Axially homogeneous, zero mean flow buoyancy-driven turbulence in a vertical pipe

We report an experimental study of a new type of turbulent flow that is driven purely by buoyancy. The flow is due to an unstable density difference, created using brine and water, across the ends of a long (length/diameter = 9) vertical pipe. The Schmidt number Sc is 670, and the Rayleigh number (Ra) based on the density gradient and diameter is about 10(8). Under these conditions the convection is turbulent, and the time-averaged velocity at any point is `zero'. The Reynolds number based on the Taylor microscale, Re-lambda, is about 65. The pipe is long enough for there to be an axially homogeneous region, with a linear density gradient, about 6-7 diameters long in the midlength of the pipe. In the absence of a mean flow and, therefore, mean shear, turbulence is sustained just by buoyancy. The flow can be thus considered to be an axially homogeneous turbulent natural convection driven by a constant (unstable) density gradient. We characterize the flow using flow visualization and particle image velocimetry (PIV). Measurements show that the mean velocities and the Reynolds shear stresses are zero across the cross-section; the root mean squared (r.m.s.) of the vertical velocity is larger than those of the lateral velocities (by about one and half times at the pipe axis). We identify some features of the turbulent flow using velocity correlation maps and the probability density functions of velocities and velocity differences. The flow away from the wall, affected mainly by buoyancy, consists of vertically moving fluid masses continually colliding and interacting, while the flow near the wall appears similar to that in wall-bound shear-free turbulence. The turbulence is anisotropic, with the anisotropy increasing to large values as the wall is approached. A mixing length model with the diameter of the pipe as the length scale predicts well the scalings for velocity fluctuations and the flux. This model implies that the Nusselt number would scale as (RaSc1/2)-Sc-1/2, and the Reynolds number would scale as (RaSc-1/2)-Sc-1/2. The velocity and the flux measurements appear to be consistent with the Ra-1/2 scaling, although it must be pointed out that the Rayleigh number range was less than 10. The Schmidt number was not varied to check the Sc scaling. The fluxes and the Reynolds numbers obtained in the present configuration are Much higher compared to what would be obtained in Rayleigh-Benard (R-B) convection for similar density differences.

Fluidity of mica particle dispersed aluminium alloy

Cast aluminium alloy-mica particle composites were made by dispersing mica particles in a vortex produced by stirring the liquid Al-4 wt% Cu-1.5 wt% Mg alloy and then casting the melt containing the suspended particles into permanent moulds. Spiral fluidity and casting fluidity of the alloy containing mica particles in suspension were determined. Both the spiral fluidity and the casting fluidity of the base alloy were found to decrease with an increase in volume or weight percent of mica particles (of a given size), and with a decrease in particle size (for a given amount of particles). The fluidities of Al-4 wt% Cu-1.5 wt% Mg alloys containing suspended mica particles were found to correlate very well with the surface area of suspended mica particles. The regression equation for spiral fluidity Y (cm) as a function of surface area of mica particles per gram of spiral X (cm2 g–1) at 700° C was found to be Y=42.62–0.42X with a correlation coefficient of 0.9634. The regression equations for casting fluidity Yprime (cm) as a functiono of surface area of mica particles per gram of fluidity test piece Xprime (cm2 g–1) at 710 and 670° C were found to be Yprime=19.71–0.17Xprime and Yprime=13.52–0.105Xprime with correlation coefficients of 0.9194 and 0.9612 respectively. The percentage decrease in casting fluidity of composite melts containing up to 2.5 wt% mica with a drop in temperature is quite similar to the corresponding decrease in the casting fluidity of base alloy melts (without mica). The change in fluidity due to mica dispersions has been discussed in terms of changes in viscosity of the composite melts. However, the fluidities of these composite alloys containing up to 2.5 wt% mica are adequate for making a variety of simple castings including bearings for which these alloys have been developed.

