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Early detection of histamine in foodstuffs/beverages could be useful in preventing various diseases. In this work, we have prepared a free-standing hybrid mat based on manganese cobalt (2-methylimodazole)–metal organic frameworks (Mn-Co(2-MeIm)MOF) and carbon nanofibers (CNFs) and explored as a non-enzymatic electrochemical sensor for determining the freshness of fish and bananas based on histamine estimation. As-developed hybrid mat possesses high porosity with a large specific surface area and excellent hydrophilicity those allow easy access of analyte molecules to the redox-active metal sites of MOF. Furthermore, the multiple functional groups of the MOF matrix can act as active adsorption sites for catalysis. The Mn-Co(2-MeIm)MOF@CNF mat-modified GC electrode demonstrated excellent electrocatalytic activities toward the oxidation of histamine under acidic conditions (pH = 5.0) with a faster electron transfer kinetics and superior fouling resistance. The Co(2-MeIm)MOF@CNF/GCE sensor exhibited a wide linear range from 10 to 1500 µM with a low limit of detection (LOD) of 89.6 nM and a high sensitivity of 107.3 µA mM −1  cm −2 . Importantly, as-developed Nb(BTC)MOF@CNF/GCE sensor is enabled to detect histamine in fish and banana samples stored for different periods of time, which thus indicates its practical viability as analytical histamine detector.

In recent years, there have been concerns about the toxicity of bisphenol A (BPA) in food packaging materials due to the potential endocrine disrupting effects it may have on humans, especially children and infants. In this present investigation, a free-standing nickel-copper pyridine-2,6-dicarboxylic acid (PDA) metal organic framework (MOF) anchored carbon nanofiber paper (Ni-Cu(PDA)MOF/CNF) was synthesized for the sensing and quantify the BPA analytes in milk and water. As-prepared bimetallic MOF hybrid materials are extremely porous, hydrophilic in nature with a huge surface area. This allows for the easy pathway of analyte molecules, which react with the redox-active metal sites of MOF matrix and enhance the sensitivity. During electrocatalysis reaction, various functional groups present in the MOF system can also act as dynamic adsorption sites. In the neutral medium (pH = 7.0), the Ni-Cu(PDA)MOF/CNF modified glassy carbon electrode (Ni-Cu(PDA)MOF/CNF/GCE) ascertained good catalytic activity and strong electrochemical sensitivity toward BPA with higher sensitivity value and lower limit of detection (LOD) value. The irreversible and diffusion-controlled oxidation reactions of BPA were observed. The bimetallic MOF modified electrode displayed an extensive linear ranging from 1 to 150 µmol/L with a LOD of 75 n mol/L for BPA detection. The MOF anchored electrode displayed exceptional anti-interference property, reproducibility and good storage stability up to one month. It is notable that the Ni-Cu(PDA)MOF/CNF/GCE has proved the competence of detecting BPA in milk and drinking water samples, which displayed satisfactory outcomes with chromatographic analysis.

The thermodynamics of the nonspecific binding of salt to a polyelectrolyte molecule is studied using a density functional approach. The polyelectrolyte molecule is modeled as an infinite, inflexible, and impenetrable charged cylinder and the counterions and co-ions are modeled as charged hard spheres of equal diameter. The density functional theory is based on a hybrid approach where the hard-sphere contribution to the one-particle correlation function is evaluated nonperturbatively and the ionic contribution to the one-particle correlation function is evaluated perturbatively. The advantage of the approach is that analytical expressions are available for all the correlation functions. The calculated single ion preferential interaction coefficients, excess free energy, and activity coefficients show a nonmonotonic variation as a function of polyion charge in the presence of divalent ions. These properties display considerable departure from the predictions of the nonlinear Poisson-Boltzmann (NLPB) equation, with qualitative differences in some cases, which may be attributed to correlation effects neglected in the NLPB theory.

