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Query: UMLS:C1862200 (RHE)
 1,093 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A series of carbon supported PtRu bimetallic catalysts with varying Pt:Ru ratio were prepared and characterised using ex situ and in situ XRD, in situ EXAFS at 0 V vs. RHE, ex situ XPS and monolayer CO stripping voltammetry. Although the catalysts were found to be well mixed/alloyed, with no evidence of unalloyed Ru (oxides) present, the surfaces of the electrocatalyst nanoparticles were found to be enriched with Pt compared to the nominal bulk composition. The methanol oxidation activities of the catalysts were determined in 1.0 mol dm(-3) H2SO4. In agreement with published studies of polycrystalline bulk PtRu alloys the catalyst with a 0.6 surface fraction of Pt was found to give the best methanol oxidation activity at 30 degrees C. However, at 80 degrees C a greater surface fraction of Ru could be tolerated, with some activity at low current densities found for a Pt surface fraction as low as 0.2. The results support the conclusion that a limited amount of methanol dehydrogenation occurs at Ru sites or Ru dominated surface ensembles at 80 degrees C.
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PMID:Effects of composition on structure and activity of PtRu/C catalysts. 1930 5

The electrochemical oxidation behaviors of the surfaces of platinum nanoparticles, one of the key phenomena in fuel cell developments, were investigated in situ and in real time, via time-resolved hard X-ray diffraction and energy dispersive X-ray absorption spectroscopy. Combining two complementary structural analyses, dynamical and inhomogenous structural changes occurring at the surfaces of nanoparticles were monitored on an atomic level with a time resolution of less than 1 s. After oxidation at 1.4 V vs RHE (reversible hydrogen electrode) in a 0.5 M H(2)SO(4) solution, longer Pt-O bonds (2.2-2.3 A that can be assigned to OHH and/or OH species) were first formed on the surface through the partial oxidation of water molecules. Next, these species turned to shorter Pt-O bonds (2.0 A, adsorbed atomic oxygen), and atomic oxygen was incorporated into the inner part of the nanoparticles, forming an initial monolayer oxide that had alpha-PtO(2)-like local structures with expanded Pt-Pt bonds (3.1 A). Finally, quasi-three-dimensional oxides with longer Pt-(O)-Pt bonds (3.5 A, precursor for beta-PtO(2)) grew on the surface, at almost 100 s after oxidation. Despite the very complex oxidation mechanism on the atomic level, XANES analysis indicated that the charge transfer from platinum to the adsorbed oxygen species was almost constant and rather small, that is, about 0.5 electrons per oxygen, up to two monolayers of oxygen. This means that ionic polarization hardly develops at this stage of the surface platinum's "oxide" growth.
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PMID:In situ and real-time monitoring of oxide growth in a few monolayers at surfaces of platinum nanoparticles in aqueous media. 1935 77

Gynaecomastia due to anti-tubercular chemotherapy is a rare side effect. Isoniazid causing breast tissue enlargement has been very rarely reported. We report a 60-year old, male patient of Pulmonary Tuberculosis who was started on antituberculous treatment (ATT) with rifampicin (R), isoniazid (H), ethambutol (E) and pyrazinamide (Z) together for initial two months and R, H & E thereon. After five months of initiation of treatment, while receiving RHE, he developed painful bilateral gynaecomastia. Isoniazid was stopped and patient was continued on R & E till completion of the treatment up to nine months. After stopping isoniazid, his breast swelling subsided to some extent and became non-tender. Follow up, at six months, after stopping the course of treatment, patient was asymptomatic except for slight bilateral non-tender breast enlargement.
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PMID:Isoniazid induced gynaecomastia: a case report. 1940 73

A single-source heterobimetallic complex Ni2Ti2(OEt)2(mu-OEt)6(acac)4 (1) (acac=2,4-pentanedionate), having a low decomposition temperature and sufficient solubility in organic solvents, was synthesized by simple chemical techniques in high yield and analyzed by melting point, FTIR, single crystal X-ray analysis and thermal analysis. The TGA analysis proved that complex (1) underwent facile thermal decomposition at 500 degrees C to give NiTiO3 residue. In-house designed aerosol assisted chemical vapor deposition equipment was used to deposit high quality thin films of NiTiO3 on a SnO2 coated conducting glass substrate at 500 degrees C. An XRD analysis of the thin films proved the formation of crystalline NiTiO3 with average grain size 42 nm. Scanning electron microscopic studies (SEM) show that the thin films consist of flat, plate-like nanoparticles. The current-potential characteristics recorded under AM1.5 illumination indicate that NiTiO3 thin films are anodic and the photocurrent density at 1.23 V vs RHE (Reversible Hydrogen Electrode) is about 40 microA cm(-2).
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PMID:Photooxidation of water by NiTiO3 deposited from single source precursor [Ni2Ti2(OEt)2(micro-OEt)6(acac)4] by AACVD. 1941 32

