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"Mohan, S."
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Micro/nano-plastics occurrence, identification, risk analysis and mitigation: challenges and perspectives
Micro/nanoplastics (MP/NPs) are emerging global pollutants that garnered enormous attention due to their potential threat to the ecosystem in virtue of their persistence and accumulation. Notably, United Nations Environment Programme (UNEP) yearbook in 2014 proposed MPs as one among ten emergent issues that the Earth is facing today. MP/NPs can be found in most regularly used products (primary microplastics) or formed by the fragmentation of bigger plastics (secondary microplastics) and are inextricably discharged into the environment by terrestrial and land-based sources, particularly runoff. They are non-degradable, biologically incompatible, and their presence in the air, soil, water, and food can induce ecotoxicological issues and also a menace to the environment. Due to micro size and diverse chemical nature, MP/NPs easily infiltrate wastewater treatment processes. This communication reviews the current understanding of MP/NPs occurrence, mobility, aggregation behavior, and degradation/assimilation in terrestrial, aquatic (fresh & marine), atmospheric depositions, wetlands and trophic food chain. This communication provide current perspectives and understanding on MP/NPs concerning (1) Source, occurrence, distribution, and properties (2) Impact on the ecosystem and its services, (3) Techniques in detection and identification and (4) Strategies to manage and mitigation.
Journal Article
Cellular, Molecular, and Physiological Aspects of In Vitro Plant Regeneration
Plants generally have the highest regenerative ability because they show a high degree of developmental plasticity. Although the basic principles of plant regeneration date back many years, understanding the cellular, molecular, and physiological mechanisms based on these principles is currently in progress. In addition to the significant effects of some factors such as medium components, phytohormones, explant type, and light on the regeneration ability of an explant, recent reports evidence the involvement of molecular signals in organogenesis and embryogenesis responses to explant wounding, induced plant cell death, and phytohormones interaction. However, some cellular behaviors such as the occurrence of somaclonal variations and abnormalities during the in vitro plant regeneration process may be associated with adverse effects on the efficacy of plant regeneration. A review of past studies suggests that, in some cases, regeneration in plants involves the reprogramming of distinct somatic cells, while in others, it is induced by the activation of relatively undifferentiated cells in somatic tissues. However, this review covers the most important factors involved in the process of plant regeneration and discusses the mechanisms by which plants monitor this process.
Journal Article
The burden of scrub typhus in India: A systematic review
Background Scrub typhus, a vector-borne zoonotic infection caused by the bacteria Orientia tsutsugamushi, is one of the most common and clinically important rickettsial infections worldwide. An estimated one million cases occur annually with a high case fatality rate. Although scrub typhus is a major public health threat in India, the burden and distribution remains unclear. We aimed to estimate the burden of scrub typhus in India. Methodology We performed a systematic review of published literature on scrub typhus from India to extract information on epidemiology, morbidity, and mortality. Important databases were searched using keywords and appropriate combinations. We identified observational, interventional, and population-based studies and extracted the data to evaluate the number of cases diagnosed using serology or PCR and the number of deaths due to scrub typhus. We conducted a systematic narrative synthesis to summarize included studies. Principal findings In the last decade, there were 18,781 confirmed scrub typhus cases reported in 138 hospital-based studies and two community-based studies. IgM ELISA was used in 122 studies to confirm the cases in majority (89%). The proportion of scrub typhus among acute undifferentiated febrile illness (AUFI) studies was 25.3%, and community seroprevalence was 34.2%. Ninety studies had data published on multiple organ involvement out of which 17.4% of cases had multiple organ dysfunction syndromes, 20.4% patients required ICU admission, and 19.1% needed ventilation. The overall case-fatality rate was 6.3%, and the mortality among those with multi-organ dysfunction syndrome was as high as 38.9%. Conclusion/significance Scrub typhus, a common acute febrile illness in India causing severe morbidity, accounts for a large number of deaths. The burden of the disease has been underappreciated. Early diagnosis and prompt treatment can significantly reduce complications and mortality. Establishing good surveillance and instituting appropriate control measures are urgently needed.
Journal Article
Underlying factors determining grain morphologies in high-strength titanium alloys processed by additive manufacturing
In recent research, additions of solute to Ti and some Ti-based alloys have been employed to produce equiaxed microstructures when processing these materials using additive manufacturing. The present study develops a computational scheme for guiding the selection of such alloying additions, and the minimum amounts required, to effect the columnar to equiaxed microstructural transition. We put forward two physical mechanisms that may produce this transition; the first and more commonly discussed is based on growth restriction factors, and the second on the increased freezing range effected by the alloying addition coupled with the imposed rapid cooling rates associated with AM techniques. We show in the research described here, involving a number of model binary as well as complex multi-component Ti alloys, and the use of two different AM approaches, that the latter mechanism is more reliable regarding prediction of the grain morphology resulting from given solute additions.
Predictive scheme for Ti alloys with equiaxed microstructures is often limited by the methods based on growth restriction factors, Q. Here, the authors present a predictive solution based on the freezing range of alloys for columnar to equiaxed transition during fusion-based additive manufacturing.
Journal Article
Obscure yet Promising Oleaginous Yeasts for Fuel and Chemical Production
The rapid depletion of petroleum-based fossil fuels has led to the development of alternative fuel and energy solutions from renewable resources. Lipid-derived oleochemicals and sugar-derived bioethanol were initially produced from plant feedstocks, but in the interest of agricultural land conservation and food security, the focus has now shifted toward so-called ‘third-generation feedstocks’, of which yeasts are a major component. The quest to identify economically lucrative bioprocesses has led to the identification of several nonconventional oleaginous yeast species that have certain advantages over existing model species. Here, we review such underexplored oleaginous yeast species and discuss their potential bioeconomy applications. We also provide a broader perspective on possible avenues for strain improvement to reduce the cost of lipid production.
