Rahul Verma - Academia.edu (original) (raw)

Papers by Rahul Verma

Gastrointestinal Endoscopy, 2006

Gastrointestinal Endoscopy, 2006

Gastrointestinal Endoscopy, 2005

BMC Gastroenterology, 2012

Accurate tests to diagnose adenocarcinoma and high-grade dysplasia among mucinous pancreatic cyst... more Accurate tests to diagnose adenocarcinoma and high-grade dysplasia among mucinous pancreatic cysts are clinically needed. This study evaluated the diagnostic utility of amphiregulin (AREG) as a pancreatic cyst fluid biomarker to differentiate non-mucinous, benign mucinous, and malignant mucinous cysts.

Tuberculosis (Edinburgh, Scotland)

Nitric oxide (NO) kills Mycobacterium tuberculosis (Mtb) in vitro, but gaseous NO is difficult to... more Nitric oxide (NO) kills Mycobacterium tuberculosis (Mtb) in vitro, but gaseous NO is difficult to administer to patients. We evaluated the consequences of intracellular delivery of NO using inhalable microparticles (MP) containing NO donors. MP containing 10% w/w of NO donors alone, or in addition to 25% each of isoniazid (INH) and rifabutin (RFB) in a polylactide-co-glycolide (PLGA) matrix were prepared by spray drying. THP-1-derived macrophages infected with Mtb H37Rv were exposed to MP or soluble NO donors. Phagosome-lysosome fusion (PLF) and bacterial killing were monitored. Colony forming units (cfu) in lungs and spleen of mice infected with a low-dose aerosol and administered inhalations of MP were enumerated. Bacterial DNA in these tissues was estimated by real-time PCR. In vitro studies indicated a bacteriostatic effect of NO donors despite significant enhancement of PLF. Daily inhalation of MP containing 10% diethylenetriamine nitric oxide adduct (DETA/NO) alone reduced log10 cfu in the lungs from 6.1 to 4.4 at the highest dose in four weeks, but did not significantly affect cfu in the spleen. Inhalations of MP containing DETA/NO in combination with INH and RFB significantly (P < 10(-5), ANOVA) reduced cfu in lungs and spleens by 4 log. Gross morphology and histology of the lungs and spleen indicated that inhaled particles were well-tolerated. Inhalable MP containing NO donors need further investigation as an adjunct to standard anti-tuberculosis chemotherapy.

Tuberculosis, 2011

Factors that are inimical to the success of inhaled therapies for tuberculosis (TB) include: (i) ... more Factors that are inimical to the success of inhaled therapies for tuberculosis (TB) include: (i) lack of access of inhaled therapies to poorly-aerated areas of the tubercular lung; (ii) limited ability to penetrate biofilms formed by extracellular bacilli; (iii) selection for resistant bacilli on account of administration of low doses of anti-TB agents; (iv) induction of inflammation and/or immunopathology in the airways and lungs; and (v) anomalies in antigen processing and presentation of vaccines delivered to the lungs. Further, the claim that inhaled therapies rescue alternatively-activated macrophages may not be applicable to all individuals. Fortunately, there are ways and means to address each of the above factors.

Communications in Computer and Information Science, 2011

Page 1. VV Das, N. Thankachan, and NC Debnath (Eds.): PEIE 2011, CCIS 148, pp. 105–108, 2011. © S... more Page 1. VV Das, N. Thankachan, and NC Debnath (Eds.): PEIE 2011, CCIS 148, pp. 105–108, 2011. © Springer-Verlag Berlin Heidelberg 2011 Wireless 3-D Gesture and Chaaracter Recoginition Gaytri Gupta and Rahul Kumar Verma ...

