Electronic, mechanical, and thermodynamic properties of americium dioxide

By performing density functional theory (DFT) +$U$ calculations, we systematically study the electronic, mechanical, tensile, and thermodynamic properties of AmO$_{2}$. The experimentally observed antiferromagnetic insulating feature [J. Chem. Phys. 63, 3174 (1975)] is successfully reproduced. It is found that the chemical bonding character in AmO$_{2}$ is similar to that in PuO$_{2}$, with smaller charge transfer and stronger covalent interactions between americium and oxygen atoms. The valence band maximum and conduction band minimum are contributed by 2$p-5f$ hybridized and 5$f$ electronic states respectively. The elastic constants and various moduli are calculated, which show that AmO$_{2}$ is less stable against shear forces than PuO$_{2}$. The stress-strain relationship of AmO$_{2}$ is examined along the three low-index directions by employing the first-principles computational tensile test method. It is found that similar to PuO$_{2}$, the [100] and [111] directions are the strongest and weakest tensile directions, respectively, but the theoretical tensile strengths of AmO$_{2}$ are smaller than those of PuO$_{2}$. The phonon dispersion curves of AmO$_{2}$ are calculated and the heat capacities as well as lattice expansion curve are subsequently determined. The lattice thermal conductance of AmO$_{2}$ is further evaluated and compared with attainable experiments. Our present work integrally reveals various physical properties of AmO$_{2}$ and can be referenced for technological applications of AmO$_{2}$ based materials.Comment: 23 pages, 8 figure

Plasma ET-1 Concentrations are Elevated in Patients with Hypertension – Meta- Analysis of Clinical Studies

Background/Aims: A recent study revealed that global overexpression of ET-1 causes a slight reduction in systemic blood pressure. Moreover, heterozygous ET-1 knockout mice are hypertensive. The role of ET-1 in human hypertension was so far not addressed by a strict meta-analysis of published human clinical studies. Methods: We included studies published between January 1, 1990 and February 28, 2017. We included case control studies analyzing untreated essential hypertension or hypertensive patients where antihypertensive medication was discontinued for at least two weeks. Based on the principle of Cochrane systematic reviews, case control studies (CCSs) in PubMed (Medline) and Google Scholar designed to identify the role of endothelin-1 (ET-1) in the pathophysiological of hypertension were screened. Review Manager Version 5.0 (Rev-Man 5.0) was applied for statistical analysis. Mean difference and 95% confidence interval (CI) were shown in inverse variance (IV) fixed-effects model or IV random-effects models. Results: Eleven studies fulfilling our in- and exclusion criteria were eligible for this meta-analysis. These studies included 450 hypertensive patients and 328 controls. Our meta-analysis revealed that ET-1 plasma concentrations were higher in hypertensive patients as compared to the control patients [mean difference between groups 1.57 pg/mL, 95%CI [0.47∼2.68, P = 0.005]. These finding were driven by patients having systolic blood pressure higher than 160 mmHg and diastolic blood pressure higher than 100 mmHg. Conclusions: This meta-analysis showed that hypertensive patients do have elevated plasma ET-1 concentrations. This finding is driven by those patients with high systolic/diastolic blood pressure. Given that the ET-1 gene did not appear in any of the whole genome association studies searching for hypertension associated gene loci, it is very likely that the elevated plasma ET-1 concentrations in hypertensive patients are secondary to hypertension and may reflect endothelial cell damage

(E)-Ethyl N′-(3-hy­droxy­benzyl­idene)hydrazinecarboxyl­ate dihydrate

The asymmetric unit of the title compound, C10H12N2O3·2H2O, contains two organic mol­ecules with similar conformations and four water mol­ecules. Each organic mol­ecule is close to planar (r.m.s. deviations = 0.035 and 0.108 Å) and adopts a trans conformation with respect to its C=N bond. In the crystal, the components are linked into a three-dimensional network by N—H⋯O, O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds, some of which are bifurcated. An R 2 2(8) loop occurs between adjacent organic mol­ecules

The effect of prestressing force on natural frequencies of concrete beams - A numerical validation of existing experiments by modelling shrinkage crack closure

This paper investigates the effect of prestressing force on the natural frequencies of reinforced concrete beams. From a pure theoretical point of view, such effects in different prestressing conditions appear to involve no ambiguity; however, in practice contradictory observations have been reported in existing research publications. Theoretical studies showed that natural frequencies would be decreasing or unchanged in different scenarios. On the other hand, some experiments that were conducted on prestressed concrete beams indicated an increasing trend of the natural frequencies with the prestressing force. This paper is aimed to provide a systematic explanation of the reasons causing the discrepancies and propose a coherent framework for the prediction of the natural frequencies under a prestressed condition. Numerical simulations using finite element model are carried out to simulate the influence of prestressing force on natural frequencies with the existence of the shrinkage cracks. The results demonstrate that such shrinkage-type cracks inside the concrete indeed tend to close when the prestressing force is applied, and this in turn increases the bending stiffness and consequently results in an increase of the natural frequencies of the beams.MOE (Min. of Education, S’pore)Accepted versio