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  • 2005-2009  (142)
  • 1995-1999  (76)
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  • 1
    Digitale Medien
    Digitale Medien
    Very high efficiency four-wave mixing in a single semiconductor traveling-wave amplifier (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2186-2188 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on high efficiency frequency-conversion obtained by four-wave mixing in a single traveling-wave semiconductor optical amplifier. Efficiency in excess of 0 dB is demonstrated for frequency conversion up to 2 THz. Measurements of the signal to the amplified spontaneous emission background ratio are also presented. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.116007
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  • 2
    Digitale Medien
    Digitale Medien
    The fauna in the upper stony littoral of Danish lakes: macroinvertebrates as trophic indicators (1998)
    Oxford, UK : Blackwell Science Ltd, UK
    Freshwater biology 39 (1998), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 1. The macroinvertebrate fauna living on stones in the exposed stony littorals of thirty-nine Danish lakes were examined by multivariate numerical methods. The data were derived from 125 semi-quantitative samples and a species list of 126 taxa. The mean number of individuals per sample was 960, and among the most common taxa were Asellus aquaticus, Gammarus, Oulimnius, Tinodes, Cricotopus and Dicrotendipes.2. The total number of species and fourteen individual taxa were positively correlated to mean depth of the lakes and eleven taxa were correlated to the total phosphorus concentration. The Shannon diversity was negatively correlated to the chlorophyll a concentration ([Chl a]).3. Community patterns were examined by detrended correspondence analysis (DCA), and the relationship between species data and selected environmental variables was analysed by canonical correspondence analysis (CCA). Mean lake depth was found to be the strongest environmental variable in explaining the species data. The [Chl a] and Secchi depth also explained significant variation in the distribution of the stony littoral invertebrates. Wind fetch and relative exposure did not explain any variation in the faunal composition among sites.4. The abilities of the macroinvertebrates to predict the lake trophic state, expressed as log ([Chl a]), were explored by means of weighted averaging (WA) regression and calibration. Two tolerance-weighted WA models using inverse and classical regression for deshrinking are presented. The models were assessed by the root mean square error (RMSE) of prediction, using bootstrapping as cross validation, and by the correlation between observed and inferred log ([Chl a]). The model using inverse deshrinking had a RMSEboot = 0.41 and r2 = 0.63. By using classical regression, the predictability in the ends of the gradient was improved but the RMSE increased: RMSEboot = 0.46.5. Although the factors determining faunal distribution patterns in the Danish lowland lakes were highly multivariate and difficult to disentangle, it seems reasonable to use the WA estimated species optima and tolerances to [Chl a] in a bio-assessment model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2427.1998.00298.x
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  • 3
    Digitale Medien
    Digitale Medien
    Gene-regulatory modules In Escherichia coli: nucleoprotein complexes formed by cAMP-CRP and CytR at the nupG promoter (1995)
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Scientific Publication
    Molecular microbiology 17 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Medizin
    Notizen: Repression by CytR depends on the formation of nucleoprotein complexes in which the CytR repressor and the cAMP-CRP activator complex bind co-operatively to the DNA. Transcription initiation from CytR-regulated promoters requires cAMP-CRP; therefore, the cAMP-CRP complex functions both as an activator and as a co-repressor in these promoters. Another interesting aspect of the CytR regulon is that each promoter appears to have individual features. Therefore, structural and functional rules governing the formation of repression and activation complexes in one promoter may not be valid for other promoters of the CytR regulon. Here we show that the Escherichia colinupG gene contains one CytR- and four CRP-binding sites in the control region. Notably, the architecture of the CytR binding site is different from previously described targets. In addition, the CytR repressor triggers a DNA repositioning of a cAMP-CRP complex in the −35 region upon binding to its operator. Thus, formation of the repression and activation complexes at the nupG promoter involves different subsets of CRP-binding sites. These findings show that the bacterium uses positive and negative regulatory modules to differentially control the expression of CytR- and cAMP-CRP-regulated genes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_17050843.x
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  • 4
    Digitale Medien
    Digitale Medien
    Carotenoids in the tiger prawn Penaeus esculentus during ovarian maturation (1995)
    Springer
