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Search Results: 1 - 10 of 194393 matches for " D Meyer Meyer "
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Editorial Comments/ Redaksionele Kommentaar
D Meyer
Health SA Gesondheid , 2006, DOI: 10.4102/hsag.v11i1.210
Abstract: This edition of Health SA Gesondheid provides thought provoking commentary on a variety of challenges experienced in the field of health care. Opsomming Hierdie uitgawe van Health SA Gesondheid verskaf kommentaar oor talle uitdagings wat in die veld van gesondheidsorg ondervind word. *Please note: This is a reduced version of the abstract. Please refer to PDF for full text.
Ferromagnetism and disorder: A dynamical mean-field study
D. Meyer
Physics , 2001, DOI: 10.1016/S0038-1098(01)00520-8
Abstract: We investigate ferromagnetism in the periodic Anderson model with diagonal disorder. Using dynamical mean-field theory in combination with the modified perturbation theory, the disorder can be included in the calculation consistently, which turns out to be equivalent to the CPA method. Disorder generally reduces the Curie temperature and can for certain configurations completely suppress ferromagnetic order. This can be ascribed to the enhanced quasiparticle damping and the special structure of the density of states.
Hutchinson’s sign as a marker of ocular involvement in HIVpositive patients with herpes zoster ophthalmicus
M van Dyk, D Meyer Meyer
South African Medical Journal , 2010,
Abstract: Background. A positive Hutchinsonfs sign indicates an increased risk of ocular involvement in herpes zoster ophthalmicus (HZO). We examined the sensitivity of Hutchinsonfs sign as an indicator of ocular involvement in a consecutive series of patients presenting with HZO. Methods. We conducted a descriptive observational prospective study of patients .18 years old presenting with HZO and consenting to pre- and post-test counselling and HIV and CD4 testing. A full ophthalmological examination focused on the extent of ocular involvement, and the presence of Hutchinsonfs sign was confirmed by two clinicians. Results. Thirty-three patients were enrolled; 29 were HIV positive, of whom 18 (62%) had not been diagnosed with HIV prior to enrolment. Of the 29 HIV-positive patients, 21 (72%) were Hutchinsonfs sign positive (HSP), all of whom had intra-ocular involvement (95% confidence interval 88 - 100%) Of the 8 HIV-positive, Hutchinsonfs sign-negative (HSN) patients, 4 did and 4 did not display intra-ocular involvement. Neither the mean CD4 count nor the average age in the HSP group differed significantly from the HSN group. Conclusion. We confirmed that a Hutchinsonfs sign- and HIVpositive patient with HZO has a very high positive predictive value for intra-ocular involvement. Neither age nor CD4 count had predictive value for ocular involvement. Young adults presenting with HZO should be suspected of having HIV, and HIV-positive patients with HZO but HSN may still have ocular involvement. All patients with HZO should be seen by an ophthalmologist.
