Proton NMR probing of stoichiometry and thermodynamic data for the complexation of Na and Li ions with 15-Crown-5 in acetonitrile-nitrobenzene mixtures

Proton NMR was used to study the complexation reaction of Li⁺ and Na⁺ ions with 15-Crown-5 (15C5) in a number of binary acetonitrile (AN)-nitrobenzene (NB) mixtures at different temperatures. In all cases, the exchange between free and complexed 15C5 was fast on the NMR timescale and only a single population average ¹H signal was observed. The formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift mole ratio data. There is an inverse relationship between the complex stability and the amount of AN in the solvent mixtures. The enthalpy and entropy values for the complexation reaction were evaluated from the temperature dependence of the formation constants. In all the solvent mixtures studied, the resulting complex is enthalpy stabilized but entropy destabilized. Finally, the experimental results were compared with theoretical ones that were obtained from molecular modeling methods. Based on our results, it is most probable that Li⁺-15C5 in solvent stays in a rather nesting complex form with greater LogK_f values, but Na⁺-15C5 forms a complete perching complex form with lower LogK_f values.     

Silica Gel‐Supported Polyphosphoric Acid (PPA/SiO2): An Efficient and Reusable Heterogeneous Catalyst for Facile Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthenes under Solvent‐free Conditions

A simple, efficient and green method for the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes by a one‐pot condensation reaction of β‐naphthol and aryl aldehydes using silica gel‐supported polyphosphoric acid (PPA/SiO₂), an effective and reusable catalyst, under solvent‐free conditions is described. The present methodology offers several advantages, such as a simple procedure with an easy work‐up, short reaction times, high yields, and the absence of any volatile and hazardous organic solvents.     

Exploring a model of a chemokine receptor/ligand complex in an explicit membrane environment by molecular dynamics simulation: the human CCR1 receptor

The seven transmembrane helices G-protein-coupled receptors (GPCRs) form one of the largest superfamilies of signaling proteins found in humans. Homology modeling, molecular docking, and molecular dynamics (MD) simulation were carried out to construct a reliable model for CCR1 as one of the GPCRs and to explore the structural features and the binding mechanism of BX471 as one of the most potent CCR1 inhibitors. In this study, BX471 has been docked into the active site of the CCR1 protein. After docking, one 20 ns MD simulation was performed on the CCR1-ligand complex to explore effects of the presence of lipid membrane in the vicinity of the CCR1-ligand complex. At the end of the MD simulation, a change in the position and orientation of the ligand in the binding site was observed. This important observation indicated that the application of MD simulation after docking of ligands is useful. Explorative runs of molecular dynamics simulation on the receptor-ligand complex revealed that except for Phe85, Phe112, Tyr113, and Ile259, the rest of the residues in the active site determined by docking are changed. The results obtained are in good agreement with most of the experimental data reported by others. Our results show that molecular modeling and rational drug design for chemokine targets is a possible approach.     

The effect of cell orientations and environmental conditions on the performance of a passive DMFC single cell

A single cell passive air-breathing liquid feed direct methanol fuel cell (DMFC) is designed and fabricated. Furthermore, the effects of cell orientation and environmental conditions such as temperature and relative humidity on the performance of such passive DMFC are tested experimentally. The obtained results indicate that both environmental temperature and relative humidity have significant effects on the performance of fabricated fuel cell. The experimental data contained within this work shows that under lower relative humidity and higher temperature, the passive air-breathing direct methanol fuel cell has higher power output and better performance. According to experimental results, flooding has a vital role on the cell performance in various relative humidity and temperatures. The results also show that cell orientation has a strong effect on the performance of passive DMFC. The best power output and performance were achieved under vertical orientation.     

