Hydrodynamic slippage of water at surfaces

2017 ◽  
Author(s):  
E. Charlaix ◽  
L. Bocquet
Keyword(s):  
Boundary Condition ◽  
Molecular Mechanisms ◽  
Slip Length ◽  
Molecular Simulations ◽  
Short Review ◽  
Solid Surfaces ◽  
Experimental Investigations

The boundary condition (B.C.) for hydrodynamic flows at solid surfaces is usually assumed to be that of no slip. However a number of molecular simulations and experimental investigations over the last two decades have demonstrated violations of the no-slip B.C., leading to hydrodynamic slippage at solid surfaces. In this short review, we explore the molecular mechanisms leading to hydrodynamic slippage of water at various surfaces and discuss experimental investigations allowing us to measure the so-called slip length

scholarly journals Structure and dynamics of the E. coli chemotaxis core signaling complex by cryo-electron tomography and molecular simulations

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
C. Keith Cassidy ◽  
Benjamin A. Himes ◽  
Dapeng Sun ◽  
Jun Ma ◽  
Gongpu Zhao ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Electron Tomography ◽  
Conformational Dynamics ◽  
Molecular Simulations ◽  
Adaptor Protein ◽  
Signaling Mechanism ◽  
E Coli ◽  
Signaling Complex ◽  
Chemical Gradients ◽  
Cryo Electron Tomography

AbstractTo enable the processing of chemical gradients, chemotactic bacteria possess large arrays of transmembrane chemoreceptors, the histidine kinase CheA, and the adaptor protein CheW, organized as coupled core-signaling units (CSU). Despite decades of study, important questions surrounding the molecular mechanisms of sensory signal transduction remain unresolved, owing especially to the lack of a high-resolution CSU structure. Here, we use cryo-electron tomography and sub-tomogram averaging to determine a structure of the Escherichia coli CSU at sub-nanometer resolution. Based on our experimental data, we use molecular simulations to construct an atomistic model of the CSU, enabling a detailed characterization of CheA conformational dynamics in its native structural context. We identify multiple, distinct conformations of the critical P4 domain as well as asymmetries in the localization of the P3 bundle, offering several novel insights into the CheA signaling mechanism.

Examination of the Slip Boundary Condition by µ-PIV and Lattice Boltzmann Simulations

2002 ◽  
Author(s):  
Derek C. Tretheway ◽  
Luoding Zhu ◽  
Linda Petzold ◽  
Carl D. Meinhart
Keyword(s):  
Boundary Condition ◽  
Shear Rate ◽  
Channel Flow ◽  
Lattice Boltzmann ◽  
Slip Velocity ◽  
Slip Length ◽  
Slip Boundary Condition ◽  
Slip Boundary ◽  
Lattice Boltzmann Simulations ◽  
Bounce Back

This work examines the slip boundary condition by Lattice Boltzmann simulations, addresses the validity of the Navier’s hypothesis that the slip velocity is proportional to the shear rate and compares the Lattice Boltzmann simulations to the experimental results of Tretheway and Meinhart (Phys. of Fluids, 14, L9–L12). The numerical simulation models the boundary condition as the probability, P, of a particle to bounce-back relative to the probability of specular reflection, 1−P. For channel flow, the numerically calculated velocity profiles are consistent with the experimental profiles for both the no-slip and slip cases. No-slip is obtained for a probability of 100% bounce-back, while a probability of 0.03 is required to generate a slip length and slip velocity consistent with the experimental results of Tretheway and Meinhart for a hydrophobic surface. The simulations indicate that for microchannel flow the slip length is nearly constant along the channel walls, while the slip velocity varies with wall position as a results of variations in shear rate. Thus, the resulting velocity profile in a channel flow is more complex than a simple combination of the no-slip solution and slip velocity as is the case for flow between two infinite parallel plates.

scholarly journals Trisomy 21 and Down syndrome: a short review

2008 ◽  
Vol 68 (2) ◽  
pp. 447-452 ◽  
Author(s):  
CA. Sommer ◽  
F. Henrique-Silva
Keyword(s):  
Gene Expression ◽  
Down Syndrome ◽  
Large Scale ◽  
Molecular Mechanisms ◽  
Global Gene Expression ◽  
Short Review ◽  
Complex Disorder ◽  
Expression Studies ◽  
Gene Expression Studies ◽  
Chromosome Segments

Even though the molecular mechanisms underlying the Down syndrome (DS) phenotypes remain obscure, the characterization of the genes and conserved non-genic sequences of HSA21 together with large-scale gene expression studies in DS tissues are enhancing our understanding of this complex disorder. Also, mouse models of DS provide invaluable tools to correlate genes or chromosome segments to specific phenotypes. Here we discuss the possible contribution of HSA21 genes to DS and data from global gene expression studies of trisomic samples.

scholarly journals Noble Gas Bonding Interactions Involving Xenon Oxides and Fluorides

Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3419 ◽  
Author(s):  
Antonio Frontera
Keyword(s):  
Crystal Engineering ◽  
Lewis Acids ◽  
Noncovalent Interactions ◽  
Noble Gas ◽  
Physical Nature ◽  
Short Review ◽  
Experimental Investigations ◽  
Inorganic Crystal Structure Database ◽  
Systematic Nomenclature ◽  
Structural Database

