Laser Doppler measurements in a rotating annular flume

1993 ◽  
Author(s):  
R. Booij ◽  
Paul J. Visser ◽  
H. Melis
Keyword(s):  
Laser Doppler ◽  
Annular Flume ◽  
Rotating Annular Flume

scholarly journals Mud-clast armoring and its implications for turbidite systems

2020 ◽  
Vol 90 (7) ◽  
pp. 687-700
Author(s):  
Jamie L. Hizzett ◽  
Esther J. Sumner ◽  
Matthieu J.B. Cartigny ◽  
Michael A. Clare
Keyword(s):  
Deep Sea ◽  
Laboratory Experiments ◽  
Turbidity Current ◽  
Cohesive Sediment ◽  
Apparent Contradiction ◽  
Annular Flume ◽  
Primary Mechanism ◽  
Rotating Annular Flume ◽  
First Time ◽  
Travel Distances

ABSTRACT Seafloor sediment density flows are the primary mechanism for transporting sediment to the deep sea. These flows are important because they pose a hazard to seafloor infrastructure and deposit the largest sediment accumulations on Earth. The cohesive sediment content of a flow (i.e., clay) is an important control on its rheological state (e.g., turbulent or laminar); however, how clay becomes incorporated into a flow is poorly understood. One mechanism is by the abrasion of (clay-rich) mud clasts. Such clasts are common in deep-water deposits, often thought to have traveled over large (more than tens of kilometers) distances. These long travel distances are at odds with previous experimental work that suggests that mud clasts should disintegrate rapidly through abrasion. To address this apparent contradiction, we conduct laboratory experiments using a counter rotating annular flume to simulate clast transport in sediment density flows. We find that as clay clasts roll along a sandy floor, surficial armoring develops and reduces clast abrasion and thus enhances travel distance. For the first time we show armoring to be a process of renewal and replenishment, rather than forming a permanent layer. As armoring reduces the rate of clast abrasion, it delays the release of clay into the parent flow, which can therefore delay flow transformation from turbidity current to debris flow. We conclude that armored mud clasts can form only within a sandy turbidity current; hence where armored clasts are found in debrite deposits, the parent flow must have undergone flow transformation farther up slope.

scholarly journals Sediment Transport of Fine Sand to Fine Gravel on Transverse Bed Slopes in Rotating Annular Flume Experiments

2018 ◽  
Vol 54 (1) ◽  
pp. 19-45 ◽  
Author(s):  
Anne W. Baar ◽  
Jaco de Smit ◽  
Wim S. J. Uijttewaal ◽  
Maarten G. Kleinhans
Keyword(s):  
Sediment Transport ◽  
Fine Sand ◽  
Flume Experiments ◽  
Annular Flume ◽  
Rotating Annular Flume ◽  
Fine Gravel

Numerical modeling of flow characteristics in a rotating annular flume

2000 ◽  
Vol 31 (1-4) ◽  
pp. 271-294 ◽  
Author(s):  
Zhaoqing Yang ◽  
António Baptista ◽  
Jeffrey Darland
Keyword(s):  
Numerical Modeling ◽  
Flow Characteristics ◽  
Annular Flume ◽  
Rotating Annular Flume

Laser-Doppler measurements of concentration and velocity of moving blood cells in rat cerebral circulation

1997 ◽  
Vol 160 (1) ◽  
pp. 123-132
Author(s):  
C. BARFOD ◽  
N. AKGÖREN ◽  
M. FABRICIUS ◽  
U. DIRNAGL ◽  
M. LAURITZEN
Keyword(s):  
Blood Cells ◽  
Cerebral Circulation ◽  
Laser Doppler

The response of skin perfusion and of rheological and immunological variables to intravenous prostanoid administration in Raynaud’s phenomenon secondary to collagenosis

VASA ◽  
2005 ◽  
Vol 34 (4) ◽  
pp. 243-249 ◽  
Author(s):  
Drinda ◽  
Neumann ◽  
Pöhlmann ◽  
Vogelsang ◽  
Stein ◽  
...  
Keyword(s):  
Laser Doppler Flowmetry ◽  
Raynaud’S Phenomenon ◽  
Raynaud's Phenomenon ◽  
Plasma Viscosity ◽  
Laser Doppler ◽  
Erythrocyte Aggregation ◽  
Control Group ◽  
Long Term Effects ◽  
Doppler Flowmetry

Background: Prostanoids are used in the treatment of Raynaud’s phenomenon and acral perfusion disorders secondary to collagenosis. In subjective terms, intravenous administration of these agents produces success in more than 50% of patients. The therapeutic outcome of clinical administration of alprostadil or iloprost may vary from individual to individual. Patients and methods: The following variables were analysed in a cross-over study in 27 patients with collagenosis and Raynaud’s phenomenon: plasma viscosity and erythrocyte aggregation (rheological variables), partial pressure of oxygen and laser Doppler flowmetry in the finger region, and lymphocyte phenotyping and interleukin (IL) determinations (immunological variables). Results: Laser Doppler flowmetry revealed significant differences between patients with secondary Raynaud’s phenomenon and a control group of 25 healthy subjects. Laser Doppler readings did not change significantly as a result of the treatments. Therapy with iloprost produced a reduction in IL-1beta, L-selectin (CD 62 L) and IL-6. Conclusion: The change in immunological variables due to iloprost may explain the long-term effects of prostaglandins in the treatment of Raynaud’s phenomenon. From our results it is not possible to infer any preference for iloprost or alprostadil.

Exploration par anémométrie laser Doppler de l'écoulement dans une pompe hélico-axiale

2001 ◽  
pp. 34-39 ◽  
Author(s):  
M. El Hajem ◽  
R. Morel ◽  
J. Y. Champagne ◽  
R. Vilagines ◽  
P. Pagnier
Keyword(s):  
Laser Doppler

Veränderungen der Mikrozirkulation bei Patienten mit Unterschenkelerysipelen vor, während und nach antibiotischer Therapie

Phlebologie ◽  
1998 ◽  
Vol 27 (04) ◽  
pp. 131-137
Author(s):  
S. Roszinski ◽  
W. Schmeller ◽  
S. Kock
Keyword(s):  
Laser Doppler ◽  
Doppler Flux

ZusammenfassungBei 12 Patienten mit Erysipelen am Unterschenkel erfolgten Messungen der Mikrozirkulation in Ruhe und bei hämodynamischen Funktionstests. Bestimmt wurden: Hauttemperatur, Erythemstärke (a-Wert der Colorimetrie), transkutaner Sauerstoffpartialdruck (tcPO2 bei 37° C und 44° C Elektrodentemperatur) sowie Laser-Doppler-Flux (LDF). Die Messungen wurden im Zentrum der Erysipele und an den gesunden kontralateralen Beinen zu Beginn, während und eine Woche nach Ende der Antibiotikatherapie durchgeführt. Zum Zeitpunkt der akuten Entzündung zeigten alle Parameter deutliche Veränderungen; diese wiesen Reaktionsmuster auf, wie sie auch bei Dermatosen mit morphologischen Veränderungen des Kapillarsystems gefunden werden. Nach klinischer Abheilung wiesen tcPO2 bei 37° C und Laser-Doppler-Flux sowohl in Ruhe als auch bei den Funktionstests noch deutliche Veränderungen auf.

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