The local structure of OH species on the V2O3(0 0 0 1) surface: a scanned-energy mode photoelectron diffraction study

Scanned-energy mode photoelectron diffraction (PhD), using O 1s photoemission, together with multiple-scattering simulations, have been used to investigate the structure of the hydroxyl species, OH, adsorbed on a V2O3(0 0 0 1) surface. Surface OH species were obtained by two alternative methods; reaction with molecular water and exposure to atomic H resulted in closely similar PhD spectra. Both qualitative assessment and the results of multiple-scattering calculations are consistent with a model in which only the O atoms of outermost layer of the oxide surface are hydroxylated. These results specifically exclude significant coverage of OH species atop the outermost V atoms, i.e. in vanadyl O atom sites. Ab initio density-functional theory cluster calculations provide partial rationalisation of this result, which is discussed the context of the general understanding of this system

Choline, an essential nutrient for humans

Choline is required to make essential membrane phospholipids. It is a precursor for the biosynthesis of the neurotransmitter acetylcholine and also is an important source of labile methyl groups. Mammals fed a choline-deficient diet develop liver dysfunction; however, choline is not considered an essential nutrient in humans. Healthy male volunteers were hospitalized and fed a semisynthetic diet devoid of choline supplemented with 500 mg/day choline for 1 wk. Subjects were randomly divided into two groups, one that continued to receive choline (control), and the other that received no choline (deficient) for three additional wk. During the 5th wk of the study all subjects received choline. The semisynthetic diet contained adequate, but no excess, methionine. In the choline-deficient group, plasma choline and phosphatidylcholine concentrations decreased an average of 30% during the 3-wk period when a choline-deficient diet was ingested; plasma and erthrocyte phosphatidylcholine decreased 15%; no such changes occurred in the control group. In the choline-deficient group, serum alanine aminotransferase activity increased steadily from a mean of 0.42 μkat/liter to a mean of 0.62 μkat/liter during the 3-wk period when a choline-deficient diet was ingested; no such change occurred in the control group. Other tests of liver and renal function were unchanged in both groups during the study. Serum cholesterol decreased an average of 15% in the deficient group and did not change in the control group. Healthy humans consuming a choline-deficient diet for 3 wk had depleted stores of choline in tissues and developed signs of incipient liver dysfunction. Our observations support the conclusion and choline is an essential nutrient for humans when excess methionine and folate are not available in the diet

Hot Quarks and Gluons at an Electron-Ion Collider

The nuclear wave-function is dominated at low- and medium-x by gluons. As the rapid growth of the gluon distribution towards low x, as derived from current theoretical estimates, would violate unitarity, there must be a mechanism that tames this explosive growth. This is most efficiently studied in colliders running in e+A mode, as the nucleus is an efficient amplifier of saturation effects occurring with high gluon densities. In fact, large A can lead to these effects manifesting themselves at energies a few orders of magnitude lower than in e+p collisions. In order to study these effects, there are proposals to build an e+A machine in the USA, operating over a large range of masses and energies. These studies will allow for an in-depth comparison to A+A collisions where results have given tantalising hints of a new state of matter with partonic degrees of freedom. In order to explain these results quantitively, the gluons and their interactions must be understood fully as they are the dominant source of hard probes at both RHIC and LHC energies.Comment: Proceedings of Hot Quarks 2008 - submitted to EPJ

Quantitative local structure determination of R,R-tartaric acid on Cu(110): Monotartrate and bitartrate phases

The local adsorption site of the monotartrate and bitartrate species of R,R-tartaric acid deposited on Cu(110) have been determined by scanned-energy mode photoelectron diffraction (PhD). In the monotartrate phase the molecule is found to adsorb upright through the O atoms of the single deprotonated carboxylic acid (carboxylate) group, which are located in different off-atop sites with associated Cu―O bond lengths of 1.92 ± 0.08 Å and 1.93 ± 0.06 Å; the plane of the carboxylate group is tilted by 17 ± 6° off the surface normal. The bitartrate species adopts a ‘lying down’ orientation, bonding to the surface through all four O atoms of the two carboxylate groups, also in off-atop sites. Three slightly different models give comparably good fits to the PhD data, but only one of these is similar to that predicted by earlier density functional theory calculations. This model is found to have Cu―O bond lengths of 1.93 ± 0.08 Å and 1.95 ± 0.08 Å, while the planes of the carboxylate groups are tilted by 38 ± 6° from the surface normal. -------------------------------------------------------------------------------