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Search Results: 1 - 10 of 463247 matches for " Norman A.; "
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Parastomal Hernia as a Risk Factor for Ileal Conduit Fistulae  [PDF]
Thomas A. A Skinner, Richard W Norman
International Journal of Clinical Medicine (IJCM) , 2011, DOI: 10.4236/ijcm.2011.23048
Abstract: Purpose: To review potential risk factors for the development of ileal conduit fistulae. Methods: Two patients were identified who had a remote history of an ileal conduit and who formed a fistula from the conduit—one to the small bowel and one to the skin. Their presentation, management and outcomes are described. Results: Both patients had parastomal hernias as the likely cause of their fistula formation. Discussion: Parastomal herniation may contribute to fistula formation due to a strangulated ischemic pressure necrosis of the adjacent ileal conduit and/or bowel.
Centenarian genes
Norman A Johnson
Genome Biology , 2001, DOI: 10.1186/gb-2001-2-11-reports0039
Abstract: Thomas Perls and his colleagues have taken a somewhat different tack to studying aging in humans, focusing on people who have extraordinary longevity. They hypothesize that these very long-lived people represent a special class of people who not only largely escape the main age-related diseases (cancer, cardiovascular disease, stroke and diabetes) but who also age more slowly than the general population. Perls' team found that siblings of centenarians are four times as likely to live to age 91 as the general population. They are now interested in more specific genetic analysis. Few centenarians have the disease-associated genetic variants such as e-4 of Apo-E, but do they also have specific genetic differences that predispose them to longer lives, apart from the relative absence of deleterious alleles? Is it the genetic variants they have or the variants they do not have that allows for their extreme longevity?Puca et al. performed a genome-wide scan for chromosomal regions associated with longevity. Their sample consisted of 137 sibships containing 308 individuals. In each of these sibships, at least one of the members (the proband) attained a minimum age of 98. In addition to the proband, each sibship had at least one other female aged 95 or greater or one male aged 91 or greater. The participants in the study were from North America and consisted of many different ethnic groups. Initially, 400 markers were screened, corresponding to an average density of one marker every 10 centimorgans. Additional markers were screened in regions suggestive of linkage. Their analysis is somewhat different from the standard analysis used in other types of mapping studies because only individuals that have the trait (longevity) are included. The researchers performed an 'Affected-only non-parametric analysis', in which they looked for chromosomal regions that showed excess sharing of variants that were identical by descent in the sibships.The combination of the genome-wide scan an
The reporting of statistics in medical educational studies: an observational study
Norman A Desbiens
BMC Medical Research Methodology , 2007, DOI: 10.1186/1471-2288-7-35
Abstract: For this observational study, we used electronic searching to identify all survey studies published in Academic Medicine and the Journal of General Internal Medicine in which an entire population was studied. We tallied whether inferential statistics were used and whether p-values were reported.Eighty-four articles were found: 62 in Academic Medicine and 22 in the Journal of General Internal Medicine. Overall, 38 (45%) of the articles reported or stated that they calculated statistics: 35% in Academic Medicine and 73% in the Journal of General Internal Medicine.Educational enumeration surveys frequently report statistical tests. Until a better case can be made for doing so, a simple rule can be proffered to researchers. When studying an entire population (e.g., all program directors, all deans, and all medical schools) for factual information, do not perform statistical tests. Reporting percentages is sufficient and proper.The inclusion of statistical tests has been inculcated into investigators as a necessary step in the reporting of medical research. While descriptive statistics may always be used (unless the data are too sparse), the employment of inferential statistics – statistics calculated from a study sample in order to make generalizations about a larger study target population – is not always appropriate.One situation in which statistical testing must be used with caution is when tests are calculated from what may be a non-random sample [1]. In the medical education literature, this situation may occur when researchers use subjects from their own institutions. The calculation of inferential statistics in these studies is only justifiable if researchers can be assured that the findings from their institution are similar to the reference population. From a strict theoretical viewpoint, they should not be calculated in these studies unless the assumption is made that the institutional sample is similar to a random sample – an inference that cannot be proven f
The Role of the Dar es Salaam Stock Exchange in Safeguarding Securities Investors in Tanzania
A.S. Norman
International Business Management , 2012, DOI: 10.3923/ibm.2010.222.228
Abstract: This study examines the roles/functions of the Dar es Salaam Stock Exchange (DSE) in safeguarding the investors of securities in Tanzania. The business of securities, both bonds and shares has taken a new dimension since its establishment in Tanzania. It has attracted many people of different cadre. However, some investors have been doubtful on whether they should invest or not. The doubts seem to be cemented on risk associated with investing. This study therefore, expounds the role of DSE through narrating measures that have been put in place for safeguarding the investors of securities. The study utilizes mixed methodologies of data collection with documentary and the use artifacts taking the leading role. The study concludes that there are measures that have been put in place through rules and regulations with the view to protecting investors of stock exchange. However, it is the investors responsibility to attain necessary information regarding the firms that sell bonds and or shares and studying, among others, the financial information of the firms so as to realize the performance and prospective opportunities of the firms.
