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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 85 (1997), S. 231-236 
    ISSN: 1570-7458
    Schlagwort(e): Glossina fuscipes fuscipes ; vegetation ; biconical trap ; temperature ; light ; relative humidity ; monitor lizard
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Glossina fuscipes fuscipes Newstead was sampled in isolated thickets and forest patches near Lake Victoria, Kenya using unbaited biconical traps, between March 1992 and June 1993. Traps set at 1 m from the forest edge caught 3.3 times as many males and 5 times as many females as those set inside or 10 m away. The corresponding figures at 1 m from the edge of thicket were about 1.43 and 1.64 times, respectively. Hourly catches of males and females were positively correlated with temperature, light intensity and host (monitor lizard) prevalence, and negatively correlated with relative humidity. Light intensity and temperature were the most important variables affecting the catches of each sex. The results are discussed in relation to control and monitoring of G. f. fuscipes using traps.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 74 (1995), S. 115-119 
    ISSN: 1570-7458
    Schlagwort(e): wheat ; aphids ; hydroxamic acids ; DIMBOA ; DIMBOA-glucoside ; EPG ; electrical penetration graph ; feeding deterrents ; antixenosis ; plant resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Feeding behaviour of five species of cereal aphids in wheat seedlings differing in hydroxamic acid (Hx) levels, was monitored via electrical penetration graphs (EPG). Aphid species could be grouped as sensitive to the feeding deterrent effect of Hx in the seedlings (Rhopalosiphum padi, Schizaphis graminum, Sitobion avenae, andMetopolophium dirhodum) or insensitive to them (Rhopalosiphum maidis). However, when feeding behaviour was studied in artificial diets containing Hx, all species were equally sensitive to Hx. The behavour ofR. maidis was further compared with that ofR. padi through detailed EPG analysis. It was found that the insensitivity ofR. maidis to Hx in seedlings may be due to a feeding strategy avoiding contact with the compounds by decreasing the number of cellular punctures in live tissues other than sieve elements during its way to the phloem.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 74 (1995), S. 283-294 
    ISSN: 1570-7458
    Schlagwort(e): hypersensitivity ; Hessian fly ; plant resistance ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Hessian flyMayetiola destructor (Say) larvae are able to obtain food from their host plant without inflicting mechanical damage to the plant surface, apparently by secreting substances which elicit release of nutrients from plant cells surrounding the feeding site. Cells of fully susceptible plants retain their normal appearances, while in resistant plants extensive areas of cellular collapse occur. These responses indicate that hypersensitivity is the basis of wheat's resistance to the Hessian fly. The fly's feeding mechanism more closely resembles that of a pathogen than of a phytophagous insect; correspondingly, both the genetic relationship and resistance mechanism of the host plant to the parasite are of the sorts commonly associated with bacterial and fungal pathogens.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 83 (1997), S. 171-180 
    ISSN: 1570-7458
    Schlagwort(e): within-plant heterogeneity ; tent caterpillars ; temperature ; circular statistics ; Lepidoptera ; Yponomeutidae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The caterpillars of Yponomeuta mahalebella Latr. (Lepidoptera: Yponomeutidae) are monophagous on Prunus mahaleb (Rosaceae) leaves. Adult females deposit eggs in batches, which determines larval gregarious behaviour. Coupled with gregarious behaviour, caterpillars spin silk tents within they will feed until pupation. Distribution of tents in the field, their effect in microenvironmental larval growth conditions and the consequences for adult body mass and survival of larvae were studied. There was a significant trend for tents to be placed with a southward orientation. Within-plant tent orientation was related to the sun-shade pattern experienced, which was the main effect determining thermal differences between the inside and the outside of the tent. These differences appeared to affect larval growth and survival, with higher survival of larvae and heavier adults emerging from tents oriented to the south-east and east, respectively.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 76 (1995), S. 121-131 
    ISSN: 1570-7458
    Schlagwort(e): Aphis gossypii ; life history ; cucumber ; temperature ; partial resistance ; biological control ; Aphidius colemani
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Life table data forAphis gossypii Glover (Homoptera: Aphididae), an important pest in glasshouse cucumber crops, were studied at 20, 25 and 30°C on two cucumber cultivars (Cucumis sativus L.) in controlled climate cabinets. The development time on the cucumber cv. ‘Sporu’ ranged from 4.8 days at 20°C to 3.2 days at 30°C. Immature mortality was approximately 20% and did not differ between temperatures. Most mortality occurred during the first instar. Reproduction periods did not differ among temperatures, but at 25 and 30°C more nymphs were produced (65.9 and 69.8 nymphs/♀, respectively) than at 20°C (59,9 nymphs/♀) because of a higher daily reproduction. Intrinsic rate of increase was greatest at 25°C (r m =0.556 day−1). At 20 and 30°C the intrinsic rate of increase was 0.426 and 0.510, respectively. On cv. ‘Aramon’, the development time ofA. gossypii was approximately 20% longer at all temperatures. Immature mortality did not differ between the two cultivars. The intrinsic rate of increase on cv. ‘Aramon’ was 15% smaller than on cv. ‘Sporu’. The use of cucumber cultivars partially resistant to aphids is discussed in relation to biological control of cotton aphid in glasshouses. Development time and immature mortality on leaves of the middle and upper leaf layer of glasshouse grown cucumber plants (cv. ‘Aramon’) were comparable to development in the controlled climate cabinets. On the lower leaves immature mortality was much higher (approximately 82%) than on leaves of the middle (24.0%) and upper leaf layer (24.5%). Reproduction was less on the lower leaf layer (45.9, 70.5 and 70.1 nymphs/♀ on leaves of the lower, middle and upper leaf layer, respectively). Aphids, successfully parasitized byAphidius colemani Viereck (Hymenoptera: Braconidae) only reproduced when they were parasitized after the third instar. Fecundity was 0.1 to 0.9 and 10.5 to 13.3 nymphs/♀ for aphids parasitized in the fourth instar or as adults, respectively. Reproduction of aphids that were stung but survived the attack was lower than for aphids not stung. Average longevity of these aphids was equal to the longevity of aphids not stung byA. colemani.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Fire technology 33 (1997), S. 195-213 
    ISSN: 1572-8099
    Schlagwort(e): point of fire origin ; fire ; temperature ; plaster ; concrete ; thermal ; damage ; biotite ; magnetization ; susceptibility ; N-rays ; P-rays ; X-rays
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Abstract Magnetic susceptibility (MS) measurements were taken to determine fire exposure patterns on noncombustible structural members and compartment boundaries. These measurements led on-site fire investigators to the cause of combustion and the point of fire origin. Thermal damage to walls and to ceilings was estimated quantitatively by measuring MS and two-valent Fe ion concentration in building materials such as concrete and plaster. It was shown that these effects are preconditioned by thermochemical transformations in the mineral biotite, which is present as a component of common building materials. For the first time, the effect of a substantial and irreversible increase in biotite magnetization exposed to powerful flows of N- and P-rays was found. It is hoped that the presence of this “magnetic trace” of radiation in building materials will allow investigators to use the magnetometric method at nuclear power plant catastrophes such as that in Chernobyl. It was also shown that the influence of N- and P-rays on biotite's magnetic properties greatly differs from the thermal influence on biotite.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 82 (1997), S. 159-166 
    ISSN: 1570-7458
    Schlagwort(e): Diaeretiella rapae ; reproduction ; life-tables ; temperature ; Diuraphis noxia ; biological control
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Diaeretiella rapae (M'Intosh), a polyphagous and cosmopolitan parasite of aphids, was imported from China to the USA for biological control of Diuraphis noxia (Mordwilko), a pest of small grains. We studied several aspects of its biology on D. noxia hosts in the laboratory at 3 constant temperatures, 10.0, 21.1, and 26.7 °C. Females lived significantly longer than males at all 3 temperatures, and longevity was greatest at 10 °C, followed by 21.1 and 26.7 °C. Fecundity (= number of mummies) did not differ significantly among the 3 temperatures studied. The ovarian egg-load was 129.1 ± 9.3, and was significantly affected by the size of adult females. A pre-oviposition period ± 0.26 days) was detected at 10 °C, but not at the other temperatures. Pre-imaginal survivorship was similar among temperatures, while R o and T c decreased with temperature, and r m increased with temperature. The offspring sex ratio (proportion females) was lowest at 26.7 °C, and similar between 10.0 and 21.1 °C. In addition, the offspring sex ratio significantly declined with the age of the female parent. The suitability of D. rapae for colonization against D. noxia in North America is discussed in relation to its responses to temperature and the climate of its home range.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 82 (1997), S. 319-333 
    ISSN: 1570-7458
    Schlagwort(e): chlorogenic acid ; light availability ; Lycopersicon esculentum ; Manduca sexta ; protein ; rutin ; temperature ; tomatine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We examined how light availability influenced the defensive chemistry of tomato (Lycopersicon esculentum: Solanaceae). Tomato plants were grown either in full sunlight or under shade cloth rated at 73%. Leaves from plants grown in full sunlight were tougher, had higher concentrations of allelochemicals (chlorogenic acid, rutin and tomatine), and had less protein than leaves from plants grown in shade. We determined how these differences in host plant quality due to light availability affected the behavior and growth of a Solanaceae specialist, Manduca sexta. Both in the greenhouse and in the field, caterpillars on shade-grown plants grew heavier in a shorter amount of time than those on plants that had previously been grown in full sunlight. In contrast, the effects of previous light availability to plants on caterpillar behavior appeared to be minor. To further investigate how light availability to plants influenced herbivore growth, we examined the effects of leaf-powder diets made from tomato leaves of different ages (new, intermediate, or mature) grown in full sunlight or shade on caterpillar performance. Caterpillars fed diets made from plants grown in shade consumed less but grew faster than larvae fed diets made from tomato plants grown in full sunlight. Caterpillars fed diets made from new leaves grew larger in less time than caterpillars fed diets made from intermediate aged leaves. Caterpillars did not survive on the mature leaf powder diets. There were plant-light treatment by larval thermal regime interactions. For example, at 26:15 °C , plant-light treatment had no effect on stadium duration, but at 21:10 °C, stadium duration was prolonged with the full sunlight-new leaf diet compared with the shaded-new leaf diet. In a second diet experiment, we examined the interactive effects of protein and some tomato allelochemicals (rutin, chlorogenic acid and tomatine) on the performance of caterpillars. There were food quality by thermal regime interactions. For instance, at 26:15 °C , neither protein nor allelochemical concentration influenced stadium duration, whereas at 21:10 °C, stadium duration was prolonged with the low protein-high allelochemical diet, which simulated full sunlight leaves. In sum, light availability to plants affected defensive chemistry and protein concentration. The difference in food quality was great enough to influence the growth of a specialist insect herbivore, but the effects were temperature-dependent.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 75 (1995), S. 127-134 
    ISSN: 1570-7458
    Schlagwort(e): bruchid ; diapause ; photoperiod ; temperature ; multivoltinism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A wild bean weevil,Kytorhinus sharpianus Bridwell (Coleoptera: Bruchidae), has a multivoltine life cycle and enters a hibernal larval diapause at the fourth instar under a short daylength (Shimada & Ishihara, 1991). Here, we investigated their diapause incidence under different photoperiods at 24°C and 27°C. The critical photoperiods for diapause induction were 14.5 h at 24°C and 14 h at 27°C. The stages susceptible to diapause-inducing stimuli were estimated by transferring larvae of various instars from long days to short days and vice versa. Then we investigated the incidence of larval diapause. The sensitive stage was estimated to be from the third to early fourth instar. Though larval diapause, which was induced under a short daylength, was terminated only by increasing the daylength, the termination was more synchronized by an exposure to a low temperature followed by increasing temperature, irrespective of photoperiod.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 84 (1997), S. 255-265 
    ISSN: 1570-7458
    Schlagwort(e): Delia radicum ; postdiapause development ; temperature ; Diptera ; Anthomyiidae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Canadian populations of D. radicum differ in their response to temperature during postdiapause development. Populations that are primarily of the early-emerging type ( $$\left( { \leqslant 256DD_{04} } \right)$$ ) (St-Jean, Quebec; London, Ontario) have high values for the parameters describing this response: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOuamaaBa% aaleaacaWGTbaabeaakiabg2da9aaa!38F2!$$R_m = $$ 12.7–13.3; $$T_m = $$ 28.0–31.8 °C ; Tσ = 10.3–14.2 ( $$R_m $$ , the maximum developmental rate at the temperature, $$T_m $$ [ °C ] where the developmental rate is highest, and Tσ , the parameter which gives the shape of the truncated normal curve fitted to the data), a low degree-day requirement for emergence (160–232 $$DD_{04} $$ ), and may lack a developmental delay at temperatures above ca. 21 °C . Populations of the late-emerging type (Kildare, Prince Edward Island) have low parameter values ( $$ R_m = 2.5$$ , $$T_m = 19.3$$ °C ; Tσ = 6.4), high degree-day requirements (530 $$DD_{04} $$ ), and a developmental delay at high temperatures. The parameters for the early-emergers in the population from Winnipeg, Manitoba (74% early) were intermediate ( $$R_m = 9.1$$ , $$T_m = 27.1$$ °C , Tσ = 10.7, $$ DD_{04} = 246 $$ ), but resembled the early rather than the late type. This population varied from 31 to 90% early type over a 10-year period and the rate of postdiapause development at 20 °C was directly related to the percentage early. In the year with the most rapid development (90% early), development was significantly slower than in the populations from other locations with predominantly early populations, and the year with the slowest development (31% early) showed significantly faster development than that from Kildare, Prince Edward Island (100% late). Therefore the parameters for early and late types of development will not be accurate for use in mixed populations, and the parameters in mixed populations will change among years. Populations of D. radicum in North America and Europe (67 locations by years) varied from 0–100% early. At Winnipeg, the percentage early was directly related to the annual temperature accumulation ( $$DD_{05} $$ ) during the growing season. The calculation of developmental parameters for the early-emergers of mixed populations provides a more accurate basis for estimating the times of first emergence and the first peak of emergence than parameters based on the whole population. Since postdiapause developmental rates vary both among and annually within locations, developmental models should be designed to include such variations.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 27 (1997), S. 1275-1282 
    ISSN: 1572-8838
    Schlagwort(e): Carbon monoxide ; Pt-Ru/C catalyst ; Tafel slopes ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract CO electrooxidation on a Pt–Ru/C catalyst was investigated in sulphuric acid electrolyte. The physico-chemical properties of the Pt–Ru/C catalyst were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The influence of temperature, CO partial pressure and proton concentration on the electrochemical oxidation rate was investigated by steady-state galvanostatic polarization measurements. The apparent activation energy decreased from 70 to 30kJmol−1 as the overpotential increased from 0.5 to 0.9V vs NHE. The reaction order with respect to carbon monoxide increased, passing from 0.4 to 1, with the increase of the overpotential from 0.5 to 0.7V vs NHE; a reaction order close to −1 with respect to the protonic concentration was observed, irrespective of the potential. Tafel slopes of about 136mVdec−1 were determined for oxidation of CO and CO/N2 mixtures.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 27 (1997), S. 1328-1332 
    ISSN: 1572-8838
    Schlagwort(e): metal hydride ; capacity ; temperature ; performance ; enthalpy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract The effect of temperature on the performance of a LaNi4.76Sn0.24 metal hydride electrode was investigated in the temperature range of 0 to 50°C. The electrode showed a maximum discharge capacity at 25°C. The total resistance increases with a decrease of temperature from 50°C to 0°C. The apparent activation enthalpies at different states of charge were determined by evaluating the polarization resistance at different temperatures. It was found that the apparent activation enthalpy is an indicator of the relative reaction rate of the charge-transfer reaction and hydrogen absorption.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Journal of polymers and the environment 3 (1995), S. 199-203 
    ISSN: 1572-8900
    Schlagwort(e): Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik , Maschinenbau
    Notizen: Abstract The thermal oxidative stability of various formulations based on emulsion-grade ABS was studied by the chemiluminescence technique. Emulsion products were found to be essentially less stable than ionic mass polymerization resins. Among the antioxidants studied, Santonox R is clearly more efficient than Irganox 1076 and Irganox 3114, and its superiority is reflected primarily in improved induction period values. The introduction of Tinuvin 770 and Tinuvin 328 UV stabilizers into emulsion resins does not change the durability of the products. In mixtures where both Irganox 1076 and UV stabilizers are present, a certain antagonistic effect was noted at high UV stabilizer concentrations.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 17 (1988), S. 581-599 
    ISSN: 1572-8927
    Schlagwort(e): Copper ; oxidation ; NaCl solutions ; ionic strength ; speciation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The rates of oxidation of Cu(I) in air saturated solutions was measured as a function of pH, temperature (5–45°C), and ionic strength (0.5 to 6m) in NaCl and NaCl−NaClO4 solutions. In pure NaCl solutions, the effect of pH is independent of ionic strength and temperature. The overall rate constant is given by logk=12.32+0.12(pH)−2064/T−3.69I1/2+ 0.73I The energy of activitation was 39±2 kJ-mol−1 and is independent of ionic strength. At a constant ionic strength (I=1, 3 and 6m) in NaCl−NaClO4 mixtures the Cl− dependence of the rates is attributed to the oxidation of the various forms of Cu(I) in the solution. The rate constants for the oxidation of the various species are found to be functions of ionic strength. At a constant ionic strength (I=1) in NaCl−NaClO4 solutions, the effect of temperature is independent of the chloride concentration. The effect of Mg2+ and HCO 3 − on the oxidation rate was determined as a function of chloride concentration (1 to 6m) at 25°C and pH=8. The addition of Mg2+ causes the rate to decrease and the addition of HCO 3 − causes the rate to increase. The possible causes of these effects are discussed. Empirical equations for the rate of oxidation of Cu(I) in Na-Mg-Cl-HCO3 solutions as a function of composition are used to make reliable estimates of the oxidation in seawater and Red Sea waters.
