Synthetic and Structural Studies of 1‐Halo‐8‐(alkylchalcogeno)naphthalene Derivatives

A series of eight 1‐halo‐8‐(alkylchalcogeno)naphthalene derivatives ( 1 – 8 ; halogen=Br, I; alkylchalcogen=SEt, SPh, SePh, TePh) containing a halogen and a chalcogen atom occupying the peri positions have been prepared and fully characterised by using X‐ray crystallography, multinuclear NMR spectroscopy, IR spectroscopy and MS. Naphthalene distortion due to non‐covalent substituent interactions was studied as a function of the bulk of the interacting chalcogen atoms and the size and nature of the alkyl group attached to them. X‐ray data for 1 , 2 , 4 and 5 – 8 were compared. Molecular structures were analysed in terms of naphthalene ring torsions, peri‐atom displacement, splay angle magnitude, X???E interactions, aromatic ring orientations and quasi‐linear X???E? C arrangements. A general increase in the X???E distance was observed for molecules that contain bulkier atoms at the peri positions. The I???S distance of 4 is comparable with the I???Te distance of 8 , and is ascribed to a stronger lone pair–lone pair repulsion due to the presence of an axial S(naphthyl) ring conformation. Density functional theory (B3LYP) calculations performed on 5 – 8 revealed Wiberg bond index values of 0.05–0.08, which indicate minor interactions taking place between the non‐bonded atoms in these compounds.     

Sterically Crowded peri‐Substituted Naphthalene Phosphines and their PV Derivatives

Three sterically crowded peri‐substituted naphthalene phosphines, Nap[PPh₂][ER] (Nap=naphthalene‐1,8‐diyl; ER=SEt, SPh, SePh) 1–3 , which contain phosphorus and chalcogen functional groups at the peri positions have been prepared. Each phosphine reacts to form a complete series of P^V chalcogenides Nap[P(E′)(Ph₂)(ER)] (E′=O, S, Se). The novel compounds were fully characterised by using X‐ray crystallography and multinuclear NMR spectroscopy, IR spectroscopy and MS. X‐ray data for 1 , 2 , n O , n S , n Se (n=1–3) are compared. Eleven molecular structures have been analysed by naphthalene ring torsions, peri‐atom displacement, splay angle magnitude, X???E interactions, aromatic ring orientations and quasi‐linear arrangements. An increase in the congestion of the peri region following the introduction of heavy chalcogen atoms is accompanied by a general increase in naphthalene distortion. P???E distances increase for molecules that contain bulkier atoms at the peri positions and also when larger chalcogen atoms are bound to phosphorus. The chalcogenides adopt similar conformations that contain a quasi‐linear E???P? C fragment, except for 3 O , which displays a twist‐axial‐twist conformation resulting in the formation of a linear O???Se? C alignment. Ab initio MO calculations performed on 2 O , 3 O , 3 S and 3 Se reveal Wiberg bond index values of 0.02 to 0.04, which indicates only minor non‐bonded interactions; however, calculations on radical cations of 3 O , 3 S and 3 Se reveal increased values (0.14–0.19).     

Thin film formation of silica nanoparticle/lipid composite films at the fluid-fluid interface

We report a new and simple method for the formation of thin films at the interface between aqueous silica Ludox dispersions and lipid solutions in decane. The lipids used are stearic acid, stearyl amine, and stearyl alcohol alongside silica Ludox nanoparticle dispersions of varying pH. At basic pH thin films consisting of a mixture of stearic acid and silica nanoparticles precipitate at the interface. At acidic and neutral pH we were able to produce thin films consisting of stearyl amine and silica particles. The film growth was studied in situ with interfacial shear rheology. In addition to that, surface pressure isotherm and dynamic light scattering experiments were performed. The films all exhibit strong dynamic rheological moduli, rendering them an interesting material for applications such as capsule formation, surface coating, or as functional membranes.     

