We report the serendipitous detection of a giant X-ray flare from the source 2XMM J043527.2-14430... more We report the serendipitous detection of a giant X-ray flare from the source 2XMM J043527.2-144301 during an XMM-Newton observation of the high latitude molecular cloud MBM20. The source has not been previously studied at any wavelength. The X-ray flux increases by a factor of more than 52 from quiescent state to peak of flare. A 2MASS counterpart has been identified (2MASS J04352724-1443017), and near-infrared colors reveal a spectral type of M8-M8.5 and a distance of (67 ± 13) pc, placing the source in front of MBM20. Spectral analysis and source luminosity are also consistent with this conclusion. The measured distance makes this object the most distant source (by about a factor of 4) at this spectral type detected in X-rays. The X-ray flare was characterized by peak X-ray luminosity of ∼ 8.2 × 10 28 erg s −1 and integrated X-ray energy of ∼ 2.3 × 10 32 erg. The flare emission has been characterized with a 2-temperature model with temperatures of ∼10 and 46 MK (0.82 and 3.97 keV), and is dominated by the higher temperature component.
Publications of the Astronomical Society of Japan, 2012
Suzaku performed observations of 3 regions in and around the Shapley supercluster: a region locat... more Suzaku performed observations of 3 regions in and around the Shapley supercluster: a region located between A3558 and A3556, at ∼ 0.9 times the virial radii of both clusters, and two other regions at 1 • and 4 • away from the first pointing. The 4 •-offset observation was used to evaluate the Galactic foreground emission. We did not detect significant redshifted Oxygen emission lines (O VII and O VIII) in the spectra of all three pointings, after subtracting the contribution of foreground and background emission. An upper limit for the redshifted O VIII Kα line intensity of the warm-hot intergalactic medium (WHIM) is 1.5 × 10 −7 photons s −1 cm −2 arcmin −2 , which corresponds to an overdensity of ∼ 380 (Z/0.1 Z ⊙) −1/2 (L/3 Mpc) −1/2 , assuming T = 3 × 10 6 K. We found excess continuum emission in the 1 •-offset and on-filament regions, represented by thermal models with kT ∼ 1 keV and ∼ 2 keV, respectively. The redshifts of both 0 and that of the supercluster (0.048) are consistent with the observed spectra. The ∼ 1 keV emission can be also fitted with Ne-rich Galactic (zero redshift) thin thermal emission. Radial intensity profile of 2 keV component suggests contribution from A3558 and A3556, but with significant steepening of the intensity slope in the outer region of A3558. Finally, we summarized the previous Suzaku search for the WHIM and discussed the feasibility of constraining the WHIM. An overdensity of < 400 can be detectable using O VII and O VIII emission lines in a range of 1.4 ×10 6 K < T < 5 ×10 6 K or a continuum emission in a relatively high temperature range T > 5 ×10 6 K with the Suzaku XIS. The non detection with Suzaku suggests that typical line-of-sight average overdensity is < 400.
The channel proteins belonging to the major intrinsic proteins (MIP) superfamily are diverse and ... more The channel proteins belonging to the major intrinsic proteins (MIP) superfamily are diverse and are found in all forms of life. Water-transporting aquaporin and glycerol-specific aquaglyceroporin are the prototype members of the MIP superfamily. MIPs have also been shown to transport other neutral molecules and gases across the membrane. They have internal homology and possess conserved sequence motifs. By analyzing a large number of publicly available genome sequences, we have identified more than 1000 MIPs from diverse organisms. We have developed a database MIPModDB which will be a unified resource for all MIPs. For each MIP entry, this database contains information about the source, gene structure, sequence features, substitutions in the conserved NPA motifs, structural model, the residues forming the selectivity filter and channel radius profile. For selected set of MIPs, it is possible to derive structure-based sequence alignment and evolutionary relationship. Sequences and structures of selected MIPs can be downloaded from MIPModDB database which is freely available at http://bioinfo .iitk.ac.in/MIPModDB.
