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  • 1995-1999  (47)
  • 1985-1989  (37)
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  • 1
    Electronic Resource
    Electronic Resource
    Increase in soluble phosphorus transported in drainflow from a grassland catchment in response to soil phosphorus accumulation (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 11 (1995), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Because of the observed variability in soil available P (Olsen) contents, phosphorus budgets were used to predict changes in the soil P status of an intensively managed 6 ha grassland catchment in Northern Ireland. The P accumulation rate of approximately 24 kg/ha/y suggested an increase of soil available P (Olsen) of 1.0 mg P/kg/y. Soluble reactive phosphorus concentrations in drainflow measured on a daily basis for a two year period (January 1981 — December 1982) were compared with the two year period January 1990 — December 1991. The median concentration had increased by 10.0 μg P/1 in 1990/91 compared with 1981/82. This difference was only apparent in mean concentrations for the two time periods, after data associated with high flow events, which were more frequent in 1981/82, were excluded from the comparison. This rate of increase of 1.1 μg P/1/y, which was interpreted as reflecting an increase in soluble reactive phosphorus concentration in soil solution, is comparable to the increase in background soluble reactive phosphorus of 1.5 ± 0.54 μg P/1/y which was reported recently over a 17 year period from diffuse sources in the much larger (4400 km2) Northern Ireland catchment of Lough Neagh.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1995.tb00957.x
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  • 2
    Electronic Resource
    Electronic Resource
    Carrier-density dependence of the photoluminescence lifetimes in ZnCdSe/ZnSSe quantum wells at room temperature (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3359-3361 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence lifetimes have been measured at room temperature as a function of carrier density in ZnCdSe/ZnSSe quantum wells. We show that, at low carrier density (5×109–5×1010 cm−2), nonradiative recombination dominates, while radiative recombination becomes more dominant as the carrier density is increased from 5×1010 to 5×1011 cm−2. Above ∼5×1011 cm−2, band filling effects are shown to produce a saturation of the lifetimes. A simple rate equation model approach can be used to describe the carrier density dependence of the photoluminescence decay data obtained on a wide range of samples. A representative band-to-band recombination coefficient of 8×10−4 cm2 s−1 and a Shockley–Read–Hall rate of 7.3×107 s−1 were determined for one of the better samples studied. We believe that the excellent quality of our samples has allowed for the radiative recombination coefficient to be characterized accurately at room temperature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123344
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  • 3
    Electronic Resource
    Electronic Resource
    Calculation of gain-current characteristics in ZnCdSe-ZnSe quantum well structures including many body effects (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3780-3782 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The gain-spontaneous recombination characteristics have been calculated for a 40 A(ring) Zn0.8Cd0.2Se-ZnSe quantum well including many body effects. We examine the effect of the inclusion of the Coulomb enhancement on the gain spectra and the gain-current relationship. We show that, in the absence of the Coulomb enhancement, the threshold current density of a 340 μm 40 A(ring) Zn0.8Cd0.2Se-ZnSe quantum well laser is underestimated by approximately 40% and the lasing wavelength overestimated by 4 nm. Our calculation of the scattering lifetime for the first electron-heavy hole transition gives a lifetime varying between 29 and 37 fs, and shows that the carrier-phonon scattering mechanism in II-VI quantum wells is more dominant than in III-V materials. We also comment on the effect the neglect of Coulomb enhancement has on the calculation of leakage currents in a laser at threshold. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115381
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  • 4
    Electronic Resource
    Electronic Resource
    Defect annealing in a II–VI laser diode structure under intense optical excitation (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 194-196 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Defect annealing under intense pulsed optical excitation has been observed in a II–VI laser diode structure at room temperature. More than one order of magnitude increase in photoluminescence intensity has been obtained when the annealed area is probed at low excitation intensity. High-resolution confocal photoluminescence images of the annealed region do not show any sign of degradation. Together, these results suggest that an initial density of intrinsic point defects present within the active region can be removed by the optical annealing. Recombination-enhanced defect reactions in the vicinity of the point defects are responsible for this nonthermal annealing effect. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120682
