Magnetoelectric effect in cobalt ferrite-barium titanate composites and their electrical properties

CoFe₂O₄-BaTiO₃ composites were prepared using conventional ceramic double sintering process with various compositions. Presence of two phases in the composites was confirmed using X-ray diffraction. The dc resistivity and thermoemf as a function of temperature in the temperature range 300 K to 600 K were measured. Variation of dielectric constant (ɛ′) with frequency in the range 100 Hz to 1 MHz and also with temperature at a fixed frequency of 1 kHz was studied. The ac conductivity was derived from dielectric constant (ɛ′) and loss tangent (tan δ). The nature of conduction is discussed on the basis of small polaron hopping model. The static value of magnetoelectric conversion factor has been studied as a function of magnetic field.     

Chemistry of substituted sulphuric acids—XVII. Complexes of V(III), Cr(III), Mn(II) and Fe(II) methylsulphates

V(III), Cr(III), Mn(II) and Fe(II) methylsulphates form stable donor-acceptor complexes with nitrogen donors. 1:1 and 1:2 complexes with bipyridyl have been prepared in respect of trivalent salts and 1:2 and 1:4 metal:base complexes have been obtained in respect of divalent metal salts with bipyridyl and pyridine respectively. Electronic spectra suggest an octahedral geometry around metal ions. IR spectra of the anhydrous metal methylsulphates have been studied and assigned. The changes in the IR spectra of the methylsulphate group in different stereochemical situations have been observed.     

Influence of various series of additives on the clouding behavior of aqueous solutions of triblock copolymers

The cloud point (CP) studies on aqueous solutions of two ethylene oxide-propylene oxide triblock copolymers (EO)_2.5(PO)₃₁(EO)_2.5 and (EO)₁₃(PO)₃₀(EO)₁₃ with varying number of ethylene oxide (EO) units were carried out in the presence of series of additives, such as alkali, acids, ionic surfactants, alcohols, salts, and hydrotropes. The results of this study show that sodium hydroxide decreases the CP of the two copolymers. Acids increase the CP in the order hydrochloric acid > acetic acid > formic acid for both the triblock copolymers. Hydrotropes increase the CP, whereas salts decrease or increase the CP based on their salting-out/salting-in nature. Alcohols, which are polar organic additives, affect the CP of the two copolymers differently. The change in the CP of the triblock copolymers depends upon the structure and concentration of the additives and on the number of EO units of the two triblock copolymers.     

A chloride selective sensor based on a calix[4]arene possessing a urea moiety

New calix[4]arene derivative 1 of 1,3-alternate conformation with a ureido moiety has been synthesized in high yield and examined for its anion recognition abilities towards anions such as fluoride, chloride, bromide, iodide, nitrate and acetate by ¹H NMR and UV-vis spectroscopy. The results show that receptor has strong binding affinity for chloride ions. A chloride ion selective electrode (ISE) was also formed which showed excellent selectivity over all the other anions tested. The limit of detection is 2.51 × 10⁻⁵ mol dm⁻³.     

Decentralized stochastic control

Decentralized stochastic control refers to the multi-stage optimization of a dynamical system by multiple controllers that have access to different information. Decentralization of information gives rise to new conceptual challenges that require new solution approaches. In this expository paper, we use the notion of an information-state to explain the two commonly used solution approaches to decentralized control: the person-by-person approach and the common-information approach.     

Mercury(II) ion-selective electrodes based on heterocyclic systems

Mercury ion-selective electrodes (ISEs) were prepared with a polymeric membrane based on heterocyclic systems: 2-methylsulfanyl-4-(4-nitro-phenyl)-l-p-tolyl-1H-imidazole (I) and 2,4-diphenyl-l-p-tolyl-1H-imidazole (II) as the ionophores. Several ISEs were conditioned and tested for the selection of common ions. The electrodes based on these ionophores showed a good potentiometric response for Hg2+ ions over a wide concentration range of 5.0 x 10(5-) - 1.0 x 10(-1)M with near-Nernstian slopes. Stable potentiometric signals were obtained within a short time period of 20 s. The detection limits, the working pH range of the electrodes were 1.0 x 10(-5) M and 1.6-4.4 respectively. The electrodes showed better selectivity for Hg2+ ions over many of the alkali, alkaline-earth and heavy metal ions. Also sharp end points were obtained when these sensors were used as indicator electrodes for the potentiometric titration of Hg2+ ions with iodide ions.     

Analysing the Wu metric on a class of eggs in ℂ<Superscript><Emphasis Type="Italic">n</Emphasis></Superscript> – II

We study the Wu metric for the non-convex domains of the form \( E_{2m} = \{ z \in \mathbb {C}^{n} : \vert {z_{1} \vert }^{2m} + \vert {z_{2}\vert }^{2} + {\cdots } + \vert {z_{n-1}\vert }^{2} + \vert {z_{n}\vert }^{2} <1 \}\), where 0 < m < 1/2. We give explicit expressions for the Kobayashi metric and the Wu metric on such pseudo-eggs E _2m . We verify that the Wu metric is a continuous Hermitian metric on E _2m , real analytic everywhere except along the complex hypersurface Z = {(0,z ₂,…,z _n ) ∈ E _2m }. We also show that the holomorphic curvature of the Wu metric for this non-compact family of pseudoconvex domains is bounded above in the sense of currents by a negative constant independent of m. This verifies a conjecture of S. Kobayashi and H. Wu for such E _2m .     

Isolation and synthesis of pygmanilines,phenylurea derivatives from the Northeastern Atlantic lichen Lichina pygmaea

A library of 864 extracts prepared from Irish marine organisms was screened in the search for novel antioxidants. Chemical investigation of the most promising extract obtained from the common lichen Lichina pygmaea led to the isolation of five resorcinol derivatives. An unusual urea moiety was found embedded in two of these compounds, pygmanilines A (1) and B (2) and their structures were confirmed by one-step chemical syntheses.     

Nonrecursive determination of orthonormal polynomials with matrix formulation

A general theoretical approach has been developed for the determination of orthonormal polynomials over any integrable domain, such as a hexagon. This approach is better than the classical Gram-Schmidt orthogonalization process because it is nonrecursvie and can be performed rapidly with matrix transformations. The determination of the orthonormal hexagonal polynomials is demonstrated as an example of the matrix approach.