Research Interests:
Research Interests:
Today, there are not many good measures for detecting influential observations in case of fitting a logistic regression model. So, the purpose of this article is to extrapolate from the pre-existing deletion diagnostics defined for... more
Today, there are not many good measures for detecting influential observations in case of fitting a logistic regression model. So, the purpose of this article is to extrapolate from the pre-existing deletion diagnostics defined for detecting influential points for multiple linear regression, i.e. the DFFITS, DFBETAS and Cook's Distance to the scenario of a binary logistic regression model and then view the multinomial model as a special case of the same. The threshold for determining whether an observation is an influential observation or not is judged using the asymptotic distribution of the Cook's Distance in the multinomial setting, both for the single and the group deleted case. The results are examined under various simulation scenarios as well as over the modified Kyphosis data-set.
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Research Interests:
Stochastic Calculus has found a wide range of applications in analyzing the evolution of many natural, but complex systems. In this article, we discuss Brownian motion and Stochastic Calculus. In Chapter 2, we have listed preliminary... more
Stochastic Calculus has found a wide range of applications in analyzing the evolution of many natural, but complex systems. In this article, we discuss Brownian motion and Stochastic Calculus. In Chapter 2, we have listed preliminary notions about Stochastic Processes. In Chapter 3, we focus on the definition and properties of Brownian motion. In Chapter 4, we first discuss the construction of Ito integral and then look at the change of variables formula of Stochastic Calculus, the Ito formula. We finish with a discussion on existence and uniqueness problem for solutions of stochastic differential equations.
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An enhanced DC-DC converter is proposed in this paper, based on the combination of the Cuk and SEPIC converters. This converter uses a single switching node which is common to both Cuk and SEPIC energy transfer stages. The converter uses... more
An enhanced DC-DC converter is proposed in this paper, based on the combination of the Cuk and SEPIC converters. This converter uses a single switching node which is common to both Cuk and SEPIC energy transfer stages. The converter uses only one switch, yet provides dual outputs in the form of a bipolar DC bus with a common ground. Since the switch is grounded, a simple, non-isolated gate driver may be used. The proposed converter uses integrated magnetics cores to couple the input and output inductors, which significantly reduces the input current ripple. The new converter is referred to as the Coupled Inductors Combined Cuk-SEPIC (CI-CCS) converter.
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Research Interests:
Research Interests:
Ghosh, Soham PhD, Purdue University, December 2014. Hierarchical Cell Fluid Extracellular Matrix Interaction in Cell Microenvironment. Major Professor: Dr. Bumsoo Han, School of Mechanical Engineering. Hierarchical structural interactions... more
Ghosh, Soham PhD, Purdue University, December 2014. Hierarchical Cell Fluid Extracellular Matrix Interaction in Cell Microenvironment. Major Professor: Dr. Bumsoo Han, School of Mechanical Engineering. Hierarchical structural interactions between components of cell microenvironment, the extracellular matrix (ECM), cytoplasm, nucleus and fluid, are important phenomena that decide cell level physiological process and tissue engineering applications. One of those tissue engineering modalities is freezing of biomaterials, important in a wide variety of biomedical applications including cryopreservation and cryosurgeries. In order to design these applications, freezing-induced changes of the cells and tissues and corresponding biophysical mechanisms need to be well understood. Although the effects of freezing on cells in suspension have been extensively studied, the intracellular mechanics of cells embedded in the extracellular matrix (ECM) during freezing are not well understood. Since ...
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State-of-the-art meta reinforcement learning algorithms typically assume the setting of a single agent interacting with its environment in a sequential manner. A negative side-effect of this sequential execution paradigm is that, as the... more
State-of-the-art meta reinforcement learning algorithms typically assume the setting of a single agent interacting with its environment in a sequential manner. A negative side-effect of this sequential execution paradigm is that, as the environment becomes more and more challenging, and thus requiring more interaction episodes for the meta-learner, it needs the agent to reason over longer and longer time-scales. To combat the difficulty of long time-scale credit assignment, we propose an alternative parallel framework, which we name "Concurrent Meta-Reinforcement Learning" (CMRL), that transforms the temporal credit assignment problem into a multi-agent reinforcement learning one. In this multi-agent setting, a set of parallel agents are executed in the same environment and each of these "rollout" agents are given the means to communicate with each other. The goal of the communication is to coordinate, in a collaborative manner, the most efficient exploration of ...
