Characteristics investigation on heat transfer growth of sonochemically synthesized ZnO-DW based nanofluids inside square heat exchanger

Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers...     

The effect of rapid rotation on a vertical bridgman furnace at large Rayleigh number

In quasi-steady operation, convection currents in a Bridgmandevice, used for producing a semi-conductor crystal, createinhomogeneities that may make the crystal unusable. It has oftenbeen suggested that additional forces due to rotation or magnetismmight be efficacious in reducing the segregation of the elementsof the alloy. It has been found that, over a wide range of rotationrates, there is no improvement in performance due to rotationabout the vertical axis. However, numerical results that havebeen obtained previously (Lee & Pearlstein, J. Crys. Growth240, 2002) indicate that, when effects of centrifugal buoyancyare introduced, a substantial reduction in segregation is achieved.In the work reported here, by contrast, in which we extend previouslarge-Rayleigh-number asymptotic analysis to include centrifugalbuoyancy, we find no improvement in radial segregation, butrather increasing segregation with increasing rotation rate.     

Determination of ascorbic acid by iodate using iodine cyanide end point; indirect determination of vanadium, and colorimetric determination of ascorbic acid

Summary Two methods for the determination of ascorbic acid are described. The first employs titration with iodate in presence of cyanide and hydrochloric acid and starch indicator with two end points, corresponding to the formation of iodine after reduction to iodide and conversion of iodine to iodine cyanide respectively. The titration is applied to the indirect determination of vanadium(V). In the second method ascorbic acid is treated with excess ferric solution and the ferrous iron formed is determined colorimetrically by ortho-phenanthroline.

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Zusammenfassung Zwei Verfahren zur Ascorbinsäurebestimmung werden beschrieben. Bei dem ersten wird in Gegenwart von KCN und Salzsäure sowie von Stärke als Indicator mit Jodatlösung titriert. Dabei werden zwei Endpunkte erhalten, die der Reduktion von Jodat zu Jodid und damit verbundener Jodbildung bzw. der Umwandlung des Jods in JCN entsprechen. Diese Titration wird auch zur indirekten Bestimmung von Vanadium(V) verwendet. Bei dem zweiten Verfahren wird die Ascorbinsäure mit überschüssiger Eisen(III)-lösung behandelt und das gebildete zweiwertige Eisen colorimetrisch mit o-Phenanthrolin bestimmt.

     

Analogues of Sialic Acids as Potential Sialidase Inhibitors Synthesis of 2-C-Hydroxymethyl Derivatives of N-Acetyl-6-amino-2,6-dideoxy-neuraminic Acid

The intramolecular cycloaddition of the previously described azidoalkene 16 , the related diacetates 7 and 13 , and the monoacetate 8 led diastereoselectivity to the (2R)- and (2S)-configurated hydropyridotriazoles 17 , 9 and 11 , 14 and 15 , and 10 and 12 , respectively (Scheme 1). Thermolysis of 16 gave also the aziridine 18 , its proportion increasing with reaction time. The diastereoselectivity of the cycloaddition- is rationalized on the basis of steric interactions and of H? bonds in the transition state. Photolysis in benzene partially transformed 9 into the aziridine 19 . Treatment of 9 with aqueous AcOH gave 19 and the tetrahydrofuran 20 , with AcOH in benzene 20 and the triacetate 23 , and with aqueous H₂SO₄ in THF, the primary alcohol 22 (room temperature) or 19 and 22 (0°). Deacetylation of 9 followed by reaction with pyridinium hydrochloride led to the tetrahydrofuran 21 and the chloride 24 (Scheme 2). The diacetate 22 and the triacetate 23 gave the tripl 25 which was deprotected to 26 . Reduction of the keto-aziridine 18 (NaBH₄) gave the alcohols 27 and 29 which were acetylated to give 28 and 19 , respectively (Scheme 3). Treatment of the aziridine 28 with AcOH in benzene followed by deacetylation gave 30 and hence 31 . AcOH in benzene transformed the triazoline 15 first into the aziridine 32 and hence into 33 , which was deprotected to give the triol 34 and hence 35 . The 2-(hydroxymethyl)piperidines 26 , 31 , and 35 inhibited Vibrio cholerae sialidase with K₁ = 3.8 · 10^?2 M, 3.4 · 10^?3 M, and 1.5 · 10^?4 M, respectively. The conformation of the glycerol side chain of these compounds and of the unbranched piperidines 2–4 deviates from the one of Neu5Ac (and Neu2en5Ac). This finding is rationalized by an H-bond between OH? C(8) and NH? C(6). The conformations and the K₁ values of 26 , 31 , and 35 correlate with each other.     

Determination of Y,Sm, Eu,Gd, Dy,Ho, Er in high purity terbium oxide by ICP-AES

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was employed to determine Y, Sm, Eu, Gd, Dy, Ho and Er in high purity terbium oxide. Terbium oxide was dissolved in 0.5 mol/l HNO₃ and nebulized into the plasma generated by a 56 MHz RF generator at 1.5 kW output power. Using a Jobin-Yvon 1-m Czenry-Turner high resolution, high dispersion scanning monochromator, lines mutually interference-free as well as free of interference from the matrix Tb were chosen for the seven analytes. A set of standards containing the analytes in the concentration range 0.01–1.0 gmg/ml with 1 mg/ml Tb was used for calibration. It was necessary to apply background correction to the gross analyte line intensities in order to obtain linear calibration plots for the analytes.     

Synthesis of novel 3-carboethoxy-6-methyl-4-oxo-4H-pyrimido[1′,2′:5,6]-[1,3,5]triazino[1,2-a]benzimidazoles

Reaction of 4-amino-2-methylbenzimidazo[1,2-a][1,3,5]triazines 2 with diethyl ethoxymethylenemalonate afforded 3-carboethoxy-6-methyl-4-oxo-4H-pyrimido[1′,2′:5,6][1,3,5]triazino[1,2-a]benzimidazoles 3 , a new ring system.     

A method for the construction of orthogonal spin eigenfunctions

A method for the construction of the essentially idempotent and Hermitian diagonal elements of the matric algebra of the permutation group S_n is proposed. For the irreducible representation [λ] = [λ₁, λ₂] characterising a spin state S of an n-electron system, it is found that this method generates the complete set of spin projections from the appropriate primitive spin functions. The method is applied to a 7-electron system in the spin state S = M_S = 1/2 and the results are listed in the Appendix.     

Quantitative study of the reaction between quinones and iron(II) in phosphoric acid medium

A simple method is described for the determination of some quinones with ammonium iron(II) sulphate, by titration potentiometrically or with cacotheline, Methylene Blue, Methylene Green, thionine, Toluidine Blue, Azure A, Azure C or Azure-2-eosin as redox indicators. The reverse titrations can be used for estimation of iron(II). Alternatively, excess of iron (II) can be added and the iron(III) produced determined colorimetrically with thiocyanate.     

Micellar effect of sodium dodecyl sulfate on the reactions between iron(II) and p-benzoquinone, and iron(III) and hydroquinone

The micellar effet of sodium dodecyl sulfate (SDS) on the initial stages of the reaction between (1) Fe(II) and p-benzoquinone, and (2) Fe(III) and hydroquinone have been investigated. In the former case acceleration was observed, the rate-[surfactant] profile showing a maximum. SDS has an inhibitory effect on the latter reaction. Kinetic analysis has been carried out using Berezin's approach.

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() 1) Fe(II) 2) Fe(III) . - . . , .