Total energy calculations from self-energy models

Density-functional theory is a powerful method to calculate total energies of large systems of interacting electrons. The usefulness of this method, however, is limited by the fact that an approximation is required for the exchange-correlation energy. Currently used approximations (LDA and GGA) are not sufficiently accurate in many physical problems, as for instance the study of chemical reactions. It has been shown that exchange-correlation effects can be accurately described via the self-energy operator in the context of many-body perturbation theory. This is, however, a computationally very demanding approach. In this thesis a new scheme for calculating total energies is proposed, which combines elements from many-body perturbation theory and density-functional theory. The exchange-correlation energy functional is built from a simplified model of the self-energy, that nevertheless retains the main features of the exact operator. The model is built in such way that the computational effort is not significantly increased with respect to that required in a typical density-functional theory calculation. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:DXN048379 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Analysis of degradation mechanisms of crystalline silicon PV modules after 12 years of operation in Southern Europe

The long-term reliability of photovoltaic modules is crucial to ensure the technical and economic viability of PV as a successful energy source. The analysis of degradation mechanisms of PV modules is key to ensure current lifetimes exceeding 25 years. This paper presents the results of the investigations carried out on the degradation mechanisms of a crystalline silicon PV installation of 2 kWp after 12 years of exposure in Málaga, Spain. The analysis was conducted by visual inspection, infrared thermography and electrical performance evaluation. By visual inspection, the most relevant defects in the modules were identified and ranked according to their frequency. The electrical performance was assessed by comparing the characteristic parameters of the individual modules, obtained by outdoor measurements at the start and end of the exposure period. The correlation of the visual defects and the shifts in the electrical parameters was analysed. The results presented show that glass weathering, delamination at the cell-EVA interface and oxidation of the antireflective coating and the cell metallization grid were the most frequently occurring defects found. The total peak power loss, including the initial light induced degradation, was 11.5%, which corresponded almost totally to a loss in short-circuit current. Copyright © 2011 John Wiley & Sons, Ltd

Low cost using ultra-thin bifacial cells

This paper presents the global results of the BiThink project. This is a project financed by DG-TREN. The BiThink objective is to develop and demonstrate an industrial technology able to exert direct influence on the cost of photovoltaic systems. BiThink focuses on three key aspects: the use of bifacial cells and albedo modules as a simple way to increase the amount of energy collected, the increase in the number of wafers obtained from the slicing of silicon ingots and the use of a simple and at last an efficient manufacturing process, able to combine high mechanical yields with reasonable cell efficiency. BiThink shows impressive figures in terms of the consumption of silicon: 5.9 grams per Watt peak using conservative yield values. Another important result is the large amount of new technology developed in the project in the areas of ingot slicing, post-slicing wafer separation, screen printing diffusion, mechanical handling, crack detection, and thin solar cell interconnection

A novel circulating microRNA for the detection of acute myocarditis

BACKGROUND The diagnosis of acute myocarditis typically requires either endomyocardial biopsy (which is invasive) or cardiovascular magnetic resonance imaging (which is not universally available). Additional approaches to diagnosis are desirable. We sought to identify a novel microRNA for the diagnosis of acute myocarditis. METHODS To identify a microRNA specific for myocarditis, we performed microRNA microarray analyses and quantitative polymerase-chain-reaction (qPCR) assays in sorted CD4+ T cells and type 17 helper T (Th17) cells after inducing experimental autoimmune myocarditis or myocardial infarction in mice. We also performed qPCR in samples from coxsackievirus-induced myocarditis in mice. We then identified the human homologue for this microRNA and compared its expression in plasma obtained from patients with acute myocarditis with the expression in various controls. RESULTS We confirmed that Th17 cells, which are characterized by the production of interleukin-17, are a characteristic feature of myocardial injury in the acute phase of myocarditis. The microRNA mmu-miR-721 was synthesized by Th17 cells and was present in the plasma of mice with acute autoimmune or viral myocarditis but not in those with acute myocardial infarction. The human homologue, designated hsa-miR-Chr8:96, was identified in four independent cohorts of patients with myocarditis. The area under the receiver-operating-characteristic curve for this novel microRNA for distinguishing patients with acute myocarditis from those with myocardial infarction was 0.927 (95% confidence interval, 0.879 to 0.975). The microRNA retained its diagnostic value in models after adjustment for age, sex, ejection fraction, and serum troponin level. CONCLUSIONS After identifying a novel microRNA in mice and humans with myocarditis, we found that the human homologue (hsa-miR-Chr8:96) could be used to distinguish patients with myocarditis from those with myocardial infarction

