The design and synthesis of analogs of natural products can be a valuable source of medicinal preparations for the pharmaceutical industry. In the present study, the structural elucidation of eleven ...derivatives of 2,4-dihalogeno substituted synthetic analogues of the natural compound carvacrol was carried out by means of NMR experiments, and of another thirteen by DFT calculations. By selective NOE experiments and the irradiation of CH signals of the isopropyl group, individual conformers were assigned as syn and anti. By comparing GIAO/B3LYP/6-311++G(d,p)-calculated and experimentally measured vicinal sup.3Jsub.CH spin-spin constants, this assignment was confirmed. An unusual relationship is reported for proton-carbon vicinal couplings: sup.3Jsub.CH (180°) < sup.3Jsub.CH (0°). The conformational mobility of carvacrols was studied by 2D EXSY spectra. The application of homonuclear decoupling technique (HOBS) to these spectra simplifies the spectra, improves resolution without reducing the sensitivity, and allows a systematic examination of the rotational barrier of all compounds via their CH signals of the isopropyl group in a wider temperature interval. The rate constants of the isopropyl rotation between syn and anti conformers were determined and the corresponding energy barriers (14–17 kcal/mol) were calculated. DFT calculations of the energy barriers in carvacrol derivatives allowed the determination of the steric origin of the restricted isopropyl rotation. The barrier height depends on the size of the 2- and 4-position substituents, and is independent of the derivatization of the OH group.
Polyethyleneimine (PEI) has been reported to have good potential for the adsorption of metal ions. In this work, PEI was covalently bound to NiFesub.2Osub.4@SiOsub.2 nanoparticles to form the new ...adsorbent NiFesub.2Osub.4@SiOsub.2–PEI. The material allowed for magnetic separation and was characterized via powder X-ray diffraction (PXRD), showing the pattern of the NiFesub.2Osub.4 core and an amorphous shell. Field emission scanning electron microscopy (FE-SEM) showed irregular shaped particles with sizes ranging from 50 to 100 nm, and energy-dispersive X-ray spectroscopy (EDX) showed high C and N contents of 36 and 39%, respectively. This large amount of PEI in the materials was confirmed by thermogravimetry–differential thermal analysis (TGA-DTA), showing a mass loss of about 80%. Fourier-transform IR spectroscopy (FT-IR) showed characteristic resonances of PEI dominating the spectrum. The adsorption of CrOsub.4 sup.2−, Nisup.2+, and Pbsup.2+ ions from aqueous solutions was studied at different pH, temperatures, metal ion concentrations, and adsorbent dosages. The maximum adsorption capacities of 149.3, 156.7, and 161.3 mg/g were obtained for CrOsub.4 sup.2−, Nisup.2+, and Pbsup.2+, respectively, under optimum conditions using 0.075 g of the adsorbent material at a 250 mg/L ion concentration, pH = 6.5, and room temperature.
Four novel seconeodolastane diterpenoids, named tricholomalides D–G, were isolated, together with the known tricholomalide C, from the fruiting bodies of Tricholoma ustaloides Romagn., a species ...belonging to the large Tricholoma genus of higher mushrooms (Basidiomycota, family Tricholomataceae). They were isolated through multiple chromatographic separations, and the structures, including the absolute configuration, were established through a detailed analysis of MS, NMR, and CD spectral data and comparison with related compounds reported in the literature, which has been thoroughly revised.
A typical piezoelectric energy harvester is a bimorph cantilever with two layers of piezoelectric material on both sides of a flexible substrate. Piezoelectric layers of lead-based materials, ...typically lead zirconate titanate, have been mainly used due to their outstanding piezoelectric properties. However, due to lead toxicity and environmental problems, there is a need to replace them with environmentally benign materials. Here, our main efforts were focused on the preparation of hafnium-doped barium titanate (BaHfsub.xTisub.1−xOsub.3; BHT) sol–gel materials. The original process developed makes it possible to obtain a highly concentrated sol without strong organic complexing agents. Sol aging and concentration can be controlled to obtain a time-stable sol for a few months at room temperature, with desired viscosity and colloidal sizes. Densified bulk materials obtained from this optimized sol are compared with a solid-state synthesis, and both show good electromechanical properties: their thickness coupling factor kt values are around 53% and 47%, respectively, and their converse piezoelectric coefficient dsub.33 sup.∗ values are around 420 and 330 pm/V, respectively. According to the electromechanical properties, the theoretical behavior in a bimorph configuration can be simulated to predict the resonance and anti-resonance frequencies and the corresponding output power values to help to design the final device. In the present case, the bimorph configuration based on BHT sol–gel material is designed to harvest ambient vibrations at low frequency (<200 Hz). It gives a maximum normalized volumetric power density of 0.03 µW/mmsup.3/Hz/gsup.2 at 154 Hz under an acceleration of 0.05 m/ssup.2.
