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  • Wiley-Blackwell  (245)
  • 1995-1999  (245)
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Year
  • 1
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A random packing hydrodynamic simulator is designed specially to carry out experiments under reduced pressures with a counter-current flow air/water system. The simulator results (air/water system) compared to those obtained in a real packed distillation column (benzylchloride/ ethylbenzene system) show a good agreement between hydrodynamic parameters like pressure drop, flooding flow rate, and total liquid hold-up. Empirical relationships derived from the simulator experimental results are proposed allowing the calculation of the pressure drop in a packed distillation column, operating in the pressure range between 10 kPa and atmospheric pressure. The influence of reduced pressure on the HETP in the distillation column and interfacial area in the simulator was also investigated.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We developed the oxidation reaction of Cu(I) ion in aqueous hydrochloric solution by oxygen in a gas-lift capillary bubble column. The method of gas-liquid absorption with chemical reaction was used. Test data confirmed that the rate constant of the reaction is strongly affected by solution compositions, and that chloride ions induce an inhibition effect. The kinetical orders found are equal to 1 and 2 for oxygen and Cu(I) respectively. The influence of temperature on reaction rate constant showed the existence of a maximum value between 303 and 313K. The effect of gas-liquid of gas-liquid system on the liquid-side mass transfer coefficient kL was also investigated.
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 18 (1995), S. 425-433 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Turbidimetry has proved to be an efficient method for the quantitative study of powder agglomeration for particle sizes in the region of 1 μm. This work presents a new application of the technique for the agglomeration of α-alumina in water and in n-heptane. The method of determining the kinetic parameters of agglomeration from the initial time-evolution of turbidity is explained.Turbulent flow in the reactor has also been characterised by laser anemometry. From the turbulence intensity, the number of collisions per unit time is calculated and the agglomeration rate can therefore be determined.Good agreement is found between the values obtained respectively from turbidimetric and hydrodynamic measurements. Addition of KOH modifies the zeta potential of alumina in water and influences the agglomeration kinetics. This can also be quantitatively characterised by turbidimetry. The experimental results obtained for alumina particles of diameter 0.3 μm and 1 μm are interpreted according to the DLVO model of interaction between particles.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of various fluorinated acrylates CH2=CHCOO(CH2)pCnF2n+1 and their kinetics of radical homopolymerization are presented. The fluoroacrylated monomers have been prepared in two steps by acrylation of the corresponding halogenated alcohols produced by radical addition of perfluoroalkyl iodides(CnF2n+1I) to ω-hydroxylated alkenes. The fluorinated acrylates differ from each other in the nature (branched or linear) and the length (n ranging from 1 to 8) of the fluorinated chain and in the nature of the spacer between this fluorinated chain and the ester group (p ranging from 1 to 11). The kinetics of polymerization led to the determination of kp2/kte. These values were compared with those of commercially available fluorinated acrylates and were found to depend upon both the spacer length and the nature of the fluorinated group.
    Additional Material: 2 Ill.
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  • 5
    ISSN: 0959-8103
    Keywords: polyurethane ; network formation ; metallic filler ; viscosity ; kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The addition of metallic fillers is recognized to impart improvement of acoustic properties to polyurethane-based materials used for marine applications. The system under consideration was obtained by the reaction of a triisocyanateterminated prepolymer with 1,4-butanediol, in the presence of various concentrations of lead powder. With increasing lead content, gelation time is reduced and an Einstein-type law does not apply. The kinetics of the reaction were determined by Fourier transform infrared spectroscopy. Deviation from the classic second order is observed for the filled systems, and the higher the lead content, the more important the deviation is, showing undoubtedly the catalytic effect of the metallic powder.
    Additional Material: 6 Ill.
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  • 6
    ISSN: 0173-0835
    Keywords: Galectins ; Hematopoietic cells ; Two-dimensional polyacrylamide gel electrophoresis ; Immunoblotting ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Vertebrate soluble β-galactoside-binding lectins form a growing protein family that recently have been named galectins. Seven different galectins have been sequenced and characterized in mammals, and there is compelling evidence for the existence of other members of this lectin family. Three among six galectins are homodimers with (i) an identical subunit of a relative molecular mass of about 14500, and (ii) amino acid sequence homologies giving rise to possible immunochemical cross-reactivities. They are indistinguishable from each other by conventional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), even when followed by immunoblottin. However, their different isoelectric points allow their identification using isoelectric focusing and two-dimensional (2-D) polyacrylamide gel electrophoresis. A strategy was developed to identify these galectins in crude extracts from cells and tissues, based on the two-dimensional electrophoresis with immobilized pH gradient (IPG-Dalt) analysis of the specific spots of purified galectins and of the spots of crude extracts, after silver staining. In addition, 2-D immunoblotting using anti-galectin 1 (Gal-1) and anti carbohydrate-binding protein 15 (CBP15) antibodies were performed on brain and leukemia cells (HL60) allowing an identification of related polypeptides. Our results indicate that the use of IPG-Dalt provides a suitable reproducibility and allows the detection of galectins or other galactoside-binding proteins even at basic p/s.
    Additional Material: 8 Ill.
