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Polymers Dec 2020The pronouncedly low thermal conductivity of polymers in the range of 0.1-0.2 W m K is a limiting factor for their application as an insulating layer in microelectronics...
The pronouncedly low thermal conductivity of polymers in the range of 0.1-0.2 W m K is a limiting factor for their application as an insulating layer in microelectronics that exhibit continuously higher power-to-volume ratios. Two strategies can be applied to increase the thermal conductivity of polymers; that is, compounding with thermally conductive inorganic materials as well as blending with aromatic units arranged by the principle of π-π stacking. In this study, both strategies were investigated and compared on the example of epoxy-amine resins of bisphenol A diglycidyl ether (BADGE) and 1,2,7,8-diepoxyoctane (DEO), respectively. These two diepoxy compounds were cured with mixtures of the diamines isophorone diamine (IPDA) and -dianisidine (DAN). The epoxy-amine resins were cured without filler and with 5 wt.-% of SiO nanoparticles. Enhanced thermal conductivity in the range of 0.4 W·m·K was observed exclusively in DEO-based polymer networks that were cured with DAN (and do not contain SiO fillers). This observation is argued to originate from π-π stacking of the aromatic units of DAN enabled by the higher flexibility of the aliphatic carbon chain of DEO compared with that of BADGE. The enhanced thermal conductivity occurs only at temperatures above the glass-transition point and only if no inorganic fillers, which disrupt the π-π stacking of the aromatic groups, are present. In summary, it can be argued that the bisphenol-free epoxy-amine resin with an epoxy compound derivable from natural resources shows favorably higher thermal conductivity in comparison with the petrol-based bisphenol-based epoxy/amine resins.
PubMed: 33375238
DOI: 10.3390/polym13010065 -
Indoor Air Mar 2021With an increasing use of indoor disinfectants such as chlorine (Cl ) and hypochlorous acid, a convenient sampler for estimating exposure to oxidants, such as effective...
With an increasing use of indoor disinfectants such as chlorine (Cl ) and hypochlorous acid, a convenient sampler for estimating exposure to oxidants, such as effective chlorine, is necessary. Here, we developed a personal passive air sampler (PPAS) composed of a redox dye, o-dianisidine, in a polydimethylsiloxane (PDMS) sheet. o-Dianisidine readily reacts with gaseous oxidants generated by bleach usage, and its color changes as the reaction progresses; hence, personal exposure to effective chlorine could be easily detected by the naked eye, while cumulative exposure could be determined by measuring concentrations of o-dianisidine reacting with it. The PPAS was calibrated, and a sampling rate of 0.00253 m /h was obtained using a small test chamber. The PPAS was tested with the help of ten volunteers whose personal exposure to Cl -equivalent gas was estimated after bathrooms were cleaned using spray and liquid-type household disinfection products, and the accumulated exposure-gas concentrations ranged from 69 to 408 ppbv and 148 to 435 ppbv, respectively. These PPAS-derived exposure concentrations were approximately two orders lower than those estimated using ConsExpo, suggesting a significant overestimation by prevailing screening models, possibly due to the ignorance of transformation reactions.
Topics: Air Pollutants; Air Pollution, Indoor; Chlorine; Dimethylpolysiloxanes; Disinfectants; Disinfection; Environmental Monitoring; Humans; Hypochlorous Acid; Inhalation Exposure
PubMed: 32978992
DOI: 10.1111/ina.12747 -
Access Microbiology 2019Honey is a natural product with many beneficial properties including antimicrobial action. Production of hydrogen peroxide (HO) in diluted honey is central to this...
