Geomorphological study of sundarban deltaic estuary

Study of landforms in Sundarbans deltaic estuary is necessary in regular basis due to its importance and impact on ecology, climate and economy. Remote sensing has proved as an important tool to study this. Multi-temporal satellite data helps to delineate the various geomorphic classes in different time domain and also provide inputs to study the coastal erosion and accretion. Finer spatial and better temporal resolution will be an added adventure for this kind of study.     

Deleterious effects of Malathion on survivality and growth of the fingerlings of Channa punctatus (BLOCH.), a freshwater murrel

The LC₅₀ of Malathion for Channu punctatus is determined for 24… 96 h of exposure as 10.95… 3.22 mg/l. At exposure to 2.5 mg./l Malathion, growth–measured by increase in weight–is significantly reduced from the 19th day and reduced by 10 % till the 31st day. During the same period of time, the RNA and protein contents of the muscle is lowered by 10 and 15 %, respectively, as compared with the control. In addition to an acute toxic effect, in sublethal concentrations Malathion has also pronounced effects on growth and metabolism.     

Probing molecular and isotopic features of meteoritic insoluble organic matter by solid‐state nuclear magnetic resonance spectroscopy with sub‐milligram sample

We recorded one‐ and two‐dimensional solid‐state nuclear magnetic resonance spectra of meteoric insoluble organic matter with unprecedented sensitivity and resolution permitting us to reveal unambiguous spectroscopic fingerprints relevant to its molecular and isotopic features. Two‐dimensional ¹H‐¹H and ¹H‐¹³C correlation experiments have unveiled the spatial proximity between aliphatic and aromatic groups proving a highly branched character of a rigid macromolecular network composed of short aliphatic chains linking together small aromatic units. One‐dimensional ²H and two‐dimensional ¹H‐²H correlation spectroscopy delivered evidence of significant reduction in the deuterium enrichment of aromatic species relevant to interstellar processes, proto‐planetary disk chemistry, and to determining the origin of the meteoritic insoluble organic matter. The experimental approach developed in this work opens new perspectives for systematic and nondestructive analysis at the molecular level of meteoritic insoluble organic matter even with a very small amount of sample from some particularly rare chondrites.     

Three-dimensional velocity measurements around bridge piers in gravel bed

The experimental results of time average velocity components measured around circular pier models during transient scour stage using acoustic Doppler velocimeter are shown for flow pattern and turbulence characteristics. Totally, four experiments were performed under clear water scour conditions in a model of gravel bed stream. Four circular pier models of diameter 6.6, 8.4, 11.5, and 13.5?cm were used for this study. Detailed controlled measurements on velocity components, and turbulence intensities near the pier and in scour hole at 0° and 180° plane are shown. Flow structure around a pier model in the presence of a scoured region was compared with the flow structure similarly noticed around all pier model runs by utilizing the observations taken at 0° and 180° plane from flow axis. Size of the primary vortex at 0° plane with largest diameter pier model in place (R4 run) is found to be maximum and was approximately 61% larger than that for smallest diameter pier model in place (R1 run). The time-averaged velocity components of turbulence intensities plots at 0° and 180° planes are also presented around each pier.     

Systematic analysis of low/hard state RXTE spectra of GX 339–4 to constrain the geometry of the system

One of the popular models for the low/hard state of black hole binaries is that the standard accretion disk is truncated and the hot inner region produces, via Comptonization, hard X-ray flux.This is supported by the value of the high energy photon index, which is often found to be small,～ 1.7( 2), implying that the hot medium is starved of seed photons. On the other hand, the suggestive presence of a broad relativistic Fe line during the hard state would suggest that the accretion disk is not truncated but extends all the way to the innermost stable circular orbit. In such a case, it is a puzzle why the hot medium would remain photon starved. The broad Fe line should be accompanied by a broad smeared reflection hump at ～ 30 ke V and it may be that this additional component makes the spectrum hard and the intrinsic photon index is larger, i.e. 2. This would mean that the medium is not photon deficient, reconciling the presence of a broad Fe line in the observed hard state. To test this hypothesis,we have analyzed the RXTE observations of GX 339–4 from the four outbursts during 2002–2011 and identify observations when the system was in the hard state and showed a broad Fe line. We have then attempted to fit these observations with models, which include smeared reflection, to understand whether the intrinsic photon index can indeed be large. We find that, while for some observations the inclusion of reflection does increase the photon index, there are hard state observations with a broad Fe line that have photon indices less than 2.     

