Search results for "POLYMER"

Diode laser welding of ABS: Experiments and process modeling

2009

International audience; The laser beam weldability of acrylonitrile/butadiene/styrene (ABS) plates is determined by combining both experimental and theoretical aspects. In modeling the process, an optical model is used to determine how the laser beam is attenuated by the first material and to obtain the laser beam profile at the interface. Using this information as the input data to a thermal model, the evolution of the temperature field within the two components can be estimated. The thermal model is based on the first principles of heat transfer and utilizes the temperature variation laws of material properties. Corroborating the numerical results with the experimental results, some impor…

Transformation of Construction Cement to a Self-Healing Hybrid Binder

2019

A new biomimetic strategy to im prove the self-healing properties of Portland cement is presented that is based on the application of the biogenic inorganic polymer polyphosphate (polyP), which is used as a cement admixture. The data show that synthetic linear polyp, with an average chain length of 40, as well as natural long-chain polyP isolated from soil bacteria, has the ability to support self-healing of this construction material. Furthermore, polyP, used as a water-soluble Na-salt, is subject to Na+/Ca2+ exchange by the Ca2+ from the cement, resulting in the formation of a water-rich coacervate when added to the cement surface, especially to the surface of bacteria-containing cement/c…

Unexplored alternative use of calcareous sludge from the paper-pulp industry in green geopolymer construction materials

2020

Abstract Calcareous sludge is an alkaline waste produced by the paper pulp industry that is commonly disposed of in land-fill. However, recent studies and the European regulations discourage such practice. This work investigates an alternative and innovative way to recycle and reuse this waste, as filler, in the production of green geopolymeric mortars intended for applications in construction. This is the first time that this calcareous sludge is used to produce novel waste-based materials, in both construction and geopolymer technology. The novel alkali-activated mortar also uses biomass fly ash – another slightly investigated waste stream – to substitute the metakaolin (70 wt% substituti…

Metakaolin geopolymer characterization and application for ammonium removal from model solutions and landfill leachate

2016

Abstract Geopolymers are aluminosilicate compounds that are amorphous analogues of zeolites, and thus possess similar cation-exchange properties. Geopolymers have been successfully applied to remove toxic metals and organic dyes from aqueous solutions. In this study, geopolymer was synthesized from metakaolin and applied to remove ammonium (NH 4 + ) from model solutions and landfill leachate. Geopolymerization increased the ammonium removal capacity, surface area and average pore width and changed the chemical structure of metakaolin. The maximum NH 4 + removal capacity of the geopolymer was 21.07 mg g − 1 which was 46% higher than the capacity of the reference clinoptilolite–heulandite zeo…

A Mechanical Approach for Evaluating the Distribution of Confinement Pressure in FRP-Wrapped Rectangular Columns

2019

In recent decades, fiber reinforced polymer (FRP) wrapping has become a common technique to retrofit reinforced concrete (RC) columns. Numerous research works have sought to verify analytically and experimentally its effectiveness in terms of enhancement of axial load bearing capacity and ductility. These studies highlighted that in the case of sharp-cornered sections, the maximum allowable confinement pressure is limited by premature failure at corners and, consequently, stress in the FRP, as well as the distribution of the confinement pressure, is not uniform. The prediction of this phenomenon is not straightforward, and existing theoretical studies propose complex numerical simulations, …

Microscopic Revelation of Charge-Trapping Sites in Polymeric Carbon Nitrides for Enhanced Photocatalytic Activity by Correlating with Chemical and El…

2019

The influences of chemical and electronic structures on the photophysical properties of polymeric carbon nitrides (PCNs) photocatalysts, which govern the microscopic mechanisms of the superior photocatalytic activity under visible-light irradiation, have been resolved in this work. Time-resolved photoluminescence and in situ electron paramagnetic resonance measurements indicate that the photoexcited electrons in the fractured PCNs swiftly transfer to the C2p-localized states where the trapped photoelectrons exhibit longer lifetime compared to those in the ordinary PCNs. Moreover, the structure deviation at the carbon (Cb) atoms around the bridging sites of heptazine ring units, where trappe…

The role of extracellular polymeric substances (EPS) on aerobic granules formation: comparison between a case of synthetic wastewater supply and anot…

2017

The paper focused on the evolution and the comparison of the extracellular polymeric substances (EPSs) content during the granulation process in two Granular Sequencing Batch Airlift Reactors (GSBAR) (3,5 L) fed with synthetic (R1) and industrial wastewater (R2). The results showed that in both the reactors the EPSs, in particular proteins (PN), were mainly produced during the feast phase because of the high substrate availability, especially under conditions of metabolic stress. Then, the EPSs content reduced during the famine period, because of biodegradation by bacteria. More in detail, during the granulation process, a greater polysaccharides (PS) consumption occurred in both reactors, …

Author response: Uncoupling of dynamin polymerization and GTPase activity revealed by the conformation-specific nanobody dynab

2017

Evaluation of Antibacterial Efficacy of Photodynamic Therapy vs. 2.5% NaOCl against E. faecalis-infected Root Canals Using Real-time PCR Technique

2017

Background Bacteria like E. faecalis can produce intra- and extra-radicular biofilms. Theoretically, the adjustable penetration ability of lasers enables better access to root canal system. Therefore the aim of the present study was to compare the ability of photoactivated laser and 2.5% NaOCl irrigation solution to eliminate E. faecalis from the root canals by real-time PCR technique. Material and methods Sixty extracted human upper central incisors were selected and sterilized in an autoclave. The root canals were infected with E. faecalis (PTCC 1237, Persian Type Culture Collection, Iran) and then incubated for 24 hours. The samples were randomly divided into 3 groups. No intervention wa…

Characteristic of Pseudomonas syringae pv. atrofaciens Isolated from Weeds of Wheat Field

2021

The aim of this study was the identification of the causative agent of the basal glume rot of wheat Pseudomonas syringae pv. atrofaciens from the affected weeds in wheat crops, and determination of its virulent properties. Isolation of P. syringae pv. atrofaciens from weeds of wheat crops was carried out by classical microbiological methods. To identify isolated bacteria, their morphological, cultural, biochemical, and serological properties as well as fatty acids and Random Amplification of Polymorphic DNA (RAPD)-PCR (Polymerase chain reaction) profiles with the OPA-13 primer were studied. Pathogenic properties were investigated by artificial inoculation of wheat plants and weed plants, fr…