A finite element method based comparative fracture assessment of carbon black and silica filled elastomers: Reinforcing efficacy of carbonaceous fillers in flexible composites

This study is focused on numerical investigation on fracture behaviors of carbon black (CB) and silica filled elastomeric composites. Finite element analysis (FEA) in compliance with multi-specimen method is used to calculate J-integral and geometry factor of the rubber composites up to a displacement of 20 mm for single edge notch in tension (SENT) and double edge notch in tension (DENT) specimens. An empirical relationship between crack tip opening displacement (CTOD) and crack advancement is established depending on notch to width ratio (NWR). The stress contours across the notches for SENT and DENT specimens is discussed briefly. It is found that fracture propagation resistance of CB filled elastomer is 125% more than that of silica filled elastomer. Although, Silica filled elastomer have good tensile strength and crosslink density but it fails to replace carbon black in terms of fracture properties. The critical J-integral for CB filled elastomer is 18.7% and 32.2% more than silica filled elastomer for SENT and DENT specimens respectively. The effect of specimen type on various fracture properties is also explored. The factor of safety is found to be significantly more in case of CB filled elastomers making them less vulnerable to crack propagation and catastrophic failure.     

Preparation and characterization of heat-resistant PET/bio-based polyester blends for hot-filled bottles

To improve the glass transition temperature (T_g) and heat resistance of polyethylene terephthalate (PET) bottle, poly (ethylene glycol 1,4-cyclohexane dimethylene isosorbide terephthalate) (PEICT) with a unique cyclic structure was introduced into PET. The miscibility of the PET/PEICT blends and their feasibility as a heat resistant bottle were investigated. The introduction of PEICT into PET increases the T_g and the PET/PEICT blends exhibit a single T_g, indicating good miscibility between PEICT and PET. Furthermore, the T_g and crystallinity of the PET/PEICT blends can be adjusted by controlling the amount of PEICT added. The PET/PEICT blends were transparent in the visible light range (no significant change in transparency) because the blends were truly miscible as confirmed by Fox equation. As expected, the introduction of PEICT into PET bottle allows for improved heat resistance and shape stability due to the rigid molecular structure and chirality of the two tetrahydrofuran rings in the isosorbide group of PEICT. Based on our results, the as-prepared PET/PEICT blends with controllable high heat resistance can be used as a cost-effective alternative material for various hot-filling conditions in the beverage industry by adjusting the optimal ratio of PEICT to PET for each product (e.g. fruit juice, tea).     

Oligosaccharides: Defense Inducers,Their Recognition in Plants,Commercial Uses and Perspectives

Plants have innate immune systems or defense mechanisms that respond to the attack of pathogenic microorganisms. Unlike mammals, they lack mobile defense cells, so defense processes depend on autonomous cellular events with a broad repertoire of recognition to detect pathogens, which compensates for the lack of an adaptive immune system. These defense mechanisms remain inactive or latent until they are activated after exposure or contact with inducing agents, or after the application of the inductor; they remain inactive only until they are affected by a pathogen or challenged by an elicitor from the same. Resistance induction represents a focus of interest, as it promotes the activation of plant defense mechanisms, reducing the use of chemical synthesis pesticides, an alternative that has even led to the generation of new commercial products with high efficiency, stability and lower environmental impact, which increase productivity by reducing not only losses but also increasing plant growth. Considering the above, the objective of this review is to address the issue of resistance induction with a focus on the potential of the use of oligosaccharides in agriculture, how they are recognized by plants, how they can be used for commercial products and perspectives.     

