Use Of Fluid Mechanics Research Articles

Quantifying surface tension and viscosity in biomolecular condensates by FRAP-ID

Many proteins with intrinsically disordered regions undergo liquid-liquid phase separation under specific conditions in vitro and in vivo. These complex biopolymers form a metastable phase with distinct mechanical properties defining the timescale of their biological functions. However, determining these properties is nontrivial, even in vitro, and often requires multiple techniques. Here we report the measurement of both viscosity and surface tension of biomolecular condensates via correlative fluorescence microscopy and atomic force microscopy (AFM) in a single experiment (fluorescence recovery after probe-induced dewetting, FRAP-ID). Upon surface tension evaluation via regular AFM-force spectroscopy, controlled AFM indentations induce dry spots in fluorescent condensates on a glass coverslip. The subsequent rewetting exhibits a contact line velocity that is used to quantify the condensed-phase viscosity. Therefore, in contrast with fluorescence recovery after photobleaching (FRAP), where molecular diffusion is observed, in FRAP-ID fluorescence recovery is obtained through fluid rewetting and the subsequent morphological relaxation. We show that the latter can be used to cross-validate viscosity values determined during the rewetting regime. Making use of fluid mechanics, FRAP-ID is a valuable tool to evaluate the mechanical properties that govern the dynamics of biomolecular condensates and determine how these properties impact the temporal aspects of condensate functionality.

Analysis on the Use of Fluid Mechanics and Thermodynamics in Future Vehicles

Petroleum is mainly used in the transportation industry and it is now becoming rarer in the world. Petroleum Geologists and analysts have predicted an imminent global peak of petroleum consumption, at which the maximum rate of petroleum extraction will be reached, and then followed by an irreversible decline. To date, 50 countries have passed the point of no return. Therefore, there is no time to delay the saving of petroleum. Since petroleum is mostly used by various means of transport, vehicles that are more efficient with less use of petroleum are needed. Under this context, this paper introduces three types of vehicles making full use of energy. Through case studies, the development tendency of future vehicles is illustrated, and a conclusion can be drawn that clean energy hybrids and hydrogen-powered fuels have become a future development trend for vehicles.

The use of fluid mechanics to explore human swimming technique

The use of fluid mechanics to explore human swimming technique

Central and peripheral pulmonary vascular resistance: Implications for who should undergo pulmonary thromboendarterectomy

Pulmonary thromboendarterectomy remains a technically challenging procedure with variable outcomes with regard to improvement in pulmonary function. Reducing the resistance to flow between the pulmonary valve and the pulmonary capillary bed is the key aim of surgery. The resistance to flow is due to the combination of resistance due to the central clot and distal capillary resistance. We hypothesise that the use of fluid mechanics in combination with modern radiology and electronic circuit theory can potentially predict who should or should not undergo a thromboendarterectomy. Electronic circuit theory of two resistors in series was utilised to demonstrate the concept of a model of a central clot and the peripheral pulmonary capillary bed. A simplified 2D model of the lungs utilising finite element analysis and Poiseuille’s law was constructed for proof of principle. Modelling predicts that cardiac output and anatomical obstruction interplay and can have profound effects on the outcomes after thromboendarterectomy. Identical pulmonary artery pressures, due to differing cardiac outputs and identical anatomical obstructions due to thrombus can have very different physiological outcomes with regard to changes in pulmonary artery pressure. Modelling the pulmonary vasculature to determine central and peripheral pulmonary vascular resistance may help in predicting who should undergo pulmonary thromboendarterectomy. Mathematical modelling can potentially predict which patients have haemodynamically significant clots in their pulmonary arteries that thromboendarterectomy may potentially help in the setting of pulmonary capillary disease.

