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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4028-4031 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoelectron spectra of KxC60− (x=1–3) have been studied in the gas phase, and the electron affinities obtained. These were found to decrease linearly with the number of K atoms. The result is consistent with an ionic description of the K–C60 chemical bonding, with each K atom donating its outer 4s electron to the t1u orbital of C60. Vibrational autodetachment from a weakly bound excited electronic state was discovered in KC60−, and a series of three equally spaced peaks were assigned to a progression in the intermolecular K–C60 stretching vibration with a frequency of 140 cm−1.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An inelastic electronic excitation has been observed in CeB6 near 47 meV (545 K) by means of neutron and Raman spectroscopy. This excitation has been identified as the Γ8→Γ7 crystalline-electric-field (CEF) transition. From the anomalous energy shift of this excitation at low temperatures, detectable due to the high resolution of Raman spectroscopy (±5 K), we deduce a Γ8 ground-state split by about 30 K. With this new CEF level scheme the first consistent interpretation of so far seemingly unrelated thermal, elastic, and magnetic data is achieved. In spite of the large body of thermal, magnetic, and elastic data of CeB6 accumulated over the past years, various diverging proposals for the CEF level scheme have been reported. In all schemes a Γ7 ground state was assumed, but the CEF splittings ranged from 10 K6 to more than 400 K. The absence of CEF excitations in direct spectroscopic measurements up to 400 K has been puzzling, and pointed to the necessity of high-energy neutron experiments. We have performed inelastic magnetic neutron scattering experiments using high-energy incident neutrons up to 185 meV from the Intense Pulsed Neutron Source at Argonne National Laboratory. An inelastic peak at 46 meV (530 K) is clearly identified as magnetic scattering by its Q dependence. The absolute intensity corresponds to the value of a Γ8→Γ7 transition. In addition, we have carried out Raman measurements on (100) faces of CeB6. At room temperature we found an inelastic excitation at 372 cm−1 (530 K). It is absent in the reference compound LaB6. From the polarization analysis we found that the transition has Γ3+ and Γ5+ symmetry. Both facts characterize this excitation as the Γ8→Γ7 CEF transition, which is the first CEF excitation seen in a metal by means of Raman spectroscopy. The high resolution of Raman spectroscopy enabled us to detect a 10-cm−1 shift of the Γ8→Γ7 transition energy to 382 cm−1 for temperatures below 20 K. This can only be explained by assuming a Γ8 ground state, which is split by 30 K. From the spectroscopic data we can establish a completely new CEF level scheme for CeB6 with a Γ8 ground state, split by about 30 K and a Γ7 state 545 K above. This allows a straightforward interpretation of various other experimental data, such as magnetic entropy, static magnetic susceptibility, high-field magnetization, magnetic form factor,8 temperature, and magnetic-field-dependent elastic constants and the antiferroquadrupolar ordering below TQ =3.3 K. A recent theoretical investigation of magnetic ordering of a periodic Anderson Hamiltonian with orbital degeneracy has been applied to CeB6. On the basis of entropy and magnetization data it was assumed that the quartet Γ8 is the ground state. Hence it was predicted that the low-temperature phase II (2.1 K〈T〈3.3 K) is due to an orbital antiferromagnetic ordered state, contrary to the conclusions of an antiferroquadrupolar ordering. This work was in part supported by Deutsche Forschungsgemeinschaft, SFB 125 and SFB 126.
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  • 3
    Publication Date: 2018-03-27
    Description: Introduction Chronic obstructive pulmonary disease (COPD) is a progressive disease affecting 3 million people in the UK, in which patients exhibit airflow obstruction that is not fully reversible. COPD treatment guidelines are largely informed by randomised controlled trial results, but it is unclear if these findings apply to large patient populations not studied in trials. Non-interventional studies could be used to study patient groups excluded from trials, but the use of these studies to estimate treatment effectiveness is in its infancy. In this study, we will use individual trial data to validate non-interventional methods for assessing COPD treatment effectiveness, before applying these methods to the analysis of treatment effectiveness within people excluded from, or under-represented in COPD trials. Methods and analysis Using individual patient data from the landmark COPD Towards a Revolution in COPD Health (TORCH) trial and validated methods for detecting COPD and exacerbations in routinely collected primary care data, we will assemble a cohort in the UK Clinical Practice Research Datalink (selecting people between 1 January 2004 and 1 January 2017) with similar characteristics to TORCH participants and test whether non-interventional data can generate comparable results to trials, using cohort methodology with propensity score techniques to adjust for potential confounding. We will then use the methodological template we have developed to determine risks and benefits of COPD treatments in people excluded from TORCH. Outcomes are pneumonia, COPD exacerbation, mortality and time to treatment change. Groups to be studied include the elderly (〉80 years), people with substantial comorbidity, people with and without underlying cardiovascular disease and people with mild COPD. Ethics and dissemination Ethical approval has been granted by the London School of Hygiene & Tropical Medicine Ethics Committee (Ref: 11997). The study has been approved by the Independent Scientific Advisory Committee of the UK Medicines and Healthcare Products Regulatory Agency (protocol no. 17_114R). An application to use the TORCH trial data made to clinicalstudydatarequest.com has been approved. In addition to scientific publications, dissemination methods will be developed based on discussions with patient groups with COPD.
    Keywords: Open access, Epidemiology, Epidemiology
    Electronic ISSN: 2044-6055
    Topics: Medicine
    Published by BMJ Publishing
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