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  • 1
    ISSN: 1573-8248
    Keywords: Nanaia ; Opuntia ; biocontrol ; evaluation ; host-specificity ; Nanaia ; Opuntia ; lutte biologique ; évaluation ; spécificité vis-à-vis de l'hôte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Résumé Nanaia sp. a été récolté surOpuntia pascoensis Britton & Rose au Pérou et introduit en Afrique du Sud pour lutter biologiquement contreOpuntia aurantiaca Lindley. Depuis l'existence de cette nouvelle association Insecte-Plante, les chances d'une lutte biologique efficace pourraient être théoriquement augmentées. Cependant, les études de laboratoire avant lâcher montraient les effets adverses de l'élevage de laboratoire, le développement larvaire était plus lent, la survie larvaire était diminuée, des adultes plus petits apparaissaient et la reproduction était supprimée surO. aurantiaca par rapport àO. pascoensis. La nouvelle associationNanaia sp./O. aurantiaca ne sera probablement pas vouée au succès, bien que des essais de plein champ devraient être développés pour le confirmer, un vaste programme d'élevage et de lâcher serait une perte de temps et un gaspillage d'argent et d'effort.
    Notes: Abstract Nanaia sp. was collected onOpuntia pascoensis Britton & Rose in Peru and introduced into South Africa for biological control ofOpuntia aurantiaca Lindley. Since this is a new insect-plant association the chances of successful biological control could theoretically be enhanced. However, pre-release insectary studies showed that apart from the adverse affects of insectary rearing, larval development was slower, less larvae survived, smaller adults emerged and reproduction was suppressed onO. aurantiaca compareded toO. pascoensis. The new association ofNanaia sp. onO. aurantiaca will probably not succeed and, although field trials should be conducted to confirm this, an extensive mass-rearing and release programme would be a waste of time, finances and effort.
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Strong evidence for nitric acid condensation at altitudes of about 18–23 km is provided by balloon-and rocket-borne measurements made near Kiruna, northern Sweden, in January 1989. Nitric acid con-densation is believed to be a necessary step in the chemical pre-conditioning required for ...
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 33 (1988), S. 933-940 
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Kurven der temperaturprogrammierten Desorption (TPD) des Ammoniak von Zeolith wurden mit verschiedenen Kinetischen Modellen ausgewertet. Ein annähernd linearer Zusammenhang wurde gefunden zwischen der Aktivierungsenergie der Desorption bzw. der Adsorptionswärme von NH3 an H-Zeolithen mit unterschiedlichem Si/Al-Verhältnis und der intermediären Elektronegativität der Zeolithe, die ein mass für die Säurestärke darstellt. Dieses Ergebnis entspricht der Verschiebung der hochfrequenten IR-Bande der OH-Gruppen und der mikrokalorimetrisch bestimmten Änderungen der Adsorptionswärme. Damit erweist sich die TPD von NH3 als brauchbare Methode zur quantitativen Charakterisierung der sauren Eigenschaften von H-Zeolithen.
    Abstract: Резюме С помощью нескольких кинетических моделе й проведена оценка кри вых температурно-програ ммируемой десорбции аммиака из цеолитов. Установлен а приблизительно линейная корреляция между энергией актив ации процесса десорбции и ли тепловой адсорбции Н-цеолитов с различным соотноше нием Si/Al и промежуточной элект роотрицательностью цеолитов,являющейся мерой их кислотности. Этот результат соответст вует изменению высокочастотной ИК п олосы поглощения ОН г рупп,а также изменению теплоты ад сорбции,найденной с помощью м икрокалориметрии. Следовательно,метод температурно-програ ммируемой десорбции аммиака яв ляется полезным мето дом количественной хара ктеристики кислотных свойств не которых Н-цеолитов.
    Notes: Abstract Curves of the temperature-programmed desorption (TPD) of ammonia from zeolites were evaluated with several kinetic models. An approximately linear correlation was found between the activation energy of desorption or the heat of adsorption of H zeolites with various Si/Al ratios and the intermediate electronegativity of the zeolites, the latter representing a measure of the acid strength. This result corresponds to the change in the high-frequency infrared band of the OH groups and also to the change in the heat of adsorption, determined by microcalorimetry. Thus, the TPD of NH3 is a useful technique for quantitative characterization of the acidic properties of several H zeolites.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 32 (1987), S. 2009-2014 
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde die Temperatur-Programmierte Desorption von Ammoniak an der H-Form eines Mordenits nach Vorbehandlung bei unterschiedlichen Temperaturen untersucht. Es konnte gezeigt werden, daß damit eine quantitative Erfassung der Anzahl der sauren OH-Gruppen möglich ist. Außerdem erhält man aus den Desorptionskurven Hinweise über die Veränderung der sauren Eigenschaften in Abhängigkeit von der Vorbehandlungstemperatur.
    Abstract: Резюме Иучена температурно-программная десорбц ия аммиака на Н-форме мор денита, предварительно обра ботанного при различ ных температурах. Показа на возможность количественного опр еделения кислотных О Н групп. Кроме того, данные пол ученные на основе кривых десорбции ука зывают на изменение к ислотных свойств морденита в з ависимости от температуры его обра ботки.
    Notes: Abstract Temperature-programmed desorption of ammonia from the H form of a modernite was carried out after pretreatment at different temperatures. It could be shown that a quantitative registration of the acidic OH groups is possible. Moreover, from the desorption curves, information is obtained about the alteration of the acidic properties as a function of the temperature of pretreatment.
