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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 196 (2001), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The reporter gene xylE (encoding catechol 2,3-dioxygenase) has been modified for a more rational use in Streptomyces. Two reporter fragments, one containing xylE, and the other containing also the upstream gene xylT (which encodes a soluble ferredoxin), have been constructed to allow precise fusion of regulatory regions to the reporter genes. Identical fusions of these xylE and xylTE reporter fragments to the Streptomyces dagA and tipA promoters, in low and high copy number plasmids, show that the levels of xylE mRNA and catechol 2,3-dioxygenase activities are significantly higher when xylT is present.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Nitrous oxide (N2O) is involved in both ozone destruction and global warming. In agricultural soils it is produced by nitrification and denitrification mainly after fertilization. Nitrification inhibitors have been proposed as one of the management tools for the reduction of the potential hazards of fertilizer-derived N2O. Addition of nitrification inhibitors to fertilizers maintains soil N in ammonium form, thereby gaseous N losses by nitrification and denitrification are less likely to occur and there is increased N utilization by the sward. We present a study aimed to evaluate the effectiveness of the nitrification inhibitor dicyandiamide (DCD) and of the slurry additive Actilith F2 on N2O emissions following application of calcium ammonium nitrate or cattle slurry to a mixed clover/ryegrass sward in the Basque Country. The results indicate that large differences in N2O emission occur depending on fertilizer type and the presence or absence of a nitrification inhibitor. There is considerable scope for immediate reduction of emissions by applying DCD with calcium ammonium nitrate or cattle slurry. DCD, applied at 25 kg ha–1, reduced the amount of N lost as N2O by 60% and 42% when applied with cattle slurry and calcium ammonium nitrate, respectively. Actilith F2 did not reduce N2O emissions and it produced a long lasting mineralization of previously immobilized added N.
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  • 3
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Intensively managed grasslands are potentially a large source of N2O in the North Coast of Spain because of the large N input, the wet soil conditions and mild temperatures. To quantify the effect of fertilizer type and management practices carried out by farmers in this area, field N2O losses were measured over a year using the closed chamber technique. Plots received two types of fertilizer: cattle slurry (536 kg N ha–1) and calcium ammonium nitrate (140 kg N ha–1). N2O losses were less in the slurry treatment than after mineral fertilizer. This was probably due to high, short-lived peaks of N2O encountered immediately following mineral N addition. In contrast, the seasonal distribution of N2O losses from the slurry amended plot was more uniform over the year. The greater N2O losses in the mineral treatment might have been enhanced by the combined effect of mineral fertilizer and past organic residues present from previous organic amendments. Weak relationships were found between N2O emission rates and soil nitrate, soil ammonium, soil water content and temperature. Better relationships were obtained in the mineral treatment than in the slurry plots, because of the wider range in soil mineral N. Water filled pore space (WFPS) was a key factor controlling N2O emissions. In the 〉 90% WFPS range no relationships were found. The best regressions were found for the mineral treatment in the 40–65% WFPS range, 49% of the variance being explained by soil nitrate and ammonium content. In the 65–90% WFPS range, 43% of the variance was explained by nitrate only, but the inclusion of soil ammonium did not improve the model as it did in the 40–65% WFPS range. This fact indicates that nitrification is likely to be an important process involved in N2O emissions at the 40–65% WFPS.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 50 (2003), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . The presence of arginine decarboxylase (ADC) enzymatic activity in Trypanosoma cruzi epimastigotes is still a matter of controversy due to conflicting results published during the last few years. We have investigated whether arginine might indeed be a precursor of putrescine via agmatine in these parasites. We have shown that wild-type T. cruzi epimastigotes cultivated in a medium almost free of polyamines stopped their growth after several repeated passages of cultures in the same medium, and that neither arginine nor ornithine were able to support or reinitiate parasite multiplication. In contrast, normal growth was quickly resumed after adding exogenous putrescine or spermidine. The in vivo labelling of parasites with radioactive arginine showed no conversion of this amino acid into agmatine, and attempts to detect ADC activity measured by the release of CO2 under different conditions in T. cruzi extracts gave negligible values for all strains assayed. The described data clearly indicate that wild-type T. cruzi epimastigotes lack ADC enzymatic activity.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The preparation of strontium bismuth tantalate (SBT) thin films at low temperatures for electronic applications is at present the subject of intense study. However, the microstructural evolution of these films has not been extensively reported, despite its importance in the determination of the final properties of the film. In this work, we study SBT thin films with various nominal compositions obtained by the crystallization at 650°3C of spin-coated solutions on a silicon-based substrate. Both the formation of the perovskite phase and the evolution of the grains are analyzed, with special attention to the formation of platelet-like grains. A process of coalescence of initially round grains is proposed to explain the grain growth in this system. We also show that the use of a preannealing step inhibits the grain growth and, therefore, should be avoided. The role that the film thickness plays in the development of large grains is discussed.
