Fast pyrolysis of biomass will produce various furan derivatives, among which 5-hydroxymethyl furfural(5-HMF) and furfural(FF) are usually the two most important compounds derived from holocellulose. In this study...Fast pyrolysis of biomass will produce various furan derivatives, among which 5-hydroxymethyl furfural(5-HMF) and furfural(FF) are usually the two most important compounds derived from holocellulose. In this study, density functional theory(DFT) calculations are utilized to reveal the formation mechanisms and pathways of 5-HMF and FF from two hexose units of holocellulose, i.e., glucose and mannose. In addition, fast pyrolysis experiments of glucose and mannose are conducted to substantiate the computational results, and the orientation of 5-HMF and FF is determined by 13C-labeled glucoses. Experimental results indicate that C1 provides the aldehyde group in both 5-HMF and FF, and FF is mainly derived from C1 to C5 segment. According to the computational results, glucose and mannose have similar reaction pathways to form 5-HMF and FF with d-fructose(DF) and 3-deoxy-glucosone(3-DG) as the key intermediates. 5-HMF and FF are formed via competing pathways. The formation of 5-HMF is more competitive than that of FF, leading to higher yield of 5-HMF than FF from both hexoses. In addition, compared with glucose,mannose can form 5-HMF and FF via extra pathways because of the epimerization at C2 position. Therefore, mannose pyrolysis results in higher yields of 5-HMF and FF than glucose pyrolysis.展开更多
Surgical accuracy has greatly improved with the advent of microsurgical techniques. However, complete functional recovery after peripheral nerve injury has not been achieved to date. The mechanisms hindering accurate ...Surgical accuracy has greatly improved with the advent of microsurgical techniques. However, complete functional recovery after peripheral nerve injury has not been achieved to date. The mechanisms hindering accurate regeneration of damaged axons after peripheral nerve injury are in urgent need of exploration. The present study was designed to explore the mechanisms of peripheral nerve regeneration after different types of injury. Femoral nerves of rats were injured by crushing or freezing. At 2, 3, 6, and 12 weeks after injury, axons were retrogradely labeled using 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate(Dil) and True Blue, and motor and sensory axons that had regenerated at the site of injury were counted. The number and percentage of Dil-labeled neurons in the anterior horn of the spinal cord increased over time. No significant differences were found in the number of labeled neurons between the freeze and crush injury groups at any time point. Our results confirmed that the accuracy of peripheral nerve regeneration increased with time, after both crush and freeze injury, and indicated that axonal regeneration accuracy was still satisfactory after freezing, despite the prolonged damage.展开更多
A novel identification algorithm is proposed to deal with the modelling issues of linear switched systems under the switching modes being unknown.The main contributions of this paper embody the following aspects:(1)fo...A novel identification algorithm is proposed to deal with the modelling issues of linear switched systems under the switching modes being unknown.The main contributions of this paper embody the following aspects:(1)for simplifying the identification problems,the label functions are proposed to replace the switching states of the modes;(2)The recursive least square algorithm is used to identify the system parameters,and the convergence performance of the proposed algorithm is studied.By using convergence analysis,the parameter estimation error can converge to zero point when the input signals satisfy persistent excited conditions and the total time of mode mismatch is limited.Finally,the effectiveness of the proposed method is verified by a simulation example.展开更多
基金financial support from the National Natural Science Foundation of China (51576064, 51676193)Beijing Nova Program (Z171100001117064)+2 种基金Beijing Natural Science Foundation (3172030)the Foundation of Stake Key Laboratory of Coal Combustion (FSKLCCA1706)the Fundamental Research Funds for the Central Universities (2017MS071, 2016YQ05)
文摘Fast pyrolysis of biomass will produce various furan derivatives, among which 5-hydroxymethyl furfural(5-HMF) and furfural(FF) are usually the two most important compounds derived from holocellulose. In this study, density functional theory(DFT) calculations are utilized to reveal the formation mechanisms and pathways of 5-HMF and FF from two hexose units of holocellulose, i.e., glucose and mannose. In addition, fast pyrolysis experiments of glucose and mannose are conducted to substantiate the computational results, and the orientation of 5-HMF and FF is determined by 13C-labeled glucoses. Experimental results indicate that C1 provides the aldehyde group in both 5-HMF and FF, and FF is mainly derived from C1 to C5 segment. According to the computational results, glucose and mannose have similar reaction pathways to form 5-HMF and FF with d-fructose(DF) and 3-deoxy-glucosone(3-DG) as the key intermediates. 5-HMF and FF are formed via competing pathways. The formation of 5-HMF is more competitive than that of FF, leading to higher yield of 5-HMF than FF from both hexoses. In addition, compared with glucose,mannose can form 5-HMF and FF via extra pathways because of the epimerization at C2 position. Therefore, mannose pyrolysis results in higher yields of 5-HMF and FF than glucose pyrolysis.
基金supported by the National Natural Science Foundation of China,No.81360194a grant from the National Basic Research Program of China,No.2014CB542200
文摘Surgical accuracy has greatly improved with the advent of microsurgical techniques. However, complete functional recovery after peripheral nerve injury has not been achieved to date. The mechanisms hindering accurate regeneration of damaged axons after peripheral nerve injury are in urgent need of exploration. The present study was designed to explore the mechanisms of peripheral nerve regeneration after different types of injury. Femoral nerves of rats were injured by crushing or freezing. At 2, 3, 6, and 12 weeks after injury, axons were retrogradely labeled using 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate(Dil) and True Blue, and motor and sensory axons that had regenerated at the site of injury were counted. The number and percentage of Dil-labeled neurons in the anterior horn of the spinal cord increased over time. No significant differences were found in the number of labeled neurons between the freeze and crush injury groups at any time point. Our results confirmed that the accuracy of peripheral nerve regeneration increased with time, after both crush and freeze injury, and indicated that axonal regeneration accuracy was still satisfactory after freezing, despite the prolonged damage.
基金supported byNational Natural Science Foundation of China[grant number 61863034].
文摘A novel identification algorithm is proposed to deal with the modelling issues of linear switched systems under the switching modes being unknown.The main contributions of this paper embody the following aspects:(1)for simplifying the identification problems,the label functions are proposed to replace the switching states of the modes;(2)The recursive least square algorithm is used to identify the system parameters,and the convergence performance of the proposed algorithm is studied.By using convergence analysis,the parameter estimation error can converge to zero point when the input signals satisfy persistent excited conditions and the total time of mode mismatch is limited.Finally,the effectiveness of the proposed method is verified by a simulation example.