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61.
The control of desired product quality attributes in the crystallization process is one of the major concerns of the pharmaceutical industries due to the established standard limits for active pharmaceutical ingredients in applications. The objective of the present work is to establish the fundamental understanding and methodology of the batch cooling sonocrystallization process to tune the crystal attributes over the range of operating parameters, i.e., ultrasound amplitude, duration of sonication, and cooling rate. For the constant cooling rate, the effect of three levels of ultrasound amplitude has been investigated over the range of durations of insonation. It is observed for a fixed cooling rate that the optimized set of ultrasound parameters shortens the induction time resulting in a finer range of particles increasing the surface area and narrowing the particle size distribution. The performance of the process in terms of thermal characteristics has been analyzed to delineate the effect of operating parameters to be employed as a function of the product characteristics. The simple expressions for temperature profiles during the process have been proposed as a function of saturation temperature to facilitate their applications in the optimization of the operating parameters for the desired product size and size range. 相似文献
62.
Pawandeep Singh Matharu;Abhishek Pratap Singh;Yuyang Song;Umesh Gandhi;Yonas Tadesse; 《Journal of polymer science. Part A, Polymer chemistry》2024,62(10):2071-2093
Soft silicone-based artificial skin is essential in soft robotics because of high elongation, safe human interaction, low energy requirements and ease of manufacturing. Inspired by nature, several attempts have been made to fabricate morphing structures using synthetic soft skin. In this study, a novel elastomeric skin is demonstrated featuring embedded actuators and micro-fluidic channels, that is capable of grasping objects. The actuators are twisted, and mandrel coiled nylon artificial muscles, with nichrome heaters that overcome key challenges in developing synthetic soft skin. The desired properties of a morphing skin are being low-cost, lightweight, highly deformable, compact size, silent cyclic actuation, fast response, and long life. The actuators are fabricated from 160 μm diameter resistance wires wrapped on twisted nylon 6 fishing line precursor fibers of 800 μm diameter. The wrapped nichrome (0.42 mm pitch) along with the twisted precursor fibers are coiled on a 1.4 mm diameter mandrel rod to obtain high strain. This muscle termed twisted, and mandrel coiled polymer fishing line muscle with nichrome is embedded in soft skin samples and tested. Characterization results on the actuators (3.2 mm in diameter) showed remarkable tensile actuation of ~36% strain from loaded length at 0.99 MPa for an input power of 4.9 W, a blocked stress of 1.27 MPa, an actuation frequency of 0.04 Hz, and a lifecycle >22,000 cycles. These actuators, when embedded in the soft skin of 4 mm thick, showed ~50% bending strain within 10s and a cyclic behavior with active water cooling. A soft gripper fabricated with embedded soft skin is integrated to our child-sized humanoid robot (HBS Robot) demonstrating its potential in grasping unconventional and deformable objects, hence advancing the progress in soft robotics. 相似文献
63.
64.
Abhishek Kumar Tripathi Mangalpady Aruna Elumalai Perumal Venkatesan Mohamed Abbas Asif Afzal Saboor Shaik Emanoil Linul 《Molecules (Basel, Switzerland)》2022,27(22)
In this paper, the impact of dust deposition on solar photovoltaic (PV) panels was examined, using experimental and machine learning (ML) approaches for different sizes of dust pollutants. The experimental investigation was performed using five different sizes of dust pollutants with a deposition density of 33.48 g/m2 on the panel surface. It has been noted that the zero-resistance current of the PV panel is reduced by up to 49.01% due to the presence of small-size particles and 15.68% for large-size (ranging from 600 µ to 850 µ). In addition, a significant reduction of nearly 40% in sunlight penetration into the PV panel surface was observed due to the deposition of a smaller size of dust pollutants compared to the larger size. Subsequently, different ML regression models, namely support vector machine (SVMR), multiple linear (MLR) and Gaussian (GR), were considered and compared to predict the output power of solar PV panels under the varied size of dust deposition. The outcomes of the ML approach showed that the SVMR algorithms provide optimal performance with MAE, MSE and R2 values of 0.1589, 0.0328 and 0.9919, respectively; while GR had the worst performance. The predicted output power values are in good agreement with the experimental values, showing that the proposed ML approaches are suitable for predicting the output power in any harsh and dusty environment. 相似文献
65.
