7,592 research outputs found
Polarization-Induced Local pH Swing Promotes Pd-Catalyzed CO2 Hydrogenation
No full textElectrochemical polarization can dramatically promote the rate of concurrent nonfaradaic catalytic reactions, but the mechanistic basis for these promotion effects at solid-liquid interfaces remains poorly understood. Herein, we establish a mechanistic framework for nonfaradaic promotion in aqueous media that operates via a local pH swing induced by a concurrent faradaic reaction. As a model system, we examined the kinetics of nonfaradaic Pd-catalyzed CO2 hydrogenation to formate and find that the reaction can be promoted by a combination of high alkalinity and high CO2 concentration. In bulk electrolyte, alkalinity and CO2 concentration are inversely correlated to each other as set by the CO2/bicarbonate equilibrium. We show that this impasse can be overcome by using electrical polarization to generate a nonequilibrium local environment that has both high alkalinity and high CO2 concentration. We find that this local pH swing promotes the rate of nonfaradaic CO2 hydrogenation to formate by nearly 3 orders of magnitude at modest potential bias. The work establishes a rigorous mechanistic model of nonfaradaic promotion in aqueous media and provides a basis for enhancing hydrogenation catalysis under mild conditions via electrical polarization.N
Implications of the Improvement of Teaching Quality for Professional Development (PD) of Academics at the Colleges of Applied Sciences (CASs) in the Sultanate of Oman
No full textThe Oman Accreditation Council (OAC), which is called later the Oman Academic Accreditation Authority (OAAA), designed a higher education institution (HEI) Quality Assurance (QA) framework for Omani public and private Higher Education Institutions (HEIs), starting with a quality audit process in 2008. The Colleges of Applied Sciences (CASs), as a public HEI, are required to ensure the quality of all services and activities to meet particular national standards (specified in the framework) in order to gain a HEI and programme certificate. In line with a quality audit scope, the quality of the fields of PD and related teaching quality should be ensured and enhanced by the promotion and contribution of the former field to the maintenance and improvement of the latter one.
The chief purpose of this study was to identify the uptake and implications of the growing requirement to improve teaching quality and the PD of academics at the CASs in the Sultanate of Oman especially in the context of the application of the QA framework. The study focused on examining the academics’ participation in professional development programmes (PDPs) and current perceptions of PD with respect to the improvement of teaching quality improvement at these colleges. The current study also dealt with a reorganization and prioritization of academics’ PD needs, barriers to effective PD, and factors to enhance PD of academics regarding teaching quality improvement in the colleges.
Based on the purpose and research objectives, the current study adopted both positivist (quantitative) and interpretive (qualitative) research paradigms. Because the study perused quantitative and qualitative data regarding certain variables, it chose a mixed-research design. The researcher designed survey questionnaire to collect quantitative data and a semi-structured interview and a focus group discussion to probe and interpret quantitative findings. After fulfillment of the validity and reliability measurements, a self-completion questionnaire was distributed to a stratified random sample of academics (170) over the six CASs. A total of 150 questionnaires (out of 170) were completed and returned and the response-rate reached 88.2%. The quantitative data was analyzed by appropriate analysis using the Statistical Package for Social sciences (SPSS), while the qualitative data was analyzed by appropriate qualitative analysis.
The findings of the study showed that the level of academics’ participation in PDPs to improve teaching quality in the last two years in the CASs seems to be unsatisfactorily low. The current perceptions of the PD situations in the colleges, relating to teaching quality improvement, signified a shortage in the number of available PDPs and/or a discouragement of academics’ participation in these programmes in the last two years. The study also revealed all the 22 PD needs of academics regarding the improvement of teaching quality are significantly demanded by participants; the higher rated needs focused on a development of ‘student centred’ skills, such as critical thinking and problem-solving skills.
Furthermore, the study illustrated that the highest significant perceived barriers to effective PD in the CASs, as related to teaching quality improvement, focus on a lack of a clear institutional PD policy and a lack of appropriately systematic PD plans. The study also revealed all 10 perceived factors to enhance PD regarding teaching quality improvement are very important. The most significant factors represented and stressed particular problematic issues (the high rated barriers) and a reduction of a heavy workload to enhance academics’ participation in PD regarding the improvement of teaching quality.
