Heat degradation studies of solar heat transfer fluids

Destructive distillation of solar heat transfer fluids was conducted to determine the types of pyrolytic products which might be formed in solar collectors under conditions of stagnation or malfunction. The distillates were analyzed by gas chromatography/mass spectrometry (GC/MS) to determine the types of compounds which were present and the minor components which might be formed. Dehydration products were formed from ethylene and propylene glycols with ethylene oxide and propylene oxide being minor products. A high aromatic petroleum heat transfer fluid yielded distillation fractions enriched in quinolines or isoquinolines and methylated derivatives thereof. Fractionation of this aromatic heat transfer fluid showed that the basic fraction of unheated fluid also contained aza-arenes which exhibited mutagenic activity in the Ames' bioassay. GC/MS showed that the basic fraction from unheated heat transfer fluid also contained benzoquinolines which appeared to be lacking in heat degraded samples of the same fluid. Fractionation of heat transfer fluids, in particular petroleum-based fluids, may often be necessary in order to concentrate minor components so that they can be identified by GC/MS and in order to detect mutagenic activities without interference from cytotoxic components.     

Variational Bayes Based Multiuser Detection for On–Off Random Access Channels

This paper considers on–off random access channels where the users transmit either a one or a zero to a base station or fusion center, and it is assumed that only a small fraction of users are active during any channel use. Under these assumptions, the problem of identifying the active users reduces to that of recovering a sparse binary vector from noisy random linear measurements. A hierarchical Bayesian approach is proposed in this paper to recover the set of active users. A fast approximate Bayesian inference based on Variational Bayes (VB) is then developed. Extensive simulation results are then provided to compare the performance of the proposed VB based Bayesian MUD approach to sparse estimation techniques such as OMP and LASSO. It is observed that the proposed approach is robust to variations in noise as well as sparsity levels. Further, for a given BER performance, the proposed approach requires substantially smaller dimensional codes as compared to OMP and LASSO, thus improving the spectral efficiency.     

Renewable energy and sustainability

Clean Technologies and Environmental Policy - Renewable energy and sustainable development are widely discussed and highly debated topics. The current and majority opinion is that for sustainable...     

Classification of a bacterial isolate, from pozol, exhibiting antimicrobial activity against several gram-positive and gram-negative bacteria, yeasts, and molds

A bacterial isolate, designated CS93, capable of producing a broad-spectrum antimicrobial compound(s) effective against gram-positive and gram-negative bacteria, yeasts, and molds was isolated from pozol, a fermented maize product. This strain was phenotypically similar to another pozol isolate that was previously designated as Agrobacterium azotophilium by other investigators. By using biochemical, phenotypic, and 16S rRNA sequence analysis, both pozol isolates were identified as members of the genus Bacillus, possibly a variant of Bacillus subtilis. While the antimicrobial compound(s) was initially produced only on a solid medium, parameters were identified for production in broth. The compound(s) was heat stable (121 degrees C for 15 min), exhibited activity over a wide pH range (pH 3 to pH 11), and was inactivated by pronase E. The antimicrobial compound(s) was bactericidal and bacteriolytic against Escherichia coli V517, bacteriostatic against Micrococcus luteus, and fungistatic against Saccharomyces cerevisiae. The inhibitory compound(s) could possibly serve as a food biopreservative.     

Intracerebral haemorrhage in a young adult: consider amphetamine abuse

We present the case of a young female who suffered a massive intracerebral bleed following the ingestion of a small quantity of amphetamine (speed). Physicians should be aware that amphetamine abuse can lead to cerebrovascular events in young adults.     

