Orientational Order Parameter in 1-Hexyl-4-(4-Isothiocyanatophenyl) Bicyclo [2,2,2] Octane using X-Rays

Abstract

1-Hexy1-4-(4-isothiocyanatophenyl)bicyclo[2,2,2]octane (HIPBO), a nematic liquid crystal which shows nematic phase in the temperature range 52.8 to 90.2°C, has been used along with imaging plate system to record X-ray Laue type diffraction pattern at different temperatures. For this purpose oriented sample was used. Orientational order parameter was obtained using Fourier method, recently reported by us, and has been compared with that of other existing methods.     

Determination of carbamate pesticides using micro-solid-phase extraction combined with high-performance liquid chromatography

We describe a simple and sensitive porous polypropylene membrane-protected micro-solid-phase extraction (μ-SPE) approach for the sample preparation and determination of carbamate pesticides in soil samples by high-performance liquid chromatography. The μ-SPE device consisted of C₁₈ sorbent held within a porous polypropylene envelope. In order to achieve optimum performance, several extraction parameters were optimized. Under the most favorable conditions, the extraction efficiency of the μ-SPE was very high, with detection limits in the range of 0.01–0.40 ng g⁻¹. This is more than two orders of magnitude lower than the limits obtained by the United States Environmental Protection Agency Methods 8321A and 8318. A linear relationship was obtained for each analyte in the range of 2 and 200 ng g⁻¹. The relative standard deviation for the analysis of aged soil samples spiked at 5 ng g⁻¹ was ≤11%. The reproducibility of separate μ-SPE device used for experiments was satisfactory (relative standard deviations ranged from 4 to 11%), indicating that the method is reliable for routine environmental analysis.     

A fractographic study of fatigue failure in two high strength steels

Results are given of a detailed fractographic study of a commercial 1 1/2 Ni-Cr-Mo steel (S95 Specification) and a high purity laboratory-made steel of similar alloy content tested in uniaxial alternating and pulsating loading. The specimens were hardened by oil quenching and tempering to strength levels of 1544 and 1930 MN/m² (100 and 125 tonf/sq. in.). tested at room temperature and the fractures examined by scanning-electron and optical microscopes and by the electron microscope employing a two stage replication technique.All fractures consisted essentially of a fatigue region and a region of tensile failure; the former appeared, in all instances, to be nucleated at non-metallic inclusions. The fatigue regions were composed of smooth featureless areas (probably resulting from micro-cleavage in the tempered martensite), areas of intergranular separation along prior austenite grain boundaries (although very seldom observed in the high purity alloy) and areas exhibiting characteristic striation. The nature of the regions of tensile failure was markedly dependent on steel purity; the primary mode of fracture in the commercial steel was along prior austenite grain boundaries while in the high purity alloy final separation occurred predominantly by ductile shearing. Estimates of fatigue crack growth rates derived from striation spacing data are given.The authors are indebted to Mr. B. E. Hopkins for his advice and encouragement throughout the programme. They would like to thank Mrs. Daphne Thomas for her painstaking work with the scanning electron microscope. The assistance of Mr. K. B. Armstrong, Mr. N. B. Owen and Mr. J. M. Jennings with the fatigue testing phase of the investigation is gratefully appreciated.The work described above has been carried out as part of the General Research Programme of the National Physical Laboratory.     

Synthesis, electrical and electromechanical properties of a tungsten-bronze ceramic oxide: Pb0.68K0.64Nb2O6

A tungsten-bronze ceramic oxide, Pb_0.68K_0.64Nb₂O₆, has been prepared by a standard solid-state reaction technique. Compound formation and phase identification has been confirmed by X-ray diffraction (XRD) studies. The dielectric permittivity and the loss tangent of the sample have been measured in a frequency range 45 Hz–5 MHz and a temperature range 35–590 °C. Electrical properties of the material were studied using an impedance spectroscopic technique. Detailed analysis of the impedance spectrum suggested that the electrical properties of the material are strongly temperature dependent. The Nyquist plots clearly showed the presence of bulk and grain boundary effect in the compound. The imaginary part of modulus at different temperatures shows a relaxation peak and its position shifts to higher frequency with increase in temperature. This suggests a temperature-dependent relaxation. The frequency dependent ac conductivity at different temperatures indicated that the conduction process is thermally activated process.     

Electrochemical investigation of magnetite-carbon nanocomposite in situ grown on nickel foam as a high-performance binderless pseudocapacitor

Journal of Solid State Electrochemistry - Magnetite-carbon nanocomposite was grown in situ on nickel foam by a novel auto-combustion method, and it was investigated for application as a...     

Radon and its short-lived progeny: variations near the ground

In the atmosphere above the surface of the Earth the concentrations of radon and its progeny are measured, along with the meteorological parameters from December 1997 to December 2000 for a continental location, Pune (18°N,74°E), India. The concentrations show maxima in the early morning hours when the turbulence mixing is minimum; whereas in the afternoon the turbulence mixing is maximum and concentrations exhibit minima. The median values of concentration are 9.70 and 2.84 Bqm⁻³, respectively, for radon and its progeny, during the observation period. Ionization rates in the atmosphere are derived for the same period. It is found that the ionization rate exhibits a median value of 5.48 ionpairscm⁻³ s⁻¹. The diurnal and seasonal variations in the concentrations of radon and its progeny, and the ionization rate due to radioactivity are found to exhibit correlation with the relative humidity, and anti-correlation with the temperature.