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Pt is one of the most employed catalysts for methanol catalysis in direct methanol fuel cell (DMFC). In this study, carbon nanotube (CNT) surface was used for catalyst reduction. By using ethylene glycol as a reducing agent, Pt catalyst precursor (H 2 PtCl6 · 6H 2 O) was reduced on the CNTs by a novel method called semi-reflux chemical reduction system (SRCRS). The SRCRS can effectively reduce the catalyst preparation time and the catalyst distribution density can also be much increased by adjusting the pH value. Cyclic voltammetry (CV) and ICP-MS results were used for electrochemical surface area (ECA) calculation. The ECA result was comparable to that of commercial available Pt.

Proton exchange membrane fuel cells (PEMFC) have received attention owing to their low operating temperature and quick start-up. Fuel cells have high material costs, low power density and short lifetime, which are major barriers to their use. In order to become commercially viable, PEMFC bipolar plates must be cheaper, lighter, and more compact. Here, carbon nanotubes (CNTs) are assessed as a reinforcement for either thermoplastic or thermoset-based nanocomposite bipolar plates, because of such properties as superior mechanical strength, high electrical and thermal properties, and light weight. CNTs have strong intrinsic van der Waals forces with each other, which hold together in ropes and bundles, resulting in very low solubility in most solvents. Therefore, homogeneous dispersion of CNTs in the matrix is key. How to achieve homogeneous dispersion of CNTs by chemical modification is discussed. Owing to the formation of effective 3D electrical conducting networks better properties are obtained such as high mechanical strength, improved electrical conductivity and cell performance when the functionalized CNT is incorporated in a bipolar plate. Functionalized CNT reinforcement is a promising method to manufacture alternative high performance bipolar plates for PEM fuel cell applications.

In many brain regions, Ca2+ influx through presynaptic P2X receptors influences GABA release from interneurones. In patch-clamp recordings of Purkinje cells (PCs) in rat cerebellar slices, broad spectrum P2 receptor antagonists, PPADS (30 mu M) or suramin (12 mu M), result in a decreased amplitude and increased failure rate of minimal evoked GABAergic synaptic currents from basket cells. The effect is mimicked by desensitizing P2X1/3-containing receptors with alpha,beta-methylene ATP. This suggests presynaptic facilitation of GABA release via P2XR-mediated Ca2+ influx activated by endogenously released ATP. In contrast, activation of P2Y4 receptors (using UTP, 30 mu M, but not P2Y1 or P2Y6 receptor ligands) results in inhibition of GABA release. Immunological studies reveal the presence of most known P2Rs in >= 20% of GABAergic terminals in the cerebellum. P2X3 receptors and P2Y4 receptors occur in approximately 60% and 50% of GABAergic synaptosomes respectively and are localized presynaptically. Previous studies report that PC output is also influenced by postsynaptic purinergic receptors located on both PCs and interneurones.The high Ca2+ permeability of the P2X receptor and the ability of ATP to influence intracellular Ca2+ levels via P2Y receptor-mediated intracellular pathways make ATP the ideal transmitter for the multisite bidirectional modulation of the cerebellar cortical neuronal network. (c) 2008 Published by Elsevier Ltd.

Storing public health data in a centralize location for biosurveillance can be expensive and susceptible to server down time. We compared the performance of a distributed data grid against a centralized database to determine if a grid framework can provide fast, reliable, and inexpensive biosurveillance system. The results demonstrated that the distributed data grid had close performance with a high-end centralized system, suggesting that a grid framework can be a solution for low-cost, decentralized system.

The increasing volume of unsolicited bulk e-mail (also known as spam) has generated a need for reliable antispam filters. Using a classifier based on machine learning techniques to automatically filter out spam e-mail has drawn many researchers' attention. In this paper, we review some of relevant ideas and do a set of systematic experiments on e-mail categorization, which has been conducted with four machine learning algorithms applied to different parts of e-mail. Experimental results reveal that the header of e-mail provides very useful information for all the machine learning algorithms considered to detect spam e-mail.

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Nitrogen-doped graphene (NGR) was incorporated as a catalyst and used as a counter electrode in dye-sensitized solar cells (DSSCs). The NGR electrodes showed a number of advantages over other electrodes that consisted solely of graphene or Pt films, including high charge transfer rates, low resistance to diffusion, and low internal resistance.

We synthesized platelet graphitic-nanofibres (GNFs) directly onto FTO glass and applied this forest of platelet GNFs as a highly porous structural counter-electrode in dye-sensitized solar cells (DSSCs). We investigated the electrochemical properties of counter-electrodes made from the highly porous structural GNFs and the photoconversion performance of the cells made with these electrodes.

