Functionalization of OEP-based benzochlorins to develop carbohydrate-conjugated photosensitizers. Attempt to target beta-galactoside-recognized proteins

meso-(2-Formylvinyl)octaethylporphyrin on reaction with cyanotrimethylsilane in the presence of various catalysts [copper triflate [Cu(OTf)(2)], indium triflate [In(OTf)(3)], or magnesium bromide diethyl etherate (MgBr(2).Et(2)O)] produced a mixture of the intermediate 3-hydroxy-3-cyanopropenoporphyrin, the corresponding trimethylsilyl ether derivative, and the unexpected propenochlorins. The yields of the reaction products were found to depend on the reaction conditions and the catalysts used. The intermediate porphyrins on treatment with concentrated sulfuric acid yielded the free-base cyanobenzochlorins in major quantity along with several other novel benzochlorins as minor products. Reduction of ethyl-3-hydroxy-1-pentenoate-porphyrin with DIBAL-H/NaBH(4) and subsequent acid treatment provided the corresponding free-base 10(3)-(2-hydroxyethyl)benzochlorin, which upon a sequence of reactions gave a free-base benzochlorin bearing a carboxylic acid functionality in good yield. It was then condensed with a variety of carbohydrates (glucosamine, galactosamine, and lactosamine), and the related conjugates were screened using the galectin-binding-ability assay. Among the carbohydrate conjugates investigated, the lactose and galactose analogues displayed the galectin-binding ability with an enhancement of about 300-400-fold compared to lactose. In preliminary studies, all photosensitizers (with or without carbohydrate moieties) were found to be active in vitro [radiation-induced fibrosarcoma (RIF) tumor cells]. However, the cells incubated with lactose (known to bind to beta-galactoside-recognized proteins) prior to the addition of the photosensitizers containing the beta-galactose moiety (e.g., galactose and lactose) produced a 100% decrease in their photosensitizing efficacy. Under similar experimental conditions, benzochlorin without a beta-galactoside moiety or the related glucose conjugate did not show any inhibition in its photosensitizing efficacy. These results in combination with the galectin-binding data indicate a possible beta-galactoside-recognized protein specificity of the galactose- and lactose-benzochlorin conjugates.     

热力联合作用弹性薄圆板的弯曲与屈曲

 导出了热力联合作用下弹性薄圆板的弯曲动力响应控制方程,讨论了其弯曲变形特点及影响失效的因素。分析表明在短时热能沉积作用下,热屈曲是弹性薄板失效的主要方式之一;反鼓包或反冲塞是热屈曲的后继行为;增加外载和热能沉积功率水平都将加速热屈曲的发生;材料的温度相关性与热能沉积的时空分布对薄板的力学行为都有重要影响,同为产生和影响热剪切失效(反冲塞)的重要因素。     

基于簇的无线传感器网络密钥预分配方案

通过把网络划分为多个六边形区域,每个节点预先存储多个子密钥空间中的密钥信息,采用基于组的部署方式,提出了一种新的基于分簇结构的无线传感器网络密钥预分配方案.该方案能够动态更新节点的密钥,从而解决了由于节点被捕获所导致的密钥连通性下降和密钥更新通信开销大等问题.性能分析和仿真结果表明,与现有的密钥预分配方案相比,该方案可以确保任意两个相邻节点之间都能够建立一个惟一的对密钥,节点所需的密钥存储空问减少,密钥建立和更新所需的通信开销很小,网络的抗攻击能力得到较大提高.     

第八届全国固体力学青年学者学术研讨会报告综述

简要介绍了在清华大学召开的第八届全国固体力学青年学者学术研讨会的会议情况,概括总结了与会专家和青年学者所做的学术报告内容,并就固体力学发展所面临的问题和挑战以及学科发展趋势提出了一些思考和建议.      

Effect of microsphere size on the drug release and experimental characterization of an electrospun naringin‐loaded microsphere/sucrose acetate isobutyrate (SAIB) depot

The aims of this study were to prepare different sizes of electrospun naringin‐loaded microspheres (Ng‐ms) and investigate the effects of the particle size of these microspheres on drug release from naringin‐loaded microsphere/sucrose acetate isobutyrate (Ng‐m‐SAIB) hybrid depots to develop an improved drug delivery system for tissue engineering. Different sizes of microspheres were produced using electrospray methods by controlling electrospinning parameters. The Ng‐m‐SAIB depots were prepared by dispersing Ng‐ms in SAIB depots. The morphology and size distributions of the electrospun Ng‐ms were characterized by polarizing microscopy and scanning electron microscopy (SEM). To better understand the release behavior of Ng‐m‐SAIB, the porosity of SAIB depots was measured. Consequently, both small (2.51 ± 0.191 μm) and large (5.03 ± 0.172 μm) microspheres exhibited smooth surfaces and good monodispersity. The initial and long‐term drug release rates of the large microspheres were lower than those of small microspheres. On the first day after 2.5‐μm and 5‐μm Ng‐m‐SAIB depots were produced, the burst release reduced dramatically from 68.79% to 3.30% and from 63.20% to 0.00%, respectively. After 92 days of release, the drug release rate of 5‐μm Ng‐m‐SAIB was still lower than that of 2.5‐μm Ng‐m‐SAIB, with values of 58.54% and 63.93%, respectively. These results demonstrate that drug release from Ng‐m‐SAIB depots can be tailored solely by varying the size of the microspheres and that good drug release behavior occurred.     

