The Case for a Two-Step Approach to Agricultural Campaign Design     

Jennifer Ihm  Macarena Pena-Y-Lillo  Katherine R. Cooper  Yannick Atouba  Michelle Shumate  Julia Bello-Bravo 《Journal Of Agricultural & Food Information》2013,14(3):203-220

Development campaigns designed to scale up effective agricultural solutions often rely on media. Information and communication technologies for development (ICT4D) proponents argue that increased media penetration is necessary for such campaigns to succeed. Interviews of 63 extension agents and 200 farmers in Burkina Faso about their disparities in media ownership, access, skills, and preferences suggest that agricultural development campaigns should account for the different media environments and preferences of target populations within countries. This research presents such an alternative approach, a two-step campaign design intended to address digital divides within countries and target population preferences.  相似文献   

Effect of ammonium and phosphorus supply on h+ production in gel by two tropical forage grasses     

Katherine A.B. Logan  Richard J. Thomas  John A. Raven 《Journal of plant nutrition》2013,36(1):41-54

The effect of the supply of ammonium (NH₄ ⁺) and phosphorus (P) in gel on the amounts of hydrogen ion (H⁺) excreted from plant roots was studied with Brachiaria humidicola (a highly acid‐soil tolerant tropical grass) and B. brizantha (less acid‐soil tolerant) grown in soil in a glasshouse. The H⁺ production was measured over 24 h in agar gel containing full nutrient solution with a range of NH/‐N levels (0, 0.25, 0.5, and 5.0 mM NH₄ ⁺‐N). Highly soluble P, K₂HPO₄, or relatively insoluble P, rock P, was supplied at four concentrations (0, 11.5, 34.5, or 115 μM p) in the gel. Increasing NH₄ ⁺ concentration in the gel increased H⁺ production for both grasses, but there was some inhibition of growth for B. brizantha at the highest N concentration. For B. humidicola, but not B. brizantha H⁺ production was greater with 34.5 μM K₂HPO₄ than 11.5 μM K₂HPO₄. At 34.5 μM P for both grasses there was no difference in H⁺ production when P was supplied as rock P or K₂HPO₄. With 11.5 μM P both grasses produced less acid in the gel with the rock P compared with K₂HPO₄. The reduced H⁺ production is probably due to a lower availability of P in the rock P compared with K₂HPO₄. This effect was greater with B. brizantha than B. humidicola, implying that 11.5 μM rock P was not able to supply sufficient P for the growth of B. brizantha. Brachiaria humidicola was able to dissolve more rock P than B. brizantha or alternatively, the growth of B. humidicola was less adversely affected by the low P supply from rock P than B. brizantha. Plant‐induced acidity does not seem to occur as a response to a lack of available P, but rather these grasses only produce acid if there are enough nutrients for growth, i.e., both NH₄ ⁺ and P. If either N or P is limiting, growth is limited as is NH₄ ⁺ uptake, so that H⁺ production is curtailed.  相似文献   

Fertilizer type and species composition affect leachate nutrient concentrations in coffee agroecosystems     

Katherine L. Tully  Stephen A. Wood  Deborah Lawrence 《Agroforestry Systems》2013,87(5):1083-1100

Intensification of coffee (Coffea arabica) production is associated with increases in inorganic fertilizer application and decreases in species diversity. Both the use of organic fertilizers and the incorporation of trees on farms can, in theory, reduce nutrient loss in comparison with intensified practices. To test this, we measured nutrient concentrations in leachate at 15 and 100 cm depths on working farms. We examined (1) organically managed coffee agroforests (38 kg N ha^?1 year^?1; n = 4), (2) conventionally managed coffee agroforests (96 kg N ha^?1 year^?1; n = 4), and (3) one conventionally managed monoculture coffee farm in Costa Rica (300 kg N ha^?1 year^?1). Concentrations of nitrate (NO₃ ^?-N) and phosphate (PO₄ ^3?-P) were higher in the monoculture compared to agroforests at both depths. Nitrate concentrations were higher in conventional than organic agroforests at 15 cm only. Soil solutions collected under nitrogen (N)-fixing Erythrina poeppigiana had elevated NO₃ ^?-N concentrations at 15 cm compared to Musa acuminata (banana) or Coffea. Total soil N and carbon (C) were also higher under Erythrina. This research shows that both fertilizer type and species affect concentrations of N and P in leachate in coffee agroecosystems.  相似文献   

Increase in Older Adults Reporting Mountaineering-Related Injury or Illness in the United States, 1973–2010     

Timothy F. Platts-Mills  Katherine M. Hunold 《The Forestry Chronicle》2013,24(1):86-88

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Plant UVR8 photoreceptor senses UV-B by tryptophan-mediated disruption of cross-dimer salt bridges     

Christie JM  Arvai AS  Baxter KJ  Heilmann M  Pratt AJ  O'Hara A  Kelly SM  Hothorn M  Smith BO  Hitomi K  Jenkins GI  Getzoff ED 《Science (New York, N.Y.)》2012,335(6075):1492-1496

