Modulable and Highly Diastereoselective Carbometalations of Cyclopropenes

The copper‐catalyzed carbomagnesiation reaction of cyclopropenyl esters 1 leads to various substituted cyclopropanes species 3 in good yields with very high diastereoselectivities. The reaction proceeds through a syn‐chelated carbomagnesiation reaction and could be extended to various cyclopropenylmethyl ester derivatives 5 . The potential of this approach was illustrated by the preparation of two consecutive all‐carbon quaternary stereocenters. However, the carbometalation reaction needs to be performed at temperature ranging from ?35 to ?20 °C to avoid subsequent fragmentation reaction into stereodefined β,γ‐nonconjugated unsaturated esters 4 . Alternatively, the carbocupration reaction with organocopper species could also be performed to leads to configurationally stable cyclopropyl copper species 2[Cu] . Additionally, when the Lewis acid character of the copper center is decreased (i.e., RCuCNLi), the reaction proceed with an anti‐selectivity. The diastereodivergent behavior of these organometallic species is of synthetic interest, since both diastereomers syn‐ 3 and anti‐ 3 can be obtained, at will, from the same precursor cyclopropenyl esters 1 .     

Cross-linked starch nanoparticles stabilized Pickering emulsion polymerization of styrene in w/o/w system

Here, we present a method to synthesize expandable spherical polystyrene beads containing well-dispersed water microdroplets. The beads, 2–3 mm in diameter, were prepared through surfactant-free Pickering emulsion polymerization in water-in-oil-in-water (w/o/w) system using cross-linked starch nanoparticles (CSTN) as emulsifier. The CSTNs were in situ surface-modified by styrene maleic anhydride copolymer as confirmed by infrared spectroscopy and contact angle analysis. The entrapped water microdroplets with the average size of 3–4 μm were shown to be surrounded by a dense layer of the CSTN. The number droplet density as well as water encapsulation efficiency in the polystyrene beads increased with the CSTN concentration. Furthermore, regardless of CSTN content, all samples exhibited high encapsulation stability of over 68 % after 3 months. These characteristics along with good expansion behavior suggest the synthesized beads as expandable polystyrene containing water as a green blowing agent.     

Aqueous-Mediated green synthesis of novel spiro[indole-quinazoline] derivatives using kit-6 mesoporous silica coated Fe3O4 nanoparticles as catalyst

In this work, a series of eight new spiro[3,4′]1,3-dihydro-2H-indol-2-one-2′-amino-4′,6′,7′,8′-tetrahydro-2′,5’(1’H,3’H)-quinazoline-diones were successfully synthesized through a three-component reaction of 1H-indole-2,3-diones (isatins), guanidine nitrate, and 1,3-cyclohexanediones, by use of Kit-6 mesoporous silica coated Fe₃O₄ nanoparticles (Fe₃O₄@SiO₂@KIT-6) as a highly efficient magnetically separable nanocatalyst in aqueous media at 60°C. Several notable features of thiseco-friendly protocol are high yields of products, short reaction times, operational simplicity, and the use of easily available and recyclable catalyst.     

An efficient and novel protocol for the synthesis of spiro[1,3]oxazino[5,6-c]quinoline derivatives by one-pot,three-component reaction

Research on Chemical Intermediates - One-pot, three-component reaction of various aryl glyoxal monohydrates, 5-methylisoxazol-3-amine and 4-hydroxyquinolin-2(1H)-one in the presence of a catalytic...     

A new and facile synthesis of 3-(2-aryl-6-nitro-1H-indol-3-yl)quinoline-2,4(1H,3H)-diones by sodium alginate as biopolymeric catalyst

Research on Chemical Intermediates - New 3-(2-aryl-6-nitro-1H-indol-3-yl)quinoline-2,4(1H,3H)-diones were synthesized, and good-to-excellent yields were achieved through one-pot, three-component...     

Water treatment: functional nanomaterials and applications from adsorption to photodegradation

Global efforts for engineering desired materials which are able to treat the water sources still are ongoing in the bench level methods. Considering adsorbent and photocatalytic materials as the main reliable candidates still are encountering with struggles because of many challenges that restrict their large-scale application. This review comprehensively considered the recent advanced materials water treatment methods which involve to magnetic, activated carbon, carbon nanotubes (CNTs), graphene (G), graphene oxide (GO), (Graphene) quantum dots, carbon nanorods, carbon nano-onions, and reduced graphene oxide (RGO), zeolite, silica and clay-based nanomaterials. The adsorption and photocatalytic properties of these nanomaterials introduced them as highly potent option for heavy metal ions and organic dyes removal and photocatalytic degradation. High specific surface area in conjugation with presenting higher kinetics of adsorption and decomposition are the main characteristics of these materials which make them appropriate to treat wastewater even in ultralow concentration of the pollutants. Considering the mechanistic aspects of the adsorption and photocatalytic decomposition process, challenges and opportunities were other subjects that have been highlighted for the discussed nanomaterials. In term of the adsorption approaches, the mechanism of adsorptions and their influence on the maximum adsorption capacity were discussed and also for photocatalyst approach the radical active spices and their role in kinetic and efficiency of the organic pollutant decomposition were provided a deep discussion.     

