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  • Industrial Chemistry  (9,655)
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  • 1
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    Geophysical and geochemical survey of a large marine pockmark on the Malin Shelf, Ireland (2012)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q01011, doi:10.1029/2011GC003787.
    Description: Marine pockmarks are a specific type of seabed geological setting resembling craters or pits and are considered seabed surface expressions of fluid flow in the subsurface. A large composite pockmark on the Malin Shelf, off the northern coast of Ireland was surveyed and ground truthed to assess its activity and investigate fluid related processes in the subsurface. Geophysical (including acoustic and electromagnetic) data confirmed the subsurface presence of signatures typical of fluids within the sediment. Shallow seismic profiling revealed a large shallow gas pocket and typical gas related indicators such as acoustic blanking and enhanced reflectors present underneath and around the large pockmark. Sulphate profiles indicate that gas from the shallow reservoir has been migrating upwards, at least recently. However, there are no chimney structures observed in the sub-bottom data and the migration pathways are not apparent. Electromagnetic data show slightly elevated electrical conductivity on the edges of the pockmarks and a drop below regional levels within the confines of the pockmark, suggesting changes in physical properties of the sediment. Nuclear Magnetic Resonance (NMR) experiments were employed to characterize the organic component of sediments from selected depths. Very strong microbial signatures were evident in all NMR spectra but microbes outside the pockmark appear to be much more active than inside. These observations coincide with spikes in conductivity and the lateral gas bearing body suggesting that there is an increase in microbial activity and biomass when gas is present.
    Description: We wish to thank the Geological Survey of Ireland, the INtegrated Mapping FOr the Sustainable Development of Ireland’s MArine Resource (INFOMAR) program, the Irish Environmental Protection Agency, Science Foundation of Ireland, QUESTOR (Queens University Belfast) and the Irish Council for Science, engineering and technology for funding this research. AJS thanks NSERC, (Strategic and Discovery Programs), the Canada Foundation for Innovation (CFI), and the Ministry of Research and Innovation (MRI) for providing Canadian funding. The survey data utilized in the research has been co‐funded by the Geological Survey of Ireland and the Offshore Irish Petroleum Infrastructure Programme (PIP; Ref. No: IS05/16 Malin Basin EM).
    Description: 2012-07-19
    Keywords: Malin Shelf ; NMR ; Electromagnetic ; Microbial ; Organic matter ; Pockmark
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Molecular phylogenetics of the Metazoan clade Lophotrochozoa (2008)
    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2003
    Description: DNA sequencing and phylogenetic analyses were conducted to investigate evolutionary relationships between taxa within the metazoan clade Lophotrochozoa. Chapter 1 presents an introduction to phylogenetics of the Metazoa and the clade Lophotrochozoa. Chapter 2 analyzes higher level relationships between the major groups within the phylum Mollusca using sequences of the nuclear ribosomal large-subunit RNA gene (LSD rDNA). Results presented provide the first molecular evidence for a close relationship between the Scaphopoda and Cephalopoda. Phylogenetic trees with this topology were found to have likelihood scores significantly better than those for phylogenies constrained to fit the Diasoma hypothesis grouping Scaphopoda and Bivalvia as sister taxa. Chapter 3 utilizes LSU rDNA sequences to analyze relationships between diverse phyla within the clade Lophotrochozoa. LSU rDNA sequences were found to provide greater resolution than has been provided by previous analyses of the nuclear small-subunit ribosomal RNA gene (SSU rDNA). Analysis ofLSU rDNA sequences recovered the monophyly of several phyla, such as Mollusca and Anelida, whose members are found to be paraphyletic using SSU rDNA sequences alone. Results also suggest that the clade Platyzoa, including rotifers and platyhelminthes, may have arisen within the Lophotrochozoa, rather than as a sister group to lophotrochozoans. Chapter 4 investigates the Hox gene complement of the bryozoan Bugula turrita. Six Hox genes were recovered, including an ortholog of the posterior class gene Post2, which is a synapomorphy for the Lophotrochozoa. The identification of a Post2 ortholog provides evidence of a close relationship between the Bryozoa and other lophotrochozoan phyla.
    Description: This work was supported by a grant from the National Science Foundation, DEB-0075618 "Genomic approaches to metazoan evolution; lophotrochozoans and Hox genes" to Kenneth Halanych. Bryozoan Hox research was supported by a Doctoral dissertation Improvement Grant from the National Science Foundation, DEB-OI04984 "Phylogenetic inference from bryozoan Hox genes" to Kenneth Halanych and Yale Passamaneck. Additional support was provided by the Woods Hole Oceanographic Institution Education Office.
    Keywords: Mollusks ; Phylogeny ; Evolution ; Genome mapping ; Homeobox genes ; Recombinant DNA ; Cladistic analysis
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of flexible lattice aluminium in zeolite beta during the nitration of toluene with nitric acid and acetic anhydride (2000)
    Springer
    Catalysis letters 70 (2000), S. 61-65 
    Details
    ISSN: 1572-879X
    Keywords: flexible lattice aluminium ; zeolite beta ; nitration ; regio‐control ; para‐selectivity ; toluene ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The nitration of toluene with nitric acid and acetic anhydride using zeolite H‐beta as catalyst was studied with multi‐nuclear solid‐state NMR spectroscopy in order to investigate the causes for the observed enhanced para‐selectivity. The reversible transformation of framework aluminium from a tetrahedral into an octahedral environment was observed by 27Al NMR upon interaction of the zeolite with the different components of the nitrating system. The octahedral co‐ordination complex between lattice aluminium and acetylnitrate might explain the surface‐catalysed para‐selective nitration reaction and suggests that the lattice flexibility plays an important role in determining the regio‐selectivity of the nitration catalysed by zeolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019015216483
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  • 4
    Electronic Resource
    Electronic Resource
    A comparative CP/MAS 13C-NMR study of cellulose structure in spruce wood and kraft pulp (2000)
    Springer
    Cellulose 7 (2000), S. 35-55 
    Details
    ISSN: 1572-882X
    Keywords: cellulose ; hemicellulose ; kraft pulp ; NMR ; spruce wood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract CP/MAS 13C-NMR spectroscopy in combination with spectral fitting was used to study the supermolecular structure of the cellulose fibril in spruce wood and spruce kraft pulp. During pulping, structures contributing to inaccessible surfaces in the wood cellulose are converted to the cellulose Iβ allomorph, that is, the degree of order is increased. This increase is also accompanied by a conversion of cellulose Iα to cellulose Iβ. Cellulose from wood composed of different cell types, that is, compression wood, juvenile wood, earlywood, latewood and normal wood exhibited a similar supermolecular structure. Assignments were made for signals from hemicellulose which contribute significantly to the spectral C-4 region (80–86 ppm) in kraft pulp spectra but substantially less to the corresponding region in wood spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009236932134
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  • 5
    Electronic Resource
    Electronic Resource
    A 29Si MAS-NMR study of Cd7[Ge6Si]O21 pyroxmangite (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 713-718 
    Details
    ISSN: 1432-2021
    Keywords: Key words Cd-pyroxmangite ; NMR ; Pyroxenoids ; Ordering ; Superperiods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Synthetic (SiGe)-pyroxenoids are often observed to have superperiods. Whether or not these superperiods grow in connection with Si-Ge ordering is a fundamental question. The size difference between Ge and Si tetrahedra leads to CdGeO3 having the pyroxmangite structure, whereas CdSiO3 has the wollastonite structure. Consequently, considerable strain is expected for a pyroxenoid with a disordered Ge-Si distribution. A 29Si MAS-NMR study of a Cd-pyroxmangite of nominal composition Cd7[Ge6Si]O7 points to considerable Si clustering, probably as GeSiSiSiGe triples corresponding to the wollastonite-like units of the siebener chain. It is proposed that such ordering relieves strain within the tetrahedral chain. Residual strain is also relieved by insertion of an extra pair of GeO4 tetrahedra into the pyroxene-like component of the siebener-chain units, leading to single neuner-chain units which terminate the superperiods. This growth pattern is cyclic. The presence of several types of superperiod may reflect similar energetics for different Ge-Si-ordering patterns within the siebener chains. Ordering of Si-rich unit cells and of unit cells having no Si is proposed as the reason for the occurrence of the superperiods in Cd-pyroxmangite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690000115
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  • 6
    Electronic Resource
    Electronic Resource
    NMR Structure Determination and Structure-Based Functional Characterization of Conserved Hypothetical Protein MTH1175 from Methanobacterium thermoautotrophicum (2000)
    Springer
    Journal of structural and functional genomics 1 (2000), S. 15-25 
    Details
    ISSN: 1570-0267
    Keywords: structural genomics ; RNase H ; NMR ; methanobacterium thermoautotrophicum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The solution structure of MTH1175, a 124-residue protein from the archaeon Methanobacterium thermoautotrophicum has been determined by NMR spectroscopy. MTH1175 is part of a family of conserved hypothetical proteins (COG1433) with unknown functions which contains multiple paralogs from all complete archaeal genomes and the archaeal gene-rich bacterium Thermotoga maritima. Sequence similarity indicates this protein family may be related to the nitrogen fixation proteins NifB and NifX. MTH1175 adopts an α/β topology with a single mixed β-sheet, and contains two flexible loops and an unstructured C-terminal tail. The fold resembles that of Ribonuclease H and similar proteins, but differs from these in several respects, and is not likely to have a nuclease activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011348803324
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  • 7
    Electronic Resource
    Electronic Resource
    Structure and Morphology of a Polyether/Polyacrylate Semi-interpenetrating Polymer Network (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 83-92 
    Details
    ISSN: 1572-8943
    Keywords: cationic and photoinitiated polymerization ; DSC ; interfacial mixing ; interpenetrating polymer network (IPN) ; glass transition temperature ; NMR ; quantitative thermal analysis of phases ; reactive epoxy and acrylate systems ; Tg broadening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study NMR and DSC are used to probe the structure, thermal characteristics and morphology of a network formed from a diepoxide/acrylate system. Separate chemistries are employed to polymerize the diepoxide and acrylate components. The cationic polymerization of the diepoxide exhibits excellent selectivity in producing a crosslinked polyether network without affecting the acrylate monomer. Subsequent photoinitiated free-radical polymerization of the acrylate produces a phase separated, semi-interpenetrating polymer network (SIPN).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010123610324
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  • 8
    Electronic Resource
    Electronic Resource
    [13C]Dynamic NMR and Molecular Modeling of 2,4-Bis(N-Pyrrolidinyl)-6-chloro-s-triazine (2000)
    Springer
    Structural chemistry 11 (2000), S. 303-306 
    Details
    ISSN: 1572-9001
    Keywords: NMR ; [13C]NMR ; 2,4-bis(N-pyrrolidinyl)6-chloro-s-triazine ; variable temperature ; molecular modeling ; rotational barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The room temperature [13C]NMR spectrum of 2,4-bis(N-pyrrolidinyl)-6-chloro-s-triazine shows doubled signals for the pyrrolidine rings, which suggests restricted rotation about the Ar-C—N bond. The rotational barrier around this bond was determined by [13C]dynamic NMR (DNMR) spectra run at different increasing temperatures and also by the PM3 Hamiltonian contained in the MOPAC package. The values thus obtained, 16.6 and 13.6 kcal mol−1, respectively, are in good agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009238326751
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  • 9
    Electronic Resource
    Electronic Resource
    An NMR Study of MeTMS Based Coatings Filled with Colloidal Silica (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 131-135 
    Details
    ISSN: 1573-4846
    Keywords: coatings ; colloids ; NMR ; organosilanes ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Coatings were prepared by mixing MeTMS and an aqueous colloidal silica. Mixing of an MeTMS hydrolysis mixture with the aqueous colloidal silica is only possible, without flocculation of the colloidal silica particles, within a certain time window. 29Si NMR was used to follow the hydrolysis/condensation reactions of MeTMS, whereas 1H NMR was used to monitor the reaction of the MeTMS monomers and oligomers with the silica surface in the coating liquid. The reaction of MeTMS with the surface of the SiO2 particles is determined by the oligomer size. Typical SiO2 surface coverage is less than 3 molecules/nm2 (approximately one monolayer). Large MeTMS oligomers and/or cyclic species do not react with the SiO2 surface. These species are probably too apolar to react or absorb at the SiO2 surface. Flocculation of the aqueous colloidal silica occurs due to the low polarity of the hydrolysis mixture. The water content and the degree of condensation of the MeTMS determine the width of the time window.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008795113990
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  • 10
    Electronic Resource
    Electronic Resource
    Non-Hydrolytic Routes for the Synthesis of NASICON (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 463-467 
    Details
    ISSN: 1573-4846
