Influence of nitrogen content on the structural, mechanical and electrical properties of TiN thin films

This paper reports on the preparation of TiNx thin films by d.c. reactive magnetron sputtering. The coating thickness ranged from 1.7 to 4.2 Am and the nitrogen content varied between 0 and 55 at.%. X-Ray diffraction showed the development of the hexagonal a-Ti phase, with strong [002] orientation for low nitrogen contents, where the N atoms fit into octahedral sites in the Ti lattice as the amount of nitrogen is increased. For nitrogen contents of 20 and 30 at.%, the q-Ti2N phase appears with [200] orientation. With further increasing the nitrogen content, the y-TiN phase becomes dominant. The electrical resistivity of the different compositions reproduces this phase behavior. The hardness of the samples varied from approximately 8 GPa for pure titanium up to 27 GPa for a nitrogen content of 30 at.%, followed by a slight decrease at the highest contents. A similar increase of stresses with nitrogen is observed. Structure and composition with the consequent changes in crystalline phases and the lattice distortion were found to be crucial in the evolution of the mechanical properties

Structural and corrosion behaviour of stoichiometric and substoichiometric TiN thin films

This paper reports the structural and electrochemical behaviour of TiN thin films prepared by d.c. reactive magnetron sputtering. x X-Ray diffraction showed the development of the hexagonal a-Ti phase, with strong w002x orientation, for low nitrogen contents. For nitrogen contents of 20 and 30 at.%, the ´-Ti N phase appears with w200x orientation. With further increasing the nitrogen 2 content, the d-TiN phase becomes dominant. Composition and the resulting changes in microstructure (crystalline phases and the lattice distortion induced by the growth conditions) are the two main parameters that seem to rule coating properties. Results of potentiodynamic polarisation tests showed that all films have a high corrosion resistance reflected by corrosion current densities below 0.7 mAycm . Also, electrochemical impedance spectroscopy tests corroborated the results obtained in the polarisation tests, 2 showing that films containing low percentages of nitrogen (less than 8%) reveal the best corrosion resistance. Further increases in nitrogen content lead to a decrease in the corrosion resistance. An exception to this behaviour was found for the film with 30 at.% N. This sample presents an excellent corrosion resistance, which in fact, increases with the immersion time. Higher nitrogen contents (52 and 55 at.%) promote a relative increase in the corrosion resistance when compared with 50 at.% films. This behaviour might be explained by the particular microstructural characteristics of the films

Bulk viscosity driving the acceleration of the Universe

The possibility that the present acceleration of the universe is driven by a kind of viscous fluid is exploited. At background level this model is similar to the generalized Chaplygin gas model (GCGM). But, at perturbative level, the viscous fluid exhibits interesting properties. In particular the oscillations in the power spectrum that plagues the GCGM are not present. Possible fundamental descriptions for this viscous dark energy are discussed.Comment: Latex file, 8 pages, 3 eps figure

Nucleation of a sodium droplet on C60

We investigate theoretically the progressive coating of C60 by several sodium atoms. Density functional calculations using a nonlocal functional are performed for NaC60 and Na2C60 in various configurations. These data are used to construct an empirical atomistic model in order to treat larger sizes in a statistical and dynamical context. Fluctuating charges are incorporated to account for charge transfer between sodium and carbon atoms. By performing systematic global optimization in the size range 1<=n<=30, we find that Na_nC60 is homogeneously coated at small sizes, and that a growing droplet is formed above n=>8. The separate effects of single ionization and thermalization are also considered, as well as the changes due to a strong external electric field. The present results are discussed in the light of various experimental data.Comment: 17 pages, 10 figure

Evaluation of neck circumference as a predictor of elevated cardiometabolic risk outcomes in 5–8-year-old Brazilian children

