Uranium removal from nitric acid raffinate solution by solvent immobilized PVC cement

The present work deals with uranium removal from a nitric acid raffinate (waste) solution using prepared solvent (tri-butyl phosphate, TBP) immobilizing PVC cement (SIC) as a suitable adsorbent. The studied relevant factors affecting uranium adsorption onto SIC adsorbent involved; contact time, solution molarity, initial uranium concentration and temperature. The obtained adsorption isotherm of uranium onto the SIC adsorbent was fitted to Langmuir, Freundlich and Dubinin–Radushkviech (D–R) adsorption models. The results showed that the obtained equilibrium data fitted well the Langmuir isotherm. Additionally, it was found that the adsorption process obeys the pseudo second-order kinetic model. On the other hand, the calculated theoretical capacity of our prepared SIC adsorbent reached about 17 g U/kg SIC. Uranium adsorption from the studied raffinate solution was carried out applying the attained optimum conditions. The obtained data showed that 58.4 mg U/5 g SIC were adsorbed. However, using of 2 M HNO₃ solution as an eluent, 93 (54.3 mg U) from the adsorbed amount were eluted.     

Rapid conversion of cellulose to 5-hydroxymethylfurfural using single and combined metal chloride catalysts in ionic liquid

Direct conversion of cellulose into 5-hydroxymethylfurfural(HMF) was performed by using single or combined metal chloride catalysts in 1-ethyl-3-methylimidazolium chloride(Cl) ionic liquid.Our study demonstrated formation of 2-furyl hydroxymethyl ketone(FHMK),and furfural(FF) simultaneously with the formation of HMF.Various reaction parameters were addressed to optimize yields of furan derivatives produced from cellulose by varying reaction temperature,time,and the type of metal chloride catalyst.Catalytic reaction by using FeCl3 resulted in 59.9% total yield of furan derivatives(HMF,FHMK,and FF) from cellulose.CrCl3 was the most effective catalyst for selective conversion of cellulose into HMF(35.6%) with less concentrations of FHMK,and FF.Improving the yields of furans produced from cellulose could be achieved via reactions catalyzed by different combinations of two metal chlorides.Further optimization was carried out to produce total furans yield 75.9% by using FeCl3/CuCl2 combination.CrCl3/CuCl2 was the most selective combination to convert cellulose into HMF(39.9%) with total yield(63.8%) of furans produced from the reaction.The temperature and time of the catalytic reaction played an important role in cellulose conversion,and the yields of products.Increasing the reaction temperature could enhance the cellulose conversion and HMF yield for short reaction time intervals(5~20 min).     

Biomimetic Mussel Adhesive Inspired Anchor to Design ZnO@Poly(3‐Hexylthiophene) Hybrid Core@Corona Nanoparticles

The functionalization of zinc oxide (ZnO) nanoparticles by poly(3‐hexylthiophene) (P3HT) brush is completed by the combination of a mussel inspired biomimetic anchoring group and Huisgen cyclo‐addition “click chemistry.” Herein, the direct coupling of an azide modified catechol derivative with an alkyne end‐functionalized P3HT is described. This macromolecular binding agent is used to access core@corona ZnO@P3HT with a stable and homogeneous conjugated organic corona. Preliminary photoluminescence measurement proves an efficient electron transfer from the donor P3HT to the acceptor ZnO nanoparticles upon grafting, thus demonstrating the potential of such a combination in organic electronics.

     

The exploring microstructural,caloric, and corrosion behavior of NiTiNb shape-memory alloys

Journal of Thermal Analysis and Calorimetry - The influence of four different quantities of niobium (Nb) on some physical and chemical properties of Ni-Ti alloy was examined in this study....     

Quality-by-Design-Based Development of n-Propyl-Gallate-Loaded Hyaluronic-Acid-Coated Liposomes for Intranasal Administration

The present study aimed to develop n-propyl gallate (PG)-encapsulated liposomes through a novel direct pouring method using the quality-by-design (QbD) approach. A further aim was to coat liposomes with hyaluronic acid (HA) to improve the stability of the formulation in nasal mucosa. The QbD method was used for the determination of critical quality attributes in the formulation of PG-loaded liposomes coated with HA. The optimized formulation was determined by applying the Box–Behnken design to investigate the effect of composition and process variables on particle size, polydispersity index (PDI), and zeta potential. Physiochemical characterization, in vitro release, and permeability tests, as well as accelerated stability studies, were performed with the optimized liposomal formulation. The optimized formulation resulted in 90 ± 3.6% encapsulation efficiency, 167.9 ± 3.5 nm average hydrodynamic diameter, 0.129 ± 0.002 PDI, and −33.9 ± 4.5 zeta potential. Coated liposomes showed significantly improved properties in 24 h in an in vitro release test (>60%), in vitro permeability measurement (420 μg/cm²) within 60 min, and also in accelerated stability studies compared to uncoated liposomes. A hydrogen-peroxide-scavenging assay showed improved stability of PG-containing liposomes. It can be concluded that the optimization of PG-encapsulated liposomes coated with HA has great potential for targeting several brain diseases.     

