Studies on the Toxicity of Some Insecticides to a Freshwater Teleost Lebistes reticulatus (PETERS)

In batch tests with daily exchange of the medium the toxicity of endosulfan, lindane, aldrin, chlordane, rogor and novocron is investigated during times of exposure of 12… 96 h. The mean survival periods and the LC₅₀ are determined. Toxicity increases in the following sequence (LC_50,96h) (in mg/1): novocron (22.65), rogor (18.97), chlordane (0.341), aldrin (0.017), lindane (0.0160), endosulfan (0.0027). The following safe concentrations in mg/1 are recommended: 0.0006 endosulfan, 0.0041 lindane, 0.0010 aldrin, 0.1436 chlordane, 5.4086 rogor and 7.2309 novocron.     

Injected radiotracer techniques in hydrology

Radioactive tracers which have several advantages over conventional tracers made significant contributions to the development of the injected tracer method in hydrology. A review of the nuclear and the physico-chemical characteristics of the possible radiotracer compounds leads us to conclude that the most effective groundwater tracers are tritiated water (HTO),⁸²Br⁻ and⁵⁸Co or⁶⁰Co as a hexacyanocobaltate complex. A discussion of the various case studies in India and abroad covering the three groups of applications mentioned helps us to conclude that well established radiotracer methods with associated interpretational techniques are available for many short range studies in surface and subsurface hydrology.     

Noble gas composition in Ogi and Siena meteorites

The elemental and isotopic composition of noble gases in two chondritic meteorites which belong to documented “falls” is reported. Ogi, which belongs to the group of H-chondrites, fell in Saga, Kyushu (Japan) at 11am on 8 June 1741 and Siena which belongs to the group of LL-chondrites, fell in Tuscany (Italy) at 7pm on 16 June 1794. The recovered mass of Ogi and Siena were 14·2 and 4 kg respectively. Their exposure ages are 13±2 m.y. and 13±3 m.y. respectively.     

Magnetometric surveys over some iron-ore occurrences in the Eastern Ghats belt of Godavari Districts,Andhra Pradesh

Iron-ore with magnetite as the chief ore mineral occurs in the Precambrians of Eastern Ghats. Vertical magnetometric surveys were carried out to delineate some of the ore bands, in the Ghats belt of Godavari Districts, Andhra Pradesh, around Addatigala, Devipatnam and Tekuru. Interpretation of the magnetic anomalies was based on the tabular models. Ore bands are at shallow depths of around 5m. The deduced inclinations of magnetisation suggest that the magnetisation is largely remanent. The intensities of magnetisation are in the range of 5 to 10·5×10^?3 emu and agree well with the laboratory measurements on the ore samples. At Devipatnam and Tekuru the magnetic background seems to be high. At Tekuru the ore band appears to be very limited in depth extent. The limited depth extent coupled with high magnetic background explains the anomaly which is not so prominent. It is concluded that in such areas, it is only the high grade magnetite ore bands of considerable depth extent that can be successfully delineated by the magnetic method.     

Geomagnetic solar and lunar daily variations at Alibag,India

Geomagnetic solar and lunar daily variationsS andL, at Alibag, India are derived, by the well-known Chapman-Miller method, from the series of homogeneous mean hourly magnetic data of the years 1932 to 1972. The data for all the three elements — declinationD and horizontal and vertical intensitiesH andZ — are analysed, by dividing the data suitably for a study of the seasonal variations, the effect of the changes in the solar and magnetic activities onS andL, the oceanic dynamo contribution toL, and their interactions with each other. The main results are as follows.

1. ForS the daily pattern and its seasonal progression conform to the type expected from a northern-hemisphere station. On the other hand, the amplitudes of all the four harmonics ofL systematically have higher values in winter, and inD andZ the harmonics show large phase differences between summer and winter. The pattern ofL in winter suggests that the lunar current system consists of a single set of vortices in the summer hemisphere rather than the conventional vortices, one set in each of the hemispheres.
2. Solar-cycle modulation on the solar ranges as well as on the amplitudes of the first three harmonics ofS is greater than that expected solely from the increase in E-region conductivity, whereas the corresponding modulation onL is comparable to that on the E-region conductivity.
3. With increasing magnetic activity the first harmonic ofS shows an increase, and the first three harmonics ofL indicate a general decrease, in amplitude.
4. Of the variability inS 96%, but inL only 32%, is found to be accounted for by the combined effect of the variations in the solar and magnetic activities.

     

Gravity anomalies of three-dimensional bodies with a variable density contrast

The exponential decrease in the density contrast of anomalous bodies is equated to a quadratic function. The three-dimensional body is divided into a series of parallel vertical polygonal sections of unit thickness each. The gravity effect of each side of the vertical polygonal cross-section with a quadratic density variation is derived in closed form. Gravity effects of a few equispaced and representative cross-sections are integrated to obtain the gravity anomaly of the entire body. When used in modelling gravity data, the method of considering vertical cross-sections has the unique advantage of easily allowing changes in theZ-coordinates of polygonal sections.     

Photogeological mapping of the parts of adilabad and karimnagar districts,Andhra Pradesh

Mapping of the Archaean, Precambrian and Permocarboniferous sedimentary formations in the northern and southern parts of Godavari river covering parts of Adilabad and Karimnagar districts through photointerpretation technique, has been found to be fairly accurate and reliable. Their unique photo characters and other recognition elements are briefly described in this paper.     

Simulation of the summer circulation over South America by two regional climate models. Part II: A comparison between 1997/1998 El Niño and 1998/1999 La Niña events

Summary This study investigates the capabilities of two regional models (the ICTP RegCM3 and the climate version of the CPTEC Eta model – EtaClim) in simulating the summer quasi-stationary circulations over South America during two extreme cases: the 1997–1998 El Ni?o and 1998–1999 La Ni?a. The results showed that both the models are successful in simulating the interannual variability of summer quasi-stationary circulation over South America. Both the models simulated the intensification of subtropical jet stream during the El Ni?o event, which favoured the blocking of transient systems and increased the precipitation over south Brazil. The models simulated the increase (decrease) of precipitation over north (west) Amazonia during the La Ni?a (El Ni?o) event. The upper level circulation is in agreement with the simulated distribution of precipitation. In general, the results showed that both the models are capable of capturing the main changes of the summer climate over South America during these two extreme cases and consequently they have potential to predict climate anomalies.     

Simulation of Storm Surges Along Myanmar Coast Using a Location Specific Numerical Model

Coastal flooding induced by storm surges associated with tropical cyclones is one of the greatest natural hazards sometimes even surpassing earthquakes. Although the frequency of tropical cyclones in the Indian seas is not high, the coastal region of India, Bangladesh and Myanmar suffer most in terms of life and property caused by the surges. Therefore, a location-specific storm surge prediction model for the coastal regions of Myanmar has been developed to carry out simulations of the 1975 Pathein, 1982 Gwa, 1992 Sandoway and 1994 Sittwe cyclones. The analysis area of the model covers from 8° N to 23° N and 90° E to 100° E. A uniform grid distance of about 9 km is taken along latitudinal and longitudinal directions. The coastal boundaries in the model are represented by orthogonal straight line segments. Using this model, numerical experiments are performed to simulate the storm surge heights associated with past severe cyclonic storms which struck the coastal regions of Myanmar. The model results are in agreement with the limited available surge estimates and observations.