Measurements of formation, degradation, and sinking velocity of diatom aggregates from laboratory studies performed at 15 °C and 4 °C

Most deep ocean carbon flux profiles show low and almost constant fluxes of particulate organic carbon (POC) in the deep ocean. However, the reason for the non-changing POC fluxes at depths is unknown. This study presents direct measurements of formation, degradation, and sinking velocity of diatom aggregates from laboratory studies performed at 15 °C and 4 °C during a three-week experiment. The average carbon-specific respiration rate during the experiment was 0.12 ± 0.03 at 15 °C, and decreased 3.5-fold when the temperature was lowered to 4 °C. No direct influence of temperature on aggregate sinking speed was observed. Using the remineralisation rate measured at 4 °C and an average particle sinking speed of 150 m d**-1, calculated carbon fluxes were similar to those collected in deep ocean sediment traps from a global data set, indicating that temperature plays a major role for deep ocean fluxes of POC.

Experimental Measurements of Velocity and Pressure Distribution on a Large Broad-Crested Weir

Basic experiments were conducted in a near full-scale broad-crested weir. Detailed velocity and pressure measurements were performed for two configurations. The results showed the rapid flow distribution at the upstream end of the weir, while an overhanging crest design may affect the flow field. The study showed further that large vortical structures might be observed immediately upstream of the weir and impact adversely on the overflow.

New measurements of radial velocities in clusters of galaxies-V

As a part of our galaxy-cluster redshift survey, we present a set of 79 new velocities in the 4 clusters Abell 376, Abell 970, Abell 1356, and Abell 2244, obtained at Haute-Provence observatory. This set now completes our previous analyses, especially for the first two clusters. Data on individual galaxies are presented, and we discuss some cluster properties. For A376, we obtained an improved mean redshift (z) over bar = 0.04750 with a velocity dispersion of sigma(V) = 860 km s(-1). For A970, we have (z) over bar = 0.05875 with sigma(V) = 881 km s(-1). We show that the A1356 cluster is not a member of the ""Leo-Virgo"" supercluster at a mean redshift (z) over bar = 0.112 and should be considered just as a foreground group of galaxies at (z) over bar = 0.0689, as well as A1435 at (z) over bar = 0.062. We obtain (z) over bar = 0.09962 for A2244 with sigma(V) = 965 km s(-1). The relative proximity of clusters A2244 and A2245 ((z) over bar = 0.08738, sigma(V) = 992 km s(-1)) suggests that these could be members of a supercluster that would include A2249; however, from X-ray data there is no indication of interaction between A2244 and A2245.

Bed shear stress measurements in dam break and swash flows

A novel shear plate was used to make direct bed shear stress measurements in laboratory dam break and swash flows on smooth, fixed, impermeable beds. The pressure gradient due to the slope of the fluid free-surface across the plate was measured using pressure transducers. Surface elevation was measured at five locations using acoustic displacement sensors. Flow velocity was measured using an Acoustic-Doppler Velocimeter and calculated using the ANUGA inundation model. The measured bed shear stress at the dam break fluid tip for an initially dry, horizontal bed was close to twice that estimated using steady flow theory. The temporal variation of swash bed shear stress showed a large peak in landward directed stress at the uprush tip, followed by a rapid decay throughout the uprush flow interior. The peak seaward directed stress during the backwash phase was less than half that measured in the uprush. Close to the still water line, in the region of bore collapse and at the time of initial uprush, favourable pressure gradients were measured. In the lower swash region predominately weak adverse pressure gradients were measured.

Detailed Measurements during a Transient Front in a Small Subtropical Estuary

High-resolution measurements of velocity and physio-chemistry were conducted before, during and after the passage of a transient front in a small subtropical system about 2.1 km upstream of the river mouth. Detailed acoustic Doppler velocimetry measurements, conducted continuously at 25 Hz, showed the existence of transverse turbulent shear between 300 s prior to the front passage and 1300 s after. This was associated with an increased level of suspended sediment concentration fluctuations, some transverse shear next to the bed and some surface temperature anomaly.

