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  • Chemistry  (114,948)
  • 1995-1999  (38,453)
  • 1980-1984  (33,715)
  • 1975-1979  (29,418)
  • 1955-1959  (13,362)
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  • 1
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-10-13
    Description: Picosecond spectroscopy is a relatively new field of science that utilizes ultrashort laser pulses to monitor events taking place in the 10(-12) second regime. The continuing development of picosecond spectroscopy has made possible the detection and measurement of the primary events in many physical and tiological processes. This article describes a currently used picosecond spectroscopy system that is capable of reliably recording picosecond events. Two areas of picosecond research are discussed; one concerns the interaction of electrons in fluids, and the second the primary events in vision.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rentzepis, P M -- New York, N.Y. -- Science. 1978 Oct 13;202(4364):174-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/694523" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Electrons ; *Kinetics ; Lasers ; Protons ; *Retinal Pigments ; *Rhodopsin ; Spectrum Analysis/*methods ; Temperature ; *Vision, Ocular
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  • 2
    Publication Date: 1979-12-14
    Description: The structure and absolute stereoconfigurations of four adenosine adducts with (+/-)-7 alpha,8 beta-dihydroxy-9 beta, 10 beta-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (BPDE) and their deoxyadenosine analogs have been determined. They result from both cis and trans addition of the N6 amino group of ademine to the 10 position of both enantiomers of BDPE. This was determined from studies of the nuclear magnetic resonance spectra, mass spectra, and circular dichroism spectra, as well as from their pKa values and chemical reactivities.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jeffrey, A M -- Grzeskowiak, K -- Weinstein, I B -- Nakanishi, K -- Roller, P -- Harvey, R G -- New York, N.Y. -- Science. 1979 Dec 14;206(4424):1309-11.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/316186" target="_blank"〉PubMed〈/a〉
    Keywords: *Benzopyrenes ; Chemical Phenomena ; Chemistry ; Circular Dichroism ; Dna ; *Deoxyadenosines/analogs & derivatives ; Magnetic Resonance Spectroscopy ; Mass Spectrometry ; Molecular Conformation ; Mutation ; Stereoisomerism
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-08-14
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klotz, I M -- Haney, D N -- King, L C -- New York, N.Y. -- Science. 1981 Aug 14;213(4509):724-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7256275" target="_blank"〉PubMed〈/a〉
    Keywords: Anemia, Sickle Cell/*drug therapy ; Aspirin/analogs & derivatives/therapeutic use ; Chemical Phenomena ; Chemistry ; *Hemoglobin, Sickle ; Humans ; Protein Binding/drug effects ; Protein Conformation ; Salicylates/*therapeutic use ; Solubility ; Structure-Activity Relationship
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  • 4
    Publication Date: 1982-09-10
    Description: Alkyl-Substituted gamma-butyrolactones were synthesized and tested for their convulsant and anticonvulsant actions in mice and guinea pigs. The alpha-substituted compounds, alpha, alpha-dimethyl-, and alpha-ethyl-alpha-methyl-gamma-butyrolactone were anticonvulsant compounds with a spectrum of activity similar to that of ethosuximide. In contrast, beta-substituted compounds were convulsant agents similar to picrotoxinin. The alpha-substituted-gama-butyrolactones represent a new class of anticonvulsant drug with experimental and clinical potential.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Klunk, W E -- McKeon, A -- Covey, D F -- Ferrendelli, J A -- GM-07200/GM/NIGMS NIH HHS/ -- GM-24483/GM/NIGMS NIH HHS/ -- NS-14834/NS/NINDS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1982 Sep 10;217(4564):1040-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6810462" target="_blank"〉PubMed〈/a〉
    Keywords: *4-Butyrolactone/analogs & derivatives/*therapeutic use/toxicity ; Animals ; *Anticonvulsants ; Chemical Phenomena ; Chemistry ; Convulsants ; Drug Evaluation, Preclinical ; Electroencephalography ; Epilepsy, Absence/drug therapy ; Ethosuximide/pharmacology ; *Furans/*therapeutic use ; Guinea Pigs ; Mice ; Structure-Activity Relationship ; Trimethadione/pharmacology
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  • 5
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-05-06
    Description: Crystalline cholesterol undergoes a phase transition a few degrees below human body temperature. The high-temperature form has an unusually complex structure with 16 independent molecules. In the transition two molecules change side chain conformation, four reorient about their long axes, and ten remain unchanged. The transition mechanism implies relatively nonspecific intermolecular interactions, qualitatively consistent with the behavior of cholesterol in biomembranes. The transition preserves a remarkably closely obeyed pseudosymmetry present in the structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hsu, L Y -- Nordman, C E -- GM15259/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 May 6;220(4597):604-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836303" target="_blank"〉PubMed〈/a〉
    Keywords: Body Temperature ; Chemical Phenomena ; Chemistry ; *Cholesterol ; Crystallization ; Humans ; Magnetic Resonance Spectroscopy ; Molecular Conformation
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  • 6
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-07-20
    Description: The iron-carbon monoxide stretching mode and the iron-carbon-oxygen bending mode in carbon monoxide-bound cytochrome oxidase have been assigned at 520 and 578 cm-1, respectively. The frequencies, widths, and intensities of these modes show that the Fe-C-O grouping in carbon monoxide-cytochrome a3 is linear but tilted from the normal to the heme plane; that the iron-histidine bond in both five- and six-coordinate cytochrome a3 is strained; and that the carbon monoxide and the proximal histidine each have characteristic, well-defined orientations in all molecules. These data can account for the binding affinities of carbon monoxide and dioxygen under physiological conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Argade, P V -- Ching, Y C -- Rousseau, D L -- New York, N.Y. -- Science. 1984 Jul 20;225(4659):329-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6330890" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Carbon Monoxide/metabolism ; Cattle ; Chemical Phenomena ; Chemistry ; Electron Transport Complex IV/*metabolism ; Myoglobin/metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Spectrum Analysis, Raman
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  • 7
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-05-06
    Description: Arachidonic acid plays a central role in a biological control system where such oxygenated derivatives as prostaglandins, thromboxanes, and leukotrienes are mediators. The leukotrienes are formed by transformation of arachidonic acid into an unstable epoxide intermediate, leukotriene A4, which can be converted enzymatically by hydration to leukotriene B4, and by addition of glutathione to leukotriene C4. This last compound is metabolized to leukotrienes D4 and E4 by successive elimination of a gamma-glutamyl residue and glycine. Slow-reacting substance of anaphylaxis consists of leukotrienes C4, D4, and E4. The cysteinyl-containing leukotrienes are potent bronchoconstrictors, increase vascular permeability in postcapillary venules, and stimulate mucus secretion. Leukotriene B4 causes adhesion and chemotactic movement of leukocytes and stimulates aggregation, enzyme release, and generation of superoxide in neutrophils. Leukotrienes C4, D4, and E4, which are released from the lung tissue of asthmatic subjects exposed to specific allergens, seem to play a pathophysiological role in immediate hypersensitivity reactions. These leukotrienes, as well as leukotriene B4, have pro-inflammatory effects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Samuelsson, B -- New York, N.Y. -- Science. 1983 May 6;220(4597):568-75.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6301011" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Arachidonic Acids/metabolism/pharmacology/physiology ; Bronchi/drug effects ; Cats ; Chemical Phenomena ; Chemistry ; Cricetinae ; Guinea Pigs ; Haplorhini ; Humans ; Hypersensitivity, Immediate/*physiopathology ; Inflammation/*physiopathology ; Leukocytes/drug effects/metabolism ; Leukotriene B4/pharmacology/*physiology ; Mice ; Microcirculation/drug effects ; Rabbits ; Rats ; SRS-A/*physiology
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  • 8
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-01-20
    Description: Peptide synthesis can be used for elucidating the roles of secondary structures in the specificity of hormones, antigens, and toxins. Intermediate sized peptides with these activities assume amphiphilic secondary structures in the presence of membranes. When models are designed to optimize the amphiphilicity of the secondary structure, stronger interactions can be observed with the synthetic peptides than with the naturally occurring analogs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kaiser, E T -- Kezdy, F J -- HL-18577/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1984 Jan 20;223(4633):249-55.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6322295" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Apolipoprotein A-I ; Apolipoproteins ; Binding Sites ; Calcitonin ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone ; Endorphins ; Glucagon ; Growth Hormone-Releasing Hormone ; *Hormones/pharmacology ; Lipoproteins, HDL ; Melitten ; Models, Structural ; *Peptides/chemical synthesis/metabolism/pharmacology ; Protein Conformation ; Structure-Activity Relationship ; beta-Endorphin
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  • 9
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-10-19
    Description: Fourier transform mass spectrometry will play an important role in the future because of its unique combination of high mass resolution, high upper mass limit, and multichannel advantage. These features have already found application in gas chromatography-mass spectrometry, multiphoton ionization, laser desorption, and secondary ion mass spectrometry. However, its most notable feature is the ability to store ions. This characteristic, when combined with the others, will allow expeditious study of the interaction of gas-phase ions with both photons (photodissociation) and neutral molecules, and the convenient application of this fundamental information for chemical analysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gross, M L -- Rempel, D L -- 2-8423576/PHS HHS/ -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):261-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6385250" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Fourier Analysis ; Ions ; Lasers ; *Mass Spectrometry/instrumentation/methods
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  • 10
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-08-31
    Description: High-resolution carbon-13 nuclear magnetic resonance (NMR) spectra of enzyme-inhibitor and enzyme-substrate complexes provide detailed structural and stereochemical information on the mechanism of enzyme action. The proteases trypsin and papain are shown to form tetrahedrally coordinated complexes and acyl derivatives with a variety of compounds artificially enriched at the site or sites of interest. These results are compared with the structural information derived from x-ray diffraction. Detailed NMR studies have provided a clearer picture of the ionization state of the residues participating in enzyme-catalyzed processes than other more classical techniques. The dynamics of enzymic catalysis can be observed at sub-zero temperatures by a combination of cryoenzymology and carbon-13 NMR spectroscopy. With these powerful techniques, transient, covalently bound intermediates in enzyme-catalyzed reactions can be detected and their structures rigorously assigned.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mackenzie, N E -- Malthouse, J P -- Scott, A I -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):883-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6433481" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Carbon Isotopes ; Carboxypeptidases/metabolism ; Carboxypeptidases A ; Catalysis ; Chemical Phenomena ; Chemistry ; Coenzymes/*metabolism ; Endopeptidases/metabolism ; Enzymes/*metabolism ; Freezing ; Fructose-Bisphosphate Aldolase/metabolism ; Magnetic Resonance Spectroscopy ; Papain/metabolism ; Pepsin A/metabolism ; Peptide Hydrolases/*metabolism ; Protease Inhibitors ; Pterins/metabolism ; Pyridoxal Phosphate/metabolism ; Serine Endopeptidases
