Numerical investigation of flow boiling characteristics of water in a rectangular microchannel

Journal of Thermal Analysis and Calorimetry - In the case of flow boiling, the prediction of vapour fraction in the horizontal microchannel is a severe issue using the numerical technique....     

Working group report: Quantum chromodynamics

This is the report of the subgroup QCD of Working Group-4 at WHEPP-9. We present the activities that had taken place in the subgroup and report some of the partial results arrived at following the discussion at the working group meetings.     

（0,1;0）-INTERPOLATION ON INFINITE INTERVAL （-∞, ＋∞）

In this paper, we study the explicit representation and convergence of （0, 1;0）-interpolation on infisite interval, which means to determine a polynomial of degree ≤ 3n - 2 when the function values areprescribed at two set of points namely the zeros of Hn（x） and H′n （x） and the first derivatives at the zerosof H′n（x）.     

Partitioning arrangements of lines II: Applications

In this paper we present efficient deterministic algorithms for various problems involving lines or segments in the plane, using the partitioning algorithm described in a companion paper [A3]. These applications include: (i) anO(m ^2/3 n ^2/3 · log^2/3 n · log^/3 (m/n)+(m+n) logn) algorithm to compute all incidences betweenm points andn lines, where is a constant <3.33; (ii) anO(m ^2/3 n ^2/3 · log^5/3 n · log^/3 (m/n)+(m+n) logn) algorithm to computem faces in an arrangement ofn lines; (iii) anO(n ^4/3 log^(+2)/3 n) algorithm to count the number of intersections in a set ofn segments; (iv) anO(n ^4/3 log^{( + 2)/3} n) algorithm to count red-blue intersections between two sets of segments, and (v) anO(n ^3/2 log^/3 n) algorithm to compute spanning trees with low stabbing number for a set ofn points. We also present an algorithm that, given set ofn points in the plane, preprocesses it, in timeO(nm log^+1/2 n), into a data structure of sizeO(m) forn lognmn ², so that the number of points ofS lying inside a query triangle can be computed inO((n/m) log^3/2 n) time.Work on this paper has been supported by Office of Naval Research Grant N00014-87-K-0129, by National Science Foundation Grant DCR-83-20085, and by grants from the Digital Equipment Corporation and the IBM Corporation. A preliminary version of this paper appears in theProceedings of the 5th ACM Symposium on Computational Geometry, 1989, pp. 11–22.     

Solution structure, mutagenesis, and NH exchange studies of the MutT enzyme–Mg-8-oxo-dGMP complex

The MutT pyrophosphohydrolase from E. coli (129 residues) catalyzes the hydrolysis of nucleoside triphosphates (NTP), including 8-oxo-dGTP, by substitution at Pβ, to yield NMP and pyrophosphate. The product, 8-oxo-dGMP is an unusually tight binding, slowly exchanging inhibitor with a K_D=52 nM, (ΔG°=−9.8 kcal/mol) which is 6.1 kcal/mol tighter than the binding of dGMP (ΔG°=−3.7 kcal/mol). The higher affinity for 8-oxo-dGMP results from a more favorable ΔH_binding (−32 kcal/mol) despite an unfavorable −TΔS°_binding (+22 kcal/mol). The solution structure of the MutT–Mg²⁺-8-oxo-dGMP complex shows a narrowed, hydrophobic nucleotide-binding cleft with Asn-119 and Arg-78 among the few polar residues. The N119A, N119D, R78K and R78A single mutations, and the R78K+N119A double mutant all showed largely intact active sites, on the basis of small changes in the kinetic parameters of dGTP hydrolysis and in ¹H–¹⁵N HSQC spectra. However, the N119A mutation profoundly weakened the active site binding of 8-oxo-dGMP by 4.3 kcal/mol (1650-fold). The N119D mutation also weakened 8-oxo-dGMP binding but only by 2.1 kcal/mol (37-fold), suggesting that Asn-119 functioned both as a hydrogen bond donor to C8=O, and a hydrogen bond acceptor from N7H of 8-oxo-dGMP, while aspartate at position −119 functioned as an acceptor of a single hydrogen bond. Much smaller weakening effects (0.3–0.4 kcal/mol) on the binding of dGMP and dAMP were found, indicating specific hydrogen bonding of Asn-119 to 8-oxo-dGMP. While formation of the wild type MutT–Mg²⁺-8-oxo-dGMP complex slowed the backbone NH exchange rates of 45 residues distributed throughout the protein, the same complex of the N119A mutant slowed the exchange rates of only 11 residues at or near the active site, indicating an increase in conformational flexibility of the N119A mutant. The R78K and R78A mutations weakened the binding of 8-oxo-dGMP by 1.7 and 1.1 kcal/mol, respectively, indicating a lesser role of Arg-78 than of Asn-119 in the selective binding of 8-oxo-dGMP, likely donating a single hydrogen bond to its C6=O. The R78K+N119A double mutant weakened the binding of 8-oxo-dGMP (K_I^slope=3.1 mM) by 6.5±0.2 kcal/mol which overlaps, within error with the sum of the effects of the two single mutants (6.0±0.3 kcal/mol). Such additive effects of the two single mutants in the double mutant are most simply explained by the independent functioning of Asn-119 and Arg-78 in the binding of 8-oxo-dGMP. Independent functioning of these two residues in nucleotide binding is consistent with their locations in the MutT–Mg²⁺-8-oxo-dGMP complex, on opposite sides of the active site cleft, with a distance of 8.4±0.5 Å between their side chain nitrogens.     

