Studies on starches: with particular reference to the characterization or their amylose and amylopeotin components; and analyses or some starch-containing materials

Starch is one of the most important natural products. It finds many industrial uses and applications, and, in different forms, is used throughout the world as a staple item of the human diet. Consequently, the structure and properties of starch have deservedly formed the subject of extensive investigations both by chemists and bio-chemists. Because of the inherent difficulties in the many problems which arose, and the continual need for development of new techniques, progress prior to 1925 was slow and uncertain. However, the subsequent elucidation of the precise structural configurations of the simpler sugars e.g. glucose, maltose and cellobiose, gave a firm foundation for future work, and steady progress ensued. One of the most important advances was the realisation of the apparent inhomogeneity of starch; this was followed in 1941 by the first quantitative fractionation into simpler components. As a result, the highly polymeric nature and main structural features of the molecule are now well estab¬ lished. In general, starches can be separated into two distinct entities, both of which are high polymers of α-D-glucopyranose units joined by α-1:4-glycosidic linkages: (a) Amylose - a mixture of very long, essentially inbranched, chains of these units. (b) Arnylopectin - a mixture of much shorter, highly branched chains of these units, the inter-chain, or branching, linkages being essentially α-l;6. Yet many problems still remain. Some are concerned with the clarification of controversial issues on which the present experimental evidence, as reported by various workers, is either at variance or considered to be inconclusive; the majority, however, are concerned with the fundamentally important details of fine structure and the molecular size and shape of the starch components. It is now accepted that there is little prospect of progress on these particular problems unless full use is made by the carbohydrate chemist of physical and enzymic methods to supplement purely chemical approaches. When the researches reported in this thesis were begun, it was apparent that, before the established physical techniques used in polymer chemistry for the determination of molecular size and shape could be profitably applied, work on the following topics was an essential preliminary in order that the materials to be studied could be adequately and accurately characterized:- (1) The development of a differential potentiometric iodine titration technique for the determination of the % amylose in starches and their fractionated components, and for the possible characterization of other a-1:4-glucosans. It was desirable that the apparatus should be considerably more sensitive and accurate than any of those previously reported, yet also be capable of simple operation as a routine analytical method. (2) A study of the oxidation of starches by the periodate ion in view of the low quoted percentage accuracy of the technique, and the then existing lack of agreement in the literature on the following points; (a) conditions for the quantitative estimation of the formic acid released, (b) the length of time required for complete oxidation, and the possibility of over-oxidation, (c) the presence of intact glucose residues after oxidation, suggesting that inter-chain linkages other than 1:6 existed in amylopectin. (3) A study of the effect of the presence of contaminating protein on results obtained by use of the potentiometric iodine titration and periodate oxidation techniques. (4) The preparation, and purification, of starches from several botanical sources which had not previously been studied, so that the use at any stage of industrial samples of unknown origin, treatment, and history could be avoided. By preparation of the starches under the mildest possible conditions, so as to minimise degradation, these same samples could later be used for physico-chemical studies of molecular size and shape. The opportunity was taken, after the extraction of each starch, to apply a graded series of extractions to the residual plant material; the fractions isolated were analysed for protein, ash, and uronic acid content, and the polysaccharide content was investigated by chromatographic analyses of the sugars liberated on hydrolysis

Heterotic Models from Vector Bundles on Toric Calabi-Yau Manifolds

We systematically approach the construction of heterotic E_8 X E_8 Calabi-Yau models, based on compact Calabi-Yau three-folds arising from toric geometry and vector bundles on these manifolds. We focus on a simple class of 101 such three-folds with smooth ambient spaces, on which we perform an exhaustive scan and find all positive monad bundles with SU(N), N=3,4,5 structure groups, subject to the heterotic anomaly cancellation constraint. We find that anomaly-free positive monads exist on only 11 of these toric three-folds with a total number of bundles of about 2000. Only 21 of these models, all of them on three-folds realizable as hypersurfaces in products of projective spaces, allow for three families of quarks and leptons. We also perform a preliminary scan over the much larger class of semi-positive monads which leads to about 44000 bundles with 280 of them satisfying the three-family constraint. These 280 models provide a starting point for heterotic model building based on toric three-folds.Comment: 41 pages, 5 figures. A table modified and a table adde

Quiver Structure of Heterotic Moduli

We analyse the vector bundle moduli arising from generic heterotic compactifications from the point of view of quiver representations. Phenomena such as stability walls, crossing between chambers of supersymmetry, splitting of non-Abelian bundles and dynamic generation of D-terms are succinctly encoded into finite quivers. By studying the Poincar\'e polynomial of the quiver moduli space using the Reineke formula, we can learn about such useful concepts as Donaldson-Thomas invariants, instanton transitions and supersymmetry breaking.Comment: 38 pages, 5 figures, 1 tabl

Heterotic Compactification, An Algorithmic Approach

We approach string phenomenology from the perspective of computational algebraic geometry, by providing new and efficient techniques for proving stability and calculating particle spectra in heterotic compactifications. This is done in the context of complete intersection Calabi-Yau manifolds in a single projective space where we classify positive monad bundles. Using a combination of analytic methods and computer algebra we prove stability for all such bundles and compute the complete particle spectrum, including gauge singlets. In particular, we find that the number of anti-generations vanishes for all our bundles and that the spectrum is manifestly moduli-dependent.Comment: 36 pages, Late