Conclusions drawn from the discussion of the findings of study include a lack of a clear PD policy at national and institutional levels and absence of a particular authority/unit concerning PD issues in Omani HEIs. The two problematic issues resulted in a lack of systematic and realistic PD plans in the CASs, involving a lack of academics’ involvement in PD plans, a misconnection of academics’ PD needs to PD, inappropriate facilities and resources allocation, and inappropriate evaluation processes of PD. In addition, the conclusions also include that PD of academics regarding the improvement of teaching quality in the colleges requires more attention and focus to manage particular significant issues perceived by participants as both barriers and potential facilitators relating to PD of academics.
Based on identified conclusions, particular implications for policy and practice to enhance PD to improve teaching quality were set at three levels: governmental, institutional, and individual. Moreover, achievements of the current study according to the research questions were identified and contributions of the study to the fields of PD, teaching quality, and the context of QA and quality audit in HE were addressed. Based on the findings and conclusions, particular directions and recommended issues were suggested to be studied by further research to benefit the enhancement of PD and related teaching quality improvement
Preparation of Pd-PS, Pd-PSB and Pd-PSC nanoparticles by gamma-irradiation and their catalytic efficiency in Sonogashira coupling reaction
No full textThe poly(styrene), PS, of 450 nm diameter, poly(styrene-co-4-vinylphenylboronic acid), PSB, nanoparticles of 220-400 nm diameter, and poly(styrene-co-4-vinylbenzoic acid), PSC, nanoparticles of 240-305 nm. were prepared by emulsifier-free emulsion polymerization. The surface of PS, PSB, and PSC nanoparticles were loaded with Pd nanoparticles by reduction of Pd ions using gamma-irradiation in order to apply catalyst in Sonogashira coupling reaction. The Pd-PS, Pd-PSB and Pd-PSC were characterized by High-Resolution Transmittance Electron Microscopy (HR-TEM), Field-Emission Scanning Electron Microscopy (FE-SEM), and Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES), respectively. The HR-TEM, XRD and ICP-AES data show that the Pd nanoparticles were loaded on the surface of PS, PSB, and PSC nanoparticles, respectively. Catalytic efficiency of the Pd-PS, Pd-PSB and Pd-PSC nanoparticles was tested in Sonogashira coupling reaction. The catalytic efficiency of the Pd-PS, Pd-PSB, and Pd-PSC nanoparticles was increased with increasing Pd nanoparticle contents. (C) 2007 Elsevier B.V. All rights reserved.This work was supported by Grant No. R01-2004-000-
10293-0 from the Basic Research Program of the Korea Science
& Engineering Foundation. In particular, the authors thank the
Korea Basic Science Institute (KBSI) for FE-TEM measurements
Screening for Penicillin Plasma Residues in Cattle by Enzyme-Linked Immunosorbent Assay
No full textIn this Study, we established a rapid prediction test for the detection of the cattle with violative tissue residues of penicillins. The recommended therapeutic doses of two penicillins, ampicillin (withdrawal time, 6 days) and amoxicillin (withdrawal time, 14 days), were administered to two groups of 10 cattle each. Blood was sampled and tested before drug administration and during the withdrawal period. The concentration of penicillins in plasma, determined by a semi-quantitative ELISA, was compared to that of internal standard (4ppb as penicillin G). The absorbance ratio of internal standard to sample (B/Bs) was introduced as an index to determine whether drug residues in cattle tissues are negative or positive. That means B/Bs ratio lower than 1 was considered residue positive and that higher than 1 negative. All 10 plasma samples from non-treated cattle showed negative results for both penicillins. Both penicillins were detected in plasma samples of cattle treated Until the 3rd day of withdrawal period. The present study lias shown that the semi-quantitative ELISA could be easily adapted for prediction of screening plasma residues for penicillin antibiotics (ampicillin and amoxicillin) in live cattle.Y
Carbon dioxide mediated, reversible chemical hydrogen storage using a Pd nanocatalyst supported on mesoporous graphitic carbon nitride
