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  • 11
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Experiments were performed in order to gain information about the primary process leading to the production of sister chromatid exchanges (SCEs). Radical-forming substances (hydroxylamine, hydrazine and the antituberculous drug isoniazid) were examined for their effectiveness in inducing SCEs. All three substances proved successful in the induction of SCEs in the V-79 cell line of the Chinese hamster. By simultaneous application of a sulfhydryl compound (cysteine), a reduction of the hydrazine-and isoniazid-induced SCEs was achieved. Isoniazid was additionally examined in the in vivo SCE-test. At concentrations of 2–100 mg/kg body weight, it does not increase the rate of SCEs in the bone marrow of the Chinese hamster.
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  • 12
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Potentiometric and fluorescence measurements of aqueous solutions of fulvic acid containing Cu(NO3)2 or Cu(ClO4)2, respectively, were carried out at 25 °C and pH 5.5 to determine naturally occurring Cu species. The fulvic acid used was isolated by XAD-8 from filtrated (0.3 μm) water of a peat bog in the Dachauer Moos near Munich. From the results an operational molecular weight of fulvic acid of about 750 g/ mol was estimated, which was confirmed by molecular weight distributions determined by high-performance size-exclusion chromatography (HPSEC), gel permeation chromatography (GPC) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Using this molecular weight and assuming that mainly 1:1 Cu-fulvic acid complexes are formed, a conditional stability constant of the Cu-fulvic acid complex of 105.9 could be calculated. These data are essential for the assessment of organic carrier-mediated migration of Cu as well as of the toxicological risk potential of Cu in aqueous environment and can be used as input parameters for geochemical modeling of the Cu species distribution in aqueous solutions.
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  • 13
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The present analytical study investigates the influence of axial heat conduction within the flow on the heat transfer in the thermal entrance region of a concentric annular duct with laminar and turbulent internal flow. The solution is based on a decomposition of the elliptic energy equation into a pair of first order partial differential equations. By using a new defined vector norm it is possible to obtain a selfadjoint eigenvalue problem for the extended Graetz problem even though the original convective diffusion operator is non-selfadjoint. The obtained exact analytical solutions for the Graetz problem with axial heat conduction are as simple to compute as the related solutions of the parabolic problem.
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  • 14
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ten new cases of accessory bisatellited marker chromosomes examined in different laboratories are reported. As a basis for genetic counselling in the context of prenatal diagnosis a cytogenetic categorization of such marker chromosomes is proposed and an estimation of the genetic risk associated with each category is carried out. The results are as follows: 1. There is no increased risk for offspring with abnormal phenotype born to a healthy carrier of an accessory bisatellited marker chromosome with either a single or two closely adjacent C-bands (Category AI or AII). 2. The unbiased sample of cases with de novo accessory bisatellited marker chromosomes of categories AI and AII is too small to allow a satisfactory estimation of the actual risk that, in case of such a prenatal finding, the foetus may not show a normal phenotype as a consequence of the marker chromosome. There is, however, evidence that this risk may be lower than 10%. 3. Accessory bisatellited marker chromosomes showing a discrete pattern of G- or R-bands situated between two distant C-bands (Category AIII) usually indicate a chromosomal imbalance giving rise to an abnormal phenotype. Mosaic carriers of such dicentric marker chromosomes may, however, present a normal phenotype.
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  • 15
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Nine new cases of prenatally detected true mosaic trisomy 20 (T20) are reported. In three instances the fetuses were aborted. One fetus showed multiple malformations associated with a high percentage of T20 cells among amniotic fluid (AF) cells and fibroblasts of different fetal tissues. In two other fetuses only a slight facial dysmorphy was seen which was accompanied by a low percentage of T20 cells among AF cells. In five instances the pregnancies were carried to term, and normal somatic and psychomotor development of the children has been observed, in one case up to the age of 24 months. In one case the pregnancy is continuing. The T20 cells were not detected among cultured lymphocytes of these children. A review of the hitherto known cases of prenatally detected mosaic T20 indicates a relationship between the prenatal findings and the fetal development. This may serve as a provisory basis for genetic counselling: in the case of a percentage above 50% of T20 cells among AF cells there seems to be a risk of about 50% for the fetus to be affected by severe anomalies. However, in cases of a prenatally detected mosaic T20 with a percentage equal to or less than 50, fetal or congenital malformations have not been observed among 23 individuals so far examined.
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  • 16
    ISSN: 1432-1041
    Keywords: Hypercholesterolaemia ; Fluvastatin ; cholestyramine ; drug treatment of hypercholesterolaemia ; LDL cholesterol ; HDL cholesterol ; triglycerides ; Lp(a) ; apolipoproteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The aim of this study was to investigate the new synthetic HMG-CoA reductase inhibitor, fluvastatin, for efficacy, safety and tolerability in comparison to cholestyramine. One hundred fifty one primary hypercholesterolaemic patients participated in this double-blind, parallel-group, randomized study. During the first 12 weeks of the study, fluvastatin (20 mg and 40 mg daily) was compared with cholestyramine (16 g per day). In the subsequent, 6-week part of the study, the comparative efficacy, safety and tolerability of 20 mg fluvastatin, combined with cholestyramine (4 g, 8 g, or 16 g) were assessed. Fluvastatin (40 mg) reduced LDL cholesterol by 28.0%, triglycerides by 10.5% and increased HDL cholesterol by 3.7%. Cholestyramine (16 g) reduced LDL cholesterol by 35.0%, but raised triglycerides and HDL cholesterol by 12.3% (p〈0.01) and 3.7% respectively. The combination of fluvastatin 20 mg and cholesty-ramine (4 g, 8 g and 16 g) induced the following reductions in LDL cholesterol: 30.4%, 35.6% and 46.6% respectively. There was no significant change in triglycerides in either group although HDL cholesterol was raised by 4.9%, 8.3% and 7.2% respectively. One patient treated with fluvastatin and two treated with cholesty-ramine were withdrawn from the study due to elevation of liver transaminases. The most frequent subjective adverse effects in both treatment groups were mild, transient gastrointestinal complaints. Thus, fluvastatin was effective as a lipid-lowering agent; the effect was further enhanced when fluvastatin was combined with cholestyramine.
