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The evolution of the UV/optical lag spectrum of NGC 7469 seen by the Liverpool Telescope
Full text linkWe present the results regarding the analysis of an intensive monitoring of the Active Galactic Nucleus (AGN) NGC 7469. We observed the source for 4 months with almost daily cadence in the ugriz bands, using the IO:O on the Liverpool Telescope. We measured the lags with respect to the u band and found a clear change in the lag spectrum between the first and the second half of the campaign. Given that the source varies on different timescales during these two segments, it is likely that different components are dominating the variability at different times. This result further confirms that reverberation models require a more complex geometry than a static illuminating point source and that particular attention has to be given in the interpretation of these delays
Temperature Evolution of Charge Transport in Chitosan Based Bio-Resistive Random-Access Memory Device
No full textThis study reports on the temperature stability of the Ag/chitosan/fluorine-doped tin oxide (Ag/chitosan/FTO)-based bio-resistive random-access memory (bio-RRAM) device through current–voltage (I–V) characteristics in the temperature range of 280–360 K. From I–V characteristics, it is affirmed that in the present device, the unipolar nature of resistive switching is highly stable and reproducible. The device is quite stable at 360 K. Activation energy is higher in the low resistance state (LRS) (≈0.096 eV) compared with the high resistance state (HRS) (≈0.076 eV) due to sufficient thermal energy to cross the barrier at high temperature. From 280 to 360 K, the conduction mechanism in the HRS of the chitosan device is followed by a direct tunneling mechanism, while the Schottky mechanism is dominated in the LRS. Barrier height calculated from Schottky mechanism in an LRS is found to increase with temperature from 0.50 eV (280 K) to 0.66 eV (360 K). Evidenced current values up to 200 pA obtained with a conducting atomic force microscope infer that conduction in the chitosan-based device is due to filaments formed by oxygen defects. It is believed that the present results are helpful for the development of future bio-RRAM devices
Lactic acid and biomethane production from bread waste: a techno-economic and profitability analysis using pinch technology
Full text linkLactic acid (LA) is a vital platform chemical with diverse applications, especially for biodegradable polylactic acid. Bread waste (BW) is sugar-rich waste biomass generated in large quantities in residential and commercial operations. Recently, we evaluated the potential of BW for LA production by Bacillus coagulans under non-sterile conditions. This work presents a techno-economic and profitability analysis for valorizing 100 metric tons of BW per day to alleviate environmental pollution with concurrent production of LA and biomethane. We compared two fermentation approaches: acid-neutral (Scenario I) and low pH (Scenario II). Traditional esterification with methanol, followed by hydrolysis of methyl lactate, was employed for downstream separation to obtain polymer-grade LA. High-pressure steam was generated from solid debris via anaerobic digestion to complement energy demands partly. Energy consumption was further attenuated by process integration using pinch technology, with around 15% and 11% utility cost savings for Scenario I and II, respectively. These processes were capital-intensive, with 42-46% of LA production cost stemming from direct and indirect costs. Utilities were the major cost-contributing factor (19-21%) due to energy-intensive water evaporation from dilute fermentation broth. Due to additional processing steps, capital investment and operating costs were slightly higher in Scenario I than in Scenario II. LA manufacturing cost was thus more for Scenario I (1.82 per kg). The minimum LA selling price for Scenario I and II were 3.22 per kg, respectively, with five-year payback periods and 8.5% internal rates of return. LA was slightly more expensive for decentralized BW processing than the market price
Life Cycle Assessment of Microbial 2,3-Butanediol Production from Brewer’s Spent Grain Modeled on Pinch Technology
Full text linkMicrobial production of 2,3-butanediol (BDO) has received considerable attention as a promising alternate to fossil-derived BDO. In our previous work, BDO concentration >100 g/L was accumulated using brewer’s spent grain (BSG) via microbial routes which was followed by techno-economic analysis of the bioprocess. In the present work, a life cycle assessment (LCA) was conducted for BDO production from the fermentation of BSG to identify the associated environmental impacts. The LCA was based on an industrial-scale biorefinery processing of 100 metric tons BSG per day modeled using ASPEN plus integrated with pinch technology, a tool for achieving maximum thermal efficiency and heat recovery from the process. For the cradle-to-gate LCA, the functional unit of 1 kg of BDO production was selected. One-hundred-year global warming potential of 7.25 kg CO2/kg BDO was estimated while including biogenic carbon emission. The pretreatment stage followed by the cultivation and fermentation contributed to the maximum adverse impacts. Sensitivity analysis revealed that a reduction in electricity consumption and transportation and an increase in BDO yield could reduce the adverse impacts associated with microbial BDO production
Computational fluid dynamics study of kaolin–water flow in a T-junction using a novel shear-thinning fluid model