The thermodynamics of the nonspecific binding of salt to a polyelectrolyte molecule is studied using a density functional approach. The polyelectrolyte molecule is modeled as an infinite, inflexible, and impenetrable charged cylinder and the counterions and co-ions are modeled as charged hard spheres of equal diameter. The density functional theory is based on a hybrid approach where the hard-sphere contribution to the one-particle correlation function is evaluated nonperturbatively and the ionic contribution to the one-particle correlation function is evaluated perturbatively. The advantage of the approach is that analytical expressions are available for all the correlation functions. The calculated single ion preferential interaction coefficients, excess free energy, and activity coefficients show a nonmonotonic variation as a function of polyion charge in the presence of divalent ions. These properties display considerable departure from the predictions of the nonlinear Poisson-Boltzmann (NLPB) equation, with qualitative differences in some cases, which may be attributed to correlation effects neglected in the NLPB theory.

About 70 % of the anthropogenic carbon dioxide (CO2) is emitted from the megacities and urban areas of the world. In order to draw effective emission mitigation policies for combating future climate change as well as independently validating the emission inventories for constraining their large range of uncertainties, especially over major metropolitan areas of developing countries, there is an urgent need for greenhouse gas measurements over representative urban regions. India is a fast developing country, where fossil fuel emissions have increased dramatically in the last three decades and are predicted to continue to grow further by at least 6 % per year through to 2025. The CO2 measurements over urban regions in India are lacking. To overcome this limitation, simultaneous measurements of CO2 and carbon monoxide (CO) have been made at Ahmedabad, a major urban site in western India, using a state-of-the-art laser-based cavity ring down spectroscopy technique from November 2013 to May 2015. These measurements enable us to understand the diurnal and seasonal variations in atmospheric CO2 with respect to its sources (both anthropogenic and biospheric) and biospheric sinks. The observed annual average concentrations of CO2 and CO are 413.0 ± 13.7 and 0.50 ± 0.37 ppm respectively. Both CO2 and CO show strong seasonality with lower concentrations (400.3 ± 6.8 and 0.19 ± 0.13 ppm) during the south-west monsoon and higher concentrations (419.6 ± 22.8 and 0.72 ± 0.68 ppm) during the autumn (SON) season. Strong diurnal variations are also observed for both the species. The common factors for the diurnal cycles of CO2 and CO are vertical mixing and rush hour traffic, while the influence of biospheric fluxes is also seen in the CO2 diurnal cycle. Using CO and CO2 covariation, we differentiate the anthropogenic and biospheric components of CO2 and found significant contributions of biospheric respiration and anthropogenic emissions in the late night (00:00–05:00 h, IST) and evening rush hours (18:00–22:00 h) respectively. We compute total yearly emissions of CO to be 69.2 ± 0.07 Gg for the study region using the observed CO : CO2 correlation slope and bottom-up CO2 emission inventory. This calculated emission of CO is 52 % larger than the estimated emission of CO by the emissions database for global atmospheric research (EDGAR) inventory. The observations of CO2 have been compared with an atmospheric chemistry-transport model (ACTM), which incorporates various components of CO2 fluxes. ACTM is able to capture the basic variabilities, but both diurnal and seasonal amplitudes are largely underestimated compared to the observations. We attribute this underestimation by the model to uncertainties in terrestrial biosphere fluxes and coarse model resolution. The fossil fuel signal from the model shows fairly good correlation with observed CO2 variations, which supports the overall dominance of fossil fuel emissions over the biospheric fluxes in this urban region.