Antimicrobial Agents and Chemotherapy, 2008

Intracellular concentrations of isoniazid and rifabutin resulting from administration of inhalabl... more Intracellular concentrations of isoniazid and rifabutin resulting from administration of inhalable microparticles of these drugs to phorbol-differentiated THP-1 cells and the pharmacokinetics and biodistribution of these drugs upon inhalation of microparticles or intravenous administration of free drugs to mice were investigated. In cultured cells, both microparticles and dissolved drugs established peak concentrations of isoniazid (ϳ1.4 and 1.1 g/10 6 cells) and rifabutin (ϳ2 g/ml and ϳ1.4 g/10 6 cells) within 10 min. Microparticles maintained the intracellular concentration of isoniazid for 24 h and rifabutin for 96 h, whereas dissolved drugs did not. The following pharmacokinetic parameters were calculated using WinNonlin from samples obtained after inhalation using an in-house apparatus (figures in parentheses refer to parameters obtained after intravenous administration of an equivalent amount, i.e., 100 g of either drug, to parallel groups): isoniazid, serum half-life (t 1/2 ) ‫؍‬ 18.63 ؎ 5.89 h (3.91 ؎ 1.06 h), maximum concentration in serum (C max ) ‫؍‬ 2.37 ؎ 0.23 g ⅐ ml ؊1 (3.24 ؎ 0.57 g ⅐ ml ؊1 ), area under the concentration-time curve from 0 to 24 h (AUC 0-24 ) ‫؍‬ 55.34 ؎ 13.72 g/ml ؊1 h ؊1 (16.64 ؎ 1.80 g/ml ؊1 h ؊1 ), and clearance (CL) ‫؍‬ 63.90 ؎ 13.32 ml ⅐ h ؊1 (4.43 ؎ 1.85 ml ⅐ h ؊1 ); rifabutin, t 1/2 ‫؍‬ 119.49 ؎ 29.62 h (20.18 ؎ 4.02 h), C max ‫؍‬ 1.59 ؎ 0.01 g ⅐ ml ؊1 (3.47 ؎ 0.33 g ⅐ ml ؊1 ), AUC 0-96 ‫؍‬ 109.35 ؎ 14.78 g/ml ؊1 h ؊1 (90.82 ؎ 7.46 g/ml ؊1 h ؊1 ), and CL ‫؍‬ 11.68 ؎ 7.00 ml ⅐ h ؊1 (1.03 ؎ 0.11 ml ⅐ h ؊1 ). Drug targeting to the lungs in general and alveolar macrophages in particular was observed. It was concluded that inhaled microparticles can reduce dose frequency and improve the pharmacologic index of the drug combination.

Page 1. Non-proportional/Non-monotonous Deformation Modeling of an Ultra High Strength Automotive... more Page 1. Non-proportional/Non-monotonous Deformation Modeling of an Ultra High Strength Automotive Steel Sheet Rahul K. Verma*, Yuki Ogihara**, Toshihiko Kuwabara*** and Kwansoo Chung**** *Research and Development ...

European Journal of Pharmaceutical Sciences, 2008

A hand-held apparatus designed for the purpose of administering dry powder inhalations to rodents... more A hand-held apparatus designed for the purpose of administering dry powder inhalations to rodents by "Nose-only" exposure was standardized. An aerosol of microparticles containing the anti-tuberculosis drugs isoniazid and rifabutin was generated and the dose available for inhalation by rodents was determined by collecting microparticles emitted at the delivery port. Separate groups of mice received inhalations of microparticles, free rifabutin orally, or free rifabutin intravenously. Rifabutin was estimated in serum and tissues by HPLC. When ~20 mg of microparticles were loaded in the apparatus, ~2.5 mg were collected at the delivery port in 30 seconds of operation. Mice inhaled ~300 μg of the 2.5 mg emitted at the delivery port. Alveolar macrophages of mice receiving inhalations for 30 sec accumulated 0.38 μg of rifabutin, while the amount in blood serum of these mice was 0.62 μg. In mice receiving 83 μg rifabutin intravenously or orally, the intracellular amounts were 0.06 and 0.07 μg respectively, while the amounts in serum were 1.02 and 0.80 μg. These observations confirmed that inhalation of microparticles targeted lung macrophages. The dose available for inhalation was consistent with the duration of exposure (10.5-13.5 CV%) and its dependence on the amount of microparticles loaded (r 2 =0.982), and on duration of exposure (r 2 =0.992), was satisfactory.

