“Islands in Sea” and “Lakes in Mainland” phases and related transitions simulated on a square lattice

We describe the Island-Mainland (IM) transition on a square lattice. Black squares are randomly dropped on a white background, with increasing concentration p. We define black (white) clusters as groups of black (white) squares, connected through edges or corners on a quasi-2D system. At a certain p the black islands in white sea (IS) phase crosses over to a mixed phase (MP). At still larger p the MP phase crosses over to the lakes in mainland (LM) phase with white lakes in a black mainland. We show that the Euler number, defined as difference between number of white clusters and number of black clusters goes through extrema near these transition points. The phenomenon is supported by experimental observations.     

Micromechanical analysis of fibrous piezoelectric composites with imperfectly bonded adherence

In this work, two-phase parallel fiber-reinforced periodic piezoelectric composites are considered wherein the constituents exhibit transverse isotropy and the cells have different configurations. Mechanical imperfect contact at the interface of the piezoelectric composites is studied via linear spring model. The statement of the problem for two-phase piezoelectric composites with mechanical imperfect contact is given. The local problems are formulated by means of the asymptotic homogenization method, and their solutions are found using complex variable theory. Analytical formulae are obtained for the effective properties of the composites with spring imperfect type of contact and different rhombic cells. Using the concept of a representative volume element (RVE), a finite element model is created, which combines the angular distribution of fibers and imperfect contact conditions (spring type) between the phases. Periodic boundary conditions are applied to the RVE, so that effective material properties can be derived. The fibers are distributed in such a way that the microstructure is characterized by a rhombic cell. The presented numerical homogenization technique is validated by comparing results with theoretical approach reported in the literature. Some studies of particular cases, numerical examples, and comparisons between the two aforementioned methods with other theoretical results illustrate that the model is efficient for the analysis of composites with presence of rhombic cells and the aforementioned imperfect contact.     

Development of surface plasmon resonance-based sensor for detection of silver nanoparticles in food and the environment

Silver nanoparticles are recognized as effective antimicrobial agents and have been implemented in various consumer products including washing machines, refrigerators, clothing, medical devices, and food packaging. Alongside the silver nanoparticles benefits, their novel properties have raised concerns about possible adverse effects on biological systems. To protect consumer's health and the environment, efficient monitoring of silver nanoparticles needs to be established. Here, we present the development of human metallothionein (MT) based surface plasmon resonance (SPR) sensor for rapid detection of nanosilver. Incorporation of human metallothionein 1A to the sensor surface enables screening for potentially biologically active silver nanoparticles at parts per billion sensitivity. Other protein ligands were also tested for binding capacity of the nanosilver and were found to be inferior to the metallothionein. The biosensor has been characterized in terms of selectivity and sensitivity towards different types of silver nanoparticles and applied in measurements of real-life samples-such as fresh vegetables and river water. Our findings suggest that human MT1-based SPR sensor has the potential to be utilized as a routine screening method for silver nanoparticles, that can provide rapid and automated analysis dedicated to environmental and food safety monitoring.     

Preconcentration and detection of chlorinated organic compounds and benzene

Remote and automated detection of organic compounds in subsurface aquifers is crucial to superfund monitoring and environmental remediation. Current monitoring techniques use expensive laboratory instruments and trained personnel. The use of a filled tubular preconcentrator combined with a chemicapacitive detector array presents an attractive option for the unattended monitoring of these compounds. Five preconcentrator materials were exposed to common target compounds of subsurface remediation projects (1,1,2-trichloroethane, trichloroethylene, t-1,2-dichloroethylene, benzene, and perchloroethylene). Rapid heating of the tube caused the collected, concentrated effluent to pass over the surface of a chemicapacitive detector array coated with four different sorbent polymers. A system containing a porous ladder polymer and the sensor array was subsequently used to sample the analytes injected onto sand in a laboratory test, simulating a subsurface environment. With extended collection times, effective detection limits of 5 ± 3 ppbV for 1,1,2-trichloroethane and 145 ± 60 ppbV for benzene were achieved. Effects of the preconcentrator material structure, the collection time, and sensor material on the system performance were observed. The resultant system presents a solution for remote, periodic monitoring of chlorinated organic compounds and other volatile organic compounds in a soil matrix.     

Design of a RF window for 170 GHz, 1 MW gyrotron for ECRH application

This paper describes the design of a large sized diamond window for 1 MW, 170 GHz gyrotron. The diameter and the thickness of the diamond window are 80 mm and 1.482 mm, respectively, whose edge is directly cooled by water. The CST microwave studio has been used for the S-parameter, and finite element analysis code ANSYS has been used for the thermal and the structural simulation. The return loss (S₁₁) and insertion loss (S₂₁) of the 170 GHz gyrotron window have been found −39.80 dB and −0.011 dB, respectively. The thermal and structural analysis of RF window the 397 K temperature at disk center and maximum displacement 0.01 mm has been found in the window disk during the thermal analysis.     

New indoles from the roots of Brassica rapa ssp. campestris

Two new indoles, 2-C-β-D-glucopyranosyl-1-methoxyindole-3-acetonitrile (1) and 6-hydroxy-1-methylindole3-acetonitrile (2), along with two known indoles [caulilexin C (3) and arvelexin (4)], were isolated from turnip roots (Brassica rapa ssp. campestris L.). The structures of the compounds were established on the basis of NMR, FAB-MS, and IR spectroscopic data.     

Pore-Scale Analysis of NAPL Blob Dissolution and Mobilization in Porous Media

A pore-scale analysis of nonaqueous phase liquid (NAPL) blob dissolution and mobilization in porous media was presented. Dissolution kinetics of residual NAPLs in an otherwise water-saturated porous medium was investigated by conducting micromodel experiments. Changes in residual NAPL volume were measured from recorded video images to calculate the mass transfer coefficient, K and the lumped mass transfer rate coefficient, k. The morphological characteristics of the blobs such as specific and intrinsic area were found to be independent of water flow rate except at NAPL saturations below 2%. Dissolution process was also investigated by separating the mass transfer into zones of mobile and immobile water. The fractions of total residual NAPL perimeters in contact with mobile water and immobile water were measured and their relationship to the mass transfer coefficient was discussed. In general, residual NAPLs are removed by dissolution and mobilization. Although these two mechanisms were studied individually by others, their simultaneous occurrence was not considered. Therefore, in this study, mobilization of dissolving NAPL blobs was investigated by an analysis of the forces acting on a trapped NAPL blob. A dimensional analysis was performed to quantify the residual blob mobilization in terms of dimensionless Capillary number (Ca _I). If Ca _I is equal to or greater than the trapping number defined as , then blob mobilization is expected.     

Influence of imperfect elastic contact condition on the antiplane effective properties of piezoelectric fibrous composites

A fiber-reinforced periodic piezoelectric composite, where the constituents exhibit transverse isotropic properties, is considered. The fiber cross-section is circular and the periodicity is the same in two orthogonal directions. Imperfect mechanic contact conditions at the interphase between the matrix and fibers are represented in parametric form. In order to analyze the influence of the imperfect interface effect over the behavior of the composite, the effective axial piezoelectric moduli are obtained by means of the Asymptotic Homogenization Method. Some numerical examples are given.