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 24 (1995), S. 153-170 
    ISSN: 1572-8927
    Schlagwort(e): Densities ; excess volume ; pressure ; temperature ; ethylbenzene ; octanol ; nonanol ; dodecanol ; order creation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The excess volume V E of binary mixtures of octanol, nonanol and dodecanol in ethylbenzene have been calculated from the densities measured with a vibrating tube densimeter at temperatures from 50 to 100 °C and at pressures from 0.1 to 7.5 MPa. The values of V E are positive for all the three mixtures in the complete temperature, pressure and mole fraction ranges studied. The maxima in V E is observed at 0.4 mole fraction of alkanol. The results are discussed in terms of specific interactions present in the binary mixtures. The second order thermodynamic quantities (∂V E /∂T)p,(∂V E /∂P)T and (∂V E /∂P)T which have been derived from the effect of temperature and pressure on V E , indicate an overall net creation of order in the binary mixtures of ethylbenzene with higher homologues of alkanols.
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 24 (1995), S. 753-769 
    ISSN: 1572-8927
    Schlagwort(e): Conductivity ; sodium trifluoromethanesulfonate ; ion association ; temperature ; pressure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The electrical conductances of dilute (0.001 to 0.1 mol-kg−1) aqueous sodium trifluoromethanesulfonate (NaCF3SO3) solutions have been measured from 0 to 450°C and pressures to 250 MPa. The limiting molar conductance $$\Lambda _0 $$ increases with increasing temperature from 0 to 300°C and decreasing density from 0.8 to 0.3 g-cm−3. Above 300°C, $$\Lambda _0 $$ is nearly temperature independent, but increases linearly with decreasing density. The logarithm of the molal association constant of NaCF3SO3 calculated at temperatures from 372 to 450°C is represented as a function of temperature (Kelvin) and density of water (g-cm−3) by $$\log K_m = 0.888 - 330.4/T - (12.83 - 5349/T)\log \rho _w $$ The relative strengths of NaCF3SO3 and NaCl are similar within the accuracy of the current measurements over the limited range of temperature and pressure that could be investigated here.
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  • 17
    ISSN: 1572-8757
    Schlagwort(e): porous carbons ; activation ; oxidation ; surface oxygen groups ; LTPD
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract A styrene/divinylbenzene copolymer has been used as precursor for making porous carbons with bimodal pore size distributions (i.e., with both microporosity and mesoporosity). Pretreatment of the as-received copolymer by mild oxidation in air, significantly increased the carbon yield after carbonization. Reactivity studies of the polymer-based chars to CO2 clearly show the influences of some important factors such as carbonization temperature, heating rate, soak time on char reactivities. Bimodal porous carbons were prepared by carbonization of the preoxidized styrene/divinylbenzene copolymer in N2, followed by activation in CO2 at different temperatures to different levels of burnoff. The pore structures of the porous carbons produced have been characterized by various techniques such as gas adsorption and mercury porosimetry. The surfaces of the porous carbons produced, and a commercial carbon adsorbent, have been modified with HNO3 and H2O2 treatment at various conditions. Characterization of the surface oxygen functionality, both quantitatively and qualitatively, has been achieved using techniques such as Linear Temperature Programed Desorption (LTPD) and selective neutralization of bases.
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  • 18
    ISSN: 1572-8765
    Schlagwort(e): carbonado ; diamond ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of carbonado type synthesized polycrystalline diamonds produced from graphite together with catalytic Ni-Mo alloy doped with TiB2 and BNcub was investigated. It was found that the addition of these boron compounds increases the oxidation resistance of the carbonado type synthesized polycrystalline diamonds. The oxidation mechanism acting on the carbonado type synthesized polycrystalline diamonds and the role of boron compounds in increasing the resistance to the oxygen reaction are discussed.
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  • 19
    ISSN: 1572-879X
    Schlagwort(e): alumina ; carbon monoxide oxidation ; ethylene oxidation ; platinum ; cerium ; sol-gel ; thermostability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Various alumina-based supports were prepared by adding metal elements such as alkaline and rare earths to sol-gel alumina synthesized from aluminium isopropoxide using 2-methylpentane-2,4-diol as a solvent and the influence of the additives on the thermostability of the supports was investigated. It was found that Ba and Sr are the most effective in improving the thermostability of the alumina, La is moderately effective while Zr, Mg and Ca are ineffective. The influence of the additives on the catalytic activities of Pt/CeO x /MO y -Al2O3 (M=Ba, Sr, La) after the calculation at 1273 K was also investigated. Pt/CeO x /BaO-Al2O3 and Pt/ CeO x /La2O3-Al2O3 showed higher catalytic activity than Pt/CeO x /Al2O3, while Pt/CeO x / SrO-Al2O3 showed lower catalytic activity. The activity order was Ba 〉 La = none 〉 Sr in terms of CO and C2H4 oxidation.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 34 (1995), S. 31-40 
    ISSN: 1572-879X
    Schlagwort(e): palladium ; PdO ; alumina ; methane ; oxidation ; carbon ; XPS ; ellipsometry ; structure sensitivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Samples of palladium supported onγ-alumina and a palladium foil were used as catalysts for methane oxidation at 550° C. The samples were quenched quickly in the reaction chamber to room temperature in flowing Ar and then transferred in vacuo for XPS analysis. Structure sensitivity was manifest from an increase in PdO stability and a decrease in carbon deposition relative to Pd with increasing particle size. The results were compared with recent ellipsometric data.
    Materialart: Digitale Medien
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  • 21
    ISSN: 1572-879X
    Schlagwort(e): fluorination ; alumina ; platinum catalysts ; oxidation ; oxidation of benzene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Platinum supported on fluorinated alumina is more active for the total oxidation of benzene than is the catalyst with the same Pt loading supported on hydrophilic unfluorinated alumina. The Pt-F/alumina catalyst contains well-dispersed small Pt particles, in contrast to Pt/alumina. The high dispersion is a consequence of a strong metal-support interaction.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 48 (1988), S. 73-84 
    ISSN: 1570-7458
    Schlagwort(e): Liriomyza trifolii ; Agromyzidae ; Diptera ; temperature ; thresholds ; life history ; feeding ; intrinsic rate of increase ; tomato ; host-plant suitability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé La vitesse de développement, la mortalité, l'alimentation, la fécondité et la longévité de L. trifolii (Burgess) élevés sur plants de tomates du cultivar ‘Moneydor’ ont été examinées au laboratoire sous 3 températures constantes (15°C, 20°C et 25°C) et une thermopériode (16/22°C, moyenne 19,5°C). Les taux de développement et les seuils de chaque stade ont été déterminés à partir des droites de régressions. Aucune corrélation n'a été mise en évidence entre ces variables biologiques et la taille des pupes. De plus, certaines données sur la biologie de L. trifolii sont fournies et discutées. Le taux intrinsèque d'accroissement, rm a varié de-0,0023 oeuf viable/femelle/jour à 15°C à 0,1254 oeuf viable/femelle/jour à 25°C et la reproduction nette de 1 oeuf femelle viable/femelle à 15°C à 26 oeufs femelles viables/femelle à 25°C. La durée d'une génération a varié de 48 jours à 15°C à 24 j à 25°C. 90% de la ponte a eu lieu dans les 115 premiers degrés jours de la vie imaginale à 20 et 25°C. La fécondité et la longévité étaient fortement liées au nombre de piqûres nutritionnelles. Ces résultats montrent que la tomate est un hôte convenable permettant aux populations de L. trifolii de se développer lorsque la température est supérieure à 16°C.
    Notizen: Abstract The effects of three constant (15°C, 20°C and 25°C) and one alternating (16–22°C, mean 19.5°C) temperatures on development, mortality, feeding, fecundity and longevity of Liriomyza trifolii (Burgess) on tomato plants cv. ‘Moneydor’ were examined in the laboratory. Development rates and thresholds for each instar were estimated by means of linear regression. No correlation was found between life history variables and pupal length. Further, data on the biology of L. trifolii are given and discussed. The intrinsic rate of increase, rm, varied from-0.0023 viable female eggs/⧫/day at 15°C to 0.1254 eggs/⧫/day at 25°C and net reproduction from one viable female egg/⧫ at 15°C to 26 eggs/⧫ at 20°C. Generation time varied from 48 days at 15°C to 24 days at 25°C. Ninety % oviposition occurred within the first 115 degree-days of adult life at both 20°C and 25°C. Fecundity and longevity were highly correlated with the number of feeding punctures. The data indicate that tomato is a suitable host plant allowing populations of L. trifolii to increase if temperatures are above 16°C.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 44 (1988), S. 203-208 
    ISSN: 1420-9071
    Schlagwort(e): Lactate dehydrogenase ; glycolytic enzyme ; subcellular localization ; membrane binding ; mitochondria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Rabbit liver mitochondrial fraction shows lactate dehydrogenase activity. The enzyme can be released from particles by increasing the pH and the ionic strength of the medium. There is a narrow range of pH (6.8–7.4) and ionic strength (20–50 mM NaCl) in which the solubilization sharply increases. It has been shown that divalent anions (SO 4 2− ) and cations (Mg2+, Ca2+) are highly effective specific solubilizing agents. NADH (1.5 mM) and ATP (1.0 mM) were effective in solubilizing 50% of the enzyme bound, whereas the same concentrations of the analogs NAD+ and ADP had little effect. Cytosolic lactate dehydrogenase bound to the mitochondrial fraction and a saturation of particles by enzyme was observed in all experiments performed. The in vitro binding requires a short period of incubation between the enzyme and particles and the binding is independent of the temperature in the 0–37°C range. Binding was prevented by 0.15 M NaCl. The bound enzyme is approximately 20% less active than the soluble one. The results described give support to the proposal that rabbit liver lactate dehydrogenase has an ambiquitous behavior, like other glycolytic enzymes, which have not a fixed intracellular localization.
    Materialart: Digitale Medien
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 44 (1987), S. 123-130 
    ISSN: 1570-7458
    Schlagwort(e): composantes phéromonales ; diffusion ; température ; vent ; Z9-12:Ac ; 12:Ac ; Z9-14:Ac ; pheromonal components ; diffusion ; temperature ; wind ; Z9-12:Ac ; 12:Ac ; Z9-14:Ac
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Summary To determine the effect of various factors influencing the emission rate of pheromones from slow release dispensers, laboratory tests were undertaken with two types of rubber (Michelin) and one type of plastic trilaminate (Hercon®) dispenser. The effects of chain length, and the presence of double bonds were tested with three pheromonal compounds, Z9-12: Ac, 12: Ac and Z9-14: Ac impregnated on both types of rubber dispenser. The influences of temperature, wind velocity, humidity and percent loading were also tested. Data obtained indicated that chain length has a greater effect than the presence of a double bond. Amongst the climatic factors tested, wind speed has a greater effect than temperature while humidity has a minimal effect.
    Notizen: Abstract Deux types de diffuseurs en caoutchouc (Michelin) et en plastique polystratifié (Hercon®) sont testés en laboratoire pour étudier quelques aspects des phénomènes de diffusion. Trois composantes phéromonales, le Z9-12: Ac, le 12: Ac et le Z9-14: Ac imprégnées dans ces différents supports servent à détermineer le rôle joué par la longueur de la chaîne de la molécule et la présence de doubles liaisons sur la vitesse de diffusion. L'influence de la température, de la vitesse du vent et de l'humidité est déterminée en cellules climatisées. Parmi les facteurs relatifs à la structure chimique, l'influence de la longueur de la chaîne est prédominante par rapport à la présence d'une double liaison. Parmi les facteurs climatiques, le vent agit plus que la température sur la diffusion, alors que l'humidité paraît secondaire.
    Materialart: Digitale Medien
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 44 (1987), S. 257-262 
    ISSN: 1570-7458
    Schlagwort(e): Heteroptera ; Pyrrhocoris apterus ; adult size ; egg weight ; starvation ; temperature ; pollution ; crowding ; duration of development
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Körpergrösse bei den Imagines eines Wildstammes der Feuerwanze Pyrrhocoris apterus wurde teilweise durch die Veränderlichkeit der Eigrösse determiniert, teilweise auch durch Hungern der Larven, niedrige Temperatur und metabolischen Produkten beeinflusst. Der Effekt letzterer Faktoren stieg mit deren Dauer und war je grösser desto näher sich die Wirkungsperiode zur Imaginalhäutung befand. Unterschiedliche Photoperioden wirkten auf die Körperlänge nicht. Wurden die Larven zwischen der ungünstigen Periode und der Imaginalhäutung noch den optimalen Bedingungen ausgesetzt, kompensierten sich die negativen Einflüsse weitgehend. Zu einer drastischen Verkleinerung der Imagines kam es nur, wenn das letzte Larven-stadium mit Hunger beeinflusst wurde und bis zur Imaginalhäutung keinen Zutritt zum Futter hatte. Minimales Gewicht, wo die Metamorphose der Larven noch möglich war, wurde zu 18 mg festgestellt.
