Impact Sensitivity Reduction Via Exo-Electron Control

Many materials, upon fracturing, emit electrons (exo-electrons) by a process called fracto-emission. For a substance or mixture that can deflagrate or detonate upon impact or friction, these exo-electrons may contribute to the initiation of deflagration or detonation. Some materials, such as p-type semiconductors, can absorb exo-electrons and, as used as additives, can reduce the impact or friction sensitivity of propellants or explosives. It was found that the addition of 1% p-type silicon powder did decrease the impact sensitivity of a propellant consisting of ammonium perchlorate in a polybutadiene matrix, but did not reduce the impact sensitivity of powdered cyclotetramethylenetetranitramine (HMX), cyclotrimethylenetrinitramine (RDX), and pentaerythritol trinitrate (PETN).     

Activatable Peptides for Rapid and Simple Visualization of Protease Activity Secreted in Living Cells

Activity-based monitoring of cell-secreted proteases has gained significant interest due to the implication of these substances in diverse cellular functions. Here, we demonstrated a cell-based method of monitoring protease activity using fluorescent cell-permeable peptides. The activatable peptide consists of anionic (EEEE), cleavable, and cationic sequences (RRRR) that enable intracellular delivery by matrix metalloproteinase-2 (MMP2), which is secreted by living cancer cells. Compared to HT-29 cells (MMP2-negative), HT-1080 cells (MMP2-positive) showed a strong fluorescence response to the short fluorescent peptide via cell-secreted protease activation. Our approach is expected to find applications for the rapid visualization of protease activity in living cells.     

Effect of coupling agent content on properties of composites made from polylactic acid and chrysanthemum waste

Chrysanthemum flower is among one of the highly sought after and widely planted flower crops, in particular for cultural and religious ceremonies. However, the chrysanthemum stem and stalk have little value and usually discard as by‐product waste from floristry. The objective of this research is to investigate the potential value of utilizing chrysanthemum stem and stalk as reinforcing fillers for thermoplastic composites. In this study, 2‐mm thick composite sheet containing predefined formulations of polylactic acid (PLA), chrysanthemum waste filler (CWF) ranging from 15 to 60 phr, and maleated polyethylene (MAPE) coupling agent up to 5 phr were prepared with the aid of Haake internal mixer and compression molding. The effect of MAPE loading on tensile, thermal, and morphological properties of PLA/CWF composites was investigated. The findings revealed that PLA/CWF composite attained improved tensile modulus compared to the neat PLA, and the tensile modulus increases with higher concentration of CWF. However, both tensile strength and elongation at break reduces with increase loading of CWF. Overall, PLA/CWF composites with MAPE shows better performance compared to those without MAPE, where an optimum strength of 21.8 MPa can be achieved with 60 phr CW and 3 phr MAPE. The measured tensile strength is comparable to alternatives natural fiber thermoplastic composites demonstrating its potential to be used in non‐structurally demanding application. J. VINYL ADDIT. TECHNOL., 26:10–16, 2020. © 2019 Society of Plastics Engineers     

Subtle variations in the structure of crosslinked epoxy networks and the impact upon mechanical and thermal properties

Presented here is an investigation of the structure–property relationships of crosslinked networks using three bi-functional glycidyl ether aromatic epoxy resins, two bi-aryl and one tri-aryl, cured with bi- and tri-aryl amines. Subtle changes to the monomer chemistry including changing aromatic substitution patterns from meta to para, methylene to isopropyl and isopropyl to ether were explored. Changing an epoxy resin backbone from methylene to isopropyl enhances backbone rigidity thus increasing glass transition temperature (T_g), yield strength, and strain despite reducing modulus. Changing meta-substitution to para increases T_g and yield strain while leaving strength unaffected and reducing modulus. Changing isopropyl linkages to ether reduces modulus, strength, T_g, and yield strain reflecting increased molecular flexibility. Using three instead of two aromatic rings increases the molecular weight between crosslinks thereby decreasing T_g and yield strain while increasing modulus and strength. Despite the complexities of multiple systems for varying epoxy resins and amine hardeners, the effect upon network properties is explained in terms of short- and long-range molecular and segmental mobility, crosslink density, and equilibrium packing density. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48874.     

A study on methane–air premixed flames interacting with syngas–air premixed flames

Numerical study on the interaction between methane–air and syngas–air premixed flames is conducted according to equivalence ratio and global strain rate in detailed chemistry. This study targets at understanding of an interacting combustion system as an alternative retrofit concept where one can modify the existing facilities minimally in industrial and power plant burners in order to reduce the emission of carbon dioxide. It is seen that methane premixed flame interacting with syngas premixed flame can be sustained even over the rich flammable limit of single methane premixed flame. The inspection of detailed flame structure such as the distributions of major species and chain carrier radicals, flame separation distance, spatial flow velocity, and spatial distribution of the rate of production and consumption of CH₄, H₂, and CO is also conducted to depict the flame interactions. The importance of global strain rate and thus the flame separation distance in the enhanced burning of methane premixed flame is also stressed through the inspection of the consumption rates of H₂, CO, and CH₄. Anomalous phenomena such as the migration of premixed flame cross the stagnation plane and the nearly constant flame separation distance are also discussed.     

‘Land for infrastructure’ in Ho Chi Minh City: land-based financing of transportation improvement

This paper explores how land-based financing mechanisms are currently used in Ho Chi Minh City as a public-private funding strategy. The Land-for-Infrastructure (LFI) mechanism appears as a solution to produce infrastructures. We found that the implementation of the LFI mechanism remains difficult, but eventually can lead to success. By ‘trial-error-transcend,’ the City managed to build two essential roads while the developers received attractive investment opportunities in urban development. This mechanism cannot, however, be seen as a panacea for the local authorities due to constraints to replicate it and potential undesired ‘side effects.’     

A stochastic reward net-based assessment of reliability,availability and operational cost for a software-defined network infrastructure

The Journal of Supercomputing - The networking infrastructure of a software-defined network (SDN) requires further study to achieve continuity and high availability of data transactions for cloud...