On exact solutions of the unsteady navierstokes equationsâ the vortex with instantaneous curvilinear axis

The unsteady pseudo plane motions have been investigated in which each point of the parallel planes is subjected to non-torsional oscillations in their own plane and at any given instant the streamlines are concentric circles. Exact solutions are obtained and the form of the curve , the locus of the centers of these concentric circles, is discussed. The existence of three infinite sets of exact solutions, for the flow in the geometry of an orthogonal rheometer in which the above non-torsional oscillations are superposed on the disks, is established. Three cases arise according to whether is greater than, equal to or less than , where is angular velocity of the basic rotation and is the frequency of the superposed oscillations. For a symmetric solution of the flow these solutions reduce to a single unique solution. The nature of the curve is illustrated graphically by considering an example of the flow between coaxial rotating disks.

Stresses around reinforced curvilinear holes in spherical shells

A perturbation technique is used to determine the stress concentration around reinforced curvilinear holes in thin pressurized spherical shells. Starting from the governing differential equations for thin shallow spherical shells, a solution is first obtained for a circular hole. The solution for an arbitrary shaped curvilinear hole is then obtained as a first-order perturbation over the circular hole solution using the conformal mapping technique. The effects of a large number of parameters involved in the design of a reinforcement around cutouts in shells are studied. The problems of symmetric and eccentric reinforcements are also considered. The results obtained would be very helpful in the design of an efficient reinforcement for elliptical and square holes in thin shallow spherical shells.

The Equations of Equilibrium in Orthogonal Curvilinear Reference Coordinates

Analytical solutions to problems in finite elasticity are most often derived using the semi-inverse approach along with the spatial form of the equations of motion involving the Cauchy stress tensor. This procedure is somewhat indirect since the spatial equations involve derivatives with respect to spatial coordinates while the unknown functions are in terms of material coordinates, thus necessitating the use of the chain rule. In this classroom note, we derive compact expressions for the components of the divergence, with respect to orthogonal material coordinates, of the first Piola-Kirchhoff stress tensor. The spatial coordinate system is also assumed to be an orthogonal curvilinear one, although, not necessarily of the same type as the material coordinate system. We show by means of some example applications how analytical solutions can be derived more directly using the derived results.

Microbial L-phenylalanine ammonia-lyase. Purification, subunit structure and kinetic properties of the enzyme from Rhizoctonia solani

Phenylalanine ammonia-lyase (EC 4.3.1.5) was purified to homogeneity from the acetone-dried powders of the mycelial felts of the plant pathogenic fungus Rhizoctonia solani. 2. A useful modification in protamine sulphate treatment to get substantial purification of the enzyme in a single-step is described. 3. The purified enzyme shows bisubstrate activity towards L-phenylalanine and L-tyrosine. 4. It is sensitive to carbonyl reagents and the inhibition is not reversed by gel filtration. 5. The molecular weight of the enzyme as determined by Sephadex G-200 chromatography and sucrose-density-gradient centrifugation is around 330000. 6. The enzyme is made up of two pairs of unidentical subunits, with a molecular weight of 70000 (alpha) and 90000 (beta) respectively. 7. Studies on initial velocity versus substrate concentration have shown significant deviations from Michaelis-Menten kinetics. 8. The double-reciprocal plots are biphasic (concave downwards) and Hofstee plots show a curvilinear pattern. 9. The apparent Km value increases from 0.18 mM to as high as 5.0 mM with the increase in the concentration of the substrate and during this process the Vmax, increases by 2-2.5-fold. 10. The value of Hill coefficient is 0.5. 11. Steady-state rates of phenylalanine ammonia-lyase reaction in the presence of inhibitors like D-phenylalanine, cinnamic, p-coumaric, caffeic, dihydrocaffeic and phenylpyruvic acid have shown that only one molecule of each type of inhibitor binds to a molecule of the enzyme. These observations suggest the involvement of negative homotropic interactions in phenylalanine ammonia-lyase. 12. The enzyme could not be desensitized by treatment with HgCl2, p-chloromercuribenzoic acid or by repeated freezing and thawing.

