104,959 research outputs found
View from the bridge: a pseudo-Jahn-Teller approach to transition metal hydrosilane complexes
Get PDFThe model complex [Cp(CO)(2)Mn(SiH4)] has been studied by time-dependent DFT methods: hence, it is shown to be unstable with respect to a pseudo-Jahn-Teller distortion which brings an equatorial Si-H moiety into contact with the Mn centre.</p
Icosahedral T-1u+T-1g Jahn-Teller problem
Get PDFThe T-1u+T-1g multimode Jahn-Teller problem in icosahedral symmetry is investigated. It is found that the pseudo-Jahn-Teller interaction between T-1u and T-1g can give rise to an increase of symmetry through the development of additional troughs in the space of ungerade modes. This result is related to a continuous group invariance of the Hamiltonian. The possible relevance to the Jahn-Teller instability of negatively charged fullerides is discussed.status: Publishe
The effect of cooperative Jahn–Teller interactions on C60− anions
Get PDFSingly charged buckminsterfullerene anions, C60−, are subject to a strong intramolecular T [circle times] h Jahn–Teller (JT) effect. When such ions interact with other C60− ions in a solid through a cooperative JT effect, they will be subject to an additional interaction. There are a number of different mechanisms that can cause this interaction. However, in the molecular field approximation, all can be modelled phenomenologically in terms of a symmetry-lowering interaction written in terms of a linear combination of electronic operators for the h modes involved in the intramolecular JT effect. We will consider the combined effect of this distortion and the intramolecular JT effect. We will analyse the lowest adiabatic potential energy surface, and calculate the energies of the resultant vibronic states. The results are shown to have a complicated dependence on the particular combination of h modes chosen, and the energies of the resultant vibronic states cannot easily be deduced from the form of the potential alone
Estimating the need for antiretroviral treatment and an assessment of a simplified HIV/AIDS case definition in rural Malawi.
No full textBACKGROUND: Surveillance in the era of antiretroviral therapy (ART) requires estimates of HIV prevalence as well as the proportion eligible for ART. We estimated HIV prevalence and assessed field staging of individuals to estimate the burden of HIV disease needing treatment in rural Malawi. METHODS: Adults aged 18-59 years in a demographic surveillance system were interviewed, examined, and HIV counselled and tested. Staging that used a simplified version of the WHO criteria ('field checklist') was compared with staging by a medical assistant using a 'clinic checklist' and to CD4 cell results. RESULTS: A total of 2129 of 2303 eligible adults (92.4%) were traced, and 2047 (96.1%) participated. Of the 1443 participants (70.5%) tested, 11.6% were HIV positive. ART eligibility classification by the field and clinic checklists were concordant in 122 of 133 HIV-positive individuals. Compared with the clinic checklist, the field checklist had a sensitivity of 50% and a specificity of 96%. Including those already known to be on ART, staging by the field and clinic checklists estimated ART eligibility at 16.3 and 17.7% of HIV-positive individuals, respectively. Using CD4 cell count under 250 cells/mul or WHO stage III/IV, the Malawi national programme criteria, 38% of HIV-positive individuals were eligible for ART, compared with 31% based on the 2006 WHO criteria of CD4 cell count under 200 cells/mul or WHO stage IV or CD4 cell count of 200-350 cells/mul and WHO stage III. CONCLUSION: The field checklist was not a suitable tool for individual staging. Criteria for ART eligibility based on clinical staging alone missed two-thirds of those eligible by clinical staging and CD4 cell count
Examination of the Jahn-Teller physics of NaNi02 and LiNi02 using x-ray absorption spectroscopy and configuration interaction
Get PDF This thesis examines available x-ray absorption spectroscopy (XAS) data for NiO, NaNi02 , and LiNi02 . The XAS examined is the Ni L-edge, 3d^n2p^6 →t 3d^(n+1)2p^5 . The experimental spectra are compared to spectra calculated using a configuration interaction approach. This approach reproduces the spectra accurately. The NaNi02 spectrum is shown to be sensitive to the Jahn-Teller distortion, while the LiNi02 spectrum is reproduced by a hybridized d^7-d^8 state that explains the lack of Jahn-Teller distortion in LiNi02 ThesisMaster of Science (MSc
Population-level effect of HIV on adult mortality and early evidence of reversal after introduction of antiretroviral therapy in Malawi.
