The maximum limit of the density variation parameter λ for a stable neutron star

A static spherically-symmetric model, based on an exact solution of Einstein's equation, gives the permissible matter density 2×10¹⁴ g cm^–3. If we use the change in the ratio of central density to the radiusr=a (i.e., central density per unit radius (₀/a), we call it radius density) minimum, we have estimated the upper limit of the density variation parameter () and minimum mass limit of a superdense star like a neutron star. This limit gives an idea of the domain where the neutron abundance with negligible number of electrons and protons (may be treated as pure neutrons) and equilibrium in neutrons begins.     

Light curves of SZ Piscium for 1977 and 1978

We present a relatively completeV-band light curve of SZ Psc for 1978 and a partial light curve for 1977. From the 1978 light curve we derive a new time of primary minimum, JD2443823.674±0.001, and a Russell-model solution,i=75°.8±0°.1,r _h =0.096±0.003,r _c =0.351±0.001, andL _h =0.253±0.002. The hotter component of this system is a F5-8 main-sequence star, the cooler component a K3-4 star well above the main sequence. The system is detached with the larger component filling only 82% of its Roche lobe. The distortion wave in this RS CVn-type binary seems not to migrate regularly as do those in many other such systems, but rather seems to change phase and amplitude more erratically. Between 1977 and 1978 its phase stayed practically constant while its amplitude decreased by a factor of three. We discuss the implications of this behavior for the spot model of RS CVn-type activity. We find that the traditional comparison star for SZ Psc, HD 219018, is very likely a constant star contrary to a recent suggestion that it is variable. Its brightness and colors,V=7.705, (B-V)=0.628, and (V-I) _c =0.688, are those of a G2V star.Visiting Astronomer, Kitt Peak National Observatory, which is operated by AURA, Inc., under contract with the National Science Foundation, and Visiting Astronomer, Prarie Observatory, University of Illinois.     

Hyperspectral Remote Sensing Classifications: A Perspective Survey

Classification of hyperspectral remote sensing data is more challenging than multispectral remote sensing data because of the enormous amount of information available in the many spectral bands. During the last few decades, significant efforts have been made to investigate the effectiveness of the traditional multispectral classification approaches on hyperspectral data. Formerly extensively established conventional classification methods have been dominated by the advanced classification approaches and many pre‐processing techniques have been developed and incorporated in hyperspectral classification. A perspective survey of hyperspectral remote sensing classification approaches is presented here. It comprehensively highlights the taxonomy of major classification approaches reported during the last two decades and describes an experimental evaluation of a few major classification algorithms. Recent advancements in the development of classification approaches are also emphasized with a set of guidelines for achieving better classification performances.     

Land use/land cover dynamics in Umngot watershed of Meghalaya using geospatial tools

Meghalaya is a landlocked state where the progress of industrialization is very slow. Majority of the population (rural) depends on agriculture. Agriculture in the state is carried on in primitive ways with Jhumming prevailing in many parts. This practice is considered destructive as vast forest areas are cleared and burnt. Such areas are used for cultivation and left out. After a gap of few years (2–3 years as of now and 15–20 years in past) the area is revisited for cultivation without allowing to rejuvenate. The present work provides a status and trend of Land use land cover dynamics in parts (at watershed level) of Meghalaya. The geospatial tools have been used to assess (a) the changes in land use land cover since 1970s to 2005; (b) patch dynamics for understanding the degree of fragmentation; (c) changes along the terrain topography. Umngot watershed of Meghalaya is taken as experimental area, which is a representative of mid-altitudinal watershed particularly in the Jaintia hills district of Meghalaya.     

Downward continuation of (Vs)L profile in 1P (time-domain) with linear excitation using point electrodes. A short notet1

It is seen that the apparent chargeability (M_a)_L anomaly over a 2D graphite body splits into two distinct (V_s)_L anomalies which closely follow the apparent resistivity profile. This suggests that the electric field amplitude is distorted due to a superficial inhomogeneity creating a (V_s)_L anomaly, which bears no relation to the polarized body. The target depth obtained by continuation of such a profile is therefore, not acceptable.     

Change of river channel and bank erosion of the burhi dihing river (assam), assessed using remote sensing data and gis

The Burhi Dining river flows in a meandering course for about 220 km through alluvial plains of Assam including a short rocky and hilly tract in between. Sequential changes in the position of banklines of the river due to consistent bank erosion have been studied from Survey of India topographic maps of 1934 and 1972, and digital satellite data of 2001 and 2004 using GIS. Two broad kinds of changes have been observed, e.g. alteration of direction of flow due to neck cut-off and progressive gradual change of the meander bends that accounts for translational, lateral, rotational, extensional and other types of movement of the meander bends. Study of bankline shift due to the bank erosion has been carried out for the periods 1934–1972, 1972–2001, 2001–2004 and 1934–2004 at 13 segments spaced at 5′ longitude interval (average 15 km) as the river course trends nearly east to west. The amounts of the bank area lost due to erosion and gained due to sediment deposition are estimated separately. The total area eroded in both banks during 1934–1972 was more (26.796 km²) as compared to sediment deposition (19.273 km²), whereas total sediment deposition was more (34.61 km²) during 1972-2001 as compared to erosion (23.152 km²). Erosion was again more in 2001–2004 (7.568 km²) as compared to sediment deposition (2.493 km²). During the entire period (1934–2004) of study the overall erosion on the both banks was 31.169 km² and overall sediment deposition was 30.101 km². The highest annual rates of bank erosion as well as bank building of the river are 21055.47 m²/km in 2001–2004 and 9665.81 m²/km in 1972-2001, respectively. Similarly the highest average annual rates of erosion as well as sediment deposition in both banks are observed during 2001–2004 and 1972–2001, respectively. The hard rocks of the hilly tract situated in between result in development of entrenched meandering and this tract has suffered minimum bank erosion.     

