Search Results - (Author, Cooperation:J. Bischoff)

2014-06-21

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; Brain/anatomy & histology ; Extinction, Biological ; *Fossils ; Genetic Drift ; Humans ; Neanderthals/*anatomy & histology/*genetics ; Organ Size ; Reproductive Isolation ; Skull/*anatomy & histology ; Spain

article

1988

Fernsehsendung ; Sekundarstufe I ; Audiovisuelles Medium ; Schulfernsehen ; Unterrichtsmaterial ; Biologie ; Waldsterben ; Ökologie ; Analyse ; Didaktische Erörterung ; Rezension

Schulpraxis, Bd. 8 (1988) H. 3, S. 57-60, 0720-8634

German

1089-7550

AIP Digital Archive

Physics

Epitaxial molecular beam epitaxy growth of nanometric Ge layers on Si (001) 2×1 has been investigated, in situ, by x-ray Si 2p photoelectron diffraction and Auger Ge LMM electron diffraction which consist essentially in preferential scattering of electrons in the direction of interatomic axes. Particular attention was paid to measuring the contrasts of this anisotropic emission in the (11¯0) plane as a function of deposition parameters. It can thus be determined how crystalline material quality and epitaxial perfection are affected by the residual pressure below 5×10−8 mbar, the substrate temperature decrease to room temperature, the deposition rate, and the Ge overlayer thickness.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

An ultrahigh vacuum compatible electron cyclotron resonance (ECR) plasma source is employed for the first time in studying the surface nitridation with N2 on Si (001)-2×1 at low substrate temperature (Ts=RT). The exposure to the efficiently activated and dissociated nitrogen flux in the microwave plasma is not limited to the silicon surface states but results in the formation of ultrathin dielectric near-stoichiometric Si3N4 layers (∼20 A(ring)) analyzed in situ by x-ray photoelectron spectroscopy (XPS). These films, without hydrogen content and silicon deposit, could easily be grown in few minutes at RT and at relatively low working pressures (∼10−4 mbar in the chamber) without destroying the underlying Si substrate as checked by x-ray photoelectron diffraction (XPD). Composition deviations to the Si3N4 stoichiometry of the grown nitride layers are also discussed in relation with the contamination oxygen content and the contribution of the interface subnitride configurations.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Hut cluster formation during Ge or Si1−xGex solid source molecular beam epitaxial growth on Si(001) is a well-known kinetic pathway for partial strain relief. It results in undulated morphologies with {105} facets allowing a(parallel) lattice parameter relaxation on the island apexes. Here, we show how subsequent Si coverages, grown at 500 °C, avoid being tensile strained and impede further increase of stored elastic strain energy. Dominant inhomogeneous Si surface diffusions take place as proven by a Ge marker technique able to provide transmission electron microscopy or high-resolution transmission electron microscopy images of the initial Si morphology stages and by reflection high-energy electron diffraction examinations. This mechanism prevails for high enough Si growth rates, able to quench lateral Ge diffusion and limit chemical strain relief. Mediated by stress variations on the noncapped island curvatures, Si is depleted from the top of the islands and accumulates in the troughs of the ripples where it accommodates mostly unstrained. By this selective Si coverage, the surface undergoes a rapid smoothing and a(parallel) recovery toward the Si bulk value. When the Ge containing islands are completely buried, their strain, dictated by the Si buffer and cap layers, ends by being mainly along the growth direction or tetragonal (Δa(parallel)=0). © 1998 American Institute of Physics.

Electronic Resource

1600-0528

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

abstract The DMFT Index, degree of fluorosis (DEGF), and enamel fluoride concentration (F) were determined in 88 children living in a high- and 79 children living in a low-fluoride area in South Africa. The following interrelationships between these parameters were found: in both areas there was a significant negative correlation between log F and age; in the high-fluoride area there was a significant positive correlation between log F and DEGF; and in the combined data from the two areas there were significant correlations between log F and area, log F and age, and log F and DEGF, and a significant association between DEGF and area. There were no significant correlations between DMFT and log F and between DMFT and DEGF.

