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  • Oxford University Press  (22)
  • American Institute of Physics (AIP)  (19)
  • Blackwell Science Ltd  (13)
  • Wiley-Blackwell
  • American Chemical Society (ACS)
  • 2000-2004  (51)
  • 1955-1959  (10)
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  • 1
    Electronic Resource
    Electronic Resource
    Electronic excited-state wave functions for quantum Monte Carlo: Application to silane and methane (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 7795-7804 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the efficient construction of guiding wave functions for use in diffusion Monte Carlo calculations of electronic excited states. We test guiding wave functions obtained from singles-only configuration interaction, time-dependent density functional theory, and complete active space self-consistent field methods. The techniques are used to study the first ionization potentials and excited states of silane and methane. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1342765
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  • 2
    Electronic Resource
    Electronic Resource
    Detailed comparison of simulated and measured plasma profiles in the scrape-off layer and edge plasma of DIII-D (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3663-3680 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of detailed comparisons between experimental measurements of the scrape-off layer and divertor plasmas and simulations using the UEDGE code for a DIII-D discharge [J. Luxon et al., Proceedings of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1986), Vol. I, p. 159] are reported. The simulations focus on understanding the flow of both fuel and impurity particles throughout the edge and scrape-off layer (SOL) plasma. The core impurity content and the core hydrogen ionization rate can be explained by sputtering and recycling in the divertor region alone. The model reproduces most of the detailed experimental measurements. The simulations include the effect of intrinsic impurities, assumed to be carbon originating from sputtering of the plasma facing surfaces. The simulations accurately reproduce the total radiated power, although the spatial profile of radiation is somewhat narrower in the simulation. The measured carbon density on closed field lines is reproduced well with the simulation. Comparison of carbon emission lines indicates the total carbon sputtering yield is a factor of 2 to 4 less than expected, although the total radiated power and core carbon content are insensitive to the sputtering yield. The agreement between simulation and experiment permits more meaningful interpretation of the experimental measurements. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1286509
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  • 3
    Electronic Resource
    Electronic Resource
    Development and characterization of a Z-pinch-driven hohlraum high-yield inertial confinement fusion target concept : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2257-2267 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Initial experiments to study the Z-pinch-driven hohlraum high-yield inertial confinement fusion (ICF) concept of Hammer, Tabak, and Porter [Hammer et al., Phys. Plasmas 6, 2129 (1999)] are described. The relationship between measured pinch power, hohlraum temperature, and secondary hohlraum coupling ("hohlraum energetics") is well understood from zero-dimensional semianalytic, and two-dimensional view factor and radiation magnetohydrodynamics models. These experiments have shown the highest x-ray powers coupled to any Z-pinch-driven secondary hohlraum (26±5 TW), indicating the concept could scale to fusion yields of 〉200 MJ. A novel, single-sided power feed, double-pinch driven secondary that meets the pinch simultaneity requirements for polar radiation symmetry has also been developed. This source will permit investigation of the pinch power balance and hohlraum geometry requirements for ICF relevant secondary radiation symmetry, leading to a capsule implosion capability on the Z accelerator [Spielman et al., Phys. Plasmas 5, 2105 (1998)]. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1348328
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  • 4
    Electronic Resource
    Electronic Resource
    Edge localized mode particle losses from the DIII-D tokamak (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 5140-5150 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Particle losses associated with edge localized mode (ELM) activity on the DIII-D tokamak [J. Luxon et al., Proceedings of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1986, Vol. I, p. 159] are evaluated quantitatively using density profile data obtained from a Thomson scattering system. It is shown that up to 10% of the total core particle content is lost with each ELM. The particle loss varies inversely with ELM frequency. The temporally averaged ELM particle loss is shown to be about 25% of the total particle loss from the confined region under a wide variety of plasma conditions. Although this ELM loss is a small fraction of the total ion flux, it is large compared to the particle input from neutral beam heating. Hence ELM particle losses are sufficient to control the density rise associated with H-mode plasma operation with neutral beam heating. In addition to controlling the average density by enhancing the total ion flow, albeit only by 25%, it is posited that the ELMs play a role in determining the density profile in the H-mode pedestal region. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1412863
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  • 5
    Electronic Resource
    Electronic Resource
