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  • 1
    Electronic Resource
    Electronic Resource
    Afterpulse measurement and correction (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5794-5798 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A pulse of electrons in a photomultiplier sometimes generates succeeding spurious pulses, called afterpulses. These are detrimental to statistical analysis of the distribution of photocounts. A method is outlined to determine the probability of occurrence of afterpulses, by analysis of the frequency distribution of output pulses produced by constant light. A related method is outlined to correct for the effect of afterpulsing, so that the original distribution of photocounts can be determined, even if the light is fluctuating. This correction technique is tested by application to measurements of twinkling starlight and shown to work very well. The method to deduce afterpulse probabilities is developed further to produce values in a form which allows comparison with previous measurements. For one tube the results agree with expectations, but not for another. A plausible reason is given for the discrepancy, illustrating the potential of the method to give information about the operation of photomultipliers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143365
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Internal CO2 Concentration as a Selection Criterion for Storage Respiration Rate in Sugarbeet (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 112 (1994), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Respiration is responsible for much of the sucrose loss that occurs during sugarbeet (Beta vulgans L.) storage. Genotypes with reduced storage respiration rates would provide an efficient method for reducing sucrose losses. However, the current techniques for measuring storage respiration are not adapted easily to breeding programs. Internal CO2 concentration has been recommended as an efficient method for measuring the respiration rate of individual sugar-beet roots in storage. This study examined the effectiveness of internal CO2 concentration as a selection criterion for reducing respiration rate of sugarbeet during storage. Lines resulting from four cycles of divergent selection for internal CO2 concentration were evaluated along with commercial hybrids and low internal CO2 germplasm lines. Selection was effective in shifting internal CO2 concentration. Relative differences in internal CO2 concentration were consistent throughout the 3-year study. Neither the fourth-cycle selections for low nor the fourth-cycle selections for high internal CO2 concentration were significantly different from the original population for evolved CO2. This lack of a close relationship between internal and evolved CO2 indicated that internal CO2 concentration is not an effective selection criterion in a breeding program.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0523.1994.tb00656.x
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of titania aerogels (1992)
    s.l. : American Chemical Society
    Chemistry of materials 4 (1992), S. 1329-1333 
    Details
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/cm00024a037
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  • 4
    Electronic Resource
    Electronic Resource
    Statistics of two-dimensional point vortices and high-energy vortex states (1991)
    Springer
    Journal of statistical physics 65 (1991), S. 495-529 
    Details
    ISSN: 1572-9613
    Keywords: Point vortices ; microcanonical ensemble ; negative temperature ; thermodynamic limit ; 2d turbulence ; U-statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results from the theory ofU-statistics are used to characterize the microcanonical partition function of theN-vortex system in a rectangular region for largeN, under various boundary conditions, and for neutral, asymptotically neutral, and nonneutral systems. Numerical estimates show that the limiting distribution is well matched in the region of major probability forN larger than 20. Implications for the thermodynamic limit are discussed. Vortex clustering is quantitatively studied via the average interaction energy between negative and positive vortices. Vortex states for which clustering is generic (in a statistical sense) are shown to result from two modeling processes: the approximation of a continuous inviscid fluid by point vortex configurations; and the modeling of the evolution of a continuous fluid at high Reynolds number by point vortex configurations, with the viscosity represented by the annihilation of close positive-negative vortex pairs. This last process, with the vortex dynamics replaced by a random walk, reproduces quite well the late-time features seen in spectral integration of the 2d Navier-Stokes equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01053742
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  • 5
    Electronic Resource
    Electronic Resource
    Does microbial biomass affect pelagic ecosystem efficiency? An experimental study (1994)
    Springer
