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Biomedical subjects

E Rotenberg

Publications and source records attributed to E Rotenberg.

At least 19 recordsLinked to original sources
PubMed2002

Differential photoelectron holography: a new approach for three-dimensional atomic imaging.

We propose differential holography as a method to overcome the long-standing forward-scattering problem in photoelectron holography and related techniques for the three-dimensional imaging of atoms. Atomic images reconstructed from experimental and theoretical Cu 3p holograms from Cu(001) demonstrate that this method suppresses strong forward-scattering effects so as to yield more accurate three-dimensional images of side- and backscattering atoms.

Journal Article↗
PubMed2001

High-temperature symmetry breaking in the electronic band structure of the quasi-one-dimensional solid NbSe3.

The electronic band structure of the Peierls compound NbSe3 has been explored for its symmetries with microspot synchrotron photoemission. The Fermi level crossings and deviations from one-dimensional behavior are identified. Density-functional calculations of the Fermi surfaces confirm the nesting conditions relevant for the two phase transitions. The instability along the chains with superstructure periodicity q = 0.44 A(-1) induces a backfolding of the electronic bands, and the Fermi level crossings appear suppressed. This broken symmetry is observed in the fluctuation regime at more than twice the critical temperature, where the correlation length is strongly reduced.

Journal Article↗
PubMed2000

Quasicrystalline valence bands in decagonal AlNiCo

Quasicrystals are metallic alloys that possess perfect long-range structural order, in spite of the fact that their rotational symmetries are incompatible with long-range periodicity. The exotic structural properties of this class of materials are accompanied by physical properties that are unexpected for metallic alloys. Considerable progress in resolving the geometric structures of quasicrystals has been made using X-ray and neutron diffraction, and concepts such as the quasi-unit-cell model have provided theoretical insights. But the basic properties of the valence electronic states--whether they are extended as in periodic crystals or localized as in amorphous materials--are still largely unresolved. Here we investigate the electronic bandstructure of quasicrystals through angle-resolved photoemission experiments on decagonal Al71.8Ni14.8Co13.4. We find that the s-p and d states exhibit band-like behaviour with the symmetry of the quasiperiodic lattice, and that the Fermi level is crossed by dispersing d-bands. The observation of free-electron-like bands, distributed in momentum space according to the surface diffraction pattern, suggests that the electronic states are not dominated by localization.

Journal Article↗
PubMed2000

Coupling between adsorbate vibrations and an electronic surface state

We report direct angle-resolved photoemission measurements of the coupling between the symmetric stretch vibrational mode of adsorbed hydrogen and a surface band on W(110). This coupling is manifested by the surface band being split into two branches at a binding energy comparable to the vibrational mode energy, as confirmed by observation of a dramatic hydrogen/deuterium isotope effect. The electron-phonon coupling parameter lambda is found to be significantly larger than that for bulk W, and to be closely related to the degree of surface localization of the surface state wave function.

Journal Article↗
PubMed2000

Photoelectron diffraction imaging for C2H2 and C2H4 chemisorbed on Si(100) reveals a new bonding configuration

A new adsorption site for adsorbed acetylene on Si(100) is observed by photoelectron imaging based on the holographic principle. The diffraction effects in the carbon 1s angle-resolved photoemission are inverted (including the small-cone method) to obtain an image of the atom's neighboring carbon. The chemisorbed acetylene molecule is bonded to four silicon surface atoms. In contrast to the C2H2 case, the image for adsorbed C2H4 shows it bonded to two Si surface atoms.

Journal Article↗
PubMed1980

Response to frusemide in acute renal failure: dissociation of renin and diuretic responses.

Eight hypertensive children with acute post-streptococcal glomerulonephritis were given intravenous frusemide, 2 mg/kg, and the results compared with 8 similar cases not given the diuretic. Mean urine flow increased from 0.24 ml/min/m2 before frusemide to 3.63 ml/min/m2 in the 6 hours afterwards and was still 0.72 ml/min/m2 48 hours later. In contrast mean urine flow remained unchanged over 48 hours in those not given frusemide. Despite similar initial blood pressures the duration of hypertension was much shorter (mean 4.7 days) after frusemide than in the controls (mean 11.0 days) and the edema-free weight was achieved more rapidly (6.8 days compared with 13.9 days). Plasma renin activity (PRA) did not rise after frusemide in the children with acute nephritis. This was in contrast to the rapid rise seen in normal humans thus indicating a dissociation between the diuretic and renin-releasing activities of frusemide in acute nephritis. Seven children with the hemolytic-uremic syndrome or acute tubular necrosis showed no significant change in either urine flow or PRA after frusemide. Frusemide is therefore effective treatment for both hypertension and oliguria in acute nephritis. Failure of PRA to rise indicates that renin release mechanisms are abnormal in renal failure and that PRA levels need to be interpreted with caution in this condition.

Acute Kidney Injury↗
PubMed1978

Renin release by parathyroid hormone in the dog.

Synthetic N-terminal 34 amino acid peptide of bovine parathyroid hormone (PTH) produced a consistent rise in plasma renin activity in saline-loaded dogs when given iv either as a single bolus dose of 400 U or infused steadily in lower dosage over a number of hours. Infusion of as little as 1 U/min produced a significant rise in plasma renin activity, but a greater effect was obtained with 2 U/min. Infusion of 4 U/min had no more effect than 2 U/min. In contrast to transient hypotension after rapid injection of a single large dose, blood pressure did not change significantly during the steady infusion of lower doses of PTH. These findings are compatible with the thesis that an increased distal tubular load of sodium stimulates renin release and suggest that the increased distal sodium absorption after the proximal effects of PTH may be regulated by the renin-angiotensin-aldosterone system.

Animals↗
PubMed1976

Diphosphonate therapy in nephrocalcinosis.

4 patients with nephrocalcinosis were treated with disodium ethane 1-hydroxy-1, 1-diphosphonate (EHDP) for a period of 13 months. No clinical side-effects were observed and growth proceeded normally. Radiographic changes of osteitis fibrosa cystica developed in 1 child and bone biopsy in 2 children showed defective osteoid mineralisation. It is suggested that EHDP prevented further crystal deposition in 3 children but did not prevent non-calcium stone formation in the 4th child. In view of this and the development of histological and radiographic evidence of osteomalacia and/or secondary hyperparathyroidism in these patients the value of EHDP remains dubious. On the other hand its use may be justified when rapidly increasing calcification is expected, as for example in hyperoxaluria.

Bartter Syndrome↗