Search Results - (Author, Cooperation:M. Fell)

2011-11-01

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Alu Elements/genetics ; Base Sequence/genetics ; Brain/*metabolism ; Caudate Nucleus/metabolism ; Clonal Evolution/genetics ; DNA Copy Number Variations/genetics ; Epistasis, Genetic ; Genome, Human/genetics ; Germ-Line Mutation/*genetics ; Hippocampus/metabolism ; Histone Deacetylase 1/genetics ; Humans ; Mosaicism ; Mutagenesis, Insertional/*genetics ; Nerve Tissue Proteins/genetics ; Organ Specificity/genetics ; Polymerase Chain Reaction ; Retroelements/*genetics ; Transcription Factors/genetics

1089-7674

AIP Digital Archive

Physics

Supersonic fluid flow and the interaction of strong shock waves to produce jets of material are ubiquitous features of inertial confinement fusion (ICF), astrophysics, and other fields of high energy-density science. The availability of large laser systems provides an opportunity to investigate such hydrodynamic systems in the laboratory, and to test their modeling by radiation hydrocodes. We describe experiments to investigate the propagation of a structured shock front within a radiation-driven target assembly, the formation of a supersonic jet of material, and the subsequent interaction of this jet with an ambient medium in which a second, ablatively driven shock wave is propagating. The density distribution within the jet, the Kelvin–Helmholz roll-up at the tip of the jet, and the jet's interaction with the counterpropagating shock are investigated by x-ray backlighting. The experiments were designed and modeled using radiation hydrocodes developed by Los Alamos National Laboratory, AWE, and Lawrence Livermore National Laboratory. The same hydrocodes are being used to model a large number of other ICF and high energy-density physics experiments. Excellent agreement between the different simulations and the experimental data is obtained, but only when the full geometry of the experiment, including both laser-heated hohlraum targets (driving the jet and counter-propagating shock), is included. The experiments were carried out at the University of Rochester's Omega laser [J. M. Soures et al., Phys. Plasmas 3, 2108 (1996)]. © 2002 American Institute of Physics.

Electronic Resource

1471-0528

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Electronic Resource

1471-0528

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Electronic Resource

1433-044X

Key words Rigid fixation • Flexible fixation • Dynamic multidirectional experimental arrangement simulating gait conditions ; Schlüsselwörter Rigide Fixation • Flexible Fixation • Symphysenruptur • Multidirektionaler dynamischer Gangbedingungssimulator

Springer Online Journal Archives 1860-2000

Medicine

Zusammenfassung Zur Stabilisierung rupturierter Symphysen wurden „rigide“ Fixationen (Plattenosteosynthesen) und flexible Fixationen (Drahtzuggurtungen, PDS-Bandings) angewandt. Für beide Verfahren waren experimentell bisher nur statische unidirektionale Zugbelastungsprüfungen durchgeführt worden. Ecke und Hofmann kamen so zu dem Ergebnis, daß mit flexiblen Fixationen gegenüber rigiden Verfahren eine vergleichbare Stabilität zu erzielen sei und diese wegen der Erhaltung der Beweglichkeit in der Symphyse zur Prophylaxe deren Ankylosierung zu präferieren sei. Durch simultan-multidirektionale dynamische experimentelle Untersuchung unter Gangsimulationsbedingungen wurden Symphysenstabilisierungen mittels DC-Platten, Rekonstruktionsplatten, Drahtzuggurtungen und PDS-Bandings vergleichend getestet. Die Symphysenpräparate wurden in Sagittal- und Vertikalrichtung synchron mit einer Frequenz von 1,5 Hz über 55 500 Lastwechsel (Schritte während 6 Wochen Mobilisation) belastet. Die Belastung erfolgte mit der Hälfte der in einer früheren Untersuchung für den Gang ermittelten mittleren Kräfte, nachdem sich bei einer Vollbelastung keine Fixationsmethode als ausreichend stabil erwies. Weder die Drahtzuggurtung, noch das PDS-Banding waren ausreichend stabil, wobei diese Verfahren bereits unmittelbar nach Versuchsbeginn eine über die physiologischen Grenzen reichende Symphysenmobilität zuließen. Im weiteren Versuchsverlauf verstärkte sich die Instabilität durch Einschneiden der Cerclagen und Bandings in den Knochen oder Bruch der Drahtcerclagen generell bis zum völligen Versagen. Bei den DC-Platten- und Rekonstruktionsplattenstabilisierungen dagegen war der Stabilisierungserfolg abhängig von der primären Stabilität der Schraubenverankerung. Bei primärer Überdrehneigung der Schrauben wurde die Plattenstabilisierung unter dynamischer Belastung immer instabiler. Bei primär stabiler Verankerung der Plattenschrauben blieb die Fixation in vollem Umfang über 55 500 Lastwechsel mit einer Belastung entsprechend dem durchschnittlich halben Körpergewicht stabil. Für die klinische Anwendung läßt sich aus diesen Ergebnissen ableiten, daß weder die Überbrückungszuggurtung mit Drahtcerclagen, noch das PDS-Banding die rupturierte Symphyse ausreichend für eine frühzeitige postoperative Mobilisierung unter Teilbelastung stabilisieren. Kann mit der DC-Platte oder der Rekonstruktionsplatte primär eine sichere Stabilisierung der rupturierten Symphyse durch gute Verankerung der Schrauben im nicht osteoporotischen Knochen erreicht werden, kann der Verletzte mit „Open-book-Verletzung“ mit Teilbelastung entsprechend dem halben Körpergewicht mobilisiert werden.

