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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 18 (1971), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Rats were fed a protein-free diet for 4 or 6 days. They were compared with rats kept on the same diet for 3 or 5 days and on adequate protein for one additional day. The incorporation of 14C-labelled amino acid into protein was studied in systems containing ATP, GTP, phosphoenolpyruvate, pyruvate kinase and if required, a mixture of unlabelled amino acids and either the 6000 g supernatant fraction of a brain homogenate or microsomes and soluble enzymes. The 6000 g supernatant fraction showed variation in amino acid incorporating activity as well as in RNase activity as measured by breakdown of labelled polyuridylic acid. There was no difference in RNase activity in isolated microsomes, but the amino acid incorporating activity was significantly higher in preparations obtained from rats fed one meal of protein after 5 days of protein-starvation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 18 (1995), S. 0 
    ISSN: 1460-2695
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau
    Notizen: A high speed steel, processed by two powder metallurgy routes and heat treated to give a range of microstructures, was investigated in 4-point bending at room temperature using smooth and precracked specimens. The finer microstructures were in the material from gas atomised powder which was hot isostatically-pressed, commercial ASP60 alloy, while the coarser microstructures derived from laboratory vacuum sintering of water-atomised powder. The resultant hardness values Hv50 were in the rage 780 to 1050, prior autenite grain sizes, 5 to 25 pm and maximum carbide sizes, 6 to 32 μm.Only some of the uncracked samples exhibited macroscopic yielding, at stresses in the range 1.64 to 2.59 GPa; the finer microstructures being asSociated with the higher strengths. Macroscopic plastic deformation never exceeded 0.33%; fracture strengths were in the range 1.46 to 2.75 GPa. Fracture toughness, Klc, varied from 12 to 17 MPa√m in the Hy50 range 920 to 800 for the directly sintered steel and only from 10 to 12 MPa√m in ASP60. The insensitivity of K1c to macroscopic hardness in ASP60 is asSociated with the plastic zone size of 1.5 μm which approximates to the average carbide spacing.Nucleation and growth of natural, i.e. stress-induced, microcracks in un notched specimens was studied by surface replica microscopy. Crack nucleation took place at stresses between 0.5 and 1.5 GPa, i.e. below those for yielding and for fracture, σF, and was by debonding of inclusions (alumina and calcium-alumino silicates) or cracking of carbides. In the coarsest microstructure monotonic stepwise subcritical crack growth was observed from stress levels of ∼1.3 GPa, i.e. ∼0.8 to 0.9σF. Similarities to the behaviour of short fatigue cracks in metallic materials and the R-curve behaviour of ceramics are referred to.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 199 (1963), S. 1284-1285 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] At about this strain rate the yield stress of niobium free of impurities is predicted2 to be ~ 2.5 kg mm2 and this is postulated to be the PeierlsNabarro force. Considering this model, the yield stress of this 'pure' niobium at 77 K should be ~ 50 kg mm2. Using a 'flash-annealing' technique the ...
