108 research outputs found
Studies of negative ions formed by low energy electron impact
In this thesis the processes responsible for the
formation of negative ions by the interaction of low energy
electrons (0 to 15eV) with molecules in the gas phase have
been investigated. Particular attention has been paid to
the processes known as associative resonance capture and
dissociative resonance capture. For a molecule AB,
associative resonance capture is described by the equation
AB + e → AB⁻, where the metastable molecular negative ion
AB⁻ is formed by the capture of slow electrons.
Dissociative resonance capture, described by the equation
AB⁻ → A⁻ + B, results in the formation of a stable negative
ion and can occur throughout the energy range studied.
A historical review of the theoretical approach to
electron-attachment is followed by detailed accounts of
the most recent theoretical treatments of associative and
dissociative resonance capture. The time-of-flight mass
spectrometer used for this study has been described in some
detail as have the experimental procedures developed. The
various devices used to overcome the problems created by the
broad electron energy distribution, which is due to the use
of thermionically emitted electron beams, have been critically
reviewed and the analytical deconvolution procedure adopted
in this study has been described in detail.
Autodetachment lifetimes and capture cross-sections
for the associative attachment of electrons by several
groups of organic and inorganic molecules have been measured
and comparisons made with the predictions of the statistical
theory for associative electron capture. Attempts to
calculate electron affinities from this theory, using the
lifetimes and cross -sections measured, met with some
success for simple molecules and enabled conclusions to be
made concerning the adequacy and limitations of the
theoretical treatment.
From studies of the electron energy dependence of
negative ion formation for several groups of inorganic
and organic molecules, various ionisation processes have
been identified. Deconvolution of the ionisation curves
has enabled accurate appearance potential data to be
determined and, in many cases, allowed bond dissociation
energies, electron affinities and heats of formation of
various species to be evaluated
Процесс фтороаммонийной переработки высокофтористых бериллиевых концентратов
В работе приведено научное обоснование способа фтороаммонийной переработки высокофтористого бериллиевого концентрата, предложены технологические режимы переработки бериллиевого концентрата. Исследование технологического процесса и определение режимов, обеспечивающих экономически эффективную переработку концентратов, проводили на специально изготовленной опытной установке. В результате работы создана и апробирована принципиальная схема переработки бериллиевых концентратов, разработано аппаратурное оформление процесса. Приведено технико-экономическое обоснование технологии.The scientific substantiation of the processing of high-fluoride beryllium concentrates by ammonium fluoride is given in graduation thesis. Technological conditions of beryllium concentrate processing are proposed. The research of the technological process and determination of the conditions providing cost-effective processing of concentrates was carried out on a specially manufactured pilot plant. As a result of the work, a basic scheme for the processing of beryllium concentrates was developed and approved, and the hardware design of the process was developed. The feasibility study of technology is shown
Spatial deorientation of upper-Stark-state-selected supersonic beams of CH3F, CH3Cl, CH3Br, and CH3I
Towards an Economy of Higher Education
This paper draws a distinction between ways thinking and acting, and hence of policy and practice in higher education, in terms of different kinds of economy: economies of exchange and economies of excess. Crucial features of economies of exchange are outlined and their presence in prevailing conceptions of teaching and learning is illustrated. These are contrasted with other possible forms of practice, which in turn bring to light the nature of an economy of excess. In more philosophical terms, and to expand on the picture, economies of excess are elaborated with reference, first, to the understanding of alterity in the work of Emmanuel Levinas and, second, to the idea of Dionysian intensity that is to be found in Nietzsche. In the light of critical comment on some current directions in policy and practice, the implications of these ways of thinking for the administrator, the teacher and the student in higher education are explored
The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey
We present the design and performance of the multi-object fiber spectrographs
for the Sloan Digital Sky Survey (SDSS) and their upgrade for the Baryon
Oscillation Spectroscopic Survey (BOSS). Originally commissioned in Fall 1999
on the 2.5-m aperture Sloan Telescope at Apache Point Observatory, the
spectrographs produced more than 1.5 million spectra for the SDSS and SDSS-II
surveys, enabling a wide variety of Galactic and extra-galactic science
including the first observation of baryon acoustic oscillations in 2005. The
spectrographs were upgraded in 2009 and are currently in use for BOSS, the
flagship survey of the third-generation SDSS-III project. BOSS will measure
redshifts of 1.35 million massive galaxies to redshift 0.7 and Lyman-alpha
absorption of 160,000 high redshift quasars over 10,000 square degrees of sky,
making percent level measurements of the absolute cosmic distance scale of the
Universe and placing tight constraints on the equation of state of dark energy.