SEADS 3.0 Sectoral Energy/Employment Analysis and Data System

SEADS 3.0, the Sectoral Energy/Employment Analysis and Data System, is a revision and upgrading of SEADS–PC, a software package designed for the analysis of policy that could be described by modifying final demands of consumer, businesses, or governments (Roop, et al., 1995). If a question can be formulated so that implications can be translated into changes in final demands for goods and services, then SEADS 3.0 provides a quick and easy tool to assess preliminary impacts. And SEADS 3.0 should be considered just that: a quick and easy way to get preliminary results. Often a thorough answer, even to such a simple question as, “What would be the effect on U. S. energy use and employment if the Federal Government doubled R&D expenditures?” requires a more sophisticated analytical framework than the input-output structure embedded in SEADS 3.0. This tool uses a static, input-output model to assess the impacts of changes in final demands on first industry output, then employment and energy use. The employment and energy impacts are derived by multiplying the industry outputs (derived from the changed final demands) by industry-specific energy and employment coefficients. The tool also allows for the specification of regional or state employment impacts, though this option is not available for energy impacts

Quality assessment metrics for whole genome gene expression profiling of paraffin embedded samples

BACKGROUND: Formalin fixed, paraffin embedded tissues are most commonly used for routine pathology analysis and for long term tissue preservation in the clinical setting. Many institutions have large archives of Formalin fixed, paraffin embedded tissues that provide a unique opportunity for understanding genomic signatures of disease. However, genome-wide expression profiling of Formalin fixed, paraffin embedded samples have been challenging due to RNA degradation. Because of the significant heterogeneity in tissue quality, normalization and analysis of these data presents particular challenges. The distribution of intensity values from archival tissues are inherently noisy and skewed due to differential sample degradation raising two primary concerns; whether a highly skewed array will unduly influence initial normalization of the data and whether outlier arrays can be reliably identified. FINDINGS: Two simple extensions of common regression diagnostic measures are introduced that measure the stress an array undergoes during normalization and how much a given array deviates from the remaining arrays post-normalization. These metrics are applied to a study involving 1618 formalin-fixed, paraffin-embedded HER2-positive breast cancer samples from the N9831 adjuvant trial processed with Illumina’s cDNA-mediated Annealing Selection extension and Ligation assay. CONCLUSION: Proper assessment of array quality within a research study is crucial for controlling unwanted variability in the data. The metrics proposed in this paper have direct biological interpretations and can be used to identify arrays that should either be removed from analysis all together or down-weighted to reduce their influence in downstream analyses

McMurdo Dry Valleys, Antarctica - A Mars Phoenix Mission Analog

The Phoenix mission (PHX; May 25 - Nov. 2, 2008) studied the north polar region of Mars (68deg N) to understand the history of water and potential for habitability. Phoenix carried with it a wet chemistry lab (WCL) capable of determining the basic solution chemistry of the soil and the pH value, a thermal and evolved-gas analyzer capable of determining the mineralogy of the soil and detecting ice, microscopes capable of seeing soil particle shapes, sizes and colors at very high resolution, and a soil probe (TECP) capable of detecting unfrozen water in the soil. PHX coincided with an international effort to study the Earth s polar regions named the International Polar Year (IPY; 2007-2008). The best known Earth analog to the Martian high-northern plains, where Phoenix landed, are the McMurdo Dry Valleys (MDV), Antarctica (Fig. 1). Thus, the IPY afforded a unique opportunity to study the MDV with the same foci - history of water and habitability - as PHX. In austral summer 2007, our team took engineering models of WCL and TECP into the MDV and performed analgous measurements. We also collected sterile samples and analyzed them in our home laboratories using state-of-the-art tools. While PHX was not designed to perform biologic analyses, we were able to do so with the MDV analog samples collected

Long-Term Potentiation: One Kind or Many?

Do neurobiologists aim to discover natural kinds? I address this question in this chapter via a critical analysis of classification practices operative across the 43-year history of research on long-term potentiation (LTP). I argue that this 43-year history supports the idea that the structure of scientific practice surrounding LTP research has remained an obstacle to the discovery of natural kinds

The Kondo effect in ferromagnetic atomic contacts

Iron, cobalt and nickel are archetypal ferromagnetic metals. In bulk, electronic conduction in these materials takes place mainly through the $s$ and $p$ electrons, whereas the magnetic moments are mostly in the narrow $d$-electron bands, where they tend to align. This general picture may change at the nanoscale because electrons at the surfaces of materials experience interactions that differ from those in the bulk. Here we show direct evidence for such changes: electronic transport in atomic-scale contacts of pure ferromagnets (iron, cobalt and nickel), despite their strong bulk ferromagnetism, unexpectedly reveal Kondo physics, that is, the screening of local magnetic moments by the conduction electrons below a characteristic temperature. The Kondo effect creates a sharp resonance at the Fermi energy, affecting the electrical properties of the system;this appears as a Fano-Kondo resonance in the conductance characteristics as observed in other artificial nanostructures. The study of hundreds of contacts shows material-dependent lognormal distributions of the resonance width that arise naturally from Kondo theory. These resonances broaden and disappear with increasing temperature, also as in standard Kondo systems. Our observations, supported by calculations, imply that coordination changes can significantly modify magnetism at the nanoscale. Therefore, in addition to standard micromagnetic physics, strong electronic correlations along with atomic-scale geometry need to be considered when investigating the magnetic properties of magnetic nanostructures.Comment: 7 pages, 5 figure