Pentoxifylline induces hyperactivation and acrosome reaction in spermatozoa of golden hamsters: changes in motility kinematics

Pentoxifylline (PF) is used to enhance motility of spermatozoa from infertile human subjects. We have previously shown that 0.45 mM PF improved capacitation of spermatozoa and fertilization of oocytes in vitro in hamsters. The present study was carried out to assess PF- induced changes in motility kinematics of hamster spermatozoa by a computer-aided sperm analyser (CASA) and determine the timing of onset of hyperactivation (HA) and acrosome reaction (AR) in PF-treated spermatozoa. Motility kinematics were analysed by CASA for 0-8 h in the absence or presence of 0.45 mM PF in Tyrode's medium supplemented with lactate, pyruvate and polyvinyl alcohol (TLP-PVA) or in TLP-PVA with bovine serum albumin (TALP-PVA). Conventional assessment was also made on the percentage of motility and quality of motility of spermatozoa; values were expressed as sperm motility index (SMI). Both in TALP-PVA and TLP-PVA, PF markedly increased SMI, especially the quality of motility (P < 0.02) by 2-3 h which was sustained up to 6 h. The motility kinematic data of PF-treated spermatozoa in TALP-PVA showed that average path velocity, curvilinear velocity and amplitude of lateral head displacement significantly (P < 0.05) increased as early as 2 h, with the expected decrease in straightness (STR) and linearity (LIN). Similar changes were also observed with PF-treated spermatozoa in TLP-PVA. Moreover, the percentage of hyperactivated spermatozoa in PF-treated samples was significantly (P < 0.001) higher than the untreated control at 2 h. To determine whether PF could induce AR, independent of bovine serum albumin, quantitative AR was assessed by observing the presence or absence of acrosomal cap on viable spermatozoa. PF significantly (P < 0.001) increased the percentage of AR as early as 2 h, reaching maximum at 4 h both in TALP-PVA (P < 0.05) and in TLP-PVA (P < 0.001). These results show that, in hamsters, PF induces early onset (by 2 h) of HA and AR and increases the proportion of spermatozoa undergoing physiological maturation.

Tyrphostin-A47 inhibitable tyrosine phosphorylation of flagellar proteins is associated with distinct alteration of motility pattern in hamster spermatozoa

To acquire fertilizing potential, mammalian spermatozoa must undergo capacitation and acrosome reaction. Our earlier work showed that pentoxifylline (0.45 mM), a sperm motility stimulant, induced an early onset of hamster sperm capacitation associated with tyrosine phosphorylation of 45-80 kDa proteins, localized to the mid-piece of the sperm tail. To assess the role of protein tyrosine phosphorylation in sperm capacitation, we used tyrphostin-A47 (TP-47), a specific protein tyrosine kinase inhibitor. The dose-dependent (0.1-0.5 mM) inhibition of tyrosine phosphorylation by TP-47 was associated with inhibition of hyperactivated motility and 0.5 mM TP-47-treated spermatozoa exhibited a distinct circular motility pattern. This was accompanied by hypo-tyrosine phosphorylation of 45-60 kDa proteins, localized to the principal piece of the intact-sperm and the outer dense fiber-like structures in detergent treated-sperm. Sperm kinematic analysis (by CASA) of spermatozoa, exhibiting circular motility (at 1st hr), showed lower values of straight line velocity, curvilinear velocity and average path velocity, compared to untreated controls. Other TP-47 analogues, tyrphostin-AG1478 and -AG1296, had no effect either on kinematic parameters or sperm protein tyrosine phosphorylation. These studies indicate that TP-47-induced circular motility of spermatozoa is compound-specific and that the tyrosine phosphorylation status of 45-60 kDa flagellum-localized proteins could be key regulators of sperm flagellar bending pattern, associated with the hyperactivation of hamster spermatozoa.

