Short-scale break-up in unsteady interactive layers: Local development of normal pressure gradients and vortex wind-up

Following the finite-time collapse of an unsteady interacting boundary layer (step 1), shortened length and time scales are examined here in the near-wall dynamics of transitional-turbulent boundary layers or during dynamic stall. The next two steps are described, in which (step 2) normal pressure gradients come into operation along with a continuing nonlinear critical-layer jump and then (step 3) vortex formation is induced typically. Normal pressure gradients enter in at least two ways, depending on the internal or external flow configuration. This yields for certain internal flows an extended KdV equation with an extra nonlinear integral contribution multiplied by a coefficient which is proportional to the normal rate of change of curvature of the velocity profile locally and whose sign turns out to be crucial. Positive values of the coefficient lead to a further finite-time singularity, while negative values produce a rapid secondary instability phenomenon. Zero values in contrast allow an interplay between solitary waves and wave packets to emerge at large scaled times, this interplay eventually returning the flow to its original, longer, interactive, boundary-layer scales but now coupled with multiple shorter-scale Euler regions. In external or quasi-external flows more generally an extended Benjamin–Ono equation holds instead, leading to a reversal in the roles of positive and negative values of the coefficient. The next step, 3, typically involves the strong wind-up of a local vortex, leading on to explosion or implosion of the vortex. Further discussion is also presented, including the three-dimensional setting, the computational implications, and experimental links

Boger fluid flow through hyperbolic contraction microchannels

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Boger fluids are characterized by their constant viscosity and elasticity and are very useful to study pure elastic flow behavior. In this paper we assess the potential of a microfluidic hyperbolic contraction as a device to measure the relaxation time of low viscosity polymer solutions, which are difficult to characterize in a conventional capillary break-up extensional rheometer. For this purpose we initially characterize the shear and extensional rheology of aqueous solutions of polyacrylamide (PAA) at different concentrations (400, 250, 125 and 50 ppm) with 1% (w/w) of NaCl, which result in low viscosity Boger fluids. Subsequently, flow visualizations of their flow through a microfluidic hyperbolic contraction were carried out in order to quantify the relation between their degree of elasticity and the vortex growth upstream of the microchannel.Fundação para a Ciência e a Tecnologia (FCT), COMPETE and FEDER through projects PTDC/ EQU-FTT/ 71800/2006, PTDC/EQUFTT/ 70727/2006, PTDC/EME-MFE/099109/ 2008, REEQ/928/EME/2005 and REEQ/298/EME/2005

Architecture of coatomer: Molecular characterization of delta-COP and protein interactions within the complex

Copyright © 2011 by The Rockefeller University Press.Coatomer is a cytosolic protein complex that forms the coat of COP I-coated transport vesicles. In our attempt to analyze the physical and functional interactions between its seven subunits (coat proteins, [COPs] alpha-zeta), we engaged in a program to clone and characterize the individual coatomer subunits. We have now cloned, sequenced, and overexpressed bovine alpha-COP, the 135-kD subunit of coatomer as well as delta-COP, the 57-kD subunit and have identified a yeast homolog of delta-COP by cDNA sequence comparison and by NH2-terminal peptide sequencing. delta-COP shows homologies to subunits of the clathrin adaptor complexes AP1 and AP2. We show that in Golgi-enriched membrane fractions, the protein is predominantly found in COP I-coated transport vesicles and in the budding regions of the Golgi membranes. A knock-out of the delta-COP gene in yeast is lethal. Immunoprecipitation, as well as analysis exploiting the two-hybrid system in a complete COP screen, showed physical interactions between alpha- and epsilon-COPs and between beta- and delta-COPs. Moreover, the two-hybrid system indicates interactions between gamma- and zeta-COPs as well as between alpha- and beta' COPs. We propose that these interactions reflect in vivo associations of those subunits and thus play a functional role in the assembly of coatomer and/or serve to maintain the molecular architecture of the complex.This work was supported by The Deutsche Forschungsgemeinschaft (SFB 352), the Human Frontier Science Program, and the Swiss National Science Foundation No. 31-43366.95

Microchannels analogues for the study of viscoelastic fluid flows through porous media

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.This work studies the flow behavior and related pressure losses of viscoelastic polymer solutions in microchannels with two different sequences of contraction/expansion, disposed in a symmetric and an asymmetric arrangement, respectively. These microfluidic devices are proposed as simplified microchannel analogues for the flow of Newtonian and viscoelastic fluids through porous media. The results show that the symmetric configuration mimics the pressure gradient of these polymer solutions through a porous medium at low flow rates (below a critical Deborah number, Decr), while the asymmetric arrangement gives the asymptotic limit at high De values (above Decr) as a consequence of the intrinsic differences in the extensional rate profiles defined by each microgeometry.Fundação para a Ciência e a Tecnologia (FCT), COMPETE and FEDER through projects PTDC/ EQU-FTT/ 71800/ 2006, PTDC/EQUFTT/ 70727/ 2006, PTDC/ EME-MFE/ 99109/ 2008 and REEQ/ 262/ EME/ 2005

