Spectroscopic, thermal and structural studies on manganous malate crystals

Prismatic crystals of manganous malate have been prepared by controlled ionic diffusion in hydrosilica gel. The structure was elucidated using single crystal X-ray diffraction. The crystals are orthorhombic with space group Pbca. Vibrations of the functional groups were identified by the FTIR spectrum. Thermogravimetric and differential thermal analyses (TG-DTA) were carried out to explore the thermal decomposition pattern of the material. Structural information derived from FTIR and TG-DTA studies is in conformity with the single crystal XRD data.     

Improving the performance of DCT-based fragile watermarking using intelligent optimization algorithms

The performance of a fragile watermarking method based on discrete cosine transform (DCT) has been improved in this paper by using intelligent optimization algorithms (IOA), namely genetic algorithm, differential evolution algorithm, clonal selection algorithm and particle swarm optimization algorithm. In DCT based fragile watermarking techniques, watermark embedding can usually be achieved by modifying the least significant bits of the transformation coefficients. After the embedding process is completed, transforming the modified coefficients from the frequency domain to the spatial domain produces some rounding errors due to the conversion of real numbers to integers. The rounding errors caused by this transformation process were corrected by the use of intelligent optimization algorithms mentioned above. This paper gives experimental results which show the feasibility of using these optimization algorithms for the fragile watermarking and demonstrate the accuracy of these methods. The performance comparison of the algorithms was also realized.     

Growth,structure and optical properties of an efficient NLO crystal-aqua maleatocopper(II)

A promising non-linear optical (NLO) crystal, aqua maleatocopper(II) (CuC₄H₂O₄·H₂O), was grown at room temperature by the controlled ionic diffusion technique. Fourier transform infrared spectrum could identify the various functional groups in the crystal. Structural analysis using single crystal XRD revealed that the compound crystallizes in the monoclinic system with space group P2₁ and unit cell parameters a = 7.7277(5) Å, b = 5.2967(3) Å, c = 7.7179(4) Å, α = γ = 109.170(5)°, β = 111.995(2)°. The thermal stability and decomposition pattern of the material were explored using thermogravimetry (TG) and differential thermal analysis (DTA). The optical band gap energy of the material was estimated as 2.2 eV from the diffuse reflectance spectroscopy. The Kurtz and Perry powder technique established the crystal to be an efficient non-linear optical (NLO) material.     

Impact of magnetic field on the nucleation and morphology of calcium carbonate crystals

The influence of static magnetic field of strength 0.75 T on the nucleation of calcium carbonate crystals has been investigated. Particle size analysis shows that magnetic field can cause marked difference in distribution. One of the major impacts of magnetic exposure is the increase in number of the critical nuclei formed. Also, magnetic field promotes the formation of parallelepipedic calcite crystals and the dissolution of the smaller crystals by Ostwald ripening mechanism. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal and infrared studies of calcium malate crystals grown in diffusion limited medium

Single crystals of the title compound Ca (C₄H₅O₅)₂.10H₂O are grown in silica gel using controlled chemical reaction method. Multifaceted single crystals of size up to 8 × 4 × 2 mm³ are obtained. Powder X‐ray Diffraction (XRD) pattern of the grown crystal and the Fourier Transform Infra‐Red (FTIR) spectrum in the range 400–4000 cm^–1 are recorded. The vibrational bands corresponding to different functional groups are assigned. Thermal decomposition stages observed in the Thermo‐gravimetric (TG) and Differential Thermal Analysis (DTA) studies are discussed. A six‐stage thermal decomposition scheme is proposed for the compound. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)