Electronic Resource

1600-0714

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract. The caries inhibitory effect of optimally fluoridated drinking water is well documented. Communities are often exposed to naturally fluoridated water with F content exceeding the optimal level. The purpose of this study was to determine the relationship between enamel fluoride, degree of fluorosis (DEGF) and caries incidence (DMFT) in an endemic fluoride area.Eighty-five 14- to 16-year-old children (37 males and 48 females) who were born and had been living continually in the town of Kenhardt in South Africa were selected for this study. The fluoride content of the common water supply is 3.2 ppm F. The DMFT and DEGF were determined clinically. Acid etch biopsies were carried out on both maxillary central incisors of each subject. Ca and F analysis were carried out and mass enamel expressed in μg and mass F in pg. Data transformations to logc, mass F (1nF), logc mass En (1nEn) and 〈inlineGraphic alt="inline image" href="urn:x-wiley:09042512:JOP224:JOP_224_mu1" location="equation/JOP_224_mu1.gif"/〉 were made. The 1nF values were corrected to a standarized depth of 10 μm (208.6 μg enamel equivalent mass) by covariance analysis. Correlations between the parameters 〈inlineGraphic alt="inline image" href="urn:x-wiley:09042512:JOP224:JOP_224_mu1" location="equation/JOP_224_mu1.gif"/〉, 1nF and DEGF were calculated, adjusting for the sex of the individual.The correlations were as follows: 〈displayedItem type="mathematics" xml:id="mu2" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:09042512:JOP224:JOP_224_mu2"/〉 A positive association among the three parameters was established.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Phosphoric acid at different concentrations has been extensively used as an etching agent to improve bonding of dental materials to enamel surfaces. Recently attention has been drawn to the possible use of polyfunctional organic acids as conditioning agents.The object of this investigation was to determine the optimal concentration of pyruvic acid as an etching agent. A commercial composite resin with an intermediary bonding system supplied with 37% H3PO4 as an etching agent was used as the control system. In addition, a comparative study was carried out to evaluate 37% H3PO4, 20% lactic acid and the optimal concentration of pyruvic acid as conditioning solutions.Etching enamel surfaces with 10% pyruvic acid resulted in the optimal tensile bond strength of the resin to etched enamel surfaces. The use of 10% pyruvic acid did not adversely affect the bond strength of the resin system when compared to enamel surfaces etched with 37% H3PO4 for the same time period. Significantly lower tensile bond strengths were recorded on enamel surfaces etched with 20% lactic acid. The rate and depth of etching obtained with 37% H3PO4 can be considerably reduced by using 10% pyruvic acid as the conditioning agent.

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] Both sides in the Yuha controversy have recognized that resolution of the controversy would require radiocarbon analysis of the bone itself, but this was initially delayed because conventional 14C methods would have required destruction of much of the skeleton5. Subsequently, the theft of the major ...

Electronic Resource

0006-291X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource

0012-821X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Geosciences

Physics

Electronic Resource

0012-821X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Geosciences

Physics

Electronic Resource

0006-291X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource

0006-291X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource

0002-1482

History

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] The Mousterian industries were succeeded by Upper Paleo-lithic industries, the handiwork of anatomically modern people, between 35 and 40 kyr BP. This time range is at the very fringe of 14C dating where the dates are particularly prone to error. Therefore, 14C dates of the upper boundary of the ...

