Pijush Ghosh

Bio: Pijush Ghosh is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Materials science & Polymer. The author has an hindex of 14, co-authored 58 publications receiving 823 citations. Previous affiliations of Pijush Ghosh include Johns Hopkins University & North Dakota State University.

Evaluation of biological potential of laryngeal carcinoma by whole organ serial section a preliminary report

Abstract: Thus it appears from our studies that serial section offers a good tool for assessing the biological nature of laryngeal cancer as well as radiation reaction. It gives an idea of spread of cancer in all three dimensions which helps immensely in planning the management. Non involvement of conus elasticus, intralaryngeal muscles, the submucous glands and cartilages suggests a good prognosis. Pre-epiglottic space was found to be invaded by tumour from anterior commissural region and supraglottis. By serial section one is able to have a good idea about the immune response that is playing a part. Stage of cell differentiation of the growth is not absolutely parallel to the invasiveness of the growth. In addition, radiation reactions can be assessed. Here we have found tumour regression by radiation therapy not to be centripetal as suggested by many.

Interfacial fracture behaviour between cement paste and epoxy coating - An experimental and phase-field approach

Abstract: Surface coatings are mainly applied to protect concrete structures against various environmental conditions. However, the interface between the concrete and coating is a weak link, and interfacial delamination is the primary mode of failure. Fracture resistance is the main design criteria for these materials, and therefore, it is necessary to investigate possible causes of interfacial failure for preventive measures. To this end, we have investigated the potential failure mechanisms and measured interfacial strength by performing a pull-off adhesion test on epoxy coated cement paste. From the pull-off adhesion test, adhesive (interface) failure between cement paste and epoxy is predominantly observed. It is observed that the adhesive (interfacial) strength for the sample tested on 50th day is more than the 28 days hydrated sample. This is due to additional curing of cement paste samples after coating epoxy which leads to higher interfacial strength. We also present the phase-field model (PFM) to predict the adhesive failure for this system. The results obtained from the PFM, i.e., load at failure and crack path are validated against experimental results. Finally, the influence of various material parameters such as elastic modulus and fracture energy of the interface on interfacial fracture behaviour is studied.

Supraglottic horizontal partial laryngectomy for Supraglottic cancer invading the base of the tongue

Abstract: The technique of horizontal partial laryngectomy can be extended for removal of Supraglottolingual cancers with preservation of the functions of phonation, respiration and swallowing. Use of the outer perichondrium, elevated from the resected part of the thyroid cartilage, helps in better healing of the thyrolingual repair and probably prevents fistula formation. Serial histology has shown the adequacy of the line of excision in the technique used in these cases. Cervical block dissection in these cases can be deferred till such time when a metastatic node appears on regular follow up, because of the immunological viewpoints held currently regarding cancer. It is therefore recommended that conservation surgery can be adopted in the supraglottolingual variety of cancers and a satisfactory end result can be expected with conservation of laryngeal function.

Engineering the Nonmorphing Point of Actuation for Controlled Drug Release by Hydrogel Bilayer across the pH Spectrum.

Abstract: Hydrogel-based pH-responsive bilayer actuators exhibit bidirectional actuation due to the differences in the concentration gradient developed across the thickness, the volume expansion due to swelling, and the mechanical stiffness of the layers involved. At a pH value (point), where the sum of these factors generates moments of equal magnitudes, the moments cancel each other and result in no net actuation. This pH point is termed here as a "nonmorphing point". In this work, we present a bilayer of chitosan (CS) and carboxymethyl cellulose (CMC) cross-linked with citric acid (CA) with tunable nonmorphing points across the pH spectrum by modulating the concentration and cross-linking density of the layers involved. The standard CS/CMC bilayer films took about 40 s to completely fold (clockwise) in 0.1 M HCl and 78 s to completely fold (anticlockwise) in 0.1 M NaOH. Generally, pH-responsive actuators are designed for targeted drug delivery to a specific site inside the body as they show bidirectional (clockwise/anticlockwise) actuation around a single nonmorphing point. The same pH-responsive system cannot be applied for drug release at another site with a different functioning pH. Thus, having a pH-responsive system with multiple nonmorphing points is highly desirable. Drug release experiments were performed with FITC and EtBr as model drugs loaded in CS and CMC layers. Moreover, the clockwise/anticlockwise actuation of the bilayer around the nonmorphing point can facilitate or inhibit the release of a drug. The clockwise actuation resulted in 55% FITC release and inhibited EtBr release to 4%; anticlockwise actuation resulted in 50% EtBr release and inhibited FITC release to 5%. We demonstrated morphing induced drug release by hydrogel bilayer films with tunable nonmorphing points across the pH spectrum.

