Ridip Sarma - Academia.edu (original) (raw)

Papers by Ridip Sarma

Springer proceedings in complexity, 2022

Tropical Doctor

Atypical agents such as Mycoplasma, Legionella, Chlamydia species, and Coxiella burnetii (Q-fever... more Atypical agents such as Mycoplasma, Legionella, Chlamydia species, and Coxiella burnetii (Q-fever agent) are responsible for some adult community-acquired pneumonia (CAP). Insufficient studies on this topic can be blamed for the failure to include atypical pathogens in empirical management. We followed adult CAP cases for two years, and samples (respiratory and serum) were tested by culture, ELISA (IgM, IgG, and IgA), and PCR. A risk factor analysis was performed. Overall in 21.3% adult CAP patients, atypical agents found were Mycoplasma pneumoniae (51.5%), Legionella pneumophila (28.8%), and Chlamydophila pneumoniae (19.7%). However, amongst patients <60 years of age and in the summer season, the proportion of atypical agents increased significantly. There is thus a need to re-examine empirical antibiotic regimes.

Astrophysics and Space Science, 2022

2020 IEEE International Conference on Plasma Science (ICOPS), 2020

Our objective is to study the linear and nonlinear behaviour of modulated envelope solitons using... more Our objective is to study the linear and nonlinear behaviour of modulated envelope solitons using Schrodinger equation and considering the contribution of higher order terms for strongly dispersive case in a three component plasma constituting electrons, positron beams and warm ions. Here, the warm ions are assumed as an inertial fluid, the electrons and positron beams are considered to be in Maxwellian state, defined by the state of thermodynamic equilibrium in space plasma. In the analysis, it is exhibited that the lower & higher order expansion terms are governed by nonlinear & linear Schrodinger equation respectively derived via a modified reductive perturbation method. In this system, the dynamics of the modulated waves are described by a varying dissipative Schrodinger equation, derived by using the concept of a scale parameter 'g’ into a power series of the smallest parameter ∊ which considers a dissipative term in association with the finite imaginary part of the nonlinearity term. Our work elucidates formation of progressive wave solution, steady state solution along with a class of periodic solutions for which the real and imaginary parts are linearly exhibited. Results from numerical simulation confirm the predictions of stability and instability criteria, bright and dark solitons, breather like soliton, kink and anti-kink solitons and also exhibit definite forms for these solutions from first to fourth order. Our analytical predictions may be useful in the investigations of various space plasmas.

2020 IEEE International Conference on Plasma Science (ICOPS), 2020

The propagation of three-dimensional (3-D)electrostatic solitary and shock waves with weakly rela... more The propagation of three-dimensional (3-D)electrostatic solitary and shock waves with weakly relativistic and ultra-relativistic degenerate electrons and positrons is investigated in a dense magnetized plasma. For this purpose, a 3-D Zakharov-Kuznetsov-Burgers (Z-K-B) equation is derived from the pair of ion continuity and momentum equation with bulk viscosity among ion fluids, and degenerate electrons and positrons. The effect of mass of pair of ions, positron concentration, magnetic field strength and the Fermi temperature of weakly relativistic and ultra-relativistic degenerate electrons and positrons are studied in the present work. The Burgers term in our system is responsible for shock structures in pair ion plasmas. Analytical prediction and numerical analysis enable us to know that the wave yields solitary profile in absence of collisions and exhibits both oscillatory and monotonic depending on collisions between pair of ions and balanced status of diisipation and dispersion. Moreover, it is exhibited that the chaotic dynamics occur when the perturbed Z-K-B equation is perturbed by external force, and we use power spectrum, phase projection, and Lyapunov exponents to observe both weak and developed chaos. For illustration purposes, we have considered the astrophysical parameters in a white dwarf.

