•Waste crumb rubber up to 5.5% replacement was evaluated as a potential substitute of fine aggregate for production of acid resistant concrete.•The formed minerals and molecular groups after acidic ...exposure were analysed through XRD and FTIR analyses.•FESEM and TGA/DTA analyses were employed to verify the changed microstructure after acidic exposure.•At 4% substitution level acid resistance improves.
Disposal of waste rubber is afflicting ecological balance across the globe. In recent years, the rate of dumping of this material has amplified. One possible approach to solve this issue is to utilize this rejected material as a replacement of fine aggregate in concrete. Hence, this study examines the behaviour of concrete with crumb rubber at various substitution levels (4%, 4.5%, 5% and 5.5%) under an acidic (sulphuric acid) aggressive environment. Performance was judged by evaluating change in weight, compressive strength and microstructure. Results show that with inclusion of crumb rubber, material separation of concrete reduces which prevents its rupture and disintegration. This was verified by X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy tests. Hence, using crumb rubber as a replacement of fine aggregate up to 4% prevents significant fall in performance under such an aggressive condition. This will also reduce the dependency on natural fine aggregate for the manufacture of concrete for non-structural elements.
Transgenic technology is a crucial tool for gene functional analysis and targeted genetic modification in the para rubber tree (Hevea brasiliensis). However, low efficiency of plant regeneration via ...somatic embryogenesis remains a bottleneck of successful genetic transformation in H. brasiliensis. Enhancing expression of GROWTH-REGULATING FACTOR 4 (GRF4)-GRF-INTERACTING FACTOR 1 (GIF1) has been reported to significantly improve shoot and embryo regeneration in multiple crops. Here, we identified endogenous HbGRF4 and HbGIF1 from the rubber clone Reyan7-33-97, the expressions of which dramatically increased along with somatic embryo (SE) production. Intriguingly, overexpression of HbGRF4 or HbGRF4-HbGIF1 markedly enhanced the efficiency of embryogenesis in two H. brasiliensis callus lines with contrasting rates of SE production. Transcriptional profiling revealed that the genes involved in jasmonic acid response were up-regulated, whereas those in ethylene biosynthesis and response as well as the S-adenosylmethionine-dependent methyltransferase activity were down-regulated in HbGRF4- and HbGRF4-HbGIF1-overexpressing H. brasiliensis embryos. These findings open up a new avenue for improving SE production in rubber tree, and help to unravel the underlying mechanisms of HbGRF4-enhanced somatic embryogenesis.
Novel pseudo-polymeric complexes of gold(III)-mercury(II) with cyclic alkylene dithiocarbamate ligands: (Au{S.sub.2CN(CH.sub.2).sub.6}.sub.2HgCl.sub.3).sub.n, ...(Au{S.sub.2CN(CH.sub.2).sub.6}.sub.2.sub.2HgCl.sub.4 * H.sub.2O).sub.n, and (Au{S.sub.2CN(CH.sub.2).sub.4O}.sub.2.sub.2Hg.sub.2Cl.sub.6).sub.n have been obtained and structurally characterized. The sophisticated supramolecular structure of the obtained compounds is realized due to secondary non-valent Au ... S interactions and includes mononuclear and binuclear cations and anions as structural units as well as cationic and anionic polymer chains. The thermal behavior of the obtained complexes has been studied by means of simultaneous thermal analysis. The products of thermal transformations of the complexes are reduced elemental gold and HgCl.sub.2. Keywords: mercury(II) dithiocarbamates, chemisorption activity, gold(III)mercmy(II) dithiocarbamato-chlorido complexes, supramolecular self-assembly DOI: 10.1134/S1070363219110185
The reaction of secondary amines with CS.sub.2 under mild conditions using reduced graphene oxide (rGO) as a green catalyst was reported, which provided an efficient access to the one-pot synthesis ...of bis(aminothiocarbonyl)disulfides. The rGO can be recycled at least four times without any loss of catalytic activity. A plausible mechanism was proposed.
A laboratory-scale experiment is conducted to remove nitrogen from nitrogen-rich wastewater using a down-flow hanging sponge (DHS) reactor. Effluent from an anaerobic–aerobic system for treating ...synthetic natural rubber wastewater, which still contains high levels of ammonia, was used as nitrogen-rich wastewater. Experimental period was divided into four phases based whether a carbon source was fed to the DHS reactor. The highest nitrogen removal efficiency (59.5 ± 5.4%) was achieved during phase 4, when a sodium acetate solution was fed into bottom section of the DHS reactor. In the DHS reactor, the nitrification occurred in the upper and middle sections. Then, after adding the sodium acetate solution, denitrification occurred. The final chemical oxygen demand, ammonia, and total inorganic nitrogen concentrations in the DHS reactor effluent were 37 ± 24 mg/L, 34 ± 5 mgN/L, and 42 ± 8 mgN/L, respectively. These concentrations were sufficient to meet the effluent standards of the Vietnamese natural rubber industry, which are the strictest in South-East Asia. The dominant bacteria in the sludge retained by the reactor's sponge media were the nitrifying bacteria Nitrosovibrio (0.2%) and Nitrospira (0.2–0.3%), the denitrifying bacteria Hylemonella (1.0–13.7%), Pseudoxanthomonas (1.2–2.1%), and Amaricoccus (2.4–3.5%), and the anammox bacterium Candidatus Brocadia (0.1–0.2%). Significant amounts of the nitrogen-fixing bacterium Xanthobacter (11.2–14.8%) and the rubber-degrading bacterium Gordonia (11.0–28.6%) were also found in the DHS reactor. These bacteria were thus considered to be the key microbes for nitrogen removal in a DHS reactor fed with a carbon source for denitrification.