A multiscale gradient-dependent plasticity model for size effects

The mechanical behaviour of polycrystalline material is closely correlated to grain size. In this study, we investigate the size-dependent phenomenon in multi-phase steels using a continuum dislocation dynamic model coupled with viscoplastic self-consistent model. We developed a dislocation-based strain gradient plasticity model and a stress gradient plasticity model, as well as a combined model, resulting in a theory that can predict size effect over a wide range of length scales. Results show that strain gradient plasticity and stress gradient plasticity are complementary rather than competing theories. The stress gradient model is dominant at the initial strain stage, and is much more effective for predicting yield strength than the strain gradient model. For larger deformations, the strain gradient model is dominant and more effective for predicting size-dependent hardening. The numerical results are compared with experimental data and it is found that they have the same trend for the yield stress. Furthermore, the effect of dislocation density at different strain stages is investigated, and the findings show that the Hall–Petch relation holds for the initial strain stage and breaks down for higher strain levels. Finally, a power law to describe the size effect and the transition zone between the strain gradient and stress gradient dominated regions is developed.     

Quadratic autocatalysis with non-linear decay

We provide a detailed, and thorough, investigation into the concentration multiplicity and dynamic stability of a prototype non-linear chemical mechanism: quadratic autocatalysis subject to non-linear decay in a continuously stirred tank reactor. This model was previously investigated in the literature using numerical path-following techniques. The contribution of this study is the application of singularity theory and degenerate Hopf-bifurcation theory to obtain analytical representations of many of the features of interest in this system. In particular, we use these presentations to identify critical values of an unfolding parameter below which specified phenomenon are no longer exhibited.     

Halide Anion Triggered Reactions of Michael Acceptors with Tropylium Ion

Tropylium bromide undergoes noncatalyzed, regioselective additions to a large variety of Michael acceptors. In this way, acrylic esters are converted into β‐bromo‐α‐cycloheptatrienylpropionic esters. The reactions are interpreted as nucleophilic attack of bromide ions at the electron‐deficient olefins and the approach of the tropylium ion to the incipient carbanion. Quantum chemical calculations were performed to elucidate the analogy to the amine‐ or phosphine‐catalyzed Rauhut–Currier reactions. Subsequent synthetic transformations of the bromo‐cycloheptatrienylated adducts are reported.     

Leptospermum petersonii as a Potential Natural Food Preservative

Leptospermum petersonii (family Myrtaceae) is often cultivated for ornamental purposes but also serves as a rich source of bioactive essential oils. While several studies focused on the activities of the essential oils, this study analysed the potential of spent L. petersonii leaves as a natural food preservative. Method: We investigated the in vitro antioxidant and antimicrobial activities of crude L. petersonii extracts against activities of the purified isolated flavonoid, 6-methyltectochrysin, which was characterized using spectroscopic methods. The antioxidant assays followed ORAC, FRAP and TEAC tests. The antimicrobial activities of the extract and purified flavonoid were analysed against six multi-drug resistant microbial strains in broth dilution assays. Result: The results revealed that both the crude extracts and isolated 6-methyltectochrysin exhibited positive radical ion scavenging antioxidant potential, however the crude extract was about 6-fold more potent antioxidant than the purified 6-methyltectochrysin. The crude extract also showed strong antimicrobial activities against Bacillus cereus, and even more potent antimicrobial agent than the reference ampicillin antibiotic against Klebsiella pneumoniae subsp. pneumoniae. A higher resistance was observed for the tested Gram-negative strains than for the Gram-positive ones. 6-methyltectochrysin was generally inactive in the antimicrobial assays. Conclusion: The crude methanolic extract showed significant bioactivity which validates the medicinal relevance of the plant. The observed biological activities, especially against a notorious strain of B. cereus, suggest that L. petersonii could be a promising natural source of food preservatives.     

Two new zinc(II) and mercury(II) complexes based on N,N′‐(cyclohexane‐1,2‐diylidene)bis(4‐fluorobenzohydrazide): synthesis,crystal structures and antibacterial activities

Reaction of N,N′‐(cyclohexane‐1,2‐diylidene)bis(4‐fluorobenzohydrazide), C₂₀H₁₈F₂N₄O₂, ( L^F ), with zinc chloride and mercury(II) chloride produced different types and shapes of neutral coordination complexes, namely, dichlorido[N,N′‐(cyclohexane‐1,2‐diylidene)bis(4‐fluorobenzohydrazide)‐κ²N,O]zinc(II), [ZnCl₂(C₂₀H₁₈F₂N₄O₂)], ( 1 ), and dichlorido[N,N′‐(cyclohexane‐1,2‐diylidene)bis(4‐fluorobenzohydrazide)‐κ⁴O,N,N′,O′]mercury(II), [HgCl₂(C₂₀H₁₈F₂N₄O₂)], ( 2 ). The organic ligand and its metal complexes are characterized using various techniques: IR, UV–Vis and nuclear magnetic resonance (NMR) spectroscopies, in addition to powder X‐ray diffraction (PXRD), single‐crystal X‐ray crystallography and microelemental analysis. Depending upon the data from these analyses and measurements, a typical tetrahedral geometry was confirmed for zinc complex ( 1 ), in which the Zn^II atom is located outside the bis(benzhydrazone) core. The Hg^II atom in ( 2 ) is found within the core and has a common octahedral structure. The in vitro antibacterial activities of the prepared compounds were evaluated against two different bacterial strains, i.e. gram positive Bacillus subtilis and gram negative Pseudomonas aeruginosa bacteria. The prepared compounds exhibited differentiated growth‐inhibitory activities against these two bacterial strains based on the difference in their lipophilic nature and structural features.