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C Strunk

Publications and source records attributed to C Strunk.

At least 19 recordsLinked to original sources
PubMed2004

Spontaneous supercurrent induced by ferromagnetic pi junctions.

We present magnetization measurements of mesoscopic superconducting niobium loops containing a ferromagnetic (PdNi) pi junction. The loops are prepared on top of the active area of a micro-Hall sensor based on high mobility GaAs/AlGaAs heterostructures. We observe asymmetric switching of the loop between different magnetization states when reversing the sweep direction of the magnetic field. This provides evidence for a spontaneous current induced by the intrinsic phase shift of the pi junction. In addition, the presence of the spontaneous current near zero applied field is directly revealed by an increase of the magnetic moment with decreasing temperature, which results in half integer flux quantization in the loop at low temperatures.

Journal Article↗
PubMed2001

Shot noise by quantum scattering in chaotic cavities.

We have experimentally studied shot noise of chaotic cavities defined by two quantum point contacts in series. The cavity noise is determined as (1/4)2e/I/ in agreement with theory and can be well distinguished from other contributions to noise generated at the contacts. Subsequently, we have found that cavity noise decreases if one of the contacts is further opened and reaches nearly zero for a highly asymmetric cavity. Heating inside the cavity due to electron-electron interaction can slightly enhance the noise of large cavities and is also discussed quantitatively.

Journal Article↗
PubMed1999

The fermionic hanbury brown and twiss experiment

A Hanbury Brown and Twiss experiment for a beam of electrons has been realized in a two-dimensional electron gas in the quantum Hall regime. A metallic split gate serves as a tunable beam splitter to partition the incident beam into transmitted and reflected partial beams. In the nonequilibrium case the fluctuations in the partial beams are shown to be fully anticorrelated, demonstrating that fermions exclude each other. In equilibrium, the cross-correlation of current fluctuations at two different contacts is also found to be negative and nonzero, provided that a direct transmission exists between the contacts.

Journal Article↗
PubMed1992

Molecular genetics of the extracellular lipase of Pseudomonas aeruginosa PAO1.

The structural gene (lipA) coding for the extracellular lipase of Pseudomonas aeruginosa PAO1 has been cloned on plasmid pSW118. Nucleotide sequence analysis revealed a gene of 936 bp. lipA codes for a proenzyme of 311 amino acids including a leader sequence of 26 amino acids. The mature protein was predicted to have a M(r) of 30134, an isoelectric point of 5.6, and a consensus sequence (IGHSHGG) typical of lipases. Furthermore it is highly homologous (greater than 60%) to other lipases from various pseudomonads. The lipA gene failed to hybridize detectably with genomic DNA from other Pseudomonas species except P. alcaligenes, even under relaxed stringency. Located 220 bp downstream of the lipA gene, is an open reading frame (ORF2, lipH) which encodes a hydrophilic protein (283 amino acids; M(r) 33587) that shows some homology to the limA gene product of P. cepacia. In complementation tests of lipase-defective mutants, lipH was shown to be necessary for expression of active extracellular lipase in P. aeruginosa PAO1.

Amino Acid Sequence↗
PubMed1989

[Psychosocial aspects of bilateral subcutaneous reduction mastectomy in breast cancer].

The authors administered a questionnaire to 56 women with breast cancer who had bilateral subcutaneous mastectomies after Stroembeck/Beller since 1985. In this study, psychological aspects were investigated. There was no change in social behavior; isolation was not noticed. The negative effects on the body image were well accepted and discussed with relatives and friends. Psychological or emotional suffering was rare compared to patients with simple mastectomy. No change in sexual behavior was reported. The sexual function of the mamillae was significantly reduced. Although some cosmetic deformities were obvious, most patients would again choose the subcutaneous reduction mastectomy as operation of choice.

Adaptation, Psychological↗
PubMed1986

Proenkephalin-A gene regulation in the rat striatum: influence of lithium and haloperidol.