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  • 11
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-03-09
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maugh, T H 2nd -- New York, N.Y. -- Science. 1984 Mar 9;223(4640):1051-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6695193" target="_blank"〉PubMed〈/a〉
    Keywords: *Air Pollutants ; *Atmosphere ; Carbon Tetrachloride ; Chemical Phenomena ; Chemistry ; *Chlorofluorocarbons, Methane ; Free Radicals ; Nitrogen Dioxide ; Nitrous Oxide ; Oxygen ; *Ozone ; Photochemistry ; Risk ; Singlet Oxygen ; Trichloroethanes ; Ultraviolet Rays
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  • 12
    Publication Date: 1984-10-19
    Description: Pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis enables qualitative and quantitative analysis of nonvolatile organic materials containing molecular assemblies of a complexity and size far beyond the capabilities of direct mass spectrometry. The state of the art in pyrolysis mass spectrometry techniques is illustrated through specific applications, including structural determination and quality control of synthetic polymers, quantitative analysis of polymer mixtures, classification and structural characterization of fossil organic matter, and nonsupervised numerical extraction of component patterns from complex biological samples.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meuzelaar, H L -- Windig, W -- Harper, A M -- Huff, S M -- McClennen, W H -- Richards, J M -- New York, N.Y. -- Science. 1984 Oct 19;226(4672):268-74.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6484572" target="_blank"〉PubMed〈/a〉
    Keywords: Biochemical Phenomena ; Biochemistry ; Chemical Phenomena ; Chemistry ; Coal ; Enterobacteriaceae/analysis/isolation & purification ; Hot Temperature ; Mass Spectrometry/*methods ; Polymers
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  • 13
    Publication Date: 1984-08-31
    Description: The splicing of messenger RNA precursors in vitro proceeds through an intermediate that has the 5' end of the intervening sequence joined to a site near the 3' splice site. This lariat structure, which has been characterized for an adenovirus 2 major late transcript, has a branch point, with 2'-5' and 3'-5' phosphodiester bonds emanating from a single adenosine residue. The excised intervening sequence retains the branch site and terminates in a guanosine residue with a 3' hydroxyl group. The phosphate group at the splice junction between the two exons originates from the 3' splice site at the precursor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Padgett, R A -- Konarska, M M -- Grabowski, P J -- Hardy, S F -- Sharp, P A -- P01-CA14051/CA/NCI NIH HHS/ -- P01-CA26717/CA/NCI NIH HHS/ -- R01-GM32467/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1984 Aug 31;225(4665):898-903.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6206566" target="_blank"〉PubMed〈/a〉
    Keywords: Adenoviruses, Human/metabolism ; Base Sequence ; Chemical Phenomena ; Chemistry ; Nucleic Acid Conformation ; Nucleic Acid Precursors/analysis/*metabolism ; Oligoribonucleotides/metabolism ; Phosphates/metabolism ; RNA/analysis/*metabolism ; RNA Precursors ; *RNA Splicing ; RNA, Messenger/analysis/*metabolism ; RNA, Viral/analysis/*metabolism
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  • 14
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-05-11
    Description: The mechanism of lipid peroxidation and the manner in which antioxidants function is reviewed. beta-Carotene is a purported anticancer agent, which is believed by some to have antioxidant action of a radical-trapping type. However, definitive experimental support for such action has been lacking. New experiments in vitro show that beta-carotene belongs to a previously unknown class of biological antioxidants. Specifically, it exhibits good radical-trapping antioxidant behavior only at partial pressures of oxygen significantly less than 150 torr, the pressure of oxygen in normal air. Such low oxygen partial pressures are found in most tissues under physiological conditions. At higher oxygen pressures, beta-carotene loses its antioxidant activity and shows an autocatalytic, prooxidant effect, particularly at relatively high concentrations. Similar oxygen-pressure-dependent behavior may be shown by other compounds containing many conjugated double bonds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Burton, G W -- Ingold, K U -- New York, N.Y. -- Science. 1984 May 11;224(4649):569-73.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6710156" target="_blank"〉PubMed〈/a〉
    Keywords: Antioxidants/*metabolism ; Carotenoids/*metabolism ; Chemical Phenomena ; Chemistry ; Free Radicals ; Humans ; Linoleic Acids/metabolism ; *Lipid Metabolism ; Oxidation-Reduction ; Oxygen/metabolism ; Partial Pressure ; Peroxides/metabolism ; Tetrahydronaphthalenes/metabolism ; beta Carotene
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  • 15
    Publication Date: 1983-12-16
    Description: Aplysiatoxin and debromoaplysiatoxin, which are isolated from the seaweed, Lyngbya gracilis, differ in their chemical structure only by the presence or absence of a bromine residue in the hydrophilic region. The function and the structure-activity relation of the hydrophilic region are not known. Aplysiatoxin increased malignant transformation, stimulated DNA synthesis, and inhibited the binding of phorbol-12,13-dibutyrate and epidermal growth factor to cell receptors. Debromoaplysiatoxin inhibited the binding of these two substances as strongly as aplysiatoxin but did not increase malignant transformation or stimulate DNA synthesis. These results indicate that a slight change in the chemical structure of the hydrophilic region of aplysiatoxin affects its abilities to increase cell transformation and stimulate DNA synthesis and that the abilities of the tumor promoters to inhibit the binding of phorbol-12,13-dibutyrate and epidermal growth factor are dissociable from their abilities to increase cell transformation and stimulate DNA synthesis under some circumstances.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shimomura, K -- Mullinix, M G -- Kakunaga, T -- Fujiki, H -- Sugimura, T -- New York, N.Y. -- Science. 1983 Dec 16;222(4629):1242-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6316505" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Caenorhabditis elegans Proteins ; Carcinogens/*pharmacology ; Carrier Proteins ; Cell Line ; Cell Transformation, Neoplastic/*drug effects ; Chemical Phenomena ; Chemistry ; DNA/biosynthesis ; Epidermal Growth Factor/metabolism ; Lactones/analysis/*pharmacology ; *Lyngbya Toxins ; Mice ; Phorbol 12,13-Dibutyrate ; Phorbol Esters/metabolism ; *Protein Kinase C ; Receptor, Epidermal Growth Factor ; Receptors, Cell Surface/metabolism ; *Receptors, Drug ; Structure-Activity Relationship
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  • 16
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-03-16
    Description: Yeast phenylalanine transfer RNA was subjected to a 12-picosecond molecular dynamics simulation. The principal features of the x-ray crystallographic analysis are reproduced, and the amplitudes of atomic displacements appear to be determined by the degree of exposure of the atoms. An analysis of the hydrogen bonds shows a correlation between the average length of a bond and the fluctuation in that length and reveals a rocking motion of bases in Watson-Crick guanine X cytosine base pairs. The in-plane motions of the bases are generally of larger amplitude than the out-of-plane motions, and there are correlations in the motions of adjacent bases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harvey, S C -- Prabhakaran, M -- Mao, B -- McCammon, J A -- New York, N.Y. -- Science. 1984 Mar 16;223(4641):1189-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6560785" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Computers ; Cytosine ; Guanine ; Hydrogen Bonding ; Nucleic Acid Conformation ; *RNA, Fungal ; *RNA, Transfer, Amino Acyl ; Yeasts/analysis
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  • 17
    Publication Date: 1984-11-16
    Description: Sequence-dependent variations in DNA revealed by x-ray crystallographic studies have suggested that certain DNA-reactive drugs may react preferentially with defined sequences in DNA. Drugs that wind around the helix and reside within one of the grooves of DNA have perhaps the greatest chance of recognizing sequence-dependent features of DNA. The antitumor antibiotic CC-1065 covalently binds through N-3 of adenine and resides within the minor groove of DNA. This drug overlaps with five base pairs for which a high sequence specificity exists.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hurley, L H -- Reynolds, V L -- Swenson, D H -- Petzold, G L -- Scahill, T A -- New York, N.Y. -- Science. 1984 Nov 16;226(4676):843-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6494915" target="_blank"〉PubMed〈/a〉
    Keywords: Antibiotics, Antineoplastic/*metabolism ; *Base Sequence ; Binding Sites ; Chemical Phenomena ; Chemistry ; DNA/*metabolism ; *Indoles ; Leucomycins/*metabolism ; Molecular Conformation ; X-Ray Diffraction
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  • 18
    Publication Date: 1984-06-15
    Description: A new class of synthetic antifungal agents, the allylamines , has been developed by modification of naftifine , a topical antimycotic. SF 86-327, the most effective of these compounds so far, is highly active in vitro against a wide range of fungi and exceeds clinical standards in the oral and topical treatment of guinea pig dermatophytoses. SF 86-327 is a powerful specific inhibitor of fungal squalene epoxidase, a key enzyme in sterol biosynthesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petranyi, G -- Ryder, N S -- Stutz, A -- New York, N.Y. -- Science. 1984 Jun 15;224(4654):1239-41.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6547247" target="_blank"〉PubMed〈/a〉
    Keywords: Allylamine/analogs & derivatives/*chemical synthesis/pharmacology ; Amines/*chemical synthesis ; Animals ; Antifungal Agents/*chemical synthesis/pharmacology ; Chemical Phenomena ; Chemistry ; Dermatomycoses/drug therapy ; Fungi/*drug effects/enzymology ; Guinea Pigs ; Naphthalenes/chemical synthesis/pharmacology ; Oxygenases/*antagonists & inhibitors ; Squalene Monooxygenase
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  • 19
    Publication Date: 1984-11-02
    Description: By recombinant DNA techniques, a disulfide bond was introduced at a specific site in T4 lysozyme, a disulfide-free enzyme. This derivative retained full enzymatic activity and was more stable toward thermal inactivation than the wild-type protein. The derivative, T4 lysozyme (Ile3----Cys), was prepared by substituting a Cys codon for an Ile codon at position 3 in the cloned lysozyme gene by means of oligonucleotide-dependent, site-directed mutagenesis. The new gene was expressed in Escherichia coli under control of the (trp-lac) hybrid tac promoter, and the protein was purified. Mild oxidation generated a disulfide bond between the new Cys3 and Cys97, one of the two unpaired cysteines of the native molecule. Oxidized T4 lysozyme (Ile3----Cys) exhibited specific activity identical to that of the wild-type enzyme when measured at 20 degrees C in a cell-clearing assay. The cross-linked protein was more stable than the wild type during incubation at elevated temperatures as determined by recovered enzymatic activity at 20 degrees C.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perry, L J -- Wetzel, R -- New York, N.Y. -- Science. 1984 Nov 2;226(4674):555-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6387910" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; DNA, Recombinant/metabolism ; Escherichia coli/enzymology ; *Genetic Engineering ; Kinetics ; Muramidase/*genetics/metabolism ; Protein Denaturation
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  • 20
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-09-09
    Description: The structures of three proteins that regulate gene expression have been determined recently and suggest how these proteins may bind to their specific recognition sites on the DNA. One protein (Cro) is a repressor of gene expression, the second (CAP) usually stimulates gene expression, and the third (lambda repressor) can act as either a repressor or an activator. The three proteins contain a substructure consisting of two consecutive alpha helices that is virtually identical in each case. Structural and amino acid sequence comparisons suggest that this bihelical fold occurs in a number of proteins that regulate gene expression, and is an intrinsic part of the DNA-protein recognition event. The modes of repression and activation by Cro and lambda repressor are understood reasonably well, but the mode of action of CAP is still unclear.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Takeda, Y -- Ohlendorf, D H -- Anderson, W F -- Matthews, B W -- GM20066/GM/NIGMS NIH HHS/ -- GM28138/GM/NIGMS NIH HHS/ -- GM30894/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1983 Sep 9;221(4615):1020-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6308768" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Chemical Phenomena ; Chemistry ; *DNA Helicases ; DNA-Binding Proteins ; Escherichia coli/genetics ; Gene Expression Regulation ; Models, Chemical ; Protein Conformation
