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  • 1
    ISSN: 1432-1939
    Keywords: Abscisic acid ; Chaparral ; Ceanothus thyrsiflorus ; Conductance ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Small shrubs ofCeanothus thyrsiflorus were grown in 19-1 pots irrigated under natural conditions in a chaparral region of Southern California and then subjected to soil drying. Characteristics of leaf gas exchange, leaf water potential, and concentrations of the stress hormone abscisic acid in the xylem sap, ABAxyl, were determined at various stages of drought. Diurnal changes in conductance were strongly correlated with leaf net photosynthesis rate, which provides an effective, integrative predictor of above-ground climate effects on conductance. In drought conditions, ABAxyl concentration increased. Increases in the concentration range of 50–500 nmol/l appeared to induce stomatal closure, restricting water loss and carbon dioxide uptake. When the momentary water potential is related to ABAxyl, ABA appeared to increase significantly only after a threshold of approximately −1.5 MPa was exceeded. At less negative water potentials, large variation in ABAxyl in the 50–1000 nmol/l range occurred for all water-potential values, because ABAxyl remains relatively constant over diurnal courses as water potentials decrease and then recover. When the water potential became more negative than −1.5 MPa, ABAxyl concentrations occurred between approximately 500 and 10 000 nmol/l and even greater in isolated cases. An approximately linear relationship is recognizable between ABAxyl and momentary water potential in this range because in plants under drought conditions, ABAxyl increases during the course of the day as water potential decreases. Increases in ABAxyl in the high concentration range were associated with relatively minor additional restrictions in gas exchange, but they might contribute to improved water use efficiency and explain diurnal changes in the potential for stomatal opening that have been observed in Mediterranean sclerophyllous species. When we examined long-term seasonal change in the response of irrigated plants, changes in average daily temperature greater than 10°C occurred (also associated with shifts in relative humidity and radiation input), which apparently led to small changes in predawn water potential in the −0.1 to −0.7 MPa range. Increases in ABAxyl occurred that were in turn negatively correlated with daily maximum leaf conductance. Thus, chaparral shrubs under non-drought conditions seem to sense even small changes in environmental conditions, in our opinion most probably due to initial drying of the uppermost soil and synthesis of ABA in the shallow roots. The results support the hypothesis that information of photosynthesis rate and predawn water potential may be used as primary variables to predict canopy conductance of Mediterranean sclerophyll shrub vegetation.
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  • 2
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Desiccation tolerance ; Desiccation-related proteins ; Exormotheca ; Marchantiales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Abscisic acid (ABA) induces formation of a set of proteins in the xerophilic liverwortExormotheca holstii. Some of them have immunological properties similar to the dehydrins of desiccated corn embryos and the desiccation-related proteins ofCraterostigma plantagineum. The fluctuations of endogenous ABA during cycles of desiccation and rehydration seem to be sufficiently high to indicate a role for ABA as a stress hormone and there by as an endogenous inductor of stress-related protein synthesis. Desiccation tolerance disappears when thalli are cultivated for a longer period under well-watered conditions; such thalli are not able to increase stress-dependent ABA biosynthesis sufficiently, or to form the desiccation-related proteins unless they are treated with external ABA. The rehydrated thalli cannot recover from a rapid water loss, while ABA-treated, non-hardened thalli regain their photosynthetic activity within two hours.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 387-390 
    ISSN: 0009-2940
    Keywords: Peroxy compounds ; Cobaloximes ; Oxygen insertion ; Radicals, alkoxy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkoxy radicals have been generated by photochemical reactions of (alkylperoxy)cobaloximes 1. The occurrence of alkoxy radicals has been proved by characteristic cyclization and β-scission reactions of the reactive intermediates.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1777-1779 
    ISSN: 0009-2940
    Keywords: Polar effects ; Radical clock ; Cobaloximes, alkyl ; Radicals, alkyl ; Chlorine abstraction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a series of structurally similar alkyl radicals 1a-c the tertiary 1,1-dimethyl-5-hexenyl radical 1c reacts 30 times faster with carbon tetrachloride than the primary 5-hexenyl radical 1a. The reactivity of the secondary 1-methyl-5-hexenyl radical 1b aligns itself in between the primary and the tertiary radical 1a and 1c. The results indicate that the increasing nucleophilicity of the alkyl radicals is the major factor contributing to the reactivity.
