Nanofluidic transport governed by the liquid/vapour interface

Liquid/vapour interfaces govern the behaviour of a wide range of systems but remain poorly understood, leaving ample margin for the exploitation of intriguing functionalities for applications. Here, we systematically investigate the role of liquid/vapour interfaces in the transport of water across apposing liquid menisci in osmosis membranes comprising short hydrophobic nanopores that separate two fluid reservoirs. We show experimentally that mass transport is limited by molecular reflection from the liquid/vapour interface below a certain length scale, which depends on the transmission probability of water molecules across the nanopores and on the condensation probability of a water molecule incident on the liquid surface. This fundamental yet elusive condensation property of water is measured under near-equilibrium conditions and found to decrease from 0.36 ± 0.21 at 30 °C to 0.18 ± 0.09 at 60 °C. These findings define the regime in which liquid/vapour interfaces govern nanofluidic transport and have implications for understanding mass transport in nanofluidic devices, droplets and bubbles, biological components and porous media involving liquid/vapour interfaces.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R10-CW-09

Presentation of a Non-invasive Method of Estimating Arterial Stiffness by Modeling Blood Flow and Arterial Wall Based on the Determination of Elastic Module of Arterial Wall

Introduction: Arterial stiffness is an important predictor of cardiovascular risk. Several indices have been  introduced to estimate the arterial stiffness based on the changes in the brachial blood pressure. Since the  substitution  of  the  blood  pressure  changes  in  the  central  arteries  such  as  carotid  with  the  blood  pressure  changes in the brachial results in error in the blood flow, it is of importance to present an elastic parameter  based on the mechanical models without any reliance on the brachial blood pressure.   Materials and Methods: Initially, a suitable dynamic model is introduced for pulsatile blood flow in the  arteries based on Navier-Stokes the equations in fluid mechanics. Then, according to the theory of elasticity,  the equations governing arterial wall are described and coupled with the equations of fluid flow. The attained  system  of  equations  is  completed  by  the  clinical  information  obtained  from  the  carotid  artery  Doppler  ultrasound images of healthy male subject. Therefore, the Doppler ultrasound images are recorded and saved  in computer after which the center-line blood velocity, the arterial wall thickness, the period of a cardiac  cycle and the arterial radius are measured by off-line processing.   Results: The results from the analytic solution of the completed equations show that the elastic modulus for  this healthy subject is 51 kpa which is in close agreement with the result obtained from other researches.   Discussion and Conclusion: By applying this method, a non-invasive method of clinically evaluating the  arterial stiffness will be possible by the Doppler ultrasound measurement of common carotid artery without  any measurement of the local blood pressure

State-of-the-art report summarizing techniques to determine residual oil saturation and recommendations on the requirements for residual oil saturation research and development

An investigation was conducted on the residual oil saturation (ROS) measurement techniques developed during the last fifteen years. Knowledge of precise ROS measurements is required for EOR project planning. The advantages, limitations, and problems of each one of the techniques are presented in tabulated form. Also, some of the possible improvements in the measurement techniques for the residual oil saturation are summarized. The following residual oil saturation techniques are discussed: core analyses, well logging, backflow tracer tests, material balance and well testing, newly developed gravity log methods, and interwell residual oil saturation measurements. Several aspects left to be improved in both instrumentations and data interpretation on pressure coring, back-flow tracer tests, well logging, material balance calculations, well testing, and interwell ROS measurements are presented. A nuclear magnetism log-inject-log method is proposed in which the need for porosity measurement for determining residual oil saturation is eliminated. 91 refs., 3 tabs