Noble gas (or aerogen) bond (NgB) can be outlined as the attractive interaction between an electron-rich atom or group of atoms and any element of Group-18 acting as an electron acceptor. The IUPAC already recommended systematic nomenclature for the interactions of groups 17 and 16 (halogen and chalcogen bonds, respectively). Investigations dealing with noncovalent interactions involving main group elements (acting as Lewis acids) have rapidly grown in recent years. They are becoming acting players in essential fields such as crystal engineering, supramolecular chemistry, and catalysis. For obvious reasons, the works devoted to the study of noncovalent Ng-bonding interactions are significantly less abundant than halogen, chalcogen, pnictogen, and tetrel bonding. Nevertheless, in this short review, relevant theoretical and experimental investigations on noncovalent interactions involving Xenon are emphasized. Several theoretical works have described the physical nature of NgB and their interplay with other noncovalent interactions, which are discussed herein. Moreover, exploring the Cambridge Structural Database (CSD) and Inorganic Crystal Structure Database (ICSD), it is demonstrated that NgB interactions are crucial in governing the X-ray packing of xenon derivatives. Concretely, special attention is given to xenon fluorides and xenon oxides, since they exhibit a strong tendency to establish NgBs.

scholarly journals Impinging jets – a short review on strategies for heat transfer enhancement

2018 ◽  
Vol 32 ◽  
pp. 01013
Author(s):  
Ilinca Nastase ◽  
Florin Bode
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Short Review ◽  
Great Difficulty ◽  
Impinging Jets ◽  
Industrial Applications ◽  
Experimental Investigations ◽  
Small Scale ◽  
Strong Shear ◽  
Flow Phenomena

In industrial applications, heat and mass transfer can be considerably increased using impinging jets. A large number of flow phenomena will be generated by the impinging flow, such as: large scale structures, large curvature involving strong shear and normal stresses, stagnation in the wall boundary layers, heat transfer with the impinged wall, small scale turbulent mixing. All these phenomena are highly unsteady and even if nowadays a substantial number of studies in the literature are dedicated, the impinging jets are still not fully understood due to the highly unsteady nature and more over due to great difficulty of performing detailed numerical and experimental investigations.

scholarly journals Training for genes - how to design it?

2017 ◽  
Vol 70 (7-8) ◽  
pp. 227-233
Author(s):  
Jelena Popadic-Gacesa
Keyword(s):  
Athletic Training ◽  
Molecular Mechanisms ◽  
Ethical Issues ◽  
Short Review ◽  
Nucleotide Polymorphisms ◽  
Training Design ◽  
Muscle Adaptation ◽  
Genetic Traits ◽  
Genetic Profiling ◽  
Wide Range

Introduction. The aim of this short review was not to be just another systematic report, but to highlight further research hypotheses regarding the challenges in performance genomics by focusing on three papers published in 2016, which offer innovative and promising approach that would be a breakthrough in more exact application of genetic data in practical work of sports experts and training design. Genes for sports. More than 200 single nucleotide polymorphisms and genetic traits associated with fitness performance have been reported in numerous studies, but genes for angiotensin converting enzyme and alpha-actinin-3 are most frequently associated with enhanced physical performance. Perspectives of epigenetics. Genotype-phenotype interactions include a wide range of molecular mechanisms with complex effects and interconnections. Gene adjusted training protocols. Using genetic profiling to match individual genotype with appropriate training modality may be a powerful tool providing personalized athletic training in the future. Conclusion. When applying genetic profiling prior to and during training programs, special consideration should be made to avoid athlete selection; it should be only used for inclusion, not for exclusion. Also, attention must be paid to social and ethical issues. Wider approach should include training interventional studies and non-athletic population in discovering new molecular pathways of muscle adaptation to exercise through genotype-phenotype interactions.

Slip Length–Based Boundary Condition for Modeling Drag Reduction Devices

AIAA Journal ◽  
2018 ◽  
Vol 56 (9) ◽  
pp. 3478-3490 ◽  
Author(s):  
Benedetto Mele ◽  
Renato Tognaccini
Keyword(s):  
Boundary Condition ◽  
Drag Reduction ◽  
Slip Length

Dispersion due to Electroosmotic Flow Through a Circular Tube With Axial Step Changes of Zeta Potential and Hydrodynamic Slippage

2013 ◽  
Author(s):  
Qi Zhou ◽  
Chiu-On Ng
Keyword(s):  
Boundary Condition ◽  
Zeta Potential ◽  
Dispersion Coefficient ◽  
Slip Length ◽  
Slip Boundary Condition ◽  
Axial Position ◽  
Hydrodynamic Dispersion ◽  
Lubrication Approximation ◽  
Slip Boundary ◽  
Zeta Potentials

The hydrodynamic dispersion of a neutral non-reacting solute due to steady electro-osmotic flow in a circular channel with longitudinal step changes of zeta potential and hydrodynamic slippage is analyzed in this study. The channel wall is periodically micro-patterned along the axial position with alternating slip-stick stripes of distinct zeta potentials. Existing studies on electrically driven hydrodynamic dispersion are based on flow subject to either the no-slip boundary condition on the capillary surface or the simplification of lubrication approximation. Taking wall slippage into account, a homogenization analysis is performed in this study to derive the hydrodynamic dispersion coefficient without subject to the long-wave constraint of the lubrication approximation, but for a general case where the length of one periodic unit of wall pattern is comparable with the channel radius. The flow and the hydrodynamic dispersion coefficient are calculated numerically, using the packages MATLAB and COMSOL, as functions of controlling parameters including the period length of the wall pattern, the area fraction of the slipping region (EOF-suppressing) in a periodic unit, the ratio of the two zeta potentials, the intrinsic hydrodynamic slip length, the Debye parameter, and the Péclet number. The dispersion coefficient is found to show notable, non-monotonic in certain situations, dependence on these controlling parameters. It is noteworthy that the introduction of hydrodynamic slippage will generate much richer behaviors of the hydrodynamic dispersion than the situation with no-slip boundary condition, as slippage interacts with zeta potentials in the EOF-suppressing and EOF-supporting regions (either likewise or oppositely charged).

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