Effect of Different Solvent Ratios (Water/Ethylene Glycol) on the Growth Process of CaMoO4 Crystals and Their Optical Properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electronic and structural properties of the (10(1)over-bar0) and (11(2)over-bar0) ZnO surfaces

The structural and electronic properties of ZnO (10 (1) over bar0) and (11 (2) over bar0) surfaces were investigated by means of density functional theory applied to periodic calculations at B3LYP level. The stability and relaxation effects for both surfaces were analyzed. The electronic and energy band properties were discussed on the basis of band structure as well as density of states. There is a significant relaxation in the (10 (1) over bar0) as compared to the (11 (2) over bar0) terminated surfaces. The calculated direct gap is 3.09, 2.85, and 3.09 eV for bulk, (10 (1) over bar0), and (11 (2) over bar0) surfaces, respectively. The band structures for both surfaces are very similar.

Rietveld refinement, microstructure, conductivity and impedance properties of Ba[Zr0.25Ti0.75]O-3 ceramic

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relationship between predation by Podisus nigrispinus and developmental phase and density of its prey, Plutella xylostella

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structure, ferroelectric/magnetoelectric properties and leakage current density of (Bi0.85Nd0.15)FeO3 thin films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural and Electronic Properties of Lithiated SnO2. A Periodic DFT Study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Observed supersymmetry of hadrons and the tachyonless string models

The experimental mesonic density of states ρmeson(m)≃ρbaryon(m) from 0.9 to 1.3 GeV. In this region the ρmeson fits the ρ(m) deduced for it from discrete bag model states. Beyond 1.3 GeV one can expect exotic mesons. If ρmeson is replaced by the baryon density (as suggested by string model studies [D. Kutasov and N. Seiberg, Nucl. Phys. B 358 (1991) 600; P.G.O. Freund and J.L. Rosner, Phys. Rev. Lett. 68 (1992) 765]), agreement with theory is obtained up to 1.7 GeV. Beyond 1.7 GeV exotic baryons may be expected.

Disordered distribution of defects in polythiophene

In this work we study the electronic structure associated to a disordered distribution of bipolarons in polythiophene. The polymer chain is modelled by a tight-binding Hamiltonian with explicit treatment of electron-phonon coupling and the elastic energy of the sigma framework. The model also includes the electrostatic interaction due to the counterions. The density of states of the disordered system is obtained by the use of the Negative Factor Counting technique. Our results show that ion-induced conformational disorder can account for the closure of the gap and that the states around the Fermi level are extended. © 1993.

The application of thermally stimulated processes to the study of poly p-phenylene sulfide

The electrical properties of poly p-phenylene sulfide (PPS) samples sandwiched between metallic electrodes are studied as a function of the applied voltage, temperature, time, electrode materials, and sample thickness. Superlinear current-voltage characteristics are observed, which are explained in terms of Schottky effect and space-charge limited currents (SCLC). The conductivity data for variable-range hopping have also been studied, but the calculated values of density of states are approximately one order of magnitude higher than those obtained by SCLC measurements. From thermally stimulated polarization currents we observed a current peak around 80°C that was related with the glass transition temperature of PPS. © 1993.

Gel'fand-Levitan equation for deletion of states from Coulomb spectra

The Gel'fand-Levitan formalism is used to study how a selected set of bound states can be eliminated from the spectrum of the Coulomb potential and also how to construct a bound state in the Coulomb continuum. It is demonstrated that a sizeable quantum well can be produced by deleting a large number of levels from the s spectral series and the edge of the Coulomb potential alone can support the von Neumann-Wigner states in the continuum. © 1998 Elsevier Science B.V.

Numerical study of the spherically symmetric Gross-Pitaevskii equation in two space dimensions

The Gross-Pitaevskii equation for Bose-Einstein condensation (BEC) in two space dimensions under the action of a harmonic oscillator trap potential for bosonic atoms with attractive and repulsive interparticle interactions was numerically studied by using time-dependent and time-independent approaches. In both cases, numerical difficulty appeared for large nonlinearity. Nonetheless, the solution of the time-dependent approach exhibited intrinsic oscillation with time iteration which is independent of space and time steps used in discretization.

Energy method to calculate the density of liquids using ultrasonic reflection techniques

In this work it is introduced a new approach to calculate the density of liquids in terms of the energies of the acoustic signals. This method is compared to other methods in the time domain (peak-to-peak amplitudes) and frequency domain magnitudes at a single frequency. It is used a measurement cell based on a multiple reflection technique, and it is developed an acoustic model for the cell. Simulations and experiments using several liquids are presented, showing that the energy method a less sensitive to noise than the other techniques. The relative errors in the density are smaller than 0.2% when compared to the values measured with a pycnometer.

First observation of the doubly charmed baryon Ξcc +

The first experimental evidence for one of the six predicted baryon states which contain two valence charmed quarks-the doubly charmed baryons. As such, there were many predictions of the masses and other properties of these states. The properties of doubly charmed baryons provide a new window into the structure of baryonic matter.

Digital radiographic evaluation of optical density of porcelains used for fabrication of inlay/onlay prosthesis

The purpose of this article was to compare the mean value of optical density of four porcelains commonly used for fabrication of inlay/ onlay prostheses using direct digital radiograph. The sample consisted of 20 2-mm thick porcelain specimens (measured by digital pachymeter): Empress (Ivoclair), Simbios (Degussa), Vita Omega 900 and Vitadur Alpha (Vita Zahnfabrik). The values of optical density of the specimens were expressed in millimeters aluminum equivalent (mm eq Al). The samples were X-rayed using two charge coupled devices (CCD) - RVG (Trophy) - Visualix (Gendex) and a phosphor plate system - Digora (Soredex). The optical density reading was performed with Image Tool 1.28 in a total of 110 measurements. Statistical analysis showed that there were statistically significant differences in all materials studied (p < 0.05) regardless of the radiographic system used. The highest optical density value was found for Omega 900 (1.8988 mmeqAl - Visualix - Gendex) and the lowest for Vitadur Alpha (0.8647 - Visualix - Gendex). Thus, the material presenting the highest degree of optical density was Omega 900, Empress and Simbios presented intermediate optical density values, Vitadur Alpha presented the lowest value, and the optical density of porcelains was not influenced by the digital radiography systems.

The effect of endodontic materials on the optical density of dyes used in marginal leakage studies

The aim of this study was to determine the effect of the exposure of different endodontic materials to different dye solutions by evaluating the optical density of the dye solutions. Seventy-five plastic tubes were filled with one of the following materials: AH Plus, Sealapex, Portland cement, MTA (Angelus and Pro Root) and fifteen control plastic tubes were not. Each specimen of material and control was immersed in a container with 1 ml of each dye solution. A 0.1 ml-dye solution aliquote was removed before immersion and after 12, 24, 48 and 72 hours of each specimen immersion to record its optical density (OD) in a spectrophotometer. Statistical analysis was performed with ANOVA and Tukey tests (5%). No significant difference was found among any of the solution OD values for AH Plus cement. Portland cement promoted different OD values after 12 hours of immersion. MTA-Angelus cement presented different OD values only for 2% rhodamine B and the MTA-Pro Root cement presented different OD values in all 2% rhodamine B samples. Sealapex cement promoted a reduction in the India Ink OD values. Dye evaluation through OD seems to be an interesting method to select the best dye solution to use in a given marginal leakage study.