    Keywords: NASICON ; NMR ; non-hydrolytic synthesis ; precursor chemistry ; solid electrolyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The study of non-hydrolytic reactions for the synthesis of NASICON is reported. Different procedures have been considered, changing the precursors and their addition order, and varying the reaction solvent; dichloromethane, acetonitrile and tetrahydrofuran (THF). The most promising results in terms of homogeneous reactivity were obtained using PO(On-C4H9)3, Zr(Ot-C4H9)4, SiCl4 and Na(Ot-C4H9) in acetonitrile. The reactions were followed using heteronuclear Nuclear Magnetic Resonance (NMR) spectroscopy (13C, 31P). NASICON powders were prepared by the thermal decomposition of the gels between 900 and 1200°C. The powders were analyzed by XRD to check the formation of the NASICON phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008707815750
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  • 11
    Electronic Resource
    Electronic Resource
    Comparative Study of Structure of Silica Gels from Different Sources (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 495-499 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; silicas ; biology ; X-ray diffraction ; IR ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The medium-range-network structure of silicas from different sources was comparatively examined by X-ray diffraction, IR and NMR analyses. Silica gels made through the conventional sol-gel route were found to have a different structure from silica glass, and considered to be composed of 4-fold siloxane ring units, irrespective of preparation conditions. Amorphous silicas in rice-hulls and bamboo leaves showed structure data close to silica glass, being suggested to consist mainly of 6-fold siloxane ring units. The modified sol-gel method, in which siloxane oligomers containing cyclic siloxane tetramers may have been ring-opened and polymerized under the catalytic reaction of NaOH or NH4F in the water-free solution, provided the silica gel of which structure was very similar to silica glass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008720118475
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  • 12
    Electronic Resource
    Electronic Resource
    Low Temperature Sol-Gel Preparation of β-Al2TiO5 Thin Films: Spectroscopic Analysis of the Precursors (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 577-580 
    Details
    ISSN: 1573-4846
    Keywords: aluminum titanate ; NMR ; MS ; thin films ; precursor chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two sol-gel syntheses allowed the preparation of β-Al2TiO5 thin films on silicon substrates at 700°C, reacting aluminum and titanium alkoxides with and without acetylacetone as a chelating agent. Nuclear magnetic resonance (NMR) and mass spectra of the sols allowed identification of the intermediate species formed and to show the formation of an Al-Ti containing polymer establishing that the synthesis without acetylacetone leads to the most extensive polymerization. The formation of β-Al2TiO5 at low temperatures is attributed to diffusion-limited crystallization process, which takes place in the conditions of high homogeneity at molecular level reached in the sol-gel synthesis. The crystallization of the films was studied as a function of the firing time and temperature and confirmed that β-Al2TiO5 with better thermal stability was obtained with the synthesis without chelating agent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008705109815
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  • 13
    Electronic Resource
    Electronic Resource
    The Structure of Hybrid Gels by Drift and NMR Spectroscopies (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 403-407 
    Details
    ISSN: 1573-4846
    Keywords: hybrid gels ; silica ; polytetrahydrofuran ; DRIFTS ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hybrid inorganic-organic gels have been prepared by the sol-gel process using tetraethoxysilane (TEOS) as precursor, mixed with a low concentration of polytetrahydrofuran (PTHF), under acid catalysis. The hybrid xerogels were characterized by DRIFTS and Solid State 1H, 13C and 29Si NMR. The DRIFT spectra indicate that the polymer is responsible for decreasing the number of free silanol groups in comparison to pure silica. Solid-state NMR spectra reveal the types of silicate structures formed and the conditions for establishing chemical bonds between the two phases, which are responsible for the silica network flexibility. We have concluded that it is possible to design a hybrid gel with tailored properties, even at very low polymer concentration, by selecting the appropriate preparation route.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008783010298
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  • 14
    Electronic Resource
    Electronic Resource
    The Effect of Nanoscaled Metal Oxide Sols on the Structure and Properties of Glycidoxypropyltrimethoxysilane Derived Sols and Gels (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 305-309 
    Details
    ISSN: 1573-4846
    Keywords: epoxide ; ring-opening ; condensation ; NMR ; hardness ; nanoparticles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Glycidoxypropyltrimethoxysilane (GPTS) is frequently used as precursor for the preparation of sol-gel derived nanoscaled hybrid polymers. The influence of nanoscaled metal oxide sols of silica, boehmite, zirconia and ceria on reactions of GPTS in ethanolic hydrolysates and in corresponding gels (epoxide ring-opening, condensation degree) was examined by liquid- and solid-state 13C and 29Si NMR with regard to a better correlation between structure and material properties. Generally, a higher condensation degree of RSi(O0.5)3 units of GPTS is found after addition of metal oxide sols compared to GPTS without additives. The metal oxide sols (10 mole% series) cause an epoxide ring-opening up to 20% in GPTS hydrolysates after 24 h. A nearly complete ring opening was found in the boehmite and silica containing hybrid gels whereas gels containing ceria and other types of silica only show a low degree of ring-opening. The results show an accelerated ring-opening with increasing content of AlO/OH-species in silica sols. 13C NMR studies reveal that the epoxide ring-opening does not completely lead to polyether structures but to considerable amounts (up to 40%) of ethylether groups which can influence the material properties (hardness).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008777414416
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  • 15
    Electronic Resource
    Electronic Resource
    Conformational Studies of a Melittin—Inhibitor Complex (2000)
    Springer
    The protein journal 19 (2000), S. 529-534 
    Details
    ISSN: 1573-4943
    Keywords: Melittin ; inhibitor ; NMR ; peptide ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The conformation of a melittin—inhibitor complex was studied by solution NMR, solid-state NMR, and circular dichroism. In solution, binding was studied by titrating inhibitor against melittin in dimethyl sulfoxide, methanol, aqueous buffer, and dodecylphosphocholine micelles. The change in chemical shift of Trp19 resonances and the formation of a precipitate at 1:1 molar ratio indicated that the inhibitor was bound to melittin. Solid-state NMR also showed a change in chemical shift of two labeled carbons of melittin near Pro14 and a change in 1H T 1 relaxation times when complexed with inhibitor. Rotational resonance experiments of melittin labeled in the proline region indicated a change in conformation for melittin complexed with inhibitor. This observation was also supported by circular dichroism measurements, indicating a reduction in α-helical structure for increasing ratios of inhibitor bound to melittin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026561701338
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  • 16
    Electronic Resource
    Electronic Resource
    Temperature, pH, and Solvent Isotope Effects on Cytochrome c Peroxidase Mutant N82A Studied by Proton NMR (2000)
    Springer
    The protein journal 19 (2000), S. 535-542 
    Details
    ISSN: 1573-4943
    Keywords: Cytochrome c peroxidase ; CcP ; NMR ; A82CcP mutant ; solvent isotope effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The mutant of baker's yeast cytochrome c peroxidase-CN with Ala82 in place of Asn82, [N82A]CcPCN, exhibits a complex solution behavior featuring dynamic interconversion among three enzyme forms that so far have only been detected by NMR spectroscopy. Proton NMR studies of [N82A]CcPCN reveal resonances from each of the three enzyme forms and show that the interconversion among forms is controlled by the pH, temperature, and isotope composition (H2O vs. D2O) of the buffer solution. No evidence for a key hydrogen bond between His52 and heme-coordinated cyanide is found in any of the enzyme forms, indicating that disruption of the extensive distal hydrogen bonding network is the source of this phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026513818176
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  • 17
    Electronic Resource
    Electronic Resource
    Analysis of the structure of lignin-carbohydrate complexes by the specific13C tracer method (2000)
    Springer
    Journal of wood science 46 (2000), S. 130-136 
    Details
    ISSN: 1611-4663
    Keywords: Lignin-carbohydrate complexes ; NMR ; 13C tracer ; Coniferin ; Ketal linkage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In the present study the specifically13C-enriched lignin precursors of biosynthesis (i.e., coniferin-[side chainα−13C], coniferin-[side chain-β−13C] and coniferin-[side chain-γ−13C]) were synthesized and administered exogeneously to ginkgo shoots (Ginkgo biloba L.) to obtain13C-enriched lignin-carbohydrate complexes (LCCs). The specifically13C-enriched LCCs were isolated from the newly formed xylem of ginkgo shoots administered with the13C-enriched precursors and degraded by enzymes. Lignin-rich fractions, so called enzyme-degraded LCCs (EDLCCs), were obtained. By determining their13C-NMR spectra, information related to the chemical structure of lignin building units and linkages between phenylpropane units of lignin and carbohydrates were obtained. It was found that these precursors were incorporated in natural lignin successfully. Three lignin-carbohydrates linkages (i.e., ether type, ester type, ketal type) were found at the C α -position of the side chain of phenylpropane units in ginkgo LCC. No lignin-carbohydrate bond at the Cβ- or Cγ-position of the lignin side chain was observed in the13C-NMR spectra of the13C-enriched LCCs. This fact indicates that a specific13C tracer technique can be useful in NMR study of the chemical structure of LCCs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00777359
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  • 18
    Electronic Resource
    Electronic Resource
    Modeling ganglioside headgroups by conformational analysis and molecular dynamics (2000)
    Springer
    Glycoconjugate journal 17 (2000), S. 283-299 
    Details
    ISSN: 1573-4986
    Keywords: ganglioside conformation ; NMR ; molecular mechanics ; molecular dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The conformations and dynamics of gangliosides GM1, GM2, 6′-GM2 and GM4 have been studied by computational means, and the results compared to NMR data. Unconstrained conformational searches were run using the AMBER* force field augmented by MNDO derived parameters for the Neu5Ac anomeric torsion, the GB/SA water solvation model, and the MC/EM alogorithm; extended (10–12[emsp4 ]ns) dynamic simulations in GB/SA water were performed with the MC/SD protocol, and the stored structures were minimized. The overall mobility of the Neu5Acα2,3Gal linkage and the position of its minimum energy conformation have been shown to depend mainly on the presence or the absence of a GalNAc residue at the adjacent position. The best quantitative agreement with the available NOE data was achieved after minimization of the structures stored during the MC/SD dynamic runs. The latter protocol appears to reproduce satisfactorily the available experimental data, and can be used with confidence to build three-dimensional models of ganglioside headgroups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007161319700
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  • 19
    Electronic Resource
    Electronic Resource
    Glycosylations versus conformational preferences of cancer associated mucin core (2000)
    Springer
    Glycoconjugate journal 17 (2000), S. 835-848 
    Details
    ISSN: 1573-4986
    Keywords: cancer vaccine ; glycopeptide ; MUC-1 ; immunotherapy ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Synthetic oligosaccharide vaccines based on core STn (sialyl α2-6 GalNAc) carbohydrate epitopes are being evaluated by a number of biopharmaceutical firms as potential immunotherapeutics in the treatment of mucin-expressing adenocarcinomas. The STn carbohydrate epitopes exist as discontinuous clusters, O-linked to proximal serine and threonine residues within the mucin sequence. In an effort to probe the structure and dynamics of STn carbohydrate clusters as they may exist on the cancer-associated mucin, we have used NMR spectroscopy and MD simulations to study the effect of O-glycosylation of adjacent serine residues in a repeating (Ser)n sequence. Three model peptides/glyco-peptides were studied: a serine trimer containing no carbohydrate groups ((Ser)3 trimer); a serine trimer containing three Tn (GalNAc) carbohydrates α-linked to the hydroxyls of adjacent serine sidechains ((Ser.Tn)3 trimer); and a serine trimer containing three STn carbohydrates α-linked to the hydroxyls of adjacent serine sidechains ((Ser.STn)3 trimer). Our results demonstrate that clustering of carbohydrates shifts the conformational equilibrium of the underlying peptide backbone into a more extended and rigid state, an arrangement that could function to optimally present the clustered carbohydrate antigen to the immune system. Steric effects appear to drive these changes since an increase in the size of the attached carbohydrate (STn versus Tn) is accompanied by a stronger shift in the equilibrium toward the extended state. In addition, NMR evidence points to the formation of hydrogen bonds between the peptide backbone NH protons and the proximal GalNAc groups in the (Ser.Tn)3 and (Ser.STn)3 trimers. The putative peptide-sugar hydrogen bonds may also play a role in influencing the conformation of the underlying peptide backbone, as well as the orientation of the O-linked carbohydrate. The significance of these results will be discussed within the framework of developing clustered STn-based vaccines, capable of targeting the clustered STn epitopes on the cancer-associated mucin.