Summary For the stabilization of the ruptured pubic symphysis, rigid forms of fixation such as plate osteosynthesis and flexible fixations such as wire loops or PDS banding have been recommended. All methods have only been tested by static unidirectional loading until failure of the system. By this experimental arrangement Ecke and Hofmann found comparable results for flexible and rigid methods of internal stabilization of the pubic symphysis. They preferred flexible methods to maintain mobility of the symphysis and to prevent symphyseal fusion. We tested dynamic compression plate osteosynthesis, reconstruction plate osteosynthesis, wire loops and PDS banding for internal fixation of injured pubic symphysis in a dynamic multidirectional experimental arrangement simulating gait conditions. The specimens were loaded with 85 N in vertical (y -) direction and 34 N in sagittal (z -) direction, which represent 50 % of the forces acting at the pubic symphysis during walking and with a frequency of 1.5 Hz over 55 500 loads simulating the conditions over a 6-week mobilization period. Loading with 100 % of the acting forces (corresponding to full weight bearing mobilization) led to early failure of the system. Our experimental analysis showed that neither wire loops nor PDS banding is able to stabilize the ruptured pubic symphysis, even immediately after fixation before loading. During the tests instability increased until failure of the system due to cutting of the bone or breaking of the wires or PDS banding. Success of plate osteosynthesis was dependent on the initial stability of the fixation. Overwinding of the screws, as in osteoporotic bone, lead to increasing loosening during repeated loading, whereas primary stable fixation of the screws was almost completely maintained during the test. In consequence, neither wire loops nor PDS banding should be used for stabilization of injured pubic symphysis if early mobilization with partial weight bearing is desired. Plate osteosynthesis (DC or reconstruction plate) tolerates early half weight bearing in patients with „open-book“ injury only if safe screw fixation is guaranteed.

Electronic Resource

1432-1459

HIV infection ; Spinal cord ; Peripheral nerve ; Neurophysiology

Springer Online Journal Archives 1860-2000

Medicine

Abstract As part of the Medical Research Council prospective study of the neurological complications of HIV infection, neurophysiological tests of spinal cord and peripheral nerve function were recorded in a cohort of homosexual or bisexual men. The studies included motor and sensory nerve conduction studies, vibration perception thresholds, somatosensory evoked potentials and motor evoked potentials elicited by magnetic stimulation. The results were compared with markers of immune function. The findings from 114 volunteers were analysed in a cross-sectional study. Fifty-nine were HIV-seropositive but asymptomatic, 26 had progressed to the symptomatic stages of HIV disease and 29 were persistently HIV-seronegative. There was some evidence of a mild sensory axonopathy in the symptomatic HIV-seropositive group. No differences were detected between the asymptomatic HIV-seropositive group and the HIV-seronegative comparison group. There were no consistently significant correlations between the neurophysiological measurements and CD4 counts and β2-microglobulin levels. On repeated testing, there was no evidence of a trend towards deterioration over a mean period of approximately 3 years in 36 HIV-seropositive subjects who remained asymptomatic compared with 22 HIV-seronegatives. These findings have failed to demonstrate neurophysiological evidence of spinal cord or peripheral nerve dysfunction in the asymptomatic stages of HIV infection.

Electronic Resource

0018-019X

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

1. Dans le système quinaire Ca++—NH4+—H+—NO3-—PO4---—H2O, nous avons étudié, pour la température de 25°, le domaine des solutions simultanément satiées de phosphate monocalcique et de phosphate bicalcique.

4 Ill.

Electronic Resource