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  • 1
    ISSN: 1040-7685
    Keywords: microcolumn liquid chromatography ; liquid chromatography/mass spectrometry ; temperature programming ; optimization methods ; fatty acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A temperature-programmed microcolumn liquid chromatography/mass spectrometry (LC/MS) system has been developed as a practical alternative to conventional solvent-programmed LC/MS. Good reproducibility of solute retention was achieved in a specially modified oven that permitted linear temperature programming between 40 and 100°C at rates of 0.1 to 0.5°C min-1. Through theoretical modelling studies performed under isocratic and isothermal conditions, the optimum separation under temperature-programmed conditions was rapidly and accurately predicted. This method enabled the complete resolution of saturated and unsaturated fatty acids in a fish oil dietary supplement with identification from their characteristic fragmentation patterns under electron-impact MS conditions. The mass spectra from the LC/MS system correlated very well with those from a standard reference library to facilitate spectral searching methods.
    Additional Material: 11 Ill.
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  • 2
    ISSN: 0887-3585
    Keywords: crystals ; bacterial esterase ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Large crystals of arylesterase from Pseudomonas fluorescens have been grown at room temperature using ammonium sulfate as a precipitant. They grow to dimensions of 0.7 × 0.7 × 0.6 mm3 within a month. The crystals belong to the trigonal space group P31 (or P32), with unit cell dimensions of a= 147.12 Å and c= 131.08 Å. The asymmetric unit seems to contain six molecules of dimeric aryles-terase, with corresponding crystal volume per protein mass (VM) of 2.53 Å3/Da and solvent fraction of 51.5% by volume. The crystals diffract to at least 2.2 Å Bragg spacing when exposed to X-rays from a rotating-anode source. X-ray data have been collected to 2.9 Å Bragg spacing from native crystals. © 1993 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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  • 3
    ISSN: 1042-7147
    Keywords: 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
    Notes: Small-angle neutron scattering studies have been used to clarify several aspects of the internal structure of latexes and subsequent film formation modes. This paper reviews work both around the world and at Lehigh University on those subjects. Two points have been made clear: (1) The appearance of core-shell phenomena in latexes depends on the size of the polymer chain to that of the latex particle; the phenomenon is most marked when the radius of gyration of the chain is about one fifth as big as the latex radius. (2) Strength build-up during film formation depends on the extent of interdiffusion of the chains. For moderate molecular weights, interdiffusion distances of one radius of gyration yield maximum strength. For both moderate (250,000 g/mol) and high (2,000,000 g/mol) molecular weights, full strength was achieved in two hour's annealing time at 144°C.
    Additional Material: 11 Ill.
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  • 4
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Nuclear magnetic relaxation techniques have been used to study the microphase structure of sodium sulfonated polystyrene ionomers. Microphase separation in the ionomers could be evidenced by the magnetization decays, which were resolved into two components. At lower temperature, 300K, the decay function for the ionomer was found to be a combination of two Gaussian functions that are indicative of more rapid dephasing of individual spins, while the magnetization decay at higher temperature, 413K, was composed of both a Gaussian function and a Lorentzian function. The relative portion of the ionic phase in the ionomer was seen to be significantly affected by the ion concentration or the temperature. From the comparison of the relative amounts of the ionic phases obtained from both the material's composition and the nuclear magnetic relaxation experiment, it is anticipated that the ionic domains contain a substantial amount of hydrocarbon segments.
    Additional Material: 5 Ill.
