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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Agriculture and human values 16 (1999), S. 141-150 
    ISSN: 1572-8366
    Keywords: Community food security ; Hunger ; Food security ; Food systems ; Planning ; Theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Practitioners and advocates of community food security (CFS) envision food systems that are decentralized, environmentally-sound over a long time-frame, supportive of collective rather than only individual needs, effective in assuring equitable food access, and created by democratic decision-making. These themes are loosely connected in literature about CFS, with no logical linkages among them. Clear articulation in a theoretical framework is needed for CFS to be effective as a guide for policy and action. CFS theory should delimit the level of analysis (i.e., what are the boundaries of “community”); show how CFS relates to individual, household, and national food security and explain emergent properties, which are important at the community level of analysis; point to the best indicators of CFS or its lack; clarify the determinants of CFS; and clarify the stages of movement toward CFS. This theoretical base would allow researchers to develop valid and reliable measures, and allow practitioners to weigh alternative options to create strategic plans. A theoretical base also would help establish common ground with potential partners by making the connections to anti-hunger work, sustainable agriculture, and community development clear.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the results from a study of the dynamical properties of polar jets in the Sun's polar regions using LASCO C2 coronagraph and EIT observations. In the simplest impulsive acceleration scenarios for jets, gravity is expected to be the dominant force on the jet following the initial acceleration, especially in the Sun's polar regions where the open magnetic fields should not significantly impede the jet's motion. Our analysis shows that although at low heights the kinematics of the jets could be consistent with a gravitational deceleration of the ejected plasma, at higher heights their motions may simply follow the ambient solar wind outflow. If so, the polar jets can be used as tracers of the solar wind in coronal holes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Boundary layer meteorology 58 (1992), S. 151-159 
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The validity of a common radiometeorological application of Monin-Obukhov (M-O) similarity theory to potential refractivity (χ), which is a nonlinear combination of θ and q, is determined by whether the properly nondimensionalized χ gradient is a universal function of z/L. We develop expressions for the flux of χ (and its scaling parameter, χ*) in terms of temperature and moisture fluxes, and an M-O similarity expression for the vertical χ gradient. Results show that even if θ and q are accepted as exactly following M-O similarity expressions, when the surface layer is stable, χ does not obey such an expression. That is, when properly nondimensionalized, the vertical gradient of χ does not collapse to a single universal function of z/L. The assumption that χ behaves as a similarity variable is approximately correct for well-mixed surface layers under unstable and near-neutral conditions. The gradient of χ is an important factor in determining microwave propagation conditions. We demonstrate the error induced in a simple algorithm when χ is assumed to obey M-O similarity theory. An alternative methodology, consistent with the application of similarity theory to θ and q, is then developed without requiring that χ itself satisfy similarity theory.
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  • 4
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Since January 1996, the Solar and Heliospheric Observatory (SOHO)has been providing unprecedented views of the extended solar coronato heliocentric distances of up to 32 solar radii. During the past threeyears we carried out studies of the morphology and dynamical evolutionof various structures in the solar corona using two instruments on boardSOHO: the Large Angle Spectrometric Coronagraph (LASCO) and the ExtremeUltraviolet Imaging Telescope (EIT). We have applied advanced image resolutionenhancement techniques to explore in detail the characteristics of thesmall-scale structures and/or the low contrast structures in the solarcorona. We describe here the results from these high-angular resolutionstudies, including of the kinematics of several Coronal Mass Ejections andpolar jets.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Methods in cell science 3 (1977), S. 601-605 
    ISSN: 1573-0603
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chemically assisted ion beam etching (CAIBE) has been used to etch InGaAsP/InP ridge laser facets. Smooth, vertical facets 4 μm deep have been etched using Ar/Cl2 CAIBE with a beam voltage of 440 V and a beam current density of 0.08 mA/cm2. Room temperature and high temperature (85 °C) L-I characteristics and device performance have been evaluated, as well as the performance of integrated back facet monitors. Output powers of 9.5 mW from the laser and a monitor current of 3.75 mA have been obtained.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The alkali cation content of HeLa cells is independent of culture density and of whether the cells are grown in suspension or attached to the culture vessel. With a cell doubling time of 28 hours, the cell K content turns over approximately once per hour. Following partial blockade of the alkali-cation transport system with ouabain, two distinct but interrelated mechanisms operate in the cellular response: (a) an increase in intracellular Na stimulates the pump so that the short-term alteration in electrolyte composition is less than would be expected from the fraction of pump sites inhibited, and (b) there is a cyclo-heximide-sensitive recovery in transport capacity reflecting a restoration of functional transport sites to their normal density on the cell surface. Experimental manipulations that mimic the effect of ouabain lead to a stimulation of transport, but they do not result in an increase in the number of ouabain-binding sites on the surface. The data are consistent with a four-to-six-hour turnover of transport sites at the surface, but there is no evidence for a specific induction of the transport system within this short-term recovery period.
