Vacuum-UV negative photoion spectroscopy of CH4

Using synchrotron radiation in the range 12-35 eV, negative ions are detected by mass spectrometry following vacuum-UV photoexcitation of methane. Ion yields for H$^-$, CH$^-$ and CH$_2^-$ are recorded, the spectra of CH$^-$ and CH$_2^-$ for the first time. All ions display a linear dependence of signal with pressure, showing that they arise from unimolecular ion-pair dissociation. Cross sections for ion-pair formation are put onto an absolute scale by calibrating the signal strengths with those of F$^-$ from SF$_6$ and CF$_4$. Following normalisation to total vacuum-UV absorption cross sections, quantum yields for anion production are reported. There is a major discrepancy in the H$^-$ cross section with an earlier measurement, which remains unresolved. The anions arise from both direct and indirect ion-pair mechanisms. For a generic polyatomic molecule AB, the former is defined as AB $\rightarrow$ A$^-$ + B$^+$ (+ neutrals), the latter as the predissociative crossing of an initially-excited Rydberg state of AB by an ion-pair state. In a separate experiment, the threshold photoelectron spectrum of the second valence band of CH$_4$, ionisation to CH$_4^+$ A $^2$A$_1$ at 22.4 eV, is recorded with an instrumental resolution of 0.004 eV; many of the Rydberg states observed in indirect ion-pair formation converge to this state. The widths of the peaks are lifetime limited, increasing with increasing $v$ in the $v_1$ (a$_1$) vibrational ladder. They are the first direct measurement of an upper value to the dissociation rate of these levels into fragment ions

Effects of Multiple Sintering Parameters on the Thermal Performance of Bi-porous Nickel Wicks in Loop Heat Pipes

This document is the Accepted Manuscript version of the following article: Y. Qu, K. Zhou, K. F. Zhang and Y. Tian, ‘Effects of multiple sintering parameters on the thermal performance of bi-porous nickel wicks in Loop Heat Pipes’, International Journal of Heat and Mass Transfer, Vol. 99: 638-646, August 2016, doi: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.04.005. This manuscript version is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License CC BY NC-ND 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.The thermal performance of a water-saturated Loop Heat Pipe (LHP) with bi-porous nickel wicks has been examined theoretically and experimentally, based on five key influencing factors including the content of foaming agent, compacting pressure, incubation time at suitable temperature, sintering temperature and particle size of foaming agent. Comparison was made among a total number of 20 tests with each influencing factor allocated by four different values, where porosity, permeability, capillary suction head and effective thermal conductivity (ETC) were examined. ETC is an important parameter of thermal performance, and its experimental values were compared with eleven theoretical models. The results showed that ETC was mostly affected by the content of foaming agent: 1.9-2.2 times compared to the effect of compacting pressure and incubation time, with the effect of sintering temperature and particle size of foaming agent ata underestimated the true ETC values. In the porosity range of 0.5-0.7, an average of the Chernysheva & Maydanik model and the Chaudhary & Bhandari model was found to be the best fit to the experimental data, providing an accurate method to predict ETC values of water-saturated LHP with bi-porous nickel wicks.Peer reviewedFinal Accepted Versio

SRS ECOLOGY ENVIRONMENTAL INFORMATION DOCUMENT -1997 UPDATE

The purpose of the SRS Ecology: Environmental Information Document is to provide a source of information on the ecology of the Savannah River Site

Use of factor analysis in Journal of Advanced Nursing: literature review

Aim. This paper reports a review analysing the use of factor analysis in papers in Journal of Advanced Nursing. Background. Factor analysis is a multivariate statistical method for reducing large numbers of variables to fewer underlying dimensions. There are several methods of factor analysis with principal components analysis being the most commonly applied. Factor analysis has been used by researchers in nursing for many years but the standards for use and reporting are variable. Method. Papers using factor analysis in Journal of Advanced Nursing were retrieved from 1982 to the end of 2004. The search term 'factor analysis' was used in the CINAHL database and applied specifically to Journal of Advanced Nursing in December 2004. Retrieved papers were included in the review if they came from Journal of Advanced Nursing and used factor analysis as part of the method of the reported study. Results. One hundred and twenty-four papers were retrieved as a result of the initial search criteria of which 116 were from Journal of Advanced Nursing. Screening of papers for the use of factor analysis left 100 papers for review. Principal components analysis was the most commonly used method of factor analysis; Eigenvalues greater than one was the most commonly applied criterion for selecting the number of factors followed by orthogonal rotation to achieve simple structure. The majority of papers did not report the whole factor solution and there were papers that did not specify anything beyond the fact that they carried out factor analysis. Confirmatory factor analysis was rarely used and exploratory methods other than principal components analysis were also rarely used. Conclusions. Factor analysis is quite commonly used in nursing research reported in Journal of Advanced Nursing. While some papers are exemplary there is room for improvement in the reporting of all aspects of factor analysis