Showing papers by "Gaurav Sharma published in 2018"

Applications of nanocomposite hydrogels for biomedical engineering and environmental protection

Abstract: Nanocomposite hydrogels are polymeric networks that possess a unique property of hydration. The presence of alcohols, carboxylic acids and amides as hydrophilic moieties in structure of nanocomposite hydrogels enhances their stiffness and water-absorbing capacity. Addition of cross-linker in the synthesis of hydrogels increases their stability under extreme conditions of temperature, pH and pressure. Natural polymer-based nanocomposite hydrogels are biodegradable, highly hydrophilic and possess good mechanical strength. Gelatin, chitin, cellulose, pectin, carrageenan, starch and alginate are natural polymers commonly used to fabricate nanocomposite hydrogels. Nanocomposite hydrogels have special characteristics such as high swelling rate, selectivity and stimuli-sensitive nature. Here we review nanocomposite hydrogels for environmental protection and biomedical engineering. Applications in biomedical engineering include drug delivery agents, wound dressing, tissue engineering and antibacterials. Applications in environmental protection include ion exchangers, adsorption, photocatalysis and soil conditioning. Many nanocomposite hydrogels show excellent adsorption selectivity for heavy metal ions: Cu2+ up to 30.35 mg/g, Pb2+ up to 35.94 mg/g, and Zn2+ and Fe3+ up to 94.34 mg/g. Xanthan gum-based nanocomposite hydrogel has removed 96% dye from industrial effluent as reported. In addition, most of the nanocomposite hydrogels showed better adsorption capacity for pollutants in the pH range from 5 to 7. The nanocomposite hydrogels could also be regenerated and successfully utilized for several times. Nanocomposite hydrogels are therefore good bio-absorbent materials for environmental detoxification.

Perovskites photovoltaic solar cells: An overview of current status

Abstract: Perovskite based solar cells have recently emerged as one of the possible solutions in the photovoltaic industry for availing cheap solution processable solar cells. Hybrid perovskites display special combination of low bulk-trap densities, ambipolar charge transport properties, good broadband absorption properties and long charge carrier diffusion lengths, which make them suitable for photovoltaic applications. The year 2015 witnessed an upsurge in the published research articles on perovskite solar cells (PSC) which is indicative of the potential of this material. Since the introduction of PSC the power conversion efficiency has reached above 22% in a relatively short period of time. However, the poor reproducibility in device fabrication and lack of uniformity of the PSCs performances is a major challenge in obtaining highly efficient large scale PSC devices. The aim of this paper is to present a brief review on the current status of perovskites based solar cell due to the use of different device architectures, fabrication techniques as well as on the use of various electron and hole interfacial layers (HTMs and ETMs). The review also discusses the basic mechanisms for device operation which provides better understanding on the properties of the various layers of device structures.

High-Performance Photocatalytic Hydrogen Production and Degradation of Levofloxacin by Wide Spectrum-Responsive Ag/Fe3O4 Bridged SrTiO3/g-C3N4 Plasmonic Nanojunctions: Joint Effect of Ag and Fe3O4

Abstract: Highly photoresponsive semiconductor photocatalysis for energy and environmental applications require judicious choice and optimization of semiconductor interfaces for wide spectral capabilities. This work aims at rational designing of highly active SrTiO3/g-C3N4 junctions bridged with Ag/Fe3O4 nanoparticles for utilizing Z-scheme transfer and surface plasmon resonance effect of Ag augmented by iron oxide. The SrTiO3/(Ag/Fe3O4)/g-C3N4 (SFC) catalyst was employed for photocatalytic hydrogen production and photodegradation of levofloxacin (LFC; 20 mg/L) under UV, visible, near infra-red, and natural solar light exhibiting high performance. Under visible light (<780 nm), SFC-3 sample (30 wt % g-C3N4 and 3% Ag/Fe3O4) shows a H2 evolution of 2008 μmol g–1 h–1 which is ∼14 times that of bare g-C3N4. In addition, 99.3% removal of LFC was degraded in 90 min under visible light with retention of activity under sun. The inherent topological properties, complete, higher charge separation, and reduced recombination a...

Impact of heavy metals and nanoparticles on aquatic biota

Abstract: Human activities such as industrialisation, urbanisation and agriculture have adversely impacted terrestrial and aquatic ecosystems. Water pollutants such as heavy metals and nanoparticles can undergo bioaccumulation and bioaugmentation. Heavy metals cannot be degraded and are hence added permanently. Nanoparticles are a potential threat because of their small size and unique properties. This article reviews the impact of various pollutants on aquatic biota and presents remediation methods. Benthic macroinvertebrates can be used as bioindicators to study the impact of pollutants on aquatic ecosystems. Fishes occupy the highest trophic level in the aquatic food chain and can therefore accumulate large amounts of metal from water, ultimately leading to biomagnification. Some organic compounds such as pesticides and fungicides are carcinogenic and sometimes resistant to degradation.

