Study of variation in slab thickness of ionospheric F-region during earthquake by wavelet analysis

The present work deals with the anomalies in ionospheric slab thickness of F-region associated with strong seismic activity. In this regard we have considered ionosonde data of Critical frequency of F2 layer (foF2) and Ionospheric Total Electron Content (ITEC) observed for Athens [38°N, 24°E] and Rome [42°N, 13°E] stations. We have considered three cases of earthquake occurring on December 20, 2007, June 08, 2008 and April 06, 2009 and analyzed the ionosonde data of foF2 and ITEC for slab thickness of F-region of the ionosphere in one-hour interval time series record by filtering the geomagnetic disturbances. The result of the study shows that some unusual perturbations were observed in slab thickness of F-region for some days before the main seismic event. It may be due to the generation of seismogenic electric field above the surface of the earth well before the seismic event. This anomalous behavior of perturbations may be used as earthquake precursor.     

Voltammetric determination of cefpirome at multiwalled carbon nanotube modified glassy carbon sensor based electrode in bulk form and pharmaceutical formulation

A new, simple and low cost voltammetric method for the determination of cefpirome in pharmaceutical preparations has been developed using multiwalled carbon nanotube modified glassy carbon electrode (MWCNT), which showed stable response with enhanced selectivity and sensitivity over the bare glassy carbon electrode. A multiwalled carbon nanotube (MWCNT) modified glassy carbon electrode (GCE) is used for the simultaneous determination of cefpirome by differential pulse voltammetry and square wave voltammetry. Results indicated that cathodic peak of cefpirome is greatly improved at MWCNT modified GC electrode as compared with the bare GC electrode showing excellent electrocatalytic activity towards cefpirome reduction. Linear calibration curves are obtained over the concentration range 100-600 μg mL(-1) in Britton Robinson buffer at pH 4.51 with limit of detection (LOD) and limit of quantification (LOQ) are 0.647 μg mL(-1) and 2.159 μg mL(-1) using SWV and 5.540 μg mL(-1) and 18.489 μg mL(-1) using DPV, respectively. The described method is rapid and can be successfully applied for the determination of cefpirome in bulk form and pharmaceutical formulations.     

Fabrication and Properties of Redox Ion Doped Few Monolayer Thick Polyelectrolyte Film for Electrochemical Biosensors at High Sensitivity and Specificity

Redox ions are deposited on a polyelectrolyte‐coated gold electrode by an electric field to fabricate an ion‐selective thin film electrode. The Fe(CN)${{{4- \hfill \atop 6\hfill}}}$ ions are deposited on a few monolayer‐coated polyelectrolyte gold electrode by a slow periodic potential cycle. The deposition process and electrode properties are quantitatively and simultaneously monitored by cyclic voltammetry and a novel technique, using a Scanning Electrometer for Electrical Double‐layers (SEED). No redox properties are obtained without the electric‐field‐deposition. Owing to the redox mediation and net charge due to the redox ion, the electrode is ion‐selective. We demonstrate the principle to detect 1 µM of dopamine in a mixture with 1 mM of ascorbic acid.     

Ionic Liquid‐Mediated Facile Synthesis of Novel Spiroheterobicyclic Rings as Potential Antifungal and Antibacterial Drugs

A pseudo four‐component reaction of urea or thiourea, diverse aryl aldehydes, and 3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one in ionic liquids yields novel azaspiro[4.5]decene derivatives. However, the corresponding reaction in volatile organic solvents gives Knoevenagel adduct as a major product with little amount of the title compound. Interestingly, the expected pyrimidine derivative was not formed in any case. The advantageous features of this methodology are the environmentally benign character, operational simplicity, high yield processing, and easy handling without any catalyst. All the compounds were subjected to in vitro antimicrobial screening against a panel of pathogenic strains of bacteria and fungi. Some of the compounds were found to be equipotent or more potent than the commercial antibiotics.     

Thermal, magnetic and spectral properties of metal quinone complexes

The reactions of 3-chloro-2-hydroxy-1,4-naphthoquinone; chlorolawsone with “Na” metal (ClLw-1), CH₃COONa (ClLw-2), NaOH (ClLw-3), KOH (ClLw-4) and K₂CO₃ (ClLw-5) have been studied. Dark brown solids obtained for ClLw-1 to ClLw-5 are characterized by elemental analysis FTIR, ¹HNMR, UV–Visible spectroscopy, thermogravimetric analysis and DSC studies. FTIR of ClLw-1 to ClLw-5 shows decrease in ν_C=O frequency after complexation of alkali metal ions and ν_OH of adsorbed as well as coordinated water molecules have been observed between 3,600 and 3,100 cm^?1. The benzenoid protons C(5)H and C(8)H shows down field shift due to intermolecular hydrogen bonding interaction with neighboring molecules and upfield shift have been observed for C(6)H and C(7)H protons in ClLw-1 to ClLw-5 in ¹HNMR spectra. Bathochromic shift ~2 to ~5 nm have been observed for band at 287 nm. The nature of pyrolytic decomposition in chlorolawsone anion in ClLw-1 to ClLw-5 has been observed to be “gradual-1–abrupt–gradual-2”. Phase transition occurred during gradual-1 pyrolytic decomposition of chlorolawsone anion in ClLw-1 to ClLw-4 has been studied by DSC.     