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  • 21
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1984-06-08
    Description: The effect of a partial pressure of nitrogen of 50 atmospheres (5065 kilopascals ) on the hydrogen evolution reaction of nitrogenase has been investigated. Evolution of hydrogen was not blocked completely by 50 atmospheres of nitrogen in any of four experiments; rather, 27.3 +/- 2.4 percent of the total electron flux through nitrogenase was directed toward production of hydrogen. The ratio of hydrogen evolved to nitrogen fixed was close to 1:1, which implies that hydrogen evolution is obligatory in the fixation of molecular nitrogen by nitrogenase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Simpson, F B -- Burris, R H -- AI-00848/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1984 Jun 8;224(4653):1095-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6585956" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Hydrogen ; *Nitrogen ; Nitrogen Fixation ; *Nitrogenase ; Partial Pressure
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  • 22
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-03-17
    Description: The history of U.S. foreign aid support of science and technology in Latin America is examined and an attempt is made to evaluate the scientific and economic growth of that area in relation to the total foreign aid effort.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Szmant, H H -- New York, N.Y. -- Science. 1978 Mar 17;199(4334):1173-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/415363" target="_blank"〉PubMed〈/a〉
    Keywords: Chemistry ; Cost-Benefit Analysis ; Education ; History, 20th Century ; International Educational Exchange ; Latin America ; *Research Support as Topic ; *Science/history ; United States
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  • 23
    Publication Date: 1980-01-04
    Description: In concentrates of water produced in a laboratory simulation of a drinking water treatment process, direct-acting, nonvolatile mutagens were readily detected by means of the Ames Salmonella test. The mutagens were shown to be produced by the chlorination process. Treatment of the water with chloramine resulted in less mutagenic activity than treatment with free chlorine. Dechlorination of drinking water with sulfite sharply reduced the mutagenic activity. Treatment with sulfur dioxide is proposed as an effective, inexpensive method of reducing the direct-acting mutagenic activity of drinking water and of aqueous industrial effluents.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cheh, A M -- Skochdopole, J -- Koski, P -- Cole, L -- New York, N.Y. -- Science. 1980 Jan 4;207(4426):90-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6985746" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; Chloramines ; Chlorine ; Mutagens/*analysis ; Salmonella typhimurium/genetics ; Sulfites ; Water Pollutants/*analysis ; Water Pollutants, Chemical/*analysis ; Water Supply/*analysis
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  • 24
    Publication Date: 1981-10-16
    Description: The DNA/RNA Synthesizer provides a complete and automated procedure for the synthesis of DNA sequences. Each base unit is added in a 30-minute cycle, permitting a tetradecamer to be constructed in 6 1/2 hours. The complete procedure is described, including a practical procedure for isolation and purification of the desired DNA sequence.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Alvarado-Urbina, G -- Sathe, G M -- Liu, W C -- Gillen, M F -- Duck, P D -- Bender, R -- Ogilvie, K K -- New York, N.Y. -- Science. 1981 Oct 16;214(4518):270-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6169150" target="_blank"〉PubMed〈/a〉
    Keywords: Automation ; Chemical Phenomena ; Chemistry ; DNA/*chemical synthesis ; *Genes, Synthetic ; RNA/*chemical synthesis ; Solubility
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  • 25
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-05-15
    Description: Research on chitin as a marine resource is pointing to novel applications for this cellulose-like biopolymer. Discovery of nondegrading solvent systems has permitted the spinning of filaments, for example, for use as surgical sutures. New methods for preparing the bioactive alkyl glycoside of N-acetyl-D-glucosamine (the monomer unit of chitin) and a microcrystalline chitin has encouraged their use as promoters for growth of bifidobacteria and as an aid in digestion of high-lactose cheese whey by domestic animals. Chitin-protein complexes of several crustacean species show great variability in ratios of chitin to covalently bound protein and in residual protein in the "purified" chitins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Austin, P R -- Brine, C J -- Castle, J E -- Zikakis, J P -- New York, N.Y. -- Science. 1981 May 15;212(4496):749-53.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7221561" target="_blank"〉PubMed〈/a〉
    Keywords: Animal Feed ; Animals ; Cheese ; Chemical Phenomena ; Chemistry ; Chickens ; *Chitin ; Crystallography ; Lactose/metabolism ; Proteins/analysis ; Sutures ; *Technology
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  • 26
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-12-18
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gilbert, W -- New York, N.Y. -- Science. 1981 Dec 18;214(4527):1305-12.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7313687" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Chemical Phenomena ; Chemistry ; DNA/*genetics ; Eukaryotic Cells/physiology ; *Genes ; Hydrazines ; Lac Operon ; Methylation ; Prokaryotic Cells/physiology ; Sulfuric Acid Esters
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  • 27
    Publication Date: 1982-07-09
    Description: A new process has been developed which is called "Boradeption" to signify boronic acid--dependent phase transfer of water-insoluble agents. Highly fluorescent boronic acid dervatives, FluoroBoras, are solubilized with a physiologically compatible carrier buffer containing a receptor group for boronate adduct formation. The system can be used to stain living cells. In another variation of the Boradeption concept, an insoluble reporter molecule containing a boronate receptor is solubilized with a carrier buffer containing a boronic acid functional group. The boronate-receptor complexes, which are in dynamic equilibrium, can be designed as vital stains and reagents for a variety of biological and medical applications.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gallop, P M -- Paz, M A -- Henson, E -- AG-00376-07/AG/NIA NIH HHS/ -- HL-20764-04A1/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1982 Jul 9;217(4555):166-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6178158" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biological Transport ; *Boron Compounds/therapeutic use ; *Boronic Acids/therapeutic use ; *Cell Membrane Permeability ; Cells, Cultured ; Chemical Phenomena ; Chemistry ; Chromogenic Compounds/metabolism ; Cricetinae ; Fibroblasts ; Fluorescent Dyes/metabolism ; Humans ; Rats ; Staining and Labeling
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  • 28
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-12-11
    Description: The scrapie agent causes a degenerative nervous system disease in sheep and goats. Studies with extensively purified preparations demonstrated that the agent contains a protein that is required for infectivity. Chemical modification of the scrapie agent by diethyl pyrocarbonate reduced the titer 1000-fold. Exposure of the inactivated agent to hydroxylamine, a strong nucleophile, resulted in complete restoration of infectivity. Presumably, nucleophilic residues within a scrapie agent protein undergo carbethoxylation on reaction with diethyl pyrocarbonate, and subsequent addition of hydroxylamine displaces these carbethoxy groups.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McKinley, M P -- Masiarz, F R -- Prusiner, S B -- NS14069/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1981 Dec 11;214(4526):1259-61.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6795721" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Assay ; Brain/microbiology ; Chemical Phenomena ; Chemistry ; Cricetinae ; Diethyl Pyrocarbonate/pharmacology ; Histidine/pharmacology ; *Prions ; Ribonucleases/pharmacology ; Serum Albumin, Bovine/pharmacology ; Viral Proteins/*isolation & purification/pharmacology
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  • 29
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-01-30
    Description: The incubation of lens proteins with reducing sugars leads to the formation of fluorescent yellow pigments and cross-like similar to those reported in aging and cataractous human lenses. Called nonenzymatic browning or the Maillard reaction, this aging process also occurs in stored foods. Reducing sugars condense with the free amino group of proteins, then rearrange and dehydrate to form unsaturated pigments and cross-linked products. Although most proteins in living systems turn over with sufficient rapidity to avoid nonenzymatic browning, some, such as lens crystallins and skin collagen, are exceptionally long-lived and may be vulnerable.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Monnier, V M -- Cerami, A -- AM 19655/AM/NIADDK NIH HHS/ -- New York, N.Y. -- Science. 1981 Jan 30;211(4481):491-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6779377" target="_blank"〉PubMed〈/a〉
    Keywords: *Aging ; Animals ; Cattle ; Chemical Phenomena ; Chemistry ; *Crystallins ; Diabetes Mellitus/physiopathology ; Glucose ; Glucosephosphates ; In Vitro Techniques ; Lysine ; *Proteins ; Spectrophotometry, Ultraviolet
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  • 30
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-03-13
    Description: Great advances have been made in fundamental scientific research in recent years. The new knowledge gathered, in addition to deepening our understanding of the physical universe, contributes a range of abilities and opportunities to society that would not otherwise be available. Much research that may be called applied because it addresses needs of society is quite fundamental in character, and support of such research at the National Science Foundation is to be handled in tandem by the research directorates. Other areas that require a refocusing of support are engineering science and education, at all levels, in science and engineering. Increasing our strength in these areas is essential to achieve our national economic, social, and political goals. Steps are being taken by the National Science Foundation to make its structure better able to deal with engineering and applied research and to provide greater mutual reinforcement between applied and basic research.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Slaughter, J B -- New York, N.Y. -- Science. 1981 Mar 13;211(4487):1131-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7466384" target="_blank"〉PubMed〈/a〉
    Keywords: Cell Biology ; Chemical Phenomena ; Chemistry ; *Forecasting ; Geological Phenomena ; Geology ; *Government Agencies ; Molecular Biology ; Neurochemistry ; Physical Phenomena ; Physics ; Research Support as Topic ; United States
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  • 31
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1982-12-10
    Description: The discovery that cis-diamminedichloroplatinum(II) (cis-DDP) has clinically useful antitumor properties and can form platinum blues spawned an extensive investigation of its chemistry in water. Several new molecules have been synthesized, some rather old ones have been characterized for the first time, and clues have begun to emerge about the chemical interaction of cis-DDP with its likely biological target, DNA.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lippard, S J -- New York, N.Y. -- Science. 1982 Dec 10;218(4577):1075-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6890712" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Cisplatin ; *Dna ; Hydrolysis ; Pigments, Biological
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  • 32
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1982-12-03