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Newsvendor problem is an extensively researched topic in inventory management. In this class of inventory problems, shortage and excess costs are considered to be proportional to the quantity lost. But, for critical goods or commodities,... more
Newsvendor problem is an extensively researched topic in inventory management. In this class of inventory problems, shortage and excess costs are considered to be proportional to the quantity lost. But, for critical goods or commodities, inventory decision is a typical example where, excess or shortage may lead to greater losses than merely the total cost. Such a problem has not been discussed much in the literature. Moreover, majority of the existing literature assumes the demand distribution to be completely known. In this paper, we propose a generalization of the newsvendor problem for critical goods or commodities with higher shortage or excess losses but of same degree. We also assume that, the parameters of the demand distribution are unknown. We also discuss different estimators of the optimal order quantity based on a random sample of demand. In particular, we provide different estimators based on (i) full sample and (ii) broken sample data (i.e with single order statistic)....
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Solar power being a renewable energy resource has tremendous potential of usage in the imminent future and this paper is going to discuss an effective strategy to maximize solar energy harvest. This study has been done using... more
Solar power being a renewable energy resource has tremendous potential of usage in the imminent future and this paper is going to discuss an effective strategy to maximize solar energy harvest. This study has been done using MATLAB/Simulink combining solar modules, incremental conductance MPPT algorithm block and boost converter control block. Though solar energy harvest is dependent of irradiance, temperature and other climatic conditions it is imperative that a photovoltaic system operates at a maximum power point (MPP) in order to extract maximum energy from the system. The incremental conductance algorithm is an energy optimization strategy that provides fast dynamic response and well regulated photovoltaic (PV) output voltages. In addition, the number of parameter needed to be monitored are significantly lower than other algorithms, making the implementation much more streamlined and cost effective. This paper is going to discuss the observations of maximum power point tracking...
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Historical wildfire patterns have experienced a recent shift in terms of its scale and intensity. Through the continuing advancements in electrical protection technology, statistical forecasting methodologies, availability of... more
Historical wildfire patterns have experienced a recent shift in terms of its scale and intensity. Through the continuing advancements in electrical protection technology, statistical forecasting methodologies, availability of meteorological field data, and regional risk-modelling, wildfire management practices can be made more proactive in the United States and around the globe. To create a comprehensive and practical operating framework, an advanced seasonal autoregressive integrated moving average time series modelling technique for wildfire forecasting is explored. These regressive models, due to their mathematical accuracy has been used in many engineering and scientific applications. The study presented here was done using a qualitative investigation approach to wildfire data. Computer automated grid search techniques were developed to determine suitable seasonal regressive model hyper-parameters. With the usage of power transforms to fit skewed statistical models under study, ...
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Bauls, the wandering minstrels of rural Bengal (of both Bangladesh and India), are a socio-religiously marginalized cultural group. While the ritualistic practices and spiritual discourses of the Bauls have received scholarly attention,... more
Bauls, the wandering minstrels of rural Bengal (of both Bangladesh and India), are a socio-religiously marginalized cultural group. While the ritualistic practices and spiritual discourses of the Bauls have received scholarly attention, scholarship on Bauls’ songs about material and communicative adversities and their emancipatory visions is lacking. Bauls’ performances and discourses are precursors to envisioning alternative emancipatory possibilities that question dominant intolerances, oppressions, and exploitations. This article documents and reflects on the works of two contemporary Bauls—Shah Abdul Karim and Manimohan Das. Through their songs and performances, they (i) question the power structure and legitimize the sufferings and struggles of the downtrodden, and (ii) seek to raise societal consciousness in imagining a free and just society.
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Dedifferentiation of chondrocytes during in vitro passaging before implantation, and post implantation in vivo, is a critical limitation in cartilage tissue engineering. Several biophysical features define the dedifferentiated state... more
Dedifferentiation of chondrocytes during in vitro passaging before implantation, and post implantation in vivo, is a critical limitation in cartilage tissue engineering. Several biophysical features define the dedifferentiated state including a flattened cell morphology and increased stress fiber formation. However, how dedifferentiation influences nuclear mechanics, and the possible long-term implications of this state, are unknown. In this study, we investigated how chondrocyte dedifferentiation affects the mechanics of the chromatin architecture inside the cell nucleus and the gene expression of the structural proteins located at the nuclear envelope. Through an experimental model of cell stretching and a detailed spatial intranuclear strain quantification, we identified that strain is amplified and distribution of strain within the chromatin is altered under tensile loading in the dedifferentiated state. Further, using a confocal microscopy image-based finite element model and simulation of cell stretching, we found that the cell shape is the primary determinant of the strain amplification inside the chondrocyte nucleus in the dedifferentiated state. Additionally, we found that nuclear envelope proteins have lower gene expression in the dedifferentiated state suggesting a weaker nuclear envelope which can further intensify the intranuclear strain amplification. Our results indicate that dedifferentiation and altered nuclear strain could promote gene expression changes at the nuclear envelope, thus promoting further deviation from chondrocyte phenotype. This study highlights the role of cell shape on nuclear mechanics and lays the groundwork to design biophysical strategies for the maintenance and enhancement of the chondrocyte phenotype during expansion with a goal of successful cartilage tissue engineering. SIGNIFICANCE Chondrocytes dedifferentiate into a fibroblast-like phenotype in a non-native biophysical environment. Using high resolution microscopy, intranuclear strain analysis, finite element method based computational modeling, and molecular biology techniques, we investigated how mechanical force causes abnormal intranuclear strain distribution in chondrocytes during the dedifferentiation process. Overall, our results suggest that the altered cell geometry aided by an altered or weakened nuclear envelope structure are responsible for abnormal intranuclear strain during chondrocyte dedifferentiation that can further deviate chondrocytes to a more dedifferentiated state.