    Notizen: Abstract The determination of body size (length or weight) of teneral adults of Pyrrhocoris apterus L. was investigated. About 50% of size variation was determined already in the egg stage (average egg weight adult length correlations were 0.67 in males and 0.71 in females). During the larval development, starvation, low temperature, and pollution by excreta combined with crowding reduced adult size and usually increased the development length. The effects were directly proportionate to the length of the stress period, and increased with larval age. Photoperiod or intrinsic variation of development time did not affect adult size. The effects of stress were largely compensated when it was followed by a period of compensation growth at optimum conditions. A dramatic reduction of size appeared when last inster larvae starved and moulted to adults without access to food. Average adult weight was then reduced by up to 48%. Threshold weight for adult moulting was 18 mg, being attained after 1–2 day feeding of the last instar.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 26
    ISSN: 1570-7458
    Schlagwort(e): Dacus tryoni ; fruit fly ; frosts ; cold ; survival ; winter ; step ; ramp ; cooling ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé L'aptitude à survivre à une ou plusieurs expositions à des températures inférieures à zéro dépend à la fois de leur sévérité et du laps de temps entre les expositions. L'effet d'une température minimale déterminée dépend de sa valeur, de sa durée et du type de refroidissement: brutal (step) ou progressif (ramp). Les effets de toute température minimale peuvent être exprimés en termes de LE50 (temps nécessaire pour obtenir une mortalité de 50% avec une exposition unique). Lorsque le temps d'application de la température minimale correspond à 35% du LE50, il n'y a pas de mortalité, de même dans le cas de répétitions quotidiennes. Lorsque le minimum est subi pendant 44% du LE50, il provoque environ 14% de mortalité après la première exposition, avec 3% supplémentaire après chaque exposition quotidienne, mais l'augmentation est nulle si l'exposition au froid n'a lieu que tous les 3 jours. Lorsque le minimum est subi pendant 88% de LE50, la mortalité après la première exposition est d'environ 40% et de même importance à chaque nouvelle exposition, même si elles sont espacées de 7 j. Lorsque la durée d'exposition au minimum correspond à 125% et à 150% de LE50, les mortalités sont respectivement d'environ 80% et 100% à la première exposition. La température maximale quotidienne, entre 15 et 25°C, semble avoir peu d'influence sur la mortalité provoquée par des expositions répétées à-5°C. Les mouches d'âges différents résistent de la même façon jusqu'à 6 expositions répétées à-6°C, mais au-delà les mouches âgées sont plus sensibles que les jeunes. Dans la mesure où, dans la nature, la durée d'exposition à la température minimale est connue et où la température dans le sol peut être calculée ou mesurée, ces résultats peuvent permettre d'interpréter la mortalité provoquée par le gel.
    Notizen: Abstract Ability to survive exposure to single or repeated periods at a subzero temperature is related to the temperature experienced, whether it is approached quickly or slowly, the time for which it prevails and the interval between exposures. The severity of any low temperature can be expressed in terms of LE50 (time required to kill 50% of individuals with one exposure). Minima enduring for 35% LE50 do not cause any mortality, even when repeated daily. Minima enduring for 44% LE50 cause ca 14% mortality on the first occurrence but no more if repeated at 3 day intervals, but 3% more per occasion if repeated daily. Minima enduring for 88% LE50 cause ca 40% mortality on first occurrence and an equal amount at each recurrence even if each is 7 days apart. Minima enduring for 125% LE50 and over 150% LE50 cause respectively ca 80% and 100% mortality respectively on first occurrence. The daily maximum temperature (in the range 15°C to 25°C) appears to have little relevance to the mortality caused by a repeated minimum of -5°C. Flies of different ages have a similar ability to survive a repeated minimum of -6°C for up to six exposures, but thereafter old flies are more susceptible than young ones. These results can be related to mortality caused by frosty conditions in the field so long as the time spent at the minimum is known and the temperature on the ground can be measured or calculated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 46 (1988), S. 19-28 
    ISSN: 1570-7458
    Schlagwort(e): Hymenoptera ; Encyrtidae ; parasitoids ; Pseudococcidae ; mealybugs ; Anagyrus pseudococci ; Leptomastix dactylopii ; Leptomastidea abnormis ; temperature ; predicting development ; thresholds ; temperate glasshouses
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé Les vitesses de développement de 3 parasitoïdes de cochenilles ont été étudiées dans les conditions de température de serre, avec thermopériode ou en température constante. En conditions constantes, la vitesse augmente jusqu'à 35°C, mais est létale à 40°C. Avec thermopériode, une thermophase de 40°C peut être tolérée pendant 12 heures. Les vitesses de développement sous thermopériodes pourraient être calculées à partir des données obtenues en conditions constantes, modifiées en fonction des durées respectives des cryophases et thermophases. Une méthode originale est présentée pour obtenir les seuils inférieurs de développement, en utilisant des thermopériodes, et pour calculer les vitesses de développement à températures élevées. Une méthode de régression polynomiale, non vérifiée préalablement, a été utilisée pour prévoir les durées moyennes des développements sous serre. Ces estimations sont beaucoup plus sûres que les prédictions basées sur le concept de degré-jour (Do), lorsque les températures extrêmes durent longtemps, mais en serre chaude elles ne présentent aucune différence significative. De plus, une méthode d'évaluation des 95% d'émergences, a donné de bonnes estimations des premières et dermières émergences en conditions périodiques.
    Notizen: Abstract Developmental rates of three encyrtid mealybug parasitoids were examined under constant, cycling and glasshouse temperatures. Under constant conditions the rate of development increased with rising temperature up to 35°C, but a constant 40°C was lethal. Under cycling conditions, 12 h periods at 40°C could be tolerated. Developmental rates under cycling conditions could be calculated from constant temperature data, by incrementing development on an h/h basis. A new technique was developed to determine the lower thresholds for development, using cycling regimes and to calculate the rates of development over short periods at high temperature. A previously untested polynomial regression technique was used to predict mean developmental periods under glasshouse conditions. These predictions were considerably more accurate than day-degree (Do) predictions when substantial periods at extreme temperatures were involved, but not significantly different from day-degree predictions under ‘hot-house’ conditions. In addition a method was developed to calculate a 95% range for emergence, which gave consistently good estimates of first and last eclosion observed under fluctuating conditions.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 47 (1988), S. 173-182 
    ISSN: 1570-7458
    Schlagwort(e): Bembidion lampros ; Pterostichus cupreus ; Carabidae ; Coleoptera ; behaviour ; temperature ; searching ; consumption ; cereal aphid ; Rhopalosiphum padi ; prey ; density ; barley
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé Les taux maximum de consommation de R. padi L. à différentes températures ont été déterminés au laboratoire chez deux carabes, B. lampros Herbstet P. cupreus L. La consommation moyenne a augmenté avec la température chez les deux espèces, B. lampros consommant un maximum de 15,9 larves des stades 1 à 3 et 9,1 pucerons adultes aptères, à 25°C. P. cupreus a été particulièrement vorace et a consommé 125,3 adultes aptères par jour à 20°C. Le comportement des deux espèces a été observé en filmant en vidéo des carabes à jeun, maintenus à différentes températures constantes, dans des enceintes semées en orge de printemps. Des éléments du comportement, communs aux deux espèces, ont été définis: 1) immabilité, 2) marche et course, 3) recherche, 4) affrontement. P. cupreus a été plus actif à toutes les températures, B. lamprosa été inactif au-dessous de 10°C. La part de temps consacrée à la recherche, le nombre de plantes prospectées, et la vitesse ont augmenté avec la température chez les deux espèces. Dans des enceintes similaires colonisées par R. padi, P. cupreus a significativement augmenté le temps consacré à la recherche dans les enceintes, parallèlement à l'augmentation de la densité des pucerons. Après la découverte d'une colonie de pucerons, P. cupreus escalade et prospecte la plante et ses voisines immédiates; tandis que les plantes des enceintes sans pucerons sont rarement escaladées. B. lampros n'a pas été observé escaladant des plantes d'enceintes avec ou sans pucerons, et il n'a pas accru son temps de prospection en fonction de la densité de pucerons. Les quelques B. lampros qui ont capturé des pucerons l'ont fait lorsque ceux-ci marchaient sur la surface du sol. La discussion a porté sur l'efficacité relative des deux carabes comme prédateurs de R. padi, et les résultats ont été comparés à ceux d'études du même type, menées ailleurs, avec des prédateurs de Sitobion avenae sur blé d'hiver.
    Notizen: Abstract Maximum consumption rates were determined for two carabids, Bembidion lampros Herbst. and Pterostichus cupreus L., feeding on the cereal aphid Rhopalosiphum padi L. at different temperatures in the laboratory. Mean daily consumption increased with increasing temperature for both species, B. lampros consuming a maximum of 16 1–3 instar nymphs and 9 apterous adult aphids at 25°C. P. cupreus was particularly voracious and consumed 125 apterous adult R. padi per day at 20°C. The behaviour of both species was analysed by video filming starved beetles, maintained at different constant temperatures, in arenas sown with spring barley. The behavioural components (1) still; (2) run/walk; (3) search and (4) confrontation were identified and were common to both species. P. cupreus was more active over the temperature range tested; B. lampros was inactive under 10°C. The proportion of time spent searching, number of plants searched, and velocity increased with increasing temperature for both species. When observed in similar arenas seeded with R. padi colonies, individuals of P. cupreus significantly increased their time spent searching in arenas with increasing aphid density. Following discovery of an aphid colony, individuals climbed and searched the host plant and its nearest neighbours. Plants in aphid free arenas were rarely climbed. B. lampros was not observed climbing in either aphid free arenas or in arenas with increasing aphid densities, and did not significantly increase its time spent searching in response to increased prey density. The few B. lampros that found aphids caught them walking on the soil surface. The relative efficiences of these two carabids as predators of R. padi are discussed, and the results are compared with similar studies elsewhere with predators of Sitobion avenae on winter wheat.
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  • 29
    ISSN: 1572-879X
    Schlagwort(e): TiO2 ; heterogeneous photocatalysis ; oxidation ; substituted toluenes ; zeolites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Photocatalytic oxidation of substituted toluenes was investigated on irradiated TiO2 and TiO2 combined with HY15 and HY20 zeolites. In all cases the oxidation occurred in the first step exclusively on either one substituent or the other, but never on both simultaneously. In the presence of a zeolite, photooxidation conversion was higher than that obtained without zeolite.
    Materialart: Digitale Medien
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  • 30
    ISSN: 1572-879X
    Schlagwort(e): Fischer-Tropsch synthesis ; cobalt catalysts ; deactivation ; oxidation ; reduction ; promoters ; rhenium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The influence of water on alumina-supported cobalt catalysts has been studied. The deactivation of supported Co catalysts was studied in a fixed-bed reactor using synthesis gas feeds containing different concentrations of water vapour. Supporting model studies were carried out using H2O/H2 feeds in conjunction with XPS and gravimetry. Rapid deactivation occurs on Re-promoted CO/Al2O3 catalysts when H2/CO/H2O feeds are used, whereas unpromoted CO/Al2O3 shows more stable activity. The results from the gravimetric studies suggest that only a small fraction of the bulk cobalt metal initially present reoxidizes to cobalt oxide during reaction. However, the XPS results indicate significant reoxidation of surface cobalt atoms or highly dispersed cobalt phases, which is likely to be the cause of the observed deactivation. Rhenium is shown to have a marked effect on the extent of reoxidation of alumina-supported cobalt catalysts.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 31
    ISSN: 1572-879X
    Schlagwort(e): support ; cerium ; alumina ; sol-gel ; thermostability ; platinum ; three-way catalyst
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Various CeOx-Al2O3 powders were prepared and the influence of the method of support preparation on the thermostability of the mixed alumina-supported Pt catalysts and on their oxidation of CO was investigated. It was found that the complexing agent-assisted sol-gel method is effective in improving the thermostability of the mixed alumina-supported Pt catalysts. Monolith Pt-Rh three-way catalysts were prepared using these aluminas and other thermostable alumina including Ba. Activity of the catalysts was also investigated after conducting accelerated thermal engine aging in order to test their durability. Under normal operating conditions of the automobile engine, the activity of the Pt-Rh three-way catalyst using the CeOx-Al2O3 support prepared by the complexing agent-assisted sol-gel method is nearly equal to that of the catalyst using the CeOx impregnated onto BaO-Al2O3 powder prepared by the same sol-gel method.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Cellulose 2 (1995), S. 265-272 
    ISSN: 1572-882X
    Schlagwort(e): Hydrogen peroxide ; oxycellulose ; bleaching ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Peroxides are important bleaching agents, industrially, for cellulosic products. They are also used in detergents. Peroxides can degrade cellulose as well as decolorize it and remove stains. Both free radicals and perhydroxyl anions have been suggested as the intermediates in the reactions occurring between cellulosic products and hydrogen peroxide. The proposed mechanisms are reviewed with emphasis primarily on cotton cellulose. Further work is required to establish unequivocally the mechanism of degradation and decolorization of cellulose products.
    Materialart: Digitale Medien
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 43 (1987), S. 95-100 
    ISSN: 1570-7458
    Schlagwort(e): Ilione albiseta ; Pherbellia cinerella ; Diptera ; Sciomyzidae ; larva ; pupa ; temperature ; Lymnaea truncatula ; snails ; biological control
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé L'action de la température a été examinée à 14, 17, 20, 23 et 26°C. Les 2 espèces sont prédatrices de L. truncatula, vecteur de la douve du foie en Irlande, où elle provoque à l'àgriculture une perte évaluée à 10 millions de livres par an. Les données recuellies en conditions contrôlées du laboratoire doivent permettre de définir les conditions optimales pour l'élevage continu de ces espèces. Ceci est indispensable pour évaluer, dans la nature leurs potentialités pour la lutte biologique. Ilione albiseta: C'est à 23°C que le développement des larves de premier et second stades sont les plus brefs; la survie du premier stade est totale à toutes les températures constantes examinées. La durée moyenne du 3ème stade décroît de 104 jours à 17°C jusqu'à 27,5 jours à 26°C. Le taux de survie total est plus élevé à 17°C qu'à 26°C. La durée moyenne de la nymphose diminue quand la température croît, et ceci se produit aussi à la température ambiante extérieure. On réduit de moitié la durée du développement de l'éclosion de l'oeuf à l'apparition de l'adulte, entre la nature et le laboratoire, en utilisant respectivement: 23°, 17° et 26°C pour les premier et second stades, le troisième stade, la nymphé. Cela devrait aider à multiplier la souche pour la lutte biologique. Pherbellia cinerella: Avec élévation de la température la durée du développement larvaire diminue, mais aussi le nombre de larves parvenant à la pupaison (100% à 14° et 33,3% à 26°C). La nymphose tendait à être plus brève aux températures les plus élevées.
