Synthesis of 2-methyl-3-(3,5-diallyl-4-hydroxyphenyl)-4-quinazolones as possible anticonvulsants

A series of 2-methyl-3-(3,5-diallyl-4-hydroxyphenyl)-4-quinazolones were prepared as possible anticonvulsants. All compounds were evaluated for their anticonvulsant activity against pentylene-tetrazol-induced seizures and their ability to potentiate sodium pentobarbital sleeping time in albino mice.     

Amplitude scintillations of ATS-6 radio beacon signals within the equatorial electrojet region (Ootacamund,dip 4° N)

The recordings of the amplitudes of radio beacon signals on 40, 140 and 360 MHz from ATS-6 (at 34° E longitude) recorded at Ootacamund, India (11.43° N, 76.70°E, dip 4°N, elevation angle 41°) have revealed largest occurrence of scintillations for about 60% of cases around 2200 hr during the nighttime, and two secondary peaks (25% of cases) around 0900 hr and 1400 hr during the daytime. During the daytime, the scintillation decreases approximately as the inverse of the frequency for higher frequencies while for lower frequencies the law is valid till scintillation index at 40 MHz does not exceed 0.9. The temporal variation of daytime scintillation shows impulsive character, the duration of activity lasts for 1–2 hours at a time. During the nighttime, the scintillation decreases inversely with frequency for weak and moderate scintillation activity. The scintillation index at 360 MHz becomes independent of that at 140 MHz when the index at 140 MHz exceeds 0.85. For the set of frequencies 40–140 MHz, on some occasions scintillation index at 40 MHz is seen to be less than that at 140 MHz. The nighttime scintillations are in general stronger and remain so for extended length of time. The daytime scintillations are suggested to be due to blanketing or some other non-q type of sporadicE layer. The nighttime scintillations are most probably due to spreadF condition and the abnormal frequency variation of the scintillations may be due to multiple scattering layer during periods of intense spreadF.     

Strip dielectric wave guide antenna-for the measurement of dielectric constant of low-loss materials

The value of dielectric constant are the most important parameters in material science technology. In micro-wave and millimeter wave circuits using dielectric materials the values of this parameters should be known accurately. It is observed that the number of methods are reported in litrature, however these methods impose difficulties in experimentation and are not very accurate. In this paper a novel approach to the measurement of the dielectric constant of low loss materials at micro-wave and millimeter wave frequencies has been discussed. In this method by using antenna theory, a metallic strip dielectric guide is taken in to constideration and band reject phenomenon of dielectric antenna is used. Frequency response of an antenna in band reject mode is a function of the dimensional parameters, such as the metallic strip period, the profile of the metallic strip and the dielectric constant of the material used. Hence if one measure the frequency responce of the antenna in band reject mode, the dielectric constant of the material is determined provided all other parameters are known. This method gives a direct measure of dielectric constant and is quite accurate as computer techniques are used for evaluating the dielectric constant. This method verified experimentally also.     

Sample preparation for gas chromatographic analysis of organic solvents in aerosol cans

Summary A method for the sampling of chemical products from aerosol cans is described. An aerosol can is frozen in liquid nitrogen, followed by puncturing the can and allowing the propellant to distill off. The conditions for the smaple preparation have been optimized. Solvent content in the products were analysed by headspace gas chromatography-mass spectrometry.     

Equatorial range spreadF and high multiple echoes from theF region

It has been shown that the post-sunset rise of the minimum virtual height (h′F) of theF region of the ionosphere near the magnetic equator during the high sunspot years is an effect of the overall rising of the completeF region. This feature of theF region produces very high order multiple reflections from theF regions. On some occasions strong spreadF is observed simultaneously with the high multiples suggesting theF region to be smooth and devoid of irregularities inside it. The irregularities causing the spreadF during the early stages of its development are suggested to be at heights below theF region.     

Equatorial sporadic E and cross-field instability

The occurrence of sporadic E at an equatorial station during magnetically quiet daytime conditions corresponds almost exactly to the time during which the horizontal component of the earth’s magnetic field is above the mean night time level. Any large decrease of H below the night time level is accompanied by the disappearance of equatorial E_s?q reflections precisely for the period when the value of H remains below its night time level. Such disappearance of E_s?q can be attributed to the reversal of the current equal to, or greater than, the normal eastward equatorial electrojet current. During magnetically disturbed conditions, however, the depressions in H are not always accompanied by the disappearance of E_s?q. Whenever the normal E and sporadic E reflections can be resolved on the equatorial ionograms, the minimum virtual height of the normal E is seen to be clearly greater than that of the sporadic E layer. The creation of E region irregularities at equatorial latitudes giving the appearance of an E_s?q layer in daytime ionograms is suggested to be due to cross-field (plasma gradient) instability. The horizontal magnetic field and the upward Hall polarisation (electric) field produce irregularities in the lower E-region where the rate of increase of ambient electron density is large and directed upward. A temporary reversal of the electrojet current indicated by a decrease in H below the night time level and the disappearance of E_s?q are due to the temporary reversal of the vertical Hall polarisation field making it downward instead of upward which being opposite to the direction of the gradient of plasma density inhibits the cross-field instabilities.     

Leaky optical waveguide for high power applications

The available fiber lasers, photonic-crystal fiber (PCF) frequency converters, and hollow-core PCFs are shown to offer realistic practical solutions for an all-fiber format of coherent anti-Stokes Raman scattering (CARS) in the gas phase. In view of the substantial enhancement of CARS in the guided modes of hollow-core PCFs, a broad class of compact ytterbium and erbium fiber laser sources become suitable for the CARS analysis of gas media. The quantum limit of the signal-to-noise ratio, S/N, in all-fiber CARS is shown to scale as λα^-1a^-2 with radiation wavelength λ, fiber loss α, and the fiber core radius,aleading, in the case of a hollow-PCF gas cell, to a dramatic improvement of S/N relative to CARS in the regime of tight focusing. PACS 42.65.Wi; 42.81.Qb