    Description: The visual response is initiated by light reception and transduction into chemical and electrical energy in the outer-segment membranes of rod and cone cells. Recent research on the molecular events controlled by light has clarified the roles of some of the rod outer-segment biomolecules. These developments and the current unresolved questions are described.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Brien, D F -- New York, N.Y. -- Science. 1982 Dec 3;218(4576):961-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6291153" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Blood Proteins/metabolism ; Calcium/metabolism ; Chemical Phenomena ; Chemistry ; Enzyme Activation ; Enzymes/metabolism ; GTP-Binding Proteins ; Light ; Membranes/metabolism ; Models, Biological ; Phosphoric Diester Hydrolases/biosynthesis ; Photoreceptor Cells/*metabolism ; Receptors, Cell Surface/metabolism ; Rhodopsin/metabolism ; Rod Cell Outer Segment/*metabolism ; Vision, Ocular/*physiology
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  • 33
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1983-06-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krenitsky, T A -- Beauchamp, L -- New York, N.Y. -- Science. 1983 Jun 10;220(4602):1106.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6857236" target="_blank"〉PubMed〈/a〉
    Keywords: Acyclovir/metabolism ; *Antiviral Agents/metabolism ; Chemical Phenomena ; Chemistry ; Humans ; Vidarabine/metabolism
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  • 34
    Publication Date: 1983-05-06
    Description: Resonance Raman spectra of photolyzed carbonmonoxyhemoglobin obtained with 10-nanosecond pulses are compared with the spectra of photolyzed carbonmonoxyhemoglobin stabilized at 80 K. In comparing the deoxy with the photodissociated species, the changes in the Raman spectra are the same for these two experimental regimes. These results show that at ambient and cryogenic temperatures the heme pocket in liganded hemoglobin is significantly different from that of deoxyhemoglobin. It is concluded that measurements of the properties of intermediate species from photodissociated hemoglobin stabilized at low temperatures can be used to probe the short-lived metastable forms of hemoglobin present after photodissociation under biologically relevant solution conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ondrias, M R -- Friedman, J M -- Rousseau, D L -- New York, N.Y. -- Science. 1983 May 6;220(4597):615-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6836305" target="_blank"〉PubMed〈/a〉
    Keywords: Carboxyhemoglobin ; Chemical Phenomena ; Chemistry ; Freezing ; *Hemoglobins ; Humans ; Ligands ; Spectrum Analysis, Raman ; Temperature
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  • 35
    Publication Date: 1983-04-15
    Description: Alkylating agents that display strong selectivity for opiate receptor types delta or mu were prepared by appropriate modification of the structures of the strong analgesics fentanyl, etonitazene, and endoethenotetrahydrooripavine. The availability of these substances should facilitate studies of the structural basis of receptor specificity and of the physiologic roles of these receptors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rice, K C -- Jacobson, A E -- Burke, T R Jr -- Bajwa, B S -- Streaty, R A -- Klee, W A -- New York, N.Y. -- Science. 1983 Apr 15;220(4594):314-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6132444" target="_blank"〉PubMed〈/a〉
    Keywords: Alkylation ; Animals ; Benzimidazoles/analogs & derivatives/metabolism ; Brain/physiology ; Cells, Cultured ; Chemical Phenomena ; Chemistry ; Enkephalin, Methionine/analogs & derivatives/metabolism ; Fentanyl/analogs & derivatives/metabolism ; *Isothiocyanates ; Ligands ; Rats ; Receptors, Opioid/*metabolism/physiology ; Thebaine/analogs & derivatives/pharmacology
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  • 36
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-04-07
    Description: Glucose reacts nonenzymatically with the NH2-terminal amino acid of the beta chain of human hemoglobin by way of a ketoamine linkage, resulting in the formation of hemoglobin AIc. Other minor components appear to be adducts of glucose 6-phosphate and fructose 1,6-diphosphate. These hemoglobins are formed slowly and continuously throughout the 120-day life-span of the red cell. There is a two- to threefold increase in hemoglobin AIc in the red cells of patients with diabetes mellitus. By providing an integrated measurement of blood glucose, hemoglobin AIc is useful in assessing the degree of diabetic control. Furthermore, this hemoglobin is a useful model of nonenzymatic glycosylation of other proteins that may be involved in the long-term complications of the disease.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bunn, H F -- Gabbay, K H -- Gallop, P M -- New York, N.Y. -- Science. 1978 Apr 7;200(4337):21-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/635569" target="_blank"〉PubMed〈/a〉
    Keywords: Blood Glucose/metabolism ; Chemical Phenomena ; Chemistry ; Diabetes Complications ; Diabetes Mellitus/*blood/diagnosis ; Diphosphoglyceric Acids/blood ; Glycosides/blood ; Glycosuria/etiology ; Hemoglobin A/*metabolism ; Hemoglobins/*analysis/*metabolism ; Humans ; Kinetics ; Oxygen/blood ; Structure-Activity Relationship
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  • 37
    Publication Date: 1979-06-08
    Description: It has been proposed that nitrilotriacetic acid be substituted for trisodium polyphosphates in detergents as a way to reduce the rate of eutrophication in the Great Lake Basin. The reaction of nitrilotriacetic acid with chlorine-containing solutions produces a hitherto unknown degradation production, N-formyliminodiacetic acid, in high yield. The toxicological and environmental implications of this reaction are unclear.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Spanggord, R J -- Tyson, C A -- New York, N.Y. -- Science. 1979 Jun 8;204(4397):1081-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/36659" target="_blank"〉PubMed〈/a〉
    Keywords: *Acetates ; Chemical Phenomena ; Chemistry ; *Chlorine ; Dicarboxylic Acids ; Environmental Pollutants ; Hydrogen-Ion Concentration ; *Imino Acids ; Mutagens ; *Nitrilotriacetic Acid
    Print ISSN: 0036-8075
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-03-16
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ferris, J P -- New York, N.Y. -- Science. 1979 Mar 16;203(4385):1135-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/218287" target="_blank"〉PubMed〈/a〉
    Keywords: Chemical Phenomena ; Chemistry ; *Hydrogen Cyanide ; *Peptides
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  • 39
    Publication Date: 1980-10-01
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bumb, R R -- Crummett, W B -- Cutie, S S -- Gledhill, J R -- Hummel, R H -- Kagel, R O -- Lamparski, L L -- Luoma, E V -- Miller, D L -- Nestrick, T J -- Shadoff, L A -- Stehl, R H -- Woods, J S -- New York, N.Y. -- Science. 1980 Oct;210(4468):385-90.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6159682" target="_blank"〉PubMed〈/a〉
    Keywords: Air Pollutants/analysis ; Chemical Phenomena ; Chemistry ; Chromatography, High Pressure Liquid ; *Dioxins/analysis ; *Fires ; Power Plants ; Smoke/analysis ; Soil Pollutants/analysis ; Tetrachlorodibenzodioxin/analysis ; Vehicle Emissions/analysis ; Water Pollutants, Chemical/analysis
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  • 40
    Publication Date: 1984-05-25
    Description: Polypeptide analogs of the known members of the corticotropin-releasing factor (CRF) family were synthesized and tested in vitro and in vivo for enhanced potency or competitive antagonism. Predictive methods and physicochemical measurements had suggested an internal secondary alpha-helical conformation spanning about 25 residues for at least three members of the CRF family. Maximization of alpha-helix-forming potential by amino acid substitutions from the native known sequences (rat/human and ovine CRF, sauvagine, and carp and sucker urotensin 1) led to the synthesis of an analog that was found to be more than twice as potent as either of the parent peptides in vitro. In contrast, certain amino-terminally shortened fragments, such as alpha-helical CRF or ovine CRF residues 8 to 41, 9 to 41, and 10 to 41, were found to be competitive inhibitors in vitro. Selected antagonists were examined and also found to be active in vivo.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rivier, J -- Rivier, C -- Vale, W -- AA03504/AA/NIAAA NIH HHS/ -- AM20917/AM/NIADDK NIH HHS/ -- AM26741/AM/NIADDK NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1984 May 25;224(4651):889-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6326264" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenocorticotropic Hormone/secretion ; Animals ; Binding, Competitive ; Chemical Phenomena ; Chemistry ; Corticotropin-Releasing Hormone/*antagonists & inhibitors ; Rats
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    Pure and applied geophysics 118 (1980), S. 128-151 
    ISSN: 1420-9136
    Keywords: Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
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    Journal of molecular evolution 15 (1980), S. 79-101 
    ISSN: 1432-1432
    Keywords: Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
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  • 43
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    Calcified tissue international 23 (1977), S. 13-17 
    ISSN: 1432-0827
    Keywords: Dental calculus ; Glycopeptide ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A method is described for the isolation and purification of a sulphated glycopeptide from human supragingival calculus. The compound was isolated after using EDTA treatment, 2 M CaCl2 extraction, proteolytic digestion, ethanol precipitation, and finally purified by DEAE cellulose chromatography. It migrated as a single component on cellulose acetate electrophoresis, and chemical and infrared spectral analysis showed the presence of covalently attached sulphate groups. The sulphated glycopeptide was distinguished from being a sulphated glycosaminoglycan.
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  • 44
    ISSN: 1432-0975
    Keywords: Key words Otolith ; Chemistry ; ICP-MS ; Stock discrimination ; Epinephelus striatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  We examined the utility of otolith minor and trace element chemistry, assayed with inductively coupled plasma mass spectrometry (ICP-MS), as a means of delineating population structure in the Nassau grouper (Epinephelus striatus). We characterized the elemental composition of otoliths collected in 1993 from three locations in Exuma Sound, Bahamas and from Glover Reef, Belize in 1995. A single location in Exuma Sound was sampled in 1994 to test temporal variability in otolith composition. Five elements (Ca, Zn, Sr, Ba and Pb) were routinely detected, at levels significantly above background, by solution-based ICP-MS. Results from analysis of variance of elemental data, expressed as a ratio to Ca, indicated that there were no significant differences among the Exuma locations for any element, but significant variability was found between Glover Reef and the pooled Exuma localities for Zn/Ca, Sr/Ca and Ba/Ca ratios. Significant inter-annual differences at one Exuma Sound location was restricted to Ba/Ca ratios. Discriminant function analysis correctly classified 86% and 95% of the Belize and pooled Exuma sites, respectively. Otoliths from Belize were characterized by low Zn/Ca and high Ba/Ca and Pb/Ca ratios compared to otoliths from fish collected in Exuma Sound. Although differences in Ba levels may be related to upwelling at Glover Reef, more data are needed to definitely link otolith composition with regional differences in water chemistry.
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  • 45
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    Calcified tissue international 23 (1977), S. 39-44 
    ISSN: 1432-0827
    Keywords: Dental cementum ; Collagen ; Protein ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Cyanogen bromide (CNBr) peptides were prepared of the insoluble collagen of bovine dental cementum. Following chromatographic separation, the peptides were identified by their amino-acid composition. Type I collagen ([α1(I)]2α2) accounted for more than 90% of the organic matrix, while Type III collagen ([α1(III)]3) was present at a level of approximately 5%. Amino-acid analyses revealed that the CNBr peptides from α1(I) and α2 chains of cementum closely resembled the corresponding peptides from calf skin. The only systematic difference was a higher level of hydroxylation of prolyl and lysyl residues of the cementum peptides.
