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Biomedical subjects

H Rosner

Publications and source records attributed to H Rosner.

At least 19 recordsLinked to original sources
PubMed2006

Superconductivity and lattice instability in compressed lithium from Fermi surface hot spots.

The highest superconducting temperature Tc observed in any elemental metal (Li with Tc approximately 18-20 K at pressure 35-48 GPa) is shown to arise from increasingly strong electron-phonon coupling concentrated along intersections of Kohn anomaly surfaces with the evolving Fermi surface. First-principles linear response calculations of the phonon spectrum and spectral function alpha2F(omega) reveal very strong Q- and phonon-polarization dependence of coupling strength, resulting in values of in the observed range. The sharp momentum dependence of the coupling even for the simple Li Fermi surface indicates more generally that a fine Q mesh is required for precise evaluation of lamda.

Journal Article↗
PubMed2006

Optical pseudogap from iron states in filled skutterudites AFe4Sb12 (A=Yb, Ca, Ba).

Optical investigations are presented of the filled skutterudites AFe4Sb12 with divalent cations A=Yb, Ca, Ba. For each of these compounds a very similar pseudogap structure in the optical conductivity develops in the far-infrared spectral region at temperatures below 90 K. Highly accurate local-density approximation electronic band structure calculations can consistently explain the origin of the pseudogap structure generated largely by transition metal 3d states. In particular, a 4f-conduction electron hybridization or strong correlations can be ruled out as origin for the pseudogap.

Journal Article↗
PubMed2006

Electron localization function in full-potential representation for crystalline materials.

The electron localization function (ELF) is implemented in the first-principles, all-electron, full-potential local orbital method. This full-potential implementation increases the accuracy with which the ELF can be computed for crystalline materials. Some representative results obtained are presented and compared with the results of other methods. Although for crystal structures with directed bonding only minor differences are found, in simple elemental metals, there are differences in the valence region, which give rise to different ELF topologies.

Journal Article↗
PubMed2003

Features of the electron density in magnesium diboride: reconstruction from X-ray diffraction data and comparison with TB-LMTO and FPLO calculations.

Features of the electron density in MgB(2) reconstructed from room-temperature single-crystal X-ray diffraction intensities using a multipole model are considered. Topological analysis of the total electron density has been applied to characterize the atomic interactions in magnesium diboride. The shared-type B-B interaction in the B-atom layer reveals that both sigma and pi components of the bonding are strong. A closed-shell-type weak B-B pi interaction along the c axis of the unit cell has also been found. The Mg-B closed-shell interaction exhibits a bond path that is significantly curved towards the vertical Mg-atom chain ([110] direction). The latter two facts reflect two sorts of bonding interactions along the [001] direction. Integration of the electron density over the zero-flux atomic basins reveals a charge transfer of approximately 1.4 (1) electrons from the Mg atoms to the B-atom network. The calculated electric-field gradients at nuclear positions are in good agreement with experimental NMR values. The anharmonic displacement of the B atoms is also discussed. Calculations of the electron density by tight-binding linear muffin-tin orbital (TB-LMTO) and full-potential non-orthogonal local orbital (FPLO) methods confirm the results of the reconstruction from X-ray diffraction; for example, a charge transfer of 1.5 and 1.6 electrons, respectively, was found.

Journal Article↗
PubMed2003

Ferromagnetic ordering in alkali-metal iron antimonides: NaFe4Sb12 and KFe4Sb12.

New alkali-metal compounds with the filled-skutterudite structure were synthesized and their chemical and physical properties investigated. X-ray diffraction, microprobe, and chemical analysis established the structure and the composition without defects on the cation site. Magnetization, ac susceptibility, specific heat, resistivity, and NMR or NQR demonstrated NaFe4Sb12 to be ferromagnetic below approximately 85 K and to exhibit an additional magnetic anomaly around 40 K. Band structure calculations find a large density of states at the Fermi energy and a ferromagnetic ground state. Similar behavior was observed for KFe4Sb12.

Journal Article↗
PubMed2003

A sulfonic anhydride derivative from dibenzyl trisulphide with agro-chemical activities.