    Marine biology 123 (1995), S. 435-441 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Female Penaeus esculentus Haswell were collected by 15 to 20 min duration trawls during 1990. Carotenoids were analysed in the digestive gland, abdominal muscle, the remainder of the body (hereafter called “integument”) and ovary of prawns in Stage 2 through Stage 4 (fully mature) of maturation. The only oxycarotenoids (xanthophylls) identified were astaxanthins or astaxanthin esters; occasionally low levels of β-carotene were detected in the digestive gland. The concentrations of astaxanthin monoesters (AM) and diesters (AD) were highest, with only minor amounts of free astaxanthins (Ast), except in the maturing ovaries, where free astaxanthins predominated (up to 80% of the total carotenoid). Of the total carotenoid, 82 to 94% was in the integument, but at maturity the digestive gland contained 10.7±3.4% and the ovary 5.6±0.9% of the total carotenoid. Only the ovary increased in mass during maturation, reaching up to 5.2% of total prawn mass. During this period, digestive gland concentrations of AM, AD and Ast all increased (tota 20 to 120 μg g-1); levels in the muscle and integument varied little throughout maturation (total ∼0.4 and 100 μg g-1, respectively); ovary AM levels remained low throughout (1.5 to 1.2 μg g-1), AD increased from only 2 to 5 μg g-1, but Ast increased from 2 to 34 μg g-1. Apart from the ovary, AM concentrations were the most variable. In common with other decapod Crustacea, the maturing ovary of P. esculentus contained high levels of carotenoids, indicating that these may have an important role in early development. The natural diet of P. esculentus includes a variety of carotenoids, but except for a little β-carotene, the digestive gland, where absorption occurs, contained astaxanthins, with only an occasional trace of β-carotene. This suggests that the conversion of dietary carotenoids to astaxanthin occurs soon after ingestion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00349222
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  • 5
    Digitale Medien
    Digitale Medien
    Carotenoids versus retinoids (Vitamin A) as essential growth factors in penaeid prawns (Penaeus semisulcatus) (1995)
    Springer
    Marine biology 124 (1995), S. 209-213 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Penaeus semisulcatus de Haan adult gravid females, eggs and non-feeding early larvae, including Protozoea I, were used to test the hypothesis that retinoid (Vitamin A) is not required in early decapod crustacean development. In the adult gravid females, retinoids were detected only in the eyes (1.56±0.23 μg g-1 wet mass), whereas there were up to 97 μg g-1 wet mass total carotenoid in digestive gland and epidermis. This was mostly esterified, except in the ovaries, where free astaxanthin predominated (30 μg g-1). No retinoids could be detected in the eggs, the naupliar stages or Protozoea I, but free astaxanthin was metabolised exponentially, falling from 19 μg g-1 in the eggs to 4 μg g-1 in Protozoea I. This suggests that retinoid is not essential in early development and that carotenoid could be taking its place. Also, including retinoids in artificial diets appears to be unnecessary, provided adequate carotenoid is supplied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00347124
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  • 6
    Digitale Medien
    Digitale Medien
    The 3-phosphoglycerate kinase gene of the yeast Yarrowia lipolytica de-represses on gluconeogenic substrates (1996)
    Springer
    Current genetics 29 (1996), S. 446-456 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Key words  Yarrowia lipolytica ; 3-Phosphoglycerate kinase ; Expression ; Disruption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract   We have isolated the 3-phosphoglycerate kinase (PGK) gene of the yeast Yarrowia lipolytica by probing a genomic library with a PCR fragment amplified with primers deduced from two highly conserved regions of various PGKs. It is a unique sequence encoding a polypeptide of 417 residues with extensive homology to other PGKs, especially to that of Aspergillus nidulans (76% identity). The expression of the Y. lipolytica PGK1 gene proved to be higher on gluconeogenic substrates than on glycolytic ones. Haploid strains harboring a disrupted allele were able to grow on mixtures of a gluconeogenic carbon source and of a glycolytic one, but required proline supplementation in the presence of glucose, and were inhibited by glycerol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002940050070
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  • 7
    Digitale Medien
    Digitale Medien
    The 3-phosphoglycerate kinase gene of the yeastYarrowia lipolytica de-represses on gluconeogenic substrates (1996)
    Springer
    Current genetics 29 (1996), S. 446-456 
    Details
    ISSN: 1432-0983
    Schlagwort(e): Yarrowia lipolytica ; 3-Phosphoglycerate kinase ; Expression ; Disruption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have isolated the 3-phosphoglycerate kinase (PGK) gene of the yeastYarrowia lipolytica by probing a genomic library with a PCR fragment amplified with primers deduced from two highly conserved regions of various PGKs. It is a unique sequence encoding a polypeptide of 417 residues with extensive homology to other PGKs, especially to that ofAspergillus nidulans (76% identity). The expression of theY. lipolytica PGK1 gene proved to be higher on gluconeogenic substrates than on glycolytic ones. Haploid strains harboring a disrupted allele were able to grow on mixtures of a gluconeogenic carbon source and of a glycolytic one, but required proline supplementation in the presence of glucose, and were inhibited by glycerol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02221513