Global and regional sources and sinks of carbon across the earth's surface have been studied extensively using atmospheric carbon dioxide (CO2) observations and atmospheric chemistry-transport model (ACTM) simulations (top-down/inversion method). However, the uncertainties in the regional flux distributions remain unconstrained due to the lack of high-quality measurements, uncertainties in model simulations, and representation of data and flux errors in the inversion systems. Here, we assess the representation of data and flux errors using a suite of 16 inversion cases derived from a single transport model (MIROC4-ACTM) but different sets of a priori (bottom-up) terrestrial biosphere and oceanic fluxes, as well as prior flux and observational data uncertainties (50 sites) to estimate CO2 fluxes for 84 regions over the period 2000–2020. The inversion ensembles provide a mean flux field that is consistent with the global CO2 growth rate, land and ocean sink partitioning of-2.9 ± 0.3 (± 1σ uncertainty on the ensemble mean) and-1.6 ± 0.2 PgC yr-1, respectively, for the period 2011–2020 (without riverine export correction), offsetting about 22 %–33 % and 16 %–18 % of global fossil fuel CO2 emissions. The rivers carry about 0.6 PgC yr-1 of land sink into the deep ocean, and thus the effective land and ocean partitioning is -2.3 ± 0.3 and -2.2 ± 0.3, respectively. Aggregated fluxes for 15 land regions compare reasonably well with the best estimations for the 2000s (∼ 2000–2009), given by the REgional Carbon Cycle Assessment and Processes (RECCAP), and all regions appeared as a carbon sink over 2011–2020. Interannual variability and seasonal cycle in CO2 fluxes are more consistently derived for two distinct prior fluxes when a greater degree of freedom (increased prior flux uncertainty) is given to the inversion system. We have further evaluated the inversion fluxes using meridional CO2 distributions from independent (not used in the inversions) aircraft and surface measurements, suggesting that the ensemble mean flux (model–observation mean ± 1σ standard deviation = -0.3 ± 3 ppm) is best suited for global and regional CO2 flux budgets than an individual inversion (model–observation 1σ standard deviation = -0.35 ± 3.3 ppm). Using the ensemble mean fluxes and uncertainties for 15 land and 11 ocean regions at 5-year intervals, we show promise in the capability to track flux changes toward supporting the ongoing and future CO2 emission mitigation policies.

The sperm quality, freezability, and fertility of crossbred bulls exhibit significant unpredictability, which consequently impacts the breeding program. The present study documents the supplementation of humanin, a mitochondria-derived peptide, on crossbred bull’s sperm quality, freezability, antioxidant status and in-vitro fertility. For this objective a total of 24 ejaculates, 8 from each of the three Vrindavani crossbred bulls, were selected based on sperm progressive motility (≥ 70%) and concentration (≥ 500 million). The selected fresh semen samples were divided into four aliquots and diluted with Tris-Fructose-Egg-Yolk-Glycerol (TFEGY) extender supplemented with various concentrations of humanin peptide; control (Group-1) without supplementation; Group II with 2.5 µM; Group III supplemented with 5 µM and Group IV supplemented with 7.5 µM. Semen quality parameters, sperm kinematics, sperm plasma membrane integrity, mitochondrial membrane potential, sperm cryo-capacitation status, ejaculate freezability rate, antioxidant status and in-vitro fertility assays were done. At the pre-freeze stage, there was no significant effect on the percentage of individual progressive motility in any group. Supplementation with 5 µM humanin resulted in an 87.5% ejaculate recovery rate after cryopreservation. At the post-thaw stage, sperm quality parameters, sperm kinematics, sperm plasma membrane integrity, mitochondrial membrane potential, sperm cryo-capacitation status, antioxidant status and in-vitro fertility were significantly improved in Group III (5 µM humanin supplementation). In conclusion, our results demonstrate that humanin supplementation in crossbred bull semen enhances semen freezability and post-thaw ejaculate recovery rate.