Acrylic Homo- and Co-polymers Based on 2, 4-dichlorophenyl Methacrylate and 8-quinolinyl Methacrylate

The monomer 2, 4-dichlorophenyl methacrylate (2,4-DMA) was synthesized from 2, 4-dichlorophenol and characterized by conventional methods. The homopolymers of 2,4-dichlorophenyl methacrylate and its copolymers with 8-quinolinyl methacrylate (8-QMA) in different feed ratio were prepared by free radical polymerization using dimethyl formamide (DMF) as a solvent and 2,2-azobis iso butyronitrile (AIBN) as an initiator. The resulting polymers were characterized by using IR spectroscopy. Reactivity ratios of monomer were evaluated using UV-spectroscopy. Average molecular weights and polydispersity were determined by gel permeation chromatography (GPC). Solution viscosity was also obtained. The thermal analysis was carried out using TGA and DSC. The homo- and co-polymers were also tested for their antimicrobial properties against selected microorganism. The metal ion uptake capacity of synthesized copolymers was estimated by batch equilibration method using different metal ion solution under different experimental conditions. It is observed that due to the presence of pendant ester bound quinoline group, the copolymers are capable of adsorbing cations from their aqueous solution.     

Creep performance of CNT reinforced glass fiber/epoxy composites: Roles of temperature and stress

Carbon nanotubes (CNTs) have been emerged as a potential nanofiller to reinforce polymeric materials to improve their mechanical properties, like strength and modulus. However, time-dependent deformation of such materials under a constant load and elevated temperature is a matter of concern for long-term durability of these materials. The present article primarily demonstrates the effects of creep temperature and stress on the reinforcement efficiency of CNT in a glass fiber/epoxy (GE) composite. Two types of materials were investigated in this study—GE which was used as a control material, as well as CNT embedded GE composite. To elucidate the impact of CNT on the long-term durability of GE composite, creep tests have been performed at different temperatures (50, 80, and 110 °C) under bending loading. As applied stress has also significant contribution toward the elevated creep deformation of materials, creep tests have also been carried out under different stresses (5, 10, and 40 MPa). The strength of the CNT-GE composite exhibited 8.7 and 18.3% higher than that of control GE composite under tensile and bending load, respectively. Results suggest CNT reinforcement to be beneficial for low temperature applications, both in terms of creep strain and strain rate. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47674.     

Electrospun microporous gelatin–polycaprolactone blend tubular scaffold as a potential vascular biomaterial

The work reported involved the fabrication of an electrospun tubular conduit of a gelatin and polycaprolactone (PCL) blend as an adventitia‐equivalent construct. Gelatin was included as the matrix for increased biocompatibility with the addition of PCL for durability. This is contrary to most of the literature available for biomaterials based on blends of gelatin and PCL where PCL is the major matrix. The work includes the assiduous selection of key electrospinning parameters to obtain smooth bead‐free fibres with a narrow distribution of pore size and fibre diameter. Few reports elucidate the optimization of all electrospinning parameters to fabricate tubular conduits with a focus on obtaining homogeneous pores and fibres. This stepwise investigation would be unique for the fabrication of gelatin–PCL electrospun tubular constructs. The fabricated microfibrous gelatin–PCL constructs had pores of size ca 50–100 μm reportedly conducive for cell infiltration. The measured value of surface roughness of 57.99 ± 17.4 nm is reported to be favourable for protein adhesion and cell adhesion. The elastic modulus was observed to be similar to that of the tunica adventitia of the native artery. Preliminary in vitro and in vivo biocompatibility tests suggest safe applicability as a biomaterial. Minimal cytotoxicity was observed using MTT assay. Subcutaneous implantation of the scaffold demonstrated acute inflammation which decreased by day 15. The findings of this study could enable the fabrication of smooth bead‐free microfibrous gelatin–PCL tubular construct as viable biomaterial which can be included in a bilayer or a trilayer scaffold for vascular tissue engineering. © 2019 Society of Chemical Industry     

Polyacrylate-coated graphene-oxide and graphene solution via chemical route for various biological application

In this work, we have developed a polyacrylate-coated graphene-oxide and then chemically reduced them into graphene. We found that polyacrylate coating can improve the colloidal stability of both graphene-oxide/graphene. They show good colloidal stability in different aqueous buffer solution with pH ranging from 5 to 10, and these solutions are stable for more than a month. The polyacrylate-coated grapheme oxide/graphene has been characterized by X-ray photoemission spectroscopy (XPS) and micro-Raman spectroscopy. Based on good colloidal stability, this graphene-oxide/graphene is most suitable for the biological application.