Generating carbon neutral fuels from oleaginous yeasts by utilizing waste feedstock as carbon sources in a circular economy is gaining importance.Recently, several nonconventional oleaginous yeast species with high lipid production efficiency were identified as potential platforms for oleochemical production.These nonconventional yeasts can use the waste feedstocks and feed on broader sugar ranges. They can also coproduce value-added chemicals in addition to lipids.Nevertheless, the genetic resources and other metabolic features of these nonconventional yeast strains need further characterization.The cost of bioprocessing will be minimized through exploration of new oleaginous yeast strains, process optimization, and strain improvement strategies.
Journal Article
Microalgal Cell Biofactory—Therapeutic, Nutraceutical and Functional Food Applications
Microalgae are multifaceted photosynthetic microorganisms with emerging business potential. They are present ubiquitously in terrestrial and aquatic environments with rich species diversity and are capable of producing significant biomass. Traditionally, microalgal biomass is being used as food and feed in many countries around the globe. The production of microalgal-based bioactive compounds at an industrial scale through biotechnological interventions is gaining interest more recently. The present review provides a detailed overview of the key algal metabolites, which plays a crucial role in nutraceutical, functional foods, and animal/aquaculture feed industries. Bioactive compounds of microalgae known to exhibit antioxidant, antimicrobial, antitumor, and immunomodulatory effects were comprehensively reviewed. The potential microalgal species and biological extracts against human pathogens were also discussed. Further, current technologies involved in upstream and downstream bioprocessing including cultivation, harvesting, and cell disruption were documented. Establishing microalgae as an alternative supplement would complement the sustainable and environmental requirements in the framework of human health and well-being.
Journal Article
Controlling Voltage Reversal in Microbial Fuel Cells
Microbial fuel cell (MFC) systems have been developed for potential use as power sources, along with several other applications, with bacteria as the prime factor enabling electrocatalytic activity. Limited voltage and current production from unit cells limit their practical applicability, so stacking multiple MFCs has been proposed as a way to increase power production. Special attention is paid to voltage reversal (VR), a common occurrence in stacked MFCs, and to identifying the mechanisms underlying this phenomenon. We also proposed realistic perspectives on stacked MFCs in an effort to control and suppress VR by balancing the kinetics in the system, such as using enriched electroactive microorganisms or altering the circuitry mode.
MFCs have been proposed as alternative renewable power sources since their inception, but the scale of MFC voltage and current production is too limited to meet market needs.Although stacks appear to provide the most suitable method for improving MFC performance, a phenomenon called voltage reversal (VR) hinders their performance.Imbalances between unit-cell performances, especially due to the current production capacity, are thought to be the major cause of VR, and the maximum current can be used as an indicator of VR.VR may be controlled and prevented using various electrical circuit configurations and electronic methods, and by understanding how to control current balance, to increase the current production capacity in stacked MFCs.Practical methods for controlling VR in stacked MFCs are useful for scaling up MFCs with higher performance.
Journal Article
Triclosan in Treated Wastewater from a City Wastewater Treatment Plant and its Environmental Risk Assessment
Triclosan (TCS) is a potential endocrine-disrupting compound (EDC), which produces an adverse impact on aquatic life and human beings. Wastewater discharge is considered as the primary source of triclosan in water bodies. The study is aimed to investigate the occurrence and environmental risk of triclosan released by municipal wastewater treatment plants (WWTP). An analytical protocol was developed and validated to determine the presence of TCS in the samples through offline solid-phase extraction (SPE) and liquid chromatography - electron spray ionization (ESI)—quadrupole mass spectrum (LC/ESI/MS). The limit of detection and quantification of protocol was estimated as 2.8 ng/L and 6.25 ng/L, respectively. The season-wise influent and effluent samples from two WWTP in Chennai, India, were monitored. The TCS concentrations in samples were found in the range of 443 to 1757 ng/L. The Risk Quotient (RQ) method was performed to evaluate the environmental (ecotoxicological and human health) risk associated with the exposure of TCS-containing wastewater. The results of the study revealed that primary producer (algae) was highly vulnerable to exposure of TCS in the aquatic environment. The estimated daily intake of TCS was much lower than the reference dosage, and this indicates that TCS did not produce any considerable risk to human health. Also, it suggested that additional treatment was required for complete removal of triclosan residues.
Journal Article
Graphene modified electrodes for bioelectricity generation in mediator-less microbial fuel cell
The present study comprises a facile and economical way of modifying carbon cloth anodes with electrochemically reduced graphene oxide employing dip coating method followed by electrochemical reduction technique without using any reducing agent. The physical characterization and validation of formation of electrochemically reduced graphene oxide and graphene oxide is accomplished using X-ray diffraction and Raman spectroscopy techniques. Electrochemical properties of electrodes are assessed using cyclic voltammetry and electrochemical impedance spectroscopy, which indubitably support higher charge storing capacity and lower charge transfer resistance in electrochemically reduced graphene oxide electrodes. Electrochemically reduced graphene oxide exhibits 17.5- and 8.75-times higher power density as compared to carbon cloth and graphene oxide, respectively. Synergistic effect of the large surface area for bacterial colonization and high conductivity of electrochemically reduced graphene oxide is responsible for its superior performance in a microbial fuel cell. The present work demonstrates power production with a cost-effective microbial fuel cell reactor configuration having graphene-based electrode as an anode, economic stainless steel as a cathode, inoculated with mixed culture and mere deionized water as catholyte, and such setup is essential for scaling up of microbial fuel cell to commercialization.
Journal Article