Draw‐Bending Analysis of a Cold Rolled DP980 Steel Sheet. [AIP Conference Proceedings 1353, 1405 ... more Draw‐Bending Analysis of a Cold Rolled DP980 Steel Sheet. [AIP Conference Proceedings 1353, 1405 (2011)]. Rahul K. Verma, Nobuyasu Noma, Kwansoo Chung, Toshihiko Kuwabara. Abstract. To assess the springback prediction ...

The constitutive model with combined isotropic-kinematic hardening along with hardening stagnatio... more The constitutive model with combined isotropic-kinematic hardening along with hardening stagnation (or permanent softening) [Verma, Kuwabara, Chung, Haldar: Int. J. Plasticity (submitted)] was used here for modeling the tension-compression behaviors of a 0.1 mm thick austenitic stainless steel sheet (SUS304), which was observed in a recent work [Kuwabara and Murakoso: Proc. CIRP 2010 Conf. (submitted)]. Springback was also experimentally measured for a shallow drawn rectangular cup here and it was verified using the above model. It was found that this model can successfully predict the Bauschinger effect and hardening stagnation. As for springback, it was found that in this particular case it depends on, other than the material model, factors like boundary conditions, in the finite element analysis (FEA), during unloading. It was also observed that incorporation of the Bauschinger effect and permanent softening is a key for accurate springback prediction and, therefore, the present model performs better than the one which is based only on isotropic hardening without any hardening stagnation.

In this work, as non-proportional/non-monotonous deformation experiments, two-stage and tension-c... more In this work, as non-proportional/non-monotonous deformation experiments, two-stage and tension-compression-tension uniaxial tests were performed, respectively, for a cold rolled ultra high strength dual phase steel sheet: DP780. Deformation behaviors under such deformation paths were found different than those of the ultra low carbon single phase steels observed by Verma et al. (Int. J. Plast. 2011, 82-101). To model the newly observed deformation behaviors, the combined type constitutive law previously proposed by Verma et al. (Int. J. Plast. 2011, 82-101) was successfully applied here. Permanent softening observed during reverse loading was properly characterized into the isotropic and kinematic hardening parts of the hardening law using tension-compression-tension test data. The cross effect observed in two-stage tests was also effectively incorporated into the constitutive law.

International Journal of Plasticity, 2011

Recently non-proportional deformation has received increased attention from researchers working i... more Recently non-proportional deformation has received increased attention from researchers working in the area of experimental and computational modeling of metal deformation. However, most of them are numerical in nature with limited experimental data available, making it further difficult to model non-proportional deformation. In the present work, two-stage uniaxial tests, along with uniaxial cyclic and biaxial tests for different stress ratios, have been performed to evaluate deformation behavior of ultra-low carbon high strength automotive steel. Behaviors like cross-effect and hardening stagnation, which are attributed to the evolution of complex dislocation structures, were observed in this steel. It was also noticed that this steel exhibits tension–compression asymmetry. As for constitutive modeling, a modified asymmetric yield function is proposed to be used with a combined isotropic–kinematic hardening model. Also methods to account for the hardening stagnation during reverse loading and the cross-effect during two-stage deformation are proposed. The resulting constitutive model showed reasonably good agreement with experimental results.

Journal of Materials Processing Technology, 2007

Share of high and advanced high strength steels in automobile is increasing, however, such steels... more Share of high and advanced high strength steels in automobile is increasing, however, such steels generally have poor formability and high amount of springback. One of the focus areas of research in high strength automotive steel is to increase the normal anisotropy to get better formability. Effect of strength and process parameters on springback has been studied by many researchers but that of anisotropy has not been studied by many. In the present work the effect of anisotropy on springback is predicted using finite element analysis for the benchmark problem of Numisheet-2005 [2005 Numisheet Benchmark 2, Springback prediction of a cross member, Proceedings of the 6th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Processes, Detroit, USA, August 15–19, 2005]. An analytical model is developed to cross check the trends predicted from the finite element analysis. The effective stress has not been treated as a constant and the radial stress is considered in the present model. Both the models (FE and analytical) predict that higher anisotropy, in general, gives higher springback. Finite element analysis of the problem shows that springback is minimum for an isotropic material.