We herein describe our use of a water–ethylene method to prepare a composite material consisting of platinum nanoparticles and graphene. Results obtained using XPS and XRD show that the degree of reduction of graphene was increased by the incorporation of Pt, and in addition, the increased concentration of defects was confirmed by the D/G ratio of the Raman spectra obtained. In comparison with Pt films, results obtained using CV and EIS showed that the electrocatalytic ability of the composite material was greater, and afforded a higher charge transfer rate, an improved exchange current density, and a decreased internal resistance. SEM images showed that the morphology of PtNP/GR counter electrodes is characterized by a smooth surface, however, resulting in a lower resistance to diffusion, thereby improving the total redox reaction rate that occurs at the counter electrode. PtNP/GR electrodes have a number of advantages over other electrodes that consist solely of graphene or Pt films, including a high rate of charge transfer, a low internal resistance, and a low resistance to diffusion. In our study, we showed that DSSCs that incorporate platinum-grafted graphene had a conversion efficiency of 6.35%, which is 20% higher than that of devices with platinized FTO.

We directly synthesized a platinum-nanoparticles/graphitic-nanofibers (PtNPs/GNFs) hybrid nanostructure on FTO glass. We applied this structure as a three-dimensional counter electrode in dye-sensitized solar cells (DSSCs), and investigated the cells' photoconversion performance.

This study fabricates dye-sensitized solar cells (DSSCs) based on TiO(2)/multi-walled carbon nanotube (MWCNT) nanocomposite photoanodes obtained by the modified acid-catalyzed sol-gel procedure. Results show that incorporating MWCNTs into a TiO(2)-based electrode efficiently improves the physicochemical properties of the solar cell. The results of dye adsorption and cell performance measurements indicate that introducing MWCNTs would improve the roughness factor (from 834 to 1267) of the electrode and the charge recombination of electron/hole (e(-)/h(+)) pairs. These significant changes could lead to higher adsorbed dye quantities, photocurrent and DSSC cell performance. Nevertheless, a higher loading of MWCNTs causes light-harvesting competition that affects the light adsorption of the dye-sensitizer, and consequently reduces the cell efficiency. This study suggests an optimum MWCNT loading in the electrode of 0.3 wt%, and proposes a sol-gel synthesis procedure as a promising method of preparing the TiO(2)-based nanocomposite.

This study presents a novel one-step preparation of functionalized multi-walled carbon nanotubes (MWCNTs) by free-radical modification. MA-POA, i.e.maleic anhydride (MA) grafted on molecular weight 400 and 2000 poly(oxyalkylene)amines (POA400 and POA2000), was attached onto the MWCNTs, forming MWCNTs/MA-POA400 and MWCNTs/MA-POA2000. The functionalized MWCNTs, especially MWCNTs/MA-POA2000, exhibited higher solubility than the pristine MWCNTs in organic solvents and were well dispersion in a vinyl ester matrix. Furthermore, this study also investigated mechanical, electrical and single fuel cell properties of functionalized MWCNT nanocomposite bipolar plates for use in polymer electrolyte membrane fuel cells (PEMFCs). The flexural strength of the nanocomposite bipolar plates containing 2 wt% MWCNTs/MA-POA2000 was increased from 28 MPa to 48.33MPa. In addition, the in-plane and through-plane electrical conductivities and half-cell resistance of the nanocomposite bipolar plates were 780%, 168% and 253%, respectivel,y higher than those of the original composite bipolar plates with the addition of only a small quantity (1 wt%) of MWCNTs/MA-POA2000. The maximum current density and power density of the single cell tests of the nanocomposite bipolar plate with 1 wt% MWCNTs/MA-POA2000 were enhanced from 1.03 to 1.32 A cm−2 and from 0.392 to 0.580 W cm−2, respectively. The overall performance confirms the MWCNTs/MA-POA2000 nanocomposite bipolar plates prepared in this study are suitable for PEMFC application.

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The coupled mode equations governing the interaction of the guided magnetic waves propagating in opposite directions along a ferrimagnetic film having a periodic array of shallow rectangular grooves on one of its surfaces are deduced using quasi‐optical techniques for the case in which the magnetization is normal to the surfaces of the film. Effects caused by the deviation of the wave frequency from the Bragg frequency and by the presence of small magnetic losses are also taken into account. For a surface corrugation extending only for a finite length along the film, the longitudinal boundary value problem is solved to obtain the reflection, the transmission, and the absorption coefficients. The coupled mode equations are found to yield correctly the power conservation relation.