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  • 5
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Conclusion The present resulte are in general agreement with those obtained earlier, e.g. in /2/. The complete removal of post-implantation defects in As-implanted Si may be achieved by thermal annealing at temperatures above 700°C and by laser annealing as well. More than 50% of the implanted As atoms enter the host lattice sites during the thermal annealing. By laser annealing, on the other hand, 9056 of the As atoms become substitutional.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 325 (1986), S. 297-297 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Reaction kinetics and catalysis letters 27 (1985), S. 305-308 
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Исследованием температурно-программированной десорбции некоторых оснований с цеолитов HY было показано, что энергия активации десорбции представляет собой меру, пригодную для характеристики кислых свойств.
    Notes: Abstract The temperature programmed desorption of several bases from a HY zeolite has shown that the activation energy of desorption represents a useful measure for characterizing the acidic properties.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 331 (1988), S. 220-222 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Modern analysis of trace elements has been carried out for many years. The quality of analysis results however still leaves a lot to be desired. Problems arise from contaminations caused by ubiquitous distribution of the trace elements during preparation of the samples. It is shown where in the laboratory sources of contamination are to be found and how they can be avoided. Experience with sample preparation, a decomposition system with low contamination and cleaning methods are described.
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  • 9
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Characterization and Catalytic Activity of Ni2+ -X and -Y Zeolites. II. Reducibility of Ni2+ by Low Olefines and the Dimerization Activity of the Ni2+ -ZeolitesThe reducibility of Ni2+ in X and Y zeolites by hydrogen, but-1-ene, propene, and ethene is compared. The degree of reduction was determined after isothermal reduction and reoxidation by the TPR method. At 673 K on X zeolites the reducibility decreases in the order: H2 〉 but-1-ene, propene 〉 ethene. On Y zeolites an inversion takes place: but-1-ene, propene 〉 H2, ethene. The mechanism of reduction by olefins should be determined by an intermediate splitting off of a hydride ion as a reducing species. Such a mechanism explains the higher degree of reduction in the more acid Y zeolites. Assuming low valent nickel as an active center in ethen dimerization the induction period results from the reduction of Ni2+ ions.
    Notes: Die Reduzierbarkeit des Ni2+ in X- und Y-Zeolithen durch Wasserstoff, But-l-en, Propen und Ethen wird verglichen. Der Reduktionsgrad wurde nach isothermer Reduktion und Reoxydation durch temperaturprogrammierte Reduktion bestimmt. Für die Reduzierbarkeit bei 673 K ergibt sich für einen X-Zeolith folgende Reihenfolge: H2 〉 But-l-en, Propen 〉 Ethen. Am Y-Zeolith erfolgt eine Umkehrung: But-l-en, Propen 〉 H2, Ethen. Der Mechanismus der Reduktion durch Olefine sollte durch einen sauer katalysierten Olefinzerfall mit intermediärer H- -Abspaltung als reduzierendem Agenz bestimmt sein. Ein solcher Mechanismus erklärt die stärkere Reduktion des Ni2+ in Y-Zeolithen durch Olefine. Nimmt man als aktives Zentrum für die Ethendimerisierung niedrigwertiges Nickel an, so wird die bei der Ethendimerisierung auftretende Induktionsperiode durch die notwendige Reduktion des Ni2+ erklärbar.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 520 (1985), S. 75-86 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Charaterization and Catalytic Activity of Ni2+ Exchanged X and Y Zeolites. I. TPR Studies on NiNaX and NiNaY Zeolites.The structure of TPR spectra of NiNaX and NaNiY zeolites variously exchanged is determined by the location of the cations. In case of X zeolites a peak appears with a maximum at 750-800 K (reduction on SII and SI, positions) and for higher exchange degrees an additional one at about 1000 K (reduction on SI positions). Three ranges of reduction may be separated in case of Y zeolites (reduction on SII, SI′, and SI). With increasing Si/Al ratios the maximum of the hightemperature peak is shifted to higher temperatures. The reduction at temperatures up to 800 K resulted in higher reduction degrees for X reolites while the overall reduction up to high temperatures led to higher reduction degrees for Y zeolites. The kinetic analysis by means of two different methods yielded the following activation energies: (85 ± 10) or (86 ± 2) kJ/mole, respectively, for the low-temperature peak, and (223 ± 12) or (214 ± 2) kJ/mole, respectively, for the high-temperature peak.
    Notes: Die Struktur der TPR-Kurven verschieden ausgetauschter NiNaX-und NiNaY-Zeolithe wird durch die unterschiedliche Kationenverteilung bestimmt. Bei X-Zeolithen erscheint ein Tieftemperturpeak mit einem Maximum im Bereich 750-800K und für höhere Austauschgrade zusätzlich ein Hochtemperaturpeak bei etwa 1000 K (Reduktion von Ni2+ suf SII- und SI′- bzw. SI-Positionen). Bei Y-Zeolithen Können drei Reduktionsbereiche (Reduction auf SII, SI und SI) unterschieden werden. Das Maximum des Hochtemperaturpeaks verschiebt sich mit steigendem Si/Al-Verhältnis zo höheren Temperaturen. Dei Reduzierbarkeit im Bereich niedrigerer Temperaturen ist für X-Zeolithe größer,dei bei Reduktion bis zo hohen Temperaturen erreichbaren Reduktionsgrade liegen für Y-Zeolithe höher. Die kinetische Analyse ergab für den Tieftemperaturpeak je nach der gewählten Methode (85 ± 10) bzw. (86 ± 2) kJ/mol Aktivierungsenergie, für den Hochtemperaturpeak (223 ± 12) bzw. (214 ± 2) kJ/mol.
    Additional Material: 7 Ill.
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