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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    International journal of biometeorology 38 (1994), S. 33-39 
    ISSN: 1432-1254
    Schlagwort(e): Virus transport ; Diffusion modeling ; Pseudorabies ; Aujeszky's disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Abstract A Gaussian diffusion model was applied to an epizootic of pseudorabies in ten swine herds located in Decatur County, Indiana, USA to test the hypothesis that the virus can be spread via aerosol. The epizootic occurred during January to March, 1988, spreading through ten farms across an area of about 150 km2. The model included a receptor component that provided an estimate of viruses received by the pig within an enclosed barn. Results show that the diffusion model can explain the spread of the virus during the epizootic for all nine farms to which the virus spread.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    International journal of biometeorology 40 (1997), S. 26-40 
    ISSN: 1432-1254
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Abstract Plant germination, growth, maturation, and productivity are heavily influenced by the quality and quantity of the light in its environment. The light environment has traditionally been quantified in terms of radiant heat energy and available photosynthetic radiation (PAR), but detailed spectral irradiance or photon flux distributions have rarely been studied. This information is needed to translate the research that plant photobiologists and photochemists have been conducting with regard to understanding the light controls on plant physiology in the field environment of plant canopies. More interest has recently been generated as the potential impacts of global climate changes on intensively managed and natural terrestrial ecosystems are identified and evaluated. Linkages between the identified impacts of various wavelengths of light on plant physiology and the light environment of the plant canopy are identified, with detailed discussion concerning the impacts of plant canopy structure on the plant light response. Solar radiation in the ultraviolet-B (280–320 nm), ultraviolet-A and blue (350–500 nm), PAR (400–700 nm), blue (400–500 nm), green (500–600 nm) red (600–700 nm), far red (700–800 nm) and near infrared (800–1100 nm) is followed from the top of the plant canopy to the photoreceptor at the cellular level within the plant phytoelement.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    International journal of biometeorology 40 (1997), S. 26-40 
    ISSN: 1432-1254
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Abstract  Plant germination, growth, maturation, and productivity are heavily influenced by the quality and quantity of the light in its environment. The light environment has traditionally been quantified in terms of radiant heat energy and available photosynthetic radiation (PAR), but detailed spectral irradiance or photon flux distributions have rarely been studied. This information is needed to translate the research that plant photobiologists and photochemists have been conducting with regard to understanding the light controls on plant physiology in the field environment of plant canopies. More interest has recently been generated as the potential impacts of global climate changes on intensively managed and natural terrestrial ecosystems are identified and evaluated. Linkages between the identified impacts of various wavelengths of light on plant physiology and the light environment of the plant canopy are identified, with detailed discussion concerning the impacts of plant canopy structure on the plant light response. Solar radiation in the ultraviolet-B (280–320 nm), ultraviolet-A and blue (350–500 nm), PAR (400–700 nm), blue (400–500 nm), green (500–600 nm) red (600–700 nm), far red (700–800 nm) and near infrared (800–1100 nm) is followed from the top of the plant canopy to the photoreceptor at the cellular level within the plant phytoelement.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    International journal of biometeorology 39 (1996), S. 201-212 
    ISSN: 1432-1254
    Schlagwort(e): UV radiation ; Modeling ; Urban climates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Abstract Stratospheric ozone loss in mid-latitudes is expected to increase the ultraviolet-B (UVB) radiation at the earth's surface. Impacts of this expected increase will depend on many factors, including the distribution of light in other wavelengths. Measurements of the photosynthetically active radiation (PAR) and UVB irradiance were made under clear skies at an open field and under the canopy of scattered trees in a suburban area in W. Lafayette, Indiana, USA (latitude 40.5°). Results showed that when there was significant sky view, the UVB penetration into sub-canopy spaces differs greatly from that of PAR. The UVBT canopy (transmittance; irradiance below canopy/irradiance in open) was inversely related to sky view. The UVB irradiance did not vary as greatly between shaded and sunlit areas as did PAR. Analysis of measurements made near a brick wall indicated that the leaf area of a canopy and the brick wall primarily acted to block fractions of the sky radiance and contributed little scattered UVB to the horizontal plant. A model was developed to predict the UVB and PART canopy based on diffuse fraction, sky view, and porosity of the crown(s) through which the beam is penetrating. The model accounted for the UVB and PART canopy to within 0.13 and 0.05 root mean squared error (RMSE), respectively. Analysis of the errors due to model assumptions indicated that care must be taken in describing the sky radiance distribution, the porosity of trees, the penetration of diffuse radiation through porous trees, and the location of sky-obstructing trees and buildings.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Boundary layer meteorology 27 (1983), S. 171-184 
