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41.
Qirko HN 《Science (New York, N.Y.)》2004,304(5667):49-51; author reply 49-51
42.
43.
Oscar Ortiz Guillermo Frias Raul Ho Hector Cisneros Rebecca Nelson Renee Castillo Ricardo Orrego Willy Pradel Jesus Alcazar Mario Bazán 《Agriculture and Human Values》2008,25(3):419-431
Participatory research (PR) has been analyzed and documented from different points of view, with emphasis on the benefits generated for farmers. The effect of PR on organizational learning has, however, received little attention. This paper analyzes the interaction between a research and a development institution, the International Potato Center (CIP) and CARE in Peru, respectively, and makes the case that PR can contribute to creating a collaborative learning environment among organizations. The paper describes the evolution of the inter-institutional collaborative environment between the two institutions for more than a decade, including an information-transfer period (1993–1996), an action-learning period (1997–2002), and a social-learning period (2003–2007). Several lessons learned from each period are described, as are changes in institutional contexts and stakeholders’ perceptions. The case shows that research and development-oriented organizations can interact fruitfully using PR as a mechanism to promote learning, flexibility in interactions, and innovation. Interactions foster the diffusion of information and the sharing of tacit knowledge within and between organizations, which in turn influences behavior. However, the paper also argues that long-term inter-organizational interactions are needed to facilitate learning, which can be used to influence the way organizations implement their interventions in a constantly changing environment. 相似文献
44.
Arias SL Theumer MG Mary VS Rubinstein HR 《Journal of agricultural and food chemistry》2012,60(22):5667-5675
Fusarium verticillioides is best known for its worldwide occurrence on maize resulting in highly variable disease symptoms, ranging from asymptomatic to severe rotting and wilting and fumonisin production. The aim of this study was to investigate the influence of hybrid genotypes in the early stages of F. verticillioides infection, and the role of fumonisins as effectors in the outcome of this complex interaction. Disease symptoms, growth parameters, root morphology, and fungal colonization were evaluated at 7, 14, and 21 days after planting in seedlings from maize seeds of resistant (RH) and susceptible (SH) hybrids inoculated with F. verticillioides or watered with solutions of fumonisins. F. verticillioides induced growth enhancement or retardation depending on the plant genetic background and the fungal colonization rate, while fumonisins caused severe reduction in biomass and fitness. Seedlings watered with high fumonisin concentrations displayed lesions similar to those seen in F. verticillioides maize seedling disease, and also elicited inhibitory effects on root growth and morphology and on functional properties. In summary, these data strongly suggest a dual role for fumonisins in the F. verticillioides-maize interaction, acting as pathogenic factors at high concentrations, or triggering the plant detoxification mechanisms at low levels. 相似文献
45.
Chen M Wang YH Wang Y Huang L Sandoval H Liu YJ Wang J 《Science (New York, N.Y.)》2006,311(5764):1160-1164
Apoptosis in the immune system is critical for maintaining self-tolerance and preventing autoimmunity. Nevertheless, inhibiting apoptosis in lymphocytes is not alone sufficient to break self-tolerance, suggesting the involvement of other cell types. We investigated whether apoptosis in dendritic cells (DCs) helps regulate self-tolerance by generating transgenic mice expressing the baculoviral caspase inhibitor, p35, in DCs (DC-p35). DC-p35 mice displayed defective DC apoptosis, resulting in their accumulation and, in turn, chronic lymphocyte activation and systemic autoimmune manifestations. The observation that a defect in DC apoptosis can independently lead to autoimmunity is consistent with a central role for these cells in maintaining immune self-tolerance. 相似文献
46.
Alzate A Cañas B Pérez-Munguía S Hernández-Mendoza H Pérez-Conde C Gutiérrez AM Cámara C 《Journal of agricultural and food chemistry》2007,55(24):9776-9783
Selenium is an essential element in the human diet. Interestingly, there has been an increased consumption of dietary supplements containing this element in the form of either inorganic or organic compounds. The effect of using selenium as a dietary supplement in yogurt has been evaluated. For this purpose, different concentrations of inorganic Se (ranging from 0.2 to 5000 microg g(-1)) have been added to milk before the fermentation process. Biotransformation of inorganic Se into organic species has been carefully evaluated by ion-exchange, reversed-phase, or size-exclusion chromatography, coupled to inductively coupled plasma mass spectrometry (ICP-MS). Yogurt fermentation in the presence of up to 2 microg g(-1) of Se(IV) produces a complete incorporation of this element into proteins as has been demonstrated applying a dialysis procedure. Analysis by SEC-ICP-MS showed that most of them have a molecular mass in the range of 30-70 kDa. Species determination after enzymatic hydrolysis has allowed the identification of Se-cystine using two different chromatographic systems. The biotransformation process that takes place during yogurt fermentation is very attractive because yogurt can act as a source of selenium supplementation. 相似文献
47.