Structure Of 5'-Deoxy-5',6-Epithio-5,6-Dihydro-2',3'-O-Isopropylideneuridine, C12h16n2o5s

Mr=300.33 , triclinic, P1, a=5.635 (2), b=11.077(2), c=11.582(2)A, a= 70.48 (1), fl= 88.16 (3), y=80.56(3) ° , V= 670.325 A3, Z=2, D x = 1.49 Mg m -3, Cu Ka, n= 1.54184 ,A, g = 2.308mm -1, F(000)=316, T=301K, R=0.054, R w = 0.093 for 1944 observed counter reflections. The sulphur position with respect to the dihydrouracil ring, which is of possible relevance to the action of thymidylate synthetase, is axial in molecule A and equatorial in B. Both molecules show the anti conformation about the glycosidic bond [torsion angle C(6)-N(1)-C(1')-O(4'), 2'CN = 21.6 (9) and 29.4 (10) °] and have the C(4')-endo, O(4')-exo (40T) sugar conformation. The dioxolane-ring conformation is O(2')-endo in A and C(7)-endo in B. The dihydrouracil rings show self base pairing with hydrogen bondsN(3A)...O(ZB) and N(3B)...O(ZA).

Access path query language for relational database systems

Database management systems offer a very reliable and attractive data organization for fast and economical information storage and processing for diverse applications. It is much more important that the information should be easily accessible to users with varied backgrounds, professional as well as casual, through a suitable data sublanguage. The language adopted here (APPLE) is one such language for relational database systems and is completely nonprocedural and well suited to users with minimum or no programming background. This is supported by an access path model which permits the user to formulate completely nonprocedural queries expressed solely in terms of attribute names. The data description language (DDL) and data manipulation language (DML) features of APPLE are also discussed. The underlying relational database has been implemented with the help of the DATATRIEVE-11 utility for record and domain definition which is available on the PDP-11/35. The package is coded in Pascal and MACRO-11. Further, most of the limitations of the DATATRIEVE-11 utility have been eliminated in the interface package.

Phase transition in ammonium aluminium and ammonium chromium alums-A high pressure EPR study

An investigation of the phase transitions at high pressures in the alums mentioned in the title has been carried out using EPR of the Cr3+ ion (at the trivalent metal ion site). It is observed that at ambient as well as at high pressures there is a change of slope in the linear variations of the zero field splitting with temperature and that the low temperature phase is characterised by a large number of lines in the EPR spectra. The transition temperature shows a large positive shift with pressure, for both the alums. All these facts are explained in terms of our model of the origin of the trigonal field at the trivalent metal ion site as well as the details of the motion of NH4+ ion.

Biochemical effects of 3,5-diethoxycarbonyl-1, 4-dihydrocollidine in mouse liver

3,5-Diethoxycarbonyl-1,4-dihydrocollidine (DDC) is a porphyrinogenic agent and is a powerful inducer of δ-aminolaevulinate synthetase, the first and rate-limiting enzyme of the haem-biosynthetic pathway, in mouse liver. However, DDC strikingly inhibits mitochondrial as well as microsomal haem synthesis by depressing the activity of ferrochelatase in vivo. The drug on repeated administration to female mice has been found to elicit hypertrophic effects in the liver microsomes initially, but the effects observed at later stages denote either hyperplasia or increase in polyploidal cells. The microsomal protein concentration shows a striking decrease with repeated doses of the drug. The rate of microsomal protein synthesis in vivo as well as in vitro shows an increase with two injections of DDC but decreases considerably with repeated administration of the drug. The activities of NADPH-cytochrome creductase and ribonuclease are not affected in the liver microsomes of drug-treated animals when expressed per mg of microsomal protein. DDC has also been found to cause degradation of microsomal haem, which is primarily responsible for the decrease in cytochrome P-450 content. The drug also leads to a decrease in mitochondrial cytochrome c levels due to inhibition of haem synthesis and also due to degradation of mitochondrial haem at later stages. The biochemical effects of the drug are compared and discussed with those reported for allylisopropylacetamide and phenobarbital.

