An abstract transmission problem in a thin layer, I: Sharp estimates

We study an elliptic transmission problem in Banach spaces. The problem is considered on the juxtaposition of two intervals, one of which of small length δ, and models physical phenomena in media constituted by two parts with different physical characteristics. We obtain results of existence, uniqueness, maximal regularity and optimal dependence on the parameter δ for Lp solutions of the problem. The main tools of our approach are impedance and admittance operators (i.e. Dirichlet-to-Neumann and Neumann-to-Dirichlet operators) and H^∞ functional calculus for sectorial operators in Banach spaces.     

Studies of cavitation and ice nucleation in 'doubly-metastable' water: time-lapse photography and neutron diffraction

High-speed photographic studies and neutron diffraction measurements have been made of water under tension in a Berthelot tube. Liquid water was cooled below the normal ice-nucleation temperature and was in a doubly-metastable state prior to a collapse of the liquid state. This transition was accompanied by an exothermic heat release corresponding with the rapid production of a solid phase nucleated by cavitation. Photographic techniques have been used to observe the phase transition over short time scales in which a solidification front is observed to propagate through the sample. Significantly, other images at a shorter time interval reveal the prior formation of cavitation bubbles at the beginning of the process. The ice-nucleation process is explained in terms of a mechanism involving hydrodynamically-induced changes in tension in supercooled water in the near vicinity of an expanding cavitation bubble. Previous explanations have attributed the nucleation of the solid phase to the production of high positive pressures. Corresponding results are presented which show the initial neutron diffraction pattern after ice-nucleation. The observed pattern does not exhibit the usual crystalline pattern of hexagonal ice [I(h)] that is formed under ambient conditions, but indicates the presence of other ice forms. The composite features can be attributed to a mixture of amorphous ice, ice-I(h)/I(c) and the high-pressure form, ice-III, and the diffraction pattern continues to evolve over a time period of about an hour.     

The structure of liquid deuterium bromide by slow-neutron scattering

Neutron diffraction measurements at 0·7 Å are reported for coexisting liquid deuterium bromide at -40°C. The results show that the deuterium bromide molecule in the liquid is little distorted as compared with the free molecule. The presence of a peak in the intermolecular pair distribution function at 3·1 Å is thought to be evidence of the formation of weak, rather long, intermolecular hydrogen bonds. As expected, both these effects are much weaker than for deuterium chloride reported in an earlier paper [2] and liquid deuterium bromide is therefore a simpler polar liquid.     

High-temperature laser annealing for thin film polycrystalline silicon solar cell on glass substrate

Thin film polycrystalline silicon films grown on glass substrate were irradiated with an infrared continuous wave laser for defects annealing and/or dopants activation. The samples were uniformly scanned using an attachment with the laser system. Substrate temperature, scan speed and laser power were varied to find suitable laser annealing conditions. The Raman spectroscopy and Suns-V _oc analysis were carried out to qualify the films quality after laser annealing. A maximum enhancement of the open circuit voltage V _oc of about 100?mV is obtained after laser annealing of as-grown polysilicon structures. A strong correlation was found between the full width half maximum of the Si crystalline peak and V _oc. It is interpreted as due to defects annealing as well as to dopants activation in the absorbing silicon layer. The maximum V _oc reached is 485?mV after laser treatment and plasma hydrogenation, thanks to defects passivation.     

First- and second-order Raman scattering from MoTe<Subscript>2</Subscript> single crystal

We report on Raman experiments performed on a MoTe₂ single crystal. The system belongs to the wide family of transition metal dichalcogenides which includes several of the most interesting two-dimensional materials for both basic and applied physics. Measurements were performed in the standard basal plane configuration, by placing the ab plane of the crystal perpendicular to the wave vector k _i of the incident beam to explore the in-plane vibrational modes, and in the edge plane configuration with k _i perpendicular to the crystal c axis, thus mainly exciting out-of-plane modes. For both configurations we performed a polarization-dependent study of the first-order Raman components and detailed computation of the corresponding selection rules. We were thus able to provide a complete assignment of the observed first-order Raman peaks, in agreement with previous literature results. A thorough analysis of the second-order Raman bands, as observed in both basal and edge plane configurations, provides new information and allows a precise assignment of these spectral structures. In particular, we have observed and assigned Raman active modes of the M point of the Brillouin zone previously predicted by ab initio calculations but never previously measured.     