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  • 5
    ISSN: 0887-6266
    Keywords: polystyrene, chain scission in fracture of ; fracture of glassy polymers, energy consuming micromechanisms ; chain scission mechanism in fracture of polystyrene ; glassy polymers, chain scission and fracture of ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The number of chain scissions per unit area that occur during the fracture of partially annealed latex films from Mn ≃ 180,000 g/mol polystyrene particles of about 275 Å radius were measured and correlated to annealing times. A curve with four regimes was found. At short annealing times the curve is nearly flat, in what is called the chain pull-out regime. In the second regime, the number of chains broken per unit area increases with a 0.8 power of annealing time as entanglement of the diffusing polymer chains increases in neighboring host particles. This is in good agreement with Wool's theory which predicts a 0.75 power dependence. Then, after reaching a peak, the number of scissions decreases in the third regime, indicating a change in fracture mechanism. The number of chain scissions increases again in the fourth regime, as final healing of the film interface takes place. Fracture surface analysis reveals a rough surface for short annealing times and a smooth surface for longer annealing times. The number of polymer chain scissions per unit area of fracture surface showed no dependence on initial molecular weights for t ≫ τr where t and τr are annealing and relaxation times, respectively. The number of chain bridges crossing a unit area of interface was suggested as the basic molecular property. © 1992 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 6
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Fourier transform surface-enhanced Raman spectra of 1 × 10-6 M lumiflavin and riboflavin were obtained in silver coloid (pH 7.2) using 1064 nm continuous-wave laser excitation. These Raman spectra imply that the flavin ring III moiety is coadsorbed on the colloidal silver metal surface through oxygens of C(2)=O and C(4)=O with the colloid preparation components, the EDTA anion or the NO3- ion.
    Additional Material: 2 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 13 (1994), S. 201-205 
    ISSN: 0730-6679
    Keywords: 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
    Notes: A rheological technique of determining molecular weight distribution (MWD) of ultra high MFR polypropylene (PP) is presented. The development of this new technique was needed for two reasons. First, the advent of high activity catalyst made possible the direct polymerization and thus the commercialization of very high MFR PP. Secondly, the polydispersity index (PI) measurement based on crossover modulus from G′ and G″ curves, which was developed by Zeichner and Patel in 1981, was proven to be inapplicable to resins with MFR higher than about 40, due to instrument limitations. This new technique utilizes G′ and G″ data at low frequencies which are obtained from a dynamic frequency sweep test at 200°C. PI values, a measure of MWD, determined by this method are proven to have an excellent correlation with those obtained by gel permeation chromatography (GPC). This method has been very useful in determining MWD of melt brown fiber resins whose MFR is normally between 30 and 1000. It has also been used as a quality control tool during the resin production in a commercial plant. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1043-1051 
    ISSN: 0006-3592
    Keywords: cybernetic model ; poly-β-hydroxybutyric acid ; Alcaligenes eutrophus ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The pathway of poly-β-hydroxybutyric acid (PHB) exhibits a mode of transcriptional control induced by environmental stress. A new cybernetic model for coordinated regulation of stress-induced metabolism was developed to predict the growth and the synthesis of PHB in Alcaligenes eutrophus. A plausible objective for this control is optimization of acetyl-CoA utilization so that the cells have a high degree of flexibility in their catabolism. The state equation for key protein synthesis was assumed to have a dependence on the nonlinear control variable. The proposed model can demonstrate the mixed-growth-associated synythesis of PHB. Reported unstructured models were compared statistically with the result of the simulation derived from the proposed model using the experimental data of this study and the literature. The proposed model appeared to provide an excellent description for the overall fermentation range. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 9
    ISSN: 0021-8995
    Keywords: 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: New heteroaromatic polymer containing quinoline unit in the main chain, poly[2,6-(p-phenoxy)-4-phenyl quinoline] (PQ), was synthesized by the acid-catalyzed self-condensation reaction [Friedländer quinoline synthesis] of 4-amino-4′-acetyl-3-benzoyldiphenyl ether, and its chemical structure was characterized by IR and NMR spectra and also by elemental analysis. The PQ was soluble in common organic solvents such as chloroform or tetrahydrofuran; thus a strong coherent film of this polymer could be easily prepared from the solution by the casting or spin-coating technique. Attributing to the wholly aromatic chemical structure, PQ appeared an extremely high thermal stability as to show no weight loss up to 550°C both in air and nitrogen atmosphere. From the UV-VIS absorption spectra, we found that PQ had a strong tendency to form the charge transfer (CT) complex with electron acceptors such as 2,4,7-trinitrofluorenone (TNF). The CT complex film of PQ-TNF showed a good photoconductivity even under the ambient room illumination and was utilized for the fabrication of photovoltaic device whose conversion efficiency was around 10-2%.
    Additional Material: 7 Ill.
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