    Notizen: Abstract The duration of larval and pupal stages of two species of predatory flies was investigated at five constant temperatures. Ilione albiseta (Scopoli): Mean duration of first and second instars was shortest at 23°C and there was 100% survival of first instar larvae at all temperatures. Mean third instar larval duration decreased from 104 days at 17°C to 27.5 days at 26°C. Total percentage larval survival was greatest at 17°C and least at 26°C. Mean pupal duration decreased as temperature increased and this occurred also under outdoor conditions. Pherbellia cinerella (Fallén): As temperature increased mean larval duration decreased but the percentage of larvae pupating also decreased (100% at 14°C, 33.3% at 26°C). There was a trend for shorter mean pupal durations at higher temperatures.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 46 (1988), S. 47-54 
    ISSN: 1570-7458
    Schlagwort(e): Coleoptera ; Curculionidae ; Sitophilus ; S. oryzae ; S. zeamais ; rice weevil ; maize weevil ; geographical strains ; digestion ; amylase ; diet ; barley ; corn ; maize ; rice ; wheat ; amylase inhibitors
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé La transformation de rang des valeur d'activité spécifique de l'α-amylase de 4 souches de S. oryzae et de 4 souches de S. zeamais montre que les niveaux les plus élevés de ces enzymes prédominantes s'observent chez les adultes nourris d'orge mondé ou de riz brun á grains longs. Des niveaux intermédiaires d'activité ont été obtenus chez les insectes élevés sur maïs jaune, et les niveaux les plus faibles chez ceux élevés sur blé. Bien que les extraits préparés à partir d'orge présentent une activité inhibitrice de deux isoamylases purifiées de S. oryzae, les niveaux des inhibiteurs naturels α-amylase de ces deux enzymes sont environ respectivement 2,2 et 6,1 fois plus concentrés dans le blé. L'ingestion de ces inhibiteurs d'amylase et la formation d'un complexe enzyme inactive/inhibiteur avec l'amylase secrétée antérieurement, peut rendre compte de la plus faible activité de l'amylase chez les charançons consommant du blé. Le niveau d'amylase de S. oryzae est 2 fois plus élevé que celui de S. zeamais pour toutes les souches élevées sur un régime donné. Des niveaux d'activité significativement différents ont été trouvés suivant les souches pour chacune des deux espèces. Puisque l'amylase est la principale hydrolase digestive de ces espèces, l'intensité de la modification des teneurs en amylase par la consommation de céréales peut indiquer leur adéquation comme hôtes potentiels.
    Notizen: Abstract Rank transformation of specific activity values of α-amylase across four strains of Sitophilus oryzae (L.) and four strains of S. zeamais Motschulsky indicates that levels of these predominant enzymes are highest in adults feeding on hulled barley or long-grain brown rice. Intermediate activity levels are found in weevils feeding on yellow corn (maize) and lowest levels are found in wheat-fed weevils. Although extracts prepared from barley contain inhibitory activity against two purified isoamylases from S. oryzae, levels of the naturally-occurring α-amylase inhibitors against these two enzymes are about 2.2-fold and 6.1-fold, respectively, more concentrated in wheat. Ingestion of these amylase inhibitors and formation of an inactive enzyme:inhibitor complex with previously secreted amylase may account for the lower activity of amylase in weevils of both species feeding on wheat. Amylase levels across all strains feeding on a given diet are about 2-fold higher in S. oryzae than in S. zeamais. Significant differences in activity levels were also found between strains in both species. Since α-amylase is a predominant digestive hydrolase in these species, the degree to which cereal diets affect amylase levels may indicate their suitability as potential hosts.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Archive of applied mechanics 67 (1997), S. 331-338 
    ISSN: 1432-0681
    Schlagwort(e): Key words frictional heating ; wear ; contact pressure ; temperature ; brake system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Summary A transient contact problem with frictional heating and wear for two nonuniform sliding half-spaces is considered. One of the two half-spaces is assumed to be slightly curved to give a Hertzian initial pressure distribution: the other is a rigid nonconductor. Under the assumption that the contact pressure distribution could be described by Hertz formulas during all the process of interaction, the problem is formulated in terms of one integral equation of Volterra type with unknown radius of contact area. A numerical solution of this equation is obtained using a piecewise-constant presentation of an unknown function. The influence of operating parameters on the contact temperature and the radius of the contact area is studied.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    European journal of nutrition 36 (1997), S. 336-339 
    ISSN: 1436-6215
    Schlagwort(e): Amino acids ; protein ; metabolism ; meal feeding ; oxidation ; breath test ; Aminosäuren ; Protein ; Stoffwechsel ; Fütterung ; Oxidation ; Atemtest
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die aktuellen Mengen an freien Aminosäuren im Blut reichen nur aus, um die Ganzkörper-Proteinsynthese für einige Minuten aufrecht zu erhalten. Das zeigt, daß die freien Aminosäurenkonzentrationen in der Zirkulation klein und konstant gehalten werden im Vergleich zu den Mengen der Aminosäuren, die täglich aufgenommen und über die Körperproteine umgesetzt werden. Das Verschwinden der Aminosäuren exogenen oder endogenen Ursprungs aus dem freien Aminosäuren-Pool, findet hauptsächlich durch die Proteinsynthese und den Aminosäurenabbau statt. Die Partitionierung der Nahrungs-Aminosäuren zwischen diesen beiden Prozessen im Kurzzeitbereich werden als bedeutsam für die Ökonomie der Ganzkörper-Aminosäuren angesehen. Eine Verbesserung der Aminosäurenökonomie könnte durch solche nutritiven Maßnahmen erreicht werden, welche die Clearance der Nahrungsaminosäuren durch die Proteinsynthese anstelle des Aminosäurenabbaus begünstigen. Diese nutritiven Maßnahmen sollten sich an den „Schwellenwerten“ des Abbaus der individuellen Aminosäuren orientieren.
    Notizen: Summary Actual amounts of free amino acids in the blood are sufficient to support whole body protein synthesis for some minutes only. This indicates that the levels of free amino acids in the circulation are kept small and constant relative to the amounts of amino acids supplied by daily intake and turnover of body proteins. The clearance of the amino acids originating from either endogenous or exogenous sources is mainly due to protein synthesis and metabolic degradation. The partitioning of dietary amino acids between these processes, on the short term, is supposed to play an important role in whole body amino acid economy. Therefore whole body amino acid economy could be improved by nutritional measures that favour the clearance of dietary amino acids by protein synthesis instead of by metabolic degradation. These nutritional measures should to be focused on threshold values for metabolic degradation of individual amino acids.
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  • 37
    ISSN: 1436-5073
    Schlagwort(e): silicon carbide ; surface ; oxidation ; FT-IR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The surface of ultrafine silicon carbide powders, prepared by a laser-driven gas-phase reaction was studied as a self-supporting disk by FT infrared spectrometry. After evacuation silicon and carbon atoms located at the surface give rise tovSiH andvCH bands. When heating in oxygen, subtraction spectra showed features which could be strictly correlated with a progressive growth of a silica layer: SiH and CH bands were replaced by new bands characteristic of amorphous silica and the typical band of surface silanol groups on silica (3745 cm−1) simultaneously increased.
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  • 38
    ISSN: 1436-5073
    Schlagwort(e): oxidation ; titanium aluminide ; SNMS ; niobium effect ; oxygen tracer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The oxidation behaviour of γ-TiAl based alloys with different Nb contents (2–10 At.%) was investigated in air and in argon-20% oxygen at 900 °C using thermogravimetric analysis. The oxide scales were characterized by a combination of optical microscopy, SEM/EDX and X-ray diffraction analyses. Although in all studied cases the presence of niobium improves the oxidation resistance of γ-TiAl, the oxidation kinetics, scale morphology and composition in air differed strongly from that in argon-oxygen. In air the oxidation resistance increases with increasing niobium-content. In Ar/O2 the niobium dependence is far more complex because internal oxidation occurs which is favoured by the presence of niobium. SNMS analysis revealed that the differences in behaviour in the two atmospheres are related to the formation of Ti-rich nitride at the scale/alloy interface during air oxidation. The positive effect of niobium on the oxidation resistance of γ-TiAl is mainly caused by a decrease of the transport processes in the heterogeneous TiO2/Al2O3-surface scale. Nitride formation and/or niobium enrichment at the scale/alloy interface also affect the oxidation behaviour, however these factors are believed to be the result of the decreased transport processes rather than the main reason for the niobium effect.
    Materialart: Digitale Medien
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Microchimica acta 125 (1997), S. 401-406 
    ISSN: 1436-5073
    Schlagwort(e): fullerenes ; intercalation ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The investigation of structural and electronic properties of the novel family of fullerenes depends on the existence of pure reference materials. Sublimation of the van-der Waals solids is a suitable purification method. Little attention has been paid to the question about the air stability of such sublimed samples in form of crystals or thin films. A combination of thermal desorption spectroscopy, thermal analysis and diffuse reflectance FT-IR spectroscopy is used to show the extent to which oxygen from dry air is intercalated into fullerenes and which detrimental reactivity occurs from attempts to thermally remove („nneal”) air-exposed samples. The conclusion is that any fullerene sample exposed to air will be transformed in part into a polymeric non-fullerene carbon upon thermal treatment to above 400 K irrespective of its initial purity.
    Materialart: Digitale Medien
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  • 40
    ISSN: 1573-0417
    Schlagwort(e): diatoms ; temperature ; climatic change ; paleoclimate proxies ; canonical correspondence analysis ; weighted-averaging ; Yukon ; Northwest Territories
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract We identified, enumerated, and interpreted the diatom assemblages preserved in the surface sediments of 59 lakes located between Whitehorse in the Yukon and Tuktoyaktuk in the Northwest Territories (Canada). The lakes are distributed along a latitudinal gradient that includes several ecoclimatic zones. It also spans large gradients in limnological variables. Thus, the study lakes are ideal for environmental calibration of modern diatom assemblages. Canonical correspondence analysis, with forward selection and Monte Carlo permutation tests, showed that maximum lake depth and summer surface-water temperature were the two environmental variables that accounted for most of the variance in the diatom data. The concentrations of sodium and calcium were also important explanatory variables. Using weighted-averaging regression and calibration techniques, we developed a predictive statistical model to infer lake surface-water temperature, and we evaluated the feasibility of using diatoms as paleoclimate proxies. This model may be used to derive paleotemperature inferences from fossil diatom assemblages at appropriate sites in the western Canadian Arctic.
    Materialart: Digitale Medien
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  • 41
    ISSN: 1573-0832
    Schlagwort(e): Anthracnose ; guava ; Colletotrichum glososporioides ; temperature ; free moisture ; inoculum density
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The influence of environmental factors (temperature and humidity), inoculum density on infection by Colletotrichum glososporioides and development of anthracnose lesions were determined on uninjured, sand-injured and punctured fruits. The optical temperature for severe infection was 30 °C, whereas the disease incidence was less at 20 and 35 °C. Inoculated guavas that received 1–60 h of continuous free moisture developed lesions, but the disease was minimal (0–7%) after 1–6 h free moisture. Infection rates of uninjured, sand-injured and punctured fruits receiving 60 h of free moisture were 34, 70 and 100%, respectively. Disease incidence increased as inoculum density increased from 101 to 106 conidia/ml. In field conditions, the development of anthracnose lesions was greater on punctured guavas than on uninjured or sand-injured ones, in both rainy and winter seasons. In general, the number of lesions was highest in sand-injured fruits, followed by punctured and uninjured fruits. In rainy season the number of lesions on injured and uninjured fruits was greater than similarly treated guavas in winter.
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    Standort Signatur Erwartet Verfügbarkeit
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Mycopathologia 139 (1997), S. 151-155 
    ISSN: 1573-0832
    Schlagwort(e): Antagonism ; biocontrol ; ginger ; postharvest rot ; Sclerotium rolfsii ; Trichoderma ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Sclerotium rolfsii is a destructive soil-borne and postharvest plant pathogen. Use of the antagonistic fungus Trichoderma sp. has been earlier reported by us to successfully control this pathogen under postharvest conditions. In the present paper we report on the effects of temperature on the growth and biocontrol potential of Trichoderma sp. on S. rolfsii. Experimental results indicated that S. rolfsii and Trichoderma sp. have different temperature optima for growth: 30–35 °C for the pathogen and 25–30 °C for the antagonist. In dual culture, Trichoderma overgrew S. rolfsii at 25 °C and 30 °C, but at 35 °C and 37 °C, S. rolfsii overgrew the colony of Trichoderma. Trichoderma produced higher concentration of fungitoxic metabolites in broth culture at higher temperatures. In bioassays using ginger slices and whole rhizomes, it has been demonstrated that Trichoderma is not very effective in suppressing S. rolfsii at temperatures above 30 °C. In light of these results, possible mechanisms of biocontrol of S. rolfsii as a postharvest pathogen has been discussed. Storage temperature has been suggested as a critical factor in biocontrol of S. rolfsii.
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  • 43
    ISSN: 1573-0832
    Schlagwort(e): odors ; volatiles ; microflora ; fungi ; wheat ; seasonality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The fungal odor compounds 3-methyl-l-butanol, l-octen-3-ol and 3-octanone were monitored in nine experimental bins in Winnipeg, Manitoba containing a hard red spring wheat during the autumn, winter and summer seasons of 1984–85. Quality changes were associated with seed-borne microflora and moisture content in both ventilated and non-ventilated bins containing wheat of 15.6 and 18.2% initial moisture content. All three odor compounds occurred in considerably greater amounts in bulk wheat in non-ventilated than in ventilated bins, particularly in those with wheat having 18.2% moisture content. The presence of these compounds usually coincided with infection of the seeds by the fungi Alternaria alternata (Fr.) Keissler, Aspergillus repens DeBarry, A. versicolor (Vuill.) Tiraboschi, Penicillium crustosum Thom, P. oxalicum Currie and Thom, P. aurantiogriseum Dierckx, and P. citrinum Thom. High production of all three odor compounds in damp wheat stored in non-ventilated bins was associated with heavy fungal infection of the seeds and reduction in seed germinability. High initial moisture content of the harvested grain accelerated the production of all three fungal volatiles in non-ventilated bins.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 12 (1987), S. 201-218 
    ISSN: 1573-0867
    Schlagwort(e): relative effectiveness ; apatites ; wheat ; initial and residual effectiveness ; bicarbonate extractable phosphorus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The initial and residual agronomic effectiveness of six apatite rock phosphates from India, one from the USA (North Carolina) and one from Australia (Queensland) were evaluated in a pot trial with wheat on a lateritic soil. All of the Indian rock phosphates were very poor sources of phosphorus. Values of initial effectiveness relative to monocalcium phosphate ranged from 〈 0.0001 to 0.02 and from 〈 0.0001 to 0.008 for measurements based on yield and phosphorus uptake respectively. The residual effectiveness relative to freshly applied monocalcium phosphate was determined by growing a second crop on the fertilized soils. The effectiveness of the Indian rock phosphates remained very low ranging from 〈 0.0001 to 0.002 and from 〈 0.0001 to 0.0004 for yield and phosphorus uptake respectively. Queensland and North Carolina rock phosphates were much superior to the Indian sources with initial effectiveness values in terms of yield of 0.08 and 0.37 and residual effectiveness values of 0.02 and 0.15 respectively. For each crop there was a single relationship between yield and phosphorus uptake (i.e. internal efficiency) for all phosphorus sources showing that variations in yield response were due solely to differences in phosphorus availability. Sodium bicarbonate extractable phosphorus values for fertilized soils sampled shortly after fertilization were not predictive of yield unless different calibration curves were used for the different phosphorus fertilizers.