Systematic variation in bond lengths of peptides

The lengths of the carbonyl as well as of the adjacent C-N and C-C bonds in peptides are shown to vary systematically with the central C-N bond length. Results of ab initio calculations on N-methylacetamide and its Li+, Na+ and Mg2+ complexes are also discussed.

An XPS study of the surface oxidation states of metals in some oxide catalysts

Calcined samples of chromia supported on Al2O3, ZnO, or SnO2 show both Cr(VI) and Cr(III) on the surface, Cr(VI) being preponderant in the case of Al2O3-supported catalysts. The proportion of Cr(VI) decreases with increase in Cr content of the calcined catalysts. Reduction of the supported chromia catalysts in H2 at 720 K for 1 hr gives rise to Cr(III) and Cr(V). On carrying out the dehydrogenation of cyclohexane on the chromia catalysts a higher proportion of Cr(V) is found than after treatment with hydrogen. Vanadia supported on Al2O3 or MoO3 shows significant proportion of V(IV) on carrying out the oxidation of toluene on the catalysts. Calcined MoO3 (10%)/Al2O3 shows only Mo(VI) on the surface at 300 K, but on heating to 670 K in vacuum shows the presence of a considerable proportion of Mo(V) which on cooling disproportionates to Mo(IV) and Mo(VI). Mo(V) is noticed on surfaces of this catalyst on reduction with hydrogen as also on carrying out dehydrogenation of cyclohexane. While Bi2MoO6 shows only Mo(VI) on the surface at 300 K, heating it to 670 K in vacuum changes it entirely to Mo(V) which then gives rise to Mo(IV) and Mo(VI) on cooling.

3,3',5,5'-Tetrabromophenolsulfonphthalein (bromphenol blue), C19H10Br4O5S

M r=670.02, monoclinic, C2/c, a= 31.003(4), b=11.037(2), c=21.183(3)A, fl= 143.7 (1) °, V= 4291.2/k 3, D,n = 2.06, D x = 2.07Mgm -3, Z=8, MoKa, 2=0.7107/k, /~=7.45 mm -1, F(000) = 2560, T= 293 K, R = 0.061 for 1697 observed reflections. The bromphenol blue molecule consists essentially of three planar groupings: the sulfonphthalein ring system and two dibromophenol rings attached to the tetrahedral C atom of the five-membered ring of the sulfonphthalein system. The dibromophenol rings are inclined with resPect to each other at 73 ° whereas they make angles of 85 and 68 ° with respect to the sulfonphthalein system. The molecules aggregate into helical columns with the non-polar regions of the molecules in the interior and the polar regions on the surface. The columns are held together by a network of hydrogen bonds.

Surface waves on the boundary of a magnetized plasma

Full dispersion curves including the effect of ions are presented for the electromagnetic surface waves propagating over a plasma-plasma interface in the direction perpendicular to the magnetic field which is parallel to the interface. The effect of ions and finite density ratio of the two media at the boundary give rise to various new features in the dispersion characteristics of these surface waves.

P-T evolution of Glenelg eclogites, NW Scotland: Did they experience ultrahigh-pressure metamorphism?

Eclogites and their retrogressed equivalents from the eastern unit of the Glenelg-Attadale Inlier in NW Scotland preserve much microstructural evidence that indicates that very high-pressure/temperature eclogite facies conditions were reached, and followed by decompression and hydration during exhumation. Rutile exsolution in garnet and quartz exsolution in omphacite and titanite formed through mineral reactions during high P-T peak metamorphism. Isochemical phase diagrams modeled for samples from three different locations indicate that the outer part of the eastern unit preserves a peak metamorphic condition of c. 850-1000 degrees C at 18-25 kbar, whereas the central part has a similar pressure (c. 23 kbar), but a lower temperature (c. 670 degrees C). Due to the limitations in the phase diagram calculations the estimated P-T conditions represent the minimum conditions attained by the peak metamorphic assemblage, and the pre-exsoived peak assemblage probably stabilized at a higher pressure. This observation is strongly supported by the presence of exsolution microstructures. The present results demonstrate that the eastern unit experienced very high P-T conditions during peak metamorphism and a tight clockwise P-T trajectory and provide the first indication of possible ultrahigh-pressure metamorphism in the Glenelg eclogites. (C) 2009 Elsevier B.V. All rights reserved.

