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  • 1
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The method of electrophoretic separation of nuclear eye-lens proteins was applied to a study of the population structure of the striped mullet Mugil cephalus L. in Hawaii. Electropherograms produced 5 pattern types, with most variations due to non-developmental genetic polymorphism. Some variations, however, were associated with size, and an ontogenetic basis was considered. The frequencies of the pattern types were significantly (p〈0.005) independent among the three geographical subpopulations examined: Kaneohe Bay, Oahu; Diamond Head, Oahu; and Kawaihae Bay, Hawaii. Growth rates of mullet eye-lens nuclei demonstrated significant (p〈0.05) differences between sexes and localities, except for Kaneohe Bay males versus Diamond Head males, which were nearly significant (p ∼0.075). These variations in eye-lens nuclei growth rates are probably regulated by genetic factors. Nearly complete genetic isolation is evident for the three subpopulations of mullet in the Hawaiian Islands. The occurrence of genetic interchange in apparently less frequent between the Oahu and Hawaii populations than between the two Oahu populations, in accordance with their respective geographical distances.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 88 (1974), S. 217-234 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The naupliar stage ofArtemia salina has been found to contain large amounts of an ATPase which requires the presence of Mg++, is stimulated by Na+ and K+, and is sensitive to ouabain. Upon cell fractionation, sixty percent of the Na+K-activated ATPase activity was present in a heavy membrane fraction which accompanied mitochondria, and twenty percent of the activity was found in the microsomal fraction. Separation of the heavy membranes containing the Na+K-activated ATPase from mitochondria was accomplished by sucrose density gradient centrifugation. Kinetic characterization of the Na+K-activated ATPase was examined with both mitochondrial and microsomal preparations. No significant differences were observed between the two preparations. Maximal enzyme activity occurred at pH 7.2 and a temperature of 45 ° C. Half maximal inhibition of enzymatic activity occurred with ouabain concentration of 8 × 10−6 M. Half maximal activation of the enzyme by ATP and MgCl2 occurred at 8 × 10−4 and 1 × 10−3 M, respectively, with an optimal Mg++/ATP ratio of 2.0. NaCl and KC1 (or NH4C1) were required for activity, with half maximal activation at 1 × 10−2 and 9 × 10−3 M (or 2.1 × 10−2 M), respectively. The optimal Na+/K+ ratio was 4.0, although enzymatic activity occurred through a wide range of ratios. In contrast, survival of nauplii was reduced in media in which the Na+/K+ ratio was less than 10. Anatomical localization of the enzyme in nauplii indicated that the abdominal region contained 44% of the total Na+K-activated ATPase activity, while the cephalothoracic region contained 54% of the total activity. Isolated larval salt glands contained 10% or less of the total activity. In contrast, the adult leg segments containing the salt-transporting organs showed 54% of the total Na+K-activated ATPase activity.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The variability associated with estimating the true concentration of teliospores of dwarf bunt (Tilletia controversa) per 50 g of wheat (TC concentration) in an export wheat shipment was studied by measuring the TC concentration in 16 test samples (50 g) taken from each of 137 export shipments. The variability among the 16 TC test sample results, as measured by the standard deviation, was found to increase with TC concentration. The functional relationship was approximately linear in a full-log plot and regression analysis was used to determine the coefficients of the regression equation. Using statistical theory, the regression equation was modified to predict the standard deviation among test sample sizes other than the 50 g size used in this study. The standard deviation and coefficient of variation associated with using a 50 g test sample to estimate the true TC concentration of a wheat shipment with 2000 spores per 50 g were estimated to be 1062·8 and 53·1%, respectively. Increasing test sample size to 1600 g reduced the standard deviation and coefficient of variation to 187·9 and 9·4%, respectively.