Browsing by Author "Ashutosh Gupta"

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A bayes analysis of modified Weibull distribution via Markov chain Monte Carlo simulation
(2010) S.K. Upadhyay; Ashutosh Gupta
This paper presents the posterior analysis of a new family defined in the literature as modified Weibull distribution. This family is a modification of the two-parameter Weibull model in the sense that it, besides covering increasing and decreasing hazard rates, also represents bathtub-shaped behaviour. Both the Gibbs sampler and the Metropolis algorithms have been used to provide complete analysis of the concerned posterior surfaces. The paper also considers examining the issue of model validation using predictive simulation ideas and the Bayesian p-value. Finally, numerical illustration has been provided based on two real data sets. © 2010 Taylor & Francis.
A bayes comparison of weibull extension and modified weibull models for data showing bathtub hazard rate
(Taylor and Francis Ltd., 2013) S.K. Upadhyay; Ashutosh Gupta; Bhaswati Mukherjee; Ankit Khokhar
A number of models have been proposed in the literature to model data reflecting bathtub-shaped hazard rate functions. Mixture distributions provide the obvious choice for modelling such data sets but these contain too many parameters and hamper the accuracy of the inferential procedures particularly when the data are meagre. Recently, a few distributions have been proposed which are simply generalizations of the two-parameterWeibull model and are capable of producing bathtub behaviour of the hazard rate function. The Weibull extension and the modified Weibull models are two such families. This study focuses on comparing these two distributions for data sets exhibiting bathtub shape of the hazard rate. Bayesian tools are preferred due to their wide range of applicability in various nested and non-nested model comparison problems. Real data illustrations are provided so that a particular model can be recommended based on various tools of model comparison discussed in the paper. © 2013 Taylor & Francis.
A Bayesian study for the comparison of generalized gamma model with its components
(Springer India, 2010) Bhaswati Mukherjee; Ashutosh Gupta; S.K. Upadhyay
Generalized gamma distribution offers a flexible family and many of the important lifetime models are obtained as component models by setting its shape parameters to unity. The flexibility of the generalized gamma model, however, occurs at the cost of its increased complexity. The present paper makes a simulation based Bayesian study to have a thorough comparison of the generalized gamma with its components in situations where the given data appear compatible with this family. Of course, if a component model is recommended the latter inferences are quite easy to deal with. The study has been conducted in two stages. First, the generalized gamma family with a scale and two shape parameters is examined to see if one or both of its shape parameters can be set to unity in order that the component models can be looked upon as possible candidates. Second, a threshold parameter added in to the family selected at the first stage is tested against zero to see if there is any desirability of threshold in the model(s). A real data set is considered for the purpose of illustration. The paper proceeds by checking compatibility of the various component models with the given data set and finally compares the models to select the one that is most pertinent with the data. © 2011, Indian Statistical Institute.
A Bayesian study for the comparison of generalized gamma model with its components
(Indian Statistical Institute, 2010) Bhaswati Mukherjee; Ashutosh Gupta; S.K. Upadhyay
Generalized gamma distribution offers a flexible family and many of the important lifetime models are obtained as component models by setting its shape parameters to unity. The flexibility of the generalized gamma model, however, occurs at the cost of its increased complexity. The present paper makes a simulation based Bayesian study to have a thorough comparison of the generalized gamma with its components in situations where the given data appear compatible with this family. Of course, if a component model is recommended the latter inferences are quite easy to deal with. The study has been conducted in two stages. First, the generalized gamma family with a scale and two shape parameters is examined to see if one or both of its shape parameters can be set to unity in order that the component models can be looked upon as possible candidates. Second, a threshold parameter added in to the family selected at the first stage is tested against zero to see if there is any desirability of threshold in the model(s). A real data set is considered for the purpose of illustration. The paper proceeds by checking compatibility of the various component models with the given data set and finally compares the models to select the one that is most pertinent with the data. © Indian Statistical Institute 2011.
Accelerated test system strength models based on Birnbaum-Saunders distribution: A complete Bayesian analysis and comparison
(2009) S.K. Upadhyay; Bhaswati Mukherjee; Ashutosh Gupta
Several models for studies related to tensile strength of materials are proposed in the literature where the size or length component has been taken to be an important factor for studying the specimens' failure behaviour. An important model, developed on the basis of cumulative damage approach, is the three-parameter extension of the Birnbaum-Saunders fatigue model that incorporates size of the specimen as an additional variable. This model is a strong competitor of the commonly used Weibull model and stands better than the traditional models, which do not incorporate the size effect. The paper considers two such cumulative damage models, checks their compatibility with a real dataset, compares them with some of the recent toolkits, and finally recommends a model, which appears an appropriate one. Throughout the study is Bayesian based on Markov chain Monte Carlo simulation. © 2009 Springer Science+Business Media, LLC.
