Some remarks concerning residuals and derivatives

Summary An analysis of the existing second derivative systems has been attempted and the superiority ofPeters' method overElkins' is brought out. Some properties of vertical derivatives have been discussed and it is clearly proved that the derivative values are independent of the regional. Finally, the weak and strong points of grid and least square methods have been assessed. Some interesting applications of the least square methods are also described.     

RARE GASES IN BANSUR,UDAIPUR AND MADHIPURA CHONDRITES

We have analysed three Indian meteorites — Bansur, Udaipur and Madhipura — for the elemental and isotopic composition of Ne, Ar, Kr and Xe and determined their radiation and gas-retention ages. It is found that Udaipur belongs to the group of unequilibrated ordinary chondrites and Madhipura probably belongs to the group of shocked hypersthene chondrites.     

Behaviour of masonry structures during the Bhuj earthquake of january 2001

A variety of masonry structures suffered damage during the recent Bhuj earthquake. Some of the traditional masonry structures had no earthquake resistant features and suffered considerable damage. This paper attempts to evaluate the behaviour of masonry structures based on the type of masonry used in places like Bhuj, Anjar, Bhachau, Morbi, Samakhyali and several other places. Quite a few masonry buildings had used earthquake resistant features like lintel bands and corner reinforcements. The cracking and failure patterns of such buildings have also been examined. The paper concludes with a discussion on the relevance of the current codal provisions for earthquake resistance of masonry structures and the direction of further research in the area.     

The Indian summer monsoon as revealed by the NCMRWF system

In this study, we present the mean seasonal features of the Indian summer monsoon circulation in the National Centre for Medium Range Weather Forecasting (NCMRWF) global data assimilation and forecast system. The large-scale budgets of heat and moisture are examined in the analyzed and model atmosphere. The daily operational analyses and forecasts (day 1 through day 5) produced for the summer seasons comprising June, July and August of 1995 and 1993 have been considered for the purpose. The principal aim of the study is two-fold. Primarily, to comprehend the influence of the systematic errors over the Indian summer monsoon, secondarily, to analyze the performance of the model in capturing the interseasonal variability. The heat and moisture balances show reduction in the influx of heat and moisture in the model forecasts compared to the analyzed atmosphere over the monsoon domain. Consequently, the diabatic heating also indicates reducing trend with increase in the forecast period. In effect, the strength of Indian summer monsoon, which essentially depends on these parameters, weakens considerably in the model forecasts. Despite producing feeble monsoon circulation, the model captures interseasonal variability realistically. Although, 1995 and 1993 are fairly normal monsoon seasons, the former received more rainfall compared to the latter in certain pockets of the monsoon domain. This is clearly indicated by the analyzed and model atmosphere in terms of energetics.     

Effect of equatorial ionization anomaly on the occurrence of spread-F

The unique geometry of the geomagnetic field lines over the equatorial ionosphere coupled with the E–W electric field causes the equatorial ionization anomaly (EIA) and equatorial spread-F (ESF). lonosonde data obtained at a chain of four stations covering equator to anomaly crest region (0.3 to 33 °N dip) in the Indian sector are used to study the role of EIA and the associated processes on the occurrence of ESF. The study period pertains to the equinoctial months (March, April, September and October) of 1991. The ratios of critical frequency of F-layer (f₀F₂) and electron densities at an altitude of 270 km between Ahmedabad (33 °N dip) and Waltair (20 °N dip) are found to shoot up in the afternoon hours on spread-F days showing strengthening of the EIA in the afternoon hours. The study confirms the earlier conclusions made by Raghava Rao et al. and Alex et al. that a well-developed EIA is one of the conditions conducive for the generation of ESF. This study also shows that the location of the crest is also important in addition to the strength of the anomaly.