Free convection about cylinders of elliptic cross section embedded in a porous medium

Numerical solutions are presented for the free convection boundary layers over cylinders of elliptic cross section embedded in a fluid-saturated porous medium. The transformed conservation equations of the nonsimilar boundary layers are solved numerically by an efficient finite-difference method. The theory was applied to a number of cylinders and the results compared very well with published analytical solutions. The results are of use in the design of underground electrical cables, power plant steam, and water distribution lines, among others.

Liquid-Liquid Interphase (Biphasic) as the Reaction Medium in the Assembly of a Hierarchy of Structures of 4,4 `-Azodibenzoic Acid with Zinc and Cadmium

The compounds Zn(C12H8N2)](2)C12N2H8(COO)(2)](2)center dot(C6H12O)center dot(H2O), I, Zn(C12H8N2)]C12N2H8(COO)(2)], II, Cd(C12H8N2)(H2O)]C12N2H8(COO)(2)]center dot(H2O), III, Zn(C10N2H8)]C12N2H8(COO)(2)]center dot 0.5(C10N2H8), IV, Cd(C12N2H8(COO)(2)center dot H2O], V, and Zn-3(mu(2)-O)(mu(3)-O)(3)]C12N2H8(COO)(2)], VI, have been synthesized by using a biphasic approach (I, III, V, VI) or regular hydrothermal method (II, IV). The compounds exhibit one (I and II), two (In), and three dimensionally (IV, V, VI) extended structures. The flexible azodibenzoate ligand gives rise to a 3-fold interpenetration (IV) when the synthesis was carried out using normal hydrothermal methods. The biphasic approach forms structures without any interpenetrations, especially in the three-dimensional structures of V and VI. Formation of Cd2O2 dimers in V and extended M-O(H)-M two-dimensional layers in VI suggests the subtle structural control achieved by the biphasic method. Transformation studies indicate that it is possible to transform I to II. Lewis acid catalytic studies have been performed to evaluate the role of the coordination environment in such reactions. All the compounds have been characterized by a variety of techniques that includes powder X-ray diffraction, infrared, thermogravitric analysis, UV-vis, photoluminescence studies.

Localization and release of ?-glucosidase in the thermophilic and cellulolytic fungus, Sporotrichum thermophile

In a medium containing cellulose as the carbon source, the rapid growth of Sporotrichum thermophile, the secretion of cellulases and the utilization of cellulose were well-correlated events. The production of beta-glucosidase in culture medium lagged behind cellulases, coinciding with the time of extensive autolysis of mycelia. By contrast, neither apparent autolysis nor secretion of beta-glucosidase occurred when S. thermophile was grown in medium containing cellobiose; the enzyme activity remained associated with mycelia. The release of beta-glucosidase in cellulose-grown cultures was correlated with the activity of the lytic enzyme in the cell wall. Immunocytochemical localization and biochemical characterization showed that a beta-glucosidase released in the cellulose medium was the same as that which remained associated with mycelia grown on cellobiose. The results indicated that the release of beta-glucosidase in the cellulose culture is incidental to the activity of the lytic enzymes which are strongly induced by cellulose. The observations minimize a functional role of the culture fluid beta-glucosidase in cellulolysis by the fungus. Rather, the available information suggests that the cellulases and beta-glucosidases associated with the hyphal cell wall may play a role in cellulolysis by the fungus. (C) 1994 Academic Press, Inc.

Heterogeneous permanganate oxidations: Synthesis of medium ring keto-lactones via substituent directed oxidative cyclisation

Homoallyl alcohols 4a-b and 5a-b undergo smooth oxidative cyclisation to give the corresponding ring enlarged keto-lactones under heterogeneous permanganate oxidation conditions.

