DBU-catalyzed transprotection of N-Fmoc-cysteine di- and tripeptides into S-Fm-cysteine di- and tripeptides

The transprotection of N-Fmoc-cysteine containing di- and tripeptides possessing a free SH group to produce the corresponding S-Fm-cysteine di- and tripeptides bearing a free amino group is accomplished efficiently with DBU in dry THF. The N-Fmoc to S-Fm transformation mechanism is discussed. S-Fm-Cysteine di- and tripeptides readily form amide bonds on coupling with N-(Pg-α-aminoacyl)benzotriazoles and N-(Pg-α-dipeptidoyl)benzotriazoles to give larger peptides.     

New ceramic microfiltration membranes from mineral coal fly ash

This work aims to develop a new mineral porous tubular membrane based on mineral coal fly ash. Finely ground mineral coal powder was calcinated at 700 °C for about 3 h. The elaboration of the mesoporous layer was performed by the slip casting method using a suspension made of the mixture of fly ash powder, water and PVA. The obtained membrane was submitted to a thermal treatment which consists in drying at room temperature for 24 h then a sintering at 800 °C. SEM photographs indicated that the membrane surface was homogeneous and did not present any macro defects (cracks, etc.). The average pore diameter of the active layer was 0.25 μm and the thickness was around 20 μm. The membrane permeability was 475 l/h m² bar.This membrane was applied to the treatment of the dying effluents generated by the washing baths in the textile industry. The performances in term of permeate flux and efficiency were determined and compared to those obtained using a commercial alumina microfiltration membrane. Almost the same stabilised permeate flux was obtained (about 100 l/h m²). The quality of permeate was almost the same with the two membranes: the COD and color removal was 75% and 90%, respectively.     

Biosensors based on cholinesterase inhibition for insecticides, nerve agents and aflatoxin B1 detection (review)

The present review reports the research carried out during last 9 years on biosensors based on cholinesterase inhibition for nerve agents, organophosphorus and carbammic insecticides, and aflatoxin B₁ detection. Relative applications in environmental and food areas are also reported. Special attention is paid to the optimization of parameters such as enzyme immobilization, substrate concentration, and incubation time in the case of reversible inhibition by aflatoxin B₁ or irreversible inhibition by organophosphorus and carbamic insecticides, and nerve agents in order to optimize and improve the analytical performances of the biosensor. Evaluation of selectivity of the system is also discussed.     

Independent components analysis coupled with 3D-front-face fluorescence spectroscopy to study the interaction between plastic food packaging and olive oil

Olive oil is one of the most valued sources of fats in the Mediterranean diet. Its storage was generally done using glass or metallic packaging materials. Nowadays, plastic packaging has gained worldwide spread for the storage of olive oil. However, plastics are not inert and interaction phenomena may occur between packaging materials and olive oil. In this study, extra virgin olive oil samples were submitted to accelerated interaction conditions, in contact with polypropylene (PP) and polylactide (PLA) plastic packaging materials. 3D-front-face fluorescence spectroscopy, being a simple, fast and non destructive analytical technique, was used to study this interaction. Independent components analysis (ICA) was used to analyze raw 3D-front-face fluorescence spectra of olive oil. ICA was able to highlight a probable effect of a migration of substances with antioxidant activity. The signals extracted by ICA corresponded to natural olive oil fluorophores (tocopherols and polyphenols) as well as newly formed ones which were tentatively identified as fluorescent oxidation products. Based on the extracted fluorescent signals, olive oil in contact with plastics had slower aging rates in comparison with reference oils. Peroxide and free acidity values validated the results obtained by ICA, related to olive oil oxidation rates. Sorbed olive oil in plastic was also quantified given that this sorption could induce a swelling of the polymer thus promoting migration.     

Solvation Rule for Solid‐Electrolyte Interphase Enabler in Lithium‐Metal Batteries

Despite the exceptionally high energy density of lithium metal anodes, the practical application of lithium‐metal batteries (LMBs) is still impeded by the instability of the interphase between the lithium metal and the electrolyte. To formulate a functional electrolyte system that can stabilize the lithium‐metal anode, the solvation behavior of the solvent molecules must be understood because the electrochemical properties of a solvent can be heavily influenced by its solvation status. We unambiguously demonstrated the solvation rule for the solid‐electrolyte interphase (SEI) enabler in an electrolyte system. In this study, fluoroethylene carbonate was used as the SEI enabler due to its ability to form a robust SEI on the lithium metal surface, allowing relatively stable LMB cycling. The results revealed that the solvation number of fluoroethylene carbonate must be ≥1 to ensure the formation of a stable SEI in which the sacrificial reduction of the SEI enabler subsequently leads to the stable cycling of LMBs.     