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  • 46
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    Calcified tissue international 23 (1977), S. 87-94 
    ISSN: 1432-0827
    Keywords: Calcium ; Osteoporosis ; Lactation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The calcium homeostatic mechanism was challenged in adult female rats by feeding them a calcium-deficient diet containing oxalate, and by subjecting them to pregnancy and lactation. The regimen caused a substantial weight loss, especially in those animals which reared their young well. Severe hypocalcaemia was observed in the lactating rats. Serum-P was slightly elevated. The content of hydroxyproline in serum was considerably elevated, reflecting the degree of calcium deprivation. Serum proteins were least influenced. The calcium depriving regimen reduced the growth of long bones, but did not stop it. The ash content of the bones was considerably reduced, the degree of reduction depended on the degree of calcium deprivation. Ash as percentage of total bone organ was reduced, but not to the same extent as total ash. Analyses of different parts of femur showed that the proximal and distal parts had lost more bone mineral than the diaphyseal shaft. The ash content of cortical bone tissue from the femur was estimated by a volumetric method. No differences were observed between test groups and controls, indicating that no measurable amounts of bone mineral had been removed from the walls of the vascular canals or by osteocytic osteolysis. Planimetric determinations on cross sections from femora disclosed that a great amount of bone had been removed from the endosteal surface of the diaphysis, while the periosteal surface demonstrated reduced bone apposition.
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  • 47
    ISSN: 1432-0827
    Keywords: Bacterial amphophile ; Purification ; Chemistry ; Resorption ; Ca influx ; Cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The bone resorptive factor and amphipathic antigen (AcA) previously identified by us in preparations fromActinomyces viscosus have been partially purified, characterized chemically, and compared. They elute at the same location on chromatography with Ac 22. The fatty acid composition of AcA and the bone resorptive factor is the same. Some differences in carbohydrate composition are observed. TheActinomyces factor does not affect calcium influx or cyclic AMP in isolated bone cells. Therefore it is concluded that AcA stimulates resorption either by gaining entrance into bone cells or by way of a yet undetermined second messenger.
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  • 48
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    Astrophysics and space science 224 (1995), S. 81-84 
    ISSN: 1572-946X
    Keywords: Chemistry ; Depletions ; Shocks ; IRAS 05338-0624 ; NGC 1333 IRAS 4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High resolution interferometer and single-dish observations of young, deeply embedded stellar systems reveal a complex chemistry in the circumstellar environments of low to intermediate mass stars. Depletions of gas-phase molecules, grain mantle evaporation, and shock interactions actively drive chemical processes in different regions around young stars. We present results for two systems, IRAS 05338-0624 and NGC 1333 IRAS 4, to illustrate the behavior found and to examine the physical processes at work.
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    Astrophysics and space science 233 (1995), S. 125-137 
    ISSN: 1572-946X
    Keywords: Interstellar Medium ; Dark Clouds ; Chemistry ; Bistability ; C-shock Waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Shock waves perturb the chemical state of the interstellar gas. We consider the effects of C-shocks on the composition of molecular clouds, for a range of values of the pre-shock gas density and magnetic induction. The time required to re-establish equilibrium in the post-shock gas depends on the initial conditions and can become very large. The significance of the two known chemical phases of dark clouds and of bistability is considered in this context.
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    Astrophysics and space science 233 (1995), S. 161-164 
    ISSN: 1572-946X
    Keywords: Stars ; Chemistry ; Diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have assessed the role of diffusion in determining chemical abundances in molecular interface regions. Chemical models have been developed which include the appropriate diffusion terms and that are appropriate to a narrow diffusion region (∼0.01pc) that may exist at the interface between a dark core and a hot, shocked T-Tauri wind. We have assumed pressure balance throughout and have calculated the chemical abundances as functions of time and position through the interface. The results show that significant enhancements of detectable molecules/transitions are expected (e.g. CO J=6→5, OH and CH). Using a realistic value of the diffusion coefficient a diffusive region of dimension 0.01pc may be established within about 104 years. In general it seems likely that diffusion processes are highly significant on these and smaller lengthscales.
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    Boundary layer meteorology 85 (1997), S. 197-222 
    ISSN: 1573-1472
    Keywords: Turbulence ; Chemistry ; Closure ; Convective boundary layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We study the interactions of chemistry and turbulent mixing of tracersin the convective boundary layer with a second-order closure model,including higher order chemistry terms. In order to limit the number of predictive equations we prescribe the profiles for ¯w¯Θ, ¯w¯θ ¯θ and the lengthscale l. However, for model validation we treat temperature and humidity asinert tracers, and compare the results with profiles observed during theAir Mass Transformation Experiment, and with similarity expressions for thesurface layer. We find good agreement of the mean profiles, but the (co-)variances are slightly underpredicted. Furthermore, the model usesdiagnostic equations expressing third moments of concentration in terms ofsecond moments and their vertical derivatives. They are compared withlarge-eddy model results, showing good agreement and, therefore, thesimplifications are justified. The model is applied to the transport of two gases subject to one bimolecular reaction. The importance of concentration correlations on themean transformation rate is studied. For two gases diffusing in oppositedirections we find for moderate and fast chemistry a 50% and90% decreased transformation rate due to the negatively correlatedconcentrations. These values are similar to large-eddy results of Schumannand Sykes et al. For two bottom-up tracers we find that the covariance ofboth reactive species is either positive or negative, increasing or reducingthe effective transformation rate depending on the Damköhler number (the ratio of the turbulent and the chemistry timescale). A significantdirect influence of chemistry on the flux divergence is found in bothcases. According to the model the effective transport to mid-levels of theboundary layer is increased when two reactive tracers diffuse in oppositedirections, and decreased in the case of two bottom-up tracers.
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    Journal of science education and technology 5 (1996), S. 193-201 
    ISSN: 1573-1839
    Keywords: Chemistry ; chemistry education ; multiple intelligences ; imagery ; visual-spatial thinking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract Chemistry has evolved from a science dominated by mathematics into a science highly dependent on spatial-visual intelligence. Yet the chemical content of introductory courses remains taught essentially the same as 40–50 years ago. Chemistry, today, is recognized by chemists as the molecular science. Yet, school chemistry is alienated from that perception. Thanks to the computer, young people are more comfortable with visual imaging than their instructors were at the same age. Thus the time is rife to reinvigorate chemistry education by means of the visual-spatial approach, an approach wholly in conformance with the way modern chemistry is thought about and practiced.
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    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2147-2156 
    ISSN: 1434-1948
    Keywords: Tetrapodal pentadentate ligand ; Ligand periphery ; Polydentate amine complex ; Nickel ; Podand ; Schiff base ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tetrapodal pentaamine ligand 2,6-bis(1′,3′-diamino-2′-methylprop-2′-yl)pyridine (1), which contains four equivalent primary amino groups, can be derivatised partly or completely by Schiff base condensation with suitable carbonyl compounds. The new ligands thus obtained are mononucleating, as shown by the X-ray crystal structures of their respective nickel(II) complexes. Reaction of 1 with 1 equiv. of salicylaldehyde and subsequent reduction allows the selective modification of one of the four sidearms. The resulting ligand 2 is hexadentate and uninegative in its nickel(II) complex {[(2)Ni]PF6} (3) with both the secondary amine and the phenoxide functionalities coordinated to the metal centre. The unreduced Schiff base form of the ligand, 4, does not form a complex with nickel(II) as readily, and only a small quantity of the mixed salt {[(4)Ni][(1)Ni(H2O)](Br)2(PF6)} (5)has been obtained. While the overall coordination of 4 resembles that of 2, there is considerably more strain in the appended chelate ring, due to the presence of the C=N double bond. Modification of one arm in 1 can also be achieved by condensation with 1 equiv. of acetylacetone, to give the new ligand 6 which, likewise, is hexadentate in its NiII complex {[(6)Ni](PF6)2} (7). In this case, however, the N/O-functional sidearm is not deprotonated. Rather, it is coordinated as the keto-imine tautomer, making 7 a rare example of a metal complex containing this structural fragment. Two-fold functionalisation of 1 is observed upon reaction with acetone, regardless of whether the ketone is present in stoichiometric amounts or in excess, to give the pentadentate ligand 8with two diagonally juxtaposed isopropylidene-imine units. The complex isolated with this ligand {[(8)Ni](PF6)2} (9) contains pentacoordinate NiII, the sixth coordination site being blocked by the rigidly positioned isopropylidene groups. When reacted with 4 equiv. of trans-cinnamaldehyde, all the primary amino groups in 1 condense to give the four-fold Schiff base 10, which acts as a pentadentate podand towards nickel(II). In this complex, {[(10)Ni(OH2)]Br2} (11), an aqua ligand completes the coordination octahedron. All ligands are stable towards hydrolysis when coordinated to the metal, despite the presence of alkyl-imine groups in some cases.
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    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2157-2166 
    ISSN: 1434-1948
    Keywords: Septadentate N5S2-ligand ; Dinuclear complexes ; Nickel ; Reactivity ; Redox chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coordination chemistry of a series of dinickel complexes of the new septadentate amine-thiolate ligand N,N′-bis[2-thio-3-aminomethyl-5-tert-butylbenzyl]diethylenetriamine, H29, has been investigated in the context of ligand binding and oxidation state changes. The complexes [Ni2(9)(L)][ClO4]2 (10), [Ni2(9)(Cl)][Cl] (11), [Ni2(9)(L)][BPh4]2 (12), and [Ni2(9)(NCS)][OH·OH2] (13) have central N2Ni(μ-SR)2NiN′3L cores [L = labile solvent molecule (10, 12), Cl- (11), and NCS- (13)] composed of dithiolate bridged planar NiN2S2 and six-coordinate NiN′3S2L units. This is demonstrated for 11 and 13 by crystal structure determinations and for 10 and 12 by UV/Vis spectroscopy and room temperature magnetic susceptibility measurements. Complexes 10, 11, or 12 readily add other co-ligands at the NiN′3S2L fragment by substitution of the solvent molecule L (10, 12) or the chloride substituent (11). The overall structure of the parent complexes is not affected by the substitution reactions. An electrochemical study has shown that complex 10 undergoes two successive one-electron oxidations at +0.88 and +0.41 V vs SCE. The oxidized species are not thermally stable, but electronic absorption spectra and EPR spectra are indicative of the presence of NiIII species.
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    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2167-2172 
    ISSN: 1434-1948
    Keywords: Macrocyclic compounds ; Amine-Thiolate Donors ; Polynuclear Complexes ; Nickel ; Condensation reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel route to macrocyclic amine-thiophenolate ligands is described. The new, air-stable thiophenolate precursor 1,2-bis(4-tert-butyl-2,6-diformyl-phenylsulfanyl)ethane (4) is readily condensed with two equivalents of 1,2-ethanediamine or 1,3-propanediamine under medium to high dilution conditions to give 2 × 4 condensation products. The smaller 1 × 2 macrocyclic compounds are not produced under these conditions. Subsequent reduction with NaBH4 (reduction of imine groups) and Na/NH3 (reductive cleavage of aryl-alkylsulfides) provides the 36- and 40-membered amine-thiophenolate ligands H46a and H46b. The macrocyclic compounds are versatile ligands for the preparation of polynuclear transition metal complexes. With divalent nickel H46a forms the di- and tetranuclear complexes [Ni2(6a)] (7) and [Ni4(6a)][ClO4]4 (8). Reaction of 8 with four equivalents of NH4SCN yields the novel isothiocyanate complex [Ni4II(6a)(NCS)4]·10MeCN (9). The structure consists of well-separated molecules of the tetranuclear complex [NiII4(6a)(NCS)4] (Ci symmetry). Two symmetry-related binuclear [N2Ni(μ2-SR)2NiN4] fragments composed of thiolate-bridged distorted planar {N2S2Ni}- and distorted cis-octahedral {(SCN)2N2S2Ni} units reside within the cavity of the macrocycle. The intramolecular distance between the two binuclear units is 6.144(1) Å.
