The determination of the topological structure of skin friction lines on a rectangular wing-body combination

A short tutorial in the application of topological ideas to the intepretation of oil flow patterns is presented. Topological concepts such as critical points, phase portraits, topological stability, and indexing are discussed. These concepts are used in an ordered procedure to construct phase portraits of skin friction lines with oil flow patterns for a wing-body combination and two angles of attack. The relationship between the skin friction phase portrait and planar cuts of the velocity field is also discussed

Clinical and Genetic Risk Factors Associated with Psoriatic Arthritis among Patients with Psoriasis.

IntroductionPsoriatic arthritis (PsA) is a chronic, inflammatory arthritis that affects an estimated 30% of patients with psoriasis. PsA is underdiagnosed in primary care and dermatology clinics due to a variety of reasons, including failure of healthcare providers to ask about symptoms, overlap of symptoms and signs with other rheumatologic conditions, and lack of a specific diagnostic test. A delay in PsA diagnosis and treatment, even as short as 6 months, can lead to decreased quality of life, increased joint damage, and worse long-term physical function. In this study, we sought to identify the clinical and genetic factors that help discriminate patients with PsA from those with cutaneous psoriasis only.MethodsWe analyzed a cohort of 974 psoriasis patients at an academic medical center, of whom 175 had confirmed PsA, and performed univariate, multivariate, and predictive modeling to determine factors associated with PsA.ResultsThe univariate analysis revealed significant positive associations of PsA with age, nail involvement, scalp involvement, skin fold involvement, elbow/knee involvement, psoriasis severity, plaque subtype, erythrodermic subtype, hypertension, type 2 diabetes, and coronary artery disease, and a significant negative association of PsA with the human leukocyte antigen (HLA)-C*06:02 allele. In the multivariate analysis, nail involvement, type 2 diabetes, and pustular psoriasis remained significantly associated with PsA, while HLA-C*06:02 positivity remained protective. There was a trend towards an association of PsA with older age, younger age of psoriasis onset, and skin fold involvement, while there was protective trend for smoking. A predictive model including both clinical and genetic factors showed reasonable discriminative ability between psoriasis and PsA, with an area under the curve of 0.87 for a receiver operating characteristic curve.ConclusionThis study identified a number of clinical and genetic features that could help stratify patients who are at higher risk for having PsA and for whom rheumatology referral may be beneficial

The Profits to Insider Trading: A Performance-Evaluation Perspective

This paper estimates the profits to insiders when they trade their company's stock. We construct a rolling purchase portfolio' that holds all shares purchased by insiders over the previous year and an analogous sale portfolio' that holds all shares sold by insiders over the previous year. We then analyze the returns to these value-weighted portfolios using performance-evaluation methods. This approach allows us to study the returns to insider transactions beginning on the day after their execution, and is free of the statistical difficulties that plague event studies on long-horizon returns. Using a comprehensive sample of reported insider transactions from 1975 - 1996, we find that the purchase portfolio earns abnormal returns of about 40 basis points per month, with about one-sixth of these abnormal returns accruing within the first five days after the initial transaction, and one-third within the first month. The sale portfolio does not earn abnormal returns. Our portfolio-based approach also allows for straightforward decompositions of the purchase and sale portfolios by various characteristics. We find that the abnormal returns to insider trades in small firms are not significantly different from those in large firms, and that top executives do not earn higher abnormal returns than do other insiders.

Estimating the Returns to Insider Trading

This paper estimates the returns to insiders when they trade their company’s stock. We first construct a rolling "purchase portfolio" that holds all shares purchased by insiders for a six-month period, and an analogous "sale portfolio" that holds all shares sold by insiders for six months. The six-month horizon is chosen to coincide with the "short-swing" rule of the Securities and Exchange Act of 1934; a rule that prohibits profit-taking by insiders for offsetting trades within six months. We then employ performance-evaluation methods to analyze the returns to the purchase and sale portfolios. This approach yields a proxy for the value-weighted returns to insider transactions beginning on the day after their execution and avoids the statistical difficulties that plague event studies on long-horizon returns. Our methods are designed to estimate the returns earned by insiders themselves and thereby differ from the previous insider-trading literature, which focuses on the "informativeness" of insider trades for other investors. Using a comprehensive sample of reported insider transactions from 1975-1996, we find that the purchase portfolio earns abnormal returns of more than 50 basis points per month. About one-quarter of these abnormal returns accrue within the first five days after the initial transaction, and one-half accrue within the first month. The sale portfolio does not earn abnormal returns. Our portfolio-based approach also allows for straightforward decompositions of performance by various characteristics; we find that the abnormal returns to insider trades in small firms are not significantly different from those in large firms, and that top executives do not earn higher abnormal returns than do other insiders.

Syntheses and fluorescence properties of sterically-hindered esters of 9-anthroic acid

For over a decade, Professor Thomas C. Werner and his students have been studying the unusual florescence properties of methyl-9-anthroate. In the ground state of this ester, the carboxyl group lies perpendicular to the anthracene rings due to steric inhibition by the peri hydrogens. Werner has postulated that, upon excitation, the carboxyl group rotates to form a planar configuration with the anthracene rings, and that this rotation is the cause of the unusual spectral properties. In our work, we have attempted to prove or disprove this hypothesis. We have chosen to synthesize analogues of methyl-9-anthroate in which carboxyl group rotation is sterically hindered. Ideally, replacing one or both of the peri hydrogens by a chlorine or methyl group would hinder carboxyl group rotation most effectively. However, after a long effort, we have been unable to synthesize one of these molecules. We have, however, synthesized two esters in which the ester groups are bulky, namely, cyclohexyl-9-anthroate and t-butyl-9-anthroate. The quantum yield of these esters is solvents of various polarity has been investigated. While our results do not shed any further light on the question of carboxyl group rotation, the data do support a hypothesis set forth by Werner and Hoffman attributing the decrease in quantum yield with increasing solvent polarity to increasing internal conversion due to excited polarity to increasing internal conversion due to excited state solute solvent interactions

