14 research outputs found
Implicit Chain Particle Model for Polymer Grafted Nanoparticles
Matrix-free nanocomposites made from polymer grafted nanoparticles (PGN)
represent a paradigm shift in materials science because they greatly improve
nanoparticle dispersion and offer greater tunability over rheological and
mechanical properties in comparison to neat polymers. Utilizing the full
potential of PGNs requires a deeper understanding of how polymer graft length,
density, and chemistry influence interfacial interactions between particles.
There has been great progress in describing these effects with molecular
dynamics (MD). However, the limitations of the length and time scales of MD
make it prohibitively costly to study systems involving more than a few PGNs.
Here, we address some of these challenges by proposing a new modeling paradigm
for PGNs using a strain-energy mapping framework involving potential of mean
force (PMF) calculations. In this approach, each nanoparticle is coarse-grained
into a representative particle with chains treated implicitly, namely, the
implicit chain particle model (ICPM). Using a chemistry-specific CG-MD model of
PMMA as a testbed, we derive the effective interaction between particles
arranged in a closed-packed lattice configuration by matching bulk
dilation/compression strain energy densities. The strain-rate dependence of the
mechanical work in ICPM is also discussed. Overall, the ICPM model increases
the computational speed by approximately 5-6 orders of magnitude compared to
the CG-MD models. This novel framework is foundational for particle-based
simulations of PGNs and their blends and accelerates the understanding and
predictions of emergent properties of PGN materials
Reutilization of waste fungal biomass for concomitant production of proteochitinolytic enzymes and their catalytic products by Alcaligenes faecalis SK10
Fungal biomass, being organic waste, could be an excellent source of protein, carbohydrate and minerals. However, it has not been exploited fully until now. Efficient management of this waste can not only address the environmental impact on its disposal but also yield value-added metabolites. In the present study, in order to explore its potential, we subjected dead fungal biomass of Aspergillus niger SKN1 as substrate for both fermentative and enzymatic biodegradation, respectively by potent proteo-chitinolytic bacteria Alcaligenes faecalis SK10 and its enzyme cocktail. The results revealed that reasonable amount of protease and chitinase could be biosynthesized by the fermentative mode of utilization, while a mixture of amino acid, peptides and low-molecular weight amino-sugar (mono and oligomeric form of N-acetylglucosamine) could be generated through enzymatic hydrolysis. The physicochemical condition of both the bioprocess was subsequently optimized through statistical approach. The projected utilization of waste zero-valued fungal biomass offer a sustainable and environmentally sound method for production of microbial metabolites and large scale execution of the same could be proficient and in tune with the principle of circular economy
A Brief Review on the Latest Developments on Pharmaceutical Compound Degradation Using g-C<sub>3</sub>N<sub>4</sub>-Based Composite Catalysts
Pharmaceutical compounds (PCs) are one of the most notable water pollutants of the current age with severe impacts on the ecosystem. Hence, scientists and engineers are continuously working on developing different materials and technologies to eradicate PCs from aqueous media. Among various new-age materials, graphitic carbon nitride (g-C3N4) is one of the wonder substances with excellent catalytic property. The current review article describes the latest trend in the application of g-C3N4-based catalyst materials towards the degradation of various kinds of drugs and pharmaceutical products present in wastewater. The synthesis procedure of different g-C3N4-based catalysts is covered in brief, and this is followed by different PCs degraded as described by different workers. The applicability of these novel catalysts in the real field has been highlighted along with different optimization techniques in practice. Different techniques often explored to characterize the g-C3N4-based materials are also described. Finally, existing challenges in this field along with future perspectives are presented before concluding the article
Predicting the Effect of Hardener Composition on the Mechanical and Fracture Properties of Epoxy Resins Using Molecular Modeling
Improving the toughness of brittle epoxy while keeping its high strength-to-weight ratio is challenging, as these two properties work against each other. Fracture processes are difficult to ascertain with experiments, as they occur at nanoscopic lengths and time scales and require higher efficiency than what can be attained with atomistic simulations. To overcome this challenge, we utilize a recently developed chemistry specific coarse-grained model to examine two different hardeners, diamine 4,4′-methylenebis(cyclohexylamine) (PACM) and propylene oxide diamine (Jeffamine), to cure bisphenol A diglycidyl ether (DGEBA) at varying stoichiometries and understand how hardener composition influences the elasticity, yield strength, and fracture toughness of epoxy resins. The results indicate that PACM mainly contributes to the modulus and that long Jeffamine chains increase fracture toughness by making the epoxy ductile, whereas short Jeffamine chains significantly improve the yield strength. Longer Jeffamines also lead to larger voids and the formation of fibrils that carry a significant amount of stress and contribute to toughness. Interestingly, the Ashby plots reveal that epoxies with intermediate-length Jeffamine chains (D800 and D2000) outperform other systems, as the toughness enhancement from flexible Jeffamine chains and the stiffness due to PACM help to overcome the strength-toughness trade-off. Our modeling framework and findings establish a path toward resin design from predictive multiscale models with no empirical input and reveal new insights into the molecular failure mechanisms of epoxy resins.</p