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Studia logica 40 (1981), S. 55-66 
    ISSN: 1572-8730
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Philosophie
    Notizen: Abstract The intuitionistic consequence operation restricted to the language with ↔ (equivalence) and ∼ (negation) as the only connectives is axiomatized by means of a finite set of sequential rules of inference.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Studia logica 32 (1973), S. 74-74 
    ISSN: 1572-8730
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Philosophie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    ISSN: 1432-2072
    Schlagwort(e): Ingestion ; Morphine ; Preference ; Rat ; Zimelidine ; 5-HT
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Zimelidine, a specific 5-HT uptake inhibitor, reduced peroral morphine consumption by morphine-addicted adult male and female Sprague-Dawley rats and old male rats in choice tests. The effect was dose dependent in male rats. Thus, the availability of central 5-HT appears to be important for the regulation of morphine preference in rat. The results are discussed in relation to recent literature where ethanol preference has been found to be attenuated by zimelidine. The results may provide insights into the complex cellular mechanisms underlying opiate addiction.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-0533
    Schlagwort(e): Pre-postnatal malnutrition ; Postnatal rehabilitation ; Soluble proteins ; S-100 protein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Rats were made protein-calorie malnourished (PCM) by pre- and postnatal food deprivation. They were killed at either 28 or 84 days of age. The body weight of the PCM rats was approximately 50% of that of normally fed animals, and the brains of the malnourished animals weighed about 20% less than controls at 28 days of age, while the brain weight curve showed that the undernourished animals started to catch up with the controls toward 84 days of age although not reaching the level of control animals. Concerning PCM animals, postnatally rehabilitated by cross fostering until weaning and afterward given full nourishment no differences in brain or body weigts as compared to controls existed at 84 days of age. At 28 days the S-100 protein of PCM rats was decreased in the occipital cerebral cortex, anterior part of cerebellar hemispheres, and in the brain stem. At 84 days PCM had caused a decreased level of S-100 protein also in other brain regions, such as parietal cortex, posterior part of cerebellar vermis, and hippocampus. Since the S-100 protein is produced by and mainly located in astrocytes the most likely explanation for the reduction of the amount of this protein would be that the susceptibility of the astroglial cells of young rats to PCM varies in different brain areas. Postnatal nutritional rehabilitation through cross fostering during lactation and administration of a full diet after weaning until 28 or 84 days of age resulted in normal S-100 levels but elevated levels of other soluble proteins in parietal cortex and in the brain stem. Since proliferation and differentiation of the S-100 containing astroglial cells takes place mainly postnatally it is conceivable that PCM restricted to the prenatal period does not affect the levels of this protein in the brain regions examined.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Archives of toxicology 43 (1980), S. 187-199 
    ISSN: 1432-0738
    Schlagwort(e): Inhalation of trichloroethylene ; Mongolian gerbils ; Polypeptide ; pattern ; S 100 protein ; Soluble brain proteins ; Brain areas
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Inhalation exposure of adult Mongolian gerbils to 320 ppm of trichloroethylene (TCE) during 8 weeks causes a decrease of soluble proteins per wet weight in frontal cerebral cortex, cerebellar anterior part of the hemispheres and in the posterior part of vermis, as well as in hippocampus, although the levels of S 100, a glial cytoplasmic protein, showed an overgoing increase back to control levels, or a significant increase. In the sensory-motor cortex, an overgoing increase of soluble proteins, as well as of the S 100, were observed during the exposure period. One of the major soluble polypeptides (m.w. 50,000–52,000) of cerebral cortex, the cerebellar hemispheres and the brain stem, decreased at the end of the exposure period. Possible candidates for such a polypeptide are among others the subunit of microtubular protein or a subunit of (Na+K+)-ATPase. The results show that inhalation of TCE effect various brain areas differently. The observed biochemical changes could be interpreted as an adaptation and in some brain areas neuronal cells seem to be more sensitive than glial cells to TCE.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 23 (1988), S. 2213-2219 
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Cast, wrought, and directly sintered smooth and precracked beam specimens of BT1 steels were studied in three- and four-point bending at room temperature. Following austenitization at 1250° C and tempering between 500 and 560° C, brittle fracture strengths varied between 1.1 and 2.8 GN m−2 and the fracture toughness of the materials was in the range 18 to 25 MN m−3/2. Combining these data, the critical Griffith-Irwin flaw sizes were calculated to be typically of the order of 100 μm. This is in reasonable agreement with the observed sizes of some failure-initiating sites, particularly pores in sintered material, but generally several times larger than the carbide and grain sizes. In wrought specimens, failure frequently originated from groups of carbides, apparently fracturing on contiguous planes. No evidence of sub-critical cracking of carbides was detected (as in BT42), in contrast to BM2, BT6 and sintered and hot isostatically pressed BT1. Only inter-powder particle parting occurred in this sintered material. Conventional fracture mechanics thus successfully interprets results on sintered specimens, but only on several of the wrought specimens. For the majority of the latter it appears necessary to invoke operation of propagation mechanisms involving “short”, ≈10 μm, cracks under monotonic loading or to associate the brittle fracture stress with that for crack nucleation: e.g. cleavage of a carbide cluster.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    International journal of fracture 17 (1981), S. R17 
    ISSN: 1573-2673
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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