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    URL: http://dx.doi.org/10.1023/A:1010909011496
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    Energy metabolism and re-establishment of intercellularadhesion complexes of gel entrapped hepatocytes (2000)
    Springer
    Cytotechnology 32 (2000), S. 219-228 
    Details
    ISSN: 1573-0778
    Keywords: alginate ; bioreactor ; energy metabolism ; hepatocytes ; microscopy ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We studied the effect of continuous medium flow on the viabilityand structural organization of hepatocytes high density entrapped inalginate gel beads in the first few hours after isolation.The metabolic energy status of the entrapped cells, monitored invivo by 31P NMR spectroscopy, was stable during theexperimental time and a physiological redox ratio was reachedafter the first three hours of culture. The morphologicalanalysis revealed that the entrapped hepatocytes placed in a fixed-bed bioreactor under continuous flow showed a polyhedricalshape with numerous microvilli on cell surface and reconstitutedtight junctions as well as bile canalicular structures, closelyresembling those present in the liver.These results suggest that continuous flow allows the culture ofhepatocytes at very high cell density within a matrix withoutloss of viability and accelerates cellular tissue reconstructionat very short times after isolation. This type of culture couldrepresent a very useful model for physiological andtoxicological studies as well as a promising approach toward thedevelopment of a bioartificial hybrid support device in acuteliver failure.
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    URL: http://dx.doi.org/10.1023/A:1008134005529
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    Structural studies of the glycopeptides of B-chain of cinnamomin – a type II ribosome-inactivating protein by nuclear magnetic resonance (2000)
    Springer
    Glycoconjugate journal 17 (2000), S. 749-759 
    Details
    ISSN: 1573-4986
    Keywords: cinnamomin ; glycopeptides ; NMR ; primary structure ; ribosome-inactivating protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cinnamomin is a plant type II ribosome-inactivating protein (RIP) isolated from the seeds of Cinnamomum camphora. It consists of two nonidentical polypeptide chains (A- and B-chain) held together through one disulfide linkage. Its A- and B-chain contain 0.3% and 3.9% sugars respectively. The B-chain of cinnamomin was digested by pronase E and then the liberated glycopeptides were separated from non-glycopeptides by gel filtration chromatography on a Bio-Gel P-4 column. Three crude glycopeptides were obtained by continuing chromatography over anion-exchange resin (AG1-X2) in the buffer of 2% pyridine-acetic acid (pH 8.3) with a polygradient elution system. Through further purification by the gel filtration chromatography and HPLC, three major glycopeptides, GP1, GP2 and GP3 were obtained. Mainly by two-dimensional Nuclear Magnetic Resonance (NMR) including TOCSY, DQF-COSY, NOESY, HMQC and HMBC, their primary structures were analyzed as: Manα1,3Manα1,6(Manα1,3)(Xylβ1,2)Manβ1,4GlcNAcβ1,4GlcNAcβ1-(Gly-)Asn-Asn-Thr(GP1), Manα1,6(Manα1,3)(Xylβ1,2)Manβ1,4GlcNAcβ1,4(Fucα1,3)GlcNAcβ1-Asn-Ala-Thr(GP2),Manα1,6(Manα1,3)Manα1,6(Manα1,2 Manα1,3)Manβ1,4GlcNAcβ1,4GlcNAcβ1-(Ala-)Asn-Gly-Thr(GP3).
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    URL: http://dx.doi.org/10.1023/A:1010957007038
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    Alkaloids of Peganum harmala (2000)
    Springer
    Chemistry of natural compounds 36 (2000), S. 602-605 
    Details
    ISSN: 1573-8388
    Keywords: Peganum harmala ; alkaloid ; dipegine ; dipeginol ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dipegine (1) and dipeginol (2) were isolated fromPeganum harmala.The structures of these alkaloids were established by mass and IR spectra
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    URL: http://dx.doi.org/10.1023/A:1017524027513
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    The Oligomeric Subunit c Rotor in the Fo Sector of ATP Synthase: Unresolved Questions in Our Understanding of Function (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 433-439 
    Details
    ISSN: 1573-6881
    Keywords: FoF1-ATP synthase ; Fo rotary motor ; subunit c ; subunit a ; transmembrane helices ; NMR ; cross linking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract We have proposed a model for the oligomeric c-rotor of the Fo sector of ATP synthase and its interaction with subunit a during H+-transport driven rotation. The model is based upon the solution structure of monomeric subunit c, determined by NMR, and an extensive series of cross-linking distance constraints between c subunits and between subunits c and a. To explain the complete set of cross-linking data, we have suggested that the second transmembrane helix rotates during its interaction with subunit a in the course of the H+-translocation cycle. The H+-transport coupled rotation of this helix is proposed to drive the stepwise movement of the c-oligomeric rotor. The model is testable and provides a useful framework for addressing questions raised by other experiments.
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    URL: http://dx.doi.org/10.1023/A:1005604722178
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    Fluorometric and NMR Studies of the Naproxen–Cyclodextrin Inclusion Complexes in Aqueous Solutions (2000)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 37 (2000), S. 383-394 
    Details
    ISSN: 1573-1111
    Keywords: naproxen ; cyclodextrins ; complexation ; association constants ; fluorescence ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Inclusion complexation processesinvolving four cyclodextrins and naproxen have beenstudied for the protonated and unprotonated forms ofthe guest molecule. The association constants havebeen evaluated from changes in the fluorescenceintensity of naproxen following addition of acyclodextrin to an aqueous naproxen solution. 1HNMR NOESY and ROESY spectra have shown that twoorientations of the guest molecule relative toβ-cyclodextrin are possible.
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    URL: http://dx.doi.org/10.1023/A:1008114815223
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    Thermal Behavior of Dispersed Vanadium Dioxide Particles in Polyethylene Glycol Matrix Containing Tetraethylammonium Bromide (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 473-478 
    Details
    ISSN: 1572-8943
    Keywords: metal-semiconductor phase transitions ; NMR ; polyethylene glycol matrix ; vanadiumdioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A study has been made on samples of dispersed vanadium dioxide (VO2) in a matrix of polyethylene glycol (PEG) doped with a quaternary ammonium salt (QAS), namely tetraethylammonium bromide. It has been established that under the influence of the dopant the heating of a sample up to the temperature of the metal-semiconductor phase transition (MSPT) results in a phase in homogeneity of the sample. On the basis of the results of this study it is possible to conclude that small concentrations of QAS in a PEG matrix can exert a strong effect on the electronic structure of dispersed VO2 particles. This is accompanied by the appearance of phase heterogeneity of VO2 which manifests itself in the fact that - with the onset of MSPT with increasing temperature - one portion of the substance passes into the metallic state, and the other remains in the semiconductive state.
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    URL: http://dx.doi.org/10.1023/A:1010166903988
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    The primary electron acceptor of green sulfur bacteria, bacteriochlorophyll 663, is chlorophyll a esterified with Δ 2,6-phytadienol (2000)
    Springer
    Photosynthesis research 63 (2000), S. 269-280 
    Details
    ISSN: 1573-5079
    Keywords: bacteriochlorophyll a epimer ; bacteriochlorophyll 663 ; chlorophyll a ; green sulfur bacteria ; FAB-mass ; NMR ; phytadienol ; primary electron acceptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The primary electron acceptor of green sulfur bacteria, bacteriochlorophyll (BChl) 663, was isolated at high purity by an improved purification procedure from a crude reaction center complex, and the molecular structure was determined by fast atom bombardment mass spectroscopy (FAB-mass), 1H- and 13C-NMR spectrometry, double quantum filtered correlation spectroscopy (DQF-COSY), heteronuclear multiple-quantum coherence (HMQC) and heteronuclear multiple-bond correlation (HMBC) spectral measurements. BChl 663 was 2.0 mass units smaller than plant Chl a. The NMR spectra showed that the macrocycle was identical to that of Chl a. In the esterifying alcohol, a singlet P71 signal was observed at the high-field side of the singlet P31 signal in BChl 663, while a doublet peak of P71 overlapped that of P111 in Chl a. A signal of P7-proton, seen in Chl a, was lacking, and the P6-proton appeared as a triplet signal near the triplet P2-proton signal in BChl 663. These results indicate the presence in BChl 663 of a C=C double bond between P6 and P7 in addition to that between P2 and P3. The structure of BChl 663 was hence concluded to be Chl a esterified with 2,6-phytadienol instead of phytol. In addition to BChl 663, two molecules of the 132-epimer of BChl a, BChl a′, were found to be present per reaction center, which may constitute the primary electron donor.
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    URL: http://dx.doi.org/10.1023/A:1006480629059
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    Volume dependence of NMR of ordered correlated electron systems (2000)
    Springer
    Hyperfine interactions 128 (2000), S. 167-181 
    Details
    ISSN: 1572-9540
    Keywords: NMR ; high pressure ; phase transitions ; magnetic materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The importance of NMR high pressure studies of ordered magnetic materials for the understanding of the ground and excited states of magnetic conductors is discussed with examples from recent work on the manganese perovskites and the rare earth compounds SmMn2Ge2 and CeIn3. A brief discussion is given of the difference between true pressure experiments and the “chemical pressure” introduced by changing the composition of a material.
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    URL: http://dx.doi.org/10.1023/A:1012631515382
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    Study of single crystal surfaces with polarized 8Li (2000)
    Springer
    Hyperfine interactions 127 (2000), S. 463-468 
    Details
    ISSN: 1572-9540
    Keywords: NMR ; surfaces ; Si(1 1 1) (7×7) ; Ru(0 0 1) ; Li adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract NMR experiments on 8Li adsorbed on semiconductor and metallic surfaces are described (Si(1 1 1)−(7×7) and Ru(0 0 1)). They yield detailed information on LDOS (EF), the local density of states at the nucleus and at Fermi energy.
