Characterization of fluid flow patterns and heat transfer in horizontal channel mixed convection

Two mechanisms of roll initiation are highlighted in a horizontal channel flow, uniformly heated from below, at constant heat flux (Γ = 10, Pr = 7, 50 ≤ Re ≤ 100, 0 ≤ Ra ≤ 10⁶). The first mechanism is the classical one, it occurs for low Rayleigh numbers and is initiated by the lateral wall effect. The second occurs for higher Rayleigh numbers and combines the previous effect with a supercritical vertical temperature gradient in the lower boundary layer, which simultaneously triggers pairs of rolls in the whole zone in between the two lateral rolls. We have found that in the present configuration, the transition between the two roll initiation mechanisms occurs for Ra/Re ² ≈ 18. Consequently, the heat transfer is significantly enhanced compared to the pure forced convection case owing to the flow pattern responsible of the continuous flooding the heated wall with cold fluid.     

A Novel ‘Domino‐Click Approach’ to Unsymmetrical Bis‐1H‐1,2,3‐triazoles

Aryl azides 1 were treated with allenylmagnesium bromide ( 2 ) to generate 1,5‐disubstituted butynyl‐1H‐1,2,3‐triazoles 3 in a domino fashion, which upon Cu^I‐catalyzed 1,3‐dipolar cycloaddition with aryl azides 4 afforded novel bis‐1H‐1,2,3‐triazoles 5 in quantitative yields (Scheme 1 and Table).     

Natural and semisynthetic polymers blended orodispersible films of citalopram

Abstract

This study was aimed at developing orodispersible films of citalopram using combination of natural and semisynthetic polymers for patients with swallowing problem. Okra biopolymer and moringa gum were utilized in combination with hydroxypropyl methylcellulose (HPMC) and pullulan. The disintegration time was less than 30?seconds and the drug content uniformity was 97.89–102.05% for all film formulations. Films formulated with HPMC (K15 and K4M) combination (F1) and combination of okra and HPMC K15 (F2) had superior mechanical properties as compared with F3 (okra and pullulan) and F4 (moringa gum and HPMC). Thermal analysis revealed stable formulations over the studied temperature range and the crystalline citalopram was completely or partially transformed into amorphous form as revealed by the differential thermal analysis, X-ray diffraction and scanning electron microscopy images. In conclusion, okra biopolymer could be used in combination with HPMC for the development of orodispersible films.     

Simple charge transfer complexes of some new and of some known heterocyclic compounds of selenium and tellurium

Charge transfer (CT) complexes (1:1) of 2,5-dihydrotellurophene and the 3-methyl and 3,4-dimethyl compounds with TCNQ and tetrachlorobenzoquinone (TCB) are reported. The organotellurium compounds failed to give complexes with p-dinitrobenzene (DNB). The variation of solid state (disc) conductivity with temperature and as a function of methyl substituents is considered. The complexes show semi-conducting behaviour and a consideration of these data, together with IR and UV spectroscopic data, in comparison with those for 1,3-dihydro-2-telluraindene given the following order of donor power with respect to TCNQ:

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With respect to a given donor, the order to acceptor power is TCNQ> TCB> DNB.

1,3-Dihydro-2-selanaindene forms a complex with TCNQ. The molecular ionisation potential of the selanaindene is 7.4 eV (by mass spectroscopy) and it has been shown that the compound may be electrochemically oxidized to materials such as C₈H₈SePF₆.

New quinoxalino-1-chalcogenacyclopentanes are reported; namely those derived from selenium, and for the 7,8-dimethyl series, those based on both selenium and tellurium. Their preparation and characterisation are described, and their chemistry shown to be strongly analogous to that of quinoxalino-1-telluracyclopentane. CT complexes of the new Se^II and Te^II compounds (1:1) are prepared with TCNQ which are believed to be strongly ionic.     

Capital adequacy and risk management in banking industry

The present paper deals with the issue of bank capital adequacy and risk management within a stochastic dynamic setting. In particular, an explicit risk aggregation and capital expression is provided regarding the portfolio choice and capital requirements special context. Such a framework leads to a nonlinear stochastic optimal control problem whose solution may be determined by means of dynamic programming algorithm. The pertaining analysis relies heavily on the stochastic dynamic modeling of such balance sheet items as securities, loans, and regulatory capital with stochastic interest rates. In this respect, the special Kalman filter approach is used for the purpose of estimating the model parameters. The reached findings reveal well that the Tunisian bank, subject of study, generally exceeds the minimum requirements and is adequately capitalized to maintain the appropriate capital amount level commensurate with the aggregate risk. Besides, empirical evidence on the regulations' impact on driving bank capitalization and risk‐taking behavior has also been highlighted. Copyright © 2015 John Wiley & Sons, Ltd.     