Profile of Keith Moffatt

Keith Moffatt was born in 1935 and raised in Edinburgh, Scotland. He was four years old when his father left home to serve in the Second World War. “At that age, you accept things,” Moffatt recalls. “It was a time of great shortage. Everything in the UK was rationed—food, clothes, fuel, even sweets!” Keith Moffatt. Photo by Jill Paton-Walsh. His Royal Highness Prince Philip visits the Newton Institute, October 1992. Keith Moffatt ( Left ) demonstrates the production of a cusp singularity at a free surface. Sir Michael Atiyah, Founder Director of the Institute ( Right ). Photo courtesy of MM Photographic. The elder Moffatt, an accountant, had introduced his son to mathematical games and arithmetic puzzles, and, when he returned at the war’s end in 1945, recreational mathematics recommenced. The early tutelage had a lasting effect: Moffatt’s facility with numbers would transform into an aptitude for applied mathematics and its use in fluid mechanics and astrophysics. His contributions to our understanding of magnetic and spin fields as well as his advocacy for the study of mathematics around the world have earned him fellowships in the Royal Societies of both London and Edinburgh. A 2005 recipient of the Royal Society of London’s Hughes Medal, he serves as an emeritus professor of mathematical physics at the University of Cambridge. He was elected as a foreign associate of the National Academy of Sciences in 2008. Moffatt completed his undergraduate studies in mathematics at the University of Edinburgh. He left Scotland for Trinity College, Cambridge, in 1957, where he came under the influence of George Batchelor, an Australian fluid dynamicist. Batchelor set Moffatt to work on his first research project and played a decisive role in his career. “George was very sympathetic to students who came from outside Cambridge, as it had been his own career path,” …

The Use of Fluid Mechanics to Predict Regions of Microscopic Thrombus Formation in Pulsatile VADs

We compare the velocity and shear obtained from particle image velocimetry (PIV) and computational fluid dynamics (CFD) in a pulsatile ventricular assist device (VAD) to further test our thrombus predictive methodology using microscopy data from an explanted VAD. To mimic physiological conditions in vitro, a mock circulatory loop is used with a blood analog that matched blood's viscoelastic behavior at 40% hematocrit. Under normal physiologic pressures and for a heart rate of 75 bpm, PIV data is acquired and wall shear maps are produced. The resolution of the PIV shear rate calculations are tested using the CFD and found to be in the same range. A bovine study, using a model of the 50 cc Penn State V-2 VAD, for 30 days at a constant beat rate of 75 beats per minute (bpm) provides the microscopic data whereby after the 30 days, the device is explanted and the sac surface analyzed using scanning electron microscopy (SEM) and, after immunofluorescent labeling for platelets and fibrin, confocal microscopy. Areas are examined based on PIV measurements and CFD, with special attention to low shear regions where platelet and fibrin deposition are most likely to occur. Data collected within the outlet port in a direction normal to the front wall of the VAD shows that some regions experience wall shear rates less than 500 s-1, which increases the likelihood of platelet and fibrin deposition. Despite only one animal study, correlations between PIV, CFD, and in vivo data show promise. Deposition probability is quantified by the thrombus susceptibility potential, a calculation to correlate low shear and time of shear with deposition.

The Application of Fluid Mobility Modelling in Wireless Cellular Networks

Mobility models, synthetic or trace, try to accurately model the movement of a single user or a group of users. Models can be used in simulators and emulators to investigate the consequences of mobility on new protocols or network management techniques. A limitation with current trace mobility models is they are based on empirical data which are limited to specific network types and environments. Limitations with synthetic models are that they are complex, computationally heavy, and lack realism. To address these issue a new approach needs to be taken. One such approach is the use of fluid mechanics and transport theory to represent user mobility. A model based on viscous free irrotational fluid mechanics with empirical data from pedestrian and vehicular studies provide a means of creating realistic group movement characteristics with smooth non random trajectories and smooth continuous velocity. The model is used in an example to provide boundary crossing rates for users in a cellular network and optimising the size of cellular location areas.