Localization and release of β-glucosidase in the thermophilic and cellulolytic fungus, Sporotrichum thermophile

n a medium containing cellulose as the carbon source, the rapid growth of Sporotrichum thermophile, the secretion of cellulases and the utilization of cellulose were well-correlated events. The production of beta-glucosidase in culture medium lagged behind cellulases, coinciding with the time of extensive autolysis of mycelia. By contrast, neither apparent autolysis nor secretion of beta-glucosidase occurred when S. thermophile was grown in medium containing cellobiose; the enzyme activity remained associated with mycelia. The release of beta-glucosidase in cellulose-grown cultures was correlated with the activity of the lytic enzyme in the cell wall. Immunocytochemical localization and biochemical characterization showed that a beta-glucosidase released in the cellulose medium was the same as that which remained associated with mycelia grown on cellobiose. The results indicated that the release of beta-glucosidase in the cellulose culture is incidental to the activity of the lytic enzymes which are strongly induced by cellulose. The observations minimize a functional role of the culture fluid beta-glucosidase in cellulolysis by the fungus. Rather, the available information suggests that the cellulases and beta-glucosidases associated with the hyphal cell wall may play a role in cellulolysis by the fungus. (C) 1994 Academic Press, Inc.

Synthesis of Trilaurin by Developing Pisa Seeds (Actinodaphne hookeri)

The developing seeds of Actinodaphne hookeri were investigated to delineate their ability to synthesize large amounts of trilaurin. Until 88 days after flowering the embryos contained 71% neutral lipids (NL) and 29% phospholipids (PL) and both these components contained C-16:0, C-18:0, C-18:2, and C-18:3 as the major fatty acids (FA). At 102 days after flowering the seeds began to accumulate triacylglycerols (TAG) and to synthesize lauric acid (C-12:0). By 165 days after flowering, when the seeds were mature, they contained about 99% NL and 1% FL. At this stage the TAG contained exclusively C-12:0, while the PL consisted of long-chain fatty acids (LCFA) only. Leaf lipids in contrast did not contain any C-12:0. Experiments on [1-C-14]acetate incorporation into developing seed slices showed that at 88 days after flowering only 4% of the label was in TAG, 1% in diacylglycerols (DAG), and 87% in FL. One hundred two days after flowering seeds incorporated only 2% of the label into TAG, 30% into DAG, and 64% into FL. In contrast at 114 days after flowering 71% of the label was incorporated into TAG, 25% into DAG, and only 2% into FL. Analysis of labeled FA revealed that up to 102 days after flowering it was incorporated only into LCFA, whereas at 114 days after flowering it was incorporated exclusively into C-12:0. Furthermore, 67% of the label in PL at 114 days after flowering was found to be dilaurylglycerophosphate. Analysis of the label in DAG at this stage showed that it was essentially in dilaurin species. These observations indicate the induction of enzymes of Kennedy pathway for the specific synthesis of trilaurin at about 114 days after flowering, Homogenates of seeds (114 days after flowering) incubated with labeled FA in the presence of glycerol-3-phosphate and coenzymes A and ATP incorporated 84% of C-12:0 and 61% of C-14:0, but not C-16:0, C-18:2, and C-18:3, into TAG. In contrast the LCFA were incorporated preferentially into FL. It is concluded that, between 102 and 114 days after flowering, a switch occurs in A. hookeri for the synthesis of C-12:0 and trilaurin which is tissue specific. Since the seed synthesizes exclusively C-12:0 at 114 days after flowering onwards and incorporates specifically into TAG, this system appears to be ideal for identifying the enzymes responsible for medium-chain fatty acid as well as trilaurin synthesis and for exploiting them for genetic engineering. (C) 1994 Academic Press, Inc.

Colloidal dispersions in a liquid crystalline medium

We have prepared stable colloidal suspensions in a lyotropic liquid crystal exhibiting an isotropic-nematic-lamellar phase sequence. Small angle neutron scattering (SANS) and dynamic light scattering (DLS) studies show the existence of attractive interparticle interactions in the nematic phase, which lead to a gas-liquid transition of the particles. The resulting liquid phase is weakly anisotropic. Further, the nematic-lamellar transition of the liquid crystal is found to be accompanied by a liquid-solid transition of the particles.

Combined convection in power-law fluids along a nonisothermal vertical plate in a porous medium

The problem of combined convection from vertical surfaces in a porous medium saturated with a power-law type non-Newtonian fluid is investigated. The transformed conservation laws are solved numerically for the case of variable surface heat flux conditions. Results for the details of the velocity and temperature fields as well as the Nusselt number have been presented. The viscosity index ranged from 0.5 to 2.0.

