To explore the role of GTPases in endocytosis, we developed an assay using Xenopus oocytes inject... more To explore the role of GTPases in endocytosis, we developed an assay using Xenopus oocytes injected with recombinant proteins to follow the uptake of the fluid phase marker HRP. HRP uptake was inhibited in cells injected with GTPγS or incubated with aluminum fluoride, suggesting a general role for GTPases in endocytosis. Injection of Rab5 into oocytes, as well as Rab5:Q79L, a mutant with decreased GTPase activity, increased HRP uptake. Injection of Rab5:S34N, the dominant-negative mutant, inhibited HRP uptake. Injection of N-ethylmaleimide–sensitive factor (NSF) stimulated HRP uptake, and ATPase-defective NSF mutants inhibited HRP uptake when coinjected with Rab5:Q79L, confirming a requirement for NSF in endocytosis. Surprisingly, injection of Rab7:WT stimulated both uptake and degradation/activation of HRP. The latter appears to be due to enhanced transport to a late endosomal/prelysosomal degradative compartment that is monensin sensitive. Enhancement of uptake by Rab7 appears to ...
Non-minimally coupled global monopole or a Schwarzschild black hole that swallowed a global monop... more Non-minimally coupled global monopole or a Schwarzschild black hole that swallowed a global monopole at the center of a galaxy can correctly describe the observed flat rotation curve of galaxies without the need of dark matter. To become a viable alternative to dark matter the global monopole based model also needs to explain the other observations hinting for the existence of dark matter. Here we have studied weak gravitational lensing due to Schwarzchild space time with global monopole and compare with the findings of galaxy-galaxy weak lensing and also the lensing observations of the rich galaxy cluster Abell 370. We find that global monopole based model cannot describe the mentioned lensing observations without the presence of dark matter.
One of the main objectives of the Compressed Baryonic Matter (CBM) experiment scheduled to be hel... more One of the main objectives of the Compressed Baryonic Matter (CBM) experiment scheduled to be held at the Facility for Anti-proton and Ion Research (FAIR), is to investigate the properties of an extended QCD matter at high baryo-chemical potential and at moderate/low temperature [1]. It would be worthwhile to examine how the known observables behave as indicators of phase transition in a baryon rich environment expected at FAIR energies. One observable that can be related to such transition, is the event-to-event (e-to-e) fluctuations of conserved quantities like net-charge, netbaryon number and net-strangenes. The fluctuation measure of such variables are found to be sensitive to the critical point in the QCD phase diagram. Different moments of the distributions of these conserved quantities, can be connected to the thermodynamic susceptibility and to the correlation length of the matter constituting the intermediate ‘fireball’ created in high-energy heavy-ion collisions [2]. In th...
The Compressed Baryonic Matter (CBM) experiment [1] to be held at the Facility for antiproton and... more The Compressed Baryonic Matter (CBM) experiment [1] to be held at the Facility for antiproton and ion research (FAIR) is being designed to investigate the baryonic matter under extreme thermodynamic conditions. The hot and dense matter produced in this experiment will be rich in baryon number. It would be worthwhile to examine how the signatures proposed for identifying and characterizing a baryon free QGP like state behave in a baryon rich environment. Event-by-event fluctuation of net electrical charge and/or baryon number is one such indicator of the formation of the QGP, used and tested in RHIC and LHC heavy-ion experiments. One starts by defining the net charge Q = (N+ − N−) and the total charge Nch = (N+ +N−) where the quantities N+ and N − are respectively, the multiplicities of positively and negatively charged particles. For a QGP like state comprising of fractional charges, the net charge fluctuation will be significantly less compared to an ordinary hadronic gas state. To...
In this work, the spacetime geometry of the halo region in spiral galaxies is obtained considerin... more In this work, the spacetime geometry of the halo region in spiral galaxies is obtained considering the observed flat galactic rotation curve feature, invoking the Tully–Fisher relation and assuming the presence of cold dark matter in the galaxy. The gravitational lensing analysis is performed treating the so-obtained spacetime as a gravitational lens. It is found that the aforementioned spacetime as the gravitational lens can consistently explain the galaxy–galaxy weak gravitational lensing observations and the lensing observations of the well-known Abell 370 and Abell 2390 galaxy clusters.