Geographical trends in research: a preliminary analysis on authors' affiliations

In the last decade, research literature reached an enormous volume with an unprecedented current annual increase of 1.5 million new publications. As research gets ever more global and new countries and institutions, either from academia or corporate environment, start to contribute with their share, it is important to monitor this complex scenario and understand its dynamics. We present a study on a conference proceedings dataset extracted from Springer Nature Scigraph that illustrates insightful geographical trends and highlights the unbalanced growth of competitive research institutions worldwide. Results emerged from our micro and macro analysis show that the distributions among countries of institutions and papers follow a power law, and thus very few countries keep producing most of the papers accepted by high-tier conferences. In addition, we found that the annual and overall turnover rate of the top 5, 10 and 25 countries is extremely low, suggesting a very static landscape in which new entries struggle to emerge. Finally, we highlight the presence of an increasing gap between the number of institutions initiating and overseeing research endeavours (i.e. first and last authors' affiliations) and the total number of institutions participating in research. As a consequence of our analysis, the paper also discusses our experience in working with affiliations: an utterly simple matter at first glance, that is instead revealed to be a complex research and technical challenge yet far from being solved

Determination of vectorial potential of Mansonia species in the transmission of Wuchereria bancrofti in Tana-Delta District, Coast-Kenya

Background: Wuchereria bancrofti are parasites causing bancroftian filariasis which is transmitted by different species of mosquitoes. Mosquitoes of Anopheles, Culex and Aedes species are known to transmit W. bancrofti parasites.Objective: To determining the potential of Mansonia species; Ma. africanus and Ma. uniformis in the transmission of W. bancrofti.Design: Cross sectional study.Setting: Villages in Tana Delta district, Kenya.Subjects: In-door collected mosquitoes.Results: A total of one thousand, six hundred and sixty two (1632) female mosquitoes were collected by gravid traps, CDC light traps and Pyrethrum spray methods. Of these, 236 representing 14.5% were identified as Mansonia species. Two filarial larvae of stage two (L2) were obtained from the dissected mosquitoes. Polymerase chain reaction assays did not show any amplified W. bancrofti DNA from the obtained larvae or the mosquitoes.Conclusion: There was no evidence that Mansonia species play a role in the transmission of W. bancrofti

Unit Automatic Main Failure (Amf) Power System Sebagai Sarana Up-dating Kompetensi Guru-guru Smk Jurusan Listrik

Prediction of electrical energy crisis in Indonesia clearly will cause losses for electricity consumers. The impact caused the activities disturb include production systems, loss of business opportunities, and loss of property intellectuals (for example, data lost), especially for the scientists and academics. Customers require backup supply of electricity when PLN have some trouble. However, switching supplies electricity to Genset, if done in a conventional addition that requires the existence of the operator, but also through a complex procedure and takes a long time. Therefore need to use an automation tool that supplies electricity more practical and economical, and can be used as a medium of education, and will solve the problem of scarcity of human resources automation field, such as the electricity supply at this time. Expected performance of these tools is able to activate the genset manually or automatically in case of interruption of supply electricity, the Power Loss, Under Voltage, Lower Voltage, frequency interference. All activities since the design to the test conducted in the Laboratory of Electrical Installation and Laboratory Data Communications, Department of Educational Electrical Engineering FT UNY. The method of this experiment is a Research and Development, and experimental data taken according to the research instrument. The data obtained and analyzed using descriptive. The result that activity is the Unit of AMF Power System based on microcontroller that is ready as a medium of education, both in the Department of Educational Electrical Engineering FT UNY and Technical High School. However, this tool only can detect the interference of Under Voltage and Upper Voltage, while the interference of frequency and the condition of fuel can not be carried out due to various technical constraints. Alamat Korespondensi: Zamtinah Jurusan Pendidikan Teknik Elektro-Fakultas Teknik Universitas Negeri Yogyakarta. Karangmalang Yogyakarta. 55281. HP. 081328797306 e-mail: [email protected]

Développement des unités de croissance de jeunes plants d’essences sahéliennes : Acacia tortilis (Forsk.) Hayne subsp.raddiana (Savi) Brenan, de Balanites aegyptiaca (L.) Del et de Zizyphus mauritiana Lam., (Dakar, Sénégal)

