A convenient synthesis of 1,5-diarylpyrazoles from Baylis-Hillman adducts using HY-zeolite

<正>A facile and convenient protocol was developed for the synthesis of 1,5-diarylpyrazoles using Baylis-Hillman adducts in the presence of HY-zeolite as an efficient recyclable heterogeneous catalyst in reasonable reaction times(1.5-2.5 h) and high yields (78-90%).     

Nanotechnology in the public eye: the case of Iran,as a developing country

Using survey data, public awareness of and attitudes toward nanotechnology are examined in Iran (N = 759). Iran is a developing country with a national nanotechnology action plan for a ten year period starting from 2003 and has been active in the field of research and development of nanotechnology meanwhile. First, the results show that majority of people are still not familiar with nanotechnology and perceived risks posed by this technology are not considered to be a lot and most people feel its benefits outweigh the risks. The emotions toward this technology are of a hopeful and positive nature and this technology is looked upon favorably in Iran. In particular, our results reveals that although the level of trust is high specially in scientists to communicate the risks with the public, there are a great number who just have some trust not quite a lot of it. Knowing that it is a hard and time-consuming effort to manage a nation’s view on nanotechnology, extensive research as well as collaboration with other countries is needed to effectively communicate the risks in time.     

Non-linear vibrations and frequency response analysis of piezoelectrically driven microcantilevers

Microcantilevers have recently received widespread attentions due to their extreme applicability and versatility in both biological and non-biological applications. Along this line, this paper undertakes the non-linear vibrations of a piezoelectrically driven microcantilever beam as a common configuration in many scanning probe microscopy and nanomechanical cantilever biosensor systems. A part of the microcantilever beam surface is covered by a piezoelectric layer (typically ZnO), which acts both as an actuator and sensor. The bending vibrations of the microcantilever beam are studied considering the inextensibility condition and the coupling between electrical and mechanical properties in the piezoelectric materials. The non-linear terms appear in the form of quadratic expression due to presence of piezoelectric layer, and cubic form due to geometrical non-linearities. The Galerkin approximation is then utilized to discretize the equations of motion. In addition, the method of multiple scales is applied to arrive at the closed form solution for the fundamental natural frequency of the system. An experimental setup consisting of a commercial piezoelectric microcantilever attached on the stand of a state-of-the-art microsystem analyzer for non-contact vibration measurement is utilized to verify the theoretical developments. It is found that the experimental results and theoretical findings are in good agreement, which demonstrates that the non-linear modeling framework could provide a better dynamic representation of the microcantilever than the previous linear models. Due to microscale nature of the system, excitation amplitude plays an important role since even a small change in the amplitude of excitation can lead to significant vibrations and frequency shift.     

On edge star sets in trees

Let A be a Hermitian matrix whose graph is G (i.e. there is an edge between the vertices i and j in G if and only if the (i,j) entry of A is non-zero). Let λ be an eigenvalue of A with multiplicity m_A(λ). An edge e=ij is said to be Parter (resp., neutral, downer) for λ,A if m_A(λ)−m_A−e(λ) is negative (resp., 0, positive ), where A−e is the matrix resulting from making the (i,j) and (j,i) entries of A zero. For a tree T with adjacency matrix A a subset S of the edge set of G is called an edge star set for an eigenvalue λ of A, if |S|=m_A(λ) and A−S has no eigenvalue λ. In this paper the existence of downer edges and edge star sets for non-zero eigenvalues of the adjacency matrix of a tree is proved. We prove that neutral edges always exist for eigenvalues of multiplicity more than 1. It is also proved that an edge e=uv is a downer edge for λ,A if and only if u and v are both downer vertices for λ,A; and e=uv is a neutral edge if u and v are neutral vertices. Among other results, it is shown that any edge star set for each eigenvalue of a tree is a matching.     

PRESSURE-VELOCITY EQUILIBRIUM HYDRODYNAMIC MODELS

This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described.     

Recent developments of metallic nanoparticles and their catalytic activity in organic reactions

During the last two decades, with the development of nanotechnology, various nanomaterials have been designed and generated. Among them, hybrid organic–inorganic nanoparticles as a particular immobilizing carrier of the catalyst active sites have shown an important contribution in the current research studies. This is due to the large area and loads of active sites. This prominent review is focused on the novel various exa about the immobilization of nanoparticles with organic compounds as versatile and efficient catalysts in organic syntheses.     

Baeyer-Villiger oxidation of cyclic ketones utilizing potassium peroxydisulfate(K_2S_2O_8) or sodium perborate(NaBO_3) in acidic media

The efficient, green, facile, mild and straightforward conversion procedure for the oxidation of cyclic ketones to lactones at room temperature utilizing potassium peroxydisulfate (K₂S₂O₈) in acidic media is satisfactory to high yields without using traditional chlorinated solvents is reported. This oxidative reagent is cheap and friendly environmental procedure for industrial purposes than use of organic peracids.     

A Fast Response Strontium Ion‐Selective Electrode Prepared by Sol‐Gel Membrane Technique

A sol‐gel electrode, based on 6‐(4‐nitrophenyl)‐2‐phenyl‐4,4‐dipropyl‐3,5‐diaza‐bicyclo [3,1,0] hex‐2‐ene (NPDBH) as a neutral ionophore, was successfully developed for the detection of Sr²⁺ in aqueous solutions. Theoretical calculations confirmed NPDBH selectivity toward strontium in comparison with some other metal ions. The electrode responds to Sr²⁺ ion with a sensitivity of 29.1±0.4 mV/decade over the range 8.0×10^?7–1.0×10^?1 M. Selectivity coefficients determined by matched potential method (MPM) indicate high selectivity for strontium ions. The electrode has a fast response time of 11 s and a working pH range of 3.0–10.0. The sol‐gel electrode shows detection limit of 7.5×10^?8 M.