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    URL: http://dx.doi.org/10.1023/A:1012678003570
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    An apparatus for NMR of laser polarized 129Xe on single crystal surfaces (2000)
    Springer
    Hyperfine interactions 127 (2000), S. 469-474 
    Details
    ISSN: 1572-9540
    Keywords: NMR ; single crystal surfaces ; optical pumping of Rb ; hyperpolarized 129Xe ; laser polarized 129Xe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Due to a lack of at least 2 orders of magnitude in the amount of sample nuclei, single crystal surfaces are out of reach for conventional NMR measurements. Our aim is to prove that highly polarized 129Xe provides a technique to overcome this restriction. Therefore an apparatus for polarizing 129Xe up to 0.7 by spin transfer from optically pumped Rb has been designed as well as an NMR spectrometer in combination with a UHV chamber with sample cleaning, cooling and characterization abilities and a special manifold of glass stopcocks with a liquid nitrogen cooled trap for dosing nitrogen free polarized Xe into the chamber onto the surface.
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    URL: http://dx.doi.org/10.1023/A:1012630120408
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    Anisotropy of the Hyperfine Field on 57Fe in Pure and Substituted Yttrium Iron Garnet (2000)
    Springer
    Hyperfine interactions 131 (2000), S. 3-19 
    Details
    ISSN: 1572-9540
    Keywords: NMR ; hyperfine field ; ferrites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using NMR, anisotropy of the hyperfine field on 57Fe nuclei was measured in Y3Fe5O12 with nonmagnetic, trivalent substitutions on d (Ga3+) and a (Y3+ - yttrium antisite defect) sites which are occupied by ferric ions in a pure, stoichiometric system. The measurements were performed by the spin-echo method at liquid helium temperature. Thorough analysis of the hyperfine field anisotropy on the 57Fe nuclei in an ideal environment and in an environment where one of Fe3+ nearest cation neighbours is replaced by the nonmagnetic impurity is given. When the Fe3+ on which the NMR is measured is on the a site and the impurity is Ga3+(d), the results may be interpreted in terms of the superposition model. On the other hand, the results for Fe3+ on the d site and Y3+(a) are in clear disagreement with the predictions of this model.
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    Nuclear Magnetic Resonance and Infrared Spectroscopic Analysis of Nedocromil Hydrates (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 619-624 
    Details
    ISSN: 1573-904X
    Keywords: NMR ; infrared ; nedocromil ; hydrates ; solvate ; methanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Nedocromil sodium (NS), which is used in the treatment ofreversible obstructive airway diseases, such as asthma, has been foundto exist in the following solid phases: the heptahemihydrate, thetrihydrate, a monohydrate, an amorphous phase, which contains variableamounts of water, and a recently discovered methanol + water (MW)solvate. Our aim was to apply 13C solid-state nuclear magneticresonance (NMR) spectroscopy and solid-state Fourier transform infrared(FTIR) spectroscopy to the study of specific interactions in the varioussolid forms of NS. Methods. The 13 solid-state NMR and FTIR spectra of the varioussolid forms of NS were obtained and were related to the crystalstructures of NS, the conformations of the nedocromil anion, and theinteractions of the water molecules in these crystals. Results. The 13C solid-state NMR spectrum is sensitive to theconformation of the nedocromil anion, while the solid-state FTIR spectrumis sensitive to interactions of water molecules in the solid state. In NSmonohydrate, for which the crystal structure has not yet been solved,and in the amorphous phase, the information about the conformationsof the nedocromil anion and the interactions of the water moleculesare deduced from the 13C solid-state NMR spectra and solid-state FTIRspectra, respectively. Conclusions. 13C solid-state NMR spectroscopy and solid-state FTIRspectroscopy are shown to be powerful complementary tools forprobing the chemical environment of molecules in the solid state,specifically the conformation of the nedocromil anion and the interactions ofwater-molecules, respectively.
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    The Molecular Complexes of Calix[4]resorcinolarene with Diglycidylmethyl Phosphonate (2000)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 36 (2000), S. 153-162 
    Details
    ISSN: 1573-1111
    Keywords: calix[4]resorcinolarene ; diglycidylmethyl phosphonate ; complexation ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation of strong molecular complexes of calix[4]recorcinolarene with the polyfunctional phosphoorganic compound diglycidylmethyl phosphonate was observed in organic media. Complexes of different compositions were obtained with the ratio of the initial reagents of 1 : 1 and 1 : 4. Three complexes were isolated and characterized by elemental analysis; their 1H and 13C NMR spectroscopic parameters are also discussed.
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    URL: http://dx.doi.org/10.1023/A:1008106732110
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    Synthesis and Conformational Studies of an Asymmetrical Dibenzo-16-crown-5 Carboxylic Acid (2000)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 36 (2000), S. 287-299 
    Details
    ISSN: 1573-1111
    Keywords: crown ether ; NMR ; complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Asymmetrical cis-5,6-dimethyl-6-oxyacetoxy-(2,3)(9,10)-dibenzo-16-crown-5 was synthesized by a multi-step sequence and its stereochemistry determined by NOE experiments. Introduction of the 6-methyl group markedly reduces the stability constant for complexation of Na+ and K+ by the ionized form of the lariat ether carboxylic acid.
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    The structure and conformation of the tryptophanyl diketopiperazines cyclo(Trp–Trp)·C2H6SO and cyclo(Trp–Pro) (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 435-447 
    Details
    ISSN: 1572-8854
    Keywords: cyclic dipeptides ; Tryptophan ; Proline ; x-rays ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure and conformation of the cyclic dipeptides [cyclo(L-Trp–L-Trp)·C2H6SO] and cyclo(L-Trp–L-Pro) have been investigated with X-ray crystallographic and spectroscopic methods. Cyclo(L-tryptophanyl-L-tryptophanyl)·DMSO solvate crystallized in the space group P2 12121 with cell dimensions a = 6.193(2), b = 11.545(3), c = 31.117(4) Å. The crystal structure is stabilized by four hydrogen bonds (three intermolecular hydrogen bonds and one intramolecular bond). The first intermolecular bond is between the oxygen of DMSO and the nitrogen of indole ring 2, in contrast to the second intramolecular hydrogen bond between the nitrogen of indole ring 1 and the oxygen of DMSO. The two remaining intermolecular hydrogen bonds are between the nitrogens of the DKP ring and the carbonyl oxygens of the DKP ring. The values of χ1A 1 (−45.764) and χ1A 2 (67.437) indicate an extended side chain conformation for Trp residue 1 (EN) and a folded conformation for Trp residue 2. The DKP ring is more planar than in other cyclic dipeptide compounds (ϕ1 = 11.414, Ψ1 = −7.516, ϕ2 = 12.471, and Ψ2 = −8.256). In cyclo(L-Trp–L-Trp) the Cβ resonance of L-tryptophan (29.88 ppm) is shifted upfield 0.82 ppm when compared with the same resonance in cyclo(L-Trp–L-Gly) (30.7 ppm) and cyclo(L-Leu–L-Trp) (30.7 ppm). Two conformations of cyclo(Trp–Pro) crystallized in the space group P1 with cell dimensions a = 5.422(1), b = 9.902(1), c = 13.443(2) Å, α = 80.42(1), β = 78.61(1), and γ = 89.13(1)°. The conformation of the backbone and the orientation of the aromatic side chains for these conformers are very similar. The DKP rings for both conformers adopt a typical boat conformation in contrast to the flattened chair conformation observed for cyclo(Tyr–Pro) and cyclo(Phe–F-Pro). The tryptophan side chains of these conformers are folded towards the diketopiperazine (DKP) ring. The pyrrolidine ring for conformer 1 can be described as an envelope (Cs–Cβ-endo) conformation in contrast to the pyrrolidine ring symmetry for conformer 2 which is an intermediate between Cs and C2 rather than pure Cs for the proline ring with Cβ-endo and Cγ-exo with respect to C′. The two prolyl rings are puckered at the β-carbon atoms which deviate from the best planes defined by the four remaining atoms. The crystal structures are stabilized by four intermolecular hydrogens bonds. An intermolecular bond between the nitrogen of the indole ring (conformer 1) and the carbonyl oxygen of the DKP ring (conformer 2) was observed. The second hydrogen bond is between the nitrogen of the indole ring (conformer 2) and the carbonyl oxygen of the DKP ring (conformer 1). The last two hydrogens involve the carbonyl oxygens of the DKP rings and the nitrogens of the DKP rings [carbonyl oxygen of DKP ring (conformer 1)––––nitrogen of DKP ring (conformer 2); nitrogen of DKP ring (conformer 1)––––––carbonyl oxygen of DKP ring (conformer 2)].
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    A Direct Carbon-13 and Nitrogen-15 NMR Study of Cerium(III)–Isothiocyanate Complexation in Aqueous Solvent Mixtures (1999)
    Springer
    Journal of solution chemistry 28 (1999), S. 193-210 
    Details
    ISSN: 1572-8927
    Keywords: carbon-13 ; nitrogen-15 ; chlorine-35 ; NMR ; cerium(III)–isothiocyanate complexes ; water–acetone–Freon ; water–methanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A study of lanthanide complexation with isothiocyanate is underway using a multinuclear magnetic resonance technique. For isothiocyanate solutions in water–acetone–Freon mixtures at low temperature, −85–−125°C, ligand exchange is slow enough to permit the observation of 13C and 15N NMR signals for coordinated and free anions. For the Ce3+–NCS− system, four coordinated anion signals, displaced from the free anion signal by about +450 to +550 ppm for 15N and +50 to +80 ppm for 13C, are observed. The 13C and 15N spectral data are complementary, showing a signal area concentration dependence and measured coordination numbers consistent with the formation of Ce(NCS)2+ through Ce(NCS)1- 4. In water–methanol, the extent of complexing is decreased, presumably because of the higher dielectric constant of this medium. In addition, the results of a competitive study of NCS− and Cl− ion binding, carried out using 35Cl NMR, is presented.
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    Molecular Modeling Study of the PtCl2 Complexes of Unsaturated S2On+1-Coronands: Dynamic Simulations and Investigation of the Ring Interconversion (1999)
    Springer
    Journal of molecular modeling 5 (1999), S. 72-77 
    Details
    ISSN: 0948-5023
    Keywords: Keywords Thiacrown ether ; NMR ; Pt(II) complexes ; Molecular dynamic simulations ; Ring interconversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract   Maleonitrile-dithiacrown ethers mn-12S2O2 - mn-21S2O5 (mn = maleonitrile) are preorganized S2On+1-coronands (n = 1–4) which force B, AB and A class metal ions into mixed S/O coordination spheres. Moreover, they form chelate complexes with MX2 salts (M = Pd, Pt; X = Cl, Br), which were studied in this paper. The structures of mn-S2On+1 and [PtCl2(mn-S2On+1)] (n = 2, 3) were investigated theoretically by empirical and semiempirical methods using SYBYL (TRIPOS force field) and MSI/DISCOVER97 (ESFF force field). mn-12S2O2 was investigated experimentally by X-ray analysis and 1D and 2D NMR spectroscopy in solution and the complex formation was studied by 1H, 13C and 195Pt NMR titration experiments, respectively. S-inversion was also investigated in order to determine the ring corresponding interconversional barriers. Different orientations of the macrocyclic ring system mn-18S2O4 and of its transition states are shown.