Honey is a natural product with many beneficial properties including antimicrobial action. Production of hydrogen peroxide (HO) in diluted honey is central to this action. Here, we describe an optimized method for measuring levels of HO in honey. This method is based on established methods, with the level of dilution, the time between dilution and reading the assay, and aeration of the samples during the assay identified as critical points for ensuring reliability and reproducibility. The method is cost-effective and easy to perform using common laboratory equipment. Using this method, we quantified the hydrogen peroxide content of five different, unprocessed polyfloral honeys collected in NC, USA. Our results show that HO production by these honeys varies greatly, with some samples producing negligible levels of HO. We assessed the effect of colour on the assay by measuring the recovery of spiked HO from light and dark honey and from serially diluted dark corn syrup, and found the amount of HO that could be detected was lower in dark corn syrup and darker honey samples.
PubMed: 32974499
DOI: 10.1099/acmi.0.000065 -
Environmental Monitoring and Assessment Sep 2020Simple, low-cost, and sensitive methods for the assessment of hexavalent chromium as an important environmental pollutant are highly desirable, especially under...
Simple, low-cost, and sensitive methods for the assessment of hexavalent chromium as an important environmental pollutant are highly desirable, especially under resource-limited settings. Therefore, herein we propose an original approach for the simple, low-cost, selective, and extremely sensitive assessment of Cr(VI) utilizing its catalysis of the micellar sensitized o-dianisidine (DA)-hydrogen peroxide reaction. The initial rate of the amended reaction is monitored by tracing the oxidation product, either by a digital camera video recording or spectrophotometrically at 440 nm, for 120 s from mixing the reactants. The optimized reaction conditions were 5 mmol L DA, 0.6 mol L HO, 2.0 v/v% Tween 20, and 10 mmol L chloroacetate buffer (pH 4.5 ± 0.1), at 30 °C. The linear calibration graph extends to 90.0 ng mL Cr(VI) with detection limits (3S) of 0.8 and 1.0 ng mL, for the video recording and spectrophotometric procedures, respectively. The amended method was successfully applied to the assessment of Cr(IV) in natural and polluted industrial wastewaters. The analytical data were in excellent statistical harmony with those of the standard ETAAS method. The proposed method is two orders of magnitude more sensitive than the diphenylcarbazide standard spectrophotometric method.Graphical abstract.
Topics: Chromium; Colorimetry; Environmental Monitoring; Hydrogen Peroxide
PubMed: 32968831
DOI: 10.1007/s10661-020-08615-5 -
The Science of the Total Environment Nov 2020Surfactants are widely used in the industry of detergents, household products, and cosmetics. SAPDMA is a cationic surfactant that is used mostly in cosmetics,...
Surfactants are widely used in the industry of detergents, household products, and cosmetics. SAPDMA is a cationic surfactant that is used mostly in cosmetics, conditioning agents and has recently gained attention as a corrosion inhibitor in the sea pipelines industry. In this regard, literature concerning the ecotoxicological classification of SAPDMA on aquatic animals is lacking. This study aims to evaluate the potential ecotoxicity of SAPDMA using the aquatic zebrafish embryo model. The potential toxic effects of SAPDMA were assessed by different assays. This includes (i) mortality/survival assay to assess the median lethal concentration (LC); (ii) teratogenicity assay to assess the no observed effect concentration (NOEC); (iii) organ-specific toxicity assays including cardiotoxicity, neurotoxicity (using locomotion assay), hematopoietic toxicity (hemoglobin synthesis using o-dianisidine staining), hepatotoxicity (liver steatosis and yolk retention using Oil Red O (ORO) stain); (iv) cellular cytotoxicity (mitochondrial membrane potential) by measuring the accumulation of JC-1 dye into mitochondria. Exposure of embryos to SAPDMA caused mortality in a dose-dependent manner with a calculated LC of 2.3 mg/L. Thus, based on the LC value and according to the Fish and Wildlife Service (FWS) Acute Toxicity Rating Scale, SAPDMA is classified as "moderately toxic". The No Observed Effect Concentration (NOEC) concerning a set of parameters including scoliosis, changes in body length, yolk, and eye sizes was 0.1 mg/L. At the same NOEC concentration (0.1 mg/L), no organ-specific toxicity was detected in fish treated with SAPDMA, except hepatomegaly with no associated liver dysfunctions. However, higher SAPDMA concentrations (0.8 mg/L) have dramatic effects on zebrafish organ development (eye, heart, and liver development). Our data recommend a re-evaluation of the SAPDMA employment in the industry setting and its strictly monitoring by environmental and public health agencies.
