Search results for "Density"

BaCoO3 monoclinic structure and chemical bonding analysis: hybrid DFT calculations

2021

Cobalt based perovskites have great potential for numerous applications. Contrary to a generally assumed hexagonal space group (SG P63/mmc) model as the ground state of BaCoO3 (BCO), our hybrid DFT calculations with B1WC density functional and the symmetry group–subgroup derived crystal structure model support the ground state of BCO to be indeed monoclinic, in agreement with recent experimental predictions [Chin et al., Phys. Rev. B, 2019, 100, 205139]. We found for the monoclinic BCO that the C-type anti-ferromagnetic low-spin (AFM LS) state (SG P2/c) is energetically only slightly more preferential at 0 K than the ferromagnetic (FM) LS state (SG C2/c). In turn, these monoclinic structure…

Porosity of anodic alumina membranes from electrochemical measurements

2005

A procedure based on the high-field mechanism of the growth of anodic oxides was developed in order to evaluate the morphological features of porous layers. Since the thickness of the barrier film, separating the porous layer from the metal, does not change during the steady-state growth of an anodic porous layer, the rate of displacement of the metal-oxide interface to the metal direction must be equal to the rate of displacement of the pore base to the oxide direction. As a consequence, porosity can be expressed in terms of the ratio i diss/i ion, where i diss is the dissolution current density at the pore base, and i ion is the ionic current density at the metal-oxide interface. Pore dia…

Biosilica-Based Strategies for Treatment of Osteoporosis and Other Bone Diseases

2011

Osteoporosis is a common disease in later life, which has become a growing public health problem. This degenerative bone disease primarily affects postmenopausal women, but also men may suffer from reduced bone mineral density. The development of prophylactic treatments and medications of osteoporosis has become an urgent issue due to the increasing proportion of the elderly in the population. Apart from medical/hormonal treatments, current strategies for prophylaxis of osteoporosis are primarily based on calcium supplementation as a main constituent of bone hydroxyapatite mineral. Despite previous reports suggesting an essential role in skeletal growth and development, the significance of …

Ecological genetics of a cyclical parthenogen in temporary habitats

1995

Populations of the rotifer Brachionus plicatilis inhabiting three temporary ponds in Torreblanca Marsh (Castellon, Spain) were regularly screened for allozyme variation, sexual reproduction levels and population densities during an annual cycle. Relevant ecological parameters in the ponds were also recorded. The electrophoretic survey of the three ponds (Poza Sur, Poza Norte and Canal Central) revealed a high level of overall genetic polymorphism in four marker loci, but only 13 multilocus genotypes were found. We classified clones into three clonal groups (SS, SM, L) characterized by unique arrays of alleles in the four marker loci, and significant differences in body shape and size. Clona…

2018

Summary Background Population estimates underpin demographic and epidemiological research and are used to track progress on numerous international indicators of health and development. To date, internationally available estimates of population and fertility, although useful, have not been produced with transparent and replicable methods and do not use standardised estimates of mortality. We present single-calendar year and single-year of age estimates of fertility and population by sex with standardised and replicable methods. Methods We estimated population in 195 locations by single year of age and single calendar year from 1950 to 2017 with standardised and replicable methods. We based t…

First-principles calculations on surface hydroxyl impurities in BaF2

2012

Abstract OH − impurities located near the (1 1 1) BaF 2 surface have been studied by using density functional theory (DFT) with hybrid exchange potentials, namely DFT-B3PW. Twenty surface OH − configurations were studied, and the hydroxyls located on the first surface layer are the energetically most favorable configurations. For the (1 1 1) BaF 2 surface atomic layers, the surface hydroxyls lead to a remarkable XY -translation and a dilating effect in the Z -direction, overcoming the surface shrinking effect in the perfect slab. Bond population analysis shows that the surface effect strengthens the covalency of surface OH − impurities. The studies on band structures and density of states (…

Cardiovascular diseases and HCV infection: a simple association or more?

2013

HCV infection, metabolic disorders and cardiovascular alterations, considered alone or in combination, are common conditions in a large proportion of the general population. Consequently, determining whether the association of HCV infection with cardiometabolic disorders is simply coincidental or, conversely, caused by pathogenetic mechanisms (in)directly linking chronic HCV infection to these disorders, would be of extreme relevance. Several clinical studies have shown that metabolic disorders—namely, type 2 diabetes,1 insulin resistance (IR)2 and hepatic steatosis3—are highly prevalent in patients with chronic hepatitis C (CHC) compared with non-infected patients. Experimental and clinica…

Population dynamics of oxiclinal species in lake Arcas-2 (Spain)

1995

‘Oxiclinal’ rotifer species show high concentrations just above the oxic-anoxic interface in the hypolimnion of some lakes. The stratification of their populations is best shown by sampling at close depth intervals and quantifying their densities by the Utermohl technique. With this technique we were able to count males which otherwise pass through filters and more accurately count egg production. We evaluated female, male and egg numbers of the two main oxiclinal species of lake Arcas-2: Filinia hofmanni and Anuraeopsis fissa, during two annual cycles (1990–91). F. hofmanni was an exclusive oxiclinal species. It had an exponential growth phase at the onset of stratification giving a distin…

Mictic patterns of the rotifer Brachionus plicatilis Müller in small ponds

1995

Populations of the rotifer Brachionus plicatilis were monitored in three small ponds in a marsh on the Mediterranean coast. Samples were taken approximately every three weeks from July 1992 to November 1993. Salinity, temperature, conductivity, pH and oxygen concentration were measured in the field. Population density was determined from preserved quantitative samples. Individuals were classified as mictic females, amictic females, non-ovigerous females, and males, differentiating between two morphotypes (‘S’ and ‘L’). From these counts, a level of mixis was calculated. We also determined the proportion of mictic females in natural populations by culturing females isolated from fresh sample…

Syntheses of Trifluoroethylated N-Heterocycles from Vinyl Azides and Togni’s Reagent Involving 1,n-Hydrogen-Atom Transfer Reactions

2020

2,2,2-Trifluoroethyl-substituted 3-oxazolines, 3-thiazolines, and 5,6-dihydro-2H-1,3-oxazines have been obtained by reacting substituted vinyl azides with a combination of Togni’s reagent and substoichiometric amounts of iron(II) chloride. The results of density functional theory calculations support the proposed mechanism involving 1,n-hydrogen-atom transfer reactions. peerReviewed