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  • 1
    Electronic Resource
    Electronic Resource
    The effects of temperature on the architecture and distribution of Macrotermes bellicosus (Isoptera, Macrotermitinae) mounds in different habitats of a West African Guinea savanna (1998)
    Springer
    Insectes sociaux 45 (1998), S. 51-65 
    Details
    ISSN: 1420-9098
    Keywords: Key words: Gallery forest, Ivory Coast, savanna, termites, thermoregulation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: We determined density and distribution of the mounds of the fungus-cultivating termite Macrotermes bellicosus (Smeathman) in two habitats (shrub savanna and gallery forest) of the Comoé National Park (Ivory Coast, West Africa). We measured height, basal width, and interior and exterior temperatures of mounds in both habitats, and established a new method to measure the surface area of mounds.¶ In the shrub savanna, M. bellicosus mounds reached high densities (up to 22.7 live mounds/ha), whereas in the gallery forest mounds could only be found in open stands and at comparatively low densities (up to 6.5 live mounds/ha).¶ Ambient temperature had an important influence on the architecture of the mounds. Mounds in the warmer, but thermally more fluctuating shrub savanna were more structured with many ridges and turrets than the dome-like, compact mounds in the cooler, more equable gallery forest. The surface complexity was quantified as the ratio of surface (= rsf), which is the quotient of the real surface to the minimal possible surface of an ideal cone of the same height and basal width as the measured mound. By manipulating ambient temperatures, we were able to demonstrate causal relationships between temperature and mound shape. In the gallery forest, where shade was reduced surface complexity increased on mounds.¶Despite their different architecture in the gallery forest, the M. bellicosus colonies could not completely compensate for the cooler environment and had a lower than optimal nest temperature. We speculate that this might be caused by the need for a sufficient surface for gas exchange. The gallery forest is a suboptimal habitat for M. bellicosus, because of lower than optimal nest temperatures. This might limit M. bellicosus to open stands in the gallery forest and may explain its surprisingly low abundance in this habitat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000400050068
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  • 2
    Electronic Resource
    Electronic Resource
    Thermoregulation of termite mounds: what role does ambient temperature and metabolism of the colony play? (2000)
    Springer
    Insectes sociaux 47 (2000), S. 357-363 
    Details
    ISSN: 1420-9098
    Keywords: Key words: Fungus, Macrotermes bellicosus, Macrotermitinae, metabolism, mound structure.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Termites are well known for their ability to regulate the environment of their nest such as temperature and humidity. The influence of fluctuating ambient temperature and mound characteristics on mean nest temperature and daily fluctuation of nest temperature was analysed quantitatively in the fungus-cultivating, mound-building termite Macrotermes bellicosus (Macrotermitinae) in the savanna of the Comoé National Park (Côte d'Ivoire). Additionally, the nest temperatures of inhabited and uninhabited mounds were compared to analyse the contribution of ambient temperature to nest temperature in relation to metabolic heat production of the termites and their fungi. Mound structure alone resulted in a relatively constant nest temperature. Abiotic heat production via solar radiation alone yielded nest temperatures that corresponded to mean ambient temperatures. However, only the production of metabolic heat by the termites and the fungi increased these temperatures to the actual nest temperature. Therefore, and due to the high heat capacities of the mounds, large colonies (mound height above 2.0 m) had higher nest temperatures than smaller ones. Only large colonies attain constant nest temperatures of 30 °C that are largely independent from ambient temperatures and optimal for the growth and development of the termites and their fungi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00001731
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental heating of Macrotermes bellicosus (Isoptera, Macrotermitinae) mounds: what role does microclimate play in influencing mound architecture? (1998)
    Springer
    Insectes sociaux 45 (1998), S. 335-342 
    Details
    ISSN: 1420-9098
    Keywords: Key words: Savanna, termites, thermoregulation, termite mounds.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Mounds of the fungus-cultivating termite Macrotermes bellicosus (Smeathman) in the Comoé-National Park (Ivory Coast, West Africa) differ in architecture between habitats. Mounds in the cooler, but thermally more stable gallery forest have been shown to be dome-shaped with thick walls, whereas mounds in the shrub savanna are more complex with many ridges and thin walls. In this investigation, we performed heating experiments to determine the thermal properties of the mounds in both habitats in order to test the hypothesis of a thermoregulatory significance of mound architecture. These experiments revealed that each mound had its characteristic individual heating up behavior that depends on its dimensions (height, surface, volume). In addition, habitat-specific traits were demonstrated: mounds of the gallery forest had higher thermal inertia, measured by the thermal capacity, than mounds of the shrub savanna. Thus, the dome-shaped mounds with thick walls in the gallery forest, with its suboptimal low temperatures, reduce loss of heat to the environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000400050092
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  • 4
    Electronic Resource
    Electronic Resource
    Theory of dipolar relaxation in lamellar system: Application to lyotropic liquid crystals (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1964-1972 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We propose a theory of dipolar spin relaxation for lamellar geometry where one of the spin species diffuses on an infinite plane while the other diffuses within an infinite layer of finite thickness. Analytical expressions of the frequency dependence of the spectral densities and spin relaxation rates are given. The theoretical frequency variation of the longitudinal relaxation rate appears to be drastically dependent of the anisotropic diffusion ratio and on the thickness of the layer. An application of this theory to lamellar lyotropic liquid crystal gives the spatial distribution of an organic counterion solute in the bilayer from the frequency variation of the 31P longitudinal relaxation rates of the surfactant. This gives some information about the surfactant-organic counterion interaction and the hydration degree of the phosphate group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459074
