Difference Discrete Variational Principles, Euler-Lagrange Cohomology and Symplectic, Multisyrnplectic Structures Ⅲ: Application to Symplectic and Multisymplectic Algorithms

In the previous papers I and H, we have studied the difference discrete variational principle and the EulerLagrange cohomology in the framework of multi-parameter differential approach. W5 have gotten the difference discreteEulcr-Lagrangc equations and canonical ones for the difference discrete versions of classical mechanics and tield theoryas well as the difference discrete versions for the Euler-Lagrange cohomology and applied them to get the necessaryand sufficient condition for the symplectic or multisymplectic geometry preserving properties in both the Lagrangianand Hamiltonian formalisms. In this paper, we apply the difference discrete variational principle and Euler-Lagrangecohomological approach directly to the symplectic and multisymplectic algorithms. We will show that either Hamiltonianschemes or Lagrangian ones in both the symplectic and multisymplectic algorithms arc variational integrators and theirdifference discrete symplectic structure-preserving properties can always be established not only in the solution spacebut also in the function space if and only if the related closed Euler Lagrange cohomological conditions are satisfied.     

Semirings which are unions of rings

Sernirings which are a disjoint union of rings form a variety S which contains the variety of all rings and the variety of all idempotent sernirings, and in particular, the variety of distributive lattices. Various structure theorems are established which bring insight into the structure of the lattice of subvarieties of S.``     

一种罗丹明6G类“Off-On”型Fe3+比色荧光探针

设计合成了一种基于罗丹明6G的新型比色荧光探针(RG),并通过核磁共振氢谱、碳谱和质谱进行了表征。该探针在pH=6的Tris-HCl缓冲溶液中可与Fe³⁺作用,溶液由无色变为粉红色,在530nm处产生强吸收,同时在557nm处发射强荧光。通过金属离子选择性实验,发现探针RG对Fe³⁺有高选择性;此外,探针溶液530nm的吸光度和557nm的荧光强度与Fe³⁺浓度呈良好的线性关系,检出限分别为1.26和3.87μmol/L。Job’s曲线分析表明探针分子与Fe³⁺的反应摩尔比为1∶1。此外,以乙二胺四乙酸为络合剂实现了探针分子的重复使用。该探针可用于实际水样中Fe³⁺的精准检测。     

Synthetic Studies Concerned with the Proposed Structure of Ribisin F,a Compound with Nerve Growth Factor Potentiating Activity Isolated from the Medicinal Fungus Phellinus ribis

The synthesis of the enantiomer of the structure assigned to the title natural product has been achieved from abundant quinic acid. However, the NMR spectral data acquired on the synthetic material do not match those reported for ribisin F (which are of rather modest quality). In an effort to establish the true structure of ribisin F, an epimer of the assigned structure was also prepared from quinic acid. A comparison of the spectral data obtained on this epimer with those reported for the natural product proved a better match and based on optical rotation data the possible true structure of this distinctive, dihydroxylated and benzofuran-containing compound is tentatively proposed.     

Reversible Handedness Inversion and Circularly Polarized Light Reflection Tuning in Self-Organized Helical Superstructures Using Visible-Light-Driven Macrocyclic Chiral Switches

A series of macrocyclic azobenzene-based chiral photoswitches have been judiciously designed, synthesized, and characterized. In the molecular structures, binaphthyl is covalently linked to ortho-positions of azobenzene, and four different substituents are linked to 6,6′-positions of binaphthyl. The photoswitches show enhanced helical twisting power (HTP) when doping in commercially available achiral liquid crystals to form self-organized helical superstructures, i.e., cholesteric liquid crystals (CLCs). All the photoswitches exhibit reversible photoisomerization driven by visible light of different wavelengths in both organic solvent and liquid crystals. The photoswitches with shorter substituents enable handedness inversion of CLCs upon photoisomerization. These are the first examples of ortho-linked azobenzene-based photoswitches that enable handedness inversion in CLCs. The photoswitches with longer substituents display only HTP values decreasing while maintaining the same handedness.     