Gastrointestinal Endoscopy, 2006

Gastrointestinal Endoscopy, 2006

Gastrointestinal Endoscopy, 2005

BMC Gastroenterology, 2012

Accurate tests to diagnose adenocarcinoma and high-grade dysplasia among mucinous pancreatic cyst... more Accurate tests to diagnose adenocarcinoma and high-grade dysplasia among mucinous pancreatic cysts are clinically needed. This study evaluated the diagnostic utility of amphiregulin (AREG) as a pancreatic cyst fluid biomarker to differentiate non-mucinous, benign mucinous, and malignant mucinous cysts.

Tuberculosis (Edinburgh, Scotland)

Nitric oxide (NO) kills Mycobacterium tuberculosis (Mtb) in vitro, but gaseous NO is difficult to... more Nitric oxide (NO) kills Mycobacterium tuberculosis (Mtb) in vitro, but gaseous NO is difficult to administer to patients. We evaluated the consequences of intracellular delivery of NO using inhalable microparticles (MP) containing NO donors. MP containing 10% w/w of NO donors alone, or in addition to 25% each of isoniazid (INH) and rifabutin (RFB) in a polylactide-co-glycolide (PLGA) matrix were prepared by spray drying. THP-1-derived macrophages infected with Mtb H37Rv were exposed to MP or soluble NO donors. Phagosome-lysosome fusion (PLF) and bacterial killing were monitored. Colony forming units (cfu) in lungs and spleen of mice infected with a low-dose aerosol and administered inhalations of MP were enumerated. Bacterial DNA in these tissues was estimated by real-time PCR. In vitro studies indicated a bacteriostatic effect of NO donors despite significant enhancement of PLF. Daily inhalation of MP containing 10% diethylenetriamine nitric oxide adduct (DETA/NO) alone reduced log10 cfu in the lungs from 6.1 to 4.4 at the highest dose in four weeks, but did not significantly affect cfu in the spleen. Inhalations of MP containing DETA/NO in combination with INH and RFB significantly (P < 10(-5), ANOVA) reduced cfu in lungs and spleens by 4 log. Gross morphology and histology of the lungs and spleen indicated that inhaled particles were well-tolerated. Inhalable MP containing NO donors need further investigation as an adjunct to standard anti-tuberculosis chemotherapy.

Tuberculosis, 2011

Factors that are inimical to the success of inhaled therapies for tuberculosis (TB) include: (i) ... more Factors that are inimical to the success of inhaled therapies for tuberculosis (TB) include: (i) lack of access of inhaled therapies to poorly-aerated areas of the tubercular lung; (ii) limited ability to penetrate biofilms formed by extracellular bacilli; (iii) selection for resistant bacilli on account of administration of low doses of anti-TB agents; (iv) induction of inflammation and/or immunopathology in the airways and lungs; and (v) anomalies in antigen processing and presentation of vaccines delivered to the lungs. Further, the claim that inhaled therapies rescue alternatively-activated macrophages may not be applicable to all individuals. Fortunately, there are ways and means to address each of the above factors.

Communications in Computer and Information Science, 2011

Page 1. VV Das, N. Thankachan, and NC Debnath (Eds.): PEIE 2011, CCIS 148, pp. 105–108, 2011. © S... more Page 1. VV Das, N. Thankachan, and NC Debnath (Eds.): PEIE 2011, CCIS 148, pp. 105–108, 2011. © Springer-Verlag Berlin Heidelberg 2011 Wireless 3-D Gesture and Chaaracter Recoginition Gaytri Gupta and Rahul Kumar Verma ...