Future contributions to Journal of Chemical Crystallography

Future contributions to Journal of Chemical Crystallography     

A partial wave analysis of thef′ region in the reactionK^ - p \to K\bar K\Lambda ^0 at 8.25 GeV/c

A partial wave analysis of theK \(\bar K\) system produced by 8.25 GeV/cK ^? mesons in the reaction \(K^ - p \to K\bar K\Lambda ^{ 0} \) has been performed, taking into account the information provided by the Λ⁰ decay. Thef′ region is dominated byD ₀ ^(?) andD ₁ ⁽⁺⁾ waves. We see no evidence for the production of new 0⁺⁺ states in the mass region 1.05 to 1.75 GeV.     

Light-mediated inhibition of protein synthesis

The regulation of protein synthesis is vital for a host of cell biological processes, but investigating roles for protein synthesis have been hindered by the inability to selectively interfere with it. To inhibit protein synthesis with spatial and temporal control, we have developed a photo-releasable anisomycin compound, N-([6-bromo-7-hydroxycoumarin-4-yl]methyloxycarbonyl)anisomycin (Bhc-Aniso), that can be removed through exposure to UV light. The area of protein synthesis inhibition can be restricted to a small light-exposed region or, potentially, the volume of two-photon excitation if a pulsed IR laser is the light source. We have tested the compound's effectiveness with an in vitro protein-translation system, CHO cells, HEK293 cells, and neurons. The photo-released anisomycin can inhibit protein synthesis in a spatially restricted manner, which will enable the specific inhibition of protein synthesis in subsets of cells with temporal and spatial precision.     

(Chloromethyl)pentacarbonylmanganese(I): a crystal structure with a non-crystallographic centre of symmetry

There are two molecules in the asymmetric unit of the P2₁/c unit cell of ClCH₂Mn(CO)₅, the first halomethyl complex of manganese to be structurally determined. The molecules are crystallographically independent, despite an apparent local centre of symmetry. The average bond parameters include Mn–C_alkyl 2.128(8) Å, C–Cl 1.811(8) Å and Mn–C–Cl 116.4(4)°.     

Molecular structure of tetrapropylammonium-2,3-dichloro-5,6-dicyano-p-benzoquinone compared toM + TCNQ− (M +=Rb+, K+, Cs+, or organic cations; TCNQ−=tetracyanoquinomethane) charge-transfer complexes

The crystal and molecular structure of tetrapropylammonium-2,3-dichloro-5,6-dicyano-p-benzoquinone (TPA⁺ DDQ^–) has been determined from single-crystal X-ray diffraction analysis. The crystals are monoclinic, space groupP2₁/n, witha=13.297(5),b=12.851(4),c=13.099(5) Å,=101.34(2)°, andZ=4. The compound consists of discrete (DDQ) ₂ ^2– anion dimers and two TPA⁺ cations inserted between the (DDQ) ₂ ^2– dimers, with an infinite stack running along b of the type (DDQ) ₂ ^2– [(C₃H₇)₄N⁺] (DDQ) ₂ ^2– 2[(C₃H₇)₄N⁺]The (DDQ) ₂ ^2– anion is formed by two DDQ^– anions dimerized through a crystallographic center of symmetry; each DDQ^– moiety is nearly planar and exhibits molecular dimensions similar to those found in analogous compounds. The comparison between the (DDQ) ₂ ^2– anion and a neutral DDQ molecule clearly shows that bond lengths are markedly influenced by the 2-anionic charge. Tetrapropylammomum cation assumes a distorted tetrahedral configuration as observed in TEA⁺ DDQ^– (TEA⁺=tetraethylammonium cation). The data are discussed in connection with the electrical conductivity of organic metals.