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  • Articles  (81)
  • 2000-2004  (81)
  • 1925-1929
  • 2000  (81)
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  • 2000-2004  (81)
  • 1925-1929
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Journal
  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Genetics 34 (2000), S. 479-497 
    ISSN: 0066-4197
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Be they prokaryotic or eukaryotic, organisms are exposed to a multitude of deoxyribonucleic acid (DNA) damaging agents ranging from ultraviolet (UV) light to fungal metabolites, like Aflatoxin B1. Furthermore, DNA damaging agents, such as reactive oxygen species, can be produced by cells themselves as metabolic byproducts and intermediates. Together, these agents pose a constant threat to an organism's genome. As a result, organisms have evolved a number of vitally important mechanisms to repair DNA damage in a high fidelity manner. They have also evolved systems (cell cycle checkpoints) that delay the resumption of the cell cycle after DNA damage to allow more time for these accurate processes to occur. If a cell cannot repair DNA damage accurately, a mutagenic event may occur. Most bacteria, including Escherichia coli, have evolved a coordinated response to these challenges to the integrity of their genomes. In E. coli, this inducible system is termed the SOS response, and it controls both accurate and potentially mutagenic DNA repair functions [reviewed comprehensively in (25) and also in (78, 94)]. Recent advances have focused attention on the umuD+C+-dependent, translesion DNA synthesis (TLS) process that is responsible for SOS mutagenesis (70, 86). Here we discuss the SOS response of E. coli and concentrate in particular on the roles of the umuD+C+ gene products in promoting cell survival after DNA damage via TLS and a primitive DNA damage checkpoint.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 10-12 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A monolithic microchannel-cooled laser diode array is demonstrated that allows multiple diode-bar mounting with negligible thermal cross talk. The heat sink comprises two main components: a wet-etched Si layer that is anodically bonded to a machined glass block. The continuous wave (cw) thermal resistance of the 10 bar diode array is 0.032 °C/W, which matches the performance of discrete microchannel-cooled arrays. Up to 1.5 kW/cm2 is achieved cw at an emission wavelength of ∼808 nm. Collimation of a diode array using a monolithic lens frame produced a 7.5 mrad divergence angle by a single active alignment. This diode array offers high average power/brightness in a simple, rugged, scalable architecture that is suitable for large two-dimensional areas. © 2000 American Institute of Physics.
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  • 3
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: The Eocene-Oligocene Upper Castle Hayne Aquifer (UCH), a well-indurated limestone with a very high percentage of secondary moldic porosity, is one of the most productive and extensively developed aquifers in the North Carolina Coastal Plain. Ground water from western wells in the UCH is Ca- and HCO3-rich and ground water from easternmost wells is alkali- and Cl-rich. In general, from west to east across the study area, Sr concentrations [Sr] and isotopic ratios of ground water from the UCH and other aquifers evolve toward those of the host aquifer. At the same well site, water from older aquifers usually has a lower 87Sr/86Sr ratio than water from younger aquifers, due to interaction between ground water and sedimentary material in the host aquifers. Comparison of 87Sr/86Sr ratios and [Sr] suggests that most UCH water represents mixing of strontium-poor recharge water from the Surficial Aquifer with varying amounts of strontium from the aquifer rock. For samples that deviate from the calculated mixing line, strontium ratios can often be used to indicate the source of strontium that did not come from UCH rock. Surface waters are characterized by high 87Sr/86Sr ratios and variable [Sr] that depend on the proportion of intermixed sea water. Water from the overlying Yorktown and Pungo River aquifers can be recognized by higher 87Sr/86Sr ratios than those of the UCH and water from the underlying LCH, Beaufort, and Peedee aquifers can be recognized by lower 87Sr/86Sr ratios and higher [Sr].
