Threshold electrical switching in As45Te55-xInx and As50Te50-xInx glasses

The electrical switching behaviour of As₄₅Te_55-xIn_x (5≤x≤15) and As₅₀Te_50-xIn_x (2.5≤x≤11.5) has been studied over a wide range of compositions. These glasses are found to exhibit threshold switching. The composition dependence of switching voltage (V_t) has been found to exhibit a change in slope and a local minimum at compositions x=10 and 12.5 for As₄₅Te_55-xIn_x and x=7.5 and 10.8 for As₅₀Te_50-xIn_x, respectively. The slope change in V_t verses x and the local minimum have been identified using two network topological effects, namely the rigidity percolation threshold and the chemical threshold. Received: 23 August 2001 / Accepted: 27 August 2001 / Published online: 11 February 2002     

测定痕量锰的锰(Ⅱ)-锌试剂-重铬酸钾体系催化分光光度法

在Na2B4O7-NaOH缓冲介质及加热条件下 ,锰 (Ⅱ )对重铬酸钾氧化锌试剂引起褪色 ,有明显的催化作用 ,据此建立了测定痕量锰的新方法 ;该法的线性范围为0.69～40μg/L,检出限为0.22μg/L ,反应表观活化能为87.1kJ/mol,反应表观速率常量1.10×10-3/s,用该法测定蒙药样品中锰含量 ,结果令人满意     

Thermal and spectral properties of some anhydrous and hydrated rare earth hydrazinecarboxylates

Thermal investigations of two novel coordination compounds, potential precursor of copper sulfides, namely [Cu₂(S₂O₃)₂(NH₃)₄]·₅H2_O and Na₂[Cu₄(S₂O₃)₅(NH₃)₈]·₂H₂O were performed either in solid state (static air atmosphere), as well as in reaction medium. During both decompositions, Cu²⁺ reduction occurs. In solid state decomposition, a mixture containing sulfides and sulfates is observed. In the reaction medium, CuS_y compounds with sulfur content y (0.66<y<1) dependent on thiosulfate concentration are obtained. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigation of surface plasmon resonance using cylindrical dielectric-metal-dielectric (C-DMD) plasmonic configuration

In this paper we have proposed a technique based on image analysis of the surface plasmon excitation at the metal-dielectric interface of inside silver coated fused silica capillary glass tube. Chemical deposition technique has been used for the deposition of silver. Angular interrogation in Kretschmann-like configuration is realized by non-radial transverse illumination of this cylindrical dielectric-metal-dielectric (C-DMD) structure with a He–Ne laser source. Here the uniform film deposition of the inside surface of the capillary is not that crucial except within the transversely illuminated working area concerned. Moreover, the proposed technique has been validated experimentally for sensing different aqueous dielectric samples inserted inside the tube.     

Computer-aided quantification of focal cartilage lesions of osteoarthritic knee using MRI

Noninvasive assessment of articular cartilage using magnetic resonance imaging (MRI) has gained popularity in the diagnosis of osteoarthritis (OA), a condition that affects 20 million Americans. Focal cartilage lesions, a defect found in roughly 19% of the OA population, currently can only be evaluated with confidence using minimally invasive arthroscopy. This article presents a computer-aided procedure using MRI to quantify focal cartilage lesions and aims to support clinical practices of diagnosis and monitoring of lesion progress. Upon a local minima search for identifying focal lesions, the proposed gradient peak method outlines lesion boundaries and then generates morphological properties, such as lesion volume and lesion area. The procedure was evaluated using simulated and in vivo data. First, a simulated lesion was created and analyzed, and the results were compared with the exact solutions. Second, an in vivo evaluation was carried out on seven human knees in which nine focal lesions were identified and quantified. Three of the subjects had follow-up analyses, at either 1 or 2 years. Finally, in an attempt to characterize local biochemical changes underlying focal lesions, MR-derived T2 values of defective cartilage within the lesion boundaries were examined and compared with the values of adjacent cartilage compartments.     

