Low-energy muon-transfer reaction from hydrogen isotopes to helium isotopes

Direct muon transfer in low-energy collisions of the muonic hydrogen H-mu and helium (He++) is considered in a three-body quantum-mechanical framework of coordinate-space integro-differential Faddeev-Hahn-type equations within two- and six-state close coupling approximations. The final-state Coulomb interaction is treated without any approximation employing appropriate Coulomb waves in the final state. This procedure of treating Coulomb interaction leads to much improved results for low-energy transfer rates. The present results agree reasonably well with previous semiclassical calculations. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Symmetry analysis of an integrable reaction-diffusion equation

In this paper, we investigate the invariance and integrability properties of an integrable two-component reaction-diffusion equation. We perform Painleve analysis for both the reaction-diffusion equation modelled by a coupled nonlinear partial differential equations and its general similarity reduced ordinary differential equation and confirm its integrability. Further, we perform Lie symmetry analysis for this model. Interestingly our investigations reveals a rich variety of particular solutions, which have not been reported in the literature, for this model. (C) 2000 Elsevier B.V. Ltd. All rights reserved.

The generator coordinate method for a reaction coordinate coupled to a harmonic oscillator bath

This paper investigates the usefulness of the generator coordinate method (GCM) for treating the dynamics of a reaction coordinate coupled to a bath of harmonic degrees of freedom. Models for the unimolecular dissociation and isomerization process (proton transfer) are analyzed. The GCM results, presented in analytical form, provide a very good description and are compared to other methods Like the basis set method and multiconfiguration time dependent self-consistent field. (C) 1998 American Institute of Physics. [S0021-9606(98)50934-8].

Black-hole back-reaction - a toy model

Using a kink of arbitrary shape as a toy model for a black hole ( horizon), we study the back-reaction of the evaporation process and find that the horizon is always pushed back ( as in the gravitational case). The associated heat capacity and entropy variation, on the other hand, can be positive or negative, depending on the parameters.

The reaction (p)over-barp -> (Lambda)over-bar(c)(-)Lambda(+)(c) close to threshold

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Charmed meson rescattering in the reaction pd -> DDN

We examine possibility to extract information about the DN and DN interactious from the pd -> D(0)D(-)p reaction. We utilize the notion that the open-charm mesons are first produced hi the annihilation of the antiproton on one nucleon in the deuteron and subsequently rescatter oil the other (the spectator) nucleon. The latter process is then exploited for investigating the DN and DN interaction.,;. We study different methods for isolating the contributions from the D(0)p and D(-)p rescattering terms.

X-ray diffraction and mossbauer spectra of nickel ferrite prepared by combustion reaction

Nickel ferrite powders with a nominal NiFe2O4 composition were synthesized by combustion reaction using urea as fuel. The powder was obtained using a vitreous silica basin heated directly on a hot plate at 480 degrees C until self-ignition occurred. After combustion, the powder was calcined at 700 degrees C for 2 h. The formation of the spinel phase and the distribution of cations in the tetrahedral and octahedral sites of the crystal structure were investigated by the Rietveld method, using synchrotron X-ray diffraction data and Mossbauer spectroscopy. The material presented a crystallite size of 120 nm and magnetic properties. The resulting stoichiometry after the Rietveld refinement was (Fe-0.989(2) Ni-0.011(2)) [Fe-1.012(2) Ni-0.989(2)] O-4.

Precipitation reaction in alpha-Cu-Al-Ag alloys

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

Reaction pathway to the synthesis of anatase via the chemical modification of titanium isopropoxide with acetic acid