Vortices and the Abel-Jacobi map
Norman A. Rink
Physics , 2013, DOI: 10.1016/j.geomphys.2013.10.017
Abstract: The abelian Higgs model on a compact Riemann surface \Sigma supports vortex solutions for any positive vortex number d \in \ZZ. Moreover, the vortex moduli space for fixed d has long been known to be the symmetrized d-th power of \Sigma, in symbols, \Sym^d(\Sigma). This moduli space is Kahler with respect to the physically motivated metric whose geodesics describe slow vortex motion. In this paper we appeal to classical properties of \Sym^d(\Sigma) to obtain new results for the moduli space metric. Our main tool is the Abel-Jacobi map, which maps \Sym^d(\Sigma) into the Jacobian of \Sigma. Fibres of the Abel-Jacobi map are complex projective spaces, and the first theorem we prove states that near the Bradlow limit the moduli space metric restricted to these fibres is a multiple of the Fubini-Study metric. Additional significance is given to the fibres of the Abel-Jacobi map by our second result: we show that if \Sigma is a hyperelliptic surface, there exist two special fibres which are geodesic submanifolds of the moduli space. Even more is true: the Abel-Jacobi map has a number of fibres which contain complex projective subspaces that are geodesic.
Non-abelian vortices on CP^1 and Grassmannians
Norman A. Rink
Mathematics , 2012, DOI: 10.1063/1.4798468
Abstract: Many properties of the moduli space of abelian vortices on a compact Riemann surface are known. For non-abelian vortices the moduli space is less well understood. Here we consider non-abelian vortices on the Riemann sphere CP^1, and we study their moduli spaces near the Bradlow limit. We give an explicit description of the moduli space as a Kahler quotient of a finite-dimensional linear space. The dimensions of some of these moduli spaces are derived. Strikingly, there exist non-abelian vortex configurations on CP^1, with non-trivial vortex number, for which the moduli space is a point. This is in stark contrast to the moduli space of abelian vortices. For a special class of non-abelian vortices the moduli space is a Grassmannian, and the metric near the Bradlow limit is a natural generalization of the Fubini--Study metric on complex projective space. We use this metric to investigate the statistical mechanics of non-abelian vortices. The partition function is found to be analogous to the one for abelian vortices.
Phenolic Profiles and Polyphenol Oxidase (PPO) Gene Expression of Red Clover (Trifolium pratense) Selected for Decreased Postharvest Browning  [PDF]
Isabelle A. Kagan, Randy D. Dinkins, Norman L. Taylor
American Journal of Plant Sciences (AJPS) , 2016, DOI: 10.4236/ajps.2016.710140
Abstract: Red clover (Trifolium pratense L.) is a legume forage abundant in phenolic compounds. It tends to brown when cut for hay, due to oxidation of phenolic compounds catalyzed by polyphenol oxidase (PPO), and subsequent binding to proteins. Selecting for a greener hay may provide information about the relationship of browning, PPO, and phenolics to each other. The red clover Kenland cultivar was selected over eight breeding cycles for decreased browning after being cut and dried 48 h in the field. Expression of PPO1 and PPO3, in Kenland and three of the eight cycles, was compared by real-time quantitative PCR. Phenolic compounds in Kenland and Cycle 8, collected 0, 24, and 48 h after cutting, were quantified by high-performance liquid chromatography (HPLC). Visual browning scores decreased 12% between Kenland and Cycle 8 (P = 0.02). PPO1 and PPO3 gene expression were not affected by selection. Clovamide decreased 26% in Cycle 8 relative to Kenland (P = 0.016). Sissotrin decreased 10% in Cycle 8 (P = 0.043). Neither total formononetin nor total biochanin A was affected by selection (P = 0.63 and 0.45, respectively). These results suggest that when selecting clover for decreased postharvest browning, a decrease occurs in a phenolic compound that can bind protein independently of PPO. However, PPO1 and PPO3 gene expression, and the major red clover isoflavones, are minimally affected.