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    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2173-2185 
    ISSN: 1434-1948
    Keywords: EPR spectroscopy ; Metallocenylboranes ; Organovanadium radicals ; Redox chemistry (CV) ; X-ray diffraction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The paramagnetic complexes di(mesityl)([5]trovacenyl)borane (5·), (mesityl)di([5]trovacenyl)borane (6··), and tri([5]trovacenyl)borane (7···) were prepared from [5]trovacenyllithium, (η5-C7H7)V(η5-C5H4Li), and (Mes)2BF, (Mes)BF2, and BF3, respectively. The propeller-shaped species 5·, 6··, and 7··· were subjected to X-ray diffraction with the aim of possibly correlating the twist angles with intramolecular intermetallic communication. Cyclic voltammetry points to successive vanadium-centered oxidation processes and boron-centered reduction, a small redox splitting δE1/2[(2+/+), (+/0)] being observed for 6··. According to EPR spectroscopy, performed in fluid solution, the exchange interaction J in the diradical 6·· approaches the fast-exchange region and is attenuated significantly by quaternization at boron in [6··-nBu]-. Although EPR spectroscopy of the triradical 7··· also indicates an extensive exchange interaction, the exchange parameters, derived from spectral simulation, follow the gradation J(7···) ≈ 1/3 J(6··). The magnetic susceptibility of 6·· and 7··· follows the same trend. As expected, compound 7··· exhibits spin frustration because it contains three antiferromagnetically coupled S = 1/2 systems that are arranged in an equilateral triangle.
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    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2187-2199 
    ISSN: 1434-1948
    Keywords: Ansa compounds ; Cp-derived chelate ligands ; Neopentane chemistry ; Spiro compounds ; Tripodal ligands ; Cyclopentadienyl compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The neopentane-derived functionalized oxetane O(CH2)2C(CH3)(CH2OMs), 1, reacts with indenyllithium (LiInd) or fluorenyllithium (LiFlu) to produce the derivatives O(CH2)2C(CH3)(CH2R) (R = indenyl, fluorenyl), 2. The oxetane ring of 2 undergoes nucleophilic ring-opening by reaction with LiPR′2 to give the chiral chelate ligands (HOCH2)(CH3)C(CH2R)(CH2PR′2) (R = indenyl, fluorenyl), 5. Nucleophilic ring-opening by LiInd or LiFlu is possible too, resulting in the functionalized ansa-Cp ligands (HOCH2)(CH3)C(CH2R)(CH2R′) (R, R′ = indenyl, fluorenyl), 12. Electrophilic ring-opening of 2 with HBr to give (HOCH2)(CH3)C(CH2R)(CH2Br) (R = indenyl, fluorenyl), 3, is also possible. The alcohol function of 3 may be activated directly, whereas activation of this group in 5 is only possible after BH3 protection of the phosphane function. The mesylates (MsOCH2)(CH3)C(CH2R)(CH2Br) (R = indenyl, fluorenyl), 4, undergo, under basic conditions, spiro cyclization to produce spirocyclobutane derivatives 9 with the α-carbons of the five-membered cycles acting as the spiro centres. Substitution of the mesylate group of 4 by PR2 nucleophiles is therefore not possible. Ansa-Cp derivative (MsOCH2)(CH3)C(CH2Ind)(CH2Flu), 12c also reacts with LiPPh2 with spiro cyclization to produce 9d, instead of giving the substitution product. Tripodal ligands (CH3)C(CH2R)(CHPPh2)2 (R = indenyl, fluorenyl), 11, are accessible by the reaction of (MsOCH2)(CH3)C(CH2PPh2)2 with LiInd or LiFlu. All compounds are fully characterized by the usual spectroscopic and analytical techniques including single-crystal X-ray analyses in several cases.
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  • 58
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    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2201-2207 
    ISSN: 1434-1948
    Keywords: Carboxylate syn-anti ; N-centered tripodal ligand ; Manganese ; Imidazole ; Helicoïdal inorganic chiral chain ; Magnetism ; π-π interaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of an infinite inorganic chain consisting of MnII and an N-centered tripodal ligand N,N-(2-pyridylmethyl)[(1-methylimidazol-2-yl)-methyl]glycinate is presented. It exhibits a chiral helical structure with a pitch of two monomeric units (each monomeric unit containing one Mn atom). Each manganese is connected to its neighbor through a carboxylate bridge in a syn-anti geometry. Around each manganese center, two carboxylates bind in a cis geometry. This peculiar bridging geometry (syn-anticis) provides a broken-line chain, running in a zig-zag manner along the b axis of the P21 space group. The magnetic properties have been investigated. They show a pseudo-2D magnetic structure, with one major pathway along the chain and an inter-chain minor one. The intrachain coupling is a weak antiferromagnetic interaction (J/k = -0.25). This low value is entirely consistent with the geometry of the bridge. The interchain coupling is a weaker antiferromagnetic coupling (J′/k = -0.11) and could be mediated through π-π interactions between pyridine and imidazole from two adjacent helixes.
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  • 59
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    AIChE Journal 3 (1957), S. 213-222 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Data were obtained in flat-plate continuous-flow thermogravitational columns to check the theory developed by Furry, Jones, and Onsaer and a modification of this theory proposed by the authors. Separations of ethyl alcohol-water and benzene-n-heptane mixtures were measured, flow rate, column length, temperature difference, spacing between plates, and inclination of the plates being varied in the experiments. Theory and data are in qualitative agreement for the range of variables studied. Quantitative agreement exists between theory and experiment in the region of practical design for liquid-thermal-diffusion plants.Equations to aid in the design of thermal-diffusion plants are developed, and a plant to treat 1,000 bbl./day of a liquid aromatic-aliphatic mixture is designed and costs are estimated.
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  • 60
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    AIChE Journal 3 (1957), S. 198-207 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A solution to the Stefan-Maxwell diffusion equations for equimolal countercurrent diffusion in a three-component gas mixture is obtained which is similar in form to Gilliland's equation for diffusion of two gases through a third inert gas. The important features of both types of diffusion are investigated and the conditions under which the following phenomena occur are determined: (1) diffusion barrier (the rate of diffusion of a component is zero even though its concentration gradient is not zero); (2) osmotic diffusion (the rate of diffusion of a component is not zero even though its concentration gradient is zero); (3) reverse diffusion (a component diffuses against the gradient of its concentration).A generalized driving force which describes these phenomena is introduced, and approximate equations are developed which give the individual rates of diffusion directly.
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    AIChE Journal 3 (1957), S. 208-212 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effective correlations of turbulent velocities and friction losses for tubes and parallel plates recently published have been analyzed further in order to simplify their use and to extend the range of Reynolds number.Working diagrams have been developed from which turbulent friction losses and local velocities for tubes and parallel plates can be calculated without interpolation or trial-and-error procedures. Tentative values of parallel-plate friction factors and average-to-maximum velocity ratios in the transition region are also included, and new experimental values of the velocity ratio in smooth tubes are reported. The working diagrams permit more rapid, accurate, and consistent calculations of fluid behavior to be made over a wider range of operating conditions than was previously possible.
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    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2221-2231 
    ISSN: 1434-1948
    Keywords: Calixarenes ; Inclusion compounds ; Imido Complexes ; Molybdenum ; Tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses, spectroscopic properties, molecular structures, and bonding of novel calix[4]arene imido compounds are described. Treatment of M(NtBu)2(NHtBu)2Ia (M = Mo), Ib (M = W) or M(NMes)2Cl2(dme) IIa (M = Mo), IIb (M = W) (Mes = 2,4,6-Me3-C6H2) with p-tBu-calix[4]arene LH4 affords calix[4]arene metal complexes LM(NR) 1a, b (M = Mo, W; R = tBu) and 2a, b (M = Mo, W; R = Mes). Analytical and spectroscopic data are consistent with monomeric structures for 1 and 2, retaining a local C4v symmetry for the calix[4]arene metal fragment. These complexes are well-suited to bind small molecules like acetonitrile, tBu-isonitrile, or water within their macrocyclic pockets. The spectroscopic data of some inclusion compounds and the crystal structures of LMo(NtBu)(NCMe) 1a(NCMe), LW(NtBu)(OH2) 1b(OH2), LW(NtBu)(CNtBu) 1b(CNt Bu), LMo(NMes)(NCMe) 2a(NCMe), and LW(NMes)(NCMe) 2b(NCMe) are reported. All complexes contain a group VI metal imido [M=NR] moiety mounted on the phenoxide rim of the calix[4]arene ligand as well as an incorporated guest molecule within the cavity. Some insights into the structures of complexes of the type L′W(NR′) (L′ = p-H-calix[4]arene; R′ = H, Me) and into bonding in these compounds are provided by density functional theory, applying the B-P86 density functional and an all SVP basis set within the RI-J-DFT approximation. At least one π bond is of importance for calix[4]arene-metal bonding in these compounds. The metal-imido bond can be described as a triple bond. A geometrically optimized minimum structure of L′W(NMe) 4 shows a calix[4]arene ligand only slightly distorted from a local C4v symmetry and an almost linear tungsten-imido moiety.
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    AIChE Journal 3 (1957), S. 230-235 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Reaction kinetics for the catalytic dehydrogenation of sec-butyl alcohol to methyl ethyl ketone has been investigated at atmospheric pressure and temperatures ranging from 650° to 750°F. in the presence of solid brass spheres, 1/8 in. in diameter. The nature of this catalyst permitted a direct evaluation of the surface involved in this reaction and allowed the definition of a surface-feed ratio to be expressed as S/F in place of the conventional weightfeed ratio W/F commonly used in catalytic studies. Feed compositions ranged from secbutyl alcohol to mixtures containing high percentages of methyl ethyl ketone and hydrogen.In these studies mass transfer effects were found to be significant and, for a proper representation of conditiated at the catalyst surface, must be taken into account. The effect of feed compositions on the initial rates of reaction showed that the rate-controlling step was the desorption of hydrogen involving a single-site mechanism.In addition, the results of these studies have been used to produce values of height of reactor unit HRU which have been found to correlate with mass velocity and temperature. The HRU provides a simple means of calculating the depth of catalyst necessary to effect a designated conversion.
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    AIChE Journal 3 (1957), S. 242-248 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Heat transfer and friction measurements were made for air flow through a smooth copper pipe and six other commercial pipes, with a ratio of diameter to equivalent sand roughness varying from 640 to 64. The Reynolds number range was 10,000 to 80,000. Though some increase in heat transfer coefficients with roughness was found, the heat transmission per unit power loss always decreased.The momentum-heat-transfer anlogies of Reynolds and Colburn are shown to be inadequate for handling the experimental data. Those of Prandtl and Taylor, von Kármán, and Pinkel fail to show a required Reynolds number dependence of jh when friction factor has become independent of Reynolds number for a rough pipe. Martinelli's equation shows such dependence and, even in approximate form, gives good prediction of the experimental results.
