Rab5ab-Mediated Yolk Cell Membrane Endocytosis Is Essential for Zebrafish Epiboly and Mechanical Equilibrium During Gastrulation

Morphogenesis in early embryos demands the coordinated distribution of cells and tissues to their final destination in a spatio-temporal controlled way. Spatial and scalar differences in adhesion and contractility are essential for these morphogenetic movements, while the role that membrane remodeling may play remains less clear. To evaluate how membrane turnover modulates tissue arrangements we studied the role of endocytosis in zebrafish epiboly. Experimental analyses and modeling have shown that the expansion of the blastoderm relies on an asymmetry of mechanical tension in the yolk cell generated as a result of actomyosin-dependent contraction and membrane removal. Here we show that the GTPase Rab5ab is essential for the endocytosis and the removal of the external yolk cell syncytial layer (E-YSL) membrane. Interfering in its expression exclusively in the yolk resulted in the reduction of yolk cell actomyosin contractility, the disruption of cortical and internal flows, a disequilibrium in force balance and epiboly impairment. We conclude that regulated membrane remodeling is crucial for directing cell and tissue mechanics, preserving embryo geometry and coordinating morphogenetic movements during epiboly.

Design and Analysis of the Multi Blade Angle Centrifugal Pump Impeller by Using CFX Tool

This project investigates the study of complex internal flows in centrifugal pump impellers with the aid of Computational Fluid Dynamics software thus facilitating the design of pumps. Here three different types of Pump impellers had been taken, the pump specifications considered for investigation are discharge and speed. A design of centrifugal pump is carried out and analyzed to get the best performance point. The design and performance analysis of centrifugal pump are chosen because it is the most useful mechanical rotodynamic machine in fluid works which widely used in domestic, irrigation, industry, large plants and river water pumping system. These specifications have been varied toper form a comparative study of these pump impellers. The impeller was modeled and the blade to blade plane of the impellers was taken for the detailed study purpose because the flow occurs through this passage only. The blade-to-blade plane is modeled and the flow analysis is carried out using FLUENT software. Thus the valid results regarding the velocity distribution and pressure distributions were predicted for different blade angles.

Experimental and numerical study on cavitation performances of a turbopump with and without an inducer

The cavitation performances and its internal flows in a centrifugal turbopump with and without a three-bladed axial inducer have been studied both experimentally and numerically. A 3D steady numerical model has been applied to simulate the cavitating flow from the inlet to the outlet ducts of the turbopump with and without an inducer by using ANSYS CFX code. In the present work, to clarify this relationship, we conducted experiments in both cold water ( T = 20°C) and hot water ( T = 80°C) with a focus on the development of vapor volume fraction and head degradation by gradually reducing the inlet pressure from atmospheric conditions to the minimum allowable value at a constant rate of about 3 mbar/s. The measured and predicted cavitation performances of the turbopump with and without an inducer have been compared under different operating conditions and the temperature of the operating fluid.

Modeling Unsteady Bénard-Marangoni Instabilities in Drying Volatile Droplets on a Heated Substrate

We study unsteady internal flows in a sessile droplet of capillary size evaporating in constant contact line mode on a heated substrate. Three-dimensional simulations of internal flows in evaporating droplets of ethanol and silicone oil have been carried out. For describing the Marangoni flows we find it necessary to account for the diffusion of vapor in air, the thermal conduction in all three phases and thermal radiation. The equations have been solved numerically by finite element method using ANSYS Fluent. As a result of the simulations, the nonstationary behavior of Bénard-Marangoni (BM) instabilities is obtained. At the first stage, a flower structure of BM cells near the triple line emerge. For smaller contact angles, the cells grow in size and occupy the central region of the droplet surface. Being closely connected with recent experimental and theoretical studies, the results obtained help to analyze and resolve the associated issues.