On the notion of cobordism for bounded manifolds

The usual concept of cobordism is concerned with closed manifolds. In this paper, we generalise the concept of cobordism to the extent of bounded manifolds and obtain a homotopy theorem similar to the theorem of Thom. Supported by the National Natural Science Foundation of China and partially supported by a grant of Zhejiang Natural Science Foundation.     

Surface Treatment and Biomimetic Mineralization of Porous Microspheres Fabricated by Calcium Gluconate-g-Poly(D,L-lactide)

Porous hybrid microspheres were fabricated by the synthesized calcium gluconate-g-poly(D,L-lactide) (CG-g-PDLLA) composites.These hybrid microspheres were treated with an alkaline solution for different period of time to control the amount of generated carboxylate groups and remained CG on the surface.The microspheres were then incubated in a supersaturated simulated body fluid (1,5 SBF) solution for different time to investigate their biomimetic mineralization behavior.The depositions were found to have a fine cluster morphology,a similar crystal structure and chemical structure to natural hydroxyapatite,and a medium Ca/P of approximately 1.30.The effect of surface treating time on the structure and mineralization behavior of these microspheres has been discussed in detail.The results indicate that the nucleation and growth of apatite on the surface are influenced by the induced carboxylate groups and the remained CG.The hybrid CG-g-PDLLA microspheres have the potential as a novel alternative in bone tissue engineering.     

古代玻璃样品表面因素对便携式X射线荧光定量分析的影响

便携式X射线荧光光谱分析技术(PXRF)是一种表面分析技术,样品表面状况对定量分析结果有很大的影响.本文采用PXRF对新疆、广西、江苏等地出土的Na2O-CaO-SiO2,K2O-SiO2和PbO-BaO-SiO2体系古代玻璃的风化表面与内部进行了定量分析,指出了主要助熔剂的含量在不同部位的变化.另外,还研究了样品与参...     

1:2型硝酸铀酰二苯并-18-冠-6氢键夹心式配合物的晶体结构

化合物[UO₂(NO₃)₂(H₂O)₂]·(DB18C6)₂晶体属单斜晶系,空间群为P21/k。晶体学参数:a=11.782(2)Å,b=8.584(2)Å,c=22.631(2),β=98.29(2)Å°,Z=2.用3024个I≥3σ(I)的三维X射线独立衍射数据进行结构解析,最终的R=0.066。结构分析表明,两个双齿配体硝酸根及两个水分子配位于线型铀酰离子的赤道平面上,铀的配位数是8,配位几何构型为稍有扭曲的六方双锥。配位水分子的4个氢原子分别与上下两层冠醚环上的氧原子生成氢键。形成夹心式分子缔合物。     

An improved method of energy calibration for position-sensitive silicon detectors

Energy calibration of resistive charge division-based position-sensitive silicon detectors is achieved by parabolic fitting in the traditional method, where the systematic variations of vertex and curvature of the parabola with energy must be considered. In this paper we extend the traditional method in order to correct the fitting function, simplify the procedure of calibration and improve the experimental data quality. Instead of a parabolic function as used in the traditional method, a new function describing the relation of position and energy is introduced.The energy resolution of the 8.088 Me V α decay of213 Rn is determined to be about 87 ke V(FWHM), which is better than the result of the traditional method, 104 ke V(FWHM). The improved method can be applied to the energy calibration of resistive charge division-based position-sensitive silicon detectors with various performances.     

Biomimetic Extreme-Temperature- and Environment-Adaptable Hydrogels

Recently, temperature-resistant hydrogels, hydrogels which are freezing- and dehydration-resistant, have garnered considerable attention in the scientific community as they extend the rage of application of hydrogels to arid and/or cold environments. Besides, these hydrogels exhibit tunable conductivity and mechanical performance while offering excellent biocompatibility and flexibility, making them interesting candidates for flexible and wearable electronics and (bio)sensors. Several biomimetic strategies were developed to fabricate anti-freezing and anti-dehydration hydrogels with a diversity of merits, such as high strain resistance and conductivity, even at sub-zero temperatures, and employed as (bio)sensors, electrodes, and energy-storage devices. This review summarizes the recent advances in the preparation and application of temperature-resistant hydrogels, indicates issues of the state-of-the-art hydrogels, and offers potential future research directions.     

Phosphorous acid promoted isomerization of propargyl alcohols to α,β-unsaturated carbonyl compounds

A metal-free and two-phase protocol for the Meyer-Schuster isomerization of propargyl alcohols to the corresponding α,β-unsaturated carbonyl compounds has been achieved in the presence of stoichiometric phosphorous acid aqueous solution, which produces the desired products in high yields with excellent stereoselectivity. Compared with the traditional methods, the procedure features broad scope of the substrates, mild conditions, and easy separation, providing an appealing alternative to the Meyer-Schuster reaction.     

Substituent effects on the isomerization of hydrazone switches driven by the intramolecular hydrogen bond

In this work, the substituent effects on hydrogen bonding in one kind of hydrazone-based switch are revealed. The E/Z isomerization ratios of these hydrazones and their intramolecular hydrogen bond strengths in the Z form were evaluated using NMR technique. Linear correlations between these parameters and Hammett empirical values for substituent effects are explored as well.     

Analytical/experimental investigation of energy absorption in grid-stiffened composite structures under transverse loading

In this paper we summarize preliminary results from an analytical/experimental study of the energy absorption characteristics of grid-stiffened composite structures under transverse loading. Tests and quasi-static finite element analysis simulations were carried out for isogrid E-glass/polypropylene panels in three-point bending. The results of the tests and simulations show that these types of structures have excellent damage tolerance and that most of the energy absorption occurs beyond initial failure. It is also observed that even though the peak load is greater for loading on the skin side, the specific energy absorption and the range of displacements over which energy is absorbed are significantly better when the load is applied on the rib side.