A simple model for the evolution of supermassive black holes and the quasar population

An empirically motivated model is presented for accretion-dominated growth of supermassive black holes (SMBH) in galaxies, and the implications are studied for the evolution of the quasar population in the Universe. We investigate the core aspects of the quasar population, including space density evolution, evolution of the characteristic luminosity, plausible minimum masses of quasars, the mass function of SMBH and their formation epoch distribution. Our model suggests that the characteristic luminosity in the quasar luminosity function arises primarily as a consequence of a characteristic mass scale above which there is a systematic separation between the black hole and the halo merging rates. At lower mass scales, black hole merging closely tracks the merging of dark haloes. When combined with a declining efficiency of black hole formation with redshift, the model can reproduce the quasar luminosity function over a wide range of redshifts. The observed space density evolution of quasars is well described by formation rates of SMBH above  ∼10⁸  M_⊙  . The inferred mass density of SMBH agrees with that found independently from estimates of the SMBH mass function derived empirically from the quasar luminosity function.     

Applications of variogram modeling to electrical resistivity data for the occurrence and distribution of saline groundwater in Domail Plain,northwestern Himalayan fold and thrust belt,Pakistan

This paper studies electrical resistivity dataset acquired for a groundwater study in the Domail Plain in the northwestern Himalayan section of Pakistan. Through a combination of geostatistical analysis, geophysical inversion and visualization techniques, it is possible to re-model and visualize the single dimension resistivity data into 2D and 3D space. The variogram models are utilized to extend the interpretation of the data and to distinguish individual lithologic units and the occurrence of saline water within the subsurface. The resistivity data has been calibrated with the lithological logs taken from the available boreholes. As such the alluvial system of the Domail Plain has formed during episodes of local tectonic activity with fluvial erosion and deposition yielding coarse sediments with high electrical resistivities near to the mountain ranges and finer sediments with medium to low electrical resistivities which tend to settle in the basin center. Thus a change is depositional setting happened from basin lacustrine environment to flash flooding during the Himalayan orogeny. The occurrence of rock salt in the northern mountains has imparted a great influence on the groundwater quality of the study area. The salt is dissolved by water which infiltrates into the subsurface through the water channels. Variogram aided gridding of resistivity data helps to identify the occurrence and distribution of saline water in the subsurface.     

Comparison of Monsoonal change of water quality parameters between 1983 and 2008 in a tropical estuary in Northeastern India: role of phytoplankton and community metabolism

Ongoing climate change and anthropogenic activities are introducing stressors that affect the structure and function of coastal ecosystems. This paper focuses on the fluvial fluxes and estuarine transport of nutrients from a tropical river (Mahanadi River) in Northeastern India and compares select nutrient and water quality parameters between 1983 and 2008. This estuary acts as a perennial source of CO₂ with a net annual flux to the atmosphere of about 135 tons. The non‐conservative fluxes showed a net annual removal of 650 and 140 tons of phosphorus and nitrogen from the water column, respectively. Negative biogeochemical feedbacks that decreased the availability of N and P in 2008 relative to 1983 levels indicate major changes in biogeochemical responses towards fluvial fluxes of nutrient.     

Characterisation of respirable dust exposure of different category of workers in Jharia Coalfields

This paper presents dust exposure study of 69 workers engaged in 11 categories of jobs over seven coalmines of Jharia Coalfields. Dust samples were analysed for dust concentration, maximum exposure limit (MEL), free silica and other minerals present, and particle size and shape. Study reveals that workers engaged in vicinity of coal/rock cutting operation, are exposed to higher dust concentration (50% samples exceeding MEL), and contain more fine particles (d ₅₀ < 5 μm) with sharp edges. Samples exceeding MEL are classified as high-risk category which needs special attention for taking preventive and protective measure like use of personal protective equipments, job rotation and reduction in dust generation through engineering control using appropriate technology of dust suppression and dust extraction as per their applicability. The study also suggests presence of kaolinite and asbestos along with quartz which make the dust more harmful in nature necessitating further investigation and careful control measures.     

腾格里沙漠盐湖氯同位素地球化学特征

δ~(37)Cl值可以用来指示盐湖演化过程中卤水的蒸发浓缩程度、可能的补给来源和控制因素,本文对腾格里沙漠地区12个代表性盐湖卤水样品开展了氯同位素组成研究.结果表明,研究区内沙漠盐湖卤水的δ~(37)Cl值变化范围为-0.10‰~1.36‰,平均值为0.55‰;其中,硫酸钠亚型卤水的δ~(37)Cl值范围为-0.10‰~1.36‰(平均值为0.56‰),硫酸镁亚型卤水的δ~(37)Cl值范围为0.14‰~0.82‰(平均值为0.48‰).对比柴达木盆地现代盐湖分析数据,发现区内沙漠盐湖的δ~(37)Cl平均值明显大于柴达木盆地盐湖的δ~(37)Cl平均值,并且,硫酸钠亚型卤水δ~(37)Cl最高,硫酸镁亚型卤水次之,氯化物型卤水最小.基于不同盐湖地下水咸化程度以及盐湖卤水中δ~(37)Cl值与Br/Cl系数关系的研究,揭示了研究区东部和东北部盐湖可能受到第三系地层咸水的补给,而其他盐湖主要受蒸发浓缩作用影响.δ~(37)Cl值分布特征则显示,腾格里沙漠地区部分盐湖在形成过程中可能受到区域构造活动诱发的第三系深部水补给及水-岩作用等多重因素的影响.     

Non-standard structure formation scenarios

Observations on galactic scales seem to be in contradiction with recent high resolution N-body simulations. This so-called cold dark matter (CDM) crisis has been addressed in several ways, ranging from a change in fundamental physics by introducing self-interacting cold dark matter particles to a tuning of complex astrophysical processes such as global and/or local feedback. All these efforts attempt to soften density profiles and reduce the abundance of satellites in simulated galaxy halos. In this contribution we are exploring the differences between a Warm Dark Matter model and a CDM model where the power on a certain scale is reduced by introducing a narrow negative feature (`dip'). This dip is placed in a way so as to mimic the loss of power in the WDM model: both models have the same integrated power out to the scale where the power of the Dip model rises to the level of the unperturbed CDM spectrum again. Using N-body simulations we show that that the new Dip model appears to be a viable alternative to WDM while being based on different physics: where WDM requires the introduction of a new particle species the Dip stems from anon-standard inflationary period. If we are looking for an alternative to the currently challenged standard ΛCDM structure formation scenario, neither the ΛWDM nor the new Dip model can be ruled out with respect to the analysis presented in this contribution. They both make very similar predictions and the degeneracy between them can only be broken with observations yet to come. This revised version was published online in August 2006 with corrections to the Cover Date.     

Geomorphic control on the formation of mixed layer clays by progressive degradation of biotite: A case study from Jutulsessen Gjelsvikfjella,East Antarctica

Eleven glacial sediment samples collected from different elevation of Jutulsessen Nunatak, Gjelsvikfjella of East Antarctica were studied for the clay mineralogical analysis using X-ray diffraction technique. The result shows prominent peak at 10, and 3.34 Å suggesting the presence of biotite possibly derived from the catchment where biotite rich granite gneisses are exposed. The detailed investigation on the shape of biotite peak of certain samples shows the signs of alteration of biotite in to a mixed layer containing tri-octahedral smectite (low charge vermiculite). The presence of mixed layer along with the biotite is found to be associated with the samples of lower geomorphic level. The progressive alteration of clay sized biotite to form a mixed layer in the lower horizons of Jutulsessen Nunatak is probably due to the periodic accumulation of melt-water during the austral summer.