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  • 1
    Electronic Resource
    Electronic Resource
    Fabry-Perot interferometer measurements of neutral winds and F2 layer variations at the magnetic equator (1998)
    Springer
    Annales geophysicae 16 (1998), S. 731-737 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (Equatorial ionosphere; Ionosphere-atmosphere interaction) ; Meteorology and Atmospheric Dynamics (General circulation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This letter presents some night-time observations of neutral wind variations at F2 layer levels near the dip equator, measured by the Fabry-Perot interferometer set up in 1994 at Korhogo (Ivory Coast, geographic latitude 9.25°N, longitude 355°E, dip latitude -2.5°). Our instrument uses the 630 nm (O1D) line to determine radial Doppler velocities of the oxygen atoms between 200 and 400 km altitude. First results for November 1994 to March 1995 reveal persistent eastward flows, and frequent intervals of southward winds of larger than 50 ms−1 velocity. Compared with the simultaneous ionospheric patterns deduced from the three West African equatorial ionosondes at Korhogo, Ouagadougou (Burkina-Faso, dip latitude +1.5°) and Dakar (Sénégal, dip latitude + 5°), they illustrate various impacts of the thermospheric winds on F2 layer density: (1) on the mesoscale evolution (a few 103 km and a few 100 minutes scales) and (2) on local fluctuations (hundreds of km and tens of minutes characteristic times). We report on these fluctuations and discuss the opportunity to improve the time-resolution of the Fabry-Perot interferometer at Korhogo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-0731-4
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  • 2
    Electronic Resource
    Electronic Resource
    Observations of thermospheric neutral winds within the polar cusp and the auroral oval using a Doppler imaging system (DIS) (1998)
    Springer
    Annales geophysicae 16 (1998), S. 1461-1474 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (Polar ionosphere) ; Meteorology and atmospheric dynamics (thermospheric dynamics; instruments and techniques)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Two Doppler imaging systems (DIS) or wide-field imaging Fabry-Perot interferometers (FPI), have recently been commissioned, one at the Auroral Station, Adventdalen, Longyearbyen, Svalbard, and the second at the IRF, Kiruna, Sweden. These instruments can provide wide-field (600 * 800 km) images of neutral wind flows in the upper thermosphere, by measuring the Doppler shift of the atomic oxygen forbidden near 630 nm, which is emitted from an altitude of approximately 240 km. From the instrument in Svalbard, at mid-winter, it is possible to observe the dayside polar cusp and the polar cap throughout the entire day, whereas from Kiruna, the night-time auroral oval is observable during the hours of darkness. Measurements of thermospheric dynamics from the DIS can be used in conjunction with observations of ionospheric plasma flows and thermal plasma densities by the EISCAT-Svalbard radar (ESR) and by EISCAT, along with other complementary observations by co-located instruments such as the auroral large-scale imaging system (ALIS). Such combined data sets will allow a wide range of scientific studies to be performed concerning the dynamical response of the thermosphere and ionosphere, and the important energetic and momentum exchange processes resulting from their complex interactions. These processes are particularly important in the immediate vicinity of the polar cusp and within the auroral oval. Early results from Svalbard in late 1995 will be discussed. The DIS in Kiruna observed two interesting geomagnetic disturbances in early 1997, the minor geomagnetic storm of 10, 11 January, and the disturbed period from 7–10 February. During these events, the thermospheric wind response showed some interesting departures from the average behaviour, which we attribute to the result of strong and variable Lorenz forcing (ion drag) and Joule and particle heating during these geomagnetic disturbances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-1461-3
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal structure of rubredoxin from Pyrococcus furiosus at 0.95 Å resolution, and the structures of N-terminal methionine and formylmethionine variants of Pf Rd. Contributions of N-terminal interactions to thermostability (1998)
    Springer
    JBIC 3 (1998), S. 484-493 
    Details
    ISSN: 1432-1327
    Keywords: Key words Rubredoxin ; Iron-sulfur proteins ; Hyperthermostability ; Protein structure ; Metalloproteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The high-resolution crystal structure of the small iron-sulfur protein rubredoxin (Rd) from the hyperthermophilic archeon Pyrococcus furiosus (Pf) is reported in this paper, together with those of its methionine ([_0M]Pf Rd) and formylmethionine (f[_0M]Pf Rd) variants. These studies were conducted to assess the consequences of the presence or absence of a salt bridge between the amino terminal nitrogen of Ala1 and the side chain of Glu14 to the structure and stability of this rubredoxin. The structure of wild-type Pf Rd was solved to a resolution of 0.95 Å and refined by full-matrix least-squares techniques to a crystallographic agreement factor of 12.8% [F〉2σ(F) data, 25 617 reflections], while those of the [_0M]Pf