Numerical simulation of natural gas/diesel dual-fuel engine for investigation of performance and emission

Journal of Thermal Analysis and Calorimetry - Due to global concerns about the emissions, limited hydrocarbon fuel resources and high fuel prices, a lot of researches have been done to improve the...     

Hybrid thermal management of lithium-ion batteries using nanofluid,metal foam,and phase change material: an integrated numerical–experimental approach

Safety issues of Li-ion batteries imposed by unfavorable thermal behavior accentuate the need for efficient thermal management systems to prevent the runaway conditions. To that end, a hybrid thermal management system is designed and further investigated numerically and experimentally in the present study. The passive cooling system is fabricated by saturating copper foam with paraffin as the phase change material (PCM) and integrated with an active cooling system with alumina nanofluid as the coolant fluid. Results for various Reynolds numbers and different heating powers indicate that the hybrid nanofluid cooling system can successfully fulfill safe operation of the battery during stressful operating conditions. The maximum time in which all PCM field is changed to the liquid phase is defined as the onset of the stressful conditions. Therefore, the start time of stressful conditions at 41 W and Re 420 is increased from 3700 s with nanofluid composed of 1% volume fraction nanoparticles (VF-1%) to 4600 s with nanofluid VF-2% during high current discharge rates. Nanofluid cooling extends the operating time of the battery in comparison with the water-based cooling system with 200-s (nanofluid with volume fraction of 1%) and 900-s (nanofluid with volume fraction of 2%) increases in operating time at Reynolds of 420. Using nanofluid, instead of water, postpones the onset of paraffin phase transition effectively and prolongs its melting time which consequently leads to a decrease in the rate of temperature rise.

     

Nonlinear Mechanical Response of Polymer Matrix Composites: A Review

Abstract

The present article provides a review on the nonlinear mechanical behavior of polymer matrix composites (PMCs). Initially, essential mechanisms driving the nonlinear response of PMCs under different loading conditions are discussed. Rate-dependence, tension-compression asymmetry, viscous behavior, unloading characteristics, interaction between stress components and effects of environmental factors on mechanical properties are briefly reviewed. This is followed by a review of major approaches and constitutive models for predicting stress–strain behavior of PMCs. Following an increasing degree of complexity, models are categorized into four major classes: nonlinear elasticity models, elastic-plastic models, elastic-plastic-viscous models and Damage-Plasticity models. The vast number of existing models is mainly due to the anisotropy and inhomogeneity of PMCs. In brief, this review focuses on informing the reader of major frameworks, rather than addressing all the models in detail.     

Fluid Flow Analysis of Integrated Porous Bone Scaffold and Cancellous Bone at Different Skeletal Sites: In Silico Study

The dynamic characteristic of bone is its ability to remodel itself through mechanobiological responses. Bone regeneration is triggered by mechanical cues from physiological activities that generate structural strain and cause bone marrow movement. This phenomenon is crucial for bone scaffold when implanted in the cancellous bone as host tissue. Often, the fluid movement of bone scaffold and cancellous bone is studied separately, which does not represent the actual environment once implanted. In the present study, the fluid flow analysis properties of bone scaffold integrated into the cancellous bone at different skeletal sites are investigated. Three types of porous bone scaffolds categorized based on pore size configurations: 1 mm, 0.8 mm and hybrid (0.8 mm interlaced with 0.5 mm) were used. Three different skeletal sites of femoral bone were selected: neck, lateral condyle and medial condyle. Computational fluid dynamics was utilized to analyze the fluid flow properties of bone scaffold integrated cancellous bone. The results of this study reveal that the localization and maximum value of shear stress in an independent bone scaffold are significantly different compared to the bone scaffold integrated with cancellous bone by about 160% to 448% percentage difference. Low shear stress and high permeability were found across models that have higher Tb.Sp (trabecular separation). Specimen C and femoral lateral condyle showed the highest permeability in their respective category.