Nitrogen-Containing Carbon Nanostructures as Oxygen-Reduction Catalysts

Nitrogen-containing carbon nanostructure (CN _x ) catalysts developed by acetonitrile pyrolysis have been studied to better understand their role in the oxygen reduction reaction (ORR) in PEM and direct methanol fuel cell environments. Additional functionalization of the CN _x catalysts with nitric acid has the ability to improve both the activity and selectivity towards ORR.     

Macrophage-like Cells Are Responsive to Titania Nanotube Intertube Spacing—An In Vitro Study

With the introduction of a new interdisciplinary field, osteoimmunology, today, it is well acknowledged that biomaterial-induced inflammation is modulated by immune cells, primarily macrophages, and can be controlled by nanotopographical cues. Recent studies have investigated the effect of surface properties in modulating the immune reaction, and literature data indicate that various surface cues can dictate both the immune response and bone tissue repair. In this context, the purpose of the present study was to investigate the effects of titanium dioxide nanotube (TNT) interspacing on the response of the macrophage-like cell line RAW 264.7. The cells were maintained in contact with the surfaces of flat titanium (Ti) and anodic TNTs with an intertube spacing of 20 nm (TNT20) and 80 nm (TNT80), under standard or pro-inflammatory conditions. The results revealed that nanotube interspacing can influence macrophage response in terms of cell survival and proliferation, cellular morphology and polarization, cytokine/chemokine expression, and foreign body reaction. While the nanostructured topography did not tune the macrophages’ differentiation into osteoclasts, this behavior was significantly reduced as compared to flat Ti surface. Overall, this study provides a new insight into how nanotubes’ morphological features, particularly intertube spacing, could affect macrophage behavior.     

Effects of project size and resource constraints on project duration through priority rule-base heuristics

Priority rules are one of the frequently used methods in project programming with resource-constraints. In this paper, the effects of project size and number of resource constraints on project duration are compared to the performances of pre-selected priority rules. Ten projects in different sizes have been programmed with 3, 5, 7, 9, and 11 limited-resource conditions by means of MRPL (Maximum Remaining Path Length), LFT (Latest Finish Time), MNSLCK (Minimum Slack Time), EFT (Earliest Finish Time), and LST (Latest Start Time) priority rules. When the number of resource constraints is low, the performance of MRPL is generally observed to be higher. As the number of resource constraints increases, a decrease in the performance of MRPL is observed in contrast with an increase in the performance of LFT.     

Modelling of alternating-current machines having multiple rotorcircuits

The modeling of a synchronous or an asynchronous machine forms the basis of simulation investigations made with high-powered computers. Many phenomena and processes require corresponding refinement of the models used, and an increase in input in the form of fictive rotor circuits. A method is presented which has been tested out over a relatively long period of time. The general equations contain none of the usual approximations, and can be programmed quite readily. Numerical examples are given as an aid in applying the procedures     

Effect of Co Content Upon the Bulk Structure of Sr- and Co-doped LaFeO3

The bulk structure was investigated for Fe-based perovskite-type oxides with the formula La_0.6Sr_0.4Co_yFe_1−yO_3−δ (y = 0.1, 0.2, and 0.3). The materials were confirmed to be stoichiometric with respect to oxygen under ambient conditions and the structural features were then further characterized under different environments as a function of temperature. Under reducing atmospheres, the degree of reduction increased with Co content, suggesting the presence of preferential oxidation of Fe over Co. Under milder conditions, oxygen vacancy formation was not proportional to Co content, which was likely caused by an electronic structure transition. The unit cell parameters were also shown to strongly depend upon Co content, temperature, and environment. A rhombohedral to cubic transition occurred at lower temperatures for higher Co content, but showed less dependence upon environment. A change in the thermal expansion behavior occurred at the temperature where oxygen vacancies formed leading to two regions of linear thermal expansion. The use of lattice parameters compared to dilatometry allowed for the simultaneous monitoring of unit cell symmetry and expansion behavior so the link between thermal properties and unit cell symmetry could be firmly established.     

Investigating the Effectiveness of Certain Priority Rules on Resource Scheduling of Housing Estate Projects

The heuristic method is one of the methods used for the scheduling of resource-constrained projects. This method is commonly used in programming the projects with high number of activities and resources such as construction investments. This paper investigates the effectiveness of three heuristic method priority rules applied in the resource scheduling of ten Turkish housing estate projects which were scheduled according to three preselected priority rules [maximum remaining path length (MRPL), latest finish time (LFT), and minimum slack time (MNSLCK)] in resource-constrained conditions. The performance of each priority rule was evaluated in relation to the duration of the project. The results revealed that MRPL priority reduced the project duration to minimum in six projects, whereas LFT priority yielded the best duration results in three projects and MNSLCK priority in only one project.     

