Spanwise Streaky Structure and Macroturbulence in Open-channel Flows

In order to reveal the interrelation between the bursting phenomenon occurring originally in the wall region and the macroturbulence such as kolk-boils and the cellular secondary current, which are observed in the outer region of an actual river, the present study has examined the spanwise spatial structures of open-channel flows with and without the cellular secondary current which was created artificially. A new conditional averaging technique, whereby the signals of a sampling probe are weight-averaged by the sorted instantaneous Reynolds-stress signals of a detection probe, has been used to evaluate the mean spanwise streaky spacings throughout the flow depth. The direct effect of the cellular secondary current on the bursting motion was not recognized. It was suggested that the coherent structures of an open-channel flow would indicate the doublestructure of turbulence, in which both the bursting and macroturbulence coexist self- consistently

Three-Dimensional Turbulent Structure and Associated Secondary Currents in Straight Rivers : Field Measurements of River Turbulence

Fundamental structures of turbulence in two-dimensional (2-D) and further three-dimensional (3-D) open-channel flows have recently been almost clarified theoretically and experimentally through accurate experimental data which were obtained using a laser-Doppler anemometer system in laboratory flumes ; this detailed knowledge is now available in an IAHR monograph written by Nezu & Nakagawa (1992). Many of these experiments have, however, been conducted at moderate Reynolds numbers, say Re 記号 10⁴. Therefore, it is not yet clear whether such laboratory data of open-channel turbulence can be applied to river turbulence at high Reynolds numbers. In this study, velocity measurements of the Biwako-Sosui River (Re = 8 × 10⁵) in Kyoto and the Aichi Irrigation Channel (Re = 6 × 10⁵) in Nagoya have been conducted, using three-component electromagnetic flow meters. It was first found that multi-cellular secondary currents and free-surface secondary currents were evident in actual rivers. The features of such secondary currents in rivers were in a good agreement with those in laboratory flumes. Key Words : turbulence-driven secondary currents ; river turbulence ; field measurements ; velocity-dip phenomenon ; effects of aspect ratio

Turbulent Structures in Unsteady Open-Channel Flows

Turbulence measurements over a smooth wall in unsteady open-channel flows were conducted accurately by the simultaneous use of a two-component LDA system and water-wave gauges. The “ general ” log-law distributions, in which the von Karman constant is a universal one of χ=0.41 but the integration constant A is a function of main-flow conditions, were obeyed well in the wall region for both the rising and falling stages of flood. On the other hand, the log-wake law was reasonably applied to the outer region including the depth-varying zone. The Coles' wake parameter Π increased for the rising stage, whereas it decreased for the falling stage. The turbulence is stronger for the rising stage than for the falling stage, except for very near the free surface. These unsteady characteristics in open-channel flows with variation of the water surface are quite different from those in closed duct flows. Of particular significance is the findings counterclockwise loops of velocity and turbulence against the varying depth in unsteady open-channel flows

Effect of 1,2-Dimethylhydrazine and Hydrogen Peroxide for the Duodenal Tumorigenesis in Relation to Blood Catalase Activity in Mice

Three different mouse strains, C3H/C^b_s C3H/HeN and B6C3 (C57BL x C3H) F1, having low, high and moderate catalase activities, were studied for duodenal tumorigenesis by the combined treatment with 1,2-dimethylhydrazine (DMH)* and hydrogen peroxide (HPO). DMH alone rarely induced duodenal tumors. Administration of HPO into 3 different mouse strains induced different frequencies of duodenal tumors ; 91.7% in C3H/C^b_s 9.5% in C3H/HeN and 31.8% in B6C3F1 mice. The incidence of duodenal tumors was significantly increased to 52.6% and 93.8% both in C3H/HeN and B6C3F1 mice by the combined administration of DMH and HPO. These increases in duodenal tumor were inversely correlated with the finding that administration of DMH or HPO alone or combined treatment of DMH and HPO significantly decreased mean blood catalase activities both in C3H and B6C3F1 mice

The manufacturing of lactobacillus microcapsules by freezing with egg yolk: The analysis of microstructure and the preservation effect against freezing and acid treatments

Encapsulation is an effective strategy to prevent probiotics from environmental damages. The survivability of Lactobacillus is generally reduced under frozen or acid environments. In this study, an attempt was made to encapsulate Lactobacillus into the egg yolk aggregates formed upon freezing. Lactobacillus broth was mixed with liquid egg yolk and frozen at selected temperatures and time periods. After thawing, the number of surviving bacteria was determined. The results showed that freezing with the addition of egg yolk improved Lactobacillus survivability. It was confirmed that freezing increased the number of egg yolk aggregates, and those aggregates coated Lactobacillus after freezing. The encapsulated Lactobacillus was treated at pH 2.5 for 10 min, and the results showed that the encapsulation process increased the acid resistance of Lactobacillus. These results indicate that freezing-induced encapsulation with egg yolk could effectively protect Lactobacillus against freezing and acid treatment. This finding could be useful for the design and preservation of probiotics-based food products

Markerless tumor-tracking algorithm using prior 4D-CBCT

Respiratory motion management is a huge challenge in radiation therapy. Respiratory motion induces temporal anatomic changes that distort the tumor volume and its position. In this study, a markerless tumor-tracking algorithm was investigated by performing phase recognition during stereotactic body radiation therapy (SBRT) using four-dimensional cone-beam computer tomography (4D-CBCT) obtained at patient registration, and in-treatment cone-beam projection images. The data for 20 treatment sessions (five lung cancer patients) were selected for this study. Three of the patients were treated with conventional flattening filter (FF) beams, and the other two were treated with flattening filter-free (FFF) beams. Prior to treatment, 4D-CBCT was acquired to create the template projection images for 10 phases. In-treatment images were obtained at near real time during treatment. Template-based phase recognition was performed for 4D-CBCT re-projected templates using prior 4D-CBCT based phase recognition algorithm and was compared with the results generated by the Amsterdam Shroud (AS) technique. Visual verification technique was used for the verification of the phase recognition and AS technique at certain tumor-visible angles. Offline template matching analysis using the cross-correlation indicated that phase recognition performed using the prior 4D-CBCT and visual verification matched up to 97.5% in the case of FFF, and 95% in the case of FF, whereas the AS technique matched 83.5% with visual verification for FFF and 93% for FF. Markerless tumor tracking based on phase recognition using prior 4D-CBCT has been developed successfully. This is the first study that reports on the use of prior 4D-CBCT based on normalized cross-correlation technique for phase recognition