Complexes of tricoordinate hypervalent pnictogens with pentamethylcyclopentadienylruthenium

The complexes of a pentamethylcyclopentadienylruthenium moiety with hypervalent tricoordinate pnictogens are reported. A unique mode of complexation is observed for each of the different pnictogens (P, As, Sb). The phosphorus derived complex exhibits an 8-electron tetrahedral bonding environment at phosphorus. The antimony derived complex maintains a 10-electron bonding system at antimony with a pseudo-trigonalbipyramidal geometry at antimony. The arsenic-containing complex is formed with destruction of the original arsenic heterocycle and formation of a trinuclear Ru–Ru–As ring. Remarkably, the formation of the arsenic ruthenium complex can be reversed to reconstruct the original arsenic heterocycle.     

Influence of Microcracks on Flow and Storage Capacities of Gas Shales at Core Scale

Transport in Porous Media - This work investigates the interplay of gas transport in the microcracks and matrix of shale using He and $$\hbox {CO}_2$$ via transient upstream pressure-pulse-decay...     

Failure of the Hasse principle for Enriques surfaces

We construct an Enriques surface X over Q with empty étale-Brauer set (and hence no rational points) for which there is no algebraic Brauer–Manin obstruction to the Hasse principle. In addition, if there is a transcendental obstruction on X, then we obtain a K3 surface that has a transcendental obstruction to the Hasse principle.     

应对智能电网的电源管理设计挑战

讨论了现代化配电网络面临的设计挑战.好的电源管理技术有助于改善配电自动化的系统设计,从而获得更高的能源利用率,改善配电系统的可维护性、预测性维护以及故障检测、隔离,并降低排放.本文介绍了电源管理的新技术,用于改善配电自动化系统设计.     

Approximate renormalization group calculation of cubic crossover

The cross-over exponent for an anisotropic cubic perturbation is calculated for all n > 1 and d = 3. It is found that the isotropic fixed point is unstable for $\text{n ? 2.3}$.     

Computer Scheduling of Vehicles from One or More Depots to a Number of Delivery Points

The problem of scheduling delivery vehicles from a number of depots to customers, subject to constraints on load and distance or time, is considered. A new algorithm is presented; this allows routes from several depots to be constructed simultaneously, subject to restrictions on numbers of vehicles at individual depots. Where too many customers require service, a flexible priority rule will select those to be served. Results for the single depot case are compared with other known algorithms; further results are given and discussed for cases of several depots.     

Correlation of ultrasonic scatterer size estimates for the statistical analysis and optimization of angular compounding

Ultrasonic scatterer size estimates generally have large variances due to the inherent noise of spectral estimates used to calculate size. Compounding partially correlated size estimates associated with the same tissue, but produced with data acquired from different angles of incidence, is an effective way to reduce the variance without making dramatic sacrifices in spatial resolution. This work derives theoretical approximations for the correlation between these size estimates, and the coherence between their associated spectral estimates, as functions of ultrasonic system parameters. A Gaussian spatial autocorrelation function is assumed to adequately model scatterer shape. Both approximations compare favorably with simulation results, which consider validation near the focus. Utilization of the correlation/coherence expressions for statistical analysis and optimization is discussed. Approximations, such as the invariance of phase and amplitude terms with angle, are made to obtain closed-form solutions to the derived spectral coherence near the focus and permit analytical optimization analysis. Results indicate that recommended parameter adjustments for performance improvement generally depend upon whether, for the system under consideration, the primary source of change in total coherence with rotation is phase term variation due to the change in the relative position of scattering sites, or field amplitude term variation due to beam movement.     

Mass separator for radioactive isotopes

A new isotope separator has been designed, constructed, and put into routine operation for separation of ¹³³Xe providing a major advancement and significant cost reduction in preparation of this radioactive isotope. The design features and advantages are discussed that expedite high purity separation of relatively small quantities of this isotope. These advantages could be easily used to expedite separation of other shorter-lived radioactive isotopes.     

Synthesis of High χ–Low N Diblock Copolymers by Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) enables the scalable synthesis of functional block copolymer nanoparticles with various morphologies. Herein we exploit this versatile technique to produce so-called “high χ–low N” diblock copolymers that undergo nanoscale phase separation in the solid state to produce sub-10 nm surface features. By varying the degree of polymerization of the stabilizer and core-forming blocks, PISA provides rapid access to a wide range of diblock copolymers, and enables fundamental thermodynamic parameters to be determined. In addition, the pre-organization of copolymer chains within sterically-stabilized nanoparticles that occurs during PISA leads to enhanced phase separation relative to that achieved using solution-cast molecularly-dissolved copolymer chains.