Weighted oscillator strengths and lifetimes for the Si II spectrum

The weighted oscillator strengths (gf) and the lifetimes for Si II presented in this work were carried out in a multiconfiguration Hartree–Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work we presented all the experimentally known electric dipole Si II spectral lines.     

Resonant Zener tunneling in two-dimensional periodic photonic lattices

We study Zener tunneling in two-dimensional photonic lattices and derive, for the case of hexagonal symmetry, the generalized Landau-Zener-Majorana model describing resonant interaction between high-symmetry points of the photonic spectral bands. We demonstrate that this effect can be employed for the generation of Floquet-Bloch modes and verify the model by direct numerical simulations of the tunneling effect.     

Role of the intracellular cavity in potassium channel conductivity

The role of several fragments of the potassium channel KcsA has been examined by the Poisson-Nernst-Planck (PNP) theory. The efficiency of the computational method allowed comparing a large number of channel models, with different intracellular gate openings, partial atomic charges, and amino acid sequences. Perhaps counter-intuitively, the calculated ion current decreases when the mean radius of the entrance cavity increases. Widening of the vestibule, in fact, increases the volume accessible to water, which is the volume with a high dielectric constant. In turn, water screens the attractive charges of the P-loop backbone. The backbone charges of the M2 helixes instead oppose the entrance of potassium ions through a complicated mechanism that can be separated in the activity of two interfering dipoles. The conductance of the KcsA models increased when two neutral residues in M2 were mutated to glutamic acid, in agreement with experimental results (Brelidze, T. I.; Niu, X.; Magleby, K. L. PNAS 2003, 100, 9017-9022). As a general conclusion, a relation between channel conductance and potassium concentration in the intracellular cavity emerged. Although the ion transport is the result of the fine balance of a number of different effects, the experimental results can be reproduced quantitatively only on the basis of electrostatic forces, which are the only driving forces modeled by the PNP theory.     

On existence, uniform decay rates and blow up for solutions of the 2-D wave equation with exponential source

This paper is concerned with the study of the nonlinear damped wave equation

On existence and asymptotic stability of solutions of the degenerate wave equation with nonlinear boundary conditions

We study the global existence of solutions of the nonlinear degenerate wave equation (ρ?0)

     

Existence and decay rate estimates for the wave equation with nonlinear boundary damping and source term

The wave equation with a source term is considered

     

Ultrastructural characterization of the hemocytes of Culex quinquefasciatus (DIPTERA: Culicidae)

Six hemocytes cell types from Culex quinquefasciatus were identified by light and transmission electron microscopy: They are prohemocytes (9.3%), spherulocytes (1.6%), adipohemocytes (0.8%), oenocytoids (4.6%), plasmatocytes (43.4%) and granulocytes (40.3%). The prohemocytes were the smallest hemocytes encountered in the hemolymph, displaying a large and centrally located nucleus, almost filling the whole cell. The spherulocytes, which were small hemocytes, presented small and numerous spherules with a lamellar pattern and an electron-dense core. Rare adipohemocytes were observed in the C. quinquefasciatus hemolymph, presenting large nucleus with an evident nucleolus, cytoplasm containing rough endoplasmic reticulum (RER), mitochondriae and lipid inclusions. C. quinquefasciatus oenocytoids showed homogeneous cytoplasm with several granules, completely or partially filled with amorphous material. These cells showed abundant smooth endoplasmic reticulum (SER) and dense mitochondriae. By light microscopy analysis we identified two morphological types of plasmatocytes, granular and agranular. However, ultrastructural investigation revealed that the granular cells contained lipid inclusion between RER membranes, instead of membrane-bounded granules. The granulocytes presented a fusiform or circular profile and displayed a unique and very complex process of granules formation, including organization of polysomes inside vesicles that protrude from the Golgi system, synthesis of a proteinaceous material, condensation of the granule matrix and recycling of endoplasmic membranes. Intense endocytic pathways were also observed in the granulocytes.     

Extended analysis of the Ar VII spectrum in the vacuum ultraviolet region

The current status of the determination of corrections to the hyperfine splitting of the ground state in hydrogen is considered. Improved calculations are provided taking into account the most recent value for the proton charge radius. Comparing experimental data with predictions for the hyperfine splitting, the Zemach radius of the proton is deduced to be 1.045(16) fm. Employing exponential parametrizations for the electromagnetic form factors we determine the magnetic radius of the proton to be 0.778(29) fm. Both values are compared with the corresponding ones derived from the data obtained in electron-proton scattering experiments and the data extracted from a rescaled difference between the hyperfine splittings in hydrogen and muonium.     

TiF(4) varnish-A (19)F-NMR stability study and enamel reactivity evaluation

The aim of this study was to develop a titanium tetrafluoride (TiF(4)) varnish and evaluate the stability of the formulation and its reactivity with dental enamel. The varnish was prepared in a resinous matrix using ethanol 96% as solvent. Samples (n=45) were aged at 65 degrees C and 30% of relativity humidity (RE n degrees 01/05-ANVISA) and after 3, 6, 9 and 12 months, nine samples were removed for evaluation and compared with fresh samples. Chemical stability of TiF(4) varnish was determinate by (19)F-NMR and the reactivity of the formulation was quantified by formation of fluoride loosely (CaF(2)) and firmly bound (fluorapatite; FA) to enamel. For reactivity comparisons, a varnish without TiF(4) was used as control. The loss of soluble fluoride was about 0.9% after one year of storage. The values of the reactivity (mean+/-S.D.) of fresh, aged at 3, 6, 9 and 12 months and control samples were: CaF(2) (microg F/mm(2)): 89.3+/-27.5(a); 54.5+/-14.3(b); 51.2+/-29.8(b); 69.3+/-21.3(a); 48.0+/-27.4(b); 0.10+/-0.07(c), FA (microg F/g): 2477.5+/-1044.0(a); 2484.8+/-992.0(a); 2580.0+/-1383.9(a); 2517.2+/-929.9(a); 2121.0+/-1059.2(a); 330.0+/-180.0(b), respectively. Means followed by distinct letters were statistically different (p<0.05). After one year of storage, the formulation was chemically stable and the levels of FA were maintained. However there was an initial decrease in the ability to form CaF(2).     

Three-dimensional molecular packing of thin organic films of PTCDI-C8 determined by surface X-ray diffraction

We have determined the full molecular 3D packing of thin organic films of the archetypical organic n-type semiconductor N, N'-dioctyl-3,4:9,10-perylene tetracarboxylic diimide (PTCDI-C 8) by surface X-ray crystallography. We show that PTCDI-C 8 forms smooth layered films on Al 2O 3 (11-20) with an outstanding degree of molecular order. The thin-film structure is found to consist of a triclinic unit cell with the plane of the aromatic core tilted by 67 +/- 2 degrees with respect to the surface plane, which differs significantly from the bulk structure. The 3D crystallites extend with vertical coherent order across the entire film thickness.