No full textReversible, carbon dioxide mediated chemical hydrogen storage was first demonstrated using a heterogeneous Pd catalyst supported on mesoporous graphitic carbon nitride (Pd/mpg-C3N4). The Pd nanoparticles were found to be uniformly dispersed onto mpg-C3N4 with an average size of 1.7 nm without any agglomeration and further exhibit superior activity for the dehydrogenation of formic acid with a turnover frequency of 144 h(-1) even in the absence of external bases at room temperature. Initial DFT studies suggest that basic sites located at the mpg-C3N4 support play synergetic roles in stabilizing reduced Pd nanoparticles without any surfactant as well as in initiating H-2-release by deprotonation of formic acid, and these potential interactions were further confirmed by X-ray absorption near edge structure (XANES). Along with dehydrogenation. Pd/mpg-C3N4 also proves to catalyze the regeneration of formic acid via CO2 hydrogenation. The governing factors of CO2 hydrogenation are further elucidated to increase the quantity of the desired formic acid with high selectivity.N
Morphology-controlled synthesis of ternary Pt-Pd-Cu alloy nanoparticles for efficient electrocatalytic oxygen reduction reactions
No full textIn the present work, we have accomplished morphology-controlled synthesis of ternary Pt-Pd-Cu alloy nanoparticles, particularly for efficient electrocatalytic oxygen reduction reactions. By controlling over the degree of galvanic displacement at room temperature, we selectively introduced porous and hollow architectures into Pt-decorated Pd-Cu alloy nanoparticles. Porous morphology was accompanied with partially facilitated Pt substitution reaction while hollow shape was exclusively achieved when the galvanic reaction was coupled with additional pre-treatment process which could eventually make the following displacement reaction more facile. Not only the both porous and hollow Pt@PdCu/C catalysts exhibited enhanced ORR performances compared to commercial Pt/C, but also they displayed outstanding durability. In addition, we investigated the alloying effects between Pt and Pd-Cu composite and the presumable influences of lattice strain through preliminary theoretical calculation to account for the enhanced ORR efficiency and durability of the present catalysts. (C) 2015 Elsevier B.V. All rights reserved.N
Transition from the thermal activation process to the viscous process in magnetization reversal behavior of the Co/Pd multilayer
No full textWe have investigated the transition from thermal activation process to viscous process in magnetization reversal behavior of the Co/Pd multilayer from the determination of the wall-motion speed and the nucleation rate via time-resolved domain observation. Interestingly, we find that the field dependencies of two activation volumes in the thermal activation regime are different from each other, which reveals that the wall-motion and nucleation experience completely different interactions. We also find that the wall-mobility in the viscous regime is much smaller than a typical value for the sandwiched Co films, which implies that the Co/Pd interfaces substantially contribute to the dynamic dissipation. (C) 2004 American Institute of Physics.This work was supported through the Creative Research
Initiatives Project of the Korean Ministry of Science and
Technology
Fullerene-like WS<sub>2</sub> supported Pd catalyst for hydrogen evolution reaction
No full textHydrogen is the most desirable green energy carrier and electrocatalytic hydrogen evolution reaction (HER) from water is a promising route for hydrogen production. The search for efficient, low-cost HER catalysts is a challenging and attracting topic. In this work, we report that inorganic fullerene-like WS2 supported Pd nanoparticles (Pd/WS2), with Pd loading of 0.76 wt%, are active for electrocatalytic HER conducted in 0.5 M H2SO4 solution, with overpotential at 10 mA cm−2 current density of ~130 mV and Tafel slope of 82.4 mV dec−1, which is comparable to that of Pt/WS2 (0.88 wt% Pt loading) with higher costs. Characteristic results indicate that WO3 impurities were in-situ produced on the WS2 surface and the Pd NPs are primarily located inside the WS2 nanocages. Contrasting experiments suggest that the WO3 impurities play a crucial role in generating Hads intermediate and the Pd NPs are active sites of H2 production, and a reaction mechanism is proposed. The Pd/WS2 catalyst also shows good long-term stability owing to the location of Pd NPs inside the WS2 cages. The high HER activity, low costs and good stability make the Pd catalyst a potential alternative to Pt catalyst for HER.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Micro and Nano Engineerin
Selective catalytic activity of ball-shaped Pd@MCM-48 nanocatalysts
No full textRemarkable selectivity is achieved in the cleavage of benzyl ethers using ball-shaped palladium nanocatalysts, Pd@MCM-48, in an MCM-48 matrix. The unique nanocatalysts not only feature unprecedented complete hydrogenolysis selectivity of a benzyl ether over hydrogenation of a double bond, but also demonstrate selective cleavage of unsubstituted benzyl ether over substituted benzyl ethers
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