Quaternary ammonium compounds (QACs) represent one of the most effective classes of disinfectant agents in dental materials and resin nanocomposites. This reviews aims to give a wide overview on the ...research in the field of antibacterial QACs in dental materials and nanocomposites.
An introduction to dental materials components as well as the microorganisms and methods of evaluation for the antimicrobial assays are presented. Then, the properties and synthesis route of QACs, as monomer and filler, are shown. Finally, antimicrobial monomers and fillers, specifically those contain quaternary ammonium salts (QASs), in dental materials are reviewed.
QACs have been used as monomer and micro/nanofiller in restorative dentistry. They possess one or more methacrylate functional groups to participate in polymerization reactions. QACs with multiple methacrylate groups can also be used as crosslinking agents. Furthermore, QACs with chain length from ∼12 to 16 have higher antimicrobial activity in cured dental resins. In general, increasing the chain length leads to a threshold value (critical point) and then it causes decrease in the antimicrobial activity.
The current state of the art of dental materials and resin nanocomposites includes a wide variety of antimicrobial materials. Among them, QACs presents low cytotoxicity and excellent long-term antimicrobial activity without leaching out over time.
While citrus waste is abundantly generated, the disposal methods used today remain unsatisfactory: they can be deleterious for ruminants, can cause soil salinity, or are not economically feasible; ...yet citrus waste consists of various valuable polymers. This paper introduces a novel environmentally safe approach that utilizes citrus waste polymers as a biobased and biodegradable film, for example, for food packaging. Orange waste has been investigated for biofilm production, using the gelling ability of pectin and the strength of cellulosic fibres. A casting method was used to form a film from the previously washed, dried, and milled orange waste. Two film-drying methods, a laboratory oven and an incubator shaker, were compared. FE-SEM images confirmed a smoother film morphology when the incubator shaker was used for drying. The tensile strength of the films was 31.67 ± 4.21 and 34.76 ± 2.64 MPa, respectively, for the oven-dried and incubator-dried films, which is within the range of different commodity plastics. Additionally, biodegradability of the films was confirmed under anaerobic conditions. Films showed an opaque appearance with yellowish colour.
The purpose of the study was to develop a less hydrophilic, and therefore more useful, material from orange waste produced in large quantities by the food industry. A new derivative of industrial ...orange waste was synthesized via esterification with maleic anhydride. The reaction was confirmed via Fourier transform infrared spectroscopy (FTIR), and the degree of substitution of the hydroxyl groups was 0.39 ± 0.01, as determined by a back-titration method. A major change in physical structure was confirmed by scanning electron microscopy (SEM). The flake-like structure of orange waste changed to a sponge-like structure after the reaction, which involved an increased volume and a reduced density by approximately 40%. The sponge-like structure was represented as an agglomeration of particles with a low specific surface area of 2.18 m2/g and a mean pore diameter of 10.7 nm. Interestingly, the grafted orange waste seemed to become more hydrophobic, which was confirmed by a contact angle test; however, the material absorbed more water vapor. Thermogravimetric analysis (TGA) confirmed a thermally more uniform, though, less heat-resistant material. This work suggests a possible way of utilizing orange waste via synthesizing a renewable material with possible applications as a filler in biocomposites.
All-polyamide composite coated-fabric (APCCF) was used as an alternative material for the construction of textile-bioreactors (TBRs), which are prepared as a replacement of the traditional stainless ...steel bioreactors (SSBRs) or concrete-based bioreactors. The material characteristics, as well as the fermentation process performance of the APCCF-TBR, was compared with a TBR made using the polyvinyl chloride (PVC)-coated polyester fabric (PVCCF). The TBRs were used for the anaerobic fermentation process using baker’s yeast; and, for aerobic fermentation process using filamentous fungi, primarily by using waste streams from ethanol industries as the substrates. The results from the fermentation experiments were similar with those that were obtained from the cultivations that were carried out in conventional bioreactors. The techno-economic analysis conducted using a 5000 m3 APCCF-TBR for a typical fermentation facility would lead to a reduction of the annual production cost of the plant by $128,000,000 when compared to similar processes in SSBR. The comparative analyses (including mechanical and morphological studies, density measurements, thermal stability, ageing, and techno-economic analyses) revealed that the APCCF is a better candidate for the material of construction of the TBR. As the APCCF is a 100% recyclable single-polymer composite, which was prepared from Nylon 66 textile production-line waste, it could be considered as an environmentally sustainable product.