Sirajudheen Anwar Jonaid Ahmad Malik Sakeel Ahmed Verma Abhishek Kameshwar Jowaher Alanazi Abdulwahab Alamri Nafees Ahemad 《Molecules (Basel, Switzerland)》2022,27(22)
Cancer is the leading cause of death and has remained a big challenge for the scientific community. Because of the growing concerns, new therapeutic regimens are highly demanded to decrease the global burden. Despite advancements in chemotherapy, drug resistance is still a major hurdle to successful treatment. The primary challenge should be identifying and developing appropriate therapeutics for cancer patients to improve their survival. Multiple pathways are dysregulated in cancers, including disturbance in cellular metabolism, cell cycle, apoptosis, or epigenetic alterations. Over the last two decades, natural products have been a major research interest due to their therapeutic potential in various ailments. Natural compounds seem to be an alternative option for cancer management. Natural substances derived from plants and marine sources have been shown to have anti-cancer activity in preclinical settings. They might be proved as a sword to kill cancerous cells. The present review attempted to consolidate the available information on natural compounds derived from plants and marine sources and their anti-cancer potential underlying EMT mechanisms. 相似文献
66.
Subhajit Laha Nimish Dwarkanath Abhishek Sharma Darsi Rambabu Sundaram Balasubramanian Tapas Kumar Maji 《Chemical science》2022,13(24):7172
Light hydrocarbon separation is considered one of the most industrially challenging and desired chemical separation processes and is highly essential in polymer and chemical industries. Among them, separating ethylene (C2H4) from C2 hydrocarbon mixtures such as ethane (C2H6), acetylene (C2H2), and other natural gas elements (CO2, CH4) is of paramount importance and poses significant difficulty. We demonstrate such separations using an Al-MOF synthesised earlier as a non-porous material, but herein endowed with hierarchical porosity created under microwave conditions in an equimolar water/ethanol solution. The material possessing a large surface area (793 m2 g−1) exhibits an excellent uptake capacity for major industrial hydrocarbons in the order of C2H2 > C2H6 > CO2 > C2H4 > CH4 under ambient conditions. It shows an outstanding dynamic breakthrough separation of ethylene (C2H4) not only for a binary mixture (C2H6/C2H4) but also for a quaternary combination (C2H4/C2H6/C2H2/CO2 and C2H4/C2H6/C2H2/CH4) of varying concentrations. The detailed separation/purification mechanism was unveiled by gas adsorption isotherms, mixed-gas adsorption calculations, selectivity estimations, advanced computer simulations such as density functional theory (DFT), grand canonical Monte Carlo (GCMC) and ab initio molecular dynamics (AIMD), and stepwise multicomponent dynamic breakthrough experiments.Industrially important C2H4 purification from multi-component hydrocarbon mixtures. 相似文献
67.
Chiranjit Mahato Sneha Menon Abhishek Singh Syed Pavel Afrose Jagannath Mondal Dibyendu Das 《Chemical science》2022,13(32):9225
Herein, we report that short peptides are capable of exploiting their anti-parallel registry to access cross-β stacks to expose more than one catalytic residue, exhibiting the traits of advanced binding pockets of enzymes. Binding pockets decorated with more than one catalytic residue facilitate substrate binding and process kinetically unfavourable chemical transformations. The solvent-exposed guanidinium and imidazole moieties on the cross-β microphases synergistically bind to polarise and hydrolyse diverse kinetically stable model substrates of nucleases and phosphatase. Mutation of either histidine or arginine results in a drastic decline in the rate of hydrolysis. These results not only support the argument of short amyloid peptides as the earliest protein folds but also suggest their interactions with nucleic acid congeners, foreshadowing the mutualistic biopolymer relationships that fueled the chemical emergence of life.Amyloid based short peptide assemblies use antiparallel registry to expose multiple catalytic residues to bind and cleave kinetically stable phosphoester bonds of nucleic acid congeners, foreshadowing interactions of protein folds with nucleic acids. 相似文献
68.