Bayesian modeling of bathtub shaped hazard rate using various Weibull extensions and related issues of model selection
(Indian Statistical Institute, 2012) S.K. Upadhyay; Ashutosh Gupta; Dipak K. Dey
Bathtub shape is one of the most important behaviors of the hazard rate function that is quite common in lifetime data analysis. Such shapes are actually the combination of three different shapes and, as such, there have been several proposals to model such behavior. One such proposal is to combine at most three different distributions, often the Weibull or some similar model, separately for decreasing, constant, and increasing shapes of the hazard rate. Sometimes combination of two different models may also result in the required bathtub shape. The other proposal includes generalizing or modifying the two-parameter distribution by adding an extra parameter into it. It is often seen that the first proposal is quite cumbersome whereas the second fails to capture some important aspects of the data. The present work considers two recent generalizations/modifications of the two-parameter Weibull model, namely the Weibull extension and the modified Weibull models, and proposes mixing the two families separately with the three-parameter Weibull distribution in order to see if the mixing results in some real benefit though at the cost of too many parameters. The paper finally considers the complete Bayes analysis of the proposed models using Markov chain Monte Carlo simulation and compares them with both Weibull extension and the modified Weibull models in a Bayesian framework. It is observed that the mixture models offer drastic improvement over the individual models not only in terms of hazard rate but also in terms of overall performance. The results are illustrated with the help of a real data based example. © 2012, Indian Statistical Institute.
Bayesian modeling of bathtub shaped hazard rate using various Weibull extensions and related issues of model selection
(Springer India, 2012) S.K. Upadhyay; Ashutosh Gupta; Dipak K. Dey
Bathtub shape is one of the most important behaviors of the hazard rate function that is quite common in lifetime data analysis. Such shapes are actually the combination of three different shapes and, as such, there have been several proposals to model such behavior. One such proposal is to combine at most three different distributions, often the Weibull or some similar model, separately for decreasing, constant, and increasing shapes of the hazard rate. Sometimes combination of two different models may also result in the required bathtub shape. The other proposal includes generalizing or modifying the two-parameter distribution by adding an extra parameter into it. It is often seen that the first proposal is quite cumbersome whereas the second fails to capture some important aspects of the data. The present work considers two recent generalizations/modifications of the two-parameter Weibull model, namely the Weibull extension and the modified Weibull models, and proposes mixing the two families separately with the three-parameter Weibull distribution in order to see if the mixing results in some real benefit though at the cost of too many parameters. The paper finally considers the complete Bayes analysis of the proposed models using Markov chain Monte Carlo simulation and compares them with both Weibull extension and the modified Weibull models in a Bayesian framework. It is observed that the mixture models offer drastic improvement over the individual models not only in terms of hazard rate but also in terms of overall performance. The results are illustrated with the help of a real data based example. © 2012, Indian Statistical Institute.
Cabazitaxel-loaded redox-responsive nanocarrier based on d-alpha-tocopheryl-chitosan and hyaluronic acid for improved anti-tumor efficacy in DMBA-induced breast cancer model
(Royal Society of Chemistry, 2024) Abhishek Jha; Manish Kumar; Pooja Goswami; Kanchan Bharti; Manjit Manjit; Ashutosh Gupta; Sudheer Moorkoth; Biplob Koch; Brahmeshwar Mishra
The study involved the formulation of cabazitaxel loaded d-alpha-tocopheryl succinate/chitosan conjugate (CSVE) and hyaluronic acid (HA) based redox-responsive nanoparticles crosslinked using 3,3′-dithiodipropionic acid (DTPA). The nanoparticle surface was functionalized with cetuximab (Cmab) to give CSVE/HA/DTPA/Cmab NP for EGFR targeted delivery of the payload. The formulations were subjected to particle analysis, morphological assessment, solid-state characterization, and in vitro drug release studies. The results showed cationic, sub-200 nm sized spherical particles with the glutathione-responsive release of cabazitaxel. In vitro studies revealed a marked decrease in the IC50 value, improved cellular uptake, and a superior apoptotic effect. To determine the in vivo efficacy of the formulation, pharmacokinetic assessment, tumor regression analysis, and survival analysis were performed. The nanoparticles showed improved pharmacokinetic and anti-tumor efficacy compared to free cabazitaxel. The prepared nanoparticles demonstrated immense potential in targeted delivery of the payload for enhanced breast cancer therapy. © 2024 RSC.