Improved DV-Hop localization algorithm using teaching learning based optimization for wireless sensor networks

Abstract: Node localization is one of the most critical issues for wireless sensor networks, as many applications depend on the precise location of the sensor nodes. To attain precise location of nodes, an improved distance vector hop (IDV-Hop) algorithm using teaching learning based optimization (TLBO) has been proposed in this paper. In the proposed algorithm, hop sizes of the anchor nodes are modified by adding correction factor. The concept of collinearity is introduced to reduce location errors caused by anchor nodes which are collinear. For better positioning coverage, up-gradation of target nodes to assistant anchor nodes has been used in such a way that those target nodes are upgraded to assistant anchor nodes which have been localized in the first round of localization. For further improvement in localization accuracy, location of target nodes has been formulated as optimization problem and an efficient parameter free optimization technique viz. TLBO has been used. Simulation results show that the proposed algorithm is overall 47, 30 and 22% more accurate than DV-Hop, DV-Hop based on genetic algorithm (GADV-Hop) and IDV-Hop using particle swarm optimization algorithms respectively and achieves high positioning coverage with fast convergence.

Aerogels and metal–organic frameworks for environmental remediation and energy production

Abstract: Environmental pollution and climate change are requiring new methods to clean pollutants and produce sustainable energy. Aerogels and metal organic frameworks are emerging as advanced porous materials with higher functionality, high surface area, high porosity and flexible chemistry. Aerogels are dried gels prepared using the sol–gel procedure, whereas metal organic frameworks are networks of organic ligands and metal ions connected by coordination bonds. Applications of aerogels include the removal of heavy metals, CO2 capture and reduction, photodegradation of pollutants, air cleanup and water splitting. This article reviews the synthesis and types of aerogels and metal organic frameworks, and the application to pollutant removal, energy production including hydrogen, methane reforming, CO2 conversion and NOx removal.

Menstrual hygiene management among women and adolescent girls in the aftermath of the earthquake in Nepal.

Abstract: Menstrual hygiene management (MHM) is an essential aspect of hygiene for women and adolescent girls between menarche and menopause. Despite being an important issue concerning women and girls in the menstruating age group MHM is often overlooked in post-disaster responses. Further, there is limited evidence of menstrual hygiene management in humanitarian settings. This study aims to describe the experiences and perceptions of women and adolescent girls on menstrual hygiene management in post-earthquake Nepal. A mixed methods study was carried out among the earthquake affected women and adolescent girls in three villages of Sindhupalchowk district of Nepal. Data was collected using a semi-structured questionnaire that captured experiences and perceptions of respondents on menstrual hygiene management in the aftermath of the Nepal earthquake. Quantitative data were triangulated with in-depth interview regarding respondent’s personal experiences of menstrual hygiene management. Menstrual hygiene was rated as the sixth highest overall need and perceived as an immediate need by 18.8% of the respondents. There were 42.8% women & girls who menstruated within first week of the earthquake. Reusable sanitary cloth were used by about 66.7% of the respondents before the earthquake and remained a popular method (76.1%) post-earthquake. None of the respondents reported receiving menstrual adsorbents as relief materials in the first month following the earthquake. Disposable pads (77.8%) were preferred by respondents as they were perceived to be clean and convenient to use. Most respondents (73.5%) felt that reusable sanitary pads were a sustainable choice. Women who were in the age group of 15-34 years (OR = 3.14; CI = (1.07-9.20), did not go to school (OR = 9.68; CI = 2.16-43.33), married (OR = 2.99; CI = 1.22-7.31) and previously used reusable sanitary cloth (OR = 5.82; CI = 2.33-14.55) were more likely to use the reusable sanitary cloth. In the immediate aftermath of the earthquake, women and girls completely depended on the use of locally available resources as adsorbents during menstruation. Immediate relief activities by humanitarian agencies, lacked MHM activities. Understanding the previous practice and using local resources, the reusable sanitary cloth is a way to address the menstrual hygiene needs in the post-disaster situations in Nepal.

Sorafenib inhibits proliferation and invasion in desmoid-derived cells by targeting Ras/MEK/ERK and PI3K/Akt/mTOR pathways.