Search for and study of photometric variability in magnetic white dwarfs

We report the results of photometric observations of a number of magnetic white dwarfs in order to search for photometric variability in these stars. These V-band observations revealed significant variability in the classical highly magnetized white dwarf GRW+70?8247 with a likely period from several days to several dozen days and a half-amplitude of about 0_. ^m 04. Our observations also revealed the variability of the well-known white dwarf GD229. The half amplitude of its photometric variability is equal to about 0_. ^m 005, and the likely period of this degenerate star lies in the 10–20 day interval. This variability is most likely due to the rotation of the stars considered.We also discuss the peculiarities of the photometric variability in a number of other white dwarfs. We present the updated “magnetic field–rotation period” diagram for the white dwarfs.     

Switch in chemical weathering caused by the mass balance variability in a Himalayan glacierized basin: a case of Chhota Shigri Glacier

Long-term data (2003–2015) on meltwater chemistry, mass balance and discharge of a benchmark glacier (Chhota Shigri Glacier, India) were studied to determine any association between these variables. To infer the factors governing the alteration of chemical weathering processes in glacierized basins, multi-annual records of the hydrochemical indices (Ca²⁺+Mg²⁺/Na⁺+K⁺) and the C-ratio were also examined. A succession of negative mass balance years has resulted in a decline in solute concentrations in the runoff, as discharge has increased. The (Ca²⁺+Mg²⁺/Na⁺+K⁺) and C-ratio are highest during periods of negative annual mass balance, when the spatial extent of the channelized drainage system increases. Conversely, these ratios are lowest in positive mass balance years, when the spatial extent of the channelized drainage system decreases, and chemical weathering in the distributed drainage system becomes more dominant. This paper is the first to show the inter-annual linkages between meltwater chemistry, mass balance and discharge for a valley glacier.     

Study of indices for drought characterization in KBK districts in Orissa (India)

Drought is a temporary, random and regional climatic phenomenon, originating due to lack of precipitation leading to water deficit and causing economic loss. Success in drought alleviation depends on how well droughts are defined and their severity quantified. A quantitative definition identifies the beginning, end, spatial extent and the severity of drought. Among the available indices, no single index is capable of fully describing all the physical characteristics of drought. Therefore, in most cases it is useful and necessary to consider several indices, examine their sensitivity and accuracy, and investigate for correlation among them. In this study, the geographical information system‐based Spatial and Time Series Information Modeling (SPATSIM) and Daily Water Resources Assessment Modeling (DWRAM) software were used for drought analysis on monthly and daily bases respectively and its spatial distribution in both dry and wet years. SPATSIM utilizes standardized precipitation index (SPI), effective drought index (EDI), deciles index and departure from long‐term mean and median; and DWRAM employs only EDI. The analysis of data from the Kalahandi and Nuapada districts of Orissa (India) revealed that (a) droughts in this region occurred with a frequency of once in every 3 to 4 years, (b) droughts occurred in the year when the ratio of annual rainfall to potential evapotranspiration (Pae/PET) was less than 0·6, (c) EDI better represented the droughts in the area than any other index; (d) all SPI, EDI and annual deviation from the mean showed a similar trend of drought severity. The comparison of all indices and results of analysis led to several useful and pragmatic inferences in understanding the drought attributes of the study area. Copyright © 2007 John Wiley & Sons, Ltd.