Get PDFBACKGROUND: Malawi, which has about 80,000 deaths from AIDS every year, made free antiretroviral therapy available to more than 80 000 patients between 2004 and 2006. We aimed to investigate mortality in a population before and after the introduction of free antiretroviral therapy, and therefore to assess the effects of such programmes on survival at the population level. METHODS: We used a demographic surveillance system to measure mortality in a population of 32,000 in northern Malawi, from August, 2002, when free antiretroviral therapy was not available in the study district, until February, 2006, 8 months after a clinic opened. Causes of death were established through verbal autopsies (retrospective interviews). Patients who registered for antiretroviral therapy at the clinic were identified and linked to the population under surveillance. Trends in mortality were analysed by age, sex, cause of death, and zone of residence. FINDINGS: Before antiretroviral therapy became available in June, 2005, mortality in adults (aged 15-59 years) was 9.8 deaths for 1000 person-years of observation (95% CI 8.9-10.9). The probability of dying between the ages of 15 and 60 years was 43% (39-49) for men and 43% (38-47) for women; 229 of 352 deaths (65.1%) were attributed to AIDS. 8 months after the clinic that provided antiretroviral therapy opened, 107 adults from the study population had accessed treatment, out of an estimated 334 in need of treatment. Overall mortality in adults had decreased by 10% from 10.2 to 8.7 deaths for 1000 person-years of observation (adjusted rate ratio 0.90, 95% CI 0.70-1.14). Mortality was reduced by 35% (adjusted rate ratio 0.65, 0.46-0.92) in adults near the main road, where mortality before antiretroviral therapy was highest (from 13.2 to 8.5 deaths per 1000 person-years of observation before and after antiretroviral therapy). Mortality in adults aged 60 years or older did not change. INTERPRETATION: Our findings of a reduction in mortality in adults aged between 15 and 59 years, with no change in those older than 60 years, suggests that deaths from AIDS were averted by the rapid scale-up of free antiretroviral therapy in rural Malawi, which led to a decline in adult mortality that was detectable at the population level
DIPHOSPHINONITRENIUM AND DIPHOSPHENIUM CATIONS, JAHN-TELLER DISTORTED ALLYL SYSTEMS
No full textSchoeller W, BUSCH T. DIPHOSPHINONITRENIUM AND DIPHOSPHENIUM CATIONS, JAHN-TELLER DISTORTED ALLYL SYSTEMS. CHEMISCHE BERICHTE. 1990;123(5):971-973
Displacive Jahn–Teller Transition in NaNiO 2
Get PDFBelow its Jahn–Teller transition temperature, T JT, NaNiO2 has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO6 and Jahn–Teller-distorted NiO6 octahedra. Above T JT where NaNiO2 is rhombohedral, diffraction measurements show the absence of a cooperative Jahn–Teller distortion, accompanied by an increase in the unit cell volume. Using neutron total scattering, solid-state Nuclear Magnetic Resonance (NMR), and extended X-ray absorption fine structure (EXAFS) experiments as local probes of the structure we find direct evidence for a displacive, as opposed to order–disorder, Jahn–Teller transition at T JT. This is supported by ab initio molecular dynamics (AIMD) simulations. To our knowledge this study is the first to show a displacive Jahn–Teller transition in any material using direct observations with local probe techniques
[Stammbuch J. G. Jahn]
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Henckel von Donnersmarck, Erdmann Heinrich; Blatt 34 (33v 34r)
Heinrich, IX., Reuss-Köstritz, Graf; Blatt 35 (34v 35r)
Heinrich, X., Reuss, Jüngere Linie, Graf; Blatt 36 (35v 36r)
Krause, Johann Gottlieb; Blatt 36a (36v 36ar)
Notizen (36av 37r)
Hallbauer, Friedrich Andreas; Blatt 52 (51v 52r)
Hertel, Johann Friedrich; Blatt 61 (60v 61r)
Bastineller, Gebhard Christian; Blatt 66 (65v 66r)
Kraus, Johann Gottfried; Blatt 67 (66v 67r)
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Hartig, A. T.; Blatt 108,2 (108v 109r)
Böhlau, Christoph Dietrich von; Blatt 109 (108v 109r)
Liebenstein, Friedrich Maximilian von; Blatt 110 (109v 110r)
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Hartmann, Johann; Blatt 117 (116v 117r)
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QUASI-JAHN-TELLER EFFECT IN CHEMICAL REACTIONS
No full textL. Wang, Chem, Phys. Lett. (a) 285 (1998) 359; (b) submitted. L. Wang, Chem, Phys. 237 (1998) 305.Author Institution: Department of Chemistry, The Ohio State UniversityIt will be demonstrated that the quasi-Jahn-Teller effect in chemical reactions is a nuclear quantum effect, , induced by electronic . Further, is equivalent to the Diagonal Born-Oppenheimer Correction. Results including and without for a model system will be . The research shows clearly that one has to consider this effect in order to obtain various quantities within a spectroscopic accuracy for systems where this effect is no longer negeligible
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