A continuous wavelet analysis is performed for pattern recognition of the pseudorapidity density ... more A continuous wavelet analysis is performed for pattern recognition of the pseudorapidity density profile of singly charged particles produced in [Formula: see text]O+Ag/Br and [Formula: see text]S+Ag/Br interactions, each at an incident energy of [Formula: see text] GeV per nucleon in the laboratory system. The experiments are compared with a model prediction based on the ultra-relativistic quantum molecular dynamics (UrQMD). To eliminate the contribution coming from known source(s) of particle cluster formation like Bose–Einstein correlation (BEC), the UrQMD output is modified by “an algorithm that mimics the BEC as an after burner.” We observe that for both interactions particle clusters are found at same pseudorapidity locations at all scales. However, the cluster locations in the [Formula: see text]O+Ag/Br interaction are different from those found in the [Formula: see text]S+Ag/Br interaction. Significant differences between experiments and simulations are revealed in the wavel...
Abstract We have studied the charged particle density fluctuations in 16O+Ag(Br) and 32S+Ag(Br) i... more Abstract We have studied the charged particle density fluctuations in 16O+Ag(Br) and 32S+Ag(Br) interactions at 200A GeV incident energy in the laboratory frame by using the detrended methods. These methods can extract (multi)fractal properties of the underlying distributions after filtering out the average trend of fluctuations associated. Multifractal parameters obtained from data analysis are systematically compared with event samples generated by the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, where Bose–Einstein correlation (BEC) effect is mimicked via a charge reassignment algorithm implemented as an after burner. Both the experimental and the simulated data are subjected to two different statistical techniques namely the multifractal detrended fluctuation analysis (MFDFA) and multifractal detrended moving average (MFDMA) analysis. The results indicate that for both the interactions considered the pseudorapidity distributions of the shower tracks are multifractal in nature. Qualitatively, both methods of analysis and both interactions considered, result in similar behavior of multifractal parameters. We do however notice significant quantitative differences in certain cases.
The multifractal structure of one dimensional charged particle density distribution in 28 Si-Ag /... more The multifractal structure of one dimensional charged particle density distribution in 28 Si-Ag / Br interactions at 14.5 GeV per nucleon is investigated by using two different techniques. The experimental measurements are compared with a microscopic transport model of particle production based on the Ultra-relativistic Quantum Molecular Dynamics (UrQMD). Various parameters related to multifractality, for example the…
To explore the role of GTPases in endocytosis, we developed an assay using Xenopus oocytes inject... more To explore the role of GTPases in endocytosis, we developed an assay using Xenopus oocytes injected with recombinant proteins to follow the uptake of the fluid phase marker HRP. HRP uptake was inhibited in cells injected with GTPγS or incubated with aluminum fluoride, suggesting a general role for GTPases in endocytosis. Injection of Rab5 into oocytes, as well as Rab5:Q79L, a mutant with decreased GTPase activity, increased HRP uptake. Injection of Rab5:S34N, the dominant-negative mutant, inhibited HRP uptake. Injection of N-ethylmaleimide–sensitive factor (NSF) stimulated HRP uptake, and ATPase-defective NSF mutants inhibited HRP uptake when coinjected with Rab5:Q79L, confirming a requirement for NSF in endocytosis. Surprisingly, injection of Rab7:WT stimulated both uptake and degradation/activation of HRP. The latter appears to be due to enhanced transport to a late endosomal/prelysosomal degradative compartment that is monensin sensitive. Enhancement of uptake by Rab7 appears to ...
Non-minimally coupled global monopole or a Schwarzschild black hole that swallowed a global monop... more Non-minimally coupled global monopole or a Schwarzschild black hole that swallowed a global monopole at the center of a galaxy can correctly describe the observed flat rotation curve of galaxies without the need of dark matter. To become a viable alternative to dark matter the global monopole based model also needs to explain the other observations hinting for the existence of dark matter. Here we have studied weak gravitational lensing due to Schwarzchild space time with global monopole and compare with the findings of galaxy-galaxy weak lensing and also the lensing observations of the rich galaxy cluster Abell 370. We find that global monopole based model cannot describe the mentioned lensing observations without the presence of dark matter.
One of the main objectives of the Compressed Baryonic Matter (CBM) experiment scheduled to be hel... more One of the main objectives of the Compressed Baryonic Matter (CBM) experiment scheduled to be held at the Facility for Anti-proton and Ion Research (FAIR), is to investigate the properties of an extended QCD matter at high baryo-chemical potential and at moderate/low temperature [1]. It would be worthwhile to examine how the known observables behave as indicators of phase transition in a baryon rich environment expected at FAIR energies. One observable that can be related to such transition, is the event-to-event (e-to-e) fluctuations of conserved quantities like net-charge, netbaryon number and net-strangenes. The fluctuation measure of such variables are found to be sensitive to the critical point in the QCD phase diagram. Different moments of the distributions of these conserved quantities, can be connected to the thermodynamic susceptibility and to the correlation length of the matter constituting the intermediate ‘fireball’ created in high-energy heavy-ion collisions [2]. In th...
