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  • 1
    Digitale Medien
    Digitale Medien
    Young's fringes from vertically integrated slab waveguides: Applications to humidity sensing (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6483-6488 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Using a multiple layer optical waveguide system consisting of two vertically slab waveguides, classical Young's fringes may be obtained in the far-field diffraction plane. In agreement with the simple theory of diffraction interference the spacing of the far-field fringes is easily observed on mm to cm dimensions without further transformation of the output light. The simple methods of fabrication and means of optical coupling should provide a readily adaptable method for examining the principles of interferometry in an integrated optical format. The structure acts to transform polarized incident plane wave input light into separate slab modes of the device which emerge as two closely spaced and coherent sources at the output. The elements required for a classical Young's fringe demonstration are therefore all embodied in this approach. The basic concept can be applied to an optical method for sensing. In one example of this we demonstrate measurement of the phase difference induced between the upper and lower propagating modes in structures due to water vapor diffusion into the layers which are formed from hydrophilic polymers. The Young's fringe patterns exhibit a spatial intensity distribution which is sensitive to water vapor introduced over the surface of the structure. Differences in the effective index between the modes of the two waveguides during the diffusion of the vapor causes phase shifts which result in redistribution in the fringe pattern. The anticipated limit of detection of these devices is lower than 1 ppm for water vapor. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.371712
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  • 2
    Digitale Medien
    Digitale Medien
    A classical dilemma (1995)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 102 (1995), S. 0 
    Details
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-0528.1995.tb11442.x
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  • 3
    Digitale Medien
    Digitale Medien
    The Products and Pathways of Glucose Catabolism in Herpetomonas muscarum ingenoplastis and Herpetomonas muscarum muscarum (1997)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 44 (1997), S. 0 
    Details
    ISSN: 1550-7408
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: . The products and pathways of glucose catabolism in the insect trypanosomatids Herpetomonas muscarum ingenoplastis and Herpetomonas muscarum muscarum have been studied with the aim of elucidating how both organisms are able to proliferate well under aerobic and anaerobic conditions. When incubated in medium containing glucose as the only exogenous carbon source, catabolism was found to be fermentative in both cases. Acetate was a major product of both organisms while H. m. ingenoplastis produced more ethanol and propionate and less succinate than H. m. muscarum. Ethanol production by H. m. ingenoplastis decreased both under anaerobic conditions and in the presence of elevated CO2 concentrations, whereas succinate and propionate release by this organism were greater in high CO2 and anoxia, respectively. Succinate production by H. m. muscarum was greatest under anaerobic conditions in elevated CO2 whereas propionate was only a minor product. The same four products were released during growth of the organisms in complex medium, but the relative proportions differed suggesting that other substrates were being used. Both organisms contained enzymes of the glycolytic and pentose phosphate pathways, but while all activities of the TCA cycle were present in H. m. muscarum. NAD-linked isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, succinate CoA synthase and succinate dehydrogenase were not detected in H. m. ingenoplastis. Fumarate reductase activity was present in both organisms. The data presented suggest that CO2-fixation and reverse flux through the TCA cycle may be important factors that enable the organisms to undergo anaerobiosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1550-7408.1997.tb05690.x
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  • 4
    Digitale Medien
    Digitale Medien
    Dermatofibrosarcoma protuberans: An early non-protuberant phase of the tumour (1999)
    Melbourne, Australia : Blackwell Science Pty
    Australasian journal of dermatology 40 (1999), S. 0 
    Details
    ISSN: 1440-0960
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: A 40-year-old female patient presented with a flat scar-like plaque on the upper chest. The patient’s perception of subtle change in the lesion was of paramount importance in the decision to biopsy this lesion of innocuous clinical appearance. Histopathological findings were those of dermatofibrosarcoma protuberans. This case illustrates the early clinical features of the tumour and a recommendation for taking a biopsy of any scar-like plaque where there is no clear history of preceding trauma.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1440-0960.1999.00313.x
