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  • 1
    Electronic Resource
    Electronic Resource
    Incorporation of exogenous long-chain alcohols into bacteriochlorophyll c homologs by Chloroflexus aurantiacus (1995)
    Springer
    Archives of microbiology 163 (1995), S. 119-123 
    Details
    ISSN: 1432-072X
    Keywords: Key words Bacteriochlorophyll ; Chloroflexus ; Chlorosome ; Green bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chloroflexus aurantiacus grown in batch culture took up exogenous alcohols and incorporated these into bacteriochlorophyll c as the esterifying alcohol. It was possible to change the distribution of the naturally occurring homologs of bacteriochlorophyll c esterified with phytol, hexadecanol, and octadecanol by adding the appropriate alcohol. The corresponding homolog then made up at least 60% of the cellular bacteriochlorophyll c. It was also possible to obtain novel bacteriochlorophyll homologs not found in detectable amounts in control cells by adding fatty alcohols with short chains (C10, C12) or long chains (C20). These changes in bacteriochlorophyll composition had no detectable effects on the spectral properties of the chlorosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00381785
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  • 2
    Electronic Resource
    Electronic Resource
    Differential magnetoreflection spectroscopy of doped and undoped II–VI semiconductor quantum wells (1997)
    Springer
    JETP letters 65 (1997), S. 45-52 
    Details
    ISSN: 1090-6487
    Keywords: 78.66.Mf ; 78.20.Ls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method has been developed for recording and analyzing the differential magnetoreflection (magnetotransmission) spectra of semiconductor structures with quantum wells. The method was used to determine the exciton g-factor in semimagnetic CdTe/(Cd, Mn)Te heterostructures with quantum wells. In nonmagnetic structures with quantum wells containing a two-dimensional electron gas, the excitonic damping depends on the spin state of the exciton. This effect is explained by the exchange contribution to exciton-electron scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.567318
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  • 3
    Electronic Resource
    Electronic Resource
    Optical creation of a metastable two-dimensional electron gas in a ZnSe/BeTe quantum structure (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 656-658 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A microstructure has been designed in which an electron gas is created optically with variable density. ZnSe and BeTe quantum wells are separated by a BeZnMgSe alloy with band gap 3 eV. When electron-hole pairs are created by ultraviolet light in the barriers, electrons accumulate in the ZnSe quantum well, and holes in the BeTe quantum well. This is because the BeTe valence band lies 900 meV higher than that of ZnSe. Reflectivity and luminescence spectra of the ZnSe well show the destabilization of excitons by an electron gas and formation of trions. The metastable charge-separated state has a very long lifetime (2 s at 2 K). © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121938
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  • 4
    Electronic Resource
    Electronic Resource
    The Ectoparasites of the European Badger, Meles meles, and the Behavior of the Host-Specific Flea, Paraceras melis (1999)
    Springer
    Journal of insect behavior 12 (1999), S. 245-265 
    Details
    ISSN: 1572-8889
    Keywords: flea ; Paraceras melis ; behavior ; ectoparasite ; host-finding ; badger ; Meles meles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The badger-specific flea, Paraceras melis, jumps repeatedly when separated from its host Meles meles; thereafter fleas settled into sheltered positions. After separation from badgers, some 42% of fleas (n = 63) voided their gut contents; this was associated with a significant increase in mean jumping distance. The maximum longevity of fleas away from the host was 89 days, with 50% mortality at around 35 days. Badger lice, Trichodectes melis, survived for up to 3 days postcapture. We conclude that the badger's habit of frequently swapping dens with a mean period of return of 6 days is unlikely to bring about significant mortality of adult fleas but may effectively eradicate lice. Fleas abandoned in “bedding” in a simulated badger sett were mobile, being drawn toward light and moving upward. This response would draw the fleas to the den entrance, which may be a suitable site to intercept returning badgers. The fleas responded to stimuli which might signal the proximity of the host: they jumped toward sources of carbon dioxide and of carbon dioxide in air current directed at the flea. The strongest response was seen when a mixture of stimuli consisting of carbon dioxide, a dark circle of card, and movement were tested; the majority of fleas jumped toward the mixed stimulus. Finally, fleas separated from the host responded to exhaled air by running and jumping; this is in marked contrast to their response to those stimuli when on the host, when fleas run downward and very rarely jump. These contrasting observations find adaptive explanation in the two contexts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020923001987
