A Catalyst‐Directed Remote Stereogenic Center Switch During the Site‐Selective Aldol Desymmetrization of Cyclohexanone‐Based Diketones

Site‐selectivity, differentiating members of the same functional group type on one substrate, is an emerging tactic for shortened advanced building block and biomolecule synthesis. Despite its potential, site‐selectivity remains less studied and especially so for ketone‐based substrates. During this work ketone site‐selectivity has been coupled with the chiral amine‐catalyzed aldol desymmetrization of 4‐keto‐substituted cyclohexanones, allowing three stereogenic centers to form in the aldol product while leaving the acyclic ketone unreacted. Unique here, compared to all previous 4‐substituted cyclohexanone desymmetrizations, is the first access to synthetically useful quantities of an epimeric (remote stereogenic center) aldol product. To demonstrate the value of these aldol products, we show their elaboration into eight keto‐acetonide and one keto‐lactone products. All compounds were isolated as single diastereomers and in high ee (≥96%). These efforts represent the first full characterization of aldol products with type III, Figure 2, relative stereochemistry, regardless of the enantiomer formed.

     

Pickering Emulsion Polymerization of Styrene using Nano-SiO2 and Subsequent Use of the Produced Core–Shell Structures as Fillers for Ethylene Vinyl Acetate Copolymer and Polypropylene

Solid particles can stabilize emulsions instead of conventional surfactants. Emulsion polymerization of styrene, as an example of polymerizable oil, was processed in the present work after ultrasonication of styrene in water in the presence of silica nanoparticles as stabilizer. Field emission scanning electron microscopy, equipped with energy-dispersive X-ray unit, and transmission electron microscopy confirmed the formation of polystyrene particles covered by a sheath of self-assembled silica. Addition of these hybrids in different loadings (2–14 wt%) to polypropylene and ethylene vinyl acetate copolymer could improve their tensile strength and hardness. The mechanical enrichment could be attributed to the action of the silica shell layer to delay the phase separation process encountered between the polystyrene from one side and polypropylene/ethylene vinyl acetate from other side, which translates into different extents of reinforcements.     

Synthesis,Characterization, and Applications of Some New Trimeric‐Type Cationic Surfactants

In recent years, trimeric surfactants have created excitement in the surfactant field because of their properties, which have been found to be better than monomeric or dimeric homologues. Only a limited number of trimeric surfactants have been synthesized and studied so far, probably owing to the difficulty in synthesis. In this article, we synthesized some novel star‐shaped trimeric cationic surfactants based on the alkylation of the 3 hydroxyl groups of the phloroglucinol nuclei as a core (i.e., spacer) with 3 dodecyl or 3 octyl groups (as tails) for the surfactant. The chemical structures were confirmed by nuclear magnetic resonance, Fourier transform infrared, mass spectrometry, and elemental analysis; also the critical micelle concentration was determined by electrical conductivity measurements. These surfactants were used in the synthesis of mesoporous silica nanoparticles by the sol–gel method. The silica particles shape and size were determined using field emission scanning electron microscopy and high‐resolution transmission electron microscopy images. Furthermore, the corrosion inhibitor capability of these surfactants was investigated by monitoring the corrosion rate of iron sheets in 0.5 M hydrochloric acid in the presence and in the absence of different surfactants at 45°C based on the weight loss method. We have used cetyltrimethylammonium bromide (CTAB) as a positive control, the obtained results showed a high inhibition efficiency at very low concentrations, and the prepared trimeric surfactants exhibited a higher anticorrosion efficiency than the CTAB surfactants.     

Comparison of component method with experimental tests for flush end-plate connections using hot-rolled perwaja steel sections

A component method has been introduced by Steel Construction Institute to predict the moment resistance of partial strength connection. The design philosophy is taken directly from Eurocode 3 with strength checks on bolts, welds, and steel which have been modified to comply with BS 5950-1:2000. The accuracy of the method however needs to be validated with the experimental tests especially for hot-rolled sections other than typical British Section (BS). Six experimental tests on beam-to-column connections have been carried out for Flush End-Plate (FEP) connections consisting of variable parameters such as thickness of end-plate, size and number of bolts, size of columns, and beams. The tests were set-up using local hot-rolled steel sections known as Perwaja Section (PS) for beams and columns instead of typical British Section (BS). The strength of materials for end-plate, column and beam sections were tested for tensile strength and used in predicting the moment resistance for component method. The moment versus rotation of the test results were plotted and compared with the moment resistance derived from component method. The study concluded that the moment resistance of the tested flush end-plate connections was higher than the predicted moment resistance from component method which showed good agreement between the two moments. The study also concluded that the tested FEP connections met the requirements and criteria of partial strength connections.     

Development of ensemble machine learning approaches for designing fiber-reinforced polymer composite strain prediction model

Engineering with Computers - Over the past few decades, it has been observed a remarkable progression in the development of computer aid models in the field of civil engineering. Machine learning...     

Wall Rock Alteration,Uranium Mineralization,and Potentiality of Uranium and Iron Dissolution from Mineralized Abu Rusheid Gneiss Rock,South Eastern Desert,Egypt

Radiochemistry - Ferrugination, sericitization, desulfitization, chloritization, and kaolinitization of hydrothermal origin are the main wall rock alterations occurring within the NNW shear zones...     

Cancer stem cell sorting from colorectal cancer cell lines by sedimentation field flow fractionation

Recently, cancer stem cells (CSCs) have been identified in many types of cancers, such as colorectal cancer (CRC). CSCs seem to be involved in initiation, growth, and tumor metastasis, as well as in radio- and chemotherapy failures. CSCs appears as new biological targets for cancer therapy, requiring the development of noninvasive cell sorting methods. In this study, we used sedimentation field flow fractionation (SdFFF) to prepare enriched populations of CSCs from eight cell lines corresponding to different CRC grades. On the basis of phenotypic and functional characterizations, "hyperlayer" elution resulted in a fraction overexpressing CSC markers (CD44, CD166, EpCAM) for all cell lines. CSCs were eluted in the last fraction for seven out of eight cell lines, but in the first for HCT116. These results suggest, according to the literature, that two different pools of CSCs exist, quiescent and activated, which can both be sorted by SdFFF. Moreover, according to CSC properties, enriched fractions are able to form colonies.     

Pedestrian detection using multiple feature channels and contour cues with census transform histogram and random forest classifier

Pattern Analysis and Applications - This paper presents a reliable and real-time method to detect pedestrians in image scenes that can vary greatly in appearance. To achieve greater reliability in...