Production of high transverse momentum prompt photons and neutral pions in proton-proton interactions at 280 GeV/c

The inclusive cross sections for production of prompt photons and π⁰ s by 280 GeV/c protons incident on a liquid hydrogen target, have been measured forp _T in the range 4.0 to 6.5 GeV/c and for |x _F |<0.45. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed. Phenomenological fits to the π⁰ and prompt photon cross sections are given.     

Source allocation of organic air pollutants by application of fuzzy c-varieties pattern recognition

Data for polynuclear aromatic hydrocarbons (PAH) from 44 air samples are processed by unsupervised clustering techniques in oder to resolve the contributions from two sources (domestic and motor vehicles). The fuzzy c-varieties (FCV) clustering algorithms are applied. The cluster configuration which best describes the characteristic properties of the samples is selected by computation of validity discriminant coefficients. the FCV method permits the data samples to belong partially to different clusters, and source apportionments are estimated by multiplying the membership values by the PAH concentrations of the individual samples. The results are compared to those obtained by other methods of dispersion or receptor modelling in the same areas. The FCV method is valuable for estimating contributions from two types of emission sources.     

Choosing ther-dimension for the FCV family of clustering algorithms

A strategy is given for selecting the dimensionr of the linear variety which is used to define the criterion functionalJ _vrm and which determines the shape of the data clusters detected by the correspondingc-Varieties (FCV) clustering algorithms.     

Electron transfer within self-assembling cyclic tetramers using chlorophyll-based donor-acceptor building blocks

The synthesis and photoinduced charge transfer properties of a series of Chl-based donor-acceptor triad building blocks that self-assemble into cyclic tetramers are reported. Chlorophyll a was converted into zinc methyl 3-ethylpyrochlorophyllide a (Chl) and then further modified at its 20-position to covalently attach a pyromellitimide (PI) acceptor bearing a pyridine ligand and one or two naphthalene-1,8:4,5-bis(dicarboximide) (NDI) secondary electron acceptors to give Chl-PI-NDI and Chl-PI-NDI(2). The pyridine ligand within each ambident triad enables intermolecular Chl metal-ligand coordination in dry toluene, which results in the formation of cyclic tetramers in solution, as determined using small- and wide-angle X-ray scattering at a synchrotron source. Femtosecond and nanosecond transient absorption spectroscopy of the monomers in toluene-1% pyridine and the cyclic tetramers in toluene shows that the selective photoexcitation of Chl results in intramolecular electron transfer from (1*)Chl to PI to form Chl(+?)-PI(-?)-NDI and Chl(+?)-PI(-?)-NDI(2). This initial charge separation is followed by a rapid charge shift from PI(-?) to NDI and subsequent charge recombination of Chl(+?)-PI-NDI(-?) and Chl(+?)-PI-(NDI)NDI(-?) on a 5-30 ns time scale. Charge recombination in the Chl-PI-NDI(2) cyclic tetramer (τ(CR) = 30 ± 1 ns in toluene) is slower by a factor of 3 relative to the monomeric building blocks (τ(CR) = 10 ± 1 ns in toluene-1% pyridine). This indicates that the self-assembly of these building blocks into the cyclic tetramers alters their structures in a way that lengthens their charge separation lifetimes, which is an advantageous strategy for artificial photosynthetic systems.     

Lentivirus-mediated transgene delivery to the hippocampus reveals sub-field specific differences in expression

Background  

In the adult hippocampus, the granule cell layer of the dentate gyrus is a heterogeneous structure formed by neurons of different ages, morphologies and electrophysiological properties. Retroviral vectors have been extensively used to transduce cells of the granule cell layer and study their inherent properties in an intact brain environment. In addition, lentivirus-based vectors have been used to deliver transgenes to replicative and non-replicative cells as well, such as post mitotic neurons of the CNS. However, only few studies have been dedicated to address the applicability of these widespread used vectors to hippocampal cells in vivo. Therefore, the aim of this study was to extensively characterize the cell types that are effectively transduced in vivo by VSVg-pseudotyped lentivirus-based vectors in the hippocampus dentate gyrus.     

Analysis of transverse momentum and event shape invN scattering

The transverse momentum distributions of hadrons produced in neutrino-nucleon charged current interactions and their dependence onW are analysed in detail. It is found that the components of the transverse momentum in the event plane and normal to it increase withW at about the same rate throughout the availableW range. A comparison withe ⁺ e ^? data is made. Studies of the energy flow and angular distributions in the events classified as planar do not show clear evidence for high energy, wide angle gluon radiation, in contrast to the conclusion of a previous analysis of similar neutrino data.     

Coherent production of π+ mesons in ν-neon interactions

The coherent production of π⁺ mesons by charged current neutrino interactions on neon nuclei in BEBC is compared to the predictions of the PCAC hypothesis and the meson dominance model. Good agreement is observed.     

Future developments for fibre optics

Amazing progress has been made since the original development of low loss optical fibres. Attenuation levels of a few tenths of a decibel have been achieved as well as bandwidths of thousands of megahertz in graded index fibres. The major current challenge of the industry is to transfer these laboratory advances into practical cost effective hardware. At the same time, trends towards longer wavelengths and multiple wavelength operation are quite evident. The next decade of optical fibre technology should see many of these trends brought to fruition with the common availability of high performance cost effective fibres.     

Comparison of polymer resolution in thermal field-flow fractionation and size-exclusion chromatography

A comparison of the resolving power of themal field-flow fractionation (thermal FFF) and size-exclusion chromatography (SEC) has been made by the experimental operation of a high-resolution system from each category. For the experimental systems used, the measured resolution for thermal FFF was found to be higher than that for SEC for three different binary polymer mixtures. Only for a single low-molecular-weight mixture falling outside the optimal operating range of thermal FFF did SEC show better resolution. The experimental resolution values were broken down into selectivity and column efficiency parameters. While selectivity was easily obtained, column efficiency required a correction for polydispersity effects. With the polydispersity correction made on the basis of thermal FFF data, true resolution values were calculated to replace the apparent or experimental resolution levels. Overall, the corrected resolution values showed that thermal FFF had a significant advantage over SEC. Prospects for future advances in these two techniques are discussed.     

Baryon antibaryon production in the central region at 85 GeV/c

In a search for glueballs and exotic states decaying into baryons and antibaryons we have investigated the production of baryon antibaryon pairs produced centrally in the reactions π⁺/pp → π⁺/p(X ⁰)p at 85 GeV/c. In particular, channels whereX ⁰ goes to \(p\bar p,p\bar p\pi ^ + \pi ^ - ,p\bar p2\pi ^ + 2\pi ^ - \) and \(\Lambda \bar \Lambda \) have been observed. No significant new structure is observed in the mass spectra.