Role of Surface Molecular Architecture and Energetics of Hydrogen Bonding Sites in Adsorption of Polymers and Surfactants

Hydrogen bonding is generally thought to be an ubiquitous adsorption mechanism, which often foils selective adsorption schemes. Through investigation of hydrogen bonding energy and its dependence on surface molecular architecture, it may be possible to develop new methodologies to control the adsorption of surfactants and polymeric flocculants, depressants, and dispersants used in particulate processing industries. A model system using St?ber silica spheres and polyethylene oxide, a polymer known for its ability to form hydrogen bonds, was examined. The effect of two different surface treatments of the silica particles, calcination and rehydroxylation, upon the adsorption of two polymer molecular weights was studied. The adsorption behavior was then linked to the respective surface structures via characterization of the surfaces using FTIR, NMR, and Raman techniques. In this paper role of hydrogen bonding sites and surface architecture on adsorption is discussed. Copyright 2000 Academic Press.     

Differential scanning calorimetry studies on aged iron(III)-chromium(III)-hydroxide coprecipitates

DSC measurements in air from 20 to 800° are reported on aged iron(III)-chromium(III) coprecipitated hydroxides (with Fe³⁺Cr³⁺ wt% ratios of 91, 73, 11, 37 and 19). A comparison of the DSC profiles of aged coprecipitates with the thermal behaviour of freshly precipitated and well characterized samples provided information on the modification occurring in the structure and reactivity of the coprecipitates on prolonged aging.

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Zusammenfassung Es werden DSC-Messungen an gealterten kogefällten Eisen(III)Chrom(III)-hydroxiden (mit Fe³⁺Cr³⁺ Gewichtsanteilen von 91, 73, 11, 37 und 19) im Temperaturbereich von 20 bis 800° beschrieben. Ein Vergleich der DSC-Profile von gealterten Kofällungen mit dem thermischen Verhalten frisch gefällter und gut definierbarer Proben lieferte Informationen über die Veränderungen in Struktur und Reaktivität der Koniederschläge bei längerem Altern.

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Dedicated to Professor Wahid U. Malik, Founder-President, Indian Council of Chemists, India, with profound regards and fond memories of his youthful enthusiasm and ceaseless and pioneering efforts towards the development of chemical education and research activities at the University of Roorkee, Roorkee, India, on the occasion of his 70th birthday.

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Paper presented at the World Conference on Thermal Analysis, Capri (Italy), 1989.

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We thank Professor J. Pescia, Dr.G. Ablart and N. Favillier of Laboratoire de Magnétisme et d'Electronique Quantique for their interest in this work. A. C. Vajpei expresses his gratefulness to C.N.R.S. and C.N.O.U.S., Paris, for financial support of this work.     

2020 Roadmap on two-dimensional nanomaterials for environmental catalysis

This roadmap demonstrates a series of two-dimensional nanomaterials, such as graphene, black phosphorus, oxides, layered double hydroxides, chalcogenides, bismuth-based layered compounds, MXenes, metal organic frameworks, covalent organic frameworks, and others, for environmental catalysis.     

Interfacial and micellar properties of binary mixtures of surfactant and phospholipid in an aqueous medium

Mixed micelles formed by zwitterionic surfactant dimethyldodecylammniopropane sulfonate and short-chain phospholipid 1,2-diheptanoyl-sn-glycero-3-phosphocholine in different proportions in an aqueous medium have been studied physicochemically at an air/water interface and in the bulk by using interfacial tension and pyrene fluorescence intensity measurements, respectively. The critical micellar concentration and free energies of micellization and of interfacial adsorption have been determined. The interfacial study reveals that a mixed monolayer is formed at the air/water interface by the adsorption of surfactant and phospholipid monomers. This has been confirmed by evaluating the interfacial parameters; the maximum surface excess, the minimum area per molecule of a surface-active compound, and the Gibbs surface excess related to surface pressure. The nonideality of mixing, expressed in the terms of the regular solution interaction parameter, #, has negative values over the whole mole fraction range. The negative # values indicate the mutual synergism between the surfactant and phospholipid monomers. The equilibrium distribution of components between micelle and monomer phases was evaluated using a theoretical treatment based on excess thermodynamics quantities evaluated by Motomura's formulation.