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have determined that Borrelia burgdorferi strain B31 MI carries 21 extrachromosomal DNA elements, the largest number known for any bacterium. Among these are 12 linear and nine circular plasmids, whose sequences total 610 694 bp. We report here the nucleotide sequence of three linear and seven circular plasmids (comprising 290 546 bp) in this infectious isolate. This completes the genome sequencing project for this organism; its genome size is 1 521 419 bp (plus about 2000 bp of undetermined telomeric sequences). Analysis of the sequence implies that there has been extensive and sometimes rather recent DNA rearrangement among a number of the linear plasmids. Many of these events appear to have been mediated by recombinational processes that formed duplications. These many regions of similarity are reflected in the fact that most plasmid genes are members of one of the genome's 161 paralogous gene families; 107 of these gene families, which vary in size from two to 41 members, contain at least one plasmid gene. These rearrangements appear to have contributed to a surprisingly large number of apparently non-functional pseudogenes, a very unusual feature for a prokaryotic genome. The presence of these damaged genes suggests that some of the plasmids may be in a period of rapid evolution. The sequence predicts 535 plasmid genes ≥300 bp in length that may be intact and 167 apparently mutationally damaged and/or unexpressed genes (pseudogenes). The large majority, over 90%, of genes on these plasmids have no convincing similarity to genes outside Borrelia, suggesting that they perform specialized functions.
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  • 5
    Electronic Resource
    Electronic Resource
    Bingley : Emerald
    Career development international 5 (2000), S. 211-215 
    ISSN: 1362-0436
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Economics
    Notes: This abstract describes research to explore the extent to which issues such as personal courage, fear and the potential for failure are addressed in mentoring relationships. How much can mentoring contribute to personal growth and why it is that some people in mentoring relationships seem to have an almost transformational development experience and yet for others it seems to have little impact? The methodology consisted of individual interviews with National Health Service managers, focus group discussions, reflection on the authors' experiences and discussions with delegates attending the 6th Annual European Mentoring Conference. The article summarises the issues of personal courage and fear addressed in different types of mentoring relationships and identifies the conditions necessary for mentoring relationships that are able to explore these issues.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Requirements engineering 5 (2000), S. 114-124 
    ISSN: 1432-010X
    Keywords: Key words: Elicitation – Epistemology – Linguistic – Prototyping – Representation – Requirements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Human and conversational aspects of requirements and knowledge identification are employed to show that requirements ‘engineering’ is not the same as civil engineering or scientific problem solving. Not only can requirements not be made fully explicit at the start of a project, they cannot be made fully explicit at all. A need is identified to enhance computer-based information systems (CBIS) development methods to accommodate: plurality of incommensurable perspectives, languages and agendas; dynamic representations of system features that can be experienced rather than abstracted and forced into an abstract paper-based representation; recognition that CBIS development is in general a continuous process where users changing their minds is a natural and necessary indication or organisational vitality.  It is suggested that prototyping and rapid application development go some way to addressing these requirements but that they require further development in the light of the theoretical light thrown on the nature of the problem.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Climate dynamics 16 (2000), S. 935-947 
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract  The mechanisms responsible for the seasonal cycle in the tropical central and eastern Pacific sea surface temperature (SST) are investigated using a coupled general circulation model. We find that the annual westward propagation of SST anomalies along the equator is explained by a two-stage process. The first stage sets the phase of the variation at the eastern boundary. The strengthening of the local Hadley Circulation in boreal summer leads to a strengthening of the northward winds that blow across the equator. These stronger winds drive enhanced evaporation and entrainment cooling of the oceanic mixed layer. The resulting change in SST is greatest in the east because the mixed layer is at its shallowest there. As the east Pacific SST cools the zonal SST gradient in the central Pacific becomes more negative. This development signals the onset of the second stage in the seasonal variation of equatorial SST. In response to the anomalous SST gradient the local westward wind stress increases. This increase drives cooling of the oceanic mixed layer in which no single mechanism dominates: enhanced evaporation, wind-driven entrainment, and westward advection all contribute. We discuss the role that equatorial upwelling plays in modulating mixed layer depth and hence the entrainment cooling, and we highlight the importance of seasonal variations in mixed layer depth. In sum these processes act to propagate the SST anomaly westward.