Methane (CH4) is one of the most important short-lived climate forcers for its critical roles in greenhouse warming and air pollution chemistry in the troposphere, and the water vapor budget in the stratosphere. It is estimated that up to about 8 % of global CH4 emissions occur from South Asia, covering less than 1 % of the global land. With the availability of satellite observations from space, variability in CH4 has been captured for most parts of the global land with major emissions, which were otherwise not covered by the surface observation network. The satellite observation of the columnar dry-air mole fractions of methane (XCH4) is an integrated measure of CH4 densities at all altitudes from the surface to the top of the atmosphere. Here, we present an analysis of XCH4 variability over different parts of India and the surrounding cleaner oceanic regions as measured by the Greenhouse gases Observation SATellite (GOSAT) and simulated by an atmospheric chemistry-transport model (ACTM). Distinct seasonal variations of XCH4 have been observed over the northern (north of 15° N) and southern (south of 15° N) parts of India, corresponding to the peak during the southwestern monsoon (July–September) and early autumn (October–December) seasons, respectively. Analysis of the transport, emission, and chemistry contributions to XCH4 using ACTM suggests that a distinct XCH4 seasonal cycle over northern and southern regions of India is governed by both the heterogeneous distributions of surface emissions and a contribution of the partial CH4 column in the upper troposphere. Over most of the northern Indian Gangetic Plain regions, up to 40 % of the peak-to-trough amplitude during the southwestern (SW) monsoon season is attributed to the lower troposphere ( ∼  1000–600 hPa), and  ∼  40 % to uplifted high-CH4 air masses in the upper troposphere ( ∼  600–200 hPa). In contrast, the XCH4 seasonal enhancement over semi-arid western India is attributed mainly ( ∼  70 %) to the upper troposphere. The lower tropospheric region contributes up to 60 % in the XCH4 seasonal enhancement over the Southern Peninsula and oceanic region. These differences arise due to the complex atmospheric transport mechanisms caused by the seasonally varying monsoon. The CH4 enriched air mass is uplifted from a high-emission region of the Gangetic Plain by the SW monsoon circulation and deep cumulus convection and then confined by anticyclonic wind in the upper tropospheric heights ( ∼  200 hPa). The anticyclonic confinement of surface emission over a wider South Asia region leads to a strong contribution of the upper troposphere in the formation of the XCH4 peak over northern India, including the semi-arid regions with extremely low CH4 emissions. Based on this analysis, we suggest that a link between surface emissions and higher levels of XCH4 is not always valid over Asian monsoon regions, although there is often a fair correlation between surface emissions and XCH4. The overall validity of ACTM simulation for capturing GOSAT observed seasonal and spatial XCH4 variability will allow us to perform inverse modeling of XCH4 emissions in the future using XCH4 data.

Atmospheric Potential Oxygen (APO, defined as O2 + 1.1 × CO2) is primarily a tracer of ocean biogeochemistry and fossil fuel burning. APO exhibits strong seasonal variability at mid-to-high latitudes, driven mainly by seasonal air-sea O2 exchange. We present results from the first version of the Atmospheric Potential Oxygen forward Model Intercomparison Project (APO-MIP1), which forward transports three air-sea APO flux products in eight atmospheric transport models or model variants, aiming to evaluate atmospheric transport and flux representations by comparing simulations against surface station, airborne, and shipboard observations of APO. We find significant spread and bias in APO simulations at eastern Pacific surface stations, indicating inconsistencies in representing vertical and coastal atmospheric mixing. A framework using airborne APO observations demonstrates that most atmospheric transport models (ATMs) participating in APO-MIP1 overestimate tracer diffusive mixing across moist isentropes (i.e., diabatic mixing) in mid-latitudes. This framework also enables us to isolate ATM-related biases in simulated APO distributions using independent mixing constraints derived from moist static energy budgets from reanalysis, thereby allowing us to assess large-scale features in air-sea APO flux products. Furthermore, shipboard observations show that ATMs are unable to reproduce seasonal APO gradients over Drake Passage and near Palmer Station, Antarctica, which could arise from uncertainties in APO fluxes or model transport. The transport simulations and flux products from APO-MIP1 provide valuable resources for developing new APO flux inversions and evaluating ocean biogeochemical processes.

Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 continue to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). The relative importance of CH4 compared to CO2 depends on its shorter atmospheric lifetime, stronger warming potential, and variations in atmospheric growth rate over the past decade, the causes of which are still debated. Two major challenges in reducing uncertainties in the atmospheric growth rate arise from the variety of geographically overlapping CH4 sources and from the destruction of CH4 by short-lived hydroxyl radicals (OH). To address these challenges, we have established a consortium of multidisciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations)