Chloride analysis in magnesium metal using ion chromatography with conductometric detection

A simple, rapid and accurate method for the determination of chloride in magnesium metal has been developed. The quantitative determination of chloride was accomplished by anion exchange chromatography with conductometric determination. A Metrosep Anion Dual 2 analytical column connected in series with a Metrosep RP guard column was used for chloride separation. A solution containing a mixture of 1.3 mM Na2CO3 and 2 mM NaHCO3 was used as eluent. The method requires a sample dissolution using nitric acid. The limit of detection for the determination of chloride is 50 mg kg(-1) and the relative standard deviation was 5% for the overall method. The recovery of chloride added was 99-102%. No interference was observed from either the closely eluting "system peak" or the nitrate peak in the determination of chloride.     

Parametric upconversion of TM and Trivelpiece-Gould (TG) modes to high frequency free electron laser (FEL)

A backward wave oscillator (BWO) filled with a strongly magnetized plasma supports TM and Trivelpiece-Gould (TG) modes. At large amplitudes these modes may act as wigglers for generating millimeter waves via free electron laser instability. The nonlinear coupling between the wiggler, the beam space charge mode, and the high frequency free electron laser wave is dominated by parallel motions. In the Raman regime the growth rate of instability goes as _pb ^1/2 / ₀ ^9/4 , where _pb is the beam plasma frequency and ₀ is the relativistic gamma factor.Department of Physics, Indian Institute of Technology, India. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 6, pp. 748–753, June, 1994.     

Effects of swift heavy ion-irradiation on mica- and coal-based rocks of Lower Himalayas in Sikkim,India

Naturally occurring mica schist and coal sedimentary sequence in Sikkimese Himalaya were collected and investigated by two micro-techniques: scanning electron microscopy/energy dispersive spectrometry and Raman spectroscopy. They were applied to identify the constituents and the structure of the minerals before and after swift heavy ion irradiation. Vibrational data and the constituents of abundantly found mica schist and coal-based rock were acquired at room temperature and were compared with those reported for their analogues in the previous reports.     

Cd1-xZnxS/ZnS core/shell quantum dot ferroelectric liquid crystal composite system: analysis of faster optical response and lower operating voltage

Cd_1?xZn_xS/ZnS core/shell-structured quantum dot (QD)-doped ferroelectric liquid crystal (FLC) Felix 17/000 has been investigated in the present study. In the SmC* phase, the effect of QD on the dielectric and electro-optical properties of FLC has been studied as a function of dopant concentration. A substantial change in the different parameters like tilt angle, spontaneous polarisation, response time and relative permittivity has been observed for the composite system. Nearly two times faster response of the composite system with lower operating voltage is one of the promising results of the present study. The faster optical response along with the decreased value of spontaneous polarisation can be utilised in low power consumption liquid crystal displays.     

Analysis of taxol and major taxoids in Himalayan yew, Taxus wallichiana.

A reversed-phase column liquid chromatography method for the analysis of taxol, 10-deacetylbaccatin III, baccatin IV, 1-hydroxybaccatin I, 2-acetoxybrevifoliol, brevifoliol, 2'-deacetoxydecinnamoyltaxinine J and 2'-deacetoxytaxinine J in yew needles has been developed using a Nova-Pak Phenyl column and a binary gradient profile. The various aspects of analysis such as extraction efficiency, detection limits, reproducibility and peak purity were validated using UV-Vis as well as photodiode array detection.     

Stress Degradation Behavior of Entacapone and Development of LC Stability-Indicating Related Substances and Assay Method

A new, sensitive, stability indicating gradient RP-LC related substances and assay method has been developed for the quantitative determination of entacapone in bulk drugs. Efficient chromatographic separation was achieved on a C18 stationary phase with simple mobile phase combination of buffer and acetonitrile. Buffer consisted of 0.1% orthophosphoric acid, delivered in a gradient mode and quantitation was carried out using ultraviolet detection at 220 nm with a flow rate of 1.5 mL min⁻¹. In the developed LC method the resolution (R _s ) between entacapone and its three potential process impurities were found to be >2.0. Regression analysis showed an r ² value (correlation coefficient) >0.99 for entacapone and its three potential impurities. This method was capable to detect all three process impurities of entacapone at a level of 0.003% with respect to test concentration of 0.5 mg mL⁻¹ for a 20 μL injection volume. The inter- and intra-day precision values for all three impurities and for entacapone was found to be within 2.0% RSD. The method has shown good and consistent recoveries for entacapone in bulk drugs (99.2–101.5%) and its three impurities (99.5–102.2%). The test solution was found to be stable in diluent for 48 h. The drug substances were subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in acid stress, base stress and oxidative conditions. The stressed test solutions were assayed against the qualified working standard of entacapone and the mass balance in each case was close to 99.7% indicating that the developed method was stability-indicating. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.

     

Measurement of the ground state 2n pickup probability for 28Si+68Zn and its role in sub-barrier fusion enhancement

The ground state and excited state transfer yields for the 2-neutron pickup channel in the ²⁸Si+⁶⁸Zn system have been measured explicitly. The recoil mass separator at the nuclear Science Centre, New Delhi was used for the measurement. A NaI(T1) detector was used for detecting the deexcitation γ’s from the transfer products. The kinematic coincidence technique was employed for the transfer measurement. Simplified coupled channels calculations show that out of all transfer channels the major contribution to the sub-barrier enhancement comes from the ground state 2 neutron pickup channel with a ground state Q-value of+1.83 MeV.     

Electronic structure and activation energy of hydrogen in NEG alloy using nonlinear response theory

Electronic structure of hydrogen in NEG alloy [Zr_0.70V_0.246Fe_0.054] is calculated by using nonlinear response theory [Kohn and Sham,Phys. Rev. A140,1133 (1965)]. The configurational energy is calculated by assuming the ideal hcp structure for NEG alloy. The calculated configurational energy predicts that hydrogen prefers octahedral (0)-site in NEG alloy.s-Type shallow bound state of energy -1.580 x 10^-5 Ryd. suggests that hydrogen does not form NEG hydride and it stays as a free ion in NEG alloy. This conclusion confirms the prediction of Tripathiet al.     

Absolute characterization of laser-induced breakdown spectroscopy detection systems

A quantitative comparison of the performance of four different laser-induced breakdown spectroscopy detection systems is presented. The systems studied are an intensified photodiode array coupled with a Czerny–Turner spectrometer, an intensified CCD coupled with a Czerny–Turner spectrometer, an intensified CCD coupled to an Echelle spectrometer, and a prototype multichannel compact CCD spectrometer system. A simple theory of LIBS detection systems is introduced, and used to define noise-equivalent spectral radiance and noise-equivalent integrated spectral radiance for spectral detectors. A detailed characterization of cathode noise sources in the intensified systems is presented.     

Characterization of ammonium dichromate doped PVA films based waveguides

We report here the study of refractive index and Propagation loss of ammonium dichromate doped poly (vinyl alcohol) thin films by using a prism coupling technique. Transmissions of the doped films have been measured. It has been observed that doping of ammonium dichromate increase the refractive index. Propagation losses are found to decrease up to dye concentration 0.02% and thereafter increase rapidly.