The alpha-effect in cyclic secondary amines: new scaffolds for iminium ion accelerated transformations

Five-membered secondary amine heterocycles containing an α-heteroatom were prepared and shown to be ineffective as catalysts for the iminium ion catalysed Diels–Alder reaction between cinnamaldehyde and cyclopentadiene. Their six-membered counterparts proved to be highly active catalysts. In stark contrast, the catalytic activity observed when comparing the non α-heteroatom cyclic amines proline methyl ester and methyl pipecolinate showed the five-membered ring amine was significantly more active. Concurrent density functional theoretical calculations suggest a rationale for the observed trends in reactivity, highlighting that LUMO activation through an iminium ion intermediate plays a key role in catalytic activity

The NIRSPEC Brown Dwarf Spectroscopic Survey II: High-Resolution J-Band Spectra of M, L and T Dwarfs

We present a sequence of high resolution (R~20,000 or 15 km/s) infrared spectra of stars and brown dwarfs spanning spectral types M2.5 to T6. Observations of 16 objects were obtained using eight echelle orders to cover part of the J-band from 1.165-1.323 micron with NIRSPEC on the Keck II telescope. By comparing opacity plots and line lists, over 200 weak features in the J-band are identified with either FeH or H2O transitions. Absorption by FeH attains maximum strength in the mid-L dwarfs, while H2O absorption becomes systematically stronger towards later spectral types. Narrow resolved features broaden markedly after the M to L transition. Our high resolution spectra also reveal that the disappearance of neutral Al lines at the boundary between M and L dwarfs is remarkably abrupt, presumably because of the formation of grains. Neutral Fe lines can be traced to mid-L dwarfs before Fe is removed by condensation. The neutral potassium (K I) doublets that dominate the J-band have pressure broadened wings that continue to broaden from ~50 km/s (FWHM) at mid-M to ~500 km/s at mid-T. In contrast however, the measured pseudo-equivalent widths of these same lines reach a maximum in the mid-L dwarfs. The young L2 dwarf, G196-3B, exhibits narrow potassium lines without extensive pressure-broadened wings, indicative of a lower gravity atmosphere. Kelu-1AB, another L2, has exceptionally broad infrared lines, including FeH and H2O features, confirming its status as a rapid rotator. In contrast to other late T objects, the peculiar T6 dwarf 2MASS 0937+29 displays a complete absence of potassium even at high resolution, which may be a metallicity effect or a result of a cooler, higher-gravity atmosphere.Comment: 53 pages, 21 figures, data will be available at http://www.astro.ucla.edu/~mclean/BDSSarchive

Development of second generation scaffolds for iminium ion catalysis

This thesis embraces two main sections that examine alternative architectures for the iminium ion catalysis of the Diels-Alder reaction - comprising acyclic and cyclic systems. Chapter 1 provides an overview of iminium ion and enamine catalysed processes. Focus is on the structural requirements of catalysts for effective and efficient transformations. Chapter 2 highlights work carried out previously within the group and provides a more in depth review of the Diels-Alder reaction, the protocol adopted for comparing catalyst activity and methods by which results were analysed. Chapter 3 describes the design and synthesis of a series of five membered cyclic catalysts based on the pyrazolidine subunit. These systems incorporated aspects of acyclic catalysts developed previously within the group to decrease reaction times and catalyst loadings. Reaction conditions were optimised with regards to solvent and acid co-catalyst. SAR studies of the cyclic and acyclic architectures lead to the expansion of the acyclic series within Chapter 4. This resulted in the most active acyclic catalyst to date with a conversion of 98% after of six hours within the iminium ion catalysed Diels-Alder reaction. Chapter 5 shows a combination of SAR studies and computer modelling that led to the design and synthesis of a series of six-membered cyclic analogues containing an a-heteroatom. These systems catalysed the Diels-Alder reaction more efficiently producing a conversion of 89% after three hows and 99% after six and would provide an effective architecture for the development of a chiral catalyst A trend was discovered relating the electronic environment of a p-carbonyl incorporated into the catalyst structure and its associated activity with supporting evidence from an associated computational project Finally, Chapter 6 describes preliminary studies into the three proposed component steps of the iminium ion catalysed Diels-Alder reaction. 1H NMR and UV spectroscopy was (and continues to be) used to examine these steps to gam valuable information iiyrilUig the mechanism of the catalytic cycle.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Breeding Habitats and New Breeding Locations for Ross’s Gull (Rhodostethia rosea) in the Canadian High Arctic