Phenolic,flavonoid contents,anticholinesterase and antioxidant evaluation of Iris germanica var; florentina

This study was designed to investigate antioxidant and anticholinesterase potential of Iris germanica var; florentina. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory potential of plant samples were investigated by Ellman’s assay. Antioxidant activity was performed using DPPH, H₂O₂ and ABTS free radical scavenging assays. Total phenolics and flavonoids contents were expressed in mg GAE/g dry weight and mg RTE/g, respectively. In AChE inhibition assay, Ig.Fl, Ig.Sp and Ig.Cf fractions exhibited highest activity with IC₅₀ values of < 0.1, 5.64 and 19 μg/mL, respectively. In BChE inhibitory assay, Ig.Fl, Ig.Sp, Ig.Cf and Ig.Cr were most active with IC₅₀ of < 0.1, < 0.1, 31 and 78 μg/mL, respectively. In DPPH assay, Ig.Fl and Ig.Cf exhibited highest inhibition of free radicals, 80.52% (IC₅₀ = 9 μg/mL) and 78.30% (IC₅₀ = 8 μg/mL), respectively. In ABTS assay Ig.Cr, Ig.Cf, Ig.Fl and Ig.Sp exhibited IC₅₀ values of < 0.1, 2, 2 and 3 μg/mL, respectively.     

Synthesis,Structure and Physical Properties of an Hybrid Compound Based on Strandberg Type Polyoxoanions and Copper Cations

Single crystals of novel Strandberg type molybdophosphonate complex, (C₅H₇N₂)₆[Cu(H₂O)₃HP₂Mo₅O₂₃]₂·4H₂O, are synthesized in aqueous solution and characterized by X-ray diffraction, spectroscopy (diffuse reflectance, UV–Vis and IR) and thermal analysis. Single crystal X-ray diffraction analysis reveals that this novel compound is composed of [Cu(H₂O)₃HP₂Mo₅O₂₃]^3? anions, three distinct 2-aminopyridinium cations as counter-ions and two distinct crystallization water molecules. The crystal packing is stabilized by H-bonds and π–π interactions, resulting in a 3D framework. In addition, the magnetic behavior of the related compound is measured. Magnetic measurements from 100 to 2 K indicate the presence of an antiferromagnetic coupling between the Cu (II) ions in (C₅H₇N₂)₆[Cu(H₂O)₃HP₂Mo₅O₂₃]₂·4H₂O complex, resulting in a maximum of an antiferromagnetic–paramagnetic transition at T_N = 7 K. Magnetic susceptibility data indicate an antiferromagnetic Curie–Weiss behavior in the studied temperature range, and molecular field theory gives the (J/k_B) values of the nearest neighbor interactions between copper ions.     

Biochemical properties of Cu/Zn-superoxide dismutase from fungal strain Aspergillus niger 26

The fungal strain Aspergillus niger produces two superoxide dismutases, Cu/Zn-SOD and Mn-SOD. The primary structure of the Cu/Zn-SOD has been determined by Edman degradation of peptide fragments derived from proteolytic digests. A single chain of the protein, consisting of 153 amino acid residues, reveals a very high degree of structural homology with the amino acid sequences of other Aspergillus Cu/Zn-SODs. The molecular mass of ANSOD, measured by MALDI-MS and ESI-MS, and calculated by its amino acid sequence, was determined to be 15821 Da. Only one Trp residue, at position 32, and one disulfide bridge were identified. However, neither a Tyr residue nor a carbohydrate chain occupying an N-linkage site (-Asn-Ile-Thr-) were found. Studies on the temperature and pH dependence of fluorescence, and on the temperature dependence of CD spectroscopic properties, confirmed that the enzyme is very stable, which can be explained by the stabilising effect of the disulfide bridge. The enzyme retains about 53% of its activity after incubation for a period of 30 min at 60 degrees C, and 15% at 85 degrees C.     

Structural,electronic and optical properties of fluorite-type compounds

An oscillator chain with dynamical traps and additive white noise is considered. Its dynamics are studied numerically. New type nonequilibrium phase transitions are shown to arise in the case when the trap effect is pronounced. Locally they manifest themselves in distortion of the symmetry of particle arrangement. Depending on the system parameters, the particle arrangement is characterized by the corresponding distributions taking either a bimodal form, or a twoscale one, or a unimodal onescale form that, however, deviates substantially from the Gaussian distribution. The particle velocities also exhibit a number of anomalies, in particular, their distribution can be extremely wide or take a quasi-cusp form. A large number of various cooperative structures and superstructures are found in the visualized time patterns. In a certain sense their evolution is independent of the individual particle dynamics, enabling us to regard them as dynamical phases.