Gamma-glutamyltransferase, arterial remodeling and prehypertension in a healthy population at low cardiometabolic risk

Plasma gamma-glutamyltransferase (GGT) was suggested to reflect the level of systemic oxidative stress. Oxidative stress induces changes in arterial structure and function and contributes to the development of hypertension. Therefore, GGT may be associated with arterial remodeling and blood pressure (BP) increment, even in absence of disease. To test this hypothesis, we evaluated, in 825 healthy subjects at low cardiometabolic risk, the associations of plasma GGT with carotid artery intima-media thickness (IMT), luminal diameter and prehypertension; in 154 subjects was evaluated also the association with aortic stiffness (cfPWV). Associations were controlled for insulin sensitivity, C-reactive protein, and life-style habits. In the main population, BP was remeasured after 3 years. Carotid diameter and cfPWV, but not IMT, were directly and independently related to plasma GGT. Subjects with prehypertension (N = 330) had higher GGT as compared with subjects with normal BP (22 [14] vs 17 [11] IU/L; adjusted P = 0.001), and within prehypertensive subjects, those who developed hypertension during 3 years had higher GGT than those without incident hypertension (27 [16] vs 21 [14] IU/L; adjusted P < 0.05). Within subjects with arterial stiffness measurement, those with prehypertension (N = 79) had higher both GGT and arterial stiffness (25 [14] vs 16 [20] IU/L and 9.11 ± 1.24 vs 7.90 ± 0.94 m/s; adjusted P < 0.01 and <0.05). In the view of previous evidence linking plasma GGT concentration to the level of systemic oxidative stress, our findings suggest a role of oxidative stress in subclinical arterial damage and in prehypertension, even in healthy subjects free of cardiometabolic risk. Arterial organ damage may represent the link between GGT and hypertension

Fatty liver is associated with insulin resistance, risk of coronary heart disease, and early atherosclerosis in a large European population

Patients with fatty liver (FL) disease have a high risk of developing diabetes and cardiovascular diseases. The aim was to evaluate the association between FL, insulin resistance (IR), coronary heart disease (CHD) risk, and early atherosclerosis in a large European population (RISC Study). In 1,307 nondiabetic subjects (age 30-60 years) recruited at 19 centers, we evaluated liver enzymes, lipids, insulin sensitivity (by euglycemic-hyperinsulinemic clamp), glucose tolerance (by 75 g oral glucose tolerance test), carotid atherosclerosis as intima media thickness (IMT), CHD risk by the Framingham Heart study prediction score, and physical activity (by accelerometer). The presence of FL was estimated using the fatty liver index (FLI;>60, likelihood>78% presence FL; FLI<20 likelihood >91«sence of FL). Subjects were divided into three groups: G1: FLI<20 (n=608); G3: FLI>60 (n=234), G2: intermediate group (n=465). Compared to G1,G3 included more men (70% versus 24%) and people with impaired glucose tolerance (23% versus 5%). IMT increased with FLI (G3= 0.64±0.08 versusG1=0.58±0.08mm,P<0.0001). FLI was associated with increased CHD risk (r = 0.48), low-density lipoprotein cholesterol (r = 0.33), alanine aminotransferase (r = 0.48), aspartate aminotransferase (r = 0.25), systolic blood pressure (r = 0.39) and IMT (r = 0.30), and reduced insulin sensitivity (r=-0.43), high-density lipoprotein cholesterol (r=-0.50), adiponectin (r=-0.42), and physical activity (r=-0.16, all P < 0.0001). The correlations hold also in multivariate analysis after adjusting for age, gender, and recruiting center. Conclusion: In middle-age nondiabetic subjects, increased IMT, CHD risk, and reduced insulin sensitivity are associated with high values of FLI. Copyright © 2009 by the American Association for the Study of Liver Diseases