Determination of t,t-muconic acid in urine samples using a molecular imprinted polymer combined with simultaneous ethyl chloroformate derivatization and pre-concentration by dispersive liquid–liquid microextraction

The present communication describes the preparation and evaluation of a molecularly imprinted polymer (MIP) as a solid-phase extraction (SPE) sorbent and simultaneous ethyl chloroformate (ECF) derivatization and pre-concentration by dispersive liquid–liquid microextraction (DLLME) for the analysis of t,t-muconic acid (t,t-MA) in urine samples using gas chromatography–mass spectrometry. The imprinting polymer was prepared using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker, 2,2-azobisisobutyronitrile as the initiator and t,t-MA as a template molecule. The imprinted polymer was evaluated for its use as a SPE sorbent by comparing both imprinted and non-imprinted polymers in terms of the recovery of t,t-MA from urine samples. Molecular modelling studies were performed in order to estimate the binding energy and efficiency of the MIP complex formed between the monomer and the t,t-MA. Various factors that can affect the extraction efficiency of MIP, such as the loading, washing and eluting conditions, were optimized; other factors that can affect the derivatization and DLLME pre-concentration were also optimized. MIP in combination with ECF derivatization and DLLME pre-concentration for t,t-MA exhibits good linearity, ranging from 0.125 to 2 μg?mL^?1 (R ²?=?0.9971), with limit of detection of 0.037 μg?mL^?1 and limit of quantification of 0.109 μg?mL^?1. Intra- and inter-day precision was found to be <6 %. The proposed method has been proven to be effective and sensitive for the selective pre-concentration and determination of t,t-MA in urine samples of cigarette smokers.

Novel PVC-based membrane sensors selective for vanadyl ions

Poly(vinyl chloride) based membranes of di-(2-ethylhexyl)phosphoric acid (DEHPA) and dibutyl(butyl)phosphonate (DBBP) have been prepared and investigated as VO²⁺-selective sensors. The membranes containing DEHPA/DBBP and sodium tetraphenylborate, an anion excluder, show near-Nernstian/Nernstian response in the concentration range 10⁻⁵–10⁻¹ M. The sensors exhibit a fast response time and good selectivity for VO²⁺ over a number of other cations. Quantitative determination of vanadium in waste V₂O₅ catalyst has been achieved by these sensors and they have also been used as indicator electrodes for the determination of the end point in the potentiometric titration of VO²⁺ against EDTA.     

Fast switching response and dielectric behaviour of fullerene/ferroelectric liquid crystal nanocolloids

The electro-optical and dielectric responses of the fullerenes C₆₀-doped ferroelectric liquid crystal (FLC) nanocolloids are reported. Order parameter and phase transition temperature remain invariant as a function of varying dopant concentration (0.10 wt% to 0.50 wt%). Faster switching response of nanocolloids comparing to that of the non-doped FLC is manifested by increase in the localised electric field (around 76% increment for 0.50 wt%), while reduction in the spontaneous polarisation could be the result of anti-parallel correlation amid dopant and FLC dipoles. Decrease in dielectric constant, absorption strength, dielectric strength and rotational viscosity of FLC nanocolloids than that of non-doped FLC is the other consequence of C₆₀ doping. Goldstone-mode relaxation frequency is found to be increased with increasing doping concentration of C₆₀ in FLC.     

Synthesis of Some New 2-(4-Methoxybenzothiazol-2′-yl amino)-4-(2-chloro-4-trifluoromethylanilino)-6-(substituted thioureido)-1,3,5-triazine as Antifungal Agents

2,4,6-Trichloro 1,3,5-triazine was selectively reacted with new nucleophilic reagents such as 4-methoxy-2-aminobenzothiazole, 2-chloro-4-trifluoromethyl-aniline, and phenylsubstituted thiourea in alkaline medium to give 2-(4-methoxybenzothiazol-2′-ylamino)-4-(phenylthioureido)-6-(substitutedthioureido)-1,3,5-triazines. The structures of these compounds were confirmed by IR, ¹H NMR, ¹⁹F NMR, mass spectral data, and elemental analysis. The compounds show fungicidal activity against Alternaria alternata, Aspergillus niger, and Macrofomina.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.