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  • Articles  (33)
  • ozone  (21)
  • Autoradiography
  • Ultrastructure
  • phase transition
  • Springer  (33)
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  • American Geophysical Union
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  • 2000-2004  (33)
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  • 2000  (33)
  • Energy, Environment Protection, Nuclear Power Engineering  (15)
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  • Articles  (33)
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  • Springer  (33)
  • American Chemical Society
  • American Geophysical Union
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  • 2000-2004  (33)
  • 1970-1974
  • 1930-1934
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 186 (2000), S. 347-357 
    ISSN: 1432-1351
    Keywords: Key words Crustacean ; Sensorimotor ; Ultrastructure ; Multilamellar sheath ; Myelinated axons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Speed of nerve impulse conduction is greatly increased by myelin, a multi-layered membranous sheath surrounding axons. Myelinated axons are ubiquitous among the vertebrates, but relatively rare among invertebrates. Electron microscopy of calanoid copepods using rapid cryofixation techniques revealed the widespread presence of myelinated axons. Myelin sheaths of up to 60 layers were found around both sensory and motor axons of the first antenna and interneurons of the ventral nerve cord. Except at nodes, individual lamellae appeared to be continuous and circular, without seams, as opposed to the spiral structure of vertebrate and annelid myelin. The highly organized myelin was characterized by the complete exclusion of cytoplasm from the intracellular spaces of the cell generating it. In regions of compaction, extracytoplasmic space was also eliminated. Focal or fenestration nodes, rather than circumferential ones, were locally common. Myelin lamellae terminated in stepwise fashion at these nodes, appearing to fuse with the axolemma or adjacent myelin lamellae. As with vertebrate myelin, copepod sheaths are designed to minimize both resistive and capacitive current flow through the internodal membrane, greatly speeding nerve impulse conduction. Copepod myelin differs from that of any other group described, while sharing features of every group.
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  • 2
    ISSN: 1573-0832
    Keywords: Autoradiography ; barley ; cytokinins ; Dreschslera maydis ; green islands ; HPLC ; maize ; Pyrenophora teres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Infection of Hordeum vulgare L. by Pyrenophora teresand of Zea mays by Dreschslera maydis were characterized by ‘green island’ formation, higher cytokinin levels and accumulation of metabolites in the infected areas. Higher cytokinin concentrations of the order 6-Y,Y-dimethylallylaminopurine 〉 zeatinriboside 〉 zeatin 〉dihydrozeatinriboside were detected at infection sites of susceptible hosts. By virtue of these cytokinins, infection sites may be acting as metabolic sinks helping proliferation of the pathogen. Existence of translocatory sinks at infection zones was confirmed from autoradiographic studies,where, accumulation of labeled metabolites was prominent at infection sites of susceptible hosts. Upon infection the lower cytokinin levels of resistant hosts decreased further with progress of infection. In the infected resistant hosts the concentrations of zeatin/zeatinriboside were the maximum among the four identified cytokinins. The pathogen is also capable of secreting cytokinins as evident from quantification of cytokinins in culture filtrate extracts using HPLC. Since detached leaves were used in the experiments the increase/decrease of various cytokinin levels may be attributed to pathogen influence. The increase in cytokinin levels in the susceptible host may be aiding the growth of the pathogen on one hand, while the decrease in the infected resistant host may signal the host to activate defenses against a potential pathogen at the early stage of infection.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 98 (2000), S. 1049-1061 
    ISSN: 1572-9613
    Keywords: Gibbs measure ; phase transition ; lattice spin system ; discrete symmetry breaking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Georgii's theorem ensures that, restricted to two-dimensional planes, a single ocean (i.e., infinite connected component) of a ground state and islands (i.e., finite connected components) are observed in lattice spin systems at sufficiently low temperature. This paper extends his results for higher dimensional hyperplanes. Our proof is mainly based on a kind of Peierls argument and is different from Georgii's, which relies on the percolation method.
