I. Nuclear magnetic resonance analysis of ferrocenylcarbonium ion. II. Ferrocene catalyzed photochemistry

I. Nuclear magnetic resonance spectra of appropriately substituted ferrocenylcarbonium ions reveal the α-protons of the substituted ring to be more shielded than β-protons. The observation is discussed in terms of various models proposed for the ferrocenylcarbonium ion and is found to support a model in which the iron is bonded to all six carbona of the substituted ring.

II. Ferrocene catalyzes the photoisomerization of the piperylenes and the photodimerization of isoprene. Our results suggest a mechanism in which a complex of ferrocene and diene is excited to its second singlet state which dissociates to a triplet-state ferrocene molecule and a triplet-state diene molecule. The triplet-state diene, then, proceeds to isomerize or attack ground-state diene to form dimers.

Topology optimization of silicon anode structures for lithium-ion battery applications

This thesis presents a topology optimization methodology for the systematic design of optimal multifunctional silicon anode structures in lithium-ion batteries. In order to develop next generation high performance lithium-ion batteries, key design challenges relating to the silicon anode structure must be addressed, namely the lithiation-induced mechanical degradation and the low intrinsic electrical conductivity of silicon. As such, this work considers two design objectives of minimum compliance under design dependent volume expansion, and maximum electrical conduction through the structure, both of which are subject to a constraint on material volume. Density-based topology optimization methods are employed in conjunction with regularization techniques, a continuation scheme, and mathematical programming methods. The objectives are first considered individually, during which the iteration history, mesh independence, and influence of prescribed volume fraction and minimum length scale are investigated. The methodology is subsequently extended to a bi-objective formulation to simultaneously address both the compliance and conduction design criteria. A weighting method is used to derive the Pareto fronts, which demonstrate a clear trade-off between the competing design objectives. Furthermore, a systematic parameter study is undertaken to determine the influence of the prescribed volume fraction and minimum length scale on the optimal combined topologies. The developments presented in this work provide a foundation for the informed design and development of silicon anode structures for high performance lithium-ion batteries.

Study of ion movements in isolated chicken retinas during spreading depression

Spreading depression (SD) is a phenomenon observed in several sections of vertebrate central nervous system. It can occur spontaneously or be evoked by a variety of stimuli, and consists of a wave of depression of the normal electrical activity of the nervous tissue which spreads slowly in all directions in the tissue. This wave of depression is accompanied by several concomitants including ion movements. All the concomitants of SD can be explained by an increase in the sodium permeability of the plasma membranes of cellular elements involved in this phenomenon.

In the chicken retina, SD is accompanied by a transparency change which can be detected with the naked eye. The isolated retina is a thin (0.1 mm) membrane in which the extracellular fluid quickly and completely equilibrates with the incubation solutions. This preparation was therefore used to study the ion movements during SD by measuring and comparing the ion contents and the extracellular space (ECS) of retinas incubated in various solutions of which some inhibited SD, whereas others allowed this phenomenon to occur.

The present study has shown that during SD there is a shift of extracellular sodium into the intracellular compartment of the retina, a release of intracellular K and a decrease in the magnitude of ECS. These results are in agreement with previous postulates about SD, although the in vitro experimental condition makes the ion movements appear larger and the loss of ECS smaller than observed in the intact cortical tissue. The movements of Na and K, in opposite directions, are reversible. The development and magnitudes of SD is very little affected by deprivation of the oxygen supply.

It was established that the inward sodium shift is not a consequence of an arrest of the Na-pump. It can be prevented, together with SD by the membrane stabilizers, magnesium and procaine. Spreading depression and the ion movements are incompletely inhibited by tetrodotoxin, which blocks the sodium influx into nerve fibers during the action potential. The replacement of Na in the bathing solution by Li does not prevent SD, which is accompanied by Li accumulation in the intracellular compartment. From these experiments and others it was concluded that the mechanism underlying SD and the ion shifts is an increase in the sodium permeability of cell membranes.

NANOPARTICLE REINFORCEMENT OF FERROUS ALLOYS: WETTABILITY AND MECHANICAL PROPERTIES

El refuerzo de matrices férricascon una fina dispersión de partículas nanométricas permite mejorar la dureza, resistencia mecánica e incluso permitiría mejorar la tenacidad del material al afinar el tamaño de grano.

