Effect of grain size on the sorption and desorption of SeO4 2− and SeO3 2− in columns of crushed granite and fracture infill from granitic water under dynamic conditions

The sorption of 2 × 10^?5 mol/dm³ Na₂SeO₄ and Na₂SeO₃ dissolved in synthetic granitic water (SGW) were investigated in columns of crushed granite and fracture infill (clay minerals) of various grain sizes. Desorption was studied using pure SGW. The goal of study was the quantification of the effect of grain size on the retardation and distribution coefficients of SeO₄ ^2? and SeO₃ ^2?, as well as on the other transport parameters (Peclet number and hydrodynamic dispersion coefficient). A model based on the erfc-function, assuming a non-linear reversible equilibrium sorption/desorption isotherm, was used for evaluation of sorption/desorption and transport parameters. The determination of selenium was performed using an ICP-MS technique. The experimental breakthrough curves were fitted using non-linear regression procedure, in the course of which the parameters mentioned were sought. Summing up, no sorption was recorded in the case of SeO₄ ^2? under these conditions. The values of retardation coefficients were practically one for all studied grain sizes. On the other hand, significant sorption was found for SeO₃ ^2?: depending on the grain size, the retardation coefficients varied between 1.6–8.7 in pure granite and 1.8–37.2 in infill materials. These values correspond to distribution coefficients of 0.2–2.5 and 0.2–12.7 cm³/g, respectively. The both parameters have similar values in a case of desorption which reflects the reversible character of sorption process. It was found that retardation and distribution coefficients and sorption capacity for SeO₃ ^2? also increase with decreasing grain size.     

Sorption of 125I−, 137Cs+, 85Sr2+ and 152,154Eu3+ during their transport in undisturbed vertical and horizontal soil cores under dynamic flow conditions

Transport and sorption of ¹²⁵I^?, ¹³⁷Cs⁺, ⁸⁵Sr²⁺ and ^152,154Eu³⁺ in undisturbed soil cores have been studied under dynamic conditions. Radionuclides were dissolved in synthetic groundwater (SGW) of 0.015 mol/dm³ ionic strength, pH 8.4 and redox potential E_h = 145 mV. The soil samples were taken vertically and horizontally from the river bed at 5–100 cm depths, about 120 m southward of the Dukovany Low and Medium Level Radioactive Waste Repository. The respective water-soluble carriers in the 10^?6 mol/dm³ concentration were added into the SGW prior to the experiments. The soil cores of 9 cm height and 3.8 cm in diameter were placed into columns made of 150 cm³ PE injection syringes of suitable dimensions. The SGW was introduced into columns from the Mariotte’s bottle through a glass manifolds to supply the soil columns by gravity flow at a constant flow-rate about 1.2 cm³/h. Into the water stream, radioactive nuclides were added individually in a form of a short pulse in 0.1 cm³ of demineralized water. In the case of ¹²⁵I^? transport, retardation and hydrodynamic dispersion coefficients were determined, using an integral form of a simple advection-dispersion equation. For each radionuclides, sorption and desorption data have been obtained, evaluated and the results were compared mutually. Residual distributions of the sorbed cationic radionuclides along the soil columns were also presented.     

An efficient and facile synthesis of Zn(II) complexes with 2-substituted benzothiazoles and glycine- and alanine-based ligands having antifungal and antibacterial activities

We carried out an efficient and facile synthesis of Zn(II) complexes with heterocyclic ligands based on 2-substituted benzothiazole moieties, 2-(2′-hydroxynaphthyl)benzothiazole, 2-(2′-hydroxyphenyl)benzothiazole, and 2-(2′-merceptophenyl)benzothiazole, and amino acids, glycine and alanine, are reported and also examined for antifungal and antibacterial activities. Ligands and complexes were characterized by FTIR, ¹H NMR, and elemental analysis.     

Synthesis of Derivatives of 2,6-Dideoxy-2,2-Difluoro-3-O-Methyl-l-Arabinopyranose (2,2-Difluorooleandrose)

Abstract

L-Oleandrose is the carbohydrate constituent of the potent anthelmintic agents the avermectins. Diethylaminosulfur tri-fluoride treatment of appropriate uloses did not give gem-difluoro sugars. Trifluorofluoroxymethane or xenon difluoride addition to the double bond of 4-O-benzoyl-6-deoxy-2-fluoro-3-O-methyl-L-glucal produced protected 2,2-difluorooleandrose derivatives activated at their anomeric center and ready for glycosidation.     

Intramolecular aglycon delivery for (1 → 2)-β-mannosylation: towards the synthesis of phospholipomannan of Candida albicans

A high yielding method for 1,2-cis-β-D-mannosylation by intra-molecular aglycon delivery (IAD) through p-methoxy benzyl ether/acetal exchange and phenylsulfoxide donor is reported, along with its application in iterative assembly of antigenic (1 → 2)-β-pentamannoside domain of phospholipomannan (PLM) of fungal pathogen Candida albicans.     