Malgré les usages multiples des plantes ligneuses du Sahel, peu d’études se sont intéressées au suivi de la mise en place des différents segments de tige de jeunes plants de Acacia tortilis (Forsk.) Haynesubsp.raddiana (Savi) Brenan, de Balanites aegyptiaca (L.) Del et de Zizyphus mauritiana Lam. Notre objectif était alors de représenter les différents ordres, leur nombre en fonction de leur période d’apparition et le rapport entre le développement successif des Unités de Croissance (UC) des jeunes plants de A. tortilis, de B. aegyptiaca et de Z. mauritiana a été suivi en milieu semi-contrôlé par une approche visuelle globale à l’échelle du houppier entre octobre 2002 et octobre 2004. Les processus de ramification à l’échelle du houppier révèlent 5 ordres différents d’UC chez A. tortilisà 16 mois, 7 chez B. aegyptiaca à 24 mois et 5 chez Z. mauritiana à 9 mois. Les UC3 et UC4 sont les plus nombreuses chez les jeunes plants de B.aegyptiaca et Z.mauritiana alors que chez ceux de A.tortilis, le nombre des UC2 est nettement supérieur. L’UC1 est la plus longue chez les trois espèces. Le diamètre de l’UC1 à 24 mois est de 79 mm chez B. aegyptiaca, de 39 mm chez Z. mauritiana et de 20 mm chez A. tortilis avec un nombre de noeuds nettement plus important chez A. tortilis. La longueur et le nombre de noeuds feuillés varient d’une espèce à l’autre.Mots-clés : Acaciatortilis, Balanites aegyptiaca, Zizyphusmauritiana, jeune plant, unité de croissance (UC),noeuds

The instantaneous helical axis of the subtalar and talocrural joints: a non-invasive in vivo dynamic study

<p>Abstract</p> <p>Background</p> <p>An understanding of rear-foot (talocrural and subtalar joints) kinematics is critical for diagnosing foot pathologies, designing total ankle implants, treating rear-foot injuries and quantifying gait abnormalities. The majority of kinematic data available have been acquired through static cadaver work or passive <it>in vivo </it>studies. The applicability of these data to dynamic <it>in vivo </it>situations remains unknown. Thus, the purpose of this study was to fully quantify subtalar, talocrural and calcaneal-tibial <it>in vivo </it>kinematics in terms of the instantaneous helical axis (IHA) in twenty-five healthy ankles during a volitional activity that simulated single-leg toe-raises with partial-weight support, requiring active muscle control.</p> <p>Methods</p> <p>Subjects were each placed supine in a 1.5 T MRI and asked to repeat this simulated toe-raise while a full sagittal-cine-phase contrast (dynamic) MRI dataset was acquired. From the cine-phase contrast velocity a full kinematic description for each joint was derived.</p> <p>Results</p> <p>Nearly all motion quantified at the calcaneal-tibial joint was attributable to the talocrural joint. The subtalar IHA orientation and position were highly variable; whereas, the talocrural IHA orientation and position were extremely consistent.</p> <p>Conclusion</p> <p>The talocrural was well described by the IHA and could be modeled as a fixed-hinge joint, whereas the subtalar could not be.</p

Wake Development behind Paired Wings with Tip and Root Trailing Vortices: Consequences for Animal Flight Force Estimates

Recent experiments on flapping flight in animals have shown that a variety of unrelated species shed a wake behind left and right wings consisting of both tip and root vortices. Here we present an investigation using Particle Image Velocimetry (PIV) of the behaviour and interaction of trailing vortices shed by paired, fixed wings that simplify and mimic the wake of a flying animal with a non-lifting body. We measured flow velocities at five positions downstream of two adjacent NACA 0012 aerofoils and systematically varied aspect ratio, the gap between the wings (corresponding to the width of a non-lifting body), angle of attack, and the Reynolds number. The range of aspect ratios and Reynolds number where chosen to be relevant to natural fliers and swimmers, and insect flight in particular. We show that the wake behind the paired wings deformed as a consequence of the induced flow distribution such that the wingtip vortices convected downwards while the root vortices twist around each other. Vortex interaction and wake deformation became more pronounced further downstream of the wing, so the positioning of PIV measurement planes in experiments on flying animals has an important effect on subsequent force estimates due to rotating induced flow vectors. Wake deformation was most severe behind wings with lower aspect ratios and when the distance between the wings was small, suggesting that animals that match this description constitute high-risk groups in terms of measurement error. Our results, therefore, have significant implications for experimental design where wake measurements are used to estimate forces generated in animal flight. In particular, the downstream distance of the measurement plane should be minimised, notwithstanding the animal welfare constraints when measuring the wake behind flying animals