This report explores the influence of lithium and haloperidol on (Met5)-enkephalin (ME) biosynthesis in the rat striatum. Male Fischer 344 rats were treated intraperitoneally with lithium chloride (4 mEq/kg/day) for 2, 4, or 6 days and sacrificed 24 hr after the last dose; in addition, the effect of lithium at 2 and 24 hr after a single dose was studied. Serum levels increased in a time-related manner on repeated administration of lithium. Lithium increased the striatal ME content (native ME) in a time-dependent fashion, reaching 160% of control following six doses; no changes in ME were observed in hypothalamus and hippocampus. ME levels recovered to control values 8 days after cessation of a 4-day course of repeated administration (4 mEq/kg/day) of lithium. In an attempt to characterize the nature of this selective increase of ME content in the striatum, the precursor content (cryptic ME) as well as the preproenkephalin mRNA abundance was determined. Lithium increased the precursor content in a time-dependent fashion and this pattern closely paralleled the increase in native ME content. The preproenkephalin mRNA abundance with respect to control was quantitated by blot-hybridization of total RNA with a 32P-labeled cDNA probe derived from rat brain. Lithium increased the mRNA abundance following repeated doses for 4 or 6 days. Concurrent administration of an opiate antagonist, naltrexone (5 mg/kg/day), for 4 days did not influence the changes induced by lithium. On repeated administration (1 mg/kg/day) for 4 days, the neuroleptic, haloperidol, increased the biosynthesis of ME which was more marked than that of lithium administered for the same period; the combination of a haloperidol and lithium regimen did not lead to an additive of synergistic effect. The results indicate that, like haloperidol, repeated injections of lithium increase the biosynthesis of ME in the basal ganglia by increasing the preproenkephalin mRNA abundance and translation process.

Animals↗
PubMed1984

Substructural study of sporogenesis in Streptomyces griseus.

A Streptomyces griseus strain deficient in the formation of aerial mycelium and arthrospore development (Amy-) was studied by electron microscopy and compared with the sporulating parental strain (Amy+). The investigations were performed with colonies grown on solid medium. The substructural characteristics of the essential events of sporogenesis could clearly been demonstrated in the aerial mycelium of the Amy+ colonies. The mycelium of the surface region of the Amy- colonies showed altered features. The most pronounced alteration was the absence of the surface sheath, normally present on the aerial hyphae of the parental strain. The cross wall type II, characteristic of sporogeneous hyphae, was not discernible in the Amy- hyphae. Some substructural features resembling the essential events of normal sporogenesis were evident in the Amy- strain, albeit diminished and interfered with by abnormalities. The resulting propagative cells were of different size and feature.

Cell Wall↗
PubMed1978

Sporogenesis in Streptomyces melanochromogenes.

The mode of spore differentiation in a strain of Streptomyces melanochromogenes was followed by analysis of ultrathin sections of sporulating aerial hyphae at various stages of sporogenesis. A special accent was laid on the formation of the sporulation septum and its alterations in the course of spore delimitation and separation. Distinct differences in formation and substructure have been observed between the cross walls of vegetative hyphae and the sporulation septa. Cross walls of vegetative hyphae are formed in a way typical for Gram-positive bacteria by a centripetal annular ingrowth of cytoplasmic membrane, on which wall material immediately is deposited. The development of the sporulation septa is characterized by the accumulation of amorphous material in addition to the newly synthesized wall layer inside the invaginating cytoplasmic membrane. This amorphous septal material will later be decomposed presumably by two lytic systems which cause the separation of the spores. The central region of the finished sporulation septum is perforated by microplasmodesmata. Spores are released by a break down of the surface sheath. The complete spores are enveloped by a two-layered cell wall and the spiny surface sheath.

Cell Wall↗
PubMed1977

[Effect of Cu++ ions on the morphological, cytological, and physiological state of Candida utilis cells in continuous culture].

Cells of Candida utilis grown in continuous culture under the influence of rather high concentrations of copper ions have been studied biochemically, morphologically, and cytologically. Although under these conditions a new steady state has been adjusted, the population is much more differentiated than under control conditions. With regard to their size, structure, and viability the cells have been arranged into 4 groups. Generally, the "copper cells" in comparison with the "normal cells" are more voluminous (average: 2.5 times; maximum: 4 times) and of altered structure. The appearance of dense particles ("copper containing particles"), globules ("lipid globules"), vacuoles, and the thickening of the cell wall, as well as the disappearance of the mitochondrial cristae have been shown as characteristic indications for damage in the cell substructure caused by the influence of copper ions. Occasionally abnormal cell shapes can be observed. A permanent influence of copper ions in the concentration used was followed also by striking disturbances of the cell metabolism. The cells take up more carbon, phosphorus, and nitrogen, whereas protein synthesis and respiratory activity decrease. Both the synthesis of lipids and polysaccharides and the phosphohydrolase activity increase. A discussion of the experimental data is presented.

Candida↗
PubMed1977

[Comparative morphological studies of yeast cells using automated image analysis].

The ultrastructural alterations in cells of Candida utilis caused by the influence of copper ions have been studied by means of quantitative image analysis. A model has been proposed which presents the following informations: The main effect of the copper ions is represented by an increase of the volume of the whole cell and of that part of the cell which consists of nucleus, vacuoles, and inclusions (particles and globules). Nevertheless, neither the absolute volume of mitochondria, nor the density of mitochondria are influenced by high concentrations of copper ions in the culture medium.

Candida↗