800 research outputs found
Use of stable isotopes, organic and inorganic chemistry to identify pollution sources and weathering processes in two small tropical rivers in southwestern India
No full textThe two main objectives of this study were to assess pollution dynamic from organic and inorganic major ion chemistry and stable isotopes (δ15N and δ18O) and to determine the weathering processes using carbon isotopes in two tropical river basins, i.e. Nethravati and Swarna, along southwest coast of India. These short length river basins (around 100 km) are characterized by high annual rainfall, warm temperature, high runo" (~3300mm) draining Precambrian basement rocks composed of green-stones, granitic-gneiss, charnockite and meta sediments. Intense silicate weathering is induced by high runo" and warm temperature (Gurumurthy et al., 2012). In this study, stable isotopes (δ15N & δ18O)of organic molecules from sewage and agricultural effluents,and carbon isotopes (δ13C) of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) were measured to trace agricultural and domestic pollution and to identify the sources of inorganic carbon and the nature of chemical weathering in these river basins. Carbon isotopes measured on DIC reveals sources of carbon into the river, such as carbonate/silicate weathering of rocks, mineralization of organic matter from C3/C4 plants, soil and atmospheric CO2. The nitrate and phosphate levels remain low, with values ranging from 5 to 9 μM, and 0 to 2 μM respectively. The δ13C DIC values range from =-9.03 +/- 0.99 for the Swarna basin to -8.08 +/-0.78 for the Nethravati basin. These values point to a mixing of carbonate and silicate weathering products with a dominance of C3 vegetation, prevalent in the Western Ghats. The DOC values for both river basins are very low and very close: 0.72 +/- 0.09 mg/L (Swarna river) and 0.62 +/-0.11 mg/L (Nethravati river). This indicates that the contributions of organic matter from the adjacent forests and the $ood plains are very low during the sampling period. The analysis of organic acids reveals low amount of Oxalate and Acetate, and trace of Malate and Tartaric acids. The dissolved and particulate organic carbon (DOC and POC) concentrations are very low in these two rivers. During the dry season, river discharge is mainly supplied by groundwater with generally low contents in dissolved and particulate fractions. Even if we observe low concentration, we measured higher DOC and POC in the Swarna river. These higher DOC concentrations are accompanied with lower SUVA value. This indicates that more labile DOC (less aromaticity) is exported within this basin during dry season. C/N values in POC also show that the organic carbon is “fresher” and is probably more autochtonous than in the Nethravati river. Indeed, C/N value are closer of an autochthonous production (C/N : 2-6) than allochthonous one (C/N: 8-20). These observations can be explained as the Svarna watershed land use is more agricultural than in Nethravati. Agricultural lands generally export signi%cant amount of nutrients to rivers and participate to enhance autochthonous productivity. Autochthonous organic carbon production is more labile and less aromatic
Interplay of non-covalent interactions in ribbon-like guanosine self-assembly : a NMR crystallography study
No full textA NMR crystallography study shows how intermolecular NH...O, NH...N, OH...N, OH...O and CH–π interactions stabilize the ribbon-like supramolecular structures of three different guanosine derivatives; guanosine dihydrate (G), 3/, 5/–O– dipropanolyl deoxyguanosine (dGC(3)2) and 3/, 5/ –O– isopropylideneguanosine hemihydrate (Gace). Experimental solid-state 1H NMR spectra obtained at 20 T using fast Magic-Angle Spinning (MAS), here at 75 kHz, are presented for a dihydrate of G. For each guanosine derivative, the role of specific interactions is probed by means of NMR chemical shifts calculated using the Density Functional Theory (DFT) Gauge-Including Projector-Augmented Wave (GIPAW) approach for the full crystal and extracted isolated single molecules. Specifically, the isolated molecule to full crystal transformations result in net changes in the GIPAW calculated 1H NMR chemical shifts of up to 8 ppm for OH...O, up to 6.5 ppm for NH...N and up to 4.6 ppm for NH...O hydrogen bonds; notably, the presence of water molecules in G and Gace reinforces the molecular stacking through strong OH...O hydrogen bonds. The sugar conformations are markedly different in G, dG(C3)2 and Gace, and it is shown that the experimental 13C solid-state NMR chemical shift at the C8 position is a reliable indicator of a ‘syn’ (> 135 ppm) or ‘anti’ (< 135 ppm) conformer
A Pseudomonas-based bio-formulation to control bacterial blight of pomegranate caused by Xanthomonas axonopodis pv. punicae
No full textPlant growth-promoting bacteria (PGPB) have emerged as sustainable tool for managing plant diseases. This study investigates the potential of a Pseudomonas-based biocontrol agent to manage bacterial blight (BB) in pomegranate. This major disease is caused by Xanthomonas axonopodis pv. punicae (Xap) and it is traditionally controlled with antibiotics. Of the 151 bacterial isolates obtained from the pomegranate rhizosphere, three (UHSPS15A, UHSPS33, and UHSPS54) demonstrated the strongest inhibitory effects against Xap in vitro, and their identification as Pseudomonas was confirmed through DNA analysis. Greenhouse trials with Xap-inoculated plants revealed that preventive application of each of the three isolates was more effective than curative, with UHSPS15A providing the highest protection. A talc-based formulation was developed using UHSPS15A. After evaluating its stability and efficacy in greenhouse Xap-inoculated pomegranates plants, open-fields trials indicated that among the three different treatment modes tested, the combined soil and foliar application achieved the highest disease protection and fruit yield, topping the standard antibiotic control. These findings recommend that integrating Pseudomonas-based bio-formulations into disease management strategies could significantly reduce reliance on synthetic chemicals, offering a sustainable alternative for controlling BB in pomegranate
Co-existence of distinct supramolecular assemblies in solution and in the solid state