Abstract: Desmoid tumors (DTs) are unusual neoplasms of mesenchymal origin that exhibit locally invasive behavior. Surgical resection is the initial treatment of choice for DTs. For patients with recurrent or unresectable disease, however, medical options are limited. Sorafenib is a multikinase inhibitor with known antitumor activity in various cancers via suppression of the PI3K/Akt/mTOR pathway. Here, we examined the effects of sorafenib on patient-derived DT cell lines, with the aim of characterizing the efficacy and molecular mechanism of action. Early passage DT-derived cells were treated with increasing doses of sorafenib (0-10 µM) and demonstrated up to 90% decrease in proliferation and invasion relative to controls. Signaling arrays identified multiple potential targets of sorafenib in the Ras/MEK/ERK and PI3K/Akt/mTOR signaling cascades. Immunoblot analysis revealed that sorafenib inhibited Akt, MEK and ERK phosphorylation, and this effect correlated with inhibition of total Akt and total MEK, while total ERK levels remained unchanged. Sorafenib also inhibited 4E-BP1 phosphorylation, and this effect correlated with decrease of p-eIF4E and total eIF4E. Finally, in combination with the mammalian target of rapamycin (mTOR) inhibitor everolimus, sorafenib decreased phosphorylation of the ribosomal protein and mTOR effector S6K in an additive manner. Taken together, our results suggest that sorafenib suppresses DT proliferation and invasion via inhibition of Ras/MEK/ERK and PI3K/Akt/mTOR signaling pathways with additional effects on translation. Sorafenib may be a promising therapeutic option in the treatment of DTs. Additional studies in DT patients are warranted to examine the efficacy of combination therapy using sorafenib.

Targeting hepatic pyruvate dehydrogenase kinases restores insulin signaling and mitigates ChREBP-mediated lipogenesis in diet-induced obese mice.

Abstract: Objective Mitochondrial pyruvate dehydrogenase kinases 1–4 (PDKs1–4) negatively regulate activity of the pyruvate dehydrogenase complex (PDC) by reversible phosphorylation. PDKs play a pivotal role in maintaining energy homeostasis and contribute to metabolic flexibility by attenuating PDC activity in various mammalian tissues. Cumulative evidence has shown that the up-regulation of PDK4 expression is tightly associated with obesity and diabetes. In this investigation, we test the central hypothesis that PDKs1-4 are a pharmacological target for lowering glucose levels and restoring insulin sensitivity in obesity and type 2 diabetes (T2D). Methods Diet-induced obese (DIO) mice were treated with a liver-specific pan-PDK inhibitor 2-[(2,4-dihydroxyphenyl) sulfonyl]isoindoline-4,6-diol (PS10) for four weeks, and results compared with PDK2/PDK4 double knockout (DKO) mice on the same high fat diet (HFD). Results Both PS10-treated DIO mice and HFD-fed DKO mice showed significantly improved glucose, insulin and pyruvate tolerance, compared to DIO controls, with lower plasma insulin levels and increased insulin signaling in liver. In response to lower glucose levels, phosphorylated AMPK in PS10-treated DIO and HFD-fed DKO mice is upregulated, accompanied by decreased nuclear carbohydrate-responsive element binding protein (ChREBP). The reduced ChREBP signaling correlates with down-regulation of hepatic lipogenic enzymes (ACC1, FAS, and SCD1), leading to markedly diminished hepatic steatosis in both study groups, with lower circulating cholesterol and triacylglyceride levels as well as reduced fat mass. PS10-treated DIO as well as DKO mice showed predominant fatty acid over glucose oxidation. However, unlike systemic DKO mice, increased hepatic PDC activity alone in PS10-treated DIO mice does not raise the plasma total ketone body level. Conclusion Our findings establish that specific targeting of hepatic PDKs with the PDK inhibitor PS10 is an effective therapeutic approach to maintaining glucose and lipid homeostasis in obesity and T2D, without the harmful ketoacidosis associated with systemic inhibition of PDKs.

Remediation of anionic dye from aqueous system using bio-adsorbent prepared by microwave activation.

Abstract: The present study was attempted to ascertain the possible application of activated carbon as a cost-effective and eco-friendly adsorbent prepared via microwave-assisted chemical activation. The activated carbon was characterized using different techniques. The various adsorption parameters have been optimized to examine the viability of activated carbon as a plausible sorbent for the remediation of Congo red (CR) dye from the aquatic system. The equilibrium data adequately fitted to the Langmuir isotherm with better R2 (0.994). The maximum adsorption capacity (qm) of activated carbon was recorded to be 68.96 mg/g. Additionally, sorptional kinetic data were examined by reaction-based and diffusion-based models such as pseudo-first-order and pseudo-second-order equations, and Elovich, intra-particle diffusion, and Dumwald–Wagner models, respectively. The computed values of thermodynamic parameters such as free energy change (ΔG0), enthalpy change (ΔH0) and entropy change (ΔS0) were recorded as −3.63...