Low-loss planar and stripe waveguides in Nd3+-doped silicate glass produced by oxygen-ion implantation

We report on the fabrication and characterization of low-loss planar and stripe waveguides in a Nd3+-doped glass by 6 MeV oxygen-ion implantation at a dose of 1x10(15) ions/cm(2). The dark mode spectroscopy of the planar waveguide was measured using a prism coupling arrangement. The refractive index profile of the planar waveguide was reconstructed from a code based on the reflectivity calculation method. The results indicate that a refractive index enhanced region as well as an optical barrier have been created after the ion beam processing. The near-field mode profiles of the stripe waveguide were obtained by an end-fire coupling arrangement, by which three quasitransverse electric modes were observed. After annealing, the propagation losses of the planar and stripe waveguides were reduced to be similar to 0.5 and similar to 1.8 dB/cm, respectively. (c) 2007 American Institute of Physics.

Ridge optical waveguide in an Er3+/Yb3+ co-doped phosphate glass produced by He+ ion implantation combined with Ar+ ion beam etching

This paper reports on the fabrication and characterization of a ridge optical waveguide in an Er3+/Yb3+ co-doped phosphate glass. The He+ ion implantation (at energy of 2.8 MeV) is first applied onto the sample to produce a planar waveguide substrate, and then Ar+ ion beam etching (at energy of 500 eV) is carried out to construct rib stripes on the sample surface that has been deposited by a specially designed photoresist mask. According to a reconstructed refractive index profile of the waveguide cross section, the modal distribution of the waveguide is simulated by applying a computer code based on the beam propagation method, which shows reasonable agreement with the experimentally observed waveguide mode by using the end-face coupling method. Simulation of the incident He ions at 2.8 MeV penetrating into the Er3+/Yb3+ co-doped phosphate glass substrate is also performed to provide helpful information on waveguide formation.

Effects of Yb ion concentration on the spectral properties of lead silica glasses

The spectral properties in different concentration of Yb ions (0.5-5 mol%)-doped silica glasses are explored in this paper. The glasses are prepared by traditional melting method. The absorption spectra and the fluorescent lifetime (tau(f)) are measured at room temperature and low temperature (18 K). The stimulated cross-section (sigma(emi)) and potential laser properties (beta(min), I-sat, I-min) are calculated based on the absorption spectra. The absorption cross-section (sigma(abs)) are in the range 1.08 x 10(-20) - 1.18 x 10(-20) cm(2) in different glasses, the fluorescence lifetime (tau(f)) change from 1.9 to 1.2 ms with the increase of Yb3+ concentration. The potential laser properties indicate that lead silica glass is a good host for highly Yb ion doping glass. (c) 2005 Elsevier B.V. All rights reserved.

Low loss waveguide in Nd3+-doped silicate glass fabricated by carbon ion implantation

Low loss index enhanced planar waveguides in Nd3+-doped silicate glass were fabricated by 3.0 MeV C+ ion implantation. The enhancement of the refractive index confined the light propagating in the waveguide. The prism-coupling method was used to measure dark modes in the waveguide. The effective refractive indices of the waveguide were obtained based on the dark modes. The moving fiber method was applied to measure the waveguide propagation loss. Loss measured in non-annealed samples is about 0.6 dB/cm. And the waveguide mode optical near-field output at 633 nm was presented. (c) 2005 Elsevier B.V. All rights reserved.

Characterization of Er3+-doped Na2O-WO3-TeO2 glass for ion-exchanged waveguide amplifiers and lasers

Er^(3+)-doped Na2O-WO3-TeO2 glass consistent with standard ion-exchange technology has been fabricated and characterized. The measured absorption and emission spectra of the glass were analyzed by the Judd-Ofelt and McCumber theories. The intensity parameters are Ω2 = 7.01

Property studies of optical waveguide formed by 6.0 MeV carbon ion implantation into Nd : silicate glass

Nd:silicate glass was implanted at room temperature by 6.0 MeV C3+ ions with a dose of 2.0 x 10(15) ions cm(-2). A waveguide with thickness of about 6.3 mu m was formed. The prism-coupling method was used to observe the dark modes of the waveguide at 633 nm and 1539 nm, respectively. There are three dark modes at 633 nm, of which one is the enhanced-index mode. The propagation loss of the enhanced-index mode in the waveguide measured at 633 nm is 0.42 dB cm(-1) after annealing at 217 degrees C for 35 min. The reflectivity calculation method was applied to simulate the refractive index profiles in the waveguide. The mode optical near-field output at 633 nm was presented.