Background: Members of major intrinsic proteins (MIPs) include water-conducting aquaporins and gl... more Background: Members of major intrinsic proteins (MIPs) include water-conducting aquaporins and glycerol-transporting aquaglyceroporins. MIPs play important role in plant-water relations. The model plants Arabidopsis thaliana, rice and maize contain more than 30 MIPs and based on phylogenetic analysis they can be divided into at least four subfamilies. Populus trichocarpa is a model tree species and provides an opportunity to investigate several tree-specific traits. In this study, we have investigated Populus MIPs (PtMIPs) and compared them with their counterparts in Arabidopsis, rice and maize. Results: Fifty five full-length MIPs have been identified in Populus genome. Phylogenetic analysis reveals that Populus has a fifth uncharacterized subfamily (XIPs). Three-dimensional models of all 55 PtMIPs were constructed using homology modeling technique. Aromatic/arginine (ar/R) selectivity filters, characteristics of loops responsible for solute selectivity (loop C) and gating (loop D) and group conservation of small and weakly polar interfacial residues have been analyzed. Majority of the non-XIP PtMIPs are similar to those in Arabidopsis, rice and maize. Additional XIPs were identified from database search and 35 XIP sequences from dicots, fungi, moss and protozoa were analyzed. Ar/R selectivity filters of dicots XIPs are more hydrophobic compared to fungi and moss XIPs and hence they are likely to transport hydrophobic solutes. Loop C is longer in one of the subgroups of dicot XIPs and most probably has a significant role in solute selectivity. Loop D in dicot XIPs has higher number of basic residues. Intron loss is observed on two occasions: once between two subfamilies of eudicots and monocot and in the second instance, when dicot and moss XIPs diverged from fungi. Expression analysis of Populus MIPs indicates that Populus XIPs don't show any tissue-specific transcript abundance. Conclusion: Due to whole genome duplication, Populus has the largest number of MIPs identified in any single species. Non-XIP MIPs are similar in all four plant species considered in this study. Small and weakly polar residues at the helix-helix interface are group conserved presumably to maintain the hourglass fold of MIP channels. Substitutions in ar/R selectivity filter, insertion/deletion in loop C, increasing basic nature of loop D and loss of introns are some of the events occurred during the evolution of dicot XIPs.
We present here the analysis of X-rays point sources detected in several observations available i... more We present here the analysis of X-rays point sources detected in several observations available in the XMM-Newton public archive. We focused, in particular, on energies below 1 keV, which are of particular relevance to the understanding of the Diffuse X-ray Background. The average field of all the exposures is 0.09 deg −2. We reached an average flux sensitivity of 5.8 × 10 −16 erg s −1 cm −2 in the soft band (0.5-2.0 keV) and 2.5 × 10 −16 erg s −1 cm −2 in the very soft band (0.4-0.6 keV). In this paper we discuss the logN-logS results, the contribution to the integrated X-ray sky flux, and the properties of the cumulative spectrum from all sources. In particular, we found an excess flux at around 0.5 keV in the composite spectrum of faint sources. The excess seems to be a general property of all the fields observed suggesting an additional class of weak sources is contributing to the X-ray emission at these energies. Combining our results with previous investigations we have also quantified the contribution of the individual components of the diffuse X-ray Background in the 3/4 keV band.
International Journal of Advanced Remote Sensing and GIS, 2017
In the present study, Morphometric analysis has been conducted using Geographical Information Sys... more In the present study, Morphometric analysis has been conducted using Geographical Information System (GIS) techniques to assess the geo-hydrological characteristics of watersheds (Mod nadi, Sapan nadi, and Negri nadi) of Mahi river basin (Jhabua region). The basin is characterized by dendritic drainage pattern. The region is semi-arid (Agro-ecological zone of India), which belong to highly drought prone zone and degraded lands. Morphometric analysis of drainage system is an important factor of characterization of watershed. It furnishes the advantageous parameters for the ground water potential zone assessment, identification of places for water harvesting structure, water resource management and geological nature of the river system. GIS techniques has been used for assessing various morphometric characteristics of the drainage basin, as they proved to be very efficient and a powerful tool for the manipulation and analysis of spatial information mainly for the feature identificatio...
