On void structure and strength of foamed concrete made without/with additives

A study has been undertaken to investigate the effect of different additives on the strength foamed concrete by characterising air-void size and shape parameters and identifying the influence of these parameters and changes to cement paste microstructure on strength. Nine different mixes, made using a pre-formed foam, were investigated with varying density (nominally 1300, 1600 and 1900 kg/m3) without/with additives (silica fume, fly ash and superplasticizer), used either individually or together. Optical microscopy and scanning electron microscopy were used in this investigation. Compared to the conventional mixes, inclusion of additives (individually or in combination) helped to improve both the cement paste microstructure and air-void structure of foamed concrete. For a given density, although the additives in combination led to increased void numbers, higher strength was achieved due to reduced void size and connectivity, by preventing their merging and producing a narrow void size distribution. Furthermore, superplasticizer has the most beneficial influence on voids when used alone and it further improves void structure (smaller and number voids) when used in combination with other additives. Not only enhancement of void structure but also improved cement paste microstructure both contribute to the strength of the foamed concrete

Flexural Behaviour of Precast Aerated Concrete Panel (PACP) with Added Fibrous Material: An Overview

The usage of precast aerated concrete panel as an IBS system has become the main alternative to conventional construction system. The usage of this panel system contributes to a sustainable and environmental friendly construction. This paper presents an overview of the precast aerated concrete panel with added fibrous material (PACP). PACP is fabricated from aerated foamed concrete with added Polypropylene fibers (PP). The influence of PP on the mechanical properties of PACP are studied and reviewed from previous research. The structural behaviour of precast concrete panel subjected to flexure load is also reviewed. It is found that PP has significant affects on the concrete mixture’s compressive stregth, tensile strength and flexural strength. It is also found that PP manage to control the crack propagation in the concrete panel

Assessment of protein silver nanoparticles toxicity against pathogenic Alternaria solani

Mycogenic synthesis of silver nanoparticles (AgNPs) was carried out in the present investigation using an aqueous extract of endophytic non-pathogenic Alternaria solani F10 (KT721914). The mycosynthesized AgNPs were characterized by means of spectroscopic and microscopic techniques. The surface plasmon resonance found at 430 nm confirmed the formation of stable AgNPs for several weeks at room temperature. Also, the results revealed the formation of spherical and monodispersed AgNPs with an average size of 14.8 +/- 1.2 nm. The FT-IR spectrum suggested that the fungal extracellular proteins and secondary metabolites had the role in Ag reduction and AgNPs capping of which protein Ag nanoconjugates were formed. Furthermore, the mycosynthesized AgNPs exhibited potent antifungal activity against different pathogenic isolates of the same Alternaria solani fungus, the causal pathogen of tomato early blight disease. The antifungal efficiency of the AgNPs at 1, 5 and 10 ppm were evaluated for 8 days after incubation by measuring the inhibition rate of fungal radial growth. The results were further supported by investigating fungal hyphae morphology alteration by scanning and transmission electron microscopy. Treated fungal hyphae showed formation of pits and pores. Also, the mycosynthesized AgNPs were able to pass and distribute throughout the fungal cell area and interact with the cell components.A financial support from European Commission by Erasmus Mundus Scholarship-ACTION 2 WELCOME program is gratefully acknowledged. Work in JAD laboratory was supported by grant BIO2014-54269-R from the Ministerio de Economia y Competividad (Spain).Abdel-Hafez, SII.; Nafady, NA.; Abdel-Rahim, IR.; Shaltout, AM.; Daros Arnau, JA.; Mohamed, MA. (2016). 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Development and biomedical applications of an improved polycation-sensitive membrane electrode.

An improved polycation-sensitive membrane electrode based on the cation exchanger dinonylnaphthalenesulfonate (DNNS) has been developed. The electrode yields a significant potentiometric response (>50 mV) towards micromolar levels of protamine and other polycations in samples as complex as whole blood. The EMF response characteristics of this electrode are consistent with the non-equilibrium steady-state response mechanism previously developed for polyanion-sensitive electrodes. The DNNS-based electrode serves as a sensitive end-point detector for measuring heparin levels (0--10 U/mL) via potentiometric titrations with protamine. Heparin concentrations measured in whole blood using the electrode correlate well with other techniques for measuring heparin levels in samples obtained from patients undergoing bypass surgery. More rapid heparin measurements can be achieved by employing a continuous infusion of protamine into the sample. By suitably modifying the membrane composition, the protamine titration method can also be applied to the determination of low molecular weight heparins (LMWHs) in whole blood. It is shown that the nature of the LMWH determines its binding affinity to protamine, thus governing its ability to be determined via manual protamine titrations. Finally, these electrodes are further used as detectors for measuring the activity of proteases by following the degradation of polycationic substrates. By employing synthetic arginine-rich peptides that contain amino acid residues specifically cleaved by the target protease, more specific assays can be developed. It is also demonstrated that this assay methodology can be applied to measure protease inhibitors (e.g., aprotinin) in buffered and treated plasma samples.Ph.D.Analytical chemistryApplied SciencesBiomedical engineeringPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131764/2/9929931.pd

Flow Behaviour Near the Leading Edge of the Vaned Diffuser

Measurements were canied out close to the leading edge of vane diffuser of a centrifugal impeller to study the flow behavior from impeller outlet to throat at different flow coefficients. The flow behavior is characterized in terms of pressure recovery coefficient from leading edge to throat and variation of Mach number and flow angle near throat. The unsteady static pressure variations at impeller outlet, leading edge and across the throat of vane diffuser were also measured to characterize the flow. Some salient features of the measurements are discussed in this paper

EPR spectroscopic studies of radical cations in a novel nonconjugated conductive polymer, poly(β-pinene)

Electrical conductivity, FTIR spectroscopy and electro-optic effect in a novel nonconjugated conductive polymer, poly(β-pinene), have been recently reported. The conductivity increases by more than ten orders of magnitude upon doping with iodine. The double bonds decrease upon doping due to charge-transfer and formation of radical cations. In this report, electron paramagnetic resonance (EPR) spectroscopic measurements of poly(β-pinene) before and after iodine doping are discussed. The results show that the EPR signal increases in proportion to the doping level consistent with the formation of radical cations upon doping. Hyperfine splitting has been observed at high doping levels due to reduction in distance between the radical cation and the iodine anion. Such splitting was not observed for a doped conjugated polymer since in that case the radical is delocalized

Topochemical photodimerization of 7-acetoxycoumarin: the acetoxy group as a steering agent

Among the various substituted coumarins investigated only 7-acetoxycoumarin is observed to photodimerize topochemically in the crystalline state and this observation may be of importance in the context of "crystal engineering"

Photodimerization of coumarins in the solid state

Photochemical dimerization of 7-methoxycoumarin occurs in the solid state to give high yields of a syn-head-to-tail dimer although the potentially reactive double bonds are not favourably oriented in the crystal of the monomer