Metal-Free Deprotection of Terminal Acetonides by Using tert-Butyl Hydroperoxide in Aqueous Medium

Employing aqueous tert-butyl hydroperoxide (70%) as an inexpensive reagent a useful methodology for the regioselective and chemoselective deprotection of terminal acetonide groups in aqueous medium is developed. A variety of acetonide derivatives on reaction with aqueous tert-butyl hydroperoxide in water:tert-butanol (1:1) furnish the corresponding acetonide deprotected diols in good yields. A large number of acid labile protecting functional groups and other functional moieties were found to be unaffected under the conditions employed for the present deprotection. This method has been successfully applied to sugar derivatives.

Experimental validation of the 1-D acoustical model for conical concentric tube resonators with moving medium

Variable cross-sectional area ducts are often used for attenuation at lower frequencies (of the order of firing frequency), whereas concentric tube resonators provide attenuation at relatively higher frequencies. In this paper, analysis of one dimensional control volume approach of conical concentric tube resonators is validated experimentally. The effects of mean flow and taper are investigated. The experimental setup is specially designed to measure the pressure transfer function in the form of Level Difference or Noise Reduction across the test muffler. It is shown that there is a reasonably good agreement between the predicted values of the Noise Reduction and the measured ones for incompressible mean flow as well as stationary medium. (C) 2011 Institute of Noise Control Engineering.

Mixed convection heat transfer from the bottom tip of a cylinder spinning about a vertical axis in a saturated porous medium

The present work is a numerical study of heat transfer characteristics from the bottom tip of a cylinder spinning about a vertical axis in an infinitely saturated porous medium. The problem is axisymmetric. The non-dimensionalized governing equations are solved using the SIMPLER algorithm on a staggered grid. The influence of rotational Reynolds numbers and Darcy numbers on the heat transfer for a Grashof number of 104 and Prandtl number of 7.0 is studied. It is found that for very high Darcy numbers, over a wide range of rotational Reynolds numbers, the heat transfer takes place mainly due to conduction. The convective heat transfer takes place for lower Darcy numbers and for higher rotational Reynolds numbers. Moreover, there is a rapid increase in the overall Nusselt number below a certain Darcy number with increase in the rotational Reynolds numbers. The effect of the Darcy number and the rotational Reynolds number on the heat transfer and fluid flow in the porous medium is depicted in the form of streamline and isotherm plots. The variation of the overall Nusselt number with respect to the Darcy number for various rotational Reynolds numbers is plotted. The variation of the local Nusselt number with respect to the radial coordinate at the heated tip of the vertical cylinder is plotted for various Darcy and rotational Reynolds numbers.

Interaction analysis of strip footing resting on a non-homogeneous elastic medium

In this paper, a plane stress solution for the interaction analysis of strip footing resting on (i) a non-homogeneous elastic half-plane and (ii) a non-homogeneous elastic layer resting on a rigid stratum has been presented. The analysis has been done using a combined analytical and FEM method in which the discretization of the half-plane is not required and thereby minimizes the computational efforts considerably. The contact pressure distribution and the settlement profile for the selected cases of varying modulus half-plane, which has more relevance to foundation engineering, have been given. Experimental verification through a photoelastic method of stress analysis has been carried out for the case of footing on Gibson elastic half-plane, and the contact pressure distribution thus obtained has been compared with the theoretical results. Copyright (C) 1996 Elsevier Science Ltd

The sputtering temperature of a cooling cylindrical rod without and with an insulated core in a two-fluid medium

Utilising Jones' method associated with the Wiener-Hopf technique, explicit solutions are obtained for the temperature distributions on the surface of a cylindrical rod without an insulated core as well as that inside a cylindrical rod with an insulated inner core when the rod, in either of the two cases, is allowed to enter, with a uniform speed, into two different layers of fluid with different cooling abilities. Simple expressions are derived for the values of the sputtering temperatures of the rod at the points of entry into the respective layers, assuming the upper layer of the fluid to be of finite depth and the lower of infinite extent. Both the problems are solved through a three-part Wiener-Hopf problem of special type and the numerical results under certain special circumstances are obtained and presented in tabular forms.