    Materialart: Digitale Medien
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 12 (1987), S. 255-261 
    ISSN: 1573-0867
    Schlagwort(e): nitrification ; nitrification inhibitor ; fertilizer N ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The transformations of urea, ammonium sulfate and dicyandiamide (DCD) were studied in an Inceptisol and three Andisols from Costa Rica, considering the influence of temperature and DCD as a nitrification inhibitor. Nitrification was very slow with or without DCD in the strongly acid Inceptisol. A higher urea dose resulting in higher pH was well nitrified without DCD and appreciably retarded by DCD. In Andisols nitrification was retarded as long as a higher DCD level existed. Higher temperatures accelerated the DCD-breakdown and were followed by a quicker nitrification. The decomposition of DCD was slower compared with the Inceptisol. According to these experiments DCD is suitable as a nitrification inhibitor in tropical soils.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 13 (1987), S. 191-197 
    ISSN: 1573-0867
    Schlagwort(e): chemical extractants ; critical levels ; semi-arid region soils ; wheat ; zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract To find critical tissue levels of Zn for wheat, and to evaluate various chemical extractants, a screen-house experiment was conducted on 21 diverse soils representing semi-arid regions in Haryana State, India. The extractants differed in the amounts of Zn extracted and the order was: 0.1 N HC1 〉 EDTA-NH4OAc 〉 EDTA-(NH4)2CO3 〉 DTPA + CaCl2. The amounts (mg kg−1) of extractable Zn associated with a yield reduction of 20% were: DTPA + CaCl2, 0.60; EDTA — (NH4)2CO3, 0.80; EDTA-NH4OAc, 0.92 and 0.1 N HCl, 1.20. The corresponding critical Zn concentration in ten weeks old plants was found to be 17 mg gm−1. The DTPA + CaCl2 method gave the best correlation (r = 0.85) between extracted Zn and Bray's per cent yield. It is recommended for assessing Zn status of soils of semi-arid region.
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 13 (1987), S. 255-267 
    ISSN: 1573-0867
    Schlagwort(e): urea ; ammonium nitrate ; model ; temperature ; rainfall ; grassland
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Direct and residual effects of urea and calcium ammonium nitrate (CAN) on dry matter (DM) response were measured at a total of 12 application times in early spring over three years. The variation in the direct effect was described by models that included temperature and long-term rainfall for CAN and, additionally, short-term rainfall for urea. The operative temperature was the accumulated mean daily air temperature for combined intervals pre-application and postapplication of N. The effect of rainfall was apparent only when the data were adjusted for temperature. Simulation studies with the models indicated that, although the influence of temperature was dominant, rainfall modified it strongly in terms of the relative efficiencies of the two N sources and the magnitude of response. For instance, the temperature-induced increase in DM response to urea between cold and normal years was 402 kg ha−1 for a specified period, whereas differences between dry and wet years were decreases of 166 and 259 kg ha−1 in the case of urea and CAN, respectively. Short-term rainfall had a positive effect on response to urea. The experimental values varied widely both between and within years. The direct effect of the application of urea at 50 kg N ha−1 varied from 0 to 750 kg DM ha−1, and the residual effect varied from 0 to 1620 kg DM ha−1. The corresponding values for apparent N recovery varied from 0.1 to 45% and from 7 to 68%, respectively. The efficiency of urea was comparable to, and in instances better than, CAN.
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 147-151 
    ISSN: 1573-0867
    Schlagwort(e): time of zinc application ; wheat ; zinc sulphate ; zinc oxide ; zinc uptake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Field experiments with wheat were conducted for two years on flood plain alluvial soils to study the effectiveness of soil application of zinc sulphate and zinc oxide at 0, 15, 45, 60, 75 and 90 days after sowing. Yield and zinc uptake of wheat increased significantly with the application of zinc. Delaying the application of both zinc sulphate and zinc oxide up to 45 days of sowing did not adversly affect the zinc nutrition of wheat. However, delaying the application for 75 or 90 days after sowing eliminated the response. Zinc sulphate, when applied within 60 days of sowing performed better than zinc oxide. In a laboratory study, zinc sulphate maintained a higher level of zinc in the soil solution than zinc oxide at least over a 3-week period.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 137-146 
    ISSN: 1573-0867
    Schlagwort(e): Ammonium-nitrate-potassium interaction ; accumulation of reduced nitrogen ; wheat ; nitrification inhibitor ; grain ; stover
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A greenhouse experiment with wheat in 3L pots filled with a sandy loam soil in a factorial design was conducted to determine the effect of potassium on nitrogen utilization. Nitrogen was applied in three NH4-N/NO3-N ratios, 0/100, 25/75 and 50/50, at three levels: 0.75, 1.50 and 3.00gN/pot, and potassium was applied at three levels: 0, 0.5 and 1.0gK/pot. The higher levels of nitrate nitrogen with or without potassium reduced dry matter yields drastically, while the same levels of a NH4-N/NO3-N mixture of 50/50 with applied potassium reduced yields only slightly. Highest grain yield and total yield were obtained with a 25/75 mixture of ammonium/nitrate nitrogen with added potassium. Potassium addition to soil increased the utilization of nitrogen fertilizers, particularly when the ratio of ammonium to nitrate was increased. The highest uptake of reduced nitrogen was at the highest level of the ammonium to nitrate nitrogen ratio (50/50) when potassium was applied. Tillering was enhanced by an increased ammonium ratio in the nitrogen mixture, and by potassium.
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  • 50
    ISSN: 1573-0867
    Schlagwort(e): farmyard manure ; maize ; nitrogen ; phosphorus ; rice ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Field experiments with rice-wheat rotation were conducted during five consecutive years on a coarse-textured low organic matter soil. By amending the soil with 12t FYM ha−1, the yield of wetland rice in the absence of fertilizers was increased by 32 per cent. Application of 80 kg N ha−1 as urea could increase the grain yield of rice equivalent to 120 kg N ha−1 on the unamended soil. Although the soil under test was low in Olsen's P, rice did not respond to the application of phosphorus on both amended and unamended soils. For producing equivalent grain yield, fertilizer requirement of maize grown on soils amended with 6 and 12 t FYM ha−1 could be reduced, respectively to 50 and 25 per cent of the dose recommended for unamended soil (120 kg N + 26.2 kg P + 25 kg K ha−1). Grain yield of wheat grown after rice on soils amended with FYM was significantly higher than that obtained on unamended soil. In contrast, grain yield of wheat which followed maize did not differ significantly on amended or unamended soils.
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  • 51
    ISSN: 1573-0867
    Schlagwort(e): 15N ; non-nod beans ; quantification of N2 fixation ; reference crops ; simulation technique ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A technique for the application of the15N isotope dilution technique for the quantification of plant associated biological nitrogen fixation (BNF) was tested and applied to quantify the BNF contribution to two genotypes ofPhaseolus vulgaris. The technique makes use of sequential measurements of the15N enrichment of soil mineral N, and the uptake of labelled N by the “N2-fixing” plant, to simulate its uptake of soil N (the “soil to plant simulation” technique). The test was made with two non-N2-fixing crops (non-nodulating beans and wheat) and two bean genotypes (PR 923450 and Puebla 152), at two levels of N fertilizer addition (10 and 40 kg N ha−1), to compare the actual N uptake with that simulated from the soil and crop15N data. The simulation of the soil N uptake by the non-nod bean crop using this “soil to plant simulation” technique underestimated by 20 to 30% the true N uptake, suggesting that the mineral N extracted from soil samples taken from the 0–15cm layer had a higher15N enrichment than that N sampled by the roots of this crop. In the case of the wheat crop the simulation resulted in a much greater underestimation of actual N uptake. In general the results using this technique suggested that BNF inputs to the bean cultivars was higher than would be expected from the nodulation and acetylene reduction data, except for the early PR beans in the 40 kg N ha−1 treatment. In this case the total N and simulated soil N accumulation were well matched suggesting no BNF inputs. An allied technique (the “plant to plant simulation technique”) was proposed where the15N enrichrnent of soil mineral N was simulated from the data for total N and labelled N accumulation taken from sequential harvests of either of the non-N2 -fixing control crops. This was then utilized in combination with the labelled N uptake data of the other crop to simulate its soil N uptake. However, the results using either technique indicated that the wheat and non-nod or nodulating beans exploited pools of N in the soil with completely different15N enrichments probably due to differences in exploitation of the soil N with depth.
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 45 (1995), S. 209-215 
    ISSN: 1573-0867
    Schlagwort(e): climate ; fertilizer recovery ; 15N fertilizer ; precipitation-evaporation quotient ; soil ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Data was assembled from experiments on the fate of15N-labelled fertilizer applied to wheat (Triticum spp.) grown in different parts of the world. These data were then ranked according to the annual precipitation-evaporation quotient for each experimental location calculated from the average long-term values of precipitation and potential evaporation. Percentage recovery of15N fertilizer in crop and soil varied with location in accordance with the precipitation-evaporation quotient. In humid environments more15N fertilizer was recovered in the crop than in the soil, while in dry environments more15N fertilizer was recovered in the soil than in the crop. Irrespective of climatic differences between locations 20% (on average) of the15N fertilizer applied to wheat crops was unaccounted for at harvest. Most of the15N fertilizer remaining in the soil was found in the 0–30 cm layer. The most likely explanation of these differences is that wheat grown in dry environments has a greater root:shoot ratio than wheat grown in humid environments and, further, that the residue of dryland crops have higher C/N ratios. Both factors could contribute to the greater recovery of15N fertilizer in the soil in dry environments than in humid ones.
    Materialart: Digitale Medien
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  • 53
    ISSN: 1573-0867
    Schlagwort(e): millet ; sorghum ; rice ; maize ; wheat ; nutrient harvest index ; post-anthesis nutrient uptake ; recovery fraction ; simulation modelling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In land use plans, fertilizer recommendations are indispensable to avoid soil nutrient depletion or soil water pollution. Nutrient relations of five cereals have been evaluated on the basis of a literature review with the aim of arriving at such fertilizer recommendations at regional level. Nutrients considered were nitrogen, phosphorus and potassium for millet, sorghum, maize, rice and wheat. The relevant nutrient relations are fertilizer nutrient application to nutrient uptake, and nutrient uptake to crop yield. In addition, post-anthesis nutrient uptake is considered. Subsequently, obtained results are used in simulation modelling exercises to calculate the time required to attain an equilibrium nutrient balance and to investigate the effect of erosion control and straw recycling. Although fertilizer requirements could be assessed for each of the five cereals, monitoring of nutrient supply from natural sources remains necessary. Moreover, research on fertilizer use should focus on improvement of fertilizer recoveries and multiperiod models for both N and P uptakes by crops to allow quantitative land use planning where the time scale is included.
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 44 (1995), S. 217-223 
    ISSN: 1573-0867
    Schlagwort(e): foliar fertilizer ; nitrate ; potassium ; urea ; wheat ; yield
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Winter wheat crops were grown with ostensibly adequate supplies of all soil nutrients in 1990 and 1991 with the aim of testing if late foliar supplements of K and N, applied at key development stages, could improve grain yield and grain N content. Foliar sprays of KNO3 solution, supplying up to 40 kg K ha−1 in total, at flag leaf unfolded, inflorescence completed and the watery-ripe stage of grain filling, had no effect on yield, yield components or grain N. Urea, supplying 40 kg N ha−1 at flag leaf unfolded, had no effects on grain yield and grain N in 1990, but in 1991 grain N was increased by 0.14% whilst yield was reduced by up to 0.6 t ha−1. Urea scorched flag leaf tips in both years. In 1990, the spring was very dry and foliar supplements might have been expected to have had an effect, but on this highly fertile soil all crop K and N requirements were met from the soil.
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 165-176 
    ISSN: 1573-0867
    Schlagwort(e): Low-grade phosphate rock ; acid extracts ; P fertiliser ; available P ; wheat ; soil pH
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Low grade phosphate rock (PR), containing high amounts of oxides of iron and aluminium is neither suitable for fertiliser production nor useful for direct application to annual crops. The fertiliser effectiveness of P extracted by H2SO4 from a low-grade phosphate rock, PR (Christmas Island C-grade PR) was evaluated for wheat (Triticum aestivum L.) on a calcareous loam (pH 8.4) and a non-calcareous loam (pH 6.9) in field and glasshouse experiments. Superphosphate was used to compare the performance of the acid extracts of PR. In the non-calcareous loam soil, crop establishment and yield were significantly reduced by the acid extracts of PR due to increased acidity. In the calcareous soil, however, the acid extracts of PR performed as well as superphosphate; similar or even higher crop yields were obtained with the former, especially when applied near the seed. The acid extracts of low-grade PR may, therefore, have a role in calcareous soils, where the extract can be applied directly or added in the irrigation waters to supply P to crops.
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 251-266 
    ISSN: 1573-0867
    Schlagwort(e): Zinc ; controlled-release ; diffusion ; pH ; temperature ; phosphate ; clay ; sand ; moisture content
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The emission and movement of zinc from planar arrangements of controlled-release (C.R.) thermoplastic matrix zinc fertilizer formulations was studied in cylindrical diffusion cells packed with a clay or a sand. The influences of a number of soil characteristics known to affect zinc diffusion were also investigated. Zinc emission was initially (over 2 days) very rapid. The rate declined markedly thereafter. Morphologically distinct C.R. zinc formulations released zinc at different rates. Zinc moved appreciably and consistently further in the sand than in the clay. Of the soil characteristics studied, increasing phosphate levels had no effect upon zinc emission or mobility in either soil. Increasing pH in the sand did not affect zinc emission, but decreased zinc mobility. Conversely, in the two soils, increasing temperature stimulated zinc emission, but had little influence on zinc mobility. At higher water contents, zinc release was increased in both soils. However, zinc movement was only increased in the sand.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 42 (1995), S. 159-163 
    ISSN: 1573-0867
    Schlagwort(e): nitrous oxide ; tropical soils ; agriculture ; N availability ; temperature ; soil water content
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract N2O emission rates seem to be higher from soils in warm climates than from soils in temperate climates. Warm and moist conditions promote microbial processes that generate N2O. Clearance of tropical forests enhances N2O formation, but emission measurements from other agricultural operations in the tropics are few. Limiting fertilizer application to recommended rates applied at appropriate times and avoiding fallow land wherever practical serves to limit N2O emissions. More specific advice for agriculture in warm climates requires further studies.