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  • 5
    Electronic Resource
    Electronic Resource
    Passive Ozone Monitoring for Forest Health Assessment (1999)
    Springer
    Water, air & soil pollution 116 (1999), S. 339-344 
    Details
    ISSN: 1573-2932
    Keywords: ozone ; passive monitor ; indigo ; forest health
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Critical levels of tropospheric ozone, established for the protection of crops and other plants, are now reported as being exceeded over large forested areas, giving rise to the need for an extensive monitoring program to confirm ambient levels within the forest and to detect related forest health effects. The requirement for an inexpensive monitor that can be used in remote locations prompted the development of the Can Oxy PlateTM passive ozone monitor and a monitoring protocol by the air pollution research group of the Canadian Forest Service, Forest Health Network. The monitors underwent initial trials in 1996 and operational trials during 1997 that involved two 2-3 week mid summer exposures in the canopy at selected forest health monitoring plots across Canada, and at adjacent forest openings. In both trials monitors were also co-located with the nearest instrumental ozone monitor. This allowed for the production of a field calibration for quality assurance assessment under field conditions. Results from 1996 indicate highly significant correlations with accumulated ambient ozone concentrations from the instrumental monitors at the co-located sites (r=0.88, p=0.0002). However, no such relationship was found between these sites and the forest plots which were up to 200 kilometres away. This may indicate spatial heterogeneity in ozone exposure between the continuous air quality monitoring sites and the forest plots. This information, together with our knowledge that strong gradients of ozone exposure are found within the canopy, underlines the importance of in situ monitoring of ozone exposure of forest health plots at risk to ozone effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005285026276
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  • 6
    Electronic Resource
    Electronic Resource
    The UV-Visible Absorption Cross-Sections and Atmospheric Photolysis Rate of HOI (1999)
    Springer
    Journal of atmospheric chemistry 34 (1999), S. 137-151 
    Details
    ISSN: 1573-0662
    Keywords: absorption cross-sections ; iodine ; photolysis rate ; reservoir species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The UV-visible absorption cross-sections of HOI have been recorded over the wavelength range 278-494 nm and at 298 K following generation of HOI in the gas phase using laser flash photolysis. The gas phase reaction of OH with I2 was used to produce HOI, and the absorption spectrum of HOI was calibrated relative to the consumption of I2. The HOI spectrum recorded exhibits 2 broad absorption maxima of σ = 3.99 × 10-19 cm2 and σ = 2.85 × 10-19 cm2, centred at 338.4 nm and 404.8 nm respectively. The spectrum is adequately described by a parameterisation consisting of two semi-logarithmic Gaussian distribution functions. The HOI spectrum is more intense than that recorded in previous work of Jenkin, but is in good agreement with more recent work by Bauer et al. The parameterised HOI absorption spectrum recorded in this work was used in a radiative model to calculate the atmospheric photolysis rate (J-value) of HOI. These results indicate that, under most sunlit conditions, HOI has a lifetime with respect to solar photolysis of the order of minutes. Experiments attempting to generate HOI by the reaction of O atoms with C2H5I led to complex absorption spectra containing a negative contribution to the absorption from the photolytic removal of an unidentified species. In addition, evidence was found for adsorption and desorption of an iodine-containing species in the reaction vessel. This behaviour is rationalised in terms of the disproportionation of HOI to I2O, and an uncalibrated spectrum tentatively attributed to I2O has been recorded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006210322389
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  • 7
    Electronic Resource
    Electronic Resource
    Two-dimensional modelling of some CFC replacement compounds (1996)
    Springer
    Journal of atmospheric chemistry 25 (1996), S. 167-199 
    Details
    ISSN: 1573-0662
