Extraction of 3D vortex structures from a turbulent puff in a pipe using two-color illumination and flakes

A novel visualization technique was proposed to extract the three-dimensional vortex structure of a turbulent puff, which is a local turbulence event that is observed in pipe flows at relatively low Reynolds numbers. The technique is based on multi-color illumination of microscopic flakes that are suspended in the flow, which makes structural visualization more informative than conventional monochrome approaches. A special optical arrangement of two laser sheets, colored green and blue, was established for the circular pipe. Based on an image analysis sequence, the internal structure of the puff is reconstructed as a cross-sectional temporal 3D image consisting of voxels with unicolor degrees between green and blue, where an individual single vortex is extracted as a pair of two-color stripes. This allows quantification of the azimuthal wavenumber of the vortical structure that characterizes the puff. The wavenumber results agreed well with the results of previous studies, thus supporting the applicability of the proposed visualization technique.

Effect of wall surface wettability on collective behavior of hydrogen microbubbles rising along a wall

This paper presents an experimental study of the influence of wall surface wettability on the behavior of hydrogen microbubbles rising along a nearly vertical wall. Multiple optical diagnostics, including particle tracking velocimetry, have been employed for the study. The microbubble behavior observed along three different kinds of wall surfaces (hydrophobic, hydrophilic, and super-hydrophilic) was characterized by the microbubble-wall attachment, bubble size distribution, bubble coalescence, and microbubble layer formation. Microbubbles rising along the wall with poor wettability soon attach to the wall and grow to millimeters in size as a result of bubble coalescence. Such millimeter-sized bubbles detach from the wall because of their increased buoyancy, and eventually enhance transverse diffusion of microbubbles, which is known as the sweep-out effect. In contrast, in the case of very good wettability, almost no microbubbles attach to the wall and smoothly form a thin microbubble layer in the wall proximity. The observed phenomena contradict our intuitive expectation of the effect of surface wettability on gas bubbles, and hence may be regarded as a feature of microbubbles that distinguishes them from large bubbles

Effect of heated wall inclination on natural convection heat transfer in water with near-wall injection of millimeter-sized bubbles

Natural convection heat transfer from a heated wall in water with near-wall injection of millimeter-sized bubbles is studied experimentally. Velocity and temperature measurements are conducted in the nearwall region. In the range of the heated wall angles from 0 to 40 degrees from the vertical, the heat transfer coefficient increases by up to an order of magnitude with bubble injection. The ratio of the heat transfer coefficient with bubble injection to that without injection increases with the wall inclination angle. Based upon measured liquid temperature distributions and liquid flow velocity profiles, enhancement of heat transfer by bubble injection is explained by two mechanisms. First, wall-parallel transport of cold liquid into the thermal boundary layer is enhanced by the bubble-driven flow. Second, wall-normal mixing of warm liquid and cold liquid occurs, as a result of wall-normal velocity fluctuations of the liquid phase activated by a combination of bubble rising motion, vortex shedding from the bubbles, and unsteady vortices formed within the boundary layer. The unsteady vortices travel along the wall together with the bubbles, primarily contributing to the enhancement of heat transfer at higher wall inclination angles

Bubble fragmentation dynamics in a subsonic Venturi tube for the design of a compact microbubble generator

Microbubble generators are in wide demand in industry following the discovery of a number of new functions of microbubble mixtures. This paper deals with a Venturi tube microbubble generator in which air bubbles at the inlet are fragmented in the diverging part of the tube. In contrast with past studies, we here regulated the flow subsonic so that fragmentation occurred without the help of pressure shock waves. Counting the microbubbles in image processing, we found that a single bubble fragmented into 20–400 microbubbles depending on the Weber number. The power efficiency is found to range from 30 to 50 percent and insensitive to the liquid viscosity. The mechanism of subsonic fragmentation is elucidated adopting particle tracking velocimetry, in association with a theoretical description of the translational motion and the shape oscillation of the bubble. The key event was found to be the bubble’s rapid slipback in the diverging part of the Venturi tube due to a positive pressure gradient. This provides a function that prevents large bubbles from being released from the subsonic Venturi tube

Characterisation of aeroelastic harvester efficiency by measuring transient growth of oscillations

With growing demand for small autonomous electrical devices, such as those in wireless sensor networks, energy harvesting has attracted interest with the promise of low maintenance and sustainable power sources. Galloping energy harvesters utilise the fluid-structure interaction to transform kinetic energy in fluid flow into electrical energy. The performance of galloping energy harvesters depends on the geometry of the tip, with the structure of the flow around the tip defining the nature of fluid-structure interaction and hence the potential efficiency of the device. In this work the curved blade tip geometry is investigated. To experimentally characterise the performance of the harvester, a method utilising the free oscillation transient is developed. The method avoids implementation of a transduction mechanism and hence optimisation of the associated parameters. The developed method is generic and can be applied to other energy generators. The power coefficient of curved blades of different curvatures is measured and the optimal range identified. The maximum coefficient of performance of the curved blade harvester occurs at tip speed ratios from to and reaches , which is 3 to 4 times lower than Savonius turbines, the best performing devices at similar Reynolds numbers. The square prism geometry is used as a comparator and found to have a coefficient of performance 10 times less than the curved blade. Flow visualisations confirm the curved blade to act as an airfoil in the highest performing cases, hence future tip shapes should be developed to promote flow attachment