In the present study, the biologically active natural product dibenzyl trisulphide (DTS) which was previously isolated from the sub-tropical shrub Petiveria alliacea was transformed to methyl benzyl sulphonic anhydride (MBSA) using a "one pot" transformation method. The anhydride was evaluated for anti-microbial activities on the bacteria, Bacillus subtilis and Pseudomonas fluorescens and found to be 2.5 fold more effective than the commercial agents isoniazid and ampicillin in inhibiting the growth of B. subtilis, while on P. fluorescens it was 2.5, 5.0 and 10.0 fold more inhibitory than isoniazid, ampicillin and dibenzyl trisulphide, respectively. DTS was inactive on B. subtillis. The MIC value (microgram/spot) found for DTS on the plant pathogenic fungus, Cladosporium cucumerinum was 5.0 microgram/spot, while MBSA gave a value of 0.1 microgram/spot, compared with 1.25 and 0.16 microgram/spot for the commercial agents ketoconazole and nystatin, respectively. On the larval nematode (Meloidogyne incognita) MBSA inflicted 97.72% and 57.47% Abbotts nematicidal activities at 125.0 and 62.5 ppm, respectively, while DTS had no effect at 125.0 ppm. Nematodes which were immobilized by the low concentrations of MBSA were unable to re-activate when exposed to 10.0 ppm picrotoxin, thus suggesting that the anhydride nematicidal activity is independent of the GABA-ergic neurophysiological pathway.MBSA demonstrated a strong dose dependent radicular suppression effect (r=0.984), on the radicles of Latuca sativa germinating seeds. DTS was weakly active.

Animals↗
PubMed2003

Effects of the mycotoxin ochratoxin A and some of its metabolites on human kidney cell lines.

The modulations of complement-regulating surface proteins on a human embryonic and a renal carcinoma cell line are described regarding the effects of ochratoxin A and some of its metabolites on the surface markers CD46, CD55 and CD59. Membrane integrity, cell proliferation and metabolic activity were reduced to different extents, depending on the kind of mycotoxin and the dosage, which was ranging from 10 to 1000 ng/ml. The number of cells carrying surface markers was suppressed significantly at 1000 ng/ml, in some cases even at 100 ng/ml, whereas the intensity of receptor expression on the positive cells was found to be stimulated. The fraction RE2 (OTC) isolated from an OTA-containing crude toxin surpassed the effects of all other ochratoxin metabolites. Apart from well-known cytotoxic and genotoxic effects modulation of cell surface marker expression by low concentrations of OTA and OTC deserves more attention with regard to its immuno-pathogenic importance. Furthermore, occurrence and impact of the mycotoxin OTC should be studied more into detail.

Antigens, CD↗
PubMed2002

Insulating ferromagnetism in La4Ba2Cu2O10: an Ab initio wannier function analysis.

Microscopic mechanisms of the puzzling insulating ferromagnetism of half-filled La4Ba2Cu2O10 are elucidated with energy-resolved Wannier states. The dominant magnetic coupling, revealed through evaluated parameters (t, U, and J), turns out to be the intersite direct exchange, a currently ignored mechanism that overwhelms the antiferromagnetic superexchange. By contrast, the isostructural Nd4Ba2Cu2O10 develops the observed antiferromagnetic order via its characteristics of a 1D chain. Surprisingly, the in-plane order of both cases is not controlled by coupling between nearest neighbors. An intriguing pressure-induced ferromagnetic to antiferromagnetic transition is predicted.

Journal Article↗
PubMed2002

Realization of a large J(2) quasi-2D spin-half Heisenberg system: Li(2)VOSiO(4).

Exchange couplings are calculated for Li(2)VOSiO(4) using the local-density approximation (LDA). While the sum of in-plane couplings J(1)+J(2) = 9.5+/-1.5 K and the interplane coupling J( perpendicular) approximately 0.2- 0.3 K agree with recent experimental data, the ratio J(2)/J(1) approximately 12 exceeds the reported value by an order of magnitude. Using geometrical considerations, high temperature expansions and perturbative mean field theory, we show that the LDA-derived exchange constants lead to a remarkably accurate description of the properties of these materials including specific heat, susceptibility, Néel temperature, and NMR spectra.

Journal Article↗
PubMed2002

Prediction of high T(c) superconductivity in hole-doped LiBC.

The layered lithium borocarbide LiBC, isovalent with and structurally similar to the superconductor MgB2, is an insulator due to the modulation within the hexagonal layers (BC vs B2). We show that hole doping of LiBC results in Fermi surfaces of B-C p sigma character that couple very strongly to B-C bond stretching modes, precisely the features that lead to superconductivity at T(c) approximately equal to 40 K in MgB2. Comparison of Li(0.5)BC with MgB2 indicates the former to be a prime candidate for electron-phonon coupled superconductivity at substantially higher temperature than in MgB2.

Journal Article↗
PubMed2002

[In vitro studies into the influence of ochratoxin A on the production of tumor necrosis factor alpha by the human monocytic cell line THP-1].

The influence of pure OTA and an Aspergillus-ochraceus crude toxin on the intracellular expression and the secretion of tumor necrosis factor (TNF) alpha by the monocytic cell line THP-1 was studied in vitro. After 4 hours exposure, the secretion of TNF alpha was inhibited to 50% by pure OTA in a concentration of 400 ng/ml and by crude toxin in a concentration of 100 ng/ml. The same concentrations of mycotoxins impaired the mitochondrial activity of THP-1 cells only marginally. The intracellular expression of TNF alpha was not disturbed by pure OTA in the concentrations tested, whereas crude toxin showed an inhibitory effect. The possible reasons for these findings are discussed.

