Towards crossbar nanoarray structure via microcontact printing

The method for patterning arrays of multiwalled carbon nanotubes (MWCNT's) in symmetric patterns to form junctions has been demonstrated. This has been achieved by incorporating the technique of microcontact printing using poly-dimethylsiloxane (PDMS) molds. Relief structures in the order of a few micrometers were fabricated that enabled the transfer of continuous horizontal arrays of MWCNT's in aqueous suspension in a controlled manner. The MWCNT's were patterned onto silicon microelectrode substrates with metallic gold electrodes. These were fabricated using standard photolithography techniques. The silicon substrates served as a base platform with suitable measurement microelectrodes for electrically characterizing the crossbar junction arrays. Using a dual alignment and stamping process, PDMS molds were inked alternatively with p-type and n-type suspensions of MWCNT's and transferred in a grid-like manner onto the base platform. Parallel alignment of the MWCNT's was achieved due to the geometry of the mold relief structures. This step-by-step assembly resulted in the formation of crossbar MWCNT array structures. Each of these crosspoints in the individual junction can function as an addressable crossbar nanodevice. The functionality of this circuit was demonstrated through the current-voltage (I-V) characteristics. Using these high-density crossarray circuit patterns, addressable nanostructures that form the building blocks of highly integrated device arrays can be built.     

Antioxidative activity of some vegetable peels determined in vitro by inducing liver lipid peroxidation

Vegetable peels are normally thrown away as kitchen wastes. In order to reveal their possible biological value, an in vitro investigation was performed on the antioxidative potential of some peel extracts such as Luffa cylindrica (Lc), Raphanus sativus (Rs), Daucus carota (Dc), Pisum sativum (Ps) and Trichosanthes dioica (Td) in ferrous sulphate (FeSO₄), hydrogen peroxide (H₂O₂) and carbon tetrachloride (CCl₄) induced lipid peroxidation (LPO) in liver, the major target organ of any drug. Effects were compared with that of a known antioxidant, butylated hydroxy anisole (BHA). A dose dependent inhibition was observed in all three, FeSO₄, H₂O₂ and CCl₄ induced hepatic LPO. However, with respect to one test peel (Rs), the two lower doses (125 and 250 μg/ml) were found to be ineffective. We suggest that the test peels have the potential to inhibit the lipid peroxidation and the observed differential antiperoxidative effects of the test peels could be the result of their poly phenol and flavonoid contents.     

Investigating the effects of chemical composition of motor oils on their viscosity indices using gas chromatography and chemometrics techniques

Abstract

In this study, we focused on combination of gas chromatography and chemometrics techniques for relating the viscosity indices (VI) of motor oils to their chemical compositions. Partial least square (PLS) algorithm was used for relating the retention times of the collected chromatograms to VI of motor oils. The constructed model showed acceptable statistical values which indicate the robustness of the developed PLS model. GC-MS analysis was used for identification of the important chemicals affecting the values of VIs. Nonane, Pentafluoropropionic acid, Phthalic acid, nonylphenol and Tetracosane were suggested to have positive impacts on the values of VIs of motor oils.     

Understanding the Effect of Tamarind Gum Proportion on the Properties of Tamarind Gum-Based Hydroethanolic Physical Hydrogels

The present study reports the analysis of properties of tamarind gum-based hydroethanolic physical hydrogels. The extent of hydrogen bonding in hydrogels decreased with an increase in tamarind gum content. The hydrogel with the highest tamarind gum content was found to be highly stable in terms of mechanical properties. There was a decrease in the resistive component of the hydrogels with an increase in tamarind gum content. The drug release from the hydrogels increased with an increase in the tamarind gum content. The antimicrobial activity of the drug-loaded hydrogels against Escherichia coli was excellent.     

First principles investigation of electronic, optical and transport properties of α- and β-phase of arsenic telluride

Crystalline arsenic telluride exists in two stable phases. The monoclinic α-phase transforms to rhombohedral β-phase under high pressure. The electronic, optical and transport properties of the two phases has been investigated using full potential linear augmented plane wave (LAPW) + local orbitals (lo) scheme, in the framework of DFT with generalized gradient approximation (GGA). We present the energy bands, density of states and optical properties like the complex dielectric functions and absorption coefficients. From the dynamic dielectric constant, the structural anisotropy for the monoclinic α-phase is clearly observed, whereas the longitudinal and transverse components are almost identical for the β-phase. The optical absorption profiles clearly indicate that β-phase has possibility of greater multiple direct and indirect interband transitions in the infrared and visible regions compared to the α-phase. The rhomohedral phase which has the Bi₂Te₃ type structure has the possibility of thermoelectric properties, therefore transport properties like electrical and thermal conductivities, Seebeck and Hall coefficients etc. are also calculated. Good agreements are found with the available experimental results.     