Polyamides (PAs) are one of the most important engineering polymers; however, the difficulty in dissolving them hinders their applications. Formic acid (FA) is the most common solvent for PAs, but it ...has industrial limitations. In this contribution, we proposed a new solvent system for PAs by replacing a portion of the FA with urea and calcium chloride (FAUCa). Urea imparts the hydrogen bonding and calcium ion from the calcium chloride, as a Lewis acid was added to the system to compensate for the pH decrease due to the addition of urea. The results showed that the proposed solvent (FAUCa) could readily dissolve PAs, resulting in a less decrease in the mechanical properties during the dissolution. The composite prepared using the FAUCa has almost the same properties as the one prepared using the FA solution. The solution was applied on a polyamide 66 fabric to make an all-polyamide composite-coated fabric, which then was characterized. The FAUCa solution had a higher viscosity than the one prepared using the neat FA solvent, which can be an advantage in the applications which need higher viscosity like preparing the all-polyamide composite-coated fabric. A more viscous solution makes a denser coating which will increase the water /gas tightness. In conclusion, using the FAUCa solvent has two merits: (1) replacement of 40% of the FA with less harmful and environmentally friendly chemicals and (2) enabling for the preparation of more viscous solutions, which makes a denser coating.
There are abundant renewable energy sources in Iran such as wind, solar, geothermal, biomass. However, Iran is fully dependent on fossil fuels for industrial, residential and transportation sectors. ...It results in the country to be in top 10 producers of greenhouse gases (GHGs) into the atmosphere. GHGs can be controlled by incorporating renewable sources to produce energy. Therefore, renewable energy resources are becoming more attractive to develop sustainable energy development in Iran. However, the transformation from traditional fossil fuel infrastructures to advanced renewable technologies needs many considerations, such as strategic and core planning. In this regard, this paper covers the current state of Iran's energy market focusing on both fossil fuels and renewable energy resources. A general review is offered over the renewable energy production status in Iran and the production potentials. Finally, in conclusion, a comparisons are made over the current state, plans and also potential opportunities of Iran over each sort of energy production.
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This work shows that incorporating highly compatible polyrhodanine nanoparticles (PRh-NPs) into a polyamide (PA) active layer allows for fabricating forward osmosis (FO) thin-film composite (TFC)-PRh ...membranes that have simultaneously improved antimicrobial, antifouling, and transport properties. To the best of our knowledge, this is the first reported study of its kind to this date. The presence of the PRh-NPs on the surface of the TFC-PRh membranes active layers is evaluated using FT-IR spectroscopy, SEM, and XPS. The microscopic interactions and their impact on the compatibility of the PRh-NPs with the PA chains were studied using molecular dynamics simulations. When tested in forward osmosis, the TFC-PRh-0.01 membrane (with 0.01 wt % PRh) shows significantly improved permeability and selectivity because of the small size and the high compatibility of the PRh-NPs with PA chains. For example, the TFC-PRh-0.01 membrane exhibits a FO water flux of 41 l/(m2·h), higher than a water flux of 34 l/(m2·h) for the pristine TFC membrane, when 1.5 molar NaCl was used as draw solution in the active-layer feed-solution mode. Moreover, the reverse solute flux of the TFC-PRh-0.01 membrane decreases to about 115 mmol/(m2·h) representing a 52% improvement in the reverse solute flux of this membrane in comparison to the pristine TFC membrane. The surfaces of the TFC-PRh membranes were found to be smoother and more hydrophilic than those of the pristine TFC membrane, providing improved antifouling properties confirmed by a flux decline of about 38% for the TFC-PRh-0.01 membranes against a flux decline of about 50% for the pristine TFC membrane when evaluated with a sodium alginate solution. The antimicrobial traits of the TFC-PRh-0.01 membrane evaluated using colony-forming units and fluorescence imaging indicate that the PRh-NPs hinder cell deposition on the TFC-PRh-0.01 membrane surface effectively, limiting biofilm formation.
