Hypophosphorous acid as a precursor to various organophosphorus compounds

The work presented in this thesis is based on the common theme, of the use of hypophosphorous acid as a starting material for the synthesis of functionalised organophosphorus compounds. Hypophosphorous acid and its salts have gained attention as potentially greener precursors, than PCl3, to a range of organophosphorus compounds. An investigation into an alternative synthesis of perfluoroalkylphosphorus(V) compounds is presented. The reaction of hypophosphorous acid derived bis(trimethylsilyl)phosphonite [(Me3SiO)2PH] (BTSP) and bis(trimethylsilyl)- phenylphosphonite [(Me3SiO)2PPh] (BTSPP) with perfluoroalkyl iodides (RfI) is investigated. A range of reactions are discussed, including the synthesis of perfluoroalkyl H-phosphinic acids, RfPO(OH)H, perfluoroalkyl phosphonic acids, RfPO(OH)2 and perfluoroalkyl(phenyl)phosphinic acids, (Rf)PhPO(OH)H. The synthesis and catalytic testing of a new Brønsted acid catalyst is presented. 2,2’-Bis(difluoromethylene)-1,1’-binaphthyl phosphinic acid was targeted, as a stronger (more acidic) Brønsted acid catalyst compared to 1,1’-binaphthyl-2,2’-diyl hydrogen phosphate (BINOL-phosphoric acid). 2,2’-Bis(difluoromethylene)-1,1’- binaphthyl phosphinic acid was synthesised in a seven-step procedure from BINOL, including a ring closure reaction in which BTSP is used. The full synthesis of 2,2’-bis(difluoromethylene)-1,1’-binaphthyl phosphinic acid is presented with full characterisation data for four novel compounds. The X-ray crystal structures of 2,2’-bis(difluoromethylene)-1,1’-binaphthyl phosphinic acid and ethyl 2,2’- bis(difluoromethylene)-1,1’-binaphthyl phosphinate were determined. Preliminary catalytic testing of 2,2’-bis(difluoromethylene)-1,1’-binaphthyl phosphinic acid, on a Nazarov cyclisation, and comparisons to known Brønsted acid catalysts are presented. An alternative route to Aryl-dichlorophosphines (ArPCl2) is discussed. These were synthesised from stable and easily accessible aryl H-phosphinic acids (ArPO2H2). A series of aryl-dichlorophosphines are presented, on a multi-gram scale, with two novel aryl-dichlorophosphines synthesised

Higher dimensional supersymmetry in 4D superspace

We present an explicit formulation of supersymmetric Yang-Mills theories from \D= 5 to 10 dimensions in the familiar \N=1,\D=4 superspace. This provides the rules for globally supersymmetric model building with extra dimensions and in particular allows us to simply write down $\N=1$ SUSY preserving interactions between bulk fields and fields localized on branes. We present a few applications of the formalism by way of illustration, including supersymmetric ``shining'' of bulk fields, orbifolds and localization of chiral fermions, anomaly inflow and super-Chern-Simons theories.Comment: Typos corrected. Added reference to early work by Marcus, Sagnotti and Siegel and a term to the non-Abelian Lagrangian for D>5 formally needed for gauge invariance. The results however remain unchange

Innovative Technologies And Vadose Zone Treatment Of Chlorinated Volatile Organic Compounds - Case Study

Over the last 10 years a mix of innovative and conventional characterization techniques has been used to assess the contamination of vadose zone sediments beneath the pilot-scale test facility known as TNX at the Savannah River Site (SRS) in South Carolina. Shallow soils and groundwater beneath the TNX facility are contaminated with chlorinated volatile organic compounds (CVOCs), trichloroethylene (TCE), carbon tetrachloride (CCl{sub 4}), perchloroethylene (PCE), and chloroform (CHCl{sub 3}). An interim pump and treat remediation system was placed in operation in 1996 to provide hydraulic containment of groundwater containing greater than 500 ug/L dissolved TCE. In 1994, a vadose zone study was initiated to determine the degree and extent of CVOC contamination above the contaminated groundwater. Headspace sampling and analysis, acoustic infrared spectroscopy, cone penetrometry, and vadose zone pumping tests were used to determine contaminant concentrations and physical properties related to soil vapor extraction. In 2001, soil vapor extraction (SVE), a presumptive remedy for CVOCs in soils similar to those present beneath TNX, was selected to treat the CVOC contamination. Cone Penetrometer Testing (CPT) with soil vapor sampling provided a detailed understanding of the subsurface geology and CVOC distribution which was essential for proper well design and placement. Twelve SVE wells were installed using direct push technology (DPT) and were tested to determine specific capacity and CVOC concentrations. This information was then used to develop a strategy for operating the SVE system. Based on the results of the baseline testing and previous studies, sets of 2 to 3 extraction wells will be treated using SVE at one month intervals. This will allow continuous operation of the SVE system and give individual wells up to 3 months for rebound between treatments. This method of operation is intended to maximize contaminant recovery from individual wells and reduce the overall capital investment and operating cost of the SVE system