Comparison of the Effect of Addition of Cyanoacrylate, Epoxy Resin, and Gum Arabic on Surface Hardness of Die Stone
(Blackwell Publishing Inc., 2016) Arvind Tripathi; Ashutosh Gupta; Soumyojeet Bagchi; Lallan Mishra; Abhina Gautam; Riti Madhok
Purpose: To observe the effects of incorporating cyanoacrylate, epoxy resins, and gum arabic on the abrasion resistance of type IV gypsum die materials. Materials and Methods: Forty specimens were prepared and divided into four groups (10 specimens in each group), namely group A (control), group B (die stone mixed with cyanoacrylate), group C (die stone mixed with epoxy resin), group D (die stone mixed with gum arabic). All the specimens were subjected to abrasion testing, wear volume analysis, Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM) analysis. Results: Abrasion testing showed maximum wear in the control group and minimum wear in the gum arabic group. Intergroup differences were statistically significant (p < 0.001). The largest mean difference was between control and gum arabic. The lowest was between cyanoacrylate and the control group. The mean wear volume was lowest in the gum arabic group (4.23 mm3) and highest in the control group (6.78 mm3). The FT-IR graphs of the gum arabic models showed the presence of CH2, which is responsible for its binding activity. SEM revealed that the irregular particles of gum arabic display an interlocking arrangement. This jigsaw puzzle pattern results in stronger physical bond formation. Conclusion: Observations from this study showed that the addition of gum arabic increases resistance to abrasion in type IV gypsum. Cyanoacrylates are good adhesives as well, but a major drawback is that they have very low resistance to chemical action with water and physical actions such as sunlight. Epoxy resins are powerful adhesives, but they attain their full efficiency when cured with heat. Cyanoacrylate and epoxy resin displayed poor physical bonding, primarily because of inhomogeneity. © 2016 American College of Prosthodontists.
Designing hydroxy-functionalized chiral salen ligand and its use in the synthesis of dioxadiazasilamacroheterocycles
(2010) M.S. Singh; Pratibha Singh; Ashutosh Gupta
Synthesis of dioxadiazasilamacroheterocycles is described. The key step involves the initial synthesis of symmetrical hydroxyl-functionalized chiral salen ligand, N, N-bis(2- hy droxy acetophenony lidene)-1, 2-diaminocy clohexane followed by sequential deprotonation with NaH to form dianion intermediate in situ, which reacts with diorganodichlorosilanes to furnish desired heterocycles. The products have been characterized by satisfactory elemental analyses and spectral (IR, 1H 13C, 29Si NMR and mass) studies.
Efficient synthesis of 13- to 20-membered Schiff base macrocycles via non-template method
(2012) M.S. Singh; R.K. Verma; Shweta Singh; Ashutosh Gupta
A set of hitherto unreported 13- to 20-membered Schiff base macrocycles have been synthesized by the reaction of Schiff base with dielectrophiles via the intermediacy of remote dianion in non-template method. The structural features of the synthesized macrocycles have been determined by their satisfactory elemental analyses and spectral (IR, 1H, 13C NMR and Mass) studies.
Facile one pot synthesis of dioxazadibenzocyclodecene-6-one, 6-thione and other homologues
(Arkat, 2009) M.S. Singh; Pratibha Singh; Pallavi Singh; Ashutosh Gupta
Previously unknown dioxazadibenzocyclodecene-6-one, -6-thione and other homologues were prepared via the intermediacy of a 1,9-dianion generated and used in situ from N-(2-hydroxymethylphenyl)salicylideneimine followed by treatment with a variety of dielectrophiles in a simple one-pot procedure. The products were characterized by satisfactory elemental analyses and spectral (IR,1H,13C NMR and Mass) studies.
