Correlation of ground and excited state dissociation constants of trans -para- and ortho-substituted cinnamic acids

The ground and excited state dissociation constants oftrans- para- and ortho-substituted cinnamic acids have been determined in 50% (v/v) dioxan-water mixture at 30°C using the Forster cycle. The measured dissociation constants are analysed in the light of single and dual substituent parameter (DSP) equations. Excited state dissociation constants ofp-substituted cinnamic acids correlate well with the exalted substituent constants. The DSP method of analysis shows that resonance effect is predominant relative to inductive effect in the excited state than in the ground state for the para-substituted acids. The single parameter equation gives poor correlation for the ortho-substituted acids. However, the DSP analysis shows fairly good correlation. The inductive effect is predominant relative to the resonance effect in the excited state than in the ground state     

Synthesis,characterization and anti-bacterial activity of divalent transition metal complexes of hydrazine and trimesic acid

Transition metal complexes of trimesic acid and hydrazine mixed-ligands with a general formula M(Htma)(N₂H₄)₂, where, M = Mn, Co, Ni, Cu and Zn; H₃tma = trimesic acid, have been prepared and characterized by elemental, structural, spectral and thermal analyses. For the complexes, the carboxylate ν_asym and ν_sym stretchings are observed at about 1626 and 1367 cm^?1 respectively, with Δν between them of ～260 cm^?1, showing the unidentate coordination of each carboxylate group. The hydrazine moieties are present as bridging bidentates. Electronic and EPR spectral studies suggest an octahedral geometry for the complexes. All these complexes show three steps of decomposition in TGA/DTA. SEM images of CuO and MnO residues obtained from the complexes show nano-sized clusters suggesting that the complexes may be used as precursors for nano-CuO and nano-MnO preparation. The antimicrobial activities of the prepared complexes, against four bacteria have been evaluated.     

Conductometric determination of carbon in uranium carbide and its solution in nitric acid

A simple but accurate method has been developed for the determination of carbon in uranium carbide powders/pellets as well as in solutions of uranyl nitrates. The methodology involves quantitative conversion of carbon present in the sample to carbon dioxide that is subsequently absorbed in a dilute solution of barium hydroxide. The conductivity shift of the barium hydroxide solution is monitored on-line continuously using a laboratory-built PC-based conductivity measurement system that has been developed in-house based on the direct conversion of conductance to the digital pulse frequency. A new gas absorption cell has been designed to ensure quantitative absorption during the residence time of the gas in the cell. The method is sensitive, accurate and precise to 1-3% at 600-1000 mug of carbon in samples of uranium carbide.     

A novel rapid method for preparation of sample solution for chemical characterisation of titanium minerals by atomic spectrometry

A new rapid decomposition and dissolution method with a mixture of sodium di-hydrogen orthophosphate and di-sodium hydrogen orthophosphate as a novel flux is described. The minerals are fused with (1:1) mixture of the above salts (flux) and the melt is dissolved in distilled water. The solution is diluted to desired volume depending on the instrumental technique used for determination. ICP-OES is used for the determination of Al, Ca, Mg, Cr, V, Si, Fe and Ti without interference from titanium, iron and sodium phosphate (introduced as flux). All the elements except Si and V are also determined by AAS. The use of nitrous oxide–acetylene flame eliminates the depression due to titanium in the measurement of Mg, Mn, Cr and Fe in air–acetylene flame. Synthetic mixture conforming to ilmenite and rutile composition are analyzed by ICP-OES and AAS to check the validity of the method. The results are in good agreement. The proposed method has been applied to natural samples and the results are evaluated against the established decomposition method using potassium bisulphate. Both ICP-OES and AAS yielded comparable results. The R.S.D. of the proposed method in case of ICP-OES varies from 0.5 to 2%, whereas for AAS it varies from 1.5 to 3% for different elements (n = 5). The novelty of the proposed sample decomposition lies in its simplicity, ease and speed of fusion with minimal skills besides being eco-friendly unlike the reported tedious complicated decomposition procedures involving variety of fluxes and lot of hazardous chemicals.     