The effect of cold acclimation on the water relations and freezing tolerance of Hordeum vulgare L

During a 5 degree C and a 5/-1 degree C cold acclimation (CA) regime there was a significant decline in the water potential of winter barley, and a concurrent decline in tissue water content of the 5/-1 degree C CA plants. Results of carbohydrate analysis illustrated a significant (P < 0.001) accumulation of sucrose, fructose and glucose in the 5/-1 degree C CA plants, which was inversely correlated to water potential. Using an infrared imaging radiometer during a convection frost test the water release time (WRT) of 5/-1 degree C CA was demonstrated to be significantly (P < 0.001) longer than that observed in non-cold acclimated plants. This observation is consistent with visual analysis of exotherm curves where the rate of cellular water release to extracellular ice is reduced in the 5/-1 degree C CA plants, compared to the non-cold acclimated plants. These biochemical and physiological changes were correlated to increased plant health following a non-lethal freezing test to -5 degree C, where non-cold acclimated plants produced 2.3 +/- 0.3 tillers and 5 degree C and 5/-1 degree C CA plants produced 2.4 +/- 0.3 and 4.7 +/- 0.7 tillers, respectively. Results from this study imply that cold acclimation leads to changes in the physical state of water that result in a less osmotically responsive cellular environment and subsequently significantly less damage to meristematic tissue.     

Atomic force microscopy of Bacillus spore surface morphology

Bacillus spore surface morphology was imaged with atomic force microscopy (AFM) to determine if characteristic surface features could be used to distinguish between four closely related species; Bacillus anthracis Sterne strain, Bacillus thuringiensis var. kurstaki, Bacillus cereus strain 569, and Bacillus globigii var. niger. AFM surface height images showed an irregular topography across the curved upper surface of the spores. Phase images showed a superficial grain structure with different levels of phase contrast and significant differences in average surface morphologies among the four species. Although spores of the same species showed similarities, there was significant variability within each species. Overall, AFM revealed that spore surface morphology is rich with information, which can be used to distinguish a sample of about 20 spores from a similar number of spores of closely related species. Statistical analysis of spore morphology from a combination of amplitude and phase images for a small sample allows differentiation between, B. anthracis and its close relatives.     

Coherent active-sterile neutrino flavor transformation in the early universe

We solve the problem of coherent Mikheyev-Smirnov-Wolfenstein resonant active-to-sterile neutrino flavor conversion driven by an initial lepton number in the early Universe. We find incomplete destruction of the lepton number in this process and a sterile neutrino energy distribution with a distinctive cusp and high energy tail. These features imply alteration of the nonzero lepton number primordial nucleosynthesis paradigm when there exist sterile neutrinos with rest masses m(s) approximately 1 eV. This could result in better light element probes of (constraints on) these particles.     

Photonuclear reaction cross sections for 12C, 14N and 16O

The results of an evaluation of the available photonuclear-reaction data for ¹²C, ¹⁴N and ¹⁶O are presented. While some reaction-yield data are given for energies up to 50 MeV, the primary emphasis is on the excitation-energy range extending from the proton separation energies up to 30 MeV. In addition to photodisintegration measurements, cross-section data derived from inverse particle-capture and electrodisintegration experiments are considered. Data are presented in graphical as well as tabular form. Included in the tables are: energy-weighted moments of the cross sections, bremsstrahlung induced reaction-yield data, radioactive-properties of reaction products, and reaction separation energies.     

Geophysical aspects of paleomagnetism

Paleomagnetism concerns the history of the earth's magnetic field as it has been recorded throughout geologic time by the remanent magnetism of rocks. It is no exaggeration to say that such studies have recently revolutionized our ideas in geology and geophysics. Field reversals, polar wander, continental drift, and sea floor spreading all essentially depend upon paleomagnetism for their demonstration. However, the theoretical basis for paleomagnetism has not developed with the same rapidity as has its application in geological thinking.     

Positive and negative deflection-angle coulomb scattering

The decomposition of the Rutherford amplitude into positive and negative deflection-angle contributions shows how Fraunhofer diffraction for charged-particle scattering is moved away from forward angles.     

Network models of concentrated polymer solutions derived from the yamamoto network theory

Several choices of the functions describing the creation and destruction processes of entanglement junctions in the Yamamoto network theory of concentrated polymer solutions have been examined. These choices are simple functions of the extension of the network segments bridging the entanglement points and it is demonstrated that the moments of the distribution function describing the network conformation can be solved for analytically. This has been done for a wide range of two-dimensional flows, both for the steady state and transient start-up and relaxation problems. The macroscopic stress tensor and flow birefringence are calculated and a variety of nonlinear effects are predicted and discussed.