A novel x-ray anode for electron spectroscopy is investigated for application in the surface analysis field, monochromatic Ag Lalpha (hnu =2984. 3eV), its energy being capable of exciting 1s electrons up to chlorine in the periodic table. Resolution available with this source is satisfactory, with a limitation of approximately 1. 3eV. An increase in sensitivity is achieved for those peaks in the range 1500-3000BE, whilst there is no serious reduction within the conventional XPS energy range. The agreement between experimental sensitivity factors and theoretical cross-section values is good, allowing the transmission function for the VG ESCA3 Mkll spectrometer to be confirmed constant from 0-3000eV. A comprehensive investigation of the LEG51 electron flood gun preceded its successful application for the charge neutralisation of insulating materials. This allowed the application of this source to such materials as chlorides, pertinent to the breakdown in passivity on stainless steels, and silicon compounds, involving thermal oxides on silicon of interest to the microchip industry, zeolites for catalysis in the petrochemical industry and siloxane copolymers for the opthalmic industry. The ability to excite the 1s orbital, together with the 2p and KLL Auger lines, affords calculation of Auger parameters and extra-atomic relaxation energies for the accurate description of the chemical environment of a particular chemical species. A method for internal energy referencing is investigated, involving the vaccum-deposition of Au, Cu and Pt metals. This allows the measurement of photoelectron binding energies to an accuracy of +/-0.1-0.2eV for insulating materials, when referenced to the vacuum level.

No description available.

No description available.

It has long been established that the physical properties of the cell’s surrounding microenvironment has the ability to impose its influence on a range of cell processes. Morphology, differentiation, and proliferation have all been shown to be sensitive to the mechanical cues inherent within the extracellular matrix. Although significant advancements in microfabrication and cell mechanics have been made, questions regarding how physical interactions guide biological systems in three dimensions remain unanswered. By utilizing cocultured systems and microfabricated channeled topographies, we reveal that the three dimensional nature of the environment is capable of driving cell patterning. Contact guidance is the phenomenon by which cells will orient themselves along the geometric patterns of a substrate. Much of its research has focused on the nano/micro scale of two dimensional topographies, affecting alignment along grooves. We have revealed that contact guidance has the ability to impose far more complex cellular behaviour in three dimensional systems. Furthermore, by modulating the elements of confinement surrounding cells, we directed the balance of binding forces between cells and substrate leading to significantly different cell type dependent morphologies. By then altering the geometry of the topography, we revealed the ability to induce cell type separation in cocultured systems. These concepts led to the subsequent discovery that confinement induces three dimensional spheroidal growth of embryonic stem cells. These results reveal that the element of confinement not only influences patterning in three dimensions but guides the fundamental early stages processes essential to all life.

<p> Variational calculations for hypernuclei and their corresponding nuclear cores have been performed with phenornenological effective Ʌ -N and N-N interactions. Effects of deformation and Majorana exchange on the Ʌ binding energies have been studied. The influence of density dependence in both the Ʌ-N and N-N force has been investigated . The three-body ɅNN interaction has also been considered qualitatively. All these effects help to reduce the Ʌ binding energies in hypernuclei. </p> <p> In addition to the variational calculations, the rigid alpha model has been used to determine the Ʌ binding energy in (5 Ʌ - He). A comparison of the methods is given. </p> Finally, excited states of some hypernuclei have been calculated using the variational ground state equilibrium size. </p> / Thesis / Doctor of Philosophy (PhD)

This work is concerned with the use of different "effective" nucleon-nucleon interactions in the calculation of binding energies and spectra of some of the oxygen isotopes. The variational procedure consists of using a complete set of Slater determinant wave functions, having the same total M value for the projection of the angular momentum, in order to minimize the ground states of various nucleonic configurations in.the 2s-ld nuclei. The parameters obtained are used'in the subsequent diagonalization of the Hamiltonian and its eigenvalues are interpreted as energy eigenvalues. The calculations performed in this work led to the conclusion that the density dependence of the effective force is extremely important and should not be neglected, at least in the calculation of binding energies. / Thesis / Master of Science (MS)