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    URL: http://dx.doi.org/10.1007/s008940050106
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    In situ MAS NMR investigations of molecular sieves and zeolite-catalyzed reactions (1999)
    Springer
    Catalysis letters 58 (1999), S. 1-19 
    Details
    ISSN: 1572-879X
    Keywords: zeolites ; chemicals ; NMR ; alkane activation ; reaction mechanism ; in situ investigation ; alkylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Solid-state MAS NMR is a powerful technique to study heterogeneous catalysts and the way by which they operate. In situ MAS NMR has been demonstrated to be a powerful method to understand reaction mechanisms, to study the nature, dynamics and reactivity of surface intermediates and active sites, and to characterize structural modifications in the catalyst itself, in particular when using 13C strategically labelled substrates. In this paper, three examples selected from our own work are used to illustrate the potential of in situ MAS NMR. They are the formation of cumene and its isomerization to n-propylbenzene on zeolite H-ZSM-11, the activation of propane at low temperature and the alkylation of benzene with propane on zeolite H-ZSM-5, and the characterization of the aluminophosphate molecular sieve VPI-5 structure with temperature. Studies of the alkylation of benzene with propene confirmed that cumene was the primary reaction product. The undesired n-propylbenzene by-product results from the intermolecular reaction between cumene and benzene, enhanced by molecular shape-selective effects in medium pore size zeolites (e.g., H-ZSM-11). It explains why large pore zeolites, e.g., zeolite Beta, are used commercially today for this process. Propane can be activated at low temperature (ca. 573 K) on bifunctional medium pore size zeolites possessing intimately related acidic Brønsted sites and a dehydrogenation function provided by Ga or Zn species. In Ga/H-ZSM-5 catalysts, at 573 K, the activation of propane was shown to occur via a protonated pseudocyclopropane (PPCP) intermediate (or transition state). The latter evolves in a manner that can be formally described by the formation of CH 3 + , C2H 2 + , and C3H 7 + carbenium ion intermediates. These species can react with olefins, alkanes, or other electron-rich molecules such as benzene. The primary reaction products of the reaction of propane with benzene are n-propylbenzene (in small amount), ethylbenzene and toluene. Their subsequent reactions lead eventually to toluene and xylenes as the final products. In the structural characterization of VPI-5, 27Al, 31P, and 27Al nutation MAS NMR spectra show that, at 294 K, fully hydrated VPI-5 contains three equally populated Al and P crystallographic sites and that one-third of Al is 6-coordinate. The VPI-5 structure then belongs to the P63 space group. Above 353 K, VPI-5, fully or partially hydrated, undergoes a structural transformation to a higher framework symmetry, i.e., the P63cm space group. The transformation occurs at nearly the same temperature in both cases, indicating that the breakdown of the hydrogen-bonded helical water structure inside the VPI-5 pores is not a factor in the process.
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    URL: http://dx.doi.org/10.1023/A:1019044926400
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    What do we know about the acidity of solid acids? (1999)
    Springer
    Catalysis letters 62 (1999), S. 1-13 
    Details
    ISSN: 1572-879X
    Keywords: acid catalysis ; zeolites ; temperature‐programmed desorption ; microcalorimetry ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract With a proper understanding of the nature of solid acidity, zeolites and other solid acids have great potential for replacing homogeneous acids in a wide range of catalytic applications. This paper describes results from our laboratory on the characterization and description of the acid sites in high‐silica zeolites, especially H‐MFI. A crucial observation from this work is the identification of stoichiometric adsorption complexes, one molecule per framework Al, for a wide range of adsorbates, including amines, alcohols, nitriles, ketones, and thiols. Examples are given in which temperature‐programmed desorption is used to identify these complexes and characterize their initial chemistries. Calorimetric measurements on the 1:1 complexes have been used to compare the enthalpies of protonation in the zeolite to enthalpies of protonation in the gas phase and in aqueous phase and to demonstrate that a gas‐phase basis provides better predictive capabilities. The issue of carbenium‐ion stabilities is discussed, as well as the unusual catalytic properties of acid sites formed by framework substitution of Fe. The effect of sorption and cavity size on reactions is described. Finally, the problems associated with trying to define or characterize solid acids by using ammonia TPD or 13C NMR isotropic shifts of ketones without proper consideration of the complicated nature of these techniques are discussed.
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    A 31P nuclear magnetic resonance study of phosphate levels in roots of ectomycorrhizal and nonmycorrhizal plants of Castanea sativa Mill. (1999)
    Springer
    Trees 13 (1999), S. 168-172 
    Details
    ISSN: 0931-1890
    Keywords: Key words Castanea sativa ; Pisolithus tinctorius ; Ectomycorrhiza ; Phosphate ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  31P-Nuclear Magnetic Resonance (NMR) was used to assess phosphate distribution in ectomycorrhizal and nonmycorrhizal roots of Castanea sativa Mill. as well as in the mycorrhizal fungus Pisolithus tinctorius in order to gain insight into phosphate trafficking in these systems. The fungus P. tinctorius accumulated high levels of polyphosphates during the rapid phase of growth. Mycorrhizal and nonmycorrhizal roots accumulate orthophosphate. Only mycorrhizal roots presented polyphosphates. The content in polyphosphates increased along the 3 months of mycorrhiza formation. In mycorrhizal roots of plants cultured under axenic conditions, the orthophosphate pool decreased along the culture time. In nonmycorrhizal roots the decrease in the orthophosphate content was less pronounced. The level of orthophosphate in mycorrhizal roots was significantly lower than in nonmycorrhizal ones, which indicates that this system relies upon the fungal polyphosphates as a major source of phosphate.
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    URL: http://dx.doi.org/10.1007/PL00009748
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    Solution structure of reduced horse heart cytochrome c (1999)
    Springer
    JBIC 4 (1999), S. 21-31 
    Details
    ISSN: 1432-1327
    Keywords: Key words Reduced cytochrome c ; Solution structure ; NMR ; Heme proteins ; Electron transfer proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  In the frame of a broad study on the structural differences between the two redox forms of cytochromes to be related to the electron transfer process, the NMR solution structure of horse heart cytochrome c in the reduced form has been determined. The structural data obtained in the present work are compared to those already available in the literature on the same protein and the presence of conformational differences is discussed in the light of the experimental method employed for the structure determination. Redox-state dependent changes are analyzed and in particular they are related to the role of propionate-7 of the heme. Also some hydrogen bonds are changed upon reduction of the heme iron. A substantial similarity is observed for the backbone fold, independently of the oxidation state. At variance, some meaningful differences are observed in the orientation of a few side chains. These changes are related to those found in the case of the highly homologous cytochrome c from Saccharomyces cerevisiae. The exchangeability of the NH protons has been investigated and found to be smaller than in the case of the oxidized protein. We think that this is a characteristic of reduced cytochromes and that mobility is a medium for molecular recognition in vivo.
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    Interaction of cis- and trans-RuCl2(DMSO)4 with the nucleotides GpA, d(GpA), ApG, d(ApG) and d(CCTGGTCC): high-field NMR characterization of the reaction products (1999)
    Springer
    JBIC 4 (1999), S. 199-208 
    Details
    ISSN: 1432-1327
    Keywords: Key words Ruthenium ; Nucleotides ; Dimethyl sulfoxide ; Anticancer ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Both cis- and trans-RuCl2(DMSO)4 (cis-Ru and trans-Ru) react with ApG, GpA, d(ApG) and d(GpA) to yield products with bifunctional metal coordination of the bases. For each dinucleotide one major product and several minor species are formed. This is in contrast to previous results on analogous reactions between trans-Ru and d(GpG) where a substantial amount of an intermediate species was found. The rates of reaction between dinucleotides and cis-Ru are approximately 20-fold slower than for trans-Ru. The compounds formed with the two isomers exhibit identical proton NMR spectra, suggesting the same coordination mode for ruthenium in the final product. The two purine bases are coordinated to ruthenium through N7 in a head-to-head conformation with the glycosidic angles being in the anti range. Coupling constants indicate a relatively pure 3′-endo conformation for the 5′-sugar and mainly 2′-endo for the 3′-sugar. The similar bifunctional binding mode of cis- and trans-Ru(II) with dinucleotides as evident from the NMR spectra are in contrast to the different mode of interaction suggested earlier for cis- and trans-Ru complexes with DNA. trans-Ru interacts with the deoxyoctanucleotide d(CCTGGTCC), giving two main products during the first 2 h of incubation time. Four H8 guanine resonances are shifted downfield, characteristic of N7 metal coordination. The products are not analyzed in detail, but it is suggested that the structures may be described as two chiral G(N7/N7) chelates.
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    The interactions of the N-terminal fusogenic peptide of HIV-1 gp41 with neutral phospholipids (1999)
    Springer
    European biophysics journal 28 (1999), S. 427-436 
    Details
    ISSN: 1432-1017
    Keywords: Key words HIV-1 fusion peptide ; EPR ; NMR ; Solid state NMR ; Circular dichroism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We have studied the interactions with neutral phospholipid bilayers of FPI, the 23-residue fusogenic N-terminal peptide of the HIV-1LAI transmembrane glycoprotein gp41, by CD, EPR, NMR, and solid state NMR (SSNMR) with the objective of understanding how it lyses and fuses cells. Using small unilamellar vesicles made from egg yolk phoshatidylcholine which were not fused or permeabilised by the peptide we obtained results suggesting that it was capable of inserting as an α-helix into neutral phospholipid bilayers but was only completely monomeric at peptide/lipid (P/L) ratios of 1/2000 or lower. Above this value, mixed populations of monomeric and multimeric forms were found with the proportion of multimer increasing proportionally to P/L, as calculated from studies on the interaction between the peptide and spin-labelled phospholipid. The CD data indicated that, at P/L between 1/200 and 1/100, approximately 68% of the peptide appeared to be in α-helical form. When P/L=1/25 the α-helical content had decreased to 41%. Measurement at a P/L of 1/100 of the spin lattice relaxation effect on the 13C nuclei of the phospholipid acyl chains of an N-terminal spin label attached to the peptide showed that most of the peptide N-termini were located in the interior hydrocarbon region of the membrane. SSNMR on multilayers of ditetradecylphosphatidyl choline at P/Ls of 1/10, 1/20 and 1/30 showed that the peptide formed multimers that affected the motion of the lipid chains and disrupted the lipid alignment. We suggest that these aggregates may be relevant to the membrane-fusing and lytic activities of FPI and that they are worthy of further study.
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    URL: http://dx.doi.org/10.1007/s002490050225
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    The solution structure of a monomeric, reduced form of human copper,zinc superoxide dismutase bearing the same charge as the native protein (1999)
    Springer
    JBIC 4 (1999), S. 795-803 
    Details
    ISSN: 1432-1327
    Keywords: NMR ; Superoxide dismutase ; Solution structure ; Monomeric mutants ; Structure-function relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: 2 , has RMSD values with respect to the average structure of 0.94 ± 0.14 Å2 and 1.50 ± 0.14 Å2 for the backbone and the heavy atoms, respectively. The overall folding, which includes the classical eight-stranded Greek-key β-barrel and a short α-helix, is very close to that of the previously characterized monomeric mutant E133QM2SOD and to that of wild-type SOD. The region involved in the subunit-subunit interactions in the dimeric protein is confirmed to be disordered in the monomeric species. It is also observed that a sizable rearrangement of the charged groups of the electrostatic loop and of Arg143 takes place in the monomeric species. The width of the active site channel, both at its entrance and at the bottleneck of the active site, is discussed in the light of the influence on the enzymatic activity and the latter with respect to the overall charge. It is also confirmed that the NH proton of His63 shields the Cu(I) from the bulk solvent, thus supporting the suggestion that superoxide may interact with the reduced metal ion in an outer-sphere fashion.