Hydrogeology of limited aquifer in a granitic terrain

 Detailed hydrogeological studies in a granitic micro-watershed have been carried out to determine the extent, behavior, and characteristics of the aquifer. The study includes analysis of lithologs, drill time log, pumping tests, and slug tests. Realistic field conditions have been taken into account for characterizing the aquifer system. Slug tests were carried out to estimate aquifer parameters at the wells which could not sustain pumping. Received: 20 November 1997 · Accepted: 23 February 1998     

Strain analysis and stratigraphic status of Nongkhya,Sumer and Mawmaram conglomerates of Shillong basin,Meghalaya, India

Shillong basin, one of the Purana basins of the Indian peninsula is situated in the central and eastern parts of the Shillong plateau of NE India. Metasedimentary and metavolcanic rocks of the basin are of Mesoproterozoic age and lithostratigraphically belong to Shillong Group (erstwhile Shillong series) comprising Lower Metapelitic Formation (LMF) and Upper Quartzitic Formation (UQF). A long, persistent, faulted and tectonically attenuated conglomerate known as Nongkhya-Sumer-Mawmaram-conglomerate separates these two formations. In the present work, quantitative strain analyses of the pebbles of Sumer, Nongkhya and Mawmaram conglomerates of Ri-Bhoi and West Khasi Hills districts of Meghalaya are carried out using manual and computerized programmes. Eight different techniques for intrapebble, interpebble and bulk rock strain estimation are applied and results are compared systematically. Sumer and Mawmaram conglomerates bear the testimony of broadly flattening type of deformation (0 < k < 1) while Nongkhya conglomerate shows constriction type (1 < k < α). The change in strain ellipsoid shape from Nongkhya to Mawmaram area is accompanied by a change of fabric from S < L to L < S tectonites. Affinity of rotational strain is more in Nongkhya conglomerate as compared to Sumer and Mawmaram conglomerates. The compactness of pebbles is high in case of Nongkhya conglomerate and low to moderate in Sumer and Mawmaram conglomerates indicating high strain in Nongkhya conglomerate (northeastern part of Shillong basin) relative to Sumer and Mawmaram conglomerates (southwestern part of Shillong basin). Thus strain magnitude increases from SW to NE direction of the Shillong basin.     

Palaeomagnetism of metadolerite dykes and sills from Proterozoic Shillong basin,NE India: Implications related to the age and magmatism

The basement gneiss of the Shillong plateau and the overlying rocks of the Shillong basin have been dissected by a number of mafic dyke swarms represented by older Proterozoic dolerite dykes and sills named as Khasi greenstone and the younger set of Cretaceous dykes. The older dolerites dykes of Shillong basin are partly metamorphosed and have undergone low-grade metamorphism compared to the fresh unmetamorphosed Cretaceous dykes dominantly exposed in the BGC of West Garo hills region. The Khasi greenstones are tholeiitic in composition and range from basalt to basaltic andesite. Most of the metamorphosed mafic dykes indicate continental nature with some amount of overlapping oceanic tectonic setting. Palaeomagnetic study of the metadolerite dykes show a direction of magnetization of Dm=29, Im=38 (α₉₅ = 28.84; k = 48.33; N = 2) with a palaeolatitude of 21.3° N to the Indian sub-continent that clearly support the Proterozoic dyke/dyke swarm emplacement in the region. The magnetic carrier as inferred from IRM studies is magnetite in the range of psuedosingle to multi domain (MD) states with minor contribution from hematite.     

Retrieval and Validation of Chlorophyll-a Concentrations in the Coastal Waters Off Yanam and Kakinada (Godavari) Basin Along East Coast of India

In this study chlorophyll measurements were made during March 2012 in the estuarine waters of Off Kakinada and Yanam coast, Bay of Bengal onboard a coastal vessel. In-situ water samples and optical data was collected at 21 stations (surface to 150 m depth) using Underwater radiometer (Hyperpro-II). In-vivo chlorophyll profiles were collected using wet labs fluorometer integrated with underwater Hyperspectral radiometer. Chlorophyll-a concentrations were estimated using HPLC by collecting the water samples at each sampling location. And also chlorophyll-a concentrations were retrieved from the OCM-2 data of OCEANSAT-2 satellite, processed using SeaDAS v.6.2 with the available global ocean colour algorithms namely, OC2 and OC4V4. A total of 33 samples used covering all the stations for chlorophyll-a estimation, and surface water samples of all the stations only being used for direct comparison among chlorophyll concentrations of HPLC, in-situ (fluorometrically integrated to Hyperpro-II) and retrieved from OCM-2. A good correlation found between the Fluorometer derived and HPLC measured chlorophyll-a concentration with an R² value of 0.78. The relation between Chlorophyll-a concentration measured from HPLC and retrieved from OCM-2 (OC2 and OC4V4 algorithms) using SeaDASv.6.2 for 10 samples has been compared for validation and obtained an R² value of 0.6. Also comparisons done with the in-situ measured (fluorometer) Chlorophyll-a concentration with OCM-2 chlorophyll data (OC4-V4 and OC2 algorithms) and validation with 10 concurrent in-situ surface measurements showed a significant overestimation by OCM-2 at low chlorophyll-a concentrations and underestimation at high chlorophyll-a concentrations.