Lung India, 2021

Background: Empirical antibiotic therapy is the mainstay of management of adult community-acquire... more Background: Empirical antibiotic therapy is the mainstay of management of adult community-acquired pneumonia (CAP) globally. Knowledge of prevalent pathogen (bacterial) profile and drug susceptibility pattern is very essential for appropriate management of CAP cases, which again calls for regular update of pathogen profile in a given locality. This study was to identify the bacterial etiology of CAP cases and their antibiotic susceptibility pattern. Methods: This cross-sectional study was done on adult CAP patients from medicine, respiratory medicine, and intensive care unit area in our tertiary care hospital between May 1, 2015, and October 30, 2016. Subjects were enrolled continuously, and expectorated sputum, bronchoalveolar lavage fluid, and blood culture were performed. Urine antigen test was done for Streptococcus pneumoniae and Legionella pneumophila. Three types of ELISA (IgM, IgG, and IgA) were performed for atypical agents (Mycoplasma, Chlamydia, and Legionella) of CAP. Isolates obtained from culture of Sputum/BAL/Blood were further processed for antibiotic susceptibility testing - by disc diffusion as well as E-test method (latter for MIC i.e. minimum inhibitory concentration, determination). Results: About 574 subjects were included, and in 266 (46.3%) cases, bacterial pathogen could be detected. Klebsiella pneumoniae (33.6%) and S. pneumoniae (32.9%) were the predominant agents identified. Atypical agents (Mycoplasma, Legionella, and Chlamydia) were at 15.1%. A high proportion of pneumococci isolates were multidrug resistant (52.6%). Resistance to beta-lactams, macrolide, and other agents was on the higher side, but fluoroquinolones were found to be less resistant (15.8%–21.1%). Extended-spectrum beta-lactamase (among Klebsiella isolates) and methicillin-resistant Staphylococcus aureus were also detected. Conclusion: A moderate-to-high degree of drug-resistant in adult CAP was evident, which is detrimental in effective empirical management of such cases. Urgent implementation of antibiotic stewardship scheme is the need of the hour.

The European Physical Journal D, 2020

Abstract The nonlinear features of Ion Acoustic (IA) waves are studied in a fully relativistic th... more Abstract The nonlinear features of Ion Acoustic (IA) waves are studied in a fully relativistic three-dimensional (3-D) plasma system with consideration of effect of both positron beam and trapped electrons. We consider a set of 3-D magnetised hydrodynamic equations with pressure expansion for our plasma model along with kinetic Vlasov equation for electrons. Applying the perturbative expansion technique, a Modified Korteweg-de Vries (m-KdV)-like equation is derived, exhibiting the evolution of small amplitude IA waves in plasma. The modified coefficient of nonlinear term in K-dV equation has arrived due to impact of vortex-like distribution of electrons. An analytical and numerical investigation of the nonlinear evolution equations is exhibited with external magnetic field effects, the time derivative pressure expansion as well as other parameters like relativistic effect, mass variation, beam velocity and temperature effect have been taken into consideration. The presence of vortex like trapped electron distribution and positron beam governs the influence of soliton structure quite significantly. The present result should help us to understand the experiments that involve particle trapping and also the salient features of astrophysical environment like ionospheric plasma together with situations in plasma describing the electrostatic solitary structures usually seen in antimatter-related environment in interplanetary region. Graphical abstract

Physics of Plasmas, 2018

Our objective is to study the nonlinear wave phenomena in a multicomponent plasma with Maxwellian... more Our objective is to study the nonlinear wave phenomena in a multicomponent plasma with Maxwellian electrons and ions. The main reason for this consideration is to exhibit the effects of dust charge fluctuations in plasma acoustic modes. Different aspects of nonlinear dynamics have been studied through the Korteweg-deVries (K-dV) equation (solitons) and the Burgers equation (shocks) derived by the reductive perturbation technique. A special method, known as the (G′/G) method, has been used for a solution. It predicts the different coherent features of various nonlinear waves successfully, and finally, their importance has been recognized in space plasmas. Evolutions have been shown with the input of appropriate typical plasma parameters to support our observations in space plasmas. All conclusions are in good agreement with the actual occurrences and could be of interest in furthering investigations in experiments and satellite observations in spaces. An important aspect of this exer...

Physics of Plasmas, 2018

Our interest is to study the nonlinear wave phenomena in complex plasma constituents with Maxwell... more Our interest is to study the nonlinear wave phenomena in complex plasma constituents with Maxwellian electrons and ions. The main reason for this consideration is to exhibit the effects of dust charge fluctuations on acoustic modes evaluated by the use of a new method. A special method (G′/G) has been developed to yield the coherent features of nonlinear waves augmented through the derivation of a Korteweg-de Vries equation and found successfully the different nature of solitons recognized in space plasmas. Evolutions have shown with the input of appropriate typical plasma parameters to support our theoretical observations in space plasmas. All conclusions are in good accordance with the actual occurrences and could be of interest to further the investigations in experiments and satellite observations in space. In this paper, we present not only the model that exhibited nonlinear solitary wave propagation but also a new mathematical method to the execution.

