On the chiral covariant approach to ρρ scattering

We examine in detail a recent work(D. Gülmez, U. G. Mei?ner and J. A. Oller, Eur. Phys. J. C,77: 460(2017)), where improvements to make ρρ scattering relativistically covariant are made. The paper has the remarkable conclusion that the J =2 state disappears with a potential which is much more attractive than for J =0,where a bound state is found. We trace this abnormal conclusion to the fact that an "on-shell" factorization of the potential is done in a region where this potential is singular and develops a large discontinuous and unphysical imaginary part. A method is developed, evaluating the loops with full ρ propagators, and we show that they do not develop singularities and do not have an imaginary part below threshold. With this result for the loops we define an effective potential, which when used with the Bethe-Salpeter equation provides a state with J =2 around the energy of the f_2(1270). In addition, the coupling of the state to ρρ is evaluated and we find that this coupling and the T matrix around the energy of the bound state are remarkably similar to those obtained with a drastic approximation used previously, in which the q~2 terms of the propagators of the exchanged ρ mesons are dropped, once the cut-off in the ρρ loop function is tuned to reproduce the bound state at the same energy.     

Preferential sites for InAsP/InP quantum wire nucleation using molecular dynamics

In this paper, stress fields at the surface of the capping layer of self-assembled InAsP quantum wires grown on an InP (001) substrate have been determined from atomistic models using molecular dynamics and Stillinger-Weber potentials. To carry out these calculations, the quantum wire compositional distribution was extracted from previous works, where the As and P distributions were determined by electron energy loss spectroscopy and high-resolution aberration-corrected Z-contrast imaging. Preferential sites for the nucleation of wires on the surface of the capping layer were studied and compared with (i) previous simulations using finite element analysis to solve anisotropic elastic theory equations and (ii) experimentally measured locations of stacked wires. Preferential nucleation sites of stacked wires were determined by the maximum stress location at the MD model surface in good agreement with experimental results and those derived from finite element analysis. This indicates that MD simulations based on empirical potentials provide a suitable and flexible tool to study strain dependent atom processes.     

Mass transport at electrodes of arbitrary geometry. Reversible charge transfer reactions in square wave voltammetry

The basis for mass transport of the electroactive species in different diffusion fields is examined, pointing out important insights in relation to the value of the surface concentrations for the case of fast electrode processes. Moreover, a general analytical solution for the transient current is given for several geometries, when an arbitrary sequence of potentials pulses is applied to macroelectrodes (planar), spheres, cylinders, discs and bands. The results are particularized for Square Wave Voltammetry. Explicit solutions for the net current and the forward and backward components are given. The effects of frequency, pulse amplitude and electrode size or shape on the peak current are studied. Moreover, the conditions for the attainment of the steady state response are analyzed in the different geometries as well as the characteristics of this response.     

Two-sex Branching Models with Random Control on the Number of Progenitor Couples

In this paper we introduce a class of two-sex branching models where, in each generation, a random control on the number of progenitor couples in the population is considered. For such a class, several probabilistic results are established. Also assuming offspring probability distribution belonging to the bivariate power series family, Bayes estimators for the mean vector and the covariance matrix of the offspring distribution are proposed. A computational method to determine highest posterior density credibility sets is stated. As illustration, a simulated example is provided.     

Direct determination of 1-naphthoxylactic acid in biological fluids by non-protected fluid room temperature phosphorimetry

A selective and sensitive room-temperature phosphorimetric method for the direct determination of 1-naphthoxylactic acid (NA) in biological fluids is described. It is based on obtaining a phosphorescence signal from NA using TlNO₃ as a heavy atom perturber and Na₂SO₃ as a deoxygenator without a protective medium. This technique is named non-protected room-temperature phosphorescence (NP-RTP), which allows to determine analytes in complex matrices without the need for tedious prior separation. Optimization of the operational conditions resulted in a detection limit for NA of 9.6 ng/mL according to the error propagation theory. The repeatability and standard deviation were also determined. This method was successfully applied to the determination of NA in urine and human serum.     

On Pitt’s Theorem for Operators between Scalar and Vector-Valued Quasi-Banach Sequence Spaces

 We find natural conditions under which all continuous linear operators between two scalar or vector-valued quasi-Banach sequence spaces are compact. In the case of scalar-valued Banach sequence spaces we show that all such operators essentially factorize through diagonal operators between suitable -spaces. (Received 21 June 1999; in revised form 27 September 1999)     

Temperature dependence of OH uptake by carbonaceous surfaces of atmospheric importance

Although OH uptake by carbonaceous surfaces is very efficient, it is thought to be negligible to affect the OH and O₃ balance in the lower troposphere. To estimate its contribution in the upper troposphere, we have studied the temperature dependence of OH uptake by carbonaceous surfaces of atmospheric importance over the temperature range from 218 to 298 K. We found that the OH uptake coefficient is weakly dependent of temperature, ranging from 0.1 to 1, as was measured under flow conditions using chemical ionization mass spectrometry. This finding was further used to estimate OH loss on carbonaceous aerosol under upper tropospheric conditions. Our calculations suggested that OH heterogeneous loss may represent a notable sink for OH in the upper troposphere, which is due to both the significantly lower diffusion limitation and weakly temperature-dependent OH uptake. The obtained results may be thus important for aerosol chemistry of the upper troposphere.     

Fused Mesoionic Heterocycles: Synthesis of 1,2,4-triazolo(4,3-b)-1,2,4-triazole derivatives

A number of mesoionic compounds derivatives of the bicyclic system 1,2,4-triazolo(4,3-b)-1,2,4-triazole have been prepared from 4-amino-1-methyl-3,5-bis(methylthio)-1,2,4-triazolium iodide and aryl isothiocyanates.     

Synthesis of bridgehead nitrogen heterocycles from pyrylium salts and β-functionalized amines

β-Functionalized primary amines are converted by the 2-ethoxycarbonyl-4,6-diphenylpyrylium cation into the corresponding bicyclic salts 2 . The N-substituted 4,6-diphenylpyridine-2-thiones 6 undergo cyclization to the byciclic compounds 8 by action of methyl iodide.