    Additional Material: 7 Ill.
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  • 8
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have measured uptake of 3H-hexoses into diploid human cells by exposing them to brief pulses of isotopic sugar during the log-growth, subconfluent-growth, and confluent-growth (contact inhibited) phases of the strain HSWP derived from human skin. 3H-deoxyglucose appears to be taken up three times faster than 3H-glucose. After exposure to 3H-glucose for longer than one minute, the cells excrete ∼70% of the isotope into the medium as lactate. If lactate production (and hence excretion) is abolished by treating the cells with iodoacetic acid or dinitrofluorobenzene, neither of which inhibits transport, the uptake of 3H-glucose is found to be in fact somewhat larger than that of 3H-deoxyglucose. If cells are deprived of glucose for 24 hours, apparent uptake of 3H-glucose is enhanced 10-fold or more. This latter increase is accounted for by 2- to 3-fold enhancement of true transport plus retention of 〉 90% of the radioactivity, since little lactate is formed or excreted in glucose-deprived cells. Deoxyglucose, galactose, or pyruvate when present during glucose deprivation each have quantitatively different effects on the cells' capacity to produce lactate from a short pulse of glucose, but none of them prevents the enhancement of hexose transport. After restoration of 5 mM glucose to starved cells, their metabolism returns to normal (in the sense that ∼70% of the glucose taken up in a pulse is again excreted as lactate), with a half-time of 0.5 hour; but the transport of hexoses returns to control levels much more slowly, with a half-time of ∼6 hours. The two processes appear to be independently regulated.
    Additional Material: 7 Ill.
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  • 9
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Protein kinase C is considered to be a major target for tumor promoting phorbol esters such as 12-O-tetradecanoylphorbol-13-acetate (TPA). We have analyzed the correlation between A-system amino acid transport and the distribution of protein kinase C (PKC) between a membrane-rich fraction (100,000 g pellet) and cytosol (supernatant) from homogenized LLC-PK1 cells, a pig kidney epithelial cell line grown in culture. During log growth 1 day after seeding the cells onto culture plates, PKC activity is high in the membrane fraction and low in the cytosol. As the cells become confluent the PKC distribution shifts to a cytosolic pool. Concomitantly, A-system amino acid transport, as measured by methylaminoisobutyric acid [14C]MeAIB uptake, decreases. TPA (0.01-1.0 μM) induces a shift of PKC activity from the cytosol back to the membrane-rich fraction in post-confluent cells with a concomitant 2-3 fold stimulation of MeAIB uptake. The same responses can be achieved by treating cells with certain diradylglycerols, either diacylglycerols such as 1-oleyl-2-acetyl-sn-glycerol (OAG) or alkylacylglycerols such as 1-hexadecenyl-2-oleyl-sn-glycerol. Both responses to TPA are blocked by cytochalasin B, but cycloheximide inhibits the transport response without affecting PKC redistribution. It is suggested that the redistribution may be a necessary but not sufficient concomitant to the transport activation.
    Additional Material: 5 Ill.
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  • 10
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Photoreactivation of growth and DNA synthesis in UV-irradiated cells and photoreactivating-enzyme activity of cell-free extracts can be demonstrated in a cell line derived from liver tissue of the African clawed toad, Xenopus laevis. This cell line, A8W2, is a favorable system for the quantitative study of photoreactivation in vertebrates.
    Additional Material: 3 Ill.
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