Comparison of direct photon production in pp collisions at s= 30.6 GeV and 53.2 GeV

We present data obtained at the ISR, on the determination of the ratio $\text{R =}\text{γ}\text{π}{}^0\text{at}\text{s}\text{= 30.6}$ GeV and we compare the results with our previous measurement at $\text{s}\text{= 53.2}$ GeV. The ratio $\text{R =}\text{γ}\text{π}{}^0$ integrated over the interval 0.1 ? χ_T ? 0.2 is (1.6 ± 0.5) × 10^?2 and we obtain an indication of a universal χ_T dependence.     

Synthesis,asymmetric aldol reactions,and x‐ray crystallography of some oxadiazinanone derivatives

A series of N₄‐substituted oxadiazinanones have been synthesized from (1R,2S)‐norephedrine by a process of either reductive alkylation or arylation, N‐nitrosation, reduction and cyclization. These derivatives (R = ‐CH₂Ph, ‐CH₂C(CH₃)₃, ‐cyclo‐C₆H₁₁, ‐C₆H₅) have been acylated with propanoyl chloride and employed in the asymmetric Aldol reaction. The observed diastereoselectivities for the formation of the “non‐Evans” syn‐adduct ranged from 88:12 to 99:1. The hydrolysis of the Aldol adducts varied with the nature of the nitrogen substituent.     

Testing for nonlinear dependence in financial markets

This article addresses the question of improving the detection of nonlinear dependence by means of recently developed nonparametric tests. To this end a generalized version of BDS test and a new test based on symbolic dynamics are used on realizations from a well-known artificial market for which the dynamic equation governing the market is known. Comparisons with other tests for detecting nonlinearity are also provided. We show that the test based on symbolic dynamics outperforms other tests with the advantage that it depends only on one free parameter, namely the embedding dimension. This does not hold for other tests for nonlinearity.     

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.     

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.     

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.     

(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.     

The structural characteristics of amorphous D2O ice by neutron diffraction

Neutron diffraction measurements have been made at several wavelengths for vapor-deposited D₂O ice at 10 K. The observed structure factor exhibits more oscillatory features than corresponding measurements on liquid D₂O water, indicating an ammorphous phase which has strong intermolecular spatial correlations. A detailed examination of the data shows that this is strongly influenced by hydrogen-bonding effects and that the local environment for each molecule is very similar to that in crystalline ice. The predictions of Boutron and Alben, based on a continuous random network model, are found to be in excellent agreement with the data.