The recently identified plant photoreceptor UVR8 (UV RESISTANCE LOCUS 8) triggers regulatory changes in gene expression in response to ultraviolet-B (UV-B) light through an unknown mechanism. Here, crystallographic and solution structures of the UVR8 homodimer, together with mutagenesis and far-UV circular dichroism spectroscopy, reveal its mechanisms for UV-B perception and signal transduction. β-propeller subunits form a remarkable, tryptophan-dominated, dimer interface stitched together by a complex salt-bridge network. Salt-bridging arginines flank the excitonically coupled cross-dimer tryptophan "pyramid" responsible for UV-B sensing. Photoreception reversibly disrupts salt bridges, triggering dimer dissociation and signal initiation. Mutation of a single tryptophan to phenylalanine retunes the photoreceptor to detect UV-C wavelengths. Our analyses establish how UVR8 functions as a photoreceptor without a prosthetic chromophore to promote plant development and survival in sunlight.  相似文献   

Immunology. Select inflammasome assembly     

Caffrey DR  Fitzgerald KA 《Science (New York, N.Y.)》2012,336(6080):420-421

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Cancer. Glycosylation to adapt to stress     

KR Mattaini  MG Vander Heiden 《Science (New York, N.Y.)》2012,337(6097):925-926

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Differential diffusivity of Nodal and Lefty underlies a reaction-diffusion patterning system     

Müller P  Rogers KW  Jordan BM  Lee JS  Robson D  Ramanathan S  Schier AF 《Science (New York, N.Y.)》2012,336(6082):721-724

Biological systems involving short-range activators and long-range inhibitors can generate complex patterns. Reaction-diffusion models postulate that differences in signaling range are caused by differential diffusivity of inhibitor and activator. Other models suggest that differential clearance underlies different signaling ranges. To test these models, we measured the biophysical properties of the Nodal/Lefty activator/inhibitor system during zebrafish embryogenesis. Analysis of Nodal and Lefty gradients revealed that Nodals have a shorter range than Lefty proteins. Pulse-labeling analysis indicated that Nodals and Leftys have similar clearance kinetics, whereas fluorescence recovery assays revealed that Leftys have a higher effective diffusion coefficient than Nodals. These results indicate that differential diffusivity is the major determinant of the differences in Nodal/Lefty range and provide biophysical support for reaction-diffusion models of activator/inhibitor-mediated patterning.  相似文献   

Estimating landscape resistance to movement: a review   总被引：3，自引：3，他引：0  

Katherine A. Zeller  Kevin McGarigal  Andrew R. Whiteley 《Landscape Ecology》2012,27(6):777-797

Resistance surfaces are often used to fill gaps in our knowledge surrounding animal movement and are frequently the basis for modeling connectivity associated with conservation initiatives. However, the methods for quantifying resistance surfaces are varied and there is no general consensus on the appropriate choice of environmental data or analytical approaches. We provide a comprehensive review of the literature on this topic to highlight methods used and identify knowledge gaps. Our review includes 96 papers that parameterized resistance surfaces (sometimes using multiple approaches) for a variety of taxa. Data types used included expert opinion (n?=?76), detection (n?=?23), relocation (n?=?8), pathway (n?=?2), and genetic (n?=?28). We organized the papers into three main analytical approaches; one-stage expert opinion, one-stage empirical, and two-stage empirical, each of which was represented by 43, 22, and 36 papers, respectively. We further organized the empirical approaches into five main resource selection functions; point (n?=?16), matrix (n?=?38), home range (n?=?3), step (n?=?1), and pathway (n?=?1). We found a general lack of justification for choice of environmental variables and their thematic and spatial representation, a heavy reliance on expert opinion and detection data, and a tendency to confound movement behavior and resource use. Future research needs include comparative analyses on the choice of environmental variables and their spatial and thematic scales, and on the various biological data types used to estimate resistance. Comparative analyses amongst analytical processes is also needed, as well as transparency in reporting on uncertainty in parameter estimates and sensitivity of final resistance surfaces, especially if the resistance surfaces are to be used for conservation and planning purposes.  相似文献   

Suspected acquired hypocobalaminaemic encephalopathy in a cat: resolution of encephalopathic signs and MRI lesions subsequent to cobalamin supplementation     

Simpson K  Battersby I  Lowrie M 《Journal of Feline Medicine and Surgery》2012,14(5):350-355

PRESENTING SIGNS AND INITIAL INVESTIGATIONS: An 8-year-old female spayed British shorthair cat was presented with a history of waxing and waning neurological signs. Neuroanatomical localisation was consistent with a diffuse forebrain disease. Blood ammonia concentration was increased. Abdominal ultrasonography and a bile acid stimulation test were normal. Magnetic resonance imaging (MRI) revealed hyperintense, bilaterally symmetrical, diffuse lesions on T2-weighted sequences, predominantly, but not exclusively, affecting the grey matter. Serum cobalamin (vitamin B12) concentration was low. Hypocobalaminaemia resulting in a urea cycle abnormality was considered a likely cause of the hyperammonaemia. TREATMENT: Daily cobalamin injections resulted in a rapid clinical improvement. Eight weeks into treatment neurological examination was unremarkable and there was complete resolution of the MRI lesions. CLINICAL IMPORTANCE: This is the first reported case of acquired feline hypocobalaminaemia resulting in an encephalopathy. Additionally, this case is unique in describing reversible brain MRI abnormalities in a cobalamin-deficient companion animal.  相似文献