Partial data inverse problems for Maxwell equations via Carleman estimates

In this article we consider an inverse boundary value problem for the time-harmonic Maxwell equations. We show that the electromagnetic material parameters are determined by boundary measurements where part of the boundary data is measured on a possibly very small set. This is an extension of earlier scalar results of Bukhgeim–Uhlmann and Kenig–Sjöstrand–Uhlmann to the Maxwell system. The main contribution is to show that the Carleman estimate approach to scalar partial data inverse problems introduced in those works can be carried over to the Maxwell system.     

Evidence for JPC=4++ for the S(1930) meson from p̄p backward elastic scattering

We report on partial results of the analysis of a p?p backward elastic scattering experiment, between 175 and 750 MeV/c. Various evidences are given of the resonant nature of a backward peak at the S-meson mass. Analysis leads to J^PC=4⁺⁺, firmly connected to other experimental data with I^G=1^?. All results agree for an assignment to the A₂ trajectory.     

Exchange of organometallic compounds with mercury metal : VII. Interaction of di-p-anisylthallium chloride with mercury in pyridine,ethylenediamine and dimethyl sulfoxide; prevailing role of homogeneous reaction

Kinetic study of the interaction of di-p-anisylthallium chloride with mercury metal, in pyridine, ethylenediamine, or dimethyl sulfoxide solutions, show that in the former two solvents with the following experimental conditions: solution volume 10 ml, mercury surface area 10 cm², 60°C, and without stirring of mercury, the Hg/Tl exchange occurs via the homogeneous reaction (80–90 percent) with dissolved mercury. In DMSO, under the same experimental conditions, the contribution of the homogeneous reaction is nearly the same as that of the heterogeneous one. This was determined by the study of the experimental exchange rate dependence on organic phase volume, and mercury or di-p-anisylthallium chloride solubilities in the solvents, as well as from analysis of kinetic curves for the exchange in saturated and unsaturated solutions of mercury metal in the solvents studied.In the same reactor (polarographic cell) the Hg/Hg exchange of organomercurials with Hg metal may be thought to occur via a heterogeneous reaction as the prevalent process. The difference in behaviour between organothallium and organomercury compounds may be explained by the far lower adsorbance of organothallium compounds when compared with the respective organomercury compounds. The possible mechanism of the Hg/Tl exchange involving organobimetallic intermediates is proposed.     

Conformation of the galactose ring adopted in solution and in crystalline form as determined by experimental and DFT 1H NMR and single-crystal X-ray analysis

The solution-state conformations of various galactose derivatives were determined by comparison of the experimental (1)H-(1)H vicinal coupling constants to those calculated using density functional theory (DFT) at the B3LYP/cc-pVTZ//B3LYP/6-31G(d,p) level of theory. The agreement between the experimental and calculated vicinal coupling constants for 1,2:3,4-di-O-isopropylidene-alpha-d-galactopyranose was good, thereby confirming an (O)S(2) skew conformation for it and its derivatives on the basis of their similar observed couplings. Single-crystal X-ray analysis of 1,2:3,4-di-O-isopropylidene-6-O-(3,4,6-tri-O-acetyl-2-deoxy-2-N-phthalimido-beta-d-glucopyranosyl)-alpha-d-galactopyranose and 1,2,3,4,6-penta-O-acetyl-alpha-d-galactopyranose provided (O)S(2) and (4)C(1) conformations, respectively, for the galactose ring in the solid state. The solid-state structures proved to be suitable starting structures for further DFT structure refinement or for immediate calculation of the coupling constants.     

The effect of poly(ethylene glycol) on the activity and structure of glucose-6-phosphate dehydrogenase in solution

The effect of poly(ethylene glycol), PEG, on the enzymatic activity of glucose-6-phosphate dehydrogenase (G-6-PDH) in the oxidation of glucose-6-phosphate (G-6-P), using NADP+ as co-enzyme was investigated. The enzymatic activity was determined by means of spectrophotometry in three different media: pure Tris–HCl buffer, solution of PEG400 (20 wt.%) and of PEG4000 (20 wt.%), both in buffer. Comparing the enzymatic activity values measured in pure buffer with those in the polymer solutions, an increase in the enzymatic activity of 20% was observed in the presence of PEG400 as well as in PEG4000. Calorimetric studies indicated the absence of preferential interactions between G-6-PDH and PEG400 or PEG4000. Nevertheless, the interaction enthalpy, ΔH_int, between NADP+ and PEG400 and PEG4000 amounted to −9.3 and −26.7 kJ/mol, respectively. Small angle X-ray scattering (SAXS) measurements were performed in a higher concentration range. Data analysis performed from SAXS curves by means of the intra-particle distance distribution function p(r) and Guinier plots yielded for G-6-PDH in pure buffer and PEG400 solutions radius of gyration, R_g, of about 70 Å and in PEG4000 solutions, R_g of about 40 Å. The latter has the same dimension as that found in the dimeric crystallographic structure of G-6-PDH, evidencing that G-6-PDH preserves its dimeric configuration in PEG4000 solution. On the contrary, different aggregates of G-6-PDH are formed in the presence of either buffer or PEG400. These findings show that the presence of PEG in solution can exert an effect on the enzyme structure and activity.