Inferred leaf senescence of rice crop and its relationship with grain yield

The possibility of detecting change in green cover of rice crop and its relationship with the grain yield was studied using the spectral data collected by an airborne scanner. The spectral data in the form of difference in vegetation index over a 35 day interval, from the time of flowering, was observed to show good relationship between change of green cover (a measure of degree of senescence) and grain yield.     

Acute Toxicity of Distillery Effluent on a Freshwater Fish and Three Pond Snails

The LC₅₀ for 12… 96 h of a distillery waste water were determined for Lebistes reticulatus, Lymnaea luteola, Lymnaea acuminata and Viviparus bengalensis in the batch experiment with daily exchange of the medium. The sensitivity of the species increases in the given sequence with values of the LC_{50,96 h} of 10.77 to 3.72 % proportion of wastewater in the medium. Compared with this, with values of the LC_{50,48 h} of 14.06… 15.71 % after 48 h of exposure there is no significant difference in sensitivity, whereas after exposure for 12 and 24 h the sensitivity grows in the following order: V. bengalensis, L. acuminata, L. luteola, Lebistes reticulatus. Toxicity is obviously primarily determined by the sulphides; with increasing time of exposure also the suspended matter and other factors act toxically.     

Global temperature changes: relative importance of greenhouse constituents of the atmosphere as calculated with a 1-d radiative-convective model

Most modelling endeavours concerning the CO₂-climate problem address only the question of the climatic response to increasing atmospheric carbon dioxide, while the amounts of other atmospheric gases remain fixed. But associated changes, either climatologically or anthropogenically induced, of minor atmospheric constituents can also be of significance in producing a substantial global warming. We have analysed the climatic response to changes in a number of atmospheric trace gases as they may enhance or counteract CO₂-induced warming if their abundance should change. A comparison of the increase in equilibrium global-mean surface temperature due to plausible changes in the concentration of several trace gases in the atmosphere based on our calculations with a one-dimensional radiative-convective model is presented in this paper. Our results indicate that roughly 35% of global surface warming could be due to changes in trace gases other than CO₂ and water vapour. The possible climatic consequences of the ongoing anthropogenic changes in the minor constituents of the atmosphere are also discussed.     

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.