A convenient synthesis of 3-aryl-5-methylidene-2-thiohydantoins

3-Aryl-5-methylidene-2-thiohydantoins were constructed in one-pot reaction of aryl isothiocyanates and 3-morpholino- alanine in alkaline medium with the subsequent treatment with boiling hydrochloric acid.     

What is the optimal cutoff surface for ore bodies with more than one mineral?

In mine planning problems, cutoff grade optimization defines a threshold at every time period such that material above this value is processed, and the rest is considered waste. In orebodies with multiple minerals, which occur in practice, the natural extension is to consider a cutoff surface. We show that in two dimensions the optimal solution is a line, and in n dimensions it is a hyperplane.     

In vitro investigation of cartilage regeneration properties of polymeric ceramic hybrid composite

There would be a major effect on the cartilage regeneration characteristics of ceramic material in a substrate implant requiring biologically active biomaterials and the reinforcement phase. At this moment, we produced collagen-hyaluronic acid @ hydroxyapatite-halloysite nanotube-single walled carbon nanotube composites, which is a successful technique for making a scaffold with a superior counter for cartilage property. FTIR, XRD, and SEM-EDAX were used to perform morphological and structural studies. The prepared composite's surface feature was investigated and discovered by HRTEM-SAED analysis, and it observed porous nature. The simulated body fluids (SBF) assessment of the materials was noticed their bioactivity and chondrocytes to determine their biocompatibility. Hybrid composite displayed promise for cartilage tissue engineering despite mesenchymal stem cells compatibility effect and magnificently demonstrated an antibacterial effect without antibiotics. The live/dead cells analysis shows that the composite can significantly improve mesenchymal stem cells, and the composite has the potential ability for cartilage regeneration. The above characteristics make the material quite interesting and important in the area for regenerative medicinal uses.     

Periodicity of Two-Dimensional Bonding of Main Group Elements

In the periodic table the position of each atom follows the ‘aufbau’ principle of the individual electron shells. The resulting intrinsic periodicity of atomic properties determines the overall behavior of atoms in two-dimensional (2D) bonding and structure formation. Insight into the type and strength of bonding is the key in the discovery of innovative 2D materials. The primary features of 2D bonding and the ensuing monolayer structures of the main-group II–VI elements result from the number of valence electrons and the change of atom size, which determine the type of hybridization. The results reveal the tight connection between strength of bonding and bond length in 2D networks. The predictive power of the periodic table reveals general rules of bonding, the bonding-structure relationship, and allows an assessment of published data of 2D materials.     

The Picone identity: A device to get optimal uniqueness results and global dynamics in Population Dynamics

This paper infers from a generalized Picone identity the uniqueness of the stable positive solution for a class of semilinear equations of superlinear indefinite type, as well as the uniqueness and global attractivity of the coexistence state in two generalized diffusive prototypes of the symbiotic and competing species models of Lotka–Volterra. The optimality of these uniqueness theorems reveals the tremendous strength of the Picone identity.     

Regularity of optimal sets for some functional involving eigenvalues of an operator in divergence form

In this paper we consider minimizers of the functional$\min \{{\lambda }_1(\mathrm{\Omega })+\cdots +{\lambda }_k(\mathrm{\Omega })+\mathrm{\Lambda }|\mathrm{\Omega }|,:\mathrm{\Omega }\subset D\text{ open}\}$ where $D\subset {\mathbb{R}}^d$ is a bounded open set and where $0<{\lambda }_1(\mathrm{\Omega })\le \cdots \le {\lambda }_k(\mathrm{\Omega })$ are the first k eigenvalues on Ω of an operator in divergence form with Dirichlet boundary condition and with Hölder continuous coefficients. We prove that the optimal sets ${\mathrm{\Omega }}^{⁎}$ have finite perimeter and that their free boundary $\partial {\mathrm{\Omega }}^{⁎}\cap D$ is composed of a regular part, which is locally the graph of a $C^{1,\alpha }$-regular function, and a singular part, which is empty if $d<d^{⁎}$, discrete if $d=d^{⁎}$ and of Hausdorff dimension at most $d-d^{⁎}$ if $d>d^{⁎}$, for some $d^{⁎}\in \{5,6,7\}$.     

基于GA_XGBoost模型的大学生科研能力预测问题研究

科学评价大学生科研创新能力对我国科研水平的提高具有重要意义.采用机器学习模型来预测大学生科研能力可以起到良好的效果,提出一种GAXGBoost模型来实现对大学生的科研能力预测.此模型是以Xgboost算法为基础,然后充分利用遗传算法的全局搜索能力自动搜索Xgboost最优超参数,避免了人为经验调参不准确的缺陷,最后采用精英选择策略以此确保每一轮都是最佳的进化结果.通过分析表明,所采用的GAXGBoost模型在大学生科研能力预测的结果中具有很高的精度,将此模型与Logistic Regression、Random Forest、SVM等模型进行对比,GAXGBoost模型的预测精度最高.     

人教版高中化学教科书“研究与实践”栏目分析与实施策略*

对人教版高中化学教科书新设计的“研究与实践”栏目的主题内容、功能价值进行分析,就如何充分发挥该栏目的教学功能和价值,发展学生的化学学科核心素养,提出了创设教学情境线索、开发为研究性学习课题、开发为校本选修课程、开发为STEM课程等实施策略。