First Principles Analysis of H2O Adsorption on the (110) Surfaces of SnO2, TiO2 and Their Solid Solutions

Both associative and dissociative H2O adsorption on SnO2(110), TiO2(110), and Ti-enriched Sn1-xTixO2(110) surfaces have been investigated at low (1/12 monolayer (ML)) and high coverage (1 ML) by density functional theory calculations using the Gaussian and plane waves formalism. The use of a large supercell allowed the simulation at low symmetry levels. On SnO2(110), dissociative adsorption was favored at all coverages and was accompanied by stable associative H2O configurations. Increasing the coverage from 1/12 to 1 ML stabilized the (associatively or dissociatively) adsorbed H2O on SnO2(110) because of the formation of intermolecular H bonds. In contrast, on TiO2(110), the adsorption of isolated H2O groups (1/12 ML) was more stable than at high coverage, and the favored adsorption changed from dissociative to associative with increasing coverage. For dissociative H2O adsorption on Ti-enriched Sn1-xTixO2(110) surfaces with Ti atoms preferably located on 6-fold-coordinated surface sites, the analysis of the Wannier centers showed a polarization of electrons surrounding bridging O atoms that were bound simultaneously to 6-fold-coordinated Sn and Ti surface atoms. This polarization suggested the formation of an additional bond between the 6-fold-coordinated Ti-6c and bridging O atoms that had to be broken upon H2O adsorption. As a result, the H2O adsorption energy initially decreased, with increasing surface Ti content reaching a minimum at 25% Ti for 1/12 ML. This behavior was even more accentuated at high H2O coverage (1 ML) with the adsorption energy decreasing rapidly from 145.2 to 101.6 kJ/mol with the surface Ti content increasing from 0 to 33%. A global minimum of binding energies at both low and high coverage was found between 25 and 33% surface Ti content, which may explain the minimal cross-sensitivity to humidity previously reported for Sn1-xTixO2 gas sensors. Above 12.5% surface Ti content, the binding energy decreased with increasing coverage, suggesting that the partial desorption of H2O is facilitated at a high fractional coverage

Serum Albumin Is Inversely Associated With Portal Vein Thrombosis in Cirrhosis

We analyzed whether serum albumin is independently associated with portal vein thrombosis (PVT) in liver cirrhosis (LC) and if a biologic plausibility exists. This study was divided into three parts. In part 1 (retrospective analysis), 753 consecutive patients with LC with ultrasound-detected PVT were retrospectively analyzed. In part 2, 112 patients with LC and 56 matched controls were entered in the cross-sectional study. In part 3, 5 patients with cirrhosis were entered in the in vivo study and 4 healthy subjects (HSs) were entered in the in vitro study to explore if albumin may affect platelet activation by modulating oxidative stress. In the 753 patients with LC, the prevalence of PVT was 16.7%; logistic analysis showed that only age (odds ratio [OR], 1.024; P = 0.012) and serum albumin (OR, -0.422; P = 0.0001) significantly predicted patients with PVT. Analyzing the 112 patients with LC and controls, soluble clusters of differentiation (CD)40-ligand (P = 0.0238), soluble Nox2-derived peptide (sNox2-dp; P < 0.0001), and urinary excretion of isoprostanes (P = 0.0078) were higher in patients with LC. In LC, albumin was correlated with sCD4OL (Spearman's rank correlation coefficient [r(s)], -0.33; P < 0.001), sNox2-dp (r(s), -0.57; P < 0.0001), and urinary excretion of isoprostanes (r(s), -0.48; P < 0.0001) levels. The in vivo study showed a progressive decrease in platelet aggregation, sNox2-dp, and urinary 8-iso prostaglandin F2 alpha-III formation 2 hours and 3 days after albumin infusion. Finally, platelet aggregation, sNox2-dp, and isoprostane formation significantly decreased in platelets from HSs incubated with scalar concentrations of albumin. Conclusion: Low serum albumin in LC is associated with PVT, suggesting that albumin could be a modulator of the hemostatic system through interference with mechanisms regulating platelet activation

Modeling chirally modified metal surfaces using the Gaussian and Plane Wave DFT formalism

ISSN:0009-429

Ab initio Dynamics of Metal Nanoparticles: Structure and Properties

ISSN:0009-429

First Principles Analysis of H2O Adsorption on the (110) Surfaces of SnO2, TiO2 and Their Solid Solutions