The ultra-small silicon nanoparticle was shown to be an electrocatalyst for the electrooxidation of glucose. The oxidation appeared to be a first order reaction which involves the transfer of 1 electron. The oxidation potential showed a low onset of -0.4V vs. Ag/AgCl (-0.62 V vs. RHE). The particle was used as the anode catalyst of a prototype hybrid biofuel cell, which operated on glucose and hydrogen peroxide. The output power of the hybrid cell showed a dependence on the enzymes used as the cathode catalyst. The power density was optimized to 3.7 microW/cm(2) when horseradish peroxidase was replaced by microperoxidase-11 (MP-11). Comparing the output power of the hybrid cell to that of a biofuel cell indicates enhanced cell performance due to the fast reaction kinetics of the particle. The long-term stability of the hybrid cell was characterized by monitoring the cell voltage for 5 days. It appeared to that the robustness of the silicon particle resulted in more cell stability compared to the long-term performance of a biofuel cell.
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PMID:A hybrid biofuel cell based on electrooxidation of glucose using ultra-small silicon nanoparticles. 1942 31

The surface structure of Pt(111) in a 0.1 M H2SO4 electrolyte was investigated in the potential range of sulfate adsorption with electrochemical scanning tunneling microscopy (STM) and cyclic voltammetry. Two ordered anion structures were observed coexisting in the potential range between 0.49 and 0.79 V (vs RHE): the well-known (radical3xradical7)R19.1 degrees superstructure with an anion coverage of 0.20 monolayer and a new, high-density (3x1) superstructure with a coverage of 0.33 monolayer. Both superstructures undergo a reversible order-disorder transition at 0.8 V. Simultaneous imaging of the adsorbed ions and of topographic details of the Pt substrate lattice allows us to study the local adsorption geometry of the sulfate. In the (radical3xradical7)R19.1 degrees, structure the sulfate ions are adsorbed close to depressions in the STM image of the Pt substrate which may be identified with face-centered cubic (fcc) hollow sites. In addition to the sulfate ions, a coadsorbed species, possibly water molecules, is observed in the unit cell of the (radical3xradical7)R19.1 degrees superstructure. Preliminary potentiodynamic STM data indicate that the transformation of the ordered sulfate adlayer into a disordered structure at 0.8 V is not directly related to adsorption/desorption features in the voltammogram commonly attributed to the adsorption/desorption of OH, and that the sulfate adlayer remains on the surface for potentials well above the adsorption potentials of OH.
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PMID:Superstructures and order-disorder transition of sulfate adlayers on Pt(111) in sulfuric acid solution. 1945 79

In situ scanning tunneling microscope (STM) was used to examine the spatial structures of pentacene molecules adsorbed onto a Au(111) single-crystal electrode from a benzene dosing solution containing 16-400 microM pentacene. Molecular-resolution STM imaging conducted in 0.1 M HClO(4) revealed highly ordered pentacene structures of ( radical31 x radical31)R8.9 degrees , (3 x 10), ( radical31 x 10), and ( radical7 x 2 radical7)R19.1 degrees adsorbed on the reconstructed Au(111) electrode dosed with different pentacene solutions. These pentacene structures and the reconstructed Au(111) substrate were stable between 0.2 and 0.8 V [vs reversible hydrogen electrode, RHE]. Increasing the potential to E > 0.8 V lifted the reconstructed Au(111) surface and disrupted the ordered pentacene adlattices simultaneously. Ordered pentacene structures could be restored by applying potentials negative enough to reinforce the reconstructed Au(111). At potentials negative of 0.2 V, the adsorption of protons became increasingly important to displace adsorbed pentacene admolecules. Although the reconstructed Au(111) structure was not essential to produce ordered pentacene adlayers, it seemed to help the adsorption of pentacene molecules in a long-range ordered pattern. At room temperature (25 degrees C), approximately 100 pentacene molecules seen in STM images could rotate and align themselves to a neighboring domain in 10 s, suggesting that pentacene admolecules could be mobile on Au(111) under the STM imaging conditions of -150 mV in bias voltage and 1 nA in feedback current.
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PMID:In situ STM imaging of the structures of pentacene molecules adsorbed on Au(111). 1951 30

