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.     

Upward moving ionospheric irregularities over kodaikanal

The occurrence of upward moving kinks first found on ionograms at Thumba (Rastogi, 1970) has been confirmed to occur at another equatorial station, Kodaikanal. These kinks have been found in many records and they occur mostly during local summer months. The occurrence of the kink is shown to be closely associated with horizontal F-region drifts, occurrence of intermediate cusp between F₁ and F₂ layers, bite-out effects of ?₀F₂ and rise of h_PF₂, all being most pronounced around 10 hr. The upward movement of the kink is due to \(\vec E \times \vec B\) drift, while its initiation is probably due to a sudden change in the electrostatic field of the equatorial electrojet. The study of the upward moving kink gives a direct measure of the height variation of the vertical upward drift of ionization over the magnetic equator.     

Peak effect studies in single crystals CeRu2 and 2H-NbS2

We have studied the peak effect (PE) phenomenon in single crystals of weakly pinned superconductors CeRu₂ and 2H-NbS₂. 2H-NbS₂ is iso-structural and iso-electronic to 2H-NbSe₂, whose similarity with CeRu₂ as regards the PE representing the order-to-disorder transformation of the flux line lattice was claimed some time ago. We report on the step change in equilibrium magnetization across the peak effect in CeRu₂. We also present the vortex phase diagram of 2H-NbS₂ obtained from the magnetization data, and compare the PE phenomenon in 2H-NbS₂ and 2H-NbSe₂.     

On the simultaneous existence of eastward and westward flowing equatorial electrojet currents

The counter-electrojet currents are evidenced by the disappearance of theq type ofEs layer (Es-q) or the appearance of the blanketing type ofEs (Es-b) at Kodaikanal, associated with the depression of the geomagneticH field and the reveisal of ionospheric drift at Thumba. The necessary condition for such an event is not the decrease of theH field below the night level but that the difference of theH field between an equatorial and a non-equatorial station should decrease below its night level. The different kinds of association between the disappearance ofEs-q and the depression in theH field are suggested due to superimposition over theSq current system (at about 107 km) of a separate westward current system at a lower level (about 100 km). The source of the reversed current over the dip equator during the daytime hours is sought in the current system generated by the lunar tides or in various magnetospheric processes generating the polar substorms. Large day-to-day variations of the solar daily range ofH at the equator independent ofSq variation at tropical latitudes are suggested to be due to superimposition at the equator of the two rather independent current systems.     

A facile approach towards synthesis,characterization, single crystal structure,and DFT study of 5-bromosalicylalcohol

5-Bromosalicylalcohol was prepared by the interaction of NaBH₄ and 5-bromosalicylaldehyde. The use of sodium borohydride makes the reaction easy, facile, economic and does not require any toxic catalyst. The compound is characterized by FTIR, ¹H NMR, ¹³C NMR, TEM and ESI-mass spectra. Crystal structure is determined by single crystal X-ray analysis. Quantum mechanical calculations of geometries, energies and thermodynamic parameters are carried out using density functional theory (DFT/B3LYP) method with 6-311G(d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental data.     

Excited state characteristics of acridine dyes: acriflavine and acridine orange

The magnitude of the Stokes shift (frequency shifts in absorption and fluorescence spectra) is observed on changing the solvents and further has been used to calculate experimentally the dipole moments (ground state and excited state) of acriflavine and acridine orange dye molecules. Theoretically, dipole moments are calculated using PM 3 Model. The dipole moments of excited states, for both molecules investigated here, are higher than the corresponding values in the ground states. The increase in the dipole moment has been explained in terms of the nature of the excited state. Acriflavine dye overcomes the non-lasing behaviour of acridine orange due to quaternization of the central nitrogen atom.     

BPS Quivers and Spectra of Complete {\mathcal{N} = 2} Quantum Field Theories

We study the BPS spectra of ${\mathcal{N}=2}$ N = 2 complete quantum field theories in four dimensions. For examples that can be described by a pair of M5 branes on a punctured Riemann surface we explain how triangulations of the surface fix a BPS quiver and superpotential for the theory. The BPS spectrum can then be determined by solving the quantum mechanics problem encoded by the quiver. By analyzing the structure of this quantum mechanics we show that all asymptotically free examples, Argyres-Douglas models, and theories defined by punctured spheres and tori have a chamber with finitely many BPS states. In all such cases we determine the spectrum.     

Solar blind photoconductivity in three-terminal devices of LaAlO3/SrTiO3 heterostructures

We report observations of photoconductivity in ultrathin films of LaAlO(3) grown on (001) SrTiO(3) at several deposition temperatures. The films show pronounced metallic behavior in the dark. The conductance of this metallic state can be enhanced by ultraviolet light (350-400 nm) of a few μW/cm(2) intensity. The decay of the photoconducting state follows stretched exponential dynamics, which can be accelerated or slowed down on the application of gate voltage, thus imparting a novel functionality to the system.     

Influence of Crystal Thickness and Topological Constraints on Chain Diffusion in Linear Polyethylene

¹³C solid‐state exchange NMR is applied to study the influence of morphology on chain diffusion between crystalline and noncrystalline regions in ultrahigh molecular weight linear polyethylene (PE). Lamellar‐doubling reduces the exchange rate by a factor of two indicating that the chain diffusion coefficient is largely independent of the lamellar thickness. This is discussed in terms of molecular processes in the crystallites leading to chain diffusion, confirming that the role of defects is minor compared to helical jumps of extended stems. Hindrance of the chain diffusion resulting from chain entanglements was only observed after the chains diffuse over long distances. Moreover, the role of the interphase between the noncrystalline and the crystalline regions on chain diffusion is discussed.

     

Autoacetylation of Purified Calreticulin Transacetylase Utilizing Acetoxycoumarin as the Acetyl Group Donor

Our earlier reports documented that calreticulin, a multifunctional Ca²⁺-binding protein in endoplasmic reticulum lumen, possessed protein acetyltransferase function termed Calreticulin Transacetylase (CRTAase). The autoacetylation of purified human placental CRTAase concomitant with the acetylation of receptor proteins by a model acetoxycoumarin, 7,8-Diacetoxy-4-methylcoumarin, was observed. Here, we have examined the autoacetylation property of CRTAase by immunoblotting and mass spectrometry. Ca²⁺ was found to inhibit CRTAase activity. The inhibition of both autoacetylation of CRTAase as well as acetylation of the receptor protein was apparent when Ca²⁺ was included in the reaction mixture as visualized by interaction with anti-acetyl lysine antibody. The acetylation of lysines residues: −48, −62, −64, −153, and −159 in N-domain and −206, −207, −209, and −238 in P-domain of CRTAase were located by high-performance liquid chromatography-electronspray ionization tandem mass spectrometry. Further, computer assisted protein structure modeling studies were undertaken to probe the effect of autoacetylation of CRTAase. Accordingly, the predicted CRTAase 3D model showed that all the loop regions of both N- and P-domain bear the acetylated lysines. Energy minimization of the acetylated residues revealed charge neutralization of lysines due to the N-ε-acetylation which may facilitate the interaction of CRTAase with the protein substrate and the subsequent transacetylase action. An erratum to this article can be found at