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Notes: Abstract We have deduced the steady-state lithospheric geotherm at c. 1 Ga in the south Indian shield area using the available data on the concentration of radioactive elements, and the P-T conditions of Proterozoic mantle xenoliths in the south Indian kimberlites as constraints. The geotherm was adjusted back to 2.5 Ga by keeping the surface temperature constant and calculating the temperature change at the top of convecting upper mantle. The reduced or mantle heat flux, which was treated as an adjustable parameter, was 20.9–21.3 mW/m2 at 1–2.5 Ga. Comparison of the calculated steady-state geotherm with the available P-T data of the Archaean (c. 2.5 Ga) charnockites and granulites from southern India suggests that the granulite facies metamorphism in this region had resulted from a major thermal perturbation, which was c. 400° C at 25 km.Seismic tomographic and gravity data essentially preclude any significant magma underplating of the granulitic crust in southern India. Previous workers have suggested that the formation of charnockites in this region was associated with copious CO2 influx from a deep-seated source, possibly the mantle. In this work, we have evaluated both the transient and steady-state thermal effects of the heat convected by CO2 outgassing from upper mantle. It is shown that the thermobarometric array of charnockites and granulites can be produced by the convective perturbation of the steady-state geotherm, and that a flux of CO2 of ±90 mol/m2 yr (corresponding to Darcy velocity of ±0.30 cm/yr) for a period of ±30 Ma was needed to produce the required perturbation. This is c. 150 times the average CO2 flux through the tectonically active area of the Earth's crust at the present time. There is, however, an uncertainty of a factor of 3 in this value.Seismic tomographic and gravity data independently suggest thickening of the crust beneath the granulite terrane compared with the adjacent Dharwar craton. This suggests thermal perturbation due to overthrusting as a major potential cause for the granulite facies metamorphism in south India. Overthrusting of a 30–35-km-thick thrust block was needed to produce the required thermal effect. The estimated thickness of the original crust from geobarometric and seismic tomographic data south of the orthopyroxene isograd or ‘transition zone’is compatible with the emplacement of a thrust block of this magnitude. However, the latter fails to match the estimated pre-uplift crustal thickness at the transition zone, if it is assumed that the crust has not thinned by non-erosional processes since the Archaean. Thus, we propose a combination of overthrusting and CO2 fluxing from a deep-seated source as the cause for the formation of charnockites in this zone. The required focusing of CO2 in this case is c. 40% of that estimated in the model where CO2 fluxing was considered to be the sole reason for thermal perturbation. This combined thrusting—CO2 fluxing model also helps explain the development of patchy charnockites in the transition zone from amphibolite facies rocks.

Notes: We have synthesized La0.83Na0.11MnO2.93 by heating La2O3 and MnCO3 in NaCl melt at 900 °C. The exact composition was arrived by analyzing each ion by an independent chemical method. The compound crystallized in a rhombohedral structure and showed an insulator-to-metal transition at 290 K. Epitaxial thin films were fabricated on LaAlO3 (100) using a pulsed laser deposition technique. The film also showed an insulator-to-metal transition at 290 K. Magnetoresistance [ΔR/R0=(RH−R0)/R0] was −71% near the insulator-to-metal transition temperature of 290 K at 6 T magnetic field. © 1997 American Institute of Physics.

Notes: Helminthosporium leaf blight (HLB) is the most important disease constraint to wheat (Triticum aestivum L.) cultivation in the eastern Gangetic Plains of South Asia. A Helminthosporium Monitoring Nursery (HMN) including potential adapted and exotic sources of HLB resistance was developed in Bangladesh, India and Nepal to assess the stability of genetic resistance across locations. The 8th, 9th and 10th HMN assessed the HLB resistance and agronomic traits of 17 wheat genotypes across 20 environments of Bangladesh, India and Nepal in the 1999-2000, 2000-2001 and 2001-2002 cropping seasons, respectively. The area under the disease progress curve (AUDPC) for HLB, grain yield, thousand-kernel weight (TKW), days to heading, days to maturity, and plant height were examined. The 17 genotypes showed a range of variability for disease and agronomic characters. Disease severity (AUDPC) differed in the 3 years and showed the highest values in 2002. The increase in AUDPC in 2002 caused the lowest grain yield, with an average 18% reduction due to HLB. A few genotypes (SW 89-5422, Yangmai-6 and Ning 8201) appeared to have stable HLB resistance across environments. However, most of the higher-yielding genotypes, except BL 1883, were unstable. The results suggest that careful selection of HLB resistance with acceptable grain yield, TKW and plant height may be possible using the wheat genotypes included in the HMN.

