Innermost Shells Research Articles

Effects of calcium buffering on glucose-induced insulin release in mouse pancreatic islets: an approximation to the calcium sensor.

1. The properties of the calcium sensor for glucose-induced insulin secretion have been studied using cell-permeant Ca2+ buffers with distinct kinetics and affinities. In addition, submembrane cytosolic Ca2+ distribution has been modelled after trains of glucose-induced action potential-like depolarizations. 2. Slow Ca2+ buffers (around 1 mmol l-1 intracellular concentration) with different affinities (EGTA and Calcium Orange-5N) did not significantly affect glucose-induced insulin release. Modelling showed no effect on cytosolic Ca2+ concentrations at the outermost shell (0.05 microm), their effects being observed in the innermost shells dependent on Ca2+ affinity. 3. In contrast, fast Ca2+ buffers (around 1 mmol l-1 intracellular concentration) with different affinities (BAPTA and Calcium Green-5N) caused a 50 % inhibition of early insulin response and completely blocked the late phase of glucose-induced insulin response, their simulations showing a decrease of [Ca2+]i at both the inner and outermost shells. 4. These data are consistent with the existence in pancreatic beta-cells of a higher affinity Ca2+ sensor than that proposed for neurons. Moreover, these data are consistent with the proposed existence of two distinct pools of granules: (i) 'primed' vesicles, colocalized with Ca2+ channels and responsible of the first phase of insulin release; and (ii) 'reserved pool' vesicles, not colocalized and responsible for the second phase.

Minor axis rotation and the intrinsic shape of the shell elliptical NGC 3923

We present kinematic observations of NGC 3923, one of the best-known examples of an elliptical galaxy with shells. Although NGC 3923 has no rotation on its major axis, it has minor axis rotation with an amplitude of some 20 km s−1 out to 25 arcsec radius. This is possibily the result of a kinematically decoupled core, but we present arguments against this hypothesis, and if the core were formed by a merger, this must have been a different merger from that which gave rise to the shells. The minor axis rotation suggests that NGC 3923 is prolate or triaxial, at least in the inner region. A prolate geometry for the whole galaxy would favour the merger model over the interaction model for the shell formation mechanism. There is other evidence, however, that the shape of the underlying galaxy changes with radius, in which case it is possible that the minor axis rotation could be confined to the galaxy core. The kinematics could reflect a triaxial mass distribution, in which the long and short axes are aligned with the photometric major and minor axes, and the axial ratios change such that the galaxy is near-prolate in the inner regions and near-oblate at larger radii. Measuring the rotation curve to about double this radius along the minor axis, as well as offset from the nucleus along the major axis at the radius of the innermost shells, would enable the true extent of the minor axis rotation to be determined.

Kinetic Study of the Fe(bpy)2+3 +S2O2−8 Reaction in Solvent Mixtures

AbstractThe kinetics of the oxidation of Fe(bpy)2+3 by S2O2−8 have been studied in water and different water‐cosolvent mixtures. The cosolvents used were methanol t‐butyl alcohol, ethane 1,2‐diol and glycerol. The results are explained assuming an additional component of the reorganization free energy of the solvent in the mixtures, caused by dynamics of the changes in the composition of the (at least) innermost solvation shells of the reactants produced by the electron transfer. A quantitative estimation of this component is attempted.

On the Validity of Electrostatic Linear Response in Polar Solvents

The standard approximation in continuum electrostatic theory, that polar liquids respond linearly to changes in electric fields, is examined on a microscopic level by molecular dynamics and thermodynamic perturbation simulations. Electrostatic free energies associated with the process of “charging” a solute in a solvent are evaluated and compared to the predictions from linear response, for a number of compounds. It is found that the linear response approximation generally holds well for monovalent ionic solutes, while it is less accurate for dipolar ones. Deviations observed for dipolar compounds are reflected by unequal curvatures of the free energy functions (potentials of mean force) near their respective minima for the “polar” and “nonpolar states”. The short-range nature of dipolar fields gives relatively larger weight to the innermost solvation shells in determining the electrostatic part of the solvation energy, compared to the case of ionic solutes. These inner shells can exhibit nonlinear respon...

Infinitesimal differential diffusion quantum Monte Carlo study of CuH spectroscopic constants

We show how to extend the formalism of infinitesimal differential diffusion quantum Monte Carlo to the case of higher derivatives of the ground-state energy of a molecule with respect to the molecular geometry for a large-Z molecule. We propose a new all-electron approach based on the idea of using different simulation time-scales for different shells of the constituent atoms, viz., a substantially smaller time-step for innermost shells, and relatively large time-steps for the valence electrons. We avoid the approximations inherent in pseudopotential methods while at the same time, when used in conjunction with variational Monte Carlo, the sampling is done on a firm theoretical basis. We use CuH as an example, obtaining properties with an accuracy on par with those from SDCI, despite our using a crude single-determinant wave function with only two adjustable parameters.