Bioresource Polymer Composite for Energy Generation and Storage: Developments and Trends

The ever-growing demand of human society for clean and reliable energy sources spurred a substantial academic interest in exploring the potential of biological resources for developing energy generation and storage systems. As a result, alternative energy sources are needed in populous developing countries to compensate for energy deficits in an environmentally sustainable manner. This review aims to evaluate and summarize the recent progress in bio-based polymer composites (PCs) for energy generation and storage. The articulated review provides an overview of energy storage systems, e. g., supercapacitors and batteries, and discusses the future possibilities of various solar cells (SCs), using both past research progress and possible future developments as a basis for discussion. These studies examine systematic and sequential advances in different generations of SCs. Developing novel PCs that are efficient, stable, and cost-effective is of utmost importance. In addition, the current state of high-performance equipment for each of the technologies is evaluated in detail. We also discuss the prospects, future trends, and opportunities regarding using bioresources for energy generation and storage, as well as the development of low-cost and efficient PCs for SCs.     

Effect of carbon nanotubes on the thermal conductivity enhancement of synthesized hydroxyapatite filled with water for dental applications: experimental characterization and numerical study

Journal of Thermal Analysis and Calorimetry - The hydroxyapatite is one of the biocompatible and insulating bioceramics, while the carbon nanotube has a high thermal conductivity potential. This...     

Enhancing Bioactive Saponin Content of Raphanus sativus Extract by Thermal Processing at Various Conditions

Pickled radish (Raphanus sativus) is a traditional Asian ingredient, but the traditional method takes decades to make this product. To optimize such a process, this study compared the saponin content of pickled radishes with different thermal processing and traditional processes (production time of 7 days, 10 years, and 20 years) and evaluated the effects of different thermal processes on the formation of radish saponin through kinetics study and mass spectrometry. The results showed that increasing the pickling time enhanced the formation of saponin in commercial pickled radishes (25 °C, 7 days, 6.50 ± 1.46 mg g⁻¹; 3650 days, 23.11 ± 1.22 mg g⁻¹), but these increases were lower than those induced by thermal processing (70 °C 30 days 24.24 ± 1.01 mg g⁻¹). However, it was found that the pickling time of more than 10 years and the processing temperature of more than 80 °C reduce the saponin content. Liquid chromatography–mass spectrometry (LC-MS) analysis showed that the major saponin in untreated radish was Tupistroside G, whereas treated samples contained Asparagoside A and Timosaponin A1. Moreover, this study elucidated the chemical structure of saponins in TPR. The findings indicated that thermal treatment could induce functional saponin conversion in plants, and such a mechanism can also be used to improve the health efficacy of plant-based crops.     

Excitation of plant growth in dormant temperature by steady magnetic field

Experimental results of applying a steady magnetic field (20 and 30 mT) on agricultural plants reveal that their growth is more than that of control plants. Considering that these plants have ferritin cells, and each ferritin cell has 4500 Fe atoms, it is obvious that they have an outstanding role in the plants’ growth. As the last spin magnetic moment (SMM) of the Fe atom posed to an external magnetic field (EMF), the composition of SMM and EMF create an oscillator in the system. Then we have a moment of force on ferritin cells. This oscillator exerts its energy, then damps and finally locates in the field direction. The relaxed energy increased the internal temperature (i.e., the effective temperature of the magnetic spin system of plant) so that it is situated in a proper temperature for growing. This phenomenon (temperature increasing) occurs in the initial minutes of applying the magnetic field. So it depends on the number of times of locating the plant in magnetic field in a day (n). If this number (n) passes the critical value, the plant reaches a burning temperature and growth is perturbed. In this paper, the plant growth rate and critical temperature in a steady magnetic field were investigated and formulated theoretically. An innovative result in this research is as follows: if a plant's environment was in the dormant temperature, we could increase the internal temperature of the plant by applying a magnetic field n times in a day (for growth).     

Electrocatalytic determination of penicillamine using multiwall carbon nanotubes paste electrode and chlorpromazine as a mediator

In this study, we describe the application of carbon paste electrode modified with multiwall carbon nanotubes as a voltammetric sensor for determination of penicillamine (PA) in the presence of chlorpromazine as a mediator. This modified electrode showed very efficient electrocatalytic activity for the anodic oxidation of PA. The peak current of linear sweep voltammograms of PA increased linearly with it’s concentration in the range of 0.5–500 μM PA. The detection limit for PA was 0.2 μM. The RSDs for 1.0 and 10.0 μM PA were 1.1 and 1.7%, respectively. The proposed sensor was successfully applied for the determination of PA in human urine and tablet.