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.

Insights on Water Dynamics in the Hygromorphic Phenomenon of Biopolymer Films

Abstract: Water-responsive biopolymer thin films with engineered matrix characteristics can accomplish desirable shape changing properties such as self-folding. Self-folding response of chitosan film is experimentally characterized by its total folding time and rate of folding. Here, atomistic simulation is employed to investigate the molecular mechanism responsible for modified self-folding behavior observed in nanoparticle reinforced chitosan films. The nanocomposite system is solvated with water content varying from 10% to 100% of total mass of the system. The free volume available for diffusion of water molecules is affected by the flexibility of glycosidic linkages present in chitosan chains. The increase in mobility of water molecules with increase in water content decides the rate of folding. A separate molecular system is modeled with confined region between nanoparticles densified with chitosan chains and water molecules. The thickness of confined region is determined from the critical distance of influenc...

Impact of β-Sheet Conformations on the Mechanical Response of Protein in Biocomposites

Abstract: Proteins in biological nanocomposites play an important role in their mechanical response. Proteins in nacre, the inner layer of seashells, have been shown to have exceptional mechanical properties. One of the important nacre proteins, Lustrin-A, has abundance of polypeptides in zig-zag conformation called β-sheets. β-sheets of protein when present close to each other in multiple numbers could take the shape of a planar β-sheath like structure or a β-barrel to form a domain. In natural proteins both these types of structures are commonly found. However, the conformation of β-sheets in Lustrin-A is not known at this time. Effort has been made through this work to study the mechanical response of these β-planar sheath and β-barrel structures when subjected to external loads. Comparative study of the stress-deformation characteristics of these two types of structures has been made. Both these structures with almost similar number of amino acids have been extracted from one single spinach protein: Ferredoxin ...

Surface dissimilarity affects critical distance of influence for confined water

Abstract: Water at interfaces and under nano-confinement is part of many natural processes. The behavior of this water is greatly influenced by the nature of the surfaces it is in contact with and the confinement distance. The objective of this study is to understand the behaviour of confined water between dissimilar (X–Y) surfaces under varying confinement spacing. The surfaces considered were hydrophilic in nature and the combinations were considered based on crystal structure and surface energy. The critical distance of influence of mineral substrates on the water molecules was determined by applying time-averaged static properties such as interfacial layer density and orientation and dynamic properties such as diffusion. It was observed that dynamic properties provide a higher value of critical distance compared to static properties for dissimilar surface combination. The reason for this disparity is probed in terms of mineral–water and water–water interactions. The disproportion of strong and weak H-bonds was observed to be significant in determining the dynamic behaviour of interfacial layer. We applied hydrophilic surface combinations of tricalcium silicate (C3S) and dicalcium silicate (C2S) for our investigations.

Changes in tracheobronchial angles as a function of age

Abstract: Earlier studies with regard to tracheobronchial angulations have put forward contradictory views. It has been established that on an average the right tracheobronchial angle is 30° while the left one is 47° with a difference of 17° between the two in all age groups (Brown & Fisk, 1980). There is another view that in children, below the age of 3 years, both tte bronchi come off the trachea at an equal angle unlike the arrangements in the adults (Adriani and Griggs, 1977). Ghosh (1987) found that on an average there is a difference of 6° between the right and left tracheobronchial angles in children and Hassan et al (1991) found this to be between 2° and 6.3°.

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)