Adsorbate structure modeling based on electron energy loss spectroscopy and lattice dynamical calculations: Application to O/A1(111).

High-resolution electron energy loss spectroscopy (EELS) and lattice dynamical calculations based on pair interactions are used to investigate oxygen chemisorption on Al(111). The O/Al(111) System is complicated by the simultaneous formation of an oxygen overlayer and underlayer. Oxygen atoms at overlayer and underlayer sites near the Al(111) surface produce well-defined vibrational loss peaks in EELS spectra, however, dynamical coupling between the oxygen atoms and with the host lattice cause vibrational energies to shift with overlayer and underlayer concentrations. These shifts as well as structural parameters of the O/Al(111) complex can be deduced from a slab model of the surface lattice dynamics.     

Polarisation in the reaction πp → KΣ at 1.11 GeV

The polarisation of the recoil sigma in the reaction π⁺p → K⁺Σ⁺ has been measured at 12 production angles at a beam momentum of 1.11 GeV/c using counters and spark chambers. The new data are compared with existing phase shift solutions of πp → KΣ channels in the low energy region.     

Temperature-dependent absorption cross-sections of HCFC-142b

Following the recent detection of HCFC-142b (1-chloro-1,1-difluoroethane) from space, laboratory infrared absorption cross-section spectra of this molecule in a pure vapour phase have been recorded in the spectral region using Fourier transform spectroscopy. The spectra have been recorded at a resolution of and a range of temperatures from 223 to 283 K. The resulting data show good agreement with the harmonic frequencies and intensities calculated using density functional theory as well as with the integrated absorption intensities of the spectral bands available in the literature. The new cross-sections will allow more accurate retrieval of atmospheric HCFC-142b concentrations using infrared spectroscopic techniques.     

Analysis of co-aggregation of cancer based on registry data

OBJECTIVE: An exploratory analysis of co-aggregation of cancers using registry-based data. METHODS: We utilized sibships from over 18,000 families who had been recruited to the NCI-sponsored multi-institutional Cancer Genetics Network. The analysis assesses co-aggregation at the individual and family level and adjusts for ascertainment. RESULTS: We found statistically significant familial co-aggregation of lung cancer with pancreatic (adjusted p < 0.001), prostate (adjusted p < 0.003), and colorectal cancers (adjusted p = 0.004). In addition, we found significant familial co-aggregation of pancreatic and colorectal cancers (adjusted p = 0.018), and co-aggregation of hematopoietic and (non-ovarian) gynecologic cancers (adjusted p = 0.01). CONCLUSION: This analysis identified familial aggregation of cancers for which a genetic component has yet to be established.     

Mean flow characteristics of a turbulent plane jet with buoyancy induced curvature

An experimental investigation of heated vertical and inclined plane air jets discharged into quiescent surroundings is described. A unique feature of this data is that Pilot tube measurements were used to define the mean trajectory of the inclined jets so that subsequent hot-wire traverses could be made normal to the curved path. While the mean velocity and temperature profiles are self-similar for the range of exit conditions studied, other aspects of the mean jet development depend on the exit Reynolds and Froude numbers, or the discharge angle. It is noted that variations between this study and other published data suggest further measurements of this flow situation are needed, with particular attention to specific features of the jet apparatus and ambient surroundings, and to the exit Reynolds number. Presently with Dept. of Mechanical Engineering, University of Alexandria, Alexandria, Egypt     

Turbulence measurements from a plane air jet with buoyancy induced curvature

An experimental investigation of the turbulence structure of a heated plane air jet discharged at various angles into quiescent surroundings is described. Hot-wire anemometry was used to obtain the profiles of mean and turbulent velocities and temperature normal and tangential to the curved path of the flow. Measurements in the buoyancy induced curved region of the jet show the relative influence of the stability induced by both buoyancy and jet curvature on the turbulence structure.     

Molecular level model for the agonist/antagonist selectivity of the 1,4-dihydropyridine calcium channel receptor

Summary Crystal structures of the 1,4-dihydropyridine (1,4-DHP) calcium channel activators Bay K 8643 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(3-nitrophenyl)-pyridine-5-carboxylate], Bay O 8495 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(3-trifluoromethylphenyl)-pyridine-5-carboxylate], and Bay O 9507 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(4-nitrophenyl)-pyridine-5-carboxylate] were determined. The conformations of the 1,4-DHP rings of these activator analogues of Bay K 8644 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyridine-5- carboxylate] do not suggest that their activator properties are as strongly correlated with the degree of 1,4-DHP ring flattening as was indicated for members of the corresponding antagonist series. The solid state hydrogen bonding of the N(1)-H groups of the activators is not, unlike that of their antagonist counterparts, to acceptors that are directly in line with the donor. Rather, acceptor groups are positioned within ± 60 degrees of the N(1)-H bond in the vertical plane of the 1,4-DHP ring. Previously determined structure-activity relationships have indicated the importance of this N(1)-H group to the activity of the 1,4-DHP antagonists. Based on these observations, a model is advanced to describe the 1,4-DHP binding site of the voltage-gated Ca²⁺ channel and its ability to accommodate both antagonist and activator ligands.     

A measurement of the charge asymmetry in the decay η → π+π−πo

An experiment has been carried out at the Rutherford Laboratory to look for a possible asymmetry in the eta decay to three pions. Eta mesons were produced in the process π^?p→ ηn. The experiment produced 165311 decays η → π⁺π^?π^o from which we determined a value for the charge asymmetry A = (0.0028 ± 0.0026). We see no evidence for C-violation in this decay.     

Influencing receptor-ligand binding mechanisms with multivalent ligand architecture

Multivalent ligands can function as inhibitors or effectors of biological processes. Potent inhibitory activity can arise from the high functional affinities of multivalent ligand-receptor interactions. Effector functions, however, are influenced not only by apparent affinities but also by alternate factors, including the ability of a ligand to cluster receptors. Little is known about the molecular features of a multivalent ligand that determine whether it will function as an inhibitor or effector. We envisioned that, by altering multivalent ligand architecture, ligands with preferences for different binding mechanisms would be generated. To this end, a series of 28 ligands possessing structural diversity was synthesized. This series provides the means to explore the effects of ligand architecture on the inhibition and clustering of a model protein, the lectin concanavalin A (Con A). The structural parameters that were varied include scaffold shape, size, valency, and density of binding elements. We found that ligands with certain architectures are effective inhibitors, but others mediate receptor clustering. Specifically, high molecular weight, polydisperse polyvalent ligands are effective inhibitors of Con A binding, whereas linear oligomeric ligands generated by the ring-opening metathesis polymerization have structural properties that favor clustering. The shape of a multivalent ligand also influences specific aspects of receptor clustering. These include the rate at which the receptor is clustered, the number of receptors in the clusters, and the average interreceptor distance. Our results indicate that the architecture of a multivalent ligand is a key parameter in determining its activity as an inhibitor or effector. Diversity-oriented syntheses of multivalent ligands coupled with effective assays that can be used to compare the contributions of different binding parameters may afford ligands that function by specific mechanisms.