    Direct and indirect transcriptional activation of virulence genes by an AraC-like protein, PerA from enteropathogenic Escherichia coli (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 54 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The plasmid-encoded Per regulatory locus of enteropathogenic Escherichia coli (EPEC) is generally considered to consist of three genes, perA, perB and perC. PerA, a member of the AraC-like family of transcriptional regulators, is known to be an activator of its own promoter (autoactivation) as well as of the plasmid-located bfp operon encoding bundle-forming pili, but its role in activation of the chromosomal locus of enterocyte effacement (LEE) pathogenicity island, which confers the property of intimate adherence on EPEC, requires clarification. Here, we show that PerA is also required for activation of the master regulatory LEE operon, LEE1, but that this activation is indirect, being achieved via autoactivation of the per promoter which ensures sufficient production of the PerC protein to activate LEE1. In contrast, PerA-dependent activation of the per and bfp promoters is direct and does not require the other Per proteins, but is modulated by the nucleoid-associated protein H-NS. The closely related VirF regulator from Shigella flexneri cannot substitute for PerA to activate these promoters, despite being able to bind their upstream regions in vitro. PerA can bind the per and bfp promoter fragments to form multiple complexes, while VirF forms only a single complex. Site-directed mutagenesis of the PerA protein suggests that, like VirF, it may use both of its carboxy-terminal helix—turn–helix motifs for DNA interaction, and may also make direct contacts with RNA polymerase. In addition, we have isolated mutations in the poorly characterized amino-terminal domain of PerA which affect its ability to activate gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04333.x
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  • 6
    Electronic Resource
    Electronic Resource
    TlpC, a novel chemotaxis protein in Rhodobacter sphaeroides, localizes to a discrete region in the cytoplasm (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 46 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: TlpC is encoded in the second chemotaxis operon of Rhodobacter sphaeroides. This protein shows some homology to membrane-spanning chemoreceptors of many bacterial species but, unlike these, is essential for R. sphaeroides chemotaxis to all compounds tested. Genomic replacement of tlpC with a C-terminal gfp fusion demonstrated that TlpC localized to a discrete cluster within the cytoplasm. Immunogold electron microscopy also showed that TlpC localized to a cytoplasmic electron-dense region. Correct TlpC–GFP localization depended on the downstream signalling proteins, CheW3, CheW4 and CheA2, and was tightly linked to cell division. Newly divided cells contained a single cluster but, as the cell cycle progressed, a second cluster appeared close to the initial cluster. As elongation continued, these clusters moved apart so that, on septation, each daughter cell contained a single TlpC cluster. The data presented suggest that TlpC is either a cytoplasmic chemoreceptor responding to or integrating global signals of metabolic state or a novel and essential component of the chemotaxis signalling pathway. These data also suggest that clustering is essential for signalling and that a mechanism may exist for targeting and localizing proteins within the bacterial cytoplasm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03252.x
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  • 7
    Electronic Resource
    Electronic Resource
    The third chemotaxis locus of Rhodobacter sphaeroides is essential for chemotaxis (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 46 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The purple photosynthetic bacterium Rhodobacter sphaeroides has three loci encoding multiple homologues of the bacterial chemosensory proteins: 13 putative chemoreceptors, four CheW, four CheA, six CheY, two CheB and three CheR. Previously, studies have shown that, although deletion of cheOp1 led to only minor changes in behaviour, deletion of cheOp2 led to a loss of taxis. The third locus encodes two CheA, one CheR, one CheB, one CheW, one CheY, a putative cytoplasmic chemoreceptor (TlpT) and a protein showing homology to the chromosomal partitioning factor Soj (designated Slp). Here, we show that every protein encoded by this locus is essential for normal chemotaxis. Phototaxis is also dependent upon all the components of this locus, except CheB2 and Slp. The two putative CheA proteins encoded in this locus are unusual. CheA3 has only the P1 domain and the P5 regulatory domain linked by a large internal domain, whereas CheA4 lacks the P1 and P2 domains required for phosphorylation and response regulator binding. These data indicate that the minimal set of proteins required for normal chemotaxis in R. sphaeroides is all the proteins encoded by cheOp2 and the third chemotaxis locus, and that the multiple chemosensory protein homologues found in R. sphaeroides are not redundant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03218.x
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  • 8
    Electronic Resource
    Electronic Resource