Intraocular pressure-lowering effect of oral paracetamol and its in vitro corneal penetration properties
Mohamed N, Meyer D
Clinical Ophthalmology , 2013, DOI: http://dx.doi.org/10.2147/OPTH.S38473
Abstract: traocular pressure-lowering effect of oral paracetamol and its in vitro corneal penetration properties Original Research (986) Total Article Views Authors: Mohamed N, Meyer D Published Date January 2013 Volume 2013:7 Pages 219 - 227 DOI: http://dx.doi.org/10.2147/OPTH.S38473 Received: 24 September 2012 Accepted: 14 November 2012 Published: 30 January 2013 Nabiel Mohamed, David Meyer Division of Ophthalmology, Faculty of Medicine and Health Sciences, University of Stellenbosch, Cape Town, South Africa Background: Several studies have confirmed the ability of cannabinoids to reduce intraocular pressure. Experimental data recently demonstrated unequivocally that the analgesic effect of paracetamol is due to its indirect action on cannabinoid receptors. The question then arises as to whether paracetamol can reduce intraocular pressure via its effect on intraocular cannabinoid receptors. Methods: A 2-week, prospective, randomized, controlled, single-center, parallel-group pilot study was carried out to determine the efficacy and safety of paracetamol 1 g orally administered every 6 hours in adult patients with primary or secondary open angle glaucoma as compared with topical levobunolol 0.5% twice a day. Patient well-being was closely monitored throughout the study and focused on hepatic safety in accordance with Drug-Induced Liver Injury Network criteria. The in vitro diffusion kinetics of acetaminophen in a phosphate-buffered solution in rabbit and human corneas was also investigated, with the view to a topical application. Results: Eighteen adult patients were enrolled in the study, with nine in the topical levobunolol group and nine in the oral paracetamol group. In the levobunolol group, the mean reduction in intraocular pressure at day 7 was 7.5 mmHg (P < 0.008) and at day 14 was 9.1 mmHg (P < 0.005), from a mean baseline intraocular pressure of 29.6 mmHg. The corresponding figures for the paracetamol group were 8.8 mmHg (P < 0.0004) at day 7 and 6.5 mmHg (P < 0.004) at day 14, from a mean baseline intraocular pressure of 29.4 mmHg. Both study regimens were well tolerated. No serious treatment-related adverse events were reported in either of the treatment groups. Liver function tests, systolic/diastolic blood pressure, or heart rate remained unchanged in both groups during the 2 weeks of the study. In the laboratory study, paracetamol 1 mg/mL in phosphate-buffered solution (pH 7.4) showed acceptable flux rates. Steady-state levels were achieved within 12 hours, thus confirming that paracetamol penetrates the cornea well. Conclusion: Paracetamol 1 g taken orally every 6 hours reduced open angle glaucoma and/or angle recession glaucoma in both groups of patients, in a way comparable with that achieved by a topical beta-adrenergic receptor antagonist.
Intraocular pressure-lowering effect of oral paracetamol and its in vitro corneal penetration properties
Mohamed N,Meyer D
Clinical Ophthalmology , 2013,
Abstract: Nabiel Mohamed, David MeyerDivision of Ophthalmology, Faculty of Medicine and Health Sciences, University of Stellenbosch, Cape Town, South AfricaBackground: Several studies have confirmed the ability of cannabinoids to reduce intraocular pressure. Experimental data recently demonstrated unequivocally that the analgesic effect of paracetamol is due to its indirect action on cannabinoid receptors. The question then arises as to whether paracetamol can reduce intraocular pressure via its effect on intraocular cannabinoid receptors.Methods: A 2-week, prospective, randomized, controlled, single-center, parallel-group pilot study was carried out to determine the efficacy and safety of paracetamol 1 g orally administered every 6 hours in adult patients with primary or secondary open angle glaucoma as compared with topical levobunolol 0.5% twice a day. Patient well-being was closely monitored throughout the study and focused on hepatic safety in accordance with Drug-Induced Liver Injury Network criteria. The in vitro diffusion kinetics of acetaminophen in a phosphate-buffered solution in rabbit and human corneas was also investigated, with the view to a topical application.Results: Eighteen adult patients were enrolled in the study, with nine in the topical levobunolol group and nine in the oral paracetamol group. In the levobunolol group, the mean reduction in intraocular pressure at day 7 was 7.5 mmHg (P < 0.008) and at day 14 was 9.1 mmHg (P < 0.005), from a mean baseline intraocular pressure of 29.6 mmHg. The corresponding figures for the paracetamol group were 8.8 mmHg (P < 0.0004) at day 7 and 6.5 mmHg (P < 0.004) at day 14, from a mean baseline intraocular pressure of 29.4 mmHg. Both study regimens were well tolerated. No serious treatment-related adverse events were reported in either of the treatment groups. Liver function tests, systolic/diastolic blood pressure, or heart rate remained unchanged in both groups during the 2 weeks of the study. In the laboratory study, paracetamol 1 mg/mL in phosphate-buffered solution (pH 7.4) showed acceptable flux rates. Steady-state levels were achieved within 12 hours, thus confirming that paracetamol penetrates the cornea well.Conclusion: Paracetamol 1 g taken orally every 6 hours reduced open angle glaucoma and/or angle recession glaucoma in both groups of patients, in a way comparable with that achieved by a topical beta-adrenergic receptor antagonist.Keywords: acetaminophen, paracetamol, glaucoma, intraocular pressure, cannabinoids
Dynamical mean-field study of ferromagnetism in the periodic Anderson model
D. Meyer,W. Nolting
Physics , 2000, DOI: 10.1103/PhysRevB.62.5657
Abstract: The ferromagnetic phase diagram of the periodic Anderson model is calculated using dynamical mean-field theory in combination with the modified perturbation theory. Concentrating on the intermediate valence regime, the phase boundaries are established as function of the total electron density, the position of the atomic level and the hybridization strength. The main contribution to the magnetic moment stems from the f-electrons. The conduction band polarization is, depending on the system parameters either parallel or antiparallel to the f-magnetization. By investigating the densities of states, one observes that the change of sign of the conduction band polarization is closely connected to the hybridization gap, which is only apparent in the case of almost complete polarization of the f-electrons. Finite-temperature calculations are also performed, the Curie temperature as function of electron density and f-level position are determined. In the intermediate-valence regime, the phase transitions are found to be of second order.
