Effectively Closed Infinite-Genus Surfaces and the String Coupling

The class of effectively closed infinite-genus surfaces, defining the completion of the domain of string perturbation theory, can be included in the category $O_G$, which is characterized by the vanishing capacity of the ideal boundary. The cardinality of the maximal set of endpoints is shown to be 2^{\mit N}. The product of the coefficient of the genus-g superstring amplitude in four dimensions by $2^g$ in the $g\to \infty$ limit is an exponential function of the genus with a base comparable in magnitude to the unified gauge coupling. The value of the string coupling is consistent with the characteristics of configurations which provide a dominant contribution to a finite vacuum amplitude.Comment: TeX, 33 page

Heat-transfer and pressure drop correlations for hydrogen and nitrogen flowing through tungsten wire mesh at temperatures to 5200 deg r

Heat transfer and friction pressure drop for forced convection of hydrogen and nitrogen through electrically heated tungsten wire mes

A 4500 deg R /2500 deg K/ flowing-gas facility

High temperature flowing gas heater consisting of four stages for heating gase

Behavioural clusters and predictors of performance during recovery from stroke

We examined the patterns and variability of recovery post-stroke in multiple behavioral domains. A large cohort of first time stroke patients with heterogeneous lesions was studied prospectively and longitudinally at 1-2 weeks, 3 months and one year post-injury with structural MRI to measure lesion anatomy and in-depth neuropsychological assessment. Impairment was described at all timepoints by a few clusters of correlated deficits. The time course and magnitude of recovery was similar across domains, with change scores largely proportional to the initial deficit and most recovery occurring within the first three months. Damage to specific white matter tracts produced poorer recovery over several domains: attention and superior longitudinal fasciculus II/III, language and posterior arcuate fasciculus, motor and corticospinal tract. Finally, after accounting for the severity of the initial deficit, language and visual memory recovery/outcome was worse with lower education, while the occurrence of multiple deficits negatively impacted attention recovery

A Computational Procedure to Detect a New Type of High Dimensional Chaotic Saddle and its Application to the 3-D Hill's Problem

A computational procedure that allows the detection of a new type of high-dimensional chaotic saddle in Hamiltonian systems with three degrees of freedom is presented. The chaotic saddle is associated with a so-called normally hyperbolic invariant manifold (NHIM). The procedure allows to compute appropriate homoclinic orbits to the NHIM from which we can infer the existence a chaotic saddle. NHIMs control the phase space transport across an equilibrium point of saddle-centre-...-centre stability type, which is a fundamental mechanism for chemical reactions, capture and escape, scattering, and, more generally, ``transformation'' in many different areas of physics. Consequently, the presented methods and results are of broad interest. The procedure is illustrated for the spatial Hill's problem which is a well known model in celestial mechanics and which gained much interest e.g. in the study of the formation of binaries in the Kuiper belt.Comment: 12 pages, 6 figures, pdflatex, submitted to JPhys

Dipole Moments of ff-Bonded Complexes

This paper deals with the information which can be obtained from dielectric measurements about the structure of H-bonded complexes in the liquid phase. In the first part the basic equations used in the determination of the dipole moments in the liquid phase are discussed. For pure polar liquid Onsager\u27s equations lead to values of the moments which may differ from those of the gas phase. According to Kirkwood these deviations are due to preferential orientation effects between the molecules. In pure liquids these deviations are only very important in the case of the formation of H-bonds. The interpretation of experimental dipole data for self associated compounds such as alcohols, carboxylic acids, amides, amines, anilines and pyridines is presented. A method used for the experimental determination of dipole moments for one-one hydrogen bonded complexes is discussed. μab depends not only on the moments of the separate partners μa and μb but also on the angles -&a and Db which these moments form with the direction of the hydrogen bond. Furthermore, flab .... also depends on the dipole increment, /),.μ, originated by the displacements of electrons and nuclei brought about by the formation of the. ...b ond. /),.μ in turn, will depend on the f),.pKa, the difference between the pK. of the conjugated acid of the proton acceptor and that of the acid. Sigmoidal curves are obtained which can be interpreted as resulting from a tautomerism between »normal« and »proton transfer« hydrogen bonds. The dependence of /),.μ on the enthalpy of bond formation, - /),.Hh, also gives a sigmoidal curve which is approximately the same for all H-bonds of a given kind (0-H ... 0, 0-H ... N etc.) in a given solvent. This dependence can be used for the calculation of /),.μ. Using this value with the experimental moments μab• μa and /lb it is then possible to deduce angular parameters for a given H-bonded complex. A few examples are discussed

Integrable Deformations of Algebraic Curves

A general scheme for determining and studying integrable deformations of algebraic curves, based on the use of Lenard relations, is presented. We emphasize the use of several types of dynamical variables : branches, power sums and potentials.Comment: 10 Pages, Proceedings Workshop-Nonlinear Physics: Theory and Experiment, Gallipoli 200

On parity functions in conformal field theories

We examine general aspects of parity functions arising in rational conformal field theories, as a result of Galois theoretic properties of modular transformations. We focus more specifically on parity functions associated with affine Lie algebras, for which we give two efficient formulas. We investigate the consequences of these for the modular invariance problem.Comment: 18 pages, no figure, LaTeX2

Polymer-mediated entropic forces between scale-free objects

The number of configurations of a polymer is reduced in the presence of a barrier or an obstacle. The resulting loss of entropy adds a repulsive component to other forces generated by interaction potentials. When the obstructions are scale invariant shapes (such as cones, wedges, lines or planes) the only relevant length scales are the polymer size R_0 and characteristic separations, severely constraining the functional form of entropic forces. Specifically, we consider a polymer (single strand or star) attached to the tip of a cone, at a separation h from a surface (or another cone). At close proximity, such that h<<R_0, separation is the only remaining relevant scale and the entropic force must take the form F=AkT/h. The amplitude A is universal, and can be related to exponents \eta governing the anomalous scaling of polymer correlations in the presence of obstacles. We use analytical, numerical and epsilon-expansion techniques to compute the exponent \eta for a polymer attached to the tip of the cone (with or without an additional plate or cone) for ideal and self-avoiding polymers. The entropic force is of the order of 0.1 pN at 0.1 micron for a single polymer, and can be increased for a star polymer.Comment: LaTeX, 15 pages, 4 eps figure