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamic effects of pair correlation functions on spin relaxation by translational diffusion in two-dimensional fluids (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 1125-1130 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamic effects of pair correlation functions (pcf) on spin relaxation by translational diffusion in infinite two-dimensional fluids are considered explicitly through a Smoluchowski equation, for the usual conditional probability, with appropriate boundary conditions, especially at the contact separation of the interacting pair of molecules. The solution of this equation by finite difference techniques permits the calculation of time correlation functions, spectral densities, and spin-relaxation rates associated with a dipolar relaxation mechanism between the spin-bearing molecules. Comparison of the two-dimensional spin-relaxation results obtained with different pcf is presented. The spectral densities and spin-relaxation rates are indeed found to be significantly altered by the pcf. For example, for a nonuniform pcf, the two-dimensional spectral densities, at (and above) the Larmor frequency ω0, are greater for translational correlation times τt that are an order of magnitude faster than τt=ω−10 which provides the maximum spectral density in bulk theory. This fast motion result is consistent with the two-dimensional dynamical results found by other techniques. Moreover for a nonuniform pcf and a single translational correlation time, two well-defined minima are found in the variation of the spin-lattice relaxation time with the diffusion coefficient. This could be very useful for interpreting the spin-relaxation data of diffusing complexes in clays, intercalation compounds, and bilayers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452254
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  • 6
    Electronic Resource
    Electronic Resource
    Size effects in the spin relaxation by bounded diffusion in two dimensional systems (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 1061-1062 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An extension of our previous theory of spin relaxation by translational diffusion in two-dimensional (2D) systems is proposed by considering the very nonuniform radial molecular distribution observed at short intermolecular distance. This increases greatly the absolute values of the spin-lattice relaxation rates T−11 and enhances the size effects on their diffusion (or temperature) dependences. The existence of two maxima in these dependences should facilitate the interpretation of experimental data in 2D heterogeneous systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448533
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  • 7
    Electronic Resource
    Electronic Resource
    Isolation and characterization of the dsRNA virus from the yeast Endomyces magnusii (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 116 (1994), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Virus-like particles (VLPs) have been isolated from the yeast Endomyces magnusii. The VLPs measure 43 nm in diameter and contain six species of dsRNA (0.78, 0.83, 1.77, 1.84, 2.64, 4.30 kb respectively). E. magnusii produces a ‘toxic’ protein, which reduces the growth, and changes the colony morphology, of sensitive strains of Hansenula sp. growing on solid media. All strains of E. magnusii tested produced the ‘toxin’ and contained the VLPs. Current procedures of curing failed to destroy the ability to produce the ‘toxin’.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1994.tb06706.x
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  • 8
    Electronic Resource
    Electronic Resource
    The role of pair distributions in the calculations of homogeneous broadenings and cross-relaxation rates
    Amsterdam : Elsevier
    Chemical Physics Letters 112 (1984), S. 420-425 
    Details
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0009-2614(84)85561-X
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  • 9
    Electronic Resource
    Electronic Resource
    Relative role of surface interactions and topological effects in nuclear magnetic resonance of confined liquids (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 7074-7081 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The relative roles of surface and topological effects on the nuclear relaxation rates T−11, T−12, and T−11ρ of polar or nonpolar liquids in porous sol-gel silica glasses are identified via their very different pore size and frequency dependences. On the basis of theory, experimental relaxation rates, and molecular dynamics simulations for the modeled porous systems, the 1/Ti's are interpreted in terms of a linear combination of bulk, confinement, and surface effects: 1/Ti = 1/Tibulk + ai/R2+ bi/R, where R is the average pore size and ai and bi are given in terms of the usual relaxation parameters of the studied molecular species. This simple expression which allows the determination of the relative roles of surface and topological effects has been used to fit the observed 1H NMR relaxation rates as a function of pore size and frequency for methylcyclohexane, nitrobenzene, pyridine, and toluene both for nonmodified and surface modified porous silica glasses. Using this method, the surface (∝1/R) and pure geometrical (∝1/R2) relaxation contributions are evaluated and the surface and translational correlation times are calculated. More generally, the experimental data allow us to explain the following seemingly paradoxical results obtained for confined liquids: (i) The pure confinement effect is independent of the polarities of the liquid molecules in pores and is very sensitive to the frequency. (ii) The finding of the frequency variation of T−11 and T−11ρ both for polar or nonpolar liquids confined to small pores, shows that the geometrical confinement effects dominate over the surface interaction effects at low frequency and for small pores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468333
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  • 10
    Electronic Resource
    Electronic Resource
    Interfacial adsorption of solvents in a porous polymer resin: a carbon-13 spin-echo and ESR study (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 6058-6060 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100169a002
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