Working group report: Flavor physics and model building

This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently.     

Synthesis of high fluorescent silica hybrid materials by immobilization of orange peel extract in silica‐silsesquioxane matrix

Sol–gel chemistry can be easily modified to the changing needs of society to produce fine‐tuned sol–gel nanostructured materials for relevant applications. In this context, there is an increasing need for natural and versatile raw materials as well as biocompatible compounds that could be extensively used as biomarkers for bioimaging in diagnosis or therapy. Silica‐based materials are widely used in the field of biomedicine due to their chemical inertness and biocompatibility. In the present paper, orange peel extract was immobilized inside inorganic silica and hybrid silica‐silsesquioxane polymeric networks. Silica and organo‐modified silica matrices were synthesized through a templated sol–gel route of TEOS and an organosilsesquioxane (octaisobutyltetracyclo[7.3.3.1^5,11] octasiloxane‐endo‐3,7‐diol), with D ‐glucose as template, and for comparison a non‐ionic surfactant (tetraethylene glycol mono‐hexadecyl ether) was also used. The bioactive properties of the molecules from orange peel extract were preserved after immobilization in both silica and silica‐silsesquioxane networks. Moreover, the fluorescence properties were amplified by 10–20 times more than the native orange peel extract. The structural properties of the final materials have been studied by FT‐IR, UV–Vis‐NIR, and fluorescence spectroscopy. Dynamic light scattering measurements and transmission electron microscopy were used to estimate the size and morphology of the hybrid materials with orange peel extract immobilized in silica networks. Copyright © 2009 John Wiley & Sons, Ltd.     

Large Seebeck coefficients in iron‐oxypnictides: a new route towards n‐type thermoelectric materials

The iron‐oxypnictide compounds, recently reported as a new class of superconductors when appropriately doped, exhibit large Seebeck coefficients, of the order of –100 µV/K, while keeping good electrical conductivity. Their power factor shows a peak at low temperatures, suggesting possible applications of these materials in thermoelectric cooling modules in the liquid nitrogen temperature range. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Letter: Note on Invariants of the Weyl Tensor

Algebraically special gravitational fields are described using algebraic and differential invariants of the Weyl tensor. A type III invariant is also given and calculated for Robinson-Trautman spaces.     

Preliminary design studies of a 100 MeV H−/H+ LINAC as injector for SNS synchrotron/ADS LINAC

It is proposed to construct a spallation neutron source (SNS) at Centre for Advanced Technology (CAT) based on a 1 GeV proton synchrotron with 100 MeV H⁻ LINAC as injector. Additionally, the LINAC can form the first 100 MeV part of a 1 GeV proton LINAC to be built in future for accelerator driven system (ADS) applications. We are exploring a configuration of the 100 MeV LINAC which will consist of an H⁻ ion source, a 4–6 MeV RFQ followed either by a 20 MeV drift tube LINAC (DTL) and 100 MeV separated function drift tube LINAC (SDTL) or a coupled cavity drift tube LINAC (CCDTL) structure. In this paper, we present the results of our preliminary physics design studies of the RFQ-SDTL, RFQ-CCDTL and RFQ-DTL-SDTL configurations. The design of the 4.5 MeV RFQ is discussed along with the matching sections between the RFQ-SDTL/DTL and RFQ-CCDTL. The choice of the accelerator configuration and that of various parameters of the individual accelerator structures under consideration are discussed. The design objectives are to arrive at a configuration which eases heat removal for CW operation and which is less prone to halo formation in order to reduce the beam loss at higher energies.     

Laboratory set-up for X-ray diffraction at high pressures

We describe here a simple set-up for X-ray diffraction under high pressure using a diamond anvil cell employing a sealed tube. The set-up works in angular dispersive geometry and is built using rather common components that are available in a research laboratory. We show that using this set-up one can routinely acquire good-quality data for the determination of structural properties under pressure and the equations of state. Technical details are presented along with examples of experimental results for sodium chloride and LiV₂O₄.     

Biomembrane phospholipid-oxide surface interactions: crystal chemical and thermodynamic basis

Quartz has the least favored surface among many oxides for bacterial attachment and for lipid bilayer or micelle interactions. Tetrahedrally coordinated crystalline silica polymorphs are membranolytic toward liposomes, lysosomes, erythrocytes, and macrophages. Amorphous silica, the octahedral silica polymorph, (stishovite), and oxides such as Al2O3, Fe2 O3, and TiO2 are less cytotoxic. Existing theories for membrane rupture that invoke interactions between oxide surfaces and cell membrane phospholipids (PLs) do not adequately explain these differences in membranolytic potential of the oxides. The author presents a crystal chemical, thermodynamic model for the initial interaction of oxide surfaces with the quaternary ammonium component of the PL's polar head group. The model includes solvation energy changes and electrostatic forces during adsorption, represented by the dielectric constant of the solid and the charge-to-radius ratio of the adsorbing solute. The nature of oxide-solute interactions compared with oxide-water, solute-water, and water-water interactions determines the membranolytic activity of the oxide, where the solute is TMA+, the quaternary ammonium moeity. Significant membrane rupture, as on quartz, requires unfavorable adsorption entropy (DeltaS(ads,TMA+)<0) to maximize disruption of normal membrane structure and requires favorable Gibbs free energy of exchange between TMA+ and the ambient Na+ ions (DeltaG(exc,TMA+/Na+) = DeltaG(ads,TMA+)-DeltaG(ads,Na+)<0) to maximize the extent of membrane affected. For amorphous silica, DeltaS(ads,TMA+) >0, so disruption of structure is limited, even though G(exc,TMA+/Na+) is <0. Stishovite and other oxides have DeltaS(ads,TMA+) <0, but now DeltaG(exc,TMA+/Na+) is>0 at the acidic to circumneutral pHs of cellular and subcellular organelle fluids. The model predicts the correct sequence of membranolytic ability: quartz > or = amorphous SiO2 >Al2O3 >Fe2O3 >TiO2. The model thus explains the relatively poor adhesion of bacterial cells to quartz and the lack of quartz as a biomineral. It is proposed that one function of extracellular polymeric substances exuded by bacteria is to render mineral surfaces more hydrophilic.     

Synthesis of a 2,2'-bipyridyl functionalized oligovinylene-phenylene using Heck and Horner-Wadsworth-Emmons reactions and X-ray crystal structure of E-(4-(4-bromostyryl)phenyl)(methyl)sulfane

The synthesis of a new 2,2'-bipyridyl functionalized oligovinylenephenylene (OVP-5) containing a methyl protected thiol using Heck coupling and the Horner-Wadsworth-Emmons reaction and is described. A key step involving a diisopropylcarbodiimide promoted dehydration of a stable β-hydroxyphosphonate intermediate was identified. The structure of precursor E-(4-(4-bromostyryl)phenyl)(methyl)sulfane was determined using X-ray crystallography.     

On the critical cluster in the two-dimensional Ising model: computer-assisted exact results

For a nearest-neighbor Ising model on a square lattice all cluster configurations with 17 or fewer spins are identified. In neglect of cluster-cluster interactions, critical sizes and barriers to nucleation are obtained as functions of temperature and magnetic field for two alternative definitions of a "critical cluster."