A new controlled release system of chlorhexidine and chlorhexidine:βcd inclusion compounds based on porous silica

The purpose of this study was to prepare and characterize a controlled release system based on porous silica loaded with chlorhexidine (Cx) and its inclusion compounds in β-cyclodextrin (βcd), and to evaluate its antimicrobial activity. Acetate chlorhexidine (CxA), gluconate chlorhexidine (CxG), βcd:chlorhexidine acetate 2:1 (βcd:CxA) and βcd:chlorhexidine gluconate 2:1 (βcd:CxG) were incorporated into porous silica. Drug loading was characterized by FTIR, powder X-ray diffraction, thermal analysis and BET, and was shown to be in an amorphous state and porous matrix. The kinetics release parameter of the drug was established, which showed that the Cx systems release profile followed zero order release until 400 h and Higuchi model release until 750 h, after the burst effect at the first 8 h. Chlorhexidine therapeutic range was reached near first hour for all systems. The chlorhexidine porous silica system was biologically active against Enterococcus faecalis and Candida albicans in vitro. The systems showed an efficient Cx controlled release modulated by the presence of the β-cyclodextrin and by the porous silica matrices, providing effective antimicrobial activity.     

The possible production of natural flavours by amino acid degradation

Abstract  

This work describes the degradation of phenylalanine and tryptophane catalysed by their complexes with Fe(II), Co(II), and Cu(II). The influences of the central atom and of the reaction conditions on the degradation of the amino acids were observed. The necessary condition of the degradation is the possibility of a redox reaction on the central atom between M(II) and M(III). Moreover, the coordination sphere of the central cation of the transition metal must not be sterically shielded. The necessary conditions are fulfilled only in the Fe(II) complexes. The degradation is strictly anaerobic because due to the influence of oxygen, an irreversible oxidation of Fe(II) to Fe(III) proceeds. This reaction results in 5-hydroxy-1H-indol instead of the mixture of the degradation products, such as benzaldehyde, phenylacetaldehyde, and phenylacetic acid. The influence of the temperature on the catabolism is very important because the reaction accelerates with temperature increase. The phenylalanine anion acts as a reducing agent, and Fe(II) is spontaneously reduced to Fe(0).     

Technologies and the development of the Automated Metadata Indexing and Analysis (AMIA) system

The Automated Metadata Indexing and Analysis (AMIA) project aims to provide an effective digital asset management (DAM) tool for large digital asset databases. We began with text-based indexing since it is still the most reliable approach as compared with other content-based media features. AMIA not only searches for the text of the file name, but also utilizes embedded information such as the metadata in Maya files. The AMIA system builds a linked map between all dependency files. We present an approach of preserving previously established metadata created by the old DAM tools, such as AlienBrain, and integrating them into the new system. Findings indicate that AMIA has significantly improved search performance comparing to previous DAM tools. Finally, the ongoing and future work in the AMIA project is described.     

Growth, optical and thermal studies on organic nonlinear optical crystal: 2-Furoic acid

2-Furoic acid (2FA), an organic third order nonlinear optical single crystal, has been synthesized and grown successfully by slow solvent evaporation technique. The space group and lattice parameters of the grown crystals were obtained by single crystal X-ray diffraction analysis. The presence of the functional groups was confirmed by Fourier Transform Infrared (FTIR) spectroscopy. Optical absorption studies reveal low absorption in the UV and visible regions and the UV cut-off wavelength is found to be at 240 nm. The thermal stability of the material examined by TGA analysis, reveals that the material is thermally stable up to 130 °C. The third order nonlinear optical parameters (nonlinear refractive index, nonlinear absorption coefficient and real and imaginary parts of the third order nonlinear optical susceptibility) were derived by Z-scan technique. This reveals that the crystal has a negative refractive index, which indicates the defocusing nature of the material.     

Growth, optical, mechanical and dielectric studies on NLO active pure and metal ion doped single crystals of bis-thiourea zinc chloride

Good quality single crystals of pure and metal ion (Ni²⁺) doped bis-thiourea zinc chloride (BTZC) possessing excellent nonlinear optical properties have been grown from aqueous solution by the slow solvent evaporation technique. The lattice parameters of the grown crystals are determined by single crystal X-ray analysis. The well defined sharp peaks in the powder X-ray diffraction pattern reveals the crystalline perfection and the EDAX spectrum confirms the presence of dopant in the lattice of the parent crystal. The DRS UV-visible spectral study reveals improved transparency for the doped crystal, ascertaining the inclusion of metal ion in the lattice. The optical band gap of the pure and doped crystals was calculated to be 4.8 and 5.2 eV respectively from the UV transmission spectrum. The vickers hardness test brings forth higher hardness value for Ni²⁺doped BTZC as compared to pure BTZC crystal. The dielectric measurement exhibits very low dielectric constant and dielectric loss at higher frequencies for both the pure and Ni²⁺doped BTZC. The existence of second harmonic generation signals in the crystal also has been confirmed by performing the Kurtz powder test.     

Physical properties of SrSn(4) single crystals

We present detailed thermodynamic and transport measurements on single crystals of the recently discovered binary intermetallic superconductor, SrSn(4). We find this material to be a slightly anisotropic three-dimensional, strongly coupled, possibly multiband, superconductor. Hydrostatic pressure causes a decrease in the superconducting transition temperature at the rate of ≈?-?0.068?K?kbar(-1). Band structure calculations are consistent with experimental data on the Sommerfeld coefficient and upper superconducting critical field anisotropy, and suggest a complex, multi-sheet Fermi surface formed by four bands.     

Reasonable scope for change

Recent proposals to redefine four of the base units of the SI, including the mole, have triggered a wide-ranging debate about the terminology as well as the definitions that form the SI. Since the SI is a practical system that is used worldwide, the reasonable scope for changing it must avoid leaving large numbers of users with obsolete implementations or significantly changed values. Changes that go beyond these limits would require consultation processes that might take decades and whose cost and complexity would be difficult to justify in view of the likely benefits.