    ISSN: 1573-1472
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract A three-prong spruce twig was modeled as three independent circular cylinders as part of a wind tunnel study of the drag and wake characteristics of twigs in flow velocities ranging from 0.5 to 4.5 m s-1. Using this model, the wake structure and twig drag were explained and length scales describing the microscale wake turbulence were proposed. Results indicate that the drag force on the twig is influenced by the two flow regimes within the range of velocities studied. The two flow regimes are separated by an apparent shift in the flow field evidenced by a rapid change in the drag coefficient at approximately 1.5 m s-1. For the low velocity regime (0.5 to 1.5 m s-1), the flow ‘sees’ a highly porous twig-cylinder with pores a function of the inter-needle spacing and a length scale related to the needle length. For the high velocity regime (1.5 to 4.5 m s-1), the flow ‘sees’ a twig-cylinder with low porosity and a dominant length scale related to the twig needle-tip to needle-tip diameter.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Boundary layer meteorology 35 (1986), S. 317-330 
    ISSN: 1573-1472
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Vertical heat and momentum fluxes were measured by the eddy correlation method under near-neutral conditions during both day and night above a spruce forest canopy. Results show that 50% of the heat transported to the spruce canopy during night and away from the canopy during the day occurs in extreme magnitude events, the majority of less than one second duration. Extreme-magnitude events were more frequent and lasted longer during the day than during the night. The distributions of the duration of extreme events in the same direction as the net heat flux and the turbulence intensity for both day and night were similar. During the night, the mean horizontal windspeed was about 1 m s-1 and the measured coincident transport of momentum and heat accounted for 36% of the total heat flux. The predominant mechanism of forced convection during the extreme nightime heat transport events was excess heat sweeps in which the duration of the event is usually less than 1 s. During the day, the mean horizontal windspeed was about 2 m s -1 and the measured coincident transport of momentum and heat accounted for only 16% of the total heat flux. Local free convection was suggested to account for 27% of the total heat flux. The predominant mechanism of mixed convection during the extreme daytime heat transport events is deficit heat inward interactions. During both night and day, about 10% of the total heat transport occurred in extreme events working against the thermal gradient.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Urban ecosystems 4 (2000), S. 193-229 
    ISSN: 1573-1642
    Schlagwort(e): ozone ; radiation measurements ; skin cancer ; urban environments ; urban trees
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik
    Notizen: 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.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Agronomy journal 91 (1999), S. 1017-1023 
    ISSN: 0002-1962
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Glycine max (L.) Merr.] cultivars on the irradiance received on the leaf surface. Measurements of the above-canopy UVB irradiance on planes having a wide range of slope and aspect were made under cloud-free skies in a soybean field during the summer of 1990. Results showed that the relative irradiance was strongly dependent on the leaf inclination angle and could be modeled by a simple function having a relative irradiance accuracy of 0.14 (root mean square error); with greater model error at small incidence angles to the sun than at large incidence angles. The developed model was then used to evaluate the influence of heliotropy on the UVB dose received on the terminal leaflet. These results suggest that heliotropy in the leaflet acts to reduce irradiance. Since the more tolerant soybean cultivars appear to orient leaflets away from the sun, results suggest that the classification of UVB tolerance may be due in part to the capacity for paraheliotropic response reducing the UVB radiation received.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 2002-05-01
    Print ISSN: 0002-1962
    Digitale ISSN: 1435-0645
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Publiziert von Wiley
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Publikationsdatum: 1999-11-01
    Print ISSN: 0002-1962
    Digitale ISSN: 1435-0645
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Publiziert von Wiley
    Standort Signatur Erwartet Verfügbarkeit
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