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  • 1
    ISSN: 1570-7458
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Tribolium confusum-Larven wurden vom Schlüpfen bis zur Larven-Puppen-Häutung an geschrotetem Weizen, fein gemahlenem Weizen, fein gemahlenem Weizen + 5% Bierhefe oder Weizenkeimlingen aufgezogen. Der Kot wurde quantitativ gesammelt und mittels Dünnschichtchromatographie, der enzymatisch-spektrophotometrischen Methode und colorimetrischen Methoden auf Stickstoff-Endprodukte analysiert. Mit geschrotetem Weizen oder Weizenkeimlingen gefütterte Larven hatten einen größeren Gesamtgehalt an Stickstoff-Metaboliten als die anderen. Die relativen Mengen von Hypoxanthin, Xanthin, Harnsäure und Allantoin, welche diesen Gesamtgehalt ergaben, wechselten mit der Diät. Auf den Gesamtgehalt bezogen blieb Allantoin prozentual relativ konstant, aber die Anteile der übrigen End-produkte variierten beträchtlich. Kot nach Ernährung mit geschrotetem oder fein gemahlenem Weizen enthielt etwa 30% Harnsäure, während Kot von mit Weizenkeimlingen oder mit gemahlenem Weizen + Bierhefe ernährten Tieren etwa 68 bzw. 50% Harnsäure und entsprechend geringere Mengen Hypoxanthin und Xanthin enthielt. Harnstoff und Ammoniak waren ebenfalls vorhanden jedoch vermutlich durch die Mikroorganismen des Kots gebildet worden.
    Notes: Abstract Tribolium confusum duVal larvae were reared from hatching to the larval-pupal ecdysis on cracked wheat, finely ground wheat, finely ground wheat plus 5% brewer's yeast, or wheat germ. Feces were collected quantitatively and analyzed for nitrogenous end products by thin layer chromatography, the enzymatic-spectrophotometric method, and colorimetric methods. Larvae fed cracked wheat or wheat germ excreted a larger total of nitrogenous metabolites than did the others. The relative quantities of hypoxanthine, xanthine, uric acid, and allantoin which made up the total varied with diet. Calculated on the basis of the total, the percent allantoin remained relatively constant, but the proportions of the other end products varied considerably. Feces derived from cracked wheat or finely ground wheat contained about 25% uric acid, while feces derived from wheat germ or ground wheat with brewer's yeast contained about 61% and 45% uric acid respectively and correspondingly reduced quantities of hypoxanthine and xanthine. Urea and ammonia were also present. Correction for the estimated urine content of the feces results in an increase in the calculated approximate digestibility and a decrease in the calculated efficiency of conversion of digested food. The changes are small, but significant. The size of the change varies with the diet.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 31 (1996), S. 5551-5554 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A variety of inorganic aluminium sols were investigated for their reactivity with colloidal silica to form polycrystalline mullite. Nuclear magnetic resonance (NMR) spectroscopy was used on the precursor aluminium sols to ascertain the co-ordination and reactivity of the species present. Differential thermal and thermogravimetric analysis and X-ray diffraction were used to analyse the products of the fired xerogels. Commercial reactants produced diphasic materials with little or no mullite formed at 1000 °C. A monomeric/dimeric sol produced in house however, showed a sharp exotherm at 920 °C and crystalline mullite formation at this temperature.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 31 (1996), S. 5583-5586 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This note describes the preparation of zirconium titanate gel fibres from an aqueous mixed zirconia titania sol. The fibres are well formed and free of shot. Heat treatment to 750 °C produces a crystalline porous zirconium titanate fibre which shows a good (1%) strain to break. Further firing to 1100 °C causes a deterioration in properties, with retention of some porosity and a reduced strain to break. Recommendations for improving the material are suggested.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 349-352 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Gel fibres of barium M ferrite, BaFe12O19, were blow spun from an aqueous inorganic sol and calcined at temperatures up to 1200°C. The ceramic fibres were shown by X-ray diffraction to be single phase crystalline M ferrite at 1000°C, and surface area and porosity measurements indicated an unusually high degree of sintering at this temperature. The fibres also demonstrated a favourable grain structure of less than 0.1 μm at this temperature and maintained a small grain size of less than 4 μm even up to 1200°C, an important factor in the magnetic properties of this material.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 353-356 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Measurements of impedance spectroscopy and dc conductivity over the temperature range 300–1000K in atmospheres of dry and wet argon on antiferromagnetic NiWO4 are presented. The measured polycrystalline material was produced by a co-precipitation route. The conductivity was found to be sensitive to moisture over the temperature range 300–450 K. Impedance spectroscopy measurements separated the contributions of the bulk lattice and grain boundaries to the conductivity. These were separated over the temperature range 615–833 K by equivalent circuit modelling and an activation energy for the bulk lattice conductivity obtained. Conductivity measurements indicated that the compound is an intrinsic semiconductor and obeys the Arrhenius conductivity equation; σ=492.7 exp(−1.15 eV/kT)Ω-1 m-1, above 625 K where K and T have their usual meaning.