Topics: Animals; Dimethylamines; Embryo, Nonmammalian; Lethal Dose 50; Surface-Active Agents; Water Pollutants, Chemical; Zebrafish
PubMed: 32886985
DOI: 10.1016/j.scitotenv.2020.140450 -
Bulletin of Experimental Biology and... May 2020A novel express method is developed to determine activity of antitumor enzyme L-lysine-α-oxidase obtained by culturing Trichoderma harzianum Rifai F-180 fungus. The...
A novel express method is developed to determine activity of antitumor enzyme L-lysine-α-oxidase obtained by culturing Trichoderma harzianum Rifai F-180 fungus. The carcinogenic reagent ortho-dianisidine-hydrochloride was replaced in the reaction medium with environmentally friendly reagents of the chromogenic mixture that included tetramethylbenzidine. This method improved precision and sensitivity of ELISA by 10 and 40 times, respectively. In addition, it could detect activity of L-lysine-α-oxidase not only in the producer strains with a pronounced activity of this enzyme, but also in the strains where this activity has not been previously determined.
Topics: Amino Acid Oxidoreductases; Antineoplastic Agents; Colorimetry; Culture Media; Drug Screening Assays, Antitumor; Hydrogen Peroxide; Hydrogen-Ion Concentration; Hypocreales; Temperature; Time Factors
PubMed: 32488773
DOI: 10.1007/s10517-020-04837-2 -
Chemistry, An Asian Journal Jun 2020In this work we have achieved epoxide to cyclic carbonate conversion using a metal-free polymeric catalyst under ambient CO pressure (1.02 atm) using a balloon setup....
In this work we have achieved epoxide to cyclic carbonate conversion using a metal-free polymeric catalyst under ambient CO pressure (1.02 atm) using a balloon setup. The triazine containing polymer (CYA-ANIS) was prepared from cyanuric chloride (CYA-Cl) and o-dianisidine (ANIS) in anhydrous DMF as solvent by refluxing under the N gas environment. The presence of triazine and amine functional groups in the polymer results in the adsorption of CO up to 7 cc/g at 273 K. This inspired us to utilize the polymer for the conversion of a series of functionalised epoxides into their corresponding cyclic carbonates in the presence of tetrabutyl ammonium iodide (TBAI) as co-catalyst. The product has wide range of applications like solvent in lithium ion battery, precursor for polycarbonate, etc. The catalyst was efficient for the conversion of different mono and di-epoxides into their corresponding cyclic carbonates under atmospheric pressure in the presence of TBAI as co-catalyst. The study indicates that epoxide attached with electron withdrawing groups (like, CH Cl, glycidyl ether, etc.) displayed better conversion compared to simple alkane chain attached epoxides. This is mainly due to the stabilization of electron rich intermediates produced during the reaction (e. g. epoxide ring opening or CO incorporation into the halo-alkoxide anion). This catalyst mixture was capable to maintain its reactivity up to five cycles without losing its activity. Post catalytic characterization clearly supports the heterogeneous and recyclable nature of the catalyst.
PubMed: 32270910
DOI: 10.1002/asia.201901277 -
Methods and Protocols Feb 2020A simple method for the identification of brush-border membrane α-glucosidases is described. The proteins were first solubilized and separated in a gel under native,...