Deep ACS Imaging in the Globular Cluster NGC 6397: The Cluster Color Magnitude Diagram and Luminosity Function

We present the CMD from deep HST imaging in the globular cluster NGC 6397. The ACS was used for 126 orbits to image a single field in two colors (F814W, F606W) 5 arcmin SE of the cluster center. The field observed overlaps that of archival WFPC2 data from 1994 and 1997 which were used to proper motion (PM) clean the data. Applying the PM corrections produces a remarkably clean CMD which reveals a number of features never seen before in a globular cluster CMD. In our field, the main sequence stars appeared to terminate close to the location in the CMD of the hydrogen-burning limit predicted by two independent sets of stellar evolution models. The faintest observed main sequence stars are about a magnitude fainter than the least luminous metal-poor field halo stars known, suggesting that the lowest luminosity halo stars still await discovery. At the bright end the data extend beyond the main sequence turnoff to well up the giant branch. A populous white dwarf cooling sequence is also seen in the cluster CMD. The most dramatic features of the cooling sequence are its turn to the blue at faint magnitudes as well as an apparent truncation near F814W = 28. The cluster luminosity and mass functions were derived, stretching from the turn off down to the hydrogen-burning limit. It was well modeled with either a very flat power-law or a lognormal function. In order to interpret these fits more fully we compared them with similar functions in the cluster core and with a full N-body model of NGC 6397 finding satisfactory agreement between the model predictions and the data. This exercise demonstrates the important role and the effect that dynamics has played in altering the cluster IMF.Comment: 43 pages including 4 tables and 12 diagrams. Figures 2 and 3 have been bitmapped. Accepted for publication in the Astronomical Journa

Sensory-based niche partitioning in a multiple predator-multiple prey community

Many predators and parasites eavesdrop on the communication signals of their prey. Eavesdropping is typically studied as dyadic predator-prey species interactions; yet in nature, most predators target multiple prey species and most prey must evade multiple predator species. The impact of predator communities on prey signal evolution is not well understood. Predators could converge in their preferences for conspicuous signal properties, generating competition among predators and natural selection on particular prey signal features. Alternatively, predator species could vary in their preferences for prey signal properties, resulting in sensory-based niche partitioning of prey resources. In the Neotropics, many substrate-gleaning bats use the mate-attraction songs of male katydids to locate them as prey. We studied mechanisms of niche partitioning in four substrate- gleaning bat species and found they are similar in morphology, echolocation signal design and prey-handling ability, but each species preferred different acoustic features of male song in 12 sympatric katydid species. This divergence in predator preference probably contributes to the coexistence of many substrate-gleaning bat species in the Neotropics, and the substantial diversity in the mate-attraction signals of katydids. Our results provide insight into how multiple eavesdropping predator species might influence prey signal evolution through sensory-based niche partitioning

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Storage stability of an egg yolk cream formulation: texture and microbiological assessment

BACKGROUND: Egg yolk cream is confectioned with egg yolk, sugar and water. Pasteurized liquid eggs may be used in order to increase product safety, although these samples may differ from the classic ones produced with raw eggs. The objective was to evaluate and compare the stability (physicochemical characteristics, such as texture assessment, pH and water activity, and microbiological assessment) of a classic formulation and an alternative one produced with pasteurized eggs, during storage at 6, 26, 30 and 37◦C. RESULTS: From a microbiological point of view (mesophile and psychrotrophic activity), no differences were observed in either formulations.At 6 and 26 ◦C, rheological behaviour of both formulations remained approximately constant. At 30 and 37 ◦C, differences were only detected after 20 days of storage. Texture was better retained in samples prepared with pasteurized eggs, while the classic samples showed an increase in complex viscosity. CONCLUSION: Cream storage did not require refrigeration. In terms of texture and microbial load, results obtained at 6 and 26 ◦C were identical. The formulations only differed in texture when stored at 30 and 37 ◦C and for long periods. These conclusions may allow reduction of costs related to refrigerated distribution/storage of either classic or alternative formulations

The Origin of a New Sex Chromosome by Introgression between Two Stickleback Fishes.

Introgression is increasingly recognized as a source of genetic diversity that fuels adaptation. Its role in the evolution of sex chromosomes, however, is not well known. Here, we confirm the hypothesis that the Y chromosome in the ninespine stickleback, Pungitius pungitius, was established by introgression from the Amur stickleback, P. sinensis. Using whole genome resequencing, we identified a large region of Chr 12 in P. pungitius that is diverged between males and females. Within but not outside of this region, several lines of evidence show that the Y chromosome of P. pungitius shares a most recent common ancestor not with the X chromosome, but with the homologous chromosome in P. sinensis. Accumulation of repetitive elements and gene expression changes on the new Y are consistent with a young sex chromosome in early stages of degeneration, but other hallmarks of Y chromosomes have not yet appeared. Our findings indicate that porous species boundaries can trigger rapid sex chromosome evolution