Identifying the Interfacial Polarization in Non-stoichiometric Lead-Free Perovskites by Defect Engineering

Recent advances in perovskite ferroelectrics have fostered a host of exciting sensors and actuators. Defect engineering provides critical control of the performance of ferroelectric materials, especially lead-free ones. However, it remains a challenge to quantitatively study the concentration of defects due to the complexity of measurement techniques. Here, a feasible approach to analyzing the A-site defect and electron in alkali metal niobate is demonstrated. The theoretical relationships among defect concentration, conductivity, and oxygen partial pressure can be established based on the defect chemistry equilibria. The type and concentration of defects are reflected through the conductivity variation with oxygen partial pressure. As a result, the variation of defect concentration gives rise to defect-driven interfacial polarization, which further leads to distinct properties of the ceramics. e.g., abnormal dielectric behavior. Furthermore, this study also suggests a strategy to manipulate defects and charges in perovskite oxides for performance optimization.     

LC-Ultrasound-Assisted Headspace Liquid Microextraction for the Analysis of Phenols in Water

An ultrasound-assisted headspace liquid microextraction method is presented. The organic solvent droplet is suspended at the bottom of a polychloroprene rubber tube. More extractant can be held and the stability of microdrop is better than by using a syringe needle so that extraction aided by ultrasonication can be carried out. Compared with traditional methods, the extraction efficiency is about ten times higher. The method has been used to determine phenols in real water samples, and good recoveries were obtained. It is a promising alternative for analyzing volatile or semivolatile pollutants in environmental samples due to its simplicity, rapidity and stability.     

A Rheological Model for Evaluating the Behavior of Shear Thickening of Highly Flowable Mortar

Neither the modified Bingham model nor the Herschel–Bulkley model can be used to characterize and calculate the performance of shear thickening of highly flowable mortar because of their incalculability of the rheological parameters. A new exponential rheological model was established to solve the characterization and calculation of shear thickening of the lubrication layer (highly flowable mortar) during the pumping of concrete in this paper. This new exponential rheological model has three rheological parameters, namely, yield stress, consistency coefficient, and consistency exponent. They can quantitatively describe the yield stress, differential viscosity, and shear thickening degree of highly flowable mortar. The calculating results of the rheological parameters of the newly established model for the mortars with different compositions showed that the consistency exponent of mortar decreased with the increase of its sand-binder ratio or the dosage of fly ash in the binder. This indicates that the shear thickening degree of mortar decreases. The consistency exponent of mortar initially decreases and subsequently increases with the increase in silica fume content or the dosage of the superplasticizer. It illustrates that the degree of the shear thickening of mortar initially decreased and subsequently increased. These varying patterns were confirmed by the rheological experiment of mortars.     

The Simulation and Experiment of In 718 in Warm Laser Shock Processing Without Coating

Journal of Russian Laser Research - A modified constitutive model, combining laser shock processing and dynamic strain aging (DSA), is used to obtain the compressive residual stress field of In 718...     

The comparative pharmacokinetics of two pyrrolizidine alkaloids, senecionine and adonifoline, and their main metabolites in rats after intravenous and oral administration by UPLC/ESIMS

Pyrrolizidine alkaloids (PAs) are considered to be one of the most hepatotoxic groups of compounds of plant origin and are present in about 3% of the world’s flowering plants. Most PAs represent a considerable health hazard to both livestock and humans through the consumption of plants and PA-contaminated products such as milk, honey, herbal teas, and medicines. This study determined the differences in the in vivo pharmacokinetic behavior of senecionine (SEN), adonifoline (ADO), and their main metabolites in rats after intravenous administration and oral administration by ultraperformance liquid chromatography/electrospray ionization mass spectrometry. Upon intravenous administration and oral administration of SEN and ADO, significant differences in pharmacokinetics were observed, with the SEN and ADO being absorbed fast with lower bioavailability and being quickly metabolized to PA N-oxides and hydroxylation products of PAs or their N-oxides. It could be seen that the plasma concentration ratio of senecionine N-oxide (SEN-NO) to SEN (C _SEN-NO/C _SEN) was significantly larger than that for adonifoline N-oxide (ADO-NO) and ADO (C _ADO-NO/C _ADO) (P < 0.001) for both dosing routes in rats. The high N-oxygenation activity and extensive toxicity of SEN, compared with ADO, in rats raised the question of whether or not the higher metabolic rate of SEN in rats in vivo was related to its potent toxicity. The toxicity of SEN-NO and ADO-NO needs to be evaluated further and compared in vitro/in vivo. This study was most helpful for interpreting the metabolism of metabolic bioactivation and detoxication, and toxicity differences among SEN, ADO and other PAs.