Arctic charr from Ennerdale Water: a pilot study

There are three fish species in the north west of England, Arctic charr (Salvelinus alpinus, L.), schelly (Coreqonus lavaretus. L.), and vendace (C. albula, L.), which have been reported as rare and vulnerable and have been identified as requiring the preparation and implementation of a conservation management plan. The presence of Arctic charr in Ennerdale Water has resulted in it being designated as a Site of Special Scientific Interest. These fish and one race of the species in Lake Windermere are the only English populations of charr known to spawn in running water. Associated with Ennerdale charr is the copepod parasite Salmincola edwardsii which has not been recorded from any other charr inhabited waters of the Lake District. However, it has been recorded on charr from four Scottish Lochs (Stack, Lee, Tay and Doon). The unique nature of Ennerdale is further highlighted by the presence of two crustaceans, Mysis relicta and Limnocalanus macrurus. The former has been recorded in Ireland while the latter is not known to exist anywhere else in the British Isles. The aim of this pilot study was to obtain baseline data on charr that spawn in Smithy Beck and the River Liza. This would indicate the current status of the population and help identify areas requiring further investigation. A total of 161 fish (95 males and 66 females) was caught and tagged over the 3 day period, 141 from Smithy Beck and 20 from the Liza. The raw data of the findings is presented in two appendices

Noncommutativity from the string perspective: modification of gravity at a mm without mm sized extra dimensions

We explore how the IR pathologies of noncommutative field theory are resolved when the theory is realized as open strings in background B-fields: essentially, since the IR singularities are induced by UV/IR mixing, string theory brings them under control in much the same way as it does the UV singularities. We show that at intermediate scales (where the Seiberg-Witten limit is a good approximation) the theory reproduces the noncommutative field theory with all the (un)usual features such as UV/IR mixing, but that outside this regime, in the deep infra-red, the theory flows continuously to the commutative theory and normal Wilsonian behaviour is restored. The resulting low energy physics resembles normal commutative physics, but with additional suppressed Lorentz violating operators. We also show that the phenomenon of UV/IR mixing occurs for the graviton as well, with the result that, in configurations where Planck's constant receives a significant one-loop correction (for example brane-induced gravity), the distance scale below which gravity becomes non-Newtonian can be much greater than any compact dimensions.Comment: 30 pages. Slight revision: clarified some points and added a referenc

Branes, Instantons, And Taub-NUT Spaces

ALE and Taub-NUT (or ALF) hyper-Kahler four-manifolds can be naturally constructed as hyper-Kahler quotients. In the ALE case, this construction has long been understood in terms of D-branes; here we give a D-brane derivation in the Taub-NUT case. Likewise, instantons on ALE spaces and on Taub-NUT spaces have ADHM-like constructions related to hyper-Kahler quotients. Here we refine the analysis in the Taub-NUT case by making use of a D-brane probe, and give an application to M-theory.Comment: 63 p

Dibaryons from Exceptional Collections

We discuss aspects of the dictionary between brane configurations in del Pezzo geometries and dibaryons in the dual superconformal quiver gauge theories. The basis of fractional branes defining the quiver theory at the singularity has a K-theoretic dual exceptional collection of bundles which can be used to read off the spectrum of dibaryons in the weakly curved dual geometry. Our prescription identifies the R-charge R and all baryonic U(1) charges Q_I with divisors in the del Pezzo surface without any Weyl group ambiguity. As one application of the correspondence, we identify the cubic anomaly tr R Q_I Q_J as an intersection product for dibaryon charges in large-N superconformal gauge theories. Examples can be given for all del Pezzo surfaces using three- and four-block exceptional collections. Markov-type equations enforce consistency among anomaly equations for three-block collections.Comment: 47 pages, 11 figures, corrected ref

Holomorphic potentials for graded D-branes

We discuss gauge-fixing, propagators and effective potentials for topological A-brane composites in Calabi-Yau compactifications. This allows for the construction of a holomorphic potential describing the low-energy dynamics of such systems, which generalizes the superpotentials known from the ungraded case. Upon using results of homotopy algebra, we show that the string field and low energy descriptions of the moduli space agree, and that the deformations of such backgrounds are described by a certain extended version of `off-shell Massey products' associated with flat graded superbundles. As examples, we consider a class of graded D-brane pairs of unit relative grade. Upon computing the holomorphic potential, we study their moduli space of composites. In particular, we give a general proof that such pairs can form acyclic condensates, and, for a particular case, show that another branch of their moduli space describes condensation of a two-form.Comment: 47 pages, 7 figure

