The Stokes force on a droplet in an unbounded fluid medium due to capillary effects

Fundamental issues relative to structural vibration and to scattering of sound from structures with imprecisely known internals are explored, with the master structure taken as a rectangular plate in a rigid baffle, which faces an unbounded fluid medium on the external side. On the internal side is a fuzzy structure, consisting of a random array of point-attached spring-mass systems. The theory predicts that the fuzzy internal structure can be approximated by a statistical average in which the only relevant property is a function mF(Ω) which gives a smoothed-out total mass, per unit plate area, of all those attached oscillators which have their natural frequencies less than a given value Ω. The theory also predicts that the exact value of the damping in the fuzzy structure is of little importance, because the structure, even in the limit of zero damping, actually absorbs energy with an apparent frequency-dependent damping constant proportional to dmF(W)/dω incorporated into the dynamical description of the master structure. A small finite value of damping within the internals will cause little appreciable change to this limiting value.

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Quality of ram spermatozoa separated with modified swim up method

Bangladesh Veterinarian ◽

10.3329/bvet.v33i2.36459 ◽

2018 ◽

Vol 33 (2) ◽

pp. 62-70 ◽

Cited By ~ 2

Author(s):

A Hossain ◽

MM Islam ◽

F Naznin ◽

RN Ferdousi ◽

FY Bari ◽

...

Keyword(s):

Semen Quality ◽

Membrane Integrity ◽

Quality Parameters ◽

Fluid Medium ◽

Normal Morphology ◽

The Mean ◽

Mass Activity ◽

Fresh Semen ◽

Artificial Vagina

Semen was collected from four rams, using artificial vagina and viability%, motility% and plasma membrane integrity% were measured. Fresh ejaculates (n = 32) were separated by modified swim-up separation using modified human tubal fluid medium. Four fractions of supernatant were collected at 15-minute intervals. The mean volume, mass activity, concentration, motility%, viability%, normal morphology and membrane integrity% (HOST +ve) of fresh semen were 1.0 ± 0.14, 4.1 ± 0.1 × 109 spermatozoa/ml, 85.0 ± 1.3, 89.4 ± 1.0, 85.5 ± 0.7, 84.7 ± 0.5 respectively. There was no significant (P>0.05) difference in fresh semen quality parameters between rams. The motility%, viability% and HOST +ve % of first, second, third and fourth fractions were 53.4 ± 0.5, 68.2 ± 0.3, 74.8 ± 0.3 and 65.5 ± 0.4; 55.5 ± 0.4, 66.2 ± 0.4, 74.5 ± 0.3 and 73.6 ± 0.3 and 66.7 ± 0.5, 66.8 ± 0.5, 65.2 ± 0.4 and 74.7 ± 0.5 respectively. The motility%, viability% and membrane integrity% of separated semen samples differed significantly (P<0.05) between four fractions. The mean motility% and viability% were significantly higher (P<0.05) in third fraction (74.8 ± 0.3%), whereas the mean HOST +ve% was significantly higher (P<0.05) in fourth fraction (74.7 ± 0.5). All quality parameters of separated spermatozoa were significantly (P<0.05) lower than that of fresh semen. The pregnancy rates were higher with fresh semen (71%) in comparison to that of separated sample (57%).Bangl. vet. 2016. Vol. 33, No. 2, 62-70

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Hamiltonian Aspects of Three-Layer Stratified Fluids

Journal of Nonlinear Science ◽

10.1007/s00332-021-09726-0 ◽

2021 ◽

Vol 31 (4) ◽

Author(s):

R. Camassa ◽

G. Falqui ◽

G. Ortenzi ◽

M. Pedroni ◽

T. T. Vu Ho

Keyword(s):

Hamiltonian Structure ◽

Linear Equations ◽

Hamiltonian Formalism ◽

Reduction Process ◽

Ideal Fluids ◽

Upper Lid ◽

Stratification Structure ◽

Special Solutions ◽

Dispersionless Limit ◽

Unbounded Fluid

AbstractThe theory of three-layer density-stratified ideal fluids is examined with a view toward its generalization to the n-layer case. The focus is on structural properties, especially for the case of a rigid upper lid constraint. We show that the long-wave dispersionless limit is a system of quasi-linear equations that do not admit Riemann invariants. We equip the layer-averaged one-dimensional model with a natural Hamiltonian structure, obtained with a suitable reduction process from the continuous density stratification structure of the full two-dimensional equations proposed by Benjamin. For a laterally unbounded fluid between horizontal rigid boundaries, the paradox about the non-conservation of horizontal total momentum is revisited, and it is shown that the pressure imbalances causing it can be intensified by three-layer setups with respect to their two-layer counterparts. The generator of the x-translational symmetry in the n-layer setup is also identified by the appropriate Hamiltonian formalism. The Boussinesq limit and a family of special solutions recently introduced by de Melo Viríssimo and Milewski are also discussed.