高温升率下LY12铝合金拉伸破坏及其机理的研究

使用Gleeble1500热力模拟实验系统研究了温升率及其历史对LY12铝合金拉伸破坏的影响.对采用不同温升率加热到给定温度后的试件的拉伸试验表明,相同工作温度下经历较高温升率历史的试件的强度较低;以不同温升率对不同预载应力水平的试件快速加热直至破坏,发现预载应力相同时经历较高温升率试件的失效温度较低.对试件断口附近材料金相组织的分析表明,当工作温度或预载应力水平相同时,较高温升率下材料的微缺陷明显增加.高温升率造成的局部热失配及材料微观组织结构的损伤,不同温度、应力和时间下材料的再结晶程度等对材料的宏观本构行为及失效具有重要影响.     

Decorating Channel Walls in Metal–Organic Frameworks with Crown Ethers for Efficient and Selective Separation of Radioactive Strontium(II)

Nuclear accidents and the improper disposal of nuclear wastes have led to serious environmental radioactive pollutions. The rational design of adsorbents for the highly efficient separation of strontium(II) is essential in treating nuclear waste and recovering radioactive strontium resources. Metal–organic frameworks (MOFs) are potential materials for the separation of aqueous metal ions owing to their designable structure and tunable functionality. Herein, a novel 3D MOF material MOF-18Cr6, in which 1D channels are formed using 18-crown-6-ether-containing ligands as channel walls, is fabricated for strontium(II) separation. In contrast to traditional MOFs designed by grafting functional groups in the framework pores, MOF-18Cr6 possesses regular 18-crown-6-ether cavities on the channel walls, which not only can transport and intake strontium(II) via the channels, but also prevent blockage of the channels after the binding of strontium(II). Consequently, the functional sites are fully utilized to achieve a high strontium(II) removal rate of 99.73 % in simulated nuclear wastewater. This study fabricates a highly promising adsorbent for the separation of aqueous radioactive strontium(II), and more importantly, can provide a new strategy for the rational design of high-performance MOF adsorbents for separating target substances from complex aqueous environments.     

Flexoelectricity induced increase of critical thickness in epitaxial ferroelectric thin films

Flexoelectricity describes the coupling between polarization and strain/stress gradients in insulating crystals. In this paper, using the Landau–Ginsburg–Devonshire phenomenological approach, we found that flexoelectricity could increase the theoretical critical thickness in epitaxial BaTiO₃ thin films, below which the switchable spontaneous polarization vanishes. This increase is remarkable in tensile films while trivial in compressive films due to the electrostriction caused decrease of potential barrier, which can be easily destroyed by the flexoelectricity, between the ferroelectric state and the paraelectric state in tensile films. In addition, the films are still in a uni-polar state even below the critical thickness due to the flexoelectric effect.     

AFM images of G1-phase premature condensed chromosomes: Evidence for 30 nm changed to 50 nm chromatin fibers

To gain evidence for 30 nm changed to 50 nm chromatin fibers, we used atomic force microscopy (AFM) to study the ultrastructural organization of G₁-phase premature condensed chromosomes (PCC). The surface of early G₁-phase PCC is smooth and fibrous structures exist around the chromatids. The height of early G₁-phase PCC is about 410 nm and the width is 1.07 ± 0.11 μm (n = 30). At late G₁-phase, the surface becomes globular. The height of late G1-phase PCC is about 370 nm and the width is 845.04 ± 82.84 nm (n = 30). Phase image reveals that early G₁-phase PCC is composed of 50 nm (48.91 ± 6.63 nm, n = 30) chromatin fibers and these 50 nm chromatin fibers tangle together, while late G₁-phase PCC is composed of 30 nm (30.96 ± 4.07 nm, n = 30) chromatin fibers. At high magnification, fibers existing around the chromatids become clear in early G₁-phase PCC. Chromatin fibers revealed by closer view of the end of chromatid are about 50 nm. In late G₁-phase PCC, the surface presents globular structures. The shape of these globular structures is regular and the diameter is 118.96 ± 11.70 nm (n = 30). Our results clearly show that 30 nm chromatin fibers change to 50 nm chromatin fibers in G₁-phase PCC and suggest that 50 nm chromatin fibers are the basic component of the mitotic chromosomes.