RS & GIS-based landslide susceptibility mapping of the Balason River basin,Darjeeling Himalaya,using logistic regression (LR) model

The present study deals with the preparation of a landslide susceptibility map of the Balason River basin, Darjeeling Himalaya, using a logistic regression model based on Geographic Information System and Remote Sensing. The landslide inventory map was prepared with a total of 295 landslide locations extracted from various satellite images and intensive field survey. Topographical maps, satellite images, geological, geomorphological, soil, rainfall and seismic data were collected, processed and constructed into a spatial database in a GIS environment. The chosen landslide-conditioning factors were altitude, slope aspect, slope angle, slope curvature, geology, geomorphology, soil, land use/land cover, normalised differential vegetation index, drainage density, lineament number density, distance from lineament, distance to drainage, stream power index, topographic wetted index, rainfall and peak ground acceleration. The produced landslide susceptibility map satisfied the decision rules and ?2 Log likelihood, Cox &; Snell R-Square and Nagelkerke R-Square values proved that all the independent variables were statistically significant. The receiver operating characteristic curve showed that the prediction accuracy of the landslide probability map was 96.10%. The proposed LR method can be used in other hazard/disaster studies and decision-making.     

Mobility centre-oriented urban regeneration: examining place value of railway stations

Urban regeneration involves the notion of reconstruction of places, where regeneration initiatives are undertaken to ameliorate the quality of physical and social spaces, accrue economic profitability of space, and finally encourage environmental sustainability. Railway stations all around the world have a very important role to play in contemporary urban regeneration strategies as places of both social and material interest. With the progress of the twentieth century several issues like rapidly growing population, seemingly relentless urbanisation, an alarming rate of vehicle emission, and consequent pollution emphasised railway stations as critical places with great potentials of infrastructure development for the optimised functioning of urban centres. Thus the huge value of railway stations and their adjacent land has been acknowledged since the last quarter of the previous century. This paper aims to analyse the place value of railway stations and their immediate neighbourhoods within the urban fabric of a city using a relevant theoretical concept i.e. the ‘Node-Place Model’. Simultaneously it also draws attention to the notion of (re)development of functional spaces in and around the railway stations as a dimension of contemporary urban regeneration strategies, with the help of some global examples. This paper thereby reveals that in the urban centres throughout the entire world the railway stations are progressively attaining the focal position within integrated transport and land use planning strategies, either under the larger concept of 'Transit-Oriented Development' (TOD) or more simply, with the label of (re)development programme. This paper will significantly contribute to the ability of spatial policymakers to direct the future of urban growth towards public transit stations so as to achieve sustainable urban development.

     

Phase transitions in ilvaite,a mixed-valence iron silicate I. A 57Fe Mössbauer study of magnetic order and spin frustration

Ilvaite, Ca(Fe²⁺,Fe³⁺)Fe²⁺Si₂O₈(OH) shows two magnetic phase transitions, which have been studied by Mössbauer spectroscopy within the temperature range 120–4 K. The continued charge localization between Fe²⁺ and Fe³⁺ ions in octahedral A-sites causes the Fe²⁺-Fe³⁺ interaction to be ferromagnetic, although the overall magnetic order is antiferromagnetic. The thermal evolution of the hyperfine fields at the Fe²⁺ (A) and Fe³⁺ (A) sites indicates B _hf: 328 and 523 kOe respectively at 0 K and T _N1= 116K. The corresponding values for Fe²⁺ (B) site are: B _hf 186 kOe and T _N2=36K. An additional hyperfine field exists at the Fe²⁺(B) site within the temperature range 116–36K due to short-range order induced by the spin ordering in A sites. The considerable difference between the two magnetic transition temperatures is due to spin frustration, because the Fe²⁺ (B) site occurs on a corner common between two triangles with respect to two sets of Fe²⁺ (A) and Fe³⁺ (A) sites with opposite spin directions.     

Land productivity assessment and mapping through integration of satellite and terrain slope data

Evaluation and mapping of spatial variations of land productivity is very important for effective landuse planning. The present study was undertaken in watershed of the Song river (Dehra Dun district, U.P.), for assessing and mapping land productivity using modified Storie Index following integrated approach. This approach utilizes soilscape information (derived from digital IRS-IA LISS-II data), soil characteristics (field observed and laboratory analysed) and terrain slope information (obtained from Survey of India topographical maps). The approach consists of preparation of Storie Index productivity rating factors such as: A (soil profile character), B (soil texture), X (soil physical and fertility conditions), and C (land slope), and computerised integration of these maps to generate land productivity map. The results indicate that in the watershed 30.6%, 19.6%, 12.2%, 11.8% and 18.8% areas have been found to be under good, fair, poor, very poor and not suitable, land productivity classes, respectively.     