Studies on achromobacter iophagus and other collagenolytic hide bacteria

From Introduction: Collagenases are enzymes capable of specifically attacking the native collagen helix under non-denaturing conditions at physiological conditions of pH, temperature and salt concentration. They are active only on collagen or its breakdown products and are without effect on any other fibrous or globular protein. In the laboratory, collagenases are used in investigations of the biosynthesis of collagen and for structural and immunochemical studies of collagens and collagen-like proteins; also they are proving their worth as agents for facilitating tissue transplantation and for cell-dispersion in tissue cultures . Established clinical applications of collagenases include the treatment of burns and dermal lesions; in addition they are being evaluated as agents for the removal of undesirable tissues such as herniated intervertebral discs and the sloughs resulting from cryogenic or cauterizing procedures. Moreover, as human collagenases are implicated in various pathological disorders involving connective tissue degradation, the roles played by these collagenases are being investigated in the hope of finding ways to arrest, control or treat the diseases

Yield and water-relation responses of soybeans to single and multiple periods of soil-moisture stress

Soybean physiological and yield responses to water stress were studied in a movable weather (rainout) shelter facility at Ames, Iowa, during the summer of 1978. Soil-moisture deficits were induced in six combinations of three stress periods during reproductive growth to investigate the possibility of physiological and yield enhancement in response to preconditioning for later water stress. Preconditioning did result in enhanced stomatal conductance, but the enhancement could not be attributed to either avoidance or toleration of low leaf water potentials. Cultivar variations in physiological responses to preconditioning were not detected;Cultivar yield differences in response to the various stress treatments resulted primarily from stress timing although evidence for less yield sensitivity to water stress was observed in some cultivars. Total plant yield reductions were approximately equally distributed on the upper 75 cm of stems and on the branches. Preconditioned plants had less yield reduction during later stress periods than did unconditioned plants which were stressed for the first time. Cultivar yield differences in response to preconditioning seemed to result from stress timing effects on unconditioned plant yields rather than on cultivar responses to preconditioning;Although the stress-induced yield reductions were closely related to above-ground dry-weight losses for each of the stress treatments, stress early in reproductive growth resulted in greater dry-matter partitioning to the seeds. The earlier the first stress occurred in reproductive growth, the greater was partitioning to the seeds; consequently, mild stress during the early flowering period of indeterminate soybeans could conceivably increase yields through partitioning effects. Preconditioned plants received their pre-stress treatment early in reproductive growth, so their partitioning to the seeds was greater than unconditioned plants;Investigations on the need for weighting of a soil-moisture stress index for growth stages revealed a curvilinear yield response to the accumulated stress. This curvilinear response was related to a very high low-stress-treatment yield for the highest-yielding cultivar. Stress during early beginning-seed filling caused less yield reductions than predicted from the stress index and may need to be weighted for better yield predictions

The infestation of molluscs by Polydora spp.

Merged with duplicate record 10026.1/2675 on 27.02.2017 by CS (TIS)Merged with duplicate record 10026.1/2675 Submitted by Collection Services ([email protected]) on 2013-11-07T13:30:24Z No. of bitstreams: 1 RICHARD MICHAEL LESLIE KENT.PDF: 5596525 bytes, checksum: 642b67eeb4f6588a9495fd9da490351c (MD5) Approved for entry into archive by Collection Services([email protected]) on 2013-11-07T13:36:35Z (GMT) No. of bitstreams: 1 RICHARD MICHAEL LESLIE KENT.PDF: 5596525 bytes, checksum: 642b67eeb4f6588a9495fd9da490351c (MD5) Made available in DSpace on 2013-11-07T13:36:35Z (GMT). No. of bitstreams: 1 RICHARD MICHAEL LESLIE KENT.PDF: 5596525 bytes, checksum: 642b67eeb4f6588a9495fd9da490351c (MD5) Previous issue date: 1977The ecology of Polydora, epp was reviewed and the infestation of molluscs by the boring, spionid polychaete, Polydora ciliata, was studied in detail. X-radiography showed that, P. ciailt a infested a wide variety of molluscan substrates, but it . occurred in greatest abundance on large, rough-surfaced, epibenthic shells, which were collected from the-sublittoral zone and the level of extreme low water spring tides, of shores sheltered from wave action. P. ciliata was contagiously dispersed on mussel--shells. Monthly radiographs of mussels indicated that maximum settlement of P. ciliata larvae in the river Fowey, 1 occurred in May. The effect of heavy infestations of P. ciliata on limpets P. vul ata , mussels (Eytilus edulis), and oysters (Crassostrea is9 was investigated. At certain times of the year, heavy infestations of P. ciliata reduced the dry weight condition and fecundity of limpets and mussels, but did not seem'to adversely affect C. i ae. Compression tests showed that P. ciliate weakened mussel shells. Predation experiments, with Cancer a s, indicated that this might increase the mussels' vulnerability to predation. Heavy P. ciliata infestation also reduced the mussels' resistance to loads which tended to force the mussele' valves apart. This may decrease the mussels' phyeico-chemical tolerance, and increase their vulnerability to starfish predation. Limpet adhesion, measured on the shore with a simple dynamometer, was impaired by P. ciliata infestation. This may reduce the limpets' resistance to wave action, and increase their vulnerability to predation. Reasons for the adverse effects of P. ciliata infestation on limpets and mussels are suggested, and the ecological and commercial implications of the infestation are discussed