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Research Interests:
Research Interests:
Nucleus deformation has been shown to play a key role in cell mechanotransduction and migration. Therefore, it is of wide interest to accurately characterize nucleus mechanical behavior. In this study we present the first computational... more
Nucleus deformation has been shown to play a key role in cell mechanotransduction and migration. Therefore, it is of wide interest to accurately characterize nucleus mechanical behavior. In this study we present the first computational investigation of the in-situ deformation of a heterogeneous cell nucleus. A novel methodology is developed to accurately reconstruct a three-dimensional finite element spatially heterogeneous model of a cell nucleus from confocal microscopy z-stack images of nuclei stained for nucleus DNA. The relationship between spatially heterogeneous distributions microscopic imaging-derived greyscale values, shear stiffness and resultant shear strain is explored through the incorporation of the reconstructed heterogeneous nucleus into a model of a chondrocyte embedded in a PCM and cartilage ECM. Externally applied shear deformation of the ECM is simulated and computed intra-nuclear strain distributions are directly compared to corresponding experimentally measure...
Research Interests: Biophysics, Materials Science, Biology, Stiffness, Euchromatin, and 3 moreCell nucleus, Nucleus, and Lamin
ABSTRACTChromatin of the eukaryotic cell nucleus comprises of microscopically dense heterochromatin and loosely packed euchromatin domains, each with distinct transcriptional ability and roles in cellular mechanotransduction. While recent... more
ABSTRACTChromatin of the eukaryotic cell nucleus comprises of microscopically dense heterochromatin and loosely packed euchromatin domains, each with distinct transcriptional ability and roles in cellular mechanotransduction. While recent methods have been developed to characterize the nucleus, measurement of intranuclear mechanics remains largely unknown. Here, we describe the development of nuclear elastography, which combines microscopic imaging and computational modeling to quantify the relative elasticity of the heterochromatin and euchromatin domains. Using contracting murine embryonic cardiomyocytes, nuclear elastography reveals that the heterochromatin is almost four times stiffer than the euchromatin at peak deformation. The relative elasticity between the two domains changes rapidly during the active deformation of the cardiomyocyte in the normal physiological condition but progresses more slowly in cells cultured in a mechanically stiff environment, although the relative ...
Research Interests: Physics, Biology, Mechanobiology, Medicine, Euchromatin, and 5 moreChromatin, Cell nucleus, Small, Nucleus, and Heterochromatin
In this article, the performance of a meander‐line‐based microstrip patch antenna with split‐ring resonator (SRR)‐based slots and defected ground is analyzed at the terahertz frequency range. The designed antenna shows a multiband... more
In this article, the performance of a meander‐line‐based microstrip patch antenna with split‐ring resonator (SRR)‐based slots and defected ground is analyzed at the terahertz frequency range. The designed antenna shows a multiband application within a frequency range of 3.77 to 6.60 THz and operates over six different frequencies (viz. 3.83 THz, 4.24 THz, 5.12 THz, 5.50 THz, 5.95 THz, and 6.50 THz). A maximum return loss of 37 is achieved over the band of 5.85 to 6.18 THz, while a maximum realized gain of 7.54 dBi and a total efficiency of 54% is obtained at 4.24 THz. The ground and radiating elements of the antenna are made of gold. Silicon dioxide is used as a substrate material. The antenna simulation is performed and reported in this study. The proposed antenna finds its applications in the detection of colon cancer, skin cancer, brain tumor, drug detection, and communication fields for point‐to‐point communication purposes.