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 114 (1995), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Relatively little is known about host-plant insect-resistance genes. Near-isogenic lines (NILs) can be a useful tool in evaluating such genes and their mechanisms of action. Through backcrossing and single-seed selection, NILs have been produced in wheat (Triticum aestivum L.) for resistance/susceptibility to biotype-E greenbug, Schizaphis graminum (Rondani). Crosses among several resistant and susceptible NILs produced segregation patterns in the F2 generation that were inconsistent with simple monogenic inheritance. The simplest genetic hypothesis consistent with the data would involve two independently segregating loci, requiring complementary expression of multiple resistance alleles. F3 segregation data were also consistent with the proposed genetic hypothesis. Multiple alleles are required to account for the observed variation, although the source of the multiple alleles is unknown. Direct comparison of specific resistant/susceptible pairs of NIL's, as well as bulked segregant analysis, should permit elucidation of resistance mechanisms. Based on the segregation data presented, new designations for the resistance loci studied are proposed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3477-3486 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Traditional methods of determining phase and group velocities are often inadequate for many thick-section materials that exhibit greater than 30 dB, frequency-dependent propagation losses across the passband of the transducer. This article describes a measurement method that addresses this problem. Our method is mechanized as a pulsed, swept-frequency interferometer. The method's accuracy and reliability are enhanced by a combination of circuit-design improvements, which increase the signal-to-noise ratio and linearity, and signal-processing methods, which remove circuit-related measurement errors and compensate for diffraction. First we describe the foundations of our measurement method and its mechanization. Then we describe the signal-processing procedures, used to calibrate the instrumentation and to determine the absolute phase and group velocities. To illustrate the method, we determine the phase velocities in a very lossy, 50-mm-thick, glass/epoxy specimen in the 0.3–1.2-MHz region.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6564-6567 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A semilogarithmic expression that accurately approximates gain-current curves of quantum-well lasers and is useful for optimization of device performance is derived. The derivation uses both a curve fitting of the calculated curves and approximate analytical evaluation of integrals that comprise the gain model. The derived expression is used to explain the observed increase in the threshold current of single- and multiple-quantum-well lasers.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2272-2274 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analytical formula that determines dependence of the threshold characteristic temperature T0 on gain in multiple quantum well lasers is derived by approximately evaluating the gain integrals. Because the threshold gain depends on lasing cavity and quantum well structures, the formula determines dependence of T0 on laser length, reflectivities, optical loss, and number of quantum wells. A very good agreement is obtained between theory and experiment.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2174-2176 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spectral emission characteristics of multiple quantum well semiconductor lasers of the Fabry–Perot type are a strong function of laser cavity length and mirror reflectivities. 15 nm theoretically predicted wavelength shifts were validated experimentally. This has immediate applications in the development of semiconductor laser-pumped solid-state lasers, where accurate control of the semiconductor laser pump spectral emission is essential.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 825-827 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The external efficiency ηd of quantum well (QW) lasers is maximum at some characteristic laser length, which is dependent upon mirror reflectivities and the number of QWs in the active layer. The observed decrease in ηd in short lasers is caused by increased optical absorption associated with a high concentration of free carriers in the QW and the surrounding waveguide layer. The carriers spill into the waveguide because of QW subband filling in short cavity lasers with high threshold gains.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 82 (1973), S. 277-289 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Naupliar brine shrimp (Artemia salina) have been used to study the salt-dependent regulation of protein synthesis. Measurement of thein vivo rates of protein synthesis was found to be very complex and dependent upon the leucine concentration of the external medium, rate of leucine entry and time of equilibration between various internal pools of leucine. Techniques were developed which permitted the measurement of rates of incorporation ofl4C-L-leucine into naupliar protein at various salinities under conditions that provided the organisms with a constant internal specific activity. It was found that salinities over 0.25 M NaC1 caused decreased rates of protein biosynthesis. A comparison of the rate of protein synthesis in the presence of chloramphenicol, cycloheximide and puromycin indicated that qualitative as well as quantitative changes in synthesis of proteins was directed by the external salinity. A feed-back mechanism based on the partitioning of available energy (ATP) between ion transport and protein synthesis is hypothesized.
    Type of Medium: Electronic Resource
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