The partial differential equations governing the transport of the slowly varying amplitudes of the interacting guided magnetic waves supported by a yttrium iron garnet film having a periodic array of shallow grooves on one of its surfaces are deduced using quasioptical techniques for the case in which the magnetization is normal to the midplane of the film and the wave vectors are inclined to the grating vector. For the periodic array extending only for a finite length along the film, the longitudinal boundary value problem is solved for an incident‐plane guided magnetic wave to obtain the reflection, the transmission, and the absorption coefficients. The important characteristics of the reflection coefficient are examined and the various dephasing effects on the reflection characteristics are investigated.

The wave-packet of a magnetic wave on reflection at an interface between a ferrimagnetic medium and free space is shown to undergo no lateral shift but only a time delay. The time delay introduced on reflection is included to obtain a quasi-optical description for the group delay of a magnetic wave guided by a planar slab of ferrimagnet in free space for the case of the magnetizations (a) normal to the surfaces of the slab, and, (b) parallel to the surfaces of the slab and to the direction of propagation. The group delay of the guided magnetic wave is caused partly by the group delay produced in the bulk of the ferrimagnet and partly by the group delay produced on reflections. The characteristics of these two contributions to the resultant group delay of the guided magnetic wave are examined.

The reflection and transmission coefficients for the backward magnetic waves on a YIG film with periodic surface corrugations are systematically deduced from the solution of the full magnetostatic boundary-value problem. The phenomenological boundary condition for the slowly varying amplitude in the coupled mode equations is also obtained.

Magnetostatic propagation in layered structures with magnetization in the plane and perpendicular to the direction of propagation has been studied theoretically and experimentally. Problems in device application of this geometry include low power saturation levels and limited delay times for reasonable film sizes. Both problems are minimized by use of normal magnetization giving volume modes having isotropic propagation in the film plane. This work reports theoretical and experimental studies for a normally‐magnetized ground plane‐dielectric‐YIG‐dielectric‐ground plane structure. The dispersion relation is derived for the magnetostatic limit and this geometry. This theory indicates that with at least one ground plane within a magnetostatic wavelength of the YIG, significant modification of the dispersion characteristic can be obtained. Nondispersive regions of approximately 10% bandwidths are predicted. Experimental studies with an LPE‐YIG film thickness of 10μm and a dielectric thickness of 8 to 20 times the YIG thickness show nondispersive propagation over bandwidths > 100MHz at 1.6GHz. Agreement between theory and experiment is good. Saturation characteristics are better than those of similar magnetostatic surface wave devices.

Platinum nanocubes (PtNCs) were deposited onto a fluorine-doped tin oxide glass by electrochemical deposition (ECD) method and utilized as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). In this study, we controlled the growth of the crystalline plane to synthesize the single-crystal PtNCs at room temperature. The morphologies and crystalline nanostructure of the ECD PtNCs were examined by field emission scanning electron microscopy and high-resolution transmission electron microscopy. The surface roughness of the ECD PtNCs was examined by atomic force microscopy. The electrochemical properties of the ECD PtNCs were analyzed by cyclic voltammetry, Tafel polarization, and electrochemical impedance spectra. The Pt loading was examined by inductively coupled plasma mass spectrometry. The DSSCs were assembled via an N719 dye-sensitized titanium dioxide working electrode, an iodine-based electrolyte, and a CE. The photoelectric conversion efficiency (PCE) of the DSSCs with the ECD PtNC CE was examined under the illumination of AM 1.5 (100 mWcm(-2)). The PtNCs in this study presented a single-crystal nanostructure that can raise the electron mobility to let up the charge-transfer impedance and promote the charge-transfer rate. In this work, the electrocatalytic mass activity (MA) of the Pt film and PtNCs was 1.508 and 4.088 mAmg(-1), respectively, and the MA of PtNCs was 2.71 times than that of the Pt film. The DSSCs with the pulse-ECD PtNC CE showed a PCE of 6.48 %, which is higher than the cell using the conventional Pt film CE (a PCE of 6.18 %). In contrast to the conventional Pt film CE which is fabricated by electron beam evaporation method, our pulse-ECD PtNCs maximized the Pt catalytic properties as a CE in DSSCs. The results demonstrated that the PtNCs played a good catalyst for iodide/triiodide redox couple reactions in the DSSCs and provided a potential strategy for electrochemical catalytic applications.

The insertion loss for the magnetic waves on a periodically corrugated YIG film magnetized normal to the film surface is deduced from the solution of the full magnetostatic boundary‐value problem taking into account the effect of the finite linewidth of the ferromagnetic resonance. It is found that the contribution to the insertion loss due to the distributed reflection and the mode conversion caused by the periodic surface corrugation is decreased as the resonance linewidth is increased.