QUALITY ASSESSMENT OF GINSENG BY CHEMICAL FUZZY PATTERN RECOGNITION

A new method of assessing ginseng and screening its bioactive constituents by fuzzy pattern recognition has been proposed.

HPLC fingerprint of Nauclea officinalis stems in different harvesting period

Objective:To establish HPLC fingerprint of Nauclea officinalis stems in different harvesting periods,and analyze the effect of harvest time on the quality of the medicinal materials by combining with chemical pattern recognition.Methods:The analysis was performed on Sun Fire-C18(150 mm×4.6 mm,5μm)column.The mobile phase consisted of acetonitrile-0.1%phosphoric acid solution(gradient elution)at a flow rate of 1.0 mL/min.Results:The HPLC fingerprint of Nauclea officinalis stems was established and 12 common peaks were determined,and 3 chromatographic peaks were identified by comparison with the mixed references.There were some differences in the quality of Nauclea officinalis in different harvesting periods.The OPLS-DA analysis successfully predicted four main markers of quality difference.Conclusion:The established HPLC fingerprint could reflect the composition characteristics of Nauclea officinalis stems in different harvesting period,and the main markers that influence the composition difference of the stems could be used as key indicators for the quality control.

From Self-assembled Monolayers to Chemically Patterned Brushes:Controlling the Orientation of Block Copolymer Domains in Films by Substrate Modification

Block copolymer lithography is emerging as one of the leading technologies for patteming nanoscale dense features. In almost all potential applications of this technology, control over the orientation of cylindrical and lamellar domains is required for pattern transfer from the block copolymer film. This review highlights the state-of-art development of brushes to modify the substrates to control the assembly behaviors of block copolymers in films. Selected important contributions to the development of self-assembled monolayers, polymer brushes and mats, and chemically patterned brushes are discussed.

Chemical patterning enhanced by increasing quenching temperature in a medium-Mn steel

Chemical heterogeneity in high-temperature austenite is an effective way to tune the austenite-to-martensite transformation during cooling.The effect of quenching temperature on microstructure evolution is investigated when the high-temperature austenite is heterogeneous.After fast austenitization from partitioned pearlite consisting of Mn-enriched cementite and Mn-depleted ferrite in Fe-0.29C-3.76Mn-1.50Si(wt.%)steel,quenching to room temperature and quenching to 130℃ followed by 400℃ partitioning are both applied.With increasing quenching temperature from 25 to 130℃,the amount of heterogeneous microstructure(lamellar ghost pearlite)increases from 10.6%to 33.6% and the thickness of Mn-enriched retained austenite film is increased from 31.9±5.9 to 51.5±4.4 nm,indicating an enhancement of chemical patterning.It is probably ascribed to the reduction in driving force for austenite-to-martensite transformation,which requires a lower Mn content for austenite retention.

Chemical profiling and rapid discrimination of Blumea riparia and Blumea megacephala by UPLC-Q-Exactive-MS/MS and HPLC

Objective:To rapidly identify the two morphologies and chemical properties of similar herbal medicines,Blumea riparia and B.megacephala as the basis for chemical constituent analysis.Methods:UPLC-Q-Exactive-MS/MS was utilized for profiling and identification of the constituents in B.riparia and B.megacephala.Chemical pattern recognition(CPR)was further used to compare and distinguish the two herbs and to identify their potential characteristic markers.Then,an HPLC method was established for quality evaluation.Results:A total of 93 constituents are identified,including 54 phenolic acids,35 flavonoids,two saccharides,one phenolic acid glycoside,and one other constituent,of which 67 were identified in B.riparia and B.megacephala for the first time.CPR indicates that B.riparia and B.megacephala samples can be distinguished from each other based on the LC–MS data.The isochlorogenic acid A to cryptochlorogenic acid peak area ratio calculated from the HPLC chromatograms was proposed as a differentiation index for distinguishing and quality control of B.riparia and B.megacephala.Conclusion:This study demonstrates significant differences between B.riparia and B.megacephala in terms of chemical composition.The results provide a rapid and simple strategy for the comparison and evaluation of the quality of B.riparia and B.megacephala.

Effect of Ink Molecular Weights and Annealing Conditions on Molecular Transfer Printing

The molecular transfer printing（MTP） technique has been invented to fabricate chemical patterns with high fidelity using homopolymer inks. In this work, we systematically studied the effects of the molecular weights of homopolymer inks and transfer conditions on the MTP process. We explored a large range of molecular weights（~3.5-56 kg·mol^（-1）） of hydroxyl-terminated polystyrene（PS-OH） and hydroxyl-terminated poly（methyl methacrylate）（PMMA-OH） in the MTP process, and found that the resulting chemical patterns on replicas from all five blends were functional and able to direct the assembly of films of the same blends. The transfer temperature and the film annealing sequences had an impact on the MTP process. MTP was sensitive to the transfer temperature and could only be performed within a certain temperature range, i.e. higher than the glass transition temperature（T_g） of copolymers and lower than the rearrangement temperature of the assembled domains. Pre-organization of the blend films was also necessary for MTP since the preferential wetting of PMMA domains at the replica surface might result in the formation of a PMMA wetting layer to prevent the presentation of underlying chemical patterns to the replica surface.

Low threading dislocation density in GaN films grown on patterned sapphire substrates

The growth process of three-dimensional growth mode（3D） switching to two-dimensional growth mode （2D） is investigated when GaN films are grown on cone-shaped patterned sapphire substrates by metal-organic chemical vapor deposition.The growth condition of the 3D-2D growth process is optimized to reduce the threading dislocation density（TDD）.It is found that the condition of the 3D layer is critical.The 3D layer keeps growing under the conditions of lowⅤ/Ⅲratio,low temperature,and high pressure until its thickness is comparable to the height of the cone-shaped patterns.Then the 3D layer surrounds the cone-shaped patterns and has inclined side facets and a top（0001） plane.In the following 2D-growth process,inclined side facets coalesce quickly and the interaction of TDs with the side facets causes the TDs to bend over.As a result,the TDD of GaN films can decrease to 1×10~8 cm^（-2）,giving full-width at half maximum values of 211 and 219 arcsec for（002） and（102） omega scans, respectively.