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Mycopathologia 103 (1988), S. 147-151 
    ISSN: 1573-0832
    Schlagwort(e): Ceratocystis ; DNA ; mitochondria ; restriction profiles ; Sporothrix
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Restriction profiles by HaeIII of mitochondrial DNA were studied for classification and distinction of Sporothrix schenckii (100 strains), S. schenckii var. luriei (1), S. curviconia (1), S. inflata (7), Ceratocystis stenoceras (17) and C. minor (7). These 6 species showed unique restriction profiles which could be discriminated from each other. S. schenckii was further separable into 11 types, S. inflata into 4 types, C. stenoceras into 4 types and C. minor into 7 types based on restriction profile heterogeneity.
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 16 (1988), S. 137-155 
    ISSN: 1573-0867
    Schlagwort(e): Superphosphate ; rock phosphate ; wheat ; oats ; barley ; field experiment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Nine soil tests for phosphate were evaluated for predicting the yield and P content of wheat, barley and oats grown on a sandy soil in Western Australia: Olsen, modified Olsen 1 (soil:solution ratio 1:5), modified Olsen 2 (soil:solution ratio 1:50), Colwell, Bray 1, Bray 2, modified Bray 2T (shaking time 10 minutes), modified Bray 2C (pH 3.7) and lactate. The soil had been fertilized 5 years previously with 20 levels each of superphosphate (OSP, range 0 to 400 kg P ha−1) and Queensland rock phosphate (QRP, range 0 to 20 000 kg P ha−1). For each species and fertilizer taken separately, all the tests, except for lactate, gave a good prediction of yield. When data for OSP and QRP were pooled, Bray 2 and modified Bray 2T tests were unsatisfactory predictors of both yield and P content. A linear relationship (P 〈 0.05) between mean soil tests value (χ) and the standard deviation (σ χ ) of the test value was observed for each soil test. For QRP, the results for lactate were the most variable (i.e.σχ/χ was greatest) followed by modified Olsen 2 〉 Bray 1 〉 Bray 2 〉 Olsen 〉 modified Bray 2C 〉 modified Olsen 1 〉 modified Bray 2T 〉 Colwell. The order for OSP fertilized soil was Bray 1 〉 modified Bray 2T 〉 Bray 2 〉 Olsen 〉 Colwell 〉 modified Bray 2C 〉 modified Olsen 1 〉 lactate 〉 modified Olsen 2. For combined OSP and QRP data, the results of the Olsen 1 and Colwell extractions were the least variable. Errors in the prediction of yield (σ Y ) for all crops resulting from an error in soil test values (σχ) were calculated. For OSP-fertilized soil variability in values for the Bray-1 test provided the highest error (about 16%) in the prediction of the yield, followed by Bray 2 (12%) 〉 Bray 2T (10%) 〉 Olsen (8%) 〉 Colwell (7%) 〉 modified Bray 2C (6%) 〉 lactate (4%). Maximum error was at yields of about 65% of maximum yield. For soil fertilized with QRP, lactate provided the highest error (about 10%) in the prediction of yield, followed by the other tests (〈 6%). Maximum error was at yields of about 35% of maximum yield. The Colwell soil test gave the most accurate overall prediction of yield for both fertilizers.
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 49 (1997), S. 91-95 
    ISSN: 1573-0867
    Schlagwort(e): greenhouse effect ; land use ; methane ; oxidation ; soils
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Intact core samples from soils with different textures and land use were tested for their capacity to oxidise methane. The soil cores were taken from arable land, grassland and forest. It was found that coarse textured soils (6.74–16.38 µg CH4 m-2 h-1) showed a higher methane uptake rate than fine textured soils (4.66–5.34 µg CH4 m-2 h-1). Increasing soil tortuosity was thought to reduce the methane oxidation rate in fine textured soils. The oxidation rate of forest soils (16.32–16.38 µg CH4 m-2 h-1), even with a pH below 4.5, was very pronounced and higher than arable land (11.40–14.47 µg CH4 m-2 h-1) and grassland (6.74–9.30 µg CH4 m-2 h-1). Within the same textural class arable land showed a faster methane uptake rate than grassland. In grassland with a fine texture, even methane production was observed. Nitrogen availability and turnover in these land use systems were thought to cause the different oxidation rates. Decreasing the moisture content slowed down the oxidation rate in all soils. This could be caused by an increased N turnover and a starvation of the methanotrophic bacteria.
    Materialart: Digitale Medien
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 49 (1997), S. 59-70 
    ISSN: 1573-0867
    Schlagwort(e): land use ; methane ; nitrogen fertilizer ; oxidation ; soil
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Aerobic soils are an important sink for methane (CH4) contributing up to 15% of annual global CH4 destruction. However, the sink strength is significantly affected by land management, nitrogen (N) fertilizers and acidity. We tested these effects on samples taken from the Broadbalk Continuous Wheat, Park Grass permanent grassland and Broadbalk and Geescroft Wilderness experiments at Rothamsted. The rates of uptake from the atmosphere of both enhanced (10 ppmv) and ambient (2 ppmv) concentrations of CH4 were measured in laboratory incubations of soil cores under controlled conditions. The most rapid rates of uptake were measured in soil from deciduous woodland at pH 7 (measured in water); acidic (pH 4) woodland soil showed no net CH4 oxidation. While disturbance of the cores used in the experiments did not affect the rate of CH4 uptake, extended (150 years) cultivation of land for arable crops reduced uptake rate by 85% compared to that in the soil under calcareous woodland. The long-term application of ammonium- (NH4) based fertilizer, but not nitrate- (NO3) based fertilizer, completely inhibited CH4 uptake, but the application for the same period of farmyard manure that contained more N than the fertilizer had no inhibitory effect. Although the effects of agricultural practice on the oxidation of CH4 in soil are significant, the differences in oxidation rates between land use types are even greater. The likely effects of forest clearance, agricultural intensification and anthropogenic emissions of CH4 over the last 2500 years have been estimated for the United Kingdom. The calculations indicate that 54% of the current CH4 uptake by UK soils is the result of increased CH4 mixing ratio. They also indicate that land use change has decreased the potential sink strength by 62% or 37 kt CH4 g-1. In countries with much larger land areas than the UK, such as China, aerobic soil is likely to be a more significant factor in calculating net fluxes of CH4. It is important that the impacts of different agricultural managements and land use systems are understood and quantified so that the best possible estimate of CH4 sinks is calculated for comparison with sources.
    Materialart: Digitale Medien
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 45 (1995), S. 163-167 
    ISSN: 1573-0867
    Schlagwort(e): Basal dressing ; Se-enriched fertilizers ; Se-uptake ; soil texture ; top-dressing ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A multisite field experiment was conducted to study the effect of topdressed Se-enriched Ca(NO3)2 (CN) and basal applied NPK on the selenium (Se) concentration in spring wheat (Triticum aestivum L.). Selenium was applied either through CN (at the rates of 0, 6.45, and 12.91 g Se ha−1) or NPK (5.83 g Se ha−1). Selenium concentration in wheat grains increased consistently with increasing rate of Se-enriched CN or NPK. However, the superiority of Se-enriched CN over NPK in raising the Se concentration in wheat grain depended on location and growth conditions. At the same rate both methods of Se-application were found to be equally effective in raising the Se concentration of wheat grains. The Se concentration of grain was generally higher in the light textured soils than in the medium to heavy textured soils. Without Se application, the Se-concentration in wheat grain was about 16µg kg−1 which is regarded insufficient to meet the Se requirement for Se in animal and human. Calcium nitrate enriched with 25 mg Se kg−1 (6.45 g Se ha−1) increased the Se concentration in wheat grain to a desired level.
    Materialart: Digitale Medien
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  • 63
    ISSN: 1572-9699
    Schlagwort(e): bioluminescence ; Pseudomonas ; root colonization ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The bioluminescently marked Pseudomonas fluorescens strain 5RL, has been used previously to follow colonisation of soy bean roots (De Weger et al. [1991] Appl. Environ. Microbiol. 57:36-41). In the present paper the method has been further developed and optimized for wheat roots and it is used to get a quick overview of the colonisation patterns of many different root systems at the same time. Colonisation was followed on wheat plants grown in our gnotobiotic sand system (Simons et al., 1996. Mol Plant Microbe Interact 9: 600–607) and the following results were obtained. (i) A spatio-temporal analysis of the colonisation of wheat roots showed that 4 days after planting the highest bacterial activity was observed at the upper part of the root. After 6 days the high bacterial activity at the upper part was further increased, whereas spot-like activities were observed on the lower root parts, possibly due to micro-colonies. (ii) Bacterial mutations causing lack of motility or auxotrophy for amino acids resulted in impaired colonisation of the lower root parts, indicating that motility and prototrophy for the involved amino acid(s) are important factors for wheat root colonisation by strain 5RL. (iii) Coinoculation of strain 5RL with other wild type Pseudomonas strains on the root influenced the colonisation pattern observed for strain 5RL. Colonisation was not visually affected when the competing strain was a poor root coloniser, but was severely reduced when the competing strain was a good root coloniser. The results show that the spatio-temporal colonisation of wheat root by P. fluorescens strain 5RL and derivatives is similar to that of strain WCS365 on tomato. The advantage of the use of lux-marked strains is that the results are obtained much quicker than when conventional methods are used and that the result is supplied as an image of the colonisation pattern of many different roots.
    Materialart: Digitale Medien
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  • 64
    ISSN: 1572-9508
    Schlagwort(e): X-ray ; calibration ; filters ; interference ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report on UV/Visible transmission measurements of aluminum coated Lexan filters designed as UV blocking filters for soft x-ray detectors. Transmission of the filters in the 2300-8000 Å wavelength range is significantly higher than expected. It cannot be accounted for applying a simple slab model of the transmission and adopting material properties reported in the literature. We show that this is due to interference effects which are strongly dependent on the filter geometry, and to oxidation of exposed aluminum surfaces and/or chemical interaction with the plastic support. The results of this work have led to the redesign of the Advanced X-ray Astrophysics Facility High Resolution Camera UV blocking filters.
    Materialart: Digitale Medien
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  • 65
    ISSN: 1420-9136
    Schlagwort(e): Middle atmosphere ; temperature ; neutral and ion composition ; turbulent transfer ; model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Using a numerical model for temperature and neutral and ion composition behaviour at middle atmospheric heights, an analysis has been made of the dependence of atmospheric structural parameters on temperature, solar activity, and on turbulent transfer intensity. For mesospheric heights, an inverse dependence of the nitric oxide density on the temperature has been found. It is thus possible to explain experimentally obtained temperature variations over a cyclc of solar activity at mesospheric and lower thermospheric heights. Numerical simulation results indicate that the temperature in the height range ∼75–120 km depends considerably on both the absolute values of turbulent transfer coefficients and their vertical gradients.
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 43 (1987), S. 439-440 
    ISSN: 1420-9071
    Schlagwort(e): Neurospora crassa ; conidia ; heat-shock ; mitochondria ; cyanide-insensitive respiration ; guanosine 5′-monophosphate (GMP)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In mitochondria of heat-shocked conidia ofNeurospora exogenous NADH and succinate were oxidized mainly via the alternative, hydroxamate-sensitive pathway (70%) and only 30% via the cytochromic, cyanide-sensitive pathway which was predominant in untreated conidia; the alternative oxidase pathway was markedly stimulated by guanosine 5′-monophosphate (GMP).
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 51 (1995), S. 260-266 
    ISSN: 1420-9071
    Schlagwort(e): Salmon ; satellite cells ; cell culture ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Temperature is known to affect fish growth, and in Atlantic salmon there is an influence on muscle cellularity. Primary muscle cell culture makes it possible to investigate direct effects of temperature on myogenic cells. Salmon myosatellite cells were cultured for the first time in this study. The cells were cultured at either 5°C or 11°C. Increased temperature led to an increase in differentiation rate and especially hypertrophic growth (Q10=4.0). No nuclear proliferation was evident in the satellite cell population isolated at either temperature. This may be due to the presence of different subpopulations of myogenic cells at different developmental ages or the presence of indirect factors in vivo.
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Aquatic sciences 57 (1995), S. 325-337 
    ISSN: 1420-9055
    Schlagwort(e): Oxygen ; temperature ; patchiness ; microscale
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The presence and extent of small scale vertical structure in dissolved oxygen were investigated in a tropical Australian lake. At a 9 m deep site an extremely high oxygen patch appeared near the bottom boundary. Light levels reaching the bottom boundary during the life of the patch exceeded 10 µEinst m−2 s−1. The patch remained for 1.5 h before gradually reaching ambient oxygen levels. The patch's disappearance coincided with decreasing light levels during the late afternoon. Differences in the extent of oxygen vertical patchiness between deep (16 m) and shallow (9 m) sites were also observed. At the deep site, the distribution of oxygen steps over the water column coincided largely with the distribution of temperature steps. This indicates the dominance of physical processes at that site. At the shallow site, marked vertical patchiness in oxygen was observed with no similar patchiness in temperature. This indicates the prevalence of biological and chemical processes.
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 35 (1988), S. 441-442 
    ISSN: 1432-1041
    Schlagwort(e): debrisoquine ; oxidation ; diurnal variation ; metabolic ratio ; oxidative phenotype
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A study was performed to show whether debrisoquine phenotyping could be performed as an overnight procedure. Phenotyping of 33 normal volunteers was carried out during the day and night. A good correlation was observed between the day-and night-time metabolic ratios, although wide variation was observed in 3 subjects.
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  • 70
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 163 (1995), S. 352-356 
    ISSN: 1432-072X
    Schlagwort(e): Key wordsThiobacillus ferrooxidans ; Sulfide ; oxidation ; Sulfur colloids ; Bioleaching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Thiobacillus ferrooxidans was cultivated on 100-nm-thick synthetic pyrite (FeS2) films. The steps of biooxidation were studied with high-resolution transmission electron microscopy. The crystallized sulfide was transformed into colloidal sulfur (4–70 nm, depending on the age of the cell and the degree of substrate oxidation; 70 nm initially and 4 nm after oxidation of the pyrite substrate), which was taken up and distributed over an organic capsule around the bacteria. This colloidal sulfur acted as intermediate energy storage and was transferred by contact to daughter cells not directly attached to the sulfide substrate.
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  • 71
    ISSN: 1432-072X
    Schlagwort(e): Key wordsNitrospira moscoviensis ; Non-marine ; bacteria ; Obligate chemolithoautotroph ; Nitrite ; oxidation ; Nitrate reduction ; 16S rRNA gene sequences
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A gram-negative, non-motile, non-marine, nitrite-oxidizing bacterium was isolated from an enrichment culture initiated with a sample from a partially corroded area of an iron pipe of a heating system in Moscow, Russia. The cells were 0.9–2.2 μm × 0.2–0.4 μm in size. They were helical- to vibroid-shaped and often formed spirals with up to three turns 0.8–1.0 μm in width. The organism possessed an enlarged periplasmic space and lacked intracytoplasmic membranes and carboxysomes. The cells tended to excrete extracellular polymers, forming aggregates. The bacterium grew optimally at 39°C and pH 7.6– 8.0 in a mineral medium with nitrite as sole energy source and carbon dioxide as sole carbon source. The optimal nitrite concentration was 0.35 mM. Nitrite was oxidized to nitrate stoichiometrically. The doubling time was 12 h in a mineral medium with 7.5 mM nitrite. The cell yield was low; only 0.9 mg protein/l was formed during oxidation of 7.5 mM nitrite. Under anoxic conditions, hydrogen was used as electron donor with nitrate as electron acceptor. Organic matter (yeast extract, meat extract, peptone) supported neither mixotrophic nor heterotrophic growth. At concentrations as low as 0.75 g organic matter/l or higher, growth of nitrite-oxidizing cells was inhibited. The cells contained cytochromes of the b- and c-type. The G+C content of DNA was 56.9 ± 0.4 mol%. The chemolithoautotrophic nitrite-oxidizer differed from the terrestrial members of the genus Nitrobacter with regard to morphology and substrate range and equaled Nitrospira marina in both characteristics. The isolated bacterium is designated as a new species of the genus Nitrospira. Comparative analysis of 16S rRNA gene sequences revealed a moderate phylogenetic relationship to Nitrospira marina, leptospirilla, Thermodesulfovibrio yellowstonii, "Magnetobacterium bavaricum," and the isolate OPI-2. Initial evidence is given that these organisms represent a new phylum of the domain bacteria.