No full textA recently proposed shear-thinning fluid model that mimics the response of seemingly viscoplastic materials is evaluated in computational fluid dynamics simulations by studying the steady flow of a kaolin–water suspension in a 2D T-junction. The velocity profiles for the kaolin–water suspension are reported at the mid-length of the main channel and the root of the bifurcation (where recirculation is expected to appear). The velocity profiles of the proposed model are compared with those from conventional viscoplastic models (Bingham plastic model and the Herschel–Bulkley model) at low (=100) and high Reynolds number (=2000). The new model predicts a recirculation zone (at the inner edge of the bifurcation arm) that conventional models do not. The effect of the variation in the model parameters (α1 and α2) on velocity profiles at low (=100) and high Reynolds numbers (=2000) is also documented. These indicate the disappearance of the recirculation zone at low Reynolds number as α1 (equivalently, viscosity) increases, whereas the recirculation zone persists even for higher values of α1 at high Reynolds number. Further, at low Reynolds number, the skewing of maximum velocity towards the outer edge of the bifurcation arm disappears as α2 increases, whereas the skewing persists even at the highest value of α2 used at the high Reynolds number
3D Printed SnS2/SnS-Based Nanocomposite Hydrogel as a Photoenhanced Triboelectric Nanogenerator
Full text linkRecent advancements in printing technologies have led to new fabrication techniques for the development of various flexible, compact, wearable, and portable energy harvesters and self-powered devices. In particular, the three-dimensional printing (3DP) technology for a nanogenerator has become advantageous due to its low cost, simplicity, and high precision in fabricating complicated structures. Therefore, we report a 3DP-based photoinduced triboelectric nanogenerator (PTNG) fabrication, a hybrid version of a conventional triboelectric nanogenerator. Here, a 3D printed poly(vinyl alcohol) (PVA) nanocomposite hydrogel (3DPH) with photoactive SnS2/SnS nanoflakes is used as a tribo-positive material and copper foil as a tribo-negative material for PTNG application. Under light illumination, the as-fabricated PTNG with an optimized weight percentage of SnS2/SnS displays the open-circuit voltage (Voc) enhancement from 29 to 37.5 V and short-circuit current (Isc) enhancement from 1.23 to 1.58 μA. In addition, the power density of the device is observed at 5.4 μW/cm2 under illumination conditions at the external load of 60 MΩ. This enhanced performance of the as-fabricated PTNG is attributed to the mutual coupling effect and improved interfacial interactions between the SnS2/SnS nanoflakes and PVA under the influence of light illumination, leading to a charge-trapping mechanism. The outstanding performance and stability of the as-fabricated PTNG surpassing all similar recent reports, establish it as an effective hybrid platform for constructing multifunctional self-powered devices
Assessment of Fiji's exchange rate
No full textThis paper empirically estimates Fiji's bilateral equilibrium real exchange rate with two of its key trading partners, the US and Australia. Applying the Behavioural Equilibrium Exchange Rate (BEER) approach, we estimate the equilibrium exchange rate by considering the productivity differential, real interest rate differential, net foreign assets, money supply, and terms of trade. Using monthly data from March 2011 to September 2022 and a system approach to cointegration, a strong relationship between the real exchange rate and its fundamentals is found, but importance of factors differed by trading partner. Our findings show that the Fijian Dollar has been undervalued against both US Dollar and Australian Dollar in recent years, but to varying degrees. Our analysis underlines the importance of assessing bilateral exchange rate misalignments in basket pegs when devising exchange rate policy
CoVe-Tracker: An Interactive SARS-CoV-2 Pan Proteome Evolution Tracker
Full text linkSARS-CoV-2 has significantly mutated its genome during the past 3 years, leading to the periodic emergence of several variants. Some of the variants possess enhanced fitness advantage, transmissibility, and pathogenicity and can also reduce vaccine efficacy. Thus, it is important to track the viral evolution to prevent and protect the mankind from SARS-CoV-2 infection. To this end, an interactive web-GUI platform, namely, CoVe-tracker (SARS-CoV-2 evolution tracker), is developed to track its pan proteome evolutionary dynamics (https://project.iith.ac.in/cove-tracker/). CoVe-tracker provides an opportunity for the user to fetch the country-wise and protein-wise amino acid mutations (currently, 44139) of SARS-CoV-2 and their month-wise distribution. It also provides position-wise evolution observed in the SARS-CoV-2 proteome. Importantly, CoVe-tracker provides month- and country-wise distributions of 2065 phylogenetic assignment of named global outbreak (PANGO) lineages and their 177564 variants. It further provides periodic updates on SARS-CoV-2 variant(s) evolution. CoVe-tracker provides the results in a user-friendly interactive fashion by projecting the results onto the world map (for country-wise distribution) and protein 3D structure (for protein-wise mutation). The application of CoVe-tracker in tracking the closest cousin(s) of a variant is demonstrated by considering BA.4 and BA.5 PANGO lineages as test cases. Thus, CoVe-tracker would be useful in the quick surveillance of newly emerging mutations/variants/lineages to facilitate the understanding of viral evolution, transmission, and disease epidemiology
A study on best simultaneous approximation through Chebyshev centers and related geometric properties in Banach spaces
Full text linkIn this work, we study the existence of (restricted) Chebyshev centers and the set-valued generalization of strong proximinality in Banach spaces. We mainly explore the concepts above in L1-predual
spaces and their subspaces.
