Continuous size-based focusing and bifurcating microparticle streams using a negative dielectrophoretic system

Dielectrophoresis (DEP) is an electrokinetic phenomenon which is used for manipulating micro- and nanoparticles in micron-sized devices with high sensitivity. In recent years, electrode-based DEP by patterning narrow oblique electrodes in microchannels has been used for particle manipulation. In this theoretic study, a microchannel with triangular electrodes is presented and a detailed comparison with oblique electrodes is made. For each shape, the behavior of particles is compared for three different configurations of applied voltages. Electric field, resultant DEP force, and particle trajectories for configurations are computed by means of Rayan native code. The separation efficiency of the two systems is assessed and compared afterward. The results demonstrate higher lateral DEP force, responsible for particle separation, distributed wider across the channel width for triangular shape electrodes in comparison with the oblique ones. The proposed electrode shape also shows the ability of particle separation by attracting negative DEP particles to or propelling them from the flow centerline, according to the configuration of applied voltages. A major deficiency of the oblique electrodes, which is the streamwise variation of the lateral DEP force direction near the electrodes, is also eliminated in the proposed electrode shape. In addition, with a proper voltages configuration, the triangular electrodes require lower voltages for particle focusing in comparison with the oblique ones.     

The applicability of neural networks in the determination of soil profiles

The drilling of a number of boreholes to determine the soil profile of a given area is time consuming and costly. This paper describes estimated soil profiles obtained using a model based on artificial neural networks (ANN). ANN is a powerful data-modelling tool capable of capturing and representing complex relationships between input and output. It deals with many multi-variate problems for which an exact analytical model does not exist or is very difficult and time consuming to develop. The main settlement in the Adapazari region was selected to demonstrate the capability of such model. The results obtained using ANN are promising when compared with the soil profile obtained from boreholes.      

Magnetotransport study on as-grown and annealed n- and p-type modulation-doped GaInNAs/GaAs strained quantum well structures

We report the observation of thermal annealing- and nitrogen-induced effects on electronic transport properties of as-grown and annealed n- and p-type modulation-doped Ga_{1 - x}In_xN_yAs_{1 - y} (x = 0.32, y = 0, 0.009, and 0.012) strained quantum well (QW) structures using magnetotransport measurements. Strong and well-resolved Shubnikov de Haas (SdH) oscillations are observed at magnetic fields as low as 3 T and persist to temperatures as high as 20 K, which are used to determine effective mass, 2D carrier density, and Fermi energy. The analysis of temperature dependence of SdH oscillations revealed that the electron mass enhances with increasing nitrogen content. Furthermore, even the current theory of dilute nitrides does not predict a change in hole effective mass; nitrogen dependency of hole effective mass is found and attributed to both strain- and confinement-induced effects on the valence band. Both electron and hole effective masses are changed after thermal annealing process. Although all samples were doped with the same density, the presence of nitrogen in n-type material gives rise to an enhancement in the 2D electron density compared to the 2D hole density as a result of enhanced effective mass due to the effect of nitrogen on conduction band. Our results reveal that effective mass and 2D carrier density can be tailored by nitrogen composition and thermal annealing-induced effects.

PACS

72.00.00; 72.15.Gd; 72.80.Ey     

Synthesis and characterization of novel fluorine‐containing methacrylate copolymers: Reactivity ratios,thermal properties,and antimicrobial activity

The free‐radical‐initiated copolymerization of 2‐(4‐acetylphenoxy)‐2‐oxoethyl‐2‐methylacrylate (AOEMA) and 2‐(4‐benzoylphenoxy)‐2‐oxoethyl‐2‐methylacrylate (BOEMA) with 2‐[(4‐fluorophenyoxy]‐2‐oxoethyl‐2‐methylacrylate (FPEMA) were carried out in 1,4‐dioxane solution at 65°C using 2,2′‐azobisisobutyronitrile as an initiator with different monomer‐to‐monomer ratios in the feed. The monomers and copolymers were characterized by FTIR and ¹H‐ and ¹³C‐NMR spectral studies. ¹H‐NMR analysis was used to determine the molar fractions of AOEMA, BOEMA, and FPEMA in the copolymers. The reactivity ratios of the monomers were determined by the application of Fineman‐Ross and Kelen‐Tudos methods. The analysis of reactivity ratios revealed that BOEMA and AOEMA are less reactive than FPEMA, and copolymers formed are statistically in nature. The molecular weights (M _w and M _n) and polydispersity index of the polymers were determined using gel permeation chromatography. Thermogravimetric analysis of the polymers reveals that the thermal stability of the copolymers increases with an increase in the mole fraction of FPEMA in the copolymers. Glass transition temperatures of the copolymers were found to decrease with an increase in the mole fraction of FPEMA in the copolymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Decolorisation treatments of azo dye waste waters including dichlorotriazinyl reactive groups by using advanced oxidation method

Decolorisation treatments of azo dye waste waters, which include dichlorotriazinyl reactive groups, were investigated by using ultraviolet (UV) radiation and hydrogen peroxide at various exposure times. Decolorisation time decreased when UV radiation power and hydrogen peroxide concentration increased. Colour removal reached 98.0–99.5% by using this method. Some environmental parameters of decolorised waste water, such as biological oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), total inorganic carbon (TIC), total carbon (TC), adsorbable organohalides (AOX), sulphate and chloride, were determined. It was concluded that TOC, COD and AOX decreased while BOD increased and sulphate ions remained unchanged. These results suggested that the dye molecules were totally destroyed and some of these decomposition products were removed as carbon dioxide and water to some degree.     

An Investigation into the Corrosion Behavior of MgO/ZrO<Subscript>2</Subscript> Nanocomposite Coatings Prepared by Plasma Electrolytic Oxidation on the AZ91 Magnesium Alloy

Plasma electrolytic oxidation (PEO) of AZ91 Mg alloys was performed in ZrO₂ nanoparticles containing Na₂SiO₃-based electrolytes. The phase composition and the microstructure of PEO coatings were analyzed by x-ray diffraction and scanning electron microscopy followed by energy dispersive spectroscopy. Pitting corrosion properties of the coatings were investigated using cyclic polarization and electrochemical impedance spectroscopy tests in a Ringer solution. The results showed the better pitting corrosion resistance of the composite coating, as compared to the oxide one, due to the thickened inner layer and the decrease in the surface defects of the composite coating. Also, the PEO process decreased the corrosion current density from 25.06 µA/cm² in the Mg alloy to 2.7 µA/cm² in the oxide coating and 0.47 µA/cm² in the composite coating.     

Ploidy and liquid-holding recovery in yeasts sensitive to radiation and nitrous acid

The effects of genome ploidy and posttreatment incubation on inactivation by nitrous acid (NA) were studied in normal, radio- and nitrous acid-sensitive strains of yeast. In normal yeast cells the increase of ploidy (haploid to triploid) resulted in "the protective effect", i.e. haploid cells were the most sensitive, triploid -- the most resistant. This "protective effect" is absent in polyploid yeast homozygous for the xrs1-5 (rad 54) mutation; in this case the NA-sensitivity rises with the increase of ploidy, i.e. haploid cells are the most resistant ones. The effect of liquid holding (LH) after the NA treatment depends on the genetic background and ploidy of treated cells. Posttreatment incubation in buffer has practically no effect on the survival of wild-type Berkeley's yeast strains (1n, 2n, 3n). The highly homozygous haploid strains from Zakharov' collection, both wild type and xrs1-5 mutant, exhibit no LH-recovery too. However the death of wild-type cells drastically rises in LH-condition as the ploidy increases. 24 hours incubation in buffer results in at least a ten-fold decrease in survival of wild type 2n, 3n, 4n cells. The loss of viability is proportional to the time of incubation, but the cell titer being constant. The strains (2n, 3n, 4n) homozygous for the xrs1-5 mutation (rad 54) show considerable LH-recovery. It is supposed that the xrs1-5 mutation results in the derepression of the prereplicative pathway of LH-recovery which eliminates the NA-INDUCED DAMAGE OF DNA.     

Phenolic resin binder for the production of metallurgical quality briquettes from coke breeze: Part III the effect of the type of acidic hardeners on the quality of the formed coke and the possibility to avoid the curing stage to produce metallurgical briquettes with enough strength

In order to avoid the curing stage in formed coke production, the effects of hardeners, on the tensile strength of the briquettes bonded with resole binders of F / P = 2.0 and N / P ratios ranging 0.1–0.5, were studied. The raw briquettes were produced by mixing the resole binders containing these hardeners, with the coke breeze. They were hardened at room temperature for 24 h and also at 200 °C for 2 h. The briquettes were also produced from the resole binders of the same N / P but containing no hardener, and cured at 200 °C for 2 h. The tensile strengths of the briquettes were measured. H₃PO₄ resulted in the briquettes having the lowest tensile strength under any conditions investigated. H₂SO₄ and p-TSA hardeners were found to be unsuitable for the aim of this investigation, because they could not fully harden the briquettes at room temperature. ATP resulted in the briquettes of the highest tensile strength of 52.13 MPa, with the resole binder of N / P = 0.1 after 24 h hardening at room temperature but resulted in briquettes of relatively lower tensile strength when the N / P ratio of resoles was increased. By blending ATP and p-TSA it became possible to produce formed coke with sufficient tensile strength by hardening them at room temperature.