含双间隙连杆机构动力学仿真与实验

为考察含双间隙连杆机构的动力学行为,进行了仿真和实验研究。在仿真中,基于ADAMS软件建立了一个非线性接触力模型。同时,设计和建立了一个实验装置来对仿真结果进行验证。分别讨论了间隙尺寸、加载频率和加载力幅值对接触碰撞力的影响。结果表明,间隙的存在会影响传递力曲线,使机构产生明显的振动冲击,间隙大小和加载速度是影响机构动态响应的主要因素。实验结果证明了本文模型的正确性。     

A Structured Family of Clustering and Tree Construction Methods

A cluster A is an Apresjan cluster if every pair of objects within A is more similar than either is to any object outside A. The criterion is intuitive, compelling, but often too restrictive for applications in classification. We therefore explore extensions of Apresjan clustering to a family of related hierarchical clustering methods. The extensions are shown to be closely connected with the well-known single and average linkage tree constructions. A dual family of methods for classification by splits is also presented. Splits are partitions of the set of objects into two disjoint blocks and are widely used in domains such as phylogenetics. Both the cluster and split methods give rise to progressively refined tree representations. We exploit dualities and connections between the various methods, giving polynomial time construction algorithms for most of the constructions and NP-hardness results for the rest.     

Synthesis of a chlorophyll-a derivative fused with an additional exo-five-membered ring and its optical properties

A C20-free chlorophyll-a derivative with an additional exo-five-membered ring was successfully prepared using an ethylene linkage at the C3- and C5-positions. A bromination at the C20-position was requisite for the cyclization of a 1-hydroxyethyl or vinyl group at the C3-position of methyl bacteriopheophorbide-d or methyl pyropheophorbide-a, respectively. By comparing optical properties of the cyclized product with those of its 3-ethyl uncyclized analog in a diluted dichloromethane solution, it was shown that the cyclization shifted the Q_x and B_x absorption maxima to longer wavelengths and reduced the Stokes shift.     

Cancer-Cell-Specific Drug Delivery by a Tumor-Homing CPP-Gossypol Conjugate Employing a Tracelessly Cleavable Linker

Tumor-targeted drug delivery is highly important for improving chemotherapy, as it reduces the dose of cytotoxic agents and minimizes the death of healthy tissues. Towards this goal, a conjugate was synthesized of gossypol and a MCF-7 cancer cell specific CPP (cell penetrating peptide), thus providing a selective drug delivery system. Utilizing the aldehyde moiety of gossypol, the tumor homing CPP RLYMRYYSPTTRRYG was attached through a semi-labile imine linker, which was cleaved in a traceless fashion under aqueous conditions and had a half-life of approximately 10 hours. The conjugate killed MCF-7 cells to a significantly greater extent than HeLa cells or healthy fibroblasts.     

多层连锁不平衡的齐一性检验

In this article, using the likelihood score theory extended to nuisance parameters we derive a new homogeneity score test for comparing linage disequilibrium across several strata. Power and sample size formulae are also obtained.     

First heterobimetallic AgI–CoIII coordination compound with both bridging and terminal –NO2 coordination modes: synthesis,characterization, structural and computational studies of (PPh3)2AgI–(μ‐κ2O,O′:κN‐NO2)–CoIII(DMGH)2(κN‐NO2)

An unusual heterobimetallic bis(triphenylphosphane)(NO₂)Ag^I–Co^III(dimethylglyoximate)(NO₂) coordination compound with both bridging and terminal –NO₂ (nitro) coordination modes has been isolated and characterized from the reaction of [CoCl(DMGH)₂(PPh₃)] (DMGH₂ is dimethylglyoxime or N,N′‐dihydroxybutane‐2,3‐diimine) with excess AgNO₂. In the title compound, namely bis(dimethylglyoximato‐1κ²O,O′)(μ‐nitro‐1κN:2κ²O,O′)(nitro‐1κN)bis(triphenylphosphane‐2κP)cobalt(III)silver(I), [AgCo(C₄H₇N₂O₂)₂(NO₂)₂(C₁₈H₁₅P)₂], one of the ambidentate –NO₂ ligands, in a bridging mode, chelates the Ag^I atom in an isobidentate κ²O,O′‐manner and its N atom is coordinated to the Co^III atom. The other –NO₂ ligand is terminally κN‐coordinated to the Co^III atom. The structure has been fully characterized by X‐ray crystallography and spectroscopic methods. Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) have been used to study the ground‐state electronic structure and elucidate the origin of the electronic transitions, respectively.     