An efficient ‘on-water’ synthesis of 1,4-dihydropyridines using Fe3O4@SiO2 nanoparticles as a reusable catalyst

An ‘on-water’, efficient, high yielding, expeditious method has been developed for the synthesis of 1,4-dihydropyridine (1,4-DHP) derivatives via an one-pot multi-component condensation of dimedone or 4-hydroxycoumarine, aldehydes, and ammonium acetate using Fe₃O₄@SiO₂ nanoparticles as a recyclable heterogeneous catalyst. This method takes advantage of the fact that water, a green solvent is used in combination with Fe₃O₄@SiO₂ nanoparticles as catalyst which can be easily recovered magnetically and reused for further runs.     

Poly-hydroxamic acid (PHA) matrix for gadolinium pre-concentration and removal

A novel hydrophilic, three dimensionally cross-linked, aliphatic backbones with pendant hydroxamic acid (HA) group as functional moiety has been synthesized and utilized targeting removal of gadolinium [Gd(III)] from laboratory waste aqueous effluent. To understand the nature of sorption, gadolinium solution of various concentrations viz., 20, 10, 5.0, 1.0, 0.5 and 0.1 ppm has been contacted with a dose rate of 1 g/100 mL for 2 h. In this study, ICP-AES has been used for determination of concentration (ppm) of gadolinium in feed, filtrate and elute. EDXRF study also ensures the presence of gadolinium in the respective medium. Loaded gadolinium matrix was eluted with 1 N HCl for determining the elution factor (0.98).     

Brief survey on phytochemicals to prevent COVID-19

BackgroundThe recent pandemic by COVID-19 is a global threat to human health. The disease is caused by SARS-CoV-2 and the infection rate is increased more quickly than MERS and SARS as their rapid adaptation to varied climatic conditions through rapid mutations. It becomes more severe due to the lack of proper therapeutic drugs, insufficient diagnostic tool, scarcity of appropriate drug, life supporting medical facility and mostly lack of awareness. Therefore, preventive measure is one of the important strategies to control. In this context, herbal medicinal plants received a noticeable attention to treat COVID-19 in Indian subcontinent. Here, 44 Indian traditional plants have been discussed with their novel phytochemicals that prevent the novel corona virus. The basic of SARS-CoV-2, their common way of transmission including their effect on immune and nervous system have been discussed. We have analysed their mechanism of action against COVID-19 following in-silico analysis. Their probable mechanism and therapeutic approaches behind the activity of phytochemicals to stimulate immune response as well as inhibition of viral multiplication discussed rationally. Thus, mixtures of active secondary metabolites/phytochemicals are the only choice to prevent the disease in countries where vaccination will take long time due to overcrowded population density.     

Supercritical CO2-assisted atomization for deposition of cellulose nanocrystals: an experimental and computational study

Nanoparticle spray deposition finds numerous applications in pharmaceutical, electronics, manufacturing, and energy industries and has shown great promises in engineering the functional properties of the coated parts. However, current spray deposition systems either lack the required precision in controlling the morphology of the deposited nanostructures or do not have the capacity for large-scale deposition applications. In this study, we introduce a novel spray system that uses supercritical CO₂ to assist the atomization process and create uniform micron-size water droplets that are used as cellulose nanocrystal (CNC) carriers. CNCs are selected in this study as they are abundant, possess superior mechanical properties, and contain hydroxyl groups that facilitate interaction with neighboring materials. We fundamentally investigate the effect of different process parameters, such as injection pressure, gas-to-liquid ratio, the axial distance between the nozzle and substrate, and CNC concentration on the final patterns left on the substrate upon evaporation of water droplets. To this end, we show how tuning process parameters control the size of carrier droplets, dynamics of evaporation, and self-assembly of CNCs, which in turn dictate the final architecture of the deposited nanostructures. We will particularly investigate the morphology of the nanostructures deposited after evaporation of micron-size droplets that has not been fully disclosed to date. Different characterization techniques such as laser diffraction, polarized microscopy, and high-resolution profilometry are employed to visualize and quantify the effect of each process parameter. Numerical simulations are employed to inform the design of experiments. Finally, it is shown that the fabricated nanostructures can be engineered based on the size of the carrier droplets controlled by adjusting spray parameters and the concentration of nanoparticles in the injected mixture. Process parameters can be selected such that nanoparticles form a ring, disk, or dome-shaped structure. Moderate operational conditions, simplicity, and time efficiency of the process, and use of abundant and biodegradable materials, i.e., water, CNCs, and CO₂ promote the scalability and sustainability of this method.

     

Conifers Phytochemicals: A Valuable Forest with Therapeutic Potential

Conifers have long been recognized for their therapeutic potential in different disorders. Alkaloids, terpenes and polyphenols are the most abundant naturally occurring phytochemicals in these plants. Here, we provide an overview of the phytochemistry and related commercial products obtained from conifers. The pharmacological actions of different phytochemicals present in conifers against bacterial and fungal infections, cancer, diabetes and cardiovascular diseases are also reviewed. Data obtained from experimental and clinical studies performed to date clearly underline that such compounds exert promising antioxidant effects, being able to inhibit cell damage, cancer growth, inflammation and the onset of neurodegenerative diseases. Therefore, an attempt has been made with the intent to highlight the importance of conifer-derived extracts for pharmacological purposes, with the support of relevant in vitro and in vivo experimental data. In short, this review comprehends the information published to date related to conifers’ phytochemicals and illustrates their potential role as drugs.