Water content - void ratio swell-shrink paths of compacted expansive soils

This paper addresses the behaviour of compacted expansive soils under swell-shrink cycles. Laboratory cyclic swell-shrink tests were conducted on compacted specimens of two expansive soils at surcharge pressures of 6.25, 50.00, and 100.00 kPa. The void ratio and water content of the specimens at several intermediate stages during swelling until the end of swelling and during shrinkage until the end of shrinkage were determined to trace the water content versus void ratio paths with an increasing number of swell-shrink cycles. The test results showed that the swell-shrink path was reversible once the soil reached an equilibrium stage where the vertical deformations during swelling and shrinkage were the same. This usually occurred after about four swell-shrink cycles. The swelling and shrinkage path of each specimen subjected to full swelling - full shrinkage cycles showed an S-shaped curve (two curvilinear portions and a linear portion). However, the swelling and shrinkage path occurred as a part of the S-shaped curve, when the specimen was subjected to full swelling - partial shrinkage cycles. More than 80% of the total volumetric change and more than 50% of the total vertical deformation occurred in the central linear portion of the S-shaped curve. The volumetric change was essentially parallel to the saturation line within a degree of saturation range of 50-80% for the equilibrium cycle. The primary value of the swell-shrink path is to provide information regarding the void ratio change that would occur for a given change in water content for any possible swell-shrink pattern. It is suggested that these swell-shrink paths can be established with a limited number of tests in the laboratory.

Turbulent flow computations using upwind RANS technique for a flat plate and an airfoil

Reynolds Averaged Navier Stokes (RANS) equations are solved using third order upwind biased Roe's scheme for the inviscid fluxes and second order central difference scheme for the viscous fluxes. The Baldwin & Lomax turbulence model is employed for Reynolds stresses. The governing equations are solved using finite-volume implicit scheme in body fitted curvilinear coordinate O-grid system. Computations axe reported for a flat plate apart from RAE 2822 and NACA 0012 airfoils. Results for the flat plate at M = 0.3, R-c = 4.0 x 10(6) compare favourably with the analytical solution. Results for the two airfoils are compared with experiment. There is a good agreement in C-p distribution between experiment and computation for both the airfoils. Comparison of C-f distribution with experiment for RAE 2822 airfoil is reasonable.

Correlation of Calcification on Excised Aortic Valves by Micro-Computed Tomography with Severity of Aortic Stenosis

Background and aim of the study: The quantification of incidentally found aortic valve calcification on computed tomography (CT) is not performed routinely, as data relating to the accuracy of aortic valve calcium for estimating the severity of aortic stenosis (AS) is neither consistent nor validated. As aortic valve calcium quantification by CT is confounded by wall and coronary ostial calcification, as well as motion artifact, the ex-vivo micro-computed tomography (micro-CT) of stenotic aortic valves allows a precise measurement of the amounts of calcium present. The study aim, using excised aortic valves from patients with confirmed AS, was to determine if the amount of calcium on micro-CT correlated with the severity of AS. Methods: Each of 35 aortic valves that had been excised from patients during surgical valve replacement were examined using micro-CT imaging. The amount of calcium present was determined by absolute and proportional values of calcium volume in the specimen. Subsequently, the correlation between calcium volume and preoperative mean aortic valve gradient (MAVG), peak transaortic velocity (V-max), and aortic valve area (AVA) on echocardiography, was evaluated. Results: The mean calcium volume across all valves was 603.2 +/- 398.5 mm(3), and the mean ratio of calcium volume to total valve volume was 0.36 +/- 0.16. The mean aortic valve gradient correlated positively with both calcium volume and ratio (r = 0.72, p <0.001). V-max also correlated positively with the calcium volume and ratio (r = 0.69 and 0.76 respectively; p <0.001). A logarithmic curvilinear model proved to be the best fit to the correlation. A calcium volume of 480 mm(3) showed sensitivity and specificity of 0.76 and 0.83, respectively, for a diagnosis of severe AS, while a calcium ratio of 0.37 yielded sensitivity and specificity of 0.82 and 0.94, respectively. Conclusion: A radiological estimation of calcium amount by volume, and its proportion to the total valve volume, were shown to serve as good predictive parameters for severe AS. An estimation of the calcium volume may serve as a complementary measure for determining the severity of AS when aortic valve calcification is identified on CT imaging. The Journal of Heart Valve Disease 2012;21:320-327

