Research on central village selection in western underdeveloped region:a case study of Lidian Town,Jingning County,Gansu Province,China

Central village selection is the priority of small town construction.Depending on the development potential analysis,classification analysis,and quantitative and qualitative analysis,this article systematically proposes the specific methods of central village selection and also constructs the indicator system used in central village selection in small towns of western underdeveloped region in China.The article also puts forward ideas and methods for selection of central village in the western underdeveloped region through an empirical research on Lidian Town,Jingning County,Gansu Province.In the final part,suggestions and recommendations on how to develop central village for Lidian Town are made.

Research Progress of Diseases on Atractylodes lancea

According to the current situation of diseases on Atractylodes lancea , the etiology, pathogenesis, symptoms and control methods of root diseases, leaf diseases and other diseases of A. lancea are analyzed, in order to provide a reference for the diagnosis and control of diseases on A. lancea .

Minimum Dwell Time for Global Exponential Stability of a Class of Switched Positive Nonlinear Systems

This paper will investigate global exponential stability analysis for a class of switched positive nonlinear systems under minimum dwell time switching, whose nonlinear functions for each subsystem are constrained in a sector field by two odd symmetric piecewise linear functions and whose system matrices for each subsystem are Metzler. A class of multiple time-varying Lyapunov functions is constructed to obtain the computable sufficient conditions on the stability of such switched nonlinear systems within the framework of minimum dwell time switching.All present conditions can be solved by linear/nonlinear programming techniques. An example is provided to demonstrate the effectiveness of the proposed result.

Palladium-Catalyzed O- and N-Glycosylation with Glycosyl Chlorides

Despite the significant progress in carbohydrate chemistry,there remains a pressing need for efficient and practical glycosylationmethods using simple glycosyl donors and with high atom economy.Herein,a new protocol for glycosylation with glycosyl chloride donors under palladium-catalyzed conditions is developed.PdII complex serves as a Lewis acid to promote the activation of glycosyl chloride for the formation of oxocarbeniumion intermediate.This new method is operationally simple,robust,and enables efficient synthesis of both O-and N-glycosides with a broad substrate scope.In particular,it offers an easy access to a range of N-ribonucleoside analogs.

Total Synthesis of C-α-Mannosyl Tryptophan via Palladium-Catalyzed C-H Glycosylation

The C2-α-mannosyl-tryptophan amino acid is produced by a unique posttranslational modification(PTM)of proteins and poses a significant synthetic challenge.A new strategy based on Pd-catalyzed auxiliary-directed remote C-H glycosylation of tryptophan was developed,which generates the C2-α-mannopyranose(Man)-Trp unit in a highly efficient and stereoselective fashion.Density functional theory(DFT)computational studies support a concerted oxidative addition mechanism for the stereospecific functionalization of a Pd(II)palladacycle intermediate with anα-mannosyl chloride donor.The utility of this method was demonstrated in the first total synthesis of insect C-glycopeptide hormone Cam-HrTH-I.