MEDINA, MARÍA E HIJJOS [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Salivary Mucocele in a Laboratory Beagle

The histologic characteristics of a salivary mucocele in a beagle used in a toxicity study are described in this report. A pale yellowish cyst under the mandibular skin containing frothy mucus was observed at necropsy. Microscopically, numerous villous projections arose from the internal surface of the cyst and were lined by stratified epithelial-like macrophages, which were immunopositive for macrophage scavenger receptor A. A ruptured sublingual interlobar duct connected to the lumen was observed near the cyst. Luminal amorphous material showed a positive reaction with Alcian blue and periodic acid-Schiff staining as did mucin in the sublingual gland. Ultrastructurally, the epithelial-like macrophages had numerous vacuoles containing electron-lucent material, which was presumed to be lysosomal in origin, and had pseudopods on their cell surfaces interdigitating with those on the adjacent cells. This case report helps to understand the diversity of the background findings in beagles used in toxicity studies

Admission systolic blood pressure as a prognostic predictor of acute decompensated heart failure: A report from the KCHF registry

[Background] Admission systolic blood pressure has emerged as a predictor of postdischarge outcomes of patients with acute decompensated heart failure; however, its validity in varied clinical conditions of this patient subset is unclear. The aim of this study was to further explore the prognostic value of admission systolic blood pressure in patients with acute decompensated heart failure. [Methods] The Kyoto Congestive Heart Failure (KCHF) registry is a prospective, observational, multicenter cohort study enrolling consecutive patients with acute decompensated heart failure from 19 participating hospitals in Japan. Clinical characteristics at baseline and prognosis were examined by the following value range of admission systolic blood pressure: <100, 100–139, and ≥140 mmHg. The primary outcome measure was defined as all-cause death after discharge. Subgroup analyses were done for prior hospitalization for heart failure, hypertension, left ventricular ejection fraction, and medications at discharge. We excluded patients with acute coronary syndrome or insufficient data. [Results] We analyzed 3564 patients discharged alive out of 3804 patients hospitalized for acute decompensated heart failure. In the entire cohort, lower admission systolic blood pressure was associated with poor outcomes (1-year cumulative incidence of all-cause death: <100 mmHg, 26.8%; 100–139 mmHg, 20.2%; and ≥140 mmHg, 15.1%, p<0.001). The magnitude of the effect of lower admission systolic blood pressure for postdischarge all-cause death was greater in patients with prior hospitalization for heart failure, heart failure with reduced left ventricular ejection fraction, and β-blocker use at discharge than in those without. [Conclusions] Admission systolic blood pressure is useful for postdischarge risk stratification in patients with acute decompensated heart failure. Its magnitude of the effect as a prognostic predictor may differ across clinical conditions of patients

Accelerator Analysis of Tributyltin Adsorbed onto the Surface of a Tributyltin Resistant Marine Pseudoalteromonas sp. Cell

Tributyltin (TBT) released into seawater from ship hulls is a stable marine pollutant and obviously remains in marine environments. We isolated a TBT resistant marine Pseudoalteromonas sp. TBT1 from sediment of a ship’s ballast water. The isolate (109.3 ± 0.2 colony-forming units mL−1) adsorbed TBT in proportion to the concentrations of TBTCl externally added up to 3 mM, where the number of TBT adsorbed by a single cell was estimated to be 108.2. The value was reduced to about one-fifth when the lysozyme-treated cells were used. The surface of ethanol treated cells became rough, but the capacity of TBT adsorption was the same as that for native cells. These results indicate that the function of the cell surface, rather than that structure, plays an important role to the adsorption of TBT. The adsorption state of TBT seems to be multi-layer when the number of more than 106.8 TBT molecules is adsorbed by a single cell

Feasibility of methotrexate discontinuation following tocilizumab and methotrexate combination therapy in patients with long-standing and advanced rheumatoid arthritis: a 3-year observational cohort study

Objectives: Methotrexate (MTX) is associated with extensive side effects, including myelosuppression, interstitial pneumonia, and infection. It is, therefore, critical to establish whether its administration is required after achieving remission with tocilizumab (TCZ) and MTX combination therapy in patients with rheumatoid arthritis (RA). Therefore, the aim of this multicenter, observational, cohort study was to evaluate the feasibility of MTX discontinuation for the safety of these patients. Methods: Patients with RA were administered TCZ, with or without MTX, for 3 years; those who received TCZ+MTX combination therapy were selected. After remission was achieved, MTX was discontinued without flare development in one group (discontinued [DISC] group, n = 33) and continued without flare development in another group (maintain [MAIN] group, n = 37). The clinical efficacy of TCZ+MTX therapy, patient background characteristics, and adverse events were compared between groups. Results: The disease activity score in 28 joints-erythrocyte sedimentation rate (DAS28-ESR) at 3, 6, and 9 months was significantly lower in the DISC group (P < .05, P < .01, and P < .01, respectively). Further, the DAS28-ESR remission rate at 6 and 9 months and Boolean remission rate at 6 months were significantly higher in the DISC group (P < .01 for all). Disease duration was significantly longer in the DISC group (P < .05). Furthermore, the number of patients with stage 4 RA was significantly higher in the DISC group (P < .01). Conclusions: Once remission was achieved, MTX was discontinued in patients who responded favorably to TCZ+MTX therapy, despite the prolonged disease duration and stage progression