The alkylation reactions of soft scorpionates are reported. The hydrotris(S‐alkyl‐methimazolyl)borate dications (alkyl=methyl, allyl, benzyl), which were prepared by the reaction of TmMe anion and primary alkyl halides, have been isolated and structurally characterised. The reaction is, however, not universally successful. DFT analysis of these alkylation reactions (C?S versus B? H alkylation) indicates that the observed outcome is driven by kinetic factors. Extending the study to incorporate alternative imine thiones (mercaptobenzothiazole, bz; thiazoline, tz) led to the structural characterisation of di[aquo‐μ‐aquohydrotris(mercaptobenzothiazolyl)boratosodium], which contains sodium atoms in the κ3‐S,S,S coordination mode. Alkylation of Na[Tbz] and Na[tzTtz] leads to decomposition resulting in the formation of the simple S‐alkylated heterocycles. The analysis of the species involved in these reactions shows an inherent weakness in the B? N bond in soft scorpionates, which has implications for their use in more advanced chemistry. 相似文献
Analyzing surface forces for myriad geometric structures facilitates the design of properties in interacting interfacial systems. Along these lines, we demonstrate a generalized technique that can be utilized to evaluate the orientation dependence of a particle interacting with multiple finite or semi‐infinite objects. Specifically, the surface element integration technique is modified to account for surface elements of a particle not directly adjacent to the object with which it is interacting; this facilitates the analysis of objects with finite shape and with arbitrary orientations. Furthermore, as a technology‐relevant proof‐of‐concept demonstration, the influence of van der Waals (vdW) forces on the performance and reliability of microstructured systems used for the collection of trace particles is reported. The importance of the location of the particle contact with the microstructure and the independence of vdW forces generated by each microstructure is demonstrated using the developed computational approach. Thus, the methodology presented here can ultimately be utilized for a variety of interfacial forces generated by nontrivial systems with heterogeneous properties in order to provide design motifs in a low‐cost, high‐throughput manner. 相似文献
A family of mem-models, including the mem-dashpots, mem-springs, and most recently, mem-inerters, is emerging as a new and powerful way of capturing complex nonlinear behaviors of materials and systems under various types of dynamic loads involving different frequency, amplitude, and loading histories (e.g., hysteresis). Under the framework of nonlinear state-space representation and hybrid dynamical systems, mem-springs may be formulated to effectively represent an inherent degradation of material state. It is shown in this study, for the first time, how the absement (time integral of strain/displacement), a signature state variable for a mem-spring, can be connected with the damage variable, a key quantity in continuum damage mechanics. The generalized momentum (time integral of stress), on the other hand, is shown to be efficient in modeling strain ratcheting via the concept of mem-dashpot. It is also shown in this study, for the first time, how two formulations of the memcapacitive system models (for mem-springs) are special cases of the Preisach model.
Restrictions imposed on the construction of gauge models with Majorana fields are discussed. An example is given for a model with right-handed weak currents where lepton number violation is required. 相似文献
We address the question: “are weak right-handed non-singlet representations of quarks and leptons necessary?” An extension of the Weinberg-Salam model to SU(2) ? U(1) ? U(1) is found to adequately describe all existing weak interaction data including the lack of parity violation in atomic physics experiments. These data tightly constrain the additional parameters introduced by adding the second weak hypercharge. Although such a model may seem regressive when considered from the standpoint of “simple” unification schemes, we feel that it is aesthetics rather than experiment which leads to non-trivial right-handed multiplet structure. In contrast to most other models, ours predicts a substantial parity-violation effect in atomic experiments on hydrogen. We note that the second weak boson in our model is not constrained to be heavy by existing data and thus might already by accessable in pp → μ+μ?X or possibly in the next generation of colliding beam facilities through e+e? → μ+μ?. 相似文献
Arytenoid dislocation is a common yet infrequently diagnosed complication of laryngeal trauma. It may result in various symptoms, including permanent dysphonia, although immediate voice change is not always present. Early reduction is the treatment of choice; however, late reduction is often successful in restoring voice. A high index of suspicion based on the history of the patient is necessary to recognize arytenoid dislocation. Thorough physical examination and objective tests are helpful in confirming this diagnosis. 相似文献
A series of single crystal thin films of gold with (hk0) surfaces ranging between (100) and (310), grown by vapor deposition, was studied in transmission in the electron microscope at 100 kV. For specimens intermediate between (100) and (310) both bright and dark field images contained line structure running parallel to [001]. In certain cases segments were observed lying at 45° and 90° to these lines. Diffraction patterns from these specimens revealed relrods at each reciprocal lattice point running parallel to [100] and [310]. In certain cases [301] and [301?] relrods were also present. No line structure or relrods were detectable for the specimens with (100) or (310) surfaces. The results are consistent with a model in which the (100) and (310) surfaces are essentially flat but surfaces with intermediate orientations consist of appropriate mixtures of (100) and (310) facets plus (301) and (301?) facets in certain cases. The line structure in the images is attributed to “thickness contrast” arising from variations in the specimen thickness due to the facets. The relrods are well explained by the specimen form factor as originally proposed by von Laue. The results prove that faceted structures on thin film surfaces can be conveniently and systematically studied under certain conditions by conventional transmission electron microscopy at 100 kV. 相似文献
The structural and electronic properties of group III rich In0.53Ga0.47As(001) have been studied using scanning tunneling microscopy/spectroscopy (STM/STS). At room temperature (300 K), STM images show that the In0.53Ga0.47As(001)–(4 × 2) reconstruction is comprised of undimerized In/Ga atoms in the top layer. Quantitative comparison of the In0.53Ga0.47As(001)–(4 × 2) and InAs(001)–(4 × 2) shows the reconstructions are almost identical, but In0.53Ga0.47As(001)–(4 × 2) has at least a 4× higher surface defect density even on the best samples. At low temperature (77 K), STM images show that the most probable In0.53Ga0.47As(001) reconstruction is comprised of one In/Ga dimer and two undimerized In/Ga atoms in the top layer in a double (4 × 2) unit cell. Density functional theory (DFT) simulations at elevated temperature are consistent with the experimentally observed 300 K structure being a thermal superposition of three structures. DFT molecular dynamics (MD) show the row dimer formation and breaking is facilitated by the very large motions of tricoodinated row edge As atoms and z motion of In/Ga row atoms induced changes in As–In/Ga–As bond angles at elevated temperature. STS results show there is a surface dipole or the pinning states near the valence band (VB) for 300 K In0.53Ga0.47As(001)–(4 × 2) surface consistent with DFT calculations. DFT calculations of the band-decomposed charge density indicate that the strained unbuckled trough dimers being responsible for the surface pinning. 相似文献