Relating monolithic and granular leaching from contaminated soil treated with different cementitious binders.

This work employed a clayey, silty, sandy gravel contaminated with a mixture of metals (Cd, Cu, Pb, Ni and Zn) and diesel. The contaminated soil was treated with 5 and 10% dosages of different cementitious binders. The binders include Portland cement, cement-fly ash, cement-slag and lime-slag mixtures. Monolithic leaching from the treated soils was evaluated over a 64-day period alongside granular leachability of 49- and 84-day old samples. Surface wash-off was the predominant leaching mechanism for monolithic samples. In this condition, with data from different binders and curing ages combined, granular leachability as a function of monolithic leaching generally followed degrees 4 and 6 polynomial functions. The only exception was for Cu, which followed the multistage dose-response model. The relationship between both leaching tests varied with the type of metal, curing age/residence time of monolithic samples in the leachant, and binder formulation. The results provide useful design information on the relationship between leachability of metals from monolithic forms of S/S treated soils and the ultimate leachability in the eventual breakdown of the stabilized/solidified soil.

Towards the formation of neuro-transistor artificial chemical synapse

Highly sensitive biosensor for detection of acetylcholine (ACh) and competitive acetylcholinesterase (AChE) inhibitor, eserine, is investigated. Peculiar microelectronic configuration of an ion-sensitive field-effect transistor (ISFET) in addition to a right choice of the pH-transducing nanolayers allows recording a response of the enzyme-modified ISFET (EnFET) to a wide range of ACh concentrations. We demonstrate a remarkable improvement of at least three orders of magnitude in dose response to ACh. Described bioelectronic system reveals clear response, when the catalytic activity of the immobilized AChE is inhibited in a reversible manner by eserine, competitive inhibitor of AChE. ©2007 IEEE.

Highly efficient detector of the neurotransmitter ACh and AChE inhibitors

Among the variety of applications for biosensors one of the exciting frontiers is to utilize those devices as post-synaptic sensing elements in chemical coupling between neurons and solid-state systems. The first necessary step to attain this challenge is to realize highly efficient detector for neurotransmitter acetylcholine (ACh). Herein, we demonstrate that the combination of floating gate configuration of ion-sensitive field effect transistor (ISFET) together with diluted covalent anchoring of enzyme acetylcholinesterase (AChE) onto device sensing area reveals a remarkable improvement of a four orders of magnitude in dose response to ACh. This high range sensitivity in addition to the benefits of peculiar microelectronic design show, that the presented hybrid provides a competent platform for assembly of artificial chemical synapse junction. Furthermore, our system exhibits clear response to eserine, a competitive inhibitor of AChE, and therefore it can be implemented as an effective sensor of pharmacological reagents, organophosphates, and nerve gases as well. © 2007 Materials Research Society.

Plastic limit solution for the response of plate anchors under combined translational and torsional undrained loading

Plate anchors are increasingly being used to moor large floating offshore structures in deep and ultradeep water. These facilities impart substantial vertical uplift loading to plate anchors. However, extreme operating conditions such as hurricane loading often result in partial system failures, with significant change in the orientation of the remaining intact mooring lines. The purpose of this study is to investigate the undrained pure translational (parallel to plate) and torsional bearing capacity of anchor plates idealized as square and rectangular shaped plates. Moreover, the interaction response of plate anchors under combined translational and torsional loading is studied using a modified plastic limit analysis (PLA) approach. The previous PLA formulation which did not account for shear-normal force interaction on the vertical end faces of the plate provides an exact solution to the idealized problem of an infinitely thin plate but only an approximate solution to the problem of a plate of finite thickness. This is also confirmed by the three-dimensional finite element (FE) results, since the PLA values exceed FE results as the thickness of the plate increases. By incorporating the shear-normal interaction relationship in the modified solution, the torsional bearing capacity factors, as well as the plate interaction responses are enhanced as they show satisfactory agreement with the FE results. The interaction relationship is then obtained for square and rectangular plates of different aspect ratios and thicknesses. The new interaction relationships could also be used as an associated plastic failure locus for combined shear and torsional loading to predict plastic displacements and rotations in translational and torsional loading modes as well. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).

Hybrid core carbon fiber composite sandwich panels: Fabrication and mechanical response

Carbon fiber reinforced polymer (CFRP) composite sandwich panels with hybrid foam filled CFRP pyramidal lattice cores have been assembled from a carbon fiber braided net, 3D woven face sheets and various polymeric foams, and infused with an epoxy resin using a vacuum assisted resin transfer process. Sandwich panels with a fixed CFRP truss mass have been fabricated using a variety of closed cell polymer and syntactic foams, resulting in core densities ranging from 44-482kgm-3. The through thickness and in-plane shear modulus and strength of the cores increased with increasing foam density. The use of low compressive strength foams within the core was found to result in a significant reduction in the compressive strength contributed by the CFRP trusses. X-ray tomography led to the discovery that the trusses develop an elliptical cross-section shape during pressure assisted resin transfer. The ellipticity of the truss cross-sections increased, and the lattice contribution to the core strength decreased as the foam density was reduced. Micromechanical modeling was used to investigate the relationships between the mechanical properties and volume fractions of the core materials and truss topology of the hybrid core. The specific strength and moduli of the hybrid cores lay between those of the CFRP lattices and foams used to fabricate them. However, their volumetric and gravimetric energy absorptions significantly exceeded those of the materials from which they were fabricated. They compare favorably with other lightweight energy absorbing materials and structures. © 2013.