Published accounts list only four breeding sites for Ross’s gull (Rhodostethia rosea) in North America, but the discovery of additional breeding sites in Queen’s Channel, Nunavut, adds to growing evidence that this species is established as a regular breeder in the Canadian High Arctic despite its current status as a Threatened Species in Canada. We present nine breeding records of Ross’s gull in Canada. Five are from Queen’s Channel alone, and these include two new breeding records from 2011. The geographic proximity and similarity in topography, microhabitat, and interspecific nesting associ­ations that characterize Ross’s gull nesting sites in the Canadian High Arctic suggest that additional surveys of surrounding suitable habitat would confirm a stable and globally significant breeding population of this very poorly known species in North America.Selon des données déjà publiées, il n’existe que quatre lieux de reproduction de la mouette rosée (Rhodostethia rosea) en Amérique du Nord. Cependant, la découverte de nouveaux lieux de reproduction dans le chenal Queens, au Nunavut, vient renforcer les preuves selon lesquelles cette espèce est établie en tant qu’oiseau nicheur régulier dans l’Extrême-Arctique canadien, même si elle fait actuellement partie de la liste des espèces menacées au Canada. Nous présentons neuf enregis­trements relatifs à la reproduction de la mouette rosée au Canada. Cinq de ces enregistrements sont relatifs au chenal Queens, dont deux nouveaux enregistrements de reproduction qui datent de 2011. La proximité géographique et les similitudes sur le plan de la topographie, du microhabitat et des associations de nidification interspécifiques caractérisant les lieux de reproduction de la mouette rosée dans l’Extrême-Arctique canadien laissent entendre que des levés supplémentaires d’habitats environnants convenables permettraient de confirmer une population d’oiseaux nicheurs stable et généralement importante de cette espèce très peu connue en Amérique du Nord

Tissue engineering a fetal membrane

The aim of this study was to construct an artificial fetal membrane (FM) by combination of human amniotic epithelial stem cells (hAESCs) and a mechanically enhanced collagen scaffold containing encapsulated human amniotic stromal fibroblasts (hASFs). Such a tissue-engineered FM may have the potential to plug structural defects in the amniotic sac after antenatal interventions, or to prevent preterm premature rupture of the FM. The hAESCs and hASFs were isolated from human fetal amniotic membrane (AM). Magnetic cell sorting was used to enrich the hAESCs by positive ATP-binding cassette G2 selection. We investigated the use of a laminin/fibronectin (1:1)-coated compressed collagen gel as a novel scaffold to support the growth of hAESCs. A type I collagen gel was dehydrated to form a material mimicking the mechanical properties and ultra-structure of human AM. hAESCs successfully adhered to and formed a monolayer upon the biomimetic collagen scaffold. The resulting artificial membrane shared a high degree of similarity in cell morphology, protein expression profiles, and structure to normal fetal AM. This study provides the first line of evidence that a compacted collagen gel containing hASFs could adequately support hAESCs adhesion and differentiation to a degree that is comparable to the normal human fetal AM in terms of structure and maintenance of cell phenotype

Template banks to search for compact binaries with spinning components in gravitational wave data

Gravitational waves from coalescing compact binaries are one of the most promising sources for detectors such as LIGO, Virgo and GEO600. If the components of the binary posess significant angular momentum (spin), as is likely to be the case if one component is a black hole, spin-induced precession of a binary's orbital plane causes modulation of the gravitational-wave amplitude and phase. If the templates used in a matched-filter search do not accurately model these effects then the sensitivity, and hence the detection rate, will be reduced. We investigate the ability of several search pipelines to detect gravitational waves from compact binaries with spin. We use the post-Newtonian approximation to model the inspiral phase of the signal and construct two new template banks using the phenomenological waveforms of Buonanno, Chen and Vallisneri. We compare the performance of these template banks to that of banks constructed using the stationary phase approximation to the non-spinning post-Newtonian inspiral waveform currently used by LIGO and Virgo in the search for compact binary coalescence. We find that, at the same false alarm rate, a search pipeline using phenomenological templates is no more effective than a pipeline which uses non-spinning templates. We recommend the continued use of the non-spinning stationary phase template bank until the false alarm rate associated with templates which include spin effects can be substantially reduced.Comment: 11 pages, 3 figure

The potential for dietary factors to prevent or treat osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease for which there are no disease-modifying drugs. It is a leading cause of disability in the UK. Increasing age and obesity are both major risk factors for OA and the health and economic burden of this disease will increase in the future. Focusing on compounds from the habitual diet that may prevent the onset or slow the progression of OA is a strategy that has been under-investigated to date. An approach that relies on dietary modification is clearly attractive in terms of risk/benefit and more likely to be implementable at the population level. However, before undertaking a full clinical trial to examine potential efficacy, detailed molecular studies are required in order to optimise the design. This review focuses on potential dietary factors that may reduce the risk or progression of OA, including micronutrients, fatty acids, flavonoids and other phytochemicals. It therefore ignores data coming from classical inflammatory arthritides and nutraceuticals such as glucosamine and chondroitin. In conclusion, diet offers a route by which the health of the joint can be protected and OA incidence or progression decreased. In a chronic disease, with risk factors increasing in the population and with no pharmaceutical cure, an understanding of this will be crucial