    Additional Material: 1 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1187-1191 
    ISSN: 0009-2940
    Keywords: Cobaloximes, alkyl- ; 5-Hexenyl, cyclization to cyclopentylmethyl ; Radicals, alkyl ; Abstraction of bromine and chlorine ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical cyclization and halogen abstraction reactions of secondary alkylcobaloximes 1b and 1d compared to their primary counterparts 1a and 1c show an enhanced reactivity of secondary alkylcobaloximes: Thus, cyclohexylcobaloxime 1d reacts 13 times faster with CCl4 than n1-hexylcobaloxime 1c, 6-hepten-2-yl-cobaloxime 1b rearranges 58 times faster to its cyclopentylmethyl isomer 4b than 5-hexenylcobaloxime 1a. Although free alkyl radicals are reactive intermediates in photolytic conversions of alkylcobaloximes 1 in organic solvents, the presence of BrCCl3 or bromobenzene in photoreactions of primary alkylcobaloximes 1a and 1c seems to cause a more efficient homolytic cleavage of the Co - C bond.
    Additional Material: 3 Tab.
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  • 6
    ISSN: 0009-2940
    Keywords: Alkylrhodoximes ; Radicals, alkyl ; Halogen abstraction ; Carbon-carbon bond formation ; Stereochemistry ; Photoreactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Primary, secondary, and tertiary alkylrhodoximes 1 were prepared from alkyl bromides and tosylates 4 and the trans1-dichlororhodium complex 3. X-ray crystallography of the previously unknown tert1-butylrhodoxime 1k reveals structural features of this tert-s̰1-alkylrhodium compound. Photochemical homolytic cleavage of the Rh - C bond in alkylrhodoximes 1 only occurs in the presence of efficient radical traps which allow further mechanistic studies.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 44 (1993), S. 410-415 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Material databaseThis paper describes a new materials database named SWDB. SWDB is the German abbreviation for „Sollwert-Werkstoff-Datenbank“ and should be read as „Specified-Materials-Database“. SWDB is a state of the art user friendly materials database which provides adequate information on standardized and not standardized materials characteristics of solid materials from ferrous and non-ferrous metals and other metallic alloys currently used in engineering practice. Apart from the chemical composition and mechanical-technological properties of metallic materials based on various standards and specifications, the database includes reference to a large number of possible alternative materials in a concise and pregnant form which is transparent and easily accessible for application engineers. The material data are composed on the basis of an absolutely new structured model and are shown as a function of the specified material, product shape, dimension, delivery condition and sampling.SWDB includes additional information on physical properties as well as exhaustive information on heat treatment, hot and cold forming, weldability and hints for application. The SWDB has a dual character: on the one hand it can be operated as an individual and independent database, on the other hand as a satellite database to support the corrosion database within the information system on corrosion and protection, „CORIS“.