An automatic algorithm for mixed mode crack growth rate based on drop potential method

A new automatic algorithm for the assessment of mixed mode crack growth rate characteristics is presented based on the concept of an equivalent crack. The residual ligament size approach is introduced to implementation this algorithm for identifying the crack tip position on a curved path with respect to the drop potential signal. The automatic algorithm accounting for the curvilinear crack trajectory and employing an electrical potential difference was calibrated with respect to the optical measurements for the growing crack under cyclic mixed mode loading conditions. The effectiveness of the proposed algorithm is confirmed by fatigue tests performed on ST3 steel compact tension-shear specimens in the full range of mode mixities from pure mode Ito pure mode II. (C) 2015 Elsevier Ltd. All rights reserved.

Linking monazite geochronology with fluid infiltration and metamorphic histories: Nature and experiment

Migmatised metapelites from the Kodaikanal region, central Madurai Block, southern India have undergone ultrahigh-temperature metamorphism (950-1000 degrees C; 7-8 kbar). In-situ electron microprobe Th-U-Pb isochron (CHIME) dating of monazites in a leucosome and surrounding silica-saturated and silica-poor restites from the same outcrop indicates three principal ages that can be linked to the evolutionary history of these rocks. Monazite grains from the silica-saturated restite have well-defined, inherited cores with thick rims that yield an age of ca. 1684 Ma. This either dates the metamorphism of the original metapelite or is a detrital age of inherited monazite. Monazite grains from the silica-poor restite, thick rims from the silica-saturated restite, and monazite cores from the leucosome have ages ranging from 520 to 540 Ma suggesting a mean age of 530 Ma within the error bars. In the leucosome the altered rim of the monazite gives an age of ca. 502 Ma. Alteration takes the form of Th-depleted lobes of monazite with sharp curvilinear boundaries extending from the monazite grain rim into the core. We have replicated experimentally these altered rims in a monazite-leucosome experiment at 800 degrees C and 2 kbar. This experiment, coupled with earlier published monazite-fluid experiments involving high pH alkali-bearing fluids at high P-T, helps to confirm the idea that alkali-bearing fluids, in the melt and along grain boundaries during crystallization, were responsible for the formation of the altered monazite grain rims via the process of coupled dissolution-reprecipitation. (C) 2015 Elsevier B.V. All rights reserved.

Efficient coupled polynomial interpolation scheme for out-of-plane free vibration analysis of curved beams

The performance of two curved beam finite element models based on coupled polynomial displacement fields is investigated for out-of-plane vibration of arches. These two-noded beam models employ curvilinear strain definitions and have three degrees of freedom per node namely, out-of-plane translation (v), out-of-plane bending rotation (theta(z)) and torsion rotation (theta(s)). The coupled polynomial interpolation fields are derived independently for Timoshenko and Euler-Bernoulli beam elements using the force-moment equilibrium equations. Numerical performance of these elements for constrained and unconstrained arches is compared with the conventional curved beam models which are based on independent polynomial fields. The formulation is shown to be free from any spurious constraints in the limit of `flexureless torsion' and `torsionless flexure' and hence devoid of flexure and torsion locking. The resulting stiffness and consistent mass matrices generated from the coupled displacement models show excellent convergence of natural frequencies in locking regimes. The accuracy of the shear flexibility added to the elements is also demonstrated. The coupled polynomial models are shown to perform consistently over a wide range of flexure-to-shear (EI/GA) and flexure-to-torsion (EI/GJ) stiffness ratios and are inherently devoid of flexure, torsion and shear locking phenomena. (C) 2015 Elsevier B.V. All rights reserved.