•Nitrogen removal was conducted by the down-flow hanging sponge (DHS) reactor.•59.5% of total nitrogen was removed by the DHS without aeration.•Nitrification and denitrification were separately occurred in the DHS.•Nitrifying, denitrifying, nitrogen-fixing bacteria contributed to nitrogen removal.
A World History of Rubber helps readers understand and gain new insights into the social and cultural contexts of global production and consumption, from the nineteenth century to today, through the ...fascinating story of one commodity. * Divides the coverage into themes of race, migration, and labor; gender on plantations and in factories; demand and everyday consumption; World Wars and nationalism; and resistance and independence * Highlights the interrelatedness of our world long before the age of globalization and the global social inequalities that persist today * Discusses key concepts of the nineteenth and twentieth centuries, including imperialism, industrialization, racism, and inequality, through the lens of rubber * Provides an engaging and accessible narrative for all levels that is filled with archival research, illustrations, and maps
We investigated the influence of two fillers-CB (carbon black) and silica-on the Hsub.2 permeation of EPDM polymers crosslinked with sulfur in the pressure ranges 1.2-90 MPa. Hsub.2 uptake in the ...CB-blended EPDM revealed dual sorption (Henry's law and Langmuir model) when exposed to pressure. This phenomenon indicates that Hsub.2 uptake is determined by the polymer chain and filler-surface absorption characteristics. Moreover, single sorption characteristics for neat and silica-blended EPDM specimens obey Henry's law, indicating that Hsub.2 uptake is dominated by polymer chain absorption. The pressure-dependent diffusivity for the CB-filled EPDM is explained by Knudsen and bulk diffusion, divided at the critical pressure region. The neat and silica-blended EPDM specimens revealed that bulk diffusion behaviors decrease with decreasing pressure. The Hsub.2 diffusivities in CB-filled EPDM composites decrease because the impermeable filler increases the tortuosity in the polymer and causes filler-polymer interactions; the linear decrease in diffusivity in silica-blended EPDM was attributed to an increase in the tortuosity. Good correlations of permeability with density and tensile strength were observed. From the investigated relationships, it is possible to select EPDM candidates with the lowest Hsub.2-permeation properties as seal materials to prevent gas leakage under high pressure in Hsub.2-refueling stations.
Kpejeglo series and Agawtaw series are two closely related pan soils in the Lower Volta Basin of Ghana. They have previously been classified variously according to Soil Taxonomy and the FAO/World ...Reference Base (WRB) systems without positively identifying the subsurface hardpan horizons. The hardpans have generally been described as compact clay loam or claypan horizons. This study was designed to 1) identify the hardpan horizons and 2) classify the soils according to the latest Soil Taxonomy and the WRB classification systems. Both soils had argillic and natric horizons. Bulk density of the pan horizons was higher than that of the horizons above them. Air-dried peds of the pan did not slake in water and 1M HCl or 40% NaOH. Up to 50% reduction in the size of the peds was only observed after alternating acid and alkali soaking for more than 5 hours. Peds from the lower limits of the hardpan of Kpejeglo Pedon 2, however, slaked in 1M HCl. The slaking characteristics show that the hardpan horizon could be a duripan, which possibly occurred with a petrocalcic horizon. Both soils were classified under Soil Taxonomy as Typic Duraqualfs. Natric horizon did not reflect in the classification because it is not presently provided at the subgroup level of Duraqualfs. We propose that due to the agronomic importance of natric horizon, Natric Duraqualfs would be more appropriate classification of the soils. The soils were also classified as Gleyic Solonetz (Duric) under the WRB system. Although Gleyic Solonetz places more emphasis on natric horizon than on petroduric horizon, the latter could be more limiting to plant growth. It would therefore be important if petroduric horizon reflects in the classification of the soils. Presently, under Solonetz, duric is only recognized as a supplementary qualifier so we propose that duric be elevated to a principal qualifier and should key out before gleyic so that the soils could be appropriately classified as Duric Solonetz.
![H[sub.2] Uptake and Diffusi...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/2073-4360/small "H[sub.2] Uptake and Diffusion Characteristics in Sulfur-Crosslinked Ethylene Propylene Diene Monomer Polymer Composites with Carbon Black and Silica Fillers after High-Pressure Hydrogen Exposure Reaching 90 MPa")