Turbulence in Hydraulic Jumps: Experimental Measurements

A hydraulic jump is the transition from a supercritical open channel flow to a subcritical regime. It is characterised by a highly turbulent flow with macro-scale vortices, some kinetic energy dissipation and a bubbly two-phase flow structure. New air-water flow measurements were performed in hydraulic jump flows for a range of inflow Froude numbers. The experiments were conducted in a large-size facility using two types of phase-detection intrusive probes: i.e., single-tip and double-tip conductivity probes. These were complemented by some measurements of free-surface fluctuations using ultrasonic displacement meters. The present study was focused on the turbulence characteristics of hydraulic jumps with partially-developed inflow conditions. The void fraction measurements showed the presence of an advective diffusion shear layer in which the void fractions profiles matched closely an analytical solution of the advective diffusion equation for air bubbles. The present results highlighted some influence of the inflow Froude number onto the air bubble entrainment process. At the largest Froude numbers, the advected air bubbles were more thoroughly dispersed vertically, and larger amount of air bubbles were detected in the turbulent shear layer. In the air-water mixing layer, the maximum void fraction and bubble count rate data showed some longitudinal decay function in the flow direction. Such trends were previously reported in the literature. The measurements of interfacial velocity and turbulence level distributions provided new information on the turbulent velocity field in the highly-aerated shear region. The present data suggested some longitudinal decay of the turbulence intensity. The velocity profiles tended to follow a wall jet flow pattern. The air–water turbulent time and length scales were deduced from some auto- and cross-correlation analyses based upon the method of CHANSON (2006,2007). The results provided the integral turbulent time and length scales of the eddy structures advecting the air bubbles in the developing shear layer. The experimental data showed that the auto-correlation time scale Txx was larger than the transverse cross-correlation time scale Txz. The integral turbulence length scale Lxz was a function of the inflow conditions, of the streamwise position (x-x1)/d1 and vertical elevation y/d1. Herein the dimensionless integral turbulent length scale Lxz/d1 was closely related to the inflow depth: i.e., Lxz/d1 = 0.2 to 0.8, with Lxz increasing towards the free-surface. The free-surface fluctuations measurements showed large turbulent fluctuations that reflected the dynamic, unsteady structure of the hydraulic jumps. A linear relationship was found between the normalized maximum free-surface fluctuation and the inflow Froude number.

High-Frequency Suspended Sediment Flux Measurements in a Small Estuary

In small estuaries, the predictions of scalar dispersion can rarely be predicted accurately because of a lack of fundamental understanding of the turbulence structure. Herein detailed turbulence measurements and suspended sediment concentrations were conducted simultaneously and continuously at high-frequency for 50 hours per investigation in a small subtropical estuary with semi-diurnal tides. The data analyses provided an unique characterisation of the turbulent mixing processes and suspended sediment fluxes. The turbulence was neither homogeneous nor isotropic, and it was not a Gaussian process. The integral time scales for turbulence and suspended sediment concentration were about equal during flood tides, but differed significantly during ebb tides. The field experiences showed that the turbulence measurements must be conducted at high-frequency to characterise the small eddies and the viscous dissipation process, while a continuous sampling was necessary to characterise the time-variations of the instantaneous velocity field, Reynolds stress tensor and suspended sediment flux during the tidal cycles.

Fast-convergent iterative scheme for filtering velocity signals and finding Kolmogorov scales

The present fundamental knowledge of fluid turbulence has been established primarily from hot- and cold-wire measurements. Unfortunately, however, these measurements necessarily suffer from contamination by noise since no certain method has previously been available to optimally filter noise from the measured signals. This limitation has impeded our progress of understanding turbulence profoundly. We address this limitation by presenting a simple, fast-convergent iterative scheme to digitally filter signals optimally and find Kolmogorov scales definitely. The great efficacy of the scheme is demonstrated by its application to the instantaneous velocity measured in a turbulent jet.

Analysis of placenta vascularization in patients with uterine altered artery Doppler flow velocity exams

Background: One of the frequent questions in obstetric practice is to determine placental vascular changes that may account for abnormal Doppler flow velocity alterations in maternal uterine vessels from women and fetuses without pregnancy pathology. Methods: A retrospective morphometric study was realized using 27 placentas from patients submitted for Doppler flow velocity exam during pregnancy. The placentas were morphologically examined using hematoxylin-eosin staining. Measurements of villi were made with the use of a video camera coupled to a common light microscope and a computer with automatic image analyzing software. Results: Of the 27 placentas, 13 (48%) were of patients showing unaltered Doppler and 14 (52%) showing altered Doppler. The number of stem villi vessels was significantly larger in the placentas of patients with Doppler exam alterations (P = 0.003). This group also presented greater stem villi vessel thickness, although without significant difference. The number of intermediary and terminal villi vessels was greater in the placentas of patients with altered Doppler exams (P < 0.001), and a greater terminal villi area was observed in these cases (P < 0.001). Conclusion: The morphological proof that uterine artery Doppler flow velocity exam alterations are associated with placental vascular alterations demonstrates the importance of this exam during prenatal care, even in the absence of maternal-fetal alterations.