Antimicrobial Agents and Chemotherapy, 2008

Intracellular concentrations of isoniazid and rifabutin resulting from administration of inhalabl... more Intracellular concentrations of isoniazid and rifabutin resulting from administration of inhalable microparticles of these drugs to phorbol-differentiated THP-1 cells and the pharmacokinetics and biodistribution of these drugs upon inhalation of microparticles or intravenous administration of free drugs to mice were investigated. In cultured cells, both microparticles and dissolved drugs established peak concentrations of isoniazid (ϳ1.4 and 1.1 g/10 6 cells) and rifabutin (ϳ2 g/ml and ϳ1.4 g/10 6 cells) within 10 min. Microparticles maintained the intracellular concentration of isoniazid for 24 h and rifabutin for 96 h, whereas dissolved drugs did not. The following pharmacokinetic parameters were calculated using WinNonlin from samples obtained after inhalation using an in-house apparatus (figures in parentheses refer to parameters obtained after intravenous administration of an equivalent amount, i.e., 100 g of either drug, to parallel groups): isoniazid, serum half-life (t 1/2 ) ‫؍‬ 18.63 ؎ 5.89 h (3.91 ؎ 1.06 h), maximum concentration in serum (C max ) ‫؍‬ 2.37 ؎ 0.23 g ⅐ ml ؊1 (3.24 ؎ 0.57 g ⅐ ml ؊1 ), area under the concentration-time curve from 0 to 24 h (AUC 0-24 ) ‫؍‬ 55.34 ؎ 13.72 g/ml ؊1 h ؊1 (16.64 ؎ 1.80 g/ml ؊1 h ؊1 ), and clearance (CL) ‫؍‬ 63.90 ؎ 13.32 ml ⅐ h ؊1 (4.43 ؎ 1.85 ml ⅐ h ؊1 ); rifabutin, t 1/2 ‫؍‬ 119.49 ؎ 29.62 h (20.18 ؎ 4.02 h), C max ‫؍‬ 1.59 ؎ 0.01 g ⅐ ml ؊1 (3.47 ؎ 0.33 g ⅐ ml ؊1 ), AUC 0-96 ‫؍‬ 109.35 ؎ 14.78 g/ml ؊1 h ؊1 (90.82 ؎ 7.46 g/ml ؊1 h ؊1 ), and CL ‫؍‬ 11.68 ؎ 7.00 ml ⅐ h ؊1 (1.03 ؎ 0.11 ml ⅐ h ؊1 ). Drug targeting to the lungs in general and alveolar macrophages in particular was observed. It was concluded that inhaled microparticles can reduce dose frequency and improve the pharmacologic index of the drug combination.

Page 1. Non-proportional/Non-monotonous Deformation Modeling of an Ultra High Strength Automotive... more Page 1. Non-proportional/Non-monotonous Deformation Modeling of an Ultra High Strength Automotive Steel Sheet Rahul K. Verma*, Yuki Ogihara**, Toshihiko Kuwabara*** and Kwansoo Chung**** *Research and Development ...

European Journal of Pharmaceutical Sciences, 2008

A hand-held apparatus designed for the purpose of administering dry powder inhalations to rodents... more A hand-held apparatus designed for the purpose of administering dry powder inhalations to rodents by "Nose-only" exposure was standardized. An aerosol of microparticles containing the anti-tuberculosis drugs isoniazid and rifabutin was generated and the dose available for inhalation by rodents was determined by collecting microparticles emitted at the delivery port. Separate groups of mice received inhalations of microparticles, free rifabutin orally, or free rifabutin intravenously. Rifabutin was estimated in serum and tissues by HPLC. When ~20 mg of microparticles were loaded in the apparatus, ~2.5 mg were collected at the delivery port in 30 seconds of operation. Mice inhaled ~300 μg of the 2.5 mg emitted at the delivery port. Alveolar macrophages of mice receiving inhalations for 30 sec accumulated 0.38 μg of rifabutin, while the amount in blood serum of these mice was 0.62 μg. In mice receiving 83 μg rifabutin intravenously or orally, the intracellular amounts were 0.06 and 0.07 μg respectively, while the amounts in serum were 1.02 and 0.80 μg. These observations confirmed that inhalation of microparticles targeted lung macrophages. The dose available for inhalation was consistent with the duration of exposure (10.5-13.5 CV%) and its dependence on the amount of microparticles loaded (r 2 =0.982), and on duration of exposure (r 2 =0.992), was satisfactory.