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 365-368 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Gel fibres of Co2Y,Ba2Co2Fe12O22, were blow spun from an aqueous inorganic sol and calcined at temperatures of up to 1200°C. The ceramic fibres were shown by X-ray diffraction to form crystalline Co2Y at 1000°C, and surface area and porosity measurements indicated an unusually high degree of sintering at this temperature. The fibres also demonstrated a small grain size of 1–3 μm across the hexagonal plane and 0.1–0.3 μm thickness at 1000°C. This only increased to 3 μm in diameter and 1 μm thickness even at temperature up to 1200°C. The fibrous nature combined with the improved microstructures could be an important factor in improving the magnetic properties of this material.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 5583-5592 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract As part of a systematic study of solid acids, a series of high surface area single-phase alumina–titania mixed oxides were prepared. These materials were found to have higher surface areas, greater porosity and enhanced specific surface acidity than comparable alumina-titania solid acids reported in the literature. The thermal stability of the phases and their textural and physicochemical properties have been studied over a range of Al∣Ti compositions and for calcinations up to 1000°C. The samples were characterized by differential thermal analysis–thermogravimetry, X-ray diffraction, nitrogen physisorption and X-ray photoelectron spectroscopy. Surface acidity was measured by temperature programmed desorption and in situ Fourier transform-infrared spectroscopy, using ammonia as a probe molecule. The strength and density of the acid sites were proportional to the Ti-content.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 33 (1998), S. 3001-3007 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The phases in the homologous series PrnO2n−2 (n=11, 10, 9 and 7) have been studied by temperature-programmed reduction (TPR), electrical conductivity and Seebeck coefficient measurements using PrO1.83 as the starting material. TPR measurements in helium indicate that oxygen evolution from PrO1.83 occurs in three distinct steps and quantification of the oxygen evolution shows the formation of the phases PrnO2n−2 (n=10, 9 and 7). Temperature-dependent electrical conductivity measurements for p(O2)=0 show breaks in the conductivity which occur at 635, 714 and 797 K, whereas in air the breaks occur only at 720 and 953 K. These correspond to the compositionally controlled phase transitions. The Arrhenius conductivity expression has been used to calculate the activation energies and pre-exponential factors in the stoichiometric regions. Results from TPR and conductivity experiments indicate that PrO1.83 and PrO1.71 have easily established temperature ranges of composition while PrO1.80 and PrO1.78 have stability ranges which are very much smaller. Seebeck coefficient measurements (thermopower) as a function of oxygen partial pressure and temperature indicate that the conduction changes from n to p type for the composition PrO1.71. The approximate independence of the Seebeck coefficient with temperature fits the Heikes theory for a hopping conductor. The discrepancies in the earlier reports on the conductivity of PrO1.83 are attributed to the variations in the p(O2) employed, rate of heating and also to a certain extent the partial hydroxylation and carbonation of the samples used. The results of the present experiments point out these aspects and clarify the discrepancies between previously published data. © 1998 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 33 (1998), S. 3229-3232 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A zirconium sol was produced from the hydrolysis and immediate peptization of a zirconium alkoxide, which was found to be stable with the addition of a large proportion of a strontium salt, even up to equimolar amounts. Get fibres were successfully blow spun from this doped sol, which on subsequent heating produced ceramic fibres of orthorhombic strontium zirconate. The fibres were characterized by various techniques. The fibres were found to begin forming SrZrO3 at 400°C and were present as single phase orthorhombic strontium zirconate at 800°C and above. The ceramic fibres had no discernible grain structure and the average crystallite size was calculated to be only 20 nm at this temperature, but the fibres contained small surface pores (〈 0.2 μm) which continued to increase in size on subsequent heating, resulting in a weak and brittle fibre. Therefore, more investigation is required into sintering and the development of high temperature properties.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 34 (1999), S. 1277-1279 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The laboratory development of sol/gel ceramic fibres requires rapid objective means of assessing the mechanical and thermal properties of a product at the earliest stages of preparation. The merits of a simple tumbling test, leading to a fibre friability index, and the Bend Stress Relaxation test, which gives a high temperature creep rating, are demonstrated on commercial Saffil and Safimax alumina fibres and a development Saffil zirconia fibre, each in staple blanket form. Measurements on Altex continuous alumina/silica fibre and Nicalon are also presented. Standard and off specification alumina fibres are readily distinguished by their friability indices which correlate with the fibre strain to break. Saffil and Safimax alumina are comparable to Nicalonin terms of creep and superior to Altex. Saffil zirconia approaches alumina creep performance after post firing to 1250°C.
    Type of Medium: Electronic Resource
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