Kondo screening and exhaustion in the periodic Anderson model
D. Meyer,W. Nolting
Physics , 2000, DOI: 10.1103/PhysRevB.61.13465
Abstract: We investigate the paramagnetic periodic Anderson model using the dynamical mean-field theory in combination with the modified perturbation theory which interpolates between the weak and strong coupling limits. For the symmetric PAM, the ground state is always a singlet state. However, as function of the hybridization strength, a crossover from collective to local Kondo screening is found. Reducing the number of conduction electrons, the local Kondo singlets remain stable. The unpaired f-electrons dominate the physics of the system. For very low conduction electron densities, a large increase of the effective mass of the quasiparticles is visible, which is interpreted as the approach of the Mott-Hubbard transition.
Density-functional study of Cu atoms, monolayers, and coadsorbates on polar ZnO surfaces
B. Meyer,D. Marx
Physics , 2003, DOI: 10.1103/PhysRevB.69.235420
Abstract: The structure and electronic properties of single Cu atoms, copper monolayers and thin copper films on the polar oxygen and zinc terminated surfaces of ZnO are studied using periodic density-functional calculations. We find that the binding energy of Cu atoms sensitively depends on how charge neutrality of the polar surfaces is achieved. Bonding is very strong if the surfaces are stabilized by an electronic mechanism which leads to partially filled surface bands. As soon as the surface bands are filled (either by partial Cu coverage, by coadsorbates, or by the formation of defects), the binding energy decreases significantly. In this case, values very similar to those found for nonpolar surfaces and for copper on finite ZnO clusters are obtained. Possible implications of these observations concerning the growth mode of copper on polar ZnO surfaces and their importance in catalysis are discussed.
Strong-coupling scenario of a metamagnetic transition
D. Meyer,W. Nolting
Physics , 2001, DOI: 10.1103/PhysRevB.64.052402
Abstract: We investigate the periodic Anderson model in the presence of an external magnetic field, using dynamical mean-field theory in combination with the modified perturbation theory. A metamagnetic transition is observed which exhibits a massive change in the electronic properties. These are discussed in terms of the quasiparticle weight and densities of states. The results are compared with the experimental results of the metamagnetic transition in CeRu_2Si_2.
Influence of spin-flip scattering on the stability of ferromagnetism in a two-band Hubbard model
D. Meyer,W. Nolting
Physics , 1999, DOI: 10.1088/0953-8984/11/30/311
Abstract: We investigate the influence of an interband exchange interaction on magnetism in a two-band Hubbard model. Our main emphasis lies on spin-flip scattering which is often neglected but is neccessary to retain the full rotational symmetry of the Hamiltonian. We find a striking dependence of the magnetization on the interband exchange coupling constant J and a substantial suppression of ferromagnetic order for a large range of values of J. The onset of an RKKY-like magnetic ordering mechanism is also observed.
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