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  • 8
    Digitale Medien
    Digitale Medien
    SuperW n gravity on compactified moduli space (1996)
    Springer
    International journal of theoretical physics 35 (1996), S. 2597-2601 
    Details
    ISSN: 1572-9575
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the divergent behavior ofW gravity theories. As a tool, we use the Grothendieck-Riemann-Roch theorem on the compactified moduli space. We show thatW n gravity has severe divergences caused by negative masses. However, for superextension ofW n gravity the divergences by negative masses are miraculously cured by the counterpart contribution of superpartners.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02085764
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  • 9
    Digitale Medien
    Digitale Medien
    The role of glycogen during the ontogenesis of Chironomus anthracinus (Chironomidae, Diptera) (1996)
    Springer
    Hydrobiologia 318 (1996), S. 51-59 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Chironomus anthracinus ; ontogenesis ; glycogen ; ecdysis ; metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Large fluctuations in glycogen content were found in larvae, pupae and adults of Chironomus anthracinus (Zetterstedt) from the profundal zone of Lake Esrom, Denmark. In 2nd, 3rd and 4th instar larvae the glycogen concentration (expressed as percentage of dry weight) increased during periods of aerobic conditions to a maximum of 25%, but decreased in periods of hypoxia longer than two months to 10–12% in young larvae. A further decrease to about 5% took place, when moulting from 2nd to 3rd or from 3rd to 4th instar occurred after overturn. Prior to pupation the glycogen concentration was restored to 26–28%. The glycogen concentration approximated 22% in young pupae, but decreased during the pupal stage and newly hatched adults contained 12–15%. Finally, the glycogen store of both males and females was further reduced during the swarming period. Thus, glycogen seems to be an important energy source (1) during periods with hypoxic conditions, (2) during periods with high internal energy requirement such as ecdyses and metamorphosis, and (3) during the non-feeding adult life stage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014131
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  • 10
    Digitale Medien
    Digitale Medien
    Effects of oxygen deficiency on survival and glycogen content of Chironomus anthracinus (Diptera, Chironomidae) under laboratory and field conditions (1995)
    Springer
    Hydrobiologia 297 (1995), S. 187-200 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Chironomus anthracinus ; oxygen deficiency ; anaerobic metabolism ; glycogen content ; Lake Esrom
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Growth and glycogen content of Chironomus anthracinus in Lake Esrom, Denmark was examined during summer stratification in 1992 and 1993. Simultaneously, effects of oxygen deficiency on glycogen utilization and survival were experimentally studied. The population consisted of almost fullgrown 4th instar larvae in 1992 and 2nd and 3rd instar larvae in 1993. Growth rate and glycogen content changed as hypolimnetic oxygen deficiency increased. During a 1st phase of stratification dry weight and glycogen content increased (2nd and 3rd instars) or was almost constant (4th instar) but decreased significantly during the following 2nd phase. This change from growth to degrowth and utilization of endogenous glycogen reserves correlated with a change in the thickness of the microxic layer (〈0.2 mg O2 1−1) above the sediment surface. The layer increased from 2–3 m in phase 1 to 4–5 m in phase 2, and we suggest that this deteriorated the oxygen conditions and resulted in a change in larval energy metabolism from fully aerobic during the 1st phase to partly anaerobic in the 2nd phase. During the 2nd phase larval metabolism was estimated at less than 20% of normoxic rate. Experimental exposure of the larvae to anoxia indicated highly different survival of young larvae (2nd and 3rd instars) and older larvae (large 4th instars). The morality of young larvae was 50% after three days in anoxia at 10 °C, whereas only 25% of the older larvae had died after 3–4 weeks under similar conditions. Extending the treatment, however, resulted in increased death rate of the 4th instar larvae with only 10% surviving after seven weeks. The anaerobic metabolism of 4th instar larvae as estimated from glycogen degradation at 10 °C was 5% of normoxia in the interval from 0–5 days but 1.5% in the interval from 20–25 days. It is concluded that survival of C. anthracinus in anoxia is very limited, but traces of oxygen in the environment allowing for faint aerobic metabolism prolong the survival time of the larvae from a few days (2nd and 3rd instars) or a few weeks (4th instar) to probably 3–4 months.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019284
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