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  • 1
    ISSN: 1432-2145
    Keywords: Key words Calmodulin ; mRNA ; Calcium ; Pollen tube ; Agapanthus umbellatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Pollen tube growth is a vital process for angiosperm fertilisation and is dependent on the presence of a tip-focused gradient of cytosolic free calcium ([Ca2+]c). In order to clarify some of the target molecules which convey the Ca2+ signal information, we investigated calmodulin distribution during tube growth. Fluorescently labelled calmodulin was pressure microinjected into pollen tubes and its distribution monitored by confocal microscopy. Calmodulin distributes evenly throughout the cell, but some of its binding sites form a V-shaped collar behind the apical region. This specific association dissipates upon growth arrest, and suggests an interaction of calmodulin with cytoskeletal-bound target proteins. The distribution of calmodulin mRNA was also analysed by microinjection of fluorescently labelled mRNA. No specific pattern was observed, with an even localisation in the body of tube and a lower concentration in the cell apex. Studies with localised application of inhibitors/activators indicate that calmodulin plays a crucial role in tip elongation but does not direct tube orientation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 56 (1984), S. 82-85 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Irradiation dose affected production of volatiles in vacuum-and aerobic-packaged cooked pork sausage, but its effect on TBARS was minor. Storage increased production of volatiles and changed their composition only in aerobic-packaged sausage. Among volatile components, 1-heptene and 1-nonene were influenced most by irradiation dose, and aldehydes by packaging type. TBARS and volatiles of vacuum-packaged irradiated cooked sausage did not correlate well. However, TBARS had very high correlation with amount of aldehydes, total volatiles, ketones and alcohols with long retention times in aerobic-packaged pork sausage. Heptene and 1-nonene could be indicators for irradiation; and propanal, pentanal, and hexanal for oxygen-dependent changes of cooked meat.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A numerical optimization approach is introduced to the subject of dynamo theory. Conventional kinematic dynamo studies treat the induction equation as an eigenvalue problem by choosing a candidate velocity field and solving for a marginally stable solution of magnetic field and critical magnetic Reynolds number. The conventional approach has told us something about dynamo action and magnetic field morphology for specific velocities, but the arbitrary choice of fluid flow is a hit-or-miss affair; not all velocities sustain dynamo action, and of those that do, few yield mathematically tractable solutions. As a result, progress has been slow. Here we adopt a new approach, a non-linear numerical variational approach, which allows us to solve the induction equation simultaneously for both the magnetic field and the velocity field. The induction equation is discretized following the Bullard-Gellman formalism and the resulting algebraic equations solved by an iterative, globally convergent, Newton-Raphson method. The particular choice of optimization constraints allows one to design a dynamo which satisfies certain conditions; in this paper we minimize a linear combination of the kinetic energy (magnetic Reynolds number) and a smoothness norm on the magnetic field to produce efficient (low magnetic Reynolds number) well-converged (smooth magnetic field) solutions. We illustrate the optimization method by designing two dynamos based on a Kumar-Roberts velocity parametrization; a specific choice of the velocity parameters, KR, sustains a 3-D kinematic model of the geodynamo. Compared with KR, one of our new models, LG1, is designed to have a higher magnetic Reynolds number but smoother magnetic field, and the other, LG2, a lower magnetic Reynolds number and somewhat rougher magnetic field. We suggest that dynamo efficiency, defined by the magnetic Reynolds number, is achieved through reduced differential rotation and a favourable spatial distribution of the helicity. These examples demonstrate the value of the optimization method as a tool for exploring dynamo action with geophysically realistic flows. It can be extended to the dynamic dynamo problem and, by changing the constraints, be used to design dynamos with good numerical convergence, which match the observed geomagnetic surface field morphology and which place useful quantitative constraints on the physical nature of the geodynamo.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-0697
    Source: Springer Online Journal Archives 1860-2000
    Topics: Philosophy , Economics
    Notes: Abstract Smokers and nonsmokers possess equal rights but those rights conflict with each other in the use of shared facilities. Medical research has established that smoking harms not only those who use the product but also those who are passively exposed to it. Laws and private regulation of smoking in shared facilities have resulted in the segregation of smokers from nonsmokers to an outright ban of tobacco use. Such controls have provided unsatisfactory results to both groups. An acceptable ethical solution, based on reduction of harm and compensation, can be derived by applying Moral Audit principles, supported by economic analysis, which does not unduly curtail the rights of both parties as to the use of tobacco products.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Simple approximations for the fields and propagation constants of low-order modes on circular weakly guiding fibres are derived using variational techniques. The high accuracy of these approximations for quasi-parabolic profiles is demonstrated in the case of the Gaussian profile, for which there are no analytical solutions of the scalar wave equation.
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  • 7
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The transverse shift in the field distribution and the correction to the propagation constant of the fundamental and symmetric cladding modes on bent finite-clad single-mode fibres and slab waveguides are evaluated from perturbation theory for effective index values extending below the cladding index. Analytical results are derived in both geometries for the step-profile that are valid within the overall limitations of the theory. However, it is found that, for the fibre geometry only, the method breaks down at certain discrete wavelengths because of degeneracies that occur between the HE12 (LP02) and TE01 (LP11) mode propagation constants.
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  • 8
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We review the important features of the right-angle X-junction diffraction model and discuss both its theoretical framework and its validity range. In addition, we present explicit new results from BPM calculations that show that the analytical model aptly describes the dominant physical processes involved and provides bounds on the numerical results. We also address some misinterpretations of the model that have recently appeared in the literature.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract It is shown that by taking advantage of the maximum in the spectral dependence of the coupling coefficient, very broad-band symmetric and asymmetric single-mode planar couplers can be designed. The symmetric coupler allows at least 95.6% coupling between the two cores over the wavelength range 1.3–1.58 μm, while the asymmetric coupler can act as a 3 dB splitter with only ±1.6% variation in the splitting ratio over the wavelength range 1.3–1.67 μm. In both cases, the design includes the curved input-output arms, and the estimated bend loss is approximately 0.1 dB.
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  • 10
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract This paper analyses the adiabatic forked splitter, a device for separating the power in different modes of a multimoded waveguide into distinct, single-mode waveguides. The concept of two-mode separation in asymmetric Y-splitters is generalized to several modal channels, and the resulting multipronged devices are studied in detail, thus addressing important issues such as (1) the achievement of optimally-short devices, (2) the minimization of radiation loss, and (3) the splicing of the device to external optical components. An approximate relationship is derived between the number of modal channels and the required device length, thus showing that there is an upper limit of about four modal channels, for practical fabrication in planar geometry.
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