The origin of relativistic effects of atomic orbitals

a(R)= integral R0 ( integral psi a psi d Omega )r2 dr curves are presented for different contributions a to the energy of atomic orbitals. While all radial shells contribute about equally to the non-relativistic kinetic and potential orbital energies, there is almost perfect cancellation of these energies in the inner shells, and the total energy of an orbital is almost solely determined by its outermost shell. In contrast to this, the first-order relativistic mass-velocity, Darwin and spin-orbit energies originate from the innermost shells only, while all radial shells contribute to the so-called indirect relativistic orbital energy correction,. The indirect effect is important also for s atomic orbitals except for the central columns of the periodic system, where the indirect destabilisation is compensated by indirect stabilisation. This explains the 'gold maximum' of relativistic corrections.

Eigenfunctions of the magnetospheric radial-diffusion operator

The magnetospheric radial-diffusion operator Λ ≡ – L2(∂/∂L)[(DLL/L2)(∂/∂L)] for radiation-belt and ring-current particles has eigenfunctions gn(L), and these can be expressed in closed form (as can the corresponding eigenvalues λn) if the diffusion coefficient DLL is exactly proportional to Lβ for some fixed β > 3. More specifically, the eigenfunctions are expressible in terms of a linear combination of ordinary Bessel functions of the first and second kinds, denoted Jv(θn) and Yv(θn), respectively. The order v of the Bessel functions is given by v = (β – 3)(β – 2), and the argument θn is proportional to L(2−β)/2. The value of the proportionality constant L(β−2)/2θn and the relative weights of Jv(θn) and Yv(θn) in the linear combination are to be chosen so as to make gn(L0) = gn(L1) = 0, where L0 and L1 are the labels of the innermost and outermost drift shells, respectively. Thus, the solution f̄(L, t) of the radial-diffusion equation ∂f̄/∂t = – Λf̄ for the drift-averaged phase-space density f̄(L, t) is expressible as the sum of a quasi-static solution f̄∞(L, t) = 0 and a time-dependent superposition of the eigenfunctions of the radial-diffusion operator Λ. The quasi-static solution instantaneously satisfies the equation Λf̄∞(L, t) = 0 and the boundary conditions that the magnetosphere imposes (at L = L0 and at L = L1) on f̄(L, t) itself. Eigenfunctions and eigenvalues are obtained here for β = 10 with L1 = 8L0 = 9 and are employed in several idealized but illustrative applications of the eigenfunction method to situations in which the value of f̄(L1, t) is made to vary with time while the value of f̄(L0, t) is made to vanish.

The shell system around NGC 3923 and its implications for the potential of the galaxy

A study of the shell galaxy NGC 3923 is presented. It is mainly based on CCD and photographic observations made at the CFHT, ESO, and AAT from 1982 to 1986. New shells have been discovered. The geometry of 22 shells is investigated in detail with an estimate of the uncertainties. The interleaving of the shells is not a clear as it has been claimed: it is well defined for the outer shells but the distances of the inner shells present a certain symmetry relative to the center. Shells have a roughly constant ellipticity of E = 1. +/- 0.4 [ E = 10 x ( 1 - b/a)]. It has been suggested by some authors that shell ellipticities are related to the elliptical potential; a brief study of current models of elliptical galaxies shows that the shell ellipticities are of the same magnitude as the equipotential ellipticities, but no clear relation id visible. Profiles were derived for 19 shells, and a simple model was fitted to these profiles. The shell thickness is typically of 0.17 kpc for the inner shells. The total B luminosity of the shell system is ~ 5 % (+/- 1 %) of the luminosity of the galaxy. The outermost shells are much more luminous than the inner ones: the outer four shells contribute ~85% of the total luminosity. A dust lane has been discovered on deep CCD exposures. If it is in a stable configuration its orientation is in contradiction with some previous studies based on numerical simulations which concluded that NGC 3923 was a prolate system. A photometric study of the galaxy is presented. The inferred central M/L ratio, is close to 10 which does not depart from the values usually found in ellipticals. Observations in the 21 cm hydrogen line with the Parkes Radio Telescope gives an upper limit of the H I content of 7 x 10^8 solar mass. The results of the present study seem compatible with the merging hypothesis but dynamical friction has to be invoked to account for the presence of the innermost shells we have observed.

Impact-Parameter Dependence ofδElectrons Emitted from the Superheavy Quasiatomic System Au on U

The electrons of ${E}_{e}^{\mathrm{c}.\mathrm{m}.}=150\ensuremath{-}800$ keV emitted during heavy-ion collisions were studied for the system Au on U at a beam energy of 3.9 MeV/u. The impact-parameter dependence is presented for the total electrons and for electrons from $1{s}_{\frac{1}{2}}\ensuremath{\sigma}$ and $2{p}_{\frac{1}{2}}\ensuremath{\sigma}$ states. The results are interpreted in terms of the strong relativistic enhancement of the electron density of the innermost quasiatomic shells with decreasing internuclear distance of the united atom system.