Deformation Mechanism of Chitosan/Hydroxyapatite Nanocomposite: A Molecular Dynamics study

Abstract: Biopolymers are new generation polymers which find applications in biomedical field, in food packaging, as edible films etc., due to its unique property of biodegradability and biocompatibility, which is a major concern in case of fossil derived polymers. The application of biopolymers gets limited due to its low mechanical properties. The mechanical properties of these biopolymers however can be enhanced by reinforcing with suitable fillers of nanometer size range, thereby forming nanocomposites. Chitosan (CS) is a polysaccharide which is one of the most extensively used biopolymer in drug delivery, bone tissue engineering etc. Chitosan/Hydroxyapatite (HAP) nanocomposite can be formed by dispersing HAP nanoparticles in chitosan matrix. The mechanical properties of nanocomposites are dependent on the interactions between nanoparticles and polymer matrix. It is thus essential to understand the mechanism between matrix and nanoparticles in order to tailor the mechanical properties for suitable applications. Molecular Dynamics (MD) is one of the possible tools to study the interactions at atomic level. It can also contribute significantly in the prediction of macro level properties. In this work, MD has been applied to study the underlying mechanisms at atomic length scale during the uniaxial deformation process of CS/HAP nanocomposites. The interaction between HAP and CS has been analyzed using radial distribution function, evolution of hydrogen bonding and electrostatic interactions during the deformation process. The initial results indicate an increase in the modulus of elasticity of CS/HAP nanocomposite when compared to pure chitosan for a given strain rate. It is observed that the primary interaction between nanoparticle and polymer matrix is in the form of an electrostatic attraction between the calcium present in HAP and the oxygen in chitosan chains.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Tailoring the photoluminescence of atomically precise nanoclusters.

Abstract: Due to their atomically precise structures and intriguing chemical/physical properties, metal nanoclusters are an emerging class of modular nanomaterials. Photo-luminescence (PL) is one of their most fascinating properties, due to the plethora of promising PL-based applications, such as chemical sensing, bio-imaging, cell labeling, phototherapy, drug delivery, and so on. However, the PL of most current nanoclusters is still unsatisfactory-the PL quantum yield (QY) is relatively low (generally lower than 20%), the emission lifetimes are generally in the nanosecond range, and the emitted color is always red (emission wavelengths of above 630 nm). To address these shortcomings, several strategies have been adopted, and are reviewed herein: capped-ligand engineering, metallic kernel alloying, aggregation-induced emission, self-assembly of nanocluster building blocks into cluster-based networks, and adjustments on external environment factors. We further review promising applications of these fluorescent nanoclusters, with particular focus on their potential to impact the fields of chemical sensing, bio-imaging, and bio-labeling. Finally, scope for improvements and future perspectives of these novel nanomaterials are highlighted as well. Our intended audience is the broader scientific community interested in the fluorescence of metal nanoclusters, and our review hopefully opens up new horizons for these scientists to manipulate PL properties of nanoclusters. This review is based on publications available up to December 2018.

Separation and Analysis of Microplastics and Nanoplastics in Complex Environmental Samples

Abstract: ConspectusThe vast amount of plastic waste emitted into the environment and the increasing concern of potential harm to wildlife has made microplastic and nanoplastic pollution a growing environmental concern. Plastic pollution has the potential to cause both physical and chemical harm to wildlife directly or via sorption, concentration, and transfer of other environmental contaminants to the wildlife that ingest plastic. Small particles of plastic pollution, termed microplastics (>100 nm and <5 mm) or nanoplastics (<100 nm), can form through fragmentation of larger pieces of plastic. These small particles are especially concerning because of their high specific surface area for sorption of contaminants as well as their potential to translocate in the bodies of organisms. These same small particles are challenging to separate and identify in environmental samples because their size makes handling and observation difficult. As a result, our understanding of the environmental prevalence of nanoplastics and ...

A critical appraisal of polymer-clay nanocomposites.

Abstract: The surge of interest in and scientific publications on the structure and properties of nanocomposites has made it rather difficult for the novice to comprehend the physical structure of these new materials and the relationship between their properties and those of the conventional range of composite materials. Some of the questions that arise are: How should the reinforcement volume fraction be calculated? How can the clay gallery contents be assessed? How can the ratio of intercalate to exfoliate be found? Does polymerization occur in the clay galleries? How is the crystallinity of semi-crystalline polymers affected by intercalation? What role do the mobilities of adsorbed molecules and clay platelets have? How much information can conventional X-ray diffraction offer? What is the thermodynamic driving force for intercalation and exfoliation? What is the elastic modulus of clay platelets? The growth of computer simulation techniques applied to clay materials has been rapid, with insight gained into the structure, dynamics and reactivity of polymer–clay systems. However these techniques operate on the basis of approximations, which may not be clear to the non-specialist. This critical review attempts to assess these issues from the viewpoint of traditional composites thereby embedding these new materials in a wider context to which conventional composite theory can be applied. (210 references)