Relativistic Description of 3He (e, e�� p)2H

The relativistic distorted-wave impulse approximation is used to describe the ³He(e, e?? p)²H process. We describe the ³He nucleus within the adiabatic hyperspherical expansion method with realistic nucleon-nucleon interactions. The overlap between the ³He and the deuteron wave functions can be accurately computed from a three-body calculation. The nucleons are described by solutions of the Dirac equation with scalar and vector (S?CV) potentials. The wave function of the outgoing proton is obtained by solving the Dirac equation with a S?CV optical potential fitted to elastic proton scattering data on the residual nucleus. Within this theoretical framework, we compute the cross section of the reaction and other observables like the transverse-longitudinal asymmetry, and compare them with the available experimental data measured at JLab.     

Free-Energy Bounds for Hierarchical Spin Models

In this paper we study two non-mean-field (NMF) spin models built on a hierarchical lattice: the hierarchical Edward–Anderson model (HEA) of a spin glass, and Dyson’s hierarchical model (DHM) of a ferromagnet. For the HEA, we prove the existence of the thermodynamic limit of the free energy and the replica-symmetry-breaking (RSB) free-energy bounds previously derived for the Sherrington–Kirkpatrick model of a spin glass. These RSB mean-field bounds are exact only if the order-parameter fluctuations (OPF) vanish: given that such fluctuations are not negligible in NMF models, we develop a novel strategy to tackle part of OPF in hierarchical models. The method is based on absorbing part of OPF of a block of spins into an effective Hamiltonian of the underlying spin blocks. We illustrate this method for DHM and show that, compared to the mean-field bound for the free energy, it provides a tighter NMF bound, with a critical temperature closer to the exact one. To extend this method to the HEA model, a suitable generalization of Griffith’s correlation inequalities for Ising ferromagnets is needed: since correlation inequalities for spin glasses are still an open topic, we leave the extension of this method to hierarchical spin glasses as a future perspective.     

Mean field bipartite spin models treated with mechanical techniques

Inspired by a continuously increasing interest in modeling and framing complex systems in a thermodynamic rationale, in this paper we continue our investigation in adapting well-known techniques (originally stemmed in fields of physics and mathematics far from the present) for solving for the free energy of mean field spin models in a statistical mechanics scenario. Focusing on the test cases of bipartite spin systems embedded with all the possible interactions (self and reciprocal), we show that both the fully interacting bipartite ferromagnet, as well as the spin glass counterpart, at least at the replica symmetric level, can be solved via the fundamental theorem of calculus, trough an analogy with the Hamilton-Jacobi theory and lastly with a mapping to a Fourier diffusion problem. All these technologies are shown symmetrically for ferromagnets and spin-glasses in full details and contribute as powerful tools in the investigation of complex systems.     

Synthesis and characterization of ternary hybrid material based on poly-o-methoxyaniline and poly(ethylene oxide) in mesostructured V<Subscript>2</Subscript>O<Subscript>5</Subscript>

New hybrid composites based on mesostructured V₂O₅ containing intercalated poly(ethylene oxide), poly-o-methoxyaniline and poly(ethylene oxide)/poly-o-methoxyaniline were prepared. The results suggest that the polymers were intercalated into the layers of the mesostructured V₂O₅. Electrochemical studies showed that the presence of both polymers in the mesostructured V₂O₅ (ternary hybrid) leads to an increase in total charge and stability after several cycles compared with binary hybrid composites. This fact makes this material a potential component as cathode for lithium ion intercalation and further, a promising candidate for applications in batteries.     

Analysis of models for the Ziegler-Natta stereospecific polymerization on the basis of non-bonded interactions at the catalytic site—I. The Cossee model

The model proposed by Cossee for Ziegler-Natta polymerization of propene is re-examined by computing the non-bonded energies for all sets of possible internal coordinates of the atoms at the catalytic site. For catalytic sites in the bulk of (110) surfaces of TiCl₃-α, it is possible to explain the regiospecificity of the reaction but, at variance with Cossee, we see no evidence that the surface conditions the methyl group of the olefin to protrude out of the crystal. The stereospecificity may arise however from the fixed, chiral orientation of the first carbon—carbon chain bond, due to interactions with the surface. Further computations seem to indicate that the polymerization could occur with much less steric hindrances on edges or reliefs of the surfaces, the relative positions of olefin and chain being exchanged in respect to the Cossee model.     

A new microbial assay for the toxicity detection of contaminated soils

A comparative study to detect toxicity prior to bioremediation treatment was set in order to investigate dehydrogenase activity inhibition of a common soil bacterium caused by soil contaminated with Cu, Pb, and As. A spectrophotometric test with Pseudomonas fluorescens strain ATCC 13525 utilising the 2,3,5-triphenyl tetrazolium chloride (TTC) reduction by microbial dehydrogenase has been adapted for this purpose. Soil samples are incubated for 48 hours at 30 +/- 1 degrees C in 18-ml tubes in the presence of TTC as an artificial electron-acceptor. The reduced TTC forms a reddish colour substance named triphenyl formazan (TPF), which can be extracted from the microbial cells and measured colorimetrically. The rapid response of biological activity in microorganisms and the reported sensitivity to the toxicants in the contaminated samples are reflected by the TTC reduction method, which is a sensitive tool for toxicity screening of contaminated sites, routine monitoring of bioremediation processes, as well as for feasibility studies of bioremediation treatments, in order to assess whether a specific pollutant or any other substance at a site location could inhibit the microbiological processes.     

Thin-layer chromatography of sulphonamides on silica gel G and polyamide layers by means of a polar mobile phase.

A thin-layer chromatographic system based on polyamide or silica gel G layers and an aqueous mobile phase was used for the separation of a series of sulphonamides. A linear relationship between RM values on polyamide layers and the acetone concentration in the mobile phase allowed the calculation of extrapolated RM values. The influence of the nature of the stationary phase on the migration of compounds is discussed.     

Model MDI/butanediol polyurethanes: Molecular structure,morphology, physical and mechanical properties

Model butanediol–MDI–polypropylene oxide polymers have been synthesized to explore the structure–property relationships in urethane/polyether polymers. The results of mechanical, thermal, and spectroscopic analyses agree remarkably well. The phase mixing in these polymers decreases with increasing hard-segment length, while the hard-segment stability increases with increasing hard-segment length. This is demonstrated clearly by dynamic mechanical, differential scanning calorimetry, infrared, and NMR studies. The importance of hydrogen bonding to the stability of the hard segment is strongly supported by the variable-temperature infrared experiments. The critical hard-segment size for phase segregation was shown to be two butanediols per hard segment. The temperature limit of the flatness of the storage modulus was tied to the thermal stability of the hard-segment hydrogen bonding which is controlled largely by the length of the hard segment and the extent of the hydrogen bonding.     

An MS Xα and ETS study of the influence of “d” orbitals on the electron affinities of thio-substituted benzenes

The electron transmission spectra of the o,o′-dimethyl substituted benzenes 2,6-(CH₃)₂C₆H₃-XR (X = O,S, NR: R = H, CH₃) show that the substituents adopt a planar (R = H) or rotated (R = CH₃) conformation depending upon their size and they suggest that in the sulphur derivatives the ²B₁ H anion states are stabilized by S3d orbital participation. MS Xα calculations performed on both the planar and orthogonal forms of the model systems p-(XH)₂-C₆H₄ (X = O, S) support this hypothesis and assign the extra resonance present in the ET spectra of the thio derivatives to electron capture into [ σ_S-R* MOS. strongly mixed with sulphur 3d orbitals ( = 33% d character).