Problems of incompressible flow past thin blades and correction of their shape

Solutions to the problem of the flow of an ideal fluid past a blade or cascade of blades with low blocking factor are found in the framework of the first approximation of the theory of perturbations of the flow past infinitely thin arcs. Problems of correction of the shape of the blades are also considered. Problems associated with the application of perturbation theory in problems of flow past bodies are discussed in Van Dyke's monograph [1]. The present paper includes an example of realization of this theory for the thin curved blades that are widely used in compressor construction. Searches for effective methods for calculating the shape of blades to ensure necessary gas-dynamic properties, for example, a given distribution on the blades of the velocity of separationless flow, led to the appearance of algorithms based on the theory of small perturbations for a thin wing of finite span [2] and a single airfoil in a gas flow [3]. In such an approach, the problem of constructing the required profile can be formulated as a sequence of corrections of the boundary of the flow region with respect to small variations of the boundary values of the flow velocity. The paper contains a general formulation of the linear problem of the correction of the flow boundary, an algorithm for its solution in the case of thin blades in an incompressible flow, and analysis of the obtained solutions. Examples of calculations are presented.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 130–137, January–February, 1992.We thank S.A. Smirnov for assistance in the calculations.     

Cobalt(II), nickel(II) and copper(II) complexes of a hexadentate pyridine amide ligand. Effect of donor atom (ether vs. thioether) on coordination geometry, spin-state of cobalt and M(III)-M(II) redox potential

Using an acyclic hexadentate pyridine amide ligand, containing a -OCH(2)CH(2)O- spacer between two pyridine-2-carboxamide units (1,4-bis[o-(pyrydine-2-carboxamidophenyl)]-1,4-dioxabutane (H(2)L(9)), in its deprotonated form), four new complexes, [Co(II)(L(9))] (1) and its one-electron oxidized counterpart [Co(III)(L(9))][NO(3)]·2H(2)O (2), [Ni(II)(L(9))] (3) and [Cu(II)(L(9))] (4), have been synthesized. Structural analyses revealed that the Co(II) centre in 1 and the Ni(II) centre in 3 are six-coordinate, utilizing all the available donor sites and the Cu(II) centre in 4 is effectively five-coordinated (one of the ether O atoms does not participate in coordination). The structural parameters associated with the change in the metal coordination environment have been compared with corresponding complexes of thioether-containing hexadentate ligands. The μ(eff) values at 298 K of 1-4 correspond to S = 3/2, S = 0, S = 1 and S = 1/2, respectively. Absorption spectra for all the complexes have been investigated. EPR spectral properties of the copper(II) complex 4 have been investigated, simulated and analyzed. Cyclic voltammetric experiments in CH(2)Cl(2) reveal quasireversible Co(III)-Co(II), Ni(III)-Ni(II) and Cu(II)-Cu(I) redox processes. In going from ether O to thioether S coordination, the effect of the metal coordination environment on the redox potential values of Co(III)-Co(II) (here the effect of spin-state as well), Ni(III)-Ni(II) and Cu(II)-Cu(I) processes have been systematically analyzed.     

Inhibition of corrosion of commercial mild steel in presence of tetrazole derivatives in acid medium

The inhibitive influence of tetrazole derivatives namely, 1-(9¹-acridinyl)-5-(4′-aminophenyl) tetrazole, 1-(9′-acridinyl)-5-(4′-hydroxy phenyl) tetrazole and 1-(9′-acridinyl)-5-(4′-chlorophenyl) tetrazole on the corrosion of commercial mild steel in 1 N hydrochloric acid medium was studied by weight loss method. The monolayer adsorption has been confirmed by fitting the data to the Langmuir adsorption isotherm. Weight loss studies have been carried out at 303K, 318K and 333K. Thermodynamic parameters like heat of adsorption, activation energy and free energy change have been calculated. The maximum inhibition of efficiency of tetrazole derivatives, 1-(9′-acridinyl)-5-(4′-amoinophenyl) tetrazole, 1-(9′acridinyl)-5-(4′-hydroxyphenyl) tetrazole and 1-(9′-acridinyl)-5-(4′-Chlorphenyl) tetrazole was found to be 60.59%, 89.00% and 92.74, respectively. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Inhibition of corrosion of aluminium in presence of fluorescein in basic medium

The influence of Fluorescein in conjunction with calcium oxide on the corrosion of Aluminium in 1.0 N NaOH was studied by galvanostatic studies and weight loss studies. It has been found that the inhibition of corrosion of aluminium increased with the increasing concentration of the inhibitor. The maximum inhibition efficiency of fluorescein alone was found to be 30.80%. However, the addition of calcium oxide increased the maximum inhibition efficiency to 53.71%. The corrosion process was found to be under the anodic control, in the presence or in the absence of inhibitor. The inhibition was found to be mixed type. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, Inida, Nov. 28–30, 2003.