Copper containing nanosilica thioalated dendritic material: A recyclable catalyst for synthesis of benzimidazoles and benzothiazoles

In this paper, the design and characterization of a new heterogeneous catalyst by incorporation of copper ions into the nanosilica modified by thiole–based dendrimer are reported. The prepared catalyst was characterized by FT–IR, TGA, elemental analysis, FE–SEM, TEM, XPS and ICP–OES techniques. This material was used as catalyst in the synthesis benzimidazoles and benzothiazoles by the reaction of substituted benzaldehydes with 1,2–diaminobenzene or 2–aminothiophenol, respectively. The advantages of the present catalytic system are high yields, mild conditions and short reaction times. On the other hand, this new synthesized catalyst was recycled very well and reused several times without significant loss of its catalytic activity.     

Payment mechanisms for electricity markets with uncertain supply

This paper provides a framework for deriving payment mechanisms for intermittent, flexible and inflexible electricity generators who are dispatched according to the optimal solution of a stochastic program that minimizes the expected cost of generation plus deviation. The first stage corresponds to a pre-commitment decision, and the second stage corresponds to real-time generation that adapts to different realizations of a random variable. By taking the Lagrangian and decoupling in different ways we study two payment mechanisms with different properties.     

Quantitative evaluation of optimal imaging parameters for single-cell detection in MRI using simulation

Super-paramagnetic iron oxide (SPIO) nanoparticles are actively investigated to enhance disease detection through molecular imaging using magnetic resonance imaging (MRI). Detection of the cells labeled by SPIO depends on the MRI protocols and pulse sequence parameters that can be optimized. To evaluate the sensitivity and specificity of the image acquisition methods and to obtain optimal imaging parameters for single-cell detection, we further developed an MRI simulator. The simulator models an object (tissue) at a microscopic level to evaluate effects of spatial distribution and concentration of nanoparticles on the resulting image. In this study, the simulator was used to evaluate and compare imaging of the labeled cells by the gradient-echo (GE), true-FISP [fast imaging employing steady-state acquisition (FIESTA)] and echo-planar imaging (EPI) pulse sequences. Effects of the imaging and object parameters, such as field strength, imaging protocol and pulse sequence parameters, imaging resolution, cell iron load, position of SPIO within the voxel and cell division within the voxel, were investigated in the work. The results suggest that true-FISP has the highest sensitivity for single-cell detection by MRI.     

On Group Choosability of Graphs,II

Given a group A and a directed graph G, let F(G, A) denote the set of all maps ${f : E(G) \rightarrow A}$ . Fix an orientation of G and a list assignment ${L : V(G) \mapsto 2^A}$ . For an ${f \in F(G, A)}$ , G is (A, L, f)-colorable if there exists a map ${c:V(G) \mapsto \cup_{v \in V(G)}L(v)}$ such that ${c(v) \in L(v)}$ , ${\forall v \in V(G)}$ and ${c(x)-c(y)\neq f(xy)}$ for every edge e = xy directed from x to y. If for any ${f\in F(G,A)}$ , G has an (A, L, f)-coloring, then G is (A, L)-colorable. If G is (A, L)-colorable for any group A of order at least k and for any k-list assignment ${L:V(G) \rightarrow 2^A}$ , then G is k-group choosable. The group choice number, denoted by ${\chi_{gl}(G)}$ , is the minimum k such that G is k-group choosable. In this paper, we prove that every planar graph is 5-group choosable, and every planar graph with girth at least 5 is 3-group choosable. We also consider extensions of these results to graphs that do not have a K ₅ or a K _3,3 as a minor, and discuss group choosability versions of Hadwiger’s and Woodall’s conjectures.     

Gradient WEB-spline finite element method for solving two-dimensional quasilinear elliptic problems

In this paper, a two-dimensional quasilinear elliptic problem of the form -divF(x,▽u)=g(x)$-\mathit{divF}(\mathbf{x}\text{,}▽u)=g(\mathbf{x})$ is considered. This problem is ill-conditioned and we therefore propose a modified iterative algorithm based on coupling of the Sobolev space gradient method and WEB-spline finite element method. Applying the preconditioned iterative method, which has been already provided by Farago and Karatson (2001) [1] reduces the our considered problem to a sequence of linear Poisson’s problems. Then the WEB-spline finite element method is applied to the approximate solution of these Poisson’s problems. In this sense, a convergence theorem is proved and the advantages of this technique than the gradient finite element method (GFEM) is also described. Finally, the presented method is tested on some examples and compared with GFEM. It is shown that the gradient WEB-spline finite element method gives better test results.     

Online affine model identification of nonlinear processes using a new adaptive neuro-fuzzy approach

This paper presents a new online identification algorithm to drive an adaptive affine dynamic model for nonlinear and time-varying processes. The new algorithm is devised on the basis of an adaptive neuro-fuzzy modeling approach. Two adaptive neuro-fuzzy models are sequentially identified on the basis of the most recent input-output process data to realize an online affine-type model. A series of simulation test studies has been conducted to demonstrate the efficient capabilities of the proposed algorithm to automatically identify an online affine-type model for two highly nonlinear and time-varying continuous stirred tank reactor (CSTR) benchmark problems having inherent non-affine dynamic model representations. Adequacy assessments of the identified models have been explored using different evaluation measures, including comparison with an adaptive neuro-fuzzy inference system (ANFIS) as the pioneering and the most popular adaptive neuro-fuzzy system with powerful modeling features.     

Brønsted Acid Ionic Liquid [(CH2)4SO3HMIM][HSO4] as Novel Catalyst for One-Pot Synthesis of Hantzsch Polyhydroquinoline Derivatives

1-(4-Sulfonic acid)butyl-3-methylimidazolium hydrogen sulfate ([(CH₂)₄SO₃HMIM][HSO₄]) efficiently catalyzed a four-component Hantzsch reaction of aldehyde, ethylacetoacetate, dimedone, and ammonium acetate to afford the corresponding polyhydroquinoline derivatives.     

Elementary excitations at magnetic surfaces and their spin dependence

The elementary surface excitations are studied by spin-polarized electron energy loss spectroscopy on a prototype oxide surface [an oxygen passivated Fe(001)-p(1×1) surface], where the various excitations coexist. For the first time, the surface phonons and magnons are measured simultaneously and are distinguished based on their different spin nature. The dispersion relation of all excitations is probed over the entire Brillouin zone. The different phonon modes observed in our experiment are described by means of ab initio calculations.     

Elementary spin excitations in ultrathin itinerant magnets

Elementary spin excitations (magnons) play a fundamental role in condensed matter physics, since many phenomena e.g. magnetic ordering, electrical (as well as heat) transport properties, ultrafast magnetization processes, and most importantly electron/spin dynamics can only be understood when these quasi-particles are taken into consideration. In addition to their fundamental importance, magnons may also be used for information processing in modern spintronics.