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  • 17
    ISSN: 1432-2242
    Keywords: Mitochondrial DNA ; Somaclonal variation ; Cytoplasmic male sterility ; Triticum timopheevi cytoplasm ; Triticale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mitochondrial DNA (mtDNA) organization of primary hexaploid cytoplasmic male-sterile (CMS) triticale regenerants containing Triticum timopheevi cytoplasm was analysed by hybridization experiments and compared with the mitochondrial genome organization of the corresponding regenerants with maintainer cytoplasm. Callus cultures had been derived from immature embryos, and 623 triticale plants were regenerated via somatic embryogenesis after three to four subcultures. The chondriome of 159 regenerants was investigated with regard to somaclonal variation. Six different mitochondrial gene probes and four different restriction enzymes were used for Southern blot analyses by the non-radioactive digoxigenin labeling technique. Alloplasmic regenerants showed a gain or loss of hybridization signals up to a high percentage, while euplasmic ones revealed only minor variability with respect to band stoichiometries. In 24 cases rearrangements in the mtDNA were proved. We suppose that recombination processes and selective amplification events are responsible for these findings.
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  • 18
    ISSN: 1432-0495
    Keywords: Key words Coal mine workers' pneumoconiosis ; Coalification ; Macerals ; Organic compounds ; Phenols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The fibrogenic and cytotoxic potential of coal mine dust is independent of the amount of quartz and other inorganic parameters. Results of coal petrographical and organic geochemical investigations of coals and coal mine dust from the Ruhr and Ibbenbüren Region of Germany demonstrate variations of organic dust amount possibly influencing these noxious properties. Coal mine dust of high rank coals is characterized by a pronounced fibrogenic risk. This risk, independent of the quantity of quartz, is probably based on shape variations of different coal macerals. With increasing coalification of the corresponding seam, the vitrinite is enriched in its dust; however, lower concentrations have been determined for inertinite. Vitrinite shows constant shapes and sizes independent of the rank of coal. Inertinite particles with elongated to fibrous shapes tend to larger sizes with increasing coalification. Strikingly, coal mine dust from miners' lungs with high degrees of coal mine workers' pneumoconiosis (CWP) is enriched in inertinite. In contrast, high cytotoxicities in cell tests are known for coal mine dust from low coalified coals. High concentrations of phenolic compounds can be extracted by dichloromethane from low coalified coal mine dust. These compounds, which are characterized by a high water solubility and therefore high bioavailability, explain the high cytotoxicities of coal mine dust. Contamination of dust by diesel emissions in the coal mine can act as additionally supporting parameters for extended cytotoxicities.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 47 (1991), S. 542-548 
    ISSN: 1420-9071
    Keywords: Bitumen ; microbial activity ; biofilm ; degradation ; gas production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Bitumen is commonly employed as a matrix for the long-term storage of low and intermediate level radioactive waste. As bitumen can be degraded by microbial activity, it is of great significance to determine the rates at which it may occur in nuclear waste repositories. Experiments have been carried out under optimal culture conditions using bitumen with a highly increased surface area. The potential of different microbial consortia to degrade bitumen has been examined. The investigations showed clearly that bitumen-degrading organisms are ubiquitous. In general the organisms formed biofilms on the accessible substrate surface area. Under oxic culture conditions a bitumen degradation rate of 20–50 g bitumen · m−2· y−1 leading to a CO2 liberation of 15–40 l was observed. Anoxic conditions yielded a 100 times smaller degradation rate of 0.2–0.6 g bitumen · m−2 · y−1 and a CO2 production of 0.15–0.45 l. Based on linear extrapolation the experimentally determined degradation rates would lead to a 25–70% deterioration of the bitumen matrix under oxic and 0.3–0.8% under anoxic conditions within 1000 years.
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  • 20
    ISSN: 1432-0630
    Keywords: PACS: 68.35.Ja; 78.47.+p; 82.65.-i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. One of the major goals in physical chemistry is to obtain a microscopic understanding of chemical reactions. Recent developments in femtosecond laser techniques provide the opportunity to resolve the timescale of elementary steps of chemical reactions at surfaces. This is exemplified for the femtosecond laser-induced oxidation of CO on Ru(001). Among other adsorbate-specific probes vibrational sum-frequency generation spectroscopy offers the possibility to monitor adsorbates or reaction intermediates directly at the surface. Recently, we have employed this technique to investigate the dynamics of the CO-stretch vibration of CO adsorbed on Ru(001) after optical excitation leading to CO desorption.
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