The lithium in weak G-band stars

The lithum abundance in weak G-band stars is found to be linearly correlated with CH deficiency. Weak G-band stars with a high Li abundance are found to show relatively least carbon deficiency, while the stars with a relatively low Li abundance show a high under-abundance of carbon.     

Sources of chloride in hydrothermal fluids from the Valles caldera, New Mexico: a Cl study

The Valles caldera in New Mexico hosts a high-temperature geothermal system, which is manifested in a number of hot springs discharging in and around the caldera. In order to determine the fluid pathways and the origin of chloride in this system, we measured ³⁶Cl/Cl ratios in waters from high-temperature drill holes and from surface springs in this region. The waters fall into two general categories: recent meteoric water samples with low Cl⁻ concentrations (< 10 mg/L) and relatively high ³⁶Cl/Cl ratios [(300–1000) × 10⁻¹⁵]; and geothermal brines with high Cl⁻ concentrations (800–9400 mg/L) but low ³⁶Cl/Cl ratios [(11–26) × 10⁻¹⁵]. The ³⁶Cl/Cl ratios for meteoric waters are slightly higher than expected for this region, suggesting a small addition of anthropogenic ³⁶Cl. Because of low ³⁶Cl/Cl ratios and high Cl⁻ concentrations in the brines, chloride in these waters must be derived from subsurface sources. A comparison between the observed ³⁶Cl/Cl ratios in the brines and those calculated for potential source formations in this region indicates that the present host formations, mainly volcanic tuffs, cannot be major sources of chloride, and that formations at greater depth, such as the Paleozoic and Precambrian formations are more likely to be sources of chloride in the brines. The results suggest that brines are meteoric waters which penetrated into the basement where they derive chloride from leaching of basement rocks and/or from saline pore fluids trapped there, along with likely addition of chloride from Paleozoic strata. Although these fluids have since come to reside in the intracaldera volcanic sequence after convective upwelling, they do not derive much Cl⁻ from the volcanic strata; and residence times of fluids in the volcanics are < 100,000 years.     

Time-dependent stratification in the Gauthami-Godavari estuary

The time-dependent salinity stratification in an environment of highly variable turbulence of Gauthami-Godavari estuary is described. From time series observations at three stations over two tidal cycles each in the winter (December 1989) and the dry (April 1990) seasons in the Gauthami-Godavari estuary, the development of stratification is correlated with periods of substantially reduced velocity shear. Stratification is observed to be greatest around the low water slacks and least around the high water slacks. The formation of stratification relaxes viscous constraints and a buoyancy circulation rapidly develops. The breakdown of stratification drastically modifies the circulation and largely removes the vertical shear associated with the density driven flow. Destratification occurs around the high water slacks in the lower reaches fairly close to the mouth of the estuary. The variations in the fields of mass will strongly affect the response of the velocity field.     

Estimation of Minkowski Dimension Using Neighborhood Operations

A method to estimate the Minkowski dimension using neighborhood operations is described. Its implementation using a software package IMAGER-2 on a square grid with eight connectivity is presented. It is observed that a range of successive pairs of dilations helps in arriving at the best estimate. The methodology is applied to find the Minkowski dimension of the skeleton of a stress corrosion crack.     

Investigation of changes in characteristics of hydrological time series by Bayesian methods

A review of literature reveals the inadequacy of Intervention analysis and spectrum based methods to adequately quantify changes in hydrologic times series. A Bayesian method is used to investigate the statistical significance of observed changes in hydrologic times series and the results are reported herein. The Bayesian method is superior to the previous methods.     

Landuse/Landcover change detection through remote sensing and its climatic implications in the godavari delta region

Interpretation of multi-date satellite imagery has revealed changes in land use/land cover pattern in the Godavari deltaic region during the past 26 years. The area under intensive agriculture has increased from 1459 to 3500 km² and the extent of wetland from 368 to 648 km² during the period 1973-1999, while the seasonal fallow has decreased by 2321 km². Analysis of the climatic data of 1970-1998 from different stations covering the entire 5100 km² area of the delta indicated that the day time temperatures have decreased by 0.2° C to 0.7° C, while the night time temperatures have increased by 0.5° C to 0.6° C during the past three decades. At the same time the rainfall has increased by about 75 to 479 mm. These trends in the climatic parameters arc attributed to the increased vegetation cover and wetland extent in the Godavari deltaic region.     

论长英质隐爆角砾岩的气热流体溶浸成矿机制——以赣南6722铀矿床为例

通过对6722铀矿床地质－地球化学特征及长英质隐爆角砾岩和围岩超微构造研究，结合U，Th等元素溶浸实验结果，得出“隐爆气热流体溶浸成矿富集机制”；来自深部的富含挥发组分（H2O、F、CO2等）的高热安粗岩浆，在早白垩世末（107Ma）沿富城花岗岩体西部蚀变带发育的火山机构中发生隐爆作用，致使围岩发生强烈脆性变形，生成长英质隐爆角砾岩带和震裂花岗岩带；压力、温度降低导致安粗岩浆中挥发组分逸出形成气热流进入稳隐爆裂隙中，并将蚀变花岗岩中的活动性成矿元素（U）浸出转移；成矿物质在物理化学条件（p,t,Eh,pH,化学组分等）急剧变化的部位（长英质隐爆角砾岩及碎裂花岗岩）沉淀富集。     

滇西上芒岗红色粘土型金矿床金的特征

通过化学分析法、X射线衍射和粒度分级、金的浸出实验，对上芒岗红色粘土型金矿床进行研究，发现矿石矿物由褐铁矿、粘土矿物和石英组成，矿石中的金与粗颗粒的多少呈正相关，为微细粒金和游离态金，被吸附于褐铁矿、粘土矿物和石项等矿物表面或裂隙中，在红色粘土剖面中与Mo、Sb、Hg、As等元素紧密共生，金在弱酸-弱碱性条件下活性、迁移，在潜水面附近再沉淀，上芒岗卡林型金矿体为红色粘土型金矿的主要矿源体。     

Comparative study of scintillations at the magnetic equator and at the crest region of the equatorial anomaly in Indian zone

Using simultaneous long-term observations of ionospheric scintillation at equator and anomaly crest region in the same longitude (Indian) zone comparative features of scintillation occurrence are brought out. The salient features are: (a) predominantly pre-midnight occurrence of scintillation at equator during winter and equinox seasons, (b) increase of pre-midnight scintillation occurrence with solar activity (c) shifting of occurrence peak during summer from post-midnight in low to pre-midnight in high solar activity periods (d) similarity of scintillation behaviour at these locations during winter and equinoxes but dissimilarity during summer. The solar activity response and magnetic effects indicate that the scintillations at the anomaly crest region in winter and equinox, particularly during high solar activity periods, are of equatorial origin while the summer events may be of local or mid-latitude origin.     

Preliminary results from very long period data collected by a broad band digital seismic station

Preliminary analysis of seismograms recorded by a wide band high dynamic range digital seismograph installed under a collaborative research programme between IPG, Paris and NGRI, Hyderabad, indicates that the crust and upper mantle structure below the Indian continent are characterized by high velocity up to a depth of 500 km. Both the group and phase velocities in the period range of 100–350s are found to be faster by 3–4% and 1–3% respectively compared with global models such as the preliminary reference earth model.