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    AIChE Journal 3 (1957), S. 248-256 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 66
    ISSN: 1434-1948
    Keywords: Arsonium salts ; Superacidic systems ; Structure elicidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of trimethylarsane in the superacidic systems hydrogen/fluoride antimony pentafluoride and hydrogen fluoride/arsenic pentafluoride leads to trimethylarsonium fluorometallates. These salts are stable up to 60 °C and 5 °C, respectively. Structures were successfully elucidated in the cases of trimethylarsonium undecafluorodiarsenate and trimethylarsonium hexafluoroantimonate. (CH3)3AsH+As2F11- crystallizes in the monoclinic space group P21/n with four formula units per unit cell with the dimensions a = 7.362(1), b = 12.589(1), c = 13.598(1) Å and β = 95.37(1)°. (CH3)3AsH+SbF6- crystallizes in the monoclinic space group P21/m with four formula units per unit cell with the dimensions a = 8.313(1), b = 8.855(1), c = 13.285(1) Å and β = 94.358(1)°.
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  • 67
    ISSN: 1434-1948
    Keywords: Molybdenum ; μ-Oxo ; Conformational equilibrium ; X-ray diffraction ; NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new thiocyanatomolybdenum(VI) dioxo-μ-oxo complex dimer bearing a 4,4′-di-tert-butyl-2,2′-bipyridine ligand (2) is shown to exist in the crystal cell unit as a meso (Mo-O-Mo angle of 180°) and d,l, pair (Mo-O-Mo angle of 155.7°). These conformers are in equilibrium in solution and have been observed clearly by 1H NMR spectroscopy.
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  • 68
    ISSN: 1434-1948
    Keywords: Macrocycles ; Lithium ; Fluorescence ; Cryptands ; Coordination ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three aza-cages with the anthracene-containing photoactive groups L1, L2, and L3 have been synthesized. All compounds are able to selectively encapsulate a lithium ion and solid complexes have been isolated. The formation equilibria have been investigated by UV/Vis and 1H, 13C and 7Li NMR spectroscopic techniques. The fluorescence emission of both free ligands and lithium complexes have been investigated. Results indicate that the CHEF (chelation enhancement of the fluorescence) effect obtained by lithium coordination exits although lower than that occurring upon full protonation.
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  • 69
    ISSN: 1434-1948
    Keywords: Copper ; Trinuclear complexes ; Formamidines ; Magnetism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three new copper(II) linear trinuclear compounds are reported, all of which were synthesized in-situ, with the general formula [Cu3(L)4](CF3SO3)2(Y)x, where L is the dehydronated ligand: N,N′-bis(pyridine-2-yl)formamidine (abbreviated as Hpdf), N,N′-bis(pyrimidine-2-yl)formamidine (abbreviated as Hpmf) and N,N′-bis(5-methylpyridine-2-yl)formamidine (abbreviated as Hmpdf), Y = EtOH or H2O and x = 0.5-1.5. The compounds were characterized by X-ray diffraction, IR, LF, and EPR spectroscopy and by magnetic susceptibility down to 4 K. The structure of the compound [Cu3(pmf)4](CF3SO3)2(H2O)1/2 was determined by X-ray crystallography; it was found to crystallise in the triclinic space group P-1 with a = 8.529(5), b = 15.760(5), c = 19.639(5) Å, α = 101.793(5), β = 101.263(5), γ = 102.389(5)°, Z = 2. The structure [Cu-Cu-Cu angle 174.96(11)°] consists of four nearly flat molecules of the ligand, which contribute to the propeller-type structure around the Cu-Cu-Cu axis. A strong antiferromagnetic interaction between the CuII ions is observed with calculated J values, based on the Hamiltonian H = -2J(S1·S2 + S2·S3) - 2J′·S1·S3, of -174(1) cm-1, -120(1) cm-1, and -167(1) cm-1 for the compounds studied with L = pdf, pmf, and mpdf, respectively. These values are in agreement with an S = 1/2 ground state below temperatures of 120-160 K.
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    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2277-2281 
    ISSN: 1434-1948
    Keywords: Boron ; Iron ; Nickel ; Carbyne complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The μ3-boryloxycarbyne complexes [{Fe(CO)3}3{μ3-COBCl{NtBu(SiMe3)}}2] (1) and [{(η5-C5H5)Ni}3{μ3-COBX(NR2)}μ3-CO] (2a: NR2 = NtBu(SiMe3), × = Cl; 2b: NR2 = N(SiMe3)2, × = Cl; 2c: NR2 = NMe2, × = BNMe2Cl) were obtained by reaction of the anionic complexes K2[{Fe(CO)3}3{μ3-CO}2] and K[{(η5-C5H5)Ni(CO)] with the corresponding chloroboranes Cl2BNR2 {NR2 = NtBu(SiMe3), N(SiMe3)2}, or 1,2-dichlorodiboranes(4) B2(NMe2)2Cl2, respectively. The products are formed by a nucleophilic attack of the CO oxygen atom at the boron centres with subsequent salt elimination. All compounds were characterized by IR and multinuclear NMR spectroscopy, and the structures of 1 and 2c in the solid state were determined by single-crystal X-ray diffraction studies.
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    AIChE Journal 3 (1957), S. 325-329 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The surface tensions against air of acetone-water solutions have been measured over the entire composition range from 20°C. to generally within 1° to 10°C. of the normal boiling points. The capillary-height method was employed and the results are thought to be accurate to better than ±0.5%.
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    AIChE Journal 3 (1957), S. 329-330 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: With stationary isotropic turbulence postulated, the rate of decrease in concentration fluctuations of a scalar contaminant is estimated in terms of the turbulence scale and the power input to the system.
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    AIChE Journal 3 (1957), S. 331-335 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Extension of the kinetics of the catalytic oxidation of nitric oxide on activated carbon and silica gel confirms the rate-controlling step postulated by previous workers. The effect of variables including water vapor on the reaction rate is expressed by an equation containing the constants a, b, c, and w, which have been evaluated for both catalysts at 30°, 45°, and 60°C. The effect of water vapor is to reduce the reaction by reversible adsorption on the active sites of the catalyst. The value of w is dependent on temperature but independent of water-vapor concentration up to a relative humidity of 20%. Above 20% the value of w for activated carbon increases greatly with relative humidity, in agreement with the effect of capillary adsorption at high water contents.
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    AIChE Journal 3 (1957), S. 343-347 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Constant layer moisture at the hot surface is found to exist during the constant-rate period of drying of sand on a hot surface in still air. It accounts not only for the constantrate period of drying itself but also largely for the length of the period.Temperature of the air-surface interface usually has minor effects on the rate of vaporization because equilibrium between vapor and the bed is not established during periods of rapid vaporization.Numerical relationships have not been established.
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    AIChE Journal 3 (1957), S. 336-342 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plate efficiencies measured on 18-in.-diam. sieve plates are reported for the acetic acid-water system and for the methyl isobutyl ketone-water system at atmospheric pressure. In the former system the major resistance to mass transfer is in the gas phase; liquid-phase resistance to mass transfer is controlling in the latter. Efficiencies are also reported for the aniline-nitrobenzene system (gas-phase resistance controlling) at 5 mm. Hg absolute on 6-in.-diam. sieve plates. Pure gas- and liquid-phase efficiencies for both plate designs were determined by the adiabatic humidification of air and the desorption of oxygen from water into air. Predicted values of plate efficiency for each of the binary systems studied were computed from the pure phase efficiencies according to the procedure outlined by Gerster et al. A comparison between measured and predicted efficiencies is presented as a guide for future research in this field.
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    AIChE Journal 3 (1957), S. 353-360 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Linear partial-differential eqations are often encountered when thermal or material diffusion in flowing systems is considered. Analytic solutions of such equations are known for only the simplest situations. In two examples a graphical method of solution is presented and demonstrated which makes feasible, without excessive labor or special computing facilities, the use of available knowledge concerning turbulent flow in the prediction of thermal or material transfers in complex situations involving linear steady flow.
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    AIChE Journal 3 (1957), S. 348-352 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The behavior of the film coefficient of heat transfer for the condensation of organic vapor mixtures was investigated experimentally to establish a satisfactory basis for applying the Nusselt equation to binary systems. Five ideal and nonideal pairs, all of which gave miscible condensates, were studied; the work was carried out under conditions of almost total condensation on a horizontal condensing surface designed to comply as rigidly as possible with the conditions for which Nusselt's equation is valid.The same behavior was observed for all systems and all concentrations studied: the experimental coefficients fell between those for the pure components and followed the behavior pattern for pure components when the temperature difference was taken as that between the bubble point of the condensate and the surface temperature, rather than between the dew point or the measured vapor temperature and the surface temperature, Correlation of the film coefficient showed it to vary approximately linearly with composition if the coefficients were compared at a constant value of the temperature difference, defined as above. This permits determination of the coefficient for a mixture by interpolation between the coefficients for the pure components, which are easily obtained, in preference to making the calculations with the properties of the mixture obtained by laborious and uncertain weighting of the corresponding properties of the pure components.When results are interpreted in the light of the theories of Colburn and Drew, the presence of a vapor-phase resistance to heat and mass transfer, as postulated by them, is indicated.
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    AIChE Journal 3 (1957), S. 361-365 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two-phase critical flow of steam-water mixtures has been investigated over a pressure range from 4 to 43 1b./sq.in. abs. and a quality range from saturated vapor to 1% (weight) vapor. Discharges were measured from 1/4-,1/2-, 3/4-, and 1-in. pipes and from annuli of intermediate cross-sectional areas. The experimental mass flow rates are always grteater than the values calculated on the basis of a homogeneous flow model. Several empirical methods for correlating the data were determined, and comparisons are presented of the predictions of several analytical flow models.
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    AIChE Journal 3 (1957), S. 366-372 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetic studies were made in a differential flow reactor of the hydogenation of α-methyl-styrene with the liquid trickling over a bed of catalyst pellets countercurrent to a stream of hydrogen. The catalysts consisted of palladium, platinum, rhodium, ruthenium, and nickel supported on the external surfaces of aluminal pellets.With palladium at pressures above 3 atm. the apparent rate-controlling step was a surface reaction between dissociated hydrogen and α-methylstyrene both adsorbed on different type of active sites. Below 3 atm. pressure the reactants competed for similar active sites. With platinum the apparent rate-controlling step was a surface reaction between dissociated hydrogen and α-methylstyrene on similar active sites. Rhodium and nickel catalyzed the polymerization α-methylstyrene together with slow hydrogenation. Ruthenium had negligible activity for catalyzing the hydrogenation under the moderate conditions used in this work.In all cases mass transfer resistances were negligible.