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Despite being the largest producer of movies in the world, Bollywood—the Hindi movie industry—is underresearched. In this article, we first identify the factors that make this industry unique in such a way that research conducted in the... more
Despite being the largest producer of movies in the world, Bollywood—the Hindi movie industry—is underresearched. In this article, we first identify the factors that make this industry unique in such a way that research conducted in the context of any other film industry may not be applicable in Bollywood. Using a mix of primary and secondary data, we provide insights into the relationship between various input and output variables. We also identify the major determinants of the satellite right price of a movie and statistically show why the current determinants are far from optimal. We also propose better factors for determining the satellite right price.
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Research Interests:
ABSTRACTEnvironmental mechanical cues are critical to guide cell fate. Forces transmit to the nucleus through the Linker of Nucleo- and Cytoskeleton (LINC) complex and are thought to influence the organization of chromatin that is related... more
ABSTRACTEnvironmental mechanical cues are critical to guide cell fate. Forces transmit to the nucleus through the Linker of Nucleo- and Cytoskeleton (LINC) complex and are thought to influence the organization of chromatin that is related to cell differentiation; however, the underlying mechanisms are unclear. Here, we investigated chromatin reorganization during murine cardiac development and found that cardiomyocytes establish a distinct architecture characterized by relocation of H3K9me3-modified chromatin from the nuclear interior to the periphery and co-localization to myofibrils. This effect was abrogated in stiff environments that inhibited cardiomyocyte contractility, or after LINC complex disruption, and resulted in the relocation of H3K27me3-modified chromatin instead. By generating high-resolution intra-nuclear strain maps during cardiomyocyte contraction, we discovered that the reorganization of H3K9me3-marked chromatin is influenced by tensile, but not compressive, nucl...
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Research Interests:
Research Interests: Evolutionary Biology, Genetics, Physiology, Biophysics, Materials Science, and 12 moreDevelopmental Biology, Computational Biology, Gene regulation, Cell Biology, Space Science, Medicine, Mechanotransduction, Skeletal Muscle, Hyperelastic material, Repetitive Strain Injury, Strain Distributions, and Biological System
Freezing of biomaterials is important in a wide variety of biomedical applications, including cryopreservation and cryosurgeries. For the success of these applications to various biomaterials, biophysical mechanisms, which determine... more
Freezing of biomaterials is important in a wide variety of biomedical applications, including cryopreservation and cryosurgeries. For the success of these applications to various biomaterials, biophysical mechanisms, which determine freezing-induced changes in cells and tissues, need to be well understood. Specifically, the significance of the intracellular mechanics during freezing is not well understood. Thus, we hypothesize that cells interact during freezing with the surroundings such as suspension media and the extracellular matrix (ECM) via two distinct but related mechanisms—water transport and cytoskeletal mechanics. The underlying rationale is that the cytoplasm of the cells has poroelastic nature, which can regulate both cellular water transport and cytoskeletal mechanics. A poroelasticity-based cell dehydration model is developed and confirmed to provide insight into the effects of the hydraulic conductivity and stiffness of the cytoplasm on the dehydration of cells in su...
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Research Interests:
The main purpose of the present paper is to make an appraisal of the existing Power Distribution Sector in India with special focus on loss reduction and efficiency improvement of power supply. Different major aspects of technical and... more
The main purpose of the present paper is to make an appraisal of the existing Power Distribution Sector in India with special focus on loss reduction and efficiency improvement of power supply. Different major aspects of technical and non-technical losses have been identified and on the basis of that a number of remedial measures have been suggested for loss reduction and to facilitate the improvement of overall efficiency of the power distribution system. This may provide further inputs to energy planners and managers.
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Research Interests:
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ABSTRACT Based on the concept of slow wave propagation, a dual-layer electromagnetic band gap (EBG) mushroom structure is used to reduce the area of a patch multi-antenna sub-system. While the inner layer aids in the antenna... more
ABSTRACT Based on the concept of slow wave propagation, a dual-layer electromagnetic band gap (EBG) mushroom structure is used to reduce the area of a patch multi-antenna sub-system. While the inner layer aids in the antenna miniaturization, the more compact upper layer helps in further reduction of the mutual coupling between the miniaturized patch antennas which is otherwise not possible for a single-layer EBG. Simulation is also performed for the mutual coupling and radiation characteristics of the multi-antenna structure for different inter-element separations which are experimentally verified.