MEMS Devices and Applications in Aerospace and Civil Engineering

J ‘‘Examination of Bulge Test for Determining Residual Stress, Young’s Modulus, and Poisson’s Ratio of 3C-SiC Thin Films,’’ describe their study of a test that is based on plate mechanics, and illustrate its capabilities within their work on silicon carbide fabrication. Another important topic within MEMS ~and its nanoscale counterpart, NEMS! research is biochemical sensing, for which dissolvable hydrogels can serve as indicators. Aluru and his colleagues from the University of Illinois, in a paper entitled ‘‘Mathematical Modeling and Simulation of Dissolvable Hydrogels,’’ present a mathematical model for hydrogel behavior with comparisons between model and experimental results. Three papers are contributed by researchers in the MEMS community describing the development of devices that can revolutionize aerospace and civil engineering practice. My colleagues from Carnegie Mellon, Xie ~now at the University of Florida! and Fedder, report on the development of vibratory gyroscopes in a paper entitled ‘‘Integrated MEMS Gyroscopes.’’ In a paper entitled ‘‘Capacitive Micromachined Ultrasonic Transducers: Theory and Technology,’’ Khuri-Yakub and his coworkers from Stanford give the reader comprehensive insight into the design, behavior, and performance of ultrasonic transducers. Liu and his coworkers, from the University of Illinois, contribute a paper entitled ‘‘Two-Dimensional Micromachined Flow-Sensor Array for Fluid Mechanics Studies’’ in which they describe the development of two novel sensors for use in fluid mechanics; they start with the physical concepts, show the development of the MEMS process and the device design, and then illustrate the results with experimental studies. I wish to thank the authors of these papers, as well as others who responded with interest and whose papers may appear in future issues of this Journal. The ideas they describe are stimulating, their research practices are exemplary, and their writing is excellent. They set a high standard and we are the beneficiaries. Irving J. Oppenheim Carnegie Mellon University

Thermal air flow analysis of an automotive headlamp:: the PIV measurement and the CFD calculation for a mass production model

In order to improve thermal endurance, mechanical durability and ventilation performance in an automotive headlamp, it is important to understand heat transfer and flow. In the present study, a newly-developed method called surface heat transfer (SHT) method, a unique technique for making an accurate estimate of temperature and velocity in the automotive headlamp without involving the use of fluid mechanics and structural mechanics, was investigated for practical use. An evaluation of SHT method was performed, and CFD results were compared with the experimental results.

Biofluidmechanics: quo vadimus?

After proposing and briefly assessing the domain, objectives and tools of biofluidmechanics—the use of fluid mechanics for the study of biological flows—the paper focuses on the problems and opportunities in the study of biological flows in the various life sciences, both basic and applied. particular emphasis is given to flows as conveyours of information, the utilization of flows as diagnostic tools, and the interaction between flow and systems considerations. Biological flows also hold potential technological implications both as providers of inspiration for new engineering devices and concepts, and as stimulus to the development of new fundamental techniques in fluid mechanics. Finally, biofluidmechanics is compared to other domains of fluid mechanics (man-made devices and inorganic nature), and the development of the field is briefly considered in terms of social and governmental factors that affect it.

Semifocusing Color Schlieren System for Use in Fluid Mechanics and Heat Transfer

Construction, theory, and operation of semifocusing color schlieren systems for use In quantaitiv experimental investigations of flows are described. Results showing photographs of boundary layers are included.

The use of a ruby laser with interferometers suitable for work in fluid mechanics

The coherence requirements of laser interferometers suitable for use in fluid mechanics are discussed. Experimental results obtained with a commercial ruby laser show that these requirements can be met with no modification other than insertion of suitable diaphragms. Even with a Fresnel number of unity, sufficient exposure for the relatively fast plates used is easily obtained. Practical difficulties and methods of adjustment are discussed.

The design of laser interferometers for use in fluid mechanics

Several workers have described interferometers for use in fluid mechanics which are designed for use with laser light. The freedom of design which is now possible leads to a multiplicity of optical arrangements, and the present paper is intended as a guide towards the choice of suitable interferometers. The paper discusses some of the general principles involved, classifies interferometer types and then shows how the use of coherent light may affect the relative merits of these types. The optical arrangements which have been suggested for each type are then reviewed, some modified designs are suggested and experimental results given. The design requirements for streak interferometry and for holography are also considered.

Some laser interferometers for use in fluid mechanics

The design of interferometers for use in aerodynamic research has been determined partly by the need to use short exposure times. Very bright light is essential, and with normal sources this means that the source must have appreciable size and spectral bandwidth. This leads to many restrictions on the design of the interferometer. The present paper shows that with laser sources these restrictions may be removed. Several appropriate designs are discussed, some being simplified versions of types already in use while others have not previously been described. All depend for their success on the coherence of the laser light source.