Synthesis and surface properties of novel fluorinated polyurethane base on F‐containing chain extender

A novel fluorinated chain extender, (1‐(ethyl(2‐hydroxyethyl)amino)‐3‐ ((3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl)oxy)propan‐2‐ol) (FPO), was synthesized and characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and elemental analysis. Poly (ether urethane)s containing various amounts of the chain extender with fluorinated side chains (FPUs) were prepared by isophorone diisocyanate (IPDI), polytetra‐methylene‐ether‐glycol (PTMG), 3‐aminopropyltriethoxysilane (KH‐550), and 1,4‐butandiol (BDO). Films of FPUs were investigated by water absorption, contact angle, pencil hardness, adhesive force, and thermal analysis. Coating FPUs on micro‐nano concave‐convex structure plate realizes superhydrophobic performance. Scanning electron microscope (SEM) and atomic force microscopy (AFM) demonstrated that there is a lot of irregular concave‐convex structure, which forms a typical air cushion model. X‐ray photoelectron spectroscopy (XPS) analysis showed that surface fluorine content is 165% more than that of film average fluorine content. The superhydrophobic plate with 10% or higher F‐containing FPUs coating is of outstanding chemical corrosion resistance, excellent solvent resistance, and wear resistance.     

Synthesis and biological evaluation of 2-substituted vinylgembisphosphonates against Plasmodium falciparum and Trypanosoma brucei

Abstract

A series of 2-substituted vinylidene-1,1-bisphosphonate esters and their acids were synthesized and tested in vitro for activity against Plasmodium falciparum and Trypanosoma brucei. For each compound, % parasite viability in treated wells was calculated relative to untreated controls for both P. falciparum and T. brucei. Fifty percentage inhibitory concentration (IC₅₀) was also determined for the compounds. Chloroquine and pentamidine were used as positive control drug standards for activity against P. falciparum and T. brucei, respectively. The esters had better antiparasitic activity compared to their corresponding acids. Some of the compounds reduced % parasite viability to as low as 24.3% for P. falciparum and down to 0.602% for T. brucei. Tetraethyl-2-(o-tolyl)-ethene-1,1-bisphosphonate (3b) recorded the best IC₅₀ against T. brucei which was 0.0345?µmol/mL.     

Preparation of polypropylene/ethylene‐propylene‐diene terpolymer/nitrile rubber ternary thermoplastics vulcanizates with good mechanical properties and oil resistance by core‐shell dynamic vulcanization

As the most successful commercialized thermoplastic vulcanizates (TPVs), polypropylene (PP)/ethylene propylene rubber (EPDM) TPVs exhibit poor oil resistance. In this work, we prepared PP/EPDM/butadiene acrylonitrile rubber (NBR) ternary TPVs with good oil resistance using core‐shell dynamic vulcanization. According to the theoretical analysis of the spreading coefficient and the transmission electron microscopy results, the rubber phases exhibited a special core‐shell structure, in which the cross‐linkedNBR‐core was encapsulated by the EPDM‐shell. The core‐shell structure effectively improved the interfacial compatibility between PP and NBR phase as the EPDM‐shell could avoid the direct contact of them, thus improving the mechanical properties of the TPVs. For example, the PP/EPDM/NBR (40/30/30) ternary TPV showed enhanced tensile strength of 12.57 MPa, compared with 10.71 MPa of PP/EPDM (40/60) TPV and 11.11 MPa of PP/NBR (40/60) TPV, respectively. Moreover, the oil resistance of the TPVs was also improved. Compared with PP/EPDM TPV, the change rates in mass, volume, tensile strength and elongation at break of PP/EPDM/NBR TPV after oil immersion decreased by 42.18%, 48.69%, 52.68% and 28.77%, respectively.     