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  • 7
    ISSN: 0006-3525
    Keywords: ACTH ; lipid-peptide interaction ; 1H-nmr ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of the 5-14, 1-14, and 1-24 fragments of ACTH with sonicated phospholipid bilayers containing egg yolk phosphatidylcholine (EPC) either pure or mixed with 10 mole % phosphatidic acid (EPA), was investigated by proton nuclear magnetic resonance (1H-nmr). The effects observed with zwitterionic EPC vesicles were small, indicating a low binding of the ACTH derivatives. The N-terminal aromatic resonances of the ACTH peptides were markedly broadened in the presence of negatively charged vesicles (EPC/EPA 9:1 M/M), while those of the C-terminal end were barely affected, showing that ACTH interacts with its N-terminal fragment. The choline resonance of the EPC molecules of the outer monolayer was shifted and broadened upon ACTH binding to the lipid vesicles, while that of the inner layer was not affected, suggesting that the peptide molecules interact only with the external leaflet of the lipid bilayer. The C2H and C4H resonances of the histidine-6 side chain were both shifted downfield upon peptide binding to the negatively charged lipid interface. In the case of the 1-24 derivative, these resonances were also split into two signals reflecting two different species of membrane-bound ACTH 1-24. Analysis of the line width and chemical shift variations of the ACTH and lipid resonances observed upon peptide binding shows that the membrane-binding potency of the shorter 5-14+1 fragment, which presents a +1 net charge, is roughly similar to that of the highly cationic 1-24+6 (net charge +6) derivative, implying that the 15-24+5 segment is not essential for membrane binding. The nmr measurements at a fixed lipid-to-peptide ratio in the presence of increasing amounts of spin-labeled lipids demonstrate that the N-terminal fragment of ACTH does not penetrate the hydrophobic core of the bilayer, and should lie parallel to the membrane surface. © 1997 John Wiley & Sons, Inc. Biopoly 42: 731-744, 1997
    Additional Material: 11 Ill.
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  • 8
    ISSN: 0887-3585
    Keywords: Protein crystallization ; X-ray crystallography ; methanogenic Archaea ; hyperthermophilic enzymes ; halophilic enzymes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Formylmethanofuran:tetrahydromethanopterin formyltransferase from the hyperthermophilic methanogenic Archaeon Methanopyrus kandleri (growth temperature optimum 98°C) was crystallized by vapor diffusion methods. Crystal form M obtained with 2-methyl-2,4-pentanediol as precipitant displayed the space group P21 with unit cell parameters of a = 87.0 Å, b = 75.4 Å, c = 104.7 Å, and β = 113.9° and diffracted better than 2 Å resolution. Crystal form P grown from polyethylene glycol 8000 belonged to the space group I4122 and had unit cell parameters of 157.5 Å and 242.1 Å. Diffraction data to 1.73 Å were recorded. Crystal form S which was crystallized from (NH4)2SO4in the space group I4122 with unit cell parameters of 151.3 Å and 249.5 Å diffracted at least to 2.2 Å resolution. All crystal forms probably have four molecules per asymmetric unit and are suitable for X-ray structure analysis. © 1996 Wiley-Liss, Inc.
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  • 9
    ISSN: 0887-3585
    Keywords: small-angle scattering ; x-rays ; allosteric enzymes ; crystal structure ; rigid body modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Solution scattering curves evaluated from the crystal structures of the T and R states of the allosteric enzyme aspartate transcarbamylase from Escherichia coli were compared with the experimental x-ray scattering patterns. Whereas the scattering from the crystal structure of the T state agrees with the experiment, large deviations reflecting a significant difference between the quaternary structures in the crystal and in solution are observed for the R state. The experimental curve of the R state was fitted by rigid body movements of the subunits in the crystal R structure which displace the latter further away from the T structure along the reaction coordinates of the T→R transition observed in the crystals. Taking the crystal R structure as a reference, it was found that in solution the distance between the catalytic trimers along the threefold axis is 0.34 nm larger and the trimers are rotated by 11° in opposite directions around the same axis; each of the three regulatory dimers is rotated by 9° around the corresponding twofold axis and displaced by 0.14 nm away from the molecular center along this axis. Proteins 27:110-117 © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 10
    ISSN: 0887-3585
    Keywords: SacY ; antiterminator ; RNA-binding motif ; crystallization ; x-ray crystallography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: SacY is the antiterminator protein involved in the induction by sucrose of the expression of the levansucrase gene (sacB) of Bacillus subtilis. In the presence of sucrose, SacY is activated and prevents premature termination of transcription by binding to a RNA-antiterminator (RAT) sequence partially overlapping with the terminator sequence. SacY consists of a RNA-binding N-terminal domain, SacY(1-55), and a regulatory domain, SacY(56-280), sensitive to the sucrose concentration. SacY(1-55) is in itself capable of binding to the RAT sequence and preventing termination independently of the sucrose concentration. In this paper we describe the overexpression, the purification, and the crystallization of SacY(1-55). We obtained six different crystal forms, some of them diffracting to high resolution (〉1.5 Å). Self rotation function calculations indicated the presence of a dimer in the asymmetric unit, which is in agreement with a proposed oligomeric state in solution as observed by high-resolution NMR measurements. The crystallization of some site-directed cysteine mutants opens the way of solving the structure by multiple isomorphous replacement. Proteins 28:590-594, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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