Design and experimental study of seed precise delivery mechanism for high-speed maize planter

Aiming at improving the seed spacing uniformity of maize planter at high forward speed,a seed precise delivery mechanism driven by electric motor has been developed and evaluated in laboratory.The mechanism was designed to deliver single seed from seed meter to furrow.Seed’s movement from the seed release point in a seed meter to the seed delivery cavity in the belt was analyzed,the mathematical model of seed movement in the seed precise delivery mechanism was established based on seed delivery time analysis.A mechanical prototype was designed and associated control system was developed.The performance contrast experiment was conducted between a traditional seed tube and newly developed seed precise delivery mechanism,and test results indicated that the qualities of feed index of the seed precise delivery mechanism were higher than those of the traditional seed tube delivery mechanism,and the coefficients of variation of the seed precise delivery mechanism were lower than those of the traditional seed tube delivery mechanism when the forward speed of planter was set at 10 km/h,12 km/h and 14 km/h,respectively.It indicated the seed precise delivery mechanism significantly improved seed spacing uniformity of maize planter compared with the traditional seed tube delivery mechanism.

Insights into the swelling process and drug release mechanisms from cross-linked pectin/high amylose starch matrices

Cross-linked pectin/high amylose mixtures were evaluated as a new excipient for matrix tablets formulations,since the mixing of polymers and cross-linking reaction represent rational tools to reach materials with modulated and specific properties that meet specific therapeutic needs.Objective:In this work the influence of polymer ratio and cross-linking process on the swelling and the mechanism driving the drug release from swellable matrix tablets prepared with this excipient was investigated.Methods:Cross-linked samples were characterized by their micromeritic properties(size and shape,density,angle of repose and flow rate)and liquid uptake ability.Matrix tablets were evaluated according their physical properties and the drug release rates and mechanisms were also investigated.Results:Cross-linked samples demonstrated size homogeneity and irregular shape,with liquid uptake ability insensible to pH.Cross-linking process of samples allowed the control of drug release rates and the drug release mechanism was influenced by both polymer ratio and cross-linking process.The drug release of samples with minor proportion of pectin was driven by an anomalous transport and the increase of the pectin proportion contributed to the erosion of the matrix.Conclusion:The cross-linked mixtures of high amylose and pectin showed a suitable excipient for slowing the drug release rates.

Applications and recent advances in transdermal drug delivery systems for the treatment of rheumatoid arthritis

Rheumatoid arthritis is a chronic,systemic autoimmune disease predominantly based on joint lesions with an extremely high disability and deformity rate.Several drugs have been used for the treatment of rheumatoid arthritis,but their use is limited by suboptimal bioavailability,serious adverse effects,and nonnegligible first-pass effects.In contrast,transdermal drug delivery systems(TDDSs)can avoid these drawbacks and improve patient compliance,making them a promising option for the treatment of rheumatoid arthritis(RA).Of course,TDDSs also face unique challenges,as the physiological barrier of the skin makes drug delivery somewhat limited.To overcome this barrier and maximize drug delivery efficiency,TDDSs have evolved in terms of the principle of transdermal facilitation and transdermal facilitation technology,and different generations of TDDSs have been derived,which have significantly improved transdermal efficiency and even achieved individualized controlled drug delivery.In this review,we summarize the different generations of transdermal drug delivery systems,the corresponding transdermal strategies,and their applications in the treatment of RA.

Flow behavior and deposition study of pollen-shape carrier particles in an idealized inhalation path model

Pollen-shape （spiked sphere） hydroxyapatite （HA） particles for drug carrier application are studied. The particle shape and size effect on flow characteristics and deposition are assessed. The pollen-shape HA particles are synthesized to have comparable size as typical carrier particles with mean diameter of 30-50 μm and effective density less than 0.3 g/cm^3. The flow behaviors of HA and commonly used lactose （LA） carrier particles are characterized by the Carr＇s compressibility index （CI）. The HA particles have lower CI than the LA particles for the same size range. The flow fields of HA and LA carrier particles are measured in an idealized inhalation path model using particle image velocimetry （PLY） technique. The particle streamlines indicate that a large portion of particles may deposit at the bending section due to inertial impaction and gravitational deposition. The flow field result shows that HA particles give smaller separation regions than the LA particles for the same size range. The pollen-shape HA particles are found to be able to follow the gas flow in the model and minimize undesired deposition. Deposition result confirms the bending section to have the most deposition. Deposition is found to be a function of particle properties. An empirical correlation is derived for the deposition efficiency of the pollen-shape particles as a function of particles Stokes number.