Indium(0)-mediated Csp 3-S/O cross-coupling approach towards the regioselective alkylation of α-enolic esters/dithioesters: A mechanistic Insight
(Wiley-VCH Verlag, 2014) Sushobhan Chowdhury; Tanmoy Chanda; Ashutosh Gupta; Suvajit Koley; B. Janaki Ramulu; Raymond C. F. Jones; Maya Shankar Singh
We have reported an indium(0)-mediated Csp3-S/O cross-coupling approach that leads to the highly regioselective alkylation of α-enolic acetate/dithioacetate systems. This hetero cross-coupling reaction does not require additional co-catalyst or promoter, and the in situ generated organoindium species promotes the reaction by acting as the coupling partner of the α-enolic acetate/dithioacetate substrates. The excellent selectivity for C-, S-, or O-alkylation is solely dependent on the nucleophilic behavior of α-enolic acetate/dithioacetate systems. These results were further supported by DFT calculations of the relative electronic energies of the substrates and products as well as the activation barriers of the respective transformations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Synthesis and characterization of porous composite with tailored porosity fabricated using rice husk by utilizing red mud and coal mine tailing
(CRC Press/Balkema, 2025) Vaibhav Pandey; Ashish Singh Pareta; Anupam Tiwari; P. K. Singh; Ashutosh Gupta; Saroja Kanta Panda
Management and use of red mud (RM) and coal mine overburden waste (MW) have drawn attention over the past decade due to their enormous scale and associated environmental problems. The harmful impact of this solid waste and its leachates has damaged the nearby ecosystem and forced industries to look for alternative solutions just rather than dumping. Despite having a lot of research, industries are still looking for a solid solution that can be implemented. Mass conversion with economic feasibility is the major obstacle faced by these wastes. The current work examines the potential use of these wastes for fabricating porous ceramic bricks by incorporating multiple quantities of their mixture with rice husk. The physical qualities of bricks have been studied in relation to variations in the MW: RM ratio, sintering temperature, and Rice husk amount. The developed porous composite possesses apparent porosity, compressive strength, and thermal conductivity in the range of 26–54%, 0.83–6.83 MPa, and 0.37–0.67 W/mK respectively. The developed porous composite with tunable pore microstructure is seen as a potential material for thermal insulation and other similar applications. © 2025 The Author(s).
Synthesis of 3-hydroxyindanones via potassium salt of amino acid catalyzed regioselective intramolecular aldolization of ortho-diacylbenzenes
(Elsevier Ltd, 2015) Tanmoy Chanda; Sushobhan Chowdhury; Namrata Anand; Suvajit Koley; Ashutosh Gupta; Maya Shankar Singh
First organocatalytic intramolecular aldolization of ortho-diacylbenzenes to construct highly functionalized 3-hydroxyindanones is described. In this transformation a high trans-selectivity is achieved by the use of metal salt of amino acid. This method allows an easy access to the strained spirocyclic 3-hydroxyindanones related to a number of natural product frameworks. Synthesis of a new class of indole skeleton substituted by 3-hydroxyindanones added an extra essence to this new protocol. © 2015 Elsevier Ltd. All rights reserved.
Synthesis of new benzosubstituted dioxaphosphonines containing quinoxaline subunit
(2010) Pallavi Singh; Rakesh Tripathi; Rajiv K. Verma; Ganesh C. Nandi; Ashutosh Gupta; Maya S. Singh
A simple and efficient synthesis of previously unknown benzosubstituted dioxaphosphonines containing a quinoxaline subunit is described. Reasonably good yields of the products, mild reaction conditions, and convenient work-up are the advantages of this method. The procedure does not require any catalyst or activator and can be efficiently achieved via dianion cyclization. All the synthesized compounds have been characterized by satisfactory elemental analyses and spectral (IR, 1H, 13C, 31P NMR, and mass) studies. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright © Taylor & Francis Group, LLC.
Weibull extension model: A Bayes study using Markov chain Monte Carlo simulation
(2008) Ashutosh Gupta; Bhaswati Mukherjee; S.K. Upadhyay
Several generalizations of the two-parameter Weibull model have been proposed to model data sets that exhibit complex non-monotone shapes of hazard rate function. The present paper focuses on one such generalization referred to as the Weibull extension model in the literature. Complete Bayesian analysis of the model has been provided using Markov chain Monte Carlo simulation. Finally, a thorough study has been conducted for checking the adequacy of the model for a given data set using some of the graphical and numerical methods based on predictive simulation ideas. A real data set is considered for illustration. © 2007 Elsevier Ltd. All rights reserved.