Evidence for linkage position determination in known feruloylated mono- and disaccharides using electrospray ion trap mass spectrometry

Various feruloylated arabinose- and galactose-containing mono- and disaccharides with known linkage configurations (2-O-(trans-feruloyl)-L-arabinopyranose, 5-O-(trans-feruloyl)-L-arabinofuranose, O-[2-O-(trans-feruloyl)-alpha-L-arabinofuranosyl]-(1-->5)-L-arabinofuranose, and O-[6-O-(trans-feruloyl)-beta-D-galactopyranosyl]-(1-->4)-D-galactopyranose) were analyzed by electrospray ionization mass spectrometry using an ion trap or a quadrupole time-of-flight (Q-TOF) mass analyzer. Collision-induced dissociation (CID) experiments using the two mass analyzers generated similar tandem mass spectrometric (MS/MS) fragmentation patterns. However, the ester-bond cleavage ions were more abundant using the Q-TOF mass analyzer. Compared with the positive ion mode, the negative ion mode produces simpler and more useful CID product-ion patterns. For arabinose-containing feruloylated compounds, results obtained with both analyzers show that it is possible to assign the location of the feruloyl group to the O-2 or O-5 of arabinosyl residues. In the characterization of the 2-O-feruloyl and 5-O-feruloyl linkages, the relative abundance of the cross-ring fragment ions at m/z 265 (-60 u or -62 u after 18O-labelling) and at m/z 217 (-108 u or -110 u after 18O-labelling) play a relevant role. For galactose-containing feruloylated compounds, losses of 60, 90 and 120 Da observed in MS3 experiment correspond to the production of 0,2A1, 0,3A1 and (0,2A1-60 Da) cross-ring cleavage ions, respectively, fixing the location of feruloyl group at the O-6 of the galactose residue.     

硫脲类衍生物及其生物活性研究

本文以氯代甲酸酯与硫氰酸钾的反应产物烷氧酰基异硫氰酸酯同各种芳胺反应合成了十个硫脲类衍生物4-芳基-3-硫代脲酸酯类化合物(1～10),其中七个化合物尚未见文献报道。通过^1HNMR,IR,MS及元素分析和熔点的测定,确定了这十个化合物的结构,并研究了它们对农杆菌的抑制作用。     

Synthesis and Qualitative Analysis of BACy and Its Self‐polymer

Many synthetic strategies of a reversible cross‐linker N,N′‐bis(acryloyl)cystamine (BACy) involve the typical condensation between the amino group of cystamine and the acyl group of acryloyl chloride in the mixed‐phase solvent system. In this study, the synthesis of BACy was performed in pure organic phase during the whole process. The yield and purity of synthesized BACy were comparable to those from aqueous/organic phase procedures. In addition, polymerization of BACy was also carried out by free radical reaction to prepare the self‐polymer and hydrogel which were characterized with FT‐IR, DSC and UV/VIS spectrophotometer. Notably, the BACy and its self‐polymer were both cleavable when exposed to the reducing agents, i.e. 1,4‐dithiothreitol (DTT) and 2‐mercaptoethanol (β‐ME). Interestingly, the reduced product of BACy contains vinyl and thiol groups, which could be further applied to the co‐polymerization with other monomeric units. On the other hand, carefully controlled reduction of BACy self‐polymer may be used to create the modified polymers with available thiol‐end groups for further chemistry. Together, our study provides modified procedure for BACy synthesis and characteristics of BACy self‐polymer and hydrogel. Further application of BACy and its self‐polymer in developing polymers with additional functionality is anticipated.