Both associative and dissociative H2O adsorption on SnO2(110), TiO2(110), and Ti-enriched Sn1-xTixO2(110) surfaces have been investigated at low (1/12 monolayer (ML)) and high coverage (1 ML) by density functional theory calculations using the Gaussian and plane waves formalism. The use of a large supercell allowed the simulation at low symmetry levels. On SnO2(110), dissociative adsorption was favored at all coverages and was accompanied by stable associative H2O configurations. Increasing the coverage from1/12 to 1 ML stabilized the (associatively or dissociatively) adsorbed H2O on SnO2(110) because of the formation of intermolecular H bonds. In contrast, on TiO2(110), the adsorption of isolated H2O groups (1/12 ML) was more stable than at high coverage, and the favored adsorption changed from dissociative to associative with increasing coverage. For dissociative H2O adsorption on Ti-enriched Sn1-xTixO2(110) surfaces with Ti atoms preferably located on 6-fold-coordinated surface sites, the analysis of the Wannier centers showed a polarization of electrons surrounding bridging O atoms that were bound simultaneously to 6-fold-coordinated Sn and Ti surface atoms. This polarization suggested the formation of an additional bond between the 6-fold-coordinated Ti6c and bridging O atoms that had to be broken upon H2O adsorption. As a result, the H2O adsorption energy initially decreased, with increasing surface Ti content reaching a minimum at 25% Ti for1/12 ML. This behavior was even more accentuated at high H2O coverage (1 ML) with the adsorption energy decreasing rapidly from 145.2 to 101.6 kJ/mol with the surface Ti content increasing from 0 to 33%. A global minimum of binding energies at both low and high coverage was found between 25 and 33% surface Ti content, which may explain the minimal cross-sensitivity to humidity previously reported for Sn1-xTixO2 gas sensors. Above 12.5% surface Ti content, the binding energy decreased with increasing coverage, suggesting that the partial desorption of H2O is facilitated at a high fractional coverage

Fluxionality of gold nanoparticles investigated by Born-Oppenheimer molecular dynamics

The structure and electronic properties of gold nanoparticles (Au 12, Au 13, Au 14, Au 15, Au 20, Au 34, and Au 55) have been investigated using Born-Oppenheimer ab initio molecular dynamic simulations of 50 to 80 ps in order to have an insight in the recently proposed fluxional character of nanosized gold. The dynamic changes in shape, symmetry, and atomic coordination of atoms within clusters, occurring in the time scale of picoseconds, which are characteristic of fluxionality, have been investigated for all the above systems at 300 K. Except for Au 20, all systems have been found to have fluxional properties. The extent and the type of fluxional behavior changed according to the number of atoms constituting the particle. At 300 K Au 12 and Au 13 rapidly generate several different topologies which cyclically interconvert. Au 14 shows a rotation of 8 external gold atoms around a core of six atoms. Au 15 is more rigid, but interestingly shows the interconversion between enantiomeric structures within the time scale of the simulation. Au 20 shows a high stability of the pyramidal topology and is the only one of the investigated systems not to show fluxionality within the assigned temperature and time scale. Au 34 and Au 55 show fluxionality of the outer shell and within the sampled time scale are able to change coordination of the outer shell atoms and thus open and close surface holes. For all the particles in study the structures forming the local minima were isolated and separately optimized, and the electronic properties of the thus obtained structures were analyzed

Modeling bulk and surface Pt using the “Gaussian and plane wave” density functional theory formalism: Validation and comparison to k-point plane wave calculations

We present a study on structural and electronic properties of bulk platinum and the two surfaces (111) and (100) comparing the Gaussian and plane wave method to standard plane wave schemes, normally employed for density functional theory calculations on metallic systems. The aim of this investigation is the assessment of methods based on the expansion of the Kohn-Sham orbitals into localized basis sets and on the supercell approach, in the description of the metallicity of Pt. Electronic structure calculations performed at Gamma-point only on supercells of different sizes, from 108 up to 864 atoms, are compared to the results obtained for the unit cell of four Pt atoms where the k-point expansion of the wave function over Monkhorst-Pack grids up to (10x10x10) has been employed. The evaluation of the two approaches with respect to bulk properties is done through the calculation of the equilibrium lattice constant, the bulk modulus, and the total and the d-projected density of states. For the Pt(111) and Pt(100) surfaces, we consider the relaxation of the first layers, the surface energies, the work function, the total density of states, as well as the center and filling of the d bands. Our results confirm that the accuracy of two approaches in the description of electronic and structural properties of Pt is equivalent, providing that consistent supercells and k-point meshes are used. Moreover, we estimate the supercell size that can be safely adopted in the Gaussian and plane wave method in order to obtain the same reliability of previous theoretical studies based on well converged plane wave calculations available in literature. The latter studies, in turn, set the level of agreement with experimental data. In particular, we obtain excellent agreement in the evaluation of the density of states for either bulk and surface systems, and our data are also in good agreement with previous works on Pt reported in literature. We conclude that Gaussian and plane wave calculations, with simulation cells of 400-800 atoms, can be safely used in the study of chemistry related problems involving transition metal surfaces

HistoNet: A Deep Learning-Based Model of Normal Histology

We introduce HistoNet, a deep neural network trained on normal tissue. On 1690 slides with rat tissue samples from 6 preclinical toxicology studies, tissue regions were outlined and annotated by pathologists into 46 different tissue classes. From these annotated regions, we sampled small 224 × 224 pixels images (patches) at 6 different levels of magnification. Using 4 studies as training set and 2 studies as test set, we trained VGG-16, ResNet-50, and Inception-v3 networks separately at each magnification level. Among these model architectures, Inception-v3 and ResNet-50 outperformed VGG-16. Inception-v3 identified the tissue from query images, with an accuracy up to 83.4%. Most misclassifications occurred between histologically similar tissues. Investigation of the features learned by the model (embedding layer) using Uniform Manifold Approximation and Projection revealed not only coherent clusters associated with the individual tissues but also subclusters corresponding to histologically meaningful structures that had not been annotated or trained for. This suggests that the histological representation learned by HistoNet could be useful as the basis of other machine learning algorithms and data mining. Finally, we found that models trained on rat tissues can be used on non-human primate and minipig tissues with minimal retraining