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  • 6
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Nitazoxanide, a 5-nitrothiazolyl derivative, is effective in the treatment of a broad range of parasitic infections. In vitro, it is active against several protozoa, including Cryptosporidiwn parvum, Blastocystis hominis, and Giardia intestinalis. The objective of this study was to determine the in vitro effect of nitazoxanide on the growth and morphology of three anaerobic protozoa (Entamoeba histolytica, Giardia intestinalis, and Trichomonas vaginalis) and to compare these effects with those of metronidazole and albendazole. A subculture method was used to determine the concentrations required to inhibit growth by 50% or 90% (IC50 and IC90). Nitazoxanide exhibited IC50 and IC90 values of 0.017 and 0.776 μg/ml respectively, against E. histolytica, 0.004 and 0.067 μg/ml against G. intestinalis, and 0.034 and 2.04 6 μg/ml against T. vaginalis. Based on the IC90 values, nitazoxanide was more toxic than metronidazole and albendazole against E. histolytica; albendazole and nitazoxanide were more toxic than metronidazole against G. intestinalis; and metronidazole was the most toxic drug against T. vaginalis. The effects of nitazoxanide on trophozoite ultrastructure of all three parasites included cell swelling and distorted cell shape, a redistribution of vacuoles, plasma membrane damage, and the formation of extensive empty areas in the cytoplasm of the protozoa.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 59 (2001), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Diet breadth (measured as the S.D. of the log of prey size per larvae; SLH) of blue whiting micromesistius poutassou larvae followed a quadratic equation with larval size. In small larvae, diet breadth in terms of size (SLH), the mean and the maximum of the log of prey size per larvae (MLH and XLH, respectively) increased with larval size as prey size selection shifted to larger prey. In contrast, large larvae tended to reduce diet breadth of prey sizes ingested, focusing on the larger prey that were abundant, instead of raising the upper limit of prey sizes because of the low abundance of larger prey. Except for larvae at the onset of first feeding, number of prey stayed constant or decreased in relation to larval size. Both patterns (in small and large larvae) maintained a constant rate of increase of gut carbon content with increase in larval size. Large larvae appear to maintain the increase in gut carbon content during ontogenetic development by reducing diet breadth (SLH) and increasing selection towards the larger prey that are abundant.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 58 (2001), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The Na+ uptake mechanism of cardinal tetras Paracheirodon axelrodi displayed specialization for operation in dilute waters of the amazonian Rio Negro. Kinetic analysis revealed low Km and high Jmax values which ensure high rates of uptake even in very dilute waters. In contrast, Na+ uptake of angelfish Pterophyllum scalare did not appear to be specialized for dilute waters at all, with much higher Km and lower Jmax values. Na+ uptake in cardinal tetras was high and completely unaffected down to pH 3·5, while uptake in angelfish was much lower and progressively inhibited by dropping pH; it was completely shut down at pH 3·5. During chronic exposure to pH 4·0 and 3·5, angelfish showed no ability to restore Na+ uptake and at pH 3·5 all individuals died between day 3 and 6 presumably due to small, but steady loss of Na+. At low pH, both species displayed a strong ability to prevent stimulation of diffusive Na+ losses. In angelfish, the ability to control diffusive ion losses at low pH was related to a high branchial affinity for Ca2+. For cardinal tetras, the rate of Na+ loss appeared to be independent of water Ca2+ concentration. The specializations of cardinal tetras are similar to other characid fishes tested, but the results for angelfish reveal a new pattern of ion regulation in acidophilic species from the Rio Negro. The differences between the species may be the result of their different distributions, cardinal tetras are found in the central Rio Negro region while angelfish are more peripheral, or they may reflect phylogenetic differences.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 16 (2000), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In order to describe the pelage and external appearance of the Mediterranean monk seal (Monachus monachus) and prepare an age-sex classification guide, 120 seals from the Cabo Blanco Peninsula colony in the Western Sahara/Mauritania were periodically photographed between 1993 and 1996. Analysis of the pigmentation pattern, pelage color and pattern of natural markings of each seal established 48 phenetic types, which were, in turn, arranged in five groups (morphological classes) with multivariate cluster analysis (UPGMA). The variables that best define these groups are size and color. The variation related to relative size, sex and age of 26 identified seals monitored over three years showed that: (1) after each molt, external appearance varied considerably only in non-adults, while adult appearance was invariable; (2) marked sexual dimorphism exists in adults' external appearance; and (3) a remarkable similarity of adult and neonate pelage exists. With these results, we propose an age-sex classification guide to facilitate monk seal identification in the field.
    Type of Medium: Electronic Resource
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