Notes: Interdiffusion barrier characteristics of molybdenum thin film with aluminum-1% Si is studied between 733 and 763 K via sheet and contact resistance measurements, Rutherford backscattering spectrometry, secondary ion mass spectrometry, and x-ray diffraction analysis. The results indicate that thermal annealing of Mo/Al-1% Si thin film couples leads to MoAl12 compound formation initially as a nonplanar front, but extensive annealing results in complete transformation of Al-1% Si to MoAl12 and a significant increase in contact resistance. The interdiffusion kinetics is diffusion controlled and shows parabolic time dependence, incubation periods, and extremely high activation energy value of 5.9 eV. The incubation periods and an high activation energy values are explained by the presence of silicon precipitates at the Mo/Al-1% Si interface. Implications of these observations to VLSI device characteristics are discussed and a safe time-temperature processing regime is proposed.

Notes: Models of retrograde metamorphism in many orogenic belts are based on crustal thickening and erosion of continental lithosphere. The pressure and temperature evolutions in such models are generally obtained by solving the advection diffusion equation with the lithosphere-asthenosphere boundary (LAB) either fixed at a specified depth or moving downwards at the same rate as erosion from the surface. However, this boundary is defined as a solid-partial-melt boundary in many geophysical interpretations. In the present work, we discuss a solution of the above problem considering the LAB as a phase boundary that moves. This solution is obtained by the Fourier series approach for a general case of surface erosion and basal heat transport. The results obtained for different models of crustal thickening show a significant movement of the LAB in response to erosion from the surface. A corresponding variation in the lithospheric thickness is also a significant result of this analysis. The earlier notion of a fixed-base lithosphere seems to be a good approximation when analysing metamorphic data, as we obtain nearly the same temperature profile in the crust as after including the LAB motion effect. However, the erosion of thickened crust is found to affect the lithospheric growth. These results indicate that metamorphic data (sampling the thermal structure of the upper lithosphere) do not preserve the signatures of such boundary motion.

Notes: Gravity and bathymetry profiles across the Carlsberg Ridge in the Indian Ocean are analysed to investigate the isostatic compensation of this part of the Indian Ocean spreading ridge system. the ridge has a rough flanking topography and a median valley, which are the characteristics of slow-spreading ridges. We use the cross-spectral technique to obtain an admittance function for isostatic studies. Admittance estimates in the long-wavelength region (125-500 km) indicate that the elastic plate thickness supporting the long-wavelength topography is in the range 5-10 km. We have also examined the isostasy of the axial region. Synthetic topography and gravity profiles computed for a cooling plate model are subtracted from the observed, to estimate the median valley signatures. the residual gravity anomaly over the ridge axis is mostly explained by the median valley topography with a uniform crustal thickness of 6 km, indicating that the median valley is not in isostatic equilibrium.

Notes: [Auszug] IT is usually assumed that under normal conditions of the ionosphere, if a radio signal is received after ground sunrise, it is likely to maintain its strength until absorption in the ionospheric region becomes pronounced during the day. It has often been found, however, during our observations ...

Notes: [Auszug] It is well known that the global thunderstrom activity is at a maximum at the temperate latitude and decreases with increasing latitudes7. The parameters or mechanisms controlling the guidance of thunderstorm-generated low-frequency waves are less effective at low latitude, however, which seems to ...

Notes: [Auszug] Fig. 1. Mutant colony (x50). Fig. 2. Parent colony (x70). Clonal and axenic culture of Nostoc linckia (Roth) Born, et Flah., isolated from local rice fields, was derived from spores. The alga grew well in Allen and Arnon's nitrogen-free medium5 in a culture room lit with daylight fluorescent ...

Notes: [Auszug] The electrojet layer is generally considered to be a thin equatorial layer sandwiched between two non-conducting layers. In the equatorial region the magnetic field becomes horizontal and is perpendicular to the equatorial belt encircling the Earth. Because of the presence of a horizontal magnetic ...