Draw‐Bending Analysis of a Cold Rolled DP980 Steel Sheet. [AIP Conference Proceedings 1353, 1405 ... more Draw‐Bending Analysis of a Cold Rolled DP980 Steel Sheet. [AIP Conference Proceedings 1353, 1405 (2011)]. Rahul K. Verma, Nobuyasu Noma, Kwansoo Chung, Toshihiko Kuwabara. Abstract. To assess the springback prediction ...

The constitutive model with combined isotropic-kinematic hardening along with hardening stagnatio... more The constitutive model with combined isotropic-kinematic hardening along with hardening stagnation (or permanent softening) [Verma, Kuwabara, Chung, Haldar: Int. J. Plasticity (submitted)] was used here for modeling the tension-compression behaviors of a 0.1 mm thick austenitic stainless steel sheet (SUS304), which was observed in a recent work [Kuwabara and Murakoso: Proc. CIRP 2010 Conf. (submitted)]. Springback was also experimentally measured for a shallow drawn rectangular cup here and it was verified using the above model. It was found that this model can successfully predict the Bauschinger effect and hardening stagnation. As for springback, it was found that in this particular case it depends on, other than the material model, factors like boundary conditions, in the finite element analysis (FEA), during unloading. It was also observed that incorporation of the Bauschinger effect and permanent softening is a key for accurate springback prediction and, therefore, the present model performs better than the one which is based only on isotropic hardening without any hardening stagnation.

In this work, as non-proportional/non-monotonous deformation experiments, two-stage and tension-c... more In this work, as non-proportional/non-monotonous deformation experiments, two-stage and tension-compression-tension uniaxial tests were performed, respectively, for a cold rolled ultra high strength dual phase steel sheet: DP780. Deformation behaviors under such deformation paths were found different than those of the ultra low carbon single phase steels observed by Verma et al. (Int. J. Plast. 2011, 82-101). To model the newly observed deformation behaviors, the combined type constitutive law previously proposed by Verma et al. (Int. J. Plast. 2011, 82-101) was successfully applied here. Permanent softening observed during reverse loading was properly characterized into the isotropic and kinematic hardening parts of the hardening law using tension-compression-tension test data. The cross effect observed in two-stage tests was also effectively incorporated into the constitutive law.

International Journal of Plasticity, 2011

Recently non-proportional deformation has received increased attention from researchers working i... more Recently non-proportional deformation has received increased attention from researchers working in the area of experimental and computational modeling of metal deformation. However, most of them are numerical in nature with limited experimental data available, making it further difficult to model non-proportional deformation. In the present work, two-stage uniaxial tests, along with uniaxial cyclic and biaxial tests for different stress ratios, have been performed to evaluate deformation behavior of ultra-low carbon high strength automotive steel. Behaviors like cross-effect and hardening stagnation, which are attributed to the evolution of complex dislocation structures, were observed in this steel. It was also noticed that this steel exhibits tension–compression asymmetry. As for constitutive modeling, a modified asymmetric yield function is proposed to be used with a combined isotropic–kinematic hardening model. Also methods to account for the hardening stagnation during reverse loading and the cross-effect during two-stage deformation are proposed. The resulting constitutive model showed reasonably good agreement with experimental results.

Journal of Materials Processing Technology, 2007

Share of high and advanced high strength steels in automobile is increasing, however, such steels... more Share of high and advanced high strength steels in automobile is increasing, however, such steels generally have poor formability and high amount of springback. One of the focus areas of research in high strength automotive steel is to increase the normal anisotropy to get better formability. Effect of strength and process parameters on springback has been studied by many researchers but that of anisotropy has not been studied by many. In the present work the effect of anisotropy on springback is predicted using finite element analysis for the benchmark problem of Numisheet-2005 [2005 Numisheet Benchmark 2, Springback prediction of a cross member, Proceedings of the 6th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Processes, Detroit, USA, August 15–19, 2005]. An analytical model is developed to cross check the trends predicted from the finite element analysis. The effective stress has not been treated as a constant and the radial stress is considered in the present model. Both the models (FE and analytical) predict that higher anisotropy, in general, gives higher springback. Finite element analysis of the problem shows that springback is minimum for an isotropic material.