In this paper, a traffic simulator is designed in order to investigate the travel demand based on GIS data and analysis. In order to evaluate the proposed simulator, four different scenarios are ...provided for the arrangement of land use services. In first scenario, all service land use are located in the middle of the region; in second scenario, land use services located on the periphery of the region; in the third scenario, land use is defined regularly in the entire area; and finally, in the last scenario, unchanged statuses are evaluated. The comparison parameters are Vehicle Miles of Travel (VMT) and Vehicle Hours of Travel (VHT), which are measured for these four scenarios. The analysis of the results shows that the regular distribution of land use service (scenario 3), with VHT, mean of 33.01 minutes is the best scenario, while scenario 2 with a VHT average of 35.12 minutes has the worst performance.
تصور کنیم در پروندة قتل عمدی ولی دم خواستار قصاص شده و حکم برابر قوانین صادر شده و قرار است اجرا شود ، پس از لحظاتی از اجرا و پیش از آن که مجرم "ازهاق نفس" شده وزندگیش پایان پذیرد ولی دم اعلام گذشت ...می کند و نیروهای حاضر در صحنه برای پایین آوردن محکوم علیه از دار مجازات تلاش می کنند. این احتمال قویا وجود دارد که مجرم آسیبی جدی دیده و متحمل ضرری در بقیه دوران حیات خود شود. البته تردیدی نیست که دامنة این دیگران و حتی جامعه را هم فرا می گیرد. بدین سان اولین پرسش این است که آیا اصولاً ولی دم می تواند در این مرحله اعلام گذشت کند؟ برای احتراز از تبعات ناخوشایند گذشت در این مرحله آیا بهتر نیست ولی دم را ملزم کنیم تا پیش از آغاز مرحلة اجرایی قصاص تصمیم قطعی خود را بگیرد؟در این مقاله سعی کرده ایم یک تأمل انتقادی در این موضوع داشته باشیم تا بلکه بتوان راهی برای اصلاح وضعیت موجود در جامعه گشود.
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•Chicory waste was used as a natural cation exchanger for the removal of Pb and Cd from aqueous solutions.•Ca-loaded chicory waste significantly improved CEC and heavy metals removal ...capacity.•Removal of Cd2+ and Pb2+ by the raw and modified chicory waste occurs mainly through the ion exchange process.•Regeneration of the synthesized ion exchanger by CaCl2 solution was more effective than NaCl and HNO3 solutions.
The ion exchange method has great potential for the removal of heavy metal ions from aqueous solutions. In this study, after the pre-selection experiments among 14 medicinal herb wastes, the ion exchange capacity of the raw chicory waste and its modified forms were evaluated for the removal of Pb2+ and Cd2+ from aqueous solutions. Furthermore, kinetics, equilibrium isotherms, and column studies were conducted. Modification of the raw chicory waste by CaCl2 increased the cation exchange capacity as well as the Pb2+ and Cd2+ removal efficiency. The maximum adsorption capacities were increased from 103.1 and 53.8 mg g−1 by raw chicory waste to 123.5 and 64.5 mg g−1 by modified chicory waste for Pb2+ and Cd2+, respectively. Exchange of Pb2+ and Cd2+ ions with alkali metals (Na+ and K+) and alkaline earth metals (Ca2+ and Mg2+) onto the waste surface during the removal experiments indicated that the ion exchange could be the dominant mechanism for the removal of Pb2+ and Cd2. In addition, the regeneration of raw and modified chicory waste loaded by Pb2+ and Cd2+ with distilled water was not possible, while eluting the waste using CaCl2, NaCl and HNO3 could effectively recover both metals. It was concluded that the prepared bio ion exchanger from chicory waste could be a promising and low-cost alternative to synthetic resins for the removal of heavy metals from the water and wastewater.
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