Indoleacetaldoxime hydro-lyase : II. Purification and properties

The purification and some properties of the enzyme indoleacetaldoxime hydrolyase (EC 4.2.1.29) from the fungus Gibberella fujikuroi, which dehydrates indoleacetaldoxime (IAOX) to indoleacetonitrile (IAN), are described. The enzyme activity in the fungus is present only under certain culture conditions. It is a soluble enzyme, has an optimum pH at 7, shows an energy of activation of —15,670 cal/mole, and has a Michaelis constant of 1.7 × 10−4 Image at 30 °. It appears to be specific for IAOX, and 1 mole of IAN is produced per mole of IAOX utilized. The enzyme is inhibited by a number of aldoximes of which phenylacetaldoxime (PAOX) is the most potent inhibitor. Inhibition by PAOX is competitive (Ki = 2.2 × 10−8 Image ). The enzyme is inhibited by SH reagents such as p-hydroxymercuribenzoate and N-ethylmaleimide, and by a number of SH compounds such as cysteine, β-mercaptoethanol, and 2,3-dimercaptopropanol (BAL). However, glutathione activates the enzyme. Metal chelating agents such as 8-OH-quinoline and diethyl dithiocarbamate inhibit the enzyme; the inhibition is partly reversed by ferric citrate. Ascorbic acid, and particularly dehydroascorbic acid (DHA), are good activators of the enzyme. Several other biological oxidants had either no action or had a slight effect. Potassium cyanide activates the enzyme at low concentration but inhibits at higher concentrations. Reduction of the enzyme with NaBH4 reduces activity, and the effect is partly reversed by pyridoxal phosphate and also by DHA. The above properties indicate that both an SH function and an oxidized function are required for activity.

Physicochemical studies on the gelation of hen's egg yolk: Delipidation of yolk plasma by treatment with phospholipase-C and extraction with solvents

A method for the delipidation of egg yolk plasma using phospholipase-C, n-heptane, and 1-butanol has been described. An aggregating protein fraction and a soluble protein fraction were separated by the action of phospholipase-C. The aggregating protein fraction freed of most of the lipids by treatment with n-heptane and 1-butanol was shown to be the apolipoproteins of yolk plasma, whereas the soluble proteins were identified as the livetins. Carbohydrate and the N-terminal amino acid analysis of these protein fractions are reported. A comparison of these protein fractions with the corresponding fractions obtained by formic acid delipidation of yolk plasma has been made. The gelation of yolk plasma by the action of phospholipase-C has been interpreted as an aggregation of lipoproteins caused by ionic interactions. The role of lecithin in maintaining the structural integrity of lipoproteins has been discussed.

Porphyrin synthesis in drug induced hepatic porphyria

Liver δ-aminolaevulate (ALA) synthetase and ALA dehydratase are induced to a greater extent in 3,5-diethoxy carbonyl-1,4-dihydrocollidine (DDC) injected mice as compared to the allyl isopropyl acetamide (AIA) injected rats. DDC treated mice do not show an increase in porphobilinogen (PEG) levels commensurate with the increase in ALA levels and the two enzyme activities, but accumulate enormous quantities of protoporphyrin in the liver. Normal mouse liver has an inherent greater capacity to convert PBG to porphyrins as compared to that of the rat. This together with the inhibition of iron incorporation into protoporphyrin in vivo at later stages of DDC administration can account for the large accumulation of protoporphyrin in these animals.