Cold Gas at High Redshift
Colin A. Norman,Robert Braun
Physics , 1995,
Abstract: We discuss the current observational and theoretical issues concerning cold gas at high redshift and present simulations showing how a number of observational issues can be resolved with planned future instrumentation.
A New Model of the Gravitational Lens 0957+561 and a Limit on the Hubble Constant
Norman A. Grogin,Ramesh Narayan
Physics , 1995, DOI: 10.1086/178171
Abstract: We present a simple mass model for the lensing galaxy in the gravitationally lensed quasar 0957+561. The model is a generalization of the singular isothermal sphere and includes a core radius, $r_c$, and a power-law index, $\eta$, defined such that mass increases as $r^\eta$ at large radius. We approximate the galaxy cluster surrounding the lensing galaxy with a quadratic potential described by its convergence $\kappa$ and shear $\gamma$. We fit the model to a recent high resolution VLBI map of the two images of 0957+561. We obtain a tight constraint on the radial index, $1.07 < \eta <1.18$, which means that the lens galaxy is nearly isothermal with increasing mass-to-light ratio out to $15 h^{-1}$ kpc. We also obtain an upper limit on the core radius, $r_c < 330 h^{-1}$ pc. We use the model to calculate the Hubble constant $H_0$ as a function of the time delay $\Delta\tau_{BA}$ between the two images: $H_0 = \left({ 82.5^{+5.9} _{-3.0} }\right) (1 - \kappa) \left({ \Delta\tau_{BA}/1.1 \,{\rm yr} }\right)^{-1}$ km/s/Mpc. Once $\Delta \tau_{BA}$ is measured, this will provide an upper bound on $H_0$ since $\kappa$ cannot be negative. In addition, the model degeneracy due to $\kappa$ can be eliminated if the one-dimensional velocity dispersion $\sigma$ of the lensing galaxy is measured. We then have $H_0 = \left({ 82.5^{+8.7} _{-5.6} }\right) (\sigma / 322\,{\rm km/s})^2 \left({ \Delta \tau_{BA} /1.1 \,{\rm yr} }\right)^{-1}$ km/s/Mpc. We investigate the effects of ellipticity in the lensing galaxy and clumpiness in the lensing cluster and find that these cause little change in our results.
Molecules at high Redshift: The Evolution of the Cool Phase of Protogalactic Disks
Colin A. Norman,Marco Spaans
Physics , 1996, DOI: 10.1086/303940
Abstract: We study the formation of molecular hydrogen, after the epoch of re-ionization, in the context of canonical galaxy formation theory due to hierarchical clustering. There is an initial epoch of $H_2$ production in the gas phase through the $H^-$ route which ends at a redshift of order unity. Star formation in the protogalactic disks can become self-regulated. The process responsible for the feedback is heating of the gas by the internal stellar radiation field which can dominate the background radiation field at various epochs. It is possible to define a maximum star formation rate during this epoch. Plausible estimates give a rate of 0.2-2 Mo yr-1 for condensations corresponding to 1 sigma and 2 sigma initial density fluctuations. Therefore, the production of metals and dust proceeds slowly in this phase. This moderate epoch is terminated by a phase transition to a cold dense and warm neutral/ionized medium once the metals and dust have increased to a level Z=0.03-0.1 Z_o. Then: (1) atoms and molecules such as C, O and CO become abundant and cool the gas to below $300 K$ ; (2) the dust abundance has become sufficiently high to allow shielding of the molecular gas and; (3) molecular hydrogen formation can occur rapidly on grain surfaces. This phase transition occurs at a redshift of approximately 1.5, with a fiducial range of 1.2
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