大气环境下的钢筋混凝土桥梁时变可靠度分析

为了探究钢筋混凝土桥梁抗力退化对桥梁可靠性能的影响,综合考虑一般大气环境下混凝土强度、钢筋强度、混凝土与钢筋黏结性能的降低,建立普通钢筋混凝土桥梁的抗力退化时变模型,分析规范车辆荷载作用的桥梁时变可靠度。研究结果表明,(1)一般大气环境下,桥梁抗力随着服役时间的增加而减小,其中钢筋强度退化对桥梁抗力的影响最大,其次是钢筋与混凝土黏结性能降低,而混凝土强度退化对桥梁抗力的影响相对较小; (2)桥梁可靠指标随着服役时间的增加而减小,密集行车占比越大,桥梁承载能力失效的概率就越大;非平稳车载作用下的桥梁可靠指标小于平稳车载,桥梁需要维修补强的时间比平稳车载提前; (3)多梁式简支梁桥在建造时应该提高边梁的安全储备,在管养时可以采取限载措施进行干预。     

Investigation of dense slurry suspensions with coaxial mixers: Influences of design variables through tomography and mathematical modelling

The coaxial mixers enhance the suspension of concentrated slurries in an agitated reactor. In this research work, the complex slurry suspension and dissemination behavior in a coaxial slurry mixing system (comprised of a close clearance anchor rotating with a low speed and an inner axial impeller rotating with a high speed) was analyzed employing ERT (electrical resistance tomography, a non-intrusive flow visualization technique), and computational fluid dynamics (CFD). The numerical models were validated by comparing the axial solid concentration profiles generated using the ERT data and the CFD simulation results. The influences of various important parameters such as the diameter of the inner axial impeller, the inner impeller type, and the inner impeller spacing on the hydrodynamic characteristics of the slurry suspensions in a coaxial mixing vessel were thoroughly analyzed. The radial and axial velocity profiles of solid particles were generated using the validated mathematical models. The assessment of energy loss due to the solid–solid collisions, the particle–fluid frictions, and the particle–vessel wall collisions was conducted. The evaluation of optimum inner impeller clearance and inner impeller diameter is essential to attain a high degree of solids suspension and dissemination in a coaxial slurry mixing system.     

3D X-ray Micro-CT Analysis of Rebar Corrosion in Reinforced Concrete Subjected to a Chloride-Induced Environment

The paper presents experimental investigations of the concrete covers’ protective ability to counteract rebar corrosion in reinforced concrete cubes. The concrete sample was subjected to a chloride-induced environment to get corroded and combined with an un-corroded sample. The chloride-accelerated technique can induce a high degree of corrosion within a controlled time. Moreover, detailed and thorough experimental measurements and analyses of reinforcement loss due to corrosion and its influence on concrete microstructure, were studied through 3D X-ray micro-computed tomography. The rebar outside the concrete was heavily corroded due to the chloride-accelerated test, whereas, only local surface corrosion products appeared inside the concrete. It turned out that the concrete cover showed protective ability to counteract the reinforcing-steel corrosion mechanism despite the accelerated corrosion environment. Moreover, the bond strength between the reinforcement rebar and concrete was not visibly affected since the failure force in the pull-out test and failure mechanisms, observed by 3D X-ray micro-CT, were similar for corroded and un-corroded samples. The failure occurred due to radial cracks with a maximum width equal to approximately 0.25 mm.     

Caseinolytic Proteins (Clp) in the Genus Klebsiella: Special Focus on ClpK

Caseinolytic proteins (Clp), which are present in both prokaryotes and eukaryotes, play a major role in cell protein quality control and survival of bacteria in harsh environmental conditions. Recently, a member of this protein family, ClpK was identified in a pathogenic strain of Klebsiella pneumoniae which was responsible for nosocomial infections. ClpK is linked to the thermal stress survival of this pathogen. The genome wide analysis of Clp proteins in Klebsiella spp. indicates that ClpK is present in only 34% of the investigated strains. This suggests that the uptake of the clpk gene is selective and may only be taken up by a pathogen that needs to survive harsh environmental conditions. In silico analyses and molecular dynamic simulations show that ClpK is mainly α-helical and is highly dynamic. ClpK was successfully expressed and purified to homogeneity using affinity and anion exchange chromatography. Biophysical characterization of ClpK showed that it is predominantly alpha-helical, and this is in agreement with in silico analysis of the protein structure. Furthermore, the purified protein is biologically active and hydrolyses ATP in a concentration- dependent manner.