Moduli Spaces of Instantons on the Taub-NUT Space

We present ADHM-Nahm data for instantons on the Taub-NUT space and encode these data in terms of Bow Diagrams. We study the moduli spaces of the instantons and present these spaces as finite hyperkahler quotients. As an example, we find an explicit expression for the metric on the moduli space of one SU(2) instanton. We motivate our construction by identifying a corresponding string theory brane configuration. By following string theory dualities we are led to supersymmetric gauge theories with impurities.Comment: 26 pages, 7 figure

Effect of renal center characteristics on mortality and technique failure on peritoneal dialysis

BACKGROUND: Recent studies report decreased mortality in patients on peritoneal dialysis (PD) over time, suggesting that advances in PD have resulted in improved patient outcomes. Our investigation sought to assess the effect of renal center characteristics on mortality and technique failure (TF) rates. METHODS: Covariates of interest included center-specific cumulative number of PD patients treated, percentage of patients who initiated dialysis on PD, and academic status. Using data obtained from the Canadian Organ Replacement Register, the 17,900 patients who received PD during the 1981 to 1997 period were studied. Mortality and TF rate ratios (RR) were estimated using Poisson regression, adjusting for age, gender, race, primary renal diagnosis, province, follow-up time, and type of PD. RESULTS: As the cumulative number of PD patients treated increased, covariate-adjusted mortality significantly decreased (P < 0.05); a weaker yet significant association was observed between number of PD patients treated and TF. As the percentage of patients initiating dialysis on PD increased, TF rates decreased significantly. No association was observed between center academic status and PD mortality or TF rates. CONCLUSIONS: These results imply that a center's experience with and degree of specialization toward PD impact strongly on PD outcomes. One hypothesis is that a center's propensity to exploit technical and non-technical advances in PD increases directly with these variables. It is also possible that, through experience, centers become more adept at identifying appropriate patients to receive PD. More detailed research is required to evaluate these hypotheses

The Bethe Ansatz for Z_S Orbifolds of N=4 Super Yang-Mills Theory

Worldsheet techniques can be used to argue for the integrability of string theory on AdS_5xS^5/Z_S, which is dual to the strongly coupled Z_S-orbifold of N=4 SYM. We analyze the integrability of these field theories in the perturbative regime and construct the relevant Bethe equations.Comment: 16 page

Effect of renal center characteristics on mortality and technique failure on peritoneal dialysis

BACKGROUND: Recent studies report decreased mortality in patients on peritoneal dialysis (PD) over time, suggesting that advances in PD have resulted in improved patient outcomes. Our investigation sought to assess the effect of renal center characteristics on mortality and technique failure (TF) rates. METHODS: Covariates of interest included center-specific cumulative number of PD patients treated, percentage of patients who initiated dialysis on PD, and academic status. Using data obtained from the Canadian Organ Replacement Register, the 17,900 patients who received PD during the 1981 to 1997 period were studied. Mortality and TF rate ratios (RR) were estimated using Poisson regression, adjusting for age, gender, race, primary renal diagnosis, province, follow-up time, and type of PD. RESULTS: As the cumulative number of PD patients treated increased, covariate-adjusted mortality significantly decreased (P < 0.05); a weaker yet significant association was observed between number of PD patients treated and TF. As the percentage of patients initiating dialysis on PD increased, TF rates decreased significantly. No association was observed between center academic status and PD mortality or TF rates. CONCLUSIONS: These results imply that a center's experience with and degree of specialization toward PD impact strongly on PD outcomes. One hypothesis is that a center's propensity to exploit technical and non-technical advances in PD increases directly with these variables. It is also possible that, through experience, centers become more adept at identifying appropriate patients to receive PD. More detailed research is required to evaluate these hypotheses

Inhomogeneous chiral symmetry breaking in noncommutative four fermion interactions

The generalization of the Gross-Neveu model for noncommutative 3+1 space-time has been analyzed. We find indications that the chiral symmetry breaking occurs for an inhomogeneous background as in the LOFF phase in condensed matter.Comment: 17 pages, 2 figures, published version, minor correction