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Biomedical subjects

W Kleemann

Publications and source records attributed to W Kleemann.

At least 19 recordsLinked to original sources
PubMed2002

Domain wall relaxation, creep, sliding, and switching in superferromagnetic discontinuous Co(80)Fe(20)/Al(2)O3 multilayers.

The ac susceptibility of a superferromagnetic discontinuous multilayer [Co(80)Fe20(1.4 nm)/Al(2)O3(3 nm)](10) is measured as a function of temperature, frequency, and field amplitude and compared to static and dynamic hysteresis loops. Its properties are successfully mapped onto the predicted [T. Nattermann, V. Pokrovsky, and V. M. Vinokur, Phys. Rev. Lett. 87, 197005 (2001)]] dynamical phase transitions, which link the relaxation, creep, sliding, and switching regimes of pinned domain walls.

Journal Article↗
PubMed2002

Polarization-based adjustable memory behavior in relaxor ferroelectrics.

The irreversible decay of the spontaneous polarization above the phase-transition temperature is a limiting factor in any application of ferroelectric crystals. Here we show that electric fields applied at high temperatures induce a preferred direction in the crystal which is stable even after repeated heating and cooling through the phase transition. This preference in direction leads to a reorientation of domains in the ferroelectric phase. We use pyroelectric measurements to show that the directional preference originates from internal charge carriers interacting with domain walls.

Journal Article↗
PubMed2001

Dynamic light scattering at domains and nanoclusters in a relaxor ferroelectric.

In the probably first successful photon correlation spectroscopy experiment on a crystalline solid, inelastic light scattering of vibrating random-field-pinned domain walls has been observed at subkilohertz frequencies in the uniaxial relaxor ferroelectric Sr(0.61--x)CexBa(0.39)Nb(2)O(6). In the paraelectric relaxor phase the response of polar nanoclusters becomes overdamped and Rayleigh-like.

Journal Article↗
PubMed1996

Bordetella pertussis infections and sudden unexpected deaths in children.

UNLABELLED: From December 1990 to November 1993 nasopharyngeal specimens were obtained for culture from 50 children (mean 4.9 +/- 3.3 months of age) who had died suddenly. Bordetella pertussis was not isolated. Subsequently, nasopharyngeal specimens for polymerase chain reaction (PCR) analysis were obtained from another 51 victims of sudden death (mean 5.4 +/- 4.4 months of age); nine (18%) were B. pertussis positive. CONCLUSION: Our findings support previous epidemiological studies which noted an association between epidemic pertussis and sudden infant death syndrome. Further PCR studies with both internal and external controls should be performed.

Cell Culture Techniques↗
PubMed1994

Does the reamer type influence the degree of lung dysfunction after femoral nailing following severe trauma? An animal study.

In multiple trauma patients with lung contusion, pulmonary complications have been reported that were attributed to intramedullary stabilization of the femur. The reaming procedure of the medullary canal is thought to play a major role. We investigated whether different types of reamers might exert different amounts of fat mobilization into the vascular system and different degrees of pulmonary dysfunction. Adult female Merino sheep were submitted to hemorrhagic shock (2 h, 50 mm Hg) and a unilateral lung contusion; in addition, a lung lymph fistula was created. Pulmonary capillary permeability, central venous triglyceride levels, 11-dehydro-thromboxane B2 (dh-TXB2) levels, and pulmonary artery pressure were determined. After recovery, animals were randomly assigned to intramedullary femoral nailing using several types of reamers: group A, AO reamer (n = 8); group B, Biomet reamer (n = 7); group H, Howmedica reamer (n = 6); group C, controls, no reaming (n = 4). Intramedullary reaming caused a significant (p < 0.05) increase in pulmonary artery pressure in groups A and B; dh-TXB2 levels increased in all groups. Statistically significant (p < 0.05) pulmonary capillary permeability damage was measured in group A only. Intramedullary femoral nailing can cause transient pulmonary hemodynamic and mediator effects as well as increased pulmonary capillary permeability. In the present study, this effect was evident in group A reamer systems only, which may be due to reamer construction.

Animals↗
PubMed1994

Posttraumatic multiple organ failure--a report on clinical and autopsy findings.

In a retrospective analysis, clinical data and histological specimens were obtained from patients (n = 59) who died of severe injury. Three groups with comparable injury severity were differentiated according to the time of death. In group A (death, within 24 h) (n = 15) despite multiple injuries, patients almost always died from brain injury. Pulmonary failure was the leading cause of death in group B (death, days 2-7) (n = 16). The majority of group C patients (death, > 7 days) (n = 28) died of multiple organ failure. Organ weights at autopsy were all pathologically high but did not show an association with the amount of intravenous volume infused during intensive care. Organ histology revealed signs of interstitial edema and infiltration of polymorphonuclear leukocytes in group B patients especially in the lung, and in all groups to a lower degree in liver and kidney. The distribution of interstitial edema and cell necrosis appeared to be organ-specific. Our data confirm the presence of a generalized inflammatory reaction in patients with severe trauma. The pattern of organ failure, in addition to known pathogenetic changes (mediators, endotoxemia, etc.), appears to be influenced by organ structure and perfusion.

Adult↗