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  • 5
    Digitale Medien
    Digitale Medien
    The use of a new viability assay to determine the susceptibility of Cryptosporidium and Eimeria sporozoites to respiratory inhibitors and extremes of pH (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 142 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract A new viability assay for Cryptosporidium and Eimeria sporozoites is described. It involves the use of both acridine orange and bis-benzimide and is more rapid, easier and less subjective than procedures used previously. The assay has been used to investigate the effects of respiratory inhibitors and pH on the sporozoites of C. parvum, C. muris and E. tenella. Neither cyanide nor azide reduced the viability of C. parvum or E. tenella, whereas they had some effect on C. muris. This latter organism, an intracellular parasite of stomach epithelial cells, also differed from the other two in being able to survive pH 2 for as long as 1 h.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08431.x
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  • 6
    Digitale Medien
    Digitale Medien
    Enzymes of energy metabolism in the bradyzoites and tachyzoites of Toxoplasma gondii (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 137 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract The bradyzoite and tachyzoite forms of Toxoplasma gondii, purified from infected animals, were analysed for their activities of phosphofructokinase, pyruvate kinase, lactate dehydrogenase, NAD+- and NADH-linked isocitrate dehydrogenases, and succinic dehydrogenase. Both developmental stages contained high activities of phosphofructokinase (specific for pyrophosphate rather than ATP), pyruvate kinase and lactate dehydrogenase, suggesting that energy metabolism in both forms may centre around a high glycolytic flux linked to lactate production. The markedly higher activity of the latter two enzymes in bradyzoites suggests that lactate production is particularly important in this developmental form. NAD+-specific isocitrate dehydrogenase was not detectable in either stage of the parasite (and proved useful as a measure of the purity of the bradyzoite preparation), whereas both parasite forms contained low activities of NADP+-linked isocitrate dehydrogenase. The results are consistent with the bradyzoites lacking a functional TCA cycle and respiratory chain and are suggestive of a lack of susceptibility of this developmental stage to atovaquone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08090.x
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  • 7
    Digitale Medien
    Digitale Medien
    Amino acid consumption by the parasitic, amoeboid protists Entamoeba histolytica and E. invadens (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 130 (1995), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract Amino acid consumption by Entamoeba histolytica and E. invadens has been measured in order to assess the possible roles of amino acids as energy substrates. Mixtures of amino acids enhanced the growth of the parasites in complex medium and their survival in simple medium. The consumption of several amino acids by the parasites suspended in simple media was greater when glucose was absent, suggesting that they may act as alternative energy sources. Under these conditions, asparagine was consumed extremely rapidly by E. histolytica in particular, and arginine, leucine and threonine were used greatly by both species. There was also a marked consumption of aspartate, but this occurred even when glucose was present. These five amino acids and phenylalanine were the ones consumed in greatest amounts during growth of E. histolytica in complex medium. Under the same growth conditions, E. invadens also used asparagine, arginine, leucine and threonine and in addition there was a large consumption of serine and especially glutamate. In contrast, the aspartate concentration in the complex medium increased and there was also a net increase in the concentration of some other amino acids. Alanine was produced by both species when the parasites were incubated in simple medium with glucose, and in greater amounts during growth in complex media, suggesting that it is an end product of energy metabolism. The findings provide support for the suggestion that energy generation through amino acid catabolism may be a characteristic feature of anaerobic parasitic protists.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6968.1995.tb07728.x
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  • 8
    Digitale Medien
    Digitale Medien
    Use of inhibitors to identify essential cysteine proteinases of Trichomonas vaginalis (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 149 (1997), S. 0 
    Details