The K-shell x-ray and ionization cross sections are measured for protons on Ag, Cd, Sn, Sb, Te, Ba, and La over the ion energy range of 0.6 to 2.0 MeV. The data are compared to the predictions of the PWBA, the PWBA with corrections for binding energy and/or Coulomb deflection, the BEA, and the constrained BEA predictions. In general, the non-relativistic PWBA with binding energy correction gives the best overall agreement with the measurements of proton-induced x-ray processes for the K-shell of the elements studied in this work. The data further suggest the need for relativistic PWBA treatment of the interactions in the K-shell for the range of binding energies represented by the elements investigated in this work.

Neste trabalho é apresentado um modelo algébrico para o cálculo de energias de ligação de núcleos pesados com N = Z baseado nas versões invariantes por isospin do Modelo de Bósons interatuantes (IBM). Com a utilização de uma interação adequada para a descrição dos modos isoescalar e isovetorial do emparelhamento nuclear adicionada àquelas interações que descrevem globalmente uma dada região de massa, foram ajustados os parâmetros da hamiltoniana e calculados núcleos com N = Z ao longo das camadas sd e pf. Deste modo, pôde-se fazer algumas predições, para suas massas do estado fundamental e para estados excitados, que oferecem um desafio às novas gerações de feixes radiativos que estão por vir. / In this work we present an algebraic model for calculating the binding energies of heavy nuclei with the same number of protons and neutrons which is based in the isospin invariant versions of the Interacting Boson Model (IBM). With an adequate interaction for the description of the isoscalar and isovector pairing modes of the residual nuclear interaction added to those terms responsible for the bulk properties of a given mass region, we have fitted the parameters of our algebraic Hamiltonian and have calculated nuclei with N=Z along the sd and pf shells. Therefore we were able to make some predictions, for their ground state masses as well as for the excited states, which offer a challenge to the new generations of radioactive nuclear beams.

Neste trabalho é apresentado um modelo algébrico para o cálculo de energias de ligação de núcleos pesados com N = Z baseado nas versões invariantes por isospin do Modelo de Bósons interatuantes (IBM). Com a utilização de uma interação adequada para a descrição dos modos isoescalar e isovetorial do emparelhamento nuclear adicionada àquelas interações que descrevem globalmente uma dada região de massa, foram ajustados os parâmetros da hamiltoniana e calculados núcleos com N = Z ao longo das camadas sd e pf. Deste modo, pôde-se fazer algumas predições, para suas massas do estado fundamental e para estados excitados, que oferecem um desafio às novas gerações de feixes radiativos que estão por vir. / In this work we present an algebraic model for calculating the binding energies of heavy nuclei with the same number of protons and neutrons which is based in the isospin invariant versions of the Interacting Boson Model (IBM). With an adequate interaction for the description of the isoscalar and isovector pairing modes of the residual nuclear interaction added to those terms responsible for the bulk properties of a given mass region, we have fitted the parameters of our algebraic Hamiltonian and have calculated nuclei with N=Z along the sd and pf shells. Therefore we were able to make some predictions, for their ground state masses as well as for the excited states, which offer a challenge to the new generations of radioactive nuclear beams.

The main focus of the current dissertation thesis is research of gold catalyzed reactions. I was using mass spectrometry as the primary research technique. I complemented the results with infrared multiphoton dissociation spectroscopy, nuclear magnetic resonance spectroscopy and quantum chemical calculations. I have investigated the interaction of the gold(I) cation with unsaturated hydrocarbons in the first part of my thesis. Secondly, I have studied gold(I) or silver(I) affinity to gold acetylides. In the last part, I have investigated the reaction mechanism of a gold mediated addition of methanol to alkynes. I found out that the gold(I) cation interacts stronger with gold acetylides than with nonactivated triple CC bonds. I showed that the complexes containing two gold atoms represent the key intermediates in the mechanism of addition of methanol to alkynes and that the ligand on the gold catalyst plays a fundamental role in the determination of the mechanism. Powered by TCPDF (www.tcpdf.org)