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1.
Adv Mater ; 31(31): e1804846, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30605247

RESUMO

While proton exchange membrane fuel cells (PEMFCs) continue to expand into commercial markets, there is still pressure to decrease cost. One of the largest opportunities to reducing cost is to reduce the amount of platinum-group metal (PGM) catalysts used in the electrodes (particularly the cathode). Over the past decade, exciting advances in the Fe/N/C family of PGM-free oxygen reduction reaction (ORR) catalysts has provided great optimism that not only can PGMs at the cathode be reduced but possibly be completely eliminated. In fact, in September 2017, Ballard Power Systems announced the commercialization of the world's first PEMFC product to utilize a PGM-free catalyst at the cathode (FCgen-micro (non-precious-metal catalyst, NPMC)). However, for these catalysts to be used in more demanding applications, an improved understanding and new design approaches for PGM-free catalyst layers will be required. Herein, some of the latest research on both modeling and experimental studies in the field of PGM-free catalyst layer research are discussed. In addition, a short discussion on Ballard's new NPMC is provided.

2.
Adv Mater ; 29(7)2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27982465

RESUMO

Rich, porous graphene frameworks decorated with uniformly dispersed active sites are prepared by using polyaniline as a graphene precursor and introducing phenanthroline as a pore-forming agent. The unprecedented fuel-cell performance of this electrocatalyst is linked to the graphene frameworks with vast distribution of pore sizes, which maximizes the active-sites accessibility, facilitates mass-transport properties, and improves the carbon corrosion resistance.

3.
ACS Appl Mater Interfaces ; 8(10): 6488-95, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26937737

RESUMO

Nitrogen-functionalized graphene materials have been demonstrated as promising electrocatalyst for the oxygen reduction reaction (ORR), owning to their respectable activity and excellent stability in alkaline electrolyte. However, they exhibit unacceptable catalytic activity in acid medium. Here, a hierarchically porous Co-N functionalized graphene aerogel is prepared as an efficient catalyst for the ORR in acid electrolyte. In the preparation process, polyaniline (PANI) is introduced as a pore-forming agent to aid in the self-assembly of graphene species into a porous aerogel networks, and a nitrogen precursor to induce in situ nitrogen doping. Therefore, a Co-N decorated graphene aerogel framework with a large surface area (485 m(2) g(-1)) and an abundance of meso/macropores is effectively formed after heat treatment. Such highly desired structures can not only expose sufficient active sites for the ORR but also guarantee the fast mass transfer in the catalytic process, which provides significant catalytic activity with positive onset and half wave potentials, low hydrogen peroxide yield, high resistance to methanol crossover, and remarkable stability that is comparable to commercial Pt/C in acid medium.

4.
Korean Circ J ; 45(6): 469-72, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26617648

RESUMO

BACKGROUND AND OBJECTIVES: We evaluated the prevalence of gastroesophageal reflux diseases (GERD) in noncardiac chest pain (NCCP) patients, risk factors for GERD, and status of prescriptions for GERD in Korean population. SUBJECTS AND METHODS: This was a retrospective non-interventional observational nation-wide 45-center study. Patients with a normal coronary angiogram (CAG) and upper gastroendoscopy within 2 years after CAG were enrolled. The prevalence of GERD was examined. Other gastrointestinal diseases including peptic ulcer diseases or gastritis were also examined. Risk factors for GERD were compared between the GERD group and non-GERD group. The ratio of patients medicated for gastrointestinal diseases (antacids or proton-pump inhibitor) was also examined. RESULTS: Nine hundred four patients were enrolled. Among the NCCP patients, GERD was present in 436 (48.2%), peptic ulcer disease in 154 patients (17.0%), and gastritis in 659 (72.9%). There was no difference in risk factors for GERD between the GERD and non-GERD patients. Medications for GERD and other gastrointestinal diseases were prescribed in 742 (82.1%) patients. CONCLUSION: GERD was common (42.8%) in Korean NCCP patients and most (82.1%) received the prescription of gastrointestinal medications. No differences were evident in risk factors between GERD and non-GERD patients.

5.
J Cardiovasc Ultrasound ; 23(1): 36-9, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25883755

RESUMO

L-transposition of the great arteries (L-TGA) is a rare congenital anomaly and could cause complete atrioventricular (AV) block at relatively younger age. We present a case of 43-year-old male who complained of dizziness due to complete AV block. We confirmed L-TGA using transthoracic echocardiography and cardiac computed tomography. Permanent pacemaker was inserted without complications. No invasive treatment including corrective surgery was performed because patient's cardiac function was almost normal and the symptom was completely resolved after pacemaker insertion.

6.
Adv Mater ; 27(7): 1229-34, 2015 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-25417577

RESUMO

Direct growth of multigrain platinum nanowires on sulfur-doped graphene (PtNW/SG) is reported. The growth mechanism, including Pt nanoparticle nucleation on SG, followed by nanoparticle attachment with orientation along the <111> direction is highlighted. PtNW/SG demonstrates improved Pt mass and specific activity compared with commercial catalysts toward oxygen reduction, in addition to dramatically improved stability through accelerated durability testing.

7.
Nat Methods ; 5(9): 789-95, 2008 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18677321

RESUMO

Physical and functional interactions define the molecular organization of the cell. Genetic interactions, or epistasis, tend to occur between gene products involved in parallel pathways or interlinked biological processes. High-throughput experimental systems to examine genetic interactions on a genome-wide scale have been devised for Saccharomyces cerevisiae, Schizosaccharomyces pombe, Caenorhabditis elegans and Drosophila melanogaster, but have not been reported previously for prokaryotes. Here we describe the development of a quantitative screening procedure for monitoring bacterial genetic interactions based on conjugation of Escherichia coli deletion or hypomorphic strains to create double mutants on a genome-wide scale. The patterns of synthetic sickness and synthetic lethality (aggravating genetic interactions) we observed for certain double mutant combinations provided information about functional relationships and redundancy between pathways and enabled us to group bacterial gene products into functional modules.


Assuntos
Escherichia coli/genética , Análise de Sequência com Séries de Oligonucleotídeos , Conjugação Genética , Genoma Bacteriano , Mutação
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