The shell structure of atoms and ions in momentum space

The radial momentum distributions for the ground states of the first 92 atoms from hydrogen to uranium, and of singly positive ions from helium to barium and from lutetium to radium, constructed from nonrelativistic SCF wave functions, are investigated. These distributions display a number of maxima that, as is shown, depend strongly on the electronic structure and can be assigned each to a particular shell—the first maximum corresponding to the outermost shell. Four maxima is the most that appear for each atom or ion studied implying that in some cases only the outermost shells are evident. This result is similar to the fact that for some atomic systems in position space, only the innermost shells lead to maxima in the radial density. As a general conclusion, if both momentum and position space radial electronic densities are considered, then all shells become evident for the atomic cases studied.

Atomic Inner-Shell Transitions---Theory and the Need for Experiments

The physics of the innermost shells of atoms is qualitatively different in several respect from that of outer electrons. For single deep holes, correlation effects are slight, while the effects of relativity are pronounced and quantum-electrodynamic shifts can be substantial. These relativistic and QED effects can be explored with high precision because many-body aspects are limited and selfconsistent-field approaches can be relied upon. Problems of particular current interest concern the screening of the self energy and the effect of the Breit interaction on multiplet splitting and on x-ray hypersatellite shifts. Experimental studies as well as calculations of the properties of few-hole and few-electron atomic systems can lead to significant tests of current theory.

Evidence for an additional coupling of the innermost shells in very heavy quasi-molecular ion-atom collisions

Due to the tremendous spin-orbit splitting of quasi-molecular levels of super-heavy collision systems (Z=Z1+Z2<or=137) bombarding energy 0.5-6 MeV N-1, unusual couplings may occur around Z approximately=165. Experimental evidence for such a theoretically predicted coupling is discussed.

Zum Gehalt von Phosphor und anderen Spurenelementen in Brauneisenerzooiden aus dem fr�nkischen Dogger beta

The material studied consists of samples of marine oolitic iron ore of the main-seam horizon of the Dogger Beta, Kleiner Johannes mine, near Pegnitz, Oberfranken. The main iron base of the ore comprizes goethite (α-FeOOH) oolites containing also Al2O3, SiO2 and about 1 percent Ti and P. The Ti is fixed mainly in the oolite cores, P2 in the outer shells. Electron probe analysis of individual oolites shows (1) correlated distribution of Ca and P; (2) that the innermost shells surrounding the core are enriched in Ca phosphate and in isomorphously substituted rare-earth elements. It seems that prior to growth of goethite shells the phosphatic shells were also formed in a marine environment.

Erratum: Calculation of Zero-Field Splitting in NH. II. One-Center Representations of Triplet States

The zero‐field‐splitting (ZFS) parameters arising from electron spin—spin dipolar interactions in the known triplet states of NH are calculated. A variety of one‐center expansion (OCE) representations are utilized, including an extended basis wavefunction for the ground state. Overlaps of limited basis OCE eigenvectors with extended basis OCE eigenvectors and with two‐center eigenvectors are calculated for 3Σ−NH. In addition, electron‐density distributions are calculated for the various 3Σ−NH representations. It is concluded that, at least for 3Σ−NH, OCE representations in general and limited basis OCE representations in particular describe the distributions of the innermost and outermost electron shells relatively better than distributions of the remaining electrons. Electron spin—spin dipolar interaction in 3Σ−NH is found to be much larger than for 3II0NH; D=1.5951 cm−1 for 3Σ−NH using a 24 basis representation and D=0.512 cm−1 for 3II0NH using a 12 basis representation. The electronic configurations of organic nitrenes are discussed qualitatively. Directions of future ZFS calculations for nitrenes are suggested.

Calculation of Zero-Field Splitting in NH. II. One-Center Representations of Triplet States

The zero-field-splitting (ZFS) parameters arising from electron spin—spin dipolar interactions in the known triplet states of NH are calculated. A variety of one-center expansion (OCE) representations are utilized, including an extended basis wavefunction for the ground state. Overlaps of limited basis OCE eigenvectors with extended basis OCE eigenvectors and with two-center eigenvectors are calculated for 3Σ−NH. In addition, electron-density distributions are calculated for the various 3Σ−NH representations. It is concluded that, at least for 3Σ−NH, OCE representations in general and limited basis OCE representations in particular describe the distributions of the innermost and outermost electron shells relatively better than distributions of the remaining electrons. Electron spin—spin dipolar interaction in 3Σ−NH is found to be much larger than for 3II0NH; D=1.5951 cm−1 for 3Σ−NH using a 24 basis representation and D=0.512 cm−1 for 3II0NH using a 12 basis representation. The electronic configurations of organic nitrenes are discussed qualitatively. Directions of future ZFS calculations for nitrenes are suggested.