The present work demonstrates the use of Cdsup.2+ as a reactivity probe of the fulvic acids (FAs), humic acids (HAs) and dissolved organic matter (DOM) compost extracts. Significant differences were ...observed between the extracts, with the HA extract showing the highest reactivity. Comparing the different composts, the largest reactivity variation was again observed for HA then FA and finally DOM extracts. The Cdsup.2+ binding extent was used to calculate the quality of composts and compared with a reference of uncomposted organic fertiliser (FLW), leading to the definition of an operational scale of compost quality. The parameter equivalent mass of fertiliser (mEF) was used for this scale sorted the seven composts from 0.353 to 1.09 kg FLW, for compost of sewage sludge (CSS) and vermicompost of domestic waste (CVDW), respectively. The significance of this parameter was verified through a correlation analysis between binding extent and the effect of compost application on lettuce crop growth in a field trial. The results demonstrate the potentiality of FA and HA extracts as markers of compost bioactivity and the use of Cdsup.2+ as a reactivity probe.
Saussurea neoserrata Nakai offers a reliable and efficient source of antioxidants that can help alleviate adverse skin reactions triggered by air pollutants. Air pollutants, such as particulate ...matter (PM), have the ability to infiltrate the skin and contribute to the higher occurrence of cardiovascular, cerebrovascular, and respiratory ailments. Individuals with compromised skin barriers are particularly susceptible to the impact of PM since it can be absorbed more readily through the skin. This study investigated the impact of protocatechuic acid and syringin, obtained from the n-BuOH extract of S. neoserrata Nakai, on the release of PGEsub.2 and PGDsub.2 induced by PMsub.10. Additionally, it examined the gene expression of the synthesis of PGEsub.2 and PGDsub.2 in human keratinocytes. The findings of this research highlight the potential of utilizing safe and efficient plant-derived antioxidants in dermatological and cosmetic applications to mitigate the negative skin reactions caused by exposure to air pollution.
Our study is focused on the structural and morphological characteristics, optical behaviour and photocatalytic properties of undoped and 5 at% Eusup.3+-, Gdsup.3+- and Ysup.3+-doped CeOsub.2 ...nanoparticles prepared by a green hybrid sol-gel combustion method. Several techniques such as X-ray diffraction powder (XRD), Transmission Electron Microscopy (TEM), UV-Vis spectroscopy, Photoluminescence spectroscopy (PL) and Electron Paramagnetic Resonance (EPR) have been used to investigate the obtained samples. Moreover, the correlation between the characteristics and properties has been studied. The nanoparticles observed by TEM exhibit a pseudo-spherical shape, except for Ysup.3+-doped CeOsub.2, which presents an acicular shape. The average size of undoped and rare-earth-doped CeOsub.2 nanoparticles is below 10 nm, in good agreement with the calculations performed based on XRD analyses. From UV-Vis analyses it has been deduced that with doping the band gap energy decreases, which shows that additional levels are introduced by doping into the CeOsub.2 band gap. The EPR spectra evidence similar behaviour for all doped samples. The photocatalytic activity was evaluated by the degradation of rhodamine B (RhB) under UV light irradiation. The photodegradation mechanism has been studied in depth based on the formation of electron-hole pairs, and to evidence the reactive oxygen species, ESR coupled with spin-trapping experiments was performed. In the case of Y-doped CeOsub.2 nanoparticles, the generation of both •OOH and •Osub.2 sup.− radicals involved in RhB photodegradation was highlighted.
![BaHf[sub.0.05]Ti[sub.0.95]O...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1996-1944/small "BaHf[sub.0.05]Ti[sub.0.95]O[sub.3] Ceramics from Sol–Gel and Solid-State Processes: Application to the Modelling of Piezoelectric Energy Harvesters")