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of biologically available phosphorus using a radiobioassay technique (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 15 (1985), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 〈list xml:id="l1" style="custom"〉1A kinetic approach in which the uptake rate of simultaneous additions of orthophosphate and carrier-free phosphorus- 32 by a standard culture of the green alga Selenastrum capricornutum under near neutral conditions was used to obtain an estimate of the readily available components of the total phosphorus pool in natural freshwater samples.2A comparison was made between the values of the biologically available phosphorus obtained using this radiobioassay technique and those obtained by the soluble reactive phosphorus procedure for thirty-one freshwater samples. Only about three-quarters of the phosphorus measured as soluble reactive phosphorus was readily available to algae. The results agreed with those obtained in an earlier study in which an enzymatic procedure was used to determine orthophosphate.3The results of tests carried out on the water samples used in this study were consistent with the conclusion that the presence of a hydrous ferric oxide-orthophosphale complex in the samples caused the soluble reactive phosphorus value to be greater than the corresponding biologically available phosphorus value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1985.tb00230.x
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  • 6
    Electronic Resource
    Electronic Resource
    Optical measurement of the ambipolar diffusion length in a ZnCdSe–ZnSe single quantum well (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 536-538 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a straightforward technique for the measurement of carrier diffusion in semiconductors. Using an optical microscope we can spatially image luminescence with a resolution of ∼500 nm. We measured the ambipolar diffusion length in a Zn0.75Cd0.25Se–ZnSe single quantum well by fitting the spatially resolved luminescence profile with the solution of the two-dimensional diffusion equation. The ambipolar diffusion length was found to be 498 nm at a carrier density of ∼1×1018 cm−3 and we deduce an ambipolar diffusion constant of 1.7 cm2 s−1. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364094
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  • 7
    Electronic Resource
    Electronic Resource
    Pathogen Alarm Behavior in a Termite: A New Form of Communication in Social Insects (1999)
    Springer
    Naturwissenschaften 86 (1999), S. 544-548 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract  Dampwood termites, Zootermopsis angusticollis, show an alarm response after detecting the presence of spores of the pathogenic fungus Metarhizium anisopliae. Termites in direct contact with a high concentration of spores (107 spores/ml) show a striking vibratory display which appears to convey information about the presence of pathogens to nearby unexposed nestmates through substrate vibration. Nestmates not directly in contact with spores that perceive the vibrational signal increase significantly their distance from the spore-exposed vibrating termites, apparently to escape from the source of infection. The fleeing response is not induced by the presence of the spores alone or by pheromones, and requires the perception of the vibrations propagated through the substrate. This "pathogen alarm behavior" appears to be a previously unrecognized communication mechanism that allows termites to reduce disease risks within the nest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001140050672
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  • 8
    Electronic Resource
    Electronic Resource
    Multiwavelength analysis of a well observed flare from SMM (1985)
    Springer
    Solar physics 99 (1985), S. 167-188 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We describe and analyse observations of an M1.4 flare which began at 17: 00 UT on 12 November, 1980. Ground based Hα and magnetogram data have been combined with EUV, soft and hard X-ray observations made with instruments on-board the Solar Maximum Mission (SMM) satellite. The preflare phase was marked by a gradual brightening of the flare site in Ov and the disappearance of an Hα filament. Filament ejecta were seen in Ov moving southward at a speed of about 60 km s−1, before the impulsive phase. The flare loop footpoints brightened in Hα and the Caxix resonance line broadened dramatically 2 min before the impulsive phase. Non-thermal hard X-ray emission was detected from the loop footpoints during the impulsive phase while during the same period blue-shifts corresponding to upflows of 200–250 km s−1 were seen in Ca xix. Evidence was found for energy deposition in both the chromosphere and corona at a number of stages during the flare. We consider two widely studied mechanisms for the production of the high temperature soft X-ray flare plasma in the corona, i.e. chromospheric evaporation, and a model in which the heating and transfer of material occurs between flux tubes during reconnection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157307
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  • 9
    Electronic Resource
    Electronic Resource
    Optical study on ultrathin InAs/InP single quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1367-1370 
    Details
    ISSN: 0392-6737
    Keywords: Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Optical properties of thin films surfaces and layer structures (superlattices, heterojunctions and multilayers) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Our interest is centred on the very thin layers consisting of only one or a few monolayers of InAs. The optical transition energies, measured by photoluminescence spectroscopy, are compared with theoretical calculations obtained in envelope function approximation and through an empirical tight-binding method. This comparison yields values for the not well-known valence band offset at the InAs/InP interface, and the luminescence lines observed at different energies could be assigned to layers between one and 13 monolayers thick.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457211
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of silicon carbide surfaces of 6H-, 15R- and 3C-polytypes by optical second-harmonic generation in comparison with X-ray diffraction techniques (1997)
    Springer
    Applied physics 65 (1997), S. 251-257 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 42.65.Nx; 78.66; 42.70.N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050574
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