Oxygen related defects excitation and photoconductivity dependence of SnO2 sol-gel films with several light sources

Since oxygen vacancies act as donors in SnO2, the electrical properties are related to deviation from stoichiometric composition. Depending on stoichiometry SnO2 can be highly insulating or may exhibit fairly high n-type conductivity. Since bandgap transitions are in the ultraviolet range, its photoconductivity is strongly dependent on the excitation source. We have measured variation of photoconductivity excitation with wavelength for tin dioxide grown by dip-coating sol-gel technique using several light sources: tungsten lamp, xenon, mercury and deuterium, and present selected results. The main band is obtained in the range 3-4eV according to light source spectrum in the ultraviolet range. The presence of oxygen in the cryostat also affects the spectrum since electron-hole pairs react with adsorbed oxygen specimens. © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.

Reduction of diameter of the left ventricle of dogs by plication of the left ventricular free wall

Objective - To determine effects of reducing the diameter of the left ventricle of dogs by plication of the left ventricular free wall. Animals - 8 healthy adult mixed-breed dogs. Procedure - Left lateral thoracotomy and a T-shaped pericardiotomy were performed. The free wall of the left ventricle was imbricated with 3 interrupted transfixing sutures applied in a horizontal mattress pattern, using 3-0 polypropylene suture assembled on a straight cutting needle. Surgeons were careful to avoid the coronary vessels. Echocardiography was performed 24 hours before and 48 hours after surgery. Electrocardiography was performed before and 1, 2, 7, 15, 21, 30, and 60 days after surgery. Results - Echocardiographic measurements revealed that the diameter of the left ventricle was reduced by a mean of 23.5%. Electrocardiography revealed ventricular premature complexes 24 hours after surgery that regressed without treatment during the first week after surgery. Conclusions and Clinical Relevance - Plication of the left ventricular free wall of dogs can reduce end-diastolic and end-systolic dimensions of the left ventricle. The technique is simple and does not require cardiopulmonary bypass. According to Laplace's law, the reduction of cardiac diameter leads to reduction on free-wall tension and may improve left ventricular function in dilatated hearts. Thus, additional studies involving dogs with dilated cardiomyopathy should be conducted.

Short-range repulsion and isospin dependence in the kaon-nucleon (KN) system

The short-range properties of the kaon-nucleon (KN) interaction are studied within the meson-exchange model of the Jülich group. Specifically, dynamical explanations for the phenomenological short-range repulsion, required in this model for achieving agreement with the empirical KN data, are explored. Evidence is found that contributions from the exchange of a heavy scalar-isovector meson [a0(980)] as well as from genuine quark-gluon exchange processes are needed. Taking both mechanisms into account, a satisfactory description of the KN phase shifts can be obtained without resorting to phenomenological pieces.

Variabilidade espacial da estabilidade de agregados e matéria orgânica em solos de relevos diferentes

Soils submitted to the same management system in places with small relief variation manifest different spatial variability on their attributes. The objective of this work was to evaluate the spatial variability of the geometric medium diameter, aggregates in the >2 mm class, aggregates in the 2-1 mm class and organic matter of an Oxisol under culture of the sugarcane. Samplings of the soil in regular intervals of 10 m, in grid form, totaling 100 points, collected in the depths of 0.0-0.2 m and 0.2-0.4 m were made. Data were submitted to descriptive statistics, geostatistics and in sequence to kriging analyzes. Values of the variation coefficient were low for organic matter in the depth of 0.0-0.2 m, mean in the depth of 0.2-0.4 m, high for geometric medium diameter and mean for aggregates in the >2 mm class, aggregates in the 2-1 mm class in all studied depths. The occurrence of space dependence was observed for all the variables, and the largest ones were observed in the depth of 0.0-0.2 m. Small variations in the forms of the relief condition spatial variability differentiated for organic matter and stability of aggregates in the studied depths.

The temperature dependence of the QCD running coupling

We study the running of the QCD coupling with the momentum squared (Q 2) and the temperature scales in the high temperature limit (T > Tc), using a mass dependent renormalization scheme to build the Renormalization Group Equations. The approach used guaranty gauge invariance, through the use of the Hard Thermal Loop approximation, and independence of the vertex chosen to renormalize the coupling. In general, the dependence of the coupling with the temperature is not logarithmical, although in the region Q2 ∼ T2 the logarithm approximation is reasonable. Finally, as known from Debye screening, color charge is screened in the coupling. The number of flavors, however, is anti-screened.