A simple method for the identification of brush-border membrane α-glucosidases is described. The proteins were first solubilized and separated in a gel under native, non-denaturing, conditions. The gel was then incubated in substrate solutions (maltose or sucrose), and the product (glucose) exposed in situ by the oxidation of o-dianisidine, which yields a brown-orange color. Nano-liquid chromatography coupled to mass spectrometry analyses of proteins (nano LC-MS/MS) present in the colored bands excised from the gels, was used to confirm the presence of the enzymes. The stain is inexpensive and the procedure permits testing several substrates in the same gel. Once enzymes are identified, their abundance, relative to that of other proteins in the brush border, can be semi-quantified using nano LC-MS/MS.
PubMed: 32050538
DOI: 10.3390/mps3010015 -
Analytical Chemistry Dec 2019This study reports a microfluidic chip-based wearable colorimetric sensor for detecting sweat glucose. The device consisted of five microfluidic channels branching out...
This study reports a microfluidic chip-based wearable colorimetric sensor for detecting sweat glucose. The device consisted of five microfluidic channels branching out from the center and connected to the detection microchambers. The microchannels could route the sweat excreted from the epidermis to the microchambers, and each of them was integrated with a check valve to avoid the risk of the backflow of the chemical reagents from the microchamber. The microchambers contained the pre-embedded glucose oxidase (GOD)-peroxidase--dianisidine reagents for sensing the glucose in sweat. It was found that the color change caused by the enzymatic oxidation of -dianisidine could show a more sensitive response to the glucose than that of the conventional GOD-peroxidase-KI system. This sensor could perform five parallel detections at one time. The obtained linear range for sweat glucose was 0.1-0.5 mM with a limit of detection of 0.03 mM. The sensor was also used to detect the glucose in sweat samples from a group of subjects engaged in both fasting and postprandial trials. The results showed that our wearable colorimetric sensor can reveal the subtle differences existing in the sweat glucose concentration after the fasting and the oral glucose uptake.
Topics: Adult; Biosensing Techniques; Colorimetry; Dianisidine; Epidermis; Fasting; Glucose; Glucose Oxidase; Healthy Volunteers; Humans; Lab-On-A-Chip Devices; Limit of Detection; Peroxidase; Postprandial Period; Sweat; Wearable Electronic Devices
PubMed: 31553565
DOI: 10.1021/acs.analchem.9b03110 -
Zebrafish Oct 2019Strategies to reduce reperfusion injury after ischemia have been considered in clinical practice, but few interventions have successfully passed the proof-of-concept...
Strategies to reduce reperfusion injury after ischemia have been considered in clinical practice, but few interventions have successfully passed the proof-of-concept stage. In this study, we developed a novel zebrafish larvae hypoxia/reoxygenation (H/R) model to simulate myocardial ischemia/reperfusion injury (MIRI), with potential utility as a drug screening tool. After H/R treatment, videos of transgenic [Tg(cmlc:EGFP)] larval zebrafish hearts were captured using a digital high-speed camera, and the heart rate, diastolic area, systolic area, and total fraction of area changed were quantified. The mRNA expression of and was quantified, and red blood cells (RBCs) were detected by O-dianisidine staining. We found that a decline in cardiac contractility occurred in zebrafish larvae 48 h after hypoxia treatment. Reoxygenation for 2-5 h after 48 h of hypoxia caused heart dysfunction in zebrafish larvae, and were determined to be the optimum conditions for simulating MIRI similar to mammalian models. Our results indicated that heart dysfunction after reoxygenation in zebrafish larvae was accompanied by an upregulated gene expression of a number of myocardial injury biomarkers and increased numbers of RBCs. In conclusion, the novel larval zebrafish H/R model developed in this study could be used for rapid screening and efficacy assessment of MIRI therapeutics.
Topics: Animals; Animals, Genetically Modified; Green Fluorescent Proteins; Hypoxia; Larva; Myocardial Contraction; Myocardial Reperfusion Injury; Oxygen; Zebrafish
PubMed: 31314708
DOI: 10.1089/zeb.2018.1722