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Designing cysteine proteinase inhibitors as antitrichomonal drugs requires knowledge of which cysteine proteinases are essential to the parasite. In an attempt to obtain such information, the effects of a number of cysteine proteinase inhibitors on trichomonad growth in vitro and proteinase activity were investigated. The broad specificity inhibitor trans-epoxysuccinyl-l-leucylamido-(4-guanidino)butane (known as E-64) had little effect on growth of Trichomonas vaginalis (27% inhibition at 280 μM, none at 28 μM) even though the addition of 2.8 μM E-64 to growth medium resulted in inhibition of all but two (apparent molecular masses: 35 k and 49 k) of the parasite's proteinases detected by gelatin SDS-PAGE. This shows that many of the parasite's cysteine proteinases are not essential for growth in axenic culture. In contrast, a peptidyl acyloxymethyl ketone, N-benzoyloxycarbonyl-Phe-Ala-CH2OCO-(2,6,-(CF3)2)Ph, at 16 μM killed T. vaginalis and severely inhibited growth of Tritrichomonas foetus. Exposure of Trichomonas vaginalis to 16 μM of this compound for 1 h resulted in both the 35 kDa and 49 kDa proteinases being inhibited, whereas some other proteinases were unaffected. Similar distinctions between the inhibitor sensitivity of the parasite's cysteine proteinases were apparent when a biotinylated peptidyl diazomethyl ketone was used to detect active proteinases. These data suggest that the growth inhibitory effects of the peptidyl acyloxymethyl ketone are through inhibition of cysteine proteinases that are not affected when the parasites are grown in the presence of E-64. At least one of these enzymes, which include the 35 kDa and 49 kDa cysteine proteinases, must be essential and so a suitable target for chemotherapeutic attack.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6968.1997.tb10306.x
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  • 9
    Digitale Medien
    Digitale Medien
    Methane oxidation potential and preliminary analysis of methanotrophs in blanket bog peat using molecular ecology techniques (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 21 (1996), S. 0 
    Details
    ISSN: 1574-6941
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract: The potential for methane oxidation was measured, and methanotroph gene sequences studied, in a peat core from the Moorhouse Nature Reserve, UK. Methane oxidation potential was observed in all depths of the peat core (down to 30 cm), and was inhibited by addition of acetylene, indicating the involvement of methane-oxidising bacteria. A peak of activity was shown in the 10–12 cm horizon, below which activity decreased with depth. Above this horizon, methane oxidation was relatively high and showed little change with depth. 16S rDNA libraries from several sections of the peat core were screened with methanotroph 16S rDNA probes designed to detect the genera Methylomonas, Methylococcus, Methylobacter and Methylosinus. Two clones, MHP14 and MHP17, hybridised strongly with the Methylosinus probe and upon complete sequencing and phylogenetic analysis were shown to group closely to the Methylosinus/Methylocystis genera of methanotrophs. However, the clones do form a distinct branch of their own, supported by BOOTSTRAP values, and may represent a novel group of acidophilic methanotrophs which have yet to be cultured.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1574-6941.1996.tb00347.x
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  • 10
    Digitale Medien
    Digitale Medien
    Comparisons of the Nucleotide Substitution Process Among Repetitive Segments of the α- and β-Spectrin Genes (1997)
    Springer
    Journal of molecular evolution 44 (1997), S. 492 -500 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Key words: Spectrin — Substitution pattern — Substitution rate — Elliptocytosis — Spherocytosis — Maximum likelihood — Gene duplication
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract. The actin–cross-linking protein spectrin is a prominent component of the membrane cytoskeleton. Spectrin is a tetramer of two antiparallel αβ-dimers which share a unique and ancient gene structure. The α-spectrin and β-spectrin genes are composed primarily of tandemly repeated 106-amino-acid segments, each of which forms a triple α-helical coiled coil. Both the genes and the repeats themselves are homologous. The two genes are thought to be the result of a gene duplication event, and each gene is the product of duplications of the 106-amino-acid repeats. In this work we compare the process of molecular evolution across the repeated segments of the α- and β-spectrin genes. We find that the α-spectrin segments have, for the most part, evolved in a homogeneous fashion, while considerable heterogeneity is found among β-spectrin segments. Several segments with unique known functions are found to have evolved differently than the others. On the basis of heterogeneity of the evolutionary process, we suggest that at least one repeat has a unique function that has yet to be documented. We also present new statistical methods for comparing the evolutionary process between different regions of DNA sequences.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00006173
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