Three types of root hair cell distribution patterns are observed in vascular plants. These distinctive patterning types indicate that the fate of the hair/nonhair cell of the root epidermis in each of these patterns is decided by different fate-determining machineries. The cell fate determiners ultimately control the hair or nonhair cell-specific genes so as to modulate hair morphogenesis. Here, we address the issue of whether or not the hair cell specificity of gene expression, i.e., the regulatory cis-element for hair cell specificity, has been conserved despite the divergence of the upstream fate-determining machineries. Our recent study in Plant Cell (the November issue online) reported that orthologs and paralogs of Arabidopsis expansin A7 (AtEXPA7) from angiosperms with different hair-distribution types have maintained a common cis-element (RHE for Root Hair Element) for root hair cell specificity. The study also identified the same functional RHE among root hair-specific cell wall genes other than those coding for expansins. These findings suggest that the same regulatory module of RHE and its transcription factor partner, which endows cell morphogenetic worker genes with hair cell specificity, have been coopted by different upstream fate-determining masters over angiosperm evolution.
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PMID:A cis-Element for Root Hair Specificity Has Been Co-opted Repeatedly Through the Divergence of Upstream Fate-Determining Machineries. 1970 54

Electrochemically active surface area (ECA) of a polycrystalline Pt electrode is measured from the pseudocapacitance (Cp) values that are associated with hydrogen underpotential deposition. The potential-dependent Cp values are extracted from the raw impedance data by removing the interferences coming from the double-layer charging and hydrogen evolution. Three different approaches have been made: (i) by using the proportionality between the capacitance and area of the capacitive peak on imaginary capacitance plots, (ii) by complex nonlinear least-squares (CNLS) fitting on both the imaginary and real part of complex capacitance with appropriate equivalent circuits, and (iii) by using the modified Kramers-Kronig (K-K) relation. The first approach is the simplest one for the Cp measurement but cannot be used in the hydrogen evolution region (<0.05 V vs RHE), whereas the measurement can be extended down to -0.01 V with the second method. The isotherm fitting on the Cp(E) profile shows that the saturation of adsorbed hydrogen is reached at -0.1 V vs RHE. Faster data acquisition is possible with the third approach since the data analysis can be made without the time-consuming low frequency data (<100 Hz). The roughness factor and ECA of the Pt electrode are calculated from the electric charge that is obtained by integrating the potential-dependent Cp values; the roughness factor (1.4-1.5) lies within the normal range for planar electrodes.
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PMID:Impedance analysis for hydrogen adsorption pseudocapacitance and electrochemically active surface area of Pt electrode. 1978 34

From a detailed analysis of the chronoamperometry of CO stripping on stepped platinum single-crystal electrodes in alkaline solution, in combination with kinetic modeling, a mechanistic and kinetic picture of the CO oxidation mechanism is derived. On Pt(111), CO oxidation starts at defect sites (steps, kinks), following a one-dimensional nucleation-and-growth mechanism, or a Langmuir-Hinshelwood mechanism with no effective competition between CO and OH. The carbonate that is formed in this reaction blocks the active oxidation sites, so that CO adsorbed on terraces further away from the defect sites can be oxidized at defects sites only very slowly. At potentials above ca. 0.75 V vs. RHE this CO is oxidized on the Pt(111) terrace. On stepped Pt electrodes, CO oxidation is also initiated at the kink (step defects) and step sites. We postulate that carbonate partially blocks the active site, but CO from the terrace still prefers to react at the steps over the terrace sites. The oxidation of terrace-bound CO at the step sites follows a competitive Langmuir-Hinshelwood mechanism. The least reactive CO on the surface is the CO that is adsorbed on the step sites, and it is oxidized by OH on terraces. Finally, on the terrace, the Tafel slope for CO stripping is close to 60 mV dec(-1), suggesting an EC mechanism, i.e. reversible OH formation followed by a chemical rate-determining step, presumably the CO + OH combination reaction. At the step site, the Tafel slope is close to 120 mV dec(-1), suggesting an electrochemical rate-determining step, ascribed to slow OH formation at the step site.
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PMID:Mechanism of electro-oxidation of carbon monoxide on stepped platinum electrodes in alkaline media: a chronoamperometric and kinetic modeling study. 2002 14


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