Arnab Kumar Nath Madhuparna Roy Chinmay Dey Abhishek Dey Somdatta Ghosh Dey 《Chemical science》2022,13(48):14305
The colocalization of heme rich deposits in the senile plaque of Aβ in the cerebral cortex of the Alzheimer''s disease (AD) brain along with altered heme homeostasis and heme deficiency symptoms in AD patients has invoked the association of heme in AD pathology. Heme bound Aβ complexes, depending on the concentration of the complex or peptide to heme ratio, exhibit an equilibrium between a high-spin mono-His bound peroxidase-type active site and a low-spin bis-His bound cytochrome b type active site. The high-spin heme–Aβ complex shows higher peroxidase activity than free heme, where compound I is the reactive oxidant. It is also capable of oxidizing neurotransmitters like serotonin in the presence of peroxide, owing to the formation of compound I. The low-spin bis-His heme–Aβ complex on the other hand shows enhanced peroxidase activity relative to high-spin heme–Aβ. It reacts with H2O2 to produce two stable intermediates, compound 0 and compound I, which are characterized by absorption, EPR and resonance Raman spectroscopy. The stability of compound I of low-spin heme–Aβ is accountable for its enhanced peroxidase activity and oxidation of the neurotransmitter serotonin. The effect of the second sphere Tyr10 residue of Aβ on the formation and stability of the intermediates of low-spin heme–Aβ has also been investigated. The higher stability of compound I for low-spin heme–Aβ is likely due to H-bonding interactions involving Tyr10 in the distal pocket.Low-spin heme-Aβ forms stable compound 0 and compound I in the presence of H2O2 where compound I is responsible for its substantial peroxidase activity. This compound I also oxidizes neurotransmitters which is a typical hallmark of Alzheimer''s disease. 相似文献
69.
The degradation of neurotransmitters is a hallmark feature of Alzheimer''s disease (AD). Copper bound Aβ peptides, invoked to be involved in the pathology of AD, are found to catalyze the oxidation of serotonin (5-HT) by H2O2. A combination of EPR and resonance Raman spectroscopy reveals the formation of a Cu(ii)–OOH species and a dimeric, EPR silent, Cu2O2 bis-μ-oxo species under the reaction conditions. The Cu(ii)–OOH species, which can be selectively formed in the presence of excess H2O2, is the reactive intermediate responsible for 5-HT oxidation. H2O2 produced by the reaction of O2 with reduced Cu(i)–Aβ species can also oxidize 5-HT. Both these pathways are physiologically relevant and may be involved in the observed decay of neurotransmitters as observed in AD patients.The mononuclear copper hydroperoxo species (Cu(ii)–OOH) of Cu–Aβ is the active oxidant responsible for serotonin oxidation by Cu–Aβ in the presence of physiologically relevant oxidants like O2 and H2O2, which can potentially cause oxidative degradation of neurotransmitters, a marker of Alzheimer''s disease. 相似文献
70.
Abhishek Verma Swati Nagpal Praveen K. Pandey P. K. Bhatnagar P. C. Mathur 《Journal of nanoparticle research》2007,9(6):1125-1131
Quantum Dots of CdS
x
Se1−x
embedded in borosilicate glass matrix have been grown using Double-Step annealing method. Optical characterization of the
quantum dots has been done through the combinative analysis of optical absorption and photoluminescence spectroscopy at room
temperature. Decreasing trend of photoluminescence intensity with aging has been observed and is attributed to trap elimination.
The changes in particle size, size distribution, number of quantum dots, volume fraction, trap related phenomenon and Gibbs
free energy of quantum dots, has been explained on the basis of the diffusion-controlled growth process, which continues with
passage of time. For a typical case, it was found that after 24 months of aging, the average radii increased from 3.05 to
3.12 nm with the increase in number of quantum dots by 190% and the size-dispersion decreased from 10.8% to 9.9%. For this
sample, the initial size range of the quantum dots was 2.85 to 3.18 nm. After that no significant change was found in these
parameters for the next 12 months. This shows that the system attains almost a stable nature after 24 months of aging. It
was also observed that the size-dispersion in quantum dots reduces with the increase in annealing duration, but at the cost
of quantum confinement effect. Therefore, a trade off optimization has to be done between the size-dispersion and the quantum
confinement. 相似文献