Perez-Rivero JJ Martinez-Maya JJ Perez-Martinez M Aguilar-Setien A Garcia-Suarez MD Serrano H 《Veterinary research communications》2009,33(1):87-95
Dog overpopulation is considered a human health risk; they are the terrestrial vector of rabies and reservoirs for other human
diseases. Surgical neutering and intratesticular injections have been used in male dogs. Physiological and morphological alterations
in reproductive organs can be induced by phytoestrogens. Our goal was to evaluate the effect of oral coumestrol on dog ejaculates
and testis histology. Two groups of 5 healthy adult dogs were used. One coumestrolcontaining biscuit was given once a week
for a 4 week period to the experimental group. Ejaculates were obtained and evaluated. After treatment, testis were obtained
and processed for histology. Compared to controls, treated dogs have reduced tubules (462 ± 1.4 vs 336 ± 2 μ2), spermatogenic epithelium (49.1 ± 0.01 vs 13.3 ± 0.01 μ2), and lumen opening (891 ± 1.4 vs 530 ± 26.9 μ). Ejaculates from treated animals have increased numbers of abnormal spermatozoa
and reduced sperm concentration. 相似文献
48.
49.
Hector?M.?MalanoEmail author Biju?A.?George Brian?Davidson 《Irrigation and Drainage Systems》2005,19(2):107-127
Sustainability of irrigation and drainage infrastructure poses many challenges to many irrigation authorities worldwide due to a mismatch between the actual cost incurred in the provision of irrigation and drainage service and pricing of this service. This shortfall often leads to inadequate expenditure on maintenance in the absence of adequate subsidies from government or other sources.The asset management modelling framework (AMMF) presented in this paper enables the quantification of on-going ownership costs and operation costs. A life cycle cost (LCC) model for the evaluation of alternative irrigation and drainage asset management strategies is also presented. The AMMF is applied to the evaluation of asset ownership costs and LCC for alternative maintenance and interest rate scenarios in the Cu Chi irrigation system, Vietnam. The cost of three renewal strategies was evaluated: linear depreciation, full annuity and partial annuity. The cost ranges between US$ 28.00/ha and US$ 41.00/ha when interest rate varies between 9 and 3%. The average maintenance expenditure during recent years was estimated to be only US$ 1.30/ha which translates into 0.68% of the total asset replacement cost.The application of a simplified LCC model reveals that the least LCC varies with the level of maintenance and interest rate between US$ 353.5/ha for 5% maintenance expenditure and 12% interest rate to US$ 522.3/ha for 3% maintenance expenditure and 6% interest rate. The importance of exercising value judgements in applying the LCC model is also emphasised and discussed. 相似文献
50.
A crucial, yet little understood, element in the economic studies of irrigation is the role played by companies who manage the supply of water. Many of these companies are publicly managed as they have the potential to act as monopolists. Possibly as a consequence of their ownership structure, analysts have questioned the economic viability and management of these firms. The case is made that many of these companies do not run profitably, that they rely on government subsidies to survive, that they do not spend enough on maintenance and that they run down their capital base. The purpose in this paper is to specify the measures that allow analysts to examine the financial viability of a publicly owned irrigation management companies and to apply these to a scheme in Vietnam. Of concern and contention in any irrigation scheme is the price that a company should charge for water in order to recover costs in the short-run. It was found that the company under investigation could not operate without subsidies and did run down their assets. It was found that a great disparity exists between what the consumers were charged for water and what the company received for supplying it. To ensure the sustainability of the Irrigation Management Companies in long term, they may have to increase the water fee by 3.75 times the current rate set by the provincial government (US$ 20 per ha). 相似文献