We report the serendipitous detection of a giant X-ray flare from the source 2XMM J043527.2-14430... more We report the serendipitous detection of a giant X-ray flare from the source 2XMM J043527.2-144301 during an XMM-Newton observation of the high latitude molecular cloud MBM20. The source has not been previously studied at any wavelength. The X-ray flux increases by a factor of more than 52 from quiescent state to peak of flare. A 2MASS counterpart has been identified (2MASS J04352724-1443017), and near-infrared colors reveal a spectral type of M8-M8.5 and a distance of (67 ± 13) pc, placing the source in front of MBM20. Spectral analysis and source luminosity are also consistent with this conclusion. The measured distance makes this object the most distant source (by about a factor of 4) at this spectral type detected in X-rays. The X-ray flare was characterized by peak X-ray luminosity of ∼ 8.2 × 10 28 erg s −1 and integrated X-ray energy of ∼ 2.3 × 10 32 erg. The flare emission has been characterized with a 2-temperature model with temperatures of ∼10 and 46 MK (0.82 and 3.97 keV), and is dominated by the higher temperature component.
Publications of the Astronomical Society of Japan, 2012
Suzaku performed observations of 3 regions in and around the Shapley supercluster: a region locat... more Suzaku performed observations of 3 regions in and around the Shapley supercluster: a region located between A3558 and A3556, at ∼ 0.9 times the virial radii of both clusters, and two other regions at 1 • and 4 • away from the first pointing. The 4 •-offset observation was used to evaluate the Galactic foreground emission. We did not detect significant redshifted Oxygen emission lines (O VII and O VIII) in the spectra of all three pointings, after subtracting the contribution of foreground and background emission. An upper limit for the redshifted O VIII Kα line intensity of the warm-hot intergalactic medium (WHIM) is 1.5 × 10 −7 photons s −1 cm −2 arcmin −2 , which corresponds to an overdensity of ∼ 380 (Z/0.1 Z ⊙) −1/2 (L/3 Mpc) −1/2 , assuming T = 3 × 10 6 K. We found excess continuum emission in the 1 •-offset and on-filament regions, represented by thermal models with kT ∼ 1 keV and ∼ 2 keV, respectively. The redshifts of both 0 and that of the supercluster (0.048) are consistent with the observed spectra. The ∼ 1 keV emission can be also fitted with Ne-rich Galactic (zero redshift) thin thermal emission. Radial intensity profile of 2 keV component suggests contribution from A3558 and A3556, but with significant steepening of the intensity slope in the outer region of A3558. Finally, we summarized the previous Suzaku search for the WHIM and discussed the feasibility of constraining the WHIM. An overdensity of < 400 can be detectable using O VII and O VIII emission lines in a range of 1.4 ×10 6 K < T < 5 ×10 6 K or a continuum emission in a relatively high temperature range T > 5 ×10 6 K with the Suzaku XIS. The non detection with Suzaku suggests that typical line-of-sight average overdensity is < 400.
The channel proteins belonging to the major intrinsic proteins (MIP) superfamily are diverse and ... more The channel proteins belonging to the major intrinsic proteins (MIP) superfamily are diverse and are found in all forms of life. Water-transporting aquaporin and glycerol-specific aquaglyceroporin are the prototype members of the MIP superfamily. MIPs have also been shown to transport other neutral molecules and gases across the membrane. They have internal homology and possess conserved sequence motifs. By analyzing a large number of publicly available genome sequences, we have identified more than 1000 MIPs from diverse organisms. We have developed a database MIPModDB which will be a unified resource for all MIPs. For each MIP entry, this database contains information about the source, gene structure, sequence features, substitutions in the conserved NPA motifs, structural model, the residues forming the selectivity filter and channel radius profile. For selected set of MIPs, it is possible to derive structure-based sequence alignment and evolutionary relationship. Sequences and structures of selected MIPs can be downloaded from MIPModDB database which is freely available at http://bioinfo .iitk.ac.in/MIPModDB.