Background: Childhood overweight and obesity is a global health problem that continues to worsen in many low- and middle-income countries. Low-cost measurements for monitoring overweight and relative metabolic risk, such as neck circumference (NC), should be evaluated in different populations and age groups. / Aim: To test associations of NC and BMI with cardiometabolic parameters in 5-8-year-old Brazilian children. / Methods: This cross-sectional study carried out from 2004–2006 measured height, weight and NC by anthropometry, and estimated fat and fat-free mass by bioelectrical impedance. Cardiometabolic risk factors assessed were systolic and diastolic blood pressure, high- and low-density lipoprotein cholesterol, triglycerides, and homeostatic model assessment of insulin resistance (HOMA). Associations of NC and BMI with cardiometabolic risk factors were tested using multiple regression and precision-recall plot analysis. / Results: Analyses included 371 children (52% female). NC associated positively with BMI, fat mass, and fat-free mass, and with systolic blood pressure and HOMA following adjustment for age in sex-stratified multiple regression models. However, the latter relationships largely disappeared following adjustment for BMI. Area under the curve for NC or BMI in association with systolic blood pressure or HOMA >90th percentile was low in the pooled sample, indicating poor classifier performance. / Conclusions: NC and BMI demonstrated similar associations with cardiometabolic risk factors, although NC mostly did not correlate with risk factors independently of BMI. In contrast to previous studies, NC was a poor classifier of cardiometabolic risk factors in children. The association of NC with both fat and fat-free mass may aid in explaining its poor performance

An insight into the sialome of Simulium guianense (DIPTERA:SIMulIIDAE), the main vector of River Blindness Disease in Brazil

<p>Abstract</p> <p>Background</p> <p>Little is known about the composition and function of the saliva in black flies such as <it>Simulium guianense</it>, the main vector of river blindness disease in Brazil. The complex salivary potion of hematophagous arthropods counteracts their host's hemostasis, inflammation, and immunity.</p> <p>Results</p> <p>Transcriptome analysis revealed ubiquitous salivary protein families--such as the Antigen-5, Yellow, Kunitz domain, and serine proteases--in the <it>S. guianense </it>sialotranscriptome. Insect-specific families were also found. About 63.4% of all secreted products revealed protein families found only in <it>Simulium</it>. Additionally, we found a novel peptide similar to kunitoxin with a structure distantly related to serine protease inhibitors. This study revealed a relative increase of transcripts of the SVEP protein family when compared with <it>Simulium vittatum </it>and <it>S. nigrimanum </it>sialotranscriptomes. We were able to extract coding sequences from 164 proteins associated with blood and sugar feeding, the majority of which were confirmed by proteome analysis.</p> <p>Conclusions</p> <p>Our results contribute to understanding the role of <it>Simulium </it>saliva in transmission of <it>Onchocerca volvulus </it>and evolution of salivary proteins in black flies. It also consists of a platform for mining novel anti-hemostatic compounds, vaccine candidates against filariasis, and immuno-epidemiologic markers of vector exposure.</p

Reduction in membrane component of diffusing capacity is associated with the extent of acute pulmonary embolism

Acute pulmonary embolism (PE) often decreases pulmonary diffusing capacity for carbon monoxide (DL,CO), but data on the mechanisms involved are inconsistent. We wanted to investigate whether reduction in diffusing capacity of alveolo-capillary membrane (DM) and pulmonary capillary blood volume (Vc) is associated with the extent of PE or the presence and severity of right ventricular dysfunction (RVD) induced by PE and how the possible changes are corrected after 7-month follow-up. Forty-seven patients with acute non-massive PE in spiral computed tomography (CT) were included. The extent of PE was assessed by scoring mass of embolism. DL,CO, Vc, DM and alveolar volume (VA) were measured by using a single breath method with carbon monoxide and oxygen both at the acute phase and 7 months later. RVD was evaluated with transthoracic echocardiography and electrocardiogram. Fifteen healthy subjects were included as controls. DL,CO, DL, CO/VA, DM, vital capacity (VC) and VA were significantly lower in the patients with acute PE than in healthy controls (P<0·001). DM/Vc relation was significantly lower in patients with RVD than in healthy controls (P = 0·004). DM correlated inversely with central mass of embolism (r = −0·312; P = 0·047) whereas Vc did not. DM, DL,CO, VC and VA improved significantly within 7 months. In all patients (P = 0·001, P = 0·001) and persistent RVD (P = 0·020, P = 0·012), DM and DL,CO remained significantly lower than in healthy controls in the follow-up. DM was inversely related to central mass of embolism. Reduction in DM mainly explains the sustained decrease in DL,CO in PE after 7 months despite modern treatment of PE