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  • 4
    ISSN: 1573-2959
    Keywords: Three-dimensional model ; anthropogenic emissions ; BVOC ; photochemistry ; ozone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This study concentrated on the effects of Biogenic Volatile Organic Compounds (BVOC) emissions on ozone (O3) in an area of the Eastern Spain on June 12, 1997, a day characterised by sea breeze. Simulation of meteorology was performed with the three-dimensional model ADREA-I. Comparisons of the model results with observations have revealed overall a good agreement in temperature and wind velocity. Two runs were performed with UAM-IV for the photochemical calculations. The first simulated the effects of the anthropogenic emissions only (run A) and the second the combined effects of anthropogenic and biogenic emissions, (run B). Comparisons of the model O3 concentrations with measurements showed a general agreement with the experimental data. Discrepancies between the calculated results and the observations during the early morning hours could be attributed to inaccuracies in nitrogen oxides (NOx) from the anthropogenic emissions inventory. Comparisons between runs A and B yielded differences up to 30% in the morning, over inland areas. It was deduced that the inclusion of BVOC in total emissions could result in an increase or decrease of tropospheric O3, depending on the available amounts of anthropogenic emissions.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Environmental monitoring and assessment 65 (2000), S. 129-137 
    ISSN: 1573-2959
    Keywords: ozone ; passive sampler ; air pollutant ; atmosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A new all season passive sampling system for monitoring O3 in the atmosphere has been developed in the laboratory and validated in the field. The unique features for this system include a newly designed passive sampler and a rain shelter, which allow the passive sampler to be installed in the field facing downwards. An equation associated with meteorological parameters is used to calculate the passive sampling rates. This system has been extensively tested in the lab (temperature from –18 to 20°C, relative humidity from 13 to 81%, and wind speed from 0.5 to 150 cm/s) and validated in the field in climates of all seasons. The accuracy of the ozone concentrations in the atmosphere obtained with the use of the new passive sampling system was higher than 85% compared to those obtained with continuous ozone analyzers. The new ozone passive sampling system can be used to measure ambient O3 concentrations ranging from 3 ppb to 1000 ppb based on one-day exposure and 0.1 ppb to 140 ppb for a monthly exposure period. It is also reasonable to conclude that the new passive sampling system can be used for eight-hour exposure study because of the low field blanks and high sampling rates.
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  • 6
    ISSN: 1573-2967
    Keywords: cluster analysis ; eastern deciduous forest ; geographic information system ; global change ; Monte Carlo simulation ; nitrogen deposition ; ozone ; scaling up ; site index ; southern pine forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Stochastic transfer of information in a hierarchy of simulators is offered as a conceptual approach for assessing forest responses to changing climate and air quality across 13 southeastern states of the USA. This assessment approach combines geographic information system and Monte Carlo capabilities with several scales of computer modeling for southern pine species and eastern deciduous forests. Outputs, such as forest production, evapotranspiration and carbon pools, may be compared statistically for alternative equilibrium or transient scenarios providing a statistical basis for decision making in regional assessments.