Beyond the Polysulfide Shuttle and Lithium Dendrite Formation: Addressing the Sluggish Sulfur Redox Kinetics for Practical High-Energy Li-S Batteries

Electrolyte modulation simultaneously suppresses polysulfide the shuttle effect and lithium dendrite formation of lithium–sulfur (Li-S) batteries. However, the sluggish S redox kinetics, especially under high S loading and lean electrolyte operation, has been ignored, which dramatically limits the cycle life and energy density of practical Li-S pouch cells. Herein, we demonstrate that a rational combination of selenium doping, core–shell hollow host structure, and fluorinated ether electrolytes enables ultrastable Li stripping/plating and essentially no polysulfide shuttle as well as fast redox kinetics. Thus, high areal capacity (>4 mAh cm⁻²) with excellent cycle stability and Coulombic efficiency were both demonstrated in Li metal anode and thick S cathode (4.5 mg cm⁻²) with a low electrolyte/sulfur ratio (10 μL mg⁻¹). This research further demonstrates a durable Li-Se/S pouch cell with high specific capacity, validating the potential practical applications.     

A simple microwave process for the preparation of cobalt oxide nanoparticles supported on carbon nanotubes for electrocatalytic applications

Journal of Solid State Electrochemistry - Cobalt oxide nanoparticles supported on multiwalled carbon nanotubes (CoOx/CNTs) were prepared by a facile and rapid solid-state synthesis using microwave...     

Synthesis of <Superscript>99m</Superscript>Tc-pefloxacin: A new targeting agent for infectious foci

Summary This investigation focused on the labeling of pefloxacin, a fluoroquinolone antibacterial agent, with ^99mTc to form ^99mTc-pefloxacin complex. The labeling process was done by direct addition of pertechnetate in isotonic solution to Sn-pefloxacin solution. The labeling technique is effective, as a high labeling yield (98%) was obtained after 30-minute reaction time. Different factors were found that influenced this labeling reaction: 0.5 mg pefloxacin or more must be used to prevent the formation of colloids in the reaction medium. Fifty micrograms of stannous chloride dihydrate were found to be sufficient to reduce all pertechnetate with activity ranging from 37 to 3700 MBq without the detection of free pertechnetate or colloids in the reaction mixture. The pH of the reaction medium was found to play an important role in the labeling process. The labeling reaction proceeds well at neutral pH (pH 6) but at acidic pH value (pH 4 or below) the yield of ^99mTc-pefloxacin complex decreased markedly to a labeling yield of 5%. The reaction mixture must be heated to 100 °C in an oil bath to enhance the formation of the ^99mTc-pefloxacin complex. The biodistribution data show that ^99mTc labeled pefloxacin was retained in infectious focus. The retention was specific since the abscess uptake of ^99mTc-pefloxacin remained high as compared to the uptake of aseptic foci at 24-hour post injection. Also, the clearance of the tracer from other tissues is rapid on the contrary to its clearance from the septic focus. This supports the hypothesis that ^99mTc-pefloxacin is retained at the infectious site because of its specific binding to the gyrase enzymes of bacterial cells.     

Micro-pillar plasticity: 2.5D mesoscopic simulations

The plastic behavior of micro- and nano-scale crystalline pillars is investigated under nominally uniform compression. The transition from forest hardening to exhaustion hardening dominated behavior is shown to emerge from discrete dislocation dynamics simulations upon reduction in the initial source density. The analyses provide new insight into the scaling of flow stress with specimen size and also highlight the connection between individual dislocation mechanisms, collective phenomena and overall behavior.     

On von Neumann regular elements in <Emphasis Type="Italic">f</Emphasis>-rings

Let B be an Archimedean reduced f-ring. A positive element \({\omega}\) in B is said to satisfy the property \({(\ast)}\) if for every f-ring A with identity e and every \({\ell}\)-group homomorphism \({\gamma : A \rightarrow B}\) with \({\gamma(e) = \omega}\), there exists a unique \({\ell}\)-ring homomorphism \({\rho: B \rightarrow B}\) such that \({\gamma = \omega \rho}\) and \({\rho(e)^{\perp \perp} = \omega^{\perp \perp}}\). Boulabiar and Hager proved that any (positive) von Neumann regular element in B satisfies the property \({(\ast)}\) and proved that the converse holds in the C(X)-case. In this regard, they asked about this converse in the general case. Our main purpose in this note is to prove, via a counter-example, that the converse in question fails in general. In addition, we shall take the opportunity to extend the direct result obtained by Boulabiar and Hager, and to get the C(X)-case we were talking about in an easier way.