The twin multi-object fiber spectrographs utilize a simple optical layout
with reflective collimators, gratings, all-refractive cameras, and
state-of-the-art CCD detectors to produce hundreds of spectra simultaneously in
two channels over a bandpass covering the near ultraviolet to the near
infrared, with a resolving power R = \lambda/FWHM ~ 2000. Building on proven
heritage, the spectrographs were upgraded for BOSS with volume-phase
holographic gratings and modern CCD detectors, improving the peak throughput by
nearly a factor of two, extending the bandpass to cover 360 < \lambda < 1000
nm, and increasing the number of fibers from 640 to 1000 per exposure. In this
paper we describe the original SDSS spectrograph design and the upgrades
implemented for BOSS, and document the predicted and measured performances.Comment: 43 pages, 42 figures, revised according to referee report and
accepted by AJ. Provides background for the instrument responsible for SDSS
and BOSS spectra. 4th in a series of survey technical papers released in
Summer 2012, including arXiv:1207.7137 (DR9), arXiv:1207.7326 (Spectral
Classification), and arXiv:1208.0022 (BOSS Overview
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POT1 mutations predispose to familial melanoma
Deleterious germline variants in CDKN2A account for around 40% of familial melanoma cases, and rare variants in CDK4, BRCA2, BAP1 and the promoter of TERT have also been linked to the disease. Here we set out to identify new high-penetrance susceptibility genes by sequencing 184 melanoma cases from 105 pedigrees recruited in the UK, The Netherlands and Australia that were negative for variants in known predisposition genes. We identified families where melanoma cosegregates with loss-of-function variants in the protection of telomeres 1 gene (POT1), with a proportion of family members presenting with an early age of onset and multiple primary tumors. We show that these variants either affect POT1 mRNA splicing or alter key residues in the highly conserved oligonucleotide/oligosaccharide-binding (OB) domains of POT1, disrupting protein-telomere binding and leading to increased telomere length. These findings suggest that POT1 variants predispose to melanoma formation via a direct effect on telomeres.D.J.A., C.D.R.-E., Z.D., J.Z.L., J.C.T., M.P. and T.M.K. were supported by Cancer Research UK and the Wellcome Trust (WT098051). C.D.R.-E. was also supported by the Consejo Nacional de Ciencia y Tecnología of Mexico. K.A.P. and A.M.D. were supported by Cancer Research UK (grants C1287/A9540 and C8197/A10123) and by the Isaac Newton Trust. N.K.H. was supported by a fellowship from the National Health and Medical Research Council of Australia (NHMRC). L.G.A. was supported by an Australia and New Zealand Banking Group Limited Trustees PhD scholarship. A.L.P. is supported by Cure Cancer Australia. The work was funded in part by the NHMRC and Cancer Council Queensland. The work of N.A.G. was in part supported by the Dutch Cancer Society (UL 2012-5489). M.H., J.A.N.-B. and D.T.B. were supported by Cancer Research UK (programme awards C588/A4994 and C588/A10589 and the Genomics Initiative). C.L.-O., A.J.R. and V.Q. are funded by the Spanish Ministry of Economy and Competitiveness through the Instituto de Salud Carlos III (ISCIII), the Red Temática de Investigación del Cáncer (RTICC) del ISCIII and the Consolider-Ingenio RNAREG Consortium. C.L.-O. is an investigator with the Botín Foundation.This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/ng.294
Good things come in small packages: is there a common set of motivators for energy behaviour?
Estimating CDKN2A mutation carrier probability among global familial melanoma cases using GenoMELPREDICT
Background: Although rare in the general population, highly penetrant germline mutations in CDKN2A are responsible for 5%-40% of melanoma cases reported in melanoma-prone families. We sought to determine whether MELPREDICT was generalizable to a global series of families with melanoma and whether performance improvements can be achieved. Methods: In total, 2116 familial melanoma cases were ascertained by the international GenoMEL Consortium. We recapitulated the MELPREDICT model within our data (GenoMELPREDICT) to assess performance improvements by adding phenotypic risk factors and history of pancreatic cancer. We report areas under the curve (AUC) with 95% confidence intervals (CIs) along with net reclassification indices (NRIs) as performance metrics. Results: MELPREDICT performed well (AUC 0.752, 95% CI 0.730-0.775), and GenoMELPREDICT performance was similar (AUC 0.748, 95% CI 0.726-0.771). Adding a reported history of pancreatic cancer yielded discriminatory improvement (P < .0001) in GenoMELPREDICT (AUC 0.772, 95% CI 0.750-0.793, NRI 0.40). Including phenotypic risk factors did not improve performance. Conclusion: The MELPREDICT model functioned well in a global data set of familial melanoma cases. Adding pancreatic cancer history improved model prediction. GenoMELPREDICT is a simple tool for predicting CDKN2A mutational status among melanoma patients from melanoma-prone families and can aid in directing these patients to receive genetic testing or cancer risk counseling
The determinants of serum vitamin D levels in participants in a melanoma case–control study living in a temperate climate
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