Studies on the decomposition of α-primary hydroperoxide of secondary butyltoluene in alkaline medium

α-Primary hydroperoxides of s-butyltoluene (SBT) are preferentially decomposed when the hydroperoxide concentrate is treated with 2 M aqueous sodium hydroxide at 70°C. The decomposition is complete in 1 h. The rate of decomposition and the nature of products formed suggest the reaction to be first order with respect to the primary-hydroperoxide concentration in accord with the Kornblum-De La Mare mechanism. Salt formation of the hydroperoxide precedes the decomposition.     

Kinetics of oxygen dissolution in molten lead

An electromotive force cell employing the ZrO₂-CaO solid electrolyte has been set up to investigate the kinetics of dissolution of oxygen in molten lead under various oxidizing conditions. The cell may be written as The cell has been so designed that the electrode chambers are completely isolated from each other. The oxygen in lead is first reduced to a very low value by bubbling hydrogen. subsequently, oxygen dissolution is achieved through gas diffusion across the free surface or through bubble metal interaction. During all these reactions the electromotive force of the cell changes continuously and is automatically recorded. The diffusion coefficient of oxygen in lead, as calculated from the experimental data, is 1.29×10⁻⁵ sq cm per sec and the liquid phase mass transfer coefficient is estimated to be 0.035 cm per sec at 750°C.     

Cationic poly(lactide-co-glycolide) nanoparticles as efficient in vivo gene transfection agents

Poly(lactide-co-glycolide) (PLGA), a biocompatible and biodegradable polyester co-polymer of PLA and PGA, has been recognized for its ability to deliver genes. However, gene delivery by PLGA nanoparticles is limited by their negative charge and their poor transport through mucosal barriers. In this study, PLGA nanoparticles were surface modified with cationic chitosan in an effort to improve their gene delivery capability. PLGA nanoparticles were synthesized by emulsion-diffusion-evaporation technique using PVA-chitosan (PLGA1) or PVA-chitosan-PEG (PLGA2) blend as stabilizers. This method is reproducible and produces nanoparticles with hydrodynamic diameter <200 nm. The nanoparticles were characterized by zetasizer, photon correlation spectroscopy and atomic force microscopy. A549 epithelial cells were transfected in vitro with PLGA particles complexed with a reporter plasmid encoding green fluorescent protein. PLGA particles transferred EGFP gene, but were less efficient than the lipofectamine control. The nanoparticles were also tested for their ability to transport across the nasal mucosa in vivo in mice. The results show that both PLGA1 and PLGA2 facilitate gene delivery and expression in vivo with increased efficiency and without causing inflammation, as measured by IL-6. Together, these results indicate that chitosan-modified PLGA nanoparticles have greater potential as gene carriers.     

Relationship analysis in requirements engineering

This research addresses a major shortcoming in todays requirements analysis techniques—the lack of a rigorous and comprehensive process to explicitly capture the relationship structure of the problem domain. Whereas other analysis techniques lightly address the relationship discovery process, relationship analysis (RA) is a systematic, domain-independent analysis technique focusing exclusively on a domains relationship structure. This paper describes RAs taxonomy of relationship types and corresponding brainstorming questions for eliciting the relationship structure from a domain expert. A preliminary case study analysis of online bookstores using RA as well as a formal experiment have both confirmed RAs effectiveness in helping the analyst produce significantly higher quality requirements. RA should become an invaluable tool for analysts, irrespective of the software engineering approach taken during systems analysis.     

经济型19"机柜系统的选择

在"911"之后的经济环境条件下,设计工程师和系统集成者们在搭建一个经济型19"机柜系统时,总是要面对一个棘手的任务--如何找出蕴涵的价值.     

Hybrid Boundary Integral-Generalized (Partition of Unity) Finite-Element Solvers for the Scalar Helmholtz Equation

Finite-element-based techniques are one of the most popular methods used to model electromagnetic field behavior, but rely on the underlying tesselation to construct the ansatz space. Recently, Babuska and his colleagues developed the generalized finite-element method (GFEM), which overcomes this constraint and admits a larger class of basis functions. Application of this technique has been largely restricted to Poisson systems. In this paper, we explore the applicability of this technique to two-dimensional Helmholtz systems. We investigate methods necessary to impose various boundary conditions. We use this analysis to build the framework for hybridizing boundary integral techniques with GFEM, thus imposing an exact boundary condition to truncate the computational domain. We validate the results against analytical data for canonical geometries, and we demonstrate h and p convergence of this technique. Finally, to further validate the proposed approach for complex scatterers, we augment GFEM with perfectly matched layers, and compare it against the results obtained by using boundary integral GFEM     

Finite-SNR diversity-multiplexing tradeoffs in fading relay channels

We analyze the diversity-multiplexing tradeoff in a fading relay channel at finite signal-to-noise ratios (SNRs). In this framework, the rate adaptation policy is such that the target system data rate is a multiple of the capacity of an additive white Gaussian noise (AWGN) channel. The proportionality constant determines how aggressively the system scales the data rate and can be interpreted as a finite-SNR multiplexing gain. The diversity gain is given by the negative slope of the outage probability with respect to the SNR. Finite-SNR diversity performance is estimated using a constrained max-flow min-cut upper bound on the relay channel capacity. Moreover, the finite-SNR diversity-multiplexing tradeoff is characterized for three practical decode and forward half-duplex cooperative protocols with different amounts of broadcasting and simultaneous reception. For each configuration, system performance is computed as a function of SNR under a system-wide power constraint on the source and relay transmissions. Our analysis yields the following findings; (i) improved multiplexing performance can be achieved at any SNR by allowing the source to transmit constantly, (ii) both broadcasting and simultaneous reception are desirable in half-duplex relay cooperation for superior diversity-multiplexing performance, and (iii) the diversity-multiplexing tradeoff at finite-SNR is impacted by the power partitioning between the source and the relay terminals. Finally, we verify our analytical results by numerical simulations     

Computer aided decision support system for mitral valve diagnosis and classification using depthwise separable convolution neural network

Multimedia Tools and Applications - The significance of mitral valve (MV) treatment is increasing recently because of an aging population. The computer vision-based acquisition and quantification...     

Solvent Free Microwave Assisted Isomerization of N‐Nitropyrazoles

This paper describes solvent‐free isomerization of N‐nitropyrazoles under microwave irradiation to achieve a new green chemistry procedure for the synthesis of C‐ nitropyrazoles in good to excellent yields. The presented procedure requires less time, offers simplified workup procedure, needs no obnoxious solvents, and may be used for the preparation of several C‐nitropyrazoles.