Oxidation of alkynes using PdCl<SUB>2</SUB>/CuCl<SUB>2</SUB> in PEG as a recyclable catalytic system: one-pot synthesis of quinoxalines

Alkynes were oxidized efficiently using the catalytic amount of PdCl2 and CuCl2 in PEG-400 in the presence of water, providing excellent yields of the corresponding 1,2-diketones. A variety of alkynes were well-suited substrates for the oxidation under the described conditions. Further, the optimized conditions were successfully utilized for the one-pot synthesis of 2,3-disubstituted quinoxaline derivatives

Radioclimatology over Southern India

7-12Radioclimatology over southern India is studied and the results are discussed. The refractivity gradient is found to be maximum during premonsoon months in the coastal areas. Incidence of super-refraction is found to be maximum during April-May while it is minimum in the months of December and January. High refractivity gradients are found to be associated with temperature inversions or isothermals and with very high vapour pressure gradients

Microwave Propagation Characteristics over Hilly Terrain

83-87Microwave propagation characteristics over hilly terrain situated in southern India have been presented. Amplitude measurements at 7.6 GHz were made round the clock during Mar 1981-Apr 1983 using an operational communication link The daytime signal is characterized with fast and small amplitude fluctuations of the order of 2-3 dB while during night and early morning large amplitude variations sometimes as high as 20-25 dB are observed. High fade rates have been observed to be dominant during premonsoon months. The distribution of fade rates indicates that during monsoon and post-monsoon the fade rate is 30-40 (fades) per hour and the fade rate is 150 per hour in premonsoon while it is 90 per hour in winter

Influence of Aerobic and Nitrogen Flush Packaging Methods and Frozen Storage on Quality Characteristics of Prune Puree Incorporated Ready-to-Eat Mutton Kheema

The present investigation was carried out to evaluate the influence of aerobic packaging and nitrogen flush packaging methods on quality characteristics (physico-chemical, microbial and sensory quality) of 15 % prune puree extended mutton kheema at 0, 30, 60 and 90 days of frozen storage (-18 ±1 °C). The results revealed that there was a significant (P<0.05) decrease in pH, thiobarbituric acid reactive substance (TBARS) values, tyrosine value and per cent free fatty acid (FFA) values with incorporation of prune puree. Furthermore, there was a significant (P<0.05) increase in the pH, TBARS values, tyrosine and FFA content as the storage progressed from 0-90 days in during frozen storage. Irrespective of storage days and treatments, nitrogen flush packaged mutton kheema recorded significantly (P<0.05) lower pH, TBARS, Tyrosine value and FFA content compared to aerobic packaging method. Prune puree added mutton kheema recorded significantly (P<0.05) lower standard plate counts (SPC) and yeast and mould counts, and these counts are increased as the storage progressed from 0 to 90 days during frozen temperature. Nitrogen flush packaging of mutton kheema also helped in limiting the microbial growth during entire period of storage. Organoleptic evaluation scores of all the products were rated as excellent to very good, except for the appearance, which was rated as good. However, the scores decreased significantly with increase in storage time during frozen temperature. Based on the results, it is concluded that prune puree could be beneficially incorporated at levels of 15 % improving the physico-chemical, microbial quality with more health benefits. Nitrogen flush pouches for packaging mutton kheema help in preserving the sensory scores of fresh product during frozen storage

Effect of Fresnel zone clearance on propagation characteristics of microwave links in hilly terrains

29-38The effect of Fresnel zone clearance on microwave propagation over a hilly terrain has been studied. The ray tracing technique for radio rays through the troposphere has also been discussed. The ray paths were traced for different elevation angles under varied meteorological conditions. Under subrefraction conditions, there was insufficient Fresnel zone clearance which leads to fade-outs of the received microwave signals. The antenna height at the transmitting end at Tiruttani was increased from 50 to 90 m to provide enough Fresnel zone clearance. A comparison of the performance of the microwave link before and after the modification of the antenna height has been presented. Propagation characteristics of Elagiri-Tirumala and Pallavaram-Tirumala microwave links situated over a hilly terrain are also presented. The field strength data have been analysed in terms of fade rate, average fade depth and scintillating index. The diurna

Microwave propagation studies and correlation with sodar structures observed over a hilly terrain in Southern India

329-333Simultaneous observations of sodar echograms and microwave amplitude measurements are carried out to study radio wave propagatIon characteristics on a line-of-sight microwave link over a hilly terrain using an operational communication link between Tirupati and Tiruttani situated in Southern India. The studies show that convective conditions do not affect the microwave signal amplitude, whereas ground-based inversions of thickness 100 m, multilayered structures and wave motions are mostly responsible for severe fading and cause deep fades of 20 dB or even more. The observed fade-outs are largely due to rising inversions, as they generate sub-refractive conditions in the convective region during the morning transition hours

A qualitative study of wave motions in atmospheric boundary layer observed over Tirupati using sodar

134-140A study of wave motions in terms of diurnal variation, occurrence percentage, period, amplitude and height of waves in atmospheric boundary layer has been made using an acoustic sounder. The wave motions are usually associated with either surface-based inversions, elevated layers or rising inversions. Most of the time the observed waves have their periods ranging between 5 and 15 min and amplitudes between 100 and 150 m and usually occur in the height range 150-600 m. Power spectral densities of wave motions associated with different structures have also been computed