Electrochemical genosensor based on colloidal gold nanoparticles for the detection of Factor V Leiden mutation using disposable pencil graphite electrodes

Electrochemical genosensors for the detection of the Factor V Leiden mutation from polymerase chain reaction (PCR) amplicons using the oxidation signal of colloidal gold (Au) is described. A pencil graphite electrode (PGE) modified with target DNA, when hybridized with complementary probes conjugated to Au nanoparticles, responded with the appearance of a Au oxide wave at approximately +1.20 V. Specific probes were immobilized onto the Au nanoparticles in two different modes: (a) Inosine-substituted probes were covalently attached from their amino groups at the 5' end using N-(3-dimethylamino)propyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide (NHS) as a coupling agent onto a carboxylate-terminated l-cysteine self-assembled monolayer (SAM) preformed on the Au nanoparticles, and (b) probes with a hexanethiol group at their 5' phosphate end formed a SAM on Au nanoparticles. The genosensor relies on the hybridization of the probes with their complementary targets, which are covalently immobilized at the PGE surface. Au-tagged 23-mer capture probes were challenged with the synthetic 23-mer target, 131-base single-stranded DNA or denatured 256-base polymerase chain reaction (PCR) amplicon. The appearance of the Au oxidation signal shortened the assay time and simplified the detection of the Factor V Leiden mutation from PCR amplified real samples. The discrimination between the homozygous and heterozygous mutations was also established by comparing the peak currents of the Au signals. Numerous factors affecting the hybridization and nonspecific binding events were optimized. The detection limit for the PCR amplicons was found to be as low as 0.78 fmol; thus, it is suitable for point-of-care applications.     

Stochastic frequency signature for chemical sensing using noninvasive neuronelectronic interface

The detection of chemical agents is important in many areas including environmental pollutants, toxins, biological and chemical pollutants. As "smart" cells, with strong information encoding ability, neurons can be treated as independent sensing elements. A hybrid circuit of a semiconductor chip with dissociated neurons formed both sensors and transducers. Stochastic frequency spectrum was used to differentiate a mixture of chemical agents with effect on the opening of different ion channels. The frequency of spike trains revealed the concentration of the chemical agent, where the characteristic tuning curve revealed the identity. "Fatigue" experiment was performed to explore the "refreshing" ability and "memory" effect of neurons by cyclic and cascaded sensing. "Neuronelectronic noses" such as this should have wide potential applications, most notably in environmental and medical monitoring.     

Sorption of acid red 57 from aqueous solution onto sepiolite

Sepiolite, a highly porous mineral, is becoming widely used as an alternative material in areas where sorptive, catalytic and rheological applications are required. High ion exchange capacity and high surface area and more importantly its relatively cheap price make it an attractive adsorbent. In this study, the adsorption of acid red 57 by natural mesoporous sepiolite has been examined in order to measure the ability of this mineral to remove coloured textile dyes from wastewater. For this purpose, a series of batch adsorption tests of acid red 57 from aqueous sepiolite solutions have been systematically investigated as a function of parameters such as pH, ionic strength and temperature. Adsorption equilibrium was reached within 1h. The removal of acid red 57 decreases with pH from 3 to 9 and temperature from 25 to 55 degrees C, whereas it increases with ionic strength from 0 to 0.5 mol L(-1). Adsorption isotherms of acid red on sepiolite were determined and correlated with common isotherm equations such as Langmuir and Freundlich models. It was found that the Langmuir model appears to fit the isotherm data better than the Freundlich model. The physical properties of this adsorbent were consistent with the parameters obtained from the isotherm equations. Approximately, 21.49% weight loss was observed. The surface area value of sepiolite was 342 m2 g(-1) at 105 degrees C, and it increased to 357 m2 g(-1) at 200 degrees C. Further increase in temperature caused channel plugging and crystal structure deformation, as a result the surface area values showed a decrease with temperature. The data obtained from adsorption isotherms at different temperatures have been used to calculate some thermodynamic quantities such as the Gibbs energy, heat and entropy of adsorption. The thermodynamic data indicate that acid red 57 adsorption onto sepiolite is characterized by physical adsorption. The dimensionless separation factor (RL) have shown that sepiolite can be used for removal of acid red 57 from aqueous solutions. The sorption capacity of the sepiolite is comparable to the other available adsorbents, and it is quite cheaper.     

Estimation of thermally stimulated current in as grown TlGaSeS layered single crystals by multilayered perceptron neural network

This paper presents an artificial neural network approach to compute thermally stimulated current (TSC) in as-grown TlGaSeS layered single crystals. The experimental data have been obtained from TSC measurements. The network has been trained by a genetic algorithm (GA). The results confirmed that the proposed model could provide an accurate computation of the TSC.