Predicting the Effect of Hardener Composition on the Mechanical and Fracture Properties of Epoxy Resins Using Molecular Modeling
Improving the toughness of brittle epoxy while keeping its high strength-to-weight ratio is challenging, as these two properties work against each other. Fracture processes are difficult to ascertain with experiments, as they occur at nanoscopic lengths and time scales and require higher efficiency than what can be attained with atomistic simulations. To overcome this challenge, we utilize a recently developed chemistry specific coarse-grained model to examine two different hardeners, diamine 4,4′-methylenebis(cyclohexylamine) (PACM) and propylene oxide diamine (Jeffamine), to cure bisphenol A diglycidyl ether (DGEBA) at varying stoichiometries and understand how hardener composition influences the elasticity, yield strength, and fracture toughness of epoxy resins. The results indicate that PACM mainly contributes to the modulus and that long Jeffamine chains increase fracture toughness by making the epoxy ductile, whereas short Jeffamine chains significantly improve the yield strength. Longer Jeffamines also lead to larger voids and the formation of fibrils that carry a significant amount of stress and contribute to toughness. Interestingly, the Ashby plots reveal that epoxies with intermediate-length Jeffamine chains (D800 and D2000) outperform other systems, as the toughness enhancement from flexible Jeffamine chains and the stiffness due to PACM help to overcome the strength-toughness trade-off. Our modeling framework and findings establish a path toward resin design from predictive multiscale models with no empirical input and reveal new insights into the molecular failure mechanisms of epoxy resins.</p
A catch bond mechanism with looped adhesive tethers for self-strengthening materials
Abstract The lifetime of chemical bonds shortens exponentially with force. Oddly, some protein-ligand complexes called catch bonds exhibit a sharp increase in lifetime when pulled with greater force. Inventing catch bond interfaces in synthetic materials would enable force-enhanced kinetics or self-strengthening under mechanical stress. Here, we present a molecular design that recapitulates catch bond behavior between nanoparticles tethered with macromolecules, consisting of one looped and one straight tether linking particles with weak adhesion. We calibrate the loop stiffness such that it opens around a target force to enable load-sharing among tethers, which facilitates a sequential to coordinated failure transition that reproduces experimental catch bond force-lifetime curve characteristics. We derive an analytical relation validated by molecular simulations to prove that loop and adhesion interactions can be tailored to achieve a spectrum of catch bond lifetime curves with this simple design. Our predictions break new ground towards designing tunable, catch-bond inspired self-strengthening materials
Solitary intracavitory cardiac metastasis
Metastatic cardiac tumors are more common than the primary ones and they most commonly involve the pericardium or myocardium. Very rarely they may show partial or total intracavitory growth. Ours is one such case of solitary intracavitory cardiac metastasis in a patient with adenocarcinoma of the right lung who presented with hemoptysis and palpitation. Echocardiography and histopathological study clinched the diagnosis
All-optical observation of giant spin transparency at the topological insulator BiSbTe1.5Se1.5/Co20Fe60B20 interface
Abstract The rise of three-dimensional topological insulators as an attractive playground for the observation and control of various spin-orbit effects has ushered in the field of topological spintronics. To fully exploit their potential as efficient spin-orbit torque generators, it is crucial to investigate the efficiency of spin injection and transport at various topological insulator/ferromagnet interfaces, as characterized by their spin-mixing conductances and interfacial spin transparencies. Here, we use all-optical time-resolved magneto-optical Kerr effect magnetometry to demonstrate efficient room-temperature spin pumping in Sub/BiSbTe1.5Se1.5(BSTS)/Co20Fe60B20(CoFeB)/SiO2 thin films. From the modulation of Gilbert damping with BSTS and CoFeB thicknesses, the spin-mixing conductances of the BSTS/CoFeB interface and the spin diffusion length in BSTS are determined. For BSTS thicknesses far exceeding the spin diffusion length, in the so-called “perfect spin sink” regime, we obtain an interfacial spin transparency as high as 0.9, promoting such systems as scintillating candidates for spin-orbitronic devices