Abstract Soil as the largest global carbon pool has played a great role in sequestering the atmospheric carbon dioxide (CO 2 ). Although global carbon sequestration potentials have been assessed since the 1980s, few investigations have been made on soil carbon sequestration (SCS) in China's cropland. China is a developing country and has a long history of agricultural activities. Estimation of SCS potentials in China's cropland is very important for assessing the potential measures to prevent the atmospheric carbon rise and predicting the atmospheric CO 2 concentration in future. After review of the available results of the field experiments in China, relationships between SCS and nitrogen fertilizer application, straw return and no‐tillage (NT) practices were established for each of the four agricultural regions. According to the current agricultural practices and their future development, estimations were made on SCS by nitrogen fertilizer application, straw return and NT in China's cropland. In the current situation, nitrogen fertilizer application, straw return and zero tillage can sequester 5.96, 9.76 and 0.800 Tg C each year. Carbon sequestration potential will increase to 12.1 Tg C yr −1 if nitrogen is fertilized on experts' recommendations. The carbon sequestration potentials of straw return and NT can reach 34.4 and 4.60 Tg C yr −1 when these two techniques are further popularized. In these measures, straw return is the most promising one. Full popularization of straw return can reduce 5.3% of the CO 2 emission from fossil fuel combustion in China in 1990, which meets the global mean CO 2 reduction requested by the Kyoto Protocol (5.2%). In general, if more incentive policies can be elaborated and implemented, the SCS in China's cropland will be increased by about two times. So, popularization of the above‐mentioned agricultural measures for carbon sequestration can be considered as an effective tool to prevent the rapid rise of the atmospheric CO 2 in China.
The term "converging technologies" is referred as NBIC (the integration of nanotechnology, biotechnology, information technology and cognitive science) and shows us a new trend and research field of technology. According to the fundament of converging technologies, this paper analyzes the system of Beijing olympic high-tech, and then tries to find the relationship between converging technologies and Beijing olympic high-tech. finally, the key field of industrializing the Beijing olympic high-tech is put forward.
Abstract This contribution reports the efficient conversion of γ‐valerolactone and its derivatives, abundant but unexplored renewable feedstocks, into sustainable and degradable polythioesters via the establishment of the first isomerization‐driven ring‐opening polymerizations (IROPs) of corresponding thionolactone intermediates. The key to this success relies on the development of a new simple and robust [Et 3 O] + [B(C 6 F 5 ) 4 ] − cationic initiator which possesses high activity, exclusive selectivity, living nature, and broad scope of thionolactones. A complete inversion of configuration during IROP of enantiopure γ‐thionovalerolactone is also disclosed, affording isotactic semicrystalline polythioesters ( T m =87.0 °C) with mechanical property compared well to the representative commodity polyolefins. The formation of a highly crystalline supramolecular stereocomplex with enhanced thermal property ( T m =117.6 °C) has also been revealed.
A series of well-defined functional polyethylene graft copolymers with high molecular weights have been conveniently synthesized via the combination of ethylene/5-norbornene-2-methyl propargyl ether (NMPE) copolymerization using bis(β-enaminoketonato)titanium catalysts and following click coupling reaction. Bis(β-enaminoketonato)titanium catalysts have been proved to be the potent catalysts for ethylene/NMPE copolymerization, producing high molecular weight copolymers with unimodal molecular weight distributions. 13C NMR (dept) and 1H NMR spectra reveal the copolymerization proceeds in a regioselective way with alkynyl group retained near the main chain. The following click coupling reactions between ethylene/NMPE copolymer and azido-terminated polymer (PEO–N3, PS–N3) have been achieved under mild conditions independent of the chemical structure and molecular weight of azido-terminated polymer, providing functional polyethylene with well-defined structure and high molecular weight.
The overall objective of the project was to enhance fish production from seasonally flooding areas and irrigation systems using a collective approach to fish culture. The project sought to examine the institutions necessary to support community-approaches to fish culture in a range of social, cultural and economic conditions, in Bangladesh, Cambodia, China, Vietnam and Mali. Technical designs for fish culture were also tested, building on successes achieved in earlier trials in Bangladesh, with an emphasis on adapting the model to develop locally appropriate culture systems. The project showed that the model is able to generate important benefits for communities in Bangladesh, China and Mali, and may have the potential to so in other countries. However, it was found that introducing fish culture into complex and dynamic institutional contexts, whereby open access waters lie over private property required a range of social, environmental and economic conditions to be in place for the adoption and continuance of the fish culture model.
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