Although it is well-known that a Chebyshev center exists for compact subsets of an L1-predual
space, we approach this problem differently. Interestingly, this approach leads us to an explicit
description of the Chebyshev centers of the compact subsets of the spaces in question. Furthermore,
we establish the validity of a geometric identity in terms of the (restricted) Chebyshev radius in
L1-predual spaces and characterize L1-predual spaces using it. This identity was first established
in 2000 by R. Esp´ınola, A. Wi´snicki and J. Wo´sko for the space of real-valued continuous functions
on a compact Hausdorff space S, denoted by C(S), which forms a major subclass of the L1-predual
spaces. We also yield a few geometric characterizations of the ideals in L1-predual spaces. In
particular, we obtain characterizations for a compact convex subset of a locally convex topological
space to be a Choquet simplex.
The study of strong (ball) proximinality gained momentum in the recent years and the main
motivation to study this property is it results in some “nice” continuity properties of the metric
projections. With the same motivation, we extend the study of the set-valued generalization of
strong proximinality, which was initiated by J. Mach in the literature. This generalization is termed
as property-(P1) by Mach. For a non-empty closed convex subset V of a Banach space X and a
family F of non-empty closed bounded subsets of X, property-(P1) is defined for a triplet (X, V, F).
We study the interconnnection between property-(P1) of a subspace and that of its closed unit ball
in a Banach space in detail. Expanding on some of the works by C. R. Jayanarayanan and S.
Lalithambigai, we establish the equivalence of strong ball proximinality and property-(P1) of the
closed unit ball of the finite co-dimensional subspaces of the L1-predual spaces. For a general
subspace of a Banach space, we prove that property-(P1) of the closed unit ball of the subspace
implies property-(P1) of the subspace itself. We also establish a similar implication in the case of
the Hausdorff metric continuity of the restricted Chebyshev-center map of the subspace and that of
its closed unit ball.
We further investigate property-(P1) and the continuity properties of the restricted Chebyshev center maps in vector-valued continuous function spaces. We derive that if Y is a proximinal finite
co-dimensional closed linear subspace of c0 then the closed unit ball of Y satisfies property-(P1)
for the non-empty closed bounded subsets of ℓ∞ and the restricted Chebyshev-center map of the
closed unit ball of Y is Hausdorff metric continuous on the class of non-empty closed bounded
subsets of ℓ∞ with equi-bounded restricted Chebyshev radii. We also prove a few stability results
of property-(P1) and the continuity of the restricted Chebyshev-center maps in ℓ∞-direct sum of
Banach spaces. Finally, we discuss a few positive results on the existence of restricted Chebyshev
centers and property-(P1) of an ideal in an L1-predual space and in particular, of an L1-predual
space in its bidual
Waste to catalyst: Role of agricultural waste in water and wastewater treatment
No full textPresently, owing to the rapid development of industrialization and urbanization activities, a huge quantity of wastewater is generated that contain toxic chemical and heavy metals, imposing higher environmental jeopardies and affecting the life of living well-being and the economy of the counties, if not treated appropriately. Subsequently, the advancement in sustainable cost-effective wastewater treatment technology has attracted more attention from policymakers, legislators, and scientific communities. Therefore, the current review intends to highlight the recent development and applications of biochars and/or green nanoparticles (NPs) produced from agricultural waste via green routes in removing the refractory pollutants from water and wastewater. This review also highlights the contemporary application and mechanism of biochar-supported advanced oxidation processes (AOPs) for the removal of organic pollutants in water and wastewater. Although, the fabrication and application of agriculture waste-derived biochar and NPs are considered a greener approach, nevertheless, before scaling up production and application, its toxicological and life-cycle challenges must be taken into account. Furthermore, future efforts should be carried out towards process engineering to enhance the performance of green catalysts to improve the economy of the process. © 2022 Elsevier B.V