Background: Members of major intrinsic proteins (MIPs) include water-conducting aquaporins and gl... more Background: Members of major intrinsic proteins (MIPs) include water-conducting aquaporins and glycerol-transporting aquaglyceroporins. MIPs play important role in plant-water relations. The model plants Arabidopsis thaliana, rice and maize contain more than 30 MIPs and based on phylogenetic analysis they can be divided into at least four subfamilies. Populus trichocarpa is a model tree species and provides an opportunity to investigate several tree-specific traits. In this study, we have investigated Populus MIPs (PtMIPs) and compared them with their counterparts in Arabidopsis, rice and maize. Results: Fifty five full-length MIPs have been identified in Populus genome. Phylogenetic analysis reveals that Populus has a fifth uncharacterized subfamily (XIPs). Three-dimensional models of all 55 PtMIPs were constructed using homology modeling technique. Aromatic/arginine (ar/R) selectivity filters, characteristics of loops responsible for solute selectivity (loop C) and gating (loop D) and group conservation of small and weakly polar interfacial residues have been analyzed. Majority of the non-XIP PtMIPs are similar to those in Arabidopsis, rice and maize. Additional XIPs were identified from database search and 35 XIP sequences from dicots, fungi, moss and protozoa were analyzed. Ar/R selectivity filters of dicots XIPs are more hydrophobic compared to fungi and moss XIPs and hence they are likely to transport hydrophobic solutes. Loop C is longer in one of the subgroups of dicot XIPs and most probably has a significant role in solute selectivity. Loop D in dicot XIPs has higher number of basic residues. Intron loss is observed on two occasions: once between two subfamilies of eudicots and monocot and in the second instance, when dicot and moss XIPs diverged from fungi. Expression analysis of Populus MIPs indicates that Populus XIPs don't show any tissue-specific transcript abundance. Conclusion: Due to whole genome duplication, Populus has the largest number of MIPs identified in any single species. Non-XIP MIPs are similar in all four plant species considered in this study. Small and weakly polar residues at the helix-helix interface are group conserved presumably to maintain the hourglass fold of MIP channels. Substitutions in ar/R selectivity filter, insertion/deletion in loop C, increasing basic nature of loop D and loss of introns are some of the events occurred during the evolution of dicot XIPs.
We present here the analysis of X-rays point sources detected in several observations available i... more We present here the analysis of X-rays point sources detected in several observations available in the XMM-Newton public archive. We focused, in particular, on energies below 1 keV, which are of particular relevance to the understanding of the Diffuse X-ray Background. The average field of all the exposures is 0.09 deg −2. We reached an average flux sensitivity of 5.8 × 10 −16 erg s −1 cm −2 in the soft band (0.5-2.0 keV) and 2.5 × 10 −16 erg s −1 cm −2 in the very soft band (0.4-0.6 keV). In this paper we discuss the logN-logS results, the contribution to the integrated X-ray sky flux, and the properties of the cumulative spectrum from all sources. In particular, we found an excess flux at around 0.5 keV in the composite spectrum of faint sources. The excess seems to be a general property of all the fields observed suggesting an additional class of weak sources is contributing to the X-ray emission at these energies. Combining our results with previous investigations we have also quantified the contribution of the individual components of the diffuse X-ray Background in the 3/4 keV band.
International Journal of Advanced Remote Sensing and GIS, 2017
In the present study, Morphometric analysis has been conducted using Geographical Information Sys... more In the present study, Morphometric analysis has been conducted using Geographical Information System (GIS) techniques to assess the geo-hydrological characteristics of watersheds (Mod nadi, Sapan nadi, and Negri nadi) of Mahi river basin (Jhabua region). The basin is characterized by dendritic drainage pattern. The region is semi-arid (Agro-ecological zone of India), which belong to highly drought prone zone and degraded lands. Morphometric analysis of drainage system is an important factor of characterization of watershed. It furnishes the advantageous parameters for the ground water potential zone assessment, identification of places for water harvesting structure, water resource management and geological nature of the river system. GIS techniques has been used for assessing various morphometric characteristics of the drainage basin, as they proved to be very efficient and a powerful tool for the manipulation and analysis of spatial information mainly for the feature identificatio...
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