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Regarding Corrections to the Stokes Force in the Knudsen Number

Russian Physics Journal ◽

10.1007/s11182-021-02282-w ◽

2021 ◽

Vol 63 (12) ◽

pp. 2122-2140

Author(s):

S. O. Gladkov ◽

Zaw Aung

Keyword(s):

Knudsen Number ◽

Stokes Force

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Disruption of inositol biosynthesis through targeted mutagenesis in Dictyostelium discoideum: generation and characterization of inositol-auxotrophic mutants

Biochemical Journal ◽

10.1042/bj20060277 ◽

2006 ◽

Vol 397 (3) ◽

pp. 509-518 ◽

Cited By ~ 11

Author(s):

Andreas Fischbach ◽

Stephan Adelt ◽

Alexander Müller ◽

Günter Vogel

Keyword(s):

Dictyostelium Discoideum ◽

Genetic Manipulation ◽

Inositol Phosphate ◽

Targeted Mutagenesis ◽

Inositol Polyphosphate ◽

Fluid Medium ◽

Physiological Processes ◽

Evolutionarily Conserved ◽

Cellular Slime

myo-Inositol and its downstream metabolites participate in diverse physiological processes. Nevertheless, considering their variety, it is likely that additional roles are yet to be uncovered. Biosynthesis of myo-inositol takes place via an evolutionarily conserved metabolic pathway and is strictly dependent on inositol-3-phosphate synthase (EC 5.5.1.4). Genetic manipulation of this enzyme will disrupt the cellular inositol supply. Two methods, based on gene deletion and antisense strategy, were used to generate mutants of the cellular slime mould Dictyostelium discoideum. These mutants are inositol-auxotrophic and show phenotypic changes under inositol starvation. One remarkable attribute is their inability to live by phagocytosis of bacteria, which is the exclusive nutrient source in their natural environment. Cultivated on fluid medium, the mutants lose their viability when deprived of inositol for longer than 24 h. Here, we report a study of the alterations in the first 24 h in cellular inositol, inositol phosphate and phosphoinositide concentrations, whereby a rapidly accumulating phosphorylated compound was detected. After its identification as 2,3-BPG (2,3-bisphosphoglycerate), evidence could be found that the internal disturbances of inositol homoeostasis trigger the accumulation. In a first attempt to characterize this as a physiologically relevant response, the efficient in vitro inhibition of a D. discoideum inositol-polyphosphate 5-phosphatase (EC 3.1.3.56) by 2,3-BPG is presented.

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On the anisotropic response of a Janus drop in a shearing viscous fluid

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.148 ◽

2015 ◽

Vol 770 ◽

Cited By ~ 3

Author(s):

Misael Díaz-Maldonado ◽

Ubaldo M. Córdova-Figueroa

Keyword(s):

Shear Flow ◽

Velocity Gradient ◽

External Flow ◽

Bodies Of Revolution ◽

Internal Interface ◽

Equal Radius ◽

Fluid Drop ◽

Resistance Matrix ◽

Shearing Motion ◽

Unbounded Fluid

The force and couple that result from the shearing motion of a viscous, unbounded fluid on a Janus drop are the subjects of this investigation. A pair of immiscible, viscous fluids comprise the Janus drop and render it with a ‘perfect’ shape: spherical with a flat, internal interface, in which each constituent fluid is bounded by a hemispherical domain of equal radius. The effect of the arrangement of the internal interface (drop orientation) relative to the unidirectional shear flow is explored within the Stokes regime. Projection of the external flow into a reference frame centred on the drop simplifies the analysis to three cases: (i) a shear flow with a velocity gradient parallel to the internal interface, (ii) a hyperbolic flow, and (iii) two shear flows with a velocity gradient normal to the internal interface. Depending on the viscosity of the internal fluids, the Janus drop behaves as a simple fluid drop or as a solid body with broken fore and aft symmetry. The resultant couple arises from both the straining and swirling motions of the external flow in analogy with bodies of revolution. Owing to the anisotropic resistance of the Janus drop, it is inferred that the drop can migrate lateral to the streamlines of the undisturbed shear flow. The grand resistance matrix and Bretherton constant are reported for a Janus drop with similar internal viscosities.

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Transient Interaction of a Circular Plate and a Fluid Medium

Journal of Applied Mechanics ◽

10.1115/1.3424523 ◽

1979 ◽

Vol 46 (1) ◽

pp. 26-30 ◽

Cited By ~ 2

Author(s):

J. W. Berglund

Keyword(s):

Boundary Conditions ◽

Circular Plate ◽

Applied Pressure ◽

Plate Boundary ◽

Fluid Medium ◽

Fluid Field ◽

Elastic Circular Plate ◽

Unstrained State ◽

State Of Rest ◽

Acoustic Fluid

The transient dynamic response of an elastic circular plate subjected to a suddenly applied pressure is determined for several edge boundary conditions. The plate boundary is attached to a semi-infinite, radially rigid tube which is filled with an acoustic fluid, and pressure is applied to the in-vacuo side of the plate. The transient solution is determined by using a technique in which the plate is subjected to a periodic pressure function constructed of appropriately signed and time-shifted Heaviside step functions, and by relying on a physical mechanism which returns the plate and fluid near the plate to an unstrained state of rest between pulses. The plate response is presented for a number of radius-to-thickness ratios and edge boundary conditions when interacting with water. Comparisons are also made with solutions obtained using a plane wave approximation to the fluid field.

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The Scattering of Shock Waves by Cylindrical Cavities in Liquids and Solids

Journal of Applied Mechanics ◽

10.1115/1.3408742 ◽

1971 ◽

Vol 38 (1) ◽

pp. 190-196 ◽

Cited By ~ 1

Author(s):

E. Y. Harper

Keyword(s):

Shock Wave ◽

Asymptotic Expansion ◽

Shielding Effect ◽

Inviscid Fluid ◽

Shadow Region ◽

Shock Diffraction ◽

Fluid Medium ◽

Acoustic Shock Wave ◽

Cylindrical Cavities ◽

Logarithmic Decay

The scattering of a plane acoustic shock wave by a cylindrical cavity in an inviscid fluid medium is calculated numerically and compared with a recently obtained asymptotic expansion. In contrast to the scattering by a rigid cylinder, the cavity displays a distinctive shielding effect in the shadow region characterized by a peak exitation and an inverse logarithmic decay. Experimental results are presented which indicate a strong counterpart in plastic shock diffraction.

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