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Research Interests:
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Thermal therapy is emerging as an effective treatment option for benign localized tumors. However, lack of reliable intraoperative monitoring techniques of the thermal lesion impedes more widespread application of thermal therapy in... more
Thermal therapy is emerging as an effective treatment option for benign localized tumors. However, lack of reliable intraoperative monitoring techniques of the thermal lesion impedes more widespread application of thermal therapy in clinical settings. In order to address this challenge, a thermometry technique using temperature dependent fluorescence of quantum dots was proposed and its feasibility was also demonstrated with an
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Research Interests: Materials Engineering, Mechanical Engineering, Biophysics, Materials Science, Thermodynamics, and 13 moreBiomedical Engineering, Microstructure, Tissue Engineering, Cryopreservation, Medicine, Extracellular Matrix, Cytoskeleton, Humans, Differential scanning calorimetry, Freezing, Mechanical Processes, Cell Survival, and Viability assay
Preservation of structural integrity inside cells and at cell-extracellular matrix (ECM) interfaces is a key challenge during freezing of biomaterials. Since the post-thaw functionality of cells depends on the extent of change in the... more
Preservation of structural integrity inside cells and at cell-extracellular matrix (ECM) interfaces is a key challenge during freezing of biomaterials. Since the post-thaw functionality of cells depends on the extent of change in the cytoskeletal structure caused by complex cell-ECM adhesion, spatiotemporal deformation inside the cell was measured using a newly developed microbead-mediated particle tracking deformetry (PTD) technique using fibroblast-seeded dermal equivalents as a model tissue. Fibronectin-coated 500 nm diameter microbeads were internalized in cells, and the microbead-labeled cells were used to prepare engineered tissue with type I collagen matrices. After a 24 h incubation the engineered tissues were directionally frozen, and the cells were imaged during the process. The microbeads were tracked, and spatiotemporal deformation inside the cells was computed from the tracking data using the PTD method. Effects of particle size on the deformation measurement method wer...
Research Interests: Mechanical Engineering, Biomechanical Engineering, Biophysics, Materials Science, Chemistry, and 15 moreBiomedical Engineering, Cell Adhesion, Cryopreservation, Medicine, Adhesion, Extracellular Matrix, Cell separation, Humans, Fibronectin, Elastic Modulus, Materials Testing, Freezing, Equipment Design, Cell Size, and fibroblasts
ABSTRACT The success of laser hyperthermia in the treatment of cancer depends on the extent of heat diffusion to the cancerous tissue. Understanding and optimising hyperthermia treatment requires accurate measurement and control of... more
ABSTRACT The success of laser hyperthermia in the treatment of cancer depends on the extent of heat diffusion to the cancerous tissue. Understanding and optimising hyperthermia treatment requires accurate measurement and control of temperature distribution. This paper reports experimental and theoretical results of surface temperature distribution and thermal lagging effect in tissue-mimics during laser irradiation. Experiments are conducted on bio-tissue mimics embedded with and without gold nanostructures irradiated by a continuous wave diode-pumped solid state laser having wavelength of 1064 nm. The experimental results of surface temperature distribution are compared with the computational prediction, obtained by solving numerically the Pennes bio-heat transfer based on classical Fourier model and on the dual phase lag model. Based on the multiple scattering phenomenon a new model for the laser attenuation in tissues is proposed. It compares well with the experimental data. In addition, the qualitative nature of damage to bio-tissue upon laser irradiation has been examined experimentally using atomic force microscopy to demonstrate the denaturation potential of the surface temperature, when gold nanostructures are used to mitigate temperature rise.
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Research Interests:
Research Interests: Computer Science, Heat Transfer, Drug delivery, Drug Delivery System, Cancer treatment, and 15 moreLow Frequency, Magnetic field, DNA, Humans, Computer Simulation, Electromagnetic Radiation, Cancer Therapy, Animals, Drug Delivery Systems, Electromagnetic Field, Diffusion Coefficient, Base Sequence, Drug Release, Antineoplastic Agents, and Magnetite Nanoparticles
Plasmonic nanomaterials have tremendous potential to improve the tumor specificity of traditional cancer ablation practices, yet little effort has been directed toward quantitatively understanding their photothermal energy conversion in... more
Plasmonic nanomaterials have tremendous potential to improve the tumor specificity of traditional cancer ablation practices, yet little effort has been directed toward quantitatively understanding their photothermal energy conversion in tumor tissues. In the present work, we develop a predictive model for plasmonic nanomaterial assisted tumor destruction under extracorporeal laser irradiation. Instead of appealing to heuristically based laser intensification models with tunable, tissue absorption and scattering coefficients, we consider fundamental characteristics of optoelectrothermal energy conversion and heat dissipation for plasmonic nanomaterials within living tumor tissues to construct a simulation tool that accurately reproduces our experimental findings, including aspects of delayed time-temperature characteristics. We believe the comprehensive modeling strategy outlined here provides a groundwork for the development of anticipatory therapeutic planning tools with individual...