Community-acquired Urinary Tract Infection (CA-UTI) is a very common condition and often treated ... more Community-acquired Urinary Tract Infection (CA-UTI) is a very common condition and often treated by empirical antibiotic therapy. This has led to the problem of drug resistance in the community pathogens. As information on profile and antibiotic resistance, especially from rural areas is very hard to come by, this study was carried out on adult CA-UTI subjects presenting in a rural tertiary care teaching hospital of lower Assam. Outdoor patients were included and urine samples were tested by standard microbiological methods. Isolated organisms were processed for antibiotic susceptibility and MIC (selected cases). Out of 1436 samples 27.1% was found to have significant bacteriuria by single agents with more infection in female than in male. E coli was the predominant agent (62.2%) followed by Coagulase Negative Staphylococcus (CONS) at 11.8%, Klebsiella (11.3%) and Entercocci (6.3%). High prevalence of drug resistance amongst the isolates was observed, especially against common agent of empirical treatments like Ciprofloxacin, Amoxycalv etc. MIC level of Ciprofloxacin in E coli seemed to be rising and in few cases, level has reached beyond 32mcg/ml. This is alarming for a community pathogen from a rural area. Urgent necessity for an evidence based antibiotic policy cannot be ruled out.

International Journal of Scientific and Engineering Research

In this model of relativistic electron-positron-ion plasma, only compressive solitons are found t... more In this model of relativistic electron-positron-ion plasma, only compressive solitons are found to exist. The amplitude becomes higher for smaller values of p e T T / = σ (= electron to positron temperature ratio). The investigation further revealed that higher values of c v / 0 (0 v is the initial ion streaming and c is the normalized velocity of light) gives higher amplitudes of compressive solitons.

Physics of Plasmas, 2012

Weakly nonlinear ion-acoustic (IA) solitary waves, which accompany electronegative plasmas compos... more Weakly nonlinear ion-acoustic (IA) solitary waves, which accompany electronegative plasmas composed of positive ions, negative ions, and nonextensive electrons are investigated. Allowing for electrons departure from Boltzmann’s distribution is shown to bear considerable new features of the IA soliton characteristics. Three different types of electronegative plasmas inspired from the experimental studies of Ichiki et al. [Phys. Plasmas 8, 4275 (2001)] are discussed, and the dependence of IA solitons basic characteristics on physical parameters is also investigated. It is found that for certain values of the negative-to-positive ion density ratio, ν, the positive-to-negative ion mass ratio, Q, and the nonextensive parameter, q, the plasma system supports rarefactive solitons.

Springer proceedings in complexity, 2022

Tropical Doctor

Atypical agents such as Mycoplasma, Legionella, Chlamydia species, and Coxiella burnetii (Q-fever... more Atypical agents such as Mycoplasma, Legionella, Chlamydia species, and Coxiella burnetii (Q-fever agent) are responsible for some adult community-acquired pneumonia (CAP). Insufficient studies on this topic can be blamed for the failure to include atypical pathogens in empirical management. We followed adult CAP cases for two years, and samples (respiratory and serum) were tested by culture, ELISA (IgM, IgG, and IgA), and PCR. A risk factor analysis was performed. Overall in 21.3% adult CAP patients, atypical agents found were Mycoplasma pneumoniae (51.5%), Legionella pneumophila (28.8%), and Chlamydophila pneumoniae (19.7%). However, amongst patients <60 years of age and in the summer season, the proportion of atypical agents increased significantly. There is thus a need to re-examine empirical antibiotic regimes.

Astrophysics and Space Science, 2022

2020 IEEE International Conference on Plasma Science (ICOPS), 2020

Our objective is to study the linear and nonlinear behaviour of modulated envelope solitons using... more Our objective is to study the linear and nonlinear behaviour of modulated envelope solitons using Schrodinger equation and considering the contribution of higher order terms for strongly dispersive case in a three component plasma constituting electrons, positron beams and warm ions. Here, the warm ions are assumed as an inertial fluid, the electrons and positron beams are considered to be in Maxwellian state, defined by the state of thermodynamic equilibrium in space plasma. In the analysis, it is exhibited that the lower & higher order expansion terms are governed by nonlinear & linear Schrodinger equation respectively derived via a modified reductive perturbation method. In this system, the dynamics of the modulated waves are described by a varying dissipative Schrodinger equation, derived by using the concept of a scale parameter 'g’ into a power series of the smallest parameter ∊ which considers a dissipative term in association with the finite imaginary part of the nonlinearity term. Our work elucidates formation of progressive wave solution, steady state solution along with a class of periodic solutions for which the real and imaginary parts are linearly exhibited. Results from numerical simulation confirm the predictions of stability and instability criteria, bright and dark solitons, breather like soliton, kink and anti-kink solitons and also exhibit definite forms for these solutions from first to fourth order. Our analytical predictions may be useful in the investigations of various space plasmas.

