Silicon Burning II: Quasi-Equilibrium and Explosive Burning

Having examined the application of quasi-equilibrium to hydrostatic silicon burning in Paper I of this series, Hix & Thielemann (1996), we now turn our attention to explosive silicon burning. Previous authors have shown that for material which is heated to high temperature by a passing shock and then cooled by adiabatic expansion, the results can be divided into three broad categories; \emph{incomplete burning}, \emph{normal freezeout} and \emph{$\alpha$-rich freezeout}, with the outcome depending on the temperature, density and cooling timescale. In all three cases, we find that the important abundances obey quasi-equilibrium for temperatures greater than approximately 3 GK, with relatively little nucleosynthesis occurring following the breakdown of quasi-equilibrium. We will show that quasi-equilibrium provides better abundance estimates than global nuclear statistical equilibrium, even for normal freezeout and particularly for $\alpha$-rich freezeout. We will also examine the accuracy with which the final nuclear abundances can be estimated from quasi-equilibrium.Comment: 27 pages, including 15 inline figures. LaTeX 2e with aaspp4 and graphicx packages. Accepted to Ap

Utility of an Empirical Method of Modeling Combined Zero Gap/Attached Electrode Membrane Chlor-Alkali Cells

An extensive survey of the Docktor-Ingenieur Dissertationen of Jakob Jörissen and Klaus-R. Menschig, both originally from the Universität Dortmund, is presented in regard to the empirical modeling of membrane chlor-alkali cells and how it can be applied to a combined zero gap/attached porous electrode layer membrane cell. Particular emphasis isplaced on Menschig\u27s work on zero gap (ZG) and attached porous electrode layer (APEL) membrane chlor-alkali cells, the first such research to appear in the open literature. Menschig developed various computer programs to characterize these ZG and APEL membrane chlor-alkali cells. He characterized these cells by using the following parameters: the current density distribution over the membrane, the species concentrations on the membrane surfaces, equivalent diffusion layer thicknesses for the mesh electrodes/current collectors and attached porous electrode layers, and the electrode overpotentials and equilibrium potentials using the surface concentrations for the ZG and APEL cell configurations. He used empirical equations first presented by Jörissen for gap membrane cells combined with his own experimental observations for a cell which used NafionTM 390, a bilayer perfluorosulfonic acid membrane, to determine values for these parameters. His empirical relations describe the dependence of the flux of OH– from catholyte to anolyte as a function of catholyte caustic concentration (cC:NaOH) and the membrane potential drop as a function of catholyte caustic (cC:NaOH) and anolyte salt concentrations (cA:NaCl). By using the experimental values for total cell potential, current density, and cell outlet concentrations with the empirical equations, Menschig calculated values for the characterizing parameters mentioned above. He used these values and other information (e.g., membrane and porous electrode layer conductivity) to predict the total cell potential for the ZG configuration. With prior knowledge of total cell potential and current efficiency for corresponding APEL and ZG cell configurations, membrane surface concentrations were derived and used in the prediction of total cell potential for a combined zero gap/attached electrode cell

Piezoelectric-based apparatus for strain tuning

We report the design and construction of piezoelectric-based apparatus for applying continuously tuneable compressive and tensile strains to test samples. It can be used across a wide temperature range, including cryogenic temperatures. The achievable strain is large, so far up to 0.23% at cryogenic temperatures. The apparatus is compact and compatible with a wide variety of experimental probes. In addition, we present a method for mounting high-aspect-ratio samples in order to achieve high strain homogeneity.Comment: 8 pages, 8 figure

Post-Newtonian gravitational radiation and equations of motion via direct integration of the relaxed Einstein equations. III. Radiation reaction for binary systems with spinning bodies

Using post-Newtonian equations of motion for fluid bodies that include radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order (O[(v/c)^5] and O[(v/c)^7] beyond Newtonian order), we derive the equations of motion for binary systems with spinning bodies. In particular we determine the effects of radiation-reaction coupled to spin-orbit effects on the two-body equations of motion, and on the evolution of the spins. For a suitable definition of spin, we reproduce the standard equations of motion and spin-precession at the first post-Newtonian order. At 3.5PN order, we determine the spin-orbit induced reaction effects on the orbital motion, but we find that radiation damping has no effect on either the magnitude or the direction of the spins. Using the equations of motion, we find that the loss of total energy and total angular momentum induced by spin-orbit effects precisely balances the radiative flux of those quantities calculated by Kidder et al. The equations of motion may be useful for evolving inspiraling orbits of compact spinning binaries.Comment: 19 pages, small corrections, equivalent to published versio

A Terraced Scanning Superconducting Quantum Interference Device Susceptometer with Sub-Micron Pickup Loops

Superconducting Quantum Interference Devices (SQUIDs) can have excellent spin sensitivity depending on their magnetic flux noise, pick-up loop diameter, and distance from the sample. We report a family of scanning SQUID susceptometers with terraced tips that position the pick-up loops 300 nm from the sample. The 600 nm - 2 um pickup loops, defined by focused ion beam, are integrated into a 12-layer optical lithography process allowing flux-locked feedback, in situ background subtraction and optimized flux noise. These features enable a sensitivity of ~70 electron spins per root Hertz at 4K.Comment: See http://stanford.edu/group/moler/publications.html for an auxiliary document containing additional fabrication details and discussio

Examining Environmental Discourses on Energy Utilisation in Select Nigerian Newspapers

This study examines the extent to which select Nigerian newspapers reflect the different environmental discourses pertaining to the use of clean or unclean energy sources. It undertakes a content analysis of newspaper articles in 156 weekly issues of published energy sections of three major Newspapers in Nigeria: The Guardian, The Punch and The Nation for all of 2013 – the year Nigeria implemented the privatisation of its power (electricity) industry and gearing up for a similar initiative for the petroleum sector. The study hinged on sustainability discourses as well as framing and environmental communication theories. Four approaches underpin it: I. A survey of the occurrence of energy issues in the sample. 2. Examination of the frames in which the sample engages on energy/environmental discourses. 3. Ascertainment of the perceptible voices prevalent in the coverage/discourses of energy issues. 4. Determination of the existence of any divide in the discourse/coverage of energy issues. Based on the findings of the study, the authors conclude that the three analysed newspapers showed a lopsided coverage of energy issues by ignoring or neglecting renewable energy issues while concentrating on oil, gas and electricity industry; depicting energy issue mainly as a business/economic frame, among others and thus contributed little or nothing to the sustainability discourse in Nigeria. Keywords: Renewable Energy, Content Analysis, Sustainabilit

Enzymatic Synthesis of Site-Specific Labeled NTPS used for In Vitro Transcription of RNAs to Facilitate Multi-Dimensional Nuclear Magnetic Resonance Spectroscopic Studies

7 p