Corn root length density and root diameter as affected by soil compaction and soil water content

Negative effects of soil compaction have been recognized as one of the problems restricting the root system and consequently impairing yields, especially in the Southern Coastal Plain of the USA. Simulations of the root restricting layers in green house studies are necessary for the development of mechanism which alleviates soil compaction problems in these soils. The selection of three distinct bulk densities based on the standard proctor test is also an important factor to determine which bulk density restricts the root layer. The experiment was conducted to assess the root length density and root diameter of the corn (Zea mays L.) crop as a function of bulk density and water stress, characterized by the soil density (1.2; 1.4, and 1.6 g cm -3), and two levels of the water content, approximately (70 and 90% field capacity). The statistical design adopted was completely randomized design, with four replicates in a factorial pattern of (3 × 2). The PVC tubes were superimposed with an internal diameter of 20 cm with a height of 40 cm (the upper tube 20 cm, compacted and inferior tube 10 cm), the hardpan with different levels of soil compaction were located between 20 and 30 cm of the depth of the pot. Results showed that: the main effects of subsoil mechanical impedance were observed on the top layer indicating that the plants had to penetrate beyond the favorable soil conditions before root growth was affected from 3.16; 2.41 to 1.37 cm cm -3 (P<0.005). There was a significant difference at the hardpan layer for the two levels of water and 90% field capacity reduced the root growth from 0.91 to 0.60 cm cm -3 (P<0.005). The root length density and root diameter were affected by increasing soil bulk density from 1.2 to 1.6 g cm -3 which caused penetration resistance to increase to 1.4 MPa. Soil water content of 70% field capacity furnished better root growth in all the layers studied. The increase in root length density resulted in increased root volume. It can also be concluded that the effect of soil compaction impaired the root diameter mostly at the hardpan layer. Soil temperature had detrimental effect on the root growth mostly with higher bulk densities.

Influence of length and diameter of implants associated with distal extension removable partial dentures

PURPOSE

Drug dependence, mental impairment and education

This study aimed to evaluate the mental conditions of cocaine-dependent individuals and school commitment/attachment. We evaluated 50 patients referred to the psychiatry emergency room due to mental disorders from chemical dependence. After clinical diagnosis, clinical interview, Hospital Anxiety and Depression Scale, Hamilton Scale for Depression and Brief Psychiatric Rating Scale were applied. The Spearman and Mann-Whitney nonparametric tests, as well as the t-Student test were utilized for statistical analysis.. The accepted significance value was 0.05. All subjects had used cocaine or crack and other substances. Only 13 (26%) did not drop out of school (group 1). Regarding the other 37 (74%), irregular class attendance , successive failures and definitive school drop out rates (group 2) were verified. These subjects presented an early substance use when compared with those which did not drop out of school (p=0.0001). Patients with an early substance use presented higher school dropout rates than those with a later initiation to substance use. Psychopathological phenomena were frequent in both groups.

Changes on transmittance mode of different composite resins

The purpose of this study was to evaluate the transmittance of seven different composite resins. Ten specimens were prepared (10 mm diameter, 2 mm thickness) for each experimental group, as follows: G1- Charisma® A 2 (Heraeus-Kulzer); G2- Filtek™ Supreme A 2E (3M/ESPE); G3- Filtek™ Supreme A2B (3M/ESPE); G4-Filtek™ Supreme YT (3M/ESPE); G5- Esthet-X® A2 (Dentsply); G6- Esthet-X® YE (Dentsply); G7- Durafill® A 2 (Heraeus-Kulzer) and G8- Filtek™ Z-100 A2 (3M/ESPE). The transmittance mode was measured using a UV-visible spectrophotometer (Cary Instruments) at 400-760 nm. The specimens were evaluated at three different times: zero hour (initial), 24 hours and 10 days after immersion in artificial saliva. The differences in transmittance were determined by two-way analysis of variance (ANOVA) and Tukey's test. The various composite resins showed significant differences in the wavelength dependence of transmittance. The mean values of transmittance increased significantly, with wavelengths increasing from 400 to 760 nm. The performance of the experimental groups was similar in terms of immersion time, considering that at time zero and after 10 days, all the groups showed similar results, which were statistically higher than the values obtained after 24 hours of immersion. The Filtek™ Supreme YT composite resin presented the highest mean transmittance values along the wavelengths at the three measured times. Esthet-X® YE and Durafill® yielded similar mean transmittance values, which were higher than those of the other groups. This study shows that the transmittance values of composite resins are directly related with the type, size and amount of inorganic filler particles.