The Compressed Baryonic Matter (CBM) experiment [1] to be held at the Facility for antiproton and... more The Compressed Baryonic Matter (CBM) experiment [1] to be held at the Facility for antiproton and ion research (FAIR) is being designed to investigate the baryonic matter under extreme thermodynamic conditions. The hot and dense matter produced in this experiment will be rich in baryon number. It would be worthwhile to examine how the signatures proposed for identifying and characterizing a baryon free QGP like state behave in a baryon rich environment. Event-by-event fluctuation of net electrical charge and/or baryon number is one such indicator of the formation of the QGP, used and tested in RHIC and LHC heavy-ion experiments. One starts by defining the net charge Q = (N+ − N−) and the total charge Nch = (N+ +N−) where the quantities N+ and N − are respectively, the multiplicities of positively and negatively charged particles. For a QGP like state comprising of fractional charges, the net charge fluctuation will be significantly less compared to an ordinary hadronic gas state. To...
In this work, the spacetime geometry of the halo region in spiral galaxies is obtained considerin... more In this work, the spacetime geometry of the halo region in spiral galaxies is obtained considering the observed flat galactic rotation curve feature, invoking the Tully–Fisher relation and assuming the presence of cold dark matter in the galaxy. The gravitational lensing analysis is performed treating the so-obtained spacetime as a gravitational lens. It is found that the aforementioned spacetime as the gravitational lens can consistently explain the galaxy–galaxy weak gravitational lensing observations and the lensing observations of the well-known Abell 370 and Abell 2390 galaxy clusters.
A continuous wavelet analysis is performed for pattern recognition of the pseudorapidity density ... more A continuous wavelet analysis is performed for pattern recognition of the pseudorapidity density profile of singly charged particles produced in [Formula: see text]O+Ag/Br and [Formula: see text]S+Ag/Br interactions, each at an incident energy of [Formula: see text] GeV per nucleon in the laboratory system. The experiments are compared with a model prediction based on the ultra-relativistic quantum molecular dynamics (UrQMD). To eliminate the contribution coming from known source(s) of particle cluster formation like Bose–Einstein correlation (BEC), the UrQMD output is modified by “an algorithm that mimics the BEC as an after burner.” We observe that for both interactions particle clusters are found at same pseudorapidity locations at all scales. However, the cluster locations in the [Formula: see text]O+Ag/Br interaction are different from those found in the [Formula: see text]S+Ag/Br interaction. Significant differences between experiments and simulations are revealed in the wavel...
Abstract We have studied the charged particle density fluctuations in 16O+Ag(Br) and 32S+Ag(Br) i... more Abstract We have studied the charged particle density fluctuations in 16O+Ag(Br) and 32S+Ag(Br) interactions at 200A GeV incident energy in the laboratory frame by using the detrended methods. These methods can extract (multi)fractal properties of the underlying distributions after filtering out the average trend of fluctuations associated. Multifractal parameters obtained from data analysis are systematically compared with event samples generated by the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, where Bose–Einstein correlation (BEC) effect is mimicked via a charge reassignment algorithm implemented as an after burner. Both the experimental and the simulated data are subjected to two different statistical techniques namely the multifractal detrended fluctuation analysis (MFDFA) and multifractal detrended moving average (MFDMA) analysis. The results indicate that for both the interactions considered the pseudorapidity distributions of the shower tracks are multifractal in nature. Qualitatively, both methods of analysis and both interactions considered, result in similar behavior of multifractal parameters. We do however notice significant quantitative differences in certain cases.
The multifractal structure of one dimensional charged particle density distribution in 28 Si-Ag /... more The multifractal structure of one dimensional charged particle density distribution in 28 Si-Ag / Br interactions at 14.5 GeV per nucleon is investigated by using two different techniques. The experimental measurements are compared with a microscopic transport model of particle production based on the Ultra-relativistic Quantum Molecular Dynamics (UrQMD). Various parameters related to multifractality, for example the…
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Papers by Amitabha Mukhopadhyay