Electronic structure calculations with GPAW: a real-space implementation of the projector augmented-wave method.

Electronic structure calculations have become an indispensable tool in many areas of materials science and quantum chemistry. Even though the Kohn-Sham formulation of the density-functional theory (DFT) simplifies the many-body problem significantly, one is still confronted with several numerical challenges. In this article we present the projector augmented-wave (PAW) method as implemented in the GPAW program package (https://wiki.fysik.dtu.dk/gpaw) using a uniform real-space grid representation of the electronic wavefunctions. Compared to more traditional plane wave or localized basis set approaches, real-space grids offer several advantages, most notably good computational scalability and systematic convergence properties. However, as a unique feature GPAW also facilitates a localized atomic-orbital basis set in addition to the grid. The efficient atomic basis set is complementary to the more accurate grid, and the possibility to seamlessly switch between the two representations provides great flexibility. While DFT allows one to study ground state properties, time-dependent density-functional theory (TDDFT) provides access to the excited states. We have implemented the two common formulations of TDDFT, namely the linear-response and the time propagation schemes. Electron transport calculations under finite-bias conditions can be performed with GPAW using non-equilibrium Green functions and the localized basis set. In addition to the basic features of the real-space PAW method, we also describe the implementation of selected exchange-correlation functionals, parallelization schemes, ΔSCF-method, x-ray absorption spectra, and maximally localized Wannier orbitals.

[Role of Gated-SPECT in the early diagnosis of ischaemic cardiopathy in the diabetic patient]. / Ruolo della Gated-SPECT nella diagnosi precoce della cardiopatia ischemica del paziente diabetico.

Diabetes presents a higher risk of both symptomatic and asymptomatic coronary artery disease (CAD). Myocardial perfusion SPECT, particularly associated with Gated acquisition, makes it possible to diagnose CAD on the basis of the presence and extent of perfusion defects, and to carry out the stratification of the cardiological risk (infarction or cardiac death) by analyzing the results of perfusion and of the functional data (ejection fraction, EF, and wall movement). Gated myocardial SPECT in the diagnosis and stratification of risk has proved superior to clinical evaluation or the exercise test alone, and it is also superior to echostress/dobutamine in the evaluation of monovasal disease. These data have been confirmed not only in the population at large but also in the diabetic population, making the technique important also in such patients also affected by coronary disease which is earlier and more advanced in diagnosis. Scintigraphic data make it possible to classify patients into various risk categories (low, intermediate and high) on the basis of which a specific therapeutic approach can be established. The present review develops the above concepts, taking into consideration the consolidated studies present in the literature, for the purpose of pinpointing the diagnostic approach in which exercise or SPECT myocardium-scintigraphy can be assigned.

Acute pancreatitis and deep vein thrombosis associated with HELLP syndrome.

The HELLP syndrome (HS) belongs to the list of obstetric complications believed to be associated with coagulation disorders. It was formerly thought that chronic intravascular clotting (DIC) in the placental vessels was the main cause. A hypercoagulable state has been reported in cases of severe HS associated with microvascular abnormalities that may involve cerebral, placental, hepatic and renal vessels. A case of acute pancreatitis and DVT of inferior cava in a pregnant woman, presenting with HS at 29 weeks, who was found to have a R506Q mutation, is reported. Preeclampsia-associated pancreatitis and DVT have rarely been reported. It is hypothesized that APC-R and Factor V Leiden mutation may prove to be new and more important markers capable of predicting a more significant maternal morbidity associated with HS. Thrombosis prophylaxis may be considered during pregnancy in order to reduce hazardous multiorgan failure (MOF) in women who are heterozygous for Factor V Leiden mutation.

Polycystic ovarian syndrome and pregnancy.

The paper describes a case of polycystic ovarian syndrome (PCOS) characterised by normal blood insulin levels and LH hypersecretion which explains the etiopathogenesis of the two voluminous ovarian masses originating from micro-cysts existing prior to pregnancy and undergoing abnormal growth during gestation owing to stimulation by beta-HCG (beta human chorionic gonadotropin). The ability of HCG ti stimulate ovarian steroidogenesis in pregnancy can result in enhanced testosterone and androstenedione levels. Our findings, like those of another recent report, emphasise the correlation between beta-HCG levels and testosterone values; the quantitative increase in beta-HCG probably plays an essential part in determining the abnormal development of the ovarian cysts, which remained morphologically unchanged up to delivery. Our patient's virilisation is explained by the increase in total testosterone in circulation. Fetal virilisation cannot be assessed in this patient because the mother gave birth to a male.

Diabetes and coronary risk factors, relative risk for single factors and aggregation of more factors in a general population sample from northern Italy.

In the course of a general population survey in Mirano (Venice), Northern Italy, a random sample of 1,903 subjects (50.1% men) aged 20-59 was examined. Fifty-five were diabetic (fasting plasma glucose greater than or equal to 140 mg/dl or diagnosed by a physician) and 1,670 non-diabetic subjects (fasting plasma glucose below 110 mg/dl). In this paper an assessment was made on the more frequent occurrence of coronary risk factors (serum cholesterol and triglycerides, body mass index (BMI), systolic blood pressure, cigarette smoking) and, in particular, of their aggregation in diabetic patients as compared to non-diabetic controls. The occurrence of any one of the coronary risk factors studied was more frequent in diabetic subjects and significantly so for triglyceridemia in both sexes and for systolic blood pressure and BMI in men. The aggregation of two or more risk factors was also more frequent in diabetic subjects than controls. Finally, the combined score of coronary risk as calculated by multiple logistic function showed higher values for diabetic subjects. These results confirm the need for a systematic search for coronary risk factors in diabetic subjects in order to prevent cardiovascular complications.

A new screening test for rotavirus infection.

A simple and rapid staphylococcal coagglutination test, using rabbit antisera prepared against Nebraska calf diarrhea virus (NCDV), is described for the detection of rotavirus in neonatal fecal specimens. When the samples were examined directly using the coagglutination test, more than 60% of the specimens agglutinated the control reagent. These non-specific reactions were markedly reduced by preincubation of the specimens with non-immune rabbit serum and further heating at 80 degrees C for 45 min. Such treatment did not reduce the specific activity in the coagglutination test when rotavirus-containing stools were tested. The coagglutination test was compared with ELISA in 290 stools positive or negative for rotavirus. The sensitivity of the coagglutination test was 92%, the specificity 91% and the predictive value 31%. These results indicate that coagglutination is a suitable test for rapid screening of rotavirus infection in clinical practice.