Dielectric Properties of Polymer Composites Filled with Different Metals

Electrically conductive composite systems based on polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA) filled with metal powders of Al and Cu have been studied. The composite preparation conditions allow the formation of a random distribution of metallic particles in the polymer matrix. Dependence of the dielectric and conductivity properties of the PVC and PMMA/fillers was studied over a broad range of frequency and volume fraction of metal fillers. The experimental results could be explained by means of the conductivity of fillers and the interface polarization between polymers and fillers. Percolation was also seen in this study when the volume fraction of conducting fillers was close to critical value, in which the composites undergo an insulator‐conductor transition. The relation among the dielectric property and the fillers with different conductivity was proposed.     

Substrate Envelope-Designed Potent HIV-1 Protease Inhibitors to Avoid Drug Resistance

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Solvent effects on oxygen atom transfer reaction between manganese(V)-oxo corrole and alkene

Pseudo-first order reaction rate constants of 5,10,15-tris（pentafluorophenyl）corrole Mn（V）-oxo (F₁₅CMn（V）-oxo),5,15-bis（pentafluorophenyl）-10-（phenyl）corrole Mn（V）-oxo(F₁₀CMn（V）-oxo),5,15- bis（phenyl）-10-（pentafluorophenyl）corrole Mn（V）-oxo（F₅CMn（V）-oxo） and 5,10,15-tris（phenyl）corrole Mn（V）-oxo（F₀CMn（V）-oxo） with a series of alkene substrates in different solvents were determined by UV-vis spectroscopy.The results indicated that the oxygen atom transfer pathway between Mn（V）-oxo corrole and alkene is solvent-dependent.     

Microwave‐assisted Aqueous Multicomponent Reaction: Facile Synthesis of Polyfunctionalized Indoline‐spiro Fused Pyran Derivatives

A green and highly efficient method for the synthesis of polyfunctionalized indoline‐spiro fused pyran derivatives has been established. This reaction was conducted by reacting readily available and inexpensive starting materials, such as isatins, cyclic‐1,3‐dicarbonyl compounds, and malononitrile in aqueous media without any catalysts under microwave irradiation. The present green synthesis shows fascinating properties such as the use of water as the reaction solution, concise one‐pot conditions, short reaction periods (8–14 min), and easy purifications. The synthesis could also set a good example to GAP (Group‐Assistant‐Purification) chemistry in which purification via chromatography can be avoided and the pure products can be easily acquired only by washing the crude products with 95% EtOH.     

Seven new alkaloids from the roots of Stemona tuberosa

Seven new alkaloids, named as 1,9-epoxy-9a-hydroxystenine (1), tuberostemoline A (2), tuberostemoline B (3), tuberostemoninol C (4), oxotuberostemonine A (5), the mixture of bisdehydrotuberostemonine D (6), and bisdehydrotuberostemonine E (7), together with four known alkaloids neotuberostemonine (8), sessilifoline B (9), stemoxazolidinone F (10), and tuberostemoninol A (11), were isolated from the roots of Stemona tuberosa. The structures of 1–7 were elucidated through extensive spectroscopic analysis, and the relative configurations of 1–6 and 8 were further confirmed by X-ray crystallographic data. Compounds 8, 9 and the mixture of 6 & 7 exhibited potential acetylcholinesterase (AChE) inhibitory activities.     

Radiostrontium separation from sodium molybdate solution and its measurement using LSA: an application to radiopharmaceutical analysis

Technetium (^99mTc), a decay product of molybdenum (⁹⁹Mo), is employed as radioisotope in nuclear medicine. Several practical devices known as generators are commercially available which enable the user to separate the daughter from the parent radionuclide. The present study is focused on quality control of chromatographic technetium generator. A properly constructed generator should comply with international requirements of radionuclide purity of ⁹⁰Sr/⁹⁹Mo ≤ 6 × 10^?8 and ⁸⁹Sr/⁹⁹Mo ≤ 6 × 10^?7. For this purpose an analytical method was optimized to quantify radiostrontium (⁸⁹Sr and ⁹⁰Sr) in sodium molybdate [Na ₂ ⁹⁹ MoO₄] solution, a fission product used for ⁹⁹Mo/^99mTc generators. Dowex 1 × 8 and alumina were used in sequence followed by tributyl phosphate extraction for radiostrontium separation. Cerenkov measurement of ⁸⁹Sr and ⁹⁰Sr (through its descendent ⁹⁰Y) was performed using Perkin Elmer Tricarb LSA 3170 with detection efficiency of 42 and 14 %, respectively. Since efficiency of Cerenkov counting is sensitive to presence of color, spectral index of sample was used to correct the counting efficiency. The chemical recovery for strontium was 22 % and for yttrium was 80 % as determined by inductively coupled plasma optical emission spectrometry. Lower limit of detection was found to be 6.3 and 14.4 Bq L^?1 for ⁹⁰Sr and ⁸⁹Sr, respectively with 60 min counting time. Hence method can be applied successfully to analyze ^89,90Sr in fission molybdenum used as radiopharmaceutical with a relative error of <10 %.     

Selenium Alleviates the Adverse Effect of Drought in Oilseed Crops Camelina (Camelina sativa L.) and Canola (Brassica napus L.)

