Correlations for heat transfer coefficient and pressure drop in the annulus of concentric helical coils

Heat transfer and pressure drop characteristics in the annulus of concentric helical coils heat exchangers were experimentally investigated. The effects of coil curvature ratio, flow configuration, number of turns and addition of surfactant were investigated. Five test coils were designed and manufactured to study the effect of different parameters on heat transfer and pressure drop. The liquids used in the present study were water and oleyl-dihydroxy-etheyl-amine-oxide (ODEAO, C₂₂H₄₅NO₃ = 371) non-ionic aqua surfactant solution flowing through the annulus side. The inner side Reynolds number range 11,000–27,000 and the annulus side range 5,000–19,000. The results showed that the annulus Nusselt number decreases as annulus curvature ratio increases and increases when number of turns decrease. Moreover, the friction factor increases with the curvature ratio and also increases as number of turns decreases. Both Nusselt number and friction factor decrease when ODEAO concentration increases.     

A minimizing property of homographic solutions

In this paper, we prove that the homographic solutions to the rhombus four body prob- lem are the variational minimizers of the Lagrangian action restricted on a holonomically constrained rhombus loop space.     

Effects of free‐stream turbulence on large‐scale coherent structures of separated boundary layer transition

It has been well established that large‐scale structures, usually called coherent structures, exist in many transitional and turbulent flows. The topology and range of scales of those large‐scale structures vary from flow to flow such as counter‐rotating vortices in wake flows, streaks and hairpin vortices in turbulent boundary layer. There has been relatively little study of large‐scale structures in separated and reattached transitional flows. Large‐eddy simulation (LES) is employed in the current study to investigate a separated boundary layer transition under 2% free‐stream turbulence on a flat plate with a blunt leading edge. The Reynolds number based on the inlet free stream velocity and the plate thickness is 6500. A dynamic subgrid‐scale model is employed to compute the subgrid‐scale stresses more accurately in the current transitional flow case. Flow visualization has shown that the Kelvin–Helmholtz rolls, which have been so clearly visible under no free‐stream turbulence (NFST) are not as apparent in the present study. The Lambda‐shaped vortical structures which can be clearly seen in the NFST case can hardly be identified in the free‐stream turbulence (FST) case. Generally speaking, the effects of free‐stream turbulence have led to an early breakdown of the boundary layer, and hence increased the randomization in the vortical structures, degraded the spanwise coherence of those large‐scale structures. Copyright © 2005 John Wiley & Sons, Ltd.     

Mixed ligand complexes of benzimidazole and pyrimidine hydroxy azo dyes with some transition metals and glycine,DL-alanine, orDL-leucine

Summary The overall formation constants of ternary complexes of Cu(II), Zn(II), and Cd(II) with glycine (Gly),DL-alanine (Ala), orDL-leucine (Leu) as primary and 2-(o-hydroxyphenylazo)-2-cyanomethyl benzimidazole (ABI) and 5-(o-hydroxyphenylazo) barbituric acid (ABA) as secondary ligands as well as those of the binary systems have been investigated potentiometrically in 40% (v/v) EtOH. The stability of the ternary complexes is compared quantitatively with that of the corresponding binary complexes. The concentration distribution of the species formed in solution was evaluated; they were characterized by means of IR and¹H NMR spectroscopy.

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Ternäre Komplexe von Hydroxyphenylazoverbindungen mit einigen Übergangsmetallen und Glycin,DL-Alanin oderDL-Leucin

Zusammenfassung Die Bildungskonstanten der ternären Komplexe von Cu(II), Zn(II) und Cd(II) mit Glycin (Gly),DL-Alanin (Ala) oderDL-Leucin (Leu) als Primärliganden und 2-(o-Hydroxyphenylazo)-2-cyanomethyl-benzimidazol (ABI) bzw. 5-(o-Hydroxyphenylazo)-barbitursäure (ABA) als Sekundärliganden wurden wurden ebenso wie jene binärer Systeme potentiometrisch in 40% (v/v) Ethanol bestimmt. Die Stabilität der ternären Komplexe wird mit jener der binären verglichen. Die Konzentration der verschiedenen Spezies in Lösung sowie ihre IR- und¹H-HMR-Spektren wurden gemessen.

     

Spectrophotometric determination of molybdenum with 7,8-dihydroxy-4-methylcoumarin and cetyltrimethylammonium bromide

The 1:2 complexes formed between molybdenum and 7,8-dihydroxy-4-methylcoumarin in the presence and absence of cetyltrimethylammonium bromide (CTAB) have been studied. The binary complex formed at pH 5.6-6.0 in the absence of CTAB exhibits an absortion maximum at 360 nm with a molar absorptivity of 5.1 x 10(4) 1.mole(-1).cm(-1). The complex formed at pH 4.8-6.0 in the presence of CTAB has a molar absorptivity of 1.32 x 10(5) 1.mole(-1).cm (-1) at 400 nm, the wavelength of maximum absorption. Optimum conditions for complex formation were investigated and a rapid, sensitive and relatively selective method for the determination of up to approximately 70% of Mo in diverse alloys and steels is described. Small amounts of zirconium and tungsten interfere.     

Regulation of Selenium/Sulfur Interactions to Enhance Chemopreventive Effects: Lessons to Learn from Brassicaceae

Selenium (Se) is an essential trace element, which represents an integral part of glutathione peroxidase and other selenoproteins involved in the protection of cells against oxidative damage. Selenomethionine (SeMet), selenocysteine (SeCys), and methylselenocysteine (MeSeCys) are the forms of Se that occur in living systems. Se-containing compounds have been found to reduce carcinogenesis of animal models, and dietary supplemental Se might decrease cancer risk. Se is mainly taken up by plant roots in the form of selenate via high-affinity sulfate transporters. Consequently, owing to the chemical similarity between Se and sulfur (S), the availability of S plays a key role in Se accumulation owing to competition effects in absorption, translocation, and assimilation. Moreover, naturally occurring S-containing compounds have proven to exhibit anticancer potential, in addition to other bioactivities. Therefore, it is important to understand the interaction between Se and S, which depends on Se/S ratio in the plant or/and in the growth medium. Brassicaceae (also known as cabbage or mustard family) is an important family of flowering plants that are grown worldwide and have a vital role in agriculture and populations’ health. In this review we discuss the distribution and further interactions between S and Se in Brassicaceae and provide several examples of Se or Se/S biofortifications’ experiments in brassica vegetables that induced the chemopreventive effects of these crops by enhancing the production of Se- or/and S-containing natural compounds. Extensive further research is required to understand Se/S uptake, translocation, and assimilation and to investigate their potential role in producing anticancer drugs.     

Statistical Properties of the Odd Binomial States with Dynamical Applications

In this paper we investigate the odd binomialstate, which interpolates between odd number and oddcoherent states. We discuss the statistical propertiesof the Glauber second-order correlation function and squeezing phenomena (normal squeezing andamplitude-squared squeezing). The phase properties inPegg-Barnett formalism are considered, and thequasiprobability distribution functions are examined.The dynamics of the Jaynes-Cummings model and theresonance fluorescence are also discussed.     

On quadratic integral equation of fractional orders

We present an existence theorem for a nonlinear quadratic integral equations of fractional orders, arising in the queuing theory and biology, in the Banach space of real functions defined and continuous on a bounded and closed interval. The concept of measure of noncompactness and a fixed point theorem due to Darbo are the main tool in carrying out our proof.