Surprising sun: a new step towards a complete picture?

Important revisions of the solar model ingredients have appeared recently. We first show that the updated CNO composition suppresses the anomalous position of the Sun in the known galactic enrichment. The following law, He/H = 0.075 + 44.6 O/H in number fraction, is now compatible with all the indicators. We then suggest some directions of investigation to solve the discrepancies between the standard model and solar seismic observations. We finally update our predicted neutrino fluxes using a seismic model and all the recent progress. We get 5.31 +/- 0.6 x 10(6)/cm2/s for the total 8B neutrinos, 66.5 +/- 4.4 SNU and 2.76 +/- 0.4 SNU for the gallium and chlorine detectors, all in remarkable agreement with the detected values including neutrino oscillations for the last two. So, the acoustic modes and detected neutrinos see the same Sun, but the standard model fails to reproduce them.     

Use of ultrasonic energy for intensification of the bio-preparation of greige cotton

Raw unscoured cotton contains approximately 90% cellulose and various noncellulosic impurities such as waxes, pectins, proteins, and fats. To remove these hydrophobic noncellulosics and produce a highly absorbent fiber that can be dyed and finished uniformly, the greige cotton is traditionally processed with relatively harsh and environmentally unfriendly chemicals. New bio-preparation processes that utilize highly specific enzymes instead of conventional organic/inorganic chemicals are becoming increasingly popular in the textile industry. The major shortcoming of this new technology is that the processing time is much longer than the conventional method. This limitation was overcome by use of ultrasound energy in combination with enzyme processing. The combined enzyme/ultrasound bio-preparation of greige cotton offers significant advantages such as less consumption of expensive enzymes, shorter processing time, better uniformity of treatment and a notable decrease in the amount and toxicity of the resulting textile wastewater effluents.     

The unexpected motional isotropy of the tin atom in a tricoordinate stannylium cation

The dynamics of the metal atom in the recently isolated tricoordinate tin complex tris(2,4,6-triisopropylphenyl)stannylium tetrakis(pentafluorophenyl)borate was examined by temperature-dependent (119)Sn M?ssbauer spectroscopy over the temperature range 90 K < T < 170 K. Contrary to expectation, the metal atom motion in this temperature range is isotropic within experimental error of the M?ssbauer data, and is only moderately anisotropic, even at 293 K, as evidenced by single crystal X-ray diffraction data. The hyperfine parameters at 90 K are completely consistent with trigonal coordination involving sp(2) hybridization of the 5s5p bonding orbitals of tin.     

Conductance oscillations in zigzag platinum chains

Using first principles simulations we perform a detailed study of the structural, electronic, and transport properties of monatomic platinum chains, sandwiched between platinum electrodes. First, we demonstrate that the most stable atomic configuration corresponds to a zigzag arrangement that gradually straightens as the chains are stretched. Second, we find that the averaged conductance shows slight parity oscillations with the number of atoms in the chain. Additionally, the conductance of chains of fixed oscillates as the end atoms are pulled apart, due to the gradual closing and opening of conductance channels as the chain straightens.     

A free,tricoordinate stannylium cation

Tris(2,4,6-triisopropylphenyl)stannylium tetrakis(pentafluorophenyl)borate constitutes a free, tricoordinate tin cation according to its X-ray structure. There is no coordination between the cation and either solvent or anion, and there are no atoms at apical positions. DFT calculations confirm the structure and indicate that there is no agostic bonding between the ortho isopropyl methinyl hydrogens and the Sn atom. Calculation of the 119Sn chemical shift is in good agreement with the observed value.     

Polyoxometalate-catalysed epoxidation of 1-octene with hydrogen peroxide in microemulsions coupled with ultrafiltration

Epoxidation of 1-octene with hydrogen peroxide catalysed by amphiphilic salts of peroxo tungstophosphate [PO4[WO(O2)2]4]3- in water-in-oil microemulsions is an efficient and environmentally benign reaction which, coupled with ultrafiltration, shows the potential for continuous production of epoxides.     

4,6,8,10,16-penta- and 4,6,8,10,16,18-hexamethyldocosanes from the cane beetle antitrogusparvulus--cuticular hydrocarbons with unprecedented structure and stereochemistry

The major cuticular hydrocarbons from the cane beetle species Antitrogus parvulus were deduced to be 4,6,8,10,16,18-hexa- and 4,6,8,10,16-pentamethyldocosanes 2 and 3, respectively. Isomers of 2,4,6,8-tetramethylundecanal 27, 36, and 37, derived from 2,4,6-trimethylphenol, were coupled with the phosphoranes 28 and 29 to furnish alkenes and, by reduction, diastereomers of 2 and 3. Chromatographic and spectroscopic comparisons confirmed 2 as either 6a or 6b and 3 as either 34a or 34b. [structure: see text]     

Halichondrin B: synthesis of a C1-C14 model via desymmetrization of (+)-conduritol E

[reaction: see text] A model C1-C14 segment (1) of halichondrin B was synthesized from (+)-conduritol E (7) in 18 steps and 2.9% overall yield. Key features of the synthesis include the novel ozonolytic desymmetrization of C(2)-symmetric diol 6, the early-stage construction of the C-ring which accompanies installation of the crucial C12 stereocenter, and the use of an enol ether C14-ketone surrogate as a precursor to the CDE-"caged" ketal.     

A structural and kinetic study of chlorine and silver chloride on Ag(100): The transition from overlayer to bulk halide

Adsorption of chlorine on Ag(100) at 298 K leads to the formation of a chemisorbed over layer of Cl atoms with Δφ = 1.4 eV and exhibiting a sharp c(2 × 2) LEED pattern. This layer is impervious to electron stimulated desorption (ESD). At 430 K (well below the desorption temperature) Δφ decreases quite rapidly to +0.9 eV, the LEED pattern deteriorates and ESD is observed. The temperature dependence of the ($\text{1}\text{2}$, $\text{1}\text{2}$) LEED beam indicates that an irreversible change in surface Debye temperature has occurred. On raising the temperature further, evaporation of the adiayer occurs with AgCl as the sole desorption product. These results suggest that an overlayer → silver chloride transition has occurred, a conclusion which is supported by studying the properties of AgCl dosed surfaces. Chlorine dosing never leads to halide growth beyond the monolayer stage. Multilayer growth of AgCl is investigated by dosing with AgCl(g). It is found that the desorption spectra evolve in an unusual way and the observed energetics of AgCl evaporation are accounted for in terms of the reduced lattice energy of small adsorbed crystallites. LEED shows that these crystallites re-orient from (100) to (111) as their size increases.