Biomedical subjects

A Prinz

Publications and source records attributed to A Prinz.

At least 19 recordsLinked to original sources

PubMed2002

Low-density spin susceptibility and effective mass of mobile electrons in Si inversion layers.

We studied the Shubnikov-de Haas (SdH) oscillations in high-mobility Si-MOS samples over a wide range of carrier densities n approximately (1-50)x10(11) cm(-2), which includes the vicinity of the apparent metal-insulator transition in two dimensions (2D MIT). Using a novel technique of measuring the SdH oscillations in superimposed and independently controlled parallel and perpendicular magnetic fields, we determined the spin susceptibility chi(*), the effective mass m(*), and the g(*) factor for mobile electrons. These quantities increase gradually with decreasing density; near the 2D MIT, we observed enhancement of chi(*) by a factor of approximately 4.7.

Journal Article↗

PubMed2002

Weak anisotropy and disorder dependence of the in-plane magnetoresistance in high-mobility (100) Si-inversion layers.

We report studies of the magnetoresistance (MR) in a two-dimensional electron system in (100) Si-inversion layers, for perpendicular and parallel orientations of the current with respect to the magnetic field in the 2D plane. The magnetoresistance is almost isotropic; this result does not support the suggestion of its orbital origin. In the hopping regime, however, the MR contains a weak anisotropic component that is nonmonotonic in the magnetic field. We found that the field, at which the MR saturates, varies for different samples by a factor of 2 at a given carrier density. Therefore, the saturation of the MR cannot be identified with the complete spin polarization of free carriers.

Journal Article↗

PubMed2002

Traveller's thrombosis 2001.

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Aircraft↗

PubMed2002

[Current aviation medicine].

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Aerospace Medicine↗

PubMed2001

Exclusion of quantum coherence as the origin of the 2D metallic state in high-mobility silicon inversion layers.

The temperature and density dependence of the phase coherence time tau(phi) in high-mobility silicon inversion layers was determined from the magnetoresistivity due to weak localization. The upper temperature limit for single-electron quantum interference effects was delineated by comparing tau(phi) with the momentum relaxation time tau. A comparison between the density dependence of the borders for quantum interference effects and the strong resistivity drop reveals that these effects are not related to each other. As the strong resistivity drop occurs in the Drude regime, the apparent metallic behavior cannot be caused by quantum coherent effects.

Journal Article↗

PubMed2001

CD4(+) T cell frequencies and Th1/Th2 cytokine patterns expressed in the acute and memory response to respiratory syncytial virus I-E(d)-restricted peptides.

The respiratory syncytial virus (RSV)-specific frequencies and cytokine expression patterns of acute and memory CD4(+) T cells from RSV strain-A- and strain-B-infected BALB/c mice were determined following restimulation with a panel of 14 predicted RSV I-E(d) peptides from NSP-2, M, SH, F, and L proteins. Ten of fourteen peptides stimulated intracellular Th1 and/or Th2 cytokines in CD4(+) T cells from the mediastinal lymph nodes (MLN) and spleens of RSV strain-A- or strain-B-immune BALB/c mice. Spleen cells exhibited a predominant Th2 cytokine expression pattern after peptide stimulation, whereas MLN cells exhibited a mixed Th1/Th2 cytokine pattern. For a few peptides, there were differences in the Th1/Th2 cytokine response to peptides from the homologous versus heterologous RSV group. None of the 10 peptides induced both Th1 and Th2 cytokines in cells from similarly immunized mice. The frequency and breadth of cytokine expression by I-E(d)-restricted CD4(+) T cells to peptide stimulation was diminished in the memory response.

Animals↗

PubMed2000

Evolutionarily conserved binding of ribosomes to the translocation channel via the large ribosomal RNA.

During early stages of cotranslational protein translocation across the endoplasmic reticulum (ER) membrane the ribosome is targeted to the heterotrimeric Sec61p complex, the major component of the protein-conducting channel. We demonstrate that this interaction is mediated by the 28S rRNA of the eukaryotic large ribosomal subunit. Bacterial ribosomes also bind via their 23S rRNA to the bacterial homolog of the Sec61p complex, the SecYEG complex. Eukaryotic ribosomes bind to the SecYEG complex, and prokaryotic ribosomes to the Sec61p complex. These data indicate that rRNA-mediated interaction of ribosomes with the translocation channel occurred early in evolution and has been conserved.

Animals↗

PubMed1999

Plant diversity and productivity experiments in european grasslands

At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location. Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.

Journal Article↗

PubMed1998

Acquired atrial septal defect as a complication of endocarditis--a case report.

Bacterial endocarditis predominantly involves cardiac valves and is associated with many potential complications. Valvular dysfunction resulting from disruption of the structural integrity of valves are not infrequent. This report illustrates a rare case of endocarditis involving the interatrial septum which subsequently produced destruction of the structure resulting in an acquired atrial septal defect.

Adult↗

PubMed1992

[Not Available].

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Brazil↗

PubMed1991

[Ethnomedicine--history of medicine. Sciences of medical thinking and behavior of man].

Ethnomedicine and the history of medicine have in common the description of medical systems, whereby the separation is geographical in the former case and historical in the latter case. As experts in both fields are not at the same time practitioners of these medical systems, they depend on source material. The interpretation of these sources is largely subordinated to the subjective personal structure of the scientist on the one hand, and is closely related to epistemiological problems, coloured by the spirit of the times, on the other hand. Above all, many medical historians even today fall victim to an unjustified cultural evolutionism, according to which ethnomedical research work in the field of "primitive medicine" may be employed to reconstruct a fictive paleopathology. The cooperation which is nowadays established between ethnomedicine and the history of medicine concerns the common structures of medical systems in their social and cultural context--so-called pattern--with the aim of establishing a theory of medical thinking and behaviour of man.

Anthropology, Cultural↗

PubMed1990

[Discovery of the cardiac effectiveness of cinchona bark and its alkaloids].

The cardiac side effects of chinchona bark were discovered very soon after its introduction to the materia medica of academic medicine towards the end of the 17th century (Georg Ernst Stahl, 1660-1734). Therapeutically these effects were utilized sporadically as early as in the first half of the 18th century (Gerhard van Swieten, 1700-1772; John Wall, 1708-1776; William Saunders, 1743-1817). Purified quinine became a standard component of cardiac therapy in the 2nd half of the 19th century (Ludwig Traube, 1818-1876; Johann Oppolzer, 1808-1871; Karel Frederik Wenckebach, 1864-1940). In 1918 quinidine was introduced by Walter Frey (1884-1972) as the common alkaloid of chinchona bark and is still used in rhythmology today.

Arrhythmias, Cardiac↗

PubMed1990

Endogenous fertility, altruistic behavior across generations, and social security systems.

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Aid to Families with Dependent Children↗

PubMed1990

Discrimination between antibodies to HIV-1 and HIV-2 in sera from northern Zaire.

136 selected sera from Northern Zaire were screened for antibodies against HIV-1 and HIV-2 using the ELISA method. Reactive sera were confirmed with commercially available Western Blots and additional tests. A data base was used for evaluation of the results. The sera were collected in the town Isiro and in remote rural areas. 36 sera were reactive in the HIV-1 ELISA (ELAVIA-1), 19 of them were confirmed in the HIV-1 Western Blot (Biorad). 21 sera were reactive in the HIV-2 ELISA, but they were not confirmed as HIV-2-specific in three HIV-2 Western Blots (Diagnostics Pasteur, Biorad, Paul-Ehrlich-Institut).

Blotting, Western↗

PubMed1990