Análise espacial de nutrientes e produção de alface cultivada em ambiente protegido

The objective of this work was to study spatial variability of some chemical soil attributes and lettuce production (total shoot fresh matter mass - MF; commercial shoot fresh matter mass - MFC; commercial shoot dry matter mass - MCS; and head commercial diameter - DCC) offering subsidies to the protected environment mapping in nutrients management areas in lettuce culture aiming for a higher productivity with application of fertilizers. The experiment was conducted in a protective environment (greenhouse) with lettuce irrigated by drip irrigation and sampling grid with 152 points. The special dependence analysis, determined by the variogram, was obtained with the aid of the GS+ Program. Considering the need for crop nutrients through the map obtained for element P (phosphorus) it was possible to establish two distinct areas for the application of this element in plantation fertilization. Through the lettuce yield maps obtained with MFC and DCC attributes was difficult to establish distinct areas for its management with data observed in only one crop cycle. Krigagem has proved useful for mapping the attributes studied.

Temperature dependence of structural and electronic properties of the spin-liquid candidate κ-(BEDT-TTF) 2Cu 2(CN) 3

We investigate the effect that the temperature dependence of the crystal structure of a two-dimensional organic charge-transfer salt has on the low-energy Hamiltonian representation of the electronic structure. For that, we determine the crystal structure of κ-(BEDT-TTF) 2Cu 2(CN) 3 for a series of temperatures between T=5 and 300 K by single crystal X-ray diffraction and analyze the evolution of the electronic structure with temperature by using density functional theory and tight binding methods. We find a considerable temperature dependence of the corresponding triangular lattice Hubbard Hamiltonian parameters. We conclude that even in the absence of a change of symmetry, the temperature dependence of quantities like frustration and interaction strength can be significant and should be taken into account. © 2012 American Physical Society.

Fracture resistance of bovine incisors restored with different glass fiber posts: Effect of the diameter of fiber post

Aim: Compare the effect of three post designs on the fracture resistance and failure modes of composite core-fiber post-crownless tooth sets. Materials and Methods: Ninety bovine incisors were selected and divided into nine groups of 10 specimens. The teeth were assigned to three groups based on the post design: Cylindrical, tapered, and double-tapered. Each group was subdivided into three subgroups in accordance with the diameter of the post: Small (No.1), medium (No.2), and large (No.3). The Panavia F system was used for post cementation. The specimens were mounted in acrylic resin blocks with a layer of silicone rubber covering the roots. A universal testing machine compressively loaded the specimens from the palatal side at a crosshead speed of 1 mm/min and at an angle of 135I to the long axis of the teeth, until failure occurred. The failure mode was determined by a stereomicroscope inspection of all the specimens. Data were analyzed by one-way ANOVA and the Tukey test (P < 0.05). Results: The fracture resistance was affected by the type of post (P < 0.0001). A narrower diameter for all of the post systems allowed for higher resistance. The main failure mode in the large cylindrical group was catastrophic fractures, while the main failures in the other eight groups were favorable. Conclusion: Narrower diameter posts showed higher fracture resistance. The dominant failure pattern was repairable fracture, except for those with large cylindrical groups.

Thickness dependence of structure and piezoelectric properties at nanoscale of polycrystalline PZT thin films

Lead zirconate titanate Pb(Zr 0.50Ti 0.50)O 3 (PZT) thin films were deposited by a polymeric chemical method on Pt(111)/Ti/SiO2/Si substrates to understand the mechanisms of phase transformations and the effect of film thickness on the structure, dielectric and piezoelectric properties in these films. PZT films pyrolyzed at temperatures higher than 350 °C present a coexistence of pyrochlore and perovskite phases, while only perovskite phase grows in films pyrolyzed at temperatures lower than 300 °C. For pyrochlore-free PZT thin films, a small (100) orientation tendency near the film-substrate interface was observed. Finally, we demonstrate the existence of a self-polarization effect in the studied PZT thin films. Results suggest that Schottky barriers and/or mechanical coupling near the filmsubstrate interface are not primarily responsible for the observed self-polarization effect in our films. © 2012 IEEE.