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    Thermal Dehydration and Miscibility of PHEMA/PMAA Blends (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1059-1063 
    Details
    ISSN: 1572-8943
    Keywords: dehydration ; miscibility ; NMR ; polymer blend ; poly(2-hydroxyethyl methacrylate) (PHEMA) ; poly(methacrylic acid) (PMAA) ; TG ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Miscibility and dehydration of poly(2-hydroxyethyl methacrylate) and poly(methacrylic acid) (PHEMA/PMAA) blends were investigated by temperature modulated DSC (TMDSC), TG and solid-state 13C NMR methods. TMDSC spectra and 1H spin-relaxation times showed that the blends are homogeneous on a scale of 5-10 nm for all compositions. From TG and 13C NMR, we elucidated that the mass loss of the blends at 300°C is ascribed to the dehydration between the hydroxyl group of PHEMA and the carboxyl group of PMAA.
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    An Improved Model for Predicting Proton NMR Shielding by Alkenes Based on Ab Initio GIAO Calculations (1999)
    Springer
    Structural chemistry 10 (1999), S. 375-380 
    Details
    ISSN: 1572-9001
    Keywords: Magnetic anisotropy ; NMR ; shielding cone ; isotropic shielding ; GIAO ; (de)shielding surface ; alkenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In a strong magnetic field, nuclei located over a carbon-carbon double bond experience NMR shielding effects that are the net result of the magnetic anisotropy of the nearby double bond and various other intramolecular shielding effects. We have used GIAO, a subroutine in Gaussian 4, to calculate isotropic shielding values and to predict the proton NMR shielding increment for a simple model system: methane held in various orientations and positions over ethene. The average proton NMR shielding increments of several orientations of methane have been plotted versus the Cartesian coordinates of the methane protons relative to the center of ethene. A single empirical equation for predicting the NMR shielding experienced by protons over a carbon-carbon double bond has been developed from these data. The predictive capability of this equation has been validated by comparing the shielding increments for several alkenes calculated using our equation to the experimentally observed shielding increments. This equation predicts the NMR shielding effects more accurately than a previous model that was based on only one orientation of methane over ethene. Deshielding is predicted by this equation for protons over the center and within about 3 Å of a carbon-carbon double bond. This result is in contrast to predictions made by the long-held “shielding cone” model based on the McConnell equation found in nearly every textbook on NMR, but is consistent with experimental observations.
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    URL: http://dx.doi.org/10.1023/A:1022095511927
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    In situ NMR of heterogeneous catalysis: new methods and opportunities (1999)
    Springer
    Topics in catalysis 8 (1999), S. 81-86 
    Details
    ISSN: 1572-9028
    Keywords: NMR ; zeolite ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In situ NMR has been extensively applied in the past decade to obtain basic mechanistic information about reactions in heterogeneous catalysis. Most studies in the literature have employed either sealed glass ampoules of catalyst and adsorbate that are heated outside of the NMR probe or variable temperature studies of samples sealed in magic‐angle spinning (MAS) rotors. In situ NMR studies of sealed samples fail to duplicate the conditions of temperature, reagent introduction and product removal found in bench‐top microreactor studies of catalysis. Previous attempts to more closely duplicate the conditions in flow reactors have motivated NMR studies using temperature jumps and the development of MAS probes with reagent flow. These methods have not yet achieved the time scales of several seconds or tenths of seconds that are typical of catalytic reactions. The pulse‐quench catalytic reactor has been developed to permit NMR studies of catalyst samples that have been prepared under actual reaction conditions. Pulse‐quench studies have provided evidence in support of a carbon‐pool mechanism for methanol‐to‐gasoline chemistry on HZSM‐5 and led to the identification of a pentamethylbenzenium cation formed in a zeolite by the alkylation of benzene with excess methanol.
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    Synthesis of CIT-6, a zincosilicate with the *BEA topology (1999)
    Springer
    Topics in catalysis 9 (1999), S. 35-42 
    Details
    ISSN: 1572-9028
    Keywords: CIT-6 ; zincosilicate ; zinc beta ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new, large pore zincosilicate denoted CIT-6 with the framework topology of zeolite beta has been synthesized from reaction mixtures containing Li+, Zn2+ and tetraethylammonium hydroxide (TEAOH) as a structure-directing agent (SDA). The effects of the concentrations of Li+, Zn2+ and TEAOH on the preparation of CIT-6 are investigated and it is shown that there are critical ranges in concentration for all three components for the crystallization of pure CIT-6. The incorporation of Zn2+ into the CIT-6 framework is confirmed by 29Si MAS-NMR and ion exchange results. CIT-6 is the first molecular sieve to contain framework zinc sites accessible to organic molecules.
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    Structural Investigation of the First Stages of Pyrolysis of Si-C-O Preceramic Polymers Containing Si–H Bonds (1999)
    Springer
    Journal of sol gel science and technology 14 (1999), S. 39-48 
    Details
    ISSN: 1573-4846
    Keywords: polysiloxanes ; oxycarbide glasses ; NMR ; mass spectrometry ; pyrolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The polymer-to-glass transformation in the Si-C-O system usually involves cross-linking reactions at the C sites, which transform for example ≡Si– $$\underline {\text{C}} $$ H3 sites into $$\underline {\text{C}} $$ (Si)4 sites, leading to the formation of a silicon oxycarbide network. Identification of the various C sites that form during pyrolysis under inert atmosphere is rather difficult from 13C MAS-NMR spectra, due to strong overlap of resonance lines, which prevents an accurate determination of the chemical shift values. This paper reports on the use of a spectral editing technique called Inversion Recovery Cross Polarization (IRCP), which, when combined with Cross Polarization (CP) technique, allows us to identify and quantify the formation of Si- $$\underline {\text{C}} $$ H2-Si bridges during the early stages of the pyrolytic transformation of a polysiloxane containing Si–CH3 and Si–H groups. Several Si-C-O systems characterized by the same initial number of Si–CH3 bonds but with increasing number of Si–H bonds, have been investigated by MAS-NMR as well as thermogravimetric analysis coupled with mass spectrometry (TG/MS). The Si—H bonds play clearly an active role in the insertion of C atoms within the silica network.
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    Silicon Oxycarbide Glasses (1999)
    Springer
    Journal of sol gel science and technology 14 (1999), S. 7-25 
    Details
    ISSN: 1573-4846
    Keywords: black glass ; silicon oxycarbide ; Nicalon ; NMR ; Raman ; TEM ; high temperature stability ; surface chemistry ; network carbon ; elemental carbon ; structure ; free carbon ; FTIR ; nanocomposite ; silicon carbide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The first attempts to introduce carbon into glass date back to 1951. But up until recently, the use of carbon or carbide raw materials, and the oxidation, volatilization and decomposition that accompany high temperature melting, have limited the synthesis of true silicon oxycarbide glasses. Here, the term silicon-oxycarbide refers specifically to a carbon-containing silicate glass wherein oxygen and carbon atoms share bonds with silicon in the amorphous, network structure. Thus, there is a distinction between black glass, which contains only a second-phase dispersion of elemental carbon, and oxycarbide glasses which usually contain both network carbon and elemental carbon. In addition to exploring the unique properties and applications of these glasses, per se, they are also of interest for developing models of the residual amorphous phases in polymer-derived silicon-carbide and silicon-nitride ceramics. The application of sol/gel techniques to glass synthesis has significantly advanced the development and characterization of silicon oxycarbide glasses. In this approach, alkyl-substituted silicon alkoxides, which are molecular precursors containing oxygen and carbon functionalities on the silicon, can be hydrolyzed and condensed without decomposition or loss of the carbon functional group. A low-temperature (〈1000°C) heat-treatment of the gel creates a glassy silicate material whose molecular structure consists of an oxygen/carbon anionic network. In addition, there is always a blackening of the material due to elemental carbon, which forms during pyrolysis and densification of the gel. The nature of the network carbon, and especially the distribution and form of the elemental carbon, are fundamental to the structure and properties of these novel materials. Their chemical and physical characteristics as revealed by NMR, Raman and TEM are discussed in the overview. In addition, the high temperature stability of these glasses (up to 1750°C), and the effect of hot-pressing, are described. It will be shown that the silicon oxycarbide network is stable up to 1000–1200°C. The network carbon is terminated with hydrogen (i.e., CH, =CH2 and –CH3), and with polyaromatic carbon (i.e., nC6Hx) wherein most of the elemental carbon resides. These glasses can be described as molecular composites of polyaromatic graphene-rings dispersed in a silicon oxycarbide network. After heating to temperatures in excess of 1000–1200°C, the oxycarbide network decomposes through the loss of hydrogen, and a two- or three-phase glass-ceramic consisting of nanocrystalline graphite, silicon carbide, and amorphous silica or cristobalite, is created. Some of the properties and applications of these glasses/glass-ceramics for coatings, composites and porous solids are summarized.
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    Topological structures of tetrahedral (Td and T) fullerenes with hexagonal and triangular faces and their vibration and NMR spectra (1999)
    Springer
    Theoretical chemistry accounts 102 (1999), S. 72-77 
    Details
    ISSN: 1432-2234
    Keywords: Key words: Fullerenes ; Tetrahedral symmetry ; IR active ; Raman active ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. On analyzing the topological structures of the three types of tetrahedral fullerenes (which consist only of triangles and hexagons), (1) C n (T d ,n=12h 2; h=1,2,…), (2) C n (T d ,n=4h 2;h=1,2,…), and (3) C n (T,n=4(h 2+hk+k 2);h〉k,h,k=1,2,…), we have obtained theoretically the Infrared and Raman active modes by means of the derived formulas for the decomposition of their nuclear motions into irreducible representations, and the 13C NMR spectra with natural abundance for 13C by using the distribution functions for all of the tetrahedral (T d and T) fullerenes, respectively.
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    A novel cytokine-inducing glycolipid isolated from the lipoteichoic acid fraction of Enterococcus hirae ATCC 9790: A fundamental structure of the hydrophilic part (1999)
    Springer
    Glycoconjugate journal 16 (1999), S. 213-221 
    Details
    ISSN: 1573-4986
    Keywords: acetolysis ; IL-6 ; MALDI-TOF-MS ; mannan ; NMR ; poly(glycerophosphate) structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Previously, we showed that quantitatively minor several glycolipids only less than 5% of the lipoteichoic acid (LTA) fraction from Enterococcus hirae ATCC 9790 possessed cytokine-inducing activity, whereas the major component (over 90%) did not [Suda et al. (1995) FEMS Immun Med Microbiol 12:97–112]. The major inactive component was shown to have the chemical structure as was proposed for the LTA by Fischer [Hashimoto et al. (1997) J Biochem 121:779–86], suggesting that so-called LTA is not a cytokine-inducing component in the Gram-positive bacteria. In the present paper, the structure of the hydrophilic part of one of the cytokine-inducing glycolipid tentatively named GL4 is elucidated. GL4 was first subjected to hydrolysis with aqueous HF to give a polysaccharide and a mixture of low molecular weight products. The polysaccharide was composed mainly of highly branching mannan as concluded from NMR and MS analyses of its acetolysis products. The low molecular weight products consisted of phosphate and glycerol, suggesting the presence of a poly(glycerophosphate) structure in the original GL4. From these observations, the hydrophilic part of GL4 was shown to consist of mannose-rich polysaccharide and poly(glycerophosphate), the latter being bound to the former by a phosphodiester linkage.