Biological Applications of Electron Paramagnetic Resonance Viscometry Using a 13C-Labeled Trityl Spin Probe

Alterations in viscosity of biological fluids and tissues play an important role in health and diseases. It has been demonstrated that the electron paramagnetic resonance (EPR) spectrum of a ¹³C-labeled trityl spin probe (¹³C-dFT) is highly sensitive to the local viscosity of its microenvironment. In the present study, we demonstrate that X-band (9.5 GHz) EPR viscometry using ¹³C-dFT provides a simple tool to accurately measure the microviscosity of human blood in microliter volumes obtained from healthy volunteers. An application of low-field L-band (1.2 GHz) EPR with a penetration depth of 1–2 cm allowed for microviscosity measurements using ¹³C-dFT in the living tissues from isolated organs and in vivo in anesthetized mice. In summary, this study demonstrates that EPR viscometry using a ¹³C-dFT probe can be used to noninvasively and rapidly measure the microviscosity of blood and interstitial fluids in living tissues and potentially to evaluate this biophysical marker of microenvironment under various physiological and pathological conditions in preclinical and clinical settings.     

Chitosan-based nanocomposites for medical applications

Chitosan as a biobased polymer is gaining increasing attention due to its extraordinary physico-chemical characteristics and properties. While a primary use of chitosan has been in horticultural and agricultural applications for plant defense and to increase crop yield, recent research reports display various new utilizations in the field of advanced biomedical devices, targeted drug delivery, and as bioimaging sensors. Chitosan possesses multiple characteristics such as antimicrobial properties, stimuli-responsiveness, tunable mechanical strength, biocompatibility, biodegradability, and water-solubility. Further, chitosan can be processed into nanoparticles, nano-vehicles, nanocapsules, scaffolds, fiber meshes, and 3D printed scaffolds for a variety of applications. In recent times, nanoparticles incorporated in chitosan matrices have been identified to show superior biological activity, as cells tend to proliferate/differentiate faster when they interact with nanocomposites rather than bulk or micron size substrates/scaffolds. The present article intents to cover chitosan-based nanocomposites used for regenerative medicine, wound dressings, drug delivery, and biosensing applications.     

Density and Excess Molar Volume of the Protic Ionic Liquid Bis(2-hydroxyethyl)ammonium Acetate with Alcohols

Densities were determined for binary mixtures containing the protic ionic liquid bis(2-hydroxyethyl)ammonium acetate [BHEAA] and an alcohol (methanol, ethanol, and 1-propanol) at four different temperatures (293.15, 303.15, 313.15, and 323.15) K and ambient pressure. Coefficients of thermal expansion and excess molar volumes were calculated from the experimental densities. The excess molar volumes were fitted using the Redlich-Kister polynomial equation. Negative deviations from ideal behavior of the excess molar volume were observed for all systems investigated in this study. The results were interpreted in terms of ion-dipole interactions and structural factors of the ionic liquid and alcohol. It was observed that an increase of the alcohol carbon chain length led to lower interactions on mixing.     

Thermophysical properties of 1-alkylpyridinum bis(trifluoromethylsulfonyl)imide ionic liquids

The thermophysical properties of 1-alkylpyridinium bis(trifluoromethylsulfonyl)imide, [C_npy][Tf₂N] ionic liquids where n = 4, 8, 10, or 12 have been determined. Density ρ, and dynamic viscosity η, were determined at T = (293.15 to 353.15) K and refractive index n_D, was measured at T = (293.15 to 333.15) K. Empirical correlations are proposed to represent the present experimental results. The values of the coefficient of thermal expansion were calculated from the experimental density values. The thermal decomposition temperature, T_d was also determined using thermogravimetric analyzer (TGA) at a heating rate of (10 and 20) K · min^?1.