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  • 8
    ISSN: 1573-8469
    Keywords: Rhizoctonia solani ; Thanatephorus cucumeris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective was to identify and characterize the causal agent of foliar necrosis and leaf scorch of Eucalyptus spp. in Brazil. Nineteen putative isolates of Rhizoctonia obtained from Eucalyptus plants during clonal propagation were compared with isolates from other hosts and with tester strains of anastomosis groups of Rhizoctonia solani. Features compared were morphological characteristics of anamorphs and teleomorphs, numbers of nuclei per cell in the vegetative hyphae, anastomosis of hyphae, and ability to produce necrotic lesions on cuttings and damping-off of E. grandis×E. urophylla hybrid seedlings. Rhizoctonia solani AG1 (‘AG1-IB like’) was the most frequent causal agent isolated from Eucalyptus plants and cuttings with symptoms of leaf scorch and foliar necrosis respectively. These isolates were highly virulent on Eucalyptus cuttings and presented naturally epiphytic growth on Eucalyptus shoots. Binucleate isolates and isolates of R. solani AG4 were also virulent on cuttings and were most virulent on Eucalyptus seedlings causing pre- and post-emergence damping-off. Virulence on Eucalyptus cuttings and seedlings was not restricted to a single species or anastomosis group of Rhizoctonia.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of plant pathology 106 (2000), S. 439-448 
    ISSN: 1573-8469
    Keywords: biological control ; Botrytis cinerea ; Clonostachys rosea ; Gliocladium roseum ; rose ; host development ; wounds ; host residues ; microflora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Development of Clonostachys rosea in rose leaves and petals and control of Botrytis cinerea by the agent were investigated. C. rosea germinated, established endophytic growth, and sporulated abundantly whether the tissues were mature, senescent or dead when inoculated. Germination incidence was moderate on mature and senescent leaves (47% and 35%) and petals (31% and 43%), and high (〉98%) on dead tissues. Sporulation of C. rosea in tissues inoculated when mature, senescent or dead averaged 41%, 61%, and 75% in leaves, and 48%, 87% and 53% in petals. When leaves were wounded with needles before inoculation, germination of C. rosea increased from 45–56% to 90–92%, but sporulation became high (〉 75%) regardless of wounds. When leaves were inoculated with C. rosea at 0–24 h after wounding and subsequently with B. cinerea, germination of the pathogen was reduced by 25–41% and sporulation by ≥ 99%. A humid period prior to inoculation of senescent or dead leaves promoted communities of indigenous fungi, reduced sporulation of C. rosea and B. cinerea, and, in dead leaves, increased control of the pathogen associated with C. rosea. Applied at high density, isolates of indigenous Penicillium sp. and Alternaria alternata from rose interacted with C. rosea and reduced control of the pathogen by 16% and 21%, respectively. In conclusion, C. rosea markedly suppressed sporulation of B. cinerea in rose leaves and petals regardless of developmental stage, minor wounds, and natural densities of microflora. This versatility should allow C. rosea to effectively control inoculum production of B. cinerea in rose production systems.
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  • 10
    ISSN: 1573-5036
    Keywords: ammonia ; ammonium ; arbuscular mycorrhiza ; landfill ; leachate ; salinity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Irrigating arbuscular mycorrhizal plants with leachate from a waste disposal centre was examined in a set of experiments. Application of leachate at half the average concentration found in the field or higher reduced the growth of the host plant, the initiation of mycorrhizal colonisation, and hyphal growth of the mycorrhizal fungus Glomus pellucidum through the soil. Causes of these reductions are complex and interrelated, and associated with the electrical conductivity of the solution, toxicity of specific ions, in particular NH4 +, NH3 and HCO3 −, and changes in the pH causing shifts in the equilibria of the soil solution.
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