    Notes: Die neu entwickelte Sollwert-Werkstoff-Datenbank (SWDB) ist eine benutzerfreundliche Werkstoff-Datenbank, die Informationen über genormte und nicht genormte Werkstoff-Kennwerte massiver, metallischer Werkstoffe bereitstellt. Der Inhalt dieser Datenbank setzt sich zusammen aus Solldaten von ingenieurmäßig gebräuchlichen, massiven Werkstoffen aus Eisen- und Nichteisenmetallen. Neben der chemischen Zusammensetzung und den mechanisch-technologischen Eigenschaften von metallischen Werkstoffen nach verschiedenen Normen und Spezifikationen sind eine Vielzahl möglicher alternativer Werkstoffkandidaten in kurzer, prägnanter und für den Anwender gut einsehbarer Form referiert. Die Daten sind auf der Basis eines völlig neu strukturierten Modells aufgebaut und in Abhängigkeit vom spezifizierten Werkstoff von der Erzeugnisform, der Abmessung, dem Lieferzustand und von der Probennahme wiedergegeben.Außerdem enthält die SWDB zusätzliche Informationen über physikalische Kennwerte sowie zahlreiche Angaben zur Wärmebehandlung, Warm- und Kaltformgebung, Schweißbarkeit und Anwendungshinweise. Die SWDB hat eine doppelte Funktion: einerseits arbeitet sie als unabhängige Datenbank eigenständig, andererseits als Satellit-Datenbank, die die Korrosionsfakten-Datenbank im Informationssystem für Korrosion und Korrosionsschutz „CORIS“ unterstützt.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Coronands with 1,2-Dithio-ethene Units. II. Crystal Structures of the Two Crown Thioethers 8,9-Dicyano-8,9-didehydro-7,10-dithia-[12]crown-4 and 11,12-Dicyano-11,12-didehydro-10,13-dithia[15]crown-5The structures of the title compounds have been determined by X-ray analysis. Both thioethers crystallize in the monoclinic system with the following crystal data. Dithia-[12]crown-4: a = 751.7(1), b = 1010.4(1), c = 1639.8(2) pm, β = 95.08(1)°, Z = 4, space group P21/n; dithia[12]crown-5: a = 1169.9(3), b = 916.7(3), c = 1414.1(4)pm, β = 92.51(2)°, Z = 4, space group P21/c. The structures were refined to final R = 0.048 (Rw = 0.031) and 0.040 (0.046), respectively. They are characterized by their structural parameters (bond lengths and angles, torsion angles, l.s. planes) and discussed in special consideration of the ring conformation and the geometric arrangement of the donor atoms.
    Additional Material: 4 Ill.
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  • 9
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Using benzenehexathiolate 1 it is possible to synthesize alkylthio-substituted benzo-1,3-dithiole-2-thiones 2, or -ones 3 and benzo-di(1,3-dithiole-2-thiones) 4, or -ones 5, resp., which were cleaved under basic conditions. The generated benzene-1,2-dithiolates 7 were isolated as benzene-dithiolato zincates 8, benzene-1,2-dithioles 11, and benzene-1-thiole-2-thiolates 10. Dibenzo[c,g](1,2,5,6)-tetrathiocins 9 were synthesized by oxidation of 7 or 8 in good yields. For the per(methylthio)-substituted tetrathiocin 9a the twist conformation was proved by x-ray structure analysis.The tetrathiocin 9a was probably formed via the orthodithiobenzoquinone 13a. Photolysis of 3a at room temperature in solution led to 9a and tetrakis(methylthio)benzo[c] (1,2,3)trithiole 12a as the main product, which was also formed by irradiation of 9a. The trithioles 12 were formed from 8 by reaction with sulfur dichloride. 12a was investigated by x-ray structure analysis. ortho-Dithiobenzoquinone 13c can be claimed as an intermediate upon irradiation of benzo-1,3-dithiol-2-one 3c in an argon matrix at 10 K. Depending on the wavelength the equilibrium lies either on the side of dithiobenzoquinone 13c or benzodithiete 14c. The same is true for system 15/16, which can be reached by flash vacuum pyrolysis of 3c.
    Notes: Alkylthiosubstituted Bis(benzene-1,2-dithiolato)zincates, Benzene-1,2-dithioles, and -1,2-dithiolates - Educts for Dibenzo[c,g](1,2,5,6)tetrathiocins, and Benzo[c](1,2,3)trithioles; Investigations on Benzodithietes and ortho-Dithiobenzochinones
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 359-366 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis, Coordination Chemistry and Mass Spectrometric Fragmentation of New N-(Thiocarbamoyl)-benzamidinesSyntheses of N-(thiocarbamoyl)benzamidines from benzimidoylchlorides and aromatic amino acids as starting materials are reported. The prepared compounds were used as ligands for complexing nickel(II) and copper(II)ions. The benzamidines were characterized by mass spectrometric methods. The fragmentation pattern of the benzamidines was derived from the corresponding MIKE-spectra.
    Additional Material: 2 Ill.
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