2020 IEEE International Conference on Plasma Science (ICOPS), 2020

The propagation of three-dimensional (3-D)electrostatic solitary and shock waves with weakly rela... more The propagation of three-dimensional (3-D)electrostatic solitary and shock waves with weakly relativistic and ultra-relativistic degenerate electrons and positrons is investigated in a dense magnetized plasma. For this purpose, a 3-D Zakharov-Kuznetsov-Burgers (Z-K-B) equation is derived from the pair of ion continuity and momentum equation with bulk viscosity among ion fluids, and degenerate electrons and positrons. The effect of mass of pair of ions, positron concentration, magnetic field strength and the Fermi temperature of weakly relativistic and ultra-relativistic degenerate electrons and positrons are studied in the present work. The Burgers term in our system is responsible for shock structures in pair ion plasmas. Analytical prediction and numerical analysis enable us to know that the wave yields solitary profile in absence of collisions and exhibits both oscillatory and monotonic depending on collisions between pair of ions and balanced status of diisipation and dispersion. Moreover, it is exhibited that the chaotic dynamics occur when the perturbed Z-K-B equation is perturbed by external force, and we use power spectrum, phase projection, and Lyapunov exponents to observe both weak and developed chaos. For illustration purposes, we have considered the astrophysical parameters in a white dwarf.

Lung India, 2021

Background: Empirical antibiotic therapy is the mainstay of management of adult community-acquire... more Background: Empirical antibiotic therapy is the mainstay of management of adult community-acquired pneumonia (CAP) globally. Knowledge of prevalent pathogen (bacterial) profile and drug susceptibility pattern is very essential for appropriate management of CAP cases, which again calls for regular update of pathogen profile in a given locality. This study was to identify the bacterial etiology of CAP cases and their antibiotic susceptibility pattern. Methods: This cross-sectional study was done on adult CAP patients from medicine, respiratory medicine, and intensive care unit area in our tertiary care hospital between May 1, 2015, and October 30, 2016. Subjects were enrolled continuously, and expectorated sputum, bronchoalveolar lavage fluid, and blood culture were performed. Urine antigen test was done for Streptococcus pneumoniae and Legionella pneumophila. Three types of ELISA (IgM, IgG, and IgA) were performed for atypical agents (Mycoplasma, Chlamydia, and Legionella) of CAP. Isolates obtained from culture of Sputum/BAL/Blood were further processed for antibiotic susceptibility testing - by disc diffusion as well as E-test method (latter for MIC i.e. minimum inhibitory concentration, determination). Results: About 574 subjects were included, and in 266 (46.3%) cases, bacterial pathogen could be detected. Klebsiella pneumoniae (33.6%) and S. pneumoniae (32.9%) were the predominant agents identified. Atypical agents (Mycoplasma, Legionella, and Chlamydia) were at 15.1%. A high proportion of pneumococci isolates were multidrug resistant (52.6%). Resistance to beta-lactams, macrolide, and other agents was on the higher side, but fluoroquinolones were found to be less resistant (15.8%–21.1%). Extended-spectrum beta-lactamase (among Klebsiella isolates) and methicillin-resistant Staphylococcus aureus were also detected. Conclusion: A moderate-to-high degree of drug-resistant in adult CAP was evident, which is detrimental in effective empirical management of such cases. Urgent implementation of antibiotic stewardship scheme is the need of the hour.

The European Physical Journal D, 2020

Abstract The nonlinear features of Ion Acoustic (IA) waves are studied in a fully relativistic th... more Abstract The nonlinear features of Ion Acoustic (IA) waves are studied in a fully relativistic three-dimensional (3-D) plasma system with consideration of effect of both positron beam and trapped electrons. We consider a set of 3-D magnetised hydrodynamic equations with pressure expansion for our plasma model along with kinetic Vlasov equation for electrons. Applying the perturbative expansion technique, a Modified Korteweg-de Vries (m-KdV)-like equation is derived, exhibiting the evolution of small amplitude IA waves in plasma. The modified coefficient of nonlinear term in K-dV equation has arrived due to impact of vortex-like distribution of electrons. An analytical and numerical investigation of the nonlinear evolution equations is exhibited with external magnetic field effects, the time derivative pressure expansion as well as other parameters like relativistic effect, mass variation, beam velocity and temperature effect have been taken into consideration. The presence of vortex like trapped electron distribution and positron beam governs the influence of soliton structure quite significantly. The present result should help us to understand the experiments that involve particle trapping and also the salient features of astrophysical environment like ionospheric plasma together with situations in plasma describing the electrostatic solitary structures usually seen in antimatter-related environment in interplanetary region. Graphical abstract

