1.03, 95% CI 0.95 to 1.11). There was a small increased risk of type 2 diabetes with selenium supplementation but this did not reach statistical significance (RR 1.06, 95% CI 0.97 to 1.15). Other adverse effects that increased with selenium supplementation, as reported in the SELECT trial, included alopecia (RR 1.28, 95% CI 1.01 to 1.62) and dermatitis grade 1 to 2 (RR 1.17, 95% CI 1.0 to 1.35). Selenium supplementation reduced total cholesterol but this did not reach statistical significance (WMD - 0.11 mmol/L, 95% CI - 0.3 to 0.07). Mean high density lipoprotein (HDL) levels were unchanged. There was a statistically significant reduction in non-HDL cholesterol (WMD - 0.2 mmol/ L, 95% CI - 0.41 to 0.00) in one trial of varying selenium dosage. None of the longer term trials examined effects on blood pressure. Overall, the included studies were regarded as at low risk of bias. Authors’ conclusions: The limited trial evidence that is available to date does not support the use of selenium supplements in the primary prevention of CVD

Green and black tea for the primary prevention of cardiovascular disease

Background: There is increasing evidence that both green and black tea are beneficial for cardiovascular disease (CVD) prevention. Objectives: To determine the effects of green and black tea on the primary prevention of CVD. Search methods: We searched the following databases on 12 October 2012 without language restrictions: CENTRAL in The Cochrane Library, MEDLINE (OVID), EMBASE (OVID) and Web of Science (Thomson Reuters). We also searched trial registers, screened reference lists and contacted authors for additional information where necessary. Selection criteria: Randomised controlled trials (RCTs) lasting at least three months involving healthy adults or those at high risk of CVD. Trials investigated the intake of green tea, black tea or tea extracts. The comparison group was no intervention, placebo or minimal intervention. The outcomes of interest were CVD clinical events and major CVD risk factors. Any trials involving multifactorial lifestyle interventions or focusing on weight loss were excluded to avoid confounding. Data collection and analysis: Two review authors independently selected trials for inclusion, abstracted data and assessed the risk of bias. Trials of green tea were analysed separately from trials of black tea. Main results: We identified 11 RCTs with a total of 821 participants, two trials awaiting classification and one ongoing trial. Seven trials examined a green tea intervention and four examined a black tea intervention. Dosage and form of both green and black tea differed between trials. The ongoing trial is examining the effects of green tea powder capsules. No studies reported cardiovascular events. Black tea was found to produce statistically significant reductions in low-density lipoprotein (LDL) cholesterol (mean difference (MD) -0.43 mmol/L, 95% confidence interval (CI) -0.56 to -0.31) and blood pressure (systolic blood pressure (SBP): MD -1.85 mmHg, 95% CI -3.21 to -0.48. Diastolic blood pressure (DBP): MD -1.27 mmHg, 95% CI -3.06 to 0.53) over six months, stable to sensitivity analysis, but only a small number of trials contributed to each analysis and studies were at risk of bias. Green tea was also found to produce statistically significant reductions in total cholesterol (MD -0.62 mmol/L, 95% CI -0.77 to - 0.46), LDL cholesterol (MD -0.64 mmol/L, 95% CI -0.77 to -0.52) and blood pressure (SBP: MD -3.18 mmHg, 95% CI -5.25 to - 1.11; DBP: MD -3.42, 95% CI -4.54 to -2.30), but only a small number of studies contributed to each analysis, and results were not stable to sensitivity analysis. When both tea types were analysed together they showed favourable effects on LDL cholesterol (MD - 0.48 mmol/L, 95% CI -0.61 to -0.35) and blood pressure (SBP: MD -2.25 mmHg, 95% CI -3.39 to -1.11; DBP: MD -2.81 mmHg, 95% CI -3.77 to -1.86). Adverse events were measured in five trials and included a diagnosis of prostate cancer, hospitalisation for influenza, appendicitis and retinal detachment but these are unlikely to be directly attributable to the intervention. Authors' conclusions: There are very few long-term studies to date examining green or black tea for the primary prevention of CVD. The limited evidence suggests that tea has favourable effects on CVD risk factors, but due to the small number of trials contributing to each analysis the results should be treated with some caution and further high quality trials with longer-term follow-up are needed to confirm this