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  • 7
    ISSN: 1573-4994
    Keywords: Nonionic surfactant ; microemulsion ; excimer ; pyrene ; phase transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The phase transition of microemulsions involving the nonionic surfactant C12E5 [C12H25(OCH2-CH2)5OH], water, and alkanes (heptane, decane and tetradecane) has been investigated through the excimer formation of pyrene. On going to the microemulsion bicontinuous phase, by changing either composition or temperature, pronounced changes in the pyrene excimer-to-monomer fluorescence intensity ratio, I E/I M, are observed. Several differences in the steady-state emission spectra and in fluorescence decay curves show that as a probe pyrene is well suited to follow the transition from the water continuous to the oil continuous phase, through an intermediate bicontinuous (continuous in both water and oil) region. The results provide information about the different characteristics and structure of these three regions (water continuous, bicontinuous, and oil continuous) of the phase diagram for C12E5/water/alkane systems.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Urban ecosystems 4 (2000), S. 193-229 
    ISSN: 1573-1642
    Keywords: ozone ; radiation measurements ; skin cancer ; urban environments ; urban trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Excess exposure to ultraviolet radiation (UV) from the sun, particularly the ultraviolet B (UVB), is cited as a cause or contributing factor for deleterious effects on human health, including skin cancers and cataracts. Rates of skin cancer have increased greatly in recent years, and increased UVB caused by reductions in stratospheric ozone may be responsible for some of the increase in rates, though quantified estimates of the effect of the UVB changes on health have low certainty. UVB exposure also affects the function of the immune system, and the potential resulting effects on infectious diseases and immunizations are a concern. Epidemiological considerations suggest that peoples' routine exposure to UV in urban areas can be significant in adverse health effects, particularly for young children. Projected trends of ozone indicate that agreements to limit ozone-depleting substances are slowing the UVB increase, but high levels will continue and apparently impact health to the middle of the current century. Urban trees greatly reduce ultraviolet irradiance in their shade when they obscure both the sun and sky. Where trees or other structures obscure only the sun, leaving much of the sky in view, UVB irradiance will be greater than suggested by the visible shade. Since air pollutants influence the UVB above the canopy, and the overlying atmosphere is usually more polluted in urban than rural areas, additional above-canopy monitoring of UV in urban areas is needed for comparison to existing rural monitoring sites. Such monitoring would facilitate the development of computer models of urban effects on UV, which are needed for epidemiological investigations, public education, and urban planning.
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  • 9
    ISSN: 1573-0689
    Keywords: D- and L-alanine and valine ; parity violation of Z0 force ; phase transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Three kinds of experiments have been designed in attempting to observe theparity violation of electroweak force at the phase transition of singlecrystals of D- and L-alanine and valine.(1) An obvious λ phasetransition at 270 ± 1 K was shown in the specific heat measurement ofalanine and valine enantiomers by differential scanning calorimetry. Thebiologically dominant L-enantiomer was found to have lower energy. (2)Magnetization of single crystals of D- and L-alanine and D-valine weremeasured as a function of temperature using the SQUID magnetometer. Thedifference of the mass susceptibility χρ ∼ T curve between theD-alanine and L-alanine is attributable to the variation of intramoleculargeometry of chirality density, which is related to the parity violationenergy shift of a chiral molecule and is a consequence of the short rangeof the weak interaction between the nuclei and electrons. (3) Laser Ramanspectra of D- and L-alanine at different low temperatures (100 K, 250 K,260 K, 270 K, 280 K and 290 K) showed that the second order Cα–Hdeformation modes at 2606 cm-1, 2724 cm-1 of D-alanine vanishedat 270 K but reappeared at 100 K. In the same method, L-alanine has nosuch phenomenon. An obvious decrease in the scattering intensity of themethyne group Cα–H stretching mode at 2964 cm-1 in D-alanineoccurs at the λ transition temperature. We present our experimentsinvolving the possible relevance of Z0 force with Salam's putativephase transition in the origin of homochirality.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of atmospheric chemistry 35 (2000), S. 1-18 
    ISSN: 1573-0662
    Keywords: ozone ; nitrogen oxides ; VOC ; ozone formation ; air pollution ; urban emissions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The ozone forming potential of VOCs and NOx for plumes observed from several cities and a power plant in eastern Germany was investigated. A closed box model with a gas phase photochemical reaction mechanism was employed to simulate several scenarios based upon aircraft observations. In several of the scenarios, the initial concentrations of NOx, VOCs, and SO2, were reduced to study the factors limiting the O3 production. Ozone production was limited by the initial VOC concentrations for all of the simulated plumes. Higher O3 concentrations were produced with reduced initial NOx. In one sample with high SO2 mixing ratios (〉100 ppb), SO2 was also identified as a significant contributor to the production of O3.
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