An assessment of maturity from anthropometric measurements

Purpose: The range of variability between individuals of the same chronological age (CA) in somatic and biological maturity is large and especially accentuated around the adolescent growth spurt. Maturity assessment is an important consideration when dealing with adolescents, from both a research perspective and youth sports stratification. A noninvasive, practical method predicting years from peak height velocity (a maturity offset value) by using anthropometric variables is developed in one sample and cross-validated in two different samples. Methods: Gender specific multiple regression equations were calculated on a sample of 152 Canadian children aged 8-16 yr (79 boys; 73 girls) who were followed through adolescence from 1991 to 1997, The equations included three somatic dimensions (height, sitting height, and leg length), CA, and their interactions. The equations were cross-validated on a Combined sample of Canadian (71 boys, 40 girls measured from 1964 through 1973) and Flemish children (50 boys, 48 girls measured from 1985 through 1999). Results: The coefficient of determination (R2) for the boys' model was 0.92 and for the girls' model 0.91 the SEEs were 0.49 and 0.50, respectively, Mean difference between actual and predicted maturity offset for the verification samples was 0.24 (SD 0.65) yr in boys and 0,001 (SD 0.68) yr in girls. Conclusion: Although the cross-validation meets statistical standards or acceptance, caution 1, warranted with regard to implementation. It is recommended that maturity offset be considered as a categorical rather than a continuous assessment. Nevertheless, the equations presented are a reliable, noninvasive and a practical solution for the measure of biological maturity for matching adolescent athletes.

Effect of cold wire inclination on temperature fluctuation measurements in a heated jet

Hot-wire anemometers at low operating currents are used as fast response resistance thermometers for the study of heated turbulent flows. Simultaneous measurement of temperature and velocity is generally performed with multi-wire arrays. In order to give good spatial resolution a new layout has been tested which uses an inclined temperature wire positioned parallel to the nearest inclined velocity wire. This leads to an asymmetric wire arrangement relative to the mean flow direction. As expected, a reduction in thermal interference from the velocity wires results when compared with an array containing a temperature wire placed normal to the flow. However, measurement of higher order moments of fluctuating quantities in an axisymmetric jet shows considerable distortion of radial distributions which is traced to alteration of the temperature field sensed by the temperature wire. When inclined velocity sensitive wires contain a temperature component, the latter may be affected by the same phenomenon.

The effects of sevoflurane and halothane anesthesia on cerebral blood flow velocity in children.

We compared cerebral blood flow velocity during anesthesia with sevoflurane and halothane in 23 children admitted for elective surgery (age, 0.4-9.7 yr; median age, 1.9 yr; ASA physical status I-II). Inhaled induction was performed in a randomized sequence with sevoflurane or halothane. Under steady-state conditions, cerebral blood flow velocity (systolic [V(s)], mean [V(mn)], and diastolic [VD]) were measured by a blinded investigator using transcranial pulsed Doppler ultrasonography. The anesthetic was then changed. CBFV measurements were repeated after washout of the first anesthetic and after steady-state of the second (equivalent minimal alveolar concentration to first anesthetic). The resistance index was calculated. VD and V(mn) were significantly lower during sevoflurane (V(mn) 1.35 m/s) than during halothane (V(mn) 1.50 m/s; P = 0.001), whereas V(s) was unchanged. The resistance index was lower during halothane (P < 0.001). Our results indicate lower vessel resistance and higher mean velocity during halothane than during sevoflurane. IMPLICATIONS: The mean cerebral blood flow velocity is significantly decreased in children during inhaled anesthesia with sevoflurane than during halothane. This might be relevant for the choice of anesthetic in children with risk of increased intracranial pressure, neurosurgery, or craniofacial osteotomies.