Anatase nanoparticles were obtained through a modified sol-gel route from titanium isopropoxide modified with acetic acid in order to control hydrolysis and condensation reactions. The modification of Ti(O(i)Pr)(4) with acetic acid reduces the availability of groups that hydrolyze and condense easily through the formation of a stable complex whose structure was determined to be Ti(OCOCH(3))(O(i)Pr)(2) by means of FTIR and (13)C NMR. The presence of this complex was confirmed with FTIR in the early stages of the process. A doublet in 1542 and 1440 cm(-1) stands for the asymmetric and symmetric stretching vibrations of the carboxylic group coordinated to Ti as a bidentate ligand. The gap of 102 cm(-1) between these signals suggests that acetate acts preferentially as a bidentate rather than as a bridging ligand between two titanium atoms. The use of acetic acid as modifier allows the control of both the degree of condensation and oligomerization of the precursor and leads to the preferential crystallization of TiO(2) in the anatase phase. A possible reaction pathway toward the formation of anatase is proposed on the basis of the intermediate species present in a 1:1 Ti(O(i)Pr)(4):CH(3)COOH molar system in which esterification reactions that introduce H(2)O into the reaction mixture were seen to be negligible. The Rietveld refinement and TEM analysis revealed that the powder is composed of isotropic anatase nanocrystallites.

Activation energy for the reverse eutectoid reaction in hypo-eutectoid Cu-Al alloys

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

Pearlitic reaction in Cu-10wt%Al alloy with Ag additions

The pearlitic reaction in Cu-10wt%Al alloy with additions of 4, 6, 8, and 10wt%Ag was studied using scanning electron microscopy, energy dispersive X-ray microanalysis, in situ X-ray diffractometry, and microhardness measurements. The results indicated that the presence of Ag changes the pearlitic phase microstructure and its mechanical properties, because of the influence of Ag in the pearlitic phase growth mechanism. (C) 2008 International Centre for Diffraction Data.

Influence of Ag additions on the activation energy for the reverse eutectoid reaction in Cu-Al alloys

The eutectoid transformation may be defined as a solid-state diffusion-controlled decomposition process of a high-temperature phase into a two-phase lamellar aggregate behind a migrating boundary on cooling below the eutectoid temperature. In substitutional solid solutions, the eutectoid reaction involves diffusion of the solute atoms either through the matrix or along the boundaries or ledges. The effect of Ag on the non-isothermal kinetics of the reverse eutectoid reaction in the Cu-9 mass%Al, Cu-10 mass%Al, and Cu-11 mass%Al alloys were studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The activation energy for this reaction was obtained using the Kissinger and Ozawa methods. The results indicated that Ag additions to Cu-Al alloys interfere on the reverse eutectoid reaction, increasing the activation energy values for the Cu-9 mass%Al and Cu-10 mass%Al alloys and decreasing these values for the Cu-11 mass%Al alloy for additions up to 6 mass%Ag. The changes in the activation energy were attributed to changes in the reaction solute and in Ag solubility due to the increase in Al content.

Double-Tagging Polymerase Chain Reaction with a Thiolated Primer and Electrochemical Genosensing based on Gold Nanocomposite Sensor for Food Safety

A novel material for electrochemical biosensing based on rigid conducting gold nanocomposite (nano-AuGEC) is presented. Islands of chemisorbing material (gold nanoparticles) surrounded by nonreactive, rigid, and conducting graphite epoxy composite are thus achieved to avoid the stringent control of surface coverage parameters required during immobilization of thiolated oligos in continuous gold surfaces. The spatial resolution of the immobilized thiolated DNA was easily controlled by merely varying the percentage of gold nanoparticles in the composition of the composite. As low as 9 fmol (60 pM) of synthetic DNA were detected in hybridization experiments when using a thiolated probe. Moreover, for the first time a double tagging PCR strategy was performed with a thiolated primer for the detection of Salmonella sp., one of the most important foodborne pathogens affecting food safety. Ibis assay was performed by double-labeling the amplicon during the PCR with a -DIG and -SH set of labeled primers. The thiolated end allows the immobilization of the amplicon on the nano-AuGEC electrode, while digoxigenin allows the electrochemical detection with the antiDIG-HRP reporter in the femtomole range. Rigid conducting gold nanocomposite represents a good material for the improved and oriented immobilization of biomolecules with excellent transducing properties for the construction of a wide range of electrochemical biosensors such as immunosensors, genosensors, and enzymosensors.