    Keywords: CFC replacement compounds ; distributions ; tropospheric lifetimes ; trifluoroacetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The Cambridge 2-D Eulerian model has been used to study the potential atmospheric distributions and lifetimes of a number of CFC replacement compounds and their degradation products. The study has focused on HFC 134a and HCFCs 123, 141b and 142b and the major products formed by their atmospheric degradation. The loss of these compounds and their products by hydroxyl radical attack, photolysis and in-cloud hydrolysis have been investigated. The study has shown that HCFCs 141b and 142b have sufficiently long lifetimes to enter the stratosphere in significant quantities, where degradation leads to an increase in the total stratospheric chlorine concentration. The study has also highlighted areas where further experimental work would be valuable, in particular characterisation of the product channels for the degradation reactions and determination of the removal rates of the products in the aqueous phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00053790
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  • 8
    Electronic Resource
    Electronic Resource
    Quantifying the fine scale (1km × 1km) exposure, dose and effects of ozone: Part 2 estimating yield losses for agricultural crops (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 1485-1490 
    Details
    ISSN: 1573-2932
    Keywords: Ozone ; wheat ; areal interpolation ; economics ; yield losses ; critical levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In Britain wheat is an important crop accounting for 41% of the total cereal production. In this study ozone concentrations for 1989 estimated as described in Part 1 of the paper are integrated with the estimated wheat distribution to derive a detailed estimate of the impact of ozone on wheat yields at a fine spatial scale (1km × 1km). These data provide estimates for calculating regional and national yield losses. The methodology can be applied to other crop species. Recent research on a range of crops has established relationships between the economic yield loss for certain crops, including wheat, and ozone exposure. Exposure is described as the accumulated exposure above a threshold experienced during the daylight hours (AOT). Critical AOT values are derived from yield exposure relationships which show linear reductions of yield loss with increasing ozone concentrations. This study has made use of land cover data from remotely sensed imagery at 25m resolution and nationally collected agricultural statistics for counties. These data were combined using an areal interpolation technique to provide more spatially articulate estimates of the location and intensity of wheat production. The results demonstrate the economic importance of ozone as a pollutant. Wheat yield losses attributed to ozone vary between different parts of the country but, for years when ozone levels are high, yield losses are likely to be significant in some areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00477191
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  • 9
    Electronic Resource
    Electronic Resource
    Motion of a solid sphere in a general flow near a plane boundary at zero Reynolds number (1996)
    Springer
    Journal of engineering mathematics 30 (1996), S. 177-213 
    Details
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract It is demonstrated how the hydrodynamic force and moment of force acting on a solid sphere may be calculated when it is placed at rest at an arbitrary position in a two dimensional flow at zero Reynolds number in which the region of flow is bounded by either an undeformable planar free surface or by a plane solid wall. The results so obtained are used to calculate the motion of a freely moving solid sphere in an asymmetric vortex in the presence of an underformable free surface. It is seen that the sphere, depending on the direction of the undisturbed flow, will either spiral into or out of the vortex. This implies that when a dilute suspension of such spherical particles undergoes such a vortex motion in the presence of the free surface, the vortex will either fill up with particles from the surrounding flow or become devoid of particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00118830
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  • 10
    Electronic Resource
    Electronic Resource
    Unnatural Language Processing (1999)
    Springer
    Journal of logic, language and information 8 (1999), S. 363-384 
    Details
    ISSN: 1572-9583
    Keywords: cognitive styles ; diagrammatic reasoning ; logic teaching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: Abstract Computer-based logic proofs are a form of “unnatural” language in which the process and structure of proof generation can be observed in considerable detail. We have been studying how students respond to multimodal logic teaching, and performance measures have already indicated that students' pre-existing cognitive styles have a significant impact on teaching outcome. Furthermore, a large corpus of proofs has been gathered via automatic logging of proof development. This paper applies a series of techniques, including corpus statistical methods, to the proof logs. The results indicate that students' cognitive styles influence the structure of their logical discourse, via their differing methods of handling abstract information in diagrams, and transferring information between modalities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008388812468
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