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    Three-dimensional structure of scorpion toxins: Towards a new model of interaction with potassium channels (1999)
    Springer
    Perspectives in drug discovery and design 15-16 (1999), S. 41-60 
    Details
    ISSN: 1573-9023
    Keywords: dipole moment ; neurotoxin ; NMR ; potassium channel ; scorpion ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Scorpion venom contains various toxins which block ion-channels, responsible for either sodium, potassium, calcium or chloride membrane permeation. This review focuses on the three-dimensional structure of scorpion toxins specific for potassium channels, and on their structure–activity relationships. The overall fold of all these toxins is similar, despite their various specificities towards different types of potassium channels. Fine studies of the influence of punctual mutations of both toxins and channels have converged on a precise description of the scorpion toxins functional maps. From this knowledge, it now becomes possible to predict the specificity of a newly described scorpion toxin. The way is thus now open that leads to the design of new potent synthetic potassium channel blockers which in turn could be used as therapeutic drugs.
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    NMR Studies of Retinoid-Protein Interactions: The Conformation of [13C]-β-Ionones Bound to β-Lactoglobulin B (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 651-659 
    Details
    ISSN: 1573-904X
    Keywords: 13C-edited ; NMR ; retinol ; retinoic acid ; β-lactoglobulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Vitamin A (retinol) and its metabolites comprise the natural retinoids. While the biological action of these molecules are thought to be primarily mediated by ca. 55 kDa nuclear retinoic acid receptors, a number of structurally similar 15-20 kDa proteins are involved in the transport, and possibly metabolism, of these compounds. The milk protein β-lactoglobulin B (β-LG) is an 18 kDa protein which binds retinol and may be involved in oral delivery of retinol to neonates. β-LG also binds drugs and other natural products and is of potential interest as a protective delivery vehicle. Methods. To examine the conformation of the model retinoid β-ionone both in solution and when bound to β-LG, NMR and computational methods have been employed. Results. Taken together, NMR studies of β-ionone in solution measuring scalar and dipolar coupling, as well as CHARMm calculations, suggest β-ionone prefers a slightly twisted 6-s-cis conformation. Isotope-edited NMR studies of l3C-labeled β-ionones bound to β-LG, primarily employing the HMQC-NOE experiment, suggest β-ionone also binds to β-LG in its 6-s-cis conformation. Conclusions. The methods employed here allow estimates of protein-bound ligand conformation. However, additional sites of ligand labeling will be necessary to aid in binding site localization.
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    URL: http://dx.doi.org/10.1023/A:1018860221492
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    NMR Investigations of the Inclusion of Thyroxine and Derivatives in Natural Cyclodextrins (1999)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 33 (1999), S. 307-319 
    Details
    ISSN: 1573-1111
    Keywords: cyclodextrins β and γ ; thyroxine ; thyroid hormones ; inclusion complex ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thyroxine T4 and its derivatives (T3, T2) are very sparingly soluble in aqueous solutions even in the form of salts. In the presence of β or γ-cyclodextrins and in buffered basic solution, their solubilities are increased by inclusion in the cavity. The inclusion of these hormones in cyclodextrins was investigated by 1H-NMR in order to derive the influence of the number and position of the iodine atoms, and of the ionization state of the phenol group on the inclusion geometries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008063601982
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    A Quantum Chemical and Electrostatic Study of Alkyl and Substituted Benzenonium Cations and Related Molecules: The Effect of Atomic Charge Distribution on Carbocation Energy and Geometry (1999)
    Springer
    Structural chemistry 10 (1999), S. 121-127 
    Details
    ISSN: 1572-9001
    Keywords: NPA ; CHELPG ; MK ; AIM ; atomic charge ; NMR ; carbocation ; benzenonium ; electrostatic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Geometries, NMR chemical shifts, atomic charges, and bond orders were calculated at the MP2/6-31G* level of theory for the isopropyl, sec-butyl, tert-butyl, benzenonium, and six methyl- and trifluoromethyl-substituted benzenonium ions. The NPA charges correlate better than the CHELPG, MK, and AIM charges with the experimental and calculated carbon chemical shifts. The electrostatic energies of isomeric ions, calculated by treatment of the NPA charges as point charges, are comparable to their MP2 energy differences. The electrostatic calculations, although classical approximations, provide a qualitative understanding of the coulombic basis of the methyl and trifluoromethyl substituent effects. It is apparent that these species are stabilized by having adjacent, oppositely charged atoms (for example, having the negatively charged carbon of a methyl group bonded to a positive carbon). It is proposed that a methyl group be termed a nucleophilic (rather than electron-donating) substituent and that a trifluoromethyl group be termed an electrophilic substituent. In the benzenonium ions and in toluene, fluoromethylbenzene, difluoromethylbenzene, and benzotrifluoride, the endocyclic angle at the substituent increases with increasing electrophilicity of the substituent. An electrostatic calculation again provides some insight into the coulombic basis of these changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022033330273
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    NMR studies of interfaces, strain and anisotropy in Co/Cu multilayers (1999)
    Springer
    Hyperfine interactions 120-121 (1999), S. 23-30 
    Details
    ISSN: 1572-9540
    Keywords: NMR ; Co/Cu ; multilayers ; anisotropy ; 59Co
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 59Co NMR studies of multilayers are able to give three direct pieces of information: (i) the crystal phase of Co, fcc (217.4 MHz), hcp (220–228 MHz) and in exotic cases bcc (198 MHz) for films measured at T= 4.2 K, (ii) the nature of the interfaces from low frequency satellite lines, and (iii) the strain state deduced from small changes in the line positions. Extensive studies of Co/Cu multilayer interfacial structures as a function of deposition technique, layer thickness, substrate/buffer layer structure and annealing temperature have been undertaken. This work has shed new light on the relationship between interfacial structure and magnetoresistance and in particular has demonstrated that flat, atomic scale, interfaces lead to greater magnetoresistance. The difference between the Co and Cu lattice constant results in an extensive, tensile in-plane strain developing in Co layers provided that some epitaxial registry is present. Information on strain effects can be obtained from the position and width of the NMR lines. The magnetic anisotropy field can be determined by measuring the field dependence of the enhancement effect due to electronic magnetisation. This provides unique insight into the distribution of magnetic anisotropy within the Co layers, as the enhancement can be investigated independently for each NMR line and, hence, provides environment specific information on magnetic anisotropy at the interfaces and in the interior of the layers.
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    URL: http://dx.doi.org/10.1023/A:1017061509311
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    Mammalian Exocrine Secretions. XII: Constituents of Interdigital Secretions of Bontebok, Damaliscus dorcas dorcas, and Blesbok, D. d. phillipsi (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 2057-2084 
    Details
    ISSN: 1573-1561
    Keywords: Damaliscus dorcas ; mammalian semiochemicals ; mammalian pheromones ; exocrine secretions ; interdigital secretions ; chemical communication ; mass spectrometry ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In addition to the nine compounds identified in the interdigital secretion of the bontebok, Damaliscus dorcas dorcas, in a previous study, 76 compounds belonging to different compound types, were identified in the interdigital secretions of the bontebok and the blesbok, D. d. phillipsi. These compounds include alkanes, alcohols, aldehydes, ketones, fatty acids, terpenoids, γ-lactones, an isopropyl ester, long-chain hydroxyesters, 2-substituted pyridines, phenols, steroids, and dimethylsulfone. No qualitative differences were found between secretions from the two sexes or from animals from different habitats. Although no attempt was made to correlate territorial behavior or other behavioral phenomena with the qualitative composition of interdigital secretions from individual animals, available information seems to indicate that quantitative differences probably do not have a major semiochemical function. Only two species of bacteria, Bacillus brevis and Planococcus citreus, were found in the interdigital pouches of male and female members of the two subspecies, regardless of the habitat of the animals. B. brevis synthesized, among other unidentified constituents, (Z)-3-penten-2-ol, 2-hexanone, 2-octanone, 2-nonanone, tetradecanoic acid, pentadecanoic acid, heptadecanoic acid, octadecanoic acid, (Z)-9-hexadecenoic acid, and isopropyl hexadecanoate in vitro, while P. citreus produced, among others, the γ-lactones dodecan-4-olide and (Z)-6-dodecen-4-olide, which is one of the major constituents of the interdigital secretions of both subspecies. Some components of the interdigital secretions are not present in the interdigital glandular tissue, and the possibility is discused that these compounds could be produced by microbiological activity in the interdigital pouch.
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    Molecular Complex Formation between Some Azacrown Ethers and 2,4,6-Trinitrophenol (1999)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 34 (1999), S. 431-443 
    Details
    ISSN: 1573-1111
    Keywords: 2,4,6-trinitrophenol ; aza-crown ethers ; molecular complexes ; spectrophotometry ; IR ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation of molecular complexes with 1 : 1 stoichiometry between 2,4,6-trinitrophenol and aza-12-crown-4, aza-15-crown-5 and aza-18-crown-6 in chloroform solution was investigated spectrophotometrically. The resulting complexes were isolated and characterized by microchemical analysis, IR and NMR spectroscopy. The equilibrium constants of the 1 : 1 adducts were evaluated from the non-linear least-squares fitting of the absorbance-mole ratio data. The overall stability of the 2,4,6-trinitrophenol complexes was found to vary in the order aza-15-crown-5 〉 aza-18-crown-6 ≈ aza-12-crown-4. The kinetics of complex formation between 2,4,6-trinitrophenol and the aza-substituted crown ethers used were investigated and in all cases the results showed the occurrence of an oscillating chemical reaction in solution.
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    URL: http://dx.doi.org/10.1023/A:1008036714492
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    New Syntheses of Flavones from Diels-Alder Reactions of 2-Styrylchromones with ortho-Benzoquinodimethanes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 135-139 
    Details
    ISSN: 1434-193X
    Keywords: Flavones ; Chromones ; ortho-Benzoquinodimethanes ; Diels-Alder reactions ; NMR ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The first reported cycloaddition reactions of 2-styrylchromones with ortho-benzoquinodimethane afforded 2-[2-(3-aryl-1,2,3,4-tetrahydronaphthyl)]chromones. These cycloadducts were converted into the corresponding 2-[2-(3-arylnaphthyl)]chromones (benzoflavone derivatives) by bromination/dehydrobromination processes. These benzoflavone derivatives were also obtained in one-pot cycloaddition reactions of 2-styrylchromones with ortho-benzoquinodibromomethane.
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    The Structures of a Tetracarba-nido-octaborane(8) and a Novel Spiro Derivative of a 2,3,5-Tricarba-nido-hexaborane(7) (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 533-537 
    Details
    ISSN: 1434-1948
    Keywords: Ab initio calculations ; Carboranes ; NMR ; X-ray analysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydroboration of bis(diethylboryl)ethyne (1) with tetraethyldiborane(6) leads to a B-ethyl-substituted tetracarba-nido-octaborane 2, a spiro-carborane 3, which belongs to the 2,3,5-tricarba-nido-carborane family, and a hexacarba-arachno-dodecaborane(12) 4, along with polymeric material. The X-ray structure analysis of carborane 2, determined here, is fully consistent with the structure deduced earlier from NMR data. The structure of 3 in solution was established by theoretical analysis of its NMR data. Ab initio calculations of the structures of 2b and 3b (b denotes the B-metyhl-substituted derivatives) and the comparison of calculated with experimental NMR data support the suggested structures of 2 and 3 in solution. The calculated structure of the carborane cage of 2a also agrees with the experimental geometry of 2.