Fasting insulin has a stronger association with an adverse cardiometabolic risk profile than insulin resistance: The RISC study

Objective: Fasting insulin concentrations are often used as a surrogate measure of insulin resistance. We investigated the relative contributions of fasting insulin and insulin resistance to cardiometabolic risk and preclinical atherosclerosis. Design and methods: The Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) cohort consists of 1326 European non-diabetic, overall healthy men and women aged 30-60 years. We performed standard oral glucose tolerance tests and hyperinsulinemic euglycemic clamps. As a general measure of cardiovascular risk, we assessed the prevalence of the metabolic syndrome in 1177 participants. Carotid artery intima media thickness (IMT) was measured by ultrasound to assess preclinical atherosclerosis. Results: Fasting insulin was correlated with all elements of the metabolic syndrome. Insulin sensitivity (M/I) was correlated with most elements. The odds ratio for the metabolic syndrome of those in the highest quartile of fasting insulin compared with those in the lower quartiles was 5.4 (95% confidence interval (CI) 2.8-10.3, adjusted for insulin sensitivity) in men and 5.1 (2.6-9.9) in women. The odds ratio for metabolic syndrome of those with insulin sensitivity in the lowest quartile of the cohort compared with those in the higher quartiles was 2.4 (95% CI 1.3-4.7, adjusted for fasting insulin) in men and 1.6 (0.8-3.1) in women. Carotid IMT was only statistically significantly associated with fasting insulin in both men and women. Conclusions: Fasting insulin, a simple and practical measure, may be a stronger and independent contributor to cardiometabolic risk and atherosclerosis in a healthy population than hyperinsulinemic euglycemic clamp-derived insulin sensitivity. © 2009 European Society of Endocrinology

Gamma-glutamyltransferase, arterial remodeling and prehypertension in a healthy population at low cardiometabolic risk

Plasma gamma-glutamyltransferase (GGT) was suggested to reflect the level of systemic oxidative stress. Oxidative stress induces changes in arterial structure and function and contributes to the development of hypertension. Therefore, GGT may be associated with arterial remodeling and blood pressure (BP) increment, even in absence of disease. To test this hypothesis, we evaluated, in 825 healthy subjects at low cardiometabolic risk, the associations of plasma GGT with carotid artery intima-media thickness (IMT), luminal diameter and prehypertension; in 154 subjects was evaluated also the association with aortic stiffness (cfPWV). Associations were controlled for insulin sensitivity, C-reactive protein, and life-style habits. In the main population, BP was remeasured after 3 years. Carotid diameter and cfPWV, but not IMT, were directly and independently related to plasma GGT. Subjects with prehypertension (N = 330) had higher GGT as compared with subjects with normal BP (22 [14] vs 17 [11] IU/L; adjusted P = 0.001), and within prehypertensive subjects, those who developed hypertension during 3 years had higher GGT than those without incident hypertension (27 [16] vs 21 [14] IU/L; adjusted P < 0.05). Within subjects with arterial stiffness measurement, those with prehypertension (N = 79) had higher both GGT and arterial stiffness (25 [14] vs 16 [20] IU/L and 9.11 ± 1.24 vs 7.90 ± 0.94 m/s; adjusted P < 0.01 and <0.05). In the view of previous evidence linking plasma GGT concentration to the level of systemic oxidative stress, our findings suggest a role of oxidative stress in subclinical arterial damage and in prehypertension, even in healthy subjects free of cardiometabolic risk. Arterial organ damage may represent the link between GGT and hypertension