Analysis of n-alkanes in water samples by means of headspace solvent microextraction and gas chromatography

A simple and efficient headspace solvent microextraction (HSME) was developed for the simultaneous determination of the trace concentrations of some n-alkanes in water samples. Therefore, a microdrop of an organic solvent was extruded from the needle tip of a gas chromatographic syringe to the headspace above the surface of the solution in a sealed vial. Then the volatile organic compounds are extracted and concentrated in the microdrop. Next, the microdrop was retracted into the microsyringe and injected directly into the gas chromatograph. Experimental parameters which control the performance of HSME such as the type of microextraction solvent, organic drop and sample volume, sample stirring rate, sample solution and microsyringe needle temperatures, salt addition and exposure time profiles were investigated and optimized. Finally, the enrichment factor, dynamic linear range (DLR), limit of detection (LOD) and precision of the method were evaluated. Using optimum extraction conditions, good linearity with correlation coefficients in the range of 0.995相似文献   

Plasma polymer coatings to aid retinal pigment epithelial growth for transplantation in the treatment of age related macular degeneration

Subretinal transplantation of functioning retinal pigment epithelial (RPE) cells grown on a synthetic substrate is a potential treatment for age-related macular degeneration (AMD), a common cause of irreversible vision loss in developed countries. Plasma polymers give the opportunity to tailor the surface chemistry of the artificial substrate whilst maintaining the bulk properties. In this study, plasma polymers with different functionalities were investigated in terms of their effect on RPE attachment and growth. Plasma polymers of acrylic acid (AC), allyl amine (AM) and allyl alcohol (AL) were fabricated and characterised using X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Octadiene (OD) hydrocarbon films and tissue culture polystyrene were used as controls. Wettability varied from hydrophobic OD to relatively hydrophilic AC. XPS demonstrated four very different surfaces with the expected functionalities. Attachment, proliferation and morphological examination of an RPE cell line and primary RPE cells were investigated. Both cell types grew on all surfaces, with the exception of OD, although the proliferation rate of primary cells was low. Good epithelial morphology was also demonstrated. Plasma polymerised films show potential as cell carrier surfaces for RPE cells in the treatment of AMD.     

Application of artificial neural network in performance prediction of PEM fuel cell

Investigations on using artificial neural networks to predict the performance of single proton exchange membrane fuel cell has been carried out. Two sets of polarization data obtained at different temperatures and flow rates are used to create and simulate the network. Cell temperature, humidification temperatures, H₂/air flow rates and current density have been used as inputs, and voltage is used as observed (output) value to train and simulate the network. This nonlinear data are batch trained, and artificial neural network has been constructed using feed forward backpropagation algorithm. Performance of the training has been improved by increasing the number of neurons to reduce the error. Simulation results are in agreement with experimental data, and the corresponding networks are used to predict the polarization behavior for unknown inputs. Copyright © 2011 John Wiley & Sons, Ltd.     

Simultaneous preconcentration and determination of U(VI), Th(IV), Zr(IV) and Hf(IV) ions in aqueous samples using micelle-mediated extraction coupled to inductively coupled plasma-optical emission spectrometry

A simple cloud point extraction method followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for simultaneous preconcentration and determination of trace amounts of U(VI), Th(IV), Zr(IV) and Hf(IV) ions in aqueous samples. The metal ions in 50 ml of aqueous solution (containing 0.1 M sodium acetate, pH 6.0) were formed complexes with dibenzoylmethane (DBM). Then, Triton X-114 (0.2%, w/v) was added to the solution. By increasing the temperature of the solution up to 50 degrees C, a phase separation occurred. After centrifugation at 4000 rpm for 6 min, the surfactant-rich phase (sediment phase) was diluted with 1.0 ml of 20:80 (v/v) of methanol/1 M HNO(3). The metal ions were then determined using ICP-OES. Finally, the main factors affecting the cloud point extraction were evaluated and optimized. Under optimized conditions, enhancement factors in the range of 37.0-43.6 were obtained. The calibration graphs were linear in the range of 0.5-1500 microg l(-1) for Th and Zr, 0.5-500 microg l(-1) for Hf and 2.5-1240 microg l(-1) for U with correlation coefficients (r(2)) better than 0.9926. The detection limits were between 0.1 and 1.0 microg l(-1) and the R.S.D. values for seven replicates were lower than 6.1%.     

Optimization of Cu(II)-ion imprinted nanoparticles for trace monitoring of copper in water and fish samples using a Box–Behnken design

We describe a nanoparticles ion-imprinted polymer (IIP) for the selective preconcentration of copper (II) ions. It was obtained by precipitation polymerization from 2-vinylpyridine (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2,2′-azobisisobutyronitrile (the initiator), 2,9-dimethyl-1,10-phenanthroline (the copper-binding ligand) and nickel nitrate (the template ion) in acetonitrile solution. The IIP particles were characterized by Fourier Transformed Infra Red Spectroscopy (FTIR), thermogravimetric and differential thermal analysis, and by scanning electron microscopy. The optimization process was carried out using the Box–Behnken design (BBD). Effects of several factors such as solution pH for adsorption, amount of polymer, type, concentration and volume of eluent for extraction, as well as adsorption and desorption times were investigated. Under the optimum conditions (type and concentration of eluent, HCl 1.6 mol L^?1; volume of eluent, 6 mL; adsorption solution pH, 6.0; amount of polymer, 30 mg; adsorption time, 25 min; desorption time, 25 min), preconcentration factor of the proposed method was approximately 100. Under the optimized conditions, the detection limit was found to be 0.1 μg L^?1, while the relative standard deviation (RSD) for six replicate measurements was calculated to be <4%.