Simultaneous Impact of a Two-Link Chain

The study of the planar collisions of a rigid two-link chain with an external surface is presented. There are two points of contact during the impact process with friction, one for each link. For the normal impact, a nonlinear collision force is employed for the elasto-plastic deformation, and the Coulomb’s law models the frictional effects. The impact of the chain is studied numerically, and the results are compared with experiment data obtained from a high-speed camera. Special attention is given to simultaneous impact, slippage, and rebounds at the contact points.     

Efficient computation of operator‐type response sensitivities for uncertainty quantification and predictive modeling: illustrative application to a spent nuclear fuel dissolver model

This work honors the 75th birthday of Professor Ionel Michael Navon by presenting original results highlighting the computational efficiency of the adjoint sensitivity analysis methodology for function‐valued operator responses by means of an illustrative paradigm dissolver model. The dissolver model analyzed in this work has been selected because of its applicability to material separations and its potential role in diversion activities associated with proliferation and international safeguards. This dissolver model comprises eight active compartments in which the 16 time‐dependent nonlinear differential equations modeling the physical and chemical processes comprise 619 scalar and time‐dependent model parameters, related to the model's equation of state and inflow conditions. The most important response for the dissolver model is the time‐dependent nitric acid in the compartment furthest away from the inlet, where measurements are available at 307 time instances over the transient's duration of 10.5 h. The sensitivities to all model parameters of the acid concentrations at each of these instances in time are computed efficiently by applying the adjoint sensitivity analysis methodology for operator‐valued responses. The uncertainties in the model parameters are propagated using the above‐mentioned sensitivities to compute the uncertainties in the computed responses. A predictive modeling formalism is subsequently used to combine the computational results with the experimental information measured in the compartment furthest from the inlet and then predict optimal values and uncertainties throughout the dissolver. This predictive modeling methodology uses the maximum entropy principle to construct an optimal approximation of the unknown a priori distribution for the a priori known mean values and uncertainties characterizing the model parameters and the computed and experimentally measured model responses. This approximate a priori distribution is subsequently combined using Bayes' theorem with the “likelihood” provided by the multi‐physics computational models. Finally, the posterior distribution is evaluated using the saddle‐point method to obtain analytical expressions for the optimally predicted values for the parameters and responses of both multi‐physics models, along with corresponding reduced uncertainties. This work shows that even though the experimental data pertains solely to the compartment furthest from the inlet (where the data were measured), the predictive modeling procedure used herein actually improves the predictions and reduces the predicted uncertainties for the entire dissolver, including the compartment furthest from the measurements, because this predictive modeling methodology combines and transmits information simultaneously over the entire phase‐space, comprising all time steps and spatial locations. Copyright © 2016 John Wiley & Sons, Ltd.     

On Local LYM Identities

The LYMinequality (Lubell, Yamamoto, Meshalkin) is a generalization of Sperner’s theorem for antichains. Kleitman and Harper independently proved that the LYM inequality and the normalized matching property (or local LYM inequality) are equivalent. Many contributions have been proposed to sharpen the LYM inequality. Noticeably, Ahlswede and Zhang lifted the LYM inequality to an identity, called the AZ identity. Thus, one expects that the same sharpening of the local LYM inequality is equivalent to the AZ identity. In this paper, we introduce a local LYM identity which sharpens the local LYM inequality and prove that it is equivalent to the AZ identity. The local LYM identity shows local relationships between components in the AZ identity.     

Recent Advances in Zeolite-like Cluster Organic Frameworks

During the past decade, research on the design and synthesis of zeolite-like metal–organic frameworks (ZMOFs) has developed greatly. As an important subclass of ZMOFs, zeolite-like cluster organic frameworks (ZCOFs) built from 4-connected metal-cluster secondary building units (SBUs) and appropriate linear organic ligand bridges have attracted sustained interest, because such materials not only integrate the merits of inorganic zeolites, ZMOFs, and metal clusters, including interesting topologies, high surface areas, extra-large cavities and channels, structural tunability, and unique physicochemical properties from various metal clusters, but also open up a new avenue to design and fabricate hybrid zeolite-like materials that have many potential applications in material sciences. In this review, recent developments in ZCOFs are summarized by classifying the ZCOFs into four categories according to the composition of the SBUs: 1) ZCOFs based on metal–halide cluster SBUs, 2) ZCOFs based on metal–oxygen cluster SBUs, 3) ZCOFs based on metal–chalcogen cluster SBUs, and 4) ZCOFs based on mixed types of metal-cluster SBUs. Besides, challenges associated with the design and synthesis of ZCOFs and the vast potential of this area are also discussed.     