Fuzzy logic based 3D localization in wireless sensor networks using invasive weed and bacterial foraging optimization

Abstract: The purpose of this paper is to improve the performance of node localization in 3D space for wireless sensor network. To achieve this objective, we propose two range free localization algorithms for 3D space in anisotropic environment using the application of bacterial foraging optimization (BFO) and invasive weed optimization (IWO). In proposed methods, only received signal strength (RSS) information between nodes is sufficient for estimating target nodes locations. The RSS information gives clue to find out the distances between target nodes and anchor nodes. To overcome the non-linearity between RSS and distance, edge weights between target nodes and their neighbouring anchor nodes are considered to estimate the positions of target nodes. To further reduce the computational complexity and to model the edge weights, we use fuzzy logic system in this paper. BFO and IWO techniques are used to further optimize the edge weights separately to achieve the better localization accuracy. The simulation results show the superiority of the proposed algorithms as compared to centroid method, weighted centroid and existing 3D localization algorithms in terms of localization accuracy, stability, positioning coverage and scalability.

Modified Energy-Efficient Range-Free Localization Using Teaching–Learning-Based Optimization for Wireless Sensor Networks

Abstract: This paper presents an energy-efficient Modified Distance Vector Hop algorithm using Teaching–Learning-Based Optimization, viz. MDV-TLBO, which is range-free, distributed localization algorithm for wireless sensor network (WSN). In the proposed algorithm, the hop size of anchor node is modified by adding correction factor. The concept of collinearity is introduced in this paper to reduce location errors caused by anchor nodes which are collinear. TLBO is used to enhance the localization accuracy, which is parameter-free, efficient optimization technique. Target nodes estimate their final coordinates after location upgradation procedure. In MDV-TLBO, anchor nodes communicate only one time with target nodes to broadcast their location. Hop size modification, optimal selection of anchor nodes, location optimization, and location upgradation are done at target node level, resulting considerable reduction in communication between nodes, due to which energy consumption of the nodes has been significantl...

Biosynthetic Potential of Bioactive Streptomycetes Isolated From Arid Region of the Thar Desert, Rajasthan (India).

Abstract: Acquisition of Actinobacteria, especially Streptomyces from previously underexplored habitats and the exploration of their biosynthetic potential have gained much attention in the rejuvenated antibiotics search programs. Herein, we isolated some Streptomyces strains, from an arid region of the Great Indian Thar Desert, which possess an ability to produce novel bioactive compounds. Twenty-one morphologically distinctive strains differing in their aerial and substrate mycelium were isolated by employing a stamping method. Among them, 12 strains were identified by a two-level antimicrobial screening method, exerting antimicrobial effects against a panel of indicator strains including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus species. Based on their potent antimicrobial activity, four isolates were further explored by 16S rRNA gene-based identification, genetic screening, and metabolomic analysis; and it was found that these strains belong to the genus Streptomyces. The selected strains were found to have polyketide synthase and non-ribosomal peptide synthetase systems. In addition, extracellular metabolomic screening revealed that the isolates produced analogs of doxorubicinol, pyrromycin, erythromycin, and 6-13 other putative novel metabolites. These results demonstrate the significance of Streptomyces inhabiting the arid region of Thar Desert, suggesting that similar arid environments can be considered as the reservoirs of novel Streptomyces strains that could have biotechnological significance.

Quantitative characteristics of the foot-and-mouth disease carrier state under natural conditions in India

Abstract: The goal of this study was to characterize the properties and duration of the foot-and-mouth disease (FMD) carrier state and associated serological responses subsequent to vaccination and naturally occurring infection at two farms in northern India. Despite previous vaccination of cattle in these herds, clinical signs of FMD occurred in October 2013 within a subset of animals at the farms containing juvenile-yearling heifers and steers (Farm A) and adult dairy cattle (Farm B). Subsequent to the outbreak, FMD virus (FMDV) asymptomatic carriers were identified in both herds by seroreactivity to FMDV non-structural proteins and detection of FMDV genomic RNA in oropharyngeal fluid. Carriers' seroreactivity and FMDV genome detection status were subsequently monitored monthly for 23 months. The mean extinction time of the carrier state was 13.1 ± 0.2 months, with extinction having occurred significantly faster amongst adult dairy cattle at Farm B compared to younger animals at Farm A. The rate of decrease in the proportion of carrier animals was calculated to be 0.07 per month. Seroprevalence against FMDV non-structural proteins decreased over the course of the study period, but was found to increase transiently following repeated vaccinations. These data provide novel insights into viral and host factors associated with the FMDV carrier state under natural conditions. The findings reported herein may be relevant to field veterinarians and governmental regulatory entities engaged in FMD response and control measures.