and f[_0M]Pf Rd variants were solved at slightly lower resolutions (1.1 Å, R=11.5%, 17 213 reflections; 1.2 Å, R=13.7%, 12 478 reflections, respectively). The quality of the data was such that about half of the hydrogen atoms of the protein were clearly visible. All three structures were ultimately refined using the program SHELXL-93 with anisotropic atomic displacement parameters for all non-hydrogen protein atoms, and calculated hydrogen positions included but not refined. In this paper we also report thermostability data for all three forms of Pf Rd, and show that they follow the sequence wild-type 〉[_0M]Pf〉formyl[_0M]Pf. Comparison of the three Pf Rd structures in the N-terminal region show that the structures of wild-type Pf Rd and f[_0M]Pf are rather similar, while that of [_0M]Pf Rd shows a number of additional hydrogen bonds involving the extra methionine group. While the salt bridge between the Ala1 amino group and the Glu14 carboxylate is not the primary determinant of the thermostability of Pf Rd, alterations to the amino terminus do have a moderate influence on the thermostability of this protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050258
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  • 4
    Electronic Resource
    Electronic Resource
    Free convection-radiation interaction from an isothermal plate inclined at a small angle to the horizontal (1998)
    Springer
    Acta mechanica 127 (1998), S. 63-73 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The interaction of free convection with thermal radiation in boundary layer flow from an inclined isothermal plate is studied numerically. Introducing appropriate transformations the equations governing the flow are expressed in the form of local nonsimilarity equations valid near the leading edge as well as in the downstream region. A group of transformations is also introduced such that the flow near the leading edge and far downstream can be described. Heated upward facing plates with positive and negative inclination angles are investigated. When the inclination is negative the boundary layer separates from the surface and the numerical solutions can be extended downstream past the point of separation. From the present investigation it may be concluded that the position of the separation point moves away from the leading edge with the increase of either of the thermal radiation parameter or the surface temperature parameter of the heated surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01170363
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  • 5
    Electronic Resource
    Electronic Resource
    Numerical study of the combined free-forced convective laminar boundary layer flow past a vertical isothermal flat plate with temperature-dependent viscosity (1998)
    Springer
    Acta mechanica 127 (1998), S. 39-50 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A modified and improved numerical solution scheme, for local nonsimilarity boundary layer analysis, is used to study the combined free-forced convective laminar boundary layer flow, past a vertical isothermal flat plate, with temperature-dependent viscosity. This numerical scheme is efficient and accurate and it can be programmed and applied easily and its application is illustrated, step by step, by the study of the above mentioned problem. Numerical results are presented graphically, for the flow field, for the case of air and water and for different values of the viscosity/temperature parameterH r over the range of the convection parameter 0.2 ≦ζ≦1.0. The analysis of the obtained results showed that the flow field is appreciably influenced by the viscosity/temperature parameter, and hence care must be taken to include the variation of viscosity with temperature in the heat transfer processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01170361
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  • 6
    Electronic Resource
    Electronic Resource
    Heat transfer response of free convection flow from a vertical heated plate to an oscillating surface heat flux (1998)
    Springer
    Acta mechanica 126 (1998), S. 101-113 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary An investigation is undertaken of the unsteady response of two-dimensional laminar free convection boundary layer flow of a viscous incompressible fluid along a semi-infinite vertical heated plate where the mean surface heat flux oscillates with a small amplitude about a steady profile. The buoyancy forces are favourable, resulting from a positive flux of heat from the surface of the plate into the fluid. The interaction of the time-periodic heat flux with the usual boundary-layer flow is examined by using a linearized theory. Solutions are obtained using three distinct methods, namely an extended series expansion method for low frequencies, an asymptotic series expansion method for high frequencies and a fully numerical finite difference method for general frequencies. Calculations have been carried out for a wide range of parameters to examine the solutions in terms of the amplitude and phase angle of the fluctuating parts of the surface shear stress and the surface temperature. It has been found that the amplitude and phase angle of both the shear stress and the surface temperature predicted by these three methods are in very good agreement in their respective ranges of validity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01172801