    Ozone effects on wheat in relation to CO2: modelling short-term and long-term responses of leaf photosynthesis and leaf duration (2000)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 6 (2000), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: A combined stomatal–photosynthesis model was extended to simulate the effects of ozone exposure on leaf photosynthesis and leaf duration in relation to CO2. We assume that ozone has a short-term and a long-term effect on the Rubisco-limited rate of photosynthesis, Ac. Elevated CO2 counteracts ozone damage via stomatal closure. Ozone is detoxified at uptake rates below a threshold value above which Ac decreases linearly with the rate of ozone uptake. Reduction in Ac is transient and depends on leaf age. Leaf duration decreases depending on accumulated ozone uptake. This approach is introduced into the mechanistic crop simulation model AFRCWHEAT2. The derived model, AFRCWHEAT2-O3, is used to test the capability of these assumptions to explain responses at the plant and crop level.Simulations of short-term and long-term responses of leaf photosynthesis, leaf duration and plant and crop growth to ozone exposure in response to CO2 are analysed and compared with experimental data derived from the literature. The model successfully reproduced published responses of leaf photosynthesis, leaf duration, radiation use efficiency and final biomass of wheat to elevated ozone and CO2. However, simulations were unsatisfactory for cumulative radiation interception which had some impact on the accuracy of predictions of final biomass. There were responses of leaf-area index to CO2 and ozone as a result of effects on tillering which were not accounted for in the present model. We suggest that some model assumptions need to be tested, or analysed further to improve the mechanistic understanding of the combined effects of changes in ozone and CO2 concentrations on leaf photosynthesis and senescence. We conclude that research is particularly needed to improve the understanding of leaf-area dynamics in response to ozone exposure and elevated CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2000.00351.x
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  • 9
    Electronic Resource
    Electronic Resource
    Distribution of benthic algae in the upper Illinois River basin in relation to geology and land use (2000)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 44 (2000), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 〈list style="custom"〉1Benthic-algal distributions in the upper Illinois River basin, IL, U.S.A., were examined in relation to geology, land use, water chemistry and stream habitat using (detrended) (canonical) correspondence analysis, autecological metrics and indicator-species analysis in order to identify the major environmental gradients influencing community variation.2Ionic composition and major nutrient [i.e. nitrogen (N) and phosphorus (P)] concentration of surface waters, salinity (Na-Cl type), substratum type and physiognomic form of dominant species were primary factors contributing to variation in benthic-algal assemblages of the basin. Basin geology was a significant contributing factor, but the explained variance associated with this factor was less than that related to land use.3Proportions of algal biomass consisting of cyanophytes, filamentous chlorophytes, halophilic diatoms and diatoms which utilize nitrogen heterotrophically were greater in eutrophic river segments than in less nutrient-enriched segments. Composition of the benthic flora indicated meso-eutrophic or eutrophic conditions throughout the basin; there were few diatoms indicative of hypertrophic waters. Shifts in diatom-assemblage structure in response to nutrient loading provided an incomplete representation of the community-response curve.4A weighted-averages regression model based on total P and benthic-algal abundances (all divisions included) yielded a highly significant correlation (r2 = 0.83) between species-inferred [WA(tol)] and observed total P, with systematic bias (increased deviation of residuals) occurring only at concentrations greater than ∼ 1.0 mg L−1 total P. This result indicates that total P regression and calibration models can be predictable for a river basin receiving excessive loadings of phosphorus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2000.00536.x
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  • 10
    Electronic Resource
    Electronic Resource
    The effects of high-concentrate diets and pasture on the concentration of conjugated linoleic acid in beef muscle and subcutaneous fat (2003)
    Oxford, UK : Blackwell Science Ltd
    Grass and forage science 58 (2003), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In view of the evidence indicating several potential benefits of high intakes of conjugated linoleic acid (CLA) on human health, an experiment was conducted to examine the effects of the diet of beef cattle on the total CLA concentration in muscle and subcutaneous fat. High-concentrate [steers consumed 515 g concentrates and 485 g grass silage kg−1 dry matter (DM) for 8 weeks followed by 887 g concentrates and 113 g grass silage kg−1 DM for 14 weeks until slaughter] and high-forage (steers consumed 803 g grass silage and 197 g concentrates kg−1 for 8 weeks followed by grass silage only for 10 weeks and then grazed perennial ryegrass-based pasture for 23 weeks until slaughter) treatments were imposed on 48 steers, which were crosses of continental beef breeds (initially 414 kg live weight) The concentrates were based on barley, extracted soyabean meal, molassed sugarbeet pulp and maize meal. The silages were of medium to low digestibility and contained 117–137 g crude protein kg−1 DM and 83–158 g ammonia-N kg−1 total N. The pasture was of high quality and contained 168 g crude protein, 234 g acid-detergent fibre and 222 g water-soluble carbohydrate kg−1 DM. Samples of muscle were taken post slaughter from the m. semimembranosus, m. gluteobiceps, m. longissimus and m. deltoideous muscles, and subcutaneous fat was taken from over the m. longissimus. Concentrations of total CLA in the tissues were for the high-concentrate and high-forage treatments, respectively (mg 100 g−1 fresh tissue), m. gluteobiceps 18 and 47 (s.e. 3·5); m. semimembranosus 9 and 20 (s.e. 1·6); m. longissimus 15 and 35 (s.e. 3·2), m. deltoideous 20 and 59 (s.e. 4·3); subcutaneous fat 584 and 1975 (s.e. 138·7). It is concluded that muscle and subcutaneous fat tissue from grass-fed cattle contained three times as much CLA as those from concentrate-fed cattle, and that the consumption of beef from grass-fed cattle should be effective in increasing the intake of CLA by humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2494.2003.00351.x
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