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Microwave-Assisted Solvent-Free or Aqueous-Based Synthesis of Biodegradable Polymers 总被引:4,自引:0,他引:4
Microwave radiation was used as the energy source for various types of chemical derivatizations of polysaccharides and for the synthesis of biodegradable polyesters in solvent-free or aqueous-based reaction systems. A medium to high degree of substitution was obtained for starch acetates, starch succinates, carboxymethyl konjac, aminated starch, and aminated chitosan. Ring-opening polymerization of lactide and -caprolactone proceeded rapidly even at low power output in the presence of tin octanoate catalyst. Complete monomer conversion and high molecular weight were achieved in less than 6 minutes under nonisothermal conditions. The yield rapidly increased with increasing power output and showed no significant change in a wide range of batch sizes. Polycaprolactone was successfully grafted from starch and konjac acetate in 3 minutes, yielding as high as 24% grafting efficiency and 25% grafting degree. 相似文献
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Improving Community-Based Conservation Near Protected Areas: The Importance of Development Variables
Balint PJ 《Environmental management》2006,38(1):137-148
Community-based conservation projects implemented in conjunction with protected area management often struggle to meet expectations.
This article argues that outcomes will improve if project leaders pay closer attention to four development indicators—rights,
capacity, governance, and revenue—that are often taken for granted or considered beyond the scope of local conservation projects.
I make the case for focusing on these variables in four steps. First, I distinguish community-based conservation linked to
protected area management from community-based institutions studied by scholars of the commons. Second, I draw on the theory
and practice of international development to highlight the central relevance of the variables highlighted in this article
to development projects at all levels. Third, I discuss the four variables in some detail, considering problems of definition
and measurement and reviewing possible interactions among them. Fourth, to illustrate the influence of the variables in particular
cases, I review outcomes from community-based conservation projects implemented near protected areas in El Salvador and Zimbabwe. 相似文献
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The monetary valuation of ecosystem services is gaining traction in policy and business communities. Several tools and decision‐making processes have been proposed, including criteria to assess the appropriateness of using monetary valuation for biodiversity conservation outcomes. These criteria include measures such as scale, uniqueness, and threat. We used case studies of monetization projects for which the outcomes were measured to explore the limitations and application of these criteria. There was limited evidence of the effectiveness of such schemes. The majority of the schemes were established in areas where the criteria specifically excluded their use in isolation. Thus, although some aspects of monetization may be beneficial for biodiversity conservation, these schemes were not being used appropriately and require some quantitative minimum (or maximum) measurements to be applied through additional policy or governance measures to ensure biodiversity conservation outcomes. 相似文献
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