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  • 72
    Digitale Medien
    Digitale Medien
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    Archives of microbiology 167 (1997), S. 106-111 
    ISSN: 1432-072X
    Schlagwort(e): Key wordsNitrosomonas ; Anaerobic ammonia ; oxidation ; Anaerobic cell growth ; Nitrogen dioxide ; Nitric oxide ; Nitrous oxide ; Dinitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Nitrosomonas eutropha, an obligately lithoautotrophic bacterium, was able to nitrify and denitrify simultaneously under anoxic conditions when gaseous nitrogen dioxide (NO2) was supplemented to the atmosphere. In the presence of gaseous NO2, ammonia was oxidized, nitrite and nitric oxide (NO) were formed, and hydroxylamine occurred as an intermediate. Between 40 and 60% of the produced nitrite was denitrified to dinitrogen (N2). Nitrous oxide (N2O) was shown to be an intermediate of denitrification. Under an N2 atmosphere supplemented with 25 ppm NO2 and 300 ppm CO2, the amount of cell protein increased by 0.87 mg protein per mmol ammonia oxidized, and the cell number of N. eutropha increased by 5.8 × 109 cells per mmol ammonia oxidized. In addition, the ATP and NADH content increased by 4.3 μmol ATP (g protein)–1 and 6.3 μmol NADH (g protein)–1 and was about the same in both anaerobically and aerobically grown cells. Without NO2, the ATP content decreased by 0.7 μmol (g protein)–1, and the NADH content decreased by 1.2 μmol (g protein)–1. NO was shown to inhibit anaerobic ammonia oxidation.
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 989-996 
    ISSN: 1572-8943
    Schlagwort(e): sol-gel ; TG ; thermal decomposition ; Y-Ba-Cu superconductors
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A precursor of Y-Ba-Cu oxides was prepared by a modified alkoxide sol-gel method and its thermal decomposition in air was studied by on-line coupled TG-FTIR and High Resolution Thermogravimetric measurements. A continuous more or less stepwise weight loss was observed between room temperature and 600°C at which all organic compounds had evolved and were progressively oxidized as the temperature increased leaving only Y and Cu oxides and bariumcarbonate. Between 700 and 800°C a final weight loss was observed due to the decomposition of bariumcarbonate into oxide.
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 1051-1067 
    ISSN: 1572-8943
    Schlagwort(e): reaction mechanisms ; sol-gel ; superconductors ; thermoanalytical techniques
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The high temperature superconducting compound YBa2Cu3O72212;δ (Y-123) is synthesised by sol-gel process using various precursors viz., acetate, acetate-citrate, nitrate-citrate and acrylamide. The phase purity of the final product depends on the homogeneity of the gels which intern depends on the bonding of the metal ions in the gels. The samples prepared by acrylamide and nitrate-citrate gel routes yielded phase pure Y-123 compound with better superconducting properties. The mechanism of formation of Y-123 in all these four gel routes is established by characterising the gels and intermediate phases using TG, DTA and XRD techniques. Kinetic analysis is carried out on the mass loss data using the method proposed by Phadni's and Deshpande. Avrami-Erofeev nuclei growth in case of acrylamide, diffusion controlled process in nitrate-citrate and phase boundary reaction mechanisms in case of acetate-citrate gels are found to be responsible for the formation of Y-123 phase.
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  • 75
    Digitale Medien
    Digitale Medien
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    Journal of thermal analysis and calorimetry 49 (1997), S. 745-753 
    ISSN: 1572-8943
    Schlagwort(e): DSC ; kerogen ; oxidation ; pyrolysis ; type determination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The rate of pyrolysis and oxidation of 8 different samples of oil shale kerogen concentrate (KC) were investigated using DSC analysis. Recently performed thermogravimetric studies (TG and DTG) with the same samples of KC indicated that the activation energy of the pyrolysis of specific KCs increases with increasing paraffinic structure in the KC. An opposite effect, i.e. a decrease of the activation energy with an increase of paraffinic structure was determined in the case of KC oxidation. In this study, using the standard ASTM E-698 method based on the determined temperature at which the maximum heat effect could be observed (exo in the case of oxidation and endo in the case of pyrolysis), an activation energy for the pyrolysis, as well as for the oxidation process was determined and also successfully correlated with the content of paraffinic structure of KC. Thus, the higher content of paraffinic structure in KCs indicates that higher values of the activation energy could be determined either in the case of pyrolysis or oxidation followed by DSC analysis.
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 857-862 
    ISSN: 1572-8943
    Schlagwort(e): analytical methods ; kinetics ; powder milk ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This work present comparative results on powder milk storage quality, obtained from analytical methods. Protein content was determined conventional (Kjeldahl) and colorimetric with biuret reagent at 540 nm and integral quality by thermogravimetric and biological methods. A method was developed for the protein separation of powder milk. Powder milk was submitted to degradation processes at 45, 60 and 80°C for 20 days. The results indicated that protein content values were inconsistent if determinations by Kjeldahl and colorimetric methods and biological tests were compared. There is evidence of thermal decomposition of powder milk as detected by biological and thermogravimetric methods.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1017-1023 
    ISSN: 1572-8943
    Schlagwort(e): degradation ; microcalorimetry ; moisture ; oxidation ; permeability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The use of isothermal microcalorimetry (MC) as a sensitive monitor for slow reactions is demonstrated in a number of examples. In Example 1 the spontaneous decomposition of a nitrate ester propellant is studied and the absolute degradation rate estimated. Example 2 illustrates how MC can be used for comparing the rate of oxidative ageing at different O2 concentrations. Synergetic effects between oxygen and moisture in accelerated ageing of nitrile rubber are evaluated from a so-called 4-point test in Example 3. The last example shows a simple MC technique for rapid determination of moisture permeability through a polymeric sealant.
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 657-664 
    ISSN: 1572-8943
    Schlagwort(e): nickel powders ; oxidation ; thermal analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Monodispersed fine metal nickel powders of uniform shape and high purity are increasingly required for specific uses in many technological areas, especially in the preparation of electronic materials such as the manufacture of conductive inks and pastes and the formation of catalysts. Metallic nickel powders were prepared in ethylene glycol by the reduction of a nickel solution. Hydrazine was used as a reducing agent. Metal powders were characterized by chemical analysis, scanning electron microscopy (SEM), thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). Particle size distributions were determined using laser light scattering. The reactivity and purity of these fine nickel powders were tested by repeated oxidation and reduction of nickel powders in oxidative and reductive atmospheres.
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  • 79
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1501-1507 
    ISSN: 1572-8943
    Schlagwort(e): calcium sulphide ; gypsum ; oxidation ; phosphogypsum ; reduction ; stability ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Using a heating rate of 2°C min−1, CaS reacts with oxygen in air from 700°C to form CaSO4, with a complete conversion at 1100°C. Synthesis of CaS from the reaction between CaSO4 containing compounds and carbon compounds in air would not be possible, as the carbon reacts from 600°C with oxygen in the air to give CO2. Heating stoichiometric amounts of carbon and pure CaSO4, synthetic gypsum or phosphogypsum in a nitrogen atmosphere, results in the formation of CaS from 850°C. Using a heating rate of 10°C min−1, the formation of CaS is completed at 1080°C. Addition of 5% Fe2O3 as a catalyst lowers the starting temperature of the reaction to 750°C. Activation energy values at different fraction reaction values (α) differ between 340 and 400 kJ mol−1. The relationship between the activation energy values and conversion (α) indicates that the reaction proceeds via multiple steps.
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  • 80
    Digitale Medien
    Digitale Medien
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    Journal of thermal analysis and calorimetry 49 (1997), S. 1161-1170 
    ISSN: 1572-8943
    Schlagwort(e): basicity ; dinitramides ; kinetics ; oxidation ; tanδ ; transition temperatures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The dinitramide salts of ammonia (ADN), hexamethylenetetramine (HDN), potassium (KDN), and sodium (NaDN) showed a linear relationship between the DSC rate of decomposition at the peak maximum and the DEA tanδ value at the low temperature transition peak. As the cation basicity increased in the series ADN〈HDN〈KDN〈NaDN, there was an increase in the low temperature transition peak, the energy barrier for relaxation, and the decomposition peak temperature, and a decrease in the tanδ value at the low temperature transition peak, specific heat capacity, and the rate and enthalpy of decomposition. The more basic salts were more thermally stable (i.e., higher decomposition temperature) and less energetic (i.e., lower enthalpy of decomposition). The more internal free volume (disorder) present in these salts, the higher the rates of relaxation and decomposition. Five aluminum powders of different surface areas were analyzed by DSC in platinum sample pans, and it was found that the enthalpy and rate of oxidation increased as the particle size of Al decreased while the enthalpy of the Al melt decreased. TG showed a two-step weight gain in the oxidation of Al with plateaus in the 650 and 1130°C regions and the percent weight gain increased as the particle size of Al decreased. Variable DSC and TG heating rate studies showed that the activation energies for the first step in the oxidation process increased as the particle size of Al increased.
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  • 81
    Digitale Medien
    Digitale Medien
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    Journal of thermal analysis and calorimetry 50 (1997), S. 105-115 
    ISSN: 1572-8943
    Schlagwort(e): BiSCCO synthesis ; fluorine substitution ; sol-gel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Sol-gel citrate technology was used to prepare BiSCCO 2223 and 2212 superconducting phases. Fluorine in the initial mixture was shown to enhance considerably formation of the 2223 phase. Fluorine substitution of up to three F atoms per Bi(Pb)SCCO 2223 formula was achieved by treatment of the sample in 80 Torr ClF3 atmosphere. A number of experimental methods have been used to characterize the samples and to trace the phase transformations in the sol-gel process: DTA/TG, XRD, atomic absorption, potentiometry with fluoride selective electrode, magnetic susceptibility measurements.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Plasma chemistry and plasma processing 15 (1995), S. 309-331 
    ISSN: 1572-8986
    Schlagwort(e): Transferred arc ; voltage-current characteristic ; inhomogeneous plasma ; optical emission spectroscopy ; electron density ; temperature ; spatial distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract The results of a twin-torch transferred de arc .study are presented. The arc system consists of two torches of opposite polarity, and a coupling zone of plasma jets located between them. The torch configuration increases the system reliability and efficiency during material plasma processing. The results of the study present data for the voltage-current characteristics, general behavior of the twin-torch arc, and spatial distribution of the plasma parameters. The plasma parameters have been measured using optical emission spectroscopy for a 200 A (20 k W) do arc, at atmospheric pressure, with argon and nitrogen introduced as plasma forming gases into the anode and the cathode units, respectively. The measurement technique used has allowed the determination of local electron density and temperature values in an inhomogeneous plasma volume having no axial sysmmetry. The data obtained illustrate the novel features of the twin-torch transfrred do arc for its applications in plasma processing.
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Plasma chemistry and plasma processing 15 (1995), S. 333-351 
    ISSN: 1572-8986
    Schlagwort(e): Hydrogen/argon plasma ; methane ; do arc jet ; atmospheric pressure ; optical emission spectroscopy ; temperature ; density ; spatial distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Spatial distributions of plasma parameters are presented for a H2/Ar plasma jet with addition of methane. The plasma has been generated at atmospheric pressure by a 200 A (20 kW) nontransferred do arc. Optical emission spectroscopy has been used for the measurements assuming the plasma jet to be optically thin and to have an axial symmetry. Local spectral ernissivity values have been evaluated using a routine Abel inversion procedure. Half- width and emissivity of Hβ spectral line have been measured to determine the electron density and temperature of the plasma. The densities of excited C, CH radicals have been evaluated from the absolute emissivities of relevant molecular emission bands measured in limited spectral intervals in the visible spectrum. The emissivity ratios have been used to fund rotational and vibrational temperatures. The results supply information on methane decomposition and the behavior of molecular radicals in close-to-thermal plasma jets.
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 10 (1997), S. 309-316 
    ISSN: 1573-4846
    Schlagwort(e): lactate dehydrogenase ; sol-gel ; biosensor ; lactic acid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Physical adsorption and physical entrapment techniques have been utilized for the immobilization of lactate dehydrogenase (LDH) on tetraethylorthosilicate (TEOS) derived sol-gel films. The enzyme (LDH) activity has been assayed as a function of time, temperature, pH and pyruvate concentration. The results of photometric measurements used for monitoring the reaction yield a response time of about 1 min, linearity over a concentration range of 0–1.5 × 10-3 M and detection limit of 5 × 10-5 M. The TEOS sol-gel films containing LDH have been found to be stable for about 30 days at temperatures 4 to 10°C.
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Journal of nondestructive evaluation 16 (1997), S. 91-100 
    ISSN: 1573-4862
    Schlagwort(e): LASER ultrasound ; anisotropic material ; group velocity ; stiffness coefficients ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Mathematik
    Notizen: Abstract Ultrasonic waves are generated through a composite material by means of a noncontact technique. It uses a Nd:Yag LASER for the generation and an interferometric probe for the detection of acoustic waveforms. From a suitable set of experimental data, an inversion scheme is used for the recovering of four stiffness coefficients. They characterize the elasticity in a principal plane of symmetry of the material which exhibits an orthorhombic symmetry. The measurements are performed at various temperatures, elevated by steps up to 300°C for two specimen. The sensitivity of the method appears convenient to measure the temperature induced stiffness changes. The anisotropic degradation of the material properties are then pointed out.
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 8 (1997), S. 77-81 
    ISSN: 1573-4846
    Schlagwort(e): iron oxide ; structural control ; complexing agent ; thin film ; sol-gel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, α -Fe2O3 with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one mole of iron nitrate and the calcination temperatures were below 400° C, γ -Fe2O3 with spinel structure appeared as the main phase and, when less than five moles of the diols were used, α -Fe2O3 appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in thin films. Thus, a transparent magnetic film composed of γ -Fe2O3 could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz and calcining the gel film at 350° C.
