Energy partition in nuclear fission

A scission point model (two spheroid model TSM) including semi-empirical, temperature-dependent shell correction energies for deformed fragments at scission is presented. It has been used to describe the mass-asymmetry-dependent partition of the total energy release on both fragments from spontaneous and induced fission. Characteristic trends of experimental fragment energy and neutron multiplicity data as function of incidence energy in the Th — Cf region of fissioning nuclei are well reproduced. Based on model applications, information on the energy dissipated during the descent from second saddle of fission barrier to scission point have been deduced.     

U-branes and T fibrations

We describe eight-dimensional vacuum configurations with varying moduli consistent with the U-duality group . Focusing on the latter less-well understood properties, we construct a class of fivebrane solutions living on lines on a three-dimensional base space. The resulting U-manifolds, with five scalars transforming under SL(3), admit a Ricci-flat Kähler metric. Based on the connection with special Lagrangian T³ fibered Calabi-Yau three-folds, this construction provides a simple framework for the investigation of Calabi-Yau mirrors.     

Asymptotic behavior of iterative M-estimartors for location

In this paper, we study the Huber M-estimator for location when they are computed by a class of numerical iterative procedures. This class includes the usual method of Newton-Raphson, iterated weighted least squares and iterated winsorization. We show that under mild conditions, the numerical iterative procedures converge and the resulting estimators are consistent and asymptotically normal.     

Schottky Uniformizations of Genus 3 and 4 Reflecting S4

Schottky uniformizations are provided of every closed Riemannsurface S of genus g {3,4} admitting the symmetric group S₄as group of conformal automorphisms. These Schottky uniformizationsreflect the group S₄ and permit concrete representations ofS₄ to be obtained in the respective symplectic group Sp_g(Z).Their corresponding fixed points, in the Siegel space, giveprincipally polarized Abelian varieties of dimension g. Forg = 3 and for some cases of g = 4 they turn out to be holomorphicallyequivalent to the product of elliptic curves.     

Fréchet differentiability of the solutions of a semilinear abstract Cauchy problem

Sufficient conditions are found under which the solutions z(t;q) of a semilinear abstract Cauchy problem of the form are Fréchet differentiable with respect to the parameter q. An explicit form is provided for the sensitivity equation satisfied by the Fréchet derivative Dqz(t;q).     

Complexation of Dimethyl 2,3-Naphthalenedicarboxylate with 2-hydroxypropyl-α-, -β- and -γ-cyclodextrins in Aqueous Solution by Fluorescence,Circular Dichroism and Molecular Mechanics

Fluorescence, circular dichroism and molecular mechanics have been used to study the complexation of 2,3-dimethyl naphthalenedicarboxylate with 2-hydroxypropyl-α-, -β and -γ-cyclodextrins (HPCDs) in aqueous solution. Emission spectra upon excitation of the naphthalenedicarboxylate group show two bands whose intensity ratio R is quite sensitive to polarity. From the change of R and lifetimes averages <τ> with HPCD concentration and temperature were obtained the stoichiometry, the association constants and the enthalpy and entropy changes during the complexation. R, <τ> and the fluorescence anisotropies (r) extrapolated at [HPCD]→∞ allows us to estimate the polarity and microviscosity of the media surrounding the guest when complexed. In addition, the analysis of quenching and induced circular dichroism experiments and molecular mechanics calculations in the presence of water, provide information about the forces responsible for the complexation and the geometry of the complexes.     

Tip-induced reduction of the resonant tunneling current on semiconductor surfaces

We report scanning tunneling microscope measurements showing a substantial decrease of the current, almost to zero, on the Si(111)-(7x7) reconstruction in the near-to-contact region under low bias conditions. First principles simulations for the tip-sample interaction and transport calculations show that this effect is driven by the substantial local modification of the atomic and electronic structure of the surface. The chemical reactivity of the adatom dangling bond states that dominate the electronic density of states close to the Fermi level and their spatial localization result in a strong modification of the electronic current.