Showing papers by "Radboud University Nijmegen published in 1988"

Electronic structure of Cu2O and CuO

Abstract: The electronic structure of copper oxides has been investigated by photoelectron (x-ray photoemission, ultraviolet photoemission), Auger electron, and bremsstrahlung isochromat spectroscopies. The experimental results are compared with one-electron band-structure calculations as well as with a cluster configuration interaction model. It is demonstrated that the results for ${\mathrm{Cu}}_{2}$O agree well with band theory, whereas those for CuO clearly show strong deviations which we argue are due to electron-correlation effects in the open-shell $d$ bands. From the comparison to cluster calculations we extract values for the $\mathrm{Cu} d\ensuremath{-}d$ and $\mathrm{O} p\ensuremath{-}p$ Coulomb interactions, the O to Cu charge transfer energy, and the degree of $\mathrm{Cu} d\ensuremath{-}\mathrm{O} 2p$ hybridization. From this we demonstrate that CuO is a charge-transfer gap insulator.

Generalized entropic uncertainty relations

Abstract: A new class of uncertainty relations is derived for pairs of observables in a finite-dimensional Hilbert space which do not have any common eigenvector. This class contains an ``entropic'' uncertainty relation which improves a previous result of Deutsch and confirms a recent conjecture by Kraus. Some comments are made on the extension of these relations to the case where the Hilbert space is infinite dimensional.

Evidence for holes on oxygen sites in the high- T c superconductors La 2 − x Sr x CuO 4 and YBa 2 Cu 3 O 7 − y

Abstract: The local oxygen density of states of p symmetry at the Fermi level of ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$${\mathrm{CuO}}_{4}$ and ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{y}}$ has been investigated as a function of x and y. Core-level excitations of oxygen 1s electrons into empty states by electron energy-loss spectroscopy has been used. Strong deviations from our calculations of the O 1s edges in the framework of a local density-functional model were observed in the superconducting and in the semiconducting compounds. They can be explained by taking into account on-site correlations of the Cu 3d electrons. The results indicate that for the superconductors, the density of states at the Fermi energy has predominantly oxygen 2p character. In this band the charge carriers in the superconducting compounds are holes. In the semiconducting compounds, the oxygen 2p band is probably completely filled.

Quality of powdered substitutes for breast milk with regard to members of the family Enterobacteriaceae.

Abstract: Members of the family Enterobacteriaceae were cultured from 52.5% of 141 milk substitute infant formulas which were obtained in 35 countries. The concentration did not exceed a level of 1 CFU/g in any product. The species which were isolated most frequently were Enterobacter agglomerans, cloacae, Enterobacter sakazakii, and Klebsiella pneumoniae. If infections due to these organisms occur, it can be useful to include a check of the hygienic precautions which are taken during the preparation and storage of the formula. Milk powders without members of the Enterobacteriaceae might offer extra protection to the newborn if some multiplication does occur in the formula.

The nuclear matrix: structure and composition.

Abstract: Introduction The pore complex-lamina The nuclear pore complexes The nuclear lamina The nucleolar residue The internal matrix Morphological and biochemical aspects Heterogeneous nuclear RNP particles Small nuclear RNP particles Nuclear actin Enzymes involved in DNA and RNA metabolism Virus-specific proteins Associated transcripts The nuclear matrix and RNA transport Behaviour of nuclear matrix components during mitosis

Differential expression of keratins in the basal and luminal compartments of rat prostatic epithelium during degeneration and regeneration.

Abstract: The role of the different epithelial compartments during degeneration and regeneration of the rat prostate is examined on basis of intermediate filament protein (IFP) expression pattern. With the monoclonal antibodies RCK 103 and RGE 53, directed against specific keratins, it was possible to differentiate between the basal (RCK 103+) and luminal (RGE 53+) cells of the prostatic epithelium. After testosterone deprivation, by orchiectomy, an extensive and rapid cell loss was observed which appeared to affect mainly the luminal cells. In the process of prostate regeneration, induced by testosterone administration, using silastic implants, the luminal compartment rapidly regained its normal thickness. A heterogeneous population of morphologically luminal cells was observed showing keratin expression patterns intermediate between basal and luminal cells. These findings support the idea of a relationship between basal and luminal cells as being members of the same lineage of differentiation.

Cadmium inhibits plasma membrane calcium transport

Abstract: The interaction of Cd2+ with the plasma membrane Ca2+-transporting ATPase of fish gills was studied. ATP-driven Ca2+-transport in basolateral membrane (BLM) vesicles was inhibited by Cd2+ with anI50 value of 3.0nm at 0.25 μm free Ca2+ using EGTA, HEEDTA and NTA to buffer Ca2+ and Cd2+ concentrations. The inhibition was competitive in nature since theK0.5 value for Ca2+ increased linearly with increasing Cd2+ concentrations while theVmax remained unchanged. The Ca2+ pump appeared to be calmodulin dependent, but we conclude that the inhibition by Cd2+ occurs directly on the Ca2+ binding site of the Ca2+-transporting ATPase and not via the Ca2+-binding sites of calmodulin. It is suggested that Cd2+-induced inhibition of Ca2+-transporting enzymes is the primary effect in the Cd2+ toxicity towards cells followed by several secondary effects due to a disturbed cellular Ca2+ metabolism. Our data illustrate that apparent stimulatory effects of low concentrations of Cd2+ on Ca2+-dependent enzymes may derive from increased free-Ca2+ levels when Cd2+ supersedes Ca2+ on the ligands.

Unreliability of Self-reported Burning Tendency and Tanning Ability

Abstract: • Burning and tanning histories were studied in 790 white students 18 to 30 years of age by means of a self-administered questionnaire. Only 325 cases (41.1%) were classifiable according to the Fitzpatrick scheme (skin types I to IV). Skin type I (always burn, never tan) was recorded only twice (0.3%). The minimal erythemal dose was measured in a subgroup of 197 students; these results showed no significant correlation with the self-reported burning tendency. In 508 students the burning-tanning histories were compared with eye and hair color, freckling tendency, and number of moles. The tanning ability showed a better correlation with skin complexion characteristics than the burning tendency. It is concluded that self-reported burning-tanning histories form an unreliable means of skin typing. (Arch Dermatol1988;124:885-888)

Calculations of magnetic x-ray dichroism in the 3d absorption spectra of rare-earth compounds

Abstract: We present atomic calculations for the recently discovered magnetic x-ray dichroism (MXD) displayed by the 3d x-ray-absorption spectra of rare-earth compounds. The spectral shapes expected at T=0 K for linear polarization parallel and normal to the local magnetic field is given, together with the temperature and field dependencies of the intensities of the spectral lines. It is concluded that strong MXD effects can be expected for all rare-earth ions except those having a ground state with either J=0 or L=0. Calculations of magnetic x-ray dichroism in the 3d absorption spectra of rare-earth compounds. - ResearchGate. Available from: http://www.researchgate.net/publication/13344010_Calculations_of_magnetic_x-ray_dichroism_in_the_3d_absorption_spectra_of_rare-earth_compounds [accessed Jun 2, 2015].

Literacy in the Information Age

Abstract: Publisher Summary This chapter focuses on the discussion about what literacy will be needed in future society and what curricular change will have to be the consequence of this need by considering the characteristics of literacy, as it has developed to this day, and by presenting, on the basis of these characteristics, an outline of some important aspects of future literacy. Information technology may well bring about a society in which literacy presupposes integrative capabilities for abstraction and construction in a reality of loosely synchronized and interacting processes perceived through data. Education has the challenging task of educating students to achieve literacy in the Information Age. To be successful, education will have to communicate complex conceptual models to the students and will have to enhance their abstraction and construction skills. This will force education to shift its attention from the data-transmission side of the communication of concepts to the personalization of information. Science education seems to be the key to literacy in the Information Age. Education in the science of informatics will have a prominent place in this education.

Adult onset Still's disease and viral infections.

Abstract: Several micro-organisms, especially viruses, have been associated with juvenile and adult onset Still's disease. In the present study a search for probable triggering viral infections in five consecutive patients with early, active adult onset Still's disease has been made. In one patient echovirus 7 was identified as a probable triggering agent. Evidence of infection with this virus was acquired by virus cultures and serological tests. In two patients the illness was probably initiated by a rubella reinfection. Both had initially high stable monospecific IgG antibody titres but no IgM antibodies to this virus. In the remaining two cases no particular triggering viral infection could be designated. Evidence of a viral infection was thus found in three of these five patients. Adult onset Still's disease may represent a reaction pattern to certain infections.

Deleterious effects of anabolic steroids on serum lipoproteins, blood pressure, and liver function in amateur body builders.

Abstract: The effects of self-administered anabolic steroids (AS) on lipoproteins, liver function, and blood pressure were studied in male amateur body builders. Twenty body builders were studied at the end of a course of AS (group 1) and 42 body builders were studied after discontinuation of the AS for a mean of 5 months (group 2). Sixteen body builders were studied after discontinuation of AS for at least 2 months and at the end of a 9-week course of AS (group 3). A group of 13 body builders who never used AS served as a control group. Both groups 1 and 2 showed higher levels of transaminas and a higher systolic blood pressure than the controls (P less than 0.05). Group 3 showed an increase of the transaminases an a slight but significant increase of systolic blood pressure (+3 mm Hg) and heart rate (+7 bts/min) after one course of AS (P less than 0.05). Group 1 showed a considerably lower high-density lipoprotein cholesterol (HDLC) (P less than 0.001), a higher low-density lipoprotein cholesterol (LDLC) (P less than 0.05), and a lower apoprotein A-l/B ratio (Apo A-l/ApoB) (P less than 0.001) than the controls and group 2. The ratio of LDLC/HDLC in group 1 was fourfold higher than in the controls (P less than 0.01). In group 3 HDLC decreased from 1.18 +/- 0.05 to 0.60 +/- 0.08 mmol/l (P less than 0.001) and LDLC increased from 3.97 +/- 0.39 to 5.74 +/- 0.71 mmol/l (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Airborne concentrations, skin contamination, and urinary metabolite excretion of polycyclic aromatic hydrocarbons among paving workers exposed to coal tar derived road tars.

Abstract: The exposure of surface dressing workers to polycyclic aromatic hydrocarbons (PAH) was studied. Four different paving sites, at which coal tar-containing binders were applied, were selected as work sites with high exposure levels of PAH. Breathing zone airborne particulates, contamination of the skin with PAH, and 1-hydroxypyrene in urine of the workers involved in chip sealing were determined. Substantial concentrations of cyclohexane-soluble airborne particulate matter were found (GM=0.2 mg/m3, n=28). Skin contamination was determined using two different methods: with exposure pads and by hand washing. Pads were mounted on several parts of the body: wrist, elbow, neck, shoulder, and ankle. The pads located on the wrist appeared to be the most contaminated (pyrene: GM=22 ng/1.77 cm2, n=40). The end-of-shift hand washing showed that the hands of the workers were contaminated with PAH (pyrene: GM=70 µg, n=35). Pireshift hand washing showed far lower, but detectable, quantities of PAH on workers'hands (pyre...

Dorsal raphe serotoninergic branching neurons projecting both to the lateral geniculate body and superior colliculus: A combined retrograde tracing–immunohistochemical study in the rat

Abstract: Injections of HRP into the superior colliculus labelled cells in the lateral cell groups of the dorsal raphe nucleus. The cytoarchitectural features and location of these cells showed remarkable similarities with those known to project to the lateral geniculate body, and, therefore, the possible existence of branching neurons in the dorsal raphe nucleus projecting to these two visual structures was tested. Injections into the lateral geniculate body and the superior colliculus of several fluorescent tracers—namely, Fast Blue, Fluoro-Gold, propidium iodide, rhodamine-B-isothiocyanate, and Diamidino Yellow, used in different combinations, showed single- and double-labelled neurons in the lateral wings of the dorsal raphe nucleus. In order to verify the chemical nature of these cells, the tissue was processed for immunofluorescence with serotonin antibodies. The results obtained showed several triple-labelled cells exhibiting two fluorescent tracers as well as 5-hydroxytryptamine-like immunoreactivity. Some immunonegative tracer-positive cells were also observed, suggesting their nonserotoninergic nature. Finally, electrolytic lesions of the lateral wings of the dorsal raphe nucleus caused a gradual disappearance of serotonin-immunoreactive fibers in these visual areas following different survival times. This correlated well with a decrease in the serotonin content studied by high-pressure liquid chromatography. These results support a role of the serotoninergic dorsal raphe projection to the lateral geniculate body and to the superior colliculus in the processing of visual information, and they suggest that serotonin may have a coordinating influence on primary visual centers.

Surface-area increase in tissue expansion.

Abstract: In this paper, the subject of surface-area gain in tissue expansion is approached from three sides. With the help of a mathematical approach, the theoretical increase in surface area was calculated in relation to the specifications of the expanders. In an in vitro model, these mathematical data were confirmed to be reliable. To determine the real surface-area gain that takes place in vivo, measurements on pigs were performed. It appears that only about 35 percent of the mathematically expected increase in surface area takes place. Moreover, a clear difference was observed between the surface-area gain for the different shapes of tissue expanders.