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  • 87
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 8 (1997), S. 83-88 
    ISSN: 1573-4846
    Schlagwort(e): sol-gel ; gelation modelling ; TiO2 gels ; simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract We present here an experimental and numerical study of the chemical and aggregative mechanisms for titanium alkoxide in a reverse micellar medium. NMR experiments were done to study the first step of the sol-gel process: hydrolysis of titanium isopropoxide. Light and X-ray scattering experiments were then conducted to characterize the clustering of aggregates and aggregation kinetics. Fractal dimension, measured by U.S.A.X.S., varies with the hydrolysis ratio and the hydration of the surfactant. This evolution was explained by polydispersity of the hydrolysis which depends on the surfactant concentration. This hypothesis was tested through a numerical simulation of irreversible aggregation using a chemically limited aggregation model. The hydrolyzed sites are distributed among the monomers by a random procedure governed by a polydispersity parameter p , varying from 0 to 1. The total number of hydrolyzed sites is governed by a parameter q belonging to the interval [0, 1]. The p -q evolution of the fractal dimension coincides rather well with the experimental data in all the region of the two dimensional phase space.
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Journal of sol gel science and technology 8 (1997), S. 107-110 
    ISSN: 1573-4846
    Schlagwort(e): sol-gel ; zinc aluminate ; spinel structure ; catalyst support
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract ZnAl2O4 was prepared by hydrolyzing a mixture of aluminum alkoxide with zinc nitrate dissolved in hexylene glycol and calcining at 800°C. The results are compared with those obtained by wet mixing and coprecipitation. The sol-gel method produces solids whose surface areas and pore volumes are 100% larger and with a more homogeneous pore size distribution.
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  • 89
    ISSN: 1573-4846
    Schlagwort(e): mullite ; organic ligand ; hydrolytic polymerization ; sol-gel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The preparation of mullite by the sol-gel method using organic polydentate ligands and the effect of the raw materials and organic polydentate ligands on the formation of mullite were investigated. Two series of samples were prepared using tetraethoxyorthosilicate (TEOS) and aluminum nitrate nonahydrate, or dibutoxyethylacetoacetatoaluminum (Al(OBu)2(AcAcEt)) as the silica and alumina sources, respectively, and using ethylene glycol (EG), 1,3-propanediol (PD), 1,3-butanediol (BD), 2-methyl-2, 4-pentanediol (MPD), diethlene glycol monoethyl ether (DEME) and ethoxyethanol as the ligands. When the alumina source was aluminum nitrate nonahydrate, mullite was apt to appear in the order of EG 〉 PD 〉 MPD. When Al(OBu)2(AcAcEt) was the alumina source, the tendency toward the appearance of mullite crystalline phase was EG 〉 BD 〉 DEME 〉 MPD. Between the two alumina sources, aluminum nitrate nonahydrate gave mullite much easier than Al(OBu)2(AcAcEt). These relationships were discussed from the viewpoints of the coordination ability of the ligands and the miscibility between the silica and alumina.
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  • 90
    Digitale Medien
    Digitale Medien
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    Journal of sol gel science and technology 9 (1997), S. 279-283 
    ISSN: 1573-4846
    Schlagwort(e): AgTCNQ ; photochromism ; sol-gel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Preparation and photochromic behavior of ormosil containing encapsulated AgTCNQ molecules were studied in this paper. The ormosil resulted from hydrolysis and polycondensation of glycidoxypropyltrimethoxysilane, dimethyldimethoxysilane and methyltrimethoxysilane. The time to add AgNO3 water solution into the resultant sol was a key factor to synthesize AgTCNQ molecules inside ormosil matrix. AgTCNQ molecules encapsulated in the ormosil showed different photochromic behavior compared with pure AgTCNQ film: normal photochromic reaction can be realized, while reverse photochromic reaction can not. The “cage” model was used to explain this phenomenon.
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  • 91
    Digitale Medien
    Digitale Medien
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    Journal of sol gel science and technology 9 (1997), S. 239-249 
    ISSN: 1573-4846
    Schlagwort(e): sol-gel ; alumina-gel ; multicomponent ; mullite ; phase transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The capacity of the sol-gel process of producing highly pure, homogeneous alumina-silica based materials had been demonstrated in the last few years. However, a full understanding on the mechanisms associated to sol formation and sol to gel transition has not yet been achieved and is required for the development of a new generation of nano-structurally tailored materials that will significantly enhance the technological importance of the sol-gel process. In this work, tetraethyl orthosilicate (TEOS) and aluminum isopropoxide were used to prepare materials within the entire silica-alumina system. Process parameters, such as gelation time, were correlated to variables of the initial stage of the process, such as pH, temperature of hydrolysis and water/alkoxide ratio. The obtained gels were dried at 105°C and subsequently heat treated at 500 and 1100°C for 3 hours. X-ray diffraction and infrared spectroscopy were used to characterize the materials and phase transformations. Structural information obtained from phase characterization and phase transformations was correlated to the effects of the process variables on sol formation and gelation, providing insights related to the mechanisms involved. The influence of temperature of aluminum isopropoxide hydrolysis on peptization and gelation of the mixtures was noted. The different behavior of mixtures hydrolyzed at low and high temperatures was suggested to be caused by different mechanisms of surface charge formation on the structurally different aluminum hydroxides. Monophasic and diphasic mullite xerogels were produced by changing temperature of aluminum isopropoxide hydrolysis, and led to formation of mullite and Al−Si spinel phases respectively, when treated at 1100°C.
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  • 92
    Digitale Medien
    Digitale Medien
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    Oxidation of metals 28 (1987), S. 195-211 
    ISSN: 1573-4889
    Schlagwort(e): Uranium ; corrosion ; oxidation ; liquid metal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The reactions of water vapor and oxygen with liquid uranium were studied by modulated molecular-beam mass spectrometric methods. Equivalent pressures of the reactant fluxes on the surface ranged from 6×10 −6 to 2×10−4 torr. Temperatures up to 1570 K were investigated. The metal surface was kept clean during reaction by mechanical removal of the oxide formed with a tungsten needle. For the clean liquid uranium surface, a water reaction probability of ∼0.4 was deduced both from measurement of the reaction-product hydrogen signal and by the temperature dependence of the scattered reactant signal. Based solely on the latter measure, a reaction probability of 0.6 was estimated for oxygen. The reaction probabilities on the clean surface were temperatureindependent. They decreased as the coverage of the surface by islands of oxide increased and, for water, appeared to approach a value of 0.08 for a surface completely covered with an oxide estimated to be 500 Å thick. Bombardment of the surface during reaction with argon ions produced an increase in the reactivity on solid uranium but had a negligible effect on the reaction probability for the liquid.
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  • 93
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    Digitale Medien
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    Oxidation of metals 28 (1987), S. 353-389 
    ISSN: 1573-4889
    Schlagwort(e): Grain growth ; nickel oxide ; high temperature ; oxidation ; nickel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract In systems such as the oxidation of nickel, in which grain-boundary diffusion in the oxide can control the rate of oxidation, understanding of the factors governing the grain structure is of importance. High-purity mechanically polished polycrystalline nickel was oxidized at 700°C, 800°C, and 1000°C for times up to 20 hr in 1 atm O2. The scale microstructures were examined by parallel and transverse cross section transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Texture coefficients were found by X-ray diffraction (XRD). Each grain in the transverse section grain boundary networks was systematically analyzed for width parallel to the Ni-NiO interface and perpendicular length, for boundary radius of curvature and for number of sides. The variation of these parameters with depth in the scale was examined. In particular, grains were increasingly columnar (i.e., with ratio of grain length to width 〉1) at higher temperatures and longer times. Columnar grain boundaries tended to be fairly static; the columnar grain width was less than the rate controlling grain size predicted from the oxidation rate. The mean boundary curvature per grain provided a guide to the tendency for grain growth, except in the region of the Ni-NiO interface, where the boundaries were thought to be pinned.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 47 (1997), S. 381-410 
    ISSN: 1573-4889
    Schlagwort(e): Ni-Base superalloys ; Astroloy ; Waspaloy ; Udimet 720 ; oxidation ; chromia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Several commercially available Ni-base superalloys were exposed isothermally in air at temperatures between 750° and 1000°C and also under cyclic conditions at 1000°C. The kinetics of oxidation were determined and the scales were analyzed by electron microscopy and X-ray diffraction. Thin adherent chromia-rich scales formed on the alloys at 750°C after 1000 hr. Although Waspaloy showed the lowest weight gain in this test, it also showed the deepest internal corrosion due to oxidation of the grain-boundary carbides. At temperatures up to 1000°C the external scales were also chromia-rich but there was greater internal corrosion. Titanium in the alloys oxidized, diffusing through the chromia scale to form faceted rutile (TiO2) grains at the surface as well as forming TiO2 and TiN internally. The amount of rutile at the oxide surface increased with temperature and alloy Ti concentration. Alumina formed as discrete internal oxides below the chromia scale, although Astroloy when oxidized isothermally at 1000°C developed a semicontinuous internal layer of alumina due to its higher Al content. Under cyclic conditions Astroloy formed a thicker, less-protective scale of transition oxides probably due to its lower Cr content.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; Incoloy 909 ; superalloy ; scale ; high temperature ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si superalloy (Incoloy 909 type alloy), was investigated at temperatures between 1000 K and 1400 K in Ar-(1, 10%)H20 atmosphere using metallographic, electron probe microanalysis, and X-ray diffraction techniques. The oxide scales consist of an external scale and an internal scale which has an intergranular scale (above 1200 K) and an intergranular scale. The oxide phases in each scale are identified asα-Fe2,O3 (below 1200 K) or FeO (above 1300 K) and CoO · Fe2O3 and FeO · Nb2O5, respectively. The morphologies, the oxide phases and the oxidation rates do not depend on the partial pressure of H2O in the range between one and ten percent in Ar gas. The rate constants for the intergranular-scale formation in this alloy are about one-tenth as large as those in Fe-36%Ni alloy reported previously. At all the temperatures the scales grow according to a parabolic rate law and the apparent activation energies for the processes are estimated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 47 (1997), S. 445-464 
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; Fe-Cr-Al alloy ; water vapor ; ESCA ; RHEED
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Fe-21.5 wt. %Cr-5.6 wt. %Al oxidation, at 1000°C, in dry or wet oxygen shows that steam has an influence on the oxide-scale growth mechanism. Steam modifies the kinetics of early-stage oxidation. In dry oxygen, an initial fast linear regime is observed during one hour. Under wet conditions, weight-gain curves follow the same parabolic regime over the entire oxidation test. The scale structure strongly depends on the presence of steam in the gaseous environment. With dry oxygen, the scale is composed mainly ofα-Al2O3 after the initial formation ofγ-Al2O3 identified by ESCA and RHEED. The kinetics transient stage corresponds to the necessary time for the internal part of the initialγ-Al2O3 scale to transform into a continuousα-Al2O3 diffusion barrier. Under wet oxygen conditions, transient oxides are identified as (Mg, Fe) (Cr, Al)2O4, MgAl2O4 (orthorhombic), Al2O3 (hexagonal), these oxides transform into MgAl2O4 (cubic), Cr3O4, Fe2O3,α-Al2O3, with time. When water vapor does not change drastically oxidation kinetics, the induced presence of iron and chromium in the oxide scale could be responsible for weakening the protectiveness of alumina scales.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 47 (1997), S. 507-524 
    ISSN: 1573-4889
    Schlagwort(e): alloys ; high temperature ; oxidation ; transient state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The initial transient high-temperature oxidation stage for binary alloys forming the most-stable oxide has been examined by means of a numerical procedure based on the finite-difference method. At variance with previous models, the present treatment takes into account the effect of the rate of the reaction at the scale/gas interface over the corrosion kinetics. The calculations concerning the transient stage are developed either using the general parabolic rate law to represent the overall scaling kinetics or using the rate law of the reaction at the scale/gas interface as a boundary condition without imposing any particular rate law to the overall process. A correct analysis of the oxidation behavior of binary alloys during the transient stage must take into account the kinetics effect of the rate of the surface reaction. The concentration of the most-reactive element at the alloy/scale interface changes regularly with time, decreasing gradually from the initial bulk value to its final steady-state value. The present results are in good agreement with those obtained by means of an approximate analytical model developed previously.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    ISSN: 1573-4889
    Schlagwort(e): high temperatures ; oxidation ; transient state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The transient state in the oxidation of solid solutions of a most-noble componentA in a most-reactive componentB (beta phase) for binaryA-B alloys presenting a limited reciprocal solubility of the two metals has been examined assuming that theirB content is sufficient for the exclusive growth of externalBO scales. Above a criticalB content of the alloy theBO scales may grow directly on the surface of the beta phase, while below this limit they can only form over a layer ofB-depleted solid solution ofB inA (alpha phase), which appears after a critical time. An approximate analytical expression for the profile of concentration ofB in the alloy has been adopted to calculate the flux ofB in the metal. Moreover, the effect of the reaction between the gas and the external oxide surface has been taken into account using a procedure developed by Wagner for the oxidation of pure metals. The corrosion kinetics as well as all the parameters involved, such as the concentration ofB at the alloy-scale interface, have been calculated as functions of the corrosion time. The results show that, as time proceeds, the instantaneous parabolic rate constant increases and the concentration ofB at the alloy-scale interface decreases, both tending gradually to their corresponding steady-state values. It is also predicted that if the rate of transformation of the beta phase in the alpha phase after the alloy reaches the composition of equilibrium at the interface with the oxide is lower than the corresponding rate of displacement of the alloy surface due to scale growth, the corrosion of beta phase alloys may eventually lead to the formation of two phase mixtures of alpha phase andBO which are expected to grow at much larger rates than in the presence of a uniform continuous alpha layer.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 48 (1997), S. 1-39 
    ISSN: 1573-4889
    Schlagwort(e): Ni-base ODS superalloys ; oxidation ; initial stages of oxidation ; alumina ; chromia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Mechanically-alloyed Ni-base ODS superalloys currently receive attention for application in future gas turbines because they exhibit outstanding mechanical properties at high temperatures. They also protect themselves against oxidation by forming chromia and/or alumina scales. However, little attention has been given so far to the initial stages of oxidation of Ni-base ODS superalloys, containing Cr as well as Al in considerable amounts. In the current work, oxidation at 1150°C was studied for different holding times up to 200 hr for the commercial materials MA6000 and PM3030 which contain. Al in increasing amounts. MA 754, a chromia former, was investigated as a reference. It was shown that for the potential alumina formers MA6000 and PM3030 the continuity and therefore protectiveness of the secondary Al2O3 at later stages is indeed determined by the initial stages of oxidation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 48 (1997), S. 129-141 
    ISSN: 1573-4889
    Schlagwort(e): decarburization ; nickel ; oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A commercial-grade nickel containing small amounts of carbon, manganese, and silicon was exposed to air for periods up to 288 hr at 1050°C to study the effect of oxidation on the formation of oxides of these impurity elements. Exposure of nickel to air led to decarburization. The maximum amount of decarburization occurred during the initial period of air exposure and the loss in carbon was more in the metal with a smaller section size. Decarburization in the metal produced voids in the oxide scale due to the formation of CO2 gas. It has been shown further that CO and/or CO2 gas bubbles, which form in high purity nickel on grain boundaries during exposure to air at elevated temperatures, cannot exist in commercial-grade nickel where manganese is present as an impurity. Instead, oxides of manganese form in the grain boundaries as well as in the matrix. This is because manganese oxide is more stable than CO or CO2 gas.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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