    Microbial ecology 27 (1994), S. 1-17 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacteria and other microorganisms in the pelagic zone participate in the recycling of organic matter and nutrients within the water column. The microbial loop is thought to enhance ecosystem efficiency through rapid recycling and reduced sinking rates, thus reducing the loss of nutrients contained in organisms remaining within the photic zone. We conducted experiments with lake communities in 5400-liter mesocosms, and measured the flux of materials and nutrients out of the water column. A factorial design manipulated 8 nutrient treatments: 4 phosphorus levels × 2 nitrogen levels. Total sedimentation rates were greatest in high-N mesocosms; within N-surplus communities, ⩾1 µM P resulted in 50% increase in total particulate losses. P additions without added N had small effects on nutrient losses from the photic zone; +2 µM P tanks received 334 mg P per tank, yet after 14 days lost only 69 mg more particulate-P than did control communities. Nutrient treatments resulted in marked differences in phytoplankton biomass (twofold N effect, fivefold P effect in +N mesocosms only), bacterioplankton densities (twofold N-effect, twofold P effects in -N and +N mesocosms), and the relative importance of autotrophic picoplankton (maximum in high NY mesocosms). Multiple regression analysis found that of 8 plankton and water chemistry variables, the ratio of autotrophic picoplankton to total phytoplankton (measured as chlorophyll α) explained the largest portion of the total variation in sedimentation loss rates (65% of P-flux, 57% of N-flux, 26% of total flux). In each case, systems with greater relative importance of autotrophic picoplankton had significantly reduced loss rates. In contrast, greater numbers of planktonic bacteria were associated with increased sedimentation rates and lower system efficiency. We suggest that different microbial components may have contrasting effects on the presumed enhanced efficiency provided by the microbial loop.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170110
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  • 6
    Electronic Resource
    Electronic Resource
    A layered approach to network management control (1993)
    Springer
    Journal of network and systems management 1 (1993), S. 41-55 
    Details
    ISSN: 1573-7705
    Keywords: TMN ; network management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Public telecommunications networks have many supporting operations systems to provide network management functions and operational support. These systems must be coordinated to provide a highly reliable network service and to make best use of network resources. With increasing automation of network control, these systems must evolve to provide total network support. One organizing principle for this evolution is the definition of control layers at which individual control functions are exercised. We describe a proposal for layered control, with particular emphasis on the role of network traffic management. Layering will be a significant study item for the next extensions to CCITT's Telecommunications Management Network (TMN) recommendations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026827
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  • 7
    Electronic Resource
    Electronic Resource
    Respiratory infection withchalmydia pneumoniae in middle-aged and older adult outpatients (1994)
    Springer
    European journal of clinical microbiology & infectious diseases 13 (1994), S. 785-792 
    Details
    ISSN: 1435-4373
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study was undertaken to characterize the epidemiology and clinical presentation of infection withChlamydia pneumoniae in a population composed primarily of middle-aged and older adults. Pharyngeal swabs and acute and convalescent phase sera were obtained from outpatients presenting with signs and symptoms of an acute respiratory infection. Sera were examined using the micro-immunofluorescence (MIF) test to detect antibody toChlamydia pneumoniae and complement fixation tests to detectMycoplasma pneumoniae, influenza A virus, influenza B virus, respiratory syncytial virus and adenovirus. Pharyngeal swab specimens were cultured forChlamydia pneumoniae and tested forChlamydia pneumoniae by the polymerase chain reaction (PCR). A total of 743 patients with a mean age of 40.5 ± 16.1 years were enrolled in the study. Twenty-one patients were serologically positive for acuteChlamydia pneumoniae infection in the MIF test. PCR was positive in 15 of the 20 serologically positive patients tested. AcuteChlamydia pneumoniae infection was identified in 3 % (2/76) of subjects with pneumonia, 5 % (12/247) of those with bronchitis, 5 % (3/61) of those with sinusitis only and 2 % (2/103) of those with pharyngitis only. Of the 21 patients withChlamydia pneumoniae infection, seven (mean age of 33 years) had an antibody pattern suggesting a primary infection while 14 (mean age of 54 years) had a reinfection pattern. Patients with reinfection had milder disease than those with primary infection. PCR testing in the current study confirms the previously proposed serologic criteria of acuteChlamydia pneumoniae infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02111337
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