Physics of Plasmas, 2018

Our objective is to study the nonlinear wave phenomena in a multicomponent plasma with Maxwellian... more Our objective is to study the nonlinear wave phenomena in a multicomponent plasma with Maxwellian electrons and ions. The main reason for this consideration is to exhibit the effects of dust charge fluctuations in plasma acoustic modes. Different aspects of nonlinear dynamics have been studied through the Korteweg-deVries (K-dV) equation (solitons) and the Burgers equation (shocks) derived by the reductive perturbation technique. A special method, known as the (G′/G) method, has been used for a solution. It predicts the different coherent features of various nonlinear waves successfully, and finally, their importance has been recognized in space plasmas. Evolutions have been shown with the input of appropriate typical plasma parameters to support our observations in space plasmas. All conclusions are in good agreement with the actual occurrences and could be of interest in furthering investigations in experiments and satellite observations in spaces. An important aspect of this exer...

Physics of Plasmas, 2018

Our interest is to study the nonlinear wave phenomena in complex plasma constituents with Maxwell... more Our interest is to study the nonlinear wave phenomena in complex plasma constituents with Maxwellian electrons and ions. The main reason for this consideration is to exhibit the effects of dust charge fluctuations on acoustic modes evaluated by the use of a new method. A special method (G′/G) has been developed to yield the coherent features of nonlinear waves augmented through the derivation of a Korteweg-de Vries equation and found successfully the different nature of solitons recognized in space plasmas. Evolutions have shown with the input of appropriate typical plasma parameters to support our theoretical observations in space plasmas. All conclusions are in good accordance with the actual occurrences and could be of interest to further the investigations in experiments and satellite observations in space. In this paper, we present not only the model that exhibited nonlinear solitary wave propagation but also a new mathematical method to the execution.

Community-acquired Urinary Tract Infection (CA-UTI) is a very common condition and often treated ... more Community-acquired Urinary Tract Infection (CA-UTI) is a very common condition and often treated by empirical antibiotic therapy. This has led to the problem of drug resistance in the community pathogens. As information on profile and antibiotic resistance, especially from rural areas is very hard to come by, this study was carried out on adult CA-UTI subjects presenting in a rural tertiary care teaching hospital of lower Assam. Outdoor patients were included and urine samples were tested by standard microbiological methods. Isolated organisms were processed for antibiotic susceptibility and MIC (selected cases). Out of 1436 samples 27.1% was found to have significant bacteriuria by single agents with more infection in female than in male. E coli was the predominant agent (62.2%) followed by Coagulase Negative Staphylococcus (CONS) at 11.8%, Klebsiella (11.3%) and Entercocci (6.3%). High prevalence of drug resistance amongst the isolates was observed, especially against common agent of empirical treatments like Ciprofloxacin, Amoxycalv etc. MIC level of Ciprofloxacin in E coli seemed to be rising and in few cases, level has reached beyond 32mcg/ml. This is alarming for a community pathogen from a rural area. Urgent necessity for an evidence based antibiotic policy cannot be ruled out.

International Journal of Scientific and Engineering Research

In this model of relativistic electron-positron-ion plasma, only compressive solitons are found t... more In this model of relativistic electron-positron-ion plasma, only compressive solitons are found to exist. The amplitude becomes higher for smaller values of p e T T / = σ (= electron to positron temperature ratio). The investigation further revealed that higher values of c v / 0 (0 v is the initial ion streaming and c is the normalized velocity of light) gives higher amplitudes of compressive solitons.

Physics of Plasmas, 2012

Weakly nonlinear ion-acoustic (IA) solitary waves, which accompany electronegative plasmas compos... more Weakly nonlinear ion-acoustic (IA) solitary waves, which accompany electronegative plasmas composed of positive ions, negative ions, and nonextensive electrons are investigated. Allowing for electrons departure from Boltzmann’s distribution is shown to bear considerable new features of the IA soliton characteristics. Three different types of electronegative plasmas inspired from the experimental studies of Ichiki et al. [Phys. Plasmas 8, 4275 (2001)] are discussed, and the dependence of IA solitons basic characteristics on physical parameters is also investigated. It is found that for certain values of the negative-to-positive ion density ratio, ν, the positive-to-negative ion mass ratio, Q, and the nonextensive parameter, q, the plasma system supports rarefactive solitons.