No full textThe formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G-quartet based assemblies are formed in chloroform depending on the nature of the cation, anion and salt concentration, as characterized by circular dichroism and time course diffusion-ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G-quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon-like assemblies as revealed by fast magic-angle spinning (MAS) NMR spectroscopy. Distinct N-H∙∙∙N and N-H∙∙∙O intermolecular hydrogen bonding interactions drive quartet and ribbon-like self-assembly resulting in markedly different 2D 1H solid-state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible - further demonstrating the changes that occur in the self-assembly process of a lipophilic nucleoside upon a solid-state to solution-state transition and vice versa. A systematic study for complexation with different cations (K+, Sr2+) and anions (picrate, ethanoate and iodide) emphasises that the existence of a stable solution or solid-state structure may not reflect the stability of the same supramolecular entity in another phase
Polyphenols fingerprinting in olive oils through maximum-quantum NMR spectroscopy
No full textAn NMR protocol based on multiple-quantum spectroscopy is presented for an analytical screening of polyphenols in olive oils. Three Italian olive oils with different total polyphenols content were used as study case. A total of 24 compounds were identified as follows: 1 polyphenol in the 5Q–1Q, 15 more in the 4Q–1Q, and 8 components in the 3Q–1Q spectra, consisting of organic phenols, secoiridoids, lignans, and flavonols. In the three Italian olive oils investigated here, the polyphenols profile turned out to be significantly different, with specific characteristics going beyond simple considerations based on the total polyphenol content. The approach presented here can be easily extended for rapid qualitative and semi-quantitative screening of the polyphenol composition in many food products
Modelling the deceleration of COVID-19 spreading
No full textBy characterizing the time evolution of COVID-19 in term of its 'velocity' (log of the new cases per day) and its rate of variation, or 'acceleration', we show that in many countries there has been a deceleration even before lockdowns were issued. This feature, possibly due to the increase of social awareness, can be rationalized by a susceptible-hidden-infected-recovered model introduced by Barnes, in which a hidden (isolated from the virus) compartment H is gradually populated by susceptible people, thus reducing the effectiveness of the virus spreading. By introducing a partial hiding mechanism, for instance due to the impossibility for a fraction of the population to enter the hidden state, we obtain a model that, although still sufficiently simple, faithfully reproduces the different deceleration trends observed in several major countries
Electro-oxidation of formoterol fumarate on the surface of novel poly(thiazole yellow-G) layered multi-walled carbon nanotube paste electrode
No full textAbstract The current study explicates the electro-oxidation behavior of formoterol fumarate (FLFT) in the presence of uric acid (UA) on the surface of poly thiazole yellow-G (TY-G) layered multi-walled carbon nanotube paste electrode (MWCNTPE). The modified (Poly(TY-G)LMWCNTPE) and unmodified (MWCNTPE) electrode materials were characterized through electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE-SEM), and cyclic voltammetry (CV) approaches. The characterization data confirms the good conducting and electrocatalytic nature with more electrochemical active sites on the Poly(TY-G)LMWCNTPE than MWCNTPE towards the FLFT analysis in the presence of UA. Poly(TY-G)LMWCNTPE easily separates the two drugs (FLFT and UA) even though they both have nearer oxidation peak potential. The electro-catalytic activity of the developed electrode is fast and clear for FLFT electro-oxidation in 0.2 M phosphate buffer (PB) of pH 6.5. The Poly(TY-G)LMWCNTPE offered a well-resolved peak with the highest electro-oxidation peak current at the peak potential of 0.538 V than MWCNTPE. The potential scan rate and oxidation peak growth time studies show the electrode reaction towards FLFT electro-oxidation is continued through a diffusion-controlled step. The variation of concentration of FLFT in the range from 0.2 to 1.5 µM (absence of UA) and 3.0 to 8.0 μM (presence of UA) provides a good linear relationship with increased peak current and a lower limit of detection (LOD) values of 0.0128 µM and 0.0129 µM, respectively. The prepared electrode gives a fine recovery for the detection of FLFT in the medicinal sample with acceptable repeatability, stability, and reproducibility
Determination of a complex crystal structure in the absence of single crystals : analysis of powder X-ray diffraction data, guided by solid-state NMR and periodic DFT calculations, reveals a new 2′-deoxyguanosine structural motif
No full textDerivatives of guanine exhibit diverse supramolecular chemistry, with a variety of distinct hydrogen-bonding motifs reported in the solid state, including ribbons and quartets, which resemble the G-quadruplex found in nucleic acids with sequences rich in guanine. Reflecting this diversity, the solid-state structural properties of 3′,5′-bis-O-decanoyl-2′-deoxyguanosine, reported in this paper, reveal a hydrogen-bonded guanine ribbon motif that has not been observed previously for 2′-deoxyguanosine derivatives. In this case, structure determination was carried out directly from powder XRD data, representing one of the most challenging organic molecular structures (a 90-atom molecule) that has been solved to date by this technique. While specific challenges were encountered in the structure determination process, a successful outcome was achieved by augmenting the powder XRD analysis with information derived from solid-state NMR data and with dispersion-corrected periodic DFT calculations for structure optimization. The synergy of experimental and computational methodologies demonstrated in the present work is likely to be an essential feature of strategies to further expand the application of powder XRD as a technique for structure determination of organic molecular materials of even greater complexity in the future
Effect of blending and nanoparticles on the ionic conductivity of solid polymer electrolyte systems
No full textEffect of annealing on the structural and electrical properties of Gd2O3/Si interface for MOS capacitors
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