Electronic Resource

1432-1238

Key words Heat shock protein 70 ; Peripheral blood mononuclear cells ; HSP70 enzyme-linked immunosorbent assay ; Lipopolysaccharide ; Severe sepsis ; Stress protein

Springer Online Journal Archives 1860-2000

Medicine

Abstract Objective: To investigate the ex vivo endotoxin-inducible heat shock protein 70 (HSP70) expression in the peripheral blood mononuclear cells (PBMC) of patients with severe sepsis in order to assess the capacity of this potentially protective response during systemic inflammation. Design: Prospective observational study in consecutive patients with severe sepsis and healthy blood donors. Setting: Surgical intensive care unit in a university hospital. Patients and participants: Eleven patients with the diagnosis of severe sepsis, one patient who had recovered from severe sepsis and 13 healthy blood donors. Interventions: None. Measurements and results: We studied the inducibility of HSP70 expression in the PBMC of patients with severe sepsis and healthy blood donors ex vivo. Human whole blood was incubated with variable lipopolysaccharide (LPS from Salmonella minnesota Re 595) concentrations (0; 0.1; 10; 100 ng/ml) for different periods of time (0.5; 2; 4; 10 h). The PBMC were separated by Ficoll density gradient and then disrupted by hypotonic lysis. HSP70 was measured by means of enzyme-linked immunosorbent assay (ELISA). We found a LPS dose- and time-dependent inhibition of ex vivo HSP70 expression in the PBMC of both patients with severe sepsis and healthy individuals. However, the levels of HSP70 expression in patients were significantly lower compared to those of healthy individuals at all LPS concentrations and incubation times. On average, HSP70 expression in the PBMC of healthy controls was 2.8 (range 1.2–3.9) times higher than in patients. HSP70 expression was inducible by thermal heat shock in the PBMC of both patients and healthy individuals. Conclusions: Endotoxin inhibits HSP70 expression in PBMC ex vivo. In vivo, the suppression of HSP70 expression induced by endotoxin and high levels of proinflammatory cytokines may contribute to the cellular dysfunction of immunocompetent cells concerning antigen presentation, phagocytosis and antibody production associated with decreased resistance to infectious insults during severe sepsis.

Electronic Resource

1432-0738

Ethanol ; Cadmium ; Liver and kidney damage ; Rats

Springer Online Journal Archives 1860-2000

Medicine

Abstract To examine the combined hepatotoxic and nephrotoxic effects of cadmium and ethanol, rats maintained on an ethanol containing liquid diet (5% w/w) were given cadmium either acutely (3×1 mg/kg IP) or sub-acutely (about 14 mg/kg/day PO for 6 weeks). Parameters tested were cadmium, zinc and copper contents of blood and various organs, metallothionein (MT) contents, polysome profile of liver and kidneys, serum SDH and GPT levels and creatinine clearance. Ethanol reduced the hepatic MT contents without altering the polysome profile and the zinc and copper contents. Cadmium on the other hand raised the MT contents in liver and kidneys. This effect of cadmium predominated in the combined treatment. Morphological examination and functional tests (SDH, GPT, creatinine clearance) indicate that cadmium does not enhance the toxic effects of ethanol, and vice versa.

Electronic Resource

1573-482X

Springer Online Journal Archives 1860-2000

Electrical Engineering, Measurement and Control Technology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract PtSi/p-strained-Si1-xGex (x=0.19 and x=0.29) Schottky barrier diodes have been fabricated and characterized for the determination of barrier height, ideality factor and the interface state density distribution with energy. Diodes having an epitaxial layer thickness of 20 and 52 nm were modeled with emphasis on comparison with experiment. To achieve better agreement with experimental data, an interfacial layer and associated series resistance were included in the model. The capacitance–voltage (C–V) technique has been used for the determination of the energy distribution of interface state density. The interface state density distribution for the Si0.81Ge0.19 and Si0.71Ge0.29 diodes is found to decrease with increasing energy from the valence band edge.

Electronic Resource

1432-1831

Springer Online Journal Archives 1860-2000

Medicine

Zusammenfassung Beschreibung der biochemischen und serologischen Eigenschaften eines neuen, aus Fischmehl erstmals isolierten Salmonellatyps (S. altona) =(8),20:r(i):z6.

Electronic Resource