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of thermal radiation on natural convection over cylinders of elliptic cross section (1998)
    Springer
    Acta mechanica 129 (1998), S. 177-186 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The effect of conduction-radiation on natural convection flow of an optically dense viscous incompressible fluid along an isothermal cylinder of elliptic cross section has been investigated. The boundary layer equations governing the flow are shown to be nonsimilar. Full numerical solutions of the governing equations are obtained using the implicit finite difference method. The solutions are expressed in terms of the Nusselt number Nu against the eccentric angle α in the range [0, π]. The working fluid is taken to have unit value of the Prandtl number, Pr, and the effects of varying the Planck number,R d, the surface temperature parameter, θw, and the parameterA O representing the ratio of the major and minor axes of the cylinder are investigated. From the present analysis it is found that the rate of heat transfer from the slender body is higher than from the blunt body and that these higher values become even higher due to an increase in the effect of radiation in the flow field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01176744
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  • 8
    Electronic Resource
    Electronic Resource
    Wheat Yield Progress Associated with Higher Stomatal Conductance and Photosynthetic Rate, and Cooler Canopies (1998)
    Springer
    Crop science 38 (1998), S. 1467-1475 
    Details
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Grain yields of eight representative semidwarf spring wheat (Triticum aestivum L.) cultivars released in northwest Mexico between 1962 and 1988 have increased linearly across years as measured in this region during 6 yr under favorable management and irrigation. To understand the physiological basis of this progress and possibly assist future selection for grain yield, leaf traits were determined during 3 yr in the same study. Stomatal conductance (g s), maximum photosynthetic rate (Amax), and canopy temperature depression (CTD), averaged over the 3 yr, were closely and positively correlated with progress in the 6-yr mean yield. The correlation was greatest with g s (r=0.94, P〈0.01). Compared with the overall yield increase of 27%, g s, increased 63%, Amax increased 23%, and canopies were 0.6° cooler. Carbon-13 isotope discrimination was also positively associated with yield progress (r=0.71, P〈0.05), but other leaf traits such as flag leaf area, specific leaf weight, percentage N and greeness were not, nor was crop growth rate around anthesis. The causal basis of the leaf activity interrelationships is reasonably clear, with both increased intercellular CO2 concentration and increased mesophyll activity contributing to the increase in Amax. However, causal links to the yield progress, and the accompanying increase in kernels per square meter, are not clear. It is concluded that g s and CTD should be further investigated as potential indirect selection criteria for yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 9
    Electronic Resource
    Electronic Resource
    Preservation of inherent contractility in isolated gut segments from herbivorous and carnivorous marine fish (1998)
    Springer
    Journal of comparative physiology 168 (1998), S. 61-72 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Patterns of inherent contractility were investigated in isolated gut segments from three species of New Zealand temperate-water labroid fish: the herbivorous butterfish Odax pullus (Family Odacidae), and the carnivorous banded wrasse Notolabrus fucicola and spotty Notolabrus celidotus (Family Labridae). To maintain the functional viability of gut tissue over extended periods, physiological solutions were formulated for each genus based on biochemical analyses of plasma constituents. A Res-Del perfusion system was used to maintain isolated gut segments under conditions of constant pH, temperature, and laminar flow dynamics. Gut segments exhibited spontaneous contractility over periods of days. Segments from N. fucicola and N. celidotus were continuously active, whereas segments from O. pullus showed discontinuous activity with evidence of daily rhythmicity. Contractions were slight in segments from O. pullus compared to the two Notolabrus species. Contractile strength correlated with gut morphology, with circular and longitudinal muscle layers markedly greater in extent in the Notolabrus species than in O. pullus. The pattern of gut activity in O. pullus is possibly associated with the retention of algal material in the intestine for lengthy periods. This hypothesis is supported by the daily feeding pattern of this species, and the probable involvement of fermentation in its digestive process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050121
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  • 10
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    Wheat Yield Progress Associated with Higher Stomatal Conductance and Photosynthetic Rate, and Cooler Canopies (1998)
    Wiley
    Details
    Publication Date: 1998-11-01
    Print ISSN: 0011-183X
    Electronic ISSN: 1435-0653
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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