Drought poses a serious threat to oilseed crops by lowering yield and crop failures under prolonged spells. A multi-year field investigation was conducted to enhance the drought tolerance in four genotypes of Camelina and canola by selenium (Se) application. The principal aim of the research was to optimize the crop yield by eliciting the physio-biochemical attributes by alleviating the adverse effects of drought stress. Both crops were cultivated under control (normal irrigation) and drought stress (skipping irrigation at stages i.e., vegetative and reproductive) conditions. Four different treatments of Se viz., seed priming with Se (75 μM), foliar application of Se (7.06 μM), foliar application of Se + Seed priming with Se (7.06 μM and 75 μM, respectively) and control (without Se), were implemented at the vegetative and reproductive stages of both crops. Sodium selenite (Na₂SeO₃), an inorganic compound was used as Se sources for both seed priming and foliar application. Data regarding physiochemical, antioxidants, and yield components were recorded as response variables at crop maturity. Results indicated that WP, OP, TP, proline, TSS, TFAA, TPr, TS, total chlorophyll contents, osmoprotectant (GB, anthocyanin, TPC, and flavonoids), antioxidants (APX, SOD, POD, and CAT), and yield components (number of branches per plant, thousand seed weight, seed, and biological yields were significantly improved by foliar Se + priming Se in both crops under drought stress. Moreover, this treatment was also helpful in boosting yield attributes under irrigated (non-stress) conditions. Camelina genotypes responded better to Se application as seed priming and foliar spray than canola for both years. It has concluded that Se application (either foliar or priming) can potentially alleviate adverse effects of drought stress in camelina and canola by eliciting various physio-biochemicals attributes under drought stress. Furthermore, Se application was also helpful for crop health under irrigated condition.     

Thermodynamics of the Interaction Between Graphene Quantum Dots with Human Serum Albumin and γ-Globulins

As one of the newly emerged nanomaterials, graphene quantum dots (GQDs) have shown great application potential as tracking probes and drug carriers in biological areas. The GQDs synthesized via the nitric acid reflux method in this study turned out to quench the fluorescence of human serum albumin (HSA) and gamma globulin (γ-globulin) in two different functional ways. The fluorescence quenching effect of GQDs on HSA is a static pattern and the predominant interaction forces are hydrogen bonds and van der Waals forces. Distinct from HSA, the interaction between GQDs and γ-globulins belongs to dynamic quenching and is driven by electrostatic forces. Ultraviolet–visible (UV–vis) differential spectrometry and transient state fluorescence spectrometry were also utilized to further confirm their quenching types. Also, thermodynamics parameters, the enthalpy change (ΔH) and entropy change (ΔS) of reaction between GQDs and proteins were obtained through a series of calculations from the van’t Hoff equation. Furthermore, the effect of GQDs on the conformational structure of proteins was characterized by synchronous fluorescence spectra (SFS), three-dimensional (3D) fluorescence and circular dichroism (CD) spectra. In addition, the binding mechanism of GQDs with HSA and γ-globulins were proposed based on the obtained experimental results. The research on the reaction between GQDs with HSA and γ-globulins offers promising insight for the further application of nanomaterials in biomedical fields.     

First-principle investigation of XSrH3 (X = K and Rb) perovskite-type hydrides for hydrogen storage

Hydrogen can be utilized as an energy source; therefore, hydrogen storage has received the most appealing examination interest in recent years. The investigations of hydrogen storage applications center fundamentally around the examination of hydrogen capacity abilities of recently presented compounds. XSrH₃ (X = K and Rb) compounds have been examined by density functional theory (DFT) calculations to uncover their different characteristics, as well as hydrogen capacity properties, for the first time. Studied compounds are optimized in the cubic phase, and optimized lattice constants are obtained as 4.77 and 4.99 Å for KSrH₃ and RbSrH₃, respectively. These hydrides have shown negative values of formation enthalpies as they are stable thermodynamically. XSrH₃ might be used in hydrogen storage applications because of high gravimetric hydrogen storage densities, which are 2.33 and 1.71 wt% for KSrH₃ and RbSrH₃, respectively. Moreover, electronic properties confirm the semiconductor nature of these compounds having indirect band gaps of values 1.41 and 1.23 eV for KSrH₃ and RbSrH₃, respectively. In addition, mechanical properties from elastic constants such as Young modulus and Pugh's ratio, also have been investigated, and these compounds were found to satisfy born stability conditions. Furthermore, Pugh's ratio and Cauchy pressure show that these hydrides have a brittle nature. Furthermore, thermodynamic properties such as entropy and Debye temperature have been examined using the quasiharmonic Debye model for different temperatures and pressures.     

Magnetoelectronic properties of ferromagnetic compounds Rb2TaZ6 (Z = Cl,Br) for possible spintronic applications

Highly spin-polarized ferromagnetic materials are essential for efficient spintronic devices. Here, 100% spin-polarized compounds Rb₂TaZ₆ (Z = Cl, Br) studied via density functional theory are reported. These compounds show stability in the ferromagnetic phase with cubic symmetry and half metallic behavior, thereby exhibiting a nonzero direct band gap in the spin-down channel and zero band gap in the spin-up configuration. The Ta-d sates contribute mainly to the net magnetic moments as explained by the crystal field theory and density of states. High Curie temperatures of 960.35 and 1021.74 K for Ra₂TaCl₆ and Rb₂TaBr₆, along with maximum spin polarizability, make these compounds favorable for efficient spintronic applications.