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    Masthead (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999) 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710301
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    Nanofiltrationsmembranen für Trennprobleme in organischen Lösungen (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 199-206 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nanofiltration Membranes for Separation Problems in Organic Solutions.Nanofiltration based on rejection and flux features intermediate between those ultrafiltration and reverse osmosis is one of the technically and scientifically interesting membrane processes with a great future. Moreover, most commercial available nanofiltration membranes are only suitable for separation processes in aqueous solutions. A small number of composite membranes with a highly cross-linked selective layer show a technically interesting resistance towards organic solvents, such as ketones, esters, ethers or alcohols. The present article describes such nanofiltration membranes used for separation of low molecular weight chemical compounds from polar or nonpolar solvents, but also for the removal of organic compound from aqueous solutions. Methods of manufacturing and modifying such solvent stable composite membranes are shown, as are the conditioning of membranes and examples of industrial application.
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    Seitliche Reaktandenzufuhr in großmaßstäblichen Wirbelschichtreaktoren - Modellierung am Beispiel der Sekundärlufteinblasung in WirbelschichtfeuerungenVorgetragen von T. KNÖBIG anläßlich der internen Arbeitssitzung des Fachausschusses „Energieverfahrenstechnik“, 20./22. April 1998 in Würzburg. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 219-222 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cite.330710307
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    Numerische Simulation der Strömungsvorgänge und des Trennverhaltens von Suspensionen im freien Einzelspalt eines TellerseparatorsVortrag auf der GVC-Tagung „Mechanische Flüssigkeitsabtrennung“, 25. März 1998 in Freiburg. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 249-253 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cite.330710315
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    CAPE in der Praxis  -  Möglichkeiten und Grenzen aus NutzersichtVortrag anläßlich der GVC-Jahrestagung, 24./26. Sept. 1997 in Dresden. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 323-327 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: CAPE in Practice - Opportunities and Limits from the User's Point of View.CAPE tools comprise computer based tools and methods for the design of chemical processes - the use of which is indispensable in modern chemical engineering. This paper discusses the degree to which CAPE is already applied and whether limitations exist. Within BASF, the CAPE framework is provided by the “ProcessNet”, which integrates numerous simulation and design tools. The engineer relies alternatively on inhouse or commercial software. The advantage of CAPE in terms of efficiency depends not only on complex programs, but also to a large extent on the multiple use of intermediate data and program modules. The ProcessNet also features a hierarchical file structure to support the engineer's desktop management. The CAPE environment is being continuously improved. The main constraints on CAPE today are, for example, the missing link between fluid and solid applications, a deficit in data management and the poor state of development of advanced or special programs. The progress of research in this area is followed with great interest.
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    Einfluß der Fluidisierungsbedingungen auf Abscheidung und Agglomeration von Aerosolen beim Durchgang durch Wirbelschichten (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 361-364 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cite.330710409
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    Modifizierung der Partikelwechselwirkung durch Beschichtung mit grenzflächenaktiven ReagenzienÜberarbeiteter Vortrag anläßlich der Sitzung des GVC-Fachausschusses „Grenzflächen“, 23. März 1998 in Freiburg. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 372-376 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cite.330710412
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    Untersuchung zur Hydrodynamik und Kinetik an KATAPAK-Packungen (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 388-392 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cite.330710416
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    Konzentrationsprogrammierte Reaktionstechnik - Eine Methode zur Beurteilung des Anwendungspotentials instationärer Prozeßführungen bei PartialoxidationenTeil eines Vortrags anläßlich der 3. Merseburger Fachtagung „Automatisierung, Meßmethoden und Experimente in der chemischen Reaktionstechnik“, 6. Nov. 1997. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 226-230 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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    Zur Kopplung von Impuls- und Stofftransport an fluiden Phasengrenzen - Teil 1: TheorieVortrag (gekürzt) anläßlich der GVC-Jahres-tagung, 24./26. Sept. 1997 in Dresden. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 472-477 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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    VerGrößerung der spezifischen Oberfläche von Kristallen durch gezieltes Nutzen von PseudopolymorphenErweiterte Fassung eines Vortrags von ST. NORDHOFF (Vortragender) und J. ULRICH anläßlich der internen Arbeitssitzung des GVC-Fachauschusses „Kristallisation“, 2./6. März 1998 in Aachen. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 487-490 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cite.330710514
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    Einfluß der Dimerisierung von Isobuten auf die MTBE-Produktion bei der reaktiven Destillation (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 500-503 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cite.330710518
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    Chemical Reaction and Reactor Design (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 518-518 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710523
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    Processing of Particulate Solids (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 520-520 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710526
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    GVC-Fachausschuß „Prozeß-und Anlagentechnik“ (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 516-517 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Die Sitzung des GVC-Fachausschusses „Prozeß- und Anlagentechnik“ fand am 25. und 26. Oktober 1998 in Kleve statt. Gemeinsam mit dem DECHEMA-Ausschuß „Computeranwendungen in der chemischen Industrie“ und dem GVC-Arbeitskreis „Produktionslogistik“ wurden aktuelle Problemstellungen aus der Industrie und neue Problemlösungsansätze aus der Forschung präsentiert und diskutiert.In seiner kurzen Begrüßung erläuterte der Ausschußvorsitzende H. SCHMIDT-TRAUB einerseits die Zielsetzung der Tagung und verdeutlichte andererseits den Teilnehmern die Ursachen und Konsequenzen des drastischen Rückgangs der Anfängerzahlen in den verfahrenstechnischen Studiengängen, was für Gesprächsstoff in den Pausen sorgte. Die anschließende Tagung umfaßte insgesamt 35 Vorträge in zehn Schwerpunktthemen.
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    Abwasser (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 523-524 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710532
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    Aktuelles (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 531-553 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cite.330710602
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    Abtrennen von Wertstoffen aus BauschuttVortrag anläßlich der GVC-Jahrestagung, 30. Sept./2. Okt. 1998 in Freiburg. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 637-642 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710619
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    Wärmeintegration bei Batch-Prozessen (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 700-704 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710710
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    Rheologische Eigenschaften von wäßrigen nicht-ionischen Tensidlösungen in stationärer ScherströmungVortrag anläßlich der Sitzung des GVC-Fachausschusses „Rheologie“, 2./6. März 1998 in Aachen. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 720-725 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710715
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    Systematische vergleichende Kostenanalyse von destillativen und extraktiven Stofftrennverfahren (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 669-673 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Systematic Comparative Cost Analysis of Separation Processes Based on Distillation and Extraction.Rectification is the most commonly used but not always the most economical method of thermal separation. Above all in the case of closely boiling mixtures it becomes very demanding with regard to both equipment and energy. It is often possible to replace rectification by another energetically more favourable separation process such as liquid-liquid distillation, decantation, or absorption. Owing to the resulting wealth of possibilities for the separation of a mixture it is desirable to gain further knowledge about the economics of individual processes and about the selection of suitable entrainers under given conditions.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cite.330710703
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    Die Hydrolyse von HCN als Zwischenschritt bei der Stickoxidbildung (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 613-618 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710614
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    Oxidische Schichten auf EisenChrom-Nickel-Werkstoffen und ihre chemischen Eigenschaften (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 609-612 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710613
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    Verfahren zum Abbau von organischen Schadstoffen durch indirekte Elektrooxidation (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 628-633 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710617
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    Kontinuierliche Dosierung und Dispergierung feindisperser, kohäsiver Feststoffe mit einem neuartigen Staubdosierer (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 685-688 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710706
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    Numerische Untersuchung der Strömungsverhältnisse im Innern von Hohlkegeldüsen mit Leitapparat (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 688-692 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710707
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    Kinetik der Umesterung von Ethanol und Butylacetat - Ein Modellsystem für die Reaktivrektifikation (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 704-708 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710711
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    BRICK - Ein 1-D-Simulationstool für Mehrphasenströmungen in Behältern (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 713-717 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710713
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    Vergleichende Untersuchungen zur nichtadiabaten Absorption im Film- und Blasen-KolbenregimeÜberarbeitete Fassung eines Postervortrages von U. HELBING anläßlich der GVC-Jahrestagung, 30. Sept./02. Okt. 1998 in Freiburg. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 844-849 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710813
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    Möglichkeiten zur Vorausberechnung von Verweilzeitverteilungen (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 795-807 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Possible Approaches to the Prediction of Residence Time Distributions Although the experimental determination of residence time distributions is based on a black-box method, the signal shape also permits certain conclusions to be drawn about the internal conditions. However, if it is to provide a sole basis for elucidating process steps in a plant this method is soon overtaxed. A deeper theoretical penetration of the pertinent transport processes opens up the way ahead. However, since residence time distributions are based on mass-oriented considerations, substantial advances in fluid mechanics, where location-based considerations predominate, have not led to improved predictive capability. Yet the computer power now available offers a variety of ways of calculating residence-time distributions for a known flow profile, thus permitting a step in the direction of better predictability of residence time distributions. This article presents utilisable methods and evaluates them with regard to their demands on time and effort and their predictive power. Problems arising in connection with the models are discussed.
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    URL: http://dx.doi.org/10.1002/cite.330710805
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    Dreiphasenrektifikation in Packungskolonnen (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 819-823 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710807
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    Einfluß von Polyelektrolytkomplexschichten auf Trennleistung und Foulingverhalten oberflächen- und bulkmodifizierter MembranenPosterbeitrag anläßlich des 7. Aachener Membran Kolloquiums, 9./11. März 1999 in Aachen. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 839-844 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710812
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    In-situ-Bestimmung momentaner Reaktionsraten von Brennstoffpartikeln durch simultane Messung von Partikeltemperatur und GrößeÜberarbeitete und ergänzte Version des Vortrages von T. REICHELT anläßlich der GVC-Jahrestagung, 30. Sept./2. Okt. 1998 in Freiburg. (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 857-861 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710816
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    Parallelisierte Synthese und schnelle katalytische Testung von Katalysatorbibliotheken für Oxidationsreaktionen (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 873-877 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710820
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    GVC-Fachausschuß „Gasreinigung“Berichterstatter: Dipl.-Ing. ACHIM DITTLER, Institut für Mechanische Verfahrenstechnik und Mechanik, Universität Karlsruhe (TH), D-76128 Karlsruhe, und Priv.-Doz. Dr.-Ing. EBERHARD SCHMIDT, DEGUSSA-HÜLS AG, D-63403 Hanau (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 882-883 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Die diesjährige interne Sitzung des GVC-Fachausschusses „Gasreinigung“ wurde zusammen mit der Arbeitssitzung des Fachausschusses „Energieverfahrenstechnik“ am 19. und 20. April im Tagungszentrum „Festung Marienburg“ in Würzburg abgehalten.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710822
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    Lime und Limestone. J.A.H. Oates Wiley-VCH, Weinheim 1998, 455 Seiten, 79 Abbildungen, 86 Tabellen, geb. DM 298,- ISBN 3-527-29527-5 (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 889-889 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330710828
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    124. Bestimmung von Trennschärfegraden bei Klassierern zum naßmechanischen Recycling von Betonrestmassen (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 1024-1025 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.3307109128
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    128. Echtzeit-Standard-Infrastrukturkonzept für die Integration von Daten, Applikationen und Präsentationen (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 1026-1026 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.3307109132
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    132. Simulationsbasierte intelligente Optimierung in der Prozeßindustrie (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 1029-1029 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.3307109136
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    140. Strukturwandel im Anlagenbau: Von der Projektierung bis zur Instandhaltung (1999)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 71 (1999), S. 1035-1035 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.3307109144
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