Synthesis,characterization and electrocatalytic performance of a dinuclear triazenidosilver(I) complex for hydrogen production

Our group has developed a series of molecular electrocatalysts for hydrogen generation based on triazenido–metal complexes (cobalt, copper, etc.). In this paper, we first present the electrocatalytic performance of a new dinuclear silver complex, [Ag₂(L)₂], formed by the reaction of the triazenido ligand 1‐[(2‐carboxymethyl)benzene]‐3‐[(2‐methoxy)benzene]triazene (HL) with AgNO₃. At room temperature, the silver complex shows photoluminescence at 653 nm. The electrocatalytic systems based on this silver complex can afford 106.57 and 1536.36 moles of hydrogen per mole of catalyst per hour from acetic acid at an overpotential (OP) of 991.6 mV and from a neutral aqueous buffer (pH = 7.0) at an OP of 837.6 mV, respectively. Electrochemical investigations show that both silver ion and triazenido ligand play a role in determining the catalytic activities of the electrocatalytic system.     

Structure Analysis of Needle-like Copper Tantalum Trisulfide Crystals by XPS and Raman Spectroscopy

High-quality needle-like CuTaS3 single crystals have been synthesized through a chemical vapor transport(CVT)process.Crystallographic data show the special double chains of edge-sharing TaS6 octahedra....     

3-甲基-4-对甲基苯基-5-(2-吡啶)-1,2,4-三唑桥联的双核铜配合物的磁性理论研究

采用对称性破损态方法结合密度泛函理论,选用反铁磁双核配合物[Cu2(MMBPT)2Cl4(H2O)2.5](MMBPT=3-甲基-4-对甲基苯基-5-(2-吡啶)-1,2,4-三唑)作为研究对象,通过与实验数据相比较,探讨了不同密度泛函方法与基组对计算铜配合物交换耦合常数的准确度.结果表明,4种混合密度泛函DFT(B3LYP,B3P86,B3PW91和PBE0)的计算结果都能和实验所观察到的值-31cm-1符号一致,但只有B3PW91方法得到的结果和实验结果吻合程度最好,同时采用方法B3PW91方法计算所得的交换耦合常数Jab对基组的依赖性较大.研究表明,2个Cu(Ⅱ)离子之间弱的反铁磁相互作用主要源于单占据分子轨道SOMOs小的能量劈裂.     

A simple,rapid and reliable liquid chromatography–mass spectrometry method for determination of methotrexate in human plasma and its application to therapeutic drug monitoring

A simple, rapid and reliable liquid chromatography–electrospray ionization tandem mass spectrometry method was established and validated for the determination of methotrexate in human plasma. After a straightforward protein precipitation by acetonitrile–water (70:30, v/v), methotrexate (MTX) and p‐aminoacetophenone (used as internal standard, IS) were separated on a Column C₁₈ column (50 × 2.1 mm, 3 µm; Column Technology, Fremont, CA, USA) using a gradient elution with mobile phase of acetonitrile and 0.03% acetic acid aqueous solution at a flow rate of 0.5 mL/min. The total chromatographic runtime was 5 min for each injection. Quantification detection was performed in a triple‐quadruple tandem mass spectrometer under positive mode monitoring the following mass transitions: m/z 455.3 → 308.3 for MTX and m/z 136.1 → 94.4 for IS. The calibration curve was linear over the range of 0.05–25.0 µmol/L with a lower limit of quantification of 0.05 µmol/L. The intra‐ and interday precisions were <5.2%, the accuracy varied from ?4.1 to 4.5%. The recovery was >94%. The LC‐MS/MS method showed an excellent agreement with the existing HPLC‐UV method using Passing–Bablok regression and Bland–Altman difference plot analysis. The validated LC‐MS/MS can be successfully applied to the routine therapeutic drug monitoring of MTX in clinical laboratories. Copyright © 2015 John Wiley & Sons, Ltd.