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    AIChE Journal 3 (1957), S. 373-381 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Applying both their own assumptions and the mechanism of lateral mixing proposed by Ranz (20), the authors obtained theoretical formulas for effective thermal conductivities ke in packed beds. Previously reported experimental data were analyzed with these equations, and the usable data for predicition of ke were shown.In order to see the influence of both packing characteristics and temperature on the effective thermal conductivities, experimental data were obtained with air for beds with various kinds of packing, i.e., iron spheres, porcelain packings, cement clinker, insulating fire brick, and Raschig rings. Correlation of these data with Equation (15) showed that this equation adequately expressed the heat transfer mechanisms in packed beds with motionless gases, especially at hight temperatures.
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    AIChE Journal 3 (1957), S. 381-385 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Heat and mass transfer and coagulation are considered as related to the mean-square relative velocity between particle and fluid uR2 and eddy diffusion as described by the mean-square particle displacement, Xp2. The mathematical methods used are similar to those employed in the early calculations of the Brownian motion.The mean-square relative velocity is obtained as a function of particle characteristics, intensity of turbulence, and a fluid correlation coefficient. In the limiting case of equal particle and fluid density uR2 = 0, and for very heavy particles uR2 → uF2.A general expression for the eddy diffusivity is obtained is obtained which reduces to the same form as that of the fluid for the stationary state. However, the correlation coefficient to be used in the calculations depends on uR2. As a first approximation, it can be assumed that at a sufficiently long time from the introduction of the particles, fluid and particle diffusivities are equal.For short times after injection, the particle spread may be much less than that of the fluid. An illustrative calculation for the initial spreading of a jet of suspended particles is offered. In all cases an effort is made to organize the available experimental data within the framework of the theory.
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  • 82
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    AIChE Journal 3 (1957), S. 386-390 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The bulk chemical properties of an impregnated chromia-alumina catalyst with respect to several gases, CO, CO2, C3H6, were determined as a function of the degree of oxidation of the surface of the catalyst. The importance of the results lies in the demonstration that a simple method described herein can be used to obtain significant data on catalytic surfaces. Briefly, the prior adsorption of oxygen by the catalyst tended to promote the adsorption of carbon monoxide and to prohibit the adsorption of carbon dioxide. Far more carbon monoxide was adsorbed by the highly oxidized surface than could be accounted for on the basis of adsorbed carbon dioxide. The quantity of propylene adsorbed also increased with an increase in the oxidation of the surface. The results are explained on the basis of two types of adsorbed oxygen atoms.
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  • 83
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    AIChE Journal 3 (1957), S. 391-394 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A rigorous method is presented for the evaluation of the heat requirements in binary batch fractionations which involve negligible column hold up. The method, in which the additional variables of the discontinuous process are taken into account, is a modification of the methods of Ponchon and Savarit for continuous operation. Two examples, one for a fractionation in which the composition of the product is constant and the other in which the reflux ratio is constant, are given as illustrations of the method.The application of the method permits more accurate evaluation of reboiler and condenser heat loads and, in turn, better design.
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  • 84
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    AIChE Journal 3 (1957), S. 395-404 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 85
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    AIChE Journal 3 (1957), S. 411-417 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the hydrogenation of α-methylstyrene by means of a suspended palladium-alumina catalyst in a stirred reactor the mass transfer of hydrogen through the liquid is the rate-controlling step and the resistance to chemical reaction at the catalyst surface is negligible except at extremely rapid rates of stirring. This system therefore provides an excellent means of establishing the effects of operating variables and mechanical construction on mass transfer coefficients in liquids in stirred reactors. It is convenient to consider the total resistance to mass transfer as consisting of two separate resistaces: in the liquid adjoining the bubbles and in the liquid adjoining the suspended solid particles; thus R = Rb + Rs.A general equation was evaluated from experimental data based upon unit volume of liquid.
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  • 86
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    AIChE Journal 3 (1957), S. 405-410 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Local convective thermal transfer is difficult to predict for nonuniform three-dimensional boundary flows. Direct measurements of local transfer from objects of practical interest are therefore useful in the prediction of thermal transfer and in an understanding of multidimensional boundary flows.Measurements of the gross and local transfer were made upon a silver sphere 0.5 in. in diameter and a ceramic porous sphere of the same size from which n-heptane was permitted to evaporate. The air stream had a level of turbulence of approximately 5.4% and only small variation in velocity with position. Temperature distributions in the boundary flows around these spheres were determined, and from these distributions local transfer coefficients were established for the forward hemisphere. The gross transfers were established from the electrical energy added to the silver sphere and from the quantity of n-heptane evaporated from the porous sphere.The local thermal transfers were in reasonable agreement with some of the theoretical analyses based upon a three-dimensional laminar-boundary layer. Satisfactory agreement was obtained between spatial integration of the local transfer and the simultaneously measured over-all values. These, in turn, were in fair agreement with correlated values of the gross thermal and material transfer from spheres.
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  • 87
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    AIChE Journal 3 (1957), S. 418-427 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of the physical properties and volume flow rate of liquids on the surface area of sprays produced by a pressure type of atomizing nozzle were determined experimentally. the specific surface area of the sprays is correlated by an equation of two dimensionless groups in terms of the variables surface tension to the -1.0 power, kinematic viscosity to the -0.4 power, and volume flow rate to the 2.4 power. The volume flow rate is correlated by an equation of two dimensionless groups containing the variables viscosity to the 0.17 power, density to the -0.58 power, and spray pressure to the 0.42 power. The conversion of compression energy to surface-area energy appears to be constant at approximately 0.1%.
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  • 88
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    AIChE Journal 3 (1957), S. 12S 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 89
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    AIChE Journal 3 (1957), S. 9S 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 90
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    AIChE Journal 3 (1957), S. 428 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Following an approach similar to that presented for the aliphatic (6, 7) and naphthenic (8) hydrocarbons, methyl-group contributions have been developed that now make possible the calculation of van der Waals' constants for aromatic hydrocarbons of considerable size and complexity. These constants are then utilized to calculate the critical temperatures, pressures, and volumes for these aromatic hydrocarbons.In addition, simple relationships have been developed that permit the evaluation of both van der Waals' constants for the unsubstituted linearly fused aromatic hydrocarbons.Comparisons of calculated critical constants with values presented in the literature for over twenty aromatic hydrocarbons produced average absolute deviations of 0.70% for the critical temperature and 2.14% for the critical pressure.
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  • 91
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    AIChE Journal 3 (1957), S. 7S 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 92
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    AIChE Journal 3 (1957) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 93
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    AIChE Journal 3 (1957), S. 431-431 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 94
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    AIChE Journal 1 (1955), S. 95-99 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general method has been devised for calculating gaseous-diffusion-stage requirements to separate gases of widely differing molecular weights. For such a mixture the actual separation factor is shown to be less than the ideal separation factor, depending on the undiffused-gas composition and the ratio of absolute pressures on each side of the barrier. The equilibrium relationship between the compositions of the diffused- and undiffused-gas streams leaving any stage is also derived by means of the Rayleigh concept. Application of the method is illustrated with a diagram, like that of McCabe and Thiele for distillation, on which are stepped off the required number of theoretical stages to separate a particular hydrogen-nitrogen mixture.
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    AIChE Journal 1 (1955), S. 111-117 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Analytical expressions are obtained for the calculation of the time required for batch rectification of binary feeds which may be treated by assuming constant relative volatility and no column holdup. The equations cover constant reflux operations and varying reflux constant product operations for the two cases involving either a large or a small number of theoretical stages. The latter type of calculation has hitherto been possible only by tedious graphical methods. This paper introduces novel pseudoequilibrium curves which lead to simple equations of considerable accuracy. The equations obtained may be rearranged or modified so that other factors such as sharpness of fractionation may be represented analytically.
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  • 96
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    AIChE Journal 1 (1955), S. 129-129 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 97
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    AIChE Journal 1 (1955), S. 157-164 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Although coarse, uniformly sized particles are not amenable to fluidization, it has been found possible by use of either gases or liquids to impart a regular cycling motion to a bed of this type of material in which the solids are rapidly carried upward by the fluid in a central well-defined core within the bed. The particles move uniformly downward in the annular space surrounding the core, thus providing dense-phase countercurrent contact between the fluid and the solids. There is no wall separating the core from the annulus. This method is called the spouted-bed technique. The effect of column diameter, fluid inlet diameter, bed depth, and physical properties of solids and fluids on spouting behavior has been investigated. The minimum fluid velocity required for spouting has been correlated, and the flow pattern of the fluid and of the solids has been stuided. The technique has been applied to the drying of wheat.
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  • 98
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    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Through the use of group contributions the van der Waals' constants, a and b, were estimated for a number of saturated aliphatic hydrocarbons from a knowledge of the chemical structure of these compounds and were used to define the critical temperature and pressure of these substances.By the use of methane as the base group, both van der Waals' constants were estimated for a number of saturated aliphatic hydrocarbons of considerable size and complexity through the additive contribution of methyl groups in the seccessive substitution of hydrogen until the desired structure of the substance was obtained. For the normal saturated hydrocarbons these contributions were found to be additive for the evaluation of a0.626 and b0.76 up through n-octane, and these exponents have been assumed to apply in the scaling up of larger normal and isomeric hydrocarbon molecules for which experimental data are lacking.The volume van der Waals' constant b alone serves to define the critical volume of these compounds through the expression γc = 3 β b, where β represents a factor which has been found to depend on the size and arrangement of the molecule.By following this procedure the critical temperatures, pressures and volumes of the normal saturated hydrocarbons through eicosane (C20H42), inclusive, and all the isomeric hydrocarbons up to and through the nonanes were calculated and compared, whenever possible, with values already available in the literature with an agreement of 0.43% for the estimation of the critical temperature, 0.69% for the critical pressure, and 0.86% for the critical volume. A combined consideration of these average deviations points to the estimation of the critical constants of the aliphatic saturated hydrocarbons with an average error of 0.7%.
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  • 99
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    AIChE Journal 1 (1955), S. 178-184 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On the basis of fluid dynamic and heat transfer studies on falling-film towers by various investigators, it has been commonly accepted by most workers that the liquid flow is essentially streamline in nature for liquid-film Reynolds numbers under 1,800 to 2,000; conseuquently it would be expected that the rate of physical gas absorption in such liquid films could be predicted directly from a knowledge of molecular diffusion rates.Measurements of the absorption of pure gases in falling liquid films at low Reynolds numbers substantiated the findings of other investigators that the mass transfer rates were manyfold greater than could have been predicted if molecular diffusion were the only transfer process. Increased interfacial area due to rippling of the liquid films could not account for the large increase in mass transfer rates found, and experiments with the addition of a dye stream to the liquid at the freer interface indicated turbulence.Dissolution rates of slightly soluble solids coated on the tube wall to liquid films were measured and showed that the liquid film was not in laminar flow even for Reynolds numbers as low as 300.An explanation is proposed which resolves these apparently conflicting results between momentum and heat and mass transfer, based on the fact that mass transfer measurements provide a more sensitive test for the presence of turbulence than do momentum or heat transfer measurements.
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    AIChE Journal 1 (1955), S. 200-209 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 20 Ill.
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