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  • 1
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Results of static fracture tests on PMMA plates with part-elliptical cracks at fastener holes are presented. Experimental configurations include three crack locations with respect to both open and loaded holes. During static testing, slow growth prior to specimen separation allows for calculation of the maximum stress-intensity factor and identification of the location on the crack border at which it occurs. The testing techniques developed produce a simple, economical means of experimentally validating theoretical analyses of crack problems.
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  • 2
    ISSN: 1573-5036
    Keywords: cerium ; computer simulation ; lanthanum ; nutrient solutions ; phosphate precipitation ; REE species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The interpretation of results of some experiments examining effects of rare earth elements (REE) on plant growth may have been complicated by rare earth phosphate precipitation. Simulations were undertaken using the computer model GEOCHEM-PC to define REE solubility limits and predict REE species in low and high ionic strength nutrient solutions. In low ionic strength solutions containing 5 μM P, lanthanum phosphate (LaPO4) precipitation is predicted to occur at solution pH〉4.0, reaching a maximum (〉95% of total) at pH 5.5. In high ionic strength solutions (1000 μM P) over 95% of the La is predicted to precipitate as phosphate at pH〉4.0. The predicted behaviour of cerium (Ce) was closely similar to that for La. At pH 5.5, the concentration of REE species in solution can be increased only after virtually all the P has been precipitated. Consequently, it is important to consider REE-P interactions in nutrient solutions when investigating REE effects on plant growth.
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  • 3
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In studies on the effect of potassium and nitrogen fertilizers on ionic relations inPanicum maximum var.trichoglume cv. Petrie (green panic) most of the non-volatile organic acids that accumulate in this species have been identified and the effect that variations in inorganic nutrition have on the relative amounts of these acids accumulated ascertained. Increasing levels of nitrogen lowered the ratio of monovalent to divalent cations in the plants and increased their total cation concentrations. A deficit of inorganic anions (C-A) that ranged from 747 to 1010 meq/kg dry weight was found in the plant tops. Much of this deficit was balanced by accumulation of oxalate, aconitate, citrate, malate, quinate and an unknown organic anion. The relative contributions that these six organic anions made towards maintenance of ionic balance was altered by changing the levels of potassium and nitrogen supplied to the plants.
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  • 4
    ISSN: 1573-5036
    Keywords: Critical external phosphorus concentration ; Flowing-solution culture ; Tropical grain legumes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Five tropical grain legume species were grown for periods from 4 to 20 days in flowing-solution culture at 7 maintained phosphorus (P) concentrations, ranging from 0.25 μM to 16 μM. Critical external P requirements were 0.8 μM for cowpea cv. Vita 4 and soybean cv. Fitzroy, 1.0 μM for pigeon pea cv. Royes, 2.0 μM for mungbean cv. Regur and 3.0 μM for guar cv. Brooks. Plant responses to P deficiency included reduced growth rate, increased root percentage, and increased P uptake potential. The long-term P uptake rates of guar plants were lower than those of the other species at each external P concentration. Guar plants had a low P uptake potential as indicated by short-term32CP-labelled uptake rate studies from 15 μM P solutions. Cowpea by contrast had high short-term uptake rates indicating a high P uptake potential.
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  • 5
    ISSN: 1573-5036
    Keywords: nutrient transport ; ion transport ; permeases ; ion channels ; heterologous expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A number of strategies for identifying and cloning genes involved in nutrient transport and assimilation processes are discussed. Particular attention is paid to phenotypic screening by heterologous complementation of mutations which affect transport processes in other organisms and use of insertion elements in plant genomes. A program in which complementation of yeast mutants is being used to clone genes involved in the uptake and assimilation of sulphate by plants is outlined. Information is provided on the isolation of yeast mutants and their characterization, choice of appropriate shuttle vectors, the construction of cDNA and genomic libraries, and screening of libraries for complementation.
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  • 6
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé Une solution numérique à équations tridimensionnelles d'élasticité est présentée pour le problème de la fissure de surface semi-elliptique située en surface ou en solide d'épaisseurs finies. La méthode proposée est utilisée pour développer des résultats numériques qui incorporent les effets des facteurs d'intensité des contraintes associée à la fois des surfaces “recto et verso” du solide. Le facteur d'intensité des contraintes est décrit pour diverses positions de la fissure et ce dans divers cas de formes et de profondeurs de fissuration. Une comparaison est faite entre les résultats de cette étude et des travaux théoriques et expérimentaux antérieurs.
    Notes: Abstract A numerical solution to the three-dimensional equations of elasticity is presented for the problem of a semi-elliptical surface crack in the surface of a finite thickness solid. The alternating method is used to develop the numerical results which incorporate the effects on the stress intensity factor due to the presence of both the front and the back surfaces. The stress intensity factor is presented as a function of position along the crack border for a variety of crack shapes and crack depths. A comparison of the results of this study is made with previous theoretical and experimental work.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 9 (1973), S. 33-41 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé On présente une solution pour le cas d'une fissure de Griffith soumise à une fonction de charge de forme arbitrairement polynomiale et telle que l'une des extrémités de la fissure ne s'ouvre pas. Des expressions de forme fermée sont proposées pour la longueur d'ouverture de la fissure et pour les contraintes et déplacements dans le plan de celle-ci. Le cas particulier de la flexion pure est présenté à titre d'exemple et, pour ce cas, on calcule le facteur d'intensité de contrainte.
    Abstract: Zusammenfassung Man schlägt eine Lösung vor für den Fall eines Griffith-Risses welcher einer Lastfunktion arbiträrer polynomialer Form unterworfen ist, wobei eines der Rißenden sich nicht öffnet. Es werden Ausdrücke in einer geschlossenen Form sowohl für die Offnungslänge des Risses, als auch für die Spannungen und die Verschiebungen in der Rißebene vorgeschlagen. Als Beispiel wird der Fall einer reinen Biegung crörtert und es wird für dieses Beispiel der Spannungsintensitätsfaktor berechnet.
    Notes: Abstract A solution is presented for a Griffith crack subjected to an arbitrary polynomial loading function which causes one end of the crack to remain closed. Closed form expressions are presented for the crack opening length and for the stress and displacements in the plane of the crack. The special case of pure bending is presented as an example and for this case the stress intensity factor is computed.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 5 (1971), S. 683-699 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The superconducting critical fields of pure Zn and of a series ofZnMn alloys have been measured as a function of temperatureT down to 0.06 K. The critical fields have been used to calculate the entropy difference between the normal and superconducting states. For all the alloys studied, the entropy in the superconducting state is proportional toT asT → 0, indicating a finite density of states at the Fermi energy. We interpret this result as evidence for the existence of localized bound states within the energy gap centered at the Mn impurities. Results obtained for the depression ofT c , for the critical field atT=0, for the jump in specific heat atT c , and for the law of corresponding states are also presented and compared with the predictions of the Abrikosov-Gor'kov theory. A simple expression relating the critical fields of these alloys to the Mn concentration has been found to be in very good agreement with experiment.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 903-905 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The initial growth of diamond films in a microwave plasma reactor has been studied using in situ two-color infrared pyrometry. Analysis of the observed oscillations of the apparent temperature has yielded the substrate temperature and also the instantaneous film growth rate and rms surface roughness σ. Two distinct regimes of growth have been clearly identified: an initial period of rapidly increasing σ before the diamond nuclei coalesce, followed by a slower increase of σ with thickness as the continuous film grows further. The differing initial roughnesses and emissivities of Si and Mo substrates have been shown to have important effects on the growth of diamond. © 1998 American Institute of Physics.
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