Calcium Channel Blockers↗
PubMed2001

Superconductivity near ferromagnetism in MgCNi3.

An unusual quasi-two-dimensional heavy band mass van Hove singularity (vHs) lies very near the Fermi energy in MgCNi3, recently reported to superconduct at 8.5 K. This compound is strongly exchange enhanced and unstable to ferromagnetism upon hole doping with approximately 12% Mg-->Na or Li (i.e., 0.04 hole/Ni). We identify an essentially infinite mass along the M-Gamma line, which accounts for the two dimensionality of this vHs. This compound provides new opportunities to probe the ferromagnetic critical point as well as introducing the novelties of 2D behavior into a 3D system.

Journal Article↗
PubMed1999

Studies on the influence of combined administration of ochratoxin A, fumonisin B1, deoxynivalenol and T2 toxin on immune and defence reactions in weaner pigs.

In weaners, combined administration of fumonisin, deoxynivalenol and T2 together with ochratoxin A in quantities expected to be present in feeds of central European origin resulted, as a rule, in changes identical to those observed after single administration of ochratoxin A. Such reactions were partly compensated. Synergistic amplification of immunosuppressive changes due to the simultaneous intake of these mycotoxins in low concentrations is not to be expected.

Animals↗
PubMed1999

Studies of the influence of ochratoxin A on immune and defence reactions in weaners.

Even in subtoxic amounts, the mycotoxin, ochratoxin A, produced immunomodulation in weaner pigs in a dose-dependent mode. In addition to increased counts of total leukocytes and neutrophils in the blood, reduced lymphocyte levels were observed. There was a striking increase in the counts of eosinophils and of apoptotic phagocytes. Functionally, there was a predominance of the production of reactive oxygen radicals in whole blood, reduced phagocytosis performance and reduced expression of a swine-specific surface marker (SWC1) on lymphocytes. In a few single experiments, clinical manifestations could be demonstrated. Lung clearance and the degree of severity of experimental pneumonia as well as cutaneous hypersensitization may be influenced by ochratoxin A.

Animals↗
PubMed1998

C-pathway polysialogangliosides are transiently expressed in the human cerebrum during fetal development.

Gangliosides are assumed to play a crucial role in processes of cellular recognition and interaction important for neural development. They are designated as cytochemical markers of neuronal maturation, as striking changes in the ganglioside pattern parallel the nervous system development. Of particular interest to us are numerous studies that reported during migration of postmitotic neurons and axon formation in developing avian and mammalian brains a transient accumulation of highly sialylated c-pathway gangliosides. However, it has thus far been thought that c-pathway gangliosides do not appear in the human cerebrum; their absence could be somehow interpreted in the light of an evolutionary trend in the pattern of brain gangliosides: by increasing the phylogenetic scale this pattern changes by an accretion of less sialylated gangliosides and switches from c- via b- to a-series, respectively. The present study presents both biochemical and immunocytochemical evidence for the existence of c-pathway gangliosides in the human cerebrum during prenatal life, and their localization in discrete neuronal populations and growing axonal pathways.

Aging↗
PubMed1996

Gabapentin adjunctive therapy in neuropathic pain states.

OBJECTIVE: This is a report of a trial of the new antiepileptic agent gabapentin in patients with intractable neuropathic pain. DESIGN: A case series of patients with a diagnosis of neuropathic pain whose previous management was inadequate were given oral gabapentin in increasing doses and were followed for a minimum of 2 months, monitored for efficacy and side effects. SETTING: An outpatient pain management center located within a major university medical center. PATIENTS: Convenience sample of patients referred for management of intractable neuropathic pain. INTERVENTIONS: Simplification of existing pharmacologic management, addition of gabapentin, and attempted reduction of opiate analgesic doses. MAIN OUTCOME MEASURES: Patient self-reports and pain scores in successive office visits. RESULTS: Gabapentin provides analgesic activity for patients with neuropathic pain and has the advantage of a low side effect profile and drug toxicity.

Acetates↗
PubMed1995

Some reflections on establishing a community legislation on mycotoxins.

A Community legislation on mycotoxins is essential to protect public health and to avoid trade barriers and competition distortions. Maximum permitted levels in food are to be fixed. Some orientations for this purpose are indicated. The verification of the compliance with maximum permitted levels shall need suitable analytical methods. Up to now, such methods were fixed by directives. This approach, however, had some disadvantages. A more flexible approach is to be planned. Among the mycotoxins to be taken into consideration, priority should be granted to the aflatoxins and to ochratoxin A. Fumonisins also deserve interest. Other mycotoxins will be taken into consideration as the need arises and scientific data are available. Some basic remarks on the rationale for establishing maximum permitted levels in food are made.

Food Analysis↗