Role of Inorganic Phosphate in the Phytoplankton Density of Hazaribag Lake,Hazaribag

Phosphorus is considered to be one of the most important factors in the maintenance of an aquatic eco-system. The study deals with the relation of available inorganic phosphate in water with phytoplankton abundance. The phytoplankton count ranged between 487 and 1711 indiv./l, while phosphate ranged between 0.18 and 1.23 mg/l. A maximum population of phytoplankton was observed in the month of January 1988 and a minimum observed in April 1988. The correlation between the changes in phosphate concentration and phytoplankton abundance revealed an inverse relationship (r= ?0.0773, P>0.05), and the regression is expressed by Y = 370 + 755 (x), indicating its link in the cycle of autotrophs though not significantly.     

Selection of spectral band combination for land cover/land use classification using a brightness value overlapping index (BVOI)

A simply defined, accurate and efficient criterion of selecting a spectral-band combination for improved land use/land cover classification using remote sensing data is discussed. Results indicate that Brightness Value Overlapping Index (BVOI) is very effective in measuring the degree of overlap in brightness values among land cover types and in selecting suitable spectral-band combination for landuse classification. The results of BVOI are also compared with the results of another band-combination selecting index - Optimum Index Factor (OIF).     

Temperature variation in the mesosphere during solar eclipse

Rocket-borne observations of the extinction of solar hydrogen Lyman-alpha radiation made during the solar eclipses of 20 May 1966 at Karistos for normal and 44% visibility and of 7 March 1970 at East Quoddy for normal, 10% and 0.6% visibility have been used to study the variation of temperature in the mesosphere during these events. It is seen that near the mesopause the decrease of temperature at Karistos is by 20° K for 44% visibility and at East Quoddy by 100° K for 0.6% visibility. Possible causes of these temperature variationsvis-a-vis molecular oxygen and pressure variations have been briefly discussed.     

Advective heat transfer and fabric development in a shallow crustal intrusive granite — the case of Proterozoic Vellaturu granite,south India

Syntectonic plutons emplaced in shallow crust often contain intermediate-to low-temperature deformation microstructures but lack a high-temperature, subsolidus deformation fabric, although the relict magmatic fabric is preserved. The Proterozoic Vellaturu granite emplaced at the eastern margin of the northern Nallamalai fold belt, south India during the late phase of regional deformation has a common occurrence of intermediate-to low-temperature deformation fabric, superimposed over magmatic fabric with an internally complex pattern. But high-T subsolidus deformation microstructure and fabric are absent in this pluton. The main crystal plastic deformation and fluid enhanced reaction softening was concentrated along the margin of the granite body. Resulting granite mylonites show Y-maximum c-axis fabric in completely recrystallized quartz ribbonds, dynamic recrystallization of perthites, and myrmekite indicative of fabric development under intermediate temperature (∼ 500–400°C). The weakly-deformed interior shows myrmekite, feldspar microfracturing and limited bulging recrystallization of quartz. The abundance of prism subgrain boundaries is indicative of continuing deformation through low-temperature (∼ 300°C). The relative rates of cooling influenced by advective heat transfer and deformation of the pluton seem to control the overall subsolidus fabric development. The rapid advective heat transfer from the interior in the early stages of subsolidus cooling was followed by slow cooling through intermediate temperature window as a well-developed phyllosilicate rich mylonitic skin around the granite body slowed down conductive heat loss. Low-T crystal plastic deformation of quartz was effected at a late stage of cooling and deformation of the shallow crustal granite body emplaced within the greenschist facies Nallamlai rocks.     

A possible origin of viscosity in Keplerian accretion disks due to secondary perturbation: Turbulent transport without magnetic fields

The origin of hydrodynamic turbulence in rotating shear flow is a long standing puzzle.Resolving it is especially important in astrophysics when the flow's angular momentum profile is Keplerian which forms an accretion disk having negligible molecular viscosity.Hence,any viscosity in such systems must be due to turbulence,arguably governed by magnetorotational instability,especially when temperature T ≥10 5.However,such disks around quiescent cataclysmic variables,protoplanetary and star-forming disks,and t...